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Alessandro GUALTIERI

Professore Ordinario
Dipartimento di Scienze Chimiche e Geologiche - Sede Dipartimento di Scienze Chimiche e Geologiche


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Pubblicazioni

- Concrete mixture comprising thermally inactivated cement- asbestos [Brevetto]
Gualtieri, Alessandro; M., Boccaletti; I., Zanatto
abstract

This invention regards the transformation of cement-asbetsos at 1200 °C to produce a secondary raw material to be recycled as pozzolanic material in the production of concrete


- Formulazione di un impasto ceramico da gres porcellanato cotto a bassa temperatura [Brevetto]
Gualtieri, Alessandro
abstract

L’invenzione riguarda la formulazione di un impasto innovativo per la produzione di piastrelle ceramiche, con le caratteristiche del grès porcellanato ma cotto a bassa temperatura, ed il relativo processo di cottura industriale. La temperatura massima di cottura di questo impasto innovativo è di 950 °C ed il ciclo di cottura ha una durata complessiva non superiore a 60 min. L’invenzione nasce dalla considerazione che la serie di reazioni chimiche (trasformazioni mineralogiche) e fisiche (sinterizzazione, greificazione, ecc) che portano alla formazione di una piastrella di grès porcellanato, può essere riprodotta partendo da una miscela di materie diverse, in un intervallo di temperatura più basso rispetto a quello utilizzato per la produzione di grès porcellanato (circa 1200 °C). La temperatura massima di cottura di questo impasto innovativo è circa 250 °C più bassa rispetto a quella normalmente utilizzata nei cicli industriali. Il ciclo di cottura è realizzabile in un comune forno a rulli da piastrelle che utilizza la tecnologia esistente. Per far avvenire reazioni di greificazione a queste basse temperature è necessario utilizzare un fondente sintetico, cioè una fritta basso-fondente che promuova, in sinergia con altre fasi, la greificazione. Il prodotto, con caratteristiche molto vicine a quello del grès porcellanato extra-white, risulta estremamente competitivo e si colloca in una fascia di costo più vicina a quello della tipologia super-white. I vantaggi di questa nuova tecnologia produttiva sono: (i) la cottura a 900 °C che permette di ottenere gamme di colori in massa diverse da quelle che si ottengono per il grès porcellanato; (ii) un risparmio dal punto di vista energetico; (iii) un risparmio su altre voci relative al processo di cottura nel forno a 900 °C quali: riduzione drastica dell’usura del forno, riduzione drastica dell’usura dei rulli, utilizzo di rulli più economici; (iiii) aumento della produttività. La produttività di questa miscela ceramica è più alta rispetto a quella di un grès porcellanato poiché il ritiro medio si attesta sul 4% rispetto al valore medio di mercato del grès porcellanato di circa 7-8%.


- Processo per la trasformazione termica di lastre di cemento- amianto utilizzando un forno continuo [Brevetto]
Gualtieri, Alessandro
abstract

Processo di lavorazione industriale per la trasformazione termica diretta di pacchi sigillati in materiale plastico, contenenti lastre di cemento-amianto derivanti da normali operazioni di rimozione e che, in alternativa, verrebbero conferiti in discarica controllata. Il processo di trasformazione termica diretta dell’intera confezione di lastre avviene utilizzando un forno industriale continuo “a tunnel”, generalmente usato per la produzione di laterizio, di lunghezza non inferiore a 50 m. Il ciclo di cottura per ottenere la completa trasformazione delle fasi dell’amianto (sia amianto di serpentino che amianto di anfibolo) in fasi silicatiche di calcio, alluminio, magnesio e ferro, innocue per la salute dell’uomo e degli animali, prevede una rampa di riscaldamento da temperatura ambiente ad una temperatura compresa fra 1200 e 1300 °C in non meno di 12 ore, una permanenza in condizioni isotermiche alla temperatura raggiunta nello step precedente non inferiore a 20 ore in modo da ottenere una temperatura al cuore del pacco di non meno di 1000 °C per 20 ore. Infine, un raffreddamento non forzato in un tempo non inferiore a 18 ore. Il forno industriale deve assicurare il completo isolamento del materiale in cottura dall’ambiente esterno e deve essere dotato di un sistema di post-combustione, con una temperatura interna non inferiore a 1200 °C, attraverso il quale devono passare tutti i fumi derivanti dai processi di trasformazione della confezione di lastre (combustione della confezione medesima, processi di disidratazione, decarbonatazione, deossidrilazione).Questo processo di lavorazione industriale è altamente innovativo perché non prevede intervento meccanico prima della cottura come la macinazione del materiale contenente amianto, operazione pericolosa che può comportare la dispersione di fibre di amianto nell’ambiente.Il forno verrà alimentato a metano al fine di contenere le emissioni in atmosfera di gas di combustione. Lo stesso impianto potrà essere utilizzato per la trasformazione termica dell’amianto friabile, di manufatti di vario tipo contenenti amianto e di amianto inglobato in materiale plastico. Dopo il trattamento, in perfetto accordo con le tecniche di trasformazione cristallochimica (modificazione chimica e ceramizzazione) descritte nella Tabella B del Decreto Ministero dell’Ambiente 29 luglio 2004, nr. 248, l’amianto è trasformato in un materiale a matrice silicatica, non fibroso, innocuo che sarà macinato a secco, omogeneizzato ed eventualmente riutilizzato come materia prima per svariate applicazioni industriali.


- Processo per la trasformazione termica di lastre di cemento-amianto utilizzando un forno industriale continuo [Brevetto]
Gualtieri, Alessandro; Zanatto, I.
abstract

This patent describes an industrial process for the direct complete temperature induced transformation (decomposition and recrystallization) of packages of plastic material containing roofing cement-asbestos slates or other asbestos containing wastes such as friable asbestos. The industrial firing process ensures a complete transformation of both the package and the asbestos containing material via a decomposition reaction of the organic compounds and a decomposition and recrystallization of all the inorganic mineral phases including the asbestos minerals.The firing process which ensures the total transformation of the packages and the mineral assemblage including the asbestos phases is accomplished using an industrial continuous tunnel kiln, with a technology comparable to that employed for the production of bricks or sanitary-wares. The length of the industrial kiln should be within 100 and 150 m to guarantee the proper firing cycle and total decomposition and recrystallization of both the hazardous serpentine and amphibole species of asbestos. The transformation via decomposition and recrystallization of these minerals leads to the formation of non hazardous crystalline Si-, Ca-; Mg-rich silicates. To this aim, the steps of the firing cycle which are required are:Step 1: a heating non-isothermal run up to the maximum firing temperature of 1200-1300 °C not shorter than 8 h;Step 2: an isotherm at the maximum firing temperature of 1200-1300 °C not shorter than 12 h;Step 3: a slow cooling non-isothermal run down to room temperature not shorter than 6 h.During the firing cycle, the industrial kiln must ensure complete isolation of the packages to be treated from the environment outside the kiln. All the volatile compounds and the asbestos fibres eventually released during the preliminary stage (Step 1) of the firing process inside the kiln will be conveyed to a post-combustion system (a supplementary heater at the top of the kiln) operating at temperature not lower than 1100 °C, to guarantee their complete thermal transformation and decomposition. The hot smokes and particulate from the post-combustor system will be successively cooled down to a temperature lower than 150 °C to allow the flow through double absolute HEPA filters before they are released in air.This industrial process is highly innovative and unique because it makes possible a safe direct thermal transformation of the packages containing the asbestos materials. The packages are not opened nor mechanically ground before the firing process. In this way, such pre-firing operations, highly dangerous because of possible dispersion of asbestos fibres in air, are avoided.The energy to the kiln will be supplied using natural gas.This industrial system will be capable to operate either with cement-asbestos sheets and friable asbestos and/or synthetic glass/wool fibers.As consequence of the thermal treatment, in agreement with the actual laws concerning the treatment and recycling of transformed asbestos containing wastes (see Table B Italian Minister Decree nr. 248, July 29th 2004), the product of transformation, composed of a mixture of innocuous non-fibrous crystalline silicates can be milled and recycled as a raw material for the formulation of a number of different industrial products such as traditional ceramics, pigments, cements and bricks.


- miscela di calcestruzzo comprendente cemento-amianto inertizzato termicamente [Brevetto]
Gualtieri, Alessandro; M. Boccaletti e. I., Zanatto
abstract

Invenzione che descriver la trasformazione termica del cemento-amianto a 1200 °C per la realizzazione di una materia prima secondaria da utilizzare come legante nelle miscele per la produzione di calcestruzzo.


2023 - Origin of a carbonate-bearing fluorapatite from Tertiary volcanics of the Veneto Volcanic Province, Italy [Articolo su rivista]
Cipriani, A.; Giovanardi, T.; Mazzucchelli, M.; Lugli, F.; Sforna, M. C.; Gualtieri, A. F.; Di Giuseppe, D.; Gaeta, M.; Brunelli, D.
abstract

We present chemical and mineralogical data on a megacryst of a unique carbonate-bearing fluorapatite from altered Tertiary volcanics of the Veneto Volcanic Province (VVP) in the western Lessini Mountain range (Veneto, northern Italy). The cm-sized specimen was identified and characterized by scanning electron microscope (SEM), X-ray powder diffraction (XRPD), micro-Raman spectroscopy and electron probe microanalyses. Major and trace elements of the carbonate-bearing fluorapatite are consistent with the crystallization at depth from a nelsonitic melt or an evolved alkaline melt derived from a mantle source metasomatized by carbonate-rich fluids. The Sr and Nd isotopic composition fits with the lavas and xenoliths from the VVP showing a DM-HIMU affinity with addition of a crustal, possibly carbonate, component. Our data are in agreement with a recent geodynamic model for the hybridization of the VVP mantle triggered by breakdown of carbonates within the subducting Tethyan oceanic slab. Cronstedtite, chabazite-Ca, calcite associated with reaction rims of amphibole and secondary carbonate-rich fluorapatite within the megacryst originated from low temperature hydrothermal alteration of the volcanics. Cronstedtite is the first occurrence in the VVP area.


2022 - Acute cytotoxicity of mineral fibres observed by time-lapse video microscopy [Articolo su rivista]
Di Giuseppe, D.; Scarfi, S.; Alessandrini, A.; Bassi, A. M.; Mirata, S.; Almonti, V.; Ragazzini, G.; Mescola, A.; Filaferro, M.; Avallone, R.; Vitale, G.; Scognamiglio, V.; Gualtieri, A. F.
abstract

Inhalation of mineral fibres is associated with the onset of an inflammatory activity in the lungs and the pleura responsible for the development of fatal malignancies. It is known that cell damage is a necessary step for triggering the inflammatory response. However, the mechanisms by which mineral fibres exert cytotoxic activity are not fully understood. In this work, the kinetics of the early cytotoxicity mechanisms of three mineral fibres (i.e., chrysotile, crocidolite and fibrous erionite) classified as carcinogenic by the International Agency for Research on Cancer, was determined for the first time in a comparative manner using time-lapse video microscopy coupled with in vitro assays. All tests were performed using the THP-1 cell line, differentiated into M0 macrophages (M0-THP-1) and exposed for short times (8 h) to 25 μg/mL aliquots of chrysotile, crocidolite and fibrous erionite. The toxic action of fibrous erionite on M0-THP-1 cells is manifested since the early steps (2 h) of the experiment while the cytotoxicity of crocidolite and chrysotile gradually increases during the time span of the experiment. Chrysotile and crocidolite prompt cell death mainly via apoptosis, while erionite exposure is also probably associated to a necrotic-like effect. The potential mechanisms underlying these different toxicity behaviours are discussed in the light of the different morphological, and chemical-physical properties of the three fibres.


2022 - Characterisation of potentially toxic natural fibrous zeolites by means of electron paramagnetic resonance spectroscopy and morphological-mineralogical studies [Articolo su rivista]
Giordani, M.; Mattioli, M.; Cangiotti, M.; Fattori, A.; Ottaviani, M. F.; Betti, M.; Ballirano, P.; Pacella, A.; Di Giuseppe, D.; Scognamiglio, V.; Hanuskova, M.; Gualtieri, A. F.
abstract

This study explored the morphological, mineralogical, and physico-chemical features of carcinogenic erionite and other possibly hazardous zeolites, such as mesolite and thomsonite, while also investigating the interacting capability of the mineral surface at the liquid/solid interface. Extremely fibrous erionite is K+ and Ca2+-rich and shows the highest Si/Al ratio (3.38) and specific surface area (8.14 m2/g). Fibrous mesolite is Na+ and Ca2+-rich and displays both a lower Si/Al ratio (1.56) and a smaller specific surface area (1.56 m2/g). The thomsonite composition shows the lowest values of Si/Al ratio (1.23) and specific surface area (0.38 m2/g). Electron paramagnetic resonance data from selected spin probes reveal that erionite has a homogeneous site distribution and interacts well with all spin probes. The surfaces of mesolite and thomsonite are less homogeneous and closer polar sites were found through consequent interaction with the probes. The mesolite surface can also clearly interact but with a lower strength and may represent a potential health hazard for humans, though with a lower degree if compared to erionite. The thomsonite surface is not inert and interacts with the probes with a low-grade capability. We can expect small fragments of thomsonite to interact with the biological environment, though with a low-grade intensity.


2022 - Identification of iron compounds in chrysotile from the Balangero mine (Turin, Italy) by micro-Raman spectroscopy [Articolo su rivista]
Fornasini, L.; Raneri, S.; Bersani, D.; Mantovani, L.; Scognamiglio, V.; Di Giuseppe, D.; Gualtieri, A. F.
abstract

Chrysotile, one of the six regulated asbestos minerals, is classified as carcinogenic to humans by the International Agency for Research on Cancer. The Balangero mine (Turin, Italy) was the largest asbestos mine in Europe, providing extraction of chrysotile fibers until 1990. Chrysotile from Balangero is currently of great interest in fibers toxicity studies focused on the understanding of the mechanisms that induce lung malignancies. One of the crucial factors in the biochemical reactions is the presence of Fe at the fibers surface. Surface reactivity is responsible for the generation of reactive oxygen species, which play an important role in asbestos cyto-genotoxicity. Moreover, the dissolution of Fe-bearing phases in the acidic environment of the lysosomes might be considered as possible release of hazardous Fe ions in the lungs. Here, chrysotile from Balangero was characterized by micro-Raman spectroscopy and scanning electron microscope-energy dispersive system (SEM-EDS) analysis to identify the Fe-bearing impurities associated with asbestos fibers. Micrometric crystals were recognized as Fe oxides, carbonates, and sulfides. Uncommonly reported phases in asbestos minerals were also identified, mainly as mackinawite (Fe(II)S), in different forms. The nature of the Fe compounds containing both Fe(II) and Fe(III) species was verified by micro-Raman spectroscopy combined with SEM-EDS analysis.


2022 - Letter to the Editor: Comments on the paper of Wylie and Korchevskiy – Carcinogenicity of fibrous glaucophane: How should we fill the data gaps? [Articolo su rivista]
Gualtieri, A. F.; Di Giuseppe, D.
abstract

Assessing the human health risk of mineral fibres is an intricate task. In the recent article by Wylie and Korchevskiy (2021) – Carcinogenicity of fibrous glaucophane: how to fill data gaps? (Curr. Res. Toxicol. Vol. 2, pp. 202–203), the authors discuss the potential toxicity and pathogenicity of fibrous glaucophane from the Franciscan Complex, California (USA). Because most of the points of discussion concerns the mineral fibre toxicity/pathogenicity model developed by our research group and the application to the case of fibrous glaucophane (Gualtieri, 2021, Curr. Res. Toxicol. Vol. 2, pp. 42–52), the aim of this Letter is to clear some basic issues, to fill some information gaps and, with a constructive spirit, to provide a complete picture on this topic.


2022 - The Acute Toxicity of Mineral Fibres: A Systematic In Vitro Study Using Different THP-1 Macrophage Phenotypes [Abstract in Rivista]
Mirata, S.; Almonti, V.; Di Giuseppe, D.; Fornasini, L.; Raneri, S.; Vernazza, S.; Bersani, D.; Gualtieri, A. F.; Bassi, A. M.; Scarfi, S.
abstract

Alveolar macrophages are the first line of defence against detrimental inhaled stimuli. To date, no comparative data have been obtained on the inflammatory response induced by different carcinogenic mineral fibres in the three main macrophage phenotypes: M0 (non-activated), M1 (pro-inflammatory) and M2 (alternatively activated). To gain new insights into the different toxicity mechanisms of carcinogenic mineral fibres, the acute effects of fibrous erionite, crocidolite and chrysotile in the three phenotypes obtained by THP-1 monocyte differentiation were investigated. The three mineral fibres apparently act by different toxicity mechanisms. Crocidolite seems to exert its toxic effects mostly as a result of its biodurability, ROS and cytokine production and DNA damage. Chrysotile, due to its low biodurability, displays toxic effects related to the release of toxic metals and the production of ROS and cytokines. Other mechanisms are involved in explaining the toxicity of biodurable fibrous erionite, which induces lower ROS and toxic metal release but exhibits a cation-exchange capacity able to alter the intracellular homeostasis of important cations. Concerning the differences among the three macrophage phenotypes, similar behaviour in the production of pro-inflammatory mediators was observed. The M2 phenotype, although known as a cell type recruited to mitigate the inflammatory state, in the case of asbestos fibres and erionite, serves to support the process by supplying pro-inflammatory mediators.


2021 - A Systematic Study of the Cryogenic Milling of Chrysotile Asbestos [Articolo su rivista]
Scognamiglio, Valentina; Di Giuseppe, Dario; Lassinantti Gualtieri, Magdalena; Tomassetti, Laura; Gualtieri, Alessandro F.
abstract

For more than 40 years, intensive research has been devoted to shedding light on the mechanisms of asbestos toxicity. Given the key role of fibre length in the mechanisms of asbestos toxicity, much work has been devoted to finding suitable comminution routes to produce fibres in desired size intervals. A promising method is cryogenic milling that, unlike other mechanical size reduction techniques, preserves the crystal–chemical properties of materials. In this study, the effect of cryogenic milling on the physical–chemical properties of commercial Russian chrysotile was studied in order to produce precise size fractions with invariant properties compared to the pristine fibres. In particular, two batches with fibres > 5 µm and < 5 µm were prepared, as this limit sets their potential toxicity. The results are fundamental for future in vitro toxicity testing of this commercial product, widely used in chrysotile-friendly countries but not yet adequately studied. Results show that fibre length can be controlled by milling time under cryogenic conditions without inducing structural defects or amorphization; short fibres (95% L < 5 µm) can be obtained by cryogenic milling for 40 min, while 10 min is enough to yield long chrysotile fibres (90% L > 5 µm)


2021 - Al-Substituted Tobermorites: An Effective Cation Exchanger Synthesized from "end-of-Waste" Materials [Articolo su rivista]
Malferrari, D.; Bernini, F.; Di Giuseppe, D.; Scognamiglio, V.; Gualtieri, A. F.
abstract

The policies to meet the "zero waste"regime and transition to sustainable circular economy can no longer ignore the use of wastes in place of natural resources, and these daunting and vital societal challenges are nowadays being faced by several nations. The main objective of this work was to search waste materials suitable for a quick and environmentally friendly production of a nanoporous geomaterial able to trap toxic metals at the solid/liquid interface. More specifically, the end-of-waste from the thermal inertization of cement-asbestos and glass powder from domestic glass containers have been employed as sources for the hydrothermal synthesis of a tobermorite-rich material (TRM) successfully tested for the selective removal of Pb2+, Zn2+, Cd2+, and Ni2+ from aqueous solutions. The synthesis was carried out in alkaline solution under mild hydrothermal conditions (120 °C) within 24 h. The quantitative phase analyses of the TRM carried out by applying the Rietveld method showed the occurrence of a large amount of well-crystallized 11 Å Al-substituted tobermorites and an amorphous phase and a lower content of aragonite and calcite. Chemical analyses and thermogravimetric measurements coupled with simultaneous evolved gas mass spectrometry highlighted that Al3+ for Si4+ substitutions in the wollastonite-like tetrahedral chains of tobermorites are balanced by the occurrence of Ca2+, Na+, and K+ cations in the interlayer rather than by (OH)- for O2- substitutions in the CaO polyhedra. Time-dependent removal tests clearly indicated that metal cations are selectively adsorbed depending on their concentration in solution. Moreover, the kinetic curves showed that the removal of metals from solution is fast and the equilibrium is almost reached in the first 8 h.


2021 - Bridging the gap between toxicity and carcinogenicity of mineral fibres by connecting the fibre crystal-chemical and physical parameters to the key characteristics of cancer [Articolo su rivista]
Gualtieri, A. F.
abstract

Airborne fibres and particularly asbestos represent hazards of great concern for human health because exposure to these peculiar particulates may cause malignancies such as lung cancer and mesothelioma. Currently, many researchers worldwide are focussed on fully understanding the patho-biological mechanisms leading to carcinogenesis prompted by pathogenic fibres. Along this line, the present work introduces a novel approach to correlate how and to what extent the physical/crystal-chemical and morphological parameters (including length, chemistry, biodurability, and surface properties) of mineral fibres cause major adverse effects with an emphasis on asbestos. The model described below conceptually attempts to bridge the gap between toxicity and carcinogenicity of mineral fibres and has several implications: 1) it provides a tool to measure the toxicity and pathogenic potential of asbestos minerals, allowing a quantitative rank of the different types (e.g. chrysotile vs. crocidolite); 2) it can predict the toxicity and pathogenicity of “unregulated” or unclassified fibres; 3) it reveals the parameters of a mineral fibre that are active in stimulating key characteristics of cancer, thus offering a strategy for developing specific cancer prevention strategies and therapies. Chrysotile, crocidolite and fibrous glaucophane are described here as mineral fibres of interest.


2021 - Characterization and assessment of the potential toxicity/pathogenicity of Russian commercial chrysotile [Articolo su rivista]
Di Giuseppe, D.; Zoboli, A.; Nodari, L.; Pasquali, L.; Sala, O.; Ballirano, P.; Malferrari, D.; Raneri, S.; Hanuskova, M.; Gualtieri, A. F.
abstract

Today, cancer is one of the main health issues faced in the workplace, with asbestos an important carcinogen in the occupational environment. Among the asbestos minerals, chrysotile is the main species of socio-economic and industrial relevance. Although chrysotile asbestos is classified as a "carcinogenic substance"by the International Agency for Research on Cancer (IARC), this fiber is still mined and used in Russia. The effective health hazard posed by the Russian commercial chrysotile has not been quantitatively assessed to date. In this work, the potential toxicity/pathogenicity of Russian chrysotile was quantitatively determined using the fiber potential toxicity index (FPTI) model. This model was applied to a representative commercial chrysotile from the Orenburg region, Russia, whose morphometric, crystal-chemical, surface activity, and biodurability related parameters were determined. We have quantitatively assessed that the toxicity/pathogenicity potential of Russian chrysotile (FPTI = 2.4) is lower than that of amphibole asbestos species but higher than the threshold limit set for "safe"mineral fibers (FPTI = 2.0), although it does not contain impurities of amphibole asbestos. Differences with other chrysotile samples were discussed, and it was found that the investigated Russian commercial chrysotile shares several features with the Italian Balangero chrysotile, indicating that widespread concern on commercial Russian chrysotile is justified.


2021 - Characterization of fibrous wollastonite NYAD G in view of its use as negative standard for in vitro toxicity tests [Articolo su rivista]
Di Giuseppe, D.; Scognamiglio, V.; Malferrari, D.; Nodari, L.; Pasquali, L.; Gualtieri, M. L.; Scarfi, S.; Mirata, S.; Tessari, U.; Hanuskova, M.; Gualtieri, A. F.
abstract

Today, despite considerable efforts undertaken by the scientific community, the mechanisms of carcinogenesis of mineral fibres remain poorly understood. A crucial role in disclosing the mechanisms of action of mineral fibres is played by in vitro and in vivo models. Such models require experimental design based on negative and positive controls. Commonly used positive controls are amosite and crocidolite UICC standards, while negative controls have not been identified so far. The extensive characterisation and assessment of toxicity/pathogenicity potential carried out in this work indicate that the commercial fibrous wollastonite NYAD G may be considered as a negative standard control for biological and biomedical tests involving mineral fibres. Preliminary in vitro tests suggest that wollastonite NYAD G is not genotoxic. This material is nearly pure and is characterized by very long (46.6 µm), thick (3.74 µm) and non-biodurable fibres with a low content of metals. According to the fibre potential toxicity index (FPTI) model, wollastonite NYAD G is an inert mineral fibre that is expected to exert a low biological response during in vitro/in vivo testing.


2021 - Commercial brucite, a worldwide used raw material deemed safe, can be contaminated by asbestos [Articolo su rivista]
Malferrari, D.; Di Giuseppe, D.; Scognamiglio, V.; Gualtieri, A. F.
abstract

Brucite is a raw material used in several applications and worldwide traded. The main active deposits are located in North America, North Europe and China and the extracted material is worked and delivered all over the world without any particular precaution as it is considered a safe inert product. But is it really true? Applying a consolidated protocol of analysis for the detection and characterization of fibers, we found asbestos in a sample of commercial brucite. The analyzed material is primarily composed of plate-like crystals of brucite; nevertheless, chemical and mineralogical analyses revealed the presence of serpentine, while morphometric observation through electron microscopy confirmed the occurrence of respirable regulated chrysotile (serpentine asbestos) fibers. The individual fibers making up the chrysotile bundles have length >5 µm, width <3 µm, length/width ratio >3, and their concentration in the investigated product is 169 mg/kg (0.02 wt%). Although paragenesis of brucite with chrysotile has been known for a long time, never before was documented a commercial brucite, distributed worldwide, contaminated with asbestos. In the light of these results, we think that certification of the absence of asbestos should be imposed to the brucite mining companies and distributors; otherwise, users should always include a careful inspection on incoming materials, at least by electron microscopy, to rule out the occurrence of asbestos.


2021 - Crystal structure determination of a lifelong biopersistent asbestos fibre using single-crystal synchrotron X-ray micro-diffraction [Articolo su rivista]
Giacobbe, C.; Di Giuseppe, D.; Zoboli, A.; Gualtieri, M. L.; Bonasoni, P.; Moliterni, A.; Corriero, N.; Altomare, A.; Wright, J.; Gualtieri, A. F.
abstract

The six natural silicates known as asbestos may induce fatal lung diseases via inhalation, with a latency period of decades. The five amphibole asbestos species are assumed to be biopersistent in the lungs, and for this reason they are considered much more toxic than serpentine asbestos (chrysotile). Here, we refined the atomic structure of an amosite amphibole asbestos fibre that had remained in a human lung for 40 years, in order to verify the stability in vivo. The subject was originally exposed to a blend of chrysotile, amosite and crocidolite, which remained in his parietal pleura for 40 years. We found a few relicts of chrysotile fibres that were amorphous and magnesium depleted. Amphibole fibres that were recovered were undamaged and suitable for synchrotron X-ray micro-diffraction experiments. Our crystal structure refinement from a recovered amosite fibre demonstrates that the original atomic distribution in the crystal is intact and, consequently, that the atomic structure of amphibole asbestos fibres remains stable in the lungs for a lifetime; during which time they can cause chronic inflammation and other adverse effects that are responsible for carcinogenesis. The amosite fibres are not iron depleted proving that the iron pool for the formation of the asbestos bodies is biological (haemoglobin/plasma derived) and that it does not come from the asbestos fibres themselves.


2021 - In vitro toxicity of fibrous glaucophane [Articolo su rivista]
Gualtieri, A. F.; Zoboli, A.; Filaferro, M.; Benassi, M.; Scarfi, S.; Mirata, S.; Avallone, R.; Vitale, G.; Bailey, M.; Harper, M.; Di Giuseppe, D.
abstract

The health hazard represented by the exposure to asbestos may also concern other minerals with asbestos-like crystal habit. One of these potentially hazardous minerals is fibrous glaucophane. Fibrous glaucophane is a major component of blueschist rocks of California (USA) currently mined for construction purposes. Dust generated by the excavation activities might potentially expose workers and the general public. The aim of this study was to determine whether fibrous glaucophane induces in vitro toxicity effects on lung cells by assessing the biological responses of cultured human pleural mesothelial cells (Met-5A) and THP-1 derived macrophages exposed for 24 h and 48 h to glaucophane fibres. Crocidolite asbestos was tested for comparison. The experimental configuration of the in vitro tests included a cell culture without fibres (i.e., control), cell cultures treated with 50 μg/mL (i.e., 15.6 μg/cm2) of crocidolite fibres and 25-50−100 μg/mL (i.e., 7.8−15.6–31.2 μg/cm2) of glaucophane fibres. Results showed that fibrous glaucophane may induce a decrease in cell viability and an increase in extra-cellular lactate dehydrogenase release in the tested cell cultures in a concentration dependent mode. Moreover, it was found that fibrous glaucophane has a potency to cause oxidative stress. The biological reactivity of fibrous glaucophane confirms that it is a toxic agent and, although it apparently induces lower toxic effects compared to crocidolite, exposure to this fibre may be responsible for the development of lung diseases in exposed unprotected workers and population.


2021 - Management of Asbestos Containing Materials: A Detailed LCA Comparison of Different Scenarios Comprising First Time Asbestos Characterization Factor Proposal [Articolo su rivista]
Pini, Martina; Scarpellini, Simone; Rosa, Roberto; Neri, Paolo; Gualtieri, Alessandro; Ferrari, Anna Maria
abstract

This work addresses the complex issue of asbestos containing materials (ACMs) management, by focusing on the scenario of six municipalities comprised in the Reggio Emilia province of Emilia Romagna Italian region. Particularly, the life cycle assessment (LCA) methodology was applied in order to assess in a quantitative and reliable manner the human toxicity as well as the ecotoxicity impacts associated with all of the different phases of ACMs management. The latter comprises mapping of ACMs, creation of a risk map for defining priority of intervention, encapsulation and removal of ACMs, as well as the as obtained asbestos containing waste (ACW) end of life. Particularly, a thermal inertisation treatment performed in a continuous industrial furnace was considered as the innovative end of life scenario to be compared with what actually was provided by the legislation of many countries worldwide, that is, the disposal of ACW in a controlled landfill for hazardous wastes. A characterization factor for asbestos fibers released both in outdoor air and in occupational setting was proposed for the first time and included in the USEtox 2.0 impact assessment method. This allowed us to reliably and quantitatively highlight that inertisation treatments should be the preferred solutions to be adopted by local and national authorities, especially if the obtained inert material finds application as secondary raw materials, thus contributing to a decrease in the environmental damage (limited to its toxicological contributions) to be associated with asbestos management.


2021 - Occurrence and characterization of tremolite asbestos from the Mid Atlantic Ridge [Articolo su rivista]
Di Giuseppe, D.; Perchiazzi, N.; Brunelli, D.; Giovanardi, T.; Nodari, L.; Della Ventura, G.; Malferrari, D.; Maia, M.; Gualtieri, A. F.
abstract

Tremolite is one of the most common amphibole species and, in the fibrous form (i.e., characterized by crystals/particles consisting of fibres with length > 5 µm, width < 3 µm and aspect ratio > 3), one of the six asbestos minerals. Until now the attention of crystallographers has focused only on samples from continental environment. Here we report the first chemical and structural data of a tremolite asbestos found along the Mid Atlantic Ridge (MAR) at the eastern intersection of the Romanche Transform Fault (Equatorial MAR). Tremolite is associated with chlorite and lizardite and was formed through the green shale facies lower than zeolite in a predominantly fluid system. MAR tremolite asbestos shows very slight deviations from the ideal crystal structure of tremolite. Differences in cation site partitioning were found with respect to tremolite asbestos from ophiolitic complexes, attributed to the different chemical–physical conditions during the mineral formation. In particular, oceanic tremolite asbestos is enriched in Al and Na, forming a trend clearly distinct from the continental tremolites.


2021 - WebFPTI: A tool to predict the toxicity/pathogenicity of mineral fibres including asbestos [Articolo su rivista]
Gualtieri, A. F.; Leoncini, M.; Rinaldi, L.; Zoboli, A.; Di Giuseppe, D.
abstract

The risk assessment for the human health of airborne mineral fibres, including asbestos minerals, is a complex task. WebFPTI is a browser-based software written in Python that allows users to calculate an index of toxicity and pathogenicity potential of mineral fibres based on their crystal-chemical-physical properties. WebFPTI can be a powerful tool for both academy and environmental/health institutions to classify the carcinogenicity potential of (respirable) mineral fibres, so that specific actions aimed at protecting workers and general public can be fostered.


2020 - Emission of fibres and atmospheric pollutants from the thermal treatment of asbestos containing waste (ACW) [Articolo su rivista]
Tomassetti, L.; Di Giuseppe, D.; Zoboli, A.; Paolini, V.; Torre, M.; Paris, E.; Guerriero, E.; Petracchini, F.; Gualtieri, A. F.
abstract

Asbestos containing materials (ACMs) are currently landfilled or encapsulated, but this may lead to the release of fibres in the environment. Hence, the destruction of asbestos containing waste (ACW) is now regarded as a preferable option. Thermal treatments based on chrysotile and amphibole asbestos dehydroxylation and recrystallization are being successfully developed for this purpose. This study investigates the emission of asbestos fibres from a prototype for asbestos treatment. Other atmospheric pollutants measured include carbon monoxide (CO), nitrogen oxides (NOx), sulfur dioxide (SO2), volatile organic compounds (VOCs), heavy metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) dioxins and furans (PCDD/Fs). Both cement-asbestos and ACM containing polyurethane were tested. No asbestos fibres were found, neither in the emission nor in the solid residue. The concentration of NOx, SO2 and heavy metals are comparable with municipal solid waste incinerators (MSWI) and cement plants. PAHs, BTEX (benzene, toluene, ethylbenzene, xylenes) and styrene are higher in the presence of polyurethane. The presence of polyvinyl chloride (PVC) in the coating of asbestos cement can increase the emission of halogenated VOCs, PCBs and PCDD/Fs. Our results confirm that asbestos inertisation is a safe process for the environment and human health, and economically competitive with landfills.


2020 - Lung cancer: Mechanisms of carcinogenesis by asbestos [Capitolo/Saggio]
Mossman, B. T.; Gualtieri, A. F.
abstract

Lung cancers have typically been reported in asbestos-exposed cohorts in smokers, and interactions between cigarette smoke and asbestos may be additive or multiplicative in the development of tumors. Research has indicated that some cellular and molecular events elicited by exposures to chemical carcinogens in cigarette smoke or asbestos fibers are different in lung epithelial cells, the target cells of lung carcinomas. We describe here contemporary concepts of lung cancer development and recent experimental studies providing an understanding of how asbestos and components of cigarette smoke act alone and together to cause lung cancers. We emphasize the importance of the tumor microenvironment including inflammation and fibrosis, interactions between different cell types in the lung that culminate in these events, and the role of epigenetics, a relatively new tool in understanding a number of common molecular events in carcinogenesis. Lastly, we provide a perspective on the multiple properties of different asbestos fiber types that may be critical in assessing their toxicity and carcinogenicity in lung tissue and the development of a quantitative model to predict the pathogenicity of mineral fibers in lung cancers.


2020 - Naturally occurring asbestos: A global health concern? State of the art and open issues [Articolo su rivista]
Gualtieri, A. F.
abstract

Naturally occurring asbestos (NOA) is a global public health issue because minerals that may be classified as asbestos are a common constituent of certain types of rock and soil, found in many regions on every continent. Disturbance of these rocks and soils, especially through construction activities, can result in airborne particles, leading to inhalation and risk of disease from these known human carcinogens. The presence of NOA in the environment affects all the human activities aimed at its modification, and all engineering/geological actions in the natural environment should take it into account. In the presence of NOA, specific procedures for sampling, evaluation of environmental risk, and monitoring should be applied to minimize the risk of exposure for the workers and the general public. Unfortunately, detailed procedures have been lacking to date, and consensus is difficult to achieve because basic issues, such as the definition of asbestos itself, are still open and being debated by scientists and regulators. While the term "asbestos" has been used in older geological publications, it is not currently defined by geologists. For the past century, "asbestos" was a commercial term used to describe minerals mined for specific purposes, and the term then entered the legal lexicon for purposes of control and compensation. All these basic matters are critically illustrated in the article. Finding clear and universally accepted definitions is mandatory; otherwise, there will continue to be controversial positions that can cause regulatory and legal issues and the outcome of lawsuits to be very subjective.


2020 - Recycling of thermally treated cement-asbestos for the production of porcelain stoneware slabs [Articolo su rivista]
Ligabue, M. L.; Gualtieri, A. F.; Lassinantti Gualtieri, M.; Malferrari, D.; Lusvardi, G.
abstract

The directives of the European Commission Environment on the management of hazardous asbestos-containing materials (ACM) are pointing towards treatment and recycling other than disposal in landfills. KRY·AS is a secondary raw material obtained by the thermal transformation of cement-asbestos (CA) and can be inserted in the production line of e.g. concrete, clay bricks, ceramics, and plastic materials. This being a possible future solution to the huge “CA-emergency” in Italy, additional recycling options are sought. In this work, KRY·AS was used for the production of glass-ceramic frits destined for the manufacturing of porcelain stoneware slabs. Two novel frits were obtained by vitrifying KRY·AS together with minor amounts of natural raw materials as well as glass waste. The resulting frits were added in a ceramic body formulation (0, 1, 3, 5 wt.%). Phase composition, microstructure and technological properties of fired samples were evaluated and the results were compared to those obtained when using a standard commercial frit. According to water absorption tests, the novel products can be classified as BIa-type. Comparable or even improved technological properties were found between the standard body and the frit-bearing ones. More precisely, the addition of 5 wt.% of the novel frits led to better stain resistance as well as higher productivity due to reduction of the linear firing shrinkage. Improved mechanical strength (ca. 75 MPa compared to ca 60 MPa for the standard) was also obtained. The novel recycling route of KRY·AS supports a conclusive solution for the management of hazardous CA in Italy.


2020 - The Oligocene-Miocene volcanism in the Apennine: discovery and characterization of baryte and phillipsite-Ba rich bed in the lower part of the Ranzano Formation (Reggio Emilia, Italy) [Articolo su rivista]
Malferrari, D.; Gualtieri, A.; Panini, F.; Fioroni, C.
abstract

This work reports the biostratigraphic assessment and the chemical and mineralogical characterization of a zeolitized and barium-rich volcanic pyroclastic bed outcropping in the lower Secchia Valley (Northern Apennines, Italy), very close to the boundary between the Ranzano and the Monte Piano Formations. To our knowledge, it is the older so far documented in the Emilian Epiligurian Succession as, through nannofossil biostratigraphy, we have documented an early Oligocene age (Rupelian CNO1 nannofossil zone) for the enclosing sediments. The chemical and mineralogical composition, the latter obtained through a multi-analytical approach combining X-ray powder diffraction (Rietveld-RIR method) with thermal analyses coupled with evolved gas mass spectrometry, revealed large amounts of Barich phillipsite, baryte, volcanic glass and subordinate quantities of sanidine and plagioclase; on the other hand, phlogopite, idiomorphic plagioclase and femic minerals, frequently found in younger volcanic layers of the Ranzano Formation, here are absent. The quantitative mineralogical assessment together with mineral associations suggest that diagenesis did not play a relevant role in the crystallization of phillipsite, but its role cannot be neglected for the crystallization of baryte. Hypothesis on the genesis and transformation of the original material and on the possible correlation with the coeval calc-alkaline magmatic sources in the circum-Mediterranean area were considered, but no definitive conclusion has been reached.


2019 - Biodurability and release of metals during the dissolution of chrysotile, crocidolite and fibrous erionite [Articolo su rivista]
Gualtieri, Alessandro F.; Lusvardi, Gigliola; Zoboli, Alessandro; Di Giuseppe, Dario; Lassinantti Gualtieri, Magdalena
abstract

Background: The mechanisms by which mineral fibers induce adverse effects in vivo are still not well understood. The mechanisms of fiber dissolution in the lungs and subsequent release of metals in the extracellular/intracellular environment must be taken into account. Aim: For the first time, the kinetics of release of metals during the acellular in vitro dissolution of chrysotile, crocidolite and fibrous erionite were determined. Methods: In vitro acellular dissolution of chrysotile, crocidolite, and fibrous erionite-Na was conducted using a solution mimicking the phagolysosome environment active during the phagocytosis process (pH=4.5, at 37 °C). The kinetics of release of a representative selection of metals were determined over a period of three months. Results: Despite the fact that the difference in Fe content between chrysotile and crocidolite is one order of magnitude, the much faster dissolution rate of chrysotile compared to crocidolite prompts greater release of available active surface Fe in the first weeks of the dissolution experiment and comparable amounts after 90 d. Such active iron may promote the formation of toxic hydroxyl radicals. The fast release of metals like Cr, Ni and Mn from chrysotile is also a source of concern whereas the release of V in solution is negligible. Conclusion: Because chrysotile undergoes fast dissolution with respect to crocidolite and fibrous erionite, it behaves like a carrier that releases its metals’ cargo in the lung environment, mimicking the phenomenon that explains the toxicity of nanoparticles. Hence, the toxicity paradigm of a non biodurable fiber like chrysotile should also take into account the release of toxic metals in the intracellular/extracellular medium during the rapid dissolution process.


2019 - Characterisation of fibrous ferrierite in the rhyolitic tuffs at Lovelock, Nevada, USA [Articolo su rivista]
Zoboli, A.; Di Giuseppe, D.; Baraldi, C.; Gamberini, M. C.; Malferrari, D.; Urso, G.; Lassinantti Gualtieri, M.; Bailey, M.; Gualtieri, A. F.
abstract

Ferrierite is the name for a series of zeolite-group of minerals which includes three species with the same ferrierite framework (FER) crystal structure but different extra-framework cations. Recent studies have shown that ferrierite can exhibit a fibrous-asbestiform crystal habit and may possess the same properties as carcinogenic fibrous erionite. Characterisation of the ferrierite in and around a mine location will be helpful in assessing the potential for toxic outcomes of exposure in the mine and any local population.The zeolite-rich tuff deposit of Lovelock, Nevada, USA is the largest occurrence of diagenetic ferrierite-Mg. A previous survey reported that ferrierite hosted in these rocks displays a fibrous morphology. However, these observations concerned a limited number of samples and until now there has been little evidence of widespread occurrence of fibrous ferrierite in the Lovelock deposit.The main goal of this study was to perform a mineralogical and morphometric characterisation of the tuff deposit at Lovelock and evaluate the distribution of fibrous ferrierite in the outcrop. For this purpose, a multi-analytical approach including powder X-ray diffraction, scanning and transmission microscopies, micro-Raman spectroscopy, thermal analyses, and surface-area determination was applied.The results prove fibrous ferrierite is widespread and intermixed with mordenite and orthoclase, although there are variations in the spatial distribution in the bedrock. The crystal habit of the ferrierite ranges from prismatic to asbestiform (elongated, thin and slightly flexible) and fibres are aggregated in bundles. According to the WHO counting criteria, most of the ferrierite fibres can be classified as breathable. While waiting for confirmatory in vitro and in vivo tests to assess the actual toxicity/pathogenicity potential of this mineral fibre, it is recommended to adopt a precautionary approach for mining operations in this area to reduce the risk of exposure.


2019 - Characterization and assessment of the potential toxicity/pathogenicity of fibrous glaucophane [Articolo su rivista]
Di Giuseppe, D.; Harper, M.; Bailey, M.; Erskine, B.; Della Ventura, G.; Ardit, M.; Pasquali, L.; Tomaino, G.; Ray, R.; Mason, H.; Dyar, M. D.; Hanuskova, M.; Giacobbe, C.; Zoboli, A.; Gualtieri, A.
abstract

In California, the metamorphic blueschist occurrences within the Franciscan Complex are commonly composed of glaucophane, which can be found with a fibrous habit. Fibrous glaucophane's potential toxicity/pathogenicity has never been determined and it has not been considered by the International Agency for Research on Cancer (IARC) as a potential carcinogen to date. Notwithstanding, outcrops hosting fibrous glaucophane are being excavated today in California for building/construction purposes (see for example the Calaveras Dam Replacement Project - CDRP). Dust generated by these excavation activities may expose workforces and the general population to this potential natural hazard. In this work, the potential toxicity/pathogenicity of fibrous glaucophane has been determined using the fibre potential toxicity index (FPTI). This model has been applied to a representative glaucophane-rich sample collected at San Anselmo, Marin County (CA, USA), characterized using a suite of experimental techniques to determine morphometric, crystal-chemical parameters, surface reactivity, biodurability and related parameters. With respect to the asbestos minerals, the FPTI of fibrous glaucophane is remarkably higher than that of chrysotile, and comparable to that of tremolite, thus supporting the application of the precautionary approach when excavating fibrous glaucophane-rich blueschist rocks. Because fibrous glaucophane can be considered a potential health hazard, just like amphibole asbestos, it should be taken into consideration in the standard procedures for the identification and assessment of minerals fibres in soil and air samples.


2019 - Depicting the crystal structure of fibrous ferrierite from British Columbia using a combined synchrotron techniques approach [Articolo su rivista]
C., Giacobbe; J., Wright; C., Dejoie; P., Tafforeau; C., Berruyer; R., Vigliaturo; R., Giere; Gualtieri, A.
abstract

The ferrierite crystal structure has often been subject to discussion because of the possible lowering of symmetry from the space group Immm. It mainly occurs in nature with a fibrous crystal habit, and because of the existence of line/planar defects in the framework, texture and preferred orientation effects it has been difficult to obtain an exact crystallographic model based only on the results from powder diffraction data. Therefore, nano-single-crystal diffraction and tomography data have been combined in order to improve the refinement with a meaningful model. High-quality single-crystal data, providing reliable structural information, and tomography images have been used as input for a Rietveld refinement which took into account a phenomenological description of stacking disorder and the analytical description of the preferred orientation, by means of spherical harmonics for strong texture effects. This is one of the first examples of application of synchrotron nano-diffraction for the structure solution of fibrous minerals of micrometre to nanometre size. The high quality of the crystals allowed collection of single-crystal X-ray diffraction data of up to 0.6 Å resolution, leading to an unambiguous solution and precise anisotropic refinement. Nano-single-crystal diffraction and phase contrast tomography data were collected at ID11 and the high-resolution powder diffraction patterns at ID22 of the European Synchrotron Radiation Facility. This detailed crystallographic characterization provides a basis for understanding the potential of ferrierite for toxicity and carcinogenicity.


2019 - Experimental quantification of the Fe-valence state at amosite-asbestos boundaries using acSTEM dual-electron energy-loss spectroscopy [Articolo su rivista]
Vigliaturo, R.; Pollastri, S.; Giere, R.; Gualtieri, A.; Drazic, G.
abstract

Determination of the oxidation state and coordination geometry of iron in Fe-bearing minerals expands our knowledge obtained by standard mineralogical characterization. It provides information that is crucial in assessing the potential of minerals to interact with their surrounding environment and to generate reactive oxygen species, which can disrupt the normal function of living organisms. Aberration-corrected scanning transmission electron microscopy dual-electron energy-loss spectroscopy (acSTEM Dual-EELS) has only rarely been applied in environmental and medical mineralogy, but it can yield data that are essential for the description of near-surface and surface mechanisms involved in many environmental and health-related processes. In this study, we have applied the energy loss near-edge structure (ELNES) and L2,3 white-line intensity-ratio methods using both the universal curve and progressively larger integrating windows to verify their effectiveness in satisfactorily describing the valence state of iron at amosite grain boundaries, and, at the same time, to estimate thickness in the same region of interest. The average valence state obtained from acSTEM Dual-EELS and from a simplified geometrical model were in good agreement, and within the range defined by the bulk and the measured surface-valence states. In the specific case presented here, the use of the universal curve was most suitable in defining the valence state of iron at amosite grain boundaries. The study of ELNES revealed an excellent correspondence with the valence state determined by the L2,3 white-line intensity-ratio method through the use of the universal curve, and it seems that the spectra carry some information regarding the coordination geometry of Fe. The combination of visual examination, reconstruction of the grain boundaries through a simple geometrical model, and Dual-EELS investigation is a powerful tool for characterizing the grain boundaries of hazardous minerals and foreseeing their potential activity in an organism, with the possibility to describe toxic mechanisms in a stepwise fashion.


2019 - Formation of tubular carbonate conduits at Athina mud volcano, eastern Mediterranean Sea [Articolo su rivista]
Tamborrinoa, L.; Himmlerb, T.; Elvert, M.; Conti, S.; Gualtieri, A.; Fontana, D.; Bohrmann, G.
abstract

Tubular carbonate conduits (TCC) represent the termination of fluid plumbing systems in environments of hydrocarbon seepage and play a relevant role in the discharge of methane from sub-seafloor sediments to the water column. However, the biogeochemical reactions and biological activities involved in their formation are not fully understood. To address this, TCC samples were collected with a remotely operated vehicle from the seabed on the SW flank of the Athina mud volcano in the eastern Mediterranean Sea. Petrographic, mineralogical, stable carbon and oxygen isotope and lipid biomarker analyses were performed to elucidate the formation processes of the tubular carbonates. Clotted and fibrous aragonite form the internal lining of the cavities, while the outer portion of the tubes is formed by micritic Mg-calcite cementing hemipelagic sediment. 13C-depleted Mg-calcite and aragonite (as low as −14.4‰ V-PDB) and lipid biomarkers (archaeol, −89.8‰ V-PDB) indicate that carbonate precipitation was influenced by sulfate-dependent anaerobic oxidation of methane (AOM). AOM locally enhances aragonite precipitation, thereby facilitating early lithification of the conduits within the mud volcano sediments. The size and morphology of the TCC comparable with the buried portion of tubeworm colonies found in the proximity of the sampling site. However, our results suggest that TCC likely formed by the action of burrowing organism rather than being mineralizations of the tubeworm colonies. This study provides new insights into the interpretation and understanding of TCC, highlighting the role of macrofaunal activity in the formation of migration pathways for hydrocarbon-rich fluids on the flank of a mud volcano


2019 - Iron from a geochemical viewpoint. Understanding toxicity/pathogenicity mechanisms in iron-bearing minerals with a special attention to mineral fibers [Articolo su rivista]
Gualtieri, Alessandro F.; Andreozzi, Giovanni B.; Tomatis, Maura; Turci, Francesco
abstract

Iron and its role as soul of life on Earth is addressed in this review as iron is one of the most abundant elements of our universe, forms the core of our planet and that of telluric (i.e., Earth-like) planets, is a major element of the Earth's crust and is hosted in an endless number of mineral phases, both crystalline and amorphous. To study iron at an atomic level inside the bulk of mineral phases or at its surface, where it is more reactive, both spectroscopy and diffraction experimental methods can be used, taking advantage of nearly the whole spectrum of electromagnetic waves. These methods can be successfully combined to microscopy to simultaneously provide chemical (e.g. iron mapping) and morphological information on mineral particles, and shed light on the interaction of mineral surfaces with organic matter. This review describes the crystal chemistry of iron-bearing minerals of importance for the environment and human health, with special attention to iron in toxic minerals, and the experimental methods used for their study. Special attention is devoted to the Fenton-like chain reaction involving Fe 2+ in the formation of highly reactive hydroxyl radicals. The final part of this review deals with release and adsorption of iron in biological fluids, coordinative and oxidative state of iron and in vitro reactivity. To disclose the very mechanisms of carcinogenesis induced by iron-bearing toxic mineral particles, crystal chemistry and surface chemistry are fundamental for a multidisciplinary approach which should involve geo-bio-scientists, toxicologists and medical doctors.


2019 - Mineral fibres and asbestos bodies in human lung tissue: A case study [Articolo su rivista]
Di Giuseppe, D.; Zoboli, A.; Vigliaturo, R.; Giere, R.; Bonasoni, M. P.; Sala, O.; Gualtieri, A.
abstract

One of the open questions regarding the asbestos problem is the fate of the mineral fibres in the body once inhaled and deposited in the deep respiratory system. In this context, the present paper reports the results of an electron microscopy study of both mineral fibres and asbestos bodies found in the lung tissue of a patient who died of malignant mesothelioma due to past occupational exposure. In concert with previous in vivo animal studies, our data provide evidence that amphibole asbestos fibres are durable in the lungs, whereas chrysotile fibres are transformed into a silica-rich product, which can be easily cleared. Amphibole fibres recovered from samples of tissue of the deceased display a high degree of crystallinity but also show a very thin amorphous layer on their surface; 31% of the fibres are coated with asbestos bodies consisting of a mixture of ferroproteins (mainly ferritin). Here, we propose an improved model for the coating process. Formation of a coating on the fibres is a defence mechanism against fibres that are longer than 10 µm and thinner than 0.5 µm, which macrophages cannot engulf. The mature asbestos bodies show signs of degradation, and the iron stored in ferritin may be released and potentially increase oxidative stress in the lung tissue.


2019 - Quantitative phase analysis using the Rietveld method: Towards a procedure for checking the reliability and quality of the results [Articolo su rivista]
Gualtieri, A.; Gatta, G. D.; Arletti, R.; Artioli, G.; Ballirano, P.; Cruciani, G.; Guagliardi, A.; Malferrari, D.; Masciocchi, N.; Scardi, P.
abstract

The quantitative phase analysis using the Rietveld method is one of the most used analytical protocols for the characterization of several types of natural and synthetic materials, and it can be performed both on fully crystalline multiphase systems and on materials containing even an amorphous fraction. Therefore, there are several applications of this method (e.g., to natural raw materials, traditional ceramics, bricks, glass-ceramics, cementitious binders, etc.). More recently, the application of the Rietveld method has disseminated also in the chemical, pharmaceutical, and other high added-value industrial areas, where it is exploited in the operational planning, formulation analysis, and in patent protection. Nowadays, in consequence of this diffusion, several academic and private laboratories provide phase quantitative analysis using the Rietveld method as customers service, but an accreditation procedure is still pending and lacks a protocol for checking the authenticity and quality of the analytical reports. In this letter, we focus on the principal elements that an analytical report of quantitative phase analysis, based on the Rietveld method, should contain, as well as some best-practice guidelines for sample preparation and data collection procedure.


2019 - Structure Model and Toxicity of the Product of Biodissolution of Chrysotile Asbestos in the Lungs [Articolo su rivista]
Gualtieri, A. F.; Lusvardi, G.; Pedone, A.; Di Giuseppe, D.; Zoboli, A.; Mucci, A.; Zambon, A.; Filaferro, M.; Vitale, G.; Benassi, M.; Avallone, R.; Pasquali, L.; Lassinantti Gualtieri, M.
abstract

Asbestos is a commercial term indicating six natural silicates with asbestiform crystal habit. Of these, five are double-chain silicates (amphibole) and one is a layer silicate (serpentine asbestos or chrysotile). Although all species are classified as human carcinogens, their degree of toxicity is still a matter of debate. Amphibole asbestos species are biopersistent in the human lungs and exert their chronic toxic action for decades, whereas chrysotile is not biopersistent and transforms into an amorphous silica structure prone to chemical/physical clearance when exposed to the acidic environment created by the alveolar macrophages. There is evidence in the literature of the toxicity of chrysotile, but its limited biopersistence is thought to explain the difference in toxicity with respect to amphibole asbestos. To date, no comprehensive model describing the toxic action of chrysotile in the lungs is available, as the structure and toxic action of the product formed by the biodissolution of chrysotile are unknown. This work is aimed at fulfilling this gap and explaining the toxic action in terms of structural, chemical, and physical properties. We show that chrysotile's fibrous structure induces cellular damage, mainly through physical interactions. Based on our previous work and novel findings, we propose the following toxicity model: inhaled chrysotile fibers exert their toxicity in the alveolar space by physical and biochemical action. The fibers are soon leached by the intracellular acid environment into a product with residual toxicity, and the dissolution process liberates toxic metals in the intracellular and extracellular environment.


2018 - Assessment of the potential hazard represented by natural raw materials containing mineral fibres—The case of the feldspar from Orani, Sardinia (Italy) [Articolo su rivista]
Gualtieri, Alessandro F.; Gandolfi, Nicola Bursi; Pollastri, Simone; Rinaldi, Roberta; Sala, Orietta; Martinelli, Giovanni; Bacci, Tiziana; Paoli, Federica; Viani, Alberto; Vigliaturo, Ruggero
abstract

This work describes the nature of the potentially hazardous fibrous amphibole found in the Orani's feldspar mine (Sardinia, Italy). To identify its nature, a protocol of analysis including morphometric, chemical and crystallographic characterizations was applied. Thanks to this approach, it was possible to classify the observed fibres as tremolite after comparing chemical data, SEM/TEM observations, FTIR/ Raman spectra and X-ray diffraction data with those reported for a standard sample. The unit cell parameters of the investigated tremolite phase are a = 9.82(1) Å, b = 18.08(3) Å, c = 5.27(1) Å, and the angle β corresponds to 104.4(1)°. The mean concentration of asbestos tremolite in the Orani's feldspar is 0.28 wt%. Most of the fibres (0.26 wt%) are respirable ‘regulated’ fibres, representing a potential hazard. Because the total amount of tremolite in the sample is 0.6 wt%, a large fraction of it has a crystal habit other than fibrous-asbestiform or acicular. The obtained results allowed us to suggest possible solutions for a safe exploitation and mineral processing of the Orani's mine. The procedure proposed herein may be a general tool suitable to identify the mineralogical nature of fibrous minerals in raw materials and assess if they may represent a potential health/environmental hazard.


2018 - Effect of grinding on chrysotile, amosite and crocidolite and implications for thermal treatment [Articolo su rivista]
Bloise, Andrea; Catalano, Manuela; Gualtieri, Alessandro Francesco
abstract

Nowadays, due to the adverse health effects associated with exposure to asbestos, its inertization is one of the most important issues of waste risk management. Based on the research line of mechano-chemical and thermal treatment of asbestos containing materials, the aim of this study was to examine the effects of dry grinding on the structure, temperature stability and fibre size of chrysotile from Balangero (Italy), as well as standard UICC (Union for International Cancer Control) amosite and standard UICC (Union for International Cancer Control) crocidolite. Dry grinding was accomplished in an eccentric vibration mill by varying the grinding time (30 s, 5 and 10 min). Results show a decrease in crystallinity, the formation of lattice defects and size reduction with progressive formation of agglomerates in the samples after the mechanical treatment. Transmission electron microscopy (TEM) results show that the final product obtained after 10 min of grinding is composed of non-crystalline particles and a minor residue of crystalline fibres that are not regulated because they do not meet the size criteria for a regulated fibre. Grinding results in a decrease of temperature and enthalpy of dehydroxylation (∆Hdehy) of chrysotile, amosite and crocidolite. This permits us to completely destroy these fibres in thermal inertization processes using a lower net thermal energy than that used for the raw samples.


2018 - In vitro acellular dissolution of mineral fibres: A comparative study [Articolo su rivista]
Gualtieri, Alessandro F.; Pollastri, Simone; Bursi Gandolfi, Nicola; Gualtieri, Magdalena Lassinantti
abstract

The study of the mechanisms by which mineral fibres promote adverse effects in both animals and humans is a hot topic of multidisciplinary research with many aspects that still need to be elucidated. Besides length and diameter, a key parameter that determines the toxicity/pathogenicity of a fibre is biopersistence, one component of which is biodurability. In this paper, biodurability of mineral fibres of social and economic importance (chrysotile, amphibole asbestos and fibrous erionite) has been determined for the first time in a systematic comparative way from in vitro acellular dissolution experiments. Dissolution was possible using the Gamble solution as simulated lung fluid (pH = 4 and at body temperature) so to reproduce the macrophage phagolysosome environment. The investigated mineral fibres display very different dissolution rates. For a 0.25 μm thick fibre, the calculated dissolution time of chrysotile is in the range 94-177 days, very short if compared to that of amphibole fibres (49-245 years), and fibrous erionite (181 years). Diffraction and SEM data on the dissolution products evidence that chrysotile rapidly undergoes amorphization with the formation of a nanophasic silica-rich fibrous metastable pseudomorph as first dissolution step whereas amphibole asbestos and fibrous erionite show minor signs of dissolution even after 9-12 months.


2018 - Infra red spectroscopy of the regulated asbestos amphiboles [Articolo su rivista]
Della Ventura, Giancarlo; Vigliaturo, Ruggero; Gieré, Reto; Pollastri, Simone; Gualtieri, Alessandro F.; Iezzi, Gianluca
abstract

Vibrational spectroscopies (Fourier Transform Infra Red, FTIR, and Raman) are exceptionally valuable tools for the identification and crystal–chemical study of fibrous minerals, and asbestos amphiboles in particular. Raman spectroscopy has been widely applied in toxicological studies and thus a large corpus of reference data on regulated species is found in the literature. However, FTIR spectroscopy has been mostly used in crystal–chemical studies and very few data are found on asbestos amphiboles. This paper is intended to fill this gap. We report new FTIR data collected on a suite of well-characterized samples of the five regulated amphibole species: anthophyllite, amosite, and crocidolite, provided by the Union for International Cancer Control (UICC) Organization, and tremolite and actinolite, from two well-known occurrences. The data from these reference samples have been augmented by results from additional specimens to clarify some aspects of their spectroscopic features. We show that the FTIR spectra in both the OH-stretching region and in the lattice modes region can be effective for rapid identification of the asbestos type.


2018 - Is fibrous ferrierite a potential health hazard? Characterization and comparison with fibrous erionite [Articolo su rivista]
Gualtieri, Alessandro F.; Gandolfi, Nicola Bursi; Passaglia, Elio; Pollastri, Simone; Mattioli, Michele; Giordani, Matteo; Ottaviani, Maria Francesca; Cangiotti, Michela; Bloise, Andrea; Barca, Donatella; Vigliaturo, Ruggero; Viani, Alberto; Pasquali, Luca; Gualtieri, Magdalena Lassinantti
abstract

Fibrous erionite is classified by the International Agency for Research on Cancer (IARC) as carcinogenic substance to humans (Group 1). In the areas where it is present in the bedrock, it may cause environmental exposure, and both professional and environmental exposures are possible when the bedrock is used for industrial applications (e.g., building materials). For health and environment protection, prevention is a priority action. In this framework, the recent guidelines of the Consensus Report of the Weinman International Conference on Mesothelioma suggest identifying locations where potentially hazardous mineral fibers (like erionite) are found in the environment, to prevent environmental exposure. The present study will show that one such potentially hazardous mineral fiber might be fibrous ferrierite. Here, the mineralogy, chemical-physical properties, and surface activity of a hydrothermal fibrous ferrierite from Monte Lake British Columbia (Canada) and a diagenetic fibrous ferrierite from Lovelock, Nevada (U.S.A.), were investigated using a combination of "state of the art" experimental methods including optical microscopy, electron microscopy and microprobe analysis, laser ablation-inductively coupled plasma-mass spectrometry (for the trace elements), vibrational spectroscopy, electron paramagnetic resonance, and synchrotron powder diffraction. The chemical-physical properties of these fibrous ferrierites (morphometric parameters, specific surface area, chemical composition with special attention to metals, mainly iron) that prompted adverse effects in vivo were compared to those of the positive carcinogenic standard fibrous erionite-Na from Jersey, Nevada (U.S.A.). The results of our study have demonstrated that, although there are differences in the crystal chemistry and genetic environment, ferrierite samples exhibit outstanding similarities with fibrous erionite samples: both fibrous erionite and fibrous ferrierite may occur in large amounts as microcrystalline fibrous-asbestiform phases in diagenetic rocks with fibers of breathable sizes. For both zeolites, iron is not structural but is associated with impurities lying at the surface of the fibers. Moreover, data useful to understand the surface activity of these fibrous ferrierites were collected. As far as hydrothermal sample is concerned, the EPR data indicate the presence of hydrophilic (SiO-, AlO-, SiOH) and hydrophobic (Si-O-Si) interacting surface groups able to bind the charged CAT1 probes at close sites and attract the probes in the water pools formed into the fiber aggregates. A high percentage of CAT1 probes weakly interacting with the surface due to competition with metal ions were observed for surface of the diagenetic sample. CAT8 probes were less adsorbed by its surface if compared to the diagenetic sample but the more charged surface provided a stronger binding strength for the diagenetic sample compared to the hydrothermal one. In summary, the results of this study indicate that fibrous ferrierite may represent a potential health hazard and, applying the precautionary principle, it should undergo a procedure of toxicity testing.


2018 - Structural characterization and functional correlation of Fe3O4 nanocrystals obtained using 2-ethyl-1,3-hexanediol as innovative reactive solvent in non-hydrolytic sol-gel synthesis [Articolo su rivista]
Sciancalepore, C.; Gualtieri, A. F.; Scardi, P.; VIVAS DE GONZALEZ, FLOR ALBA; Allia, P.; Tiberto, P.; Barrera, Giulia; Messori, M.; Bondoli, F.
abstract

An original non-hydrolytic sol-gel approach, using 2-ethyl-1,3-hexanediol as reactive solvent, was proposed to synthetize nanostructured magnetite. Iron-oxide nanoparticles were prepared and studied as a function of the precursor-to-solvent ratio. The crystallization degree of nanoparticles was followed by the combined Rietveld and Reference Intensity Ratio method. This procedure has allowed the determination of both amorphous and crystalline content of nanomagnetite, using hematite as suitable internal standard. The results of Rietveld method show that the crystalline content decreases as the precursor-to-solvent is increased, ranging from 67 to 60 wt%. Information on the crystallite size-strain distribution and microstructural evolution of nanocrystals was supplied by line profile analysis of the powder diffraction patterns, employing the Whole Powder Pattern Modeling analysis: the obtained log-normal distribution curves become increasingly narrow and symmetrical, while nanoparticle microstrain increases as the precursor concentration is increased. The dimensional analysis of the Transmission Electron Microscopy images has allowed to obtain the nanoparticle grain-size distribution. Nanoparticle dimensions decreases from 15 to 9 nm increasing the precursor concentration. The comparison between the results of X-ray diffraction and microscopic characterization techniques highlighted the effect of several factors, such as size, shape and microstructure of magnetite nanoparticles, on their functional magnetic response. Magnetic characterizations show that magnetite nanoparticles are not in the superparamagnetic phase even at room temperature, independent of the precursor concentration. On the other hand, the room-temperature saturation magnetization, ranging from 73 to 60 emu/g, is a function of the nanoparticle average size, decreasing as the precursor concentration increases.


2018 - Synchrotron Nano-Diffraction Study of Thermally Treated Asbestos Tremolite from Val d’Ala, Turin (Italy) [Articolo su rivista]
Giacobbe, Carlotta; Wright, Jonathan P.; Di Giuseppe, Dario; Zoboli, Alessandro; Zapparoli, Mauro; Gualtieri, Alessandro F.
abstract

Nowadays, due to the adverse health effects associated with exposure to asbestos, its removal and thermal inertization has become one of the most promising ways for reducing waste risk management. Despite all the advances in structure analysis of fibers and characterization, some problems still remain that are very hard to solve. One challenge is the structure analysis of natural micro-and nano-crystalline samples, which do not form crystals large enough for single-crystal X-ray diffraction (SC-XRD), and their analysis is often hampered by reflection overlap and the coexistence of multiple fibres linked together. In this paper, we have used nano-focused synchrotron X-rays to refine the crystal structure of a micrometric tremolite fibres from Val d’Ala, Turin (Italy) after various heat treatment. The structure of the original fibre and after heating to 800◦C show minor differences, while the fibre that was heated at 1000◦C is recrystallized into pyroxene phases and cristobalite.


2018 - The effect of grinding on tremolite asbestos and anthophyllite asbestos [Articolo su rivista]
Bloise, Andrea; Kusiorowski, Robert; Gualtieri, Alessandro F.
abstract

The six commercial asbestos minerals (chrysotile, fibrous actinolite, crocidolite, amosite, fibrous tremolite, and fibrous anthophyllite) are classified by the IARC as carcinogenic to humans. There are currently several lines of research dealing with the inertisation of asbestos minerals among which the dry grinding process has received considerable interest. The effects of dry grinding on tremolite asbestos and anthophyllite asbestos in eccentric vibration mills have not yet been investigated. Along the research line of the mechanical treatment of asbestos, the aim of this study was to evaluate the effects of dry grinding in eccentric vibration mills on the structure, temperature stability, and fibre dimensions of tremolite asbestos from Val d’Ala, (Italy) and UICC standard anthophyllite asbestos from Paakkila mine (Finland) by varying the grinding time (30 s, 5 min, and 10 min). After grinding for 30 s to 10 min, tremolite asbestos and anthophyllite asbestos showed a decrease in dehydroxylation and breakdown temperatures due to the increase in lattice strain and the decrease in crystallinity. Moreover, after grinding up to 10 min, tremolite and anthophyllite fibres were all below the limits defining a countable fibre according to WHO.


2018 - Towards a quantitative model to predict the toxicity/pathogenicity potential of mineral fibers [Articolo su rivista]
Gualtieri, Alessandro F.
abstract

Some mineral fibers represent a health hazard because they are classified as cancer-causing chemical/physical toxicants upon (chronic) dust inhalation. Although in the last decades they have been the subject of intensive multidisciplinary investigations, the mechanisms by which mineral fibers induce toxic and pathogenic adverse effects on human health and environment are not yet fully understood. The major intricacy of the biological approach that prevents the design of a conclusive shared model of behavior of mineral fibers in a biological system stems from their very nature with intrinsic variability in chemical, molecular, structural and morphometric parameters, biodurability and surface reactivity. This paper presents the first attempt to devise a quantitative predictive model of toxicity/pathogenicity of minerals fibers based on their physical/chemical and morphological parameters. Although the author is aware that all parameters should be measured in comparable in vivo systems that accurately simulate the lung and or pleural environment, this preliminary model was conceived to deliver a fiber potential toxicity/pathogenicity index (FPTI) to be integrated with the biological approach so to create a quantitative predictive model of behavior of mineral fibers in a biological system. The FPTI model is thought to be a predictive tool aimed at ranking the toxicity and pathogenicity potential of fibers like asbestos or unregulated/unclassified mineral fibers. It may eventually be applied to other materials like man-made synthetic fibers and elongated mineral particles (EMP). Work is in progress to revise and validate the model in joint collaboration with international competent organizations, and to deliver a FPTI model-based user-friendly code.


2017 - Crop evapotranspiration assessment under climate change in the Pannonian basin during 1991–2050 [Articolo su rivista]
Nistor, M. M.; Cheval, S.; Gualtieri, A. F.; Dumitrescu, A.; Boţan, V. E.; Berni, A.; Hognogi, G.; Irimuş, I. A.; Porumb-Ghiurco, C. G.
abstract

The impact of climate on crop evapotranspiration (ETc) was assessed in the Pannonian basin for the present (1991–2020) and future (2021–2050). Annual temperature, annual precipitation and monthly potential evapotranspiration are the main climate data used in the present study. The European land cover database was used for the spatial recognition of terrain vegetation of the countries which are found in the Pannonian basin. A difference of maximum annual temperature from 19.9 to 20.8∘C was observed in the investigated area between 1991–2020 and 2021–2050. Precipitation rates decrease from west (1800 mm) to east (below 400 mm), and the potential evapotranspiration varies from 500 to 800 mm. Four stages of crop growth were identied and for each stage the crop co-efcients were assessed. For present projections of climate data, the annual c rop evapotranspiration variability is from 105 to 1087 mm and records the highest values in mid-season stage, ove r 630 mm. Future projections indicate that in the central and southern part of the Pannonian basin the annual crop evapotranspiration will increase. For both present and future projections, the lowest crop evapotranspiration was found in the cold season, because of lack of heat and lower values of the crop co-efficient.


2017 - Crystal structure of mineral fibres [Capitolo/Saggio]
Ballirano, P.; Bloise, A.; Gualtieri, A. F.; Lezzerini, M.; Pacella, A.; Perchiazzi, N.; Dogan, M.; Dogan, A. U.
abstract

This chapter deals with the crystal structure of regulated and unregulated mineral fibres. The aim is to provide readers, both specialists and researchers broadly interested in environmental problems, with up-to-date information on a topic that is expanding daily. The chapter describes specifically the structure of the fibrous modification whenever available and outlines possible differences from the corresponding prismatic variety. Details of the experimental techniques used for structure determination/refinement are reported also, if appropriate, to outline the experimental difficulties faced due to the small dimensions, sensitivity and chemical complexity of mineral fibres.


2017 - Introduction [Mineral fibres] [Capitolo/Saggio]
Gualtieri, Alessandro F.
abstract

This introductory chapter presents the state of the art in the multidisciplinary research field of asbestos and mineral fibres in general. The book describes the world of mineral fibres with its huge complexity and poorly understood, detrimental bio-chemical interaction with the human body. The approach of the chemist/mineralogist/ crystallographer adopts the perspective of the fibre itself (the invader of the body) whereas the approach of the bio-chemist/toxicologist/physician adopts the perspective of the organism (the invaded) interacting with the fibre. Both perspectives must be considered in synergy in an attempt to outline a conclusive model explaining the toxicity of mineral fibres, and provide a robust scientific basis that can be used by political and social partners to resolve finally the global issue of asbestos.


2017 - Investigation of the Setting Reaction in Magnesium Phosphate Ceramics with Quasielastic Neutron Scattering. [Articolo su rivista]
Viani, A.; Zbiri, M.; Bordallo, H. N.; Gualtieri, A. F.; Mácová, P.
abstract

Magnesium phosphate ceramics are a class of acid-base cements for bioengineering and civil engineering applications. We report on quasielastic neutron scattering results focusing on the evolution of the state of water in the system during the setting reaction, to shed light on the reaction mechanisms and the nature of the products. In the first few minutes, a consistent fraction of water molecules appears as immobile, and after a transient time, they start to be progressively bound into a reaction product. The kinetics of this last process has been described with an equation combining an Avrami model and a first-order reaction model with apparent activation energies of 18 and 6 kJ/mol, respectively. The results indicate that during the reaction the water molecules experience confinement effects inside a restricted space. The size of the confining volume decreases as the reaction progresses. It is proposed that an amorphous precursor with high surface area, bonding a relevant fraction of water, but also hosting mobile water, forms first. After an induction period, this phase undergoes further transformation into a product, still amorphous, considered as a further precursor of the final crystalline phase. With the reaction being kinetically driven, nonclassical mechanisms of nucleation and growth may lead to the formation of prenucleation clusters developing the first intermediate compound by coalescence. The mutating pH conditions trigger the transformation of the precursors, which likely contain structural motifs of the crystalline phase, similar to those observed in Ca and Zn, phosphate hydrate systems.


2017 - New insights into the toxicity of mineral fibres: A combined in situ synchrotron μ-XRD and HR-TEM study of chrysotile, crocidolite, and erionite fibres found in the tissues of Sprague-Dawley rats [Articolo su rivista]
Gualtieri, Alessandro F.; Bursi Gandolfi, Nicola; Pollastri, Simone; Burghammer, Manfred; Tibaldi, Eva; Belpoggi, Fiorella; Pollok, Kilian; Langenhorst, Falko; Vigliaturo, Ruggero; Gorandražić,
abstract

Along the line of the recent research topic aimed at understanding the in vivo activity of mineral fibres and their mechanisms of toxicity, this work describes the morpho-chemical characteristics of the mineral fibres found in the tissues of Sprague-Dawley rats subjected to intraperitoneal/intrapleural injection of UICC chrysotile, UICC crocidolite and erionite-Na from Nevada (USA). The fibres are studied with in situ synchrotron powder diffraction and high resolution transmission electron microscopy to improve our understanding of the mechanisms of toxicity of these mineral fibres. In contact with the tissues of the rats, chrysotile fibres are prone to dissolve, with leaching of Mg and production of a silica rich relict. On the other hand, crocidolite and erionite-Na fibres are stable even for very long contact times within the tissues of the rats, showing just a thin dissolution amorphous halo. These findings support the model of a lower biopersistence of chrysotile with respect to crocidolite and erionite-Na but the formation of a silica-rich fibrous residue after the pseudo-amorphization of chrysotile may justify a higher cytotoxic potential and intense inflammatory activity of chrysotile in the short term in contact with the lung tissues.


2017 - Preface [Relazione in Atti di Convegno]
Gualtieri, A. F.
abstract


2017 - Production of nanoparticles during experimental deformation of smectite and implications for seismic slip [Articolo su rivista]
Aretusini, S.; Mittempergher, S.; Plümper, O.; Spagnuolo, E.; Gualtieri, A. F.; Di Toro, G.
abstract

Nanoparticles and amorphous materials are common constituents of the shallow sections of active faults. Understanding the conditions at which nanoparticles are produced and their effects on friction can further improve our understanding of fault mechanics and earthquake energy budgets. Here we present the results of 59 rotary shear experiments conducted at room humidity conditions on gouge consisting of mixtures of smectite (Ca-montmorillonite) and quartz. Experiments with 60, 50, 25, 0 wt.% Ca-montmorillonite, were performed to investigate the influence of variable clay content on nanoparticle production and their influence on frictional processes. All experiments were performed at a normal stress of 5 MPa, slip rate of , and at a displacement of 3 m. To monitor the development of fabric and the mineralogical changes during the experiments, we investigated the deformed gouges using scanning and transmission electron microscopy combined with X-ray powder diffraction quantitative phase analysis. This integrated analytical approach reveals that, at all slip rates and compositions, the nanoparticles (grain size of 10–50 nm) are partly amorphous and result from cataclasis, wear and mechanical solid-state amorphization of smectite. The maximum production of amorphous nanoparticle occurs in the intermediate slip rate range (), at the highest frictional work, and is associated to diffuse deformation and slip strengthening behavior. Instead, the lowest production of amorphous nanoparticles occurs at co-seismic slip rates (), at the highest frictional power and is associated with strain and heat localization and slip weakening behavior. Our findings suggest that, independently of the amount of smectite nanoparticles, they produce fault weakening only when typical co-seismic slip rates (>0.1 ms−1) are achieved. This implies that estimates of the fracture surface energy dissipated during earthquakes in natural faults might be extremely difficult to constrain.


2017 - Sharing different perspectives to understand asbestos-induced carcinogenesis: A comment to Jiang et al. (2016) [Articolo su rivista]
Gualtieri, A. F.
abstract

This letter reports some constructive observations on the recent findings by Jiang et al. Cancer Sci (2016) that have inspired a more general comment on how the research on asbestos should take advantage of the different existing multidisciplinary perspectives so to flow into a final comprehensive model of asbestos-induced carcinogenesis.


2017 - The crystal structure of mineral fibres. 2. Amosite and fibrous anthophyllite [Articolo su rivista]
Pollastri, Simone; Perchiazzi, Natale; Gigli, Lara; Ferretti, Paolo; Cavallo, Alessandro; Bursi Gandolfi, Nicola; Pollok, Kilian; Gualtieri, Alessandro F.
abstract

This study reports for the frst time crystal-structure data for amosite and fibrous anthophyllite. The chemical composition of the two fibre species was determined from EMPA. Crystal structures were refned using powder-diffraction data, using both laboratory sources and synchrotron radiation. Results were compared with the available literature data for the non-fibrous varieties grunerite and anthophyllite, respectively. The calculated site-occupancies for all samples are in agreement with the chemical compositions calculated from EMPA. The existing structure models of grunerite and orthorhombic anthophyllite also applies to the corresponding fibrous varieties amosite and fibrous anthophyllite, respectively. In amosite, both Fe 2+ and Fe 3+ atoms are found at the sites M(1), M(2) and M(3) and Fe 2+ ions is the only atomic species found at site M(4). Mg is disordered over the C sites with a preference for site M(2). Minor Ca and Na have been assigned to the A site. In fibrous anthophyllite, Mg is the only atomic species found at the M1, M2 and M3 sites. Fe 2+ , Mg (and minor Mn) have been assigned to the M4 site, whereas minor Ca has been assigned to the A site. In both structures, the environment at the M(4) site in amosite and M4 site in fibrous anthophyllite is highly distorted. This work can be considered a basis for studies aimed at understanding the potential toxicity/pathogenicity of these mineral fibres.


2017 - The crystal structure of mineral fibres. 3. Actinolite asbestos [Articolo su rivista]
Pollastri, Simone; Gigli, Lara; Ferretti, Paolo; Andreozzi, Giovanni B.; Bursi Gandolfi, Nicola; Pollok, Kilian; Gualtieri, Alessandro F.
abstract

The present work reports chemical and structural data of actinolite asbestos from Aurina Valley, Bolzano (Italy). The chemical composition was determined using EMPA and TG analysis, and the Fe3+/Fetot ratio was accurately evaluated with independent 57Fe Mössbauer spectroscopy. Morphology and crystallinity were also investigated through SEM and TEM investigations. Crystal structure was refined using high-resolution synchrotron XRPD data. The iron content of Aurina Valley sample is lower compared to two representative asbestiform actinolite samples (with structure refinement) taken from the literature (FeOtot 7.77 wt% against 12÷13 wt%, respectively), accounting for the reduced cell volume here measured (910.29 ų against 912÷918 ų, respectively). Refined site scattering values of Aurina Valley sample are in agreement with those calculated from chemical compositions, and the optimized structural formula is: K0.02Na0.05(Na0.08Ca1.92)Ʃ=2.00(Mg3.80Fe2+0.79Fe3+0.11Al0.20Mn0.05Ni0.02Cr0.01)Ʃ=4.98(Si7.67Al0.25)Ʃ=7.92O21.69(OH)2.31. The C sites M(1), M(2) and M(3) are occupied by Mg and Fe in a proportion of ~4:1, whereas the M(4) site contains mainly Ca and a very small amount of Na. Iron exclusively occupies the octahedral C sites, with Fe 2+ ions occurring at the M(1,2,3) sites and the small amount of Fe 3+ (13% of Fe tot) ordered at the M(2) site. The refined crystal structure and cation distribution are fully consistent with results previously obtained on asbestiform and non-asbestiform samples belonging to the tremolite-actinolite-ferro– actinolite substitutional series.


2017 - Thermal behaviour of mineral fibres [Capitolo/Saggio]
Bloise, A.; Kusiorowski, R.; Lassinantti Gualtieri, M.; Gualtieri, A. F.
abstract

This chapter deals with the synthesis and thermal stability ofmineral fibres. The different structural assemblages within mineral fibres and their resistance to high temperature changes fromspecies to species. In general, the formation of such minerals takes place in hydrothermal environments. The thermal decomposition process consists of three main stages: the loss of water adsorbed on the surface of the fibre and the zeolitic water below 200250ºC; the removal of the structure water (the hydroxyl groups) in the range 5001100ºC and recrystallization into new stable crystalline phases. The thermal stability of chrysotile, amphiboles fibres and erionite will be described in detail and will be followed by specific sections describing how the concept of thermal decomposition is used for the remediation of wastes containing asbestos to produce secondary raw materials to be recycled in various industrial application.


2017 - Towards a general model for predicting the toxicity and pathogenicity of mineral fibres [Capitolo/Saggio]
Gualtieri, A. F.; Mossman, B. T.; Roggli, V. L.
abstract

This chapter provides a comprehensive description of the physical, chemical, biological and mineralogical parameters that play a role in determining the toxicity and pathogenicity of mineral fibres. The first steps towards a general toxicity/pathogenicity model of mineral fibres are described here. Eventually the model can be generalized and may be applied to biodurable man-made mineral fibres and other natural and synthetic fibres in addition to silicates. Because of the complexity of the topic, a truly multidisciplinary approach is essential. A concept that will be stressed in the final notes of the chapter is that a full understanding of the toxicity/pathogenicity of mineral fibres aimed at finding effective solutions for the prevention and treatment of asbestos-related diseases can only be the outcome if an holistic approach is applied which takes advantage of synergistic research activity and communication between biochemists, mineralogists/crystallographers, pathologists, physicians, physicists and toxicologists, all sharing their distinct but interrelated perspectives. This is a great challenge for all such scientific individuals to work together to resolve and develop predictivemodels that incorporate their research findings and conclusions.


2016 - Assessment of asbestos body formation by high resolution FEG-SEM after exposure of Sprague-Dawley rats to chrysotile, crocidolite, or erionite [Articolo su rivista]
Bursi gandolfi, N.; Gualtieri, A. F.; Pollastri, S.; Tibaldi, E.; Belpoggi, F.
abstract

This work presents a comparative FEG-SEM study of the morphological and chemical characteristics of both asbestos bodies and fibres found in the tissues of Sprague-Dawley rats subjected to intraperitoneal or intrapleural injection of UICC chrysotile, UICC crocidolite and erionite from Jersey, Nevada (USA), with monitoring up to 3 years after exposure.Due to unequal dosing based on number of fibres per mass for chrysotile with respect to crocidolite and erionite, excessive fibre burden and fibre aggregation during injection that especially for chrysotile would likely not represent what humans would be exposed to, caution must be taken in extrapolating our results based on instillation in experimental animals to human inhalation. Notwithstanding, the results of this study may help to better understand the mechanism of formation of asbestos bodies.For chrysotile and crocidolite, asbestos bodies are systematically formed on long asbestos fibres. The number of coated fibres is only 3.3% in chrysotile inoculated tissues. In UICC crocidolite, Mg, Si, and Fe are associated with the fibres whereas Fe, P and Ca are associated with the coating. Even for crocidolite, most of the observed fibres are uncoated as coated fibres are about 5.7%. Asbestos bodies do not form on erionite fibres. The crystal habit, crystallinity and chemistry of all fibre species do not change with contact time, with the exception of chrysotile which shows signs of leaching of Mg.A model for the formation of asbestos bodies from mineral fibres is postulated. Because the three fibre species show limited signs of dissolution in the tissue, they cannot act as source of elements (primarily Fe, P and Ca) promoting nucleation and growth of asbestos bo dies. Hence, the limited number of coated fibres should be due to the lack of nutrients or organic nature.


2016 - Climate change effects on crop evapotranspiration in the Carpathian Region from 1961 to 2010 [Articolo su rivista]
Nistor, ; M., -M.; Gualtieri, A. F.; Cheval, S.; Dezsi, Ş.; Boţan, V. E.
abstract

In this study, the annual and seasonal crop evapotranspiration at the spatial level of the Carpathian Region were evaluated over 1961–2010. The temperature, precipitation and actual evapotranspiration grid monthly climate data and land cover were analysed and processed on a seasonal basis to compute the annual crop evapotranspiration. The land cover evapotranspiration rate was assigned through evapotranspiration coefficients from the literature. Geographical Information System (GIS) techniques, such as conversions from vector to raster data and the ‘Raster Calculator’ function, were used to assess the spatial distribution of the crop evapotranspiration at a regional scale. In particular, two datasets from different periods (1961–1990 and 1990–2010) were used to compute the seasonal and annual crop evapotranspiration for the Carpathian region. The results of climate parameters indicate a rise in temperature and crop evapotranspiration values between the first and the second period. In addition, significant spatial changes were observed with a shift of maximum values from south to north.


2016 - Consensus Report of the 2015 Weinman International Conference on Mesothelioma [Articolo su rivista]
Carbone, Michele; Kanodia, Shreya; Chao, Ann; Miller, Aubrey; Wali, Anil; Weissman, David; Adjei, Alex; Baumann, Francine; Boffetta, Paolo; Md, ; Buck, Brenda; de Perrot, Marc; Umran Dogan, A.; Gavett, Steve; Gualtieri, Alessandro; Hassan, ; Hesdorffer, Mary; Hirsch, Fred R.; Larson, David; Mao, Weimin; Masten, Scott; Pass, Harvey I.; Peto, Julian; Pira, Enrico; Steele, Ian; Tsao, Anne; Alida Woodard, Gavitt; Yang, Haining; Malik, Shakun
abstract

On November 9 and 10, 2015, the International Conference on Mesothelioma in Populations Exposed to Naturally Occurring Asbestiform Fibers was held at the University of Hawaii Cancer Center in Honolulu, Hawaii. The meeting was cosponsored by the International Association for the Study of Lung Cancer, and the agenda was designed with significant input from staff at the U.S. National Cancer Institute and National Institute of Environmental Health Sciences. A multidisciplinary group of participants presented updates reflecting a range of disciplinary perspectives, including mineralogy, geology, epidemiology, toxicology, biochemistry, molecular biology, genetics, public health, and clinical oncology. The group identified knowledge gaps that are barriers to preventing and treating malignant mesothelioma (MM) and the required next steps to address barriers. This manuscript reports the group's efforts and focus on strategies to limit risk to the population and reduce the incidence of MM. Four main topics were explored: genetic risk, environmental exposure, biomarkers, and clinical interventions. Genetics plays a critical role in MM when the disease occurs in carriers of germline BRCA1 associated protein 1 mutations. Moreover, it appears likely that, in addition to BRCA1 associated protein 1, other yet unknown genetic variants may also influence the individual risk for development of MM, especially after exposure to asbestos and related mineral fibers. MM is an almost entirely preventable malignancy as it is most often caused by exposure to commercial asbestos or mineral fibers with asbestos-like health effects, such as erionite. In the past in North America and in Europe, the most prominent source of exposure was related to occupation. Present regulations have reduced occupational exposure in these countries; however, some people continue to be exposed to previously installed asbestos in older construction and other settings. Moreover, an increasing number of people are being exposed in rural areas that contain noncommercial asbestos, erionite, and other mineral fibers in soil or rock (termed naturally occurring asbestos [NOA] ) and are being developed. Public health authorities, scientists, residents, and other affected groups must work together in the areas where exposure to asbestos, including NOA, has been documented in the environment to mitigate or reduce this exposure. Although a blood biomarker validated to be effective for use in screening and identifying MM at an early stage in asbestos/NOA-exposed populations is not currently available, novel biomarkers presented at the meeting, such as high mobility group box 1 and fibulin-3, are promising. There was general agreement that current treatment for MM, which is based on surgery and standard chemotherapy, has a modest effect on the overall survival (OS), which remains dismal. Additionally, although much needed novel therapeutic approaches for MM are being developed and explored in clinical trials, there is a critical need to invest in prevention research, in which there is a great opportunity to reduce the incidence and mortality from MM.


2016 - In situ high-temperature X-ray diffraction and spectroscopic study of fibroferrite, FeOH(SO4)·5H2O [Articolo su rivista]
Ventruti, Gennaro; Ventura, Giancarlo Della; Corriero, Nicola; Malferrari, Daniele; Gualtieri, Alessandro; Susta, Umberto; Lacalamita, Maria; Schingaro, Emanuela
abstract

The thermal dehydration process of fibroferrite, FeOH(SO4)·5H2O, a secondary iron-bearing hydrous sulfate, was investigated by in situ high-temperature synchrotron X-ray powder diffraction (HT-XRPD), in situ high-temperature Fourier transform infrared spectroscopy (HT-FTIR) and thermal analysis (TGA-DTA) combined with evolved gas mass spectrometry. The data analysis allowed the determination of the stability fields and the reaction paths for this mineral as well as characterization of its high-temperature products. Five main endothermic peaks are observed in the DTA curve collected from room T up to 800 °C. Mass spectrometry of gases evolved during thermogravimetric analysis confirms that the first four mass loss steps are due to water emission, while the fifth is due to a dehydroxylation process; the final step is due to the decomposition of the remaining sulfate ion. The temperature behavior of the different phases occurring during the heating process was analyzed, and the induced structural changes are discussed. In particular, the crystal structure of a new phase, FeOH(SO4)·4H2O, appearing at about 80 °C due to release of one interstitial H2O molecule, was solved by ab initio real-space and reciprocal-space methods. This study contributes to further understanding of the dehydration mechanism and thermal stability of secondary sulfate minerals.


2016 - In situ synchrotron powder diffraction study of the setting reaction kinetics of magnesium-potassium phosphate cements [Articolo su rivista]
Viani, A.; Peréz-Estébanez, M.; Pollastri, S.; Gualtieri, A. F.
abstract

This work reports a kinetic study of the formation of magnesium-potassium phosphate cements accomplished using in-situ synchrotron powder diffraction. The reaction: MgO + KH 2 PO 4 + 5H 2 O → MgKPO 4 · 6H 2 O was followed in situ in the attempt of contributing to explain the overall mechanism and assess the influence of periclase (MgO) grain size and calcination temperature (1400-1600 °C) on the reaction kinetics. Numerical kinetic parameters for the setting reaction have been provided for the first time. The best fit to the kinetic data was obtained using a weighted nonlinear model fitting method with two kinetic equations, representing two consecutive, partially overlapping processes. MgO decomposition could be described by a first order (F1) model followed by a Jander diffusion (D3) controlled model. Crystallization of the product of reaction was modelled using an Avrami model (A n ) followed by a first order (F1) chemical reaction. A reaction mechanism accounting for such results has been proposed.


2016 - Kinetic study of the drying process of clay bricks [Articolo su rivista]
Gualtieri, A. F.; Ricchi, A.; Lassinantti Gualtieri, M.; Maretti, S.; Tamburini, M.
abstract

This work deals with the drying kinetics of three red clays with different mineralogical composition and grain size distribution used for the production of clay bricks. The kinetic study was performed using thermo-gravimetry (TG) in both non-isothermal and isothermal mode in the 50-200 °C range. To the knowledge of the authors, this is the first time that the drying process of clay bricks is studied using the TG method to present a general model at molecular scale of the phenomenon. The observed drying mechanism is composed of a fast initial step and a slow final step. The former is characterized by an Avrami-like mechanism with an Avrami coefficient n 1 comprised between 1 and 2. This kinetic parameter indicates a diffusive control in three dimensions with instantaneous or deceleratory nucleation and refers to desorption of adsorbed water from the surface of all mineral phases. The second step is also characterized by an Avrami-like mechanism with n 2 = 1 and points to a diffusion-controlled reaction in two dimensions, with instantaneous nucleation. This step involves dehydration of plastic clay minerals such as illite, smectite and IS through diffusion of water molecules within the two-dimensional interlayer. The apparent activation energies related to the first fast mechanism have similar values ( < 32 kJ mol -1 ) for all samples. The apparent activation energy E a for the second slower step is dependent upon the mineralogical composition and is > 35 kJ mol -1 . The dependency of the apparent activation energies on grain size distribution and sample mass was also assessed.


2016 - Miniera di Pralongo. Una mineralizzazione cuprifera presso canal San Bovo (Valle del Vanoi, Trento). [Articolo su rivista]
Conedera, M.; Bursi Gandolfi, N.; Ferretti, P.; Gualtieri, A. F.; Rocchetti, I.
abstract

Miniera di Pralongo. Una mineralizzazione cuprifera presso canal San Bovo (Valle del Vanoi, Trento).


2016 - Progress in mineralogical quantitative analysis of rock samples: Application to quartzites from Denali National Park, Alaska Range (USA) [Articolo su rivista]
Nistor, M. M.; Har, N.; Marchetti Dori, S.; Bigi, S.; Gualtieri, A. F.
abstract

This work deals with the determination of the mineralogical composition of three quartzite samples, selected as case study to verify the viability and accuracy of various experimental techniques commonly used in geometallurgy and petrography for the determination of the mineralogical composition of rock samples. The investigated samples are from the North-Eastern side of the Denali National Park (Alaska Range, USA). The mineralogical phase abundance of the samples was determined by digitally assisted optical modal point counting, scanning electron microscopy (SEM) + energy dispersive spectroscopy (EDS) modal and digital image analysis, normative calculation from bulk chemistry calculation, and modal Rietveld X-ray powder diffraction. The results of our study indicate that the results provided by modal optical and SEM digitalized counting seem less accurate than the others. The determination with EDS mapping was found to be inaccurate only for one sample. Agreement was found between the X-ray diffraction estimates and bulk chemistry calculation. For both modal optical and SEM digitalized counting, the statistics was probably insufficient to provide accurate results. The estimates obtained from the various methods are compared with each other in the attempt to attain general indications on the precision, accuracy, advantages/disadvantages of each method.


2016 - Removal of fluoroquinolone contaminants from environmental waters on sepiolite and its photo-induced regeneration [Articolo su rivista]
Sturini, Michela; Speltini, Andrea; Maraschi, Federica; Profumo, Antonella; Tarantino, Serena; Gualtieri, Alessandro F.; Zema, Michele
abstract

Sepiolite is studied as sorbent for removal of Fluoroquinolone (FQ) contaminants from water. Marbofloxacin (MAR) and Enrofloxacin (ENR) were chosen as model FQs since they are the two most commonly employed veterinary FQs in livestock farming in northern Italy. Adsorption experiments on two sepiolites (SP-1 and SSE16) were carried out in tap water at pH 7.5 to better mimic real conditions. The sorption experimental data were fitted by Freundlich, Langmuir and S-Logistic1 models. The latter better described MAR and ENR adsorptions. Adsorption capacities of SP-1 and SSE16, respectively, were 132 mg g−1 and 121 mg g−1 for MAR, and 112 mg g−1 and 93 mg g−1 for ENR. X-ray powder diffraction, performed on clay samples enriched with each FQ and on the pristine clays, showed no substantial differences between the two sepiolites and evidenced no significant structural changes after FQs uptake, as also verified by infrared spectroscopy. This indicates that adsorption occurs only on the external surface of the mineral and not in the intracrystalline microporosity, likely due to the interaction between the FQ carboxylic group and the sepiolite surface. For the first time solid-state photodegradation of the adsorbed FQs was investigated for regenerating the sorbent. Results showed that the adsorbed drugs are effectively photodegraded by solar light, thus allowing sepiolite to be reused. The efficiency of this material for remediation of contaminated water was proved on ditch water, collected downstream a swine farm, containing some tens of ng L−1 of MAR and ENR.


2016 - Stability of mineral fibres in contact with human cell cultures. An in situ μXANES, μXRD and XRF iron mapping study [Articolo su rivista]
Pollastri, Simone; Gualtieri, Alessandro F.; Vigliaturo, Ruggero; Ignatyev, Konstantin; Strafella, Elisabetta; Pugnaloni, Armanda; AlessandroCroce,
abstract

Relevant mineral fibres of social and economic importance (chrysotile UICC, crocidolite UICC and a fibrous erionite from Jersey, Nevada, USA) were put in contact with cultured diploid human non-tumorigenic bronchial epithelial (Beas2B) and pleural transformed mesothelial (MeT5A) cells to test their cytotoxicity. Slides of each sample at different contact times up to 96 h were studied in situ using synchrotron XRF, μ-XRD and μ-XAS (I18 beamline, Diamond Light Source, UK) and TEM investigations. XRF maps of samples treated for 96 h evidenced that iron is still present within the chrysotile and crocidolite fibres and retained at the surface of the erionite fibres, indicating its null to minor mobilization in contact with cell media; this picture was confirmed by the results of XANES pre-edge analyses. μ-XRD and TEM data indicate greater morphological and crystallinity modifications occurring in chrysotile, whereas crocidolite and erionite show to be resistant in the biological environment. The contact of chrysotile with the cell cultures seems to lead to earlier amorphization, interpreted as the first dissolution step of these fibres. The formation of such silica-rich fibre skeleton may prompt the production of HO in synergy with surface iron species and could indicate that chrysotile may be much more reactive and cytotoxic in vitro in the (very) short term whereas the activity of crocidolite and erionite would be much more sluggish but persistent in the long term.


2016 - TG/DSC study of the thermal behaviour of hazardous mineral fibres [Articolo su rivista]
Bloise, Andrea; Catalano, Manuela; Barrese, Eugenio; Gualtieri, Alessandro; Bursi Gandolfi, Nicola; Capella, Silvana; Belluso, Elena
abstract

This paper reports a systematic and comparative study of the thermal behaviour of fibres of social, health, economic and industrial relevance using thermogravimetric and differential scanning calorimetry (TG/DSC). The mineral fibres selected for the study are: three chrysotile samples, crocidolite, tremolite asbestos, amosite, anthophyllite asbestos and asbestiform erionite. Powder X-ray diffraction and scanning electron microscopy were used for the characterization of the mineral fibres before and after heating at 1000 or 1100 °C to identify the products of the thermal decomposition at a microscopic and structural scale and characterize their thermal behaviour. TG/DSC data allowed the determination of the structural water content and temperature stability. Furthermore, thermal analysis provided a sensitive and reliable technique for the detection of small quantities of different mineral phases occurring as impurities. After thermal treatment, fibrous samples were completely transformed into various iron oxide, cristobalite and other silicate phases which preserved the original overall fibrous morphology (as pseudomorphosis). Only crocidolite at 1100 °C was partially melted, and an amorphous surface was observed.


2016 - Texture analysis of magnesium potassium phosphate ceramics [Banca dati]
Viani, A; Gualtieri, A; Puente Orench, I; Zucali, M
abstract


2016 - The crystal structure of mineral fibres. 1. Chrysotile [Articolo su rivista]
Pollastri, Simone; Perchiazzi, Natale; Lezzerini, Marco; Plaisier, Jasper R.; Cavallo, Alessandro; Chiara Dalconi, Maria; Bursi Gandolfi, Nicola; Gualtieri, Alessandro F.
abstract

This work reports the results of the structural study of three representative chrysotile samples of different provenance (Canadian UICC, and Italian Balangero and Valmalenco). Chemical composition was determined using EMPA and TG data. An innovative wet cryo-milling procedure was used to powder the flexible and durable chrysotile fibres. X-ray powder diffraction patterns were collected using both conventional and nonconventional sources. Collected data were used for Rietveld structural refinements and results were compared with available literature data. The three samples display similar structure models, although small differences were detected in the position of the oxygen atoms. Both the structural refinements and spectroscopic investigations confirms that Fe 2+ and Fe 3+ atoms in chrysotile are located in the octahedral cavities only, substituting for Mg 2+ . Regarding the atom coordinates, UICC chrysotile is the closest to the model reported by Falini et al. (2004). About the lattice parameters, the Valmalenco chrysotile is the closest, if compared with the Balangero and UICC, to both the model proposed by Whittaker (1956a,b) and Falini et al. (2004). This work is intended as a basis for subsequent studies aimed at understanding the toxicity of these mineral fibres.


2016 - Trace elements in hazardous mineral fibres [Articolo su rivista]
Bloise, A.; Barca, D.; Gualtieri, A. F.; Pollastri, S.; Belluso, E.
abstract

Both occupational and environmental exposure to asbestos-mineral fibres can be associated with lung diseases. The pathogenic effects are related to the dimension, biopersistence and chemical composition of the fibres. In addition to the major mineral elements, mineral fibres contain trace elements and their content may play a role in fibre toxicity. To shed light on the role of trace elements in asbestos carcinogenesis, knowledge on their concentration in asbestos-mineral fibres is mandatory. It is possible that trace elements play a synergetic factor in the pathogenesis of diseases caused by the inhalation of mineral fibres. In this paper, the concentration levels of trace elements from three chrysotile samples, four amphibole asbestos samples (UICC amosite, UICC anthophyllite, UICC crocidolite and tremolite) and fibrous erionite from Jersey, Nevada (USA) were determined using inductively coupled plasma mass spectrometry (ICP-MS). For all samples, the following trace elements were measured: Li, Be, Sc, V, Cr, Mn, Co, Ni, Cu, Zn, As, Rb, Sr, Y, Sb, Cs, Ba, La, Pb, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, U. Their distribution in the various mineral species is thoroughly discussed. The obtained results indicate that the amount of trace metals such as Mn, Cr, Co, Ni, Cu and Zn is higher in anthophyllite and chrysotile samples, whereas the amount of rare earth elements (REE) is higher in erionite and tremolite samples. The results of this work can be useful to the pathologists and biochemists who use asbestos minerals and fibrous erionite in-vitro studies as positive cyto- and geno-toxic standard references.


2016 - Where is iron in erionite? A multidisciplinary study on fibrous erionite-Na from Jersey (Nevada, USA) [Articolo su rivista]
Gualtieri, A. F.; Nicola Bursi, Gandolfi; Simone, Pollastri; Kilian, Pollok; Falko, Langenhorst
abstract

Fibrous erionite is a mineral fibre of great concern but to date mechanisms by which it induces cyto- and geno-toxic damage, and especially the role of iron associated to this zeolite species, remain poorly understood. One of the reasons is that we still don’t know exactly where iron is in natural erionite. This work is focused on fibrous erionite-Na from Jersey (Nevada, USA) and attempts to draw a general model of occurrence of iron in erionite and relationship with toxicity mechanisms. It was found that iron is present as 6-fold coordinated Fe3+ not part of the zeolite structure. The heterogeneous nature of the sample was revealed as receptacle of different iron-bearing impurities (amorphous iron-rich nanoparticles, micro-particles of iron oxides/hydroxides, and flakes of nontronite). If iron is not part of the structure, its role should be considered irrelevant for erionite toxicity, and other factors like biopersistence should be invoked. An alternative perspective to the proposed model is that iron rich nano-particles and nontronite dissolve in the intracellular acidic environment, leaving a residue of iron atoms at specific surface sites anchored to the windows of the zeolite channels. These sites may be active later as low nuclearity groups.


2016 - XANES and micro-Raman spectroscopy study of the barium titanosilicates BaTiSi2O7 and BaTiSi4O11 [Articolo su rivista]
Viani, A.; Pollastri, S.; Macova, P.; Palermo, A.; Peréz-Estébanez, M.; Gualtieri, A. F.
abstract

The coordination environment around Ti4+ in the photoluminescent compound BaTiSi2O7 and in BaTiSi4O11 was investigated with X-ray absorption near-edge structure spectroscopy and micro-Raman spectroscopy. The presence of VTi in TiO5 pyramidal units with one short Ti–O bond involving the apical oxygen was detected in both compounds. Interpretation of the vibrational signal from the silicate framework suggested that BaTiSi4O11 is a metasilicate containing building units of SiO4 tetrahedra, which are larger than in other barium titanosilicates. These results confirmed the same structural environment of Ti4+ as recently disclosed by structure refinement of BaTiSi2O7 and provided new insights into the unknown structure of BaTiSi4O11 in the light of the study of its physical properties as potential functional material.


2015 - Cava Pralongo. Nuove segnalazioni dalle pegmatiti della Valle del Vanoi (Canal San Bovo, Trento). [Articolo su rivista]
Ferretti, P.; Gualtieri, A. F.; Rocchetti, I.; Vecchi, F.
abstract

Cava Pralongo. Nuove segnalazioni dalle pegmatiti della Valle del Vanoi (Canal San Bovo, Trento).


2015 - Frictional properties of fault zone gouges from the J-FAST drilling project (Mw9.0 2011 Tohoku-Oki earthquake) [Articolo su rivista]
Remitti, Francesca; Smith, S. A. F.; Mittempergher, Silvia; Gualtieri, Alessandro; Di Toro, G.
abstract

Smectite-rich fault gouges recovered during Integrated Ocean Drilling Program Expedition 343 (Japan Trench Fast Drilling Project (J-FAST)) from the plate boundary slip zone of the 2011 Mw 9.0 Tohoku-Oki earthquake were deformed at slip velocities of 10 µm s−1 to 3.5 m s−1 and normal stresses up to 12 MPa. Water-dampened gouges (1) are weaker (apparent friction coefficient, μ* &lt;0.1) than room-humidity gouges (apparent friction coefficient, μ* ~0.1–0.35) at all slip velocities, (2) are velocity insensitive to velocity weakening at all slip velocities, unlike room-humidity gouges that are velocity strengthening at intermediate velocities (V = 0.001–0.1 m s−1), and (3) have negligible peak μ* at high slip velocities (V &gt; 0.1 m s−1). A significant amount of amorphous material formed in room-humidity experiments at low- and high-slip velocities, likely by comminution and disordering of smectite. Our results indicate that the frictional properties of water-dampened gouges could have facilitated propagation of the Tohoku-oki rupture to the trench and large coseismic slip at shallow depths.


2015 - In situ high-temperature XRD and FTIR investigation of hohmannite, a water-rich Fe-sulfate, and its decomposition products [Articolo su rivista]
Ventruti, G.; Della Ventura, G.; Scordari, F.; Susta, U.; Gualtieri, A. F.
abstract

The thermal dehydration of hohmannite, Fe 2 [O(SO 4 ) 2 ]·8H 2 O, a secondary iron-bearing hydrous sulfate, was investigated by in situ high-temperature X-ray powder diffraction and in situ high-temperature Fourier transform infrared spectroscopy. Combination of the data from both techniques allowed determining the stability fields and reaction paths for this mineral and its high temperature products. Five main dehydration/transformation steps for hohmannite have been identified in the heating range of 25-800 °C. Temperature behavior of the different phases was analyzed, and the heating-induced structural changes are discussed.


2015 - Influence of sol counter-ions on the anatase-to-rutile phase transformation and microstructure of nanocrystalline TiO2 [Articolo su rivista]
Tobaldi, D. M.; Pullar, R. C.; Gualtieri, A. F.; Belen Jorge, A.; Binions, R.; Mcmillan, P. F.; Seabraa, M. P.; Labrincha, J. A.
abstract

Amongst nanomaterials, metal oxides play an increasingly dominant role, with titanium dioxide (titania, TiO2) being widely used for various applications, such as light-to-energy conversion and storage, and photocatalysis. In this work, TiO2 has been synthesised via an aqueous sol–gel method, using three different mineral acids (HNO3, HCl and HBr) to peptise the sol, and hence provide counter-ions. Dried sols were thermally treated at three different temperatures (450, 600 and 800 °C), using three different dwell times (2, 4, and 8 h). Advanced X-ray methods were used to monitor the effect that the counter-ions had on the anatase-to-rutile phase transformation (ART). Quantitative phase analysis (QPA) using the Rietveld method was applied to assess the true amount of crystalline phases in the systems, and the amount of amorphous phase. Furthermore, the average crystalline domain diameter was also investigated, using whole powder pattern modelling (WPPM). With the advanced XRPD data (actual crystalline phase weight fraction in the samples and their average domain diameter and size distribution), it was possible to carry out a semi-quantitative study of the ART transformation kinetics. At a low temperature of 75 °C, the Cl− counter-ion was the most favourable to obtain anatase as the major crystalline phase, delaying the onset of the ART. Conversely, the Br− ions, maintained more anatase at 450 °C, with a lower ART rate. In general, halides were more effective in delaying the ART than NO3− counterions. Moreover, we observed an inverse linear relationship between the lattice volume expansion of rutile and the increase of its crystalline domain size at 450 and 600 °C isotherms. As the domain sizes increased with temperature, this effect reversed and became a direct linear dependence at the 800 °C isotherm, suggesting a critical size limit <90 nm for this effect.


2015 - Inorganic polymers from laterite using activation with phosphoric acid and alkaline sodium silicate solution: Mechanical and microstructural properties [Articolo su rivista]
Gualtieri, Eva Magdalena; Romagnoli, Marcello; Pollastri, Simone; Gualtieri, Alessandro
abstract

Geopolymers from laterite, an iron-rich soil available in developing countries, have great potential as building materials. In this work, laterite from Togo (Africa) was used to prepare geopolymers using both phosphoric acid and alkaline sodium silicate solution. Microstructural properties were investigated by scanning electron microscopy, X-ray powder diffraction and mercury porosimetry, whereas thermal properties were evaluated by thermal analyses. The local environment of iron was studied by X-ray Absorption Spectroscopy (XANES region). The mechanical properties were determined. Modulus of Rupture and Young's modulus fell in the ranges 3.3–4.5 MPa and 12–33 GPa, respectively, rendering the materials good candidates for construction purposes. Heating above 900 °C results in weight-gain, presumably due to iron redox reactions. X-ray Absorption Spectroscopy data evidence changes in the chemical and structural environments of iron following thermal treatment of geopolymers. These changes indicate interaction between the geopolymer structure and iron during heating, possibly leading to redox properties.


2015 - Investigation of setting reaction of magnesium-potassium phosphate ceramics by qualsi-elastic neutron scattering [Banca dati]
Viani, A; Gualtieri, A; Pollastri, S; Zbiri, M
abstract


2015 - Nitrogen-modified nano-titania: True phase composition, microstructure and visible-light induced photocatalytic NOx abatement [Articolo su rivista]
Tobaldi, D. M.; Pullar, R. C.; Gualtieri, A. F.; Otero-Iruruet, G.; Singh, M. K.; Seabra, M. P.; Labrincha, J. A.
abstract

Titanium dioxide (TiO2) is a popular photocatalyst used for many environmental and anti-pollution applications, but it normally operates under UV light, exploiting ∼5% of the solar spectrum. Nitrification of titania to form N-doped TiO2 has been explored as a way to increase its photocatalytic activity under visible light, and anionic doping is a promising method to enable TiO2 to harvest visible-light by changing its photo-absorption properties. In this paper, we explore the insertion of nitrogen into the TiO2 lattice using our green sol–gel nanosynthesis method, used to create 10 nm TiO2 NPs. Two parallel routes were studied to produce nitrogen-modified TiO2 nanoparticles (NPs), using HNO3+NH3 (acid-precipitated base-peptised) and NH4OH (totally base catalysed) as nitrogen sources. These NPs were thermally treated between 450 and 800 °C. Their true phase composition (crystalline and amorphous phases), as well as their micro-/nanostructure (crystalline domain shape, size and size distribution, edge and screw dislocation density) was fully characterised through advanced X-ray methods (Rietveld-reference intensity ratio, RIR, and whole powder pattern modelling, WPPM). As pollutants, nitrogen oxides (NOx) are of particular concern for human health, so the photocatalytic activity of the NPs was assessed by monitoring NOx abatement, using both solar and white-light (indoor artificial lighting), simulating outdoor and indoor environments, respectively. Results showed that the onset of the anatase-to-rutile phase transformation (ART) occurred at temperatures above 450 °C, and NPs heated to 450 °C possessed excellent photocatalytic activity (PCA) under visible white-light (indoor artificial lighting), with a PCA double than that of the standard P25 TiO2 NPs. However, higher thermal treatment temperatures were found to be detrimental for visible-light photocatalytic activity, due to the effects of four simultaneous occurrences: (i) loss of OH groups and water adsorbed on the photocatalyst surface; (ii) growth of crystalline domain sizes with decrease in specific surface area; (iii) onset and progress of the ART; (iv) the increasing instability of the nitrogen in the titania lattice.


2015 - Preparation of phosphoric acid-based geopolymer foams using limestone as pore forming agent - Thermal properties by in situ XRPD and Rietveld refinements [Articolo su rivista]
Gualtieri, Eva Magdalena; Romagnoli, Marcello; Gualtieri, Alessandro
abstract

In this work, geopolymer foams were obtained by reacting metakaolin with phosphoric acid and using natural calcite/dolomite as foaming agent. Total porosity and thermal conductivity were ca. 70% and 0.083 ± 0.008 W/mK, respectively. Rietveld refinements, using both ex- and in situ XRPD data, were performed in order to elucidate the phase stability of the formed binder up to 1200°C. The results showed that the amorphous matrix partially crystallized in tridymite and cristobalite type structures of AlPO4-SiO2 solid solutions at about 700°C. At 1000 °C, 3:2 mullite started to crystallize, possibly from unreacted metakaolinite, resulting in co-crystallization of SiO2 cristobalite. At the same time, the amount of tridymite-type structure decreased, possibly due to selective phase transformation of AlPO4 tridymite to cristobalite, leaving behind the SiO2 isostructure. The geopolymer paste composition allows to tailor the mullite content in the refractory foam.


2015 - Quantitative phase analysis and microstructure characterization of magnetite nanocrystals obtained by microwave assisted non-hydrolytic sol–gel synthesis [Articolo su rivista]
Sciancalepore, Corrado; Bondioli, Federica; Manfredini, Tiziano; Gualtieri, Alessandro
abstract

An innovative preparation procedure, based on microwave assisted non-hydrolytic sol-gel synthesis, to obtain spherical magnetite nanoparticles was reported together with a detailed quantitative phase analysis and microstructure characterization of the synthetic products. The nanoparticle growth was analyzed as a function of the synthesis time and was described in terms of crystallization degree employing the Rietveld method on the magnetic nanostructured system for the determination of the amorphous content using hematite as internal standard. Product crystallinity increases as the microwave thermal treatment is increased and reaches very high percentages for synthesis times longer than 1 h. Microstructural evolution of nanocrystals was followed by the integral breadth methods to obtain information on the crystallite size-strain distribution. The results of diffraction line profile analysis were compared with nanoparticle grain distribution estimated by dimensional analysis of the transmission electron microscopy (TEM) images. A variation both in the average grain size and in the distribution of the coherently diffraction domains is evidenced, allowing to suppose a relationship between the two quantities. The traditional integral breadth methods have proven to be valid for a rapid assessment of the diffraction line broadening effects in the above-mentioned nanostructured systems and the basic assumption for the correct use of these methods are discussed as well.


2015 - Raw and thermally treated cement asbestos exerts different cytotoxicity effects on A549 cells in vitro [Articolo su rivista]
Pugnaloni, Armanda; Lucarini, Guendalina; Rubini, Corrado; Smorlesi, Arianna; Tomasetti, Marco; Strafella, Elisabetta; Armeni, Tatiana; Gualtieri, Alessandro F.
abstract

Raw cement asbestos (RCA) undergoes a complete solid state transformation when heated at high temperatures. The secondary raw material produced, high temperatures-cement asbestos (HT-CA) is composed of newly-formed crystals in place of the asbestos fibers present in RCA. Our previous study showed that HT-CA exerts lower cytotoxic cell damage compared to RCA. Nevertheless further investigations are needed to deepen our understanding of pathogenic pathways involving oxidative and nitrative damage. Our aim is to deepen the understanding of the biological effects on A549 cells of these materials regarding DNA damage related proteins (p53, its isoform p73 and TRAIL) and nitric oxide (NO) production during inducible nitric oxide synthase (iNOS)-mediated inflammation. Increments of p53/p73 expression, iNOS positive cells and NO concentrations were found with RCA, compared to HT-CA and controls mainly at 48 h. Interestingly, ferrous iron causing reactive oxygen species (ROS)-mediated DNA damage was found in RCA as a contaminant. HT-CA thermal treatment induces a global recrystallization with iron in a crystal form poorly released in media. HT-CA slightly interferes with genome expression and exerts lower inflammatory potential compared to RCA on biological systems. It could represent a safe approach for storing or recycling asbestos and an environmentally friendly alternative to asbestos waste.


2015 - Structure and stability of BaTiSi2O7 [Articolo su rivista]
Viani, A.; Palermo, A.; Zanardi, S.; Demitri, N.; Petrícek, V.; Varini, F.; Belluso, E.; Ståhl, K.; Gualtieri, A. F.
abstract

Due to their optical, photo-luminescence (PL), and afterglow properties, barium titanosilicates are compounds of great interest for functional materials and light-emitting devices. Among them, BaTiSi2O7 (BTS2) is certainly one of the most intriguing; it displays peculiar properties (e.g. PL orange emission) whose exhaustive explanation has been hampered to date by the lack of a structure model. In this work, BTS2 and the related compound BaTiSi4O11 (BTS4) were synthesized through conventional solid-state reaction methods. BTS2 invariably shows complex twinning patterns. Thus, its structure solution and Rietveld structure refinement were attempted using synchrotron powder diffraction. BTS2 was found to be an intergrowth of monoclinic and triclinic crystals. The monoclinic phase has the space group P21/n and unit cell a = 7.9836 (3), b = 10.0084 (4), c = 7.4795 (3) Å, and [beta] = 100.321 (3)°, whereas the triclinic phase has the space group Par 1 and unit cell a = 7.99385 (4), b = 10.01017 (5), c = 7.47514 (3) Å, [alpha] = 90.084 (8), [beta] = 100.368 (8) and [gamma] = 89.937 (9)°. These lattices can be seen as a distortion of that of tetragonal synthetic [beta]-BaVSi2O7 with Ti in place of V. The structure models obtained from this study confirm the presence of fivefold coordinated Ti atoms in a distorted pyramidal configuration. The proposed solution supports existing theories for the explanation of the PL orange colour in BTS2.


2015 - Study of the asbestos bodies and chemical-physical modification of mineral fibres in rat histological tissues using electron microscopy and micro-Raman spetroscopy [Abstract in Atti di Convegno]
Bursi Gandolfi, N; Pollastri, S; Viani, A; Gualtieri, Af
abstract


2015 - The chemical environment of iron in mineral fibres. A combined X-ray absorption and Mössbauer spectroscopic study [Articolo su rivista]
Pollastri, Simone; D’Acapito, Francesco; Trapananti, Angela; Colantoni, Ivan; Andreozzi, Giovanni B.; Gualtieri, Alessandro F.
abstract

Although asbestos represents today one of the most harmful contaminant on Earth, in 72% of the countries worldwide only amphiboles are banned while controlled use of chrysotile is allowed. Uncertainty on the potential toxicity of chrysotile is due to the fact that the mechanisms by which mineral fibres induces cyto- and geno-toxic damage are still unclear. We have recently started a long term project aimed at the systematic investigation of the crystal-chemistry, bio-interaction and toxicity of the mineral fibres. This work presents a systematic structural investigation of iron in asbestos and erionite (considered the most relevant mineral fibres of social and/or economic-industrial importance) using synchrotron X-ray absorption and Mössbauer spectroscopy. In all investigated mineral fibres, iron in the bulk structure is found in octahedral sites and can be made available at the surface via fibre dissolution. We postulate that the amount of hydroxyl radicals released by the fibers depends, among other factors, upon their dissolution rate; in relation to this, a ranking of ability of asbestos fibres to generate hydroxyl radicals, resulting from available surface iron, is advanced: amosite &gt; crocidolite ≈ chrysotile &gt; anthophyllite &gt; tremolite. Erionite, with a fairly high toxicity potential, contains only octahedrally coordinated Fe3+. Although it needs further experimental evidence, such available surface iron may be present as oxide nanoparticles coating and can be a direct cause of generation of hydroxyl radicals when such coating dissolves.


2014 - Accuracy in quantitative phase analysis of mixtures with large amorphous contents. The case of stoneware ceramics and bricks [Articolo su rivista]
Gualtieri, Alessandro; Riva, Vincenzo; Bresciani, Andrea; Maretti, Stefano; Tamburini, Marco; Viani, Alberto
abstract

For the first time, this work inspects the accuracy of quantitative phase analysis of both crystalline and amorphous components of stoneware tiles and bricks. A number of variables were considered: the nature of the internal standard, experimental conditions and counting statistics. The so-called G-factor method has also been applied. The results of the X-ray powder diffraction analysis have been compared with the results obtained with optical microscopy and image analysis. Only the mixtures spiked with corundum and silicon yielded accurate weight estimates of the amorphous fraction, whereas the use of highly X-ray absorbing internal standards (such as fluorite, rutile and zincite) resulted in gross underestimations. In fact, microabsorption effects are found to drastically reduce the accuracy of the results when standards with linear X-ray absorption coefficients higher than 100 cm-1 are employed. It was found that very low counting statistics reduced the calculated amorphous fractions in both bricks and stoneware tiles owing to partial masking of the major peak of the internal standard, namely corundum. The application of the G-factor method to the systems investigated was also evaluated. The results are poorer than those obtained using the internal standard.


2014 - Accuracy in quantitative phase analysis of mixtures with large amorphous contents. The case of zircon-rich sanitary-ware glazes [Articolo su rivista]
Bernasconi, Andrea; Dapiaggi, Monica; Gualtieri, Alessandro
abstract

The accuracy of quantitative phase analysis (QPA) of samples with dominant amorphous content, reproducing zircon-rich sanitary-ware glazes, has been investigated. X-ray powder diffraction (XRPD) methods were applied using both conventional Cu K[alpha] radiation and high-resolution synchrotron data. In this work, a combination of the reference intensity ratio (RIR) and Rietveld methods was applied to an artificial mixture (90 wt% glass, 10 wt% zircon), taking into account some of the most common effects that may affect the accuracy in amorphous quantification, such as the degree of crystallinity of the phases, microabsorption and sample preparation. Certified NIST SRM 676a ([alpha]-Al2O3) [Cline, Von Dreele, Winburn, Stephens &amp; Filliben (2011). Acta Cryst. A67, 357-367] was used to quantify the amorphous content in zircon and in the different internal standards commonly used when a certified standard is not available or not applicable: the results show that all of the phases invariably contain amorphous material in the range 2.0-15.0 wt%. If the amorphous content of the standard is taken into account, the accuracy of the QPA of the artificial mixture is improved. It was observed that the Brindley correction for microabsorption does not significantly improve the results. Care must be applied if grinding time is increased, since this may increase the amorphous content in the sample. Finally, the sensitivity of the RIR-Rietveld method to the addition of a small amount of zircon (~1 wt%) has been considered, showing that accurate results can be achieved if great care is taken in the sample preparation and refinement strategy.


2014 - Crystal chemistry of clinker relicts from aged cementitious materials [Articolo su rivista]
Secco, Michele; Peruzzo, Luca; Palasse, Laurie; Artioli, Gilberto; Viani, Alberto; Gualtieri, Alessandro
abstract

Despite the general tendency to consider Portland cement virtually fully hydrated within a few years, the occurrence of non-reacted clinker phases in cementitious materials that are several decades old is rather common. In this work, the integration of microstructural analysis by scanning electron microscopy and quantitative microchemical and micromineralogical characterization techniques, such as electron microprobe analysis and electron backscatter diffraction, allowed the definition of the crystal-chemical properties of partially hydrated cement residuals within different types of aged cementitious materials. The results on several clinker relicts show that the calcium silicate phases are transformed systematically and pervasively by hydration reactions, whereas the aluminate and ferrite phases do frequently persist in the anhydrous state. These relict phases may be distinguished through their peculiar chemical, mineralogical and textural features. These observations raise interesting questions concerning the long-term hydration kinetics of clinker phases and the durability behaviour of cementitious materials in operating conditions.


2014 - Determination of the concentration of asbestos minerals in highly contaminated mine tailings: An example from abandoned mine waste of Cretaz and Emarese (Valle d'Aosta, Italy) [Articolo su rivista]
Gualtieri, Alessandro; Pollastri, Simone; Ronchetti, Francesco; Gandolfi, N. B.; Albonico, C.; Cavallo, A.; Zanetti, G.; Marini, P.; Sala, O.
abstract

For the first time, this work reports concentration maps of asbestos minerals in contaminated mine tailings drawn using the results of Rietveld quantitative phase analysis (QPA). The investigated sites are located in the Valle d’Aosta region (Italy): Crètaz, the most important Italian magnetite mine, active until 1979 and Emarèse, one the most important chrysotile asbestos mines in Italy, active until 1968. The results of the study permit to draw the spatial distribution of the asbestos (chrysotile and tremolite in this specific case) concentration, useful to plan reclamation of the sites, with priority given to the areas with the highest asbestos concentration. Because of the complexity of the mineral assemblage, which includes, among the others, antigorite, chlorite, talc, and tremolite, the concentration of chrysotile was cross-checked using different experimental techniques such as X-ray powder diffraction (XRPD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), polarized light optical microscopy (PCOM), and differential thermal analysis (DTA). The accuracy of the results was validated by analyzing standard samples with known concentrations of chrysotile and tremolite. The comparison allowed to point out the advantages and disadvantages of each experimental method. At Crètaz, chrysotile ranges from 4.4 to 22.8 wt% and tremolite from 1.0 to 10.3 wt%, whereas at Emarèse the concentration of chrysotile varies from 3.3 to 39.5 wt% and tremolite from 5.9 to 12.4 wt%. Antigorite and chlorite are the major accompanying phases with variable amounts of other accessory minerals including magnetite, carbonates, talc, olivine, pyroxene, talc, and brucite. The results of our study are of key importance for the local environmental policies as the knowledge of the spatial distribution of the asbestos concentration allows to plan a detailed reclamation agenda of the contaminated sites. The spots with the highest surface contamination of both chrysotile and tremolite were identified and classified as priority areas in the reclamation plan.


2014 - Facile synthesis of B-type carbonated nanoapatite with tailored microstructure [Articolo su rivista]
Gualtieri, M. L.; Romagnoli, M.; Hanuskova, M.; Fabbri, E.; Gualtieri, A. F.
abstract

Nanolime and a phosphate-based chelating agent were used to synthesize B-type carbonated apatite. Developed Rietveld refinement strategies allowed one to determine process yield, product crystallinity as well as structural (unit cell) and microstructural (size, strain) parameters. The effect of synthesis temperature (20-60 °C) as well as Ca/P ratio (1.5-2.5) and solid content (10-30 wt%) of the starting batch on these properties were investigated. FTIR, TEM and gas adsorption data provided supporting evidence. The process yield was 42-60 wt% and found to be governed by the Ca/P ratio. The purified products had high specific surface area (107-186 m2/g) and crystallinity (76-97%). The unit cell parameters, correlated to the degree of structural carbonate, were sensitive to the Ca/P ratio. Instead, temperature governed the microstructural parameters. Less strained and larger crystals were obtained at higher temperatures. Long-term aging up to 6 months at 20 °C compensated for higher crystal growth kinetics at higher temperature. © 2014 Elsevier Inc.


2014 - Frictional properties of fault rocks along the shallow part of the JapanTrench décollement: insights from samples recovered during the Integrated Ocean Drilling Project Expedition 343 (the JFAST project). [Abstract in Rivista]
Remitti, Francesca; Smith, S.; Gualtieri, Alessandro; Di Toro, G.; Nielsen, S.
abstract

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2014 - Magnetic and nuclear structure of goethite (α-FeOOH): a neutron diffraction study [Articolo su rivista]
E. Zepeda Alarcon, H. Nakotte; Gualtieri, Alessandro; G., King; K., Page; S. C., Vogel; H. W., Wang; H. R., Wenk
abstract

The magnetic structure of two natural samples of goethite ([alpha]-FeOOH) with varying crystallinity was analyzed at 15 and 300 K by neutron diffraction. The well crystallized sample has the Pb'nm color space group and remained antiferromagnetic up to 300 K, with spins aligned parallel to the c axis. The purely magnetic 100 peak, identifying this color space group, was clearly resolved. The nanocrystalline sample shows a phase transition to the paramagnetic state at a temperature below 300 K. This lowering of the Néel temperature may be explained by the interaction of magnetic clusters within particles. The nuclear structure, refined with the Rietveld and pair distribution function methods, is consistent with reports in the literature.


2014 - Mg-phosphate ceramics produced from the product of thermal transformation of cement-asbestos [Articolo su rivista]
Perez-Estebanez, M.; Macova, P.; Sasek, P.; Viani, A.; Gualtieri, A.
abstract

According to recent European directives, the need for environmentally friendly alternative solutions to landfill disposal of hazardous wastes, such as asbestos-containing materials, prompts their recycling as secondary raw materials. In this work, magnesium phosphate ceramics were prepared using the product of inertization of cement-asbestos. Magnesium phosphate ceramics show interesting properties like good water resistance and high strength that make them attractive materials for several applications. Asbestos containing materials were mixed with magnesium carbonate and annealed at two different temperatures (1100 and 1300 °C). During thermal treatment complete destruction of asbestos minerals with their transformation into new phases, and crystallization of MgO from magnesium carbonate decomposition, occurs. Upon addition of potassium di-hydrogen phosphate and water, the magnesium oxide in the product of thermal treatment, contributes to the onset of a setting reaction whose product is magnesium potassium phosphate hydrate. The reactivity of periclase was found to be dependent on the calcination temperature. Lower reaction rates were observed for the MgO obtained at lower temperature. The setting reaction of the magnesium phosphate ceramic has been followed in time up to 6 months by means of the X-rays powder diffraction trechnique. Quantitative phase analysis was performed using the Rietveld method and both crystalline and amorphous phases were quantified. The amount of magnesium potassium phosphate was found to increase with time, and was accompained by a decrease in the amount of the amorphous fraction. This fact supports the hypothesis of the formation of an amorphous precursor of the crystalline MKP during the hydration reaction. SEM images showing elongated magnesium potassium phosphate hydrate crystals emerging from what appears as an amorphous matrix, further confirms this view. Since the mechanical properties of magnesium phosphate ceramics are known to increase with time, we can conclude that the main contribution to the development of strenght comes from the crystalline magnesium potassium phosphate hydrate. In this work, we describe a procedure for simultaneous destruction of asbestos minerals and formation of cementitious compounds, which represents a recycling opportunity for this class of hazardous wastes, bringing benefits in terms of energy requirements and preservation of natural resources in cement manufacturing.


2014 - Preparation of magnesium phosphate cement by recycling the product of thermal transformation of asbestos containing wastes [Articolo su rivista]
Viani, Alberto; Gualtieri, Alessandro
abstract

Asbestos containing wastes have been employed for the first time in the formulation of magnesium phosphate cements. Two samples were mixed with magnesium carbonate and calcined at 1100 and 1300 °C. Under these conditions, complete destruction of asbestos minerals is known to occur. The product, containing MgO, after reaction with water-soluble potassium di-hydrogen phosphate, led to the formation of hydrated phases at room temperature. Crystalline and amorphous reaction products were detected, with the latter being likely the metastable precursor of the former. Measured strengths were found to be in line with data from the literature, suggesting that this material may be used as cement. The process here described represents a viable recycling opportunity for this class of hazardous wastes. Simultaneous destruction of asbestos minerals and formation of reactive MgO during thermal treatment, bring benefits in terms of energy requirements and preservation of natural resources in cement manufacturing.


2014 - Silver-Modified Nano-titania as an Antibacterial Agent and Photocatalyst [Articolo su rivista]
Tobaldi, D. M.; Piccirillo, C.; Pullar, R. C.; Gualtieri, Alessandro; Seabra, M. P.; Castro, P. M. L.; Labrincha, J. A.
abstract

With the increasing demand for nanomaterials, it is essential that they are produced, where possible, by sustainable or “green” synthesis methods, avoiding environmentally harmful processes and solvents, with the aim of reducing the production of hazardous byproducts and wastes and minimizing environmental impact. In this work, Ag-modified titania nanoparticles (NPs) were synthesized via a green aqueous sol–gel method. The products of the synthesis were thermally treated at 450 and 600 °C, and their photocatalytic (in liquid–solid and gas–solid phases) and antibacterial properties were assessed using both UV- and visible-light exposure. The microstructure and phase composition of the prepared samples were also characterized using advanced X-ray powder diffraction methods (whole powder pattern modeling). Results showed that both the amount of Ag and the thermal treatment greatly influenced not only the phase composition and microstructure but also the functional properties of the TiO2. The increasing levels of Ag retarded the anatase-to-rutile phase transition to a greater extent, and 2 mol % was the optimum amount of Ag for methylene blue photodegradation with both UV- and visible-light irradiation. When using a UV-light source, samples showed a much greater antibacterial activity toward Escherichia coli (E. coli; Gram-negative) than methicillin-resistant Staphylococcus aureous (Gram-positive). It was observed that UV light caused a change in the oxidation state of silver, from ionic silver to metallic (Ag+ → Ag0 NPs), this being detrimental for the antibacterial activity. However, under artificial white light irradiation this did not occur and the material kept its excellent antibacterial properties (higher activity than commercial P25); because of this, it could be suitable for use in health care, helping to greatly reduce the spread of Gram-negative type bacteria such as E. coli.


2014 - The concept of 'end of waste' and recycling of hazardous materials: In depth characterization of the product of thermal transformation of cement-asbestos [Articolo su rivista]
Croce, A.; Allegrina, M.; Trivero, P.; Rinaudo, C.; Viani, A.; Pollastri, S.; Gualtieri, A. F.
abstract

Selected samples of asbestos-containing material (ACM) with different Ca/Si ratios have been treated thermally at 1200°C for 15 min to obtain an 'end of waste geo-inspired material'. Before and after treatment, micro-Raman spectroscopy allowed the investigation of both powdered and massive samples by directing the laser beam onto crystals with elongated morphology, thin fibres and the matrix. In the raw samples, chrysotile and/or crocidolite were detected. After the thermal treatment, no asbestos phases were identified in the Raman spectra collected on fibrous or fibre-like morphologies. The scanning electron microscopy/energy dispersive spectroscopy investigations confirmed the onset of a pseudomorphic process during annealing, leading to the complete transformation of asbestos minerals into non-hazardous magnesium or calcium magnesium silicates such as forsterite, monticellite, åkermanite and merwinite. The identification of such mineral assemblages was inspired by the close inspection of a natural counterpart, the high-temperature contact metamorphic imprint due to the intrusion of a sill into carbonate rocks. The process turned out to occur largely at the solid state and involved substantial mobilization of Ca and Mg to form a spinel phase (namely MgFe2O4) which was recognized in the matrix and within, or close to elongated morphologies.


2014 - The zeta potential of mineral fibres [Articolo su rivista]
Pollastri, Simone; Gualtieri, Alessandro; Gualtieri, Eva Magdalena; Hanuskova, Miriam; Cavallo, Alessandro; Gaudino, Giovanni
abstract

For the first time, the zeta (ξ) potential of pathogenic mineral fibres (chrysotiles, amphiboles and erionite) was systematically investigated to shed light on the relationship between surface reactivity and fibre pathogenicity. A general model explaining the zeta potential of chrysotile, amphiboles and erionite has been postulated. In double distilled water, chrysotiles showed positive values while crocidolite and erionite showed negative values. In contact with organic solutions, all fibres exhibited negative values of zeta potential. The decrease of the surface potential is deemed to be a defensive chemical response of the macrophage cells to minimize hemolytic damage. Negatively charged surfaces favour the binding of collagen and redox activated Fe-rich proteins, to form the so-called asbestos bodies and prompt the formation of HO via the reaction with peroxide (H2O2+e(-)→HO+HO(-)). An additional mechanism accounting for higher carcinogenicity is possibly related to the Ca(2+) sequestration by the fibres with surface negative potential, impairing the mitochondrial apoptotic pathway. It was also found that with a negative zeta potential, the attractive forces prevailed over repulsions and favoured processes such as agglomeration responsible of a tumorigenic chronic inflammation.


2014 - Transformations through pseudomorphosis of asbestos minerals in thermally processed asbestos-containing materials investigated through SEM/EDS and micro-Raman spectroscopy: implications for recycling of hazardous wastes [Abstract in Atti di Convegno]
Viani, A; Gualtieri, Af; Macova, P; Pollastri, S
abstract

Asbestos-containing materials, extensively used in the past in many European countries, are now considered hazardous wastes of great concern. It has been proved that inertization can be obtained via thermal treatment above 1100 °C. This solution relies upon the scientific evidence that all asbestos minerals at high temperature transform into stable crystalline silicates via a solid state recrystallization process [1]. Asbestos fibres preserve the same external crystal habit although a complete modification of the structure at a molecular scale occurred. This phenomenon is called pseudomorphosis. With increasing the temperature of the thermal treatment above 650-750 °C, the transformation sequence of chrysotile asbestos predicts the crystallization of forsterite (Mg2SiO4) and enstatite (MgSiO3 ) [1]. In a system high in Ca, such as cement-asbestos, crystallization of cement phases such as larnite (Ca2SiO4), ferrite (ideally Ca4Al2Fe2O10), and Al-,Ca-,Mg-rich silicates, such as akermanite (ideally Ca2MgSi2O7) and merwinite (ideally Ca3MgSi2O8), occurs. In this work, analytical and spectroscopic techniques coupled with microscopy allowed for the study of individual residual pseudo-morphosed fibre bundles, in cement-asbestos samples heat treated at 1200 °C. Phases detected were mainly monticellite (CaMgSiO4) or akermanite. They likely formed through the reactions: CaO + MgSiO3 (en) -&gt; CaMgSiO4 (mtc), and CaMgSiO4 (mtc) + CaO + SiO2 -&gt; Ca2MgSiO7 (ake). This suggests that, although transformation reactions occurred largely at the solid state, a substantial mobilisation of Ca and Mg resulted. Such a process is essential for the attainment of the bulk mineralogical composition predicted by the phase diagrams in the system CaO-MgO-SiO2 [2]; however, because of crystallization under non equilibrium conditions, departures from the expected bulk phase composition are still observed. This study contributes to the definition of factors conditioning the recycling of transformed cement-asbestos as secondary raw material [2-3].


2013 - Anisotropy of green stoneware evaluated by ultrasound measurements in combination with texture analyses [Articolo su rivista]
Romagnoli, Marcello; Gualtieri, Eva Magdalena; Gualtieri, Alessandro; Reimondas, Šliteris; Rymantas, Kažys; Giuliano, Tari
abstract

Anisotropic microstructure of uniaxially pressed powders has been reported in the literature, and is often reflected in direction-dependent physical properties such as thermal conductivity and firing shrinkage. Quantification of direction-dependency could be an important tool to predict such physical variations. For the first time, an ultrasound technique in combination with a microstructural investigation were applied to access anisotropy in green uniaxially pressed stoneware tiles. The longitudinal ultrasound wave velocity was measured parallel and perpendicular to the pressing direction. The sample microstructure was investigated by scanning electron microscopy, porosimetry and X-ray powder diffraction analyses in combination with crystallographic texture analyses using the Rietveld method. It was found that the anisotropic character, quantified as the ratio between the velocities measured perpendicular and parallel to the pressing direction, increased with increasing compact density. Based on the microstructure analyses, these results were attributed to texture of the porous structure as well as the constituting minerals.


2013 - Crystal chemistry of cement-asbestos [Articolo su rivista]
Viani, A.; Gualtieri, Alessandro; Secco, M.; Peruzzo, L.; Artioli, G.; Cruciani, G.
abstract

A study of a representative number of cement-asbestos (CA) samples removed from different localities in Italy has been accomplished with a combination of analytical techniques, including XRF, XRPD, SEM/EDS, micro-Raman, and electron backscattered diffraction (EBSD), to elucidate the mineralogical and chemical variability of this class of building materials on a large scale. We describe a complex mineralogy including phases of cement hydration, residual non-hydrated components, and a relevant fraction attributed to various processes of deterioration. With the aid of the CaO-MgO-SiO2 compositional diagram, three groups of CAs have been identified on the basis of their chemical parameters. This result is important for environmental and waste management issues.


2013 - Crystal chemistry of the high temperature product of transformation of cement-asbestos [Articolo su rivista]
Viani, Alberto; Gualtieri, Alessandro; Pollastri, Simone; Rinaudo, Caterina; Croce, Alessandro; Urso, Giancarlo
abstract

In this work, the high-temperature inertization product of a representative batch of samples of cement-asbestos (CA) from different localities in Italy have been characterized with a multidisciplinary approach. All the raw CA samples were heated at 1200°C for 15 min. After firing, they underwent a series of solid state reactions leading to global structural changes of the matrix. Effects of annealing time and temperature on the crystallization kinetics were thoroughly investigated. Both factors acted in favour of equilibrium. Three classes of CA were identified with the aid of phase diagrams and of specific plots relating chemical and mineralogical parameters. This result was considered of importance in view of the potential use of transformed cement-asbestos as a secondary raw material. In principle, the content of CA packages removed from the environment and their corresponding heat-treated products can be classified simply using XRF. This method allows for the selection of appropriate fractions in function of the most suitable recycling solution adopted. Samples belonging to the class called larnite-rich, turned out to be of great interest as possible candidate for substituting a fraction of cement in many building materials and innovative green cement productions.


2013 - Mechanism of lustre formation in scheelite-based glazes [Articolo su rivista]
Gualtieri, Alessandro; Canovi, Lorenzo; Viani, Alberto; Bertocchi, Paolo; Corradini, Cecilia; Gualtieri, Eva Magdalena; Gazzadi, gian carlo; Zapparoli, Mauro; Berthier, Serge
abstract

This work elucidates the mechanism responsible for the lustre effect of scheelite-based glazes for single-firing wall tiles. The surface decoration is obtained with a thin film composed of a Si–Ca–Zn–Al–K–B frit and 10 wt% WO3 on zircon-engobed substrates for single-firing wall tiles (maximum temperature of 1130 °C for 50 min). The observed lustre effect is sub-adamantine and pearlescent. It is sub-adamantine because scheelite nanocrystals at the surface, with a relatively high refractive index (n = 1.93), cause considerable reflection of light. The lustre is also weakly pearlescent because the nano-crystals oriented with the (004) plane parallel to the surface give interference with the underlying glassy layer (n ≈ 1.5), where randomly dispersed scheelite crystals occur. This model apparently applies to the glazes decorated with ceria, although the latter exhibits iridescence due to the high refractive index of ceria (n = 2.05) which yields stronger interference effect with the underlying glassy substrate.


2013 - Phase composition, crystal structure and microstructure of silver and tungsten doped TiO2 nanopowders with tuneable photochromic behaviour [Articolo su rivista]
Tobaldi, D. M.; Pullar, R. C.; Gualtieri, Alessandro; Seabra, M. P.; Labrincha, J. A.
abstract

Titanium dioxide exists in a large number of polymorphs, the most common ones being, in order of abundance, rutile, anatase and brookite. Recently, there has been an increasing degree of attention on TiO2, due to its photocatalytic and antibacterial properties. In this work, titania nanopowders synthesized via an aqueous sol–gel method were modified with silver and/or tungsten, with potential application as photocatalysts and antibacterial agents. The dried gels were thermally treated at two temperatures, and the occurrence of amorphous phase—in both dried and calcined gels—was obtained using the Rietveld method. In powders calcined at 600 °C, the crystal structure of rutile was determined with the Rietveld method on the full profile fitting of the X-ray powder diffraction patterns, while microstructural information was achieved by means of Williamson–Hall plots and line broadening analysis methods. The photochromic property of the Ag and W/Ag modified samples—when subjected to both UV- and visible-light irradiation and for different time exposures—was also investigated via UV–Vis spectroscopy. Powders were shown to possess a tuneable photochromism due to the surface plasmon resonance of the added silver, depending on the firing temperature, light (and time) exposure, and on whether or not tungsten was present in the nanopowders.


2013 - Preliminary results of the spectroscopic and structural characterization of mesothelioma inducing crocidolite fibers injected in mice [Articolo su rivista]
Gualtieri, Alessandro; C., Giacobbe; C., Rinaudo; A., Croce; M., Allegrina; G., Gaudino; H., Yang; M, Carbone
abstract

To investigate the structure and microstructure changes of crocidolite asbestos incorporated in biological tissues, fibers of this mineral phase were injected in mice peritoneum. Histological sections of different organs of mice developing mesothelioma after crocidolite inoculation were prepared and analysed by optical microscopy. The tumours developed within the peritoneal cavity, wrapped around the surrounding organs. Many fibres were observed in the fibrotic areas of the peritoneum lining pancreas and spleen. The raw fibers before inoculation and those embedded in mice tissues were characterized using Micro-Raman spectroscopy and in situ synchrotron X-ray diffraction at ESRF- Grenoble. Preliminary results indicate shifts of some bands on the Raman spectra and enlargement of the X-Ray diffraction peaks of the fibers localized in the mice tissue sections. A preliminary structural picture of the fibers incorporated in mice tissues suggests inter-crystalline migration of the iron and sodium ions.


2013 - Recycling asbestos containing material (ACM) from construction and demolition waste (CDW) [Capitolo/Saggio]
Gualtieri, Alessandro
abstract

Asbestos containing materials (ACMs) are a class of hazardous waste ...


2013 - Recycling the product of thermal transformation of cement-asbestos for the preparation of calcium sulfoaluminate clinker [Articolo su rivista]
Viani, Alberto; Gualtieri, Alessandro
abstract

According to recent resolutions of the European Parliament (2012/2065(INI)), the need for environmentally friendly alternative solutions to landfill disposal of hazardous wastes, such as asbestos-containing materials, prompts their recycling as secondary raw materials (end of waste concept). In this respect, for the first time, we report the recycling of the high temperature product of cement-asbestos, in the formulation of calcium sulfoaluminate cement clinkers (novel cementitious binders designed to reduce CO₂ emissions), as a continuation of a previous work on their systematic characterization. Up to 29 wt% of the secondary raw material was successfully introduced into the raw mix. Different clinker samples were obtained at 1250 °C and 1300 °C, reproducing the phase composition of industrial analogues. As an alternative source of Ca and Si, this secondary raw material allows for a reduction of the CO₂ emissions in cement production, mitigating the ecological impact of cement manufacturing, and reducing the need for natural resources.


2013 - Sol–gel synthesis, characterisation and photocatalytic activity of pure, W-, Ag- and W/Ag co-doped TiO2 nanopowders [Articolo su rivista]
Tobaldi, D. M.; Pullar, R. C.; Gualtieri, Alessandro; Seabra, M. P.; Labrincha, J. A.
abstract

Tungsten, silver and tungsten/silver co-doped titania nanopowders were synthesised via an aqueous sol–gel method. The size distribution and zeta potential of the starting sols were determined via photon correlation spectroscopy (PCS). The dried gels were thermally treated at two different temperatures, and the occurrence of amorphous phase was assessed using the combined Rietveld–RIR X-ray powder diffraction method. A systematic study of the optical properties of the powders was made with diffuse reflectance spectroscopy (DRS), and the energy band gaps were calculated using the differential reflectance method; while their morphology was investigated using electron microscopy analysis (TEM). The photocatalytic activity of the samples was assessed in liquid–solid phase, under UVA-light and visible-light irradiation, monitoring the degradation of an organic dye. The influence of the phase composition, optical properties, dimensions, and specific surface area of the powders on the photocatalytic activity was thoroughly discussed.


2013 - THE CONCEPT OF END OF WASTE IN VIEW OF DEVELOPING SUSTAINABLE SECONDARY RAW MATERIALS [Abstract in Atti di Convegno]
Gualtieri, Af; Viani, A; Pollastri, S
abstract

The concept of end of waste, adopted by the European Commission on December 2005, regards under which conditions a waste could cease to be waste and could be regarded as a non-waste material. This is a revolutionary way to think of wastes not just as refuse to be dismissed but as secondary raw material to be exploited, with an enormous social and economic impact. In this scenario, the creativity of materialsscientists is highly stimulated and the key to success is the development of innovative and sustainable means to transform a waste into a secondary raw material of potential economic value. To this aim, stimulus comes from the so called geo-inspiring materials. This contribution presents the results of a long-term project aimed to recycle asbestos containing materials (ACMs), into secondary raw materials for various industrial applications. The high temperature product of transformation of ACM can be successfully recycled in clay bricks, rock-wool, glass–ceramics, ceramic pigments[1], geopolymers [2], concrete [3], and recently also for innovative formulations of calcium sulfoaluminate cement clinkers [4 ] and magnesium phosphate cements [5].


2013 - The thermal stability of sideronatrite and its decomposition products in the system Na2O–Fe2O3–SO2–H2O [Articolo su rivista]
Ventruti, Gennaro; Scordari, Fernando; Ventura, Giancarlo Della; Bellatreccia, Fabio; Gualtieri, Alessandro; Lausi, Andrea
abstract

The thermal stability of sideronatrite, ideally Na2Fe3+(SO4)2(OH)·3(H2O), and its decomposition products were investigated by combining thermogravimetric and differential thermal analysis, in situ high-temperature X-ray powder diffraction (HT-XRPD) and Fourier transform infrared spectroscopy (HT-FTIR). The data show that for increasing temperature there are four main dehydration/transformation steps in sideronatrite: (a) between 30 and 40 °C sideronatrite transforms into metasideronatrite after the loss of two water molecules; both XRD and FTIR suggest that this transformation occurs via minor adjustments in the building block. (b) between 120 and 300 °C metasideronatrite transforms into metasideronatrite II, a still poorly characterized phase with possible orthorhombic symmetry, consequently to the loss of an additional water molecule; X-ray diffraction data suggest that metasideronatrite disappears from the assemblage above 175 °C. (c) between 315 and 415 °C metasideronatrite II transforms into the anhydrous Na3Fe(SO4)3 compound. This step occurs via the loss of hydroxyl groups that involves the breakdown of the [Fe3+(SO4)2(OH)] ∞ 2− chains and the formation of an intermediate transient amorphous phase precursor of Na3Fe(SO4)3. (d) for T > 500 °C, the Na3Fe(SO4)3 compound is replaced by the Na-sulfate thenardite, Na2SO4, plus Fe-oxides, according to the Na3Fe3+(SO4)3 → 3/2 Na2(SO4) + 1/2 Fe2O3 + SOx reaction products. The Na–Fe sulfate disappears around 540 °C. For higher temperatures, the Na-sulfates decomposes and only hematite survives in the final product. The understanding of the thermal behavior of minerals such as sideronatrite and related sulfates is important both from an environmental point of view, due to the presence of these phases in evaporitic deposits, soils and sediments including extraterrestrial occurrences, and from the technological point of view, due to the use of these materials in many industrial applications.


2013 - To Teach is To Learn: High-School Students, Local University and Informal Science Educators Collaborate in Communicating Science to the Public [Articolo su rivista]
Padovani, Veronica; Buckler, Carlyn S.; Gualtieri, Alessandro; Vescogni, Alessandro
abstract

Background: Informal education, especially if in collaboration with formal education, can be an important vehicle for communicating current research in science to the public as well as significant in drawing the young nearer to science and helping them to understand the inherent processes. Methods: In this paper we describe an international collaboration between a group of high-school students in Italy and Earth scientists and museum professionals from Italy and the US to plan and implement a scientific exhibition on symmetry, a topic chosen because of its connections to both Earth science and evolution. Results: By directly involving the high-school students in the design and implementation of the exhibition, they were given ownership of the project as well as ‘hands-on’ experience of communicating science to the public. The students involved helped design the content and layout of the exhibition, as well as with the design and fabrication of exhibition elements, marketing of the exhibition and evaluation. The design allowed the project manager to collect input from the students on how to make exhibitions more ‘user friendly’ to their age demographic, as well as to children and young adults in general. Although more research on similar projects is needed, evaluation results from this project showed that the response of the students - and of visitors - to the exhibition was significantly positive, and suggest that the project was engaging, cost effective and easy to implement. Conclusions: This project may serve as a template for other formal and informal educators to develop these types of collaborations, using informal science education as a bridge to link science researchers and middle- and high-school students in creating an environment where students learn through actively participating in the public communication of science.


2012 - CRYSTAL CHEMISTRY OF CEMENT-ASBESTOS AND ITS HIGH TEMPERATURE PRODUCTS [Abstract in Atti di Convegno]
Viani, A; Gualtieri, Af; Pollastri, S; Rinaudo, C; Croce, A; Cruciani, G
abstract

Asbestos-containing materials (ACM) are an example of hazardous waste which has become matter of greatconcern due to its widespread diffusion. Cement asbestos (CA) are the most represented ACM. Recently, anindustrial process for the thermal destruction of CA wastes was developed [1] in compliance with the Europeandirectives and Italian legislation. Sealed packages of CA slates undergo prolonged annealing in the temperaturerange 1200-1300 C, during which both serpentine and amphibole asbestos minerals are completely transformedinto newly-formed silicates.The potential of this product as secondary raw material relies on the effectiveness and reproducibility of theinertization process at the industrial scale, and on the choice of suitable recycling solutions. At the scope, is of greatinterest to investigate how the high temperature transformed product is affected by the chemistry and mineralogyof the starting CA material. Literature data on CA slates are scarce and incomplete, and a comprehensive picturewith emphasis on areal distribution and compositional variability at a large scale is lacking.In this work, 27 CA samples coming from different localities in Italy, and their high-temperature inertizationproducts were characterized with a combination of analytical techniques, including XRF, XRPD, SEM/EDS, FTIRand micro-Raman. Raw materials revealed a complex mineralogy comprising cement hydrated phases, a residualnon-hydrated component, and a relevant fraction attributable to various processes of alteration. The industrialinertization process was reproduced at the laboratory scale by heat treating small chunks of cement-asbestosat 1200 C. A series of solid state reactions leading to global structural changes of the matrix with completetransformation of asbestos minerals was observed. Chemical gradients due to limited ionic diffusion testifiedrecrystallization under non-equilibrium conditions. This didn’t prevented the use of the CaO-SiO2-MgO phasediagram in order to relate the mineralogy of thermally treated samples with their chemistry. Effects of annealingtime and temperature on the crystallization kinetics were investigated with further thermal treatments. With theaid of thermodynamic calculations both factors were considered to act in favour of equilibrium. Three classes ofheat-treated CA, showing distinct chemical and mineralogical fingerprints, were identified. XRF data allow forthe content of CA packages, and thus, the corresponding heat-treated products, to be quickly classified. Analysescould be carried out indifferently before or after the thermal treatment. This result is of importance in view of thepotential recycling applications. Classes of transformed product can be selected and eventually mixed in functionof the solution adopted. This is the case of larnite-rich products, already recognized as larnite-rich cements highin magnesium, potential constituent of green cements, and tested as substitute for cement in commercial concrete[2].


2012 - Full quantitative phase analysis of hydrated lime using the Rietveld method [Articolo su rivista]
Gualtieri, Eva Magdalena; Romagnoli, Marcello; Miselli, Paola; Cannio, Maria; Gualtieri, Alessandro
abstract

Full quantitative phase analysis (FQPA) using X-ray powder diffraction and Rietveld refinements is a well-established method for the characterization of various hydraulic binders such as Portland cement and hydraulic limes. In this paper, the Rietveld method is applied to hydrated lime, a non-hydraulic traditional binder. The potential presence of an amorphous phase in this material is generally ignored. Both synchrotron radiation and a conventional X-ray source were used for data collection. The applicability of the developed control file for the Rietveld refinements was investigated using samples spiked with glass. The results were cross-checked by other independent methods such as thermal and chemical analyses. The sample microstructure was observed by transmission electron microscopy. It was found that the consistency between the different methods was satisfactory, supporting the validity of FQPA for this material. For the samples studied in this work, the amount of amorphous material was in the range 2–15 wt.%.


2012 - HIGH TEMPERATURE REACTIONS OF SERPENTINE GROUP MINERALS [Abstract in Atti di Convegno]
Giacobbe, C; Gualtieri, Af; Viani, A
abstract

Serpentine minerals are important components of the oceanic crust and play a chief role in lithosphere dynamics; for this reason, their structural and mineralogical modification with temperature have major implications(e.g.,Ulmer and Trommsdorff 1995; Escartin et al. 2001;). Despite the huge amount of work devoted to the temperature-induced dehydroxylation and recrystallization reactions of serpentine minerals in air at ambient pressure, several issues are still open to debate: the nature and stability of amorphous dehydroxylate phases, thenature and stability field of talc- and chlorite-like phases possibly appearing during the reaction path, possible topotactic relationships between the serpentine and newly formed phases forsterite and enstatite, the nature of the pyroxene phase, and a comprehensive model based on kinetic parameters is still missing. The thermaltransformation, stability field, and reaction kinetics of serpentine minerals antigorite, chrysotile, and lizardite havebeen studied to draw a comprehensive model for their dehydroxylation and recrystallization reactions. In situ Xray powder diffraction (XRPD) and kinetic studies were combined with transmission electron microscopy (TEM)observations to describe the mechanisms of dehydroxylation and later high-temperature crystallization.It was found that the three serpentine polymorphs decompose at different temperatures. Chrysotile is stable upto 750 C, lizardite up to 775 C and antigorite decomposes at 800 C. During dehydroxylation, a metastable transition phase with a characteristic peak around 9 Å was observed in antigorite and, to a minor extent, in lizardite (Gualtieri et al. 2012). Rietveld refinements confirmed that the 9 Å phase actually possesses a talc-like structure. It was found that when the heating rate is fast (that is &gt; 30 C/min), the talc-like phase is not observed.When the heating rate is slower (&lt; 30 C/min), the talc-like phase is observed. Regardless the rate of heating,talc is never observed in chrysotile indicating both a crystal chemical (thermodynamic) and kinetic control of the reaction. The kinetic parameters and reaction mechanism for lizardite and antigorite dehydroxylation in air at ambient pressure were calculated using the Avrami models and compared to those of chrysotile. For both lizardite and antigorite, the kinetics of dehydroxylation is controlled by diffusion. Apparent activation energy of the reaction in the temperature range 612–708 C was 184, 221 and 255 kJ/mol for chrysotile, lizardite and antigorite,respectively. The reaction sequences of chrysotile, lizardite, and antigorite leading to the formation of stable high-temperature products (i.e. forsterite and enstatite) are described taking into account previous topotactic and dissolution-recrystallization models.


2012 - In vitro biodurability of the product of thermal transformation of cement–asbestos [Articolo su rivista]
Gualtieri, Alessandro; Alberto, Viani; Giulia, Sgarbi; Lusvardi, Gigliola
abstract

To safely recycle the product of the thermal transformation of cement–asbestos as secondary raw material,its toxicity potential should be assessed by in vitro biodurability tests. In this work, the acellularin vitro biodurability of the products of transformation of cement–asbestos at 1200 ◦C (named KRY·AS)was tested using both inorganic and organic simulated lung fluids at pH 4.5. The dissolution kineticswere followed using chemical, mineralogical and microstructural analyses. The total dissolution timeestimated from the experiments with inorganic HCl diluted solution is one order of magnitude higherthan that determined from the experiments with buffered Gamble solution (253 days vs. 20 days). Thekey parameter determining the difference in dissolution rate turns out to be the solidus/liquidus ratiowhich prompts a fast saturation of the solution with monosilicic acid. The calculated dissolution rateconstants showed that the biodurability in vitro of KRY·AS is much lower with respect to that of standardchrysotile asbestos (total estimated dissolution time of 20 days vs. 298 days, respectively). This proves alow potential toxicity of this secondary raw material.


2012 - Mineral fibrebased building materials and their health hazards [Capitolo/Saggio]
Gualtieri, Alessandro
abstract

Asbestos minerals have always been considered somehow magic ...


2012 - Mineralogical and Optical Characterization of SiO2-, N-, and SiO2/N-Co-Doped Titania Nanopowders [Articolo su rivista]
Tobaldi, David M.; Gao, Lian; Gualtieri, Alessandro; Škapin, Andrijana Sever; Tucci, Antonella; Giacobbe, Carlotta
abstract

Silica, nitrogen, and nitrogen-plus-silica co-doped titania powders were synthesized via sol–gel method. The products of the synthesis were thermally treated in air and under ammonia flow. The determination of Si and/or N into the TiO2 lattice, and the doped samples' crystal structure, was made by means of X-ray powder diffraction, whilst the occurrence of amorphous phase was obtained using the combined Rietveld-RIR method. The optical properties of the powders were obtained by diffuse reflectance spectroscopy and their energy band gaps were calculated using the differential reflectance method. The photocatalytic activity of the doped samples was assessed in gas phase under UV-light and visible-light irradiation, monitoring the degradation of an organic compound. In addition, the morphology of the samples was further on characterized by means of HRTEM. Nitrogen, silica, and co-doping shifted the anatase-to-rutile (A [RIGHTWARDS ARROW] R) phase transition toward higher temperatures. Silica was found to enter the anatase lattice, and nitrogen was presumed to enter the titania crystal structure as well. Nitrogen doping and SiO2/N-co-doping shifted the light absorption toward the visible region.


2012 - Recycling of the product of thermal inertization of cement-asbestos in geopolymers [Articolo su rivista]
Gualtieri, Alessandro; Veratti, Linda; Tucci, Antonella; Esposito, Leonardo
abstract

Recycling of secondary raw materials has become a priority of waste handling in the worldwide environmental agenda. A novel secondary raw material of great importance is the product of the thermal transformation of cement-asbestos, which is chemically comparable to a Mg-rich clinker. Recently, this secondary raw material called KRY•AS has been successfully used for the production of concrete. In this work it has been used for the production of geopolymers. Geopolymers represent a class of synthetic alumino-silicate based materials potentially used in several industrial fields, and in particular in substitution of cements or mortars, with the positive advantage of reducing the emissions of carbon dioxide developed during the clinkering phase. Geopolymers are the result of a reaction of an alumino-silicate, usually metakaolinite, activated with an alkaline silicate solution at room temperature. In the present work, geopolymers obtained from alumino-silicate natural materials mixed with KRY•AS were prepared and characterized. The composition with 2.5 wt.% of KRY•AS presents the best physical and mechanical properties. The presence of KRY•AS introduces about 30 wt.% of amorphous phase in the system. The crystalline component of KRY•AS decomposes in strong basic conditions releasing elements such as calcium and silicon that promote the formation of calcium precipitates and/or minor paracrystalline silicate hydrates. These are responsible for the improved technological performances.


2012 - Symmetria frammenti di armonia universale [Monografia/Trattato scientifico]
Gualtieri, Alessandro; Padovani, VERONICA editori; autori capitoli: R., Bertolani; A. I., Telloni; A. F., Gualtieri; V., Padovani; F., Catellani Degani; C., Jacoboni; A., Forni; A., Vescogni; A., Chiesi; R., Mattioli; B., Salvarani
abstract

non diponibile


2012 - The dehydroxylation of serpentine group minerals [Articolo su rivista]
Gualtieri, Alessandro; Giacobbe, Carlotta; Viti, C.
abstract

The thermal transformation, stability field, and reaction kinetics of serpentine minerals (antigorite, chrysotile, and lizardite) have been studied to draw a comprehensive model for their dehydroxylation and recrystallization reactions. In situ X-ray powder diffraction (XRPD) and kinetic studies were combined with transmission electron microscopy (TEM) observations to describe the mechanisms of dehydroxylation and later high-temperature crystallization. During dehydroxylation, a metastable transition phase with a characteristic peak around 9 Å was observed in antigorite and, to a minor extent, in lizardite. Rietveld refinements confirmed that the 9 Å phase actually possesses a talc-like structure. The appearance of this phase is controlled by structure and kinetic factors. The kinetic parameters and reaction mechanism for lizardite and antigorite dehydroxylation in air at ambient pressure were calculated using the Avrami models and compared to those of chrysotile. For both lizardite and antigorite, the kinetics of dehydroxylation is controlled by diffusion. Apparent activation energy of the reaction in the temperature range 612–708 °C was 221 and 255 kJ/mol for lizardite and antigorite, respectively. The reaction sequences of chrysotile, lizardite, and antigorite leading to the formation of stable high-temperature products (i.e., forsterite and enstatite) are described taking into account previous topotactic and dissolution-recrystallization models.


2011 - Crystal structure of Na3Fe(SO4)3: a high-temperature product (ca. 400 °C) of sideronatrite [Na3Fe(SO4)2OH•3H2O]. [Articolo su rivista]
F., Scordari; G., Ventruti; Gualtieri, Alessandro; A., Lausi
abstract

The iron sulfate Na3Fe(SO4)3 studied here has been obtained as a high-temperature (HT) product (∼400 °C) from the thermal decomposition of sideronatrite from Sierra Gorda (Chile) having compositionNa2Fe(SO4)2(OH)⋅3H2O. The structure determination was carried out using synchrotron X‑ray powder diffraction. Structural data refined by the Rietveld method, up to Rp = 11.95%, are: space group R3, lattice parameters a = b = 13.6231(1) Å and c = 9.0698(1) Å, V = 1457.76(2) Å3, and Z = 6. The structure of Na3Fe(SO4)3 can be described in terms of FeO6 octahedra connected to sulfate tetrahedra by corner-sharing to form infinite chains [Fe(SO4)3]∞, running along c. These chains are joined together by Na atoms to build up a three-dimensional network of strong (Fe-O-S) and weak (Na-O) bonds. The topological relationships of Na3Fe(SO4)3 to the structure of some analog minerals are also discussed.


2011 - Influence of body composition on the technological properties and mineralogy of stoneware: A DOE and mineralogical–microstructural study [Articolo su rivista]
Gualtieri, Eva Magdalena; Romagnoli, Marcello; Gualtieri, Alessandro
abstract

This paper reports a systematic and comprehensive investigation of the effects of the starting mixture composition on the mineralogy and propertiesof porcelain stoneware tiles using mixture design and full quantitative phase analyses by the Rietveld method. Functional relationships betweenproperties and the raw material mixture proportions were obtained and related to the mineralogical composition of the fired product. Mullitecrystallisation depended on the chemical environment. Dissolved quartz mounted to 10 wt% of the dry body regardless on initial amount, indicatingsaturation of the surrounding melt. The paramount role of the amorphous content on the stoneware properties was disclosed quantitatively. Openporosity decreased with increasing amount of amorphous content, and consequently both the stain and wear resistance increased. The CIE-Labcolour parameters a* and b* increased with increased amorphous content due to interaction with surface iron in hematite. The mullite contentincreased wear resistance, thus supporting the mullite strengthening theory.


2011 - Quantitative determination of chrysotile in massive serpentinites using DTA: Implications for asbestos determinations. [Articolo su rivista]
C., Viti; C., Giacobbe; Gualtieri, Alessandro
abstract

There is increasing concern about the health hazard of asbestos from natural geologic deposits such as greenstones [natural occurring asbestos (NOA)]. Therefore, quantitative determination of the chrysotile asbestos content within massive serpentinites is a recurrent requirement of recent asbestos-inherent law regulations, due to the possible health hazard associated with the release of chrysotile fibers. Unfortunately, the obtainment of accurate and precise quantitative figures of the actual chrysotile content is strongly complicated by typical serpentinite textures, consisting of fine-to-ultrafine intergrowths of fibrous and non-fibrous serpentine minerals, often difficult to identify by conventional methods, such as X-ray diffraction or microanalytical approaches.In this paper, we propose a reliable and straightforward method for the quantitative determination of chrysotile asbestos within bulk massive serpentinites, based on thermal analysis data and, specifically, on the distinctive thermal behavior of chrysotile, lizardite, and antigorite during dehydroxylation at 500–800 °C. Deconvolution processing of DTA endothermic signals in the dehydroxylation temperaturerange revealed good linear correlation between peak area ratios and chrysotile content, for both lizardite + chrysotile and antigorite + chrysotile samples. The DTA correlation curves have been used to determine the chrysotile content in two test serpentinites, revealing surprisingly high-chrysotile content. This novel method is of vast importance as it represents one of the most promising tools for chrysotile quantitative determinations in massive serpentinites, providing unbiased and accurate responses to recent asbestos-related law requirements.


2011 - Recycling of the product of thermal inertization of cement-asbestos for the production of concrete. [Articolo su rivista]
Gualtieri, Alessandro; M., Boccaletti
abstract

A novel field of research in materials science is the recycling of secondary raw materials for constructionand building materials such as concrete. This paper describes the successful recycling of as much as20 wt% of the product of thermal transformation of cement–asbestos for the formulation of concrete.The main mineralogical phases present in the product of transformation of cement–asbestos are C2S, ferrite,and Al-, Ca-, Mg-rich silicates such as akermanite (ideally Ca2MgSi2O7) and merwinite (ideallyCa3Mg2Si2O8). The behavior of this secondary raw material, termed KRYAS, in commercial concretewas investigated using five different mixtures in which various portions (0, 5, 10, 15 and 20 wt%) ofcement were substituted by KRYAS. The results of preliminary technological tests (slump test, compressivestrength, flexural strength after 28 days, and depth of penetration of water under pressure after28 days) were discussed and interpreted with the aid of chemical, mineralogical and SEM analyses.One of the major results is that after 28 days, although all the concrete samples are invariably classifiedas ‘‘ordinary concrete’’ according to the UNI 6132 tests, those diluted with KRYAS display a lower resistanceto compression with respect to the standard. On the other hand, they recover compressive strengthand display values identical to that of the standard after 90 days. The addition of the secondary raw materialhas the effect to slow down the kinetics of setting/hardening because the main cement phase presentin KRYAS is C2S which has a slower rate of hydration with respect to C3S.


2011 - Recycling of the product of thermal inertization of cement–asbestosfor various industrial applications [Articolo su rivista]
Gualtieri, Alessandro; Giacobbe, Carlotta; Lorenza, Sardisco; Michele, Saraceno; Magdalena Lassinantti, Gualtieri; Lusvardi, Gigliola; Cinzia, Cavenati; Ivano, Zanatto
abstract

Recycling of secondary raw materials is a priority of waste handling in the countries of the Europeancommunity. A potentially important secondary raw material is the product of the thermal transformationof cement–asbestos, produced by prolonged annealing at 1200–1300C. The product is chemically comparableto a Mg-rich clinker. Previous work has assured the reliability of the transformation process. Thecurrent challenge is to find potential applications as secondary raw material. Recycling of thermally treatedasbestos-containing material (named KRY-AS) in traditional ceramics has already been studied withsuccessful results.The results presented here are the outcome of a long termed project started in 2005 and devoted to therecycling of this secondary raw materials in various industrial applications. KRY-AS can be added in medium-high percentages (10–40 wt%) to commercial mixtures for the production of clay bricks, rock-woolglasses for insulation as well as Ca-based frits and glass–ceramics for the production of ceramic tiles. Thesecondary raw material was also used for the synthesis of two ceramic pigments; a green uvarovite-basedpigment [Ca3Cr2(SiO4)3] and a pink malayaite-based pigment [Ca(Sn,Cr)SiO5]. The latter is especiallyinteresting as a substitute for cadmium-based pigments. This work also shows that KRY-AS can replacestandard fillers in polypropylene plastics without altering the properties of the final product. For eachapplication, a description and relevant results are presented and discussed.


2011 - Structural and spectroscopic characterization of anorthite synthesized from secondary raw materials [Articolo su rivista]
Gualtieri, Alessandro; Giovanni B., Andreozzi; Carlotta, Giacobbe; Lusvardi, Gigliola; Cecilia, Viti
abstract

Recycling of secondary raw materials is a priority of waste handling in the countries of theEuropean community. A virtual secondary raw material of great importance is the product ofthe thermal transformation of cement – asbestos. This work illustrates the study of calcinationproducts obtained starting from the product of the thermal transformation of cement-asbestosat 1200 °C, added to primary raw materials (kaolin, aluminum hydroxide) and boric acid asmineralizing agent. The calcination has been conducted at 1200 °C for 1 hour. Thecrystallization kinetics has been monitored using in situ high temperature X-ray powderdiffraction. The microscopic characterization of the final product of calcination has beenconducted with SEM and TEM imaging supported by X-ray microanalysis. The structurerefinement was conducted on the powder sample using the Rietveld method. The results arecompared with the spectroscopic characterization including Mössbauer and UV-Visspectroscopies. The final product of the calcination is essentially anorthite (about 89 wt%)with minor spinel (11 wt%). All experimental data converge to support the hypothesis thatthe anorthite is stoichiometric, and the small amounts of iron detected (1.32 wt%) is Fe3+hosted in the structure of spinel


2011 - The formation of talc during the dehydroxylation reaction of serpentine minerals [Articolo su rivista]
Giacobbe, C; Gualtieri, Af; Viani, A
abstract

The occurrence of talc which may form during the dehydroxylation reaction of the serpentine minerals antigorite, lizardite and chrysotile has been studied. Several experiments were carried out both ex situ and in situ in order to better understand the conditions of formation of this phase. Talc is observed as a metastable phase only during the dehydroxylation reaction of antigorite and, to a lesser extent, of lizardite. On the other hand, talc formation was not observed during the dehydroxylation reaction of chrysotile because of its corrugated unstable cylindrical lattice that readily prompts the formation of forsterite.


2010 - Biological effects and comparative cytotoxicity of thermal transformed asbestos-containing materials in a human alveolar epithelial cell line [Articolo su rivista]
Federica, Giantomassi; Gualtieri, Alessandro; Lory, Santarelli; Marco, Tomasetti; Lusvardi, Gigliola; Guendalina, Lucarini; Mario, Governa; Armanda, Pugnaloni
abstract

Asbestos fibres can be transformed into potentially non-hazardous silicates by high-temperature treatmentvia complete solid-state transformation.A549 cells were exposed to standard concentrations of raw cement asbestos (RCA), chrysotile and cement asbestos subjected to an industrial process at 1200C (Cry_1200 and KRY-AS, respectively),raw commercial grey cement (GC). Cell growth rate and viability (MTT test) were detected in vitro. RCA and KRY-AS subjected to comprehensive microstructural study by electron microscopy were furtherin vitro assayed to compare their cytotoxic potential by morphostructural studies, proliferation index (Ki-67 antigen), apoptosis induction (AO/EB staining) assays and detection of intracellular reactive oxygen species (ROS) with the fluorescent DCFA dye. More severe cytotoxic damage was induced by RCA than by KRY-AS after each incubation period. Exposure to KRY-AS and GC resulted in comparable cell growth rates and cytotoxic effects. Cells incubated with RCA showed greater apoptotic induction and ROS production and a lower cell proliferation index than those exposed to KRY-AS. Chrysotile asbestos and RCA subjected to heat treatment underwent complete microstructure transformation. The final productof heat treatment of cement asbestos, KRY-AS, was considerably more inert and had lower cytotoxic potential than the original asbestos material in all in vitro tests


2010 - Multidisciplinary geological excursion in the open-air laboratory of the Island of Malta. 11-18 November 2010. Field-Trip Guide. [Monografia/Trattato scientifico]
Soldati, Mauro; Barbieri, Massimo; S., Biolchi; Buldrini, Fabrizio; Devoto, Stefano; E., Forte; S., Furlani; Gualtieri, Alessandro; Lugli, Stefano; M., Mantovani; A., Mocnik; Padovani, Veronica; A., Pasuto; Piacentini, Daniela; Prampolini, Mariacristina; Remitti, Francesca; J., Schembri; Tonelli, Chiara; Vescogni, Alessandro
abstract

Si tratta della guida all'escursione geologica multidisciplinare tenutasi a Malta dall'11 al 18 novembre 2010, nell'ambito del progetto di internazionalizzazione dell'Università di Modena e Reggio Emilia dal titolo "Multidisciplinary research in the open-air laboratory of the island of Malta: an internazional network for landslide hazard assessment in coastal areas" (2008-2010) finanziato dalla Fondazione Cassa di Risparmio di Modena e Reggio Emilia, per i Corsi di Laurea Triennale in Scienze Geologiche e Magistrale in Scienze e Tecnologie Geologiche.


2010 - Se Plinio avesse un diffrattometro… le trasformazioni ad alta temperatura del serpentino rivelate. [Articolo su rivista]
Gualtieri, Alessandro; C., Giacobbe; M., Tonelli; C., Viti
abstract

La famiglia dei minerali del serpentino comprende principalmente il crisotilo (o amianto bianco), la lizardite e l’antigorite. Il più famoso di questi è sicuramente l’amianto bianco che grazie alle sue eccezionali proprietà è noto sin dall’antichità. Plinio il vecchio nel Naturalis Historiae (36, 139 D.C.) ne descrive la capacità di resistere al fuoco. Oggi siamo in grado di comprendere a fondo questa proprietà e definire fino a che punto la struttura molecolare è in grado di resistere al fuoco.In questo lavoro, è stato studiato il campo di stabilità in temperatura dei minerali del serpentino, i relativi prodotti di trasformazione e le cinetiche di reazione dei tre principali polimorfi per una migliore comprensione dei fenomeni petrologici e delle applicazioni in campo industriale ed ambientale.


2010 - Spectroscopic study of the product of thermal transformation of chrysotile-asbestos containing materials (ACM) [Articolo su rivista]
Giacobbe, C.; Gualtieri, A. F.; Quartieri, S.; Rinaudo, C.; Allegrina, M.; Andreozzi, G. B.
abstract

In Italy, reclamation of asbestos-containing materials (ACM) such as friable asbestos and cement-asbestos is accomplished by their removal, packaging and dumping in controlled landfills. An alternative way to landfill disposal is the thermal transformation of ACM and recycling of the transformation product as secondary raw material. The aim of this work is to integrate preliminary X-ray diffraction and microscopic investigations on the secondary raw material described earlier with a detailed study on the product of transformation at 1200 °C of friable chrysotile-asbestos and cement-asbestos, using (micro)Raman, (micro)FTIR, 57Fe Mössbauer and XANES at the Fe K-edge. Micro-Raman spectra reveal that the absorption bands generated by chrysotile are no longer present in the high-temperature products, and this is further confirmed by micro-FTIR results. In the core of the former fibres of loose chrysotile asbestos, the newly formed phases are olivine and enstatite, whereas the product of transformation of cement-asbestos is composed of olivine together with several other phases such as hematite and (Ca, Mg, Al)-silicates. The Mössbauer absorption spectra of raw chrysotile reveal that iron is contained in a paramagnetic phase (40 %) as well as in accessory magnetite (60 %). The paramagnetic contribution, attributed to chrysotile, is represented by Fe2+ (10 % of Fetot) and Fe3+ (30 % of Fe tot), both octahedrally coordinated. The spectrum of thermally treated chrysotile clearly shows that the magnetic phases are now oxidized magnetite/maghemite and hematite, and the paramagnetic contribution is quite unaltered, though likely due to the newly formed olivine. The spectrum of untreated cement-asbestos has no evidence of accessory magnetic phases and is made of Fe2+ (15 % of Fetot) and Fe3+ (85 % of Fetot), both octahedrally coordinated. In the thermally treated sample all iron is oxidized, but a phase transition occurred, because Fe 3+ is tetrahedrally coordinated. Also XANES spectra show that in all samples the dominant iron oxidation state is 3+. XANES data on standard chrysotile are compatible with the possible presence of magnetite. In the high-temperature product of cement-asbestos, the high intensity of the pre-edge peak is comparable with that of the reference compound Fe-silicalite, with ferric iron hosted in the framework. This result indicates that in this product ferric iron is likely hosted in a crystalline phase in four-fold coordination, in agreement with Mössbauer spectroscopy results. Such crystalline phase could be Fe-bearing akermanite-gehlenite. © 2010 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart.


2010 - Thermal conductivity of fired clays: Effects of mineralogical and physical properties of the raw materials [Articolo su rivista]
Gualtieri, M. L.; Gualtieri, A. F.; Gagliardi, S.; Ruffini, P.; Ferrari, R.; Hanuskova, M.
abstract

The physical, chemical and mineralogical properties of representative commercial Italian clays were investigated by X-ray powder diffraction and Rietveld refinements, laser granulometry, X-ray fluorescence spectroscopy and calcimetry. The clays were used to prepare bricks by both extrusion and uniaxial pressing. The effective thermal conductivity of the fired bricks was determined and correlated with physical and mineralogical properties of the raw materials. Unfortunately, the complex nature of the system with many influencing parameters and interactions did not allow linear correlations with single parameters. Hence, a multiple linear regression approach was attempted and a statistically valid model was built for extruded samples. Although the model cannot be regarded as conclusive, due to the system complexity and the limited number of observations, the results gave some indications regarding the role played by the raw materials properties on the effective thermal conductivity of the bricks. The pore forming effect of organic material decreases the thermal conductivity of the bricks. On the contrary, the thermal conductivity increases with decreasing particle size, possibly due to an increased sintering rate and/or improved particle packing. © 2010 Elsevier B.V.


2009 - Ambient monitoring of asbestos in selected Italian living areas [Articolo su rivista]
Gualtieri, Alessandro; Dario, Mangano; Magdalena Lassinantti, Gualtieri; Anna, Ricchi; Elisabetta, Foresti; Giorgio, Lesci; Norberto, Roveri; Mauro, Mariotti; Giovanni, Pecchini
abstract

This paper presents the results of an intensive monitoring activity of the particulate, fall-out and soil of selected living areas in Italy with the aim to detect the asbestos concentration in air and subsequent risk of exposure for the population in ambient living environments, and to assess the nature of the other mineral phases composing the particulate matrix. Some areas were sorted out because of the presence of asbestos containing materials on site whereas others were used as blank spots in the attempt to detect the background environmental concentration of asbestos in air. Because the concentration of asbestos in ambient environments is presumably very low, and it is well known that conventional low-medium flow sampling systems with filters of small diameter (25 mm) may collect only a very small fraction of particulate over a short period, for the first time here, an intense monitoring activity was conducted with a high flow sampling system. The high flow system requires the use of large cellulose filters with the advantage that, increasing the amount of collect dust, the probability to collect asbestos fibers increases. Both the protocol of monitoring and analysis are novel and prompted by the need to increase the sensitivity towards the small number of expected fibers. With this goal, the collection of fall-out samples (the particulate falling into a collector filled with distilled water during the monitoring shift) and soil samples was also accomplished. The analytical protocol of the matrix particulate included preliminary X-ray powder diffraction (XRPD), optical microscopy and quantitative electron microscopy (SEM and TEM). Correlations with climatic trends and PM10 concentration data were also attempted.The surprising outcome of this work is that, despite the nature of the investigated site, the amount of dispersed asbestos fibers is very low and invariably lower than the theoretical method detection limits of the SEM and TEM techniques for identification and counting of asbestos fibers. The results are compared to the literature data worldwide and an updated model for asbestos fibers dispersion in ambient environment is proposed.


2009 - Development of low-firing B-fluxed stoneware tiles [Articolo su rivista]
Gualtieri, A. F.
abstract

In a global period of economic recession, innovation is a key requisite to get over this critical phase and prompt an upturn in the economy. Even the market of traditional ceramics is in a stalemate and producers desperately seek for new ideas which may supersede the long-used stoneware tiles. This paper presents the full characterization of a new potential class of ceramics named low-temperature stoneware tiles, highlighting their advantages and disadvantages. The body formulation and the firing process are both covered by an Italian Patent. This innovative product exhibits technological and esthetical features analogous to those of the traditional stoneware tile bodies but is fired at a maximum temperature of 950°C, about 250°C lower than the firing temperature of stoneware tiles. This is possible thanks to the addition of a B-rich frit to the mixture composed of quartz, feldspars, and clays. The frit acts as a low-temperature flux and promotes the melting of the feldspars. Within the fired body, the residual phases are quartz and feldspars. The newly formed phases can be β-spodumene if Li is present in the frit or spinel if Mg is present in the natural materials. The best body formulations have been characterized with mineralogical, microscopic, and technological methods. The major weakness of these ceramic bodies is their unresistance to acids. The chemical nature of the sintered matrix, with a high content of alkalies and B, triggers off the tendency of the ceramic body to react in contact with acidic solutions. Another penalty factor is the cost of the B-rich frit used in the formulation of the ceramic mixture which increases the overall cost of the ceramic body. © 2009 The American Ceramic Society.


2009 - In situ synchrotron powder diffraction study of the thermal decomposition of cement-asbestos: Preliminary results [Articolo su rivista]
Gualtieri, A. F.; Lassinantti Gualtieri, M.; Meneghini, C.
abstract

The elimination of asbestos-containing materials like cement-asbestos, is an environmental priority. An industrial process for the safe recovery of cement-asbestos slates was recently developed and permits the thermal transformation of asbestos fibres into non-fibrous crystalline phases in a tunnel kiln. Optimisation of the process requires knowledge of the reaction dynamics. Here, time-resolved synchrotron powder diffraction was used to follow the thermal transformation of cement-asbestos. The use of a closed capillary as sample holder allowed to closely resemble the atmospheric conditions found in the industrial reactor. In this preliminary work, we describe the reaction sequence which undergoes cementasbestos during its thermal decomposition. The excellent time resolution of the collected data allowed the observation of meta-stable phases at non-ambient conditions. © by Oldenbourg Wissenschaftsverlag, München.


2009 - The rietveld structure refinement of an exceptionally pure sample of clinoptilolite from Ecuador and its Na-, K-, and Caexchanged forms [Articolo su rivista]
Snellings, R. A.; Gualtieri, A. F.; Elsen, J.
abstract

The crystal structures of a highly pure, sedimentary clinoptilolite and the Na-, K-, and Ca-exchanged forms were refined by the Rietveld method using X-ray diffraction data collected with both conventional and synchrotron sources and different instrumental geometries. The refined structures showed that the clinoptilolite framework is not sensitive to cation exchange with Na +, K + or Ca 2+. The M1 extraframework cation site is occupied by Na, Ca, and Ba, M2 by Ca, M3 by K, and M4 by Mg. The M1 site occupancy significantly influences the configuration of extraframework water molecules. © by Oldenbourg Wissenschaftsverlag, München.


2009 - The thermal transformation of man made vitreous fibers (MMVF) and safe recycling as secondary raw materials (SRM) [Articolo su rivista]
Gualtieri, Alessandro; Foresti, E.; Lesci, I. G.; Roveri, N.; Gualtieri Lasinantti, M.; Dondi, M.; Zapparoli, M.
abstract

This work describes the high temperature reaction sequence of commercial Man Made Vitreous Fibers(MMVF) Cerafiber, Superwool, Rock wool and Glass wool which may be used as substitute for asbestosin some industrial applications. Knowledge of the reaction path and transformation sequence is veryimportant to assess whether carcinogenic crystalline phases are formed during devitrification, whichmay occur when used as insulators. In addition, knowledge about the nature of the phases formed at hightemperature is mandatory to assess if thermally transformed MMVF can be safely recycled as secondaryraw material (SRM). In this scenario, this study provides useful information for the optimization of theindustrial annealing process aimed to attain a safe, recyclable product.The results of this work show that one of the high-temperature products of Cerafiber and Superwoolis cristobalite which is classified as a carcinogenic. It was possible to define the temperature interval atwhich Cerafiber and Superwool fibers can be safely used as thermal insulators (e.g. insulators in tunneland/or roller kilns, etc.). As cristobalite is formed in both synthetic fiber products at temperatures higherthan 1200 ◦C, their use should be limited to devices operating at lower temperatures.Rock and Glass wool melt upon thermal treatment. As far as the industrial process of inertization isconcerned, a maximum firing temperature of 1100 and 600 ◦C is required to melt Rock wool and Glasswool, respectively, with the high-temperature products that can be safely recycled as SRM. Recycling ofthese products in stoneware tile mixtures were subsequently attempted. The addition of 1–2 wt.% of themelts of Rock and Glasswool gave promising results in terms of viscous sintering reactions and resistanceto staining with the only weak characteristic being the color properties of the fired bodies which tend toworsen.


2008 - A 15 anni dal bando dell’amianto in Italia. Stato dell’arte e prospettive per una soluzione dell’emergenza [Articolo su rivista]
Gualtieri, Alessandro
abstract

Siamo a 15 anni dal bando dell’amianto in Italia. In questo arco di tempo, è continuato costante il numero di decessi per malattie amianto-correlate, sviluppate soprattutto per inalazione di fibre in ambito professionale. Accorciare i tempi di questa lunga scia di morte, eliminando la coda dovuta al contributo di esposizione ambientale, dipende essenzialmente dall’efficacia delle politiche e delle azioni intraprese per fronteggiare l’emergenza. Che speranze ci sono e quali sono le soluzioni concrete per arrivare alla soluzione definitiva del problema amianto in Italia?


2008 - Annealing effects on plasma-sprayed Ni: and XRPD study [Articolo su rivista]
Gualtieri, Eva Magdalena; Gualtieri, Alessandro; Prudenziati, Maria
abstract

Plasma-sprayed alumina coatings mainly consist of γ-alumina with minor amounts of α-alumina due to incorporation of incompletely fusedpowder. The presence of amorphous materials has also been mentioned in the literature, but not quantified. In this work, X-ray powder diffractionand Rietveld refinements were explored as potential tools for the determination of the amorphous content in plasma sprayed alumina coatings. Tocross-check the accuracy of the Rietveld analysis, standard additions of amorphous alumina were performed. Both approaches provided consistentresults supporting the validity of the Rietveld method for routine quantification of the amorphous phase in plasma-sprayed alumina. For the assprayedcoatings studied in the present work, the amount of amorphous alumina was found to be 12.0±0.7 wt.%.


2008 - Direnzoite, [NaK6MgCa2(Al13Si47O120)•36H2O], a new zeolite from Massif Central (France): Description and crystal structure [Articolo su rivista]
Galli, Ermanno; Gualtieri, Alessandro
abstract

The crystal structure of direnzoite, a new natural zeolite found in the cavities of a xenolitic rock from the Massif Central (France) is reported. Apparently, direnzoite was formed throughout a process of hydrothermal crystallization within the vugs of a highly porphyric basalt. The determination of the crystal structure of this new zeolite was at the limits of the existing experimental techniques because of the paucity of available specimen, mainly composed of three tiny aggregates of fibrous microcrystals. The structure of direnzoite, solved by powder methods, was shown to be the K-dominant equivalent of the synthetic zeolite ECR-1 with a framework composed of layers of mordenite (MOR) and mazzite (MAZ) connected in a regular 1:1 stacking sequence with assigned framework topology EON. The chemical composition of direnzoite determined from the structure refinement is (Na0.94K6.62Mg1.42 Ca2.24)(Si,Al)60O120·36.8H2O. The unit cell determined from the Rietveld structure refinement is a = 7.57887(18) Å, b = 18.20098(57) Å, c = 26.15387(83) Å, and the space group is Pmmn.Six extra-framework sites and 14 water molecules were identified within the zeolite micropores. Three extra-framework sites are occupied by K+ ions. The others are occupied by Na+, Ca++, and Mg++. Although direnzoite and ECR-1 share the same framework, the distribution of their extra-framework cations is rather different. In direnzoite, there are no equivalent positions to C1, C2, and C4 positionsfound in ECR-1. Only sites C3 and C3b correspond respectively to K3 and Ca in direnzoite. In direnzoite, K1, K2, and Na correspond to water molecules sites (H2O1, H2O11, and H2O8, respectively)in ECR-1.


2008 - GEO-benessere: segreti e piaceri. Mostra, Museo Universitario “Gemma 1786”, Dipartimento di Scienze della Terra, 19-20 aprile 2008 [Esposizione]
Bertacchini, Milena; Debbi, G.; Ferraro, G.; Galli, Ermanno; Gibertini, G.; Gualtieri, Alessandro; Iannuccelli, Valentina; Padovani, Veronica; Reginelli, M.; Rossi, Antonio; Zinanni, M.
abstract

Argille, terme, fanghi e i prodotti che dall'argilla si ricavano per un benessere della persona sia fisico che psichico, hanno animato la mostra realizzata nell'ambito dell'iniziativa "GEO-benessere, approfondimenti e incontri su Geologia, Salute e Wellness", che il Museo Universitario "Gemma 1786" del Dipartimento di Scienze della Terra ha organizzato in occasione della rassegna “Musei da gustare 2008” della Provincia di Modena.Il percorso espositivo è stato realizzato in collaborazione con: Argital (Pozzallo, RG), Smalticeram Unicer (Castellarano, RE), Terme della Salvarola (Sassuolo, MO), Dipartimento di Scienze Farmaceutiche dell’Università di Modena e Reggio Emilia insieme al Gruppo Colorobbia (Sovigliana Vinci, FI).Hanno collaborato alla realizzazione delle visite guidate alla mostra alcuni studenti del Corso di Laurea in Scienze Naturali: Chiara Tonelli; e del Corso di Laurea in Scienze dei beni Culturali: Francesca Amato, Maria Elena Ansaloni, Ambra Mattioli, Eleonora Righi, Laura Rivi, Paola Santisi, Maria Lucia Scarpa.


2008 - In situ ESEM study of the thermal decomposition of chrysotile asbestos in view of safe re cycling of the transformation product [Articolo su rivista]
Gualtieri, Alessandro; Gualtieri, Eva Magdalena; M., Tonelli
abstract

The thermal transformation of asbestos into non-hazardous crystalline phases and their recycling is a promising solution for the “asbestosproblem”. The most common asbestos-containing industrial material produced worldwide is cement-asbestos. Knowledge of the kinetics ofthermal transformation of asbestos fibers in cement-asbestos is of paramount importance for the optimization of the firing process at industrialscale. Here, environmental scanning electron microscopy (ESEM) was used for the first time to follow in situ the thermal transformation ofchrysotile fibers present in cement-asbestos. It was found that the reaction kinetics of thermal transformation of chrysotile was highly slowed downin the presence of water vapor in the experimental chamber with respect to He. This was explained by chemisorbed water on the surface of thefibers which affected the dehydroxylation reaction and consequently the recrystallization into Mg-silicates. In the attempt to investigate alternativeand faster firing routes for the decomposition of asbestos, a low melting glass was mixed with cement-asbestos and studied in situ to assess towhich extent the decomposition of asbestos is favored. It was found that the addition of a low melting glass to cement-asbestos greatly improvedthe decomposition reaction and decreased the transformation temperatures.


2008 - In situ high-temperature synchrotron powder diffraction study of the thermal decomposition of cement-asbestos [Articolo su rivista]
Gualtieri, A. F.; Gualtieri, M. L.; Meneghini, C.
abstract

Time-resolved synchrotron powder diffraction was used to follow the thermal transformation of cement-asbestos. Thermal transformation of asbestos fibers into nonfibrous crystalline phases is a promising solution for the elimination of these hazardous minerals. Time resolution offered by the use of an imaging plate detector with a high-brightness X-ray source allowed for the observation of metastable phases, commonly not detectable with conventional instrumentation. In addition, the use of a closed capillary as a sample holder mimicked the real, novel industrial reactor where cement-asbestos slates are sealed in a tunnel kiln. The changing gas atmosphere in the closed system was shown to affect the final composition of the recrystallized product. This study demonstrates the importance of advanced powder diffraction techniques in this field of applied research. © 2008 International Centre for Diffraction Data.


2008 - In situ study of dehydration of ECR1: Na-as synthesized and NH4-exchanged in comparison [Relazione in Atti di Convegno]
Arletti, R.; Gualtieri, A. F.; Di Renzo, F.
abstract

The thermal behavior of Na-as synthesized and NH4 exchanged samples of ECR-1 has been studied by synchrotron radiation powder diffraction. The temperature resolved experiments were performed in capillary using a translating imaging plate system. The aim of this study is to follow in situ the dehydration mechanism of the zeolite ECR1, in its as-synthesized and NH4-exchanged form in order to determine its thermal stability and whether the structure undergoes phase transition during dehydration. The as-synthesized sample is stable up to 715°C, whereas the NH4-exchanged one is stable up to 925°C. Cell parameter refinements show a total volume decrease of 0.95% for the as-synthesized phase and of 3.82% for the NH4 form. © 2008 Elsevier B.V. All rights reserved.


2008 - In situ study of the dehydration of ECR-1: Na-as synthesized and NH4-exchanged in comparison [Relazione in Atti di Convegno]
Arletti, R.; Gualtieri, Alessandro; Di Renzo, F.
abstract

The thermal behavior of Na-as synthesized and NH4 exchanged samples of ECR-1 has been studied by synchrotron radiation powder diffraction. The temperature resolved experìments were performed in capillary using a translating imaging piate System. The aim of this study is to follow in sifu thè dehydratìon mechanism of thè zeolite ECR-1, in its as-synthesized and NH4-exchanged forni in order to determine its thermal stability and whether thè structure undergoes phase transition during dehydration. The as-synthesized sample is stable up to 715 °C, whereas the NH4-exchanged one is stable up to 925 °C. Cell parameter refinements show a total volume decrease of 0.95% for thè as-synthesized phase and of 3.82 % for thè NH4 form.


2008 - KRY•AS, materia prima secondaria dal processo di trasformazione termica del cemento-amianto: caratteristiche e proposta di riciclo nel grès porcellanato [Articolo su rivista]
Gualtieri, Alessandro; L., Veratti; C., Cavenati; I., Zanatto
abstract

Il problema amianto nel nostro paese è ancora di preoccupante attualità se si considera che a tutt'oggi in Italia sono presenti più di 2 miliardi di m2 di coperture in cemento amianto che prima o poi andranno bonificate. Grazie al D.M. 29 luglio 2004 n. 248, è possibile intravedere la soluzione definitiva al problema attraverso la trasformazione termica dei rifiuti contenenti amianto ed il successivo riciclo del prodotto di trasformazione. Le nuove normative consentono di industrializzare il processo e di realizzare un impianto di inertizzazione in grado di garantire l’effettiva trasformazione dei materiali contenenti amianto in un composto inerte e riciclabile. E’ possibile affermare che il trattamento termico ed il riciclo dell’amianto trasformato rappresentino oggi una delle frontiere di ricerca applicata più stimolanti. Se guardiamo all'amianto non più come rifiuto, ma come materia prima secondaria (M.P.S.) possiamo affermare che ve ne sia grande disponibilità: solo in regioni come l’Emilia Romagna vengono smaltite circa 9000 ton di cemento-amianto all'anno. Il prodotto della trasformazione, una materia prima secondaria inerte è assolutamente compatibile con l’ambiente e destinato al riutilizzo per diverse possibili applicazioni industriali. In questo contributo verrà descritto il riciclo del prodotto di inertizzazione del cemento-amianto, denominato KRY•AS, in sostituzione di una frazione di materie prime primarie come feldspato sodico e argilla caolinitica per la produzione di piastrelle da grès porcellanato. Lo studio è stato condotto attraverso una completa caratterizzazione chimico-fisica, mineralogica e tecnologica dei materiali di partenza e dei prodotti cotti al fine di valutare l’efficacia della sostituzione dal punto di vista tecnico ed economico.


2008 - Seeded growth of TPA-MFI films using the fluoride route [Articolo su rivista]
Gualtieri, Eva Magdalena; Gualtieri, Alessandro; Prudenziati, Maria
abstract

The fluoride route in combination with surface seeding was used for the preparation of TPA-MFI films on dense amorphous silica glass supports. The use of F− as mineralizing agent allowed the crystallization of TPA-MFI at near-neutral pH (6.7 ± 0.1). The supports were seeded with colloidal TPA-MFI crystals and hydrothermally treated in a synthesis gel at 100 °C for various durations (24–192 h). The synthesis products were characterized by scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). A film growth rate of about 9 nm/h was found. The crystals in these films exhibit a preferred orientation, with the (1 0 1) planes of the crystals parallel or near parallel to the support surface. Film growth in the near-neutral synthesis gel was also attempted on seeded porous α-alumina supports. However, epitaxial growth of the seed crystals was inhibited by the formation of a uniform layer of colloidal silica particle which covered the seed crystals even in an early stage of hydrothermal treatment. Continuous films could only be prepared by increasing the pH of the initial synthesis mixture from 6.7 to 9.6, thus using both OH− and F− as mineralizing agents. These films are composed of a columnar layer on top of a layer built up of small grains. Such microstructure has previously been reported in the literature for TPA-MFI films grown in conventional synthesis mixtures.


2008 - Structural characterization of the clay mineral illite-1M [Articolo su rivista]
Gualtieri, Alessandro; S., Ferrari; M., Leoni; G., Grathoff; R., Hugo; M., Shatnawi; G., Paglia; S., Billinge
abstract

Illite is one of the major clay minerals found on the Earth’s surface, constituent of the soils, and araw material used for a variety of industrial applications. It is an Al-K mica-like, non-expanding,dioctahedral mineral that crystallizes in the monoclinic system. Its structure is very similar to that of2:1 mica, where two tetrahedral sheets sandwich an octahedral one, to build up the T-O-T sheet. Katoms, and possibly water molecules are hosted in the interlayer region.This work presents the results of the structural characterization of illite-1M from Northern Hungarywith the first attempt to refine the structure model and locate the interlayer water molecules. Thestructural characterization was accomplished using current state of the art analytical methodsavailable for the structural characterization of clays. The results illustrate the status of techniquesfor clay structure determination, as well as a structural model for illite.A chemical formula for the illite-1M under investigation can be written as:K0.78Ca0.02Na0.02(Mg0.34Al1.69Fe’’’0.02)[Si3.35Al0.65]O10(OH)2×nH2O.Structure simulations with WILDFIRE yielded a model with 30% of cis-vacant layers andexpandability percentage of 10 %. The value of the percentage of expandability was confirmed withNEWMOD whose best simulation was obtained with 90% of di-octahedral mica, 10% ofexpandable layers, and K = 0.8 in the interlayer region. The best structure simulation obtained withDIFFaX was obtained with a population of the K atoms of 80%. To obtain the best fit, 6 cells alongc (in agreement with the results of the TEM study) and an average dimension of the particles in thea-b plane of 300 nm were used.Besides the determination of the basic structure unit (the results are consistent with those obtainedwith the local information provided by the fit of the PDF data) and the model of disorder, therefinement with DIFFaX+ made it possible attempt to locate the interlayer water molecule and torefine its site population. Although physically sound, both the observed tetrahedral layercorrugation and the location of the water molecule need further experimental support, because thefinal fit of the observed pattern is still imperfect. The reasons for this misfit are thoroughlydiscussed.


2008 - Synthesis of zeolite LTA films in the presence of nucleation suppressors [Relazione in Atti di Convegno]
Gualtieri, M. L.; Gualtieri, A. F.; Prudenziati, M.
abstract

The preparation of LTA zeolite films using seeding in combination with film growth in the presence of nucleation suppressors is presented. The films were characterized by X-ray powder diffraction and scanning electron microscopy. It was found that the films had columnar microstructure and that they were preferably oriented with the [111] direction perpendicular (and parallel) to the film surface. The development of preferred orientation was explained by the competitive growth model. © 2008 Elsevier B.V. All rights reserved.


2008 - The comparison of the crystal structures of direnzoite, a new zeolite from Massif Central (France), and its synthetic counterpart ECR-1 [Relazione in Atti di Convegno]
Gualtieri, Alessandro; E., Galli
abstract

The structures of the natural zeolite direnzoite and its synthetic counterpart ECR-1 were unravelled almost simultaneously using synchrotron powder diffraction. As a matter of fact, the structure refinement of Na-ECR-1 was crucial for the structure solution of direnzoite, which is the lastest discovered natural zeolite. The two structures are distinguished by a 1:1 polysomatic sequence of mordenite (MOR) and mazzite (MAZ) layers. Here, both the crystal structures are discussed and compared in the attempt to disclose their structure directing chemical and kinetic factors.


2008 - The transformation sequence of cement-asbestos slates up to 1200 °C and safe recycling of the reaction product in stoneware tile mixtures [Articolo su rivista]
Gualtieri, Alessandro; C., Cavenati; I., Zanatto; M., Meloni; G., Elmi; Gualtieri, Eva Magdalena
abstract

Cement–asbestos is the main asbestos containing material still found in most of the European countries such as Italy. Man- and weatheringinduceddegradation of the cement–asbestos slates makes them a source of dispersion of asbestos fibres and represents a priority cause of concern.This concern is the main prompt for the actual policy of abatement and disposal of asbestos containing materials in controlled wastes. An alternativesolution to the disposal in dumping sites is the direct temperature-induced transformation of the cement–asbestos slates into non-hazardous mineralphases. This patented process avoids the stage of mechanical milling of the material before the treatment, which improves the reactivity of thematerials but may be critical for the dispersion of asbestos fibres inworking and life environment. For the first time, this paper reports the descriptionof the reaction path taking place during the firing of cement–asbestos slates up to the complete transformation temperature, 1200 ◦C. The reactionsequence was investigated using different experimental techniques such as optical and electron microscopy, in situ and ex situ quali-quantitativeX-ray powder diffraction. The understanding of the complex reaction path is of basic importance for the optimization of industrial heating processesleading to a safe recycling of the transformed product.For the recycling of asbestos containing materials, the Italian laws require that the product of the crystal chemical transformation of asbestoscontaining materials must be entirely asbestos-free, and should not contain more than 0.1 wt% fraction of the carcinogenic substances such ascristobalite. Moreover, if fibrous phases other than asbestos (with length to diameter ratio >3) are found, they must have a geometrical diameterlarger than 3m. We have demonstrated that using an interplay of different experimental techniques, it is possible to safely verify the completetransformation of asbestos minerals in this temperature-induced process.The product of transformation of cement–asbestos (CATP) has a phase composition similar to that of a natural or a low temperature clinker withthe exception of having a larger content of aluminium, iron and magnesium. This product can be safely recycled for the production of stonewaretile mixtures. The addition of 3–5 mass% of CATP does not bear significant variations to the standard parameters of white porcelain tile mixtures.


2008 - Una soluzione tecnologica definitiva al problema amianto in italia [Articolo su rivista]
Gualtieri, Alessandro
abstract

Questo lavoro fa seguito all’articolo dal titolo A 15 anni dalbando dell’amianto in Italia. Stato dell’arte e prospettive peruna soluzione dell’emergenza apparso sul numero di aprile.L’articolo in questione presenta un quadro globale delproblema amianto e accenna alle possibilità esistenti perarrivare alla soluzione definitiva dell’emergenza in Italia. Inquesto contributo viene descritta in dettaglio una soluzionetecnologica denominata KRY•AS, alternativa all’interramentoin discarica, per la trasformazione totale dei rifiuticontenenti amianto e l’eventuale riutilizzo del prodotto ditrasformazione come materia prima seconda.


2007 - Crack formation in α-alumina supported MFI zeolite membranes studied by in situ high temperature synchrotron powder diffraction [Articolo su rivista]
Gualtieri, Eva Magdalena; C., Andersson; F., Jareman; J., Hedlund; Gualtieri, Alessandro; M., Leoni; C., Meneghini
abstract

Cracks are frequently formed in α-alumina supported MFI membranes during calcination. To better understand crack formation, in situ powder diffraction data were collected during calcination of a type of MFI membrane (ca. 1800 nm thick) which is known to crack reproducibly. In addition, data for MFI powder and a blank support were also collected. Both a synchrotron radiation facility and an in-house instrument were used. The unit cell parameters were determined with the Rietveld method, and the strain in the direction perpendicular to the film surface was calculated for the film as well as for the support. The microstrain in the support was also estimated. Based on the results obtained here, a model for crack formation in this type of MFI membrane was proposed. The lack of cracks in other types of MFI membranes (ca. 500 nm) prepared in our laboratory is also explained by the model. In thicker MFI films, the crystals are well intergrown. During heating, the MFI crystals contract and the α-alumina support expands. Consequently, a thermal stress develops in the composite which eventually leads to formation of cracks in the film and structural defects in the support. In thinner films, the crystals are less well intergrown and the thermal expansion mismatch leads to opening of grain boundaries rather than cracks.


2007 - Cronstedt’s zeolite [Articolo su rivista]
C., Colella; Gualtieri, Alessandro
abstract

Axel F. Cronstedt (1722-1765), famous Swedish mineralogist, was the first scientist to describe,250 years ago, the distinctive property of zeolites, i.e., the unique frothing characteristics whenheated in a blow-pipe flame. Cronstedt examined two specimens: one from Svappavaara inNorthern Sweden and one that was said to come generically from Iceland. From Cronstedt’sindications, the occurrence of the first specimen was near the mining area of Kiruna. Themorphological characteristics of the specimen suggested the zeolite species is stilbite which wouldmake it the first discovered zeolite mineral.This paper is devoted to the description of the structure and microstructure of that first discoverednatural zeolite from Svappavaara (Northern Sweden). The SEM investigation of all the sample rockcavities filled with the zeolite crystals and the optical observation of the separated zeolite crystalsrevealed that the sample is mainly composed of stellerite with subordinate stilbite crystals which arepresent only in a few cavities together with stellerite. The chemical formula of the stellerite crystalsderived from the EPMA and TG analyses is (Ca4.03Mg0.01Na0.03K0.11)[Si27.81Al8.19O72]×28.6H2O. Theresults of the structure refinement confirm that the investigated specimen is actually stellerite. Thestructure refinement evidenced no ordering in the tetrahedral sites. The extraframework cation Ca islocated in the centre of the main channel parallel to the a axis, on the mirror plane and issurrounded by water molecules with no contact with framework oxygen atoms. The coordination ofCa is 6-fold. A number of short water-water distances are possible by considering the differentpossible schemes around the Ca atom. Considering the short water-water distances and the partialoccupancy of water sites, a number of octahedral coordination around Ca are possible.


2007 - Crystallization Kinetics of Bioactive Glasses in the ZnO-Na2O-CaO-SiO2 System [Articolo su rivista]
Malavasi, Gianluca; Lusvardi, Gigliola; Pedone, Alfonso; Menziani, Maria Cristina; M., Dappiaggi; Gualtieri, Alessandro; Menabue, Ledi
abstract

The crystallization kinetics of Na2OâCaOâ2SiO2 (x ) 0) and 0.68ZnOâNa2OâCaOâ2SiO2 (x ) 0.68, where xis the ZnO stoichiometric coefficient in the glass formula) bioactive glasses have been studied using bothnonisothermal and isothermal methods. The results obtained from isothermal XRPD analyses have showedthat the first glass crystallizes into the isochemical Na2CaSi2O6 phase, whereas the Na2ZnSiO4 crystallinephase is obtained from the Zn-rich glass, in addition to Na2CaSi2O6. The activation energy (Ea) for thecrystallization of the Na2OâCaOâ2SiO2 glass is 193 ( 10 and 203 ( 5 kJ/mol from the isothermal in situXRPD and nonisothermal DSC experiments, respectively. The Avrami exponent n determined from theisothermal method is 1 at low temperature (530 °C), and its value increases linearly with temperature increaseup to 2 at 607 °C. For the crystallization of Na2CaSi2O6 from the Zn-containing glass, higher values of boththe crystallization temperature (667 and 661 °C) and Ea (223 ( 10 and 211 ( 5 kJ/mol) have been foundfrom the isothermal and nonisothermal methods, respectively. The Na2ZnSiO4 crystalline phase crystallizesat lower temperature with respect to Na2CaSi2O6, and the Ea value is 266 ( 20 and 245 ( 15 kJ/mol fromthe isothermal and nonisothermal methods, respectively. The results of this work show that the addition ofZn favors the crystallization from the glass at lower temperature with respect to the Zn-free glass. In fact, itcauses an increase of Ea for the Na diffusion process, determined using MD simulations, and consequentlyan overall increase of Ea for the crystallization process of Na2CaSi2O6. Our results show good agreementbetween the Ea and n values obtained with the two different methods and confirm the reliability of thenonisothermal method applied to kinetic crystallization of glassy systems. This study allows the determinationof the temperature stability field of the crystalline phases with the view of creating a different glass ceramicuseful in the field of bioactive materials.


2007 - Erratum to "Quantitative determination of the amorphous phase in plasma sprayed alumina coatings using the Rietveld method" [Surface and Coatings Technology 201 (2006) 2984-2989] (DOI:10.1016/j.surfcoat.2006.06.009) [Articolo su rivista]
Gualtieri, M. L.; Prudenziati, M.; Gualtieri, A. F.
abstract


2007 - Il monitoraggio outdoor del particolato atmosferico, con particolare attenzione all’amianto. Studio di ambienti di vita nelle Province di Bologna, Modena e Reggio Emilia [Articolo su rivista]
Gualtieri, Alessandro; D., Mangano; G., Torri; A., Ricchi; E., Foresti; G., Lesci; N., Roveri; M., Mariotti; G., Pecchini
abstract

In questo lavoro vengono riportati i principali risultati di un progetto di ricerca a lungo termine, finanziato dalla Fondazione Cassa di Risparmio di Modena, per lo studio delle fasi aerodisperse, con particolare riferimento alle fasi dell’amianto, in ambienti outdoor di vita nelle Province di Bologna, Modena e Reggio Emilia. Il monitoraggio dell’aerodisperso è stato possibile grazie ad un campionatore ad alto flusso messo a disposizione dall’A.R.P.A. di Reggio Emilia. Oltre al particolato atmosferico, per ogni stagione sono stati raccolti campioni di terreno e campioni di fall out. I siti studiati hanno natura diversa ed alcuni, come quelli industriali con coperture di cemento-amianto, possono rappresentare una minaccia per la salute dei lavoratori che abitualmente operano in prossimità della copertura.In un clima di crescente allarmismo nei confronti del problema amianto in Italia e di generale confusione nella letteratura esistente riguardo la concentrazione atmosferica di amianto, questo lavoro contribuisce a definire il reale livello di rischio di esposizione ad amianto per la cittadinanza negli ambienti di vita esterni.Inoltre, mancando riferimenti normativi sui limiti di concentrazione di fibre aerodisperse in ambiente outdoor di vita, questo contributo può essere di aiuto per definire la concentrazione ambientale media (livello di fondo) e cercare di fissarne il limite.


2007 - In situ study of dehydration of ECR-1: Na- as synthesized and NH4 exchanged in comparison [Relazione in Atti di Convegno]
Arletti, R.; GUALTIERI A., F; DI RENZO, F
abstract


2007 - Mineralogical and microstructural study of the phases developed during the hydration process of industrial cement mixtures [Capitolo/Saggio]
Lusvardi, Gigliola; Malavasi, Gianluca; Menabue, Ledi; Gualtieri, Alessandro; C., Montanari
abstract

The phases identified in two industrial cement mixtureswere qualitatively and quantitatively characterizedbefore and during their hydration process. The studywas carried out as a function of time, water/cement ratioand temperature; the characterization was performedusing XRPD (with the Rietveld method to obtainquantitative phase analysis, hereafter QPA), SEM/EDSand ESEM techniques. QPA revealed that the drymixtures have similar composition and that differ for thesource of calcium sulphates. The use of differentcalcium sulphates need different w/c ratios and givesrise to a different amounts of C6AS3H32, amorphousphase and to a different reaction rate. Results fromESEM technique agree with XRPD results and confirmthe different behaviour of the mixtures. Hightemperature reduces the difference in the reaction rate


2007 - Thermal behavior of the raw materials forming porcelain stoneware mixtures by combined optical and in situ X-Ray dilatometry [Articolo su rivista]
Gualtieri, Alessandro
abstract

The dilatometric behavior of the raw materials forming a porcelainstoneware tile mixture was investigated at a molecular/microscopical scale by combined in situ optical dilatometry andX-ray powder diffraction. Each single raw material was investigatedseparately and mixed with all the others to simulate astandard production mixture. Thus, it was possible to evaluatewhether the reaction path taking place during the firing of theraw materials is changed during the firing of the combined mixture.A general classification of the causes of contraction and/orexpansion events has been attempted. Causes are subdivided intostructural (S, intra-mineral) and microstructural (M, inter-mineral).Contractions can be generated by: loss of volatiles (S);structure collapse of the pseudo-amorphous products of dehydroxylationof clay minerals (S); solid state or viscous sintering(M); crystallization from amorphous precursor (S) and relatedvolume reduction (densification) (M); displacive phase transitionwith a volume decrease (S); and melting generally at T48001C(S). Expansion can be generated by thermal expansion (S);displacive phase transition with a volume increase (S); glasstransitions (S) and related volume change (M); and overfiring/pyroplastic deformation (M). Many reactions observed in thesingle raw materials have also been observed in the mixture. Themajor variations concern (i) crystallization of cristobalite is observedonly in the kaolin and not in the mixture, where silicasegregated from the reaction of formation of mullite from metakaoliniteis readily incorporated in the alkaline amorphousphase; (ii) quartz alone is stable with temperature but tends tobe partly decomposed in contact with the alkaline melt in themixture; and (iii) in the illite-rich clay, melting of the system andsubsequent expansion caused by pyroplastic deformation of theK-rich melt begins at relatively low temperature (11501C). Thisbehavior is not observed in the mixture below 13501C where apresumably less viscous melt is formed.


2007 - Utilizzo di cemento-amianto inertizzato termicamente per la produzione di lana di vetro e roccia [Articolo su rivista]
G., Torri; Gualtieri, Alessandro
abstract

All’interno di un progetto più ampio, in questolavoro abbiamo verificato con successo la possibilitàdi riciclare il prodotto di inertizzazione delcemento-amianto all’interno delle miscele impiegateper la produzione di materiali isolanti comelana di vetro e lana di roccia. Oltre al prodotto inertizzato,nella formulazione delle lane è statoaggiunto un feldspato di basso costo dall’Isolad’Elba ed argille rosse dell’AppenninoSettentrionale e della Sardegna.


2006 - Analytical evaluation of wastes containing asbestos after inertization treatment by pirolitic process [Relazione in Atti di Convegno]
G., Pecchini; Gualtieri, Alessandro; E., Renna; O., Sala; L., Calzavacca; T., Bacchi; F., Paoli; V., Biancolini
abstract

Wastes recovery efficiency bave been slightly improved by Decree n.248 of 29/7/2004 on" Rules on determination and disciplines of recovery activities of products and goods of asbestos and containing asbestos" by defining processes and treatment able to bring to a complete transformation of crystallochemical features of asbestos.Such treatments if properly applied allows to avoid thè disposai of wastes in dumps. They also allow thè reutilizalion of processed wastes. No adequate power plants suitable for thè mentioned treatment presently exist in Italy.Intense research activity is devoted to thè start up of pyrolitic processes applied to wastes deriving from concrete/asbestos to be reutilized in environmental recovery. Decree n.248 reports characteristics of processed material whìch must be asbestos free and accompanied by mineralogical composition of final produci.Present paper propose an analytical protocol suitable for law need and able to guarantee safety conditions of wastes after crystallochemical transformation.In order to verìfy such trans formations analytical procedures adopted in qualifìed laboratories on asbestos analysis nave been utilized. Pure chrysotile and concrete/asbestos samples have been analyzed by MOCF, DRX, SEM and FTIR after 2 hours heating at 600-700-800-900-1000 °C in muffle fornace. Some samples processed by pilot power plani by Aspireco have also been analyzed.


2006 - Asbestos monitoring in civil and industrial environments of selected Italian sites [Relazione in Atti di Convegno]
D., Mangano; Gualtieri, Alessandro; S., Ferrari; A., Ricchi; E., Foresti; G., Lesci; N., Roveri; M., Mariotti; G., Pecchini
abstract

This paper presents the results of an intensive monitoring activity of thè air, fall-out and soil of a Ceramic factory in Sassuolo (Modena, Italy) with sheds made of cement-asbestos. The monitoring protocol accomplished a 1 week long collection time performed during each season. Filters and samples of fall-out and soils were analysed with XRPD, electron and optical microscopy, and FTIR. The surprising outcome of this work is that the calculated amount of dispersed asbestos fibers is practically null with a minor concentration during thè autumn season.


2006 - Kinetics of illite dehydroxylation [Articolo su rivista]
Gualtieri, Alessandro; Ferrari, Stefano
abstract

Illite is a dioctahedral K-deficient mica with an interlayer cation content of 0.6-0.85 atoms per formula unit. 1M and 2M(1) are the illite polytypes more abundant in nature. Because illite is one of the major component of clays used for the production of traditional ceramics, the understanding of its high temperature transformations is of paramount importance for the knowledge of the structural and microstructural properties of fired ceramic products. To our knowledge, the study of the illite dehydroxylation kinetics has not been attempted to date. Hence, this work presents the investigation of the reaction mechanism of dehydroxylation of illite for the first time. The natural sample investigated in this study is a 1M-polytype from Hungary. Several classical methods of kinetic analysis were used (isoconversional method, Avrami method, direct fit with kinetic expressions, and others) to achieve a complete picture of the dehydroxylation mechanism. The proposed model for the dehydroxylation of illite is a multi-step reaction sequence with (1) condensation of the water molecule in the octahedral layer; (2) one-dimensional diffusion of the water molecules through the tetrahedral ring (rate limiting step of the reaction); (3) two-dimensional diffusion of the water molecules through the interlayer region (rate limiting step of the reaction).


2006 - Metodi di studio ed ottimizzazione utili nel processo ceramico. La previsione del ritiro ceramico ed applicazioni in campo industriale [Articolo su rivista]
Romagnoli, Marcello; T., Bellarmi; Gualtieri, Alessandro; C., Bes; S., Celestini; A., Sevagen
abstract

E' stata mostrata la possibilità di raggiungere rapidamente l'ottimizzazione di formulazioni d'impasti con evidenti vantaggi economici e qualitativi. I metodi proposti sono quelli della regressione lineare a più variabili e dell'approccio neurale. Entrambe consentono di ottenere un modello matematico col quale simulare virtualmente il comportamento del sistema in diverse condizioni. Quest'ultimo viene ottenuto utilizzando i dati storici presenti in azienda oppure da dati sperimentali. Nell'intervento è stata mostrato un esempio applicato agli impasti: ì modelli sono stati costruiti sui dati di ritiro in relazione alla composizione, espressa comepercentuale delle singole materie prime, e alla temperatura massima di cottura. I modelli sono stati testati con venti formulazioni di prova mostrando una ottima capacità predittiva. La disponibilità di softwares in grado dì eseguire i calcoli necessari e la ridotta richiesta di conoscenze matematiche rende le due metodologie di facile e rapida introduzione in ambito industriale.Based on the linear regression with variables and artificial neural network, a math. model was developed enabling the simulation of the system behavior under different conditions. Existing historical data or through test results were employed in obtaining the model. As an example, the capability of the model to predict the shrinkage in processing of ceramic materials, i.e. between the dried state and after heat treatment cycles, was shown, the compn. expressed as raw materials percentage, and max. firing temp. being taken into account. The models were tested with twenty different formulas and showed excellent predictive capacity. The availability of software packages that could perform all necessary calcns. and the little math. knowledge enabled the easy and rapid introduction of the developed model in industrial processes.


2006 - Model of structure disorder of illite: preliminary results [Articolo su rivista]
Ferrari, Simone; Gualtieri, Alessandro; Gh, Grathoff; M., Leoni
abstract

This paper presents preliminary results of the structure model of a pure illite sample from Hungary. The clay sample mined in the Tokaj region (Northern Hungary) is composed of predominating illite and minor smectite and quartz. Enrichment by sedimentation in water solvent of the illite fraction led to a nearly pure sample which was fully characterized using conventional microscopic and chemical analyses. Although, illite is a well known clay mineral used for many industrial applications (its crystallinity index is used to establish the degree of illitization in oil source rocks linked to oil generation) a structure model has never been refined to date. This is due to the fact that pure samples to be used for structure characterization are a rarity in nature and because the structure is affected by extensive planar disorder. Thus, the structural characterization of this sample is of great importance for the understanding of the structure of illite in general. The planar disorder prevents a simple structure refinement using the Rietveld method and different algorithms must be used. Here, we present the results of structure simulations of powder patterns using NEWMOD, WILDFIRE and DIFFaX, which reveal the structure features and structure model of disorder. They are a good starting point for the combined structure/microstructure refinement which will be attempted using DIFFaX(+).


2006 - Quantitative determination of the amorphous phase in plasma sprayed alumina coatings using the Rietveld method [Articolo su rivista]
Gualtieri, Eva Magdalena; Gualtieri, Alessandro; Prudenziati, Maria
abstract

Plasma-sprayed alumina coatings mainly consist of γ-alumina with minor amounts of α-alumina due to incorporation of incompletely fused powder. The presence of amorphous materials has also been mentioned in the literature, but not quantified. In this work, X-ray powder diffraction and Rietveld refinements were explored as potential tools for the determination of the amorphous content in plasma sprayed alumina coatings. To cross-check the accuracy of the Rietveld analysis, standard additions of amorphous alumina were performed. Both approaches provided consistent results supporting the validity of the Rietveld method for routine quantification of the amorphous phase in plasma-sprayed alumina. For the as-sprayed coatings studied in the present work, the amount of amorphous alumina was found to be 12.0 ± 0.7 wt.%.


2006 - Quantitative phase analysis of hydraulic limes using the Rietveld method [Articolo su rivista]
Gualtieri, Alessandro; A., Viani; C., Montanari
abstract

Quantitative phase analyses of three commercial samples of hydraulic limes have been per-formed using the Rietveld method. Although the Rietveld method has been already applied to cement analysis, we report here the first application to different classes of hydraulic binders, such as hydraulic limes (HL) and natural hydraulic limes (NHL). Unlike HL, that are simple diluted cement, NHL are specific product of great interest for its application in building restoration and conservation. Samples were also characterized by laser granulometry and chemical analysis. Thermogravimetric analysis/Differential Scanning Calorimetry (TG/DSC) and calcimetric analyses were conducted to compare the results of such well-established techniques with those obtained with the Rietveld method. Taking advantage of the Rietveld method with the addition of an internal standard, the phase fraction of all the crystalline phases as well as the amorphous component, have been accurately determined. This technique offers a valid support for the characterization of hydraulic limes in the light of the EN classification of such industrial products.


2006 - Rietveld structure refinement of NH4-exchanged natural chabazite [Articolo su rivista]
Gualtieri, Alessandro; Passaglia, Elio
abstract

In this work the results of the X-ray Rietveld structure refinement of a natural and the corresponding NH4-exchanged chabazite from Nova Scotia (Canada) are exposed. Experimental data were collected using a laboratory powder diffractometer equipped with copper tube and graphite crystal monochromator. The outcome of this crystal-structure study is useful for (i) understanding the structure modifications induced by the NH4+ exchange: (ii) understanding the physical-chemical and technological properties of NH4-chabazite, a zeolite vastly used for industrial applications, (iii) understanding the mechanism of proton conductivity of the NH4-exchanged zeolites, precursors of catalytically active H+ forms. The position and orientation of the NH4+ ion were initially refined using the rigid body model and later with the aid of soft constraints. The coordination number of the ammonium ion is 9 with two equally possible and mutually exclusive configurations. One coordination environment includes 3 oxygen atoms O3, 3 oxygen atoms O4, and 3 H2O molecules W2a. The other environment includes 3 oxygen atoms O3. 3 oxygen atoms O4, and 3 H2O molecules W3. As already shown for other NH4-zeolites, the N-O distances are larger than the N-H2O distances. The local geometry of the ammonium ion points to a monodentate configuration. A bidentate configuration of the hydrogen bonds for NH4+ is also possible if the long H2(center dot center dot center dot)O3 separation is considered to be at bond distance. For industrial and technological applications, knowledge of the local environment of NH4+ in the cavities of zeolites is important. Weak hydrogen bonds with framework oxygen atoms implies that the ammonium molecule can be easily exchanged or desorbed. This property is attractive for agronomy, horticulture and soil remediation where zeolite can be added to chemical fertilizers to improve the soil's chemical and physical properties for plant growth, to increase fertilizer efficiency and to reduce the leaching of nutrients, to reduce the dissolution rate of a soluble fertilizer via ion exchange or combination of mineral dissolution and ion exchange, and to act as remediation agents in soils.


2006 - Rietveld structure refinement of zeolite ECR-1 [Articolo su rivista]
Gualtieri, Alessandro; S., Ferrari; Galli, Ermanno; F., DI RENZO; W., VAN BEEK
abstract

In this work, we present the structure refinement of ECR-1 to give the first direct evidence of the proposed structure of this synthetic zeolite. In fact, a model of the structure of ECR-1 was proposed on the basis of high-resolution transmission electron microscopy (HRTEM) evidence and the structure solution of the synthetic gallo-silicate TNU-7, but it has not been refined to date. The proposed model consists of structure layers of mordenite (MOR) and mazzite (MAZ) connected in a regular 1: 1 stacking sequence and framework topology EON. Because single crystals of ECR-1 cannot be synthesized, the structure was refined using the Rietveld method. High-resolution synchrotron powder diffraction data were collected on both the synthetic Na-ECR-1 and NH4-ECR-1 samples at ESRF. Na atoms located on the axis of the eight-member ring channels in mordenite and zeolite omega are not present in Na-ECR-1. In Na-ECR-1, the equivalent sites lay near the walls of the eight-membered-ring channels. This difference is presumably at the basis of the formation of ECR-1 because, during growth, the local symmetry deformation of the eight-membered-ring channel prevents the formation of the MOR or MAZ structures and justify the periodical shift from one structure to the other. A quantitative explanation of the anisotropic peak broadening observed in the powder patterns is also given.


2006 - The influence of heating rate on template removal in silicalite-1: An in situ HT-XRPD study [Articolo su rivista]
Gualtieri, Eva Magdalena; Gualtieri, Alessandro; J., Hedlund
abstract

The effect of heating rate on thermal behavior of TPA-silicalite-1 during calcination and the reaction kinetics for TPA decomposition were investigated. The cell parameters of the TPA-silicalite-1 during the heating cycles were determined with the aid of high temperature X-ray diffraction data and the Rietveld method. The template decomposition is accompanied by a large contraction of the unit cell. The unit cell dimensions during template removal are not affected significantly by the heating rate. Consequently, the rate of contraction is approximately proportional to the heating rate. The intensity of some diffraction peaks changes during heating, especially the 101/011 and the 200/020 peaks. The intensity change of those peaks shows the same dependence with temperature as the TPA occupancy, indicating that these parameters are related. An analysis of the kinetics for TPA decomposition based on the intensity change of the 101/011 and the 200/020 peaks was performed. The apparent activation energy (Ea) of the template decomposition in silicalite-1 determined with the Kissinger and the Flynn–Wall–Ozawa methods was 138 (±25) and 138 (±29) kJ mol−1, respectively. The reaction order, determined with the method of Kennedy and Clark, was close to 0.5 indicating that the rate-limiting step is mono-dimensional diffusion. Ea was 140 (±30) kJ mol−1, in good agreement with the results obtained with the other methods.


2006 - The structure of K-hydrosodalite [Articolo su rivista]
Gualtieri, Alessandro; P., Aprea
abstract

Hydrosodalite, Na-6[AlSiO4](6)center dot 8H(2)O, is a synthetic modification of natural sodalite with water molecules replacing for the anion at the centre of the beta cage. Hydrosodalite has a cubic structure with space group P (4) over bar 3n and a approximate to 8.9 angstrom. Cation ordering and framework distortions leading to symmetry reduction were observed for synthetic sodalites but have never been reported for hydrosodalite. This work reports the first experimental evidence of a symmetry reduction in hydrosodalite. The investigated sample is a K-exchanged hydrosodalite with chemical formula K-6[AlSiO4](6)center dot 7.8H(2)O. The structure refinement was performed using synchrotron powder diffraction data in space group P1 with a = 9.196(1) angstrom, b = 9.188(1) angstrom, and c = 9.205(1) angstrom, alpha = 89.69(1)degrees, beta = 90.43(1)degrees, and gamma = 89.791(9)degrees. K+ strongly interacts with all the framework oxygen atoms of the hexagonal ring and provokes anisotropic distortion of the framework. In the distorted framework, the only possible distribution scheme for the K+ ions is ordered, to prevent any Coulomb repulsion between adjacent ions. In addition, the ordered scheme is the only to ensure even distribution of the positive cation charges with respect to the Al atoms (AI:K ratio is 1: 1). In fact, each of the six Al atoms has three K+ ions at a distance of 3.5-3.9 angstrom and in turn, each of the six K+ ions has three Al atoms at a distance of 3.5-3.9 angstrom. K+ ions display a coordination number from 8 to 10 and mean K-O distance, including the water molecules, of 2.921-3.043 angstrom. (c) 2006 Elsevier Inc. All rights reserved.


2006 - The use of illitic clay in the production of stoneware tile ceramics [Articolo su rivista]
S., Ferrari; Gualtieri, Alessandro
abstract

Illite is one of the main clay phases used for the preparation of mixtures for traditional ceramics. The raw materials used for production of white porcelain stoneware tiles mainly consist of feldspars, quartz, and clay minerals (kaolinite, smectite and illite). In this study, eight clayey raw materials with a different content of illite up to 70 wt.%, have been considered. The crystalline phases present in different amounts are illite, smectite, kaolinite, illite-smectite mixed-layers, K-feldspar, plagioclases, quartz, and accessory phases (anatase, goethite). The clays have been chemically and physically characterized as raw and fired materials with X-ray diffraction, X-ray fluorescence, and SEM. Moreover they were added in the percentage of 35 wt.% to a mixture composed of albite, feldspar sand and quartz sand, to reproduce that commonly used for the production of porcelain stoneware tiles. We focused on the quantitative mineralogical aspects of the unfired and fired bodies and their relationship with the technological properties due to the presence of illite. Increasing illite content yields higher percentage of glass phase and lower water absorption because of the lowering of the melting point. Because of the pyroplastic deformation, linear shrinkage decreases with illite content. The presence of illite inhibits the formation of mullite and cristobalite, since silica and alumina tend to form alkaline glass. Although in clays from Hungary, transition elements are present in very low percentage, the colour of the fired bodies is darker. These clays contain goethite, which may be rapidly oxidized with temperature, and show a very low percentage of newly formed mullite which could eventually host Fe in its structure.


2006 - Understanding the high temperature reaction sequence during the thermal treatment of cement-asbestos slates [Relazione in Atti di Convegno]
Gualtieri, Alessandro; G., Elmi
abstract

This paper reports the description of the reaction path taking place during the firing of cement-asbestos slates followed using different experimental techniques (optical microscopy, SEM, TEM , quali- quantitative X-Ray powder diffraction, FTIR). It will be demonstrated that only an interplay of different experimental techniques (mainly diffraction end electron microscopy) can lead to a safe verification of the yield of thermal transformation of asbestos minerals. The understanding of the complex temperature induced reaction path is of paramount importance for the optimization of industrial heating processes to yield a safe transformed product to be eventually recycled.


2006 - Valutazione analitica del rifiuto di cemento amianto dopo trattamento di inertizzazione con processo pirolitico [Articolo su rivista]
G., Pecchini; Gualtieri, Alessandro; E., Renna; O., Sala; L., Calzavacca; T., Bacci; F., Paoli; V., Biancolini
abstract

In questo studio è stata fatta la valutazione analitica del rifiuto di cemento amianto dopo trattamento di inertizzazione con processo pirolitico. Sono stati valutati gli effetti sia sull'amianto di serpentino che quello di anfibolo. Le tecniche utilizzate sono state XRPD, FTIR e SEM.


2005 - Possibilità di impiego dell’illite di Füzérradvány (Ungheria) in impasti da grès porcellanato [Articolo su rivista]
S., Ferrari; E., Ori; Gualtieri, Alessandro; A., Tucci; A., Csebi; J., Biber
abstract

Con il termine illite si intende un i di alluminio e potassio simile alle miche, che non espande, diottraedrìco e che si ritrova nella frazione argillosa. Insieme alla caolinite, alla clorite e alla smectite è uno dei 4 maggiori costituenti delle rocce argillose. L'illite è una fase in parte ancora sconosciuta a causa della difficile reperibilità come minerale puro; spesso è associata a smectite, dalla quale è impossìbile separarla.In questo lavoro viene presentato un giacimento illite situatonell'Ungheria Nord-orientale, vicino al paese di Fuzérradvany, non ancora descrìtto nella letteratura mineralogica intenazionale. La regione dell'Ungheria Nord-orientale ai confini con la Slovacchia, appartiene al complesso monfuoso dei Monti Tokaj, ed in quanto tale è costituita da rocce acide dì origine vulcanica. La formazione di questo importante giacimento è dovuta all'alterazione da parte di fluidi idrotermali, che hanno interessato rocce riolitiche.La miniera dì Fuzérradvany è in grado di produrre 4 diverse qualità dì argilla illitica: EXTRA, A, B e C. ln questo studio sono state prese in esame le due qualità con un maggiore contenuto di illite: EXTRA ed A. Le due argille sono state caratterizzate dal punto di vista chimico-fisico. Inoltre, è stato studiato ìl comportamento in temperatura. Alle variazioni osservate nelcomportamento dilatometrico è stato dato un significato in termini mineralogici e microstrutturali, potendo seguire le trasformazioni con diffrazione a Raggi X in situ e microscopia elettronica a scansione.Questo lavoro si inquadra in un progetto generale ai studio i argille illitiche nel campo dei ceramici tradizionali, che prende in esame argille con un diverso contenuto di illite dal 5 ai 70%; ottenendo importanti ìnformazioni su come l'impasto stesso modifichi le sue caratteristiche quando il minerale viene inserito in percentuali diverse. Dai confronti dì tutti i dati ottenuti ci si propone infatti dì valutare gli effetti della presenza di illite in impasto e come la variazione delle sue percentuali possa modificare le proprietà del prodotto finito, in modo tale da ottimizzare le condizioni di uso di questa importante nuova materia prima ceramica.


2005 - Preliminary characterization of an unknown mineral from Mont Peylenc (Massif Central, France) [Relazione in Atti di Convegno]
Ferrari, S.; Galli, Ermanno; Gualtieri, Alessandro
abstract

The discovery of a new natural zeolite phase is a rare event since only less than one hundred natural zeolites are known to date. We have been recently involved in a research project aimed at the investigation of a microscopic aggergate coming from the Massif Central (France) that appears to be anew zeolite species. The sample was collected more than 30 years ago by Professors Glauco Gottardi and Ermanno galli and since then, many unsuccesful attempts have been made to disclose the crystal chemistry of this new3 species. The quantity of available material is very limited, and single crystals are not available. For this reason, structure determination from powder diffraction data is attempted. This work represents the result of preliminary chemical, microscopy and minralogical charcterization of this apparently unknown mineral, mainly using X-ray podwer diffraction. All data point to a new zeolite species and the results will be hopefully integrated in the future with the crystal strcture solution by the powder methods.


2005 - Reduction of the Na content of irrigation waters using chabazite-rich tuff [Relazione in Atti di Convegno]
Passaglia, Elio; S., Poppi; P., Azzolini; Gualtieri, Alessandro
abstract

Lab experiments showed that the Italian chabasite-rich tuff from Sorano (Grosseto) is able to remove Na from low quality irrigation waters, harmful for agriculture, and turn them into high quality waters. The treatment is obtained via a three steps process: water percolation through natural zeolitite bed, regeneration of the exhausted zeolitite with NH4 or with K, and water percolation through the regenerated zeolitite. The quantity of treated water is inversely proportional to the content of Na of the original water. The efficiency of the zeolitite is slightly improved after regeneration. The process was successfully applied to a large-scale in two horticultural farms which Supplied the irrigation waters utilized for the lab tests.


2005 - Riciclo di amianto inertizzato termicamente in impasti da grès porcellanato. [Relazione in Atti di Convegno]
L., Esposito; E., Rambaldi; A., Tucci; E., Gaetti; Gualtieri, Alessandro
abstract

Nella presente ricerca si è valutata la possibilità di riciclare amianto inertizzato termicamente con torcia al plasma, in impasti da grès porcellanato. Il materiale inertizzato, denominato INERTAM, è costituito per circa 50% da una fase amorfa. Il restante 50% è costituito da fasi cristalline fra le quali prevale la gehlenite-akermanite (ca. 36% del totale). Considerando il carattere refrattario dell'INERTAM, si è ritenuto opportuno sostituirlo ai materiali, quali le sabbie, che negli impasti ceramici svolgono una funzione smagrante e strutturale. Partendo da un impasto da grès porcellanato commerciale, scelto come riferimento, è stato preparato un nuovo impasto, sostituendo il 2.5% di sabbia feldspatica con l'1%di INERTAM.Il nuovo impasto ha messo in evidenza caratteristiche migliori rispetto al materiale standard, presentando a 1220°C, valori di assorbimento d'acqua inferiori, 0,82%, e un ritiro lineare di 7,9%. Le analisi al microscopio elettronico a scansione (SEM), dei provini sinterizzati, hanno evidenziato una microstruttura più omogenea e meno porosa rispetto a quella dell'impasto standard.


2005 - The order-disorder character of FeOHSO4 obtained from the thermal decomposition of metahohmannite, Fe2(3+H2O)4[O(SO4)(2)] [Articolo su rivista]
G., Ventruti; F., Scordari; E., Schingaro; Gualtieri, Alessandro; C., Meneghini
abstract

The iron sulfate FeOHSO4 studied was obtained as a dehydration product of metahohmannite Fe-2(H2O)(4)[O(SO4)(2)] during a synchrotron real-time powder diffraction experiment. As quoted in the literature, FeOHSO4 has iron atoms octahedrally coordinated with two hydroxyl groups and four sulfate O atoms, while each hydroxyl group is bonded to two iron atoms. This compound is commonly described in the orthorhombic system with space group Pnma, lattice parameters a(J) = 7.33, b(J) = 6.42, and c(J) = 7.14 angstrom (a(J), b(J), and c(J) are the Johansson lattice parameters), and Z = 4. However a preliminary Rietveld refinement of the pattern at about 220 degrees C using the structural model from the literature yielded a poor fit of the observed data and a final R-p value of about 23%. A careful analysis of the calculated powder diffraction pattern showed unexpected peaks, not observed in the experimental trace, for h = 2n + 1, while sharp reflections for h = 2n seemed to point to different lattice constants and space group. The recognition of the order-disorder character of the FeOHSO4 compound was the key to successfully interpreting the unexpected features of the experimental powder pattern and the misfit with respect to the calculated pattern. In fact, FeOHSO4 belongs to a family of OD structures formed by equivalent layers of symmetry Pbmm. Only two MDO (Maximum Degree of Order) polytypes are possible. MDO1 results from a regular alternation of stacking operators 2(1/2) and 2(-1/2), and yields an orthorhombic structure with space group Prima and lattice parameters a(J) = 7.33, b(J) = 6.42, and c(J) = 7.14 angstrom. MDO2 results from the 2(1/2)/2(1/2)/2(1/2)... sequence of symmetry operators and yields a monoclinic structure with space group P2(1)/c, a(M) = 7.33, b(M) = 7.14, c(M) = 7.39 angstrom, and = 119.7 degrees. The analysis of one-dimensional stacking disorder was performed by fitting the observed XRPD pattern with a calculated intensity curve generated by DIFFaX. The disorder model was investigated by taking into account a probability matrix for the occurrence of OD layer sequences. The best fit (R-P = 0.009) to the observed powder pattern was obtained with a 61:39 ratio of monoclinic and orthorhombic polytypes for a fully disordered OD layers sequence.


2004 - Accurate measurement of the thermal expansion of MFI zeolite membranes by in situ HTXRPD [Relazione in Atti di Convegno]
Gualtieri, Eva Magdalena; Gualtieri, Alessandro; Hedlund, J.; Jareman, F.; Sterte, J.; Dapiaggi, M.
abstract

Template removal by calcination of MFI type membranes is often accompanied by crack formatìon. The thermal behavior of MFI type membranes, synthesized with and without masking, was studied to understand the mechanìsm. Masking prevents growth of zeolite in thè interior of the support during membrane synthesis. Rietveld refìnements of powder diffraction data collected in situ at high temperature allowed to accurately determine the change in thermal expansion of thè MFI film and thè porous a-alumìna support. During heating, a relatively large contraction of the celi volume during template removal occurred in thè zeolite powder and in thè film of thè membrane prepared with masking. The much smaller decrease in thè non-masked sample indicates that this membrane is under stress during heating and as a consequence, cracks are formed. The stress imposed in the membrane prepared without masking may be due to the opposite thermal behavior of the substrate in combination with strong bonds between thè membrane and thè support.


2004 - Argille illitiche: composizione, struttura, microstruttura e comportamento negli impasti ceramici da grès porcellanato [Articolo su rivista]
M., Mariani; P., Pizzoli; R., Santini; P., Caliceti; S., Ferrari; Gualtieri, Alessandro
abstract

La relazione vuole raccogliere lo stato dei lavori che stiamo portando avanti nel nostro laboratorio riguardo alla ricerca e l'indagine sulle materie da impasto. Abbiamo posto l'attenzione sulla plasticità delle argille e sulle interconnessioni, alcune note e altre un po' meno, tra le caratteristiche tecniche di lavorabilità e le composizioni chimiche e mìneralogiche di questi materiali. Abbiamo preso in considerazione 7 argille diverse, utilizzate attualmente in impasti ceramici nazionali e non, aventi tenori di allumina dal 20 al 28%. Questo lavoro presenta la fase preliminare di un progetto più vasto in cui si intende raccogliere un numero molto più consistente di dati e creare un data base significativo in termini statistici.


2004 - Dissolution kinetics and diffusivity of silver in glassy layers for hybrid microelectronics [Articolo su rivista]
Prudenziati, Maria; Morten, Bruno; Gualtieri, Alessandro; M., Leoni
abstract

Silver and palladium/silver compositions are widely used in hybrid microelectronics, as electrodes for dielectric layers and multilayers, terminations of thick film resistors and interconnections. Interactions between Ag and the adjacent films are known to affect the microcircuit performances. The present study is aimed at collecting data on the behavior of Ag-based films in contact with glassy layers. Most experiments were performed with a glass with composition 68.2 PbO:30.5 SiO2:1.3 Al2O3 wt%. Two different systems were analyzed. The first system consists of thick films prepared from a paste containing glass and either 3 or 15 wt% silver particles; both fine (spherical grains, 0.5-1 mum diameter) and coarse (flakes, 2-5 mum, &lt; 1 μm thick) Ag powders were used for these pastes. The distribution of Ag in the film was studied with X-ray diffraction, scanning electron microscopy and fluorescence analysis. The results show that Ag floats on the glassy layer. Diffraction of X-rays generated by a synchrotron radiation source allowed us to study the kinetics of silver dissolution in the glass; this phenomenon is consistent with the Avrami theory, with an apparent activation energy E-dis = 0.69 +/- 0.04 eV. The second system analyzed, Ag-based terminations of glass layers fired at various peak temperatures, enabled us to obtain quantitative values for both Ag solid solubility (about 2.5 wt%) and Ag diffusion coefficients D-Ag(T). Typical values of D-Ag(850°C) are 30.3 +/- 11.9 10(-8) cm(2)/S; an apparent activation energy of the diffusion process is E-a = 0.6 +/- 0.1 eV.


2004 - Illite dell'Ungheria Nord-Orientale [Articolo su rivista]
Ferrari, S.; Gualtieri, A. F.; Csebi, A.; Biber, J.
abstract


2004 - Kinetics of the decomposition of crocidolite asbestos: A preliminary real-time X-ray powder diffraction study [Relazione in Atti di Convegno]
Gualtieri, Alessandro; D., Levy; E., Belluso; M., Dapiaggi
abstract

This work is a preliminary kinetic study of the crocidolite decomposition followed in situ at high temperature using real time conventional powder diffraction and DTA in the temperature range 720-795 degreesC. The data analysis using the Avrami models indicates that the rate limiting step of the reaction is monodimensional ion diffusion (n=0.5) with an activation energy of 129 (10) kcal/mole.


2004 - Ottimizzazione di impasti da monoporosa [Articolo su rivista]
Reginelli, M.; Settembre, D.; Bertoni, A.; Rovini, A.; Vezzalini, Maria Giovanna; Gualtieri, Alessandro; Carpenito, G.
abstract

In questo studio sono state analizzate le proprietà tecnologiche di impasti da gres smaltato con composizioni chìmiche molto diverse, indagando quanto il chimismo e la mineralogia possano influenzare il coefficiente di dilatazione del prodotto finito. Attraverso le analisi condotte è stato possibile ipotizzare un rapporto ottimale SiO2/Al2O3 e Na2O/K2O rispetto ai parametri più critici del processo produttivo: macinazione, smaltatura e cottura. Questi dati, rappresentano la prima fase di un progetto di ricerca più ampio, nel corso del quale si dovranno studiare gli effetti della macinazione, della natura e delia quantità della fase vetrosa, sul coefficiente di dilatazione, fornendo un contributo, al confronto in corso sul tema, sia alle aziende, che agli enti dì ricerca istituzionaii.


2004 - Rapid and accurate quantitative phase analysis using a fast detector [Articolo su rivista]
Gualtieri, Alessandro; Brignoli, G.
abstract

The accuracy of the weight fractions calculated with the Rietveld method for various polycrystalline systems using data collected for very short times (545 min) with an RTMS (real-time multiple strip) detector was verified. The weight estimates were compared with those obtained using the same conventional Bragg-Brentano geometry, a gas proportional detector and a 13 h data acquisition. The analysed samples were monophasic and polyphasic mixtures with different degrees of complexity: the standard corundum NIST 676; a sample (labelled 1g) provided as a standard sample for the IUCr CPD Quantitative Phase Analysis Round Robin; a natural pyroclastic rock from Riano (Rome, Italy) containing zeolitic minerals and a glass phase; and a hydraulic lime. The results of the refinements show estimated weights consistent with both those obtained with a gas proportional detector and with the nominal values, indicating a very good accuracy. Only when variable slits are used, the accuracy of the estimated weights slightly decreases. The outcome of this work is a very important step forward towards fast and accurate QPA for production control and quality management, obtained by combining the use of a rapid detector and existing user-friendly software.


2004 - Simultaneous refinement of structure and microstructure of layered materials [Articolo su rivista]
M., Leoni; Gualtieri, Alessandro; N., Roveri
abstract

The recursive description of stacking in layered crystals, originally developed by Treacy et al. [Proc. R. Soc. London Ser. A (1991), 433, 499-520] and implemented in the DIFFaX code, is enclosed in a non-linear least-squares minimization routine and combined with additional models (of specimen-related broadening and instrumental broadening) to allow the simultaneous refinement of both structural and microstructural parameters of a layered crystal. This implementation is named DIFFaX+. As examples, the refinements both of a simulated pattern of diamond, showing fault clustering, and of the observed powder pattern of a synthetic stoichiometric nanocrystalline chrysotile are reported.


2004 - Sorbate rearrangement and cation migration in HFC-134 loaded NaY zeolite: A temperature dependent synchrotron powder diffraction study [Relazione in Atti di Convegno]
Gualtieri, Alessandro; Norby, P; Grey, Cp; Hanson, Jc
abstract

The HFC-134/NaY binding has been monitored by temperature dependent X-ray powder diffraction. Diffraction patterns were obtained as a function of different loading levels to investigate the rearrangement of the cations and of the HFC-134 molecules, in the temperature range 100-230 K. In situ real-time data were collected using a Translating Imaging Plate System (TIPS) at the NSLS (USA). Rietveld structure refinements were performed for the HFC-134 (32 molecules per unit cell [m/uc = molecules per unit cell] or 4 molecules per supercage [m/sc = molecules per supercage]) using data collected from 100 to 230 K. A phase transition is observed at about 180 K (A to B phase transition) where a disordering of the HFC-134 molecule takes place and modification of its surrounding due to Na+ migrations is observed. These results are preliminary and the experiment with the 32 m/ue should be repeated in order to assess whether the observed effect is reproducible.


2004 - The atomic structure of bakerite and its relationship to datolite [Articolo su rivista]
Perchiazzi, N; Gualtieri, Alessandro; Merlino, S; Kampf, Ar
abstract

Four samples of bakerite, Ca4B5Si3O15(OH)(5), were studied by means of IR, TG/DSC, EPMA, and X-ray and neutron diffraction. Chemical analyses can readily discriminate bakerite from datolite, Ca4B4Si4O16(OH)(4), by the distinctly lower SiO2 content of the former. The Rietveld refinement of the combined neutron and X-ray powder data allow the determination of the crystal structure of bakerite to R-p 3.09%. The crystal structure can be derived from that of datolite by the substitution 0.25Si(4+) + 0.25O(2-) <----> 0.25B(3+) + 0.25(OH)(-) at the Si-centered tetrahedral site. This leads to the crystal chemical formula Ca(4)B(5)Si(3)0O(15)(OH)(5). Both of the two hydrogen positions in the bakerite structure, one with full occupancy, the other with 25% occupancy, were precisely located. The water molecule generally thought to be present in bakerite structure is actually absent. The excess water detected in chemical analyses can be attributed to the presence of minor impurities. Given the consistent composition of bakerite from various localities and no evidence for Substitution of B for Si in datolite, bakerite is retained as a distinct species. A possible explanation of the peculiar 5:3 boron to silicon ratio in bakerite is provided.


2004 - The quantitative determination of the crystalline and amorphous content by the Rietveld method: application to glass ceramics with different absorption coefficients [Capitolo/Saggio]
Gualtieri, Alessandro; Guagliardi, A.; Iseppi, A.
abstract

The Rietveld method provides an accurate determination of the crystalline and the amorphous fractions in polyphase mixtures. To determine the content of the amorphous phase, the sample is diluted with an internal standard which is considered as a component itself and refined with the other phases. Although the method is accurate for systems containing crystalline and amorphous phases with an absorption coefficient comparable to that of the standard, it was not thoroughly tested for systems containing a weakly or highly absorbing amorphous phase. Commonly, this is the case for glass ceramics which may contain elements with fairly different atomic number.X-ray powder diffraction data refined with the Rietveld method were utilized for the determination of the amorphous content in a number of systems containing glasses with different absorption coefficients (Li-, B-, Al-, P-, Zn-, Zr-, Ba-, Pb-glass) to check the accuracy of the method. The mixtures were prepared diluting the glass phase with corundum NIST 676 and hydroxyapatite NIST 2910 in fixed proportions. The refinements were carried out with GSAS and the new code QUANTO, especially developed for automatic quantitative phase analysis (QPA) of polycrystalline mixtures eventually including an amorphous component.The glass weights estimated by the two programs are both in good agreement with the nominal value (45 wt%) although a minor dependency of the calculated amorphous fraction on the linear absorption coefficient of the glass was observed and attributed to microabsorption effects. The Brindley (1945) correction applied here according to the formulation of Taylor and Matulis (1991) revealed not to be fully satisfactory for mixture containing an amorphous component with a very different absorption coefficient, especially when highly accurate determinations are required. This is in concert with the general concern that the existing models for the correction of microabsorption effects should be revised as they are not adequate even for systems containing only crystalline phases (Madsen et al., 2001).The method was successfully applied to a commercial glass ceramic indicating that it can be applied with a good accuracy also to glass ceramics with fairly different absorption coefficients.


2004 - The structure of metahohmannite, Fe-2(3+)[O(SO4)(2)]center dot 4H(2)O, by in situ synchrotron powder diffraction [Articolo su rivista]
Scordari, F; Ventruti, G; Gualtieri, Alessandro
abstract

Metahohmannite, Fe-2(3+)[O(SO4)(2)].4H(2)O, is a hydrated sulfate of ferric iron that occurs in sulfate deposits in the desert areas of Northern Chile. The compound used for this study was obtained as a dehydration product of hohmannite, Fe-2(3+)[O(SO4)(2)].(4+4)H2O. Intensities for the structure analysis were collected from a powdered sample using in situ synchrotron X-ray powder diffraction at ESRF (Grenoble, France). The structure was solved ab initio by profile deconvolution and the application of standard Patterson and difference Fourier maps. The structure was refined to R-p = 5.46% using the Rietveld method. Metahohmannite crystallizes in the triclinic system, space group P (1) over bar with unit-cell parameters a = 7.3484(5) Angstrom, b = 9.7710(6) Angstrom, c = 7.1521(5) Angstrom, alpha = 91.684(5)degrees, beta = 98.523 (5), gamma = 86.390(5)degrees, and Z = 2. The structure consists of four Fe3+ octahedra and four sulfate tetrahedra, which share vertices and edges to form a complex building block of Fe-4(3+)[O-2(SO4)(4)].8H(2)O composition. Such blocks are connected to form chains running parallel to the c axis. A complicated system of hydrogen bonds connects adjacent chains into a three-dimensional network. Finally, the crystal structures of metahohmannite, hohmannite, and amarantite are compared and the geometrical features discussed in detail.


2004 - The use of nepheline-syenite in a body mix for porcelain stoneware tiles [Articolo su rivista]
L., Esposito; A., Salem; A., Tucci; Gualtieri, Alessandro; S. H., Jazayeri
abstract

In the study, the possibility to use nepheline-syenite, as fluxing agent, in a body mix used for porcelain stoneware tile, was determined. Starting from the reference mix composition, different amounts, 5.0, 10.0 and 15.6 wt.%, of sodium feldspar were replaced with the same amounts of nepheline-syenite. Different sintering cycles were used to understand the role of the nepheline-syenite in the development of the final microstructure. The presence of nepheline-syenite strongly favours the sintering behaviour, by reducing the sintering time necessary to reach the water absorption values, requested by the International Standard. Furthermore, the microstructure results more homogeneous and the mechanical characteristics are increased. The better mechanical performances can also be attributed to the different mineralogical compositions, in particular with lower amount of glassy phase, higher flexural strength values are obtained.


2004 - Tubular-shaped stoichiometric chrysotile nanocrystals [Articolo su rivista]
G., Falini; E., Foresti; M., Gazzano; GUALTIERI, Alessandro; M., Leoni; IG, Lesci; N., Roveri
abstract

Stoichiometric chrysotile tubular nanocrystals have been synthesized as possible starting materials for applications toward nanotechnology, and as a standard reference sample for the investigation of the molecular interactions between chrysotile, the most utilized asbestos, and biological systems. Chrysotile nanocrystals have been synthesized under controlled hydrothermal conditions, and have been characterized by chemical, morphological, structural, spectroscopic and microcalorimetric analyses. They show a constant cylinder-in-cylinder morphology constituted by two or three concentric subunits. Each single nanocrystal has a tubular shape of about 49 +/- 1 nm in outer maximum diameter, and a hollow core of about 7 +/- 1 nm. Structural investigation carried out on an Xray powder pattern allowed to improve the structural model proposed for chrysotile mineral samples. Synthetic chrysotile crystallizes in the monoclinic Cc space group with a= 0.5340(l) nm, b = 0.9241(l) nm, and c = 1.4689(2) nm, beta = 93.66(3)degrees.


2004 - Utilizzo del talco in impasti da grès porcellanato superbianchi: caratteristiche mineralogiche, chimiche e microstrutturali [Articolo su rivista]
S., Ferrari; Gualtieri, Alessandro; T., Bellarmi; C., Pasquali
abstract

Lo scopo di questo studio sul talco è quello di valutare il suo impiego negli impasti da grés porcellanato superbianco. Lo studio è stato svolto utilizzando tecniche di laboratorio di carattere tecnologico e tecniche analitiche quali XRD, XRF, SEM per la caratterizzazione mineralogica, chimica e microstrutturale dei materiali naturali e edei cotti. Con questo lavoro, ci si propone quindi di indicare quale sia la materia prima contenente talco più idonea per gli impasti da grés porcellanato superbianchi e di ottimizzarne la quantità da aggiungere all'impasto stesso.


2003 - A new method for the detection of low levels of free fibres of chrysotile in contaminated soils by X-ray powder diffraction [Articolo su rivista]
G., Falini; E., Foresti; M., Gazzano; Gualtieri, Alessandro; I. G., Lesci; G., Pecchini; E., Renna; N., Roveri
abstract

A new method for the determination of free fibres of chrysotile in contaminated soils is described. The detection limit of 0.5 wtparts per thousand is reached by an enrichment process of the asbestos fraction of the sample using a standard laboratory elutriator for sedimentation analysis. The analysis of the enriched fraction is performed by X-ray powder diffraction using a conventional instrument. The procedure can be successfully applied to several soils of different nature throughout thermal treatment and removal of possible interferences due to some matrix components. This method is straightforward, routinized and has been especially developed to fulfil the request of public and private institutions for an appropriate quantitative determination of chrysotile free fibres in contaminated soils.


2003 - Determination of low levels of free fibres of chrysotile in contaminated soils by X-ray diffraction and FTIR spectroscopy [Articolo su rivista]
E., Foresti; M., Gazzano; Gualtieri, Alessandro; Ig, Lesci; B., Lunelli; G., Pecchini; E., Renna; N., Roveri
abstract

A new analytical method for the determination of low levels (0.01-1 wt%) of free fibres of chrysotile in contaminated clayey, sandy and sandy-organic soils is described. The detection limit of 0.01 wt% is reached with an enrichment of free fibres of chrysotile in the sample using a standard laboratory elutriator for sedimentation analysis. The chrysotile quantitative determination is performed both by X-ray powder diffraction, using the internal standard and reference intensity ratio methods, and by Fourier-transform infrared absorption spectroscopy. The procedure can be successfully applied to different soils after removal, by a thermal treatment, of the matrix components which can interfere. This straightforward method fulfils the request of public institutions and private companies for an appropriate quantitative determination of chrysotile-free fibres in contaminated soils.


2003 - Erratum: Exploring the damage limitation possibilities of mineral fibres for future integrated solutions: An in vitro study (The International Journal of Artificial Organs (2003) 26 1 (73-79)) [Articolo su rivista]
Gabbanelli, F.; Mattioli-Belmonte, M.; Giantomassi, F.; Rimondini, L.; Viticchi, C.; Biagini, G.; Torricelli, P.; Gualtieri, A. F.; Lesci, I. G.; Giardino, R.
abstract


2003 - Exploring the damage limitation possibilities of mineral fibres for future integrated solutions: An in vitro study [Articolo su rivista]
Gabbanelli, F.; Mattioli-Belmonte, M.; Giantomassi, F.; Rimondini, L.; Viticchi, C.; Biagini, G.; Torricelli, P.; Gualtieri, A. F.; Lesci, I. G.; Giardino, R.
abstract

Owing to their possible carcinogenic effect, asbestos and other silica derivatives have been identified as priority substances for risk reduction and prevention of pollution. Neutralisation procedures have thus become a topical research subject in many European and American countries. In the present study, silica derivatives (asbestos-containing and asbestos substitutes like slag wool, rock wool, cement asbestos) were fully impregnated with an epoxy resin according to the procedure used for the in situ impregnation with viscous polymeric media, which penetrate and cement the fibres in place and reduce the risk of their dispersion in air. Untreated and treated samples were used to investigate their in vitro interaction with a human continuous epithelial cell line (NCTC 2544 keratinocytes) and test the resin's efficiency in passivating the surface activity of the fibrous particulate. SEM and morpho-quantitative data evidenced that impregnation with the epoxy resin modifies the mineral fibres' bioactivity (reduction of cell adhesion and decreased spread/round cell ratio) and demonstrated the value of in vitro cell testing after passivation as a risk-assessment procedure. These tests could be used for the rapid determination of the level of passivation of new synthetic mineral fibrous materials subjected to resin impregnation.


2003 - Kinetic study of the dehydroxylation of chrysotile asbestos with temperature by in situ XRPD [Articolo su rivista]
A., Cattaneo; Gualtieri, Alessandro; G., Artioli
abstract

The kinetics of the dehydroxylation of chrysotile was followed in situ at high temperature using real-time conventional and synchrotron powder diffraction (XRPD). This is the first time kinetics parameters have been calculated for the dehydroxylation of chrysotile. The value of the order of the reaction mechanism calculated using the Avrami model indicates that the rate-limiting step of the reaction is a one-dimensional diffusion with an instantaneous nucleation or a deceleratory rate of nucleation of the reaction product. Hence, the rate-limiting step is the one-dimensional diffusion of the water molecules formed in the interlayer region by direct condensation of two hydrogen atoms and an oxygen atom. The calculated apparent activation energy of the reaction in the temperature range 620-750 degreesC is 184 kJ mol(-1). The diffusion path is along the axis of the fibrils forming the fibers. The amorphous or short-range ordered dehydroxylate of chrysotile is extremely unstable because forsterite readily nucleates in the Mg-rich regions. Moreover, it is less stable than the dehydroxylate of kaolinite, the so-called metakaolinite, which forms mullite at about 950 degreesC. This difference is interpreted in terms of the different nature of the two ions Mg2+ and Al3+ and their function as glass modifier and glass-forming ion, respectively.


2003 - Phase transformations and reaction kinetics during the temperature-induced oxidation of natural olivine [Articolo su rivista]
Gualtieri, Alessandro; Gemmi, M; Dapiaggi, M.
abstract

This work describes the sequence of transformations and their reaction kinetics during the oxidation of olivine in air at high temperature. A natural olivine sample from the layered series of the Ivrea-Verbano igneous complex (Western Alps, Italy) was heated in the temperature range 25-1300 degreesC in air and investigated by in situ, real time powder X-ray diffraction (PXRD). The evolution of the peaks (measured integrated intensities) was followed in non-isothermal conditions using variable heating rates (b = 20, 22, 25, 27, and 30degreesC/min). The total time of the experiments ranged from about 256 (b = 30degreesC/min) to 277 (b = 20degreesC/min) min including the time for the data collections. An additional isothermal run was performed at 800degreesC. The analysis of the kinetic data was attempted with the use of different equations including the classical Avrami theory for solid-state reactions. The kinetic results were confirmed by independent experimental data from electron microscopy (SEM, TEM). In the transformation sequence, hematite appears at about 600degreesC producing amorphous segregations. of silica that later recombine with forsterite to form pyroxene Hematite is stable up to 1130degreesC where it is transformed into magnetite. The rate limiting step for the formation of hematite is a two-dimensional diffusion with constant or decelerating nucleation rate and apparent activation energy of 15 kcal/mol. The concentration of Fe3+ in Fe-rich regions favors the heterogeneous nucleation of hematite, which may take place on existing defects or at the grain boundaries with impurity phases such as serpentine. At 1130degreesC, magnetite is formed at the expenses of hematite, with a contracting volume interface-controlled reaction in two or three dimensions with an apparent activation energy of 30-31 kcal/mol. The hematite to magnetite transformation is direct, without a metastable amorphous intermediate. It is described by the shrinking core model, with the formation of a magnetite outer layer at the surface of the hematite particles that proceeds toward the core of the reacting hematite by diffusion of the oxygen throughout the newly formed magnetite layer. Its rate is limited by the advancement of the reaction front. The rate-limiting step for the formation of pyroxene is two-dimensional diffusion with decelerating nucleation rate with an apparent activation energy of 29 kcal/mol.


2003 - Synthesis of mullite from kaolinite: Use in tradiational ceramics as stain or glaze component [Articolo su rivista]
Porta, A.; Gualtieri, A. F.
abstract

This work describes the crystal chemistry of synthetic mullite doped with Fe, Mn, Cr, Co, V, Pr, Cd, Ni, Cu, Zn and Zr. The synthesis was achieved at 1500°C for 4 h starting from caolinite and aluminum hydroxide. The solubility of the doping element in mullite was investigated. Synthetic mullites can be classified with respect to their degree of crystallization: (1) good crystallization (Fe-, Mn-, V-mullite); (2) rather good crystallization (undoped-, Cr-, Co-, Ni-, Pr-, Zn-, Zr-mullite); (3) poor crystallization (Cd-, Cu-mullite). The application of mullite as a bulk pigment in stoneware products and as a component for "matt" glazes was promising only for the latter application.


2003 - Template Burning inside TS-1 and Fe-MFI Molecular Sieves: An in Situ XRPD Study [Articolo su rivista]
Milanesio, M.; Artioli, G.; Gualtieri, A. F.; Palin, L.; Lamberti, C.
abstract

The high X-ray flux available at the European Synchrotron Radiation Facility (ESRF), combined with the use of a suitably designed area detector setup, allowed us to follow in real time the structural changes occurring during the template burning processes inside TS-1 and Fe-silicalite MFI zeolites with a X-ray powder diffraction technique (XRPD). Rietveld analysis of the XRPD patterns collected in the 350-1000 K interval, integrated each 15 K, yields to the determination of the template overall occupancy factor versus T with an accuracy comparable with that obtained by thermogravimetric measurements, routinely employed for this purpose. The evolution of the structural parameters (V, a, b, c, site occupancy factor of the template molecule) vs Thas been obtained. These data allow us to have, for the first time, a complete view of the structural rearrangements induced by the template burning process on the zeolitic framework. The differences caused by the different heteroatom inserted in the MFI lattice (Ti or Fe) are discussed. For both TS-1 and Fe-MFI, the kinetics of the reaction were investigated, to obtain the activation energy of the calcinations process employing the nonisothermal data according to the theory recently proposed by Kennedy and Clark [Thermochim. Acta, 1997, 307, 27-35]. For TS-1 only, the time-resolved template burning experiment has been repeated in isothermal conditions at four different temperatures, to obtain the activation energy from isothermal data, according to the standard procedure. Comparison between Arrhenius plots obtained from isothermal and nonisothermal data demonstrates that the Kennedy and Clark method can be also applied to complex materials such as the MFI zeolites. This approach, when applied to time-resolved XRPD studies, is much less time consuming (requesting, in principle, one single nonisothermal run) with respect to the classic approach, which requests at least three isothermal runs. Moreover, it allows a remarkably lower associated error (151 ± 11 versus 146 ± 30 kJ mol-1) due to the much higher number of experimental points employed to perform the linear fit.


2002 - Dehydration dynamics of Ba-phillipsite: an in situ synchrotron powder diffraction study [Articolo su rivista]
Sani, A; Cruciani, G; Gualtieri, Alessandro
abstract

The stepwise dehydration process of the Ba-exchanged form of the zeolite phillipsite was studied by in situ synchrotron X-ray powder diffraction. A series of structure refinements were performed using the Rietveld method on powder diffraction data measured in the interval between 332 and 712 K. At 482 K, more than half of the water molecules were lost. The continuous water loss causes the Ba cations to migrate inside the zeolite channels in order to achieve a stable coordination with the framework oxygens. The dehydration process was completed at 663 K, where a new, completely dehydrated stable phase was detected. The temperature range of stability of this phase was more than 100 K, thanks to the stable coordination of the Ba cations with the framework oxygens. This phase is the first example of completely dehydrated zeolite containing divalent (barium) cations.


2002 - Ion exchange selectivity of phillipsite [Relazione in Atti di Convegno]
Gualtieri, Alessandro; Passaglia, Elio; Galli, Ermanno
abstract

Phillipsite is one of the main components of the sedimentary zeolite-rich rocks called zeolitites used in a variety of applications (i.e., in the field of pollution abatement and agriculture). The interest for the understanding of the cation exchange properties for a proper and efficient use in industrial applications prompted in 1995 a long term project on the systematics of cation exchanged phillipsites, their crystal chemistry and properties. Natural phillipsite samples with different Si/(Si+Al) ratio were selected for the research project and exchanged with a number of either monovalent and divalent cations. In this paper we describe a general picture of the changes which occur in the structure of phillipsite in response to the cation exchange either in terms of framework relaxation/contradion and cation migration, ion exchange selectivity and properties, and their prediction.


2002 - Lead-free thick film resistors: an explorative investigation [Articolo su rivista]
Prudenziati, Maria; F., Zanardi; Morten, Bruno; Gualtieri, Alessandro
abstract

Pastes prepared with seven lead-free glass particles were screen-printed and fired on 96\%-Al2O3 substrates. The fired films were studied in terms of sintering, devitrification, crack propagation and bleeding. The most promising glass compositions were selected for the preparation of RuO2-based thick film resistors (TFRs), on pre-fired PtAu- or PdAg-based terminations; electrical properties of the resistors (sheet resistance vs. RuO2 volume fraction, temperature coefficient of resistance and size effects) were investigated. The study evidenced a myriad of complex phenomena, including devitrification, relevant bleeding of the glass on alumina substrates, anomalous distribution of conductive grains in the glassy matrix, phase separations. Contrarily to what happens in traditional systems, it is difficult to get a wide resistance range simply by changing the fraction of the conductive phase. These results emphasize the criticality in the choice of the glass composition for the preparation of lead-free thick film resistors.


2002 - Mineralogy of the Grès de Thiviers (northern Aquitaine, France) [Articolo su rivista]
Sempio, A.; Gualtieri, A. F.
abstract

This paper reports the mineralogical characterisation of the Grès de Thiviers (GT), a unique natural pigment used in the industry of traditional tile ceramics. The only occurrence of this raw material, composed of quartz and goethite, is a small region in the SW of France were it is exploited and exported to the European and Far East markets. GT is mainly used as a bulk red pigment for white stoneware and its stability in firing is a direct consequence of the unique nature. In fact, despite the nature of the raw materials composing the ceramic mixture and their behaviour at high temperature, GT invariably yields a final red colour to the fired ceramic body. The stability stems from the fact that goethite (yellow colour) which later transforms into hematite (red colour) is the cement of quartz grains. Thus, in firing, because of the protective shield formed by the inert quartz grains, the newly-formed hematite crystals do not get in contact with other reacting phases such as the alkaline glass and retain the red colour (Sempio and Gualtieri,2001). The mineralogy of the GT deposits was described in the light of the peculiar genesis and chemical variability. In fact, GT occurrence is closely related to the karstic system permeating the late Cretaceous limestone in this region. According to the different formation environment it was possible to describe the four typical GT textures: laminar, oolitic, dendritic, and homeoblastic. GT samples contain amorphous substance with composition [SiO2+Fe2O 3 or FeO(OH)] which is the colloidal precursor of the crystalline phases quartz and goethite.


2002 - Natural red pigment for single-fired ceramic glaze [Articolo su rivista]
Gualtieri, Alessandro
abstract


2002 - Proposal of plant for the treatment of cement-asbestos slabs (eternit) and recycle as raw material for ceramic pigments [Articolo su rivista]
Carani, M.; Gualtieri, A. F.
abstract

Because of its outstanding physical and technological properties, asbestos has been widely used in the past for several industrial applications in all the industrialized countries such as Italy. Asbestos in Italy was one of the main raw materials for cements (the well known cement-asbestos or eternit). Nowadays it is generally accepted that asbestos is a priority substance for health hazard and one of the main concerns is the recover of the areas which contain asbestos and the buildings built with cement-asbestos. In this work we will define the conditions for the thermal inertization of the raw cement-asbestos slabs, define the main characteristics of an industrial plant for the thermal treatment of asbestos, estimate its production capacity. In addition, we will indicate a possible use of the treated product (recycle) as raw material for traditional bulk ceramic pigments.


2002 - The nature of disorder in montmorillonite by simulation of X-ray powder patterns [Articolo su rivista]
Viani, A.; Gualtieri, A. F.; Artioli, G.
abstract

The planar disorder of Ca-montmorillonite (Fuller's earth) has been investigated using structural simulations of X-ray powder patterns. A standard sample was fully characterized using chemical, microscopic, and diffraction methods. Earlier models of disorder taken from the literature and newly formulated combined models were used to generate simulated powder patterns to be compared with the experimental spectrum. A new model of disorder with random shifts of -a/3 and ±b/3, with a total density of defects of 75%, gives the best fit to the observed data. Thus, the sample cannot be classified as a turbostratic structure (fully disordered) and consequently turbostratic disorder does not invariably apply to all smectite samples. These findings open a debate on the nature and application of turbostratic disorder: is it possible for smectite samples to have intermediate degrees of disorder between a fully disordered stacking (turbostratic) and a highly faulted but well-defined stacking or is the result obtained for the Ca-montmorillonite just an exception? This model of disorder is useful for the quantitative phase analysis by X-ray powder diffraction based on the Rietveld method, which can now benefit from a more reliable initial structure model for Ca-montmorillonite and which will improve the accuracy of the weight-fraction estimates.


2001 - Behaviour of the natural red pigment "grès de thiviers" in por-celanised gres [Articolo su rivista]
Sempio, A.; Gualtieri, A. F.
abstract

This work deals with the characterisation of the Grès de Thiviers (GT), a unique natural red pigment for traditional ceramics. The only occurrence of this raw material, composed of quartz and goethite, is a region in SW of France were it is exploited, enriched and exported all over the world. GT is mainly used as a bulk red pigment for white stoneware and its stability in firing is a direct consequence of its unique mineralogy and texture. In fact, despite of the nature and behaviour in temperature of the raw materials in the ceramic mixture, GT yields a final red colour to the fired ceramic body. The reason of this stability stems from the fact that goethite which transforms into hematite is the cement of quartz grains. In particular we studied the stability of GT in mixtures for porcelanised grès with totally different features (i.e. from highly refractory to poorly refractory). This work is aimed to demonstrate that the application of the mineralogical knowledge in synergy with the use of advanced techniques of material characterisation is capable to give a detailed conclusive picture of the physical-chemical and technological properties of materials of ceramic interest.


2001 - Characterization of Mg-calcites from marbles of the Mediterranean area [Articolo su rivista]
A., Viani; Gualtieri, Alessandro; Gorgoni, Carlo; P., Pallante; G., Cruciani
abstract

Mg-rich calcites from marbles of the Mediterranean area were accurately characterized by Rietveld X-ray powder diffraction (XRPD) and X-ray fluorescence (XRF) for the determination of the Mg content of the samples. The data set seems to be highly consistent, despite the different metamorphic environment under which calcite grains have formed. Results indicate that previously reported determinative curves, regarding synthetic Mg-calcites, relating the c/a ratio to the Mg content of the carbonate, do not hold for these natural inorganic samples which display an ideal, or nearly ideal, behaviour of the calcite - dolomite solid solution for compositions between 0 and 4 % mole MgCO3.


2001 - Crystal structure chemistry and color of doped-forsterites revisited by X-ray powder diffraction and UVNis/NIR spectroscopy [Articolo su rivista]
Gualtieri, A. F.; Bagni, S.
abstract

The goal of this work is to revisit the crystal chemistry of synthetic forsterite containing doping elements in the octahedral site. A number of doping elements was systematically investigated: Li+, Mn2+, Co2+, Ni2+, Zn2+, Fe2+, Cr 3+, Cu2+, Ca2+, Cd2+, Al 3+, V5+. The synthetic phases were obtained in air at high temperature (1350 °C for 3h) and environmental pressure. Results permit to revise and improve the knowledge on the crystal chemistry of forsterite and clarify the role of the doping elements in the structure modification and physical properties. The structures of the synthetic samples were analyzed either on a local and on a long range by the combination of UV/Vis/NIR spectroscopy data and Rietveld refinements. It was possible to assess the factors that rule the solubility of the doping elements in olivine, mainly their charge and ionic radius for Co2+, Ni2+, Ca2+, Cd2+, V5+, crystal field for Cu2+ and Zn 2+, kinetics and oxygen fugacity for Fe2+ and Mn 2+. The modifications of the structure were described only with respect to the distortion in the octahedral site induced by the doping element because there are no modifications of the tetrahedral polyhedra. Cation partitioning was also described and depends upon the ionic radius of the doping element. Exceptions are due to CFSE and differences in the cation-anion electronegativity. The color of the synthesized powders was predicted using the crystal field theory and corroborated by the results of the spectroscopy experiments which clearly indicate a relationship between color and structure changes.


2001 - Devitrification kinetics of high lead glass for hybrid microelectronics [Articolo su rivista]
Prudenziati, Maria; Morten, Bruno; B., Forti; Gualtieri, Alessandro; G., MIHAI DILLIWAY
abstract

In order to elucidate crystallization phenomena in high lead glasses for hybrid microelectronics, we studied the devitrification in screen printed and annealed films made with borosilicate glass particles with the composition PbO-SiO2-B(2)iO(3) = 65:25:10 % wt. Formation of SiO2 polymorphs, beta -cristobalite and quartz, was observed in films printed on alumina (Al2O3) or beryllia (BeO) and fired in the temperature range from 700 to 1000 degreesC. X-ray diffraction of samples annealed in isothermal conditions enabled the collection of data for studying the kinetics of formation and dissolution of the crystalline phases. The crystallization of beta -cristobalite on both substrates is governed by an Avrami model. At lower temperatures, the reaction order coefficient indicates an interface controlled reaction with an instantaneous or deceleratory nucleation rate and 3D growth. The apparent activation energy of the crystallization process is independent of the substrate being 15(1) kcal/mol and 14.7(9) kcal/mol for samples on Al2O3 and BeO substrates, respectively, whereas the decomposition reaction is favored on alumina, with E-d = 30(2) kcal/mol in this case, but 55(3) kcal/mol for beryllia substrates. (C) 2001 Elsevier Science Ltd. All rights reserved.


2001 - In situ dehydration of yugawaralite [Articolo su rivista]
Artioli, G; Stahl, K; Cruciani, G; Gualtieri, Alessandro; Hanson, Jc
abstract

The structural response of the natural zeolite yugawaralite (CaAl2Si6O16. 4H(2)O) upon thermally induced dehydration has been studied by Rietveld analysis of temperature-resolved powder diffraction data collected in situ in the temperature range 315-791 K using synchrotron radiation. The room-temperature monoclinic structure [Pc, a = 6.73200(9), b = 14.0157(2), c = 10.0607(1) Angstrom, beta = 111.189(1) degrees, Z = 2, at 315 K] has the Ca cations in the channels coordinated to four framework O atoms and to four water molecules, with two of the water sites (OW1 and OW4) showing positional disorder progressively disappearing as the dehydration proceeds. The yugawaralite structure reacts to the release of water molecules with small changes in the Ca-O bond distances and minor distortions of the tetrahedral framework up to about 695 K. Above this temperature the Ca coordination falls below 7 (four framework O atoms and three water molecules) and a major rearrangement in the cation coordination takes place, causing a first order phase transition involving both a large decrease in the cell volume and the change in the space group symmetry. A satisfactory structure model for the high-temperature phase stable in the range 695-791 K could not be obtained because of the complexity of the structure. A model approximately describing the average structure [Pn, a = 12.703(1), b = 13.067(1), c = 9.839(1) Angstrom, beta = 110.894(9), Z = 4, at 749 K] has been used to follow the temperature evolution of the cell parameters in the measured temperature range. This model involves a sixfold coordination of the Ca cations (five framework O atoms and one water molecule). There is no indication of significant structure changes before collapse, likely occurring when the last water molecule is expelled from the structure and the cation coordination drops below 6, as observed in other Ca-rich zeolites (i.e., laumontite, scolecite, mesolite).


2001 - Multipurpose imaging-plate camera for in-situ powder XRD at the GILDA beamline [Articolo su rivista]
Meneghini, C; Artioli, G; Balerna, A; Gualtieri, Alessandro; Norby, P; Mobilio, S.
abstract

An Imaging-Plate (IP) camera for X-ray powder diffraction (XRPD) experiments was installed on the synchrotron radiation beamline GILDA at the ESRF. The IP camera can be used in fixed data-collection mode of the whole diffraction rings, or in translation mode for time-dependent experiments. The apparatus is ideal for collecting medium- to relatively high-resolution diffraction data from diluted or weakly scattering samples and to investigate in situ phase changes induced by temperature and/or chemical reactions. The possibility to rapidly collect several good quality diffraction patterns coupled with tunable beam energy allow for multiwavelength experiments such as anomalous XRPD.


2001 - Quantitative phase analysis of natural raw materials containing montmorillonite [Relazione in Atti di Convegno]
Gualtieri, A. F.; Viani, A.; Banchio, G.; Artioli, G.
abstract

One of the limits of quantitative phase analysis of natural clays using the Rietveld method is the lack of an applicable structure model for the highly disordered phases such as montmorillonite. The description of disorder of montmorillonite, the main dioctrahedral smectite, was accomplished using the DIFFaX program [1] which allows the calculation of simulated powder patterns. We followed the strategy successfully used for kaolinite [2] in which simulated powder patterns calculated using different models of disorder are compared to the observed one. Since DIFFaX is bases upon a recursive method and produces a statistical crystal, a super-cell composed of n layers describing the average disordered structure was re-defined to be used in the codes which apply the deterministic Rietveld algorithm. Therefore, a working structure composed of 4 layers (an ideal layer, a b/3 shifted layer, a -b/3 shifted layer, and a -a/3 shifted layer) was described and used in GSAS [3] to fit a natural international standard of Ca-montmorillonite.


2001 - Structure of Mg-exchanged phillipsites [Relazione in Atti di Convegno]
Gualtieri, A. F.
abstract

The structure of the Mg-exchanged forms of three natural phillipsite samples with SU(Si+Al)=0.63, 0.72, and 0.76 arc described. In the more acidic samples, exchanged Mg concentration is lower than 2 a.f.u. and Mg is fully hosted in site II. In sample (1), Mg is 2.4 a.f.u. and occupies and intermediate position between II and II'. As a consequence residual K in site I migrates to the centre of the type I cage inducing a relaxation in the structure which changes from monoclinic P2(1)/m to orthorhombic B2mb. The structure solution was troublesome because some phillipsite crystals surprisingly did not exchange for Mg.


2001 - Synthesis of sodium zeolites from a natural halloysite [Articolo su rivista]
Gualtieri, Alessandro
abstract

The kinetics of hydrothermal crystallisation of sodium zeolites from a natural mixture of halloysite and amorphous silica with Si/Al approximate to 4 was investigated. The sample collected at Scarpara (Tuscania, Italy) is the final product of an intense hydrothermal alteration process on the pre-existing leucitic tufities. In order to enhance its reactivity in the NaOH solution, the sample was thermally activated at 600 degreesC for 1 h. The hydrothermal crystallisation sequence of zeolites formed in the range 90-150 degreesC has been followed using real-time synchrotron powder diffraction. The reaction kinetics of Na-X. Na-P and analcime were analysed using a model developed for the study of the kinetic data from X-ray diffraction experiments. Na-X and Na-P cocrystallize with an autocatalytic nucleation at lower isothermal temperatures and with a heterogeneous nucleation at higher isothermal temperatures. Na-X tends to dissolve before Na-P, which in turn transforms into analcime. This work is part of a general project on the kinetics of formation of zeolites from clay precursors which is important for either engineering and production of valuable industrial materials and for the interpretation of poorly understood processes of formation of zeolites in natural hydrothermal environments.


2001 - The crystal chemistry of paulingite [Articolo su rivista]
Passaglia, Elio; Gualtieri, Alessandro F.; Marchi, Eugenia
abstract

The crystal chemistry of the uncommon zeolite paulingite, updated and revised on the basis of chemical compositions and cell constants of ten samples representative of almost all the occurrences known to date. The framework cation content, defined as R = Si/(Si+Al), shows slight variations ranging from 0.73 to 0.79. The extraframework cations are mainly K, Ca, Na, and minor Ba. Mg and Sr are absent or negligible. The K, Ca and Na contents are extremely variable so that all three types of cation-dominance are found. The cell constant shows small variations (from 35.03 to 35.24 Å) and no significant correlation with the chemical variables. The (K+Na) content is positively correlated with the Si content, and a strong negative correlation between Ca and Na is found. The water content is variable and independent upon the chemical parameters. The dehydration process of the Ca-dominant sample is significantly different from that of both K- and Na-dominant samples.


2001 - Use of organic additives as binders in raw mixtures for ceramic tiles [Articolo su rivista]
Viani, A.; Gualtieri, A. F.; Magnani, A.
abstract

The aim of this work is the study of the role played by organic additives used as binders in raw mixtures for ceramic tiles. Such binders are extensively used for the production of advanced ceramic materials. In traditional ceramics, they can, in principle, allow for a drastic education of the clay fraction and consequently a very positive effect on the colour of the ceramic body without affecting its peculiar physical properties. Polyvinyl alcohol (PVA) was added in proportions of less than 0.5 wt% to different typical raw ceramic mixtures in which the weight fraction of clay minerals was reduced of about 50 wt%. In each case, it was possible to obtain very good mechanical properties of the green bodies. Clay minerals are the component of the mixture with the highest price and the highest content of iron and titanium (known to have negative effects on the whiteness of the ceramic body). Decreasing the amount of clay minerals makes possible to produce ceramic bodies with the same colour, using less quality (i.e. less expensive) raw materials. This can also lead to reconsider the use of several raw materials present on the national territory. Furthermore, superwhite ceramic bodies can easily be obtained even without the introduction of very expensive components such as zircon and alumina. Possible drawbacks appear to be not severe as the milling times are increased of less than 3% (in laboratory), and additional costs due to the organic additive are overwhelmed by the savings due to the choice of less expensive raw materials and the reduction of the clay fraction (up to 20%).


2000 - A solution for the full impregnation of asbestos: the use of an epoxy polymer resin [Articolo su rivista]
Gualtieri, Alessandro
abstract

Asbestos has been identified as priority substance for risk reduction and pollution prevention given its carcinogenic effects. Because of its wide occupational exposures and widespread use in commerce in the past, there is a big concern that it may present a general health hazard. Therefore, the identification of asbestos-containing materials and their neutralization has become a topic plan of social prevention and intervention in many European and American countries. If the presence of asbestos in buildings (i.e., schools) is detected, the abatement program usually accomplishes the removal of the asbestos-containing materials and displacement in controlled waste disposals (ex situ technique). Removal has many disadvantages: high costs, large production of toxic refuses, high risks of exposure for removal workers, and high risk of environmental pollution during and after the operations. Thus, the search for alternative in situ techniques has been recently promoted and full impregnation seems to be the best candidate given its reduced risks for both workers and environment, and its low costs. In this paper, a technique for the in situ full impregnation of asbestos by an epoxy polymeric resin is proposed, and the results of its application for the neutralization of either chrysotile or amphibole asbestos-containing materials is described.


2000 - Accuracy of XRPD QPA using the combined Rietveld-RIR method [Articolo su rivista]
Gualtieri, Alessandro
abstract

QPA (quantitative phase analysis) of polycrystalline materials using XRPD (X-ray powder diffraction) can be performed using the combined Rietveld and reference intensity ratio (RIR) methods, providing an estimate of both the crystalline and the amorphous phase in a mixture. Although the accuracy of estimates of the phase composition of simple ternary or quaternary mixtures is generally very good, uncertainties remain and bias the accuracy of phase determinations in complex systems such as pyroclastic rocks, which may contain two or more zeolite species, a number of other phases (generally up to four or five), and glass. The contribution of the incoherent scattering, biasing accuracy, in the glass determination has been discussed in an earlier work on the modal analysis of pyroclastic rocks [Gualtieri (1996). Powder Diffr. 11, 97-106]. In this work, the assumption of the crystal structure, the influence of the spike addition, background and atomic (thermal) displacement parameters are discussed. It is shown that the structure-model assumption no longer holds for systems containing complex phases such as zeolites, as the accuracy is degraded and, as far as the influence of the added spike is concerned, there is an underestimation of the glass content with increasing amounts of added spike. (C) 2000 International Union of Crystallography Printed in Great Britain - all rights reserved.


2000 - Crystallization kinetics and phase relations of wollastonite by real time synchrotron powder diffraction [Relazione in Atti di Convegno]
Gualtieri, A. F.; Mazzucato, E.; Tang, C. C.; Cernik, R. J.
abstract

The crystallization kinetics of 1T-wollastonite in the CaO-SiO2 system starting from a stoichiometric glass has been investigated in situ by X-ray synchrotron powder diffraction in the temperature range 800-900 °C. At higher temperature, 1T-wollastonite converts into the 2M polytype. The collected data were analyzed by the Avrami models and kinetic parameters seem to indicate a nucleation deceleratory controlled mechanism with one-dimensional growth. The preliminary results of this study are part of a general project aimed to investigate polymorphism and polytypism of wollastonite and the related phases, especially the role of the kinetic parameters in the formation of the polytypes in the pyroxenoid series.


2000 - Formation of alpha-eucryptite, LiAlSiO4: An in-situ synchrotron X-ray powder diffraction study of a high temperature hydrothermal synthesis [Articolo su rivista]
Norby, P; Hanson, Jc; Fitch, An; Vaughan, G; Flaks, L; Gualtieri, Alessandro
abstract

Hydrothermal conversion of zeolite Li-A(BW), LiAlSiO4 H2O, into alpha-eucryptite, LiAlSiO4, occurs at temperatures above 350 degrees C. We report here the first in-situ study of a high-temperature hydrothermal synthesis using time-resolved powder diffraction. The following hydrothermal reactions were studied: 4 M NaNO3:LiAlSiO4 [ABW] --&gt; Li(Na)AlSiO4 H2O [ABW] --&gt; Na(6)Al(6)Si6O(24).2NaNO(3) [SOD]; 2 M LiCl:LiAlSiO4 H2O [ABW] --&gt; alpha-LiAlSiO4; 2 M LiCl:LiAlSiO4[ABW] --&gt; LiAlSiO4.H2O [ABW] --&gt; alpha-LiAlSiO4. The hydrothermal syntheses were performed in stainless steel capillaries. To maintain hydrothermal conditions, a hydraulic pressure of 2-300 atm was applied. Synchrotron X-ray radiation with energies of 35-40 keV was used in order to penetrate the steel capillaries. Room temperature Imaging Plate powder diffraction data were collected on a sample of zeolite Li-A(BW) contained in a steel capillary in an aqueous solution at 200 atm. pressure. With the use of a 10 min exposure, it was possible successfully to refine the crystal structure of zeolite Li-A(BW) using Rietveld refinement. Angle dispersive time-resolved in-situ powder diffraction patterns were collected using a Translating Imaging Plate (TIP) camera. Crystallization and degradation curves for the high-temperature hydrothermal conversion experiments were determined using integrated intensities of selected diffraction lines. The kinetic curves were analyzed using first-order rate expressions.


2000 - Kinetics of Ag distribution in high lead glass by real time synchrotron powder diffraction [Relazione in Atti di Convegno]
Forti, B.; Gualtieri, A. F.; Leoni, M.; Prudenziati, M.; Tang, C. C.
abstract

In the present work we studied the time-temperature behaviour of Ag dispersed in high lead glass layers printed on an 96% alumina substrate. The inks used for the samples were prepared from glass, silver powders and an organic vehicle. The kinetic mechanism of Ag dissolution in the glassy matrix has been investigated by synchrotron XRPD (at beamline 2.3, Daresbury Laboratory, UK) in isothermal conditions. The behaviour versus firing temperature of fine Ag grains dispersed in the thick film dielectric has been investigated by SEM, SEM-EDS and conventional XRD. The kinetic analysis shows an Avrami-like dissolution mechanism: the order of the reaction n is in the range 2.3÷3.7. There is a small but significant decrease of n with temperature. The change could be related to faster heat motion so that the reaction is favoured. The calculated apparent activation energy is 16(1) kcal/mole. The SEM-EDS and XRD analyses show a characteristic floating of Ag as the firing temperature changes.


2000 - Lead free glasses for new generation of thick-film resistors: an explorative investigation [Abstract in Atti di Convegno]
Prudenziati, Maria; Zanardi, F.; Morten, Bruno; Gualtieri, A. F.
abstract

Pastes prepared with seven lead-free glass particles were screen-printed and fired on 96%-Al2O3 substrates. The fired films were studied in terms of sintering, devitrification, crack propagation and bleeding. The most promising glass compositions were selected for the preparation of RuO2-based tghick-film resistors (TFRs), on pre-fired PtAu - or PdAg based terminations; electrical properties of resistors (Rsvs:RuO2 volume fraction, temperature coefficient of resistanceand size effects) were investigated. The study eviced a myriad of complex phenomena occuring in the films, and emphasized the criticality in the choice of glass composition.


2000 - Optimization of the strategy for the quantitative phase analysis of ceramic materials using the rietveld method [Articolo su rivista]
Banchio, G.; Gualtieri, A. F.; Schedoni, A.; Sola, E.
abstract

In this space of work we describe the optimization of the strategy and times for the quantitative phase analysis of ceramic materials using the Rietveld method in order to accomplish a routinary technique for ceramic laboratories equipped with an X-ray powder diffraction instrumentation. We reduced the data collection, reduction and processing times. The time of the data collection was significantly shortened although the statistics was kept good enough to give reliable estimates on the calculated weights of the crystalline phases. The sinergy between the Rietveld method and the chemical analysis results in a full characterization of the ceramic raw materials and products. This work is the outcome of a partnership project involving an academic institution (The University of Modena and Reggio Emilia) and an industrial Laboratory (the "Modena Centro Prove").


2000 - Rietveld structure refinement of Pr doped zirconia [Relazione in Atti di Convegno]
Ferrari, Anna Maria; Bonamartini Corradi, Anna; Bondioli, Federica; Tamburini, Umberto Anselmo; Gualtieri, Alessandro
abstract

This work deals with the synthesis and Rietveld structure refinement of a zirconium-praseodymium yellow pigment prepared either by a traditional ceramic process route and by an unconventional synthesis method based on SHS (Self-Propagating High-Temperature Synthesis). in order to confirm the effective formation of the solid solutions, SEM imaging and EDS analysis, and leaching tests have also been performed. The results proved the applicability of the unconventional processing route for obtaining yellow solid solutions.


2000 - Study of NH4+ in the zeolite phillipsite by combined synchrotron powder diffraction and IR spectroscopy [Articolo su rivista]
Gualtieri, Alessandro
abstract

The Rietveld refinement on synchrotron data of three natural hydrated NH4+-exchanged phillipsites with different Si/Al ratios allowed acceptable assignment of the NH4+ sites. These phillipsites display the typical monoclinic P2(1)/m cell, whose volume increases with increasing numbers of NH4+ ions, which are refined in the two sites labelled I and II. Some residual Na+ is retained in the site labelled II'. Distortion of the Si/Al tetrahedra, which affects some absorption bands in the IR spectra, seems to be mainly due to the distribution of Al in the framework, while the interaction of NH4+ with the O atoms of the framework seems to play a minor role. NH4+ in both sites acts as a donor in hydrogen bonding with O atoms of the framework and water molecules. NH4+ in site I has three H atoms interacting with O atoms of the framework and a number of interactions with water O atoms. In all three samples, monocentric and dicentric connections are formed. NH4+ in site II has one H atom interacting with O atoms of the framework and a number of interactions with water O atoms. Two monocentric connections and a quadricentric one were found in sample (1), three dicentric connections and a monocentric one in sample (2), and three monocentric connections and a dicentric one in sample (3).


2000 - Thermal decomposition of asbestos and recycling in traditional ceramics [Articolo su rivista]
Gualtieri, Alessandro; Tartaglia, A.
abstract

Given the known carcinogenic effects, its wide occupational exposures and widespread use in the past, asbestos is considered a general health hazard and a priority treatment for pollution prevention. In this context, asbestos can be entirely transformed to a mixture of non hazardous silicate phases throughout a thermal treatment at 1000-1250 degrees C and to a silicate glass at T&gt;1250 degrees C. These products may be recycled for the production of traditional ceramics. In this paper we describe the recycle of thermally treated asbestos containing materials as a raw material for glass ceramics and traditional ceramics. A significant improvement of the technological properties of porcelainised stoneware, obtained by high sintering of unglazed ceramic bodies, is accomplished by the addition of 5 wt% of an asbestos-based glass ceramic. (C) 2000 Elsevier Science Ltd. All rights reserved.


2000 - Wollastonite polytypes in the CaO-SiO2 system. Part I. Crystallisation kinetics [Articolo su rivista]
Mazzucato, E; Gualtieri, Alessandro
abstract

This work deals with the identification and kinetics of crystallisation of the wollastonite polytypes which form in the system CaO-SiO2 in the temperature range 700-1000 degrees C. The kinetics of phase transformations in the system have been determined from analysis of in situ synchrotron X-ray powder diffraction data. Two different systems with the same compositions were investigated: one is more reactive, having grains with a larger surface area per unit volume, the other is less reactive, being composed of grains with a smaller surface area per unit volume. 1T-wollastonite forms first and progressively transforms in an intermediate 1Td-wollastonite disordered form. Both phases in turn transform into 2M-wollastonite polytype. Differences in the polytypes forming and reaction kinetics were observed for the two systems. In the more reactive system, the conversion 1T to 1Td polytypes is the dominant process. The kinetic parameters calculated using the Avrami models fully describe the reaction process of formation of both polytypes and transformation of one polytype into the other.


2000 - XANES study of the local environment of iron in natural kaolinites [Articolo su rivista]
Gualtieri, Alessandro; Moen, A; Nicholson, Dg
abstract

Kaolinite exists in nature with a variable degree of structural disorder ranging from partially to completely disordered. Kaolinite invariably contains iron although it is not clear whether it is accommodated in the structure, contained in impurities such as iron hydroxides, or a mixture of the two. The samples studied here are the ordered and disordered international standards KGa-1 and KGa-2 with different iron contents. To obtain the partially dehydroxylated metakaolinite phase, and the completely anhydrous amorphous phase precursor of mullite, the two samples were calcined at 600 degrees C and 900 degrees C, respectively. The local environment of iron was studied by X Ray Absorption Spectroscopy (specifically the XANES region) for either natural and calcined samples. It was found that natural kaolinites KGa-1 and KGa-2 mainly contain 6-fold coordinated Fe3+. The disordered sample KGa-2 shows some 4-fold coordinated iron. Upon heating, for both kaolinites, iron goes into a 4-fold coordination. Fe3+ (and Fe2+) are substituting for Al3+ in kaolinite and thus follow the structure changes to metakaolinite and subsequent high temperature amorphous phase. It is not possible to rule out the possibility that some iron is also contained in amorphous and/or crystalline intercalated hydroxides since at 600 degrees C there is still some Fe3+ in an octahedral environment. Notwithstanding, metakaolinite also has some Al3+ (and possibly Fe3+) retained in a distorted octahedral environment. At 900 degrees C Fe3+ is in 4-fold and partly in 6-fold coordination as it is the case for Al3+ in mullite.


1999 - Chemistry of levynes and epitaxially overgrown erionites [Articolo su rivista]
Passaglia, Elio; E., Marchi; Gualtieri, Alessandro
abstract

This paper deals with the chemistry of 12 levyne-erionite intergrowths. The two zeolite species differ for both framework and extraframework cation contents being levyne constantly Si- and K-poorer and Ca-richer than overgrown erionite. The relative increase of K in the parent solution during the crystallization process is considered the main responsible for the growth of erionite instead of levyne. The dominance of Na among extraframework cations in both levyne and overgrown erionite crystals of three samples of sea-shore occurrence is justified with later cation exchange with sea-water.


1999 - Chromium crystal chemistry mullite-spinel refractory ceramics [Articolo su rivista]
Levy, D; Artioli, G; Gualtieri, Alessandro; Quartieri, S; Valle, M.
abstract

A small amount of chromium oxide was added to a mullite-spinel refractory mixture to improve its thermal and mechanical properties. Two different compositions of mullite-spinel refractory were studied to define the crystal structures hosting the chromium cations, and the chromium solubility in spinel (MgAl2-xCrxO4) was determined. Powder X-ray diffraction (XRD), X-ray absorption near edge spectroscopy (XANES), and scanning electron microscopy (SEM) elemental distribution maps were used to determine the chromium crystal chemistry in the system. The observed maximum solubility of chromium in spinel was found at x = 1.2, but the presence of mullite in the mixture caused a strong decrease of this value. The chromium distribution among the crystal phases reflects the different reaction paths of the two samples: a stage involving spinel and melt drives all present chromium in the spinel, while a simultaneous crystallization of spinel-mullite distributes chromium cations between mullite, spinel, and secondary corundum.


1999 - Dehydration dynamics of analcime by in situ synchrotron powder diffraction [Articolo su rivista]
Cruciani, G; Gualtieri, Alessandro
abstract

The continuous structural transformation of tetragonal analcime (Na15.87Al15.20Si32.64 O-96. 16.3H(2)O) upon dehydration was studied, using Rietveld structure analysis of temperature-resolved powder diffraction data collected using synchrotron radiation. The variation of the a-e axis length difference and normalized intensity of the (200) reflection as a function of temperature suggest that tetragonal analcime evolves toward a cubic structure at high temperature. The removal of water was accompanied by a spreading of the initial Na sites into many positions bonded to the framework O atoms. The migration of H2O molecules through the [111] channels during dehydration caused the six-member ring apertures to open as widely as possible: this was accompanied by a twisting of the tetragonal prism, constituting the analcime framework, which led to an opposite tilting of tetrahedra connecting the prisms. These modifications induced by water diffusion an not energetically favored because they would increase the elastic energy of the system, and require a substantial thermal activation energy. The analcime framework reached a maximum distortion at about 650 K, the temperature of complete water loss, then underwent a relaxation process during which the T-O-T angles were restored to the starting value. The relative variation of cell volume associated with the opening of wide six-member ring channels during water migration, and then due to the framework relaxation process after complete dehydration, provides an explanation of the negative thermal expansion (i.e., volume contraction) effect in dehydrated analcime, which is complementary to that based on the Rigid Unit Modes theory.


1999 - Determination of Nichel(II) oxide in ceramic pigments [Articolo su rivista]
Gualtieri, A. F.; Mazzuccato, E.; Venturelli, P.; Viani, A.; Zannini, Paolo; Petras, L.
abstract

Determination of Nichel(II) oxide in ceramic pigments, by means of high temperature XRD


1999 - Differential anomalous wide-angle X-ray scattering and X-ray absorption experiments to investigate the formation of glass ceramics in the CaO-SiO2-ZrO2 system [Articolo su rivista]
Meneghini, C; Gualtieri, Alessandro; Siligardi, Cristina
abstract

The structure of a CaO-SiO2-ZrO2-based glass ceramic has been investigated by X-ray diffraction, X-ray absorption spectroscopy and differential anomalous scattering techniques as a function of the thermal treatment of the sample. The microstructure of the glass has been investigated at room temperature, before the recrystallization of the glass ceramic, and on two samples annealed at 1073 and 1273 K for 1 h to follow the early stages of nucleation of the quartz and wollastonite crystalline phases. Indications on the roles of Ca, Si and Zr during the devitrification process are given.


1999 - High temperature dehydroxylation of muscovite-2M(1): a kinetic study by in situ XRPD [Articolo su rivista]
Mazzucato, E; Artioli, G; Gualtieri, Alessandro
abstract

Muscovite-2M(1) shows a major phase transition at about 800 degrees C, which is generally attributed in the literature to the structural dehydroxylation process, although a number of structural models have been proposed for the dehydroxylated phase, and different transformation mechanisms have also been put forward. The observed first order transformation involves an increase in the cell volume, and it is not clear to date how the cell expansion is related to the loss of hydroxyl groups. The phase change has been re-investigated here by in situ high temperature powder diffraction, both in non-isothermal and isothermal modes, to combine for the first time the structural and the kinetic interpretation of the transformation. The results unequivocally confirm that the reaction taking place in the temperature range 700-1000 degrees C is truly a dehydroxylation process, involving the nucleation and growth of the high temperature dehydroxylated phase, having Al in 5-fold coordination. Structural simulations of the basal peaks of the powder diffraction patterns indicate that the model originally proposed by Udagawa et al. (1974) for the dehydroxylated phase correctly describes the high temperature phase. The kinetic analysis of the isothermal data using an Avrami-type model yields values for the reaction order compatible with a reaction mechanism limited by a monodimensional diffusion step. Apparent activation energy of the process in vacuum is about 251 kJ/mol. Experiments carried out at temperatures much higher than the onset temperature of the reaction show that the dehydroxylation reaction overlaps with the reaction of formation of mullite, the final product in the reaction pathway.


1999 - In situ study of the goethite-hematite phase transformation by real time synchrotron powder diffraction [Articolo su rivista]
Gualtieri, Alessandro; Venturelli, P.
abstract

The temperature induced goethite-hematite phase transformation that occurs at about 250 degrees C was studied using in situ synchrotron X-ray powder diffraction with a capillary Debye-Scherrer geometry and a translating image plate system (TIPS). To our knowledge, this is the first time the goethite-hematite transformation has been investigated in real time. The sample was a pure, synthetic, stoichiometric goethite with 1 mu m long needle-shaped crystals, The microstructural characterization showed that the sample was well crystallized. The Rietveld refinement of 30 powder patterns extracted from the image in the range 25-800 degrees C demonstrates that an intermediate phase with non-stoichiometric composition (protohematite) forms after the decomposition of goethite. The cell parameter b of goethite dramatically decreased during the phase transformation while a and c instead continued to increase. Protohematite is iron-deficient and retains residual hydroxyls for charge balance. With temperature protohematite progressively transforms into hematite. Empty layers (pores) are consequently formed about the hematite clusters. The distribution of iron vacancies was modeled in the powder patterns with stacking faults that were simulated using anisotropic broadening coefficients of the pseudo-Voigt profile function. Its disappearance with temperature was effectively followed with a decrease of the density of stacking faults.


1999 - Ion exchange selectivity of phillipsite for Cs (+): a structural investigation using the Rietveld method [Articolo su rivista]
Gualtieri, Alessandro; Caputo, D; Colella, C.
abstract

Different ion exchange selectivities for Cs of two phillipsites, one sedimentary and one synthetic, having similar framework compositions, were interpreted by means of Rietveld structural analysis. Both phillipsites were pre-exchanged to achieve Na forms throughout exhaustive elution using an NaCl solution and then enriched in Cs by contact with mixed Cs+ and Na+ solutions. X-ray diffraction data of the original and Cs-exchanged samples were refined using the Rietveld method. Four extra-framework sites labelled I, II, II', and II were refined. Cation distribution in the four sites showed that, although sites I and II are readily occupied by Cs, some Na is prone to be retained in site II', which displays therefore a reduced selectivity for Cs. The new site II is occupied by Cs. The synthetic sample retains much more Na than the sedimentary sample, and this is the reason for the higher selectivity of the sedimentary phillipsite for Cs compared with the synthetic one. The results of this work also suggest that phillipsite may be utilized as a selective cation exchanger for the removal of Cs+ radionuclide in nuclear waste. (C) 1999 Elsevier Science B.V. All rights reserved.


1999 - Mineralogical quantitative phase analysis using the rietveld method. Applications to problems of interest for ceramic industry [Articolo su rivista]
Viani, A.; Gualtieri, A. F.; Mazzucato, E.; Venturelli, P.
abstract

The application of the Rietveld method represents the definitive technique for mineralogical quantitative phase analysis of a wide range of materials from powder diffraction data. The Rietveld method allows high accurate quantitative phase analyses to be performed from samples that cannot be analysed by other experimental techniques. The determination of clay and amorphous phases is of great interest for the ceramic industry, covering all the possible materials involved in the ceramic production cycle, from raw materials to ceramic glasses, from pigments to porcelainized grès. We report here examples of quantitative phase analyses of raw materials and ceramic products accomplished at the Dipartimento di Scienze della Terra of the Università di Modena e Reggio Emilia, as results of collaboration projects with ceramic industries and in the context of scientific research projects.


1999 - Modelling the nature of disorder in talc by simulation of X-ray powder patterns [Articolo su rivista]
Gualtieri, Alessandro
abstract

A sample of talc from Borgotaro (Parma, Italy) has been selected for its phase purity in order to investigate the nature of layer stacking disorder in talc. Earlier models describing disorder in talc have been fully revised using simulated powder patterns generated by DIFFaX. A new model has been suggested consisting of a random sequence of layers, stacked by a/3 along one of the pseudohexagonal X directions, affected by random planar disorder with components of +/-b/3. Modelling the planar disorder effects does not suffice alone to perfectly reproduce the experimental powder pattern, and other microstructure effects such as preferred orientation and size of the coherent crystallite domains must also be considered.


1999 - Rietveld structure refinement of Sr-exchanged phillipsites [Articolo su rivista]
Gualtieri, Alessandro; Passaglia, Elio; Galli, Ermanno; A., Viani
abstract

The structures of three Sr-exchanged phillipsites with different Si/(Si+Al) ratio were refined by the Rietveld method on data collected with a conventional Bragg-Brentano geometry. The distribution of Sr in the extra-framework sites depends on its amount in the sample and hence on the value of Si/(Si+Al). The typical PZ,lin cell with Sr distributed over sites I and II is displayed in the two samples with Si/(Si+Al) = 0.72 and 0.76 respectively. The sample with Si/(Si+Al) = 0.63 instead undergoes a cell modification with Sr distributed in an ordered fashion in sites I, I', II, and II' of four adjacent cavities along the a axis. This ordered site distribution has the effect of changing the typical unit cell with a approximate to 9.8 Angstrom, b approximate to 14.0 Angstrom, c approximate to 8.6 Angstrom, and beta approximate to 124 degrees to a pseudo B-centered monoclinic cell with a approximate to 16.5 Angstrom, b approximate to 14.0 Angstrom, c approximate to 8.6 Angstrom and beta approximate to 99.4 degrees. Nevertheless, the B-centering is broken by the ordered extra-framework site distribution. This study may help in the understanding of the interaction mechanism of Sr-cation exchange in phillipsite for the potential use as a countermeasure amendment in radiostrontium-contaminated soils, and as sieve for Sr-90 in natural waters of nuclear facilities. (C) 1999 Elsevier Science B.V. All rights reserved.


1999 - The aid of X-Ray powder diffraction to the characterisation and treatment of asbestos containing materials [Articolo su rivista]
Gualtieri, A. F.
abstract

Fibrous asbestos minerals have been identified as priority substances for risk reduction and pollution prevention. Because of the well known hazardous effects associated with past occupational exposures to asbestos and because of its widespread use in commerce, exposures to asbestos present a general health hazard. Therefore, the identification and quantification of asbestos in bulk materials which are still sited in a number of plants and public buildings is fundamental for a proper plan of social prevention and general intervention. X-ray powder diffraction is considered an effective tool of investigation of bulk materials with a high statistical significance. The combined Rietveld-RIR method, has been successfully applied for the quantitative determination in the past of asbestos in bulk materials such as insulating cements, mixed asbestos- slag wools, contaminated soils, and others. The University of Jussieu in Paris has been partly evacuated because the framework of the building is composed of an asbestos rich material. This paper reports the description of the characterisation of that material and a possible plan of intervention for the treatment of the hazardous material in situ.


1999 - X-ray powder diffraction quantitative analysis performed in situ at high temperature [Abstract in Atti di Convegno]
Mazzucato, E.; Gualtieri, A. F.; Venturelli, P.; Viani, A.
abstract


1999 - X-ray powder diffraction quantitative analysis performed in situ at high temperature: application to the determination of NiO in ceramic pigments [Articolo su rivista]
Gualtieri, Alessandro; E., Mazzucato; P., Venturelli; A., Viani; Zannini, Paolo; L., Petras
abstract

Although nickel(II) oxide (NiO) is a potential carcinogenic agent, it is still used in the synthesis of ceramic pigments because during their preparation at high temperature, NiO is thought to combine with other compounds, crystallizing as new phases with spinel-like structures. Unfortunately, there are no widely accepted methods for the determination of free NiO in ceramics, the main reason being experimental difficulties. In fact, quantitative phase analysis (QPA) by X-ray powder diffraction (XRPD) may fail because diffraction peaks of NiO with space group Fm (3) over bar m and a similar or equal to 4.18 Angstrom overlap with those of the spinel with space group Fd (3) over bar m and a similar or equal to 8.4 Angstrom. To overcome this problem, in this work QPA has been performed in situ at high temperature to resolve the peak overlap of NiO and spinel by taking advantage of the different thermal expansion of each phase. It is believed that this is the first report of the application of this technique.


1999 - Zeolite content and cation exchange capacity of zeolite-rich rocks [Relazione in Atti di Convegno]
Gualtieri, Alessandro; Marchi, E; Passaglia, Elio
abstract

The zeolite fraction of zeolite-rich rocks of different occurrence was calculated using quantitative phase analysis by combined Rietveld and Reference Intensity Ratio (RIR) methods and cation exchange capacity (CEC) by NH, solution. The cross-check results are in good agreement apart from a clinoptilolite-rich sample whose zeolite content from CEC was significantly underestimated.


1998 - Cation migration in zeolites: An in situ powder diffraction and MAS NMR study of the structure of zeolite Cs(Na)-Y during dehydration [Articolo su rivista]
Norby, P; Poshni, Fi; Gualtieri, Alessandro; Hanson, Jc; Grey, Cp
abstract

In situ synchrotron X-ray powder diffraction and Cs-133 and Na-23 MAS NMR have been used to investigate the cation migration and ordering in samples of cesium-exchanged zeolite NaY as a function of temperature and cesium cation-exchange level and during dehydration. Samples were prepared with cesium-exchange levels varying from 68 to 83% of the total cation content by carrying out repeated ion-exchange and calcination steps. Lower cesium content samples contain sodium cations in the sodalite cages and cesium cations in the supercages (SII and SIII) directly after the ion-exchange process. After dehydration at 350 degrees C and above, sodium cations are observed in the supercages (in SII) and in the double B-rings (SI). A maximum of 8 cesium cations/unit cell (1/sodalite cage) migrate from the super to the sodalite cages, occupying SII' and SI' positions. The supercage sodium cations are then exchanged for cesium in the subsequent ion-exchange steps, increasing the cesium content. In situ X-ray data, collected during dehydration, showed that the sodium migration from SI' to SI occurs initially (at &gt; 180 degrees C). This migration appears to be accompanied by, or drives, the migration of Cs+ from the supercages to the sodalite cages, which occurs at approximately the same temperature (&gt; 200 degrees C). It is not until &gt; 300 degrees C that the migration of SI' sodium cations to SII is observed. Significant variations in the cation occupancies within the cages are seen at different temperatures in the dehydrated samples. For example, at 500 degrees C, there are an equal number of SII and SIII' cesium cations in the lower cesium content sample. On cooling, the cesium cations order in the SII position, the SIII' occupancy dropping from 12.5 to 7. An ordering scheme for the cations in the supercage is suggested to explain these observations. A number of resonances are seen in the Cs-133 MAS NMR, which are assigned, making use of the occupancies obtained from the Rietveld refinements, to the various cesium positions. The lack of spinning sidebands associated with some of the resonances indicates that the some cations in the supercages are mobile, even at room temperature. When the temperature is raised, a number of SII and Sm resonances coalesce, as the cation mobility in the supercages increases.


1998 - Crystal chemistry of the zeolites erionite and offretite [Articolo su rivista]
Passaglia, E.; Artioli, G.; Gualtieri, A.
abstract

Many known occurrences of the zeolites erionite and offretite have been characterized by electron probe microanalysis, X-ray powder diffraction and optical microscopy. For the first time, a substantial amount of experimentally consistent and homogeneous chemical and crystallographic data have been evaluated for these natural zeolites. Systematic analysis of the data, performed by statistical multivariate analysis, leads to the following conclusions: (1) the two zeolites have well-defined compositional fields in the chemical space describing the extraframework cation content, best illustrated in a Mg-Ca(+Na)-K(+Sr+Ba) diagram; (2) no discrimination is possible on the basis of the framework Si/Al ratio because of the extensive compositional overlap between the two species, however the Si-Al content in the framework tetrahedra is the major control on the unit-cell volume dimensions, particularly in erionite; (3) the crystal chemistry of the Mg cations is a major factor in controlling the crystallization of the mineral species; (4) cation compositions at the boundary of the recognized compositional fields might be due to chemical averaging of two-phase intergrowths, although these mixed-phase occurrences are much less common than previously thought; (5) the sign of optical elongation is not a distinctive character of the two phases, it is related to the Si/Al ratio in the framework tetrahedra of each zeolite type and cannnot be used for identification purposes; (6) the zeolite mineral species epitaxially overgrown on levyne in all cases is identified as erionite; in a few cases offretite was found to be overgrown on chabazite; (7) erionite samples epitaxially overgrown on levyne are substantially more Al-rich and Mg-poor than the erionite samples associated with other zeolites.


1998 - Crystal structure crystal chemistry relationships in the zeolites erionite and offretite [Articolo su rivista]
Gualtieri, Alessandro; G., Artioli; Passaglia, Elio; S., Bigi; A., Viani; J. C., Hanson
abstract

This study clarifies the crystal structure variations and relationships in the zeolites erionite and offretite. The crystal structure analyses used Rietveld analysis of X-ray powder diffraction data, obtained both by synchrotron radiation and conventional X-ray sources, and on diffraction patterns obtained by transmission electron microscopy. The framework Al atoms in erionite are preferentially located in the single six-membered ring of tetrahedra (T2 site), whereas the Si-Al distribution is essentially disordered on the tetrahedral framework sites in offretite. In both zeolites, the center of the cancrinite cage is always occupied by K cations in similar amounts in both minerals. The erionite cage in erionite is occupied by Ca and Na atoms distributed on four distinct cation sites. Mg ions can be present up to 0.8 atoms per cell and are located between the Ca1 and Ca3 sites and very close to the Ca2 site on the symmetry axis. In offretite, the Mg site is located on the trigonal axis of the gmelinite cage and the Mg atoms are bonded to a variable number (five or six) of H2O molecules, depending on the site population. The structural data and TEM analysis clearly show that the crystal chemistry of the extraframework cations, Mg in particular, is a major factor controlling whether erionite or offretite crystallizes, the Si-Al distribution in the framework, and the possible stacking intergrowths of the two minerals.


1998 - Dehydroxylation kinetics of muscovite-2M1 [Relazione in Atti di Convegno]
Mazzucato, E.; Artioli, G.; Gualtieri, A.
abstract

The high temperature phase transition of muscovite-2M1 was investigated by "in situ" isothermal X-ray powder diffraction data. The results confirm that the reaction taking place in temperature range 700-1000°C is truely a dehydroxylation process, involving nucleation and growth stages of the dehydroxylated phase having Al in 5-fold coordination The structural simulations agree with the structural model originally proposed by Guggenheim et al for the dehydroxylated high temperature phase. The kinetic mechanism of the reaction has been interpreted in the frame of the Avrami model, with diffusion as the rate limiting step. The experiments in the upper temperature range (∼1000-1200°C) indicate that mullite is the final high temperature product in the reaction pathway, and the process of mullite formation overlaps and interferes with the kinetics of the dehydroxylation process.


1998 - Interactions between bismuth oxide and ceramic substrates for thick film technology [Articolo su rivista]
Immovilli, S; Morten, Bruno; Prudenziati, Maria; Gualtieri, Alessandro; Bersani, M.
abstract

We investigated the interactions between screen printed and fired layers of Bi2O3 and ceramic substrates of alumina and beryllia. It was found that the reaction products are invariably crystalline in nature. Several transitions of Bi2O3 in its polymorphic phases were found to occur on BeO substrates, while newly formed compounds have been observed to grow on alumina substrates, i.e., Al4Bi2O9 on 99.9% Al2O3 and Bi12SiO20 On 96% Al2O3 Bismuth deeply penetrates in the ceramic interstices in all the cases. Until Bi2O3 is not completely reacted, this penetration is diffusion limited (penetration depth w approximate to t(d)(1/2), where t(d) is the reaction time) with values of the activation energy ranging from 3.7 +/- 0.6 eV (BeO substrate) to 1.4 +/- 0.06 eV (96% Al2O3 substrate). It is shown that these processes are notably different to those occurring in PbO/ceramic systems; moreover, they imply different adhesion phenomena of thick films on different substrates.


1998 - Kinetics of hydrothermal synthesis of Li-A(BW) from metakaolinite by time resolved synchrotron diffraction [Relazione in Atti di Convegno]
Gualtieri, A. F.; Norby, P.
abstract

This work deals with the synthesis of Li-A(BW), an orthorhombic zeolite with composition Li-4[Al4Si4O16]. 4H(2)O, from thermally activated kaolinites exhibiting a different degree of stacking disorder in LiOH solution. The kinetic analysis of the data yields informations on the activation energies of the nucleation and growth processes, the related frequency factors, and the reaction mechanism which are discussed in the light of the nature of the precursor. The results should be a support to the general picture on the kinetics of synthesis of zeolites from thermally activated kaolinites drawn for the synthesis of Na-A and hydroxysodalite.


1998 - Modelling the structure of the metastable phases in the reaction sequence kaolinite-mullite by X-ray scattering experiments [Articolo su rivista]
Gualtieri, Alessandro; Bellotto, M.
abstract

The crystal structure of two kaolinites with a different degree of planar disorder and their high temperature (HT) decomposition products have been investigated by means of symmetrical transmission powder X-ray diffractometry and the subsequent calculation of the radial distribution function (RDF). An ordered and a disordered kaolinite (international standard Kga-1 and Kga-2) were selected along with their HT reaction products at 600 degrees C (metakaolinite) and at 900 degrees C (mullite precursor). The calcinations and quenches have been carried out ex-situ prior to the data collection. The procedure for collection and reduction of the data and their interpretation is outlined. The structural characterization of the HT phase transformations is obtained by qualitative analysis of the RDF curves and is related to the extent of planar disorder in the original material. A model for the structure of metakaolinite is proposed on the basis of the present experiments, and of a review of literature data. According to this model, the structure of metakaolinite displays an almost uncollapsed structure with a short-range order in which Al is mainly in four-fold coordination. An ab initio modelling of the RDF curves provides a quantitative evaluation of the proposed structural model. Differences in the HT products from different kaolinites are directly correlated with the density of stacking faults in the starting kaolinites. Moreover the structure of the precursor of mullite is described and discussed with respect to the literature data. The nature and role of gamma-alumina is discussed as well. Finally the DTA exothermic peak of kaolinite is interpreted in the light of the proposed general model.


1998 - Quantitative determination of crystalline and amorphous phase in traditional ceramics by combined Rietveld-RIR method [Relazione in Atti di Convegno]
Gualtieri, Alessandro; Zanni, M.
abstract

A mixture composed of quartz, clay minerals, and feldspars was heated at different temperatures in the range 1085-1215 degrees C for the production of traditional single firing white paste ceramics. The products display different physical and mechanical properties as a function of temperature. The variation of the physical properties such as the linear shrinkage,the water absorption, and others is directly related to changes in the phase composition and their microstructure, The quantitative determination of both crystalline (mullite, quartz, corundum, zircon, and albite) and amorphous phase (mainly alkali-aluminosilicatic glass), and the determination of some microstructural features of the phases have been calculated using the combined Rietveld-RIR method, a powerful X-Ray powder diffraction full profile fitting technique which was succesfully employed in a variety of applications (quantitative determination of asbestos in bulk materials, quantitative determination of the zeolite fraction and glass in pyroclastic tuffs, and others).


1997 - Combined MAS NMR and X-ray powder diffraction structural characterization of hydrofluorocarbon-134 adsorbed on zeolite NaY: Observation of cation migration and strong sorbate-cation interactions [Articolo su rivista]
Grey, Cp; Poshni, Fi; Gualtieri, Alessandro; Norby, P; Hanson, Jc; Corbin, Dr
abstract

Na-23 MAS NMR and synchrotron X-ray powder diffraction methods have been used to study the binding of hydrofluorocarbon-134 (HFC-154, CF2HCF2H) in zeolite NaY. A contraction of the volume of the unit cell is observed on gas adsorption, and the interaction of HFC-134 with the extraframework sodium cations is so strong that extraframework sodium cations in the sodalite cages (site I') migrate into the supercages. These sodium cations are found on positions close to the site III' positions of zeolite NaX. Both ends of the HFC molecules are bound to sodium cations, the HFC molecule bridging the site II and III' cations in the supercages. The strong cation-HFC interaction results in a considerable displacement of the sodium site II cation along the [111] direction into the supercage and an increase in the T-O-T bond angle for the three oxygen atoms coordinated to this cation. A decrease in the Na-23 quadrupole coupling constant on HFC adsorption from 4.4 to less than 2.8 MHz, for the sodium cations originally located in the sodalite cages (site I'), is consistent with the sodium cation migrations.


1997 - Dehydration dynamics of stilbite using synchrotron X-ray powder diffraction [Articolo su rivista]
Cruciani, G; Artioli, G; Gualtieri, Alessandro; Stahl, K; Hanson, Jc
abstract

The continuous structural transformation of the natural zeolite stilbite (Na3.62K0.44Ba0.03Ca6.32Sr0.28Mg0.04[Fe(0.01)(3+)A1(17.33)Si(54.64)O(144)].6OH(2)O) upon dehydration has been studied using Rietveld structure analysis of temperature-resolved powder diffraction data collected with synchrotron radiation. In the initial stage of heating, the monoclinic F2/m stilbite structure (the so-called A phase) behaves as a noncollapsible framework, featuring only a slight framework distortion and a slight cell-volume contraction. At about 420 K, a first-order phase transition occurs changing the symmetry to an orthorhombic Amma phase, whose framework is collapsible and shows a large cell-volume contraction with temperature. The cell contraction is related to the process of T-O-T bond breaking and leads to a high-temperature stilbite phase with the same Amma space group and a collapsed structure similar to the previously described B phase in stellerite and barrerite. The structural refinement indicates that the dynamics of bond breaking is related to the shift of the Ca cations in the channels to achieve optimal coordination after the release of the H2O molecules. Refined statistical occupancies of the tetrahedral atoms involved in the bond-breaking process (T1 and T1P) are consistent with a random rupture and re-formation of the T-O-T bonds. This is the first experimental study of the dynamic bond breaking of T-O-T bonds in a framework structure.


1997 - Interactions between lead oxide and ceramic substrates for thick film technology [Articolo su rivista]
Bersani, M; Morten, Bruno; Prudenziati, Maria; Gualtieri, Alessandro
abstract

This paper deals with the mechanisms and kinetics of interactions between screen printed and fired PbO layers and ceramic substrates: alumina and beryllia. The interaction with alumina occurs via two main processes: (i) a reaction between PbO and Al2O3 grains, which induces the formation of a crystalline phase, Pb2Al2O5; and (ii) an interdiffusion process involving Pb and the intergranular amorphous phase in the ceramic substrate. This latter process results in a compositional change of the intergranular phase at considerable depths inside the ceramic substrate, as well as in the formation of a high lead glass layer on the substrate surface, Since PbO is not completely reacted, the Pb penetration in the ceramic is diffusion limited (penetration depth w approximate to t(d)(1/2) where t(d) is the reaction time) with an activation energy of 1.20 +/- 0.05 eV. The ceramic microstructure significantly affects the interaction processes.


1997 - Kinetic study of hydroxysodalite formation from natural kaolinites by time-resolved synchrotron powder diffraction [Articolo su rivista]
Gualtieri, Alessandro; Norby, P; Artioli, G; Hanson, J.
abstract

Real-time synchrotron powder diffraction was employed to investigate the crystallization process of hydroxysodalite (SOD) from natural kaolinites, The powder diffraction experiments were carried out in isothermal mode using a transmission geometry with capillary samples, and an image plate detector. Natural kaolinites with different densities of planar disorder were thermally activated at 800 degrees C to obtain precursor materials for the syntheses. The metakaolinite precursor was also prepared from the ordered kaolinite at 600 degrees C. The hydrothermal syntheses were accomplished by leaching the activated precursor materials with a 1 M NaOH solution at temperatures in the range from 100 to 130 degrees C. The analysis of the isothermal runs permits calculation of the kinetic parameters and interpretation of the mechanism of hydroxysodalite formation in the light of the structural state of the precursor material. At 100 degrees C, prior to the crystallization of hydroxysodalite, zeolite A (LTA) is formed as an intermediate metastable phase. The mechanisms of nucleation and competing growth of the two zeolites are interpreted on the basis of the obtained kinetic parameters, and of the structural relationship between the two phases.


1997 - Kinetics of formation of zeolite Na-A [LTA] from natural kaolinites [Articolo su rivista]
Gualtieri, A.; Norby, P.; Artioli, G.; Hanson, J.
abstract

The kinetics and mechanism of hydrothermal formation of zeolite A from natural kaolinites have been studied using as starting materials two international kaolinite standards (KGa-1 and KGa-2 from Georgia, USA) exhibiting a different degree of stacking disorder. Precursors utilized for the synthesis were prepared by heating the kaolinites at 800°C. Metakaolinite was also prepared from KGa-1 by thermal activation at 600°C. The hydrothermal syntheses were accomplished by heating the samples in NaOH solutions at temperatures between 70 and 110°C. The kinetic experiments were per-formed by time-resolved synchrotron powder diffraction in isothermal mode using a transmission geometry and an Image Plate detector. The results of the kinetic analysis arc interpreted in the light of the structural state of the starting kaolinite, and of the temperature of activation of the precursor material. For kaolinite activated at high temperature the nucleation and crystallization of zeolite A is essentially independent of the defect density of the original kaolinite, and the thermal history of the precursor seems to be the main controlling parameter. The formation process of zeolite A from metakaolinite materials obtained at lower activation temperatures shows significantly faster reaction rates and lower apparent activation energies. This is again interpreted in the light of the short range inhomogeneities present in metakaolinite. As the reaction proceeds metastable zeolite A transforms into hydroxy-sodalite.


1997 - Powder X-ray diffraction data for the new polymorphic compound omega-Bi2O3 [Articolo su rivista]
Gualtieri, Alessandro; Immovilli, S; Prudenziati, Maria
abstract

A Bi2O3 compound which is unknown to date has been synthesized at 800 degrees C on a BeO substrate. alpha-Bi2O3 at 800 degrees C undergoes a phase transition to a metastable new compound named omega-Bi2O3 which in turn transforms to stable delta-Bi2O3 at 900 degrees C. X-ray powder diffraction data were collected, indexed, and refined in order to obtain a unit cell (probable space group P (1) over bar: a = 7.2688(4), b = 8.6390(6), c = 11.9698(8) Angstrom, alpha = 87.713(6), beta = 93.227(6), gamma = 86.653(4)degrees. This compound is of interest for the thick films circuits and sensors technology. (C) 1997 International Centre for Diffraction Data.


1996 - Modal analysis of pyroclastic rocks by combined Rietveld and RIR methods [Articolo su rivista]
Gualtieri, A.
abstract

The modal analysis of samples belonging to the zeolite-rich pyroclastic formation named "Neapolitan yellow tuff" (Central and Southern Italy) has been determined by full-profile refinement of X-ray powder diffraction (XRPD) data using a combined Rietveld-RIR method. The quantitative analysis and especially the zeolite content is a profitable source for geo-petrographic and genetic considerations and as well an essential source to assess the physical and chemical properties of the bulk material for a feasible use in industrial applications. Albeit a wealth of methods are used for the quantitative determination of zeolite content in pyroclastites they all fail for lack of accuracy as far as concerns the absolute standard deviation of the quantitative data. The outstanding outcomes achievable by using the Rietveld method make it as the most promising technique to fulfill this lack. The glass content in each sample is calculated by a combined Rietveld-RIR method in which a known amount of an internal standard is added to the mixture to rescale the Rietveld refined weight fractions into absolute values. Then, it is reasonable to designate this method as an external method according to the definition given by Hill and Howard (1987). Its counterpart is the internal method developed by Riello et al. (1995a,b). Other techniques such as the addition method and the background scattering volume calculation are developed to accomplish a further determination of the glass content. The results are compared to the values obtained from the Rietveld-RIR analysis. These experimental methods yield an over-estimation of the amorphous phase because the incoherent scattering contribution (air, absorption, sample holder, Compton scattering) is accounted for as the amorphous fraction itself. The glass content of each sample acquired from the Rietveld-RIR refinement on the "raw data" is compared to that accomplished from the refinement of incoherent scattering subtracted data. In addition, some largely used XRPD quantitative techniques such as the external standard and RIR (reference intensity ratio) and the influence of the sample loading method are accounted for in an internally consistent comparison among different procedures of analysis. © 1996 International Centre for Diffraction Data.


1996 - Rietveld refinement using Debye-Scherrer film techniques [Relazione in Atti di Convegno]
Lutterotti, L.; Gualtieri, A.; Aldrighetti, S.
abstract

The advent of modern diffractometers has overcome the old film techniques that were used during the past years. One reason is that computer-controlled diffractometers made available data in a formal ready for the analyses, and the intensities obtained do not suffer for non-linear correction and are very much reliable. The Rietveld method also is established on data obtained from Bragg-Brentano diffractometers equipped with scintillation detectors. However recently, a need for speeding up the analyses is growing, and several experiments have been made to use position-sensitive detectors or energy dispersive detectors for data collection. Very little effort has been involved to resume the old film techniques, coupled with microphotometer systems, that can be used potentially as low cost position sensitive detectors. The film method can be easily improved by simple collection strategies and arrangement on the film-scanning side. The Rietveld method has be successfully applied to the data obtained by the Debye-Scherrer film-technique for structure refinement of a corundum and a quartz samples. A comparison with the results obtainable by a standard Bragg-Brentano diffractometer has been made. Another advantage of the present measurement method is that slight preferred orientations can be easily corrected by rotating the capillary sample holder.


1996 - Rietveld refinement using synchrotron X-ray powder diffraction data collected in transmission geometry using an imaging-plate detector: Application to standard m-ZrO2 [Articolo su rivista]
Gualtieri, Alessandro; Norby, P; Hanson, J; Hriljac, J.
abstract

The results of Rietveld refinements using synchrotron X-ray powder diffraction data collected in transmission mode with a new flat imaging-plate (IF) technique agree with those obtained from other techniques. m-ZrO2 was chosen as test compound because it was the standard selected by the Commission on Powder Diffraction of the International Union of Crystallography for a round robin of Rietveld refinement using data obtained by different techniques and from different laboratories [Hill &amp; Cranswick (1994). J. Appl. Cryst. 27, 802-844]. For comparison, new data were also collected using a gas-filled position-sensitive detector. Powder diffraction using a flat IP detector requires a modification to the geometric term of the Lorentz factor and the zero-shift correction. Other factors that were accurately taken into account are the polarization of the synchrotron beam, the angle-dependent variations induced by the use of a flat detector and the absorption.


1995 - DIAGENETIC MORDENITE FROM PONZA, ITALY [Articolo su rivista]
Passaglia, Elio; Artioli, G; Gualtieri, Alessandro; Carnevali, R.
abstract

Diagenetically altered rhyolitic rocks consisting of major mordenite and minor cristobalite and smectite occur beneath a thick (about 90 m) smectite-rich layer in an abandoned quarry at Cala Fontana, in the northwestern part of the Ponza Island (Thyrrenian Sea, Gulf of Gaeta). The structure of the mordenite was refined by full-profile Rietveld analysis on X-ray powder diffraction data. Quantitative mineralogical analysis of the specimen having the highest zeolite content from the Rietveld-refined phase-scale factors yield: mordenite 72.8%, smectite 2.0%, cristobalite 5.9%, illite 3.0%, sanidine 13.9%, augite 2.4%. The chemical composition of the mordenite from electron microprobe analysis resulted in a content of tetrahedral atoms [Si/(Si + Al) = 0.83] in agreement with the range (0.80-0.85) known for this zeolite. Both the chemical analysis and the structure refinement showed a high K content among the extraframework cations. The assemblage of the authigenic minerals is interpreted as the result of diagenetic alteration of the rhyolitic glass by meteoric or ground water in an hydrologically open system, and the crystallization of mordenite instead of the most common smectite is interpreted as due to locally high pH conditions.


1995 - KINETIC-STUDY OF THE KAOLINITE-MULLITE REACTION SEQUENCE .1. KAOLINITE DEHYDROXYLATION [Articolo su rivista]
Bellotto, M; Gualtieri, Alessandro; Artioli, G; Clark, Sm
abstract

The decomposition reaction of kaolinite has been investigated as a function of the defectivity of the starting material and the temperature of reaction. Time resolved energy-dispersive powder diffraction patterns have been measured using synchrotron radiation, both under a constant heating rate (heating rates from 10 to 100 degrees C/min) and in isothermal conditions (in the temperature range 500 to 700 degrees C). The apparent activation energy of the dehydroxylation process is different for kaolinites exhibiting a different degree of stacking fault density. The results of the analysis of the kinetic data indicate that the starting reaction mechanism is controlled by diffusion in the kaolinite particle. The diffusion process is dependent on the defective nature of both kaolinite and metakaolinite. At high temperatures, and at higher heating rates, the reaction mechanism changes and the resistance in the boundary layer outside the crystallites becomes the rate-limiting factor, and nucleation begins within the reacting particle. During the final stage of the dehydroxylation process the reaction is limited by heat or mass transfer, and this might be interpreted by the limited diffusion between the unreacted kaolinite domains and the metakaolinite matrix.


1995 - KINETIC-STUDY OF THE KAOLINITE-MULLITE REACTION SEQUENCE .2. MULLITE FORMATION [Articolo su rivista]
Gualtieri, Alessandro; Bellotto, M; Artioli, G; Clark, Sm
abstract

The present work is a follow-up of the investigation on the decomposition reaction of kaolinite as a function of the defectivity of the starting material and the temperature of reaction. In the present work we study the high temperature reaction of mullite synthesis from kaolinite, from the starting point of the results obtained in the first part. Time resolved energy-dispersive powder diffraction patterns have been measured using synchrotron radiation in isothermal conditions. The apparent activation energy for mullite nucleation and growth is found to be related to the defective structure of the starting kaolinite, which thus must have an influence on the chemical homogeneity of the amorphous intermediate phase. The analysis of the kinetic data indicate that the initial reaction mechanism is controlled by mullite nucleation, while as the reaction proceeds it shifts towards a grain growth-limited process which is intermediate between phase boundary and diffusion controlled. The order of the reaction obtained from standard analysis of the isothermal kinetic data is lower in the case of the ordered kaolinite KGa-1, in agreement with a rate limiting process more strongly limited by diffusion. For each sample there is a small but significant decrease in the order of the reaction at higher temperature: we interpret the change as related to the variation of the diffusion process in the amorphous phase due to the growing grains of mullite and cristobalite. The values of the activation energies and induction times are comparable neither to a model of mullite formation from a monophasic gel, nor mullite formation from a diphasic gel, being intermediate between the two. We can infer that the amorphous precursors from natural kaolinites can be considered pseudo-monophasic gel-like phases, approaching the monophasic gel-like behaviour as the defectivity of the initial kaolinite increases.


1995 - NATURE OF STRUCTURAL DISORDER IN NATURAL KAOLINITES - A NEW MODEL-BASED ON COMPUTER-SIMULATION OF POWDER DIFFRACTION DATA AND ELECTROSTATIC ENERGY CALCULATION [Articolo su rivista]
Artioli, G; Bellotto, M; Gualtieri, Alessandro; Pavese, A.
abstract

A new model for the description of the structural disorder in natural kaolinite materials is proposed, based on the stacking of two 1:1 layers and their enantiomorphs, and encompassing previously proposed models. The layers, where randomly stacked along the c axis (using probabilistic functions nested in recursive algorithms), correctly describe the observed powder diffraction patterns of natural kaolinites with any density of structural faults. The proposed model was evaluated using electrostatic energy calculations against earlier models of disorder based on layer shift, layer rotation, statistical occupancy of the Al octahedra, or enantiomorphic layers. The present 4-layer model has a minimum of potential energy with respect to the previous models. As expected, the fully ordered triclinic structure of kaolinite possesses the absolute minimum of potential energy.


1995 - Variation in the Vector Competence of Aedes Polynesiensis for Wuchereria Bancrofti [Articolo su rivista]
Gualtieri, A.
abstract

Because of their potential to induce a number of pathological diseases and their widespread industrial usage in the past, the fibrous minerals forming asbestos have been the subject of a number of studies in the past. Although quantification of asbestos minerals by optical and electron microscopy (SEM, TEM) is a routine technique in the case of dispersed airbom fibers, the detection and the quantification of small amount of fibrous minerals like chrysotiie in bulk materials such as building materials is exceedingly difficult. A method for the detection and evaluation of asbestos minerals in massive samples is described, based on a combination of Rietveld and RIR (Reference Intensity Ratio) methods. Lower detection limits are about 0.5-1.0 wt % for chrysotiie, depending on powder pattern, counting statistics, and matrix absorption. The chrysotiie wt % determined on powder diffraction profiles collected on a conventional instrument is precise to about 1.0 wt % absolute (relative error in the range 0-10%). The technique is of straightforward application. If compared with the commonly used microscopic or spectroscopic techniques, it is of much advantage from the point of view of time, and the results are more accurate and statistically significant of the bulk material. A model for the cylindrically disordered structure of fibrous chrysotiie is especially developed for the simulation of the X-ray powder patterns, and it is proposed here. © 1995, Cambridge University Press. All rights reserved.


1994 - High temperature phase transition of muscovite-2M1: Angle and energy dispersive powder diffraction studies [Relazione in Atti di Convegno]
Gualtieri, A.; Artioli, G.; Bellotto, M.; Clark, S. M.; Palosz, B.
abstract

The `in situ' thermal behaviour of muscovite-2M1 in the range 25-1300 °C has been studied by high temperature X-ray powder diffraction, using both conventional angle-dispersive Bragg-Brentano geometry, and energy-dispersive configuration with synchrotron radiation. The reaction starting at about 850 °C shows a phase transition from muscovite-2M1 to muscovite-1M, which is the precursor of a mullite phase, stable at higher temperatures. The temperature dependence of the lattice parameters is discussed, together with the high temperature structural distortions. The parametrization through the tetrahedra rotation angle indicate a more symmetrical ditrigonal cavity at high temperature. The high temperature diffraction spectra collected in the angle-dispersive mode have been analyzed with the aid of powder profile computer simulation and full-profile multiphase Rietveld refinement.


1993 - Mineralogical characterization of sericite-chlorite clays from Davoli (Calabria, south Italy): a proposal for ceramic products [Articolo su rivista]
Bertolani, M.; Gualtieri, A.; David, M. G.
abstract

The mineralogical, physical and chemical characteristics of a clay deposit near Davoli are discussed and related to minerogenesis. The material is composed of a chlorite-sericite clayey fraction plus quartz and sodium feldspar. X-ray diffraction, thermal analysis, microprobe analysis and firing tests in gradient kilns were used to detect about the properties and a possible use of this clay as a ceramic raw material. High temperature products such as mullite and spinel were revealed by X-ray powder diffraction (XRPD) technique. -Authors


1992 - Mullite and cristobalite formation in fired products starting from halloysitic clay [Articolo su rivista]
Gualtieri, A.; Bertolani, M.
abstract

Ceramic raw materials from High Latium (Central Italy) consisting of halloysite-10 Å, amorphous silica, sanidine and other accessory phases were subjected to heat treatment by rapid- and slow-firing processes. The products were studied by X-ray diffraction and optical microscopy. The main newly-formed high-temperature phases were mullite and cristobalite. The discussion centres around the formation and features of these newly-formed crystalline phases. Particular attention is paid to any mineralogical differences between the products from the two modes of firing. © 1992.


1991 - Ceramic raw materials in the Viterbo district [Articolo su rivista]
Gualtieri, A.; Bertolani, M.
abstract

North Latium is characterized by widespread volcanic areas; at present we observe evidence of hydrothermal and fumarolic processes that often produce transformations in the original volcanites. As products of these changes we found new mineralogical phases together with original phases. Sometimes there are also modifications due to sintering reactions. We recognized Halloysite, Sanidine, Zeolites, Amorphous Silica, Smectite. The presence of sulphates like Alunite, Gypsum and Jarosite makes those minerals unsuitable for the ceramics industry. SIV (Viterbo's Industrial Society) promoted a joint research with the University of Modena to have a better knowledge on raw materials of the Viterbo's district. Known raw materials outcrops are described and new ones of Halloysite, Zeolites, Sanidine, Smectite and Amorphous Silica have been identified. The possibility of industrial use is discussed on the basis of Sulphates content.