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Eva Magdalena GUALTIERI

Ricercatore t.d. art. 24 c. 3 lett. A
Dipartimento di Ingegneria "Enzo Ferrari"

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Pubblicazioni

2023 - High-Throughput Nanoindentation Mapping of aMicrosegregated CoCrFeNi Multi-Principal Element Alloy(MPEA): Challenges and Limitations [Articolo su rivista]
Gualtieri, Eva Magdalena; Colombini, Elena; Testa, Veronica; Bolelli, Giovanni; Giovanardi, Roberto; Veronesi, Paolo
abstract

2023 - Influence of Different Filler Metals on the Mechanical and Microstructural Characteristics of Arc-Welded Joints Made of Dissimilar Titanium Alloys [Articolo su rivista]
Gaiani, S.; Gozzi, M.; Ferrari, E.; Menozzi, A.; Lassinantti Gualtieri, M.; Colombini, E.; Veronesi, P.
abstract

In the motorsport industry, the choice of material for manufacturing the heat resistant components often falls on titanium alloys. In most cases, the production flow for this kind of part involves CNC machining and subsequent assembly by welding process, to other parts obtained by cold plastic forming and possibly made using different titanium alloys. Hence, the alloying element-content in the joint area can be extremely heterogeneous and variable point-by-point. To investigate this topic further, dissimilar welding of the alpha/beta alloy Ti6Al4V and of the oxidation-resistant alpha alloy KS-Ti 1.2 ASN-EX was made by GTAW technology and using different filler metals. Chemical and mechanical properties of the welds were investigated by XRD, SEM-EDS, microhardness maps, and tensile and bending tests. Results show that, despite the different alloying elements present in the two filler wires investigated, static properties of the welds are similar. Results also show that the local V/Al content ratio affects the microhardness as it is responsible for the creation of supersaturated alpha phases during the cooling of the weld beads.

2023 - Life cycle impact assessment of solution combustion synthesis of titanium dioxide nanoparticles and its comparison with more conventional strategies [Articolo su rivista]
Rosa, Roberto; Paradisi, Enrico; Gualtieri, Eva Magdalena; Mugoni, Consuelo; Cappucci, GRAZIA MARIA; Ruini, Chiara; Neri, Paolo; Ferrari, Anna Maria
abstract

This paper represents the first attempt to quantitatively and reliably assess the environmental sustainability of solution combustion synthesis (SCS) with respect to other soft chemistry strategies, which are more conventionally employed in the preparation of engineered oxide nanomaterials, namely hydrolytic and non-hydrolytic sol-gel syntheses (i.e., HSGS and NHSGS). Indeed, although SCS is well known to rely on significant reduction in the energy as well as time required for the obtainment of the desired nanocrystals, its quantitative environmental assessment and a detailed comparison with other existing synthetic pathways represents an absolute novelty of high scientific desirability in order to pursue a more sustainable development in the inorganic chemistry as well as materials science research fields. TiO2 nanoparticles were selected as the material of choice, for the production of which three slightly modified literature procedures were experimentally reproduced and environmentally evaluated by the application of the comprehensive Life Cycle Assessment (LCA) methodology. Particularly, SCS was compared from an environmental perspective with sol-gel approaches performed both in water and in benzyl alcohol. The results of the present study were also framed among those recently obtained in a systematic study assessing seven further chemical, physical and biological routes for the synthesis of TiO2 nanoparticles, comprising also flame spray pyrolysis (typically used in industrial productions), highlighting and quantifying the excellent environmental performances of SCS.

2023 - Recycling Of Spent Powders From Additive Manufacturing Processing Of Inconel 625 For The Synthesis Of Cocrfenimoxnb0.4x (X=0-0.1) Multi-Principal Element Alloys (Mpeas) By Spark Plasma Sintering (SPS) Of Mechanically Alloyed Powders [Relazione in Atti di Convegno]
Veronesi, P.; Gualtieri, M. L.; Feltrin, A. C.; Akhtar, F.; Colombini, E.
abstract

Sieve residues from the powder recycling stream in Laser powder bed fusion (L-PBF) processing of Inconel 625 are currently disposed of as hazardous waste, which conflicts with circular economy thinking. Here, the synthesis of metal matrix composites (MMCs) based on carbide- and oxide-strengthening phases finely dispersed in a Multi-Principal Element Alloy (MPEA) matrix was explored as a recycling option for these powders. In particular, mixtures of virgin metal powders and a spent Inconel 625 powder were mechanical alloyed and consolidated by Spark Plasma Sintering (SPS). The process control agent (PCA, ethanol) used during mechanical alloying acted as a source for C and O in the subsequent crystallization of nano-sized carbides and oxides during sintering. By carefully controlling the powder mixture composition, MPEA matrices with different contents of Nb and Mo in the face-centered cubic structure were obtained, as revealed by X-ray Powder diffraction. The bulk samples were further characterized by Scanning Electron Microscopy (SEM) and preliminary mechanical analyses using instrumented indentation. The results showed that spent powder of Inconel 625 was a valuable source of 4d transition metals for the synthesis of MMCs based on a MPEA matrix with enhanced solid solution strengthening and finely dispersed ceramic phases.

2023 - Recycling Of Spent Powders From Laser Powder Bed Fusion Processing Of Inconel 625 For The Mechanical Synthesis Of Cocrfenimoxnb0.4x (X=0-0.1) Multi-Principal Element Alloys (Mpeas) [Relazione in Atti di Convegno]
Colombini, E.; Gualtieri, M. L.; Paggetti, S.; Veronesi, P.
abstract

2023 - Synthesis of Multi-Principal Element Alloys by a Conventional Powder Metallurgy Process [Relazione in Atti di Convegno]
Valsecchi, G.; Colombini, E.; Gualtieri, M. L.; Mortalo, C.; Deambrosis, S. M.; Montagner, F.; Zin, V.; Miorin, E.; Fabrizio, M.; Veronesi, P.
abstract

The development of tailored microstructures of Multi-principal element alloys (MPEAs) is currently a hot topic in physical metallurgy. The most targeted systems are equimolar alloys composed of 3d transition metals including the so-called Cantor alloy (i.e. CoCrFeMnNi) and derivatives such as CoCrFeNi and CoCrFeNiAlx. Powder metallurgy is a promising route for this purpose and include manufacturing techniques such as hot pressing of mechanically activated or prealloyed powders or the less popular press-sinter route of mixed powders. In this work, cold pressing followed by fast vacuum sintering (1h) at various temperatures (Tmax =1100-1300 °C) of mixed powders of CoCrFeNi and CoCrFeNiAl0.4 were explored for the synthesis of structurally and chemically homogeneous alloys. This approach is promising for the synthesis of bulk alloys of higher purity with respect to hot pressing of mechanically prealloyed powders. Microstructural investigations were performed by X-ray Powder diffraction (XRPD) and Scanning electron microscopy (SEM). It will be shown that the reactive sintering kinetics of the investigated systems require a Tmax of 1200 °C for effective alloying at the short holding time employed for CoCrFeNi. Instead, 1300 °C is needed for CoCrFeNiAl0.4.

2022 - In-house synthesis of CoCrFeNi ingots using an electric furnace [Articolo su rivista]
Colombini, E.; Lassinantti Gualtieri, M.; Mortalo, C.; Deambrosis, S. M.; Veronesi, P.
abstract

Bulk Multi-Principal Element Alloys (MPEAs) are generally synthesized by casting, a process needing specific equipment. Here, a standard laboratory electric furnace was used to synthesize bulk CoCrFeNi by melting of prealloyed powders followed by natural cooling. The use of prealloyed powders guaranteed atomic-level mixing. In accordance with the literature, the resulting ingot had a face-centered cubic structure. A typical dendritic-interdendritic microstructure was obtained which was explained by partitioning during solidification and grain boundary wetting phenomenon. Post-annealing treatment improved chemical homogeneity without crystallographic phase change. This work shows the feasibility of melt-aided synthesis of CoCrFeNi HEA under static conditions using a conventional laboratory furnace.

2022 - Powder Metallurgy Route for the Synthesis of Multiprincipal Element Alloys Sputtering Targets [Articolo su rivista]
Colombini, E.; Lassinantti Gualtieri, M.; Mortalo, C.; Deambrosis, S. M.; Montagner, F.; Zin, V.; Miorin, E.; Valsecchi, G.; Fabrizio, M.; Veronesi, P.
abstract

Sputter deposition of multiprincipal element alloys (MPEAs) is a relatively new field of research with high functional potential. The multicomponent design space is immense and practically unexplored. An important obstacle for academic research of such sputtered films is the availability of single-alloy targets and technical difficulties in using cosputtering of multiple metal targets or powder targets. This article focuses on the development of a simple powder metallurgy route, including cold uniaxial pressing of powder mixtures followed by pressureless sintering, for the preparation of targets made of two common base alloys forming simple solid solutions, i.e., FeNiCrCo and FeNiCrMn. In addition, targets of the former one containing 10 at% Al are also prepared. The sintered pellets are composed of randomly oriented crystallites with face-centered cubic structures and an optimum chemical homogeneity. Oxide inclusions and residual porosity, inherent to consolidation and sintering of metal precursors, are observed and possible solutions to overcome these challenging problems are discussed. Nevertheless, encouraging results from preliminary deposition tests of FeNiCrCoAl0.4 using both direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS) are presented.

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 - 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 - 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 - Lightweight concretes based on wheat husk and hemp hurd as bio-aggregates and modified magnesium oxysulfate binder: Microstructure and technological performances [Articolo su rivista]
Barbieri, V.; Lassinantti Gualtieri, M.; Manfredini, T.; Siligardi, C.
abstract

Using lightweight building materials from ecological resources reduces the environmental impact of buildings. Most attention has been paid to lime-based agro-concretes, but low binder-aggregate compatibility as well as slow strength gain are drawbacks. The use of magnesia-based binders has the potential to mitigate these problems. Here, a modified magnesium oxysulfate (MOS) cement was used to manufacture lightweight concretes using wheat husk, a highly available and unexploited resource, and hemp hurd as bio-aggregate. A combined microstructural-technological study was performed, filling gaps in existing literature. Through microstructural observations made by X-ray Powder Diffraction, microscopy imaging (optical, electron) and mercury porosimetry, mechanical and thermal properties in the different concretes were elucidated. It will be shown that the developed lightweight concretes are technologically competitive with lime-based ones, having the advantage of possessing high early strength.

2021 - Synthesis and characterization of (68-x) CuO – xV2O5 – 32TeO2 (x = 0–68 mol%) and (35-x) CuO – xV2O5 – 65TeO2 (x = 0–35 mol%) glasses: Conduction mechanism, structure and EPR study [Articolo su rivista]
Mugoni, C.; Rosa, R.; Giovanardi, R.; Affatigato, M.; Gualtieri, M. L.; Siligardi, C.; Andronenko, S. I.; Misra, S. K.
abstract

In this work, two series of glasses, i.e. (68-x) CuO – xV2O5 – 32TeO2 (x = 0–68 mol%, Te32 series) and (35-x) CuO – xV2O5 – 65TeO2 (x = 0–35 mol%, Te65 series), were synthesized by the melt-quenching method and subjected to physical, thermal and electrical characterization. Their vitreous nature was confirmed by X-Ray diffraction and differential scanning calorimetry, while their structural units were determined by Raman spectroscopy. CuO substitution by V2O5 led to a decrease in density and glass-transition temperature, together with a conductivity increase. Conduction mechanism was interpreted as mainly due to small polaron hopping from the lower (V4+) to the higher (V5+) vanadium valence states. Te32 glasses, possessing the highest electronic conductivities (ranging from 2 E−4 to 5 E−7 Ω−1 cm−1), were investigated by the Electron Paramagnetic Resonance technique, in order to more deeply analyze their structure-conductivity correlation. Particularly, the observed signals were determined to consist in a superposition of a first line due to paramagnetic Cu2+ ions and a second line due to exchange-coupled CuO clusters. Differences in the spectra were determined between samples with higher (i.e. 20-30 mol%) Cu2+ concentrations and samples with lower Cu2+ concentrations, suggesting they are located in different local environments. Finally, it was found that the Cu2+ ions are not involved in the process of electron transfer.

2021 - The effect of zr addition on melting temperature, microstructure, recrystallization and mechanical properties of a cantor high entropy alloy [Articolo su rivista]
Campari, E. G.; Casagrande, A.; Colombini, E.; Gualtieri, M. L.; Veronesi, P.
abstract

The effect of Zr addition on the melting temperature of the CoCrFeMnNi High Entropy Alloy (HEA), known as the “Cantor’s Alloy”, is investigated, together with its micro-structure, mechanical properties and thermomechanical recrystallization process. The base and Zr-modified alloys are obtained by vacuum induction melting of mechanically pre-alloyed powders. Raw materials are then cold rolled and annealed. recrystallization occurred during the heat treatment of the cold-rolled HEA. The alloys are characterized by X-ray diffraction, electron microscopy, thermal analyses, mechanical spectroscopy and indentation measures. The main advantages of Zr addition are: (1) a fast vacuum induction melting process; (2) the lower melting temperature, due to Zr eutectics formation with all the Cantor’s alloy elements; (3) the good chemical alloy homogeneity; and (4) the mechanical properties improvement of re-crystallized grains with a coherent structure. The crystallographic lattice of both alloys results in FCC. The Zr-modified HEA presents a higher recrystallization temperature and smaller grain size after recrystallization with respect to the Cantor’s alloy, with precipitation of a coherent second phase, which enhances the alloy hardness and strength.

2020 - Hydration kinetics and microstructural development of a magnesium oxysulfate cement modified by macromolecules [Articolo su rivista]
Barbieri, V.; Lassinantti Gualtieri, M.; Manfredini, T.; Siligardi, C.
abstract

Magnesium oxysulfates (MOS), obtained by hydration of MgO in MgSO4 solution, are highly interesting as binders in lightweight building materials due to their environmental sustainability and promising technological properties. Recent focus has been concentrated on tailoring the phase composition towards 5Mg(OH)2·MgSO4·7H2O (517 phase) by using various additives (e.g. citric acid) that generally act as retarders of the direct hydration of Mg(OH)2, a competing phase in this system. In this work, macromolecules of vegetal origin were investigated as possible retarders to promote the crystallization of the 517 phase. Isothermal and semi-adiabatic hydration experiments were performed, together with thorough microstructural investigations of hardened cements by electron microscopy techniques (SEM, TEM) as well as X-ray powder diffraction and quantitative phase analyses by Rietveld refinements. The results show a temperature and time dependent retardant effect that is only effective in promoting the crystallization of the 517 phase at ambient temperature. Implications for the manufacturing of lightweight concrete are discussed.

2020 - In Vivo Biodistribution of Respirable Solid Lipid Nanoparticles Surface-Decorated with a Mannose-Based Surfactant: A Promising Tool for Pulmonary Tuberculosis Treatment? [Articolo su rivista]
Truzzi, Eleonora; Leite Nascimento, Thais; Iannuccelli, Valentina; Costantino, Luca; Martins Lima, Eliana; Leo, Eliana Grazia; Siligardi, Cristina; Gualtieri, Eva Magdalena; Maretti, Eleonora
abstract

The active targeting to alveolar macrophages (AM) is an attractive strategy to improve the therapeutic efficacy of ‘old’ drugs currently used in clinical practice for the treatment of pulmonary tuberculosis. Previous studies highlighted the ability of respirable solid lipid nanoparticle assemblies (SLNas), loaded with rifampicin (RIF) and functionalized with a novel synthesized mannose-based surfactant (MS), both alone and in a blend with sodium taurocholate, to efficiently target the AM via mannose receptor-mediated mechanism. Here, we present the in vivo biodistribution of these mannosylated SLNas, in comparison with the behavior of both non-functionalized SLNas and bare RIF. SLNas biodistribution was assessed, after intratracheal instillation in mice, by whole-body real-time fluorescence imaging in living animals and RIF quantification in excised organs and plasma. Additionally, SLNas cell uptake was determined by using fluorescence microscopy on AM from bronchoalveolar lavage fluid and alveolar epithelium from lung dissections. Finally, histopathological evaluation was performed on lungs 24 h after administration. SLNas functionalized with MS alone generated the highest retention in lungs associated with a poor spreading in extra-pulmonary regions. This effect could be probably due to a greater AM phagocytosis with respect to SLNas devoid of mannose on their surface. The results obtained pointed out the unique ability of the nanoparticle surface decoration to provide a potential more efficient treatment restricted to the lungs where the primary tuberculosis infection is located.

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 - Wheat husk: A renewable resource for bio-based building materials [Articolo su rivista]
Barbieri, V.; Lassinantti Gualtieri, M.; Siligardi, C.
abstract

The huge annual production of wheat husk in Europe (10 million tons) creates management problems. Valorization options are thus sought. Here, insulting lime concrete was designed using native wheat husk as lightweight aggregate. Physical-chemical and technological properties of both particles and concretes were determined. Comparisons with hemp concrete manufactured with the same process were made. Similar thermal conductivities for the two types of concretes were obtained (ca. 0.09 W/(m·K)), whereas slightly lower compressive strength was found for wheat husk concrete due to weaker particle-binder interface. Nevertheless, results highlight the high potential of raw wheat husk for development of bio-based materials with interesting performances.

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 - Novel engineered lipid-based nanoparticles for pulmonary tuberculosis inhalation therapy [Poster]
Maretti, Eleonora; Truzzi, Eleonora; Costantino, Luca; Rustichelli, Cecilia; Martins Lima, Eliana; Leite Nascimento, Thais; Siligardi, Cristina; Gualtieri, Eva Magdalena; Miselli, Paola; Buttini, Francesca; Leo, Eliana Grazia; Iannuccelli, Valentina
abstract

Priorities to achieve the WHO goal of ending tuberculosis (TB) epidemic by 2030 include new drug treatments to simplify and shorter conventional drug regimens. TB is caused by Mycobacterium tuberculosis residing and surviving inside alveolar macrophages (AM). Considering that 75-80% of cases of infection remain localized in the lungs, the easiest and most successful therapy could involve the inhalation route offering benefits in terms of patient’s autonomy and compliance, by-passing hepatic metabolism, reducing dose amount, dose frequency, and treatment duration, thus minimising the risk of drug-resistant mutants, toxicity, and side effects. Inhalable powder formulations of repurposed drugs entail engineering techniques such as micro- or nanoparticulate carriers enabling drug emission by Dry Powder Inhaler devices, deposition onto alveolar epithelia, and transport into AM. Within this context, Solid Lipid Nanoparticle assemblies (SLNas) loaded with rifampicin, a clinically useful anti-TB drug, were produced by processing accepted excipients for DPI formulations through an optimized methodology that avoids organic solvents and is suitable for a large-scale production. The prototypes were functionalized by means of newly synthesized AM receptor-specific targeting agents as the ligands anchored on SLNas surface without chemical reactions. In vitro and in vivo preclinical studies highlighted functionalized SLNas with adequate respirability performance, safety, AM internalization ability, and mice lung deposition in an encouraging perspective of a potential efficacious pulmonary TB therapy. This research was supported by a grant on the project “FAR interdisciplinare 2017” from the University of Modena and Reggio Emilia, Modena, Italy (PI Prof. Luca Costantino)

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.

2019 - The Impact of Lipid Corona on Rifampicin Intramacrophagic Transport Using Inhaled Solid Lipid Nanoparticles Surface-Decorated with a Mannosylated Surfactant [Articolo su rivista]
Maretti, Eleonora; Rustichelli, Cecilia; Gualtieri, Eva Magdalena; Costantino, Luca; Siligardi, Cristina; Miselli, Paola; Buttini, Francesca; Montecchi, Monica; Leo, Eliana Grazia; Truzzi, Eleonora; Iannuccelli, Valentina
abstract

The mimicking of physiological conditions is crucial for the success of accurate in vitro studies. For inhaled nanoparticles, which are designed for being deposited on alveolar epithelium and taken up by macrophages, it is relevant to investigate the interactions with pulmonary surfactant lining alveoli. As a matter of fact, the formation of a lipid corona layer around the nanoparticles could modulate the cell internalization and the fate of the transported drugs. Based on this concept, the present research focused on the interactions between pulmonary surfactant and Solid Lipid Nanoparticle assemblies (SLNas), loaded with rifampicin, an anti-tuberculosis drug. SLNas were functionalized with a synthesized mannosylated surfactant, both alone and in a blend with sodium taurocholate, to achieve an active targeting to mannose receptors present on alveolar macrophages (AM). Physico-chemical properties of the mannosylated SLNas satisfied the requirements relative to suitable respirability, drug payload, and AM active targeting. Our studies have shown that a lipid corona is formed around SLNas in the presence of Curosurf, a commercial substitute of the natural pulmonary surfactant. The lipid corona promoted an additional resistance to the drug diffusion for SLNas functionalized with the mannosylated surfactant and this improved drug retention within SLNas before AM phagocytosis takes place. Moreover, lipid corona formation did not modify the role of nanoparticle mannosylation towards the specific receptors on MH-S cell membrane.

2018 - Glass recycling in the production of low-temperature stoneware tiles [Articolo su rivista]
Lassinantti Gualtieri, M.; Mugoni, C.; Guandalini, Sara; Cattini, A.; Mazzini, D.; Alboni, C.; Siligardi, . C.
abstract

The current study deals with the development of low-temperature stoneware tiles with boron-rich waste glass as sintering promotor in a modified triaxial ceramic body. The obtained results are part of a larger project financed by the Italian region of Emilia Romagna and aiming at developing novel formulations for sustainable ceramic products classified as porcelain stoneware. We successfully obtained highly vitrified ceramic tiles (BIa class) at a firing temperature almost 140 °C lower than that normally applied for this product by modifying a traditional triaxial composition and including waste glass. The ecological sustainability was thus improved by lower emissions and substitution of natural raw materials with secondary ones. Pilot scale trials confirmed full adaptability to existing powder processing routes. The microstructure and the temperature-induced phase evolution were analyzed by scanning electron microscopy (SEM) and quantitative phase analyses using X-ray powder diffraction (XRPD) and the Rietveld method. It will be shown that the triaxial body minerals are highly reactive in the boron-rich viscous melt leading to eutectic melting and recrystallization. The high reactivity renders this particular ceramic system flexible in terms of liquid phase composition and post-firing crystal assemblages and is therefore suitable as a base system for design of sustainable ceramic products.

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 - 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 - Microstructural evolution in porous ceramics subjected to freezing-thawing cycles: Modelling experimental outcomes [Articolo su rivista]
Pia, G.; Gualtieri, Ml.; Casnedi, L.; Meloni, P.; Delogu, F.; Siligardi, C.
abstract

Clay roofing tiles have been subjected to freezing-thawing cycles. Analyses performed on the ceramic material highlight changes in the pore size distribution, and the consequent modification of the capillary suction behaviour. A model using intermingled fractal units (IFU) to mimic the porous structure satisfactorily describes the observed porosity evolution. Additionally, it successfully predicts the sorptivity coefficient. The results obtained are in good agreement with the experimental ones. In order to verify the ability of the IFU model to predict sorptivity coefficient, a comparison has been shown with other two analytical procedures. It is possible to note that IFU model better fits experimental values than other models found in the literature

2018 - Photocatalytic enamel/TiO2coatings developed by electrophoretic deposition for methyl orange decomposition [Articolo su rivista]
Morelli, Stefania; Pérez, Rosalina; Querejeta, Amaia; Muñoz, Josemari; Lusvarghi, Luca; Lassinantti Gualtieri, Magdalena; Bolelli, Giovanni; Grande, Hans-Jürgen
abstract

The aim of this study was to obtain photocatalytic coatings, capable to decompose organic pollutants, through Electrophoretic Deposition (EPD) of enamels containing respectively 0%, 5%, 10%, 15% (in wt%) of TiO2onto carbon steel substrates. High quality and homogeneous coatings were obtained by applying 12.5 V during 10 s, as the best EPD conditions. The layers were subsequently heat treated at 740 °C for 10 min, in order to obtain dense glazes. Rietveld refinement of XRD patterns and Raman results show that, after the heat treatment at 740 °C, TiO2mostly exists as anatase, responsible of the photocatalytic effect. Semi-quantitative chemical analysis indicate segregation of TiO2on the coatings surface, reaching saturation in the sample with 10 wt% TiO2. FEG-SEM observations reveal rod-like and spherical Ti-rich phases along the cross section of the coatings; some Ti was also dissolved into the enamel. 3D topographical mapping shows that, by adding TiO2, surface roughness increases significantly. Photocatalytic tests were carried out using a 2 × 10−5M aqueous solution of Methyl Orange (MO) as an organic pollutant. By comparing the decomposition rate of MO achieved with the pure enamel (0% of TiO2) and with the sample with 10% of TiO2, it was shown that the addition of 10% of TiO2results in 90% photocatalytic efficiency. Moreover, the permeation of organic compounds and their UV degradation were studied by measuring the water contact angle onto the enamel surface directly after dipping into oleic acid and after various UV irradiation times. The longer the UV irradiation time, the lower the contact angle, down to a minimum of 14.54° after 8 h of UV irradiation. This means, the compound was initially adsorbed on the enamel/TiO2coating surface (10 wt% TiO2) but was efficiently decomposed upon UV irradiation.

2018 - Properties of HVOF-sprayed Stellite-6 coatings [Articolo su rivista]
Sassatelli, Paolo; Bolelli, Giovanni; Lassinantti Gualtieri, Magdalena; Heinonen, Esa; Honkanen, Mari; Lusvarghi, Luca; Manfredini, Tiziano; Rigon, Rinaldo; Vippola, Minnamari
abstract

Stellite-6 coatings were deposited onto AISI 304 stainless steel substrate by gas-fueled HVOF spraying, systematically varying the process parameter settings. By operating the HVOF torch with a fuel-rich mixture, dense coatings (<1% porosity) are produced, containing up to ≈3 vol% oxide inclusions. A substantial amount of a Cr-rich f.c.c. phase is found, mainly produced by quenching of molten lamellae, and distinct from the equilibrium, Co-based f.c.c. solid solution retained in unmelted particles. These coatings exhibit pseudo-passive behavior and survive 5 cycles (100 h) of the Corrodkote test (ASTM B380-97) with no substrate corrosion. Coatings obtained from oxygen-rich mixtures, on the other hand, contain fewer oxide inclusions but also greater porosity, and do not protect the substrate against corrosion. The wear behavior of the coatings is less influenced by deposition conditions. In ball-on-disk dry sliding tests, all coatings exhibit wear rates of 2–3 × 10−5mm3/(N·m), higher than those reported for bulk or clad Stellite, because of interlamellar delamination. Strain-induced, “martensitic” phase transformation from the f.c.c. structure to a h.c.p. one is observed over a 1–2 μm depth below the contact surface. Additional tribo-oxidation is onset when frictional heat dissipation has heated the wear debris enough to trigger its reaction with the environment. Correspondingly, a transition to a regime of higher friction occurs (from ≈0.6 to ≈0.8). At 400 °C, lamellar delamination is suppressed but wear rates rise to 5–8 × 10−5mm3/(N·m) because of abrasive and adhesive wear. At 800 °C, a dense “glaze” tribofilm is formed by sintered debris particles, firmly bonded to a thermally grown oxide scale on the underlying metal surface. The “glaze” protects the coating, lowering the wear rate to ≈1 × 10−5mm3/(N·m) and the friction coefficient to <0.45. Under high-stress particle abrasion conditions, wear rates of ≈1 × 10−3mm3/(N·m) are found.

2018 - SPS-assisted Synthesis of SICp reinforced high entropy alloys: reactivity of SIC and effects of pre-mechanical alloying and post-annealing treatment [Articolo su rivista]
Colombini, E.; Lassinantti Gualtieri, M.; Rosa, R.; Tarterini, F.; Zadra, M.; Casagrande, A.; Veronesi, P.
abstract

In this work a traditional high entropy alloy (FeCoNiCrAl) was reinforced by uniformly distributed reactive silicon carbide (SiC) particles by a powder metallurgy synthetic route, using as precursors simply mixed powders or mechanically prealloyed ones. The reactive sintering produced a single isomorphic BCC structure. The sample microstructure resulted equiassic, more homogenous in samples based on prealloyed powders. The instability of SiC in the presence of metal precursors resulted in the formation of more stable carbides and silicides, as well as in carbon diffusion in the high entropy alloy matrix and partially unreacted SiC particles. The formation of these newly formed fine precipitates, as well as the presence of residual SiC were useful to increase the hardness of the alloy.

2018 - Suspension HVOF spraying of TiO2using a liquid-fueled torch [Articolo su rivista]
Puddu, Pietro; Popa, Septimiu; Bolelli, Giovanni; Krieg, Peter; Lassinantti Gualtieri, Magdalena; Lusvarghi, Luca; Killinger, Andreas; Gadow, Rainer
abstract

TiO2coatings were deposited by suspension spraying using, for the first time, a liquid (kerosene)-fueled torch. A ball-milled TiO2powder with d50= 5.67 μm was dispersed in isopropanol and, using a peristaltic pump, it was radially delivered in between the combustion chamber and the conical expansion barrel of the HVOF torch, replacing the conventional dry powder ports with adapted liquid injection nozzles. Coatings are made up of highly flattened splats, whose diameter varies reflecting the size distribution of the feedstock powder, and <2% porosity is obtained when the torch is operated using adequate kerosene and oxygen flow rates and low standoff distances. Substantial amounts of anatase were produced even though the feedstock consisted solely of rutile, due to the particularly rapid cooling of molten droplets impacting on the underlying surface at velocities that could be as high as 1000 m/s. Ball-on-disk dry sliding wear tests reveal relatively low wear rates that decrease from ≈10−4mm3/(N·m) to <10−6mm3/(N·m) when the temperature increases from ≈25 °C up to 450 °C. The denseness of the coatings allows them to produce micro-scale plastic deformation with limited brittle fracture.

2018 - The effect of alkaline earth carbonates on the microstructure and mechanical properties of impermeable and lightweight ceramics [Articolo su rivista]
Lassinantti Gualtieri, M.; Colombini, E.; Mazzini, D.; Alboni, C.; Manfredini, T.; Siligardi, C.
abstract

Lightweight impermeable ceramic bodies were designed by combining pore templating and controlled viscous sintering through in-situ crystallization. Various amounts of limestone were added to a glass-fluxed low-temperature stoneware tile formulation. Closed porosity was created by decomposition of carbonates prior to sintering, thus leaving voids that were not completely filled by the viscous melt. The resulting oxides chemically modified the liquid phase and promoted the crystallization of β-wollastonite, diopside and anorthite. Hence, viscous sintering was affected. The addition of limestone brought on several advantages: the temperature of maximum sintering rate was decreased (<900 °C); the dimensional stability range was extended; the matrix was reinforced by newly-formed crystals that compensated for the global structure weakening evoked by increased porosity; an increase in whiteness was observed in concomitance to crystallization, reaching values only obtained when using zircon as opacifier (L*=87)

2017 - Temperature-induced microstructural changes of fiber-reinforced silica aerogel (FRAB) and rock wool thermal insulation materials: A comparative study [Articolo su rivista]
Siligardi, Cristina; Miselli, Paola; Francia, Elena; Gualtieri, Eva Magdalena
abstract

The strive for improved energy efficiency in the building sector has motivated extended research on high-performance thermal insulation materials, leading to new products available on the market. Fiber-reinforced aerogel is a state-of-the-art material suitable as a substitute for traditional ones such as rock wool, especially for retrofitting and refurbishment of historic buildings where interior insulation may be the only alternative. In view of fire safety, commercial products are already tested and classified according to European standards. However, these tests do not give information on microstructural changes which is important to gain full understanding of the material. Knowledge of the reaction dynamics leading to functional changes of the material is needed in order to take actions to improve product quality. Here, the thermally induced microstructure development of fiber-reinforced silica aerogel blankets and rock wool were investigated using in-situ techniques such as thermogravimetry and hot stage microscopy. In addition, X-ray powder diffraction and Scanning electron microscopy analyses were performed ex-situ on thermally treated materials. Flammability was evaluated using cone calorimetry. The results obtained for the two different materials were compared and discussed in view of relationship between microstructure development and fire performance.

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.

2016 - Interactive powder mixture concept for the preparation of geopolymers with fine porosity [Articolo su rivista]
Gualtieri, Eva Magdalena; Cavallini, Alice; Romagnoli, Marcello
abstract

A new concept of chemical foaming is proposed for the preparation of geopolymers with fine porosity. The use of an interactive powder mixture of gas releasing agent and carrier particles, potentially combines the benefits of small point sources of gas with easy homogenization in the fresh geopolymer. This concept was exploited here for the preparation of porous flyash-based geopolymers. The interactive powder mixture was a SiC powder containing reactive submicron FeSi/FeSi2 particles. Premature foaming was avoided due to prolonged induction period and slow reaction rate of the active phase. Samples were characterized using scanning electron microscopy, mercury porosimetry, tree-point bending tests and thermal conductivity measurements. In addition, total porosity was determined using measured apparent and real densities. It was found that fine pore structure (diameter 140 ± 80 μm) not normally obtained using chemical foaming, was achieved in a reproducible manner with this approach.

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 - Preparation of an aqueous graphitic ink for thermal drop-on-demand inkjet printing [Articolo su rivista]
Romagnoli, Marcello; Gualtieri, Eva Magdalena; Cannio, Maria; Barbieri, Francesco; Giovanardi, Roberto
abstract

A graphitic ink for thermal DOD inkjet printing was developed. Challenges to be met were related to the small size of the getting nozzle (20 μm), demanding high dispersion stability of submicron particles, as well as to the physical requirements of the printer. In addition, solvents potentially hazardous to human health were excluded a priori. These necessities led to the development of a ternary aqueous solvent system based on 2-propanol and monoethylene glycol, offering an environmental-friendly alternative to conventional graphene solvents. In addition, high flexibility in terms of physical properties (e.g. surface tension, viscosity, density) important for jetting is obtained. Size reduction and exfoliation, accomplished by wet-grinding of graphite in the presence of a surfactant, were followed by laser diffraction and XRD line broadening analyses, respectively. The separated graphitic colloids used for preparation of inks were composed of ca 30 layers of AB–stacked graphene flakes, as determined by line broadening analyses (XRD data). Jetting of an ink with a solid content of 0.3 mg/mL gave a thickness increase of ca. 25 nm/pass, as determined by FESEM. Electrical characterization evidenced the need to remove residual organic molecules to regain the electrical properties of the graphitic particles.

2016 - Stabilization and thermal conductivity of aqueous magnetite nanofluid from continuous flows hydrothermal microwave synthesis [Articolo su rivista]
Cannio, Maria; Ponzoni, Chiara; Gualtieri, Magdalena Lassinantti; Lugli, Eleonora; Leonelli, Cristina; Romagnoli, Marcello
abstract

Magnetite, Fe3O4, nanoparticles, synthesized by hydrothermal microwave assisted technique in continuous flow, are characterized by X-ray diffraction, FTIR and TEM. The suspension stabilization of the nanoparticles dispersed in aqueous media is evaluated by the zeta potential trend and particle size distribution. The effect of the pH, the addition of a phosphate based dispersant and the sonication time on the suspension stabilization are investigated in detail. Moreover, once identified the most stable nanofluid, its thermal properties are measured to evaluate its possible application as heat transfer fluid. The preliminary results indicate a significant enhancement of magnetite water based nanofluid thermal conductivity with respect to water (up to 25%) and conventional water based fluid.

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 - 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.

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 - Rheological characterization of fly ash-based suspensions [Articolo su rivista]
Romagnoli, Marcello; Sassatelli, Paolo; Gualtieri, Eva Magdalena; G., Tari
abstract

The importance of flow properties in most handling techniques requires specific characterizations of geopolymer rheology in the fresh state. In this work, a Design of Experiment (DOE) approach was used to evaluate the influence of solid load, temperature and dispersant on apparent viscosity and yield stress of fly ash-based geopolymers. The solid load was found to be the most influential variable on viscosity. An increase in solid load led to an increase in apparent viscosity but also of yield stress. Apparent viscosity was found to have an Arrhenius type relationship with temperature. The influence of dispersant on yield stress and viscosity appeared to be minor.

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.

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 - Effect of drying method on the specific surface area of hydrated lime: A statistical approach [Articolo su rivista]
Romagnoli, Marcello; Gualtieri, Eva Magdalena; Hanuskova, Miriam; Rattazzi, Andrea; Polidoro, Costantino
abstract

Lime putty is a traditional binder, experiencing a new advent in the preservation of historical buildings. Recently it was shown that lime putty microstructure evolves with ageing time, generally resulting in a continuous quality improvement, but possibly also passing a minima/maxima. Hence, periodical quality checks during ageing are needed to optimize quality and avoid excessive storage. The specific surface area (SSA) of lime putty is a potentially valuable parameter for quality control as it influences the workability and setting of lime mortars. Gas adsorption and the Brunauer–Emmet–Teller (BET) theory is a popular method for its determination, requiring a dry powder. Generally, freeze-drying is used for powder preparation as this method is assumed to diminish particle aggregation. However, no systematic investigation of the effect of powder preparation method on BET SSA has previously been reported. In addition, reproducibility evaluations of such methods are also lacking. This work was aimed to fulfil these gaps, using both calcitic and dolomitic lime putties. Freeze-drying was compared to heat-induced drying (105 °C) under air as well as at low pressure. In addition, sample microstructure was evaluated using X-ray Powder Diffraction data and Rietveld refinements as well as Electron Microscopy techniques (SEM, TEM). It was statistically proven that freeze-drying, compared to the other dehydration methods, resulted in a 20–35% higher BET SSA for calcitic lime putties consisting mainly of nanoparticles. Instead, BET SSA of a dolomitic lime putty containing micrometre-sized hexagonal platelet crystals was not influenced by drying method. No statistically significant difference in phase composition was found between the samples dried by the different methods, excluding carbonation of the hydroxides as influencing factor. Finally, high reproducibility of BET specific surface area was obtained regardless of drying method which is an important characteristic of a standard test method for quality control.

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.

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 - Rheology of geopolymer by DOE approach [Articolo su rivista]
Romagnoli, Marcello; Leonelli, Cristina; Elie, Kamse; Magdalena Lassinantti, Gualtieri
abstract

The effects of solid/liquid content, temperature, curing time and deflocculant concentration on some fundamental rheological parameters of metakaolin-based geopolymer suspensions activated by NaOH were studied by statistical DOE approach. Solid content appears to be the most important parameter among the studied ones. As well known, it has an influence both on viscosity, shear behaviour and yield stress. Instead the additive, an industrial grade sodium polyacrilate, has demonstrated to have a poor effect on the viscosity and yield stress. In synergy with curing time, temperature showed a different effect with respect to its classic rheological influence. In countertrend, increasing the temperature resulted in an increased viscosity due to acceleration of the geopolymerisation reactions.Rheological parameters have proven to be very sensitive to chemical changes in the studied system. In combination with DOE methodology, it is a potent tool for monitoring the microstructural evolution of geopolymers during curing.

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 - 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.

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 - Advantages in using Design of Experiment and Artificial Neural Networks in the study and optimisation of ceramic systems [Articolo su rivista]
Romagnoli, Marcello; Gualtieri, Eva Magdalena
abstract

Design of Experiments (ODE) and Artificial Neural Networks (ANN) are suitable for studies of complex systems. In DOE, experiments are properly distributed within the factor space in order to minimize the number of experiments required to obtain a statistically valid functional relationship between a response and factors. ANN is a computer model inspired by the neural network structure of the brain. Although these methods are based on mathematical theories, their use do not require advanced mathematical skills as efficient PCs and software tools are available. Major advantages of these experimental approaches over traditional ones, such as the onefactor-at-a-time method (OFATl, include the possibility to reveal interactions between factors and determine their setting for a desired response. Despite these advantages, their use is still limited, probably due to lack of familiarity. This report will give a short introduction to these methods and their use in traditional ceramics.

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 - 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 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 - 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 - Electrical properties of thermally sprayed Ni- and Ni20Cr-based resistors [Articolo su rivista]
Prudenziati, Maria; Gualtieri, Eva Magdalena
abstract

Five laboratories were asked to deposit Ni and Ni20Cr powders to obtain resistors; we studied their electrical properties in the temperature range 20-500 C and interpreted the results in the light of their microstructure. Resistors sprayed from Ni powders consist of NiOx "islands" embedded in a Ni matrix. The temperature dependence of resistance (TCR) is in perfect agreement with that of pure Ni, indicating that the matrix detections. the electrical transport. Annealing at temperatures from 200 to 400C results in an irreversible decrease of resistance. A multiphase microstructure is observed in resistors prepared from 80Ni20Cr powders. The major phase in these resistors is a NiCr alloy but with a Ni:Cr ratio larger than 80:20. Minor amounts of metal oxides are also detected. The TCR in these samples spans from 180 ppm/C to 2830 ppm/C, and is attributed to different degree of oxidation and segregation of the metals in the alloy.

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 - 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 - 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 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.

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 - 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

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 - 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.

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.