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Professore Associato presso: Dipartimento di Ingegneria "Enzo Ferrari"

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- Procedimento di inertizzazione di amianti mediante applicazioni di microonde [Brevetto]

Il brevetto descrive un metodo per poter riscaldare in un forno a microonde diverse pezzature di amianto o materiali contenenti amianto. Il riscaldamento a microonde, trasferendo energia sotto forma del campo elelttromagnetico, riesce a riscaldare in breve tempo l'amianto che è un noto isolante termico. A seguito del riscaldamento il minerale fibroso degrada in un materiale assolutamente innocuo attuando così l'auspicata inertizzazione ed azzerando la tossicità del prodotto iniziale. Il brevetto riporta dati sperimentali eseguiti presso i laboratori attrezzati dell'ENEA. Si riporta anche l'idea di avere applicatori aperti in grado di realizzare l'inertizzaizone su superfici piane di amianto o di materiali conteneti amianto, come ad esempio l'Eternit.

2019 - Building a Sustainability Benchmarking Framework of Ceramic Tiles Based on Life Cycle Sustainability Assessment (LCSA) [Articolo su rivista]
Ferrari, Anna Maria; Volpi, Lucrezia; Pini, Martina; Siligardi, Cristina; Enrique García-Muiña, Fernando; Settembre-Blundo, Davide

The purpose of this paper is to determine indices of environmental, economic and social sustainability related to the Italian production of ceramic tiles in porcelain stoneware in order to contribute to the construction of a reference benchmarking useful to decision makers, designers and end users of ceramic tiles. To achieve this goal, this paper is based on the Life Cycle Sustainability Assessment (LCSA) framework that incorporates the three dimensions of sustainability with cradle-to-grave Life Cycle Assessment (LCA), Life Cycle Costing (LCC) and Social Life Cycle Assessment (S-LCA) tools. The study has shown that in the production of porcelain stoneware one of the major environmental problems, in addition to production in the strict sense, is the distribution systemof the product to end users and, to a lesser extent but always significant, the process of supplying raw materials. Finally, it was highlighted that the joint use of the three impact assessment tools (LCA, LCC, S-LCA) requires further methodological work to avoid the risk of double counting of sustainability performance. This research has adopted a detailed methodological approach, both in the collection and in the processing of data, keeping the main phases of the production process separate. In this way, it has been possible to highlight that the major environmental criticalities are just beyond the “gate” of the ceramic factories, along the logistics chain. The study also proposes for the Italian ceramic sector not only indicators of environmental sustainability but also economic and social.

2019 - E-LCA of Two Microwave Absorbers Obtained from Slag of Copper Primary Production [Articolo su rivista]
Zerazion, E.; Pini, M.; Mugoni, C.; Siligardi, C.; Veronesi, P.; Ferrari, A. M.

Purpose: This research investigates the environmental performance of two products obtained using slag derived from copper primary production (copper slag, CS). The first is a tile produced as a traditional stoneware ceramic plate (CS tile) and the second product is a glass–ceramic sample obtained by melt quenching method (CS bulk sample). The products are intended for use in industrial plants as auxiliary heating elements aimed at absorbing microwave. Methods: The environmental assessment was carried out using LCA methodology, and the obtained outcomes were compared to the results calculated for a traditional tile containing silicon carbide (SiC tile). Results: The analyses show that the innovative products have an environmental load of 74% for the CS tile and 54% for the CS bulk sample lower than the environmental impact calculated for the traditional SiC-based material tile. The latter presents a high environmental load due to the incidence on the total impact of the raw materials production. In fact, LCA analysis proves that copper slag production has an impact of 96% lower with respect to the SiC production. Conclusions: This study identifies a possible waste reduction strategy in accordance with the European end-of-waste criteria, but these results should be supported by a site analysis in order to provide an appropriate context for decision making.

2019 - Lime-cement textile reinforced mortar (TRM) with modified interphase [Articolo su rivista]
Signorini, Cesare; Sola, Antonella; Nobili, Andrea; Siligardi, Cristina

Background: Lack of interphase compatibility between the fabric and the matrix significantly impairs the load-bearing capacity of textile reinforced mortar (TRM). In this study, we consider the application of two inorganic surface coatings for enhancing the interphase bond properties. Methods: Either of two silica-based coatings, namely nano- and micro-silica, were applied to alkali-resistant glass (ARG) and to hybrid carbon–ARG woven fabric. Mechanical performance of TRM reinforced with the uncoated and the coated fabric was compared in uniaxial tensile tests. Results: Mechanical testing provides evidence of a remarkable enhancement in terms of ultimate strength and deformability for the coated specimens. This effect can be ascribed to the improved hydrophilicity of the fibers’ surface and to the activation of pozzolanic reaction at the interphase. In addition, penetration of nano- and microparticles in the bundle of the textile yarns reduces the occurrence of telescopic failure.

2019 - New strategy for microplastic degradation: Green photocatalysis using a protein-based porous N-TiO2 semiconductor [Articolo su rivista]
Siligardi, Cristina; Barbirei, Virginia; CEDILLO GONZALEZ, ERIKA IVETH

Currently, the global community considers microplastics as a marine pollutant of emerging concern. To mitigate the oceanic microplastic pollution, it is necessary to reduce inputs from inland. In this sense, we present the first report on the use of photocatalysis for the degradation of HDPE microplastics extracted from a commercially available facial scrub. This was achieved by using two proposed semiconductors based on N-TiO2. One was green synthesized using the extrapallial fluid of fresh blue mussels, which presented an excellent capacity to promote photocatalytic degradation in solid and aqueous environments; while the second photocatalyst, obtained from a conventional sol-gel synthesis, presented good capacity to promote mass loss of the as-extracted microplastics in an aqueous environment. Mass losses, SEM and FTIR analysis confirmed HDPE degradation. Results showed that environmental conditions, microplastics/N-TiO2 interaction and the N-TiO2 surface area should be carefully set and monitored in order of avoiding the arrest of photocatalysis

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

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 - Sustainability as source of competitive advantages in mature sectors The case of Ceramic District of Sassuolo (Italy) [Articolo su rivista]
Settembre Blundo, Davide; Enrique García-Muiña, Fernando; Pini, Martina; Volpi, Lucrezia; Siligardi, Cristina; Ferrari, Anna Maria

Purpose – The purpose of this paper is to explore how sustainability can become a source of competitive advantage for mature manufacturing sectors where technologies are standardized, and innovation is mainly generated across the value chain and not by individual companies. Design/methodology/approach – From the methodological point of view, this research estimates the sustainability status of ceramic production in the Sassuolo district (Italy), using the Life Cycle Sustainability Assessment (LCSA) model, and changing the observation point for the analysis, from the enterprise (micro level) to the entire sector (meso level). Findings – This paper provides an analysis of the environmental, economic and social impacts of the four main types of ceramic tiles manufactured in Italy, both in aggregate terms for the entire sector and per square meter of product. Practical implications – The methodological approach used in this research is easy to replicate both for companies when designing their sustainability strategies and for public decision makers when assessing the sustainability performance of a sector or supply chain. Social implications – For the first time, a socio-economic impact assessment is proposed for the ceramic sector, conducted in parallel with the environmental impact assessment through stakeholder mapping and prioritization.

2019 - Sustainable mineral coating of alkali-resistant glass fibres in textile-reinforced mortar composites for structural purposes [Articolo su rivista]
Signorini, Cesare; Nobili, Andrea; Siligardi, Cristina

The mechanical performance of a silica-based mineral nano-coating applied to alkali-resistant glass textile-reinforced composite materials aimed at structural strengthening is investigated experimentally. The silica nano-film is directly applied to the alkali-resistant glass fabric by sol–gel deposition. Two lime mortars are adopted as embedding matrix, which differ by the ultimate compressive strength and elongation. Uni-axial tensile tests of prismatic coupons are carried out according to the ICC AC434 guidelines. Remarkable strength and ductility enhancements could be observed in the silica-coated group, as compared to the uncoated group, for both mortar types. Digital image correlation, electron scanning and optical microscopy provide evidence of improved interphase strength. X-ray diffraction of the anhydrous mortars brings out the role of the mineralogical composition of the embedding media on the overall bonding properties of the composites. Consideration of design limits and energy dissipation capabilities reveals the crucial role of matrix ductility in bringing the contribution of interphase enhancement to full effect. We conclude that best performance requires optimizing the pairing between fabric-to-matrix adhesion and matrix ductility

2019 - Vitrocrystalline foams produced with EPS as pore former: Processingand characterization [Articolo su rivista]
de Moraesa, E. G.; Bigib, M.; Stocheroa, N. P.; Arcaroa, S.; Siligardi, C.; Novaes de Oliveira, A. P.

tIn this work, discarded soda-lime-silica glasses (from glass bottles) and expandable Styrofoam, EPS(d50< 1 mm) were successfully converted into vitrocrystalline foams for thermal insulation applications.Physical, chemical and thermal properties of the selected and prepared raw materials (wastes) were char-acterized. Batches containing well mixed glass powder (d50< 5 m), EPS powder beads (10–40 vol.%) andBonder Plus®(Na2SiO3solution) were prepared so that powder compacts uniaxially pressed at 20 MPawere obtained. The powder compacts were dried at room temperature for 24 h and then fired at 850◦C,10◦C/min for 30 min. Vitrocrystalline foams with interconnected cells sizes between 150 and 850 m,homogeneously distributed in a crack free matrix were produced and characterized from the point ofview of their typical physical, chemical, morphological, thermal conductivity and mechanical properties.The results showed that it is possible to obtain vitrocrystalline foams (cristobalite and devitrite as crys-talline phases), with porosity up to 90%, compressive strength of 2.75 MPa and thermal conductibilityof 0.06 W/m K, for foams containing 40 vol% of pore former. The magnitude of the measured propertiesof the produced vitrocrystalline foams are adequate for a number of applications requiring low thermalconductivity.

2018 - Accelerated biological ageing of solar reflective and aesthetically relevant building materials [Articolo su rivista]
Santunione, G.; Ferrari, C.; Siligardi, C.; Muscio, A.; Sgarbii, E.

The properties of building materials relevant to their thermal or aesthetical performance can be seriously influenced by the colonization of external surfaces by microorganisms. Deterioration phenomena due to biological aggression cause the loss of energy performance of solar reflective materials because of the decrease of solar reflectance. Bio-deterioration also affects cultural heritage, damaging the aesthetic appearance and thus the historic value. In order to investigate the consequences of biological aggression in short times, an accelerated test method based on a laboratory-reproducible set-up is proposed. Specific and controlled environmental conditions are chosen to accelerate as much as possible biological growth on building materials. In this regard, a reproducible bio-ageing protocol has been outlined and it allows a set of materials to reach an advanced bio-aged level in a short time (8 weeks or less). This test method is aimed to comparatively evaluate different materials under a given set of ageing conditions. Through surface, microstructural and chemical analysis, the evolution of the materials’ properties after ageing is investigated. Attention is also paid to bacterial and algal growth rate by analysing time-progressive images.

2018 - Below room temperature:how the photocatalytic activity of dense and mesoporous TiO2 coatings is affectes" [Articolo su rivista]
Cedillo Gonzalez, E. I.; Riccò, R.; Costacurta, S.; Siligardi, C.; Falcaro, P.

Different parameters such as morphology, porosity, crystalline phase or doping agents affect the self-cleaning performance of photocatalytic TiO2-based coatings. However, also environmental conditions have been found to play a major role on the photocatalytic self-cleaning property. Substrate temperature is a significant environmental variable that can drastically affect this process. This variable becomes of great importance especially for outdoor applications: many self-cleaning photocatalytic materials have been designed to be exposed to outdoor environments and consequently, can be exposed to variable temperatures depending on the season of the year and the typical weather of the geographical zone. Thus, understanding the influence of the most common outdoor temperatures on the self-cleaning performance of TiO2-based coatings is essential for the fabrication of any kind of photocatalytic self-cleaning materials (fabricated by coating technology) that is expected to be subjected to outdoor environments. In this work, the photocatalytic activity was studied by Fourier Transformed Infrared (FTIR) Spectroscopy varying the temperature in the 0 to 30 °C range for dense and mesoporous TiO2 coatings. The temperature conditions at which these coatings present better performances were identified, providing a deeper insight for the practical application of TiO2-based self-cleaning coatings. © 2017 Elsevier B.V.

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

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 - Influence of domestic and environmental weathering in the self-cleaning performance and durability of TiO2 photocatalytic coatings [Articolo su rivista]
Erika Iveth Cedillo-Gonzáleza, ; Barbieri, Virginia; Paolo, Falcaro; Torres-Martínez, Leticia M.; Isaías, Juárez-Ramírez; Laura, Villanova; Montecchi, Monica; Pasquali, Luca; Siligardi, Cristina

Weathering of photocatalytic TiO2 coatings represents an important issue for the successful application of TiO2- based self-cleaning materials. Photocatalytic efficiency of the as-prepared materials is crucial for commercialization; however, changes in the coating performance due to weathering become a critical factor for practical applications. Moreover, chemical durability should be considered as weathering can promote the release of photocatalyst nanoparticles, which can pollute the environment and be hazardous for human health. In this study, two photocatalytic TiO2 coatings with different microstructures (namely compact and mesoporous) were exposed to chemical treatments to simulate domestic and environmental weathering. Results show that dense TiO2 coatings with a slow photocatalytic activity are suitable for domestic applications as minimum leaching of photoactive material was observed. Conversely, once exposed to chemical solutions commonly present in domestic environments, the initially highly active mesoporous TiO2 coatings showed a dramatic drop of the selfcleaning performance and a significant release of nanoparticles in the surrounding environment. It is expected that the results reported here will be of particular relevance for the construction sector, as the manuscript discloses important knowledge for the development of TiO2-based self-cleaning materials once exposed to indoor or outdoor environments.

2018 - Lifecycle-oriented design of ceramic tiles in Sustainable Supply Chains (SSCs) [Articolo su rivista]
Settembre Blundo, Davide; Enrique García Muiña, Fernando; Pini, Martina; Volpi, Lucrezia; Siligardi, Cristina; Ferrari, Anna Maria

Purpose – The purpose of this paper is to analyse the production cycle of glazed porcelain stoneware, from the extraction of raw materials to the packaging of the finished product, with the aim of verifying the effects of integrating an environmental impact assessment into the decision-making process for managing the life cycle, tomake it economically and ecologically sustainable, in a holistic approach along the supply-chain. Design/methodology/approach – The research is performed using the life cycle assessment and life cycle costing methodologies, to identify environmental impacts and costs, that occur during extraction of raw materials, transportation, ceramic tiles production, material handling, distribution and end-of-life stages within a cradle to grave perspective. Findings – Through the use of a comprehensive analysis of the environmental impact assessment and related externalities, three possible strategic options to improve the environmental performance and costs of ceramic tile production were formulated, leveraging sustainability as a competitive advantage.

2018 - Lithium and copper transport properties in phosphate glasses: A Molecular Dynamics study [Articolo su rivista]
Broglia, Giulia; Mugoni, Consuelo; Siligardi, Cristina; Montorsi, Monia

Recently glasses have been considered as potential candidates for solid-state batteries applications due to the peculiar properties that they show if compared to crystalline ones. In this work, the dynamic properties of copper (Cu1 +) and lithium (Li1 +) ions in phosphate glasses, in which Cu2O was progressively substituted to Li2O, were investigated and correlated with the glass structure analysis by using Molecular Dynamic (MD) simulations. The diffusion of Li+ ions and how it is influenced by Cu2 + and Cu1 + ions were highlighted. In this vitreous system, the Cu1 + ions diffuse interacting with the lithium diffusion. This results in the general increase of the activation energy of Li1 + as a function of the Cu2O content in these glasses. At the same time the substitution of Li2O by Cu2O leads to the decrease of the Ea of the Cu1 +, mainly due to structural changes that promote the disruption of the Li1 + pathway and the creation of more stable Cu1 + sites. This explains the increased migration of this ion in higher copper content system.

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.

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 - Silica coating for interphase bond enhancement of carbon and AR-glass Textile Reinforced Mortar (TRM) [Articolo su rivista]
Signorini, C.; Nobili, A.; Cedillo González, E. I.; Siligardi, C.

In this paper, we investigate the effect of silica nano-coating for interphase bond enhancement on the mechanical performance of Textile Reinforced Mortar (TRM) composite materials aimed at structural rehabilitation and strengthening. Alkali-resistant glass (ARG) and carbon fabric reinforcements are preliminarily treated via sol-gel deposition of SiO2coating to promote bond formation capability with the mortar matrix. Optical and electron microscopy provide evidence of interphase bond enhancement. Mechanical performance is assessed both in traction, through uni-axial elongation of prismatic coupons, and in flexure, by three-point bending of laminated masonry bricks. Results are given in terms of mean strength curves, ultimate and design strength and strain values, cracked and uncracked moduli, mean crack spacing, mean crack width and energy dissipation. It is shown that mean absolute performance of silica coating offers a significant improvement over uncoated fabric, yet it is inferior to that of specimens which have been treated with a liquid partially-organic adhesion promoter (polymer coating). However, when design values are considered which incorporate the dispersion of experimental data, silica coating proves superior or at least equivalent to polymer coating, respectively for carbon and ARG fabric. These promising results describe the first application of silica nano-coating to fabric reinforced composite materials.

2018 - Structural and optical properties of cerium oxide doped barium bismuth borate glasses [Articolo su rivista]
Barbi, Silvia; Mugoni, Consuelo; Montorsi, Monia; Affatigato, Mario; Gatto, Corrado; Siligardi, Cristina

This study focuses on the characterization of heavy metal oxide glasses containing CeO2 as dopant with the aim to enhance its density, as many optical applications of glasses (eg: heavy particles measurement in high energy physics) are heavily dependent on the density of the glass itself. Different concentrations of CeO2 were added to a barium bismuth borate base glass and the relative structural and optical properties were studied. The structure of the obtained material was analysed by means of density measurement, molar volume calculation, X-Ray diffraction, thermal analysis and Raman spectroscopy. The results show that CeO2 promotes the formation of a crystalline phase and improves the density of the base glass. Optical properties were studied, such as transmittance and luminescence, and the obtained results suggest that the crystalline formation scatters light transmittance through the sample, preventing luminescent emission. Further improvements in glass formulation have been suggested in order to enhance its optical properties together with its density

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.

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 - Assessment of environmental performance of TiO2 nanoparticles coated self-cleaning float glass [Articolo su rivista]
Pini, Martina; Cedillo González, Erika; Neri, Paolo; Siligardi, Cristina; Ferrari, Anna Maria

In recent years, superhydrophilic and photocatalytic self-cleaning nanocoatings have been widely used in the easy-to-clean surfaces field. In the building sector, self-cleaning glasses were one of the first nanocoating applications. These products are based on the photocatalytic property of a thin layer of TiO2 nanoparticles deposited on the surface of any kind of common glass. When exposed to UV radiation, TiO2 nanoparticles react with the oxygen and water molecules adsorbed on their surface to produce radicals leading to oxidative species. These species are able to reduce or even eliminate airborne pollutants and organic substances deposited on the material’s surface. To date, TiO2 nanoparticles benefits are substantiated, however, their ecological and human health risk is still under analysis. The present work studies the ecodesign of industrial scale up of TiO2 nanoparticles self-cleaning coated float glass production performed by LCA (Life Cycle Assessment) methodology and applies new human toxicity indicators into the impact assessment stage. Production, in particular the TiO2 nanoparticles application, is the life cycle phase that mainly contributes to the total damage. In according with ecodesign approach, the production choices carried out have led to optimize the environmental burdens.

2017 - Failure analysis of glazed LAS glass-ceramic containing cerium oxide [Articolo su rivista]
Barbi, Silvia; Miselli, Paola; Siligardi, Cristina

In this study a deep investigation of the correlation between microstructure and mechanical properties was performed on glass-ceramic materials containing cerium oxide. The glass-ceramic materials investigated were lithium-aluminum silicate based (LAS), obtained through different thermal cycles from the same parent glass. The mechanical properties were tested on the glass-ceramics with and without the application of a glaze. All the glass-ceramics were characterized by means of scanning electron microscopy (SEM), also in field emission guns geometry (FEG), energy-dispersive spectrometry (EDS), X-Ray diffraction (XRD), and 3-points mechanical flexural strength resistance test. This study has revealed that the microstructure of the glass-ceramic is mainly affected by the heating treatments holding times. The application of a glass coating leads to the formation of cerium oxide crystals at the glaze/glass-ceramic interface. This phenomenon is one of the main principal causes of the mechanical properties failure when a glaze is applied.

2017 - On a solar reflective ceramic based glaze for asphalt shingle [Articolo su rivista]
Ferrari, Chiara; Mugoni, Consuelo; Montorsi, Monia; Siligardi, Cristina; Ferrari, Chiara

Solar reflective materials are one of the most effective solutions to counteract Urban Heat Island effect. Among them, asphalt shingles are one of the most widely used products. To improve solar reflectance of these surfaces usually both polymeric paint on the final product or ceramic glazes applied directly on the granules surface through rotary kiln are used. In this study the Design of Experiment approach is applied to an industrial formulation for ceramic glaze for asphalt shingles in order to find the optimal combination between pigment (Rutile and Talc), liquid phase (Sodium Silicate and Water) and heat treatment (700 °C −1100 °C). On the most significant samples, moreover, XRD and ESEM characterization has been performed in order to better understand the behaviour of the studied system. Interesting values in Solar reflectance were obtained, reaching ρsol=0.882 creating a good solar reflective product ready to be applied, through rotary kiln, on mineral granules for asphalt shingles.

2017 - Recycling of yttria-stabilized zirconia waste powders in glazes suitable for ceramic tiles [Articolo su rivista]
Siligardi, Cristina; Barbi, Silvia; Casini, Roberto; Tagliaferri, Luca; Vito, Remigio

The aim of this work is to demonstrate the feasibility of valorizing and recycling Yttria-stabilized Zirconia thermal spray waste into high value products for industrial and residential use. Based on the powders chemistry and morphology, this work aims to realize products, like frits suitable for white glazes and ceramic tiles. The focus is on one class of powder: high-temperature and abrasion-resistant ceramics, like Yttria-stabilized zirconia. This study has revealed that the substitution of pure zirconia with waste Yttria-stabilized zirconia is possible in high percentages, up to 100% to prepare frits suitable for white glazes

2017 - Structural and optical properties of rare-earths doped barium bismuth borate glasses [Articolo su rivista]
Barbi, Silvia; Mugoni, Consuelo; Montorsi, Monia; Affatigato, Mario; Gatto, Corrado; Siligardi, Cristina

Recently, great importance has been devoted to different glass systems doped with rare-earth ions because of their peculiar properties, in particular in the field of high-energy physics for particle energy measurement. The purpose of the present study was to investigate the optical and physical properties of Dy3 +, Er3 +, Nd3 + doped glasses belonging to the 20BaO-20Bi2O3-60B2O3 system in which several rare-earths oxide concentrations were added to encounter the requirements for particle energy measurement. High density, low refractive index, high emission intensity (or high scintillation yield) are required for this purpose. Moreover, molar volume, glass transition and melting temperatures, X-ray diffraction and Raman spectra were measured and discussed in order to characterize the glass state. All the properties measured have shown a non-linear trend moving from 1 mol% to 10 mol% of rare-earths content. At the same time comparison between the trend derived by samples with same stoichiometry but containing different rare earths highlight different behaviors. In particular the highest density has been reached with the glass where Dy2O3 is at 2,5 mol%.

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

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.

2016 - A composite cool colored tile for sloped roofs with high 'equivalent' solar reflectance [Articolo su rivista]
Ferrari, Chiara; Libbra, Antonio; Cernuschi, Federico Maria; De Maria, Letizia; Marchionna, Stefano; Barozzi, Matteo; Siligardi, Cristina; Muscio, Alberto

Mediterranean cities are characterized by sloped roofs with ceramic tiles of traditional colors such as brick red in different tones. Their solar reflectance is generally low and can cause overheating of the building due to solar gains during the hot season. In this work, an innovative approach is tested to achieve roof tiles with high capacity of rejecting solar radiation. It consists of using a cool-colored tile with relatively high solar reflectance, combined with a thin insulating layer attached below the tile and made of a silica-gel super-insulating material. An aluminum foil with very low thermal emittance is also applied below the insulating layer. Along the perimeter of each tile, line brushes are attached in order to enclose an almost sealed air space between the aluminum foil and the roof slab below when the tiles are supported on wooden battens. Composite tiles like that outlined here can provide a strong increase of roof thermal resistance, helpful to control either heat loss in winter, or building overheating in summer. They can be installed onto an existing roof, for instance the sloped tile roof of a historical or traditional building, with no need to modify the roof height and structure.

2016 - Analisi LCA del recupero di zirconia da un processo di termospruzzatura [Abstract in Atti di Convegno]
Ferrari, Anna Maria; Braglia, Federica; Neri, Paolo; Barbi, Silvia; Siligardi, Cristina

La termospruzzatura è una tecnologia di rivestimento molto versatile, al momento utilizzata per depositare spessi strati di metalli e materiali ceramici per diverse applicazioni nell’industria meccanica, aeronautica ed energetica, nonché nell’industria biomedica (protesi metalliche odontoiatriche e ortopediche). All’interno del mercato della termospruzzatura un ruolo molto importante è giocato dal campo dei motori e turbine degli aerei, dove la produzione di Thermal Barrier Coatings (TBC) protegge i componenti in superlega di Ni e Co delle turbine a gas con un sistema di doppio strato solitamente composto da una lega di NiCoCrAlY resistente all’ ossidazione e un rivestimento ceramico fatto di zirconia che funge da protezione termica. Tra le problematiche ambientali associate a questo processo vi è quello delle polveri sovraspruzzate fino a oggi inviate in discarica come rifiuti speciali con conseguenti impatti ambientali e costi elevati. Durante l’operazione di spruzzatura, infatti, un’ingente percentuale di polveri non si deposita sul substrato. Per la natura imprevedibile dell’iniezione di particelle e del trattamento all’interno del flusso di gas, alcune particelle potrebbero raggiungere il substrato senza un’adeguata velocità o temperatura facendo si che non si depositino sul substrato. L’obiettivo del presente studio è la valutazione della sostenibilità ambientale, mediante metodologia LCA, di un processo di recupero di zirconia da termospruzzatura effettuato da un’azienda che produce rivestimenti protettivi per componenti utilizzati in turbine a gas industriali e motori aereonautici. In particolare viene valutato il danno ambientale dovuto al reimpiego di tali materiali secondari in materiali ceramici per uso abitativo e industriale.

2016 - Development of a Solar-reflective Ceramic Tile Ready for Industrialization [Articolo su rivista]
Ferrari, Chiara; Muscio, Alberto; Siligardi, Cristina

Solar-reflective surfaces represent an effective countermeasure to UHI. The market of "cool" materials is dominated by polymeric solutions which, under UV exposure, are damaged. On the other hand, an increasing attention was paid recently to ceramic-based solar-reflective surfaces, characterized by very long lifespan. A ceramic tile is typically made by a three layers structure: substrate-engobe-glaze. This structure has been exploited to develop a cool ceramic tile that can be produced in the same production facilities of common products to create a whole tile by merging technological results and industrial production needs, to achieve a compromise between performance and costs.

2016 - Pore size distribution and porosity influence on Sorptivity of cerami ctiles:From experimental data to fractal modelling [Articolo su rivista]
Pia, G.; Siligardi, Cristina; Casnedi, L.; Sanna, U.

The Sorptivity is a coefficient very important to characterize porous materials. It is associated to principal properties such as mechanical durability, thermal and electrical conductivity, etc. In this work, the Sorptivity coefficient of several systems of porous ceramics has been measured following the experimental procedure. Indifferent situations, this very simple test could be not performed; in cultural heritage ordering an optimised industrial process. Major reasons for this inability include that it would demand great quantitates of materials impossible to withdraw from the protected building ,as well as the experimental test can last for several days ,which reduces the possibility to correct/improve the industrial production process. Starting from its capability to reproduce entirely the pore size distributions of porous materials, IFU is used to simulate water absorption process and to estimate the Sorptivity coefficient. The obtained results are in good agreement with experimental data and others two models predictions. This fact allows considering IFU model as a future tool for design materials and to predict their service life.

2016 - Preparation and Characterization of LAS Glass Based Materials for Dental Applications [Relazione in Atti di Convegno]
Barbi, Silvia; Montorsi, Monia; Mugoni, Consuelo; Siligardi, Cristina

Glass ceramic materials are widely used in dental application because of their strong similarity with natural teeth. In this study LAS glass ceramic/glass materials were prepared by glazing processing and characterized in terms of mechanical flexural strength. The selected glass ceramic support derives from an industrial process. Different glasses were applied to the glass ceramic support in order to investigate firstly their effect on the glass ceramic/glass interface and secondly how these structural changes are correlated to the flexural strength property. Different thermal cycles were applied to the glass ceramic in order to promote the increasing of mechanical flexural strength. Preliminary results clearly points out that the application of a glass on the support leads to the decrease of the flexural strength if compared to the materials without any coating applied.

2016 - Structural origin of electrical conductivity of copper lithium metaphosphate glasses [Articolo su rivista]
Mugoni, Consuelo; Jain, H; Montorsi, Monia; Montecchi, Monica; Kovalskiy, A.; Siligardi, Cristina

Wehave sought the structural origin of the recently reported electrical conductivity of lithium copper phosphate glass system (50-x) Li2O-xCu2O-50 P2O5, as lithium oxide is gradually replaced by Cu2O. The structure of these glasses was determined by X-ray photoelectron spectroscopy, Fourier Transform Infrared Spectroscopy and Raman spectroscopy. The results show the presence of both mobile Cu+ and relatively immobile Cu2+ ions. The relative fraction of Cu2+ [Cu2+ / Cutot] and non-bridging oxygen increases with x; the latter indicating a tendency towards depolymerization of the network. On the other hand, there is enhanced crosslinking within the network as P\\O⋯Li bonds are replaced by relatively covalent P\\O⋯Cu bonds. This leads to a more crosslinked structure and a progressive reduction of the optimumsites for the jumping of both Li+ and Cu+, in agreement with the observed increase of the energy barrier for ion transport as Li2O is replaced by Cu2O.

2015 - Comparison of precipitated calcium carbonate/polylactic acid and halloysite/polylactic acid nanocomposites [Articolo su rivista]
Shi, X.; Zhang, G.; Siligardi, C.; Ori, G. ; Lazzeri, A.

PLA nanocomposites with stearate coated precipitated calcium carbonate (PCC) and halloysite natural nanotubes (HNT) were prepared by melt extrusion. The crystallization behavior, mechanical properties, thermal dynamical mechanical analysis (DMTA), and the morphology of the PCC/PLA, HNT/PLA, and HNT/PCC/PLA composites were discussed. Compared to halloysite nanotubes, PCC nanoparticles showed a better nucleating effect, which decreased both the glass transition and cold crystallization temperatures. The tensile performance of PLA composites showed that the addition of inorganic nanofillers increased Young’s modulus but decreased tensile strength. More interestingly, PLA composites with PCC particles exhibited an effectively increased elongation at break with respect to pure PLA, while HNT/PLA showed a decreased ultimate deformation of composites. DMTA results indicated that PLA composites had a similar storage modulus at temperatures below the glass transition and the addition of nanofillers into PLA caused to shift to lower temperatures by about 3°C. The morphological analysis of fractures surface of PLA nanocomposites showed good dispersion of nanofillers, formation of microvoids, and larger plastic deformation of the PLA matrix when the PCC particles were added, while a strong aggregation was noticed in composites with HNT nanofillers, which has been attributed to a nonoptimal surface coating.

2015 - Design of a cool color glaze for solar reflective tile application [Articolo su rivista]
Ferrari, C.; Muscio, Alberto; Siligardi, Cristina; Manfredini, Tiziano

Solar reflective materials, so called cool roofs, can be identified as one of the most promising solutions to counteract urban heat island. Cool roof market is nowadays dominated by polymeric product, which can ensure good optical properties but poor durability against weathering and ageing. Ceramic-based products can be an excellent solution combining both good solar properties and higher durability against time, in particular if glazed. Embedded colored pigments, moreover, can help the introduction of these materials in Mediterranean building policies. These cool colored ceramic-based products, in fact, match naturally high thermal emissivity (ε=0.90) with higher mechanical, chemical and physical durability. A traditionally engobed porcelain stoneware tile was used as a substrate for a new generation of colored glazes characterized by different surfaces reaching promising values in solar reflectance.

2015 - Design of glass foams with low environmental impact [Articolo su rivista]
Mugoni, Consuelo; Montorsi, Monia; Siligardi, Cristina; Andreola, Fernanda; Lancellotti, Isabella; Bernardo, Enrico; Barbieri, Luisa

Raw materials and their granulometry play a fundamental role in ceramic tile production especially as concern the mechanical properties of the final body. Aim of the present work is to accurately investigate the role of the raw materials granulometry on the mechanical properties of a green porcelanized stoneware body. Correlations existing between the particle size distribution and flexural strength and Young's modulus of a standard gres mixture were investigated by using the Design of Experiments method. In particular, a starting mixture of clay, which composition was kept constant, feldspar and quartz, considered in two different granulometry, was used to define a statistical combination of components-mixture. After statistical analysis of the experimental data, regression models were calculated, relating the mechanical properties of the green ceramic body to the starting granulometry. Results obtained from the present study were considered for further investigations in order to produce gres with specific properties.

2015 - Effect of Additives on the Dispersion and Electrophoretic Deposition of Highly Diluted Enamel Suspensions [Articolo su rivista]
Andreola, F. ; Dignatici, M. ; Chavez-Valdez, A. ; Siligardi, C. ; Boccaccini, A.R.

This work examines the rheological behaviour of aqueous highly diluted suspensions (1 mass-%) to identify additives that may improve the application of vitreous enamel coatings by electrophoretic deposition (EPD). Slurries for EPD were prepared by ball milling frit glass in water with suspending agents. The effect of different additives in the solids concentration range from 0.2 to 2.0 mass-% on the rheological properties of coating solutions was investigated using rotational rheometry and zeta potential measurements. Different sedimentation times were observed for the tested dispersant, binder and coagulator additives. Densicer, an organic-inorganic mix additive, showed the best properties in terms of suspension stability. The high zeta potential measured with this product confirms its potential suitability as a suspension additive for vitreous enamel coatings applied by EPD.

2015 - LCA of microwaves absorbers obtained from copper slags [Altro]
Zerazion, Elisabetta; Mohaddes, Sara; Mugoni, Consuelo; Neri, Paolo; Pini, Martina; Siligardi, Cristina; Ferrari, Anna Maria

Copper slag is generated during pyrometallurgical production of copper from copper ores containing materials like iron, alumina, calcium oxide and silica. Every ton of metal production generates about 1,63 ton of slag [1] which dumping or disposal cause environmental and space problems [2,3,4]. Despite its high iron content, this slag is currently disposed of in landfills, further processed as inert material, or used as an abrasive in industrial processes. However, this last option is not a sustainable solution, because the granules derived from the slag and used as an abrasive are themselves disposed of after re-use. However, because it is composed of iron oxides and silicates, the slag has semi-conductive and mild ferromagnetic properties and could be used to produce innovative advanced materials for heating applications, substituting materials with much higher embodied energy and bringing environmental benefits

2015 - Lanthanum glass infiltrated alumina/alumina composites for dental prosthetic applications [Articolo su rivista]
Mugoni, C.; Licciulli, A.; Diso, D.; Siligardi, C.

Lanthanum glass frits suitable for infiltration in pre-sintered alumina were developed in order to obtain innovative alumina–glass composites, which are promising materials for all-ceramic dental prosthetic restorations, such as single crowns and fixed partial dentures. Glass compositions belonging to the lanthanum-silicate-borate system were synthesized in order to reinforce and give an improved esthetic appearance to the pre-sintered Al2O3. Fifteen formulations, defined by using a mixture design approach, were melted and quenched in water at room temperature in order to obtain the frits. Those exhibiting the lower melting temperatures were tested for infiltration into Al2O3 to obtain Al2O3/glass composites. The frits and the composites were characterized by X-Ray diffraction, differential thermal analyses, hot stage microscopy, colorimetry (Hunter color scale) and scanning electron microscopy. The mechanical properties of the composites, in terms of flexure strength, were evaluated using a three-point bending tests.

2015 - Life cycle assessment of a sintered tile containing copper slag: is recycling always convenient? [Articolo su rivista]
Mohaddes Khorassani, Sara; Mugoni, Consuelo; Siligardi, Cristina; Ferrari, Anna Maria

Copper production causes environmental problems related to copper slag disposal. Within this experimental work, copper slag have been used as secondary raw material for the production of sintered tiles, which potential environmental impact was assessed through the Life Cycle Assessment methodology.

2015 - Review on the Influence of Biological Deterioration on the Surface Properties of Building Materials: Organisms, Materials, and Methods [Articolo su rivista]
Ferrari, C.; Santunione, G.; Libbra, A.; Muscio, A.; Sgarbi, E.; Siligardi, C.; Barozzi, G.S.

A strong attention is recently paid to surface properties of building materials as these allows controlling solar gains of the building envelope and overheating of buildings and urban areas. In this regard, deterioration phenomena due to biological aggression can quickly damage solar-reflecting roof surfaces and thus increase sharply solar gains, discomfort, air-conditioning costs and waterproofing degradation. The same deterioration problem has deleterious effect on cultural heritage, ruining its huge historic and artistic value. This work is aimed at providing an overview on the different organisms that affect the surface of most used building materials, to support the design of new building materials with long-lasting surface properties and to find a way to preserve cultural heritage. Artificial ageing is the long-term aim of this investigation, in which what in nature happens after months or years is compressed in a very short time by forcing the growth of microorganisms through a strict control on the different conditioning factors. Both natural and artificial ageing are eventually outlined in the last part of this work to provide a comprehensive idea of what is necessary to study in a complete way biological ageing protocols on building materials. Several characterization techniques are also introduced to analyse the influence of microorganisms on the surface of different building materials.

2014 - Analisi LCA della riqualificazione del Municipio di Fiorano Modenese – Modena [Poster]
Pini, Martina; Ferrari, Anna Maria; Marinelli, Simona; Neri, Paolo; Siligardi, Cristina; Riccardi, Maria Pia; Settembre Blundo, Davide

Il progetto di riqualificazione riguarda villa Cuoghi – Vignocchi, sede attuale del Municipio di Fiorano Modenese in Piazza Ciro Menotti. Nata nel 1850 come villa privata, venne acquistata nel 1929 dal Comune. Al momento dell’acquisto la proprietà Cuoghi – Vignocchi era composta dalla villa padronale, terreni e giardini, nei quali venne ricavata la piazza intitolata a Ciro Menotti, eroe risorgimentale. Successivamente, nel 1939 la villa venne ampliata con una nuova ala verso nord e con una torretta e venne inaugurata come sede del Municipio, funzione attualmente mantenuta.L’applicazione dell’analisi LCA al progetto di riqualificazione in esame ha come obiettivo la valutazione dell’impatto ambientale del progetto di ristrutturazione. L’unità funzionale è il sistema edificio nell’arco di tempo che intercorre dalla sua costruzione fino alla sua dismissione finale, considerandone la riqualificazione. Si ipotizza che la riqualificazione avvenga nell’anno 2013 e si considera un tempo di vita utile dell’edificio riqualificato di 100 anni. L’analisi preliminare degli impatti eseguita col metodo IMPACT 2002+ opportunamente modificato per garantire una maggiore rappresentatività del sistema studiato è stata eseguita considerando indicatori culturali allo scopo di considerare i vantaggi che possono provenire dalla riqualificazione di un edificio. Sono stati inseriti indicatori come il Valore culturale, che ha come variabili di riferimento (substances) l’età dell’edificio, la testimonianza storica e il valore estetico, il Benessere umano, la Funzione e il Valore urbano. Dall’analisi, tali categorie emergono come vantaggi ambientali (segno negativo). Si nota inoltre un vantaggio ambientale nella categoria di danno Respiratory organics dovuto all’uso dei materiali funzionalizzati che abbattono sostanze inquinanti quali NOx e VOC. Il danno ambientale maggiore è dato dalla fase d’uso, in particolare dall’energia necessaria al riscaldamento invernale (510,74Pt) e dall’energia elettrica per l’illuminazione artificiale (127,73 Pt ). Il danno totale vale 1069,8 Pt

2014 - Analisi ambientale di smalto ceramico ottenuto da scorie derivanti dalla produzione del rame [Relazione in Atti di Convegno]
Mohaddes Khorassani, Sara; Neri, Paolo; Pini, Martina; Siligardi, Cristina; Zerazion, Elisabetta; Ferrari, Anna Maria

Obiettivo dello studio è la valutazione ambientale relativa alla produzione di uno smalto ceramico ottenuto utilizzando scorie a base di silicati di ferro derivanti dalla produzione del rame. Attraverso la metodologia LCA è stato quantificato il danno ambientale associato alla produzione dello smalto e quello relativo al ciclo di vita di una piastrella in grès porcellanato sulla quale tale smalto venga applicato. La fritta ceramica che compone lo smalto è risultato il processo più impattante ed è stata confrontata con una fritta composta con materie prime tradizionali. I risultati hanno dimostrato un vantaggio ambientale nell’utilizzo delle scorie come materie prime seconde, dovuto al minore impiego di processi di estrazione e lavorazione di materie prime per la composizione dello smalto.

2014 - Analisi del ciclo di vita del progetto di restauro del chiostro del complesso di San Felice a Pavia [Poster]
Tomasetta, Camilla; Neri, Paolo; Riccardi, Maria Pia; Siligardi, Cristina; Zucchella, Antonella; Ferrari, Anna Maria

Il Complesso di San Felice in Pavia ha subito molteplici interventi nel corso degli anni che ne hanno, di volta in volta, profondamente modificato le strutture. Le notizie più antiche, risalenti al sec. VIII, parlano di un monastero, mentre l’impianto della chiesa, ad aula unica ed abside tripartita, sovrastante una cripta di analogo disegno, risale all’epoca longobarda. Il complesso è attualmente sede della Facoltà di Economia e Commercio dell’Università di Pavia. Il chiostro, una volta recuperato potrebbe essere valorizzato ed aperto ai visitatori nell’ambito di un percorso museale cittadino. Risulta evidente il conseguente valore sociale aggiunto della ristrutturazione.Gli interventi verranno analizzati mediante la procedura di Life Cycle Assessment (LCA), avvalendosi del software SimaPro (versione 8.0). Nell’ambito dell’LCA, verrà scelto l’appropriato metodo di valutazione d’impatto ideoneo a valutare e quantificare gli impatti ambientali, sociali e sulla salute umana derivanti dal progetto di restauro. Inoltre, verranno analizzati i costi interni ed esterni associati al progetto, secondo la procedura del Life Cycle Costing (LCC).

2014 - Effect of aging processes on solar reflectivity of clay roof tiles [Articolo su rivista]
Ferrari, Chiara; A., Gholizadeh Touchaei; M., Sleiman; Libbra, Antonio; Muscio, Alberto; Siligardi, Cristina; H., Akbari

Clay roof tiles are widely used as roofing materials because of their good mechanical and esthetical properties. The exposure to atmospheric agents and, most of all, to pollutants and smog affects negatively the solar reflectance of a tile surface. The aim of this study is to analyze the influence of aging on the solar reflectance of clay roof tiles. We studied samples provided by manufacturer in Greece and USA. Samples were coated with either organic or inorganic coatings. Natural aging processes were used for samples with inorganic coating, and artificial aging simulation was performed on all samples. Samples were naturally aged in a test farm in Arizona, with an exposure time of three years. In artificial aging processes, the surface of the tiles was subjected to the application of two different mixtures simulating exposure to (i) Arizona weathering agents such as clay, salts and soot and (ii) Arizona, Florida and Ohio weathering agents through an average mixture made by clay, salts, particulate organic matter and soot. The amount of soiling mixture deposited on the surface of the samples was aimed at reproducing a three-year exposure. Soiled samples were subjected to air blowing and rinsing under running water to simulate the wind and rain effects, respectively. The effects of both natural aging and artificial soiling on the surface reflectivity of the clay roof tiles were assessed in the ultraviolet–visible–near infrared range (range from 300 to 2500 nm). The two different soiling conditions were found to affect significantly the solar reflectance of the samples, in particular the samples soiled with the average mixture present a decrease up to 0.20, while Arizona weathering condition affects the solar reflectance up to 0.05, and neither air blowing nor rinsing seem to permit a significant recovery of the surface properties. All solar reflectance measurements were computed by averaging the spectral reflectivity weighted by the air-mass 1 global horizontal solar spectral irradiance.

2014 - Electrical conductivity of copper lithium phosphate glasses [Articolo su rivista]
Mugoni, Consuelo; Montorsi, Monia; Siligardi, Cristina; Himanshu, Jain

Copper based oxide glasses are especially interesting for the possibility of ionic-electronic mixed conduction, which has potential applications in energy and switching devices. Accordingly, lithium metaphosphate glasses are investigated within the (100-x) Li2O - xCu2O - 50P2O5 series, where Li+ ions are gradually replaced by copper ions. Based on the changes in glass transition temperature and thermal stability via structural modification, the glasses are shown to be predominantly ionic conductors. In fact, they exhibit signs of classic mixed mobile ion effect (MMIE), a hallmark of ion conduction in glass, which would be due to Li+ and Cu+ ions in the present case. © 2013 Elsevier B.V. All rights reserved.

2014 - Isola di calore e surriscaldamento estivo: cool colors in laterizio [Articolo su rivista]
C. Ferrari; A. Libbra; A. Muscio; C. Siligardi

La riflettanza solare delle coperture varia a seconda del tempo e del luogo di esposizione ed è influenzata dai fenomeni naturali. I manti in laterizio si dimostrano un eccellente candidato, in funzione dell’edilizia ad alta efficienza energetica, sia per il contrasto dell’isola di calore urbana che per comfort indoor e la limitazione dei consumi estivi

2014 - Lithium vanado-phosphate glasses: Structure and dynamics properties studied by molecular dynamics simulations [Articolo su rivista]
Broglia, Giulia; Mugoni, Consuelo; Jincheng, Du; Siligardi, Cristina; Montorsi, Monia

Lithium vanado-phosphate glasses have been designated as possible cathode material for the next generation of solid state batteries, due to their high conductivity and mixed electronic–ionic conducting behaviours, which derive from the small polaron hopping between the vanadium ions with different valence state and the lithium ion diffusion. Therefore, the understanding of the behaviour of these glasses at the atomistic level can be an important aspect in designing compositions for these applications. To reach this goal, the structure and lithium ion diffusion behaviour in lithium vanado-phosphate glasses with mixed V4 + and V5 + ions were studied using molecular dynamics simulations. The results show that vanadium oxide generally plays an intermediate role in glass structure while there are subtle details depending on its concentration and oxidation states. The phosphorus network is depolymerized by the content of vanadium oxide, but phosphorus ions always contribute to the glass network, interposing to vanadium polyhedra. The V4 +single bondOsingle bondV5 + linkages, responsible for the polaron hopping mechanism, show a linear dependence to the V2O5/P2O5 ratio, which highlights a strong role of the interaction between the former ions. The lithium ion diffusion was studied by mean square displacement calculations and it was found that the self-diffusion coefficient just depends on the Li content.

2014 - Preparation of innovative metallic composite glazes for porcelainized stoneware tiles [Articolo su rivista]
Siligardi, Cristina; Tagliaferri, L.; Lusvarghi, Luca; Bolelli, Giovanni; Venturelli, D.

Innovative metallic glazes for porcelain stoneware tiles, containing stainless steel and a special Ni-based alloy (NiCoCrAlY, commonly used as bond coating material in thermal barrier coating systems on Turbogas superalloy components), have been studied. These new products, called “ metallic composite glazes ” (MCGs), showed different aesthetic properties than usual lustres or metallic glazes. After heating, the surfaces of these innovative glazes did not display any interesting behaviour, but, after polishing, a particular metallic aesthetic effect has been found. These new glazes can be described as composite materials made of a glass matrix reinforced with metal particulates. A deep characterisation of metallic powders and MCGs was performed by using several techniques. The glazes containing the NiCoCrAlY powders manifested the best aesthetic, microstructural, thermal and chemical properties.

2014 - Recycling in ceramic glazes of zirconia overspray from thermal barrier coatings manufacturing [Articolo su rivista]
Siligardi, Cristina; Lusvarghi, Luca; Giolli, C.; Scrivani, A.; Venturelli, D.

Glazed ceramic tiles are the most common building material for floor and wall covering. Glazes are produced from frits. The aim of this work is to make a total or partial replacement of a raw material, zircon, widely used in ceramic tiles manufacturing, with a waste material, in order to prepare ceramic frits. The waste material used in this work, is the overspray zirconia, which is produced during the deposition process by atmospheric plasma spraying (APS) of thermal barrier coatings (TBC) on turbine blades. In particular, a replacement of 100. wt%, 1. wt% and 0.2. wt% of zirconium silicate with zirconia has been studied. Ceramic glazes prepared mixing frits and other raw materials are applied on a single-fired tile. The glazes obtained were characterized with different analytical techniques. This study has revealed that the substitution of zircon with waste zirconia is possible in small percentages due to the presence of small amount of chromophore ions in the overspray zirconia, which tend to colour the glaze.

2014 - Self-cleaning glass prepared from a commercial TiO2 nano-dispersion and its photocatalytic performance under common anthropogenic and atmospheric factors [Articolo su rivista]
Erika Iveth Cedillo, González; Raffaele, Ricco; Montorsi, Monia; Mauro, Montorsi; Paolo, Falcaro; Siligardi, Cristina

Nowadays, a wide range of self-cleaning building materials or colloidal solutions for the fabrication of photocalytic coatings are already commercially available. However, some practical limitations still restrict their widespread use in the building sector. For example, in normal household conditions, photocatalytic building materials are exposed to factors that can compromise their efficiency or promote the release of nanoparticles to the environment. In addition, most of the building materials are commonly exposed to atmospheric variables that may greatly differ depending on the geographical zone or the season of the year. In this work, TiO2 films prepared from a commercially available dispersion of nanoparticles were deposited over soda-lime glass substrates. The effects of (i) NaCl residues from the TiO2 nano-dispersion; (ii) treatment with model solutions that simulate the environmental and domestic weathering; (iii) the relative humidity and (iv) the substrate temperature on the photocatalytic activity versus stearic acid were evaluated. The obtained results indicate that these films are more efficient in environments with low humidity levels and relatively high temperatures. Therefore, their commercialization in dry and hot geographic zones would enable the best performance. Furthermore, it was found that these materials can be applied in houses without appreciable loss of efficiency, due to weathering from common cleaning agents or atmospheric factors, like rain or acid rain.

2013 - Analisi LCA di un vetro float autopulente funzionalizzato con nanoTiO2 [Relazione in Atti di Convegno]
Martina Pini; Erika Iveth Cedillo González1; Simona Marinelli; Paolo Neri; Cristina Siligardi; Anna Maria Ferrari

Negli ultimi anni è aumentato l’impiego di nanoTiO2 grazie alle proprietà chimiche e fisiche che la caratterizzano, quali il forte potere ossidante, l’iperidrofilicità e le proprietà antibatteriche che la rendono particolarmente interessante per la preparazione di materiali nanocompositi con caratteristiche autopulenti, antiappannamento ed antibatteriche. Il vetro autopulente rappresenta una delle principali applicazioni in ambito edile/architettonico di materiali funzionalizzati con nanoTiO2. Quando il vetro viene colpito da raggi UV, la nanoTiO2 viene attivata generando, grazie al fenomeno della fotocatalisi, la riduzione della maggior parte dei contaminanti presenti nell'aria e/o depositati sulla superficie del materiale. Il presente studio riguarda l’ecodesign, eseguito attraverso la metodologia LCA (Life Cycle Assessment), della realizzazione su scala industriale di un vetro float autopulente partendo da dati di laboratorio.

2013 - Design of ceramic tiles with highsolar reflectance through the development of a functional engobe [Articolo su rivista]
Ferrari, Chiara; Libbra, Antonio; Muscio, Alberto; Siligardi, Cristina

Roofing solutions with high capacity to reflect incident solar radiation, the so-called cool roofs, can provide an effective answer to summer overheating of either individual buildings or whole urban areas. Nowadays, commercial cool roofs products are mainly represented by organic membranes and coatings, but ceramic tiles can represent an interesting alternative or complement in view of their low maintenance cost. In this work, it is illustrated how a high reflectance engobe can affect in a positive way the solar reflectance of a glazed tile thanks to the introduction of suitable raw materials and pigments. The reflectance was in fact found to be affected by either the support, the mineralogical composition, the engobe thickness or the glaze. The procedure through which the glazed tile is developed and tested is discussed, in the perspective of production through commonly used industrial processes.

2013 - Effect of ageing processes on solar reflectivity of clay roof tiles [Relazione in Atti di Convegno]
C. Ferrari; A.G. Touchaei; M. Sleiman; A. Libbra; A. Muscio; C. Siligardi; H. Akbari

Clay roof tiles are widely used as roofing materials because of their good mechanical and aesthetical properties. The exposure to atmospheric agents and, most of all, to pollutants and smog affects negatively the solar reflectance of atile surface. The aim of this study is toanalyzethe influence of ageing on the solar reflectance of clay roof tiles. We studied samples provided by manufacturer in Greece and USA. Samples were coated with either organic or inorganic based coating. Natural ageing processes were used for samples with inorganic coating, and artificial ageing simulation was performed on all samples. Samples were naturally aged in a test farm in Arizona, with an exposure time of 3 years. In artificial ageing processes, the surface of the tiles was subjected to the application of two different mixtures simulating exposure to i) Arizona weathering agents such as clay, salts and soot and ii) Arizona, Florida and Ohio weathering agents through an average mixture made by clay, salts, particulate organic matter and soot. The amount of soiling mixture deposited on the surface of the samples was aimed at reproducing a 3 years exposure. Soiled samples were subjected to air blowing and rinsing under running water to simulate the wind and rain effects, respectively. The effects of both natural ageing and artificial soiling on the surface reflectivity of the clay roof tiles were assessed in the UV-Vis-NIR range (range from 300 to 2500 nm). The two different soiling conditions were found to affect significantly the solar reflectance of the samples, in particularthe samples soiled with the average mixture present a decrease up to 0.20, while Arizona weathering condition affects the solar reflectance up to 0.05, and neither air blowing nor rinsing seem to permit a significant recovery of the surface properties. All solar reflectance measurements were computed by averaging the spectral reflectivity weighted by the AM1GH solar spectral irradiance.

2013 - Energy performance of opaque building elements in summer:Analysis of a simplified calculation method in force in Italy [Articolo su rivista]
A. Libbra; A. Muscio; C. Siligardi

The Italian technical standard for calculation of building energy needs in summer allows a monthlyaverage method, in which solar gains through opaque building elements are evaluated distinguishingbetween dark, intermediate or light-colored surfaces, and a fixed value of solar absorptance is assigned toeach surface category. The method is aimed at ease of operation, but its steady-state calculation approachmay not allow taking into proper account dynamic effects due to thermal inertia. Moreover, roofingsolutions typical of Italy such as roof tiles, sealing membranes or painted sheet metal panels can showsimilar colors, but significantly different values of the solar absorption coefficient. On the other hand, aneasy to apply calculation method may enable most designers of the building sector to take advantage ofsolutions for control of solar gains such as cool roofs and cool colors, thus favoring their dissemination.In this paper, the calculation method currently in use in Italy is briefly presented, with the focus onthe role of opaque building elements. Either the accuracy of steady-state calculation or the reliabilityof the color-based evaluation approach is then discussed, analyzing by numerical simulation the actualdynamic behavior of most common types of roof element.

2013 - Evaluation of the Properties of Iron Oxide-Filled Castor Oil Polyurethane [Articolo su rivista]
Eleonora Mussattia; Claudia Merlini; Guilherme Mariz de Oliveira Barra; Saulo Güths; Antonio Pedro Novaes de Oliveira; Cristina Siligardi

The aim of this study was to obtain and evaluate the electrical, thermal and mechanical properties of iron oxide-filled castor oil polyurethane (PU/Fe2O3). The iron oxide used in this study was a residue derived from the steel pickling process of a Brazilian steel rolling industry. Polymeric composites with different iron oxide volume fractions (2.5, 5.0, 7.5, 10.0 and 12.5%) were prepared through the casting process followed by compression molding at room temperature. The composites were analyzed by FTIR, XRD and densities, tensile strength, Young’s modulus, electrical and thermal conductivities measurements. By increasing the iron oxide content, the apparent density, tensile strength, Young’s modulus and electrical conductivity values of the composites were also increased. The iron oxide additions did not change significantly the value of thermal conductivity (from 0.191 W.mK–1 for PU up to 0.340 W.mK–1 for PU enriched with 12.5% v/v of iron oxide). Thus, even at the higher iron oxide concentration, the compounds as well as the pure polyurethane can be classified as thermal insulators.

2013 - Improvement of the adhesion between TiO2 nanofilm and glass substrate by roughness modifications [Articolo su rivista]
Erika Iveth Cedillo, Gonzalez; Montorsi, Monia; Mugoni, Consuelo; Mauro, Montorsi; Siligardi, Cristina

An increase of the adhesion between soda-lime glass substrate and TiO2 nanofilm was achieved by roughness modifications, treating the glass surface with acid or basic solutions. The study was organised through a D-optimal experimental design. The roughness (measured by AFM) and the weight loss were statistically analysed using MODDE 9.0 software. Subsequently, the correlation between the surface roughness and the adhesion (measured by scratch test) of the films was studied. The statistic analysis of the results indicates how the chemical treatments modify the roughness of the glasses and it was found that smooth surfaces enhance the adhesion of the films.

2013 - Influence of the irradiance spectrum on solar reflectance measurements [Articolo su rivista]
Ferrari, Chiara; Libbra, Antonio; Muscio, Alberto; Siligardi, Cristina

Solar reflectance (SR) is the key performance parameter of cool roof and cool pavement materials. For its assessment, the measured spectral reflectivity of the sample is weighted by a reference spectrum of solar irradiance. Several standard and non-standard spectra are, however, available, taking into account different climate conditions, angle of incidence of the solar beam, and the contribution of the diffuse radiation content. This study is aimed at investigating the impact of using different solar irradiance spectra as specified by existing standards or suggested by qualified research institutions, and verifying if those spectra can yield equivalent SR values from the viewpoint of assessment of standard performance and comparison of commercial products. Several actual material are considered, either white or coloured ones and with assorted spectral behaviour.

2013 - Influence of the solar irradiance spectrum on solar reflectance measuremens [Relazione in Atti di Convegno]
C. Ferrari; A. Libbra; A. Muscio; C. Siligardi

Solar reflectance is the key performance parameter of cool roof and cool pavement materials. For its assessment, the measured spectral reflectivity of the sample is weighted by a reference spectrum of solar irradiance. Several standard and non-standard spectra are however available, taking into account different climate conditions, angle of incidence of the solar beam, contribution of the diffuse radiation content. This study is aimed at investigating the impact of using different solar irradiance spectra as specified by existing standards or suggested by qualified research institutions, and verifying if those spectra can yield equivalent solar reflectance values from the viewpoint of assessment of standard performance and comparison of commercial products. Several actual material are considered, either white or coloured ones and with assorted spectral behaviour.

2013 - Life cycle assessment of nanoTiO2 coated self-cleaning float glass [Relazione in Atti di Convegno]
Pini, Martina; Cedillo González, E. I.; Neri, P.; Siligardi, Cristina; Ferrari, Anna Maria

In recent years superhydrophilic and photocatalytic selfcleaning coatings have been used mainly in easy-to-clean surfaces field. Self-cleaning glasses are one of the first building nanocoating applications. These products are based on the photocatalytic property of a thin layer of TiO2 deposited at the surface of the glass. When exposed to UVA radiation, TiO2 reacts with the oxygen and water molecules present in the atmosphere to produce free radicals leading to oxidative species. These species are able to reduce the concentrations of airborne pollutants and organic substances deposited on the materials surface. The present study concerns the ecodesign of industrial scale up of nanoTiO2 self-cleaning coated float glass production performed by LCA (life Cycle Assessment) methodology. This work is a part of a regional Italian project named “ARACNE”. The main aim of this project is to study and ecodesign eco-friendly building materials with higher technological properties.

2013 - Thermal dehydroxylation of kaolinite from an industrial kaolin: insights from IR autocorrelation spectrum [Articolo su rivista]
Gasparini, E.; Tarantino, S. C.; Ghigna, P.; Riccardi, M. P.; Cedillo Conzalez, E. I.; Siligardi, Cristina; Zema, M.

The dehydroxylation reaction of kaolinite from the industrial kaolin Sl-K (Germany) has been studied by thermal analyses (TG, DTA) and ex situ annealing experiments. Heating experiments were performed at 450, 500, 550 and 600 °C. At each working temperature, different heating times were used in order to follow the evolution of the dehydroxylation process with time until completion of the reaction. Every heating run was performed on a new batch of sample, which was weighted before and after the heat-treatment. At the end of the heating run, each sample was characterised by X-ray powder diffraction (XRPD) and FT-infrared attenuated total reflectance spectroscopy (FTIR-ATR). The dehydroxylation process was followed by monitoring the gradual mass loss and the corresponding decrease in intensity of the most significant peaks both in the diffraction patterns (disappearing of kaolinite peaks) and in the FTIR-ATR spectra (disappearing and changes in OH and Si\O\Al bands), as determined by peak-profile and autocorrelation analyses. A kinetic analysis was performed using the Avrami method on the basis of sample mass loss and changes in the intensities of XRPD and FTIR-ATR peaks under isothermal conditions. Two temperature regimes are found, with only the data in range 500–600 °C being isokinetic. The activation energy values obtained in this temperature range on the basis of the three measured parameters are comparable and are between 127 and 139 kJ mol−1.

2012 - Characterization of vitreous enamel–steel interface by using hot stage ESEM and nano-indentation techniques [Articolo su rivista]
Zucchelli, A.; Dignatici, Matteo; Montorsi, Monia; Carlotti, R.; Siligardi, Cristina

In this study, phase transformation of the vitreous enamel and the interface steel–enamel during firing was analyzed. The thermal transformation of vitreous coating on steel was observed “in situ” with an environmental scanning electron microscopy and the mechanical properties of the steel–enamel interface were studied by using a nano-indenter. The interface reactions and the resulting structure can strongly influence the adhesion mechanism between glass coatings and the metal substrate. An in-depth investigation and structural characterization was therefore performed todefine the correlation between interface morphology and the final chemical and mechanical properties of the enamel–steel interface.

2012 - Immobilization of Monolayer Protected Lipophilic Gold Nanorods on a Glass Surface [Articolo su rivista]
G., Ori; D., Gentili; Cavallini, Michela; M., Comes Franchini; Zapparoli, Mauro; Montorsi, Monia; Siligardi, Cristina

We present a novel process of immobilization of gold nanorods (GNRs) on a glass surface. Wedemonstrate that by exploiting monolayer protection of the GNRs, their unusual opticalproperties can be completely preserved. UV–visible spectroscopy and atomic forcemicroscopy analysis are used to reveal the optical and morphological properties of monolayerprotected immobilized lipophilic GNRs, and molecular dynamics simulations are used toelucidate their surface molecule arrangements.

2011 - Assessment and improvement of the performance of antisolar surfaces and coatings [Articolo su rivista]
Libbra, Antonio; Muscio, Alberto; Siligardi, Cristina; Tartarini, Paolo

Solar reflectance and thermal emittance are key parameters to evaluate solar heat gains through opaquebuilding elements. A high solar reflectance allows building surfaces to minimize absorption of solarenergy, whereas a high thermal emittance allows returning to the environment most of the solar energythat is however absorbed by any actual surface. Therefore, summer overheating of buildings can beprevented by selecting external coatings with proper values of both properties.In this work, the role of radiative properties is explained in quantitative terms. Standard test methodsfor their measurement are also presented. The behavior of some typical cool roof surfaces is then analyzed,in order to point out the limits of qualitative selection criteria and demonstrate the need of quantitativeapproaches to enable product comparison and development. Eventually, the perspectives offered by theuse of advanced materials and coatings are also highlighted.

2011 - Electrical and Structural Characteristic of Copper Oxide (I) Containing Lithium Phosphate Glasses [Articolo su rivista]
Mugoni, Consuelo; Montorsi, Monia; Siligardi, Cristina; Jain, Himanshu

Oxide glasses containing transition metal ions are of enhanced interest because of their applications in information storage, electrical and optical switching devices. The aim of the present work is to design, fabricate and characterize semiconducting glasses containing copper oxide. In such glasses copper is expected to provide mixed conduction with contributions from copper ions as well as from polarons to ionic and electronic conductivity, respectively. Different compositions belonging to the (50-x)Li 2O-xCu 2O-50P 2O 5 (0<x<20 mol%) system were synthesized by melt quench method. The P 2O 5 mol% was kept constant at 50 mol% while the effect of both Cu 2O and Li 2O on the electrical properties of the glass material was investigated considering the progressive substitution of the mol% Cu 2O by Li 2O. Varying the mole percentage of copper oxide in lithium cuprous phosphate (Li 2O-Cu 2O-P 2O 5) system, we are assessing these relative contributions to overall conduction process.

2011 - Flame retardant SBS-clay nanocomposites [Capitolo/Saggio]
Mauro Comes-Franchini; Massimo Messori; Guido Ori; Cristina Siligardi

Polymer nanocomposites have revolutionized material performance, most notably in the plastcs, automotive, and aerospace industries. In this book leaders in the field outline the mechanism behind the generation of suitable polymer systems, pulling together recent research to provide a unified and up-to-date assessment of recent technological advances.

2011 - Influence of CaO-ZrO2-Al2O3-SiO2 glass-ceramic frits on the technological properties of porcelain stoneware bodies [Articolo su rivista]
C. Siligardi; P. Miselli; L. Lusvarghi; M. Reginelli

In the present work, the effect of the addition to a porcelain stoneware body of glass-ceramic frits belonging to the CaO-ZrO2-Al2O3-SiO2 (CZAS, containing 1, 3, 5, 10 mol% of Al2O3) system as replacement of the “state of art” frit belonging to CaO-ZrO2-SiO2 system (CZS) was evaluated. The firing process was performed in a furnace able to complete the thermal cycle in 50 min, in order to simulate the industrial process.Technological properties such as water absorption, firing shrinkage, flexural strength, thermal expansion behaviour were measured. Aesthetical properties were also evaluated. X-ray diffraction and scanning electron microscopy studies were also carried out to analyse the microstructure and the phase compositions of the studied samples. It was found that the sample containing the CZAS frit with 5%mol of Al2O3 shows, in general, the best combination of properties in term of mechanical, physical and aesthetical properties

2011 - Influence of glass phase on Al2O3 fiber-reinforced Al2O3 composites processed by slip casting [Articolo su rivista]
A. Licciulli; V. Contaldi; S. K. Padmanabhan; A. Balakrishnan; C. Siligardi; D. Diso

The present work describes the processing of alumina fiber reinforced alumina ceramic preforms consisting of chopped Al2O3 fibers (33 wt%) and Al2O3 (67 wt%) fine powders by slip casting. The preforms were pre-sintered in air at 1100 °C for 1 h. A lanthanum based glass was infiltrated into these preforms at 1250 °C for 90 min. Linear shrinkage (%) was studied before and after glass infiltration. Pre-sintered and infiltrated specimens were characterized by scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, porosimetry and flexural strength. The alumina preforms showed a narrow pore size distribution with an average pore size of 50 nm. It was observed that introducing Al2O3 fibers into Al2O3 particulate matrix produced warp free preforms with minor shrinkage during pre-sintering and glass infiltration. It was observed that the infiltration process fills up the pores and considerably improves the strength and reliability of alumina preform.

2011 - Insight into the Structure of Vanadium containing Glasses: a Molecular Dynamics Study [Articolo su rivista]
Ori, Guido; Montorsi, Monia; Pedone, Alfonso; Siligardi, Cristina

In this manuscript, classical molecular dynamics simulations (MD) have been applied to study the short and medium range order of very complex vanadium containing glasses with the aim of improving the first microscopic picture of such materials. A rigid ionic force-field has been extended to include the V5+-O, V4+-O and Cu2+-O interatomic pair parameters and tested to reproduce structural properties of known crystal phases with quite good accuracy. Then the structure of Na2O-SiO2, CaO-MgO-Al2O3-SiO2 and Na2O-P2O5 glass compositions in which vanadium is present in the range 1-72 wt% (0.3-60 mol.%) have been fully described in terms of vanadium local structure and Qn distributions. A fairly good agreement was found with experimental data further validating our computational models and providing a computational approach that could be used and extend to investigate in detail the structural information (V-V distances, V-O-V linkages and BO/NBO) directly correlated to macroscopic properties of application interest.

2010 - Ceria-containing frit for luster in modern ceramic glaze [Articolo su rivista]
Siligardi, Cristina; Montecchi, Monica; Montorsi, Monia; Pasquali, Luca

The main goal of this work was to study the formation of theluster effect in a glaze manufactured from a ceria-containingfrit. The glazes obtained under industrial firing were studied usingX-ray photoelectron spectroscopy, X-ray diffraction at roomtemperature and high temperature, and scanning electron microscopywith energy-dispersion spectroscopy. The mechanismof the luster effect on the surface was explained. The resultsindicated that the glaze presents iridescent colors on the surface,mainly associated with the formation of a very thin layer ofCeO2 crystals.Moreover, the CeO2 crystals show a preferentialorientation and different dimensions. The CeO2 crystallizationon the glaze was also studied using a hot-stage X-ray technique.

2010 - Microstructural Characterisation and Electrical Properties of Multiwalled Carbon Nanotube/Glass-Ceramic Nanocomposites [Articolo su rivista]
Giovanardi, Roberto; Montorsi, Monia; Ori, Guido; Cho, . J.; Subhani, T.; Boccaccini, A. R.; Siligardi, Cristina

We report on an improved processing method for fabricating multiwalled carbon nanotubes/glass-ceramic nanocomposites based on vanadium doped silicate glass matrices. Starting from the design of a stable aqueous dispersion of CNTs, achieved using a cationic surfactant, the interaction of CNTs with glass particles in suspension was improved using a co-solvent that provided access to nanocomposites exhibiting high quality CNT distribution in the matrix, which was confirmed by detailed micro/nano-structural and morphological characterisation. Considering that very few studies have focused on the functional properties of CNT/glass composites, in the present investigation the electrical resistivity of CNT/glass composites was measured and it was demonstrated that higher electrical conductivity values were obtained compared to previous similar materials fabricated by conventional powder processing.

2010 - Montmorillonite as efficient carrier of gentamicin used for antibiotic treatment: comparison of MD simulations with experiments [Abstract in Atti di Convegno]
G. Ori; M. Montorsi; A. Bellini; V. Iannuccelli; C. Siligardi

The presented work shows the potential of a montmorillonite-based clay mineral (bentonite) to contribute to the development of novel antibiotic materials. In our knowledge, it is the first time the have been tested the intercalation of gentamicin molecules in montmorillonite as a drug delivery carriers for antibiotic treatment.Comparison of experimental measurements (XRD, TGA, DTA) with simulations (MD modelling) have provided a more detailed understanding of the geometry, organization of gentamicin molecules confined in the cationic clay. By MD simulations it has been possible obtain a further insight into the interactions between the organic guest and the clay framework in view to optimize the cationic exchange process.

2010 - Placas Cerâmicas Esmaltadas com Fina Camada VitrocerâmicaObtidas por Biqueima Rápida [Articolo su rivista] Freitas Nunes; L. Corradini; B. Goulart de Oliveira;T. M. Novais de Oliveira; M.A.Viana Nascimento;C.Siligardi; A. P.Novaes de Oliveira

Resumo: Este trabalho reporta resultados experimentais referentes à preparação e obtenção de placascerâmicas, tipo grés porcelanato, esmaltadas, por serigrafia rotativa, com a aplicação (110 g.m–2) de finas camadas(30 μm) de esmalte vitrocerâmico do sistema LZSA (Li2O-ZrO2-SiO2-Al2O3) e queimadas (800 °C por 5 minutos,segunda queima) por meio de processo de biqueima rápida. A partir dos resultados obtidos, é possível dizer que ospavimentos cerâmicos obtidos são potenciais candidatos em algumas aplicações, mas em particular nos casos ondelimpeza e higiene são requisitos importantes já que a porosidade da camada de esmalte é praticamente inexistentee a rugosidade superficial, Ra foi de 1,44 μm antes do processo abrasivo e de 1,74 μm após 12.000 revoluçõesno equipamento de abrasão.

2010 - Processamento e caracterizacao de espumas vitroceramics do sistema SNCP (SiO2-Na2O-CaO-P2O5) [Articolo su rivista]
K.B. Mundstock; E Guzi de Moraes; D. Hotza; A. P. Novaes de Oliveira; C. Siligardi; S. Ota Rugero

PROCESSING AND CHARACTERIZATION OF SNCP (SiO2-Na2O-CaO-P2O5) GLASS-CERAMIC FOAMS. Glass-ceramics foams prepared from glasses of the SiO2-Na2O-CaO-P2O5 by replication process were obtained and characterized in terms of their chemical and physical properties by X-ray fluorescence, X-ray diffraction, laser diffraction, thermal analysis, density, mechanical strength, microstructural and cytotoxic analysis. The results showed that it is possible to produce glass-ceramic foams by the replication method with optimized properties but cytotoxic analysis indicates that the glass-ceramic foams are not bioactive materials. Mechanical strength values varying from 0.5 to 1.0 MPa and from 0.8 to 2.3 MPa were reached for mean particle sizes of 10 and 6 μm, respectively.

2010 - Production of Foundry Filters Using Al2O3 from the Al-Anodizing Process [Relazione in Atti di Convegno]
Graziela G. Moraes; Bianca G. Oliveira; Cristina Siligardi; Murilo D.M. Innocentini; Amir A.M. Oliveira Jr.; João B. Rodrigues Neto; Dachamir Hotza; Antonio Pedro Novaes de Oliveira

The manufacturing and materials transformation industries generate residues, which do not always have an adequate ecological destination. In many cases, however, these secondary products can be directly re-used as raw materials in other industrial processes. In this context, this article presents the characterization of the sludge generated in the aluminum anodizing process and emphasizes the application potential of this residue as a raw material for the production of industrial ceramic filters. Results show that the high alumina contents (89-96 wt%) and composition constancy, as well as the low particle size (~1 m) after calcination and milling, render this residue a suitable raw material to produce alumina filters with optimized properties for casting engineering metal components with better performance.

2010 - Production of foundry filters using Al2O3 from Al-anodizing process [Capitolo/Saggio]
G.G. Moraes; B.G. Oliveira; C. Siligardi; M.D.M. Innocentini; A.A.M. Oliveira Jr.; J.B. Rodrigues Neto; D. Hotza; A.P. Novaes de Oliveira

The manufacturing and materials transformation industries generate, to a greater or lesser extent, amounts of residues, which do not always have an adequate ecological destination. In many cases, however, these secondary products can be directly re-used as raw materials in other industrial processes. In this context, this article presents the characterization of the sludge generated in the aluminum anodizing process and emphasizes the application potential of this residue as a raw material for the production of industrial ceramic filters. Results show that the high alumina contents (89-97 wt%) and composition constancy, as well as the low particle size (~1 m) after calcination, render this residue a suitable raw material to produce alumina filters with optimized properties for filtration and so purification of liquid metals to cast engineering components with higher performance.

2010 - Structural Characterization of Erbium Containing Glasses by Using Molecular Dynamics Simulation [Capitolo/Saggio]
Montorsi, Monia; Ori, Guido; Siligardi, Cristina

Erbium containing glasses cover an important role in optical communications such as optical amplifiers. It is well know that the concentration of erbium into the glass influences the optical response of the material, therefore in the last years particular attention was devoted to the analysis and characterization of the erbium local distribution in the glass network. The presence of high erbium concentration in the glass is correlated to the formation of Er3+ based clusters and this inhomogeneous distribution of the rare earth ions induces changes in the energy transfer between neighbouring ions leading to the concentration quenching of luminescence, experimentally observed for this class of optical materials. In this communication, the structural evolution occurring in the erbium sites, its modifier role and the changes induced by the alumina addition in the glasses have been extensively studied by using molecular dynamics technique. The effect of alumina on the clustering effect, typical of the glasses containing high erbium concentration, was defined for three main systems characterized by the presence of increased percentage of erbium oxide in the glass formulation.

2009 - Chemical durability and microstructural analysis of glasses soaked in water and in biological fluids [Articolo su rivista]
V. Cannillo; F. Pierli; I. Ronchetti; C. Siligardi; D. Zaffe

A new glass, obtained from Bioglass BG45S5 original composition by substituting CaO with MgO, was produced and its chemical durability and microstructural characteristics were compared with that of Bioglass1. The two glasses (labelled as BG45 and MG45) were soaked up to 4 weeks at physiological temperature in different solutions, i.e. bi-distilled water, Hank’s Buffered Salt Solution 61200 (labelled as HBSS+), Hank’s Buffered Salt Solution 14170 (labelled as HBSS ), and Kokubo’s SBF. Moreover, the influence of either flat or flake surfaces was analysed for both glasses. Results showed that the chemical durability of a glass in saline at 37 8C, evaluated through pH and ICP-AES chemical analysis of the leached components, depended mainly on the chemical composition of the soaking solution. Moreover, the MG45 glass never exhibited hydroxyapatite crystal formation on its surface also after soaking in calcium- containing solutions. The apatite crystallisation and deposition mechanism, typical of a bioactive glass, was induced only if the glass itself contained calcium. The contemporaneous presence of calcium in the glass and in the soaking solution improved the reactivity of the glass, as apatite crystals nucleated in a shorter time and grew more quickly. As regards the morphology of the glass surface, rougher surfaces favoured the formation of hydroxyapatite crystals on glasses containing calcium

2009 - Lead free Cu-Containing Frit for Modern Metallic Glaze [Articolo su rivista]
Siligardi, Cristina; Montecchi, Monica; Montorsi, Monia; Pasquali, Luca

A lead-free frit containing high amount of copper and its glazeconceived for fine porcelain stoneware tiles were investigated.The glazes obtained under industrial firing were studied using Xrayphotoelectron spectroscopy, X-ray diffraction, optical andscanning electron microscopy with energy dispersion spectroscopy.The mechanism of the red color formation on the surfacewas explained. The results indicated that the glaze presents ametallic gloss and iridescent colors on the surface, mainly associatedto the formation of CuO crystallites and Cu metallicparticles. Moreover, the Cu glaze showed a good chemical durability;this is particularly interesting because commercial Cufrits usually present poor chemical properties.

2009 - Lustre Ce-glazes: scientific aspects of materials having high aesthetic properties [Relazione in Atti di Convegno]
Cristina Siligardi; Monica Montecchi; Luca Pasquali; Claudio Ansaloni

Three frits conceived for high porosity single firing tiles containing different amounts of cerium oxide and their glazes were investigated. The glazes obtained under industrial firing were studied using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersion spectroscopy (EDS). The mechanism of the lustre effect on the surface was explained. The results indicate that the glaze presents iridescent colours on the surface, mainly associated to the formation of a very thin layer of CeO2 crystals. Moreover, the CeO2 crystals present a preferential orientation and different dimensions.

2009 - Nova frita pertencente ao sistema CaO-ZnO-SiO2 para aplicacoes ceramicas [Articolo su rivista]
C. Siligardi; C. Mugoni; D. venturelli; M. Montorsi; A.P. Novaes de Oliveira

O desenvolvimento deste trabalho se originou do conhhecimento adquirido e compartlhado, com empresas produtoras e, em geral, com a opiniao publica, sobre a importancia da sustendabilidade ambiental das atividades industriais. Neste contexto a visando reduzir o imacto ambiental, foi utilizada una nova frita, pertecente ao sistema CaO-ZnO-SiO2 (CZnS), como materia prima integrante de massa de gres porcelanato e em substitucao a maetrias prima comunemente utilizada na preparacao de esmaltes para suportes ceramicos.

2009 - Rheological behaviour and mechanical properties of porcelainstoneware bodies containing Italian clay added with bentonites [Articolo su rivista]
F. Andreola a; C. Siligardi; T. Manfredini; C. Carbonchi

This paper presents the results obtained by replacing German and Ukrainian clays in a porcelain stoneware body with a clay from Sardiniaisland, Italy, added with 10 wt% of different bentonites available on Italian territory in order to lower the body costs. Two series of bodies wereprepared: a first series by substituting completely German clay and partially Ukrainian clay (5 wt%) and a second series by substituting completelythe Ukraine clay. Rheological measures were carried out on the suspensions prepared in order to verify the effect of the bentonites presence on theshear and time dependence. The fired specimens were characterized across the technological parameters (water absorption, linear shrinkage, etc.),mechanical and aesthetical properties and compared with a standard/industrial composition.

2009 - Thermal and physical characterisation of apatite/wollastonite bioactive glass-ceramics [Articolo su rivista]
Cannillo, Valeria; Pierli, F.; Sampath, S.; Siligardi, Cristina

Glass–ceramics, containing apatite and wollastonite (A/W) crystals in the MgO–CaO–SiO2–P2O5 glassy matrix, show the ability to form tight chemical bonds with living tissues when implanted in the body, as demonstrated by Kokubo and co-workers. However, the medical applications are mainly limited to non-load bearing conditions because of their poor mechanical properties. To overcome this drawback, a coating of the A/W glass–ceramic could be deposited onto a titanium substrate, in order to combine the good bioactivity of the bioceramic and the good mechanical strength of the titanium alloy base material. In this study, A/W powders obtained from commercial raw materials were thermally sprayed by APS (atmospheric plasma spraying) on Ti–6Al–4V substrates. Since in the as-sprayed conditions the coating microstructure was defective because of pores and cracks, thermal treatments on A/W plasma-sprayed coatings were conducted to enhance the coating microstructure. In order to gain a de...

2008 - Bentonite-based organoclays as innovative flame retardants agents for SBS copolymer [Articolo su rivista]
M. Comes Franchini; P. Fabbri; A. Frache; G. Ori; M. Messori; C. Siligardi; A. Ricci

Two organophilic bentonites, based on nitrogen-containing compounds, have been synthesised viaion exchange starting from pristine bentonite with octadecyltrimethylammonium bromide (OTAB)and with synthetic melamine-derived N2,N4-dihexadecyl-1,3,5-triazine-2,4,6-triamine (DEDMEL).The chemical and morphological characterization of the organoclays was based on XRD, TEM,Laser Granulometry, X-Ray Fluorescence and CEC capacity. Copoly(styrene-butadiene-styrene)-nanocomposites (SBS-nanocomposites) were obtained by intercalation of the SBS-copolymer intothese new organoclays by melt intercalation method. XRD and TEM analysis of the organoclaysand of the micro/nano-composites obtained are presented. The effect of the organoclays on theSBS-nanocomposite’s flammability properties was investigated using cone calorimeter. An encouragingdecrease of 20% in the peak heat released rate (PHRR) has been obtained confirming theimportant role of melamine’s based skeleton and its derived organoclays to act as effective fireretardants and for the improvement of this important functional property in SBS copolymers.

2008 - Cobalt doped glass for the fabrication of percolated glass-alumina functionally graded materials [Articolo su rivista]
Cannillo, Valeria; Mazza, D.; Siligardi, Cristina; Sola, Antonella

The present research was focused on the development of a new glass to produce glass–alumina FGMs. The glass formulation, belonging to theCaO–ZrO2–SiO2 system, was doped with cobalt, by adding a small molar percentage (about 0.1 mol%) of CoO, in order to obtain a blue glass,which could be useful to appreciate the final compositional gradient. The glass was accurately characterized, evaluating its thermal behaviour, itsmechanical properties, and its attitude to crystallize during a thermal treatment. Subsequently, the glass was used to produce glass–alumina FGMsvia percolation and the so obtained specimens were analysed in order to evaluate the effect of the glass infiltration. The possible development ofnew crystal phases, in particular, was tested via micro X-ray diffraction and the elastic properties gradient associated with the compositionalgradient was measured via depth-sensing Vickers microindentation.

2008 - Densification and crystallization of Ba-exchanged zeolite A powders [Articolo su rivista]
Andreola, Nora Maria; Romagnoli, Marcello; Siligardi, Cristina; Manfredini, Tiziano; Ferone, C.; Pansini, M.

The effect of thermal treatment, Na content and mineralizer ion on the sintering process of Ba-exchanged zeolite A on the zeolite ! celsianthermal transformation are investigated. The powder samples containing different amounts of Na+ and Li+ were pressed at 30 MPa and thermallytreated at temperatures from 1000 to 1400 8C for times up to 5 h and subsequently were characterized by room temperature X-ray diffraction and byscanning electron microscopy. Increasing the Na residual content in the Ba-zeolite A samples improves the sintering process, even if the highest Nacontent appears to inhibit the zeolite! celsian transformation, since a new crystalline phase appears at the highest temperature. Moreover, theporosity of all samples thermally treated is quite high. Finally the manufacture of pressed samples allowed lower temperatures and times to be usedto obtain the transformation zeolite Ba-A ! monoclinic celsian, which suggests it is a potential method to prepare celsian low temperaturerefractory materials. At last an ANOVA analysis was carried out to identify the independent parameters from a statistical point of view.

2008 - Effects of different production techniques on glass-alumina functionally graded materials [Articolo su rivista]

Glass–alumina functionally graded materials were obtained using two different methods: percolation, which was representative of naturaltransport based processes, and plasma spraying, which was representative of constructive processes. The specimens produced in this way wereinvestigated to evaluate the effect of production techniques on the final microstructure and gradient, which, in turn, govern the properties andperformances of the graded systems. Moreover, post-production heat treatments were performed in order to improve the reliability of the materialsexamined.

2008 - Local and medium range structure of erbium containing glasses: a molecular dynamics study [Articolo su rivista]
Corradi, Anna; Cannillo, Valeria; Montorsi, Monia; Siligardi, Cristina

Erbium containing glasses cover an important role in optical communications and laser technology. The local environment of the ionsconstituting the three dimensional network exerts a strong influence on the chemical and physical properties of the glasses. In particularthe network modifier cations strongly influence the short and intermediate range order of the glass structure. The structural modificationsinduced by the alumina addition in the glass matrix, as a function of the erbium oxide concentration, have been studied using moleculardynamics (MD) simulations. While at low Er2O3 concentration the network former action of the Al3+ leads to a more polymerized glassnetwork, at higher Er2O3 content the influence of the alumina on the erbium local structure is limited. Further investigation points outmicro-heterogeneity in the Na+ and Ca2+ distribution as a function of the alumina concentration.

Cristina Siligardi; Davide Settembre; Mauro Montorsi; Massimiliano Reginelli

The authors carried out a study to investigate the behaviour of three industrial bodies (two monoporosa bodies and one double firing body) which differ principally in their carbonate content. Moreover four different binary mixtures containing illitic or kaolinitic clay and calcite or dolomite were prepared to investigate their reactivity during firing. In this study it has been observed that ghelenite and anorthite were formed in all samples as new phases and MgO residues remain inside monoporosa and fast double firing products after heat treatment in the sample containing dolomite.

2008 - Sintering and crystallization of CaO-Al2O3-ZrO2-SiO2 glasses containing different amount of Al2O3 [Articolo su rivista]
Siligardi, Cristina; Montorsi, Monia; Lusvarghi, Luca; Vernia, Cecilia

In this work several complementary techniques have been employedto carefully characterize the sintering and crystallizationbehavior of CaO–Al2O3–ZrO2–SiO2 glass powder compactsafter different heat treatments. The research started from a newbase glass 33.69 CaO–1.00 Al2O3–7.68 ZrO2–55.43SiO2(mol%) to which 5 and 10 mol% Al2O3 were added. The glasseswith higher amounts of alumina sintered at higher temperatures(9531C [lower amount] vs. 9871C [higher amount]). Acombination of the linear shrinkage and viscosity data allowedto easily find the viscosity values corresponding to the beginningand the end of the sintering process. Anorthite and wollastonitecrystals formed in the sintered samples, especially at lowertemperatures. At higher temperatures, a new crystalline phasecontaining ZrO2 (2CaO. 4SiO2 . ZrO2) appeared in all studiedspecimens.

2007 - BAS, CMAS and CZAS glass coatings deposited by plasma spraying [Articolo su rivista]
Bolelli, Giovanni; Lusvarghi, Luca; Manfredini, Tiziano; Parsini, E.; Siligardi, Cristina

In this study, three different industrial frits BaO–Al2O3–SiO2 (BAS), CaO–MgO–Al2O3–SiO2 (CMAS), CaO–ZrO2–Al2O3–SiO2 (CZAS) havebeen deposited on porcelainized stoneware tiles by plasma spraying. In the as-sprayed conditions, the microstructure of the coatings is defectivebecause of pores, microcracks and low intersplat cohesion. Hot stage microscope and differential thermal analysis measurements made on the glasspowders allowed to characterize the frits thermal behaviour. Post process thermal treatments have been arranged, following these indications as wellas preliminary tests, in order to achieve the lowest porosity and the highest resistance to abrasion. At the chosen temperatures, a microstructuralimprovement has been induced, but in the BAS specimens, an optimal sintering has not been accomplished because of the unavoidable fulloverlapping of the sintering and crystallization processes.

2007 - Ceramizzazione di vetri mediante tecnica D.O.E. (Design of Experiment) [Articolo su rivista]
C.Siligardi; M.Romagnoli

Il procedimento descritto in questo articolo è volto ad ottimizzare il processo termico adottato per la de-vetrificazione del vetro al fine di ottenere materiali vetro-ceramici. Questo studio è stato realizzato adottando la tecnica DOE, che consiste nel programmare le prove e valutare i dati sperimentali su base statistica. Tre fattori sono stati identificati in grado di caratterizzare il trattamento termico: la temperatura di nucleazione, il tempo di nucleazione e il temperatura di accrescimento. Tali variabili indipendenti sono stati messe in relazione, per mezzo di equazioni polinomiali, con variabili dipendenti quali durezza e resistenza. I campioni sono stati inoltre esaminati mediante SEM-examd e caratterizzati con diffrattometria a raggi X su polveri. La tecnica DOE ha permesso di individuare per ogni campione, il corretto trattamento termico, che è il risultato della combinazione ottimizzata dei fattori presi in considerazione, in grado di ottimizzare la durezza e la resistenza dei campioni. I modelli sono poi stati convalidati con la realizzazione di ulteriori campioni i cui valori sperimentali sono stati confrontati con quelli calcolati.

2007 - Characterization of glass-alumina functionally graded coatings obtained by plasma spraying [Articolo su rivista]
V. Cannillo; L. Lusvarghi; C. Siligardi; A. Sola

Glass-alumina functionally graded coatings (FGCs) were produced Via plasma spraying, a deposition technique for thick (> 10-20 mu m) coatings production, which ensures high flexibility and good reliability. The samples were obtained by building a graded glass-alumina coating onto an alumina substrate; the coatings were designed as multi-layered systems, each layer having a mean composition slightly different from the neighbouring ones. Two different compositional gradients were considered (front 100 vol.% alumina to 100 vol.% glass and from 80-20 vol.% glass to 100 vol.% glass) and several heat treatments were performed in order to improve the substrate-coating interface and induce a controlled transformation (sintering and/or crystallization) of the glassy phase. After a preliminary screening of the as-sprayed and the heat treated samples, the most interesting ones were carefully characterized, especially from a mechanical point of view. In fact, tests Such as Vickers micro-indentation allowed to appreciate the effects of the graded compositional profile and the consequences induced by thermal treatments. (c) 2006 Elsevier Ltd. All rights reserved.

2007 - Devitrification behaviour of plasma-sprayed glass coatings [Articolo su rivista]

Glass and glass-ceramic coatings on ceramic tiles have been manufactured by plasma-spraying high-performance CAS (in wt%-SiO2, 60%; Al2O3, 15%; CaO, 23%; others, traces) and CZS (in Wt%-SiO2, 50%; CaO, 31%; ZrO2, 16.5%; Al2O3, 2%; others, traces) glass frits. The CZS system has a surface crystallization at about 1050 degrees C. Such behaviour would not easily allow to obtain a fully crystalline bulk glass-ceramic, but the defectiveness of the plasma-sprayed coating supplies many nucleation sites. Thus, it becomes completely crystalline and well sintered after a 850 degrees C for 30 min + 1050 degrees C for 15 min treatment. The CAS frit, designed not to produce significant crystallization, is well sintered after a 850 degrees C for 30 min + 950 degrees C for 30 min thermal treatment, but remains too brittle due to its glassy nature. A 1050 degrees C treatment allows a few pseudowollastonite crystals to form in a glassy matrix; their formation also hinders sintering. Thus, mechanical properties are inferior to heat-treated plasma-sprayed CZS. (c) 2006 Elsevier Ltd. All rights reserved.

2007 - Glass-alumina Functionally Graded Materials produced by plasma-spraying [Monografia/Trattato scientifico]

The present work was focused on glass-alumina functionally graded materials. Thesamples, produced by plasma spraying, were built as multi-layered systems by depositing severallayers of slightly different composition, since their alumina and glass content was progressivelychanged. After fabricating the graded materials, several, proper characterization techniques were setup to investigate the gradient in composition, microstructure and related performances. A particularattention was paid to the observation of the graded cross sections by scanning electron microscopy,which allowed to visualize directly the graded microstructural changes. The scanning electronmicroscopy (SEM) inspection was integrated with accurate mechanical measurements, such assystematic depth-sensing Vickers microindentation tests performed on the graded cross sections.

2007 - Glass-ceramic Functionally Graded Materials produced with different methods [Articolo su rivista]
Cannillo, Valeria; Lusvarghi, Luca; Manfredini, Tiziano; Montorsi, Monia; Siligardi, Cristina; Sola, Antonella

Functionally graded materials (FGMs) are innovative composite materials characterized by a gradual spatial change in composition, microstructure and related properties. This work was focused on glass-alumina functionally graded materials, produced via percolation of molten glass into a sintered polycrystalline alumina substrate and via plasma spraying. The glass composition, belonging to the CaO-ZrO2-SiO2 system, was purposely designed in order to minimize the difference between the coefficients of thermal expansion of the constituent phases, which may induce thermal residual stresses in service or during fabrication. The ingredient materials as well as the resultant FGMs were carefully characterized. In particular, a great attention was devoted to the microstructural investigation of the penetration profile. (c) 2006 Elsevier Ltd. All rights reserved.

2007 - Prediction of the elastic properties profile in glass-alumina functionally graded materials [Articolo su rivista]

Glass-alumina functionally graded materials were obtained by percolation and alternatively by plasma spraying. The paper develops a reliable model to predict the functional gradient of the analysed systems. A finite element code, which was able to handle microstructural images, was employed to estimate the effective elastic properties along the gradient direction. The calculated values were compared with experimental data acquired by means of systematic microindentation tests. The computational approach was compared with analytical tools such as the rule of mixture. The results revealed that the elastic properties were significantly influenced by microstructural features such as the shape of the ingredient materials domains and the presence of pores at the grain boundaries. This was particularly evident in the sprayed FGMs, due to their peculiar lamellar microstructure. Even if the coating-substrate interface properties were difficult to include in the model, the numerical simulations fitted fairly well the experimental data. (c) 2006 Elsevier Ltd. All rights reserved.

2007 - Surface acoustic wave depth profiling of functionally graded material [Articolo su rivista]
Goossens, J.; Leclaire, P.; Xu, X.; Glorieux, C.; Martinez, L.; Sola, Antonella; Siligardi, Cristina; Cannillo, Valeria; VAN DER DONK, T.; Celis, J. P.

The potential and limitations of Rayleigh wave spectroscopy to characterize the elastic depth profileof heterogeneous functional gradient materials are investigated by comparing simulations of thesurface acoustic wave dispersion curves of different profile-spectrum pairs. This inverse problem isshown to be quite ill posed. The method is then applied to extract information on the depth structureof a glass-ceramic alumina functionally graded material from experimental data. The surfaceacoustic wave analysis suggests the presence of a uniform coating region consisting of a mixture ofAl2O3 and glass, with a sharp transition between the coating and the substrate. This is confirmed byscanning electron microscope with energy dispersive x-ray analysis.

2007 - Valorization of Italian clay added bentonites for porcelain stoneware bodies.Study of the rheological behaviour and mechanical properties [Relazione in Atti di Convegno]
F. Andreola; C. Siligardi; T. Manfredini; C. Carbonchi; P. Danasino

This paper present the results obtained using a clayfrom Sardinia island, Italy, added with 10 wt% ofdifferent bentonites available on Italian territory inorder to obtain a decreasing of the body costs. Twoserie of bodies was prepared a first serie substitutingcompletely Germany clay and partially Ukraine clay(5wt%), a second serie substituting completely theUkraine clay into a porcelain stoneware body.Rheological measures were carried out on thesuspensions prepared in order to verify the effect of thebentonites presence on the shear and time dependence.The fired specimens were characterized across thetechnological parameters, mechanical and aestheticalproperties and compared with a standard/industrialcomposition.

2006 - Application of Microwave to Glaze and Ceramic Industry [Capitolo/Saggio]
Leonelli, Cristina; Siligardi, Cristina; Veronesi, Paolo; Corradi, Anna

Glaze sintering and crystallization processes; synthesis of ceramic pigments by solid state reactivity; and wax burnout in advanced ceramic pieces was investigated together with addition of polishing sludge to porcelain stoneware body are some of the themes developed recently at Modena University in the field of industrial ceramics.

2006 - Design and optimisation of glass-celsian composites [Articolo su rivista]
Cannillo, Valeria; E., Carlier; Manfredini, Tiziano; Montorsi, Monia; Siligardi, Cristina

The aim of this paper is to fabricate novel glass matrix composites reinforced by means of celsian particulate. In fact. the attractive features of celsian, such as chemical stability and high mechanical resistance, can be favourably exploited in order to obtain enhanced-performance composites with respect to bulk glass. A design of experiments (DOE) procedure has been utilized to optimise the fabrication route of glass-celsian composites. This method allowed the determination of the optimal processing conditions for the obtainment of a fully dense material with a good particulate dispersion.

A., Motori; F., Patuelli; A., Saccani; Andreola, Nora Maria; F., Bondioli; Siligardi, Cristina; Ferrari, Anna Maria

Abstract Monoclinic celsian has been obtained by a non-conventional way, i.e. the thermal treatment of 4A-type commercial zeolite: a stoichiometric amount of barium ions was included in the zeolite by means of a cation-exchange treatment. A small concentration of alkali ions (either sodium or lithium) was also present in the exchanged zeolite, since previous studies had underlined the positive effect of these ions on the formation of monoclinic celsian. This particular synthesis proves to be economic, due to the low-cost precursors, the low temperatures and the short times required. However, the presence of even a small content of alkali ions and a residual amorphous phase can negatively affect the insulating properties of the material, thus hindering its use in electrical insulating systems. The results so far obtained show that the material keeps good insulating properties at low temperature, but its conductivity and dielectric losses strongly increase above 200 °C. --------------------------------------------------------------------------------

2006 - Glass-alumina functionally graded materials: their preparation and compositional profile evaluation [Articolo su rivista]
V. Cannillo; T. Manfredini; C. Siligardi; A. Sola

This work was focused on glass-alumina functionally graded materials (FGMs). For the glass phase, a proper composition was chosen belonging to the ternary system CaO-ZrO2-SiO2 and the substrate was made up of a sintered, high-purity polycrystalline alumina. Both of the ingredient materials were carefully characterized. The fabricated functionally graded materials were analysed in detail, by observing them under a scanning electron microscope (SEM) coupled with an X-ray energy dispersive spectrometer (X-EDS). The depth of penetration of the glass and the compositional profile were evaluated by means of a SEM-image elaboration. Moreover, this work applied an analytical model to predict the depth of penetration as a function of time and fabricating parameters such as temperature.

2006 - Influence of Al2O3 addition on thermal and structural properties of erbium doped glasses [Articolo su rivista]
Corradi, Anna; Cannillo, Valeria; Montorsi, Monia; Siligardi, Cristina

Changes in the structural properties of Er3+ doped soda-lime silicate glasses were investigated as a function of Al2O3 content. A combined approach of experimental techniques and molecular dynamic simulations (MD) was used to evaluate the structural features directly correlated to the glass properties. The experimental results in term of density, thermal properties as well as microstructural and mineralogical data showed a significant variation when increasing the alumina content from 10 mol% to 15 mol%. These results were compared to the MD information and discussed: changes in erbium and aluminium local configuration, due to the glass structural evolution as a function of the alumina concentration, have been investigated.

2006 - Microscale computational simulation and experimental measurement of thermal residual stresses in glass-alumina functionally graded materials [Articolo su rivista]
Cannillo, Valeria; Montorsi, Monia; Siligardi, Cristina; Sola, Antonella; G., DE PORTU; L., Micele; G., Pezzotti

Glass-alumina functionally graded materials are new attractive composite materials, that can achieve peculiar mechanical properties due to their gradual compositional variation. Nevertheless, the difference between the coefficients of thermal expansion of the constituent phases may result in significant thermal residual stresses in service or during fabrication. A proper (glass formulation can minimize the mismatch in thermo-mechanical properties, thus relevantly reducing the mean value of the resultant thermal stresses. However, it is a crucial requirement to evaluate the effect of microstructural discreteness and randomness oil the actual stress distribution in functionally graded materials. With this aim,a computational model which applies the finite element method at the microscale is used. The careful modelling of the real microstructural details enables to accurately predict the local stress values and distribution. In order to verify the reliability of the computational simulations, the residual thermal stresses were also experimentally measured by means of a piezo-spectroscopic technique. The comparison between the numerical and the experimental results validate the microstructure-based model.

2006 - Microstructure-based modelling and experimental investigation of crack propagation in glass-alumina functionally graded materials [Articolo su rivista]
Cannillo, Valeria; Manfredini, Tiziano; Montorsi, Monia; Siligardi, Cristina; Sola, Antonella

The aim of the present work was the determination of the fracture mechanisms in glass-alumina functionally graded materials (FGMs). The investigation was performed by means of a combined approach based on microscale computational simulations, which provided for an accurate modelling of the actual FGM microstructure, and experimental analysis. The numerical results proved that microstructural defects, such as pores, deeply influenced the damage evolution. On the contrary, the minimization of the mismatch in the coefficients of thermal expansion of the ingredient materials allowed to obtain low thermal residual stresses, which did not relevantly affect the crack propagation. In order to support the numerical model, microindentation tests were performed on the cross-section of FGM specimens and the experimentally observed crack paths were compared to the computationally predicted ones. (c) 2005 Elsevier Ltd. All rights reserved.

2006 - Non conventional synthesis of monoclinic celsian from Ba-exhanged zeolite A: study of the effect of residual Na and forming pressure [Capitolo/Saggio]
C. Ferone; M. Pansini; F. Andreola; L. Barbieri; C. Siligardi; T. Manfredini

Four samples of Ba-exchanged zeolite A, bearing 0.27, 0.43, 0.58 and 0.74 meq/g Na residual amounts, were thermally treated in the temperature range 200-1500 °C for times up to 28 hours. The same samples were pressed at 30 and 60 MPa to manufacture cylindrical pellets, which were thermally treated at 1300 °C for 5 hours. Thermally treated materials were characterized by room temperature XRD. The sequence of thermal transformations that Ba-exchanged zeolite A undergoes (zeolite ® amorphous phase ® hexacelsian ® monoclinic celsian) and the strong mineralizing action developed by Na are confirmed. Pressing the Ba-exchanged zeolite A powder-like samples to obtain cylindrical pellets is found to expedite the sluggish final phase transition hexacelsian ® monoclinic celsian. The optimum residual Na content of Ba-exchanged zeolite A to be transformed into monoclinic celsian is assessed to range between 0.27 and 0.43 meq/g.

2006 - Preparation and experimental characterization of glass-alumina functionally graded materials [Articolo su rivista]
Cannillo, Valeria; Manfredini, Tiziano; Siligardi, Cristina; Sola, Antonella

This work aims at investigating the effects of the processing conditions on the final microstructure of glass-alumina functionally graded materials (FGMs). The ingredient materials, i.e. a polycrystalline sintered alumina and a CaO-ZrO2-SiO2 glass, were accurately characterized, since their mechanical and thermal properties may deeply influence the fabricating process and the overall FGM behaviour. The functionally graded materials were obtained by means of percolation of the molten glass into the alumina substrate. Two types of samples were considered-the Bulk FGMs, produced starting from a glass bulk, and the Powder FGMs, produced starting from a glass powder; in both cases four different heating cycles were attempted. The functionally graded materials were analysed using a SEM-EDS and a X-ray diffractometer. Great attention was devoted to the resulting microstructure; moreover the depth of penetration was measured and related to the fabricating parameters, such as time and temperature.

2006 - Sintering and crystallisation of vanadium doped CaO-ZrO2-SiO2 glass-ceramics [Articolo su rivista]

The effect of addition of V2O5 on densification and crystallisation of glass powder compacts in the system CaO-ZrO2-SiO2 has been investigated. A well crystallized material of relatively high density (95% of theoretical density) was obtained after sintering at 900 degrees C for 1 h by adding 5 mol% V2O5. Crystalline phases identified were wollastonite, calcium zirconium silicate and calcium zirconium oxide. The addition of V2O5 was shown to reduce the sintering temperature and also to enhance the electrical conductivity of the base CaO-ZrO2-SiO2 glass-ceramic. Possible applications of the present vanadium containing glass-ceramics are the production of coloured glazes and in coatings and enamels with anti-static behaviour.

2006 - Structure, magnetic and positron lifetime studies on CaO-ZrO2-SiO2 glass system doped with vanadium oxide [Articolo su rivista]
EE Assem; KR Mahmoud; T. Sharshar; C. Siligardi

The structure of CaO-ZrO2-SiO2 glasses doped with V2O5 (0.1-2 mole%) was studied using density and molar volume measurements. It was observed that the molar volume increased while the density decreased with increasing V2O5 content. Magnetic susceptibility measurements showed the diamagnetic behaviour of this glass system. The free volume was probed using ortho-positronium pick-off annihilation lifetime parameters. The mean free volume and fractional free volume have also been calculated from the positron annihilation lifetime data. The overall measured parameters from the structural and/or positron annihilation spectra indicated that the majority of the vanadium ions in the range 0-0.5 mole% of V2O5 are in the V5+ valence state which act as a glass former. On the other hand, the majority of the vanadium ions in the range 0.7-2 mole% of V2O5 are the V3+ and V4+ states acting as a glass modifier.

2006 - Waste treatment under microwave irradiation [Relazione in Atti di Convegno]
Corradi, Anna; Lusvarghi, Luca; Rivasi, Maria Rosa; Siligardi, Cristina; Veronesi, Paolo; Marucci, G.; Annibali, M.; Ragazzo, G.

Waste treatments to induce stabilization or recovery of waste materials is an important part of modern research efforts. Microwave processing has proved to be a powerful tool to convey energy exactly where it is needed by the process, as well as to allow operation in peculiar environments, even in remote-controlled modality. The present work is a summary of three years of joint research between Modena's University and ENEA investigation regarding microwave assisted thermal treatments lead on wastes of different nature, performed at the 2.45 GHz ISM frequency. The heat-treatments regarded the inertisation and vitrification of asbestos and the stabilization in a glassy matrix of a multi-oxide mixture simulating nuclear waste. Either single-mode or multi-mode applicators were used during the preliminary tests, and hybrid heating was exploited, if necessary. In some cases, additives ensuring a better microwave coupling were used to improve the process speed or the overall yield. © Springer-Verlag Berlin Heidelberg 2006.

2005 - Aluminum co-doping of soda-lime silicate glasses: Effect on optical and spectroscopic properties [Articolo su rivista]
S. Berneschi; M. Bettinelli; M. Brenci; GN Conti; S. Pelli; S. Sebastiani; C. Siligardi; A. Speghini; GC Righini

One of the limits of using silicate glasses as a host for Er3+ is the emission bandwidth, which is smaller than in the case of other oxide glasses, such as phosphates and tellurites. The bandwidth can be increased by adding aluminum to the composition. Here we present an experimental investigation of the effect of increasing aluminum content on optical and spectroscopic properties of this glass. Glass samples were prepared by melting at 1550 degrees C reagent grade SiO2, Al2O3, Na2CO3, K2CO3, CaCO3, (NH4)(3)PO4 and Er2O3; Al2O3 concentration ranged from 0.99 to 20 mol%. Both heating and cooling rates were equal to 0.17 degrees C s(-1). Measurements of the fluorescence bandwidth were then made and as a function of alumina content. Judd-Ofelt analysis was performed and calculated radiative lifetimes were compared with experimental ones. Planar waveguides were also fabricated by using ion-exchange technology, and some optical properties measured by the prism coupling technique. These waveguides had losses of the order of 1 dB/cm at 635 nm.

2005 - Experimental characterization and computational simulation of glass-alumina functionally graded surfaces [Relazione in Atti di Convegno]
V. Cannillo; T. Manfredini; M. Montorsi; C. Siligardi; A. Sola

Functionally graded materials are a new and attractive class of materials incorporating an engineered spatial variation in composition and/or microstructure: this idea has immediately revealed successful since it allows to reach peculiar mechanical properties such as resistance to wear and contact damage. As a matter of fact, the final behaviour of a Functionally Graded Material is mainly influenced by its graded composition and/or microstructure. Therefore a good fabrication technique should provide a high control and reproducibility of the spatial variation in composition and/or microstructure; on the other hand, a reliable model should take into account the gradient in order to accurately predict the final behaviour of a Functionally Graded Material. The present study is focused on glass-alumina FGMs: the compositional variation, which occurs along only one direction, has been realized through percolation of a molten glass into a bulk polycrystalline alumina. The resulting Functionally Graded Coatings have been carefully characterized through Scanning Electron Microscopy, X-ray diffraction, classical mechanical tests and analysis. Moreover, their behaviour has been modeled by means of a microstructure-based FEM method. A great attention has been paid to the validation of the computational model on the basis of the experimental data. Furthermore, the experimental and the computational approaches have been combined in order to define the correlation between fabrication parameters, such as time and temperature, and resulting gradients in composition and microstructure as well as related performances. Since changes in material properties can be easily evaluated, the resulting model may be useful to simulate the material response to a given thermo-mechanical loading and to tailor the gradient as a function of the specific application.

2005 - Influence of the manufacturing process on the crystallization behavior of a CZS glass system [Articolo su rivista]
Lusvarghi, Luca; Manfredini, Tiziano; Siligardi, Cristina; Bolelli, Giovanni

A glass belonging to the CaO-ZrO2-SiO2 (CZS) System has been plasma-sprayed on ceramic tiles. The crystallization behavior of plasma-sprayed coatings has been compared to the devitrification processes of the bulk glass and sintered glass powders of the same composition. DTA experiments reveal a crystallization peak at about 1323 K, with a quite high activation energy, indicating the bulk crystallization process is difficult, because of the high viscosity of the glass. Bulk samples require higher treatment temperatures (approximate to 1423 K) to develop significant amounts of crystalline phases. Furthermore, being the crystallization mostly superficial, high residual stresses develop between the crystalline surface and the glassy core. Sintered samples are fully crystalline, because crystallization starts from the particle surface, the specimens show a considerable shrinkage. After an 1123 K 30´ + 1323 K 15´ thermal treatment, plasma-sprayed coatings, possessing numerous defects and a slight degree of devitrification induced by thermal cycling during plasma deposition, become very well sintered and completely crystalline, because the as-sprayed microstructural features promote heterogeneous nucleation. In this case, the shrinkage is quite negligible, since partial sintering occurs already during the deposition process. In the fully crystalline coatings, excellent mechanical properties (microhardness, fracture toughness and abrasion resistance) are achieved, overcoming those of traditional industrial glazes.

2005 - Integrated optical amplifiers and microspherical lasers based on erbium-doped oxide glasses [Articolo su rivista]

Er3+-doped glasses have been a subject of great interest in the recent years for their application in the areas of guided wave optical amplifiers and lasers. Oxide-glass matrices, in particular, offer the advantage of relatively simple fabrication processes-both for bulk glasses and optical fibers-and have demonstrated quite good properties in the 1.5 mu m wavelength band. Here we present some results we have obtained in the development of different silica-based glasses and in their application to the production of integrated optical amplifiers and microspherical lasers. As to the former application, two classes of silica glasses have been produced and investigated, namely a melted soda-lime-alumino-silicate glass and a sol-gel silica-hafnia glass. Both of them exhibit a wide emission bandwidth and seem quite promising for broadband optical amplifiers. We also demonstrated low-threshold microlasers, based on whispering gallery mode spherical resonators, fabricated in different oxide glasses.

2005 - New frontiers in engineered materials: fabrication processes and relevant applications of Functionally Graded Materials [Articolo su rivista]
Cannillo, Valeria; Manfredini, Tiziano; Montorsi, Monia; Siligardi, Cristina; Sola, Antonella

Functionally GradedMaterials (FGMs) are a newand attractive class ofcomposite materials,characterized by anengineered spatial variationin composition andmicrostructure. Anappropriate design of thecompositional andmicrostructural gradientensures a gradual change ofproperties andperformances, which can betailored to the assignedapplication requirements.The optimization of the finalFGM, however, isconditioned not only by theunderstanding of thecorrelation existing betweencomposition/microstructureand material behaviour, butalso by the adoption of asuitable fabricationtechnique. In the presentpaper, therefore, specialattention will be paid to theproduction of FunctionallyGraded Materials. Finally abrief overview of theirapplications will beprovided

2005 - New glass-ceramic inclusion pigment [Articolo su rivista]
F., Bondioli; Manfredini, Tiziano; Siligardi, Cristina; Ferrari, Anna Maria

Recently, the traditional ceramic industry has demonstrated increased interest in obtaining inclusion pigments to stabilize unstable chromophores, such as hematite or cadmium sulfoselenide, at firing temperature and in studying the actions of molten glasses. This present work focuses on a new method for synthesizing hematite-zircon inclusion pigments from an unconventional mixture of precursors. For this purpose, a glassy composition that belongs to the LiO2-ZrO2-SiO2 system and that crystallizes into zircon during the calcination step has been chosen.

2005 - Plasma-sprayed glass-ceramic coatings on ceramic tiles: microstructure, chemical resistance and mechanical properties [Articolo su rivista]
Bolelli, Giovanni; Cannillo, Valeria; Lusvarghi, Luca; Manfredini, Tiziano; Siligardi, Cristina; C., Bartuli; A., Loreto; T., Valente

This article reports the characterisation and optimisation of glass-ceramic coatings plasina-sprayed on traditional ceramic substrates, dealing with microstructures, chemical resistance, and superficial mechanical properties. A CaO-ZrO2-SiO2 (CZS) frit, capable of complete crystallization after proper thermal treatment, has been employed: due to its refractory nature, its firing temperature in a traditional process would be unbearable for common substrates. The frit was plasma-sprayed onto ceramic tiles and a post-process thermal treatment has been developed in order to sinter and crystallize the coating, employing much lower temperatures than a traditional ceramic firing cycle. The microstructure of both as-sprayed and treated coatings has been evaluated with SEM and EDS, acid resistance tests have been performed. Vickers microhardness, superficial fracture toughness, deep abrasion resistance, elastic modulus and coating adhesion have been evaluated. Unglazed stoneware and an industrial glaze were also tested for comparison and an experiment was made to produce a CZS-based glaze to ascertain the inadequacy of traditional firing. As-sprayed coatings have a typical plasma-spraying defective microstructure, but a thermal treatment with 30´ isotherm at 850 degrees C plus 15´ isotherm at 1050 degrees C allows good densification, excellent adhesion and complete crystallization, with formation of wollastonite-2M and many small Ca2ZrSi4O12 grains. Thus, the coating outperforms stoneware by 50% in abrasion resistance, possessing higher fracture toughness, thanks to the continuous crack deflections due to the numerous crystals. Fracture toughness appears to be the property most correlated to abrasion resistance, because brittle fracture is the dominant abrasion mechanism. Hardness and elastic modulus reflect quite well the coating inner cohesion. Treated coatings porosity is lower than industrial glazes and stoneware.

2005 - Structural characterization of neodymium containing glasses by molecular dynamics simulation [Articolo su rivista]
Corradi, Anna; Cannillo, Valeria; Montorsi, Monia; Siligardi, Cristina; Cormack, An

Structural characterization of neodymium containing glasses was performed by using molecular dynamic simulations. Chemical and physical properties of glasses are strongly related to the local environment of the different ions constituting the three dimensional network. In rare earth containing glasses the modifications of the basic structural units and the physical properties of the host material strongly depend on the rare earth ion content. In this work molecular dynamic simulations (MD) have been used to characterize the structural modification induced by the Nd3+ addition into a silicate glasses. The increase of the NBO species in the glass structure has been observed as a results of the increasing Nd2O3 content. This results compare well with the experimental evidences that indicates the glass depolymerization promoted by the neodymium addition. The structural length scale associated with the rare earth clustering process, experimentally observed, have been also investigated. MD results reveals the presence of Nd-O-Nd linkages which indicate the possibility of the rare earth cations to clusterize in the glass network. The presence of Nd3+ rich regions promotes the concentration quenching phenomena that are associated to the drastic changes in the glass amplification efficiency experimentally observed for neodymium containing glasses.

2004 - A new glass-ceramic red pigment [Articolo su rivista]
F. Bondioli; T. Manfredini; C. Siligardi; AM Ferrari

Recently in the traditional ceramic industry there has been an increasing interest in the obtainment of inclusion pigments to stabilize at the firing temperature and towards the actions of molten glasses unstable cromophore such as hematite or cadmium sulphoselenide. This work focuses on a new synthesis of hematite-zircon inclusion pigment obtained from sintering of non-conventional mixture of precursors. To this purpose a glass composition belonging to the Li2O-ZrO2-SiO2 system that during the sintering/devetrification steps crystallizes zircon has been chosen. The employment of two different Fe precursors (oxide and goethite) have been also analyzed. Finally, a mechanism of pigment formation is proposed.

2004 - Characterisation of CaO-ZrO2-SiO2 glasses by MAS-NMR and molecular dynamics [Articolo su rivista]
Barbieri, Luisa; Cannillo, Valeria; Leonelli, Cristina; Montorsi, Monia; Siligardi, Cristina; P., Mustarelli

In this work a wide series of compositions, belonging to the CZS ternary system, are analysed. The linear expansion coefficient of the glass materials is experimentally determined and the results are interpreted by comparison with the structural information derived by molecular dynamics simulations and by Si-29-MAS-NMR. The analysis of the alpha values indicate that, while the ZrO2 acts as network former in these glasses, CaO shows network modifier behaviour producing a decrease of the network complexity. The characterisation of the short and intermediate range structure, obtained by the MD and Si-29-MAS-NMR analysis, allows one to define the relationships between the structure modifications induced by the different oxides, and the physical properties of the glasses experimentally observed.

2004 - Comparison of models for dense particle packing [Relazione in Atti di Convegno]

Analisi di modelli per l'ottenimento della massima densità di impaccamento di polveri con morfologia irregolare.

2004 - Computational simulations for the optimisation of the mechanical properties of alumina-glass Functionally Graded Materials [Capitolo/Saggio]

Functionally graded materials are finding increasing applications especially as protective coatings, due to their mechanical properties such as resistance to wear and contact damage. It is well known that the microstructure of FGMs governs the resulting global properties. Finite element simulations can be successfully used to characterize the performance of these materials, provided that the computational model is able to take into account microstructural variations along the thickness. In this work, Functionally Graded Materials obtained by percolation of a glass into a bulk polycrystalline alumina are considered and the effect of the microstructure on the overall behavior is investigated by means of a microstructure-based FEM approach. The model is validated by comparison with experimental data, and can be employed in order to optimize the design of these graded surfaces.

2004 - Computational simulations for the optimization of the mechanical properties of alumina-glass functionally graded materials [Capitolo/Saggio]
Cannillo, Valeria; Manfredini, Tiziano; Montorsi, Monia; Siligardi, Cristina; Sola, Antonella

Computational simulations for the optimization of the mechanical properties of alumina-glass functionally graded materials

2004 - Extruded LZS glass-ceramics [Articolo su rivista]

A sintered glass-ceramic material belonging to Li2O-ZrO2-SiO2 system with optimized properties was successfully obtained using an extrusion process

2004 - Li2O-ZrO2-SiO2 sintered glass-ceramics for ceramic tile applications [Articolo su rivista]

Sintering and crystallization behavior as well as properties of a glass-ceramic belonging to the Li2O-ZrO2-SiO2 system were investigated and compared with commercial ceramic materials

2004 - Microwave assisted burn-out of organic compounds in ceramic systems [Relazione in Atti di Convegno]
C. Leonelli; G.C. Pellacani; C. Siligardi; P. Veronesi

Ceramic materials containing organic compounds, as a result of a manufacturing process or coming from an unwanted pollution, can be efficiently beat-treated using microwaves rapid, volumetric and selective heating. Electromagnetic field modelling of microwave-matter interactions inside the microwave applicator helped choosing the best experimental conditions, leading to fast cycles and to the maximisation of energy transfer from the microwave source to the load. The debinding process of Al2O3, ZrO2 and TiO2 components and the complete recovery of Al2O3 millimetric spheres has been performed by microwave heating, allowing a drastic manufacturing time reduction. Microwaves, proved to be a powerful tool to speed up the hear treatment of the aforementioned ceramic systems containing significant percentages of organic compounds, which present a strong and preferential coupling to microwaves at low temperature.

2004 - Microwave processing of glass [Relazione in Atti di Convegno]
Leonelli, Cristina; Siligardi, Cristina; Veronesi, Paolo;

Microwaves at the ISM frequency of 2.45 GHz have been applied to heat the molten salt bath used for ion exchange. A commercial soda-lime silicate has been used in order to investigate the processing time and the exchange depth resulting from the microwave assisted treatment, compared to the conventional one. Provided the molten salt, having an high electrical conductivity, does not shield the glass sample from microwave exposure, there is evidence of an increased ion mobility under microwave irradiation. In particular, this is confirmed by the higher calculated diffusion coefficient and by the increased potassium concentration in the exchanged layers.

2004 - Reactivity of tosylhydrazones under microwave irradiation in solvent-free environment [Articolo su rivista]

The results of the interaction of microwave irradiation (multimode, 2.45 GHz, 100-600 W power) on tosylhydrazones, T.I., interesting intermediates in many organic reactions, were presented. T.I. were supported on silica, silica gel and alumina powders. Different inorganic salts (K2CO3,Fe(NO3)(3).9H(2)O) were added to the reaction mixture. The results obtained, starting from a range of different T.I., were investigated by means of mass spectrometry and (HNMR)-H-1 in order to understand the role of microwave irradiation and presence of inorganic additives on the reaction pathway and yields.

2004 - Strctural characterization of rare earth containing glasses by molecular dynamic simulation [Relazione in Atti di Convegno]
A.Bonamartini Corradi; V. Cannillo; M. Montorsi; C. Siligardi; A.N. Cormack

rare-earth (RE) containing glasses are largely used in technological applications such as optical fiber amplifiers, upconversion and glass laser. Glasses containing respectively Nd2O3 and Er2O3 are considered and the data obtained by MD simulations are used to analyse the different environment of Nd3+ and Er3+ in the glass matrix.

2004 - The structure of ZrO2 phases and devetrification processes in a Ca-Zr-Si-O-based glass ceramic: a combined a-XRD and XAS study [Articolo su rivista]
C., Meneghini; S., Mobilio; Lusvarghi, Luca; F., Bondioli; Ferrari, Anna Maria; Manfredini, Tiziano; Siligardi, Cristina

The structure of Zr atomic environment in a CaO-ZrO2-SiO2 glass-ceramic has beenstudied combining x-ray absorption spectroscopy (XAS), X-ray diffraction (XRD) andanomalous-XRD (a-XRD) techniques as a function of thermal treatments. The analysisof XRD patterns demonstrates that the devitrification process, as a function ofthermal treatment, proceeds through the partial segregation of Zr-depleted phases(Wollastonite-like) and Zr-rich phases (Zr-oxides). The XAS and a-XRD measurementsat the Zr K edge have been exploited to get a closer insight on the atomicstructure around Zr ions. In the as quenched glass the Zr is 6-fold coordinated to Oxygenatoms in an amorphous environment rich of Ca and Si. Thermal treatment firstly(T=1000 - 1050 oC) determines the partial segregation of Zr in form of oxide whichcrystalline structure is that of tetragonal Zirconia (t-ZrO2). Raising the temperature(T=1100 oC) provokes the formation of ZrO2 crystallites in the monoclinic crystallographicphase (Baddeleyite: m-ZrO2). The analysis of XAS data demonstrates that aconsiderable amount of Zr still remains in an amorphous Calcium-Silicate phase.

2003 - Comparison of various solvent media efficiency in the grinding of a frit containing zirconium oxide [Articolo su rivista]
F. Andreola; MC D'Arrigo; C. Leonelli; C. Siligardi; GC Pellacani

In the present work thermal and chemical properties of a glass-ceramic frit containing zirconium oxide are evaluated after milling in various polar and nonpolar solvents. Particle-size distribution is one of the main variables investigated to evaluate the efficiency of several solvents. Milling in various solvents does not affect the thermal properties of the glass while the presence of polar groups in the solvent molecule increases the cation release from the glass.

2003 - Effect of V2O5 addition on the crystallisation of glasses belonging to the CaO-ZrO2-SiO2 system [Articolo su rivista]
AM Ferrari; C. Leonelli; GC Pellacani; C. Siligardi

The crystallisation of CaO-ZrO2-SiO2 glasses doped with V2O5 (0.1-5 mol%) has been investigated in terms of microstructure and thermal parameters. Results indicate that crystallisation is predominantly controlled by a surface nucleation mechanism, even though a partial bulk nucleation has been encountered in compositions containing more than 2 mol% of doping oxide. As detected from differential thermal analysis curves, glass transition temperature and crystallisation temperature, are strongly dependent upon V2O5 content varying from 0.0 to 2.0 mol%, while the crystallisation activation energy values decrease with a parabolic trend from B-glass (0.0 mol% V2O5 content, 495 +/- 7) to V-0.7 (0.7 mol% V2O5 content, 420 +/- 6) composition, increasing again to 442 +/- 5 kJ/mol K with higher amount of V2O5. The microstructure of the glass-ceramic materials clearly showed a marked dependence upon the amount of V2O5, also due to the presence of phase separation for content higher than 0.7 mol%. Wollastonite, CaO . SiO2 and a calcia-zirconia-silicate, 2CaO . 4SiO(2) . ZrO2, are the main crystalline phases whose ratio slightly varies with vanadium oxide content. The glass ceramics obtained from the studied materials are greenish and bluish coloured, so it is possible to use the studied glasses as coloured frits for tile glazes. (C) 2003 Elsevier Science B.V. All rights reserved.

2003 - Experimental and MD simulations study of CaO-ZrO2-SiO2 glasses [Articolo su rivista]
Barbieri, Luisa; Cannillo, Valeria; Leonelli, Cristina; Montorsi, Monia; P., Mustarelli; Siligardi, Cristina

Glasses belonging to the CaO-ZrO2-SiO2 ternary system were prepared by melting raw materials at 1600°C. Several properties of the glassy materials, such as density and thermal behavior, were experimentallydetermined, and the results were interpreted by comparison with the structural information derived frommolecular dynamics simulations and from 29Si-MAS NMR. A detailed analysis of the short- and intermediaterangestructure was performed to define the role played by the different atoms present in the glass formulationand to correlate the structural modifications to the macroscopic properties of this class of glasses.

2003 - Tecniche di analisi termica applicate ai ceramici [Articolo su rivista]
C. Siligardi; L. Lusvarghi

L'analisi termica può essere definita come la misura delle proprietà fisiche e chimiche di un materiale in funzione della temperatura. Con i moderni strumenti possono essere studiate una grande varietà di sostanze in quanto la maggior parte dei solidi sono attivi termicamente in un modo e nell'altro possono essere analizzati con profitto con l'analisi termica.

2003 - The effect of ZrO2 in 30K2O-70SiO2 glass: a comparison with 30Li2O-70SiO2 [Articolo su rivista]
L. Barbieri; A. Corradi; I. Lancellotti; C. Leonelli; C. Siligardi

The influence of the introduction of ZrO2 in concentrations of up to 5 mol% into a 30K(2)O-70SiO(2) base glass composition has been investigated with the aid of differential thermal analysis (DTA), FT-IR spectroscopy, as well as chemical durability tests (pH, conductivity and AES-Inductively Coupled Plasma measurements) and refraction index determination. Several differences have been found by comparison with similar compositions belonging to the Li2OZrO2SiO2 system. The higher ionic radius and the lower field strength of K+ with respect to Li+ is responsible for higher stability towards crystallisation and lower chemical durability. Moreover, even though Zr4+ increases glass polymerisation (higher glass transition temperature, chemical durability and refraction index), the presence of high water content as highlighted by spectroscopy measurements, seems to weaken the glass structure.


A systematic study of 10 glasses belonging to the system diopside-anorthite has been carried out. An interpretation of the structure of theese glasses has been sought by means of thermal, thermophysical and physical measurements.

Lancellotti, Isabella; Leonelli, Cristina; Montorsi, Monia; Pellacani, Gian Carlo; Siligardi, Cristina; C., Meneghini

In this work several complementary techniques have been employed to carefully characterise the structure of CaO–ZrO2–SiO2 glasses as a function of Zr content. The research started from the basic binary system 40CaO.60SiO2 (wt%) to which 5, 10, 15 and 20 wt% ZrO2 has been added.Chemical and physical characterisation has been performed using classical techniques such as thermal analyses (differential thermal analysis and dilatometery) and water chemical resistance. Deeper insight on the intimate structure of the glasses has been achieved through molecular dynamics simulations and x-ray absorption spectroscopy. All results have been combined in order to accurately describe the role played by the different oxides in determining the properties of the glass. Particular carehas been devoted to the role of zirconia.

2002 - CaO-ZrO2-SiO2 glass-frit addition to porcelainized stoneware: enhancement of tiles colouring capabilities [Articolo su rivista]

Porcelainized stoneware tiles have experienced many aesthetic improvements in the last few years, occasionally accompanied by some depletion of surface properties. The introduction of 5–10 mass-% of an easily devitrifiable glass frit leads to a significant increase in the white index of the ceramic body, simultaneously allowing a better exploitation of pastel hues colouring additives in bulk coloured porcelainized stoneware tiles. Optimum sintering temperature, densification, and water absorption of compositions with glass-frit addition are comparable to large-scale production porcelainized stoneware tiles. Moreover, when ceramic tiles are fired according to the typical industrial fast-firing cycle of 60 min up to 1200 °C, the flexural strength, indicated by the modulus of rupture measured values, benefits from glass-frit addition.

2002 - Effetto di additivi promotori di fluidità su materiali ceramici tradizionali ottenuti per pressatura uniassiale. [Relazione in Atti di Convegno]

Studio di additivi capaci di incrementare la fluidità di polveri ceramiche per pressatura uniassiale.

2002 - Evolution of macropores in a glass-ceramic under microwave and conventional sintering [Articolo su rivista]
MC D'Arrigo; C. Siligardi; C. Leonelli; JY So; HS Kim

Densification and microstructural evolution of a CaO-ZrO2-SiO2 glass powder were studied during heating in order to produce a glass-ceramic material. Microwave (2.45 GHz) and conventional heating were used for different soaking times and temperatures. Macropores, as visible from the last stage of glass sintering, were monitored as a function of temperature by SEM microscopy and image elaboration. The porosity as a results of micropores has proved to be negligible. Other important densification parameters, such as initial powder size distribution and green pellet density, which would have affected macropores evolution were kept constant. Microwave prepared samples have been compared to conventionally treated ones. The effect of microwaves was to speed up the sintering process, but did not affect the crystallization evolution of glass-ceramic materials differently when compared to the conventional sintering.

2002 - Experimental versus computer simulation analysis of zirconia containing glasses [Monografia/Trattato scientifico]
Montorsi, Monia; Menziani, Maria Cristina; Siligardi, Cristina; Manfredini, Tiziano; A. N., Cormack

Zirconia containing glasses: computational and experimental study.


The influence of the introduction of ZrO2 up to 5 mol% into a 30K2O-70SiO2 base glass composition has been investigated with the aid of differential thermal analysis (DTA), FT-IR spectroscopy, as well as chemical durability tests (pH, conductivity and AES-Inductively Coupled Plasma measurements) and refraction index determination. Several differences have been carried out by comparison with similar compositions belonging to the Li2O-ZrO2-SiO2 system. The higher ionic radius and the lower field strength of K+ with respect to Li+ are responsible for higher stability towards crystallisation and lower chemical durability. Moreover, even though Zr4+ increases glass polymerisation (higher glass transition temperature, chemical durability and refraction index), the presence of high water content as highlighted by spectroscopy measurements, seams to weaken glass structure.

2002 - Glass formation and devitrification in the K2O-ZrO2-SiO2 system [Articolo su rivista]


2002 - Importancia do Controle da velocidade de resfriamento na Obtencao de Vidrados Vitro-Cristalinos [Articolo su rivista]
Quinteiro, Eduardo; Boschi, Anselmo Ortega; Sanches Arantes, Flavio Josè ; Leonelli, Cristina; Manfredini, Tiziano; Siligardi, Cristina;

Industrial compositons of glass-ceramics used for tile glazes have been investigated with reference to the cooling rate.

2002 - Microwave and conventional hydrothermal synthesis of zirconia doped powders [Abstract in Atti di Convegno]
F. Bondioli; C. Leonelli; C. Siligardi; G.C. Pellacani; S. Komarneni

Hydrothermal synthesis of powders is a very attractive process to directly prepare submicrometer- and nanometer-sized crystalline powders because of reduced contamination and low synthesis temperature. The application of microwave radiation during the process enhances the reaction kinetics by 1-2 orders of magnitude. Nanosized Pr-doped zirconium oxide powders were prepared by adding NaOH to a zirconyl chloride aqueous solution under microwave-hydrothermal conditions. The properties of the powders produced are compared with those of powders obtained by conventional hydrothermal synthesis

2002 - Microwave technology applications in the synthesis of ceramic pigments [Relazione in Atti di Convegno]

Long before chemists began altering this word, humans were interested in coloring their painting and their bodies as well as any objects they happened to make. Color is an economical way of creating new intereste in an existing product and is also the mosti immediately noticeable and least-expensive element in decoration. Thus, color is a primary tool in product development and marketing, especially in the ceramic tile industry, where product always becomes part of a general color scheme. This word resumes the experimental word done in the last few years by the CerMIC (Ceramic Investigation Center) at the University of Modena (Italy) regarding the application of the microwave technology to the synthesis of inorganic pigments. The choice has been done trying to reproduce in MW some of the most diffused and interesting crystalline structures capable of inducing coloration in ceramic tile body and coating, that is to say capable of thermal and chemical stability in the glazes or in the body at temperatures as high as 1250 degreesC for short period of times, (5-10 min), in order to evaluated the possible benefic effects of microwave heating treatments in this field.

2002 - Porous molybdenum particle reinforced glass matrix composites fabricated by microwave processing [Relazione in Atti di Convegno]
AR Boccaccini; P. Veronesi; C. Siligardi; C. Leonelli

Microwave-assisted densification was used to fabricate porous borosilicate glass matrix composites containing spherical porosity and molybdenum particle inclusions. The inverse thermal gradient typical of microwave heating and the presence of Mo particles led to the development of a layered porous structure of the compacts, consisting of a highly porous core and a relatively dense outer shell. Such a layered porosity was not obtained in glass compacts without Mo particles.

2002 - Vanadium doping in CaO-ZrO2-SiO2 glasses [Articolo su rivista]

Structural and colour changes induced by increasing amounts of vanadium oxide. V2O5, are presented for a near formulation of glass with composition 37CaO, 6ZrO(2), 57SiO(2) (mol%). Property changes were evaluated by measuring density, chemical durability and microhardness of glasses with increasing amount of vanadium oxide. Vanadium oxide imparts to tire glass a light green colour, not dissimilar to that from chromium, at low content, while at higher concentration the colour changes to dark brown. Spectroscopic technique, VIS-NIR and ESR were rued to identify tire chromophore centres in terms of vanadium oxidation state and coordination which there subsequently correlated to property changes. Experimental evidence is reported for an equilibrium between two species. V5+-tetrahedral and V4+ tetragonally distorted octahedral.

2001 - La tecnologia a microonde applicata ai fanghi di levigatura del gres porcellanato [Articolo su rivista]
C. Siligardi; C. Leonelli; P. Veronesi

The possibility of reusing the sludges derived from porcelain stoneware tiles polishing to produce ceramic products microwave thermal treatments is investigated. A 980 W, 2.45 GHz, multimode commercial microwave furnace with SiC susceptor was used in this study. This heating technique lead to develop of ceramic products as belonging to BIII class according to the EN 87.

2001 - Microwave industrial applications in the ceramic field [Articolo su rivista]
P. Veronesi; C. Siligardi; M. Franchini; C. Leonelli

The industrial applications of microwaves in the ceramics field are described. Microwaves greatly contribute to heat transfer in large formed shapes, speed up the entire manufacturing process, and offer the possibility of creating novel microstructures. Uses include the synthesis of ultrafine powders; drying; debinding; slip casting; sol-gel process; joining; sintering; CVD; and coating. It is shown that microwaves offer the possibility of very fast manufacturing cycles, lower production costs, decreased power consumption, obtaining new products or improving the quality of existing ones, and increasing the efficiency and productivity of processes. Most of the benefits of microwaves are derived, however, only after careful experimental laboratory work, and preliminary cost-benefit analysis is always uncertain due to the difficulties inherent in extrapolating to the industrial scale. The use of hybrid systems can help in this respect. The advantages of a well-designed microwave system are noted. 17 refs.

2001 - Microwave-hydrothermal synthesis of nanocrystalline zirconia powders [Articolo su rivista]
F. Bondioli; AM Ferrari; C. Leonelli; C. Siligardi; GC Pellacani

Nanosized zirconium oxide (ZrO2) powders were prepared by adding NaOH to a zirconyl chloride aqueous solution under microwave-hydrothermal conditions. The obtained results showed that the tetragonal polymorph increased with increasing NaOH concentration in the starting solution and reached the maximum value by using 1M ZrOCl2. The microwave-assisted hydrothermal synthesis is expected to be able to process continuously, and may lead to energy savings because of rapid heating to temperature and increased kinetics of crystallization. This method is very simple and can lead to powders with desirable characteristics such as very fine size, narrow size distribution, and good chemical homogeneity.

2001 - New tile glaze families based on glass ceramic systems [Articolo su rivista]
Leonelli, Cristina; Manfredini, Tiziano; Siligardi, Cristina;

The paper reports the study of different glass ceramics system used into ceramic glazes.

2001 - Synthesis of Oxide Pigment Powders by Microwave Treatments [Capitolo/Saggio]
Leonelli, Cristina; Bondioli, F.; Siligardi, Cristina; Veronesi, Paolo; Corradi, A.


2001 - Synthesis of oxide pigments powders by microwave treatments [Relazione in Atti di Convegno]
A. Corradi; C. Leonelli; F. Bondioli; C. Siligardi; P. Veronesi; GC Pellacani

In this paper the authors report the use of microwave technology to synthesize inorganic pigment to color traditional ceramic material

2001 - The application of microwaves in the synthesis of Ce0.9Pr0.1O2 nanostructured powders [Articolo su rivista]
Bondioli, Federica; Ferrari, Anna M. ; Leonelli, Cristina; Siligardi, Cristina; Hart, Neil A.; Evans, Nigel G.;

In this work Ce0.9Pr0.1O2 powders were synthesised by the co-precipitation method starting from the solution of cation nitrates. The possible use of microwave technology in both drying and calcination steps was evaluated. XRD analysis, dielectric properties measurements, and colour characterisation were used in order to determine the microwave benefits.

2001 - “Applicazione di pigmenti fosfatici ottenuti mediante trattamento termico convenzionale e microonde” [Articolo su rivista]
Ferrari A. M.; Bondioli F.; Leonelli C.; Siligardi C.

Alcuni fosfati metallici contenenti nichel, cobalto o rame sono stati sintetizzati calcinando sia per via convenzionale sia mediante trattamento a microonde, i relativi alchilfosfonati. le polveri dei pigmenti ottenuti sono state caratterizzate con diverse tecniche quali XRD, DTA, spettroscopie IR e UV-Vis con misure di colore. Particolare attenzone è stata rivolta all'applicabilità di questi composti nella colorazione di materiali ceramici.

2000 - Bulk crystallization of glasses belonging to the calcia-zirconia-silica system by microwave energy [Articolo su rivista]
C. Siligardi; MC D'Arrigo; C. Leonelli; GC Pellacani; TE Cross

This paper reports results that show the effect of microwave absorption on the bulk crystallization of two glasses in the CaO-ZrO2SiO2 system. The glass samples were de vitrified using either microwave or conventional heating, to compare the results obtained from the two different techniques. Remarkably different crystallization paths were observed, depending mostly on the composition of the glass. This observation was especially true when microwave heating was used, where the dielectric losses observed in silicate glasses are related to the ZrO2 content. X-ray diffraction analysis was performed on the powdered samples, to determine the crystalline phases present. The microstructure and microanalysis results of these glass-ceramic compositions are presented and are related to the different ZrO2 contents.

2000 - Characterization of microwave inertized asbestos containing materials [Capitolo/Saggio]
Marucci, G.; Annibali, M.; Carboni, G.; Gherardi, G.; Ragazzo, G.; Siligardi, Cristina; Veronesi, Paolo; Lusvarghi, Luca; Rivasi, M. R.


2000 - Colour development during devitrification in Li2O-ZnO-Al2O3SiO2 glasses under conventional and microwave heating [Articolo su rivista]
C. Siligardi; L. Barbieri; A.B. Corradi; C. Leonelli; M. De Sanctis; A. Lazzeri

The paper examines the effects of a series of heat treatments on the appearance and microstructure of Li2O-ZnO-Al2O2-SiO2 glasses with varying ZnO/Li2O. The base glasses coloured yellowish, become violet at temperatures between 700-800 degrees C. The glass remains transparent and the obtained colour is stable during cooling. When heated at temperatures >800 degrees C the samples become opaque violet and finally opaque white at 900 degrees C. The effect of the heat treatment on the physical and chemical properties of these materials is explained on the basis of changes in composition and morphology of the residual amorphous and crystalline phases. Electron microscopic observations individuated an initial glass nucleation induced by phase separation, which occurs at lower temperatures, followed at intermediate temperatures by the crystallisation of beta-quartz (ss) which at higher temperatures converts to beta-spodumene as shown by x-ray diffraction and thermal analysis. Mie light scattering as a consequence of phase separation have been proved to be responsible for bulk glass colouring. Besides microwave irradiation effects on the crystalline phases evolution has been explained on the basis of ionic diffusion.

2000 - Densification of glass powders belonging to the CaO-ZrO2-SiO2 system by microwave heating [Articolo su rivista]
Siligardi, Cristina; Leonelli, Cristina; F., Bondioli; Corradi, Anna; Pellacani, Gian Carlo

Densification and microstructural changes of two glassy compositions belonging to the wollastonite and zirconia stability fields in the ternary CaO-ZrO2-SiO2 system were studied in a 2.45 GHz multimode microwave cavity. The effect of microwaves is to lower the sintering and devitrification temperature with stronger influence for high zirconia content composition. Correlation was found between dielectric properties and heating rate, showing lower interaction temperature for high zirconia content composition which starts to absorb microwave energy at about 400 degrees C compared to 800 degrees C for the low-zirconia one. Sintering and crystallization processes evolved in complex ways during heat treatment so that the two final glass-ceramic materials exhibit different microstructures, crystalline phases and mechanical properties. (C) 2000 Elsevier Science Ltd. All rights reserved.

2000 - Effect of silicon carbide whisker reinforcement on the CaO-ZrO2-SiO2 glass-ceramic system [Articolo su rivista]

An industrial frit formulated in the new CaO-ZrO2--SiO2 glass-ceramic system was studied as a matrix for whisker reinforced composites. The frit was ball milled in acetone and wt ultrasonically mixed with 5, 10, 20 and 30 vol.-% SiC whiskers in order to overcome whisker agglomeration and obtain intimate mixing of the two phases. The samples were hot pressed at 14 MPa in graphite dies, using a N-2 atmosphere, for 2 h at 1280 degreesC. In order to investigate the effect of whiskers as a reinforcement, flexural strength as well as crack configuration and propagation were taken into consideration. Whisker orientation perpendicular to the hot pressing direction was found by SEM observation, and no carbon layer at the whisker/matrix interface was detected by EPMA. Further characterisation of the specimens involved physical (density, elastic modulus) and microstructural properties (XRD, SEM, TEM). The result of glass devitrification was inter-locked wollastonite crystals. BCT/436.

2000 - Microwave technology applied to the recycling of fine stoneware tiles polishing sludge compared to conventional firing [Articolo su rivista]

Microwave technology was a useful heating process when applied to the recycling of fine stoneware tiles polishing sludge. The manufact processed were characterized by low porosity, much lower than that registered for the same formulation heated with conventional firing.The different microstructure has been explained by considering the selective heating phenomenon generated by microwave irradiation: the SiC particles could heat much faster that the aluminosilicate matrix so that to melt the surroundings with a sort of encapsulation process.Conventional heating lead to SiC reaction with oxygen promoting its conversion in CO2 thus creating large pores.

2000 - Sintering behavior of glass-ceramic frits [Articolo su rivista]
C. Siligardi; C. Leonelli; MC D'Arrigo

Combining DTA and HEMA data may provide a simple and quick method for describing the sintering/crystallization process for different glass compositions

2000 - Transparent glass-ceramics obtained during cooling [Articolo su rivista]
C. Siligardi; C. Leonelli; GC Pellacani; WC LaCourse; P. Mustarelli; C. Tomasi

This paper examines the microstructure of glass-ceramics obtained during cooling melts of different compositions in the ternary Li2O-Al2O3-SiO2 system. The effects of MgO, ZnO, and TiO2 additions revealed necessary to attain the crystallisation during cooling. The microstructure of the transparent glass-ceramics, once obtained with a 15-min soak in the temperature range of 700-800 degreesC, is stable at room temperature. An interesting colour change has been noted during the treatment and TEM investigations confirmed that such coloration is produced by phase separation. The crystalline phase evolved are mixed titanates of Mg and Zn which develop from the phase separated glass, soon after T-g, and grow to form the nucleation centres for other crystalline phases. The evolution from phase separated glass to glass-ceramic has been followed by modulated DSC and NMR spectroscopies.

1999 - Influence of some transition metal cations on the properties of BaO-containing glasses and glass-ceramics [Articolo su rivista]

Copper, iron, and manganese oxides were added separately to melts of BaO-MgO-Al2O3-SiO2 glasses up to a maximum of 5 mol%, than devetrified at 100 degrees C for 1 h. The transition cations acted as fluxes on the glass properties by reducing the temperature of glass transition and the exothermic crystallization peak temperature. The activation energy for crystallization was slightly reduced, remaining in the feldspatic phase range. The effects on other properties, such as hardness and toughness, were evaluated in terms of indentation tests and related toation field strength and heating treatment. The presence of copper and manganese oxides inhibited the formation of hexacelsian crystals in the glass-ceramics, thus avoiding dangerous dimensional stress due to phase transformation. The complex evolution of the remaining crystalline phases is discussed in light of XRD, FT-IR, and SEM observations.

1999 - Studio di sinterizzazione di polveri di fritte vetro-ceramiche [Articolo su rivista]
C. Siligardi; C. Leonelli; G. Baldi; E. Generali

Lo scopo del lavoro è quello di poter prevedere il meccanismo di sinterizzazione di polveri vetrose durante il riscaldamento che porta alla formazione di materiali vetroceramici. Tale studio è stato eseguito sulla base dei dati ottenuti dall'analisi termica differenziale e dal microscopio riscaldante

1998 - Microwave synthesis of Al2O3-Cr2O3(ss) ceramic pigments [Articolo su rivista]

A pink ceramic pigment belonging to the Al2O3/Cr2O3 oxide system was successfully obtained by drying and firing microwave treatments starting from inorganic coprecipitated hydroxide gets. Compared with rite pigments obtained by conventional industrial ceramic methods, the introduction of microwave treatment can lead to a more continuous and efficient process consuming a small fraction of the energy and time of conventional treatment.

1997 - Conventional and Microwave Preparation of the Al2O3/Cr2O3 (ss) pink pigment [Relazione in Atti di Convegno]

In this paper the authors report an unconventional synthesis to obtain the pink pigment Alumina/Chromia.

1997 - Effect of TiO2 addition on the properties of complex aluminosilicate glasses and glass-ceramics [Articolo su rivista]

The nucleating effect of titania during glass crystallization has been studied in a complex glassy system where some particular oxides, such as ZnO and MgO, which present chemical and thermodynamic affinity for titanium have been added. Such additions tend to produce phase separation in the glass and leads to titanate phases formation in the glass-ceramic. Moreover, the presence of lithia has a promoting effect on both mechanisms because the lowered viscosity increases cation diffusion. Various thermal, microscopic, and diffractometric techniques have been used to investigate the amorphous and the crystalline phase.

1997 - Feasibility of using cordierite class-ceramics as tile glazes [Articolo su rivista]
AM Ferrari; L. Barbieri; C. Leonelli; T. Manfredini; C. Siligardi; A. Corradi Bonamartini

Basic principles of fabricating tile glazes based on cordieritic glass-ceramics are explained. Glass compositions from the MgO-Al2O3SiO2 three-component phase diagram have been melted with and without the nucleating agent TiO2. Additionally, a sodium borosilicate glass that is commonly used in the the glaze industry has been wet milled, together with the previous compositions, to produce a coating slip. Studies are focused on the role of the nucleating agent and glassy formulation in the crystallization of the glass-ceramic system using differential thermal analysis, X-ray diffractometry, and scanning electron microscopy. When added to a borosilicate glass, only one composition is capable of crystallizing cordierite under a fast-firing cycle used for ''monoporosa'' production. The porosity of the glaze layer is sufficiently low and the crystal size is small to ensure good mechanical and chemical properties, The presence of cordierite crystals in the glaze should enhance abrasion and acid resistance, in comparison to a traditional matte glaze that contains mostly enstatite or diopside crystals.

1997 - Nucleation and crystallization of a lithium aluminosilicate glass [Articolo su rivista]

An aluminosilicate glass of composition 61SiO(2) . 6Al(2)O(3) . 10MgO . 6ZnO . 12Li(2)O . 5TiO(2) (mol%) has been prepared by a melting process and investigated as far as crystallization is concerned. Glass-ceramic is easily obtained because glass shows a high tendency to crystallize starting from 700 degrees C. The crystalline phases evolve with temperature, showing the aluminosilicates to be the main phase up to 1050 degrees C, followed by metasilicates and silicates, some of which have lower melting points. The titanates of Mg and Zn develop from the phase-separated glass, soon after T-g, and grow to form nucleation centers for the other crystalline phases. The evolution from phase-separated glass to glass-ceramic has been followed by many thermal, diffractometric, spectroscopic, and microscopic techniques.

1997 - Processing of a silicon-carbide-whisker-reinforced glass-ceramic composite by microwave heating [Articolo su rivista]
L. Chen; C. Leonelli; T. Manfredini; C. Siligardi

A calcium magnesium aluminosilicate-based glass that contained 10 wt% of silicon carbide whiskers (SiCw) as reinforcement was prepared by tape casting, followed by sintering either in a conventional furnace or in a microwave oven. The results were consistent with retardation of glass sintering through whisker bridging. The glass, by itself, was sintered to almost-full density at 750 degrees C for 4 h by conventional furnace sintering; the best sintered composite, with an estimated density of similar to 90%, was obtained at 800 degrees C with a dwell time of 4 h. Sintering at a temperature of >800 degrees C did not improve the densification but rather resulted in severe whisker oxidation. A reduced densification rate was observed for the samples that were sintered in nitrogen. By contrast, in the microwave oven, almost-full density for the glass and similar to 95% of the theoretical density for the composite were obtainable at 850 degrees C for 15 min, which represented a reduction of similar to 10 h of the total processing time and a reduced SiCw oxidation.

1996 - Densification and properties of CMAS glass-ceramic prepared from compacts of pressed powders and of tape cast powder multilayers [Articolo su rivista]

Calcia magnesia alumina silica (CMAS) glass ceramics containing anorthite, diopside, and barium feldspars as crystalline phases have been fabricated by uniaxial pressing of tape cast glass powder multilayers. The sinterability of the parent glass was investigated from observations of the densification process and the extent of crystallisation determined by changes in the microstructure and mechanical properties of sintered compacts which were prepared below 1100 degrees C. The results showed that glass ceramics produced by tape casting had a higher density and lower porosity than those obtained by uniaxial pressing of loose powders. The tape cast material also showed superior mechanical properties, characterised by Vickers microhardness and elastic modulus, and achieved a higher degree of crystallinity at a temperature 100 K lower than for the pressed powder samples. The low porosity (0.5-1.0%), Vickers hardness (700 HV (25 g)), and elastic modulus (125 GN m(-2)) indicate that the sintering of multilayer tape cast glass powder is a viable method for producing glass ceramics.

1995 - Effects of nucleating agents on diopside crystallization in new glass-ceramics for tile-glaze application [Articolo su rivista]
G., Baldi; Pellacani, Gian Carlo; Leonelli, Cristina; Manfredini, Tiziano; E., Generali; Siligardi, Cristina

The effect of crystallization produced by addition of TiO2, ZrO2 and P2O5 oxides to glass-ceramic of the system CaO-MgO-SiO2 was studied using structural and thermal techniques. The devitrification process was independent of thermal treatment. X-ray diffraction studies performed on the glass-ceramic system indicated that diopside crystalline phase was more thermodynamically favourable than other phases. The effect of the nucleating agent depends on its nature: TiO2 decreased the activation energy while P2O5 and ZrO2 did not. SEM analysis of the doped glass-ceramics showed randomly distributed crystals with significant dimensional variations from those of the undoped system. All these formulations, showing a high crystallization rate, and a fast heating rate, can be used as tile glazes and/or tile-glaze components.

1995 - Glass ceramics belonging to the CaO-SiO2-ZrO2 system as tile glaze components [Relazione in Atti di Convegno]
G. Baldi; L. Frassinelli; E. Generali; C. Leonelli; T. Manfredini; G.C. Pellacani; C. Siligardi; C. Svicher

In order to verify the possibility of using new glass-ceramic materials as tile glaze coatings, the devitrification process of a formulation belonging to the wollastonite stability field of the CaO-ZrO2-SiO2 system was investigated by DTA, XRD and SEM techniques.

1995 - Microindentation test as parameter for evaluating the sintering and interface properties of SiC-Whiskers reinforced CMAS glass-ceramic composites [Articolo su rivista]



In this paper the capability of surface nucleated barium and strontium feldspars glass-ceramics of being sintered was investigated by means of density and porosity measurements, X-ray diffraction measurements, microscopic observations and indentation testing and the results compared with those recorded on the corresponding bulk crystallized samples. The densification degree, higher than 95% of the theoretical density, and the favoured formation of thermally stable crystalline phases, such as celsian and Sr-celsian, with respect to those which present non-linear thermal expansion, hexacelsian, make sintering very useful for the production of low porosity, less than 3 vol%, materials. The microhardness values (470-780 Kg/mm2) and elastic modulus (57-115 GPa) of the sintered glass-ceramics, together with the refractoriness of the developed phases make these systems particularly suitable for structural applications.

1994 - Preparazione di un pigmento ceramico nero per calcinazione di miscele di ossidi o di polveri ottenute per co-precipitazione [Articolo su rivista]
Ferrari A.M.; Manfredini T.; Monari G.; Pellacani G.C.; Siligardi C.

Scopo del lavoro è la messa a punto di una metodologia di riferimento per la sintesi di pigmenti ceramici. Sono state valutate le variabili di processonella preparazione di un pigmento ceramico e le tecniche più opportune per la caratterizzazione chimico-fisica. Allo scopo è stato scelto un pigmento nero ferro-cromo di notevole interesse industriale.

1994 - Solubility, reactivity and nucleation effect of Cr2O3 in the CaO-MgO-Al2O3-SiO2 glassy system [Articolo su rivista]
L. Barbieri; C. Leonelli; T. Manfredini; G.C. Pellacani; C. Siligardi; E. Tondello; R. Bertoncello

The effect of Cr2O3 on some anorthite-diopside glass-ceramics has been investigated up to amounts of 5 mol%. The solubility in the glassy compositions analysed is total for the oxide, but for amounts higher than 0.5 mol%, an insoluble spinel form, MgCr2O4, precipitates. Ultraviolet-visible spectroscopy has proved to be the most sensitive technique to the presence of Cr(III) in a crystalline spinel site, followed by X-ray diffraction and scanning electron microscopy observations. Electron spin resonance and X-ray photoelectron spectroscopy techniques excluded any oxidation state, other than Cr3+. The influence:of the transition cation on glass nucleation is that of an increasing bulk effect with chromium, and thus chromium-spinel, content. The magnesium content affects spinel formation, while heat treatments up to 1100 degrees C do not. The spinel formation influences the anorthite-diopside ratio in the glass-ceramic, with a large favour towards the pyroxene.

1994 - Structural studies on RO-MgO-Al2O3-SiO2 (R=Ca, Sr or Ba) glassy systems by density measurements [Articolo su rivista]


1994 - Vetroceramici appartenenti al sistema CaO-SiO2-ZrO2 come componenti di smalti per piastrelle [Articolo su rivista]


Corradi, Anna; Leonelli, Cristina; Manfredini, Tiziano; Siligardi, Cristina

Preliminary results of a study on the effects of the forming pressure on the reactivity, sintering and microstructure of very fine natural zircon powder compacts. The effects of compaction pressure on the green densities and sintered densities are also discussed. The relationship between the density and the compaction pressure governs the mechanism that occurs in the consolidation process. The investigation has demonstrated changing the compaction pressure in the range 45-180MPa does not influence the onset temperature of sintering of powdered zircon (1150-1170 °C) but does influence the apparent density of the green compacts and consequently the porosity of the sintered specimens. Low relative density values were obtained in these sintering conditions.



1993 - Non-isothermal kinetic equations applied to crystallization of glasses [Articolo su rivista]