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Tiziano MANFREDINI

Professore Ordinario
Dipartimento di Ingegneria "Enzo Ferrari"

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Pubblicazioni

2022 - Corrosion and wear performances of alternative TiC-based thermal spray coatings [Articolo su rivista]
Testa, V.; Morelli, S.; Bolelli, G.; Bosi, F.; Puddu, P.; Colella, A.; Manfredini, T.; Lusvarghi, L.
abstract

Thermal spray WC-Co based coatings are considered among the best solutions against wear and corrosion of industrial components, but it is necessary to reduce their usage due to sustainability and safety issues. In this respect, the paper is focused on the deposition and characterization of TiC-bases coating systems with cobalt-free matrices. Three alternative formulations, TiC-33 vol%NiCr, TiC-40 volþNiCr, TiC-18 vol%WC-33 vol%NiCr, manufactured by high-energy ball milling (HEBM) and deposited by HVOF, are employed in order to assess the effects of binder concentration, composition, and addition of some WC as second hard phase on their wear and corrosion resistance in comparison with WC-CoCr and Cr3C2-NiCr references. It was found that all coatings exhibit a combination of shallow abrasive grooving, surface fatigue (lamellar delamination) and tribo-oxidation under sliding conditions at room temperature. At 400 °C, surface fatigue is less relevant but abrasive grooving becomes more prevent and some adhesive wear also occurs. The performance of all coatings is intermediate between those of the WC-CoCr and Cr3C2-NiCr references. More specifically, the TiC-33 vol%NiCr composition exhibits similar performance as a TiC-25 vol% composition previously studied by the authors. The addition of WC led to the formation of a W-rich shell around the TiC particles through in-flight reactions during spraying. This limited in-flight oxidation of TiC but it could not prevent post-deposition oxidation of hot lamellae. Because interlamellar oxides formed at this stage have the most significant negative effect on wear resistance, overall the TiC-WC-NiCr composition did not exhibit any tribological advantage over pure TiC-NiCr. The Ti-FeNiCr composition is especially sensitive to surface fatigue but, to the contrary, provides good corrosion protection with no performance deficit compared to the same volume fraction of a NiCr matrix. All the TiC-based coatings are not suitable to protect against high-stress abrasion due to the overly negative influence of their interlamellar brittleness under these conditions.

2022 - Solar reflective properties of porcelain tiles for UHI mitigation: effect of highly reflective frits in the engobe's formulation [Articolo su rivista]
Governatori, M.; Cedillo Gonzalez, E. I.; Manfredini, T.; Siligardi, Cristina
abstract

The 2030 Agenda for Sustainable Development charts the course for transforming the world socially, economically, and environmentally by 2030. Cities represent a critical issue in this transformation: the population growth and the intense anthropogenic activity make them centers of strong environmental impact. For instance, cities have become Urban Heat Islands (UHIs) due to the significant increase in temperatures caused by pollution and heat produced by human activities. The urgency to make cities sustainable from an environmental point of view urges the search for innovative solutions to counter this phenomenon. One of those solutions is reflective tiles, as they absorb less heat and stay cooler than traditional materials and are considered an effective mitigation technique against the UHI phenomenon. This study investigated the obtaining of solar reflective ceramic tiles through the modification of the engobe's formulation. To achieve this goal, a glass-ceramic frit with high solar reflectance (SR) property (0.95) was incorporated into the formulation of a commercially available ceramic engobe. To verify whether the modified engobe can be used to prepare solar reflective cool color ceramic tiles, the tiles were decorated in quadrichromy by ink-jet printing according to the four-color CMYK color model. The Gray Scale (GS) printing system was used to investigate five different printing intensities. The results suggest that when a glass-ceramic frit with a high intrinsic SR value is incorporated into the formulation of an industrial engobe, it can raise its SR value, passing from 0.69 to 0.75. However, the productive process used to obtain ceramic tiles limits the SR values due to crystallization. It was also found that ink-jet decoration negatively affects the solar reflective property of the tiles prepared with the new engobe due to its coverage by the inks and their mineralogical composition. Thus, the results presented in this work evidence that changing the engobe's formulation is not enough to obtain ceramic tiles with high solar reflective properties.

2021 - Lightweight concretes based on wheat husk and hemp hurd as bio-aggregates and modified magnesium oxysulfate binder: Microstructure and technological performances [Articolo su rivista]
Barbieri, V.; Lassinantti Gualtieri, M.; Manfredini, T.; Siligardi, C.
abstract

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

2021 - Preparation and characterization of glass ceramic frits with high solar reflectance [Articolo su rivista]
Governatori, M.; Ferrari, C.; Manfredini, T.; Siligardi, C.
abstract

The temperature of cities increases due to the UHI phenomenon and climate change. Among the mitigation strategies, high solar reflectance materials make an important contribution, in particular ceramic materials on which studies have shown that the functionalization of the ceramic engobe allows to increase solar reflectance (SR). This study attempted to improve the SR of ceramic tiles, starting from studies correlating the heat treatment temperatures of glass-ceramic frits with SR, because frit is fundamental for the preparation of an engobe, which plays, as some studies have shown, an increasingly important role in solar reflectance. Five glass-ceramic frits have been analysed: four of these are commercial frits, while one has been obtained and optimized experimentally.

2020 - Design and Optimization of the Thermo-Mechanical Behavior in Glass Reinforced Polyamide 6 For Automotive Application [Capitolo/Saggio]
Barbi, Silvia; Cattani, Luca; Manfredini, Tiziano; Montorsi, Monia
abstract

In this work a rational approach, such as Design of Experiments, has been used to design E-glass and S2-glass reinforced polyamide 6 composites. The models, derived by the multivariate analysis of the experimental tests, allowed deriving response surfaces in which the effect of reinforce’s composi- tion, content and shape on the thermo-mechanical have been related to com- posite’s behavior during cycling loads and high temperatures. These composites find application in the developing of a sensor used in the automotive engine compartment where thermal and vibration effects must be taken in account to avoid premature failure. Thirty experiments were planned by Design of Exper- iments and analyzed through Analysis Of Variance to correlate reinforce’s properties to coefficient of thermal expansion, Young Modulus and damping over temperature/frequency variation. Statically reliable models were calculated to obtain a numerical estimation of the overall quadratic and cubic interactions among reinforce’s properties, explaining how matrix/reinforce interaction affects composite’s properties. Nevertheless, the employment of S2-glass led to restrained coefficient of thermal expansion of the composites, reinforce’s content of E-glass fibers over 30wt% is in a better agreement with the composite’s overall requirements for this tailored application, due to restrained mechanical damping.

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

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

2020 - The circular economy of agro and post‐consumer residues as raw materials for sustainable ceramics [Articolo su rivista]
Andreola, Nora Maria; Lancellotti, Isabella; Manfredini, Tiziano; Barbieri, Luisa
abstract

The circular economy in the area of waste management implies their re‐use as a raw material in different production cycles. Both the qualitative and quantitative characteristics of the residues from the agro sector and those of the products of the ceramics sector make possible to think of a feasible application. This review will illustrate some examples of recycling of residues deriving from animal and vegetable sectors (and two post consume products, spent coffee grounds, and packaging glass cullet), studied by the authors, falling within the concept of urban and agricultural sustainable development. Not only the most traditional products such as glass‐ceramics, glazes, bricks, but also the most innovative lightweight aggregates for plant structures or in and out soil cultivation, as well as additives such as deflocculants for ceramic suspensions, which will be illustrated from the design/production, characterization, and comparison with commercial products.

2019 - Building up WC-Co coatings by cold spray: A finite element simulation [Articolo su rivista]
Bolelli, G.; Dosta, S.; Lusvarghi, L.; Manfredini, T.; Guilemany, J. M.; Cano, I. G.
abstract

The impact of porous WC-12wt%Co and WC-17wt%Co particles onto homologous, smooth surfaces is simulated through a coupled Eulerian-Lagrangian, three-dimensional finite element model, in order to study the build-up mechanisms of cold sprayed WC-Co coatings. Deformation of hardmetal particles upon impact involves compaction and spreading of a rim, whose bottom face experiences heating, close to or even above the melting point of the matrix, and develops large equivalent plastic strain. The rim therefore adheres strongly to the underlying hardmetal. SEM observations of cold sprayed WC-Co particles deposited onto a smooth hardmetal surface show metallurgic bonding of the heated matrix and mechanical fixation as WC grains from the particle indent and penetrate into the underlying material. Little deformation and heating are instead seen in the middle of the contact surface, where adhesion is limited. Deformation of the particle requires the criterion for ductile failure of the hardmetal to be exceeded. This means the deformed rim is also extensively failed and ejects fragments as it spreads. Increasing the momentum of the particle enhances the spreading of the rim and promotes its bonding to the underlying surface, but also causes ejection of larger fragments, as well as the elastic storage of a greater amount of rebound energy, which can result in eventual rebounding of the entire particle or its poorly bonded central portion. It is therefore inferred that the deposition efficiency of cold sprayed hardmetals cannot increase linearly with impact velocity, and it is further impaired with stiff, dense particles and/or with very hard materials (e.g. WC-12Co as compared to WC-17Co).

2019 - Influence of hardmetal feedstock powder on the sliding wear and impact resistance of High Velocity Air-Fuel (HVAF)sprayed coatings [Articolo su rivista]
Lyphout, C.; Bolelli, G.; Smazalova, E.; Sato, K.; Yamada, J.; Houdkova, ; Lusvarghi, L.; Manfredini, T.
abstract

The present work aimed to clarify how the characteristics of WC-CoCr hardmetal feedstock powders, namely the grain size of the WC carbides and of the binder and the compressive strength of the sintered aggregates, affect the dry sliding wear and impact resistance of coatings deposited by High Velocity Air-Fuel (HVAF)spraying. Ball-on-Disc tests, which mimic a sliding wear process in the presence of hard asperities as it may occur e.g. in hydraulic seal joints or papermaking components, resulted in mild wear through near-surface microscale plastic flow, the exact nature of which was significantly affected by WC size. Finite element simulations of a single-asperity sliding process indeed showed that large WC grains concentrate contact stresses, thus undergoing very localised deformation. It is experimentally seen that repeated deformation of the carbide grains resulted in their cracking and pull-out. Uniformly distributed, fine carbides allowed the matrix to take on some stress, thus undergoing more homogeneous plastic flow. Block-on-Ring tests elicited adhesive wear as it may happen e.g. in metal-to-metal contacts (e.g. petrochemical valves). This could be effectively restrained by low matrix mean free path. Cyclic impact resistance of coarse-grained coatings was better than that of fine-grained ones, because of better large-scale cohesive strength.

2019 - Rational design and characterization of bioplastics from Hermetia illucens prepupae proteins [Articolo su rivista]
Barbi, Silvia; Messori, Massimo; Manfredini, Tiziano; Pini, Martina; Montorsi, Monia
abstract

In this study proteins extracted from prepupae of Hermetia illucens, also known as black soldier fly,are investigated as promising base for a new type of bioplastics for agricultural purposes. Designof experiments techniques are employed to perform a rational study on the effects of differentcombination of glycerol as plasticizer, citric acid as cross-linking agent and distilled water as solventon the capability of proteins to form a free-standing film through casting technique, keeping asfixed the quantity of proteins. Glycerol shows interesting properties as plasticizer contributing tothe formation of homogenous and free-standing film. Moreover, mechanical and thermalcharacterizations are performed to estimate the effect of increasing amounts of proteins on thefinal properties and thickness of the specimens. Proteins derived from H. illucens can be success-fully employed as base for bioplastics to be employed for agricultural purposes.

2019 - Study of a porous magnesia-based cement [Poster]
Malchiodi, Beatrice; Barbieri, Virginia; Eva Madgalena Lassinantti Gualtieri, ; Siligardi, Cristina; Manfredini, Tiziano
abstract

2018 - Bone regeneration by novel bioactive glasses containing strontium and/or magnesium: A preliminary in-vivo study [Articolo su rivista]
Bellucci, Devis; Cannillo, Valeria; Anesi, Alexandre; Salvatori, Roberta; Chiarini, Luigi; Manfredini, Tiziano; Zaffe, Davide
abstract

In this work, a set of novel bioactive glasses have been tested in vivo in an animal model. The new compositions, characterized by an exceptional thermal stability and high in vitro bioactivity, contain strontium and/or magnesium, whose biological benefits are well documented in the literature. To simulate a long-term implant and to study the effect of the complete dissolution of glasses, samples were implanted in the mid-shaft of rabbits' femur and analyzed 60 days after the surgery; such samples were in undersized powder form. The statistical significance with respect to the type of bioactive glass was analyzed by Kruskal-Wallis test. The results show high levels of bone remodeling, several new bone formations containing granules of calcium phosphate (sometimes with amounts of strontium and/or magnesium), and the absence of adverse effects on bone processes due to the almost complete glass dissolution. In vivo results confirming the cell culture outcomes of a previous study highlighted that these novel bioglasses had osteostimulative effect without adverse skeletal reaction, thus indicating possible beneficial effects on bone formation processes. The presence of strontium in the glasses seems to be particularly interesting.

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

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

2018 - Rice Husk Ash (RHA) Recycling in Brick Manufacture: Effects on Physical and Microstructural Properties [Articolo su rivista]
Andreola, F.; Lancellotti, I.; Manfredini, T.; Bondioli, F.; Barbieri, L.
abstract

In this study RHA was used as silica source in the obtainment of clay bricks. Different compositions were prepared, substituting the clays with diverse percentages of RHA (0–20 wt%) and requested water contents. The pastes obtained were extruded in laboratory, dried and then fired in an industrial camera kiln. Technological tests were performed after drying (linear shrinkage and naphtha absorption) and firing [(24-h immersion) water absorption, linear shrinkage, weight loss, average flexural strength] steps. Besides, to analyze the effect on the microstructure and mineralogy, SEM/EDS and XRD analysis of the fired bricks were performed. From the tests conducted it is possible to note that RHA content contributes to reduce the linear shrinkage during drying while an opposite effect is observed for the water absorption. Regarding mechanical test, the products containing up to 5 wt% of RHA are in according to the recommended values for roof. Bricks containing higher amounts of RHA could be used in building manufacturing (light weighted faced load bearing walls) where moderate strengths and penetration protection (porosity/permeability) are required. The carbon unburned present in the RHA contributes to increase the final porosity and the weight loss of the bricks.

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

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

2018 - Tribology of FeVCrC coatings deposited by HVOF and HVAF thermal spray processes [Articolo su rivista]
Bolelli, Giovanni; Bursi, Marcello; Lusvarghi, Luca; Manfredini, Tiziano; Matikainen, Ville; Rigon, Rinaldo; Sassatelli, Paolo; Vuoristo, Petri
abstract

This work studies FeVCrC-based coatings as potential alternatives to conventional Ni- and Co-based alloys for wear protection. Specifically, the microstructure and tribological properties of the coatings are characterized as a function of the particle size distribution of the feedstock powder, of the deposition technique – High Velocity Oxygen-Fuel (HVOF) or High Velocity Air-Fuel (HVAF) spraying – and of specific processing parameters. HVOF-sprayed coatings obtained from fine feedstock powder exhibit numerous oxide inclusions, which provide high hardness (≈ 900 HV0.3) but do not excessively impair fracture toughness, as determined through scratch testing techniques. HVAF-sprayed coatings obtained from the same feedstock powder contain much fewer oxide inclusions, and some of them possess simultaneously high hardness and high toughness. Defects (e.g. speckles) are instead formed in case unsuitable HVAF torch hardware is employed. A coarse feedstock powder always results in unmelted inclusions, which impair the cohesion of the coatings, particularly of the HVAF-sprayed ones. Most coatings anyway exhibit very low sliding wear rates &lt; 3 × 10−6mm3/(N m); abrasive grooving and surface fatigue-induced pitting are the main wear mechanisms. Oxide inclusions do not affect negatively the response of HVOF coatings, whereas too many unmolten particles increase pitting under severe test conditions. Rubber-wheel abrasion testing produces comparatively more severe grooving.

2017 - “Hybrid” plasma spraying of NiCrAlY+Al2O3+h-BN composite coatings for sliding wear applications [Articolo su rivista]
Bolelli, Giovanni; Candeli, Alessia; Lusvarghi, Luca; Manfredini, Tiziano; Denoirjean, Alain; Valette, Stéphane; Ravaux, Alice; Meillot, Erick
abstract

A novel plasma-spray process, featuring simultaneous injections of dry powders and multiple liquid streams, was employed to produce composite coatings where sub-micrometric particles of Al2O3 and hexagonal BN (h-BN) are dispersed within a NiCrAlY metal matrix. Various coatings, containing up to ≈10 wt% Al2O3 and ≈9 wt% h-BN, were obtained. A co-deposition effect was noted whereby a higher h-BN feed also increases Al2O3 incorporation in the coating, even under a constant flow rate of Al2O3 suspension. Although the microhardness (≈600 HV0.3) seemed rather insensitive to the composition of the coatings, their sliding wear resistance (tested under ball-on-disk configuration against corundum spheres at various temperatures) improved with increasing contents of Al2O3 and h-BN. The improvement was more significant at room temperature, but some beneficial effect also emerged when testing at 400 °C and 700 °C. Al2O3 and h-BN indeed promote the formation and enhance the mechanical stability of an oxide-based tribofilm, protecting the coating surface from direct contact with the counterbody. Specific tribofilm formation mechanisms however vary with temperature. Overall, coatings containing ≥5 wt% of Al2O3 and h-BN keep a reasonably stable wear rate (&lt;5*10−4 mm3/(Nm)) over a wide temperature range.

2016 - Improvement of color quality and reduction of defects in the ink jet-printing technology for ceramic tiles production: A Design of Experiments study [Articolo su rivista]
Montorsi, Monia; Mugoni, Consuelo; Passalacqua, Alessio; Annovi, A. .; Marani, F.; Fossa, L; Capitani, R; Manfredini, Tiziano
abstract

The aim of the present work was to study the effect of different process parameters on the color and defects of tiles produced by ink-jet printing technology. The Design of Experiment approach was used to guarantee a rational planning of the experiments and to ensure objective conclusions through the statistical analysis of the data. Particularly, correlations between the process parameters and the quality of decorated tiles in terms of color and presence of surface defects were extensively investigated. Microstructural analysis was used to explain the results derived by the statistical analysis of the data obtained by the rational plan of the experiments allowing further insight in the structural features and mechanisms correlated to the macroscopic properties of the tiles. The study supplied an efficient way to control the final quality of the decorated tiles satisfying the quality standards required by the market demand. © 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

2016 - Manufacturing and Properties of High-Velocity Oxygen Fuel (HVOF)-Sprayed FeVCrC Coatings [Articolo su rivista]
Sassatelli, Paolo; Bolelli, Giovanni; Lusvarghi, Luca; Manfredini, Tiziano; Rigon, Rinaldo
abstract

This paper studies the microstructure, sliding wear behavior and corrosion resistance of high-velocity oxygen fuel (HVOF)-sprayed FeVCrC-based coatings. Various process parameters were tested to evaluate their effects on the coating properties, which were also compared to those of HVOF-sprayed NiCrBSi and Stellite-6 coatings. The Fe alloy coatings are composed of flattened splats, originating from molten droplets and consisting of a super-saturated solid solution, together with rounded particles, coming from partially unmolten material and containing V- and Fe-based carbide precipitates. All process parameters, apart from “extreme” settings with excess comburent in the flame, produce dense coatings, indicating that the feedstock powder is quite easily processable by HVOF. These coatings, with a microhardness of 650-750 HV0.3, exhibit wear rates of ≈2 × 10−6 mm3/(Nm) in ball-on-disk tests against sintered Al2O3 spheres. They perform far better than the reference coatings, and better than other Fe- and Ni-based alloy coatings tested in previous research. On the other hand, the corrosion resistance of the coating material (tested by electrochemical polarization in 0.1 M HCl solution) is quite low. Even in the absence of interconnected porosity, this results in extensive, selective damage to the Fe-based matrix. This coating material is therefore unadvisable for severely corrosive environments.

2016 - Recycling of industrial wastes in ceramic manufacturing: State of art and glass case studies [Articolo su rivista]
Andreola, Nora Maria; Barbieri, Luisa; Lancellotti, Isabella; Leonelli, Cristina; Manfredini, Tiziano
abstract

Nowadays, ceramic tile are manufactured at zero emissions permitting to recycle all by-products and part of residues derived from depuration treatments (exhausted lime, glazing sludge and polishing sludge). In addition to this environmentally friendly tendency, in the last years an increasing number of scientific studies demonstrated the feasibility to use alternative raw materials in substitution of different component of the ternary clay-feldspar-quartz system. In the first part of the paper is reported the state of the art of industrial waste recycling in the ceramic sector, with the focus on review studies related to both ceramic tiles and bricks..In the second part of the work are reported two case studies conducted by the authors with the aim to formulate ceramic bodies using alternative raw materials. New tailored compositions were obtained replacing clays, flux and/or inert compounds (higher than 60. wt%) by scraps from packaging waste glass in tiles, and cathode ray tube glasses and packaging waste glass up to 20. wt% in the brick compositions.

2016 - Valorization of wastes, "end of waste" and by-products using hot and cold techniques [Capitolo/Saggio]
Barbieri, L.; Andreola, F.; Taurino, R.; Ponzoni, C.; Manfredini, T.; Leonelli, C.; Lancellotti, I.
abstract

2016 - Valorization of wastes, “end of waste” and by-products using hot and cold techniques [Capitolo/Saggio]
Barbieri, L.; Andreola, F.; Taurino, R.; Ponzoni, C.; Manfredini, T.; Leonelli, C.; Lancellotti, I.
abstract

The Framework Directive 2008/98/EC, implemented in Italy by Legislative Decree no. 205/2010, in addition to reporting specific criteria and targets, gave the impression of a new cultural attitude that offers the combination of sustainable use of resources coupled with sustainable management of waste. The adoption of the best available technologies for processing and valorization respects first of all the proximity of the production of the waste. The final aim is the increase of recycling practice to reduce the pressure on the demand for raw materials with a double effect: reuse valuable materials, that would otherwise end up as waste, and reduce energy consumption and emissions of greenhouse gases in the process of extraction and machining. By 2020, we must manage waste as a resource through those instruments and actions that will affect the diffusion of wastes separated collection, promotion of efficient and of high-quality recycling. Contemporary we will assist to the development of markets for the new raw materials obtained by waste recovery and energy recovery limited to the non-recyclable materials regardless of the decrease in per capita and the removal of illegal shipments as well as the landfill.

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

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 - Microstructure-based thermo-mechanical modelling of thermal spray coatings [Articolo su rivista]
Bolelli, Giovanni; Candeli, Alessia; Koivuluoto, Heli; Lusvarghi, Luca; Manfredini, Tiziano; Vuoristo, Petri
abstract

This paper demonstrates how microstructure-based finite element (FE) modelling can be used to interpret and predict the thermo-mechanical behaviour of thermal spray coatings. Validation is obtained by comparison to experimental and/or literature data.Finite element meshes are therefore constructed on SEM micrographs of high velocity oxygen-fuel (HVOF)-sprayed hardmetals (WC-CoCr, WC-FeCrAl) and plasma-sprayed Cr2O3, employed as case studies. Uniaxial tensile tests simulated on high-magnification micrographs return micro-scale elastic modulus values in good agreement with depth-sensing Berkovich micro-indentation measurements. At the macro-scale, simulated and experimental three-point bending tests are also in good agreement, capturing the typical size-dependency of the mechanical properties of these materials. The models also predict the progressive stiffening of porous plasma-sprayed Cr2O3 due to crack closure under compressive loading, in agreement with literature reports.Refined models of hardmetal coatings, accounting for plastic behaviours and failure stresses, predict crack initiation locations as observed by indentation tests, highlighting the relevance of stress concentrations around microstructural defects (e.g. oxide inclusions).Sliding contact simulations between a hardmetal surface and a small spherical asperity reproduce the fundamental processes in tribological pairings. The experimentally observed "wavy" morphologies of actual wear surfaces are therefore explained by a mechanism of micro-scale plastic flow and matrix extrusion.

2015 - Physical-mechanical properties of new green building materials based on glass waste [Articolo su rivista]
Taurino, Rosa; Andreola, Nora Maria; Leonelli, Cristina; Manfredini, Tiziano; Gastaldi, Paolo; Barbieri, Luisa
abstract

Recently several innovative suggestions on how industrial wastes can be utilised in new products have been presented in literature, e.g. as filler or additives in concrete, incorporated in ceramic materials to produce glass-ceramics and pavement construction. In this work, metallurgical materials from secondary aluminium scrap processing and glass waste derived from treatments of packaging and fluorescent lamps were considered for fabrication of new ceramic materials using powder technology and sintering process. The effect of composition and heat treatment temperature, on the sintering process and then final properties, were evaluated. The results showed that, with the proper firing temperature, lightweight ceramic materials containing high amount of glass waste and an innovative product resulting from the processing of secondary aluminum (ArgAlum) can be produced. The low water absorption (< 1%), low density (< 2 g/cm3) and the good flexural strength (16-20 MPa) associated to relatively low sintering temperatures obtained with the addition of ArgAlum can be considered as promising initial results to obtain new green building materials.

2015 - Properties of Al2O3 coatings by High Velocity Suspension Flame Spraying (HVSFS): Effects of injection systems and torch design [Articolo su rivista]
Bolelli, Giovanni; Cannillo, Valeria; Gadow, R.; Killinger, A.; Lusvarghi, Luca; Manfredini, Tiziano; Müller, P.
abstract

Through the High Velocity Suspension Flame Spraying (HVSFS) process, fine (sub-micrometric) oxide ceramic particles can be sprayed at high velocity to achieve denser and more finely structured layers, compared to those obtained by conventional thermal spraying. This paper explores the effect of some key HVSFS hardware components on the properties of Al2O3 coatings. Two feedstock powders with different particle size distributions, dispersed in isopropanol medium, were processed by setting up the HVSFS torch with combustion chambers of different lengths and with two distinct injection systems: a water-cooled mechanical injector, delivering a con- tinuous stream of suspension, or a gas-atomiser injector. The use of the atomising injection system and of longer combustion chambers, promoting better fragmentation of the liquid stream and better homogenisation with the gas flow, can suppress the formation of defects between coating layers, resulting in remarkably high tensile adhesive/cohesive strength values, up to ≈70 MPa. All coat- ings are under compressive residual stress, the magnitude of which varies between −150 MPa and −300 MPa depending on the maximum surface temperature attained during spraying, and have a microhardness of 1000–1200 HV0.1. Quite mild wear rates of ≈1 ∗ 10−6 mm3/(Nm) are obtained by ball-on-disk tests performed under sliding conditions severe enough to cause complete failure of reference HVOF-sprayed Al2O3. Wear mech- anisms involve the formation and fatigue delamination of a smooth surface tribofilm. Detailed analyses of both coatings and single splats also reveal that extremely fast quenching of very small mol- ten droplets caused the formation of ≈20 wt.% glassy Al2O3. Glass transition at 527 °C and three crystallisation reactions at about 800, 1000 and 1180 °C were revealed by differential thermal analysis (DTA).

2015 - Pulsed current effect on hard anodizing process of 7075-T6 aluminium alloy [Articolo su rivista]
Bozza, Andrea; Giovanardi, Roberto; Manfredini, Tiziano; Mattioli, Paolo
abstract

The aim of this work is to study the influence of pulsed current on hard anodizing process (in sulphuric acid bath) of AA 7075-T6, a commercial heat treated aluminium alloy widely used in several innovative and strategic mechanical sectors (military, automotive, aerospace, etc).Exploiting different pulsed current procedures (slow square pulse mode), combining different duty cycles and current levels it was possible to obtain thick and hard anodic oxides with a good interfacial adhesion. The optical microscopy characterization shows that the use of pulsed current minimizes the growth of defects at the oxide/alloy interface caused by the presence of intermetallic precipitates characteristic of AA 7075-T6. Moreover nano-indentation profiles, evaluated along the coatings cross section, highlight the oxide hardness increase of the samples obtained employing pulsed current cycles (PC) compared to those obtained with standard direct current process (DC) or multistep direct current procedures (MSDC).

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

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

2015 - Tribological and mechanical performance evaluation of metal prosthesis components manufactured via metal injection molding [Articolo su rivista]
Melli, Virginia; Juszczyk, Mateusz; Sandrini, Enrico; Bolelli, Giovanni; Bonferroni, Benedetta; Lusvarghi, Luca; Cigada, Alberto; Manfredini, Tiziano; De Nardo, Luigi
abstract

The increasing number of total joint replacements, in particular for the knee joint, has a growing impact on the healthcare system costs. New cost-saving manufacturing technologies are being explored nowadays. Metal injection molding (MIM) has already demonstrated its suitability for the production of CoCrMo alloy tibial trays, with a significant reduction in production costs, by holding both corrosion resistance and biocompatibility. In this work, mechanical and tribological properties were evaluated on tibial trays obtained via MIM and conventional investment casting. Surface hardness and wear properties were evaluated through Vickers hardness, scratch and pin on disk tests. The MIM and cast finished tibial trays were then subjected to a fatigue test campaign in order to obtain their fatigue load limit at 5 millions cycles following ISO 14879-1 directions. CoCrMo cast alloy exhibited 514 HV hardness compared to 335 HV of MIM alloy, furthermore it developed narrower scratches with a higher tendency towards microploughing than microcutting, in comparison to MIM CoCrMo. The observed fatigue limits were (1,766&nbsp;±&nbsp;52) N for cast tibial trays and (1,625&nbsp;±&nbsp;44) N for MIM ones. Fracture morphologies pointed out to a more brittle behavior of MIM microstructure. These aspects were attributed to the absence of a fine toughening and surface hardening carbide dispersion in MIM grains. Nevertheless, MIM tibial trays exhibited a fatigue limit far beyond the 900&nbsp;N of maximum load prescribed by ISO and ASTM standards for the clinical application of these devices.

2014 - An efficent and fast analytical procedure for the bromine determination in waste electrical and electronic equipment plastics [Articolo su rivista]
Taurino, Rosa; Cannio, Maria; Manfredini, Tiziano; Pozzi, Paolo
abstract

n this study, X-ray fluorescence (XRF) spectroscopy was used, in combination with micro-Raman spectroscopy, for a fast determination of bromine concentration and then of brominated flame retardants (BFRs) compounds in waste electrical and electronic equipments. Different samples from different recycling industries were characterized to evaluate the sorting performances of treatment companies. This investigation must be considered of prime research interest since the impact of BFRs on the environment and their potential risk on human health is an actual concern. Indeed, the new European Restriction of Hazardous Substances Directive (RoHS 2011/65/EU) demands that plastics with BFRs concentration above 0.1%, being potential health hazards, are identified and eliminated from the recycling process. Our results show the capability and the potential of Raman spectroscopy, together with XRF analysis, as effective tools for the rapid detection of BFRs in plastic materials. In particular, the use of these two techniques in combination can be considered as a promising method suitable for quality control applications in the recycling industry.

2012 - Natural raw materials in "Traditional" ceramic manufacturing [Articolo su rivista]
Manfredini, Tiziano; Hanuskova, Miriam
abstract

New typologies of ceramic tiles represent well all the innovations in body and glaze compositions, preparation of powders, application of new integrated industrial strategies, and consequently rational utilization of all the necessary raw materials available. Italy is a representative example of growing of the ceramic tile industry, being one of the larger producer of wall and floor tiles in the world. The optimal utilization of minerals and raw materials is directly proportional to the level of knowledge about the ceramic materials and the effects of minerals and their impurities on the process and on the properties of the end-products. The same mineral can be used for simple, bulk products, but after small modification it may well be used for high quality products.

2012 - Superfici smart per i beni culturali: applicazione di film fotocatalitici di TiO2 su travertino [Relazione in Atti di Convegno]
Bondioli, Federica; Manfredini, Tiziano; G. B., Goffredo; E., Quagliarini; A., Licciulli; P., Munafò
abstract

In questo lavoro si riportano i risultati relativi all'utilizzo di un film sottile fotocatalitico al biossido di titanio per il trattamento di beni architettonici in travertino. Lo sviluppo e l’applicazione di un trattamento fotocatalitico ed autopulente per superfici storiche e architettoniche potrebbe portare, ad un significativo miglioramento della conservazione, protezione e manutenzione dei Beni Culturali. La sospensione di titania applicata è stata ottenuta attraverso un processo sol-gel seguito da cristallizzazione idrotermale (134°C) ed applicata mediante spray coating. L’applicazione di film a diverso spessore è stata condotta in modo da studiare l’effetto dello spessore del coating sulle proprietà funzionali. Le superfici sono state attentamente caratterizzate per valutare, in termini di brillantezza e colore, le eventuali variazioni delle caratteristiche visive della pietra trattata. L’attività fotocatalitica è stata valutata seguendo la normativa di riferimento relativa agli inquinanti solidi e gassosi. Gli incoraggianti risultati di laboratorio ottenuti sono stati di supporto per progettare l’applicazione sulla Chiesa di Sant’Andrea Apostolo ad Ascoli Piceno.

2011 - Application of natural raw materials in ceramic manufacturing [Poster]
M., Hanuskova; Manfredini, Tiziano
abstract

During the meeting were discussed the application of natural raw materials in ceramic manufacturing.

2011 - Natural and synthetic raw materials in traditional ceramic manufacturing [Poster]
Bondioli, Federica; M., Hanuskova; Manfredini, Tiziano
abstract

Results on application of natural and synthetic raw materials in traditional ceramic manufacturing, are presented.

2011 - Natural raw materials in “traditional” ceramic manufacturing [Poster]
Manfredini, Tiziano; M., Hanuskova
abstract

The presentation focuses on application of natural raw materials in “traditional” ceramic manufacturing

2011 - Particle size analysis by laser light scattering to control ceramic process [Poster]
Bondioli, Federica; M., Hanuskova; Manfredini, Tiziano
abstract

The main results of a research on application of particle size analysis by laser light scattering to control ceramic process are shown

2011 - Wollastonite as sintering-aid in tiles manufacturing [Poster]
Bondioli, Federica; M., Hanuskova; Manfredini, Tiziano
abstract

The paper focuses on industrial application of wollastonite as sintering-aid in tiles manufacturing

2010 - Application of natural raw materials in ceramic manufacturing. [Poster]
M., Hanuskova; Manfredini, Tiziano
abstract

Natural raw materials, applications, ceramic manufacturing.

2010 - Characterization of Rice Husk Ash and Its Recycling as Quartz Substitute for the Production of Ceramic Glazes [Articolo su rivista]
F., Bondioli; Barbieri, Luisa; Ferrari, Anna Maria; Manfredini, Tiziano
abstract

In this work a complete characterization of rice husk ash (RHA)was conducted in order to evaluate mainly the composition andthe thermal reactivity in terms of crystalline phase evolution.Moreover, the screening results of the research conducted on thepossibility to use RHA as silica precursor in ceramic materials,such as ceramic glazes, were reported. The selected frits wereprepared in a semiindustrial furnace and the obtained glasseswere investigated in comparison with the frits prepared frompure quartz. Besides, laboratory glazes were obtained and characterizedfollowing the technical rules. This work allows to confirmthe possibility to use RHA as silica precursor for thedevelopment of glazes for ceramic tile. The results evidenced,however, that it is not possible for a generalized production substitutionof quartz with RHA.

2010 - Cristallizazione e bioattività: gli effetti del trattamento termico sui vetri bioattivi [Articolo su rivista]
Bellucci, Devis; Cannillo, Valeria; Manfredini, Tiziano; Sola, Antonella
abstract

2010 - Functionalisation of ceramic tile surface by soluble salts addition: part I [Articolo su rivista]
Bondioli, Federica; Manfredini, Tiziano; M., Giorgi; G., Vignali
abstract

The aim of this investigation was the surface functionalization of industrial ceramic tiles by soluble salts addition to improve mechanical properties (resistance to scratch and wear) preserving the aesthetical aspect of the final product. This objective was pursued through the application of different solution of zirconium capable to be transformed in zirconia nanoparticles during the material sintering. The solutions, in different concentrations, were deposited (300 g/m2) on unglazed green tiles by air-brushing. The obtained products were polished and characterized in terms of microstructure, surface micromechanical and technological properties based on the UNI EN ISO reference rules. The final aesthetical aspect of the products and the obtained hue variation were evaluated by means of UV-Visible spectroscopy and colorimetric analysis.

2010 - Functionalisation of ceramic tile surface by soluble salts addition: part II. Titanium and Silver addition [Articolo su rivista]
Bondioli, Federica; Dinelli, Martina; Giovanardi, Roberto; Manfredini, Tiziano
abstract

The aim of this study was to assess surface functionalization of industrial ceramic tiles through the addition of soluble salts to improve mechanicalproperties (scratch and wear resistance) and conductivity, while preserving the aesthetic aspects of the finished product. This objective was pursuedthrough the application of different solutions of titanium and silver with a potential for transformation into titania and silver nanoparticles during thesintering of the material. The solutions, in different concentrations, were applied (300 g/m2) to unglazed green tiles by air brushing. The resultingproducts were polished and characterized in terms of microstructural, surface micromechanical, and technological properties based on the UNIEN ISO reference standards. The electrical conductivity deriving from the presence of titania and silver was also established with specific tests.The results were found to correlate with the results obtained from the addition of zirconium solutions as reported in part I of the paper.

2010 - L’applicazione di materie prime naturali nella produzione ceramica [Articolo su rivista]
M., Hanuskova; Manfredini, Tiziano
abstract

L'articolo presenta una rassegna dello stato dell'arte nazionale ed internazionale relativamente all'impiego di materie prime naturali nella produzione ceramica.

2009 - Alumina-YAG composites: preparation, experimental characterization and numerical modelling [Articolo su rivista]
Cannillo, Valeria; P., Palmero; Manfredini, Tiziano; L., Montanaro
abstract

Al2O3/YAG composite powders have been synthesised by reverse strike precipitation. The powders were characterised by DTA/TG simultaneous analysis, the phase evolution was studied by XRD analysis, while the crystallite formation and growth were followed by TEM observations. A fully dense, homogenous material was obtained by sintering 900°C pre-treated powders at 1600°C for 3 h. For limiting grain growth, both a doping with 500 ppm MgO followed by a free sintering and a fast sintering procedure involving a high heating rate (50°C/min) were performed. The sintered bodies were then characterised by SEM observation and Vickers indentation. Moreover, a numerical model was employed in order to estimate the mechanical properties of the composite materials starting fromthe single constituent phase properties.

2009 - Application of natural raw materials in ceramic manufacturing [Articolo su rivista]
M., Hanuskova; Manfredini, Tiziano
abstract

The paper reports the most important considerations on the application of natural raw materials in ceramic manufacturing

2009 - Corrigendum to "Densification and crystallization of Ba-exchanged zeolite A powders" [Ceram. Int. 34 (2008) 543-549] (DOI:10.1016/j.ceramint.2006.12.010) [Articolo su rivista]
Andreola, F.; Romagnoli, M.; Siligardi, C.; Manfredini, T.; Ferone, C.; Pansini, M.
abstract

2009 - Quantitative analysis of cristalline phases in a LZS glass-ceramic [Articolo su rivista]
A. P., Novaes de Oliveira; Manfredini, Tiziano
abstract

1.A.P. Novaes de Oliveira and T.Manfredini, “Quantitative analysis of cristalline phases in a LZS glass-ceramic”, Am. Ceram. Soc. Bull., 88 (2), 28-31 (2009).

2009 - Quantitative analysis of crystalline phases in a LZS glass-ceramic [Articolo su rivista]
De Oliveira, A. P. N.; Manfredini, T.
abstract

Results of adequately heat-treated Li2O-ZrO2-SiO 2 (LZS) glass-ceramic that consider the identification and quantification of crystalline and glassy-formed phases and their concentration profiles using the Chung method were presented. The batch produced 100 g of glass was placed into a platinum crucible and melted at 1450°C for 7 h in an electrically heated furnace and quenched onto a steel mold. X-ray diffraction (XRD) patterns show ZrSiO2 formation at 850°C, while at 900°C, the intensity of the compound increases and Li2O-2SiO 2 appears. The peak intensities registered at 950°C show an increased volume fraction occupied by the crystals. The compositions of LiSi2O5 and ZrSiO4 and total glass-ceramic crystalline phase are the function of the applied heat-treatment temperature.

2009 - Rheological behaviour and mechanical properties of porcelain stoneware bodies containing Italian clay added with bentonites [Articolo su rivista]
F., Andreola a; Siligardi, Cristina; Manfredini, Tiziano; C., Carbonchi
abstract

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.

2008 - Ceramic tiles in the XXIst century [Relazione in Atti di Convegno]
Manfredini, T.
abstract

2008 - Color in ceramic glazes: analysis of pigments and opacifier grain size distribution effect by spectrophotometer [Articolo su rivista]
Schabbach, L; F., Bondioli; Ferrari, Anna Maria; Manfredini, Tiziano; PETTER C., O; Fredel, M. C.
abstract

The analysis of the physical interactions between pigments, opacifiers and glazes is fundamental to understand the optical behavior of ceramic glazes. In particular the pigment and opacifier grain size distribution is fundamental to determine the optical properties of the glazes directly changing the color of the product. In this work the influence of the grain size distribution of both zircon (ZrSiO4) opacifier and yellow zircon-praseodymium pigment ((Zr,Pr)SiO4) on the color developed by an opaque glaze was evaluated. The glazes were prepared by addition of zircon opacifier (three different grain size distribution) and yellow Pr-zircon pigment (before and after its micronization) to a commercial frit. The color of the glazes were measured with a spectrophotometer and the absorption and scattering properties of the obtained glazes were explained through the Kubelka-Munk model. The opacifier grain size has the major effect on the scattering of the light while the micronization of the yellow Pr-pigment do not affected significantly the reflectance and thus the color of the evaluated glazes.

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

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 - Effect of synthesis parameter on hematite-silica red pigment obtained using a coprecipitation route [Articolo su rivista]
Bondioli, Federica; Manfredini, Tiziano; HOSSEINI ZORI, M; TAHERI NASSAJ, E.
abstract

The traditional ceramic industry has recently witnessed increasing interest in the obtainment of inclusion pigments to stabilize at firing temperature and in the action of molten glass’ unstable chromophores such as hematite or cadmium sulphoselenide. This work focuses on the optimization of the synthesis of hematite-silica inclusion pigment. To improve the inclusion efficiency a coprecipitation route was chosen. The use of various precipitant agents (NaOH and NH4OH), and mineralisers were analyzed

2008 - Il terzo fuoco: l'esaltazione dell'estetica ceramica. [Articolo su rivista]
Manfredini, Tiziano
abstract

L'articolo riporta i più recenti risultati e lo stato dell'arte tecnologico relativo alla realizzazione della decorazione ceramica.

2008 - Le nanopolveri nella funzionalizzazione delle superfici ceramiche [Articolo su rivista]
Bondioli, Federica; Manfredini, Tiziano
abstract

In questo articolo, dopo una brave introduzione sul significato di nano, nanotecnologia e nanopolvere, si valutano le possibili applicazioni nella funzionalizzazione della superficie dei materiali ceramici tradizionali.

2008 - Predizione del colore con il modello di Kubelka-Munk: l’esempio di uno smalto opaco con il giallo al praseodimio [Articolo su rivista]
L. M., Schabbach; M. C., Fredel; F., Bondioli; Ferrari, Anna Maria; Manfredini, Tiziano; C. O., Petter
abstract

Il modello sviluppato da Kubelka e Munk, che correla la luce riflessa, ossia il colore, alla concentrazione dei pigmenti aggiunti in una determinata matrice, è il modello su cui si basano tutti i software di formulazione del colore (Color Matching). In questo studio è stata valutata la sua efficienza nella predizione del colore di uno smalto opaco (silicato di zirconio (ZrSiO4)) colorato con il pigmento giallo al praseodimio ((Zr,Pr)SiO4). Smalti con differenti percentuali di pigmento giallo e opacizzante sono stati preparati per determinare le costanti di assorbimento e diffusione della luce del modello di Kubelka-Munk. I risultati ottenuti hanno dimostrato che non c’è una correlazione lineare tra i parametri colorimetrici a* e b* e la concentrazione del pigmento giallo aggiunto. Tal linearità è invece riscontrata se si considerano le costanti ottiche del modello di Kubelka-Munk. Inoltre, le curve di riflettanza predette dal modello di Kubelka-Munk sono in buon accordo con le curve sperimentali. In definitiva il modello di Kubelka-Munk permette di correlare la concentrazione dei pigmenti aggiunti con il colore del materiale alla base di tutti i softwares commerciali per l’analisi tintometrica.

2008 - Room-Temperature Degradation of t-Zr(Pr)O2 in an Aqueous Suspension Revealed by Perturbed Angular Correlations [Articolo su rivista]
Caracoche, Mc; MARTINEZ J., A; RIVAS P., C; Andreola, Nora Maria; F., Bondioli; Ferrari, Anna Maria; Manfredini, Tiziano
abstract

This paper deals with the phase stability of an aqueous suspension of tetragonal Zr0.9Pr0.1O2 (20 wt%/vol%) at room temperature as a function of the aging time. The suspension is investigated in situ using the highly localized Perturbed Angular Correlations technique. The results indicate that an almost fully reversible degradation process toward monoclinic zirconia takes place through a first-order reaction of rate constant k = 0.7-1day. Two successive diffusion mechanisms are observed that are interpreted as OH ions’ migration in the grain surface and then, as proton defects’ diffusion into the bulk.

2008 - The clay beds in the Velabrum and the earliest tiles in Rome [Articolo su rivista]
A., Ammerman; I., Iliopoulos; Bondioli, Federica; D., Filippi; J., Hilditch; Manfredini, Tiziano; L., Pennisi; N. A., Winter
abstract

In this paper the clay beds in the Velabrum in Roma were studied both from a storical and chemical point of view to study the technology of earliest roman tile

2008 - The future of the ceramic industry: to know to innovate for the market. [Articolo su rivista]
Manfredini, Tiziano
abstract

The paper discusses the possible strategies for the future of the ceramic industry.

2008 - Use of instrumental analyses for sanitary fitting defect understanding [Articolo su rivista]
Manfredini, Tiziano
abstract

The paper reports examples on the use of instrumental analyses for sanitary fitting defect understanding

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

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 - Bentoniti nazionali per applicazioni nell’industria ceramica [Articolo su rivista]
F., Cinicola; Distasio, Raffaele; M., Guglielmi; M., Rocca; M., Hanuskova; Manfredini, Tiziano
abstract

L'articolo riporta un quadro significativo relativo alle caratteristiche ed alle applicazioni di una bentonite nazionale con riferimento particolare ad impieghi nell’industria ceramica.

2007 - Comparison between Plasma- and HVOF-sprayed ceramic coatings. Part 2: tribological behaviour [Articolo su rivista]
Bolelli, Giovanni; Lusvarghi, Luca; T., Manfredini; E., Turunen; T., Varis; S. P., Hannula
abstract

This is the second part of comparative study between High Velocity Oxygen-Fuel (HVOF) flame-sprayed and Atmospheric Plasma-Sprayed (APS) ceramics. Dry particles abrasion test and dry sliding wear test at room temperature, 400°C and 700°C are performed. In dry sliding against SiC, at room temperature stable tribofilms are formed and mild wear (<10–6 mm3/(Nm)) occurs for all coatings. When temperature and normal load increase, making brittle cracking a significant wear mechanism, HVOF coatings become superior to APS ones, thanks to higher toughness. In dry particles abrasion, brittle fracture prevails; therefore, the tougher HVOF coatings outperform APS ones.

2007 - Comparison between plasma- and HVOF-sprayed ceramic coatings. Part I: microstructure and mechanical properties [Articolo su rivista]
Bolelli, Giovanni; Lusvarghi, Luca; Manfredini, Tiziano; F., Pighetti Mantini; R., Polini; E., Turunen; T., Varis; S. P., Hannulla
abstract

Few papers deal with High Velocity Oxygen-Fuel (HVOF)sprayed ceramics. This two-part study thoroughly compares HVOFsprayed Al2O3, nanostructured Al2O3, Cr2O3 to Atmospheric Plasma Sprayed(APS) ones. The first part discusses microstructure and micromechanics.HVOF-sprayed ceramics achieve superior cohesion (lower porosity and lower average pore area). Size effects in Vickers microindentation tests are differentfor HVOF and APS ceramics. At 1N load, hardness is higher for HVOFcoatings (no cracking). Under 5 N and 10 N loads, hardness decreasesgradually for HVOF coatings; APS coatings are largely cracked at 5 N.HVOF-sprayed ceramics are tougher than APS ones and have higher elasticmodulus.

2007 - Devitrification behaviour of plasma-sprayed glass coatings [Articolo su rivista]
Bolelli, Giovanni; Lusvarghi, Luca; Siligardi, Cristina; Manfredini, Tiziano
abstract

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 - Effect of rice husk ash (RHA) in the synthesis of (Pr,Zr)SiO4 ceramic pigment [Articolo su rivista]
F., Bondioli; Andreola, Nora Maria; Barbieri, Luisa; Manfredini, Tiziano; Ferrari, Anna Maria
abstract

In this work the screening results of the scientific activity conducted on the possibility to use rice husk ash as silica precursor for ceramic pigments are reported. Ceramic pigments were synthesized by solid-state reactions and the color developed in a suitable ceramic glaze was investigated in comparison with the color developed by the pigments prepared from pure SiO2.

2007 - Glass-alumina Functionally Graded Materials produced by plasma-spraying [Relazione in Atti di Convegno]
Cannillo, Valeria; Lusvarghi, Luca; Manfredini, Tiziano; Montorsi, Monia; Siligardi, Cristina; Sola, Antonella
abstract

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
abstract

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 - Influence of firing temperature on the color developed by a (Zr,V)SiO4 pigmented opaque ceramic glaze [Articolo su rivista]
Lm, Schabbach; F., Bondioli; Ferrari, Anna Maria; Manfredini, Tiziano; Co, Petter; Mc, Fredel
abstract

The analysis of the physical interactions between pigments, opacifiers and glazes is fundamental to understand the optical behavior of ceramic glazes. Furthermore is important to verify if the glaze devitrifies because the crystallized phases can contribute to the optical properties of the system. The size and the quantity of the formed crystals can change significantly the glaze color. The mean goal of this study was to evaluate the influence of firing temperature on the color stability of an opaque ceramic glaze colored by a blue vanadium-zircon pigment taking into account all the optical components. Quantitative X-ray diffraction analysis was conducted in order to evaluate the pigment dissolution at the three studied temperature and the quantity of the in situ formed zircon crystals from the used frit. The reported study demonstrated the importance to consider all the components in a multicomponent optical system as a ceramic glaze. (c) 2006 Elsevier Ltd. All rights reserved.

2007 - Synthesis and sinterability of hydroxyapatite-coated zirconia nanopowders [Relazione in Atti di Convegno]
F., Bondioli; Cannillo, Valeria; Ferrari, Anna Maria; Manfredini, Tiziano
abstract

Hydroxyapatite (HAp), is a well-known and a valuable implant material with biocompatibility and bioactive properties. Full utilisation of the unique properties of hydroxyapatite bulk ceramics is, however, possible only after its proper reinforcement, i.e. by preparation of composites. In zirconia reinforced hydroxyapatite composites (HAp-ZrO2) it is possible to combine extremely advantageous properties of both biomaterials, previously applied separately. The goal of this study was to synthesized a HAp-coated zirconia composite powder by the precipitation of HAp in presence of zirconia. HAp was precipitated in order to obtain 3, 5, 10, 15, 30 and 50 wt % zirconia reinforced composite powders. The obtained powders were fully characterized in order to determine their properties and sinterability.

2007 - Technological properties of celsian reinforced glass matrix composites [Articolo su rivista]
Cannillo, Valeria; Manfredini, Tiziano; A., Motori; F., Patuelli; A., Saccani; Sola, Antonella
abstract

Monoclinic celsian derived from an innovative route, i.e. cation exchanged zeolites heat-treated at low temperature, was added at differentcontents (10, 20, 30 wt%) to a glass matrix, in order to improve its mechanical and electrical performances. The effect of the celsian reinforcementwas evaluated by testing several properties of the composite materials, such as the elastic modulus, abrasion resistance, flexural strength andelectrical insulation. The results so far obtained suggest that the addition of the monoclinic celsian to the glass matrix may produce low-costparticulate composites with interesting technological properties.

2007 - Thermal spraying to coat traditional ceramic substrates: Case studies [Articolo su rivista]
Bartuli, C; Lusvarghi, Luca; Manfredini, Tiziano; Valente, T.
abstract

Thermal spray is a group of continuous, line of sight, deposition methods, where usually particles (1-50 mu m) are melted and accelerated, through either a combustion or a plasma flame. The molten droplets impinge on a substrate and rapidly solidify to form thin layers (splats). Among these techniques, plasma spraying is particularly fit for spraying ceramics and applied in many industrial applications on metallic surfaces. However, it has seldom been used for spraying glasses and even less to coat ceramic substrates, in particular traditional ones. In this paper, layered refractory ceramics coatings on sintered refractories have been deposited to improve the substrate resistance to molten glass. Some examples of plasma sprayed high-performance or waste glasses applied on porcelanized stoneware and porous single-firing bodies are presented, too. The coatings have been subsequently thermally treated and microstructural, chemical, mechanical analysis have been carried out both on as-sprayed and treated samples. (c) 2006 Elsevier Ltd. All rights reserved.

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

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 - Analysis of crack propagation in alumina-glass functionally graded materials [Relazione in Atti di Convegno]
Cannillo, V.; Lusvarghi, L.; Manfredini, T.; Montorsi, M.; Siligardi, C.; Sola, A.
abstract

abstract

2006 - Color matching algorithms in ceramic tile production [Articolo su rivista]
Bondioli, Federica; Manfredini, Tiziano; Romagnoli, Marcello
abstract

In the present work, the possibility of transferring in the ceramic tiles production the know-how developed in the field of the paints by using the Kubelka-Munk theory, in the form used for opaque surface coatings, have been evaluated. Five different target colors have been chosen as target and tried to reproduce with an industrial glaze in a cycle for fine porcelain stoneware tiles. Four industrial pigments have been chosen as basic stains for the formulations. The results show a good efficiency of the color matching algorithm applied to pigments for glazes for fine porcelain stoneware tiles. All the formulations, in fact, have allowed to obtain a value of Delta E* lower to the accepted limit.

2006 - Corrosion resistance of HVOF-sprayed coatings for hard chrome replacement [Articolo su rivista]
Bolelli, Giovanni; Giovanardi, Roberto; Lusvarghi, Luca; Manfredini, Tiziano
abstract

HVOF-sprayed coatings (WC-17Co, WC-10Co-4Cr, Co-28Mo-17Cr-3Si) and electrolytic hard chrome (EHC) coatings corrosion resistances have been compared through electrochemical polarization tests (0.1 N HCl, 0.1 N HNO3) and Corrodkote test. EHC coatings passivate in HNO3, but undergo pitting corrosion in HCl and in Corrodkote test too. HVOF coatings do not passivate, but possess more noble corrosion potentials. Both in HNO3 and HCl, they undergo more generalized corrosion, with similar i(corr); crevice corrosion along splat boundaries is sometimes detected after the HCl test. Their i(corr) in 0.1 N HCl solution is lower than in several of EHC coatings. No visible damage in the HVOF coatings has occurred after the Corrodkote test. (c) 2006 Elsevier Ltd. All rights reserved.

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

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.

2006 - Glass alumina composite coatings by plasma spraying. Part II: microstructure-based modelling of mechanical properties [Articolo su rivista]
Bolelli, Giovanni; Cannillo, Valeria; Lusvarghi, Luca; Manfredini, Tiziano; Montorsi, Monia
abstract

The mechanical properties of composite glass-alumina coatings produced by plasma spraying, as described in Part 1, were numerically characterized with relation to the peculiar microstructure. Finite element meshes were created for the most significant coating typologies, starting from SEM acquired microstructures. The coatings elastic properties and fracture behaviour were characterized as a function of relevant microstructural features. The results confirm that the coatings are anisotropic, with a lower elastic modulus in the direction perpendicular to the substrate plane (spray direction), because of the lamellar microstructure; increasing the alumina volume fraction increases the elastic modulus value both in the spray and transverse direction. Moreover, it is found that cracks start from large, irregular pores, and propagate easily through the glass areas, but are stopped by alumina. Smaller individual glass areas hinder crack propagation. The post-deposition thermal treatment described in Part I produces tensile residual stresses in the glass and compressive ones in the alumina; thus, the arresting effect of the latter on cracks propagation is greatly enhanced. (c) 2005 Elsevier B.V. All rights reserved.

2006 - Glass-alumina composite coatings by plasma spraying. Part I: Microstructural and mechanical characterization [Articolo su rivista]
Bolelli, Giovanni; Cannillo, Valeria; Lusvarghi, Luca; Manfredini, Tiziano
abstract

Composite coatings on ceramic tiles have been produced by plasma-spraying waste glass powders together with alumina as reinforcing phase. Obtaining a tough coating, in which a high amount of waste glass can be recycled, is the aim of the study. Glass powders with different particle size distributions were tested; coatings with increasing glass volume fractions (0%, 20%, 40%, 60%, 80%, 100%) were sprayed. Furthermore, two different kinds of alumina feedstocks were employed, namely, a commercial plasma-spray powder and a more economical laboratory manufactured spray-dried powder. Vickers microhardness, fracture toughness and abrasion resistance have been measured. The coatings were tested both in as-sprayed condition and after a thermal treatment. An abrasion resistance comparable to common industrial glazes has been obtained with as much as 60% of glass volume fraction, employing fine glass powders (< 45 mu m). No significant decrease in mechanical proper-ties has been noticed replacing the commercial alumina powder with the spray-dried one. (c) 2005 Elsevier B.V. All rights reserved.

2006 - Glass-alumina functionally graded materials: their preparation and compositional profile evaluation [Articolo su rivista]
Cannillo, Valeria; Manfredini, Tiziano; Siligardi, Cristina; Sola, Antonella
abstract

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 - 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
abstract

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; Andreola, Nora Maria; Barbieri, Luisa; Siligardi, Cristina; Manfredini, Tiziano
abstract

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 - Plasma-sprayed graded ceramic coatings on refractory materials for improved chemical resistance [Articolo su rivista]
Bolelli, Giovanni; Cannillo, Valeria; C., Lugli; Lusvarghi, Luca; Manfredini, Tiziano
abstract

Plasma-sprayed ceramic coatings were manufactured on sintered alumina-mullite refractory bricks to improve their chemical resistance to molten glass. Mullite and alumina powders were employed. Graded layered coatings were designed and produced, to reduce the thermal expansion mismatch with the substrate: in all cases, the upper layer consisted in pure alumina (very resistant to chemical attack); alumina-mullite intermediate layers were added to match the low thermal expansion of the porous substrates. Plasma-sprayed coatings definitely improved both the abrasion resistance and the chemical resistance to long-time (8 h at 1400 degrees C) contact with molten glass, since the coating preserved its original microstructure. However, in thermal shock tests, some transverse cracks appeared; thus, thermal cycling tests in presence of molten glass indicated that, after a few cycles, the glass can penetrate down to these cracks. The tested samples were studied by means of scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS) and X-ray diffraction (XRD).

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

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 - Sintesi del pigmento giallo (Pr,Zr)SiO4: ruolo dei mineralizzatori e determinazione del meccanismo di reazione [Articolo su rivista]
Bondioli, Federica; Manfredini, Tiziano; Ferrari, Anna Maria; G., Baldi
abstract

in questo articolo viene valutato il ruolo dei mineralizzatori (NaF e NaCl) nell'ottenimento del pigmento ceramico giallo al praseodimio. In particolare i dati ottenuti mediante analisi Rietveld-RIR dei diffrattogrammi a raggi X, permettono di ottimizzare il processo di sintesi.

2006 - Synthesis and characterization of nanosized ceria powders by microwave-hydrothermal method [Articolo su rivista]
A., BONAMARTINI CORRADI; F., Bondioli; Ferrari, Anna Maria; Manfredini, Tiziano
abstract

Nanocrystalline ceria powders (CeO2) have been prepared by adding NaOH to a cerium ammonium nitrate aqueous solution under microwave-hydrothermal conditions. In particular the effect of the synthesis conditions (time, pressure and concentration of both the precursor and the precipitant agent solutions) on the physical properties of the crystals have been evaluated. Microwave-hydrothermal treatment of 5 min at 13.4 atm allows to obtain almost crystallized powders (amorphous phase 4%) as underlined by Rietveld-reference intensity ratio (RIR) results.

2006 - Synthesis and nanocomposite sintering of hydroxyapatite-coated zirconia nanopowders [Relazione in Atti di Convegno]
Bondioli, Federica; Cannillo, Valeria; Lusvarghi, Luca; Manfredini, Tiziano; Ferrari, Anna Maria
abstract

Hydroxyapatite (HAP), Ca10(PO4)6(OH)2, is a well-known and a valuable implant material with biocompatibility and bioactive properties. Full utilisation of the unique properties of hydroxyapatite bulk ceramics is, however, enhanced by a proper reinforcement, i.e. by preparation of composites. The goal of this study was to synthesize a HAP-coated zirconia composite powder by the precipitation of HAP in presence of zirconia. The idea was to avoid uncontrolled agglomeration of the zirconia nanostructured reinforcement during the sintering step. ZrO2 nanopowders, previously synthesized by hydrothermal crystallisation, were added in an appropriate amount to an intensively stirred aqueous suspension of Ca(OH)2. HAP was precipitated by addition of H2PO4 at controlled pH in order to obtain a 50:50 composite powders. The obtained powders, fully characterized by TEM, XRD, TG-DTA and BET, were used for the preparation of the nanostructured composite speciments. The sintered materials were characterized in order to evaluate their structural and morphological properties.

2006 - Synthesis of (Pr,Zr)SiO4 Ceramic Pigment: Role of Mineralizers and Reaction Mechanism Determination [Articolo su rivista]
F., Bondioli; Manfredini, Tiziano; Ferrari, Anna Maria; G., Baldi
abstract

The formation mechanism of praseodymium-doped zircon, a market leader ceramic pigment in the high temperature color range, has been mainly studied by Rietveld-R.I.R. analysis of the X-ray diffraction data, SEM analysis and color measurements. The obtained results put in evidence the reaction between SiO2, praseodymium oxide (Pr2O3) and mineralizers which produces a viscous and successively, as the temperature is increased, a volatile phase that reacts with ZrO2 at the ZrO2 sites, confirming the hypothesis made by the authors in a previous work.

2006 - Wear behaviour of thermally sprayed ceramic oxide coatings [Articolo su rivista]
Bolelli, Giovanni; Cannillo, Valeria; Lusvarghi, Luca; Manfredini, Tiziano
abstract

The wear resistance of plasma-sprayed ceramic coatings (Al2O3, Al2O3-13%TiO2, Cr2O3) has been investigated through pin-on-disk and dry sand-steel wheel tests, has been correlated to microstructural and micromechanical characteristics (microhardness, fracture toughness) and has been compared to well-known platings (such as Cr electroplating and electroless Ni) and HVOF-sprayed cermets (WC-17%Co, WC-10%Co-4%Cr). Plasma-sprayed ceramics are hard but brittle: dry particles abrasion occurs through splats detachment. The toughest coating (Al2O3) displays the highest wear resistance, which in fact overcomes HVOF-sprayed cermets and Cr electroplating, when a low number of wheel revolutions are considered. In pin-on-disk tests, no coating undergoes wear loss against the 100Cr6 ball, that possess lower hardness. Against the alumina ball, Al2O3 and Al2O3-TiO2. coatings show high wear rates and friction coefficients (due to chemical affinity), while Cr2O3 possesses better wear resistance, lower friction coefficient and inflicts less wear on the counterpart. Cr2O3 wear scar consists in plastically deformed splats and debris forming a quite adherent protective tribofilm. (c) 2006 Elsevier B.V. All rights reserved.

2005 - Applicazioni delle argille nell'industria ceramica [Capitolo/Saggio]
Andreola, Nora Maria; Manfredini, Tiziano
abstract

I ceramici “tradizionali” sono prodotti ottenuti da materie prime largamente diffuse in natura quali argille, feldspati e sabbie quarzifere foggiati generalmente a freddo e sottoposti ad opportuni trattamenti termici in grado di innescare le trasformazioni fisiche (cambiamenti di fase, passaggio dallo stato cristallino a quello vetroso e viceversa,etc) e chimiche (reazioni di decomposizione, formazione di nuove fasi cristalline) che li rendono appropriati per il loro utilizzo (Ricciardiello& Palmonari, 1996). Vengono usualmente indicati per applicazioni in edilizia (piastrelle, laterizi e sanitari), per uso domestico (stoviglieria, porcellana) e per uso industriale (porcellane tecniche e refrattari). Nel saggio vengono descritte le composizioni degli impasti per piastrelle da pavimentazione e rivestimento che negli ultimi anni hanno subito un’evoluzione importante adattandosi fondamentalmente ai cicli di cottura rapida (inferiori a 60 min.).

2005 - Argille per applicazioni ceramiche e nella produzione degli smalti [Articolo su rivista]
Manfredini, Tiziano
abstract

Sono studiate le principali tipologie di argille per applicazioni ceramiche e nella produzione degli smalti

2005 - Characterisation of glass matrix composites reinforced with lead zirconate titanate particles [Articolo su rivista]
Cannillo, Valeria; Manfredini, Tiziano; Montorsi, Monia; F., Tavoni; Ej, Minay; Ar, Boccaccini
abstract

A new type of glass matrix composite reinforced with ferroelectric particulate secondary phase was investigated. Samples containing lead zirconate titanate (PZT) particles in a silicate lead glass were fabricated. Various sintering strategies were tested in order to optimise the processing route. The densest samples were obtained by hot-pressing. The composites were characterized by means of SEM observations, X-ray diffraction, differential thermal analysis and Vickers indentations. In order to get a deeper insight into the thermo-mechanical behaviour of the material, a FEM based numerical model was prepared and applied. In particular, the crack-particle interaction was assessed and thus possible toughening mechanisms were investigated. By means of the numerical modelling supported by SEM observations, traditional toughening mechanisms (e.g. crack deflection, particle debonding) were ruled out. Since the experimentally measured indentation fracture toughness of the composite is significantly higher than that of the unreinforeed glass, the findings suggest that a new toughening mechanism may be active, based on the piezoelectric effect.

2005 - Experimental characterization and computational simulation of glass-alumina functionally graded surfaces [Relazione in Atti di Convegno]
Cannillo, Valeria; Manfredini, Tiziano; Montorsi, Monia; Siligardi, Cristina; Sola, A.
abstract

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 - Il Color Matching: Fondamenti Teorici della Formulazione Computerizzata del Colore [Articolo su rivista]
L., Maccarini Schabbach; Bondioli, Federica; Manfredini, Tiziano; Romagnoli, Marcello; Ferrari, Anna Maria
abstract

L'articolo riporta alcuni studi sperimentali sulla possibilità di gestire il colore in ceramica

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
abstract

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 - Mechanical performance and fracture behaviour of glass-matrix composites reinforced with molybdenum particles [Articolo su rivista]
Cannillo, Valeria; Leonelli, Cristina; Manfredini, Tiziano; Montorsi, Monia; Veronesi, Paolo; E. J., Minay; A. R., Boccaccini
abstract

A borosilicate glass-matrix composite has been fabricated by addition of molybdenum particles in various volume fractions. In order to systematically investigate the effect of metallic particulate reinforcement on the overall composite mechanical behaviour, a FEM based numerical model was prepared. The study focused on the global elastic and fracture response of the composites. By studying crack propagation patterns, toughening mechanisms such as crack deflection and load transfer were detected, thus enabling to assess the influence of second phase volume fraction on composite fracture toughness. Microscopy observations of fracture surfaces were performed to support the numerical results. © 2005 Elsevier Ltd. All rights reserved.

2005 - Microwave-hydrothermal synthesis and hyperfine characterization of praseodymium-doped nanometric zirconia powders [Articolo su rivista]
F., Bondioli; Leonelli, Cristina; Manfredini, Tiziano; Ferrari, Anna Maria; M. C., Caracoche; P. C., Rivas; A. M., Rodriguez
abstract

This work focuses on the microwave-assisted hydrothermal synthesis of praseodymium-doped zirconia and on the subsequent evaluation of the effect of synthesis conditions on powder properties. Pure and 10 mol% Pr-doped zirconia samples have been analyzed by X-ray diffraction (XRD) and the perturbed angular correlations hyperfine technique, which probes the nearest environments of zirconium ions. At atomic scale, as determined from perturbed angular correlation data, the XRD amorphous fraction of the as-obtained powders exhibits a tetragonal-like structure. The pure powder becomes partially stabilized and the doped powder is a substitutional solid solution of praseodymium in tetragonal zirconia.

2005 - Nanoscopic characterization of Pr2Zr2O7 at Zr sites [Articolo su rivista]
Ja, Martinez; Mc, Caracoche; Pc, Rivas; Am, Rodriguez; Bondioli, Federica; Manfredini, Tiziano; Ferrari, Anna Maria
abstract

By using Perturbed Angular Correlation Spectroscopy, a suitable technique to explore internal fields at nanoscopic scale, the electric field gradients at Zr4+ sites in the Pr2Zr2O7 compound have been determined as a function of temperature. Three nonequivalent nanoconfigurations are present, which have been interpreted with the aid of point charge model calculations. Two of them correspond to pyrochlore - oxygen defective and perfect structures -, and the third one to the pyrochlore-related defect fluorite structure. The most abundant interaction is a disordered and fluctuating electric field gradient, which describes the oxygen defective pyrochlore. As temperature increases, its gradual and reversible transformation towards the perfect form is observed. Below 750 degrees C the oxygen vacancies movement, which exhibits an activation energy of 0.14 eV, is assumed to be due to vacancies jumping among 48f equivalent sites. At higher temperatures the movement is interpreted as the fast diffusion of oxygen vacancies involving 48f and 8b sites, thus giving place to anionic disorder. The activation energy for this movement has been determined to be of 0.85 eV.

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
abstract

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
abstract

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
abstract

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 - Synthesis and characterization of praseodymium-doped ceria powders by a microwave-assisted hydrothermal (MH) route [Articolo su rivista]
Bondioli, Federica; Ferrari, Anna Maria; Lusvarghi, Luca; Manfredini, Tiziano; Nannarone, Stefano; Pasquali, Luca; Selvaggi,
abstract

Nanocrystalline Pr-doped ceria powders were prepared for the first time by a microwave-assisted hydrothermal route. The effect of the microwave treatment in relation to the conventional hydrothermal technique was evaluated. The samples prepared were characterized in terms of composition, crystalline structure, particle shape and size distribution by X-ray diffraction, transmission electron microscopy (TEM) and specific surface area analysis (BET). The color properties of these solid solutions were also evaluated as a function of synthesis conditions and composition. Finally the oxidation state of the Pr cations and the relative quantities of Pr(IV) and Pr( III) were investigated by X-ray absorption at the M-4,M-5 Pr absorption edge.

2004 - A new glass-ceramic red pigment [Articolo su rivista]
Bondioli, Federica; Manfredini, Tiziano; Siligardi, Cristina; Ferrari, Anna Maria
abstract

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 - Computational simulations for the optimisation of the mechanical properties of alumina-glass Functionally Graded Materials [Capitolo/Saggio]
Cannillo, Valeria; Manfredini, Tiziano; Montorsi, Monia; Siligardi, Cristina; Sola, Antonella
abstract

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
abstract

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

2004 - Hyperfine characterization of metastable tetragonal configurations in Pr-doped zirconias [Articolo su rivista]
M. C., Caracoche; J. A., Martinez; P. C., Rivas; A. M., Rodriguez; Bondioli, Federica; Manfredini, Tiziano; Ferrari, Anna Maria; S., Conconi
abstract

The PrxZr1-xO2 ceramic system obtained by coprecipitation has been investigated at zirconium sites as a function of Pr content (1, 10, and 15 mol %) and of annealing temperature by means of the perturbed angular correlations (PAC) technique. Praseodimium enters zirconia forming a tetragonal solid solution whose extent increases with Pr content. In 10 and 15 mol % Pr-doped samples, metastable tetragonal zirconia is present in its two known t- and t'-forms, the latter form being the one which involves a higher dopant concentration. While Rietveld refinement and thermal analyses indicate the uncompleted crystallization of the as-obtained powders, PAC allows the phase identification of the amorphous residues. Minor changes observed in the hyperfine interaction at high temperatures reveal the incipient ceramic degradation. Experiments indicate that, up to 15 mol % of dopant content, Pr behaves as an efficient zirconia stabilizer.

2004 - I materiali nanostrutturati: preparazione, proprietà e prospettive di applicazione dei nanoceramici [Articolo su rivista]
Cannillo, Valeria; Manfredini, Tiziano
abstract

preparazione, proprietà e prospettive di applicazione dei nanoceramici

2004 - Investigation of the mechanical properties of Mo-reinforced glass-matrix composites [Articolo su rivista]
Cannillo, Valeria; Manfredini, Tiziano; Montorsi, Monia; A. R., Boccaccini
abstract

One approach for reducing the inherent brittleness and flaw sensitivity of glass is to fabricate a composite material by incorporating particles or fibers in the glass matrix. In order to fully understand the toughening mechanisms in composites, it is useful to develop predictive models able to describe the mechanical behavior and its dependence on microstructure. To this aim, numerical models can be used in order to assess the effect of the glass-matrix composite microstructure on the effective macroscopic mechanical and fracture properties. An innovative microstructure-based finite element code is used to describe the mechanical performance of glass matrix composites. This code is able to convert digitized images of the material microstructure into a finite element grid, so that all microstructural details such as inclusion size, morphology and volume fraction can be incorporated in the model. In this study, a borosilicate glass matrix composite reinforced with molybdenum particles is characterized using the aforementioned microstructure-based FEM approach in terms of residual stresses and elastic properties.

2004 - Li2O-ZrO2-SiO2 sintered glass-ceramics for ceramic tile applications [Articolo su rivista]
A. P., NOVAES DE OLIVEIRA; Siligardi, Cristina; Manfredini, Tiziano
abstract

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 - Prediction of opaque ceramic enamel color using the Kubelka-Munk [Articolo su rivista]
L. M., Schabbach; M. C., Fredel; C. O., Petter; Manfredini, Tiziano; Bondioli, Federica
abstract

In this paper the possibility to predict the color of a ceramic glaze by the Kubelka-Munk theory has been evaluated

2004 - Preparation, characterisation and computational study of poly(epsilon-caprolactone) based nanocomposites [Articolo su rivista]
M., Avella; Bondioli, Federica; Cannillo, Valeria; Me, Errico; Ferrari, Anna Maria; B., Focher; M., Malinconico; Manfredini, Tiziano; Montorsi, Monia
abstract

In recent years, scientific and industrial interest has been focused on the preparation of organic/inorganic nanocomposites because of their unique hybrid properties correlated with the enormous interfacial adhesion region that is a characteristic of nanoparticles. The objective of the whole research was to improve poly-caprolactone (PCL) mechanical and barrier performances by using silica spherical nanoparticles for filling. In particular, in order to improve the polymeric matrix/inorganic nanofiller's interfacial adhesion and consequently to achieve a fine nanometric dispersion, silica nanoparticles have been chemically modified by grafting onto them a hydroxyl end-capped PCL, after wheich they have been melt blended with high molecular weight PCL. In the present paper, details on the synthesis, morphology and mechanical properties of the prepared nanocomposites are reported. Moreover, a numerical tool has been used to predict the mechanical properties of the nanocomposite, starting from the morphology of the material observed by scanning electron micrography, and the individual properties of the constituents.

2004 - The role of sodium hexametaphosphate in the dissolution process of kaolinite and kaolin [Articolo su rivista]
Andreola, Nora Maria; Castellini, Elena; Manfredini, Tiziano; Romagnoli, Marcello
abstract

Suspensions of kaolinite and ceramic grade kaolin in sodium hexametaphosphate solutions at different concentrations were prepared and kept at constant temperature for 4 h: the solutions obtained after centrifugation and filtration were analysed using a ICP technique to determine the concentration of significant cations. The results allowed to stress the role of NaHMP in the dissolution process of kaolinite and ceramic grade kaolin. The role of accessory minerals in ceramic grade kaolin dissolution was discussed in the light of the obtained data.

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
abstract

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.

2004 - Use of numerical approaches to predict mechanical properties of brittle bodies containing controlled porosity [Articolo su rivista]
Cannillo, Valeria; Manfredini, Tiziano; Montorsi, Monia; Ar, Boccaccini
abstract

when designing a porousmaterial, it is important to control not only the porosityand pore morphology, but also the pore spatial positioning,if the mechanical properties, in particular fracturestrength, are to be optimized. To this aim, suitableproduction techniques should be developed in order toguarantee an homogeneous dispersion of pores.

2003 - Computational simulations for the assessment of the mechanical properties of glass with controlled porosity [Articolo su rivista]
Cannillo, Valeria; Leonelli, Cristina; Manfredini, Tiziano; Montorsi, Monia; Ar, Boccaccini
abstract

Porous glass with closed controlled porosity is used as a model system in order to numerically assess the effect of pores on the macroscopic mechanical and fracture behavior of brittle solids. A computational code called OOF, which converts digitalized two-dimensional (2-D) images of materials microstructures into finite element meshes, is adopted, so that the effect of 2-D microstructural features (e. g. pore size and shape) on the global mechanical response of the material can be determined. Firstly, microstructures of porous glass bodies containing isolated pores were considered. These specimens were numerically investigated in terms of fracture initiation and propagation: the numerical model predicted that larger pores initiate fracture, in agreement with experimental results. Then, the effect of porosity on the elastic and fracture properties was thoroughly investigated by means of model two-dimensional microstructures consisting of selected area fractions of pores (equivalent to pore volume fractions in three dimensions) and with prescribed pore shape, orientation and dimensions. In particular, the effect of pore dimension and shape was studied, finding that the critical stress for crack initiation scales with pore dimension and aspect ratio, i.e. oblate and larger pores oriented perpendicularly to the stress direction cause a higher reduction of strength of the specimen. Finally, several 2-D microstructures characterized by different values of area fraction of pores of the same shape were investigated, in order to determine the variation of elastic properties and the fracture response of porous glasses with pore content. The study confirms the suitability of the 2-D OOF code to investigate the mechanical and fracture behavior of porous materials. Issues regarding the limitation of the model due to its 2-D character are also discussed where appropriate.

2003 - Effect of ionic strength and temperature on the interaction between kaolin suspensions and sodium hexametaphosphate [Abstract in Atti di Convegno]
Andreola, Nora Maria; Castellini, Elena; Manfredini, Tiziano; Romagnoli, Marcello
abstract

The effect of ionic strength on the interaction between kaolin and sodium hexametaphosphate has been investigated at different temperatures.

2003 - Euroclay 2003 [Altro]
Brigatti, Maria Franca; Manfredini, Tiziano
abstract

10th Conference of the European Clay Groups Association

2003 - Functionally Graded Materials: a review of fabrication processes and modelling of properties [Articolo su rivista]
Cannillo, Valeria; Manfredini, Tiziano; Montorsi, Monia; Siligardi, Cristina; Sola, A.
abstract

Review of FGM

2003 - Porcelainized stoneware: processing and characteristics [Articolo su rivista]
Manfredini, Tiziano; Romagnoli, Marcello
abstract

Unglazed fast fired porcelainized stoneware tiles, for pavering and for exteriors, are the main innovative products present on the tile market. They are prepared using mainly kaolinitic clays, quartz and large amounts of fluxes to increase the sintering. The raw materials are more highly milled than those used for other kinds of tiles and the bodies are fired at 1200-1220°C. Tiles are not glazed and may be coloured. Its structure consists of a glassy matrix with mullite and residual quartz. The basic product presents high mechanical and technical qualities and peculiar abrasion resistance and surface hardness.

2003 - Simulazioni computazionali per lo studio di materiali di interesse applicativo [Articolo su rivista]
Cannillo, Valeria; Manfredini, Tiziano; Montorsi, Monia
abstract

descrizione di tecniche di modeling per materiali di interesse applicativo

2002 - Ceramic tile glazes: Design, trends and applications [Relazione in Atti di Convegno]
Manfredini, Tiziano
abstract

The purpose of this lecture is to describe the state of the art of glazes for applications in ceramic tile industry. A glaze for application in ceramic tile industry must satisfy certain requirements, which may be divided into two large groups, one in relation to its preparation and industrial utilisation and the other specific of the product utilisation. In order to design glaze compositions certain aspects must be taken into account. Viscosity and surface tension of the melt matching the body requirements, linear thermal expansion, nucleation and crystal growth processes occurring during firing, durability and optical properties must be designed and adjusted in the industrial practice. Glass-ceramic systems are the more suitable compositions for innovative glazes for fast firing of wall and floor tiles.

2002 - Clays in manufacturing of unglazed porcelainized stoneware [Articolo su rivista]
M., Hanuskovà; Manfredini, Tiziano
abstract

Clay based minerals are the main components of unglazed porcelainized stoneware ("gres porcellanato") bodies and their amount generally ganges from 40 to 60 wt%. They confer plasticity and workability in the green state and fournish the main oxides involved, with fluxes and other sintering aids, in the strenghening mechanism of the body during firing. Kaolinitic clays can improve the formation of mullite and , in general, by widenong the sintering temperature range reduce swelling and deformation of tiles during firing. Low titanium and iron oxides content is foundamental in developing colours.

2002 - ESEM investigation of the reaction mechanism in Pr-doped zircon [Relazione in Atti di Convegno]
F., Bondioli; Ferrari, Anna Maria; Manfredini, Tiziano
abstract

The formation mechanism of praseodymium-doped zircon stain was studied, using environmental scanning electron microscopy (ESEM) primarily. The significance of ESEM as a processing tool for studying chemical and morphological dynamic changes was evaluated, with respect to the traditional investigation methods. In particular ESEM observation permits to define the role of the mineralizers and indicates a two-step mechanism.

2002 - Effetto di additivi promotori di fluidità su materiali ceramici tradizionali ottenuti per pressatura uniassiale. [Relazione in Atti di Convegno]
Manfredini, Tiziano; Romagnoli, Marcello; Siligardi, Cristina
abstract

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

2002 - Experimental versus computer simulation analysis of zirconia containing glasses [Relazione in Atti di Convegno]
Montorsi, Monia; Menziani, Maria Cristina; Siligardi, Cristina; Manfredini, Tiziano; A. N., Cormack
abstract

The addition of zirconia to lime silicate glasses produces consistent glass structure modifications which can be consider directly responsible of the improvement in chemical resistance, optical, thermal and mechanical properties of the glass. Therefore, this class of materials represents an interesting topics in science and material engineering, especially as concerning the design and development of new glass materials for industrial applications. In this work, molecular dynamic simulations have been used to complement the glass structure characterisation experimentally determined and to correlate the structural modifications induced by zirconia in the glass network to the chemical and physical properties macroscopically measured for the CaO-ZrO2-SiO2 system.

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
abstract

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

2002 - La fabbricazione e l'applicazione di ossidi nell'industria ceramica [Articolo su rivista]
Bondioli, Federica; Manfredini, Tiziano; Romagnoli, Marcello
abstract

In questo articolo gli autori presentano i principali ossidi ceramici utilizzati nell'industria ceramica

2002 - Microwave technology applications in the synthesis of ceramic pigments [Relazione in Atti di Convegno]
Pellacani, Gian Carlo; Bondioli, Federica; Leonelli, Cristina; Siligardi, Cristina; Veronesi, Paolo; Manfredini, Tiziano
abstract

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 - Numerical models of the effect of heterogeneity on the behavior of graded materials [Relazione in Atti di Convegno]
Cannillo, Valeria; Manfredini, Tiziano; Corradi, Anna; Wc, Carter
abstract

Gradients in the elastic modulus of a surface can affect the hardness of that surface, as demonstrated in recent papers [1, 2]. It has been experimentally verified that enhanced hardness can be obtained by dispersing a variable concentration of second phase particles in a matrix and cosintering. However, the nature of the processing conditions results in a microstructure that has variations in its lateral (in-surface-plane) properties and variations about the optimal gradient due to the discrete nature of the second phase particulate microstructure: these materials have stochastically graded microstructures, In this paper, we generate a series of microstructures that have the same average surface gradient, but with variable placement of the second phase, in order to analyze numerically the effect of stochasticity on the predicted optimal material properties. We characterize the effect of stochastic placement of second phase particles on the hardness and toughness of these materials which have a specified gradient in their surface elastic coefficients.

2002 - Porcelainized stoneware: processing and characteristics [Articolo su rivista]
Manfredini, Tiziano
abstract

An overwiew on research results on porcelainized stoneware: raw materials, processing and characteristics

2002 - Recycling of the waste waters into porcelainized stoneware ceramic tiles: effect on the rheological, thermal and aesthetical properties [Relazione in Atti di Convegno]
Andreola, Nora Maria; Barbieri, Luisa; Lancellotti, Isabella; Manfredini, Tiziano
abstract

The importance of the porcelainized stoneware production, this product reached the 36% (218.106 m2) of the total Italian production in the last year, and the impossibility to reuse both the ceramic residues and the process waste waters with the similar practice developed previously for the other typologies have brought to find new solutions to applied at this kind of wastes. The aim of the work is to evaluate the possibility to recycle waste waters, deriving from different technological ceramic cycles, inside the porcelainized stoneware body. The use of these waters does not change the parameters of the productive cycle, obtaining a final product with the similar quality and aesthetic characteristics required from the market and avoiding a possible spilling of the waste water after purification in sewers or in superficial river courses.

2002 - Tape casting sotto pressione di sospensioni acquose di allumina [Relazione in Atti di Convegno]
Andreola, Nora Maria; Manfredini, Tiziano; Romagnoli, Marcello
abstract

Tape casting sotto pressione di sospensioni acquose di allumina

2002 - Use of municipal incinerator bottom ash as sintering promoter in industrial ceramics [Articolo su rivista]
Barbieri, Luisa; Corradi, Anna; Lancellotti, Isabella; Manfredini, Tiziano
abstract

The use of glassy frits obtained from municipal incinerator bottom ash and glass cullet, as sintering promoters in the production process of porcelainized stoneware, was investigated. The emphasis was on studying the similarities and differences with respect tothe standard body. The characterization involved the application of several techniques: chemical analysis, X-ray powder diffraction, linear shrinkage during firing, water absorption, bending strength and spot resistance test. The results show that, the addition of these glassy frits in the body improve the characteristics of water absorption and spot resistance which is related to the absence of surface porosity originated by the glassy phase. Moreover, addition of glassy frits to the porcelanized stoneware body does not change significantly its bending strength. In the firing conditions used there is a slight worsening in the tiles planarity, while there is a significant modification of the color, which becomes darker with respect to the base body.

2002 - Utilisation of municipal incinerator grate slag for manufacturing porcelainized stoneware tiles manufacturing [Articolo su rivista]
Andreola, Nora Maria; Barbieri, Luisa; Corradi, Anna; Lancellotti, Isabella; Manfredini, Tiziano
abstract

Porcelainized stoneware tiles containing up to 20 wt.% of municipal incinerator grate slag have been fabricated by cold uniaxial pressing and conventional fast firing cycles. The sinterability of these samples was investigated from density and shrinkage measurements together with mechanical (Vickers microhardness and Young's modulus) and esthetical (spot resistance and colour parameters analysis) properties. The comparison with the porcelainized stoneware tiles containing no waste suggest a good compatibility between the ceramic body and the waste that does not significantly change the properties of the final products and the conditions of the firing cycle. Nevertheless, the porosity increase, proportional to the waste content, causes a decrease in density, shrinkage, spot resistance and whiteness. (C) 2002 Elsevier Science Ltd. All rights reserved.

2001 - CN-Special Asia in Mandarin [Articolo su rivista]
Manfredini, T.
abstract

2001 - Characterization of Pr-doped zircon by comparing hyperfine technique (PAC) and Rietveld refinement [Abstract in Atti di Convegno]
Bondioli, F.; Ferrari, A. M.; Manfredini, T.; Caracoche, M. C.; Robio-Puzzo, L.
abstract

Nowadays, some widely used inorganic pigments (vanadium blue, praseodymium yellow, and iron-coral pink) are based on ZrSi04 stoichiometry where the color is prevalently obtained by substitutional doping. This work deals with provided structural information on pure and praseodymium-doped zircon powders synthesized by the traditional ceramic route in order to evaluate the location of the dopant ion and the modification introduced in the zircon lattice. The information obtained by using the extremely localized perturbed angular correlation technique was compared with Rietveld structure refinement data. The kinetic of zircon pigment formation was followed by environmental scanning electron microscopy.

2001 - ESEMPI DI INERTIZZAZIONE E VALORIZZAZIONE DI CENERE VOLANTE DI ACCIAIERIA [Articolo su rivista]
Barbieri, Luisa; Bondioli, Federica; Corradi, Anna; Lancellotti, Isabella; Manfredini, Tiziano
abstract

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2001 - Enhancing the mechanical properties of porcelain stoneware tiles: a microstructural approach [Articolo su rivista]
Leonelli, C.; Bondioli, F.; Veronesi, Paolo; Romagnoli, Marcello; Manfredini, Tiziano; Pellacani, Gian Carlo; Cannillo, Valeria
abstract

This paper focuses on the complexities of the microstructure and phase development in porcelain stoneware tiles produced following industrial fast single firing cycles. A microstructural investigation was conducted to determine if the addition of selected low cost minerals would improve mechanical properties. The minerals tested were quartz, mullite and kyanite. Uniaxially pressed samples were submitted to the same industrial firing schedule and tested according to the European tile standards before further microstructural analysis. All the requirements specified in UNI EN normative concerning BIa class tiles were fulfilled; moreover, mullite and kyanite added formulations showed sensible increases in mechanical properties, especially as far as flexural strength and abrasion resistance are concerned.

2001 - Micromechanics principles applied to fracture propagation in porcelain stoneware tiles [Relazione in Atti di Convegno]
Leonelli, Cristina; F., Bondioli; Veronesi, Paolo; Cannillo, Valeria; Romagnoli, Marcello; Manfredini, Tiziano
abstract

The possibility of discussing the mech. properties of porcelain stoneware tiles with a scientific approach typically used in the investigation of the composite materials is studied. A thorough microstructural investigation was conducted to det. if the addn. of selected low-cost minerals would improve mech. properties. The minerals tested were quartz, mullite, and kyanite. Uniaxially pressed samples were submitted to the same industrial firing schedule and tested according to European tile stds. before further microstructural anal.

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

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

2001 - Nucleation and crystallization of new glasses from fly ash originating from thermal power plants [Articolo su rivista]
Barbieri, Luisa; Lancellotti, Isabella; Manfredini, Tiziano; Pellacani, Gian Carlo; Jm, Rincon; M., Romero
abstract

The nucleation and crystallization kinetics of new glasses obtained by melting mixtures of a Spanish carbon fly ash with glass cullet and dolomite stag at 1500 degreesC has been evaluated by a calculation method. These glasses, whose microstructure was examined by TEM carbon replica, were susceptible to controlled crystallization in the 800 degrees -1100 degreesC range. The resulting glass-ceramics developed acicular and branched wollastonite crystals or a network of dendritic pyroxene mixed with anorthite feldspar (SEM and EDX analysis). The time-temperature-transformation curves (processing of the XRD data) showed the crystallization kinetics and the critical cooling rate to be in the 12 degrees -42 degreesC/min range.

2001 - Principali materiali per pavimentazione e rivestimento a confronto [Articolo su rivista]
Manfredini, Tiziano
abstract

L'articolo riporta un interessante confronto tra i diversi materiali utilizzati nelle pavimentazioni e nei rivestimenti.

2001 - Recycling in the Italian ceramic tile factories [Capitolo/Saggio]
Andreola, Nora Maria; Barbieri, Luisa; Lancellotti, Isabella; Manfredini, Tiziano
abstract

In the Italian reality the unfired and fired by-products are totally recycled in the manufacturing cycle, and only those residues coming from depuration processes (glaze sludges and exhausted lime) cause technological problems, being less useful for recycling. Statistical data of the produced quantities, treated and recycled, divided by categories, are shown. Furthermore, we analyze a new category of ceramic residue, polishing sludges, that owing to their chemical characteristics, are not recycled in the ceramic bodies. We propose to reuse them as secondary raw materials to obtain porous materials with insulating properties by controlled thermal treatments.

2001 - Sintering and crystallisation of a P2O5-added Li2O-ZrO2-SiO2 glass powder system [Articolo su rivista]
A. P., Novaes De Oliveira; Manfredini, Tiziano
abstract

Sintering and crystallisation of a 11.5 wt % Li2O, 22.8 wt % ZrO2, 65.7 wt % SiO2 glass powder with P2O5 added were investigated. By means of thermal shrinkage measurements, sintering was found to start at about 650 degreesC and was completed in a very short temperature interval (DeltaT approximate to 100 degreesC) in less than 30 min. Crystallisation took place just after completion of densification and was almost completed at about 900 degreesC in 20 min. Secondary porosity prevailed over the primary porosity during the crystallisation stage. The glass powder compacts first crystallised into lithium metasilicate (Li2SiO3) and/or zircon (ZrSiO4) and tridymite (SiO2) which transformed and/or grew into lithium disilicate (Li2Si2O5), zircon and tridymite after the crystallisation process was essentially complete, so that, a crystallinity degree between 52.4 +/- 2.0 and 68.5 +/- 3.2 wt % was obtained. P2O5 doping little affected the densification. However, adding P2O5 remarkably enhanced the zircon and tridymite crystallisation while delaying the Li2SiO3 to Li2Si2O5 transformation. The microstructure is characterised by fine crystals uniformly distributed arbitrarily oriented throughout the residual glass phase.

2001 - The possibility to recycle solid residues of the municipal waste incineration into a ceramic tile body [Articolo su rivista]
Andreola, Nora Maria; Barbieri, Luisa; Corradi, Anna; Lancellotti, Isabella; Manfredini, Tiziano
abstract

The feasibility of utilising solid residues of the municipal wastes incineration such as grate (bottom) ash and electrofilter and sleeve filter fly ash, in combination with a porcelain stoneware body, in the preparation of tiles has been investigated. While the chemical, mineralogical, thermal and rheological characterisation of the waste raw materials carries out some problems arising by using fly ash, these seem to be overcome with the bottom ash. The introduction of up to 20 wt% of this powder into the ceramic body does not substantially change the mineralogical and thermal behaviour of the product.

2000 - Applicazione di tecniche a raggi X nello studio di reperti ceramici [Articolo su rivista]
Manfredini, Tiziano
abstract

L'articolo rappresenta un intressante studio di reperti ceramici del XVI e XVIII secolo effettuato tramite l'ausilio di tecniche di analisi sofisticate.

2000 - Ceramic facing tiles (EN 159) obtained from dry-ground Italian raw materials. Part I. [Articolo su rivista]
Manfredini, T.; Romagnoli, Marcello; Visentin, C.; Visentin, P.; Manuskova, M.
abstract

Optimization of dry grinding of paste, contg. exclusively Italian raw materials, for use in prodn. of porous ceramic facing tiles (EN 159) was studied using a rolling vertical mill (Pfeiffer MPS 141A); the results obtained demonstrate that it is possible, using cycles of single-firing (39 min at max. temp 1080 C) and rapid double-firing (28 min firing, 7 min drying, inertization at max. temp 1065 C, and glazing 45 min at max. temp. 1055 C), to obtain products with the functional properties required by the strict European std. Baiso 160 clay is predominantly illite and chlorite with high contents of Ca and Mg oxides; Alloero Refrattoria is predominantly illite and chlorite with high content of free qt and trace carbonates.

2000 - Crystallisation kinetics of a 2·3Li2O. 1·1ZrO2.6·6SiO2 glass [Articolo su rivista]
Novaes de Oliveira, A. P.; Alarcon, O. E.; Manfredini, T.; Pellacani, G. C.; Siligardi, C.
abstract

The nucleation and growth of zircon (ZrSiO4) crystals on the free surface of a 2·3Li2O.1·1ZrO2.6·6 SiO2 glass was investigated through differential thermal analysis (DTA), x-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystallisation was completed at about 860°C with an activation energy value corresponding to 740 kJmol-1. Samples with polished free surfaces were nucleated at selected temperatures in the range 640-690°C and then heated at 750°C for 30 rain for crystal growth. A dominant effect of surface nucleation was observed and the number of ZrSiO4 crystals per unit area and the mechanism of crystallisation were determined. It was concluded that the nucleation starts from a fixed number of surface nuclei which reach a maximum at 670°C corresponding to a zircon crystal number density of 1·33×1011 m-2 and that at 880°C a uniform surface crystalline layer was formed with a rate of growth of 1·93 μm min-1.

2000 - Efeito de adição de wolastonita no processo de consolidação de massas cerâmicas para grês porcelanato [Articolo su rivista]
M., Hanuskovà; Manfredini, Tiziano; Romagnoli, Marcello
abstract

O artigo reporta um amplo estudo sobre o emprego da wollastonita em ceramica, em particular como coadjuvante na sinterizacao das massas.

2000 - Effetti dell'aggiunta di wollastonite sul consolidamento degli impasti ceramici per grès porcellanato. [Articolo su rivista]
Manfredini, Tiziano; Romagnoli, Marcello; M., Hanuskovà
abstract

La wollastonite è una materia prima di notevole interesse ceramico impiegata nella preparazione di fritte, di smalti ceramici e nella formulazione di impasti in particolare per la produzione di piastrelle di gres porcellanato. L'articolo riporta un ampio studio condotto sull'impiego della wollastonite in ceramica in particolare come coadiuvante nella sinterizzazione degli impasti.

2000 - Environmental scanning electron microscopy (ESEM) investigation of the reaction mechanism in praseodymium-doped zircon [Articolo su rivista]
Bondioli, Federica; Corradi, Anna; Ferrari, Anna Maria; Manfredini, Tiziano; G., Baldi
abstract

The formation mechanism of praseodymium-doped zircon stain was studied, using environment scanning electron microscopy (ESEM) primarily. The significance of ESEM as a processing tool for studying chemical and morphologic dynamic changes under controlled temperature conditions was evaluated, with respect to the traditional investigation methods.

2000 - Estrutura dos Materiais Cerâmicos Parte - I [Articolo su rivista]
Manfredini, Tiziano
abstract

Estrutura dos Materiais Cerâmicos

2000 - Glass-ceramics sintered by glassy powders of no hazardous special wastes [Articolo su rivista]
Barbieri, Luisa; Corradi, Anna; Lancellotti, Isabella; Manfredini, Tiziano; Andreola, Nora Maria
abstract

An alternative method for recycling municipal incinerator grate ash is proposed. The glassy powder is sintered to obtain glass-ceramic materials. The results obtained from mineralogical, physical and microstructural analyses show that it is possible to obtain dense finished products consisting of common silicate crystalline phases (wollastonite, diopside) by firing treatments with shorter time and lower temperature with respect to bulk devitrification. 20 refs.

2000 - Grey ceramic pigment (Fe, Zn)Cr2O4 obtained from industrial fly ash [Articolo su rivista]
Bondioli, Federica; Barbieri, Luisa; Manfredini, Tiziano
abstract

In this paper the possibility to use fly ash to synthesize a ceramic pigment has been evaluated.

2000 - I materiali vetroceramici: struttura, proprietà ed applicazioni. Parte II: aspetti applicativi [Articolo su rivista]
Manfredini, Tiziano; Leonelli, Cristina
abstract

L'articolo riporta le principali proprietà e le applicazioni dei materiali vetroceramici

2000 - Il grès porcellanato: caratteristiche ed applicazioni [Articolo su rivista]
Manfredini, Tiziano
abstract

Fra i prodotti emergenti e destinati a ricoprire una fascia di mercato sempre più ampia particolare interesse è attualmente rivolto al gres porcellanato (prodotto non smaltato, molto sinterizzato e avente porosità espressa come assorbimento di acqua generalmente inferiore a 0,3%) di cui vanno continuamente aumentando i volumi sia nazionali che mondiali.

2000 - Inorganic Pigments [Articolo su rivista]
Manfredini, Tiziano; Bondioli, Federica
abstract

In this paper the authors report the main characteristic of inorganic pigments used to color industrial ceramic materials

2000 - Non-conventional synthesis of praeseodymiun-doped ceria by flux method [Articolo su rivista]
Bondioli, Federica; Corradi, Anna; Manfredini, Tiziano; Leonelli, Cristina; R., Bertoncello
abstract

The synthesis of Ce1-xPrxO2 solid solutions by three different methods (flux method, coprecipitation, and solid-state reactivity) has been investigated to establish optimal preparation conditions. The system studied was chosen because of its thermal and chemical properties and because of its utility as red and orange ceramic pigments. The results obtained showed that the Ce1-xPrxO2 solid solution can be achieved using all three preparation techniques. The three synthesis methodssflux, coprecipitation, and solid-state reactions vary with regard to both the time and temperature used in the heat treatments, and the characteristics of the powders obtained (purity, morphology, granularity). In the preparation of powders by the flux method, the use of molten salts ensures a notable acceleration of the reaction kinetics. We found that the eutectic NaOH-KOH is particularly effective. The samples obtained exhibited a clearly spherical shape together with a considerable fineness. This nonconventional technique thus enables the synthesis of extremely homogeneous compounds that are especially suitable in industrial application such as pigments used in decorative ceramic materials. The solid solutions obtained are, indeed, able to develop an intense red coloring, especially these with a Pr content of 5 mol %.

2000 - Piastrelle ceramiche da rivestimento (EN 159) ottenute con materie prime nazionali macinate a secco. Parte I: aspetti tecnologici. [Articolo su rivista]
Manfredini, T.; Romagnoli, Marcello; Visentin, C.; Visentin, P.; Hanuslova, M.
abstract

L'articolo riporta i risultati piu important! di uno studio per l'ottimizzazione della macinazione a secco di impasti, contenenti esclusivamente materie prime nazionali, da utilizzare nella produzione di piastrelle ceramiche porose da rivestimento (EN 159). I risultati ottenuti dimostrano come sia possibile, mediante cicli di monocottura e bicottura rapida, ottenere prodotti con le proprieta funzionali richieste dalla normative europea vigente.

2000 - Piastrelle ceramiche da rivestimento: caratteristiche ed applicazioni [Articolo su rivista]
Manfredini, Tiziano
abstract

Le pistrelle ceramiche hanno rappresentato da tempo immemorabile e rappresentano tutt'ora, un elemnto insostituibile per il conferimento sia di igienicità che di aspetti artistico-decorativi nell'ambito dell'edilizia sia residenziale che commerciale.

2000 - Preparation of (Fe,Cr)2O3 solid solution as black pigment [Articolo su rivista]
Manfredini, Tiziano; Bondioli, Federica; Romagnoli, Marcello
abstract

in this paper the authors report the optimal synthesis condition to obtain a black ceramic pigment

2000 - Reaction Mechanism in Alumina/Chromia (Al2O3/Cr2O3) Solid Solutions Obtained by Co-Precipitation [Articolo su rivista]
Bondioli, Federica; Ferrari, Anna Maria; Leonelli, Cristina; Manfredini, Tiziano; L., Linati; P., Mustarelli
abstract

The aim of this work is to study the structural characteristics and properties of the solid solution (Al,Cr)(2)O-3. XRD analysis, Al-27 MAS-NMR measurements, and microstructural characterization were used to determine the relationship between color and crystallochemical properties of the compounds formed, In particular, to determine more accurately the mechanism of solid solution formation above the miscibility gap of the system, the marker technique was used. In order to define the behavior of the system for temperatures below the miscibility gap at 1 bar pressure, the composition Al2O3:Cr2O3 1:1 was studied with high-temperature XRD.

2000 - Study of the reactivity of zircon pigments in glass matrix [Relazione in Atti di Convegno]
Bondioli, Federica; Leonelli, Cristina; Manfredini, Tiziano; Wc, Lacourse
abstract

In this paper the authors report the reactivity of 3 different zircon-based pigments in ceramic glaze studied by an optical microscopy.

2000 - The search for new red pigments [Articolo su rivista]
Bondioli, Federica; Manfredini, Tiziano
abstract

In this paper the authors report the application of a ceria-based red pigment to color industrial ceramic material

1999 - Applicazioni della Meccanosintesi nella Produzione di Pigmenti Inorganici Industriali [Articolo su rivista]
Bondioli, Federica; Manfredini, Tiziano
abstract

In questo articolo gli autori riportano la sintesi mediante una tecnologia innovativa quale la meccanosintesi di pigmenti ceramici per uso industriale

1999 - Applicazioni della cromite Naturale nella Colorazione degli Impasti per Grés Porcellanato [Articolo su rivista]
Bondioli, Federica; Manfredini, Tiziano; Romagnoli, Marcello
abstract

In questo articolo gli autori, dopo una caratterizzazione chimica, fisica e mineralogica, valutano l'applicabilità di cromite naturale per la colorazione di materiali ceramici industriali

1999 - Ceramic Oxide (MeO2) Solid Solution Obtained by Mechanical Alloying [Relazione in Atti di Convegno]
Bondioli, Federica; Romagnoli, Marcello; Barbieri, Luisa; Manfredini, Tiziano
abstract

This work has to be regarded as a laboratory study concerning the synthesis and the application as ceramic pigments of powders obtained by mechanochemistry. In ceramic industry pigments, that must show thermal and chemical stability at high temperature and must be inert to the chemical action of the molten glazes, were traditionally obtained by calcination of raw materials. These heat treatment was carried out adding mineralizers (fluorides) to lower the high synthesis temperatures (1200-1400°C). The possibility to obtain them at room temperature and without mineralizers is of great interest: avoiding high calcination temperatures can cause dramatic reduction in toxic gase emission and minimizes high temperature technology investments.

1999 - Design, obtainment and properties of glasses and glass-ceramics from coal fly ash [Articolo su rivista]
Barbieri, Luisa; Lancellotti, Isabella; Manfredini, Tiziano; I., Queralt; J. M., Rincon; M., Romero
abstract

Glasses and glass-ceramics were obtained by mixing up to 50 wt% of Italian or Spanish coal fly ash with other wastes (glass cullet and float dolomite). The behaviour of 10 compositions was investigated by thermal (DTA) and mineralogical (XRD) analysis, microstructural (SEM) characterization, mechanical and chemical measurements. It was verified that the contribution of the alkaline-earth elements in the original composition is fundamental to easily obtain glass-ceramics with a fine microstructure which improves the mechanical properties. Otherwise, with a small addition of Ay ash and without dolomite, very stable glassy materials were obtained that did not exhibit any visible etching either in water or in acid media. Therefore, the combined vitrification/devitrification technique is a suitable methodology for the recycling and exploitation of coal fly ash. (C) 1998 Elsevier Science Ltd. All rights reserved.

1999 - Inorganic pigments for ceramic tiles: Characteristics and industrial applications [Articolo su rivista]
Bondioli, F.; Manfredini, T.; Pellacani, G. C.
abstract

This paper aims at presenting an overview of recent trends in the industrial applications of inorganic pigments in the tile industry. Examples of applications of natural and synthetic inorganic pigments to colour-glazed and unglazed tiles at high temperatures are presented. The most important aspects concerning the physical and chemical properties of pigments, the design of new pigments and application of unconventional synthesis methods are discussed.

1999 - Iron- and calcite-rich ceramic bodies for porous tiles manufacturing by fast double-firing [Articolo su rivista]
Manfredini, Tiziano; Romagnoli, Marcello
abstract

Porous glazed tiles are very important products used for decorative wall coverings. It ¡s possible to obtain porous fast-fired biscuit (35-40 min firing cycle) to produce fast double-fired tiles by using natural ¡ron- and calcite-rich clays, as used in the production of traditional, slow-fired cottoforte (20-30 h firing cycle). Anorthite and diopside are the main crystalline phases developed ¡n fired pressed tiles. A large amount of chlorite and calcite is fundamental to diopside-anorthite formation and to the enhancement of mechanical properties and dimensional stability.

1999 - LASER PARTICLE SIZE ANALYSIS: A TOOL IN DESIGNING TRADITIONAL CERAMIC PROCESSES [Articolo su rivista]
Manfredini, Tiziano; M., Hanuskova; Romagnoli, Marcello
abstract

Simply by using modern analysis techniques based on light scattering, it is possible to check the characteristics of raw materials or semi-finished products, to impose production control in various stages of the process or to intervene to solve production problems.

1999 - Nanosized CeO2 powders obtained by flux method [Articolo su rivista]
Bondioli, Federica; Corradi, Anna; Leonelli, Cristina; Manfredini, Tiziano
abstract

Cerium(IV) oxide (CeO2) powders were prepared by the flux method, adding cerium ammonium nitrate ((NH4)(2)Ce(NO3)(6)) to an eutectic mixture of molten salts, followed by washing and drying. To evaluate the effect of the molten salts on the powders, three different fluxes were used: KOH/NaOH, NaNO3/KNO3, and LiCl/KCl eutectic mixtures. The temperature and the stoichiometry of each reaction were determined by thermogravimetric analysis. Specific surface area analysis (BET), transmission electron microscopy (TEM), and X-ray techniques were used to study the morphology and particle size distribution of the solid products. Results showed the presence, in the reaction products, of homogeneously sized and shaped particles of a single nanosized CeO2 phase. The powder obtained with chlorides out of molten salts had the finer particle size distribution, with a very narrow dimensional range of 20-10

1998 - Characterisation of the surface conductivity of glassy materials by means of impedance spectroscopy measurements [Articolo su rivista]
Fontanesi, C.; Leonelli, C.; Manfredini, T.; Siligardi, C.; Pellacani, G. C.
abstract

Abstract The phenomenon of tin dioxide doping by antimony, Sb(V), atoms in semiconductive glazes is discussed. In particular, the impedance spectra of the glaze surface at room temperature were experimentally determined, and the results were analysed in terms of equivalent circuits. The parameters resulting from the fitting procedure were related to the SnO2/Sb(V) relative content, the SnO2/Sb (V) percentage in the glaze, and the microstructure as observed by SEM. It is proposed that the addition of SnO2 and Sb2O3 to a common glaze for ceramic tile results in a semiconductive continuous phase, whose electrical characteristics fulfil the antistatic floor regulation, as far as surface conductivity is concerned. As a whole the obtained results suggest that the thermal cycle used in fast firing technology is capable to promote the oxidation of Sb2O3 to Sb2O4, resulting in a sufficient amount of Sb(V) capable of generating a semiconductive behaviour of the SnO2 crystalline phase dispersed in the glaze. © 1998 Elsevier Science Limited. All rights reserved.

1998 - Colouring effects of synthetic inorganic cobalt-pigments in fast-fired porcelainized stoneware tiles [Articolo su rivista]
Ferrari, Anna Maria; Leonelli, Cristina; Manfredini, Tiziano; Miselli, P; Monari, G; Pellacani, Gian Carlo
abstract

The paper reports a laboratory and industrial study on the rationalization of using synthetic cobalt oxide, aluminate and silicate pigments (0.5-4.0 wt%) for colouring porcelainized stoneware tiles. The addition of pigments to the base body in amounts up to about 1-2 wt% does not appreciably modify microstructure, nature and amount of phases of the fired tiles; while higher amounts, promoting liquid-phase formation, favour the sintering and can cause swelling of compact samples. On the basis of the results, inorganic cobalt-pigments seem very appropriate to produce coloured porcelainized stoneware tiles, but the better results are obtained by using CoO.AI(2)O(3). By controlling type and amount of pigment, it is possible to tailor different blue shades conferring to the product particularly interesting aesthetic effects.

1998 - Inorganic Pigments: production and industrial applications [Articolo su rivista]
Bondioli, Federica; Manfredini, Tiziano; P. N., Deoliveira
abstract

In this paper the authors report the main characteristic of inorganic pigments used to color industrial ceramic materials

1998 - Kinetic study of conventional solid-state synthesis of BaTiO3 by in situ HT-XRD [Relazione in Atti di Convegno]
Bondioli, Federica; Corradi, Anna; Ferrari, Anna Maria; Manfredini, Tiziano; Pellacani, Gian Carlo
abstract

The reaction path for the solid state synthesis of barium titanate, from barium carbonate and anatase, was first identified. In this work, plots of f(alpha) versus time, where alpha is the reacted fraction, were used to distinguish the reaction mechanisms of BaTiO3 formation by using an KT-XRD (high temperature x-ray diffraction) technique. On the basis of kinetic analysis, an overall process with two distinct regimes was proposed: for the first regime nucleation and growth are the dominant processes, while diffusion controls the second one. The reaction rates of both the processes were also determined.

1998 - LA DIFFRATTOMETRIA A RAGGI X SU POLVERI A TEMPERATURA VARIABILE NELL'INDUSTRIA CERAMICA [Articolo su rivista]
Manfredini, Tiziano
abstract

L'articolo riporta un interessante studio sull'applicazione della diffrattometria a raggi X a temperatura variabile su materiali ceramici.

1998 - Microwave synthesis of Al2O3-Cr2O3(ss) ceramic pigments [Articolo su rivista]
Bondioli, Federica; Corradi, Anna; Ferrari, Anna Maria; Leonelli, Cristina; Siligardi, Cristina; Manfredini, Tiziano; Ng, Evans
abstract

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.

1998 - Pigmenti Inorganici: Progettazione, Produzione ed Applicazioni Industriali [Articolo su rivista]
Bondioli, Federica; Manfredini, Tiziano
abstract

in questo articolo gli autori riportano le principali caratteristiche dei pigmenti inorganici per la colorazione dei materiali ceramici

1998 - Properties of glasses belonging to the Li2O-ZrO2-SiO2 system [Articolo su rivista]
APN de, Oliveira; Leonelli, Cristina; Manfredini, Tiziano; Pellacani, Gian Carlo; G., Ramis; M., Trombetta; G., Busca
abstract

The behaviour and some physical, chemical and thermal properties of Li2O-SiO2 glasses with ZrO2 additions (in the form of ZrSiO4) of up to 13.00 mol% in the as-quenched state were investigated with the aid of x-ray diffraction (XRD), FT-IR spectroscopy, thermal expansion, microhardness and density measurements as well as chemical durability measurements. Transparent glasses prepared by the addition of ZrO2 up to about 11.00 mol% were obtained. For successive addition of ZrO2 and decreasing Li2O/SiO2 ratio, the expansion coefficients revealed decreasing values from 12.60x10(-6) to 8.69x10(-6)degrees C-1. The glass transition and softening point temperatures of the glasses showed a reverse behaviour. By increasing the ZrO2 content in the base glasses the hardness and density values increased. However, while hardness increases even with the decrease of the Li2O/SiO2 ratio the density showed a contrary behaviour, i.e. it increased with the ZrO2 content but decreased when the Li2O/SiO2 ratio decreased, with the highest values of 6.73 GPa and 2.71 g/cm(3), respectively. On the other hand, the chemical durability, in the case of 30Li(2)O.70SiO(2) base glass, decreased with time in water solution and increased with ZrO2 content tending to be almost constant for ZrO2 contents higher than 4.76 mol% at 60 min and 6.98 mol% in the time range from 5 to 30 min, respectively.

1998 - Sintering and crystallization of a glass powder in the Li 2O-ZrO2-SiO2 system [Articolo su rivista]
A. P., Novaes De Oliveira; Manfredini, Tiziano; Barbieri, Luisa; Leonelli, Cristina; Pellacani, Gian Carlo
abstract

Sintering and crystallization of a 23.12 mol% Li2O, 11.10 mol% ZrO2, 65.78 mol% SiO2 glass powder was investigated. By means of thermal shrinkage measurements, sintering was found to start at about 650°C and completed in a very short temperature interval (ΔT ≈ 100°C) in less than 30 min. Crystallization took place just after completion of sintering and was almost complete at about 900°C in 20 min. Secondary porosity prevailed over the primary porosity during the crystallization stage. The glass powder compacts first crystallized into lithium metasilicate (Li2SiO3), which transformed into lithium disilicate (Li2Si2O5), zircon (ZrSiO4), and tridymite (SiO2) after the crystallization process was essentially complete. The microstructure was characterized by fine crystals uniformly distributed and arbitrarily oriented throughout the residual glass phase.

1998 - Syntheses of Fe2O3/silica red inorganic inclusion pigments for ceramic applications [Articolo su rivista]
F., Bondioli; Ferrari, Anna Maria; Leonelli, Cristina; Manfredini, Tiziano
abstract

The work focuses on the syntheses of red inorganic ceramic pigments by inclusion of hematite in a fumed silica matrix. Leaching tests in boiling solutions of concentrated (36 wt%) hydrochloric acid demonstrated that, starting from mixtures of fumed silica and synthetic goethite, the occlusion of hematite occurs by calcination at 1150-1200 degrees C for 2-4 h. Better results were obtained by using fumed silica having surface area ranging from 300 to 400 m(2)/g. A continuos change in colour was measured by comparing L-a-b values of the calcined samples and more information were obtained by the Kubelka-Munk absorption function. Because its chemical and thermal stability, the obtained heteromorphic pigment may be considered a suitable red pigment for ceramic manufacturing by fast firing cycles.

1997 - Chromite as a Pigment for Fast-Fired Porcelain Tiles [Relazione in Atti di Convegno]
Bondioli, Federica; Ferrari, Anna Maria; Leonelli, Cristina; Manfredini, Tiziano
abstract

In this paper the authors report the main characteristic of inorganic pigment used to color industrial ceramic materials

1997 - Conventional and Microwave Preparation of the Al2O3/Cr2O3 (ss) pink pigment [Relazione in Atti di Convegno]
Bondioli, Federica; Ferrari, Anna Maria; Leonelli, Cristina; Siligardi, Cristina; Manfredini, Tiziano
abstract

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]
Barbieri, Luisa; Corradi, Anna; Leonelli, Cristina; Siligardi, Cristina; Manfredini, Tiziano; Pellacani, Gian Carlo
abstract

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]
Ferrari, Anna Maria; Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano; Siligardi, Cristina; Corradi, Anna
abstract

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 - Glass-ceramic as tile glazes [Articolo su rivista]
Barbieri, Luisa; Corradi, Anna; Leonelli, Cristina; Manfredini, Tiziano
abstract

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1997 - Nucleation and crystallization of a lithium aluminosilicate glass [Articolo su rivista]
Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano; Siligardi, Cristina; Corradi, Anna; P., Mustarelli; C., Tomasi
abstract

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; Leonelli, Cristina; Manfredini, Tiziano; Siligardi, Cristina
abstract

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.

1997 - Relationship between microstructure and mechanical properties in fully vitrified stoneware [Articolo su rivista]
Barbieri, Luisa; L., Bonfatti; Ferrari, Anna Maria; Leonelli, Cristina; Manfredini, Tiziano; D., SETTEMBRE BLUNDO
abstract

Fully vitrified stoneware tiles are very important low-porosity products obtained by high-sintering of unglazed ceramic bodies and used for exterior applications and as frost-resistant materials. The dense microstructure of thp fired tiles is characterized by strongly interlocked crystals of quartz and mullite embedded in an amorphous glassy phase. Vickers microhardness (4.94-6.09 GPa), Young's modulus (68.7-73.6 GPa) and abrasion resistance (1.48-1.84 g/30x30 tile) of industrial fully vitrified stoneware tiles were measured and well represent the mechanical properties of the tiles. The microstructure is responsible for the peculiar abrasion resistance and hardness, and correlations among these mechanical properties and microstructure are discussed.

1997 - Vitrification of fly ash from thermal power stations [Articolo su rivista]
Barbieri, Luisa; Manfredini, Tiziano; I., Queralt; Jm, Rincon; M., Romero
abstract

Samples of fly ash from Spanish thermal power plants were vitrified after mixing with other inorganic wastes such as dolomite slag and glass cullet. The relative viscosity and crystallisation behaviour of the glasses obtained were investigated by hot stage microscopy (HSM) and differential thermal analysis, from which reheating schedules were chosen for recrystallisation. X-ray diffraction analysis (XRD) showed that diopside (augite) and/or wollastonite could be crystallised from these glasses, giving rise to dendritic and/or acicular microstructures which were observed and analysed by scanning electron microscopy (SEM/EDX). It was shown that the glass ceramics so obtained had improved mechanical properties compared with the untreated glasses, with Vickers microhardness (H-v) = 5-6.9 GPa, elasticity modulus (E) = 59-101 GPa and toughness (K-1C) = 1.7-1.8 MPa m(1/2) maximum ranges from glass ceramics products showing better properties.

1997 - Zeolititi nazionali nella depurazione di acque reflue e loro successivo utilizzo in impasti ceramici [Articolo su rivista]
Andreola, Nora Maria; Manfredini, Tiziano; Passaglia, Elio; Pellacani, Gian Carlo
abstract

Vengono riportati i risultati di uno studio eseguito con lo scopo di valutare la capacità di una zeolite italiana nella depurazione di una soluzione contenente Pb, Ba e Zn ed il suo successivo utilizzo all'interno di imapsti ceramici per la produzione di piastrelle da pavimentazione.

1996 - Alumina-chopped fibres as reinforcements for glass-ceramic materials [Articolo su rivista]
Leonelli, C.; Manfredini, T.; Pellacani, G. C.; Blundo, D. S.
abstract

The paper reports a preliminary study about alumina short fibres (20 mass-%) and particulate reinforced glass-ceramic matrix composites. The fabrication techniques used are: a) preparation of pellet containing randomly distributed fibres and particulate, by wet mixing, cold pressing and sintering of the dried powders; b) tape casting. The nature of the matrix was investigated in order to obtain good interfacial properties; a new calcium and magnesium aluminosilicate (CMAS) glass ceramic formulation is proposed. The sintering behaviour of composites was studied at different temperatures, ranging from 800 to 1000°C, using scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). The evaluation of linear shrinkage and density was sufficient to define the best sintering conditions, while SEM and XRD indicated the nature of matrix/fibre interface's.

1996 - Coloring effects of synthetic inorganic cobalt pigments in fast-fired porcelainized tiles [Capitolo/Saggio]
Monari, G.; Manfredini, T.
abstract

This paper reports a laboratory and industrial study on the rationalization of using synthetic cobalt oxide, aluminate, and silicate pigments (0.5-4.0 wt%) for coloring porcelainized stoneware tiles. Adding about 1-2 wt% of pigments to the base body does not appreciably modify the microstructure, nature, and amount of phases of the fired tiles, while higher amounts, by promoting liquid phase formation, favor the sintering and can cause swelling of compact samples.

1996 - Densification and properties of CMAS glass-ceramic prepared from compacts of pressed powders and of tape cast powder multilayers [Articolo su rivista]
Leonelli, Cristina; Barbieri, Luisa; Manfredini, Tiziano; D. S., Blundo; Siligardi, Cristina; Corradi, Anna
abstract

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.

1996 - Electrical properties and microstructure of glass-ceramic materials from CaO-MgO-Al2O3-SiO2 system [Articolo su rivista]
Saccani, A; Sandrolini, F; Leonelli, Cristina; Manfredini, Tiziano
abstract

The electrical (volume conductivity) and dielectric (loss factor and dielectric constant) properties of glass-ceramics belonging to the CaO-MgO-Al2O3-SiO2 system have been studied, as a function of microstructure, in their glassy and ceramized forms on samples obtained as bulk materials or sintered powders. A possible application of these materials as substrates for electronic devices can be envisaged, on account of their low conductivities (<10(-14) Scm(-1) up to 250 degrees C), loss factor and permittivity values.

1996 - Gres porcelanico: aplicaciones arquitectonicas, procesado ypropiedades fisico - mecanicas [Porcelainized stoneware: architectural, processing and physico-mechanical properties] [Articolo su rivista]
Romagnoli, Marcello; J. M., Rincon; Manfredini, Tiziano
abstract

Porcelainized stoneware is an extremely hard and homogeneous unglazed ceramic material obtained by fast-firing of kaolinitic ceramic bodies containing a large amount of fluxes. The obtained tiles, available in a large variety of colours, shape size and surface finish, are characterized by very low porosity (&lt;0.3wt% expressed as wafer absorption) and are ideal for heavy-traffic areas subject to mechanical and chemical stresses. Porcelainized stoneware tiles offer alternative valid (and in many cases necessary) solutions to the traditional glazed tiles either for interiors or for exteriors both in modem or classic constructions for flooring and covering.

1996 - Physical properties of quenched glasses in the Li2O-ZrO2-SiO2 system [Articolo su rivista]
AP NOVAES DE, Oliveira; Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano; Pellacani, Gian Carlo
abstract

The behavior and some physical and thermal properties of a 30Li(2)O-70SiO(2) base glass composition with addition of ZrSiO4 in the as quenched state was investigated with the aid of X-ray diffraction (XRD), differential thermal analysis (DTA), thermal expansion and microhardness measurements, as well as density measurements. Transparent glasses prepared by the addition of ZrSiO4 up to 10.30 mol% were obtained, ZrSiO4 was found to decrease the expansion coefficient of the investigated glasses from 11.0 x 10(-6) to 7.96 x 10(-6)degrees C-1. The glass transition and softening point temperatures of the glasses showed a reverse behavior. On the other hand, both hardness and density increased for successive increases of the ZrSiO4 amounts, with the highest values of 6.3 GPa and 2.65 g/cm(3), respectively.

1996 - Quantitative determination of pyrite in, ceramic clay raw materials by DTA [Articolo su rivista]
Corradi, Anna; Leonelli, Cristina; Manfredini, Tiziano; Pennisi, L; Romagnoli, Marcello
abstract

The thermal oxidative decomposition in air of 0-1.5 wt% of pyrite added to two traditional powdered clays was investigated by non-isothermal DTA. It emerged that the first step of the exothermic oxidation of pyrite, in the 350-500 degrees C range, partly overlapped the endothermic dehydroxylation of clay minerals, centred at 590 degrees C, and the result was dependent on the pyrite contents. Based on the values of the area of the oxidative peak and of the corresponding oxidation heat, it is possible to calculate quantitatively the amount of pyrite present in the industrial clay bodies and therefore to inform the technicians of the factories so they can avoid the negative effects of reducing reactions that could occur during firing of ceramic raw materials.

1996 - Technological and product requirements for fast firing glass-ceramic glazes [Relazione in Atti di Convegno]
Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano
abstract

In the ceramic tile industry, the change in firing technology from traditional double firing to the faster single firing process has involved different formulations and compositions of the glazes based on new types of glasses. In consideration of their peculiar physicomechanical and chemical properties, glass-ceramics seem to be suitable for obtaining good floor tile glazes. These innovative materials have enabled the formulation of ceramic glazes to be produced on an industrial scale, and recently some industrial formulations that were based on the classic Li2O-Al2O3-SiO2, CaO-MgO-SiO2, and MgO-Al2O3-SiO2 systems and were compatible with the body properties have found practical application as tile glazes for fast firing technologies. This resulted in finished ceramic floor tile products having enhanced abrasion and wear resistance with improved mechanical properties. Both traditional and innovative firing technologies can be used.

1996 - The effect of the addition of ZrSiO4 on the crystallization of 30Li(2)O/70SiO(2) powdered glass [Articolo su rivista]
A. P., NOVAES DE OLIVEIRA; Corradi, Anna; Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano
abstract

The effects of the addition of ZrSiO4 to 30Li(2)O/70SiO(2) powdered glass on its crystallization behaviour were investigated by means of differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Transparent glasses with a ZrSiO4 content of up to 10.30 mol% were obtained. Li2Si2O5 and/or ZrSiO4, Li2Si2O5 and tridymite were crystallized after appropriate heat treatments. Kinetics parameters for surface crystallization were estimated from the DTA curves. The crystallization was completed in the 590-907 degrees C temperature range for activation energy values between 460.5 and 715.9 kJ mol(-1). The resulting materials are potential candidates for useful sintered glass-ceramics with a wide number of applications.

1995 - Correlazioni fra proprietà microstrutturali e meccaniche nel gres porcellanato [Articolo su rivista]
Barbieri, Luisa; L., Bonfatti; Ferrari, Anna Maria; Leonelli, Cristina; Manfredini, Tiziano; D., SETTEMBRE BLUNDO
abstract

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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
abstract

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; Leonelli, Cristina; Manfredini, Tiziano; G. C., Pellacani; Siligardi, Cristina; C., Svicher
abstract

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 - Glass ceramics belongings to the CaO-SiO2-ZrO2 system as tiles glazes components [Articolo su rivista]
Baldi di, G.; Barbieri, L.; Frassinelli, L.; Generali, E.; Leonelli, C.; Manfredini, T.; Pellacani, G. C.; Siligardi, C.; Svicher, E. C.
abstract

In order to verify the possibility to use new glass ceramic materials as glazes for floor tiles, the devetrification process of a formulation belonging to the wollastonite stability field in the CaO-SiO2-ZrO2 system was investigated by DTA, XRD and SEM techniques. The investigated system shows a high tendency toward crystallisation, that brings to the separation, also at very high heating/cooling speed, of CaO·SiO2 (wollastonite) and 2CaO·ZrO2·4SiO2 (calcium and zirconium silicate) as main crystalline phases. Industrial tests demonstrate how the formulation can be used as prevalent component in the tile glaze preparation.

1995 - La depuracion y el reciclaje de residuos en la industria ceramica de baldosas [Articolo su rivista]
Andreola, Nora Maria; Manfredini, T.; Pellacani, G. C.; Pozzi, Paolo
abstract

Studio dell'utilizzo di residui della depurazione di acque industriali in materiali ceramici

1995 - MgO-CaO-Al2O3-SiO2 glassy and glass-ceramic systems: the effect of substitution of CoO or NiO in place of MgO or CaO [Articolo su rivista]
Barbieri, Luisa; Ferrari, Anna Maria; Leonelli, Cristina; Manfredini, Tiziano; Pellacani, Gian Carlo; S., Bruni; F., Cariati
abstract

Nickel and cobalt were separately incorporated in MgO-CaO-Al2O3-SiO2 glasses Their effect on the crystallisation phenomenon of the amorphous materials into a glass ceramic was investigated by means of thermal analysis and x-ray powder diffraction. These two transition cations decrease the crystal growth of anorthite and diopside and nickel produces forsterite formation. The ionic state and the coordination geometry of Ni and Co ions in the vitreous and the devitrified states have been characterised by means of electronic spectroscopy. Divalent ions were observed for nickel and cobalt in both the glasses and the glass ceramics; in the glasses both Ni2+ and Co2+ are in tetrahedral symmetry, while in glass ceramics the symmetry is predominantly octahedral. Colour changes from glass to glass ceramics correlated well with the cations coordination. The atomic distribution of Ni and Co in the glass ceramics obtained by x-ray fluorescence dispersion spectroscopy complement the information about their coordination environment, the first being present in some crystalline areas and the second being mostly segregated in the residual glass at the grain boundary of crystalline zones.

1995 - Microestructura y propriedades de baldosas de ares porcelanico obtenidas por monococcion rapida de una tipica pasta ceramica caolinitica [Articolo su rivista]
Andreola, Nora Maria; Manfredini, T.; Pellacani, G. C.; Romagnoli, Marcello
abstract

Este estudio tiene como objetivo profundizar el conocimiento de la evoluciòn de la microestructura y correlarlas a las materias primas utilizadas; investigar las reacciones quìmicas entre los componentes presentes en las formulaciones de las pastas usadas para la producciòn de grès porcelànico y en particular los efectos de los materiales caolìniticos en el desarrollo de la microestructura del producto durante la cocciòn.

1995 - Microindentation test as parameter for evaluating the sintering and interface properties of SiC-Whiskers reinforced CMAS glass-ceramic composites [Articolo su rivista]
Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano; Pellacani, Gian Carlo; D., SETTEMBRE BLUNDO; Siligardi, Cristina
abstract

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1995 - PORCELAINIZED STONEWARE TILE [Articolo su rivista]
Manfredini, Tiziano; Pellacani, Gian Carlo; Romagnoli, Marcello; Pennisi, L.
abstract

Dense, low-porosity, small-pore-size tile can be manufactured from kaolin clays at maximum firing temperatures. The unglazed porcelainized stoneware tile can be used for exterior applications and as frost-resistant materials.

1995 - Pigmenti inorganici sintetici contenenti cobalto per la colorazione del gres porcellanato [Articolo su rivista]
Ferrari, Anna Maria; Leonelli, Cristina; Manfredini, Tiziano; Miselli, Paola; Monari, G.; Pellacani, G. C.
abstract

L'articolo riporta uno studio sulla possibilità di utilizzare ossido, alluminato e silicato di cobalto per colorare piastrelle di gres porcellanato. L'aggiunta dei pigmenti all'impasto base ne aumenta il ritiro lineare causando in alcuni casi il rigonfiamento delle piastrelle. Controllando la quantità e il tipo di pigmento è possibile realizzare diverse sfumature di blu e ottenere maggiore brillantezza.

1995 - Recycling of Ceramic wastes to reduce pollution [Articolo su rivista]
Andreola, Nora Maria; Manfredini, Tiziano; Pellacani, Gian Carlo; Pozzi, Paolo; Romagnoli, Marcello
abstract

Exhausted limes and sludges (containing prevalently glass frits and glaze components), are waste substances to be eliminated. Recycling of about 0.10-0.15 wt% of exhausted lime and about 0.50 wt% of glass frits permits their complete elimination without affecting the industrial process. Release tests demonstrate as the firing process acts in the inertization of soluble heavy-metals ions.

1995 - Study of barium feldspar polymorphism as a function of temperature and calcium content [Articolo su rivista]
Barbieri, Luisa; Corradi, Anna; Leonelli, Cristina; Manfredini, Tiziano; Pellacani, Gian Carlo
abstract

A family of new glass-ceramic materials, of the general formula (25-x)CaO.xBaO.yMgO. zAl(2)O(3).5OSiO(2), where x=1, 2, 5, 10, 15, 20, 25, y=20 or 14 and z=5 or 11 (mol%), has been prepared by melting raw materials in two parent glasses and performing heat treatments. The systematic substitution of BaO for CaO in the base glasses allows the effect of feldspars' isomorphism and polymorphism to be studied in a series of glass-ceramics where the structural environment around the bivalent cations, Ca2+ and Ba2+, is systematically altered. Ba2+ has a large effect on the glass transition temperature and dilatometric softening point, causing a decrease with increasing BaO. The crystalline phases have been identified and found to be dependent on the preparation conditions, which are the BaO and Al2O3 contents, the heating rate and the soaking temperature adopted for the crystallization treatments. The infrared spectroscopy technique helped to identify the different polymorphs of barium feldspar, that were not clearly distinguishable by X-ray powder diffractometry due to preferred orientations. The kinetic parameters for the formation of the different crystals have also been determined and correlated with their thermal stability resumed in the well-known time-temperature-transformation curves.

1995 - THE MICROSTRUCTURE AND MECHANICAL-PROPERTIES OF SINTERED CELSIAN AND STRONTIUM-CELSIAN GLASS-CERAMICS [Articolo su rivista]
Barbieri, Luisa; Corradi, Anna; Leonelli, Cristina; Manfredini, Tiziano; Romagnoli, Marcello; Siligardi, Cristina
abstract

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.

1995 - Use of Kaolin in Stoneware Tile [Articolo su rivista]
Manfredini, T.; Pellacani, Gc; Romagnoli, Marcello; Pennisi, L.
abstract

Dense, low porosity, small-pore size tile can be manifactured from Kaolin clays at maximum firing temperature. The unglased porcelainised stoneware tile can be used for exterior application and as frost resistant materials.

1994 - CONCENTRATED GLAZE SUSPENSIONS [Articolo su rivista]
Andreola, Nora Maria; Corradi, Anna; Manfredini, Tiziano; Pellacani, Gian Carlo; Pozzi, Paolo
abstract

The effect of grinding time, solid slip content, kaolin plasticizer and Ca2+ flocculating agent on the rheological behavior of a typical industrial frit used in glazes for monoporosa wall tile are described.

1994 - Deflocculation of concentrated aqueous clay suspensions with sodium polymethacrylates [Articolo su rivista]
Corradi, Anna; Manfredini, Tiziano; Pellacani, Gian Carlo; Pozzi, Paolo
abstract

The ability of sodium polymethacrylate salts with various molecular weights (1200 to 30000 g.mol(-1)) to deflocculate concentrated aqueous suspensions (58 wt%) of two clays, widely used for stoneware ceramic tile production, was investigated. Rheological measurements were made in distilled water or in water containing calcium ions (O to 6 x 10(-3) mol.dm(-3)) to evaluate the practical applications of these salts as deffocculants in the ceramic tile industry. All slips presented a non-Newtonian behavior. Polymethacrylates with low molecular weights were the most efficient deflocculants for clay suspensions. The salts acted by an essentially electrosteric stabilization mechanism, in combination with a high sequestering ability toward flocculating cations. For their efficient deflocculating capabilities toward concentrated aqueous clay suspensions, sodium(I) polymethacrylates may be considered for practical industrial application, in particular for the preparation of liquid deflocculants.

1994 - Evolution of ruthenate-based thick-film cermet resistors [Articolo su rivista]
Morten, Bruno; Masoero, A.; Prudenziati, Maria; Manfredini, Tiziano
abstract

An experimental investigation has been carried out to study variations of microstructure, composition., and electrical properties (sheet resistance and its temp. coefficient) occurring in thick-film (cermet) resistors during the annealing process which transforms the initial ink into a resistive layer. Resistors based on Bi2Ru2O7 and a lead silica glass have been studied. Analyses have been performed on the inks using thermogravimetric measurements, and on annealed (fired) layers by means of x-ray diffraction, atomic absorption, electron microscopy, microprobe analysis, and other complementary techniques. The results point out the role of exchange reactions and redox reactions inside the resistor body and emphasize the complexity of the phenomena which concur to define the final elecrical properties of these resistive systems. Interrelations between microstructure, composition , and elecrical properties have been found and tentative explanations proposed.

1994 - Influence of mica coating on interfacial debonding of a SiC fibers reinforced glass-ceramic [Articolo su rivista]
Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano; Pellacani, Gian Carlo; D., SETTEMBRE BLUNDO; S., Meriani; O., Sbaizero
abstract

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1994 - Influenza del rivestimento di mica su fibre SiC sul distacco interfacciale in vetroceramici compositi [Articolo su rivista]
Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano; Pellacani, Gian Carlo; D., SETTEMBRE BLUNDO; S., Meriani; O., Sbaizero
abstract

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1994 - Preparazione di un pigmento ceramico nero per calcinazione di miscele di ossidi o di polveri ottenute per co-precipitazione [Articolo su rivista]
Ferrari, Anna Maria; Manfredini, Tiziano; Monari, G.; Pellacani, Gian Carlo; Siligardi, Cristina
abstract

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 - Rheological behaviour of aqueous concentrated suspensions of an Italian zeolite [Articolo su rivista]
Andreola, Nora Maria; Manfredini, T.; Pellacani, G. C.; Pozzi, Paolo; Romagnoli, Marcello
abstract

The paper reports a laboratory study on the rheological behaviour of concentrated aqueous suspensions of zeolitite, belonging to the geological formations of «tufo giallo napoletano» in the Phlegraean Fields (Campania). Rheological measurement performed by means of a rotational viscometer demonstrated how the suspensions show a practically newtonian behaviour up to about 40 wtOfo of solid content in absence of deflocculants and up to about SO wtOfo of solid content in presence of Na-SIL and Na-TPP detlocculants. At higher solid concentrations they assume a non-newtonian behaviour. Na-TPP shows a greater deflocculating ability toward zeolite suspensions than Na-SIL. This may be explained by considering, in particular, its sequestering action towards the flocculating ions.

1994 - SINTERING BEHAVIOR OF TAPE-CAST CMAS GLASS-CERAMIC REINFORCED WITH ALUMINA CHOPPED FIBERS [Articolo su rivista]
Leonelli, Cristina; Manfredini, Tiziano; Pellacani, Gian Carlo; Blundo, Ds
abstract

The sintering behaviour of CMA S glass-ceramic and CMAS glass-ceramic/alumina chopped fibre (20 wt%) composites was studied at different temperatures, ranging. from 800 to 1000-degrees-C, using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and porosimetry investigations. The evaluation of linear shrinkage, density and porosity were sufficient to define the best sintering conditions, while SEM and XRD allowed the nature of the matrix/fibre interface to be studied.

1994 - STRUCTURAL, THERMAL, AND ELECTRICAL CHARACTERIZATION OF BIS(ETHYLETHYLENE)DIAMMONIUM DICHLORIDE TETRACHLOROCADMATE(II) WITH PEROVSKITE-LIKE STRUCTURE [Articolo su rivista]
Corradi, Anna; Cramarossa, Mr; Manfredini, Tiziano; Giusti, J; Battaglia, Lp; Saccani, A; Sandrolini, F.
abstract

The synthesis, thermal and electrical characterization of a chlorocadmate(II) system with perovskite-like structure of formula (etenH-2)2[CdCl4].Cl2 (etenH-2 = ethylethylenediamine dication) are described. The compound crystallizes in space group P2(1)/c. The unit-cell dimensions are a = 19.214(1) angstrom, b = 7.301(1) angstrom, c = 7.227(3) angstrom, beta = 100.23(1)-degrees, V = 997.7(4) angstrom3, Z = 2. The final R value is 0.0486 (R(w) = 0.0497). The crystal structure consists of inorganic layers of (CdCl6) corner-sharing octahedra, organic dications intercalated between them and uncoordinated chloride ions. Only one end of the organic dications interact via hydrogen bonds with the inorganic layers, with the second end involved in hydrogen bonds with the free chloride ions. Furthermore a network of hydrogen bond interactions among the inorganic layers, the organic dications, and the uncoordinated chlorine atoms contribute to the crystal packing. The compound, thermally stable up to the melting point, behaves as an electrical insulator at low temperatures, approaching semiconductor values at higher ones.

1994 - Solubility, reactivity and nucleation effect of Cr2O3 in the CaO-MgO-Al2O3-SiO2 glassy system [Articolo su rivista]
Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano; Pellacani, Gian Carlo; Siligardi, Cristina; E., Tondello; R., Bertoncello
abstract

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]
Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano; Siligardi, Cristina
abstract

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1994 - Utilization of an Italian zeolitite in ceramic bodies [Articolo su rivista]
Andreola, Nora Maria; Manfredini, Tiziano; Passaglia, Elio; Pellacani, Gian Carlo; Pozzi, Paolo; Romagnoli, Marcello
abstract

UTILIZATION OF ITALIAN ZEOLITITE IN CERAMIC BODIESThe papers reports a laboratory and industrial study on the possibility of using an Italian natural zeolitite, both in natural and Pb-; Ba- exchanged form, in a tile ceramic body. Because of their exchangeable cation contents (Na+, K+; Ca+2, Ba+2, Pb+2), natural and exchanged zeolitites can be added (up to 20 and 5wt%, respectively) in a ceramic body, thus favouring its sinterability and unaffecting the crystalline phase formation and the final products characteristics. The addition of higher amounts enhaces the swelling of the tiles during firing and strongly modifies the features of the fired tiles. Release tests in acetic and nitric acid solutions on unfired and fired tiles containing exchanged zeolitites demostrated the inertization of lecheable Pb+2 during firing.

1994 - Vetroceramici appartenenti al sistema CaO-SiO2-ZrO2 come componenti di smalti per piastrelle [Articolo su rivista]
G., Baldi; Barbieri, Luisa; L., Frassinelli; E., Generali; Leonelli, Cristina; Manfredini, Tiziano; Pellacani, Gian Carlo; Siligardi, Cristina; C., Svicher
abstract

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1993 - Addition of exhausted lime in ceramic bodies: possibilities for an environmentally compatible tile production [Articolo su rivista]
Andreola, Nora Maria; L., Bonfatti; Manfredini, Tiziano; Pellacani, Gian Carlo; Pozzi, Paolo; Romagnoli, Marcello
abstract

Pollution caused by inorganic wastes in the traditional ceramics industry is minimised by utilising exhausted limes, which are the byproducts in bag filters after the purification of flue gases in wet tile production. This study determined which quantities of exhausted lime added to tile bodies did not significantly affect the physico-chemical properties of the slips (i.e. density /viscosity/deflocculant amount) during wet grinding in ball mills. The results demonstrated that these conditions are obtained when exhausted lime in the bodies does not exceed 0.10 to 0.12 mass%. Furthermore, any increase in fluorine emission in the firing of tiles with exhausted lime can be trapped in the bag filters by increasing the lime content by about 10 mass%. The laboratory and industrial results are also compared.

1993 - Addition of exhausted lime in ceramic bodies: possibilities for an environmentally compatible tile production III: Industrial Results [Articolo su rivista]
Andreola, Nora Maria; Bonfatti, L.; Manfredini, T.; Pellacani, G. C.; Pozzi, Paolo; Romagnoli, Marcello
abstract

study uses exhausted lime in ceramic

1993 - Additions and Corrections: Structural and Spectroscopic Correlations in Cadmium(II) Halide Complexes of 2,2-Dimethylpropane-1,3-diamine: (Inorg. Chem. (1992) (31)8, (1401–1406) (10.1021/ic00034a020)) [Articolo su rivista]
Masciocchi, N.; Moret, M.; Sironi, A.; Bruni, S.; Cariati, F.; Pozzi, A.; Manfredini, T.; Menabue, L.; Pellacani, G. C.
abstract

Page 1401. The space group for compound 1, Cd(dmpd)2l2 (dmpd = 2,2-dimethylpropane-1,3-diamine), has been misprinted, both in the Abstract and in Table I, as P21/c (No. 14). The correct space group should read as P21 (No. 4), to which all reported computations and geometrical parameters correctly refer. © 1993, American Chemical Society. All rights reserved.

1993 - Caratterizzazione delle proprietà meccaniche di materiali ceramici e vetrosi sottoposti a prove di durezza Vickers e Knoop. 1a parte: Approccio teorico [Articolo su rivista]
Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano; D., SETTEMBRE BLUNDO
abstract

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1993 - Colouring inorganic oxides in MgO-CaO-Al2O3-SiO2 glass-ceramic systems [Articolo su rivista]
Barbieri, Luisa; C. L., Bianchi; S., Bruni; F., Cariati; Leonelli, Cristina; Manfredini, Tiziano; M., Paganelli; Pellacani, Gian Carlo; U., Russo
abstract

Glasses in the system MgO-CaO-Al2O3-SiO2, in which CuO, Fe2O3 and MnO were substituted for CaO, were prepared and crystallized in absence of nucleating agents. Surface nucleation dominated for all compositions, and was followed by growth of only anorthite and diopside. The relative amount of each crystal was influenced by the chemical composition and the nature of the transition metal cation. Cu and Mn segregated at the grain boundary during crystallization and Fe did not. Changes in the coordination symmetry and oxidation states of the transition metal ions in the glassy and glass-ceramic phases are as follows: Cu(II) is sixfold coordinated with regularly octahedral symmetry in glass and distorted in glass-ceramic, while the ratio Cu(II)/Cu(I) is decreased from 5 to 2 during crystallization. Fe(III) is fourfold coordinated with a symmetry C2v and Fe(II) is present, more in the glass-ceramic than in the glass, with an octahedral symmetry. Mn(II) is in cubic site symmetry with a rhombic distortion, more visible in the glass; Mn(III) is sixfold coordinated with octahedral symmetry in a constant ratio (Mn(III): Mn(II) is 2:1) during crystallization.

1993 - Determinazione della microdurezza Vickers e Knoop di materiali ceramici smaltati e tipo gres porcellanato. 2a parte [Articolo su rivista]
Barbieri, Luisa; Ferrari, Anna Maria; Leonelli, Cristina; Manfredini, Tiziano; D., SETTEMBRE BLUNDO
abstract

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1993 - EFFECT OF FORMING PRESSURE ON THE REACTIVITY AND MICROSTRUCTURE OF ZIRCON POWDER COMPACTS [Articolo su rivista]
Corradi, Anna; Leonelli, Cristina; Manfredini, Tiziano; Siligardi, Cristina
abstract

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 - Fiber, whisker and particulate reinforced new glass-ceramic matrix for innovative composites [Articolo su rivista]
Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano; Pellacani, Gian Carlo; D., SETTEMBRE BLUNDO
abstract

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1993 - INFLUENCE OF VISCOSITY ON THE CRYSTALLIZATION OF SOME ANORTHITE DIOPSIDE GLASS PRECURSORS [Articolo su rivista]
Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano; Siligardi, Cristina
abstract

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1993 - Non-isothermal kinetic equations applied to crystallization of glasses [Articolo su rivista]
Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano; Romagnoli, Marcello; Pellacani, Gian Carlo; Siligardi, Cristina
abstract

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1993 - Preparation end properties of fast-fired porcelain tiles containing natural chromite [Articolo su rivista]
Corradi, Anna; Leonelli, Cristina; Manfredini, Tiziano; Pozzi, Paolo; Romagnoli, Marcello
abstract

Natural magnesium iron chromite can be used as a pigment for coloring high-sintered porcelain tiles. However, it is important to control the amount, firing time and temperature, and size distribution of the chromite powders to produce different color shades of the fired tiles from gray to black.

1993 - Recycling of ceramic wastes in tile bodies to reduce pollution [Articolo su rivista]
Andreola, Nora Maria; Manfredini, Tiziano; Pellacani, Gian Carlo; Pozzi, Paolo; Romagnoli, Marcello
abstract

During recent years, special attention has been devoted both to solving pollution problems during the manufacturing of ceramics and to learning how ceramics can themselves be a solution. Waste encapsulation opportunities for structural clay products have been studied. These opportunities affect environmental isolation within the semivitreous matrix of the product and remove and destroy volatile organic components of the waste and recrystallized incinerator slags and encapsulant for such heavy metals as lead. To reduce hazards to workers and community and to realize a safe environment, some manufacturers have planned for a production process that recycles wastes. This plan represents the best option to reduce or minimize pollution by permitting the complete elimination of wastes and thus avoiding their very expensive storage in appropriate dumps. Studies have been performed to evaluate the effects of the presence of exhausted lime and sludges in tile bodies and to obtain information for the rationalization of the recycling process. The focus has been on the evaluation of the effects of the presence of wastes on the rheological and thermal behavior of the tile bodies. In addition, the efficiency of the firing process on the wastes and heavy-metals inertization has been determined by release tests of the fired products in different acidic media.

1993 - Reuse of waste lime in a ceramic body that generated it. [Articolo su rivista]
Andreola, Nora Maria; Manfredini, T.; Romagnoli, Marcello
abstract

Results are presented from studies of the effect of addns. of waste lime on the rheol. behavior of tile-body slips, the dilatometric behavior of tile bodies, water absorption and shrinkage of fired tiles, and the tile microstructure development during firing. A <0.1 wt.% addn. of waste lime had negligible effect on the apparent viscosity of slips, and an .apprx.0.5 wt.% addn. did not product significant changes in the microstructure. Control of F emissions due to recycling of the CaF2-contg. waste lime is discussed.

1993 - Rheology of a Low-Plastic Ceramic Body Containing Na-Bentonite. [Relazione in Atti di Convegno]
FERNANDA ANDREOLA, N. M.; Manfredini, T.; Pellacani, G. C.; Pozzi, Paolo; Romagnoli, Marcello
abstract

This paper reports the results of a study on the rheological behavior of slips prepared using a low-plastic body with 0-4 wt% of alkali-activated bentonite added as strengthening agent. The presence of bentonite increases the plasticity of the slips and their viscosity and thixotropy, and addition of bentonite to about2 wt% does not greatly affect the rheological conditions that regulate the industrial steps. Higher percentages of bentonite strongly modify the rheology of the slips, and in order for them to be workable, it is necessary to reduce the solid content and/or amounts of deflocculant greater than 0.5 wt%.

1993 - SYNTHESIS AND CHARACTERIZATION OF ONE-DIMENSIONAL POLYMERIC CHLOROCADMATE(II) SYSTEMS [Articolo su rivista]
Corradi, Anna; Bruckner, S; Cramarossa, Mr; Manfredini, Tiziano; Menabue, Ledi; Saladini, Monica; Saccani, A; Sandrolini, F; Giusti, J.
abstract

In this paper we report the synthesis and the structural, thermal, electrical properties of 1-D polymeric chlorocadmates(II), having N-methylpropane-1,3-diammonium (mepnH2) and NN-diethylpropane-1,3-diammonium (et2pnH-2) as countercations. The (mepnH2)2[Cd3CI10] crystallizes in space group P2(1)/c. The unit cell dimensions are a = 10.164 (3) angstrom, b = 13.434 (10) angstrom, c = 10.099 (3) angstrom, beta = 112.04 (3)-degrees, V = 1278 (i) angstrom3, z = 2. The final R value for 2124 reflections (I > 2sigma(I)) is 0.0445 (R(w) = 0.0384). Its structure consists of N-methylpropane-1,3-diamine dications and infinite chains of [(Cd3Cl10)n4n-]n moieties forming 1-D polymer running along the x axis. The (et2pnH2)2[Cd5Cl14].2H2O crystallizes in space group P1BAR. The unit cell dimensions are a = 6.874 (1) angstrom, b = 10.381 (1) angstrom, c = 14.572 (i) angstrom, a = 100.14 (1)-degrees, beta = 99.31 (1)-degrees, gamma = 97.46 (1)-degrees, V = 996.7 (2) angstrom3, Z = 1. The final R value for 3405 reflections (I > 2sigma(I)) is 0.0452 (R(w) = 0.0393). Its structure consists of N,N-diethylpropane-1,3-diamine dications, infinite alternate stacked pseudoplanar trinuclear [Cd3Cl8]2- and dinuclear [Cd2Cl6]2- dianions and uncoordinated water molecules. Both the packings are strengthened by N-H ... Cl hydrogen bonds between anions and cations. A first-order phase transition of (mepnH2)2[Cd3CI10] has been identified by DSC measurements and X-ray powder diffraction, related to the disordering of the hydrocarbon chains at high temperature. This increases the cell volume. The electrical conductivity of the compounds can be envisaged as protonic, and the whole electrical behavior can be correlated to their structures and phase transition.

1993 - Synthesis and structural, thermal and electrical properties of piperazinium lodocuprates(I) [Articolo su rivista]
Corradi, A. B.; Cramarossa, M. R.; Manfredini, T.; Battaglia, L. P.; Pelosi, G.; Saccani, A.; Sandrolini, F.
abstract

The iodocuprate(I) systems [H-2pipz]2[Cu2I6].H2O 1 and [H-2pipz] [Cu2I4] 2 (L = pipz = piperazine) have been prepared and their structural, thermal and electrical properties investigated. Compound 1 is monoclinic, space group P2(1)/n, a = 8.609(3), b = 20.072(4), c = 13.763(4) angstrom, beta = 101.3(l)-degrees, Z = 4, R = 0.050. The crystal structure consists of organic cations, unco-ordinated water molecules and dimeric [Cu2I6]- anions composed of two CuI4 tetrahedra sharing a common edge. Hydrogen bonds between organic counter cations and water molecules are present. Compound 2 is triclinic, space group P1BAR, a = 7.559(3), b = 7.465(3), c = 6.826(3) angstrom, alpha = 68.1 (1 ), beta = 69.1 (1 ), gamma = 89.4(l)-degrees, Z = 1, R = 0.050. The crystal structure consists of organic dications and infinite chains of [CuI2]- units forming a one-dimensional polymer running along the [001] axis. The chains are composed of edge-sharing CuI4 tetrahedra. Hydrogen-bond interactions between organic counter cations and inorganic chains are present and contribute to the crystal packing. Differential scanning calorimetry measurements did not show the presence of any structural phase transitions. Electrical measurements revealed an essentially ionic mechanism of conduction, especially at high temperature, protons involved in the hydrogen bonds being the charge carriers.

1992 - Addition of exhausted lime in ceramic bodies:possibilities for an environmentally compatible tile production II:thermal behaviour of bodies [Articolo su rivista]
Andreola, Nora Maria; Bonfatti, L.; Manfredini, T.; Pellacani, G. C.; Pozzi, Paolo
abstract

study uses exhausted lime in ceramic

1992 - Kinetic study of surface nucleated MgO-CaO-Al2O3-SiO2 glasses [Articolo su rivista]
Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano; M., Paganelli; Pellacani, Gian Carlo
abstract

The paper investigated, by means of thermal analysis measurements. the validity of three different methods for the evaluation of the activation energy of crystallization for surface nucleated glasses belonging to the MgO-CaO-Al2O3-SiO2 system, separating anorthite and diopside crystals. The values obtained from Kissinger equation of the activation energy for crystallization are comparable with those obtained by other authors for similar glassy systems, 90 to 150 kcal/mol. The results of the kinetic analysis using single-crystallization-peak method should be corrected taking into account the dimensionality of crystal growth.

1992 - Microstructure and thermal properties in the RO-MgO-Al2O3-SiO2 (R=Ca, Sr, Ba, Zn) glass-ceramic systems [Articolo su rivista]
Barbieri, Luisa; Leonelli, Cristina; Manfredini, Tiziano; M., Paganelli; Pellacani, Gian Carlo
abstract

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1992 - Reactivity of CaF2 Toward Components of Ceramic Bodies. [Relazione in Atti di Convegno]
Andreola, Nora Maria; Manfredini, Tiziano; Pellacani, Gian Carlo; Romagnoli, Marcello
abstract

The production of ceramic tiles results in the expulsion of many wastes. One of the waste substances which could be eliminated from the tile-making process is the exhausted lime which contains calcium fluoride as the main component. The maximum amount of exhausted lime which can be recycled without modifying the properties of the tiles is determined. The effects of the calcium fluoride on the microstructure of the tiles is investigated. It is discovered that addition of CaF2 greater than 0.5-1.0 wt% results in a strongly modified microstructure. Anorthite is produced at the expense of mullite leading to swelling of the tiles at the industrial firing temperatures.

1992 - STRUCTURAL AND SPECTROSCOPIC CORRELATIONS IN CADMIUM(II) HALIDE-COMPLEXES OF 2,2-DIMETHYLPROPANE-1,3-DIAMINE [Articolo su rivista]
Masciocchi, N; Moret, M; Sironi, A; Bruni, S; Cariati, F; Pozzi, Paolo; Manfredini, Tiziano; Menabue, Ledi; Pellacani, Gian Carlo
abstract

Compounds of formula Cd(dmpd)2X2 (dmpd = 2,2-dimethylpropane-1,3-diamine; X = Cl, Br, I) were prepared and investigated by means of structural and spectroscopic (IR and Raman) measurements. The Cd(dmpd)2I2 compound crystallizes in the monoclinic P2(1)/c space group, with two formula units in a cell of dimensions a = 6.235 (5) angstrom, b = 18.462 (9) angstrom, c = 8.294 (5) angstrom, and beta = 93.37 (6)-degrees, with R = 0.039 and R(w) = 0.044. The structure consist of discrete [Cd(dmpd)2I2] monomeric units, where the Cd atom is surrounded by four nitrogen atoms of two in-plane chelating dmpd molecules and by two iodine atoms asymmetrically coordinated axial positions. The Cd(dmpd)2Br2 compound crystallizes in the triclinic P1BAR space group, with Z = 3 and a cell of dimensions a = 12.713 (2) angstrom, b = 16.592 (2) angstrom, c = 6.281 (3) angstrom, alpha = 91.22 (2)-degrees, beta = 96.67 (2)-degrees, and gamma = 78.72 (3)-degrees, with R = 0.031 and R(w) = 0.036. The structure consists of 1:1 molecular packing of Cd(dmpd)2Br2 monomeric and [Cd(dmpd)2Br2]2 dimeric units. In the monomer the Cd atom is octahedrally coordinated by four in-plane nitrogen atoms of two chelating dmpd molecules and by two bromine atoms in axial positions. The dimer consists of a pair of octahedrally coordinated Cd atoms, related by an inversion center, connected in a 12-membered metallacycle by two ambidentate dmpd molecules. The octahedral arrangement each Cd atom in the dimer is completed by an in-plane chelating dmpd and by two bromine atoms, axially coordinated. The Cd(dmpd)2Cl2 compound is isomorphous with the bromide derivative, with unit cell dimensions a = 12.714 (3) angstrom, b = 16.228 (3) angstrom, c = 6.087 (5) angstrom, alpha = 91.61 (3)-degrees, beta = 96.02 (3)-degrees, and gamma = 77.76 (4)-degrees. The CdN stretching vibrations are discussed and assigned in the light of the known structures.

1992 - SYNTHESIS AND CHARACTERIZATION OF LAYERED CHLOROCADMATES(II) WITH PEROVSKITE-LIKE STRUCTURES [Articolo su rivista]
Battaglia, Lp; Corradi, Anna; Pelosi, G; Cramarossa, Mr; Manfredini, Tiziano; Pellacani, Gian Carlo; Motori, A; Saccani, A; Sandrolini, F; Brigatti, Maria Franca
abstract

The synthesis and the structural, thermal, and electrical characterization of tetrachlorocadmate(II) systems, with perovskite-like structures, are described. The countercations are diprotonated amines, such as the ethylenediamine and propane-1,3-diamine dications. The structural model of the compounds consists of layers extending to the ab plane of CdCl6 corner sharing octahedra. The holes between these layers are occupied by alkylammonium ions stabilizing the structure through hydrogen bonding. Thermal analysis shows the presence of a first-order phase transition in the propane-1,3-diammonium compound, related to the disordering of the hydrocarbon chains at high temperatures which causes a decrease in the c parameter and minor differences in the a and b parameters. The electrical conductivity of the investigated compounds is apparenly protonic and seems to increase as the distance between the layers containing the inorganic chains increases.

1992 - addition of exhausted lime in ceramic bodies: possibilities for an environmentally compatible tile production I: rheological of slips [Articolo su rivista]
Andreola, Nora Maria; Bonfatti, L.; Manfredini, T.; Pellacani, G. C.; Pozzi, Paolo
abstract

study of the rheology of ceramic suspension with recicling material presence

1991 - CRYSTALLIZATION OF SOME ANORTHITE DIOPSIDE GLASS PRECURSORS [Articolo su rivista]
Leonelli, Cristina; Manfredini, Tiziano; Paganelli, M; Pozzi, Paolo; Pellacani, Gian Carlo
abstract

Anorthite and diopside have been obtained from complete devitrification of glasses belonging to the quaternary system MgO-CaO-Al2O3-SiO2. Microstructure, the natural trend of the nucleation mechanism and kinetic studies on the crystallization phenomenon have been investigated by means of optical and electron microscopies, thermal and thermomechanical techniques and X-ray powder diffractometry. All the glasses investigated show a complete crystallization starting from a simple surface nucleation process. The activation energy for the crystallization process proved to be higher than that for viscous flow, leading to an important aspect modification in the sample during ceramization. Thermal stability and physical properties of both glass and glass-ceramic materials have been tested, suggesting the possible use of these materials in industrial application.

1991 - Coordinative capability of propane-1,3-diamine: spectroscopic and structural properties of a complex of formula [Cd(pnH)4Cl2]Cl4 [Articolo su rivista]
G., Ciani; N., Masciocchi; A., Sironi; S., Bruni; F., Cariati; A., Pozzi; Forti, Luca; Manfredini, Tiziano; Menabue, Ledi
abstract

The compound [Cd(pnH)4Cl2]Cl4 (pn = propane-1,3-diamine) has been prepared and studied by means of spectroscopic (IR and Raman) and structural investigations. It crystallizes in the tetragonal P4nc space group (No. 104), with two formula units in a cell of dimensions: a = b = 11.972(4), c = 9.129(4) angstrom. The structure consists of an ionic packing of chlorine anions and of discrete [Cd(pnH)4Cl2]4+ cations; the Cd atoms are octahedrally coordinated to four nitrogen atoms of four distinct monoprotonated diamines and to two chlorine atoms in trans position to each other, showing very loose Cd-Cl bonding interactions (2.680(3) and 2.884(2) angstrom). The protonated ends of the propane-1,3-diamines interact with the non-coordinated chlorine ions via hydrogen bonding. The Cd-N and Cd-X stretching vibrations are discussed and assigned in the light of the known structures.

1991 - DISCONTINUOUS WET-GRINDING OF RAW-MATERIALS IN THE PRODUCTION OF TRADITIONAL CERAMIC TILES [Articolo su rivista]
Manfredini, Tiziano; Pellacani, Gian Carlo; Pozzi, Paolo; Corradi, Anna
abstract

The paper reports a laboratory and semi-industrial study on the discontinuous wet-grinding raw-material process which is widely used in the ceramic tile industry for body preparations. It focuses on the importance of controlling the rheology and particle size distribution of the aqueous suspensions and the mineralogical characteristics and amounts of the grinding residues of three raw materials-two clays (named Badia and Riola), and one sand-and of their 1/1/1 mix, generally used in factories for the production of porous, single-fired ceramic wall tiles. The apparent viscosities of the electrostatically deflocculated slips strongly depend on the grinding times. The highest solids content of the slips, enabling a good industrial workability, is about 55 to 57 wt% for both the clays, 70 to 72 wt% for the sand, and 60 to 62 wt% and 66 wt% for the mix (body) examined in the laboratory and semi-industrial experiments, respectively In all the samples, the weighted grinding residues on the 45-mu-m sieves, formed of the hard unclayey materials. decrease with increasing grinding times, attaining practically constant values at about 20 and 150 min, respectively, in the laboratory and semi-industrial experiments. The optimum apparent viscosity values, which enable the best grinding action on a ceramic body in a drum ball mill, are greater than those required for moving the final slip to the spray dryer. The results suggest that the grinding action is exerted only on the nonplastic materials. Therefore, the individual grinding of the raw materials forming the ceramic body is strongly indicated for optimization of the wet-grinding process. Other useful hints for the rationalization of the wet-grinding process, which may contribute to increasing production, lowering costs, and improving quality, are suggested.

1991 - LI2O-SIO2-AL2O3-MEIIO GLASS-CERAMIC SYSTEMS FOR TILE GLAZE APPLICATIONS [Articolo su rivista]
Leonelli, Cristina; Manfredini, Tiziano; Paganelli, M.; Pellacani, Gian Carlo; Albaro, J. L. A.; Navarro, J. E. E.; Orts, M. J.; Bruni, S.; Cariati, F.
abstract

In order to verify the possibility of using glass-ceramic materials as tile coatings, the devitrification processes of three industrial formulations belonging to the Li2O-Al2O3-SiO2 glass-ceramic system were investigated by differential thermal analysis, X-ray diffractometry, scanning electron microscopy, and IR spectroscopy. Compositional variations were made by addition of large amounts of MgO or CaO or PbO (ZnO) oxides as well as through smaller additions of other oxides. In these systems the surface crystallization contributes appreciably to the bulk crystallization mechanism. All the systems investigated show a high tendency toward crystallization even at very high heating rates, developing a very close network of interlocked crystals of synthetic beta-spodumene-silica solid solutions (LiAlSi4O10). The results of this research are expected to establish the conditions under which these glass-ceramic systems can be practically used as tile glazes.

1991 - ORTHORHOMBIC TO TETRAGONAL PHASE-TRANSITION IN YBA2CU3O7-X OBSERVED BY DYNAMIC YOUNGS MODULUS MEASUREMENTS [Articolo su rivista]
Bonetti, E; Campari, Eg; Manfredini, Tiziano; Mantovani, S.
abstract

Dynamic Young's modulus measurements, have been performed by the vibrating reed technique (10(2)-10(4) Hz) on polycrystalline YBa2Cu3O7-x samples in the temperature range 300-900 K. A strong modulus softening, indicative of a phase transition, is measured at about x = 0.45. DTG measurements versus temperature show in correspondence a maximum in the oxygen desorption rate. Long time modulus isotherms display an exponential trend linked to a thermally activated structural process with activation energy H = 0.9 +/- 0.1 eV. On the basis of the experimental results a model for the structural transformation linked to the twinned interfaces mobility and to oxygen diffusion is presented and discussed.

1991 - SPECTRAL, MAGNETIC AND THERMAL STUDIES ON HALOCOBALTATES(II) OF THE 2-THIO-DIMETHYLPYRIMIDINIUM CATION [Articolo su rivista]
Battistuzzi, R; Manfredini, Tiziano
abstract

Some halocobaltate(II) complexes of the 2-thio-4,6-dimethyl-pyrimidinium cation were prepared and characterized by elemental and thermal analyses, molar conductivity, magnetic measurements and electronic and i.r. spectroscopy. The visible solid state spectra and magnetic moments show that the cobalt(II) has a tetrahedral stereochemistry in all the compounds. On the basis of the thermogravimetric (TG, DTG) results the probable decomposition sequences of thermal dissociation of the complexes in nitrogen atmosphere are proposed.

1991 - THE RECYCLING OF CERAMIC SLUDGES IN THE PRODUCTION PROCESS - AN OPTION FOR CERAMIC TILE FACTORIES TO REACH ZERO POLLUTION [Articolo su rivista]
Manfredini, Tiziano; Marzola, G; Nunziello, S; Pellacani, Gian Carlo; Pozzi, Paolo; Tubertini, O.
abstract

The paper considers a way of minimizing the pollution due to ceramic sludges, by rationalizing the addition of waste waters and sludges in tile production processes. The analytical and rheological results, obtained on the body slips used for white gres tile production in waste or purified waters, demonstrate that the addition of dried sludges up to 5% wt (in place of the < 2% wt amount till now used) makes the slip completely compatible with industrial requirements. This paper evidences the possibility of direct use of waste waters, containing sludges, in the wet grinding process, making purification treatments of waters unnecessary and greatly reducing the economical engagement.

1990 - A THERMAL STUDY ON ISOMORPHOUS METAL FORMATES [Articolo su rivista]
Baraldi, Pietro; Manfredini, Tiziano
abstract

vengono esaminate le proprietà di stabilità termica di una serie di formiati isomorfi mediante la considerazione degli spettri registrati in funzione della temperatura

1990 - CRYSTAL-STRUCTURE, THERMAL-PROPERTIES, AND SPECTROSCOPY OF (N,N'-DIMETHYLPIPERAZINIUM)[CUCL3(H2O)]2 AND (2-AMINOPYRIMIDINIUM)[CUCL3(H2O)] [Articolo su rivista]
Manfredini, Tiziano; Pellacani, Gian Carlo; Corradi, Anna; Battaglia, Lp; Guarini, Ggt; Giusti, Jg; Pon, G; Willett, Rd; West, Dx
abstract

CRYSTAL-STRUCTURE, THERMAL-PROPERTIES, AND SPECTROSCOPY OF (N,N'-DIMETHYLPIPERAZINIUM)[CUCL3(H2O)]2 AND (2-AMINOPYRIMIDINIUM)[CUCL3(H2O)]

1990 - Le bentoniti e la plasticità degli impasti ceramici [Articolo su rivista]
L., Boscardin; Manfredini, Tiziano; G. F., Marzola; C., Pasquali; Pellacani, Gian Carlo; Pozzi, Paolo
abstract

Vengono riportati i risultati relativi ad uno studio sull'effetto dell'aggiunta di bentoniti sulla plasticità degli impasti ceramici

1990 - Monomeric and oligomeric phosphates as deflocculants of concentrated aqueous clay suspensions [Articolo su rivista]
Manfredini, Tiziano; Pellacani, Gian Carlo; Pozzi, P.; Bonamartini Corradi, A.
abstract

The paper discusses on effects of monomeric and oligomeric phosphates as deflocculants of concentrated aqueous clay suspensions

1990 - NICKEL-BASED AIR-FIRABLE THICK-FILM CONDUCTORS [Articolo su rivista]
Sirotti, F; Prudenziati, Maria; Manfredini, Tiziano; Giardullo, B; Anzolin, W.
abstract

The evolution of microstructure/composition of Ni-based thick films prepd. from air-firable pastes was investigated. The pastes contain elemental and/or a B-rich component which effectively competes with the oxidation of Ni grains. The evolution of the electrical properties of the film was studied. Even when the films are not made on sintered Ni grains, relatively high conductivities and high temperature coefficients of resistance are observed

1990 - New experimental method for ceramic powder compaction control [Articolo su rivista]
J. L., Amoros Albaro; A., Blasco Fuentes; J. E., Enrique Navarro; F., Negre Medall; Manfredini, Tiziano; Pozzi, Paolo
abstract

The paper regards some consideration on a new experimental method for ceramic powder compaction control

1990 - Studio sulle trasformazioni chimico-fisiche indotte da piccole aggiunte di particolari componenti negli smalti [Articolo su rivista]
Manfredini, Tiziano; M. Michelini e. G., Monari
abstract

L'articolo riporta risultati di una ricerca eseguita al fine di verificare l'effetto sulle caratteristiche e sulle trasformazioni chimico-fisiche indotte da piccole aggiunte di particolari componenti negli smalti

1989 - A spectral and thermal study on nickel(II) hydroxides [Articolo su rivista]
Baraldi, Pietro; Davolio, Giovanni; Fabbri, Gianfranco; Manfredini, Tiziano
abstract

The paper reports significative results about the spectral and thermal properties of nickel(II) hydroxides

1989 - Coordinative capabilities of substituted propane-1,3-diamine: Zinc(II) halide adducts of 2,2-dimethylpropane-1,3-diamine. [Articolo su rivista]
N., Masciocchi; M., Moret; A., Sironi; S., Bruni; F., Cariati; A., Pozzi; Manfredini, Tiziano; Menabue, Ledi; Benedetti, Adriano
abstract

A series of compounds of formula Zn(dmpd)nX2· mH2O (dmpd = 2,2-dimethylpropane-1,3-diamine, X = Cl, Br, I; n = 2, m = 0; n = 3, m = 1) has been prepared and studied by means of spectroscopic (IR and Raman) and structural investigations. The [Zn(dmpd)2]I2 (I) compound crystallizes in the tetragonal P42/nmc space group, with two formula units in a cell of dimensions: a = b = 8.417(2), c = 12.726(2) Å. The structure consists of an ionic packing of iodide anions and of discrete [Zn(dmpd)2]2+ cations, where the Zn atoms are tetrahedrally coordinated to four nitrogen atoms of two chelating amine molecules. The [Zn(dmpd)3]Cl2·H2O (II) compound crystallizes in the triclinic space group P1, with Z = 2 and cell of dimensions: a = 9.021(2), b = 12.087(3), c = 13.785(3) Å, α = 59.01(2), β = 70.35(2), γ = 76.01(2)°. The crystal consists of an ionic packing of discrete [Zn(dmpd)3]2+ cations and chloride anions plus two clathrate water molecules per unit cell. The Zn atom presents a trigonal bipyramidal geometry, being surrounded by four nitrogen atoms of two chelating dmpd molecules and one nitrogen of a monodentate dmpd ligand. The structures were solved by conventional Patterson and Fourier methods and refined by full matrix least-squares to R and Rw of 0.053 and 0.073, and 0.040 and 0.046 for I and II respectively. The ZnN stretching vibrations are discussed and assigned in the light of the determined structures.

1989 - Flexibility in coordinative behavior of propane-1,3-diamine toward Zn(II) and Cd(II) halides:[M(1,3pn)2X2 (M=Zn, Cd; X=Cl, Br,I)]. [Articolo su rivista]
G., Ciani; M., Moret; A., Sironi; S., Bruni; F., Cariati; A., Pozzi; Manfredini, Tiziano; Menabue, Ledi; Pellacani, Gian Carlo
abstract

A series of compounds of formula M(1,3pn) 2X 2 (M Zn(II), Cd(II); 1,3pn=propane-1,3-diamine; X Cl, Br, I) has been prepared; two of them (M Zn, X Cl) and (M Cd, X I) have been structurally characterized. The Zn(1,3pn) 2Cl 2 (I) compound crystallizes in the P2 1/c space group, with eight formula units in a cell of dimensions: a=12.833(4), b=16.753(9), c=13.010(4) Å, β=118.88(3) °. The Cd(1,3pn) 2I 2 (II) compound crystallizes in the P2 1/n space group with four formula units. The structures were solved with the heavy-atom method and refined by full matrix least-squares to R and R w values of 0.029 and 0.038, 0.042 and 0.058 for I and II respectively. The asymmetric unit of I consists of a dimeric [Zn- (1,3pn) 2] 2 4+ moiety, where both Zn ions are tetrahedrally coordinated to four nitrogen atoms belonging to one chelating and two bridging 1,3pn ligands. The dimeric moiety generates an infinite chain upon translation of one cell in the direction of the diagonal (1,0,1). The structure of II shows a polymeric arrangement of octahedral Cd atoms sharing both iodine atoms and 1,3pn ligands. The MN stretching vibrations are discussed and assigned in the light of the known structures

1989 - Nuove metodologie di controllo del processo ceramico. L'Importanza delle caratteristiche delle polveri ceramiche da sottoporre a pressatura [Articolo su rivista]
Amoros Albaro, J. L.; Blasco Fuentes, A.; Enrique Navarro, J. E.; Negre Medall, F.; Manfredini, Tiziano; Pozzi, P.
abstract

L'articolo tratta sulle nuove metodologie di controllo del processo ceramico e l'Importanza delle caratteristiche delle polveri ceramiche da sottoporre a pressatura.

1989 - Out- and in-diffusion of oxygen in YBa2Cu3O7 - x oxide [Articolo su rivista]
Ottaviani, G.; Nobili, C.; Nava, F.; Affronte, M.; Manfredini, T.; Matacotta, F. C.; Galli, E.
abstract

In situ resistance measurements have been used to investigate the oxygen out- and in-diffusion in YBa2Cu3O7 - x oxide. The oxygen content has been measured by nuclear reaction and by weighing; X-ray diffraction has been used to determine the crystalline structure. Polycrystalline sintered material has been used. Out-diffusion has been investigated by heating samples with x = 0.1 in argon atmosphere at fixed temperature and as a function of the time. The resistance increases exponentially and reaches saturation after 5000 min at 550 °C. The oxygen content, after an initial decrease which occurs in the first 100 min, remains constant. Order-disorder transformation can be responsible for the exponential increase in resistance. The in-diffusion has been studied with a material having x = 0.65 heated in oxygen. As a function of the time the resistance curves continuously decrease and present two slopes: fast at the beginning and slow after a certain time. At first the material is tetragonal and non-superconducting. The sharp decrease in resistivity can be attributed to the presence of a thin continuous conductive skin around the grain or, more likely, to a disorder-order transformation activated by the presence of oxygen and involving a large part of the material. © 1989.

1989 - Oxygen in-diffusion processes in tetragonal YBa2Cu3O7-x oxide [Articolo su rivista]
Ottaviani, G.; Nobili, C.; Nava, F.; Affronte, M.; Manfredini, T.; Matacotta, F. C.; Galli, E.
abstract

In situ resistance measurements have been used to investigate the oxygen in diffusion in tetragonal YBa2Cu3O7-x oxide. The oxygen content has been measured by nuclear reaction and by weighing; x-ray diffraction has been used to determine the crystalline structure. The polycrystalline bulk material with x=0.65 has been heated in oxygen to 200370°C. As a function of time the resistance curves continuously decrease and present two slopes: fast at the beginning and slow later. At first the material is tetragonal and nonsuperconducting. Complementary weight measurements indicate a significant increase only after a delay, and the oxygen uptake is associated with the slow variation of resistance. The initial slopes of the isothermal resistance versus time curves follow, in an Arrhenius plot, a straight line, suggesting a process with an activation energy of 0.400.05 eV. The sharp decrease in resistivity can be attributed to the presence of a thin continuous conductive skin around the grains or, more likely, to a disorder-order transformation activated by the presence of oxygen and involving a large part of the material. A process having an activation energy of 0.90.1 eV is responsible for the slow variation of the resistance. This is in agreement with published data obtained for oxygen in diffusion in similar conditions. © 1989 The American Physical Society.

1989 - Polymeric 1-D linear-chain piperidinium and morpholinium trichlorocadmates (II): Synthesis and structural, thermal and electrical properties [Articolo su rivista]
Manfredini, T.; Pellacani, G. C.; Battaglia, L. P.; Corradi, A. B.; Giusti, J.; Motori, A.; Saccani, A.; Sandrolini, F.
abstract

The crystal structures of two polymeric 1-D linear-chain piperidinium and morpholinium trichlorocadmates(II) have been determined. The CdCl3(pdH) (pdH = piperidinium cation) salt is orthorhombic with the following space group and lattice constants: Ama2, a = 6.770(1) A ̊, b = 18.421(6) A ̊, c = 7.642(1) A ̊, Z = 4. Its structure consists of piperidinium cations and polymeric 1-D endless chains of triangular-face sharing distorted octahedral (CdCl6)4- ions, joined via three bridging chlorine atoms. The CdCl3(mfH) (mfH = morpholinium cation) salt is orthorhombic with the following space group and lattice constants: P212121, a = 17.524(4) A ̊, b = 14.368(3) A ̊, c = 7.000(1) A ̊, Z = 4. Its structure consists of zwitterionic 1-D linear Cd2Cl6(mfH)2 chains in which two unequivalent cadmium atoms, Cd(1) surrounded by six chlorine atoms and Cd(2) by four chlorine atoms and two oxygen coordinated morpholinium cations, are present. Alternate CdCl4(cis-Cl2) and CdCl4(cis-O2) distorted octahedra share edges by two chlorine atoms, forming chains of Cd2Cl6(mfH)2 units, running along the z axis. The compounds are also investigated by means of thermal, optical microscopy, X-Ray powder spectra and d.c. and a.c. electrical measurements. In particular for the CdCl3(mfH) salt the two phase transitions appearing at 201 and 211°C are tentatively explained on the basis of the above cited measurements. Correlations among the different parameters and the known structures of these materials are also drawn. © 1989.

1989 - Some general consideration on the rheological behaviour of aqueous clay suspensions: dependence on the physico-chemical properties of inorganic salts, calcium(II)ion presence and grinding times [Articolo su rivista]
Manfredini, Tiziano; Pellacani, Gian Carlo; Pozzi, Paolo; A., Blasco Fuentes; F., Negre Medall
abstract

The paper reports some general consideration on the rheological behaviour of aqueous clay suspensions: dependence on the physico-chemical properties of inorganic salts, calcium(II)ion presence and grinding times

1989 - Synthesis, structural, and spectroscopic study of rhenium(III) and rhenium(V) 4,6-dimethylpyrimidine-2-thiolate/triphenylphosphine mixed complexes: Crystal and molecular structure of ∥ReCl2(pymS)(PPh3)2∥·C3H6O and ∥ReOCl2(pymS)(PPh3)∥ [Articolo su rivista]
Battistuzzi, R.; Manfredini, T.; Battaglia, L. P.; Bonamartini Corradi, A.; Marzotto, A.
abstract

4,6-dimethylpyrimidine-2(1H)-thione reacts with rhenium(V) precursors trans-∥ReOX3(PPh3)2∥ (X=Cl, Br) in acetone, to afford two classes of crystalline pyrimidinethiolate/triphenylphosphine mixed complexes:trans-∥ReIIIX2(C6H7N2S)(PPh3)2∥·C3H6O and ∥RevOX2(C6H7N2S)(PPh3)∥ (X=Cl, Br). The crystal structures of trans-∥ReCl2(C6H7N2S)(PPh3)2∥·C3H6O (I) and ∥ReOCl2(C6H7N2S)(PPh3)∥ (II) have been determined from single-crystal diffractometer data and refined to R factors of 0.0496 and 0.0365, respectively. (I) crystallizes in the triclinic space group P-1 with a=16.875(4), b=13.969(7), c=9.510(2) Å;α=81.78(2)°, β=85.15(12)°, γ=107.97(8)° and Z=2. The coordination geometry around the rhenium center exhibit mutually trans phosphine groups and chloride ligands disposed trans to the nitrogen and sulfur donors of the pyrimidinethiolate ligand which form a four-membered chelate ring with the metal. (II) crystallizes in the monoclinic space group P21/c with a=12.554(3), b=10.501(1), c=19.200(5) Å;β=106.54(2)° and Z=4. The rhenium atom presents a very distorted octahedral configuration with a chlorine atom trans to phosphine ligand in the axial position and the N,S-chelate ligand in the equatorial plane with the sulfur donor atom trans the Re=Ooxo group. The compounds were characterized also by means of ir and nmr spectroscopic measurements; reaction pathways are discussed on the basis of structural data. © 1989 Plenum Publishing Corporation.

1988 - Alcune considerazioni generali sul comportamento reologico di sospensioni acquose di argille in funzione delle proprietà chimico-fisiche di deflocculanti inorganici, della presenza di Ioni calcio(II) e dei tempi di macinazione [Articolo su rivista]
Manfredini, Tiziano; Pellacani, Gian Carlo; Pozzi, Paolo; A. Blasco Fuentes e. F., Negre Medall
abstract

L'articolo riporta alcune considerazioni generali sul comportamento reologico di sospensioni acquose di argille in funzione delle proprietà chimico-fisiche di deflocculanti inorganici, della presenza di Ioni calcio(II) e dei tempi di macinazione

1988 - New Procedures for Ceramic Process Control. The Importance of the Characteristics of the Ceramic Powders to be Pressed. [Articolo su rivista]
Amoros Albaro, J. L.; Blasco Fuentes, A.; Enrique navaroo, J. E.; Negre Medall F., '; Manfredini, T.; Pozzi, P.
abstract

Analysis of the most common defects in ceramic products shows that they are directly attributable to the powder types and properties, to the dried porosity of the ceramic products and to possible changes of these characteristics within the products themselves. Among the methods of preparing ceramic products, pressing is the one most widely used. To optimize the entire powder compaction process, a complete knowledge of the powder types and characteristics and the parameters of the die filling is very important. Within the framework of a systematic investigation with the aim of characterizing new experimental methods for ceramic process control, the authors have studied the powder fluidity as a function of powder type, grain size and humidity by means of a new apparatus developed by the authors which enables a rapid check on the powder die filling.

1988 - Structural and Magnetic Properties of Dimorpholinium Hexahalodicuprate(II) Salts: Study of two Planar Cu2X62- Dimers [Articolo su rivista]
Scott, B.; Geiser, U.; Willett, R. D.; Patyal, B.; Landee, C. P.; Greeney, R. E.; Manfredini, T.; Pellacani, G. C.; Corradi, A. B.; Battaglia, L. P.
abstract

The chloride and bromide analogues of the title compound were synthesized, and the X-ray crystal structure of the former compound was determined. Magnetic susceptibility and EPR studies were carried out on both compounds. The crystal structure of the chloride salt yielded a triclinic structure, space group P̅1, with a = 7.414 (2) Å,b = 8.686 (2) Å, c = 14.766 (4) Å, α = 79.16 (2)°, β = 82.20 (2)°, γ = 74.19 (2)°, Z = 2, dcalcd = 1.94 g/cm3, and R = 0.0527. The structure consists of isolated planar dimers with each copper atom semicoordinated to two oxygen atoms in what may be described, on the average, as a 4+2 elongated octahedral geometry. The magnetic exchange interaction in the two compounds is predominantly antiferromagnetic with a singlet-triplet splitting energy of J/k = -43.5 (1) K for the chloride and J/k = -131 (2) K for the bromide. EPR and magnetic studies on both compounds indicate that magnetically these compounds are not isolated dimers. EPR studies supplement both the structural and magnetic studies. © 1988, American Chemical Society. All rights reserved.

1988 - The crystal structure, magnetic and electrical properties of two polymeric chlorocuprate(II) compounds. [Articolo su rivista]
L. P., Battaglia; Corradi, Anna; U., Geiser; R. D., Willett; A., Motori; F., Sandrolini; Antolini, Luciano; Manfredini, Tiziano; Menabue, Ledi; Pellacani, Gian Carlo
abstract

The crystal structures of piperidinium trichlorocuprate(II) [Hpip][CuCl3], and piperazinium hexachlorodicuprate(II), [H2pipz][Cu2Cl6], have been determined by X-ray diffraction techniques. [Hpip][CuCl3] is monoclinic, space group C2/c, with a = 18.385(7), b = 8.439(4), c = 11.878(5) Å, and β = 103.63(5)° while [H2pipz][Cu2Cl6] is triclinic, P1, with a = 7.984(4), b = 7.054(4), c = 6.104(3) Å, α = 111.23(8), β = 99.95(9), γ = 81.26(7)°. Both salts contain infinite chains of [Cu2Cl6]2- dimers. The [Cu2Cl6]2- dimers show significant distortions from planarity due to formation of semi-co-ordinate bonds between adjacent dimers, with a larger distortion for the Hpip salt. This bifold distortion gives each copper(II) ion a (4 + 1) co-ordination geometry. The chains have slightly different configurations. In the H2pipz salt, adjacent dimers are related by unit-cell translations, while in the Hpip salt they are related by a c-glide operation. Magnetic susceptibility measurements show that the H2pipz salt is an alternating antiferromagnetic chain with J/k = -13.35(7) K and J′/k = -7.6(3) K, while the Hpip salt is an alternating ferro- antiferro-magnetic chain with J/k = 26(3) K and J′/k = -0.24(1) K. Thus, the intradimer coupling (J) becomes less antiferromagnetic as the distortion from planarity increases. Comparison with other bifolded dimers confirms correlation of J with the bifold angle, both experimentally and theoretically. Electrical measurements reveal the presence of an activated process for electrical conduction with activation parameters of 0.44 eV for [Hpip][CuCl3] and 0.34 eV for [H2pipz][Cu2Cl6]. The charge carriers are proposed to be the protons in N-H ⋯ Cl hydrogen bonds

1988 - The crystal structures and spectroscopic, thermal and electrical properties of linear and perovskite-type polymeric chlorocadmates (II) [Articolo su rivista]
Manfredini, T.; Pellacani, G. C.; Battaglia, L. P.; Corradi, A. B.; Motori, A.; Sandrolini, F.
abstract

The crystal structures of two polymeric chlorocadmates(II), having triprotonated amines as counterions, have been determined. The CdCl5 (denH3) salt is orthorhombic with the following space group and lattice constants: Pnma, a = 7.208(1) A ̊, b = 24.663(6) A ̊, c = 7.225(1) A ̊, α= β = γ = 90.0°, Z = 4. Its structure consists of sequences of alternating layers of corner-sharing (CdCl6) octahedra (perovskite-type structure) anchored by interposed sheets of aligned diethylenetriammonium cations and of uncoordinated chlorine ions. The Cd2 Cl7 (NametpzH3) · 3H2O salt is triclinic with the following space group and lattice constants: P1̄, a = 9.711(3) A ̊, b = 12.984(3) A ̊, c = 9.201(3) A ̊, α= 107.91(5)°, β = 113.99(5)°, γ = 83.29(3)°, Z = 2. Its structure consists of linear chains of (Cd2 Cl7 (OH2))n3- anions, NametpzH33+ cations and two uncoordinated water molecules. Thermal, far-infrared spectra and d.c. and a.c. electrical measurements are also performed on both the above cited compounds and the anhydrous Cd2 Cl7 (NametpzH3) salt. Correlations among the different electrical parameters (electrical conductivity, dielectric constant and loss factor) and the known structures of these materials are also drawn. © 1988.

1987 - Crystal and molecular structure of Triaqua-tri-μ-chloro-hexachloro-triangulo- trirhenium(III)-Bis[4, 6-dimethylpyrimidine- 2(1H)thione hydrochloride]-dihydrate [Articolo su rivista]
Battaglia, L. P.; Corradi, A. B.; Battistuzzi, R.; Manfredini, T.
abstract

Reaction between rhenium(III) chloride and 4, 6-dimethylpyrimidine-2(lH)-thione hydrochloride in concentrated HC1 solution results in the formation of [Re3Cl9(H2O)3].2(C6H7N2S.HCl).- 2H20. The compound crystallizes in the orthorhombic space group Pnma with cell dimensions a 16·797(4), b 21·917(4), c 9·514(1) A and Z 4. The structure was solved by the heavy-atom method and refined by least-squares calculations to a final R value of 0·0517 (R'0·0602). The structure consists of discrete [Re3Cl9(H20)3] units, protonated organic molecules, chloride ions, and water molecules. In the cluster three rhenium atoms are linked to form a triangle, with chlorine atoms bridging each pair of rheniums which present short Re-Re bonds [2·440(1), 2·433(1) and 2·444(1) A], Three water molecules in the equatorial plane and six chlorine atoms perpendicular to it (three above and three below) make the coordination around each rhenium distorted pentagonal bipyramidal. © 1987 ASEG.

1987 - Na-Silicates as Deflocculating Agents for Clays [Articolo su rivista]
Manfredini, T.; Pellacani, G. C.; Pozzi, P.
abstract

In this paper the rheological behavior of clay aqueous suspensions added with various commercial sodium silicates is investigated, in order to evaluate their utilization as deflocculating agents in practical industrial applications. In the sample preparations the industrial experimental conditions have been reproduced as nearly as possible. The best deflocculating conditions of the studied clays were obtained by using a sodium silicate compound having a SiO//2/Na//2O molar ratio of 2/1. This may be explained, since this silicate is the most effective as pH corrector, as deflocculant cation sequestering agent and as colloidal protector.

1987 - New Experimental Method Measuring Apparent Density of Ceramic Tiles: Technical and Applicational Aspects [Articolo su rivista]
Amoros Albaro, J.; Blasco Fuentes, A.; Manfredini, T.; Pozzi, P.
abstract

Analysis of the most common defects associated with the manufacture of ceramic tiles for floor and wall covering has shown that the said defects can be directly correlated to the porosity of the tiles before firing, to the fluctuaton of this porosity during the manufacturing process and to its nonhomogeneous distribution within the tiles. Various difficulties can be encountered in direct measurements of porosity, thus, for a rapid and reproducible check on the variable of condensation of ceramic tiles, it is more convenient to measure apparent density, which is directly linked to porosity.

1987 - Sodium silicates as deflocculating agents for clays [Articolo su rivista]
Manfredini, Tiziano; G. C., Pellacani; Pozzi, Paolo
abstract

Rheology of clays suspensions are discussed

1987 - Structures and magnetic properties of trinuclear copper(II) halide salts [Articolo su rivista]
T. E., Grigereit; B. L., Ramakrishna; H. L., Place; R. D., Willett; Pellacani, Gian Carlo; Manfredini, Tiziano; Menabue, Ledi; Corradi, Anna; L. P., Battaglia
abstract

The crystal structures of a series of trinuclear copper(II) halide salts have been determined. These all contain pseudoplanar, symmetrically bibridged Cu3X82- (Ia) or Cu3X7L- (Ib) anions. A2Cu3Cl8 or A2Cu3Cl8 salts are formed with A being the (Chemical Equation Presented) N-methylpiperazinium (NMPZ), 3-methyl-2-aminopyridinium (3MAP), and 5-methyl-2-aminopyridinium (5MAP) cations. A Cu3Br83- analogue is found with the 5-bromo-6-methyl-2-aminopyridinium (5B6MAP) cation. With the methylphenethylammonium (NMPH) cation, a (NMPH)Cu3Cl7·EtOH salt is isolated. The salts are all monoclinic with the following space group and lattice constants: NMPZ, C5H14N2Cu3Cl8, P21/c, a = 6.840 (3) Å, b = 14.321 (9) Å, c = 9.890 (5) Å, β = 102.90 (5)°, Z = 4; 3MAP, C12H18N4Cu3Cl8, C2/c, a = 26.05 (1) Å, b = 13.687 (4) Å, c = 7.099 (3) Å, β = 117.95 (3)°, Z = 4; NMPH, C11H20NOC3Cl7, P21/n, a = 11.843 (4) Å, b = 7.626 (3) Å, c = 23.840 (10) Å, β = 79.61 (3)°, Z = 4; 5B6MAP, C12N10N4-Cu3Br10, P21/n, a = 13.216 (3) Å, b = 4.076 (1) Å, c = 24.614 (6) Å, β = 91.65 (2)°, Z = 2. Each copper ion extends its primary coordination by formation of two semicoordinate bonds to halide ions in adjacent oligomers, yielding the familiar 4+2 coordination geometry for copper(II) complexes. These additional linkages cause the oligomers to aggregate into stacks, yielding stacking patterns of type IIa (NMPZ, 3MAP salts) or type IIb (NMPH, 5MAP, and 5B6MAP). Cu-X distances are approximately 2.3 (Figure Presented) Å (Cl) or 2.4 Å (Br) within the oligomers and 2.7-3.3 Å (Cl) or 3.2-3.3 Å (Br) between oligomers. The bridging Cu-X-Cu angles within the trimer average near 94°. Magnetic susceptibility measurements have been made on the NMPZ, NMPH, 3MAP, and 5MAP chloride salts. In addition, measurements were performed on Cu3Cl6(CH3CN)2, which contains neutral trinuclear oligomers. All compounds have doublet ground states arising from antiferromagnetic exchange coupling between neighboring copper(II) ions. The value of J/k is typically -20 to -35 K, consistent with the structural characteristics of the trimeric species

1987 - Una nuova metodologia sperimentale per la misura della densità apparente dei pezzi ceramici. Aspetti tecnici ed applicativi [Articolo su rivista]
Amoros Albaro, J. L.; Blasco Fuentes, A.; Manfredini, Tiziano; Pozzi, P.
abstract

The paper regards a new technique for apparent density measurement

1986 - Crystal and molecular structure of [H3N(CH2)2NH2(CH2) 2NH3]2HgCl8: A compound containing a discrete axially-compressed trigonal-bipyramidal pentachloromercurate anion [Articolo su rivista]
L. P., Battaglia; Corradi, Anna; Antolini, Luciano; Manfredini, Tiziano; Menabue, Ledi; Pellacani, Gian Carlo; G., Ponticelli
abstract

The compound [NH3(CH2)2NH2(CH2) 2NH3]2HgCl8 has been prepared and investigated by an X-ray structural analysis and vibrational spectroscopy. The compound crystallizes with two formula units in space group P2/n of the monoclinic system in a cell of dimensions a = 11.530(2), b = 6.638(1), c = 15.028(3) Å, β = 93.00(2)°, and Z = 2. The crystal structure was determined by threedimensional X-ray diffraction and refined to R = 0.048, R′ = 0.051. The structure consists of diethylenetriammonium cations, chloride anions and discrete [HgCl5]3- anions. Co-ordination around the metal, which lies on the two-fold axis, can be described as a compressed trigonal bipyramid, where the equatorial positions are occupied by three weakly bonded chlorine atoms, two of them related by the two-fold axis [Hg-Cl(2) 3.029(3) Å]. The apices of the bipyramid are occupied by two shortly bonded chlorine atoms [Hg-Cl(1) 2.327(4) Å]. This is an example of a trigonal-bipyramidal d10 metal ion in which the axial bonds are significantly shorter than the equatorial bonds. Therefore it may be considered to consist of a linear HgCl2 molecule, with a bond angle [Cl(1)-Hg-Cl(1′) 178.8(1)°] perturbed by the interaction of three weakly bonded chlorine atoms. Packing is determined by a network of hydrogen bonds involving the diethylenetriammonium cation and co-ordinated and unco-ordinated chlorine atoms. The vibrational spectra of the [HgCl5]3- anion are rationalized in terms of D3h symmetry and a correlation between the values of mercury-chlorine stretching frequencies and the related bond distances in HgCl2 units is also discussed.

1986 - Indagini reologiche su sospensioni di argille per l'ottimizzazione di processi di deflocculazione [Articolo su rivista]
G. C., Pellacani; Manfredini, Tiziano
abstract

Many kinds of inorganic deflocculants for clay suspensions are tested

1986 - Rheological Investigations of Clay Suspensions for the Optimization of Deflocculation Process [Articolo su rivista]
Pellacani, G. C.; Manfredini, T.
abstract

The rheological properties of clay aqueous suspensions are investigated in order to optimize the deflocculating dosages. The effects of four deflocculants have been investigated on the slip casting performance. The laboratory study on the deflocculation of casting slips has yielded the parameters from which the most efficient and economically advantageous deflocculant or mixture of deflocculants can be proposed for each ceramic body.

1986 - The hydrogen bonding effect on the halobismuthate(III) geometry: thermal, spectroscopic and structural properties of halobismuthate complexes of 4,6-dimethylpyrimidine-2(1H)-thione [Articolo su rivista]
Battaglia, L. P.; Corradi, A. B.; Battistuzzi, R.; Manfredini, T.
abstract

Reactions involving Bi(III) halides and 4,6- dimethylpyrimidine-2(1H)-thione (L) in HX solution result in the formation of [HL]3[BiX6]·2H2O (X=C1, Br) and [HL]3[Bi2I9]. These compounds together with the organic molecule in the form of the hydrochloride, (HLCl) were characterized by means of spectroscopic and thermogravimetric measurements. For HLCl·H2O (1) and [HL]3[BiCl6]·2H2O (2), X-ray structures were determined. In 1, which crystallizes in the space group Pca21, with four molecules in the cell, the structure consists of roughly planar protonated organic molecules stacked along the [100] axis and built up by hydrogen bonds involving chlorine atoms and water molecules. For 2, the space group is P21/n, Z=4, the structure contains [BiCl6]3- anions, protonated organic molecules stacked along the [010] axis and water molecules which form strong hydrogen bonds with the [BiCl6]3- anions. The final R indices are 0.0320 and 0.0465 for 1 and 2, respectively. © 1986.