Orientador: Sebastião Gomes de Carvalho / Banca: Antenor Zanardo / Banca: Eduardo Quinteiro / Banca: Kátia Regina Ferrrari / Banca: Sergio Christofoletti / Resumo: Nos últimos anos, a perda de produção promovida por contaminações nas massas na indústria tem sido um dos desafios para a indústria Cerâmica de Revestimentos. Estas perdas influenciam diretamente os custos e consequentemente o desempenho da competitividade das indústrias frente ao mercado. A região de Santa Gertrudes é considerada atualmente, no Brasil, o maior pólo cerâmico na fabricação de pisos e revestimentos cerâmicos e com tendência ao crescimento. O Pólo situa-se sobre a formação geológica do Corumbataí que é fonte rica de matérias-primas para a produção de revestimentos cerâmicos. Este estudo avalia o comportamento das argilas carbonáticas da Formação Corumbataí e também o comportamento de vários carbonatos aditivados em massas cerâmicas utilizadas no processo de fabricação de pisos e revestimentos do Pólo. Comprova-se que as argilas carbonáticas da Formação Corumbataí podem produzir produtos de alta porosidade e que as reações do calcário podem provocar furos, depressões, rompimento tardio da camada do esmalte e elevação na absorção de água nos revestimentos cerâmicos. Os defeitos produzidos por calcários podem ser reduzidos e eliminados através da racionalização do processo de escolha e beneficiamento das matérias-primas que compõe as massas, além do aprimoramento do conhecimento da matéria-prima e um planejamento de lavra adequado / Abstract: In recent years, the loss of production has been promoted by the mass contamination in industry, that has been one of the challenges for the Ceramic coating industry . These losses directly affect the costs and consequently the performance of the competitiveness of industries facing the market. The region of Santa Gertrudes is today, in Brazil, the largest center for the manufacture of ceramic floor and wall tiles and prone to growth. The Pole is situated on the geological formation of Corumbataí which has rich source of raw materials for the production of ceramic tiles. This study evaluates the behavior of clays and carbonates Training Corumbataí also the behavior of various carbonates containing additives on ceramic used in the manufacture of floor of the Pole. Proves that the formation of Corumbatai carbonate clays can produce high porosity and the reaction of the lime can cause holes, depression, later disruption of the enamel layer and increase in water absorption in ceramic tiles. The defects produced by lime can be reduced or eliminated by streamlining the selection and the processing of raw materials that make up the masses, in addition to improving the knowledge of raw materials and an appropriate mine planning / Doutor

Orientador: Osmir Batista de Oliveira Junior / Banca: Paulo Francisco Cesar / Banca: Luis Geraldo Vaz / Resumo: O objetivo deste trabalho foi avaliar a resistência à flexão de cerâmicas de zircônia estabilizada por ítrio em função de marca comercial e espessura. A resistência à flexão (MPa) foi testada pelo método uniaxial de 3 pontos, conforme Norma ISO 6872/2005 em Máquina de Ensaios Universal EMIC DL 2000, usando célula de carga de 5kN, velocidade de 0,5 mm/min. e suporte com 20 mm de distância entre os apoios. Foram testados 2 sistemas cerâmicos de zircônia parcialmente estabilizada por ítrio (Y-TZP) ZirCAD© - Ivoclar Vivadente e LavaTM Framework - 3MESPE e 2 espessuras (norma ISO: 2,00 mm e uso clinico: 0,7 mm): ZC_2; ZC_0,7; LV_2 e LV_0,7. ANOVA one way e post Hoc de Bonferroni foram utilizados com significância para p<0,05. Não houve diferença estatisticamente significativa entre as médias de resistência a flexão entre ZC_2 (Média = 673,62 e dp = 129,95), ZC_0,7 (Média = 533,63 e dp = 129,84), LV_2 (Média = 593,56 e dp = 122,78) e LV_0,7 (Média = 673,02 e dp = 81,36). Conclusão: Os sistemas cerâmicos Y=TZP ZirCAD e Lava apresentam resistência a flexão (MPa) semelhantes independente da espessura. Espessuras de 0,7 mm podem ser utilizadas nos testes de resistência a flexão para melhor simular as situações de uso clinico dos sistemas cerâmicos Y-TZP / Abstract: The objective of this study was to evaluate the flexural strength of ceramics by Yttrium stabilized zirconia as a function of thickness and trademark. Flexural strength (MPa) was tested by the method of three uniaxial points, in accordance with ISO 6872/2005. The Universal Testing Machine EMIC DL 2000, using a 5 kN load cell, crosshead speed of 0.5 mm / min. and holder with 20 mm distance between supports was used. We tested 2 systems ceramic zirconia partially stabilized by yttrium (Y-TZP) ZirCAD © - Ivoclar Vivadente and LavaTM Framework - 3MESPE and 2 thicknesses (ISO: 2.00 mm and clinical use: 0.7 mm): ZC_2; ZC_0 7; LV_2 and LV_0, 7. One-way ANOVA and post hoc Bonferroni was used with significance for p <0.05. There was no statistically significant difference between the mean flexural strength between ZC_2 (Mean = 673.62 and SD = 129.95), ZC_0, 7 (mean = 533.63 and SD = 129.84), LV_2 (Average = 593 , 56 and SD = 122.78) and LV_0, 7 (mean = 673.02 and SD = 81.36). Conclusion: Y-TZP ceramic systems ZirCAD and Lava have flexural strength (MPa) similar independent of the thickness. Thickness of 0.7 mm can be used in tests of flexural strength for better simulate the clinical conditions of use of Y-TZP ceramic systems / Mestre

No description available.

This dissertation seeks to explore the nature of the occupation of Lower Nubia between the third and sixth centuries A.D. through a study of the material culture of the 'X-group', and the cultural influences exerted thereupon. It draws upon a detailed examination of artefactual evidence and particularly ceramics from published and unpublished sites throughout the study area, with especial reference to unpublished data from the citadel of Qasr Ibrim which both the archaeological and historical records indicate to have been of key importance at this time. The study concludes that the previously assumed homogeneity of 'X-group' material culture cannot be accepted for much of the period under consideration, and that separate cultural traditions can be identified which indicate the settlement of new groups within the area alongside the small pre-existing population. These can now be more successfully linked with historical sources than has previously proved possible, and also provide clear evidence of the mechanisms by which the late Roman administration in Egypt sought to maintain stability in the territory immediately beyond its southern frontier. Ceramics are used extensively in the study in the assessment of the cultural influences present in Lower Nubia, their effect on local production, and their significance. Particularly important is the definition of a previously unrecognised 'post-Meroitic' ceramic assemblage of limited distribution, which is clearly antecedent to the well-known 'X-group' ceramic tradition. Ceramics also provide evidence of dating, and were used in seriation analysis in order to investigate more closely the chronology and sequence of occupation of Lower Nubia.

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Sliding wear of metal-on-ceramic, ceramic-on-metal, and ceramic-on-ceramic have been investigated using a tri-pin-on-disc machine. A technique has been developed for thin foil preparation for transmission electron microscopic examination perpendicular to the wear surface. The role of transformation toughening in the wear behaviour of zirconia ceramics has been investigated. In addition, the role of high strain deformation in a steel surface has been evaluated. The wear factor of 316L stainless steel pins worn against a zirconia disc was found to decrease as the load was increased, believed to be associated with metal oxide formation. TEM of the stainless steel revealed a worn surface which consisted of a mechanical mixture of metal oxide and heavily deformed metal. Deformation of the metal had occurred by shear banding with a microstructure similar to that observed in rolled specimens, although the texture formed was a wire texture rather than a rolling texture. The crystallite size was found to decrease towards the surface, demonstrating that the shear stress was a maximum at the surface. The shear bands at the surface had always been formed by the passage of the last asperity indicating that contact was plastic over the load range 6-60N/pin. The majority of wear occurred by transfer resulting from plastic overload, although a contribution to the material loss was made by metal extruded off the end of the pin as a result of the high strains. The depth of deformation correlated closely with the wear volume. The wear of the zirconia discs was found to be dominated by metal transfer. With Mg-PSZ, transformation occurred cooperatively in crystallographically determined bands. Microcrack coalescence led to preferential wear in these bands. However, with a Y-TZPdisc transformation appeared to have been responsible for widespread surface fracture. The wear of zirconia pins against a bearing steel disc gave limited metal transfer. Very little transformation of tetragonal to monoclinic was observed. However, milder forms of the transformation related wear mechanism did occur. Zirconia had formed a solid solution with the iron oxide, leading to the conclusion that the wear mechanism was tribochemically based. TZP worn against a ZTA disc showed evidence of very high temperature rises at the interface. The surface layer was amorphous and contained a mixture of alumina and zirconia suggesting that melting had occurred at the interface during sliding. At a depth of O.5pm. the surface consisted of heavily elongated tetragonal grains, with a low dislocation density, indicating a strain of at least 1.7. At a depth of 2-4pm a layer of monoclinic was found. There was evidence that the stresses imposed by friction extended to at least 8-10pm from the surface. TZP containing 20vol% SiC whiskers gave exceptionally low wear rates when worn against a ZTA disc. The greater wear resistance is believed to be a result of the improved load bearing capacity and of the higher thermal conductivity. It is clear that the poor thermal conductivity of zirconia dominates its tribological behaviour. Temperature generation was high enough to substantially reduce the driving force for transformation of the tetragonal to monoclinic, with a high enough temperature for plastic' deformation where a low thermal conductivity counterface was used. Where transformation occurred, its effect was to increase the wear rate.

The mechanical properties of ion implanted ceramics are primarily a function of the radiation damage produced by the implantation process. For crystalline ceramics this damage is chiefly nuclear displacements, though for glasses electronic effects have also been observed. In this study a number of single crystal and polycrystalline ceramics and a soda-lime-silica glass have been implanted with a range of ions in the energy range 90keV to 400keV and the changes in mechanical properties produced have been followed using hardness, indentation fracture and scratch testing. The damage structures which remain after implantation will control both the indentation hardness and surface fracture properties of cetamics. Changing the temperature of the substrate during implantation (in the range. 150K to 760K) has been found to alter this damage state and hence produce changes in the measured mechanical properties. In this temperature range, the effects of damage annealing at low doses were found to be minor for sapphire although for MgO damage annealing was found to result in a eduction of the radiation-induced hardening above 473K. The surface softening and stress relief accompanying amorphisation at higher doses was found to be strongly temperature dependent. Thus, the recrystallisation of amorphous material is important in determining the final mechanical properties of the implanted specimens. The tribological properties of the implanted ceramics were investigated using single pass scratch tests. Friction coefficients were found to increase with dose up to the onset of amorphisation, even when visible scratch tracks were produced. This increse is due to changes in adhesion between the slider and the flat induced by ion implantation. The reasons for these changes are as of yet unclear, though a possible explanation could be the removal of surface adsorbates which has been observed for MgO. Similar mechanical and tribological property changes observed for the polycrystalline ceramics as for the single crystal systems, but some extra effects were observed.

Vitrification is a well-established waste treatment method that has been used for silicate based wastes to achieve waste volume reduction and improve chemical stability before further use. However, the poor mechanical strength of the vitrified products has led to a low commercial value and thus an unjustifiable use of energy-intensive thermal technology over the cheaper, although environmentally unsatisfactory, land disposal option. To overcome this issue, the emphasis of this work lies in demonstrating the feasibility of fabricating dense glass-ceramics from several types of waste and combination of wastes, which are generally superior to their parent glasses in their mechanical performance, as well as highly porous glassceramics to be used in building industries as an alternative to conventional waste disposal. The first part of the research work demonstrated the ease of production of an array of relatively dense glass-ceramic material from coal ash from thermal power plants using powder sintering technology. These products had robust physical and mechanical properties suitable to compete against commercially available building materials such as granite and marble for the floor and wall covering applications. A fully-dense, fine-grained, high-strength glass-ceramic was also fabricated from Feslag using an economically viable single-stage melt heat-treatment route. The ironslag derived glass-ceramic material had a unique composition, with an associated microstructure containing a high content of titanium-rich compounds, and has the potential for non-critical load-bearing applications. Finally, the thesis provides the results of an experimental study concerning with the production of highly porous glass-ceramic foams from a mixture of coal ash and waste glass with the addition of an inorganic foaming agent. The correlations between physical, thermal, and mechanical properties were carried out based on results from practical experiments, physical model studies and numerical simulations using X-ray microtomography and finite element analysis. It was concluded that, these waste-derived materials have the potential to be used in building applications where there can be a large demand to meet the large volumes of wastes available.

This research aims to develop cross-cultural approaches to contemporary Western glass Jewellery design by using the Chinese philosophical notion of ‗harmony between man and nature‘ on glass and metal jewellery. By analysing the principle of ‗harmony between man and nature‘, new approaches are developed. This is achieved by using cross-cultural practices, 3D prototyping techniques and glass studio practices to create glass jewellery designs. The methodologies include: philosophical methodology and experimental research. Tacit knowledge drawn from previous experience is deployed to encourage experimentation with materials and the ways they are used in glass and jewellery practices. The research also utilises Chinese ‗holistic approaches‘, such as ‗harmony‘, ‗balance‘, ‗flexibility‘ and ‗change‘ to glass and jewellery making and the resulting aesthetics provide new practical strategies and contemporary glass jewellery designs. By analysing Chinese culture and traditions I have facilitated six case studies which explore philosophical understandings through studio practice including the following six philosophical approaches: ‗Integration of Yin and Yang‘, ‗Unification of Time and Space‘, ‗Same Structure of Man and Nature‘, ‗the Concept of Change‘, ‗Self-cognition and External-cognition‘ and ‗Combination of Subject and Object‘. Case studies are also used to examine personal approaches to studio practice using Chinese paintings and interpreting them into 3D designs and glass jewellery. Other studio techniques include: machine productions, 3D printing, water-jet cutting, hand making, silversmith, kiln casting and lampworking. The resulting contemporary glass jewellery designs; informed by Chinese philosophy and traditions of ‗harmony between man and nature‘ provide a different and innovative approach to the field of glass and jewellery design and offers a new contribution to knowledge.