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Made available in DSpace on 2014-06-11T19:25:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-08Bitstream added on 2014-06-13T20:14:12Z : No. of bitstreams: 1 gasparotto_g_me_araiq.pdf: 3340587 bytes, checksum: bbf8cb1346b8377c9399b7fc2540fdc4 (MD5) / A cerâmica Titanato Zirconato de Chumbo, PZT, se destaca por suas notáveis características piezoelétricas, sendo candidata a várias aplicações tecnológicas como transdutores, dispositivos ressonantes, entre outras, devido também a seu baixo custo e facilidade na fabricação (DESHPANDE, 1994). A adição de íons modificadores pode melhorar as propriedades da cerâmica, tornando-a mais eficiente. Inúmeros íons como nióbio (Nb+5) e estrôncio (Sr+2) podem ser usados para alterar parâmetros estruturais ad estrutura perovskita A(B’B”)O3 . O método Pechini é um dos mais empregados para síntese de pós cerâmicos com homogeneidade adequada ao estudo da dopagem. Neste trabalho, este método foi utilizado para síntese de pós de PZTS e PZTSN seguindo a composição Pb(1-x)Srx(Zr0,5Ti0,5)O3 e Pb(1-x)Srx[(Zr0,5Ti0,5)Nb0,04]O3, respectivamente, onde 0,01<x<0,1. O objetivo deste trabalho foi otimizar a concentração de dopantes e o processamento dos pós e da cerâmica PZT estabelecendo condições adequadas para a estabilidade de fase, obtenção de pequeno tamanho de partícula, tal que na sinterização pudesse resultar em cerâmicas de alta densidade e microestrutura controlada, potencializando a utilização da mesma em transdutores, ressonadores, som de alta fidelidade, hidrofones, vibradores, entre outras. Os pós cerâmicos foram calcinados a 750oC durante 4 horas e moídos por 1 1/2 hora, utilizando álcool isopropílico como solvente. Ainda como pós, foram caracterizados por BET, IV e DRX. Os pós foram prensados uniaxialmente e isostaticamente a 210 MPa em forma de cilindros com 12mm de diâmetro e aproximadamente 2mm de espessura e, então, sinterizados em forno tubular a 1100oC durante 4 e 15 horas. A presença de estrôncio deslocou Tc para temperaturas inferiores à cerâmica pura, atingindo aproximadamente 310oC para a... / Lead zirconate titanate, PZT, is well known because of its excellent piezoelectric properties and has been rised for several technologic applications including: transducers, ressonant devices, and advantages such as low cost and ease to fabricate. The addition of modifiers ions could improve the ceramic properties favoring their applications. Several ions as niobium (Nb+5) and strontium (Sr+2) could be used to change structural parameter of perovskite cell A(B’B”)O3. The Pechini’s method is one of the most important method to obtain ceramic powders with adequated homogeneity. Related to this method was used to synthetise PSZT and PSZTN. The dopant powders following the compositions Pb(1-x)Srx(Zr0,5Ti0,5)O3 and Pb(1-x)Srx[(Zr0,5Ti0,5)Nb0,04]O3 , respectively, where 0,01<x<0,1. The ceramics powders were calcinated at 750oC for 4 hours and milled at ½ hour using isopropilic alchool. The powders were characterized by BET, IV and DRX. After that, the powders were isostatically pressed at 210 Mpa in a cilynder form with 12mm diameter and approximately 2mm thickness and then sintered in a tubular furnace at 1100oC for 4 and 15 hours. The higher sintered time increases the grain size. The presence of strontium changes Tc for lower temperatures comparing to the pure PZT, reaching approximately 310oC for the compositions where x=0,1. The dielectric constant for this samples was about 9000.

Resumo: Neste trabalho, apresenta-se uma rota alternativa para produção de cerâmicas de mulita (3Al2O3.2SiO2), a partir da mistura de pós de alumina (Al2O3) e sílica (SiO2), para uma possível aplicação em um dispositivo de perfuração de rochas por jato supersônico quente (thermal spallation). Os pós precursores foram utilizados de dois modos diferentes: no primeiro com tamanho micrométrico, tal como fornecido pelos fabricantes; no segundo, a alumina foi moída e misturada separadamente com ácido silícico e aerosil nanométricos, ambos usados como fontes de sílica. O processo consistiu basicamente na mistura a úmido dos pós, secagem, prensagem e sinterização. Além do tamanho das partículas dos pós, foi avaliada a influência da pressão de prensagem (40 a 300 MPa), dos aditivos de sinterização (MgO, CaO e Y2O3), do meio de dispersão (água e álcool), da calcinação dos pós, da temperatura (1600 e 1650 ºC) e do tempo (1 e 3h) de sinterização. As cerâmicas obtidas foram caracterizadas de acordo com a contração, perda de massa, porosidade e densidade aparente e resistência à flexão. A microestrutura foi caracterizada por meio da microscopia óptica e microscopia eletrônica de varredura (MEV), e complementada com difração de raios X. Os resultados obtidos mostram que cerâmicas de mulita para aplicações comerciais, que requerem resistência mecânica até aproximadamente 207 MPa, podem ser obtidas utilizando pós de alumina moída e aerosil 380, com 1 % de CaO, homogeneizadas com álcool, calcinadas a 600 ºC, prensadas com 160 MPa (ou mais), pré-sinterizadas a 1000 ºC por 1h e sinterizadas a 1650 ºC por 1h. Estas cerâmicas demonstram também, grande potencial para uso em queimadores para fornos e tubeiras para thermal spallation. / Abstract: The present study was made in order to obtain an alternative process to produce mullite ceramic (3Al2O3.2SiO2), from powder mixture of alumina (Al2O3) and silica (SiO2), for a possible use in a device for rock drilling hot supersonic jet (thermal spallation). The precursors powders were employed in two different ways: the first powder, in micrometric size, was used as supplied by the manufacturer; the second, milled alumina was alternated with silicic acid and nanometric aerosil®, both used as silica sources. The ceramic processing consisted basically of four steps: mixture of humid powders, drying, pressing and sintering. Besides the powder particle size, it was also evaluated the influence of the pressing (40 to 300 MPa), the sintering additives (MgO, CaO and Y2O3), the middle of dispersion (water and alcohol), the powder calcination and the time (1 and 3h) and sintering temperature (1600 and 1650 ºC). The obtained ceramics were characterized according to the contraction, mass loss, porosity, densification and resistance to flexing. The microstructure was analyzed by light microscopy, scanning electron microscopy (SEM) besides X-ray diffraction. The obtained results show that mullite ceramic for commercial applications requiring mechanical resistance up to about approximately 207 MPa, it can be obtained using milled alumina powder and aerosil 380® with 1 % CaO, homogenized with alcohol, calcined in 600 ºC, pressed with 160 MPa (or more), pre-sintered to 1000 ºC for 1h and sintered to 1650 ºC for 1h. These ceramic also show, great potential to be used in burners for ovens and nozzles for thermal spallation. / Orientador: Elson de Campos / Coorientador: Demétrio Bastos Netto / Banca: Rogério Pinto Mota / Banca: Eduardo Bellini Ferreira / Banca: Francisco Cristovâo Lourenço de Melo / Banca: Gilmar Patrocínio Thim / Doutor

Orientador: Marco Antonio Alves do Valle / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Artes / Made available in DSpace on 2018-08-24T21:07:18Z (GMT). No. of bitstreams: 1 Marcao_Cloves_M.pdf: 23323593 bytes, checksum: b494de6e9c7b7ba7dea9e3743afba9ac (MD5) Previous issue date: 2014 / Resumo: O objetivo deste projeto é estudar o trabalho de Akiko Fujita, dentro do contexto da cerâmica contemporânea, abordando os conceitos que a colocam dentro deste contexto de contemporaneidade, discutindo também as mudanças que ocorreram e deram as características desta prática ceramista contemporânea. Estudar o uso que a artista faz da cerâmica para o desenvolvimento de suas obras tridimensionais. Pretende-se identificar quais suas inspirações para o desenvolvimento do trabalho, técnicas usadas, materiais. E, sobretudo qual importância que o seu trabalho trouxe para o cenário artístico brasileiro durante sua estadia no país. Abordamos também as dificuldades enfrentadas pela artista durante sua estadia, tanto pela incompreensão de seu trabalho, como também pela nossa pouca tradição neste tipo de trabalho. Estudamos sua relação com o público, sua contribuição para os que tiveram contato com ela, não apenas dando enfoque as suas obras, mas também com suas preocupações sobre a disseminação do conhecimento, bem como o papel social do artista. Esta pesquisa seguiu a abordagem analítica dos estudos bibliográficos, e para tal realizou a consulta de estudos abrangentes e de outros mais específicos, consultados em livros, artigos e periódicos científicos que trataram das temáticas que foram analisadas. Permitindo, desta forma, discutir questões estéticas e conceituais. Tal análise foi pautada nos estudos conceituais dos artistas e movimentos artísticos abordados, e seus traços característicos, considerando a cerâmica contemporânea e a escultura. Também nos baseamos em relatos de pessoas que tiveram contato com a artista durante sua estada no país. Com esta pesquisa pude entrar em contato com outras formas de se pensar e fazer arte, estabelecendo conhecimento de outra teoria filosófica que ajudou a entender o meu próprio envolvimento com o suporte artístico abordado / Abstract: The objective of this project is to study the work of Akiko Fujita, within the context of contemporary ceramics. Address the concepts that lay within this contemporary context, also discussing the changes that have occurred and have the characteristics of contemporary ceramist practice. The use that the artist makes pottery for the development of its three-dimensional works. What are your inspirations for the development work, techniques used, materials. And above all what importance that his work brought to the Brazilian art scene during his stay in the country. We also analyze the difficulties faced by the artist during his stay, either by misunderstanding of his work, but also for our little tradition in this type of work. His relationship with the public, their contribution to those who had contact with her, not only focusing their works, but also with their concerns about the spread of knowledge and the social role of the artist. This research followed the analytical approach of bibliographical studies, and the consultations for such comprehensive studies and other more specific interest in books, articles and scientific journals that addressed the issues that were analyzed. Thereby enabling discuss aesthetic and conceptual issues. This analysis was based on studies of conceptual artists addressed, and their characteristic traits, considering the contemporary ceramics and sculpture. Also we rely on reports with people who had contact with the artist during his stay in the country. With this research we can get in touch with other ways of thinking and making art, by contacting another philosophical theory and that helped understand my own involvement with the artistic support addressed / Mestrado / Artes Visuais / Mestre em Artes Visuais

The study of ceramic variability in Chinese archaeology is conventionally understood in the context of temporal and regional differences, where emphasis is placed on explaining variability in terms of identifying regional styles and long-term changes. In this thesis, I examine ceramic variability of Shang pottery between two contiguous daily-use contexts at Huanbei, a Middle Shang period (1400-1250 BCE) site located in the Central Plains of China. Based on the analysis of pottery sherds collected from daily-use contexts at Hanwangdu (HWD) and Huyuanzhuang (HYZ), I argue that ceramics collected within a single-site context can be highly varied and distinct due to differences in use-context. Assemblage differences and ceramic variation are evaluated according to rim sherd attributes including vessel shape, rim and lip shape, dimensional properties, and surface treatment styles. Possible interpretive models for explaining observed patterns of variability are presented. Results of this study suggest that siginificant variability in pottery vessel design can be observed in the samples examined from the Huanbei site. Consumers from the HWD (a palace context) consumed a greater variety of pottery vessel types but with a more limited range of shapes and decorative styles. In contrast, consumers from HYZ (a non-palatial context) consumed a limited range of pottery vessel types but with a greater variability in the range of shapes and decoration. The observed patterns of variation reinforce current assumptions regarding the contextual differences between HWD and HYZ, and also provide new insight into the differential pottery consumption patterns by different social classes at Huanbei. Results of this study indicate the potential value of studying intra-site ceramic variation in Chinese archaeology and its importance in creating new knowledge on the material consumption behavior of different social classes. / Arts, Faculty of / Anthropology, Department of / Graduate

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This work is the subject of an EPSRC-Tioxide Industrial CASE Award, the principal area of study being factors affecting the achievable steady state permeate flux during the crossflow microfiltration of concentrated titania dispersions. The performance of this continuous thickening process is of particular interest to Tioxide as a potential alternative to current batch filtration processes, which delay the manufacturing process.

OBJECTIVES: This study aims to fabricate graded composite structures with different ceramic materials and explore the effect of the various ceramic materials on the microstructure, surface topography, crystal characterization, bioactivity, and mechanical properties of the ceramic scaffold. MATERIALS AND METHODS: Ceramic matrix specimens were prepared with a slip casting technique. After sintering, specimens were examined for their physical, chemical, and mechanical properties including microstructure, surface roughness, elemental composition, crystal characterization and biaxial flexural strength. Specimens from each group were immersed in a calcification solution and were evaluated for the deposition of calcium phosphate through microscopy, elemental analysis, and crystal characterization. RESULTS: Graded ceramic matrix materials were successfully fabricated using a slip-casting technique. Scanning electron microscopy revealed different surface topography as well as the deposition of calcium phosphate crystals on the specimen surface after immersion in calcification solution. Elemental composition and X-Ray Diffraction (XRD) spectra confirmed phase transformation in the composite specimen after sintering. Particle grain size significantly affected surface topography in terms of surface area roughness and topographical patterns. Moreover, the combination of alumina and bioactive glass improved mechanical properties compared to bioactive glass alone. CONCLUSIONS: 1. The ceramic matrix containing bioactive glass presented greater surface roughness compared to other ceramic matrix without bioactive glass. 2. Two crystal phases: tricalcium silicate (Ca3Si3O9) and calcium metasilicate (CaSiO3) were found in high temperature sintered bioactive glass. The combination of bioactive glass with alumina or hydroxyapatite presented another tricalcium silicate phase such as Ca3(SiO4)O. 3. The XRD analysis of the combination of alumina and hydroxyapatite detected two new phases including grossite (CaAl4O7) and calcium aluminophosphate (Ca9Al(PO4)7). 4. Ceramic matrix containing bioactive glass or hydroxyapatite presented greater deposition of calcium phosphate crystals while the combination of bioactive glass and hydroxyapatite showed the greatest amount of the precipitated crystals. 5. Alumina ceramic matrix showed the highest biaxial flexural strength while hydroxyapatite and bioactive glass presented low biaxial flexural strength. 6. The combination of alumina with hydroxyapatite or bioactive glass improved biaxial flexural strength. 7. The combination of hydroxyapatite with bioactive glass had lower biaxial flexural strength compared to a single-phase ceramic matrix.