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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

CaracterizaÃÃo MecÃnica e Microestrutural de CerÃmicas Porosas Obtidas A Partir de Diferentes Aluminas / Mechanical and Microstructural Characterization of Porous Ceramics Obtained from Different Aluminas The

Andrà Gustavo de Sousa Galdino 25 March 2003 (has links)
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O interesse em cerÃmicas porosas vem aumentando, à medida que novos processos vÃo sendo desenvolvidos, e as aplicaÃÃes decorrentes representam oportunidades tecnolÃgicas e econÃmicas substanciais. Para cada aplicaÃÃo, hà pelo menos uma propriedade relevante e deve ser avaliada, dependendo da funÃÃo: fÃsica, quÃmica e biolÃgica. Dentre as vÃrias aplicaÃÃes de cerÃmicas porosas, podem ser citadas: separadores de cÃlula para bateria, queimadores, suportes para catÃlise, filtros, sensores de gÃs, dentre outras. A alumina se destaca como matÃria-prima para corpos cerÃmicos devido as suas propriedades, tais como alta dureza, elevada resistÃncia ao desgaste, baixo coeficiente de atrito, alta resistÃncia à corrosÃo tanto à temperatura ambiente quanto em altas temperaturas ao ar, ausÃncia de transformaÃÃes no estado sÃlido, e o fato de que o material mantÃm sua resistÃncia mesmo em altas temperaturas (1500ÂC-1800ÂC). O objetivo deste trabalho à avaliar algumas propriedades mecÃnicas da alumina (Al2O3) com diferentes nÃveis de porosidade. As amostras forma produzidas pelos mÃtodos da esponja polimÃrica, adiÃÃo de cera polimÃrica e barras cerÃmicas com e sem bicarbonato de sÃdio. A sinterizaÃÃo foi realizada em duas temperaturas: a 1450ÂC e 1550ÂC. As propriedades analisadas foram: resistÃncia à flexÃo e dureza atravÃs das normas da ASTM, porosidade aparente, densidade aparente, retraÃÃo linear de queima, retraÃÃo linear de secagem e absorÃÃo de Ãgua, mÃtodo de Souza Santos para argilas. Os resultados obtidos mostraram-se bastante satisfatÃrios, onde foi mostrado que os corpos cerÃmicos porosos obtiveram valores de resistÃncia à flexÃo e dureza coerentes com os da literatura. Realizou-se tambÃm uma caracterizaÃÃo via difraÃÃo de raios-x (DRX) e microscopia eletrÃnica de varredura (MEV) das amostrar confeccionadas pelos dois mÃtodos. / The interest in porous ceramics is increasing, as new processes and technologies are going to be developed and hence applications representtechnological and economical opportunities. For each application, there is at least one important property that must be evaluated, depending on its function: physical, chemical and biological. There are many applications for porous ceramics bodies, such as: battery fuel cell separators, burners, catalyst supports, filters, gas sensors, etc. Alumina is a wild raw material used because of its properties, such as high hardness, high wear resistance, low friction coefficient, high resistance to corrosion at room temperature and at high temperature on air, the absence of transformations within the entire temperature range of solid state, and the fact that the material retains its strength even at very high temperatures (1500ÂC â 1800ÂC). This research describes the evaluation of some mechanical properties of alumina (Al2O3) with different levels of porosity obtained by the polymeric sponge method and by adding polymeric wax at 1450ÂC and 1550ÂC. Flexural strength and hardness were assessed using ASTM specifications. Apparent porosity, apparent density, linear shrinkage after sintering, linear shrinkage after drying and water absorption by Souza Santos clay method. Data showed to be satisfactory, where it was shown that porous ceramic bodies had flexural strength and hardness values corroborating with literature. Analyses were performed by x â rays diffraction (XRD) and scanning electronic microscopy (SEM) for both samples made by each method. In a general way, both samples made by each method had a similar behavior; however, samples made by adding polymeric wax presented less porosity homogeneity than those made by polymeric sponge method, and showed better sinterization at both temperatures either.

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