Sinteses de cordierita por sol-gel utilizando TEOS ou acido silicico : a influencia do acido citrico na cristalização

AUTOR(ES)

Aloizio Virgulino de Souza Junior

DATA DE PUBLICAÇÃO

2003

RESUMO

Cordierite (2MgO.2Al2O3.5SiO2) is a strategically important glass-ceramics with interesting mechanical, thermal and chemical properties. The addition of organic acids on ceramic material precursors obtained by sol-gel synthesis has been reported. Additives can modify temperature and rate of cordierite crystallization, as well as the crystalline phase yeld. The purpose of this work was to investigate the citric acid influence on Al and Mg incorporation into silica network before cordierite crystallization and its influence on m-cordierite yeld between 850-900°C. Cordierite powder was synthesized both from gelation of TEOS (tetraethylorthosilicate) and silicic acid in a medium containing aluminum and magnesium nitrates and citric acid with additive. The Al ions incorporation into silica network in the precursors prepared with citric acid was observed after the samples were heated at 300°C while the precursors in absence of citric acid presented almost total incorporation of Al ions during gel formation. The Mg incorporation occurred in the temperature range of 700-850°C for all samples, simultaneously with an intense densification and crystallization of the material. However for precursors prepared without citric acid, the cordierite crystallization and densification was less intense. Amorphous precursors prepared with citric acid presented higher m-cordierite yelds than the others.

ASSUNTO(S)

material ceramico materiais isolantes

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