Síntese de mulita a partir de caulim e alumina.

Abstract

The mullite is an extremely important mineral for the field of ceramic applications due to its excellent physical, chemical, thermal and mechanical. As this material is rare in nature, many studies focus on the synthesis of the same through processes that are economically viable. One of the methods used for obtaining mullite consists in heating at high temperatures mixing sources of silica with alumina, some aluminosilicates are often used for this purpose. Kaolin is one of the most important materials in the traditional ceramic industry because of its relatively low cost, easy to obtain as well as being relatively pure. When kaolin is subjected to heat treatment occur microstructural changes, among them the formation of mullite. This study aims to obtain mullite from compositions containing kaolin and alumina and evaluate the influence of different particle sizes of alumina on the mullite crystals. Initially the precursors were subjected to chemical characterization, particle size and mineralogical. The alumina passed through a milling process for 15, 45 and 60 minutes. After formulation of the masses, these were pressed and sintered at temperatures of 1200, 1300 and 1400 ° C with a heating rate of 5 ° C / min time 60 minutes residence. Subsequently, the samples were subjected to physical and mechanical characterizations: linear shrinkage, apparent porosity, water absorption and apparent density. The best results were observed for the composition containing kaolin and alumina subjected to milling for 45 minutes. The results show the influence of surface area on the kinetics of reactions, also emphasizing the granulometric distribution of the larger particles.