Low temperature pressureless sintering of sol-gel derived mullite

Mullite of stoichiometric composition has been synthesized by sor-gel proce ss. Aluminium nitrate and ethyl silicate are used as the starting materials to prepare the single phase mullite powder. DTA shows that the mullitizati on starts at 971 degrees C. It is observed from XRD analysis that the amorp hous mullite completely transforms to orthorhombic crystalline mullite at 1 300 degrees C. Wet milling operation has enhanced the sintering density of pure mullite by 12% more than that of dry milling. The naturally available raw material, clay has been identified as one of the suitable sintering aid s for mullite. The addition of clay to the mullite powder enhances the dens ity up to 95% of TD even at a very low temperature, 1450 degrees C by press ureless sintering. A viscous flow sintering mechanism during densification is one of the main criteria to achieve good densification. (C) 1999 Elsevie r Science S.A. All rights reserved.