Low temperature transformation of alumino-silicate gels

Polymeric alumino-silicate gel obtained by hydrolytic polycondensation from metal salts of alumina and alkoxide sol of silica is a suitable method for mullite processing. In this work were investigated the effects of the processing variables (dilution, pH, gelling temperature and water content) on the mullite formation. Monophasic gel was synthesized from aluminium nitrate nanohydrate dissolved in absolute ethyl alcohol and silica sol mixture. The gelling is performed at room temperature and at 60 degrees C. Experimentally it was found that temperature for mullite formation depends on the microstructure of the gel. (C) 1998 Elsevier Science Limited and Techna S.r.l.