LOW-TEMPERATURE TRANSFORMATION OF ALUMINOSILICATE 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 effe cts of the processing variables (dilution, pH, gelling temperature and water content) on the mullite formation. Monophasic gel was synthesiz ed from aluminium nitrate nanohydrate dissolved in absolute ethyl alco hol and silica sol mixture. The gelling is performed at room temperatu re and at 60 degrees C. Experimentally it was found that temperature f or mullite formation depends on the microstructure of the gel. (C) 199 8 Elsevier Science Limited and Techna S.r.l.