Transactions of the INDIAN CERAMIC SOCIETY Vol. 56 1997
Further Studies on Thermal Transformation
of Diphasic AI20 3-Si02 Gel
A. K. CHAKRAVORTY
Pages : 9-15
DOI : 10.1080/0371750X.1997.10804781
Abstract
Diphasic muUite gel (Si/AI=tl3) has been synthesized in situ h)
hydrolyzing an aqueous solution of silica sol and aluminium salt
with the help of NHPH solution. It has been characte1ized by
DT A. The formation of Si-Al spinel during non-eqilibrium heating
of the gel and its subsequent transformation have been recorded
hy XRD technique. The result shows that Si-Al spinel
crystallizes very slowly at 500°-800°C and then very rapidly at
- 1200°C which corresponds with the exhibition of a broad
exotherm between 1100° and 1300°C in DTA. Accordingly this
exotherm is attributed to the formation of Si-Al spinel. It suddenly
transforms to predominant amount of orthorhombic fo1m
of ~ullite with consequent exhibition of an exotherm at 1320°C
in DT A. The residual non-crystalline aluminosilicate phase also
crJstallizes into mullite and accounts for the second mullitization
process in diphasic gel.
