Reaction between different mixtures of tetra ethyl orthosilicate and aluminum nitrate nonahydrate at varying conditions have been studied by DTA technique. The result reveals that the two components react with the exhibition of an exotherm at similar to110degreesC. During isothermal heating at similar to80degreesC mixtures show rise in temperature with vigorous evolution of NO2 fumes and form gels those on heating to similar to500degreesC form aluminosilicate precursor phase. The composition of it may be close to the approximate composition of mullite. (C) 2004 Elsevier B.V. All rights reserved.