PREPARATION OF MULLITE POWDER BY CALCINATION OF THE PRODUCTS HYDROTHERMALLY TREATED FROM MIXED ALKOXIDE OR MIXED SOL.

Mullite powders were obtained by calcination of the products hydrothermally treated from mixed alkoxide or mixed sol, containing Al//2O//3:SiO//2 equals 3:2 (molar ratio). Pseudoboehmite-like phase, which contained both Al and Si components, was obtained by the hydrothermal treatment of mixed alkoxide or mixed sol, under 50 MPa at 300-400 degree C for 2 h. The pseudoboehmite-like phase particles from alkoxide were finer and more homogeneous than those from sol. The reaction among Al//2O//3, SiO//2 and H//2O was promoted to form aluminosilicates by the hydrothermal treatment under 50 MPa at 500-600 degree C for 2 h, using sol as a starting material.