Low temperature synthesis of a monolithic silica glass by the pyrolysis of a silica gel

Abstract

The reaction process in the pyrolysis of silica gel has been investigated as the basic study on the low temperature synthesis of monolithic glass from a metal alkoxide. A large volume change which may cause stress-induced fracture of a gel occurred in the following process stages: (a) the decompostion of residual organic compounds into carbon dioxide (300 to 500° C); (b) small pore collapse (400 to 500° C); (c) larger pore collapse (700 to 900° C). A fracture-free monolithic silica glass was successfully prepared from a dry silica gel formed by the hydrolysis of silicon methoxide by careful heat-treatment. The properties of the synthetic silica glass were similar to those of commercial vitreous silica.