PREPARATION OF MONOLITHIC SILICA AEROGELS, AEROGELS SO OBTAINED AND USE THEREOF IN THE PREPARATION OF SILICA GLASS ARTICLES AND THERMALLY ISOLATING MATERIALS

摘要

The invention relates to a process for the preparation of monolithic silica aerogels by drying silica gels under hypercritical conditions, which is characterized by the absence of washing of the silica gel, a high heating rate in the autoclave and purging of the autoclave after substantial removal of the solvent. Other preferred conditions are the use of an amount of water not exceeding 1.5 times the stoichiometric amount for the hydrolysis, hypercritical conditions corresponding to a temperature of 265 DEG -275 DEG C. and to a pressure of 150-200 bars, and so on. Use of the aerogels for the preparation of silica glass bodies or articles and of heat-insulating materials.