DRYING OF SILICA ALCOGELS BY LIQUID AND SUPERCRITICAL CO2

Gels dried in supercritical conditions give a new class of materials c alled aerogels. The process of silica aerogel production in which extr action with liquid (or supercritical) carbon dioxide is used, consists of four main stages: elution, diffusion, heating and evacuation. Aero gel production from silica gels prepared from tetraethoxysilane is des cribed. The autoclave process which started with alcohol-liquid carbon dioxide exchange was followed by supercritical evacuation. Some impor tant technical aspects of the process are considered. The effect of el ution rate, temperature and duration of diffusion is investigated.