GLASSES FROM AEROGELS .2. THE AEROGEL GLASS TRANSFORMATION

Silica glasses are obtained by the densification of aerogels. The transformation of the material into a glass is followed by differential thermal analyis, thermo-gravimetric analysis, dilatometry and by the evolution of the structural, textural and mechanical properties of the material. The organic species and the hydroxyl groups are removed by oxidation and chlorination heat treatments in such a way as to avoid bloating and crystallization phenomena during sintering. Densification is obtained by heat treatment at a low temperature (1100 to 1300 ° C). The densified aerogel shows physical properties identical to those of molten silica. Moreover, this material is very pure and its water content is low. The same process can be extrapolated to multicomponent glasses and composite materials. © 1990 Chapman and Hall Ltd.