Calcination of SiO2-aerogel in oxidizing atmosphere

Differences in mass loss occurring in the course of dynamic and isothermal heating of SiO2-aerogel and changes of specific surface and hydrophylicity during calcination were studied by thermal analysis. SiO2-aerogel was prepared from tetramethoxysilane (TMOS) hydrolyzed by ammonia solution at 0 degrees C with molar ratio TMOS: H2O:NH4OH 4:1:0.01. Differences are caused mainly by oxidation of organic matter and by diffusion of products of the oxidation. Heat transfer has none or little effect on the differences. Samples calcined at temperatures about 300 degrees C reach maximum hydrophilicity though they still contain small amounts of residual organic matter.