Effect of heat treatment on texture and structure of silica xerogels

Aerogels are new low density nano-porous non-crystalline solid materials, and have continuous random network structure. Because of nano-size granules and distribution of nano-pore, aerogels have lots of particular properties. Two-step acid-base catalyzed silica xerogels were prepared through sol-gel and ambient pressure drying. Texture and structure of silica xerogels were contrasted and analyzed at room temperature, 300, 600, 900°C and 1200°C by means of DTA-TG, XRD, SEM and IR. The results showed that the viscous flow leaded to thermal sintering of silica xerogels. After heat treatment, grains grew, at the same time the pores reduced. Materials, which had Si-O-Si short chain structure, shrank and became stiff and compact under the high temperature.