Synthesis of low-density silica gel at ambient pressure: Effect of heat treatment

A silica gel with the density of 0.2 g/cm(3) and porosity of 90% was synthesized. The silica wet gel was dried and heat-treated under the ambient pressure after modification of the surface by TMCS. The specific surface area and total pore volume of the dried gel increased with increasing heat treatment temperature and represented the maximum value of 1050 m(2)/g and 3.2 cm(3)/g, respectively, under 350 degrees C. The surface characteristic of the gel was hydrophobic when heat-treated in nitrogen and converted to hydrophilic after heat-treatment in air. As the result of pore characteristics, and microstructure of gel, the properties of the gel were considered to be similar to those of conventional aerogel. (C) 2000 Kluwer Academic Publishers.