Fine low density silica powders prepared by supercritical drying of gels derived from silicon tetrachloride

Abstract

Silica gels were prepared by the hydrolysis of silicon tetrachloride in pure water or in a tetrahydrofuran/water solution; hydrolysis in an ammonia/water solution yielded precipitated silica. After solvent transfer in acetone followed by supercritical point drying using liquid carbon dioxide, aerogel powders with high surface areas (up to 900 m2/g) and low tapping densities (down to 0.040 g/cm3) were produced. The powders were characterised by transmission electron microscopy, thermogravimetric analysis and infrared spectroscopy. © 1995, All rights reserved.