Structure and Chemistry of Sol-Gel Derived Transparent Silica Aerogel

摘要

Transparent silica aerogels are being studied because of their excellent thermal insulation properties for window glazing materials. The chemistry of the base catalyzed Si(OC sub 2 H sub 5 ) sub 4 sol-gel process to produce transparent aerogels is presented. The results of a factorial design set of experiments are discussed in which five process parameters are simultaneously varied. The goal of these experiments was to optimize the process conditions and to analyze the importance of various parameters in improving the properties of the aerogel. A novel technique of ambient temperature supercritical drying of alcogels is described. In this process, supercritical drying occurs at less than or equal to 40 C instead of at greater than or equal to 270 C and greater than or equal to 1700 PSI (12 MPa), by substituting CO sub 2 for alcohol in the alcogel. The time of drying is reduced from 2 to 3 days to 8 to 10 hours. It is shown that light scattering, microstructural properties and other characteristics of aerogels produced by this process and by the high temperature supercritical drying are similar. (ERA citation 10:025860)