Transparent Silica Aerogels through Ternary Azeotropic Mixture

A two-step sol-gel process was performed to prepare monolithic silica aerogels in the temperature range from 85 to 250degC. The wet gel synthesis process involves an acid/base catalyzed procedure using TEOS as the Si precursor in the IPA media, followed by exchange of n-Butanol for IPA, surface modification of wet gels by 5% TMCS alcohol (n-Butanol) solution and step by step exchanges of the porous liquid from n-Butanol to pure octane. The ambient pressure drying process includes two-step temperature annealing of wet gels: 86degC-24hrs/130-250degC-24hrs. The silica aerogel samples prepared by ambient pressure drying of wet gels through ternary azeotropic mixture water/n-Butanol/octane are transparent, crack-free with surface area ~ 1000 (m²/g), bulk density ~ 0.4-0.48 (g/cm³) and porosity 82-85%.