Effects of processing conditions on silica aerogel during aging: Role of solvent, time and temperature

Effective parameters that enhanced mechanical properties of silica aerogel during aging were investigated. Silica aerogel was made by tetraethyl orthosilicate (TEOS), water, methanol and ammonium fluoride (NH4F) as catalyst using a one-step method. Aging on the samples were performed under three different solvents including n-hexane, methanol and water for different time periods and also different temperatures. Subsequently, solvent exchange with n-hexane, modification under trimethyl chlorosilane (TMCS) solution and the ambient pressure drying (APD) were applied on all samples. The Fourier transform infrared spectroscopy (FTIR), Brunauer, Emmett and Teller (BET) method and compression tests were carried out on the produced samples. Both the compression strength and compression modulus of the gel increased with increasing of the time and temperature of aging. Those samples aged under water showed higher mechanical properties. On the contrary, the specific compression strength and modulus of samples aged in water were declined drastically.