Fabrication and Characterization of TEOS-based Silica Aerogels for Window Applications

The loss of heat through windows accounts for 25% of in-home heating and cooling losses. Due to climate change, conserving energy is more important than ever. If the interspace of windows was filled with silica-based aerogel, which has low thermal conductivity (0.012-0.020 W/mK), it would result in significant energy savings. Monolithic silica-based aerogels have been previously synthesized using tetraethyl orthosilicate (TEOS) with transparency from 700-800 nm of 45%-73%. This presentation focuses on using a design-of-experiments approach to testing the conditions needed to produce monolithic TEOS-based aerogels with sufficient transparency for window applications by a patented rapid supercritical extraction (RSCE) method. Two design of experiments (DOE) were carried out. The variables (1) quantity of time mixed in hydrolysis step, (2) quantity of time waiting in the hydrolysis step, (3) quantity of ethanol, (4) concentration of oxalic acid, (5) concentration of ammonia catalyst, and (6) quantity of water were tested to determine their effects on translucency and cracking of the resulting aerogel. The DOE results indicated that the concentration of ammonia catalyst and the quantity of time waiting in the hydrolysis step had the largest effect on the resulting aerogel's translucency.