Mechanical properties of silica aerogels controlled by synthesis parameters

Development of silica aerogels for real applications requires control of their mechanical properties. Based on the sol-gel procedure and using the alkoxide precursor of silica (TMOS), native silica aerogels were synthesized. This work explores the influence of three synthesis parameters, namely, TMOS concentration, catalyst concentration, and solvents (MeOH, EtOH, IPA), on the gel point, shrinkage and mechanical properties of aerogels. Structural studies were conducted to determine how the analysed synthesis parameters influenced the spatial network of aerogels and their elasticity. The analysis of the relationship between Young's modulus (E) and bulk density (ρ), E∝ρα, showed that the catalyst concentration appeared the most interesting parameter because, while the ρ did not change with an increase in the catalyst concentration, there was a significant increase in the E. We associate this observation with an increase in specific surface area, reflecting an increase in bond diameter between secondary particles formed in the aerogel.