Parameters affecting elastic properties of silica aerogels

The Young's modulus of silica aerogels is measured, using the three point flexural technique. Various parameters have been investigated, such as the concentration of silicon compounds as well as the catalyting conditions used to develop the initial alcogel and the heat treatment performed to densify the material. The elastic behavior of aerogels depends on the conditions of gel preparation, and the Young's modulus is shown to obey the power dependence E ≃ ρ^3.7. This scaling exponent is compared to the percolation model predictions. On the other hand, the elastic behavior of different sets of aerogels is related to the spatial arrangement of the particles pointed out by fractal features.