Elastic properties of xerogels and sintered aerogels probed by inelastic light scattering

• Published in: Journal of non-crystalline solids 1998-04, Vol.225 (1-3), p.277-281
• Main Authors: Terki, F, Pelous, J, Dieudonné, P, Woignier, T
• Format: Article
• Language: English
• Subjects: Chemistry; Colloidal gels. Colloidal sols; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Inelastic light scattering; Sintered aerogels; Xerogels
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/S0022-3093(98)00129-X

Elastic properties of silica xerogels and sintered aerogels of densities from ρ=0.5 g/cm 3 to 2.2 g/cm 3 were investigated by Brillouin light scattering. Sound velocities and acoustic attenuation at hypersonic frequencies was measured as a function of density. The elastic modulus C follows a scaling power law C= ρ α with α=3.3±0.1 and confirms previous data at low frequencies. For xerogels, the comparison between as prepared and oxidized samples after heat treatments, shows an increase of the elastic constant greater than 50% without significant change of the α exponent. This α value is close to that observed for densified aerogels emphasizing that this exponent seems to be independent on the sample treatment and preparation. Therefore, the fractal behavior of the material is not essential to explain power-law dependence. The acoustic attenuation has also been determined as a function of the density. A relaxational process coupled to acoustic vibrations disappears after heat treatment. This effect is also related to large inelastic light contribution in the very low-frequency part of the Raman spectra.