From colloidal-silica sols to aerogels and xerogels

Abstract

By destabilization of quasi-monodisperse silica sols, fractal clusters can be obtained. Solvent evacuation gives a porous solid with fractal structure. Structural investigations of these colloidal aerogels by small-angle neutron scattering are presented, and compared to similar observations in concentrated sols and xerogels. An investigation of the vibrational modes of these materials by inelastic neutron scattering gives clear evidence of a strong non-Debye contribution in the low-frequency regime.