SiO2–TiO2 Binary Aerogels: A Small-Angle Scattering Study

Abstract

Structural analysis in the range of characteristic sizes from 1 nm to ~1.5 µm was performed for SiO2–TiO2 aerogels prepared in supercritical CO2, isopropanol, hexafluoroisopropanol, or methyl-tert-butyl ether using small-angle X-ray scattering and neutron scattering complementary methods. A two-level model that accounts for scattering by individual inhomogeneities and their aggregates, which have fractal properties, satisfactorily describes the aerogel structures over the entire range of scales. It is shown for the first time that the titania concentration is the key factor in the small-angle neutron and X-ray scattering by SiO2–TiO2 aerogels. The phase composition of an aerogel does not significantly affect the aerogel structure in the range of scales from 1 nm to ~1.5 µm, as probed by small-angle X-ray and neutron scattering.