SMALL-ANGLE SCATTERING AND THE STRUCTURE OF AEROGELS

Small angle scattering of X-rays or neutrons is known to be a powerful non-destructive technique to explore the structure of aerogels. Several models to evaluate scattering data are considered in order to decide which model parameters can be reliably related to real geometric sizes of various structural features. This includes calculation of mean particle and pore sizes, description of network morphology (fractal aspects), derivation of particle and pore size distributions, characterization of particle surfaces and the determination of the skeletal density. As an example, the appropriate interpretation of SAXS data with respect to structural modifications induced by supercritical drying and isothermal sintering of silica aerogels is quoted. Although some of these considerations refer to the aerogel structure, the results can, in principle, be used for a variety of nanoporous materials.