Light Scattering for Structural Investigations of Silica Aerogels and Alcogels (original) (raw)

1989, Le Journal de Physique Colloques

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Bulk and Surface Light-Scattering from Transparent Silica Aerogel

Optical Materials Technology for Energy Efficiency and Solar Energy Conversion Xi: Selective Materials, Concentrators and Reflectors, Transparent Insulation and Superwindows, 1992

Elastic light scattering has been used to study structural properties of different transparent aerogels, which may be used as filling materials in super-windows. With a goniometer having an angular resolution better than 0.6 ° and a He-Ne laser as the light source we investigated the angular distribution of scattered intensity from transparent silica aerogels and one xerogel. The densities ranged between 0.11 and 0.60 g cm -3. An exponential correlation function for the density fluctuations of a random porous medium has been utilised to analyse the large-angle scattering, which is dominated by bulk scattering, for different polarisation of the incident light. The determination of correlation lengths in the nanometre range was possible, because the absolute scattering intensities were determined. For relative angular dependence measurements, this range would have been accessible only to small angle X-ray scattering (SAXS). The resulting mean pore sizes between 8 nm and 50 nm and specific surface areas between 500 and 700 m2/g agree well with nitrogen-porosimetry data from the literature.

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