Theoretical model of radiative transfer in opacified aerogel based on realistic microstructures

Abstract

Opacified silica aerogels are composite insulating materials containing silica nanoparticles and microsize opacifier grains. The radiative heat transfer in this dispersed medium was analyzed using a realistic microstructure model to calculate the opacified aerogel’s optical properties. The aerogel matrices were simulated using aggregates generated by a DLA algorithm, where the particle sizes and numbers were determined from the basic physical parameters. The theoretical predictions of the aerogel’s optical parameters agreed well with experimental data. A geometric unit containing one opacifier particle and a large number of aerogel particles was then built to study the coupled radiation effect between the aerogel and the opacifier. The optical parameters were computed using a multi-sphere T-matrix code with comparisons with Mie scattering solutions. The results show how the opacifier’s modified optical properties reduce the aerogel’s radiative conductivity.