GAS-PERMEABILITY OF PARTIALLY DENSIFIED AEROGELS

Gas flows through partially densified aerogels were measured fur samples of various densities (0.4-1.2 g cm(-3)). Measurements were done at various pressure drops with argon and nitrogen. The gas flow in these partially densified aerogels is always molecular at the pressures and temperature examined. The permeability and conductivity of two sets of samples obtained from aerogels having different initial densities were studied. The conductivity always decreases when the density increases. The difference of gas conductivity between samples of the same density but prepared from aerogels having different initial density is explained using a model previously reported for the sintering of fractal silica aerogels. These results were analyzed using classical models for porous materials and are linked to pore size distribution obtained by thermoporometry and Hg porosimetry.