SYNTHESIS OF NANOPARTICULATE SILICA COMPOSITE MEMBRANES BY THE PRESSURIZED SOL-GEL TECHNIQUE

A crack-free silica composite membrane has been synthesized from a nan oparticulate silica sol (particle diameter <10 nm) by a pressurized so l-gel coating technique developed in this study. The microporous silic a layers with an estimated pore radius of 0.78 nm were deposited insid e the pores (average pore size of 0.1 mu m) of slip cast alpha-alumina support tubes. The microstructure of the coated layer was controlled by adjusting sol properties and pressurizing conditions. The room-temp erature intrinsic permeability of N-2 through the silica membrane laye r after heat treatment at 200 degrees C is about 4.9 X 10(-12) mol(.)m /m(2.)s(.)Pa, and the mechanism of gas transport is Knudsen flow. The thermal stability of the silica composite membrane is excellent up to 500 degrees C.