A hydrogen-permselective amorphous silica membrane derived from polysilazane

A microporous amorphous silica membrane has been synthesized by thermal conversion in air of polysilazane on a silicon nitride (Si3N4) porous substrate. The porous substrate near the surface layer was penetrated by polysilazane, and converted into mesoporous amorphous silica/Si3N4 composite layer. Then, an active molecular sieving microporous amorphous silica thin layer was synthesized on the surface of the mesoporous composite layer. The polysilazane-derived amorphous silica membrane exhibited H-2 permeance of 1.3 x 10(-8) mol/m(2) s Pa at 573 K, and the permeability ratio of H-2/N-2 was measured to be 141. The effects of heat treatment condition on the meso/microporous structure development of the polysilazane-derived amorphous silica within the Si3N4 porous substrate are discussed from a viewpoint of fabricating hydrogen-permselective amorphous silica membranes through polymeric precursor route. (C) 2004 Elsevier Ltd. All rights reserved.