| 摘要 |
A composite membrane is disclosed which operates as a filter for liquids, solids and gases and combinations thereof, having high permeability for the filtrate, e.g., nitrogen passing therethrough, and high selectivity for matter retained thereby, e.g., volatile organic compounds, so that the N2/VOC selectivity is at least about 50/1 or greater; prepared by a low pressure chemical vapor deposition process comprising: (a) providing as a first component thereof, a mesoporous membrane substrate having pore diameters greater than about 20 ANGSTROM ; (b) contacting surfaces, including pore surfaces, of the membrane with at least two reactant gas streams in an opposing reactant geometry, wherein the smallest reactant gas molecule has a kinetic diameter intermediate in size between that of the matter retained by said filter and the filtrate passing therethrough; the reactant gases are capable upon reaction of depositing thereon as a second component thereof, a reaction product which by coating the surfaces, including pore surfaces of said mesoporous substrate, substantially reduces the pore diameters thereof, resulting in a substantially uniform microporous film having pore diameters in the range of from about 4 ANGSTROM to about 8 ANGSTROM ; the reaction product comprises predominantly silicon oxide, -Si-O-, and may optionally include for the purpose of optimizing the stress, and other mechanical, chemical and thermal properties of said film, minor amounts of one or more members, in any combination thereof, selected from the group consisting of polysilicon, -Si-Si-, silicon carbide, -Si-C-, and silicon nitride, -Si-N-; and wherein said reactant gas streams comprise: (1) as the source of silicon and optionally carbide, a di-alkylsilane of the formula R1(R2)SiH2.
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