Oriented Inorganic Thin Film Channel Structures with Uni-Directional Monosize Micropores

The goal of this project was to develop a novel technology that may be used to eventually manufacture a new generation of inorganic membranes and sensors with oriented, uni-directional monosized pores. The premise is that very thin membranes with oriented channels as pores will have a high flux in addition to being highly selective. Applications include: 1) gas separation membranes for oxygen enrichment, partial oxidation, dehydrogenation, and purification of natural gas; 2) refractory catalytic membrane reactors; and 3) molecular recognition sensors. The methodology for making such membranes was to combine Langmuir Blodgett (LB) technology with sol-gel chemistry to engineer pore channels within the range 3 to 20 Å. The channel structure was fabricated of amorphous SiO2 because of its good thermal, chemical, and mechanical stability. Our approach was to use LB techniques to uniformly place organic molecular spacers throughout a thin silica precursor matrix and apply this film to a substrate. LB films of solid solutions of commercially available silane amphiphiles and organic amphiphiles were fabricated. The siloxane groups were then hydrolyzed to form silica and the organic portions of the amphiphiles removed by thermal decomposition. With the completely fugitive organic spacer amphiphiles removed, a thin silica film with micropores resulted. The pore size was in the range of 6 8 Å and in an ultra-thin configuration. With further development this technique may be useful for fabrication of inorganic membranes which satisfy all the criteria of the ideal membrane.