Pore structures of sol-gel silica membranes

Abstract

Silica membranes have been formed by floating a solution of tetraethyl orthosilicate (TEOS)-water-ethanol on a dense, non-polar organic liquid. The solution reacts with atmospheric moisture and gels to a flexible skin. During gelation, ethanol escapes to the free surface of the gel. Bubbles of ethanol intersect the surface creating circular pores in a closely packed arrangement. When peeled off of the organic liquid, the silica skin stiffens to give 100 μm silica sheets. The top surface, bottom surface and subsurface microstructures have been studied for various sheet thicknesses. The features observed in the gels are similar to those found in organic membranes which are formed at a liquid interface. © 1988.