Synthesis and characterization of microporous silica membranes fabricated through pore size reduction of mesoporous silica membranes using catalyzed atomic layer deposition

This work presents the development of a new mesoporous silica membrane. A dip coating technique was employed to deposit a thin film on macroporous supports. The dipping solution consisted of a stable silica sol organized around surfactant micelles. The templated silica film was found to have a three dimensional pore structure with nitrogen gas permeance in the range of 10-6 mol m-2s-1 Pa-1.; This thesis introduces a novel type of microporous silica membrane. The surface limited chemical vapor deposition technique known as catalyzed atomic layer deposition was used to deposit monolayers of silica within the pores of mesoporous silica membranes. The use of pyridine as a catalyst enable the pore size reduction process to be performed much lower temperatures and much shorter exposure times than un-catalyzed atomic layer deposition. The pyridine catalyst was found to act a template for the final pore size of the membranes. Subsequent exposure cycles after the exclusion of pyridine failed to further reduce the pore diameter. The process thus proved to be a self-limiting pore size reduction. The process also proved to be effective in reducing viscous flow defects into the Knudsen diffusion regime without greatly decreasing the overall gas permeance of the membrane.; Membranes produced by catalyzed atomic layer deposition were modified with two different aminopropyl silanes in order to enhance the carbon dioxide permeance through the membrane. An atomic layer deposition technique using ethylenediamine to promote the surface attachment of aminopropyldimethylethoxysilane to the pore surface was found to provide the greatest increase in carbon dioxide permeance.