Abstract
Amorphous silica membrane has loose structure in comparison with cristobalite crystal structure, so that helium and hydrogen with small molecular size can permeate through amorphous structure. The potential for thin layer formation of less than 100 nm via chemical vapor deposition (CVD) and sol–gel method in comparison with other inorganic materials can dramatically improve He and H2 permselectivity. Here, sol–gel derived silica membranes are reviewed in terms of control of silica network size, which is important issue for a practical application of amorphous silica membranes in industry. The spacer method utilizing bridged alkoxide with organic groups between 2 Si atoms and fluorine doping into amorphous structure is introduced.
