Dependence of presence of defect in gamma-Al2O3 toplayer on structure of support

The permeation properties of two types of supports with different pore sizes were investigated with five kinds of gases, i.e. nitrogen, hydrogen, helium, propane and argon. It is indicated that the gas permeation through these supports occur mainly via viscous flow mechanism. gamma-Al2O3 composite membranes were made on two types of supports by sol-gel technique. The integrity of gamma-Al2O3 toplayer was checked by gas permeation method. Furthermore, the influence of pore size of support on the defects or defect-free of the toplayer was studied. The defect-free toplayer can be formed on the support with smaller pore size by dipping twice. The permeation through the toplayer can be described mainly by Knudsen diffusion mechanism.