| Zirconia membranes are attracting considerable interest owing to their good chemical, thermal stability and other properties such as catalysis and permselectivity for oxygen. Sol-gel is one of the most important methods of the zirconia porous membranes preparation.The defect-free YSZ ultrafiltration with aperture of 20nm and thickness of 5μm are prepared by sol-gel method on the alumina substrate. Zirconium oxychloride, Yttria nitrate and hexamethy lenete tramine are used as the precursor, stabilizing agent and precipitator, respectively. The influence of the content of peptizator and ultrasonic on the transparent sol is investigated and the sols with suitable viscosity and good casting property are obtained. 5% Polyvinyl alcohol is added to the sol before coating. And zirconia undiluted ytttium is prone to be transformed from tetragonal phase to monoclinic phase at 500~550℃with traditional methods, while the temperature of crystal transformation of zirconia is increased to 630℃with the improved method. Between 700~900℃, only the tetragonal zirconia does exist by the interaction between 8% Yttria nitrate and zirconia. The main parameters of YSZ membranes such as porosity and average pore size are determined. The thermal stability, phase transformation, surface morphology of the YSZ membranes are investigated by using scanning electron microscopy(SEM) and X-ray diffraction(XRD), ect.A mass transfer resistance model that describes the gas permeation through the composite membranes is developed. The influence of pore size, the effective porosity and the thickness of the top layer on the gas permeation resistance in the porous support of the composite membrane have been analyzed. The results show that the top layer with smaller pores and smaller effective porosity possesses relatively large resistance, which dominates the mass transfer in the entire composite membrane. The study is very important to synthesize the composite membranes.
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