Preparation and characterization of Al2O3-ZrO2 composite membranes

Al2O3-ZrO2 Composite membranes supported on Al2O3 hollow fiber were prepared by sol-gel process from aluminium iso-propoxide and zirconyl chloride as their raw materials. The thermal stability, phase transformation, structure and morphology of composite membranes were characterized by thermogravimetric analysis and differential thermal analysis (TGA-DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that the thermal stability of composite membranes is better than pure Al2O3 or ZrO2 membrane. The crystal phase of composite membranes is tetragonal ZrO2 below 1100degreesC but monoclinic ZrO2 and alpha Al2O3 appear at 1200degreesC. Investigation with SEM showed that the membranes were defect-free. Gas permeation testing showed that the membranes were of gas selectivity, and the separation factor of nitrogen to argon were 1. 191 and 1. 185 at 0. 3MPa and 0. 5MPa, respectively, which were similar to theoretical separation factor( alpha = 1. 194). This showed that gas diffusion through membranes was governed by Knudsen diffusion mechanism. The most probable pore diameter of an unsupported composite membrane was about 4. 3nm as characterized by nitrogen isothermal absorption measurement.