Preparation of ZrO 2–Al 2O 3 composite membranes by sol–gel process and their characterization

Abstract

ZrO 2–Al 2O 3 composite membranes with 50 mol% zirconia were prepared by sol–gel process on the porous ceramic tube. X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), nitrogen isothermal absorption measurement and gas permeability test were used to characterize the membranes. It was identified by XRD that, from 700 to 1100 °C, the composite membranes existed in only tetragonal ZrO 2, and neither monoclinic ZrO 2 nor alpha Al 2O 3 appeared. The thermal stability of the composite membranes was improved greatly, compared to that of pure Al 2O 3 or ZrO 2 membranes. Scanning electron microscopy (SEM) images showed that the membranes were defect-free. The most concentrative pore diameter of the composite membranes determined was about 4.3 nm. Gas permeability test suggest that the composite membranes possessed gas selectivity, and the separation factors for N 2/Ar were 1.119 at 0.3 MPa and 1.140 at 0.5 MPa, respectively, which were slightly smaller than the value expected from the ideal Kundsen diffusion ( α=1.194).