Thermal stability of silica-zirconia membranes

The thermal stability, phase transformation, surface morphology, pore size distribution and permeation of the defect-free silica-zirconia membrane were investigated by using X-ray diffraction (XRD), atomic force microscopy (AFM), gas adsorption analyzer (BET), and gas permeation apparatus, respectively. Using silica as the stabilizing agent, the defect-free membrane was much more stable than pure zirconia. The crystal transformation of zirconia in the silica-stabilized membrane could be prohibited by the interaction between silica and zirconia. ZrO2 crystals were kept tetragonal below 900 degrees C, the size of which did not change with temperature between 700 degrees C and 900 degrees C. It was further verified by the AFM observation, pore size analysis and permeation study. This thermal stability makes the silica-zirconia membrane a good choice as the intermediate layer for zeolite and Pd-based membranes.