Influences of sol and phase stability on the structure and performance of mesoporous zirconia membranes

Zirconia membranes have been prepared by the sol-gel method with zirconium oxychloride as a precursor. Effects of five organic solvents (formaldehyde, acetone, methanol, ethanol, ethyleneglycol) on the apparent stability of zirconyl oxalate sols have been investigated, which shows that ethyleneglycol has the best stabilization. Stability of sols, which have the same concentration of ethyleneglycol (25% in volume ratio, 25vol% for short) but differ in that of methylcellulose (MC) have been measured by a method called 'centrifugal sedimentation-light transmittance’. The development of pure zirconia and YSZ treated at temperatures ranging from 773 to 1373K were characterized by X-ray diffraction (XRD). The active zirconia layer is characterized by scanning electron microscopy (SEM), liquid-liquid displacement porometry (LLDP) and clean water filtration. It is found that the stabilized sol with 25vol% ethyleneglycol is suitable for preparing perfect zirconia mesoporous membrane. With the firing temperature rising, the pore size of the membrane increases, and so does clean water permeation (CWP). It is identified by XRD that YSZ exists in only cubic modification, while pure zirconia exists in cubic and monoclinic ones. However, no distinct influence of phase transformation on membrane pore structure and performance has been found.