Preparation of nanoporous silica–zirconia layers by in situ sol–gel method

Abstract

Silica–zirconia membranes were prepared using a sol–gel process, never before used on this system. Thin layers of gel were grown on the outside of porous alumina support tubes using the permeation of water through pores of the tube to control the rate of hydrolysis with a reactive silica–zirconia alkoxide solution. A recipe was developed and optimum coating conditions were found to be the ratios of tetraethylorthosilicate (TEOS) to Zr propoxide to 1-propanol molar ratios (1:0·5:17), with a coating time of 300 s. The method allowed the formation of a membrane in a single step compared with repeated coating and firing. The coatings could be prepared adherent and without cracks when properly prepared.