Fabrication and microstructure of Al2O3-TiO2 composite membranes with ultrafine pores

A ceramic membrane consisting of an alpha-Al2O3 support and an Al2O3-TiO2 top layer, which is thermally stable up to 900 degrees C, was prepared by the sol-gel method. The supported Al2O3-TiO2 top layer was made by dip-coating the support in a mixed sol. The microstructure of the composite membranes was studied by SEM and TEM after calcination at 850-1000 degrees C. After sintering at 850 degrees C for Ih, the average particle diameter of the Al2O3-TiO2 top layer was about 15 nm. The supported Al2O3-TiO2 composite membranes exhibited much higher heat resistance than the TiO2 membranes. Although significant grain growth was observed for the TiO2 membrane after heating above 700 degrees C due to phase transformation, the Al2O3-TiO2 composite membrane retained a crack-free microstructure and narrow particle size distribution even after calcination up to 900 degrees C. (C) 1997 Elsevier Science Limited and Techna S.r.l.