FABRICATION AND MICROSTRUCTURE OF AL2O3-TIO2 COMPOSITE MEMBRANES WITHULTRAFINE PORES

A ceramic membrane consisting of an alpha-Al2O3 support and an Al2O3-T iO2 top layer, which is thermally stable up to 900 degrees C, was prep ared by the sol-gel method. The supported Al2O3-TiO2 top layer was mad e by dip-coating the support in a mixed sol. The microstructure of the composite membranes was studied by SEM and TEM after calcination at 8 50-1000 degrees C. After sintering at 850 degrees C for Ih, the averag e particle diameter of the Al2O3-TiO2 top layer was about 15 nm. The s upported Al2O3-TiO2 composite membranes exhibited much higher heat res istance 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 a fter calcination up to 900 degrees C. (C) 1997 Elsevier Science Limite d and Techna S.r.l.