Microporous alumina substrate with porosity >70% by gelcasting

Microporous alumina membrane substrate in tubular and planar configurations have been prepared by gelcasting of alumina powder slurry using high amount of urea–formaldehyde as gelling agent followed by humidity controlled drying, binder removal and sintering of the gelled bodies. Porosity of the substrate samples sintered at 1350 °C was more than 70% as measured by mercury porosimeter. More than 51% porosity could be retained even after sintering of the samples at 1450 °C. Average pores size of the membrane substrate samples sintered at temperature in the range from 1250 to 1550 °C varied between 0.42 and 0.56 with a maximum at 1350 °C. More uniform pores were observed in sample sintered at 1450 °C. Urea-formaldehyde polymer present in the gelcast body acts as template for micropores.