Porous α-Al2O3 ceramics prepared by gelcasting

Gelcasting is a novel method of forming ceramics and has been increasingly employed in preparing complex-shaped, near-net-shape advanced materials. However, this technology is rarely reported for preparing macroporous ceramics. We present the results of a successful attempt to develop a gelcasting process to fabricate porous ceramics from different alpha-Al2O3 powders with d(50) values of 16.14, 17.98, and 21.12 mu m. The porosities of the three specimens sintered at 1550 degrees C for 5 h were measured to be 41.4%, 40.0%, and 42.5%, respectively. The mean pore diameters obtained from the pore size distribution measured by the bubble-point technique were 1.92, 2.13, and 3.65 mu m, respectively, and their permeations to nitrogen correspondingly were in the range of 1.74-3.18 km(3)/m(2) . bar . h. These values demonstrate the reliability of the new gelcasting process for preparing useful porous ceramics. (C) 1997 Elsevier Science Ltd.