POROUS ALPHA-AL2O3 CERAMICS PREPARED BY GELCASTING

Gelcasting is a novel method of forming ceramics and has been increasi ngly employed in preparing complex-shaped, near-net-shape advanced mat erials. However, this technology is rarely reported for preparing macr oporous ceramics. We present the results of a successful attempt to de velop 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 me an pore diameters obtained from the pore size distribution measured by the bubble-point technique were 1.92, 2.13, and 3.65 mu m, respective ly, and their permeations to nitrogen correspondingly were in the rang e of 1.74-3.18 km(3)/m(2) . bar . h. These values demonstrate the reli ability of the new gelcasting process for preparing useful porous cera mics. (C) 1997 Elsevier Science Ltd.