Preparation and properties of porous alumina ceramics with oriented cylindrical pores produced by an extrusion method

Porous alumina ceramics with unidirectionally-oriented pores were prepared by extrusion. Carbon fibers of 14 mu m diameter and 600 mu m length to be used as the pore-forming agent were kneaded with alumina, binder and dispersing agent. The resulting paste was extruded, dried at 100 degrees C, degreased at 1000 degrees C and fired at 1600 degrees C for 2 h. SEM showed a microstructure of dispersed highly oriented pores in a dense alumina matrix. The pore area in the cross section was 25.3% with about 1700 pores/mm(2). The pore size distribution of the fired body measured by Hg porosimetry showed a sharp peak corresponding to the diameter of the burnt-out carbon fibers. The resulting porous alumina ceramics with 38% total porosity showed a fracture strength of 171 MPa and a Young's modulus of 132 GPa. This strength is significantly higher than the reported value for other porous alumina ceramics even though the present pore size is much larger. (c) 2005 Elsevier Ltd. All rights reserved.