Preparation and properties of porous alumina ceramics with oriented pores

Porous alumina ceramics with unidirectionally oriented pores were prepared by an extrusion method. Pastes for extrusion were prepared by mixing alumina powder with nylon 66 fibers (av. 19 μm in diameter), together with dispersants and binders. The resulting pastes were extruded, dried at room temperature, freed from the binder at 600°C and fired at 1500°C for 2 h. The pore size distribution of the samples showed pores of 16 μm diameter, in good agreement with the original nylon 66 fibers. The pore size observed from SEM photographs of the sintered body was 16 μm corresponding to the burnt-out nylon 66 fibers. A very high degree of cylindrical pore orientation was seen in the SEM micrographs of the samples. The orientation increases with decreasing fiber loading.