Fabrication on porous alumina tube by centrifugal molding

The material design model for porous materials is proposed. Porous alumina tubes are fabricated by using two different alpha-alumina powders with narrow size distribution (AES-12 and TM-D) by centrifugal molding technique. The experimental results show TM-D is limited to get the homogenous structure and AES-12 offers a good flexibility in gradient design, which depends on the slurry character. The bimodal pore structure of the tubes is constructed from large spherical pores about 10 mu m formed by PMMA particles and small sub-micrometer pores which are the results of the lower packing density in centrifugal process and the lower sintering temperature. The ratio of the macro spherical pore to sub-micrometer pore varies with the amount of PMMA particles, and hence the bimodal pore structure of porous tubes is very useful to control the air permeability. The fracture strength of O-ring increases with the decrease in porosity regardless of the pore gradient of the tubes. The pore-graded tubes show the higher strength than homogenous tubes while keeping the same porosity in the inner wall. (c) 2004 Elsevier Ltd. All rights reserved.