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 α-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 μm 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.