Fracture Behavior and Microstructure of the Porous Alumina Tube

Abstract

Porous alumina tubes with continuous and stepwise pore-gradient along the radial direction were successfully fabricated, where PMMA particles were used as pore forming agent. The tubes were expected to function as high temperature filters. The tube is designed in such a way that the inner part will act as the separation media while the outer part will function as mechanical support with the presence of the porosity gradient. Alumina and PMMA particles were mixed with water to form an aqueous slurry, compacted using the continuous and stepwise methods in centrifugal molding technique. The green body was dried in partial vacuum atmosphere, calcinated at 773 K to remove the organic component, sintered at 1623 K to obtain sintered porous α-alumina tubes. The microstructure observation on porous alumina tubes was carried out. The binary pores of 10μm and submicrometer in diameter were visible, which were formed by the buming-out of PMMA particles and partial sintering, respectively. The fracture behavior of the porous tube was observed by using the ring diametral compression testing. The experimental results show that fracture behavior varies with the amount of pore-forming agent, regardless of the pore-gradient along the radial direction. A reduction in fracture strength is observed with increasing the laminate number, and the minimum strength is found in continuous graded tubes.