Fabrication and characteristic of porous alumina developed with SiC nano-fiber or nano-whisker

Abstract

Porous alumina green bodies were fabricated by a gel-casting method, for which the slurries of alumina (AKP-30) and PMMA (polymethylmetacrylate) bead were mixed and dispersed at 1: 1, 1:2, 1:3, and 1:4 volume ratios. PMMA bead as precursor of carbon source was used for growing SiC nano-fiber or nano-whisker during a VLS (vapor-liquid-solid) reaction at 1450 degrees C for 9hrs. PMMA beads are converted to carbon particles after calcination at 1300 degrees C for 9hrs in static argon (Ar) atmosphere. Finally, carbon particles remain in pores of alumina bodies connected by continuous pore channels. Fe solution was infiltrated into the porous alumina bodies, which are absorbed on the carbon particles in pores. Fe precursor functions as a seed to develop the SiC nano-fiber or nano-whisker in the porous alumina bodies. The liquid droplets formed at the end of the SiC fiber or whisker are evident for the typical VLS mechanism. The microstructure of the SiC fiber or whisker grown by the VLS reaction was observed by SEM. The porosity was measured by mercury porosimeter. The formation behavior of SiC fiber or whisker is dependent on volume ratio of carbon converted from PMMA bead.