Effect of aluminum hydroxide content on porosity and strength of porous mullite-bonded silicon carbide ceramics

Abstract

Porous mullite-bonded silicon carbide (SiC) ceramics were prepared from SiC and aluminum hydroxide [Al(OH)3] powders. The Al(OH)3 content was varied from 14.5 to 47.3 wt %, and porous SiC ceramics were fabricated via reaction sintering at 1450–1550°C for 2 h. The microstructure showed large SiC grains embedded in a matrix of small and loosely packed mullite/alumina particles. It was demonstrated that the porosity decreased and flexural strength increased with increase in Al(OH)3 content. The porosity varied from 46 to 54%, and flexural strength varied from 3 to 14 MPa with the variation in Al(OH)3 content and sintering temperature. Typically, porous mullite-bonded SiC ceramics of 14 MPa strength and 47% porosity were obtained when SiC and 47.3 wt % Al(OH)3 powders were sintered at 1500°C.