Effects of aluminum, boron and carbon additives on microstructure of porous silicon carbide ceramics and their properties

Abstract

Abstract Porous SiC ceramics with in-situ plate-like grain growth were fabricated by pressureless-sintering using Al, B and C additives, and the effects of Al, B and C additives on the microstructure of porous SiC ceramics and their properties were investigated. Whereas the porous SiC ceramics sintered with B-C additives mostly consisted of fine SiC grains without grain growth, Al additives with B-C system enhanced plate-like grain growth of SiC in the porous SiC ceramics. Notably, the porous SiC ceramics sintered with 0.1 wt% Al and B-C additives consisted of plate-like SiC grains of around 10-20 μm, and the plate-like SiC grains stuck out of the walls of pores and the sintered surface in the porous SiC ceramics. XRD results suggested that the plate-like SiC grains formed in the porous SiC ceramics sintered with Al-B-C additives mainly consisted from 6H (α-SiC) phase. Compressive strength and thermal conductivity of the porous SiC ceramics sintered with 0.1 wt% Al and B-C additives at room temperature were 50 MPa and 10 W/m·K, respectively. From these results, it is concluded that high performance porous SiC ceramics with unique morphology of entangled large plate-like SiC grains were successfully achieved based on in-situ grain growth.