Fabrication and properties of SiC/mullite composite porous ceramics

SiC/mullite composite porous ceramics were prepared from a mixture of calcined kaolin, aluminum hydroxide, silicon carbide, and graphite. The above mixture was heated in air at 1250–1450 °C to produce pores by burning graphite and bond the SiC particles by reaction-derived mullite. The reaction bonding behavior, open porosity, firing shrinkage, and mechanical strength of the composites were investigated as a function of the mass ratio of calcined kaolin and Al(OH)3, sintering temperature, holding time, and graphite content. In addition, the phase composition and microstructure of the composites were also studied. The results show that when the mass ratio of calcined kaolin:Al(OH)3 is 1:1.5, in the absence of graphite, the flexural strength and the open porosity of the composites were 48.14 MPa and 33.97%, respectively. However, when 15% graphite was added to the above composition, a flexural strength of 27.26 MPa was achieved at an open porosity of 48.80%.