Fabrication and Properties of SiC Porous Ceramics by Slip Casting Process

The silicon carbide particles were employed as the skeleton material, while the mixture of feldspar and clay in eutectic composition to form the glassy grain-boundary phase serving as the binder to hold the SiC grains together, particulate carbon to be oxidized and generate pores. Slip casting process was investigated and some properties of the porous ceramics were discussed. The isoelectric Zeta potential point of the SiC particles corresponded to the pH value of 5.2, and the pH values of the slurry were controlled between 8 and 12 to provide the perfect stability and fluidity. The increase in the firing temperature decreases the range of the pore size distribution, with the principal pore diameter keeps relatively constant. The neck-bridging structure exists among the SiC grains due to the viscous flow of the grain-boundary phase at high temperatures, which helps to improve the binding behaviour. The oxidation product of SiC reacts with the grain-boundary phase, and leads to the precipitation of needle-like mullite crystals, which gives rise to the abnormal increase in the strength of the porous ceramics.