Preparation and properties of porous silicon carbide ceramics through coat-mix and composite additives process

The core-shell structure silicon-resin precursor powders were synthesized through coat-mix process and addition of Al2O3-SiO2-Y2O3 composite additives. A series of porous silicon carbide ceramics were produced after molding, carbonization and sintering. The phase, morphology, porosity, thermal conductivity, thermal expansion coefficient, and thermal shock resistance were analyzed. The results show that porous silicon carbide ceramics can be produced at low temperature. The grain size of porous silicon carbide ceramic is small, and the thermal conductivity is enhanced significantly. Composite additives also improve the thermal shock resistance of porous ceramics. The bending strength loss rate after 30 times of thermal shock test of the porous ceramics which were added Al2O3-SiO2-Y2O3 and sintered at 1 650 °C is only 6.5%. Moreover, the pore inside of the sample is smooth, and the pore size distribution is uniform. Composite additives make little effect on the thermal expansion coefficient of the porous silicon carbide ceramics.