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Abstract

The freeze-drying combining solid sintering is a good method to fabricate porous SiC ceramics with good high temperature mechanical properties. Though SiC ceramics are sintered at a high temperature of 2150 °C, there are still large quantity of macropores generated by sublimating large ice crystals and micropores in the ceramic wall caused by small ice crystals sublimating, SiC particles stacking, and burning out of polyvinyl alcohol (PVA). The content of PVA affects the microstructure and strength. As increasing the content of PVA, the size of pores caused by sublimating the ice crystals decreases while both open porosity and room temperature strength increase. After being treated at a temperature of 1200 and 1500 °C, the ceramics exhibit good thermal shock damage resistance.