Microstructures and Properties of Porous Liquid-Phase-Sintered SiC Ceramic by Hot Press Sintering

Porous liquid-phase-sintered SiC (L-SiC) ceramics were successfully fabricated by hot press sintering (HP) at 1800 °C in argon, using Al₂O₃ and Y₂O₃ as oxide additions. By varying the starting coarse SiC particle size, the relationships between pore microstructures and flexural strength as well as gas permeability of porous L-SiC were examined. All the as-sintered samples possessed homogeneous interconnected pores. The porosity of porous L-SiC decreased from 34.0% to 25.9%, and the peak pore size increased from 1.1 to 3.8 μm as the coarse SiC particle sizes increased. The flexural strengths of porous L-SiC ceramics at room temperature and 1000 °C were as high as 104.3 ± 7.3 MPa and 78.8 ± 5.1 MPa, respectively, though there was a decrease in accordance with their increasing pore sizes and particle sizes. Moreover, their gas permeability increased from 1.4 × 10^-14 m² to 4.6 × 10^-14 m² with the increase of pore size in spite of their decreased porosity.