SiC Ceramic‐Bonded Carbon Fabricated With Si ₃ N ₄ and Carbon Powders

New composites called ceramic‐bonded carbon ( CBCs ), consisting of a three‐dimensional structure of carbon particles bonded with thin ceramic boundaries, were developed. To fabricate light and tough CBCs and to understand their reinforcing mechanism, Si ₃ N ₄ and carbon powders (25:75 in volume ratio) were gelcasted and then sintered by spark plasma sintering at temperatures of 1700–1900°C. The ceramic boundary of SiC was formed in situ at above 1700°C by the reaction of Si ₃ N ₄ and C . The sintered CBCs showed a unique microstructure consisting of carbon particles and ceramic boundaries of 15 μm in size and 0.5–3 μm in thickness, respectively. With an increase in sintering temperature, physical bonding of ceramic grains to the carbon particles was enhanced as the grain growth of SiC increased. The SiC / CBCs sintered at 1900°C were highly dense (97% theoretical density), lightweight (2.36 mg/m ³ ), and had both relatively high bending strength and thermal conductivity (135 MPa and 140 W/mK, respectively).