SiC Ceramic-Bonded Carbon Fabricated With Si3N4 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, Si3N4 and carbon powders (25:75 in volume ratio) were gelcasted and then sintered by spark plasma sintering at temperatures of 17001900 degrees C. The ceramic boundary of SiC was formed in situ at above 1700 degrees C by the reaction of Si3N4 and C. The sintered CBCs showed a unique microstructure consisting of carbon particles and ceramic boundaries of 15 similar to mu m in size and 0.53 similar to mu m 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 degrees C were highly dense (97% theoretical density), lightweight (2.36 similar to mg/m3), and had both relatively high bending strength and thermal conductivity (135 similar to MPa and 140 similar to W/mK, respectively).