Effect of SiO2 layer intermediation on direct carbothermal synthesis of SiC nanopowders

Beta-SiC was synthesized by direct carbothermal reaction using silicon and SiO2-layer-coated carbon powders. It is usually difficult to control the rate of the direct carbothermal reaction of silicon because the reaction rapidly progresses. Therefore coarse powders are obtained although it has the advantage of low synthesis temperature. To evade the above difficulty we tried to insert SiO2 layers between carbon and silicon powders, and the effect of SiO2 layer intermediation on the SiC synthesis was examined. SiO2 was coated on carbon black powders by using a 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) solution. The mixture of silicon and SiO2-coated carbon powders was reacted at 1200-1500 degrees C for 1 h in an Ar gas atmosphere. The morphologies of SiO2-coated carbon and synthesized SiC powders were observed. Thermal and phase evolution during the synthesis of SiC powders were analyzed. We obtained beta-SiC powders with a particle size of around 100 nm at the synthesis temperature of more than 1400 degrees C, which is a considerably lower reaction temperature than that of a usual carbothermal reaction.