Induction plasma synthesis of ultrafine SiC powders from silicon and CH4
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Ultrafine SiC powders have been synthesized from elemental silicon and methane using induction plasma technology. The powder products were characterized by X-ray diffraction, thermogravimetric analysis, scanning and transmission electron microscopy, electron probe microanalysis, infrared spectroscopy, and surface area measurement. The powders collected from various sections of the reactor system showed different features reflecting different compositions and powder morphologies. The purest SiC powder was collected in the metallic filter. It was composed of both α-and β-phase of SiC with small levels of free silicon and carbon. The reaction route used is based on the evaporation of the injected pure silicon starting powder, followed by carburization of the silicon vapour using methane. The silicon evaporation rate was found to depend strongly on the particle size of the silicon powder. Using silicon powder with a mean particle diameter of 100 μm, at a plasma power level of P=43.2 kW, the conversion of silicon to SiC and the overall SiC content in the product powder was 44.2% and 50.8 wt%, respectively. The injection probe position was Z=9.3 cm, the silicon feed rate was 4 g min−1, and the C/Si molar ratio was 0.7. Using silicon particles with a mean diameter of 45 μm, the conversion and overall content of SiC increased to 70.4% and 73.9 wt%, respectively, under the same plasma operating conditions and powder feed rates. By appropriate selection of experimental conditions, ultrafine SiC powder of high quality was achieved.
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