Synthesis And Characterization Of SiC Powder

SiC ceramic has been extensively applied in precision bearings, sealing element, steam-turbine rotor, burner nozzle, heat interchanger parts, atomic reactor materials and etc. because of its excellent properties in high temperature mechanical properties, antioxidatio, abrasion resistance, thermal stability, smaller coefficient of thermal expansion, larger thermal conductivity, hardness, thermal shock and chemical corrosion. It has attracted increasing attention in recent years and has a wide application foreground. At present, the main method to synthesize SiC powder for trade—carbonthermal reduction method need high temperature (﹥1600℃) and long time (﹥5h), which not only increases the size of the powder but also enhances the production cost that largely affect the spreading and application of SiC powder.Many research indicated that improving the homogeneous mixing extent of the starting materials and adding appropriate additives were the effective ways to accelerate the reaction rate. In this paper, nano-SiO2 and activated carbon were used to synthesize SiC powder by carbonthermal reduction method. The rare earth lanthanum or ceria were used as the additives. The experimental results showed that SiC ultrafine powder was synthesized at 1500℃for 120 minutes by used rare earth lanthanum as additive. Its primary particle size was about 100nm and aggregated particle size was about 360nm and the particle shape was regulation, non-aggregation and well dispersibility. While the rare earth ceria used as the additive, SiC ultrafine powder was synthesized at 1500℃for 150 minutes but the particle shape was irregulation and seriously agglomerated and had numerous crystal whiskers. The results indicated that the effect of lanthanum was better than ceria in the process of synthesize SiC by carbonthermal reduction method. Comparing with the traditional carbonthermal reduction method, the synthesis temperature was not only reduced, but also the time of reaction was shortened. Therefore, ultrafine powder of SiC could be produced with non-aggregation and regulate particle shape. In this paper, the reaction mechanism for synthesize SiC powder by carbonthermal reduction method was also discussed. There were two reaction mechanisms: for first, if the reaction happens in a closed vessel, the reaction between the gas and gas phase would be happened through controlling the synthetic temperature and adjusting the partial pressure of CO. for second, if the reaction happens in the atmosphere of Ar the reaction between the gas and...