Field-assisted Carbothermal Reduction Synthesis And Sintering Of Silicon Carbide Powders

In this paper, silicon carbide powder was synthesized by spark plasma-assisted and microwave-assisted carbothermal reduction using quartz sand as raw material, owing to the natural and geographical advantages of quartz sand in Hainan Province with high purity and large reserves. The preparation process, phase evolution, microstructure, particle size distribution and so on were studied systematically. Meantime spark plasma sintering of silicon carbide powders produced by two kinds of different combustion synthesis routes.In the experiments of spark plasma-assisted carbothermal reduction of silicon carbide,quartz sand, carbon black and phenolic resin with account for 10% weight of total carbon content were used as raw materials. When the synthesis temperature is 1800 ℃ for 5min, the purity of 97.95% and the average particle size of 1.2 μm silicon carbide powder was synthesized. Under the condition of prolonging the holding time, the synthesis temperature was kept at 1700 ℃ for 10 min, and the near-spherical silicon carbide powder with uniform particle size distribution was obtained. To further optimize the process conditions, the raw material was subjected to spark plasma and hot pressing treatment, silicon carbide powder was obtained at 1650 ℃ for 5 min with the purity of 99.52%. Compared with the traditional carbon thermal reduction method, the preparation temperature was significantly reduced and the holding time was greatly shortened.In the experiment of microwave-assisted carbothermal reduction,quartz sand,carbon black and phenolic resin with account for 20% weight of total carbon content were used as raw materials. The synthesis temperature was maintained at 1650 ℃ for 30 min to obtain silicon carbide powder with high purity.Silicon carbide powder was prepared by two ways of spark-plasma assisted and microwave-assisted carbothermal reduction. After the acid treatment, the silicon carbide ceramics were prepared without sintering aid in the spark plasma sintering system. The relative density was 92.4% and the bending strength reached 400.43 MPa at 1900 ℃ when the spark plasma system pressure was set at 50 MPa sintering temperature of 1950 ℃ for 10 min,used silicon carbide powder prepared by spark plasma-assisted as raw material. In addition, at the sintering temperature of 1950 ℃, the relative density and flexural strength were 93.4% and 307.30 MPa, respectively, used silicon carbide powder prepared by microwave-assisted as raw material.