Experimental Research On A Pilot-Scale Synthesized β-SiC Micropowder Using Infinite-Mini-heat Sources Furnace

β-SiC has been extensively applied in aerospace, machinery,metallurgy,electron,military industry,and etc.because of its excellent properties in high hardness,wear resistance,antioxidation,high mechanical strength,high thermal conductivity,small linear expansion coefficient,and wide band gap.At present,although high purity ultrafineβ-SiC powders could be prepared by various methods,but there are many disadvantages,such as high cost,low yield and difficult to industrialization.The author participates in pilot-scale research which our team invented synthesis technology ofβ-SiC powder by infinite-mini-heat source furnace.One-time Charging weight increased to 2500kg ,andβ-SiC powder can be stably produced. The yield ofβ-SiC powder reached 70 percent and unit Consumption reduced to 23Kwh/kg.Through calculation , simulation and numerical fitting the change law of forced filling rate , resistance and power, the main technology parameters determined are as follows: mixing time is 20min, holding power is 100Kw, synthesis time is 130 hours and power supply system is divided into four stages.The results show that main crystal phase isβ-SiC in first-grade products and second- grade products,there are graphite impurity in the third-grade products by XRD phase analysis. The appearance ofβ-SiC powder which was observed by SEM was amorphous or subidiomorphic crystal and had agglomeration to some extent. Characterization result of laser particle size analyzer suggested that average D95 of particle size was about 62μm,and average D50 of particle size was about 25μm. Purity ofβ-SiC powder product by primary synthesis reached over 98 percent.This paper discusses conductive mechanism of composite powders which consist of different raw materials.The resistance of composite powders is non-ohmic characteristic,and is a percolating systems in macroscale. The percolation threshold which was determined by experiment is from 13 percent to 23 percent.There are mainly three conductive mechanisms on the composite powders. The main conduction mode is that contactile conductive particulates form conducting channel network in composite powders system. Secondly, isolated conductive particulates or clusters produce tunneling effect under the thermal vibration condition.Once again,there is effect of electric field emission which is a special kind of tunneling effect. The production of emission current attribution to effect of electric field in conductive particulates. This three conduction mode affect non-ohmic characteristic of composite powders in different extent.