Study Of The Processing Of SiC Crystals Of Microwave Synthesis

As a new and environment friendly way of heating, microwave heating is receiving wide attention of domestic and foreign researchers with its energy saving,high efficient, clean and environmental protection. The preparation of SiC crystals by microwave heating technology has become one of hotspots, but the current study still stay at different experimental conditions, lacking of research on mechanism of microwave heating and kinetics of SiC crystal growth. In this subject, SiO2 as silica source, coal and hydrothermal carbon spheres are selected as carbon source respectively, which study the effect of microwave heating process on the formation of SiC crystal. The mechanism of thermal effect in the process of microwave heating was studied by combining the different size distribution of coal particle, and the kinetic process of SiC crystal growth was revealed.The results show that with natural coal and hydrothermal carbon spheres as carbon source, respectively, SiC crystals was synthesized at the heating temperature of 1100°C, 1200°C, 1300°C and 1400°C, holding for 10 min. With natural coals as carbon resource, SiC whiskers had been synthesized at different heating temperature.When heating temperature was 1200°C, quantity of Si C crystals was largest. But with thermal carbon spheres as carbon resource, SiC whiskers had been synthesized only at 1100°C.Different sizes of coal particles also affected morphology of SiC crystal:when middle size of coal particles as carbon resource and heating temperature being1100°C for 10 min, morpholoy of SiC obtained mainly is whisker. Meanwhile,direction of SiC whiskers along <111> orientation, in line with the growth mechanism of V-S. When large size of coal particles as carbon resource and heating temperature being 1100°C for 30 min, Radioactive space growth crystals of SiC were obtained and its growth kinetic was intrinsic coupling thermal effect of coal. When middle size of coal particles as carbon resource and heating temperature being 1100°C~1500°C,only SiC particles were obtained; When temperaure further increased to 1700°C,plasma was inspired and sizes of SiC particles reduced.Combined with relationships of input power, reflected power and temperature,mechanism of microwave heating was put forward. First of all, intrinsic of coal particles provide heat, raising the temperature. Then the intensity of intrinsiccoupling thermal effect coal particles gradually weaken, meanwhile the intensity of twice coupled thermal effect of SiC particles increase. Different coal particle sizes owed different intensity of coupled thermal effect. The optimal size of coupling thermal effect was 125 to 200μm;...