Simulation Study In Mechanism And Thermodynamic Process Of Microwave Synthesis SiC

Microwave heating has advantages of rapidity,environmental protection and energy saving.It has attracted worldwide attention.Microwave synthesis of SiC is one of the research hotspots in the field of material synthesis.Although there have been a large number of experimental studies,due to limitations of experimental conditions,there are still many problems in microwave synthesis of SiC.Unclear electric field distribution affects the heating stability and limits the promotion of microwave technology.The thermal effect of the material in the heating process is not clear,and the microwave heating mechanism is not systematic.The atomic reaction diffusion process is complicated and the growth of SiC crystals is not controllable.With the rapid development and maturation of computer technology and numerical methods,researchers have developed a series of simulation software that has been successfully applied to materials synthesis and other fields.Computer simulation is based on theoretical and practical experience.Overcoming the harsh conditions of the experimental conditions and the harshness of the experimental environment,and can effectively interpret the black box type experimental process and analyze the physical and chemical mechanism.The finite element simulation software ANSYS was used to simulate the electric field distribution in the resonant cavity under different resonant modes.The law of the electric field caused by the position and quantity of the sample was studied.The multi-physics coupling software COMSOL was used to simulate the temperature rise of the sample,showing the distribution of the internal temperature field and analyzing the mechanism of the thermal effect;Finally,the influencing factors of carbon atom diffusion were simulated by the CASTEP module in the molecular dynamics simulation software Materials Studio.The simulation results show that when the resonator length is an integral multiple of half wavelength,the electromagnetic resonance in the different modes is the highest,and the electromagnetic resonance uniformity is the best at the center of the resonator.The temperature field at the center of C is the most favorable for the synthesis of SiC.Rational design of electric field distribution in microwave resonant system can achieve simultaneous stable sintering of multiple samples.The microwave thermal effect is the result of the combined effect of dielectric loss and conductance loss.The conduction loss of C is continuously weakened during the synthesis of SiC,and the dielectric loss is gradually increased.The two kinds of loss contribute to increase the heating rate;dielectric constant,conductivity,Al₂O₃ doping has a positive effect on the coupled thermal conversion of C;the electric field promotes the diffusion of C atoms.When there are impurities and vacancy defects,the promotion effect is more significant.