Study On The Growth Mechanism Of SiC Powder Synthesized Under The Action Of Catalyst By Microwave

Silicon carbide（SiC）has high forbidden band width,high breakdown voltage,electrical conductivity,thermal conductivity and excellent high temperature stability.In recent years,it has also been discovered that the wave absorbing properties of SiC gradually increase with increasing temperature,making SiC a potential high temperature resistant wave absorbing material of great interest.At present,there are still many challenges to overcome regarding the preparation and heating of SiC powders,such as complicated preparation of precursors,expensive raw materials,environmental pollution,and difficulties in large-scale preparation.Some researchers have achieved some results in the efficient preparation of SiC by adding catalysts.However,the reaction mechanism of the catalyst in the actual heating and preparation process is not well studied,and the thermal effect of the coupling between the material and microwave during the reaction process is not clear.In this paper,SiC powder was synthesized by using industrial coal and ethyl orthosilicate as raw materials,and the precursors were prepared by sol-gel method,combined with microwave heating to catalyze the synthesis of SiC powder using the interaction between metal particles and microwave,and the coupling relationship between raw materials and microwave was studied by comparing different metal catalysts.The results showed that different Ni Cl₂ contents had a large influence on the morphology of the generated SiC crystals,which gradually transitioned from granular to fibrous with the increase of Ni Cl₂content.The SiC fibers were synthesized by the reaction with CO under the induction of the microwave electromagnetic field,and the RL of the samples catalyzed by 5%Ni Cl₂ reached-36.74 d B at a thickness of 4 mm and a frequency of 4.06 GHz.The presence of Ni-Si compounds improved the wave absorption performance of the SiC fibers to a large extent.In the case of metallic particles Ni as catalyst,3C-SiC in the form of rods was synthesized at 900°C,and SiC fibers with lengths of several to several tens of microns and diameters of several tens to several hundreds of nanometers were synthesized at 1000°C.The morphology of the synthesized SiC under Cu catalysis consisted of regularly shaped particles and a few fine fibers;particles and fibers of uneven size and morphology were generated under Fe catalysis.A large number of uniformly sized SiC fibers were synthesized with a minimum RL of-26.18 d B at a sample thickness of 5.5 mm and a frequency of 2.36 GHz.The minimum RL value was-20.32 d B and the overall RL values of the samples were observed to be below-10 d B,with a wide effective absorption bandwidth.