Synthesis And Microwave Absorption Property Research Of Dendritic Silicon Carbide

Silicon carbide is equipped with excellent chemical stability,good microwave absorbing property,the advantage of easy access of raw materials and low cost,which make it promising for the application in the field of microwave absorption.Nevertheless,it is still an urgent problem how to improve the microwave absorbing properties of silicon carbide.As the morphology of the wave absorbing material plays an important role in the microwave absorbing properties,it has been proved an effective method to improve the microwave absorbing performance by controlling the morphology of the materials.The dendritic structured microwave absorbing materials possess special morphologies and exhibit unique microwave absorbing behaviors,which has been turned out favourable for the improvement of the microwave absorption property.Since silicon carbide is usually prepared under high temperatures,the methods by which other dendritic materials are made can hardly be applied to the synthesis of dendritic silicon carbide directly.Therefore,this problem seriously slows down the improvement of microwave absorbing properties of dendritic silicon carbide.Herein,this dissertation synthesized dendritic SiC along with the idea of changing the surface state of raw materials by using electroless plating of Fe and impregnation of Ni(NO3)2,respectively.The structure,morphology and microwave absorption performance of the synthesized SiC were investigated,respectively.Firstly,high temperature sintering method using different forms of carbon,sol-gel precursor method and chemical vapor deposition method were taken to synthesize the linear SiC.The results of morphology characterization demonstrate that the chemical vapor deposition method produce the best linear SiC.Based on this,electroless plating of Co,Ni,Fe were conducted to catalyze the growth of SiC branches under the high temperature.Results show that the most significant dendritic structure is obtained by electroless plating of Fe.Secondly,by construct of the microwave absorption performance of the linear and dendritic SiC,it is found that the maximum reflection loss(RL)of dendritic SiC whisker higher than that of the linear ones,and the effective absorption bandwidth is more broad.When it comes to the SiC nanowires synthesized from the chemical vapor deposition,the maximum RL of the dendritic structured SiC nanowires is higher than the linear ones,so does the effective absorption bandwidth.The microwave absorption of both SiC whiskers and nanowires can be enhanced by introducing the dendritic structure.Finally,the structure,morphology and microwave absorption property of SiC produced from carbon fiber cloth soaked in the Ni(NO3)2 were studied.Results indicate that the presence of Ni(NO3)2 can not only decrease the reaction temperature,but also change the morphology on the surface of the products and form tube brush-like SiC.The effect of reaction time and concentration of Ni(NO3)2 on the morphology and structure of tube brush-like SiC were studied.Results show that the density of dendritic SiC primarily rises up and then falls down with the increase of the temperature.The aspect ratio shows decrease tendency with the increase of the concentration of Ni(NO3)2.The microwave absorption property of the tube brush-like SiC exhibits increase tendency with the increase of aspect ratio and the increase of density of dendritic structured SiC.