Preparation And Properties Of SiC Aerogels Electromagnetic Wave Absorbing Materials

Radar wave absorbing material is a key technology to improve the survivability of weapons and equipment on the battlefield."Thin,light,wide and strong" has become the goal of this material.Among them,SiC-based ceramics are the current research hotspots of high temperature resistant wave absorbing materials.If it is made into aerogel form,the material not only has the characteristics of light weight,high temperature resistance and wave absorption,but also can play a thermal insulation function.The related research is still in its infancy.In this paper,SiC aerogels were prepared based on sol-gel and carbothermal reduction.For the first time,SiC aerogel blocks were prepared by atmospheric drying,and their electromagnetic wave absorption and thermal insulation properties were studied.The effects of atmospheric drying process,reactant concentration,APTES ratio in silicon source,ratio of carbon source to silicon source,carbonization and carbothermal reduction process on the aerogel phase and structure were systematically studied.The results show that with the optimization of the preparation process,the decrease of the reactant concentration,the increase of the APTES ratio and the increase of the silicon source content,the density of the SiC aerogel decreases and the specific surface area increases.The optimal preparation process system was determined to obtain a SiC aerogel block with a low density of 0.49 g/cm3,a high specific surface area of 484.7 m2/g,and a high porosity of 87.5%.Taking SiC aerogel powder as the wave absorber and dispersing in the wavepermeable paraffin matrix,the influence of the content and composition of the wave absorber on the electromagnetic properties and electromagnetic wave absorbing properties of the composites was studied.As the content of the powder increases,both the real and imaginary parts of dielectric constant increase,the loss capability increases,but the level of impedance matching decreases.At the same powder content,as the SiC crystal phase in the aerogel increases,the loss capacity of the material increases;as the residual amount of the Si O2 component increases,the impedance matching level increases.Through adjustment to achieve a balance of impedance matching and attenuation capabilities,RS12-10%(carbon source silicon source ratio 1:2,aerogel powder mass fraction 10%)composite material has excellent wave absorption performance,the peak reflectance reaches-64.946 d B@2.4mm,15.44 GHz,and the effective absorption bandwidth reaches 7.52 GHz.Through the calculation method of dielectric properties of SiC aerogel/paraffin composite materials,the dielectric properties and wave absorption properties of bulk SiC aerogels were obtained by inversion.Combined with finite element analysis to simulate the thermal insulation effect of aerogels.The research shows that the bulk aerogel still has better absorption performance in the X-band.When the thickness of RS14 material is 2.1mm,the minimum reflectance is-18.585 GHz,and the absorption bandwidth reaches 4.56 GHz.In addition,the material has the best thermal insulation performance,its thermal conductivity at room temperature is 0.031 W/(m·K),which rises to 0.054 W/(m·K)at 800?.The results of the study indicate that SiC aerogel is a potential waveabsorbing/insulation integrated material.