Research On The Preparation And Microwave Absorbing Properties Of Porous Carbon-based Materials

With the rapid development of wireless technology,while electromagnetic waves bring convenience to human society,electromagn etic pollution is inevitably caused.In order to solve electromagnetic pollution and meet the high requirements of industrial and military fields,it is urgent to develop absorbing materials that convert electromagnetic energy into other forms of energy.Carbon-based materials have the advantages of high electrical conductivity,low density,good thermal stability,and strong corrosion resistance.Among them,porous carbon materials with rich pore structure have attracted attention from researchers.This article aims to investigate the effects of preparation temperature,filling rate and doping modification on the preparation and microwave absorption properties of porous carbon-based materials,and to explore the microwave loss mechanism of porous carbon-based materials.The main research contents of this paper are as follows:（1）Using pine wood as raw material,biomass porous carbon was prepared by the activation method,and the effects of carbonization temperature and filling rate on its microwave absorbing properties were studied.The results show that the higher the carbonization temperature and the filling rate,the stronger the dielectric properties.When the carbonization temperature is 1400℃,the filling rate is 20 wt%,and the absorber has a thickness of 3.8 mm and a test frequency of 7.68 GHz,the minimum return loss（RLmin）value obtained is-42.20dB.（2）Using pine wood and nickel chloride hexahydrate as raw materials,Ni/C composites were prepared by the activation-in-situ one-step method,and the effect of Ni content on its microwave absorbing properties was studied.The results show that the introduction of Ni particles is beneficial to the graphitization process of biomass carbon.The microwave absorption performance of Ni/C can be adjusted by adjusting the content of Ni in the composite material.When the concentration of the nickel chloride hexahydrate solution is 0.013 g/ml,the thickness of the Ni/C absorber is 5.7mm,and the test frequency is 6.00 GHz,the RLmin value is-50.38dB.（3）Using pine wood,urea,and boric acid as raw materials,C/BN composites were prepared by the activation-in-situ one-step method,and the effect of BN content on its microwave absorbing properties was studied.The results show that the introduction of BN can effectively adjust the dielectric properties of composite materials and improve impedance matching.Soaked in a mixture of 10 g urea and 20 g boric acid,the absorber has a thickness of 2.5 mm and a test frequency of 10.88 GHz,and its RLmin value is-56.57dB.（4）Using SiO₂,furfuryl alcohol,and oxalic acid as raw materials,the lightweight hierarchical hollow porous carbon was prepared by the template method,and the effect of carbonization temperature and filling rate on the microwave absorbing performance was studied.The results show that adjusting the carbonization temperature can control the density and the degree of graphitization of the lightweight hierarchical hollow porous carbon.Changing the filling rate can adjust the dielectric properties and impedance matching of the absorber.When the carbonization temperature is950℃,the density is 59±1.4 mg/cm³;when the filling rate is 7.5 wt%,the thickness is 1.7 mm,and the test frequency is 16.4 GHz,the RL min value of the absorber can reach-57.20dB and the effective bandwidth（EAB）is 4.4GHz.