| With the advancement of technology and development of economy,people are also facing many challenges while enjoying an intelligent are.It is urgent to prevent and control electromagnetic wave pollution.New expectations for absorbing materials are also put forward:lightweight,having broad absorbing bandwidth and strong absorbing ability.Searching for materials with excellent absorbing properties that can meet the requirements of practical applications has become a research hotspot.Both carbon-based and magnetic materials have their own advantages in the field of microwave absorption,but there are also some shortcomings that hinder the further application.Porous carbon has the advantages of good chemical stability and high conductivity of traditional carbon materials.The unique internal structure not only reduces the density but also has a positive impact on absorbing effect.However,its poor impedance matching cause electromagnetic waves to be reflected away,which is not conducive to electromagnetic waves entering the interior of material.Magnetic materials have good hysteresis loss and permeability,but the defect of high density limits their range of action.So,we consider organically compounding porous carbon and magnetic materials.The two cooperate with each other to obtain composite materials with excellent absorbing properties.In this paper,polyvinyl alcohol is used as carbon source,nickel chloride and ferric nitrate as the source of magnetic particles.Using mechanical foaming,in-situ reduction method and electrostatic spinning technology to prepare carbon/magnetic particle composite materials.Absorbing effect and mechanism of composites under different conditions are explored by adjusting process parameters.After a series of studies,the following results were obtained:(1)Nickel-modified porous carbon materials(NiPCs)were prepared by mechanical foaming,impregnation and in-situ reduction.The analysis of micro-morphology shows that there are a large number of interconnected pores in the material.Nickel is uniformly modified inside the pores.Exploring influence of temperature on absorbing performance,it is found that NiPC-800 with temperature of 800? exhibits better loss and attenuation characteristics.When carbonization temperature is unchanged and impregnation concentration of nickel chloride is changed,the 0.5NiPC-800 has excellent microwave absorption.In the frequency of 2-18 GHz,the maximum RL value can reach-46.6 dB,the widest effective absorption bandwidth(RL<-10 dB)is 4.3 GHz.(2)With ferric nitrate as impregnating solution,in order to explore the influence of different magnetic substances on absorbing performance,porous carbon materials loaded with ferromagnetic FePCs were prepared.The concentration of ferric nitrate is a variable in the experiment.We found that as impregnation concentration increases,the RL value increases firstly and then decreases.Among them,FePC-0.75 obtained at 800? has the best microwave absorpyion performance,which maximizes synergistic effect of iron particles and porous carbon.There is a maximum reflection loss of-56.9 dB at 11.3 GHz,which can achieve 5.2 GHz broadband absorption covers most of the Ku band.(3)We use electrospinning technology to prepare a fibrous carbon material loaded with iron particles(FeFC).Compare with FePC-0.75,analyzing influence of internal structure on iron/carbon composite absorber.Iron particles formed after in-situ reduction are evenly distributed along carbon fiber.The combination of experimental and calculations data found that:compared with FeFC samples,porous structured materials have better impedance matching and electromagnetic wave attenuation characteristics.When porous structured carbon combined with ferromagnetic mater ials,the impedance matching and loss characteristics are better than fibrous materials. |
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