Preparation And Microwave Absorption Properties Of FeSiCr Magnetic Nanocomposites

With the rapid development of electromagnetic technology and the widespread use of all kinds of electronic products,electromagnetic waves of different frequency bands flood people's living space,causing serious electromagnetic pollution,causing serious harm to the development of society and people's health.Microwave absorbing materials can effectively solve the problem of electromagnetic pollution.Therefore,the traditional FeSiCr soft magnetic materials are taken as the research object in this paper.It has the characteristics of the coexistence of magnetic loss and dielectric loss,low price and abundant raw materials.From the composition and structure control of magnetic nanoparticles of FeSiCr,in order to reach the qualitative light,strong absorption of microwave absorbing materials,such as the thickness of the thin requirements,its surface modification and obtain a series of FeSiCr magnetic nanocomposites,and research influence FeSiCr magnetic nanocomposites microwave absorbing performance of the factors,the main research contents and conclusions are as follows:(1)The FeSiCr@ZnFe₂O₄ nanocomposites with core-shell structure were successfully prepared by DC arc evaporation and hydrothermal method.By controlling the addition of Zn²⁺,ZnFe₂O₄ is generated on the surface of FeSiCr nanoparticles,which regulates the complex dielectric constant of FeSiCr nanoparticles,optimizes impedance matching,and improves the microwave absorption capacity of the materials.The results show that the microwave absorption performance of FeSiCr@ZnFe₂O₄ nanocomposite is the best when 0.3 g Zn(CH₃COO)₂ is added.When the frequency is 15.9 GHz and the coating thickness is 1.5 mm,the minimum reflection loss of FeSiCr@ZnFe₂O₄ nanocomposite can reach-44.2 dB,and the effective absorption band range is from 12.2?18 GHz.(2)The FeSiCr nanoparticles with different degree of flake shape were obtained by mechanical ball milling.The results show that the longer the milling time is,the more obvious the agglomeration of FeSiCr nanoparticles is and the more obvious the flaking degree is.When the milling time is 6 h,the FeSiCr nanoparticles obtain the best microwave absorption performance.At a frequency of 6.2 GHz and a thickness of 2.2 mm,the minimum reflection loss value of the sample is-41.5 dB.The effective absorption bandwidth range is 4.5?8.1 GHz.The minimum reflection loss of the samples with ball-milling time of 4 h was slightly higher than that of the samples with ball-milling time of 6 h,which was-40.1 dB.The improved absorption of FeSiCr nanoparticles is due to the sheet particles are more suitable for conducting electricity and enhancing the spatial charge polarization between the metal particles.(3)In order to avoid the agglomeration phenomenon caused by long milling time and shorten the experimental process,graphene oxide(GO)was composite with samples after 4 h ball milling to obtain flake GO modified FeSiCr nanoparticles.The experimental results show that the trace amount of GO has little effect on the complex permeability of FeSiCr nanoparticles after ball milling for 4 h,and the real part of the complex dielectric constant increases with the increase of GO.The optimal wave absorption performance was obtained after the composite of 0.2 g of GO.When the frequency is 8.0 GHz and the thickness is 1.9 mm,the minimum reflection loss value can reach-45.0 dB,and the effective absorption band range is6.6?10.3 GHz.(4)After 4h of ball milling,the FeSiCr nanoparticles were oxidized and heat treated to obtain the flake FeSiCr@Fe₂O₃ nanoparticles with different Fe₂O₃ content.The experimental results show that the content of Fe₂O₃ increases with the increasing of the temperature of oxidation heat treatment.When the oxidation heat treatment temperature is 200 ^oC,the sample obtains the best wave absorption performance.When the frequency is 4.6 GHz and the coating thickness is 3.5 mm,the minimum reflection loss value is-.35.8 dB,and the effective absorption band width range is 3.9?5.7 GHz.The minimum reflection loss is-66.2 dB in the coating thickness range of 1?5 mm.