Synthesis And Electromagnetic Properties Of High Electric Loss-based Electrical/Magnetic Composite Absorber

Electromagnetic(EM)wave absorbing material is one kind of functional material which can convert EM wave energy into heat energy or other forms of energy.In view of the needs of EM wave pollution protection and military stealth technology,it is urgent to develop high-performance EM wave absorbing material.The absorber is the effective loss component in the EM wave absorbing material and it is difficult for single-component absorber to meet the requirements of"thin thickness,lightweight,broad frequency and strong absorption".In this paper,from the perspective of different loss characteristics,based on high electric loss material,the preparation of new type of electrical/magnetic composite absorbers were carried out.The structure,morphology and composition of the composite absorbers were analyzed in detail and their electromagnetic properties,especially the EM wave absorption performance were studied,and the possible absorption mechanism was explained.The main contents and conclusions are as follows:Porous cubic rod-like nickel ferrite(NiFe₂O₄)was prepared by polymer-assisted deposition and post-heat treatment first,then multi-walled carbon nanotubes(MWCNT)was anchored on the surface of silica(SiO₂)coated NiFe₂O₄ by electrostatic adsorption to obtain NiFe₂O₄@SiO₂/MWCNT.The composite absorber was verified to be as expected through the characterization of morphology,structure and composition.The loss mechanism and absorbing performance of the material were analyzed.It was found that dielectric loss played a dominat role,and its absorbing properities can be effectively adjusted by changing the filler loading and matching thickness.The reflection loss(RL)was optimized to-67.8 dB at the thickness of 1.9 mm,and the effective absorption bandwidth(EAB)was 4.5 GHz(13.5-18 GHz)at the thickness of only 1.5 mm with the filler loading 40 wt%.The EAB can reach 5.3 GHz(12.7-18 GHz)at the thickness of only2.2 mm with the filler loading 30 wt%,which basically covered the Ku band.The excellent absorption performance was attributed to the higher dielectric loss caused by the multiple polarization,multi reflection and scattering of EM wave originated from special structure,good impedance matching and the synergistic effect of dielectric loss and magnetic loss.Few-layered Ti₃C₂T_x MXene(f-Ti₃C₂T_x)were prepared by ion etching and ultrasonic stripping first,then the f-Ti₃C₂T_x was coated on the surface of carbonyl iron powder(CIP)by electrostatic adsorption to obtain f-Ti₃C₂T_x/CIP(denoted as M/C),and M/C-400(400means 400?)and M/C-800 were obtained by heat treatment at different temperatures.The composite absorber was verified to be as expected through the characterization of morphology,structure and composition.The loss mechanism of the material was analyzed,and it was found that magnetic loss played a dominant role,but its dielectric loss can be effectively regulated by changing the contents of f-Ti₃C₂T_x and the heat treatment temperatures.The composite absorber showed high absorption performance in multiple frequency bands.The EAB of M/C-20-400(20 represents the reaction volume of f-Ti₃C₂T_xsolution was 20 m L,the density of solution was 5.43 mg/m L)can reach 6.16 GHz(11.68-17.84 GHz)at the thickness of 2.1 mm,which basically coverd the Ku band;The minimum RL of M/C-20-800 can reach-44.6 dB at 12.08 GHz with the thickness of 2.7mm,and its EAB was larger than 4.18 GHz,when the thickness was in the range of 2.3-3.1mm and completely covered the X band at the thickness of 3.1-3.2 mm.The excellent absorption performance was attributed to the high magnetic loss,multi polarization mechanism,improved impedance matching and the synergistic effect of different loss.In general,combining different loss type material through a certain structure can introduce multiple loss mechanism,improve the absorption performance,which provides a new technical approach for the preparation of high-performance electromagnetic wave absorption material.