Preparation And Electromagnetic Wave Absorption Performance Of Graphene Hybrid Materials

With the development of science and technology,all kinds of electronic equipment and communication facilities provide convenience for the society,but the electromagnetic radiation pollution caused by them is becoming increasingly serious.It can not only interfere with the normal operation of electronic devices,but also seriously affect human health.In order to solve the above problems,the application of electromagnetic wave absorbing materials has become an important part of modern electronic equipment.Therefore,it is of great significance to explore lightweight and effective absorbing materials for modern life,economic construction and national defense construction.Graphene has the characteristics of low density,large specific surface area and high conductivity,and is considered to be one of the most suitable materials for improving the absorption performance.However,graphene's single electromagnetic loss mechanism and poor dispersion in the matrix greatly limit its application.Therefore,combining graphene with magnetic loss materials to design graphene-based absorbing materials is a necessary means to improve the absorption performance.In this paper,three types of graphene-based absorbing materials?RGO/AC/Fe₃O₄,LRGO@AC/CoFe₂O₄ and CI/SiO₂/RGO?were prepared by using reduced graphene oxide?RGO?,biomass activated carbon?AC?,ferrite?Fe₃O₄ and CoFe₂O₄?,carbonyl iron?CI?and SiO2 as components by freeze-drying,solvothermal and thermal reduction methods,respectively.Moreover,the microscopic morphology,chemical structure and absorption performance of the absorbing material were characterized by means of SEM,XRD,TEM and other characterization methods,and its practical application in the field of stealth was simulated.The specific research contents are as follows:?1?The graphene oxide?GO?suspension and Fe₃O₄ magnetic nanoparticles were prepared by using the modified Hummers and solvothermal method,respectively.Then the Fe₃O₄ and the pretreated cornstalk?ZnCl₂ activation?were added into the GO suspension through simple mixing process.Finally,the 3D hierarchically porous structure RGO/AC/Fe3O4 absorbing material was synthesized by freeze-drying and thermal reduction process.The results show that the well-constructed 3D hierarchically porous microstructure was beneficial for good synergistic effect and multiple transmission-absorption mechanism.With 5%mass fraction of RGO/AC/Fe₃O₄ in paraffin wax,the minimum RL value reached-34.78 dB at 11.90 GHz,and the absorption bandwidth?RL<-10 dB?was 5.82 GHz with a matching thickness of 3.0 mm.Furthermore,HFSS simulation results show that the radar cross section?RCS?value of aluminum alloy coated with RGO/AC/Fe3O4 can be reduced from 12.37 dBm² to 3.68 dBm².?2?The large-sized GO?LGO?was prepared by centrifugation method,then LRGO@AC and CoFe2O4 were prepared by thermal reduction and solvothermal method,respectively.Finally,the LRGO@AC/CoFe₂O₄/epoxy resin absorbing material with 3D conductive network structure was successfully synthesized by simple physical mixing method.The microstructure,chemical structure and absorbing properties of the absorbing materials were tested and characterized.The results show that the composite presented excellent EM wave absorption performance at a 5 wt.%loading of LRGO@AC and CoFe2O4.The minimum RL value reached-42.70 dB at 11.24 GHz and the effective absorption bandwidth reached 5.45GHz with a thickness of 3.0 mm.The improvement of electromagnetic wave absorption performance is mainly attributed to the 3D conductive network structure formed by LRGO,which is not only conducive to the dispersion of LRGO@AC and CoFe2O4 in the resin matrix,but also promotes the synergistic effect of electromagnetic loss.Furthermore,HFSS simulation results show that the RCS value of aluminum alloy coated with LRGO@AC/CoFe₂O₄ coating can be reduced to-2.45 dBm².?3?The CI/SiO2/RGO absorbing agent with core-shell structure was prepared by chemical modification and thermal reduction means.The microstructure and chemical structure of the absorbing materials were characterized by SEM and XRD,and the electromagnetic loss mechanism was investigated.The results show that the introduction of SiO₂ could make it easier for electromagnetic waves to enter into the material,thus effectively improving the impedance matching characteristics.With 10%mass fraction of CI/SiO₂/RGO,the minimum RL value reached-46.43 dB at 10.79 GHz with a thickness of 2.0 mm,and the effective absorption bandwidth was 6.47 GHz,covering the entire X band.Moreover,the simulation results show that the RCS value of CI/SiO2/RGO coating can be effectively reduced to-3.14 dBm².