Study On Improved Electromagnetic Absorption Properties Of RGO/CoFe₂O₄ Composite By Compounding SiC Or Al

With the development of society,electronic equipment can be seen everywhere in People’s Daily life.The generation of mobile phones,computers and other equipment makes life more convenient,but also makes people suffer more electromagnetic radiation.The effects of electromagnetic radiation on human beings and the environment cannot be ignored.Therefore,it is urgent to develop electromagnetic absorption materials to solve the negative effects of electromagnetic radiation.Electromagnetic wave absorbing material is a new type of functional material which can transform the incident electromagnetic wave energy into heat energy or other forms of energy through electromagnetic loss.In order to meet the actual demand,electromagnetic wave absorbing materials should meet the four performance indicators:thin absorption thickness,light material weight,wide effective absorption bandwidth and strong absorption capacity of electromagnetic wave.Generally,due to poor impedance matching,a single component material cannot achieve the expected electromagnetic wave absorption performance,so multi-component composite should be carried out to improve the electromagnetic wave absorption performance of the material.The physical and chemical properties of graphene oxide（GO）have a positive effect on the absorption of electromagnetic waves,but GO cannot be used as a wave-absorbing material alone.Because of the van der Waals force in each layer of GO,GO is prone to agglomeration,and its high conductivity leads to poor impedance matching.Cobalt ferrite（CoFe₂O₄）is a kind of ferrite,which has excellent magnetic properties such as moderate saturation magnetization and high coercivity.However,the high resistance of CoFe₂O₄ makes its single absorbing mechanism limited its application in the field of absorbing materials.Due to the existence of a large number of oxygen-containing functional groups and defects on the surface of GO,it is possible to grow CoFe₂O₄ on the surface of GO composite,which will be reduced to reduced graphene oxide（rGO）.In rGO/CoFe₂O₄ system,due to the poor impedance matching between GO and CoFe₂O₄ and the poor dielectric loss capacity,the high proportion of CoFe₂O₄ in rGO/CoFe₂O₄ system leads to the high density of the material,and it is difficult to obtain a thin matching thickness of the material.In order to solve this problem,A low density material is introduced to improve impedance matching and dielectric loss capacity of rGO/CoFe₂O₄ system.In this paper,rGO/CoFe₂O₄/Si C and rGO/CoFe₂O₄/Al triadic electromagnetic absorbents were constructed by adding silicon carbide（Si C）and flake aluminum（Al）powders with good dielectric properties to rGO/CoFe₂O₄ system as matrix.The main research contents of this paper are as follows:（1）Four different ratios of rGO/CoFe₂O₄/Si C composites were obtained by adding a certain amount of ethylene glycol and Si C and different contents of CoFe₂O₄into the GO dispersion solution with a fixed content.Excellent impedance matching and synergistic action between dielectric loss and magnetic loss make rGO/CoFe₂O₄/Si C composites have excellent electromagnetic wave absorption performance.The minimum reflection loss of S3 sample is-62.39 d B when the matching thickness is 2.43 mm at 7.4GHz.Effective absorption bandwidth is 1.4 GHz（6.8～8.2 GHz）.When the matching thickness is 1.39 mm at 13.2 GHz,the minimum reflection loss is-59.77 d B,and the effective absorption bandwidth is 3.2 GHz（11.8～15GHz）.When the matching thickness is 1.06 mm at 17.2 GHz,the minimum reflection loss is-65.49d B,and the effective absorption bandwidth is 2.3 GHz（15.7～18 GHz）.（2）Three rGO/CoFe₂O₄/Al composites of different proportions were obtained by adding a certain amount of CoFe₂O₄ and different amounts of flake Al powder into the GO dispersion solution with a fixed content.The Al powder was pretreated with acetone and fully dispersed and mixed for hydrothermal reaction.rGO/CoFe₂O₄/Al composite has excellent impedance matching,dielectric loss and magnetic loss,and the material has obtained good electromagnetic wave absorption performance.The minimum reflection loss of S2 sample is-68.03 d B when the matching thickness is 1.38 mm at15.5 GHz.The effective absorption bandwidth and infrared emissivity are 3.3GHz（13.6～16.9 GHz）and 0.63 GHz,respectively.