Preparation And Modulation Of Electromagnetic Properties Of Reduced Graphene Oxide-based Electromagnetic Wave Absorbers

Electromagnetic(EM)wave absorbers can be used in the field of EM pollution prevention,EM compatibility and stealth technology,and play an important role in the development of national economy and national defense construction.Reduced graphene oxide(rGO)is usually used as the matrix material of composite EM wave absorbers due to its excellent properties of low density,large specific surface area and high electrical conductivity.The main line of this paper is EM property regulation and performance optimization of rGO-based composite absorbers.Dielectric loss type(Mo-Ni₂P/rGO),electromagnetic synergistic loss type(Fe_x-1O_x/C/rGO)and three-dimensional(3D)electromagnetic synergistic loss type(Co/C/rGOA)composite absorbers are synthesized,respectively.The influence of composition and structure of composite absorbers on impedance matching and absorbing performance is studied.The EM loss mechanism of rGO-based composite absorber is also explained.The main research contents and results are as follows:(1)The impedance matching characteristics and absorbing performance of rGO based composite EM wave absorbers are optimized by dielectric regulation strategy.Dielectric loss Mo-Ni₂P/rGO composite absorber is synthesized b y hydrothermal and phosphating process with 2D rGO as conductive substrate.The doping amount of Mo was regulated by controlling the phosphating temperature,the influence of Mo doping amount on the impedance matching characteristics of composite absorber is studied.The synergistic effect between dielectric and dielectric in composite absorber is improved,and the EM wave absorption performance of composite material is optimized.The results show that when the filling ratio of Mo-Ni₂P/rGO-700 in paraffin wax is 58.3%and the coating thickness is 2.9 mm,the minimum reflection loss(RL_min)is-47.23 d B and the effective absorption bandwidth(EAB)is 2.44 GHz.(2)The impedance matching characteristics and absorbing performance of rGO based composite EM wave absorbers are optimized by magnetic medium regulaion strategy.2D rGO is used as conductive substrate,electromagnetic synergistic loss Fe_x-1O_x/C/rGO composite absorber is synthesized by hydrothermal and pyrolysis processes.The effects of magnetic components on impedance matching characteristics of composite absorbers are studied by controlling pyrolysis temperature to regulate the content of magnetic components in precursor derivatives.The synergistic effect of magnetic loss and dielectric loss is enhanced to further optimize the absorbing performance of rGO-based composites.The results show that when the filling ratio of S-400 in paraffin wax is 50%and the coating thickness is 2.90 mm,the RL_min of S-400 is-56.09 d B and the EAB is 4.64 GHz.Compared with Mo-Ni₂P/rGO-700,the filling ratio of S-400 decreases by 8.3%and the effective absorption bandwidth increases by 47.4%.(3)The characteristics of impedance matching and absorbing performance of rGO based composite EM wave absorbers are optimized by using 3D porous structure regulation strategy.3D rGO aerogel(rGOA)is used as a conductive skeleton,3D electromagnetic synergistic loss Co/C/rGOA composite absorber is constructed by chemical reduction,freezing casting,impregnation and pyrolysis process.The load amount of magnetic metal in rGOA is regulated by controlling pyrolysis temperature,the effects of 3D porous structure and magnetic metal on the EM properties of composite materials are studied.Further optimize the impedance matching characteristics,enhance the absorbing performance,and finally obtain lightweight and efficient composite aerogel absorber.The results show that the RL_min and EAB of Co/C/rGOA-800 are-47.01 d B and 7.52 GHz when the filling ratio of Co/C/rGOA-800 in paraffin wax is 0.92%and the coating thickness is 2.9 mm.Compared with Fe_x-1O_x/C/rGO composite,the filling ratio of Co/C/rGOA-800 decreases by 49.08%and the EAB increases by 38.3%.In summary,rGO is used as the matrix material of composite EM wave absorbers in this paper.The EM properties of composite absorbers are adjusted by dielectric regulation strategy,magnetic component modification and 3D porous network construction.The impedance matching characteristics of composite materials are optimized.Finally,the composite absorbing material with light weight,strong absorption and wide bandwidth is obtained.