Preparation And Performance Study Of Two-dimensional Reduced Graphene Oxide-based Microwave Absorbing Material

At present,the problem of electromagnetic wave（EMW）pollution in the environment is becoming more and more serious,and the research and development of high performance EMW absorbing materials has a non-negligible role in solving the problem of EMW pollution.Two-dimensional reduced graphene oxide（rGO）has good conductivity,low density and unique microstructure,and has great development potential as a"wide,strong,thin and light"electromagnetic absorbing material,but when it absorbs EMW as a single material,its dielectric constant is too high,and impedance mismatch leads to poor absorption performance.Therefore,more and more researchers are developing high performance EMW absorbing materials based on reduced graphene oxide compounding with other materials.In this thesis,magnetic and dielectric materials are introduced to composite with reduced graphene oxide,respectively,with the idea of regulating electromagnetic parameters,enriching attenuation loss mechanisms and promoting impedance matching.The graphene-magnetic composite systems of ferric oxide/reduced graphene oxide（Fe₃O₄/rGO）and copper ferric oxide/reduced graphene oxide（CuFe₂O₄/rGO）,and the graphene-dielectric composite system of molybdenum diselenide/reduced graphene oxide（MoSe₂/rGO）were constructed,respectively.The results of the study are as follows:（1）Fe₃O_4/rGO composites are prepared by hydrothermal method successfully,and the doping amount of Fe₃O₄is changed to obtain excellent properties.The data shows that when the mass ratio of GO to Fe₃O₄is 1:10,the minimum reflection loss(RL_min)is-53.80 d B at thickness of 1.80 mm and frequency of 12.73 GHz,and the effective absorption bandwidth（EAB）is 3.36 GHz;At thickness of 1.50 mm,the maximum effective absorption bandwidth(EAB_max)is 4.29 GHz.The EMW absorption mechanism of the system is that the introduction of magnetic material Fe₃O₄makes the composite have the magnetic loss ability.Under the synergetic effect of dielectric loss and magnetic loss mechanism,the impedance matching is improved and the absorption loss is enhanced.（2）CuFe₂O₄/rGO composites are prepared by hydrothermal method successfully,and the doping amount of CuFe₂O₄is varied to obtain excellent properties.The data shows that when the mass ratio of GO to CuFe₂O₄is 1:15,RL_min-71.70 d B is obtained at thickness of 4.63 mm and frequency of 6.66 GHz.When the mass ratio of GO to CuFe₂O₄is 1:10,at thickness of2.08 mm,EAB_max5.44 GHz is obtained,covering 90%of Ku band.The EMW absorption mechanism of the system is the enhanced loss intensity and improved impedance matching of the composite material under the synergistic effect of dielectric loss of rGO and magnetic loss mechanism of CuFe₂O₄.Compared with Fe₃O₄/rGO composites system,this system has significantly improved its absorption performance.（3）MoSe₂/rGO composites are prepared by hydrothermal and calcination methods successfully,and the doping amount of MoSe₂is changed to obtain excellent properties.The data shows that when the mass ratio of GO to MoSe₂is 1:10,RL_min-59.96 d B is obtained at thickness of 4.30 mm and frequency of 4.75 GHz.And in the thickness range of 1.43-5.50mm,the RL_minof the sample are all less than-20 d B.In this range,more than 99%of EMW are absorbed,showing broad and excellent EMW absorption performance.When the mass ratio of GO to MoSe₂is 1:15,at thickness of 1.50 mm,the EAB_maxis 4.65 GHz.The EMW absorption mechanism of this system is that MoSe₂with low dielectric property is compounded with rGO to adjust the dielectric constant and improve the impedance matching.The large number of interfaces between the two materials enhances both the reflection and scattering of electromagnetic waves,as well as the polarization,thus improving the wave absorption performance.