Preparation And Research On Electromagnetic Wave Absorption Properties Of 3D Graphene Nanocomposites

Nowadays,serious problems arising from lectromagnetic?EM?radiation pollution are emerging.It not only affects the normal operation of electronic equipment,but also does harm to the human health.And higher requirements have been set for stealth technology in national defense at the same time.An imperative way to solve these issues is exploiting a new type of material with light weight,thin thickness,strong absorption ability and wide effective absorption bandwidth.Graphene,one 2D material with the merits of high specific surface area,low density,high conductivity,excellent chemical stability,good thermal stability,good mechanical properties and high electron mobility,is expected to be a promising candidate as a lightweight and highly effective EM wave absorber.However,the EM wave absorption properties of sole graphene are restricted to poor dispersity in the matrix,impedance mismatching,and limited loss mechanism.Therefore,combination with other lossy materials has been extensively explored as the important way to improve its EM wave absorption performance.Based on the structural design,three-dimensional graphene?3DG?was prepared by modified template method,and its microscopic morphology and absorption properties were analyzed.The results show that 3DG displays a three-dimensional network porous structure,eliminates EM wave by dielectric loss mechanism.At a thickness of 1.4 mm,the minimum reflection loss is only-3.77 dB.Therefore,it is necessary to combine 3DG with other lossy absorbing materials to improve their EM absorption properties.Popcorn-like?-Fe₂O₃ nanoparticle decorated 3DG??-F/3DG?nanocomposites were obtained by coprecipitation method.By changing the content of?-Fe₂O₃,the electromagnetic parameters were adjusted,the impedance matching and attenuation characteristics were improved,and accompolish the goal of enhancement of absorbing performance.The?-F/3DG-1 reveals the best absorption properties.When the thickness is only 1.40 mm,the minimum reflection loss reaches-55.70 dB.It has the widest effective absorption bandwidth of 4.42 GHz at a thickness of 1.70 mm.The main reasons for the excellent absorbption properties of?-F/3DG nanocomposites can be summarized as:interfacial polarization and related relaxation caused by a large number of interfaces of?-F/3DG,dipole polarization and interface polarization of three-dimensional graphene,magnetic loss mechanism including natural resonance and exchange resonance generated by magnetic particle?-Fe₂O₃,and extremely high specific surface area and defects of?-F/3DG make electromagnetic waves subject to multiple reflection and scatter,improving electromagnetic wave absorption performance.3DG/ZnO?3DGZ?nanocomposites were prepared by in-situ crystallization method,which exhibited excellent absorption properties.The 3DGZ-2 has the widest effective absorption bandwidth?4.08 GHz?and minimum reflection loss?-48.05 dB?at thicknesses of1.50 mm and 1.82 mm,respectively.The excellent absorbption properties of 3DGZ nanocomposites are mainly due to the following reasons.The large number of interfaces resulting from uniformly dispersed ZnO nanoparticles enhance the interfacial polarization.In addition,lattice defects in ZnO nanocrystals further improve polarization.The porous structure and large specific surface area of 3DGZ promote electromagnetic waves to perform multiple reflections and diffuse scattering,which prolongs the propagation path of electromagnetic waves and improves the EM wave absorption ability.Our study show a great potential in developing high-efficient,lightweight and high-temperature EM wave absorbing materials.