Preparation And Microwave Absorption Properties Of Reduced Graphene/magnetic-nanomaterials

The ideal microwave absorbing material should have the properties of thin thickness,light weight,wide absorption band,strong absorption,excellent chemical stability and oxidation resistance.Graphene is a kind of carbon material with a variety of great physical and chemical properties.It has superb conductivity,thermal conductivity,mechanical strength and high specific surface area,However,the single graphene has only dielectric properties which are difficult to meet the impedance matching properties of microwave absorbing materials.In this paper,graphene were used as carriers to prepare nanocomposites by loading different magnetic nanomaterials.The products were characterized and measured,It was found that nanocomposites have unique microstructure and excellent microwave absorbing properties.We synthesized hexagonal SrM nanosheets by hydrothermal method,graphene oxide was prepared by improved Hummers method,The RGO/SrM nanocomposites were prepared by stirred with GO and SrM without addition of reductan.The introduction of graphene led to a significant increase in the complex permittivity and dielectric loss tangent of the composites,it was derived from reduced graphene with excellent electrical conductivity.Interfacial polarization and charge polarization were enhanced due to reduced grapheme,which has a large surface area and a large number of suspension bonds and defects on the surface.,these factors contribute to the excellent microwave absorbing properties of the composites.That the maximum reflection loss(RL)is-49.94 dB at 16.24 GHz at thickness of 2.2 mm for RGO/SrM nanocomposites.The Ni@C nanocapsules were prepared by the arc discharge method,RGO/ Ni@C nanocomposites were prepared by a simple mechanical mixing method.The onion like Ni@C nuclear shell nanocapsules and RGO formed multiple interface that enhanced the interfacial polarization effect.A large amount of charge in the Ni@C nanocapsule was transferred through the carbon conductive network of graphene,which produced a variety of polarization in the action of the electromagnetic wave.The complex permittivity and dielectric loss of nanocomposites increase significantly compared to the single Ni@C and RGO,in addition,the apparent dielectric dispersion effect of nanocomposites is beneficial to the improvement of impedance matching performance.RGO/ Ni@C-paraffin composite with RL values less than-10 d B is 6.54 GHz,when the layer thickness was 3.1 mm,the maximum RL in the nanocomposites reached-47.5 d B at 9.75 GHz.which better than that single of Ni@C or RGO.FeCo soft magnetic alloys with different ratio of atoms were synthesized by liquid phase reduction method,FeCo alloy particles were inserted into the graphene layer to prepare RGO/FeCo nanocomposites.RGO/FeCo nanocomposites exhibit typical properties of soft magnetic materials.With the increase of the content of Co,the saturation magnetization and coercive force show a tendency to increase first and then decrease.When the ratio of Fe/Co is 1:2,the imaginary part of the complex permittivity was obviously improved,and the dielectric polarization in the high frequency region was enhanced.The change of Fe/Co ratio had a significant effect on the microwave absorption properties of the sample,When the ratio of Fe/Co was 1:2,the maximum RL in the nanocomposites reached-55.6 dB.