Preparation And Microwave-absorption Properties Of Graphene-barium Ferrite Composite

Graphene is considered as a potential dielectric-loss type absorbing material due tothe excellent properties combination such as low density, high electrical conductivityand outstanding thermal stability. Meanwhile, Barium ferrite with sheet like structure isgood magnetic-loss absorbent materials owing to the strong absorption and wideabsorption band, high magnetic anisotropy field and high natural resonance frequency.In this paper, taking charge of the advantages of graphene and barium ferrite, thehydrothermal method and ultrasonic dispersion method were carried out to preparegraphene/barium ferrite composites, and the effects of microstructure on microwaveabsorbing properties were investigated. The phase and chemical composition, as well asmicrostructure of graphene, barium ferrite and graphene-BaFe₁₂O₁₉composites arecharacterized via XRD, SEM, XPS, AFM. The electromagnetic wave absorptionproperty and electromagnetic parameters of Graphene-BaFe₁₂O₁₉composites fabricatedby different methods were analyzed by vibration magnetometer （VSM）, vector networkanalysis instrument. In addition, the matlab simulation was also carried out tocharacterize the effects of different graphene contents and different absorbing layerthicknesses on absorbing performance.The results show that Graphene oxide obtained by modified Hummers method hasthickness of0.7-0.9nm. The reduction degree of graphene by hydrothermal reduction isup to64.1%and51.3%by DMF hydrazine, respectively. The obtained graphenethickness is0.694nm. Graphene-BaFe₁₂O₁₉composite by hydrothermal method hascylindrical macro morphology. BaFe₁₂O₁₉particles in the composite are absorbed on thesurface of graphene sheets or insertion between graphene sheets, thus presenting amultilayer structure in micro-scale. The milling BaFe₁₂O₁₉powders tend to decomposeto form Fe₂O₃dominated phases during hydrothermal reduction process due to ahigh-energy state after milling treatment of BaFe₁₂O₁₉.The electromagnetic wave absorption test results show that graphene content has agreat effect on electromagnetic properties of graphene-BaFe₁₂O₁₉, with the increasinggrapheme content, the saturation magnetization, remnant magnetization and coercivityof the composites decrease. At the same time, the reflection absorbing peaks shift tolower frequency band, accompanied by a decreasing peak value and declining wavewidth. The grapheme-BaFe₁₂O₁₉composite with10wt.%graphene prepared bymechanical mixing exhibits a reflectivity peak value of22.9dB at15.3GHz and1.5mm thickness, and RL <-10dB in the bandwidth of about4.4GHz （13.6¹8GHz）. Inaddition, the graphene/BaFe₁₂O₁₉composite with10wt.%graphene prepared by synthesized by hydrothermal method presents grapheme-BaFe₁₂O₁₉multilayer structure,which is beneficial to strengthen the attenuation of electromagnetic waves. Thegraphene/BaFe₁₂O₁₉composite by hydrothermal method has a reflectivity peak value of-22.98dB at12.74GHz and RL <-10dB in the range of bandwidth4.26GHz （11.13to15.39GHz）.