Structural,Magnetic And Microwave Absorbing Properties Of Nano Ferrite/Graphene Composites

The spinel ferrite has many advantages as a kind of traditional microwave absorbing materials,such as high absorbing efficiency,broad frequency band,but high density and poor thermal performance restrict its application.While graphene's low density,excellent mechanical behavior and electrical properties will remedy the disadvantages of ferrite if combined with it.In this research,ferrite/graphene composites were synthesized through hydrothermal method,and the structure,morphology and surface elements of GO,graphene and composite were studied by XRD,FTIR,Raman and SEM.The magnetic property was researched by VSM.The electromagnetic parameters were characterized by the vector network analyzer.The reflection loss was calculated and the absorbing mechanism was also discussed.XRD revealed that the diffraction peak of GO around 12°was replaced by the broad weak diffraction peak of RGO reduced by hydrazine hydrate method and hydrothermal method at about 20°³0°.FTIR spectrum demonstrated that numerous kinds of oxygen-containing functional groups existed in GO and removed after the reduction.Raman spectrum revealed that the sp² hybrid area of RGO became smaller,the degree of disorder and the number of defects both increased.DSC-TGA illustrated its thermal stability under 500?.The stacked lamellar structure could be observed from SEM.Compared to hydrazine hydrate method,the hydrothermal was more suitable for reduction.The optimal conditions during preparation of composites is 180?and 12h.The SEM indicated that the composites were made up of stacked sheets and agglomerated micron spherical particles.The M_s reached the maximum?45.6emu/g?for Ni_xCo_1-xFe₂O₄ while x=0.4.The absorbing property test showed that Ni_0.4Co_0.6Fe₂O₄/RGO composites with 15%GO and the thickness of 3.0mm could get the best performance:the reflection loss of the composites reached-3.2dB.The M_s reached 59.7emu/g for Ni_0.4Co_x Zn_0.6-x.6-x Fe₂O₄ while x=0.2.The optimal parameters to get the best absorbing performance were 20%GO and the thickness of 5.0mm.The reflection loss reached-3.4dB while at 9.2GHz,which was better than the NiCo ferrite.It is expected that the composites with a better microwave absorbing ability can be achieved by improving preparation process of ferrite and composite technology,enhancing magnetic loss and dielectric properties.