Preparation And Wave-Absorbing Properties Of Graphene/Ferrite Nanocomposite Fibers

Wave-absorbing materials are a class of materials that can attenuate incident electromagnetic waves through dielectric and magnetic losses to reduce electromagnetic echoes,and are widely used in military stealth and civil security.In order to design and preparate high-performance radar absorbing materials,the design ideas of compounding and low-dimensionality,and the experimental methods such as electrostatic spinning are utilized in this paper.The binary and ternary composite nanofibers of ferrite-graphene-polyacrylonitrile（PAN）are prepared by those methods and their wave absorbing properties have been studied systematically.The main research contents are as follows:Firstly,the preparation of ferrite-PAN nanocomposite fibers and their wave absorption properties are investigated.Four kinds of ferrite-PAN nanocomposite fibers are prepared by solution immersion method and electrostatic spinning method,and the final samples were obtained by carbonization.The results show that although the solution immersion method can significantly enhance the content of ferrite in binary composites,the bonding of ferrite with PAN nanofibers is not strong,and the enhancement of wave absorption performance of the composites is not ideal;The spinning method can combine the ferrite powder with PAN nanofiber more closely,which can better realize the regulation of the electromagnetic parameters of the material and obtain better wave absorption performance.The maximum reflection loss value of Ni Co（Fe₂O₄）₂-PAN prepared by the spinning method is-20.4 d B at 14.0 GHz when the thickness is 1.5 mm,and the effective absorption bandwidth reaches 3.5 GHz（12.3-15.8 GHz）.On the contrary,Ni Co（Fe₂O₄）₂-PAN prepared by immersion method requires a higher ferrite content to achieve the same wave absorption effect.Secondly,the preparation of graphene-PAN nanocomposite fibers and their wave absorption properties are carried out.A series of graphene-PAN binary composites were prepared by electrostatic spinning combined with high temperature carbonization method,where graphene is reduced graphene oxide（RGO）and physical graphene（PG）.The results show that the graphene-PAN composites have excellent dielectric loss properties and radar absorbing properties.With a thickness of 2.3 mm,the RGO-PAN achieves a maximum reflection loss value of-71.7 d B at 10.0 GHz and an effective absorption bandwidth of 4.52 GHz（13.1-17.62 GHz）at a thickness of 1.6 mm.Finally,several ferrite-graphene-PAN ternary nanocomposite fibers are prepared by electrostatic spinning combined with high temperature carbonization method,and the wave absorption properties of the composites were investigated.The results show that the maximum reflection loss value increases and the effective absorption bandwidth becomes wider and shifts toward lower frequencies when the ternary composite is compared with the pure PAN nanofiber.The maximum reflection loss value of the Zn Fe₂O₄-PG-PAN sample increased from-18.0 d B to-30.1 d B,and the effective absorption bandwidth increased and shifted from 1.5 GHz（4.4-5.9 GHz）to 2.0 GHz（5.5-7.5 GHz）.The research work in this paper reveals the relationship between the composition,microstructure,electromagnetic parameters and preparation process of graphene-ferrite composite absorbers and their absorbing performance,which can provide guidance for the design of multifaceted graphene-based composite absorbers and the regulation of their electromagnetic parameters,and lay the technical foundation for the research of high-performance graphene-based composite absorbers.