Preparation And Properties Of Biomass Carbon/Ferrite Microwave Absorbing Materials

The rapid architecture of 5G networks and the further development of a new generation of stealth warplanes have made the development of high-performance electromagnetic wave absorbing materials a hot direction for researchers.Traditional wave absorbing materials such as ferrite and magnetic metal particles do not meet the demand for wave absorbing materials for the development of science and technology in the new era due to their high density and impedance mismatch.As a result,carbon-based materials（e.g.graphene,carbon nanotubes and biomass carbon）,which are lightweight and have a large specific surface area,are gradually replacing traditional absorbers.However,the development of graphene and carbon nanotubes is limited by their complicated preparation and high price.Biomass carbon absorbers are promising in the field of electromagnetic wave absorption due to their low density,easy preparation,wide source and economic recyclability.Besides,pure biomass carbon materials have poor absorption performance due to impedance mismatch,so materials with high magnetic loss（e.g.ferrite）can be selected to be compounded with biomass carbon materials in order to obtain good absorption performance.In this work,physical blending grapefruit peel carbon（GPC）/Ni_0.5Co_0.5Fe₂O₄absorbers,in-situ generation GPC/Ni_0.5Co_0.5Fe₂O₄absorbers and 3D layered porous corn straw（CSC）/GPC/Ni_0.5Co_0.5Fe₂O₄absorbers were prepared by freeze-drying,physical blending,and solvothermal processes.SEM,XRD,FTIR and other characterization methods were used to test and characterize the microscopic morphology,chemical structure and absorbing properties of the absorbing materials.The details of the study are as follows.（1）The Ni_0.5Co_0.5Fe₂O₄and GPC with uniform particle size were prepared respectively,and the final samples were prepared by simple physical blending method.The skeleton structure formed by GPC can not only effectively improve the conductive loss,but also extend the propagation path of electromagnetic waves.Besides,the absorber with a great quantity defects and heterogeneous interfaces delivers interfacial polarization and dipole polarization.Also,the Ni_0.5Co_0.5Fe₂O₄particles with good dispersion on GPC are beneficial toward dielectric-magnetic combination,resulting in impedance matching.The minimum reflection loss（RL）reaches-41.6 d B and the effective absorption bandwidth（EAB,RL<-10 d B）is 4.3GHz with the thickness of 3 mm.（2）GPC/Ni_0.5Co_0.5Fe₂O₄graphene-like porous composites were successfully prepared by in situ generation of Ni_0.5Co_0.5Fe₂O₄magnetic particles on GPC.The graphene-like porous structure effectively improved the conductive loss and multi-polarization strength of the samples.Meanwhile,the synergistic effect of dielectric properties and magnetic properties facilitates the formation of impedance matching of the samples.In addition,the presence of a large number of pores contributes to multiple reflections and scattering of electromagnetic waves,resulting in good wave absorption properties.By adjusting the carbonization temperature,a wide EAB（5.14 GHz）was achieved for the very thin thickness（1.7 mm）of the sample.（3）The ternary CSC/GPC/Ni_0.5Co_0.5Fe₂O₄composites were successfully prepared.By adjusting the ratio of CSC/GPC,3D hierarchically porous structure composed of0D Ni_0.5Co_0.5Fe₂O₄,1D CSC and 2D GPC was gained.This unique structure can effectively improve the conductive loss and multiple polarization intensity.Meanwhile,it contributes to the dielectric-magnetic combination and further improving the impedance matching degree of the sample.The minimum RL reaches-43.95 d B and the corresponding EAB is up to 4.81 GHz with 3 mm thickness.