Preparation And Microwave Absorption Properties Of Magnetic Composite Nanomaterials

With the development of wireless communication,electronic products have been widely used in our daily life,which results in more and more serious electromagnetic pollution.How to decrease electromagnetic radiation has become a hot issue.To solve this problem,developing high-performance microwave absorbing materials is an effective strategy.Because of the high magnetic loss,large Snoek limit,moderate saturation magnetization and moderate coercivity,spinel ferrites have been regarded as excellent magnetic microwave absorption materials.However,poor impedance characteristics also hinds their application in microwave absorption.In this paper,nanocomposites,loading graphene and graphene-like materials on spinel ferrite,with different morphologies,structures and loss mechanisms are prepared.The experimental results show that the magnetic nanocomposites with capsule-like structure or nest-like core-shell structure exhibit suprior microwave absorption properties.The research content of this paper mainly includes two parts.On the one hand,the encapsulated ternary magnetic nanocomposites CoFe₂O₄/rGO@PVP were prepared by simple hydrothermal method,where the morphology and structure of magnetic nanocomposites can be controlled by changing the concentration of(PVP).Cobalt ferrite(CoFe₂O₄),reduced graphene oxide(rGO)and PVP have multiple interface characteristics,which can not only enhance the interface polarization effect,but also optimize the impedance matching.In addition,the residual functional groups and defects of rGO can enhance the dipole polarization.The experimental results show that,when the mass ratio of PVP to ferric nitrate nonahydrate[Fe(NO3)3·9H2O]is 3:1,the nanocomposite CoFe₂O₄/rGO@PVP have an optimal reflection loss of-56.8dB at the thickness of 1.96 mm and an effective absorption bandwidth of 6.8 GHz at the thickness of 2.2 mm.The enhanced microwave absorption of the magnetic nanocomposites CoFe₂O₄/rGO@PVP is mainly attributed to the special capsule structure,excellent impedance matching characteristics and the synergistic effect between magnetic loss and dielectric loss.On the other hand,superparamagnetic nanospheres CoFe₂O₄ and multiphase molybdenum disulfide(1T/2H-MoS₂)with hollow structure are synthesized by simple solvothermal method.The nest-like core-shell nanocomposites CoFe₂O₄@1T/2H-MoS₂ are prepared by adding superparamagnetic nanospheres CoFe₂O₄ during the preparation of 1T/2H-MoS₂.The nest-like core-shell nanocomposites CoFe₂O₄@1T/2H-MoS₂ exhibit an optimal reflection loss of-68.50 dB at the thickness of 1.81 mm and an effective absorption bandwidth of 4.56 GHz at the thickness of 1.6 mm.The total effective absorption bandwidth of the nanocomposites can reach up to 14.5 GHz by adjusting the coating thickness of the nanocomposites from 1.5 mm to 5.0 mm.The experimental results show that enhancement of microwave absorption of the nest like core-shell nanocomposites CoFe₂O₄@1T/2H-MoS₂ is mainly attributed to the special core-shell structure,excellent impedance matching characteristics and moderate attenuation capability.This study provides a new idea of structural design and ferrite/dielectric composite,and also explores a new development direction for the research and development of high-performance microwave absorbing materials.