Study On Fe-Based Magnetic Metal And Its Graphene Composite Absorbing Materials

With the rapid development of the electronics industry,electromagnetic radiation has become more and more serious,which has seriously affected people's health and electronic equipment.Absorbing materials can convert electromagnetic radiation into heat energy,thus effectively weakening the electromagnetic radiation hazard.Fe-based metal magnetic powder is an excellent magnetic loss absorbing material with high magnetic permeability and high dielectric properties,and sheet-like Fe-based metal can be more and more widely recognized by the Snoek limitation.Graphene is a new type of planar crystal structure carbon material.Graphene Oxide?GO?is an important derivative of graphene,both of which have excellent mechanical properties,electrical properties and thermal properties.It is particularly important that graphene and GO have excellent electrical conductivity and their high dielectric constant makes them useful as dielectric loss absorbing substrates.In this paper,GO/Fe-based composite absorbing materials and rGO/Fe-based metal composite absorbing materials were prepared by high-energy ball milling of Fe-based metal magnetic powders with GO and reduced graphene oxide?rGO?respectively.The milling time and coupling agent pair were studied.The effects of microscopic morphology,phase structure and electromagnetic parameters were studied.The relationship between the absorbing properties of the rapidly quenched NdFeCoB nanocomposite absorbing materials and the change of rare earth Nd doping amount was studied.It mainly includes the following contents:?1?GO/magnetic metal composite absorbing materials were prepared by ball milling with FeCoV and FeSiCr alloy powders respectively,and their morphology,phase structure and absorbing properties were analyzed.The SEM results show that the GO/Fe-based magnetic metal composite absorbing materials all have a sheet-like structure,and the surface of the sample with the coupling agent is smooth.The XRD results show that the phase structure of the composite absorbing material exhibits a single?-Fe phase.Under the same ball milling condition,the GO/FeCoV composite absorbing material has better absorbing properties than the FeCoV alloy,and the peak of reflection loss shifts to high frequency.In the four samples of GO/FeCoV composite absorbing materials,the composite sample with ball-milling for 1 h was the best absorbing property.When the matching thickness was 1 mm,the reflection loss value reached-8.7 dB,and the reflection loss was less than the-5dB bandwidth reaches 3.9GHz?4.1⁸.0GHz?.?2?RGO was prepared by using ascorbic acid as a reducing agent,then rGO was separately ball-milled with FeCoV and FeSiCr alloy powder to prepare rGO composite absorbing material.RGO is uniformly coated on the surface of the metal particles,and the composite material exhibits a sheet-like particle having a certain thickness.XRD results show that the composite absorbing materials basically exhibit?-Fe body-centered cubic structure.Compared with metal magnetic powder,the rGO composite absorbing material under the same ball milling condition has better microwave absorption performance,and the absorption peak shifts to a high frequency band.In the four samples of rGO/FeCoV composite absorbing material,no coupling agent was added and the peak value of the reflection loss of ball-milled 2h sample reached-10.5dB?thickness=1mm?,and the effective absorption bandwidth?RL<-5dB?is 8.5GHz?5.8¹4.3GHz?.?3?The phase structure,magnetic properties and microwave absorption properties of the melt spun Nd_xFe_85-xCo₄B₁₁?x=3,5,7,9?nanocomposites were investigated.The analyses of XRD spectra suggest that all samples only have the single a-Fe phase.The hysteresis loop curve shows that the Nd_xFe_85-xCo₄B₁₁?x=3,5,7,9?alloy samples have higher saturation magnetization and coercive force,and the saturation magnetization?Ms?decreases with the increase of Nd content.The coercivity?Hc?is gradually increasing.In the frequency range of 2¹8GHz,with the increase of Nd content,the complex permittivity and complex permeability of the sample increase first and then decrease,and the nanocomposite exhibits excellent absorbing properties in the range of 2¹8GHz.The minimum reflection loss of the Nd_xFe_85-xCo₄B₁₁ composite at 9.8 GHz is-23.1 dB?thickness=2 mm?.