Effect Of Rare Earth On Electromagnetic Properties Of Ferromagnetic Metals

With the progress of electronic science and technology and the development of the information age,the high power communication equipment of electronic devices has produced a lot of electromagnetic radiation,which affects people’s health.The arms race among countries requires the new weapons to have the characteristics of anti-interference,anti-radiation,stealth and so on.The wave-absorbing materials emerge at the right moment.On the one hand,electromagnetic protection and shielding can be realized through reasonable construction of electromagnetic wave-absorbing materials to protect people’s life safety.On the other hand,weapon stealth is realized to achieve the effect of surprise.In recent years,ferromagnetic metal micropowder has been widely studied as a wave absorbing material due to its high saturation magnetization,initial permeability,Curie temperature and other characteristics.However,pure ferromagnetic metal has high conductivity and high eddy current loss,resulting in a rapid decrease of the virtual part of permeability with the increase of frequency,which makes the magnetic loss characteristics of the material unable to be fully played.Based on metallic magnetic micropowder materials,this study first controlled the eddy current effect by adjusting the morphology,and then realized the regulation of the electromagnetic characteristics of ferromagnetic particles by introducing rare earth and heat treatment to regulate the crystalline phase of the material,so as to summarize the influence law of rare earth on the electromagnetic characteristics of ferromagnetic metals and provide support for obtaining wide-frequency response absorbing materials.Firstly,the spherical carbonyl iron was transformed into flake carbonyl iron powder by mechanical ball milling,and then the rare earth compounds were introduced into the ferromagnetic particle system in the ball milling process.After heat treatment,the rare earth modified metal magnetic micropowders composed of different crystalline phases were obtained.According to the morphology analysis,the particles after ball milling and heat treatment had flake structure.It is found that the electromagnetic properties of ferromagnetic particles are affected by rare earth species,proportion,heat treatment temperature and atmosphere.Among them,the mass of the compound containing rare earth Ce in carbonyl iron particles is 5%,the heat treatment temperature is 400℃,and the heat treatment atmosphere is nitrogen.The 5-Ce-400 synthesized shows good absorbing ability.When the thickness of the sample is 1.19 mm,the minimum reflection loss value reaches-15.6 d B,and the corresponding matching frequency is 15.6 GHz.Less than-10 d B effective bandwidth up to 6.32 GHz.Secondly,this study successfully synthesized sheet Fe-Co alloy(Fe Co),and explored the influence of grinding medium,temperature,sample proportion and other factors on electromagnetic properties.It was found that the Fe-Co alloy obtained after annealing at400℃ in nitrogen atmosphere showed good electromagnetic wave absorption ability,and the minimum reflection loss value reached-40.2d B at the thickness of 1.31 mm.The corresponding frequency is 15.6 GHz,which is less than-10 d B and the effective bandwidth is up to 5.6 GHz.At the same time,rare earths La,Dy,Sm and Ce are introduced into the preparation of chip Fe-Co alloy samples.It is found that when rare earths La are added,the samples maintain good electromagnetic wave absorption ability.The minimum reflection loss is-58.6d B;Under the thickness of 1.29 mm,the effective bandwidth of less than-10 d B can reach 6.88 GHz.