The Study Of Prepartion And Microwave Absorbing Properties Of Fe-Si Powder With Flaky And Textured Structure

At present,we are in the rapidly developing information age.Gigahertz-level equipment is widely used,which brings great convenience to people's production and life.At the same time,the electromagnetic interference problems generated by these devices have severely affected the normal operation of other surrounding electronic instruments and human health,caused economic losses and casualties,and brought hidden dangers to national defense security.The development of microwave absorbing materials with thin thickness,light weight,strong absorption,and wide frequency band becomes important.Lanthanide rare earths have unique properties and are widely used,but excessive mining leads to a decline in reserves and processes such as smelting and separation can pollute the environment Recycling of rare earth-containing materials has become a top priority for the treatment of rare earths.Fe-Si alloys are applied to microwave absorbing materials with the advantages of good stability and good soft magnetic properties.However,they have the disadvantages of high density,skin effect and single loss mechanism.We selected the La-Fe-Si alloy and used high energy ball milling method to prepare La-Fe-Si powder with large shape anisotropy.Subsequently,the dealloying process is used to prepare the flaky and textured structure Fe-Si powder,which improves its permittivity and permeability.Finally,annealing treatment is carried out to reduce strain and further improve magnetic properties.Phase analysis,micro-morphology analysis,magnetic properties and microwave absorbing properties were tested.The effect of flaky and textured structure on the absorbing properties of Fe-Si powder was studied.The main conclusions are as follows:(1)La-Fe-Si alloy was selected for two-step ball milling to prepare flaky La-Fe-Si powder.The optimal wet grinding time is 4 h,and the flaky La-Fe-Si powders prepared by the ball milling process with 6 mm diameters have good soft magnetic properties.The particle size of the powder is about 0.3~1.5 ?m,the thickness is 0.2 ?m,and the diameter to thickness ratio is 7.5 ~ 10.0.(2)The flaky and textured La-Fe-Si powders prepared by the ball milling process with a grinding ball diameter of 6 mm and 10 mm were dealloyed and annealed,and the optimal grinding ball diameter was 6 mm and the optimal dealloying time was 20 min.The flaky and textured Fe-Si powder prepared by this process has excellent wave absorbing properites: when the coating thickness is 2.2 mm,the RL was-46.47 dB,and the frequency bandwidth is 5.69 GHz.Moderate ball diameter and dealloying time are conducive to the formation of textured structure.On the contrary,excessive dealloying will not only destroy the textured structure of the powder,but also cause the deterioration of the absorbing properties.(3)The improvement of the permittivity of the powder is inseparable from the macroscopic interface polarization caused by the unique coral-like and flocculent textured structure and the microscopic polarization caused by the unique coral-like and flocculent textured structure and the microscopic polarization caused by the interface of the soft magnetic phase.The higher saturation magnetization,lower magnetocrystalline anisotropy constant and internal strain make the permeability increase.The excellent wave absorbing properties with thin coating(2.2 mm),strong absorption(RL =-46.47 dB)and wide frequency band(5.69 GHz)is the result of the comprehensive influence of the adjustment of the electromagnetic parameters of the material,the enhancement of the dielectric polarization and the magnetic loss mechanism,and the interference cancellation effect caused by the specific coating thickness.