Preparation Of Low-loss Iron-based Soft Magnetic Composite Materials Under High-frequency Conditions By The Double-layer Insulation Coating Design Method

Soft magnetic composite materials are widely used in energy,information,transportation,national defense and other fields,it is usually required to obtain materials with low coercivity,high permeability,high saturation magnetization,and low magnetic loss.If the high-frequency magnetic loss of the material is high,it will affect the actual use of the material.Therefore,domestic and foreign researchers use materials with certain soft magnetic properties as the main material.By physical or chemical methods,the surface of soft magnetic particles is coated with an insulating material with higher resistivity,thereby improving the overall resistivity of the material,retaining the basic soft magnetic properties of the material,and obtaining lower magnetic loss at high frequencies.In this paper,carbonyl iron powder is used as the raw material,combined with sol-gel technology to prepare a series of micron carbonyl iron powder as the core,Carbonyl-iron soft magnetic powder particles with core-shell structure with nano SiO₂ or Ni ZnFe₂O₄ as the insulating layer,especially the SiO₂/Ni ZnFe₂O₄ double-layer insulating coated powder particles are prepared,and using spark plasma sintering technology to prepare the powder into bulk soft magnetic composite material,the influence of the insulating coating process on the soft magnetic properties is comparatively studied,and the element diffusion problem in the insulating layer is preliminary discussed.The specific research content is as follows:(1)To determine the specific experimental parameters of the coated insulating material.The sol-gel method is used to insulate the carbonyl iron powder,when covering with SiO₂ insulating layer,the ratio of silicon source used and the amount of silicon source added,and when the Ni ZnFe₂O₄ insulating layer is coated,the ratio of nickel to zinc in the precursor solution is the experimental factor,and the magnetization of the soft magnetic composite powder prepared is the experimental indicator.By changing the experimental factors and reaction time,the experiment was arranged reasonably,a series of Fe/SiO₂ and Fe/Ni ZnFe₂O₄ soft magnetic insulating powders were obtained,and it was finally determined experiment parameters,when the ratio of silicon source KH540:TEOS was 4:6,the total amount of silicon source was 0.002mol,and the ratio of nickel to zinc in the Ni ZnFe₂O₄ precursor solution is 5:5,the material has the best insulation coating effect.(2)Combining with specific experimental parameters,a serious of double-layer insulation-coated soft magnetic composite materials are prepared to determine whether SiO₂ acts as an intermediate insulation layer to block the diffusion of elements between the Fe particles and the Ni ZnFe₂O₄ insulation layer.Through the analysis of SEM,VSM and other means,the structure and performance of the three soft magnetic composite materials are further studied.It is found that the resistivity and high-frequency loss of the single-layer coated Fe/SiO₂ soft magnetic composite material have been significantly improved.When the AC soft magnetic test conditions are₈)=0.05T and1)=10k Hz,the coercivity is 42.38%of the raw material.The total magnetic loss of the material is reduced by 85.15%compared with the raw material,and it is reduced by 77.68%when the frequency is1)=100k Hz.The Fe/SiO₂/Ni ZnFe₂O₄ soft magnetic composite material with double-layer insulation design,the soft magnetic properties of the materials are improved on the basis of Fe/SiO₂,the best coercivity of the material is 13.29%of the raw material,and the best amplitude permeability exceeds 204.71 of the raw material.When the test condition is at₈)=0.05T,the test frequency is1)=10k Hz and1)=100k Hz,comparing with the raw materials,the Fe/SiO₂/Ni ZnFe₂O₄ soft magnetic composite materials are respectively reduced by 95.6%and 88.7%.In this paper,the soft magnetic composite materials prepared by the sol-gel method and SPS spark plasma sintering process effectively suppress the magnetic loss of the material under high frequency.