Interface Design And Magnetic Control Of Fe-based Soft Magnetic Composites

The soft magnetic composite material is a soft magnetic material composed of metal soft magnetic particles through an interface insulation coating.As an electromagnetic conversion functional material,it has the advantages of high saturation magnetization of metal soft magnetic and high resistivity and low loss of ferrite soft magnetic.It is widely used in the fields of power,communication,energy and transportation.At present,the main problem restricting the development of soft magnetic composite materials is that the non-magnetic coating layer"dilutes"the magnetic induction strength of the material,and the non-magnetic gap reduces the effective magnetic permeability of the soft magnetic composite material.Therefore,how to optimize the magnetic properties of soft magnetic composite materials through reasonable interface design,selection of appropriate insulation media,and improvement of heterogeneous interfaces has become the focus of research on optimizing the magnetic properties of soft magnetic composites.In this paper,a high-resistance Fe₄N magnetic insulating layer was prepared in situ on the surface of Fe powder by vapor phase nitridation method,and a high-resistance soft ferrite coating was synthesized in situ on the surface of an iron-based alloy by co-precipitation method.The prepared interface coating has both high electrical resistivity,high magnetic permeability,and excellent coating properties,and it is expected to fundamentally improve the comprehensive soft magnetic properties of soft magnetic composite materials.The specific research contents and conclusions are as follows:(1)Preparation of spherical Fe₄N/Fe soft magnetic composites by gas-phase nitriding method and study of AC and DC soft magnetic properties.Spherical Fe powder was nitrided in an atmosphere of 550°C and an ammonia-hydrogen ratio of 1to obtain Fe₄N/Fe.The results show that with the increase of nitriding time,the Fe₄N content increases,the magnetic loss of the sample decreases,the quality factor increases,and the DC bias performance is better.In the range of 20-590 k Hz,as the magnetic flux density increases from 10 to 30 m T,the main source of sample magnetic loss changes from eddy current loss to hysteresis loss.(2)Gas-phase nitridation of flake Fe₄N/Fe soft magnetic composites in situ preparation and study of AC and DC soft magnetic properties.The spherical Fe powder was flattened by a mechanical ball milling method,and was nitrided in an atmosphere of 550°C and an ammonia-hydrogen ratio of 1 to obtain flaky Fe₄N/Fe.The results show that with the increase of nitriding time,the Fe₄N content increases,the magnetic loss of the sample decreases,the quality factor increases,and the DC bias performance is better.In the range of 20-590 k Hz,as the magnetic flux density increases from 10 to 30 m T,the main source of sample magnetic loss changes from eddy current loss to hysteresis loss.Compared with spherical Fe₄N/Fe,the diameter-to-thickness ratio of flake Fe₄N/Fe samples increases,the shape anisotropy increases,and the magnetic permeability becomes larger.(3)In-situ preparation of Ni_0.5Zn_0.5Fe₂O₄/FeSiAl soft Magnetic composites by coprecipitation method and study of AC and DC soft magnetic properties.Co-precipitation method was used to directly synthesize NiZn ferrite insulating layers with different contents on the surface of FeSiAl powder.The results showed that the best calcination temperature for the co-precipitation in situ growth method was 650°C.NiZn ferrite insulating layer can effectively reduce high frequency eddy current loss.The sample with 3%NiZn ferrite has a high saturation magnetization of 128.6 emu/g and the largest figure of merit.In the range of 2-10 m T and 20-590 k Hz,the magnetic loss of the sample mainly comes from the hysteresis loss.(4)Preparation of Mn_0.5Zn_0.5Fe₂O₄/Fe₄N soft magnetic composite material and study of its AC and DC magnetic properties.Mn Zn ferrite was prepared by co-precipitation method,Fe₄N was prepared by vapor phase nitridation method,and Mn Zn/Fe₄N soft magnetic composite materials were prepared according to different proportions.The results show that with the increase of Mn Zn ferrite coating,the eddy current loss of the sample decreases,the quality factor increases,and the soft magnetic performance is better.In the range of 2-10 m T and 20-590 k Hz,the magnetic loss of the sample mainly comes from the hysteresis loss.In this paper,the key factors affecting the performance of soft magnetic composite materials are analyzed in depth.After reasonable interface design,a vapor-phase nitriding method and a co-precipitation method are used to prepare an insulating coating on the surface of iron-based soft magnetic particles in situ.The research results show that by optimizing the interface structure,the high-frequency magnetic loss of the iron-based soft magnetic composite can be effectively reduced,and the effective magnetic permeability of the magnet can be increased.