Optimization Of The Resistivity And Permeability Of Soft Magnetic Composites Prepared By Spark Plasma Sintering

Our country put forward the manufacturing strong country plan.Its purpose is to promote the rapid transformation of manufacting in dustry development.For the past few years,AIT,automation and other fields are continually developing.The transformer and inductor as the main device gained widespread attention.Now,the power devices is developing toward integration,miniaturization,high efficiency.High frequency characteristics of soft magnetic character is of the basic direction.As the core material,SMCs?Soft Magnetic Composite materials?should be high-speed,high performance,high power density.Therefore,it is particularly important that SMCs are developed with high saturation flux density,high permeability,low loss,low coercive force.High resistivity of insulating material coated magnetic powder by plysical and chemical methods.It is the main way to get excellent magnetic and increase the resistance and reduce the eddy current loss.Coating ferrite with high resistivity on the surface of Fe base amorphous materails,then sintering by SPS,the resistivity of them can bu up to 1300??·cm.But it still has big deviation with the calculated value.We want to explore the influence of SPS sintering of the resistivity,the pure Fe powder as substrate and Al₂O₃nano-powders as coatings.Through physical grinding method and SPS sintering,the influence of different coating thickness and sintering temperature on the material resistivity were observed.The Fe/Al₂O₃ composites have high density.The resistivity of samples decrease with the increase of sintering temperature.And the downward trend of different thickness of coationg layer is different.This is due to the different diffusion mechenism of Fe element during sintering.When it is beneficial to occurring of interface discharge phenomena,the diffusion of interface Fe element was mainly affected bu plasma activated diffusion effect.So the resistivity of samples drops rapidly.In addition,people generally use powder metallurgy to suppress shape in order to obtain the good performance of the magnetic powder cores.But there has a problem that diffusion of elements destroys the interface insulation.For getting higher comprehensive performance,SMCs can have nice soft magnetic properties under the high frequency.In order to separate from Fe powder,the barrier layer was coated.Thus inhibits Fe element diffusion to the ferrite insulation layer,it can avoid Fe²⁺ion concentration increasing and improve the effect of the insulation layer.MgF₂ has strong chemical stability and good thermostability.Above 600 ^oC,it hardly reacts wity pure iron.The ferrite layer by sol-gel was thin and substrace.Fe/MgF₂/?ZnNi?Fe₂O₄ composites were obtained by SPS.With same thickness of the ferrite,the resistivity increase with the increase of content of MgF₂.The composites have excellent magnetic electric and comprehensive mechanical propertes.It provides innovation to improve the resistivity and develope the high frequency application performance.