The Research On Soft Magnetic And DC Bias Performance Of Fe-based Soft Magnetic Amorphous Powder Cores

Soft magnetic powder cores occupy an indispensable position in electromagnetic conversion,transmission and storage.Fe-based amorphous magnetic powder cores(AMPCs),with the advantages of high saturation induction,remarkable effective permeability(?_e),high resistivity,low coercivity(H_c),low core loss(P_cv)and low price,have attracted much attention.However,in some AC circuits,there is often a DC component.The invasion of DC current into the AC transformer will cause core saturation,temperature increase,and other negative effects.Therefore,improving the DC bias performance of the AMPCs is also a key factor for high-frequency and high-current devices.The purpose of this study is to investigate the effects of different fabrication processes on the DC bias performance of the AMPCs.(1)The effects of pressure and annealing temperature on the properties of Fe Si BPNb Cr AMPCs were first studied.With the increase of the pressing pressure,?_eand?_e in 100 Oe increases,P_cv decreases,the soft magnetic performance gradually optimized.With the increase of the annealing temperature,the soft magnetic properties are gradually optimized.The optimal pressing pressure is 1800 MPa and the optimal annealing temperature is 460?.(2)A high-filling Al₂O₃/EP nanocomposite with improved thermal stability and insulation performance has been successfully designed as an organic–inorganic coating layer for the AMPCs.Unlike the organic coating,the organic–inorganic hybrid coating cores exhibits superior magnetic properties without compromising on saturation magnetization and permeability.The core loss declined by 39%,and the quality factor was 13% higher as half Al₂O₃ was introduced into the epoxy resin matrix.(3)Dense and pinhole-free poly-para-xylylene(PPX)layer has been successfully deposited on the surface of powder via chemical vapor deposition(CVD)polymerization and the corresponding AMPCs are also prepared.Compared to commonly used epoxy resins,PPX layer had higher thermal stability and lower dynamic friction coefficient,resulting in higher resistivity and green density of the AMPCs,thus reduced the P_cv(12% lower)and enhanced magnetic flux density(B_s)(8.5%enhanced),as well as DC bias performance(24%enhanced).(4)Novel AMPCs composed of a mixture of water-atomized Fe Si BPNb Cr amorphous powder and FeCo alloy powder are successfully fabricated.FeCo alloy powder,which exhibits a high B_s of 2.35 T,can improve the B_s and DC bias performance of the AMPCs.Compared to raw AMPCs,the B_s and DC bias performance of AMPCs containing 30%FeCo powder are improved by 35%and 24%,respectively.P_cv maintain in a low level(5)In this study,the theoretical analysis and discussion of the influence mechanism of the control during the integration of AMPCs on the DC bias and soft magnetic performance.It is believed that improving B_s of the AMPCs,including increasing pressure and mixing crystalline powder,are beneficial to improve the DC bias and soft magnetic properties of the AMPCs.Optimization of the structure of the coating layer,using a high heat-resistant,dense and uniform coating layer is effective to reduce eddy current path between particles,and increase the demagnetizing field inside the core and impeding magnetization,improve the DC bias and soft magnetic properties of the AMPCs.(6)According to the optimized process conditions of this study,laboratory samples of industrial specifications were trial-produced.The performance of the AMPCs surpass the existing Fe,Fe Si,and Fe Si Al powder cores,and the cost is lower than that of Fe Ni and Fe Ni Mo powder cores.The AMPCs fabricated in this study with excellent comprehensive magnetic properties,was a potential candidate for medium and high frequency electric-magnetic devices.