Preparation And Magnetic Properties Research Of Fe Based Soft Magnetic Composites

Soft magnetic composites?SMCs?are important magnetic materials and widely applied in electromagnetic conversion equipment.But with the development of electronic equipment,the performances requirements of SMCs are also getting higher,such as low magnetic losses,stable magnetic permeability and high saturation magnetization.In view of the problem of high eddy current loss of Fe-based soft magnetic composites,the high insulating coating and reliable coating method are explored to prepare Fe-based soft magnetic composites.By controlling the insulating coating and the structure of the insulating layer,the electromagnetic performance is improved.The specific research results are as follows:The mechanical ball milling process was applied to mix nano-scale MnO₂ and Fe powders to prepare Fe/MnO₂ composite powders,and then obtained composite powder were used to prepared Fe/MnO₂ SMC.The effects of different MnO₂ coating amounts on microstructure and electromagnetic properties were investigated.The results show that nano-MnO₂ powders can be uniformly coated on the surface of Fe powders to form Fe/MnO₂ composite powders.As the coating amount of MnO₂ increases,the thickness of MnO₂ coating layer gradually increase.The saturation magnetization of Fe/MnO₂ SMC gradually decreases and the coercive force gradually increases.Because of the barrier effect of the MnO₂,the resistance is increasing and the magnetic loss continues to decrease.The Fe/MnO₂ SMC with 7.5wt.%MnO₂ shows good performance,low magnetic loss 11.04W/kg?20mT,5 kHz?,and relatively good soft magnetic properties,such as high saturation magnetization?191.2 A·m²/kg?and stable magnetic permeability?29.4?.Through mechanical ball milling process,different mass fractions nano-scale ZrSiO₄powders were uniformly mixed with Fe powders.Obtained Fe/ZrSiO₄ composite powders were prepared to Fe/ZrSiO₄ SMC combined with high-temperature sintering and heat treatment.The effects of the content of ZrSiO₄ on the microstructure and magnetic properties were studied.The results show that the nano-scale ZrSiO₄ powder can be successfully coated on the surface of Fe particles the ball milling process.After high temperature sintering and heat treatment,the dense Fe/ZrSiO₄ SMC was obtained.With the increase of the ZrSi O₄ amount,the coating layer is gradually obvious,the resistivity is increased,and the magnetic loss is continuously reduced.But,the saturation magnetization of the soft magnetic composite material gradually decreases,the coercive force continues to increase.Fe/ZrSiO₄ SMC with 7.5wt.%ZrSiO₄ has good performance,high saturation magnetic induction intensity?202.20 A·m²/kg?,stable magnetic permeability?29.39?and low magnetic loss?4.53 W/kg at 20mT,5 kHz?.Based on the characteristics of high temperature pyrolysis of zinc acetate to ZnO,Fe/ZnO composite powders were prepared through the sol-gel method combined with pyrolysis progress.Then,SMCs with a specific shape was prepared by high temperature sintering.In addition,the heat treatment process can improve the performance of soft magnetic composite materials.Compared to uncoated raw Fe,Fe/ZnO SMC has higher resistivity and lower magnetic loss(W_20mT/10kHz=5.24 W/kg)and maintains good frequency stability(26_10kHz)and high saturation magnetization?188 A·m²/kg?,which has a positive impact on the development and application of Fe SMCs.