【作者】 王敏；

【导师】 沈宝龙； 刘天成；

【作者基本信息】 东南大学 ， 材料与化工（专业学位）， 2025， 硕士

【摘要】 随着第三代半导体的应用,电力电子系统正加速向高频化、高效化及小型化方向演进。这一趋势对磁粉心提出更高要求:高频低损耗、高饱和磁感应强度、高磁导率及优异直流偏置特性。在此背景下,本研究通过合金成分优化设计、绝缘包覆工艺改进及复合粉体结构调控,成功制备出综合软磁性能优异的铁基纳米晶磁粉心,并揭示磁粉心高频损耗机制,为纳米晶磁粉心的应用拓展提供实验与理论指导。首先,在FeSiBPCCuNb系铁基合金中微量添加Co元素,通过Fe-Co原子间的强交换耦合作用将合金的饱和磁感应强度从1.32 T提升至1.36 T。该设计策略在维持合金非晶形成能力前提下,显著提高了合金的软磁性能。基于优化后的合金体系(Fe_0.72Co_0.04P_0.05C_0.02B_0.08Si_0.09)_97.7Cu_0.8Nb_1.5,采用环氧树脂包覆工艺制备的纳米晶磁粉心经510℃、30 min热处理后,展现出优异的综合性能:饱和磁感应强度达0.99 T,有效磁导率为55（1 A/m、1 MHz）,且频率稳定性良好,直流偏置特性为50%（100 Oe）,磁心损耗为110 mW/cm³（0.05 T、100 kHz）,这些性能的提升表明,Co元素添加对优化磁粉心的性能具有显著效果。为进一步提高纳米晶磁粉心的高频特性,本研究采用钼酸铵原位热分解法在粉末表面构筑氧化钼绝缘层。通过调控钼酸铵浓度（0～9 wt.%）,实现了氧化层厚度与致密度的控制。该氧化层显著降低了磁粉心在交流磁场下颗粒间涡流损耗,进而提高其高频软磁性能。当处理浓度为5 wt.%时,形成连续致密的氧化钼绝缘层,使材料高频磁心损耗显著降低至2131 mW/cm³（0.05 T、1 MHz）,同时保持47的有效磁导率（1 A/m、1 kHz）并且频率稳定至20 MHz,直流偏置特性提升至61%（100 Oe）,饱和磁感应强度为0.97 T。最后,针对绝缘包覆造成的磁稀释以及磁粉心内部非磁性孔隙较多导致磁导率较低的问题,系统研究了磷化铁镍粉复合对磁粉心微观结构及软磁性能的影响。研究表明,适量磷化铁镍粉能够有效填充球形粉末间较大的非磁性孔隙,有利于磁粉心损耗降低与磁导率的提升。然而,当磷化铁镍粉添加过量时,细小的铁镍粉易于团聚,界面增多,导致孔隙率增加,软磁性能发生恶化。当磷化铁镍粉添加量为5 wt.%时,磁粉心综合性能最佳:饱和磁感应强度达到1.03 T,有效磁导率提升至60（1 A/m、1 kHz）,直流偏置特性增加至53%（100 Oe）,损耗降低至86mW/cm³（0.05 T、100 kHz）和2441 mW/cm³（0.05 T、1 MHz）。通过优化磷化铁镍粉的添加量,可有效改善磁粉心的高频磁性能。更多还原

【Abstract】 With the application of third-generation semiconductors,power electronic systems are advancing rapidly towards high frequency,high efficiency and miniaturisation.This trend imposes higher function on soft magnetic composites such as low core loss,high saturation magnetic flux density,high permeability,and excellent direct current bias performance.In response to these equirements,the present study successfully develops Fe-based nanocrystalline magnetic powder core materials with outstanding overall soft magnetic properties through a combination of alloy composition optimization,improvements in insulation coating processes,and regulation of composite powder structures.Furthermore,this study elucidates the high-frequency loss mechanisms in magnetic powder cores,providing both experimental and theoretical insights to guide the expanded application of nanocrystalline magnetic powder cores.Firstly,the trace addition of Co to FeSiBPCCuNb alloys enhances the saturation magnetic induction of the alloys from 1.32 T to 1.36 T through the strong exchange couples between Fe-Co atoms.This strategy significantly enhances the soft magnetic properties of the alloy while maintaining its glass-forming ability..Based on this optimized alloy system,nanocrystalline magnetic powder core were fabricated using an epoxy resin coating technique,followed by heat treatment at 510°C for 30 minutes.These materials exhibited excellent overall performance:saturation flux density reached 0.99 T,effective permeability was 55(1 A/m,1 MHz),and the permeability exhibited excellent frequency stability.The DC bias characteristic was 50%(100 Oe),and the core loss was 110 mW/cm~3 at 0.05 T and 100 kHz.These improvements underscore the significant role of Co in optimizing the performance of magnetic powder core materials.To further enhance the high-frequency properties of the nanocrystalline magnetic powder cores,an in-situ thermal decomposition method using ammonium molybdate tetrahydrate was employed to form a molybdenum oxide insulation layer on the powder surface.By carefully adjusting the concentration of ammonium molybdate tetrahydrate(0～9 wt.%),precise control over the thickness and density of the oxide layer was achieved.This oxide layer substantially reduced eddy current losses between the powder particles under alternating magnetic fields,thereby enhancing the high-frequency soft magnetic performance.At a concentration of 5 wt.%ammonium molybdate,a continuous dense molybdenum oxide insulating layer is formed,which significantly reduces the material’s high-frequency core loss to 2131 mW/cm~3(0.05 T,1 MHz),while maintaining an effective permeability of 47(1 A/m,1 MHz)and frequency stability up to 20 MHz,with an improved DC bias characteristic of 61%(100Oe)and saturation flux density of 0.97 T.Finally,to mitigate magnetic dilution from the insulating cladding and the low effective permeability caused by non-magnetic pores,the influence of phosphated FeNi powder on the microstructure and soft magnetic properties of magnetic powder cores was systematically studied.Results showed that adding an optimal amount of phosphated FeNi powder effectively filled large pores between spherical particles,reducing losses and enhancing permeability.However,excessive addition led to particle agglomeration and increased non-magnetic contact,degrading magnetic performance.When the phosphated FeNi powder content was 5 wt.%,the magnetic powder cores exhibited favorable soft magnetic properties:saturation magnetic induction reached1.03 T,effective permeability improved to 60(1 A/m,1 MHz),the DC bias characteristic increased to 53%(100 Oe),and core loss were reduced to 86 mW/cm~3(0.05 T,100 kHz)and 2441 mW/cm~3(0.05 T,1 MHz).These findings indicate that optimizing the proportion of phosphated FeNi powder can significantly enhance the performance of magnetic powder cores.更多还原