Abstract: Soft magnetic composite cores (SMCs) are considered the most promising electromagnetic conversion device due to their excellent properties, including high saturation magnetisation, high permeability, and relatively low core loss. However, core loss and permeability, as the key performance parameters for the effective operation of electromagnetic devices, are often restricted. Therefore, by adjusting the distribution characteristics of the powder matrix, the insulating layer, and increasing the ferromagnetic filling factor within the soft magnetic composite core, in-situ coating of the insulating layer can be realised, which helps to simultaneously reduce core loss and improve magnetic permeability. In this work, a novel interface solid-phase reaction strategy was designed. Firstly, calcium acetate was uniformly coated on the surface of Fe-Si-Al soft magnetic alloy powder using hydrothermal method. Subsequently, Fe-Si-Al based soft magnetic composite cores were prepared by hot pressing sintering. The effects of sintering temperature and insulation layer phase transition on the morphology, microstructure, and magnetic properties of the prepared soft magnetic composite cores were studied. The results showed that calcium acetate was successfully coated onto Fe-Si-Al alloy powder surface by hydrothermal method, forming a core-shell heterostructure with the Fe-Si-Al alloy powder as the core and calcium acetate as the shell. This provided powder materials for subsequent preparation of soft magnetic composite cores. Raising sintering temperature eliminated internal pores within soft magnetic composite cores while promoting transition from calcium acetate to calcium carbonate to Al2O3?SiO2?CaSiO3, ultimately providing high-quality insulation. The insulating layer of the soft magnetic composite core prepared by high temperature sintering at 850℃ was dense and uniform, and the magnetic dilution effect was minimised. At 10 mT and 100 kHz, the soft magnetic composite core had the highest permeability (67.2), the lowest core loss (9.24×10-5 kW/cm3), and a relatively higher saturation magnetisation (129.0 emu/g), which had the best comprehensive performance, and provided a solution to restrict the reverse relationship between permeability and loss in traditional soft magnetic materials. Therefore, insulation methods based on thermal decomposition and oxidation of organic salt compounds are expected to be an important supplement to the magnetic property optimisation strategy of soft magnetic composite cores based on interfacial solid phase reaction engineering.

Key words: soft magnetic composite cores, insulating layer, interfacial solid phase reaction, magnetic properties, optimisation strategy

摘要： 因具有高饱和磁化强度、高磁导率和相对较低的磁芯损耗等优异性能，软磁复合铁芯被认为是最具发展潜力的电磁转换器件。但软磁复合铁芯的能量损耗和导磁性作为保证电磁器件有效运行的关键性能参数，却往往呈制约关系。因此，通过调控粉末基体与包覆层分布特征，增加软磁复合铁芯内部的铁磁填充因子，实现绝缘层的原位包覆，有助于达到同时限制能量损耗和提高导磁性的目的。本工作设计了一种新的界面固相反应策略，首先通过水热法将乙酸钙均匀地包覆在Fe-Si-Al软磁合金粉末表面，再利用热压烧结制备Fe-Si-Al基软磁复合铁芯，研究了烧结温度和包覆层相变对制备的软磁复合铁芯形貌、微观结构和磁性能的影响。结果表明，通过水热法乙酸钙被成功包覆在Fe-Si-Al合金粉末表面，形成了以Fe-Si-Al合金粉末为核、乙酸钙为壳的核壳异质结构；烧结温度的提高消除了软磁复合铁芯内部的孔隙，促使绝缘层发生从乙酸钙到碳酸钙再到Al2O3?SiO2?CaSiO3的转变，最终为软磁复合铁芯提供了高质量的复合绝缘层；在850℃下高温烧结制备的软磁复合铁芯绝缘包覆层致密均匀，磁稀释效应被降到最低，在10 mT、100 kHz时拥有最高的磁导率(67.2)、最低的损耗(9.24×10-5 kW/cm3)和相对更高的饱和磁化强度(129.0 emu/g)，综合性能最优，为制约传统软磁材料中导磁性与损耗间的反向关系提供了解决方案。因此，基于有机盐类化合物热分解氧化的绝缘包覆方法有望成为基于界面固相反应工程的软磁复合铁芯性能优化策略的重要补充。

关键词: 软磁复合铁芯, 绝缘包覆, 界面固相反应, 磁性能, 优化策略