Abstract: Soft magnetic cores consist of a highly saturated ferromagnetic powder core and a high resistivity insulating shell, resulting in core-shell heterogeneous structure, and could therefore have high permeability, high saturation magnetization, high resistance, and low eddy current loss, which is the basis for limiting eddy current operation and reducing high-frequency losses during AC magnetization. Therefore, maintaining the integrity and homogeneity of the core-shell heterostructure within soft magnetic cores during the sintering molding process is critical for optimizing the magnetic properties. In this work, Fe-Si/SiO2 soft magnetic cores were prepared by hot-pressing sintering, and the evolution behavior of Fe-Si/SiO2 soft magnetic cores' core-shell heterostructure with sintering time and the influence on the magnetic properties were systematically studied. These obtained results showed that the Fe-Si/SiO2 soft magnetic core core-shell heterostructure tended to be more complete with the prolongation of the sintering time range from 3 min to 10 min, and the SiO2 insulating layer began to crystallize when the sintering time was up to 9 min. When the sintering time was greater than 11 min, the core-shell heterostructure began to collapse due to the overheating phenomenon caused by the superposition of two thermal effects in the gradient temperature field during the hot-pressing sintering process. Under the condition that the core-shell heterostructure remained intact and dense, the Fe-Si/SiO2 soft magnetic cores with a sintering time of 10 min exhibited the best magnetic properties among all 8 samples, the saturation magnetization was 220.9 emu/g, the resistivity was 0.72 mΩ?cm, and the total loss in 10 mT and 100 kHz was 627.5 kW/m3. Compared to the sample with destroyed core-shell heterostructures (13 min), the total loss decreased by about 38.7%, of which the eddy current loss decreased by about 33.1%, and the hysteresis loss decreased by about 14.7%.

Key words: sintering time, core-shell heterostructure, soft magnetic core, evolutionary behavior, magnetic properties

摘要： 软磁铁芯由铁基软磁合金粉末和作为绝缘层的氧化物陶瓷组成，这二者在软磁铁芯中形成的核壳异质结构是限制交流磁化过程中涡流运转和降低高频损耗的基础，因此在烧结成型过程中保持软磁铁芯内核壳异质结构的完整性和均匀性对优化其磁性能至关重要。本工作制备了Fe-Si/SiO2软磁铁芯，并研究了Fe-Si/SiO2核壳异质结构随烧结时间的演化行为及对软磁铁芯磁性能的影响。结果表明，在3~10 min范围内，随烧结时间的延长Fe-Si/SiO2软磁铁芯内核壳异质结构逐渐趋于完整，烧结时间为9 min时，SiO2绝缘层开始结晶；当烧结时间超过11 min时，由于热压烧结过程中的梯度温度场引起的过热现象，导致核壳异质结构坍塌。在核壳异质结构保持完整的情况下，烧结时间为10 min的Fe-Si/SiO2软磁铁芯性能较佳，饱和磁化强度为220.9 emu/g，电阻率为0.72 mΩ?cm，总损耗Pcv (10 mT, 100 kHz)为627.5 kW/m3。相比于核壳异质结构坍塌的样品(13 min)，总损耗Pcv (10 mT, 100 kHz)降低约38.7%，其中涡流损耗降低了约33.1%，磁滞损耗降低了约14.7%。

关键词: 烧结时间, 核壳异质结构, 软磁铁芯, 演化行为, 磁性能