In this study, we suggest a rotating closed reaction system for oxidizing Fe powder at 500 ℃. This rotation leads to the homogeneous oxidation of large amounts of Fe powder. The analysis of the oxygen content in the oxidized Fe powder shows that all oxygen gas supplied to the closed system is consumed for the oxidation of Fe powder. This indicates that the thickness of the Fe₃O₄ layer formed by oxidation increases proportionally with the amount of oxygen gas supplied to the reactor. It was observed that the loss of the toroidal core decreased as the thickness of the Fe₃O₄ layer increased. The change in hysteresis loss was negligible compared with the change in eddy current loss. The eddy current loss decreased from 364.2 W/kg to 139 W/kg (@ 1 T, 400 Hz) as the Fe₃O₄ layer thickened from 30 to 110 nm. Because the Fe₃O₄ layer did not provide sufficient insulation, another approach was attempted to coat the silicone resin (>10¹³ Ω∙cm) with a specific resistivity approximately 10¹⁵ times higher than that of Fe₃O₄ on the Fe₃O₄ layer. To observe this double-layer structure, a thermally evaporated Ni film was coated on top of the double-insulating layer. The energy-dispersive X-ray spectroscopy analysis of a cross-sectional transmission electron microscopy image showed that the Ni film successfully protected the silicone resin layer from the ion-beam irradiated during FIB sampling, making it possible to observe the double-layer structure. When a ∼30 nm thick silicone resin layer was coated on the ∼30 nm thick Fe₃O₄ layer, the eddy current loss was abruptly reduced from 364.2 W/kg to 8.6 W/kg (@ 1 T, 400 Hz). It was found that the silicone resin layer with high electrical resistivity contributed significantly in reducing eddy current loss, and a resin layer several of tens nanometers thick was sufficient to insulate Fe powder from each other.

在这项研究中，我们提出了一种用于在 500 ℃ 下氧化铁粉的旋转封闭反应系统。这种旋转导致大量铁粉的均匀氧化。对氧化铁粉中氧含量的分析表明，所有供应到封闭系统的氧气都被消耗用于铁粉的氧化。这表明通过氧化形成的Fe ₃ O ₄层的厚度随着供应到反应器的氧气量成比例地增加。据观察，环形磁芯的损耗随着 Fe ₃ O _{4的厚度而降低}层数增加。与涡流损耗的变化相比，磁滞损耗的变化可以忽略不计。_{随着 Fe 3} O ₄层从 30 nm 增厚到 110 nm ，涡流损耗从 364.2 W/kg 降低到 139 W/kg（@ 1 T，400 Hz） 。由于 Fe ³ _O 4_{层没有提供足够}的绝缘性，因此尝试了另一种_方法，即_在Fe ³欧₄层。为了观察这种双层结构，在双层绝缘层的顶部涂上了一层热蒸发的镍膜。横截面透射电子显微镜图像的能量色散 X 射线光谱分析表明，镍膜成功地保护了有机硅树脂层免受 FIB 采样期间照射的离子束的影响，从而可以观察到双层结构。_{当在～30 nm 厚的 Fe 3} O ₄上涂覆～ 30 nm 厚的有机硅树脂层时层，涡流损耗从 364.2 W/kg 突然降低到 8.6 W/kg（@ 1 T，400 Hz）。结果发现，电阻率高的有机硅树脂层对降低涡流损耗有显着贡献，几十纳米厚的树脂层足以使铁粉彼此绝缘。