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摘要
Gas-atomized Fe-Si-Al soft magnetic powder cores with different fine powder mass ratios were prepared by the epoxy/silica composite insulation method in this paper. High-quality insulation layer based on silica was found to form on the surface of Fe-Si-Al magnetic particles. It limited the eddy current within the core effectively and thus resulted in good frequency stability of the core's effective permeability. The influence of the fine powder on the core's magnetic properties was investigated in detail. It was found that adding appropriate amount of fine powder helped the increase of the density of the powder core and the reduction of the core's effective demagnetizing field. As the consequence, both the effective permeability and the core loss were improved at the expense of the DC-Bias performance. However, the excessive addition of fine powder was found to be harmful for the core's magnetic properties. It reduced the core's density and enhanced the core's effective demagnetizing field, which resulted in the decrease of the effective permeability and the increase of the core loss. A preliminary study on the magnetic mechanism of the powder core prepared with fine powder was performed through separating the core loss at different frequencies for all the samples into the hysteresis loss and the eddy-current loss based on the Bertotti model. It was found that at frequencies below 120 kHz for the powder core, with the amount of fine powder increasing, the hysteresis loss, same as the total core loss, exhibited an increasing tendency after the initial decrease, while the eddy-current loss kept decreasing. This indicated that the eddy-current loss could be effectively restrained by the addition of the powder with a small size and the loss in the common frequency range below 100 kHz for powder core was mainly determined by the hysteresis mechanism based on the effective demagnetizing field. ? 2020, Editorial Board of Journal of Functional Materials. All right reserved.
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