Preparation and magnetic performance optimization of FeSiAl/Al2O3–MnO–Al2O3 soft magnetic composites with particle size adjustment

FeSiAl soft magnetic composites (SMCs) with unique three-shell structured Al2O3–MnO–Al2O3 composite coatings were designed and prepared via sintering ball milled FeSiAl/MnO2 core–shell structured composite powders. The electromagnetic performance of the FeSiAl SMCs was optimized by regulating the average particle size of FeSiAl powders systematically. Owing to the interfacial reaction between MnO2 coating and Al with high reactivity from the FeSiAl alloy cores, the composite coatings were formed. When the average particle size decreased from 144 to15 μm, both the average thickness of the MnO2 coating and the relative density of the FeSiAl SMCs were decreased, resulting in the weakened permeability and deteriorated coercivity as well as the increased hysteresis loss, but the saturation magnetization showed a slight enhancement. And the resistivity was increased when the average particle size was smaller, which led to the obvious reduction of both the inter-particle and intra-particle eddy current losses.