Temperature-controlled synthesis of FeSiAl/Al2O3 soft magnetic composites via acetic acid passivation for high-frequency applications
摘要
With the increasing demand for high-frequency motor drives, FeSiAl soft magnetic composites (SMCs) have attracted attention because of their low core loss and isotropic magnetic behavior. However, their practical application is still limited by the trade-off between permeability and energy dissipation. In this work, an acetic acid passivation strategy was used to form an aluminium acetate precursor on FeSiAl particle surfaces, followed by hot-press sintering at 750–1050 °C to investigate the effect of sintering temperature on the insulating layer, microstructure, and electromagnetic properties of FeSiAl/Al2O3 powder cores. The results show that the precursor-derived oxide layer evolves from loose γ-Al2O3 to denser α-Al2O3 with increasing temperature, while excessive sintering at 1050 °C causes deterioration and local disruption of the insulating layer, accompanied by degradation of the core–shell structure. The sample sintered at 950 °C exhibits the best overall performance, with a permeability of 30.5, a saturation magnetisation of 177.9 emu/g, a total core loss of 547.3 kW/m3 at 30 mT and 200 kHz, and a DC-bias retention above 70% at 94.8 Oe. This work provides useful guidance for optimising FeSiAl-based SMCs for high-frequency applications.