Structure evolution and performance of soft magnetic composites transformed from FeSiAl/NiO composites

FeSiAl/NiO is successfully evolved into FeSiAl/(Al 2 O 3 -Ni) and further FeSiAlNi/Al 2 O 3 . • Structure evolution and performance of the fabricated SMCs were investigated. • Al 2 O 3 -Ni coating maintains high stability at sintering temperatures below 900 °C. • Sintering above 950 °C accelerates interdiffusion to form the FeSiAlNi alloy phase. • The saturation magnetization and magnetic loss were improved simultaneously. High-frequency power electronic devices require soft magnetic composites (SMCs) with low magnetic loss and high saturation magnetization. In this study, FeSiAl/(Al 2 O 3 -Ni) and FeSiAlNi/Al 2 O 3 SMCs were fabricated via sintering FeSiAl/NiO composites at various temperatures. The structural evolution and performance of the resulting SMCs were systematically investigated. At sintering temperatures of 850℃–900℃, a chemical reaction between aluminum (Al) (derived from FeSiAl) and NiO at the FeSiAl/NiO interface, yielded FeSiAl/(Al 2 O 3 -Ni) SMCs with a composite coating comprising a uniform Al 2 O 3 layer and a ferromagnetic nickel (Ni) layer. Sintering temperatures exceeding 950℃ accelerated the interdiffusion of Al from the FeSiAl core and that of Ni from the composite coating, facilitated the alloying of FeSiAl and Ni and reduced the homogeneity of the Al 2 O 3 layer, ultimately generating FeSiAlNi/Al 2 O 3 SMCs. The prepared SMCs exhibited low magnetic loss and considerably enhanced saturation magnetization, 8.5%–21.3% greater than that of the raw FeSiAl powder. This work provides a novel strategy for constructing high-quality coatings in SMCs, with the potential to advance the development of high-performance SMCs for high-frequency power electronic applications. Download: Download high-res image (225KB) Download: Download full-size image