Ultra-low inter-particle eddy current loss of Fe3Si/Al2O3 soft magnetic composites evolved from FeSiAl/Fe3O4 core-shell particles

FeSiAl/Fe3O4 core-shell composite particles and transformed Fe3Si/Al2O3 composite compacts have been prepared via ball milling coating combined with subsequent spark plasma sintering (SPS) process. The formation mechanism of the Al2O3 insulating layer and the magnetic properties of the Fe3Si/Al2O3 composite compacts have been investigated systematically. The FeSiAl particles are coated with uniform Fe3O4 nanoparticles by ball milling method. And during SPS process, the new phase Fe3Si/Al2O3 composite compacts are formed due to the high temperature solid phase reaction between FeSiAl alloy core and Fe3O4 coatings. The Fe3Si phase possesses excellent soft magnetic properties and the uniform Al2O3 layer shows good insulativity. Therefore, the Fe3Si/Al2O3 composite compacts exhibit superior soft magnetic performance such as enhanced saturation magnetization, reduced coercivity, good permeability stability, high resistivity and thus low core loss at high frequency compared with the original FeSiAl compacts. The investigated results in this work indicate that FeSiAl alloy particles coated with iron oxides can be transformed into soft magnetic composite materials with new insulating layer via high temperature solid phase reaction, which provides a promising approach to develop new-style soft magnetic composites with excellent electro-magnetic properties.