Properties of Fe2SiO4/SiO2 coated Fe-Si soft magnetic composites prepared by sintering Fe-6.5wt%Si/Fe3O4 composite particles

Abstract In this work, Fe2SiO4/SiO2 coated Fe-Si soft magnetic composites (SMCs) have been prepared successfully via ball milling Fe-6.5wt%Si/Fe3O4 composite particles combined with subsequent spark plasma sintering (SPS) process. The formation mechanism of Fe2SiO4/SiO2 insulating layer and effect of Fe3O4 coating content on the microstructure and properties for the Fe-Si SMCs were investigated in detail. It is interesting that high temperature SPS process would lead to the occurrence of redox reactions between Fe3O4 and Si from Fe-Si alloy cores, and resulted in the transformation from Fe3O4 coating layer to Fe2SiO4/SiO2 insulating layer. As a consequence, the novel Fe-Si SMCs exhibited superior performances including high saturation magnetization (190.4 emu/g) and low core loss (9.02 mW/cm3 at 10 kHz) decreased by 89.1% compared to that of the uncoated Fe-Si SMCs (83.08 mW/cm3 at 10 kHz). The results indicated that the method of preparing insulating layer by the redox reactions is a simple and effective way to synthesize new SMCs with high performance for electro-magnetic energy conversion equipments.