High-performance Fe/SiO_2 soft magnetic composites for low-loss and high-power applications

摘要

High-performance Fe/SiO_2 soft magnetic composites (SMCs) by coating pure iron particles with amorphous SiO_2 layers have been fabricated by controlled hydrolysation of tetraethyl orthosilicate (TEOS). Microstructural studies show that the pure iron particles are uniformly and entirely coated with the SiO_2 insulating layers to form Fe/SiO _2 core-shell structure. The dielectric SiO_2 layers lead to the electrical insulation behaviour of the SiO_2-coated iron particles, which results in low core loss of the compacted Fe/SiO_2 SMCs in application of alternating current. The core loss measured at a frequency of 50 Hz and an induction level of 1 T is 3.5 W kg~(-1), which is much lower than that of the commercial SMCs prepared by coating iron particles with phosphate layers. The Fe/SiO_2 SMCs exhibit nearly the same coercivity as that of pure iron, and saturation magnetization of 18.2 kG, a little lower than that of pure iron due to the nonmagnetic SiO_2 layers. The low core loss and high saturation magnetization promise the great potential of Fe/SiO_2 SMCs in high-power applications. High-frequency measurements reveal that the working frequency of the Fe/SiO_2 SMCs can reach up to 20 MHz.