FeSiCr-Based Soft Magnetic Composites with SiO2 Insulation Coating Prepared Using the Elemental Silicon Powder Hydrolysis Method

Abstract

In this work, FeSiCr powders were coated with a SiO2 insulation layer for soft magnetic composites (SMCs) through elemental silicon powder hydrolysis, without using any expensive precursors. The effects of the reaction temperature and ammonia concentration on the structure and performance of SMCs were investigated. Through the elemental silicon powder hydrolysis process, the formation of an FeSiCr–SiO2 core-shell structure effectively reduced the core loss, increased resistivity, and improved the quality factor of SMCs. SMCs prepared with 0.10 mL/g ammonia concentration at 50 °C exhibited the best combination of properties, with saturation magnetization Ms = 169.40 emu/g, effective permeability μe = 40.46, resistivity ρ = 7.1 × 106 Ω·cm, quality factor Q = 57.07 at 1 MHz, and core loss Ps = 493.3 kW/m3 at 50 mT/100 kHz. Compared to the uncoated sample, SMCs with a SiO2 coating exhibit 23% reduction in Ps, with only 6.6% reduction in μe. Compared to SMCs fabricated using the traditional sol-gel method, the sample prepared through hydrolysis of elemental silicon powder has higher permeability and lower core loss. In particular, this new approach gives an effective coat solution for the mass production of high-temperature-resistant SMCs.