Preparation of high-performance Fe-Si soft magnetic powder cores using complete and dense SiO2 coated powder

A complete, dense coating is essential for reducing eddy current losses in soft magnetic composites (SMCs) and improving their overall performance. In this study, 3-aminopropyltriethoxysilane (APTES) was utilized to modify the surface of Fe-Si powders through organosilane functionalization, followed by the hydrolysis-condensation reaction of tetraethyl orthosilicate (TEOS) to form a SiO 2 insulating layer. TEM, powder resistivity and electrochemical testing indicate a complete and dense surface coating on the powder. Furthermore, the surface modification of the powder with APTES reduces the impact of excess non-magnetic phase coating on the magnetic hysteresis loss of soft magnetic powder cores, which facilitates the regulation of magnetic permeability to obtain powder core samples with low loss and high direct current (DC) bias performance according to corresponding specifications. Experimental results show that for APTES-modified powders, when the TEOS dosage is 5 wt%, the fabricated soft magnetic powder core with a permeability grade of 60 μ exhibits excellent comprehensive performance: a DC bias retention of 70.7% at 100 kHz/100 Oe, a core loss of 1141 mW/cm 3 at 100 kHz/100 mT, and a low permeability temperature coefficient of 30 ppm/°C within −20 °C to 140 °C, indicating temperature stability. This study provides guidance on the fabrication of high-power, high-current soft magnetic powder cores and on controlling magnetic permeability specifications while minimizing losses.