Magnetic and Mechanical Properties of Iron-Based Soft Magnetic Composites Coated with Silane Synergized by Bi₂O₃

Fe-based soft magnetic composites (SMCs) co-coated with Bi₂O₃ and silane, used as the low melting point binder and the insulating layer, respectively, were successfully prepared. The SMCs show improved mechanical strength, thermal stability, and insulation compared to other soft magnetic composite materials. The obtained SMCs exhibit a high B_m of 1.2607 T at 5000 A/m, 50 Hz, a high μ_max of 497, and a low P_cm of 81.8 W/kg at 50 kHz and 50 mT for a completely homogeneous thin insulating coating. In addition, the transverse rupture strength of such materials is up to 81.2 MPa, which is extremely important for high-speed motors. Furthermore, the permeability and magnetic loss are stable under stress. Nonlinear curve fitting was used to build the loss model and then separated into the hysteresis loss, the eddy current loss, and the excess loss. The loss mechanism of SMCs with different coatings and micro-stress was explored and verified via this model. When compared to traditional SMCs, this material coated with Bi₂O₃ and silane shows a lower loss and a higher transverse rupture strength. This research expands the application fields of iron-based SMCs, especially in practical applications of soft magnetic components in high-speed motors.