Effect of SiO2/Organosilicone Double Insulation Coating Processes on the Properties of Ferrosilicon Magnetic Cores

A nano-SiO2 inorganic insulation layer was coated on the surface of FeSi magnetic powder via in situ fluidised vapour deposition. The surface was then coated with organosilicon resin to form an inorganic/organic double-insulating layer. Post-forming and annealing, a ferrosilicon magnetic powder core was prepared. The effects of organosilicon resin content and pressing pressure on the permeability and loss of the ferrosilicon magnetic core were studied. When the ferrosilicon magnetic core was doubly insulated with SiO2/silicone resin, the silicone resin content increased, the insulation coating gradually thickens, and the saturation magnetic-induction intensity of the magnet gradually decreases; the density and effective permeability showed a trend of increasing first and then decreasing. Increasing the forming pressure can reduce the loss of the core, thereby improving the performance of the core and increasing the permeability without damaging the double-cladding layer. In the powder with the optimised silicone resin content (1.5 wt.%), the magnetic properties of the magnetic core were maximised after preparation at 1500 MPa followed by heat treatment at 773 K. The saturation magnetisation was 187.5 emu/g and the resistivity and permeability reached 10.5 Ω·cm and 49.6, respectively, at 100 mT and 50 kHz. The total loss was 905 mW/cm3.