Carbon-Based Oxygen Carriers and Boric Acid as Precursors for In Situ Electrical Insulation of an Iron Powder-Based Soft Magnetic Composite

Insulated ferromagnetic particles with inorganic layer allow heat treatment at relatively high temperatures, which improves the magnetic permeability and hysteresis loss behavior of SMCs. However, as the particle core is more susceptible to plastic deformation than the insulating coating, the electrical insulation can be damaged during the compaction process. Such insulation breakage leads to more intense eddy currents, which reduces the SMC performance due to higher dynamic losses. This work addresses a solution to this well-known problem by completely generating the insulation between iron particles in a post-compaction heat treatment by combining two classes of precursors: carbon-based oxygen carriers (hydrothermal carbon spheres and graphene oxide) and boric acid. The synergistic mechanism of this double-layer SMC resulted in a reduction in dynamic losses of up to 61% compared to single-layer SMC. The results also indicate that precursors with a high surface to volume ratio can maximize this material magnetic performance.