Boosting Electromagnetic Properties of Nanocrystalline Soft Magnetic Composites by Constructing a Heterogeneous...

Constructing a uniform coating layer with reliable insulating properties on the surfaces of Fe-based amorphous or nanocrystalline flake powders remains a challenge for soft magnetic composites (SMCs). Herein, by employing a phosphate coating combined with a TiO₂ deposition strategy, a dense and uniform insulating layer was successfully fabricated on amorphous FeSiBCuNb flake powders, which were obtained from crushed melt-spun alloy ribbons. Subsequent crystallization annealing of the amorphous SMCs not only transformed them to nanocrystalline SMCs but also induced the in situ formation of a well-defined TiO₂/phosphate/(SiO₂,Nb₂O₅) heterogeneous multilayer insulating structure on the nanocrystalline powder surfaces. This engineered insulating architecture and optimized coating thickness effectively suppress eddy current distribution, alleviate current density concentration on the powder surface, and significantly improve the electromagnetic performance of SMCs. The resulting nanocrystalline SMCs exhibit an effective permeability (μ_e) of 53, a DC bias performance (%μ_e) of 55% at 100 Oe, and a low core loss (P_cv) of 110.5 mW/cm³ at 100 kHz and 0.05 T. This work demonstrates a viable strategy for achieving high-performance insulation in practical nanocrystalline SMCs applications.