Mechanism of adding carbonyl iron powder to enhance the magnetic properties of Fe-Si-B-Cu-Nb nanocrystalline soft magnetic composites

In this study, Fe-Si-B-Cu-Nb powders were transformed from amorphous structure to nanocrystalline/amorphous two-phase structure by heat treatment, then mixed with different ratios of carbonyl iron powder (CIP) and pressed into composite cores. The effect of the ratio of CIP on the magnetic properties of Fe-Si-B-Cu-Nb/CIP composite core was studied, and the mechanism of the effect was explained. It was found that as the ratio of CIP increased, the structure of the composites changed from "single-particle" to "two-particle" and then back to "single-particle" structure, and the magnetic properties of the composites also changed with the structural change. When the ratio of CIP was 30 wt%, the composites had the highest relative density of 84.12%, the highest permeability of 35.3, the lowest coercivity of 23.34 A/m and the lowest core loss 281.87 mW/cm3 (Bm=50 mT, frequency=100 kHz). Thus, it was confirmed that adding appropriate amount of CIP as gap-filling particles to Fe-Si-B-Cu-Nb nanocrystalline powders can improve the magnetic properties of the composites.