Efficient synthesis of TiO2-coated layer for Fe-based soft magnetic composites and their regulation mechanism analysis on magnetic properties

The high-quality TiO2 insulating layer on the commercial gas-atomized FeSiAl powder surface was efficiently prepared within a total time of 1 h at room temperature via a one-pot sol–gel method based on a developed industry-oriented coating equipment. The core-shell structure for the chemically coated FeSiAl powders was detected by the joint tools of SEM, EDS, and FTIR. Combined with the establishment of loss separation fitting model, the regulation mechanism analysis on soft magnetic properties was carried out for the FeSiAl powder cores insulated with different TiO2 coating amounts. It is found that the interface-pinning effect, which is closely related to the core’s density, is an important factor affecting the magnetic properties of powder cores. With the elevating TiO2 coating amount, the hysteresis loss, the excess loss, and DC-bias property of the core specimen exhibit the same increasing tendency, while the real part of complex permeability at 100 kHz gradually decreases owing to the increase of non-magnetic gap between the particles in the core, which can impede the domain-wall motion during magnetization. Correspondingly, the eddy current loss persistently decreases and contributes only 18.7% ~ 21.6% of total core loss when the precursor concentration is over 0.08 ml/g due to the formation of the intergranular insulated structure blocking the inter-particle eddy current flows in the composites. These results offer insights into subtly regulating magnetic properties when the adjusting process parameters for the soft magnetic composites are used in high-power and high-frequency applications.