Insulation layer design for soft magnetic composites by synthetically comparing their magnetic properties and coating process parameters

Abstract

The soft magnetic performances of the Fe-6.5 wt.%Si (FeSi) soft magnetic composites (SMCs) insulated with different materials, including organic, inorganic, and soft magnetic materials with high resistivity, and composite coating of inorganic-magnetic layer, under the same fabrication condition have been compared and analyzed by synchronously considering their coating preparation parameters. The core–shell structure of the coated powder was characterized by using a combination of SEM-EDS, FTIR, and XRD. Loss separation fitting model was established to evaluate the source of each part loss for the corresponding FeSi SMCs above. Due to the fact that the SMCs insulated with inorganic or/and magnetic ferrite materials exhibit high bulk resistivity more than 1.4 Ω·m, their eddy current losses account for lower contribution of only 20.2 ~ 22.1% of total core loss compared with that of 61.9% for the SMCs coated alone with organic resin. As compared to the other insulation materials, the SMCs coated using inorganic material (SiO2 or TiO2) exhibit a better DC-bias over 75.5%, higher retain real-part permeability exceed 44.6 at an applied field of 7960 A/m, a relatively low total core loss of 1040.6 kW/m3 at 100 kHz, 0.1 T, and can be fabricated at room temperature with a total preparation time of 70 min, which is favorable for being widely used in industry. The results of this work offered a referable ideal to design insulating layer for other SMCs.