Achieving high effective permeability and low core loss in Fe-6.5 wt%Si soft magnetic composites via plasma coating method

Simultaneously achieving high effective permeability and low core loss in soft magnetic composites (SMCs) remains challenging. To address this issue, we report a plasma coating method to fabricate Fe-6.5 wt%Si SMCs with organic resin insulation layer and further clarify the underlying coating mechanism. Relative to convention coating, interestingly, the plasma coating can result in the more uniform and thinner insulation layer, eliminate powder agglomeration and consequently improve the flowability for the Fe-6.5 wt%Si powders. This leads to the greater electrical resistance and higher density in the plasma-coated Fe-6.5 wt%Si SMCs. Accordingly, the plasma-coated SMCs achieve the high effective permeability of 110.7 and low core loss of 373.5 kW/m3 at 50 mT and 100 kHz, which are respectively 33.4% greater and 34.5% lower than the corresponding ones in the conventional-coated SMC. The excellent soft magnetic properties are far superior to those of other typical SMCs reported so far. Basically, the plasma coating mechanism includes the pyrolyzing of insulation resin and its repolymerizing on the surface of Fe-6.5 wt%Si powders under discharge plasma effect in vibration condition, thereby forming a uniform and thin insulation layer without powder agglomeration. Our work provides a novel pathway for achieving superior comprehensive soft magnetic properties of SMCs.