Synthesis of well-insulated Fe–Si–Al soft magnetic composites via a silane-assisted organic/inorganic composite coating route

Abstract In this study, an organic/inorganic composite coating method based on silane, silicon oil, and tetraethyl orthosilicate was developed to prepare Fe–Si–Al soft magnetic composites (SMCs). The insulation reaction processes may have involved the hydroxylation of magnetic powder and condensation of silanol groups. Analyses of the microstructure and high frequency stability of the effective permeability of the SMCs demonstrated the formation of a high-quality silicon oxide coating layer on the surfaces of the Fe–Si–Al particles. The effects of the insulation content on the density, resistivity, and magnetic properties were studied for the well-insulated Fe–Si–Al SMCs, and the underlying physical mechanisms were clarified. The results showed that increasing the insulation content reduced the effective permeability and the eddy current loss, but increased the DC-bias performance and hysteresis loss. The enhancement of the effective demagnetizing field indicated by the decrease in the density of the SMCs may have been responsible for the enhanced hysteresis. In addition, the increase in the resistivity of the SMCs may have contributed to the decrease in the eddy current.