Soft magnetic composites with improved heat resistance and mechanical strength realized using Fe@SiO2 powders with a variable thickness insulation layer

Here, we demonstrate a novel Fe@SiO2-powder-based soft magnetic composite that can withstand high-temperature heat treatment and that exhibits unprecedented mechanical strength. Fe@SiO2 powders are prepared by forming a uniform and continuous SiO2 insulation layer on the surface of Fe powder through sol-gel method based on a hydrolysis and condensation reaction mechanism. The sol-gel kinetics responded with a different tetraethyl orthosilicate (TEOS) concentration in the solution from 0.01 to 0.25 ml/g; SiO2 reactant is produced at different rates and accumulates at different thicknesses on the surfaces of Fe powders. The SMC core with dense and uniform SiO2 insulating layer contributes to better magnetic performance, including much higher electrical resistance, lower eddy current loss, and better frequency stability compared to those characteristics of the conductive Fe-based powder core. Furthermore, Fe@SiO2 SMC maintains its internal insulation matrix and low core loss even after high-temperature heat treatment, which densifies the SiO2 insulation layer and greatly enhances the mechanical strength of the SMCs. As a result, the Fe@SiO2 SMC core with an optimally controlled insulation thickness not only demonstrated a remarkably low core loss of 98 W/kg at 1 kHz and 500 mT but also a high mechanical flexural strength of 82 MPa, attributable to the uniform and dense internal SiO2 insulating matrix with high-temperature annealing resistance.

Automated summary

In this study, a novel Fe@SiO2-powder-based soft magnetic composite that can withstand high-temperature heat treatment and exhibit unprecedented mechanical strength was developed. By forming a uniform and continuous SiO2 insulation layer on the surface of Fe powder using the sol-gel method, the magnetic performance was improved and the internal insulation matrix and low core loss were maintained even after high-temperature heat treatment.