With the miniaturization and high frequency of electronic devices, the performance requirements for soft magnetic composites (SMCs) are increasing. FeSiAl-based SMCs have become a research hotspot in recent years due to their high saturation magnetization, high resistivity, and low cost. However, traditional FeSiAl SMCs suffer from low permeability, high power loss, and poor mechanical strength, which limit their application. Therefore, the development of FeSiAl SMCs with excellent comprehensive performance has become an urgent problem to be solved.
Methods
This study employs a novel method to construct dual Al₂O₃ insulation layers on the surface of FeSiAl powder. Firstly, NaAlO₂ is used to catalyze the reaction between Al atoms on the FeSiAl surface and water, forming an in-situ epitaxial Al₂O₃ inner layer. Then, an amorphous Al₂O₃ outer layer is generated by NaAlO₂ hydrolysis, resulting in a double Al₂O₃ coating structure. The microstructure and chemical composition of the materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). In addition, the magnetic and mechanical properties of the composites were also tested.
Highlights
Double guarantee, effective insulation: Dual Al₂O₃ insulation layers were successfully constructed on the surface of FeSiAl powder, effectively improving the insulation performance of the material and reducing eddy current loss. High permeability, low loss: The prepared FeSiAl/NaAlO₂ SMCs exhibit excellent magnetic properties, with a permeability as high as 101 and a power loss as low as 128 mW/cm³ (50 mT, 100 kHz). Significantly improved mechanical properties: The in-situ Al₂O₃/amorphous Al₂O₃ double-layer structure enhances the interfacial bonding strength, resulting in a compressive strength of 36.5 MPa for the composite.
The dual Al₂O₃ insulation layer preparation method developed in this study effectively improves the comprehensive performance of FeSiAl SMCs and provides a new approach for the preparation of high-performance SMCs. This method has the advantages of simple process and low cost, and is expected to promote the wide application of FeSiAl SMCs in power electronics, and other fields.
Fig. 2. (a, b) Cross-sectional image and corresponding EDS mapping of FeSiAl/H₃PO₄ SMC. (c, d) Magnified cross-sectional images of FeSiAl/H₃PO₄ SMC corresponding to the orange and cyan boxes in (a). (e-g) Fractured surface morphology of FeSiAl/H₃PO₄ SMC with different magnifications. (h) EDS mapping corresponding to (f).
The first author of this work is Prof. Hong-Xia Li from Hangzhou Dianzi University. Prof. Guo-Hua Bai and Prof. Xue-Feng Zhang from Hangzhou Dianzi University are the corresponding authors of this paper.
