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In this study, core-shell structured FeSiBCCr@SiO2&ZrO2 amorphous magnetic powder cores (AMPCs) were successfully prepared by the sol-gel method using tetraethyl orthosilicate (TEOS) and zirconium oxychloride hydrate (ZrOCl2·8H2O) as raw materials. The growth mechanism and potential chemical reactions of the SiO2&ZrO2 mixed insulation layer were analyzed by XRD, XPS and SEM‒EDS. In addition, the effect of the insulation layer content on the soft magnetic properties of FeSiBCCr@SiO2&ZrO2 AMPCs was systematically investigated. The SiO2&ZrO2 insulation layer can significantly increase the resistivity, effectively improve the DC bias performance and reduce the core loss of AMPCs. S2* (1.2 mL TEOS and 1.4 g ZrOCl2·8H2O) had a minimum core loss of 2290 mW/cm3 at high frequency (50 mT, 1 MHz). It had a high effective permeability of 48.2 and a superior direct current (DC) bias performance of 77.9% at 8 kA/m. This study provides a valid method to practically produce SMPCs with high resistivity, low core loss at high frequency and excellent DC bias performance through a novel insulation coating process. [ABSTRACT FROM AUTHOR]

In this study, the electromagnetic properties of FeSiCr soft magnetic powder cores (SMPCs) were optimized by providing a novel insulation process. Magnesium acetate tetrahydrate and oxalic acid dihydrate were used as raw materials for the sol-gel method. The powder was then heat-treated at 700 °C so that it was evenly coated by an insulating layer. Thermogravimetric analysis-differential scanning calorimetry, X-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy were used to demonstrate that the layer heat-treated at 700 °C was the ideal MgO layer and was uniformly coated on the surface of the FeSiCr powder. Additionally, the potential reactions and growth mechanism of the MgO layer were analyzed. The effects of the magnesium acetate tetrahydrate content on the soft magnetic properties of the FeSiCr@MgO SMPCs were investigated. The optimal soft magnetic performance (P cv = 248.48 mW/cm3, measured at 2500 kHz and 10 mT) was achieved at a magnesium acetate tetrahydrate content of 0.50 wt%, yielding a direct current-bias performance of up to 92.3% at 100 Oe. In addition, the FeSiCr@MgO SMPCs effectively improved the heat dissipation performance, which is necessary to avoid high-temperature damage, thereby enhancing their applicability in high-frequency and high-current environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ZrO 2 coating layer were prepared by the hydrolysis-precipitation method. • Homogeneous ZrO 2 coating layer coated on the FeSiBNbCu nanocrystalline powder. • The micromorphology, chemical composition, and conversion mechanisms were studied. • The effect of ZrO 2 coating layer on the soft magnetic properties was investigated. • The presence of ZrO 2 coating layer reduce P cv while improving DC bias performance. The insulation coating plays a crucial role in minimizing core loss (P cv) in soft magnetic powder cores (SMPCs). In this work, we prepared ZrO 2 coating layer on FeSiBNbCu spherical powder by the hydrolysis-precipitation method and investigated the magnetic properties of the FeSiBNbCu@ZrO 2 nanocrystalline SMPCs. ZrO 2 coating layer were successfully fabricated on the powder by adding a proper amount of K 2 ZrF 6 in alkaline ethyl alcohol solution. The micromorphology and chemical structure of the ZrO 2 coating layer on the surface of FeSiBNbCu nanocrystalline powder, as well as the conversion mechanisms, has been investigated. The presence of the ZrO 2 coating reduces the P cv by significantly lowers eddy loss (P e) of the nanocrystalline SMPCs, meanwhile improves DC bias performance and slightly decreases their permeability. When the additive amount of K 2 ZrF 6 is 1.0 wt%, the nanocrystalline SMPCs has best comprehensive soft magnetic properties, including stable effective permeability (μ e) of 57.8 up to 1 MHz, excellent DC bias performance of 59.3 % at a bias field of 100 Oe, and the lowest P cv of 194.7 mW/cm3 at a frequency (f) of 150 kHz and maximum magnetic induction (B m) of 50 mT. [ABSTRACT FROM AUTHOR]

[Display omitted] • Al 1.5 (Co x Fe 6-x) 6 Cr high-entropy alloy soft magnetic powder cores were first designed and prepared via gas atomization and insulation. • The effects of Co/Fe ratio on the phase formation, microstructure evolution and soft magnetic properties of the Al 1.5 (Co x Fe 6-x) 6 Cr high-entropy alloy soft magnetic powder cores were systematically investigated. • The association of magnetic domains, grain size and particle size with H c variation of Al 1.5 (Co x Fe 6-x) 6 Cr high-entropy alloys was analyzed. Al 1.5 (Co x Fe 6-x) 6 Cr high-entropy alloy (HEA) soft magnetic powder cores (SMPCs) were designed and prepared via gas atomization and insulation, and the effects of the Co/Fe ratio on their phase formation, microstructure evolution, and soft magnetic properties were systematically investigated. An increase in Co content promoted the precipitation of the B2 phase from the body-centered cubic (BCC) matrix, and the content of the B2 phase was greater than that of the BCC phase at x = 4, thus replacing the BCC phase as the matrix, which contributed to the optimization of the soft magnetic properties of the AlCoFeCr HEA. The SMPC composed of the BCC single phase exhibits the lowest eddy current loss (P e) of 55.1 mW/cm3 (@100 kHz, 50 mT), excellent direct current (DC) bias performance of 80.6 % at 100 Oe, and high stable effective permeability (μ e) of 49.9 up to 1 MHz. The association of magnetic domains, grain size, and particle size with H c variation was analyzed, providing guidelines for subsequent studies to obtain HEAs with good soft magnetic properties. By comprehensively and systematically comparing the microstructural differences of diverse matrix-phase HEAs and SMPCs, the specific application of this HEA system under high-temperature conditions can be expanded. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of heat treatment on the structural of SMPCs was investigated. • Effect of heat treatment on the magnetic properties of SMPCs was investigated. • SMPCs showed high effective permeability (49.1) and low core loss (135.6 mW/cm3). The effect of heat treatment temperature on the structural evolution and soft magnetic properties of FeSiBNbCu soft magnetic powder cores (SMPCs) was systematically investigated. The comprehensive magnetic properties of the SMPCs first increased and then decreased with an increase in temperature. At 600 °C, the SMPCs grain size was approximately 8.8 nm, presenting a concentrated nanocrystalline structure, and showing the best soft magnetic properties, including low core loss of 135.6 mW/cm3 (50 mT, 100 kHz), stable effective permeability of 49.1 up to 10 MHz and high DC bias performance of 60.3% at 100 Oe. This study provides an effective solution for the preparation of Fe-based nanocrystalline SMPCs with excellent performance and validates the application prospects under working conditions of different frequencies and ripple currents. [ABSTRACT FROM AUTHOR]