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The phosphating treatment method has been extensively applied in the field of insulating soft magnetic powders because of its simplicity and ease of operation; however, the specific nanoscale morphology of phosphate coating layers and the interface/connection/interaction with the outer resin are still unclear. In this study, soft magnetic powder cores (SMPCs) with a nanoporous-structured phosphate coating were fabricated, in which the coating has a beneficial adsorption effect on the outer resin and can enhance the bonding force between the organic/inorganic coating. Optimized soft magnetic properties were obtained for the SMPCs with a phosphoric acid content of 0.6 wt%, including a high effective permeability of 61, low core loss of 134.6 mW/cm3 (measured at 100 mT, 50 kHz), and high DC bias performance of 56% under a superimposed field of 100 Oe due to the favorable interactions between the insulating coating layers. These properties can be used to manufacture micro-magnetic components. [ABSTRACT FROM AUTHOR]

Toroid-shaped Fe-based soft magnetic powder cores (SMPCs) were prepared by cold pressing commercial FeSiCr and carbonyl iron powder (CIP) insulated with epoxy resin. The effect of the CIP mass ratio on the magnetic properties of powder cores, which included the dependences of the effective permeability (μe), DC bias characteristic, and core loss (Pcv), was investigated. By optimizing the CIP content, the μe of the magnetic powder cores reaches 31 when the CIP content is 30 wt%, and it exhibits a stable permeability in the frequency range up to 1 MHz. Meanwhile, the DC bias characteristic increases to 78%, and the Pcv is minimized to 1684 mW/cm3, which is reduced by 15% at 50 mT and 250 kHz. [ABSTRACT FROM AUTHOR]

A high-filling alumina/epoxy nanocomposite with improved thermal stability and insulation performance has been successfully designed as an organic–inorganic coating layer for the toroid-shaped FeSiBPNbCr amorphous magnetic powder cores (AMPCs). Unlike the organic coating, the organic–inorganic hybrid coating cores exhibited superior magnetic properties without compromising on saturation magnetization and permeability. The core loss declined by 40%, and the quality factor was 13% higher as half alumina was introduced into the epoxy resin matrix. A thin and uniform-coating layer of alumina/epoxy nanocomposite led to better high-frequency characteristics than those obtained with direct coating of the cores with alumina. Besides the outstanding magnetic properties, the Fe-based AMPCs with a convenient insulation-coating process cost lesser than Fe–Ni magnetic powder cores, thereby rendering the Fe-based AMPCs a potential candidate for a variety of industrial applications. [ABSTRACT FROM AUTHOR]

Thermosetting organic resins are widely applied as insulating coatings for soft magnetic powder cores (SMPCs) because of their high electrical resistivity. However, their poor thermal stability and thermal decomposition lead to a decrease in electrical resistivity, thus limiting the annealing temperature of SMPCs. The large amount of internal stress generated by soft magnetic composites during pressing must be mitigated at high temperatures; therefore, it is especially important to find organic resins with excellent thermal stabilities. In this study, we prepared SMPCs using poly-silicon-containing arylacetylene resin, an organic resin resistant to high temperatures, as an insulating layer. With 2 wt % PSA as an insulating layer and annealed at 700 °C for 1 h, the FeSiAl SMPCs achieved the best magnetic properties, including the lowest core loss of 184 mW/cm3 (measured at 0.1 T and 50 kHz) and highest permeability of 96. [ABSTRACT FROM AUTHOR]

The effect of different particle size distribution of Fe-6.5 wt%Si powder on the microstructure and soft magnetic properties of the corresponding soft magnetic powder cores (SMPCs) was investigated. By optimizing particle size distribution, the density of SMPCs increased and the total core loss significantly decreased. According to the result of loss separation, density of SMPCs is inversely proportional to hysteresis loss, while with increasing the content of the fine particles, the eddy current loss significantly decreased. It was found that with magnetic powder of particle size-grading as 10%, 10%, 60%, and 20% for particles with size between −75 to +38, −38 to +23, −23 to +13, and −13 μm, respectively, the Fe-6.5 wt%Si SMPCs exhibit optimal comprehensive magnetic performances with the effective permeability of about 60, the percent permeability at 100 Oe is up to 70%, and the lowest core loss of 553 mW/cm3. [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 FeSiBPC/Fe 3 O 4 @EP double-layer core-shell structure was successfully prepared. • The FeSiBPC AMPCs exhibited excellent magnetic performance with superior Q of 160. • The FeSiBPC AMPCs exhibited low P cv of 187 mW/cm3 at 100 kHz @0.05 T. • The thickness of the insulation coating is controlled by hydrothermal oxidation time. Fe-based amorphous magnetic powder cores (AMPCs) with excellent comprehensive properties were successfully fabricated via using the uniform double insulating layer core-shell structured FeSiBPC/Fe 3 O 4 @Epoxy resin (EP). The effects of the in-situ hydrothermal oxidized time on the magnetic properties of the AMPCs have been systematically investigated on the basis of the growth mechanism of the insulating layer of spherical amorphous powder in alkaline environment. The hydrothermal oxidation process could well ensure the uniformity of the oxide layer composed of Fe 3 O 4 nanoparticle. The evolution of the insulating layer is a process of homogeneous nucleation and growth at different hydrothermal oxidation time. After 10 h of hydrothermal oxidation, a thin and dense layer composed of Fe 3 O 4 nanoparticle was formed on the surface of the amorphous powder. As a consequent, the FeSiBPC AMPCs exhibit excellent performance such as stable effective permeability of 49.5 at 2 MHz, a very low core loss of 187 mW/cm3 at 100 kHz@0.05 T and high-quality factor of 160 at 600 kHz. The results indicate that the thickness of the Fe 3 O 4 insulating layer can be completely controlled via the reaction parameters, and can effectively suppress the eddy current loss, which is promising for high-frequency electromagnetic systems. [ABSTRACT FROM AUTHOR]

• The uniform TiO 2 insulating coating layer was successfully fabricated. • The process of nucleation and growth of TiO 2 coating layer were explored. • Excellent magnetic properties were achieved for the FeSiBCCr/TiO 2 composite cores. • The soft magnetic performance of the composite cores can be well tuned. The Fe-based soft magnetic amorphous powder cores (AMPCs) with excellent comprehensive magnetic properties were successfully designed and fabricated using the core-shell structured FeSiBCCr/TiO 2 composite powders. The influence of the concentration of water (H 2 O) for the magnetic performance of the AMPCs has been systematically studied based on careful analysis of the process of nucleation and growth of TiO 2 under different H 2 O concentration in the reaction system. The growth process for the TiO 2 coating layer with the H 2 O concentration in the range of 0.01–0.02 ml/g corresponds to the heterogeneous nucleation phase, while the mixing phase of heterogeneous and homogeneous nucleation occurs when the concentration of H 2 O increases to 0.03 ml/g. Optimized soft magnetic properties have been achieved for the AMPCs with H 2 O concentration of 0.02 ml/g, including high permeability of 81.5 with a high frequency stability up to 10 MHz, high quality factor of 102 at 530 kHz, low core loss of 42 mW/cm3 at 500 kHz for B m = 0.01 T, and better DC-bias property of 52% at a bias field of 100 Oe due to the uniform and proper thickness insulation coating layer, which can be used to produce miniature magnetic components for applications in medium and high-frequency fields. [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]

• Ti element was used for the first time to optimize the soft magnetic properties of Fe 85 Si 9.6 Al 5.4 SMPCs. • The effects of Ti content on the soft magnetic properties of Fe 85- x Si 9.6 Al 5.4 Ti x SMPCs were studied systematically • Fe 85- x Si 9.6 Al 5.4 Ti x SMPCs showed high effective permeability (62.9) and low core loss (140.6 mW/cm3). • The addition of Ti element made the FeSiAl SMPCs exhibit good corrosion resistance. In this study, the effects of Ti content on the soft magnetic properties of Fe 85- x Si 9.6 Al 5.4 Ti x soft magnetic powder cores (SMPCs) were studied systematically. The addition of nonmagnetic Ti gradually decreased the saturation magnetization (M s) of the Fe 85- x Si 9.6 Al 5.4 Ti x alloys powder, whereas the resistivity and density gradually increased, leading to a significant decrease in core loss (P cv). The SMPCs doped with 0.5 wt% Ti showed the best magnetic properties, including low P cv of 140.6 mW/cm3, stable effective permeability (μ e) of 62.9 up to 1 MHz, and high DC bias performance of 46% at 100 Oe. Furthermore, the corrosion resistance of the Fe 85- x Si 9.6 Al 5.4 Ti x SMPCs gradually improved as the Ti content increased, reaching a maximum at a Ti content of 2.5 wt%, at which the corrosion current density decreased to a minimum of 1.45 × 10−6 A/cm2. The addition of Ti can effectively improve the corrosion resistance of Fe 85 Si 9.6 Al 5.4 SMPCs. [ABSTRACT FROM AUTHOR]

In this paper, a novel type of nano-CaCO 3 /epoxy nanocomposites insulating layer for the FeSiCr/carbonyl-iron soft magnetic composites (SMCs) has been successfully developed. The novel inorganic/resin nanocomposites can greatly reduce the core loss of the SMCs while maintain other excellent magnetic properties. By optimizing the content of insulating layer, the FeSiCr/carbonyl-iron SMCs exhibits the lowest core loss of 466.5 ​mW/cm3 at a maximum magnetic induction of 50 ​mT and frequency of 100 ​kHz, which is greatly reduced by 24.2%, compared with the sample only coated by epoxy resin. Meanwhile, the effective permeability and quality factor remains high. In addition, the production process of the novel nano-CaCO 3 /epoxy nanocomposites insulating layer exhibits the advantages of simplicity, convenience and low cost compared with other ceramic coatings (Al 2 O 3 , MgO, SiO 2 , etc.) and surface nitride coatings, which is more suitable for the industrialization of molded inductors, and therefore has a variety of industrial application prospects. A novel nano-CaCO 3 /epoxy nanocomposites insulating layer was successfully formed on the surface of FeSiCr/carbonyl-iron magnetic powders by surface modification method, which improved the resistivity of the insulation layer, reduced the core loss of soft magnetic composites, and improved the DC-bias performance. [Display omitted] • EDS mapping confirmed that the composite powders were coated with nano-CaCO 3 /epoxy nanocomposites insulating coating layer. • The high-resistivity of nanocomposites insulating layer are beneficial for the reduction of P cv. • T 1.0 possessed optimum P cv ​= ​466.5 ​mW/cm3 (at 50 ​mT, 100 ​kHz, and 25 ​°C). [ABSTRACT FROM AUTHOR]

• The inorganic-organic hybrid insulating layer was successfully prepared. • The μ e of the AMPCs maintained excellent frequency stability up to 10 MHz. • Performance of Fe-based AMPCs declines after the crystallization appears. • The AMPCs annealed at 480 °C exhibited lower core loss and superior permeability. In order to improve the magnetic properties of soft magnetic composites (SMCs), the Fe-based amorphous powder cores (AMPCs) based on spherical FeSiBCCr amorphous magnetic powders coated with inorganic-organic (TiO 2 -epoxy resin) hybrid insulating layer were prepared. The influence of annealing temperature on the soft magnetic properties of the AMPCs has been systematically researched in this work. It was found that the reasonable annealing temperature could increase the permeability and decrease the core loss of the AMPCs. The AMPCs annealed at 480 °C showed a constant permeability of 81.5 up to 10 MHz, and low total core loss of 275 mW/cm3. This study demonstrated that the present Fe-based AMPCs with inorganic-organic hybrid insulating layer have a great promising future in the field of medium and high frequency for the various electronic components. [ABSTRACT FROM AUTHOR]