Enhanced permeability and reduced loss in FeSiAl soft magnetic composites via phosphating and ferrite coating

Evolution of phosphate coatings during high-temperature annealing and its influence on the Fe and FeSiAl soft magnetic composites

Choosing a suitable core loss model and accurately predicting energy loss are crucial in designing magnetic devices with high efficiency based on soft magnetic composites (SMCs). In this work, FeSiAl and FeSi SMCs with a uniform insulating layer were fabricated by a phosphating process. The effects of excitation waveform and DC bias field on core loss have been investigated in depth. The results show that different remagnetization rates of SMC under ideal sinusoidal and square waves result in different core losses at the same frequency and flux density. The improved general Steinmetz equation and the modified Steinmetz equation were shown to be suitable for calculating core loss under square excitation waves without DC bias field. When the DC bias field is applied, the core loss of FeSiAl and FeSi SMCs was found to increase significantly due to the magnetization state gradually approaching saturation. Interestingly, the variation tendency of core loss can be accurately predicted using the waveform coefficient Steinmetz equation under square excitation conditions with a DC bias environment. This work not only provides deep insights into core loss under different excitation waveforms and DC bias fields but also determines the application scope of different core loss models.

Influence of oxidation temperature on microstructure and electromagnetic performance of Fe-Si/Fe2SiO4 soft magnetic composites

Soft magnetic materials are a core element of power electronics and electrical machines. However, none of the soft magnetic materials is able to exploit the full potential of wide bandgap semiconductors, which operate above MHz frequency for efficient energy conversion in power electronic systems. Here, a high‐performance Fe–Si soft magnetic composites with a 2D ordered domain structure are reported, enabling efficient energy conversion at MHz frequencies. By transforming spherical particles into flakes and arranging them in layers, 2D magnetic domains are created within the composite. This leads to a 90% increase in permeability and a tenfold decrease in loss at 3 MHz compared to composite made with spherical particles. The significantly increased cut‐off frequency indicates that the ordered flaky particles are suitable for MHz applications, unlike the disordered spherical particles. These findings provide an effective approach for fabricating high performance soft magnetic composites from traditional spherical particles and miniaturizing magnetic devices for efficient power electronics operation.

Improvement in core losses for FeSiAl soft magnetic composites induced by powder annealing treatment

Soft magnetic composites (SMCs) have rapidly become the hot spots of research, because of competitive magnetic saturation and high electrical resistivity. Although the magnetic properties have been continuously improved, the nonmagnetic separation and high demagnetization in structure result in low permeability. In this study, Fe–Si–Al SMCs with various particle orientations are designed and prepared under magnetic field. The effects of structures with various orientations on hysteresis loops, effective permeability, magnetic loss and electrical resistance are studied. The results show that the electrical and magnetic properties are totally determined by particle orientation. Especially, compared with non-oriented samples, the permeability of fully oriented samples with particles perpendicular to the normal axis has been greatly improved. This work is of great significance for the research and application of SMCs.

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

Properties of FeSiAl-based soft magnetic composites with AlN/Al2O3 and hybrid phosphate–silane insulation coatings

Microstructure and magnetic properties of the FeSiAl soft magnetic composite with a NiFe2O4-doped phosphate insulation coating

Simultaneous improvements of effective magnetic permeability, core losses and temperature characteristics of Fe-Si soft magnetic composites induced by annealing treatment

Alumina has been prepared by sol–gel method as the coating layer in the fabrication of FeSiAl soft magnetic composites (SMCs). Influence of the Al2O3 content on the magnetic properties of the SMCs has been studied, and optimized effective permeability (μ e = 116.3) and core loss (P cv = 331.2 mW cm−3) measured at 50 kHz, 100 mT was achieved with 0.8 wt% Al2O3. Hybrid phosphate-alumina coating has also been used to prepare the FeSiAl SMCs with a total addition of 0.8 wt%. Significantly improved performance of the SMCs can be achieved with the hybrid coating compared to single phosphate or alumina coating. The addition of 0.2 wt% H3PO4 and 0.6 wt% Al2O3 gives rise to the optimal magnetic properties (μ e = 123.4; P cv = 226.4 mW cm−3) of the FeSiAl SMCs. For the hybrid coating, the inner phosphate layer grown by direction reaction at the powder surfaces gives rise to excellent adhesion. Also, investigation on the thermal stability of the coatings indicates that the outer Al2O3 layer hinders the decomposition of the phosphate layer, leading to enhanced magnetic performance of the SMCs.

Soft magnetic materials are crucial in motors, generators, transformers, and many electronic devices. We synthesized the FeSi soft magnetic composites (SMCs) with different doping contents of Fe2O3 nanopowders as fillers via the hot-press sintering technique. This work explores the incorporation of high-resistivity magnetic fillers through a novel compaction technique and investigates the influence of Fe2O3 nanopowder on the structure and magnetic properties of Fe2O3 nanopowder-filled composites. The finding reveals that Fe2O3 nanopowders effectively fill the air gaps between FeSi powders, increasing SMC density. Moreover, all samples exhibit excellent effective permeability frequency stability, ranging from 15 kHz to 100 kHz. Notably, the effective permeability µe improves from 22.32 to 30.45, a 36.42% increase, when the Fe2O3 doping concentration increases from 0 to 2 wt%. Adding Fe2O3 nanopowders also enhances electrical resistivity, leading to a 37.21% reduction in eddy current loss in samples for 5 wt% Fe2O3 addition, compared to undoped samples. Furthermore, as Fe2O3 content increases from 0 to 5 wt%, the power loss Pcv of the Fe2O3-doped Fe-6.5Si SMCs decreases from 25.63 kW/m3 to 16.13 kW/m3, a 37% reduction. These results suggest that Fe2O3-doped FeSi SMCs, with their superior soft magnetic properties, hold significant potential for use in high-power and high-frequency electronic applications.

Insulation layer design for soft magnetic composites by synthetically comparing their magnetic properties and coating process parameters

Soft magnetic composites based on the Fe elemental, binary and ternary alloy systems fabricated by surface nitridation

Low core loss and high DC bias performance of FeSiAl soft magnetic composites cores with hybrid insulating layers of MgO/SiO2