Effect of Polyimide-Phosphating Double Coating and Annealing on the Magnetic Properties of Fe-Si-Cr SMCs

An easy-plane FeSi3.5 composite with excellent magnetic properties and loss properties at MHz were proposed. The easy-plane FeSi3.5 composite has ultra-low loss at 10 MHz and 4 mT, about 372.88 kW/m3. In order to explore the reason that the Pcv of easy-plane FeSi3.5 composite is ultra-low, a none easy-plane FeSi3.5 composite, without easy-plane processing as a control group, measured the microstructure, and the magnetic and loss properties. We first found that the real reason why magnetic materials do not work properly at MHz due to overheat is dramatical increase of the excess loss and the easy-plane composite can greatly re-duce the excess loss by loss measurement and separation. The total loss of none easy-plane FeSi3.5 composite is much higher than that of easy-plane FeSi3.5 composite, where the excess loss is a major part in the total loss and even over 80% in the none easy-plane FeSi3.5 composite. The easy-plane FeSi3.5 composite can greatly reduce the total loss compared to the none easy-plane FeSi3.5 composite, from 2785.8 kW/m3 to 500.42 kW/m3 (3 MHz, 8 mT), with the main reduction being the excess loss, from 2435.2 kW/m3 to 204.93 kW/m3 (3 MHz, 8 mT), reduced by 91.58%. Furthermore, the easy-plane FeSi3.5 composite also has excellent magnetic properties, high permeability and ferromagnetic resonance frequencies. This makes the easy-plane FeSi3.5 composite become an excellent soft magnetic composite and it is possible for magnetic devices to operate properly at higher frequencies, especially at the MHz band and above.

Section: Discussionmentioning

confidence: 99%

“… The

calculate curve of the none easy-plane FeSi 3.5 composite and the easy-plane FeSi 3.5 composite at 500 kW/m 3 ( a ). The

of different SMCs at 500 kW/m 3 ( b ) [ 19 , 20 , 21 , 22 ]. …”

Section: Figurementioning

confidence: 99%

“…In the up-to-date published SMCs, measurement frequency of most studies are 1 MHz and below, such as FeSiCr (

= 37, 560 kW/m 3 at 1 MHz, 20 mT and

= 47.5, 7086 kW/m 3 at 1 MHz, 50 mT) [ 19 , 20 ], Fe 73 Si 6 B 10 P 5 C 3 Mo 3 (

= 34.63, ~500 kW/m 3 at 1 MHz, 20 mT) [ 21 ], flake pure iron (

= 67, 306.6 kW/m 3 at 1 MHz, 3 mT and

= 10, 3.285 kW/m 3 at 3.5 MHz, 0.1 mT) [ 22 ], etc. There are almost no studies with high frequency and high maximum magnetic flux density.…”

Section: Introductionmentioning

confidence: 99%

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A Study on an Easy-Plane FeSi3.5 Composite with High Permeability and Ultra-Low Loss at the MHz Frequency Band

Yang

Huang

et al. 2023

“…There are two types of insulation coating for FeSiCr-based SMCs: organic and inorganic. Epoxy resin, silicone resin, and polyimide resin are generally used as the organic coating [11], while phosphides, SiO 2 , ZrO 2 , Al 2 O 3 , ferrite, etc., can be employed as inorganic coating [12][13][14]. The organic coating materials facilitate the formability of the powder core during compaction, and the inorganic coating materials mainly provide high resistivity to reduce the eddy current losses of SMCs at high frequencies [15].…”

Section: Introductionmentioning

confidence: 99%

Optimizing FeSiCr-Based Soft Magnetic Composites Using the Deionized Water as the Phosphating Solvent

Li,

Yu,

Wang

et al. 2024

To prepare a soft magnetic powder core, the magnetic powder surface has to be insulated by phosphating treatment. Organic chemicals such as ethanol and acetone are generally used as solvents for phosphoric acid, which may cause serious environmental problems. This work proposed deionized water as the environmentally friendly phosphating solvent for FeSiCr powder. The soft magnetic composites (SMCs) were prepared using phosphoric acid for inorganic coating and modified silicon polymer for organic coating. The effect of different phosphating solvents, including deionized water, ethanol, and acetone, on the structure and magnetic properties of SMCs were investigated. It is found that the solvent affects the phosphating solution’s stability and the phosphoric acid’s ionization. The phosphoric acid is more stable in deionized water than in ethanol and acetone. The phosphating reaction in deionized water is also more stable in deionized water, resulting in a dense phosphate coating on the particle surface. The effects of phosphoric acid concentration and temperature on the magnetic properties of FeSiCr-based SMCs were further studied. With the increase in phosphoric acid concentration and temperature, the magnetic permeability and saturation magnetization of the powder core decrease, and the core loss decreases, followed by an increase. The optimized combination of properties was obtained for the SMCs phosphated with 0.2 wt.% phosphoric acid in deionized water at 35 °C, including a high effective permeability μe of 25.7, high quality factor Q of 80.2, low core loss Pcv of 709.5 mW/cm3 measured at 0.05 T @ 100 kHz, and high withstanding voltage of 276 V, due to the formation of uniform and dense insulating coating layers. In addition, the SMCs prepared with phosphated powder show good corrosion resistance. The anti-corrosion properties of the SMCs using deionized water as a phosphating solvent are better than those using ethanol and acetone.

“…Adding different materials into composites could have an influence on the final performance as well as the milling condition of sample preparation. For example, adding Cr can improve corrosion resistance and the mechanical strength of the material [21]; depending on the nickel percentage in Fe-Ni alloys. Final products can be used for highfrequency devices, or in cases requiring a high level of the initial permeability; Co in Fe-Co alloys enables a high saturation density to be expected, and consequently they can be used for the motors of high-speed generators [22,23].…”

Section: Introductionmentioning

confidence: 99%

Exploring the Impact of Different Milling Parameters of Fe/SiO2 Composites on Their Structural and Magnetic Properties

Rudeichuk,

Olekšáková,

Maciaszek

et al. 2024

This research focuses on the production process of soft magnetic composites in the form of 3D bulk compacts made from insulated powder particles using different milling parameters, aiming to enhance their magnetic properties and to study an innovative method of the powder surface “smoothing” technique. A structure analysis using scanning electron microscopy (SEM), EDS, and optical microscopy is also included. We found out that the samples made by the innovative method have lower density values. This can be caused by a more consistent SiO2 insulation layer on highly pure iron powder particles. A correlation between the mechanical smoothing method and better insulation of powder particles can help to provide eco-friendlier solutions for the preparation of soft magnetic composites, such as less usage of reagents and more consistent coverage of powder particles with lower final insulation thickness. The magnetic properties of these compacts are evaluated by coercive field, permeability, and loss measurements. The particle-level smoothing technique in some cases can reduce the value of coercivity up to 20%. For some samples, the ball-to-powder ratio has a bigger impact on magnetic properties than surface treatment, which can be caused by an increased amount of insulation in the SMC compacts.