Method for manufacturing a soft magnetic powder core

Abstract

A method for preparing a soft magnetic powder core includes the following steps: 1) obtaining h-BN powder; 2) solution preparation: dispersing h-BN powder and surfactant in a polar solvent, subjecting it to ultrasonic or shearing treatment to obtain an h-BN mixture; 3) h-BN activation: adding the h-BN mixture to an acid solution, ultrasonically treating it, then washing it with water until neutral, and drying it to obtain activated h-BN; 4) coating solution preparation: preparing a reaction solution and adding the activated h-BN; 5) mixing: mixing the coating solution with the metal soft magnetic powder for 0.5–30 hours; 6) separation: separating the mixed liquid substance from the solid substance; 7) powder heat treatment: heating the separated solid substance to obtain metal soft magnetic powder coated with h-BN; 8) powder mixing and forming; 9) heat treatment; 10) impregnation; 11) curing. This invention has a simple preparation process, high magnetic properties, high thermal conductivity, high corrosion resistance and stability, and is safe and environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of soft magnetic composite materials, and specifically relates to a method for preparing a soft magnetic powder core. Background Technology

[0002] Iron, cobalt, and nickel are the three ferromagnetic elements that make up magnetic materials. Soft magnetic metallic materials are composed of these three elements as the main components, or a single metal, or a combination of two or more of them, or with the addition of one or more other elements.

[0003] Soft magnetic composite materials are made by mixing and pressing powders of the aforementioned soft magnetic metallic materials with an insulating medium. The material between adjacent magnetic powder particles forms an insulating layer, exhibiting 3D isotropic magnetic properties, high saturation magnetic flux density, a wide operating frequency range, and low power loss. Furthermore, due to the use of powder metallurgy for pressing, various complex shapes such as C-shaped, E-shaped, I-shaped, U-shaped, and ring-shaped materials can be fabricated. With the increasing miniaturization and high-frequency development of electronic devices, the application of soft magnetic composite materials, characterized by high saturation magnetic induction, high resistivity, and low power loss, will become even more widespread.

[0004] Traditional motor stators are made by stamping laminated silicon steel. Laminated silicon steel has two-dimensional properties, and due to the limitations of the stamping process, the layers are only stacked axially, resulting in a relatively simple shape. With the development of industries such as robotics, new energy vehicles, and drones, silicon steel has high losses and low mass and volumetric power density, failing to meet the power density requirements of mobile applications. Amorphous ribbon can also be used to fabricate motor stators, meeting high-frequency requirements. However, amorphous ribbon is expensive and cannot meet the demands of large-scale production. For motors with high quality and volumetric power density, axial flux motors are often used. The stator structure of axial flux motors is complex, gradually changing along the axial direction, making stamping difficult to achieve. However, soft magnetic composite powder, after forming and heat treatment, can well meet the requirements for axial flux motor stators and powder cores.

[0005] Soft magnetic composite powders primarily consist of insulating materials coated onto the surface of magnetically conductive powder particles. To obtain high-performance soft magnetic composites, it is essential to minimize their losses in alternating magnetic fields. High-frequency losses in soft magnetic composites are mainly eddy current losses, which can be further divided into eddy current losses between magnetic powder particles and eddy current losses within the particles. Eddy current losses within the particles can be eliminated by reducing internal stress and impurities, while the dominant eddy current losses between particles require reduction through insulating coating.

[0006] For soft magnetic composite powder, insulating coating is mainly divided into organic coating and inorganic coating. Organic coating includes thermosetting resins (silicone resin, phenolic resin, epoxy resin, etc.) and thermoplastic resins (such as polypropylene, nylon, etc.). There are many methods for organic insulating coating of soft magnetic composite materials, including: (1) dissolving the organic material in an organic solvent, then dispersing and mixing the magnetic powder, and finally evaporating the solvent; (2) growing an organic coating film in situ on the surface of the magnetic powder. Since non-magnetic insulators have a magnetic dilution effect, the content of the insulating coating medium should be as low as possible under the premise of uniform coating. Studies have shown that compared with other coated samples, soft magnetic composite materials have better magnetic permeability when the epoxy resin content is 3wt%. Therefore, organic insulating coating should ensure uniform coating while minimizing the content of organic resin. Soft magnetic composite materials with organic resin insulating coating have poor thermal stability, are prone to decomposition during high-temperature annealing, and have relatively poor mechanical and magnetic properties, which cannot meet the needs of industrial applications.

[0007] Inorganic coating includes phosphate coating and metal oxide coating. Phosphate coating involves placing metal magnetic powder in a phosphoric acid passivation solution of a certain concentration, stirring and mixing thoroughly for a certain period, followed by filtration, washing, and drying to obtain the magnetic powder to be shaped. The iron in the magnetic metal powder reacts with phosphoric acid as follows:

[0008] Fe + 2H₃PO₄ → Fe(H₂PO₄)₂ + H₂↑

[0009] The hydrogen produced is released in a gaseous state. Hydrogen is a flammable and explosive substance, and if it accumulates to a certain extent, it will become a safety hazard in the production process.

[0010] Phosphate-coated films exhibit good adhesion to magnetic powder matrices, and the process is simple and suitable for industrial production, making it the most widely used coating method currently. The coating layer remains stable at 500℃; however, the resistivity of the soft magnetic composite material significantly decreases due to phosphate crystallization during annealing. Furthermore, the relatively small amount of phosphate added makes it difficult to ensure that every soft magnetic powder particle is covered with phosphate, leading to unstable core performance.

[0011] The oxides used for metal oxide coating include MgO, Al2O3, and Fe2O3. The sol-gel method yields a relatively uniform insulating coating layer. The loss of MgO-coated metal magnetic powder and phosphate-coated samples varies with frequency. After annealing at 600℃, the loss of the MgO-coated sample is significantly lower than that of the phosphate-coated sample. Compared to phosphate-coated samples, the MgO-coated samples exhibit better thermal stability, better release of internal stress in the soft magnetic composite material, and lower eddy current loss at the same frequency. However, due to the inherent brittleness of metal oxides, the coating film prepared using wet chemical methods and then applied to the surface of the metal magnetic powder is prone to cracking or even detachment during subsequent pressing and molding, resulting in reduced resistivity and unsatisfactory insulation performance. Using ferrite to insulatingly coat the soft magnetic composite material can minimize the magnetic dilution effect of the insulating medium. Iron powder was insulated using Mn-Zn ferrite nanoparticles. Compared to non-magnetic insulating media, the ferrite-coated samples exhibited higher magnetic permeability, with a 33.5% increase in permeability at a test frequency of 10 kHz. For metal oxides, an insulating medium, the brittleness of the oxides leads to easy cracking of the film, limiting the requirements for obtaining high-density samples through compression molding. Furthermore, the poor bonding between oxides and the magnetic powder matrix results in low magnetic permeability.

[0012] The main structure of the organic-inorganic composite coating is a phosphate-silane inorganic-organic composite insulating coating layer. When phosphate-coated samples are annealed at temperatures above 500℃, the resistivity decreases sharply, causing a rapid increase in losses. However, high-temperature annealing has little impact on the losses of phosphate-silane composite coated samples. Furthermore, volatile organic compounds are emitted during heat treatment, which has a negative impact on environmental protection.

[0013] During the magnetization process, some energy in soft magnetic powder cores is generated as heat, causing the temperature of the powder core (inductor) to rise. The coating material is mostly inorganic or organic, making it difficult for heat to be transferred to the surface. Ultimately, the temperature rise leads to deterioration of magnetic properties and creates serious safety hazards.

[0014] Therefore, it is necessary to improve the existing metal magnetic material powder coating process for soft magnetic composite materials to meet the requirements of safety, low loss and high frequency of use. Summary of the Invention

[0015] The technical problem to be solved by the present invention is to provide a method for preparing a safe, low-loss, and high-frequency soft magnetic powder core, which is in response to the above-mentioned technical status.

[0016] The technical solution adopted by this invention to solve the above-mentioned technical problems is: a method for preparing a soft magnetic powder core, characterized by comprising the following steps:

[0017] 1) h-BN raw material processing: h-BN raw material is ball-milled to a particle size ≤30μm to obtain h-BN powder;

[0018] 2) Solution preparation: Disperse h-BN powder and surfactant in a polar solvent at a concentration of 0.05-500 g / L, and initially mix by stirring at room temperature for 30-60 minutes, followed by ultrasonic or shear treatment to obtain h-BN mixture; the mass ratio of h-BN powder to polar solvent is 0.5-400 g / L.

[0019] 3) h-BN activation: The h-BN mixture is added to the acid solution and ultrasonically treated at room temperature to 80°C for 0.1 to 10 hours to introduce surface hydroxyl groups into h-BN. Then, it is washed with water until neutral and dried to obtain activated h-BN. The acid solution includes concentrated H2SO4 and concentrated HNO3, and the volume ratio of concentrated H2SO4 to concentrated HNO3 is 0.1 to 10:1.

[0020] 4) Preparation of coating solution: Prepare reaction solution and add the activated h-BN to introduce amino groups onto h-BN. The reaction product constitutes the coating solution.

[0021] 5) Mixing: Mix the coating liquid with the soft magnetic metal powder at a temperature of 25-80℃ and under ultrasonic or stirring conditions for 0.5-30 hours. The mass-volume ratio of the soft magnetic metal powder to the coating liquid is 1-5000 g / L.

[0022] 6) Separation: Separate the liquid and solid substances after mixing in step 6);

[0023] 7) Powder heat treatment: In pure nitrogen, the separated solid material is heated at 300-500℃ for 10-600 minutes to obtain metal soft magnetic powder coated with h-BN;

[0024] 8) Powder mixing and molding: The above-mentioned metal soft magnetic powder coated with h-BN is added to a lubricant and a forming agent, and then molded to obtain a molded part;

[0025] 9) Heat treatment: The above-formed parts are heat-treated at 450-1000℃ for 5-500 minutes to obtain heat-treated parts. The heat treatment atmosphere is an inert gas.

[0026] 10) Impregnation: The heat-treated part is immersed in a liquid containing epoxy resin, allowing the liquid to penetrate into the pores of the powder core of the heat-treated part to obtain a powder core containing epoxy resin.

[0027] 11) Curing: The epoxy resin-containing powder core is cured in air at 150-250°C for 10-300 minutes to obtain a soft magnetic powder core.

[0028] Preferably, in step 2), the polar solvent includes at least one of NMP (N-methylpyrrolidone, C5H9NO), DMF (N,N-dimethylformamide, C3H7NO), and isopropanol, and the surfactant includes SDS (sodium dodecyl sulfate, C5H9NO). 12 H 25 NaSO4), CTAB (hexadecyltrimethylammonium bromide, C 16 H 33 At least one of N(CH3)3Br.

[0029] Preferably, in step 2), the ultrasonic or shearing treatment is performed as follows: peeling with a probe-type ultrasonic instrument for 0.5–24 hours, or peeling with a bath-type ultrasonic instrument for 1–72 hours, or peeling with a high-speed shearing machine for 0.5–10 hours; wherein the power of the probe-type ultrasonic instrument is 200–800W, the power of the bath-type ultrasonic instrument is 500–1000W, and the rotation speed of the high-speed shearing machine is 10000rpm. The probe-type ultrasonic instrument, bath-type ultrasonic instrument, and high-speed shearing machine are all existing equipment.

[0030] In this invention, step 1) involves ball milling the h-BN raw material to a particle size ≤30μm, which results in smaller h-BN powder size and improves subsequent peeling efficiency.

[0031] During the stripping process, circulating cooling water can be used to prevent solvent overheating. A small amount of SDBS (sodium dodecylbenzenesulfonate) can be selectively added during the stripping process to improve dispersion stability. If SDBS is added, it must be removed through subsequent purification.

[0032] The thinner the h-BN layer after peeling, the less impact it has on magnetic properties and the higher the thermal conductivity of the powder core. Therefore, h-BN should be peeled off as much as possible.

[0033] In the above scheme, preferably, in step 4), the reaction solution is an ethanol solution containing a coupling agent, the concentration of the coupling agent in the ethanol solution is 0.1-20%, and the coupling agent is APTES, APTS (γ-aminopropyltrimethoxysilane), AEAPTS (N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane), C8H 22 At least one of N2O3Si; Step 4) is: add the above-activated h-BN to the reaction solution, and stir magnetically at room temperature to 80°C for 1 to 30 hours under nitrogen protection to obtain the coating solution.

[0034] Taking APTES as an example, the reaction is: APTES + h-BN-OH → h-BN-O-Si(CH2)3NH2 + ethanol.

[0035] APTES is 3-aminopropyltriethoxysilane, with the chemical formula C9H. 23 NO3Si.

[0036] Preferably, in step 4), the reaction solution is a volume ratio of EDA to DMF of 1:10, and the solid-liquid ratio of activated h-BN to the reaction solution is 1:50 g / mL. Step 4) involves adding the activated h-BN to the reaction solution and reacting at 120–150°C (oil bath heating is acceptable) for 12–48 hours under nitrogen protection. Sonication for 30 minutes can be used to promote dispersion during the initial stage of the reaction. The resulting h-BN-coated soft magnetic metal powder can be washed alternately with DMF and ethanol, centrifuged, and vacuum dried at 60°C.

[0037] Even using the ethylenediamine (EDA) liquid-phase method, EDA acts as an amino donor and undergoes a nucleophilic substitution reaction with the B atoms on the surface of h-BN in a strongly polar solvent to form a B-NH2 bond.

[0038] Preferably, in step 4), the reaction solution is concentrated ammonia and deionized water. The activated h-BN, concentrated ammonia, and deionized water are added to a polytetrafluoroethylene-lined reactor at a ratio of 1:10:20 g / mL. The reaction temperature is 180–220°C, the self-generated pressure is 1–5 MPa, and the reaction time is 12–72 h. The subsequently coated h-BN metal soft magnetic powder can be washed and dried with deionized water. The aforementioned self-generated pressure refers to the pressure generated during the reaction due to exothermic reactions or changes in the state of matter (such as volatilization or decomposition), which spontaneously forms without the need for external pressure.

[0039] Preferably, step 6) employs at least one of the following methods for separation: magnetic separation, centrifugal separation, filtration separation, vacuum drying separation, heating drying separation, membrane filtration separation, and gravity sedimentation separation.

[0040] Preferably, in step 8), the lubricant is at least one of stearic acid, stearate, and wax, and the forming agent is silicone resin or epoxy resin.

[0041] In the above schemes, preferably, in step 5), the metal soft magnetic powder is at least one of pure iron powder, iron-silicon alloy powder, iron-silicon-aluminum alloy powder, iron-aluminum alloy powder, iron-chromium alloy powder, amorphous metal soft magnetic powder, iron-nickel alloy powder, iron-nickel-molybdenum alloy powder, iron-cobalt alloy powder, and iron-silicon-chromium alloy powder, and is prepared by at least one of water atomization, gas atomization, mechanical crushing, reduction, carbonylation, and water-vapor combined atomization.

[0042] Further, in step 5), the particle size of the soft magnetic metal powder is: d 50 <40μm, d 99<80μm.

[0043] Compared with the prior art, the advantages of the present invention are as follows:

[0044] 1. Simplified preparation process: The preparation method of the present invention is simple, requiring only one coating followed by calcination, which reduces the preparation cost and increases the possibility of application in large-scale continuous production;

[0045] 2. Improved magnetic properties: The coating obtained by coating is thinner, which will not significantly reduce the magnetic properties of the magnetic material, nor will it increase its weight, making it more suitable for various applications;

[0046] 3. Reduced thermal conductivity and losses: The coated h-BN has good insulation properties, which can reduce eddy current losses. At the same time, its high thermal conductivity reduces the temperature rise of the device, thereby improving the utilization efficiency and service life of the prepared soft magnetic composite material powder.

[0047] 4. Improved corrosion resistance and stability: The improved surface properties of the material and the complete and uniform coating can effectively protect the core particles of ferromagnetic powder, improve its corrosion resistance and stability, and thus improve the service life of magnetic materials.

[0048] 5. Low flash point organic solvents such as methyl acetate and chemical reagents such as phosphoric acid are not used, reducing the emission of volatile organic compounds during the coating process. No hydrogen is generated during the process, ensuring production safety. Attached Figure Description

[0049] Figure 1 This is a surface SEM image of the metal soft magnetic powder coated with h-BN in Embodiment 1 of the present invention. Detailed Implementation

[0050] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0051] Unless otherwise specified, all reagents and materials used in the examples are commercially available.

[0052] Example 1:

[0053] The steps for preparing soft magnetic powder cores from pure Fe powder are as follows:

[0054] (1) h-BN raw material processing: h-BN raw material was ball-milled to obtain h-BN powder. The particle size of h-BN powder is shown in Table 1, and the mass is 300g.

[0055] (2) Selection and preparation of dispersion solvent: h-BN powder and surfactant were dispersed in a polar solvent and initially mixed at room temperature by magnetic stirring for 30-60 minutes. Then, ultrasonic / shear exfoliation was performed (ultrasonic vibration was applied to the solution, and h-BN was subjected to shear force under the action of ultrasonic waves. Under the action of shear force, h-BN separated into smaller layered h-BN particles) to obtain h-BN mixture; the selection of polar solvent and surfactant and the amount of each substance are shown in Table 1.

[0056] (3) h-BN activation: h-BN mixture was added to concentrated H2SO4 / HNO3 mixture, the ratio of concentrated H2SO4 / HNO3 is shown in Table 1, ultrasonic treatment was performed at 60℃ for 2h to introduce surface hydroxyl groups (-OH), washed with water until neutral, and dried to obtain activated h-BN.

[0057] (4) Coupling reaction: Prepare an ethanol solution with coupling agent (the concentration of coupling agent in the ethanol solution is 2%). The types and volumes of coupling agents are shown in Table 1. Then add the activated h-BN and stir magnetically for 2 hours at room temperature to 80°C under nitrogen protection to obtain the coating solution.

[0058] (5) Preparation of soft magnetic metal powder: Pure iron soft magnetic metal powder was prepared by water atomization. The loose packing density of this soft magnetic metal powder was 3.1 g / cm³. 3 d 50 100μm, d 99 The particle size was 230 μm. The soft magnetic metal powder was prepared according to a volume ratio of 1:1 (metal soft magnetic powder to coating liquid). The powder mass is shown in Table 1.

[0059] (6) Mixing: Mix the coating liquid with the soft magnetic metal powder under ultrasonic or stirring conditions at 25°C for 1 hour.

[0060] (7) Separation: Separate the liquid substance from the solid substance after step (6).

[0061] (8) Powder heating treatment: In pure nitrogen, the separated solid material is heated at 300°C for 200 minutes to obtain metal soft magnetic powder coated with h-BN.

[0062] (9) Powder mixing: Add lubricant and forming agent to the above-mentioned metal soft magnetic powder coated with h-BN. The forming agent is silicone resin or epoxy resin, and the lubricant is stearic acid or / and stearate or wax.

[0063] (10) Molding: The powder containing the above-mentioned lubricant and forming agent is molded under high pressure to obtain a molded part.

[0064] (11) Heat treatment: The above-mentioned molded parts are heat treated at 450°C for 100 minutes to obtain heat-treated parts. The heat treatment atmosphere is nitrogen.

[0065] (12) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the resin liquid to penetrate into the pores of the powder core.

[0066] (13) Curing: The epoxy resin-containing powder core is cured in air at 150-250°C for 10-300 minutes to obtain a soft magnetic powder core.

[0067] The morphology of the calcined h-BN-coated soft magnetic metal powder is shown in the figure. Figure 1 ,from Figure 1 It can be seen that there are many h-BN microparticles on the surface of the magnetic powder, which can play a good role in thermal conductivity and insulation. The properties of the cured soft magnetic powder core are shown in Table 2.

[0068] Example 2:

[0069] The steps for preparing soft magnetic powder cores from pure Fe powder are as follows:

[0070] (1) h-BN raw material processing: h-BN raw material was ball-milled to obtain h-BN powder. The particle size of h-BN powder is shown in Table 1, and the mass is 50g.

[0071] (2) Selection and preparation of dispersion solvent: h-BN powder and surfactant were dispersed in a polar solvent and initially mixed for 50 minutes at room temperature by magnetic stirring. Then, ultrasonic vibration was applied to the solution, and h-BN was subjected to shear force under the action of ultrasound. Under the action of shear force, h-BN separated into smaller layered h-BN particles, and h-BN mixture was obtained. The selection of polar solvent and surfactant and the amount of each substance are shown in Table 1.

[0072] (3) h-BN activation: h-BN mixture was added to concentrated H2SO4 / HNO3 mixture, the ratio of concentrated H2SO4 / HNO3 is shown in Table 1, ultrasonic treatment was performed at 50℃ for 3h to introduce surface hydroxyl groups (-OH), washed with water until neutral, and dried to obtain activated h-BN.

[0073] (4) Coupling reaction: Prepare an ethanol solution with coupling agent (the concentration of coupling agent in the ethanol solution is 5%). The types and volumes of coupling agents are shown in Table 1. Then add the activated h-BN and stir magnetically for 5 hours at room temperature to 80°C under nitrogen protection to obtain the coating solution.

[0074] (5) Preparation of soft magnetic metal powder: Pure iron soft magnetic metal powder was prepared by water atomization. The loose packing density of this soft magnetic metal powder was 3.2 g / cm³. 3 d 50 It is 130μm, d 99 The thickness is 250 μm. Soft magnetic metal powder was prepared according to a volume ratio of 0.01–100 between the soft magnetic metal powder and the coating liquid. The powder mass is shown in Table 1.

[0075] (6) Mixing: Mix the coating liquid with the soft magnetic metal powder under ultrasonic or stirring conditions at 25°C for 1 hour.

[0076] (7) Separation: Separate the liquid substance from the solid substance after step (6).

[0077] (8) Powder heating treatment: In pure nitrogen, the separated solid material is heated at 350°C for 100 minutes to obtain metal soft magnetic powder coated with h-BN.

[0078] (9) Powder mixing: Add lubricant and forming agent to the above-mentioned metal soft magnetic powder coated with h-BN. The forming agent is silicone resin or epoxy resin, and the lubricant is stearic acid or / and stearate or wax.

[0079] (10) Molding: The powder containing the above-mentioned lubricant and forming agent is molded under high pressure to obtain a molded part.

[0080] (11) Heat treatment: The above-mentioned molded parts are heat treated at 450°C for 100 minutes to obtain heat-treated parts. The heat treatment atmosphere is nitrogen.

[0081] (12) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the resin liquid to penetrate into the pores of the powder core.

[0082] (13) Curing: The epoxy resin-containing powder core is cured in air at 150-250°C for 10-300 minutes to obtain a soft magnetic powder core.

[0083] The properties of the cured soft magnetic powder core are shown in Table 2.

[0084] Example 3:

[0085] The steps for preparing soft magnetic powder cores from Fe-Si powder are as follows:

[0086] (1) h-BN raw material processing: h-BN raw material was ball-milled to obtain h-BN powder. The particle size of h-BN powder is shown in Table 1, and the mass is 50g.

[0087] (2) Selection and preparation of dispersion solvent: h-BN powder and surfactant were dispersed in a polar solvent and initially mixed for 40 minutes at room temperature by magnetic stirring. Then, ultrasonic vibration was applied to the solution, and h-BN was subjected to shear force under the action of ultrasound. Under the action of shear force, h-BN separated into smaller layered h-BN particles, and h-BN mixture was obtained. The selection of polar solvent and surfactant and the amount of each substance are shown in Table 1.

[0088] (3) h-BN activation: h-BN mixture was added to concentrated H2SO4 / HNO3 mixture, the ratio of concentrated H2SO4 / HNO3 is shown in Table 1, ultrasonic treatment was performed at 50℃ for 3h to introduce surface hydroxyl groups (-OH), washed with water until neutral, and dried to obtain activated h-BN.

[0089] (4) Coupling reaction: Prepare an ethanol solution with coupling agent (the concentration of coupling agent in the ethanol solution is 5%). The types and volumes of coupling agents are shown in Table 1. Then add the activated h-BN and stir magnetically for 15 hours at room temperature to 80°C under nitrogen protection to obtain the coating solution.

[0090] (5) Preparation of soft magnetic metal powder: Fe-5wt%Si soft magnetic metal powder was prepared by water vapor atomization. The loose packing density of this soft magnetic metal powder was 4.2 g / cm³. 3 d 50 It is 26μm, d 99 The thickness is 55 μm. Soft magnetic metal powder was prepared according to a volume ratio of 0.01–100 between the soft magnetic metal powder and the coating liquid. The powder mass is shown in Table 1.

[0091] (6) Mixing: Mix the coating liquid with the soft magnetic metal powder under ultrasonic or stirring conditions at 25°C for 1 hour.

[0092] (7) Separation: Separate the liquid substance from the solid substance after step (6).

[0093] (8) Powder heating treatment: In pure nitrogen, the separated solid material is heated at 350°C for 100 minutes to obtain metal soft magnetic powder coated with h-BN.

[0094] (9) Powder mixing: Add lubricant and forming agent to the above-mentioned metal soft magnetic powder coated with h-BN. The forming agent is silicone resin or epoxy resin, and the lubricant is stearic acid or / and stearate or wax.

[0095] (10) Molding: The powder containing the above-mentioned lubricant and forming agent is molded under high pressure to obtain a molded part.

[0096] (11) Heat treatment: The above-mentioned molded parts are heat treated at 550°C for 100 minutes to obtain heat-treated parts. The heat treatment atmosphere is nitrogen.

[0097] (12) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the resin liquid to penetrate into the pores of the powder core.

[0098] (13) Curing: The epoxy resin-containing powder core is cured in air at 150°C for 90 minutes to obtain a soft magnetic powder core.

[0099] The properties of the cured soft magnetic powder core are shown in Table 3.

[0100] Example 4:

[0101] The steps for preparing soft magnetic powder cores from Fe-Si-Al powder are as follows:

[0102] (1) h-BN raw material processing: h-BN raw material was ball-milled to obtain h-BN powder. The particle size of h-BN powder is shown in Table 1, and the mass is 180g.

[0103] (2) Selection and preparation of dispersion solvent: h-BN powder and surfactant were dispersed in a polar solvent and initially mixed for 20 minutes at room temperature by magnetic stirring. Then, ultrasonic vibration was applied to the solution, and h-BN was subjected to shear force under the action of ultrasound. Under the action of shear force, h-BN separated into smaller layered h-BN particles, and h-BN mixture was obtained. The selection of polar solvent and surfactant and the amount of each substance are shown in Table 1.

[0104] (3) h-BN activation: h-BN mixture was added to concentrated H2SO4 / HNO3 mixture, the ratio of concentrated H2SO4 / HNO3 is shown in Table 1, ultrasonic treatment was performed at 50℃ for 4h to introduce surface hydroxyl groups (-OH), washed with water until neutral, and dried to obtain activated h-BN.

[0105] (4) Coupling reaction: Prepare an ethanol solution with coupling agent (the concentration of coupling agent in the ethanol solution is 5%). The types and volumes of coupling agents are shown in Table 1. Then add the activated h-BN and stir magnetically for 20 h at room temperature to 80°C under nitrogen protection to obtain the coating solution.

[0106] (5) Preparation of soft magnetic metal powder: Fe-8.5wt%Si-5.7wt%Al soft magnetic metal powder was prepared by gas atomization. The loose packing density of the soft magnetic metal powder was 3.8 g / cm³. 3 d 50 33μm, d 99 The thickness was 48 μm. The soft magnetic metal powder was prepared at a volume ratio of 0.5 (metal soft magnetic powder to coating liquid). The powder mass is shown in Table 1.

[0107] (6) Mixing: Mix the coating liquid with the soft magnetic metal powder under ultrasonic or stirring conditions at 25°C for 1 hour.

[0108] (7) Separation: Separate the liquid substance from the solid substance after step (6).

[0109] (8) Powder heating treatment: In pure nitrogen, the separated solid material is heated at 350°C for 100 minutes to obtain metal soft magnetic powder coated with h-BN.

[0110] (9) Powder mixing: Add lubricant and forming agent to the above-mentioned metal soft magnetic powder coated with h-BN. The forming agent is silicone resin or epoxy resin, and the lubricant is stearic acid or / and stearate or wax.

[0111] (10) Molding: The powder containing the above-mentioned lubricant and forming agent is molded under high pressure to obtain a molded part.

[0112] (11) Heat treatment: The above-mentioned molded parts are heat treated at 550°C for 100 minutes to obtain heat-treated parts. The heat treatment atmosphere is nitrogen.

[0113] (12) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the resin liquid to penetrate into the pores of the powder core.

[0114] (13) Curing: The epoxy resin-containing powder core is cured in air at 150°C for 90 minutes to obtain a soft magnetic powder core.

[0115] The properties of the cured soft magnetic powder core are shown in Table 3.

[0116] Example 5:

[0117] The steps for preparing soft magnetic cores from Fe-Ni powder are as follows:

[0118] (1) h-BN raw material processing: h-BN raw material was ball-milled to obtain h-BN powder. The particle size of h-BN powder is shown in Table 1, and the mass is 180g.

[0119] (2) Selection and preparation of dispersion solvent: h-BN powder and surfactant were dispersed in a polar solvent and initially mixed at room temperature by magnetic stirring for 30-60 minutes. Then, ultrasonic vibration was applied to the solution, and h-BN was subjected to shear force under the action of ultrasound. Under the action of shear force, h-BN separated into smaller layered h-BN particles, and h-BN mixture was obtained. The selection of polar solvent and surfactant and the amount of each substance are shown in Table 1.

[0120] (3) h-BN activation: h-BN mixture was added to concentrated H2SO4 / HNO3 mixture, the ratio of concentrated H2SO4 / HNO3 is shown in Table 1, ultrasonic treatment was performed at 50℃ for 4h to introduce surface hydroxyl groups (-OH), washed with water until neutral, and dried to obtain activated h-BN.

[0121] (4) Coupling reaction: Prepare an ethanol solution with coupling agent (the concentration of coupling agent in the ethanol solution is 5%). The types and volumes of coupling agents are shown in Table 1. Then add the activated h-BN and stir magnetically for 3 hours at room temperature to 80°C under nitrogen protection to obtain the coating solution.

[0122] (5) Preparation of soft magnetic metal powder: Fe-49wt%Ni soft magnetic metal powder was prepared by gas atomization. The soft magnetic metal powder was prepared according to a volume ratio of 0.5 between the soft magnetic metal powder and the coating liquid. The powder quality is shown in Table 1.

[0123] (6) Mixing: Mix the coating liquid with the soft magnetic metal powder under ultrasonic or stirring conditions at 25°C for 1 hour.

[0124] (7) Separation: Separate the liquid substance from the solid substance after step (6).

[0125] (8) Powder heating treatment: In pure nitrogen, the separated solid material is heated at 350°C for 100 minutes to obtain metal soft magnetic powder coated with h-BN.

[0126] (9) Powder mixing: Add the above-mentioned soft magnetic metal powder coated with h-BN to a lubricant and a forming agent. The forming agent is silicone resin or epoxy resin, and the lubricant is stearic acid or / and stearate or wax.

[0127] (10) Molding: The powder containing the above-mentioned lubricant and forming agent is molded under high pressure to obtain a molded part.

[0128] (11) Heat treatment: The above-mentioned molded parts are heat treated at 550°C for 100 minutes to obtain heat-treated parts. The heat treatment atmosphere is nitrogen.

[0129] (12) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the resin liquid to penetrate into the pores of the powder core.

[0130] (13) Curing: The epoxy resin-containing powder core is cured in air at 150°C for 90 minutes to obtain a soft magnetic powder core.

[0131] The properties of the cured soft magnetic powder core are shown in Table 3.

[0132] Example 6:

[0133] The steps for preparing soft magnetic powder cores from iron-based amorphous powder are as follows:

[0134] (1) h-BN raw material processing: h-BN raw material was ball-milled to obtain h-BN powder. The particle size of h-BN powder is shown in Table 1, and the mass is 180g.

[0135] (2) Selection and preparation of dispersion solvent: h-BN powder and surfactant were dispersed in a polar solvent and initially mixed at room temperature by magnetic stirring for 30-60 minutes. Then, ultrasonic vibration was applied to the solution, and h-BN was subjected to shear force under the action of ultrasound. Under the action of shear force, h-BN separated into smaller layered h-BN particles, and h-BN mixture was obtained. The selection of polar solvent and surfactant and the amount of each substance are shown in Table 1.

[0136] (3) h-BN activation: h-BN mixture was added to concentrated H2SO4 / HNO3 mixture, the ratio of concentrated H2SO4 / HNO3 is shown in Table 1, ultrasonic treatment was performed at 40℃ for 7h to introduce surface hydroxyl groups (-OH), washed with water until neutral, and dried to obtain activated h-BN.

[0137] (4) Coupling reaction: Prepare an ethanol solution with coupling agent (the concentration of coupling agent in the ethanol solution is 5%). The types and volumes of coupling agents are shown in Table 1. Then add the activated h-BN and stir magnetically for 27 h at room temperature to 80 °C under nitrogen protection to obtain the coating solution.

[0138] (5) Preparation of soft magnetic metal powder: Fe-11wt%Si-8wt%B-4wt%C-1.5wt%Cr soft magnetic metal powder was prepared by gas atomization. The loose packing density of the soft magnetic metal powder was 3.77 g / cm³. 3 The tap density is 4.52 g / cm³. 3 d 50 It is 15μm, d 99 The thickness was 40 μm. The soft magnetic metal powder was prepared at a volume ratio of 0.5 (metal soft magnetic powder to coating liquid). The powder mass is shown in Table 1.

[0139] (6) Mixing: Mix the coating liquid with the soft magnetic metal powder under ultrasonic or stirring conditions at 25°C for 1 hour.

[0140] (7) Separation: Separate the liquid substance from the solid substance after step (6).

[0141] (8) Powder heating treatment: In pure nitrogen, the separated solid material is heated at 250°C for 70 minutes to obtain metal soft magnetic powder coated with h-BN.

[0142] (9) Powder mixing: Add lubricant and forming agent to the above-mentioned metal soft magnetic powder coated with h-BN. The forming agent is silicone resin or epoxy resin, and the lubricant is stearic acid or / and stearate or wax.

[0143] (10) Molding: The powder containing the above-mentioned lubricant and forming agent is molded under high pressure to obtain a molded part.

[0144] (11) Heat treatment: The above-mentioned molded parts are heat treated at 550°C for 100 minutes to obtain heat-treated parts. The heat treatment atmosphere is nitrogen.

[0145] (12) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the resin liquid to penetrate into the pores of the powder core.

[0146] (13) Curing: The epoxy resin-containing powder core is cured in air at 150°C for 90 minutes to obtain a soft magnetic powder core.

[0147] The properties of the cured soft magnetic powder core are shown in Table 3.

[0148] Example 7:

[0149] The steps for preparing soft magnetic cores from Fe-Si-Cr powder are as follows:

[0150] (1) h-BN raw material processing: h-BN raw material was ball-milled to obtain h-BN powder. The particle size of h-BN powder is shown in Table 1, and the mass is 80g.

[0151] (2) Selection and preparation of dispersion solvent: h-BN powder and surfactant were dispersed in a polar solvent and initially mixed at room temperature by magnetic stirring for 30-60 minutes. Then, ultrasonic vibration was applied to the solution, and h-BN was subjected to shear force under the action of ultrasound. Under the action of shear force, h-BN separated into smaller layered h-BN particles, and h-BN mixture was obtained. The selection of polar solvent and surfactant and the amount of each substance are shown in Table 1.

[0152] (3) h-BN activation: h-BN mixture was added to concentrated H2SO4 / HNO3 mixture, the ratio of concentrated H2SO4 / HNO3 is shown in Table 1, ultrasonic treatment was performed at 40℃ for 7h to introduce surface hydroxyl groups (-OH), washed with water until neutral, and dried to obtain activated h-BN.

[0153] (4) Coupling reaction: Prepare an ethanol solution with coupling agent (the concentration of coupling agent in the ethanol solution is 2%). The types and volumes of coupling agents are shown in Table 1. Then add the activated h-BN and stir magnetically for 20 h at room temperature to 80°C under nitrogen protection to obtain the coating solution.

[0154] (5) Preparation of soft magnetic metal powder: Fe-6wt%Si-2wt%Cr soft magnetic metal powder was prepared by gas atomization. The loose packing density of this soft magnetic metal powder was 4.17 g / cm³. 3 d 50 20μm, d 99 The diameter is 39 μm. The tap density is 4.52 g / cm³. 3 d 50 It is 15μm, d 99 The thickness was 40 μm. The soft magnetic metal powder was prepared at a volume ratio of 0.5 (metal soft magnetic powder to coating liquid). The powder mass is shown in Table 1.

[0155] (6) Mixing: Mix the coating liquid with the soft magnetic metal powder under ultrasonic or stirring conditions at 25°C for 1 hour.

[0156] (7) Separation: Separate the liquid substance from the solid substance after step (6).

[0157] (8) Powder heating treatment: In pure nitrogen, the separated solid material is heated at 250°C for 70 minutes to obtain metal soft magnetic powder coated with h-BN.

[0158] (9) Powder mixing: Add lubricant and forming agent to the above-mentioned metal soft magnetic powder coated with h-BN. The forming agent is silicone resin or epoxy resin, and the lubricant is stearic acid or / and stearate or wax.

[0159] (10) Molding: The powder containing the above-mentioned lubricant and forming agent is molded under high pressure to obtain a molded part.

[0160] (11) Heat treatment: The above-mentioned molded parts are heat treated at 550°C for 100 minutes to obtain heat-treated parts. The heat treatment atmosphere is nitrogen.

[0161] (12) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the resin liquid to penetrate into the pores of the powder core.

[0162] (13) Curing: The epoxy resin-containing powder core is cured in air at 150°C for 90 minutes to obtain a soft magnetic powder core.

[0163] The properties of the cured soft magnetic powder core are shown in Table 3.

[0164] Table 1 shows the formulations of the primary coating solution for Examples 1-7 (based on 1000g of iron powder):

[0165]

[0166] Table 2 Magnetic properties of Examples 1-2

[0167]

[0168] Table 3 Magnetic properties of Examples 3-7

[0169]

[0170] All the above embodiments involve a single coating followed by calcination to obtain h-BN-coated soft magnetic powder. The resulting coating is thin, complete, and uniform, minimizing its impact on the magnetic properties of the magnetic material. It also effectively protects the core particles of the soft magnetic powder, improving their corrosion resistance and stability, thereby extending the lifespan of the magnetic material. Furthermore, the coated h-BN possesses excellent insulation properties, reducing eddy current losses, and its high thermal conductivity reduces device temperature rise, thus improving the efficiency and lifespan of the resulting soft magnetic powder core.

Claims

1. A method for preparing a soft magnetic powder core, characterized in that... Includes the following steps: 1) h-BN raw material processing: h-BN raw material is ball-milled to a particle size ≤30μm to obtain h-BN powder; 2) Solution preparation: Disperse h-BN powder and surfactant in a polar solvent at a concentration of 0.05-500 g / L, and initially mix by stirring at room temperature for 30-60 minutes, followed by ultrasonic or shear treatment to obtain h-BN mixture; the mass ratio of h-BN powder to polar solvent is 0.5-400 g / L. 3) h-BN activation: The h-BN mixture is added to the acid solution and ultrasonically treated at room temperature to 80°C for 0.1 to 10 hours to introduce surface hydroxyl groups into h-BN. Then, it is washed with water until neutral and dried to obtain activated h-BN. The acid solution includes concentrated H2SO4 and concentrated HNO3, and the volume ratio of concentrated H2SO4 to concentrated HNO3 is 0.1 to 10:

1. 4) Preparation of coating solution: Prepare reaction solution and add the activated h-BN to introduce amino groups onto h-BN. The reaction product constitutes the coating solution. 5) Mixing: Mix the coating liquid with the soft magnetic metal powder at a temperature of 25-80℃ and under ultrasonic or stirring conditions for 0.5-30 hours. The mass-volume ratio of the soft magnetic metal powder to the coating liquid is 1-5000 g / L. 6) Separation: Separate the liquid and solid substances after mixing in step 6); 7) Powder heat treatment: In pure nitrogen, the separated solid material is heated at 300-500℃ for 10-600 minutes to obtain metal soft magnetic powder coated with h-BN; 8) Powder mixing and molding: The above-mentioned metal soft magnetic powder coated with h-BN is added to a lubricant and a forming agent, and then molded to obtain a molded part; 9) Heat treatment: The above-formed parts are heat-treated at 450-1000℃ for 5-500 minutes to obtain heat-treated parts. The heat treatment atmosphere is an inert gas. 10) Impregnation: The heat-treated part is immersed in a liquid containing epoxy resin, allowing the liquid to penetrate into the pores of the powder core of the heat-treated part to obtain a powder core containing epoxy resin. 11) Curing: The epoxy resin-containing powder core is cured in air at 150-250°C for 10-300 minutes to obtain a soft magnetic powder core.

2. The preparation method according to claim 1, characterized in that: In step 2), the polar solvent includes at least one of NMP, DMF, and isopropanol, and the surfactant includes at least one of SDS and CTAB.

3. The preparation method according to claim 1, characterized in that: In step 2), the ultrasonic or shearing treatment is as follows: a probe-type ultrasonic instrument is used for ablation for 0.5 to 24 hours, or a bath-type ultrasonic instrument is used for ablation for 1 to 72 hours, or a high-speed shearing machine is used for ablation for 0.5 to 10 hours; wherein, the power of the probe-type ultrasonic instrument is 200 to 800W, the power of the bath-type ultrasonic instrument is 500 to 1000W, and the speed of the high-speed shearing machine is 10000rpm.

4. The preparation method according to claim 1, characterized in that: In step 4), the reaction solution is an ethanol solution containing a coupling agent, the concentration of which is 0.1-20%. The coupling agent is APTES, APTS, AEAPTS, or C8H. 22 At least one of N2O3Si; Step 4) is: add the above-activated h-BN to the reaction solution, and stir magnetically at room temperature to 80°C for 1 to 30 hours under nitrogen protection to obtain the coating solution.

5. The preparation method according to claim 1, characterized in that: In step 4), the reaction solution is EDA and DMF in a volume ratio of 1:10, and the solid-liquid ratio of the activated h-BN to the reaction solution is 1:50 g / mL; step 4) is: add the above-mentioned activated h-BN to the reaction solution, and react at 120-150℃ for 12-48 h under nitrogen protection.

6. The preparation method according to claim 1, characterized in that: In step 4), the reaction solution is concentrated ammonia and deionized water. The activated h-BN, concentrated ammonia and deionized water are added to the polytetrafluoroethylene-lined reactor in a ratio of 1:10:20 g / mL. The reaction temperature is 180-220℃, the reaction pressure is 1-5 MPa, and the reaction time is 12-72 h.

7. The preparation method according to claim 1, characterized in that: Step 6) Separate using at least one of the following methods: magnetic separation, centrifugal separation, filtration separation, vacuum drying separation, heating drying separation, membrane filtration separation, and gravity sedimentation separation.

8. The preparation method according to claim 1, characterized in that: In step 8), the lubricant is at least one of stearic acid, stearate, and wax, and the forming agent is silicone resin or epoxy resin.

9. The preparation method according to any one of claims 1 to 8, characterized in that: In step 5), the metal soft magnetic powder is at least one of pure iron powder, iron-silicon alloy powder, iron-silicon-aluminum alloy powder, iron-aluminum alloy powder, iron-chromium alloy powder, amorphous metal soft magnetic powder, iron-nickel alloy powder, iron-nickel-molybdenum alloy powder, iron-cobalt alloy powder, and iron-silicon-chromium alloy powder, and is prepared by at least one of water atomization, gas atomization, mechanical crushing, reduction, carbonylation, and water-vapor combined atomization.

10. The preparation method according to claim 9, characterized in that: In step 5), the particle size of the soft magnetic metal powder is: d 50 <40μm, d 99 <80μm.

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