Preparation method of soft magnetic powder core

Abstract

The invention discloses a preparation method of a soft magnetic powder core. The preparation method comprises the following steps: 1) preparing a coating solution: dissolving a boron source and a nitrogen source in a solvent to obtain the coating solution; 2) transferring: transferring the coating solution and the metal soft magnetic powder into a reaction kettle with a polytetrafluoroethylene lining, and sealing; 3) coating reaction: heating the reaction kettle to 150-350 DEG C, and keeping the temperature for 0.1-100 hours to obtain h-BN coated metal soft magnetic powder; 4) post-treatment: opening the reaction kettle after the temperature of the reaction kettle is reduced to 80 DEG C or below and the pressure is reduced to atmospheric pressure, collecting the h-BN-coated metal soft magnetic powder, and washing with a washing solution to remove impurities; 5) separation: separating and drying the h-BN coated metal soft magnetic powder containing the washing liquid; (6) powder mixing and forming; 7) heat treatment; (8) impregnation; and 9) curing. Compared with the prior art, the invention has the advantages of simple preparation process, high magnetic property, high thermal conductivity, high corrosion resistance, high stability, safety and environmental protection.

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. As electronic devices become increasingly miniaturized and higher-frequency, the applications 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 the requirements for high-frequency applications. 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 (such as 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 organic matter in organic solvent, then dispersing and mixing magnetic powder, and finally evaporating the solvent; (2) growing organic coating film in situ on the surface of magnetic powder. Since non-magnetic insulators have a magnetic dilution effect, the content of 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 not only ensure uniform coating, but also reduce the content of organic resin as much as possible. 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) Preparation of coating solution: Dissolve boron source and nitrogen source in solvent to obtain coating solution. The solvent is deionized water or organic solvent. When deionized water is used as solvent, the molar ratio of boron atoms to nitrogen atoms is 1:(0.1-20). When organic solvent is used as solvent, the molar ratio of boron atoms to nitrogen atoms is (0.1-10):1.

[0018] 2) Transfer: Transfer the coating solution and the soft magnetic metal powder to a polytetrafluoroethylene-lined reactor and seal it, with the volume ratio of the soft magnetic metal powder to the coating solution being 0.01 to 100.

[0019] 3) Coating reaction: The reactor is heated to 150-350℃ and held for 0.1-100 hours. When deionized water is used as solvent, the pressure of the reactor is 0.5-6MPa. When organic solvent is used as solvent, the pressure of the reactor is 1-30MPa. The resulting metal soft magnetic powder coated with h-BN is obtained.

[0020] 4) Post-processing: After the temperature of the reactor has cooled to below 80°C and the pressure has dropped to atmospheric pressure, open the reactor, collect the soft magnetic metal powder coated with h-BN, and wash it with washing liquid to remove impurities;

[0021] 5) Separation: The soft magnetic metal powder coated with h-BN containing washing liquid is separated and dried;

[0022] 6) Powder mixing and molding: The soft magnetic metal powder coated with h-BN obtained in step 5) is added to a lubricant and a forming agent, and then molded to obtain a molded part;

[0023] 7) Heat treatment: The above-mentioned formed parts are heat-treated at 450-1000℃ for 5-500 minutes in an inert gas atmosphere (such as nitrogen, argon, etc.) to obtain heat-treated parts;

[0024] 8) 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.

[0025] 9) 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.

[0026] The order of addition in step 2) above can be: first add the coating solution, then add the soft magnetic metal powder; or first add the soft magnetic metal powder, then add the coating solution; or first mix the coating solution and the soft magnetic metal powder together and add them to the reactor.

[0027] The washing solution in step 4) above is preferably water or ethanol.

[0028] Preferably, in step 3), the reactor for the coating reaction is heated to 180–240°C and held at that temperature for 5–6 hours, with a pressure of 2–3 MPa.

[0029] The drying temperature in step 5) is preferably 60-90°C to avoid oxidation.

[0030] Preferably, when deionized water is used as the solvent, the boron source includes at least one of boric acid (H3BO3), boron oxide (B2O3), and borax (Na2B4O7), and the nitrogen source includes at least one of urea (CO(NH2)2), melamine (C3H6N6), and ammonia (NH3·H2O); when an organic solvent is used as the solvent, the boron source includes at least one of trimethyl borate ((CH3O)3B), boron trichloride (BCl3), boron bromide (BBr3), sodium borohydride (NaBH4), and boric acid (H3BO3), and the nitrogen source includes at least one of urea (CO(NH2)2), melamine (C3H6N6), ammonia (NH3), lithium nitride (Li3N), sodium nitride, and potassium nitride.

[0031] More preferably, when deionized water is used as the solvent, the boron source is boric acid (H3BO3), the nitrogen source is urea (CO(NH2)2), and the preferred molar ratio of boric acid to urea is 1 mol: 4 mol. The following reaction occurs during the coating reaction:

[0032] Urea hydrolysis: CO(NH2)2 + H2O → 2NH3 + CO2;

[0033] The reaction of ammonia with boric acid: H3BO3 + NH3 → BN + other intermediate products;

[0034] In this way, an h-BN coating is formed on the surface of the soft magnetic metal powder.

[0035] More preferably, when an organic solvent is used as the solvent, the boron source is trimethyl borate, the nitrogen source is melamine (C3H6N6), and the preferred molar ratio of trimethyl borate (C3H9BO3) to melamine is 1 mol:1 mol. The following reaction occurs during the coating reaction:

[0036] Ethylene glycol → CH3CHO + H2O (solvent dehydration at high temperature)

[0037] (CH3O)3B + C3H6N6 → h-BN + COx + H2O + CH4 + ..., reaction temperature 200-300℃

[0038] In this way, an h-BN coating is formed on the surface of the soft magnetic metal powder particles.

[0039] Preferably, the organic solvent includes at least one of ethylene glycol, toluene, ethylenediamine, and ethanol.

[0040] Preferably, the mixture further includes a surfactant, wherein the surfactant is at least one of oleic acid, cetyltrimethylammonium bromide (CTAB), and polyethylene glycol (PEG), wherein the surfactant is added to the organic solvent, and when the surfactant is a liquid, the volume ratio of the surfactant to the organic solvent is 0.01 to 10 vol%, and when the surfactant is a solid, the mass ratio of the added surfactant to the volume ratio of the organic solvent is 0.01 to 10 g / 100 ml.

[0041] In the above scheme, preferably, in step 5), the dried h-BN-coated soft magnetic metal powder is calcined at 700–1100°C in an inert gas atmosphere. When deionized water is used as the solvent, the calcination time is 0.5–20 hours; when an organic solvent is used, the calcination time is 0.1–48 hours. The calcined h-BN-coated soft magnetic metal powder is then subjected to step 6) for powder mixing and forming. Calcination can be selectively performed to improve crystallinity. If the magnetic properties and losses of the dried h-BN-coated soft magnetic metal powder meet the requirements, the calcination process can be omitted to shorten the process flow.

[0042] Preferably, step 5) 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.

[0043] Preferably, in step 2), the soft magnetic metal 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, 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.

[0044] Further, in step 2), the particle size of the soft magnetic metal powder is: d 50 <40μm, d 99 <80μm.

[0045] Preferably, in step 2), the total volume of the soft magnetic metal powder and the coating solution is ≤ 80% of the total capacity of the reactor; in step 6), the lubricant is at least one of stearic acid, stearate, and wax, and the forming agent is silicone resin or epoxy resin.

[0046] In the above schemes, preferably, in step 1), when deionized water is used as the solvent, the pH value of the coating solution is adjusted to 8-12. An alkaline environment can further promote the reaction.

[0047] Compared with the prior art, the advantages of the present invention are as follows:

[0048] 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;

[0049] 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;

[0050] 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 can reduce the temperature rise of the device, thereby improving the utilization efficiency and service life of the prepared soft magnetic composite material powder.

[0051] 4. Improve the efficiency of h-BN synthesis: Adding iron-containing soft magnetic metal powder to the selected coating solution can promote the decomposition of urea into NH3 and accelerate the formation of boron-nitrogen bonds (BN). Iron oxides (such as Fe2O2) or iron complexes can serve as templates to guide the directional growth of the h-BN layered structure. Iron ions participate in the formation of intermediate products (such as Fe-BO / N complexes), which decompose into crystalline h-BN at high temperatures. Simultaneously, the h-BN growth time is shortened, the synthesis temperature is lowered, and the h-BN coating is thinner.

[0052] 5. 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 extend the service life of magnetic materials.

[0053] 6. This invention eliminates the need for low-flash-point organic solvents such as methyl acetate and chemical reagents such as phosphoric acid, reducing the emission of volatile organic compounds during the coating process. The process generates no hydrogen, ensuring safe production. Attached Figure Description

[0054] Figure 1 This is a surface SEM image of the metal soft magnetic powder coated with h-BN in Example 1 of the present invention.

[0055] Figure 2 This is a cross-sectional SEM image of the metal soft magnetic powder coated with h-BN according to Example 1 of the present invention.

[0056] Figure 3 This is a surface SEM image of the metal soft magnetic powder coated with h-BN in Example 7 of the present invention.

[0057] Figure 4 This is a surface SEM image of the metal soft magnetic powder coated with h-BN in Example 8 of the present invention. Detailed Implementation

[0058] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0059] Unless otherwise specified, all reagents and materials used in the examples are commercially available.

[0060] Example 1:

[0061] The steps for preparing soft magnetic composite material powder and soft magnetic powder core from pure Fe powder are as follows:

[0062] (1) Selection of coating material precursors and preparation of coating solution: Boron source and nitrogen source were used as coating material precursors and dissolved in solvent to obtain coating solution. The amounts of boron source, nitrogen source and solvent are shown in Table 1. The pH was adjusted to 10 to be alkaline to promote the reaction.

[0063] (2) Preparation of soft magnetic metal powder: Pure iron soft magnetic metal powder was prepared by water atomization. The loose packing density of the soft magnetic metal powder was 3.1 g / cm³. 3 d 50 100μm, d 99 The thickness is 230 μm. The coating solution and the soft magnetic metal powder were transferred to a polytetrafluoroethylene-lined reactor and sealed. The volumes of the soft magnetic metal powder and the coating solution are shown in Table 1, and the total volume of the soft magnetic metal powder and the coating solution does not exceed 80% of the total capacity of the reactor.

[0064] (3) Coating reaction: The above reaction vessel is heated to 190°C and kept at that temperature for 10 hours. The pressure of the reaction vessel is 3MPa.

[0065] (4) Post-processing and separation: After the temperature of the reactor is cooled to 70°C and the pressure is reduced to atmospheric pressure, the reactor is opened, the metal soft magnetic powder coated with h-BN is collected, and impurities are removed by washing with deionized water and ethanol; then the metal soft magnetic powder containing water and ethanol is separated and dried at low temperature to avoid oxidation.

[0066] (5) Calcination: The dried product is mostly amorphous / low crystallinity h-BN, which needs to be calcined at 900℃ for 2 hours under N2 / Ar atmosphere to improve crystallinity;

[0067] (6) Powder mixing: Add lubricant and forming agent to the calcined 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.

[0068] (7) Molding: The powder containing lubricant and forming agent is molded under high pressure to obtain the molded part;

[0069] (8) Heat treatment: The above-mentioned molded parts are heat-treated at 600℃ for 70 minutes to obtain heat-treated parts. The heat treatment atmosphere is inert gas such as nitrogen and argon.

[0070] (9) 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.

[0071] (10) Curing: The epoxy resin-containing powder core is cured in air at 180°C for 120 minutes to obtain a soft magnetic powder core.

[0072] The morphology of the calcined h-BN-coated soft magnetic metal powder is shown in the figure. Figure 1 and Figure 2 ,from Figure 1 It can be seen that the particle surface has a uniform coating distribution. From Figure 2 As can be seen, the coating thickness on the particle surface is approximately 50 nanometers, and the thickness is uniform, indicating a good insulating coating effect. The properties of the cured soft magnetic powder core are shown in Table 2.

[0073] Example 2:

[0074] The steps for preparing soft magnetic composite material powder and soft magnetic powder core from pure Fe powder are as follows:

[0075] (1) Selection of coating material precursors and preparation of coating solution: Boron source and nitrogen source were used as coating material precursors and dissolved in solvent to obtain coating solution. The amounts of boron source, nitrogen source and solvent are shown in Table 1. The pH was adjusted to 10 to present an alkaline environment to promote the reaction;

[0076] (2) 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 3.3 g / cm³. 3 d 50 It is 120μm, d 99 The thickness is 260 μm. The coating solution and the soft magnetic metal powder were transferred to a polytetrafluoroethylene-lined reactor and sealed. The volumes of the soft magnetic metal powder and the coating solution are shown in Table 1, and the total volume of the soft magnetic metal powder and the coating solution does not exceed 80% of the total capacity of the reactor.

[0077] (3) Coating reaction: The above reaction vessel is heated to 260°C and kept at that temperature for 6 hours. The pressure of the reaction vessel is 4MPa.

[0078] (4) Post-processing and separation: After the reactor temperature cools to 70℃ and the pressure drops to atmospheric pressure, open the reactor, collect the metal soft magnetic powder coated with h-BN, and wash it with deionized water and ethanol to remove impurities. Separate the metal soft magnetic powder containing water and ethanol and dry it at low temperature to avoid oxidation;

[0079] (5) Calcination: The dried product is mostly amorphous / low crystallinity h-BN, which needs to be calcined at 1000℃ for 1.5 hours under N2 / Ar atmosphere to improve crystallinity;

[0080] (6) Powder mixing: Add lubricant and forming agent to the calcined 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.

[0081] (7) Molding: The powder containing lubricant and forming agent is molded under high pressure to obtain the molded part;

[0082] (8) Heat treatment: The above-mentioned molded parts are heat-treated at 650°C for 90 minutes to obtain heat-treated parts. The heat treatment atmosphere is inert gas such as nitrogen and argon.

[0083] (9) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the liquid to penetrate into the pores of the powder core of the heat-treated part.

[0084] (10) Curing: The epoxy resin-containing powder core is cured in air at 200°C for 100 minutes to obtain a soft magnetic powder core.

[0085] The properties of the cured soft magnetic powder core are shown in Table 2.

[0086] Example 3:

[0087] The steps for preparing soft magnetic composite powder and soft magnetic powder core from Fe-Si powder are as follows:

[0088] (1) Selection of coating material precursors and preparation of coating solution: Boron source and nitrogen source were used as coating material precursors and dissolved in solvent to obtain coating solution. The amounts of boron source, nitrogen source and solvent are shown in Table 1. The pH was adjusted to 9 to present an alkaline state to promote the reaction;

[0089] (2) Preparation of soft magnetic metal powder: Fe-5wt%Si soft magnetic metal powder was prepared by 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. The coating solution and the soft magnetic metal powder were transferred to a polytetrafluoroethylene-lined reactor and sealed. The volumes of the soft magnetic metal powder and the coating solution are shown in Table 1, and the total volume of the soft magnetic metal powder and the coating solution does not exceed 80% of the total capacity of the reactor.

[0090] (3) Coating reaction: The above reaction vessel is heated to 300°C and kept at that temperature for 4 hours. The pressure of the reaction vessel is 3MPa.

[0091] (4) Post-processing and separation: After the reactor temperature cools to 70℃ and the pressure drops to atmospheric pressure, open the reactor, collect the metal soft magnetic powder coated with h-BN, and wash it with deionized water and ethanol to remove impurities. Separate the metal soft magnetic powder containing water and ethanol and dry it at low temperature to avoid oxidation;

[0092] (5) Calcination: The dried product is mostly amorphous / low crystallinity h-BN, which needs to be calcined at 750℃ for 1.5 hours under N2 / Ar atmosphere to improve crystallinity;

[0093] (6) Powder mixing: Add lubricant and forming agent to the calcined 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.

[0094] (7) Molding: The powder containing lubricant and forming agent is molded under high pressure to obtain the molded part;

[0095] (8) Heat treatment: The above-mentioned molded parts are heat-treated at 650°C for 90 minutes to obtain heat-treated parts. The heat treatment atmosphere is inert gas such as nitrogen and argon.

[0096] (9) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the liquid to penetrate into the pores of the powder core of the heat-treated part.

[0097] (10) Curing: The epoxy resin-containing powder core is cured in air at 220°C for 50 minutes to obtain a soft magnetic powder core.

[0098] The properties of the cured soft magnetic powder core are shown in Table 3.

[0099] Example 4:

[0100] The steps for preparing soft magnetic composite powder and soft magnetic powder core from Fe-Si-Al powder are as follows:

[0101] (1) Selection of coating material precursors and preparation of coating solution: Boron source and nitrogen source were used as coating material precursors and dissolved in solvent to obtain coating solution. The amounts of boron source, nitrogen source and solvent are shown in Table 1. The pH was adjusted to 9 to present an alkaline state to promote the reaction;

[0102] (2) 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 is 48 μm. The coating solution and the soft magnetic metal powder were transferred to a polytetrafluoroethylene-lined reactor and sealed. The volumes of the soft magnetic metal powder and the coating solution are shown in Table 1, and the total volume of the soft magnetic metal powder and the coating solution does not exceed 80% of the total capacity of the reactor.

[0103] (3) Coating reaction: The above reaction vessel is heated to 320°C and kept at that temperature for 2 hours. The pressure of the reaction vessel is 2MPa.

[0104] (4) Post-processing and separation: After the reactor temperature cools to 70℃ and the pressure drops to atmospheric pressure, open the reactor, collect the metal soft magnetic powder coated with h-BN, and wash it with deionized water and ethanol to remove impurities. Separate the metal soft magnetic powder containing water and ethanol and dry it at low temperature to avoid oxidation;

[0105] (5) Calcination: The dried product is mostly amorphous / low crystallinity h-BN, which needs to be calcined at 800℃ for 3 hours under N2 / Ar atmosphere to improve crystallinity;

[0106] (6) Powder mixing: Add lubricant and forming agent to the calcined 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.

[0107] (7) Molding: The powder containing lubricant and forming agent is molded under high pressure to obtain the molded part;

[0108] (8) Heat treatment: The above-mentioned molded parts are heat treated at 750°C for 120 minutes to obtain heat-treated parts. The heat treatment atmosphere is inert gas such as nitrogen and argon.

[0109] (9) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the liquid to penetrate into the pores of the powder core of the heat-treated part.

[0110] (10) Curing: The epoxy resin-containing powder core is cured in air at 220°C for 50 minutes to obtain a soft magnetic powder core.

[0111] The properties of the cured soft magnetic powder core are shown in Table 3.

[0112] Example 5:

[0113] The steps for preparing soft magnetic composite powder and soft magnetic powder core from Fe-Ni powder are as follows:

[0114] (1) Selection of coating material precursors and preparation of coating solution: Boron source and nitrogen source were used as coating material precursors and dissolved in solvent to obtain coating solution. The amounts of boron source, nitrogen source and solvent are shown in Table 1. The pH was adjusted to 10 to make it alkaline to promote the reaction;

[0115] (2) Preparation of soft magnetic metal powder: Fe-49wt%Ni soft magnetic metal powder was prepared by gas atomization. The loose packing density of the soft magnetic metal powder was 4.5 g / cm³. 3 d 50 It is 24μm, d 99 The thickness is 56 μm. The coating solution and the soft magnetic metal powder were transferred to a polytetrafluoroethylene-lined reactor and sealed. The volumes of the soft magnetic metal powder and the coating solution are shown in Table 1, and the total volume of the soft magnetic metal powder and the coating solution does not exceed 80% of the total capacity of the reactor.

[0116] (3) Coating reaction: The above reaction vessel is heated to 220°C and kept at that temperature for 2 hours. The pressure of the reaction vessel is 4MPa.

[0117] (4) Post-processing and separation: After the reactor temperature cools to 70℃ and the pressure drops to atmospheric pressure, open the reactor, collect the metal soft magnetic powder coated with h-BN, and wash it with deionized water and ethanol to remove impurities. Separate the metal soft magnetic powder containing water and ethanol and dry it at low temperature to avoid oxidation;

[0118] (5) Calcination: The dried product is mostly amorphous / low crystallinity h-BN, which needs to be calcined at 800℃ for 3 hours under N2 / Ar atmosphere to improve crystallinity;

[0119] (6) Powder mixing: Add lubricant and forming agent to the calcined 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.

[0120] (7) Molding: The powder containing lubricant and forming agent is molded under high pressure to obtain the molded part;

[0121] (8) Heat treatment: The above-mentioned molded parts are heat treated at 750°C for 120 minutes to obtain heat-treated parts. The heat treatment atmosphere is inert gas such as nitrogen and argon.

[0122] (9) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the liquid to penetrate into the pores of the powder core of the heat-treated part.

[0123] (10) Curing: The epoxy resin-containing powder core is cured in air at 220°C for 50 minutes to obtain a soft magnetic powder core.

[0124] The properties of the cured soft magnetic powder core are shown in Table 3.

[0125] Example 6:

[0126] The steps for preparing soft magnetic composite powder and soft magnetic powder core from Fe-Si-Cr powder are as follows:

[0127] (1) Selection of coating material precursors and preparation of coating solution: Boron source and nitrogen source were used as coating material precursors and dissolved in solvent to obtain coating solution. The amounts of boron source, nitrogen source and solvent are shown in Table 1. The pH was adjusted to 10 to make it alkaline to promote the reaction;

[0128] (2) 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 the soft magnetic metal powder was 4.17 g / cm³. 3 d 50 20μm, d 99The thickness is 39 μm. The coating solution and the soft magnetic metal powder are transferred to a polytetrafluoroethylene-lined reactor and sealed. The volumes of the soft magnetic metal powder and the coating solution are shown in Table 1, and the total volume of the soft magnetic metal powder and the coating solution does not exceed 80% of the total capacity of the reactor.

[0129] (3) Coating reaction: The above reaction vessel is heated to 190°C and kept at that temperature for 2 hours. The pressure of the reaction vessel is 5MPa.

[0130] (4) Post-processing and separation: After the reactor temperature cools to 70℃ and the pressure drops to atmospheric pressure, open the reactor, collect the metal soft magnetic powder coated with h-BN, and wash it with deionized water and ethanol to remove impurities. Separate the metal soft magnetic powder containing water and ethanol and dry it at low temperature to avoid oxidation;

[0131] (5) Calcination: The dried product is mostly amorphous / low crystallinity h-BN, which needs to be calcined at 800℃ for 3 hours under N2 / Ar atmosphere to improve crystallinity;

[0132] (6) Powder mixing: Add lubricant and forming agent to the calcined 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.

[0133] (7) Molding: The powder containing the lubricant and the forming agent is molded under high pressure to obtain a molded part;

[0134] (8) Heat treatment: The above-mentioned molded parts are heat-treated at 700°C for 90 minutes to obtain heat-treated parts. The heat treatment atmosphere is inert gas such as nitrogen and argon.

[0135] (9) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the liquid to penetrate into the pores of the powder core of the heat-treated part.

[0136] (10) Curing: The epoxy resin-containing powder core is cured in air at 200°C for 80 minutes to obtain a soft magnetic powder core.

[0137] The properties of the cured soft magnetic powder core are shown in Table 3.

[0138] Table 1 shows the coating solution composition formulas (based on 1000g of iron powder) for Examples 1-6.

[0139]

[0140]

[0141] Table 2 Magnetic properties of Examples 1-2

[0142]

[0143] Table 3 Magnetic properties of Examples 3-6

[0144]

[0145] Example 7:

[0146] The steps for preparing soft magnetic composite material powder and soft magnetic powder core from pure Fe powder are as follows:

[0147] (1) Selection of coating material precursor and preparation of coating solution: Boron source and nitrogen source are used as coating material precursors and dissolved in solvent to obtain coating solution. The amounts of boron source, nitrogen source and solvent are shown in Table 4.

[0148] (2) Preparation of soft magnetic metal powder: Pure iron soft magnetic metal powder was prepared using a water atomization method. The loose packing density of this soft magnetic metal powder was 3.1 g / cm³. 3 d 50 100μm, d 99 The particle size is 230 μm. Powder mass is shown in Table 4.

[0149] (3) Coating reaction: The coating solution and the soft magnetic metal powder were transferred to a high-pressure reactor lined with polytetrafluoroethylene and sealed. The volumes of the soft magnetic metal powder and the coating solution are shown in Table 4. The total volume of the soft magnetic metal powder and the coating solution shall not exceed 80% of the total capacity of the reactor. The reactor was heated to 200°C and held at that temperature for 10 hours. The pressure of the reactor was 4 MPa.

[0150] (4) Post-processing and separation: After the reactor temperature cools to below 80℃ and the pressure drops to atmospheric pressure, open the reactor, collect the metal soft magnetic powder coated with h-BN, and wash it with deionized water and ethanol to remove impurities. Separate the metal soft magnetic powder containing water and ethanol and dry it at low temperature (50℃) to avoid oxidation;

[0151] (5) Calcination: The dried product is a powder coated with amorphous / low crystallinity h-BN, which is calcined at 800℃ for 2 hours under N2 / Ar atmosphere;

[0152] (6) Powder mixing: Add lubricant and forming agent to the calcined 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.

[0153] (7) Molding: The powder containing lubricant and forming agent is molded under high pressure to obtain the molded part;

[0154] (8) Heat treatment: The above-mentioned molded parts are heat treated at 600°C for 90 minutes to obtain heat-treated parts. The heat treatment atmosphere is nitrogen.

[0155] (9) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the liquid to penetrate into the pores of the powder core of the heat-treated part.

[0156] (10) Curing: The epoxy resin-containing powder core is cured in air at 200°C for 100 minutes to obtain a soft magnetic powder core.

[0157] The morphology of the calcined soft magnetic composite material powder is shown in Figure 3 As can be seen, there are some ceramic insulating particles on the surface of the soft magnetic composite powder, indicating that the highly thermally conductive ceramic has been tightly bonded to the powder surface, giving the material good thermal conductivity and insulation properties. The properties of the cured soft magnetic powder core are shown in Table 5.

[0158] Example 8:

[0159] The steps for preparing soft magnetic composite material powder and soft magnetic powder core from pure Fe powder are as follows:

[0160] (1) Selection of coating material precursor and preparation of coating solution: Boron source and nitrogen source are used as coating material precursors and dissolved in solvent to obtain coating solution. The amounts of boron source, nitrogen source and solvent are shown in Table 4.

[0161] (2) Preparation of soft magnetic metal powder: Pure iron soft magnetic metal powder was prepared using a water atomization method. The loose packing density of this soft magnetic metal powder was 3.3 g / cm³. 3 d 50 It is 130μm, d 99 The particle size is 260 μm. Powder mass is shown in Table 4.

[0162] (3) Coating reaction: The coating solution and the soft magnetic metal powder were transferred to a high-pressure reactor lined with polytetrafluoroethylene and sealed. The volumes of the soft magnetic metal powder and the coating solution are shown in Table 4. The total volume of the soft magnetic metal powder and the coating solution shall not exceed 80% of the total capacity of the reactor. The reactor was heated to 230°C and held at that temperature for 8 hours. The pressure of the reactor was 5 MPa.

[0163] (4) Post-processing and separation: After the reactor temperature cools to below 80℃ and the pressure drops to atmospheric pressure, open the reactor, collect the metal soft magnetic powder coated with h-BN, and wash it with deionized water and ethanol to remove impurities. Separate the metal soft magnetic powder containing water and ethanol and dry it at low temperature (50℃) to avoid oxidation;

[0164] (5) Calcination: The dried product is a powder coated with amorphous / low crystallinity h-BN, which is calcined at 850℃ for 1.8 hours under N2 / Ar atmosphere;

[0165] (6) Powder mixing: Add lubricant and forming agent to the calcined 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.

[0166] (7) Molding: The powder containing lubricant and forming agent is molded under high pressure to obtain the molded part;

[0167] (8) Heat treatment: The above-mentioned molded parts are heat treated at 630°C for 80 minutes to obtain heat-treated parts. The heat treatment atmosphere is nitrogen.

[0168] (9) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the liquid to penetrate into the pores of the powder core of the heat-treated part.

[0169] (10) Curing: The epoxy resin-containing powder core is cured in air at 180°C for 120 minutes to obtain a soft magnetic powder core.

[0170] The morphology of the calcined soft magnetic composite material powder is shown in Figure 4 As can be seen, the surface of the soft magnetic composite powder contains some ceramic insulating particles, indicating a good powder coating effect, high thermal conductivity, and low loss in the powder core. The properties of the cured soft magnetic powder core are shown in Table 5.

[0171] Example 9:

[0172] The steps for preparing soft magnetic composite powder and soft magnetic powder core from Fe-Si powder are as follows:

[0173] (1) Selection of coating material precursor and preparation of coating solution: Boron source and nitrogen source are used as coating material precursors and dissolved in solvent to obtain coating solution. The amounts of boron source, nitrogen source and solvent are shown in Table 4.

[0174] (2) Preparation of soft magnetic metal powder: Fe-5wt%Si soft magnetic metal powder was prepared by gas atomization. The loose packing density of the soft magnetic metal powder was 4.2 g / cm³. 3 d 50 It is 26μm, d 99 The particle size is 55 μm. Powder quality is shown in Table 4.

[0175] (3) Coating reaction: The coating solution and the soft magnetic metal powder were transferred to a high-pressure reactor lined with polytetrafluoroethylene and sealed. The volumes of the soft magnetic metal powder and the coating solution are shown in Table 4. The total volume of the soft magnetic metal powder and the coating solution shall not exceed 80% of the total capacity of the reactor. The reactor was heated to 180°C and held at that temperature for 20 hours. The pressure of the reactor was 3 MPa.

[0176] (4) Post-processing and separation: After the reactor temperature cools to below 80℃ and the pressure drops to atmospheric pressure, open the reactor, collect the metal soft magnetic powder coated with h-BN, and wash it with deionized water and ethanol to remove impurities. Separate the metal soft magnetic powder containing water and ethanol and dry it at low temperature (70℃) to avoid oxidation;

[0177] (5) Calcination: The dried product is a powder coated with amorphous / low crystallinity h-BN, which is calcined at 880℃ for 3 hours under N2 / Ar atmosphere;

[0178] (6) Powder mixing: Add lubricant and forming agent to the calcined 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.

[0179] (7) Molding: The powder containing lubricant and forming agent is molded under high pressure to obtain the molded part;

[0180] (8) Heat treatment: The above-formed parts are heat treated at 730°C for 120 minutes to obtain heat-treated parts. The heat treatment atmosphere is nitrogen.

[0181] (9) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the liquid to penetrate into the pores of the powder core of the heat-treated part.

[0182] (10) Curing: The epoxy resin-containing powder core is cured in air at 150°C for 100 minutes to obtain a soft magnetic powder core.

[0183] The properties of the cured soft magnetic powder core are shown in Table 6.

[0184] Example 10:

[0185] The steps for preparing soft magnetic composite powder and soft magnetic powder core from Fe-Si-Al powder are as follows:

[0186] (1) Selection of coating material precursor and preparation of coating solution: Boron source and nitrogen source are used as coating material precursors and dissolved in solvent to obtain coating solution. The amounts of boron source, nitrogen source and solvent are shown in Table 4.

[0187] (2) 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 particle size is 48 μm. Powder mass is shown in Table 4.

[0188] (3) Coating reaction: The coating solution and the soft magnetic metal powder were transferred to a high-pressure reactor lined with polytetrafluoroethylene and sealed. The volumes of the soft magnetic metal powder and the coating solution are shown in Table 4. The total volume of the soft magnetic metal powder and the coating solution shall not exceed 80% of the total capacity of the reactor. The reactor was heated to 250°C and held at that temperature for 6 hours. The pressure of the reactor was 6 MPa.

[0189] (4) Post-processing and separation: After the reactor temperature cools to below 80℃ and the pressure drops to atmospheric pressure, open the reactor, collect the metal soft magnetic powder coated with h-BN, and wash it with deionized water and ethanol to remove impurities. Separate the metal soft magnetic powder containing water and ethanol and dry it at low temperature (80℃) to avoid oxidation;

[0190] (5) Calcination: The dried product is a powder coated with amorphous / low crystallinity h-BN, which is calcined at 920℃ for 4 hours under N2 / Ar atmosphere;

[0191] (6) Powder mixing: Add lubricant and forming agent to the calcined 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.

[0192] (7) Molding: The powder containing lubricant and forming agent is molded under high pressure to obtain the molded part;

[0193] (8) Heat treatment: The above-formed part is heat-treated at 780°C for 150 minutes to obtain a heat-treated part. The heat treatment atmosphere is nitrogen.

[0194] (9) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the liquid to penetrate into the pores of the powder core of the heat-treated part.

[0195] (10) Curing: The epoxy resin-containing powder core is cured in air at 250°C for 80 minutes to obtain a soft magnetic powder core.

[0196] The properties of the cured soft magnetic powder core are shown in Table 6.

[0197] Example 11:

[0198] The steps for preparing soft magnetic composite powder and soft magnetic powder core from Fe-Ni powder are as follows:

[0199] (1) Selection of coating material precursor and preparation of coating solution: Boron source and nitrogen source are used as coating material precursors and dissolved in solvent to obtain coating solution. The amounts of boron source, nitrogen source and solvent are shown in Table 4.

[0200] (2) Preparation of soft magnetic metal powder: Fe-49wt%Ni soft magnetic metal powder was prepared by gas atomization. The loose packing density of the soft magnetic metal powder was 4.5 g / cm³. 3 d50 It is 24μm, d 99 The particle size is 56 μm. Powder mass is shown in Table 4.

[0201] (3) Coating reaction: The coating solution and the soft magnetic metal powder were transferred to a high-pressure reactor lined with polytetrafluoroethylene and sealed. The volumes of the soft magnetic metal powder and the coating solution are shown in Table 4. The total volume of the soft magnetic metal powder and the coating solution shall not exceed 80% of the total capacity of the reactor. The reactor was heated to 300°C and held at that temperature for 3 hours. The pressure of the reactor was 4 MPa.

[0202] (4) Post-processing and separation: After the reactor temperature cools to below 80℃ and the pressure drops to atmospheric pressure, open the reactor, collect the metal soft magnetic powder coated with h-BN, and wash it with deionized water and ethanol to remove impurities. Separate the metal soft magnetic powder containing water and ethanol and dry it at low temperature (50℃) to avoid oxidation;

[0203] (5) Calcination: The dried product is a powder coated with amorphous / low crystallinity h-BN, which is calcined at 1000℃ for 2 hours under N2 / Ar atmosphere;

[0204] (6) Powder mixing: Add lubricant and forming agent to the calcined 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.

[0205] (7) Molding: The powder containing lubricant and forming agent is molded under high pressure to obtain the molded part;

[0206] (8) Heat treatment: The above-formed parts are heat-treated at 820°C for 100 minutes to obtain heat-treated parts. The heat treatment atmosphere is nitrogen.

[0207] (9) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the liquid to penetrate into the pores of the powder core of the heat-treated part.

[0208] (10) Curing: The epoxy resin-containing powder core is cured in air at 200°C for 50 minutes to obtain a soft magnetic powder core.

[0209] The properties of the cured soft magnetic powder core are shown in Table 6.

[0210] Example 12:

[0211] The steps for preparing soft magnetic composite powder and soft magnetic powder core from Fe-Si-Cr powder are as follows:

[0212] (1) Selection of coating material precursor and preparation of coating solution: Boron source and nitrogen source are used as coating material precursors and dissolved in solvent to obtain coating solution. The amounts of boron source, nitrogen source and solvent are shown in Table 4.

[0213] (2) 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 the soft magnetic metal powder was 4.17 g / cm³. 3 d 50 20μm, d 99 The particle size is 39 μm. Powder mass is shown in Table 4.

[0214] (3) Coating reaction: The coating solution and the soft magnetic metal powder were transferred to a high-pressure reactor lined with polytetrafluoroethylene and sealed. The volumes of the soft magnetic metal powder and the coating solution are shown in Table 4. The total volume of the soft magnetic metal powder and the coating solution shall not exceed 80% of the total capacity of the reactor. The reactor was heated to 240°C and held at that temperature for 2 hours. The pressure of the reactor was 7 MPa.

[0215] (4) Post-processing and separation: After the reactor temperature cools to below 80℃ and the pressure drops to atmospheric pressure, open the reactor, collect the metal soft magnetic powder coated with h-BN, and wash it with deionized water and ethanol to remove impurities. Separate the metal soft magnetic powder containing water and ethanol and dry it at low temperature (40℃) to avoid oxidation;

[0216] (5) Calcination: The dried product is a powder coated with amorphous / low crystallinity h-BN, which is calcined at 850℃ for 5 hours under N2 / Ar atmosphere;

[0217] (6) Powder mixing: Add lubricant and forming agent to the calcined 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.

[0218] (7) Molding: The powder containing lubricant and forming agent is molded under high pressure to obtain the molded part;

[0219] (8) Heat treatment: The above-mentioned molded parts are heat treated at 780°C for 80 minutes to obtain heat-treated parts. The heat treatment atmosphere is nitrogen.

[0220] (9) Impregnation: Immerse the heat-treated part in a liquid containing epoxy resin, allowing the liquid to penetrate into the pores of the powder core of the heat-treated part.

[0221] (10) Curing: The epoxy resin-containing powder core is cured in air at 200°C for 50 minutes to obtain a soft magnetic powder core.

[0222] The properties of the cured soft magnetic powder core are shown in Table 6.

[0223] Table 4 shows the coating solution composition formulas (based on 1000g of iron powder) for Examples 7-12.

[0224]

[0225]

[0226] Table 5 Magnetic properties of Examples 7-8

[0227]

[0228] Table 6 Magnetic properties of Examples 9-12

[0229]

[0230] 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) Preparation of coating solution: Dissolve boron source and nitrogen source in solvent to obtain coating solution. The solvent is deionized water or organic solvent. When deionized water is used as solvent, the molar ratio of boron atoms to nitrogen atoms is 1:(0.1-20). When organic solvent is used as solvent, the molar ratio of boron atoms to nitrogen atoms is (0.1-10):

1. 2) Transfer: Transfer the coating solution and the soft magnetic metal powder to a polytetrafluoroethylene-lined reactor and seal it, with the volume ratio of the soft magnetic metal powder to the coating solution being 0.01 to 100. 3) Coating reaction: The reactor is heated to 150-350℃ and held for 0.1-100 hours. When deionized water is used as solvent, the pressure of the reactor is 0.5-6MPa. When organic solvent is used as solvent, the pressure of the reactor is 1-30MPa. The resulting metal soft magnetic powder coated with h-BN is obtained. 4) Post-processing: After the temperature of the reactor has cooled to below 80°C and the pressure has dropped to atmospheric pressure, open the reactor, collect the soft magnetic metal powder coated with h-BN, and wash it with washing liquid to remove impurities; 5) Separation: The soft magnetic metal powder coated with h-BN containing washing liquid is separated and dried; 6) Powder mixing and molding: The soft magnetic metal powder coated with h-BN obtained in step 5) is added to a lubricant and a forming agent, and then molded to obtain a molded part; 7) Heat treatment: The above-mentioned molded parts are heat-treated at 450-1000℃ for 5-500 minutes in an inert gas atmosphere to obtain heat-treated parts; 8) 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. 9) 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: When deionized water is used as the solvent, the boron source includes at least one of boric acid (H3BO3), boron oxide (B2O3), and borax (Na2B4O7), and the nitrogen source includes at least one of urea (CO(NH2)2), melamine (C3H6N6), and ammonia (NH3·H2O); when an organic solvent is used as the solvent, the boron source includes at least one of trimethyl borate, boron trichloride, boron bromide, sodium borohydride, and boric acid, and the nitrogen source includes at least one of urea, melamine, ammonia, lithium nitride, sodium nitride, and potassium nitride.

3. The preparation method according to claim 1, characterized in that: The organic solvent includes at least one of ethylene glycol, toluene, ethylenediamine, and ethanol.

4. The preparation method according to claim 3, characterized in that: It also includes a surfactant, wherein the surfactant is at least one of oleic acid, hexadecyltrimethylammonium bromide, and polyethylene glycol, wherein the surfactant is added to the organic solvent, and when the surfactant is a liquid, the volume ratio of the surfactant to the organic solvent is 0.01 to 10 vol%, and when the surfactant is a solid, the mass ratio of the surfactant added to the volume ratio of the organic solvent is 0.01 to 10 g / 100 ml.

5. The preparation method according to claim 1, characterized in that: In step 5), the dried h-BN-coated soft magnetic metal powder is calcined at 700–1100°C in an inert gas atmosphere. When deionized water is used as the solvent, the calcination time is 0.5–20 hours, and when an organic solvent is used as the solvent, the calcination time is 0.1–48 hours. The calcined h-BN-coated soft magnetic metal powder is then mixed and shaped in step 6.

6. The preparation method according to claim 1, characterized in that: Step 5) 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.

7. The preparation method according to claim 1, characterized in that: In step 2), the soft magnetic metal 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, 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.

8. The preparation method according to claim 7, characterized in that: In step 2), the particle size of the soft magnetic metal powder is: d 50 <40μm, d 99 <80μm.

9. The preparation method according to claim 1, characterized in that: In step 2), the total volume of the soft magnetic metal powder and the coating solution is ≤ 80% of the total capacity of the reactor; in step 6), the lubricant is at least one of stearic acid, stearate, and wax, and the forming agent is silicone resin or epoxy resin.

10. The preparation method according to any one of claims 1 to 9, characterized in that: In step 1), when using deionized water as a solvent, adjust the pH of the coating solution to 8-12.

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