A magnetic powder core with an in-situ generated insulation coating layer, a preparation method and application thereof

Abstract

The application provides a magnetic powder core with an in-situ generated insulating coating layer and a preparation method and application thereof, and relates to the technical field of soft magnetic materials. The magnetic powder core has a transition layer / ferromagnetic insulating layer / carbon coating layer composite multilayer insulating structure, which combines the advantages of each layer, can improve the resistivity of the magnetic powder core, reduce the core loss, and ensure that the magnetic powder core has high permeability and saturation magnetic induction strength. The preparation method controls the oxygen content in the heat treatment atmosphere, promotes the enrichment and diffusion of metal elements in the soft magnetic powder to the surface of the soft magnetic powder to form a metal oxide transition layer, crystallizes a ferromagnetic precursor to form a ferromagnetic insulating layer, and carbonizes an epoxy resin to form a carbon coating layer, thereby preparing the magnetic powder core with the in-situ generated insulating coating layer. The steps of the preparation method are relatively simple to operate, the raw materials and equipment involved are common in industrial production, and are easy to obtain and operate, and are suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of soft magnetic materials technology, specifically to a magnetic powder core with an in-situ generated insulating coating layer, its preparation method, and its application. Background Technology

[0002] Magnetic powder cores are a type of soft magnetic composite material made by mixing magnetic powder, insulating medium, and binder. Eddy current loss is the main cause of power loss in soft magnetic composite materials with magnetic powders such as metals and alloys as the matrix. In order to reduce the eddy current loss of magnetic powder cores, it is necessary to insulate and coat the magnetic powder.

[0003] Currently, commonly used coating methods include organic coating, inorganic coating, and organic-inorganic composite coating. Among organic coating technologies, thermoplastic resins were initially used for magnetic powder core coating. However, due to their easy solubility in industrial solutions, difficulty in maintaining a stable morphology, and low melting point, they limited the temperature range of subsequent heat treatment processes for magnetic powder cores, failing to meet the requirements for preparing high-performance magnetic powder cores. Therefore, the industry turned to thermosetting resins such as epoxy resins. However, thermosetting resins still suffer from insufficient thermal stability and weak aging resistance, resulting in a short overall service life for magnetic powder cores, still unable to meet the needs of long-term, stable applications.

[0004] Currently, commonly used inorganic coating methods include phosphate coating and ferrite coating. Although phosphate coating has been used for a longer period, the resistivity of the resulting coating layer is low, leading to a significant increase in eddy current losses in the magnetic powder core at high frequencies. Furthermore, the plating solution in phosphate coating preparation is unstable, the operation process is complex, and the use of harmful substances such as phosphoric acid poses significant risks to personnel health. Additionally, because phosphate coating introduces non-magnetic materials into the magnetic powder core, it reduces the permeability and saturation magnetic induction. Ferrite coating, on the other hand, minimizes the impact of the coating material on the magnetic properties of the substrate and maintains stable magnetic properties in the megahertz range, thus gaining widespread application. However, due to the high brittleness of ferrite, the ferrite coating layer is prone to fracture during pressing, leading to delamination of the magnetic powder core and increased eddy current losses.

[0005] Therefore, it is of great significance to develop an insulated coated magnetic powder core that can simultaneously possess low eddy current loss, high permeability, high saturation magnetic induction intensity, and high resistivity to meet the demand for high-performance magnetic powder cores in long-term and stable application scenarios. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a magnetic powder core with an in-situ generated insulating coating, its preparation method, and its application. The magnetic powder core possesses low eddy current loss, high permeability, high saturation magnetic induction, and high resistivity.

[0007] The specific technical solution of this invention is as follows:

[0008] In a first aspect, the present invention provides a magnetic powder core having an in-situ generated insulating coating layer, comprising:

[0009] Soft magnetic powder;

[0010] A metal oxide transition layer is generated in situ to coat the surface of the soft magnetic powder. The metal element in the metal oxide transition layer is selected from at least one of Cr, Al and Ti, and the soft magnetic powder contains the metal element.

[0011] A ferrite insulating layer is generated in situ to coat the surface of the metal oxide transition layer;

[0012] And an in-situ carbon coating layer is formed on the surface of the ferrite insulating layer.

[0013] In one possible implementation, the soft magnetic powder is selected from at least one of Fe-Si-BC-Cr amorphous nanocrystalline soft magnetic powder, Fe-Si-Al alloy powder, Fe-Ni-Cr alloy powder, Fe-Ni-Ti alloy powder, and Fe-Cr alloy powder.

[0014] In one possible implementation, the ferrite is selected from any one of Ni-Zn ferrite, Mn-Zn ferrite, Cu-Zn ferrite, Ni-Cu-Zn ferrite, and Mg-Zn ferrite.

[0015] In one possible implementation, the thickness of the metal oxide transition layer is 10-50 nm, and the thickness of the ferrite insulating layer is 20-500 nm.

[0016] In one possible implementation, the resistivity of the magnetic powder core is ≥2×10⁻⁶. 8 Ω·sq, eddy current loss ≤240 kW / m under 100 kHz and 50 mT conditions. 3 Permeability μ e The range is 30-90, and the saturation magnetic induction intensity Bs ≥ 1.2 T.

[0017] Secondly, the present invention provides a method for preparing the above-mentioned magnetic powder core having an in-situ generated insulating coating layer, comprising the following steps:

[0018] S1. Soft magnetic powder is dispersed in a ferrite precursor solution and mixed evenly. Then, a pH adjuster is added dropwise until the pH value is 9-11. After co-deposition and solvent removal, magnetic powder coated with ferrite precursor is obtained.

[0019] S2. The magnetic powder obtained in step S1 is mixed with the epoxy resin solution, and after the solvent is evaporated, magnetic powder coated with epoxy resin and ferrite precursor is obtained.

[0020] S3. The magnetic powder obtained in step S2 is added into the mold and pressed to obtain a magnetic powder core blank.

[0021] S4. The magnetic powder core blank obtained in step S3 is subjected to heat treatment, in which a metal oxide transition layer, a ferrite insulating layer and a carbon coating layer are sequentially formed in situ on the surface of the soft magnetic powder. The heat treatment temperature is 300-1000℃, and the oxygen partial pressure in the heat treatment atmosphere is 20%-80% of the oxygen partial pressure in the atmosphere before heat treatment, so as to obtain a magnetic powder core with an in situ generated insulating coating layer.

[0022] In one possible implementation, the specific process of the heat treatment is as follows: First, the magnetic powder core blank described in step S3 is placed in the sample chamber of the heat treatment device, and carbon powder is arranged around the magnetic powder core blank. The temperature in the sample chamber is raised to 450-520 ℃ and held for 10-20 min, and then argon gas is introduced to purge for 5-10 min. After that, the argon gas is stopped, and the temperature is held for another 10-20 min, and then argon gas is introduced to purge for another 5-10 min. This process is repeated multiple times until the heat treatment is completed.

[0023] Furthermore, the mass of the carbon powder accounts for 0.2 wt.%-2 wt.% of the mass of the magnetic powder core green body.

[0024] In one possible implementation, the pH adjuster in step S1 is selected from any one of NaOH solution, KOH solution, and ammonia water.

[0025] In one possible implementation, the mixing in step S1 is carried out under stirring conditions, the stirring speed is 200-600 rpm, and the co-deposition temperature is 40-90 ℃.

[0026] In one possible implementation, the epoxy resin in the epoxy resin solution in step S2 has a mass fraction of 2 wt.%-15 wt.%.

[0027] In one possible implementation, the pressure of the compression in step S3 is 500-2200 MPa.

[0028] Thirdly, the present invention provides the application of the above-mentioned magnetic powder core with an in-situ generated insulating coating in power inductors, transformers or filters.

[0029] The positive and progressive effects of this invention are as follows:

[0030] This invention provides a magnetic powder core with an in-situ generated insulating coating, its preparation method, and its application. The magnetic powder core with the in-situ generated insulating coating has a multi-layered insulating structure composed of a transition layer / ferrite insulating layer / carbon coating layer, combining the advantages of each layer. The ferrite layer has high resistivity and good magnetic property compatibility; the transition layer improves the interlayer bonding strength and optimizes the magnetic phase ratio within the magnetic powder; and the carbon coating layer further enhances insulation performance and facilitates pressing and molding. This multi-layered insulating structure can improve resistivity and reduce core loss while ensuring the magnetic powder core has high permeability and saturation magnetic induction. The preparation method employs a two-step coating and heat treatment process. By controlling the oxygen content in the heat treatment atmosphere, metal elements in the soft magnetic powder are encouraged to diffuse and enrich towards the surface of the soft magnetic powder to form a metal oxide transition layer, ferrite precursor crystallizes to form a ferrite insulating layer, and epoxy resin carbonizes to form a carbon coating layer, thus obtaining a magnetic powder core with an in-situ generated insulating coating. The preparation method is relatively simple in each step, and the raw materials and equipment involved are common in industrial production, easy to obtain and operate, and have high process feasibility, making it suitable for large-scale industrial production. Attached Figure Description

[0031] Figure 1 This is a cross-sectional view of the magnetic powder core prepared in Example 1.

[0032] Figure 2 This is an elemental line distribution analysis diagram of a local cross-section of the magnetic powder core prepared in Example 1.

[0033] Figure 3 The images show SEM and EDS spectra of the Fe-Si-BC-Cr amorphous nanocrystalline soft magnetic powder before and after coating with the ferrite precursor in Example 1.

[0034] Figure 4 The graph shows the effective magnetic permeability data of the magnetic powder cores prepared in Examples 1-4 and Comparative Examples 1-3.

[0035] Figure 5 The graph shows the magnetization data of the magnetic powder cores prepared in Examples 1-4 and Comparative Examples 1-3.

[0036] Figure 6 The graph shows the quality factor data of the magnetic powder cores prepared in Examples 1-4 and Comparative Examples 1-3.

[0037] Figure 7 The graph shows the iron loss data of the magnetic powder cores prepared in Examples 1-4 and Comparative Examples 1-3.

[0038] Figure 8 The graph shows the hysteresis loss data of the magnetic powder cores prepared in Examples 1-4 and Comparative Examples 1-3.

[0039] Figure 9The graph shows the eddy current loss data of the magnetic powder cores prepared in Examples 1-4 and Comparative Examples 1-3.

[0040] Figure 10 This is a flowchart of the preparation of the magnetic powder core in Example 1. Detailed Implementation

[0041] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the present invention.

[0042] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0043] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0044] Terminology Explanation

[0045] Magnetic loss: When a metal magnetic powder core operates in an alternating magnetic field, it is magnetized and energy is lost simultaneously. The total energy loss is called magnetic loss. Magnetic loss consists of magnetostrictive loss, eddy current loss, and residual loss.

[0046] Eddy current loss: When the external magnetic field changes with frequency, an induced current will be generated in the material due to electromagnetic induction, resulting in eddy current loss. The higher the frequency of the alternating magnetic field, the greater the eddy current. The insulating coating can block the eddy current inside the magnetic powder particles, thereby reducing the eddy current between the magnetic powder particles and thus reducing the eddy current loss of the magnetic powder core.

[0047] Magnetoresistive loss: Power loss caused by magnetization of magnetic materials in an alternating magnetic field due to magnetostriction. It is related to the coercivity of the magnetic powder core. Adding too much non-magnetic material will increase the coercivity and thus increase the hysteresis loss. Nano- and micro-scale thin insulating coating films can maintain low hysteresis loss.

[0048] Residual loss: In low-frequency weak field, residual loss is mainly magnetic aftereffect loss. In high-frequency cases, residual loss is mainly size resonance loss, domain wall resonance loss and natural resonance loss.

[0049] Resistivity: The property of a material to impede the flow of electric current, which is related to factors such as material type, pressure, temperature, and magnetic field.

[0050] Coercivity: After a magnetic material is saturated with magnetization, its magnetic flux density (B) does not return to zero when the external magnetic field returns to zero. A magnetic field of a certain magnitude needs to be applied in the opposite direction of the original magnetization field to bring the magnetic flux density back to zero; this magnetic field is called coercivity. The type and proportion of substances other than magnetic powder will affect the soft magnetic coupling effect between magnetic powder particles. The addition of non-magnetic substances and excessively low pressing density will also increase the coercivity of the magnetic powder core, leading to an increase in hysteresis loss.

[0051] The specific technical solution of this invention is as follows:

[0052] In a first aspect, the present invention provides a magnetic powder core having an in-situ generated insulating coating layer, comprising:

[0053] Soft magnetic powder;

[0054] A metal oxide transition layer is generated in situ to coat the surface of the soft magnetic powder. The metal element in the metal oxide transition layer is selected from at least one of Cr, Al and Ti, and the soft magnetic powder contains the metal element.

[0055] A ferrite insulating layer is generated in situ to coat the surface of the metal oxide transition layer;

[0056] And an in-situ carbon coating layer is formed on the surface of the ferrite insulating layer.

[0057] The present invention provides a magnetic powder core with an in-situ generated insulating coating layer. Through the synergistic cooperation of soft magnetic powder, metal oxide transition layer, ferrite insulating layer and carbon coating layer, the magnetic powder core simultaneously possesses low eddy current loss, high permeability, high saturation magnetic induction intensity and high resistivity.

[0058] The in-situ enrichment of metallic elements within the soft magnetic powder to form a metal oxide transition layer on its surface significantly enhances the bonding strength between the ferrite insulation layer and the soft magnetic powder, preventing the ferrite layer from breaking and detaching during pressing. Furthermore, the metal oxide transition layer effectively blocks electrical pathways between the soft magnetic powder particles, reducing eddy current conduction and thus lowering eddy current losses. The ferrite insulation layer itself possesses high resistivity; further coating the metal oxide transition layer adds another layer of electrical insulation to the powder core, further preventing eddy current diffusion. The carbon coating layer, also possessing excellent insulation properties, encapsulates the surface of the ferrite insulation layer, preventing external factors from damaging the internal insulation structure and further ensuring that the powder core maintains low eddy current losses during operation. The combined effect of the carbon coating layer, ferrite insulation layer, and metal oxide transition layer greatly improves the overall electrical insulation performance of the powder core, effectively reducing eddy current losses.

[0059] Soft magnetic powder, as the main body of the magnetic powder core, possesses excellent soft magnetic properties, which is the fundamental guarantee for the high permeability of the magnetic powder core. Metal elements in the in-situ generated metal oxide transition layer diffuse from the soft magnetic powder to its surface, reducing the content of non-magnetic phase metal elements within the soft magnetic powder and relatively increasing the proportion of magnetic phase elements, thus contributing to improved permeability of the magnetic powder core. Ferrite and soft magnetic powder have good matching properties in terms of magnetic properties, providing insulation without significantly reducing permeability, which helps the magnetic powder core maintain high permeability. The carbon coating layer provides insulation and protection without disrupting the basic magnetic domain structure of the soft magnetic powder. The metal oxide transition layer, ferrite insulating layer, and carbon coating layer, while playing their respective roles, synergistically improve the permeability of the magnetic powder core.

[0060] The soft magnetic powder itself has a high saturation magnetic induction intensity. The subsequent metal oxide transition layer, ferrite insulating layer and carbon coating layer are uniformly coated on the surface of the magnetic powder, which optimizes the coupling effect between the magnetic powders and reduces factors that are not conducive to the improvement of saturation magnetic induction intensity, such as the demagnetization effect between magnetic powders. This helps the magnetic powder core as a whole to exhibit a high saturation magnetic induction intensity.

[0061] The metal oxide transition layer, ferrite insulating layer, and carbon coating layer in the magnetic powder core together constitute a multi-layered insulating structure. The metal oxides in the metal oxide transition layer have high resistivity; the ferrite insulating layer also has relatively high resistivity, and its spinel structure effectively prevents electron conduction; the carbon coating layer further enhances the overall insulation performance. The three layers work together to form a continuous and high-resistivity insulating system, giving the magnetic powder core its high resistivity.

[0062] In summary, the technical features of soft magnetic powder, transition layer, ferrite insulating layer and carbon coating layer work together from different angles to give the magnetic powder core excellent properties such as low eddy current loss, high permeability, high saturation magnetic induction intensity and high resistivity.

[0063] In one possible implementation, the soft magnetic powder is selected from at least one of Fe-Si-BC-Cr amorphous nanocrystalline soft magnetic powder, Fe-Si-Al alloy powder, Fe-Ni-Cr alloy powder, Fe-Ni-Ti alloy powder, and Fe-Cr alloy powder. All of the above powders contain one or more active metal elements with high oxygen affinity (such as Cr, Al, Ti). During a specific oxygen partial pressure heat treatment process, these elements can preferentially diffuse from the interior of the powder to the surface and react with oxygen in the atmosphere, thereby generating a dense, uniform metal oxide transition layer with extremely high bonding strength to the matrix in situ.

[0064] In one possible implementation, the ferrite in the ferrite insulating layer is selected from any one of Ni-Zn ferrite, Mn-Zn ferrite, Cu-Zn ferrite, Ni-Cu-Zn ferrite, and Mg-Zn ferrite. The aforementioned ferrite insulating layer and the metal oxide transition layer exhibit good affinity and compatibility in chemical properties and crystal structure, enabling the formation of strong chemical bonds at the interface. This enhances the integrity and mechanical strength of the multilayer coating structure, making the coating layer less prone to cracking or peeling during subsequent harsh pressing and use.

[0065] In one possible implementation, the thickness of the metal oxide transition layer is 10-50 nm, and the thickness of the ferrite insulating layer is 20-500 nm. When the thickness of the metal oxide transition layer is 10-50 nm, it ensures the formation of a continuous and complete transition layer film on the surface of the soft magnetic powder, fully utilizing the transition layer's functions of stress relief and crack propagation inhibition, while also maximizing the retention of the magnetic properties of the soft magnetic powder. When the thickness of the ferrite insulating layer is 20-500 nm, on the one hand, it ensures the formation of a dense and continuous ferrite insulating layer; on the other hand, the thin ferrite insulating layer minimizes the dilution of the magnetic properties of the soft magnetic powder and the disruption of the magnetic circuit, allowing the compact density and magnetic properties of the magnetic powder core to approach the theoretical limits of the original soft magnetic powder, thus maximizing the magnetic properties of the magnetic powder core.

[0066] In one possible implementation, the resistivity of the magnetic powder core is ≥2×10⁻⁶. 8 Ω·sq, eddy current loss ≤240 kW / m under 100 kHz and 50 mT conditions. 3 Permeability μ e The range is 30-90, and the saturation magnetic induction intensity Bs ≥ 1.2 T. This is achieved by limiting the resistivity of the magnetic powder core to ≥ 2 × 10⁻⁶.8 Ω·sq can effectively block the eddy current path between soft magnetic powder particles, confining the eddy current within a single particle; limiting the eddy current loss of the magnetic powder core to ≤240 kW / m³ under 100 kHz and 50 mT conditions is beneficial for reducing the heat generation of the magnetic powder core during operation and improving the energy conversion efficiency, which can meet the application requirements of magnetic powder core in terms of miniaturization, lightweighting and high efficiency; by limiting the magnetic permeability μ of the magnetic powder core e With a range of 30-90, when magnetic powder cores are applied to inductors, it means that fewer coil turns are needed to obtain the required inductance, which can significantly reduce copper losses, reduce component size and overall cost; the saturation magnetic flux density Bs of the magnetic powder core is limited to ≥1.2 T, which enables the magnetic powder core to handle larger instantaneous currents and power, and has higher power handling capability and better DC bias characteristics.

[0067] Secondly, the present invention provides a method for preparing the above-mentioned magnetic powder core having an in-situ generated insulating coating layer, comprising the following steps:

[0068] S1. Soft magnetic powder is added to ferrite precursor solution and mixed evenly. Then, pH adjuster is added dropwise to adjust the pH value to 9-11. After co-deposition and solvent removal, magnetic powder coated with ferrite precursor is obtained.

[0069] S2. The magnetic powder obtained in step S1 is mixed with the epoxy resin solution, and after the solvent is evaporated, magnetic powder coated with epoxy resin and ferrite precursor is obtained.

[0070] S3. The magnetic powder obtained in step S2 is added into the mold and pressed to obtain a magnetic powder core blank.

[0071] S4. The magnetic powder core blank obtained in step S3 is subjected to heat treatment, in which a metal oxide transition layer, a ferrite insulating layer and a carbon coating layer are sequentially formed in situ on the surface of the soft magnetic powder. The heat treatment temperature is 300-1000 ℃, and the oxygen partial pressure in the heat treatment atmosphere is 20%-80% of the oxygen partial pressure in the atmosphere before heat treatment, so as to obtain a magnetic powder core with an in situ generated insulating coating layer.

[0072] The present invention provides a method for preparing a magnetic powder core with an in-situ generated insulating coating layer. This method employs a two-step coating process combined with low-temperature heat treatment to achieve in-situ generation and firm bonding of a metal oxide transition layer, a ferrite insulating layer, and a carbon coating layer. First, soft magnetic powder is added to a ferrite precursor solution and mixed uniformly. Then, a pH adjuster is added dropwise to adjust the pH to 9-11, which promotes the uniform co-deposition of the ferrite precursor on the surface of the soft magnetic powder, ensuring the uniformity of the subsequently formed ferrite insulating layer. Second, the magnetic powder coating the ferrite precursor is mixed with an epoxy resin solution. After solvent evaporation, the epoxy resin uniformly coats the surface of the ferrite precursor, further enhancing the stability of the coating structure. The epoxy resin not only acts as an insulator but also serves as a lubricant and binder, reducing wear on the mold and increasing the pressing density of the magnetic powder core green body. During subsequent heat treatment, it carbonizes to form a carbon coating layer. Subsequently, by pressing the magnetic powder into a mold, the powder particles are tightly packed together, reducing internal voids and improving the structural stability and density of the magnetic powder core. Following this, heat treatment is performed within a temperature range of 300-1000 ℃. This temperature ensures sufficient energy for the metal elements in the soft magnetic powder to diffuse to the surface while also carbonizing the epoxy resin. Combined with controlling the oxygen partial pressure in the heat treatment atmosphere to be 20%-80% of the oxygen partial pressure in the atmosphere before heat treatment, a suitable environment is provided for the formation of the metal oxide transition layer and the ferrite insulating layer. This satisfies the requirement for the metal elements in the soft magnetic powder to form the metal oxide transition layer through selective oxidation, while avoiding excessive oxidation that would lead to the formation of strongly magnetic impurities in the soft magnetic powder body, significantly reducing magnetic permeability. Without oxygen partial pressure control, direct treatment in air or pure oxygen would result in excessive oxidation of the powder surface, increasing the hysteresis loss of the magnetic powder core. Furthermore, the steps of the above preparation method are relatively simple to operate, and the raw materials (such as soft magnetic powder, ferrite precursor, epoxy resin, etc.) and equipment (ordinary stirring equipment, molds, heat treatment furnaces, etc.) involved are common in industrial production, easy to obtain and operate, have high process feasibility, and are suitable for large-scale industrial production.

[0073] In one possible implementation, the specific process of the heat treatment is as follows: First, the magnetic powder core blank described in step S3 is placed in the sample chamber of the heat treatment device, and carbon powder is arranged around the magnetic powder core blank. The temperature inside the sample chamber is raised to 450-520 ℃ and held for 10-20 min, then argon gas is introduced for purging for 5-10 min. After that, the argon gas is stopped, and the temperature is held for another 10-20 min, and then argon gas is introduced for purging for another 5-10 min. This process is repeated multiple times until the heat treatment is completed. The carbon powder arranged around the magnetic powder core blank can consume the free oxygen in the sample chamber through oxidation reaction, stabilizing the oxygen partial pressure within the optimal range (20%-80%) required for "metal element oxidation to form a transition layer" and "ferrite precursor crystallization". Purging with argon gas (an inert gas) for 5-10 min after each holding period can quickly remove the CO2 / CO gas generated by carbon powder oxidation in the sample chamber, preventing its accumulation and causing abnormal local oxygen partial pressure. The "heat preservation-purging" cycle mode can ensure that the oxidation reaction proceeds fully and maintain the purity of the atmosphere through purging, thus ensuring the uniformity of the composition of the transition layer and the ferrite layer.

[0074] Furthermore, the carbon powder accounts for 0.2 wt.%-2 wt.% of the mass of the magnetic powder core green body. When the carbon powder accounts for 0.2 wt.%-2 wt.% of the mass of the magnetic powder core green body, during each heat treatment stage, the carbon powder slowly consumes the trace amount of oxygen that has permeated in, maintaining the oxygen partial pressure in the heat treatment atmosphere at 20%-80% of the oxygen partial pressure in the atmosphere before heat treatment. This satisfies the requirement for the oxidation of elements such as Cr and Al to form a dense transition layer, and also ensures the crystallization of the ferrite precursor to form a Ni-Zn ferrite spinel structure.

[0075] In one possible implementation, the pH adjuster in step S1 is selected from any one of NaOH solution, KOH solution, and ammonia solution. The dissociation products of NaOH and KOH are Na+. + / K + With OH - Na + K + It belongs to light metal ions and can evaporate with the moisture in subsequent solvent removal steps (such as drying) or escape in gaseous form during heat treatment, leaving no residue in the system; the dissociation product of ammonia water is NH4. + With OH - NH4 + During the drying or low-temperature preheating stage, it can be decomposed into NH3 and H2O and volatilized without any solid impurities remaining; the three regulators achieve pH control without impurities remaining, ensuring the intrinsic magnetic properties of the soft magnetic powder.

[0076] In one possible implementation, the mixing in step S1 is carried out under stirring conditions, with a stirring speed of 200-600 rpm and a co-deposition temperature of 40-90 °C. Limiting the stirring speed to 200-600 rpm breaks down the mass transfer resistance of the system, ensuring sufficient contact between the soft magnetic powder and the ferrite precursor solution, while suppressing the spontaneous agglomeration of precursor particles. The co-deposition temperature of 40-90 °C significantly increases the reaction rate of the endothermic co-deposition reaction, improving production efficiency. Furthermore, the ferrite precursor solution achieves optimal co-deposition on the surface of the soft magnetic powder.

[0077] In one possible implementation, the epoxy resin in the epoxy resin solution in step S2 has a mass fraction of 2-15 wt.%. Limiting the mass fraction of epoxy resin in the epoxy resin solution to 2 wt.%-15 wt.% ensures that epoxy resin molecules are fully adsorbed on the surface of the magnetic powder to form a uniformly thick epoxy resin coating layer, while also preventing magnetic powder agglomeration and ensuring that each magnetic powder particle is protected by an independent resin film layer.

[0078] In one possible implementation, the pressing pressure in step S3 is 500-2200 MPa. Limiting the pressing pressure to 500-2200 MPa overcomes the van der Waals forces between particles and the elastic resistance of the resin film, forcing the magnetic powder particles to adhere tightly, ultimately increasing the green packing density of the magnetic powder core to 4.2-7.0 g / cm³. 3 .

[0079] Thirdly, the present invention provides the application of the above-mentioned magnetic powder core with an in-situ generated insulating coating in power inductors, transformers or filters.

[0080] The technical solution of the present invention will be further described below with reference to specific embodiments and comparative examples. All reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing. The instruments used in the embodiments are also commercially available.

[0081] Example 1

[0082] This embodiment provides a magnetic powder core with an in-situ generated insulating coating, which is prepared by the following steps:

[0083] S0. Preparation of ferrite precursor solution: Weigh 0.17 g of NiCl2, 0.16 g of ZnCl2 and 1.3 g of Fe(OH)2, dissolve them in deionized water to prepare a precursor mixed solution; separately prepare a 1 mol / L NaOH solution to adjust the pH value of the precursor mixed solution; place the above precursor mixed solution in a water bath at 80℃, and then add the prepared NaOH solution dropwise while stirring, until the pH value of the precursor mixed solution stabilizes at 10±0.3, thus obtaining the ferrite precursor solution;

[0084] S1, Ferrite precursor coating: 10 g of Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder was added to the ferrite precursor solution prepared in step S0, and the Fe content was controlled. 73 Si 11 B 11 The solid-liquid ratio of C3Cr2 amorphous nanocrystalline soft magnetic powder to ferrite precursor solution was 1 g: 10 mL. The stirring device was started and stirred uniformly at 300 r / min for 10 min to fully disperse the Fe-Si-BC-Cr amorphous nanocrystalline soft magnetic powder in the ferrite precursor solution, resulting in a mixed system. After stirring, 1 mol / L NaOH solution was added dropwise to adjust the pH of the mixed system until the pH value stabilized at 10 ± 0.3. Stirring was stopped, and the mixed system was allowed to stand in an 80 ℃ water bath for 2 h to allow the ferrite precursor to fully deposit on the surface of the soft magnetic powder. After deposition, the mixed system was filtered, the filter cake was collected, and then dried in an 80 ℃ oven for 2 h to obtain soft magnetic powder coated with the ferrite precursor (referred to as magnetic powder@ferrite precursor).

[0085] S2. Epoxy Resin Coating: Prepare an acetone-epoxy resin solution, wherein the mass fraction of epoxy resin is 2 wt.%; add the magnetic powder@ferrite precursor obtained in step S1 to the acetone-epoxy resin solution, controlling the amount of epoxy resin added to be 2 wt% of the total mass of the magnetic powder@ferrite precursor; then place it in a water bath at 50 ℃ and stir at 400 r / min until the acetone is completely evaporated, so that the epoxy resin is uniformly coated on the surface of the magnetic powder@ferrite precursor; then place the epoxy resin-coated magnetic powder in an oven at 80 ℃ for 2 h to obtain a soft magnetic powder with a surface coated with epoxy resin and ferrite precursor (referred to as magnetic powder@ferrite precursor@epoxy resin composite powder).

[0086] S3. Press molding: The magnetic powder@ferrite precursor@epoxy resin composite powder obtained in step S2 is loaded into a ring mold and pressed under a pressure of 1800 MPa for 60 s to obtain a ring-shaped magnetic powder core blank.

[0087] S4. Annealing treatment: Place the annular magnetic powder core green blank obtained in step S3 into a tube annealing furnace. Evenly place carbon powder around the annular magnetic powder core green blank, with the mass of carbon powder accounting for 1.6 wt.% of the mass of the annular magnetic powder core green blank. Control the oxygen partial pressure in the atmosphere inside the annealing furnace to maintain 20% of the oxygen partial pressure in the atmosphere before heat treatment. Start the tube annealing furnace and begin heating at a rate of 5 ℃ / min until the temperature reaches 480 ℃. Hold the temperature at 480 ℃ for 15 min, then introduce an argon gas flow at a rate of 40 mL / min for 5 min. After that, stop the argon gas flow, continue holding the temperature for 15 min, and then introduce argon gas for 5 min again. Repeat this process 3 times to ensure a stable atmosphere inside the furnace and to achieve ferrite sintering at a lower temperature and the formation of a Cr element oxide layer. Then, cool the temperature to room temperature at a rate of 3 ℃ / min and remove the finished magnetic powder core with a ferrite and Cr element transition coating layer.

[0088] Example 2

[0089] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 1 in that:

[0090] In step S4, the mass of carbon powder accounts for 1.2 wt.% of the mass of the annular magnetic powder core green blank, and the oxygen partial pressure in the atmosphere inside the annealing furnace is controlled to be maintained at 40% of the oxygen partial pressure in the atmosphere before heat treatment.

[0091] Example 3

[0092] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 1 in that:

[0093] In step S4, the mass of carbon powder accounts for 0.8 wt.% of the mass of the annular magnetic powder core green blank, and the oxygen partial pressure in the atmosphere inside the annealing furnace is controlled to be maintained at 60% of the oxygen partial pressure in the atmosphere before heat treatment.

[0094] Example 4

[0095] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 1 in that:

[0096] In step S4, the mass of carbon powder accounts for 0.4 wt.% of the mass of the annular magnetic powder core green blank, and the oxygen partial pressure in the atmosphere inside the annealing furnace is controlled to be maintained at 80% of the oxygen partial pressure in the atmosphere before heat treatment.

[0097] Example 5

[0098] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0099] Replace NiCl2 with MnCl2;

[0100] Replace NaOH with KOH;

[0101] Fe 85 Si 9.6 Al 5.4 Alloy powder replacing Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0102] Example 6

[0103] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0104] Replace NiCl2 with MnCl2;

[0105] Replace NaOH with KOH;

[0106] Fe 48 Ni 32 Cr 20 Alloy powder replacing Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0107] Example 7

[0108] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0109] Replace NiCl2 with MnCl2;

[0110] Replace NaOH with KOH;

[0111] Fe 72 Ni 27 Ti alloy powder replaces Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0112] Example 8

[0113] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0114] Replace NiCl2 with MnCl2;

[0115] Replace NaOH with KOH;

[0116] Fe 91 Cr9 alloy powder replaces Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0117] Example 9

[0118] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0119] Replace NiCl2 with CuCl2;

[0120] Replace NaOH with KOH;

[0121] Fe 85 Si 9.6 Al 5.4 Alloy powder replacing Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0122] Example 10

[0123] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0124] Replace NiCl2 with CuCl2;

[0125] Replace NaOH with KOH;

[0126] Fe 48 Ni 32 Cr 20 Alloy powder replacing Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0127] Example 11

[0128] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0129] Replace NiCl2 with CuCl2;

[0130] Replace NaOH with KOH;

[0131] Fe 72 Ni 27 Ti alloy powder replaces Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0132] Example 12

[0133] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0134] Replace NiCl2 with CuCl2;

[0135] Replace NaOH with KOH;

[0136] Fe 91 Cr9 alloy powder replaces Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0137] Example 13

[0138] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0139] The ferrite precursor solution also contains CuCl2, and the mass of CuCl2 is 0.12 g;

[0140] Replace NaOH with ammonia;

[0141] Fe 85 Si 9.6 Al 5.4 Alloy powder replacing Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0142] Example 14

[0143] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0144] The ferrite precursor solution also contains CuCl2, and the mass of CuCl2 is 0.12 g;

[0145] Replace NaOH with ammonia;

[0146] Fe 48 Ni 32 Cr 20 Alloy powder replacing Fe73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0147] Example 15

[0148] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0149] The ferrite precursor solution also contains CuCl2, and the mass of CuCl2 is 0.12 g;

[0150] Replace NaOH with ammonia;

[0151] Fe 72 Ni 27 Ti alloy powder replaces Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0152] Example 16

[0153] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0154] The ferrite precursor solution also contains CuCl2, and the mass of CuCl2 is 0.12 g;

[0155] Replace NaOH with ammonia;

[0156] Fe 91 Cr9 alloy powder replaces Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0157] Example 17

[0158] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0159] Replace NiCl2 with MgCl2;

[0160] Replace NaOH with ammonia;

[0161] Fe 85 Si 9.6 Al 5.4 Alloy powder replacing Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0162] Example 18

[0163] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0164] Replace NiCl2 with MgCl2;

[0165] Replace NaOH with ammonia;

[0166] Fe 48 Ni 32 Cr 20 Alloy powder replacing Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0167] Example 19

[0168] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0169] Replace NiCl2 with MgCl2;

[0170] Replace NaOH with ammonia;

[0171] Fe 72 Ni 27 Ti alloy powder replaces Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0172] Example 20

[0173] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0174] Replace NiCl2 with MgCl2;

[0175] Replace NaOH with ammonia;

[0176] Fe 91 Cr9 alloy powder replaces Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0177] Example 21

[0178] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0179] Fe73 Si 11 B 11 The solid-liquid ratio of C3Cr2 amorphous nanocrystalline soft magnetic powder to ferrite precursor solution is 1 g: 3 mL, the mass fraction of epoxy resin in epoxy resin solution is 10 wt.%, and the solvent of epoxy resin solution is ethanol.

[0180] Example 22

[0181] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0182] Fe 73 Si 11 B 11 The solid-liquid ratio of C3Cr2 amorphous nanocrystalline soft magnetic powder to ferrite precursor solution is 1 g: 5 mL, and the mass fraction of epoxy resin in epoxy resin solution is 15 wt.%.

[0183] Example 23

[0184] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0185] The pressing pressure is 1550 MPa, and the time is 60 s;

[0186] The annealing furnace is heated to 350 ℃.

[0187] Example 24

[0188] This embodiment provides a magnetic powder core with an in-situ generated insulating coating layer, the preparation process of which differs from that of Embodiment 3 in that:

[0189] The pressing pressure is 2200 MPa, and the time is 30 seconds;

[0190] The annealing furnace is heated to 1000 ℃.

[0191] Comparative Example 1

[0192] This comparative example provides a carbon-coated magnetic powder core, which is prepared through the following steps:

[0193] S1. Epoxy Resin Coating: Prepare an acetone-epoxy resin solution, wherein the mass fraction of epoxy resin is 5 wt.%. Add Fe... 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder was added to an acetone-epoxy resin solution, with the amount of epoxy resin added controlled to be Fe. 73 Si 11 B 112 wt% of the total mass of C3Cr2 amorphous nanocrystalline soft magnetic powder was then placed in a water bath at 50 ℃ and stirred at 400 r / min until the acetone was completely evaporated, allowing the epoxy resin to uniformly coat the Fe. 73 Si 11 B 11 The surface of C3Cr2 amorphous nanocrystalline soft magnetic powder is then coated with epoxy resin and dried in an oven at 80 ℃ for 2 h to obtain Fe2O3 surface-coated magnetic powder. 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder;

[0194] S2, Compression Molding: The surface of the material obtained in step S1 is coated with epoxy resin Fe 73 Si 11 B 11 C3Cr2 amorphous nanocrystalline soft magnetic powder is loaded into a ring mold and pressed into shape under a pressure of 1800 MPa for 40 s to obtain a ring-shaped magnetic powder core green body.

[0195] S3. Annealing treatment: The annular magnetic powder core green blank obtained in step S2 is placed in a tube annealing furnace. The tube annealing furnace is started and the temperature is raised at a rate of 5 ℃ / min until it reaches 480 ℃. The temperature is then maintained at 480 ℃ for 1 h. The temperature is then lowered to room temperature at a rate of 3 ℃ / min. The carbon-coated magnetic powder core finished product is then obtained.

[0196] Comparative Example 2

[0197] This comparative example provides a magnetic powder core with a composite coating layer, the preparation process of which differs from that of Example 3 in that:

[0198] S4. Annealing treatment: Place the annular magnetic powder core green blank obtained in step S3 into a tube annealing furnace, start the tube annealing furnace, and first perform a vacuum treatment inside the furnace to a vacuum degree of 1×10⁻⁶. -3 Then, the temperature was increased at a rate of 5 °C / min until it reached 480 °C. The temperature was then maintained at 480 °C for 1 hour, and then cooled to room temperature at a rate of 3 °C / min. The resulting magnetic powder core with a composite coating was then obtained.

[0199] Comparative Example 3

[0200] This comparative example provides a magnetic powder core with a composite coating layer, the preparation process of which differs from that of Example 3 in that:

[0201] S4. Annealing treatment: Place the annular magnetic powder core green blank obtained in step S3 into a tube annealing furnace, start the tube annealing furnace, start heating, the heating rate is 5 ℃ / min, and the temperature is raised to 480 ℃; continue to hold at 480 ℃ for 1 h, and then cool down to room temperature at a cooling rate of 3 ℃ / min, and take out the finished magnetic powder core with composite coating layer.

[0202] The performance of the magnetic powder cores in Examples 1-24 and Comparative Examples 1-3 was tested, and the results are as follows.

[0203] Figure 1 This is a cross-sectional view of the magnetic powder core prepared in Example 1. As shown in the figure, the magnetic powder core prepared in Example 1 has a multi-layered core-shell structure, Fe... 73 Si 11 B 11 The outer surface of C3Cr2 magnetic powder particles is sequentially coated with an oxide transition layer formed by in-situ enrichment of Cr, a ferrite insulating layer, and a carbon coating layer. As can be seen from the figure, there are no gaps between these layers, and the coating layer and Fe... 73 Si 11 B 11 The C3Cr2 magnetic powder particles are well bonded.

[0204] Figure 2 This is an elemental line distribution analysis diagram of a local cross-section of the magnetic powder core prepared in Example 1. A comparison of the scanning path (red-marked area) in the upper square region with the curves showing the change in elemental signal intensity with distance below reveals that the signal intensity of Cr element has a certain distribution in the initial stage, and then gradually decreases. This indicates that Cr element may exist near the surface or in a specific transition region, which is consistent with the mechanism of Cr element in-situ diffusion on the surface of soft magnetic powder to form an oxide transition layer. That is, Cr is enriched on the surface of the magnetic powder, and then the Cr content decreases with increasing depth (distance). The scanning path covers the structural regions from the organic coating layer (containing C), the ferrite coating layer (containing Fe, Ni, and Zn, etc.), the Cr transition layer, and the soft magnetic powder matrix. The decay of carbon, the transition of Cr, and the enrichment of Fe on the surface and inside correspond to the differences in elemental composition between the organic coating layer, the ferrite layer, the transition layer, and the matrix. This reflects the gradient change characteristics of the elemental distribution in the multilayer coating structure, which is consistent with the expected results of the elemental distribution of the multilayer structure formed by in-situ diffusion and coating processes in Example 1. This verifies the effectiveness of the relevant processes in controlling elemental distribution.

[0205] Figure 3 Fe in Example 1 73 Si 11 B 11 SEM images and EDS spectra of C3Cr2 amorphous nanocrystalline soft magnetic powder before and after coating with ferrite precursor. Figure 3 Figure (a) shows Fe before coating. 73 Si 11 B 11 The images show the SEM images of C3Cr2 amorphous nanocrystalline soft magnetic powder, (b) the coated magnetic powder, (c) the EDS energy spectrum of Ni, (d) the EDS energy spectrum of Zn, (e) the EDS energy spectrum of O, (f) the EDS energy spectrum of Si, (g) the EDS energy spectrum of Cr, and (h) the EDS energy spectrum of Fe. As can be seen from the images, the coated Fe... 73 Si 11 B 11 The surface of the C3Cr2 amorphous nanocrystalline soft magnetic powder becomes rough, and the ferrite precursor coated by chemical deposition has been uniformly distributed in the Fe. 73 Si 11 B 11 The surface of C3Cr2 amorphous nanocrystalline soft magnetic powder.

[0206] Figure 4 The figures show the effective permeability data of the magnetic powder cores prepared in Examples 1-4 and Comparative Examples 1-3. As can be seen from the figures, the effective permeability of the magnetic powder cores prepared in Examples 1-4 is generally higher than that of the magnetic powder cores prepared in Comparative Examples 2 (vacuum heat treatment) and 3 (air heat treatment). The effective permeability of the magnetic powder cores prepared in Examples 1 and 2 is comparable to that of Comparative Example 1, while the effective permeability of the magnetic powder cores prepared in Examples 3 and 4 is significantly higher than that of Comparative Example 1. Among them, the magnetic powder core prepared in Example 3 has the highest and most stable permeability, maintaining high permeability over a wide frequency range; the permeability of Comparative Example 3 is the lowest and fluctuates greatly. This indicates that Examples 1-4 significantly improved the magnetic permeability of soft magnetic materials at mid-to-high frequencies through multilayer coating, element diffusion, and other techniques, while Comparative Examples 1-3 have lower permeability and insufficient stability due to the lack of a metal oxide transition layer or poor ferrite coating.

[0207] Figure 5 The graph shows the magnetization data of the magnetic powder cores prepared in Examples 1-4 and Comparative Examples 1-3. As can be seen from the graph, the magnetization saturation values ​​of the magnetic powder cores prepared in Examples 1-4 are generally higher than those in Comparative Examples 1-3. The positive saturation magnetization of Example 3 (oxygen partial pressure of 60%) is close to 150 emu / g, while the positive saturation magnetization of Comparative Examples 2 and 3 is significantly lower. This indicates that the magnetic powder cores in Examples 1-4, which utilize in-situ diffusion-formed metal oxide transition layer, ferrite insulating layer, and carbon coating layer technology, have stronger magnetization capabilities, meaning they are more easily magnetized by a magnetic field and have superior magnetic properties.

[0208] Figure 6The figures show the quality factor data for the magnetic powder cores prepared in Examples 1-4 and Comparative Examples 1-3. The quality factor Q reflects the energy utilization efficiency of soft magnetic materials under an alternating magnetic field. A higher Q value indicates lower magnetic loss and better energy transfer or storage efficiency. The peak quality factor of the magnetic powder cores prepared in Examples 1-4 is significantly higher than that of the magnetic powder cores prepared in Comparative Examples 1-3. The peak value of the magnetic powder core prepared in Example 3 is close to 70, while the peak value of Comparative Example 3 is only about 50. This indicates that the magnetic powder cores in Examples 1-4, which utilize in-situ diffusion-formed metal oxide transition layer, ferrite insulating layer, and carbon coating layer technology, have lower energy loss and better performance at medium and high frequencies.

[0209] Figure 7 The graphs show the iron loss data of the magnetic powder cores prepared in Examples 1-4 and Comparative Examples 1-3. Iron loss reflects the energy loss of soft magnetic materials in an alternating magnetic field due to effects such as hysteresis and eddy currents. The lower the iron loss, the higher the energy utilization efficiency of the soft magnetic material. Comparing the iron loss data of the magnetic powder cores prepared in Examples 1-4 and Comparative Examples 1-3 at different frequencies, it can be seen that the iron loss of the magnetic powder cores prepared in Examples 1-4 is significantly lower than that of the magnetic powder cores prepared in Comparative Examples 1-3. At the same frequency (e.g., 100 kHz), the magnetic powder core prepared in Example 3 has the lowest iron loss. This indicates that the magnetic powder cores in Examples 1-4, which utilize in-situ diffusion-formed metal oxide transition layer, ferrite insulating layer, and carbon coating layer technology, have lower energy loss and better performance at mid-frequency.

[0210] Figure 8 The graph shows the hysteresis loss data of the magnetic powder cores prepared in Examples 1-4 and Comparative Examples 1-3. Hysteresis loss reflects the energy loss of soft magnetic materials due to repeated domain flipping in an alternating magnetic field. The lower the hysteresis loss, the higher the energy utilization efficiency of the soft magnetic material. Comparing the hysteresis loss data of the magnetic powder cores prepared in Examples 1-4 and Comparative Examples 1-3 at different frequencies, it can be seen that the hysteresis loss of the magnetic powder cores prepared in Examples 1-4 is significantly lower than that of the magnetic powder cores prepared in Comparative Examples 1-3. This indicates that the magnetic powder cores in Examples 1-3, which utilize in-situ diffusion-formed metal oxide transition layer, ferrite insulating layer, and carbon coating layer technology, have lower domain flipping loss and better performance at mid-frequency.

[0211] Figure 9The figures show eddy current loss data for the magnetic powder cores prepared in Examples 1-4 and Comparative Examples 1-3. Eddy current loss reflects the energy loss of soft magnetic materials due to induced eddy currents in an alternating magnetic field. The lower the eddy current loss, the higher the energy utilization efficiency of the soft magnetic material. Under a magnetic field of 20 mT, the eddy current loss of the magnetic powder cores prepared in Examples 1-4 is significantly lower than that of the magnetic powder cores prepared in Comparative Examples 1-3. At the same frequency (e.g., 800 kHz), the eddy current loss of the magnetic powder core prepared in Example 3 is the lowest. This indicates that the magnetic powder cores in Examples 1-4, which employ in-situ diffusion-formed metal oxide transition layer, ferrite insulating layer, and carbon coating layer technology, have lower eddy current loss and better performance at mid-frequency.

[0212] Figure 10 This is a flowchart of the preparation of the magnetic powder core in Example 1. It mainly includes five steps: preparing a ferrite precursor solution, coating the ferrite precursor, coating with epoxy resin, hot pressing, and annealing.

[0213] The resistivity of the magnetic powder cores prepared in Example 2 and Comparative Example 1 was tested. The resistivity of the magnetic powder core prepared in Comparative Example 1 was measured to be 1.31 × 10⁻⁶. 8 The resistivity of the magnetic powder core prepared in Example 2 is 2.4 × 10⁻⁶ Ω·sq, while the resistivity of the magnetic powder core prepared in Example 2 is 2.4 × 10⁻⁶ Ω·sq. 8 Ω·sq. This indicates that the magnetic powder core provided by this invention has a higher resistivity.

[0214] Table 1 shows the magnetic properties of the magnetic powder cores prepared in Examples 1-24 and Comparative Examples 1-3. The data in the table show that the magnetic powder cores prepared in Examples 1-24 exhibit significantly lower eddy current losses at 50 mT and 100 kHz than those in Comparative Examples 1-3, and their effective permeability is between 32 and 86. This indicates that the magnetic powder cores with in-situ generated insulating coatings provided by this invention not only reduce eddy current losses but also possess high effective permeability.

[0215] Table 1. Magnetic property data of the magnetic powder cores prepared in Examples 1-24 and Comparative Examples 1-3

[0216]

[0217] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A magnetic powder core with an in-situ generated insulating coating, characterized in that, include: Soft magnetic powder; An in-situ metal oxide transition layer is generated to coat the surface of the soft magnetic powder. The metal oxide transition layer is formed by controlling the oxygen partial pressure in the heat treatment atmosphere to enrich, diffuse and oxidize the metal elements in the soft magnetic powder to the surface. The metal elements in the metal oxide transition layer are selected from at least one of Cr, Al and Ti, and the soft magnetic powder contains the metal elements. A ferrite insulating layer is generated in situ to coat the surface of the metal oxide transition layer. The ferrite insulating layer is formed by crystallizing the ferrite precursor coated on the surface of the metal oxide transition layer through the heat treatment. A carbon coating layer is generated in situ to coat the surface of the ferrite insulating layer. The carbon coating layer is formed by carbonizing the epoxy resin coated on the surface of the ferrite precursor through the heat treatment.

2. The magnetic powder core with an in-situ generated insulating coating layer according to claim 1, characterized in that, The soft magnetic powder is selected from at least one of Fe-Si-BC-Cr amorphous nanocrystalline soft magnetic powder, Fe-Si-Al alloy powder, Fe-Ni-Cr alloy powder, Fe-Ni-Ti alloy powder, and Fe-Cr alloy powder.

3. The magnetic powder core with an in-situ generated insulating coating layer according to claim 1, characterized in that, The ferrite is selected from any one of Ni-Zn ferrite, Mn-Zn ferrite, Cu-Zn ferrite, Ni-Cu-Zn ferrite and Mg-Zn ferrite.

4. The magnetic powder core with an in-situ generated insulating coating layer according to claim 1, characterized in that, The thickness of the metal oxide transition layer is 10-50 nm, and the thickness of the ferrite insulating layer is 20-500 nm.

5. The magnetic powder core with an in-situ generated insulating coating layer according to claim 1, characterized in that, The resistivity of the magnetic powder core is ≥2×10⁻⁶. 8 Ω·sq, eddy current loss ≤240 kW / m under 100 kHz and 50 mT conditions. 3 Permeability μ e The range is 30-60, and the saturation magnetic induction intensity Bs ≥ 1.2 T.

6. A method for preparing a magnetic powder core with an in-situ generated insulating coating as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Soft magnetic powder is dispersed in a ferrite precursor solution and mixed evenly. Then, a pH adjuster is added dropwise until the pH value is 9-11. After co-deposition and solvent removal, magnetic powder coated with ferrite precursor is obtained. S2. The magnetic powder obtained in step S1 is mixed with the epoxy resin solution, and after the solvent is evaporated, magnetic powder coated with epoxy resin and ferrite precursor is obtained. S3. The magnetic powder obtained in step S2 is added into the mold and pressed to obtain a green magnetic powder core. S4. The magnetic powder core blank obtained in step S3 is subjected to heat treatment, in which a metal oxide transition layer, a ferrite insulating layer and a carbon coating layer are sequentially formed in situ on the surface of the soft magnetic powder. The heat treatment temperature is 300-1000 ℃, and the oxygen partial pressure in the heat treatment atmosphere is 20%-80% of the oxygen partial pressure in the atmosphere before heat treatment, so as to obtain a magnetic powder core with an in situ generated insulating coating layer.

7. The preparation method according to claim 6, characterized in that, The specific process of the heat treatment is as follows: First, the magnetic powder core blank described in step S3 is placed in the sample chamber of the heat treatment device, and carbon powder is arranged around the magnetic powder core blank. The temperature in the sample chamber is raised to 450-520 ℃ and held for 10-20 min. Then, argon gas is introduced to purge for 5-10 min. After that, the argon gas is stopped, and the temperature is held for another 10-20 min. Then, argon gas is introduced to purge for another 5-10 min. This process is repeated multiple times until the heat treatment is completed.

8. The preparation method according to claim 7, characterized in that, The carbon powder accounts for 0.2 wt.%-2 wt.% of the mass of the magnetic powder core green body.

9. The preparation method according to claim 6, characterized in that, The pH adjuster mentioned in step S1 is selected from any one of NaOH solution, KOH solution, and ammonia water.

10. The preparation method according to claim 6, characterized in that, The mixing in step S1 is carried out under stirring conditions, the stirring speed is 200-600 rpm, and the co-deposition temperature is 40-90 ℃.

11. The preparation method according to claim 6, characterized in that, The epoxy resin in the epoxy resin solution in step S2 has a mass fraction of 2 wt.%-15 wt.%.

12. The preparation method according to claim 6, characterized in that, The pressing pressure described in step S3 is 500-2200 MPa.

13. The application of the magnetic powder core with an in-situ generated insulating coating as described in any one of claims 1-5 in power inductors, transformers or filters.

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