A method for preparing a FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder core

Abstract

This invention belongs to the field of integrally molded inductor materials and provides a method for preparing FeSiBCuNb nanocrystalline / carbonyl iron composite magnetic powder cores to solve the problems of low thermal conductivity, high high-frequency loss, and poor interfacial bonding between inorganic fillers and the matrix in existing technologies. Firstly, by optimizing the gradation of FeSiBCuNb nanocrystalline powder and carbonyl iron powder, the density of the composite magnetic powder core is significantly improved by utilizing the filling effect of powders with different particle sizes. An in-situ phosphating passivation process is introduced before mixing to construct a first dense insulating layer on the surface of the metal particles. Then, h-BN and the silane coupling agent KH550 are introduced to construct a strong metal-organic-inorganic interfacial bonding system, achieving a dual breakthrough in thermal conductivity and magnetic properties. Simultaneously, the h-BN layer and the outer resin layer together constitute a multi-layer insulating structure, effectively cutting off high-frequency eddy current losses and significantly reducing magnetic losses, thereby preparing a high-performance composite magnetic powder core with both high thermal conductivity and low loss characteristics.

Description

Technical Field

[0001] This invention belongs to the field of integrally molded inductor materials, specifically providing a method for preparing FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder cores. Background Technology

[0002] With the widespread application of third-generation semiconductors (SiC, GaN) in new energy and high-frequency power supply fields, magnetic components are developing towards higher frequency and higher power density. As core passive components, integrally molded inductors require the magnetic powder core to carry a larger current within a limited package volume. This inevitably leads to a sharp increase in the loss density per unit volume inside the device. These losses will eventually be converted into heat energy. If the heat cannot be dissipated in time, it will seriously affect the magnetic performance and reliability of the device. At present, soft magnetic composite materials mostly use epoxy resin or silicone resin as insulating coating agents. Although they can effectively reduce eddy current losses, the resin itself has extremely low thermal conductivity, forming a thermal barrier layer between the magnetic powder particles. This makes it difficult for the heat accumulated inside the magnetic powder core to dissipate quickly, becoming a bottleneck restricting the heat dissipation performance of the magnetic powder core.

[0003] Hexagonal boron nitride (h-BN), a two-dimensional material with a graphite-like layered structure, possesses both excellent electrical insulation and extremely high in-plane thermal conductivity. Studies have shown that introducing h-BN into magnetic powder cores can improve particle flowability during the pressing process, and h-BN, as an insulating and thermally conductive filler, can construct an effective thermal conduction network between particles. However, in practical applications, directly adding h-BN often faces significant technical challenges. First, the h-BN surface exhibits high chemical inertness and low surface energy, resulting in extremely poor interfacial compatibility with metal magnetic powder and organic resins. It is difficult to achieve uniform coating through simple physical mixing, easily causing interfacial delamination and leading to a significant decrease in mechanical strength. Second, the nanoscale h-BN sheets have a huge specific surface area, making them prone to agglomeration under van der Waals forces. These agglomerates not only fail to form continuous thermal conduction pathways but also become obstacles to magnetic flux flow, leading to a decrease in the density and permeability of the magnetic powder core.

[0004] To improve the dispersion of h-BN in composite magnetic powder systems, existing technologies mostly employ physical mixing methods such as mechanical ball milling. For example, patent document CN113593801A proposes a method for preparing soft magnetic composite materials by mixing h-BN with metal magnetic powder through ball milling. Although this method can improve the mixing uniformity, it still has significant shortcomings: high-energy ball milling easily destroys the two-dimensional lamellar structure of h-BN, weakening its thermal conductivity, and at the same time introduces residual stress inside the metal magnetic powder, leading to increased coercivity and exacerbating high-frequency hysteresis loss.

[0005] Therefore, relying solely on mechanical ball milling or traditional resin blending processes makes it difficult to simultaneously achieve low loss and high heat dissipation performance. There is an urgent need to develop a preparation process that can effectively improve the surface activity of h-BN, enabling it to oriented and firmly bond with the resin matrix on the magnetic powder surface, thereby overcoming the thermal management challenges of the magnetic powder core while ensuring low loss. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing FeSiBCuNb nanocrystalline / carbonyl iron composite magnetic powder cores, in order to solve the problems of low thermal conductivity, high high-frequency loss, and poor interfacial bonding between inorganic fillers and the matrix in existing technologies. This invention adopts an interfacial coupling and double insulation strategy, using the silane coupling agent KH550 as a molecular bridge to directionally coat the highly thermally conductive h-BN onto the surface of the phosphated mixed magnetic powder, and combining it with composite resin coating to construct a dense insulating and thermally conductive network, thereby significantly improving the thermal conductivity of the material while reducing high-frequency magnetic loss.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder cores, characterized by comprising the following steps:

[0009] Step 1: Prepare an organic solvent containing phosphoric acid as a passivation solution, and completely immerse FeSiBCuNb nanocrystalline powder and carbonyl iron powder in it. Stir continuously at room temperature to carry out the surface passivation reaction, and generate a dense phosphate insulating layer (phosphating layer) in situ on the surface of the metal particles. This step can effectively passivate the surface of the magnetic powder and reduce eddy current loss. The treated powder is sieved and dried to obtain passivated magnetic powder with an insulating layer on the surface.

[0010] Step 2: Mix the passivated FeSiBCuNb nanocrystalline powder obtained in Step 1 with the passivated carbonyl iron powder at a predetermined mass ratio to improve the packing density by utilizing the gradation effect of powders with different particle sizes, and use it as a composite matrix powder for modification.

[0011] Step 3: Disperse the composite matrix powder from Step 2 in anhydrous ethanol to form a suspension; simultaneously, pre-hydrolyze the silane coupling agent KH550 in ethanol and deionized water; under stirring conditions, slowly add the pre-hydrolyzed silane coupling agent KH550 solution to the magnetic powder suspension, react for a certain time, and after the reaction is completed, vacuum filter and dry to allow the silanol groups of the coupling agent to undergo a condensation reaction with the phosphating layer on the surface of the magnetic powder, thereby coupling an organic layer with active amino functional groups on the surface of the magnetic powder to obtain KH550 modified magnetic powder;

[0012] Step 4: Using the high-energy cavitation effect of an ultrasonic disperser, and with the addition of 0.1~0.2 wt.% dispersant, the layered h-BN powder is fully exfoliated and dispersed in acetone to obtain a uniform and stable h-BN dispersion.

[0013] Step 5: Redisperse the KH550 modified magnetic powder obtained in step 3 in acetone solution, and slowly add the h-BN dispersion obtained in step 4 under stirring. Utilize the physical adsorption and chemical interaction between the KH550 active functional groups on the surface of the magnetic powder and the h-BN sheets to make h-BN uniformly and firmly coated on the surface of individual magnetic powder particles, forming core-shell composite particles of magnetic powder-coupling agent-hBN.

[0014] Step 6: Add an insulating resin solution composed of epoxy resin and silicone resin dropwise to the suspension in Step 5. Under continuous stirring, as the solvent evaporates, the insulating resin gradually deposits and completely coats the outside of the magnetic powder particles with attached h-BN, eventually forming a composite powder with a multilayer structure of magnetic powder-coupling agent-hBN-resin. This structure simultaneously achieves high insulation and high thermal conductivity between layers.

[0015] Step 7: Stir the above mixture at room temperature until the solvent is completely evaporated to prevent premature resin agglomeration. After the powder is loose, sieve and granulate. Then dry it in a constant temperature equipment to completely remove residual solvent.

[0016] Step 8: Fill the dried composite magnetic powder into the mold and press it into a green body of specified size under a certain pressure; then perform two heat treatments: first, cure the resin layer at a lower temperature under a protective atmosphere to fully cross-link and cure it; then perform high-temperature annealing to effectively eliminate residual stress inside the powder body and optimize the magnetic domain structure, thereby obtaining the final composite magnetic powder core product with high magnetic properties, low loss and high thermal conductivity.

[0017] Furthermore, in step 1, the passivation solution is prepared by dissolving 0.3-0.8 wt.% of phosphoric acid in 10-30 wt.% of acetone solvent, based on the mass of the magnetic powder.

[0018] Furthermore, in step 1, the passivation reaction time is 20-40 min, and the sample is passed through a 100-mesh or 200-mesh sieve; then dried at 60-80 ℃ for 1-2 h.

[0019] Furthermore, in step 2, the composite matrix powder is composed of 60-80 wt.% passivated FeSiBCuNb nanocrystalline powder and 20-40 wt.% passivated carbonyl iron powder.

[0020] Furthermore, in step 3, the amount of silane coupling agent KH550 added is 0.15~0.60 wt.% of the mass of the mixed matrix powder, the reaction time is 1~3 h, and the drying conditions are drying in an oven at 60~80 ℃ for 30~60 min.

[0021] Furthermore, in step 4, the amount of h-BN powder added is 0.5~3.0 wt.% of the mass of the mixed matrix powder, and the dispersant is BYK-110.

[0022] Furthermore, in step 4, the ultrasonic disperser is operated in pulse mode: it operates at 50%~70% power for 10~15 minutes, then pauses for 2~5 minutes, and performs ultrasonic treatment for 1~2 hours.

[0023] Furthermore, in step 6, based on the mass of the matrix powder, the content of the insulating resin is: epoxy resin: 1~2 wt.%, silicone resin: 2~4 wt.%, and the composite resin solution is composed of the insulating resins dissolved together in 10~30 wt.% acetone.

[0024] Furthermore, in step 7, the granulation is performed by passing the material through a 40-60 mesh sieve, and the drying conditions are drying at 60-80 ℃ for 0.5-2 h.

[0025] Furthermore, in step 8, the molding pressure is 615~1015 MPa, the geometric dimensions of the green blank are 10 mm outer diameter × 6 mm inner diameter × 3.2 mm height, the thermosetting treatment conditions are to hold at 150~200 ℃ in a tube furnace for 0.5~1.5 h, the high-temperature annealing treatment conditions are to hold at 450~550 ℃ in a tube furnace for 1~3 h, and the protective atmosphere is argon atmosphere.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This invention provides a method for preparing FeSiBCuNb nanocrystalline / carbonyl iron composite magnetic powder cores. Firstly, by optimizing the gradation of FeSiBCuNb nanocrystalline powder and carbonyl iron powder, the problem of limited filling density of single magnetic powder is effectively solved. Utilizing the filling effect of powders with different particle sizes, the density of the composite magnetic powder core is significantly improved. Furthermore, an in-situ phosphating passivation process is introduced before mixing to construct a first dense insulating layer on the surface of the metal particles. Based on this, this invention innovatively introduces h-BN and the silane coupling agent KH550 to construct a strong interfacial bonding system of "metal-organic-inorganic," achieving a dual breakthrough in thermal conductivity and magnetic properties. Addressing the pain points of h-BN's poor wetting and easy agglomeration, KH550 is used as a molecular bridge to construct chemical bonds between the magnetic powder and h-BN, significantly reducing phonon scattering at the interface and constructing a highly efficient phonon transport network. This causes the thermal conductivity of the composite magnetic powder core to jump to 6.78 W / (m·K) at 25 °C, significantly overcoming the thermal management bottleneck of traditional organic resins. Meanwhile, the h-BN layer and the outer resin together form a multi-layer insulation structure, effectively cutting off high-frequency eddy current losses and reducing the magnetic loss at 100 kHz@50mT to 188.13 kW / m. 3 This allows for the preparation of high-performance composite magnetic powder cores that possess both high thermal conductivity and low loss characteristics. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the preparation process of the FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder core in this invention.

[0029] Figure 2 This is a cross-sectional morphology diagram of the FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder core in this invention.

[0030] Figure 3 The images show the morphology of the FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder core and the corresponding EDS surface scan distribution of Fe, Si, and N elements in this invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Unless otherwise specified, the experimental or testing methods described in the following embodiments are conventional methods, and the materials and reagents described are obtained from conventional commercial channels unless otherwise specified.

[0032] This invention provides a FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder core and its preparation method, specifically providing three examples and one comparative example.

[0033] Example 1

[0034] This embodiment provides a method for preparing FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder cores, the process of which is as follows: Figure 1 As shown, it includes the following steps:

[0035] (1) Weigh 100 g of FeSiBCuNb nanocrystalline powder and carbonyl iron powder respectively. Dissolve 0.5 g of phosphoric acid in acetone in two containers respectively. Immerse FeSiBCuNb nanocrystalline powder and carbonyl iron powder completely in phosphating solution. Stir continuously at room temperature for 30 min. After the solvent evaporates naturally, pass the powder through a 100-mesh sieve and dry it in an 80 ℃ oven for 2 h to obtain passivated FeSiBCuNb nanocrystalline powder and passivated carbonyl iron powder with phosphate insulating layer on the surface.

[0036] (2) Weigh 70 g of passivated FeSiBCuNb nanocrystalline powder and 30 g of passivated carbonyl iron powder and mix them evenly;

[0037] (3) Weigh 0.15 g of silane coupling agent KH550 and dissolve it in anhydrous ethanol, and add deionized water for pre-hydrolysis; disperse the mixed matrix powder obtained in step (2) in anhydrous ethanol to form a suspension, and slowly add the pre-hydrolyzed KH550 solution to the powder suspension under mechanical stirring, and continue the reaction for 2 h; after the reaction is completed, filter under vacuum, and dry the filter cake at 60 ℃ for 1 h to obtain KH550 modified magnetic powder;

[0038] (4) Weigh 0.5 g of h-BN powder and add it to 10 g of acetone solvent. Add 0.1 g of dispersant BYK-110 and use an ultrasonic disperser to work at 50% power for 1 h. Use ultrasonic cavitation to peel off the interlayer of h-BN and disperse it evenly to obtain h-BN dispersion.

[0039] (5) Under mechanical stirring, the h-BN dispersion obtained in step (4) is slowly added dropwise to the KH550 modified magnetic powder suspension in step (3). The bridging effect of the KH550 molecular chain on the surface of the magnetic powder on h-BN is utilized to make h-BN adsorbed on the surface of the magnetic powder in a directional manner, forming magnetic powder-coupling agent-hBN core-shell structure particles.

[0040] (6) Weigh 1.5 g of epoxy resin and 3 g of organosilicon resin, and dissolve them together in 15 g of acetone to prepare a composite resin solution; add the composite resin solution dropwise to the suspension in step (5) and keep stirring until the solvent evaporates;

[0041] (7) After the mixed powder in step (6) is stirred at room temperature until it is dry and loose, it is granulated by passing it through a 50-mesh sieve; then the powder is placed in a 70 ℃ constant temperature oven to dry for 2 h;

[0042] (8) The composite powder prepared above is filled into a mold and pressed into an annular green blank with an outer diameter of 10 mm, an inner diameter of 6 mm and a height of 3.2 mm under a pressure of 815 MPa. The green blank is placed in a tube furnace and cured at 165 °C for 1 h under argon protection. Then it is heated to 550 °C for annealing for 2 h and naturally cooled to obtain the sample to be tested.

[0043] Example 2

[0044] This embodiment provides a method for preparing FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder cores, the process of which is as follows: Figure 1 As shown, it includes the following steps:

[0045] (1) Weigh 100 g of FeSiBCuNb nanocrystalline powder and carbonyl iron powder respectively. Dissolve 0.5 g of phosphoric acid in acetone in two containers respectively. Immerse FeSiBCuNb nanocrystalline powder and carbonyl iron powder completely in phosphating solution. Stir continuously at room temperature for 30 min. After the solvent evaporates naturally, pass the powder through a 100-mesh sieve and dry it in an 80 ℃ oven for 2 h to obtain passivated FeSiBCuNb nanocrystalline powder and passivated carbonyl iron powder with phosphate insulating layer on the surface.

[0046] (2) Weigh 70 g of passivated FeSiBCuNb nanocrystalline powder and 30 g of passivated carbonyl iron powder and mix them evenly;

[0047] (3) Weigh 0.15 g of silane coupling agent KH550 and dissolve it in anhydrous ethanol, and add deionized water for pre-hydrolysis; disperse the mixed matrix powder obtained in step (2) in anhydrous ethanol to form a suspension, and slowly add the pre-hydrolyzed KH550 solution to the powder suspension under mechanical stirring, and continue the reaction for 2 h; after the reaction is completed, filter under vacuum, and dry the filter cake at 60 ℃ for 1 h to obtain KH550 modified magnetic powder;

[0048] (4) Weigh 1.5 g of h-BN powder and add it to 10 g of acetone solvent. Add 0.1 g of dispersant BYK-110 and use an ultrasonic disperser to work at 50% power for 1 h to obtain h-BN dispersion.

[0049] (5) Under mechanical stirring, the h-BN dispersion obtained in step (4) is slowly added dropwise to the KH550 modified magnetic powder suspension in step (3). The bridging effect of the KH550 molecular chain on the surface of the magnetic powder on h-BN is utilized to make h-BN adsorbed on the surface of the magnetic powder in a directional manner, forming magnetic powder-coupling agent-hBN core-shell structure particles.

[0050] (6) Weigh 1.5 g of epoxy resin and 3 g of organosilicon resin, and dissolve them together in 15 g of acetone to prepare a composite resin solution; add the composite resin solution dropwise to the suspension in step (5) and keep stirring until the solvent evaporates;

[0051] (7) After the mixed powder in step (6) is stirred at room temperature until it is dry and loose, it is granulated by passing it through a 50-mesh sieve; then the powder is placed in a 70 ℃ constant temperature oven to dry for 2 h;

[0052] (8) The composite powder prepared above is filled into a mold and pressed into an annular green blank with an outer diameter of 10 mm, an inner diameter of 6 mm and a height of 3.2 mm under a pressure of 815 MPa. The green blank is placed in a tube furnace and cured at 165 °C for 1 h under argon protection. Then it is heated to 550 °C for annealing for 2 h and naturally cooled to obtain the sample to be tested.

[0053] Example 3

[0054] This embodiment provides a method for preparing FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder cores, the process of which is as follows: Figure 1 As shown, it includes the following steps:

[0055] (1) Weigh 100 g of FeSiBCuNb nanocrystalline powder and carbonyl iron powder respectively. Dissolve 0.5 g of phosphoric acid in acetone in two containers respectively. Immerse FeSiBCuNb nanocrystalline powder and carbonyl iron powder completely in phosphating solution. Stir continuously for 30 min at room temperature. After the solvent evaporates naturally, pass the powder through a 100-mesh sieve and dry it in an 80 ℃ oven for 2 h to obtain passivated FeSiBCuNb nanocrystalline powder and passivated carbonyl iron powder with phosphate insulating layer on the surface.

[0056] (2) Weigh 70 g of passivated FeSiBCuNb nanocrystalline powder and 30 g of passivated carbonyl iron powder and mix them evenly;

[0057] (3) Weigh 0.15 g of silane coupling agent KH550 and dissolve it in anhydrous ethanol, and add deionized water for pre-hydrolysis; disperse the mixed matrix powder obtained in step (2) in anhydrous ethanol to form a suspension, and slowly add the pre-hydrolyzed KH550 solution to the powder suspension under mechanical stirring, and continue the reaction for 2 h; after the reaction is completed, filter under vacuum, and dry the filter cake at 60 ℃ for 1 h to obtain KH550 modified magnetic powder;

[0058] (4) Weigh 2.0 g of h-BN powder and add it to 10 g of acetone solvent. Add 0.1 g of dispersant BYK-110 and use an ultrasonic disperser to work at 50% power for 1 h to obtain h-BN dispersion.

[0059] (5) Under mechanical stirring, the h-BN dispersion obtained in step (4) is slowly added dropwise to the KH550 modified magnetic powder suspension in step (3); by utilizing the bridging effect of the KH550 molecular chain on the surface of the magnetic powder on h-BN, h-BN is directionally adsorbed on the surface of the magnetic powder to form magnetic powder-coupling agent-hBN core-shell structure particles.

[0060] (6) Weigh 1.5 g of epoxy resin and 3 g of organosilicon resin, and dissolve them together in 15 g of acetone to prepare a composite resin solution; add the composite resin solution dropwise to the suspension in step (5) and keep stirring until the solvent evaporates;

[0061] (7) After the mixed powder in step (6) is stirred at room temperature until it is dry and loose, it is granulated by passing it through a 50-mesh sieve; then the powder is placed in a 70 ℃ constant temperature oven to dry for 2 h;

[0062] (8) The composite powder prepared above is filled into a mold and pressed into a ring-shaped green blank with an outer diameter of 10 mm, an inner diameter of 6 mm and a height of 3.2 mm under a pressure of 815 MPa. The green blank is placed in a tube furnace and cured at 165 °C for 1 h under argon protection. Then it is heated to 550 °C for annealing for 2 h and naturally cooled to obtain the sample to be tested.

[0063] The density of the composite magnetic powder core samples prepared in Examples 1-3 was tested using the Archimedes displacement method. After winding, the inductance L of the samples was tested using a Tonghui TH2826 precision LCR meter, and the effective permeability of the samples was calculated using a formula. The test conditions were a frequency f = 100 kHz. The magnetic loss was tested using an Iwasaki SY-8218 BH analyzer at 25 ℃ and 100 kHz @ 50 mT. The thermal conductivity of the samples was tested using a DRL-V thermal conductivity meter at 25 ℃. The test results are shown in Table 1.

[0064] Table 1. Test results of magnetic properties and thermal conductivity

[0065]

[0066] As shown in Table 1, the thermal conductivity of the FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder core in Examples 1-3 is superior to that of the prior art. In particular, in Example 2, the thermal conductivity of the composite magnetic powder core at 25 °C jumps to 6.78 W / (m·K), indicating that the present invention uses KH550 as a molecular bridge to build chemical bonds between the magnetic powder and h-BN, which greatly reduces phonon scattering at the interface and builds a highly efficient phonon transport network, thereby breaking through the thermal management bottleneck of traditional organic resins.

[0067] Furthermore, such as Figure 2The image shows a cross-sectional morphology of the FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder core in Example 1. As can be seen from the image, particles of different sizes are mixed together, with smaller powder particles uniformly filling the pores of the larger particles. Figure 3 The figure shows the morphology of the FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder core and the corresponding EDS surface scan distribution of Fe, Si and N elements in this invention. As can be seen from the figure, as a characteristic signal of h-BN, the N element is relatively completely attached to the periphery of the magnetic powder and presents a diffuse distribution state. This dispersion state helps the insulating filler to effectively encapsulate the metal particles and reduce the micropores remaining inside the structure.

[0068] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A method for preparing FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder cores, characterized in that, Includes the following steps: Step 1, Raw material passivation treatment: FeSiBCuNb nanocrystalline powder and carbonyl iron powder were respectively immersed in a passivation solution containing phosphoric acid to carry out surface passivation reaction, resulting in passivated magnetic powder with a phosphate insulating layer on the surface. Step 2, Mixing raw materials: The two passivation magnetic powders obtained in step 1 are mixed in a predetermined ratio to obtain the matrix powder; Step 3: Silanization modification of magnetic powder surface: The matrix powder from step 2 was dispersed in anhydrous ethanol to form a suspension, and reacted with a pre-hydrolyzed silane coupling agent solution. After the reaction was completed, the mixture was vacuum filtered and dried to obtain modified magnetic powder with active functional groups on the surface. Step 4: Preparation of h-BN dispersion: Hexagonal boron nitride (h-BN) powder was added to an organic solvent and a dispersant was added. The mixture was then subjected to ultrasonic treatment to exfoliate and disperse it uniformly, resulting in an h-BN dispersion. Step 5, h-BN coating: The modified magnetic powder obtained in step 3 is redispersed in an organic solvent and mixed with the h-BN dispersion in step 4 to form particles with a core-shell structure. Step 6, Resin Coating: Add an insulating resin solution to the suspension in step 5 to coat the core-shell structure with resin and form a multi-layered composite powder. Step 7, Mixing and Granulation: The multilayer composite powder obtained in step 6 is stirred until the solvent is completely evaporated, and then sieved, granulated and dried to obtain composite magnetic powder. Step 8: Compression molding and heat treatment: The composite magnetic powder from step 7 was pressed into shape, followed by curing and high-temperature annealing to obtain FeSiBCuNb nanocrystals / carbonyl iron composite magnetic powder cores.

2. The preparation method of FeSiBCuNb nanocrystals / carbonyl iron composite magnetic powder core according to claim 1, characterized in that, In step 1, the passivation solution is prepared as follows: based on the mass of the magnetic powder, 0.3~0.8 wt.% of phosphoric acid is weighed and dissolved in 10~30 wt.% of acetone solvent.

3. The method for preparing FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder core according to claim 1, characterized in that, In step 1, the passivation reaction takes 20-40 minutes. After the reaction, the powder is sieved and dried at 60-80 ℃ for 1-2 hours.

4. The method for preparing FeSiBCuNb nanocrystals / carbonyl iron composite magnetic powder cores according to claim 1, characterized in that, In step 2, the matrix powder is composed of 60-80 wt.% passivated FeSiBCuNb nanocrystalline powder and 20-40 wt.% passivated carbonyl iron powder.

5. The method for preparing FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder core according to claim 1, characterized in that, In step 3, the amount of silane coupling agent KH550 added is 0.15~0.60 wt.% of the matrix powder, the reaction time is 1~3h, and the drying conditions are drying in an oven at 60~80 ℃ for 30~60 min.

6. The method for preparing FeSiBCuNb nanocrystals / carbonyl iron composite magnetic powder cores according to claim 1, characterized in that, In step 4, the amount of h-BN powder added is 0.5~3.0 wt.% of the matrix powder mass; the dispersant used is BYK-110, and the amount added is 0.1~0.2 wt.% of the matrix powder mass; the ultrasonic disperser is operated in pulse mode: after working at 50%~70% power for 10~15 min, it is paused for 2~5 min, and ultrasonic treatment is carried out for 1~2 h.

7. The method for preparing FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder core according to claim 1, characterized in that, In step 5, the reaction time is 30-50 minutes.

8. The method for preparing FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder core according to claim 1, characterized in that, In step 6, based on the mass of the matrix powder, the composite resin solution is formed by dissolving the insulating resin in 10-30 wt.% acetone. The insulating resin consists of 1-2 wt.% epoxy resin and 2-4 wt.% silicone resin.

9. The method for preparing FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder core according to claim 1, characterized in that, In step 7, the granulation is carried out by passing through a 40-60 mesh sieve, and the drying conditions are: drying at 60-80 ℃ for 0.5-2 h.

10. The method for preparing FeSiBCuNb nanocrystal / carbonyl iron composite magnetic powder core according to claim 1, characterized in that, In step 8, the thermosetting treatment is specifically performed by holding the temperature at 150~200 ℃ for 0.5~1.5 h in a tube furnace, and the high-temperature annealing treatment is specifically performed by holding the temperature at 450~550 ℃ for 1~3 h in a tube furnace, with an argon atmosphere as the protective atmosphere.

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