Fe-based magnetic powder core with double strong magnetic layer and preparation method thereof

Abstract

The application belongs to the technical field of electronic components, and particularly relates to a Fe-based magnetic powder core with double strong magnetic conductive layers, a preparation method and application thereof, the Fe-based magnetic powder core comprising Fe-based magnetic powder and a coating layer coated on the Fe-based magnetic powder, the coating layer is a four-layer structure, and from inside to outside, the four-layer structure comprises an Fe-rich layer, a high-resistivity oxide insulating layer, a magnetic metal elemental Fe layer and a C layer; the preparation method is simple in process, controllable in cost, and can comprehensively improve the performance of the magnetic powder core, thereby providing a high-performance magnetic material solution for the field of electronic components; the Fe-rich layer on the surface of the magnetic powder particles of the Fe-based magnetic powder core and the external elemental Fe layer form double strong magnetic conductive layers, which can effectively improve the saturation magnetization intensity and magnetic permeability of the magnetic powder core, the high-resistivity oxide insulating layer can reduce the loss of the magnetic powder core, and the Fe-based magnetic powder core can be applied in devices such as transformers, switching power supplies, transformers, AI servers and the like.

Description

Technical Field

[0001] This invention belongs to the field of electronic component technology, specifically relating to an Fe-based magnetic powder core with a double strong magnetic permeability layer, its preparation method, and its application. Background Technology

[0002] In the field of electronic components, magnetic powder cores, as a key magnetic material, are widely used in electromagnetic devices such as transformers and inductors. While traditional Fe-based magnetic powder cores possess certain magnetic properties, they still have limitations in terms of high saturation magnetization, high permeability, and low loss. As electronic devices develop towards miniaturization, high performance, and high efficiency, the performance requirements for magnetic powder cores are becoming increasingly stringent. For example, in applications such as high-frequency switching power supplies and new energy vehicles, the loss of the magnetic powder core directly affects the efficiency and heat dissipation performance of the equipment, while saturation magnetization and permeability determine the power density and electromagnetic performance of the equipment.

[0003] Currently, methods to improve the performance of magnetic powder cores mainly include optimizing the particle size distribution, composition, and coating process of the magnetic powder. However, these methods often present certain balancing challenges in improving performance. For example, increasing the particle size of the magnetic powder can increase the saturation magnetization, but may lead to increased losses; while optimizing the composition can improve performance to some extent, it is difficult to simultaneously achieve high saturation magnetization, high permeability, and low losses.

[0004] Insulating coating is a key process in the preparation of soft magnetic composite materials. By coating the surface of magnetic particles with a layer of nanoscale insulating material (such as epoxy resin, ceramic, or phosphate), a resistive barrier is formed between the particles; this treatment can significantly increase the resistivity of the material (up to 10). 6 -10 8This significantly reduces high-frequency eddy current losses (Ω·m). Simultaneously, it promotes dense particle packing during pressing, increasing the magnetic powder core density and improving compressive strength. In traditional SMC coating processes, excessive insulating coating material is typically added to reduce high-frequency eddy current losses, leading to magnetic dilution and deteriorating the overall magnetic properties of the magnetic powder core. Therefore, current research on magnetic powder cores focuses on maximizing permeability while maintaining low losses at high frequencies. Patent document CN119296948A discloses a method for simultaneously reducing hysteresis loss and eddy current loss in FeSiAl magnetic powder cores. This method can only form a high-resistivity insulating layer, but cannot produce a Fe-rich layer or a Fe elemental layer, thus failing to improve the saturation magnetization of the magnetic powder core. The paper "Interfacial Reaction Enhanced Liquid-Phase Sintering of Metal / OxideSoft Magnetic Composite" obtained a high-resistivity Al2O3 insulating layer and Mo elemental, but Mo elemental lacks ferromagnetism and cannot improve the magnetic permeability of the magnetic powder core; instead, it increases eddy current loss. Furthermore, the Fe on the FeSiAl surface does not form a Fe-rich layer but diffuses outward, reacting with some O in MoO3 to form Fe2O3 nanoparticles, which cannot improve the saturation magnetization of the magnetic powder core. The paper "High-performance FeSiAl / (Al2O3-Ni)soft magnetic composites prepared by insitu synthesis" further supports this approach. The method produces an Al2O3 insulating layer and Ni elemental, but the ball milling method introduces a large amount of internal stress, which is not conducive to reducing losses. At the same time, the Ni elemental layer has a low saturation magnetization, which is not very effective in improving the magnetic permeability of the sample. Most importantly, this method relies on the discharge effect generated during the spark plasma sintering process, which will generate discharge on the surface of magnetic powder and NiO, inducing the formation of new oxides, and cannot generate a Fe-rich layer inside FeSiAl. Summary of the Invention

[0005] Based on the aforementioned shortcomings and deficiencies in existing technologies, the purpose of this invention is to provide an Fe-based magnetic powder core with a double strong magnetic permeability layer, its preparation method, and its applications. This not only significantly improves the saturation magnetization and permeability of the magnetic powder core but also enhances its properties through N... x O y The layer effectively reduces the loss of the magnetic powder core. Compared with the prior art, the preparation method of the present invention is simple in process, cost controllable, and can achieve a comprehensive improvement in the performance of the magnetic powder core, providing a high-performance magnetic material solution for the field of electronic components.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A Fe-based magnetic powder core with dual strong magnetic permeability layers includes Fe-based magnetic powder and an outer coating layer. The coating layer has a four-layer structure, consisting of an Fe-rich layer, a high-resistivity oxide insulating layer, a magnetic metal elemental Fe layer, and a C layer from the inside out.

[0008] As a preferred embodiment, the high resistivity oxide insulating layer is N x O y , N is Al, Si, Cr, Zr, Nb or Ta.

[0009] As a preferred embodiment, the Fe-based magnetic powder is one of FeSi, FeSiAl, FeZr, FeSiCr, FeSiB, FeSiBCr, and FeSiCuBNb alloys.

[0010] This invention also provides a method for preparing Fe-based magnetic powder cores as described in any of the preceding embodiments, comprising the following steps:

[0011] (1) Preparation of salt solution: Dissolve the metal salt containing Fe in a solvent to prepare a solution;

[0012] (2) Impregnation: Add Fe-based magnetic powder to the solution prepared in step (1) and stir to soak;

[0013] (3) First heat treatment: The magnetic powder obtained after step (2) is filtered and dried, and then calcined at 200-600℃ for 0.5-5h to obtain Fe-based magnetic powder@Fe m O n Precursor;

[0014] (4) Press molding: Fe-based magnetic powder@Fe m O n The precursor is mixed evenly with the binder and release agent, dried, and pressed into shape to obtain the magnetic powder core blank;

[0015] (5) Secondary heat treatment: The magnetic powder core blank is kept in an annealing furnace at 300-1000℃ for 0.5-2h to obtain Fe-based magnetic powder core.

[0016] As a preferred embodiment, in step (1), the concentration of the solution is between 0.001% and 90%.

[0017] As a preferred embodiment, in step (1), the solvent is water, acetone, ethanol or toluene.

[0018] As a preferred embodiment, in step (1), the metal salt containing Fe contains O.

[0019] As a preferred embodiment, in step (1), the metal salt containing Fe is one of Fe(NO3)3, Fe2(CO3)3, Fe(NO3)2, Fe(NO2)3, and FeSO4.

[0020] As a preferred option, in step (2), the stirring and soaking time generally needs to be greater than 1 second.

[0021] As a preferred option, in step (3), the calcination atmosphere can be air or gases such as argon or nitrogen.

[0022] As a preferred embodiment, in step (4), the adhesive is an organic resin or an inorganic resin, and the release agent is zinc stearate, aluminum stearate or magnesium stearate.

[0023] The pressure for compression molding is 800-2500MPa.

[0024] As a preferred embodiment, in step (5), the secondary heat treatment is carried out in an inert atmosphere. To prevent oxidation, a reducing gas such as hydrogen can also be introduced.

[0025] The present invention also provides applications of Fe-based magnetic powder cores as described in any of the preceding embodiments or Fe-based magnetic powder cores prepared by the preparation method described in any of the preceding embodiments, for use in current transformers, switching power supplies, transformers or AI servers.

[0026] Compared with the prior art, the beneficial effects of this invention are:

[0027] The Fe-based magnetic powder core of the present invention has a double strong magnetic permeability layer consisting of a Fe-rich layer on the surface of the magnetic powder particles and an outer Fe monolithic metal layer, which can effectively improve the saturation magnetization and permeability of the magnetic powder core, and the high resistivity oxide insulating layer can reduce the loss of the magnetic powder core. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the FeSiAl@Fe3O4 precursor in Embodiment 1 of the present invention;

[0029] Figure 2 This is a schematic diagram of the structure of the Fe-based magnetic powder core of Embodiment 1 of the present invention;

[0030] Figure 3 These are TEM images (a) and STEM line scan images (b) of the Fe-based magnetic powder core of Embodiment 1 of the present invention. Detailed Implementation

[0031] The technical solution of the present invention will be further explained and illustrated below through specific embodiments.

[0032] Example 1:

[0033] The method for preparing FeSiAl / Fe-rich@Al2O3 / Fe / C magnetic powder cores with high saturation magnetization, high permeability, and low loss in this embodiment includes the following steps:

[0034] Step 1: Prepare Fe(NO3)3 salt solution by dissolving Fe(NO3)3 salt containing Fe element in water to prepare a 5wt% solution;

[0035] Step 2: Add FeSiAl magnetic powder to the solution in Step 1, stir and soak for 30 minutes to allow Fe(NO3)3 to be adsorbed on the surface of FeSiAl magnetic powder;

[0036] Step 3: Filter and dry the solution from Step 2, then calcine it at 500℃ under a nitrogen atmosphere for 1 hour to obtain the following... Figure 1 The FeSiAl@Fe3O4 precursor shown is obtained in situ via a liquid-solid reaction method. The Fe3O4 thickness can be controlled by adjusting the solution concentration and adsorption time.

[0037] Step 4: Mix the precursor from Step 3 with 1.5% silicone resin (percentage relative to the precursor) and 0.5% zinc stearate (percentage relative to the precursor), dry it, and press it into shape at 1500 MPa to obtain the magnetic powder core preform.

[0038] Step 5: Heat-treat the magnetic powder core blank from Step 4 at 700℃ for 1 hour to obtain the final FeSiAl / Fe-rich@Al2O3 / Fe / C magnetic powder core. The magnetic powder core structure is as follows: Figure 2 As shown, the magnetic powder core synthesized in this embodiment has a unique four-layer coating structure: from the inside out, it consists of an Fe-rich layer, a high-resistivity oxide Al2O3 insulating layer, a magnetic elemental Fe layer, a binder or release agent, and its high-temperature decomposition product C layer. Among them, the Fe-rich layer and the elemental Fe layer are double strong magnetic permeable layers, which together with the matrix form a weak magnetic-strong magnetic-non-magnetic-strong magnetic-non-magnetic-strong magnetic-non-magnetic-strong magnetic-weak magnetic composite magnetic permeable structure. This structure can effectively conduct magnetism and hinder interparticle eddy currents, thereby improving the magnetic permeability of the magnetic powder core and reducing losses. Moreover, the double strong magnetic permeable layer itself has a high saturation magnetization intensity, which can weaken the magnetic dilution effect caused by traditional non-magnetic insulating layer coating.

[0039] like Figure 3 As shown, the red dashed line in (a) is the insulating coating layer, and the element distribution in (b) corresponds to the area of ​​the arrow in (a). It can be seen that the outer layer is obviously enriched with Fe elements. The shaded area in (b) corresponds to the Al2O3 layer, and the inner side shows another Fe-rich layer.

[0040] Example 2:

[0041] The method for preparing a FeSiBCr / Fe-rich@Cr2O3 / Fe / C magnetic powder core with high saturation magnetization, high permeability, and low loss in this embodiment includes the following steps:

[0042] Step 1: Prepare Fe(NO3)3 salt solution by dissolving Fe(NO3)3 salt containing Fe element in water to prepare a 10wt% solution;

[0043] Step 2: Add FeSiBCr magnetic powder to the solution in Step 1, stir and soak for 10 minutes to allow Fe(NO3)3 to be adsorbed on the surface of FeSiBCr magnetic powder;

[0044] Step 3: Filter and dry the solution from Step 2, and calcine it at 400℃ in a nitrogen atmosphere for 1 hour to obtain the FeSiBCr@Fe3O4 precursor;

[0045] Step 4: Mix the precursor from Step 3 with 2.0% silicone resin and 0.5% zinc stearate, dry it, and then press it into shape at 2300 MPa to obtain the magnetic powder core preform.

[0046] Step 5: Heat-treat the magnetic powder core blank from Step 4 at 480℃ for 1 hour to obtain the final FeSiBCr / Fe-rich@Cr2O3 / Fe / C magnetic powder core.

[0047] Example 3:

[0048] The method for preparing FeSi / Fe-rich@SiO2 / Fe / C magnetic powder cores with high saturation magnetization, high permeability, and low loss in this embodiment includes the following steps:

[0049] Step 1: Prepare FeSiO4 salt solution by dissolving FeSiO4 in water to prepare a specific 2% solution;

[0050] Step 2: Add FeSi magnetic powder to the solution in Step 1, stir and soak for 45 minutes to allow FeSiO4 to be adsorbed on the surface of FeSi magnetic powder;

[0051] Step 3: Filter and dry the solution from Step 2, then calcine it at 500℃ in an argon atmosphere for 1 hour to obtain FeSi@Fe. x O y Precursor;

[0052] Step 4: Mix the precursor from Step 3 with 2.5% silicone resin and 0.5% zinc stearate, dry it, and then press it into shape at 900 MPa.

[0053] Step 5: Heat-treat the magnetic powder core blank from Step 4 in an argon atmosphere at 720℃ for 2 hours to obtain the final FeSi / Fe-rich@SiO2 / Fe / C magnetic powder core.

[0054] Comparative Example 1:

[0055] The preparation method of the FeSiAl / Fe-rich@Al2O3 / Ni / C magnetic powder core in this comparative example includes the following steps:

[0056] Step 1: Prepare Ni(NO3)3 salt solution by dissolving Ni(NO3)3 salt in water to prepare a specific 5% solution;

[0057] Step 2: Add FeSiAl magnetic powder to the solution in Step 1, stir and soak for 30 minutes to allow Ni(NO3)3 to be adsorbed on the surface of FeSiAl magnetic powder;

[0058] Step 3: Filter and dry the solution from Step 2, and calcine it at 500℃ in a nitrogen atmosphere for 1 hour to obtain the FeSiAl@NiO precursor;

[0059] Step 4: Mix the precursor from Step 3 with 1.5% silicone resin and 0.5% zinc stearate, dry it, and then press it into shape at 1500 MPa.

[0060] Step 5: Heat-treat the magnetic powder core blank from Step 4 at 700℃ for 1 hour to obtain the final FeSiAl / Fe-rich@Al2O3 / Ni / C magnetic powder core.

[0061] Comparative Example 2:

[0062] The preparation method of the FeSiAl@Fe2O3 / Al2O3 / Mo magnetic powder core in this comparative example includes the following steps:

[0063] Step 1: Mix ammonium molybdate and FeSiAl evenly and add them to the graphite mold;

[0064] Step 2: The above mixed powder was sintered at 850℃ and 60MPa for 90 minutes using spark plasma sintering technology to obtain FeSiAl@Fe2O3 / Al2O3 / Mo magnetic powder core.

[0065] The magnetic properties of the magnetic powder cores from Examples 1-3 and Comparative Examples 1-2 were tested, and the results are shown in Table 1:

[0066] Table 1 Performance parameters of the magnetic powder cores in Examples 1-3 and Comparative Examples 1-2

[0067]

[0068] In Comparative Example 1, the outermost layer obtained was a Ni single-element layer, whose saturation magnetization was significantly lower than that of the Fe single-element layer, resulting in a low saturation magnetization of the sample. In Comparative Example 2, spark plasma sintering technology was used. Although the sample surface temperature was 850℃, the temperature in the local area between particles was extremely high during the discharge process, making it difficult to obtain an effective Fe-rich layer. The innermost layer was transformed into Fe2O3 nanoparticles due to atomic diffusion, which affected the improvement of magnetic permeability.

[0069] Given that there are numerous embodiments of the present invention, and the raw materials and quantities involved can be selected within a limited range according to actual needs, and that the experimental data for each embodiment are extensive and numerous, it is not suitable to list and describe them one by one here. However, the content to be verified and the final conclusions obtained in each embodiment are similar. Therefore, the verification content of each embodiment will not be described one by one here.

[0070] The above description is merely a detailed explanation of preferred embodiments and principles of the present invention. For those skilled in the art, there may be changes in specific implementation methods based on the ideas provided by the present invention, and these changes should also be considered within the scope of protection of the present invention.

Claims

1. A Fe-based magnetic powder core with a double strong magnetic permeability layer, characterized in that, It includes Fe-based magnetic powder and its outer coating layer. The coating layer has a four-layer structure, consisting of an Fe-rich layer, a high-resistivity oxide insulating layer, a magnetic metal elemental Fe layer, and a C layer from the inside out.

2. The Fe-based magnetic powder core according to claim 1, characterized in that, The high resistivity oxide insulating layer is N x O y , N is Al, Si, Cr, Zr, Nb or Ta.

3. The Fe-based magnetic powder core according to claim 1, characterized in that, The Fe-based magnetic powder is one of FeSi, FeSiAl, FeZr, FeSiCr, FeSiB, FeSiBCr, and FeSiCuBNb alloys.

4. The method for preparing the Fe-based magnetic powder core according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Preparation of salt solution: Dissolve the metal salt containing Fe in a solvent to prepare a solution; (2) Impregnation: Add Fe-based magnetic powder to the solution prepared in step (1) and stir to soak; (3) First heat treatment: The magnetic powder obtained after step (2) is filtered and dried, and then calcined at 200-600℃ for 0.5-5h to obtain Fe-based magnetic powder@Fe m O n Precursor; (4) Press molding: Fe-based magnetic powder@Fe m O n The precursor is mixed evenly with the binder and release agent, dried, and pressed into shape to obtain the magnetic powder core blank; (5) Secondary heat treatment: The magnetic powder core blank is kept in an annealing furnace at 300-1000℃ for 0.5-2h to obtain Fe-based magnetic powder core.

5. The preparation method according to claim 4, characterized in that, In step (1), the solvent is water, acetone, ethanol or toluene.

6. The preparation method according to claim 4, characterized in that, In step (1), the metal salt containing Fe contains O.

7. The preparation method according to claim 6, characterized in that, In step (1), the metal salt containing Fe is one of Fe(NO3)3, Fe2(CO3)3, Fe(NO3)2, Fe(NO2)3, and FeSO4.

8. The preparation method according to claim 4, characterized in that, In step (4), the adhesive is an organic resin or an inorganic resin, and the release agent is zinc stearate, aluminum stearate or magnesium stearate. The pressure for compression molding is 800-2500MPa.

9. The preparation method according to claim 4, characterized in that, In step (5), the secondary heat treatment is carried out in an inert atmosphere.

10. The application of the Fe-based magnetic powder core according to any one of claims 1-3 or the Fe-based magnetic powder core prepared by the preparation method according to any one of claims 4-9, characterized in that, Used in current transformers, switching power supplies, transformers, or AI servers.

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