A nanocrystalline magnetic core material and its preparation method

Abstract

The present invention relates to a nanocrystalline magnetic core material and a preparation method thereof. The nanocrystalline magnetic core material of the present invention comprises the following components: nanocrystalline alloy, boron nitride and molybdenum disulfide; wherein, the molecular formula of the nanocrystalline alloy is: Fe a Ni b Si c Mn d La e . In the present invention, both boron nitride and molybdenum disulfide are layered structure materials with good lubricity and low friction coefficient. Applying them as a coating layer to the surface of the nanocrystalline magnetic core material can reduce the friction and wear between magnetic particles, improve the interfacial contact between particles, and thus may improve the processing performance and yield of the material.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic core materials, and in particular to a nanocrystalline magnetic core material and a preparation method thereof. Background Art

[0002] Due to their unique size effect, surface effect and quantum confinement effect, nanomagnetic core materials exhibit magnetic properties different from those of traditional macroscopic magnetic materials, including enhanced magnetization intensity, improved magnetic loss characteristics, higher magnetic permeability, and potential new magnetic phenomena. Nanomagnetic core materials have broad application prospects in modern technology, and the main application fields include: information storage, magnetic sensors, high-frequency devices, magnetic random access memories, biomedical applications, energy conversion and storage, etc.

[0003] Although significant technological progress has been made in these materials, there are still some technical challenges and problems. Under the current conventional technology, during the preparation process of nanocrystalline magnetic core materials, particle agglomeration is likely to occur, resulting in uneven particle size distribution of the magnetic core materials. Moreover, due to their high surface area, nanocrystalline materials are often more prone to oxidation or corrosion than traditional materials, leading to unsatisfactory magnetic performance of the materials. Therefore, those skilled in the art are committed to developing new materials, by adjusting the chemical composition, microstructure design and processing technology of the materials, in order to prepare a new type of magnetic core material with stable magnetic properties and oxidation resistance. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a nanocrystalline magnetic core material and a preparation method thereof.

[0005] The first object of the present invention is to provide a nanocrystalline magnetic core material, which, by mass fraction, comprises the following components:

[0006] 60 - 80 parts of nanocrystalline alloy; wherein, the molecular formula of the nanocrystalline alloy is: Fe a Ni b Si c Mn d La e ; wherein, a, b, c, d and e respectively represent the atomic percentage contents of the corresponding elements: 60 ≤ a ≤ 70, 10 ≤ b ≤ 20, 5 ≤ c ≤ 10, 3 ≤ d ≤ 5, e = 100 - a - b - c - d;

[0007] 15 - 30 parts of boron nitride;

[0008] 10 - 15 parts of molybdenum disulfide.

[0009] In some specific embodiments of the present invention, a, b, c, d, and e respectively represent the atomic percentage contents of the corresponding elements: 65 ≤ a ≤ 70, 10 ≤ b ≤ 15, 5 ≤ c ≤ 10, 3 ≤ d ≤ 5, and e = 100 - a - b - c - d.

[0010] The second object of the present invention is to provide a method for preparing the nanocrystalline magnetic core material, comprising the following steps:

[0011] S1. Select metals for batching according to the molecular formula FeaNibSicMndLae of the nanocrystalline alloy, and perform vacuum smelting to obtain a metal alloy ingot; then use the single-roll rapid quenching method to prepare an alloy strip from the metal alloy ingot;

[0012] S2. In an inert atmosphere, place the obtained alloy strip into a heating device for heat treatment to obtain a nanocrystalline alloy;

[0013] S3. Ball-mill and mix boron nitride and molybdenum disulfide, and then disperse them in a solvent using a high-shear disperser to obtain a suspension;

[0014] S4. Add the nanocrystalline alloy obtained in step S2 into the suspension obtained in step S3, adjust the pH value of the mixed solution to 7 - 9, mix and stir, and let it stand to form a coating layer containing boron nitride and molybdenum disulfide on the surface of the nanocrystalline alloy;

[0015] S5. Perform solid-liquid separation on the reaction solution obtained in step S4 and take the solid phase, wash and dry it to obtain the nanocrystalline magnetic core material.

[0016] In some specific embodiments of the present invention, in step S2, the gas in the inert atmosphere is nitrogen or argon;

[0017] The conditions for heat treatment are: heat to 290°C - 360°C and hold for 1.5 h - 3 h; then heat to 500°C - 600°C and hold for 2.5 h - 4 h.

[0018] In some specific embodiments of the present invention, in step S3, the solvent is selected from ethanol;

[0019] The rotation speed of the high-shear disperser is 2000 rpm / min - 5000 rpm / min.

[0020] In some specific embodiments of the present invention, in step S4, the standing time is 1 h - 3 h.

[0021] In some specific embodiments of the present invention, in step S5, the drying temperature is 50 - 80°C and the drying time is 1 - 2 h.

[0022] The third object of the present invention is to provide a magnetic core, and the magnetic core comprises the nanocrystalline magnetic core material.

[0023] A fourth object of the present invention is to provide a transformer, an inductor core, a relay, a high-frequency sensor or a wireless charger, comprising the magnetic core.

[0024] The above technical solution of the present invention has the following advantages compared with the prior art:

[0025] The present invention uses boron nitride as an additive. Modified boron nitride can improve the heat resistance, wear resistance and insulation of materials. At the same time, due to its high thermal conductivity, it helps with thermal management, prevents local overheating, which is particularly important for high-frequency applications. Molybdenum disulfide can improve the lubricity of materials and reduce friction and wear, which is beneficial for applications that require frequent flux reversals, and can improve the service life and reliability of materials. Boron nitride has good stability to a variety of chemicals and is not easily chemically reacted with other materials, which helps to protect the magnetic core from corrosion or oxidation, especially in applications working in harsh environments.

[0026] Boron nitride also has good mechanical strength and wear resistance. Used as a coating or additive, it can enhance the hardness and wear resistance of nanocrystalline magnetic core materials and extend the service life of devices. As an excellent electrical insulating material, boron nitride can provide the necessary electrical insulation performance while maintaining the original magnetic properties of magnetic materials. This is particularly important for magnetic components that require insulating coatings or isolation layers, such as in high-frequency transformers or inductors, which can avoid the risks of electric leakage and short circuits. Boron nitride has high thermal conductivity and can be used as a heat dissipation material. When applied to the surface treatment of nanocrystalline magnetic core materials or as part of a composite material, it can significantly improve the thermal conduction efficiency of the magnetic core, help heat dissipate quickly, reduce the temperature rise during operation, and thus improve the stability and reliability of the magnetic core in high-temperature or high-power applications.

[0027] The present invention utilizes that both boron nitride and molybdenum disulfide are layered structure materials with good lubricity and low friction coefficients. Applying them as a coating layer to the surface of nanocrystalline magnetic core materials can reduce the friction and wear between magnetic particles, improve the interfacial contact between particles, and thus may improve the processing performance and yield of materials. Boron nitride is one of the materials known to have relatively high thermal conductivity, while although the thermal conductivity of molybdenum disulfide is not as high as that of boron nitride, it also has good heat transfer ability. Using these two materials as a coating layer or dispersing them in nanocrystalline magnetic powder, their synergistic effect can effectively improve the thermal management performance of the magnetic core and accelerate the dissipation of heat, especially under high-frequency working conditions, which is crucial for maintaining the stability of magnetic properties.

[0028] The present invention utilizes the good chemical stability of molybdenum disulfide and boron nitride. As a coating layer, it can form a barrier to protect the internal nanocrystalline magnetic material from being eroded by environmental factors (such as humidity, oxygen, etc.), thereby extending the service life of the material. Although boron nitride and molybdenum disulfide do not directly enhance magnetism, by improving the microstructure and thermodynamic properties of the material, they indirectly contribute to stabilizing the electromagnetic properties of the magnetic material under different conditions, especially its performance in high-temperature or high-frequency working environments. Detailed implementation manners

[0029] In order to solve the technical problems pointed out in the background art: during the preparation of the magnetic core material, particle agglomeration easily occurs, resulting in uneven particle size distribution of the magnetic core material; and due to its high surface area, the nanocrystalline material is prone to oxidation or corrosion, leading to unsatisfactory magnetic performance of the material. Therefore, the present invention achieves its object through the following solutions.

[0030] The following further illustrates the present invention with specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the exemplified embodiments do not limit the present invention.

[0031] The present invention provides a nanocrystalline magnetic core material. By mass fraction, the nanocrystalline magnetic core material includes the following components:

[0032] 60 - 80 parts of nanocrystalline alloy; wherein, the molecular formula of the nanocrystalline alloy is: Fe a Ni b Si c Mn d La e ; wherein, a, b, c, d, and e respectively represent the atomic percentage contents of the corresponding elements: 60 ≤ a ≤ 70, 10 ≤ b ≤ 20, 5 ≤ c ≤ 10, 3 ≤ d ≤ 5, e = 100 - a - b - c - d;

[0033] 15 - 30 parts of boron nitride;

[0034] 10 - 15 parts of molybdenum disulfide.

[0035] In a specific embodiment of the present invention, a, b, c, d, and e respectively represent the atomic percentage contents of the corresponding elements: 65 ≤ a ≤ 70, 10 ≤ b ≤ 15, 5 ≤ c ≤ 10, 3 ≤ d ≤ 5, e = 100 - a - b - c - d.

[0036] In the present invention, the nanocrystalline alloy is applicable to the conventional nanocrystalline alloys in the art and can also be obtained by the conventional preparation methods in the art. For example, in the process of preparing strip materials, the metal melting method, the single-roll rapid quenching method, and the heat treatment of strip materials are all conventional methods in the art without special limitations. The present invention aims to perform a wrapping treatment on the nanocrystalline alloy. Therefore, the nanocrystalline alloy can be obtained by purchasing or by preparing it according to the methods described in the literature.

[0037] For example, the steps for preparing an alloy strip by the single-roll rapid quenching method can be as follows:

[0038] Prepare the corresponding metal or alloy raw materials according to a predetermined alloy composition ratio (such as Fe a Ni b Si c Mn d La e , where a, b, c, d, and e respectively represent the atomic percentage contents of the corresponding components);

[0039] Vacuum smelt the prepared raw materials at 1200 - 1500 °C for 10 - 20 min to ensure that the raw materials are fully melted and mixed evenly to obtain an alloy ingot;

[0040] After crushing the obtained alloy ingot, place it in a test tube with a nozzle and remelt it under high-frequency induction heating; under the action of pressure, spray the melted alloy out of the nozzle and directly onto a high-speed rotating water-cooled copper roll to finally obtain an alloy strip. Due to the high-speed rotation and strong cooling ability of the copper roll, the alloy solution is rapidly cooled and solidified into a continuous thin strip. The cooling rate can be about 10 K / s, and at this temperature, the grain size can reach the nanoscale, and the roll speed is 30 m / s.

[0041] The present invention also provides a method for preparing the nanocrystalline magnetic core material, including the following steps:

[0042] S1. According to the molecular formula of the nanocrystalline alloy Fe a Ni b Si c Mn d La e Select metal raw materials for batching and vacuum smelt to obtain a molten metal alloy; then use the single-roll rapid quenching method to prepare an alloy strip from the molten metal alloy;

[0043] S2. In an inert atmosphere, place the obtained alloy strip in a heating device for heat treatment to obtain a nanocrystalline alloy;

[0044] S3. Ball-mill and mix boron nitride and molybdenum disulfide, and then disperse them in a solvent using a high-shear disperser to obtain a suspension;

[0045] S4. Add the nanocrystalline alloy obtained in step S2 into the suspension obtained in step S3, adjust the pH value of the mixture to 7-9, mix and stir, and then let it stand, so that the surface of the nanocrystalline alloy is coated with a coating layer containing boron nitride and molybdenum disulfide;

[0046] S5. Perform solid-liquid separation on the reaction solution obtained in step S4 and take the solid phase, wash and dry it to obtain the nanocrystalline magnetic core material.

[0047] In a specific embodiment of the present invention, in step S2, the gas in the inert atmosphere is nitrogen or argon;

[0048] The heat treatment conditions are: heating to 290°C - 360°C and holding for 1.5 h - 3 h; then heating to 500°C - 600°C and holding for 2.5 h - 4 h.

[0049] In a specific embodiment of the present invention, in step S3, the solvent is selected from ethanol;

[0050] The rotation speed of the high-shear disperser is 2000 rpm / min - 5000 rpm / min. Through this rotation speed setting, boron nitride and molybdenum disulfide can be fully mixed, increasing the shear between the solid substance and the solvent and enhancing the dispersion performance.

[0051] In a specific embodiment of the present invention, in step S4, the standing time is 1 h - 3 h. During the standing time of the present invention, the mixed suspension of boron nitride and molybdenum disulfide can be evenly coated on the surface of the nanocrystalline alloy; when it is less than 1 h, the thickness of the coating layer is insufficient and the effect is minimal; when it is greater than 2 h, the thickness of the coating layer is too thick, and the coating layer may hinder the magnetic performance of the magnetic core, reducing its magnetic permeability and saturation magnetization intensity. This is because the coating layer itself has no magnetism or weak magnetism, thus diluting the magnetism of the overall material. In an alternating magnetic field, an overly thick coating layer may lead to an increase in eddy current loss. This is because the interface between the coating layer and the magnetic core may become an obstacle to the current loop, causing eddy currents to be generated in the coating layer, thereby resulting in energy loss.

[0052] In a specific embodiment of the present invention, in step S5, the drying temperature is 50 - 80°C and the drying time is 1 - 2 h.

[0053] The present invention also provides a magnetic core, and the magnetic core includes the nanocrystalline magnetic core material.

[0054] The present invention also provides a transformer, an inductor core, a relay, a high-frequency sensor or a wireless charger, including the magnetic core.

[0055] Example 1

[0056] This example provides a nanocrystalline magnetic core material, wherein the molecular formula of the nanocrystalline alloy is Fe70 Ni 15 Si 10 Mn 3 La 2 , the specific steps are as follows:

[0057] S1. According to the molecular formula of the nanocrystalline alloy Fe 70 Ni 15 Si 10 Mn 3 La 2 Select metals for batching, vacuum smelt at 1350 °C for 20 min to obtain a molten metal alloy; then use the single-roll rapid quenching method to prepare an alloy strip from the molten metal alloy;

[0058] S2. Under an inert atmosphere, put the obtained alloy strip into a heating device for heat treatment. Heat treatment conditions: heat to 320 °C and hold for 2 h; then heat to 500 °C and hold for 2.5 h to obtain the nanocrystalline alloy;

[0059] S3. Ball-mill and mix 15 parts by mass of boron nitride and 15 parts by mass of molybdenum disulfide, and then disperse them in 150 ml of ethanol solvent at a speed of 5000 rpm / min using a high-shear disperser to obtain a suspension;

[0060] S4. Add 60 parts by mass of the nanocrystalline alloy obtained in step S2 to the suspension obtained in step S3, adjust the pH value of the mixed solution to 7, mix and stir, and let it stand for 2 h to make the surface of the nanocrystalline alloy be coated with a coating layer containing boron nitride and molybdenum disulfide;

[0061] S5. Filter the reaction solution obtained in step S4, and wash and dry the solid matter obtained by filtration. Among them, the drying temperature is 60 °C to obtain the nanocrystalline magnetic core material.

[0062] Example 2

[0063] This example provides a nanocrystalline magnetic core material, wherein the molecular formula of the nanocrystalline alloy is Fe 65 Ni 20 Si 10 Mn 3 La 2 , the specific steps are as follows:

[0064] S1. According to the molecular formula of the nanocrystalline alloy Fe 65 Ni 20 Si 10 Mn 3 La 2 Select metals for batching, vacuum smelt at 1350 °C for 20 min to obtain a molten metal alloy; then use the single-roll rapid quenching method to prepare an alloy strip from the molten metal alloy;

[0065] S2. Under an inert atmosphere, put the obtained alloy strip into a heating device for heat treatment. The heat treatment temperature process is as follows: heat to 310 °C and hold for 1.5 h; then heat to 500 °C and hold for 2.5 h to obtain a nanocrystalline alloy;

[0066] S3. Ball-mill and mix 15 parts by mass of boron nitride and 15 parts by mass, and then disperse them in 150 ml of ethanol solvent at a rotation speed of 5000 rpm using a high-shear disperser to obtain a suspension;

[0067] S4. Add 60 parts by mass of the nanocrystalline alloy obtained in step S2 to the suspension obtained in step S3, adjust the pH value of the mixed solution to 7, mix and stir, and let it stand for 2 h so that the surface of the nanocrystalline alloy is coated with a coating layer containing boron nitride and molybdenum disulfide;

[0068] S5. Filter the reaction solution obtained in step S4, wash and dry the solid matter obtained by filtration. Among them, the drying temperature is 50 °C to obtain the nanocrystalline magnetic core material.

[0069] Example 3

[0070] Similar to Example 1, the difference is that the molecular formula of the nanocrystalline alloy is Fe 67 Ni 18 Si 10 Mn 3 La 2 .

[0071] Comparative Example 1

[0072] Similar to Example 1, the difference is that the coating layer does not include boron nitride.

[0073] Comparative Example 2

[0074] Similar to Example 1, the difference is that the coating layer does not include molybdenum disulfide.

[0075] Comparative Example 3

[0076] Similar to Example 1, the difference is that the coating layer is not prepared.

[0077] Comparative Example 4

[0078] Similar to Example 1, the difference is that during the preparation of the coating layer, in step S4, the standing time is 5 h.

[0079] Performance Test

[0080] The nanocrystalline magnetic core materials obtained from the examples and comparative examples were subjected to performance tests, specifically including tests of magnetic flux density and magnetic permeability, as well as stability tests under high-temperature and high-humidity conditions. The experimental results are shown in Tables 1 and 2.

[0081] Table 1 Test Results of Magnetic Flux Density and Magnetic Permeability

[0082]

[0083]

[0084] The nanocrystalline magnetic core materials obtained from Example 1 and Comparative Example 3 were placed under the conditions of a temperature of 85 °C and a humidity of 85% RH for 1000 h (in multiple batches), and the changes in the relevant magnetic properties of the nanocrystalline magnetic core materials were detected. The results are shown in Table 2.

[0085] Table 2 Stability Test under High-Temperature and High-Humidity Conditions

[0086]

[0087] From the data in Table 1, it can be seen that compared with Comparative Examples 1-3, in the presence of the mixed coating layer of boron nitride and molybdenum disulfide in Example 1, it will not directly cause too much change in the magnetic permeability. However, from the magnetic flux density, it can be seen that by increasing the coating layer of boron nitride and molybdenum disulfide, the magnetic flux density of the nanocrystalline magnetic core material has been improved to a certain extent. Thus, it can be seen that the presence of the mixed coating layer of boron nitride and molybdenum disulfide can not only improve the magnetic properties of the magnetic core material but also well protect the material stability of the nanocrystals. From Example 1 and Comparative Example 4, it is known that in Comparative Example 4, the standing time in step S4 is 5 h. The longer the time, the greater the thickness of the formed coating layer. The greater the thickness, the more it will affect the magnetic properties of the nanocrystalline magnetic core material. For example, the magnetic permeability decreases, such as the magnetic permeability in Comparative Example 4 is lower than that in Example 1. Therefore, it is necessary to reasonably set the standing time to achieve reasonable coating of the nanocrystalline magnetic core material, which can enhance the magnetism of the magnetic core material to a certain extent. Otherwise, the opposite effect may occur.

[0088] As can be seen from Table 2, under high-temperature and high-humidity conditions, the reduction in the magnetism of the nanocrystalline magnetic core material obtained in Example 1 is relatively small. However, for the nanocrystalline magnetic core material of Comparative Example 3, since no coating layer is provided on the surface, it is possible that an oxidation reaction may occur on the surface of the nanocrystalline magnetic core material under high-temperature and high-humidity conditions, resulting in a more significant reduction in the magnetic properties of the nanocrystalline magnetic core material.

[0089] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A nanocrystalline magnetic core material, characterized in that: The nanocrystalline magnetic core material comprises the following components in parts by mass: 60-80 parts of nanocrystalline alloy; wherein the molecular formula of the nanocrystalline alloy is: Fe a Ni b Si c Mn d La e ; Wherein, a, b, c, d and e represent the atomic percentage of the corresponding elements respectively: 60≤a≤70, 10≤b≤20, 5≤c≤10, 3≤d≤5, e=100-abcd; Boron nitride 15-30 parts; 10-15 parts of molybdenum disulfide; The preparation method of the nanocrystalline magnetic core material comprises the following steps: S1, according to the molecular formula of nanocrystalline alloy Fe a Ni b Si c Mn d La e Select metals for batching, perform vacuum smelting, and obtain metal alloy ingots; then, use a single-roller rapid quenching method to prepare alloy strips from the metal alloy ingots; S2. In an inert atmosphere, placing the obtained alloy strip in a heating device for heat treatment to obtain a nanocrystalline alloy; S3, ball-milling the boron nitride and molybdenum disulfide, and then dispersing them in a solvent using a high shear disperser to obtain a suspension; S4, adding the nanocrystalline alloy obtained in step S2 to the suspension obtained in step S3, adjusting the pH value of the mixed solution to 7-9, mixing and stirring, and standing to allow the surface of the nanocrystalline alloy to be coated with a coating layer containing boron nitride and molybdenum disulfide; S5, performing solid-liquid separation on the reaction solution obtained in step S4 and taking the solid phase, washing and drying to obtain the nanocrystalline magnetic core material.

2. The nanocrystalline magnetic core material according to claim 1, characterized in that: a, b, c, d and e represent the atomic percentage of the corresponding elements respectively: 65≤a≤70, 10≤b≤15, 5≤c≤10, 3≤d≤5, e=100-abcd.

3. The nanocrystalline magnetic core material according to claim 1, characterized in that: In step S2, the gas in the inert atmosphere is nitrogen or argon; The heat treatment conditions are: heating to 290°C~360°C and keeping warm for 1.5h~3h; then heating to 500°C~600°C and keeping warm for 2.5h~4h.

4. The nanocrystalline magnetic core material according to claim 1, characterized in that: In step S3, the solvent is selected from ethanol; and the rotation speed of the high shear disperser is 2000 rpm / min~5000 rpm / min.

5. The nanocrystalline magnetic core material according to claim 1, characterized in that: In step S4, the standing time is 1 h to 3 h.

6. The nanocrystalline magnetic core material according to claim 1, characterized in that: In step S5, the drying temperature is 50-80° C. and the drying time is 1-2 hours.

7. A magnetic core, characterized in that: The magnetic core comprises the nanocrystalline magnetic core material according to any one of claims 1 to 6.

8. A transformer, an inductor core, a relay, a high-frequency sensor or a wireless charger, characterized in that: Comprising the magnetic core as claimed in claim 7.

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