An iron-based nanocrystalline magnetic core and a preparation method thereof

Abstract

The present invention relates to a preparation method of an iron-based nanocrystalline magnetic core. The steps include: S1. After subjecting the strip of the iron-based nanocrystalline magnetic core to compressive stress treatment, winding it to obtain a first magnetic core; S2. Applying a magnetic field to the first magnetic core and performing heat treatment in an inert environment to obtain a second magnetic core; S3. Performing surface treatment on the second magnetic core and drying it to obtain the iron-based nanocrystalline magnetic core; wherein, the chemical solution used for the surface treatment includes at least one of an aqueous sodium nitrate solution, an aqueous sodium sulfate solution or an aqueous sodium chloride solution, and an aqueous sodium hydroxide solution. The present invention also relates to an iron-based nanocrystalline magnetic core prepared by the above-mentioned preparation method. The preparation method of the present invention releases internal stress in the microstructure of the nanocrystals through compressive stress treatment and heat treatment, thereby reducing the loss; by depositing a paramagnetic and magnetic conducting layer (magnetite) through surface treatment, the coercivity is further reduced, and at the same time, the magnetic permeability and the saturation magnetic induction intensity are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic core devices, and in particular to an iron-based nanocrystalline magnetic core and a preparation method thereof. Background Art

[0002] With the progress of technology, especially after entering the 5G era, the development of Internet of Everything and network technology, as well as the development of fields such as high-density recording technology and high-power high-frequency magnetic devices, require that the metal functional materials such as soft magnetic alloys for preparing magnetic devices continuously improve their performance and reduce costs. As a new generation of functional materials, the high saturation magnetic induction intensity sub-nanocrystalline soft magnetic alloy has excellent soft magnetic properties compared with conventional amorphous nanocrystals, such as high saturation magnetic induction intensity and large saturation current intensity. Now it is partially applied to fields such as wireless charging of electronic wearable devices, transformers, and inductors.

[0003] With the development of various devices towards the direction of high functionality, small size, light weight, and low cost, traditional amorphous nanocrystals can no longer meet the requirements for miniaturization, high saturation current intensity, and high frequency power. As the saturation magnetic induction intensity of soft magnetic alloys increases, the coercivity and loss also increase. Therefore, it is necessary to change the magnetic domains and magnetism through processes such as depositing paramagnetic and permeable layers, magnetic field heat treatment, and mechanical compressive stress to reduce the coercivity and loss, and improve the magnetic permeability and saturation magnetic induction intensity of the magnetic core. Therefore, reducing the coercivity and loss of high saturation magnetic induction intensity nanocrystals and improving the magnetic permeability and saturation magnetic induction intensity of the magnetic core have become technical problems that need to be urgently solved by those skilled in the art. Summary of the Invention

[0004] The purpose of the present invention is to provide an iron-based nanocrystalline magnetic core and a preparation method thereof for the deficiencies in the prior art.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] The first aspect of the present invention is to provide a preparation method of an iron-based nanocrystalline magnetic core, and the steps include:

[0007] S1. After performing compressive stress treatment on the strip of the iron-based nanocrystalline magnetic core, winding it to obtain a first magnetic core;

[0008] S2. In an inert environment, applying a magnetic field to the first magnetic core and performing heat treatment to obtain a second magnetic core;

[0009] S3. Performing surface treatment on the second magnetic core and drying it to obtain the iron-based nanocrystalline magnetic core;

[0010] Wherein, the chemical solution used for the surface treatment includes at least one of an aqueous sodium nitrate solution, an aqueous sodium sulfate solution, or an aqueous sodium chloride solution, and an aqueous sodium hydroxide solution;

[0011] Among them, the surface treatment includes: (a1) an electrochemical process in which iron on the surface of the iron-based nanocrystalline magnetic core is converted into divalent iron ions (Fe 2+ ): O2 + 4e - + 2H2O → 4OH - , Fe - 2e - + 2OH - → Fe(OH)2, 2Fe + 2H2O + O2 → 2Fe(OH)2; (b1) ferrous hydroxide is directly oxidized, 3Fe(OH)2 + O2 → Fe3O4 + 3H2O; or (a2) iron on the surface of the iron-based nanocrystalline magnetic core is oxidized to iron oxyhydroxide by an oxidant present in a strong alkali solution, 4Fe + 2H2O + 3O2 → 4FeOOH; (b2) iron oxyhydroxide is reduced by gaining electrons, FeOOH + e - → HFeO2 - ; (c2) taking iron oxyhydroxide as the base and hydroferrate as the acid, a neutralization dehydration reaction occurs, 2FeOOH + HFeO2 - → Fe3O4 + OH - + H2O;.

[0012] Preferably, the compressive stress treatment includes: using a roller with a pressure of 50 kg - 150 kg to form regular or irregular pattern lines on the surface of the strip.

[0013] Preferably, the applied magnetic field strength is 1000 A / m - 3000 A / m; the temperature of the heat treatment is 450°C - 600°C, and the time is 50 min - 180 min.

[0014] Preferably, the heat treatment includes: heating from 200°C - 300°C to 450°C - 500°C, holding for 50 min - 100 min; heating to 500°C - 600°C, holding for 50 min - 100 min; cooling to 200°C - 300°C.

[0015] Preferably, the concentration of the sodium hydroxide aqueous solution is 17.5 mol / L - 27.5 mol / L.

[0016] Preferably, the concentration of the sodium nitrate aqueous solution is 1.18 mol / L - 2.94 mol / L.

[0017] Preferably, the concentration of the sodium sulfate aqueous solution is 0.11 mol / L - 0.56 mol / L.

[0018] Preferably, the concentration of the sodium chloride aqueous solution is 0.31 mol / L - 0.43 mol / L.

[0019] Preferably, the temperature of the surface treatment is 60°C - 145°C, and the time is 10 min - 30 min.

[0020] The second aspect of the present invention is to provide an iron-based nanocrystalline magnetic core prepared by the preparation method described above.

[0021] Adopting the above technical solutions, compared with the prior art, the present invention has the following technical effects:

[0022] The preparation method of the present invention releases internal stress in the microstructure of the nanocrystals through compressive stress treatment and heat treatment, thereby reducing losses; by depositing a paramagnetic and magnetic conductive layer (magnetite) through surface treatment, the coercivity is further reduced, and at the same time, the magnetic permeability and saturation magnetic induction intensity are increased. Description of the Drawings

[0023] Figure 1 is the device used in Example 1 of the present invention;

[0024] Figure 2 is a physical surface diagram of an iron-based nanocrystalline magnetic core without a deposited paramagnetic and magnetic conductive layer on the surface in the comparative example of the present invention;

[0025] Figure 3 is a physical surface diagram of an iron-based nanocrystalline magnetic core with a deposited paramagnetic and magnetic conductive layer on the surface in the embodiment of the present invention;

[0026] Among them, the reference numerals include:

[0027] Strip 1; First roller 2; Second roller 3; Third roller 4; First magnetic core 5; Strip surface 6. Detailed Embodiments

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0029] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0030] The following further illustrates the present invention with reference to the accompanying drawings and specific embodiments, but is not a limitation of the present invention.

[0031] Embodiment

[0032] This embodiment provides an iron-based nanocrystalline magnetic core and a preparation method thereof. The steps of the preparation method include:

[0033] S1. Use the device as Figure 1 shown to perform compressive stress treatment on the strip of the iron-based nanocrystalline magnetic core, and wind it to obtain the first magnetic core. Specifically, it includes: using the first roller 2 and the second roller 3 to form a pattern on the strip surface 6 of the strip 1, and winding it through several third rollers 4 to obtain the first magnetic core 5 with a specified size. The pressure between the first roller 2 and the second roller 3 is 50 kg - 150 kg;

[0034] S2. Transport the first magnetic core to a heating furnace chamber filled with an inert gas (e.g., nitrogen), apply a magnetic field with a magnetic field intensity of 2600 A / m, heat from 250 °C to 490 °C, and keep it warm for 90 min; heat up to 550 °C and keep it warm for 90 min; cool down to 200 °C to obtain the second magnetic core;

[0035] S3. After degreasing the second magnetic core, transport the second magnetic core into the surface treatment solution. The solute, its concentration, temperature, and time are shown in Table 1, and dry it to obtain the iron-based nanocrystalline magnetic core.

[0036] The performance tests of the initial permeability (μi), saturation magnetic induction intensity (Bs), and coercive force (Hc) of the surface treatment solution with different solutes, different concentrations, different temperatures, and different times are shown in the following table:

[0037] Table 2

[0038]

[0039] Obviously, the example is superior to Comparative Example 1, indicating that depositing the paramagnetic and magnetic conductive layer (magnetite) reduces the coercive force, while increasing the magnetic permeability and saturation magnetic induction intensity; at the same temperature and time, Example 1 has the best performance, so the solute and its molar concentration are preferably those of Example 1.

[0040] Comparative Example 2

[0041] This comparative example uses a preparation method different from that of the example. The specific different steps are as follows:

[0042] Do not perform compressive stress treatment on the strip of the iron-based nanocrystalline magnetic core, and directly wind it to obtain the first magnetic core; and

[0043] Do not perform surface treatment on the second magnetic core.

[0044] Comparative Example 3

[0045] This comparative example uses a preparation method different from that of the example. The specific different steps are as follows:

[0046] Do not apply a magnetic field during the heat treatment of the first magnetic core; and

[0047] Do not perform surface treatment on the second magnetic core.

[0048] Comparative Example 4

[0049] This comparative example uses a preparation method different from that of the embodiment. The specific different steps are as follows:

[0050] Do not perform compressive stress treatment on the strip of the iron-based nanocrystalline magnetic core, and directly wind it to obtain the first magnetic core;

[0051] Do not apply a magnetic field during the heat treatment of the first magnetic core; and

[0052] Do not perform surface treatment on the second magnetic core.

[0053] Comparative Example 5

[0054] This comparative example uses a preparation method different from that of the embodiment. The specific different steps are as follows:

[0055] Do not perform surface treatment on the second magnetic core.

[0056] The performance tests of the loss (Pu) and coercive force (Hc) of Comparative Examples 1-4 are shown in the following table:

[0057] Table 2

[0058] Whether to perform compressive stress treatment Whether to apply a magnetic field Hc (A / m) Pu (Goe) Comparative Example 2 No Yes 3.9 764 Comparative Example 3 Yes No 3.6 758 Comparative Example 4 No No 4.5 960 Comparative Example 5 Yes Yes 2.5 650

[0059] Obviously, both the compressive stress treatment alone and the heat treatment with magnetic field application alone can achieve the effect of reducing loss, and the combination of compressive stress treatment and heat treatment with magnetic field application has the best effect of reducing coercive force and loss.

[0060] Comparative Examples 6-10

[0061] Comparative Examples 6-10 use the preparation method of Comparative Example 3, and the difference is only that:

[0062] Perform compressive stress treatment with different pressures between rollers.

[0063] The performance tests of the remanent magnetic induction intensity and coercive force (Hc) of Comparative Examples 6-10 are shown in the following table:

[0064] Table 3

[0065] Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Pressure between rollers (kg) 30 50 100 150 200 Hc (A / m) 3.5 3.58 3.60 3.75 4.22 Residual magnetic induction intensity (mT) 380 265 245 238 234

[0066] Obviously, as the pressure between rollers increases, the coercive force shows an upward trend, while the remanent magnetic induction intensity shows a downward trend. Therefore, the pressure between rollers is preferably 50 kg - 150 kg.

[0067] In summary, the preparation method of the present invention releases internal stress in the microstructure of nanocrystals through compressive stress treatment and heat treatment, thereby reducing losses; by surface treatment to deposit a paramagnetic and permeable layer (magnetite), the coercivity is further reduced, and at the same time, the magnetic permeability and saturation magnetic induction intensity are improved.

[0068] The above are only preferred embodiments of the present invention, and do not limit the implementation manners and protection scope of the present invention. For those skilled in the art, it should be realized that all equivalent replacements and obvious changes made by using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an iron-based nanocrystalline magnetic core, characterized in that the steps Including: S1. After subjecting the strip of the iron-based nanocrystalline magnetic core to compressive stress treatment, winding it to obtain a first magnetic core; S2. Under an inert environment, applying a magnetic field to the first magnetic core and performing heat treatment to obtain a second magnetic core; S3. Performing surface treatment on the second magnetic core and drying it to obtain the iron-based nanocrystalline magnetic core; Wherein, the chemical solution used for the surface treatment includes at least one of an aqueous sodium nitrate solution, an aqueous sodium sulfate solution, or an aqueous sodium chloride solution, and an aqueous sodium hydroxide solution; Among them, the surface treatment is to deposit a ferromagnetic layer of magnetite, including: (a1) the electrochemical process of converting the iron on the surface of the iron-based nanocrystalline magnetic core into divalent iron ions (Fe 2+ ): O2 + 4e - + 2H2O → 4OH - , Fe - 2e - + 2OH - → Fe(OH)2, 2Fe + 2H2O + O2 → 2Fe(OH)2; (b1) ferrous hydroxide is directly oxidized, 3Fe(OH)2 + O2 → Fe3O4 + 3H2O; or (a2) the iron on the surface of the iron-based nanocrystalline magnetic core is oxidized to iron oxyhydroxide by the oxidant present in the strong alkali solution, 4Fe + 2H2O + 3O2 → 4FeOOH; (b2) iron oxyhydroxide is reduced by gaining electrons, FeOOH + e - → HFeO2 - ; (c2) taking iron oxyhydroxide as the base and hydroferrate as the acid, a neutralization dehydration reaction occurs, 2FeOOH + HFeO2 - → Fe3O4 + OH - + H2O.

2. The preparation method according to claim 1, characterized in that, The compressive stress treatment includes: using a roller with a pressure of 50 kg - 150 kg to form regular or irregular pattern lines on the surface of the strip; 3. The preparation method according to claim 1, characterized in that, The applied magnetic field intensity is 1000 A / m - 3000 A / m; the temperature of the heat treatment is 450°C - 600°C, and the time is 50 min - 180 min; 4. The preparation method according to claim 3, characterized in that, The heat treatment includes: heating from 200°C - 300°C to 450°C - 500°C, holding for 50 min - 100 min; heating to 500°C - 600°C, holding for 50 min - 100 min; cooling to 200°C - 300°C; 5. The preparation method according to claim 1, characterized in that, The concentration of the aqueous sodium hydroxide solution is 17.5 mol / L - 27.5 mol / L; 6. The preparation method according to claim 1, characterized in that, The concentration of the aqueous sodium nitrate solution is 1.18 mol / L - 2.94 mol / L; 7. The preparation method according to claim 1, characterized in that, The concentration of the aqueous sodium sulfate solution is 0.11 mol / L - 0.56 mol / L; 8. The preparation method according to claim 1, wherein, The concentration of the aqueous sodium chloride solution is 0.31 mol / L - 0.43 mol / L; 9. The preparation method according to claim 1, characterized in that, The temperature of the surface treatment is 60°C - 145°C, and the time is 10 min - 30 min; 10. An iron-based nanocrystalline magnetic core prepared by the preparation method according to any one of claims 1 - 9.

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