Iron-silicon magnetic powder core and preparation method and application thereof
By growing a thin SiO2 oxide coating layer in situ on the surface of iron-silicon powder and combining it with recrystallization heat treatment, the problem of caking of iron-silicon powder during high-temperature heat treatment was solved, and a FeSi/SiO2 composite magnetic powder core with low loss and high DC bias resistance was prepared.
Patent Information
- Application Number
- CN202511719399.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-21
- Publication Date
- 2026-02-27
AI Technical Summary
Existing iron-silicon powders are prone to metallurgical bonding between particles during high-temperature heat treatment, leading to caking and limiting their widespread application in high-frequency, high-power, and other high-end application scenarios.
A thin SiO2 oxide coating layer was grown in situ on the surface of iron-silicon powder using the sol-gel method, and combined with recrystallization heat treatment technology to eliminate internal stress in the powder and reduce losses.
A FeSi/SiO2 composite magnetic powder core with low loss and high DC bias resistance was prepared to prevent metallurgical bonding between particles and improve magnetic permeability.
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Figure CN121583751A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of magnetic materials, in particular to a FeSi magnetic powder core and a preparation method and application thereof. BACKGROUND
[0002] The FeSi magnetic powder core is a kind of soft magnetic material prepared by mixing and pressing FeSi magnetic powder and insulating medium, and becomes an important material in the field of power electronics and new energy due to its low cost, high saturation magnetic induction, low loss, good temperature stability and DC bias characteristics. The existing FeSi powder will introduce a large amount of internal stress in the process of atomization preparation. By high-temperature stress relief annealing treatment of the powder, the internal stress of the powder can be eliminated and the loss can be reduced.
[0003] However, the existing FeSi powder is easy to cause metallurgical bonding between particles during high-temperature heat treatment, which causes hardening phenomenon and leads to high loss, which greatly limits its wide application in high-end application scenarios such as high frequency and high power. SUMMARY
[0004] The present application provides a FeSi magnetic powder core and a preparation method and application thereof. The FeSi / SiO2 composite powder core with low loss and high DC bias resistance is prepared by in-situ growth of SiO2 oxide on FeSi powder for powder surface modification by sol-gel method, and combining recrystallization annealing technology to greatly eliminate the internal stress of the powder and reduce the loss of the powder core.
[0005] In order to solve the above technical problems, one of the purposes of the present application is to provide a preparation method of FeSi magnetic powder core, comprising the following steps: (1) stirring the catalyst solution with pH of 10-11 and the magnetic powder premix liquid uniformly, then slowly adding the precursor solution, stirring and reacting at room temperature, and then drying to obtain FeSi / SiO2 composite powder; The catalyst solution comprises an alkaline catalyst, the magnetic powder premix liquid comprises polyvinylpyrrolidone and FeSi magnetic powder with a mass ratio of (0.01-0.1):1, and the precursor solution comprises a silicon source, and the mass ratio of the silicon source and FeSi magnetic powder is (0.01-0.1):1; (2) placing the FeSi / SiO2 composite powder in an atmosphere furnace for recrystallization heat treatment to obtain FeSi / SiO2 composite soft magnetic powder; (3) mixing silicon resin, dispersing agent and FeSi / SiO2 composite soft magnetic powder uniformly, then pressing and forming, and then annealing heat treatment in vacuum or nitrogen atmosphere to prepare FeSi / SiO2 composite magnetic powder core.
[0006] The application adopts sol-gel method to perform surface modification on FeSi magnetic powder, can in-situ grow SiO2 oxide thin coating layer with high resistivity on the surface of FeSi magnetic powder, can effectively prevent the problem of agglomeration caused by metallurgical combination between particles in the process of high-temperature heat treatment of powder, and then adopts recrystallization heat treatment technology for high-temperature pretreatment, can greatly eliminate the internal stress of powder, and reduce the loss of powder core, so that the prepared FeSi / SiO2 composite magnetic powder core has the performances of low loss, high DC bias resistance and high magnetic permeability.
[0007] In some embodiments, in step (1), the basic catalyst is NH3·H2O.
[0008] In some embodiments, in step (1), the silicon source is at least one of tetraethoxysilane, sodium silicate, methyl orthosilicate, and silica sol.
[0009] In some embodiments, in step (1), the mass ratio of the catalyst solution and the precursor solution is (0.5-2):1.
[0010] In some embodiments, in step (2), the recrystallization heat treatment temperature is 500-1100 ℃, and the holding time is 30-180 min. If the recrystallization temperature is too low, the grain growth and stress release are insufficient, and if the recrystallization temperature is too high, the grains grow excessively, the coating layer is damaged, resulting in low magnetic permeability and high loss. Controlling the recrystallization heat treatment temperature can reduce the loss of FeSi magnetic powder core and improve the magnetic permeability.
[0011] In some embodiments, in step (3), phosphoric acid, silicone, dispersant and FeSi / SiO2 composite soft magnetic powder are uniformly mixed, and the mass ratio of the phosphoric acid and the FeSi / SiO2 composite soft magnetic powder is (0.001-0.02):1.
[0012] In some embodiments, in step (3), the mass ratio of the silicone and the FeSi / SiO2 composite soft magnetic powder is (0.001-0.05):1.
[0013] In some embodiments, in step (1), the catalyst solution comprises a basic catalyst and water.
[0014] In some embodiments, the precursor solution comprises a silicon source with a mass fraction of 5%-50% and a solvent.
[0015] In some embodiments, the magnetic powder premix solution further comprises a solvent, and 0.5-2 mL of solvent is added per 1 g of FeSi magnetic powder.
[0016] In some embodiments, the solvent is anhydrous ethanol and / or acetone.
[0017] In some embodiments, in step (3), the dispersing agent is ethanol and / or propanol.
[0018] In some embodiments, in step (3), the dispersing agent is 5%-20% of the mass of the FeSi / SiO2 composite soft magnetic powder.
[0019] In some embodiments, in step (3), the pressing pressure of the press forming is 1000-3000 MPa.
[0020] In some embodiments, in step (3), the annealing heat treatment temperature is 500-800 ℃, and the holding time is 30-240 min.
[0021] To solve the above technical problems, the second object of the present application is to provide a FeSi magnetic powder core prepared by the preparation method of the FeSi magnetic powder core.
[0022] To solve the above technical problems, the third object of the present application is to provide an application of the FeSi magnetic powder core in the field of electronic equipment or new energy equipment.
[0023] Compared with the prior art, the present application has the following beneficial effects: 1. The FeSi powder will introduce a large amount of internal stress in the atomization preparation process, and the powder needs to be subjected to high-temperature stress relief annealing treatment. The present application uses a sol-gel method to modify the surface of the FeSi magnetic powder, which can grow a thin coating layer of SiO2 oxide with high resistivity on the surface of the FeSi magnetic powder in situ, which can effectively prevent the problem of agglomeration caused by metallurgical bonding between particles during high-temperature heat treatment of the powder.
[0024] 2. The FeSi powder of the present application uses recrystallization heat treatment technology to pre-treat the FeSi / SiO2 composite powder at high temperature, which can greatly eliminate the internal stress of the powder, reduce the loss of the powder core, and make the finally prepared FeSi / SiO2 composite magnetic powder core have the properties of low loss, high DC bias resistance and high magnetic permeability. BRIEF DESCRIPTION OF DRAWINGS
[0025] Figure 1 : Process flow chart of a preparation method of a FeSi magnetic powder core in the present application embodiment 1; Figure 2 : SEM surface morphology diagram of the FeSi / SiO2 composite magnetic powder core in the present application embodiment 1 (Note: a, b-FeSi raw powder in step (1); c, d-FeSi / SiO2 composite soft magnetic powder in step (3); e, f-FeSi / SiO2 composite magnetic powder core in step (4)). DETAILED DESCRIPTION
[0026] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.
[0027] It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value in the stated range, and any other stated value or intermediate value in the stated range, is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.
[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In the case of conflict between any document incorporated by reference and the present specification, the present specification controls.
[0029] As used herein the terms "about," "substantially," "approximately," and "almost" mean that the recited characteristic, parameter, or value needs not be achieved exactly, but that deviations, within margins that are acceptable, are permitted. In general, these terms are used herein to cover variations that can exist in the values that the variables represent. In these embodiments, the parts and percentages described are by mass, unless otherwise indicated.
[0030] "and / or" is used to indicate one or both stated cases can occur, for example, A and / or B includes (A and B) and (A or B).
[0031] In the description of the present application, it should be understood that the terms "upper", "lower", "left", "right", "top", "bottom", and the like indicate the orientation or positional relationship shown only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.
[0032] In order to further illustrate the present application, the present application will be described in detail below in combination with the embodiments, but they should not be understood as limiting the scope of protection of the present application. In the following examples and comparative examples of the present application, the sources of raw materials used are as follows, unless otherwise specified: the raw materials used are all commercially available, and the same raw materials are used in parallel experiments.
[0033] Example 1 A preparation method of a FeSi magnetic powder core, as shown in the figure, comprising the following steps: Figure 1 (1) Polyvinylpyrrolidone (PVP) is mixed with anhydrous ethanol and then stirred uniformly in a three-necked flask, then FeSi magnetic powder is added and mixed uniformly, the supernatant in the flask is poured out, and a magnetic powder premix is obtained; NH3·H2O is dissolved in an ethanol aqueous solution with a volume concentration of 95% to control the pH to be 10, and a catalyst solution is obtained; tetraethoxysilane (TEOS) is dissolved in anhydrous ethanol to obtain a precursor solution, and the mass concentration of TEOS in the precursor solution is 40%; In the magnetic powder premix, the mass ratio of PVP to FeSi magnetic powder is 0.01:1, and 1 mL of anhydrous ethanol is added per 1 g of FeSi magnetic powder; (2) The catalyst solution is poured into the three-necked flask containing the magnetic powder premix and stirred uniformly, then the precursor solution is slowly dropped into the three-necked flask containing the magnetic powder premix, the mass ratio of TEOS to FeSi magnetic powder is controlled to be 0.01:1, and the mass ratio of the catalyst solution to the precursor solution is 1:1, after stirring at room temperature for 30 min, drying is performed, and a FeSi / SiO2 composite powder with SiO2 coating is obtained; (3) The FeSi / SiO2 composite powder is placed in an atmosphere furnace, vacuumized, and then subjected to recrystallization heat treatment in a nitrogen atmosphere, heated to 1100 ℃, and kept for 30 min, to obtain a FeSi / SiO2 composite soft magnetic powder; (4) Phosphoric acid, silicone resin, acetone dispersant, and FeSi / SiO2 composite soft magnetic powder are thoroughly mixed and uniformly formed into a multi-layer insulation coating, wherein the mass ratio of phosphoric acid, silicone resin, and FeSi / SiO2 composite soft magnetic powder is 0.005:0.008:1, the acetone dispersant is 10% of the mass of the FeSi / SiO2 composite soft magnetic powder, then compression molding is performed, the compression pressure is 1800 MPa, then annealing heat treatment is performed in a vacuum atmosphere, the heat treatment temperature is 800 ℃, and the holding time is 30 min, to obtain a FeSi / SiO2 composite magnetic powder core.
[0034] Example 2 A preparation method of a FeSi magnetic powder core, comprising the following steps: (1) Polyvinylpyrrolidone (PVP) is mixed with anhydrous ethanol and then stirred uniformly in a three-necked flask, then FeSi magnetic powder is added and mixed uniformly, the supernatant in the flask is poured out, and a magnetic powder premix is obtained; NH3·H2O is dissolved in an ethanol aqueous solution with a volume concentration of 95% to control the pH to be 11, and a catalyst solution is obtained; tetraethoxysilane (TEOS) is dissolved in anhydrous ethanol to obtain a precursor solution, and the mass concentration of TEOS in the precursor solution is 40%; Wherein, in the magnetic powder premix solution, the mass ratio of PVP and FeSi magnetic powder is 0.1:1, 1 mL of anhydrous ethanol is added for every 1 g of FeSi magnetic powder; (2) Pour the catalyst solution into the three-necked flask containing the magnetic powder premix solution and stir until uniform, then slowly drop the precursor solution into the three-necked flask containing the magnetic powder premix solution, control the mass ratio of TEOS and FeSi magnetic powder to be 0.1:1, and the mass ratio of catalyst solution and precursor solution to be 1:1, after stirring at room temperature for 45 min, perform drying to obtain FeSi / SiO2 composite powder with SiO2 coating; (3) Place the FeSi / SiO2 composite powder in an atmosphere furnace, perform recrystallization heat treatment in a nitrogen atmosphere after vacuumizing, heat to 500 ℃, and keep for 180 min to obtain FeSi / SiO2 composite soft magnetic powder; (4) Mix phosphoric acid, silicone, acetone dispersant, and FeSi / SiO2 composite soft magnetic powder uniformly to form multi-layer insulation coating, wherein the mass ratio of phosphoric acid, silicone, and FeSi / SiO2 composite soft magnetic powder is 0.02:0.001:1, the acetone dispersant is 10% of the mass of FeSi / SiO2 composite soft magnetic powder, then perform compression molding, the compression pressure is 1800 MPa, then perform annealing heat treatment in a vacuum atmosphere, the heat treatment temperature is 500 ℃, and the holding time is 240 min to prepare FeSi / SiO2 composite magnetic powder core.
[0035] Example 3 A method for preparing a FeSi magnetic powder core, comprising the following steps: (1) Mix polyvinylpyrrolidone (PVP) and anhydrous ethanol, then pour into a three-necked flask and stir until uniform, then add FeSi magnetic powder and mix until uniform, pour out the supernatant from the flask to obtain a magnetic powder premix solution; dissolve NH3·H2O in a 95% by volume ethanol aqueous solution to adjust the pH to 10.2 to obtain a catalyst solution; dissolve tetraethoxysilane (TEOS) in anhydrous ethanol to obtain a precursor solution, the mass concentration of tetraethoxysilane in the precursor solution is 40%; Wherein, in the magnetic powder premix solution, the mass ratio of PVP and FeSi magnetic powder is 0.08:1, 1 mL of anhydrous ethanol is added for every 1 g of FeSi magnetic powder; (2) Pour the catalyst solution into the three-necked flask containing the magnetic powder premix solution and stir until uniform, then slowly drop the precursor solution into the three-necked flask containing the magnetic powder premix solution, control the mass ratio of TEOS and FeSi magnetic powder to be 0.04:1, and the mass ratio of catalyst solution and precursor solution to be 1:1, after stirring at room temperature for 60 min, perform drying to obtain FeSi / SiO2 composite powder with SiO2 coating; (3) The FeSi / SiO2 composite powder is placed in an atmosphere furnace, vacuumized, and then recrystallized and heat-treated in a nitrogen atmosphere, heated to 600 DEG C, and kept for 120 min to obtain FeSi / SiO2 composite soft magnetic powder; (4) The phosphoric acid, silicone resin, acetone dispersant, and FeSi / SiO2 composite soft magnetic powder are mixed uniformly to form a multi-layer insulation coating, wherein the mass ratio of the phosphoric acid, silicone resin, and FeSi / SiO2 composite soft magnetic powder is 0.005:0.008:1, the acetone dispersant is 10% of the mass of the FeSi / SiO2 composite soft magnetic powder, and then compression molding is performed, the compression pressure is 1800 MPa, and then annealing heat treatment is performed in a vacuum atmosphere, the heat treatment temperature is 600 DEG C, and the holding time is 180 min to prepare a FeSi / SiO2 composite magnetic powder core.
[0036] Example 4 A preparation method of a FeSi magnetic powder core, comprising the following steps: (1) Polyvinylpyrrolidone (PVP) and anhydrous ethanol are mixed and then stirred uniformly in a three-necked flask, and then FeSi magnetic powder is added and stirred uniformly, the supernatant in the flask is poured out, and a magnetic powder premix is obtained; NH3·H2O is dissolved in a 95% volume concentration ethanol aqueous solution to control the pH to 10.4, and a catalyst solution is obtained; tetraethoxysilane (TEOS) is dissolved in anhydrous ethanol to obtain a precursor solution, and the mass concentration of the tetraethoxysilane in the precursor solution is 40%; In the magnetic powder premix, the mass ratio of PVP to FeSi magnetic powder is 0.06:1, and 1 mL of anhydrous ethanol is added per 1 g of FeSi magnetic powder; (2) The catalyst solution is poured into the three-necked flask containing the magnetic powder premix and stirred uniformly, and then the precursor solution is slowly dropped into the three-necked flask containing the magnetic powder premix, the mass ratio of TEOS to FeSi magnetic powder is controlled to be 0.06:1, and the mass ratio of the catalyst solution to the precursor solution is 1:1, after stirring at room temperature for 75 min, drying is performed to obtain FeSi / SiO2 composite powder with SiO2 coating; (3) The FeSi / SiO2 composite powder is placed in an atmosphere furnace, vacuumized, and then recrystallized and heat-treated in a nitrogen atmosphere, heated to 800 DEG C, and kept for 90 min to obtain FeSi / SiO2 composite soft magnetic powder; (4) The phosphoric acid, silicone resin, acetone dispersant and FeSi / SiO2 composite soft magnetic powder are mixed uniformly to form a multi-layer insulation coating, wherein the mass ratio of the phosphoric acid, silicone resin and FeSi / SiO2 composite soft magnetic powder is 0.008:0.01:1, the acetone dispersant is 10% of the mass of the FeSi / SiO2 composite soft magnetic powder, then compression molding is performed, the compression pressure is 1800 MPa, and then annealing heat treatment is performed in a vacuum atmosphere, the heat treatment temperature is 700 ℃, and the holding time is 120 min, to prepare a FeSi / SiO2 composite magnetic powder core.
[0037] Example 5 A preparation method of a FeSi magnetic powder core, comprising the following steps: (1) Polyvinylpyrrolidone (PVP) and anhydrous ethanol are mixed and then stirred uniformly in a three-necked flask, and then FeSi magnetic powder is added and stirred uniformly, and the supernatant in the flask is poured out to obtain a magnetic powder premix solution; NH3·H2O is dissolved in an ethanol aqueous solution with a volume concentration of 95% to control the pH to be 10.6 to obtain a catalyst solution; tetraethoxysilane (TEOS) is dissolved in anhydrous ethanol to obtain a precursor solution, and the mass concentration of the tetraethoxysilane in the precursor solution is 40%; In the magnetic powder premix solution, the mass ratio of PVP to FeSi magnetic powder is 0.04:1, and 1 mL of anhydrous ethanol is added for every 1 g of FeSi magnetic powder; (2) The catalyst solution is poured into the three-necked flask containing the magnetic powder premix solution and stirred uniformly, and then the precursor solution is slowly dropped into the three-necked flask containing the magnetic powder premix solution, the mass ratio of TEOS to FeSi magnetic powder is controlled to be 0.08:1, and the mass ratio of the catalyst solution to the precursor solution is 1:1, after stirring at room temperature for 90 min, drying is performed to obtain FeSi / SiO2 composite powder with SiO2 coating; (3) The FeSi / SiO2 composite powder is placed in an atmosphere furnace, vacuumized, and then recrystallization heat treatment is performed in a nitrogen atmosphere, the temperature is raised to 1000 ℃, and the temperature is kept for 60 min to obtain FeSi / SiO2 composite soft magnetic powder; (4) The phosphoric acid, silicone resin, acetone dispersant and FeSi / SiO2 composite soft magnetic powder are mixed uniformly to form a multi-layer insulation coating, wherein the mass ratio of the phosphoric acid, silicone resin and FeSi / SiO2 composite soft magnetic powder is 0.01:0.03:1, the acetone dispersant is 10% of the mass of the FeSi / SiO2 composite soft magnetic powder, then compression molding is performed, the compression pressure is 1800 MPa, and then annealing heat treatment is performed in a vacuum atmosphere, the heat treatment temperature is 700 ℃, and the holding time is 120 min, to prepare a FeSi / SiO2 composite magnetic powder core.
[0038] Example 6 A preparation method of a FeSi magnetic powder core, each step and reagents, equipment and process parameters used in each step are the same as those in example 5, the difference is that in step (4), the mass ratio of phosphoric acid, silicone resin and FeSi / SiO2 composite soft magnetic powder is 0:0.03:1.
[0039] Example 7 A preparation method of a FeSi magnetic powder core, each step and reagents, equipment and process parameters used in each step are the same as those in example 5, the difference is that in step (3), the recrystallization heat treatment is heated to 500 ℃ and kept for 180 min.
[0040] Example 8 A preparation method of a FeSi magnetic powder core, each step and reagents, equipment and process parameters used in each step are the same as those in example 5, the difference is that in step (3), the recrystallization heat treatment is heated to 600 ℃ and kept for 120 min.
[0041] Example 9 A preparation method of a FeSi magnetic powder core, each step and reagents, equipment and process parameters used in each step are the same as those in example 5, the difference is that in step (3), the recrystallization heat treatment is heated to 800 ℃ and kept for 90 min.
[0042] Example 10 A preparation method of a FeSi magnetic powder core, each step and reagents, equipment and process parameters used in each step are the same as those in example 5, the difference is that in step (3), the recrystallization heat treatment is heated to 1100 ℃ and kept for 30 min.
[0043] Comparative example 1 A preparation method of a FeSi magnetic powder core, comprising the following steps: (1) polyvinylpyrrolidone (PVP) and anhydrous ethanol are mixed and then stirred uniformly in a three-necked flask, then FeSi magnetic powder is added and stirred uniformly, the supernatant in the flask is poured out, and a magnetic powder premix is obtained; NH3·H2O is dissolved in a 95% volume concentration ethanol aqueous solution to control the pH to 10.6, and a catalyst solution is obtained; tetraethoxysilane (TEOS) is dissolved in anhydrous ethanol to obtain a precursor solution, and the mass concentration of tetraethoxysilane in the precursor solution is 40%; In the magnetic powder premix, the mass ratio of PVP and FeSi magnetic powder is 0.04:1, and 1 mL of anhydrous ethanol is added per 1 g of FeSi magnetic powder; (2) The catalyst solution is poured into the three-necked flask containing the magnetic powder premix solution and stirred uniformly, then the precursor solution is slowly dropped into the three-necked flask containing the magnetic powder premix solution, the mass ratio of TEOS to FeSi magnetic powder is controlled to be 0.08:1, the mass ratio of the catalyst solution to the precursor solution is 1:1, after stirring at room temperature for 90 min, drying is performed to obtain the FeSi / SiO2 composite powder coated with SiO2; (3) The phosphoric acid, silicone resin, acetone dispersant and the FeSi / SiO2 composite powder coated with SiO2 are fully mixed uniformly to form a multi-layer insulation coating, wherein the mass ratio of the phosphoric acid, silicone resin and FeSi / SiO2 composite powder is 0.01:0.03:1, the acetone dispersant is 10% of the mass of the FeSi / SiO2 composite powder, then compression molding is performed, the compression pressure is 1800 MPa, then annealing heat treatment is performed in a vacuum atmosphere, the heat treatment temperature is 700 ℃, and the holding time is 120 min, to prepare the FeSi / SiO2 composite magnetic powder core.
[0044] Comparative Example 2 A preparation method of a FeSi magnetic powder core, comprising the following steps: The phosphoric acid, silicone resin, acetone dispersant and FeSi magnetic powder are fully mixed uniformly to form an insulation coating, wherein the mass ratio of the phosphoric acid, silicone resin and FeSi magnetic powder is 0.01:0.03:1, the acetone dispersant is 10% of the mass of the FeSi / SiO2 composite soft magnetic powder, then compression molding is performed, the compression pressure is 1800 MPa, then annealing heat treatment is performed in a vacuum atmosphere, the heat treatment temperature is 700 ℃, and the holding time is 120 min, to prepare the FeSi magnetic powder core.
[0045] Comparative Example 3 (1) The FeSi magnetic powder is placed in an atmosphere furnace, vacuumized, and then recrystallization heat treatment is performed in a nitrogen atmosphere, the temperature is raised to 1000 ℃, and the holding time is 60 min, to obtain FeSi soft magnetic powder; (2) The phosphoric acid, silicone resin, acetone dispersant and FeSi soft magnetic powder are fully mixed uniformly, wherein the mass ratio of the phosphoric acid, silicone resin and FeSi soft magnetic powder is 0.01:0.03:1, the acetone dispersant is 10% of the mass of the FeSi / SiO2 composite soft magnetic powder, then compression molding is performed, the compression pressure is 1800 MPa, then annealing heat treatment is performed in a vacuum atmosphere, the heat treatment temperature is 700 ℃, and the holding time is 120 min, to prepare the FeSi magnetic powder core.
[0046] Comparative Example 4 A preparation method of a FeSi magnetic powder core, each step and the reagents, equipment and process parameters used in each step are the same as those of Example 5, the difference lies in that in step (1), anhydrous ethanol is poured into a three-necked flask and stirred uniformly, then FeSi magnetic powder is added and stirred uniformly, the supernatant in the flask is poured out, and a magnetic powder premix is obtained; NH3·H2O is dissolved in an ethanol aqueous solution with a volume concentration of 95% to control the pH to be 10.6, and a catalyst solution is obtained; tetraethoxysilane (TEOS) is dissolved in anhydrous ethanol to obtain a precursor solution, and the mass concentration of tetraethoxysilane in the precursor solution is 40%; In the magnetic powder premix, 1 mL of anhydrous ethanol is added per 1 g of FeSi magnetic powder.
[0047] Comparative Example 5 A preparation method of a FeSi magnetic powder core, each step and the reagents, equipment and process parameters used in each step are the same as those of Example 5, the difference lies in that in the magnetic powder premix of step (1), the mass ratio of PVP to FeSi magnetic powder is 0.2:1.
[0048] Comparative Example 6 A preparation method of a FeSi magnetic powder core, each step and the reagents, equipment and process parameters used in each step are the same as those of Example 5, the difference lies in that in step (2), the mass ratio of TEOS to FeSi magnetic powder is controlled to be 0.2:1.
[0049] Comparative Example 7 A preparation method of a FeSi magnetic powder core, each step and the reagents, equipment and process parameters used in each step are the same as those of Example 5, the difference lies in that in step (4), the acetone dispersant and the FeSi / SiO2 composite soft magnetic powder are fully mixed and uniformly dispersed, the mass of the acetone dispersant is 10% of the mass of the FeSi / SiO2 composite soft magnetic powder, no other coating agent is added, and then the FeSi / SiO2 composite soft magnetic powder is pressed and formed, the pressing pressure is 1800 MPa, and then the FeSi / SiO2 composite magnetic powder core is prepared by annealing and heat treatment in a vacuum atmosphere, the heat treatment temperature is 700 ℃, and the holding time is 120 min.
[0050] Performance detection test 1. Magnetic permeability and loss: a Japanese Iwasaki B-H analyzer (IWATSU, SY-8219) is used for testing under the following conditions: double-wire winding 26 turns, test frequency 50 kHz, and test magnetic field strength 100 mT, and the test results are shown in Table 1 below.
[0051] 2. DC bias capability: the DC bias capability is detected by a TH2839+TH1779 device under the following conditions: single-wire winding 15 turns and test current 33.7 A (i.e., magnetic field strength 100 Oe), and the test results are shown in Table 1 below.
[0052] Table 1 - Performance test results of FeSi magnetic powder cores prepared by the embodiments and comparative examples of the present application As shown in Table 1, in the embodiments 1-5 of the present application, the SiO2 oxide thin coating layer with high resistivity is grown in-situ on the surface of FeSi magnetic powder by sol-gel method, which can effectively prevent the problem of agglomeration caused by metallurgical bonding between particles during high-temperature heat treatment. Then, the recrystallization heat treatment technology is used for high-temperature pretreatment, and the annealing of the powder can make the powder between the particles grow more fully, greatly eliminate the internal stress of the powder, and reduce the loss of the powder core, so that the prepared FeSi / SiO2 composite magnetic powder core has low loss and high DC bias characteristics. Compared with example 5, the internal stress of the powder cannot be effectively removed in comparative example 1 which does not use recrystallization heat treatment technology for high-temperature pretreatment, resulting in an increase in the loss of the FeSi magnetic powder core and a decrease in the DC bias capability.
[0053] Compared with example 5, in comparative example 2, FeSi magnetic powder without SiO2 surface modification coating and recrystallization heat treatment is directly mixed with phosphoric acid, silicone resin and acetone to form a mixture and then is pressed into a shape. In comparative example 3, FeSi magnetic powder without SiO2 surface modification coating is directly subjected to recrystallization heat treatment. Since the surface of the FeSi magnetic powder is not coated with a SiO2 layer, the FeSi magnetic powder will agglomerate due to metallurgical bonding between particles during annealing heat treatment, and the internal stress of the FeSi magnetic powder is large, ultimately resulting in an increase in the loss of the FeSi magnetic powder core and a decrease in the DC bias capability.
[0054] Compared with example 5, in comparative example 4, PVP is not added to the magnetic powder premix solution in step (1). PVP can increase the stickiness of the surface of FeSi magnetic powder, which is helpful for the in-situ growth of SiO2. The lack of PVP will affect the integrity of the coating structure of SiO2 on the surface of FeSi magnetic powder, resulting in an increase in the loss of the FeSi magnetic powder core and a decrease in the DC bias capability.
[0055] Compared with example 5, in comparative example 5, the ratio of PVP to FeSi magnetic powder in the magnetic powder premix solution in step (1) is 0.2:1. Too much PVP will cause SiO2 to agglomerate, so that a uniform coating structure cannot be formed on the surface of FeSi magnetic powder, ultimately resulting in an increase in the loss of the FeSi magnetic powder core and a decrease in the magnetic permeability.
[0056] Compared with example 5, in comparative example 6, the ratio of TEOS to FeSi magnetic powder in step (2) is 0.2:1. Too much TEOS will reduce the alkaline environment of the system, resulting in insufficient hydrolysis of TEOS and affecting the in-situ growth of SiO2 on the surface of FeSi magnetic powder.
[0057] Compared with Example 5, the comparative example 7 does not use silicon resin and phosphoric acid to form an insulating coating layer on the surface of the FeSi / SiO2 composite soft magnetic powder in step (4), so that the magnetic powder core is more stable during annealing, the coating layer is not damaged, the loss of the iron-silicon magnetic powder core is reduced, and the direct current bias capability is improved.
[0058] Compared with Example 5, the Example 6 does not add phosphoric acid in step (4). The addition of phosphoric acid for coating treatment can construct a high-quality and high-resistivity insulating layer on the surface of the metal magnetic powder particles through chemical reaction. However, the Example 6 does not add phosphoric acid, which may cause problems such as reduction of insulation of the magnetic powder core, high eddy current loss, insufficient frequency stability, and limited thermal stability.
[0059] The above specific embodiments further illustrate the purpose, technical solutions and advantages of the present application. It should be understood that the above description is only for specific embodiments of the present application and is not intended to limit the protection scope of the present application. It is particularly pointed out that any modification, equivalent replacement, improvement, etc. made by those skilled in the art within the spirit and principles of the present application shall be included in the protection scope of the present application.
Claims
1. A method for preparing an iron-silicon magnetic powder core, characterized in that, Includes the following steps: (1) Stir the catalyst solution with pH 10-11 and the magnetic powder premix evenly, then slowly add the precursor solution, stir the reaction at room temperature, and dry to obtain FeSi / SiO2 composite powder. The catalyst solution includes an alkaline catalyst, the magnetic powder premix includes polyvinylpyrrolidone and FeSi magnetic powder in a mass ratio of (0.01-0.1):1, and the precursor solution includes a silicon source in a mass ratio of (0.01-0.1):
1. (2) The FeSi / SiO2 composite powder is placed in an atmosphere furnace for recrystallization heat treatment to obtain FeSi / SiO2 composite soft magnetic powder; (3) Mix the silicone resin, dispersant and FeSi / SiO2 composite soft magnetic powder evenly, then press it into shape, and then anneal it under vacuum or nitrogen atmosphere to prepare FeSi / SiO2 composite magnetic powder core.
2. The method for preparing the iron-silicon magnetic powder core as described in claim 1, characterized in that, In step (1), the alkaline catalyst is NH3·H2O; And / or, in step (1), the silicon source is at least one of tetraethoxysilane, sodium silicate, methyl orthosilicate, and silica sol; And / or, in step (1), the mass ratio of the catalyst solution to the precursor solution is (0.5-2):
1.
3. The method for preparing the iron-silicon magnetic powder core as described in claim 1, characterized in that, In step (2), the recrystallization heat treatment temperature is 500-1100 ℃ and the holding time is 30-180 min.
4. The method for preparing the iron-silicon magnetic powder core as described in claim 1, characterized in that, In step (3), phosphoric acid, silicone resin, dispersant and FeSi / SiO2 composite soft magnetic powder are mixed evenly, and the mass ratio of phosphoric acid to FeSi / SiO2 composite soft magnetic powder is (0.001-0.02):1; And / or, in step (3), the mass ratio of the silicone resin and FeSi / SiO2 composite soft magnetic powder is (0.001-0.05):
1.
5. The method for preparing the iron-silicon magnetic powder core as described in claim 1, characterized in that, In step (1), the catalyst solution comprises an alkaline catalyst and water; And / or, the precursor solution comprises a silicon source and a solvent with a mass fraction of 5%-50%; And / or, the magnetic powder premix also includes a solvent, with 0.5-2 mL of solvent added per 1g of FeSi magnetic powder.
6. The method for preparing the iron-silicon magnetic powder core as described in claim 5, characterized in that, The solvent is anhydrous ethanol and / or acetone.
7. The method for preparing the iron-silicon magnetic powder core as described in claim 1, characterized in that, In step (3), the dispersant is ethanol and / or propanol; And / or, in step (3), the dispersant is 5%-20% of the mass of FeSi / SiO2 composite soft magnetic powder.
8. The method for preparing the iron-silicon magnetic powder core as described in claim 1, characterized in that, In step (3), the pressing pressure for compression molding is 1000-3000 MPa; And / or, in step (3), the annealing heat treatment temperature is 500-800 ℃ and the holding time is 30-240 min.
9. An iron-silicon magnetic powder core prepared by the method for preparing an iron-silicon magnetic powder core as described in any one of claims 1-8.
10. The application of the iron-silicon magnetic powder core as described in claim 9 in the field of electronic equipment or new energy equipment.