A high permeability low coercivity soft magnetic composite material and a method of making the same

Abstract

The application relates to the field of magnetic materials, in particular to a high-permeability low-coercivity soft magnetic composite material and a preparation method thereof. 17 Magnetic powder, FeNi magnetic powder and Mn x Zn y Fe z O4 magnetic powder to obtain mixed magnetic powder; wherein 0.51<=x<=0.75, 0.51<=y<=0.75, 2.01<=z<=2.10, and x+y+z=3; S2: passivating the mixed magnetic powder; S3: mixing polyurethane powder and polysilazane powder, dissolving the mixed polyurethane powder and polysilazane powder in acetone, then adding the mixed magnetic powder obtained in the step S2, and ultrasonically drying the acetone until the product is oriented in a magnetic field and mixed magnetic powder green bodies are obtained; S4: pressing the mixed magnetic powder green bodies obtained in the step S3; S5: heat treatment under the protection of an inert atmosphere to ceramize the polysilazane, and then annealing treatment and cooling; the soft magnetic composite material has excellent magnetic performance and can have high permeability and low coercivity.

Description

Technical Field

[0001] This invention relates to the field of magnetic materials, specifically to a soft magnetic composite material with high permeability and low coercivity, its preparation method, and its applications. Background Technology

[0002] Currently, commonly used soft magnetic materials mainly include iron-nickel alloys, ferrites, and amorphous and nanocrystalline materials. Iron-nickel alloys have high permeability and high saturation magnetic induction, but they are easily deformable and have limited resistance to eddy currents, making it difficult to fully meet practical needs. Ferrite soft magnetic materials have high resistivity and strong resistance to eddy currents, but their low saturation magnetic induction (-0.6T) poses a significant challenge to the optimization design of bias magnetic fields in magnetic circuit design, affecting the design and effective use of the magnetic circuit system. Amorphous and nanocrystalline materials are not pressure-resistant and have high mechanical losses. Therefore, traditional soft magnetic materials are increasingly unable to meet the requirements of some special application fields.

[0003] Metal-based rare earth composite soft magnetic materials are a type of composite soft magnetic material developed to meet the needs of the electronics industry. The outstanding features of this material are its relatively excellent high-frequency characteristics and high permeability, which to a certain extent achieves synergistic optimization of permeability and cutoff frequency.

[0004] Chinese patent application CN121394155A discloses a 2:17 type rare-earth soft magnetic / Fe-based soft magnetic laminate composite material and its preparation method. The method involves sieving and insulating 2:17 type rare-earth soft magnetic powder and Fe-based soft magnetic powder separately, mixing them with polyurethane, and then orienting them using a magnetic field to obtain a thin ring green body. The 2:17 type rare-earth soft magnetic thin ring green body and the Fe-based soft magnetic thin ring green body are then alternately stacked along a direction perpendicular to the plane of the green body and hot-pressed. This invention achieves high permeability and low loss to a certain extent. However, the low resistivity of FeNi metal powder (approximately between 40-60 μΩ·cm) also leads to increased high-frequency eddy current losses. Summary of the Invention

[0005] The first aspect of this invention is to provide a method for preparing a soft magnetic composite material with high magnetic permeability and low coercivity, comprising the following steps: S1: Sm2Co 17 Magnetic powder, FeNi magnetic powder and Mn x Zn y Fe z O4 magnetic powder is mixed to obtain mixed magnetic powder; wherein, 0.51≤x≤0.75, 0.51≤y≤0.75, 2.01≤z≤2.10, and x+y+z=3; S2: Add the mixed magnetic powder obtained in step S1 to acetone containing phosphoric acid solution for passivation to obtain the passivated mixed magnetic powder; S3: After mixing polyurethane powder and polysilazane powder, dissolve them in acetone, then add the mixed magnetic powder obtained in step S2, sonicate until the acetone evaporates, and then perform magnetic field orientation on the obtained product to obtain a mixed magnetic powder green body. S4: Press the mixed magnetic powder green body obtained in step S3 into a mixed soft magnetic composite material; S5: The polysilazane is ceramized by heat treatment under an inert atmosphere, followed by annealing and cooling to obtain the soft magnetic composite material.

[0006] In some implementations, x is 0.51, y is 0.42, and z is 2.07.

[0007] In some implementations, x is 0.75, y is 0.15, and z is 2.10.

[0008] In some implementations, x is 0.64, y is 0.29, and z is 2.07.

[0009] In some embodiments, in step S3, the total weight of the polyurethane powder and the polysilazane powder is 5% of the mass of the mixed magnetic powder.

[0010] In some embodiments, the mass ratio of the polyurethane powder to the polysilazane powder is 1:1 to 1:4.

[0011] In some embodiments, the mass ratio of the polyurethane powder to the polysilazane powder is 1:1, 1:3, or 1:4.

[0012] In some embodiments, the mass ratio of the polyurethane powder to the polysilazane powder is 1:4.

[0013] In some implementations, the heat treatment conditions in step S5 are 600°C for 60 to 180 minutes.

[0014] In some implementations, the heat treatment conditions in step S5 are 600°C for 60 min.

[0015] In some implementations, the heat treatment conditions in step S5 are 600°C for 90 min.

[0016] In some implementations, the heat treatment conditions in step S5 are 600°C for 120 min.

[0017] In some implementations, the heat treatment conditions in step S5 are 600°C for 180 min.

[0018] In some implementations, the passivation process in step S2 is as follows: add phosphoric acid solution dropwise to acetone, stir ultrasonically until homogeneous, then add the mixed magnetic powder obtained in step S1, stir ultrasonically until the acetone evaporates to dryness.

[0019] In some implementations, the specific process of pressing in step S4 is as follows: the mixed magnetic powder green body is held under pressure at 1200 MPa and 100°C for a period of time.

[0020] In some implementations, the specific process of ceramicization in step S5 is as follows: under argon protection, the temperature is increased from 200 °C to 600 °C at a heating rate of 5 °C / min, and then subjected to constant temperature heat treatment for 90 min.

[0021] In some implementations, the annealing process in step S5 is as follows: annealing at 400°C for 120 min under argon protection, followed by rapid cooling to room temperature.

[0022] In some embodiments, the maximum permeability of the high-permeability, low-coercivity soft magnetic composite material is greater than or equal to 34.

[0023] In some embodiments, the maximum permeability of the high-permeability, low-coercivity soft magnetic composite material is greater than or equal to 34 and less than or equal to 45.

[0024] In some embodiments, the maximum permeability of the high-permeability, low-coercivity soft magnetic composite material is greater than or equal to 40.

[0025] In some embodiments, the coercivity of the high-permeability, low-coercivity soft magnetic composite material is less than or equal to 4 A / m.

[0026] In some embodiments, the coercivity of the high-permeability, low-coercivity soft magnetic composite material is less than or equal to 3 A / m.

[0027] In some embodiments, the coercivity of the high-permeability, low-coercivity soft magnetic composite material is less than or equal to 2.5 A / m.

[0028] In a second aspect, the present invention provides a high permeability, low coercivity soft magnetic composite material, which is prepared by the preparation method of the high permeability, low coercivity soft magnetic composite material described in any of the foregoing embodiments.

[0029] A third aspect of the present invention provides the use of the high permeability and low coercivity soft magnetic composite material described in any of the foregoing embodiments in the fabrication of inductors.

[0030] Compared with the prior art, the present invention has the following beneficial effects: 1. The MnZn ferrite introduced in this invention has extremely high electrical resistance and high eddy current resistance, which can significantly reduce the eddy current loss of soft magnetic composite materials. The polysilazane used in this invention can be ceramized at high temperatures, effectively blocking the electrical contact between magnetic powder particles and confining eddy currents within individual particles. This significantly reduces overall structural eddy current losses, achieving high permeability and low coercivity under high resistance (low eddy current loss) conditions, meeting the stringent requirements for eddy current resistance in mid-to-high frequency electromagnetic field environments. It provides a better solution for high-performance, low-power soft magnetic components used in high-frequency applications.

[0031] 2. This invention utilizes the high ductility and high-temperature resistance of polysilazane to achieve stress-relieving annealing at 600℃. This significantly reduces coercivity while maintaining the stability of the material structure and achieving low eddy current loss. Detailed Implementation

[0032] I. Definitions and Explanations In this invention, unless otherwise stated, the scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, the related terms and laboratory procedures used herein are all widely used terms and routine procedures in the respective fields. To better understand this invention, definitions and explanations of related terms are provided below.

[0033] In the description herein, references to “some embodiments,” “some implementations,” or “some implementation schemes” describe a subset of all possible embodiments. However, it is understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0034] As used herein and unless otherwise stated, the terms “comprising,” “including,” “having,” “containing,” and their grammatical equivalents, including their grammatical equivalents, should generally be understood as open-ended and non-restrictive, e.g., not excluding other unlisted elements or steps.

[0035] In this specification and the claims reported herein, the phrase “and / or” is interpreted as meaning “any one or both” of the elements, that is, the elements may exist together in some cases or the elements may exist separately in other cases.

[0036] In this article, the term "magnetic permeability" refers to a physical quantity that characterizes the magnetization energy of a magnetic medium. When a certain current flows through a coil, the magnetic field strength changes due to the presence of the magnetic medium. The magnetic induction intensity at each point will be several times stronger or weakened to a fraction of the magnetic field strength when the magnetic medium is absent (assuming the magnetic medium is homogeneous and fills the entire space occupied by the magnetic field). The influence of various materials on the magnetic field strength is measured by magnetic permeability: the ratio of the magnetic induction intensity B at a point in a material to the magnetic field strength at that point (in MKS units) is the magnetic permeability μ of that material at that moment.

[0037] In this article, the term "coercivity" refers to the phenomenon in ferromagnetic materials where the change in magnetic flux density B always lags behind the change in magnetic field strength H during repeated magnetization. This means that for the same value of H, the change in magnetic field strength will result in different values ​​of B when the external magnetic field increases or decreases; this irreversible phenomenon is called hysteresis. When the applied magnetic field strength H drops to zero, the value of B does not return to zero but remains constant; this is called remanent magnetic induction, or simply remanence. To bring the value of B back to zero, a reverse magnetic field strength Hc must be applied; Hc is called the coercive magnetic field strength, commonly known as coercivity. Coercivity is not only related to the properties of the ferromagnetic material but also depends on its original magnetization. The difference in coercivity is one of the important distinctions between soft and hard magnetic materials. When manufacturing transformer cores or electromagnets, materials with lower coercivity (such as soft iron and silicon steel) need to be selected, while materials with higher coercivity (such as AlNiCo) need to be selected when manufacturing permanent magnets to preserve magnetism as much as possible.

[0038] II. Examples The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0039] Example 1: Sm2Co 17 / Mn 0.51 Zn 0.42 Fe 2.07 Preparation of O4 / FeNi soft magnetic composite material (1) Sm2Co 17 Magnetic powder, FeNi magnetic powder and Mn 0.51 Zn 0.42 Fe 2.07 O4 magnetic powder was sieved separately to control the particle size to be less than 10μm; the three powders were then uniformly mixed by ball milling to obtain mixed magnetic powder. (2) Add phosphoric acid solution to 6 mL of acetone, stir evenly with ultrasonication, and then add 2.0 g of the mixed magnetic powder obtained in the previous step (the amount of phosphoric acid solution added is 0.3% of the mass of the mixed magnetic powder). Continue to stir with ultrasonication until the acetone is completely evaporated to obtain the passivated mixed magnetic powder. (3) Weigh polyurethane powder and polysilazane powder (the total weight ratio is 5% of the mass of the mixed magnetic powder obtained in the previous step, and the mass ratio of polyurethane powder to polysilazane powder is 1:1), dissolve them in 10 mL of acetone, and ultrasonically stir until the powder is completely dissolved. Then add the passivated mixed magnetic powder obtained in the previous step and continue ultrasonic stirring until the acetone is completely evaporated to obtain mixed magnetic powder-polyurethane-polysilazane. Orient it in a magnetic field at 1.2T for 60s to obtain a mixed magnetic powder green body with a thickness of about 200 μm. (4) The mixed magnetic powder green body is kept under pressure at 1200 MPa and 100 °C for a period of time to obtain the mixed soft magnetic composite material; (5) The pressed hybrid soft magnetic composite material was heated to 200℃ for 80 min at a heating rate of 5℃ / min under argon protection, and then heat-treated at 600℃ for 90 min under argon protection to ceramicize the polysiloxane. Under argon protection, it was annealed at 400℃ for 120 min, and then rapidly cooled to room temperature to obtain the soft magnetic composite material described in the title.

[0040] Example 2: Sm2Co 17 / Mn 0.51 Zn 0.42 Fe 2.07 Preparation of O4 / FeNi soft magnetic composite material (1) Sm2Co 17 Magnetic powder, FeNi magnetic powder and Mn 0.51 Zn 0.42 Fe 2.07 O4 magnetic powder was sieved separately to control the particle size to be less than 10μm; the three powders were then uniformly mixed by ball milling to obtain mixed magnetic powder. (2) Add phosphoric acid solution to 6 mL of acetone, stir evenly with ultrasonication, and then add 2.0 g of the mixed magnetic powder obtained in the previous step (the amount of phosphoric acid solution added is 0.3% of the mass of the mixed magnetic powder). Continue to stir with ultrasonication until the acetone is completely evaporated to obtain the passivated mixed magnetic powder. (3) Weigh polyurethane powder and polysilazane powder (the total weight ratio is 5% of the mass of the mixed magnetic powder obtained in the previous step, and the mass ratio of polyurethane powder to polysilazane powder is 1:4), dissolve them in 10 mL of acetone, and ultrasonically stir until the powder is completely dissolved. Then add the passivated mixed magnetic powder obtained in the previous step and continue ultrasonic stirring until the acetone is completely evaporated to obtain mixed magnetic powder-polyurethane-polysilazane. Orient it in a magnetic field at 1.2T for 60s to obtain a mixed magnetic powder green body with a thickness of about 200 μm. (4) The mixed magnetic powder green body is kept under pressure at 1200 MPa and 100 °C for a period of time to obtain the mixed soft magnetic composite material; (5) The pressed hybrid soft magnetic composite material was heated to 200℃ for 80 min at a heating rate of 5℃ / min under argon protection, and then heat-treated at 600℃ for 90 min under argon protection to ceramicize the polysiloxane. Under argon protection, it was annealed at 400℃ for 120 min, and then rapidly cooled to room temperature to obtain the soft magnetic composite material described in the title.

[0041] Example 3: Sm2Co 17 / Mn 0.75 Zn 0.15 Fe 2.10 Preparation of O4 / FeNi soft magnetic composite material (1) Sm2Co 17 Magnetic powder, FeNi magnetic powder and Mn 0.75 Zn 0.15 Fe 2.10 O4 magnetic powder was sieved separately to control the particle size to be less than 10μm; the three powders were then uniformly mixed by ball milling to obtain mixed magnetic powder. (2) Add phosphoric acid solution to 6 mL of acetone, stir evenly with ultrasonication, and then add 2.0 g of the mixed magnetic powder obtained in the previous step (the amount of phosphoric acid solution added is 0.3% of the mass of the mixed magnetic powder). Continue to stir with ultrasonication until the acetone is completely evaporated to obtain the passivated mixed magnetic powder. (3) Weigh polyurethane powder and polysilazane powder (the total weight ratio is 5% of the mass of the mixed magnetic powder obtained in the previous step, and the mass ratio of polyurethane powder to polysilazane powder is 1:3), dissolve them in 10 mL of acetone, and ultrasonically stir until the powder is completely dissolved. Then add the passivated mixed magnetic powder obtained in the previous step and continue ultrasonic stirring until the acetone is completely evaporated to obtain mixed magnetic powder-polyurethane-polysilazane. Orient it in a magnetic field at 1.2T for 60s to obtain a mixed magnetic powder green body with a thickness of about 200 μm. (4) The mixed magnetic powder green body is kept under pressure at 1200 MPa and 100 °C for a period of time to obtain the mixed soft magnetic composite material; (5) The pressed hybrid soft magnetic composite material was heated to 200℃ for 80 min at a heating rate of 5℃ / min under argon protection, and then heat-treated at 600℃ for 90 min under argon protection to ceramicize the polysiloxane. Under argon protection, it was annealed at 400℃ for 120 min, and then rapidly cooled to room temperature to obtain the soft magnetic composite material described in the title.

[0042] Example 4: Sm2Co 17 / Mn 0.64 Zn 0.29 Fe 2.07 Preparation of O4 / FeNi soft magnetic composite material (1) Sm2Co 17Magnetic powder, FeNi magnetic powder and Mn 0.64 Zn 0.29 Fe 2.07 O4 magnetic powder was sieved separately to control the particle size to be less than 10μm; the three powders were then uniformly mixed by ball milling to obtain mixed magnetic powder. (2) Add phosphoric acid solution to 6 mL of acetone, stir evenly with ultrasonication, and then add 2.0 g of the mixed magnetic powder obtained in the previous step (the amount of phosphoric acid solution added is 0.3% of the mass of the mixed magnetic powder). Continue to stir with ultrasonication until the acetone is completely evaporated to obtain the passivated mixed magnetic powder. (3) Weigh polyurethane powder and polysilazane powder (the total weight ratio is 5% of the mass of the mixed magnetic powder obtained in the previous step, and the mass ratio of polyurethane powder to polysilazane powder is 1:3), dissolve them in 10 mL of acetone, and ultrasonically stir until the powder is completely dissolved. Then add the passivated mixed magnetic powder obtained in the previous step and continue ultrasonic stirring until the acetone is completely evaporated to obtain mixed magnetic powder-polyurethane-polysilazane. Orient it in a magnetic field at 1.2T for 60s to obtain a mixed magnetic powder green body with a thickness of about 200 μm. (4) The mixed magnetic powder green body is kept under pressure at 1200 MPa and 100 °C for a period of time to obtain the mixed soft magnetic composite material; (5) The pressed hybrid soft magnetic composite material was heated to 200℃ for 80 min at a heating rate of 5℃ / min under argon protection, and then heat-treated at 600℃ for 90 min under argon protection to ceramicize the polysiloxane. Under argon protection, it was annealed at 400℃ for 120 min, and then rapidly cooled to room temperature to obtain the soft magnetic composite material described in the title.

[0043] Example 5: Sm2Co 17 / Mn 0.51 Zn 0.42 Fe 2.07 Preparation of O4 / FeNi soft magnetic composite material (1) Sm2Co 17 Magnetic powder, FeNi magnetic powder and Mn 0.51 Zn 0.42 Fe 2.07 O4 magnetic powder was sieved separately to control the particle size to be less than 10μm; the three powders were then uniformly mixed by ball milling to obtain mixed magnetic powder. (2) Add phosphoric acid solution to 6 mL of acetone, stir evenly with ultrasonication, and then add 2.0 g of the mixed magnetic powder obtained in the previous step (the amount of phosphoric acid solution added is 0.3% of the mass of the mixed magnetic powder). Continue to stir with ultrasonication until the acetone is completely evaporated to obtain the passivated mixed magnetic powder. (3) Weigh polyurethane powder and polysilazane powder (the total weight ratio is 5% of the mass of the mixed magnetic powder obtained in the previous step, and the mass ratio of polyurethane powder to polysilazane powder is 1:3), dissolve them in 10 mL of acetone, and ultrasonically stir until the powder is completely dissolved. Then add the passivated mixed magnetic powder obtained in the previous step and continue ultrasonic stirring until the acetone is completely evaporated to obtain mixed magnetic powder-polyurethane-polysilazane. Orient it in a magnetic field at 1.2T for 60s to obtain a mixed magnetic powder green body with a thickness of about 200 μm. (4) The mixed magnetic powder green body is kept under pressure at 1200 MPa and 100 °C for a period of time to obtain the mixed soft magnetic composite material; (5) The pressed hybrid soft magnetic composite material was heated to 200℃ for 80 min at a heating rate of 5℃ / min under argon protection, and then heat-treated at 600℃ for 60 min under argon protection to ceramicize the polysiloxane. Under argon protection, it was annealed at 400℃ for 120 min, and then rapidly cooled to room temperature to obtain the soft magnetic composite material described in the title.

[0044] Example 6: Sm2Co 17 / Mn 0.51 Zn 0.42 Fe 2.07 Preparation of O4 / FeNi soft magnetic composite material (1) Sm2Co 17 Magnetic powder, FeNi magnetic powder and Mn 0.51 Zn 0.42 Fe 2.07 O4 magnetic powder was sieved separately to control the particle size to be less than 10μm; the three powders were then uniformly mixed by ball milling to obtain mixed magnetic powder. (2) Add phosphoric acid solution to 6 mL of acetone, stir evenly with ultrasonication, and then add 2.0 g of the mixed magnetic powder obtained in the previous step (the amount of phosphoric acid solution added is 0.3% of the mass of the mixed magnetic powder). Continue to stir with ultrasonication until the acetone is completely evaporated to obtain the passivated mixed magnetic powder. (3) Weigh polyurethane powder and polysilazane powder (the total weight ratio is 5% of the mass of the mixed magnetic powder obtained in the previous step, and the mass ratio of polyurethane powder to polysilazane powder is 1:3), dissolve them in 10 mL of acetone, and ultrasonically stir until the powder is completely dissolved. Then add the passivated mixed magnetic powder obtained in the previous step and continue ultrasonic stirring until the acetone is completely evaporated to obtain mixed magnetic powder-polyurethane-polysilazane. Orient it in a magnetic field at 1.2T for 60s to obtain a mixed magnetic powder green body with a thickness of about 200 μm. (4) The mixed magnetic powder green body is kept under pressure at 1200 MPa and 100 °C for a period of time to obtain the mixed soft magnetic composite material; (5) The pressed hybrid soft magnetic composite material was heated to 200℃ for 80 min at a heating rate of 5℃ / min under argon protection, and then heat-treated at 600℃ for 90 min under argon protection to ceramicize the polysiloxane. Under argon protection, it was annealed at 400℃ for 120 min, and then rapidly cooled to room temperature to obtain the soft magnetic composite material described in the title.

[0045] Example 7: Sm2Co 17 / Mn 0.51 Zn 0.42 Fe 2.07 Preparation of O4 / FeNi soft magnetic composite material (1) Sm2Co 17 Magnetic powder, FeNi magnetic powder and Mn 0.51 Zn 0.42 Fe 2.07 O4 magnetic powder was sieved separately to control the particle size to be less than 10μm; the three powders were then uniformly mixed by ball milling to obtain mixed magnetic powder. (2) Add phosphoric acid solution to 6 mL of acetone, stir evenly with ultrasonication, and then add 2.0 g of the mixed magnetic powder obtained in the previous step (the amount of phosphoric acid solution added is 0.3% of the mass of the mixed magnetic powder). Continue to stir with ultrasonication until the acetone is completely evaporated to obtain the passivated mixed magnetic powder. (3) Weigh polyurethane powder and polysilazane powder (the total weight ratio is 5% of the mass of the mixed magnetic powder obtained in the previous step, and the mass ratio of polyurethane powder to polysilazane powder is 1:3), dissolve them in 10 mL of acetone, and ultrasonically stir until the powder is completely dissolved. Then add the passivated mixed magnetic powder obtained in the previous step and continue ultrasonic stirring until the acetone is completely evaporated to obtain mixed magnetic powder-polyurethane-polysilazane. Orient it in a magnetic field at 1.2T for 60s to obtain a mixed magnetic powder green body with a thickness of about 200 μm. (4) The mixed magnetic powder green body is kept under pressure at 1200 MPa and 100 °C for a period of time to obtain the mixed soft magnetic composite material; (5) The pressed hybrid soft magnetic composite material was heated to 200℃ for 80 min at a heating rate of 5℃ / min under argon protection, and then heat-treated at 600℃ for 120 min under argon protection to ceramicize the polysiloxane. Under argon protection, it was annealed at 400℃ for 120 min, and then rapidly cooled to room temperature to obtain the soft magnetic composite material described in the title.

[0046] Example 8: Sm2Co 17 / Mn 0.51 Zn 0.42 Fe 2.07 Preparation of O4 / FeNi soft magnetic composite material (1) Sm2Co 17Magnetic powder, FeNi magnetic powder and Mn 0.51 Zn 0.42 Fe 2.07 O4 magnetic powder was sieved separately to control the particle size to be less than 10μm; the three powders were then uniformly mixed by ball milling to obtain mixed magnetic powder. (2) Add phosphoric acid solution to 6 mL of acetone, stir evenly with ultrasonication, and then add 2.0 g of the mixed magnetic powder obtained in the previous step (the amount of phosphoric acid solution added is 0.3% of the mass of the mixed magnetic powder). Continue to stir with ultrasonication until the acetone is completely evaporated to obtain the passivated mixed magnetic powder. (3) Weigh polyurethane powder and polysilazane powder (the total weight ratio is 5% of the mass of the mixed magnetic powder obtained in the previous step, and the mass ratio of polyurethane powder to polysilazane powder is 1:3), dissolve them in 10 mL of acetone, and ultrasonically stir until the powder is completely dissolved. Then add the passivated mixed magnetic powder obtained in the previous step and continue ultrasonic stirring until the acetone is completely evaporated to obtain mixed magnetic powder-polyurethane-polysilazane. Orient it in a magnetic field at 1.2T for 60s to obtain a mixed magnetic powder green body with a thickness of about 200 μm. (4) The mixed magnetic powder green body is kept under pressure at 1200 MPa and 100 °C for a period of time to obtain the mixed soft magnetic composite material; (5) The pressed hybrid soft magnetic composite material was heated to 200℃ for 80 min at a heating rate of 5℃ / min under argon protection, and then heat-treated at 600℃ for 180 min under argon protection to ceramicize the polysiloxane. Under argon protection, it was annealed at 400℃ for 120 min, and then rapidly cooled to room temperature to obtain the soft magnetic composite material described in the title.

[0047] Comparative Example 1: Sm2Co 17 Preparation of FeNi soft magnetic composite materials (1) Sm2Co 17 The magnetic powder and FeNi magnetic powder were sieved separately to control the particle size to be less than 10μm; the two powders were then uniformly mixed using a ball mill to obtain mixed magnetic powder. (2) Add phosphoric acid solution to 6 mL of acetone, stir evenly with ultrasonication, and then add 2.0 g of the mixed magnetic powder obtained in the previous step (the amount of phosphoric acid solution added is 0.3% of the mass of the mixed magnetic powder). Continue to stir with ultrasonication until the acetone is completely evaporated to obtain the passivated mixed magnetic powder. (3) Weigh polyurethane powder (total weight percentage is 5% of the mass of the mixed magnetic powder obtained in the previous step), dissolve it in 10 mL of acetone, and ultrasonically stir until the powder is completely dissolved. Then add the passivated mixed magnetic powder obtained in the previous step and continue ultrasonic stirring until the acetone is completely evaporated to obtain mixed magnetic powder-polyurethane. Orient it in a magnetic field at 1.2T for 60s to obtain a mixed magnetic powder green body with a thickness of about 200 μm. (4) The mixed magnetic powder green body is kept under pressure at 1200 MPa and 100 °C for a period of time to obtain the mixed soft magnetic composite material; Comparative Example 2: Sm2Co 17 / Mn 0.51 Zn 0.42 Fe 2.07 Preparation of O4 / FeNi soft magnetic composite material (1) Sm2Co 17 Magnetic powder, FeNi magnetic powder and Mn 0.51 Zn 0.42 Fe 2.07 O4 magnetic powder was sieved separately to control the particle size to be less than 10μm; the three powders were then uniformly mixed by ball milling to obtain mixed magnetic powder. (2) Add phosphoric acid solution to 6 mL of acetone, stir evenly with ultrasonication, and then add 2.0 g of the mixed magnetic powder obtained in the previous step (the amount of phosphoric acid solution added is 0.3% of the mass of the mixed magnetic powder). Continue to stir with ultrasonication until the acetone is completely evaporated to obtain the passivated mixed magnetic powder. (3) Weigh polyurethane powder (total weight percentage is 5% of the mass of the mixed magnetic powder obtained in the previous step), dissolve it in 10 mL of acetone, and ultrasonically stir until the powder is completely dissolved. Then add the passivated mixed magnetic powder obtained in the previous step and continue ultrasonic stirring until the acetone is completely evaporated to obtain mixed magnetic powder-polyurethane. Orient it in a magnetic field at 1.2T for 60s to obtain a mixed magnetic powder green body with a thickness of about 200 μm. (4) The mixed magnetic powder green body is kept under pressure at 1200 MPa and 100 °C for a period of time to obtain the mixed soft magnetic composite material; Test example: The maximum permeability, coercivity, and electrical resistance of the soft magnetic composite materials obtained in the examples and comparative examples were measured. The results are shown in Table 1 below.

[0048] "-" indicates that it has not been tested.

[0049] As shown in Table 1, the coercivity, maximum permeability, and resistivity of the materials were simultaneously improved in Examples 1-8 by adding both ferrite and polysilazane. The technical solution of this invention, by introducing MnZn ferrite with high resistivity and using polysilazane as a binder, and by in-situ ceramizing the polysilazane during heat treatment, fills the microscopic gaps between the particles of the soft magnetic composite material, reduces the gaps between magnetic particles, significantly reduces the "magnetic dilution effect," and while increasing the maximum permeability, also significantly improves the overall resistivity and suppresses eddy current losses between particles.

[0050] Furthermore, this invention releases the internal stress generated during the preparation process of the soft magnetic composite material by performing isothermal heat treatment at 600°C and annealing at 400°C, thereby repairing lattice defects and significantly improving the maximum magnetic permeability. This invention also found that the optimal isothermal heat treatment time at 600°C is 90 minutes. When the isothermal time exceeds 90 minutes, significant abnormal grain growth begins, damaging part of the ceramicized insulating layer, resulting in a rebound in coercivity with increasing isothermal time.

[0051] While certain features of the invention have been set forth and described herein, many modifications, substitutions, variations, and equivalents will now occur to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and variations that fall within the true scope of the invention.

Claims

1. A method for preparing a soft magnetic composite material with high permeability and low coercivity, characterized in that, Includes the following steps: S1: Sm2Co 17 Magnetic powder, FeNi magnetic powder and Mn x Zn y Fe z O4 magnetic powder is mixed to obtain mixed magnetic powder; wherein, 0.51≤x≤0.75, 0.51≤y≤0.75, 2.01≤z≤2.10, and x+y+z=3; S2: Add the mixed magnetic powder obtained in step S1 to acetone containing phosphoric acid solution for passivation to obtain the passivated mixed magnetic powder; S3: After mixing polyurethane powder and polysilazane powder, dissolve them in acetone, then add the mixed magnetic powder obtained in step S2, sonicate until the acetone evaporates, and then perform magnetic field orientation on the obtained product to obtain a mixed magnetic powder green body. S4: Press the mixed magnetic powder green body obtained in step S3 into a mixed soft magnetic composite material; S5: The polysilazane is ceramized by heat treatment under an inert atmosphere, followed by annealing and cooling to obtain the soft magnetic composite material.

2. The preparation method according to claim 1, characterized in that, x is 0.51, y is 0.42, and z is 2.07; x is 0.75, y is 0.15, and z is 2.10; or x is 0.64, y is 0.29, and z is 2.

07.

3. The preparation method according to claim 1, characterized in that, In step S3, the total weight of polyurethane powder and polysilazane powder is 5% of the mass of the mixed magnetic powder.

4. The preparation method according to any one of claims 1-3, characterized in that, The mass ratio of the polyurethane powder to the polysilazane powder is 1:1 to 1:

4.

5. The preparation method according to claim 4, characterized in that, The mass ratio of the polyurethane powder to the polysilazane powder is 1:

4.

6. The preparation method according to any one of claims 1-3, characterized in that, The heat treatment conditions in step S5 are 600℃ for 60~180 min.

7. The preparation method according to any one of claims 1-3, characterized in that, The specific passivation process in step S2 is as follows: add phosphoric acid solution dropwise to acetone, stir ultrasonically until homogeneous, then add the mixed magnetic powder obtained in step S1, stir ultrasonically until the acetone evaporates to dryness; The specific process of pressing and molding in step S4 is as follows: the mixed magnetic powder green body is held under pressure at 1200MPa and 100℃ for a period of time; The specific ceramization process described in step S5 is as follows: under argon protection, the temperature is increased from 200 °C to 600 °C at a heating rate of 5 °C / min, and then held at that temperature for 90 min; and / or The specific process of the annealing treatment in step S5 is as follows: under argon protection, anneal at 400°C for 120 min, and then rapidly cool to room temperature.

8. The method for preparing the high permeability and low coercivity soft magnetic composite material according to any one of claims 1-3, characterized in that, The maximum permeability of the high permeability and low coercivity soft magnetic composite material is greater than or equal to 34. The coercivity of the high permeability, low coercivity soft magnetic composite material is less than or equal to 4 A / m.

9. A soft magnetic composite material with high permeability and low coercivity, characterized in that, It is prepared using the method for preparing high permeability and low coercivity soft magnetic composite materials as described in any one of claims 1-8.

10. The use of the high permeability and low coercivity soft magnetic composite material according to claim 9 in the preparation of inductors.

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