FeSiBCuNb / MgFe2O4 soft magnetic composite material and preparation method thereof

Abstract

The application relates to the technical field of soft magnetic composite materials, and provides a FeSiBCuNb / MgFe2O4 soft magnetic composite material and a preparation method thereof, which comprises the following steps: through a solvothermal reaction, green body pressing and heat treatment, a MgFe2O4 insulation layer is in-situ coated on the surface of flaky FeSiBCuNb nanocrystalline magnetic powder after phosphorization, a FeSiBCuNb / MgFe2O4 soft magnetic composite material formed by core-shell powder composed of FeSiBCuNb nanocrystalline magnetic powder as the core and MgFe2O4 as the shell is formed. The application can form a dense MgFe2O4 insulation layer with good interface bonding on the surface of the flaky FeSiBCuNb nanocrystalline magnetic powder, can keep the magnetic powder matrix structure, can take into account low magnetic dilution effect and high resistivity, and can obtain a soft magnetic composite material with high magnetic permeability and low loss.

Description

Technical Field

[0001] This invention relates to the field of soft magnetic composite materials technology, and in particular to a FeSiBCuNb / MgFe2O4 soft magnetic composite material and its preparation method. Background Technology

[0002] FeSiBCuNb-based nanocrystalline soft magnetic composites are composed of magnetic metal powder and an insulating layer. They possess advantages such as high saturation magnetic induction (up to 1.2T or more) and low loss, making them ideal magnetic powders for preparing high-frequency, low-loss soft magnetic composites. However, direct contact between magnetic powder particles easily leads to increased eddy current losses. Therefore, constructing a dense, uniform, and firmly bonded insulating layer on the surface of the magnetic powder is a key technical approach to realizing high-frequency, low-loss soft magnetic composites.

[0003] Currently, organic insulating layers (such as silicone resin and epoxy resin) in insulating coating materials have insufficient heat resistance, making it difficult to match the annealing process requirements of soft magnetic composite materials above 500℃. Traditional inorganic insulating layers (such as SiO2 and Al2O3), while exhibiting good thermal stability, lack chemical bonding with magnetic powder, resulting in weak interfacial adhesion and susceptibility to detachment and cracking. In recent years, spinel-type ferrites have attracted attention due to their combination of high resistivity, good chemical stability, and similar coefficients of thermal expansion. Among them, MgFe2O4, as an environmentally friendly lightweight ferrite, combines high resistivity (far higher than Fe3O4) with weak magnetism (magnetic dilution effect less than non-magnetic coating layers), making it an ideal insulating coating material for high-frequency soft magnetic composite materials. However, in existing ferrite coating technologies, the mechanical mixing method relies on physical adsorption to attach ferrite particles to the surface of magnetic powder. The lack of chemical bonding between the insulating layer and the matrix leads to easy detachment during subsequent pressing and annealing processes, resulting in discontinuous insulating layers. While the sol-gel method can achieve molecular-level mixing, subsequent high-temperature crystallization can easily lead to grain coarsening or phase transformation of the nanocrystalline magnetic powder, damaging its soft magnetic properties. In-situ oxidation is extremely sensitive to the control of pH, temperature, and oxidant concentration in the reaction system, making it difficult to precisely control the thickness and uniformity of the insulating layer, and it easily forms non-uniform island-like deposits on the magnetic powder surface. Although the solvothermal method can achieve controllable coating at lower temperatures (<200℃), ferrite nanoparticles are prone to self-aggregation during nucleation and growth, making it difficult to uniformly anchor on the surface of sheet-like magnetic powder, and the lack of strong interfacial bonding between the insulating layer and the substrate affects the density and stability of the insulating layer.

[0004] Chinese patent CN114220645A discloses a method for preparing amorphous composite magnetic powder cores. The method uses a process route of "surface modification + double-layer insulation coating" to prepare amorphous composite magnetic powder cores. In this scheme, MgZnFe2O4 is used as the insulating layer. The introduction of zinc will significantly change the interfacial chemical bonding characteristics and weaken the bonding strength between the insulating layer and the magnetic powder matrix.

[0005] Therefore, how to construct an insulating coating layer with strong interfacial bonding, uniform coating, and controllable thickness on the surface of magnetic powder through process optimization, while maintaining excellent comprehensive soft magnetic properties and improving resistivity, is a key technical problem that urgently needs to be solved in the field of soft magnetic composite materials. Summary of the Invention

[0006] In view of this, in order to overcome the shortcomings of the prior art, the present invention aims to provide a FeSiBCuNb / MgFe2O4 soft magnetic composite material and its preparation method.

[0007] According to a first aspect of the present invention, a method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material is provided. The method includes: in-situ coating a MgFe2O4 insulating layer on the surface of phosphated sheet-like FeSiBCuNb nanocrystalline magnetic powder by solvothermal reaction, green pressing and heat treatment, to form a FeSiBCuNb / MgFe2O4 soft magnetic composite material composed of core-shell powder with FeSiBCuNb nanocrystalline magnetic powder as the core and MgFe2O4 as the shell.

[0008] Optionally, the preparation method of the FeSiBCuNb / MgFe2O4 soft magnetic composite material of the present invention involves coating an iron source and a magnesium source onto the outside of a phosphated sheet-like FeSiBCuNb nanocrystalline magnetic powder via a solvothermal reaction to form a FeSiBCuNb / MgFe2O4 composite powder. The FeSiBCuNb / MgFe2O4 composite powder is then pressed into a green compact, and the green compact is heat-treated in a protective atmosphere to obtain a FeSiBCuNb / MgFe2O4 soft magnetic composite material with a core-shell structure.

[0009] Optionally, the preparation method of the FeSiBCuNb / MgFe2O4 soft magnetic composite material of the present invention involves preparing the FeSiBCuNb / MgFe2O4 composite powder in the following manner: placing an iron source and a magnesium source in a reaction solvent to prepare a coating solution, placing the coating solution in a reaction vessel for solvothermal reaction, and then centrifuging, washing, and drying to obtain the FeSiBCuNb / MgFe2O4 composite powder.

[0010] Optionally, in the preparation method of the FeSiBCuNb / MgFe2O4 soft magnetic composite material of the present invention, the coating solution is prepared as follows: 30-150g of phosphated flake FeSiBCuNb nanocrystalline magnetic powder, 1mol of ferric nitrate nonahydrate, 1mol of magnesium nitrate hexahydrate, 10mol of sodium acetate and 0.01mol of polyethylene glycol are placed in 50ml of ethylene glycol solution and stirred at 500rpm for 3.5h at 25°C to obtain the coating solution.

[0011] Optionally, in the preparation method of the FeSiBCuNb / MgFe2O4 soft magnetic composite material of the present invention, when preparing FeSiBCuNb / MgFe2O4 composite powder, the coating solution is placed in a reaction vessel, heated to 160°C at a rate of 10°C / min under a reaction pressure of 3MPa, held at the temperature for 6-24h and then naturally cooled, and the reaction product after centrifugation and washing is dried at 60°C for 12h.

[0012] Optionally, in the preparation method of the FeSiBCuNb / MgFe2O4 soft magnetic composite material of the present invention, when pressing the FeSiBCuNb / MgFe2O4 composite powder into a green body, 100 parts by weight of the FeSiBCuNb / MgFe2O4 composite powder are added to 10 parts by weight of an organic solvent, wherein the organic solvent contains 1.5 parts by weight of a binder. The mixture is stirred until the organic solvent is completely evaporated. The stirred material is then mixed evenly with 1 part by weight of a lubricant. The mixture is then pressed to obtain a green body.

[0013] Optionally, in the preparation method of the FeSiBCuNb / MgFe2O4 soft magnetic composite material of the present invention, the organic solvent is acetone, the binder is organosilicon resin, and the lubricant is zinc stearate.

[0014] Optionally, the preparation method of the FeSiBCuNb / MgFe2O4 soft magnetic composite material of the present invention involves pressing the mixture at 1800MPa for 30s at 25°C to obtain a ring-shaped green body.

[0015] Optionally, the preparation method of the FeSiBCuNb / MgFe2O4 soft magnetic composite material of the present invention involves heat-treating the green blank in a protective atmosphere as follows: placing the green blank in a nitrogen atmosphere, heating it to 520-580°C at a rate of 10°C / min, holding it at that temperature for 60 min, and then cooling it to room temperature in the furnace.

[0016] According to a second aspect of the present invention, a FeSiBCuNb / MgFe2O4 soft magnetic composite material is provided, which is prepared according to the method described above.

[0017] The FeSiBCuNb / MgFe2O4 soft magnetic composite material and its preparation method of the present invention have the following beneficial technical effects:

[0018] An insulating layer of MgFe2O4 was in situ coated on the surface of phosphated sheet-like FeSiBCuNb nanocrystalline magnetic powder using a solvothermal method. The interfacial chemical bonding formed during the reaction process significantly enhanced the bonding strength between the insulating layer and the magnetic powder matrix, avoiding the problems of easy detachment and cracking of the insulating layer in mechanical mixing, sol-gel methods and in-situ oxidation methods.

[0019] The solvothermal reaction temperature is below 200℃, avoiding grain coarsening or phase transformation of the nanocrystalline magnetic powder caused by high-temperature crystallization, thus fully preserving the soft magnetic properties of the magnetic powder. By controlling the reaction time and coating concentration, controllable growth of MgFe2O4 is achieved, precisely regulating the thickness and density of the insulating layer, effectively inhibiting the agglomeration of ferrite nanoparticles, and forming a uniform and continuous insulating layer on the surface of the sheet-like magnetic powder. This significantly improves the resistivity of the composite powder and reduces high-frequency eddy current losses.

[0020] By controlling the solvothermal reaction time, coating concentration, and heat treatment process, the FeSiBCuNb / MgFe2O4 soft magnetic composite material obtained exhibits a high permeability of 102.3 and a low magnetic loss of 109.9 kW / m under the test conditions of Bm = 0.1 T and f = 50 kHz. 3 This meets the application requirements of high-efficiency and miniaturized soft magnetic materials for high-frequency power electronic devices. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The image shows the SEM morphology of the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 1 of this invention.

[0023] Figure 2 The image shows the SEM morphology of the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 2 of this invention.

[0024] Figure 3 The image shows the SEM morphology of the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 3 of this invention.

[0025] Figure 4 The XRD phase analysis diagrams are of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 2, 4 and 5 of this invention.

[0026] Figure 5 This is a schematic diagram of the saturation magnetization of the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Examples 2, 4 and 5 of the present invention.

[0027] Figure 6This is a schematic diagram showing the relationship between the effective magnetic permeability and frequency of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 1-3 and the FeSiBCuNb soft magnetic composite material prepared in Comparative Example 1.

[0028] Figure 7 This is a schematic diagram showing the relationship between loss and frequency for the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 1-3 and the FeSiBCuNb soft magnetic composite material prepared in Comparative Example 1.

[0029] Figure 8 This is a schematic diagram showing the relationship between the effective magnetic permeability and frequency of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 2, 4 and 5 of the present invention.

[0030] Figure 9 This is a schematic diagram showing the relationship between loss and frequency of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 2, 4 and 5 of this invention;

[0031] Figure 10 This is a schematic diagram showing the relationship between the effective magnetic permeability and frequency of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 4, 6 and 7 of the present invention.

[0032] Figure 11 This is a schematic diagram showing the relationship between loss and frequency of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 4, 6 and 7 of this invention. Detailed Implementation

[0033] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0034] It should be noted that, in the absence of conflict, the following embodiments and features can be combined with each other; and, based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0035] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0036] Example 1

[0037] Exemplary Example 1 of the present invention provides a method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material. In this embodiment, the method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material is implemented in the following manner.

[0038] Step 1: Preparation of coating solution

[0039] 150g of phosphated flake FeSiBCuNb nanocrystalline magnetic powder with a particle size of 180 mesh, 1mol of ferric nitrate nonahydrate, 1mol of magnesium nitrate hexahydrate, 10mol of sodium acetate and 0.01mol of polyethylene glycol were placed in 50ml of ethylene glycol solution and stirred at 500rpm for 3.5h at 25℃ to obtain a coating solution.

[0040] Step 2: Preparation of FeSiBCuNb / MgFe2O4 composite powder

[0041] The coating solution was placed in a reaction vessel and heated to 160°C at a rate of 10°C / min under a reaction pressure of 3 MPa. After holding at this temperature for 6 hours, the mixture was allowed to cool naturally. The reaction product, after centrifugation and washing, was dried at 60°C for 12 hours to obtain FeSiBCuNb / MgFe2O4 composite powder.

[0042] Step 3: Preparation of green body

[0043] 100 parts by weight of FeSiBCuNb / MgFe2O4 composite powder were added to 10 parts by weight of an organic solvent, wherein the organic solvent contained 1.5 parts by weight of a binder. The mixture was stirred until the organic solvent was completely evaporated. The stirred material was then mixed evenly with 1 part by weight of a lubricant. The mixture was pressed at 25°C and a pressure of 1800 MPa for 30 seconds to obtain a ring-shaped green body. In this embodiment, the organic solvent was acetone, the binder was silicone resin, and the lubricant was zinc stearate.

[0044] Step 4: Preparation of FeSiBCuNb / MgFe2O4 soft magnetic composite material

[0045] The green blank was placed in a nitrogen atmosphere and heated to 560℃ at a rate of 10℃ / min. After holding at this temperature for 60 min, it was cooled to room temperature in the furnace to obtain the FeSiBCuNb / MgFe2O4 soft magnetic composite material.

[0046] Example 2

[0047] Exemplary Example 2 of the present invention provides a method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material. In this embodiment, the method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material is implemented in the following manner.

[0048] Step 1: Preparation of coating solution

[0049] 150g of phosphated flake FeSiBCuNb nanocrystalline magnetic powder with a particle size of 180 mesh, 1mol of ferric nitrate nonahydrate, 1mol of magnesium nitrate hexahydrate, 10mol of sodium acetate and 0.01mol of polyethylene glycol were placed in 50ml of ethylene glycol solution and stirred at 500rpm for 3.5h at 25℃ to obtain a coating solution.

[0050] Step 2: Preparation of FeSiBCuNb / MgFe2O4 composite powder

[0051] The coating solution was placed in a reaction vessel and heated to 160°C at a rate of 10°C / min under a reaction pressure of 3 MPa. After holding at this temperature for 15 h, the mixture was allowed to cool naturally. The reaction product, after centrifugation and washing, was dried at 60°C for 12 h to obtain FeSiBCuNb / MgFe2O4 composite powder.

[0052] Step 3: Preparation of green body

[0053] 100 parts by weight of FeSiBCuNb / MgFe2O4 composite powder were added to 10 parts by weight of an organic solvent, wherein the organic solvent contained 1.5 parts by weight of a binder. The mixture was stirred until the organic solvent was completely evaporated. The stirred material was then mixed evenly with 1 part by weight of a lubricant. The mixture was pressed at 25°C and a pressure of 1800 MPa for 30 seconds to obtain a ring-shaped green body. In this embodiment, the organic solvent was acetone, the binder was silicone resin, and the lubricant was zinc stearate.

[0054] Step 4: Preparation of FeSiBCuNb / MgFe2O4 soft magnetic composite material

[0055] The green blank was placed in a nitrogen atmosphere and heated to 560℃ at a rate of 10℃ / min. After holding at this temperature for 60 min, it was cooled to room temperature in the furnace to obtain the FeSiBCuNb / MgFe2O4 soft magnetic composite material.

[0056] Example 3

[0057] Exemplary Example 3 of the present invention provides a method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material. In this embodiment, the method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material is implemented in the following manner.

[0058] Step 1: Preparation of coating solution

[0059] 150g of phosphated flake FeSiBCuNb nanocrystalline magnetic powder with a particle size of 180 mesh, 1mol of ferric nitrate nonahydrate, 1mol of magnesium nitrate hexahydrate, 10mol of sodium acetate and 0.01mol of polyethylene glycol were placed in 50ml of ethylene glycol solution and stirred at 500rpm for 3.5h at 25℃ to obtain a coating solution.

[0060] Step 2: Preparation of FeSiBCuNb / MgFe2O4 composite powder

[0061] The coating solution was placed in a reaction vessel and heated to 160°C at a rate of 10°C / min under a reaction pressure of 3 MPa. After holding at this temperature for 24 h, the mixture was allowed to cool naturally. The reaction product, after centrifugation and washing, was dried at 60°C for 12 h to obtain FeSiBCuNb / MgFe2O4 composite powder.

[0062] Step 3: Preparation of green body

[0063] 100 parts by weight of FeSiBCuNb / MgFe2O4 composite powder were added to 10 parts by weight of an organic solvent, wherein the organic solvent contained 1.5 parts by weight of a binder. The mixture was stirred until the organic solvent was completely evaporated. The stirred material was then mixed evenly with 1 part by weight of a lubricant. The mixture was pressed at 25°C and a pressure of 1800 MPa for 30 seconds to obtain a ring-shaped green body. In this embodiment, the organic solvent was acetone, the binder was silicone resin, and the lubricant was zinc stearate.

[0064] Step 4: Preparation of FeSiBCuNb / MgFe2O4 soft magnetic composite material

[0065] The green blank was placed in a nitrogen atmosphere and heated to 560℃ at a rate of 10℃ / min. After holding at this temperature for 60 min, it was cooled to room temperature in the furnace to obtain the FeSiBCuNb / MgFe2O4 soft magnetic composite material.

[0066] Example 4

[0067] Exemplary Example 4 of the present invention provides a method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material. In this embodiment, the method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material is implemented in the following manner.

[0068] Step 1: Preparation of coating solution

[0069] 100g of phosphated flake FeSiBCuNb nanocrystalline magnetic powder with a particle size of 180 mesh, 1mol of ferric nitrate nonahydrate, 1mol of magnesium nitrate hexahydrate, 10mol of sodium acetate and 0.01mol of polyethylene glycol were placed in 50ml of ethylene glycol solution and stirred at 500rpm for 3.5h at 25℃ to obtain a coating solution.

[0070] Step 2: Preparation of FeSiBCuNb / MgFe2O4 composite powder

[0071] The coating solution was placed in a reaction vessel and heated to 160°C at a rate of 10°C / min under a reaction pressure of 3 MPa. After holding at this temperature for 15 h, the mixture was allowed to cool naturally. The reaction product, after centrifugation and washing, was dried at 60°C for 12 h to obtain FeSiBCuNb / MgFe2O4 composite powder.

[0072] Step 3: Preparation of green body

[0073] 100 parts by weight of FeSiBCuNb / MgFe2O4 composite powder were added to 10 parts by weight of an organic solvent, wherein the organic solvent contained 1.5 parts by weight of a binder. The mixture was stirred until the organic solvent was completely evaporated. The stirred material was then mixed evenly with 1 part by weight of a lubricant. The mixture was pressed at 25°C and a pressure of 1800 MPa for 30 seconds to obtain a ring-shaped green body. In this embodiment, the organic solvent was acetone, the binder was silicone resin, and the lubricant was zinc stearate.

[0074] Step 4: Preparation of FeSiBCuNb / MgFe2O4 soft magnetic composite material

[0075] The green blank was placed in a nitrogen atmosphere and heated to 560℃ at a rate of 10℃ / min. After holding at this temperature for 60 min, it was cooled to room temperature in the furnace to obtain the FeSiBCuNb / MgFe2O4 soft magnetic composite material.

[0076] Example 5

[0077] Exemplary Example 5 of the present invention provides a method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material. In this embodiment, the method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material is implemented in the following manner.

[0078] Step 1: Preparation of coating solution

[0079] 30g of phosphated flake FeSiBCuNb nanocrystalline magnetic powder with a particle size of 180 mesh, 1mol of ferric nitrate nonahydrate, 1mol of magnesium nitrate hexahydrate, 10mol of sodium acetate and 0.01mol of polyethylene glycol were placed in 50ml of ethylene glycol solution and stirred at 500rpm for 3.5h at 25℃ to obtain the coating solution.

[0080] Step 2: Preparation of FeSiBCuNb / MgFe2O4 composite powder

[0081] The coating solution was placed in a reaction vessel and heated to 160°C at a rate of 10°C / min under a reaction pressure of 3 MPa. After holding at this temperature for 15 h, the mixture was allowed to cool naturally. The reaction product, after centrifugation and washing, was dried at 60°C for 12 h to obtain FeSiBCuNb / MgFe2O4 composite powder.

[0082] Step 3: Preparation of green body

[0083] 100 parts by weight of FeSiBCuNb / MgFe2O4 composite powder were added to 10 parts by weight of an organic solvent, wherein the organic solvent contained 1.5 parts by weight of a binder. The mixture was stirred until the organic solvent was completely evaporated. The stirred material was then mixed evenly with 1 part by weight of a lubricant. The mixture was pressed at 25°C and a pressure of 1800 MPa for 30 seconds to obtain a ring-shaped green body. In this embodiment, the organic solvent was acetone, the binder was silicone resin, and the lubricant was zinc stearate.

[0084] Step 4: Preparation of FeSiBCuNb / MgFe2O4 soft magnetic composite material

[0085] The green blank was placed in a nitrogen atmosphere and heated to 560℃ at a rate of 10℃ / min. After holding at this temperature for 60 min, it was cooled to room temperature in the furnace to obtain the FeSiBCuNb / MgFe2O4 soft magnetic composite material.

[0086] Example 6

[0087] Exemplary Example 6 of the present invention provides a method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material. In this embodiment, the method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material is implemented in the following manner.

[0088] Step 1: Preparation of coating solution

[0089] 100g of phosphated flake FeSiBCuNb nanocrystalline magnetic powder with a particle size of 180 mesh, 1mol of ferric nitrate nonahydrate, 1mol of magnesium nitrate hexahydrate, 10mol of sodium acetate and 0.01mol of polyethylene glycol were placed in 50ml of ethylene glycol solution and stirred at 500rpm for 3.5h at 25℃ to obtain a coating solution.

[0090] Step 2: Preparation of FeSiBCuNb / MgFe2O4 composite powder

[0091] The coating solution was placed in a reaction vessel and heated to 160°C at a rate of 10°C / min under a reaction pressure of 3 MPa. After holding at this temperature for 15 h, the mixture was allowed to cool naturally. The reaction product, after centrifugation and washing, was dried at 60°C for 12 h to obtain FeSiBCuNb / MgFe2O4 composite powder.

[0092] Step 3: Preparation of green body

[0093] 100 parts by weight of FeSiBCuNb / MgFe2O4 composite powder were added to 10 parts by weight of an organic solvent, wherein the organic solvent contained 1.5 parts by weight of a binder. The mixture was stirred until the organic solvent was completely evaporated. The stirred material was then mixed evenly with 1 part by weight of a lubricant. The mixture was pressed at 25°C and a pressure of 1800 MPa for 30 seconds to obtain a ring-shaped green body. In this embodiment, the organic solvent was acetone, the binder was silicone resin, and the lubricant was zinc stearate.

[0094] Step 4: Preparation of FeSiBCuNb / MgFe2O4 soft magnetic composite material

[0095] The green blank was placed in a nitrogen atmosphere and heated to 520℃ at a rate of 10℃ / min. After holding at this temperature for 60 min, it was cooled to room temperature in the furnace to obtain the FeSiBCuNb / MgFe2O4 soft magnetic composite material.

[0096] Example 7

[0097] Exemplary Example 7 of the present invention provides a method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material. In this embodiment, the method for preparing FeSiBCuNb / MgFe2O4 soft magnetic composite material is implemented in the following manner.

[0098] Step 1: Preparation of coating solution

[0099] 100g of phosphated flake FeSiBCuNb nanocrystalline magnetic powder with a particle size of 180 mesh, 1mol of ferric nitrate nonahydrate, 1mol of magnesium nitrate hexahydrate, 10mol of sodium acetate and 0.01mol of polyethylene glycol were placed in 50ml of ethylene glycol solution and stirred at 500rpm for 3.5h at 25℃ to obtain a coating solution.

[0100] Step 2: Preparation of FeSiBCuNb / MgFe2O4 composite powder

[0101] The coating solution was placed in a reaction vessel and heated to 160°C at a rate of 10°C / min under a reaction pressure of 3 MPa. After holding at this temperature for 15 h, the mixture was allowed to cool naturally. The reaction product, after centrifugation and washing, was dried at 60°C for 12 h to obtain FeSiBCuNb / MgFe2O4 composite powder.

[0102] Step 3: Preparation of green body

[0103] 100 parts by weight of FeSiBCuNb / MgFe2O4 composite powder were added to 10 parts by weight of an organic solvent, wherein the organic solvent contained 1.5 parts by weight of a binder. The mixture was stirred until the organic solvent was completely evaporated. The stirred material was then mixed evenly with 1 part by weight of a lubricant. The mixture was pressed at 25°C and a pressure of 1800 MPa for 30 seconds to obtain a ring-shaped green body. In this embodiment, the organic solvent was acetone, the binder was silicone resin, and the lubricant was zinc stearate.

[0104] Step 4: Preparation of FeSiBCuNb / MgFe2O4 soft magnetic composite material

[0105] The green blank was placed in a nitrogen atmosphere and heated to 580℃ at a rate of 10℃ / min. After holding at this temperature for 60 min, it was cooled to room temperature in the furnace to obtain the FeSiBCuNb / MgFe2O4 soft magnetic composite material.

[0106] Comparative Example 1

[0107] Exemplary Comparative Example 1 of the present invention provides a method for preparing FeSiBCuNb soft magnetic composite material. In this comparative example, the method for preparing FeSiBCuNb soft magnetic composite material is implemented in the following manner.

[0108] Step 1: Preparation of FeSiBCuNb green body

[0109] 100 parts by weight of phosphated flake FeSiBCuNb nanocrystalline magnetic powder with a particle size of 180 mesh were added to 10 parts by weight of an organic solvent, wherein the organic solvent contained 1.5 parts by weight of a binder. The mixture was stirred until the organic solvent was completely evaporated. The stirred material was then mixed evenly with 1 part by weight of a lubricant. The mixture was pressed at 25°C and a pressure of 1800 MPa for 30 seconds to obtain a ring-shaped green body. In this comparative example, the organic solvent was acetone, the binder was silicone resin, and the lubricant was zinc stearate.

[0110] Step 2: Preparation of FeSiBCuNb soft magnetic composite material

[0111] The green blank was placed in a nitrogen atmosphere and heated to 560°C at a rate of 10°C / min. After holding at this temperature for 60 min, it was cooled to room temperature in the furnace to obtain the FeSiBCuNb soft magnetic composite material.

[0112] Example 8

[0113] The microstructure of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 1, 2, and 3 was observed using a Regulus 8230 high-resolution field emission scanning electron microscope. The accelerating voltage used was 3 kV. The FESEM images of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 1, 2, and 3 are shown in the attached images. Figure 1 , Figure 2 and Figure 3 .

[0114] Figure 1 The image shows the SEM morphology of the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 1 of this invention. Figure 1 As shown, in the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 1, MgFe2O4 is coated on the surface of the sheet-like FeSiBCuNb nanocrystalline magnetic powder in a uniform lattice form, forming a thin and regular initial coating layer. Figure 2 The image shows the SEM morphology of the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 2 of this invention. Figure 2 As shown, in the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 2, MgFe2O4 is continuously, uniformly and densely coated on the surface of the sheet-like FeSiBCuNb nanocrystalline magnetic powder, forming a coating layer with suitable thickness and good density. Figure 3 The image shows the SEM morphology of the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 3 of this invention. Figure 3 As shown, in the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 3, the MgFe2O4 particles further grow, forming a complete and thickened insulating layer.

[0115] The FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 2, 4 and 5 were analyzed by XRD using a D / MAX2500VL / PC X-ray diffractometer. Figure 4 The XRD phase analysis diagrams of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 2, 4, and 5 of this invention are shown below. Figure 4As shown, the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 2, 4 and 5 all exhibit three diffraction peaks at 45.0°, 65.5° and 83.0°, corresponding to the (110), (200) and (211) crystal planes of the FeSiBCuNb nanocrystalline magnetic powder, respectively. Small peaks were observed near 30.1°, 35.5° and 43.1°, 53.5°, 62.6° and 74.1°, corresponding to the (220), (311), (400), (422), (440) and (620) crystal planes of MgFe2O4, respectively. This indicates that the present invention forms a MgFe2O4 insulating layer on the surface of the magnetic powder through a solvothermal reaction.

[0116] The saturation magnetization of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 2, 4, and 5 was measured using a LakeShore 7404 vibrating sample magnetometer. Figure 5 This is a schematic diagram showing the saturation magnetization of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 2, 4, and 5 of this invention. Figure 5 As shown. The saturation magnetization of the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 2 is approximately 131.8 emu / g; the saturation magnetization of the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 4 is approximately 134.2 emu / g; and the saturation magnetization of the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 5 is approximately 125.7 emu / g.

[0117] The effective permeability and loss of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 1-7 and Comparative Example 1 were measured using a BH analyzer (model IWATSU SY-8219). The test results are as follows: Figure 6-11 As shown, their respective effective permeability (μ) e ) and loss (P cv The specific data is shown in Table 1.

[0118] Table 1

[0119]

[0120] Figure 6 This diagram illustrates the relationship between the effective magnetic permeability and frequency of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 1-3 and the FeSiBCuNb soft magnetic composite material prepared in Comparative Example 1. Figure 6As shown, the soft magnetic composite materials treated with MgFe2O4 insulating coating (Examples 1-3 of this invention) all exhibit higher permeability than the uncoated material (Comparative Example 1), with an overall improvement of over 25%, fully demonstrating the key role of the MgFe2O4 insulating coating layer in optimizing magnetic properties. Specifically, the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 2 achieved a permeability of 100.4, approximately 1.47 times that of the FeSiBCuNb soft magnetic composite material prepared in Comparative Example 1, demonstrating a significant improvement in permeability. The permeabilities of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 1-3 were 85.6, 100.4, and 83.9, respectively, indicating that by extending the reaction time, the MgFe2O4 particles fully grow and interconnect, increasing the thickness of the insulating layer and forming a complete, dense, and continuous insulating layer. This effectively prevents direct contact between magnetic powders, optimizes the coupling behavior between magnetic powders, promotes uniform arrangement of magnetic domains, and improves the material's permeability.

[0121] Figure 7 This diagram illustrates the relationship between loss and frequency for the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 1-3 and the FeSiBCuNb soft magnetic composite material prepared in Comparative Example 1. Figure 7 As shown, the loss of the soft magnetic composite material first decreases and then increases with the extension of reaction time. Under the test conditions of 0.1T and 50kHz, the loss of the FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 1 is 136.0 kW / m. 3 The FeSiBCuNb / MgFe2O4 soft magnetic composite material prepared in Example 2 has a loss of 120.5 kW / m. 3 The FeSiBCuNb soft magnetic composite material (150.1 kW / m²) prepared with uncoated MgFe₂O₄ (Comparative Example 1) was compared with that prepared with uncoated MgFe₂O₄. 3 Compared to the previous method, the loss was reduced by 19.7%. This indicates that by controlling the reaction time, MgFe2O4 forms a complete and dense insulating layer. At the same time, the anchoring points on the surface of the phosphating magnetic powder and the interfacial covalent bonds formed in situ by solvothermal treatment (such as Fe-OP) synergistically enhance the bonding between the insulating layer and the substrate, reduce interfacial defects, and thus simultaneously suppress eddy current loss and hysteresis loss, resulting in a significant reduction in total loss.

[0122] Figure 8 This is a schematic diagram showing the relationship between the effective magnetic permeability and frequency of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 2, 4, and 5 of this invention. Figure 8As shown, when 100g of phosphated sheet-like FeSiBCuNb nanocrystalline magnetic powder is used, the steric hindrance of polyethylene glycol and the complexation-electrostatic stabilization effect of sodium acetate are utilized to obtain a MgFe2O4 insulating layer with moderate thickness and dense uniformity, which effectively isolates particles and has good interfacial bonding, and the magnetic permeability can reach 102.3.

[0123] Figure 9 This is a schematic diagram showing the relationship between loss and frequency for the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 2, 4, and 5 of this invention. Figure 9 As shown, when 100g of phosphated flake FeSiBCuNb nanocrystalline magnetic powder is used, a uniform and dense MgFe2O4 coating layer can be formed, which isolates the magnetic powder particles from each other, thereby significantly improving resistivity and reducing eddy current loss. Simultaneously, the coating layer and the magnetic powder matrix interface are well matched, resulting in low hysteresis loss and a total loss as low as 109.9 kW / m. 3 .

[0124] Figure 10 This is a schematic diagram showing the relationship between the effective magnetic permeability and frequency of the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 4, 6, and 7 of this invention. Figure 10 As shown, when the heat treatment temperature is 560℃, the magnetic powder undergoes moderate nanocrystallization, precipitating uniform and fine α-Fe(Si) nanocrystals. At the same time, residual stress is effectively released, the magnetic domain wall displacement resistance decreases, and the magnetic permeability increases.

[0125] Figure 11 This is a schematic diagram showing the relationship between loss and frequency for the FeSiBCuNb / MgFe2O4 soft magnetic composite materials prepared in Examples 4, 6, and 7 of this invention. Figure 11 As shown, when the heat treatment temperature is 560℃, the dense insulating layer effectively suppresses eddy current loss, while the appropriate nanocrystals and internal stress release reduce hysteresis loss, enabling the soft magnetic material to obtain excellent comprehensive soft magnetic properties.

[0126] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a FeSiBCuNb / MgFe2O4 soft magnetic composite material, characterized in that, The method includes: in-situ coating a MgFe2O4 insulating layer onto the surface of phosphated sheet-like FeSiBCuNb nanocrystalline magnetic powder through solvothermal reaction, green pressing and heat treatment, to form a FeSiBCuNb / MgFe2O4 soft magnetic composite material composed of core-shell powder with FeSiBCuNb nanocrystalline magnetic powder as the core and MgFe2O4 as the shell.

2. The preparation method of the FeSiBCuNb / MgFe2O4 soft magnetic composite material according to claim 1, characterized in that, Iron and magnesium sources are coated onto the outside of phosphated sheet-like FeSiBCuNb nanocrystalline magnetic powder via a solvothermal reaction to form FeSiBCuNb / MgFe2O4 composite powder. The FeSiBCuNb / MgFe2O4 composite powder is pressed into a green body and then heat-treated in a protective atmosphere to obtain a FeSiBCuNb / MgFe2O4 soft magnetic composite material with a core-shell structure.

3. The preparation method of the FeSiBCuNb / MgFe2O4 soft magnetic composite material according to claim 1, characterized in that, FeSiBCuNb / MgFe2O4 composite powder is prepared as follows: an iron source and a magnesium source are placed in a reaction solvent to prepare a coating solution, the coating solution is placed in a reaction vessel for solvothermal reaction, and after centrifugation, washing, and drying, FeSiBCuNb / MgFe2O4 composite powder is obtained.

4. The preparation method of the FeSiBCuNb / MgFe2O4 soft magnetic composite material according to claim 1, characterized in that, The coating solution is prepared as follows: 30-150g of phosphated flake FeSiBCuNb nanocrystalline magnetic powder, 1mol of ferric nitrate nonahydrate, 1mol of magnesium nitrate hexahydrate, 10mol of sodium acetate and 0.01mol of polyethylene glycol are placed in 50ml of ethylene glycol solution and stirred at 500rpm for 3.5h at 25℃ to obtain the coating solution.

5. The preparation method of the FeSiBCuNb / MgFe2O4 soft magnetic composite material according to claim 1, characterized in that, In preparing FeSiBCuNb / MgFe2O4 composite powder, the coating solution was placed in a reaction vessel and heated to 160℃ at a rate of 10℃ / min under a reaction pressure of 3MPa. After holding at this temperature for 6-24h, the mixture was allowed to cool naturally. The reaction product, after centrifugation and washing, was dried at 60℃ for 12h.

6. The preparation method of the FeSiBCuNb / MgFe2O4 soft magnetic composite material according to claim 1, characterized in that, When pressing FeSiBCuNb / MgFe2O4 composite powder into a green body, 100 parts by weight of FeSiBCuNb / MgFe2O4 composite powder are added to 10 parts by weight of organic solvent, wherein the organic solvent contains 1.5 parts by weight of binder. The mixture is stirred until the organic solvent is completely evaporated. The stirred material is then mixed evenly with 1 part by weight of lubricant. The mixture is then pressed to obtain a green body.

7. The preparation method of the FeSiBCuNb / MgFe2O4 soft magnetic composite material according to claim 6, characterized in that, The organic solvent is acetone, the adhesive is silicone resin, and the lubricant is zinc stearate.

8. The method for preparing the FeSiBCuNb / MgFe2O4 soft magnetic composite material according to claim 6, characterized in that, The mixture was pressed at 25°C and 1800 MPa for 30 seconds to obtain a ring-shaped green body.

9. The method for preparing the FeSiBCuNb / MgFe2O4 soft magnetic composite material according to claim 1, characterized in that, The green billet is heat-treated in a protective atmosphere as follows: the green billet is placed in a nitrogen atmosphere and heated to 520-580°C at a rate of 10°C / min, held at that temperature for 60 min, and then cooled to room temperature in the furnace.

10. A FeSiBCuNb / MgFe2O4 soft magnetic composite material, characterized in that, The FeSiBCuNb / MgFe2O4 soft magnetic composite material is prepared by the method according to any one of claims 1-9.

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