A high-frequency low-loss magnetic powder core and its preparation method

Abstract

The present invention belongs to the technical field of soft magnetic materials and discloses a high-frequency, low-loss magnetic powder core and a preparation method thereof. The method comprises the following preparation steps: (1) subjecting an iron alloy soft magnetic powder having a particle size of 5 to 50 μm to an insulation coating treatment to obtain an insulation-coated iron alloy soft magnetic powder; (2) uniformly mixing the insulation-coated iron alloy soft magnetic powder obtained in step (1) with a ferrite powder having a particle size of less than 5 μm and a binder, and then injecting the mixture into a mold for compression molding, and then heating the mixture to 600 to 900°C for annealing to obtain a high-frequency, low-loss magnetic powder core. The magnetic powder core of the present invention is prepared by mixing and compounding large-particle iron alloy soft magnetic powder and small-particle ferrite powder, which can significantly improve the insulation performance of the magnetic powder core to reduce its high-frequency loss, and increase its molding density to reduce the adverse effect on the inductance value.

Description

Technical Field

[0001] The invention belongs to the technical field of soft magnetic materials, and in particular relates to a high-frequency low-loss magnetic powder core and a preparation method thereof. Background Art

[0002] Ferroalloy soft magnetic materials have high magnetic permeability and low coercivity and are widely used in the radio electronics industry, precision instruments and meters, remote control, and automatic control systems. Ferroalloy soft magnetic materials mainly include iron-nickel (FeNi) soft magnetic alloys, iron-silicon (FeSi) soft magnetic alloys, and iron-silicon-aluminum (FeSiAl) soft magnetic alloys, according to their composition. With the advancement of electronic technology, the requirements for magnetic devices are becoming increasingly higher, mainly developing in the direction of miniaturization and high frequency, and placing higher demands on magnetic loss and temperature rise performance. Ferroalloy soft magnetic materials have high eddy current losses at high frequencies due to their high electrical conductivity, which limits their application. Therefore, it is generally necessary to insulate and coat ferroalloy soft magnetic materials.

[0003] Ferrite soft magnetic materials are ferrimagnetic oxides with Fe2O3 as the main component, mainly including manganese zinc (MnZn) ferrite, copper zinc (CuZn) ferrite, nickel zinc (NiZn) ferrite, etc. Compared with iron alloys, ferrite soft magnetic materials have high resistance and high insulation characteristics, but relatively low magnetic permeability. Therefore, it is expected that the insulation properties of iron alloy magnetic powder cores can be further improved by compounding with appropriate ferrite content to reduce their high-frequency losses, while minimizing the impact on magnetic permeability and inductance.

[0004] The patent document with publication number CN 111316385 A discloses a powder magnetic core that can significantly reduce iron loss. y Fe 3-y The spinel ferrite grain boundary layer represented by O4 coats soft magnetic particles containing pure iron or iron alloys. After annealing, the powder core exhibits high resistivity due to the compound layer in the grain boundary layer, and can reduce eddy current loss and hysteresis loss. However, this requires spraying a ferrite forming liquid (reaction liquid) on the surface of the powder coated with the silicone resin layer to prepare a composite phase coating layer. The corresponding coating process is relatively complex, and the coating with a ferrite layer also has a significant impact on the magnetic permeability and inductance. Summary of the Invention

[0005] In view of the shortcomings and deficiencies of the above prior art, the primary purpose of the present invention is to provide a method for preparing a high-frequency and low-loss magnetic powder core.

[0006] Another object of the present invention is to provide a high-frequency low-loss magnetic powder core prepared by the above method.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for preparing a high-frequency low-loss magnetic powder core comprises the following steps:

[0009] (1) subjecting an iron alloy soft magnetic powder having a particle size of 5 to 50 μm to an insulation coating treatment to obtain an insulation-coated iron alloy soft magnetic powder;

[0010] (2) The insulating coated iron alloy soft magnetic powder obtained in step (1) is evenly mixed with ferrite powder with a particle size of less than 5 μm and a binder, and then injected into a mold for pressing and molding, and then heated to 600-900° C. for annealing to obtain a high-frequency low-loss magnetic powder core.

[0011] Furthermore, the iron alloy soft magnetic powder in step (1) is iron nickel (FeNi) soft magnetic alloy powder, iron silicon (FeSi) soft magnetic alloy powder or iron silicon aluminum (FeSiAl) soft magnetic alloy powder, which are commonly used iron alloy soft magnetic powder materials in the art.

[0012] Furthermore, the insulation coating treatment in step (1) refers to the use of silicon dioxide for insulation coating treatment or the use of silicon dioxide-aluminum phosphate composite for insulation coating treatment. Preferably, the use of silicon dioxide-aluminum phosphate composite for insulation coating treatment.

[0013] Furthermore, the method for performing insulation coating treatment on the silica-aluminum phosphate composite is as follows:

[0014] 1) adding phytic acid to an alcohol aqueous solution to dissolve it, then adding an aluminum alkoxide solution to mix and react to obtain a phytic acid aluminum sol, and then uniformly mixing the phytic acid aluminum sol with a silica sol to obtain an insulating coating solution;

[0015] 2) The iron alloy soft magnetic powder is evenly mixed with the insulating coating liquid of step 1), first dried at a temperature of 60 to 100° C. to remove the solvent, and then heated to 300 to 800° C. for heat treatment to obtain an iron alloy soft magnetic powder with a silicon dioxide-aluminum phosphate composite insulation coating.

[0016] Preferably, the alcohol aqueous solution in step 1) is an ethanol aqueous solution with an ethanol volume percentage of 80-95%; the aluminum alkoxide solution is an aluminum triethanolate solution, an aluminum propoxide solution, an aluminum isopropoxide solution or an aluminum n-butoxide solution; and the amount of the aluminum alkoxide solution added is such that the pH value of the reaction system is 5-7.

[0017] Preferably, the amount of silica sol added in step 1) is 20-60% of the mass of phytic acid in terms of silicon dioxide content.

[0018] Preferably, the amount of the insulating coating liquid added in step 2) is 0.2-2% of the mass of the ferroalloy soft magnetic powder in terms of its solid content.

[0019] Preferably, the drying and removing of the solvent in step 2) is carried out under vacuum conditions; the heat treatment is carried out under nitrogen protection conditions, and the heat treatment time is 3 to 10 hours.

[0020] Furthermore, the ferrite powder in step (2) is manganese zinc (MnZn) ferrite, copper zinc (CuZn) ferrite, or nickel zinc (NiZn) ferrite powder; the amount of ferrite powder added is 5% to 20% of the mass of the insulating coated iron alloy soft magnetic powder. Within the above ferrite powder content range, the high-frequency loss performance of the magnetic powder core is significantly improved, and the inductance value is less affected. The above ferrite powder is a ferrite soft magnetic powder material commonly used in the art.

[0021] Furthermore, the binder in step (2) is an epoxy resin binder or a silicone resin binder; the amount of the binder added is 0.2 to 1% of the total mass of the insulating coated iron alloy soft magnetic powder and the ferrite powder in terms of its solid content.

[0022] Furthermore, the temperature of the press molding in step (2) is 60-100° C., and the pressure is 500-800 MPa; and the time of the annealing treatment is 15-120 min.

[0023] A high-frequency, low-loss magnetic powder core is prepared by the above method.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The magnetic powder core of the present invention is prepared by mixing and compounding large-particle iron alloy soft magnetic powder and small-particle ferrite powder, which can significantly improve the insulation performance of the magnetic powder core to reduce its high-frequency loss and increase its molding density to reduce the adverse effect on the inductance value.

[0026] (2) The present invention further uses a silicon dioxide-aluminum phosphate composite to perform insulation coating treatment on the iron alloy soft magnetic powder, which can significantly improve the insulation coating effect and the bonding molding effect, thereby further reducing high-frequency loss and increasing the inductance value. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below with reference to examples, but the embodiments of the present invention are not limited thereto.

[0028] Example 1

[0029] A method for preparing a high-frequency low-loss magnetic powder core comprises the following steps:

[0030] (1) Sendust soft magnetic powder with an average particle size of 10 μm and silica sol with a solid content of 20% were stirred and mixed uniformly. The amount of silica sol added was 0.5% of the mass of the sendust soft magnetic powder based on its solid content. The mixture was first dried in vacuum at 80°C to remove the solvent. Then, the mixture was heated to 500°C under nitrogen protection and heat treated for 5 hours to obtain an iron alloy soft magnetic powder with a silica insulation coating.

[0031] (2) The insulating coated iron alloy soft magnetic powder obtained in step (1) is evenly mixed with manganese zinc ferrite powder with an average particle size of 2 μm and an epoxy resin ethanol solution binder (solid content 15%), wherein the epoxy resin content is 0.5% of the total mass of the insulating coated iron alloy soft magnetic powder and the ferrite powder. The mixture is then injected into a mold and pressed into shape at a pressure of 600 MPa and a temperature of 80°C. The mixture is then heated to 800°C under nitrogen protection and annealed for 60 minutes to obtain a high-frequency low-loss magnetic powder core.

[0032] In this embodiment, the addition amount of manganese-zinc ferrite powder is adjusted to 0%, 5%, 10%, 15%, 20%, and 25% of the mass of the insulating-coated iron alloy soft magnetic powder, respectively. The density, inductance value, and high-frequency loss (1MHz / 50mT) test results of the obtained magnetic powder core are shown in Table 1 below.

[0033] Table 1

[0034] Ferrite addition amount, % <![CDATA[Density, g / cm 3 > Inductance, μH <![CDATA[Loss, kW / m 3 > 0％ 5.675 12.87 2154 5％ 5.712 13.22 1952 10％ 5.830 13.25 1545 15％ 5.857 12.86 1327 20％ 5.863 11.73 1205 25％ 5.862 10.14 1136

[0035] The results in Table 1 show that the density of the powder core increases with increasing small-particle ferrite powder content. This is because small-particle ferrite powder can fill the gaps between the larger-particle sendust soft magnetic powder, improving the molding density. The loss of the powder core decreases with increasing ferrite powder content, demonstrating that the incorporation of ferrite powder effectively reduces the high-frequency loss of the iron alloy soft magnetic powder core. The inductance of the powder core increases first and then decreases with increasing ferrite powder content. This is because ferrite has a low magnetic permeability, so its addition negatively affects the inductance of the powder core. However, an appropriate amount of small-particle ferrite powder can increase the molding density of the core, thereby reducing the negative impact on the inductance. When the ferrite powder content ranges from 5% to 20% of the mass of the insulating iron alloy soft magnetic powder, the resulting powder core exhibits excellent overall magnetic properties.

[0036] Example 2

[0037] A method for preparing a high-frequency low-loss magnetic powder core comprises the following steps:

[0038] (1) Iron-silicon soft magnetic powder with an average particle size of 20 μm and silica sol with a solid content of 20% were stirred and mixed uniformly. The amount of silica sol added was 1% of the mass of the iron-silicon soft magnetic powder based on its solid content. The mixture was first vacuum dried at 80°C to remove the solvent. Then, the mixture was heated to 600°C under nitrogen protection and heat treated for 6 hours to obtain iron alloy soft magnetic powder with silica insulation coating.

[0039] (2) The insulating coated iron alloy soft magnetic powder obtained in step (1) is uniformly mixed with copper-zinc ferrite powder having an average particle size of 4 μm and an epoxy resin ethanol solution binder (solid content 15%), wherein the amount of copper-zinc ferrite powder added is 10% of the mass of the insulating coated iron alloy soft magnetic powder, and the epoxy resin content is 0.8% of the total mass of the insulating coated iron alloy soft magnetic powder and the ferrite powder. The mixture is then injected into a mold, pressed into shape at a pressure of 700 MPa and a temperature of 80°C, and then heated to 750°C under nitrogen protection for annealing for 60 minutes to obtain a high-frequency low-loss magnetic powder core.

[0040] Example 3

[0041] A method for preparing a high-frequency low-loss magnetic powder core comprises the following steps:

[0042] (1) Iron-nickel soft magnetic powder with an average particle size of 5 μm and silica sol with a solid content of 20% were stirred and mixed uniformly. The amount of silica sol added was 2% of the mass of the iron-nickel soft magnetic powder based on its solid content. The mixture was first vacuum dried at 80°C to remove the solvent, and then heated to 700°C under nitrogen protection for 8 hours to obtain iron alloy soft magnetic powder with silica insulation coating.

[0043] (2) The insulating coated iron alloy soft magnetic powder obtained in step (1) is uniformly mixed with nickel zinc ferrite powder having an average particle size of 1 μm and an epoxy resin ethanol solution binder (solid content 15%), wherein the amount of nickel zinc ferrite powder added is 10% of the mass of the insulating coated iron alloy soft magnetic powder, and the epoxy resin content is 1% of the total mass of the insulating coated iron alloy soft magnetic powder and the ferrite powder. The mixture is then injected into a mold, pressed into shape at a pressure of 800 MPa and a temperature of 80° C., and then heated to 800° C. under nitrogen protection for annealing for 60 minutes to obtain a high-frequency low-loss magnetic powder core.

[0044] Example 4

[0045] A method for preparing a high-frequency, low-loss magnetic powder core, compared with Example 1, uses an insulating coating liquid prepared by the following method instead of silica sol to perform insulation coating treatment on sendust soft magnetic powder:

[0046] Phytic acid was dissolved in an 85% ethanol solution by volume, and then an ethanol solution of aluminum isopropoxide was added for mixing and reaction. The pH of the reaction system was adjusted to 6 by controlling the amount of aluminum isopropoxide added to obtain a phytic acid aluminum sol. This sol was then mixed evenly with silica sol, with the silica sol added in an amount equal to 40% of the mass of the phytic acid, based on the silica content, to obtain an insulation coating solution with a solid content of 20%.

[0047] In this embodiment, the density of the obtained magnetic powder core is 5.915 g / cm2 under the condition that the addition amount of manganese zinc ferrite powder is 10% of the mass of the insulating coated iron alloy soft magnetic powder. 3 , the inductance is 17.25μH and the loss is 854kW / m 3 .

[0048] Example 5

[0049] A method for preparing a high-frequency, low-loss magnetic powder core, compared with Example 1, uses an insulating coating liquid prepared by the following method instead of silica sol to perform insulation coating treatment on sendust soft magnetic powder:

[0050] Phytic acid was dissolved in a 90% ethanol solution by volume, and then an ethanol solution of aluminum triethoxide was added for mixing and reaction. The pH of the reaction system was adjusted to 5 by controlling the amount of aluminum triethoxide added to obtain a phytic acid aluminum sol. This sol was then mixed evenly with silica sol, with the silica sol added in an amount equal to 20% of the mass of the phytic acid, based on the silica content, to obtain an insulation coating solution with a solid content of 20%.

[0051] In this embodiment, the density of the obtained magnetic powder core is 5.918 g / cm2 under the condition that the addition amount of manganese zinc ferrite powder is 10% of the mass of the insulating coated iron alloy soft magnetic powder. 3 , the inductance is 17.31μH and the loss is 870kW / m 3 .

[0052] Example 6

[0053] A method for preparing a high-frequency, low-loss magnetic powder core, compared with Example 1, uses an insulating coating liquid prepared by the following method instead of silica sol to perform insulation coating treatment on sendust soft magnetic powder:

[0054] Phytic acid was dissolved in a 95% ethanol solution by volume, and then an ethanol solution of aluminum isopropoxide was added for mixing and reaction. The amount of aluminum isopropoxide added was controlled to adjust the pH of the reaction system to 7, thereby obtaining a phytic acid aluminum sol. This sol was then mixed evenly with silica sol, with the silica sol added in an amount equal to 60% of the mass of the phytic acid, based on the silica content, to obtain an insulation coating solution with a solid content of 20%.

[0055] In this embodiment, the density of the obtained magnetic powder core is 5.909 g / cm2 under the condition that the addition amount of manganese zinc ferrite powder is 10% of the mass of the insulating coated iron alloy soft magnetic powder. 3 , the inductance is 16.96μH and the loss is 855kW / m 3 .

[0056] By comparing the results of Examples 4 to 6 with Example 1, it can be seen that the present invention further uses a mixed insulating coating liquid of phytic acid aluminum sol and silica sol to perform insulating coating treatment on the ferroalloy soft magnetic powder, which can significantly enhance its insulating coating effect and improve its bonding molding effect, thereby significantly improving the comprehensive magnetic properties.

[0057] Comparative Example 1

[0058] A method for preparing a high-frequency, low-loss magnetic powder core. Compared with Example 1, manganese-zinc ferrite powder with an average particle size of 10 μm is used instead of manganese-zinc ferrite powder with an average particle size of 2 μm.

[0059] In this comparative example, the density of the magnetic powder core obtained under the condition that the addition amount of manganese zinc ferrite powder is 10% of the mass of the insulating coated iron alloy soft magnetic powder is 5.679g / cm 3 , the inductance is 10.26μH and the loss is 1630kW / m 3 .

[0060] Comparison with Example 1 shows that using ferrite powder with the same particle size as the iron alloy soft magnetic powder reduces losses while significantly lowering the inductance of the resulting magnetic powder core. This further demonstrates that mixing large-particle iron alloy soft magnetic powder with small-particle ferrite powder can reduce the adverse effects on inductance.

[0061] The above embodiments are preferred implementations of the present invention, but the implementations of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a high-frequency low-loss magnetic powder core, characterized in that: The method comprises the following preparation steps: (1) treating iron alloy soft magnetic powder with a particle size of 5 to 50 μm by insulation coating to obtain insulation coated iron alloy soft magnetic powder; (2) The insulating coated iron alloy soft magnetic powder obtained in step (1) is mixed evenly with ferrite powder having a particle size of less than 5 μm and a binder, and then injected into a mold for pressing and molding, and then heated to 600-900°C for annealing to obtain a high-frequency low-loss magnetic powder core; The iron alloy soft magnetic powder in step (1) is iron-nickel soft magnetic alloy powder, iron-silicon soft magnetic alloy powder or iron-silicon-aluminum soft magnetic alloy powder; the insulation coating treatment refers to the use of a silicon dioxide-aluminum phosphate composite for insulation coating treatment; the method for the insulation coating treatment of the silicon dioxide-aluminum phosphate composite is as follows: 1) adding phytic acid to an alcohol aqueous solution to dissolve it, then adding an aluminum alkoxide solution to react and mix to obtain a phytic acid aluminum sol, which is then mixed evenly with a silica sol to obtain an insulating coating solution; 2) uniformly mixing the iron alloy soft magnetic powder with the insulating coating liquid of step 1), first drying at a temperature of 60-100° C. to remove the solvent, and then heating to 300-800° C. for heat treatment to obtain an iron alloy soft magnetic powder insulatingly coated with a silica-aluminum phosphate composite; The ferrite powder in step (2) is manganese zinc ferrite, copper zinc ferrite or nickel zinc ferrite powder; the amount of ferrite powder added is 5% to 20% of the mass of the insulating coated iron alloy soft magnetic powder.

2. The method for preparing a high-frequency low-loss magnetic powder core according to claim 1, characterized in that: In step 1), the alcohol aqueous solution is an ethanol aqueous solution having an ethanol volume percentage of 80-95%; the aluminum alkoxide solution is an aluminum triethanolate solution, an aluminum propoxide solution, an aluminum isopropoxide solution, or an aluminum n-butoxide solution; the aluminum alkoxide solution is added in an amount such that the pH value of the reaction system is 5-7; and the silica sol is added in an amount of 20-60% of the mass of the phytic acid, calculated as the silicon dioxide content.

3. The method for preparing a high-frequency low-loss magnetic powder core according to claim 1, characterized in that: The amount of the insulating coating liquid added in step 2) is 0.2-2% of the mass of the ferroalloy soft magnetic powder in terms of its solid content.

4. The method for preparing a high-frequency low-loss magnetic powder core according to claim 1, characterized in that: The drying and removal of the solvent in step 2) is carried out under vacuum conditions; the heat treatment is carried out under nitrogen protection conditions, and the heat treatment time is 3 to 10 hours.

5. The method for preparing a high-frequency low-loss magnetic powder core according to claim 1, characterized in that: The binder in step (2) is an epoxy resin binder or a silicone resin binder; the amount of the binder added is 0.2-1% of the total mass of the insulating coated iron alloy soft magnetic powder and the ferrite powder in terms of its solid content.

6. The method for preparing a high-frequency low-loss magnetic powder core according to claim 1, characterized in that: The temperature of the pressing molding in step (2) is 60-100° C. and the pressure is 500-800 MPa; the time of the annealing treatment is 15-120 min.

7. A high-frequency low-loss magnetic powder core, characterized in that: It is prepared by the method according to any one of claims 1 to 6.