CN115631940A - Magnetic powder core coated with nano boron nitride-aluminum oxide composite film and preparation method thereof - Google Patents
Magnetic powder core coated with nano boron nitride-aluminum oxide composite film and preparation method thereof Download PDFInfo
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- CN115631940A CN115631940A CN202211390925.2A CN202211390925A CN115631940A CN 115631940 A CN115631940 A CN 115631940A CN 202211390925 A CN202211390925 A CN 202211390925A CN 115631940 A CN115631940 A CN 115631940A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0206—Manufacturing of magnetic cores by mechanical means
- H01F41/0246—Manufacturing of magnetic circuits by moulding or by pressing powder
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/24—Magnetic cores
- H01F27/255—Magnetic cores made from particles
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
- H01F2027/348—Preventing eddy currents
Abstract
The invention belongs to the technical field of metal soft magnetic materials, and particularly relates to a magnetic powder core coated with a nano boron nitride-aluminum oxide composite film and a preparation method thereof. Mixing boron nitride powder and magnetic powder, adding the mixture into a ball milling tank for ball milling to obtain adhered nanometer boron nitride magnetic powder, adding the adhered nanometer boron nitride magnetic powder and aluminum nitrate hexahydrate into a proper amount of purified water, stirring and dispersing to obtain aluminum nitrate-magnetic powder mixed slurry, dropwise adding an ammonia water solution, stirring and dispersing, standing and filtering to obtain a magnetic powder coated nanometer boron nitride-aluminum oxide precursor, roasting at a high temperature to obtain coated nanometer boron nitride-aluminum oxide composite membrane magnetic powder, pressing and forming to obtain a magnetic powder core green body, and performing three-stage heating and sintering heat treatment on the magnetic powder core green body to obtain the magnetic powder core coated with the nanometer boron nitride-aluminum oxide composite membrane. The method of the invention has the advantages of safety, reliability, simple operation and good magnetic powder core pressing forming capability, and the obtained magnetic powder core product has higher heat resistance and resistivity and can effectively reduce the eddy current loss of the magnetic powder core.
Description
Technical Field
The invention belongs to the technical field of magnetic materials, and particularly relates to a magnetic powder core coated with a nano boron nitride-aluminum oxide composite film and a preparation method thereof.
Background
The metal magnetic powder core is widely applied to the fields of electronics, photovoltaics, communication and the like. Under the condition of alternating magnetic field, especially under the condition of high frequency, the magnetic powder core can produce larger eddy current, so that the working performance of the device is seriously reduced. Therefore, it is required to increase the resistivity of the metal magnetic powder core to reduce the eddy current loss. Generally, the surface of the metal magnetic powder is coated with an insulating film, and the eddy current loss of the magnetic powder core is affected differently by the difference of the insulating film material.
At present, most of insulating films coated on the surface of a magnetic powder core are single insulating films, and the technical problems of limited resistivity improvement range, unsatisfactory magnetic powder core press forming property and the like exist. Therefore, it is urgent to develop a low core eddy current loss, high performance cladding material for magnetic powder core composite film to solve the above problems.
Disclosure of Invention
Aiming at the problems, the invention provides a preparation method of a magnetic powder core coated with a nano boron nitride-alumina composite film, wherein the nano boron nitride and the nano alumina both have very high resistivity, and the two nano materials are coated on the surface of magnetic powder to form the composite film, so that the eddy current loss of the magnetic powder core can be obviously reduced, and the product performance of the magnetic powder core can be effectively improved.
The first purpose of the invention is to provide a preparation method of a magnetic powder core coated with a nano boron nitride-alumina composite film, which comprises the steps of mixing boron nitride powder and magnetic powder, adding the mixture into a ball milling tank for ball milling to obtain adhered nano boron nitride magnetic powder, adding the adhered nano boron nitride magnetic powder and aluminum nitrate hexahydrate into a proper amount of purified water, stirring and dispersing to obtain aluminum nitrate-magnetic powder mixed slurry, dropwise adding an ammonia water solution, stirring and dispersing, standing and filtering to obtain a magnetic powder coated nano boron nitride-alumina precursor, roasting at a high temperature to obtain magnetic powder coated with a nano boron nitride-alumina composite film, pressing and forming to obtain a magnetic powder core green body, and carrying out three-stage heating and sintering heat treatment on the magnetic powder core green body to obtain the magnetic powder core coated with the nano boron nitride-alumina composite film.
Further, a preparation method of the magnetic powder core coated with the nano boron nitride-alumina composite film comprises the following specific steps:
s1, mixing boron nitride powder of 400-800 meshes with magnetic powder of 100-300 meshes, and adding the mixture into a ball milling tank for ball milling at the ball milling speed of 100-500rpm for 0.5-6h to obtain the adhered nano boron nitride magnetic powder;
s2, adding the adhered nanometer boron nitride magnetic powder obtained in the S1 and aluminum nitrate hexahydrate into a proper amount of purified water, and mechanically stirring for 10-30min to obtain aluminum nitrate-magnetic powder mixed slurry;
s3, gradually dripping 100-1500mL of ammonia water solution into the aluminum nitrate-magnetic powder mixed slurry obtained in the step S2 under the stirring condition, continuously stirring and dispersing for 0.5-2h after finishing dripping, standing for 0.5-1h, and filtering to obtain a magnetic powder coated nano boron nitride-alumina precursor;
s4, placing the magnetic powder coated nanometer boron nitride-alumina precursor at 500-850 ℃, and roasting for 1-3h under the protection of argon gas to obtain coated nanometer boron nitride-alumina composite membrane magnetic powder;
s5, pressing the magnetic powder coated with the nano boron nitride-aluminum oxide composite film obtained in the step S4 into a magnetic powder core green body under the pressure of 100-600 MPa;
and S6, carrying out three-section heating sintering heat treatment process on the magnetic powder core green body to obtain the magnetic powder core coated with the nano boron nitride-aluminum oxide composite film.
Furthermore, in S1, the mass ratio of the boron nitride powder to the magnetic powder is (0.8-3): (97-99.2).
Furthermore, in S1, the ball-milling tank has a ball-powder mass ratio of 1:2.
Furthermore, in S2, the mass ratio of the adhered nanometer boron nitride magnetic powder to the aluminum nitrate hexahydrate is (0.5-1.5): (98.5-99.5).
Further, in S3, the stirring speed of the stirring is 100-150rpm.
Further, in S3, the mass concentration of the ammonia water solution is 0.5-10%.
Furthermore, in S3, the dropping control speed is 0.5-15mL/min.
Further, in S6, the three-stage heating sintering is respectively: the first stage is sintering at 100-300 deg.C for 0.5-2h, the second stage is sintering at 300-500 deg.C for 0.2-1h, and the third stage is sintering at 500-800 deg.C for 0.2-0.3h.
The second purpose of the invention is to provide a magnetic powder core coated with the nanometer boron nitride-alumina composite film.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention provides a preparation method of a magnetic powder core coated with a nano boron nitride-aluminum oxide composite film, wherein both nano boron nitride and nano aluminum oxide have very high resistivity, and the two nano materials are coated on the surface of magnetic powder to form the composite film, so that the eddy current loss of the magnetic powder core can be obviously reduced, the product performance of the magnetic powder core can be effectively improved, and the technical problems that most of insulating films coated on the surface of the magnetic powder core in the prior art are single insulating films, the resistivity improvement range is limited, the press forming property of the magnetic powder core is not ideal and the like are solved.
2. The method of the invention has the advantages of safety, reliability, simple operation, low production cost and good magnetic powder core pressing forming capability, and the obtained magnetic powder core product has higher heat resistance and resistivity, can effectively reduce the eddy current loss of the magnetic powder core and has higher effective magnetic conductivity.
Detailed Description
In order to make the purpose, technical solution and advantages of the embodiments of the present invention more apparent, the technical solution of the present invention will be described clearly and completely with reference to the detailed description below.
The experimental procedures in the following examples are conventional unless otherwise indicated, and the starting materials and reagents used in the present invention are all commercially available products and are commercially available.
Example 1
A preparation method of a magnetic powder core coated with a nano boron nitride-alumina composite film comprises the following steps:
s1, mixing the components in a mass ratio of 0.8: mixing the boron nitride powder of 400 meshes with the magnetic powder of 200 meshes of 99.2, adding the mixture into a ball milling tank with the ball powder mass ratio of 1:2, and carrying out ball milling at the ball milling speed of 300rpm for 2 hours to obtain the adhered nanometer boron nitride magnetic powder;
s2, adding the adhered nanometer boron nitride magnetic powder obtained in the S1 and aluminum nitrate hexahydrate into a proper amount of purified water according to the mass ratio of 0.5;
s3, gradually dripping 500mL of ammonia water solution with the mass concentration of 1% into the aluminum nitrate-magnetic powder mixed slurry obtained in the step S2 under the stirring condition of 100rpm, controlling the dripping speed to be 1.0mL/min, continuously stirring and dispersing for 1h after the dripping is finished, standing for 0.5h, and filtering to obtain a magnetic powder coated nano boron nitride-aluminum oxide precursor;
s4, placing the magnetic powder coated nanometer boron nitride-alumina precursor at 600 ℃, and roasting for 2 hours under the protection of argon gas to obtain coated nanometer boron nitride-alumina composite membrane magnetic powder;
s5, pressing the magnetic powder coated with the nano boron nitride-alumina composite film obtained in the S4 into a magnetic powder core green body under the pressure of 200 MPa;
s6, sintering the magnetic powder core green body for 1 hour at 100 ℃ in the first stage, sintering for 0.5 hour at 300 ℃ in the second stage and sintering for 0.2 hour at 700 ℃ in the third stage to obtain the magnetic powder core coated with the nano boron nitride-aluminum oxide composite film.
The magnetic powder core product obtained in example 1 is tested under the conditions of 50mT and 100KHz, and the eddy current loss of the magnetic powder core is 174mW/cm 3 The effective permeability was 45.
Example 2
A preparation method of a magnetic powder core coated with a nano boron nitride-alumina composite film comprises the following steps:
s1, mixing the components in a mass ratio of 1.5:97.8, mixing the boron nitride powder with 400 meshes and the magnetic powder with 200 meshes, adding the mixture into a ball milling tank with the ball powder mass ratio of 1:2, and carrying out ball milling at the ball milling speed of 300rpm for 2 hours to obtain the adhered nanometer boron nitride magnetic powder;
s2, adding the adhered nanometer boron nitride magnetic powder obtained in the S1 and aluminum nitrate hexahydrate into a proper amount of purified water according to the mass ratio of 0.8;
s3, gradually dripping 500mL of ammonia water solution with the mass concentration of 1% into the aluminum nitrate-magnetic powder mixed slurry obtained in the step S2 under the stirring condition of 100rpm, controlling the dripping speed to be 1.0mL/min, continuously stirring and dispersing for 1h after the dripping is finished, standing for 0.5h, and filtering to obtain a magnetic powder coated nano boron nitride-aluminum oxide precursor;
s4, placing the magnetic powder coated nanometer boron nitride-alumina precursor at 600 ℃, and roasting for 2 hours under the protection of argon gas to obtain coated nanometer boron nitride-alumina composite membrane magnetic powder;
s5, pressing the magnetic powder coated with the nano boron nitride-alumina composite film obtained in the step S4 into a magnetic powder core green body under the pressure of 200 MPa;
s6, sintering the magnetic powder core at 100 ℃ for 1h in the first stage, sintering at 300 ℃ for 0.5h in the second stage and sintering at 700 ℃ for 0.2h in the third stage to obtain the magnetic powder core coated with the nano boron nitride-aluminum oxide composite film.
The magnetic powder core product obtained in example 2 is tested under the conditions of 50mT and 100KHz, and the eddy current loss of the magnetic powder core is 162mW/cm 3 The effective permeability is 48.
Example 3
A preparation method of a magnetic powder core coated with a nano boron nitride-alumina composite film comprises the following steps:
s1, mixing the components in a mass ratio of 2.5:97.5, mixing the boron nitride powder with 400 meshes and the magnetic powder with 200 meshes, adding the mixture into a ball milling tank with the ball powder mass ratio of 1:2, and carrying out ball milling at the ball milling speed of 300rpm for 2 hours to obtain the adhered nanometer boron nitride magnetic powder;
s2, adding the adhered nanometer boron nitride magnetic powder obtained in the S1 and aluminum nitrate hexahydrate into a proper amount of purified water according to the mass ratio of 1.0;
s3, gradually dripping 500mL of ammonia water solution with the mass concentration of 1% into the aluminum nitrate-magnetic powder mixed slurry obtained in the step S2 under the stirring condition of 100rpm, controlling the dripping speed to be 1.0mL/min, continuously stirring and dispersing for 1h after the dripping is finished, standing for 0.5h, and filtering to obtain a magnetic powder coated nano boron nitride-aluminum oxide precursor;
s4, placing the magnetic powder coated nanometer boron nitride-alumina precursor at 600 ℃, and roasting for 2 hours under the protection of argon gas to obtain coated nanometer boron nitride-alumina composite membrane magnetic powder;
s5, pressing the magnetic powder coated with the nano boron nitride-alumina composite film obtained in the S4 into a magnetic powder core green body under the pressure of 200 MPa;
s6, sintering the magnetic powder core green body for 1 hour at 100 ℃ in the first stage, sintering for 0.5 hour at 300 ℃ in the second stage and sintering for 0.2 hour at 700 ℃ in the third stage to obtain the magnetic powder core coated with the nano boron nitride-aluminum oxide composite film.
For the magnetic powder core product obtained in example 3, the eddy current loss of the magnetic powder core is 153mW/cm when tested under the conditions of 50mT and 100KHz 3 The effective permeability is 50.
Comparative example 1
A preparation method of a magnetic powder core coated with a nano boron nitride insulating film comprises the following steps:
s1, mixing the components in a mass ratio of 2.5:97.5, mixing the boron nitride powder with 400 meshes and the magnetic powder with 200 meshes, adding the mixture into a ball milling tank with the ball powder mass ratio of 1:2, and carrying out ball milling at the ball milling speed of 300rpm for 2 hours to obtain the adhered nanometer boron nitride magnetic powder;
s2, pressing the coated nano boron nitride magnetic powder obtained in the S1 into a magnetic powder core green body under the pressure of 200 MPa;
and S3, sintering the magnetic powder core green compact obtained in the step S2 at 100 ℃ for 1 hour in the first stage, sintering at 300 ℃ for 0.5 hour in the second stage, and sintering at 700 ℃ for 0.2 hour in the third stage to obtain the magnetic powder core coated with the nano boron nitride insulating film.
When the magnetic powder core product obtained in the comparative example 1 is tested under the conditions of 50mT and 100KHz, the eddy current loss of the magnetic powder core is 256mW/cm 3 The effective permeability is 30.
Comparative example 2
A preparation method of a magnetic powder core coated with a nano alumina insulating film comprises the following steps:
s1, adding 200-mesh magnetic powder and aluminum nitrate hexahydrate into a proper amount of purified water according to a mass ratio of 1.0;
s2, gradually dripping 500mL of ammonia water solution with the mass concentration of 1% into the aluminum nitrate-magnetic powder mixed slurry obtained in the step S1 under the stirring condition of 100rpm, controlling the dripping speed to be 1.0mL/min, continuously stirring and dispersing for 1h after the dripping is finished, standing for 0.5h, and filtering to obtain a magnetic powder coated nano boron nitride-aluminum oxide precursor;
s3, placing the magnetic powder coated nano alumina precursor at 600 ℃, and roasting for 2 hours under the protection of argon gas to obtain coated nano alumina film magnetic powder;
s4, pressing the magnetic powder coated with the nano aluminum oxide film obtained in the S3 into a magnetic powder core green body under the pressure of 200 MPa;
and S5, sintering the magnetic powder core green body for 1 hour at 100 ℃ in the first stage, sintering for 0.5 hour at 300 ℃ in the second stage and sintering for 0.2 hour at 700 ℃ in the third stage to obtain the magnetic powder core coated with the nano aluminum oxide insulating film.
When the magnetic powder core product obtained in comparative example 2 is tested under the conditions of 50mT and 100KHz, the eddy-current loss of the magnetic powder core is 246mW/cm 3 The effective permeability is 35.
As can be seen from the results of the tests on the magnetic powder core products obtained in examples 1-3 and comparative examples 1-2 above, the magnetic powder core product coated with only one kind of insulating film had eddy current loss of 246mW/cm and 256mW/cm, respectively 3 The effective magnetic conductivity is respectively 30 and 35, and the magnetic loss of the magnetic powder core product coated with the composite film is 153-174mW/cm 3 The effective magnetic conductivity is 45-50, so that the eddy current loss of the magnetic powder core product only coated with one insulating film is far higher than that of the magnetic powder core product coated with the composite film, and meanwhile, the magnetic powder core product coated with the composite film has higher effective magnetic conductivity and more excellent magnetic performance.
While the preferred embodiments of this patent have been described in detail, this patent is not limited to the embodiments described above, and variations and modifications in other forms may occur to those skilled in the art, within the knowledge of the person skilled in the art. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A preparation method of a magnetic powder core coated with a nano boron nitride-aluminum oxide composite film is characterized in that boron nitride powder and magnetic powder are mixed and then added into a ball milling tank for ball milling to obtain adhered nano boron nitride magnetic powder, the adhered nano boron nitride magnetic powder and aluminum nitrate hexahydrate are added into a proper amount of purified water, aluminum nitrate-magnetic powder mixed slurry is obtained after stirring and dispersing, ammonia water solution is dripped, stirring and dispersing are carried out, standing is carried out, filtering procedures are carried out to obtain a magnetic powder coated nano boron nitride-aluminum oxide precursor, finally, the precursor is roasted under a high temperature condition to obtain coated nano boron nitride-aluminum oxide composite film magnetic powder, magnetic powder core green bodies are obtained through pressing and forming, and the magnetic powder core green bodies are subjected to three-stage heating and sintering heat treatment processes to obtain the magnetic powder core coated with the nano boron nitride-aluminum oxide composite film.
2. The preparation method according to claim 1, comprising the following specific steps:
s1, mixing 400-800 mesh boron nitride powder and 100-300 mesh magnetic powder, adding the mixture into a ball milling tank, and carrying out ball milling at a ball milling speed of 100-500rpm for 0.5-6h to obtain adhered nano boron nitride magnetic powder;
s2, adding the adhered nanometer boron nitride magnetic powder obtained in the S1 and aluminum nitrate hexahydrate into a proper amount of purified water, and mechanically stirring for 10-30min to obtain aluminum nitrate-magnetic powder mixed slurry;
s3, gradually dripping 100-1500mL of ammonia water solution into the aluminum nitrate-magnetic powder mixed slurry obtained in the step S2 under the stirring condition, continuously stirring and dispersing for 0.5-2h after finishing dripping, standing for 0.5-1h, and filtering to obtain a magnetic powder coated nano boron nitride-alumina precursor;
s4, placing the magnetic powder coated nanometer boron nitride-alumina precursor at 500-850 ℃, and roasting for 1-3h under the protection of argon gas to obtain coated nanometer boron nitride-alumina composite membrane magnetic powder;
s5, pressing the magnetic powder coated with the nano boron nitride-aluminum oxide composite film obtained in the step S4 into a magnetic powder core green body under the pressure of 100-600 MPa;
and S6, carrying out three-stage heating sintering heat treatment on the magnetic powder core green body to obtain the magnetic powder core coated with the nano boron nitride-aluminum oxide composite film.
3. The production method according to claim 2, wherein in S1, the mass ratio of the boron nitride powder to the magnetic powder is (0.8-3): (97-99.2).
4. The preparation method according to claim 2, wherein in S1, the ball-milling tank has a ball-powder mass ratio of 1:2.
5. The method according to claim 2, wherein in S2, the mass ratio of the adhered nano boron nitride magnetic powder to the aluminum nitrate hexahydrate is (0.5-1.5): (98.5-99.5).
6. The production method according to claim 2, wherein in S3, the stirring rate of the stirring is 100 to 150rpm.
7. The method according to claim 2, wherein the mass concentration of the aqueous ammonia solution in S3 is 0.5 to 10%.
8. The method according to claim 2, wherein the dropping control rate in S3 is 0.5 to 15mL/min.
9. The preparation method according to claim 2, wherein in S6, the three-stage temperature-raising sintering is respectively as follows: the first stage is sintering at 100-300 deg.C for 0.5-2h, the second stage is sintering at 300-500 deg.C for 0.2-1h, and the third stage is sintering at 500-800 deg.C for 0.2-0.3h.
10. A magnetic powder core of the coated nano boron nitride-alumina composite film obtained by the preparation method of any one of claims 1 to 9.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116376321A (en) * | 2023-03-30 | 2023-07-04 | 武汉理工大学 | Preparation method and application of aluminum oxide coated hexagonal boron nitride composite powder |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116376321A (en) * | 2023-03-30 | 2023-07-04 | 武汉理工大学 | Preparation method and application of aluminum oxide coated hexagonal boron nitride composite powder |
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