CN110610788B - Method for preparing soft magnetic composite material with core-shell structure - Google Patents
Method for preparing soft magnetic composite material with core-shell structure Download PDFInfo
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- 239000005642 Oleic acid Substances 0.000 claims description 21
- QXJSBBXBKPUZAA-UHFFFAOYSA-N isooleic acid Natural products CCCCCCCC=CCCCCCCCCC(O)=O QXJSBBXBKPUZAA-UHFFFAOYSA-N 0.000 claims description 21
- ZQPPMHVWECSIRJ-KTKRTIGZSA-N oleic acid Chemical compound CCCCCCCC\C=C/CCCCCCCC(O)=O ZQPPMHVWECSIRJ-KTKRTIGZSA-N 0.000 claims description 21
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- 238000001291 vacuum drying Methods 0.000 claims description 12
- 238000005406 washing Methods 0.000 claims description 12
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- 239000000725 suspension Substances 0.000 claims description 10
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- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 9
- 239000002245 particle Substances 0.000 claims description 2
- 238000005303 weighing Methods 0.000 claims 1
- 229910052751 metal Inorganic materials 0.000 abstract description 36
- 239000002184 metal Substances 0.000 abstract description 36
- 239000002904 solvent Substances 0.000 abstract description 22
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 abstract description 18
- 150000004670 unsaturated fatty acids Chemical class 0.000 abstract description 11
- 235000021122 unsaturated fatty acids Nutrition 0.000 abstract description 11
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 abstract description 9
- 238000005253 cladding Methods 0.000 abstract description 5
- 238000010438 heat treatment Methods 0.000 abstract description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 3
- 229910052799 carbon Inorganic materials 0.000 abstract description 3
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- 238000000576 coating method Methods 0.000 description 13
- 239000010410 layer Substances 0.000 description 13
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- 239000011248 coating agent Substances 0.000 description 11
- 239000006247 magnetic powder Substances 0.000 description 11
- 235000019441 ethanol Nutrition 0.000 description 9
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 8
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 8
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 230000007062 hydrolysis Effects 0.000 description 5
- 238000006460 hydrolysis reaction Methods 0.000 description 5
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 4
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 4
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 4
- 239000005456 alcohol based solvent Substances 0.000 description 4
- -1 iron-silicon-aluminum Chemical compound 0.000 description 4
- DNIAPMSPPWPWGF-GSVOUGTGSA-N (R)-(-)-Propylene glycol Chemical compound C[C@@H](O)CO DNIAPMSPPWPWGF-GSVOUGTGSA-N 0.000 description 3
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- 229910021486 amorphous silicon dioxide Inorganic materials 0.000 description 3
- VAWNDNOTGRTLLU-UHFFFAOYSA-N iron molybdenum nickel Chemical compound [Fe].[Ni].[Mo] VAWNDNOTGRTLLU-UHFFFAOYSA-N 0.000 description 3
- UGKDIUIOSMUOAW-UHFFFAOYSA-N iron nickel Chemical compound [Fe].[Ni] UGKDIUIOSMUOAW-UHFFFAOYSA-N 0.000 description 3
- 238000007885 magnetic separation Methods 0.000 description 3
- 230000005415 magnetization Effects 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 2
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- 229920002050 silicone resin Polymers 0.000 description 2
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- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
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- 238000002149 energy-dispersive X-ray emission spectroscopy Methods 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
- H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
- H01F1/20—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder
- H01F1/22—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together
- H01F1/24—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together the particles being insulated
-
- 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
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- Engineering & Computer Science (AREA)
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- Manufacturing & Machinery (AREA)
- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Powder Metallurgy (AREA)
- Soft Magnetic Materials (AREA)
Abstract
The invention relates to a method for preparing a soft magnetic composite material with a core-shell structure, which comprises the following steps: adding a first alcohol solvent into the magnetic metal powder, and uniformly stirring; adding an unsaturated fatty acid containing one ethylenic bond with the carbon number of 12-18 into the mixture of the magnetic metal powder and the first alcohol solvent, and carrying out ultrasonic treatment; adding a pH adjusting solution and a second glycol solvent to the ultrasonically treated mixture under stirring to obtain a surface-treated mixture; and adding tetraethoxysilane into the surface treatment mixture under stirring to obtain the soft magnetic composite material with the core-shell structure. The method forms amorphous SiO with controllable thickness on the surface of magnetic metal powder2And a cladding layer, thereby providing a soft magnetic composite material with low magnetic loss and high temperature heat treatment capability.
Description
Technical Field
The invention relates to a method for preparing a soft magnetic composite material, in particular to a method for preparing a soft magnetic composite material with a core-shell structure.
Background
The magnetic metal-based soft magnetic composite material (also called magnetic powder core) has the performance characteristics of high magnetic induction intensity, high magnetic conductivity, low coercive force and low loss, and has attractive application prospects in the fields of electricity, computers, communication and the like. With the shortage of earth energy, it is an urgent requirement to reduce energy loss, so that the low loss of the soft magnetic composite material has great advantages for replacing the current motor stator and other applications.
The magnetic powder core has various types, and the common magnetic powder cores include iron powder cores, iron-nickel magnetic powder cores, iron-silicon-aluminum magnetic powder cores, iron-nickel-molybdenum magnetic powder cores, iron-silicon-nickel magnetic powder cores and the like. The most studied iron powder core has the advantages of good formability, high saturation induction density, high effective magnetic conductivity and low cost, and is very suitable for industrial production and application. However, the iron powder core has low resistivity, works under an alternating current electric field, and has overlarge eddy current loss, high magnetic loss and poor high-frequency performance.
In order to solve the defect of high eddy current loss of the iron powder core, effective insulation coating is the key. The common coating methods at present are divided into organic coating and inorganic coating. The organic coating includes coating with an organic material such as epoxy resin, phenolic resin, and silicone resin, but when stress is released by annealing in a subsequent process, the organic coating layer is easily decomposed, resulting in coating failure. The inorganic coating comprises coating with inorganic materials such as phosphate, inorganic oxide and the like, and has the advantages of high melting point and good thermal stability of the inorganic coating. Therefore, the inorganic coating has better prospect.
Chinese patent 1051495574A discloses a method for generating a layer of Fe with controllable thickness on the surface of iron powder by nitriding the surface at high temperature4And a coating layer of N. Fe4The N coating layer can improve the resistivity of the material, reduce the eddy current loss at high frequency and simultaneously ensure that the magnetic powder core keeps better magnetic performance. However, the method has complex process and higher energy consumption, and does not meet the original purpose of energy conservation and emission reduction at present.
In the Chinese patent 101996723A, a layer of Fe is formed on the surface of iron powder by controlled oxidation method3O4And the shell layer is formed by bonding and pressing silicone resin. The magnetic powder prepared by the method has higher saturation magnetization, and the magnetic powder core has better intrinsic magnetic property. However, the method needs to be carried out in a low-vacuum controllable oxidation furnace, and the cost is high.
It can be seen that the focus of the current research is on finding different cladding materials and cladding methods, and that little research is focused on how to precisely control the cladding layer thickness and understand the relationship between the cladding layer thickness and the soft magnetic material properties. The invention adopts an optimized tetraethoxysilane hydrolysis method to generate a layer of amorphous SiO with controllable thickness on the surface of iron powder2And coating layers, and providing a coating method with controllable coating layer thickness by adjusting various parameters.
Disclosure of Invention
The invention provides a method for preparing a soft magnetic composite material with a core-shell structure. The method can provide the magnetic powder core composite material with low magnetic loss and high-temperature heat treatment.
According to an aspect of the present invention, there is provided a method for preparing a soft magnetic composite material having a core-shell structure, comprising the steps of:
adding a first alcohol solvent into the magnetic metal powder, and uniformly stirring;
adding an unsaturated fatty acid containing one ethylenic bond with the carbon number of 12-18 into the mixture of the magnetic metal powder and the first alcohol solvent, and carrying out ultrasonic treatment;
adding a pH adjusting solution and a second glycol solvent to the ultrasonically treated mixture under stirring to obtain a surface-treated mixture;
and adding tetraethoxysilane into the surface treatment mixture under stirring to obtain the soft magnetic composite material with the core-shell structure.
According to a specific embodiment, the method further comprises washing the soft magnetic composite material with the second glycol solvent and deionized water, performing magnetic separation, and performing vacuum drying.
Preferably, the first alcoholic solvent and the second alcoholic solvent may be the same or different and each is independently selected from the group consisting of anhydrous methanol, anhydrous ethanol, anhydrous propanol, and anhydrous butanol.
Based on per gram of the magnetic metal powder, the dosage of the first alcohol solvent is 5-15 mL.
The unsaturated fatty acid is preferably oleic acid.
Based on each gram of the magnetic metal powder, the addition amount of the unsaturated fatty acid is 50-100 mu L.
According to another specific embodiment, the amount of the tetraethoxysilane is 1-3 mL per gram of the magnetic metal powder.
The magnetic metal powder is selected from the group consisting of iron nickel powder, iron silicon aluminum powder, iron nickel molybdenum powder and iron silicon nickel powder.
The pH adjusting solution is ammonia water, sodium hydroxide solution, potassium hydroxide solution, hydrochloric acid or phosphoric acid.
Drawings
Fig. 1 shows a scanning electron microscope EDS analysis picture of the soft magnetic composite powder prepared according to example 1.
Detailed Description
The invention provides a method for preparing a soft magnetic composite material with a core-shell structure, which comprises the following steps:
adding a first alcohol solvent into the magnetic metal powder, and uniformly stirring;
adding unsaturated fatty acid containing one ethylenic bond with the carbon number of 12-18 into the mixture of the magnetic metal powder and the first alcohol solvent, and carrying out ultrasonic treatment;
adding a pH adjusting solution and a second glycol solvent to the ultrasonically treated mixture under stirring to obtain a surface-treated mixture;
and adding tetraethoxysilane into the surface treatment mixture under stirring to obtain the soft magnetic composite material with the core-shell structure.
The first alcohol-based solvent and the second alcohol-based solvent may be the same or different, and independently may be a lower aliphatic alcohol, preferably an anhydrous lower aliphatic alcohol, for example, an anhydrous C1-4 aliphatic alcohol. Specifically, the first alcohol-based solvent and the second alcohol-based solvent may be one or more of absolute methanol, absolute ethanol, absolute propanol, and absolute butanol, respectively, and absolute ethanol is more preferable.
The magnetic metal powder may be selected from the group consisting of iron nickel powder, iron silicon aluminum powder, iron nickel molybdenum powder, and iron silicon nickel powder. The iron powder is preferably a high-purity iron powder (for example, an iron powder having a purity of 99% or more). The magnetic metal powder has a particle size of, for example, 100 to 200 mesh, preferably 150 to 180 mesh.
The using proportion of the first alcohol solvent to the magnetic metal powder is 5-15 mL, preferably 7-10 mL per gram of the metal powder, and the first alcohol solvent and the magnetic metal powder can be uniformly mixed to wet the surface of the magnetic metal powder.
The fatty acid having 12 to 18 carbon atoms and containing one ethylenic bond is more preferably oleic acid. The addition amount of the unsaturated fatty acid is 50-100 mu L, preferably 60-95 mu L, more preferably 65-90 mu L, and most preferably 70-85 mu L per gram of the magnetic metal powder.
After the unsaturated fatty acid is ultrasonically mixed with magnetic metal powder and a first alcohol solvent, the hydrophilic chain end of the unsaturated fatty acid is bonded to the surface of the magnetic metal powder such as iron powder, and the other end of the unsaturated fatty acid is lipophilic to capture ethyl orthosilicate (TEOS) molecules which are added subsequently. Hydrolyzing the captured tetraethoxysilane molecules in an aqueous solution with a proper pH (such as 4-7 or 10-12) to form amorphous SiO2. The amorphous SiO2Attached to the surface of the magnetic metal powder, so as to form a coating layer thereon, namely a core-shell structure.
When the amount of the unsaturated fatty acid is less than 50 μ L/g of the metal powder, the surface of the metal powder cannot be sufficiently modified, so that sufficient TEOS molecules cannot be captured on the surface of the metal powder, and a coating layer (shell layer) having a sufficient thickness cannot be formed on the surface of the metal powder. When the dosage of the unsaturated fatty acid is higher than 100 mu L/g of metal powder, excessive TEOS molecules are captured, so that partial captured TEOS molecules cannot be hydrolyzed fully, or an excessively thick coating layer (shell layer) is formed on the surface of the metal powder, so that the magnetic property is reduced excessively.
In the present invention, the pH of the system can be adjusted using a conventional pH adjusting solution. For example, the pH of the mixture for surface treatment is adjusted to 4 to 7 or 10 to 12. Preferably, one or more of ammonia, sodium hydroxide solution and potassium hydroxide solution can be used as the pH adjusting solution, and the system pH can be adjusted to 10-12, preferably 11. More preferably, ammonia water is used as the pH adjusting solution. Alternatively, one or more of hydrochloric acid and phosphoric acid may be used as the pH adjusting solution, and the pH of the system may be adjusted to 4 to 7, preferably 5. More preferably, dilute hydrochloric acid is used as the pH adjusting solution.
Adding tetraethoxysilane to the surface treatment mixture containing the pH-adjusted solution and the second glycol-based solvent, SO that tetraethoxysilane is hydrolyzed in the above-mentioned suitable pH range to form amorphous SO2. The dosage of the ethyl orthosilicate is 1-3 mL, preferably 1.5-2.5 mL, and more preferably 2mL per gram of the magnetic metal powder. If the dosage of the tetraethoxysilane is lower than 1mL/g of the metal powder, an effective coating layer cannot be formed on the surface of the metal powder; if the dosage of the tetraethoxysilane is more than 3mL/g of metal powder, the tetraethoxysilane is trappedThe tetraethoxysilane cannot be hydrolyzed sufficiently or amorphous SO generated by hydrolysis is caused2The thickness of the coating layer is too large to control the thickness of the coating layer accurately.
According to one embodiment, the hydrolysis temperature of the tetraethoxysilane may be in the range of 20 to 40 ℃, preferably 25 to 35 ℃, more preferably 30 ℃.
The amount of the second glycol solvent used may be the same as that of the first alcohol solvent, i.e., 5 to 15mL of the second glycol solvent per gram of the metal powder, preferably 7 to 10mL of the second glycol solvent per gram of the metal powder.
According to another embodiment of the present invention, the soft magnetic composite material according to the present invention is further washed with the above-mentioned second glycol solvent and deionized water, subjected to magnetic separation, and then vacuum-dried. The vacuum drying step may be carried out under conventional conditions, for example, 0.01MPa, 60-80 ℃.
The soft magnetic composite material prepared by the method has a core-shell structure, and a shell layer with controllable thickness, namely amorphous SiO is formed on the surface of the magnetic metal powder of the core2And coating the layer to obtain the soft magnetic composite material with the shell layer thickness of 1-5 microns, preferably 2-4 microns and the core-shell structure. The soft magnetic composite material has excellent magnetic performance, low magnetic loss and high temperature heat treatment.
To better illustrate the invention, exemplary embodiments of the invention are given below:
example 1
1. 20g of high purity (> 99%) iron powder was weighed, washed with absolute ethanol and then 200mL of absolute ethanol was added.
2. And dripping 1.5mL of oleic acid into the mixture to perform surface treatment on the high-purity iron powder, performing ultrasonic treatment for 1h at room temperature (25 ℃), and standing for 30min to ensure that the oleic acid is fully combined with the surface of the iron powder.
3. 25mL of 25% by mass aqueous ammonia and 200mL of absolute ethanol were added to a pH of 12, and the mixture was stirred at room temperature (25 ℃).
4. TEOS was added dropwise to the suspension at 20 ℃ with stirring for a total of 30mL at a rate of 10mL/h, sonicating for 5min per hour.
5. And (4) sequentially washing the product obtained in the step (4) with absolute ethyl alcohol and deionized water, carrying out magnetic separation, and carrying out vacuum drying at 80 ℃ to obtain soft magnetic composite material powder.
Example 2
1. 20g of high purity (> 99%) iron powder was weighed, washed with absolute ethanol and then 200mL of absolute ethanol was added.
2. And dripping 1.5mL of oleic acid into the mixture to perform surface treatment on the high-purity iron powder, performing ultrasonic treatment for 1h at room temperature (25 ℃), and standing for 30min to ensure that the oleic acid is fully combined with the surface of the iron powder.
3. 25mL of 25% by mass aqueous ammonia and 200mL of absolute ethanol were added to a pH of 12, and the mixture was stirred at room temperature (25 ℃).
4. TEOS was added dropwise to the suspension at 35 ℃ with stirring for a total of 30mL at a rate of 10mL/h, sonicating for 5min per hour.
5. Washing with absolute ethyl alcohol and deionized water, magnetically separating, and vacuum drying at 80 deg.c to obtain soft magnetic composite material powder.
Example 3
1. 20g of high purity (> 99%) iron powder was weighed, washed several times with absolute ethanol and then 200mL of absolute ethanol was added.
2. And dripping 1.5mL of oleic acid into the mixture to perform surface treatment on the high-purity iron powder, performing ultrasonic treatment for 1h at room temperature (25 ℃), and standing for 30min to ensure that the oleic acid is fully combined with the surface of the iron powder.
3. 25mL of 25% by mass aqueous ammonia and 200mL of absolute ethanol were added to a pH of 12, and the mixture was stirred at room temperature (25 ℃).
4. TEOS was added dropwise to the suspension at 25 ℃ with stirring at a rate of 10mL/h for a total of 20mL, sonicating for 5min per hour.
5. Washing with absolute ethyl alcohol and deionized water, magnetically separating, and vacuum drying at 80 deg.c to obtain soft magnetic composite material powder.
Example 4
1. 20g of high purity (> 99%) iron powder was weighed, washed several times with absolute ethanol and then 200mL of absolute ethanol was added.
2. And dripping 1.5mL of oleic acid into the mixture to perform surface treatment on the high-purity iron powder, performing ultrasonic treatment for 1h at room temperature (25 ℃), and standing for 30min to ensure that the oleic acid is fully combined with the surface of the iron powder.
3. 15mL of 25% by mass aqueous ammonia and 200mL of absolute ethanol were added to a pH of 10, and the mixture was stirred at room temperature (25 ℃).
4. TEOS was added dropwise to the suspension at a rate of 10mL/h, with stirring, at a total of 20mL, at 40 ℃ for 5min per hour of sonication.
5. Washing with absolute ethyl alcohol and deionized water, magnetically separating, and vacuum drying at 80 deg.c to obtain soft magnetic composite material powder.
Example 5
1. 20g of high purity (> 99%) iron powder was weighed, washed several times with absolute ethanol and then 200mL of absolute ethanol was added.
2. And dripping 1.5mL of oleic acid into the mixture to perform surface treatment on the high-purity iron powder, performing ultrasonic treatment for 1h at room temperature (25 ℃), and standing for 30min to ensure that the oleic acid is fully combined with the surface of the iron powder.
3. 15mL of dilute hydrochloric acid and 200mL of absolute ethanol were added to pH 7, and the mixture was stirred at room temperature (25 ℃).
4. TEOS was added dropwise to the suspension at 20 ℃ with stirring for a total of 30mL at a rate of 10mL/h, sonicating for 5min per hour.
5. Washing with absolute ethyl alcohol and deionized water, magnetically separating, and vacuum drying at 80 deg.c to obtain soft magnetic composite material powder.
Example 6
1. 20g of high purity (> 99%) iron powder was weighed, washed several times with absolute ethanol and then 200mL of absolute ethanol was added.
2. And dripping 1.5mL of oleic acid into the mixture to perform surface treatment on the high-purity iron powder, performing ultrasonic treatment for 1h at room temperature (25 ℃), and standing for 30min to ensure that the oleic acid is fully combined with the surface of the iron powder.
3. 20mL of dilute hydrochloric acid and 200mL of absolute ethanol were added to pH 4, and the mixture was stirred at room temperature (25 ℃).
4. TEOS was added dropwise to the suspension at 40 ℃ with stirring, at a rate of 10mL/h, for a total of 50mL, and sonicated for 5min per hour.
5. Washing with absolute ethyl alcohol and deionized water, magnetically separating, and vacuum drying at 80 deg.c to obtain soft magnetic composite material powder.
Comparative example 1
1. 20g of high purity (> 99%) iron powder was weighed, washed several times with absolute ethanol and then 200mL of absolute ethanol was added.
2. And dripping 1.5mL of oleic acid into the mixture to perform surface treatment on the high-purity iron powder, performing ultrasonic treatment for 1h at room temperature (25 ℃), and standing for 30min to ensure that the oleic acid is fully combined with the surface of the iron powder.
3. 10mL of 25% by mass aqueous ammonia and 200mL of absolute ethanol were added to a pH of 8, and the mixture was stirred at room temperature (25 ℃).
3. TEOS was added dropwise to the suspension at 20 ℃ with stirring for a total of 30mL at a rate of 10mL/h, sonicating for 5min per hour.
4. Washing with absolute ethyl alcohol and deionized water, magnetically separating, and vacuum drying at 80 deg.c to obtain soft magnetic composite material powder.
Comparative example 2
1. 20g of high purity (> 99%) iron powder was weighed, washed several times with absolute ethanol and then 200mL of absolute ethanol was added.
2. And dripping 1.5mL of oleic acid into the mixture to perform surface treatment on the high-purity iron powder, performing ultrasonic treatment for 1h at room temperature (25 ℃), and standing for 30min to ensure that the oleic acid is fully combined with the surface of the iron powder.
3. 55mL of dilute hydrochloric acid and 200mL of absolute ethanol were added to a pH of 2, and the mixture was stirred at room temperature (25 ℃).
3. TEOS was added dropwise to the suspension at a rate of 10mL/h, with stirring, at a total of 20mL, at 40 ℃ for 5min per hour of sonication.
4. Washing with absolute ethyl alcohol and deionized water, magnetically separating, and vacuum drying at 80 deg.c to obtain soft magnetic composite material powder.
Comparative example 3
1. 20g of high purity (> 99%) iron powder was weighed, washed several times with absolute ethanol and then 200mL of absolute ethanol was added.
2. 25mL of 25% by mass aqueous ammonia and 200mL of absolute ethanol were added to a pH of 2, and the mixture was stirred at room temperature (25 ℃).
3. TEOS was added dropwise to the suspension at 30 ℃ with stirring for a total of 20mL at a rate of 10mL/h, sonicating for 5min per hour.
4. Washing with absolute ethyl alcohol and deionized water, magnetically separating, and vacuum drying at 80 deg.c to obtain soft magnetic composite material powder.
Performance testing
1. Characterization of the core-Shell Structure of the Soft magnetic composite powder obtained in example 1
The soft magnetic composite powder prepared in example 1 was prepared into a metallographic sample, the surface was polished, and then analyzed by scanning electron microscopy (EDS), and the picture is shown in FIG. 1. Referring to FIG. 1, iron powder-SiO can be clearly seen2A core-shell structure.
2. Measurement of coating layer thickness for Soft magnetic composite powder obtained in examples 1 to 6
The soft magnetic composite material powders were respectively prepared into metallographic samples, the surfaces thereof were polished, and then the thickness of the coating layer was analyzed by scanning electron microscopy (EDS), and the results are shown in Table 1.
3. The soft magnetic composite powder prepared in examples 1 to 6 was examined for eddy current loss, magnetic stability, magnetization and high-temperature heat-treatable property
The soft magnetic composite powder prepared in examples 1 to 6 was measured for flow loss, magnetic stability, magnetization strength, and magnetic properties that could be heat-treated at high temperature, respectively, using a digital bridge. The measurement results are shown in table 1.
TABLE 1
As can be seen from the above Table 1, when the pH is controlled within the range of 10 to 12 or 4 to 7, the thickness of the coating layer can be well controlled within the range of 2 to 4 μm, so that the eddy current loss can be controlled within the range of 80 to 90W/kg, and the heat treatable temperature can be 625 to 810 ℃.
In conclusion, in examples 1 to 6, the method of the present invention can be used to simply and practically prepare the core-shell structure soft magnetic composite material using the magnetic metal powder such as high purity iron powder as the matrix and amorphous silicon dioxide as the insulation coating layer. The method can accurately regulate and control the thickness of the insulating coating layer, and the soft magnetic composite material with low loss and excellent magnetic property is obtained.
In contrast, comparative example 1, which produced a clad layer having a thickness of only 1.6 μm, an eddy current loss of 98W/kg, and a heat treatable temperature of 520 ℃ which was significantly lower than that of the soft magnetic composite material produced in example 1, was at pH 8 as compared with example 1.
Comparative example 2 compared with example 6, pH was 2, and the clad layer produced was only 1.3 μm thick, eddy current loss reached 103W/kg, and the heat treatable temperature of 515 ℃ was also significantly lower than that of the soft magnetic composite material produced in example 1.
Comparative example 3 compared to example 1, no oleic acid was added, a completely clad core-shell structure could not be prepared, and the magnetic properties thereof were also much inferior to those of the soft magnetic composite material prepared in example 1.
In summary, the method according to the invention has the following advantages:
1. the process is simple and the controllability is good. The regulation and control of the thickness of the coating layer can be effectively realized by controlling parameters such as hydrolysis temperature of the tetraethoxysilane, pH value of the hydrolysis solution, TEOS addition amount and the like.
2. The prepared soft magnetic composite material has the characteristics of low eddy current loss of 80-95W/kg, high magnetic conductivity of 5-8 and high-temperature heat treatment temperature of 600-850 ℃.
3. The method has good repeatability and low cost, can realize mass production in industry, and has good market prospect.
The prepared soft magnetic composite material has the characteristic of three-dimensional isotropy after being pressed, so that the soft magnetic composite material can be prepared into a soft magnetic application device with small size and low loss under high frequency.
Claims (1)
1. A method for preparing a soft magnetic composite material having a core-shell structure, comprising the steps of:
step 1: weighing 20g of high-purity iron powder with the particle size of 150-180 meshes, washing the iron powder with absolute ethyl alcohol for several times, and then adding 200mL of absolute ethyl alcohol;
step 2: dripping 1.5mL of oleic acid into the mixture to perform surface treatment on the high-purity iron powder, performing ultrasonic treatment for 1h at room temperature, and standing for 30min to ensure that the oleic acid is fully combined with the surface of the iron powder;
and step 3: adding 25mL of 25 mass percent ammonia water and 200mL of absolute ethyl alcohol to the pH value of 12, and stirring at room temperature;
and 4, step 4: adding TEOS (tetraethyl orthosilicate) dropwise into the suspension at the speed of 10mL/h at 25 ℃ under stirring for 20mL, and carrying out ultrasonic treatment for 5min per hour;
and 5: washing with absolute ethyl alcohol and deionized water, magnetically separating, and vacuum drying at 80 deg.c to obtain soft magnetic composite material powder.
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| CN101599334A (en) * | 2009-04-21 | 2009-12-09 | 北京科技大学 | A kind of preparation method of high resistivity and high magnetic permeability FeSiAl soft magnetic material |
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| WO2016020524A1 (en) * | 2014-08-08 | 2016-02-11 | Universität Für Bodenkultur Wien | Ultra-dense shell core-shell nanoparticles |
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| CN101599334A (en) * | 2009-04-21 | 2009-12-09 | 北京科技大学 | A kind of preparation method of high resistivity and high magnetic permeability FeSiAl soft magnetic material |
| CN101694800A (en) * | 2009-09-08 | 2010-04-14 | 清华大学 | Compound soft magnetic material with operational performances of high-frequency and large power and process for preparing same |
| WO2016020524A1 (en) * | 2014-08-08 | 2016-02-11 | Universität Für Bodenkultur Wien | Ultra-dense shell core-shell nanoparticles |
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