阅读说明：本技术 制备具有核壳结构的软磁复合材料的方法 (Method for preparing soft magnetic composite material with core-shell structure ) 是由 屈云鹏 高启龙 刘峣 孙蕾 于 2018-06-15 设计创作，主要内容包括：本发明涉及一种制备具有核壳结构的软磁复合材料的方法,包括以下步骤：向磁性金属粉中加入第一醇类溶剂,搅拌均匀；向所述磁性金属粉与所述第一醇类溶剂的混合物中加入碳原子数为12至18的包含一个烯键的不饱和脂肪酸,进行超声处理；搅拌下,向超声处理后的混合物中加入pH调节溶液和第二醇类溶剂,得到表面处理混合物；搅拌下,向所述表面处理混合物加入正硅酸乙酯,得到具有核壳结构的软磁复合材料。所述方法在磁性金属粉表面形成厚度可控的非晶SiO<Sub>2</Sub>包覆层,从而提供磁损耗低、可高温热处理的软磁复合材料。(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 powder 2 And a cladding layer, thereby providing a soft magnetic composite material with low magnetic loss and high temperature heat treatment capability.)

1. 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.

2. The method according to claim 1, further comprising washing the soft magnetic composite material with the second glycol solvent and deionized water, performing magnetic separation, and performing vacuum drying.

3. The method according to claim 1, wherein the first alcoholic solvent is the same as or different from the second alcoholic solvent, and each is independently selected from the group consisting of anhydrous methanol, anhydrous ethanol, anhydrous propanol, and anhydrous butanol.

4. The method according to any one of claims 1 to 3, wherein the first alcohol solvent is used in an amount of 5 to 15mL per gram of the magnetic metal powder.

5. The method of any one of claims 1 to 3, the unsaturated fatty acid being oleic acid.

6. The method according to any one of claims 1 to 3, wherein the unsaturated fatty acid is added in an amount of 50 to 100 μ L per gram of the magnetic metal powder.

7. The method according to any one of claims 1 to 3, wherein the amount of the ethyl orthosilicate is 1 to 3mL per gram of the magnetic metal powder.

8. The method according to any one of claims 1 to 3, the magnetic metal powder is selected from the group consisting of iron nickel powder, iron silicon aluminum powder, iron nickel molybdenum powder, iron silicon nickel powder.

9. The method according to any one of claims 1 to 3, wherein the pH adjusting solution is ammonia water, a sodium hydroxide solution, a potassium hydroxide solution, hydrochloric acid or phosphoric acid.

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 has higher cost。

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 captured tetraethoxysilane cannot be hydrolyzed fully 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: