阅读说明：本技术 一种铁氮化物包覆金属软磁复合材料及其制备方法 (Iron nitride coated metal soft magnetic composite material and preparation method thereof ) 是由 张雪峰 刘先国 孙玉萍 李红霞 李忠 陈文潮 于 2020-12-24 设计创作，主要内容包括：本发明涉及磁性材料技术领域,尤其涉及一种铁氮化物包覆金属软磁复合材料及其制备方法,包括以下步骤：(1)将可溶性铁盐溶解于有机溶剂中,加入有机胺,常温搅拌,形成悬浊液；(2)将悬浊液加入金属软磁粉末中混合,搅拌均匀后,烘干；(3)与粘结剂和润滑剂混合均匀,压制成型,得坯体；(4)在氮气中进行热处理,冷却,喷涂。本发明采用有机胺为有机氮源,通过络合性能增强Fe-N间相互作用,制备高品质的铁氮化物。首先在磁粉表面形成均匀的有机胺-铁-有机溶剂化合物,然后经过压制成型和在氮气中高温热处理,有机胺-铁-有机溶剂化合物层转变为致密均匀的铁氮化物绝缘层,避免了铁氧化物绝缘层在压制过程中的破裂。(The invention relates to the technical field of magnetic materials, in particular to an iron nitride coated metal soft magnetic composite material and a preparation method thereof, wherein the preparation method comprises the following steps: (1) dissolving soluble ferric salt in an organic solvent, adding organic amine, and stirring at normal temperature to form a suspension; (2) adding the suspension into the metal soft magnetic powder, mixing, stirring uniformly, and drying; (3) mixing with binder and lubricant, and press molding to obtain blank; (4) heat treatment in nitrogen, cooling and spraying. According to the invention, organic amine is used as an organic nitrogen source, and Fe-N interaction is enhanced through complexation performance, so that the high-quality iron nitride is prepared. Firstly, forming a uniform organic amine-iron-organic solvent compound on the surface of magnetic powder, then, performing compression molding and high-temperature heat treatment in nitrogen, converting the organic amine-iron-organic solvent compound layer into a compact and uniform iron nitride insulating layer, and avoiding the breakage of the iron oxide insulating layer in the compression process.)

1. The preparation method of the iron nitride coated metal soft magnetic composite material is characterized by comprising the following steps of:

(1) dissolving soluble ferric salt in an organic solvent, adding organic amine after the soluble ferric salt is completely dissolved, and stirring at normal temperature to form a suspension;

(2) adding the suspension obtained in the step (1) into the metal soft magnetic powder, mixing, stirring uniformly at normal temperature, and drying to obtain insulated metal soft magnetic powder;

(3) uniformly mixing the insulated metal soft magnetic powder obtained in the step (2) with a binder and a lubricant, and performing compression molding to obtain a blank;

(4) and (4) carrying out heat treatment on the blank obtained in the step (3) in nitrogen, cooling and spraying to obtain the iron nitride coated metal soft magnetic powder core.

2. The production method according to claim 1, wherein in step (1):

the soluble iron salt is selected from FeCl₃、Fe₂(SO₄)₃And Fe (NO)₃)₃One or more of the components are mixed;

the organic solvent is selected from one or a mixture of acetone, toluene, xylene and p-xylene;

the organic amine is selected from one or a mixture of ethylene diamine, isobutylamine, diisopropylamine, 1, 2-propane diamine and 1, 4-butane diamine.

3. The production method according to claim 1,

in the step (1), stirring for 20-40 min;

in the step (2), the drying temperature is 90-120 DEG C ^oAnd C, the time is 20-40 min.

4. The production method according to claim 1, wherein in the step (2), the metallic soft magnetic powder is one selected from the group consisting of Fe, FeSi, fesai, and FeSiB.

5. The preparation method according to claim 1, wherein the soluble iron salt is added in an amount of 1 to 3wt% based on the total mass of the metallic soft magnetic powder; the addition amount of the organic solvent is 2-6 wt%, and the addition amount of the organic amine is 3-9 wt%.

6. The preparation method according to claim 1, wherein in the step (3), the binder is one or more selected from epoxy resin, silicone resin, silica, glass powder and water glass; the addition amount of the binder is 0.5-1 wt% based on the total mass of the metal soft magnetic powder.

7. The production method according to claim 1, wherein in the step (3), the lubricant is one or two selected from zinc stearate and barium stearate; the lubricant is added in an amount of 0.5-1 wt% based on the total mass of the metal soft magnetic powder.

8. The production method according to claim 1, wherein in the step (3), the pressure of the press molding is 1500 to 2000 MPa.

9. The method according to claim 1, wherein the heat treatment temperature in step (4) is 600 to 750 ℃ for 0.5 to 2 hours.

10. An iron nitride-coated metal soft magnetic composite material prepared by the preparation method as claimed in any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of magnetic materials, in particular to an iron nitride coated metal soft magnetic composite material and a preparation method thereof.

Background

The metal soft magnetic composite material (also called magnetic powder core) is widely applied to the field of electronics and electricians due to the advantages of low medium-high frequency loss, low cost, easy preparation of complex shapes and the like. With the rapid development of information technology and electromechanical industry, magnetic devices are required to be high-frequency, small, intelligent and low-loss. The insulation coating process is one of the key steps for preparing the metal soft magnetic composite material. The insulation coating is to uniformly coat an insulation film on the surface of the magnetic particles so as to reduce the loss of the metal soft magnetic composite material when the metal soft magnetic composite material is used at high frequency. From the actual production process and comprehensive performance, the insulating coating layer is generally required to be thin, uniform, high in thermal stability, high in resistivity and high in strength so as to reduce energy loss and improve comprehensive processing performance of the magnetic powder core.

The traditional preparation process of the soft magnetic composite material is to passivate with phosphoric acid to form iron phosphide, then add a binder and press the material to form, and in order to reduce hysteresis loss, anneal at a higher temperature to eliminate internal stress generated during pressing, thereby obtaining a soft magnetic powder core. Since iron phosphide decomposes at higher temperatures, resulting in a decrease in insulation properties. Therefore, in recent years, different methods for preparing magnetic powder cores coated with oxides have appeared, and for example, mitsubishi corporation invented a method for coating an MgO insulating layer on the surface of iron powder by vapor deposition. Reports of using sol-gel method to prepare oxide coated magnetic powder core have also appeared at home and abroad. The magnetic powder core prepared by the method can be annealed at a higher temperature, so that the internal stress of press forming can be eliminated.

However, the non-magnetic insulating layer causes magnetic dilution, resulting in a decrease in saturation induction of the magnetic powder core. The iron nitride material becomes an important branch of magnetic materials due to excellent mechanical strength, wear resistance, corrosion resistance, oxidation resistance and excellent magnetic performance, and has certain prospects in the aspects of magnetic recording materials, drug carriers, medical diagnosis and the like.

Iron nitrides can be classified into FeN and Fe according to their nitrogen contents₂N,Fe₃N,Fe₄N,Fe₁₆N₂And the like. The Fe-N bond in the iron nitride material has atomic bond, ionic bond and covalent bond components at the same time, and is a more complex chemical action, so that the iron nitride material has a series of unique physical and chemical properties. E.g. Fe₁₆N₂Saturation magnetization (M)_S) Can reach 230emu/g, is known to have the maximum M at present_SThe substance of (1). Fe having good soft magnetism₄N is other than M of the simple substance of the comparable iron_S(208emu/g, 218emu/g for iron), and also has a mechanical strength of about 550 HV. epsilon-Fe₃M of N_S(134emu/g) is still about 30% higher than the ferrite material. Therefore, iron nitride has been widely used for the insulating layer of the metallic soft magnetic composite material.

Chinese patent literature discloses an insulation coating treatment method for soft magnetic composite materials, and the application publication number is CN104028746A, the invention puts soft magnetic powder into a quartz tube at the center of a tube furnace, and introduces flowing nitrogen, heats to the nitriding temperature of more than 1000 ℃, keeps the temperature for more than 20min, continues to introduce nitrogen during heat preservation, cools along with the furnace to obtain the insulation coated soft magnetic powder, and the surface of the insulation coated soft magnetic powder forms an insulation film of metal nitride and oxide.

Chinese patent literature discloses a preparation method of a double-shell soft magnetic composite material, the application publication number of which is CN108057878A, and the invention prepares a nitride/oxide double-shell structure on the surface of high-purity iron powder by a chemical heat treatment process. Wherein, the inner layer oxide is used as a transition layer and is matched with the crystal lattice of the substrate; the outer layer oxide further improves the resistivity of the powder core on the basis of nitridation, and is beneficial to reducing the loss of the iron powder core. Meanwhile, the nitriding and oxidizing double-shell layers have ferromagnetism, so that the magnetic dilution effect is greatly reduced, and the saturation magnetization intensity of the composite material is improved. However, the preparation method has complicated steps, a large amount of ammonia gas or nitrogen gas flow is input, the control on the atmosphere flow rate is strict, the tail gas treatment difficulty is high, and the mass production is difficult to realize.

The Chinese patent literature discloses a preparation method of a core-shell structure soft magnetic composite material, the application publication number of which is CN104036899A, and the steps of the invention are as follows: 1) introducing high-purity hydrogen to carry out reduction reaction on the high-purity iron powder at 450-600 ℃ for 60-120 min; 2) introducing mixed gas of ammonia and hydrogen for surface nitriding, wherein the nitriding temperature is 400-650 ℃, and the nitriding time is 3-7 h; 3) after the nitriding process is finished, the mixed gas of ammonia gas and hydrogen gas is continuously introduced to finally generate the surface-coated Fe₄Iron powder of N film and core-shell structure, Fe₄The thickness of the N film is 0.5 to 10 μm.

The method for preparing the iron nitride by adopting ammonia gas or nitrogen gas has simple mechanism and high purity of a synthetic sample, and is the most widely researched and reported method at present. However, the method needs a long time, complicated steps, and a large amount of ammonia gas or nitrogen gas flow is input, so that the requirements on the control of the atmosphere pressure and the flow rate are high, and the environmental protection requirement on tail gas treatment is strict. In addition, the loss of a large amount of energy also limits the synthesis and application of materials to a certain extent.

Disclosure of Invention

The invention provides a preparation method of the iron nitride coated metal soft magnetic composite material, aiming at overcoming the technical problems in the prior art, and the preparation method is simple to operate, does not need ammonia gas, is environment-friendly, has low energy consumption and is suitable for industrial production.

The invention also provides the iron nitride coated metal soft magnetic composite material prepared by the preparation method, the iron nitride coated metal soft magnetic powder core has the characteristics of low loss, high magnetic conductivity and good bonding strength, and the prepared iron nitride insulating layer is thin, so that the magnetic dilution effect is reduced, and the high-frequency stability of the metal magnetic powder core is enhanced.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of an iron nitride coated metal soft magnetic composite material comprises the following steps:

(1) dissolving soluble ferric salt in an organic solvent, adding organic amine after the soluble ferric salt is completely dissolved, and stirring at normal temperature to form a suspension;

(2) adding the suspension obtained in the step (1) into the metal soft magnetic powder, mixing, stirring uniformly at normal temperature, and drying to obtain insulated metal soft magnetic powder;

(3) uniformly mixing the insulated metal soft magnetic powder obtained in the step (2) with a binder and a lubricant, and performing compression molding to obtain a blank;

(4) and (4) carrying out heat treatment on the blank obtained in the step (3) in nitrogen, cooling and spraying to obtain the iron nitride coated metal soft magnetic powder core. The step has high strength after heat treatment, the product has good comprehensive performance, high-temperature roasting of the iron nitride precursor by ammonia gas or nitrogen gas is avoided, the iron nitride precursor nitriding and heat treatment processes are creatively integrated, and the energy consumption is reduced.

According to the invention, organic amine is used as an organic nitrogen source, and the Fe-N interaction is enhanced through the complexation performance, so that the high-quality iron nitride is prepared. Firstly, forming a uniform organic amine-iron-organic solvent compound on the surface of magnetic powder, then, performing compression molding and high-temperature heat treatment in nitrogen, converting the organic amine-iron-organic solvent compound layer into a compact and uniform iron nitride insulating layer, avoiding the high-temperature roasting process of an iron nitride precursor and the breakage of an iron oxide insulating layer in the compression process, improving the resistivity of the magnetic powder core, facilitating the release of internal stress in a blank by the high-temperature heat treatment, and greatly reducing the loss of the magnetic powder core; meanwhile, the outer iron nitride insulating layer is ferromagnetic, so that the magnetic dilution effect can be reduced, and the magnetic performance of the composite material is further improved. The preparation method disclosed by the invention is simple to operate, free of pollution, low in cost and suitable for industrial large-scale production.

Preferably, in step (1):

the soluble iron salt is selected from FeCl₃、Fe₂(SO₄)₃And Fe (NO)₃)₃One or more of the components are mixed; the soluble iron salts of the invention all contain Fe³⁺Acting on the surface of the metal soft magnetic powderForming a soluble iron salt coating.

The organic solvent is selected from one or a mixture of acetone, toluene, xylene and p-xylene; the oxygen atoms in the organic solvent ensure water, oxygen and the like in the air, and the influence on a reaction system is less.

The organic amine is selected from one or a mixture of ethylene diamine, isobutylamine, diisopropylamine, 1, 2-propane diamine and 1, 4-butane diamine. The organic amine can provide a nitrogen source for the reaction process and can react with Fe³⁺The lone pair electron coordination exists, and ammonia gas does not need to be decomposed or added as a nitrogen source.

Preferably, in the step (1), the stirring time is 20-40 min;

in the step (2), the drying temperature is 90-120 ℃, and the time is 20-40 min.

Preferably, in the step (2), the metallic soft magnetic powder is one selected from Fe, FeSi, FeSiAl, and FeSiB.

Preferably, the addition amount of the soluble ferric salt is 1-3 wt% based on the total mass of the metal soft magnetic powder; the addition amount of the organic solvent is 2-6 wt%, and the addition amount of the organic amine is 3-9 wt%. The addition amount of the soluble ferric salt is critical, the poor insulation property of the composite soft magnetic powder can be caused by the excessively low addition amount, the high loss can be caused, and the magnetic conductivity of the metal soft magnetic powder can be reduced by the excessively high addition amount. Too low addition of the organic solvent can lead to incomplete dissolution of the soluble ferric salt, and too high addition can lead to prolonged drying time and oxidation of the metal soft magnetic powder. The low addition of the organic amine can cause ferrite in the insulating layer, and the high addition of the organic amine can cause the over-thickness of the iron nitride insulating layer, thereby affecting the overall magnetic performance.

Preferably, in the step (3), the binder is selected from one or more of epoxy resin, silicone resin, silica, glass powder and water glass; the addition amount of the binder is 0.5-1 wt% based on the total mass of the metal soft magnetic powder. The binder is added in an amount that is too low, resulting in poor binding properties of the soft metal magnetic powder, and the binder is added in an amount that is too high, resulting in a decrease in magnetic permeability of the soft metal magnetic powder.

Preferably, in the step (3), the lubricant is selected from one or two of zinc stearate and barium stearate; the lubricant is added in an amount of 0.5-1 wt% based on the total mass of the metal soft magnetic powder.

Preferably, in the step (3), the pressure of the compression molding is 1500-2000 MPa. .

Preferably, in the step (4), the heat treatment temperature is 600-750 ℃ and the time is 0.5-2 h. The heat treatment temperature is critical, the internal stress generated in the pressing process cannot be released due to too low heat treatment temperature, the magnetic performance cannot reach the optimal value, and the binder can be damaged due to too high heat treatment temperature, so that the metal magnetic powder is further oxidized.

The iron nitride coated metal soft magnetic composite material prepared by any one of the preparation methods.

The insulating layer of the iron nitride coated metal magnetic powder core prepared by the process is thin, the magnetic dilution effect is reduced, and the high-frequency stability of the iron nitride coated metal magnetic powder core is enhanced on the premise of not obviously reducing the magnetic performance; the iron nitride coated metal magnetic powder core has the characteristics of low loss, high magnetic conductivity and good bonding strength, and can solve the problem of large eddy current loss of the metal soft magnetic powder core at medium-high frequency.

Therefore, the invention has the following beneficial effects:

(1) organic amine is used as an organic nitrogen source, and Fe-N interaction is enhanced through complexation performance, so that the high-quality iron nitride is prepared. Firstly, forming a uniform organic amine-iron-organic solvent compound on the surface of magnetic powder, then, converting the organic amine-iron-organic solvent compound layer into a compact and uniform iron nitride insulating layer through compression molding and high-temperature heat treatment in nitrogen, and avoiding the breakage of the iron oxide insulating layer in the compression process;

(2) the high-temperature roasting process of the iron nitride precursor is avoided, the high-temperature roasting process and the heat treatment process are creatively integrated, the energy consumption is reduced, the phase formation of the iron nitride can be controlled through the heat treatment temperature, and the magnetic property and the resistivity are regulated and controlled;

(3) the preparation method has simple operation, low cost and no pollution to the environment, and is suitable for large-scale industrial production;

(4) the iron nitride coated metal soft magnetic powder core prepared by the process has a thin insulating layer, has ferromagnetism, reduces the magnetic dilution effect, and enhances the high-frequency stability of the iron nitride coated metal soft magnetic powder core on the premise of not obviously reducing the magnetic performance; the iron nitride coated metal soft magnetic powder core has the characteristics of low loss, high magnetic conductivity and good bonding strength, and can solve the problem of large eddy current loss of the metal magnetic powder core at medium-high frequency.

Detailed Description

The technical solution of the present invention is further specifically described below by way of specific examples.

In the present invention, all the equipment and materials are commercially available or commonly used in the art, and the methods in the following examples are conventional in the art unless otherwise specified.

Example 1

(1) FeCl is added₃Mixing with acetone, adding certain volume of ethylenediamine, and stirring at room temperature for 40min to obtain suspension. Taking the total mass of FeSiAl metal soft magnetic powder as a reference, FeCl₃The addition amount of (B) is 3 wt%; the addition amount of acetone is 6wt%, and the addition amount of ethylenediamine is 9 wt%;

(2) adding the suspension obtained in the step (1) into FeSiAl metal soft magnetic powder, mixing, stirring uniformly at normal temperature, and drying at 120 ℃ for 40min to obtain FeSiAl metal soft magnetic powder @ ethylenediamine-Fe³⁺-an acetone precursor;

(3) uniformly mixing the insulated metal soft magnetic powder obtained in the step (2) with epoxy resin and zinc stearate, and performing compression molding under the pressure of 1500MPa to obtain a blank with the outer diameter of 33.00mm, the inner diameter of 19.90mm and the height of 10.7 mm; taking the total mass of the FeSiAl metal soft magnetic powder as a reference, the adding amount of the epoxy resin is 1wt%, and the adding amount of the zinc stearate is 1 wt%;

(4) and (3) carrying out heat treatment on the blank obtained in the step (3) in nitrogen, wherein the heat treatment temperature is 750 ℃, the time is 2 hours, cooling and spraying are carried out, and the FeSiAl metal magnetic powder core coated with the iron nitride is obtained, and the tested magnetic parameters are as follows:

example 2

(1) Mixing Fe₂(SO₄)₃Mixing with toluene, adding isobutylamine in certain volume after complete dissolution, and stirring at normal temperature for 20min to form suspension. Based on the total mass of the FeSi metal soft magnetic powder, Fe₂(SO₄)₃The addition amount of (B) is 1 wt%; the addition amount of acetone is 2 wt%; the addition amount of ethylenediamine is 3 wt%;

(2) adding the suspension obtained in the step (1) into FeSi metal soft magnetic powder for mixing, uniformly stirring at normal temperature, and drying at 90 ℃ for 20min to obtain FeSi metal soft magnetic powder @ isobutylamine-Fe³⁺-a toluene precursor;

(3) uniformly mixing the insulated metal soft magnetic powder obtained in the step (2) with silicone resin and barium stearate, and performing compression molding under the pressure of 2000MPa to obtain a blank with the outer diameter of 33.00mm, the inner diameter of 19.90mm and the height of 10.7 mm; taking the total mass of the FeSi metal soft magnetic powder as a reference, the adding amount of the epoxy resin is 0.5 wt%, and the adding amount of the zinc stearate is 0.5 wt%;

(4) and (3) carrying out heat treatment on the blank obtained in the step (3) in nitrogen at the heat treatment temperature of 600 ℃ for 0.5h, cooling and spraying to obtain the FeSi metal magnetic powder core coated with the iron nitride, wherein the tested magnetic parameters are as follows:

example 3

(1) Mixing Fe (NO)₃)₃Mixing with dimethylbenzene, adding isobutylamine with a certain volume after completely dissolving, and continuously stirring at normal temperature for 40min to form suspension. Fe (NO) based on the total mass of the FeSiB metal soft magnetic powder₃)₃The addition amount of (B) is 2 wt%; the addition amount of xylene was 4 wt%; the addition amount of diisopropylamine is 6 wt%;

(2) adding the suspension obtained in the step (1) into FeSiB metal soft magnetic powder, mixing, stirring uniformly at normal temperature, and drying for 30min at 100 ℃; obtaining FeSiB metal soft magnetic powder @ diisopropylamine-Fe³⁺-a xylene precursor;

(3) uniformly mixing the insulated metal soft magnetic powder obtained in the step (2) with silicone resin and barium stearate, and performing compression molding under the pressure of 1800MPa to obtain a blank with the outer diameter of 33.00mm, the inner diameter of 19.90mm and the height of 10.7 mm; taking the total mass of the FeSiB metal soft magnetic powder as a reference, the adding amount of the epoxy resin is 0.8 wt%, and the adding amount of the zinc stearate is 0.8 wt%;

(4) and (3) carrying out heat treatment on the blank obtained in the step (3) in nitrogen at the heat treatment temperature of 650 ℃ for 1.0h, cooling and spraying to obtain the FeSiB metal magnetic powder core coated with the iron nitride, wherein the tested magnetic parameters are as follows:

the above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and other variations and modifications may be made without departing from the spirit of the invention as set forth in the claims.