阅读说明：本技术 一种高强度陶瓷包覆的铁基复合软磁材料及其制备方法 (High-strength ceramic-coated iron-based composite soft magnetic material and preparation method thereof ) 是由 杨白 马洁 于荣海 于 2021-08-23 设计创作，主要内容包括：本发明公开了属于金属基复合软磁材料领域的一种高强度的Fe/Al-(2)SiO-(5)复合磁粉芯及其制备方法。采用化学沉积工艺将非晶纳米Al-(2)O-(3)和SiO-(2)陶瓷复合包覆层均匀地涂覆在大粒径高纯铁粉颗粒表面上形成Fe/Al-(2)O-(3)-SiO-(2)核壳结构复合颗粒,对上述铁-陶瓷复合颗粒采用压制成型和低温烧结技术制备成高致密度和高强度的块状Fe/Al-(2)SiO-(5)复合磁粉芯。这种高强度硅酸铝陶瓷包覆铁基磁粉芯同时具有良好的内禀磁性和技术磁性,作为结构与磁性的一体化增强的高性能金属基软磁材料,在航空航天、高端汽车制造和核工业等领域有着广泛的应用前景。本发明涉及到的原料来源丰富,材料制备工艺简单且适合规模化生产。(The invention discloses a high-strength Fe/Al alloy, belonging to the field of metal-based composite soft magnetic materials 2 SiO 5 A composite magnetic powder core and a preparation method thereof. Amorphous nano Al is deposited by chemical deposition process 2 O 3 And SiO 2 The ceramic composite coating layer is uniformly coated on the surface of the large-particle-size high-purity iron powder particles to form Fe/Al 2 O 3 ‑SiO 2 The iron-ceramic composite particles are prepared into high-density and high-strength blocky Fe/Al by adopting press forming and low-temperature sintering technology 2 SiO 5 And (4) compounding a magnetic powder core. The high-strength aluminum silicate ceramic coated iron-based magnetic powder core has good intrinsic magnetism and technical magnetism, is used as a high-performance metal-based soft magnetic material with integrally enhanced structure and magnetism, and has wide application prospects in the fields of aerospace, high-end automobile manufacturing, nuclear industry and the like. The raw materials related to the inventionThe source is rich, the material preparation process is simple and the method is suitable for large-scale production.)

1. A high-strength ceramic-coated iron-based composite soft magnetic powder core is characterized in that: the component and material structure of the composite soft magnetic powder core are Fe/Al₂SiO₅Composite structures, i.e. made of amorphous nano-Al₂O₃And SiO₂The ceramic composite coating layer is uniformly coated on the surface of the large-particle-size high-purity iron powder particles to form Fe/Al₂O₃-SiO₂The iron-based composite particles are prepared into high-density and high-strength blocky Fe/Al by adopting press forming and low-temperature sintering technologies₂SiO₅And (4) compounding a magnetic powder core. Wherein the average grain diameter of the high-purity iron powder particles (the mass fraction of Fe element is about 99%) is 70-180 μm.

2. The high strength ceramic-coated iron-based composite soft magnetic powder core according to claim 1, wherein: the Al is₂SiO₅The ceramic-coated iron-based composite soft magnetic powder core has the characteristics of high breaking strength, high saturation magnetization, low magnetic loss, high magnetic permeability and good frequency.

3. The method for preparing a high-strength ceramic-coated iron-based composite soft magnetic powder core according to claim 1, comprising the steps of:

step one, adding a proper amount of amorphous Al₂O₃Uniformly coating the surface of the high-purity iron powder particles to obtain Fe/Al₂O₃Core-shell structured composite particles;

step two, in the Fe/Al₂O₃The surface of the core-shell structure composite particle is continuously coated with a proper amount of amorphous SiO₂To obtain a catalyst having Fe/Al₂O₃-SiO₂Iron-based composite soft magnetic powder with a core-shell structure;

step three, mixing the Fe/Al₂O₃-SiO₂The composite soft magnetic powder is prepared into a compact block by adopting a powder metallurgy compaction process, and then is sintered at a proper temperature under a protective atmosphere to prepare the high-density and high-strength blocky Fe/Al₂SiO₅And (4) compounding a magnetic powder core.

4. The method for preparing a high-strength ceramic-coated iron-based composite soft magnetic powder core according to claim 1, wherein the method comprises the following steps: the method of claim 3, wherein the first preparation step is carried out by pouring a suitable amount of high-purity iron powder particles into a mixed solution of oleic acid and absolute ethyl alcohol (the volume ratio of oleic acid to absolute ethyl alcohol is 1: 30-1: 80), placing the mixture into an ultrasonic dispersion apparatus, ultrasonically dispersing for 1-2 hours, and removing the liquid to obtain surface-treated iron powder particles; adding 1/10-3 times of aluminum isopropoxide of the mass of iron powder into a mixed solution of acetylacetone and absolute ethyl alcohol with the volume ratio of 1: 10-1: 30, and fully stirring for 1-2 hours to form white emulsion; pouring the obtained white emulsion into surface-treated high-purity iron powder particles, stirring for 5-10 minutes at a stirring speed of 1000 revolutions per minute by using a stirrer, adding a mixed solution of deionized water and concentrated nitric acid (the pH value is adjusted to be 4-6) in a volume ratio of 4: 1-1: 4, continuing stirring for 1-2 hours, and standing for 30-60 minutes; removing the residual solution after the reaction to obtain a reaction product, alternately cleaning the reaction product for 6-10 times by using deionized water and absolute ethyl alcohol, and then drying the reaction product in a vacuum drying oven at the temperature of 30-90 ℃ for 0.5-4 hours to obtain the Fe particles with the surfaces uniformly coated with amorphous Al₂O₃Fe/Al of₂O₃Core-shell structured composite particles.

5. The method for preparing a high-strength ceramic-coated iron-based composite soft magnetic powder core according to claim 1, wherein the method comprises the following steps: the method of claim 3, wherein said preparing step is carried out by adding an appropriate amount of said Fe/Al₂O₃Pouring the composite particles into a mixed solution of oleic acid and absolute ethyl alcohol in a volume ratio of 1: 30-1: 80 to form a solid-liquid mixture, placing the solid-liquid mixture into ultrasonic dispersion equipment for ultrasonic dispersion for 1-2 hours, and adding a proper amount of ammonia water (the concentration is 25%, the same below) and absolute ethyl alcohol, wherein the volume of the ammonia water is 1/12-1/6 times that of the mixed solution of oleic acid and absolute ethyl alcohol, and the volume of the absolute ethyl alcohol is 1-2 times that of the mixed solution of oleic acid and absolute ethyl alcohol; stirring the mixture containing Fe/Al₂O₃Stirring the composite particle solid-liquid mixture at the rotation speed of 500-1000 revolutions per minute for 1-2 hours, and adding 1/8-1/2 times of tetraethoxysilane based on the mass of the iron powder into the mixture every 20-60 minutes while stirring; then, continuing to add a proper amount of ammonia water and tetraethoxysilane (the volume of the ammonia water is 1/12-1/6 times of the volume of the mixed solution of oleic acid and absolute ethyl alcohol, and the mass of the tetraethoxysilane is 1/8-1 times of the mass of the iron powder), and fully stirring for 2-4 hours; removing residual solution after reaction to obtain solid reaction product, cleaning the reaction product with deionized water and anhydrous ethanol for 6-10 times, and drying in vacuum drying oven at 30-90 deg.C for 0.5-4 hr to obtain Fe/Al₂O₃-SiO₂An iron-based composite soft magnetic powder with a core-shell structure.

6. The method for preparing a high-strength ceramic-coated iron-based composite soft magnetic powder core according to claim 1, wherein the method comprises the following steps: the method of claim 3, wherein said step of preparing is achieved by subjecting said Fe/Al alloy to a process comprising₂O₃-SiO₂Preparing compact block from iron-based composite soft magnetic powder with core-shell structure by powder metallurgy compaction process, placing the pressed block into a controlled atmosphere sintering furnace, heating to 1000-1200 ℃ at a heating rate of 2-10 ℃/min in a flowing high-purity argon or high-purity nitrogen atmosphere, preserving heat for 1.5-2.5 hours, and then cooling along with the furnace to obtain block Fe/Al with high breaking strength₂SiO₅And (4) compounding a magnetic powder core.

Technical Field

The invention relates to a metal matrix composite soft magnetic material and a preparation method thereof, in particular to an iron matrix composite soft magnetic material with high-strength ceramic coating and a preparation method thereof.

Background

The soft magnetic material with low loss, high magnetic conductivity and high saturation magnetic induction can be used for preparing devices or components for electromagnetic generation, distribution and conversion in electronic, electrical and power equipment, such as rotors or stators of high-temperature engines and generators and the like, and has potential application prospects and huge economic benefits in the fields of aerospace, high-end automobile manufacturing, nuclear industry and the like. With the development of science and technology, the requirements for soft magnetic materials and devices thereof are increasing day by day, and meanwhile, the soft magnetic materials and devices thereof are required to have high saturation magnetic induction density, high magnetic permeability, low magnetic loss, good frequency characteristics, high mechanical properties and the like. Although traditional metal soft magnetic materials such as silicon steel have higher saturation magnetic induction intensity, the resistivity is lower, and the application in high frequency is limited; while the soft magnetic ferrite has higher resistivity, the saturation magnetic induction intensity is lower, which is not beneficial to realizing the miniaturization of the device.

In order to improve the defects of the conventional metal soft magnetic material and the performance of the soft magnetic ferrite, the metal-based soft magnetic powder core can be prepared by a reasonable composite process, namely, after organic and inorganic insulating layers with proper thickness are coated on the surface of the metal soft magnetic powder, a compact block material is prepared by adopting a powder metallurgy forming process. The insulating layer on the surface of the metal soft magnetic powder not only improves the resistivity of the metal-based magnetic powder core, but also has lower magnetic loss under the medium-high frequency use condition, and simultaneously can keep higher saturation magnetic induction intensity and magnetic conductivity. The application of the organic resin coated magnetic powder core under the high temperature condition is limited due to the poor thermal stability of the organic resin. Meanwhile, it is difficult to obtain high density and high mechanical strength of the organic resin coated magnetic powder core due to low density and low strength of the organic resin. In addition, the organic resin coating process has certain harm to the environment. In order to improve the defects of the preparation process and material performance of the organic matter coated magnetic powder core, various physical or chemical coating processes can be adopted to coat high-resistivity or insulating inorganic matters such as phosphate and Fe on the surface of the metal magnetic particles₃O₄、MnZn、SiO₂MgO and Al₂O₃And the like. A large amount of research work shows that the magnetic powder core coated by the inorganic substance can improve the thermal stability of the metal magnetic powder core and keep better soft magnetic performance, but the mechanical strength is lower, and the application range is limited.

Therefore, it is necessary to develop a metal-based soft magnetic powder core with integrated enhancement of magnetism and structure, i.e. high saturation magnetic induction, low loss and high mechanical property, which is one of the key technical problems that the development and application of a high-performance metal-based magnetic powder core are urgently needed to solve.

Disclosure of Invention

The invention aims to provide a high-strength ceramic-coated iron-based composite soft magnetic powder core prepared by coating amorphous nano Al₂O₃And SiO₂Coating high-purity iron powder with large particle size (average particle size of 70-180 μm, and mass fraction of Fe element of about 99%) on the surface of the particles to obtain Fe/Al₂O₃-SiO₂Core-shell structure composite particles, pressing and molding the iron-based composite particles, and sintering at a proper temperature to prepare blocky Fe/Al₂SiO₅The composite magnetic powder core greatly enhances the mechanical property of the magnetic powder core through the ceramic coating on the surface of the iron particles, and realizes the integrated enhancement of magnetism and structure in the metal-based magnetic powder core.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a high-strength ceramic-coated iron-based composite soft magnetic powder core is composed of Fe/Al₂SiO₅Composite structures, i.e. Al₂SiO₅The ceramic is uniformly coated on the surface of the high-purity iron powder.

High strength Al₂SiO₅The preparation method of the ceramic-coated iron-based composite soft magnetic powder core comprises the following steps:

1. pouring a proper amount of high-purity iron powder particles into a mixed solution formed by oleic acid and absolute ethyl alcohol (the volume ratio of the oleic acid to the absolute ethyl alcohol is 1: 30-1: 80), putting the mixed solution into ultrasonic dispersion equipment, performing ultrasonic dispersion for 1-2 hours, and removing liquid to obtain surface-treated iron powder particles;

2. adding 1/10-3 times of aluminum isopropoxide of the mass of iron powder into a mixed solution of acetylacetone and absolute ethyl alcohol with the volume ratio of 1: 10-1: 30, and fully stirring for 1-2 hours to form white emulsion;

3. pouring the surface-treated high-purity iron powder particles into the white emulsion obtained by fully stirring, stirring for 5-10 minutes by using a stirrer at the stirring speed of 500-1000 revolutions per minute, adding a mixed solution of deionized water and concentrated nitric acid (the PH value is adjusted to 4-6) in a volume ratio of 4: 1-1: 4, continuously stirring for 1-2 hours, and standing for 30-60 minutes;

4. removing the residual solution after reaction to obtain reaction product, alternately cleaning the reaction product with deionized water and anhydrous ethanol for 6-10 times, and drying in a vacuum drying oven at 30-90 deg.C for 0.5-4 hr to obtain amorphous Al₂O₃Coated Fe/Al₂O₃Core-shell structured composite particles;

5. adding proper amount of the Fe/Al₂O₃The composite particles are poured into a mixed solution of oleic acid and absolute ethyl alcohol with the volume ratio of 1: 30-1: 80 to form a mixture containing Fe/Al₂O₃Putting the solid-liquid mixture of the composite particles into an ultrasonic dispersion device, ultrasonically dispersing for 1-2 hours, and then adding a proper amount of ammonia water (the concentration is 25%, the same below) and absolute ethyl alcohol, wherein the volume of the ammonia water is 1/12-1/6 times that of the mixed solution of oleic acid and absolute ethyl alcohol, and the volume of the absolute ethyl alcohol is 1-2 times that of the mixed solution of oleic acid and absolute ethyl alcohol;

6. stirring the mixture containing Fe/Al₂O₃Stirring the solid-liquid mixture of the composite particles for 1 to 2 hours at the rotating speed of 500-1000 revolutions per minute, and adding ethyl orthosilicate which is 1/8 to 1/2 times of the mass of the iron powder into the mixed solution every 20 to 60 minutes while stirring;

7. adding appropriate amount of ammonia water and ethyl orthosilicate (the volume of the ammonia water is 1/12-1/6 times of the volume of the mixed solution of oleic acid and absolute ethyl alcohol, and the mass of the ethyl orthosilicate is 1/8-1 time of the mass of the iron powder), and stirring for 2-4 hours;

8. removing residual solution after reaction to obtain solid reaction product, cleaning the reaction product with deionized water and anhydrous ethanol for 6-10 times, and drying in vacuum drying oven at 30-90 deg.C for 0.5-4 hr to obtain Fe/Al₂O₃-SiO₂An iron-based composite soft magnetic powder with a core-shell structure.

9. The Fe/Al is added₂O₃-SiO₂Preparing compact block from iron-based composite soft magnetic powder with core-shell structure by powder metallurgy compaction process, placing the pressed block into a controlled atmosphere sintering furnace, and flowingHeating to 1000-1200 ℃ at the heating rate of 2-10 ℃/min under the atmosphere of high-purity argon or high-purity nitrogen, preserving the heat for 1.5-2.5 hours, and then cooling along with the furnace to obtain the Fe/Al with high fracture strength₂SiO₅And (4) compounding a magnetic powder core.

The invention adopts the chemical deposition process to realize the deposition of the nano Al on the surfaces of the iron powder particles with large particle size₂O₃And SiO₂Obtaining Fe/Al by composite coating of ceramic₂O₃-SiO₂The core-shell structure composite particles are combined with a powder compaction forming process and a low-temperature sintering technology to prepare the Fe/Al with high strength₂SiO₅The high-strength magnetic powder core has high saturation magnetic induction strength and low loss, can be used for preparing high-power electromagnetic components under high-frequency and high-temperature use conditions, such as high-temperature-resistant magnetic cores, high-temperature and high-speed motor rotors and the like, and has potential wide application and good economic benefit in the fields of aerospace, nuclear industry, modern automobile industry and the like. The raw materials related by the invention have rich sources, the material preparation process is simple and suitable for large-scale production, and the preparation process is environment-friendly. The invention also provides a new idea for designing and manufacturing the novel high-performance metal magnetic powder core.

Drawings

FIG. 1 is an external view of a ring-shaped composite magnetic powder core according to a first embodiment, wherein:

FIG. (a) shows Fe/Al before sintering₂O₃-SiO₂The appearance of the composite magnetic powder core;

FIG. b shows Fe/Al after sintering₂SiO₅Appearance diagram of the composite magnetic powder core.

FIG. 2 is an X-ray diffraction (XRD) spectrum of the composite magnetic powder core of the first embodiment, wherein:

line (a) represents Fe/Al before sintering₂O₃-SiO₂X-ray diffraction pattern of the composite magnetic powder core;

line (b) represents Fe/Al after sintering₂SiO₅X-ray diffraction pattern of the composite magnetic powder core.

FIG. 3 is a Scanning Electron Microscope (SEM) morphology of the composite magnetic powder core in the first embodiment, wherein:

FIGS. (a) and (b) represent surface-coated Fe/Al₂O₃-SiO₂SEM topography of the compound soft magnetic powder of nucleocapsid;

FIG. c represents Fe/Al after sintering₂SiO₅Secondary electron image of the cross section of the composite magnetic powder core.

FIG. 4 shows the iron powder and the surface-coated Fe/Al in example I₂O₃-SiO₂A magnetic hysteresis loop of the core-shell composite soft magnetic powder measured when the maximum external magnetic field is 10kOe, wherein:

loop (a) represents the hysteresis loop of the raw iron powder;

the loop (b) represents surface-coated Fe/Al₂O₃-SiO₂Hysteresis loop of the core-shell composite soft magnetic powder.

FIG. 5 is a graph of magnetic permeability of the raw iron powder core and the composite magnetic powder core in example one, in which:

FIG. (a) represents the low-frequency band raw iron powder core, Fe/Al before sintering₂O₃-SiO₂Composite magnetic powder core and sintered Fe/Al₂SiO₅A real part atlas of the magnetic conductivity of the composite magnetic powder core;

FIG. b shows the high-frequency raw iron powder core, Fe/Al before sintering₂O₃-SiO₂Composite magnetic powder core and sintered Fe/Al₂SiO₅A real part atlas of the magnetic conductivity of the composite magnetic powder core;

FIG. c shows the raw iron powder core, Fe/Al before sintering₂O₃-SiO₂Composite magnetic powder core and sintered Fe/Al₂SiO₅And (3) a composite magnetic powder core magnetic conductivity imaginary part spectrum.

FIG. 6 shows Fe/Al after sintering in example one₂SiO₅A bending load-displacement curve of the composite magnetic powder core and a Scanning Electron Microscope (SEM) morphology graph of a fracture, wherein:

FIG. (a) shows Fe/Al after sintering₂SiO₅The bending load-displacement curve of the composite magnetic powder core;

FIG. b shows Fe/Al after sintering₂SiO₅And (3) a fracture SEM topography of the composite magnetic powder core.

Detailed Description

Example one

1. Pouring 10g of high-purity iron powder particles into a mixed solution formed by oleic acid (2ml) and absolute ethyl alcohol (110ml) (the volume ratio of the oleic acid to the absolute ethyl alcohol is 1:55), putting the mixed solution into ultrasonic dispersion equipment, performing ultrasonic dispersion for 1.5 hours, and removing liquid to obtain surface-treated iron powder particles;

2. adding aluminum isopropoxide (10g) with the same mass as that of the iron powder into a mixed solution of acetylacetone (10ml) and absolute ethyl alcohol (100ml) in a volume ratio of 1:10, and fully stirring for 1.5 hours to form white emulsion;

3. pouring the surface-treated high-purity iron powder particles into the white emulsion obtained by fully stirring, stirring for 8 minutes at a stirring speed of 700 revolutions per minute by using a stirrer, adding 1ml of a mixed solution of deionized water and concentrated nitric acid with a volume ratio of 1:1 (regulating the pH value to be 5), continuously stirring for 1.5 hours, and standing for 30 minutes;

4. removing the residual solution after the reaction to obtain a reaction product, alternately cleaning the reaction product for 8 times by using deionized water and absolute ethyl alcohol, and drying in a vacuum drying oven at 60 ℃ for 1.5 hours to obtain the Fe particle with the surface uniformly coated with amorphous Al₂O₃Fe/Al of₂O₃Core-shell structured composite particles.

5. 10g of the Fe/Al mixture prepared above₂O₃The composite particles are poured into a mixed solution of oleic acid (2ml) and absolute ethyl alcohol (110ml) with the volume ratio of 1:55 to form a mixture containing Fe/Al₂O₃After the solid-liquid mixture of the composite particles is placed into ultrasonic dispersion equipment for ultrasonic dispersion for 1.5 hours, adding a proper amount of ammonia water (12.4ml) and absolute ethyl alcohol (168ml), wherein the volume of the ammonia water is 1/9 times that of the mixed solution of oleic acid and absolute ethyl alcohol, and the volume of the absolute ethyl alcohol is 1.5 times that of the mixed solution of oleic acid and absolute ethyl alcohol;

6. stirring the mixture containing Fe/Al₂O₃The solid-liquid mixture of the composite particles was stirred at a rotation speed of 700 rpm for 1.5 hours, and 1/5 ethyl orthosilicate (2g) in an iron powder mass was added to the mixed solution every 45 minutes while stirring;

7. continuously adding 12.4ml of ammonia water and 9.1g of tetraethoxysilane (the volume of the ammonia water is 1/9 times of the volume of the mixed solution of oleic acid and absolute ethyl alcohol, and the mass of the tetraethoxysilane is 1/1.1 time of the mass of the iron powder), and fully stirring for 3 hours;

8. after the reaction is finished, removing the residual solution after the reaction to obtain a solid reaction product, alternately cleaning the reaction product for 8 times by using deionized water and absolute ethyl alcohol, and drying in a vacuum drying oven at 60 ℃ for 1.5 hours to obtain Fe/Al₂O₃-SiO₂An iron-based composite soft magnetic powder with a core-shell structure.

9. The Fe/Al is added₂O₃-SiO₂Preparing compact block from iron-based composite soft magnetic powder with a core-shell structure by adopting a powder metallurgy compaction process, putting the pressed block into a controlled atmosphere sintering furnace, heating to 1200 ℃ at a heating rate of 4 ℃/min under the protective atmosphere of flowing high-purity argon, preserving heat for 2 hours, and then cooling along with the furnace to obtain Fe/Al with high breaking strength₂SiO₅And compounding soft magnetic powder core.

FIG. 1 is an external view of a ring-shaped sample obtained by press molding in this example before and after sintering. Due to amorphous Al₂O₃And amorphous SiO₂Al is formed by chemical combination reaction during sintering₂SiO₅The sintered magnetic powder core shows a clear ceramic coating appearance. The density of the magnetic powder core before sintering is 7.15g/cm³The density of the sintered magnetic powder core is 7.07g/cm³。

FIG. 2 is an X-ray diffraction (XRD) spectrum of the composite magnetic powder core in example one, and Fe/Al can be seen from the spectrum (a)₂O₃-SiO₂The composite magnetic powder core contains amorphous components; the results of X-ray energy spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) tests of the sample show that the amorphous component is amorphous Al₂O₃And amorphous SiO₂And (3) mixing. Combining the test results of XRD, EDS and XPS, the peak position of the spectral line (b) can be determined to be Fe and Al₂SiO₅And Fe₃O₄Peak position of (1), i.e. Al formed after sintering of magnetic powder core₂SiO₅Ceramics, with small amount of Fe appearing on the surface₃O₄The iron element on the surface of the magnetic powder core is formed by light and micro oxidation in a flowing protective atmosphere。

Fe/Al in this example₂O₃-SiO₂The Scanning Electron Microscope (SEM) morphology of the core-shell composite soft magnetic powder is shown in FIG. 3(a) and FIG. 3(b), and amorphous Al can be seen₂O₃And amorphous SiO₂The shell layer is uniformly and completely coated on the surface of the iron powder particles. FIG. 3(c) shows Fe/Al obtained after sintering₂SiO₅The secondary electron image of the cross section of the composite magnetic powder core shows that the ceramic insulating layer exists between the deformed iron powder particles.

FIG. 4 is a graph showing the measurement of Fe/Al prepared in this example using a Vibrating Sample Magnetometer (VSM)₂O₃-SiO₂A magnetic hysteresis loop of the core-shell composite soft magnetic powder when the maximum external magnetic field is 10 kOe. It can be seen that Fe/Al₂O₃-SiO₂The intrinsic coercive force of the core-shell composite soft magnetic powder is basically the same as that of the raw material iron powder, and the saturation magnetization is slightly reduced, which shows that the Fe/Al₂O₃-SiO₂The core-shell composite soft magnetic powder has better intrinsic magnetic property.

FIG. 5 shows Fe/Al prepared in this example measured by an impedance analyzer₂SiO₅The permeability of the composite magnetic powder core is plotted against the frequency, and as can be seen from FIGS. 5(a) and 5(b), Fe/Al₂SiO₅The composite magnetic powder core has higher magnetic conductivity in a low-frequency band and better frequency characteristic in a high-frequency band; from FIG. 5(c), Fe/Al can be seen₂SiO₅The composite magnetic powder core has extremely low magnetic loss.

Fe/Al prepared in this example was measured using an electronic universal tester₂SiO₅Transverse Rupture Strength (TRS) of composite magnetic powder core, Fe/Al, as shown in FIG. 6(a)₂SiO₅The TRS value of the composite magnetic powder core is up to 259.5 MPa. FIG. 6(b) shows Fe/Al₂SiO₅The SEM appearance of the fracture of the composite magnetic powder core shows that no cavity or crack exists in the sintered magnetic powder core, the fracture keeps the deformation state of obvious iron powder particles and shows obvious ceramic fracture trace, so that Al can be seen₂SiO₅The coating layer helps to strengthen Fe/Al₂SiO₅The mechanical property of the composite magnetic powder core.

Example two

1. Pouring 10g of high-purity iron powder particles into a mixed solution formed by oleic acid (3ml) and absolute ethyl alcohol (240ml) (the volume ratio of the oleic acid to the absolute ethyl alcohol is 1:80), putting the mixed solution into ultrasonic dispersion equipment, performing ultrasonic dispersion for 2 hours, and removing liquid to obtain surface-treated iron powder particles;

2. adding 3 times of aluminum isopropoxide (30g) of the mass of iron powder into a mixed solution of acetylacetone (20ml) and absolute ethyl alcohol (600ml) in a volume ratio of 1:30, and fully stirring for 2 hours to form white emulsion;

3. pouring the surface-treated high-purity iron powder particles into the white emulsion obtained by fully stirring, stirring for 10 minutes at a stirring speed of 1000 revolutions per minute by using a stirrer, adding a mixed solution of deionized water and concentrated nitric acid with a volume ratio of 1:4 (regulating the pH value to be 6), continuously stirring for 2 hours, and standing for 60 minutes;

4. removing the residual solution after the reaction to obtain a reaction product, alternately cleaning the reaction product for 10 times by using deionized water and absolute ethyl alcohol, and then placing the reaction product in a vacuum drying oven at 90 ℃ for drying for 30 minutes to obtain Fe/Al₂O₃Composite particles.

5. 10g of the Fe/Al prepared above₂O₃The composite particles are poured into a mixed solution of oleic acid (3ml) and absolute ethyl alcohol (240ml) with the volume ratio of 1:80 to form the composite particles containing Fe/Al₂O₃After the solid-liquid mixture of the composite particles is placed into an ultrasonic dispersion device for ultrasonic dispersion for 2 hours, adding a proper amount of ammonia water (40.5ml) and absolute ethyl alcohol (486ml), wherein the volume of the ammonia water is 1/6 times that of the mixed solution of oleic acid and absolute ethyl alcohol, and the volume of the absolute ethyl alcohol is 2 times that of the mixed solution of oleic acid and absolute ethyl alcohol;

6. stirring the mixture containing Fe/Al₂O₃The composite particle mixture was stirred at 1000 rpm for 2 hours, and ethyl orthosilicate (5g) in an amount of 1/2 powder was added to the mixture every 60 minutes while stirring;

7. continuously adding 40.5ml of ammonia water and 10g of tetraethoxysilane (the volume of the ammonia water is 1/6 times of the volume of the mixed solution of oleic acid and absolute ethyl alcohol, and the mass of the tetraethoxysilane is the same as that of the iron powder), and fully stirring for 4 hours;

8. after the reaction is finished, removing the residual solution after the reaction to obtain a solid reaction product, alternately cleaning the reaction product for 10 times by using deionized water and absolute ethyl alcohol, and drying in a vacuum drying oven at 90 ℃ for 30 minutes to obtain Fe/Al₂O₃-SiO₂Iron-based composite soft magnetic powder with a core-shell structure;

9. the Fe/Al is added₂O₃-SiO₂Preparing compact block from iron-based composite soft magnetic powder with core-shell structure by powder metallurgy compaction process, placing the pressed block into a controlled atmosphere sintering furnace, heating to 1100 ℃ at a heating rate of 10 ℃/min in a flowing high-purity nitrogen atmosphere, preserving heat for 2.5 hours, and then cooling with the furnace to obtain Fe/Al with breaking strength of 120.4MPa₂SiO₅And compounding soft magnetic powder core. Fe/Al prepared in this example₂SiO₅The composite soft magnetic powder core has high density, high saturation magnetization, low magnetic loss, high magnetic permeability and good frequency characteristics.

EXAMPLE III

1. Pouring 10g of high-purity iron powder particles into a mixed solution formed by oleic acid (4ml) and absolute ethyl alcohol (120ml) (the volume ratio of the oleic acid to the absolute ethyl alcohol is 1:30), putting the mixed solution into ultrasonic dispersion equipment, performing ultrasonic dispersion for 1 hour, and removing liquid to obtain surface-treated iron powder particles;

2. 1/10 aluminum isopropoxide (1g) with the mass of iron powder is added into a mixed solution of acetylacetone (1ml) and absolute ethyl alcohol (15ml) with the volume ratio of 1:15, and the mixture is fully stirred for 1 hour to form white emulsion;

3. pouring the surface-treated high-purity iron powder particles into the white emulsion obtained by fully stirring, stirring for 5 minutes at a stirring speed of 500 revolutions per minute by using a stirrer, adding a mixed solution of deionized water and concentrated nitric acid with a volume ratio of 4:1 (regulating the pH value to be 4), continuously stirring for 1 hour, and standing for 30 minutes;

4. removing the residual solution after the reaction to obtain a reaction product, alternately cleaning the reaction product for 6 times by using deionized water and absolute ethyl alcohol, and then drying the reaction product in a vacuum drying oven at the temperature of 30 ℃ for 4 hours to obtain Fe/Al₂O₃Composite particles.

5. 10g of the Fe/Al prepared above₂O₃The composite particles are poured into a mixed solution of oleic acid (4ml) and absolute ethyl alcohol (120ml) with the volume ratio of 1:30 to form the composite particles containing Fe/Al₂O₃After the solid-liquid mixture of the composite particles is placed into ultrasonic dispersion equipment for ultrasonic dispersion for 1 hour, adding a proper amount of ammonia water (10.3ml) and absolute ethyl alcohol (124ml), wherein the volume of the ammonia water is 1/12 times that of the mixed solution of oleic acid and absolute ethyl alcohol, and the volume of the absolute ethyl alcohol is 1 time that of the mixed solution of oleic acid and absolute ethyl alcohol;

6. stirring the mixture containing Fe/Al₂O₃The solid-liquid mixture of the composite particles was stirred at a rotation speed of 500 rpm for 1 hour, and 1/8 ethyl orthosilicate (1.25g) in an iron powder mass was added to the mixed solution every 20 minutes while stirring;

7. continuously adding 10.3ml of ammonia water and 1.25g of tetraethoxysilane (the volume of the ammonia water is 1/12 times of the volume of the mixed solution of oleic acid and absolute ethyl alcohol, and the mass of the tetraethoxysilane is 1/8 times of the mass of the iron powder), and fully stirring for 2 hours;

8. after the reaction is finished, removing the residual solution after the reaction to obtain a solid reaction product, alternately cleaning the reaction product for 6 times by using deionized water and absolute ethyl alcohol, and drying the reaction product in a vacuum drying oven at the temperature of 30 ℃ for 4 hours to obtain Fe/Al₂O₃-SiO₂An iron-based composite soft magnetic powder with a core-shell structure.

9. The Fe/Al is added₂O₃-SiO₂Preparing compact block from iron-based composite soft magnetic powder with core-shell structure by powder metallurgy compaction process, placing the pressed block into a controlled atmosphere sintering furnace, heating to 1000 ℃ at a heating rate of 2 ℃/min under a flowing high-purity argon atmosphere, preserving heat for 1.5 hours, and then cooling along with the furnace to obtain Fe/Al with breaking strength up to 110.4MPa₂SiO₅And compounding soft magnetic powder core. Fe/Al prepared in this example₂SiO₅The composite soft magnetic powder core has high density, high saturation magnetization, low magnetic loss, high magnetic permeability and good frequency characteristics.