Preparation method of topological insulator coated metal magnetic powder core

Abstract

The invention discloses a preparation method of a metal magnetic powder core coated with a topological insulator, which is characterized in that in FeSi, FeSiAl and FeNi series alloys, a uniform and compact coating film is obtained by combining manufacturing processes such as topological insulator interface quantum regulation and control and low-temperature annealing, so that the synergistic breakthrough of magnetic conductivity and resistivity of the magnetic powder core is realized, and the magnetic conductivity and resistivity of the magnetic powder core are improved. And meanwhile, the preparation method has the advantages of being simple in process, easy to realize batch production and the like, and the requirements of the metal magnetic powder core under high frequency can be well met.

Description

Technical Field

[0001] The invention relates to a method for preparing an insulation-coated metal magnetic powder core, in particular to a method for preparing a topological insulator-coated metal magnetic powder core, and belongs to the technical field of metal soft magnetic materials. Background Art

[0002] In recent years, with the continuous development of technology, magnetic materials have played an increasingly important role in many fields such as electronic power, information communication and energy conversion. Soft magnetic materials have the characteristics of low coercivity, high magnetic permeability and high saturation magnetization, so they are widely used. Soft magnetic materials can generally be divided into three categories: metal soft magnetic materials, ferrite materials, and soft magnetic composite materials. Soft magnetic composite materials (also known as magnetic powder cores) are usually prepared by combining metal magnetic powder particles with insulating media through powder metallurgy. Common magnetic powder cores include FeSi alloys, FeNi alloys and amorphous nanocrystalline alloys.

[0003] With the development of electronic technology in high-tech fields such as aerospace, information and communication, higher requirements are put forward for the performance of electronic components such as inductors, which need to meet the development trend of miniaturization, high frequency and low energy consumption. The main part of the inductor component is the magnetic powder core. The magnetic powder core should have the following characteristics: high saturation magnetic induction intensity, high magnetic permeability, high operating frequency, low power loss, and high DC bias performance. The performance of the magnetic powder core can be improved and improved by controlling the particle size and morphology, molding pressure, coating agent and heat treatment process parameters. The method to improve the high-frequency loss of the magnetic powder core is mainly to wrap the insulating layer on the surface of the magnetic powder particles. On the one hand, it blocks the eddy current between the particles and reduces its loss; on the other hand, in the subsequent pressing and sintering process, high magnetic powder core strength and density can be obtained.

[0004] At present, researchers have conducted a lot of research work on the insulation technology of metal magnetic powder cores and the reduction of high-frequency losses from the perspective of materials and processes. The types of coating agents for metal magnetic powder cores are generally divided into organic coatings, inorganic coatings, and organic-inorganic composite coatings. Organic coating agents are generally silicone resins, polyamide resins, epoxy resins, and polyvinyl ketone. Commonly used inorganic coating agents include phosphoric acid, phosphates, mica, kaolin, magnesium aluminum silicate, and oxide layers.

[0005] Guangdong Academy of Sciences Institute of Materials and Processing provides a metal magnetic powder core and a preparation method thereof, comprising the following steps: (I) insulating and coating the surface-treated iron-based soft magnetic powder to obtain an iron-based soft magnetic powder coated with an oxide layer; the particle size of the iron-based soft magnetic powder is 200 to 2000 meshes, the insulating coating method is atomic layer deposition (ALD), and the thickness of the oxide layer is 10 to 100 nm; (II) mixing the dried iron-based soft magnetic powder coated with the oxide layer, an organic silicone resin and an organic solvent, and then pressing and molding the green body after the organic solvent is volatilized; (III) annealing the green body at 200 to 500°C under anaerobic conditions. The preparation method of the metal magnetic powder core of the present invention coats the oxide layer on the iron-based soft magnetic powder by an atomic layer deposition method, and the oxide layer has a uniform thickness, good density, controllable thickness, and good interface bonding, which is beneficial to reducing the magnetic loss of the metal magnetic powder core while maintaining a certain magnetic permeability (application number: CN2021102624616). The organic coating of the magnetic powder core is easily carbonized at high temperature, which in turn destroys the insulation between the magnetic powder particles and deteriorates the magnetic properties of the magnetic powder core.

[0006] Southwest University of Science and Technology has disclosed a method for preparing a composite material of FeNiMo / SiO2 soft magnetic powder core, comprising: placing atomized FeNiMo powder into a vacuum tube furnace, introducing H 2 / Ar mixed gas, heating up for sintering to obtain sintered FeNiMo powder; the sintered FeNiMo powder is subjected to SiO 2 Insulation coating, SiO 2 Coated FeNiMo composite powder; SiO 2 The coated FeNiMo composite powder is mixed with epoxy resin and lubricant, and then pressed to obtain a pre-pressed composite powder core; the pre-pressed composite powder core is sintered to obtain FeNiMo / SiO 2 Soft magnetic powder core composite material. The FeNiMo / SiO 2 The composite powder core has excellent soft magnetic properties. The insulating coating after the high-temperature pretreatment process in a reducing atmosphere can greatly improve the magnetic permeability of the soft magnetic powder core composite material and reduce its loss, providing a new strategy for improving the performance of the soft magnetic powder core composite material (application number: CN2021116432823). Although the sol-gel method can prepare a coating film with controllable thickness, uniform and dense, and can also prepare magnetic powder cores with excellent performance, the cost is high, and the coating process is complicated to operate and the pollution is relatively serious, which is not suitable for large-scale production.

[0007] The Ningbo Institute of Materials Technology and Engineering of the Chinese Academy of Sciences provides a method for preparing a sendust soft magnetic powder core. By selecting sendust magnetic powder, the method creatively designs a three-layer coating structure of phosphate-silane-silicon-containing aromatic resin, combines organic coating with inorganic coating, and realizes uniform coating of magnetic powder, which can greatly improve the temperature resistance of the material. Compared with the existing coating materials, the annealing temperature of the magnetic powder is further increased, and a sendust soft magnetic powder core with an effective magnetic permeability of up to 66 is prepared. The core has excellent soft magnetic properties, especially the DC performance of the soft magnetic powder core is greatly improved. The DC bias performance of the powder core under 100Oe conditions is higher than 55%, and the volume loss under 50kHz and 100mT conditions is less than 170mW / cm 3 (Application number: CN2021107580563). Although the mixed coating process of inorganic and organic substances is relatively simple, the thickness of the formed coating film is uneven, and the organic matter is carbonized after heat treatment, which does not play a good insulating role between the particles.

[0008] In summary, how to propose a new coating material and coating process to prepare a metal magnetic powder core with low high-frequency loss is an urgent problem to be solved. Summary of the invention

[0009] The present invention aims to solve the deficiencies in the prior art and provides a method for preparing a metal magnetic powder core coated with a topological insulator. In FeSi, FeSiAl and FeNi alloys, a uniform and dense coating film is obtained by combining topological insulator interface quantum control with low-temperature annealing and other manufacturing processes, thereby achieving a synergistic breakthrough in the magnetic permeability and resistivity of the magnetic powder core, preparing a metal magnetic powder core with low high-frequency loss, and overcoming the shortcomings of the above-mentioned process.

[0010] In order to achieve the above object, the present invention adopts the following technical solution:

[0011] The present invention discloses a method for preparing a metal magnetic powder core coated with a topological insulator, which is characterized by comprising the following steps: pre-treating a metal raw material powder, depositing a transition layer on the powder by an atomic layer deposition method, depositing a coating layer by a magnetron sputtering method, then annealing to obtain a mixed powder 1, then adding a binder to the mixed powder 1 for granulation to obtain a mixed powder 2, then pressing the mixed powder 2 to obtain a green compact, and finally sintering to obtain a metal magnetic powder core product;

[0012] The atomic layer deposition method uses a precursor 1 and a precursor 2, wherein the precursor 1 is one of titanium tetrachloride gas and trimethylaluminum gas, and the precursor 2 is water vapor, and the deposition temperature is 200-300° C.;

[0013] The transition layer composition is TiO 2 and Al 2 O 3One of the above, with a thickness of 2 to 4 nm;

[0014] The coating layer composition is Bi 2 Se 3 、Bi 2 Te 3 and Sb 2 Te 3 One of the above, with a thickness of 5 to 8 nm;

[0015] The annealing process is to place the powder after the coating layer is deposited in a heat treatment furnace, and heat it to a temperature of 300-350°C at a heating rate of 3-5°C / min under the protection of a hydrogen atmosphere, and keep it at a temperature of 1-2h, and then cool it to room temperature with the furnace.

[0016] The sintering process is to place the formed blank in a sintering furnace, heat it to 350-400° C. at a heating rate of 3-5° C. / min under the protection of a nitrogen atmosphere, keep it warm for 1-2 hours, and cool it to room temperature along with the furnace.

[0017] As a preferred embodiment, the present invention provides a method for preparing a topological insulator-coated metal magnetic powder core, characterized in that the chemical composition of the metal raw material powder is one of Fe-6.5% Si, Fe-9% Si-6% Al and Fe-50% Ni.

[0018] As a preferred embodiment, the present invention provides a method for preparing a topological insulator-coated metal magnetic powder core, characterized in that the metal raw material powder is prepared by one of gas atomization, water atomization and water-gas combined atomization, and the average particle size of the powder is 10 to 30 μm.

[0019] As a preferred embodiment, the present invention provides a method for preparing a topological insulator-coated metal magnetic powder core, characterized in that the pretreatment is to add the metal raw material powder to a hydrochloric acid solution with a concentration of 8 to 10%, mechanically stir and clean it for 20 to 30 minutes, rinse it with deionized water, put it in a drying oven, and dry it at 80 to 100° C. in a vacuum environment for 1 to 2 hours.

[0020] As a preferred embodiment, the present invention provides a method for preparing a topological insulator-coated metal magnetic powder core, characterized in that the atomic layer deposition process is to fix the pretreated powder on a rotating tray in a reaction chamber in a vacuum environment with a vacuum degree of <5×10 -3 Pa, precursor 1 is introduced into the reaction chamber for 0.5-1s, and then the reaction chamber is flushed with Ar gas for 10-20s, and then precursor 2 is introduced for 0.5-1s, and the reaction chamber is flushed with Ar gas again for 10-20s. The above is one cycle, and a total of 15-25 cycles are required to complete the deposition.

[0021] As a preferred embodiment, the present invention provides a method for preparing a topological insulator-coated metal magnetic powder core, characterized in that the magnetron sputtering process is to place the powder after the transition layer is deposited on a rotating sample table in a vacuum environment with a vacuum degree of less than 5×10 -3 Pa, choose Bi 2 Se 3 、Bi 2 Te 3 and Sb 2 Te 3 A target material in the method uses high-purity argon as the shielding and ionizing gas, the sputtering power is 60-100w, and the sputtering time is 10-20min.

[0022] As a preferred embodiment, the present invention provides a method for preparing a topological insulator-coated metal magnetic powder core, characterized in that the binder is an epoxy resin acetone solution, wherein the mass fraction of the epoxy resin is 2-4%.

[0023] As a preferred embodiment, the present invention provides a method for preparing a topological insulator-coated metal magnetic powder core, characterized in that the granulation process is to add an epoxy resin acetone solution to a mixed powder 1, mechanically stir for 10 to 20 minutes, put it into a drying oven, and keep it warm at 60 to 80° C. for 1 to 2 hours in a vacuum environment to obtain a mixed powder 2, wherein the amount of the epoxy resin acetone solution added accounts for 1 to 2% of the mass percentage of the powder.

[0024] As a preferred embodiment, the present invention provides a method for preparing a topological insulator-coated metal magnetic powder core, characterized in that the forming process comprises: loading the mixed powder 2 into a mold for forming, applying longitudinal pressure to the powder, the pressure being 1000 to 1200 MPa, and the holding time being 30 to 50 s.

[0025] As a preferred embodiment, the present invention provides a method for preparing a topological insulator-coated metal magnetic powder core, characterized in that the maximum magnetic permeability μm of the obtained magnetic powder core is 250 to 350 mH / m (test conditions: the thickness of the magnetic powder core is 0.2 mm), and the resistivity is 120 to 160 μΩ·cm.

[0026] Principles and advantages

[0027] In view of the problems existing in the existing coating process of metal magnetic powder cores, such as complex process, high production cost, and inability to simultaneously improve the magnetic permeability and resistivity, the present invention conducts in-depth research and exploration from two aspects of coating materials and coating process.

[0028] In terms of coating materials. For the first time, topological insulators were selected as coating materials, TiO 2 and Al 2 O 3As a transition layer between magnetic powder and coating material. Topological insulators are a new type of quantum material with special electronic states. Their core properties are as follows: 1) The internal electronic structure has an energy gap (insulator properties) and extremely high resistivity (>10 8 Ω·cm), there is a topologically protected metallic state on the surface, and the electrons have the property of spin-momentum locking (the spin direction is perpendicular to the momentum direction), forming a dissipation-free conductive channel; 2) The spin-orbit interaction leads to band inversion, forming a topologically non-trivial electronic structure, which gives the surface state robustness (insensitive to impurities and defects); 3) In the absence of an external magnetic field, the surface state electrons are spin-polarized, forming an edge current protected by time reversal symmetry, which suppresses backscattering losses; 4) Thermodynamic stability, topological insulators (such as Bi 2 Se 3 、Bi 2 Te 3 and Sb 2 Te 3 ) has high chemical stability, decomposition temperature > 400°C, and is suitable for magnetic powder core processing. Because of the above characteristics, topological insulators are very helpful in improving the magnetic permeability and resistivity of magnetic powder cores. First, the spin-momentum locking characteristics of the surface state electrons of the topological insulator are coupled with the magnetic moment of the magnetic particles (such as FeSi, FeSiAl and FeNi systems) to form a spin-polarized interface, which reduces the pinning energy of the magnetic domain wall. At the same time, the spin current of the topological surface state electrons produces an equivalent magnetic field, which offsets the magnetocrystalline anisotropy field of the magnetic particles, making the magnetization process easier to proceed along the external field direction, thereby improving the magnetic permeability. Second, the high resistivity of the topological insulator bulk phase (>10 8 Ω·cm) blocks the direct electron transmission between magnetic particles and inhibits the formation of vortex. The surface state electrons only allow electrons with a specific spin direction to pass through, increasing the scattering probability. At the same time, the Fermi level difference between the topological insulator and the magnetic particles leads to an interface barrier, which further hinders the transfer of charges across the interface and increases the overall resistivity.

[0029] In topological insulators (such as Bi 2 Se 3 ) and a magnetic matrix (such as FeSiAl) to choose TiO 2 or Al 2 O 3 As a transition layer, there are several reasons: 1) to inhibit interface reaction and element diffusion. 2 Se 3 ) is in direct contact with magnetic metals (Fe, Al, etc.), element interdiffusion or chemical reaction (such as the formation of Bi-Fe intermetallic compounds) is likely to occur during high-temperature processes, destroying the topological surface state and reducing insulation. 2 or Al 2 O 3Both are highly stable oxides that can effectively isolate Bi2Se3 and FeSiAl and inhibit interface diffusion. 2) Optimize interface bonding and stress buffering. The nanoscale transition layer (2-5 nm) can alleviate the stress of topological insulators (such as Bi 2 Se 3 ) and the magnetic matrix (such as FeSiAl) to inhibit the cracking of the coating layer. 3) Improve the insulation performance. 2 and Al 2 O 3 Both are wide bandgap insulators (bandgap width: Al 2 O 3 ≈8.8eV; TiO 2 ≈3.2eV), resistivity>10 14 Ω·cm, which can block the leakage current between magnetic particles.

[0030] In terms of coating process, the transition layer is prepared by atomic layer deposition (ALD), the coating layer is prepared by magnetron sputtering and combined with annealing heat treatment to achieve a simultaneous improvement in magnetic permeability and resistivity.

[0031] ALD is an advanced thin film preparation technology. The entire reaction cycle includes four steps: 1) Precursor A pulse: The first precursor (such as metal organic compound) is introduced into the reaction chamber and adsorbed on the substrate surface to form a single layer of chemical adsorption. 2) Purge: Inert gas (such as Ar, N 2 ) Remove unreacted precursor A and byproducts. 3) Precursor B pulse: Introduce a second precursor (such as H 2 O, O 3 NH 3 etc.), react chemically with the adsorbed A to generate a solid film and release by-products. 4) Secondary purge: remove unreacted B and by-products again to complete a deposition cycle. Each cycle only deposits a film thickness of about 0.1-0.3nm, and the film thickness can be precisely controlled by repeating the number of cycles. ALD uses layer-by-layer growth characteristics to make the film thickness linearly related to the number of deposition cycles, with sub-nanometer accuracy; it can achieve uniform coverage on the surface of complex three-dimensional structures with high aspect ratios (>1000:1); self-limiting reactions reduce impurity doping, and the film is dense and has few defects. The present invention introduces ALD technology to achieve atomic-level precision film growth through layer-by-layer self-limiting surface chemical reactions, and precisely control the transition layer TiO 2 or Al 2 O 3 Thickness is reduced to inhibit interface reaction and element diffusion, achieving the purpose of stress buffering and improving insulation performance.

[0032] The working principle of magnetron sputtering is that electrons collide with argon atoms in the process of flying to the substrate under the action of the electric field E, causing them to ionize and produce Ar positive ions and new electrons; the new electrons fly to the substrate, and the Ar ions are accelerated to fly to the cathode target under the action of the electric field, and bombard the target surface with high energy, causing the target material to sputter. The advantages of preparing the coating by magnetron sputtering are as follows: 1) High-purity target material (≥99.99%) combined with precise control of sputtering parameters (power, gas pressure) ensures Bi 2 Se 3 The Bi:Se atomic ratio in materials such as MgO2 is close to 2:3, reducing intrinsic defects. 2) The high-energy particle bombardment of magnetron sputtering promotes film densification. Compared with the sol-gel method, the sputtered film is denser. 3) Magnetron sputtering can evenly coat the topological insulator layer (thickness 5-8nm) on the surface of irregular magnetic powder to achieve core-shell structure design.

[0033] After the transition layer and coating layer are deposited on the magnetic powder, annealing heat treatment is added. First, eliminate internal stress. Processes such as magnetron sputtering will introduce lattice distortion and residual stress. Annealing reorganizes the lattice through atomic thermal diffusion, reduces defect density (such as dislocations and vacancies), and improves magnetic permeability. Second, optimize the magnetic domain structure. During the annealing process of the magnetic material, the atoms are rearranged to form more uniform magnetic domains, reduce the domain wall pinning effect, and reduce high-frequency losses. Third, regulate the performance of topological insulators. Topological insulators (such as Bi 2 Se 3 ) may be amorphous after sputtering, and annealing promotes crystallization to ensure surface conductivity.

[0034] Compared with the prior art, the advantages of the present invention are as follows:

[0035] 1) Introduce novel coating materials and new coating processes to expand the application areas of topological insulators and ALD;

[0036] 2) Excellent performance, solving the contradiction that magnetic permeability and resistivity cannot be optimized simultaneously;

[0037] 3) The process is simple, easy to realize mass production, and highly feasible.

[0038] In summary, the present invention obtains a uniform and dense coating film in FeSi, FeSiAl and FeNi alloys by combining topological insulator interface quantum control with manufacturing processes such as low-temperature annealing, achieves a synergistic breakthrough in the magnetic permeability and resistivity of the magnetic powder core, and prepares a metal magnetic powder core with low high-frequency loss. At the same time, it has the advantages of simple process and easy batch production, and can well meet the demand for metal magnetic powder cores under high frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] none. DETAILED DESCRIPTION

[0040] The method of the present invention is further described below with reference to three examples.

[0041] Embodiment 1:

[0042] A method for preparing a metal magnetic powder core coated with a topological insulator, the process of which is as follows:

[0043] A. Raw material preparation: Fe-6.5% Si alloy powder prepared by gas atomization method was used, and the average particle size of the powder was 20 μm;

[0044] B. Pretreatment: Add the raw material powder into a 10% hydrochloric acid solution, mechanically stir and clean for 30 minutes, rinse with deionized water, put it into a drying oven, and dry it at 90°C in a vacuum environment for 1.5 hours;

[0045] C. Deposition of transition layer: Fix the pre-treated powder on the rotating tray of the reaction chamber in a vacuum environment with a vacuum degree of <5×10 -3 Pa, the reaction chamber temperature was 200 ° C, titanium tetrachloride gas was introduced into the reaction chamber for 0.5 s, then Ar gas was used to flush the reaction chamber for 15 s, then water vapor was introduced for 0.5 s, and Ar gas was used to flush the reaction chamber again for 15 s. The above was one cycle, and a total of 20 cycles were performed to complete the TiO 2 Deposition, the transition layer thickness is 3nm;

[0046] D. Deposition of coating layer: Place the powder after deposition of transition layer on a rotating sample stage in a vacuum environment with a vacuum degree of <5×10 -3 Pa, choose Bi 2 Se 3 For the target material, high-purity argon was used as the shielding and ionizing gas, the sputtering power was 80w, the sputtering time was 15min, and the coating thickness was 6nm;

[0047] E. Annealing: placing the powder after the coating layer is deposited in a heat treatment furnace, and heating it to 300°C at a heating rate of 5°C / min under the protection of a hydrogen atmosphere, and keeping the temperature for 2 hours, and cooling it to room temperature with the furnace to obtain a mixed powder 1;

[0048] F. Granulation: Add 3% epoxy resin acetone solution to the mixed powder 1, mechanically stir for 15 min, put into a drying oven, keep warm at 70° C. for 1.5 h in a vacuum environment, and dry to obtain a mixed powder 2, wherein the epoxy resin acetone solution is added in an amount of 2% by mass of the powder;

[0049] G. Forming: The mixed powder 2 is placed in a mold for forming, and a longitudinal pressure of 1200 MPa is applied to the powder for a holding time of 40 seconds;

[0050] H. Sintering: Place the formed blank in a sintering furnace, and heat it to 400°C at a heating rate of 5°C / min under the protection of a nitrogen atmosphere. Keep it at this temperature for 1 hour, and then cool it to room temperature along with the furnace.

[0051] Embodiment 2:

[0052] A method for preparing a metal magnetic powder core coated with a topological insulator, the process of which is as follows:

[0053] A. Raw material preparation: Fe-9%Si-6%Al alloy powder prepared by water-gas combined atomization method was used, and the average particle size of the powder was 15 μm;

[0054] B. Pretreatment: Add the raw material powder into a 10% hydrochloric acid solution, mechanically stir and clean for 30 minutes, rinse with deionized water, put it into a drying oven, and dry it at 90°C in a vacuum environment for 1.5 hours;

[0055] C. Deposition of transition layer: Fix the pre-treated powder on the rotating tray of the reaction chamber in a vacuum environment with a vacuum degree of <5×10 -3 Pa, the reaction chamber temperature was 250 ° C, titanium tetrachloride gas was introduced into the reaction chamber for 0.8 s, then the reaction chamber was flushed with Ar gas for 15 s, and then water vapor was introduced for 0.8 s, and the reaction chamber was flushed with Ar gas again for 15 s. The above was one cycle, and a total of 25 cycles were performed to complete the TiO 2 Deposition, the transition layer thickness is 3.5nm;

[0056] D. Deposition of coating layer: Place the powder after deposition of transition layer on a rotating sample stage in a vacuum environment with a vacuum degree of <5×10 -3 Pa, choose Bi 2 Te 3 The target material uses high-purity argon as the shielding and ionizing gas, the sputtering power is 90w, the sputtering time is 20min, and the coating thickness is 7nm;

[0057] E. Annealing: placing the powder after the coating layer is deposited in a heat treatment furnace, and heating it to 350°C at a heating rate of 5°C / min under the protection of a hydrogen atmosphere, and keeping the temperature for 1 hour, and cooling it to room temperature with the furnace to obtain a mixed powder 1;

[0058] F. Granulation: Add 3% epoxy resin acetone solution to the mixed powder 1, mechanically stir for 15 min, put into a drying oven, keep warm at 70° C. for 1.5 h in a vacuum environment, and dry to obtain a mixed powder 2, wherein the epoxy resin acetone solution is added in an amount of 2% by mass of the powder;

[0059] G. Forming: The mixed powder 2 is placed in a mold for forming, and a longitudinal pressure of 1100 MPa is applied to the powder for a holding time of 30 seconds;

[0060] H. Sintering: Place the formed blank in a sintering furnace, and heat it to 350°C at a heating rate of 5°C / min under the protection of a nitrogen atmosphere, keep it at this temperature for 2 hours, and then cool it to room temperature along with the furnace.

[0061] Embodiment 3:

[0062] A method for preparing a metal magnetic powder core coated with a topological insulator, the process of which is as follows:

[0063] A. Raw material preparation: Fe-50% Ni alloy powder prepared by water-gas combined atomization method is used, and the average particle size of the powder is 20 μm;

[0064] B. Pretreatment: Add the raw material powder into a 10% hydrochloric acid solution, mechanically stir and clean for 30 minutes, rinse with deionized water, put it into a drying oven, and dry it at 90°C in a vacuum environment for 1.5 hours;

[0065] C. Deposition of transition layer: Fix the pre-treated powder on the rotating tray of the reaction chamber in a vacuum environment with a vacuum degree of <5×10 -3 Pa, the reaction chamber temperature was 250 ° C, trimethylaluminum gas was introduced into the reaction chamber for 0.8 s, then the reaction chamber was flushed with Ar gas for 15 s, and then water vapor was introduced for 0.8 s, and the reaction chamber was flushed with Ar gas again for 15 s. The above was one cycle, and a total of 20 cycles were performed to complete the Al 2 O 3 Deposition, the transition layer thickness is 3nm;

[0066] D. Deposition of coating layer: Place the powder after deposition of transition layer on a rotating sample stage in a vacuum environment with a vacuum degree of <5×10 -3 Pa, choose Sb 2 Te 3 For the target material, high-purity argon was used as the shielding and ionizing gas, the sputtering power was 90w, the sputtering time was 15min, and the coating thickness was 6nm;

[0067] E. Annealing: placing the powder after the coating layer is deposited in a heat treatment furnace, and heating it to 350°C at a heating rate of 3°C / min under the protection of a hydrogen atmosphere, and keeping the temperature for 1 hour, and cooling it to room temperature with the furnace to obtain a mixed powder 1;

[0068] F. Granulation: Add 3% epoxy resin acetone solution to the mixed powder 1, mechanically stir for 15 min, put into a drying oven, keep warm at 70° C. for 1.5 h in a vacuum environment, and dry to obtain a mixed powder 2, wherein the epoxy resin acetone solution is added in an amount of 2% by mass of the powder;

[0069] G. Forming: The mixed powder 2 is placed in a mold for forming, and a longitudinal pressure of 1200 MPa is applied to the powder for a holding time of 30 seconds;

[0070] H. Sintering: Place the formed blank in a sintering furnace, and heat it to 400°C at a heating rate of 5°C / min under the protection of a nitrogen atmosphere. Keep it at this temperature for 1 hour, and then cool it to room temperature along with the furnace.

[0071] Comparative Example 1:

[0072] The only difference from Example 1 is the absence of transition layer material and related preparation process.

[0073] Comparative Example 2:

[0074] The only difference from Example 1 is that there is no annealing process.

[0075] Comparative Example 3:

[0076] The only difference from Example 1 is that the coating process is to use conventional sol-gel to prepare SiO 2 .

[0077] The performance of the magnetic powder cores prepared in Examples 1-3 and Comparative Examples 1-3 was tested, and the results are shown in the following table:

[0078]

[0079] It can be seen from the table that the magnetic powder cores prepared in Examples 1-3 of the present invention are superior to those in Comparative Examples 1-3 in terms of maximum magnetic permeability and resistivity, indicating that the preparation method of the present invention can effectively improve the comprehensive performance of the magnetic powder cores.

[0080] The above-described examples are only preferred implementation methods of the present invention, and therefore cannot be used to limit the scope of implementation of the present invention. Other equivalent changes, modifications, substitutions and combinations made in accordance with the principles and contents of the present invention still fall within the protection scope of the present invention.

Claims

1. A method for preparing a topological insulator-coated metal magnetic powder core, characterized in that: The following steps are involved: The metal raw material powder is pretreated, a transition layer is deposited on the powder by an atomic layer deposition method, and a coating layer is deposited by a magnetron sputtering method, followed by annealing to obtain a mixed powder 1, and then a binder is added to the mixed powder 1 for granulation to obtain a mixed powder 2, and then the mixed powder 2 is pressed into a green body, and finally sintered to obtain a metal magnetic powder core product; The atomic layer deposition method uses a precursor 1 and a precursor 2, wherein the precursor 1 is one of titanium tetrachloride gas and trimethylaluminum gas, and the precursor 2 is water vapor, and the deposition temperature is 200-300° C.; The transition layer is composed of one of TiO2 and Al2O3, and has a thickness of 2-4 nm; The coating layer is composed of one of Bi2Se3, Bi2Te3 and Sb2Te3, and has a thickness of 5-8nm; The annealing process is to place the powder after the coating layer is deposited in a heat treatment furnace, and heat it to a temperature of 300-350°C at a heating rate of 3-5°C / min under the protection of a hydrogen atmosphere, and keep it at a temperature of 1-2h, and then cool it to room temperature with the furnace; The sintering process is to place the formed blank in a sintering furnace, heat it to 350-400°C at a heating rate of 3-5°C / min under the protection of a nitrogen atmosphere, keep it at a temperature for 1-2 hours, and cool it to room temperature along with the furnace.

2. The method for preparing a topological insulator-coated metal powder core according to claim 1, characterized in that: The chemical composition of the metal raw material powder is one of Fe-6.5%Si, Fe-9%Si-6%Al and Fe-50%Ni.

3. The method for preparing a topological insulator-coated metal powder core according to claim 1, characterized in that: The metal raw material powder is prepared by one of gas atomization, water atomization and water-gas combined atomization, and the average particle size of the powder is 10-30 μm.

4. The method for preparing a topological insulator-coated metal powder core according to claim 1, characterized in that: The pretreatment is to add the metal raw material powder into a hydrochloric acid solution with a concentration of 8-10%, mechanically stir and clean it for 20-30 minutes, rinse it with deionized water, put it into a drying oven, and dry it at 80-100° C. in a vacuum environment for 1-2 hours.

5. The method for preparing a topological insulator-coated metal powder core according to claim 1, characterized in that: The atomic layer deposition process is to fix the pre-treated powder on a rotating tray in a reaction chamber in a vacuum environment with a vacuum degree of <5×10 -3 Pa, precursor 1 is introduced into the reaction chamber for 0.5~1s, and then the reaction chamber is flushed with Ar gas for 10~20s, and then precursor 2 is introduced for 0.5~1s, and the reaction chamber is flushed with Ar gas again for 10~20s. The above is one cycle, and a total of 15~25 cycles are required to complete the deposition.

6. The method for preparing a topological insulator-coated metal powder core according to claim 1, characterized in that: The magnetron sputtering process is to place the powder after the transition layer is deposited on a rotating sample table in a vacuum environment with a vacuum degree of <5×10 -3 Pa, select one of the target materials among Bi2Se3, Bi2Te3 and Sb2Te3, use high-purity argon as the shielding and ionization gas, the sputtering power is 60~100w, and the sputtering time is 10~20min.

7. The method for preparing a topological insulator-coated metal powder core according to claim 1, characterized in that: The binder is an epoxy resin acetone solution, wherein the mass fraction of the epoxy resin is 2-4%.

8. The method for preparing a topological insulator-coated metal magnetic powder core according to claim 1, characterized in that: The granulation process comprises adding the epoxy resin acetone solution to the mixed powder 1, mechanically stirring for 10-20 minutes, placing in a drying oven, and drying at 60-80° C. for 1-2 hours in a vacuum environment to obtain the mixed powder 2, wherein the amount of the epoxy resin acetone solution added accounts for 1-2% of the mass percentage of the powder.

9. The method for preparing a topological insulator-coated metal powder core according to claim 1, characterized in that: The forming process is to put the mixed powder 2 into a mold for forming, apply longitudinal pressure to the powder, the pressure is 1000-1200 MPa, and the pressure holding time is 30-50 seconds.

10. A method for preparing a topological insulator-coated metal magnetic powder core according to any one of claims 1 to 9, characterized in that: The maximum magnetic permeability μm of the obtained magnetic powder core is 250~350mH / m (test condition: the thickness of the magnetic powder core is 0.2mm), and the resistivity is 120~160μΩ•cm.

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