A rare earth alloy nitride composite soft magnetic material and a method for preparing the same

Abstract

This invention discloses a rare-earth alloy nitride composite soft magnetic material and its preparation method, belonging to the field of metallic soft magnetic materials. The material comprises an alloy nitride and a coating layer located on the surface of the alloy nitride and covering the alloy nitride; wherein the alloy nitride has the composition Ce2(Fe2+)2. x Co 1‑x ) 17 N 3‑δ The coating layer is composed of Fe4N, and the rare earth alloy nitride composite material is represented as Ce2(Fe x Co 1‑x ) 17 N 3‑δ @Fe4N, where x is the Fe atomic ratio and δ is the nitrogen deficiency coefficient. This invention uses nitrogen-rich compounds to target Ce2(Fe x Co 1‑x ) 17 In-situ nitriding of materials can generate Ce2(Fe) x Co 1‑x ) 17 N 3‑δ Furthermore, a Fe4N-based coating layer can be formed on its surface to obtain a composite material. Compared to Ce2(Fe x Co 1‑x ) 17 The composite material improves high-frequency magnetism while significantly reducing eddy current loss.

Description

Technical Field

[0001] This invention relates to a rare earth alloy nitride composite soft magnetic material and its preparation method, specifically in the field of metallic soft magnetic materials. Background Technology

[0002] Soft magnetic composite materials are one of the indispensable key materials in the field of power electronics. With the rapid development of communication technology and the new energy industry, high frequency, high efficiency, and low power consumption are required for various power electronic components. The performance of traditional soft magnetic materials is limited by high-frequency resonance, making it difficult to maintain permeability and causing a sharp increase in residual losses. Some rare-earth transition metal alloys, such as RE2Me, are used in this field. 17 (RE represents rare earth elements, and Me represents Fe or Co) It has the characteristic of having multiple easily magnetized axes in the same plane. This easy-plane characteristic can break through the limitations of high-frequency magnetic resonance and has high complex permeability and resonance frequency in the MHz band.

[0003] CN108777931A discloses a high-permeability electromagnetic wave absorbing material, characterized in that the electromagnetic wave absorbing material is composed of a thin-film iron-based nanocrystalline alloy and Ce2Fe. 17 Composed of N3, including Ce2Fe 17 Nitrogen (N3) constitutes 15%–50% of the weight of the mixed powder, with a particle size less than 5 micrometers. This invention utilizes a gas atomization device to prepare spherical amorphous powder, and obtains Ce2Fe through melting Ce-Fe alloy ingots, rapid quenching, and high-temperature, high-pressure nitriding. 17 N3, with a nitriding temperature of 400–500℃, a holding time of 1–2 h, and a nitriding pressure of 0.7–1 MPa, is mixed with silicone rubber to form a viscous fluid slurry. A polymer composite electromagnetic wave absorbing film is then prepared using a casting process. This composite material is mainly composed of two-phase metals and intermetallic compounds, and its purpose is to improve the electromagnetic wave absorption performance of the resulting material in the GHz frequency range.

[0004] CN101880817A discloses a planar 2:17 rare-earth-3d transition metal intermetallic compound electromagnetic wave absorbing material with the general formula R2(Co 1-x Fe x ) 17In the general formula, R is Nd or Ce, and when R is Nd, 0 ≤ x ≤ 1; when R is Ce, 0.6 ≤ x ≤ 0.8. The preparation method involves melting rare earth elements, iron, and cobalt into an alloy, homogenizing it at high temperature, quenching it, then pulverizing and grinding the alloy into fine particles, followed by ball milling to obtain metal powder. The composite material preparation method involves placing the aforementioned material into an uncured binder, mixing it thoroughly, and then placing it into a mold made of non-magnetic material. The mold is then placed in a magnetic field. The binder is a polymer such as resin, paraffin, polyethylene, or polypropylene. This intermetallic compound material uses metallic elements as its main constituent elements, and its purpose is to improve the electromagnetic wave absorption performance of the resulting alloy in the GHz frequency range.

[0005] CN101699577A discloses a Nd2(CoFe) compound. 17 The high-frequency soft magnetic intermetallic compound material is prepared by melting neodymium, cobalt, and iron into ingots according to a material ratio, followed by heating the ingots for thorough homogenization; or by melting neodymium, cobalt, and iron transition metals into ingots according to a material ratio, followed by melt quenching to form thin strips, and then pulverizing and grinding the homogenized ingots or thin strips made by melt quenching into powder with a particle size of 5 micrometers or less. The composite material is prepared by placing the above materials into an uncured binder, mixing thoroughly, and then placing the mixture into a mold made of a non-magnetic material. The mold is then placed in a magnetic field. The binder is a polymer such as resin, paraffin, polyethylene, or polypropylene. This intermetallic compound material uses metallic elements as its main constituent elements, and its purpose is to improve the electromagnetic wave absorption performance of the resulting alloy in the GHz frequency range.

[0006] The three patent examples above demonstrate that the applications of rare-earth intermetallic compound materials are all manifested in GHz frequency absorption, but not in electromagnetic conversion applications in the MHz range. Furthermore, RE2Me 17 Three interstitial N atoms can also be introduced into the unit cell to form rare earth alloy nitrides, which can further regulate high-frequency magnetism.

[0007] CN 113871124 A discloses a method for preparing high-performance samarium iron nitride permanent magnet materials with high nitriding efficiency. The method involves: preparing Sm2Fe 17 The alloy powder was graded and screened in the 300-2000 mesh range, and the tower vacuum nitriding furnace was evacuated to a low vacuum of 1×10⁻⁶ using a vacuum pump. -3 A high-speed, high-purity nitrogen gas flow (10–30 m / s) is continuously introduced from the bottom of a tower-type vacuum nitriding furnace for nitriding treatment for 10–30 hours. The method for preparing high-performance samarium iron nitride permanent magnet materials with high nitriding efficiency provided by this invention involves rinsing Sm2Fe with a nitrogen gas flow. 17 Alloy powder, making Sm2Fe 17The alloy powder can fully contact nitrogen gas, thus improving the nitriding efficiency. This method employs high-pressure equipment and a high-pressure N2 gas flow to carry out the nitriding process, aiming to increase the nitrogen content and nitriding efficiency of the resulting alloy.

[0008] CN 115537711 A discloses a method for improving the nitriding rate of samarium iron nitride (SMR) permanent magnet materials. The method involves: first, preparing an active component solution by mixing an active metal (nickel, cobalt, copper, or zinc) salt and an initiator; then, mixing the active component solution with a carbon support, curing (3-4 hours), and calcining (1.5-3 hours) to prepare a nitriding catalyst; subsequently, mixing the nitriding catalyst with a samarium iron alloy and heating in a nitrogen-containing atmosphere for 3-10 hours to obtain a solid mixture; finally, separating the solid mixture to obtain the SMR permanent magnet material. This method employs a catalyst mixing approach to implement the nitriding process, aiming to increase the nitrogen content and nitriding efficiency of the resulting alloy.

[0009] The two patent examples above show that, on the one hand, to improve nitriding efficiency, high-pressure flowing N2 gas must be used, and the nitriding process requires 10-30 hours; or additional catalysts or reducing agents must be used, and the nitriding process requires 3-30 hours. Therefore, the overall process complexity is increased, as are the material and equipment costs of the overall process. At the same time, the nitriding efficiency needs to be further improved.

[0010] Furthermore, due to the low intrinsic resistivity of metallic soft magnetic materials, their high-frequency applications are also limited by eddy current losses. Therefore, it is usually necessary to perform an insulating coating treatment on the surface of the soft magnetic powder matrix to improve the resistivity of the composite material and reduce eddy current losses. CN 115475935 A discloses a method for preparing iron-based soft magnetic composite powder and the iron-based soft magnetic composite powder. The method involves first generating a phosphate protective layer in situ on the surface of the iron-based powder using a phosphoric acid solution, and then continuing the reaction using a mixture of potassium permanganate and phosphoric acid to obtain an insulating protective layer with a gradient distribution of phosphate and oxide content along the thickness direction. This method uses a liquid-phase method to implement the coating process, aiming to improve the insulation performance of the obtained alloy powder.

[0011] CN 114050043 A discloses a method for preparing an oxide-coated iron-silicon-cadmium soft magnetic composite material. The method includes: (1) pretreating iron-silicon-cadmium metal alloy powder to obtain metal powder; (2) subjecting the metal powder to a first mixing and heating decomposition treatment with a magnesium acetate solution to obtain a semi-finished metal powder; and (3) subjecting the semi-finished metal powder to a second mixing and drying treatment with an organic binder to obtain an oxide-coated iron-silicon-cadmium soft magnetic composite material. This method employs a liquid-phase coating process to improve the insulation performance of the obtained alloy powder.

[0012] For surface-forming rare-earth soft magnetic materials, the rare-earth elements in the structure are easily oxidized. Traditional liquid-phase chemical methods or corrosive liquid-phase methods are used to coat 100μm-sized surface-forming rare-earth soft magnetic powder materials. However, due to their large surface area, it is difficult to ensure the stability of their composition. Therefore, there is a lack of effective methods to improve their bulk resistance or perform primary process insulation coating. Summary of the Invention

[0013] In view of this, the present invention provides a rare earth alloy nitride composite soft magnetic material and its preparation method. Firstly, the present invention utilizes the pyrolysis of nitrogen-rich compounds to release NH3, providing a locally high-pressure active NH3 atmosphere to enable N to enter Ce2(Fe2+)2. x Co 1-x ) 17 The process of crystallization and solid solution formation enhances N penetration into Ce2(Fe) lattice. x Co 1-x ) 17 The invention improves lattice efficiency and enhances the resonant frequency and complex permeability in the MHz range. Simultaneously, it allows for the formation of an in-situ coating structure on the surface of soft magnetic powder, effectively increasing the resistivity of the composite material and reducing eddy current losses. Furthermore, compared to traditional flowing atmosphere reduction methods, the nitriding process of this invention eliminates the need for high-pressure flowing gas, thus avoiding safety and exhaust gas treatment issues. Additionally, the nitriding process requires no additional catalysts or reducing agents, thereby reducing overall process complexity and making the process simpler and cheaper.

[0014] The present invention achieves the above objectives through the following technical solutions.

[0015] On one hand, the present invention provides a rare earth alloy nitride composite soft magnetic material, comprising an alloy nitride and a coating layer located on the surface of the alloy nitride and covering the alloy nitride; wherein the alloy nitride is composed of Ce2(Fe2+)2. x Co 1-x ) 17 N 3-δ The coating layer is composed of Fe4N, and the rare earth alloy nitride composite soft magnetic material is represented as Ce2(Fe x Co 1-x ) 17 N 3-δ @Fe4N;

[0016] Where x is the proportion of Fe atoms in the structure, 0.6≤x<1;

[0017] Where δ is the nitrogen deficiency coefficient in the structure, 1≤δ≤2.5.

[0018] Preferably, the thickness of the coating layer is 0.1-2 μm.

[0019] On the other hand, the present invention also provides a method for preparing the rare earth alloy nitride composite soft magnetic material, which includes the following steps:

[0020] 1) The rare earth alloy material is crushed and sieved to obtain uniform alloy powder;

[0021] 2) Mix the alloy powder with a nitrogen-rich compound to obtain a mixture;

[0022] 3) The mixture is subjected to nitriding treatment to obtain the rare earth alloy nitride composite soft magnetic material having alloy nitride and coating layer.

[0023] According to a preferred embodiment of the present invention, the chemical composition of the rare earth alloy material is Ce2(Fe). x Co 1-x ) 17 Where x is the Fe atomic ratio, 0.6≤x<1, and the purity of the raw material is at least industrial purity.

[0024] According to a preferred embodiment of the present invention, the particle size of the alloy powder ranges from 75 micrometers to 150 micrometers.

[0025] According to a preferred embodiment of the present invention, the nitrogen-rich compound has a chemical structure rich in -NH3 groups and can pyrolyze at 100-400°C to release NH3; the nitrogen-rich compound is selected from one or more of urea, ammonium bicarbonate, and amino acids, and its purity is at least industrial grade.

[0026] According to a preferred embodiment of the present invention, the mass ratio of the alloy powder to the nitrogen-rich compound is 3 to 8:1.

[0027] According to a preferred embodiment of the present invention, step 3) specifically involves: placing the mixture into an inert atmosphere furnace or a heating device that can provide inert atmosphere protection, and performing nitriding treatment at 550–650°C under an initial nitrogen pressure greater than or equal to 0.1 MPa, with the nitriding process taking 1–3 hours after reaching the target temperature.

[0028] According to a preferred embodiment of the present invention, during the nitriding process at 550–650°C, no flowing nitrogen source gas or hydrogen gas flow is provided.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) The preparation process of this invention is simple and feasible. After reaching the nitriding temperature, the nitriding depth is not less than 75 micrometers within a short time. The required Ce2(Fe) x Co 1-x ) 17 The powder particle size can be selected from 75 to 150 micrometers, which significantly improves the nitriding efficiency; it can rapidly form Ce2(Fe)x Co 1-x ) 17 N 3-δ Intermediate compounds increase the system's resistance.

[0031] (2) The preparation process of this invention can achieve simultaneous (one-step) coating, that is, during nitriding to form Ce2(Fe) x Co 1-x ) 17 N 3-δ The same process as the intermediate compound, in Ce2(Fe x Co 1-x ) 17 N 3-δ A layer of iron-based compound coating is formed on the surface, compared to Ce2(Fe) x Co 1-x ) 17 It can significantly reduce magnetic loss. Attached Figure Description

[0032] Figure 1 The X-ray diffraction patterns of the material before and after nitriding in Example 1 of the present invention are shown, where (a) is before nitriding and (b) is after nitriding.

[0033] Figure 2 This is a static magnetic property diagram of the material before and after nitriding at room temperature in Example 1 of the present invention.

[0034] Figure 3 This is an electron probe scanning cross-sectional image of a bulk material subjected to nitriding under the same experimental conditions as the material in Example 1 of this invention.

[0035] Figure 4 The graph showing the relationship between complex permeability and frequency was obtained from the composite material ring test in Example 1 of this invention.

[0036] Figure 5 The graph shows the relationship between loss and frequency obtained from the composite ring test in Example 1 of this invention, where (a) is before nitriding and (b) is after nitriding.

[0037] Figure 6 The X-ray diffraction patterns of the material before and after nitriding in Example 2 of the present invention are shown, where (a) is before nitriding and (b) is after nitriding.

[0038] Figure 7 This is a static magnetic property diagram of the material before and after nitriding at room temperature in Example 2 of the present invention.

[0039] Figure 8 This is an electron probe scanning cross-sectional image of a bulk material subjected to nitriding under the same experimental conditions as the material in Example 2 of this invention.

[0040] Figure 9 The graph showing the relationship between complex permeability and frequency was obtained from the composite material ring test in Example 2 of this invention.

[0041] Figure 10 The graph shows the relationship between loss and frequency obtained from the composite ring test in Example 2 of this invention, where (a) is before nitriding and (b) is after nitriding. Detailed Implementation

[0042] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0043] This invention provides a rare-earth alloy nitride composite soft magnetic material. This invention discovers that nitrogen (N) can be dissolved into Ce2(Fe) through the pyrolysis of nitrogen-rich compounds (NH3). x Co 1-x ) 17 The alloy, with its high local NH3 partial pressure, improves nitriding efficiency and depth, and can obtain alloy nitrides (rare earth alloy intermediate nitride materials) with a primary nitriding depth of not less than 75 micrometers. At the same time, the formation of an Fe4N coating layer on the surface of the alloy nitride not only improves the domain wall displacement and natural resonance frequency of the alloy nitride while maintaining good composite permeability in the MHz range, but also reduces losses, thus obtaining a high-performance rare earth alloy nitride composite soft magnetic material.

[0044] This rare-earth alloy nitride composite soft magnetic material comprises an alloy nitride and a coating layer located on the surface of the alloy nitride and covering the alloy nitride; wherein the alloy nitride has the composition Ce2(Fe) x Co 1-x ) 17 N 3-δ The coating layer is composed of Fe4N, and the rare earth alloy nitride composite soft magnetic material can be represented as Ce2(Fe x Co 1-x ) 17 N 3-δ @Fe4N. It may contain unavoidable impurities. Wherein, x is the mass ratio of Fe in the structure, 0.6≤x<1, preferably 0.6<x<0.9, more preferably 0.7<x<0.9, and even more preferably 0.7<x≤0.8, for example, x is 0.8;

[0045] Wherein, δ is the nitrogen deficiency coefficient in the structure, 1≤δ≤2.5, preferably 1≤δ≤2, more preferably 1≤δ≤1.5, and even more preferably 1≤δ≤1.2, for example, δ is 1;

[0046] According to a specific embodiment of the present invention, the chemical composition of the alloy nitride is RE2(Fe x Co 1-x ) 17 N2.

[0047] The method for preparing rare earth alloy intermediate nitride composite soft magnetic material of the present invention includes the following steps: (1) rare earth alloy material powder preparation step; (2) powder mixing step; (3) nitriding treatment step. After the nitriding treatment step, the rare earth alloy nitride composite soft magnetic material can be obtained. If further consideration is given to the subsequent application of the material, step (4) pressing the composite material into a ring can be added.

[0048] The following provides a detailed description of each step. It should be noted that these specific steps are merely illustrative of the invention and should not be construed as limiting the scope of the invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these modifications and improvements are all within the scope of protection of this invention.

[0049] Step (1) Rare earth alloy material powder preparation steps:

[0050] Ce, Fe, and Co metals were weighed according to a molar ratio of 2:17x:17(1-x), and a master alloy was obtained using a smelting furnace. This master alloy was then annealed in a vacuum furnace to obtain Ce2(Fe). x Co 1-x ) 17 Master alloy. Ce2(Fe) x Co 1-x ) 17 The master alloy is crushed and screened to obtain alloy powder.

[0051] RE2Fe 17 The crushing and screening range of the master alloy is selected from 50 to 200 micrometers, preferably 75 to 150 micrometers.

[0052] In this invention, there are no particular limitations on the method for obtaining the alloy from a single metal, and any method known in the art can be used. For example, high-frequency arc melting, medium-frequency casting, and strip casting can be used.

[0053] When using the medium-frequency casting method, a Φ50mm*50mm copper mold or a quartz crucible can be used. In some embodiments, the medium-frequency casting method may include the following steps: Ce, Fe, and Co metals are weighed according to a molar ratio of 2:17x:17(1-x) and placed in a crucible; the coil power is increased, the alloy mixture begins to melt and continues to mix to obtain a master alloy; the cut master alloy is placed in a vacuum furnace and annealed at 1000℃ for 10 days; after the annealing process, Ce2(Fe) x Co 1-x ) 17 The master alloy is quenched to obtain Ce2(Fe) x Co 1-x ) 17 alloy.

[0054] In this invention, Ce2(Fe) x Co 1-x ) 17 There are no particular limitations on the methods for obtaining alloy powder by crushing and screening the master alloy; any method known in the art can be used. For example, direct crushing and ball milling can be employed.

[0055] Step (2) Powder mixing step:

[0056] In this invention, the nitrogen-rich compound can be a compound containing a -NH3 functional group, which can be pyrolyzed at 100-200°C to release NH3. Preferably, the nitrogen-rich compound is selected from one or more of urea, ammonium bicarbonate, and amino acids. More preferably, the nitrogen-rich compound is selected from one of urea, ammonium bicarbonate, and amino acids. According to a specific embodiment of the present invention, the nitrogen-rich compound is urea.

[0057] The mass ratio of the nitrogen-rich compound to the alloy powder is 3 to 8:1, preferably 5 to 8:1, more preferably 6 to 8:1, and even more preferably 7 to 8:1.

[0058] Step (3) Nitriding treatment step:

[0059] The precursor is subjected to nitriding treatment to obtain the rare earth alloy nitride composite soft magnetic material.

[0060] Specifically, this includes placing the mixture into a heating device that can provide inert atmosphere protection, and subjecting it to nitriding treatment at 550–650°C for 1–3 hours under an initial inert gas pressure greater than or equal to 0.1 MPa.

[0061] During the nitriding process at 550–650°C, no flowing nitrogen source gas (such as N2, NH3, etc.) or hydrogen gas flow is provided.

[0062] Thus, on the one hand, this invention utilizes the pyrolysis of nitrogen-rich compounds to release NH3 components, providing a locally high-pressure active NH3 atmosphere to enable N to enter Ce2(Fe2+)2. x Co 1-x ) 17 The process of crystallizing and forming solid solution compounds; on the other hand, in the process of heating and annealing the mixture, the pyrolysis of nitrogen-rich compounds provides locally high-pressure NH3, which improves the penetration of N into Ce2(Fe) x Co 1-x ) 17Lattice efficiency and depth. Compared with traditional flowing atmosphere reduction methods, on the one hand, the entire nitriding process in this invention does not require the use of flowing gas to stabilize the gas pressure, thus avoiding the use of additional reducing agents or safety and exhaust gas treatment issues; on the other hand, the nitriding process in this invention is highly efficient and deep, reducing the particle size requirements of the alloy powder, and thus reducing the requirements for the powder's oxidation resistance; therefore, the overall process complexity is reduced, making the process simpler and cheaper.

[0063] In this invention, the inert atmosphere can be an initial protective gas atmosphere formed using nitrogen. The heating device described in this invention, capable of providing inert atmosphere protection, can be an inert atmosphere furnace.

[0064] The annealing temperature can be 550–650°C, preferably 550–600°C, and more preferably 550–580°C. The annealing time can be 1–3 hours, preferably 1.5–3 hours, and more preferably 2–2.5 hours.

[0065] The inventors of this application believe that Ce2(Fe) begins to form when the temperature rises to 400-450°C. x Co 1-x ) 17 N 3-δ Nanocrystals are formed and then dissolved in solid solution during the subsequent heating and annealing process to form an intermediate phase compound structure.

[0066] Step (4) Pressing into a ring:

[0067] The nitrided material powder was mixed with polyurethane (30-35 at.%, filler volume) and stirred under ultrasonic treatment using a solvent (e.g., acetone). Finally, the resulting mixture was placed in a ring mold with an outer diameter of 12 mm and an inner diameter of 6 mm, and molded at 90°C and 300 MPa for 10 min to obtain a composite material test ring. Its magnetic spectrum from 1 to 1000 MHz was then measured.

[0068] The following examples and comparative examples describe some of the test methods:

[0069] Electron probe image: JXA-IHP200F Hyper probe was used.

[0070] XRD pattern: Bruker D8 Advance.

[0071] Room temperature static magnetic properties plot: Quantum Design VersaLab.

[0072] High-frequency magnetic parameter diagram: using Agilent E4991A.

[0073] Example 1

[0074] The alloy nitride (rare earth alloy intermediate nitride material) in this embodiment is Ce2(Fe) 0.8 Co 0.2 ) 17 N2, i.e., x = 0.8, δ = 1.

[0075] The preparation method of this rare earth alloy intermediate nitride material is as follows:

[0076] Based on the molar ratio of Ce, Fe, and Co, the corresponding amounts of metals were cast in a medium-frequency induction furnace to obtain a master alloy; then, Ce2(Fe) was obtained by annealing in a vacuum furnace at 1000℃ for 10 days. 0.8 Co 0.2 ) 17 Master alloy; Ce2(Fe 0.8 Co 0.2 ) 17 The master alloy was crushed and screened to select Ce2(Fe) particles with a diameter of 100-150 micrometers. 0.8 Co 0.2 ) 17 1g of powder material;

[0077] Take 8g of urea and mix it thoroughly with the alloy powder to obtain a mixture; place the mixture in an inert atmosphere annealing apparatus, providing an initial N2 atmosphere of 0.1MPa; anneal at 575℃ for 120 minutes to obtain Ce2(Fe 0.8 Co 0.2 ) 17 N2 material.

[0078] X-ray diffraction patterns before and after nitriding are shown in the figure. Figure 1 The static magnetic properties at room temperature are visible Figure 2 Electron probe microanalysis cross-sectional images of bulk materials under the same nitriding conditions are shown below. Figure 3 High-frequency magnetic properties can be seen Figure 4 For loss performance, see Figure 5 .

[0079] Depend on Figure 1 It can be seen that the material obtained in Example 1 is Ce2Fe. 17 N3 phase (XRD-cobalt target), conforming to standard card PDF#97-065-8561.

[0080] Depend on Figure 2 It can be seen that the Ce2(Fe) obtained in this example 1 0.8 Co 0.2 ) 17 The N2 powder material achieves a static magnetic property of 140 emu / g at room temperature.

[0081] Depend on Figure 3It can be seen that the Ce2(Fe) obtained in this example 1 0.8 Co 0.2 ) 17 For N2 bulk materials, under the same nitriding conditions, the nitriding depth is not less than 75 μm, and a nitride structure is formed on the surface.

[0082] Depend on Figure 4 It can be seen that the composite material ring obtained in Example 1 has a theoretical domain wall displacement resonance frequency of 103.5MHz and a domain wall spin resonance frequency of 316.2MHz, according to magnetic spectrum simulation.

[0083] Depend on Figure 5 It can be seen that the composite ring obtained in Example 1, compared with the unnitrided Ce2(Fe) ring, has a higher density and better performance. 0.8 Co 0.2 ) 17 Material, Ce2(Fe) 0.8 Co 0.2 ) 17 The total loss of N2, especially the eddy current loss, is significantly reduced.

[0084] Example 2

[0085] In this embodiment, the rare earth alloy intermediate nitride material is Ce2(Fe). 0.6 Co 0.4 ) 17 N 1.5 That is, x = 0.6, δ = 1.5.

[0086] The preparation method of this easy-to-surface rare-earth alloy intermediate nitride soft magnetic material is as follows:

[0087] Based on the molar ratio of Ce and Fe, the corresponding amounts of metal are cast in a medium-frequency induction furnace to obtain a master alloy; then, Ce2(Fe) is obtained by annealing in a vacuum furnace at 1000℃ for 10 days. 0.6 Co 0.4 ) 17 Master alloy; Ce2Fe 17 The master alloy was crushed and screened to select Ce2(Fe) particles with a diameter of 63-100 micrometers. 0.6 Co 0.4 ) 17 1g of powder material;

[0088] 7.5g of urea was thoroughly mixed with alloy powder to obtain a mixture; the mixture was placed in an inert atmosphere annealing apparatus, with an initial N2 atmosphere of 0.1MPa; and annealed at 570℃ for 120 minutes to obtain Ce2(Fe 0.6 Co 0.4 ) 17 N 1.5 Material.

[0089] X-ray diffraction patterns before and after nitriding are shown in the figure. Figure 6 The static magnetic properties at room temperature are visible Figure 7 Electron probe microanalysis cross-sectional images of bulk materials under the same nitriding conditions are shown below. Figure 8 High-frequency magnetic properties can be seen Figure 9 For loss performance, see Figure 10 .

[0090] Depend on Figure 6 It can be seen that the material obtained in Example 2 is Ce2Fe. 17 N3 phase (XRD-cobalt target), conforming to standard card PDF#97-065-8561.

[0091] Depend on Figure 7 It can be seen that the Ce2(Fe) obtained in this example 2 0.6 Co 0.4 ) 17 N 1.5 The powder material achieves a static magnetic property of 121 emu / g at room temperature.

[0092] Depend on Figure 8 It can be seen that the Ce2(Fe) obtained in this example 2 0.6 Co 0.4 ) 17 N 1.5 For bulk materials, under the same nitriding conditions, the nitriding depth is greater than or equal to 75 μm, and a nitride structure is formed on the surface.

[0093] Depend on Figure 9 As can be seen from the magnetic spectrum simulation, the theoretical domain wall displacement resonance frequency of the composite ring in Example 2 is 113.6MHz and the domain wall spin resonance frequency is 206.9MHz.

[0094] Depend on Figure 10 It can be seen that the composite ring obtained in Example 2, compared with the unnitrided Ce2(Fe) ring, has a higher density and better performance. 0.6 Co 0.4 ) 17 Material, Ce2(Fe) 0.6 Co 0.4 ) 17 The total loss of N2, especially the eddy current loss, is significantly reduced.

[0095] Examples 3-7

[0096] Examples 3-7 used the same raw materials and preparation methods as Example 2, differing only in x, δ, annealing temperature, annealing time, and urea content. The static magnetic properties and composite surface resistivity of the materials obtained by nitriding in Examples 3-7 at room temperature are shown in the Ms column of Table 1. Comparative Examples 1-5 used a conventional 0.5MPa N2 atmosphere nitriding method (the specific nitriding process was as follows: at the temperatures set in each comparative example in Table 2, a flowing nitrogen source gas flow was introduced according to the gas flow rate in Table 2, and the nitriding process lasted for a set time). The static magnetic properties of the materials obtained by nitriding at room temperature and the surface resistivity of their composite materials are shown in the column of Table 2.

[0097] Table 1 List of material performance data in other embodiments

[0098]

[0099] Table 2 lists the performance data of the materials in Comparative Examples 1-5.

[0100]

[0101] As can be seen from Table 1 above, the nitriding condition window provided by the present invention can adjust Ce2(Fe) in a shorter time. x Co 1-x ) 17 N 3-δ To achieve higher nitrogen content and Ms, and simultaneously to obtain higher surface resistivity of the composite material by adjusting the coating layer. However, as shown in Table 2, the traditional high-flow-rate N2 gas nitriding method requires a longer time and higher initial gas pressure to adjust Ce2Fe. 17 N 3-δ Due to the low nitrogen content and Ms, the nitriding efficiency is low, and it is impossible to obtain a controllable coating structure or coating layer to significantly improve the surface resistivity of the composite material.

[0102] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A rare earth alloy nitride composite soft magnetic material, characterized in that, It includes an alloy nitride and a coating layer located on the surface of the alloy nitride and covering the alloy nitride; wherein the alloy nitride has the composition Ce2(Fe) x Co 1-x ) 17 N 3-δ The coating layer is composed of Fe4N, and the rare earth alloy nitride composite soft magnetic material is represented as Ce2(Fe x Co 1-x ) 17 N 3-δ @Fe4N; Where x is the proportion of Fe atoms in the structure, 0.6≤x<1; Where δ is the nitrogen deficiency coefficient in the structure, 1≤δ≤2.

5.

2. The rare earth alloy nitride composite soft magnetic material according to claim 1, characterized in that, The thickness of the coating layer is 0.1-2 μm.

3. A method for preparing the rare earth alloy nitride composite soft magnetic material according to claim 1 or 2, characterized in that, Includes the following steps: 1) The rare earth alloy material is crushed and sieved to obtain uniform alloy powder; 2) Mix the alloy powder with a nitrogen-rich compound to obtain a mixture; 3) The mixture is subjected to nitriding treatment to obtain the rare earth alloy nitride composite soft magnetic material having alloy nitride and coating layer.

4. The preparation method according to claim 3, characterized in that, The rare earth alloy material has a chemical composition of Ce2(Fe) x Co 1-x ) 17 Where x is the Fe atomic ratio, 0.6≤x<1, and the purity of the raw material is at least industrial purity.

5. The preparation method according to claim 3, characterized in that, The particle size range of the alloy powder is 75 micrometers to 150 micrometers.

6. The preparation method according to claim 3, characterized in that, The nitrogen-rich compound has a chemical structure rich in -NH3 groups and can pyrolyze at 100-400℃ to release NH3; the nitrogen-rich compound is selected from one or more of urea, ammonium bicarbonate, and amino acids, and its purity is at least industrial grade.

7. The preparation method according to claim 3, characterized in that, The mass ratio of the alloy powder to the nitrogen-rich compound is 3 to 8:

1.

8. The preparation method according to claim 3, characterized in that, Step 3) specifically involves placing the mixture into an inert atmosphere furnace or a heating device that can provide inert atmosphere protection, and performing nitriding treatment at 550–650°C under an initial nitrogen pressure greater than or equal to 0.1 MPa. After reaching the target temperature, the nitriding process takes 1–3 hours.

9. The preparation method according to claim 8, characterized in that, During the nitriding process at 550–650°C, no flowing nitrogen source gas or hydrogen gas stream is provided.

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