A device and method for surface coating and modification of rare earth permanent magnetic powder, and the magnetic powder and application thereof

Abstract

The application discloses a device and method for surface coating and modification of rare earth permanent magnetic powder, and a magnetic powder prepared by the method and application. The device comprises a box body and a reaction unit. The box body is provided with an air inlet, an air outlet and a transition bin. The reaction unit is arranged in the box body and comprises a reaction space composed of parallel vapor reactors, a deposition coating device and a container cover arranged above the vapor reactors and the deposition coating device. The method comprises the following steps: placing rare earth permanent magnetic powder and coating metal in the deposition coating device and a vapor generator respectively, heating the vapor generator and the deposition coating device to a required temperature, making coating metal vapor from the vapor generator enter the deposition coating device to form a coating layer on the surface of the magnetic powder, controlling the temperature of the deposition coating device for in-situ heat treatment, and cooling down to obtain the product. By setting and controlling the temperature and other conditions of the two reactors respectively, the coating modification process is realized, and the rare earth permanent magnetic powder is prevented from caking, decomposing or oxidizing.

Description

Technical Field

[0001] This invention belongs to the field of permanent magnet material preparation technology, and particularly relates to an apparatus and method for surface coating and modification of rare earth permanent magnet powder, as well as the magnetic powder obtained therefrom and its applications. Background Technology

[0002] Permanent magnet materials are widely used in high-tech fields such as new energy vehicles, 3C consumer electronics, aerospace, and advanced robotics. The thermal stability of permanent magnet materials is crucial to their service performance; generally, increasing the coercivity of the magnet helps improve thermal stability. Therefore, it is usually necessary to add heavy rare earth elements, such as Dy or Tb, to the starting alloy, or to use grain boundary diffusion technology to permeate heavy rare earth elements from the surface into the sintered NdFeB magnet to enhance the magnet's coercivity. However, these methods have drawbacks such as low utilization of heavy rare earth elements or limited diffusion depth leading to restrictions on magnet shape.

[0003] The current methods of coating and modifying permanent magnet powder cannot achieve efficient and precise processing of magnetic powder, and the performance and production efficiency of the magnetic powder cannot meet the needs of industrialization.

[0004] Patent 201710852677.1 discloses a surface treatment method for neodymium iron boron magnetic powder. However, the elemental rare earth metals used in this method have high melting points, which can cause the rare earth permanent magnet powder to clump together, rendering it unusable. Therefore, although the performance of the prepared bulk magnet is improved, no improvement in the oxidation resistance and magnetic properties of the magnetic powder itself is provided. Furthermore, the rotary heat treatment method used requires mixing the magnetic powder and the coating material together and heating them simultaneously, making it impossible to precisely control the coating amount.

[0005] Patent 201710848593.0 discloses another similar surface treatment method for neodymium iron boron magnetic powder, which also cannot effectively control the temperature and coating amount of the magnetic powder, and cannot perform heat treatment on the magnetic powder to further regulate its performance.

[0006] Patents 201811578159.6 and 201911076839.2 both disclose a surface treatment method for NdFeB anisotropic bonded magnetic powder, which is aimed at the modification of HDDR magnetic powder and is not applicable to the preparation of sintered magnets. Furthermore, they do not provide the magnetic properties and oxidation resistance of the magnetic powder after surface treatment.

[0007] Patent 202410766578.1 discloses a surface treatment method for anisotropic NdFeB magnetic powder, which modifies the surface of the magnetic powder using a non-aqueous chemical plating method. However, its preparation process is complex, and the oxygen content and magnetic properties of the modified powder are not disclosed.

[0008] Patent 202010060938.8 discloses a method to improve the oxidation corrosion resistance of NdFeB powder by using Al, Zn, Ni, Cu metals or their alloys to perform barrel plating on the magnetic powder. Although this improves the oxidation resistance of the magnetic powder, it does not improve the magnetic properties.

[0009] In view of the above, this application is hereby submitted. Summary of the Invention

[0010] The purpose of this invention is to provide an apparatus and method for coating and modifying the surface of rare earth permanent magnet powder, as well as the magnetic powder obtained therefrom and its applications. By setting up independent heating containers for holding rare earth permanent magnet powder and coating metal in a sealable box, and controlling the temperature of the two containers respectively, the coating metal evaporates and is uniformly deposited on the surface of rare earth permanent magnet powder. This allows for in-situ heat treatment and element surface diffusion of the coated powder, thereby avoiding agglomeration, decomposition or oxidation of the rare earth permanent magnet powder.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] In a first aspect, the present invention provides an apparatus for coating and modifying the surface of rare earth permanent magnet powder, comprising a housing and a reaction unit.

[0013] The housing is provided with an air inlet, an exhaust outlet, and a transition chamber for conveying or transferring materials; the reaction unit is located inside the housing and includes a reaction space consisting of a steam generator, a deposition coating device, and a container cover located above the steam generator and the deposition coating device, which connects the steam generator and the deposition coating device.

[0014] Secondly, the present invention also provides a method for coating and modifying the surface of rare earth permanent magnet powder using the aforementioned device, comprising the following steps:

[0015] Rare earth permanent magnet powder and coated metal are placed in the deposition coating device and vapor generator respectively, the container lid is closed, and the box is evacuated and / or a protective gas is introduced.

[0016] According to the temperature requirements for evaporating the coating metal and the coating temperature requirements, the vapor generator and the deposition coating device are heated to the required temperatures respectively, so that the coating metal vapor enters the deposition coating device from the vapor generator, contacts the rare earth permanent magnet powder, and forms a uniform coating layer on its surface.

[0017] Stop heating the steam generator and / or pass cooling water through the water-cooling pipes around the steam generator to solidify the cladding metal, thereby controlling the amount of steam generated;

[0018] Adjust the heating of the deposition coating device and / or introduce cooling water into the water-cooling pipes around the deposition coating device to control the temperature of the deposition coating device, so as to perform in-situ heat treatment or element diffusion treatment on the coated magnetic powder.

[0019] After the heat treatment is completed, heating of the deposition coating device is stopped and / or cooling water is introduced into the water-cooling pipes around the deposition coating device to rapidly cool the magnetic powder, thus obtaining the final product.

[0020] Thirdly, the present invention also provides a magnetic powder obtained using the described apparatus or the method described above. The magnetic powder can be used in the production of magnets in fields such as sintering, bonding, injection molding, and additive manufacturing.

[0021] Compared with the prior art, the present invention has the following technical effects:

[0022] This invention, by setting up independent heating containers for rare earth permanent magnet powder and coated metal in a sealable box, and controlling the temperature of the two containers separately, can simultaneously achieve functions such as coating metal melting, metal vapor generation, vapor deposition on the surface of permanent magnet powder, prevention of permanent magnet powder agglomeration or decomposition, permanent magnet powder heat treatment, and surface element diffusion.

[0023] The described apparatus and method are applicable to coated metals of any shape, melting temperature, and saturated vapor pressure. They can deposit and coat magnetic powder at any temperature, and the coating amount and thickness can be arbitrarily adjusted by controlling temperature and time. By employing a separate heating technology for the coating agent and magnetic powder, the problem of magnetic powder agglomeration when heated together with the coating agent in traditional methods is effectively avoided. In-situ heat treatment can also be performed to obtain magnetic powder with good oxidation resistance and magnetic properties. The obtained modified magnetic powder is not only suitable for preparing sintered magnets but also for preparing bonded magnets and other fields. The preparation process of this invention is simple, has low production cost, and is easy to scale up, demonstrating significant economic benefits and application prospects. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0025] Figure 1 This is a cross-sectional schematic diagram of the rare earth permanent magnet powder surface coating and modification device of the present invention.

[0026] Figure 2 This is a microscopic morphology diagram of the original magnetic powder.

[0027] Figure 3The images show the microstructure of the surface of the coated modified magnetic powder prepared in Example 1 of this invention, as well as the EDS spot scan elemental quantification results.

[0028] Figure 4 This is an EDS surface scan elemental distribution map of the coated modified magnetic powder surface obtained in Example 1 of the present invention.

[0029] Figure 5 This is a microscopic morphology diagram of the coated modified magnetic powder prepared in Comparative Example 1 of the present invention.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1-Rare earth permanent magnet powder; 2-Coated metal; 3-Coated metal vapor; 4-Box body; 5-Vapor generator; 6-Deposition coating device; 7-Heating wire; 8-Water cooling pipe; 9-Stirring device; 10-Container lid; 11-Air inlet; 12-Air extraction port; 13-Exhaust port; 14-Feed inlet; 15-Discharge port; 16-Insulation layer; 17-Transition chamber. Detailed Implementation

[0032] The embodiments of the present invention will be described in detail below with reference to specific examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the examples are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Any proportions and mass ratios not explicitly stated are arbitrary.

[0033] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0034] This invention provides an apparatus for coating and modifying the surface of rare earth permanent magnet powder, such as... Figure 1 As shown, it includes box 4 and reaction unit.

[0035] In this embodiment, the housing 4 is provided with an air inlet 11, an exhaust outlet 13, and a transition chamber 17 for conveying or transferring materials; the reaction unit is located inside the housing 4 and includes a reaction space consisting of a steam generator 5, a deposition coating device 6, and a container cover 10 located above the steam generator 5 and the deposition coating device 6, which connects the steam generator 5 and the deposition coating device 6.

[0036] The vapor generator 5 is used to hold the coated metal 2, and the deposition coating device 6 is used to hold the rare earth permanent magnet powder 1. The reaction space is a non-sealed space to facilitate subsequent vacuuming or introduction of protective gas. The container lid 10 helps to control the flow of the coated metal vapor 3 to the deposition coating device 6.

[0037] In a preferred embodiment, the inner surfaces of the steam generator 5 and the deposition coating 6 include replaceable inner liners. In a preferred embodiment, the container lid 10 can be made of a material with high thermal conductivity, such as a copper lid, to reduce the temperature difference between the container lid 10 and the steam generator 5, thereby effectively reducing the deposition of metal vapor on the container lid 10.

[0038] In this embodiment, both the steam generator 5 and the deposition coating device 6 are equipped with spaced-apart heating wires 7 and water-cooling pipes 8 on their outer peripheries, respectively, to control the temperature of the steam generator 5 and the deposition coating device 6. The spaced-apart water-cooling pipes 8 on the outer peripheries of the steam generator 5 and the deposition coating device 6 can rapidly cool the coated metal and rare-earth permanent magnet powder as needed, thereby controlling the amount of metal vapor generated and the coating amount on the surface of the permanent magnet powder, and achieving regulation of the rare-earth permanent magnet powder performance. Simultaneously, the combination of the water-cooling pipes 8 and the heating wires 7 allows for more precise and rapid temperature control.

[0039] In this embodiment, the deposition coating device 6 is equipped with a stirring device 9, which can fully mix the permanent magnet powder and the metal vapor, ensuring that the coating metal vapor is uniformly deposited on the powder surface to form a uniform coating layer, while avoiding powder agglomeration.

[0040] In this embodiment, the housing is also provided with an air extraction port 12 for evacuating the housing 4 and the reaction space of the steam generator 5 and the deposition coating device 6.

[0041] In this embodiment, a heat insulation layer 16 is also provided on the outer periphery of the heating wire 7 and water-cooling pipe 8 located at the intervals on the steam generator 5 and the deposition coating device 6. At the same time, a heat insulation layer 16 is also provided on the top surface and outer periphery of the container cover 10.

[0042] In this embodiment, a feed inlet 14 is provided above the box 4, and a discharge outlet 15 is provided below the box 4. These can be used to replace the transition chamber 17 or cooperate with the transition chamber 17 for the large-scale transportation and transfer of materials.

[0043] In this embodiment, the housing 4 is also provided with an operating hole (not shown in the figure), similar to the structure of a glove box, for operating the transfer of materials and / or the opening and closing of the container lid 10. The operating hole is provided with a glove cover for closing the operating hole.

[0044] This invention also provides a method for surface coating and modification of rare earth permanent magnet powder using the aforementioned device, comprising the following steps:

[0045] Rare earth permanent magnet powder 1 and coated metal 2 are placed in deposition coating device 6 and vapor generator 5 respectively, container lid 10 is covered, and the box 4 is evacuated and / or a protective gas is introduced.

[0046] According to the temperature requirements for evaporating the coating metal 2 and the coating temperature requirements, the steam generator 5 and the deposition coating device 6 are heated to the required temperatures, so that the coating metal vapor 3 enters the deposition coating device 6 from the steam generator 5, contacts the rare earth permanent magnet powder 1 and forms a coating layer on its surface.

[0047] Stop heating the steam generator 5 and / or introduce cooling water into the water-cooled pipe 8 around the steam generator 5 to solidify the cladding metal in order to control the amount of steam generated;

[0048] Adjust the temperature of the heated deposition coating device 6 and / or introduce cooling water into the water-cooling pipe 8 around the outer periphery of the deposition coating device 6 to control the temperature of the deposition coating device 6, so as to perform in-situ heat treatment on the coated magnetic powder.

[0049] After the heat treatment is completed, the heating of the deposition coating device 6 is stopped and / or cooling water is introduced into the water-cooling pipe 8 around the deposition coating device 6 to rapidly cool the magnetic powder and obtain the coated and modified magnetic powder.

[0050] In the embodiments, the rare earth permanent magnet powder 1 is preferably an alloy powder obtained by processes such as smelting, rapid solidification, hydrogen breaking, and air jet milling of rare earth iron-based alloys.

[0051] In the embodiments, the coating metal includes rare earth elements or rare earth-containing alloys LRE-HRE-M1-M2-M3;

[0052] The rare earth elements include Dy and / or Tb;

[0053] The LRE includes one or more of Pr, Nd, La, Ce or Y; the HRE includes Tb and / or Dy; and M1, M2, and M3 respectively include one or more of Cu, Al, Co, Sn, Bi, Mg, Ga, Zr or Zn.

[0054] In the embodiment, in the alloy LRE-HRE-M1-M2-M3, the atomic percentage of LRE is 35-45%, the atomic percentage of HRE is 15-30%, the atomic percentage of M1 is 10-20%, the atomic percentage of M2 is 10-20%, and the atomic percentage of M3 is 10-20%.

[0055] For example, the general chemical formula of the rare earth-containing alloy can be: Pr 17 Nd 24 Tb 15 Dy5Cu 15.4 Al13.6 Sn 10 Y7Pr 10 Nd 24 Tb 15 Dy5Co 15.4 Bi 13.6 Zn 10 Ce7Pr 10 Nd 24 Tb 15 Dy5Sn 15.4 Zn 13.6 Zr 10 、La7Pr 10 Nd 24 Tb 15 Dy5Mg 15. 4Ga 13.6 Zr 10 or Ce7Pr 10 Nd 24 Tb 15 Dy5Ga 15.4 Cu 13.6 Al 10 etc.

[0056] In the embodiments, the amount and ratio of rare earth permanent magnet powder 1 and coated metal 2 added are not specifically limited.

[0057] In this embodiment, the vacuuming is preferably performed to achieve a vacuum level of 3 × 10⁻⁶ within the system. -3 Below Pa. The protective gas can be nitrogen or argon.

[0058] In this embodiment, when forming the coating layer, the stirring device 9 is activated to ensure that the coating metal vapor 3 comes into full contact with the rare earth permanent magnet powder 1, forming a uniform coating layer on its surface. The stirring speed of the stirring device 9 is not limited in this embodiment, as long as it can prevent the rare earth permanent magnet powder from clumping and achieve a uniform deposition; preferably, the stirring speed is 30-40 r / min.

[0059] In this embodiment, the heating temperature of the steam generator 5 is not limited, as long as it is sufficient to cause the coated metal to evaporate and form steam; preferably, the evaporation temperature of the coated metal is 600-750°C.

[0060] In this embodiment, the heating temperature of the deposition coating device 6 is not limited, as long as it can achieve the effect of preventing rare earth permanent magnet powder from agglomerating and effectively depositing; preferably, the coating temperature is 400-550℃. Meanwhile, the coating time is not limited and is determined according to the required coating layer thickness; the preferred coating time range of this invention is 3-5 hours.

[0061] In this embodiment, the heat treatment temperature and time are not limited, as long as the diffusion effect and performance requirements are met; preferably, the heat treatment temperature is 450-600℃.

[0062] This invention also provides a magnetic powder prepared using the aforementioned apparatus or method. The magnetic powder can be used in the production of magnets using techniques such as sintering, bonding, injection molding, and additive manufacturing; furthermore, the magnetic powder can be used as a precursor powder for sintered magnets, bonded magnets, injection-molded magnets, and 3D-printed magnets.

[0063] The present invention will be further illustrated by the following examples.

[0064] Example 1

[0065] A method for surface coating and modification of rare earth permanent magnet powder:

[0066] (1) According to the general chemical formula Pr 17 Nd 24 Tb 15 Dy5Cu 15.4 Al 13.6 Sn 10 The chemical stoichiometric ratio in the formula is used to obtain alloy sheets as coating metal 2 through rapid solidification process, and the coating metal 2 and rare earth permanent magnet powder 1 are prepared according to a mass ratio of 2:1.

[0067] (2) The coated metal 2 and rare earth permanent magnet powder 1 from step (1) are transported from the transition chamber 17 through the operation hole and placed in the steam generator 5 and the deposition coating device 6 respectively, and the container cover 10 is closed; the exhaust port 12 is closed, the exhaust port 13 and the air inlet 11 are opened, and the air inside the box 4 is purged with high-purity argon until the oxygen content is below 0.1ppm.

[0068] (3) Close the exhaust port 13 and the air inlet 11, close the glove cover on the operating port, open the evacuation port 12, and evacuate the system to 1×10⁻⁶. -3 Below Pa;

[0069] (4) Heat the steam generator 5 to 750°C, and keep the deposition coating device 6 at 500°C by heating and cooling water, with an error of no more than 5°C. Start the stirring device 9 and keep it at 30 r / min for 5 hours of deposition coating.

[0070] (5) After the reaction is completed, the steam generator 5 stops heating and cools water is introduced to reduce the temperature to room temperature. The deposition coating device 6 stops cooling water and is heated to 600°C for in-situ heat treatment for 2 hours.

[0071] (6) After heat treatment, cooling water is introduced into the deposition coating device 6 to rapidly cool it to room temperature, thus obtaining the coated modified magnetic powder, such as Figure 3 and Figure 4 As shown, Figure 3 Elemental content analysis was performed on three points (1, 2, and 3). Based on the content, distribution, and microstructure of Tb / Cu, it can be seen that a coating layer was formed on the surface of the magnetic powder.

[0072] Performance testing was conducted using a vibrating sample magnetometer (VSM) to measure the magnetic properties of both the uncoated raw magnetic powder and the coated modified magnetic powder. Simultaneously, the oxygen content of the coated modified magnetic powder was measured after it was placed in air for 12 hours.

[0073] Example 2

[0074] The difference from Example 1 is that the coating metal 2 is Y7Pr. 10 Nd 24 Tb 15 Dy5Co 15.4 Bi 13.6 Zn 10 The performance testing method is the same as in Example 1.

[0075] Example 3

[0076] The difference from Example 1 is that the coating metal 2 is La7Pr. 10 Nd 24 Tb 15 Dy5Mg 15.4 Ga 13.6 Zr 10 The performance testing method is the same as in Example 1.

[0077] Example 4

[0078] The difference from Example 1 is that the coating metal 2 is Ce7Pr. 10 Nd 24 Tb 15 Dy5Sn 15.4 Zn 13.6 Zr 10 The performance testing method is the same as in Example 1.

[0079] Example 5

[0080] The difference from Example 1 is that the coating metal 2 is Ce7Pr. 10 Nd 24 Tb 15 Dy5Ga 15.4 Cu 13.6 Al 10 The performance testing method is the same as in Example 1.

[0081] Example 6

[0082] The difference from Example 1 is that the coating metal 2 is a Dy block. The performance testing method is the same as in Example 1.

[0083] Example 7

[0084] The difference from Example 1 is that the coating metal 2 is a Tb block. The performance testing method is the same as in Example 1.

[0085] The properties of the different coated metal-modified magnetic powders in Examples 1-7 are shown in Table 1.

[0086] Table 1. Performance comparison of different coated and modified magnetic powders in Examples 1-7

[0087]

[0088] As shown in Table 1, after the vapor formed by the melting of the coating metal is deposited on the surface of the magnetic powder, the coercivity is improved and the saturation magnetization is slightly reduced after in-situ heat treatment. Furthermore, the oxygen content of the coated magnetic powder does not increase significantly after 12 hours of exposure to air. Therefore, the coated magnetic powder exhibits good oxidation resistance and magnetic properties.

[0089] Example 8

[0090] The difference from Example 1 is that the deposition coating time in step (4) is 1 hour.

[0091] Example 9

[0092] The difference from Example 1 is that the deposition coating time in step (4) is 3 hours.

[0093] The thickness of the magnetic powder coating is shown in Table 2.

[0094] Table 2 Comparison of average thickness of magnetic powder coating obtained in Examples 1, 8, and 9

[0095]

[0096] Table 2 shows that by rapidly cooling the coated metal and rare earth permanent magnet powder, the amount of metal vapor generated and the amount of coating on the surface of the rare earth permanent magnet powder can be controlled, thereby achieving the regulation of the performance of the permanent magnet powder.

[0097] Comparative Example 1

[0098] A method for surface coating and modification of rare earth permanent magnet powder:

[0099] Step (1) is the same as in Example 1;

[0100] (2) The coated metal 2 and rare earth permanent magnet powder 1 from step (1) are transported from the transition chamber 17 through the operation hole and placed in different positions in the same reactor, that is, in the same heating environment. At the same time, it is ensured that the coated metal will not come into contact with the magnetic powder after melting, and the container lid 10 is covered. The exhaust port 12 is closed, the exhaust port 13 and the air inlet 11 are opened, and the air inside the box 4 is purged with high-purity argon until the oxygen content is below 0.1 ppm.

[0101] Step (3) is the same as in Example 1;

[0102] (4) Heat the same reactor to 750°C to reach the volatilization temperature of the coating agent and carry out evaporation coating for 5 hours;

[0103] (5) After the reaction is completed, the same reactor is cooled to 600℃ and subjected to in-situ heat treatment for 2 hours;

[0104] (6) After the heat treatment is completed, the same reactor is circulated with cooling water to quickly cool down to room temperature, and the coated modified magnetic powder is obtained.

[0105] The difference between this comparative example and Example 1 is that the coated metal and rare earth permanent magnet powder are placed in the same reactor. Therefore, the coated metal and rare earth permanent magnet powder are in the same heating environment and are not stirred. Other processes remain unchanged, such as... Figure 5 As shown, the magnetic powder obtained in Comparative Example 1 exhibited agglomeration, which is different from... Figure 2 The original magnetic powder and Figure 3 The coated modified magnetic powder obtained in Example 1 presents a stark contrast. Therefore, when the coated metal and rare earth permanent magnet powder are placed in the same reactor, in order to prevent the magnetic powder from agglomerating, the melting point of the coated metal cannot be higher than the agglomeration temperature of the magnetic powder. This places higher demands on the melting point of the coated metal, making the process more complex and increasing the difficulty of coating.

[0106] Comparative Example 2

[0107] A method for surface coating and modification of rare earth permanent magnet powder:

[0108] Steps (1) to (4) are the same as in Example 1;

[0109] (5) After the reaction is completed, cooling water is introduced into the steam generator 5 and the deposition coating device 6 to quickly cool down to room temperature, thus obtaining the coated modified magnetic powder.

[0110] Performance testing was conducted by using a vibrating sample magnetometer (VSM) to test the magnetic properties of the obtained coated modified magnetic powder.

[0111] The difference between this comparative example and Example 1 is that no subsequent heat treatment was performed after evaporation deposition.

[0112] Table 3 Comparison of magnetic properties of the original magnetic powder and the coated modified magnetic powder obtained in Example 1 and Comparative Example 2

[0113]

[0114] As shown in Table 3, in Comparative Example 2, when the rare earth permanent magnet powder particles underwent only one alloy coating without heat treatment, their coercivity increased by 2.35 kOe. In Example 1, after two heat treatments, the remanence and saturation of the magnetic powder did not change significantly, but the coercivity increased substantially. Therefore, heat treatment further enhances the performance of the magnetic powder.

[0115] Comparative Example 3

[0116] The difference from Example 1 is that no stirring was performed in step (4). The magnetic properties of the obtained coated modified magnetic powder were tested using a vibrating sample magnetometer (VSM).

[0117] Table 4. Comparison of magnetic properties of the coated modified magnetic powders obtained in Example 1 and Comparative Example 3

[0118]

[0119] As can be seen from Table 4, the performance of the coated modified magnetic powder obtained in Comparative Example 3 is slightly reduced. This may be due to uneven coating. Therefore, adding a stirring process during the deposition process can make the coating layer on the surface of the magnetic powder more uniform, thereby obtaining better performance.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0121] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. An apparatus for surface coating and modification of rare earth permanent magnetic powders, characterized in that, include The housing is provided with an air inlet, an exhaust outlet, and a transition chamber for conveying or transferring materials; The reaction unit is located inside the box and includes a reaction space consisting of a steam generator, a deposition coating device, and a container cover located above the steam generator and the deposition coating device, which connects the steam generator and the deposition coating device to each other; the reaction space is a non-sealed space, the steam generator is used to hold the coating metal, and the deposition coating device is used to hold rare earth permanent magnet powder. The outer periphery of both the steam generator and the deposition coating device is provided with spaced heating wires and water-cooling pipes, which are used to control the temperature of the steam generator and the deposition coating device, respectively. The deposition coating device is equipped with a stirring device; The container lid is made of a material with high thermal conductivity to reduce the temperature difference between the container lid and the steam generator, thereby reducing the deposition of metal vapor on the container lid.

2. The apparatus of claim 1, wherein, The box is also equipped with an air extraction port.

3. The apparatus of claim 2, wherein, A heat insulation layer is also provided on the outer periphery of the heating wires and water-cooling pipes located at the intervals on the steam generator and the deposition coating device; The top surface and / or outer periphery of the container lid are also provided with a heat insulation layer.

4. The apparatus of claim 1, wherein, The box body is also equipped with a feed inlet at the top; And / or, a discharge port is also provided at the bottom of the box; And / or, the housing is also provided with an operating hole.

5. A method for surface coating and modification of rare earth permanent magnetic powders using the apparatus of any one of claims 1-4, characterized in that, Includes the following steps: Rare earth permanent magnet powder and coated metal are placed in the deposition coating device and vapor generator respectively, the container lid is closed, and the box is evacuated and / or a protective gas is introduced. According to the temperature requirements for evaporating the coating metal and the coating temperature requirements, the vapor generator and the deposition coating device are heated to the required temperatures respectively, so that the coating metal vapor enters the deposition coating device from the vapor generator, contacts the rare earth permanent magnet powder, and forms a uniform coating layer on its surface. Stop heating the steam generator and introduce cooling water into the water-cooling pipes around the steam generator to rapidly solidify the cladding metal in order to control the amount of steam generated. Adjust the heating of the deposition coating device and / or introduce cooling water into the water-cooling pipes around the deposition coating device to control the temperature of the deposition coating device, so as to perform in-situ heat treatment on the coated magnetic powder. After the heat treatment is completed, heating of the deposition coating device is stopped and / or cooling water is introduced into the water-cooling pipes around the deposition coating device to rapidly cool the magnetic powder, thus obtaining the final product.

6. The method according to claim 5, characterized in that, When forming the coating layer, the stirring device is activated to allow the coating metal vapor to come into full contact with the rare earth permanent magnet powder, forming a uniform coating layer on its surface.

7. The method according to claim 5, characterized in that, The coating metal includes rare earth elements or rare earth-containing alloys LRE-HRE-M1-M2-M3; The rare earth elements include Dy and / or Tb; The LRE includes one or more of Pr, Nd, La, Ce or Y; the HRE includes Tb and / or Dy; and M1, M2, and M3 respectively include one or more of Cu, Al, Co, Sn, Bi, Mg, Ga, Zr or Zn.

8. The method according to claim 5, characterized in that, The temperature at which the coating metal evaporates is 600-900℃; And / or, the coating temperature is 400-550°C; And / or, the temperature of the heat treatment is 450-600℃.

9. A magnetic powder prepared by the apparatus according to any one of claims 1-4 or by the method according to any one of claims 5-8.

10. The magnetic powder according to claim 9, characterized in that, The magnetic powder is used in the fields of sintering, bonding, injection molding and additive manufacturing to produce magnets.

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