A rare earth permanent magnet diffusion source material and preparation method and grain boundary diffusion method
Through the preparation of rare earth permanent magnet diffusion source materials and grain boundary diffusion methods, the use of low thermal expansion coefficient ceramic carrier plates and blocking layers, combined with rare earth metal diffusion source layers, the oxidation problem of neodymium iron boron magnets was solved, the magnetic properties were improved and the process was simplified, making it suitable for large-scale production.
Patent Information
- Application Number
- CN202510929777.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-07
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2045-07-07
AI Technical Summary
Existing grain boundary diffusion technology easily leads to oxidation of NdFeB magnets, affecting magnetic properties and stability. In addition, traditional methods are complex and costly.
Rare earth permanent magnet diffusion source materials are used, including a carrier plate, a blocking layer and a diffusion source layer, and are prepared using vacuum coating technology. The carrier plate is made of low thermal expansion coefficient and high-temperature resistant ceramic materials, the blocking layer is composed of materials such as boron carbide, and the diffusion source layer is composed of rare earth metals and optional transition metals. The magnetic properties are improved through thermal diffusion.
It effectively prevents NdFeB magnets from oxidation, simplifies processes, improves coercivity and thermal stability, reduces costs, and is suitable for large-scale mass production.
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Figure CN120425293B_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the field of rare earth permanent magnet technology, and in particular relates to a rare earth permanent magnet diffusion source material, a preparation method, and a grain boundary diffusion method. Background Art
[0002] With the widespread application of sintered NdFeB materials in new energy vehicles, industrial robots, and mobile intelligence, the demand for lighter, thinner, smaller, and more energy-efficient products is increasing. This, in turn, places higher demands on the magnetic energy product, coercivity, and thermal stability of NdFeB magnets. However, under traditional manufacturing processes, it is difficult to achieve both high coercivity and high magnetic energy product in sintered NdFeB. While doping with heavy rare earth elements such as Dy or Tb can increase coercivity, it significantly reduces remanence and is expensive. Therefore, further increasing coercivity while maintaining high remanence has become a key challenge for industry research and development.
[0003] In recent years, grain boundary diffusion technology has emerged. This technology forms a heavy rare earth film on the surface of NdFeB magnets, which then enters the magnets along the grain boundaries through vacuum heat treatment, forming a high-coercivity shell. This effectively increases the coercivity while minimizing the reduction in remanence. Currently, this technology is primarily achieved through two methods: one is to use terbium and / or dysprosium targets as diffusion source materials, coating the NdFeB magnets by sputtering or evaporation, followed by thermal diffusion, or through multiple coating and thermal diffusion steps. However, NdFeB magnets undergo multiple manufacturing processes and are exposed to a variety of environments, making them susceptible to damage and oxidation. Oxidation can lead to the formation of a loose oxide layer (such as iron and neodymium oxides) on the magnet surface, destroying the grain boundary structure and reducing the continuity of the magnetic domains, resulting in a decrease in coercivity and remanence loss. Furthermore, the energy product of oxidized magnets degrades more significantly at high temperatures, and this also affects the stability of the NdFeB magnets. Another method is to print or coat slurry on the surface of the NdFeB magnet, and then perform high-temperature degreasing and thermal diffusion. However, during the degreasing process, the NdFeB magnet is easily oxidized, which deteriorates the magnetic properties. In addition, the degreasing may not be complete, and there is a risk of organic matter residue, which reduces the coercive force improvement effect.
[0004] Therefore, there is an urgent need to develop a rare earth permanent magnet diffusion source material that can significantly improve the magnetic properties of NdFeB magnets. Summary of the Invention
[0005] The purpose of this application is to provide a rare earth permanent magnet diffusion source material, a preparation method and a grain boundary diffusion method, aiming to solve the problem that the existing grain boundary diffusion technology easily leads to oxidation of neodymium iron boron magnets.
[0006] To achieve the above application objectives, the technical solutions adopted in this application are as follows:
[0007] In a first aspect, the present application provides a rare earth permanent magnet diffusion source material, comprising:
[0008] Loading plate;
[0009] A blocking layer formed on at least one surface of the carrier plate;
[0010] a diffusion source layer formed on a surface of the blocking layer away from the carrier plate;
[0011] Wherein, the carrier plate is made of a material with a thermal expansion coefficient lower than 12×10 -6 / ℃, made of ceramic material with heat-resistant temperature higher than 1000℃;
[0012] The material of the blocking layer includes at least one of boron carbide, boron nitride, tungsten carbide, silicon nitride, and titanium boride;
[0013] The material of the diffusion source layer includes rare earth metals and optionally transition metals.
[0014] In a second aspect, the present application provides a method for preparing a rare earth permanent magnet diffusion source material, comprising the following steps:
[0015] Provide a carrier plate;
[0016] A blocking layer target material is used as a raw material, and a vacuum coating technology is used to deposit a blocking layer on at least one surface of the carrier plate; the blocking layer target material includes at least one of a boron carbide target material, a boron nitride target material, a tungsten carbide target material, a silicon nitride target material, and a titanium boride target material;
[0017] A diffusion source layer is prepared on the surface of the blocking layer away from the supporting plate to obtain a rare earth permanent magnet diffusion source material.
[0018] In a third aspect, the present application provides a grain boundary diffusion method, comprising the following steps:
[0019] Pre-treating the substrate to be diffused;
[0020] The substrate to be diffused is placed on the rare earth permanent magnet diffusion source material provided in this application or the diffusion source layer of the rare earth permanent magnet diffusion source material prepared by the preparation method provided in this application, and then subjected to thermal diffusion treatment to obtain a rare earth permanent magnet.
[0021] Compared with the prior art, this application has the following beneficial effects:
[0022] The rare earth permanent magnet diffusion source material provided in the first aspect of the present application includes a supporting plate as the matrix of the diffusion source material, providing mechanical support, and is made of a material with a low thermal expansion coefficient and high temperature resistance, effectively preventing deformation or cracking during high temperature thermal diffusion, thereby preventing the blocking layer and the diffusion source layer from peeling off, and preventing the diffusion source from reversely penetrating and affecting the diffusion effect of the rare earth permanent magnet. The blocking layer provided between the supporting plate and the diffusion source layer has good material stability, corrosion resistance, low oxidation resistance, and does not react with rare earth metals and transition metals, thereby effectively blocking the migration of rare earth metal and transition metal atoms to the supporting plate, thereby effectively improving the diffusion effect of the rare earth permanent magnet. The rare earth metal contained in the diffusion source layer is used to diffuse into the grain boundaries of the rare earth permanent magnet through the grain boundaries, thereby improving the magnetic properties of the rare earth permanent magnet, such as coercivity and thermal stability, and the optional transition metal helps to promote the liquid phase diffusion of rare earth along the grain boundaries, promote the diffusion depth and shorten the diffusion time. Therefore, the rare earth permanent magnet diffusion source material of the present application can significantly improve the magnetic properties of the rare earth permanent magnet through the synergistic effects of the thermal stability of the supporting plate, the reverse diffusion blocking of the blocking layer, and the grain boundary optimization of the diffusion source layer; at the same time, it simplifies the thermal diffusion process, effectively avoids damage and oxidation of the rare earth permanent magnet, and can perform thermal diffusion treatment on rare earth permanent magnets in large quantities.
[0023] The second aspect of the present application provides a method for preparing a rare earth permanent magnet diffusion source material. By utilizing vacuum coating technology to deposit a blocking layer on at least one surface of a carrier plate, and then preparing a diffusion source layer on a surface of the blocking layer away from the carrier plate, the rare earth permanent magnet diffusion source material can be prepared. Therefore, the preparation process of the diffusion source material of the present application is simple, easy to operate, and suitable for large-scale mass production.
[0024] The third aspect of this application provides a grain boundary diffusion method that simply places the substrate to be diffused on a diffusion source layer of the rare earth permanent magnet diffusion source material provided herein for thermal diffusion. Compared to conventional methods that involve coating the substrate to be diffused and then thermally diffusing it, this method offers a simpler process and a single contact environment, effectively protecting the rare earth permanent magnet from damage and oxidation. This method can significantly increase coercivity while maintaining high remanence. Furthermore, this method can also be used to thermally diffuse rare earth permanent magnets in large quantities, improving production efficiency and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.
[0026] Figure 1This is a schematic structural diagram of a rare earth permanent magnet diffusion source material provided in one embodiment of the present application;
[0027] Figure 2 This is a schematic structural diagram of a rare earth permanent magnet diffusion source material provided by another embodiment of the present application;
[0028] Figure 3 This is a schematic diagram of loading the matrix to be diffused - rare earth permanent magnet diffusion source material provided in one embodiment of the present application;
[0029] Figure 4 This is a schematic diagram of loading the matrix to be diffused - rare earth permanent magnet diffusion source material provided by another embodiment of the present application;
[0030] Figure 5 This is a schematic diagram of loading the matrix to be diffused - rare earth permanent magnet diffusion source material provided by another embodiment of the present application.
[0031] Among them, the reference numerals in the figures are:
[0032] 1—carrying plate, 2—blocking layer, 3—diffusion source layer. DETAILED DESCRIPTION
[0033] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.
[0034] The first aspect of the embodiment of the present application provides a rare earth permanent magnet diffusion source material, such as Figure 1 and Figure 2 As shown, including:
[0035] Loading plate 1;
[0036] a blocking layer 2 formed on at least one surface of the carrier plate 1;
[0037] a diffusion source layer 3 formed on a surface of the blocking layer 2 away from the carrier plate 1;
[0038] The load-bearing plate 1 has a thermal expansion coefficient lower than 12×10 -6 / ℃, made of ceramic material with heat-resistant temperature higher than 1000℃;
[0039] The material of the blocking layer 2 includes at least one of boron carbide, boron nitride, tungsten carbide, silicon nitride, and titanium boride;
[0040] The material of the diffusion source layer 3 includes rare earth metals and optionally transition metals.
[0041] The rare earth permanent magnet diffusion source material provided in the embodiment of the present application, the carrier plate contained therein serves as the matrix of the diffusion source material, provides mechanical support, and is made of a material with low thermal expansion coefficient and high temperature resistance, effectively preventing deformation or cracking during high temperature thermal diffusion, thereby preventing the blocking layer and the diffusion source layer from peeling off, and preventing the diffusion source from reversely penetrating or generating other components at high temperature and affecting the diffusion effect of the rare earth permanent magnet. The blocking layer provided between the carrier plate and the diffusion source layer has good material stability, corrosion resistance, non-oxidation, and does not react with rare earth metals and transition metals, thereby effectively blocking the migration of rare earth metal and transition metal atoms to the carrier plate, thereby effectively improving the diffusion effect of the rare earth permanent magnet. The rare earth metal contained in the diffusion source layer is used to diffuse into the grain boundaries of the rare earth permanent magnet through the grain boundaries, thereby improving the magnetic properties of the rare earth permanent magnet, such as coercivity and thermal stability, and the optional transition metal helps to promote the liquid phase diffusion of rare earth along the grain boundaries, promote the diffusion depth and shorten the diffusion time. Therefore, the rare earth permanent magnet diffusion source material of the present application can significantly improve the magnetic properties of the rare earth permanent magnet through the synergistic effects of the thermal stability of the supporting plate, the reverse diffusion blocking of the blocking layer, and the grain boundary optimization of the diffusion source layer; at the same time, it simplifies the thermal diffusion process, effectively avoids damage and oxidation of the rare earth permanent magnet, and can perform thermal diffusion treatment on rare earth permanent magnets in large quantities.
[0042] In some embodiments, the cross-sectional shape of the rare earth permanent magnet diffusion source material can be selected in a variety of ways. Figure 1 and 2 As shown, its cross-sectional shape can be designed to be square or arc-shaped, etc., so that it is easy to match or load with the substrate to be diffused in a strip or ring structure, as shown in FIG. Figure 3 and 5 Of course, this is not a fixed pattern. Considering the diverse needs in practical applications, rare earth permanent magnet diffusion source materials can also be made into various special-shaped structures to meet the special requirements of different scenarios.
[0043] In some embodiments, the material of the diffusion source layer 3 may comprise only rare earth metals, which may include one or more of terbium, dysprosium, and praseodymium. Terbium and / or dysprosium form a high-coercivity shell through grain boundary diffusion, which can significantly improve the coercivity and temperature stability of the rare earth permanent magnet. At the same time, terbium and / or dysprosium form a non-ferromagnetic rare earth-rich phase at the grain boundaries, which can inhibit the nucleation of antimagnetic domains, avoid the magnetic dilution effect of the main phase grains, and reduce remanence loss. Praseodymium coexists with neodymium at the grain boundaries to form a low-melting-point eutectic phase, which can enhance the permeability of the grain boundaries and optimize the continuity of the grain boundaries.
[0044] In some embodiments, the material of the diffusion source layer 3 may include rare earth metals and transition metals. The rare earth metals include one or more of terbium, dysprosium, and praseodymium; and the transition metals include one or more of aluminum and copper. Aluminum and / or copper can promote liquid phase diffusion of rare earth elements along grain boundaries, increasing diffusion depth and shortening diffusion time.
[0045] In some embodiments, the ceramic material includes alumina or zirconia. Both alumina and zirconia have low thermal expansion coefficients and good high-temperature stability. Therefore, using alumina or zirconia as the carrier plate not only effectively prevents deformation or cracking during high-temperature thermal diffusion, preventing the blocking layer and diffusion source layer from flaking, but also effectively prevents reverse permeation of the diffusion source, ensuring the diffusion effect of the rare earth permanent magnet.
[0046] In some embodiments, the relative density of the carrier plate is 95-99.5%, preferably 98-99.5%. This relative density range ensures that the carrier plate has high mechanical strength and does not deform during subsequent thermal diffusion treatment.
[0047] In some embodiments, the flatness of the carrier plate is 0.1~0.3mm, and the roughness Ra is 0.1~0.5μm; this flatness and roughness range can ensure that the roughness Ra of the subsequently formed blocking layer is 0.2~1μm, and the roughness Ra of the diffusion source layer is 0.5~2μm, which is beneficial to increase the contact area between the diffusion source layer and the rare earth permanent magnet and ensure the thermal diffusion effect.
[0048] In some embodiments, the blocking layer has a thickness of 1 to 50 μm, preferably 5 to 30 μm; this thickness range effectively blocks reverse osmosis of the diffusion source layer and improves the diffusion effect.
[0049] In some embodiments, the thickness of the diffusion source layer is 2-50 μm, preferably 5-30 μm. The thickness of the diffusion source layer can be adjusted according to actual application conditions.
[0050] A second aspect of the present application provides a method for preparing the rare earth permanent magnet diffusion source material described above, comprising the following steps:
[0051] S11: Provide a carrier plate;
[0052] S12: using a blocking layer target as a raw material, depositing a blocking layer on at least one surface of the carrier plate by using a vacuum coating technology; the blocking layer target comprises at least one of a boron carbide target, a boron nitride target, a tungsten carbide target, a silicon nitride target, and a titanium boride target;
[0053] S13: preparing a diffusion source layer on the surface of the blocking layer away from the supporting plate to obtain a rare earth permanent magnet diffusion source material.
[0054] The method for preparing rare earth permanent magnet diffusion source materials provided in the embodiments of the present application utilizes vacuum coating technology to deposit a blocking layer on at least one surface of a carrier plate, and then prepares a diffusion source layer on a surface of the blocking layer away from the carrier plate, thereby achieving the preparation of rare earth permanent magnet diffusion source materials. Therefore, the preparation process of the diffusion source materials of the present application is simple, easy to operate, and suitable for large-scale mass production.
[0055] In the above-mentioned step S11, in some embodiments, the step of preparing the supporting plate includes: configuring the ceramic powder into a slurry; the ceramic powder includes alumina powder and zirconia powder; the slurry is injection molded and dried, or the slurry is spray granulated and isostatically pressed to obtain a green body; the green body is sintered and machined to obtain the supporting plate.
[0056] In some specific embodiments, the step of preparing the ceramic powder into a slurry may include adding the ceramic powder, polyethylene glycol, higher alcohol, and pure water to a ball mill and milling at a speed of 200 to 1500 rpm for 6 to 18 hours to obtain a slurry having a solid content of 60 to 70%. The amount of polyethylene glycol added is 0.1 to 1% by weight of the ceramic powder, and the amount of higher alcohol added is 0.1 to 0.5% by weight of the ceramic powder.
[0057] In some specific embodiments, the steps of slip casting and drying the slurry may include: placing the slurry into a vacuum tank, vacuum degassing, and then injecting the slurry into a sealed resin or graphite mold cavity at a pressure of 0.2~1.5MPa until no water drips out of the mold, opening the mold, taking out the solidified green body, and standing it at room temperature for 24 hours to obtain the green body.
[0058] In some specific embodiments, the steps of spray granulation and isostatic pressing of the slurry may include: introducing the slurry into a centrifugal spray granulator, setting the inlet temperature to 200~250°C and the outlet temperature to 80~100°C, and then spray granulating to obtain granulated powder; loading the granulated powder into a stainless steel mold, pre-pressing and then isostatically pressing at a pressure of 200~250MPa to obtain a green body.
[0059] In some embodiments, the sintering process is performed at a temperature of 1400-1600° C. and for a time of 12-48 hours.
[0060] In some embodiments, the machining process may be grinding, lapping or polishing the sintered body so that the flatness of the surface of the carrier plate is 0.1-0.3 mm and the roughness Ra is 0.1-0.5 μm.
[0061] In some embodiments, the supporting plate may be a square block or a circular block with a thickness of 5 to 20 mm.
[0062] In step S12, the boron carbide target, boron nitride target, tungsten carbide target, silicon nitride target, titanium boride target, and the like can all be commercially available, conventional products. Vacuum coating techniques may include magnetron sputtering or reactive plasma deposition. Coating can be performed using techniques and conditions described in relevant literature or according to product specifications. Parameters such as coating time can be adjusted based on the actual thickness of the blocking layer. Specifically, the blocking layer can be deposited on one or more surfaces of a carrier plate.
[0063] In the above step S13, in some embodiments, the step of preparing a diffusion source layer on the surface of the blocking layer away from the carrier plate includes: using a rare earth metal target as a raw material, and using vacuum coating technology to deposit the diffusion source layer on the surface of the blocking layer away from the carrier plate; the rare earth metal target includes a rare earth metal and optionally a transition metal; specifically, the vacuum coating technology may include magnetron sputtering or reactive plasma deposition, and the coating can be carried out according to the technology or conditions described in the literature in this field, or according to the product manual. Parameters such as the coating time can be adjusted according to the actual diffusion layer thickness. The rare earth metal target can include only rare earth metals, or it can include rare earth metals and transition metals. When the rare earth metal target includes rare earth metals and transition metals, the mass ratio of rare earth metals to transition metals is preferably (1-4) / (6-9). The rare earth metal targets in the embodiments of the present application, whether pure rare earth metal targets or rare earth metal targets doped with transition metals such as aluminum and copper, can be conventional products obtained from the market.
[0064] In some embodiments, a rare earth metal diffusion source slurry is coated on the surface of the blocking layer away from the carrier plate, and then dried and degreased to form a diffusion source layer; the rare earth metal diffusion source slurry includes rare earth metal powder and optionally transition metal powder.
[0065] In some specific embodiments, the particle size of the rare earth metal powder is 1-5 μm; the particle size of the transition metal powder is 1-5 μm. This particle size range can ensure the coating uniformity and density of the diffusion source layer, thereby helping to improve the grain boundary diffusion efficiency.
[0066] In some specific embodiments, the rare earth metal diffusion source slurry includes the following components in weight percentage: rare earth metal powder and optionally transition metal powder 50-80%, isobutanol 13-36%, diethyl phthalate 2-4%, and hydroxyethyl cellulose 5-10%; wherein, the rare earth metal diffusion source slurry may include only rare earth metal powder or may include rare earth metal powder and transition metal powder. When the rare earth metal diffusion source slurry includes only rare earth metal powder, the weight percentage of the rare earth metal powder in the rare earth metal diffusion source slurry is 50-80%; when the rare earth metal diffusion source slurry includes rare earth metal powder and transition metal powder, the weight percentage of the rare earth metal powder in the rare earth metal diffusion source slurry is 5-32%, and the weight percentage of the transition metal powder is 45-48%.
[0067] In some specific embodiments, the rare earth metal powder includes at least one of terbium powder, dysprosium powder, and praseodymium powder; and the transition metal powder includes at least one of aluminum powder and copper powder.
[0068] A third aspect of the present application provides a grain boundary diffusion method, comprising the following steps:
[0069] S21: pre-treating the substrate to be diffused;
[0070] S22: placing the substrate to be diffused on the rare earth permanent magnet diffusion source material provided in the present application or the diffusion source layer of the rare earth permanent magnet diffusion source material prepared by the preparation method provided in the present application, and then performing thermal diffusion treatment to obtain a rare earth permanent magnet.
[0071] The grain boundary diffusion method provided in the embodiments of the present application simply places the substrate to be diffused on the diffusion source layer of the rare earth permanent magnet diffusion source material provided in the present application for thermal diffusion treatment. Compared with the conventional method of coating the substrate to be diffused and then thermally diffusing, the grain boundary diffusion method of the present application for rare earth permanent magnets has a simple process and a single contact environment, effectively protecting the rare earth permanent magnets from damage and oxidation, thereby significantly improving the coercive force while maintaining high remanence. Furthermore, the grain boundary diffusion method of the present application can also be used to thermally diffuse rare earth permanent magnets in large quantities, improving production efficiency and reducing costs.
[0072] In some embodiments, the pre-treatment includes: performing surface treatment on the substrate to be diffused, specifically degreasing, cleaning, and pickling the substrate to be diffused, so that the surface of the substrate to be diffused is free of impurities and oxide skin, thereby helping to improve the grain boundary diffusion effect of the diffusion source.
[0073] In some embodiments, the thermal diffusion treatment is performed at a temperature of 750-950° C. and for a time of 2-48 hours.
[0074] In some embodiments, in order to improve the grain boundary diffusion efficiency and the magnetic properties of the matrix to be diffused, the matrix to be diffused can be treated by double-sided grain boundary diffusion, specifically as follows: Figure 4 As shown. That is, the pre-treated substrate to be diffused is first placed on the diffusion source layer of the rare earth permanent magnet diffusion source material provided in this application or the rare earth permanent magnet diffusion source material prepared by the preparation method provided in this application, and then the rare earth permanent magnet diffusion source material provided in this application or the diffusion source layer of the rare earth permanent magnet diffusion source material prepared by the preparation method provided in this application is inverted on the substrate to be diffused, and then thermal diffusion treatment is performed to obtain a rare earth permanent magnet. This double-sided grain boundary diffusion method can not only improve the efficiency of grain boundary diffusion, but also use the inverted rare earth permanent magnet diffusion source material to press the substrate to be diffused, so that the substrate to be diffused and the diffusion source layer are closely fitted, thereby enhancing the grain boundary diffusion effect.
[0075] The following describes the details in conjunction with specific embodiments.
[0076] 1. Rare earth permanent magnet diffusion source materials and preparation methods
[0077] Example A1
[0078] This embodiment provides a rare earth permanent magnet diffusion source material comprising: an alumina carrier plate (size: 50×50×10 mm), a boron carbide blocking layer formed on the surface of the carrier plate, and a rare earth diffusion source layer formed on the surface of the blocking layer away from the carrier plate; wherein the carrier plate has a relative density of 99.1%, a flatness of 0.2 mm, a roughness Ra of 0.3 μm, a thickness of the blocking layer of 25 μm, a roughness Ra of 0.5 μm, a thickness of the rare earth diffusion source layer of 30 μm, a roughness Ra of 1.0 μm, and the material is Tb (terbium).
[0079] The method for preparing the rare earth permanent magnet diffusion source material of this embodiment includes the following steps:
[0080] S11: Preparation of alumina carrier plate
[0081] Alumina powder, polyethylene glycol, higher alcohol and pure water were added to a ball mill and ball milled at 800 rpm for 12 h to obtain a slurry with a solid content of 65%. The amount of polyethylene glycol added was 0.5% of the mass of the alumina powder, and the amount of higher alcohol added was 0.3% of the mass of the alumina powder.
[0082] The slurry was placed in a vacuum tank and after vacuum degassing, the slurry was injected into the sealed graphite mold cavity at a pressure of 0.8 MPa until no water dripped out of the mold. The mold was opened, the solidified green body was taken out, and it was left to stand at room temperature for 24 hours to obtain the green body;
[0083] The green body is placed in a high-temperature sintering furnace, initially heated to 1500°C and kept warm for 24 hours, and then naturally cooled and ground and polished to obtain an alumina carrier plate;
[0084] After testing, the flatness of the load-bearing plate is 0.2mm and the roughness Ra is 0.3μm;
[0085] S12: Preparation of Boron Carbide Blocking Layer
[0086] Using boron carbide target as raw material and alumina carrier plate as substrate, magnetron sputtering equipment is used to perform sputtering coating under the conditions of argon atmosphere, pressure of 1.0 Pa and sputtering power of 100 W to form a boron carbide blocking layer on the surface of the carrier plate;
[0087] After testing, the thickness of the boron carbide blocking layer is 25μm and the roughness Ra is 0.5μm;
[0088] S13: Preparation of diffusion source layer
[0089] Using a Tb target (purity of 99.99%) as a raw material and an alumina carrier plate with a boron carbide blocking layer deposited on it as a substrate, a magnetron sputtering device was used to perform sputtering coating under the conditions of an argon atmosphere, a pressure of 1.0 Pa, and a sputtering power of 100 W. A rare earth diffusion source layer was formed on the boron carbide blocking layer to obtain a rare earth permanent magnet diffusion source material.
[0090] After testing, the thickness of the rare earth diffusion source layer is 30 μm and the roughness Ra is 1.0 μm.
[0091] Example A2
[0092] This embodiment provides a rare earth permanent magnet diffusion source material, which differs from embodiment A1 in that the boron carbide blocking layer is replaced with a boron nitride blocking layer.
[0093] The method for preparing the rare earth permanent magnet diffusion source material in this embodiment is different from that in embodiment A1 in that step S12 uses a boron nitride target as a raw material to obtain a boron nitride blocking layer.
[0094] Example A3
[0095] This embodiment provides a rare earth permanent magnet diffusion source material. The difference from embodiment A1 is that the material of the rare earth diffusion source layer is replaced with Tb 0.7 Pr 0.1 Al 0.1 Cu 0.1 .
[0096] The difference between the method for preparing rare earth permanent magnet diffusion source materials in this embodiment and that in embodiment A1 is that step S13 is to use Tb 0.7 Pr 0.1 Al 0.1Cu 0.1 The target material is the raw material.
[0097] Comparative Example A1
[0098] This comparative example provides a rare earth permanent magnet diffusion source material including: an alumina carrier plate (size 50×50×10 mm) and a rare earth diffusion source layer formed on the surface of the alumina carrier plate; wherein, the relative density of the carrier plate is 99.1%, the flatness is 0.2 mm, the roughness Ra is 0.3 μm, the thickness of the rare earth diffusion source layer is 30 μm, the roughness Ra is 0.9 μm, and the material is Tb (terbium).
[0099] The preparation method of the rare earth permanent magnet diffusion source material of this comparative example comprises the following steps:
[0100] S11: Preparation of alumina carrier plate
[0101] Alumina powder, polyethylene glycol, higher alcohol and pure water were added to a ball mill and ball milled at 800 rpm for 12 h to obtain a slurry with a solid content of 65%. The amount of polyethylene glycol added was 0.5% of the mass of the alumina powder, and the amount of higher alcohol added was 0.3% of the mass of the alumina powder.
[0102] The slurry was placed in a vacuum tank and after vacuum degassing, the slurry was injected into the sealed graphite mold cavity at a pressure of 0.8 MPa until no water dripped out of the mold. The mold was opened, the solidified green body was taken out, and it was left to stand at room temperature for 24 hours to obtain the green body;
[0103] The green body is placed in a high-temperature sintering furnace, initially heated to 1500°C and kept warm for 24 hours, and then naturally cooled and ground and polished to obtain an alumina carrier plate;
[0104] After testing, the flatness of the load-bearing plate is 0.2mm and the roughness Ra is 0.3μm;
[0105] S12: Preparation of diffusion source layer
[0106] Using a Tb target (purity of 99.99%) as a raw material and an alumina carrier plate as a substrate, a magnetron sputtering device was used to perform sputtering coating under the conditions of an argon atmosphere, a pressure of 1.0 Pa, and a sputtering power of 100 W to form a rare earth diffusion source layer on the surface of the alumina carrier plate to obtain a rare earth permanent magnet diffusion source material;
[0107] After testing, the thickness of the rare earth diffusion source layer is 30 μm and the roughness Ra is 0.9 μm.
[0108] Comparative Example A2
[0109] This comparative example provides a rare earth permanent magnet diffusion source material, which differs from Example A1 in that the aluminum oxide carrier plate is replaced with a chromium nitride carrier plate.
[0110] The preparation method of the rare earth permanent magnet diffusion source material in this comparative example differs from that in Example A1 in that:
[0111] S11: Preparation of chromium nitride carrier plate
[0112] Chromium nitride powder and calcium oxide powder are uniformly mixed in a mass ratio of 0.95 / 0.5 to obtain a mixed powder;
[0113] The mixed powder was loaded into a mold and placed in a hot pressing furnace for hot pressing and sintering at a pressure of 25 MPa and a temperature of 1750° C. for 2 hours to obtain a chromium nitride carrier plate with a relative density of 99.0%.
[0114] Comparative Example A3
[0115] This comparative example provides a rare earth permanent magnet diffusion source material, which differs from Example A1 in that the boron carbide blocking layer is replaced by a molybdenum blocking layer.
[0116] The difference between the preparation method of the rare earth permanent magnet diffusion source material in this comparative example and that in Example A1 is that step S12 uses a molybdenum target as a raw material to obtain a molybdenum blocking layer.
[0117] 2. Grain boundary diffusion method for rare earth permanent magnets
[0118] Example B1
[0119] This embodiment provides a grain boundary diffusion method for rare earth permanent magnets, comprising the following steps:
[0120] S21: Pre-processing
[0121] Degreasing, cleaning and pickling the substrate to be diffused;
[0122] S22: Thermal Diffusion Treatment
[0123] The substrate to be diffused (NdFeB substrate) was placed on the surface of the rare earth permanent magnet diffusion source material provided in Example A1, and then transferred to a tubular diffusion furnace and evacuated to 1×10 -2 Pa, introduce argon, start to raise the temperature to 850℃, keep it for 6h, and obtain rare earth permanent magnet.
[0124] Example B2
[0125] This embodiment provides a grain boundary diffusion method for rare earth permanent magnets, which differs from embodiment B1 in that in step S22, the rare earth permanent magnet diffusion source material provided in embodiment A1 is replaced with the rare earth permanent magnet diffusion source material provided in embodiment A2.
[0126] Example B3
[0127] This embodiment provides a grain boundary diffusion method for rare earth permanent magnets, which differs from embodiment B1 in that in step S22, the rare earth permanent magnet diffusion source material provided in embodiment A1 is replaced with the rare earth permanent magnet diffusion source material provided in embodiment A3.
[0128] Comparative Example B1
[0129] This comparative example provides a grain boundary diffusion method for rare earth permanent magnets, which differs from Example B1 in that in step S22, the rare earth permanent magnet diffusion source material provided in Example A1 is replaced by the rare earth permanent magnet diffusion source material provided in Comparative Example A1.
[0130] Comparative Example B2
[0131] This comparative example provides a grain boundary diffusion method for rare earth permanent magnets, which differs from Example B1 in that in step S22, the rare earth permanent magnet diffusion source material provided in Example A1 is replaced by the rare earth permanent magnet diffusion source material provided in Comparative Example A2.
[0132] Comparative Example B3
[0133] This comparative example provides a grain boundary diffusion method for rare earth permanent magnets, which differs from Example B1 in that in step S22, the rare earth permanent magnet diffusion source material provided in Example A1 is replaced by the rare earth permanent magnet diffusion source material provided in Comparative Example A3.
[0134] Comparative Example B4
[0135] This comparative example provides a method for grain boundary diffusion of a rare earth permanent magnet, comprising the following steps:
[0136] S21: Prepare a diffusion source layer on the substrate to be diffused
[0137] Using Tb target (purity of 99.99%) as raw material, the substrate to be diffused is placed in the coating chamber of the magnetron sputtering equipment and vacuumed to 1×10 -3 Pa below, sputter coating for 10 hours under the conditions of argon atmosphere, pressure of 1.0 Pa and sputtering power of 100 W to form a diffusion source layer on the surface of the substrate to be diffused;
[0138] S22: Thermal Diffusion Treatment
[0139] The diffusion substrate with the diffusion source layer formed on the surface was placed in a tubular diffusion furnace and vacuumed to 1×10 -2 Pa, introduce argon, start to raise the temperature to 850℃, keep it for 6h, and obtain rare earth permanent magnet.
[0140] Comparative Example B5
[0141] This comparative example provides a method for grain boundary diffusion of a rare earth permanent magnet, comprising the following steps:
[0142] S21: Prepare a diffusion source layer on the substrate to be diffused
[0143] A rare earth permanent magnet diffusion source slurry was prepared by mixing 68% terbium powder with a particle size D50 of 1.5 μm, 21% isobutyl alcohol, 3% diethyl phthalate, and 8% hydroxyethyl cellulose.
[0144] Applying rare earth permanent magnet diffusion source slurry on the surface of the substrate to be diffused to form a diffusion source layer;
[0145] S22: Thermal Diffusion Treatment
[0146] The diffusion substrate with a diffusion source layer formed on the surface was diffused at 900° C. for 5 hours and then sintered at 500° C. for 2 hours to obtain a rare earth permanent magnet.
[0147] Related performance test analysis:
[0148] 1. According to GBT3217-2013 “Test Methods for Magnetic Properties of Permanent Magnetic Materials”, the magnetic properties of the rare earth permanent magnets corresponding to Examples B1 to B3 and Comparative Examples B1 to B5 were tested. The test results are shown in Table 1 below.
[0149] Table 1
[0150]
[0151] As can be seen from Table 1, the remanence, coercive force, and maximum magnetic energy product of the rare earth permanent magnet produced in Example B1 are significantly superior to those in Comparative Examples B1 and B3. This indicates that the rare earth permanent magnet diffusion source material of this embodiment of the present application has a blocking layer between the carrier plate and the diffusion source layer, which is characterized by excellent material stability, corrosion resistance, non-oxidation, and non-reactive with rare earth metals and transition metals. This effectively blocks the migration of rare earth metal and transition metal atoms toward the carrier plate or the blocking layer, enhancing the grain boundary diffusion of the rare earth, thereby significantly improving the magnetic properties of the NdFeB matrix after thermal diffusion. Comparative Example B3, on the other hand, exhibits poor diffusion performance, primarily due to the rare earth portion of the diffusion source layer diffusing into the blocking layer, thereby affecting the grain boundary diffusion of the rare earth.
[0152] The remanence, coercive force, and maximum magnetic energy product of the rare earth permanent magnet produced in Example B1 were significantly greater than those in Comparative Example B2. This indicates that the carrier plate in this embodiment, made of a material with a low thermal expansion coefficient and high temperature resistance, significantly enhances the grain boundary diffusion of the rare earth elements, resulting in a significant improvement in the magnetic properties of the NdFeB matrix after thermal diffusion. Comparative Example B2 exhibited poor diffusion, primarily due to the decomposition of the chromium nitride carrier plate during thermal diffusion (e.g., above 700°C), which impaired the diffusion of the rare earth elements.
[0153] The remanence, coercive force and maximum magnetic energy product of the rare earth permanent magnet prepared in Example B1 are significantly greater than those of Comparative Examples B4 and B5, indicating that the rare earth permanent magnet diffusion source material provided in the embodiment of the present application is used to directly perform grain boundary diffusion on the NdFeB matrix. Compared with Comparative Examples B4 and B5 using the traditional grain boundary diffusion method, that is, forming a diffusion source layer on the surface of the NdFeB matrix and then performing grain boundary diffusion, the process of the present application is simple and the contact environment is single, which can effectively prevent the oxidation of the rare earth permanent magnet, thereby improving the magnetic properties of the NdFeB matrix after thermal diffusion.
[0154] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.
Claims
1. A rare earth permanent magnet diffusion source material, characterized in that: include: Loading plate; A blocking layer formed on at least one surface of the carrier plate; a diffusion source layer formed on a surface of the blocking layer away from the carrier plate; Wherein, the carrier plate is made of a material with a thermal expansion coefficient lower than 12×10 -6 / ℃, made of ceramic material with heat-resistant temperature higher than 1000℃; The material of the blocking layer includes at least one of boron carbide, boron nitride, tungsten carbide, silicon nitride, and titanium boride; The material of the diffusion source layer includes rare earth metal and optionally includes at least one of aluminum and copper.
2. The rare earth permanent magnet diffusion source material according to claim 1, characterized in that: The rare earth metal includes at least one of terbium, dysprosium and praseodymium; And / or, the ceramic material includes aluminum oxide or zirconium oxide.
3. The rare earth permanent magnet diffusion source material according to claim 1 or 2, characterized in that: At least one of the following conditions is met: The relative density of the carrier plate is 95-99.5%; The flatness of the carrier plate is 0.1-0.3 mm, and the roughness Ra is 0.1-0.5 μm; The thickness of the blocking layer is 1 to 50 μm; The roughness Ra of the blocking layer is 0.2~1μm; The thickness of the diffusion source layer is 2-50 μm; The roughness Ra of the diffusion source layer is 0.5-2 μm.
4. A method for preparing a rare earth permanent magnet diffusion source material according to any one of claims 1 to 3, characterized in that: The following steps are involved: Provide a carrier plate; A blocking layer target material is used as a raw material, and a vacuum coating technology is used to deposit a blocking layer on at least one surface of the carrier plate; the blocking layer target material includes at least one of a boron carbide target material, a boron nitride target material, a tungsten carbide target material, a silicon nitride target material, and a titanium boride target material; A diffusion source layer is prepared on the surface of the blocking layer away from the supporting plate to obtain a rare earth permanent magnet diffusion source material.
5. The preparation method according to claim 4, wherein The steps of preparing the carrier plate include: The ceramic powder is configured into a slurry; the ceramic powder includes alumina powder and zirconia powder; Slip casting and drying the slurry, or spray granulating and isostatically pressing the slurry to obtain a green body; The green body is sintered and machined to obtain a carrier plate.
6. The preparation method according to claim 5, wherein The sintering process is carried out at a temperature of 1400-1600° C. and for a time of 12-48 hours.
7. The preparation method according to claim 4, wherein The step of preparing a diffusion source layer on the surface of the blocking layer away from the supporting plate comprises: A diffusion source layer is deposited on the surface of the blocking layer away from the carrier plate using a rare earth metal target as a raw material by using a vacuum coating technique; the rare earth metal target comprises a rare earth metal and optionally at least one of aluminum and copper; Alternatively, a rare earth metal diffusion source slurry is coated on the surface of the blocking layer away from the carrier plate, and then dried and degreased to form a diffusion source layer; the rare earth metal diffusion source slurry includes rare earth metal powder and optionally at least one of aluminum powder and copper powder.
8. The preparation method according to claim 7, wherein At least one of the following conditions is met: The vacuum coating technology includes magnetron sputtering or reactive plasma deposition; The rare earth metal diffusion source slurry comprises the following components in percentage by weight: rare earth metal powder and optionally aluminum powder and / or copper powder 50-80%, isobutyl alcohol 13-36%, diethyl phthalate 2-4%, and hydroxyethyl cellulose 5-10%; The rare earth metal powder includes at least one of terbium powder, dysprosium powder and praseodymium powder; The particle size of the rare earth metal powder is 1-5 μm; The particle size of the aluminum powder and the copper powder is 1-5 μm.
9. A grain boundary diffusion method, characterized in that: The following steps are involved: Pre-treating the substrate to be diffused; The substrate to be diffused is placed on the diffusion source layer of the rare earth permanent magnet diffusion source material according to any one of claims 1 to 3 or the rare earth permanent magnet diffusion source material prepared by the preparation method according to any one of claims 4 to 8, and then subjected to thermal diffusion treatment to obtain a rare earth permanent magnet.
10. The grain boundary diffusion method according to claim 9, wherein: The pre-treatment includes: performing surface treatment on the substrate to be diffused; And / or, the thermal diffusion treatment is performed at a temperature of 750-950° C. and for a time of 2-48 hours.