A solvothermal process for the preparation of rare earth hydride nanoparticles
The preparation of rare earth hydride nanoparticles by a solvothermal method solves the problem of low diffusion efficiency caused by large particles in traditional methods, achieves efficient rare earth hydride diffusion, improves the thermal stability and coercivity of NdFeB magnets, and reduces production costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANXI RUIKE NEW MATERIALS CO LTD
- Filing Date
- 2026-01-22
- Publication Date
- 2026-05-12
AI Technical Summary
Traditional rare earth hydride preparation methods produce large particle sizes, resulting in low grain boundary diffusion efficiency and failing to effectively improve the thermal stability and coercivity of NdFeB magnets.
Rare earth hydride nanoparticles were prepared by a solvothermal method using rare earth metal salts, lithium hydride, and graphene as raw materials. The reaction was carried out under an inert atmosphere to prepare rare earth hydride nanoparticles with small particle size and uniform distribution, which were then used for grain boundary diffusion in neodymium iron boron magnets.
It improves the diffusion efficiency and depth of rare earth hydrides, significantly enhances the thermal stability and coercivity of NdFeB magnets, and reduces the amount of heavy rare earth used and production costs.
Smart Images
Figure CN121553902B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of nanoparticle preparation technology, specifically a solvothermal method for preparing rare earth hydride nanoparticles. Background Technology
[0002] Sintered neodymium iron boron (NdFeB) magnets possess excellent magnetic properties, making them the most widely used permanent magnet material in the world. Sintered NdFeB rare-earth permanent magnets are rapidly developing in new energy industries such as hybrid electric vehicles and wind power generation. The operating temperature of permanent magnet motors, key components in these industries, is typically above 150°C at high speeds. However, NdFeB magnets usually operate below 100°C, exhibiting poor thermal stability and a tendency to demagnetize at high temperatures, thus limiting their development in the field of high-temperature motors.
[0003] Currently, conventional methods improve the thermal stability and coercivity of sintered NdFeB magnets by directly adding heavy rare earth elements such as dysprosium (Dy) or terbium (Tb). However, excessive addition of dysprosium (Dy) or terbium (Tb) can lead to a significant decrease in the remanence and energy product of sintered NdFeB magnets, and also increase costs.
[0004] Grain boundary diffusion technology uses rare-earth hydride nanoparticles as a diffusion source to form a rare-earth hydride nanoparticle coating on the surface of sintered NdFeB magnets. The advantages of this process include a significant reduction in the amount of heavy rare-earth elements used, thus lowering costs; a good improvement in magnet coercivity; and minimal change in the magnet's remanence and maximum energy product. Therefore, grain boundary diffusion technology can effectively improve the thermal stability of sintered NdFeB magnets and achieve a substantial increase in magnet coercivity.
[0005] Furthermore, in grain boundary diffusion technology, rare earth hydride nanoparticles can adjust the chemical composition and structure of grain boundaries, optimize the microstructure of magnets, and improve the magnetic isolation effect of grain boundaries, thereby significantly enhancing the coercivity of NdFeB magnets while reducing production costs and rare earth resource consumption (the hydrogen in the hydride will eventually be released and will not hinder the diffusion of rare earth elements, so rare earth elements can reach the interior of the magnet).
[0006] Traditional rare earth hydrides are typically prepared using a rare earth metal hydrogen absorption-crushing method, which mainly involves the reaction of rare earth metals with hydrogen and the automatic crushing of the material. This method produces rare earth hydrides with large particle sizes, resulting in low diffusion efficiency. In contrast, using rare earth hydride nanoparticles can improve diffusion efficiency and increase diffusion depth, thereby improving the utilization rate of rare earth elements. Summary of the Invention
[0007] The purpose of this invention is to solve the technical problem of large product particles and low diffusion efficiency when used for grain boundary diffusion in traditional rare earth hydride preparation methods, and to provide a low-cost and high-efficiency solvothermal preparation process for rare earth hydride nanoparticles, providing important technical support for improving the coercivity of NdFeB.
[0008] To achieve its purpose, the present invention adopts the following technical solution:
[0009] This invention provides a solvothermal preparation process for rare earth hydride nanoparticles, which uses rare earth metal salts, lithium hydride, and graphene as raw materials. These are added to a high-pressure reactor containing an organic solvent and mixed evenly. The mixture is stirred and heated to 100-120°C under an inert atmosphere and kept at this temperature for 1.5-2.5 hours. After the reaction is completed, the mixture is cooled to room temperature, the black product is collected by filtration, washed with an organic solvent, and finally dried under vacuum at 65-75°C to obtain the rare earth hydride nanoparticles.
[0010] As a further preferred embodiment of the technical solution of the present invention, the rare earth metal salt is dysprosium chloride or terbium chloride.
[0011] Furthermore, the molar ratio of the rare earth metal salt to lithium hydride is 1:2.5-4, the amount of graphene added is 10 mg / mmol of rare earth metal salt, and the amount of organic solvent added to the high-pressure reactor is 45-65 mL.
[0012] Furthermore, the organic solvent is one of tetrahydrofuran, toluene, ethylene glycol dimethyl ether, dimethyl ether, or cyclodiene.
[0013] Furthermore, the organic solvent used for cleaning is the same as the organic solvent used for the reaction.
[0014] Furthermore, the inert atmosphere is an argon atmosphere.
[0015] Furthermore, the temperature of the heat preservation reaction was 100℃, and the reaction time was 2 hours.
[0016] Furthermore, the vacuum drying temperature is 70°C.
[0017] Compared with the existing rare earth metal hydrogen absorption-crushing method, the beneficial effects of the preparation process of this invention are as follows:
[0018] This invention employs a solvothermal method to prepare rare earth hydride nanoparticles. The process is simple and efficient, and the resulting product has small particle size, uniform distribution, and high purity. When used in the grain boundary diffusion technology of NdFeB magnets, it can effectively adhere to the grain boundary region of the NdFeB magnet, decompose and release active rare earth elements at high temperatures, thereby regulating the composition and structure of the grain boundary. This can significantly improve the thermal stability and coercivity of the magnet, while reducing the amount of heavy rare earth used and the production cost. Attached Figure Description
[0019] Figure 1 This is a scanning electron micrograph of the DyH3 nanoparticles prepared in Example 1 of this invention;
[0020] Figure 2 The energy dispersive X-ray spectrum of DyH3 nanoparticles prepared in Example 1 of this invention;
[0021] Figure 3 This is a scanning electron micrograph of the DyH3 nanoparticles prepared in Example 2 of this invention;
[0022] Figure 4 The energy dispersive X-ray spectrum of DyH3 nanoparticles prepared in Example 2 of this invention;
[0023] Figure 5 This is a scanning electron micrograph of the TbH3 nanoparticles prepared in Example 3 of this invention;
[0024] Figure 6 The energy dispersive X-ray spectrum of TbH3 nanoparticles prepared in Example 3 of this invention;
[0025] Figure 7 This is a scanning electron micrograph of the TbH3 nanoparticles prepared in Example 4 of this invention;
[0026] Figure 8 This is the energy-dispersive X-ray spectrum of the TbH3 nanoparticles prepared in Example 4 of this invention. Detailed Implementation
[0027] The solvothermal preparation process of rare earth hydride nanoparticles of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
[0028] Example 1
[0029] This embodiment provides a solvothermal preparation process for rare earth hydride nanoparticles. Using 2 mmol of DyCl3, 6 mmol of LiH, and 20 mg of graphene as raw materials, these are added to a high-pressure reactor containing 50 mL of toluene and mixed thoroughly. The mixture is then stirred and heated to 100°C under an argon atmosphere and maintained at this temperature for 1.5 h. After the reaction is complete, the mixture is cooled to room temperature, filtered to collect the black product, and 30 mL of toluene is added. The mixture is centrifuged at 10000 r / min for 3 min, and the washing process is repeated twice. The precipitate is then collected and vacuum dried at 70°C for 1 h to obtain the DyH3 nanoparticle product.
[0030] The scanning electron micrograph and energy-dispersive X-ray spectrum of the DyH3 nanoparticle product are shown below. Figure 1 and Figure 2As shown. From Figure 1 As can be seen, the DyH3 nanoparticles exhibit a uniform, near-spherical structure, with a particle size of 250-400 nm, and are basically uniformly distributed. From... Figure 2 As can be seen, the DyH3 nanoparticles exhibit a uniform elemental distribution, with no impurity phases detected. These results confirm that this method can prepare high-purity rare-earth hydride nanoparticles with uniform particle size distribution.
[0031] Example 2
[0032] This embodiment provides a solvothermal preparation process for rare earth hydride nanoparticles. Using 4 mmol of DyCl3, 16 mmol of LiH, and 40 mg of graphene as raw materials, these are added to a high-pressure reactor containing 60 mL of cyclodiene and mixed thoroughly. The mixture is stirred and heated to 110°C under an argon atmosphere and maintained at this temperature for 2 h. After the reaction is complete, the mixture is cooled to room temperature, filtered, and the black product is collected. 30 mL of cyclodiene is added, and the mixture is centrifuged at 10000 r / min for 3 min. The mixture is washed twice, and the precipitate is collected. The precipitate is then vacuum dried at 65°C for 1.5 h to obtain the DyH3 nanoparticle product.
[0033] The scanning electron micrograph and energy-dispersive X-ray spectrum of the DyH3 nanoparticle product are shown below. Figure 3 and Figure 4 As shown. From Figure 3 As can be seen, the DyH3 nanoparticles exhibit a uniform, near-spherical structure, with a particle size of 250-400 nm, and are basically uniformly distributed. From... Figure 4 As can be seen, the DyH3 nanoparticles exhibit a uniform elemental distribution, with no impurity phases detected. These results confirm that this method can prepare high-purity rare-earth hydride nanoparticles with uniform particle size distribution.
[0034] Example 3
[0035] This embodiment provides a solvothermal preparation process for rare earth hydride nanoparticles. Using 2 mmol of TbCl3, 8 mmol of LiH, and 20 mg of graphene as raw materials, these are added to a high-pressure reactor containing 55 mL of tetrahydrofuran and mixed thoroughly. The mixture is stirred and heated to 120°C under an argon atmosphere and maintained at this temperature for 2.5 h. After the reaction is complete, the mixture is cooled to room temperature, filtered, and the black product is collected. 30 mL of tetrahydrofuran is added, and the mixture is centrifuged at 10000 r / min for 3 min. The mixture is washed twice, and the precipitate is collected. The precipitate is then vacuum dried at 75°C for 1.5 h to obtain the TbH3 nanoparticle product.
[0036] The scanning electron micrograph and energy-dispersive X-ray spectrum of the TbH3 nanoparticle product are shown below. Figure 5 and Figure 6 As shown. From Figure 5 As can be seen, the TbH3 nanoparticles exhibit a uniform, near-spherical structure, with particle sizes ranging from 100 to 300 nm, and are generally evenly distributed. From... Figure 6 As can be seen, the TbH3 nanoparticles exhibit a uniform elemental distribution, with no impurity phases detected. These results confirm that this method can prepare high-purity rare-earth hydride nanoparticles with uniform particle size distribution.
[0037] Example 4
[0038] This embodiment provides a solvothermal preparation process for rare earth hydride nanoparticles. Using 4 mmol of TbCl3, 12 mmol of LiH, and 40 mg of graphene as raw materials, these are added to a high-pressure reactor containing 45 mL of ethylene glycol dimethyl ether and mixed thoroughly. The mixture is stirred and heated to 120°C under an argon atmosphere and maintained at this temperature for 2.5 h. After the reaction is complete, the mixture is cooled to room temperature, filtered, and the black product is collected. 30 mL of ethylene glycol dimethyl ether is added, and the mixture is centrifuged at 10000 r / min for 3 min. The mixture is washed twice, and the precipitate is collected. The precipitate is then vacuum dried at 75°C for 2 h to obtain the TbH3 nanoparticle product.
[0039] The scanning electron micrograph and energy-dispersive X-ray spectrum of the TbH3 nanoparticle product are shown below. Figure 7 and Figure 8 As shown. From Figure 7 As can be seen, the TbH3 nanoparticles exhibit a uniform, near-spherical structure, with particle sizes ranging from 100 to 300 nm, and are generally evenly distributed. From... Figure 8 As can be seen, the TbH3 nanoparticles exhibit a uniform elemental distribution, with no impurity phases detected. These results confirm that this method can prepare high-purity rare-earth hydride nanoparticles with uniform particle size distribution.
Claims
1. A solvothermal preparation process for rare earth hydride nanoparticles, characterized in that, Rare earth metal salts, lithium hydride, and graphene were used as raw materials. They were added to a high-pressure reactor containing organic solvent and mixed evenly. The mixture was stirred and heated to 100-120°C under an inert atmosphere and kept at that temperature for 1.5-2.5 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the black product was collected. The product was washed with organic solvent and then vacuum dried at 65-75°C for 1-2 hours to obtain the rare earth hydride nanoparticles. The rare earth metal salt is dysprosium chloride or terbium chloride; the molar ratio of the rare earth metal salt to lithium hydride is 1:3-4.
2. The solvothermal preparation process of rare earth hydride nanoparticles according to claim 1, characterized in that, The amount of graphene added is 10 mg / mmol of rare earth metal salt, and the amount of organic solvent added to the high-pressure reactor is 45-65 mL.
3. The solvothermal preparation process of rare earth hydride nanoparticles according to claim 2, characterized in that, The organic solvent is one of tetrahydrofuran, toluene, ethylene glycol dimethyl ether, dimethyl ether, or cyclodiene.
4. The solvothermal preparation process of rare earth hydride nanoparticles according to any one of claims 1-3, characterized in that, The organic solvent used for cleaning is the same as the organic solvent used for the reaction.
5. The solvothermal preparation process of rare earth hydride nanoparticles according to any one of claims 1-3, characterized in that, The inert atmosphere is an argon atmosphere.
6. The solvothermal preparation process of rare earth hydride nanoparticles according to any one of claims 1-3, characterized in that, The temperature for the heat preservation reaction was 100℃, and the reaction time was 2 hours.
7. The solvothermal preparation process of rare earth hydride nanoparticles according to any one of claims 1-3, characterized in that, The vacuum drying temperature is 70°C.