Rare earth-based permanent magnet single crystal nanomaterial and preparation method thereof
By bombarding rare earth metals and transition metal salts with Ar/H2 ion beams and combining the reaction with vacuum or ammonia atmosphere annealing, the problems of high-temperature agglomeration and high oxidation rate of rare earth-based permanent magnet materials in the prior art have been solved, and the preparation of rare earth-based permanent magnet single crystal nanomaterials with low cost and high yield has been realized.
Patent Information
- Application Number
- CN202310124905.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-02-16
- Publication Date
- 2026-02-24
- Estimated Expiration
- 2043-02-16
AI Technical Summary
Existing methods for preparing rare earth-based permanent magnet materials suffer from problems such as high-temperature agglomeration, high oxidation rate, high cost, and complex procedures, making it difficult to achieve large-scale production of nanomaterials with high magnetic properties.
Rare earth hydride nanoparticles were prepared by bombarding rare earth metals with Ar/H2 ion beams. Combined with the reaction of transition metal salts, oleic acid and oleylamine, rare earth-based permanent magnet single crystal nanomaterials were prepared by ultrasonic dispersion and vacuum or ammonia atmosphere annealing, avoiding high temperature, high pressure and water washing processes.
It achieves low-temperature annealing, avoids particle agglomeration, reduces costs, improves magnetic properties and yield, and is suitable for large-scale production of rare earth-based permanent magnet single-crystal nanomaterials.
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Figure CN116356414B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of magnetic rare earth alloy nanomaterials technology, and specifically relates to a rare earth-based permanent magnet single crystal nanomaterial and its preparation method. Background Technology
[0002] Rare earth-based permanent magnet materials have high magnetocrystalline anisotropy and low saturation magnetization. As an important medium for realizing the conversion of electrical energy and mechanical energy, they have broad application prospects in aerospace engines, magnetic levitation train tracks, wind power generation, as well as drones, intelligent robots and lithography machines.
[0003] Existing permanent magnets mainly include sintered permanent magnets and bonded permanent magnets. Sintered permanent magnets are brittle and difficult to process, while bonded permanent magnets have the advantages of flexibility and plasticity during processing, such as Sm2Fe. 17 N3 and other bonded permanent magnets possess high magnetic properties. Bonded permanent magnets can be prepared by controlling the orientation of single-crystal magnetic particles and the binder, and the performance of bonded permanent magnets mainly depends on the performance of the single-crystal magnetic particles.
[0004] Currently, the classic method for preparing magnetic particles is the reduction-diffusion method in chemical processes. This method mainly involves mixing oxides or hydroxides with metallic Ca, followed by annealing at high temperatures to reduce the oxides or hydroxides into elemental alloys. The mixture is then washed with water to remove excess Ca and CaO, ultimately yielding small, single-crystal rare-earth alloy particles. However, the reduction-diffusion process requires relatively high temperatures (>900℃), which can lead to particle agglomeration and uncontrollable size variations. Furthermore, the reduction process uses Ca, followed by washing away excess Ca and CaO. During this washing process, the material is easily oxidized or produces hydride intermediates, significantly impacting the magnetic properties of the rare-earth alloy particles. In addition, the reduction-diffusion method is costly and complex, hindering the industrialization of magnetic nanoparticles.
[0005] Therefore, there is an urgent need to provide a method for preparing nanomaterials with high magnetic properties on a large scale. Summary of the Invention
[0006] To address one or more technical problems existing in the prior art, this invention provides a rare earth-based permanent magnet single-crystal nanomaterial and its preparation method. The preparation method of this invention does not require the use of metallic calcium, has a low annealing temperature, high yield, and can be used for the large-scale preparation of rare earth-based permanent magnet single-crystal nanomaterials.
[0007] The present invention provides a method for preparing rare-earth-based permanent magnet single-crystal nanomaterials in a first aspect, characterized in that the preparation method includes the following steps:
[0008] S1. Rare earth metals were bombarded with Ar / H2 ion beams to obtain rare earth hydride nanoparticles;
[0009] S2. A transition metal salt, oleic acid, and oleylamine are mixed and reacted to obtain transition metal nanoparticles;
[0010] S3. The rare earth hydride nanoparticles and the transition metal nanoparticles are ultrasonically dispersed to obtain rare earth hydride / transition metal nanocomposite powder.
[0011] S4. The rare earth hydride / transition metal nanocomposite powder is subjected to vacuum annealing to obtain the rare earth-based permanent magnet single crystal nanomaterial; or, the rare earth hydride / transition metal nanocomposite powder is subjected to vacuum annealing and ammonia atmosphere annealing in sequence to obtain the rare earth-based permanent magnet single crystal nanomaterial.
[0012] Preferably, the rare earth metal is placed at the positive electrode, a tungsten electrode is used as the negative electrode, an Ar / H2 mixed gas is introduced, and an arc voltage and arc current are applied between the positive and negative electrodes to obtain rare earth hydride nanoparticles.
[0013] Preferably, the rare earth metal is one of Sm, Pr, and Ce; preferably, Ar accounts for 60-70 vol.% of the Ar / H2 mixture.
[0014] Preferably, the arc voltage is 10–50V and the arc current is 50–150A.
[0015] Preferably, the ratio of the transition metal salt, oleic acid and oleylamine is (160-200) g: (90-140) mL: (3800-4500) mL.
[0016] Preferably, the transition metal salt is one of cobalt acetylacetonate and iron acetylacetonate;
[0017] Preferably, the concentration of oleic acid is 70%;
[0018] Preferably, the concentration of the oleylamine is 90%.
[0019] Preferably, the mixing involves dissolving a transition metal salt and oleic acid in oleylamine at 100–140°C; and / or
[0020] The reaction involves heating to 230–260°C and holding at that temperature for 1–2 hours; preferably, the heating rate is 2–8°C / min.
[0021] Preferably, the molar ratio of rare earth metal atoms in the rare earth hydride nanoparticles to transition metal atoms in the transition metal nanoparticles is 1:(4-12), more preferably 1:(4.8-11.7);
[0022] Preferably, the solvent used for ultrasonic dispersion is n-hexane; and the ultrasonic dispersion time is 2-3 hours.
[0023] Preferably, the ultrasonic dispersion process further includes a step of blowing gas into the mixing system; more preferably, the blowing is performed by introducing argon gas into the mixing system at 50-80°C under stirring conditions.
[0024] Preferably, the vacuum annealing process is performed under vacuum conditions, heating to 650–800°C and holding at that temperature for 80–120 minutes; preferably, the vacuum degree of the vacuum annealing process is not less than 3 × 10⁻⁶. -4 Pa; the heating rate is 2–8 °C / min.
[0025] Preferably, the ammonia atmosphere annealing treatment is performed by heating to 450-550°C and holding at that temperature for 4-8 hours in an ammonia atmosphere; more preferably, the heating rate is 2-8°C / min.
[0026] Preferably, the particle size of the rare earth hydride nanoparticles is 50–100 nm;
[0027] The transition metal nanoparticles have a particle size of 8–12 nm; and / or
[0028] The particle size of the rare earth-based permanent magnet single crystal nanomaterial is 100-200 nm, preferably 150-170 nm.
[0029] In a second aspect, the present invention provides a rare-earth-based permanent magnet single-crystal nanomaterial, which is prepared by the preparation method described in the first aspect above.
[0030] Compared with the prior art, the present invention has at least the following beneficial effects:
[0031] This invention first prepares rare earth hydride nanoparticles by bombarding rare earth metal blocks with ion beams, and prepares transition metal nanoparticles by solvothermal method. Then, the rare earth hydride nanoparticles and transition metal nanoparticles are mixed to obtain rare earth hydride / transition metal nanocomposite powder. The rare earth hydride / transition metal nanocomposite powder is then annealed to prepare rare earth-based permanent magnet single crystal nanomaterials. Compared with the existing technology of mixing oxides or hydroxides with metal Ca and then annealing at high temperature to prepare single alloys, this invention (1) has a lower annealing temperature, which can effectively avoid excessive particle agglomeration and obtain rare earth-based permanent magnet single crystal nanomaterials with controllable size. At the same time, it can save energy and reduce costs; (2) it can effectively avoid the use of Ca and subsequent water washing process, effectively reduce the oxidation rate of rare earth-based permanent magnet single crystal nanomaterials, thereby effectively improving the magnetic properties of the material.
[0032] The preparation method of the present invention has good reproducibility and high yield (up to 97% or more), and can be mass-produced to realize the large-scale preparation of rare earth-based permanent magnet single crystal nanomaterials. Attached Figure Description
[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0034] Figure 1 These are the hysteresis loops of SmCo5 nanoparticles provided in Example 1 of this invention at different temperatures;
[0035] Figure 2 This is a TEM image of the SmH2 / Co nanocomposite powder provided in Example 1 of this invention;
[0036] Figure 3 This is a TEM image of the SmCo5 nanoparticles provided in Example 1 of this invention;
[0037] Figure 4 The Sm2Fe provided in Embodiment 3 of this invention 17 Magnetic hysteresis loop of nanoparticles at room temperature;
[0038] Figure 5 The hysteresis loop of PrCo5 nanoparticles at room temperature provided in Example 5 of this invention;
[0039] Figure 6 The Sm2Fe provided in Embodiment 8 of this invention 17 hysteresis loop of N3 nanoparticles at room temperature;
[0040] Figure 7 The Sm2Fe provided in Embodiment 8 of this invention 17 TEM image of N3 nanoparticles. Detailed Implementation
[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0042] The present invention provides a method for preparing rare-earth-based permanent magnet single-crystal nanomaterials in a first aspect, characterized in that the preparation method includes the following steps:
[0043] S1. Rare earth metals were bombarded with Ar / H2 ion beams to obtain rare earth hydride nanoparticles;
[0044] S2. A transition metal salt, oleic acid, and oleylamine are mixed and reacted to obtain transition metal nanoparticles;
[0045] S3. The rare earth hydride nanoparticles and the transition metal nanoparticles are ultrasonically dispersed to obtain rare earth hydride / transition metal nanocomposite powder.
[0046] S4. The rare earth hydride / transition metal nanocomposite powder is subjected to vacuum annealing to obtain the rare earth-based permanent magnet single crystal nanomaterial; or, the rare earth hydride / transition metal nanocomposite powder is subjected to vacuum annealing and ammonia atmosphere annealing in sequence to obtain the rare earth-based permanent magnet single crystal nanomaterial.
[0047] This invention first prepares rare earth hydride nanoparticles by bombarding rare earth metal blocks with ion beams, and prepares transition metal nanoparticles by solvothermal method. Then, the rare earth hydride nanoparticles and transition metal nanoparticles are mixed to obtain rare earth hydride / transition metal nanocomposite powder. The rare earth hydride / transition metal nanocomposite powder is then annealed to prepare rare earth-based permanent magnet single crystal nanomaterials. Compared with the existing technology of mixing oxides or hydroxides with metal Ca and then annealing at high temperature to prepare single alloys, this invention (1) has a lower annealing temperature, which can effectively avoid excessive particle agglomeration and obtain rare earth-based permanent magnet single crystal nanomaterials with controllable size. At the same time, it can save energy and reduce costs; (2) it can effectively avoid the use of Ca and subsequent water washing process, effectively reduce the oxidation rate of rare earth-based permanent magnet single crystal nanomaterials, thereby effectively improving the magnetic properties of the material.
[0048] The preparation method of the present invention has good reproducibility and high yield (up to 97% or more), and can be mass-produced to realize the large-scale preparation of rare earth-based permanent magnet single crystal nanomaterials.
[0049] According to some preferred embodiments, the rare earth metal is placed at the positive electrode, a tungsten electrode is used as the negative electrode, an Ar / H2 mixed gas is introduced, and an arc voltage and arc current are applied between the positive and negative electrodes to obtain rare earth hydride nanoparticles.
[0050] Preferably, the rare earth metal is one of Sm, Pr, and Ce;
[0051] Preferably, Ar accounts for 60-70 vol.% of the Ar / H2 mixture; and / or
[0052] Preferably, the arc voltage is 10–50V and the arc current is 50–150A.
[0053] In some specific embodiments of the present invention, the method for preparing rare earth hydride nanoparticles includes: placing 100.0 g of rare earth metal (M) block on the positive electrode, using a tungsten electrode as the negative electrode, and evacuating the cavity to 5 × 10⁻⁶ using a molecular pump. -4 Pa is then filled with Ar / H2 (Ar / H2 is a mixture of Ar and H2 gases, wherein Ar and H2 are mixed at 60-70 vol.% and 30-40 vol.% respectively). An arc voltage (10-50 V) and an arc current (50-150 A) are then applied between the negative and positive electrodes to ionize the Ar / H2. The resulting Ar / H2 ion beam bombards M under the applied voltage, forming M atoms. Furthermore, during evaporation, these M atoms recombine into M particles due to thermal motion. Finally, stable M particles are formed upon contact with the cooling chamber wall, and then combine with H2 ions to transform into MH2 particles. The MH2 particles are further separated into different sizes by a powerful blower and filtration system, ultimately selecting MH2 particles of 50-100 nanometers. The MH2 particles are collected under a protective atmosphere and transferred to a glove box. Generally, 100.0 g of M yields approximately 25.0 g of MH2 nanoparticles with a size of 50-100 nanometers.
[0054] It should be noted that the rare earth hydride nanoparticles of this invention were prepared using the HYRE-500 evaporation and condensation equipment from Beijing Heyan Technology Co., Ltd.
[0055] According to some preferred embodiments, the ratio of the transition metal salt, oleic acid and oleylamine is (160-200) g: (90-140) mL: (3800-4500) mL;
[0056] Preferably, the transition metal salt is one of cobalt acetylacetonate and iron acetylacetonate;
[0057] Preferably, the concentration of oleic acid is 70%;
[0058] Preferably, the concentration of the oleylamine is 90%.
[0059] According to some preferred embodiments, the mixing involves dissolving the transition metal salt and oleic acid in oleylamine at 100–140°C (e.g., 100°C, 110°C, 120°C, 130°C, or 140°C); and / or
[0060] The reaction involves heating to 230–260°C (e.g., 230°C, 235°C, 240°C, 245°C, 250°C, 255°C, or 260°C) and holding at that temperature for 1–2 hours (e.g., 1 hour, 1.5 hours, or 2 hours); preferably, the heating rate is 2–8°C / min (e.g., 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, or 8°C / min).
[0061] According to some preferred embodiments, the molar ratio of rare earth metal atoms in the rare earth hydride nanoparticles to transition metal atoms in the transition metal nanoparticles is 1:(4-12) (for example, it can be 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11 or 1:12), preferably 1:(4.8-11.7) (for example, it can be 1:4.8, 1:5, 1:6, 1:7, 1:8, 1:8.2, 1:9, 1:10 or 1:11.7);
[0062] Preferably, the solvent used for ultrasonic dispersion is n-hexane; the ultrasonic dispersion time is 2 to 3 hours (for example, 2 hours, 2.5 hours or 3 hours).
[0063] This invention disperses a mixture of rare earth hydride nanoparticles and transition metal nanoparticles into n-hexane using an ultrasonic method to ensure uniform mixing of the rare earth hydride nanoparticles and transition metal nanoparticles.
[0064] According to some preferred embodiments, the ultrasonic dispersion further includes a step of blowing gas into the mixing system; preferably, the blowing is performed at 50-80°C (for example, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C) under stirring conditions, and argon gas is introduced into the mixing system.
[0065] In this invention, under stirring conditions at 50–80°C, argon gas is blown in to expel n-hexane, ultimately yielding rare earth hydride / transition metal nanocomposite powder.
[0066] According to some preferred embodiments, the vacuum annealing process involves heating to 650–800°C (e.g., 650°C, 660°C, 680°C, 700°C, 720°C, 740°C, 760°C, 780°C, or 800°C) under vacuum conditions and holding at that temperature for 80–120 minutes (e.g., 80 minutes, 85 minutes, 90 minutes, 95 minutes, 100 minutes, 105 minutes, 110 minutes, or 120 minutes); preferably, the vacuum degree of the vacuum annealing process is not less than 3 × 10⁻⁶. -4Pa; the heating rate is 2 to 8 °C / min (for example, it can be 2 °C / min, 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min or 8 °C / min).
[0067] This invention achieves the size control of rare-earth-based permanent magnet single-crystal nanomaterials by controlling the temperature and time of vacuum annealing within the aforementioned range. If the temperature is too low, an alloy cannot be formed; if the temperature is too high, excessive particle agglomeration can occur, leading to abnormal grain growth and preventing the acquisition of size controllable rare-earth-based permanent magnet single-crystal nanomaterials. If the vacuum annealing time is too short, the reaction cannot be completed, and the target product cannot be obtained. If the vacuum annealing time is too long, particle agglomeration will occur.
[0068] According to some preferred embodiments, the ammonia atmosphere annealing treatment involves heating the gas to 450–550°C (e.g., 450°C, 460°C, 480°C, 500°C, 520°C, 540°C, or 550°C) in an ammonia atmosphere and holding the temperature for 4–8 hours (e.g., 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, or 8 hours); preferably, the heating rate is 2–8°C / min (e.g., 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, or 8°C / min).
[0069] According to some preferred embodiments, the particle size of the rare earth hydride nanoparticles is 50-100 nm (for example, it can be 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm).
[0070] The transition metal nanoparticles have a particle size of 8–12 nm (e.g., 8 nm, 9 nm, 10 nm, 11 nm, or 12 nm); and / or
[0071] The particle size of the rare earth-based permanent magnet single-crystal nanomaterial is 100-200 nm (e.g., it can be 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm or 200 nm), preferably 150-170 nm (e.g., it can be 150 nm, 155 nm, 160 nm, 165 nm or 170 nm).
[0072] In a second aspect, the present invention provides a rare-earth-based permanent magnet single-crystal nanomaterial, which is prepared by the preparation method described in the first aspect above.
[0073] The rare-earth-based permanent magnet single-crystal nanomaterials provided by this invention have excellent magnetic properties and can be used to prepare bonded permanent magnets.
[0074] The materials and reagents used in this invention can be purchased directly from the market or synthesized in-house, and there are no restrictions on the specific models.
[0075] Example 1
[0076] S1. Preparation of SmH2 nanoparticles: 100g of Sm block was placed on the positive electrode of the instrument, and a tungsten electrode was used as the negative electrode. The cavity was evacuated to 5×10⁻⁶ using a molecular pump. -4 Pa was then used to fill the cavity with Ar / H2 (volume ratio 60% / 40%), followed by the application of a voltage of 10–50 V and a current of 50–150 A to ionize the Ar / H2. The resulting Ar / H2 ion beam bombarded the Sm block under the applied voltage, forming Sm atoms. Furthermore, during the evaporation process, due to thermal motion, the Sm atoms recombine to form Sm particles. Finally, upon contact with the cooling chamber wall, stable Sm particles are formed, which then combine with H2 ions to transform into SmH2 particles. The SmH2 particles are further separated into different sizes by a blower and filtration system, ultimately yielding 25.0 g of SmH2 particles with a size of 50–100 nanometers. The SmH2 particles are collected under a protective atmosphere and transferred to a glove box.
[0077] S2. Preparation of Co nanoparticles: At 120°C, 175g of cobalt acetylacetonate and 100mL of 90% oleic acid were dissolved in 4000mL of 70% oleylamine for 30 minutes to obtain a mixture. The mixture was then transferred to a polytetrafluoroethylene container in a 5.0L high-pressure reactor and heated to 250°C at a heating rate of 2°C / min under constant stirring and held for 1 hour. The mixture was then washed by centrifugation and n-hexane, dried in a vacuum furnace, and immediately transferred to a glove box to obtain approximately 40g of Co nanoparticles (approximately 10nm in size).
[0078] S3. Preparation of SmH2 / Co nanocomposite material: In a glove box, 15.24g of SmH2 and 28.27g of Co nanoparticles (the molar ratio of Sm:Co atoms is 1:4.8) were mixed, and then the mixed particles were dispersed into 500mL of n-hexane by ultrasonic vibration for 2 hours. The mixed solution was transferred to a three-necked flask and stirred continuously at 60℃. The n-hexane was blown away with Ar gas, and then the SmH2 / Co nanocomposite powder was collected.
[0079] S4. Preparation of SmCo5 nanoparticles: Under a protective atmosphere, the SmH2 / Co nanocomposite powder was directly transferred to a vacuum annealing furnace, and then the annealing furnace was evacuated to 3×10⁻⁶. -4 Pa was heated to 700℃ at a heating rate of 2℃ / min, then held for 90min, and after cooling, 42g of SmCo5 black nanomaterial was collected and stored in a glove box.
[0080] The SmCo5 nanoparticles prepared in Example 1 showed no obvious oxidation phenomenon, making them one of the strongest magnetic SmCo5 nanoparticles prepared by chemical methods to date, with a yield of over 97%.
[0081] Depend on Figure 1 It can be seen that the SmCo5 nanoparticles prepared in Example 1 have a saturation magnetization of 86.2 emu / g at room temperature and a coercivity as high as 35.4 kOe. The coercivity can reach 44.2 kOe and 50.2 kOe at 200 K and 100 K, respectively. It should be noted that this invention… Figure 1 From the inside out, the hysteresis loops are 298K (room temperature), 200K, and 100K respectively.
[0082] Examples 2-7 are basically the same as Example 1, with the differences shown in Table 1.
[0083] Table 1
[0084]
[0085] It should be noted that "number of repetitions" in the table refers to the number of times the preparation process is repeated. For example, if the number of repetitions is 4, it means that the same product can be obtained in 4 repetitions, indicating that the preparation method of the present invention has good reproducibility. The "yield" in the table corresponds to the average yield of the four repetitions.
[0086] Depend on Figure 4 It can be seen that the Sm2Fe prepared in Example 3 17 The saturation magnetization of the nanoparticles reaches as high as 125.2 emu / g at room temperature.
[0087] Depend on Figure 5 It can be seen that the saturation magnetization of the PrCo5 nanoparticles prepared in Example 5 is 99.7 emu / g and the coercivity is 13.7 kOe under room temperature conditions.
[0088] Example 8
[0089] S1. Preparation of SmH2 nanoparticles: 100g of Sm block was placed on the positive electrode of the instrument, and a tungsten electrode was used as the negative electrode. The cavity was evacuated to 5×10⁻⁶ using a molecular pump. -4Pa was then used to fill the cavity with Ar / H2 (volume ratio 60% / 40%), followed by the application of a voltage of 10–50 V and a current of 50–150 A to ionize the Ar / H2. The resulting Ar / H2 ion beam bombarded the Sm block under the applied voltage, forming Sm atoms. Furthermore, during the evaporation process, due to thermal motion, the Sm atoms recombine to form Sm particles. Finally, upon contact with the cooling chamber wall, stable Sm particles are formed, which then combine with H2 ions to transform into SmH2 particles. The SmH2 particles are further separated into different sizes by a blower and a filtration system, ultimately yielding 25.0 g of SmH2 particles with a size of 50–100 nanometers. The SmH2 particles are collected under a protective atmosphere and transferred to a glove box.
[0090] S2. Preparation of Fe nanoparticles: At 120°C, 190g of ferric acetylacetone and 100mL of 90% oleic acid were dissolved in 4000mL of 70% oleylamine for 30 minutes to obtain a mixture. The mixture was then transferred to a polytetrafluoroethylene container in a 5.0L high-pressure reactor and heated to 250°C at a heating rate of 2°C / min under constant stirring and held for 1 hour. The mixture was then washed by centrifugation and n-hexane, dried in a vacuum furnace, and immediately transferred to a glove box to obtain approximately 43g of Fe nanoparticles (approximately 10nm in size).
[0091] S3. Preparation of SmH2 / Fe nanocomposite material: In a glove box, 11.0 g of SmH2 nanoparticles and 33.02 g of Fe nanoparticles were mixed (the molar ratio of Sm:Fe atoms was 1:8.2). The mixed particles were then dispersed into 500 mL of n-hexane by ultrasonic vibration for 2 hours. The mixed solution was transferred to a three-necked flask and stirred continuously at 60 °C. The n-hexane was slowly blown away with Ar gas, and then the SmH2 / Fe nanocomposite powder was collected.
[0092] S4. Preparation of Sm2Fe 17 Nanoparticles: Under a protective atmosphere, SmH2 / Fe nanocomposite powder was directly transferred to a vacuum annealing furnace, and then the annealing furnace was evacuated to 3×10⁻⁶. -4 Pa was heated to 780°C at a heating rate of 2°C / min, then held for 80 min, and after cooling, Sm2Fe was collected. 17 Nanoparticles, and stored in a glove box.
[0093] S5. Preparation of Sm2Fe 17 N3 nanoparticles: 43.3g Sm2Fe 17 The nanoparticle powder was placed in an annealing furnace, and ammonia gas was introduced into the furnace. After 15 minutes, the temperature was increased to 500°C at a rate of 2°C / min and held at this temperature for 6 hours, yielding 44 g of Sm2Fe.17 N3 nanomaterials.
[0094] Depend on Figure 6 It can be seen that the Sm2Fe prepared in Example 8 17 The saturation magnetization and coercivity of N3 nanoparticles at room temperature reached 142 emu / g and 25.2 kOe, respectively.
[0095] Example 9
[0096] S1. Preparation of CeH2 nanoparticles: 100g of Ce block was placed on the positive electrode of the instrument, and a tungsten electrode was used as the negative electrode. The cavity was evacuated to 5×10⁻⁶ using a molecular pump. -4 Pa was then used to fill the cavity with Ar / H2 (volume ratio 60% / 40%), followed by the application of a voltage of 10–50 V and a current of 50–150 A to ionize the Ar / H2. The resulting Ar / H2 ion beam bombarded the Ce blocks under the applied voltage, forming Ce atoms. Furthermore, during the evaporation process, due to thermal motion, the Ce atoms recombine to form Ce particles. Finally, upon contact with the cooling chamber wall, stable Ce particles are formed, which then combine with H2 ions to transform into CeH2 particles. The CeH2 particles are further separated into different sizes by a blower and a filtration system, ultimately yielding 25.0 g of CeH2 particles with a size of 50–100 nanometers. The CeH2 particles are collected under a protective atmosphere and transferred to a glove box.
[0097] S2. Preparation of Fe nanoparticles: At 120℃, 170g of ferric acetylacetone and 100mL of 90% oleic acid were dissolved in 4000mL of 70% oleylamine for 30 minutes to obtain a mixture. The mixture was then transferred to a polytetrafluoroethylene container in a 5.0L high-pressure reactor and heated to 250℃ at a heating rate of 2℃ / min under constant stirring and held for 1h. After centrifugation and washing with n-hexane, the mixture was dried in a vacuum furnace and immediately transferred to a glove box to obtain approximately 38g of Fe nanoparticles (approximately 10nm in size).
[0098] S3. Preparation of CeH2 / Fe nanocomposite material: In a glove box, 10.6g of CeH2 nanoparticles and 34.15g of Fe nanoparticles (the molar ratio of Ce:Fe atoms is 1:8.2) were mixed. The mixed particles were then dispersed into 500mL of n-hexane by ultrasonic vibration for 2 hours. The mixed solution was transferred to a three-necked flask and stirred continuously at 60℃. The n-hexane was slowly blown away with Ar gas. The CeH2 / Fe nanocomposite material powder was then collected.
[0099] S4. Preparation of Ce2Fe 17Nanoparticles: Under a protective atmosphere, CeH2 / Fe nanocomposite powder was directly transferred to a vacuum annealing furnace, which was then evacuated to a vacuum of 3 × 10⁻⁶. -4 Pa was heated to 700℃ at a heating rate of 2℃ / min, then held for 90 min, and after cooling, Ce2Fe was collected. 17 Nanoparticles, and stored in a glove box.
[0100] S5. Preparation of Ce2Fe 17 N3 nanoparticles: 44.2g Ce2Fe 17 The nanoparticle powder was placed in an annealing furnace, and ammonia gas was introduced into the furnace. After 15 minutes, the temperature was increased to 500°C at a rate of 2°C / min and held at this temperature for 6 hours, yielding approximately 45g of Ce₂Fe. 17 N3 nanoparticles (approximately 10 nm in size).
[0101] Comparative Example 1
[0102] The process is basically the same as in Example 1, except that: S4. Under a protective atmosphere, the SmH2 / Co nanocomposite powder is directly transferred to a vacuum annealing furnace, and then the annealing furnace is evacuated to 3×10⁻⁶ ℃. -4 Pa was heated to 700℃ at a heating rate of 2℃ / min, then held for 60 min, and after cooling, SmCo3 / SmCo5 nanoparticles were collected.
[0103] Comparative Example 2
[0104] The process is basically the same as in Example 1, except that: S4. Preparation of SmCo5 nanoparticles: Under a protective atmosphere, the SmH2 / Co nanocomposite powder is directly transferred to a vacuum annealing furnace, and then the annealing furnace is evacuated to 3×10⁻⁶. -4 Pa was heated to 700℃ at a heating rate of 2℃ / min, then held for 30 min, and after cooling, SmCo2 nanoparticles were collected.
[0105] The differences between Comparative Examples 1-2 and Example 1 are shown in Table 2.
[0106] Table 2
[0107]
[0108] It should be noted that "number of repetitions" in the table refers to the number of times the preparation process is repeated. For example, if the number of repetitions is 4, it means that the same product can be obtained in 4 repetitions, indicating that the preparation method of the present invention has good reproducibility. The "yield" in the table corresponds to the average yield of the four repetitions.
[0109] As shown in Table 2, the vacuum annealing time of Comparative Examples 1-2 was too short, resulting in incomplete reaction, low yield, and failure to obtain SmCo5 nanoparticles.
[0110] 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 of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing rare-earth-based permanent magnet single-crystal nanomaterials, characterized in that, The preparation method includes the following steps: S1. Rare earth metals are bombarded with Ar / H2 ion beams to obtain rare earth hydride nanoparticles; the rare earth metals are... One of Sm, Pr, and Ce; S2. A transition metal salt, oleic acid, and oleylamine are mixed and reacted to obtain transition metal nanoparticles; the transition metal salt is one of cobalt acetylacetonate and iron acetylacetonate. S3. The rare earth hydride nanoparticles and the transition metal nanoparticles are ultrasonically dispersed to obtain rare earth hydride / transition metal nanocomposite powder. S4. The rare earth hydride / transition metal nanocomposite powder is subjected to vacuum annealing to obtain the rare earth-based permanent magnet single crystal nanomaterial; or, the rare earth hydride / transition metal nanocomposite powder is subjected to vacuum annealing and ammonia atmosphere annealing in sequence to obtain the rare earth-based permanent magnet single crystal nanomaterial. The vacuum annealing process involves heating to 650-800°C and holding at that temperature for 80-120 minutes under vacuum conditions.
2. The preparation method according to claim 1, characterized in that, The rare earth metal is placed at the positive electrode, and a tungsten electrode is used as the negative electrode. An Ar / H2 mixture is introduced, and an arc voltage and arc current are applied between the positive and negative electrodes to obtain rare earth hydride nanoparticles.
3. The preparation method according to claim 2, characterized in that, Ar accounts for 60-70 vol.% of the Ar / H2 mixture.
4. The preparation method according to claim 2, characterized in that, The arc voltage is 10~50V and the arc current is 50~150A.
5. The preparation method according to claim 1, characterized in that, The ratio of the transition metal salt, oleic acid and oleylamine used is (160~200)g:(90~140)mL:(3800~4500)mL.
6. The preparation method according to claim 5, characterized in that, The concentration of oleic acid is 70%.
7. The preparation method according to claim 5, characterized in that, The concentration of oleylamine is 90%.
8. The preparation method according to claim 1, characterized in that, The mixing process involves dissolving a transition metal salt and oleic acid in oleylamine at 100-140°C; and / or The reaction involves heating to 230-260°C and holding at that temperature for 1-2 hours.
9. The preparation method according to claim 8, characterized in that, In the reaction, the heating rate is 2~8℃ / min.
10. The preparation method according to claim 1, characterized in that, The molar ratio of rare earth metal atoms in the rare earth hydride nanoparticles to transition metal atoms in the transition metal nanoparticles is 1:(4~12).
11. The preparation method according to claim 10, characterized in that, The molar ratio of rare earth metal atoms in the rare earth hydride nanoparticles to transition metal atoms in the transition metal nanoparticles is 1:(4.8~11.7).
12. The preparation method according to claim 10, characterized in that, The solvent used for ultrasonic dispersion is n-hexane; the ultrasonic dispersion time is 2-3 hours.
13. The preparation method according to claim 1, characterized in that, The ultrasonic dispersion process also includes a step of blowing air into the mixture.
14. The preparation method according to claim 13, characterized in that, The blowing is performed by introducing argon gas into the mixing system at 50~80℃ under stirring conditions.
15. The preparation method according to claim 1, characterized in that, The vacuum degree of the vacuum annealing process is not less than 3×10⁻⁶. -4 Pa; In the vacuum annealing process, the heating rate is 2~8℃ / min.
16. The preparation method according to claim 1, characterized in that, The ammonia atmosphere annealing process involves heating the gas to 450-550°C and holding it at that temperature for 4-8 hours in an ammonia atmosphere.
17. The preparation method according to claim 16, characterized in that, In the ammonia atmosphere annealing process, the heating rate is 2~8℃ / min.
18. The preparation method according to claim 1, characterized in that, The particle size of rare earth hydride nanoparticles is 50~100nm; The transition metal nanoparticles have a particle size of 8-12 nm; and / or The particle size of the rare earth-based permanent magnet single crystal nanomaterial is 100~200nm.
19. The preparation method according to claim 18, characterized in that, The particle size of the rare earth-based permanent magnet single-crystal nanomaterial is 150~170nm.