A method for preparing high magnetic performance (Sm x Y 1-x )Co5 rare earth magnetic particles by chemical process

Abstract

A method for preparing high magnetic performance (Sm x Y 1‑x )Co5 rare earth magnetic particles by chemical method belongs to the field of rare earth magnetic materials. Specifically relates to a kind of new technology using chemical liquid phase synthesis combined with calcium reduction reaction, preparation of high magnetic performance (Sm x Y 1‑x )Co5 ternary alloy magnetic powder. Through chemical coprecipitation combined with hydrothermal reaction, Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 crystalline state mixed precursor is prepared, and a certain amount of metal calcium particles, KCl and CaCl2 diffusion medium are uniformly mixed in argon atmosphere to occur complete calcium reduction reaction, and the magnetic powder is prepared. The incorporation of yttrium element improves the saturation magnetization and remanence of the magnetic powder, but the coercivity of the magnetic powder is slightly reduced. This method provides a new idea for preparing high-performance rare earth magnetic particles.

Description

Technical Field

[0001] This invention relates to a novel method for preparing materials with high coercivity, high saturation magnetization, high remanent magnetization, and uniaxial anisotropy (Sm). x Y 1-x The method for producing Co5 rare earth magnetic particles specifically involves a method for preparing nanoscale hydroxide composite precursors using a co-precipitation combined with hydrothermal synthesis, and then obtaining rare earth magnetic particles using calcium reduction diffusion technology, which belongs to the field of rare earth magnetic materials. Background Technology

[0002] SmCo5, a rare-earth permanent magnet material, is a first-generation permanent magnet widely used in aerospace, precision instruments, microwave devices, and other fields. Its advantages include high coercivity, high energy product, and good thermal stability. Its disadvantage is its low saturation magnetization M. s With the development of science and technology, the demand for magnets in terms of high magnetic performance and lightweight design has greatly increased. Therefore, research on the high-performance preparation of rare-earth magnetic particles in magnet manufacturing has gradually attracted attention. Currently, researchers are using methods such as rational structural design, experimental improvement, and element doping to obtain submicron and nanoscale rare-earth magnetic particles with high coercivity, high saturation magnetization, and high remanent magnetization, thereby affecting the magnetic properties of the prepared magnets. Yttrium, as a highly abundant rare-earth element, is more abundant than samarium. Replacing samarium in SmCo5 with yttrium is beneficial for promoting the high-value application of high-abundance yttrium and reducing the production cost of magnetic powder. Adding yttrium is a promising and cost-effective method to improve the magnetic properties of 1:5 type permanent magnets.

[0003] Currently, methods for preparing magnetic particles can be divided into two types: physical methods and chemical methods, and numerous experimental studies have been conducted. Physical methods are the most common for mass production, including ball milling and electron beam deposition. Ball milling involves placing the prepared bulk material in a milling jar and subjecting it to high-speed collisions with a certain number of zirconia balls to obtain uniform particles; the milling time determines the particle size. Electron beam deposition involves pulverizing the prepared bulk material into small particles under a high-energy electron beam and then collecting them on a cooled substrate. Chinese patent CN202011082726 describes a method for preparing anisotropic samarium cobalt magnetic powder. First, a rapid solidification process is used to obtain samarium cobalt castings. After aging treatment, a hydrogen-based process is used to prepare 10-200 μm anisotropic magnetic powder. This method can be applied to large-scale magnetic powder production. However, the prepared anisotropic samarium cobalt magnetic powder has a wide particle size distribution and an average particle size of 100 μm, which inevitably reduces the high coercivity of SmCo5 magnetic powder, failing to meet the practical application requirements of high coercivity in SmCo5 magnets. Chinese patent CN202210459967 discloses a method for preparing high-performance rare-earth cobalt-based permanent magnet materials, and designs (Y) 1-y-x Sm yRE x (Co) 1-a-b-c Fe a Cu b Zr c ) z Multi-element alloy materials are melted into ingots via electromagnetic induction, then coarsely crushed and pulverized using an air jet mill to obtain 2-6 μm magnetic powder for subsequent magnet fabrication. However, this method is complex, energy-intensive, and the resulting magnetic powder is prone to agglomeration and oxidation. A patent uses yttrium-cobalt as a matrix, adding multi-element alloys to obtain magnets with high remanent magnetization of 10.7-11.7 kGs. This invention also proposes whether doping yttrium during the preparation of SmCo5 magnetic powder can achieve the same effect of improving the remanent magnetization. In summary, rare-earth magnetic particles prepared by physical methods generally suffer from problems such as wide particle size distribution, large average particle size, low magnetic properties, and high energy consumption.

[0004] Chemical methods for preparing rare-earth magnetic particles mainly include direct liquid-phase synthesis, sol-gel method, mechanochemical method, and liquid-phase synthesis combined with calcium reduction and diffusion method. Chemical methods offer easier control over the size and properties of the synthesized samples. Among these, the liquid-phase synthesis combined with calcium reduction and diffusion method can successfully prepare high-performance nanoparticles. It is simple to operate, low in cost, and has minimal environmental impact, making it a scientific method worthy of further research. Chinese patent CN202010094572 uses an alcoholic thermal method to prepare Co / Sm(OH)3 precursors, followed by a short-term incomplete calcium reduction reaction to prepare Co / SmCo composite magnetic particles. Soft magnetic Co and hard magnetic SmCo form a core-shell structure, resulting in exchange coupling to achieve high saturation magnetization. However, the coercivity of the SmCo5 magnetic powder prepared by this method is approximately 15 kOe, which is low. Furthermore, the incomplete calcium reduction reaction leads to waste of calcium particles, which is not conducive to large-scale production.

[0005] Therefore, designing an efficient method for preparing SmCo-based magnetic particles that results in particles with a narrow particle size distribution, small average particle size, high coercivity, high remanent magnetization, and high saturation magnetization is of great significance for the production of samarium cobalt-based permanent magnets. Summary of the Invention

[0006] To address the problems of existing technologies, this invention provides a novel chemical method for preparing high magnetic properties (Sm x Y 1-x The method for preparing SmCo5 rare earth magnetic particles specifically involves a new technique combining chemical co-precipitation with calcium reduction reaction. Based on the preparation of SmCo5 magnetic powder, yttrium is doped to obtain ternary alloy magnetic powder. This significantly improves saturation magnetization and remanent magnetization at the cost of slightly reducing the coercivity of the magnetic powder, resulting in high-magnetic-performance (SmCo5) rare earth magnetic particles. x Y 1-xCo5 magnetic powder. This invention uses a co-precipitation method combined with a high-temperature and high-pressure reactor to prepare a mixed precursor of Sm(OH)3 / Y(OH)3 / Co(OH)2 by controlling the proportion of different raw materials. Then, a Ca(OH)2 shell is used to encapsulate the precursor, preparing a Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 composite precursor. A certain amount of metallic calcium particles, KCl, and CaCl2 diffusion medium are weighed and mixed evenly with the sample to be treated and placed in a tube furnace. Heat treatment parameters are set, and calcium participates in the overall reduction reaction under an argon atmosphere to avoid incomplete reaction of the precursor. After the reaction, the mixture is rapidly cooled to room temperature, and then ultrasonically washed with ice water and glacial acetic acid to remove impurities from the surface of the magnetic powder. The magnetic powder obtained by incorporating yttrium and adjusting the heat treatment process parameters has better magnetic properties.

[0007] To achieve the above, the process route of the present invention is implemented through the following steps.

[0008] A chemical method for preparing high magnetic properties (Sm x Y 1-x The method for producing Co5 rare earth magnetic particles is characterized by comprising the following steps:

[0009] (1) Precursors were prepared by selecting SmCl3·6H2O, YCl3·6H2O, CoCl2·6H2O and NaOH as raw materials;

[0010] (2) Weigh out SmCl3·6H2O, YCl3·6H2O and CoCl2·6H2O raw materials according to a certain molar ratio and place them in a beaker. Add deionized water to dissolve them completely, and then stir them evenly at room temperature on a magnetic stirrer.

[0011] Preferably, the molar ratio of nSm / nY (Sm / Y) is set to 1:0-0:1, for example, 1:0, 3:1, 1:1, 1:3, 0:1. Raw materials are weighed according to different molar ratios, preferably Sm and Y are not 0. During this process, the molar ratio of n(Sm,Y) / nCo (the molar ratio of Sm and Y to Co) is kept constant. Considering the loss of Sm and Y elements during heat treatment, excess Sm and Y are added during the precursor preparation process. Generally, the molar ratio of n(Sm,Y) / nCo is between 1:4.5 and 1:4.7.

[0012] (3) Weigh a certain amount of sodium hydroxide solid particles, add deionized water, and after completely dissolving and mixing, add it to the mixed solution obtained in step (2). Then stir continuously for 1 hour to generate amorphous hydroxides such as Sm(OH)3, Y(OH)3, and Co(OH)2.

[0013] Preferably, the NaOH reacts chemically with SmCl3·6H2O, YCl3·6H2O, and CoCl2·6H2O to generate amorphous hydroxides such as Sm(OH)3, Y(OH)3, and Co(OH)2. To ensure complete reaction of the raw materials, the molar amount of NaOH is controlled to exceed the theoretical value by 20%. The prepared NaOH solution is added dropwise to ensure the homogeneity of the generated products.

[0014] (4) Place the amorphous hydroxide solution stirred evenly in step (3) into a polytetrafluoroethylene liner, and then put it into a high-temperature and high-pressure reactor for heat treatment. The heat treatment conditions are set as follows: heating rate 5℃ / min, heating temperature 180℃, and holding time 720min.

[0015] Preferably, this reaction step converts the amorphous hydroxide mixture prepared by the co-precipitation method into crystalline hydroxide, and the reaction is maintained at this temperature for 720 min to ensure complete reaction. The precursor particles prepared by this method are in the nanoscale, which is beneficial for the subsequent preparation of small-sized rare earth magnetic particles.

[0016] (5) Take out the precursor after heat treatment in step (4), use deionized water to ultrasonically disperse and wash, then centrifuge and wash multiple times and dry. For example, place it in a centrifuge and centrifuge at 6000 r / min for 3 min. Repeat the operation on the precipitate 3-5 times to make the pH=7. Then put the precipitate into a drying oven and dry at 60℃ for 720 min. The dried precursor is ground into powder using a mortar and pestle to finally obtain the gray-brown mixed hydroxide precursor Sm(OH)3 / Y(OH)3 / Co(OH)2.

[0017] (6) Add the precursor Sm(OH)3 / Y(OH)3 / Co(OH)2 from step (5) to anhydrous ethanol and sonicate until homogeneous. First, add a certain molar concentration of CaCl2 aqueous solution and mix well. Then, slowly add the corresponding KOH solution and stir at room temperature for 8 hours to coat the generated Ca(OH)2 with Sm(OH)3 / Y(OH)3 / Co(OH)2. Then, use anhydrous ethanol to ultrasonically centrifuge and wash and dry the sample. For example, centrifuge and wash the sample 3 times and then dry it at 60°C. Grind the dried powder through a 400-mesh sieve to obtain an ultrafine powder in the Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor.

[0018] Preferably, in the above-mentioned precipitation method, CaCl2 reacts with KOH during stirring to generate Ca(OH)2, which is slightly soluble in water. After the solution is saturated, the precursor is precipitated and encapsulated. The amount of Ca(OH)2 encapsulated is controlled to be 0.2g-1g per 1g of Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor. The solubility of Ca(OH)2 in water is 0.165g. The total volume of fixed CaCl2 aqueous solution and added KOH aqueous solution is 40ml per 1g of Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor. The amount of Ca(OH)2 encapsulated is increased by increasing the molar concentration of CaCl2 and KOH. The number of moles of KOH is sufficient to generate Ca(OH)2. The amount of anhydrous ethanol is not limited, as long as it can ensure that the Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor is uniformly dispersed.

[0019] (7) Mix the precursor, calcium particles, KCl and CaCl2 obtained in step (6), preferably in a mass ratio of 1:4:2:1. Mix the above substances evenly and place them in a stainless steel crucible.

[0020] (8) Place the stainless steel crucible from step (7) into a vacuum tube furnace for heat treatment. First, clean the furnace cavity with argon gas three times, then evacuate to 100°C. -2 Pa, set the heating rate to 8℃ / min, the heat treatment temperature to 925-1000℃, the holding time to 90-120min, and use a fan for rapid cooling.

[0021] (9) Place the product after heat treatment in step (8) into ice water for rapid reaction to remove the calcium oxide generated in the reaction and the unreacted diffusion media KCl and CaCl2; since ice water cannot completely remove impurities, start adding glacial acetic acid dropwise while stirring, until the solution pH = 7; remove the supernatant and ultrasonically wash the obtained magnetic powder with alcohol 4-5 times. Store the prepared magnetic powder in alcohol to prevent oxidation.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] This invention provides a novel method for preparing (Sm) x Y 1-x(1) This invention utilizes a one-step chemical method to prepare a mixed precursor of hydroxides, Sm(OH)3, Y(OH)3, and Co(OH)2 in the same reaction vessel, thereby improving the uniformity of the mixed precursor and enabling more uniform preparation of magnetic powder. (2) The precursor prepared by the hydrothermal method is crystalline, and Co(OH)2 is in the form of nanosheets with a width of 250nm-400nm and a thickness of 30nm-40nm. The nanorods Sm(OH)3 and Y(OH)3 have a length of 150nm-350nm and a diameter of 15nm-25nm. The nanorods are loaded on the surface of the nanosheets. This structure is conducive to growing magnetic particles of similar shape on the Co(OH)2 nanosheets as a substrate, and ensures that the average particle size of the prepared particles is in the submicron range. (3) The Ca(OH)2 shell is designed to encapsulate the precursor in a very small reaction space, and the Ca(OH)2 is converted into CaO during heat treatment, further improving the uniformity of the generated magnetic powder particle size. (4) The use of rare earth yttrium doping solves the application problem of yttrium, a rare earth element with high abundance in southern China, improves its utilization rate, and reduces the production cost of rare earth magnetic particles. (5) The rare earth magnetic particles prepared by this method have high coercivity, significantly improved remanent magnetization and saturation magnetization, and provide new technical support for high-performance magnetic particle samples, with a wide range of applications. Attached Figure Description

[0024] Figure 1 The XRD and VSM patterns of the magnetic powder prepared in Example 1 are shown.

[0025] Figure 2 The image shows a SEM image of the magnetic powder prepared in Example 1. Detailed Implementation

[0026] To illustrate the technical content, objectives, and effects of the present invention in detail, the following description is provided in conjunction with the embodiments. However, the present invention is not limited to the following embodiments.

[0027] Example 1

[0028] (1) Weigh out SmCl3·6H2O, YCl3·6H2O and CoCl2·6H2O raw materials according to the molar ratio nSm:nY:nCo=0.5:0.5:4.6 and place them in a beaker. Add deionized water to dissolve them completely and stir on a magnetic stirrer at room temperature.

[0029] (2) Weigh 14.64 mmol of sodium hydroxide solid particles, add 20 ml of deionized water, dissolve and mix thoroughly, then add dropwise to the mixed solution obtained in step (1), and then continue stirring for 1 h.

[0030] (3) Place the well-stirred solution in a polytetrafluoroethylene liner and then put it into a high-temperature and high-pressure reactor for hydrothermal reaction. The heat treatment conditions are set as follows: heating rate 5℃ / min, heating temperature 180℃, and holding time 720min.

[0031] (4) Take out the precursor after heat treatment in step (3), wash it with deionized water by ultrasonic dispersion, and then centrifuge it at 6000 r / min for 3 min. Repeat the operation on the precipitate 3-5 times to make the pH=7. Then put the precipitate into a drying oven and dry it at 60℃ for 720 min.

[0032] (5) The precursor dried in step (4) is ground into powder using a mortar and pestle to finally obtain the gray-brown mixed hydroxide precursor Sm(OH)3 / Y(OH)3 / Co(OH)2.

[0033] (6) Add 1g of the precursor Sm(OH)3 / Y(OH)3 / Co(OH)2 from step (5) to 40ml of anhydrous ethanol and sonicate until homogeneous. Add 20ml of CaCl2 solution of a certain molar concentration, mix well, and then slowly add 20ml of the prepared KOH solution. Stir at room temperature for 8h. Then wash the sample three times with anhydrous ethanol by ultrasonic centrifugation, followed by drying at 60℃. Grind the dried powder through a 400-mesh sieve to obtain an ultrafine powdered Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor. Adjust the concentration of CaCl2 so that the Ca(OH)2 coating amount is 0.2g.

[0034] (7) Weigh 1g of the precursor obtained in step (6), then weigh 4g of calcium granules, 2g of KCl, and 1g of CaCl2. Mix the above substances evenly and place them in a stainless steel crucible. Then place it in a vacuum tube furnace. First, clean the furnace cavity with argon gas three times, then evacuate to 100°C. -2 Pa, set the heating rate to 8℃ / min, the heat treatment temperature to 1000℃, and the holding time to 120min.

[0035] (8) Place the product after heat treatment in step (7) in ice water for rapid reaction to remove the generated calcium oxide and unreacted diffusion medium. Since ice water cannot completely remove impurities, start adding glacial acetic acid dropwise while stirring, until the solution pH = 7. Remove the supernatant and ultrasonically wash the obtained magnetic powder with alcohol 4-5 times. Store the prepared magnetic powder in alcohol to prevent oxidation. XRD and VSM tests of the magnetic powder are as follows. Figure 1 As shown, the SEM characterization of the magnetic powder is as follows: Figure 2 As shown.

[0036] Example 2

[0037] (1) Weigh out SmCl3·6H2O, YCl3·6H2O and CoCl2·6H2O raw materials according to the molar ratio nSm:nY:nCo=0.25:0.75:4.6 and place them in a beaker. Add deionized water to dissolve them completely and stir on a magnetic stirrer at room temperature.

[0038] (2) Weigh 14.64 mmol of sodium hydroxide solid particles, add 20 ml of deionized water, dissolve and mix thoroughly, then add dropwise to the mixed solution obtained in step (1), and then continue stirring for 1 h.

[0039] (3) Place the well-stirred solution in a polytetrafluoroethylene liner and then put it into a high-temperature and high-pressure reactor for hydrothermal reaction. The heat treatment conditions are set as follows: heating rate 5℃ / min, heating temperature 180℃, and holding time 720min.

[0040] (4) Take out the precursor after heat treatment in step (3), wash it with deionized water by ultrasonic dispersion, and then centrifuge it at 6000 r / min for 3 min. Repeat the operation on the precipitate 3-5 times to make the pH=7. Then put the precipitate into a drying oven and dry it at 60℃ for 720 min.

[0041] (5) Grind the dried precursor from step (4) into powder using a mortar and pestle, and then pass it through a 400-mesh sieve to finally obtain the grayish-brown mixed hydroxide precursor Sm(OH)3 / Y(OH)3 / Co(OH)2.

[0042] (6) Add 1g of the precursor Sm(OH)3 / Y(OH)3 / Co(OH)2 from step (5) to 40ml of anhydrous ethanol and sonicate until homogeneous. Add 20ml of CaCl2 solution of a certain molar concentration, mix well, and then slowly add 20ml of the prepared KOH solution. Stir at room temperature for 8h. Then wash the sample three times with anhydrous ethanol by ultrasonic centrifugation, followed by drying at 60℃. Grind the dried powder through a 400-mesh sieve to obtain an ultrafine powdered Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor. Adjust the CaCl2 solution concentration so that the Ca(OH)2 coating amount is 0.2g.

[0043] (7) Weigh 1g of the precursor obtained in step (6), then weigh 4g of calcium granules, 2g of KCl, and 1g of CaCl2. Mix the above substances evenly and place them in a stainless steel crucible. Then place it in a vacuum tube furnace. First, clean the furnace cavity with argon gas three times, then evacuate to 100°C. -2 Pa, set the heating rate to 8℃ / min, the heat treatment temperature to 1000℃, and the holding time to 120min.

[0044] (8) Place the product after heat treatment in step (7) in ice water for rapid reaction to remove the calcium oxide generated in the reaction and the unreacted diffusion medium. Since ice water cannot completely remove impurities, start adding glacial acetic acid dropwise while stirring, until the solution pH = 7. Remove the supernatant and ultrasonically wash the obtained magnetic powder with alcohol 4-5 times. Store the prepared magnetic powder in alcohol to prevent oxidation.

[0045] Comparative Example 1

[0046] (1) Weigh YCl3·6H2O and CoCl2·6H2O raw materials according to the molar ratio nY:nCo=1:4.6 and place them in a beaker. Add deionized water to completely dissolve them and place them on a magnetic stirrer to stir at room temperature.

[0047] (2) Weigh 14.64 mmol of sodium hydroxide solid particles, add 20 ml of deionized water, dissolve and mix thoroughly, then add dropwise to the mixed solution obtained in step (1), and then continue stirring for 1 h.

[0048] (3) Place the well-stirred solution in a polytetrafluoroethylene liner and then put it into a high-temperature and high-pressure reactor for hydrothermal reaction. The heat treatment conditions are set as follows: heating rate 5℃ / min, heating temperature 180℃, and holding time 720min.

[0049] (4) Take out the precursor after heat treatment in step (3), wash it with deionized water by ultrasonic dispersion, and then centrifuge it at 6000 r / min for 3 min. Repeat the operation on the precipitate 3-5 times to make the pH=7. Then put the precipitate into a drying oven and dry it at 60℃ for 720 min.

[0050] (5) Grind the dried precursor from step (4) into powder using a mortar and pestle, and then pass it through a 400-mesh sieve to finally obtain the gray-brown mixed hydroxide precursor Y(OH)3 / Co(OH)2.

[0051] (6) Add the precursor Y(OH)3 / Co(OH)2 from step (5) to anhydrous ethanol and sonicate until homogeneous. Add a CaCl2 solution of a certain molar concentration, mix well, and then slowly add the prepared KOH solution. Stir at room temperature for 8 hours. Then wash the sample three times with anhydrous ethanol by ultrasonic centrifugation, followed by drying at 60°C. Grind the dried powder through a 400-mesh sieve to obtain an ultrafine powdered Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor, with a Ca(OH)2 coating amount of 0.2 g.

[0052] (7) Weigh 1g of the precursor obtained in step (6), then weigh 4g of calcium granules, 2g of KCl, and 1g of CaCl2. Mix the above substances evenly and place them in a stainless steel crucible. Then place it in a vacuum tube furnace. First, clean the furnace cavity with argon gas three times, then evacuate to 100°C. -2 Pa, set the heating rate to 8℃ / min, the heat treatment temperature to 1000℃, and the holding time to 120min.

[0053] (8) Place the product after heat treatment in step (7) in ice water for rapid reaction to remove the calcium oxide generated in the reaction and the unreacted diffusion medium. Since ice water cannot completely remove impurities, start adding glacial acetic acid dropwise while stirring, until the solution pH = 7. Remove the supernatant and ultrasonically wash the obtained magnetic powder with alcohol 4-5 times. Store the prepared magnetic powder in alcohol to prevent oxidation.

[0054] Comparative Example 2

[0055] (1) Weigh the raw materials according to the molar ratio nSm:nY:nCo=0.5:0.5:4.6 and place them in a beaker. Add deionized water to dissolve them completely and place them on a magnetic stirrer to stir at room temperature.

[0056] (2) Weigh 14.64 mmol of sodium hydroxide solid particles, add 20 ml of deionized water, dissolve and mix thoroughly, then add dropwise to the mixed solution obtained in step (1), and then continue stirring for 1 h.

[0057] (3) Place the well-stirred solution in a polytetrafluoroethylene liner and then put it into a high-temperature and high-pressure reactor for hydrothermal reaction. The heat treatment conditions are set as follows: heating rate 5℃ / min, heating temperature 180℃, and holding time 720min.

[0058] (4) Take out the precursor after heat treatment in step (3), wash it with deionized water by ultrasonic dispersion, and then centrifuge it at 6000 r / min for 3 min. Repeat the operation on the precipitate 3-5 times to make the pH=7. Then put the precipitate into a drying oven and dry it at 60℃ for 720 min.

[0059] (5) Grind the dried precursor from step (4) into powder using a mortar and pestle, and then pass it through a 400-mesh sieve to finally obtain the grayish-brown mixed hydroxide precursor Sm(OH)3 / Y(OH)3 / Co(OH)2.

[0060] (6) Weigh 1g of the precursor obtained in step (7), then weigh 4g of calcium granules, 2g of KCl, and 1g of CaCl2. Mix the above substances evenly and place them in a stainless steel crucible. Then place it in a vacuum tube furnace. First, clean the furnace cavity with argon gas three times, then evacuate to 100°C. -2Pa, set the heating rate to 8℃ / min, the heat treatment temperature to 1000℃, and the holding time to 120min.

[0061] (7) Place the product after heat treatment in step (8) in ice water for rapid reaction to remove the calcium oxide generated in the reaction and the unreacted diffusion medium. Since ice water cannot completely remove impurities, start adding glacial acetic acid dropwise while stirring, until the solution pH = 7. Remove the supernatant and ultrasonically wash the obtained magnetic powder with alcohol 4-5 times. Store the prepared magnetic powder in alcohol to prevent oxidation.

[0062] The magnetic properties of the magnetic powders prepared in the examples and comparative examples were compared, as shown in Table 1.

[0063] Table 1: Magnetic property data obtained from VSM tests in embodiments and comparative examples of the present invention.

[0064]

[0065]

[0066] The table above shows that the pure YCo5 particles prepared in Comparative Example 1 have low coercivity but high saturation magnetization and remanent magnetization. Samples from Examples 1 and 2 were obtained using the chemical method for preparing Sm-Y-Co ternary alloy magnetic powder proposed in this patent. Based on the magnetic results, it was found that slightly reducing the yttrium doping level significantly increased the coercivity of the magnetic powder, but decreased the saturation magnetization and remanent magnetization. The rare-earth magnetic particles prepared using the method of this invention are not only simple, easy to implement, highly controllable, and widely applicable, but also solve the problem of large particle size and low magnetic performance in existing technologies. Furthermore, it proposes a new method for addressing the application of yttrium, a high-abundance rare-earth element in southern regions.

Claims

1. A chemical method for preparing high magnetic properties (Sm x Y 1-x) The method for producing Co5 rare earth magnetic particles is characterized by... Includes the following steps: (1) Precursors were prepared by selecting SmCl3·6H2O, YCl3·6H2O, CoCl2·6H2O and NaOH as raw materials; (2) Weigh out SmCl3·6H2O, YCl3·6H2O and CoCl2·6H2O raw materials according to a certain molar ratio and place them in a beaker. Add deionized water to dissolve them completely, and then stir them evenly at room temperature on a magnetic stirrer. (3) Weigh a certain amount of sodium hydroxide solid particles, add deionized water, and after completely dissolving and mixing, add it to the mixed solution obtained in step (2). Then stir continuously for 1 hour to generate amorphous hydroxides Sm(OH)3, Y(OH)3, and Co(OH)2. (4) Place the amorphous hydroxide solution stirred evenly in step (3) into a polytetrafluoroethylene liner, and then put it into a high-temperature and high-pressure reactor for heat treatment. The heat treatment conditions are set as follows: heating rate 5℃ / min, heating temperature 180℃, and holding time 720min. (5) Take out the precursor after heat treatment in step (4), use deionized water to ultrasonically disperse and wash, then centrifuge and wash several times and dry; grind the dried precursor into powder using a mortar and pestle to finally obtain the gray-brown mixed hydroxide precursor Sm(OH)3 / Y(OH)3 / Co(OH)2. (6) Take the precursor Sm(OH)3 / Y(OH) from step (5) 3 / Co(OH)2 was added to anhydrous ethanol and sonicated until homogeneous. First, a CaCl2 aqueous solution of a certain molar concentration was added and mixed evenly. Then, the corresponding KOH solution was slowly added dropwise and stirred at room temperature for 8 hours to allow the generated Ca(OH)2 to coat the Sm(OH)3 / Y(OH)3 / Co(OH)2. Then, the mixture was washed and dried by ultrasonic centrifugation with anhydrous ethanol. The dried powder was then ground through a 400-mesh sieve to obtain an ultrafine powder precursor of Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2. (7) Mix the precursor, calcium particles, KCl and CaCl2 obtained in step (6) and place the mixture evenly in a stainless steel crucible. (8) Place the stainless steel crucible from step (7) into a vacuum tube furnace for heat treatment. First, clean the furnace cavity with argon gas three times, then evacuate to 100°C. -2 Pa, set the heating rate to 8℃ / min, the heat treatment temperature to 925-1000℃, the holding time to 90-120min, and use a fan for rapid cooling; (9) Place the product after heat treatment in step (8) into ice water for rapid reaction to remove the calcium oxide generated by the reaction and the unreacted diffusion medium KCl and CaCl2; since ice water cannot completely remove impurities, start adding glacial acetic acid dropwise while stirring, until the solution pH = 7; remove the supernatant and use alcohol to ultrasonically wash the obtained magnetic powder 4-5 times; store the prepared magnetic powder in alcohol to prevent oxidation.

2. The method according to claim 1, characterized in that, Step (2) Set nSm / nY = 1:0-0:1; In this process, control the molar ratio of n(Sm,Y) / nCo to remain constant. Due to the burn-off of Sm and Y elements during the heat treatment process, add excess Sm and Y during the precursor preparation process, and the molar ratio of n(Sm,Y) / nCo is 1:4.5-1:4.

7.

3. The method according to claim 1, characterized in that, In step (6), CaCl2 reacts with KOH during stirring to generate Ca(OH)2. Ca(OH)2 is slightly soluble in water. After the solution is saturated, the precursor is precipitated and encapsulated. Each 1g of Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor corresponds to a fixed total volume of 40ml of CaCl2 aqueous solution and added KOH aqueous solution. The amount of Ca(OH)2 encapsulated is increased by increasing the molar concentration of CaCl2 and KOH. The number of moles of KOH ensures that Ca(OH)2 can be generated.

4. The method according to claim 1, characterized in that, The amount of Ca(OH)2 encapsulated in each 1g of Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor is controlled to be 0.2g-1g.

5. The method according to claim 1, characterized in that, In step (7), the mass ratio of precursor, calcium particles, KCl, and CaCl2 is 1:4:2:

1.

6. The high magnetic properties (Sm) prepared according to the method of any one of claims 1-5 x Y 1-x) Co5 rare earth magnetic particles.

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