Method for preparing (SmxY1-x) Co5 rare earth magnetic particles with high magnetic properties by chemical method

Abstract

The invention discloses a method for preparing (SmxY1-x) Co5 rare earth magnetic particles with high magnetic properties by a chemical method, and belongs to the field of rare earth magnetic materials. The invention particularly relates to a novel technology for preparing (SmxY1-x) Co5 ternary alloy magnetic powder with high magnetic properties by combining chemical liquid phase synthesis with calcium reduction reaction. A Sm (OH) 3 / Y (OH) 3 / Co (OH) 2 (at) Ca (OH) 2 crystalline state mixed precursor prepared by chemical coprecipitation and a hydrothermal reaction is uniformly subjected to a complete calcium reduction reaction with a certain amount of metal calcium particles, KCl and CaCl2 diffusion media in an argon atmosphere, and the magnetic powder is prepared. The saturation magnetization intensity and the residual magnetization intensity of the magnetic powder are improved by doping the yttrium element, but the coercive force of the magnetic powder is slightly reduced, and the method provides a new thought for preparing high-performance rare earth magnetic particles.

Description

Technical Field

[0001] The present invention relates to a novel method for preparing a high coercive force, high saturation magnetization, high residual magnetization, uniaxial anisotropy (Sm x Y 1-x )Co5 rare earth magnetic particles, specifically involving a method of preparing nano-scale hydroxide composite precursors by co-precipitation combined with hydrothermal synthesis, and obtaining rare earth magnetic particles by combining calcium reduction diffusion technology, belonging to the field of rare earth magnetic materials. Background Art

[0002] Rare earth permanent magnet material SmCo5 is the first generation of permanent magnets, which are widely used in aerospace, precision instruments, microwave devices and other fields. Its advantages are high coercivity, high magnetic energy product and good thermal stability. Its disadvantage is that it has a low saturation magnetization intensity M. s . With the development of science and technology, the demand for magnets in terms of high magnetic properties and lightweight size has greatly increased. Therefore, the research on the high-performance preparation of rare earth magnetic particles in the process of preparing magnets has gradually attracted people's attention. At present, researchers have obtained submicron and nanometer rare earth magnetic particles with high coercivity, high saturation magnetization, and high residual magnetization through reasonable structural design, experimental improvement, element doping and other methods, which in turn affect the magnetic properties of the prepared magnets. As a high-abundance rare earth element, the rare earth yttrium element is more abundant than samarium. Replacing samarium in SmCo5 with yttrium is conducive to promoting the high-value application of high-abundance yttrium elements and reducing the production cost of magnetic powder. Adding Y element is a promising and cost-effective method to improve the magnetic properties of 1:5 permanent magnets.

[0003] At present, the methods for preparing magnetic particles can be divided into two types: physical method and chemical method, and many experimental studies have been made. The physical method is currently the most common method for mass production, including ball milling and electron beam deposition. The ball milling method is to place the prepared block in a ball mill and collide with a certain number of zirconium oxide balls at high speed to obtain uniform particles, and the ball milling time determines the size of the particles. The electron beam deposition method is to prepare the block and turn it into small particles under the special high-energy electron beam and then collect it on a cooled substrate. The method for preparing anisotropic samarium cobalt magnetic powder in Chinese patent CN202011082726 is to first use a rapid solidification process to obtain samarium cobalt castings, and then use a hydrogen cracking process to prepare 10-200μm anisotropic magnetic powder after aging treatment. This method can be applied to the preparation and production of large-scale magnetic powder. However, the prepared anisotropic samarium cobalt magnetic powder has a wide particle size distribution range and the average particle size of the particles is 100μm, which will inevitably reduce the high coercive force magnetic properties of SmCo5 magnetic powder, and cannot meet the actual application requirements of high coercive force of SmCo5 magnets. Chinese patent CN202210459967 provides a method for preparing high-performance rare earth cobalt-based permanent magnet materials, design (Y 1-y-x Sm yRE x )(Co 1-a-b-c Fe a Cu b Zr c ) z The multi-component alloy material is melted by electromagnetic induction to obtain an ingot, and then coarsely crushed and airflow milled to obtain 2-6μm magnetic powder for subsequent magnet preparation. However, this method has a complex process flow and high energy consumption, and the prepared magnetic powder is prone to agglomeration and oxidation. The patent uses yttrium and cobalt elements as the matrix, and adds multi-element alloys to obtain a magnet with a high residual magnetization of 10.7-11.7kGs. Drawing on this method, it is also proposed whether the present invention can achieve the effect of increasing the residual magnetization of the magnetic powder by doping yttrium elements in the preparation process of SmCo5 magnetic powder. In summary, the rare earth magnetic particles prepared by physical methods generally have problems such as a wide particle size distribution range, a large average particle size, low magnetic properties, and high energy consumption in the process flow.

[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 diffusion method. The chemical method is easier to control the size and performance of the synthesized sample. Among them, liquid phase synthesis combined with calcium reduction diffusion method can successfully prepare high-performance nanoparticles. It is simple to operate, low cost, and has little harm to the environment. It is a scientific method worthy of in-depth study. Chinese patent CN202010094572 uses an alcohol thermal method to prepare Co / Sm(OH)3 precursors, and a short-time incomplete calcium reduction reaction to prepare Co / SmCo composite magnetic particles. The soft magnetic Co and the hard magnetic SmCo form a core-shell structure and exchange coupling to obtain a higher saturation magnetization, but the coercive force of the SmCo5 magnetic powder prepared by this method is approximately 15kOe, the coercive force is low, and the incomplete calcium reduction reaction causes the waste of calcium particles, which is not conducive to large-scale production.

[0005] Therefore, designing a method for efficiently preparing SmCo-based magnetic particles so that the prepared particles have a narrow particle size distribution range, a small average particle size, high coercive force, high residual magnetization and high saturation magnetization is of great significance for the production of samarium cobalt-based permanent magnets. Summary of the invention

[0006] In order to solve the existing technical problems, the present invention provides a new chemical method for preparing high magnetic properties (Sm x Y 1-x )Co5 rare earth magnetic particles operation method, specifically relates to a method of using a chemical coprecipitation method combined with a new calcium reduction reaction technology, on the basis of SmCo5 magnetic powder preparation, doping yttrium element to obtain ternary alloy magnetic powder, at the cost of slightly reducing the coercive force of the magnetic powder, significantly improving the saturation magnetization intensity and residual magnetization intensity, and obtaining high magnetic performance (Sm x Y 1-x)Co5 magnetic powder. The present invention uses a co-precipitation method combined with a high-temperature and high-pressure reactor to adjust the ratio of different raw materials to prepare a Sm(OH)3 / Y(OH)3 / Co(OH)2 mixed precursor, and then uses a Ca(OH)2 shell to wrap it to prepare a Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 composite precursor. A certain amount of metal calcium particles, KCl, and CaCl2 diffusion medium are weighed and mixed evenly with the sample to be treated and put into a tubular furnace, and the heat treatment parameters are set. Calcium participates in the overall reduction reaction under an argon atmosphere to avoid incomplete reaction of the precursor. After the reaction is completed, it is quickly cooled to room temperature, and then ice water and glacial acetic acid are used for ultrasonic washing to remove impurities on the surface of the magnetic powder. The magnetic powder obtained by the addition of yttrium and the adjustment of heat treatment process parameters has better magnetic properties.

[0007] To achieve the above content, 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) Selecting SmCl3·6H2O, YCl3·6H2O, CoCl2·6H2O and NaOH as raw materials to prepare precursors;

[0010] (2) Weigh SmCl3·6H2O, YCl3·6H2O, and CoCl2·6H2O in a certain molar ratio and place them in a beaker, add deionized water to completely dissolve them, and stir and mix them evenly on a magnetic stirrer at room temperature;

[0011] Preferably, nSm / nY (Sm / Y molar ratio) is set to 1:0-0:1, for example, 1:0, 3:1, 1:1, 1:3, 0:1, and raw materials are weighed according to different molar ratios, preferably Sm and Y are not 0 respectively; in this process, the molar ratio of n(Sm, Y) / nCo (the molar ratio of Sm and Y to Co) is controlled to remain unchanged; considering the burning of Sm and Y elements during the heat treatment process, excessive Sm and Y are added during the precursor preparation process, and the molar ratio of n(Sm, Y) / nCo is generally 1:4.5-1:4.7;

[0012] (3) Weigh a certain amount of sodium hydroxide solid particles, add deionized water, completely dissolve and mix, then add to the mixed solution obtained in step (2), and then continue stirring 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, CoCl2·6H2O to generate amorphous hydroxides such as Sm(OH)3, Y(OH)3, Co(OH)2. To ensure complete reaction of the raw materials, the molar amount of NaOH is controlled to exceed 20% of the theoretical value. The prepared NaOH solution is added dropwise to ensure uniformity of the generated product.

[0014] (4) placing the amorphous hydroxide solution stirred evenly in step (3) into a polytetrafluoroethylene liner, and then placing it into a high-temperature and high-pressure reactor for heat treatment, wherein the heat treatment conditions are set at a heating rate of 5°C / min, a heating temperature of 180°C, and a holding time of 720min;

[0015] Preferably, the amorphous hydroxide mixture prepared by the coprecipitation method is converted into crystalline hydroxide by this step reaction, and the temperature is kept for 720 minutes to ensure complete reaction. The precursor particle size prepared by this method is in the nanometer scale, which is conducive to the subsequent preparation of small-sized rare earth magnetic particles.

[0016] (5) The precursor after the heat treatment in step (4) is taken out, and ultrasonically dispersed and washed with deionized water, and then centrifuged and washed multiple times and dried, such as placing it in a centrifuge at 6000 r / min for 3 min, repeating the operation 3-5 times for the precipitate to make the pH = 7, and then placing the precipitate in a drying oven at 60°C and drying it for 720 min; the dried precursor is ground into powder using a mortar, and finally a gray-brown mixed hydroxide precursor Sm(OH)3 / Y(OH)3 / Co(OH)2 is obtained.

[0017] (6) The precursor Sm(OH)3 / Y(OH)3 / Co(OH)2 of step (5) is added to anhydrous ethanol and ultrasonically homogenized. First, a certain molar concentration of CaCl2 aqueous solution is added, and after uniform mixing, the corresponding KOH solution is slowly added dropwise, and stirred at room temperature for 8 hours to allow the generated Ca(OH)2 to be coated on the outside of Sm(OH)3 / Y(OH)3 / Co(OH)2. Then, anhydrous ethanol is used for ultrasonic centrifugal washing and drying. For example, the sample is centrifuged and washed 3 times, and then dried at 60°C. The dried powder is ground through a 400-mesh sieve to obtain an ultrafine powder of 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, and the encapsulated precursor is precipitated after the solution is saturated; the amount of Ca(OH)2 encapsulated per 1g of Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor is controlled to be 0.2g-1g; the solubility of Ca(OH)2 in water is 0.165g, and the total volume of the fixed CaCl2 aqueous solution and the added KOH aqueous solution corresponding to each 1g of Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor is 40ml, and the molar concentration of CaCl2 and KOH is increased to increase the amount of Ca(OH)2 encapsulated; the molar number of KOH ensures that Ca(OH)2 can be generated; the amount of anhydrous ethanol used is not limited, as long as the Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor can be evenly dispersed.

[0019] (7) Mixing the precursor, calcium particles, KCL and CaCl2 obtained in step (6), preferably the mass ratio of the precursor, calcium particles, KCL and CaCl2 is 1:4:2:1, and evenly mixing the above substances in a stainless steel crucible;

[0020] (8) The stainless steel crucible of step (7) was placed in a vacuum tube furnace for heat treatment. The furnace chamber was first flushed with argon gas for 3 times, and then evacuated to 10 -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 to cool quickly.

[0021] (9) The product after heat treatment in step (8) is placed in 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, glacial acetic acid is added dropwise, stirring while adding until the solution pH = 7; the supernatant is removed, and the obtained magnetic powder is ultrasonically washed with alcohol for 4-5 times. The prepared magnetic powder is stored in alcohol to prevent oxidation.

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

[0023] The present invention provides a novel preparation method (Sm x Y 1-x) Technology for preparing submicron magnetic powders with high coercive force, high residual magnetization and high saturation magnetization by chemical method. This technology provides a new idea for preparing submicron magnetic powders with high coercive force, high residual magnetization and high saturation magnetization by chemical method, and solves the problem of large particle size and low magnetic performance of magnetic powders prepared by existing technology to a certain extent. (1) The present invention uses a one-step chemical method to prepare a hydroxide mixed precursor. Sm(OH)3, Y(OH)3 and Co(OH)2 are in the same reaction container, which improves the uniformity of the mixed precursor and can prepare magnetic powder more uniformly. (2) The precursor prepared by hydrothermal method is crystalline, Co(OH)2 is a nanosheet with a width of 250nm-400nm and a thickness of 30nm-40nm, and the nanorods Sm(OH)3 and Y(OH)3 are 150nm-350nm in length and 15nm-25nm in diameter. The nanorods are loaded on the surface of the nanosheets. This structure is conducive to growing magnetic particles of similar shape based on Co(OH)2 nanosheets, and ensures that the average particle size of the prepared particles is at the submicron level. (3) The Ca(OH)2 shell coating is designed to confine the precursor in a very small reaction space, and Ca(OH)2 is converted into CaO during the heat treatment process, further improving the uniformity of the particle size of the generated magnetic powder. (4) The use of the rare earth yttrium element doping solves the application problem of yttrium, a high-abundance rare earth element in the south, 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 coercive force, significantly improved residual magnetization and saturation magnetization, providing new technical support for high-performance magnetic particle samples and a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 XRD and VSM diagrams of the magnetic powder prepared in Example 1.

[0025] Figure 2 The SEM image of the magnetic powder prepared in Example 1. DETAILED DESCRIPTION

[0026] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in conjunction with the implementation modes, but the present invention is not limited to the following embodiments.

[0027] Example 1

[0028] (1) SmCl3·6H2O, YCl3·6H2O and CoCl2·6H2O are weighed into a beaker according to a molar ratio of nSm:nY:nCo=0.5:0.5:4.6, deionized water is added to completely dissolve the raw materials, and the mixture is stirred on a magnetic stirrer at room temperature.

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

[0030] (3) The uniformly stirred solution was placed in a polytetrafluoroethylene liner and then placed in a high-temperature and high-pressure reactor for hydrothermal reaction. The heat treatment conditions were set at a heating rate of 5°C / min, a heating temperature of 180°C, and a holding time of 720min.

[0031] (4) The precursor after heat treatment in step (3) was taken out, ultrasonically dispersed and washed with deionized water, and then centrifuged at 6000 r / min for 3 min in a centrifuge, and the operation was repeated 3-5 times for the precipitate to adjust the pH to 7. The precipitate was then placed in a drying oven at 60° C. and dried for 720 min.

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

[0033] (6) Add 1 g of the precursor Sm(OH)3 / Y(OH)3 / Co(OH)2 from step (5) to 40 ml of anhydrous ethanol and mix them evenly by ultrasonication. Add 20 ml of a CaCl2 solution of a certain molar concentration, mix evenly, and slowly drop 20 ml of the prepared KOH solution. Stir for 8 h at room temperature. Then wash the sample 3 times by ultrasonic centrifugation with anhydrous ethanol, and then dry it at 60°C. Grind the dried powder through a 400-mesh sieve to obtain an ultrafine powder Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor. Adjust the concentration of CaCl2 so that the amount of Ca(OH)2 encapsulation is 0.2 g.

[0034] (7) Weigh 1g of the precursor obtained in step (6), then weigh 4g of calcium particles, 2g of KCL, and 1g of CaCl2, mix the above substances evenly and place them in a stainless steel crucible. Then put them in a vacuum tube furnace, first wash the furnace chamber with argon gas 3 times, and then evacuate to 10 -2 Pa, set the heating rate to 8℃ / min, the heat treatment temperature to 1000℃, and keep warm for 120min.

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

[0036] Example 2

[0037] (1) SmCl3·6H2O, YCl3·6H2O and CoCl2·6H2O are weighed into a beaker according to a molar ratio of nSm:nY:nCo=0.25:0.75:4.6, deionized water is added to completely dissolve the raw materials, and the mixture is stirred at room temperature on a magnetic stirrer.

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

[0039] (3) The uniformly stirred solution was placed in a polytetrafluoroethylene liner and then placed in a high-temperature and high-pressure reactor for hydrothermal reaction. The heat treatment conditions were set at a heating rate of 5°C / min, a heating temperature of 180°C, and a holding time of 720min.

[0040] (4) The precursor after heat treatment in step (3) was taken out, ultrasonically dispersed and washed with deionized water, and then centrifuged at 6000 r / min for 3 min in a centrifuge, and the operation was repeated 3-5 times for the precipitate to adjust the pH to 7. The precipitate was then placed in a drying oven at 60° C. and dried for 720 min.

[0041] (5) The precursor dried in step (4) was ground into powder using a mortar and then passed through a 400-mesh sieve to finally obtain a gray-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 prepared in step (5) to 40ml of anhydrous ethanol and mix them evenly by ultrasonication. Add 20ml of a CaCl2 solution of a certain molar concentration, mix evenly, and slowly drop 20ml of the prepared KOH solution. Stir for 8h at room temperature. Then wash the sample 3 times by ultrasonic centrifugation with anhydrous ethanol and dry it at 60°C. Grind the dried powder through a 400-mesh sieve to obtain an ultrafine powder of Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor. Adjust the concentration of the CaCl2 solution so that the amount of Ca(OH)2 encapsulation is 0.2g.

[0043] (7) Weigh 1g of the precursor obtained in step (6), then weigh 4g of calcium particles, 2g of KCL, and 1g of CaCl2, mix the above substances evenly and place them in a stainless steel crucible. Then put them in a vacuum tube furnace, first wash the furnace chamber with argon gas 3 times, and then evacuate to 10 -2 Pa, set the heating rate to 8℃ / min, the heat treatment temperature to 1000℃, and keep warm for 120min.

[0044] (8) The product after heat treatment in step (7) is placed in ice water for rapid reaction to remove the calcium oxide generated by the reaction and the unreacted diffusion medium. Since ice water cannot completely remove impurities, glacial acetic acid is added dropwise, stirring while adding until the pH of the solution is 7. The supernatant is removed, and the obtained magnetic powder is ultrasonically washed with alcohol for 4-5 times. The prepared magnetic powder is stored in alcohol to prevent oxidation.

[0045] Comparative Example 1

[0046] (1) YCl3·6H2O and CoCl2·6H2O raw materials were weighed according to the molar ratio of nY:nCo=1:4.6 and placed in a beaker. Deionized water was added to completely dissolve the raw materials. The raw materials were placed on a magnetic stirrer and stirred at room temperature.

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

[0048] (3) The uniformly stirred solution was placed in a polytetrafluoroethylene liner and then placed in a high-temperature and high-pressure reactor for hydrothermal reaction. The heat treatment conditions were set at a heating rate of 5°C / min, a heating temperature of 180°C, and a holding time of 720min.

[0049] (4) The precursor after heat treatment in step (3) was taken out, ultrasonically dispersed and washed with deionized water, and then centrifuged at 6000 r / min for 3 min in a centrifuge, and the operation was repeated 3-5 times for the precipitate to adjust the pH to 7. The precipitate was then placed in a drying oven at 60° C. and dried for 720 min.

[0050] (5) The precursor dried in step (4) was ground into powder using a mortar and then passed through a 400-mesh sieve to finally obtain a 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 mix well with ultrasound. Add a CaCl2 solution of a certain molar concentration, mix well, and then slowly drop the prepared KOH solution. Stir for 8 hours at room temperature. Then use anhydrous ethanol to wash the sample 3 times by ultrasonic centrifugation, and then dry it at 60°C. Grind the dried powder through a 400-mesh sieve to obtain an ultrafine powder Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor, and set the Ca(OH)2 coating amount to 0.2g.

[0052] (7) Weigh 1g of the precursor obtained in step (6), then weigh 4g of calcium particles, 2g of KCL, and 1g of CaCl2, mix the above substances evenly and place them in a stainless steel crucible. Then put them in a vacuum tube furnace, first wash the furnace chamber with argon gas 3 times, and then evacuate to 10 -2 Pa, set the heating rate to 8℃ / min, the heat treatment temperature to 1000℃, and keep warm for 120min.

[0053] (8) The product after heat treatment in step (7) is placed in ice water for rapid reaction to remove the calcium oxide generated by the reaction and the unreacted diffusion medium. Since ice water cannot completely remove impurities, glacial acetic acid is added dropwise, stirring while adding until the pH of the solution is 7. The supernatant is removed, and the obtained magnetic powder is ultrasonically washed with alcohol for 4-5 times. The prepared magnetic powder is stored in alcohol to prevent oxidation.

[0054] Comparative Example 2

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

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

[0057] (3) The uniformly stirred solution was placed in a polytetrafluoroethylene liner and then placed in a high-temperature and high-pressure reactor for hydrothermal reaction. The heat treatment conditions were set at a heating rate of 5°C / min, a heating temperature of 180°C, and a holding time of 720min.

[0058] (4) The precursor after heat treatment in step (3) was taken out, ultrasonically dispersed and washed with deionized water, and then centrifuged at 6000 r / min for 3 min in a centrifuge, and the operation was repeated 3-5 times for the precipitate to adjust the pH to 7. The precipitate was then placed in a drying oven at 60° C. and dried for 720 min.

[0059] (5) The precursor dried in step (4) was ground into powder using a mortar and then passed through a 400-mesh sieve to finally obtain a gray-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 particles, 2g of KCL, and 1g of CaCl2, mix the above substances evenly and place them in a stainless steel crucible. Then put them in a vacuum tube furnace, first wash the furnace chamber with argon gas 3 times, and then evacuate to 10 -2Pa, set the heating rate to 8℃ / min, the heat treatment temperature to 1000℃, and keep warm for 120min.

[0061] (7) The product after the heat treatment in step (8) is placed in ice water for rapid reaction to remove the calcium oxide generated by the reaction and the unreacted diffusion medium. Since ice water cannot completely remove impurities, glacial acetic acid is added dropwise, stirring while adding until the pH of the solution is 7. The supernatant is removed, and the obtained magnetic powder is ultrasonically washed with alcohol for 4-5 times. The prepared magnetic powder is stored in alcohol to prevent oxidation.

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

[0063] Table 1: Magnetic properties data obtained by VSM test of the embodiments of the present invention and the comparative examples

[0064]

[0065] It can be seen from the above table that the pure YCo5 particles prepared in comparative example 1 have low coercivity but high saturation magnetization and residual magnetization. The samples of Example 1 and Example 2 are obtained by the chemical method for preparing Sm-Y-Co ternary alloy magnetic powder proposed in this patent. According to the magnetic results, when the doped yttrium element is slightly reduced, the coercivity of the magnetic powder is significantly improved, but the saturation magnetization and residual magnetization are reduced. The rare earth magnetic particles prepared by the method of the present invention are not only simple and easy, highly controllable, and widely applicable, but also solve the problem of large particle size and low magnetic properties of particles prepared by the prior art. And a new method is proposed to solve the application of yttrium, a rare earth element with high abundance in the south.

Claims

1. A chemical method for preparing high magnetic properties (Sm x Y 1-x ) Co5 rare earth magnetic particles, characterized in that, The following steps are involved: (1) Selecting SmCl3·6H2O, YCl3·6H2O, CoCl2·6H2O and NaOH as raw materials to prepare precursors; (2) Weigh SmCl3·6H2O, YCl3·6H2O, and CoCl2·6H2O in a certain molar ratio and place them in a beaker, add deionized water to completely dissolve them, and stir and mix them evenly on a magnetic stirrer at room temperature; (3) Weigh a certain amount of sodium hydroxide particles, add deionized water, completely dissolve and mix, then add to the mixed solution obtained in step (2), and then continue stirring for 1 hour to generate amorphous hydroxides such as Sm(OH)3, Y(OH)3, and Co(OH)2; (4) placing the amorphous hydroxide solution stirred evenly in step (3) into a polytetrafluoroethylene liner, and then placing it into a high-temperature and high-pressure reactor for heat treatment, wherein the heat treatment conditions are set at a heating rate of 5°C / min, a heating temperature of 180°C, and a holding time of 720min; (5) taking out the precursor after the heat treatment in step (4), washing it with ultrasonic dispersion using deionized water, then washing it by centrifugation for multiple times and drying it; grinding the dried precursor into powder using a mortar to finally obtain a gray-brown mixed hydroxide precursor Sm(OH)3 / Y(OH)3 / Co(OH)2; (6) The precursor Sm(OH)3 / Y(OH)3 / Co(OH)2 of step (5) is added to anhydrous ethanol and ultrasonically homogenized. First, a certain molar concentration of CaCl2 aqueous solution is added, and after mixing, the corresponding KOH solution is slowly added dropwise, and stirred at room temperature for 8 hours to allow the generated Ca(OH)2 to be coated on the outside of Sm(OH)3 / Y(OH)3 / Co(OH)2. Then, anhydrous ethanol is used for ultrasonic centrifugation washing and drying. The dried powder is ground through a 400-mesh sieve to obtain an ultrafine powder of Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor; (7) Mix the precursor obtained in step (6), calcium particles, KCL, and CaCl2, and evenly mix the above substances in a stainless steel crucible; (8) The stainless steel crucible of step (7) was placed in a vacuum tube furnace for heat treatment. The furnace chamber was first flushed with argon gas for 3 times, and then evacuated to 10 -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 to quickly cool; (9) placing the product after the heat treatment in step (8) in 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, begin to add glacial acetic acid dropwise while stirring until the solution has a pH of 7; remove the supernatant, and use alcohol ultrasonic washing for 4-5 times to obtain the magnetic powder; and store the prepared magnetic powder in alcohol to prevent oxidation.

2. The method according to claim 1, characterized in that Step (1) sets nSm / nY=1:0-0:1; in this process, the molar ratio of n(Sm, Y) / nCo is controlled to remain unchanged. Due to the burning of Sm and Y elements during the heat treatment process, excessive Sm and Y are added during the precursor preparation process. Generally, 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 (2), CaCl2 reacts with KOH to generate Ca(OH)2 by precipitation method during stirring. Ca(OH)2 is slightly soluble in water, and the encapsulated precursor is precipitated after the solution is saturated. The total volume of the fixed CaCl2 aqueous solution and the added KOH aqueous solution corresponding to each 1g Sm(OH)3 / Y(OH)3 / Co(OH)2@Ca(OH)2 precursor is 40ml, and the molar concentration of CaCl2 and KOH is increased to increase the Ca(OH)2 encapsulation amount. The molar number of KOH ensures that Ca(OH)2 can be generated.

4. The method according to claim 1, characterized in that The Ca(OH)2 encapsulation amount corresponding to 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 The mass ratio of the precursor, calcium particles, KCL and CaCl2 in step (8) is 1:4:2:

1.

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

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