A preparation method of nanoscale SmFeN magnetic powder

Abstract

The present invention belongs to the technical field of permanent magnet materials, and particularly relates to a preparation method of nano-scale SmFeN magnetic powder. The present invention provides a preparation method of nano-scale SmFeN magnetic powder, comprising the following steps: mixing a water-soluble samarium salt, a water-soluble iron salt and water, and carrying out a coprecipitation reaction under alkaline conditions to obtain a precursor; carrying out a reduction reaction on the precursor and a reducing agent under the action of calcium oxide and potassium chloride, and then carrying out a nitriding treatment to obtain the nano-scale SmFeN magnetic powder. The preparation method provided by the present application has no requirement on the size of raw materials. By using the precursor prepared by the coprecipitation method as a raw material, the nano-scale SmFeN magnetic powder can be directly obtained through a reduction reaction and a nitriding treatment, with a relatively low cost and being suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of permanent magnetic materials, and in particular relates to a method for preparing nano-level SmFeN magnetic powder. Background Art

[0002] Rare earth permanent magnet materials refer to alloys formed by rare earth metals and transition metals. They are permanent magnet materials made by certain processes and are widely used in the fields of electronics, clean energy, electric vehicles, and aerospace. NdFeB permanent magnet material is a permanent magnet material with the best comprehensive performance. However, the Curie temperature of NdFeB permanent magnet material is relatively low (310℃), resulting in a low operating temperature. The Curie temperature of Sm-Fe-based permanent magnet material is 470℃, and it has superior high-temperature magnetic properties, making it a promising alternative to NdFeB permanent magnet material.

[0003] In the prior art, Sm-Fe based permanent magnet materials are usually prepared by calcium thermal reduction method, which is to mix fine iron powder and Sm2O3 powder in a certain proportion, add calcium particles and keep them at a certain temperature for a certain time to obtain the required Sm2Fe 17 Phase, then water washing and acid washing to remove the non-magnetic phase in the material, after ball milling or air flow milling to obtain fine alloy powder, nitriding treatment is performed to obtain the final SmFeN magnetic powder. For SmFeN magnetic powder, the smaller the particle size, the better the corresponding magnetic properties. In the above preparation method, in order to obtain magnetic powder with a smaller particle size, iron powder with a smaller particle size is required, and the smaller the particle size of the iron powder, the higher the cost. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing nano-scale SmFeN magnetic powder. The method provided by the present invention has low cost.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing nano-scale SmFeN magnetic powder, comprising the following steps:

[0007] A water-soluble samarium salt, a water-soluble iron salt and water are mixed and subjected to a coprecipitation reaction under alkaline conditions to obtain a precursor;

[0008] The precursor and the reducing agent are subjected to a reduction reaction under the action of calcium oxide and potassium chloride, and then subjected to a nitridation treatment to obtain the nano-scale SmFeN magnetic powder.

[0009] Preferably, the molar ratio of the water-soluble samarium salt to the water-soluble iron salt is 1:5.6-6.8.

[0010] Preferably, the usage ratio of the water-soluble samarium salt to water is 1 g: 40-90 mL.

[0011] Preferably, the pH value of the alkaline condition is 7.0 - 8.0.

[0012] Preferably, the mass ratio of calcium oxide to the precursor is 3 - 5:10;

[0013] The mass ratio of potassium chloride to the precursor is 5 - 10:10;

[0014] The reducing agent includes an alkali metal reducing agent or a calcium reducing agent; the mass ratio of the reducing agent to the precursor is 1:1.

[0015] Preferably, the temperature of the reduction is 860 - 900 °C, and the time is 90 min.

[0016] Preferably, the reduction reaction is carried out under a protective atmosphere.

[0017] Preferably, the gas used for the nitriding treatment is any two of nitrogen, hydrogen, and ammonia.

[0018] Preferably, the temperature of the nitriding treatment is 375 - 525 °C, and the time ≥ 3 h.

[0019] Preferably, the pressure of the nitriding treatment ≥ 0.1 MPa.

[0020] The present invention provides a method for preparing nanoscale SmFeN magnetic powder, which includes the following steps: mixing a water-soluble samarium salt, a water-soluble iron salt, and water, and carrying out a coprecipitation reaction under an alkaline condition to obtain a precursor; after carrying out a reduction reaction on the precursor and a reducing agent under the action of calcium oxide and potassium chloride, and then carrying out a nitriding treatment, the nanoscale SmFeN magnetic powder is obtained. This application has no requirements for the size of the raw materials. By using the precursor prepared by the coprecipitation method as the raw material, the nanoscale SmFeN magnetic powder can be directly obtained through a reduction reaction and a nitriding treatment, with a low cost and being suitable for industrial production. Description of the Drawings

[0021] Figure 1 XRD pattern of the Sm2Fe 17 powder obtained in Example 1;

[0022] Figure 2 XRD pattern of the nanoscale Sm2Fe 17 N3 magnetic powder obtained in Example 1;

[0023] Figure 3 SEM image of the Sm2Fe 17 powder obtained in Example 1;

[0024] Figure 4 SEM image of the nanoscale Sm2Fe 17SEM image of N3 magnetic powder;

[0025] Figure 5 The nano-scale Sm2Fe obtained in Example 2 17 SEM image of N3 magnetic powder. Specific implementation mode

[0026] The present invention provides a method for preparing nano-scale SmFeN magnetic powder, comprising the following steps:

[0027] Mix a water-soluble samarium salt, a water-soluble iron salt and water, and carry out a coprecipitation reaction under alkaline conditions to obtain a precursor;

[0028] After carrying out a reduction reaction on the precursor and a reducing agent under the action of calcium oxide and potassium chloride, and then carrying out a nitriding treatment, the nano-scale SmFeN magnetic powder is obtained.

[0029] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well-known to those skilled in the art.

[0030] The present invention mixes a water-soluble samarium salt, a water-soluble iron salt and water, and carries out a coprecipitation reaction under alkaline conditions to obtain a precursor.

[0031] In the present invention, the water-soluble samarium salt preferably includes samarium chloride, samarium nitrate or samarium sulfate; the samarium chloride is further preferably SmCl3·6H2O. In the present invention, the water-soluble iron salt preferably includes ferric chloride, ferric nitrate or ferric sulfate; the ferric chloride is further preferably FeCl3·6H2O.

[0032] In the present invention, the molar ratio of the water-soluble samarium salt to the water-soluble iron salt is preferably 1:5.6 - 6.8; further preferably 1:5.8 - 6.5, and more preferably 1:6.0 - 6.3.

[0033] In the present invention, the dosage ratio of the water-soluble samarium salt to water is preferably 1 g:40 - 90 mL, further preferably 1 g:45 - 85 mL, and more preferably 1 g:50 - 80 mL.

[0034] In the present invention, the mixed raw materials preferably further include calcium oxide. In the present invention, when the mixed raw materials include calcium oxide, the mixing process is preferably: mixing the soluble samarium salt, the soluble iron salt, calcium oxide and water, and carrying out a coprecipitation reaction under alkaline conditions to obtain a precursor. In the present invention, the mass ratio of calcium oxide to the water-soluble samarium salt is preferably 1:2 - 3.

[0035] In the present invention, the mixing is preferably carried out under stirring; the rotation speed of the stirring is preferably 30 - 120 r / min, more preferably 40 - 110 r / min, and even more preferably 50 - 100 r / min. The present invention has no special limitation on the stirring time, as long as the water-soluble samarium salt and the water-soluble iron salt can be completely dissolved.

[0036] In the present invention, the pH value of the alkaline condition is preferably 7.0 - 8.0, more preferably 7.2 - 7.8, and even more preferably 7.4 - 7.6; when the pH value is not within the above range, it is preferably adjusted to the above range by adding sodium hydroxide.

[0037] In the present invention, the coprecipitation reaction is preferably carried out under stirring; the rotation speed of the stirring is preferably 60 r / min, and the time is preferably 1 h.

[0038] After the coprecipitation reaction is completed, the present invention preferably further includes successively filtering, washing, and drying the obtained reaction solution.

[0039] In the present invention, the filtering method is preferably suction filtration or pressure filtration. The present invention has no special limitation on the process of the suction filtration or pressure filtration, and it can be carried out by using a process well-known to those skilled in the art.

[0040] In the present invention, the washing preferably includes water washing and alcohol washing successively. In the present invention, the process of the water washing is preferably: mixing the precipitate obtained by filtration with water, stirring for 10 min and then filtering to collect the precipitate. The present invention has no special limitation on the stirring process, and it can be carried out by using a process well-known to those skilled in the art. In the present invention, the filtering method is preferably the same as the filtering method defined above, and will not be elaborated here.

[0041] In the present invention, the process of the alcohol washing is preferably: mixing the precipitate obtained by the water washing with absolute ethanol, stirring for 10 min and then filtering to collect the precipitate. The present invention has no special limitation on the stirring process, and it can be carried out by using a process well-known to those skilled in the art. In the present invention, the filtering method is preferably the same as the filtering method defined above, and will not be elaborated here.

[0042] In the present invention, the drying temperature is preferably 80 - 200 °C, more preferably 100 - 180 °C, and even more preferably 120 - 150 °C. The present invention has no special limitation on the drying time, as long as dry materials can be obtained.

[0043] In the present invention, the particle size of the precursor is preferably 100 - 500 nm, more preferably 200 - 400 nm, and even more preferably 250 - 350 nm.

[0044] After obtaining the precursor, in the present invention, the precursor and a reducing agent are subjected to a reduction reaction under the action of calcium oxide and potassium chloride, and then subjected to a nitriding treatment to obtain the nanoscale SmFeN magnetic powder.

[0045] In the present invention, when the raw materials for the coprecipitation reaction are water-soluble samarium salt, water-soluble iron salt and water, the process of the reduction reaction is preferably as follows: the precursor, the reducing agent, calcium oxide and potassium chloride are mixed to carry out a reduction reaction (denoted as Method 1).

[0046] In the present invention, the reducing agent preferably includes an alkali metal reducing agent or a calcium reducing agent. In the present invention, the mass ratio of the reducing agent to the precursor is preferably 1:1.

[0047] In the present invention, the mass ratio of the calcium oxide to the precursor is preferably 3-5:10; more preferably 3.2-4.8:10, and even more preferably 3.5-4.5:10. In the present invention, the calcium oxide has a high melting point and is characterized by a dispersed distribution. When added to the precursor for the reduction reaction, it can prevent the sintering of the SmFe powder and inhibit the growth of crystal grains.

[0048] In the present invention, the mass ratio of the potassium chloride to the precursor is preferably 5-10:10, more preferably 6-9:10, and even more preferably 7-8:10. In the present invention, the potassium chloride has a low melting point. During the reduction reaction process, it is in a molten state and can accelerate the diffusion of the precursor; at the same time, potassium chloride is easily soluble in water, and in the subsequent water washing and impurity removal process, it can make the sintered block easy to disintegrate and accelerate the process of water washing and impurity removal.

[0049] In the present invention, when the raw materials for the coprecipitation reaction are water-soluble samarium salt, water-soluble iron salt, calcium oxide and water, the process of the reduction reaction is preferably as follows: the precursor, the reducing agent and potassium chloride are mixed to carry out a reduction reaction (denoted as Method 2).

[0050] In the present invention, the addition amounts of the reducing agent, calcium oxide and potassium chloride are the same as those defined above, and will not be elaborated here.

[0051] In the present invention, when mixing is carried out by Method 2, during the coprecipitation reaction process, the calcium oxide reacts with water to form calcium hydroxide precipitate, and the obtained calcium hydroxide precipitate generates calcium oxide in the subsequent reduction reaction, thereby playing a role in preventing the sintering of the SmFe powder and inhibiting the growth of crystal grains.

[0052] In the present invention, the mixing method is preferably grinding. The present invention has no special limitation on the grinding process, and the process well-known to those skilled in the art can be adopted.

[0053] In the present invention, the temperature of the reduction reaction is preferably 860 - 900 °C, more preferably 870 - 890 °C, and still more preferably 880 °C; the heating rate for heating to the reduction reaction temperature is preferably 5 - 15 °C / min, more preferably 6 - 13 °C / min, and still more preferably 8 - 12 °C / min; the time is preferably 60 - 180 min, more preferably 70 - 170 min, and still more preferably 80 - 160 min.

[0054] In the present invention, the reduction reaction is preferably carried out in a protective atmosphere; the protective atmosphere is preferably high-purity argon.

[0055] In the present invention, the process of the reduction reaction is preferably as follows: place the raw materials for the reduction reaction in a crucible, then place the crucible in an atmosphere furnace, evacuate the vacuum degree of the atmosphere furnace cavity to 10 -3 Pa, and then fill it with a protective gas and heat to carry out the reduction reaction.

[0056] In the present invention, the crucible is preferably an alumina crucible or an iron container.

[0057] After the reduction reaction is completed, the present invention preferably further includes post-treating the obtained material; the post-treatment preferably includes cooling, primary water washing, pH adjustment, primary separation, secondary water washing, alcohol washing, secondary separation, and drying in sequence.

[0058] In the present invention, the cooling method is preferably furnace cooling to room temperature.

[0059] In the present invention, the process of the primary water washing is preferably as follows: rinse the material in the crucible with clear water until there is no material residue on the inner wall of the crucible to obtain a turbid liquid.

[0060] In the present invention, the reagent used for pH adjustment is preferably glacial acetic acid or hydrochloric acid. The present invention has no special requirements for the concentration of the glacial acetic acid or hydrochloric acid, and those well-known to those skilled in the art can be used. In the present invention, the pH value after pH adjustment is preferably neutral. In the present invention, the pH adjustment is preferably carried out under stirring conditions. In the present invention, the stirring time is preferably 30 min. The present invention has no special limitation on the stirring process, and the process well-known to those skilled in the art can be used. In the present invention, residual calcium oxide can be removed by pH adjustment.

[0061] In the present invention, the method of primary separation is preferably centrifugal separation or magnetic separation. The present invention has no special limitation on the separation process, and the process well-known to those skilled in the art can be used. In the present invention, the liquid is removed by primary separation and the precipitate is collected.

[0062] In the present invention, the number of times of the secondary water washing is preferably 2 to 3 times. In the present invention, the residual glacial acetic acid or hydrochloric acid can be removed by the secondary water washing. In the present invention, the alcohol washing is preferably carried out with anhydrous ethanol, and the number of times of the alcohol washing is preferably 2 to 3 times. In the present invention, the residual moisture can be removed by the alcohol washing, the subsequent drying time can be greatly reduced, and the oxidation degree during the drying process can be reduced.

[0063] In the present invention, the manner of the secondary separation is the same as that of the primary separation, and will not be elaborated herein.

[0064] In the present invention, the drying is preferably carried out under vacuum or in a protective atmosphere. In the present invention, the temperature of the drying is preferably 80 to 200 °C, more preferably 90 to 190 °C, and even more preferably 100 to 180 °C; the time is preferably 60 to 300 min, more preferably 70 to 280 min, and even more preferably 80 to 270 min.

[0065] In the present invention, the chemical formula of the powder obtained through the reduction reaction is preferably Sm2Fe 17 . In the present invention, the particle size of the powder is preferably 100 to 500 nm, more preferably 150 to 450 nm, and even more preferably 200 to 400 nm.

[0066] In the present invention, the temperature of the nitriding treatment is preferably 375 to 525 °C, more preferably 400 to 500 °C, and even more preferably 425 to 475 °C; the heating rate for heating to the nitriding treatment temperature is preferably 5 to 15 °C / min, more preferably 6 to 13 °C / min, and even more preferably 8 to 12 °C / min; the time is preferably ≥3 h, more preferably 4.5 to 8 h, and even more preferably 5 to 6 h.

[0067] In the present invention, the gas used for the gas nitriding treatment is preferably any two of nitrogen, hydrogen and ammonia. In the present invention, in the mixed gas, the volume ratio of any one gas is preferably ≥25%. In the present invention, the pressure of the nitriding treatment is preferably ≥0.1 MPa, more preferably 0.12 to 0.3 MPa, and even more preferably 0.16 to 0.2 MPa.

[0068] In the present invention, the process of the nitriding treatment is preferably as follows: placing the powder obtained through the reduction reaction in an atmosphere furnace, pumping the vacuum degree of the atmosphere furnace cavity to 10 -3 Pa, then introducing gas until the pressure of the nitriding treatment, and then heating up for the nitriding treatment.

[0069] After the nitriding treatment is completed, the present invention preferably further includes post-treating the obtained material; the post-treatment preferably includes the following steps: evacuating at the temperature of the nitriding treatment, and then introducing high-purity argon until the pressure is 0.1 MPa, and cooling with the furnace to room temperature. The present invention has no special limitation on the time of evacuation, as long as the hydrogen in the material can be removed.

[0070] In the present invention, the chemical formula of the nanoscale SmFeN magnetic powder is preferably Sm2Fe 17 N3. In the present invention, the particle size of the nanoscale SmFeN magnetic powder is preferably 200-900 nm, more preferably 300-800 nm, and even more preferably 400-700 nm.

[0071] The present invention has no special requirements for the size of the raw materials. By using the co-precipitation method to prepare the precursor as the raw material, the nanoscale SmFeN magnetic powder can be directly obtained through the reduction reaction and nitriding treatment. There is no need to add a ball milling process in the subsequent process, with low cost and simple preparation process, which is suitable for industrial production.

[0072] To further illustrate the present invention, the following describes in detail a method for preparing a nanoscale SmFeN magnetic powder provided by the present invention with reference to the drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0073] Example 1

[0074] Take 3.65 g of SmCl3·6H2O, 15.15 g of FeCl3·6H2O and 200 mL of water, stir and mix at a speed of 60 r / min for 30 min. During the mixing process, add sodium hydroxide to adjust the pH value of the mixed solution to 7.5, then stir for 1 h, and then filter by suction to collect the precipitate; mix the obtained precipitate and water, stir for 10 min and then filter to collect the precipitate; mix the precipitate obtained by washing with water and absolute ethanol, stir for 10 min and then filter to collect the precipitate; heat the precipitate in an oven to 150 °C and dry it to obtain the precursor;

[0075] Mix 5 g of the precursor, 5 g of metal calcium particles, 1.5 g of calcium oxide and 2.5 g of potassium chloride, grind them evenly and place them in an alumina crucible, and then place the crucible in an atmosphere furnace. Evacuate the vacuum degree of the atmosphere furnace cavity to 10 -3 Pa, then fill with high-purity argon, heat up to 900 °C at a heating rate of 10 °C / min, keep the temperature for 90 min for the calcium thermal reduction reaction, and after the reaction is completed, cool with the furnace to room temperature;

[0076] Take out the crucible and rinse the materials in the crucible with clear water until there is no material residue on the inner wall of the crucible to obtain a turbid liquid; add glacial acetic acid to the turbid liquid until it is neutral, remove the liquid by magnetic separation to obtain a powder, wash the obtained powder with clear water twice and then with absolute ethanol twice, collect the precipitate by magnetic separation, and then heat the precipitate to 120 °C under vacuum for drying to obtain Sm2Fe 17 powder;

[0077] Put the obtained Sm2Fe 17 powder in an atmosphere furnace, evacuate the vacuum degree of the atmosphere furnace cavity to 10 -3 Pa, introduce a mixed gas of ammonia and hydrogen (where the volume ratio of ammonia to hydrogen is 1:3) until the pressure in the cavity reaches 0.1 MPa, then heat it up to 425 °C at a heating rate of 10 °C / min, keep it warm for 3 h for nitriding treatment. After the nitriding treatment is completed, evacuate the hydrogen in the powder at 425 °C for 1 h, then introduce high-purity argon until the pressure is 0.1 MPa, and cool it down to room temperature with the furnace to obtain the nanoscale Sm2Fe 17 N3 magnetic powder.

[0078] Example 2

[0079] Take 3.65 g of SmCl3·6H2O, 18.38 g of FeCl3·6H2O and 150 mL of water, stir and mix them at a rotation speed of 30 r / min for 30 min. During the mixing process, add sodium hydroxide to adjust the pH value of the mixed solution to 7.5, then stir for 1 h, and then filter by suction filtration to collect the precipitate; mix the obtained precipitate with water, stir for 10 min and then filter to collect the precipitate; mix the precipitate obtained by washing with water and absolute ethanol, stir for 10 min and then filter to collect the precipitate; heat the precipitate in an oven to 150 °C for drying to obtain a precursor;

[0080] Mix 5 g of the precursor, 5 g of metal calcium particles, 1.5 g of calcium oxide and 2.5 g of potassium chloride, grind them evenly and put them in an alumina crucible, then place the crucible in an atmosphere furnace, evacuate the vacuum degree of the atmosphere furnace cavity to 10 -3 Pa, then fill it with high-purity argon, heat it up to 860 °C at a heating rate of 10 °C / min, keep it warm for 90 min for calcium thermal reduction reaction, and after the reaction is completed, cool it down to room temperature with the furnace;

[0081] Take out the crucible and rinse the materials in the crucible with clear water until there is no material residue on the inner wall of the crucible to obtain a turbid liquid; add glacial acetic acid to the turbid liquid until it is neutral, remove the liquid by magnetic separation to obtain a powder, wash the obtained powder with clear water twice and then with absolute ethanol twice, collect the precipitate by magnetic separation, and then dry the precipitate by heating it to 150 °C under vacuum to obtain Sm2Fe 17 powder;

[0082] Put the obtained Sm2Fe 17 powder in an atmosphere furnace, evacuate the vacuum degree of the atmosphere furnace cavity to 10 -3 Pa, introduce a mixed gas of nitrogen and ammonia (where the volume ratio of nitrogen to ammonia is 1:1) until the pressure in the cavity reaches 0.2 MPa, then heat it at a heating rate of 10 °C / min to 475 °C, keep it warm for 4.5 h for nitriding treatment. After the nitriding treatment is completed, evacuate the vacuum at 475 °C for 0.5 h to remove hydrogen in the powder, and then introduce high-purity argon until the pressure is 0.1 MPa, and cool it to room temperature with the furnace to obtain the nanoscale Sm2Fe 17 N3 magnetic powder.

[0083] Example 3

[0084] Take 3.65 g of SmCl3·6H2O, 15.15 g of FeCl3·6H2O, 1.5 g of calcium oxide and 250 mL of water, stir and mix them at a rotation speed of 90 r / min for 30 min. During the mixing process, add sodium hydroxide to adjust the pH value of the mixed solution to 8.0, then stir for 1 h, and then filter by suction to collect the precipitate; mix the obtained precipitate with water, stir for 10 min and then filter to collect the precipitate; mix the precipitate obtained by washing with water and absolute ethanol, stir for 10 min and then filter to collect the precipitate; dry the precipitate by heating it to 150 °C in an oven to obtain a precursor;

[0085] Mix 5 g of the precursor, 5 g of metal calcium particles and 2.5 g of potassium chloride, grind them evenly and put them in an alumina crucible, then place the crucible in an atmosphere furnace, evacuate the vacuum degree of the atmosphere furnace cavity to 10 -3 Pa, and then fill it with high-purity argon, heat it to 880 °C at a heating rate of 10 °C / min, keep it warm for 90 min for calcium thermal reduction reaction, and after the reaction is completed, cool it to room temperature with the furnace;

[0086] Take out the crucible and rinse the materials in the crucible with clean water until there is no material residue on the inner wall of the crucible to obtain a turbid liquid; add glacial acetic acid to the turbid liquid until it is neutral, remove the liquid by magnetic separation to obtain a powder, wash the obtained powder with clean water twice and then with absolute ethanol twice, collect the precipitate by magnetic separation, and then dry the precipitate by heating it to 80 °C under vacuum to obtain Sm2Fe 17 powder;

[0087] Put the obtained Sm2Fe 17 powder in an atmosphere furnace, evacuate the vacuum degree of the atmosphere furnace cavity to 10 -3 Pa, introduce a mixed gas of ammonia and hydrogen (where the volume ratio of nitrogen and ammonia is 1:3) until the pressure in the cavity reaches 0.12 MPa, then heat it up at a heating rate of 10 °C / min to 450 °C, keep it warm for 4.5 h for nitridation treatment. After the nitridation treatment is completed, evacuate the hydrogen in the powder at 450 °C for 1 h, then introduce high-purity argon until the pressure is 0.1 MPa, and cool it down to room temperature with the furnace to obtain the nanoscale Sm2Fe 17 N3 magnetic powder.

[0088] Example 4

[0089] Take 3.65 g of SmCl3·6H2O, 18.38 g of FeCl3·6H2O, 1.5 g of calcium oxide and 300 mL of water, stir and mix them at a rotation speed of 120 / min for 30 min. During the mixing process, add sodium hydroxide to the mixed solution to adjust the pH value of the mixed solution to 8.0, then stir for 1 h, and then filter by suction to collect the precipitate; mix the obtained precipitate with water, stir for 10 min and then filter to collect the precipitate; mix the precipitate obtained by washing with water and absolute ethanol, stir for 10 min and then filter to collect the precipitate; dry the precipitate by heating it to 150 °C in an oven to obtain a precursor;

[0090] Mix 5 g of the precursor, 5 g of metal calcium particles and 2.5 g of potassium chloride, grind them evenly and put them in an alumina crucible, then place the crucible in an atmosphere furnace, evacuate the vacuum degree of the atmosphere furnace cavity to 10 -3 Pa, then fill it with high-purity argon, heat it up at a heating rate of 10 °C / min to 860 °C, keep it warm for 90 min for calcium thermal reduction reaction, and after the reaction is completed, cool it down to room temperature with the furnace;

[0091] Take out the crucible and rinse the materials in the crucible with clear water until there is no material residue on the inner wall of the crucible to obtain a turbid liquid; add glacial acetic acid to the turbid liquid until it is neutral, remove the liquid by magnetic separation to obtain a powder, wash the obtained powder with clear water twice and with absolute ethanol twice, then collect the precipitate by magnetic separation, and then heat the precipitate to 200 °C under vacuum for drying to obtain Sm2Fe 17 powder;

[0092] Put the obtained Sm2Fe 17 powder in an atmosphere furnace, pump the vacuum degree of the atmosphere furnace cavity to 10 -3 Pa, introduce a mixed gas of nitrogen and ammonia (where the volume ratio of nitrogen to ammonia is 1:1) until the pressure in the cavity reaches 0.16 MPa, then heat it up at a heating rate of 10 °C / min to 500 °C, keep it warm for 6 h for nitriding treatment. After the nitriding treatment is completed, evacuate the hydrogen in the powder at 500 °C for 0.5 h, then introduce high-purity argon until the pressure is 0.1 MPa, and cool it down to room temperature with the furnace to obtain the nanoscale Sm2Fe 17 N3 magnetic powder.

[0093] Performance test

[0094] Test example 1

[0095] Perform XRD tests on the Sm2Fe 17 powder and the nanoscale Sm2Fe 17 N3 magnetic powder obtained in Example 1. The test results are as shown in Figure 1 and 2 . Among them, Figure 1 is the XRD pattern of the Sm2Fe 17 powder. It can be seen from Figure 1 that the high-purity Sm2Fe 17 powder is obtained in the present invention, and no obvious soft magnetic phase α-Fe, impurity phases such as calcium oxide and calcium are detected; Figure 2 is the XRD pattern of the nanoscale Sm2Fe 17 N3 magnetic powder. It can be seen from Figure 2 that the high-purity phase of Sm2Fe 17 N3 is obtained in the present invention. Due to the infiltration of N atoms, the lattice expands, and the diffraction peaks shift to a smaller angle as a whole compared with Sm2Fe 17 .

[0096] Test example 2

[0097] Perform scanning electron microscopy tests on the Sm2Fe 17 powder obtained in Example 1 and the nanoscale Sm2Fe 17 N3 magnetic powder obtained in Example 1 and Example 2. The test results are as shown in Figures 3 to 5As shown, the Sm2Fe 17 The SEM image of the powder is as follows Figure 3 As shown, from Figure 3 It can be seen that the average particle size of the powder is about 250 μm; the nano-scale Sm2Fe 17 The SEM image of N3 magnetic powder is as follows Figure 4 As shown, from Figure 4 It can be seen that the average particle size of the powder is about 600 μm; the nano-scale Sm2Fe 17 The SEM image of N3 magnetic powder is as follows Figure 5 As shown, from Figure 5 It can be seen that the average particle size of the powder is about 300 μm.

[0098] Test Example 3

[0099] The nano-sized Sm2Fe obtained in Examples 1 to 4 17 The magnetic properties of N3 magnetic powder were tested by using a Microsense EV9 vibrating sample magnetometer.

[0100] The test results are shown in Table 1.

[0101] Table 1 Nano-scale Sm2Fe obtained in Examples 1 to 4 17 Magnetic properties test results of N3 magnetic powder

[0102] <![CDATA[Residual magnetic flux density B r / kGs]]> <![CDATA[Intrinsic coercive force H cj / kOe]]> <![CDATA[Maximum magnetic energy product (BH) max / MGOe]]> Example 1 13.6 11.7 36.1 Example 2 13.2 13.6 35.0 Example 3 13.5 12.2 35.8 Example 4 13.0 14.3 34.6

[0103] It can be seen from Table 1 that the nano-scale Sm2Fe 17 N3 magnetic powder has excellent magnetic properties.

[0104] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing nano-scale SmFeN magnetic powder, characterized in that, The steps are as follows: Mix a water-soluble samarium salt, a water-soluble iron salt and water, and carry out a coprecipitation reaction under alkaline conditions to obtain a precursor; After carrying out a reduction reaction on the precursor and a reducing agent under the action of calcium oxide and potassium chloride, and then carrying out a nitriding treatment, the nanoscale SmFeN magnetic powder is obtained; After the reduction reaction is completed, it further includes post-treating the obtained material; the post-treatment includes cooling, primary water washing, pH adjustment, primary separation, secondary water washing, alcohol washing, secondary separation and drying carried out in sequence; After the nitriding treatment is completed, it further includes post-treating the obtained material; the post-treatment includes the following steps: evacuating at the temperature of the nitriding treatment, and then introducing high-purity argon until the pressure is 0.1 MPa, and cooling with the furnace to room temperature.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the water-soluble samarium salt to the water-soluble iron salt is 1:5.6 - 6.

8.

3. The preparation method according to claim 1 or 2, characterized in that, The dosage ratio of the water-soluble samarium salt to water is 1 g:40 - 90 mL.

4. The preparation method according to claim 1, wherein The pH value of the alkaline condition is 7.0 - 8.

0.

5. The preparation method according to claim 1, wherein The mass ratio of the calcium oxide to the precursor is 3 - 5:10; The mass ratio of the potassium chloride to the precursor is 5 - 10:10; The reducing agent includes an alkali metal reducing agent or a calcium reducing agent; the mass ratio of the reducing agent to the precursor is 1:

1.

6. The preparation method according to claim 1, wherein, The temperature of the reduction reaction is 860 - 900 °C, and the time is 90 min.

7. The preparation method according to claim 1 or 6, characterized in that, The reduction reaction is carried out under a protective atmosphere.

8. The preparation method according to claim 1, characterized in that, The gas used for the nitriding treatment is any two of nitrogen, hydrogen and ammonia.

9. The preparation method according to claim 8, wherein The temperature of the nitriding treatment is 375 - 525 °C, and the time ≥ 3 h.

10. The preparation method according to claim 9, characterized in that, The pressure of the nitriding treatment ≥ 0.1 MPa.

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