SmFeN powder and method for producing the same

Abstract

The present application relates to a kind of SmFeN powder and its preparation method, the surface of the SmFeN powder is coated with acetate.Said preparation method includes the following steps: based on chemical formula Sm2Fe 17 , Sm powder and Fe powder are weighed, then mixed with dispersant, ammonia-containing liquid and high-energy ball milling are carried out;Wherein, Sm powder is 5%-20% more than theoretical dosage;After high-energy ball milling, surfactant and butyl acetate are added to it for secondary ball milling, and the slurry obtained after the secondary ball milling is separated and dried to obtain the SmFeN powder.By coating the surface of SmFeN powder with acetate, the activity of the powder is reduced, the violent reaction after contacting air is avoided, and the safety problem in the production process is eliminated.

Description

Technical Field

[0001] This invention belongs to the field of magnetic materials technology, and particularly relates to an SmFeN powder and its preparation method. Background Technology

[0002] Since Coey synthesized the rare-earth permanent magnet alloy SmFeN in 1990, SmFeN has attracted widespread attention due to its superior intrinsic magnetic properties compared to NdFeN. In recent years, with the increasing price of neodymium and its compounds, samarium-iron-nitrogen alloys, which do not contain precious rare-earth elements such as neodymium and dysprosium, have gained more significant economic advantages and application prospects. Furthermore, samarium-iron-nitrogen materials exhibit better intrinsic magnetic properties and oxidation resistance than neodymium-iron-boron materials, playing an irreplaceable role, especially in high-temperature applications.

[0003] In recent years, the main methods for preparing samarium-iron-nitrogen alloys have included: smelting, mechanized alloying, rapid quenching, reduction-diffusion, and high-energy ball milling. Smelting and rapid quenching methods tend to produce impurity α-iron phases in the alloys, and require lengthy ball milling processes, resulting in high costs and irregular particle morphology after milling, which affects performance.

[0004] Currently, the reduction-diffusion method is widely used. This method employs metals such as Ca, CaH2, and CaCl2, along with inexpensive metal oxides or chlorides and Fe, under a high-temperature Ar or N2 atmosphere. Utilizing the strong reducing properties of Ca or CaH2, a redox reaction occurs with the metal oxides to generate the desired alloy. CN1424165A discloses a method for manufacturing Sm-Fe-N permanent magnet alloy powder using the reduction-diffusion method. The method includes: raw material selection and pretreatment → reactant proportioning → reactant mixing → metal thermal reduction and diffusion alloying → chemical separation of reaction products → dehydration and drying of metal powder → powder nitriding treatment → manufacturing anisotropic bonded Sm-Fe-N magnets. Rare earth chlorides and selectively controlled iron powder particle size are used, with metallic Ca and CaH2 as the reducing agents. A reduction-diffusion reaction is carried out at 760-860℃ to generate Sm-Fe alloy and byproducts. After chemical separation, the Sm-Fe alloy is pulverized and nitrided to obtain Sm-Fe-N magnetic alloy powder with the required composition and particle size.

[0005] CN108648907A discloses a method for preparing anisotropic SmFeN permanent magnet alloy powder, the method comprising: based on the chemical formula Sm2Fe 17Raw materials Sm₂O₃ and iron powder are weighed; Sm₂O₃ is added in excess of 1 at% to 10 at% based on the theoretical amount of Sm atoms. The weighed raw materials are mechanically ground to form flakes of iron powder, which is then thoroughly mixed with Sm₂O₃. Calcium particles are added to the mixture obtained in the previous step, and a full reduction-diffusion reaction is carried out to obtain samarium-iron alloy. After washing with water and nitriding treatment, flake-shaped anisotropic SmFeN permanent magnet alloy powder is obtained. However, during the reduction-diffusion process, Ca compounds are generated and Ca residues remain. If these impurities are mixed in the alloy, they will have a significant impact on the product performance.

[0006] In existing technologies, high-energy ball milling utilizes frequent collisions between the ball mill, the milling jar, and the powder phase to induce intense plastic deformation and cold welding of powder particles, forming composite powders with a lamellar structure. This process of repeated cold welding, cracking, and re-welding achieves alloying. However, the powders prepared by high-energy ball milling are too reactive and are prone to violent reactions during drying, which can not only affect material properties but also pose a danger during production.

[0007] Therefore, there is a need to improve existing methods to prepare SmFeN permanent magnet materials safely, easily, and at low cost. Summary of the Invention

[0008] To solve the above-mentioned technical problems, the present invention provides SmFeN powder and its preparation method. By coating the surface of SmFeN powder with acetate, the possibility of violent powder reaction is greatly reduced while ensuring material performance, thus eliminating safety issues in the production process.

[0009] To achieve the above-mentioned technical effects, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides an SmFeN powder, wherein the surface of the SmFeN powder is coated with an acetate.

[0011] Although SmFeN has excellent magnetic properties, the powder prepared during the production process is highly reactive and prone to danger. This invention coats the powder surface with acetate to reduce powder activity, prevent violent reactions upon contact with air, and eliminate safety issues during the production process.

[0012] As a preferred embodiment of the present invention, the SmFeN powder is composed of the following components by mass percentage: Sm 22%-25%, C 0.2%-0.8%, N 2%-5%, O 1%-4%, with the balance being Fe and unavoidable impurities.

[0013] In this invention, the mass percentage of Sm in the SmFeN powder is 22%-25%, for example, it can be 22%, 23%, 24% or 25%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] In this invention, the mass percentage of C in the SmFeN powder is 0.2%-0.8%, for example, it can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7% or 0.8%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] In this invention, the mass percentage of N in the SmFeN powder is 2%-5%, for example, it can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] In this invention, the mass percentage of the SmFeN powder O is 1%-4%, for example, it can be 1%, 2%, 3% or 4%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Preferably, the acetate accounts for 0.5%-5% of the mass percentage of the SmFeN powder, for example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] Preferably, the acetate includes ammonium acetate and / or sodium acetate.

[0019] In a second aspect, the present invention provides a method for preparing SmFeN powder as described in the first aspect, the method comprising the following steps:

[0020] (1) Based on the chemical formula Sm2Fe 17 Weigh out Sm powder and Fe powder, then mix them with dispersant and ammonia-containing liquid and perform high-energy ball milling;

[0021] Among them, the Sm powder should be used in excess of the theoretical amount by 5-20%;

[0022] (2) After the high-energy ball milling in step (1), a surfactant and butyl acetate are added to the ball mill for secondary ball milling. The slurry obtained after the secondary ball milling is dried to obtain the SmFeN powder.

[0023] The ball milling process of this invention is divided into two stages. The purpose of high-energy ball milling is to generate SmFeN. A dispersant is added during the high-energy ball milling process, followed by low-frequency ordinary ball milling. An anionic surfactant and butyl acetate are added during the second ball milling process to form acetate coating on the powder surface, which reduces the powder activity, prevents the powder from being oxidized in subsequent processes, and ensures the safety of the production process.

[0024] This invention utilizes anionic surfactants that generate hydrophobic anions in water, which can make the particle surface negatively charged, forming a stable system with a double electric layer structure. During secondary ball milling, a small amount of cations are ionized in the water. In addition, the cations generated by the hydrolysis of butyl acetate neutralize the negative charge of the anionic surfactant itself, reducing the charge density, causing a decrease in surface potential and compression of the double electric layer thickness, thereby lowering the potential barrier. As more and more positively charged ions are adsorbed, the potential barrier gradually disappears. When the potential barrier disappears, the surface potential approaches zero. At this time, the anionic surfactant carries the anions ionized from butyl acetate and coats the powder surface, reducing the powder activity and preventing violent reactions after contact with air, thus obtaining a high-performance SmFeN alloy.

[0025] As a preferred technical solution of the present invention, the mass ratio of Sm powder to Fe powder in step (1) is (300-400):(900-1000), for example, it can be 300:900, 310:920, 330:930, 340:950, 350:955, 360:960 or 400:1000, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably (305-360):(950-960).

[0026] Preferably, the dispersant in step (1) comprises sodium sulfonate.

[0027] In this invention, an ammonia-containing liquid is used as the high-energy ball milling medium. To avoid powder aggregation during the ball milling process, sodium sulfonate is used as a dispersant. Sodium sulfonate is readily soluble in water under alkaline conditions and has good solubility in ammonia water.

[0028] Preferably, the mass ratio of the dispersant in step (1) is 5%-20% of the total mass of the Sm powder and Fe powder, for example, it can be 5%, 7%, 9%, 10%, 12%, 14%, 16%, 18% or 20%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] As a preferred technical solution of the present invention, the ammonia-containing liquid in step (1) is contained in a ball mill container.

[0030] Preferably, step (1) is based on the chemical formula Sm2Fe 17Weigh out Sm powder and Fe powder, with Sm powder in 5-20% excess of the theoretical amount. Then mix with dispersant and ammonia-containing liquid, ensuring the liquid level of the ammonia-containing liquid is higher than the height of the milling steel balls in the milling container.

[0031] Preferably, the ammonia-containing liquid in step (1) includes ammonia water and / or liquid nitrogen.

[0032] Preferably, the liquid level of the ammonia-containing liquid is 3-4 cm higher than the milling steel ball, for example, it can be 3 cm, 3.2 cm, 3.4 cm, 3.6 cm, 3.8 cm or 4 cm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] As a preferred technical solution of the present invention, the high-energy ball milling process in step (1) specifically includes: stopping ball milling and cooling after each high-energy ball milling, and then repeating the high-energy ball milling process again.

[0034] Preferably, the frequency of the high-energy ball mill is 80-150Hz, such as 80Hz, 90Hz, 100Hz, 110Hz, 120Hz, 130Hz, 140Hz or 150Hz, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] Preferably, the total time for high-energy ball milling is 2-10 hours, for example, it can be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, the single-stage ball milling time in the high-energy ball mill is 7-15 minutes, for example, it can be 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes or 15 minutes, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] Preferably, the cooling time in the high-energy ball mill is 7-15 min, for example, it can be 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min or 15 min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] As a preferred technical solution of the present invention, the surfactant in step (2) includes polyacrylamide and / or sodium stearate.

[0039] Preferably, the mass ratio of the surfactant in step (2) is 5%-25% of the total mass of the Sm powder and Fe powder, for example, it can be 5%, 7%, 9%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24% or 25%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the mass ratio of butyl acetate in step (2) is 10%-30% of the total mass of Sm powder and Fe powder, for example, it can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28% or 30%, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] As a preferred technical solution of the present invention, the frequency of the secondary ball milling in step (2) is 4-8Hz, for example, it can be 4Hz, 5Hz, 6Hz, 7Hz or 8Hz, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] Preferably, the total time for the secondary ball milling is 20-50 minutes, for example, it can be 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes or 50 minutes, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] As a preferred technical solution of the present invention, the drying temperature in step (2) is 10-100℃, for example, it can be 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or 100℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 30-60℃.

[0044] Preferably, the drying time in step (2) is 1-3 hours, for example, it can be 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] In this invention, the drying process can be carried out under normal pressure or under vacuum, and the specific choice can be made according to the circumstances. No specific limitation is made here.

[0046] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0047] (1) Based on the chemical formula Sm2Fe 17Weigh out Sm powder and Fe powder, with Sm powder in 5%-20% excess of the theoretical amount. Then add them and the dispersant into a ball mill container filled with ammonia liquid for high-energy ball milling at 80-150 Hz for a total time of 2-10 h. Stop ball milling and cool for 7-15 min after each high-energy ball milling segment.

[0048] The mass ratio of Sm powder to Fe powder is (300-400):(900-1000), and the mass ratio of the dispersant is 5%-20% of the total mass of Sm powder and Fe powder.

[0049] (2) After the high-energy ball milling in step (1), a surfactant and butyl acetate are added to the ball mill for 4-8 Hz and 20-50 min. The slurry obtained after the second ball milling is dried at 10-100℃ for 1-3 h to obtain the SmFeN powder.

[0050] The surfactant is present in a mass ratio of 5%-25% of the total mass of the Sm powder and Fe powder, and the butyl acetate is present in a mass ratio of 5%-25% of the total mass of the Sm powder and Fe powder.

[0051] This invention incorporates a slight excess of butyl acetate along with a surfactant. While butyl acetate is difficult to hydrolyze in a neutral environment, it hydrolyzes into acetic acid and butanol in an alkaline environment, effectively neutralizing the alkalinity of the medium. Furthermore, butyl acetate ceases hydrolysis when the medium is neutral. Simultaneously, the generated acetic acid can be used for powder coating in subsequent processes without the need for additional acid, and the generated butanol is highly volatile. The added butyl acetate does not introduce impurities.

[0052] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] (1) The present invention provides a SmFeN powder, which reduces the powder activity by coating the surface of the SmFeN powder with acetate, avoids violent reaction after contact with air, and eliminates safety problems in the production process.

[0055] (2) The preparation method provided by the present invention generates SmFeN in the high-energy ball milling process through a secondary ball milling process, and then achieves powder coating in the secondary ball milling process, so that the intrinsic coercivity of SmFeN powder is ≥13.86KOe. Detailed Implementation

[0056] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0057] Example 1

[0058] This embodiment provides a method for preparing SmFeN powder, the method comprising the following steps:

[0059] (1) Based on the chemical formula Sm2Fe 17 Weigh 130g Sm powder and 380g Fe powder, then add them along with 35g sodium sulfonate into a ball mill container filled with ammonia water. After adding the materials, the ammonia water level is 3-4cm higher than the ball mill steel balls. Perform high-energy ball milling at 120Hz for a total time of 8h. Stop the ball milling after each 10min high-energy ball milling segment and cool for 10min.

[0060] (2) After the high-energy ball milling in step (1), 50g of polyacrylamide and 85g of butyl acetate are added for a second ball milling at 5Hz for 20min. The slurry obtained after the second ball milling is dried at 40℃ for 1h to obtain the SmFeN powder.

[0061] Example 2

[0062] This embodiment provides a method for preparing SmFeN powder, the method comprising the following steps:

[0063] (1) Based on the chemical formula Sm2Fe 17 Weigh 140g Sm powder and 370g Fe powder, then add them along with 40g sodium sulfonate into a ball mill container filled with ammonia water. After adding the materials, the ammonia water level is 3-4cm higher than the ball mill steel balls. Perform high-energy ball milling at 100Hz for a total time of 10h. Stop the ball milling and cool for 10min after each high-energy ball milling segment.

[0064] (2) After the high-energy ball milling in step (1), 60g of sodium stearate and 95g of butyl acetate are added for a second ball milling at 6Hz for 40min. The slurry obtained after the second ball milling is dried at 60℃ for 1h to obtain the SmFeN powder.

[0065] Example 3

[0066] This embodiment provides a method for preparing SmFeN powder. Except for step (1) where 280g of Fe powder is added, all other conditions are the same as in Example 1.

[0067] Example 4

[0068] This embodiment provides a method for preparing SmFeN powder. Except for step (1) where 450g of Fe powder is added, all other conditions are the same as in Example 1.

[0069] Example 5

[0070] This embodiment provides a method for preparing SmFeN powder. Except for step (1) where 15g of sodium sulfonate is added, all other conditions are the same as in Example 1.

[0071] Example 6

[0072] This embodiment provides a method for preparing SmFeN powder. Except for step (1) where 120g of sodium sulfonate is added, all other conditions are the same as in Example 1.

[0073] Example 7

[0074] This embodiment provides a method for preparing SmFeN powder. Except for step (1), where the ammonia water level is 0.5 cm higher than the ball milling steel ball after feeding, all other conditions are the same as in Example 1.

[0075] Example 8

[0076] This embodiment provides a method for preparing SmFeN powder. Except for step (1), where the ammonia water level is 6 cm higher than the ball milling steel ball after feeding, all other conditions are the same as in Example 1.

[0077] Example 9

[0078] This embodiment provides a method for preparing SmFeN powder. Except for the addition of 18g of polyacrylamide in step (2), all other conditions are the same as in Example 1.

[0079] Example 10

[0080] This embodiment provides a method for preparing SmFeN powder. Except for the addition of 150g of polyacrylamide in step (2), all other conditions are the same as in Example 1.

[0081] Example 11

[0082] This embodiment provides a method for preparing SmFeN powder. Except for the addition of 16g ​​of butyl acetate in step (2), all other conditions are the same as in Example 1.

[0083] Example 12

[0084] This embodiment provides a method for preparing SmFeN powder. Except for the addition of 170g of butyl acetate in step (2), all other conditions are the same as in Example 1.

[0085] Example 13

[0086] This embodiment provides a method for preparing SmFeN powder. Except for the frequency of the secondary ball milling in step (2) being 2 Hz, all other conditions are the same as in Example 1.

[0087] Example 14

[0088] This embodiment provides a method for preparing SmFeN powder. Except for the frequency of the secondary ball milling in step (2) being 10 Hz, all other conditions are the same as in Example 1.

[0089] Comparative Example 1

[0090] This comparative example provides a method for preparing SmFeN powder, except that sodium sulfonate is not added in step (1), and all other conditions are the same as in Example 1.

[0091] Comparative Example 2

[0092] This comparative example provides a method for preparing SmFeN powder. Except for step (2) where polyacrylamide is not added, all other conditions are the same as in Example 1.

[0093] Comparative Example 3

[0094] This comparative example provides a method for preparing SmFeN powder, except that butyl acetate is not added in step (2), and all other conditions are the same as in Example 1.

[0095] Comparative Example 4

[0096] This comparative example provides a method for preparing SmFeN powder. Except for adding 35g sodium sulfonate, 50g polyacrylamide and 85g butyl acetate to a ball milling container filled with ammonia before high-energy ball milling in step (1), all other conditions are the same as in Example 1.

[0097] The SmFeN powders prepared in the above examples and comparative examples were subjected to samarium content, carbon content, oxygen content, nitrogen content, powder D50, SEM electron microscopy, and intrinsic coercivity tests. Oxygen content was used to characterize the degree of oxidation, nitrogen content to characterize the nitriding effect of high-energy ball milling, powder D50 to characterize the particle size of the powder after ball milling, SEM electron microscopy to test the average thickness of acetate coating, and intrinsic coercivity to characterize the magnetic properties after ball milling. The test results are shown in Table 1.

[0098] Table 1

[0099]

[0100]

[0101] The following points can be drawn from Table 1:

[0102] (1) The SmFeN powder obtained by the preparation method provided in Examples 1-2 of the present invention has a particle size D50 of 3.98-4 μm, an average thickness of 0.53 μm of acetate coating, a low degree of oxidation, and no combustion or explosion phenomenon occurred during the preparation process. The intrinsic coercivity of the SmFeN powder is ≥13.86 KOe. This shows that the preparation method of the present invention ensures the activity and magnetism of the product while the acetate coating effectively improves the safety.

[0103] (2) As can be seen from the comparison between Example 1 and Example 3-4, when the amount of Fe powder added in step (1) is too small or too large, it is not conducive to improving the magnetic properties of SmFeN powder; As can be seen from the comparison between Example 1 and Example 5-6, when the amount of dispersant added in step (1) is too small, it is not conducive to improving the magnetic properties of SmFeN powder; when the amount of dispersant added in step (1) is too large, although it will not affect the thickness of the acetate coating layer and the magnetic properties, it will increase the production cost.

[0104] (3) As can be seen from the comparison between Example 1 and Example 7-8, when too little ammonia is added in step (1), it is not conducive to improving the magnetic properties of SmFeN powder; but when too much ammonia is added, it leads to an excessively thick acetate coating layer.

[0105] (4) As can be seen from the comparison between Example 1 and Examples 9-10, when the amount of surfactant added in step (2) is too small, it is not conducive to improving the magnetic properties of SmFeN powder. When the amount of surfactant added in step (2) is too large, although it will not affect the thickness of the acetate coating layer and the magnetic properties, it will increase the production cost. As can be seen from the comparison between Example 1 and Examples 11-12, when the amount of butyl acetate added in step (2) is too small, the acetate coating layer becomes too thin, which further leads to a decrease in magnetic properties.

[0106] (5) As can be seen from the comparison between Example 1 and Example 13-14, when the frequency of the secondary ball milling is too low or too high, the coating effect is not ideal. If the frequency is too high, the already coated acetate will be lost in the collision between the powder and the steel ball. If the frequency is too low, the coating efficiency will be reduced, and some powder may not be completely coated.

[0107] (6) As can be seen from the comparison between Example 1 and Comparative Examples 1-3, when no dispersant or surfactant is added, the acetate coating layer is too thin, and the powder is prone to oxidation. The oxygen content is as high as 4.36% and 4.24%, respectively. When no butyl acetate is added, there is almost no acetate on the surface, and the average thickness of the coating cannot be measured. At the same time, when the powder is taken out after drying, sparks appear and then it burns violently.

[0108] (7) As can be seen from the comparison between Example 1 and Comparative Example 4, when the raw materials are directly mixed and added for high-energy ball milling, the acetate coating layer is too thin, and powder oxidation is easy to occur, with an oxygen content as high as 3.28%.

[0109] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. An SmFeN powder, characterized in that, The surface of the SmFeN powder is coated with acetate; The SmFeN powder is composed of the following components by mass percentage: Sm 22%-25%, C 0.2%-0.8%, N 2%-5%, O 1%-4%, with the balance being Fe and unavoidable impurities; The acetate accounts for 0.5%-5% of the mass of the SmFeN powder; The preparation method of the SmFeN powder includes the following steps: (1) Based on the chemical formula Sm2Fe 17 Weigh out Sm powder and Fe powder, then mix them with dispersant and ammonia-containing liquid and perform high-energy ball milling; Among them, the Sm powder should be used in excess of the theoretical amount by 5%-20%; (2) After the high-energy ball milling in step (1), a surfactant and butyl acetate are added for secondary ball milling. The slurry obtained after the secondary ball milling is dried to obtain the SmFeN powder.

2. The SmFeN powder according to claim 1, characterized in that, The acetates include ammonium acetate and / or sodium acetate.

3. A method for preparing SmFeN powder as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) Based on the chemical formula Sm2Fe 17 Weigh out Sm powder and Fe powder, then mix them with dispersant and ammonia-containing liquid and perform high-energy ball milling; Among them, the Sm powder should be used in excess of the theoretical amount by 5%-20%; (2) After the high-energy ball milling in step (1), a surfactant and butyl acetate are added for secondary ball milling. The slurry obtained after the secondary ball milling is dried to obtain the SmFeN powder.

4. The preparation method according to claim 3, characterized in that, The mass ratio of Sm powder to Fe powder in step (1) is (300-400):(900-1000).

5. The preparation method according to claim 4, characterized in that, The mass ratio of Sm powder to Fe powder is (305-360):(950-960).

6. The preparation method according to claim 3, characterized in that, The dispersant in step (1) includes sodium sulfonate.

7. The preparation method according to claim 3, characterized in that, In step (1), the mass ratio of the dispersant is 5%-20% of the total mass of the Sm powder and Fe powder.

8. The preparation method according to claim 3, characterized in that, The ammonia-containing liquid in step (1) is contained in a ball mill container.

9. The preparation method according to claim 3, characterized in that, Step (1) is based on the chemical formula Sm2Fe 17 Weigh out Sm powder and Fe powder, with Sm powder in 5-20% excess of the theoretical amount. Then mix with dispersant and ammonia-containing liquid, ensuring the liquid level of the ammonia-containing liquid is higher than the height of the milling steel balls in the milling container.

10. The preparation method according to claim 3, characterized in that, The ammonia-containing liquid in step (1) includes ammonia water and / or liquid nitrogen.

11. The preparation method according to claim 3, characterized in that, The level of the ammonia-containing liquid is 3-4 cm higher than that of the milling steel ball.

12. The preparation method according to claim 3, characterized in that, The high-energy ball milling process in step (1) specifically includes: stopping the ball milling and cooling after each high-energy ball milling, and then repeating the high-energy ball milling process again.

13. The preparation method according to claim 3, characterized in that, The frequency of the high-energy ball mill is 80-150Hz.

14. The preparation method according to claim 3, characterized in that, The total time for the high-energy ball milling is 2-10 hours.

15. The preparation method according to claim 3, characterized in that, The single-stage ball milling time in the high-energy ball mill is 7-15 minutes.

16. The preparation method according to claim 3, characterized in that, The cooling time in the high-energy ball mill is 7-15 minutes.

17. The preparation method according to claim 3, characterized in that, The surfactant in step (2) includes polyacrylamide and / or sodium stearate.

18. The preparation method according to claim 3, characterized in that, The mass ratio of the surfactant in step (2) is 5%-25% of the total mass of the Sm powder and Fe powder.

19. The preparation method according to claim 3, characterized in that, In step (2), the mass ratio of butyl acetate is 10%-30% of the total mass of the Sm powder and Fe powder.

20. The preparation method according to claim 3, characterized in that, The frequency of the secondary ball milling in step (2) is 4-8 Hz.

21. The preparation method according to claim 3, characterized in that, The total time for the secondary ball milling is 20-50 minutes.

22. The preparation method according to claim 3, characterized in that, The drying temperature in step (2) is 10-100℃.

23. The preparation method according to claim 22, characterized in that, The drying temperature is 30-60℃.

24. The preparation method according to claim 3, characterized in that, The drying time in step (2) is 1-3 hours.

25. The preparation method according to claim 3, characterized in that, The preparation method includes the following steps: (1) Based on the chemical formula Sm2Fe 17 Weigh out Sm powder and Fe powder, with Sm powder in 5%-20% excess of the theoretical amount. Then add them and the dispersant into a ball mill container filled with ammonia liquid for high-energy ball milling at 80-150Hz for a total time of 2-10h. Stop ball milling and cool for 7-15min after each high-energy ball milling segment. The mass ratio of Sm powder to Fe powder is (300-400):(900-1000), and the mass ratio of the dispersant is 5%-20% of the total mass of the Sm powder and Fe powder. (2) After the high-energy ball milling in step (1), a surfactant and butyl acetate are added and the mixture is ball-milled again at 4-8 Hz for 20-50 min. The slurry obtained after the second ball milling is dried at 10-100℃ for 1-3 h to obtain the SmFeN powder. The surfactant is present in a mass ratio of 5%-25% of the total mass of the Sm powder and Fe powder, and the butyl acetate is present in a mass ratio of 10%-30% of the total mass of the Sm powder and Fe powder.

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