A method for preparing a samarium iron nitride magnetic powder

Abstract

The application provides a preparation method of samarium-iron-nitrogen magnetic powder, which comprises the following steps: mixing iron, samarium oxide and rare earth hydride (as a reducing agent, preferably lanthanum hydride and / or cerium hydride), performing ball milling treatment, and performing briquetting treatment on the obtained mixture to obtain a blank; performing vacuum heat treatment on the blank to obtain a coarse samarium-iron-magnetic powder material; placing the coarse samarium-iron-magnetic powder material into an ammonia atmosphere after performing crushing treatment, and performing high-temperature nitriding treatment to obtain a coarse samarium-iron-nitrogen magnetic powder; and transferring the coarse samarium-iron-nitrogen magnetic powder into a washing liquid to perform cleaning treatment, so as to remove the residual non-magnetic impurities in the solid phase, and obtain the samarium-iron-nitrogen magnetic powder; the preparation method provided by the application has the advantages of small reducing agent dosage, low heat treatment temperature, short time, etc., and effectively reduces the preparation cost of the samarium-iron-nitrogen magnetic powder.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet powder preparation technology, and in particular to a method for preparing samarium iron nitrogen magnetic powder. Background Technology

[0002] Rare earth permanent magnet materials are widely used in information technology, industrial production, aerospace, and emerging fields such as new energy vehicles and robotics due to their excellent magnetic properties. With the development of precision, integration, and personalization of magnetic components, higher requirements are being placed on the magnetic properties of materials and the manufacturing cost.

[0003] Compared to neodymium iron boron permanent magnets, samarium iron nitrogen (Sm2Fe) 17 N3 permanent magnet materials exhibit higher Curie temperatures and larger magnetocrystalline anisotropy fields, making them promising for a wide range of applications; current methods for preparing Sm2Fe... 17 The main methods for producing N3 permanent magnet materials are reduction diffusion and powder metallurgy. Since the price of Sm2O3 is more than an order of magnitude lower than that of pure metal Sm, and its price fluctuates less, the reduction diffusion method has a significant advantage in terms of economic benefits compared to the powder metallurgy method.

[0004] Preparation of Sm2Fe by Related Reduction-Diffusion Method 17 In this process, metallic calcium is often used as a reducing agent. Solid Ca must first melt (melting point 842 °C) to form liquid Ca, which then diffuses into samarium oxide. The required reduction temperature is typically above 1000 °C to overcome the solid-solid reaction barrier, resulting in high energy consumption. Furthermore, the fluidity of liquid Ca easily leads to localized over- or under-reaction. In addition, the byproduct CaO (melting point 2614 °C) readily forms a dense oxide layer on the surface of the reactant particles. The CaO encapsulation effect hinders the contact between Ca and unreacted samarium oxide, leading to incomplete reaction. On the other hand, the production of metallic calcium itself mainly employs electrolysis and thermal reduction methods, both of which are accompanied by high energy consumption and costs, resulting in a persistently high calcium price. This indirectly increases the cost of preparing samarium-iron-nitrogen permanent magnet materials using the reduction-diffusion method.

[0005] Therefore, developing efficient and low-cost methods for preparing samarium iron nitrogen magnetic powder has become a current research hotspot. Summary of the Invention

[0006] To address the problems existing in the background art, the present invention provides an efficient and low-cost method for preparing samarium iron nitrogen magnetic powder; the specific contents of the invention are as follows:

[0007] This invention provides a method for preparing samarium iron nitrogen magnetic powder, the method comprising:

[0008] Iron, samarium oxide and rare earth hydrides are mixed and then ball-milled. The resulting mixture is then pressed into briquettes to obtain a billet.

[0009] The blank is subjected to vacuum heat treatment to obtain coarse samarium iron magnetic powder material;

[0010] After the crude samarium iron magnetic powder material is crushed, it is placed in an ammonia atmosphere and subjected to high-temperature nitriding treatment to obtain crude samarium iron nitrogen magnetic powder.

[0011] The crude samarium iron nitrogen magnetic powder is cleaned to remove residual non-magnetic impurities in the solid phase, and then dried to obtain the samarium iron nitrogen magnetic powder.

[0012] The rare earth hydrides are selected from lanthanum hydride and / or cerium hydride.

[0013] Optionally, the molar ratio of samarium oxide, iron and rare earth hydride is 1:(8~14):(2~3).

[0014] Optionally, the ball-to-material ratio of the ball mill is (10-20):1, the ball milling speed is 400rpm~700rpm, and the ball milling time is 2-10h.

[0015] Optionally, the briquetting process is carried out by cold pressing, and the pressure used for the briquetting is 20-30 MPa.

[0016] Optionally, the target temperature for the vacuum heat treatment is 850-1050 ℃, and the holding time is 20 min-5 h.

[0017] Optionally, the cleaning process includes: sequentially using an acidic washing solution, deionized water, and an ethanol solution to perform multi-step cleaning on the crude samarium iron nitrogen magnetic powder; the acidic washing solution is a hydrochloric acid solution or a glacial acetic acid solution with a concentration of 1-5%.

[0018] Optionally, the rare earth hydride is obtained by hydrogen explosion of lanthanum or cerium metal.

[0019] The particle size of the reducing agent rare earth hydride is 50-150 μm.

[0020] Optionally, the iron powder has a particle size of 5 μm to 20 μm.

[0021] Optionally, before ball milling, the samarium oxide is subjected to vacuum heat treatment at 200-400 °C for 3-6 hours to remove residual moisture and obtain dry anhydrous samarium oxide.

[0022] Optionally, the method further includes: adding an appropriate amount of flux to the mixture, mixing it evenly, and then pressing it into briquettes to obtain a green body;

[0023] The flux is selected from BiCl3, KCl and / or LaCl3.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] This invention provides a method for preparing samarium iron nitrogen magnetic powder. The method includes: mixing iron powder, samarium oxide powder, and rare earth hydride, then ball milling the mixture and pressing it into briquettes to obtain a green body; subjecting the green body to vacuum heat treatment to obtain coarse samarium iron magnetic powder material; crushing the coarse samarium iron magnetic powder material and then placing it in an ammonia atmosphere for high-temperature nitriding treatment to obtain coarse samarium iron nitrogen magnetic powder; transferring the coarse samarium iron nitrogen magnetic powder to a washing liquid for cleaning to remove residual non-magnetic impurities in the solid phase, thereby obtaining the samarium iron nitrogen magnetic powder. The preparation method of samarium iron nitrogen magnetic powder provided by this invention has the advantages of a short preparation process, low reducing agent dosage, low heat treatment temperature and short time; and effectively reduces the preparation cost of samarium iron nitrogen magnetic powder. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A flowchart illustrating the preparation method of samarium iron nitrogen magnetic powder provided in an embodiment of the present invention is shown;

[0028] Figure 2 The Sm2Fe shown in Embodiment 1 of the present invention is illustrated. 17 XRD pattern of alloy powder;

[0029] Figure 3 The Sm2Fe shown in Embodiment 1 of the present invention is illustrated. 17 XRD pattern of N3 magnetic powder;

[0030] Figure 4 The Sm2Fe shown in Embodiment 1 of the present invention is illustrated. 17 SEM image of N3 magnetic powder;

[0031] Figure 5 The Sm2Fe in Comparative Example 1 of the present invention is shown. 17 XRD pattern of alloy powder;

[0032] Figure 6 The Sm2Fe in Comparative Example 2 of the present invention is shown. 17 XRD pattern of alloy powder. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0034] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0035] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0036] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] Referring to existing processes for reducing samarium oxide with lanthanum, to ensure a sufficient reaction rate, the reduction process typically requires high temperatures of 1200°C to 1500°C, with reaction times ranging from 15 to 22 hours, resulting in significant energy consumption. Furthermore, if lanthanum is used as the reducing agent for Sm₂Fe₂… 17 The preparation of alloys or samarium iron nitrogen magnetic powder, due to Sm2Fe 17 The alloy has a melting point of only 1280℃, and the generated Sm will undergo violent volatilization. This volatilization-precipitation phenomenon severely disrupts the stoichiometry of the target product, ultimately hindering the formation of single-phase Sm2Fe. 17 Stable generation.

[0038] Therefore, this invention provides a method for preparing samarium iron nitrogen magnetic powder. This method uses iron powder and samarium oxide powder as reactants, and lanthanum hydride and / or cerium hydride as reducing agents. The samarium iron nitrogen magnetic powder is prepared through a diffusion reduction reaction and a nitrogen doping reaction. Because rare earth hydrides (such as LaH...)x In the crystal structure of La x+ With H - Bonded by ionic bonds, rare earth hydride crystals exhibit superior lattice vibration and ion migration capabilities compared to metallic calcium or metallic lanthanum / cerium at the same temperature. Therefore, rare earth hydrides can initiate the reduction reaction of samarium oxide under milder vacuum heat treatment conditions. This also means that at the same reaction temperature, the reaction rate using lanthanum hydride or cerium hydride as reducing agents is faster, reducing the need for reducing agents. Furthermore, the H2 generated by the decomposition of rare earth hydrides forms microbubble flows within the reactants. This airflow disturbance prevents reactant particles from agglomerating at high temperatures, ensuring complete reaction of samarium oxide.

[0039] Taking lanthanum hydride as an example, the reaction pathway of lanthanum hydride with samarium oxide is: Sm₂O₃ + 2LaH₂O x →2Sm+La2O3+xH2↑; In this process, H in lanthanum hydride - Released as hydrogen gas, the byproduct La2O3, though solid, is kept loose due to its fine particle size (50-150 μm) after ball milling and the microchannels formed during H2 desorption. It can be quickly dissolved with only 1-5% dilute hydrochloric acid / glacial acetic acid. In contrast, the traditional calcium thermal reduction method requires high-temperature melting and slag removal of the generated byproduct CaO, a complex and energy-intensive process. Alternatively, large amounts of water are used to remove CaO, releasing significant heat and requiring post-treatment with a strong alkaline solution, leading to substantial costs. Furthermore, excess calcium reacts with Fe to form CaFe2, requiring acid washing, alkali washing, and secondary ball milling to remove these impurities, increasing the number of steps and reducing the magnetic powder yield.

[0040] Furthermore, the mining process of rare earth minerals reveals their symbiotic nature. Lanthanum and cerium are not mined independently, but rather are byproducts of the separation process in rare earth deposits such as bastnaesite. Their marginal cost approaches zero, avoiding the additional capital and energy investment required for the entire limestone calcination-molten salt electrolysis process necessary for calcium extraction. Moreover, the waste heat and byproduct steam from La electrolysis in the combined plant can be reused, making the use of lanthanum hydride / cerium hydride as a reducing agent even more economically viable.

[0041] The specific embodiments of the present invention are described below:

[0042] This invention provides a method for preparing samarium iron nitrogen magnetic powder. Figure 1 A flowchart illustrating the preparation method of samarium iron nitrogen magnetic powder according to an embodiment of the present invention is shown, as follows: Figure 1 As shown, the method includes:

[0043] S1. Iron powder, samarium oxide powder and rare earth hydride are mixed and ball-milled, and the resulting mixture is then pressed into briquettes to obtain a green body.

[0044] In this step, the reducing agent rare earth hydride is selected from lanthanum hydride and / or cerium hydride; this step uses ball milling to mix the raw materials required for the preparation process while activating the reaction activity. The ball-to-material ratio used for ball milling is preferably (10-20):1, the ball milling speed is 400rpm~700rpm, and the ball milling time is 2-10h.

[0045] In the specific implementation of this step, follow the Sm2Fe 17 The raw material dosage determined by the stoichiometric ratio is: the molar ratio of samarium oxide, iron and rare earth hydrides is 1:(8~14):(2~3). The samarium oxide powder in the raw material is appropriately in excess to compensate for the evaporation loss of samarium during the thermal reduction process.

[0046] It should be noted that the reducing agent rare earth hydride used in this invention can be commercially available or obtained by hydrogen explosion of lanthanum or cerium metal. Currently, hydrogen explosion treatment is a relatively mature process, and this invention does not limit the specific details of hydrogen explosion treatment. The particle size of the obtained rare earth hydride is preferably 50-150 μm. The iron is preferably commercially available nano or micro iron with a particle size of 5 nm-20 μm.

[0047] It should be noted that all raw materials used must be strictly dried (moisture content less than 0.1%) before ball milling to avoid oxidation caused by moisture and resulting impurities. Specifically, samarium oxide can be vacuum heat-treated at 200-400 ℃ for 3-6 h to remove residual moisture and obtain dry anhydrous samarium oxide for ball milling.

[0048] In some embodiments, this step employs cold pressing during briquetting, with a pressure of 20-30 Pa increasing the density of the blank and the contact area between particles by 30%-50%. - It can be directly transferred to Sm through the interparticle interface 3+ This avoids the reaction dead zone caused by the obstruction of liquid Ca permeation in traditional calcium reduction.

[0049] In some embodiments, a flux accounting for 5% by mass can be added to the mixture obtained by ball milling. The flux can further reduce the activation energy of the thermal reduction reaction, promote uniform grain growth, and improve the crystallinity of the alloy. The flux is preferably BiCl3, KCl and / or LaCl3.

[0050] S2. Vacuum heat treatment is performed on the blank to obtain crude samarium iron magnetic powder material;

[0051] This step benefits from the use of rare earth hydrides as reducing agents. Without the addition of additional additives, the reduction and alloying reactions can be completed at a minimum temperature of 850 °C, effectively lowering the reaction initiation threshold. Furthermore, the generated byproduct La2O3 has a loose structure and does not hinder the normal progress of the reduction reaction. In contrast, using the traditional calcium reduction method, the generated byproduct CaO (melting point 2614 °C) easily forms a dense oxide layer on the surface of Sm particles. The encapsulation effect of CaO hinders the contact between Ca and unreacted samarium oxide, requiring extended holding time (usually >8 hours) or increased temperature to break down the barrier.

[0052] In this step, the preferred target temperature for vacuum heat treatment is 850-1050 ℃, and the holding time is 20 min-5 h. Compared with calcium thermal reduction, this reaction condition reduces both the reaction temperature and the reaction time, thereby increasing the production capacity per unit time, reducing the preparation cost, and fundamentally solving the problem of byproduct obstacles.

[0053] S3. After crushing the crude samarium iron magnetic powder material, it is placed in an ammonia atmosphere and subjected to high-temperature nitriding treatment to obtain crude samarium iron nitrogen magnetic powder.

[0054] In this step, after crushing the coarse samarium iron magnetic powder obtained from heat treatment (the particle size of the crushed coarse samarium iron magnetic powder is no larger than 100 mesh), a high-temperature nitriding treatment is performed to embed nitrogen atoms into the Sm2Fe in the coarse samarium iron magnetic powder material. 17 In the alloy composition, Sm2Fe is formed. 17 N3 magnetic phase. The insertion of nitrogen atoms makes Sm2Fe 17 Lattice expansion further optimizes the magnetic anisotropy of the magnetic powder, meeting the requirements for permanent magnet materials; and the nitriding reaction does not destroy Sm2Fe. 17 Its crystal structure, formed only through interstitial solid solutions, significantly enhances the material's magnetic properties such as saturation magnetization and coercivity.

[0055] In this specific step, the process conditions controlled for the high-temperature nitriding treatment are: 0.1~1.0 MPa, 400~500℃, and a holding time of 2~8 hours. It should be noted that the ammonia atmosphere used is high-purity ammonia (purity ≥99.999%).

[0056] S4. The crude samarium iron nitrogen magnetic powder is cleaned to remove the non-magnetic impurities remaining in the solid phase, and then dried to obtain the samarium iron nitrogen magnetic powder.

[0057] In practice, the main byproducts in crude samarium iron nitrogen magnetic powder are lanthanum / cerium oxides and residual impurities, with almost no Fe-containing byproducts. Therefore, no additional impurity removal process is required. The heat-treated blocks only need to be crushed and placed in a washing solution to remove the lanthanum / cerium oxides.

[0058] In specific implementation, the cleaning process includes: sequentially using acidic detergent, deionized water and ethanol solution to perform multi-step cleaning on the crude samarium iron nitrogen magnetic powder; wherein, the acidic detergent can be selected from hydrochloric acid solution or glacial acetic acid solution, with a concentration of 1-5%.

[0059] To enable those skilled in the art to more clearly understand the present invention, the following embodiments will be used to describe in detail the preparation method of samarium iron nitrogen magnetic powder according to the present invention.

[0060] Example 1

[0061] Samarium oxide powder, iron powder and lanthanum hydride particles were weighed in a molar ratio of 1:10:3; they were placed in a ball mill jar and subjected to high-energy ball milling at room temperature. The total mass ratio of reactants to grinding balls was 1:15. The mixture was milled at a rate of 600 rpm for 2 h in a ball mill. Then, under a protective atmosphere, the powder in the ball mill jar was removed and pressed into a green embryo. The pressing pressure was 30 MPa.

[0062] The green embryo was placed in a covered stainless steel crucible, which was then sealed with the lid and placed in a heat treatment furnace for annealing under argon protection. The annealing temperature was 1000 °C, and the holding time was 2 h. After the reaction was completed, Sm₂Fe was obtained. 17 Coarse samarium iron magnetic powder material of alloys and by-products.

[0063] Crushed coarse samarium iron magnetic powder was partially processed into powder. This powder was washed with glacial acetic acid solution, then with deionized water, and finally rinsed three times with alcohol. The washed powder was then placed in a vacuum drying oven and dried to obtain Sm₂Fe. 17 alloy powder.

[0064] The remaining powdered material was placed in a reactor, and after evacuating the reactor, high-purity ammonia gas (99.999% purity) was introduced. The reactor was then held at 1.0 MPa and 400 °C for 2 h to obtain Sm₂Fe by nitriding. 17 N3 magnetic powder and byproducts. Crude samarium iron nitrogen magnetic powder was obtained after cooling.

[0065] Crude samarium iron nitrogen magnetic powder was washed with glacial acetic acid solution, then with deionized water, and finally rinsed three times with alcohol. The washed powder was placed in a vacuum drying oven and dried to obtain Sm₂Fe. 17 N3 magnetic powder.

[0066] Nitrogen content testing (using a N-3000 steel research and development laboratory) confirmed that the Sm2Fe prepared in Example 1... 17 The nitrogen content in N3 magnetic powder is 3.26 wt%.

[0067] Figure 2 The Sm2Fe shown in Embodiment 1 of the present invention is illustrated. 17XRD pattern of alloy powder, from Figure 2 It can be seen that the sample contains Sm2Fe after heat treatment. 17 Phase formation, without α -Fe phase and other alloys are present.

[0068] Figure 3 The Sm2Fe shown in Embodiment 1 of the present invention is illustrated. 17 XRD pattern of N3 magnetic powder, from Figure 3 It can be seen that after nitriding, Sm2Fe is present. 17 N3 phase formation, no α The presence of the Fe phase and other alloys further indicates that Sm2Fe is nitrided. 17 Samarium iron nitrogen magnetic powder is obtained by fully combining alloy powder with nitrogen.

[0069] Figure 4 The Sm2Fe shown in Embodiment 1 of the present invention is illustrated. 17 SEM images of N3 magnetic powder, from Figure 4 It can be seen that the Sm2Fe after byproduct separation 17 The N3 magnetic powder consists entirely of uniformly distributed, near-spherical particles, Sm2Fe. 17 N3 magnetic powder.

[0070] Example 2

[0071] Samarium oxide powder, iron powder and lanthanum hydride particles in a molar ratio of 1:12:2.5 were weighed and placed into a ball mill jar. High-energy ball milling was carried out at room temperature with a total mass ratio of reactants to grinding balls of 1:10. The mixture was ground in a ball mill at a rate of 400 rpm for 10 h. Then, under a protective atmosphere, the powder in the ball mill jar was removed and pressed into a green embryo at a pressure of 30 MPa.

[0072] The green embryo was placed in a covered stainless steel crucible, which was then sealed with the lid and placed in a heat treatment furnace for annealing under argon protection. The annealing temperature was 950 °C, and the holding time was 3 h. After the reaction was completed, Sm₂Fe was obtained. 17 Coarse samarium iron magnetic powder material of alloys and by-products.

[0073] The remaining powdered material was placed in a reactor, and after evacuating the reactor, high-purity ammonia gas (99.999% purity) was introduced. The reactor was then held at 1.0 MPa and 500 °C for 2 h to obtain Sm₂Fe by nitriding. 17 N3 magnetic powder and byproducts. Crude samarium iron nitrogen magnetic powder was obtained after cooling.

[0074] Crude samarium iron nitrogen magnetic powder was washed with glacial acetic acid solution, then with deionized water, and finally rinsed three times with alcohol. The washed powder was placed in a vacuum drying oven and dried to obtain Sm₂Fe. 17 N3 magnetic powder.

[0075] Nitrogen content testing (using a N-3000 steel research and development laboratory) confirmed that the Sm2Fe prepared in Example 2... 17 The nitrogen content in N3 magnetic powder is 3.15 wt%.

[0076] Example 3

[0077] Samarium oxide powder, iron powder and cerium hydride particles in a molar ratio of 1:14:2 were weighed and placed into a ball mill jar. High-energy ball milling was carried out at room temperature with a total mass ratio of reactants to grinding balls of 1:20. The mixture was milled at a rate of 700 rpm for 4 h. Then, under a protective atmosphere, the powder in the ball mill jar was removed and pressed into a green embryo at a pressure of 30 MPa.

[0078] The green embryo was placed in a covered stainless steel crucible, which was then sealed with the lid and placed in a heat treatment furnace for annealing under argon protection. The annealing temperature was 1050 °C, and the holding time was 1 h. After the reaction was completed, Sm₂Fe was obtained. 17 Coarse samarium iron magnetic powder material of alloys and by-products.

[0079] Crush coarse samarium iron magnetic powder material, place the obtained powdered material in a reactor, evacuate the reactor and then introduce high-purity ammonia gas (purity 99.999%). The mixture is held at 1.0 MPa and 400 ℃ for 2 h to obtain Sm2Fe by nitriding. 17 N3 magnetic powder and byproducts. Crude samarium iron nitrogen magnetic powder was obtained after cooling.

[0080] Crude samarium iron nitrogen magnetic powder was washed with glacial acetic acid solution, then with deionized water, and finally rinsed three times with alcohol. The washed powder was placed in a vacuum drying oven and dried to obtain Sm₂Fe. 17 N3 magnetic powder.

[0081] Nitrogen content testing (using a N-3000 steel research and development laboratory) confirmed that the Sm2Fe prepared in Example 1... 17 The nitrogen content in N3 magnetic powder is 2.95 wt%.

[0082] Comparative Example 1

[0083] The difference between Comparative Example 1 and Example 2 is that Comparative Example 1 uses Sm2Fe 17 The reducing agent used in the alloy preparation process was lanthanum particles, and the rest of the preparation process was the same as in Example 1.

[0084] Figure 5 The Sm2Fe in Comparative Example 1 of the present invention is shown. 17 XRD patterns of alloy powders; Comparative Example 1 uses lanthanum metal as a reducing agent. Figure 5 and Figure 2 The comparison shows that, Figure 4 Sm2Fe 17 The alloy powder showed obvious α The presence of -Fe diffraction peaks indicates that the annealing temperature in Comparative Example 1 did not reach the required reduction temperature, thus failing to obtain pure phase Sm2Fe. 17 alloy powder.

[0085] Comparative Example 2

[0086] The difference between Comparative Example 1 and Example 2 is that Comparative Example 1 uses Sm2Fe 17 In the alloy preparation process, samarium oxide powder, iron powder and lanthanum hydride particles in a molar ratio of 1:10:3 were mixed and then directly pressed into a green compact without ball milling. The rest of the preparation process was the same as in Example 1.

[0087] Figure 6 The Sm2Fe in Comparative Example 2 of the present invention is shown. 17 XRD pattern of alloy powder, as shown Figure 6 As shown, in Comparative Example 2, compared to Example 1, no ball milling was performed, resulting in uneven mixing of lanthanum hydride particles with samarium oxide powder and iron powder, thus leading to incomplete reaction. Figure 6 and Figure 2 The comparison shows that Sm2Fe in Comparative Example 2 17 The alloy powder showed obvious α -Fe diffraction peaks were observed, but pure phase Sm2Fe was not obtained. 17 alloy powder.

[0088] Comparing the results of the above embodiments and comparative examples, it can be seen that the method provided by the present invention can prepare samarium iron alloy powder by lanthanum hydride or cerium hydride, and after nitriding, samarium iron nitrogen magnetic powder with a high nitrogen content can be obtained, with a nitrogen content of 2-3.5 wt%. Furthermore, when the reducing agent is changed or the reactants are not ball-milled during the preparation process, the samarium iron nitrogen magnetic powder provided by the present invention cannot be obtained.

[0089] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0090] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0091] The method for preparing samarium iron nitrogen magnetic powder provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing samarium iron nitrogen magnetic powder, characterized in that, The method includes: Iron, samarium oxide and rare earth hydrides are mixed and then ball-milled. The resulting mixture is then pressed into briquettes to obtain a billet. The blank is subjected to vacuum heat treatment to obtain coarse samarium iron magnetic powder material; After the crude samarium iron magnetic powder material is crushed, it is placed in an ammonia atmosphere and subjected to high-temperature nitriding treatment to obtain crude samarium iron nitrogen magnetic powder. The crude samarium iron nitrogen magnetic powder is cleaned to remove residual non-magnetic impurities in the solid phase, and then dried to obtain the samarium iron nitrogen magnetic powder. The rare earth hydrides are selected from lanthanum hydride and / or cerium hydride; The molar ratio of samarium oxide, iron and rare earth hydride is 1:(8~14):(2~3).

2. The method for preparing samarium iron nitrogen magnetic powder according to claim 1, characterized in that, The ball-to-material ratio of the ball mill is (10-20):1, the ball mill speed is 400rpm~700rpm, and the ball milling time is 2-10h.

3. The method for preparing samarium iron nitrogen magnetic powder according to claim 1, characterized in that, The briquetting process is carried out by cold pressing, and the pressure used for the briquetting is 20-30 MPa.

4. The method for preparing samarium iron nitrogen magnetic powder according to claim 1, characterized in that, The target temperature for the vacuum heat treatment is 850-1050 ℃, and the holding time is 20 min-5 h.

5. The method for preparing samarium iron nitrogen magnetic powder according to claim 1, characterized in that, The cleaning process includes: sequentially using an acidic washing solution, deionized water, and an ethanol solution to perform a multi-step cleaning of the crude samarium iron nitrogen magnetic powder; the acidic washing solution is a hydrochloric acid solution or a glacial acetic acid solution with a concentration of 1-5%.

6. The method for preparing samarium iron nitrogen magnetic powder according to claim 1, characterized in that, The rare earth hydrides are obtained by hydrogen explosion of lanthanum or cerium metal. The particle size of the reducing agent rare earth hydride is 50-150 μm.

7. The method for preparing samarium iron nitrogen magnetic powder according to claim 1, characterized in that, The iron powder has a particle size of 5 μm-20 μm.

8. The method for preparing samarium iron nitrogen magnetic powder according to claim 1, characterized in that, Before ball milling, the samarium oxide is subjected to vacuum heat treatment at 200-400 °C for 3-6 h to remove residual moisture and obtain dry anhydrous samarium oxide.

9. The method for preparing samarium iron nitrogen magnetic powder according to claim 1, characterized in that, The method further includes: adding an appropriate amount of flux to the mixture, mixing it evenly, and then pressing it into a block to obtain a green body; The flux is selected from BiCl3, KCl and / or LaCl3.

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