Method for preparing samarium-iron-nitrogen magnetic powder based on microwave-assisted combustion method

Abstract

The invention discloses a method for preparing samarium-iron-nitrogen magnetic powder based on a microwave-assisted combustion method. The method comprises the following steps: 1, preparing a samarium-iron oxide precursor by the microwave-assisted combustion method; 2, hydrogen pre-reduction; thirdly, Sm2Fe17 is prepared through reduction and diffusion; and 4, nitriding to prepare Sm < 2 > Fe < 17 > N < 3 >. According to the method disclosed by the invention, samarium nitrate and ferric nitrate are directly converted into a samarium-iron oxide nano precursor in which Sm and Fe elements are uniformly distributed within extremely short reaction time through a microwave-assisted combustion method, so that sintering and agglomeration of high-temperature calcined powder are avoided; the submicron Sm2Fe17N3 magnetic powder with uniform components is obtained by combining pre-reduction, reduction diffusion and nitridation, the magnetic performance of the magnetic powder is improved, meanwhile, the method is simple in reaction step and parameter setting, high in preparation efficiency and low in labor and energy consumption cost, industrial continuous production is achieved, and the method is suitable for the technical field of metal magnetic materials.

Description

Technical Field

[0001] This invention belongs to the field of metallic magnetic materials technology, and in particular relates to a method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion. Background Technology

[0002] In recent years, the energy conversion market has seen a surge in demand for high-performance permanent magnet materials to make devices more energy-efficient with smaller size and weight. Neodymium iron boron (Nd-Fe-B) permanent magnets dominate the rare earth permanent magnet market with their excellent magnetic properties and are widely used in electric vehicle drive systems and wind power generation devices. However, their inherent defects significantly limit their application under extreme conditions: a low Curie temperature leads to a sharp decline in magnetic properties at high temperatures; and poor oxidation resistance makes them susceptible to environmental corrosion. Compared to NdFeB, samarium iron nitride (Sm-Fe-N) permanent magnet materials have a higher Curie temperature, nearly double the thermal stability, and stronger oxidation and corrosion resistance, which is expected to supplement and expand the application scenarios of rare earth permanent magnet materials.

[0003] The core of Sm-Fe-N permanent magnet materials is Sm2Fe. 17 The magnetic properties of N3 permanent magnet powder mainly depend on factors such as compositional uniformity and particle size. (Sm2Fe) 17 The higher the compositional uniformity of N3 magnetic powder, the closer the particle size is to the single-domain critical size (pure ternary Sm2Fe). 17 The critical size of a single domain in N3 is approximately 0.3 μm, and its magnetic properties are stronger. This is due to the fact that Sm2Fe... 17 Transformation into Sm2Fe 17 The nitriding process of N3 occurs at relatively low temperatures (typically around 380℃~420℃), which generally prevents particle growth and agglomeration. Furthermore, the uniform distribution of N can be achieved by adjusting the nitriding time. Therefore, Sm2Fe 17 The key to uniform composition and particle size control of N3 magnetic powder lies in first achieving Sm2Fe 17 The high uniformity of samarium and iron elements and the control of particle size in the alloy are crucial. However, current methods for preparing Sm2Fe... 17 In alloying methods, commonly used physical methods (such as powder metallurgy, melt quenching, and mechanical alloying) suffer from compositional segregation and grain size coarsening, making it difficult to further improve magnetic properties. Traditional reduction-diffusion methods, on the other hand, suffer from uneven mixing of raw materials such as samarium oxide, iron, and reducing agents, and also struggle to directly obtain submicron-sized Sm₂Fe. 17 Alloy particles. Additionally, Sm2Fe prepared by the above method... 17 Sm2Fe formed after alloy nitriding 17N3 magnetic powder often requires ball milling or air jet milling to reduce particle size and improve coercivity. However, oxidation and defects on the powder surface caused during the crushing process reduce local magnetocrystalline anisotropy and deteriorate the powder's performance.

[0004] Chemical methods, such as the sol-gel method and co-precipitation method, are effective for preparing Sm2Fe. 17 N3 magnetic powder possesses unique advantages. It achieves high uniformity of composition in the Sm-Fe-O precursor through atomic-level mixing of Sm and Fe in a liquid-phase reaction, and allows for precise control of particle size based on reaction conditions. The samarium iron oxide precursor is synthesized into Sm2Fe through a reduction-diffusion method. 17 The alloy transformation, with its high homogeneity and small particle size, can moderately reduce the reaction temperature and shorten the reaction time, making it easier to prepare small-sized Sm2Fe. 17 Particles, which are then subjected to nitriding treatment to obtain small-sized Sm2Fe particles. 17 N3 magnetic powder can be produced without the need for crushing. However, the sol-gel method requires multiple steps, including hydrolysis, condensation, drying, and high-temperature calcination, significantly increasing the total time and consuming large amounts of volatile organic solvents. The co-precipitation method requires precise control of key parameters such as solution pH, titration rate, and aging time, resulting in a long overall process time and the potential for hard agglomerates during the drying stage. Furthermore, all of the above chemical methods for preparing Sm-Fe-O precursors involve lengthy high-temperature calcination steps, leading to high energy consumption and hindering their application to large-scale production. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing samarium iron nitrate magnetic powder based on microwave-assisted combustion. This method uses microwave-assisted heating to rapidly and completely combust a mixture of samarium nitrate, ferric nitrate, and urea, avoiding prolonged high-temperature calcination, and directly obtaining a samarium iron oxide nano-precursor with highly uniform composition and particle size. Then, submicron-sized Sm₂Fe is prepared through hydrogen pre-reduction and reduction diffusion processes. 17 Submicron-sized Sm2Fe alloy powder can be obtained through low-temperature nitriding and washing to remove impurities without crushing. 17 N3 magnetic powder solves the problem of Sm2Fe preparation by existing technologies. 17 The N3 magnetic powder suffers from poor compositional uniformity and large particle size.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion, characterized in that the method includes the following steps: Step 1: Preparation of samarium iron oxide precursor by microwave-assisted combustion: Samarium nitrate, ferric nitrate, urea and water are mixed to form a mixture, and then microwave-heated to obtain samarium iron oxide precursor; Step 2, hydrogen pre-reduction: The samarium iron oxide precursor obtained in Step 1 is subjected to pre-reduction heat treatment in a hydrogen atmosphere to obtain Sm2O3-Fe composite powder. Step 3: Reduction-diffusion preparation of Sm2Fe 17 The Sm2O3-Fe composite powder obtained in step two is mixed evenly with calcium hydride and potassium chloride, and then a reduction-diffusion reaction is carried out under an inert atmosphere to obtain Sm2Fe. 17 / Ca-CaO-KCl mixed particles; Step 4: Nitriding to prepare Sm2Fe 17 N3: The Sm2Fe obtained in step three 17 / Ca-CaO-KCl mixed particles were subjected to nitriding treatment and ultrasonic washing to obtain Sm2Fe 17 N3 magnetic powder.

[0007] This invention prepares samarium iron oxide precursors using a microwave-assisted combustion method. By leveraging the interaction between microwave radiation and dipole molecules and ions, the temperature of the mixture of samarium nitrate, ferric nitrate, and urea is increased, promoting combustion and achieving homogeneity throughout the reaction system. Due to the deep penetration and uniform distribution of microwaves, the gradient temperature problem encountered in traditional heating methods is avoided, ensuring a highly uniform distribution of samarium and iron elements in the samarium iron oxide precursor produced by the combustion reaction. This is beneficial for the reduction-diffusion reaction and nitriding reaction. Then, through hydrogen pre-reduction and mixing with calcium hydride as a reducing agent and potassium chloride as a flux, a reduction-diffusion reaction is carried out. Finally, nitriding treatment is performed to achieve submicron-sized Sm2Fe. 17 Preparation of N3 magnetic powder.

[0008] The above-mentioned method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion is characterized in that, in step one, the molar ratio of ferric nitrate to samarium nitrate in the mixture is 5.5~7.0:1, the molar ratio of urea to the total molar ratio of ferric nitrate and samarium nitrate in the mixture is 1.0~1.5:1, and the molar ratio of water to the total molar ratio of ferric nitrate, samarium nitrate and urea in the mixture is 1.0~1.5:1.

[0009] This invention, by setting the molar ratio of ferric nitrate to samarium nitrate to 5.5~7.0:1, can ensure the stability of Sm2Fe 17 The alloy exhibits stable phase formation and avoids the formation of impurities such as α-Fe or samarium-rich phases; when the molar ratio is below 5.5:1, samarium-rich phases are easily formed; when the molar ratio is above 7.0:1, α-Fe phases are easily formed. By setting the molar ratio of urea to the total molar ratio of ferric nitrate and samarium nitrate to 1.0~1.5:1, rapid and complete combustion between the raw materials can be ensured, resulting in a samarium iron oxide precursor with uniform composition and small particle size. When the molar ratio is higher than 1.5:1, the excess of urea as the combustion agent will lead to a violent exothermic reaction, causing the precursor particles to sinter and grow. When the molar ratio is lower than 1.0:1, the insufficient urea as the combustion agent makes it difficult to maintain the combustion reaction, and the samarium iron oxide precursor cannot be completely formed. By setting the molar ratio of the solvent deionized water to the sum of the molar numbers of the solutes nitrate and urea to 1.0~1.5:1, it is possible to ensure that the raw materials are fully dissolved and a uniform combustion reaction occurs. When the molar ratio is higher than 1.5:1, a large amount of solvent may cause splashing due to violent boiling in the microwave field. When the molar ratio is lower than 1.0:1, insufficient solvent will prevent the raw materials from being fully dissolved and forming a concentration gradient.

[0010] The above-mentioned method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion is characterized in that the power of microwave heating in step one is 600W~900W, and the duration of microwave heating is 2min~5min.

[0011] This invention ensures that the mixture will not fail to ignite due to insufficient power by setting the microwave heating power to 600W~900W, while excessive power may cause samarium iron oxide products to decompose. By setting the reaction time to 2min~5min, it can ensure rapid and complete combustion between the mixtures, generating fluffy precursor powder. However, setting the time too long will cause the precursor powder to thermally agglomerate, and the larger precursor particle size will not meet the design expectations.

[0012] The method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion is characterized in that the hydrogen flow rate in the hydrogen atmosphere in step two is 0.1 L / min to 0.2 L / min.

[0013] The above-mentioned method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion is characterized in that the pre-reduction heat treatment method in step two is: heating to 700℃~900℃ at a rate of 2℃ / min~5℃ / min and holding at that temperature for 90min~180min.

[0014] This invention ensures that the samarium iron oxide precursor can be fully pre-reduced to generate Sm2O3-Fe composite powder by setting the heating rate of hydrogen pre-reduction to 2℃ / min~5℃ / min, the temperature to 700℃~900℃, and the holding time to 90min~180min. If the pre-reduction is insufficient, the Sm2O3-Fe composite powder will contain SmFeO3 compounds.

[0015] The above-mentioned method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion is characterized in that, in step three, the mass ratio of calcium hydride to the Sm2O3-Fe composite powder is 0.4~0.7:1, and the mass ratio of potassium chloride to calcium hydride is 0.1~0.2:1.

[0016] This invention ensures a sufficient reduction-diffusion reaction by setting the mass ratio of calcium hydride to the Sm2O3-Fe composite powder to 0.4~0.7:1. A mass ratio lower than 0.4:1 will result in insufficient reduction of Sm2O3, affecting the reduction of Sm2Fe. 17 Stable phase formation; when the mass ratio is higher than 0.7:1, it will cause Sm2Fe to form. 17 The product clumps together into hard lumps and has too much residual calcium, which makes it difficult to grind into particles. By setting the mass ratio of potassium chloride to calcium hydride to 0.1~0.2:1, the fluidity of calcium hydride in the high-temperature molten state can be enhanced, and the utilization rate of calcium hydride can be improved. When the mass ratio is lower than 0.1:1, the effect of enhancing fluidity is not significant; when the mass ratio is higher than 0.2:1, the concentration of the reducing agent will be diluted, affecting the reduction diffusion reaction effect, which is not conducive to Sm2Fe 17 The alloy forms a stable phase.

[0017] The method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion is characterized in that the inert atmosphere in step three is argon gas, and the argon gas flow rate is 0.1 L / min to 0.3 L / min.

[0018] The above-mentioned method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion is characterized in that the reduction diffusion reaction in step three is as follows: the temperature is increased to 910℃~1010℃ at a rate of 2℃ / min~5℃ / min, and held for 90min~180min.

[0019] This invention ensures that the Sm2O3-Fe composite powder fully completes the reduction-diffusion reaction to generate Sm2Fe by setting the heating rate of the reduction diffusion to 2℃ / min~5℃ / min, the temperature to 910℃~1010℃, and the holding time to 90min~180min. 17 Alloy powder is used to avoid the formation of impurity phases or particle agglomeration caused by excessive sintering.

[0020] The above-mentioned method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion is characterized in that the nitriding treatment in step four is as follows: under an ammonia / hydrogen mixed atmosphere, the temperature is increased to 380℃~420℃ at a rate of 2℃ / min~3℃ / min, and held for 360min~600min.

[0021] This invention sets the nitriding heating rate to 2℃ / min~3℃ / min, the temperature to 380℃~420℃, and the holding time to 360min~600min. The relatively low heating rate promotes the nitriding of Sm2Fe. 17 The alloy powder is thoroughly nitrided. The nitriding effect is ensured by controlling the temperature and holding time to achieve the theoretical nitrogen content. However, excessively high temperatures or excessively long holding times will lead to problems with Sm2Fe content. 17 Decomposition of N3 magnetic powder.

[0022] The above-mentioned method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion is characterized in that the ammonia / hydrogen mixed atmosphere is a mixed gas composed of ammonia and hydrogen in a volume ratio of 1:2, and the flow rate of the mixed gas is 0.3L / min~0.6L / min.

[0023] This invention utilizes a mixture of ammonia and hydrogen gas, which takes advantage of the high nitriding efficiency of NH3 and suppresses the harmful irreversible lattice distortion caused by excess N atoms through H2, thereby improving the structural stability of the material while ensuring the nitriding effect.

[0024] Compared with the prior art, the present invention has the following advantages: 1. This invention prepares uniformly composed samarium iron oxide nano-precursors through simple stirring and mixing and microwave-assisted rapid combustion. Compared with other chemical preparation methods in the prior art, it can significantly reduce reaction steps, shorten reaction time, and simplify the parameters that need to be controlled during the reaction process. In addition, the rapid and complete combustion reaction can directly obtain nano-scale precursors, avoiding long-term high-temperature calcination and greatly reducing energy consumption.

[0025] 2. This invention successfully prepares Sm2Fe by employing microwave-assisted combustion combined with hydrogen pre-reduction, reduction diffusion, and low-temperature nitriding. 17 N3 magnetic powder, through pre-reduction, reduces iron oxide in Sm2O3-Fe composite powder to α-Fe, reducing the amount of calcium hydride used as a subsequent reducing agent. The samarium iron oxide nano-precursor prepared by microwave-assisted combustion solves the problem of uneven mixing of raw materials in physical methods or traditional reduction-diffusion methods. Furthermore, the nanoscale precursor particles can appropriately lower the reaction temperature of reduction-diffusion, shorten the reaction time, and facilitate the preparation of submicron-sized Sm2Fe. 17 Particles, which are then nitrided to obtain submicron-sized Sm2Fe particles. 17 N3 magnetic powder, without the need for crushing, ensures that the powder possesses both high coercivity and high remanence, which is beneficial for further enhancing Sm2Fe. 17 Magnetic properties of N3 magnetic powder.

[0026] 3. Preparation of Sm2Fe by this invention 17The reaction steps and parameter settings for N3 magnetic powder are simple, the reaction conditions are mild, fewer equipment is required, the preparation efficiency is high, the labor and energy costs are low, and the product phase and magnetic properties are good, which is conducive to realizing continuous industrial production.

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0028] Figure 1 The Sm2Fe obtained in Example 1 17 XRD pattern of N3 magnetic powder.

[0029] Figure 2 The Sm2Fe obtained in Example 2 17 XRD pattern of N3 magnetic powder.

[0030] Figure 3 The Sm2Fe obtained in Example 3 17 XRD pattern of N3 magnetic powder. Detailed Implementation

[0031] Example 1 The method in this embodiment includes the following steps: Step 1: Preparation of samarium iron oxide precursor by microwave-assisted combustion: Weigh 2.22g of samarium nitrate hexahydrate, 11.11g of ferric nitrate nonahydrate, 2.93g of urea and 2.2mL of deionized water and stir until a paste mixture is formed. Then transfer it to a microwave oven and microwave heat it at 600W for 5 minutes. After complete combustion, a dark red powder is generated. Wash and dry the powder with anhydrous ethanol to obtain the samarium iron oxide precursor. Step 2, hydrogen pre-reduction: The samarium iron oxide precursor obtained in Step 1 is loaded into an alumina crucible and transferred to a tube furnace. Hydrogen gas is introduced at a flow rate of 0.1 L / min, and the temperature is raised to 900℃ at a rate of 2℃ / min and held for 90 min to obtain Sm2O3-Fe composite powder. Step 3: Reduction-diffusion preparation of Sm2Fe 17 Take 8g of the Sm2O3-Fe composite powder obtained in step two, 3.2g of calcium hydride powder, and 0.32g of potassium chloride granules, mix them evenly, place them in a stainless steel crucible, and put them in a tube furnace. Introduce argon gas at a flow rate of 0.1L / min, heat to 1010℃ at a rate of 2℃ / min, and hold for 90min to obtain Sm2Fe. 17 / Ca-CaO-KCl mixed particles; Step 4: Take the Sm2Fe obtained in Step 3... 17Ca-CaO-KCl mixed particles were loaded into an alumina crucible and transferred to a tube furnace. Ammonia gas was introduced at a rate of 0.1 L / min and hydrogen gas at a rate of 0.2 L / min, and the temperature was increased to 420 °C and held for 360 min at a rate of 2 °C / min to complete nitriding and form a black powder. Then, ultrasonic washing was performed to remove the byproducts Ca, CaO, and KCl, yielding Sm2Fe. 17 N3 magnetic powder.

[0032] The Sm2Fe prepared in this embodiment 17 XRD analysis of N3 magnetic powder, such as Figure 1 As shown, the Sm2Fe prepared in this embodiment 17 The N3 magnetic powder phase composition is single-phase Sm2Fe. 17 N3, Sm2Fe prepared in this embodiment 17 The particle size of N3 magnetic powder is approximately 0.5μm to 1.5μm.

[0033] Example 2 The method in this embodiment includes the following steps: Step 1: Preparation of samarium iron oxide precursor by microwave-assisted combustion: Weigh 2.22g of samarium nitrate hexahydrate, 14.14g of ferric nitrate nonahydrate, 2.4g of urea and 1.5mL of deionized water and stir evenly to form a paste mixture. Then transfer it to a microwave oven and microwave heat it at 900W for 2 minutes. After complete combustion, a dark red powder is generated. Wash and dry it with anhydrous ethanol to obtain the samarium iron oxide precursor. Step 2, hydrogen pre-reduction: The samarium iron oxide precursor obtained in Step 1 is loaded into an alumina crucible and transferred to a tube furnace. Hydrogen gas is introduced at a flow rate of 0.2 L / min, and the temperature is raised to 700℃ at a rate of 5℃ / min and held for 180 min to obtain Sm2O3-Fe composite powder. Step 3: Reduction-diffusion preparation of Sm2Fe 17 Take 8g of the Sm2O3-Fe composite powder obtained in step two, 5.6g of calcium hydride powder, and 1.12g of potassium chloride granules, mix them evenly, place them in a stainless steel crucible, and put them in a tube furnace. Introduce argon gas at a flow rate of 0.3L / min, heat to 910℃ at a rate of 5℃ / min, and hold for 180min to obtain Sm2Fe. 17 / Ca-CaO-KCl mixed particles; Step 4: Take the Sm2Fe obtained in Step 3... 17Ca-CaO-KCl mixed particles were loaded into an alumina crucible and transferred to a tube furnace. Ammonia gas was introduced at a rate of 0.2 L / min and hydrogen gas at a rate of 0.4 L / min, and the temperature was increased to 380 °C at a rate of 3 °C / min and held for 600 min to complete nitriding and form a black powder. Then, ultrasonic washing was performed to remove the byproducts Ca, CaO, and KCl, yielding Sm2Fe. 17 N3 magnetic powder.

[0034] The Sm2Fe prepared in this embodiment 17 XRD analysis of N3 magnetic powder, such as Figure 2 As shown, the Sm2Fe prepared in this embodiment 17 The N3 magnetic powder phase composition is single-phase Sm2Fe. 17 N3, Sm2Fe prepared in this embodiment 17 The particle size of N3 magnetic powder is approximately 0.5μm to 1.5μm.

[0035] Example 3 The method in this embodiment includes the following steps: Step 1: Preparation of samarium iron oxide precursor by microwave-assisted combustion: Weigh 2.22g of samarium nitrate hexahydrate, 13.13g of ferric nitrate nonahydrate, 2.93g of urea and 2mL of deionized water, stir well to form a paste mixture, then transfer to a microwave oven and microwave heat at 800W for 3min. After complete combustion, a dark red powder is generated. Wash and dry with anhydrous ethanol to obtain the samarium iron oxide precursor. Step 2, hydrogen pre-reduction: The samarium iron oxide precursor obtained in Step 1 is loaded into an alumina crucible and transferred to a tube furnace. Hydrogen gas is introduced at a flow rate of 0.15 L / min, and the temperature is raised to 800℃ at a rate of 3℃ / min and held for 150 min to obtain Sm2O3-Fe composite powder. Step 3: Reduction-diffusion preparation of Sm2Fe 17 Take 8g of the Sm2O3-Fe composite powder obtained in step two, 4.4g of calcium hydride powder, and 0.66g of potassium chloride granules, mix them evenly, place them in a stainless steel crucible, and put them in a tube furnace. Introduce argon gas at a flow rate of 0.2L / min, heat to 950℃ at a rate of 3℃ / min, and hold for 120min to obtain Sm2Fe. 17 / Ca-CaO-KCl mixed particles; Step 4: Take the Sm2Fe obtained in Step 3... 17Ca-CaO-KCl mixed particles were loaded into an alumina crucible and transferred to a tube furnace. Ammonia gas was introduced at a rate of 0.15 L / min and hydrogen gas at a rate of 0.3 L / min. The temperature was increased to 400 °C at a rate of 2.5 °C / min and held for 480 min to complete nitriding and form a black powder. Then, ultrasonic washing was performed to remove the byproducts Ca, CaO, and KCl, yielding Sm2Fe. 17 N3 magnetic powder.

[0036] The Sm2Fe prepared in this embodiment 17 XRD analysis of N3 magnetic powder, such as Figure 3 As shown, the Sm2Fe prepared in this embodiment 17 The N3 magnetic powder phase composition is single-phase Sm2Fe. 17 N3, Sm2Fe prepared in this embodiment 17 The particle size of N3 magnetic powder is approximately 0.5μm to 1.5μm.

[0037] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion, characterized in that, The method includes the following steps: Step 1: Preparation of samarium iron oxide precursor by microwave-assisted combustion: Samarium nitrate, ferric nitrate, urea and water are mixed to form a mixture, and then microwave-heated to obtain samarium iron oxide precursor; Step 2, hydrogen pre-reduction: The samarium iron oxide precursor obtained in Step 1 is subjected to pre-reduction heat treatment in a hydrogen atmosphere to obtain Sm2O3-Fe composite powder; Step 3: Preparation of Sm2Fe by reduction diffusion 17 The Sm2O3-Fe composite powder obtained in step two is mixed evenly with calcium hydride and potassium chloride, and then a reduction-diffusion reaction is carried out under an inert atmosphere to obtain Sm2Fe. 17 / Ca-CaO-KCl mixed particles; Step 4: Nitriding to prepare Sm2Fe 17 N3: The Sm2Fe obtained in step three 17 / Ca-CaO-KCl mixed particles were subjected to nitriding treatment and ultrasonic washing to obtain Sm2Fe 17 N3 magnetic powder.

2. The method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion according to claim 1, characterized in that, In step one, the molar ratio of ferric nitrate to samarium nitrate in the mixture is 5.5~7.0:1, the molar ratio of urea to the total molar ratio of ferric nitrate and samarium nitrate in the mixture is 1.0~1.5:1, and the molar ratio of water to the total molar ratio of ferric nitrate, samarium nitrate and urea in the mixture is 1.0~1.5:

1.

3. The method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion according to claim 1, characterized in that, The microwave heating power in step one is 600W~900W, and the microwave heating duration is 2min~5min.

4. The method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion according to claim 1, characterized in that, The hydrogen flow rate in the hydrogen atmosphere described in step two is 0.1 L / min to 0.2 L / min.

5. The method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion according to claim 1, characterized in that, The pre-reduction heat treatment method described in step two is as follows: heat to 700℃~900℃ at a rate of 2℃ / min~5℃ / min, and hold at that temperature for 90min~180min.

6. The method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion according to claim 1, characterized in that, In step three, the mass ratio of calcium hydride to Sm2O3-Fe composite powder is 0.4~0.7:1, and the mass ratio of potassium chloride to calcium hydride is 0.1~0.2:

1.

7. The method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion according to claim 1, characterized in that, The inert atmosphere mentioned in step three is argon gas, and the argon gas flow rate is 0.1L / min to 0.3L / min.

8. The method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion according to claim 1, characterized in that, The reduction diffusion reaction method described in step three is as follows: heat to 910℃~1010℃ at a rate of 2℃ / min~5℃ / min, and hold at that temperature for 90min~180min.

9. The method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion according to claim 1, characterized in that, The nitriding treatment method described in step four is as follows: under an ammonia / hydrogen mixed atmosphere, the temperature is increased to 380℃~420℃ at a rate of 2℃ / min~3℃ / min, and held for 360min~600min.

10. A method for preparing samarium iron nitrogen magnetic powder based on microwave-assisted combustion according to claim 9, characterized in that, The ammonia / hydrogen mixed atmosphere is a mixture of ammonia and hydrogen in a volume ratio of 1:2, and the flow rate of the mixed gas is 0.3 L / min to 0.6 L / min.

Images