A method for preparing refined samarium iron alloy powder based on submicron monodisperse samarium iron precursor

Abstract

The invention discloses a method for preparing refined samarium iron alloy powder based on a submicron monodisperse samarium iron precursor, the method comprising: 1. coprecipitation reaction; 2. diffusion medium incorporation; 3. pre-reduction; 4. ultrasonic dispersion; 5. reduction diffusion; 6. washing and decalcification. The invention obtains a submicron monodisperse samarium iron precursor by controlling the process of the coprecipitation reaction, which is beneficial to the refinement of the samarium iron alloy powder during the reduction diffusion process. Combined with the addition of a diffusion medium during the preparation of the samarium iron precursor, the reduction diffusion reaction of the samarium iron precursor is promoted to be fully and uniformly carried out, without the need for a pulverization process, and the amount of metallic calcium is reduced, the production cost and the difficulty of washing are reduced, and a spherical refined samarium iron alloy powder with a particle size of less than 4 μm is obtained. When applied to the preparation of samarium iron nitrogen magnetic powder by nitriding treatment, it is beneficial to improve the coercivity of the samarium iron nitrogen magnetic powder; the preparation process has low equipment investment, simple process, and readily available raw materials, and is easy to achieve industrial scale-up.

Description

Technical Field

[0001] The invention belongs to the technical field of metal magnetic material preparation, and in particular relates to a method for preparing refined samarium-iron alloy powder based on a submicron monodisperse samarium-iron precursor. Background Art

[0002] Permanent magnet material is one of the core functional raw materials. As a unique permanent magnet material, rare earth permanent magnet is widely used in many fields such as automobile, wind power, electronics, aviation, etc. With the rapid development of green industry, the global demand for rare earth permanent magnet materials has increased rapidly. Samarium iron nitrogen has become a high-potential permanent magnet material comparable to the "king of magnets" neodymium iron boron. It has the huge advantages of high saturation magnetic polarization intensity, high Curie temperature (nearly 160℃ higher than neodymium iron boron), high magnetic anisotropy field, and low cost. It is also superior to neodymium iron boron in terms of oxidation resistance and corrosion resistance.

[0003] The preparation of SmFeN magnetic powder includes Sm 2 Fe 17 The preparation of alloy powder and nitridation treatment are two steps, the former is the key to produce high-performance SmFeN magnetic powder. 2 Fe 17 The main preparation methods include powder metallurgy, melt quenching, mechanical alloying, hydrogenation and disproportionation, and reduction diffusion. However, some shortcomings of the above methods restrict their development: powder metallurgy and melt quenching have the disadvantages of large samarium volatilization, difficult to control composition, waste of resources and difficult operation; mechanical alloying has the disadvantages of long cycle, high energy consumption and easy oxidation; hydrogenation and disproportionation have complex reactions, and the microstructure evolution process and grain refinement mechanism involved are still unclear. The reduction diffusion method uses metallic calcium or sodium to reduce samarium oxide to metallic samarium, and then diffuses with pure iron to obtain samarium-iron alloy powder. Its advantage is to avoid the direct use of metallic samarium and avoid the process stages of alloy smelting, annealing and coarse crushing. It is an economical chemical preparation method. The more significant advantage of this method is that high-quality samarium-iron alloy powder with controllable morphology and size and few surface defects can be prepared based on high-quality samarium-iron precursors. Existing studies have confirmed that the refinement of Sm 2 Fe 17 The particles and the reduction of their surface defects play a great role in improving the nitridation efficiency and the coercive force of SmFeN magnetic powder. They can reduce the diffusion distance of nitrogen atoms and increase the contact area of ​​nitrogen source. The preparation of SmFeN particles close to the single domain size (~300nm) can eliminate the domain walls to improve the coercive force, while surface defects (such as surface roughness and oxidation, edges, etc.) will promote the nucleation of the reverse magnetization domain and reduce the coercive force.

[0004] The traditional reduction diffusion method uses samarium oxide and iron powder as raw materials. Its disadvantage is that the raw materials cannot be completely evenly dispersed and the prepared samarium iron alloy particles are large in size (generally ball milling is required). The use of co-precipitation to prepare samarium iron precursors can effectively overcome the above shortcomings. Patents CN110662617A and CN114898960A disclose a method for preparing samarium iron nitrogen magnetic powder based on a precursor obtained by co-precipitation. The former uses alkali to co-precipitate samarium salts and iron salts into samarium-iron compounds. After drying and crushing, a samarium iron precursor composed of iron, samarium iron oxide and samarium oxide with an average particle size of less than 1 μm is obtained by pre-reduction treatment, and then metal calcium reduction diffusion is used to obtain Sm 2 Fe 17 This method has the following shortcomings: (1) the coprecipitation reaction process is not controlled, and the morphology and size of the precursor cannot be effectively controlled; (2) the average particle size of the obtained precursor is large and the dispersibility is unknown, which is not conducive to the Sm 2 Fe 17 The particle size is small; (3) the obtained precursor contains samarium iron oxide, which increases the consumption of metal calcium during the reduction diffusion process, increasing the cost and washing difficulty; (4) the diffusion medium is not added, which is not conducive to the full reduction diffusion reaction. The latter uses the samarium-iron compound obtained by alkali co-precipitation as a precursor, and reduces and diffuses under the action of reducing agents, calcium chloride and potassium chloride to obtain Sm 2 Fe 17 In addition to the lack of effective control over the coprecipitation reaction process, this method uses the coprecipitate as a precursor to cause a large consumption of metallic calcium, calcium chloride and potassium chloride in the reduction diffusion process, resulting in high costs and difficulty in washing. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing refined samarium iron alloy powder based on submicron monodisperse samarium iron precursor in view of the deficiencies of the above-mentioned prior art. The present invention effectively controls the coprecipitation reaction process to prepare a submicron monodisperse samarium iron precursor, and adds a diffusion medium during the preparation of the samarium iron precursor, which promotes the reduction and diffusion reaction of the samarium iron precursor to be fully and uniformly carried out, reduces the amount of metallic calcium used, reduces the production cost and washing difficulty, and obtains a spherical refined samarium iron alloy powder with a particle size of less than 4μm, which solves the problem that the existing preparation method cannot control the morphology and size of the samarium iron alloy powder, and the consumption of metallic calcium is large and the cost is high.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing refined samarium-iron alloy powder based on a submicron monodisperse samarium-iron precursor, characterized in that the method comprises the following steps:

[0007] Step 1, coprecipitation reaction: using ammonium bicarbonate solution to coprecipitate water-soluble samarium salt and iron salt, and controlling the coprecipitation process by adding a dispersant, controlling the solution mixing method and controlling the pH of the reaction solution to obtain samarium-iron hydroxide;

[0008] Step 2: Incorporation of diffusion medium: The samarium-iron hydroxide obtained in step 1 is placed in a high melting point salt solution and subjected to ultrasonic treatment to be uniformly dispersed, and then placed in an oven at 60° C. to 100° C. to dry;

[0009] Step 3: Pre-reduction: The dried samarium-iron hydroxide in step 2 is placed in a tube furnace for thermal decomposition and pre-reduction with reducing gas to obtain a product composed of α-Fe and Sm 2 O 3 The composition of the samarium iron precursor;

[0010] Step 4: Ultrasonic dispersion: The samarium iron precursor obtained in step 3 is placed in a volatile organic solution for ultrasonic treatment for 1 h to 3 h and dried to obtain a monodisperse samarium iron precursor; the monodisperse samarium iron precursor is a spherical α-Fe and Sm with an average particle size of 500 nm to 750 nm, monodispersity and uniform element distribution. 2 O 3 mixture;

[0011] Step 5, reduction diffusion: the monodisperse samarium iron precursor obtained in step 4 is mixed with metallic calcium, loaded into a stainless steel crucible with a lid and placed in a vacuum tube furnace, and then an inert gas is introduced at a flow rate of 0.05L / min to 0.2L / min, and the temperature is raised to 950°C to 1050°C at a rate of 2°C / min to 6°C / min for a reduction diffusion reaction for 3h to 6h;

[0012] Step 6, washing and decalcification: using deionized water and dilute acetic acid as washing media, repeatedly washing the reduction diffusion reaction product in step 5 by a magnetic separation-grinding washing process to remove by-products and high melting point salts, until the pH of the washing water reaches 7, and then continue to use anhydrous organic alcohol to wash 2 to 4 times, and then place it in a vacuum oven at 50°C to 80°C to dry, to obtain a refined samarium-iron alloy powder; the refined samarium-iron alloy powder is a spherical powder with a particle size of less than 4 μm, and the phase composition is Sm 2 Fe 17 or SmFe 9 .

[0013] The above-mentioned method for preparing refined samarium-iron alloy powder based on a submicron monodisperse samarium-iron precursor is characterized in that the samarium salt in step one is derived from samarium chloride, samarium nitrate, samarium sulfate and hydrates thereof, the iron salt is derived from ferric chloride, ferric nitrate, ferric sulfate and hydrates thereof, and the molar ratio of the iron salt to the samarium salt is 7.0 to 7.6:1; the dispersant is one or more combinations of polyethylene glycol, polyvinyl pyrrolidone, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide and activated carbon, and the amount of the dispersant is 0.5% to 2.0% of the total mass of the reaction solution; the solution mixing method is a parallel feeding method based on a flow control pump, and the feeding flow rate is 2 mL / min to 10 mL / min; the pH of the reaction solution is 5.3 to 6.5.

[0014] The invention adopts the methods of adding a dispersant, controlling a solution mixing mode and controlling the pH value of a reaction solution to control a coprecipitation reaction process. Specifically, the water surface energy is reduced and a steric hindrance is formed by adding the dispersant, and the amount of the dispersant is strictly controlled to avoid excessive addition of the dispersant, which may cause the solution to become viscous, affect the formation of precipitation and make subsequent washing difficult, and avoid adding too little dispersant, which may be detrimental to the dispersion of samarium iron precursor particles and the reduction of the particle size; the pH value of the reaction solution system is maintained constant by adding materials in parallel, and the phenomenon that the pH value of the reaction solution system changes continuously and the precipitation is unevenly generated during the feeding process due to conventional forward and reverse feeding is avoided; the feeding flow rate of the reaction liquid is controlled by a flow control pump to control the precipitation generation speed, and the phenomenon that the local reaction liquid is too concentrated due to the feeding flow rate being too fast is avoided, resulting in uneven precipitation particles, easy aggregation and many surface defects, and the precipitation particles are easy to grow due to too slow a feeding speed is avoided.

[0015] The above-mentioned method for preparing refined samarium-iron alloy powder based on submicron monodisperse samarium-iron precursor is characterized in that, in step one, a samarium-iron salt mixed aqueous solution with an iron salt concentration of 0.1M to 0.5M is first prepared, and then a dispersant is added and stirred continuously at room temperature for 8h to 12h, and then an equal volume of ammonium bicarbonate aqueous solution is added, and after the addition is completed, stirring is continued at room temperature for 1h to 4h, and the solid phase obtained by centrifugation and washing is samarium-iron hydroxide; the molar amount of ammonium bicarbonate in the added ammonium bicarbonate aqueous solution is 3 to 3.3 times the total molar amount of iron salt and samarium salt. The present invention controls the amount of ammonium bicarbonate to adjust the pH of the reaction solution, avoiding the phenomenon that the pH of the reaction solution is too high due to excessive ammonium bicarbonate, the precipitation is generated too quickly and is easy to aggregate, and the pH of the reaction solution is too low due to too little ammonium bicarbonate, the precipitation is generated too slowly and the reaction is incomplete.

[0016] The above-mentioned method for preparing refined samarium iron alloy powder based on submicron monodisperse samarium iron precursor is characterized in that the high melting point salt in the high melting point salt solution in step 2 is one or more combinations of potassium chloride, sodium chloride and calcium chloride, which are water-soluble salt substances with a melting point higher than 700°C, and the mass of the high melting point salt is 1% to 3% of the total mass of the samarium salt and the iron salt. The present invention promotes the reduction diffusion reaction by forming a molten salt environment by incorporating the above-mentioned high melting point salt, avoiding the dilution of the concentration of metallic calcium by excessive use of the high melting point salt, and the failure to achieve the molten salt environment effect by too small an amount of the high melting point salt, both of which will make the reduction diffusion reaction incomplete and affect the crystallinity of the samarium iron alloy.

[0017] The above-mentioned method for preparing refined samarium-iron alloy powder based on a submicron monodisperse samarium-iron precursor is characterized in that in step three, the dried samarium-iron hydroxide is ground into powder until there is no obvious granularity, loaded into a porcelain boat and placed in a tube furnace, first heated to 700°C~850°C at a rate of 5°C / min~10°C / min in an air atmosphere and kept warm for 1h~4h, then after blowing in an inert gas, a reducing gas is introduced at a flow rate of 0.02L / min~0.2L / min, and the temperature is raised to 750°C~900°C at a rate of 1°C / min~5°C / min and kept warm for 1h~3h, and the samarium-iron precursor is obtained after natural cooling. The invention generates samarium-iron oxide by calcining in an air atmosphere, and the calcining conditions should be suitable to avoid the increase of particle size and deterioration of dispersibility of samarium-iron precursor particles due to too high calcining temperature and too long holding time, and to avoid the insufficient calcination reaction due to too low calcining temperature and too short holding time, which affects subsequent production; the invention reduces the iron element in the samarium-iron oxide to elemental iron by introducing a reducing gas, so as to reduce the amount of metal calcium in the reduction diffusion reaction, and the reduction conditions should be suitable to avoid the increase of particle size and deterioration of dispersibility of samarium-iron precursor particles due to too high reduction temperature and too long holding time, and to avoid the insufficient reduction of iron element and residual iron oxide and samarium-iron oxide due to too low reduction temperature and too short holding time.

[0018] The above-mentioned method for preparing refined samarium-iron alloy powder based on submicron monodisperse samarium-iron precursor is characterized in that the reducing gas in step three is hydrogen or ethane.

[0019] The above-mentioned method for preparing refined samarium-iron alloy powder based on submicron monodisperse samarium-iron precursor is characterized in that the volatile organic solution in step 4 is an organic substance such as methanol, ethanol, isopropanol or acetone.

[0020] The above-mentioned method for preparing refined samarium iron alloy powder based on submicron monodisperse samarium iron precursor is characterized in that the mass of the metal calcium in step 5 is 12.8% to 23.4% of the mass of the monodisperse samarium iron precursor; and the inert gas is argon or helium. The present invention uses metal calcium to carry out a reduction diffusion reaction, and by controlling the amount of metal calcium, it avoids excessive use of metal calcium to increase production costs and subsequent washing difficulties, and at the same time avoids insufficient reduction diffusion reaction due to insufficient use of metal calcium.

[0021] The above-mentioned method for preparing refined samarium-iron alloy powder based on submicron monodisperse samarium-iron precursor is characterized in that the organic alcohol in step six is ​​organic methanol, ethanol, isopropanol or n-butanol.

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

[0023] 1. The present invention controls the process of coprecipitation reaction to obtain a submicron monodisperse samarium-iron precursor. The submicron size is beneficial to the refinement of the samarium-iron alloy powder during the reduction-diffusion process, and is beneficial to the uniform distribution of samarium and iron elements and the reduction-diffusion reaction, thereby reducing the loss of samarium. At the same time, the monodispersity is beneficial to the monodisperse preparation of the samarium-iron alloy powder and the subsequent samarium-iron-nitrogen magnetic powder. Finally, the present invention can prepare a spherical refined samarium-iron alloy powder with a particle size of less than 4 μm without adopting a pulverization process, and avoids oxidation of the refined samarium-iron alloy powder and the formation of surface defects.

[0024] 2. The present invention adopts the methods of adding dispersants, controlling the solution mixing mode and controlling the pH of the reaction solution to control the coprecipitation reaction process. The water surface energy is reduced and steric hindrance is formed by adding dispersants. The pH of the reaction solution is adjusted by adjusting the amount of ammonium bicarbonate. The pH of the reaction solution system is maintained constant by adding materials in parallel. The flow rate of the reaction liquid is controlled by a flow control pump to control the precipitation generation rate. The above control means cooperate with each other to efficiently control the coprecipitation reaction process. Combined with ultrasonic treatment, a spherical monodisperse samarium iron precursor with an average particle size of 500nm to 750nm, monodispersity and uniform distribution of elements is prepared. The composition and particle size are controllable. The control means has the outstanding advantages of simple and easy to obtain equipment, convenient and easy to control operation and low cost.

[0025] 3. The present invention places samarium-iron hydroxide in a high melting point salt solution and performs ultrasonic treatment, so that the high melting point salt of the diffusion medium is incorporated and evenly dispersed in the samarium-iron hydroxide, thereby improving the dispersibility and uniformity of the diffusion medium, thereby forming a uniform molten salt environment during the reduction diffusion reaction to promote the reaction to proceed fully and evenly, and prevent the growth of samarium-iron alloy particles.

[0026] 4. The present invention adds a high melting point salt to samarium-iron hydroxide to construct a uniform molten salt environment, thereby promoting the reduction diffusion reaction to reduce the amount of reducing agent metal calcium, and the pre-reduction products are α-Fe and Sm 2 O 3 The monodispersed samarium iron precursor of the mixture is free of iron oxide and samarium iron oxide, thereby further reducing the amount of reducing agent metal calcium used in the subsequent reduction diffusion reaction, reducing the raw material cost, and reducing the difficulty of post-washing treatment.

[0027] 5. The preparation method of the present invention can be produced by using common industrial equipment, with low equipment investment, simple process, easy to obtain raw materials, economical and efficient, easy to achieve industrial scale-up, and conducive to promotion and application.

[0028] 6. The particle size prepared by the present invention is less than 4 μm and the phase composition is Sm 2 Fe 17 or SmFe 9 The spherical refined samarium-iron alloy powder with low surface defects is beneficial to improving the nitriding efficiency and further improving the coercive force of the samarium-iron-nitrogen magnetic powder when used in nitriding treatment to prepare samarium-iron-nitrogen magnetic powder.

[0029] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a process flow chart of the preparation method of the present invention.

[0031] Figure 2 This is the XRD diffraction pattern of the samarium iron precursor prepared in Example 1 of the present invention.

[0032] Figure 3 This is a scanning electron microscope image of the samarium iron precursor prepared in Example 1 of the present invention.

[0033] Figure 4 This is the element distribution diagram of the samarium iron precursor prepared in Example 1 of the present invention.

[0034] Figure 5 This is the particle size distribution diagram of the samarium iron precursor prepared in Example 1 of the present invention.

[0035] Figure 6 This is the XRD diffraction pattern of the refined samarium-iron alloy powder prepared in Example 1 of the present invention.

[0036] Figure 7 This is a scanning electron microscope image of the refined samarium-iron alloy powder prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0037] The mass purity of the samarium salt, iron salt and ammonium bicarbonate used in Examples 1 to 4 of the present invention is all above 99%.

[0038] Example 1

[0039] like Figure 1 As shown, this embodiment includes the following steps:

[0040] Step 1: Coprecipitation reaction: Weigh 29.48 g of Fe(NO) 3 9H 2 O and 4.44 g of Sm(NO 3 ) 3 6H 2 O was dissolved in 200 mL of deionized water to prepare a samarium-iron salt mixed aqueous solution with an iron salt concentration of 0.365 M and a samarium salt concentration of 0.050 M. Then 6.00 g of dodecyltrimethylammonium bromide was added and stirred at room temperature for 12 h. 20.86 g of NH 4 HCO 3 Dissolve in 200 mL of deionized water to prepare an ammonium bicarbonate solution, then use a flow control pump to add the samarium salt-iron salt mixed aqueous solution and the ammonium bicarbonate solution to the reactor in parallel, and the feed flow rate is 2 mL / min. After the dropwise addition is completed, the pH of the reaction solution is controlled to be 6.1, and the reaction is continued by stirring for 1 hour. After centrifugation and water washing, the solid phase obtained is samarium-iron hydroxide;

[0041] Step 2, diffusion medium incorporation: weigh 0.50 g of KCl and dissolve it in 10 g of deionized water to obtain a KCl solution, then place the samarium-iron hydroxide obtained in step 1 in the KCl solution and perform ultrasonic treatment for 2 h to uniformly disperse it, and then place it in a 90° C. oven to dry;

[0042] Step 3, pre-reduction: Grind the dried samarium-iron hydroxide in step 2 into powder until there is no obvious granularity, put it into a porcelain boat and place it in a tube furnace, first heat it to 700°C at a rate of 5°C / min in an air atmosphere and keep it warm for 3 hours, then blow in argon gas and introduce hydrogen at a flow rate of 0.15L / min, heat it to 800°C at a rate of 2°C / min and keep it warm for 2 hours, and then cool it down naturally to obtain a product composed of α-Fe and Sm 2 O 3 The composition of the samarium iron precursor;

[0043] Step 4: Ultrasonic dispersion: The samarium iron precursor obtained in step 3 is ultrasonically treated in anhydrous ethanol for 2 hours and dried to obtain a monodisperse samarium iron precursor; the monodisperse samarium iron precursor is a spherical α-Fe and Sm iron precursor with an average particle size of 602 nm, monodispersity, and uniform distribution of Sm and Fe elements. 2 O 3 mixture;

[0044] Step 5, reduction diffusion: the monodisperse samarium iron precursor obtained in step 4 is mixed with metallic calcium, and the mass of the metallic calcium is 20.84% ​​of the mass of the monodisperse samarium iron precursor, and is placed in a stainless steel crucible with a lid and placed in a vacuum tube furnace, and then argon is introduced at a flow rate of 0.1L / min, and the temperature is raised to 1050°C at a rate of 3.33°C / min for a reduction diffusion reaction for 4h;

[0045] Step 6: Washing and decalcification: Use deionized water and dilute acetic acid as the washing medium, and use the magnetic separation-grinding washing process to repeatedly wash the reduction diffusion reaction product in step 5 to remove by-products and high melting point salts until AgNO 3 Check the wash water for Cl-free - After the pH of the washing water reaches 7, the washing is continued with anhydrous ethanol for 3 times, and then placed in a vacuum oven at 80°C for drying to obtain a refined samarium-iron alloy powder; the refined samarium-iron alloy powder is a spherical powder with a particle size of less than 4 μm and a phase composition of Sm 2 Fe 17 .

[0046] Figure 2 The XRD diffraction pattern of the samarium iron precursor prepared in this embodiment is as follows: Figure 2 It can be seen that the phase composition of the samarium iron precursor is α-Fe and Sm 2 O 3 , without impurity phases such as iron oxide and samarium iron oxide.

[0047] Figure 3 This is a scanning electron microscope image of the samarium iron precursor prepared in this example. Figure 3 It can be seen that the samarium iron precursor is submicron, monodisperse spherical particles with uniform particle size and distribution.

[0048] Figure 4 This is the element distribution diagram of the samarium iron precursor prepared in this example. Figure 4 It can be seen that the Fe, Sm and O elements are evenly distributed in the samarium iron precursor without single element aggregation.

[0049] Figure 5 The particle size distribution diagram of the samarium iron precursor prepared in this example is as follows: Figure 5 It can be seen that the particle size distribution diagram of the samarium iron precursor presents a normal distribution curve, and the average particle size of the particle group is 602 nm.

[0050] Figure 6 The XRD diffraction pattern of the refined samarium-iron alloy powder prepared in this embodiment is as follows: Figure 6 It can be seen that the refined samarium-iron alloy powder is Sm 2 Fe 17 Pure phase, no other impurity phase.

[0051] Figure 7 This is a scanning electron microscope image of the refined samarium-iron alloy powder prepared in this embodiment. Figure 7 It can be seen that the refined samarium-iron alloy powder is spherical particles with a particle size of less than 4 μm, and the particle size and distribution are uniform.

[0052] The samarium salt in step 1 of this embodiment can also be derived from Sm(NO 3 ) 3 6H 2 O, iron salts can also be derived from samarium chloride, samarium nitrate, samarium sulfate and their hydrates, in addition to Fe(NO) 3 9H 2 O; the dispersant may also be one or more combinations of polyethylene glycol, polyvinyl pyrrolidone, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide and activated carbon other than dodecyltrimethylammonium bromide; the high melting point salt in step 2 may also be one or more combinations of potassium chloride, sodium chloride and calcium chloride other than potassium chloride; the reducing gas in step 3 may also be ethane; the volatile organic solution in step 4 may also be methanol, isopropanol or acetone; the inert gas in step 5 may also be helium; the anhydrous organic alcohol in step 6 may also be methanol, isopropanol or n-butanol.

[0053] Example 2

[0054] like Figure 1 As shown, this embodiment includes the following steps:

[0055] Step 1: Coprecipitation reaction: Weigh 15.34 g of Fe(NO) 3 9H 2 O and 2.22 g of Sm(NO 3 ) 3 6H 2 O was dissolved in 160 mL of deionized water to prepare a samarium-iron salt mixed aqueous solution with an iron salt concentration of 0.237 M and a samarium salt concentration of 0.031 M. Then 3.50 g of polyvinyl pyrrolidone was added and stirred at room temperature for 8 h. 11.22 g of NH 4 HCO 3 Dissolve in 160 mL of deionized water to prepare an ammonium bicarbonate solution, then use a flow control pump to add the samarium salt-iron salt mixed aqueous solution and the ammonium bicarbonate solution to the reactor in parallel, and the feed flow rate is 10 mL / min. After the addition is completed, the pH of the reaction solution is controlled to be 6.3, and the reaction is continued with stirring for 2 hours. After centrifugation and water washing, the solid phase obtained is samarium-iron hydroxide;

[0056] Step 2: Addition of diffusion medium: Weigh 0.35 g of CaCl 2Dissolve in 10g deionized water to obtain CaCl 2 solution, and then place the samarium-iron hydroxide obtained in step 1 in CaCl 2 The solution was ultrasonically treated for 1.5 h to disperse evenly and then dried in an oven at 60 °C;

[0057] Step 3, pre-reduction: Grind the dried samarium-iron hydroxide in step 2 into powder until there is no obvious granularity, put it into a porcelain boat and place it in a tube furnace, first heat it to 800°C at a rate of 6°C / min in an air atmosphere and keep it warm for 1 hour, then blow in argon gas and introduce hydrogen at a flow rate of 0.02L / min, heat it to 850°C at a rate of 1°C / min and keep it warm for 1 hour, and then cool it down naturally to obtain a composite material composed of α-Fe and Sm 2 O 3 The composition of the samarium iron precursor;

[0058] Step 4: Ultrasonic dispersion: The samarium iron precursor obtained in step 3 is ultrasonically treated in anhydrous methanol for 1 hour and dried to obtain a monodisperse samarium iron precursor; the monodisperse samarium iron precursor is a spherical α-Fe and Sm iron precursor with an average particle size of 733 nm, monodispersity, and uniform distribution of Sm and Fe elements. 2 O 3 mixture;

[0059] Step 5, reduction diffusion: the monodisperse samarium iron precursor obtained in step 4 is mixed with metallic calcium, and the mass of the metallic calcium is 12.83% of the mass of the monodisperse samarium iron precursor, and is placed in a stainless steel crucible with a lid and placed in a vacuum tube furnace, and then argon is introduced at a flow rate of 0.05 L / min, and the temperature is raised to 950°C at a rate of 2°C / min for reduction diffusion reaction for 3 hours;

[0060] Step 6: Washing and decalcification: Use deionized water and dilute acetic acid as the washing medium, and use the magnetic separation-grinding washing process to repeatedly wash the reduction diffusion reaction product in step 5 to remove by-products and high melting point salts until AgNO 3 Check the wash water for Cl-free - After the pH of the washing water reaches 7, the washing is continued with anhydrous methanol for 3 times, and then placed in a vacuum oven at 50°C for drying to obtain a refined samarium-iron alloy powder; the refined samarium-iron alloy powder is a spherical powder with a particle size of less than 4 μm and a phase composition of Sm 2 Fe 17 .

[0061] Example 3

[0062] like Figure 1 As shown, this embodiment includes the following steps:

[0063] Step 1: Coprecipitation reaction: Weigh 14.36 g of Fe(NO) 39H 2 O and 2.22 g of Sm(NO 3 ) 3 6H 2 O was dissolved in 300 mL of deionized water to prepare a samarium-iron salt mixed aqueous solution with an iron salt concentration of 0.119 M and a samarium salt concentration of 0.017 M. Then 3.10 g of polyethylene glycol was added and stirred at room temperature for 10 h. 10.00 g of NH 4 HCO 3 Dissolve in 300 mL of deionized water to prepare an ammonium bicarbonate solution, then use a flow control pump to add the samarium salt-iron salt mixed aqueous solution and the ammonium bicarbonate solution to the reactor in parallel, and the feed flow rate is 5 mL / min. After the addition is completed, the pH of the reaction solution is controlled to be 5.9, and stirring is continued to react for 3 hours. After centrifugation and water washing, the solid phase obtained is samarium-iron hydroxide;

[0064] Step 2, diffusion medium incorporation: weigh 0.17 g of KCl and dissolve it in 10 g of deionized water to obtain a KCl solution, then place the samarium-iron hydroxide obtained in step 1 in the KCl solution and perform ultrasonic treatment for 1 h to uniformly disperse it, and then place it in an oven at 80° C. to dry;

[0065] Step 3, pre-reduction: The dried samarium-iron hydroxide in step 2 is ground into powder until there is no obvious granularity, loaded into a porcelain boat and placed in a tube furnace, first heated to 700°C at a rate of 10°C / min in an air atmosphere and kept warm for 2 hours, then after blowing in argon gas, hydrogen is introduced at a flow rate of 0.1L / min, and the temperature is raised to 750°C at a rate of 3.33°C / min and kept warm for 2 hours. After natural cooling, a molten iron precipitate composed of α-Fe and Sm is obtained. 2 O 3 The composition of the samarium iron precursor;

[0066] Step 4: Ultrasonic dispersion: The samarium iron precursor obtained in step 3 is placed in anhydrous ethanol for ultrasonic treatment for 1 hour and dried to obtain a monodisperse samarium iron precursor; the monodisperse samarium iron precursor is a spherical α-Fe and Sm iron precursor with an average particle size of 650nm, monodispersity, and uniform distribution of Sm and Fe elements. 2 O 3 mixture;

[0067] Step 5, reduction diffusion: the monodisperse samarium iron precursor obtained in step 4 is mixed with metallic calcium, and the mass of the metallic calcium is 23.37% of the mass of the monodisperse samarium iron precursor, and is placed in a stainless steel crucible with a lid and placed in a vacuum tube furnace, and then argon is introduced at a flow rate of 0.08 L / min, and the temperature is raised to 1050°C at a rate of 4°C / min for a reduction diffusion reaction for 4 hours;

[0068] Step 6: Washing and decalcification: Use deionized water and dilute acetic acid as the washing medium, and use the magnetic separation-grinding washing process to repeatedly wash the reduction diffusion reaction product in step 5 to remove by-products and high melting point salts until AgNO 3 After checking that there is no Cl- in the washing water and the pH of the washing water reaches 7, the washing water is continuously washed with anhydrous methanol for 2 times, and then placed in a vacuum oven at 60°C for drying to obtain a refined samarium-iron alloy powder; the refined samarium-iron alloy powder is a spherical powder with a particle size of less than 4 μm, and the phase composition is Sm 2 Fe 17 .

[0069] Example 4

[0070] like Figure 1 As shown, this embodiment includes the following steps:

[0071] Step 1: Coprecipitation reaction: Weigh 57.53 g of Fe(NO) 3 9H 2 O and 8.44 g of Sm(NO 3 ) 3 6H 2 O was dissolved in 300 mL of deionized water to prepare a samarium-iron salt mixed aqueous solution with an iron salt concentration of 0.475 M and a samarium salt concentration of 0.063 M. Then 12.30 g of polyethylene glycol was added and stirred at room temperature for 12 h. 38.60 g of NH 4 HCO 3 Dissolve in 300 mL of deionized water to prepare an ammonium bicarbonate solution, then use a flow control pump to add the samarium salt-iron salt mixed aqueous solution and the ammonium bicarbonate solution to the reactor in parallel, and the feed flow rate is 2 mL / min. After the dropwise addition is completed, the pH of the reaction solution is controlled to be 5.4, and the stirring is continued to react for 4 hours. After centrifugation and water washing, the solid phase obtained is samarium-iron hydroxide;

[0072] Step 2: Incorporation of diffusion medium: 1.97 g of NaCl was weighed and dissolved in 10 g of deionized water to obtain a NaCl solution, and then the samarium-iron hydroxide obtained in step 1 was placed in the NaCl solution for ultrasonic treatment for 1.5 h to be uniformly dispersed, and then placed in an oven at 100° C. to dry;

[0073] Step 3, pre-reduction: Grind the dried samarium-iron hydroxide in step 2 into powder until there is no obvious granularity, put it into a porcelain boat and place it in a tube furnace, first heat it to 850°C at a rate of 5°C / min in an air atmosphere and keep it warm for 4 hours, then blow in argon gas and introduce hydrogen at a flow rate of 0.2L / min, heat it to 900°C at a rate of 5°C / min and keep it warm for 3 hours, and then cool it down naturally to obtain a composite material composed of α-Fe and Sm 2 O 3 The composition of the samarium iron precursor;

[0074] Step 4: Ultrasonic dispersion: The samarium iron precursor obtained in step 3 is ultrasonically treated in anhydrous methanol for 3 hours and dried to obtain a monodisperse samarium iron precursor; the monodisperse samarium iron precursor is a spherical α-Fe and Sm iron precursor with an average particle size of 694 nm, monodispersity, and uniform distribution of Sm and Fe elements. 2 O 3 mixture;

[0075] Step 5, reduction diffusion: the monodisperse samarium iron precursor obtained in step 4 is mixed with metallic calcium, and the mass of the metallic calcium is 16.73% of the mass of the monodisperse samarium iron precursor, and is placed in a stainless steel crucible with a lid and placed in a vacuum tube furnace, and then argon is introduced at a flow rate of 0.2L / min, and the temperature is raised to 1050°C at a rate of 6°C / min for reduction diffusion reaction for 6h;

[0076] Step 6: Washing and decalcification: Use deionized water and dilute acetic acid as the washing medium, and use the magnetic separation-grinding washing process to repeatedly wash the reduction diffusion reaction product in step 5 to remove by-products and high melting point salts until AgNO 3 Check the wash water for Cl-free - After the pH of the washing water reaches 7, the washing is continued with anhydrous ethanol for 4 times, and then placed in a vacuum oven at 60°C for drying to obtain a refined samarium-iron alloy powder; the refined samarium-iron alloy powder is a spherical powder with a particle size of less than 4 μm and a phase composition of Sm 2 Fe 17 .

[0077] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing refined samarium-iron alloy powder based on submicron monodisperse samarium-iron precursor, characterized in that, the method comprises the following steps: Step 1. Coprecipitation reaction: Using ammonium bicarbonate solution to coprecipitate water-soluble samarium salt and iron salt, and controlling the coprecipitation process by adding a dispersant, controlling the solution mixing method and controlling the pH of the reaction solution to obtain samarium-iron hydroxide; Step 2. Incorporation of diffusion medium: The samarium-iron hydroxide obtained in Step 1 is placed in an aqueous solution of high-melting-point salt for ultrasonic treatment to be uniformly dispersed, and then dried in an oven at 60°C to 100°C; Step 3: Pre-reduction: The dried samarium-iron hydroxide in step 2 is placed in a tube furnace for thermal decomposition and pre-reduction with reducing gas to obtain a product composed of α-Fe and Sm 2 O 3 The composition of the samarium iron precursor; Step 4: Ultrasonic dispersion: The samarium iron precursor obtained in step 3 is placed in a volatile organic solution for ultrasonic treatment for 1 h to 3 h and dried to obtain a monodisperse samarium iron precursor; the monodisperse samarium iron precursor is a spherical α-Fe and Sm with an average particle size of 500 nm to 750 nm, monodispersity and uniform element distribution. 2 O 3 mixture; Step 5. Reduction diffusion: The monodisperse samarium-iron precursor obtained in Step 4 is mixed with metallic calcium, loaded into a stainless-steel crucible with a lid and placed in a vacuum tube furnace, and then an inert gas is introduced at a flow rate of 0.05 L / min to 0.2 L / min, and the temperature is raised to 950°C to 1050°C at a rate of 2°C / min to 6°C / min for a reduction diffusion reaction for 3 h to 6 h; Step 6, washing and decalcification: using deionized water and dilute acetic acid as washing media, repeatedly washing the reduction diffusion reaction product in step 5 by a magnetic separation-grinding washing process to remove by-products and high melting point salts, until the pH of the washing water reaches 7, and then continue to use anhydrous organic alcohol to wash 2 to 4 times, and then place it in a vacuum oven at 50°C to 80°C to dry, to obtain a refined samarium-iron alloy powder; the refined samarium-iron alloy powder is a spherical powder with a particle size of less than 4 μm, and the phase composition is Sm 2 Fe 17 or SmFe 9 .

2. The method for preparing refined samarium-iron alloy powder based on submicron monodisperse samarium-iron precursor according to claim 1, characterized in that, the samarium salt in Step 1 is derived from samarium chloride, samarium nitrate, samarium sulfate and their hydrates, the iron salt is derived from ferric chloride, ferric nitrate, ferric sulfate and their hydrates, and the molar ratio of the iron salt to the samarium salt is 7.0 to 7.6:1; the dispersant is one or a combination of polyethylene glycol, polyvinylpyrrolidone, dodecyltrimethylammonium bromide, cetyltrimethylammonium bromide and activated carbon, and the dosage of the dispersant is 0.5% to 2.0% of the total mass of the reaction solution; the solution mixing method is a parallel feeding method based on a flow control pump, and the feeding flow rate is 2 mL / min to 10 mL / min; the pH of the reaction solution is 5.3 to 6.

5.

3. The method for preparing refined samarium-iron alloy powder based on submicron monodisperse samarium-iron precursor according to claim 1, characterized in that, in Step 1, first prepare an aqueous solution of samarium salt-iron salt with an iron salt concentration of 0.1 M to 0.5 M, then add a dispersant and continuously stir at room temperature for 8 h to 12 h, and then add an equal volume of ammonium bicarbonate aqueous solution. After the addition, continue to stir at room temperature for reaction for 1 h to 4 h. After centrifugation and washing, the solid phase obtained is samarium-iron hydroxide; the molar amount of ammonium bicarbonate in the added ammonium bicarbonate aqueous solution is 3 to 3.3 times the total molar amount of the iron salt and the samarium salt.

4. The method for preparing refined samarium-iron alloy powder based on submicron monodisperse samarium-iron precursor according to claim 1, characterized in that, the high-melting-point salt in the high-melting-point salt aqueous solution in Step 2 is one or a combination of water-soluble salt substances such as potassium chloride, sodium chloride and calcium chloride with a melting point higher than 700°C, and the mass of the high-melting-point salt is 1% to 3% of the total mass of the samarium salt and the iron salt.

5. The method for preparing refined samarium-iron alloy powder based on submicron monodisperse samarium-iron precursor according to claim 1, characterized in that, In step three, the dried samarium-iron hydroxide is ground into powder until there is no obvious granularity, loaded into a porcelain boat and placed in a tube furnace, first heated to 700°C~850°C at a rate of 5°C / min~10°C / min in an air atmosphere and kept warm for 1h~4h, then after blowing in an inert gas, a reducing gas is introduced at a flow rate of 0.02L / min~0.2L / min, and the temperature is increased to 750°C~900°C at a rate of 1°C / min~5°C / min and kept warm for 1h~3h, and the samarium iron precursor is obtained after natural cooling.

6. A method for preparing refined samarium-iron alloy powder based on submicron monodisperse samarium-iron precursor according to claim 1, It is characterized in that The reducing gas in step 3 is hydrogen or ethane.

7. A method for preparing refined samarium-iron alloy powder based on submicron monodisperse samarium-iron precursor according to claim 1, It is characterized in that The volatile organic solution in step 4 is an organic substance such as methanol, ethanol, isopropanol or acetone.

8. The method for preparing refined samarium-iron alloy powder based on submicron monodisperse samarium-iron precursor according to claim 1, It is characterized in that In step 5, the mass of the metallic calcium is 12.8% to 23.4% of the mass of the monodisperse samarium iron precursor; and the inert gas is argon or helium.

9. The method for preparing refined samarium-iron alloy powder based on submicron monodisperse samarium-iron precursor according to claim 1, It is characterized in that The organic alcohol in step six is ​​organic methanol, ethanol, isopropanol or n-butanol.

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