A method for modifying a samarium iron nitride magnetic powder

Abstract

This invention relates to a method for modifying samarium iron nitrogen (SFI) magnetic powder. The method includes sequentially modifying the SFI with phosphoric acid, polyethylene glycol, and resin to obtain modified SFI. The modification method provided by this invention achieves effective coating of the SFI through a multi-layered modification process, which is beneficial for maintaining the magnetic properties of the SFI at high temperatures and further extends its service life.

Description

Technical Field

[0001] This invention relates to the field of magnetic materials technology, and specifically to a method for modifying samarium iron nitrogen magnetic powder. Background Technology

[0002] Currently, in recent years, due to the widespread use of rare earth NdFeB permanent magnet materials in air conditioning compressors, new energy vehicles, wind power generation, and other fields, the prices of rare earth Nd and Pr have risen rapidly. How to utilize relatively abundant rare earth resources such as Sm and Ce, which are cheaper, has become a hot topic in the field of magnetic materials. The saturation magnetization of SmFeN compounds is 1.54T, comparable to 1.6T of NdFeB compounds. Its Curie temperature is 470℃, and its anisotropic field is 14T, both higher than those of NdFeB compounds. These superior intrinsic magnetic properties make SmFeN compounds considered to have the potential to become a new generation of rare earth permanent magnet materials.

[0003] Compared to NdFeB permanent magnets, SmFeN compounds suffer from irreversible decomposition at temperatures exceeding 550°C, making it difficult to fabricate dense magnets using traditional sintering processes. Therefore, SmFeN compounds are typically mixed with binders to prepare bonded magnets. The most common method involves mixing SmFeN magnetic powder with plastic binders such as PA and PPS at 200-300°C using a twin-screw extruder, followed by granulation and injection molding at a slightly higher temperature (180-330°C) to produce bonded magnets. For example, CN106317875A discloses a method for preparing high-performance polyphenylene sulfide / Samarium iron nitride magnetic composite materials, comprising the following steps: First, using polyphenylene sulfide resin as a matrix, a multifunctional masterbatch is prepared by combining plasticizers, lubricants, and antioxidants using a twin-screw extruder; second, surface-treated Samarium iron nitride powder is combined with the masterbatch prepared in the first step and extruded using a twin-screw extruder to prepare the magnetic composite material. The polyphenylene sulfide / smarium iron nitride magnetic composite material prepared by this method exhibits high fluidity, magnetic properties, and good mechanical properties, making it suitable for injection molding to manufacture devices. This method offers advantages such as simple preparation process, low equipment requirements, and suitability for industrial production.

[0004] CN108447639A discloses a rare-earth magnetic powder composition for magnetic masterbatches or magnetic fibers, and a method for preparing the rare-earth magnetic powder composition. Specifically, the rare-earth permanent magnet material magnetic powder composition for strong magnetic fibers of the present invention comprises: 80-95 parts by weight of rare-earth permanent magnet material magnetic powder, 0-5 parts by weight of additives, and 5-15 parts by weight of coating agent, wherein the coating agent is selected from one or more of polyalphaolefin, silicone oil, vegetable oil, and liquid paraffin, and the additives are selected from one or more of silicone additives, ethylene bis-stearamide, ethylene-acrylic acid copolymer, amide wax, polyethylene wax, and polypropylene wax. This composition not only enables rare-earth permanent magnet materials to have better stability and magnetism, but also allows for smooth processing when used to prepare magnetic masterbatches or spin strong magnetic fibers, solving the defects of existing rare-earth permanent magnet materials that are difficult to transport and store.

[0005] During the mixing, granulation, and injection molding processes, SmFeN magnetic powder readily reacts with oxygen at high temperatures, thereby reducing its coercivity. Furthermore, the coercivity temperature coefficient of SmFeN magnetic powder is -5.0% / ℃, and its coercivity further decreases at high temperatures. Therefore, improving the temperature stability of SmFeN magnetic materials, reducing the coercivity temperature coefficient, and preparing SmFeN composite permanent magnet materials with better temperature performance are urgent problems to be solved. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a modification method for samarium iron nitrogen magnetic powder to solve the problem of samarium iron nitrogen magnetic powder being used in high temperature environments.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides a method for modifying samarium iron nitrogen magnetic powder, the method comprising: sequentially modifying samarium iron nitrogen magnetic powder with phosphoric acid, polyethylene glycol and resin to obtain modified samarium iron nitrogen magnetic powder.

[0009] The modification method provided by this invention achieves effective coating of samarium iron nitrogen magnetic powder through a multi-level modification method, which is beneficial to the maintenance of magnetic properties of samarium iron nitrogen magnetic powder when used at high temperatures, and further improves the service life of samarium iron nitrogen magnetic powder.

[0010] In this invention, the samarium iron nitrogen magnetic powder can be generated by reacting samarium oxide, iron powder, and ammonia.

[0011] In this invention, after phosphoric acid modification, polyethylene glycol modification and resin modification, corresponding drying and sieving (screen mesh size of 80 mesh) can be carried out to obtain well dispersed powder, thereby ensuring the subsequent processing.

[0012] As a preferred technical solution of the present invention, the mass concentration of phosphoric acid used in the phosphoric acid modification is 20-80%, for example, it can be 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, or 80%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0013] In this invention, the solvent for the phosphoric acid solution used in the phosphoric acid modification includes ethanol. That is, the solvent and phosphoric acid of a specific mass concentration are mixed and then the magnetic powder is treated. The amount of solvent used is 6-8% of the mass of the magnetic powder, for example, it can be 6%, 6.2%, 6.4%, 6.6%, 6.8%, 7%, 7.2%, 7.4%, 7.6%, 7.8%, or 8%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0014] Preferably, the mass ratio of phosphoric acid to samarium iron nitrogen magnetic powder used in the phosphoric acid modification is (2-3):100, for example, it can be 2:100, 2.05:100, 2.1:100, 2.15:100, 2.2:100, 2.25:100, 2.3:100, 2.35:100, 2.4:100, 2.45:100, 2.5:100, 2.55:100, 2.6:100, 2.65:100, 2.7:100, 2.75:100, 2.8:100, 2.85:100, 2.9:100, 2.95:100 or 3:100, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0015] As a preferred technical solution of the present invention, the phosphoric acid modification is to mix phosphoric acid and samarium iron nitrogen magnetic powder for 20-50 minutes, for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes or 50 minutes, etc., but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] As a preferred embodiment of the present invention, the polyethylene glycol used in the polyethylene glycol modification has a molecular weight of 200-6000, for example, it can be 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, etc. 3000, 3100, 3200, 3300, 3400, 3500, 3600, 3700, 3800, 3900, 4000, 4100, 4200, 4300, 4400, 4500, 4600, 4700, 4800, 4900, 5000, 5100, 5200, 5300, 5400, 5500, 5600, 5700, 5800, 5900, or 6000, etc., but not limited to the listed values; other unlisted values ​​within this range also apply.

[0017] Preferably, the mass ratio of polyethylene glycol to samarium iron nitrogen magnetic powder used in the polyethylene glycol modification is (4-6):100, for example, it can be 4:100, 4.1:100, 4.2:100, 4.3:100, 4.4:100, 4.5:100, 4.6:100, 4.7:100, 4.8:100, 4.9:100, 5:100, 5.1:100, 5.2:100, 5.3:100, 5.4:100, 5.5:100, 5.6:100, 5.7:100, 5.8:100, 5.9:100 or 6:100, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0018] As a preferred technical solution of the present invention, the polyethylene glycol modification involves mixing the polyethylene glycol solution and the powder obtained by phosphoric acid modification for 5-10 minutes, for example, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes or 10 minutes, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] In this invention, the polyethylene glycol solution used in the polyethylene glycol modification is obtained by mixing polyethylene glycol with an alcohol such as ethanol or methanol. The mass concentration of the polyethylene glycol solution is 92-94%, for example, it can be 92%, 92.2%, 92.4%, 92.6%, 92.8%, 93%, 93.2%, 93.4%, 93.6%, 93.8%, or 94%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0020] As a preferred embodiment of the present invention, the resin used in the resin modification includes thermosetting resin.

[0021] As a preferred technical solution of the present invention, the resin used in the resin modification includes one or a combination of at least two of furfuryl alcohol resin, phenolic resin, or furfural-acetone resin.

[0022] As a preferred technical solution of the present invention, the mass ratio of resin to samarium iron nitrogen magnetic powder used in the resin modification is (3-5):100, for example, it can be 3:100, 3.2:100, 3.4:100, 3.6:100, 3.8:100, 4:100, 4.2:100, 4.4:100, 4.6:100, 4.8:100 or 5:100, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0023] As a preferred technical solution of the present invention, the resin modification involves mixing the resin solution and the powder obtained by polyethylene glycol modification for 5-10 minutes, for example, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes or 10 minutes, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] In this invention, the resin solution used in the resin modification process is obtained by mixing a thermosetting resin, an alcohol, and an inorganic acid. The alcohol can be methanol, ethanol, etc., and the inorganic acid can be sulfuric acid, hydrochloric acid, or nitric acid, etc. The mass concentration of the inorganic acid is 0.5-1%, for example, it can be 0.5%, 0.52%, 0.54%, 0.56%, 0.58%, 0.6%, 0.62%, 0.64%, 0.66%, 0.68%, 0.7%, 0.72%, 0.74%, 0.76%, 0.78%, 0.8%, 0.82%, 0.84%, 0.86%, 0.88%, 0.9%, 0.92%, 0.94%, 0.96%, 0.98%, or 1%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0025] In this invention, the amount of alcohol added to the resin solution used in the resin modification is 6-8% of the mass of the polyethylene glycol-modified powder, for example, it can be 6%, 6.2%, 6.4%, 6.6%, 6.8%, 7%, 7.2%, 7.4%, 7.6%, 7.8%, or 8%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] In this invention, the amount of acid added to the resin solution used in the resin modification is 2-3% of the mass of the polyethylene glycol-modified powder, for example, it can be 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] As a preferred technical solution of the present invention, the modification method includes: sequentially modifying samarium iron nitrogen magnetic powder with phosphoric acid, polyethylene glycol and resin to obtain modified samarium iron nitrogen magnetic powder;

[0028] The phosphoric acid modification involves mixing phosphoric acid and samarium iron nitrogen magnetic powder for 20-50 minutes; the mass concentration of phosphoric acid used in the phosphoric acid modification is 20-80%; and the mass ratio of phosphoric acid to samarium iron nitrogen magnetic powder used in the phosphoric acid modification is (2-3):100.

[0029] The polyethylene glycol modification involves mixing a polyethylene glycol solution with a powder obtained from phosphoric acid modification for 5-10 minutes; the molecular weight of the polyethylene glycol used in the polyethylene glycol modification is 200-6000; the mass ratio of polyethylene glycol to samarium iron nitrogen magnetic powder used in the polyethylene glycol modification is (4-6):100.

[0030] The resin modification involves mixing the resin solution and the powder obtained by polyethylene glycol modification for 5-10 minutes; the resin used in the resin modification includes one or a combination of at least two of furfural resin, phenolic resin, or furfural-acetone resin; the mass ratio of the resin used in the resin modification to samarium iron nitrogen magnetic powder is (3-5):100.

[0031] Compared with existing technical solutions, the present invention has the following beneficial effects:

[0032] The modification method provided by this invention utilizes polyethylene glycol to form a positively charged state on the surface of magnetic powder. The resin has good fluidity and thermosetting properties, allowing the resin and polyethylene glycol to further coat the magnetic powder, resulting in a near-spherical particle. Simultaneously, it also better isolates oxygen, preventing oxidation of the magnetic powder by atmospheric oxygen. Detailed Implementation

[0033] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0034] Example 1

[0035] This embodiment provides a method for modifying samarium iron nitrogen magnetic powder, specifically including the following:

[0036] (1) Select 60% phosphoric acid and mix it with ethanol (7% of the magnetic powder mass) to prepare the first coating solution for later use.

[0037] (2) Select polyethylene glycol with a molecular weight of 2000, dissolve polyethylene glycol in anhydrous ethanol to prepare a second coating solution (polyethylene glycol mass concentration of 93%) for later use. The mass of polyethylene glycol is 5% of the mass of magnetic powder.

[0038] (3) Furfuryl alcohol resin was selected as the third coating agent.

[0039] (4) Mix furfuryl alcohol resin and ethanol, and add 0.5% sulfuric acid solution to prepare a third coating solution for later use. The amount of resin is 3% of the mass of magnetic powder, the amount of ethanol is 7% of the mass of magnetic powder, and the amount of acid is 2.5% of the mass of magnetic powder.

[0040] (5) Add the untreated SmFeN magnetic powder to a beaker containing the first coating solution (solid-liquid ratio of 100:2.5), stir thoroughly (35 min), and then place it in an oven to dry at 60°C for 30 min. Pass the dried powder through an 80-mesh sieve.

[0041] (6) Add the sieved powder to a beaker containing the second coating solution, stir thoroughly (7 min), and then dry in an oven at 60°C for 30 min. Pass the dried powder through an 80-mesh sieve.

[0042] (7) Add the sieved powder to a beaker containing the third coating solution, stir thoroughly (7 min), and then dry in an oven at 60°C for 30 min. Pass the dried powder through an 80-mesh sieve to obtain modified SmFeN powder.

[0043] Example 2

[0044] The only difference from Example 1 is that 20% phosphoric acid is added in step (1).

[0045] Example 3

[0046] The only difference from Example 1 is that in step (1), 80% phosphoric acid is added.

[0047] Example 4

[0048] The only difference from Example 1 is that polyethylene glycol with a molecular weight of 200 is added in step (2).

[0049] Example 5

[0050] The only difference from Example 1 is that polyethylene glycol with a molecular weight of 6000 is added in step (2).

[0051] Example 6

[0052] The only difference from Example 1 is that phenolic resin is selected as the third coating agent in step (3).

[0053] Example 7

[0054] The only difference from Example 1 is that furfural-acetone resin is selected as the third coating agent in step (3).

[0055] Comparative Example 1

[0056] Unmodified samarium iron nitrogen magnetic powder is provided, which is the samarium iron nitrogen magnetic powder in Example 1.

[0057] Comparative Example 2

[0058] The only difference from Example 1 is that in steps (6) and (7), anhydrous ethanol is used instead of the coating solution. After thorough stirring, the powder is placed in an oven and dried at 60°C for 30 minutes. The dried powder is then passed through an 80-mesh sieve.

[0059] Comparative Example 3

[0060] The only difference from Example 1 is that in steps (5) and (7), anhydrous ethanol is used instead of the coating solution. After thorough stirring, the powder is placed in an oven and dried at 60°C for 30 minutes. The dried powder is then passed through an 80-mesh sieve.

[0061] Comparative Example 4

[0062] The only difference from Example 1 is that in steps (5) and (6), anhydrous ethanol is used instead of the coating solution. After thorough stirring, the powder is placed in an oven and dried at 60°C for 30 minutes. The dried powder is then passed through an 80-mesh sieve.

[0063] Comparative Example 5

[0064] The only difference from Example 1 is that step (6) is not performed, i.e., polyethylene glycol modification is not performed.

[0065] Comparative Example 6

[0066] The only difference from Example 1 is that step (5) is not performed, i.e., phosphoric acid modification is not performed.

[0067] Comparative Example 7

[0068] The only difference from Example 1 is that step (7) is not performed, that is, resin modification is not performed.

[0069] Comparative Example 8

[0070] The only difference from Example 1 is that the order of steps (5) and (6) is changed, that is, polyethylene glycol modification is performed first, followed by phosphoric acid modification.

[0071] Comparative Example 9

[0072] The only difference from Example 1 is that the order of steps (6) and (7) is changed, that is, resin modification is performed first, and then polyethylene glycol modification is performed.

[0073] The composition of the samarium-iron-nitrogen magnetic powder used in the above embodiments and comparative examples is samarium:iron:nitrogen = 21:77:2.

[0074] Application Example 1

[0075] This application example specifically provides an application process for modified samarium iron nitrogen magnetic powder to demonstrate the performance of the obtained modified samarium iron nitrogen magnetic powder, specifically including the following:

[0076] (1) The modified samarium iron nitrogen magnetic powder obtained in the above powder examples and comparative examples is mixed with polyphenylene sulfide resin at a mass ratio of 100:8.

[0077] (2) The mixed powder is granulated by a twin-screw extruder to obtain granules for injection molding.

[0078] (3) The above granules are injection molded in an injection molding machine to obtain the target product and test its performance.

[0079] (4) Place the target product in a forced-air drying oven and heat it at 180°C for 60 minutes, then retest its performance.

[0080] The performance parameters obtained from the test are detailed in Table 1.

[0081] Table 1

[0082]

[0083]

[0084] The results from the application examples show that the modification method provided by the present invention, by adopting a specific modification process and setting multiple specific coating layers, achieves stable performance of samarium iron nitrogen magnetic powder, which is beneficial to the good performance of samarium iron nitrogen magnetic powder at high temperatures.

[0085] The present invention is described above through the embodiments to illustrate its detailed structural features, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0086] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0087] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0088] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method of modifying a samarium iron nitride magnetic powder, characterized by, The modification method includes: sequentially modifying samarium iron nitrogen magnetic powder with phosphoric acid, polyethylene glycol and resin to obtain modified samarium iron nitrogen magnetic powder; After the phosphoric acid modification, polyethylene glycol modification and resin modification are carried out, corresponding drying and sieving processes are also performed. The mass concentration of phosphoric acid used in the phosphoric acid modification is 22-80%; The polyethylene glycol used in the polyethylene glycol modification has a molecular weight of 200-5900; The resin used in the resin modification includes one or a combination of at least two of furfuryl alcohol resin, phenolic resin, or furfural-acetone resin.

2. The modification method of claim 1, wherein, The mass ratio of phosphoric acid and samarium iron nitrogen magnetic powder used in the phosphoric acid modification is (2-3):

100.

3. The method of claim 1, wherein the modifying comprises, The phosphoric acid modification involves mixing phosphoric acid and samarium iron nitrogen magnetic powder for 20-50 minutes.

4. The method of claim 1, wherein the modifying comprises, The mass ratio of polyethylene glycol to samarium iron nitrogen magnetic powder used in the polyethylene glycol modification is (4-6):

100.

5. The method of claim 1, wherein the modifying comprises, The polyethylene glycol modification involves mixing a polyethylene glycol solution with a powder obtained from phosphoric acid modification for 5-10 minutes.

6. The method of claim 1, wherein the modifying comprises, The resins used in the resin modification include thermosetting resins.

7. The method of claim 1, wherein the modifying comprises, The mass ratio of resin to samarium iron nitrogen magnetic powder used in the resin modification is (3-5):

100.

8. The method of claim 1, wherein the modifying comprises, The resin modification involves mixing the resin solution and the powder obtained by polyethylene glycol modification for 5-10 minutes.

9. The method of claim 1, wherein the modifying comprises, The modification method includes: the phosphoric acid modification involves mixing phosphoric acid and samarium iron nitrogen magnetic powder for 20-50 minutes; the mass concentration of phosphoric acid used in the phosphoric acid modification is 22-80%; the mass ratio of phosphoric acid to samarium iron nitrogen magnetic powder used in the phosphoric acid modification is (2-3):100; The polyethylene glycol modification involves mixing a polyethylene glycol solution with a powder obtained from phosphoric acid modification for 5-10 minutes; the molecular weight of the polyethylene glycol used in the polyethylene glycol modification is 200-5900; the mass ratio of polyethylene glycol to samarium iron nitrogen magnetic powder used in the polyethylene glycol modification is (4-6):

100. The resin modification involves mixing the resin solution and the powder obtained by polyethylene glycol modification for 5-10 minutes; the resin used in the resin modification includes one or a combination of at least two of furfural resin, phenolic resin, or furfural-acetone resin; the mass ratio of the resin used in the resin modification to samarium iron nitrogen magnetic powder is (3-5):100.

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