Preparation method of surface-modified SmFeN powder

Abstract

The invention relates to the technical field of samarium-iron-nitrogen materials, and relates to a preparation method of surface-modified SmFeN powder, which comprises the following steps: in an inert atmosphere, grinding 100 parts by weight of SmFeN powder, 0.1-20 parts by weight of a surfactant, 0.1-20 parts by weight of a silane coupling agent, 0-10 parts by weight of a surface passivation acid solution, 100-1000 parts by weight of a solvent and grinding balls in a grinding device to obtain grinding slurry; and drying the grinding slurry to obtain surface modified SmFeN powder. According to the preparation method of the surface-modified SmFeN powder, powder refinement and surface modification can be carried out at the same time, the surface-modified SmFeN powder is obtained, the residual magnetism and the maximum magnetic energy product performance of the surface-modified SmFeN powder are excellent, and oxidation of the SmFeN powder is effectively inhibited.

Description

Technical Field

[0001] The invention belongs to the technical field of samarium iron nitrogen materials and relates to a method for preparing surface-modified SmFeN powder. Background Art

[0002] In recent years, with the development of green energy technologies such as electric vehicles and wind turbines, the demand for large block magnets of rare earth permanent magnet materials has been increasing. Since the common NdFeB on the market has consumed resources for more than 40 years, and the heavy rare earths of dysprosium and terbium are widely used to improve the temperature resistance of NdFeB magnets, the cost of NdFeB magnets is increasing year by year. Therefore, SmFeN materials that do not contain heavy rare earths and metallic neodymium have more significant economic advantages and application prospects.

[0003] SmFeN material was discovered in 1990. It produces hard magnetism because nitrogen atoms enter the SmFe lattice to form interstitial compounds. The coercivity of SmFeN is heavily dependent on the size effect. It has a higher coercivity when the particle size is reduced to 1-5μm. This fine magnetic powder has high surface activity and is easily oxidized in the air, and even spontaneously combusts. Therefore, while refining the SmFeN powder and improving the powder performance, the surface passivation of the powder is extremely important.

[0004] There have been reports on the surface antioxidant technology of SmFeN permanent magnet powder in China, such as: using silane coupling agent KH550 to coat the surface of SmFeN permanent magnet powder, and studying the oxidation behavior and magnetic property change law of magnetic powders in different coating states below 300°C; using phosphate film to coat SmFeN magnetic powder, adding inorganic acid while stirring the slurry of SmFeN powder, water and phosphate compound, keeping the solution pH at 2, promoting continuous film-forming reaction, and preparing SmFeN powder with uniform phosphate film coating, which improves coercivity while suppressing magnetic Reduction of powder remanence; Chinese patent application text (publication number: CN113707444A) discloses a method for preparing high-performance rare earth magnetic powder by ball milling and in-situ double passivation, wherein the coarse magnetic powder is ball milled and simultaneously passivated in situ in a passivating agent containing an acid medium and a coupling agent in an inert atmosphere protection environment to obtain a high-performance fine magnetic powder with a double passivation film on the surface. However, the pretreatment time of the passivating agent is long, which is not conducive to improving the efficiency. At the same time, the low ball milling energy of the magnetic powder leads to poor performance of the samarium iron nitrogen magnetic powder.

[0005] Therefore, under the premise of ensuring powder refinement, the problem that needs to be solved at present is to achieve surface modification without the powder undergoing violent oxidation reaction when encountering air, while at the same time not significantly reducing the magnetic properties of the powder. Summary of the invention

[0006] The purpose of the present invention is to solve the above problems in the prior art and to propose a method for preparing surface-modified SmFeN powder by simultaneously performing powder refinement and surface modification. The prepared surface-modified SmFeN powder has good magnetic properties and good antioxidant properties.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A method for preparing surface-modified SmFeN powder comprises:

[0009] Under an inert atmosphere, 100 parts by weight of SmFeN powder, 0.1-20 parts by weight of a surfactant, 0.1-20 parts by weight of a silane coupling agent, 0-10 parts by weight of a surface passivation acid solution, 100-1000 parts by weight of a solvent and a grinding ball are placed in a grinding device to grind to obtain a grinding slurry, and the surface-modified SmFeN powder is obtained after the grinding slurry is dried.

[0010] Preferably, the mass ratio of SmFeN powder, surfactant, silane coupling agent, surface passivation acid solution and solvent is 100:(0.5-10):(0.5-10):(0-5):(100-500).

[0011] More preferably, the mass ratio of SmFeN powder, surfactant, silane coupling agent, surface passivation acid solution and solvent is 100:(0.1-5):(1-5):(0.5-5):(200-300).

[0012] Preferably, the surface passivation acidic solution includes one or more of phosphoric acid, nitric acid and oxalic acid.

[0013] Preferably, the surfactant includes one or more of oleic acid, oleylamine and stearic acid.

[0014] Preferably, the silane coupling agent includes one or more of KH550, KH560, and KH570.

[0015] Preferably, the solvent includes one or more of ethanol, methanol, gasoline and n-hexane.

[0016] Preferably, the average particle size of the SmFeN powder is 20-50 μm, and the average particle size of the surface-modified SmFeN powder is 2-5 μm.

[0017] Preferably, the ball-to-material ratio in the grinding device is (1-25):1.

[0018] Further preferably, the ball-to-material ratio in the grinding device is (3-15):1.

[0019] Preferably, the grinding speed is 100-2000 r / min.

[0020] More preferably, the grinding speed is 200-1000 r / min.

[0021] Preferably, the grinding time is 1-1000 min.

[0022] More preferably, the grinding time is 30-120 min.

[0023] A high-performance samarium iron nitrogen composite magnet is prepared by mixing surface-modified SmFeN powder with epoxy adhesive, and then subjecting the mixture to molding orientation and heat treatment.

[0024] Preferably, the mass ratio of the surface-modified SmFeN powder to the epoxy adhesive is 100:(0.1-10).

[0025] Preferably, the intensity of the mold orientation magnetic field is 1-10 T, the pressure is 100-10000 MPa, and the holding time is 0.1-10 min.

[0026] More preferably, the intensity of the mold orientation magnetic field is 5-8 T, the pressure is 700-2000 MPa, and the holding time is 0.2-3 min.

[0027] Preferably, the heat treatment temperature is 110-180°C and the time is 1-12h.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The preparation method of the surface-modified SmFeN powder of the present invention can simultaneously perform powder refinement and surface modification to obtain the surface-modified SmFeN powder, which has excellent remanence and maximum magnetic energy product performance and effectively inhibits the oxidation of the SmFeN powder, and the high-temperature oxidation weight gain rate is significantly reduced.

[0030] 2. The preparation method of the present invention has simple process, few procedures, high efficiency and great economic value.

[0031] 3. The maximum magnetic energy product performance of the magnet made from the surface-modified SmFeN powder prepared in the present invention is significantly improved. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below through specific embodiments. It should be understood that the specific embodiments described here are only used to help understand the present invention and are not specifically limited to the present invention.

[0033] Unless otherwise specified, the materials used in the present invention are conventional commercial products, and the methods used are conventional technical means.

[0034] The SmFeN powder used in the present invention is a commercially available product; or it can be obtained by mixing raw materials according to metallurgical process, and then undergoing rapid solidification belt throwing or smelting ingot casting, hydrogen crushing or medium crushing, air flow grinding, and nitriding.

[0035] Example 1

[0036] 100 parts of SmFeN powder (average particle size 30 μm) were weighed and mixed with 230 parts of ethanol, 2 parts of oleic acid, and 1 part of silane coupling agent (KH550) to obtain a mixed material;

[0037] Under an inert atmosphere, the mixed material and grinding balls were placed in a grinding jar and placed on an omnidirectional planetary ball mill for grinding at a ball-to-material ratio of 5:1 and a rotation speed of 500 r / min. After ball milling for 4 h, a crushed powder slurry was obtained.

[0038] The polishing slurry was taken out, and the powder was washed and dried under the protection of inert gas to obtain surface-modified SmFeN powder with an average particle size of 3.2 μm.

[0039] Performance test of surface modified SmFeN powder:

[0040] 1. Orient the surface-modified SmFeN powder in a 2T magnetic field and fix it with a binder, and use a VSM vibrating sample magnetometer to test the magnetic properties of the sample along the orientation direction;

[0041] 2. The surface-modified SmFeN powder was placed in a drying oven at 200°C and heated for 60 minutes. The weight difference before and after heating was then measured to compare the weight gain rate before and after high-temperature oxidation.

[0042] The performance results are shown in Table 1.

[0043] Example 2

[0044] 100 parts of SmFeN powder (average particle size 30 μm) were weighed and mixed with 230 parts of ethanol, 2 parts of oleic acid, and 5 parts of silane coupling agent (KH550) to obtain a mixed material;

[0045] Under an inert atmosphere, the mixed material and grinding balls were placed in a grinding jar and placed on an omnidirectional planetary ball mill for grinding at a ball-to-material ratio of 5:1 and a rotation speed of 500 r / min. After ball milling for 4 h, a crushed powder slurry was obtained.

[0046] The polishing slurry was taken out, and the powder was washed and dried under the protection of inert gas to obtain surface-modified SmFeN powder with an average particle size of 3.0 μm.

[0047] The performance test was carried out in the manner of Example 1. The results are shown in Table 1.

[0048] Example 3

[0049] 100 parts of SmFeN powder (average particle size 30 μm) were weighed and mixed with 230 parts of ethanol, 2 parts of oleic acid, and 10 parts of silane coupling agent (KH550) to obtain a mixed material;

[0050] Under an inert atmosphere, the mixed material and grinding balls were placed in a grinding jar and placed on an omnidirectional planetary ball mill for grinding at a ball-to-material ratio of 5:1 and a rotation speed of 500 r / min. After ball milling for 4 h, a crushed powder slurry was obtained.

[0051] The polishing slurry is taken out, and the powder is washed and dried under the protection of an inert gas to obtain a surface-modified SmFeN powder.

[0052] The performance test was carried out in the manner of Example 1. The results are shown in Table 1.

[0053] Example 4

[0054] 100 parts of SmFeN powder (average particle size 30 μm) were weighed and mixed with 230 parts of ethanol, 2 parts of oleic acid, 0.5 parts of silane coupling agent (KH550), and 0.5 parts of phosphoric acid to obtain a mixed material;

[0055] Under an inert atmosphere, the mixed material and grinding balls were placed in a grinding jar and placed on an omnidirectional planetary ball mill for grinding at a ball-to-material ratio of 5:1 and a rotation speed of 500 r / min. After ball milling for 4 h, a crushed powder slurry was obtained.

[0056] The polishing slurry is taken out, and the powder is washed and dried under the protection of an inert gas to obtain a surface-modified SmFeN powder.

[0057] The performance test was carried out in the manner of Example 1. The results are shown in Table 1.

[0058] Example 5

[0059] 100 parts of SmFeN powder (average particle size 30 μm) were weighed and mixed with 230 parts of ethanol, 2 parts of oleic acid, 0.5 parts of silane coupling agent (KH550), and 1 part of phosphoric acid to obtain a mixed material;

[0060] Under an inert atmosphere, the mixed material and grinding balls were placed in a grinding jar and placed on an omnidirectional planetary ball mill for grinding at a ball-to-material ratio of 5:1 and a rotation speed of 500 r / min. After ball milling for 4 h, a crushed powder slurry was obtained.

[0061] The polishing slurry is taken out, and the powder is washed and dried under the protection of an inert gas to obtain a surface-modified SmFeN powder.

[0062] The performance test was carried out in the manner of Example 1. The results are shown in Table 1.

[0063] Example 6

[0064] 100 parts of SmFeN powder (average particle size 30 μm) were weighed and mixed with 230 parts of ethanol, 2 parts of oleic acid, 0.5 parts of silane coupling agent (KH550), and 5 parts of phosphoric acid to obtain a mixed material;

[0065] Under an inert atmosphere, the mixed material and grinding balls were placed in a grinding jar and placed on an omnidirectional planetary ball mill for grinding at a ball-to-material ratio of 5:1 and a rotation speed of 500 r / min. After ball milling for 4 h, a crushed powder slurry was obtained.

[0066] The polishing slurry is taken out, and the powder is washed and dried under the protection of an inert gas to obtain a surface-modified SmFeN powder.

[0067] The performance test was carried out in the manner of Example 1. The results are shown in Table 1.

[0068] Example 7

[0069] 100 parts of SmFeN powder (average particle size 30 μm) were weighed and mixed with 300 parts of ethanol, 5 parts of stearic acid, 7 parts of silane coupling agent (KH560), and 3 parts of phosphoric acid to obtain a mixed material;

[0070] Under an inert atmosphere, the mixed material and grinding balls were placed in a grinding jar and placed on an omnidirectional planetary ball mill for grinding at a ball-to-material ratio of 10:1 and a rotation speed of 800 r / min. After ball milling for 6 h, a crushed powder slurry was obtained.

[0071] The polishing slurry was taken out, and the powder was washed and dried under the protection of inert gas to obtain surface-modified SmFeN powder with an average particle size of 2.3 μm.

[0072] The performance test was carried out in the manner of Example 1. The results are shown in Table 1.

[0073] Comparative Example 1

[0074] 100 parts of SmFeN powder (average particle size 30 μm) were weighed and mixed with 230 parts of ethanol and 2 parts of oleic acid to obtain a mixed material;

[0075] Under an inert atmosphere, the mixed material and grinding balls were placed in a grinding jar and placed on an omnidirectional planetary ball mill for grinding at a ball-to-material ratio of 5:1 and a rotation speed of 500 r / min. After ball milling for 4 h, a crushed powder slurry was obtained.

[0076] The polishing slurry is taken out, and the powder is washed and dried under the protection of an inert gas to obtain a surface-modified SmFeN powder.

[0077] The performance test was carried out in the manner of Example 1. The results are shown in Table 1.

[0078] Comparative Example 2

[0079] 100 parts of SmFeN powder (average particle size 30 μm) were weighed and mixed with 230 parts of ethanol and 3 parts of oleic acid to obtain a mixed material;

[0080] Under an inert atmosphere, the mixed material and grinding balls were placed in a grinding jar and placed on an omnidirectional planetary ball mill for grinding at a ball-to-material ratio of 5:1 and a rotation speed of 500 r / min. After ball milling for 4 h, a crushed powder slurry was obtained.

[0081] The polishing slurry is taken out, and the powder is washed and dried under the protection of an inert gas to obtain a surface-modified SmFeN powder.

[0082] The performance test was carried out in the manner of Example 1. The results are shown in Table 1.

[0083] Comparative Example 3

[0084] 100 parts of SmFeN powder (average particle size 30 μm) were weighed and mixed with 230 parts of ethanol to obtain a mixed material;

[0085] Under an inert atmosphere, the mixed material and grinding balls were placed in a grinding jar and placed on an omnidirectional planetary ball mill for grinding at a ball-to-material ratio of 5:1 and a rotation speed of 500 r / min. After ball milling for 4 h, a crushed powder slurry was obtained.

[0086] The polishing slurry is taken out, and the powder is cleaned and dried under the protection of an inert gas to obtain a refined SmFeN powder.

[0087] The performance test was carried out in the manner of Example 1. The results are shown in Table 1.

[0088] Comparative Example 4

[0089] 100 parts of SmFeN powder were weighed by weight and milled by air flow milling to an average particle size of 3 μm. Then 230 parts of ethanol, 2 parts of oleic acid, 0.5 parts of silane coupling agent (KH550) and 5 parts of phosphoric acid were added. Under the protection of inert gas, mechanical stirring was performed at room temperature for 4 hours. Then the powder was washed and dried to obtain surface-modified SmFeN powder.

[0090] The performance test was carried out in the manner of Example 1. The results are shown in Table 1.

[0091] Application Example 1

[0092] The surface-modified SmFeN powder in Example 1 was mixed with epoxy glue (W-6C) in a mass ratio of 100:2, placed in a compression molding device, and a 7T orientation magnetic field was applied. After maintaining the pressure at 1000Mpa for 60s, a samarium iron nitride magnet was prepared; the prepared magnet was a Φ10*8mm cylinder, and the orientation field was consistent with the pressing direction.

[0093] The magnetic properties such as coercivity Hcj, remanence Br, and maximum magnetic energy product (BH)max were measured using a permanent magnet material high temperature measurement system. The performance results are shown in Table 2.

[0094] Application Examples 2-7

[0095] The surface-modified SmFeN powders in Examples 2-7 were used in accordance with the method of Application Example 1 to prepare samarium iron nitrogen magnets.

[0096] The performance results are shown in Table 2.

[0097] Application Comparative Examples 1-4

[0098] The surface-modified SmFeN powders in Comparative Examples 1-4 were used in accordance with the method of Application Example 1 to prepare samarium iron nitrogen magnets.

[0099] The performance results are shown in Table 2.

[0100] Table 1. Performance data of surface modified SmFeN powder

[0101]

[0102] Table 2. Performance data of SmFeN magnets

[0103] HkDJ Br / kGs BH(max) / MGOe Application Example 1 8.31 7.71 11.34 Application Example 2 8.34 7.55 10.80 Application Example 3 7.84 7.23 9.89 Application Example 4 8.34 7.74 11.30 Application Example 5 7.81 7.25 10.04 Application Example 6 8.68 7.41 9.52 Application Example 7 9.47 6.98 9.11 Application Comparative Example 1 8.52 7.51 9.56 Application Comparative Example 2 10.02 6.84 9.07 Application Comparative Example 3 9.83 6.63 8.83 Application Comparative Example 4 11.19 6.42 9.77

[0104] According to the above content, the present invention completes surface passivation by ball milling the SmFeN powder, and the surface-modified SmFeN powder obtained has good magnetic properties, and the oxidation weight gain rate can be reduced by more than 3 times (compared with Example 7 and Comparative Example 3), effectively inhibiting the oxidation of the powder. In addition, the passivation process of the present invention does not require heating, has a simple process, fewer processes, and is low-carbon and environmentally friendly.

[0105] In summary, the preparation method of the surface-modified SmFeN powder of the present invention can simultaneously perform powder refinement and surface modification, the remanence and maximum magnetic energy product performance of the surface-modified SmFeN powder obtained are improved, and the oxidation of the SmFeN powder is effectively inhibited, the heating oxidation weight gain rate is significantly reduced, and the maximum magnetic energy product performance of the magnet made of the surface-modified SmFeN powder is significantly improved.

[0106] The various aspects, embodiments, and features of the present invention should be considered to be illustrative in all aspects and not limiting of the present invention, the scope of which is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

[0107] In the preparation method of the present invention, the order of each step is not limited to the order listed. For those skilled in the art, without creative work, the order of each step is also within the protection scope of the present invention. In addition, two or more steps or actions can be performed simultaneously.

[0108] Finally, it should be noted that the specific embodiments described herein are merely examples of the present invention, and are not intended to limit the implementation methods of the present invention. A person skilled in the art of the present invention may make various modifications or supplements to the specific embodiments described, or replace them in a similar manner. It is not necessary and impossible to provide all examples of all implementation methods here. However, these obvious changes or modifications derived from the essential spirit of the present invention still fall within the scope of protection of the present invention, and interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A method for preparing surface-modified SmFeN powder, characterized in that: The preparation method comprises: in an inert atmosphere, by weight, placing 100 parts of SmFeN powder, 0.1-20 parts of a surfactant, 0.1-20 parts of a silane coupling agent, 0-10 parts of a surface passivation acid solution, 100-1000 parts of a solvent and a grinding ball in a grinding device to grind to obtain a grinding slurry, and after the grinding slurry is dried, a surface-modified SmFeN powder is obtained.

2. The method for preparing the surface-modified SmFeN powder according to claim 1, characterized in that: The mass ratio of the SmFeN powder, surfactant, silane coupling agent, surface passivation acid solution and solvent is 100:(0.1-5):(1-5):(0.5-5):(200-300).

3. The method for preparing the surface-modified SmFeN powder according to claim 1, characterized in that: The surface passivation acidic solution includes one or more of phosphoric acid, nitric acid and oxalic acid.

4. The method for preparing the surface-modified SmFeN powder according to claim 1, characterized in that: The surfactant includes one or more of oleic acid, oleylamine and stearic acid.

5. The method for preparing the surface-modified SmFeN powder according to claim 1, characterized in that: The solvent includes one or more of ethanol, methanol, gasoline and n-hexane.

6. The method for preparing the surface-modified SmFeN powder according to claim 1, characterized in that: The average particle size of the SmFeN powder is 20-50 μm, and the average particle size of the surface-modified SmFeN powder is 2-5 μm.

7. A high performance samarium iron nitrogen composite magnet, characterized in that: The surface-modified SmFeN powder of claim 1 is mixed with epoxy adhesive, and then molded, oriented, and heat-treated to obtain the product.

8. The high performance samarium iron nitrogen composite magnet according to claim 7, characterized in that: The mass ratio of the surface-modified SmFeN powder to the epoxy adhesive is 100:(0.1-10).

9. The high performance samarium iron nitrogen composite magnet according to claim 7, characterized in that: The mold-pressing orientation magnetic field strength is 1-10T, the pressure is 100-10000MPa, and the holding time is 0.1-10min.

10. The high performance samarium iron nitrogen composite magnet according to claim 7, characterized in that: The heat treatment temperature is 110-180° C. and the time is 1-12 hours.

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