A flexible neodymium-iron-nitrogen magnet and a method for producing the same

Abstract

This invention discloses a flexible neodymium iron nitride (NdFeN) magnet and its preparation method, belonging to the field of magnetic materials technology. The preparation method includes the following steps: NdFeN oxide, iron oxide powder and / or iron powder, calcium powder and / or calcium hydride are ball-milled in a vacuum ball mill jar for mixing; the mixed raw materials undergo a reduction-diffusion reaction in argon gas to obtain a NdFeN alloy block containing reaction byproducts; the NdFeN alloy block is crushed and nitrided to obtain NdFeN coarse powder containing reaction byproducts; the nitrided NdFeN coarse powder is rapidly washed with ultrapure water to remove reaction byproducts, obtaining a pure NdFeN coarse powder slurry; the obtained NdFeN slurry is ball-milled and refined using anhydrous ethanol as a medium and then vacuum-dried to obtain NdFeN magnetic powder. Finally, the target NdFeN magnetic powder is collected and dried, and then kneaded and rolled with a binder. The prepared NdFeN exhibits excellent magnetic properties, with particularly good flexibility and stability, meeting the requirements for preparing flexible magnets.

Description

Technical Field

[0001] This invention belongs to the field of magnetic materials technology, specifically relating to a flexible neodymium iron nitride magnet and its preparation method. Background Technology

[0002] Flexible NdFeB magnets are a type of bonded permanent magnet, widely used in home appliances, computers, automobiles, and automation in manufacturing and factories. With the rapid development of global information, electronics, and transportation industries, and the rapid rise of my country's IT industry, the demand for high-performance magnetic materials in the computer, automotive, and consumer electronics markets is experiencing explosive growth. The demand for manufacturing various micromotors and magnetic devices is also increasing, with bonded permanent magnets growing at a rate of approximately 30% annually. Flexible NdFeB magnets possess high magnetic properties, good flexibility, and oxidation resistance, making them suitable for various complex shapes and miniaturized applications, such as consumer electronics, micromotors, and wearable devices. Furthermore, these magnets exhibit excellent corrosion resistance and demagnetization resistance, meeting the needs of high-end applications.

[0003] Patent application CN1594209A discloses a flexible rare-earth bonded magnet and its manufacturing method. It is made by uniformly mixing anisotropic neodymium-iron-nitrogen magnetic powder, a binder, and processing aids, followed by calendering, flat pressing, or a combination of calendering and flat pressing. The magnet's composition and weight content are: 80-98% anisotropic neodymium-iron-nitrogen magnetic powder, 1.5-15% binder, 0-5% vulcanizing agent, and 0.1-5% processing aids. It possesses excellent magnetic properties, good flexibility, and low cost. However, the final molding method used in this method involves molding in a vulcanizing mold. Due to limitations in the size of the vulcanizing machine and the vulcanizing process, this molding method restricts the size of the magnet and production efficiency. Therefore, it is impossible to produce magnets with virtually unlimited length, and the production process is complex and inefficient. Summary of the Invention

[0004] The purpose of this invention is to provide a flexible neodymium iron nitride magnet and its preparation method, so as to solve the problem that the production process of neodymium iron nitride magnets is too complicated.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for preparing a flexible neodymium iron nitrogen magnet involves preparing a neodymium iron alloy by reduction diffusion, then preparing neodymium iron nitrogen magnetic powder through crushing, nitriding, washing, ball milling, and drying processes; then coating the neodymium iron nitrogen magnetic powder with a binder, mixing and rolling it, and finally magnetizing it to obtain the flexible neodymium iron nitrogen magnet.

[0007] As a further preferred embodiment of the present invention, the reaction temperature in the reduction diffusion method is 950-1200℃ and the reaction time is 2-8h.

[0008] As a further preferred embodiment of the present invention, the reduction diffusion method includes the following steps:

[0009] Under vacuum conditions, neodymium oxide, iron oxide powder and / or iron powder, and calcium reducing agent are thoroughly ball-milled and mixed. After mixing, the mixture is reacted under an argon atmosphere to obtain a neodymium-iron alloy. The calcium reducing agent is calcium powder and / or calcium hydride. The neodymium element is in excess by 10% to 30% based on a neodymium-iron molar ratio of 2:17, and the calcium reducing agent in the ball-milled mixture is in excess by 20% to 60%.

[0010] In this invention, the ball milling mixing method involves ball milling and mixing the raw materials, namely neodymium oxide, iron oxide powder / iron oxide powder and / or iron powder, calcium powder and / or calcium hydride particles, in a vacuum ball mill jar. The ball milling speed is 150-550 rpm, and the ball milling time is 0.5h-3h. The purpose of thoroughly grinding the raw materials in the vacuum ball mill jar is to completely disperse and refine the agglomerated raw material particles without oxidizing the Fe and Ca raw materials, so that the raw materials are fully and uniformly mixed, which helps to generate the neodymium iron alloy phase.

[0011] The neodymium-iron alloy block obtained from the reduction-diffusion reaction was crushed using a vibratory crusher. The crushed coarse neodymium-iron alloy powder was then nitrided. This powder was a mixture of the reduced-diffusion neodymium-iron alloy and a large amount of CaO and Ca. Preliminary nitriding of the coarse neodymium-iron alloy particles promoted the formation of Nd₂Fe. 17 The N3 phase further enhances the magnetic properties of the powder and improves the oxidation resistance of the neodymium-iron alloy, reducing the oxidation of the powder in subsequent washing steps.

[0012] As a further preferred embodiment of the present invention, the nitriding step is carried out in a heat treatment furnace at a temperature of 450-500°C under a N2 atmosphere for 3-6 hours.

[0013] As a further preferred embodiment of the present invention, the washing method is ultrasonic stirring washing, in which the powder is rapidly washed and calcium is removed using an ultrasonic stirring device, the washing medium is ultrapure water, and the mass ratio of material to water is 1-10:250; the washing time is 5-10 minutes, and the washing is repeated 3-6 times; wherein the stirring speed is 500-2000 rpm and the ultrasonic frequency is 30-60 kHz.

[0014] As a further preferred embodiment of the present invention, the crude NdFeB-N slurry obtained after washing is ball-milled, and further refined by ball milling in a ball milling jar using anhydrous ethanol as the ball milling medium. The ball-to-material ratio is 5-10:1, the ball milling speed is 200-600 rpm, and the ball milling time is 5-16 hours.

[0015] As a further preferred embodiment of the present invention, the drying step is as follows: collecting the slurry after ball milling and drying it with a vacuum dryer to obtain pure neodymium iron nitrogen magnetic powder, wherein the fine powder has a particle size ≤10μm;

[0016] As a further preferred embodiment of the present invention, the adhesive includes at least one of silicone rubber, nitrile rubber, ethylene propylene rubber, CPE (chlorinated polyethylene) and PVC (polyvinyl chloride);

[0017] As a further preferred embodiment of the present invention, the mixing temperature is 70-200℃; the mixing pressure is 0.5-10MPa.

[0018] As a further preferred embodiment of the present invention, the rolling temperature is 40-100℃; the rolling thickness is 1mm; the rolled magnetic sheet is cut and magnetized, the cutting size is 80×40mm, the magnetization voltage is 2500V, and the magnetization spacing is 4mm.

[0019] As a further preferred embodiment of the present invention, a method for preparing a flexible neodymium iron nitride magnet includes the following steps:

[0020] (1) Neodymium oxide, iron oxide powder and / or iron powder, calcium powder and / or calcium hydride are fully ball-milled in a vacuum ball mill to mix the materials.

[0021] (2) The mixed raw materials were subjected to a reduction diffusion reaction in argon to obtain a neodymium-iron alloy block containing reaction byproducts;

[0022] (3) The neodymium iron alloy block is crushed and nitrided to obtain neodymium iron nitrogen coarse powder containing reaction by-products;

[0023] (4) The nitrided NdFeNi coarse powder was rapidly washed with ultrapure water to remove reaction byproducts and obtain pure NdFeNi coarse powder slurry.

[0024] (5) The obtained NdFeNi slurry was ball-milled and vacuum-dried using anhydrous ethanol as the medium to obtain NdFeNi magnetic powder.

[0025] (6) Finally, the target neodymium iron nitrogen magnetic powder is collected and dried, and then mixed and rolled with binder to obtain flexible neodymium iron nitrogen magnetic sheet.

[0026] A flexible neodymium iron nitrogen magnet is prepared by the above-described preparation method.

[0027] The beneficial effects of this invention are:

[0028] This invention discloses a flexible neodymium iron nitride (NdFeN) magnet and its preparation method. The method involves first preparing a NdFeN alloy via a reduction-diffusion method, then preparing NdFeN magnetic powder through crushing, nitriding, washing, ball milling, and drying processes. The NdFeN magnetic powder is then coated, mixed with a binder, rolled, and magnetized to obtain the flexible NdFeN magnet. The NdFeN magnet prepared by this invention exhibits excellent magnetic properties, as well as relatively excellent flexibility and stability, meeting the requirements for preparing flexible magnets. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] Obviously, the following description is merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0031] However, there may be instances where unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters or repetitive descriptions of essentially the same structure may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand this application and is not intended to limit the subject matter of the claims.

[0032] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions, and all technical features and optional technical features of this application can be combined to form new technical solutions.

[0033] Example 1

[0034] This embodiment provides a method for preparing a flexible neodymium iron nitride magnet, including the following steps:

[0035] (1) Ingredients: 44.3g neodymium oxide (with 25% excess neodymium oxide based on theoretical basis); 100.0g iron powder; 22.1g calcium granules (with 40% excess calcium based on theoretical basis). Seal the raw materials in an argon-protected vacuum ball mill jar;

[0036] (2) Mixing: The raw materials are fully mixed by ball milling in a horizontal ball mill at a speed of 250 rpm for 3 hours and a ball-to-material mass ratio of 8:1.

[0037] (3) Loading: Take the evenly mixed material from the ball mill into the glove box filled with argon gas, load it into the iron crucible and compact it;

[0038] (4) Reduction-diffusion reaction: The crucible containing the reaction raw materials is placed in a heat treatment furnace to carry out the reduction-diffusion reaction. The entire reaction is carried out under an argon atmosphere, at a reaction temperature of 1100℃ and a reaction time of 4h.

[0039] (5) Crushing and nitriding: The NdFe alloy block containing a large amount of reaction byproducts generated after the reaction is crushed in a crusher under atmospheric conditions; then the crushed NdFe alloy mixture is nitrided in a tube furnace at a nitriding temperature of 500℃ and a nitriding time of 9h to obtain NdFe nitrogen mixed powder containing a large amount of calcium element impurities (Ca, CaO).

[0040] (6) Rapid cleaning: The NdFeB-N mixed coarse powder was rapidly cleaned and calcium removed using an ultrasonic stirring device. The cleaning medium was ultrapure water, and the mass ratio of powder to water was 8:250. The washing time was 8 minutes, and the washing was repeated 4 times. The stirring speed was 1000 rpm and the ultrasonic frequency was 50 kHz.

[0041] (7) Ball milling refinement: The nitrided NdFeNi was ball-milled using anhydrous ethanol as the medium to further refine the powder. The ball-to-powder mass ratio was 10:1, the ball milling speed was 450 rpm, and the ball milling time was 7 hours. Then, the water-washed NdFeNi was washed with anhydrous ethanol to remove excess water stains and reduce the degree of oxidation of NdFeNi during ball milling and drying. The powder-to-anhydrous ethanol mass ratio was 1:20, the washing time was 8 minutes, and the washing was repeated twice.

[0042] (8) Collection and drying: The NdFeB N magnetic powder slurry obtained from ball milling is collected and dried in a vacuum drying oven to obtain crude NdFeB N alloy powder;

[0043] (9) Internal mixing: The dried neodymium iron nitrogen magnetic powder is mixed with nitrile rubber and internally mixed at 150 rpm for 1 hour in a mixer at 140℃ and 3MPa.

[0044] (10) Calendering and magnetization: The powder after intensive mixing is calendered at 65°C into NdFeNi sheet with a thickness of 1 mm; the obtained NdFeNi sheet is cut into 80×40 mm size and magnetized with a magnetization voltage of 2500V and a magnetization spacing of 4 mm to obtain the flexible NdFeNi magnet.

[0045] Example 2

[0046] This embodiment provides a method for preparing flexible neodymium iron nitrogen, which is the same as in Example 1, except that nitrile rubber is replaced with silicone rubber; the other raw materials and preparation process are the same as in Example 1.

[0047] Example 3

[0048] This embodiment provides a method for preparing flexible neodymium iron nitrogen, which is the same as in Example 1, except that nitrile rubber is replaced with ethylene propylene rubber; the other raw materials and preparation process are the same as in Example 1.

[0049] Example 4

[0050] This embodiment provides a method for preparing flexible neodymium iron nitrogen that is the same as in Example 1, except that the reduction diffusion reaction temperature is changed to 1000℃; the other raw materials and preparation process are the same as in Example 1.

[0051] Example 5

[0052] This embodiment provides a method for preparing flexible neodymium iron nitrogen that is the same as in Example 1, except that the reduction diffusion reaction temperature is changed to 1200℃; the other raw materials and preparation process are the same as in Example 1.

[0053] Example 6

[0054] This embodiment provides a method for preparing flexible neodymium iron nitrogen, which is the same as in Example 1, except that the reduction diffusion reaction time is changed to 2 hours; the other raw materials and preparation process are the same as in Example 1.

[0055] Example 7

[0056] This embodiment provides a method for preparing flexible neodymium iron nitrogen, which is the same as in Example 1, except that the reduction diffusion reaction time is changed to 6 hours; the other raw materials and preparation process are the same as in Example 1.

[0057] Example 8

[0058] This embodiment provides a method for preparing flexible neodymium iron nitrogen, which is the same as in Example 1, except that the reduction diffusion reaction time is changed to 8 hours; the other raw materials and preparation process are the same as in Example 1.

[0059] Comparative Example 1

[0060] This comparative example provides a method for preparing flexible NdFeN, which is the same as in Example 1. The difference from Example 1 is that the raw material Nd element is in 0% excess, that is, the theoretical amount is used; the other raw materials and preparation process are the same as in Example 1.

[0061] Comparative Example 2

[0062] This comparative example provides a method for preparing flexible NdFeN, which is the same as in Example 1. The difference from Example 1 is that the raw material Nd element is in 40% excess based on the theoretical basis; the other raw materials and preparation process are the same as in Example 1.

[0063] Comparative Example 3

[0064] This comparative example provides a method for preparing flexible neodymium iron nitrogen that is the same as in Example 1, except that the reduction diffusion reaction temperature is changed to 800°C; the other raw materials and preparation process are the same as in Example 1.

[0065] Comparative Example 4

[0066] This comparative example provides a method for preparing flexible neodymium iron nitrogen that is the same as in Example 1, except that the reduction diffusion reaction temperature is changed to 1300℃; the other raw materials and preparation process are the same as in Example 1.

[0067] Measurement and Analysis: Analysis of Nd2Fe using X-ray diffraction (XRD) 17 Nd2Fe obtained after reduction diffusion reaction 17 N3 powder, Nd2Fe after ball milling, was analyzed using a vibrating sample magnetometer (VSM). 17 N3 magnetic powder was used for hysteresis loop testing.

[0068] Tensile strength and elongation testing: The prepared flexible NdFeB magnet tensile specimen was mounted on the fixture of a tensile testing machine. An axial tensile force was applied to the specimen at a tensile speed of 5 mm / min until fracture. During the tensile process, the testing machine automatically recorded the tensile force and displacement data, and calculated the tensile strength and elongation based on these data. Tensile strength is the ratio of the maximum tensile force the specimen could withstand before fracture to the original cross-sectional area of ​​the specimen; elongation is the ratio of the elongation at fracture to the original gauge length, calculated using the following formula:

[0069] Tensile strength: Where σ is the tensile strength and F is the tensile strength. max The maximum tensile force is equal to the original cross-sectional area A.

[0070] Elongation: Where δ is the elongation, L is the length at fracture, and L0 is the original length.

[0071] Performance tests were conducted on Examples 1-8 and Comparative Examples 1-4, and the results are shown in Table 1:

[0072] Table 1

[0073]

[0074]

[0075] The test results show that the flexible NdFeN material prepared by this invention has excellent magnetic properties, as well as relatively good flexibility and stability, which meets the needs of preparing flexible magnets.

[0076] During the high-temperature reaction, due to the low vapor pressure of neodymium, some neodymium is lost at high temperatures, resulting in a lower actual neodymium content participating in the reaction. Therefore, an excess of neodymium is needed to ensure the magnetism of the material. However, the amount of neodymium should not be too much or too little, as excessive neodymium content will increase costs. In Comparative Examples 1 and 2, by adjusting the degree of neodymium excess, too low a neodymium content affects the improvement of magnetism, while too high a neodymium content will increase the brittleness of the material, affecting the processing and application of the magnet.

[0077] The temperature during the reduction-diffusion reaction affects the material's properties. The reaction temperature should not be too high or too low. In Comparative Example 3, controlling the temperature below 900℃ resulted in an incomplete reaction. In Comparative Example 4, controlling the temperature above 1200℃ caused excessive loss of neodymium metal, forming a large amount of α-Fe phase (impurity phase), which affected the magnetic properties and also reduced the material's mechanical properties.

[0078] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0079] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method of producing a flexible neodymium-iron-nitrogen magnet, characterized by, Neodymium iron alloy is prepared by reduction diffusion method, and then neodymium iron nitrogen magnetic powder is prepared by crushing, nitriding, washing, ball milling and drying process; then the neodymium iron nitrogen magnetic powder is coated and mixed with binder for intensive mixing and rolling, and after magnetization, a flexible neodymium iron nitrogen magnet is obtained; the reduction diffusion method includes the following steps: Under vacuum conditions, neodymium oxide, iron oxide powder and / or iron powder, and calcium reducing agent are thoroughly ball-milled and mixed. After mixing, the mixture is reacted under an argon atmosphere to obtain a neodymium-iron alloy. The calcium reducing agent is calcium powder and / or calcium hydride. The neodymium element is in excess by 10% to 30% based on a neodymium-iron molar ratio of 2:

17. The calcium reducing agent in the ball-milled mixture is in excess by 20% to 60%.

2. The method for preparing a flexible neodymium iron nitride magnet according to claim 1, characterized in that, The reduction-diffusion method involves a reaction temperature of 950-1200℃ and a reaction time of 2-8 hours.

3. The method for preparing a flexible neodymium iron nitride magnet according to claim 1, characterized in that, The nitriding is carried out in a heat treatment furnace at a temperature of 450~500℃ under a N2 atmosphere for 3~6 hours.

4. The method for preparing a flexible neodymium iron nitride magnet according to claim 1, characterized in that, The washing method is ultrasonic stirring washing, the cleaning medium is ultrapure water, the mass ratio of material to water is 1~10:250; the washing time is 5~10 minutes, and the washing is repeated 3~6 times; the stirring speed is 500~2000 rpm, and the ultrasonic frequency is 30~60kHz.

5. The method for preparing a flexible neodymium iron nitride magnet according to claim 4, characterized in that, The crude NdFeB-N slurry obtained after washing was ball-milled at a ball-to-material ratio of 5-10:1, a ball milling speed of 200-600 rpm, and a ball milling time of 5-16 hours.

6. The method for preparing a flexible neodymium iron nitride magnet according to claim 1, characterized in that, The drying step is as follows: the slurry after ball milling is collected and vacuum dried to obtain neodymium iron nitrogen magnetic powder with a particle size ≤10μm.

7. The method for preparing a flexible neodymium iron nitride magnet according to claim 1, characterized in that, The adhesive includes at least one of silicone rubber, nitrile rubber, ethylene propylene rubber, CPE and PVC.

8. The method for preparing a flexible neodymium iron nitride magnet according to claim 1, characterized in that, The mixing temperature is 70~200℃; The pressure of the mixing gas is 0.5~10MPa; The calendering temperature is 40~100℃; the calendering thickness is 1mm; the calendered magnetic sheet is cut and magnetized, the cutting size is 80×40mm, the magnetization voltage is 2500V, and the magnetization spacing is 4mm.

9. A flexible neodymium iron nitride magnet, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

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