Diffusion source for neodymium-iron-boron magnet as well as preparation method and application of diffusion source

Abstract

The invention relates to a diffusion source for a neodymium-iron-boron magnet and a preparation method and application of the diffusion source. The invention discloses a rare-earth metal catalyst which comprises the following components in percentage by mass: 46%-49% of an organic solvent, 0.1%-2% of an adhesive, 0.1%-5% of a metal oxide and 46%-49% of rare-earth metal, and the melting point of the metal oxide is higher than that of the neodymium-iron-boron magnet. The specific organic solvent, the adhesive, the metal oxide and the rare earth metal are matched for use according to a specific matching relation, so that the diffusion source is more stable, the diffusion effect is improved, and when the magnet attached with the diffusion source is subjected to thermal diffusion treatment, the rare earth metal can be diffused into the magnet so as to improve the coercive force and other properties of the magnet. In the process, the high-melting-point metal oxide is adhered to the surface of the magnet and then serves as a spacer, the adhesion phenomenon of the magnet in the high-temperature sintering diffusion process is reduced or avoided, grain boundary diffusion is further promoted, and the performance of the magnet is improved.

Description

Technical Field

[0001] The present application relates to the technical field of rare earth permanent magnet materials, and in particular to a diffusion source for neodymium iron boron magnets, a preparation method thereof, and an application thereof. Background Art

[0002] Permanent magnets are widely used in numerous key areas, including the Industrial Internet, new energy, high-speed rail transit, 5G communications, and intelligent manufacturing. They have become a key area in which countries around the world are competing to overcome technological challenges. Neodymium iron boron permanent magnets, with their excellent magnetic properties, hold over 50% of the permanent magnet market share.

[0003] However, sintered NdFeB has the problem of poor magnetic stability and is difficult to operate stably in high temperature environments, which greatly limits its application and further development in the field of high-tech. In order to improve the comprehensive performance of NdFeB, the main method currently used is to add heavy rare earth metals dysprosium and terbium. 14 B(Tb2Fe 14 The B) phase has a higher anisotropy field and lower magnetic saturation intensity. The addition of Dy (Tb) elements can significantly increase the coercive force and increase the Curie temperature of the magnet, thereby effectively improving the temperature stability of the magnet and enabling sintered NdFeB materials to be used in higher temperature environments.

[0004] Currently, there are two main methods for adding heavy rare earths: one is during smelting, but this method suffers from severe burnout and results in significant waste; the other is during the powder-making process, which has limited effect on improving magnet performance. Therefore, traditional techniques still need improvement. Summary of the Invention

[0005] Based on this, it is necessary to provide a diffusion source for NdFeB magnets and a preparation method thereof that can reduce the use of heavy rare earths, reduce product adhesion during high-temperature sintering, and improve magnet performance. The specific solution is as follows:

[0006] One aspect of the present application provides a diffusion source for NdFeB magnets, comprising the following components, calculated by mass percentage: 46% to 49% rare earth metal, 0.1% to 5% metal oxide, 46% to 49% organic solvent, and 0.1% to 2% adhesive; the melting point of the metal oxide is higher than the melting point of the NdFeB magnet.

[0007] In some embodiments, the mass ratio of the rare earth metal to the organic solvent is 0.9-1.1:1.

[0008] In some embodiments, the melting point of the metal oxide is 1800° C. to 2800° C.;

[0009] and / or, the particle size of the metal oxide is 25µm to 47µm;

[0010] Optionally, the metal oxide includes one or more of aluminum oxide, ceria and zirconium oxide.

[0011] In some embodiments, the particle size of the rare earth metal is less than or equal to 10 μm;

[0012] Optionally, the rare earth metal includes one or more of dysprosium, terbium, praseodymium and scandium;

[0013] and / or, the adhesive comprises one or more of polyvinyl butyral, polyvinyl acetal glue and polyvinyl alcohol;

[0014] And / or, the organic solvent includes one or more of ethanol, acetone and ethyl acetate.

[0015] Another aspect of the present application provides a method for preparing a diffusion source for NdFeB magnets, comprising the following steps: mixing an organic solvent, an adhesive, a metal oxide, and a rare earth metal to prepare a diffusion source for NdFeB magnets;

[0016] Based on the total mass of the diffusion source, the mass of the organic solvent accounts for 46% to 49%, the mass of the adhesive accounts for 0.1% to 2%, the mass of the metal oxide accounts for 0.1% to 5%, and the mass of the rare earth metal accounts for 46% to 49%; the melting point of the metal oxide is higher than the melting point of the neodymium iron boron magnet.

[0017] Another aspect of the present application provides a method for preparing a modified NdFeB magnet, comprising the following steps:

[0018] The above diffusion source is coated on at least a portion of the surface of the NdFeB magnet, and the obtained NdFeB magnet is subjected to a heating diffusion treatment to prepare a modified NdFeB magnet.

[0019] In some embodiments, based on the total mass of the diffusion source and the NdFeB magnet, the mass of the diffusion source accounts for 0.37% to 0.42%.

[0020] In some embodiments, during the heating and diffusion process, the NdFeB magnets are placed in at least one of a flat arrangement and a vertical stacking arrangement;

[0021] And / or, the temperature of the heating diffusion treatment is 800° C. to 1000° C., and the time of the heating diffusion treatment is 1 hour to 30 hours.

[0022] In some embodiments, the heating and diffusion step further includes an annealing step;

[0023] Optionally, the annealing treatment temperature is 500° C. to 700° C., and the annealing treatment time is 1 hour to 8 hours.

[0024] Another aspect of the present application provides a modified NdFeB magnet, which is prepared by the above-mentioned method for preparing the modified NdFeB magnet.

[0025] Another aspect of the present application provides a modified NdFeB magnet, which is prepared by the above-mentioned method for preparing the modified NdFeB magnet.

[0026] The diffusion source for NdFeB magnets of the present application has a specific component with a specific ratio. Among them, rare earth metals are key components for improving magnet performance. They enter the interior of the magnet through grain boundary diffusion and improve the coercive force and other properties of the magnet. Organic solvents help to evenly mix the other components and facilitate operation when coating, so that the diffusion source can be evenly covered on the magnet surface. Adhesives can firmly adhere rare earth metals and metal oxides to the magnet surface to form a stable adhesion layer, which not only ensures the stability of the metal oxides on the magnet surface so that they can better play a barrier role, but also improves the interface bonding between the diffusion source and the magnet surface, which is conducive to the uniform conduction of the diffusion process. Specific organic solvents, adhesives, metal oxides and rare earth metals are used in conjunction with specific ratios to make the diffusion source more stable and improve the diffusion effect. When the magnet attached to the diffusion source is subjected to thermal diffusion treatment, the rare earth metals will diffuse into the interior of the magnet to improve the coercive force and other properties of the magnet. During this process, high-melting-point metal oxides adhere to the surface of the magnet and act as insulators, reducing or avoiding adhesion between magnets during high-temperature sintering and diffusion, which affects subsequent processes. It can further increase the wettability of the diffusion source in the grain boundary channels inside the magnet, promote the diffusion of heavy rare earth grain boundaries, and improve the performance of the magnet.

[0027] Furthermore, the above preparation method has a simple process and is easy to operate, so that the magnet can achieve improved performance through grain boundary diffusion while avoiding the adhesion problem between magnets caused by heat treatment, thereby improving production efficiency and finally successfully preparing a modified NdFeB magnet. DETAILED DESCRIPTION

[0028] To facilitate understanding of the present application, the present application will be described in more detail below, along with preferred embodiments thereof. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure herein.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] The term "comprises", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment comprising a series of elements includes not only those elements, but also includes other elements not clearly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements limited by the sentence "comprising a ..." do not exclude the presence of other identical elements in the process, method, article or equipment comprising the elements. The indefinite articles "a" and "an" before the elements or components of the present application have no restriction on the quantity requirements (i.e., the number of occurrences) of the elements or components. Therefore, "a" or "a" should be interpreted as including one or at least one, and the elements or components in the singular also include the plural form, unless the quantity obviously refers only to the singular form. The meaning of "plurality" is at least two, for example two, three, etc., unless otherwise clearly and specifically defined.

[0031] Except as shown in the operating examples or otherwise indicated, all numbers used in the specification and claims to express the amount of ingredients, physicochemical properties, etc. are understood to be adjusted by the term "about" in all cases. For example, therefore, unless otherwise indicated, the numerical parameters listed in the above specification and the appended claims are approximate values, and those skilled in the art will be able to appropriately change these approximate values using the teachings disclosed herein to seek to obtain the desired properties. The use of numerical ranges expressed as endpoints includes all numbers within the range and any range within the range, for example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4 and 5, etc.

[0032] As shown in the background technology, in the conventional technology, the abundance of heavy rare earth elements in the earth's crust is very low and the reserves are limited, resulting in a high price of heavy rare earth elements, which greatly increases the cost of adding heavy rare earth elements to produce high-performance magnets. Research results show that grain boundary diffusion processing technology, as a relatively mature means at present, is effective for improving the coercive force of sintered NdFeB. Grain boundary diffusion technology mainly uses coating, adhesion, evaporation, sputtering and other methods to make heavy rare earth elements or their compounds adhere to the magnet surface, and then diffuse and penetrate them through heat treatment and perform tempering treatment, so as to regulate the magnet composition, optimize the microstructure organization and then improve the coercive force of the magnet. In the large-scale production process, in order to ensure production efficiency, the magnets with heavy rare earth elements need to be stacked and loaded into the sintering furnace. However, in the high-temperature diffusion sintering stage, under vacuum, when the sintering temperature reaches the melting point of neodymium metal, the neodymium-rich phase of the magnet is easily converted into a liquid phase, which makes the stacked magnets produce adhesion on the surfaces in contact with each other. In severe cases, the sintered product can become damaged and scrapped due to adhesion. Currently, the common industrial method is to use molybdenum wire sheets or other materials as separators between the magnets for layered sintering. However, these separators are not only expensive and dense, but also increase the number of placement steps and reduce the loading capacity of the NdFeB magnets, further increasing production costs.

[0033] Based on this, one embodiment of the present application provides a diffusion source for NdFeB magnets, which includes the following components, calculated by mass percentage: 46% to 49% rare earth metals, 0.1% to 5% metal oxides, 46% to 49% organic solvents, and 0.1% to 2% adhesives; the melting point of the above-mentioned metal oxides is higher than the melting point of the NdFeB magnets.

[0034] The diffusion source for NdFeB magnets of the present application has a specific component with a specific ratio. Among them, rare earth metals are key components for improving magnet performance. They enter the interior of the magnet through grain boundary diffusion and improve the coercive force and other properties of the magnet. Organic solvents help to evenly mix the other components and facilitate operation when coating, so that the diffusion source can be evenly covered on the magnet surface. Adhesives can firmly adhere rare earth metals and metal oxides to the magnet surface to form a stable adhesion layer, which not only ensures the stability of the metal oxides on the magnet surface so that they can better play a barrier role, but also improves the interface bonding between the diffusion source and the magnet surface, which is conducive to the uniform conduction of the diffusion process. Specific organic solvents, adhesives, metal oxides and rare earth metals are used in conjunction with specific ratios to make the diffusion source more stable and improve the diffusion effect. When the magnet attached to the diffusion source is subjected to thermal diffusion treatment, the rare earth metals will diffuse into the interior of the magnet to improve the coercive force and other properties of the magnet. During this process, high-melting-point metal oxides adhere to the surface of the magnet and act as insulators, reducing or avoiding adhesion between magnets during high-temperature sintering and diffusion, which affects subsequent processes. It can further increase the wettability of the diffusion source in the grain boundary channels inside the magnet, promote the diffusion of heavy rare earth grain boundaries, and improve the performance of the magnet.

[0035] It should be noted that the range of rare earth metal values is "46% to 49%", which means the minimum and maximum values within the range of 46% to 49%, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values in the embodiments and the following point values: 46.0%, 46.1%, 46.2%, 46.3%, 46.4%, 46.5%, 46.6%, 46.7%, 46.8%, 46.9%, 47.0%, 47.1%, 47.2%, 47.3%, 47.4%, 47.5%, 47.6%, 47.7%, 47.8%, 47.9%, 48.0%, 48.1%, 48.2%, 48.3%, 48.4%, 48.5%, 48.6%, 48.7%, 48.8%, 48.9%, or 49%; or a range consisting of any two of these values, including, for example, 47% to 49%.

[0036] The value range of the metal oxide is "0.1%~5%", which means that the minimum value and maximum value in the range of 0.1%~5% can be taken, as well as every value between the minimum value and the maximum value. Specific examples include, but are not limited to, the point values in the embodiments and the following point values: 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9% or 5.0%; or a range consisting of any two of these values, including, by way of example, 0.1% to 4%.

[0037] The range of the organic solvent is "46% to 49%", which means the minimum and maximum values in the range of 46% to 49%, and every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values in the embodiments and the following point values: 46.0%, 46.1%, 46.2%, 46.3%, 46.4%, 46.5%, 46.6%, 46.7%, 46.8%, 46.9%, 47.0%, 47.1%, 47.2%, 47.3%, 47.4%, 47.5%, 47.6%, 47.7%, 47.8%, 47.9%, 48.0%, 48.1%, 48.2%, 48.3%, 48.4%, 48.5%, 48.6%, 48.7%, 48.8%, 48.9%, or 49%; or a range consisting of any two of these values, including, for example, 47% to 49%.

[0038] The value range of the adhesive is "0.1% to 2%", which means the minimum and maximum values in the range of 0.1% to 2%, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values in the embodiments and the following point values: 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2.0%; or a range consisting of any two of these values, including, for example, 0.5% to 2%.

[0039] In some embodiments, the mass ratio of the rare earth metal to the organic solvent is 0.9-1.1:1.

[0040] It can be understood that controlling the rare earth metal and the organic solvent within the above-mentioned specific range can ensure the addition amount of the rare earth metal, and sufficient organic solvent can ensure the fluidity of the rare earth element, so that it can be better coated on the product surface.

[0041] In some embodiments, the composition includes the following components, calculated by mass percentage: 48% to 49% organic solvent, 0.5% to 1.5% binder, 2% to 4% metal oxide, and 48% to 49% rare earth metal.

[0042] Furthermore, by controlling the composition ratio of the diffusion source within the preferred range, the diffusion source is used in the preparation process of the NdFeB magnet so that the magnets do not adhere to each other during high-temperature sintering and the magnet performance is better.

[0043] In a specific example, the composition includes the following components, calculated by mass percentage: 48.5% organic solvent, 1% binder, 3% metal oxide, and 48.5% rare earth metal.

[0044] In some embodiments, the melting point of the metal oxide is 1800°C to 2800°C.

[0045] In some embodiments, the particle size of the metal oxide is 25 μm to 47 μm.

[0046] It can be understood that the metal oxide forms an isolation layer on the surface of the magnet. During high-temperature heat treatment, due to its large particle size, it can effectively prevent the neodymium-rich liquid phase of adjacent magnets from directly contacting each other on the contact surface, thereby avoiding adhesion between the magnets and reducing product damage and scrap.

[0047] In some embodiments, the metal oxide includes one or more of aluminum oxide, ceria, and zirconium oxide.

[0048] In some embodiments, the particle size of the rare earth metal is less than or equal to 10 μm.

[0049] In some embodiments, the chemical formula of the NdFeB magnet is (PrNd) 27 Dy 2.0 Ho 2.5 Fe 66.8 Al 0.3 Co 0.5 B 0.9 The melting point of the above-mentioned NdFeB magnet is 1200°C~1500°C.

[0050] In some embodiments, the rare earth metal includes one or more of dysprosium, terbium, praseodymium, and scandium.

[0051] In some embodiments, the adhesive includes one or more of polyvinyl butyral, polyvinyl acetal glue, and polyvinyl alcohol.

[0052] In some embodiments, the organic solvent includes one or more of ethanol, acetone and ethyl acetate.

[0053] Another embodiment of the present application further provides a method for preparing a diffusion source for NdFeB, comprising the following steps: mixing an organic solvent, an adhesive, a metal oxide, and a rare earth metal to prepare a diffusion source for NdFeB magnets;

[0054] Based on the total mass of the above-mentioned diffusion sources, the mass of the organic solvent accounts for 46%~49%, the mass of the adhesive accounts for 0.1%~2%, the mass of the metal oxide accounts for 0.1%~5%, and the mass of the rare earth metal accounts for 46%~49%; the melting point of the above-mentioned metal oxides is higher than the melting point of the neodymium iron boron magnet.

[0055] Another embodiment of the present application provides a method for preparing a modified NdFeB magnet, comprising the following steps: coating the above-mentioned diffusion source on at least a portion of the surface of the NdFeB magnet, and heating and diffusing the obtained NdFeB magnet to prepare a modified NdFeB magnet.

[0056] In some embodiments, based on the mass of the NdFeB magnet, the mass of the diffusion source accounts for 0.37% to 0.42%.

[0057] In some embodiments, during the heating and diffusion process, the NdFeB magnets are placed in at least one of a flat arrangement and a vertical stack.

[0058] Furthermore, the vertical stacking is stacked one on top of another in the horizontal direction.

[0059] It is understood that the coated magnets should be placed with their longest side, smallest area, facing downward, based on the NdFeB magnet's specifications, to maximize the number of magnets placed. For example, if the NdFeB magnets are thin sheets, the sheets can be stood upright, overlapping at their largest areas, and stacked upright. Because the magnets are placed close together, the heavy rare earth layers formed on their surfaces can interpenetrate each other, which can enhance diffusion to a certain extent.

[0060] In some embodiments, the temperature of the heating diffusion treatment is 800° C. to 1000° C., and the time of the heating diffusion treatment is 1 hour to 30 hours.

[0061] It should be noted that the temperature range of the heat diffusion treatment is "800°C to 1000°C", that is, the minimum and maximum values within the range of 800°C to 1000°C, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the points in the embodiments and the following points: 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, and 1000°C; or a range consisting of any two of these values, including, for example, 900°C to 1000°C.

[0062] The time range for the heating diffusion treatment is "1 hour to 30 hours", that is, the minimum and maximum values within the range of 1 hour to 30 hours, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values in the embodiments and the following point values: 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, 25 hours, 26 hours, 27 hours, 28 hours, 29 hours, or 30 hours; or a range consisting of any two of these values, including, for example, 20 hours to 30 hours.

[0063] In some embodiments, the heating and diffusion step further includes an annealing step.

[0064] In some embodiments, the annealing temperature is 500° C. to 700° C., and the annealing time is 1 hour to 8 hours.

[0065] Furthermore, the above preparation method has a simple process and is easy to operate, so that the magnet can achieve improved performance through grain boundary diffusion while avoiding the adhesion problem between magnets caused by heat treatment, and finally successfully prepares a modified NdFeB magnet.

[0066] One embodiment of the present application further provides a modified NdFeB magnet, which is prepared using the above-mentioned method for preparing the modified NdFeB magnet.

[0067] The modified NdFeB magnet has both good coercivity and squareness.

[0068] The present application will be described below in conjunction with specific embodiments, but the present application is not limited to the following embodiments. It should be understood that the attached claims summarize the scope of the present application. Under the guidance of the concept of the present application, those skilled in the art should realize that certain changes made to the various embodiments of the present application will be covered by the spirit and scope of the claims of the present application.

[0069] In order to make the purpose, technical solutions and advantages of this application more concise and clear, this application is illustrated with the following specific examples, but this application is by no means limited to these examples. The embodiments described below are only preferred embodiments of this application and can be used to describe this application. They should not be understood as limiting the scope of this application. It should be pointed out that any modifications, equivalent replacements and improvements made within the spirit and principles of this application should be included in the scope of protection of this application.

[0070] Example 1

[0071] 1. Preparation of diffusion sources for NdFeB magnets

[0072] The diffusion source was prepared by mixing dysprosium, alcohol (99.5% by mass), a binder (polyvinyl butyral), and cerium oxide in a mass ratio of 48.5%:48.5%:1%:3%.

[0073] 2. Preparation of NdFeB Magnets

[0074] (1) Select brand 40SH magnets and cut the original magnet blanks into 6 mm thick blocks with length and width of 20*20 cm respectively.

[0075] (2) Clean the oil stains on the surface of the magnet and dry it, then use sandpaper to remove the surface oxide layer.

[0076] (3) Place the diffusion magnet in the coating equipment, control the spraying process (control the chain running speed to 2.8 Hz, the preheating temperature to 100 ° C, and the reciprocating speed of the spray gun to 500 mm / s), and adhere the above-mentioned diffusion source to the surface of the magnet. Based on the mass of the magnet, the mass of the above-mentioned diffusion source accounts for 0.4%, and a magnet with attached diffusion source is obtained.

[0077] (4) The magnets with the diffusion source attached are stood up, with the longest side with the smallest area (the area of the length multiplied by the thickness) facing downward, and are stacked tightly, that is, one on top of another in the horizontal direction and one on top of another in the vertical direction in a heat treatment container. The magnets with the diffusion source attached are then heat treated at 900°C for 25 hours, and then tempered at 500°C for 5 hours to obtain modified NdFeB magnets.

[0078] (5) The prepared modified NdFeB magnet was subjected to performance testing.

[0079] Example 2

[0080] The preparation method of the NdFeB magnet in Example 2 is basically the same as that in Example 1, except that the magnet is placed in a different way in step (4). The magnet with the diffusion source attached is laid flat with the longest side with the largest area (the area of length multiplied by width) facing downward in the sintering heat treatment container and loaded in a layered manner using partitions such as molybdenum wire mesh.

[0081] Other step conditions and parameters are the same as those in Example 1.

[0082] Example 3

[0083] The preparation method of the NdFeB magnet in Example 3 is basically the same as that in Example 1, except that the composition ratio of the diffusion source is different, specifically, the mass ratio of dysprosium, alcohol (99.5% by mass), adhesive (specifically polyvinyl butyral) and alumina is 48.5%:48.5%:1%:3%.

[0084] Other step conditions and parameters are the same as those in Example 1.

[0085] Example 4

[0086] The preparation method of the NdFeB magnet in Example 4 is basically the same as that in Example 3, except that the magnet is placed in a different way in step (4). The magnet with the diffusion source attached is laid flat with the longest side and the largest area facing downward in the sintering heat treatment container and loaded in a layered manner using partitions such as molybdenum wire mesh.

[0087] Other step conditions and parameters are the same as those in Example 1.

[0088] Example 5

[0089] The preparation method of the NdFeB magnet in Example 5 is basically the same as that in Example 1, except that the composition ratio of the diffusion source is different, specifically, dysprosium, alcohol, adhesive and alumina are mixed in a mass ratio of 49%:48%:0.5%:0.5%.

[0090] Other step conditions and parameters are the same as those in Example 1.

[0091] Example 6

[0092] The preparation method of the NdFeB magnet in Example 6 is basically the same as that in Example 1, except that the composition ratio of the diffusion source is different, specifically, dysprosium, alcohol, adhesive and alumina are mixed in a mass ratio of 46%:47%:2%:5%.

[0093] Other step conditions and parameters are the same as those in Example 1.

[0094] Example 7

[0095] The preparation method of the NdFeB magnet in Example 7 is basically the same as that in Example 1, except that the composition ratio of the diffusion source is different, specifically, the mass ratio of terbium, alcohol, adhesive and cerium oxide is 48.5%:48.5%:1%:3%.

[0096] Other step conditions and parameters are the same as those in Example 1.

[0097] Example 8

[0098] The preparation method of the NdFeB magnet in Example 8 is basically the same as that in Example 1, except that the composition ratio of the diffusion source is different, specifically, the mass ratio of dysprosium, alcohol, adhesive and zirconium oxide is 48.5%:48.5%:1%:3%.

[0099] Other step conditions and parameters are the same as those in Example 1.

[0100] Comparative Example 1

[0101] The preparation methods of the NdFeB magnets in Comparative Example 1 are basically the same as those in Example 1, except that the composition ratio of the diffusion source is different, specifically, the mass ratio of dysprosium, alcohol, adhesive and alumina is 49.5%:49.5%:1%:0%.

[0102] Other step conditions and parameters are the same as those in Example 1.

[0103] Comparative Example 2

[0104] The preparation methods of the NdFeB magnets in Comparative Example 2 and Comparative Example 1 are basically the same, with the only difference being that the magnets are placed differently in step (4). The magnets with the diffusion source attached are laid flat with the longest side and the largest area facing downward in a sintering heat treatment container, and are loaded in a layered manner using partitions such as molybdenum wire mesh.

[0105] Other step conditions and parameters are the same as those in Example 1.

[0106] Comparative Example 3

[0107] The preparation method of the NdFeB magnet in Comparative Example 3 is basically the same as that in Example 1, except that the composition ratio of the diffusion source is different, specifically, dysprosium, alcohol, adhesive and alumina are mixed in a mass ratio of 44%:52%:1%:3%.

[0108] Other step conditions and parameters are the same as those in Example 1.

[0109] Comparative Example 4

[0110] The preparation method of the NdFeB magnet in Comparative Example 4 is basically the same as that in Example 1, except that a rare earth metal, an organic solvent, and an adhesive are first mixed on the surface of the magnet to form a rare earth coating layer, and then a high-temperature resistant metal oxide layer is superimposed on the rare earth coating layer, specifically:

[0111] (1) Select brand 40SH magnets and cut the original magnet blanks into 6mm thick blocks.

[0112] (2) Clean the oil stains on the surface of the magnet and dry it, then use sandpaper to remove the surface oxide layer.

[0113] (3) Place the diffusion magnet in a coating device and spray a rare earth coating layer: mix dysprosium, alcohol and an adhesive to obtain a mixed liquid, apply the mixture to the surface of the magnet by spraying, and dry it to form a rare earth coating layer; then, perform a high-temperature resistant alumina attachment treatment on the magnet with the rare earth coating layer to obtain a high-temperature resistant layer, thereby preparing a magnet with an attached diffusion source.

[0114] (4) The above magnets are stood up, with the longest side and the smallest area facing downward, and tightly stacked in a heat treatment container. The above magnets are then heat treated at 900°C for 25 hours, and then tempered at 500°C for 5 hours to obtain modified NdFeB magnets.

[0115] (5) The prepared modified NdFeB magnets were subjected to the following performance tests.

[0116] 1. The modified NdFeB magnets prepared in each embodiment and comparative example were subjected to remanence tests, specifically referring to the national standard GB / T 41967-2022;

[0117] 2. The coercivity of the modified NdFeB magnets prepared in each embodiment and comparative example was tested, specifically referring to the national standard GB / T 41967-2022;

[0118] 3. The maximum magnetic energy product test was performed on the modified NdFeB magnets prepared in each embodiment and comparative example, with specific reference to the national standard GB / T 41967-2022;

[0119] 4. The squareness of the modified NdFeB magnets prepared in each embodiment and comparative example was tested, specifically referring to the national standard GB / T 41967-2022. The specific results are shown in Table 1 below.

[0120] Table 1

[0121]

[0122] Table 1 shows the performance data of the magnets from Examples 1-8 and Comparative Examples 1-4. It shows that, compared with Example 2, the coercivity of the magnets sintered in Example 1, where the high-melting-point metal is adhered to the surface with an adhesive and placed in close contact, is approximately 0.47 kOe higher than that of the magnets sintered in layers using molybdenum wire mesh. This is likely due to the close placement of the magnets, which results in surface-to-surface contact. At high temperatures, the adhesive film decomposes, allowing cross-diffusion between the magnets and indirectly increasing the concentration of the heavy rare earth diffusion source. Furthermore, the products exhibit no adhesion and are completely separated.

[0123] Compared with Example 4, the coercivity of the magnet sintered in Example 3, in which the high-melting-point metal was adhered to the surface with an adhesive and placed in close contact, was approximately 0.43 kOe higher than that of the magnet sintered in layers using molybdenum wire mesh. This is likely due to the close contact between the product surfaces. At high temperatures, the adhesive film decomposes, allowing cross-diffusion between the magnets, which in turn increases the concentration of heavy rare earth diffusion sources. Furthermore, the products exhibited no adhesion and were completely separated.

[0124] In Comparative Examples 1 and 2, the coercivity of the magnets sintered with a high-melting-point metal adhered to the surface with an adhesive in close contact was approximately 0.32 kOe higher than that of the magnets sintered in layers using molybdenum wire mesh. This is likely due to the close contact between the product surfaces. At high temperatures, the adhesive film decomposes, allowing cross-diffusion between the magnets and indirectly increasing the concentration of heavy rare earth diffusion sources. However, the products adhered, and some were not completely separated.

[0125] In summary, compared with the magnets prepared in the comparative example, the magnets prepared in the embodiments of the present application have reduced product adhesion and less reduction in remanence, and have a significantly increased coercive force, thereby improving magnet performance.

[0126] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0127] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A diffusion source for NdFeB magnets, characterized in that: Calculated by mass percentage, the invention comprises the following components: 46% to 49% rare earth metal, 0.1% to 5% metal oxide, 46% to 49% organic solvent and 0.1% to 2% adhesive; the melting point of the metal oxide is higher than that of the neodymium iron boron magnet.

2. The diffusion source according to claim 1, wherein The mass ratio of the rare earth metal to the organic solvent is 0.9-1.1:

1.

3. The diffusion source according to any one of claims 1 to 2, characterized in that The melting point of the metal oxide is 1800° C. to 2800° C.; and / or, the particle size of the metal oxide is 25µm to 47µm; Optionally, the metal oxide includes one or more of aluminum oxide, ceria and zirconium oxide.

4. The diffusion source according to any one of claims 1 to 2, characterized in that The particle size of the rare earth metal is less than or equal to 10µm; Optionally, the rare earth metal includes one or more of dysprosium, terbium, praseodymium and scandium; and / or, the adhesive comprises one or more of polyvinyl butyral, polyvinyl acetal glue and polyvinyl alcohol; And / or, the organic solvent includes one or more of ethanol, acetone and ethyl acetate.

5. A method for preparing a diffusion source for NdFeB magnets, characterized in that: The method comprises the following steps: mixing an organic solvent, an adhesive, a metal oxide and a rare earth metal to prepare a diffusion source for a neodymium iron boron magnet; Based on the total mass of the diffusion source, the mass of the organic solvent accounts for 46% to 49%, the mass of the adhesive accounts for 0.1% to 2%, the mass of the metal oxide accounts for 0.1% to 5%, and the mass of the rare earth metal accounts for 46% to 49%; the melting point of the metal oxide is higher than the melting point of the neodymium iron boron magnet.

6. A method for preparing a modified NdFeB magnet, characterized in that: The steps include: The diffusion source according to any one of claims 1 to 4 is coated on at least a portion of the surface of a NdFeB magnet, and the obtained NdFeB magnet is subjected to a heating diffusion treatment to prepare a modified NdFeB magnet.

7. The method for preparing a modified NdFeB magnet according to claim 6, wherein: Based on the mass of the NdFeB magnet, the mass of the diffusion source accounts for 0.37% to 0.42%.

8. The method for preparing modified NdFeB according to any one of claims 6 to 7, wherein: During the heating and diffusion process, the NdFeB magnets are placed in at least one of a flat arrangement and a vertical stacking arrangement; And / or, the temperature of the heating diffusion treatment is 800° C. to 1000° C., and the time of the heating diffusion treatment is 1 hour to 30 hours.

9. The method for preparing a modified NdFeB magnet according to any one of claims 6 to 7, wherein: The step of heating and diffusion treatment further includes an annealing step; Optionally, the annealing treatment temperature is 500° C. to 700° C., and the annealing treatment time is 1 hour to 8 hours.

10. A modified NdFeB magnet, characterized in that: The modified NdFeB magnet is prepared by the preparation method of any one of claims 6 to 9.

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