Sintered neodymium-iron-boron magnet and method for producing the same

Abstract

The present disclosure relates to a sintered Nd-Fe-B magnet and a preparation method thereof, the preparation method comprising the following steps: subjecting a Nd-Fe-B magnet on which a heavy rare earth element film is deposited to diffusion heat treatment and annealing heat treatment under vacuum to obtain the sintered Nd-Fe-B magnet; wherein the temperature of the diffusion heat treatment is lower than the temperature of the annealing heat treatment. The preparation method defined in the present disclosure can not only save the amount of heavy rare earth elements but also improve the magnetic properties of the magnet.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of permanent magnetic materials, in particular to a sintered Nd-Fe-B magnet and a preparation method thereof, in particular to a grain boundary diffusion Ce-based sintered Nd-Fe-B magnet and a preparation method thereof. BACKGROUND

[0002] Nd-Fe-B magnets are increasingly used due to their excellent magnetic properties and are widely used in medical magnetic resonance imaging, computer hard drives, audio, mobile phones, etc. With the requirements of energy saving and low-carbon economy, Nd-Fe-B magnets have also begun to be applied in automotive parts, household appliances, energy-saving and control motors, hybrid electric vehicles, wind power generation, etc. With the rapid development of new energy vehicles and wind power generation, heavy rare earth (HER) grain boundary diffusion technology (GBD technology) has gradually become the most commonly used means to improve sintered Nd-Fe-B magnets.

[0003] However, with the wide application of grain boundary diffusion sintered Nd-Fe-B magnets, the demand for rare earths has also experienced rapid and unbalanced growth. On the one hand, the use of praseodymium (Pr), neodymium (Nd), terbium (Tb), dysprosium (Dy) in existing rare earth permanent magnets, which have low crust abundance, has led to rapid consumption and soaring prices of the above rare earths. On the other hand, the large accumulation of rare earths such as cerium (Ce, which is only 5% of the price of Pr / Nd) with high crust abundance and low price has caused a great imbalance in resource utilization, and environmental pollution during the separation of rare earths.

[0004] In order to solve the above problems, grain boundary diffusion Ce-based sintered Nd-Fe-B magnets have emerged as one of the important directions of rare earth permanent magnet research, and have important application and research value. However, most of the current research still follows the traditional grain boundary diffusion process, resulting in low magnetic properties of the grain boundary diffusion Ce-based sintered Nd-Fe-B magnets.

[0005] Therefore, it is necessary to provide a new preparation method of grain boundary diffusion Ce-based sintered Nd-Fe-B magnets. SUMMARY

[0006] In order to solve the above technical problems, the present disclosure provides a sintered Nd-Fe-B magnet and a preparation method thereof.

[0007] In a first aspect, the present disclosure provides a preparation method of a sintered Nd-Fe-B magnet, the preparation method comprising the following steps:

[0008] diffusion heat treatment and annealing heat treatment on the Nd-Fe-B magnet on which the heavy rare earth element film is deposited under vacuum to obtain the sintered Nd-Fe-B magnet;

[0009] wherein the temperature of the diffusion heat treatment is lower than the temperature of the annealing heat treatment.

[0010] As a preferred technical solution of the present disclosure, the diffusion heat treatment has a temperature of 650-800℃ and a time of 10-30h.

[0011] As a preferred technical solution of the present disclosure, the annealing heat treatment has a temperature of 850-950℃ and a time of 4-30h.

[0012] As a preferred technical solution of the present disclosure, the Nd-Fe-B magnet is a Ce-based sintered Nd-Fe-B magnet, and has a general structure of (Ce 0.3+x R 0.7-x ) y Fe z T m B n , wherein:

[0013] R is any combination of Pr and Nd;

[0014] T is any combination of transition metals Co, Al, Mn, Cu, Ga and Si;

[0015] 0≤x≤0.3, 28≤y≤32, 65≤z≤72, 0≤m≤2, 0.8≤n≤1.1.

[0016] As a preferred technical solution of the present disclosure, the preparation method of the Nd-Fe-B magnet with a heavy rare earth film comprises:

[0017] S1: pretreating the Nd-Fe-B magnet;

[0018] S2: forming a heavy rare earth element film on the surface of the pretreated Nd-Fe-B magnet.

[0019] As a preferred technical solution of the present disclosure, the pretreatment method comprises polishing or polishing after removing the surface oxide layer.

[0020] As a preferred technical solution of the present disclosure, the method for forming the heavy rare earth element film comprises a coating method commonly used for rare earth permanent magnet grain boundary diffusion, such as spraying, magnetron sputtering, electrophoretic deposition or screen printing.

[0021] The heavy rare earth element contained in the heavy rare earth element film is Dy and / or Tb.

[0022] As a preferred technical solution of the present disclosure, the preparation method comprises:

[0023] (1) polishing treatment or polishing treatment after removing the surface oxide layer on the Ce-based sintered Nd-Fe-B magnet;

[0024] (2) sputtering deposition of heavy rare earth elements on the surface of the pretreated Ce-based sintered Nd-Fe-B magnet to form a heavy rare earth element film.

[0025] (3) under vacuum, the Ce-based sintered neodymium-iron-boron magnet on which the heavy rare earth element film is deposited is subjected to heat diffusion treatment at 650-800 DEG C for 10-30 h, and then is heated to 850-950 DEG C for annealing heat treatment for 4-30 h, to obtain the sintered neodymium-iron-boron magnet.

[0026] In a second aspect, the disclosure provides a sintered neodymium-iron-boron magnet prepared by the preparation method of the first aspect.

[0027] In a third aspect, the disclosure provides an application of the sintered neodymium-iron-boron magnet of the second aspect in the preparation of energy exchange materials.

[0028] The technical scheme provided by the embodiments of the disclosure has the following advantages compared with the prior art:

[0029] (1) The preparation method defined in the disclosure can not only save the amount of heavy rare earth elements but also improve the magnetic properties of the magnet;

[0030] (2) The heat treatment time of the disclosure is short, which can greatly shorten the preparation time and has a higher cost performance;

[0031] (3) The sintered neodymium-iron-boron magnet obtained by the preparation method provided by the disclosure has more excellent magnet properties and can be better applied to the preparation of energy exchange materials. DETAILED DESCRIPTION

[0032] In order to more clearly understand the above-mentioned purposes, features and advantages of the disclosure, the schemes of the disclosure will be further described below. It should be noted that the embodiments of the disclosure and the features in the embodiments can be combined with each other without conflict.

[0033] In the following description, many specific details are set forth in order to provide a thorough understanding of the disclosure, but the disclosure can also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only a part of the embodiments of the disclosure, not all the embodiments.

[0034] In the prior art, in order to solve the imbalance of rare earth element consumption, and at the same time to optimize the performance of neodymium-iron-boron magnet, Ce element is introduced into the neodymium-iron-boron magnet to form a Ce-based neodymium-iron-boron magnet, and at the same time the performance of the neodymium-iron-boron magnet can be further improved by diffusion technology. However, the magnetic properties of the existing grain boundary diffusion Ce-based neodymium-iron-boron magnet are still not high enough to meet the application requirements. Therefore, the disclosure provides a new preparation method of sintered neodymium-iron-boron magnet.

[0035] In a first aspect, the disclosure provides a preparation method of a sintered neodymium-iron-boron magnet, the preparation method comprising the following steps:

[0036] The sintered Nd-Fe-B magnet is subjected to diffusion heat treatment and annealing heat treatment under vacuum to obtain the sintered Nd-Fe-B magnet.

[0037] The temperature of the diffusion heat treatment is lower than the temperature of the annealing heat treatment.

[0038] The present disclosure uses a lower temperature for diffusion first, so that the heavy rare earth diffuses along the grain boundary and does not replace the crystal grain when entering the magnet, which can effectively enter the heavy rare earth and slow down the growth of the magnet crystal grain, thus reducing the amount of heavy rare earth; when the heavy rare earth enters the magnet along the grain boundary, a higher temperature is used for treatment, which can make the heavy rare earth replace the crystal grain to form a hard (Nd, HRE)2·Fe 14 The hard magnetic shell further improves the magnetic performance of the magnet; therefore, the preparation method defined in the present disclosure can not only save the amount of heavy rare earth but also improve the magnetic performance of the magnet.

[0039] As a preferred technical solution of the present disclosure, the temperature of the diffusion heat treatment is 650-800℃, for example, 660℃, 680℃, 700℃, 720℃, 730℃, 750℃, 760℃, 780℃, etc., and the time is 10-30h, for example, 12h, 15h, 18h, 20h, 22h, 25h, 28h, etc.

[0040] As a preferred technical solution of the present disclosure, the temperature of the annealing heat treatment is 850-950℃, for example, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, etc., and the time is 4-30h, for example, 5h, 10h, 15h, 20h, 25h, etc.

[0041] Compared with the sintered Nd-Fe-B magnet obtained by using high temperature for diffusion first and then using low temperature for annealing in the prior art, the sintered Nd-Fe-B magnet obtained by the preparation method provided by the present disclosure saves a large amount of heavy rare earth under the same magnet performance, and greatly improves the performance of the magnet under the same amount of heavy rare earth, and the heat treatment time of the present disclosure is short, which can greatly shorten the preparation time and has a higher cost performance.

[0042] As a preferred technical solution of the present disclosure, the Nd-Fe-B magnet is a Ce-based sintered Nd-Fe-B magnet, and the structural general formula is (Ce 0.3+x R 0.7-x ) y Fe z T m B n , wherein:

[0043] R is any combination of Pr and Nd;

[0044] T is any combination of transition metals Co, Al, Mn, Cu, Ga and Si;

[0045] 0≤x≤0.3, 28≤y≤32, 65≤z≤72, 0≤m≤2, 0.8≤n≤1.1.

[0046] The "R" and "T" described in the present disclosure not only represent one element, but also can be a combination of multiple elements, when it is a combination of multiple elements, the relative molar amount of all elements added together meets 0.7-x, and the same applies to T. For example:

[0047] The Ce-based sintered Nd-Fe-B magnet is (Ce 0.3 Pr 0.05 Nd 0.65 ) 30 Fe 67.7 Co1Ga 0.1 Al 0.2 B1, in the above structure, R is a combination of Pr and Nd, and the sum of the two is 0.7 (x=0), T is a combination of Co, Ga and Al, and the sum of the three is 1.3.

[0048] For another example:

[0049] The Ce-based sintered Nd-Fe-B magnet is (Ce 0.5 Pr 0.1 Nd 0.4 ) 32 Fe 66.4 Ga 0.5 Al 0.2 B 0.9 , in the above structure, R is a combination of Pr and Nd, and the sum of the two is 0.5 (x=0.2), T is a combination of Ga and Al, and the sum of the three is 0.7.

[0050] As a preferred technical solution of the present disclosure, the preparation method of the Nd-Fe-B magnet deposited with heavy rare earth film comprises:

[0051] S1: pretreating the Nd-Fe-B magnet;

[0052] S2: forming a heavy rare earth element film on the surface of the pretreated Nd-Fe-B magnet.

[0053] A pure and smooth magnet surface is conducive to the subsequent deposition of heavy rare earth elements, therefore, as a preferred technical solution of the present disclosure, the pretreatment method comprises polishing or removing the surface oxide layer and then polishing.

[0054] The polishing method is not limited in the present disclosure as long as the surface of the magnet is smooth and clean. As an embodiment of the present disclosure, the polishing method or the polishing method after removing the surface oxide layer includes:

[0055] The Nd-Fe-B magnet is polished by using 800, 1500, and 2000 mesh sandpaper in sequence, polishing the surface, or removing the oxide layer on the surface of the magnet by means of dilute acid cleaning, and then polishing the surface, etc. as long as the surface of the magnet is smooth and clean, which is beneficial to the close deposition of heavy rare earth.

[0056] As a preferred technical solution of the present disclosure, the method for forming the heavy rare earth element film includes spraying, magnetron sputtering, electrophoretic deposition, or screen printing, which are common coating methods for rare earth permanent magnet grain boundaries. Preferably, the method is magnetron sputtering.

[0057] As a preferred technical solution of the present disclosure, the heavy rare earth element contained in the heavy rare earth element film is Dy and / or Tb.

[0058] As a preferred technical solution of the present disclosure, when the method for forming the heavy rare earth element film is the magnetron sputtering, the sputtering step includes:

[0059] The pretreated Nd-Fe-B magnet is sputtered by using high-purity Tb (99.9wt%), Dy (99.9wt%), or TbDy alloy (99.9wt%), wherein the vacuum is extracted to 5×10 -4 Pa or below, high-purity argon is filled, the working gas pressure is 0.5-2 Pa, and the sputtering power is 70-100 W.

[0060] As an embodiment of the present disclosure, the sputtering step includes: placing the polished Nd-Fe-B magnet into a magnetron sputtering sample table, placing high-purity Tb (99.9wt%), Dy (99.9wt%), or TbDy alloy (99.9wt%) in the corresponding strong magnetic target position, extracting the vacuum to 5×10 -4 Pa or below, filling high-purity argon, the working gas pressure is 0.5-2 Pa, the sputtering power is 70-100 W, and the sputtering time is controlled to obtain heavy rare earth element films with different thicknesses.

[0061] As a preferred technical solution of the present disclosure, the thickness of the heavy rare earth element film is 0.1-0.4% of the thickness of the pretreated Nd-Fe-B magnet, for example, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, etc.

[0062] In the present disclosure, 0.1-0.4% of the thickness of the Nd-Fe-B magnet is understood as:

[0063] For Nd-Fe-B magnets, the number of faces of the required heavy rare earth element film is N, and the thickness of the single-face heavy rare earth element film is (0.1-0.4%) / N, for example:

[0064] When the Nd-Fe-B magnet only needs a single-face film, the thickness of the single-face heavy rare earth element film is (0.1-0.4%) / 1, i.e. 0.1-0.4% of the thickness of the Nd-Fe-B magnet;

[0065] When the Nd-Fe-B magnet needs a two-face film, the thickness of the heavy rare earth element film on each face is (0.1-0.4%) / 2, i.e. 0.05-0.2% of the thickness of the Nd-Fe-B magnet;

[0066] When the Nd-Fe-B magnet needs a six-face film, the thickness of the heavy rare earth element film on each face is (0.1-0.4%) / 6, i.e. 0.016-0.06% of the thickness of the Nd-Fe-B magnet.

[0067] That is, the volume or weight of the sputtering material and the raw material is used in a certain proportion, and since the density is basically unchanged, the total amount of heavy rare earth elements is certain whether it is a single face or multiple faces.

[0068] As a preferred technical solution of the present disclosure, the preparation method comprises:

[0069] (1) polishing or polishing after removing the surface oxide layer of the Ce-based sintered Nd-Fe-B magnet;

[0070] (2) sputtering deposition of heavy rare earth elements on the surface of the pretreated Ce-based sintered Nd-Fe-B magnet to form a heavy rare earth element film;

[0071] (3) under vacuum, the Ce-based sintered Nd-Fe-B magnet with the heavy rare earth element film is subjected to thermal diffusion treatment at 650-800℃ for 10-30h, and then heated to 850-950℃ for annealing heat treatment for 4-30h to obtain the sintered Nd-Fe-B magnet.

[0072] In the second aspect, the present disclosure provides a sintered Nd-Fe-B magnet prepared by the preparation method of the first aspect.

[0073] In the third aspect, the present disclosure provides an application of the sintered Nd-Fe-B magnet of the second aspect in the preparation of energy exchange materials.

[0074] The sintered Nd-Fe-B magnet prepared by the preparation method provided by the present disclosure has more excellent magnet performance and can be better applied in the preparation of energy exchange materials.

[0075] The following is illustrated by specific examples:

[0076] Example 1

[0077] The embodiment provides a preparation method of a sintered neodymium-iron-boron magnet, as follows:

[0078] (1) Initial magnet pretreatment

[0079] Ce-based sintered neodymium-iron-boron magnets with a structural formula of (Ce 0.3 Pr 0.05 Nd 0.65 ) 30 Fe 67.7 Co1Ga 0.1 Al 0.2 B1 are cut into 50*30*3mm square samples, wherein the sample size along the c-axis direction is 3mm;

[0080] The cut samples are polished on the surface with 800, 1500 and 2000 mesh sandpaper in sequence;

[0081] (2) Heavy rare earth element film deposition

[0082] The polished neodymium-iron-boron magnet is placed into a magnetron sputtering sample table, high-purity Dy (99.9wt%) is placed in a corresponding strong magnet target position, vacuum is extracted to 5*10 -4 Pa, high-purity argon is filled, the gas flow is adjusted to adjust the working gas pressure to 1Pa, the sputtering power is 100W, and the sputtering time is controlled to obtain a Dy layer with a thickness of 2um (4um in total, 0.13% of the thickness of the neodymium-iron-boron magnet) on both sides (the sputtering layer is perpendicular to the c-axis of the magnet);

[0083] (3) Vacuum heat treatment

[0084] The magnet with the deposited heavy rare earth element film is placed into a vacuum heat treatment furnace, vacuum is extracted to 5*10 -4 Pa, and the following heat treatment program is set:

[0085] first, thermal diffusion treatment is performed at 650 DEG C for 30h, and then annealing heat treatment is performed at 900 DEG C for 4h;

[0086] After the heat treatment is completed, the furnace cavity is naturally cooled to room temperature, and the sintered neodymium-iron-boron magnet (sintered neodymium-iron-boron magnet after grain boundary diffusion) is taken out.

[0087] Embodiment 2

[0088] The embodiment provides a preparation method of a sintered neodymium-iron-boron magnet.

[0089] The difference from the embodiment 1 is that, in the embodiment, the initial Ce-based sintered neodymium-iron-boron magnet is (Ce 0.5 Pr 0.1 Nd 0.4 ) 32 Fe 66.4 Ga 0.5Al 0.2 B 0.9 The heat treatment procedure is as follows:

[0090] First, heat diffusion treatment is performed at 700℃ for 20h, and then annealing heat treatment is performed at 900℃ for 16h.

[0091] Example 3

[0092] This example provides a preparation method of sintered neodymium-iron-boron magnet, as follows:

[0093] (1) Initial magnet pretreatment

[0094] Ce-based sintered neodymium-iron-boron magnets with the structural formula (Ce 0.35 Nd 0.65 ) 29 Fe 69.81 Ga 0.3 B 0.89 are cut into 50x10x7mm cubic samples, wherein the sample size along the c-axis direction is 7mm;

[0095] The cut samples are polished on the surface with 800, 1500, and 2000 mesh sandpaper in sequence;

[0096] (2) Heavy rare earth element film deposition

[0097] The polished neodymium-iron-boron magnet is placed into a magnetron sputtering sample table, high-purity Tb (99.9wt%) is placed in the corresponding strong magnetic target position, vacuum is extracted to 5x10 -4 Pa or below, 99.999% high-purity argon gas is filled, the gas flow is adjusted to adjust the working gas pressure to 2Pa, the sputtering power is 70W, and the sputtering time is controlled to obtain a Tb layer with a thickness of 6μm on both sides (a total of 12μm, which is 0.17% of the thickness of the neodymium-iron-boron magnet) (the sputtering layer is perpendicular to the c-axis of the magnet);

[0098] (3) Vacuum heat treatment

[0099] The magnet with the deposited heavy rare earth element film is placed into a vacuum heat treatment furnace, vacuum is extracted to 5x10 -4 Pa or below, and the following heat treatment procedure is set:

[0100] First, heat diffusion treatment is performed at 750℃ for 30h, and then annealing heat treatment is performed at 890℃ for 30h;

[0101] After the heat treatment is completed, the furnace cavity is naturally cooled to room temperature and taken out, obtaining a sintered neodymium-iron-boron magnet (sintered neodymium-iron-boron magnet after grain boundary diffusion).

[0102] Example 4

[0103] This example provides a preparation method of sintered neodymium-iron-boron magnet.

[0104] The difference from Example 1 is that in this example, the initial Ce-based sintered neodymium-iron-boron magnet is (Ce 0.5 Pr 0.2 Nd 0.3 ) 32 Fe 66.6 Cu 0.2 Al 0.2 B1, the heat treatment procedure is:

[0105] First, heat diffusion treatment is performed at 800°C for 10h, and then annealing heat treatment is performed at 900°C for 8h.

[0106] Example 5

[0107] This example provides a method for preparing a sintered neodymium-iron-boron magnet.

[0108] The difference from Example 1 is that in this example, the initial Ce-based sintered neodymium-iron-boron magnet is (Ce 0.6 Pr 0.4 ) 28 Fe 69.7 Co 0.8 Cu 0.2 Al 0.2 B 1.1 , the heat treatment procedure is:

[0109] First, heat diffusion treatment is performed at 800°C for 15h, and then annealing heat treatment is performed at 950°C for 4h.

[0110] Example 6

[0111] This example provides a method for preparing a sintered neodymium-iron-boron magnet.

[0112] The difference from Example 1 is that in this example, by controlling the sputtering time of deposition, a Dy, Tb layer (ratio of 1:1, sputtered layer perpendicular to the c-axis of the magnet) with a thickness of 6μm on both sides (total 12μm, 0.4% of the thickness of the neodymium-iron-boron magnet) is obtained.

[0113] The heat treatment procedure is:

[0114] First, heat diffusion treatment is performed at 750°C for 20h, and then annealing heat treatment is performed at 850°C for 30h.

[0115] Comparative Example 1

[0116] This example provides a method for preparing a sintered neodymium-iron-boron magnet.

[0117] The only difference from Example 1 is that the heat treatment procedure is different, in this comparative example, the heat treatment procedure is:

[0118] First heat diffusion treatment at 900°C for 4h, then annealing heat treatment at 600°C for 5h.

[0119] Comparative Example 2

[0120] This comparative example provides a method for preparing a sintered neodymium-iron-boron magnet.

[0121] The difference from Example 2 is only in the heat treatment procedure, in this comparative example, the heat treatment procedure is:

[0122] First heat diffusion treatment at 900°C for 16h, then annealing heat treatment at 500°C for 5h.

[0123] Comparative Example 3

[0124] This comparative example provides a method for preparing a sintered neodymium-iron-boron magnet.

[0125] The difference from Example 1 is only in the heat treatment procedure, in this comparative example, the heat treatment procedure is:

[0126] First heat diffusion treatment at 900°C for 4h, then heat treatment at 650°C for 30h.

[0127] Comparative Example 4

[0128] This comparative example provides a method for preparing a sintered neodymium-iron-boron magnet.

[0129] The difference from Example 1 is only in the heat treatment procedure, in this comparative example, the heat treatment procedure is:

[0130] First heat diffusion treatment at 900°C for 30h, then heat treatment at 650°C for 4h.

[0131] Comparative Example 5

[0132] This comparative example provides a method for preparing a sintered neodymium-iron-boron magnet, which is the initial (Ce 0.3 Pr 0.05 Nd 0.65 ) 30 Fe 67.7 Co1Ga 0.1 Al 0.2 B1of Example 1.

[0133] Performance Test

[0134] The sintered neodymium-iron-boron magnets provided in Examples 1-6 and Comparative Examples 1-5 were tested for performance, in the following manner:

[0135] The permanent magnetic performance of the samples was measured using a hysteresis loop instrument, and the results are shown in Table 1:

[0136] Table 1

[0137]

[0138] It can be known from the examples and performance tests that the sintered neodymium-iron-boron magnet prepared by the preparation method provided by the present disclosure has a higher coercivity and a higher magnetic property, and the preparation of the Ce-based sintered neodymium-iron-boron magnet is realized.

[0139] It can be known from the comparison of Example 1 and Comparative Example 5 that, compared with the initial neodymium-iron-boron magnet, the coercivity of the sintered neodymium-iron-boron magnet obtained by Example 1 is increased by more than 4 kOe, which has a large amplitude of increase; it can be known from the comparison of Example 1 and Comparative Examples 1, 3 and 4, and the comparison of Example 2 and Comparative Example 2 that, compared with the sintered neodymium-iron-boron magnet prepared by the traditional grain boundary diffusion method, the magnetic property of the magnet can be maximally improved by using the heat treatment procedure defined by the present disclosure.

[0140] In Example 2, the coercivity of the initial neodymium-iron-boron magnet is 7.12 kOe, and the coercivity of the sintered neodymium-iron-boron magnet obtained by Example 2 is increased by more than 2 kOe.

[0141] In Example 3, the coercivity of the initial neodymium-iron-boron magnet is 9.87 kOe, and the coercivity of the sintered neodymium-iron-boron magnet obtained by Example 3 is increased by more than 6 kOe.

[0142] It should be noted that, in this document, relational terms such as“first” and“second”, and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual relationship or order between such entities or actions. Moreover, the terms“comprises”,“comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without more limitations, an element preceded by“comprises... a” does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the stated elements.

[0143] The above description is merely one specific implementation of the present disclosure, which enables a person skilled in the art to understand or implement the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to these embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of producing a sintered neodymium-iron-boron magnet, characterized by, The preparation method comprises the following steps: The sintered Nd-Fe-B magnet is obtained by diffusion heat treatment and annealing heat treatment of the Nd-Fe-B magnet on which the heavy rare earth element film is deposited under vacuum; The temperature of the diffusion heat treatment is lower than the temperature of the annealing heat treatment; The temperature of the diffusion heat treatment is 650-800℃, and the time is 10-30h; The temperature of the annealing heat treatment is 850-950℃, and the time is 4-30h; The neodymium-iron-boron magnet is a Ce-based sintered neodymium-iron-boron magnet, and the general structure is (Ce 0.3+x R 0.7-x ) y Fe z T m B n Wherein: R is any combination of Pr and Nd; T is any combination of transition metals Co, Al, Mn, Cu, Ga and Si; 0≤x≤0.3, 28≤y≤32, 65≤z≤72, 0≤m≤2, 0.8≤n≤1.

1.

2. The production method according to claim 1, characterized by, The preparation method of the Nd-Fe-B magnet on which the heavy rare earth element film is deposited comprises: S1: pretreatment of the Nd-Fe-B magnet; S2: forming a heavy rare earth element film on the surface of the pretreated Nd-Fe-B magnet.

3. The production method according to claim 2, characterized by, The pretreatment method comprises polishing or polishing after removing the surface oxide layer.

4. The production method according to claim 3, characterized by, The method for forming the heavy rare earth element film comprises spraying, magnetron sputtering, electrophoretic deposition or screen printing; The heavy rare earth element contained in the heavy rare earth element film is Dy and / or Tb.

5. The production method according to any one of claims 1 to 4, characterized by, The preparation method comprises: (1) polishing treatment or polishing treatment after removing the surface oxide layer of the Ce-based sintered Nd-Fe-B magnet; (2) sputtering deposition of heavy rare earth elements on the surface of the pretreated Ce-based sintered Nd-Fe-B magnet to form a heavy rare earth element film; (3) heat diffusion treatment of the Ce-based sintered Nd-Fe-B magnet on which the heavy rare earth element film is deposited at 650-800℃ for 10-30h under vacuum, and then annealing heat treatment at 850-950℃ for 4-30h to obtain the sintered Nd-Fe-B magnet.

6. A sintered Nd-Fe-B magnet prepared by the preparation method of any one of claims 1-5.

7. Use of the sintered Nd-Fe-B magnet of claim 6 in preparation of energy exchange materials.

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