阅读说明：本技术 用于提高稀土永磁体的矫顽磁场强度的钕的电化学沉积 (Electrochemical deposition of neodymium for increasing coercive field strength of rare earth permanent magnets ) 是由 M.鲁里格 G.萨潘 于 2015-09-14 设计创作，主要内容包括：本发明涉及一种用于制备稀土永磁体、特别是高能稀土永磁体的方法,其包括步骤：-制备具有稀土基的硬磁性纳米复合材料(S1)的永磁体基体；-在所述永磁体基体上电化学沉积轻稀土材料钕Nd(S2)；-在涂有钕Nd的永磁体基体上进行晶界扩散处理(S3)；以及相应地制备稀土永磁体。(The invention relates to a method for producing rare earth permanent magnets, in particular high-energy rare earth permanent magnets, comprising the steps of: -preparing a permanent magnet matrix of hard magnetic nanocomposite material with a rare earth base (S1); -electrochemically depositing a light rare earth material neodymium, Nd, on said permanent magnet matrix (S2); -performing grain boundary diffusion treatment on the neodymium Nd coated permanent magnet matrix (S3); and a rare earth permanent magnet prepared accordingly.)

1. A method for producing rare earth permanent magnets, in particular high-energy rare earth permanent magnets, comprising the steps of:

-preparing a permanent magnet matrix of hard magnetic nanocomposite material with a rare earth base (S1);

-electrochemically depositing a light rare earth material neodymium, Nd, on said permanent magnet matrix (S2); and

-performing grain boundary diffusion treatment on the Nd coated permanent magnet matrix (S3).

2. The method according to claim 1, characterized in that the electrochemical deposition is carried out in an ionic liquid.

3. The method according to claim 2, characterized in that the ionic liquid is free of water.

4. A process according to claim 2 or 3, characterized in that the cation of the ionic liquid is selected from tetraalkylphosphonium, trialkylthio-nium, tetraalkylammonium radicals, 1-dialkylpyrrolidinium, 1, 3-dialkylimidazolium and/or 1,2, 3-trialkylimidazolium.

5. The method according to claim 4, wherein the alkyl groups each independently have 1 to 14 carbon atoms.

6. The method according to claim 4 or 5, characterized in that the radicals Ri are independently selected and comprise from 1 to 20 carbon atoms and comprise branched or unbranched alkyl, cycloalkyl, heteroalkyl, oligoether, oligoester, oligoamide and/or oligoacrylamide.

7. A process according to claim 6, characterised in that the oligoether substituent has the structure [ -CH₂-CH₂-O-]_nWherein the integer n is 1-10.

8. A process according to claim 6 or 7, characterised in that the oligoester substituent has the structure [ -CH₂-CO-O-]_nWherein the integer n is 1-10.

9. The process as claimed in claim 6, 7 or 8, characterized in that the oligomeric amide substituent has the structure [ -CO-NR-]_nWherein the integer n is 1-10.

10. The method of claim 6, 7, 8 or 9, wherein the oligopolyacrylamide substituent has the structure [ -CH ]₂-CHCONH₂-]_nWherein the integer n is 1-10.

11. The method according to claim 6, 7, 8, 9 or 10, characterized in that the branched or unbranched alkyl, cycloalkyl and/or heteroalkyl group has additional groups.

12. A method according to claim 11, characterised in that the additional groups comprise ethoxy groups, methoxy groups, ester groups, amide groups, carbonate groups and/or nitrile groups.

13. Process according to one of claims 6 to 12, characterized in that the alkyl, cycloalkyl and/or heteroalkyl, branched or unbranched, is partially or fully fluorinated.

14. Process according to one of claims 2 to 13, characterized in that the anion of the ionic liquid is selected from perfluoroacetate, perfluoroalkylsulfonate, bis (fluorosulfonyl) imide, bis (perfluoroalkylsulfonyl) imide, tris (perfluoroalkyl) trifluorophosphate, bis (perfluoroalkyl) tetrafluorophosphate, penta (perfluoroalkyl) fluorophosphate, hexafluorophosphate, tris (perfluoroalkyl) methide, tetracyanoborate, perfluoroalkylborate, tetrafluoroborate and/or mixed borate ions.

15. The process according to claim 14, characterized in that if more than one perfluoroalkyl group is comprised in the anion, the perfluoroalkyl groups are each independently selectable.

16. Method according to one of claims 2 to 15, characterized in that neodymium is dissolved as a neodymium salt in the ionic liquid.

17. A method according to claim 16, characterized in that the anode dissolves neodymium as a metal or from a metal salt.

18. The method according to claim 16 or 17, characterized in that said neodymium salt is chosen from nd (III) halides, neodymium (III) bis (perfluoroalkylsulfonyl) imide, neodymium alcoholates, neodymium perfluoroacetate, neodymium tetrafluoroborate or neodymium hexafluorophosphate.

19. A method according to claim 16, 17 or 18, wherein said neodymium salt is constituted by an anion which is the same as or chemically similar to the anion of said ionic liquid.

20. A method according to claim 19, characterised in that a neodymium salt free of water is used.

21. A rare earth permanent magnet, especially a high-energy rare earth permanent magnet, is characterized in that neodymium (Nd) is electrochemically deposited on a permanent magnet matrix containing rare earth in the preparation process, and then grain boundary diffusion treatment is carried out.

22. Rare earth permanent magnet according to claim 21, characterized in that it is prepared according to the method of one of claims 1 to 20.

Technical Field

The invention relates to a rare earth permanent magnet, in particular to a preparation method of a high-energy rare earth permanent magnet and the corresponding rare earth permanent magnet.

Background

Nowadays, Nd-Fe-B based nanoscale permanent magnets are attracting attention because of their special properties. In particular, rare earth-poor alloys prepared in a nano state by rapid solidification are currently under special investigation. So-called MQ powders or so-called HDDR powders are produced in the nano-state by rapid solidification. Those alloys and methods of preparation that do not require or require only small additions of heavy rare earth metals (e.g., Dy or Tb) are considered particularly attractive. The prime mover of these studies is primarily the material issue for the metal. The key mechanism for achieving the coercive field strength (also called coercivity) in the nanoscale material is based on the fact that the crystallite size in the material can be adjusted below the so-called single domain size. The monodomain nature combined with the large crystalline anisotropy of the substrate (phase 2-14-1) leads to significantly more difficult repeated magnetization of the material and to the possibility of omitting as far as possible the addition of heavy rare earth metals which are otherwise added to increase the coercive field strength. Since magnets composed of these alloys are generally prepared by hot pressing, the total rare earth content can be significantly reduced, unlike conventional sintered NdFeB magnets. Conventional sintering with high rare earth residuals can cause grain growth in nanoscale powders and thus deteriorate hard magnetic properties. The fundamental role as a characteristic feature of sintered magnets is of course lost due to the lack of rare earth-rich grain boundary phases in the nanocomposite. Here, a rare earth-rich, non-magnetic grain boundary phase is formed during sintering. Such a neodymium-rich non-magnetic phase between the crystal grains has, in addition to the sintering action (in particular in the case of liquid-phase sintering), also Nd of a single hard magnetic nature₂Fe₁₄Magnetic decoupling of the B grains. This phase makes a decisive contribution to the improvement of the coercive field strength through said decoupling.

Neodymium alloys containing, for example, Nd and Cu are disclosed in [1] "Sepehri-Amin et al, script Material 63,1124-1127(2010)", in which neodymium is introduced into the material by mixing with HDDR-treated NdFeB powder in a powder metallurgy process.

Disclosure of Invention

The object of the invention is to provide a method for producing rare earth permanent magnets, in particular high-energy rare earth permanent magnets, having a higher coercive field strength than conventional, in particular Nd-Fe-B-based, nanoscale permanent magnets, wherein the method should be able to be carried out faster and more economically than in the prior art.

The technical problem is solved by a method according to the main claim and a corresponding rare earth permanent magnet according to the side-by-side claims.

According to a first aspect, a method for producing a rare earth permanent magnet, in particular a high-energy rare earth permanent magnet, is proposed comprising the following steps:

-preparing a permanent magnet matrix of hard magnetic nanocomposite material with a rare earth base;

-electrochemically depositing a light rare earth material neodymium, Nd, on said permanent magnet matrix;

grain Boundary Diffusion (Grain Boundary Diffusion) treatment on a permanent magnet matrix coated with neodymium Nd.

The coated magnetic material of the permanent magnet matrix should be effectively improved by coating or deposition.

According to a second aspect, a rare earth permanent magnet, in particular a high-energy rare earth permanent magnet, is proposed, during the preparation of which neodymium Nd is electrochemically deposited on a rare earth-containing permanent magnet matrix, followed by a grain boundary diffusion treatment.

The deposition of neodymium on different substrates may be performed in different applications. In the present invention, the deposition of neodymium on a rare earth-based permanent magnet is used for subsequent grain boundary diffusion, thereby increasing the coercive field strength with negligible influence on magnetization.

Further advantageous embodiments are protected in conjunction with the dependent claims.

According to an advantageous embodiment, the electrochemical deposition can be carried out in an ionic liquid. The method for electrochemically depositing terbium on a substrate or base is carried out in an ionic liquid.

According to another advantageous embodiment, the ionic liquid may be free of water. Electrochemical deposition of metals is known and used on an industrial scale.

According to a further advantageous embodiment, the ionic liquid may comprise a cation selected from tetraalkylphosphonium (tetraalkylphosphonium), Trialkylsulfonium (Trialkylsulfonium), tetraalkylammonium radical (tetraalkylammonium), 1-Dialkylpyrrolidinium (1,1-Dialkylpyrrolidinium), 1, 3-dialkylimidazolium (1, 3-dialkylimidazolium) and/or 1,2,3-Trialkylimidazolium (1,2, 3-Trialkylimidazolium).

According to another advantageous embodiment, the alkyl groups can each independently have from 1 to 14 carbon atoms. The conductive material has the conductivity of 1-200 mS/cm, the electrochemical window of 4-6V wide and the thermal stability of 400 ℃.

According to a further advantageous embodiment, the radicals Ri (R1 to R4) are independently selectable and comprise from 1 to 20 carbon atoms and comprise branched or unbranched alkyl, cycloalkyl, heteroalkyl, oligoether substituents, oligoester substituents, oligoamide substituents and/or oligoacrylamide substituents.

According to another advantageous embodiment, the oligoether substituent has the structure [ -CH₂-CH₂-O-]_nWherein the integer n is 1-10 and is terminated with H.

According to another advantageous embodiment, the oligoester substituent has the structure [ -CH₂-CO-O-]_nWherein the integer n is 1-10 and is terminated with H.

According to a further advantageous embodiment, the oligomeric amide substituent (Oligoamid-Substitenen) has the structure [ -CO-NR-]_nWherein the integer n is 1 to 10 and is terminated with H, wherein R is hydrogen or alkyl (e.g., methyl).

Similarly, the oligomeric amide substituent has the structure [ -CO-NR-]_nThe structure of the oligoacrylamide substituent is [ -CH₂-CHCONH₂-]_nWherein the integer n is 1-10 and is terminated with H.

If the radicals R1 to R4(Ri) are selected from alkyl, cycloalkyl, heteroalkyl having branched or unbranched C1 to C20, the radicals may at the same time also have additional ether group substituents, such as ethoxy, methoxy, etc., ester group substituents, amide group substituents, carbonate group substituents, nitrile group substituents, or halogen substituents, and in particular they may be partially or fully fluorinated. The basic structure is shown in fig. 2.

In order to satisfy the above conditions, suitable anions to be combined with the cation of the present invention are selected from perfluoroacetate (perfluoroacetate), perfluoroalkylsulfonate (perfluoralkylsufonate), bis (fluorosulfonyl) imide (bis (fluorosulfonyl) imide), bis (perfluoroalkylsulfonyl) imide (bis (perfluoroalkylsulfonyl) imide), tris (perfluoroalkyl) trifluorophosphate (tris (perfluoroalkylphosphate) trifluorphosphate), bis (perfluoroalkyl) tetrafluorophosphate (bis (perfluoroalkylphosphate) Tetrafluoroborate), penta (perfluoroalkyl) fluorophosphate (penta (perfluoroalkyl) fluorophosphate), Hexafluorophosphate (hexafluorofluorophosphate), tris (perfluoroalkyl) methide (perfluoroborate), Tetracyanoborate (perfluoroalkylborate), Tetrafluoroborate (Tetrafluoroborate), and Tetrafluoroborate (Tetrafluoroborate) mixed anions.

If more than one perfluoroalkyl group is included in the anion, these perfluoroalkyl groups may each independently be different perfluoroalkyl groups.

According to the method of the invention, the neodymium salt is dissolved in a suitable ionic liquid as described above. This can be done either by anodic dissolution of the metal in the ionic liquid or by anodic dissolution of a suitable metal salt in the ionic liquid.

Suitable neodymium salts may be, for example, nd (III) halides, neodymium (III) bis (perfluoroalkylsulfonyl) imide (neodym (III) bis (perfluoroalkylsulfonyl) imide), neodymium alcoholate (alkoxide), neodymium perfluoroacetate, neodymium tetrafluoroborate, neodymium hexafluorophosphate.

Preferably, a neodymium salt containing no water should be used and consisting of an anion which is identical or chemically similar to the anion of the ionic liquid used.

Drawings

The invention is described in detail according to embodiments with reference to the accompanying drawings. The figures show:

FIG. 1 shows an embodiment of the method of the present invention;

FIGS. 2a-f show examples of basic structures of cations proposed by the present invention;

fig. 3a-e show examples of the basic structure of the anions proposed by the present invention.

Detailed Description

An embodiment of the method of the invention is described with reference to fig. 1. The method relates to the preparation of rare earth permanent magnets, in particular high-energy rare earth permanent magnets, having a step S1: preparing a permanent magnet matrix with rare earth; s2: electrochemically depositing a rare earth material, namely neodymium (Nd), on the permanent magnet substrate; s3: a permanent magnet substrate coated with neodymium was subjected to grain boundary diffusion treatment.

In the case of using a rare earth-poor alloy prepared in a nanocrystalline state by rapid solidification, a preferred example of the permanent magnet matrix with rare earth is a Nd-Fe-B-based nanoscale permanent magnet. Alloys should also be used which are feasible with no or only a small addition of heavy rare earth metals. In particular, hard magnetic nanocomposites should be effectively improved in terms of coercive field strength. The coercive field strength should be effectively increased compared to conventional permanent magnets.

According to the present invention, a process is proposed with which hard magnetic nanocomposites, preferably prepared by hot pressing or by thermoforming (e.g. pressing (strangpress)), can subsequently be endowed with a non-magnetic grain boundary phase. In this way it is also possible to prevent exchange interactions between the grains in the nanocomposite and thus to increase the coercive field strength.

For this purpose, a heat treatment similar to what is known as grain boundary diffusion or grain boundary diffusion (korngren-diffusion-procezes) is proposed, which introduces the material from the outside along the grain boundaries into the interior of the magnet. The material is then preferably deposited along grain boundaries. The heat treatment should be used to store neodymium for the case of poor neodymium grain boundaries. The method comprises first applying a Nd layer on the magnet by means of electrolysis. The Nd layer forms a diffusion source during subsequent thermal processing. In this case, neodymium Nd diffuses into the inside along the grain boundary of the magnet and decouples the nanocrystal grains. In this way, the coercive field strength of the magnet is increased without further addition of heavy rare earth elements.

In order to form a thin Nd layer on a substrate, some physical (i.e. sputtering) and chemical vapor deposition methods, such as CVD or ALD, are known to those skilled in the art. The disadvantage of this method is that the evaporation time is extremely long for the production of thick layers (i.e. in the μm range) necessary for improved magnetic properties. Furthermore, the purchase and maintenance of the coating equipment is extremely expensive.

Electrochemical deposition of metals has long been well known and used commercially on a large scale. The aqueous medium is mainly used in electroplating, since the redox potential of most technically relevant metals is within the electrochemical window of the water bath used. Neodymium, as a rare earth element, has a redox potential of-2.32, and therefore falls outside the electrochemical window for water. Another reason to avoid the use of an aqueous medium is the substrate itself. Thermoformed or hot pressed Nd-Fe-B magnets are extremely sensitive to water reactions because they themselves contain high levels of rare earth metals. In the case of contact with water, the rare earth metal element is oxidized and generates hydrogen gas which further embrittles and damages the magnet. Reactive elements, such as aluminum, are separated industrially from organic solutions. Many serious fires have occurred due to the use of such volatile and flammable organic solvents. This precludes the use of such solvents. An electrochemical method for the deposition of terbium from a high-temperature molten salt such as NaCl/KCl at a temperature of 700 ℃ is known (see [2] "Yasuda et al, electrochim. acta,92,349-355 (2013)"). However, high temperature molten salts are extremely corrosive and the required operating temperatures preclude the use of numerous substrates or permanent magnet matrices. Furthermore, there are safety concerns during operation and high operating costs due to high energy consumption.

The invention is therefore also based on the provision of an advantageous method for the electrochemical deposition of neodymium under anhydrous conditions.

Fig. 2 shows an example of the basic structure of the cation proposed by the present invention. Figure 2a shows imidazolium. Fig. 2b shows Pyridinium (Pyridinium). Figure 2c shows pyrrolidinium. Figure 2d shows ammonium ions. FIG. 2e shows phosphonium. Figure 2f shows a sulfonium.

Fig. 3 shows an example of the basic structure of the anion proposed by the present invention. FIG. 3a shows Trifluoromethane Sulfonate (triflate-Sulfonate). Figure 3b shows Dicyanamide (Dicyanamide). Figure 3c shows hexaalkylphosphate. FIG. 3d shows bis (trifluoromethylsulfonyl) imide (bis (trifluoromethylsulfonyl) imide). Figure 3e shows tetrafluoroborate.