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Method for preparing rare earth permanent magnetic material

A technology of rare earth permanent magnets and permanent magnets, which is applied in the fields of magnetic materials, inductors/transformers/magnets manufacturing, electrolytic coatings, etc. It can solve the problems of waste of heavy rare earth metals, increase the price of magnets, increase the number of processes, etc., and reduce the amount of heavy rare earths , the cost-effective advantage of the product, and the effect of improving the coercive force

Active Publication Date: 2012-11-14
ADVANCED TECHNOLOGY & MATERIALS CO LTD
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Problems solved by technology

[0003] However, at present, coating, sticking and sputtering are used to make the surface of the sintered magnet with metal powder or compound of heavy metal element Dy / Tb, and then heat treatment makes Dy / Tb diffuse into the main phase of the sintered magnet through the grain boundary to improve The method of magnetic properties has some problems to be solved urgently: (1) The method of attaching Dy or Tb to the surface of NdFeB sintered magnet by sputtering method has low productivity and high process cost, and a large amount of rare earth metals are scattered in the heating furnace during the evaporation process. chamber, resulting in unnecessary waste of heavy rare earth metals
(2) The method of attaching the fluoride or oxide powder of Dy or Tb to the surface of the magnet and heating it, or the method of filling the mixed powder of these powders and hydrogenated Ca powder with a magnet and heating it is also as follows, the number of steps increases, and the cost In addition, the NdFeB magnet is machined, the surface is cleaned by cleaning, pickling, etc., and then it is set to a state where surface treatment such as nickel plating or aluminum ion plating can be performed, and fluoride or oxide powder is attached to the magnet. After heating, a surface layer consisting of oxides or fluorides in which part of Dy or Tb is substituted for Nd will be formed on the surface. Although the operation of attaching fluoride or oxide powders is cheap, removing such The surface layer process will also increase the price of the magnet; there is also the problem of limited coercive force improvement when the surface is coated with rare earth oxides or fluorides and heated and diffused.
At present, the study of improving the coercivity by depositing layered rare earth hydroxides (LRHs) onto the surface of NdFeB and treating the magnet with grain boundary diffusion has not been reported so far.

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  • Method for preparing rare earth permanent magnetic material
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  • Method for preparing rare earth permanent magnetic material

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preparation example Construction

[0031] The above-mentioned LRHs can be obtained by the following preparation method: slowly drop the mixed alkali solution into the vigorously stirred rare earth metal cation solution, the speed of the vigorously stirred is 500~1500r / min, when the pH value of the system reaches 6.7-6.9 , stop adding the mixed alkali solution dropwise, and then mechanically stir the slurry at room temperature for 30 minutes to crystallize the slurry at 100-120°C for 24-48 hours, then filter, wash and dry to obtain LRHs powder, wherein the mixed The alkali solution is an aqueous solution with a concentration of sodium hydroxide of 0.1-0.4 mol / L and a concentration of soluble sodium salt of 0.1-0.3 mol / L, and the total concentration of rare-earth metal cations in the rare-earth metal cation solution is 0.1-0.4 mol / L , can be one or more rare earth metal cations, and the rare earth metal cation solution or the mixed alkali solution contains X, that is, the interlayer anion.

[0032] The NdFeB perm...

Embodiment 1

[0041] (1) Prepare Tb(NO at a concentration of 0.1mol / L 3 ) 3 Aqueous solution, placed in a four-necked bottle; weigh solid NaOH and solid NaNO respectively 3 , and then add water to make NaOH concentration 0.1mol / L, NaNO 3 Concentration is the mixed alkali solution of 0.1mol / L; The above-mentioned mixed alkali solution is slowly added dropwise to the above-mentioned Tb(NO 3 ) 3 In the solution, when the pH value of the system reaches 6.80, stop adding the mixed alkali solution dropwise, move the slurry to the reaction kettle after mechanical stirring at room temperature for 30 minutes, crystallize at 120°C for 24 hours, filter, wash, and dry to obtain a layered Rare earth hydroxide (Tb) 2 (OH) 5 NO 3 ·nH 2 O powder (n=2~5);

[0042] (2) The sintered NdFeB magnet is processed into thin slices with the specifications shown in Table 1, soaked in a degreasing tank for 10 minutes to remove the oil on the surface of the magnet, and then wash the surface with water and then ...

Embodiment 2

[0046] (1) Prepare a Dy(NO3)3 solution with a concentration of 0.2mol / L and place it in a four-necked bottle; prepare 0.15mol / L NaOH and 0.2mol / L NaNO 3 The mixed alkali solution; the mixed alkali solution was slowly added dropwise to the vigorously stirred Dy(NO3) solution, and when the pH value of the system reached 6.85, the dropwise addition of the mixed alkali solution was stopped, and the slurry was transferred after 30 minutes of mechanical stirring at room temperature. into the reaction kettle, crystallized at 120°C for 24h, filtered, washed, and dried to obtain layered rare earth hydroxide (Dy) 2 (OH) 5 NO 3 ·nH 2 O powder (n=2~5);

[0047] (2) The sintered NdFeB magnet is processed into thin slices with the specifications shown in Table 1, soaked in a degreasing tank for 10 minutes to remove the oil on the surface of the magnet, and then wash the surface with water and then use dilute HNO 3 Pickling for about 40s, then washing with water, ultrasonic treatment for...

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Abstract

The invention provides a method for preparing a rare earth permanent magnetic material, which belongs to the technical field of rare earth permanent magnetic materials. The method takes the colloidal solution of LRHs powder as a cathode electrophoretic solution, an NdFeB permanent magnet which is undergone surface pretreatment is subjected to cathode electrophoresis, and through controlling the electrophoretic voltage and the electrophoretic time, an attachement film which has the preset thickness and is rich in heavy rare earth elements is obtained on the surface of the NdFeB permanent magnet; and then, the NdFeB permanent magnet which is adhered with the attachement film is subjected to vacuum heat treatment, cooling treatment and tempering sequentially, and thus the NdFeB rare earth permanent magnetic material with improved performance is obtained. The coercive force of the NdFeB rare earth permanent magnetic material which is obtained by the method is obviously improved, and can be improved by 2000-7000Oe before the treatment; compared with non-treatment, the coercive force of the treated sintered NdFeB permanent magnetic material can be improved by 10-50%, and meanwhile, the residual magnetism is basically not reduced obviously, and is only lowered by 1-2%; and in addition, the usage of the heavy rear earth is greatly reduced.

Description

technical field [0001] The invention belongs to the technical field of rare earth permanent magnet materials, and particularly relates to a preparation method of rare earth permanent magnet materials. The method is to deposit layered rare earth hydroxides (LRHs) on the surface of neodymium iron boron (NdFeB) and perform high temperature treatment and low temperature aging. Thereby improving the magnet performance. Background technique [0002] NdFeB permanent magnet material is a functional material with a wide range of applications, and its applications in hybrid vehicles, wind power and other fields are expanding day by day. Since magnets are required to work at high temperatures for a long time in these fields, magnets are required to have higher coercivity (Hcj). An effective way to increase the coercive force of NdFeB sintered magnets is to replace the main phase Nd of the magnet with heavy rare earth elements such as Dy and Tb. 2 Fe 14 Nd in B, forming (Nd, Dy) 2 F...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C25D13/02H01F1/053
CPCH01F41/0293
Inventor 周磊王琳李建喻晓军
Owner ADVANCED TECHNOLOGY & MATERIALS CO LTD
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