KR102317748B1 - Magnetic material and cleaning method thereof - Google Patents

Abstract

A method of cleaning a magnetic material according to an embodiment of the present invention comprises the steps of sintering a mixture containing a rare earth metal precursor, iron, and boron in the presence of calcium to prepare a magnet powder, and the magnetic powder at room temperature with non-aqueous fatty acids and hydrocarbons. and washing using an organic solvent.

Description

Magnetic material and cleaning method thereof

The present invention relates to a magnetic material and a method for cleaning the same, and more particularly, to a method for cleaning an NdFeB-based magnetic material and a magnetic material manufactured by the method.

The NdFeB-based magnet is a permanent magnet having a composition of neodymium (Nd), a rare earth element, and Nd ₂ Fe ₁₄ B, a compound of iron and boron (B). After being developed in 1983, it has been used as a general-purpose permanent magnet for 30 years. These NdFeB-based magnets are used in various fields such as electronic information, automobile industry, medical equipment, energy, and transportation. In particular, it is used in products such as machine tools, electronic information devices, home appliances, mobile phones, robot motors, wind power generators, and small motors and drive motors for automobiles, in line with the recent trend of light weight and miniaturization.

For the general manufacture of NdFeB-based magnets, a strip/mold casting or melt spinning method based on metal powder metallurgy is known. First, in the case of the strip/mold casting method, an ingot is manufactured by melting a metal such as neodymium (Nd), iron, boron (B), etc. through heating, and coarsely pulverizing and refining the grain particles. It is a process for manufacturing micro-particles through a process. By repeating this, a powder is obtained, and an anisotropic sintered magnet is manufactured through a process of pressing and sintering under a magnetic field.

In addition, the melt spinning method melts metal elements, then pours them into a wheel rotating at a high speed, quenches them, and after jet milling and pulverization, blends them with polymers to form bonded magnets, or presses them into magnets. manufacture

However, all of these methods have problems in that a grinding process is essential, the grinding process takes a long time, and a process of coating the surface of the powder after grinding is required.

Recently, a method for producing a magnetic powder by a calcium reduction-diffusion method has been attracting attention. However, when manufactured by this method, calcium oxide (CaO) of the NdFeB-based powder particles remains, and a method for effectively removing it is required.

Embodiments are to provide a cleaning method of a magnetic material capable of removing by-products without decomposition of the magnetic material itself during cleaning of a magnetic material manufactured by a reduction-diffusion method, and a magnetic material manufactured by the method.

However, the problems to be solved by the embodiments of the present invention are not limited to the above problems and may be variously expanded within the scope of the technical idea included in the present invention.

A method of cleaning a magnetic material according to an embodiment of the present invention comprises the steps of sintering a mixture containing a rare earth metal precursor, iron, and boron in the presence of calcium to prepare a magnet powder, and the magnetic powder at room temperature with non-aqueous fatty acids and hydrocarbons. and washing using an organic solvent.

The manufacturing of the magnet powder may further include mixing a metal fluoride and magnesium.

In the step of preparing the magnet powder, the magnet powder may be prepared by a reduction-diffusion method.

Preparing the magnet powder by the reduction-diffusion method includes preparing a primary mixture by mixing neodymium oxide, boron, and iron, adding and mixing calcium to the primary mixture to prepare a secondary mixture, and It may include heating the secondary mixture to 800 degrees Celsius to 1100 degrees Celsius.

In the step of preparing the first mixture, the calcium may be mixed in the form of elemental calcium and fluoride.

The preparing of the secondary mixture may further include mixing magnesium.

The carbon number of the non-aqueous fatty acid may be at least 5 or more.

The non-aqueous fatty acid may be caprylic acid, and the hydrocarbon-based organic solvent may be isoparaffin.

The washing of the magnetic material may not use an aqueous solvent.

The magnetic material according to an embodiment of the present invention is manufactured by the cleaning method described above.

According to embodiments, the decomposition of the manufactured magnetic material may be prevented by allowing the residual reducing agent and by-product to react with the non-aqueous fatty acid and washing at room temperature using a hydrocarbon-based organic solvent.

1 is a graph showing an XRD pattern of a magnet powder cleaned according to Example 1 of the present invention.
FIG. 2 is a graph showing an XRD pattern of a magnet powder cleaned according to Comparative Example 1. FIG.

Hereinafter, with reference to the accompanying drawings, various embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily implement them. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In addition, throughout the specification, when a part "includes" a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.

A method of cleaning a magnetic material according to an embodiment of the present invention comprises the steps of sintering a mixture containing a rare earth metal precursor, iron, and boron in the presence of calcium to prepare a magnet powder, and the magnetic powder at room temperature with non-aqueous fatty acids and hydrocarbons. and washing using an organic solvent. Here, the rare earth metal precursor may be a metal oxide, and the metal oxide may include neodymium.

The manufacturing of the magnet powder may further include mixing a metal fluoride and magnesium. The metal fluoride may include CaF ₂ and CuF ₂ . The metal fluoride and magnesium are uniformly mixed with the rare earth metal precursor, iron and boron, so that the particle size and size of the magnetic powder particles to be manufactured can be controlled.

In the step of preparing the magnet powder, the magnet powder may be prepared by a reduction-diffusion method. The reduction-diffusion method of preparing the magnet powder includes preparing a primary mixture by mixing neodymium oxide, boron, and iron, adding and mixing calcium to the primary mixture to prepare a secondary mixture, and the It may include heating the secondary mixture to 800 degrees Celsius to 1100 degrees Celsius.

In this manufacturing method, raw materials such as neodymium oxide, boron, and iron are mixed, and Nd ₂ Fe ₁₄ B alloy powder is formed by reduction and diffusion of the raw materials at a temperature of 800 degrees Celsius to 1100 degrees Celsius. In this step, metal fluoride and magnesium are uniformly mixed in the raw material, so that the particle size and size of the magnet powder particles to be manufactured can be adjusted. In particular, the size of the alloy powder produced by adjusting the size of the iron powder used as a raw material can be adjusted.

Calcium according to the present embodiment may be included in the form of fluoride while being included as a calcium element as a raw material.

However, when the magnet powder is manufactured by the calcium reduction-diffusion method, calcium oxide and/or calcium hydroxide, which are by-products generated in the manufacturing process, are formed, and a process for removing them is required.

According to an embodiment of the present invention, Nd ₂ Fe ₁₄ B by, washed at room temperature using a hydrocarbon-based organic solvent and the residue reducing agent and reduction by-products generated in the process for preparing the alloy powder to react with the non-aqueous fatty Nd ₂ Fe ₁₄ Residual reducing agent and reduction by-products can be removed without decomposition of alloy B powder itself. In this embodiment, the non-aqueous fatty acid is a material that is immiscible with water.

Conventionally, in order to remove CaO, washing was performed using water or a weak acid using water as a solvent. However, there is a problem in that the manufactured magnet powder particles are exposed to oxygen in the aqueous solution during the cleaning process, and the surface of the manufactured magnet powder particles is oxidized by the oxygen remaining in the aqueous solution.

However, the cleaning method of a magnetic material according to an embodiment of the present invention avoids the existing water-based cleaning process, allows the reduction by-product to react with the non-aqueous fatty acid, and washes using a hydrocarbon-based organic solvent, thereby excluding water and oxygen. can be cleaned of powder particles. Therefore, oxidation of the manufactured magnet powder particles can be prevented.

In the cleaning process of the magnet powder according to an embodiment of the present invention, _{the removal of the residual reducing agent Ca and the reduction by-products CaO, Ca(OH) 2} may be performed by a reaction as shown in Schemes 1 to 3 below.

[Scheme 1]

Ca + 2RCOOH → Ca(RCOO) ₂ + H ₂

[Scheme 2]

CaO + 2RCOOH → Ca(RCOO) ₂ + H ₂ O

[Scheme 3]

Ca(OH) ₂ + 2RCOOH → Ca(RCOO) ₂ + 2H ₂ O

In Schemes 1 to 3, since RCOOH refers to a non-aqueous fatty acid, R may be CH ₃ (CH ₂ ) _n (n≥3), and the carbon number of the non-aqueous fatty acid of RCOOH may be 5 or more.

In the cleaning method according to the present embodiment, the reduction by-products can be efficiently removed while preventing the decomposition of the magnetic particles by repeatedly washing at room temperature without heating in a state in which the magnetic powder particles and the fatty acid are mixed. If heated during the cleaning process, the amount of residual Ca may be reduced, but the raw material Nd-Fe-B magnet particles themselves may be decomposed. Here, the room temperature may be a temperature of about 15 to 25 degrees.

The fatty acid according to this embodiment may have at least 5 carbon atoms and preferably caprylic acid. In addition, the process of washing with caprylic acid may be repeated three or more times. If the number of carbon atoms of the fatty acid is less than 5, it is easy to mix with a polar solvent such as water, and thus the effect of preventing the particles of the raw material from being decomposed by using the non-aqueous fatty acid may be reduced.

Hereinafter, the present invention will be described in detail through Examples and Comparative Examples. However, the following embodiments correspond to examples for describing the present invention, and are not limited to these embodiments.

Example 1

After _{uniformly mixing Nd 2} O ₃ 3.4350 g, Fe 6.9499 g, B 0.105 g, Ca 1.8412 g with metal fluoride (CaF ₂ , CuF ₂ ) and Mg 0.1675 g for particle size and size control, an arbitrary shape After evenly pouring into a stainless steel container of All subsequent washing processes are performed at room temperature. After grinding with an agate mortar to make a fine powder, 5.0-6.0 mL of caprylic acid is added to the pulverized powder and further pulverized with an agate mortar. Remove the liquid cloudy by calcium caprylate, add the same amount of caprylic acid again, and repeat the process of grinding with a mortar about 3 times. After washing the powder with hexane and transferring it to a beaker, 150-200 mL of isoparaffin is added, and the washing process is repeated 3 times using a homogenizer. Finally, after washing with hexane and vacuum drying, Nd ₂ Fe ₁₄ B powder is obtained.

Comparative Example 1

1.2 g of the powder sample synthesized by the method described in Example 1 above was put into 10 mL of caprylic acid, heated at 80 degrees Celsius for 5 hours and 20 hours, and then pulverized with caprylic acid in an agate mortar into a mortar, and ethanol was added Add 150~200mL and repeat the washing process 3 times using a homogenizer. Finally, after washing with ethanol and vacuum drying, Nd ₂ Fe ₁₄ B powder is obtained.

1 is a graph showing an XRD pattern of a magnet powder cleaned according to Example 1 of the present invention. FIG. 2 is a graph showing an XRD pattern of a magnet powder cleaned according to Comparative Example 1. FIG. Table 1 below shows the elemental analysis results of _{the Nd 2} Fe ₁₄ B powder washed according to Example 1 and Comparative Example 1.

% by mass of element Sample name Nd Fe B Ca Mg O N H before washing 22.7 59.2 1.00 12.0 0.21 7.45 4.47 0.34 After washing according to Example 1 25.4 67.0 1.01 0.77 <0.01 0.86 0.46 0.12 After washing according to Comparative Example 1 26.2 71.3 1.16 0.27 <0.01 0.74 0.24 0.08

In Table 1, the mass % of the remaining Ca is all reduced to 1 or less, but this indicates only the ratio of elements in the sample, and information on the decomposition of the phase is unknown. Referring to the XRD diffraction patterns of FIGS. 1 and 2 , in the case of Example 1 of FIG. 1, the Nd ₂ Fe ₁₄ B single phase (indicated by ■) is clearly maintained, but in the case of Comparative Example 1 of FIG. 2, Nd ₂ Fe ₁₄ B phase (indicated by □) other than the phase (indicated by □) appears, and it can be observed that the phase is decomposed as the XRD diffraction peak broadens. Specifically, in the case of Example 1 of FIG. 1, a single sharp XRD pattern is shown. On the contrary, in the case of Comparative Example 1 of FIG. 2, several patterns having a wide width are observed. It can be seen that the phase is decomposed in the case of Comparative Example 1.

Although the preferred embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the

Claims (10)

sintering a mixture containing a rare-earth metal precursor, iron and boron in the presence of calcium to prepare a magnet powder by a reduction-diffusion method, and
and cleaning the magnetic powder using a non-aqueous fatty acid and a hydrocarbon-based organic solvent at room temperature. In claim 1,
The manufacturing of the magnetic powder may further include mixing a metal fluoride and magnesium. delete In claim 1,
The step of preparing the magnet powder by the reduction-diffusion method is
Preparing a first mixture by mixing neodymium oxide, boron, and iron,
adding and mixing calcium to the first mixture to prepare a second mixture, and
A method of cleaning a magnetic material comprising the step of heating the secondary mixture to 800 degrees Celsius to 1100 degrees Celsius. In claim 4,
In the step of preparing the first mixture, the calcium is mixed in the form of elemental calcium and fluoride cleaning method of a magnetic material. In claim 5,
The step of preparing the secondary mixture is a cleaning method of a magnetic material further comprising the step of mixing magnesium. In claim 1,
A method for cleaning a magnetic material, wherein the carbon number of the non-aqueous fatty acid is at least 5 or more. In claim 1,
The non-aqueous fatty acid is caprylic acid, and the hydrocarbon-based organic solvent is isoparaffin. In claim 1,
The cleaning of the magnetic material is a method of cleaning a magnetic material without using an aqueous solvent. A magnetic material produced by the cleaning method of any one of claims 1, 2, and 4 to 9.

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