Method of preparing magnetic powder and magnetic powder

Patent metadata

Field	Value
Publication number	US-2024363270-A1
Application number	US-202318376273-A
Country	US
Kind code	A1
Filing date	Oct 3, 2023
Priority date	Apr 27, 2023
Publication date	Oct 31, 2024
Grant date	—

Abstract

A method of preparing a magnet powder, and a magnet powder, are disclosed. The method includes: preparing a neodymium praseodymium (Nd, Pr) mixed oxide containing Nd and Pr; preparing iron (Fe) oxide; preparing boron (B) oxide; mixing the prepared (Nd, Pr) mixed oxide, iron oxide, and boron oxide to prepare a first mixture; mixing the first mixture with calcium (Ca) to prepare a second mixture; inducing diffusion while shaping and pressing the second mixture; reducing the shaped and pressed second mixture to prepare a magnetic substance containing Nd, Fe, and B; powdering the reduced magnetic substance; and removing reduction by-products from the powdered magnetic substance.

First claim

What is claimed is:

1 . A method of preparing a Nd—Fe—B based magnetic powder comprising:
preparing (Nd, Pr) mixed oxide containing neodymium (Nd) and praseodymium (Pr) in a first precursor preparation step;
preparing iron oxide (Fe 2 O 3 ) in a second precursor preparation step;
preparing boron oxide (B 2 O 3 ) in a third precursor preparation step;
mixing the prepared (Nd, Pr) mixed oxide, the Fe 2 O 3 , and the B 2 O 3 to prepare a first mixture in a first mixing step;
mixing the first mixture with calcium (Ca) to prepare a second mixture in a second mixing step;
inducing diffusion while shaping and pressing the second mixture in a shaping step;
reducing the shaped and pressed second mixture to prepare a reduced magnetic substance containing Nd, iron (Fe), and boron (B) in a calcium reduction step;
powdering the reduced magnetic substance to prepare a powdered magnetic substance in a powdering step; and
removing reduction by-products from the powdered magnetic substance in a by-product removal step.

2 . The method of claim 1 , wherein the (Nd, Pr) mixed oxide prepared in the first precursor preparation step is extracted from a waste permanent magnet, and wherein the Fe 2 O 3 prepared in the second precursor preparation step is prepared through a water spray process.

3 . The method of claim 1 , wherein, in the first mixing step, the (Nd, Pr) mixed oxide, Fe 3 O 2 , and B 302 are mixed in a molar ratio of 5-7:13-15:2-5.

4 . The method of claim 1 , further comprising:
calcinating the first mixture in a calcination step after the first mixing step.

5 . The method of claim 4 , wherein the calcination step is carried out in an air atmosphere at a temperature in a range of 780 to 820° C. for 2 to 4 hours.

6 . The method of claim 5 , wherein a rate of increasing the temperature in the calcination step is in a range of 4 to 6° C./min.

7 . The method of claim 4 , further comprising:
reducing the calcinated first mixture with hydrogen in a hydrogen reduction step after the calcination step.

8 . The method of claim 7 , wherein the hydrogen reduction step is carried out in a hydrogen atmosphere at a temperature in a range of 600 to 650° C. for 1 to 3 hours.

9 . The method of claim 8 , wherein, in the hydrogen reduction step, the rate of increasing the temperature is in a range of 4 to 6° C./min.

10 . The method of claim 1 , wherein, in the second mixing step, the first mixture and calcium are mixed in a mass ratio of 3:1 to 1:2 to prepare the second mixture.

11 . The method of claim 1 , wherein, in the shaping step, the second mixture is shaped by pressing at a pressure in a range of 10 to 25 megapascal (MPa).

12 . The method of claim 1 , wherein the calcium reduction step is carried out in an inert atmosphere at a temperature in a range of 750 to 900° C. for 2 to 4 hours.

13 . The method of claim 12 , wherein in the calcium reduction step, the rate of increasing the temperature is in a range of 4 to 6° C./min.

14 . The method of claim 1 , wherein, in the by-product removal step, the powdered magnetic substance is dispersed in a cleaning solution of a mixture of ammonium salt and methanol to remove the reducing by-products.

15 . The method of claim 14 , further comprising:
obtaining the magnetic powder remaining in the cleaning solution; and then drying the magnetic powder in a drying step after the by-product removal step.

16 . A magnetic powder prepared by the method of claim 1 .

17 . The magnet powder of claim 16 , wherein the magnetic powder is (Nd, Pr) 2 Fe 14 B.

18 . The magnetic powder of claim 16 , wherein the magnetic powder has an average particle size of 1 μm or less.

Assignees

• Hyundai Motor Co Ltd
• Kia Corp
• Iucf Hyu Erica Campus

Inventors

• Han Bo Kyeong
• Yun Sae Mee
• Koo Kang Mo
• Choa Yong Ho
• Jang Byung Kwon

Classifications

• B22F9/04

  starting from solid material, e.g. by crushing, grinding or milling ({C22C1/1084 takes precedence}; crushing, grinding or milling, in general, see the relevant subclasses, e.g. B02C) · CPC title

• B22F2003/1014

  Getter · CPC title

• B22F3/1007

  Atmosphere (B22F3/1021 takes precedence) · CPC title

• C11D7/10

  Salts · CPC title

• C11D7/5022

  containing oxygen · CPC title