Method for producing anisotropic magnetic powder, and anisotropic magnetic powder

Patent metadata

Field	Value
Publication number	US-2023238161-A1
Application number	US-202118002272-A
Country	US
Kind code	A1
Filing date	Jun 16, 2021
Priority date	Jun 19, 2020
Publication date	Jul 27, 2023
Grant date	—

Abstract

Provided is an anisotropic magnetic powder having a low oxygen concentration, a small average particle size, a narrow particle size distribution, and a high remanence, and a method for producing the anisotropic magnetic powder. The present disclosure relates to a method for producing an anisotropic magnetic powder, including: pretreating an oxide containing Sm and Fe by heat-treating the oxide in a reducing gas atmosphere to obtain a partial oxide; heat-treating the partial oxide in the presence of a reducing agent to obtain alloy particles; nitriding the alloy particles to obtain a nitride; and treating the nitride with an alkali to obtain a magnetic powder.

First claim

What is claimed is:

1 - 5 . (canceled)

6 . A method for producing an anisotropic magnetic powder, comprising:
pretreating an oxide containing Sm and Fe by heat-treating the oxide in a reducing gas atmosphere to obtain a partial oxide; heat-treating the partial oxide in the presence of a reducing agent to obtain alloy particles; nitriding the alloy particles to obtain a nitride; and treating the nitride with an alkali to obtain a magnetic powder.

7 . The method for producing an anisotropic magnetic powder according to claim 6 ,
wherein the method further comprises treating the magnetic powder with an acid after the treating with the alkali.

8 . The method for producing an anisotropic magnetic powder according to claim 7 , wherein the acid comprises at least one of hydrogen chloride or nitric acid.

9 . The method for producing an anisotropic magnetic powder according to claim 7 ,
wherein the method further comprises dehydrating the magnetic powder after the treating with the acid.

10 . The method for producing an anisotropic magnetic powder according to claim 6 ,
wherein the treating with the alkali comprises treating the nitride with an aqueous solution containing calcium hydroxide or an aqueous solution containing sodium hydroxide.

11 . A method for producing an anisotropic magnetic powder, comprising:
pretreating an oxide containing Sm and Fe by heat-treating the oxide in a reducing gas atmosphere to obtain a partial oxide; heat-treating the partial oxide in the presence of a reducing agent to obtain alloy particles; nitriding the alloy particles to obtain a composite containing magnetic particles and contaminants including at least one of Ca3N 2 , CaO, and metallic calcium in a sintered bulk form; and treating the composite with an alkali to obtain a magnetic powder.

12 . The method for producing an anisotropic magnetic powder according to claim 11 ,
wherein the method further comprises treating the magnetic powder with an acid after the treating with the alkali.

13 . The method for producing an anisotropic magnetic powder according to claim 12 ,
wherein the acid comprises at least one of hydrogen chloride or nitric acid.

14 . The method for producing an anisotropic magnetic powder according to claim 12 ,
wherein the method further comprises dehydrating the magnetic powder after the treating with the acid.

15 . The method for producing an anisotropic magnetic powder according to claim 11 ,
wherein the treating with the alkali comprises treating the composite with an aqueous solution containing calcium hydroxide or an aqueous solution containing sodium hydroxide.

16 . An anisotropic magnetic powder having an average particle size of at least 1.5 μm but not more than 7 μm as measured with a laser diffraction-type particle size distribution analyzer under a dry condition,
wherein the powder has a span of not more than 1.6 as defined by the following equation:
Span=( D 90 −D 10)/ D 50

wherein D10, D50, and D90 represent particle sizes corresponding to 10th, 50th, and 90th percentiles, respectively, in a cumulative particle size distribution by volume, and
wherein the powder comprises Sm, Fe, N, and O and has an O content of at least 0.05% by mass but not higher than 0.65% by mass.

17 . The anisotropic magnetic powder according to claim 16 ,
wherein the average circularity of the anisotropic magnetic powder is not less than 0.75.

18 . The method for producing an anisotropic magnetic powder according to claim 7 ,
wherein the acid is hydrogen chloride or nitric acid.

19 . The method for producing an anisotropic magnetic powder according to claim 12 ,
wherein the acid is hydrogen chloride or nitric acid.

Assignees

• Nichia Corp

Inventors

• Maehara Hisashi

Classifications

• H01F1/059 Primary

  and Va elements, e.g. Sm2Fe17N2 · CPC title

• H01F1/065

  obtained by a reduction · CPC title

• B22F9/22 Primary

  using gaseous reductors · CPC title

• B22F1/145

  Chemical treatment, e.g. passivation or decarburisation · CPC title

• B22F9/10

  using centrifugal force · CPC title