Iron-nitride magnet by nitriding a porous structure

Patent metadata

Field	Value
Publication number	US-12014853-B2
Application number	US-201917058882-A
Country	US
Kind code	B2
Filing date	May 28, 2019
Priority date	May 28, 2018
Publication date	Jun 18, 2024
Grant date	Jun 18, 2024

Abstract

In general, the disclosure is directed to bulk iron-nitride materials having a polycrystalline microstructure having pores including a plurality of crystallographic grains surrounded by grain boundaries, where at least one crystallographic grain includes an iron-nitride phase including any of a body centered cubic (bcc) structure, a body centered tetragonal (bct), and a martensite structure. The disclosure further describes techniques producing a bulk iron-nitride material having a polycrystalline microstructure, including: melting an iron source to obtain a molten iron source; fast belt casting the molten iron source to obtain a cast iron source; cooling and shaping the cast iron source to obtain a bulk iron-containing material having a body-centered cubic (bcc) structure; annealing the bulk iron-containing material at an austenite transformation temperature and subsequently cooling the bulk iron-containing material; and nitriding the bulk iron-containing material to obtain the bulk iron-nitride material.

First claim

The invention claimed is:

1. A bulk iron-nitride material having a polycrystalline microstructure comprising:
a plurality of crystallographic grains surrounded by grain boundaries, wherein at least one crystallographic grain comprises an iron-nitride phase comprising any of a body centered cubic (bcc) structure, a body centered tetragonal (bet), and a martensite structure, wherein the microstructure comprises pores;
wherein the iron-nitride phase comprises an α″-Fe 16 N 2 phase.

2. The bulk iron-nitride material of claim 1 , wherein an iron-containing material used to obtain the bulk iron-nitride material has a porous structure in a form of any of foil, ribbon, sheet, foam, and a composite bulk.

3. The bulk iron-nitride material of claim 1 , wherein at least one of the crystallographic grains is recrystallized.

4. The bulk iron-nitride material of claim 1 , wherein an average grain size of the plurality of crystallographic grains is in a range of from about 200 nm to about 1 μm.

5. The bulk iron-nitride material of claim 1 , wherein an average grain size of the plurality of crystallographic grains is in a range of from about 10 nm to about 200 nm.

6. The bulk iron-nitride material of claim 1 , wherein a width of at least one grain boundary is 20 nm or less.

7. The bulk iron-nitride material of claim 1 , wherein a width of at least one grain boundary is 5 nm or less.

8. The bulk iron-nitride material of claim 1 , wherein at least one grain boundary comprises a non-magnetic element selected from the group consisting of Al, Cu, Ti, W, Mn, Cr, Zr, Ta, Nb, B, C, Ni, Ru, SiO 2 , Al 2 O 3 , Ta (x) O (y) , CrO, Cr 2 O 3 , TiO 2 , BN, Si (x) N (y) , AL (x) N (y) , Cr x N y , Mn x N y or combinations thereof, wherein each of x and y is larger than 0 and less than 1.

9. The bulk iron-nitride material of claim 1 , wherein one or more dimensions of the bulk iron-nitride material are 1 μm or more.

10. The bulk iron-nitride material of claim 1 , wherein one or more dimensions of the bulk iron-nitride material are 10 μm or more.

11. The bulk iron-nitride material of claim 1 , wherein one or more dimensions of the bulk iron-nitride material are 0.1 mm or more.

12. The bulk iron-nitride material of claim 1 , wherein one or more dimensions of the bulk iron-nitride material are 1 mm or more.

13. The bulk iron-nitride material of claim 1 , wherein a phase ratio of Fe 16 N 2 /(non-Fe 16 N 2 ) of the Fe phases in the grains is 1.0 or higher.

14. The bulk iron-nitride material of claim 1 , wherein a phase ratio of Fe 16 N 2 /(non-Fe 16 N 2 ) Fe phases in the grains is 1.3 or higher.

15. The bulk iron-nitride material of claim 1 , wherein a phase ratio of Fe 16 N 2 /(non-Fe 16 N 2 ) Fe phases in the grains is 2 or higher.

16. The bulk iron-nitride material of claim 1 , wherein a saturation magnetization of the bulk iron-nitride material is 140 emu/g or higher.

17. The bulk iron-nitride material of claim 1 , wherein a coercivity of the bulk iron-nitride material is 600 Oe or higher.

18. The bulk iron-nitride material of claim 1 , wherein a coercivity of the bulk iron-nitride material is 1000 Oe or higher.

19. The bulk iron-nitride material of claim 1 , wherein a coercivity of the bulk iron-nitride material is 3000 Oe or higher.

20. The bulk iron-nitride material of claim 1 , wherein a coercivity of the bulk iron-nitride material is 5000 Oe or higher.

21. The bulk iron-nitride material of claim 1 , wherein a volume of pores in the bulk iron-nitride material is 1% or higher.

22. The bulk iron-nitride material of claim 1 , wherein a volume of pores in the bulk iron-nitride material is 10% or higher.

23. The bulk iron-nitride material of claim 1 , wherein a volume of pores in the bulk iron-nitride material is 50% or higher.

24. A bulk iron-nitride material having a polycrystalline microstructure comprising:
a plurality of crystallographic grains surrounded by grain boundaries, wherein at least one crystallographic grain comprises an iron-nitride phase comprising any of a body centered cubic (bcc) structure, a body centered tetragonal (bet), and a martensite structure, wherein the microstructure comprises pores;
wherein a width of at least one grain boundary is 20 nm or less.

25. The bulk iron-nitride material of claim 24 , wherein an iron-containing material used to obtain the bulk iron-nitride material has a porous structure in a form of any of foil, ribbon, sheet, foam, and a composite bulk.

26. The bulk iron-nitride material of claim 24 , wherein at least one of the crystallographic grains is recrystallized.

27. The bulk iron-nitride material of claim 24 , wherein an average grain size of the plurality of crystallographic grains is in a range of from about 200 nm to about 1 μm.

28. The bulk iron-nitride material of claim 24 , wherein an average grain size of the plurality of crystallographic grains is in a range of from about 10 nm to about 200 nm.

29. The bulk iron-nitride material of claim 24 , wherein at least one grain boundary comprises a non-magnetic element selected from the group consisting of Al, Cu, Ti, W, Mn, Cr, Zr, Ta, Nb, B, C, Ni, Ru, SiO 2 , Al 2 O 3 , Ta (x) O (y) , CrO, Cr 2 O 3 , TiO 2 , BN, Si (x) N (y) , AL (x) N (y) , Cr x N y , Mn x N y or combinations thereof, wherein each of x and y is larger than 0 and less than 1.

30. The bulk iron-nitride material of claim 24 , wherein one or more dimensions of the bulk iron-nitride material are 1 μm or more.

31. The bulk iron-nitride material of claim 24 , wherein a phase ratio of Fe 16 N 2 /(non-Fe 16 N 2 ) of the Fe phases in the grains is 1.0 or higher.

32. The bulk iron-nitride material of claim 24 , wherein a saturation magnetization of the bulk iron-nitride material is 140 emu/g or higher.

33. The bulk iron-nitride material of claim 24 , wherein a coercivity of the bulk iron-nitride material is 600 Oe or higher.

34. The bulk iron-nitride material of claim 24 , wherein a volume of pores in the bulk iron-nitride material is 1% or higher.

35. A bulk iron-nitride material having a polycrystalline microstructure comprising:
a plurality of crystallographic grains surrounded by grain boundaries, wherein at least one crystallographic grain comprises an iron-nitride phase comprising any of a body centered cubic (bcc) structure, a body centered tetragonal (bet), and a martensite structure, wherein the microstructure comprises pores;
wherein a volume of pores in the bulk iron-nitride material is 10% or higher.

36. The bulk iron-nitride material of claim 35 , wherein an iron-containing material used to obtain the bulk iron-nitride material has a porous structure in a form of any of foil, ribbon, sheet, foam, and a composite bulk.

37. The bulk iron-nitride material of claim 35 , wherein at least one of the crystallographic grains is recrystallized.

38. The bulk iron-nitride material of claim 35 , wherein an average grain size of the plurality of crystallographic grains is in a range of from about 200 nm to about 1 μm.

39. The bulk iron-nitride material of claim 35 , wherein an average grain size of the plurality of crystallographic grains is in a range of from about 10 nm to about 200 nm.

Assignees

• Univ Minnesota

Inventors

• Wang Jian-Ping
• Liu Jinming
• Ma Bin
• Zhang Fan
• Guo Guannan
• Wu Yiming
• Zhang Xiaowei

Classifications

• H01F41/0253

  for manufacturing permanent magnets · CPC title

• C23C8/26

  of ferrous surfaces · CPC title

• C23C8/02

  Pretreatment of the material to be coated (C23C8/04 takes precedence) · CPC title

• C01P2006/42

  Magnetic properties · CPC title

• C01P2004/04

  obtained by TEM, STEM, STM or AFM · CPC title