Applied magnetic field synthesis and processing of iron nitride magnetic materials
A method may include annealing a material including iron and nitrogen in the presence of an applied magnetic field to form at least one Fe 16 N 2 phase domain. The applied magnetic field may have a strength of at least about 0.2 Tesla (T).
1. A method comprising:
annealing a material including iron and nitrogen at a temperature in a range of from about 150° C. to 160° C. in the presence of an applied magnetic field to form at least one Fe 16 N 2 phase domain, wherein the applied magnetic field has a strength of at least about 0.2 Tesla (T) wherein the material has a collective iron and nitrogen content of at least 92 atomic percent, and wherein the material has a minimum dimension of at least about 1 mm.
2. The method of claim 1 , wherein the strength of the applied magnetic field is greater than about 2.5 T.
3. The method of claim 1 , wherein the strength of the applied magnetic field is between about 8 T and about 10 T.
4. The method of claim 1 , wherein the strength of the applied magnetic field is greater than about 9 T.
5. The method of claim 1 , wherein annealing, the material comprises heating, the material for between about 10 hours and about 100 hours.
6. The method of claim 5 , wherein annealing the material comprises heating the material for between about 10 hours and about 30 hours.
7. The method of claim 1 , wherein the material comprises at least one of a pellet, rod, powder.
8. The method of claim 1 , wherein the material further comprises at least one dopant.
9. The method of claim 8 , wherein the at least one dopant comprises at least one of Al, Mn, La, Cr, Co, Ti, Ni, or a rare earth metal.
10. The method of claim 8 , wherein the at least one dopant comprises at least one of B, C, P, Si, or O.
11. The method of claim 1 , wherein annealing the material in the presence of the applied magnetic field transforms an {acute over (α)}-Fe 8 N phase in the material to an {acute over (α)}-Fe 16 N 2 phase.
12. The method of claim 11 , wherein a transformation yield of the {acute over (α)}-Fe 8 N phase to the {acute over (α)}-Fe 16 N 2 phase is at least 70%.
13. The method of claim 1 , wherein, after annealing, the {acute over (α)}-Fe 16 N 2 phase in the material is at least 20% of the material by volume.
14. The method of claim 1 , wherein the applied magnetic field is applied in substantial alignment with a c axis of at least one iron crystal in the material.
15. The method of claim 1 , further comprising:
prior to annealing the material, solutionizing the material in the presence of an applied magnetic field with a strength of at least about 0.2 T; and
after solutionizing the material, quenching the material.
16. The method of claim 1 , wherein, prior to annealing the material, the concentration of nitrogen in the material is between about 8 atomic percent (at. %) and about 9 at. %.
17. A method comprising:
nitridizing a material including iron in the presence of an applied magnetic field to form an iron-nitride-containing material, wherein the iron-nitride-containing material has a collective iron and nitrogen content of at least 92 atomic percent, and wherein the iron-nitride-containing material has a minimum dimension of at least about 1 mm; and
annealing the iron-nitride-containing material at a temperature in a range of from about 150° C. to 160° C. in the presence of the applied magnetic field to form at least one Fe 16 N 2 phase domain, wherein the applied magnetic field has a strength of at least about 0.2 Tesla (T).
18. The method of claim 17 , wherein the material including iron comprises an iron-based powder.
19. The method of claim 17 , wherein the material comprises at least one of an iron oxide, iron carbide, iron chloride, or iron-metal solid solution.
20. The method of claim 17 , wherein nitridizing the material and annealing the iron-nitride-containing material to form at least one Fe 16 N 2 phase domain occur in situ in the presence of the applied magnetic field.
21. The method of claim 17 , further comprising, prior to nitridizing the material, reducing the material in at least one of hydrogen, nitrogen, or ammonia gas, wherein reduction of the material occurs in situ in the presence of the applied magnetic field.
22. The method of claim 21 , wherein reducing the material comprises reducing a carbon-coated iron powder in hydrogen gas for about 1 hour at a temperature of between about 375° C. and about 425° C.
23. The method of claim 17 , wherein the strength of the applied magnetic field is greater than about 2.5 T.
24. The method of claim 17 , wherein the strength of the applied magnetic field is between about 8 T and about 10 T.
25. The method of claim 17 , wherein the strength of the applied magnetic field is greater than about 9 T.
26. The method of claim 17 , wherein annealing the iron-nitride-containing material comprises heating the iron-nitride-containing material for between about 10 hours and about 100 hours.
27. The method of claim 17 , wherein the iron-nitride-containing material further comprises at least one dopant.
28. The method of claim 27 , wherein the at least one dopant comprises at least one of Al, Mn, La, Cr, Co, Ti, Ni, or a rare earth metal.
29. The method of claim 27 , wherein the at least one dopant comprises at least one of B, C, P, Si, or O.
30. The method of claim 17 , wherein annealing the iron-nitride-containing material in the presence of the applied magnetic field transforms an {acute over (α)}-Fe 8 N phase in the iron-nitride-containing material to an {acute over (α)}-Fe 16 N 2 phase.
31. The method of claim 30 , wherein a transformation yield of the {acute over (α)}-Fe 8 N phase to the {acute over (α)}-Fe 16 N 2 phase is at least 70%.
32. The method of claim 17 , wherein, after annealing, the {acute over (α)}-Fe 16 N 2 phase in the iron-nitride-containing material is at least 20% of the iron-nitride-containing material by volume.
33. The method of claim 17 , wherein the applied magnetic field is applied in substantial alignment with a c axis of at least one iron crystal in the iron-nitride-containing material.
34. A workpiece comprising iron nitride material made by annealing a material including iron and nitrogen at a temperature in a range of from about 150° C. to 160° C. in the presence of an applied magnetic field to form at least one Fe 16 N 2 phase domain, wherein the iron nitride material has a minimum dimension of at least about 1 mm, wherein the iron nitride material has a collective iron and nitrogen content of at least 92 atomic percent, and wherein the applied magnetic field has a strength of at least about 0.2 Tesla (T).
35. The work piece of claim 34 , wherein the workpiece is a pellet, rod, or powder.
36. An article comprising a plurality of workpieces, wherein at least one workpiece of the plurality of workpieces comprise iron nitride material made by annealing a material including iron and nitrogen at a temperature in a range of from about 150° C. to 160° C. in the presence of an applied magnetic field to form at least one Fe 16 N 2 phase domain, Wherein the applied magnetic field has a strength of at least about 0.2 Tesla (T), wherein the iron nitride material has a minimum dimension of at least about 1 mm, wherein the iron nitride material has a collective iron and nitrogen content of at least 92 atomic percent, and wherein the at least one workpiece is a pellet, rod, or powder.
37. The article of claim 36 , wherein the workpieces are arranged so the <001> axes of the respective iron nitride materials are substantially aligned.
38. The article of claim 37 , wherein the article is an electric motor, a generator, a sensor, an actuator, a component of an automotive vehicle, or a component of a wind turbine.
39. The method of claim 1 , wherein after annealing, the Fe 16 N 2 phase in the material is at least 20% of the material by volume.