# US 12,014,853 B2 · Iron-nitride magnet by nitriding a porous structure > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,014,853 B2 - Document ID: US12014853B2 - Status: Granted - Kind: B2 - Application number: 17/058,882 - Filed: 2019-05-28 - Published: 2021-07-01 - Granted: 2024-06-18 - Earliest claimed: 2018-05-28 - Assignees: Regents of the University of Minnesota - Applicants: Regents of the University of Minnesota - Inventors: Jian-Ping Wang; Jinming Liu; Bin Ma; Fan Zhang; Guannan Guo; Yiming Wu; Xiaowei Zhang - Web page: https://patentgrep.com/patent/US12014853B2 ## CPC - C23C 8/10: Oxidising - H01F 1/047: Alloys characterised by their composition - C01B 21/0622: {with iron, cobalt or nickel} - C23C 8/02: Pretreatment of the material to be coated (C23C8/04 takes precedence) - C23C 8/26: of ferrous surfaces - H01F 41/0253: {for manufacturing permanent magnets} - C01P 2002/60: Compounds characterised by their crystallite size - C01P 2002/72: by d-values or two theta-values, e.g. as X-ray diagram - C01P 2002/77: by unit-cell parameters, atom positions or structure diagrams - C01P 2004/02: obtained by optical microscopy - C01P 2004/03: obtained by SEM - C01P 2004/04: obtained by TEM, STEM, STM or AFM - C01P 2006/42: Magnetic properties - C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04) - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES - C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C} - C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS ## 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. ## Claims ### Claim 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″-Fe16N2 phase. ### Claim 2 (depends on 1) 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. ### Claim 3 (depends on 1) The bulk iron-nitride material of claim 1, wherein at least one of the crystallographic grains is recrystallized. ### Claim 4 (depends on 1) 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. ### Claim 5 (depends on 1) 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. ### Claim 6 (depends on 1) The bulk iron-nitride material of claim 1, wherein a width of at least one grain boundary is 20 nm or less. ### Claim 7 (depends on 1) The bulk iron-nitride material of claim 1, wherein a width of at least one grain boundary is 5 nm or less. ### Claim 8 (depends on 1) 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, SiO2, Al2O3, Ta(x)O(y), CrO, Cr2O3, TiO2, BN, Si(x)N(y), AL(x)N(y), CrxNy, MnxNy or combinations thereof, wherein each of x and y is larger than 0 and less than 1. ### Claim 9 (depends on 1) The bulk iron-nitride material of claim 1, wherein one or more dimensions of the bulk iron-nitride material are 1 μm or more. ### Claim 10 (depends on 1) The bulk iron-nitride material of claim 1, wherein one or more dimensions of the bulk iron-nitride material are 10 μm or more. ### Claim 11 (depends on 1) 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. ### Claim 12 (depends on 1) The bulk iron-nitride material of claim 1, wherein one or more dimensions of the bulk iron-nitride material are 1 mm or more. ### Claim 13 (depends on 1) The bulk iron-nitride material of claim 1, wherein a phase ratio of Fe16N2/(non-Fe16N2) of the Fe phases in the grains is 1.0 or higher. ### Claim 14 (depends on 1) The bulk iron-nitride material of claim 1, wherein a phase ratio of Fe16N2/(non-Fe16N2) Fe phases in the grains is 1.3 or higher. ### Claim 15 (depends on 1) The bulk iron-nitride material of claim 1, wherein a phase ratio of Fe16N2/(non-Fe16N2) Fe phases in the grains is 2 or higher. ### Claim 16 (depends on 1) The bulk iron-nitride material of claim 1, wherein a saturation magnetization of the bulk iron-nitride material is 140 emu/g or higher. ### Claim 17 (depends on 1) The bulk iron-nitride material of claim 1, wherein a coercivity of the bulk iron-nitride material is 600 Oe or higher. ### Claim 18 (depends on 1) The bulk iron-nitride material of claim 1, wherein a coercivity of the bulk iron-nitride material is 1000 Oe or higher. ### Claim 19 (depends on 1) The bulk iron-nitride material of claim 1, wherein a coercivity of the bulk iron-nitride material is 3000 Oe or higher. ### Claim 20 (depends on 1) The bulk iron-nitride material of claim 1, wherein a coercivity of the bulk iron-nitride material is 5000 Oe or higher. ### Claim 21 (depends on 1) The bulk iron-nitride material of claim 1, wherein a volume of pores in the bulk iron-nitride material is 1% or higher. ### Claim 22 (depends on 1) The bulk iron-nitride material of claim 1, wherein a volume of pores in the bulk iron-nitride material is 10% or higher. ### Claim 23 (depends on 1) The bulk iron-nitride material of claim 1, wherein a volume of pores in the bulk iron-nitride material is 50% or higher. ### Claim 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. ### Claim 25 (depends on 24) 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. ### Claim 26 (depends on 24) The bulk iron-nitride material of claim 24, wherein at least one of the crystallographic grains is recrystallized. ### Claim 27 (depends on 24) 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. ### Claim 28 (depends on 24) 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. ### Claim 29 (depends on 24) 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, SiO2, Al2O3, Ta(x)O(y), CrO, Cr2O3, TiO2, BN, Si(x)N(y), AL(x)N(y), CrxNy, MnxNy or combinations thereof, wherein each of x and y is larger than 0 and less than 1. ### Claim 30 (depends on 24) The bulk iron-nitride material of claim 24, wherein one or more dimensions of the bulk iron-nitride material are 1 μm or more. ### Claim 31 (depends on 24) The bulk iron-nitride material of claim 24, wherein a phase ratio of Fe16N2/(non-Fe16N2) of the Fe phases in the grains is 1.0 or higher. ### Claim 32 (depends on 24) The bulk iron-nitride material of claim 24, wherein a saturation magnetization of the bulk iron-nitride material is 140 emu/g or higher. ### Claim 33 (depends on 24) The bulk iron-nitride material of claim 24, wherein a coercivity of the bulk iron-nitride material is 600 Oe or higher. ### Claim 34 (depends on 24) The bulk iron-nitride material of claim 24, wherein a volume of pores in the bulk iron-nitride material is 1% or higher. ### Claim 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. ### Claim 36 (depends on 35) 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. ### Claim 37 (depends on 35) The bulk iron-nitride material of claim 35, wherein at least one of the crystallographic grains is recrystallized. ### Claim 38 (depends on 35) 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. ### Claim 39 (depends on 35) 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. ### Claim 40 (depends on 35) The bulk iron-nitride material of claim 35, wherein a width of at least one grain boundary is 5 nm or less. ### Claim 41 (depends on 35) The bulk iron-nitride material of claim 35, 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, SiO2, Al2O3, Ta(x)O(y), CrO, Cr2O3, TiO2, BN, Si(x)N(y), AL(x)N(y), CrxNy, MnxNy or combinations thereof, wherein each of x and y is larger than 0 and less than 1. ### Claim 42 (depends on 35) The bulk iron-nitride material of claim 35, wherein one or more dimensions of the bulk iron-nitride material are 1 μm or more. ### Claim 43 (depends on 35) The bulk iron-nitride material of claim 35, wherein a phase ratio of Fe16N2/(non-Fe16N2) of the Fe phases in the grains is 1.0 or higher. ### Claim 44 (depends on 35) The bulk iron-nitride material of claim 35, wherein a saturation magnetization of the bulk iron-nitride material is 140 emu/g or higher. ### Claim 45 (depends on 35) The bulk iron-nitride material of claim 35, wherein a coercivity of the bulk iron-nitride material is 600 Oe or higher.