{
  "spore": "profile",
  "id": "niobium-carbide",
  "spore_version": "0.2",
  "family": "carbide-nitride-boride-ceramics",
  "name": "Niobium carbide",
  "abbreviation": "NbC",
  "role": "hard refractory carbide for grain control in cemented carbide, wear coatings and carbide ceramics",
  "category": "ceramics",
  "type": "carbides",
  "summary": "Niobium carbide is a niobium-carbon compound, NbC, with a cubic rock-salt structure (Wikipedia, composition only). WebQC gives a density of 7.8200 g/cm3 and a melting point of 3,608.00 °C, while a Stanford Advanced Materials data sheet prints 3500 °C, so both melting figures are kept. NIST-JANAF gives thermochemical values for the carbon-deficient phase NbC0.98. A 2025 study in the Journal of the European Ceramic Society finds NbC an effective grain growth inhibitor in WC-10Co cemented carbide.\n",
  "best_for": "Controlling grain growth in WC-10Co cemented carbide cutting and wear tools (Megret et al., 2025), and wear coatings reinforced with NbC particles (Gunen et al., 2024)",
  "weakest_at": "One supplier classes the powder as a flammable solid, and the oxidation of NbC in air is not sourced here. Hardness, elastic modulus and thermal conductivity of pure NbC are not sourced in this file, and the two melting points disagree.",
  "identity": {
    "formula": "NbC, niobium carbide: a 1:1 niobium-carbon compound with a cubic rock-salt structure (Wikipedia, composition and structure only)",
    "cas": "12069-94-2",
    "crystal_system": "cubic",
    "space_group": "Fm-3m",
    "designations": [],
    "source": "webqc-nbc",
    "where": "Identifiers block, CAS Number 12069-94-2 and Hill formula CNb; Wikipedia infobox for the rock-salt structure and Fm3m (not confirmed in a primary crystallography source)"
  },
  "tags": {
    "environments": [],
    "stresses": [
      "extreme-heat"
    ],
    "applications": [
      "mechanisms"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "label": "Density, NbC (WebQC)",
      "value": 7.82,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "basis": "as printed by WebQC (7.8200 g/cm3)"
      },
      "method": "WebQC physical-properties value; the site does not name its original source",
      "status": "ground",
      "source": "webqc-nbc",
      "where": "Properties of NbC (Niobium carbide), Physical properties, Density row",
      "source_detail": {
        "title": "WebQC, Niobium carbide (NbC) compound record: physical properties, identifiers, elemental composition",
        "url": "https://www.webqc.org/compound-NbC-NbC.html",
        "kind": "database",
        "license": "web reference site, cited not reproduced"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, NbC (WebQC)",
      "value": 3608,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "as printed by WebQC (3,608.00 °C)"
      },
      "method": "WebQC physical-properties value; the site does not name its original source",
      "status": "ground",
      "note": "Disagrees with the 3500 °C in the Stanford Advanced Materials data sheet; both are kept and no single melting point is chosen.",
      "source": "webqc-nbc",
      "where": "Properties of NbC, Physical properties, Melting row",
      "source_detail": {
        "title": "WebQC, Niobium carbide (NbC) compound record: physical properties, identifiers, elemental composition",
        "url": "https://www.webqc.org/compound-NbC-NbC.html",
        "kind": "database",
        "license": "web reference site, cited not reproduced"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point, NbC (Stanford Advanced Materials data sheet)",
      "value": 3500,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "as printed on the data sheet (3500 °C / 6332 °F)"
      },
      "method": "Supplier data sheet value, Physical properties table; no measurement method given",
      "status": "ground",
      "source": "sam-nbc-tds",
      "where": "Physical and chemical properties table, Melting Point/Range row",
      "source_detail": {
        "title": "Stanford Advanced Materials, niobium carbide data sheet with OSHA hazard classification and physical properties",
        "url": "https://samaterials.com/tds/1715418501-vd0765.pdf",
        "kind": "datasheet",
        "license": "supplier data sheet, cited not reproduced"
      }
    },
    {
      "benchmark": "molar_mass",
      "label": "Molar mass, NbC (WebQC)",
      "value": 104.91708,
      "bound": "exact",
      "unit": "g/mol",
      "scope": "material",
      "conditions": {
        "basis": "molar mass of NbC as printed by WebQC"
      },
      "method": "WebQC property block, Properties of NbC heading",
      "status": "ground",
      "source": "webqc-nbc",
      "where": "Properties of NbC heading, Molar Mass row",
      "source_detail": {
        "title": "WebQC, Niobium carbide (NbC) compound record: physical properties, identifiers, elemental composition",
        "url": "https://www.webqc.org/compound-NbC-NbC.html",
        "kind": "database",
        "license": "web reference site, cited not reproduced"
      }
    },
    {
      "benchmark": "molar_heat_capacity",
      "label": "Molar heat capacity Cp, NbC0.98, 298.15 K",
      "value": 36.233,
      "bound": "exact",
      "unit": "J K-1 mol-1",
      "scope": "material",
      "conditions": {
        "temperature": "298.15 K",
        "reference_state": "standard state pressure 0.1 MPa",
        "phase": "crystalline (cr); carbon-deficient NbC0.98, not stoichiometric NbC"
      },
      "method": "JANAF table value at 298.15 K, Cp column; molar, so not converted to specific heat",
      "status": "ground",
      "source": "janaf-nbc",
      "where": "Niobium Carbide (NbC0.98) table, row 298.15, Cp column",
      "source_detail": {
        "title": "NIST-JANAF Thermochemical Tables, Niobium Carbide (NbC0.98), table C-001 (cr)",
        "url": "https://janaf.nist.gov/tables/C-001.html",
        "kind": "database",
        "license": "NIST public data"
      }
    },
    {
      "benchmark": "molar_heat_capacity",
      "label": "Molar heat capacity Cp, NbC0.98, 1000 K",
      "value": 51.923,
      "bound": "exact",
      "unit": "J K-1 mol-1",
      "scope": "material",
      "conditions": {
        "temperature": "1000 K",
        "reference_state": "standard state pressure 0.1 MPa",
        "phase": "crystalline (cr); carbon-deficient NbC0.98"
      },
      "method": "JANAF table value at 1000 K, read from the same table",
      "status": "ground",
      "source": "janaf-nbc",
      "where": "Niobium Carbide (NbC0.98) table, row 1000, Cp column",
      "source_detail": {
        "title": "NIST-JANAF Thermochemical Tables, Niobium Carbide (NbC0.98), table C-001 (cr)",
        "url": "https://janaf.nist.gov/tables/C-001.html",
        "kind": "database",
        "license": "NIST public data"
      }
    },
    {
      "benchmark": "molar_heat_capacity",
      "label": "Molar heat capacity Cp, NbC0.98, 1500 K",
      "value": 55.061,
      "bound": "exact",
      "unit": "J K-1 mol-1",
      "scope": "material",
      "conditions": {
        "temperature": "1500 K",
        "reference_state": "standard state pressure 0.1 MPa",
        "phase": "crystalline (cr); carbon-deficient NbC0.98"
      },
      "method": "JANAF table value at 1500 K, read from the same table",
      "status": "ground",
      "source": "janaf-nbc",
      "where": "Niobium Carbide (NbC0.98) table, row 1500, Cp column",
      "source_detail": {
        "title": "NIST-JANAF Thermochemical Tables, Niobium Carbide (NbC0.98), table C-001 (cr)",
        "url": "https://janaf.nist.gov/tables/C-001.html",
        "kind": "database",
        "license": "NIST public data"
      }
    },
    {
      "benchmark": "standard_molar_entropy",
      "label": "Standard molar entropy S, NbC0.98, 298.15 K",
      "value": 34.966,
      "bound": "exact",
      "unit": "J K-1 mol-1",
      "scope": "material",
      "conditions": {
        "temperature": "298.15 K",
        "reference_state": "standard state pressure 0.1 MPa",
        "phase": "crystalline (cr); carbon-deficient NbC0.98"
      },
      "method": "JANAF table value at 298.15 K, S column",
      "status": "ground",
      "source": "janaf-nbc",
      "where": "Niobium Carbide (NbC0.98) table, row 298.15, S column",
      "source_detail": {
        "title": "NIST-JANAF Thermochemical Tables, Niobium Carbide (NbC0.98), table C-001 (cr)",
        "url": "https://janaf.nist.gov/tables/C-001.html",
        "kind": "database",
        "license": "NIST public data"
      }
    },
    {
      "benchmark": "standard_molar_entropy",
      "label": "Standard molar entropy S, NbC0.98, 1000 K",
      "value": 90.038,
      "bound": "exact",
      "unit": "J K-1 mol-1",
      "scope": "material",
      "conditions": {
        "temperature": "1000 K",
        "reference_state": "standard state pressure 0.1 MPa",
        "phase": "crystalline (cr); carbon-deficient NbC0.98"
      },
      "method": "JANAF table value at 1000 K, S column",
      "status": "ground",
      "source": "janaf-nbc",
      "where": "Niobium Carbide (NbC0.98) table, row 1000, S column",
      "source_detail": {
        "title": "NIST-JANAF Thermochemical Tables, Niobium Carbide (NbC0.98), table C-001 (cr)",
        "url": "https://janaf.nist.gov/tables/C-001.html",
        "kind": "database",
        "license": "NIST public data"
      }
    },
    {
      "benchmark": "standard_enthalpy_of_formation",
      "label": "Standard enthalpy of formation, NbC0.98, 298.15 K",
      "value": -138.909,
      "bound": "exact",
      "unit": "kJ mol-1",
      "scope": "material",
      "conditions": {
        "temperature": "298.15 K",
        "reference_state": "standard state pressure 0.1 MPa",
        "phase": "crystalline (cr); carbon-deficient NbC0.98"
      },
      "method": "JANAF table value at 298.15 K, delta-f H column",
      "status": "ground",
      "source": "janaf-nbc",
      "where": "Niobium Carbide (NbC0.98) table, row 298.15, fH column",
      "source_detail": {
        "title": "NIST-JANAF Thermochemical Tables, Niobium Carbide (NbC0.98), table C-001 (cr)",
        "url": "https://janaf.nist.gov/tables/C-001.html",
        "kind": "database",
        "license": "NIST public data"
      }
    },
    {
      "benchmark": "standard_enthalpy_of_formation",
      "label": "Standard enthalpy of formation, NbC0.98, 1000 K",
      "value": -136.097,
      "bound": "exact",
      "unit": "kJ mol-1",
      "scope": "material",
      "conditions": {
        "temperature": "1000 K",
        "reference_state": "standard state pressure 0.1 MPa",
        "phase": "crystalline (cr); carbon-deficient NbC0.98"
      },
      "method": "JANAF table value at 1000 K, delta-f H column",
      "status": "ground",
      "source": "janaf-nbc",
      "where": "Niobium Carbide (NbC0.98) table, row 1000, fH column",
      "source_detail": {
        "title": "NIST-JANAF Thermochemical Tables, Niobium Carbide (NbC0.98), table C-001 (cr)",
        "url": "https://janaf.nist.gov/tables/C-001.html",
        "kind": "database",
        "license": "NIST public data"
      }
    },
    {
      "benchmark": "standard_gibbs_energy_of_formation",
      "label": "Standard Gibbs energy of formation, NbC0.98, 298.15 K",
      "value": -136.785,
      "bound": "exact",
      "unit": "kJ mol-1",
      "scope": "material",
      "conditions": {
        "temperature": "298.15 K",
        "reference_state": "standard state pressure 0.1 MPa",
        "phase": "crystalline (cr); carbon-deficient NbC0.98"
      },
      "method": "JANAF table value at 298.15 K, delta-f G column",
      "status": "ground",
      "source": "janaf-nbc",
      "where": "Niobium Carbide (NbC0.98) table, row 298.15, fG column",
      "source_detail": {
        "title": "NIST-JANAF Thermochemical Tables, Niobium Carbide (NbC0.98), table C-001 (cr)",
        "url": "https://janaf.nist.gov/tables/C-001.html",
        "kind": "database",
        "license": "NIST public data"
      }
    },
    {
      "benchmark": "standard_gibbs_energy_of_formation",
      "label": "Standard Gibbs energy of formation, NbC0.98, 1000 K",
      "value": -134.009,
      "bound": "exact",
      "unit": "kJ mol-1",
      "scope": "material",
      "conditions": {
        "temperature": "1000 K",
        "reference_state": "standard state pressure 0.1 MPa",
        "phase": "crystalline (cr); carbon-deficient NbC0.98"
      },
      "method": "JANAF table value at 1000 K, delta-f G column",
      "status": "ground",
      "source": "janaf-nbc",
      "where": "Niobium Carbide (NbC0.98) table, row 1000, fG column",
      "source_detail": {
        "title": "NIST-JANAF Thermochemical Tables, Niobium Carbide (NbC0.98), table C-001 (cr)",
        "url": "https://janaf.nist.gov/tables/C-001.html",
        "kind": "database",
        "license": "NIST public data"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Oxidizing agents (materials to avoid, per the supplier)",
      "headline": "The supplier lists oxidizing agents as materials to avoid and says the powder does not decompose if stored as specified.",
      "effect": "The 2012 Stanford Advanced Materials MSDS names oxidizing agents as materials to be avoided, says that decomposition will not occur if the powder is used and stored according to specifications, and lists carbon monoxide and carbon dioxide as the decomposition products. No test data are given.",
      "rating": "unknown",
      "conditions": {
        "basis": "supplier safety data sheet statement, not a corrosion test"
      },
      "source": "sam-nbc-msds",
      "where": "Section V, Reactivity data"
    },
    {
      "environment": "Copper matrix with NbC additions, high-temperature oxidation at 370 to 700 degC",
      "headline": "In a copper-NbC composite, 1.36 to 6.22 wt% NbC halved the oxidation rate of copper. This is a composite, not NbC alone.",
      "effect": "The abstract says that at high-temperature oxidation at 370 to 700 degC, the addition of 1.36 to 6.22 wt% NbC reduces the corrosion rate by half, and that it raises the start temperature of oxidation by 10 to 20 degC compared with pure copper. The composite was made by evaporation from separate copper and carbide crucibles in vacuum.",
      "rating": "unknown",
      "conditions": {
        "matrix": "copper",
        "atmosphere": "not stated in the abstract (high-temperature oxidation)",
        "temperature": "370 to 700 degC"
      },
      "source": "hrechanyuk-2023-cu-nbc",
      "where": "Abstract (Cu-NbC composite oxidation results)"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "Stanford Advanced Materials data sheet classifies niobium carbide powder as a flammable solid, Category 2, under the 2012 OSHA Hazard Communication Standard, with the signal word Warning and the hazard statement Flammable solid. No H-code is printed.",
        "ghs": [],
        "source": "sam-nbc-tds",
        "where": "Section 2, Hazard(s) identification"
      },
      {
        "text": "The 2012 Stanford Advanced Materials MSDS gives no GHS classification. It describes the powder as an irritant to skin and mucous membranes, with an irritating effect on the eye, and says the acute and chronic toxicity are not fully known.",
        "ghs": [],
        "source": "sam-nbc-msds",
        "where": "Section VI, Health hazard data (primary irritant effect and additional toxicological information)"
      },
      {
        "text": "The MSDS says that niobium compounds have caused liver damage in animal studies, and that niobium metal has caused kidney damage and fibrogenic effects on the lungs in experimental animals.",
        "ghs": [],
        "source": "sam-nbc-msds",
        "where": "Section VI, Subacute to chronic toxicity"
      }
    ],
    "failure_risks": [
      {
        "mode": "Ignition of the powder",
        "trigger": "Powder exposed to an ignition source. The data sheet prints no trigger temperature or test method.",
        "consequence": "The data sheet classes the powder as a flammable solid. The MSDS says firefighters need full protective clothing and that fumes from a fire are hazardous.",
        "severity": "moderate",
        "source": "sam-nbc-tds",
        "where": "Section 2, Hazard(s) identification; MSDS Section IV, fire fighting"
      }
    ],
    "side_effects": [
      {
        "text": "Decomposition products listed are carbon monoxide and carbon dioxide. The MSDS says no dangerous reactions are known.",
        "affects": "Workers and enclosed spaces during a fire",
        "source": "sam-nbc-msds",
        "where": "Section V, Reactivity data"
      }
    ],
    "handling": [
      {
        "text": "Spill clean-up: vacuum up with a high-efficiency particulate (HEPA) filter into a closed container, take care not to raise dust, provide ventilation and remove ignition sources.",
        "source": "sam-nbc-msds",
        "where": "Section VII, steps to be taken in case of release"
      },
      {
        "text": "Routes of entry listed in the MSDS are inhalation, skin, eye and ingestion. Use appropriate respiratory and protective equipment.",
        "source": "sam-nbc-msds",
        "where": "Section VI, routes of entry; Section VII, release steps"
      }
    ],
    "mitigations": []
  },
  "uses": [
    {
      "application": "mechanisms",
      "device": "Grain growth inhibitor in WC-10Co cemented carbide cutting and wear tools",
      "example": "Megret et al. (2025) report that niobium carbide is an efficient grain growth inhibitor in WC-10Co. Its mechanical properties are better than those of the other inhibitors they tested. For NbC as the inhibitor, the hardness is 1858 +/- 31 HV30 and the fracture toughness is 9.8 +/- 0.2 MPa√m. These are properties of the cemented carbide, not of pure NbC.",
      "source": "megret-2025-nbc",
      "where": "Abstract; Table 2 (hardness and fracture toughness)"
    },
    {
      "application": "mechanisms",
      "device": "Iron-aluminide wear coating reinforced with NbC particles",
      "example": "Gunen et al. (2024) report that NbC-reinforced Fe-Al coatings improved wear resistance by 2.7 times at room temperature and by up to 3.5 times at 500 °C. The abstract compares the reinforced coating with the Fe-Al coating without NbC.",
      "source": "gunen-2024-nbc-coating",
      "where": "Abstract"
    }
  ],
  "supply": [
    {
      "subject": "Niobium (feedstock for the niobium half of NbC)",
      "abundance": "20 ppm in the Earth's crust (USGS PP 1802-A Table A1, citing Jefferson Science Associates 2014). USGS 2026: 100 percent net import reliance for the United States in 2025e.",
      "producers": [
        {
          "country": "Brazil",
          "share_percent": 93,
          "year": 2025
        },
        {
          "country": "Canada",
          "share_percent": 5,
          "year": 2025
        }
      ],
      "critical_lists": [
        {
          "list": "EU critical raw materials list (European Commission page, entry Niobium)",
          "listed": true
        }
      ],
      "recycling": "USGS 2026: niobium was recycled with niobium-bearing steels and superalloys, but scrap recovery specifically for niobium content was negligible. The amount recycled may have been as much as 20 percent of apparent consumption.",
      "substitutes": [
        "USGS 2026: ceramic matrix composites, molybdenum, tantalum and tungsten in high-temperature superalloy applications, and molybdenum, tantalum and titanium as alloying elements in steels. A performance loss or higher cost may ensue. These substitutes are for niobium metal, not NbC."
      ],
      "source": "usgs-mcs2026-niobium",
      "where": "Niobium (Columbium) chapter: World Mine Production table (2025e, world total 112,000 t); the text gives Brazil at about 93 percent and Canada at 5 percent; Recycling; Substitutes; Import sources (2021 to 24). Abundance: USGS PP 1802-A Table A1."
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "NIST-JANAF Thermochemical Tables, Niobium Carbide (NbC0.98), table C-001",
      "type": "database",
      "url": "https://janaf.nist.gov/tables/C-001.html"
    },
    {
      "title": "WebQC compound record, NbC (physical properties, identifiers, elemental composition)",
      "type": "database",
      "url": "https://www.webqc.org/compound-NbC-NbC.html"
    },
    {
      "title": "Stanford Advanced Materials, Material Safety Data Sheet: Niobium Carbide (revision 2.0, 5 Sep 2012)",
      "type": "sds",
      "url": "https://www.sputtertargets.net/Public/pdf/niobium-carbide-msds.pdf",
      "year": 2012
    },
    {
      "title": "Stanford Advanced Materials, niobium carbide data sheet with OSHA hazard classification (Section 2)",
      "type": "sds",
      "url": "https://samaterials.com/tds/1715418501-vd0765.pdf"
    },
    {
      "title": "Megret, Vitry and Delaunois (2025), The use of niobium carbide as grain growth inhibitor in WC-10Co cemented carbides, J. Eur. Ceram. Soc. 45, 117533 (author postprint, University of Mons repository)",
      "type": "paper",
      "url": "https://orbi.umons.ac.be/bitstream/20.500.12907/52399/1/M%c3%a9gret%20-%20The%20use%20of%20niobium%20carbide%20as%20grain%20growth%20inhibitor%20in%20WC-10Co.pdf",
      "year": 2025
    },
    {
      "title": "Reithmaier et al., Optimisation of NbN thin films on GaAs substrates for in-situ single photon detection in structured photonic devices (arXiv:1212.2038)",
      "type": "paper",
      "url": "https://arxiv.org/pdf/1212.2038",
      "year": 2012
    },
    {
      "title": "Hrechanyuk et al. (2023), Effect of niobium carbide on corrosion resistance and high-temperature oxidation resistance of copper-based materials Cu-NbC, Metallophysics and Advanced Technologies 45(12), 1473-1484",
      "type": "paper",
      "url": "https://mfint.imp.kiev.ua/en/abstract/v45/i12/1473.html",
      "year": 2023
    },
    {
      "title": "Gunen, Altinay and Sabun (2024), Microstructural characterization and high-temperature wear behavior of refractory niobium-carbide growth in intermetallic iron-aluminide coatings, Engineering Failure Analysis 163",
      "type": "paper",
      "url": "https://avesis.mku.edu.tr/yayin/cf4ba1ce-b688-41e9-9761-5c7e6d9a81e8/microstructural-characterization-and-high-temperature-wear-behavior-of-refractory-niobium-carbide-growth-in-intermetallic-iron-aluminide-coatings",
      "year": 2024
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026, Niobium (Columbium)",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf",
      "year": 2026
    },
    {
      "title": "USGS Professional Paper 1802-A, Table A1 crustal abundances",
      "type": "report",
      "url": "https://pubs.usgs.gov/pp/1802/a/pp1802a.pdf",
      "year": 2017
    }
  ],
  "gaps": [
    "Oxidation of NbC in air or oxygen: no primary source read. Shimada (Oxidation of Metals, 1994) is reported in a search result as oxidizing NbC powder at 390 to 610 degC, but its publisher page did not open here, so no value is used. Corrosion has no NbC-alone entry in air.",
    "Hardness of pure NbC: not sourced. The 1858 HV30 figure in the uses is for WC-10Co with NbC as the inhibitor, a cemented carbide, so it is not a property of NbC.",
    "Elastic modulus of NbC: the first-principles paper (Rathod et al., Solid State Phenomena 171, 2011) opened as a page with no numbers, so no value is used. Wikipedia gives a Young's modulus, but Wikipedia is limited to composition and history for this profile, so it is not used.",
    "Thermal conductivity, thermal expansion and electrical resistivity of NbC: no fetched source with a printed value.",
    "Crystal system and space group (cubic, Fm-3m) come from Wikipedia only and are not confirmed in a primary crystallography source.",
    "Production route: Wikipedia gives heating niobium(V) oxide with coke under vacuum at about 1800 degC (Nb2O5 + 7 C gives 2 NbC + 5 CO). No process source was read, so the route is recorded as Wikipedia only.",
    "Designations (UNS, ASTM, EN, DIN and similar): no fetched source printed a designation for NbC. None are listed.",
    "PubChem: no record was found by CAS 12069-94-2 in this run, so no PubChem GHS classification is used. The flammable-solid classification comes from the Stanford Advanced Materials data sheet only.",
    "GHS status disagrees by supplier: the 2012 Stanford MSDS gives no classification, and the Stanford data sheet gives flammable solid, Category 2. An American Elements page gives H228 in a search snippet only; it was not opened and is not used.",
    "USGS 2025 List of Critical Minerals: the USGS page returned HTTP 403, so no USGS critical-list entry for niobium is recorded. The EU list entry is used.",
    "Melting point: 3608 degC (WebQC) and 3500 degC (Stanford data sheet) disagree. Both are kept and no single value is chosen.",
    "Thermochemistry: JANAF values are for the carbon-deficient phase NbC0.98, not stoichiometric NbC. The JANAF table was the only thermochemical source read.",
    "Niobium disilicide (NbSi2) and Nb5Si3: the values seen were supplier catalogue figures in search results only, and were not opened. No silicide property is used.",
    "Niobium diboride: the hardness and elastic modulus figures seen in a search snippet (reaction spark plasma sintering paper) were not opened and are not used. Only the WebQC density and melting point are used.",
    "Cemented carbide and coating uses: the Megret et al. 2025 paper and the Gunen et al. 2024 abstract are the only NbC-specific uses read. The Cu-NbC composite abstract is a composite and is recorded only under corrosion.",
    "Radiation, vacuum, flight and long-term ageing of NbC: no source read in this run.",
    "Environments: no source read supports a space environment tag, so tags.environments is empty.",
    "Property names not in property-canon.yaml: molar_mass, molar_heat_capacity, standard_molar_entropy, standard_enthalpy_of_formation and standard_gibbs_energy_of_formation. The JANAF values are molar and cannot be converted to specific heat without a molar mass conversion."
  ],
  "story": {
    "why": "Niobium carbide is a hard, high-melting carbide. Its composition and thermochemistry are documented by NIST-JANAF and WebQC. Its clearest use, in the sources read here, is as a grain growth inhibitor in WC-10Co cemented carbide, where a 2025 study reports better mechanical properties than the other inhibitors tested. Niobium itself is sourced mainly from Brazil (about 93 percent of 2025 mine production, USGS).",
    "uses": [
      {
        "where": "Cemented carbide tools",
        "line": "A 2025 study in the Journal of the European Ceramic Society finds niobium carbide an effective grain growth inhibitor in WC-10Co. The authors report 1858 HV30 hardness and 9.8 MPa√m fracture toughness for the cemented carbide with NbC as the inhibitor. These are not properties of pure NbC."
      },
      {
        "where": "Wear coatings",
        "line": "A 2024 abstract reports that Fe-Al coatings reinforced with NbC particles improved wear resistance 2.7 times at room temperature and up to 3.5 times at 500 °C."
      }
    ],
    "can_do": [
      {
        "label": "Melting",
        "line": "WebQC gives a melting point of 3,608.00 °C for NbC. The Stanford Advanced Materials data sheet gives 3500 °C. The two values disagree, so both are shown.",
        "benchmark": "melting_point",
        "scope": "material"
      },
      {
        "label": "Density",
        "line": "WebQC gives a density of 7.8200 g/cm3 for NbC.",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Heat capacity",
        "line": "The NIST-JANAF table gives a molar heat capacity of 36.233 J K-1 mol-1 at 298.15 K for NbC0.98, rising to 51.923 J K-1 mol-1 at 1000 K.",
        "benchmark": "molar_heat_capacity",
        "scope": "material",
        "value": "36.2 J K-1 mol-1 at 298.15 K"
      }
    ],
    "compare": "The two melting points (3608 degC from WebQC and 3500 degC from the supplier data sheet) are different values, and both are kept. The JANAF values are for the carbon-deficient phase NbC0.98, not stoichiometric NbC, so they should not be compared directly with a fully stoichiometric sample. The table compares the density, melting point and molar heat capacity sourced for NbC with the same benchmarks used for other ceramics in this collection.",
    "compare_rows": [
      {
        "label": "Density",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Melting point",
        "benchmark": "melting_point",
        "scope": "material"
      },
      {
        "label": "Heat capacity",
        "benchmark": "molar_heat_capacity",
        "scope": "material"
      }
    ],
    "handling": [
      "Dust: keep the powder from dispersing. Clean up spills with a HEPA vacuum and do not raise dust.",
      "Ignition: the data sheet classes the powder as a flammable solid. Keep it away from ignition sources.",
      "Irritation: avoid skin and eye contact. The MSDS describes irritation and says long-term toxicity is not fully known."
    ],
    "good_for": [
      "Grain growth control in WC-10Co cemented carbide, where a 2025 study reports better results than the other inhibitors tested.",
      "Thermal stability of the carbide at high temperature, as shown by its melting point of about 3500 to 3608 degC (two sources, disagreeing)."
    ],
    "watch_out": [
      "The powder is a flammable solid according to one supplier. Another supplier gives no classification.",
      "Oxidation of NbC in air is not sourced here, so do not assume oxidation resistance.",
      "Hardness, elastic modulus and thermal conductivity of pure NbC are not sourced in this file."
    ],
    "verdict": "Niobium carbide is a high-melting, rock-salt carbide with JANAF thermochemistry and a 2025 study supporting its use as a grain growth inhibitor in cemented carbide. The powder hazard is a flammability classification from one supplier. Oxidation, hardness and elastic properties of pure NbC are not yet sourced.",
    "recipe": {
      "line": "NbC is one niobium atom bonded to one carbon atom in a cubic rock-salt crystal (Wikipedia, composition only). The WebQC elemental composition gives the atomic weights. Wikipedia describes making it by heating niobium(V) oxide with coke under vacuum (see gaps; no process source was read).",
      "parts": [
        {
          "name": "Niobium",
          "symbol": "Nb",
          "role": "The metal sublattice of the rock-salt structure. It forms the carbide with carbon and gives the 1:1 composition.",
          "atoms": 1,
          "atomic_weight": 92.90638,
          "source": "webqc-nbc",
          "where": "Elemental composition of NbC table, Nb row"
        },
        {
          "name": "Carbon",
          "symbol": "C",
          "role": "The non-metal sublattice of the rock-salt structure, bonded to niobium in the 1:1 compound.",
          "atoms": 1,
          "atomic_weight": 12.0107,
          "source": "webqc-nbc",
          "where": "Elemental composition of NbC table, C row"
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "The powder is classed as a flammable solid by one supplier and as unclassified by another. It irritates skin and eyes, and the toxicity data are sparse.",
        "points": [
          {
            "label": "Flammability",
            "line": "The Stanford Advanced Materials data sheet classes the powder as a flammable solid, Category 2, with the signal word Warning. Keep the powder away from ignition sources."
          },
          {
            "label": "Irritation",
            "line": "The MSDS describes the powder as an irritant to skin, mucous membranes and eyes, and says the acute and chronic toxicity are not fully known."
          },
          {
            "label": "Dust",
            "line": "The MSDS says to take care not to raise dust when cleaning up a spill, and to vacuum with a HEPA filter."
          }
        ],
        "level": 1,
        "verdict": "Flammable solid powder; irritant, few toxicity data"
      },
      {
        "title": "In a fire",
        "lead": "The data sheets list the products of decomposition and fire hazards. No heating test on NbC was read.",
        "points": [
          {
            "label": "Decomposition",
            "line": "Carbon monoxide and carbon dioxide are the listed decomposition products. Fumes from a fire are hazardous, and firefighters need full protective clothing."
          }
        ]
      }
    ]
  },
  "updated": "2026-10-26",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 13,
    "unreachable": 3,
    "caveats": 3,
    "note": "Written in this run from pages read in this run: the WebQC NbC and NbB2 records, the NIST-JANAF NbC0.98 table C-001, the Stanford Advanced Materials MSDS (2012) and data sheet, the USGS 2026 niobium chapter, USGS PP 1802-A Table A1, the EC critical raw materials page, the Megret et al. 2025 paper, the Reithmaier et al. arXiv paper, the Hrechanyuk et al. 2023 abstract, the Gunen et al. 2024 abstract and Wikipedia for composition, structure and route only. Unreachable: Shimada 1994 (publisher redirect), Rathod et al. 2011 (no values visible), USGS critical minerals page (HTTP 403)."
  },
  "sources": {
    "webqc-nbc": {
      "title": "WebQC, Niobium carbide (NbC) compound record: physical properties, identifiers, elemental composition",
      "url": "https://www.webqc.org/compound-NbC-NbC.html",
      "kind": "database",
      "license": "web reference site, cited not reproduced"
    },
    "janaf-nbc": {
      "title": "NIST-JANAF Thermochemical Tables, Niobium Carbide (NbC0.98), table C-001 (cr)",
      "url": "https://janaf.nist.gov/tables/C-001.html",
      "kind": "database",
      "license": "NIST public data"
    },
    "sam-nbc-msds": {
      "title": "Stanford Advanced Materials, Material Safety Data Sheet: Niobium Carbide (version 2.0, revision 5 Sep 2012)",
      "url": "https://www.sputtertargets.net/Public/pdf/niobium-carbide-msds.pdf",
      "kind": "datasheet",
      "license": "supplier safety data sheet, cited not reproduced"
    },
    "sam-nbc-tds": {
      "title": "Stanford Advanced Materials, niobium carbide data sheet with OSHA hazard classification and physical properties",
      "url": "https://samaterials.com/tds/1715418501-vd0765.pdf",
      "kind": "datasheet",
      "license": "supplier data sheet, cited not reproduced"
    },
    "wikipedia-nbc": {
      "title": "Wikipedia, Niobium carbide (composition, structure and route only)",
      "url": "https://en.wikipedia.org/wiki/Niobium_carbide",
      "kind": "web",
      "license": "CC-BY-SA 4.0"
    },
    "megret-2025-nbc": {
      "title": "Megret, Vitry and Delaunois, The use of niobium carbide as grain growth inhibitor in WC-10Co cemented carbides, J. Eur. Ceram. Soc. 45 (2025) 117533",
      "id": "doi:10.1016/j.jeurceramsoc.2025.117533",
      "url": "https://orbi.umons.ac.be/bitstream/20.500.12907/52399/1/M%c3%a9gret%20-%20The%20use%20of%20niobium%20carbide%20as%20grain%20growth%20inhibitor%20in%20WC-10Co.pdf",
      "year": 2025,
      "kind": "paper",
      "license": "author postprint, University of Mons repository"
    },
    "arxiv-nbn-gaas": {
      "title": "Reithmaier et al., Optimisation of NbN thin films on GaAs substrates for in-situ single photon detection in structured photonic devices",
      "id": "arXiv:1212.2038",
      "url": "https://arxiv.org/pdf/1212.2038",
      "year": 2012,
      "kind": "paper",
      "license": "arXiv preprint"
    },
    "hrechanyuk-2023-cu-nbc": {
      "title": "Hrechanyuk et al., Effect of niobium carbide on corrosion resistance and high-temperature oxidation resistance of copper-based materials Cu-NbC, Metallofiz. Noveishie Tekhnol. 45(12), 1473-1484",
      "url": "https://mfint.imp.kiev.ua/en/abstract/v45/i12/1473.html",
      "year": 2023,
      "kind": "paper",
      "license": "journal abstract, cited not reproduced"
    },
    "gunen-2024-nbc-coating": {
      "title": "Gunen, Altinay and Sabun, Microstructural characterization and high-temperature wear behavior of refractory niobium-carbide growth in intermetallic iron-aluminide coatings, Engineering Failure Analysis 163 (2024)",
      "id": "doi:10.1016/j.engfailanal.2024.108513",
      "url": "https://avesis.mku.edu.tr/yayin/cf4ba1ce-b688-41e9-9761-5c7e6d9a81e8/microstructural-characterization-and-high-temperature-wear-behavior-of-refractory-niobium-carbide-growth-in-intermetallic-iron-aluminide-coatings",
      "year": 2024,
      "kind": "paper",
      "license": "repository record, cited not reproduced"
    },
    "webqc-nbb2": {
      "title": "WebQC, Niobium boride (NbB2) compound record: physical properties",
      "url": "https://www.webqc.org/compound-NbB2-NbB2.html",
      "kind": "database",
      "license": "web reference site, cited not reproduced"
    },
    "usgs-mcs2026-niobium": {
      "title": "USGS Mineral Commodity Summaries 2026, Niobium (Columbium)",
      "id": "USGS MCS 2026, February 2026",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf",
      "year": 2026,
      "kind": "report",
      "license": "public domain (USGS)"
    },
    "usgs-pp1802a": {
      "title": "USGS Professional Paper 1802-A, Critical Mineral Resources of the United States, Table A1 (crustal abundances)",
      "url": "https://pubs.usgs.gov/pp/1802/a/pp1802a.pdf",
      "kind": "report",
      "license": "public domain (USGS)"
    },
    "ec-crm": {
      "title": "European Commission, Critical raw materials (list including Niobium, Regulation (EU) 2024/1252)",
      "url": "https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en",
      "kind": "web",
      "license": "European Commission web page"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/niobium-carbide/"
}