Niobium carbide NbC
NbC, niobium carbide: a 1:1 niobium-carbon compound with a cubic rock-salt structure (Wikipedia, composition and structure only) · CAS 12069-94-2 · cubic, Fm-3m
Niobium carbide is a niobium-carbon compound, NbC, with a cubic rock-salt structure (Wikipedia, composition only).
Evidence level
2 of 5
Lab-measured
- 0Predicted only. No one has made it, or no measurement exists.
- 1Calculated. Only calculated or predicted values from sources.
- 2Lab-measured. Measured properties with their conditions stated.
- 3Space-relevant tests. Measured in conditions relevant to space, such as vacuum or atomic oxygen.
- 4Ground-qualified. Qualified for an application on the ground.
- 5Flown or field-proven. Flight or field results exist.
Melting
3608 °C
Density
7.82 g/cm³
Heat capacity
36.2 J K-1 mol-1 at 298.15 K
Recipe, share of the weight
- Nb 88.6%Niobium
- C 11.4%Carbon
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.
Risk at a glance
- People Low. Flammable solid powder; irritant, few toxicity data
- If it fails Moderate. Ignition of the powder
- Corrosion No data. No corrosion data recorded
Quick facts: NbC
| Property | Value | Basis |
|---|---|---|
| Density | 7.82 g/cm³ | 1 sourced value |
| Melting point | 3,500 to 3,608 °C | 2 sourced values across conditions |
What is the density of Niobium carbide (NbC)?
Niobium carbide (NbC) has a density of 7.82 g/cm³. The source and test conditions are listed in the properties table on this page.
What is the melting point of Niobium carbide (NbC)?
Niobium carbide (NbC) has a melting point of 3,500 to 3,608 °C. The range covers 2 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is Niobium carbide (NbC) used for?
Uses recorded in the sources include Grain growth inhibitor in WC-10Co cemented carbide cutting and wear tools; Iron-aluminide wear coating reinforced with NbC particles.
Why it exists
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).
Where it's used
Cemented carbide tools
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.
Wear coatings
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.
Recipe
NbC, niobium carbide: a 1:1 niobium-carbon compound with a cubic rock-salt structure (Wikipedia, composition and structure only)
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).
| Ingredient | Atoms per unit | Share of the weight | What it does |
|---|---|---|---|
| Niobium Nb | 1 | 88.6% | The metal sublattice of the rock-salt structure. It forms the carbide with carbon and gives the 1:1 composition. |
| Carbon C | 1 | 11.4% | The non-metal sublattice of the rock-salt structure, bonded to niobium in the 1:1 compound. |
Weight shares are calculated from standard atomic weights.
What it can do
Melting
3608 °C
measured
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.
Density
7.82 g/cm³
measured
WebQC gives a density of 7.8200 g/cm3 for NbC.
Heat capacity
36.2 J K-1 mol-1 at 298.15 K
measured
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.
How it compares
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.
The same measurements for each material, so you can compare them. Each row names the key condition under the value; the full conditions and methods are in the numbered notes under Technical details. Other materials are shown beside it; each was measured under its own conditions, so open its page before comparing closely. Compare every grade in the family.
| Measurement | NbC | Al4C3 | B4C | HfC | MAX | Mo2C | SiC | TaC | TiC | ZrC |
|---|---|---|---|---|---|---|---|---|---|---|
| Capacity and energy | ||||||||||
| Molar heat capacity Cp, NbC0.98, 298.15 K | 36.23 J K-1 mol-14 | 116.8 J K-1 mol-1 | 53.76 J K-1 mol-1 | no data | no data | no data | no data | no data | 33.81 J K-1 mol-1 | no data |
| Molar heat capacity Cp, NbC0.98, 1000 K | 51.92 J K-1 mol-15 | 116.8 J K-1 mol-1 | 53.76 J K-1 mol-1 | no data | no data | no data | no data | no data | 33.81 J K-1 mol-1 | no data |
| Molar heat capacity Cp, NbC0.98, 1500 K | 55.06 J K-1 mol-16 | 116.8 J K-1 mol-1 | 53.76 J K-1 mol-1 | no data | no data | no data | no data | no data | 33.81 J K-1 mol-1 | no data |
| Standard Gibbs energy of formation, NbC0.98, 298.15 KJANAF table value at 298.15 K, delta-f G column | -136.8 kJ mol-111 | -203.4 kJ mol-1 | no data | no data | no data | no data | no data | no data | -180.4 kJ mol-1 | no data |
| Standard Gibbs energy of formation, NbC0.98, 1000 KJANAF table value at 1000 K, delta-f G column | -134 kJ mol-112 | -203.4 kJ mol-1 | no data | no data | no data | no data | no data | no data | -180.4 kJ mol-1 | no data |
| Thermal behavior and safety | ||||||||||
| Melting point, NbC (WebQC) | 3608 °C2 | 2100 °C | no data | 3890 °C | 1663 K | 2687 °C | no data | 3880 °C | 3290 K | 3532 °C |
| Melting point, NbC (Stanford Advanced Materials data sheet) | 3500 °C3 | 2100 °C | no data | 3890 °C | 1663 K | 2687 °C | no data | 3880 °C | 3290 K | 3532 °C |
| Physical and electrical | ||||||||||
| Density, NbC (WebQC) | 7.82 g/cm³1 | 2.36 g/cm³ | 2.5 gm/cm³ | 12.2 g/cm³ | 4.47 g/cm³ | 9.18 g/cm³ | 3.08 g/cm³ | 14.5 g/cm³ | 4.93 g/cm³ | 6.73 g/cm³ |
| Other measurements | ||||||||||
| Molar mass, NbC (WebQC)WebQC property block, Properties of NbC heading | 104.9 g/mol | 144 g/mol | no data | no data | no data | no data | no data | no data | 59.88 g/mol | no data |
| Standard molar entropy S, NbC0.98, 298.15 KJANAF table value at 298.15 K, S column | 34.97 J K-1 mol-17 | 88.97 J K-1 mol-1 | 27.18 J K-1 mol-1 | no data | no data | no data | no data | no data | 24.23 J K-1 mol-1 | no data |
| Standard molar entropy S, NbC0.98, 1000 KJANAF table value at 1000 K, S column | 90.04 J K-1 mol-18 | 88.97 J K-1 mol-1 | 27.18 J K-1 mol-1 | no data | no data | no data | no data | no data | 24.23 J K-1 mol-1 | no data |
| Standard enthalpy of formation, NbC0.98, 298.15 KJANAF table value at 298.15 K, delta-f H column | -138.9 kJ mol-19 | -215.7 kJ mol-1 | -62.68 kJ mol-1 | no data | no data | no data | no data | no data | -184.1 kJ mol-1 | no data |
| Standard enthalpy of formation, NbC0.98, 1000 KJANAF table value at 1000 K, delta-f H column | -136.1 kJ mol-110 | -215.7 kJ mol-1 | -62.68 kJ mol-1 | no data | no data | no data | no data | no data | -184.1 kJ mol-1 | no data |
Why choose it, and why not
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 for
- 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.
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.
Technical details
For scientists and researchers. Everything above comes from the record below: every number with its method, its conditions and its source.
Notes
The method, full conditions and any caveat for the numbered rows above.
| # | Measurement | Method | Conditions | Caveat |
|---|---|---|---|---|
| 1 | Density, NbC (WebQC) | WebQC physical-properties value; the site does not name its original source | basis as printed by WebQC (7.8200 g/cm3) | — |
| 2 | Melting point, NbC (WebQC) | WebQC physical-properties value; the site does not name its original source | basis as printed by WebQC (3,608.00 °C) | Disagrees with the 3500 °C in the Stanford Advanced Materials data sheet; both are kept and no single melting point is chosen. |
| 3 | Melting point, NbC (Stanford Advanced Materials data sheet) | Supplier data sheet value, Physical properties table; no measurement method given | basis as printed on the data sheet (3500 °C / 6332 °F) | — |
| 4 | Molar heat capacity Cp, NbC0.98, 298.15 K | JANAF table value at 298.15 K, Cp column; molar, so not converted to specific heat | temperature 298.15 Kreference state standard state pressure 0.1 MPaphase crystalline (cr); carbon-deficient NbC0.98, not stoichiometric NbC | — |
| 5 | Molar heat capacity Cp, NbC0.98, 1000 K | JANAF table value at 1000 K, read from the same table | temperature 1000 Kreference state standard state pressure 0.1 MPaphase crystalline (cr); carbon-deficient NbC0.98 | — |
| 6 | Molar heat capacity Cp, NbC0.98, 1500 K | JANAF table value at 1500 K, read from the same table | temperature 1500 Kreference state standard state pressure 0.1 MPaphase crystalline (cr); carbon-deficient NbC0.98 | — |
| 7 | Standard molar entropy S, NbC0.98, 298.15 K | — | temperature 298.15 Kreference state standard state pressure 0.1 MPaphase crystalline (cr); carbon-deficient NbC0.98 | — |
| 8 | Standard molar entropy S, NbC0.98, 1000 K | — | temperature 1000 Kreference state standard state pressure 0.1 MPaphase crystalline (cr); carbon-deficient NbC0.98 | — |
| 9 | Standard enthalpy of formation, NbC0.98, 298.15 K | — | temperature 298.15 Kreference state standard state pressure 0.1 MPaphase crystalline (cr); carbon-deficient NbC0.98 | — |
| 10 | Standard enthalpy of formation, NbC0.98, 1000 K | — | temperature 1000 Kreference state standard state pressure 0.1 MPaphase crystalline (cr); carbon-deficient NbC0.98 | — |
| 11 | Standard Gibbs energy of formation, NbC0.98, 298.15 K | — | temperature 298.15 Kreference state standard state pressure 0.1 MPaphase crystalline (cr); carbon-deficient NbC0.98 | — |
| 12 | Standard Gibbs energy of formation, NbC0.98, 1000 K | — | temperature 1000 Kreference state standard state pressure 0.1 MPaphase crystalline (cr); carbon-deficient NbC0.98 | — |
Corrosion and compatibility
What happens when it meets other materials and environments.
| Environment | Concern | What happens |
|---|---|---|
| Oxidizing agents (materials to avoid, per the supplier) | not rated | The supplier lists oxidizing agents as materials to avoid and says the powder does not decompose if stored as specified.1 |
| Copper matrix with NbC additions, high-temperature oxidation at 370 to 700 degC | not rated | 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.2 |
| # | Environment | Details | Test conditions |
|---|---|---|---|
| 1 | Oxidizing agents (materials to avoid, per the supplier) | 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. | basis supplier safety data sheet statement, not a corrosion test |
| 2 | Copper matrix with NbC additions, high-temperature oxidation at 370 to 700 degC | 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. | matrix copperatmosphere not stated in the abstract (high-temperature oxidation)temperature 370 to 700 °C |
Risks and side effects
Hazards to people, what happens when a cell overheats, and how the material is handled and stored.
For people
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.
- Flammability
- 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.
- Irritation
- 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.
- Dust
- The MSDS says to take care not to raise dust when cleaning up a spill, and to vacuum with a HEPA filter.
In a fire
The data sheets list the products of decomposition and fire hazards. No heating test on NbC was read.
- Decomposition
- Carbon monoxide and carbon dioxide are the listed decomposition products. Fumes from a fire are hazardous, and firefighters need full protective clothing.
Test details
The original wording and numbers from the sources, for readers who want them.
Failure risks
| Failure | Trigger and consequence |
|---|---|
| Ignition of the powdermoderate severity | Powder exposed to an ignition source. The data sheet prints no trigger temperature or test method.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. |
Side effects on surrounding parts
| Affects | Effect |
|---|---|
| Workers and enclosed spaces during a fire | Decomposition products listed are carbon monoxide and carbon dioxide. The MSDS says no dangerous reactions are known. |
Handling and storage
- 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.
- Routes of entry listed in the MSDS are inhalation, skin, eye and ingestion. Use appropriate respiratory and protective equipment.
Supply and geography
How common the raw materials are and where they come from.
Niobium (feedstock for the niobium half of NbC)
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.
- Top producers (2025)
- Brazil 93%, Canada 5%
- Critical mineral lists
- EU: listed
- 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.
Documents
Datasheets, safety data sheets, papers and standards you can open.
Full record
The complete spore, as stored. Free to reuse under CC-BY-4.0. Images keep the licence shown with each one.
Show the full YAML
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.
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
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
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
- benchmark: melting_point
label: Melting point, NbC (WebQC)
value: 3608
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
- benchmark: melting_point
label: Melting point, NbC (Stanford Advanced Materials data sheet)
value: 3500
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
- benchmark: molar_mass
label: Molar mass, NbC (WebQC)
value: 104.91708
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
- benchmark: molar_heat_capacity
label: Molar heat capacity Cp, NbC0.98, 298.15 K
value: 36.233
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
- benchmark: molar_heat_capacity
label: Molar heat capacity Cp, NbC0.98, 1000 K
value: 51.923
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
- benchmark: molar_heat_capacity
label: Molar heat capacity Cp, NbC0.98, 1500 K
value: 55.061
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
- benchmark: standard_molar_entropy
label: Standard molar entropy S, NbC0.98, 298.15 K
value: 34.966
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
- benchmark: standard_molar_entropy
label: Standard molar entropy S, NbC0.98, 1000 K
value: 90.038
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
- benchmark: standard_enthalpy_of_formation
label: Standard enthalpy of formation, NbC0.98, 298.15 K
value: -138.909
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
- benchmark: standard_enthalpy_of_formation
label: Standard enthalpy of formation, NbC0.98, 1000 K
value: -136.097
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
- benchmark: standard_gibbs_energy_of_formation
label: Standard Gibbs energy of formation, NbC0.98, 298.15 K
value: -136.785
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
- benchmark: standard_gibbs_energy_of_formation
label: Standard Gibbs energy of formation, NbC0.98, 1000 K
value: -134.009
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
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
note: Composite result. The rating is left unknown because the abstract gives no rating and the matrix is copper, not NbC.
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
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.'
related:
- name: Niobium nitride (NbN) superconducting films
formula: NbN
line: NbN is a superconductor in thin-film form. Reithmaier et al. (arXiv:1212.2038) sputtered NbN on GaAs at an optimum growth temperature of about 475 degC. The critical temperature was 12.6 +/- 0.2 K for a 22 nm film and 10.2 +/- 0.2 K for a 4 nm film. Single-photon detectors made from the 4 nm films reached detection efficiencies up to 21 +/- 2 percent.
source: arxiv-nbn-gaas
where: Abstract; Results (critical temperature, growth temperature, detector efficiency)
- name: Niobium diboride (NbB2)
formula: NbB2
line: WebQC gives a density of 6.9700 g/cm3 and a melting point of 3,050.00 degC for niobium diboride. These are database values; no measurement method is named.
source: webqc-nbb2
where: Compound record, Physical properties (density and melting rows)
- name: Niobium silicide (NbSi2)
formula: NbSi2
line: No niobium disilicide property was read in a fetched primary source, so this entry carries no values. The supplier catalogue figures seen in search results are not used.
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).'
story:
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
atoms: 1
atomic_weight: 92.90638
role: The metal sublattice of the rock-salt structure. It forms the carbide with carbon and gives the 1:1 composition.
source: webqc-nbc
where: Elemental composition of NbC table, Nb row
- name: Carbon
symbol: C
atoms: 1
atomic_weight: 12.0107
role: The non-metal sublattice of the rock-salt structure, bonded to niobium in the 1:1 compound.
source: webqc-nbc
where: Elemental composition of NbC table, C row
risk_groups:
- title: For people
level: 1
verdict: Flammable solid powder; irritant, few toxicity data
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.
- 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.
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
benchmark: melting_point
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.
- label: Density
benchmark: density
line: WebQC gives a density of 7.8200 g/cm3 for NbC.
- label: Heat capacity
benchmark: molar_heat_capacity
value: 36.2 J K-1 mol-1 at 298.15 K
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.
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
- label: Melting point
benchmark: melting_point
- label: Heat capacity
benchmark: molar_heat_capacity
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.
updated: '2026-10-26'
license: CC-BY-4.0
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
References
Every number above carries a reference number. Click one to see the source and where in it the value comes from.