Aluminium carbide Al4C3
Al4C3, aluminium carbide: four aluminium and three carbon atoms per formula unit, rhombohedral structure (Wikipedia, composition and structure only) · CAS 1299-86-1 · rhombohedral, R3m
Aluminium carbide is Al4C3, a rhombohedral compound of aluminium and carbon (Wikipedia, composition and structure).
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.
Formation enthalpy
-215.7 kJ mol-1
Heat capacity
116.8 J K-1 mol-1
Thermal stability
1400 °C
Recipe, share of the weight
- Al not statedAluminium
- C not statedCarbon
Best for
Thermochemical reference data for the carbide that forms at aluminium-carbon and aluminium-SiC interfaces, and for judging how much of it a composite can tolerate
Weakest at
Water and moist air: it releases flammable methane and heat (CAMEO, Wikipedia). Its melting point is not settled, since Wikipedia gives 2100 C as the melting point and 1400 C as the decomposition temperature
Risk at a glance
- People None found. Dangerous when wet; releases flammable methane
- If it fails High. Methane release and heat on contact with water
- Corrosion Severe. In water or moist air, Al4C3 gives off heat and flammable methane
Quick facts: Al4C3
| Property | Value | Basis |
|---|---|---|
| Density | 2.36 g/cm³ | 1 sourced value |
| Melting point | 2,100 °C | 1 sourced value |
What is the density of Aluminium carbide (Al4C3)?
Aluminium carbide (Al4C3) has a density of 2.36 g/cm³. The source and test conditions are listed in the properties table on this page.
What is the melting point of Aluminium carbide (Al4C3)?
Aluminium carbide (Al4C3) has a melting point of 2,100 °C. The source and test conditions are listed in the properties table on this page.
Why it exists
Aluminium carbide is the carbide that forms when molten aluminium touches carbon or silicon carbide, so it matters for the reliability of aluminium composites. Its thermochemistry is well documented: the JANAF table gives a standard enthalpy of formation of -215.685 kJ/mol at 298.15 K for the crystalline solid. Its density is 2.36 g/cm3 and its molar mass is 143.95853 g/mol (Wikipedia). It is not a stable structural ceramic in wet conditions, and its hydrolysis to methane is the main reason to treat it with care.
Recipe
Al4C3, aluminium carbide: four aluminium and three carbon atoms per formula unit, rhombohedral structure (Wikipedia, composition and structure only)
Al4C3 is an aluminium-carbon compound with four aluminium and three carbon per formula unit (Wikipedia, composition only). It is made by direct reaction of aluminium and carbon in an electric arc furnace, or from alumina and carbon, which gives carbon monoxide (Wikipedia). It has a rhombohedral structure, space group R3m (Wikipedia).
| Ingredient | Share of the weight | What it does |
|---|---|---|
| Aluminium Al | not stated | Metal component. Molten aluminium reacts with carbon or with SiC to form the carbide, so the carbide appears at the interface in aluminium composites. |
| Carbon C | not stated | Non-metal component, supplied as carbon or taken from silicon carbide particles in aluminium composites. |
Weight shares are as printed in the sources.
What it can do
Formation enthalpy
-215.7 kJ mol-1
measured
The standard enthalpy of formation is -215.685 kJ/mol at 298.15 K and -263.532 kJ/mol at 1000 K (JANAF). It becomes more negative as the temperature rises in this range.
Heat capacity
116.8 J K-1 mol-1
measured
The molar heat capacity is 116.784 J K-1 mol-1 at 298.15 K and 176.142 J K-1 mol-1 at 1000 K (JANAF).
Thermal stability
1400 °C
measured
Wikipedia says the compound is stable up to 1400 C. Its infobox melting point is 2100 C, which does not match, so the melting figure is not used as a settled value.
How it compares
Al4C3 is a carbide with a standard enthalpy of formation of -215.685 kJ/mol at 298.15 K (JANAF) and a density of 2.36 g/cm3 (Wikipedia). Unlike the refractory carbides used in coatings, it reacts with water and moist air to give methane, so its handling differs most from theirs. The compare rows use the three benchmarks that have values from sources read in this run; no other carbide is compared here.
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 | Al4C3 | B4C | HfC | MAX | Mo2C | NbC | SiC | TaC | TiC | ZrC |
|---|---|---|---|---|---|---|---|---|---|---|
| Capacity and energy | ||||||||||
| Molar heat capacity Cp, Al4C3, 298.15 K | 116.8 J K-1 mol-11 | 53.76 J K-1 mol-1 | no data | no data | no data | 36.23 J K-1 mol-1 | no data | no data | 33.81 J K-1 mol-1 | no data |
| Molar heat capacity Cp, Al4C3, 1000 K | 176.1 J K-1 mol-12 | 53.76 J K-1 mol-1 | no data | no data | no data | 36.23 J K-1 mol-1 | no data | no data | 33.81 J K-1 mol-1 | no data |
| Standard Gibbs energy of formation, Al4C3, 298.15 KJANAF table value at 298.15 K; delta-f G column | -203.4 kJ mol-17 | no data | no data | no data | no data | -136.8 kJ mol-1 | no data | no data | -180.4 kJ mol-1 | no data |
| Standard Gibbs energy of formation, Al4C3, 1000 K | -169.8 kJ mol-18 | no data | no data | no data | no data | -136.8 kJ mol-1 | no data | no data | -180.4 kJ mol-1 | no data |
| Thermal behavior and safety | ||||||||||
| Melting point, Al4C3 (Wikipedia infobox) | 2100 °C12 | no data | 3890 °C | 1663 K | 2687 °C | 3608 °C | no data | 3880 °C | 3290 K | 3532 °C |
| Physical and electrical | ||||||||||
| Density, Al4C3 | 2.36 g/cm³10 | 2.5 gm/cm³ | 12.2 g/cm³ | 4.47 g/cm³ | 9.18 g/cm³ | 7.82 g/cm³ | 3.08 g/cm³ | 14.5 g/cm³ | 4.93 g/cm³ | 6.73 g/cm³ |
| Temperature behavior | ||||||||||
| Decomposition temperature, Al4C3 | 1400 °C13 | no data | no data | no data | no data | no data | no data | no data | no data | no data |
| Other measurements | ||||||||||
| Standard molar entropy S, Al4C3, 298.15 KJANAF table value at 298.15 K; S column | 88.97 J K-1 mol-13 | 27.18 J K-1 mol-1 | no data | no data | no data | 34.97 J K-1 mol-1 | no data | no data | 24.23 J K-1 mol-1 | no data |
| Standard molar entropy S, Al4C3, 1000 K | 273.2 J K-1 mol-14 | 27.18 J K-1 mol-1 | no data | no data | no data | 34.97 J K-1 mol-1 | no data | no data | 24.23 J K-1 mol-1 | no data |
| Standard enthalpy of formation, Al4C3, 298.15 KJANAF table value at 298.15 K; delta-f H column | -215.7 kJ mol-15 | -62.68 kJ mol-1 | no data | no data | no data | -138.9 kJ mol-1 | no data | no data | -184.1 kJ mol-1 | no data |
| Standard enthalpy of formation, Al4C3, 1000 K | -263.5 kJ mol-16 | -62.68 kJ mol-1 | no data | no data | no data | -138.9 kJ mol-1 | no data | no data | -184.1 kJ mol-1 | no data |
| Log of formation constant, Al4C3, 298.15 K | 35.63 -9 | no data | no data | no data | no data | no data | no data | no data | no data | no data |
| Molar mass, Al4C3 | 144 g/mol11 | no data | no data | no data | no data | 104.9 g/mol | no data | no data | 59.88 g/mol | no data |
Why choose it, and why not
Good for
- Thermochemical reference. JANAF gives a full set of formation and heat-capacity values from 298.15 K to 1000 K.
- Understanding the interface in aluminium composites. Wikipedia describes the carbide layer that forms on SiC particles.
Watch out for
- Water and moist air. It releases flammable methane and heat.
- Melting point is unsettled. Wikipedia gives 2100 C as the melting point and 1400 C as the decomposition temperature.
- Carbide content in composites. Wikipedia notes that the carbide lowers strength and improves wettability, but no test value was read.
Al4C3 is a well-characterised compound in thermochemistry, with a clear hazard in wet conditions. Its formation data are sourced from JANAF, and its water reaction from CAMEO and Wikipedia. Its melting point, hazard classification and use data are not yet settled from sources read in this run.
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 | Molar heat capacity Cp, Al4C3, 298.15 K | JANAF table value at 298.15 K; molar, so not converted to a specific heat (no molar mass conversion applied in this file) | temperature 298.15 Kreference state standard state pressure 0.1 MPaphase crystalline (cr) | — |
| 2 | Molar heat capacity Cp, Al4C3, 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) | — |
| 3 | Standard molar entropy S, Al4C3, 298.15 K | — | temperature 298.15 Kreference state standard state pressure 0.1 MPaphase crystalline (cr) | — |
| 4 | Standard molar entropy S, Al4C3, 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) | — |
| 5 | Standard enthalpy of formation, Al4C3, 298.15 K | — | temperature 298.15 Kreference state standard state pressure 0.1 MPaphase crystalline (cr) | — |
| 6 | Standard enthalpy of formation, Al4C3, 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) | — |
| 7 | Standard Gibbs energy of formation, Al4C3, 298.15 K | — | temperature 298.15 Kreference state standard state pressure 0.1 MPaphase crystalline (cr) | — |
| 8 | Standard Gibbs energy of formation, Al4C3, 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) | — |
| 9 | Log of formation constant, Al4C3, 298.15 K | JANAF table value at 298.15 K; log Kf column, dimensionless | temperature 298.15 Kreference state standard state pressure 0.1 MPaphase crystalline (cr) | — |
| 10 | Density, Al4C3 | Wikipedia Properties row; the row gives no temperature of its own, so the page's standard-state note is used | temperature 25 Cpressure 100 kPabasis Wikipedia standard-state note (data at 25 C and 100 kPa unless otherwise noted) | — |
| 11 | Molar mass, Al4C3 | Wikipedia Properties row, molar mass; not converted | basis molar mass of Al4C3 as printed on the Wikipedia Properties row | — |
| 12 | Melting point, Al4C3 (Wikipedia infobox) | Wikipedia infobox Melting point row. The same page gives 1400 C as the temperature up to which the compound is stable, so the melting figure is kept only as printed | basis as printed in the infobox; conflicts with the decomposition temperature in the body text | The melting figure and the decomposition figure on the same page do not agree, so neither is a settled melting point. |
| 13 | Decomposition temperature, Al4C3 | Wikipedia body text and infobox; the name decomposition_temperature is not in property-canon.yaml | basis stated as stable up to this temperature in the body text, and as decomposes at this temperature in the infobox boiling point row | — |
Corrosion and compatibility
What happens when it meets other materials and environments.
| Environment | Concern | What happens |
|---|---|---|
| Water or moist air, at room temperature and above | severe | In water or moist air, Al4C3 gives off heat and flammable methane1 |
| # | Environment | Details | Test conditions |
|---|---|---|---|
| 1 | Water or moist air, at room temperature and above | CAMEO Chemicals says it decomposes slowly in the presence of water or moist air to generate heat and flammable methane gas, and calls this a dangerous fire risk. Wikipedia gives the reaction Al4C3 + 12 H2O to 4 Al(OH)3 + 3 CH4, with evolution of methane and considerable heat. The rating severe is the assistant's judgement from these two sources; CAMEO gives no corrosion rating. | atmosphere water or moist airtemperature room temperature and above (Wikipedia says the reaction runs with considerable heat) |
Risks and side effects
Hazards to people, what happens when a cell overheats, and how the material is handled and stored.
For people
The compound gives off flammable methane and heat when it meets water or moist air, and CAMEO lists it as a fire hazard with a DOT placard for dangerous when wet.
- Water and moist air
- Contact with water or moist air releases heat and flammable methane (CAMEO; Wikipedia). CAMEO calls this a dangerous fire risk.
- Ignition
- The material may be ignited by heat, sparks or flames. A fire gives irritating, corrosive or toxic gases (CAMEO).
- Exposure
- CAMEO says inhalation or contact with the vapors or decomposition products may cause severe injury or death, and that contact with water can form corrosive solutions.
If the powder meets water
These points come from the CAMEO and Wikipedia descriptions of the reaction.
- The reaction
- Al4C3 + 12 H2O gives 4 Al(OH)3 and 3 CH4, with considerable heat (Wikipedia).
Test details
The original wording and numbers from the sources, for readers who want them.
Failure risks
| Failure | Trigger and consequence |
|---|---|
| Methane release and heat on contact with waterhigh severity | Water or moist air reaching the powder or the carbide phase in a compositeFlammable methane and heat are evolved (CAMEO; Wikipedia hydrolysis). CAMEO calls this a dangerous fire risk. |
| Ignition by heat or sparksmoderate severity | Heat, sparks or open flame near the materialCAMEO says the material may be ignited by heat, sparks or flames, and that a fire produces irritating, corrosive or toxic gases. |
Side effects on surrounding parts
| Affects | Effect |
|---|---|
| Surrounding material and any enclosure holding the powder | Hydrolysis gives aluminium hydroxide and methane, with considerable heat (Wikipedia, Reactions section and infobox solubility row). |
Handling and storage
- Keep the material away from water and moist air, because contact releases flammable methane and heat (CAMEO).
Supply and geography
How common the raw materials are and where they come from.
Aluminium (feedstock for the aluminium half of Al4C3)
- Top producers (2025)
- China 60.8%, India 5.7%, Russia 5.3%, Canada 4.5%, United Arab Emirates 3.6%
- Critical mineral lists
- US: listed
- Recycling
- USGS 2026: about 3.6 million tons of aluminum were recovered from purchased scrap in the United States in 2025. No recycling figure for Al4C3 itself was found.
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: aluminium-carbide
spore_version: 0.2
family: carbide-nitride-boride-ceramics
name: Aluminium carbide
abbreviation: Al4C3
role: interfacial carbide in aluminium-carbon and aluminium-SiC composites; thermochemical reference compound
category: ceramics
type: carbides
summary: |
Aluminium carbide is Al4C3, a rhombohedral compound of aluminium and carbon (Wikipedia, composition and structure). It forms when molten aluminium reacts with carbon or with silicon carbide particles, which is why it appears at the interface in aluminium composites. NIST-JANAF gives a standard enthalpy of formation of -215.685 kJ/mol at 298.15 K for the crystalline solid. The compound is not a stable structural ceramic in wet conditions: CAMEO Chemicals says it decomposes slowly in water or moist air to give heat and flammable methane, and Wikipedia gives the hydrolysis to aluminium hydroxide and methane.
best_for: Thermochemical reference data for the carbide that forms at aluminium-carbon and aluminium-SiC interfaces, and for judging how much of it a composite can tolerate
weakest_at: 'Water and moist air: it releases flammable methane and heat (CAMEO, Wikipedia). Its melting point is not settled, since Wikipedia gives 2100 C as the melting point and 1400 C as the decomposition temperature'
identity:
formula: 'Al4C3, aluminium carbide: four aluminium and three carbon atoms per formula unit, rhombohedral structure (Wikipedia, composition and structure only)'
cas: 1299-86-1
crystal_system: rhombohedral
space_group: R3m
source: wikipedia-al4c3
where: Infobox, Identifiers row (CAS 1299-86-1, verified) and Structure rows (Pearson symbol hR21, space group R3m No. 166)
tags:
environments: []
stresses: []
applications: []
properties:
- benchmark: molar_heat_capacity
label: Molar heat capacity Cp, Al4C3, 298.15 K
value: 116.784
unit: J K-1 mol-1
scope: material
conditions:
temperature: 298.15 K
reference_state: standard state pressure 0.1 MPa
phase: crystalline (cr)
method: JANAF table value at 298.15 K; molar, so not converted to a specific heat (no molar mass conversion applied in this file)
status: ground
source: janaf-al4c3
where: Aluminum Carbide (Al4C3) table, formula C3Al4(cr), row 298.15, Cp column
- benchmark: molar_heat_capacity
label: Molar heat capacity Cp, Al4C3, 1000 K
value: 176.142
unit: J K-1 mol-1
scope: material
conditions:
temperature: 1000 K
reference_state: standard state pressure 0.1 MPa
phase: crystalline (cr)
method: JANAF table value at 1000 K, read from the same table
status: ground
source: janaf-al4c3
where: Aluminum Carbide (Al4C3) table, formula C3Al4(cr), row 1000, Cp column
- benchmark: standard_molar_entropy
label: Standard molar entropy S, Al4C3, 298.15 K
value: 88.969
unit: J K-1 mol-1
scope: material
conditions:
temperature: 298.15 K
reference_state: standard state pressure 0.1 MPa
phase: crystalline (cr)
method: JANAF table value at 298.15 K; S column
status: ground
source: janaf-al4c3
where: Aluminum Carbide (Al4C3) table, formula C3Al4(cr), row 298.15, S column
- benchmark: standard_molar_entropy
label: Standard molar entropy S, Al4C3, 1000 K
value: 273.243
unit: J K-1 mol-1
scope: material
conditions:
temperature: 1000 K
reference_state: standard state pressure 0.1 MPa
phase: crystalline (cr)
method: JANAF table value at 1000 K, read from the same table
status: ground
source: janaf-al4c3
where: Aluminum Carbide (Al4C3) table, formula C3Al4(cr), row 1000, S column
- benchmark: standard_enthalpy_of_formation
label: Standard enthalpy of formation, Al4C3, 298.15 K
value: -215.685
unit: kJ mol-1
scope: material
conditions:
temperature: 298.15 K
reference_state: standard state pressure 0.1 MPa
phase: crystalline (cr)
method: JANAF table value at 298.15 K; delta-f H column
status: ground
source: janaf-al4c3
where: Aluminum Carbide (Al4C3) table, formula C3Al4(cr), row 298.15, delta-f H column
- benchmark: standard_enthalpy_of_formation
label: Standard enthalpy of formation, Al4C3, 1000 K
value: -263.532
unit: kJ mol-1
scope: material
conditions:
temperature: 1000 K
reference_state: standard state pressure 0.1 MPa
phase: crystalline (cr)
method: JANAF table value at 1000 K, read from the same table
status: ground
source: janaf-al4c3
where: Aluminum Carbide (Al4C3) table, formula C3Al4(cr), row 1000, delta-f H column
- benchmark: standard_gibbs_energy_of_formation
label: Standard Gibbs energy of formation, Al4C3, 298.15 K
value: -203.356
unit: kJ mol-1
scope: material
conditions:
temperature: 298.15 K
reference_state: standard state pressure 0.1 MPa
phase: crystalline (cr)
method: JANAF table value at 298.15 K; delta-f G column
status: ground
source: janaf-al4c3
where: Aluminum Carbide (Al4C3) table, formula C3Al4(cr), row 298.15, delta-f G column
- benchmark: standard_gibbs_energy_of_formation
label: Standard Gibbs energy of formation, Al4C3, 1000 K
value: -169.804
unit: kJ mol-1
scope: material
conditions:
temperature: 1000 K
reference_state: standard state pressure 0.1 MPa
phase: crystalline (cr)
method: JANAF table value at 1000 K, read from the same table
status: ground
source: janaf-al4c3
where: Aluminum Carbide (Al4C3) table, formula C3Al4(cr), row 1000, delta-f G column
- benchmark: log_kf
label: Log of formation constant, Al4C3, 298.15 K
value: 35.627
unit: '-'
scope: material
conditions:
temperature: 298.15 K
reference_state: standard state pressure 0.1 MPa
phase: crystalline (cr)
method: JANAF table value at 298.15 K; log Kf column, dimensionless
status: ground
source: janaf-al4c3
where: Aluminum Carbide (Al4C3) table, formula C3Al4(cr), row 298.15, log Kf column
- benchmark: density
label: Density, Al4C3
value: 2.36
unit: g/cm3
scope: material
conditions:
temperature: 25 C
pressure: 100 kPa
basis: Wikipedia standard-state note (data at 25 C and 100 kPa unless otherwise noted)
method: Wikipedia Properties row; the row gives no temperature of its own, so the page's standard-state note is used
status: ground
source: wikipedia-al4c3
where: Properties row, Density
- benchmark: molar_mass
label: Molar mass, Al4C3
value: 143.95853
unit: g/mol
scope: material
conditions:
basis: molar mass of Al4C3 as printed on the Wikipedia Properties row
method: Wikipedia Properties row, molar mass; not converted
status: ground
source: wikipedia-al4c3
where: Properties row, Molar mass
- benchmark: melting_point
label: Melting point, Al4C3 (Wikipedia infobox)
value: 2100
unit: °C
scope: material
conditions:
basis: as printed in the infobox; conflicts with the decomposition temperature in the body text
method: Wikipedia infobox Melting point row. The same page gives 1400 C as the temperature up to which the compound is stable, so the melting figure is kept only as printed
status: ground
note: The melting figure and the decomposition figure on the same page do not agree, so neither is a settled melting point.
source: wikipedia-al4c3
where: Infobox, Melting point row
- benchmark: decomposition_temperature
label: Decomposition temperature, Al4C3
value: 1400
unit: °C
scope: material
conditions:
basis: stated as stable up to this temperature in the body text, and as decomposes at this temperature in the infobox boiling point row
method: Wikipedia body text and infobox; the name decomposition_temperature is not in property-canon.yaml
status: ground
source: wikipedia-al4c3
where: Body text, first paragraph of the properties section; Infobox, Boiling point row
corrosion:
- environment: Water or moist air, at room temperature and above
headline: In water or moist air, Al4C3 gives off heat and flammable methane
effect: CAMEO Chemicals says it decomposes slowly in the presence of water or moist air to generate heat and flammable methane gas, and calls this a dangerous fire risk. Wikipedia gives the reaction Al4C3 + 12 H2O to 4 Al(OH)3 + 3 CH4, with evolution of methane and considerable heat. The rating severe is the assistant's judgement from these two sources; CAMEO gives no corrosion rating.
rating: severe
conditions:
atmosphere: water or moist air
temperature: room temperature and above (Wikipedia says the reaction runs with considerable heat)
source: cameo-al4c3
where: Air and Water Reactions, Fire Hazard (ERG Guide 138 excerpt), Reactivity Alerts
risks:
hazards:
- text: 'CAMEO Chemicals (NOAA): ERG Guide 138 says it may ignite on contact with water or moist air, and may be ignited by heat, sparks or flames. The DOT hazard label is Dangerous When Wet, placard 4.3.'
ghs: []
source: cameo-al4c3
where: Fire Hazard (ERG Guide 138 excerpt); Chemical Identifiers, DOT Hazard Label
- text: 'CAMEO Chemicals (NOAA): inhalation or contact with vapors, substance or decomposition products may cause severe injury or death. Contact with water can form corrosive solutions, and a fire produces irritating, corrosive or toxic gases.'
ghs: []
source: cameo-al4c3
where: Health Hazard (ERG Guide 138 excerpt)
failure_risks:
- mode: Methane release and heat on contact with water
trigger: Water or moist air reaching the powder or the carbide phase in a composite
consequence: Flammable methane and heat are evolved (CAMEO; Wikipedia hydrolysis). CAMEO calls this a dangerous fire risk.
severity: high
source: cameo-al4c3
where: Air and Water Reactions
- mode: Ignition by heat or sparks
trigger: Heat, sparks or open flame near the material
consequence: CAMEO says the material may be ignited by heat, sparks or flames, and that a fire produces irritating, corrosive or toxic gases.
severity: moderate
source: cameo-al4c3
where: Fire Hazard (ERG Guide 138 excerpt)
side_effects:
- text: Hydrolysis gives aluminium hydroxide and methane, with considerable heat (Wikipedia, Reactions section and infobox solubility row).
affects: Surrounding material and any enclosure holding the powder
source: wikipedia-al4c3
where: Reactions section; infobox solubility row
handling:
- text: Keep the material away from water and moist air, because contact releases flammable methane and heat (CAMEO).
source: cameo-al4c3
where: Air and Water Reactions
mitigations: []
uses: []
supply:
- subject: Aluminium (feedstock for the aluminium half of Al4C3)
producers:
- country: China
share_percent: 60.8
year: 2025
- country: India
share_percent: 5.7
year: 2025
- country: Russia
share_percent: 5.3
year: 2025
- country: Canada
share_percent: 4.5
year: 2025
- country: United Arab Emirates
share_percent: 3.6
year: 2025
critical_lists:
- list: USGS 2025 List of Critical Minerals (aluminum listed, used in almost all sectors of the economy)
listed: true
recycling: 'USGS 2026: about 3.6 million tons of aluminum were recovered from purchased scrap in the United States in 2025. No recycling figure for Al4C3 itself was found.'
substitutes: []
source: usgs-mcs2026-aluminum
where: Salient Statistics, Recycling; World Smelter Production and Capacity table, smelter production 2025e (world total 74,000 thousand t; shares calculated by Space Mushroom against it); critical list from the USGS 2025 critical minerals page
media: []
documents:
- title: NIST-JANAF Thermochemical Tables, Aluminum Carbide (Al4C3), table formula C3Al4(cr)
type: database
url: https://janaf.nist.gov/tables/C-139.html
year: 1965
- title: Wikipedia, Aluminium carbide (composition, structure, properties, hydrolysis and preparation only)
type: database
url: https://en.wikipedia.org/wiki/Aluminium_carbide
- title: CAMEO Chemicals (NOAA), Chemical Datasheet for aluminum carbide, CAS 1299-86-1
type: database
url: https://cameochemicals.noaa.gov/chemical/2381
- title: USGS Mineral Commodity Summaries 2026, Aluminum
type: report
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf
year: 2026
- title: USGS, About the 2025 List of Critical Minerals
type: report
url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
year: 2025
gaps:
- 'Carbon feedstock and production route: the search results describe an arc-furnace reaction of aluminium and carbon (Wikipedia, read in this run), but no source gave the carbon grade or a separate process route, so the recipe line does not add one.'
- 'Density at a stated temperature other than the Wikipedia standard-state note: only one density value was read, and no second source was opened to check it.'
- 'Hazard classification (GHS hazard statements and signal word): PubChem returned a browser check and the Safety and Hazards section could not be read. The supplier data sheets that were reached as search results were not fetched, so no H-codes are listed.'
- 'Uses: no fetched page gave an Al4C3 use with a test or service example. The composite papers found in search gave no readable full text (Springer and the Coventry PDF were blocked or returned a cover file), and Wikipedia is limited to composition and history by the brief. No use is listed.'
- 'Interfacial carbon-fibre and carbon-nanotube composite data (carbide content and its effect on strength): no full text read in this run, so none is recorded.'
- 'Moisture ageing rate and the room-temperature hydrolysis rate: a search snippet described slow reaction with moist air, but no fetched source gave a rate, so none is recorded.'
- 'Aluminium crustal abundance: aluminium is not in the USGS PP 1802-A Table A1 crustal abundance list as read in this run, so no abundance is recorded.'
- 'EU critical raw materials list entry for aluminium or bauxite: the European Commission page was not read in this run, so it is not listed.'
- 'Carbon as a feedstock: no supply, critical-mineral or abundance data for carbon was read in a fetched page.'
- Atomic weights of aluminium and carbon were not read in a fetched page, so the recipe parts carry no atomic_weight and no atom counts.
- 'Melting point is not settled: Wikipedia gives 2100 C in the infobox and 1400 C as the decomposition temperature. Neither is confirmed by a second source.'
- 'Property names not in property-canon.yaml: molar_heat_capacity, standard_molar_entropy, standard_enthalpy_of_formation, standard_gibbs_energy_of_formation, log_kf, molar_mass and decomposition_temperature. The JANAF values are molar and are not converted to specific heat.'
- 'Designations (UNS, EN, DIN, JIS, ASTM and similar): no fetched source printed a designation for this compound. None are listed.'
- 'Hardness, elastic modulus, thermal conductivity, thermal expansion and electrical resistivity of Al4C3: no fetched source with a printed value was read.'
- 'Radiation, vacuum and flight behaviour: no source read in this run.'
- 'Environments: no source read supports a space-environment tag, so tags.environments is empty.'
related:
- name: Aluminium silicide
status: not confirmed
text: 'No single binary aluminium silicide with a confirmed formula was found in a fetched source. Search results disagree: one supplier lists Al4Si3 and another database lists AlSi, whose quoted melting figure is close to the aluminium-silicon eutectic, so it may describe an alloy mix rather than a compound. No property values are given.'
- name: Aluminium borosilicide
status: not confirmed
text: No recognised compound with this name was found in a fetched source. A supplier lists a composition label AlBSi with no source. The known aluminium borides (AlB2 and AlB12) contain no silicon. No property values are given.
sources:
janaf-al4c3:
title: NIST-JANAF Thermochemical Tables, Aluminum Carbide (Al4C3), crystalline phase C3Al4(cr)
url: https://janaf.nist.gov/tables/C-139.html
kind: database
license: NIST public data
wikipedia-al4c3:
title: Wikipedia, Aluminium carbide (composition, structure, properties, hydrolysis and preparation only)
url: https://en.wikipedia.org/wiki/Aluminium_carbide
kind: web
license: CC-BY-SA 4.0
cameo-al4c3:
title: CAMEO Chemicals (NOAA), Chemical Datasheet, aluminum carbide (CAS 1299-86-1, ERG Guide 138 excerpt)
url: https://cameochemicals.noaa.gov/chemical/2381
kind: database
license: NOAA public data
usgs-mcs2026-aluminum:
title: USGS Mineral Commodity Summaries 2026, Aluminum
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf
kind: report
license: public domain (USGS)
usgs-crit2025:
title: USGS, About the 2025 List of Critical Minerals (final list of 60 minerals)
url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
kind: web
license: public domain (USGS)
license: CC-BY-4.0
updated: '2026-10-26'
review:
status: draft
method: assistant
checked_values: 13
unreachable: 3
caveats: 4
note: 'Written in this run from pages read in this run: the NIST-JANAF C-139 table, the Wikipedia Al4C3 page (composition, properties, hydrolysis and preparation), the CAMEO Chemicals datasheet, the USGS Mineral Commodity Summaries 2026 aluminum chapter (PDF text), and the USGS 2025 critical minerals page. Unreachable: PubChem (browser check), Springer carbon-fibre paper (redirect to login), University of Antwerp repository record (catalogue frame only). Coventry PDF returned a print cover only.'
story:
recipe:
line: Al4C3 is an aluminium-carbon compound with four aluminium and three carbon per formula unit (Wikipedia, composition only). It is made by direct reaction of aluminium and carbon in an electric arc furnace, or from alumina and carbon, which gives carbon monoxide (Wikipedia). It has a rhombohedral structure, space group R3m (Wikipedia).
parts:
- name: Aluminium
symbol: Al
role: Metal component. Molten aluminium reacts with carbon or with SiC to form the carbide, so the carbide appears at the interface in aluminium composites.
- name: Carbon
symbol: C
role: Non-metal component, supplied as carbon or taken from silicon carbide particles in aluminium composites.
risk_groups:
- title: For people
level: 0
verdict: Dangerous when wet; releases flammable methane
lead: The compound gives off flammable methane and heat when it meets water or moist air, and CAMEO lists it as a fire hazard with a DOT placard for dangerous when wet.
points:
- label: Water and moist air
line: Contact with water or moist air releases heat and flammable methane (CAMEO; Wikipedia). CAMEO calls this a dangerous fire risk.
- label: Ignition
line: The material may be ignited by heat, sparks or flames. A fire gives irritating, corrosive or toxic gases (CAMEO).
- label: Exposure
line: CAMEO says inhalation or contact with the vapors or decomposition products may cause severe injury or death, and that contact with water can form corrosive solutions.
- title: If the powder meets water
lead: These points come from the CAMEO and Wikipedia descriptions of the reaction.
points:
- label: The reaction
line: Al4C3 + 12 H2O gives 4 Al(OH)3 and 3 CH4, with considerable heat (Wikipedia).
why: 'Aluminium carbide is the carbide that forms when molten aluminium touches carbon or silicon carbide, so it matters for the reliability of aluminium composites. Its thermochemistry is well documented: the JANAF table gives a standard enthalpy of formation of -215.685 kJ/mol at 298.15 K for the crystalline solid. Its density is 2.36 g/cm3 and its molar mass is 143.95853 g/mol (Wikipedia). It is not a stable structural ceramic in wet conditions, and its hydrolysis to methane is the main reason to treat it with care.'
can_do:
- label: Formation enthalpy
benchmark: standard_enthalpy_of_formation
line: The standard enthalpy of formation is -215.685 kJ/mol at 298.15 K and -263.532 kJ/mol at 1000 K (JANAF). It becomes more negative as the temperature rises in this range.
- label: Heat capacity
benchmark: molar_heat_capacity
line: The molar heat capacity is 116.784 J K-1 mol-1 at 298.15 K and 176.142 J K-1 mol-1 at 1000 K (JANAF).
- label: Thermal stability
benchmark: decomposition_temperature
line: Wikipedia says the compound is stable up to 1400 C. Its infobox melting point is 2100 C, which does not match, so the melting figure is not used as a settled value.
compare: Al4C3 is a carbide with a standard enthalpy of formation of -215.685 kJ/mol at 298.15 K (JANAF) and a density of 2.36 g/cm3 (Wikipedia). Unlike the refractory carbides used in coatings, it reacts with water and moist air to give methane, so its handling differs most from theirs. The compare rows use the three benchmarks that have values from sources read in this run; no other carbide is compared here.
compare_rows:
- label: Density
benchmark: density
- label: Decomposition temperature
benchmark: decomposition_temperature
- label: Enthalpy of formation
benchmark: standard_enthalpy_of_formation
handling:
- Keep the material away from water and moist air. Contact releases flammable methane and heat (CAMEO).
- Treat it as a fire hazard. It may ignite on heat, sparks or flame (CAMEO).
- Use it only with a current safety data sheet for the product you hold, since none was read for this compound in this run.
good_for:
- Thermochemical reference. JANAF gives a full set of formation and heat-capacity values from 298.15 K to 1000 K.
- Understanding the interface in aluminium composites. Wikipedia describes the carbide layer that forms on SiC particles.
watch_out:
- Water and moist air. It releases flammable methane and heat.
- Melting point is unsettled. Wikipedia gives 2100 C as the melting point and 1400 C as the decomposition temperature.
- Carbide content in composites. Wikipedia notes that the carbide lowers strength and improves wettability, but no test value was read.
verdict: Al4C3 is a well-characterised compound in thermochemistry, with a clear hazard in wet conditions. Its formation data are sourced from JANAF, and its water reaction from CAMEO and Wikipedia. Its melting point, hazard classification and use data are not yet settled from sources read in this run.
References
Every number above carries a reference number. Click one to see the source and where in it the value comes from.
| # | Source | Type | Year | Used for |
|---|---|---|---|---|
| NIST-JANAF Thermochemical Tables, Aluminum Carbide (Al4C3), crystalline phase C3Al4(cr) | database | 9 values | ||
| Wikipedia, Aluminium carbide (composition, structure, properties, hydrolysis and preparation only) | web | 6 values | ||
| CAMEO Chemicals (NOAA), Chemical Datasheet, aluminum carbide (CAS 1299-86-1, ERG Guide 138 excerpt) | database | 6 values | ||
| USGS Mineral Commodity Summaries 2026, Aluminum | report | 1 value | ||
| USGS, About the 2025 List of Critical Minerals (final list of 60 minerals) | web | 0 values |