Aluminium carbide

Aluminium carbide

Names
Preferred IUPAC name Aluminum carbide
Other names Aluminium carbide
Identifiers
CAS Number	1299-86-1 Y 12656-43-8 N
3D model (Jmol)	Interactive image
ChemSpider	21241412 Y
ECHA InfoCard	100.013.706
EC Number	215-076-2
MeSH	Aluminum+carbide
PubChem CID	16685054
UN number	UN 1394
InChI InChI=1S/3C.4Al/q3*-4;4*+3 Y Key: TWHBEKGYWPPYQL-UHFFFAOYSA-N Y InChI=1/3C.4Al/q3*-4;4*+3 Key: TWHBEKGYWPPYQL-UHFFFAOYAR
SMILES [Al+3].[Al+3].[Al+3].[Al+3].[C-4].[C-4].[C-4]
Properties
Chemical formula	Al4C3
Molar mass	143.95853 g/mol
Appearance	colorless (when pure) hexagonal crystals
Odor	odorless
Density	2.36 g/cm3
Melting point	2,200 °C (3,990 °F; 2,470 K)
Boiling point	decomposes at 1400 °C
Solubility in water	decomposes
Structure
Crystal structure	Rhombohedral, hR21, space group R3m, No. 166. a = 0.3335 nm, b = 0.3335 nm, c = 0.85422 nm, α = 78.743 °, β = 78.743 °, γ = 60 °
Thermochemistry
Specific heat capacity (C)	116.8 J/mol K
Std molar entropy (So298)	88.95 J/mol K
Std enthalpy of formation (ΔfHo298)	-209 kJ/mol
Gibbs free energy (ΔfG˚)	-196 kJ/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Aluminum carbide, chemical formula Al₄C₃, is a carbide of aluminum. It has the appearance of pale yellow to brown crystals. It is stable up to 1400 °C. It decomposes in water with the production of methane.

Aluminum carbide has an unusual crystal structure that consists of alternating layers of Al₂C and Al₂C₂. Each aluminum atom is coordinated to 4 carbon atoms to give a tetrahedral arraignment. Carbon atoms exist in 2 different binding environments; one is a deformed octahedron of 6 Al atoms at a distance of 217 pm. The other is a distorted trigonal bipyramidal structure of 4 Al atoms at 190–194 pm and a fifth Al atom at 221 pm. Other carbides (IUPAC nomenclature: methides) also exhibit complex structures.

Aluminum carbide hydrolyses with evolution of methane. The reaction proceeds at room temperature but is rapidly accelerated by heating.

Similar reactions occur with other protic reagents:

Aluminum carbide is prepared by direct reaction of aluminum and carbon in an electric arc furnace.

An alternative reaction begins with alumina, but it is less favorable because of generation of carbon monoxide.

Silicon carbide also reacts with aluminum to yield Al₄C₃. This conversion limits the mechanical applications of SiC, because Al₄C₃ is more brittle than SiC.

In aluminum-matrix composites reinforced with silicon carbide, the chemical reactions between silicon carbide and molten aluminum generate a layer of aluminium carbide on the silicon carbide particles, which decreases the strength of the material, although it increases the wettability of the SiC particles. This tendency can be decreased by coating the silicon carbide particles with a suitable oxide or nitride, preoxidation of the particles to form a silica coating, or using a layer of sacrificial metal.

An aluminum-aluminum carbide composite material can be made by mechanical alloying, by mixing aluminum powder with graphite particles.