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Aluminium carbide
Names
	Preferred IUPAC name Aluminium carbide
	Other names Tetraaluminium tricarbide
Identifiers
CAS Number	1299-86-1 ; 12656-43-8 ;
3D model (JSmol)	Interactive image;
ChemSpider	21241412 ;
ECHA InfoCard	100.013.706
EC Number	215-076-2;
MeSH	Aluminum+carbide
PubChem CID	16685054;
UN number	1394
CompTox Dashboard (EPA)	DTXSID10107594 ;
	InChI InChI=1S/3C.4Al/q3-4;4+3 Key: TWHBEKGYWPPYQL-UHFFFAOYSA-N ; 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	2,100 °C (3,810 °F; 2,370 K)
Boiling point	decomposes at 1400 °C
Solubility in water	reacts to make natural gas
Structure
Crystal structure	Rhombohedral, hR21, space group
Space group	R3m（No. 166）
Lattice constant	a = 0.3335 nm, b = 0.3335 nm, c = 0.85422 nm α = 78.743°, β = 78.743°, γ = 60°
Thermochemistry
Heat capacity (C)	116.8 J/mol K
Std molar; entropy (S⦵298)	88.95 J/mol K
Std enthalpy of; formation (ΔfH⦵298)	-209 kJ/mol
Gibbs free energy (ΔfG⦵)	-196 kJ/mol
Hazards
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H261, H315, H319, H335
Precautionary statements	P231+P232, P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P370+P378, P402+P404, P403+P233, P405, P501
NFPA 704 (fire diamond)	2 2 2 W
Safety data sheet (SDS)	Fisher Scientific
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Aluminium carbide, chemical formula Al₄C₃, is a carbide of aluminium. 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.

Structure

Aluminium carbide has an unusual crystal structure that consists of alternating layers of Al₂C and Al₂C₂. Each aluminium atom is coordinated to 4 carbon atoms to give a tetrahedral arrangement. 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.^[3]^[4] Other carbides (IUPAC nomenclature: methides) also exhibit complex structures.

Reactions

Aluminium carbide hydrolyses with evolution of methane. The reaction proceeds at room temperature but is rapidly accelerated by heating.^[5]

Al₄C₃ + 12 H₂O → 4 Al(OH)₃ + 3 CH₄

Similar reactions occur with other protic reagents:^[1]

Al₄C₃ + 12 HCl → 4 AlCl₃ + 3 CH₄

Reactive hot isostatic pressing (hipping) at ≈40 MPa of the appropriate mixtures of Ti, Al₄C₃ graphite, for 15 hours at 1300 °C yields predominantly single-phase samples of Ti₂AlC_0.5N_0.5, 30 hours at 1300 °C yields predominantly single-phase samples of Ti₂AlC (Titanium aluminium carbide).^[6]

Preparation

Aluminium carbide is prepared by direct reaction of aluminium and carbon in an electric arc furnace.^[3]

4 Al + 3 C → Al₄C₃

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

2 Al₂O₃ + 9 C → Al₄C₃ + 6 CO

Silicon carbide also reacts with aluminium to yield Al₄C₃. This conversion limits the mechanical applications of SiC, because Al₄C₃ is more brittle than SiC.^[7]

4 Al + 3 SiC → Al₄C₃ + 3 Si

In aluminium-matrix composites reinforced with silicon carbide, the chemical reactions between silicon carbide and molten aluminium 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.^[8] 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.^[9]

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

Occurrence

Small amounts of aluminium carbide are a common impurity of technical calcium carbide. In electrolytic manufacturing of aluminium, aluminium carbide forms as a corrosion product of the graphite electrodes.^[10]

In metal matrix composites based on aluminium matrix reinforced with non-metal carbides (silicon carbide, boron carbide, etc.) or carbon fibres, aluminium carbide often forms as an unwanted product. In case of carbon fibre, it reacts with the aluminium matrix at temperatures above 500 °C; better wetting of the fibre and inhibition of chemical reaction can be achieved by coating it with e.g. titanium boride.^{[citation needed]}

Applications

Aluminium carbide particles finely dispersed in aluminium matrix lower the tendency of the material to creep, especially in combination with silicon carbide particles.^[11]

Aluminium carbide can be used as an abrasive in high-speed cutting tools.^[12] It has approximately the same hardness as topaz.^[13]

References

^ ^a ^b ^c Mary Eagleson (1994). Concise encyclopedia chemistry. Walter de Gruyter. p. 52. ISBN 978-3-11-011451-5.
^ ^a ^b Gesing, T. M.; Jeitschko, W. (1995). "The Crystal Structure and Chemical Properties of U2Al3C4 and Structure Refinement of Al4C3". 50. Zeitschrift für Naturforschung B, A journal of chemical sciences: 196–200. {{cite journal}}: Cite journal requires |journal= (help)
^ ^a ^b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 297. ISBN 978-0-08-037941-8.
^ Solozhenko, Vladimir L.; Kurakevych, Oleksandr O. (2005). "Equation of state of aluminum carbide Al4C3". Solid State Communications. 133 (6): 385–388. Bibcode:2005SSCom.133..385S. doi:10.1016/j.ssc.2004.11.030. ISSN 0038-1098.
^ qualitative inorganic analysis. CUP Archive. 1954. p. 102.
^ Barsoum, M.W.; El-Raghy, T.; Ali, M. (30 June 1999). "Processing and characterization of Ti2AlC, Ti2AlN, and Ti2AlC0.5N0.5". Metallurgical and Materials Transactions A. 31 (7): 1857–1865. doi:10.1007/s11661-006-0243-3. S2CID 138590417.
^ Deborah D. L. Chung (2010). Composite Materials: Functional Materials for Modern Technologies. Springer. p. 315. ISBN 978-1-84882-830-8.
^ Urena; Salazar, Gomez De; Gil; Escalera; Baldonedo (1999). "Scanning and transmission electron microscopy study of the microstructural changes occurring in aluminium matrix composites reinforced with SiC particles during casting and welding: interface reactions". Journal of Microscopy. 196 (2): 124–136. doi:10.1046/j.1365-2818.1999.00610.x. PMID 10540265. S2CID 24683423.
^ Guillermo Requena. "A359/SiC/xxp: A359 Al alloy reinforced with irregularly shaped SiC particles". MMC-ASSESS Metal Matrix Composites. Archived from the original on 2007-08-15. Retrieved 2007-10-07.
^ Jomar Thonstad; et al. (2001). Aluminum Electrolysis : Fundamentals of the Hall-Héroult Process 3rd ed. Aluminum-Verlag. p. 314. ISBN 978-3-87017-270-1.
^ S.J. Zhu; L.M. Peng; Q. Zhou; Z.Y. Ma; K. Kucharova; J. Cadek (1998). "Creep behaviour of aluminum strengthened by fine aluminum carbide particles and reinforced by silicon carbide particulates DS Al-SiC/Al4C3composites". Acta Technica CSAV (5): 435–455. Archived from the original (abstract) on 2005-02-22.
^ Jonathan James Saveker et al. "High speed cutting tool" U.S. patent 6,033,789, Issue date: Mar 7, 2000
^ E. Pietsch, ed.: "Gmelins Hanbuch der anorganischen Chemie: Aluminum, Teil A", Verlag Chemie, Berlin, 1934–1935.