Aluminium carbide

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.

Aluminium carbide
Unit cell ball and stick model of aluminium carbide
Names
Preferred IUPAC name
Aluminium carbide
Other names
Aluminium carbide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.013.706
EC Number
  • 215-076-2
MeSH Aluminum+carbide
UN number UN 1394
  • InChI=1S/3C.4Al/q3*-4;4*+3 checkY
    Key: TWHBEKGYWPPYQL-UHFFFAOYSA-N checkY
  • InChI=1/3C.4Al/q3*-4;4*+3
    Key: TWHBEKGYWPPYQL-UHFFFAOYAR
  • [Al+3].[Al+3].[Al+3].[Al+3].[C-4].[C-4].[C-4]
Properties
Al4C3
Molar mass 143.95853 g/mol
Appearance colorless (when pure) hexagonal crystals[1]
Odor odorless
Density 2.93 g/cm3[1]
Melting point 2,200 °C (3,990 °F; 2,470 K)
Boiling point decomposes at 1400 °C[2]
reacts to make natural gas
Structure
Rhombohedral, hR21, space group[2]
R3m（No. 166）
a = 0.3335 nm, b = 0.3335 nm, c = 0.85422 nm
α = 78.743°, β = 78.743°, γ = 60°
Thermochemistry
116.8 J/mol K
88.95 J/mol K
-209 kJ/mol
-196 kJ/mol
Hazards
GHS labelling:
GHS02: FlammableGHS07: Exclamation mark
Warning
H261, H315, H319, H335
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
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

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 Ti2AlC0.5N0.5, 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.

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]

See also

References
  1. Mary Eagleson (1994). Concise encyclopedia chemistry. Walter de Gruyter. p. 52. ISBN 978-3-11-011451-5.
  2. 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)
  3. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 297. ISBN 978-0-08-037941-8.
  4. 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.
  5. qualitative inorganic analysis. CUP Archive. 1954. p. 102.
  6. 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.
  7. Deborah D. L. Chung (2010). Composite Materials: Functional Materials for Modern Technologies. Springer. p. 315. ISBN 978-1-84882-830-8.
  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.
  9. 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.
  10. 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.
  11. 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.
  12. Jonathan James Saveker et al. "High speed cutting tool" U.S. Patent 6,033,789, Issue date: Mar 7, 2000
  13. E. Pietsch, ed.: "Gmelins Hanbuch der anorganischen Chemie: Aluminum, Teil A", Verlag Chemie, Berlin, 1934–1935.
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