 | |
| Names | |
|---|---|
| Preferred IUPAC name Aluminium carbide | |
Other names
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| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.013.706 |
| EC Number |
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| MeSH | Aluminum+carbide |
| UN number | 1394 |
| |
| |
| Properties | |
| Al4C3 | |
| Molar mass | 143.95853 g/mol |
| Appearance | colorless (when pure) hexagonal crystals[1] |
| Odor | odorless |
| Density | 2.36 g/cm3[1] |
| Melting point | 2,100 °C (3,810 °F; 2,370 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) | |
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: | |
  | |
| 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 | |
| NFPA 704 (fire diamond) | |
| Safety data sheet (SDS) | Fisher Scientific |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Aluminium carbide is achemical compound with thechemical formulaAl4C3. It is acarbide ofaluminium. It has the appearance of pale yellow to brown crystals. It is stable up to 1400 °C. It decomposes inwater with the production ofmethane.
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 217pm. 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.
Aluminium carbide hydrolyses with evolution ofmethane. The reaction proceeds at room temperature but is rapidly accelerated by heating.[5]
Similar reactions occur with other protic reagents:[1]
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]
Aluminium carbide is prepared by direct reaction of aluminium and carbon in anelectric arc furnace.[3]
An alternative reaction begins with alumina, but it is less favorable because of generation ofcarbon monoxide.
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]
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 asilica coating, or using a layer ofsacrificial metal.[9]
An aluminium-aluminium carbide composite material can be made by mechanical alloying, by mixing aluminium powder withgraphite particles.
Small amounts of aluminium carbide are a common impurity of technicalcalcium carbide. In electrolytic manufacturing of aluminium, aluminium carbide forms as a corrosion product of the graphite electrodes.[10]
Inmetal matrix composites based on aluminium matrix reinforced with non-metal carbides (silicon carbide,boron carbide, etc.) orcarbon 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]
Aluminium carbide particles finely dispersed in aluminium matrix lower the tendency of the material tocreep, especially in combination withsilicon carbide particles.[11]
Aluminium carbide can be used as anabrasive in high-speedcutting tools.[12] It has approximately the same hardness astopaz.[13]
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