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Aluminum carbide has a unique crystal structure

wallpapers News 2021-05-08
About aluminum carbide
Aluminum carbide, chemical formula Al4C3, is a carbide of aluminum. It has a pale yellow to brown crystal appearance. It's stable at 1400 degrees Celsius. It breaks down in the water to produce methane.
Aluminum carbide has a unique crystal structure consisting of alternating layers of Al2C and Al2C2. Each aluminum atom is coordinated with four carbon atoms to form a tetrahedral arrangement. Carbon atoms exist in two different binding environments; One is a deformed octahedron made up of six aluminum atoms at a distance of 217 PM. The other is a twisted triangular bicone structure consisting of four 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 is prepared by direct reaction of aluminum and carbon in an electric arc furnace
4 al + 3 c - > Al4C3
The other reaction starts with alumina, but it is less favorable due to the production of carbon monoxide.
2Al2O3 + 9C →Al4C3 + 6CO
Silicon carbide also reacts with aluminum to form Al4C3. This conversion limits the mechanical application of SiC because Al4C3 is more brittle than SiC
4Al + 3SiC →Al4C3 + 3Si
In SiC reinforced aluminum matrix composites, SiC and molten aluminum react chemically, forming a layer of SiC layer on the SiC particles, although the wettability of SiC particles is enhanced, However, this trend can be reduced by coating the SiC particles with a suitable oxide or nitride, peroxidizing the SiC particles to form a silicon coating or using a sacrificial metal layer.
Aluminum carbide composite was prepared by the mechanical alloying method by mixing aluminum powder and graphite particles.
Small amounts of aluminum carbide are common impurities in industrial calcium carbide. In the electrolytic manufacture of aluminum, aluminum carbide is the corrosion product of graphite electrodes.
In metal matrix composites based on reinforced aluminum matrix composites such as non-metallic silicon carbide, boron carbide or carbon fiber, aluminum carbide is usually not needed. For carbon fiber, it reacts with aluminum matrix at a temperature above 500℃. Coating the surface of fibers with materials such as titanium boride can improve the wettability of fibers and inhibit chemical reactions.