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Aluminium oxide (or aluminium(III) oxide) is a chemical compound of aluminium and oxygen with the chemical formula Al 2 O 3. It is the most commonly occurring of several aluminium oxides, and specifically identified as aluminium oxide. It is commonly called alumina and may also be called aloxide, aloxite, or alundum in various forms and ...
Although a molten aluminium salt could be used instead, aluminium oxide has a melting point of 2072 °C (3762°F) [4] so electrolysing it is impractical. In the Hall–Héroult process, alumina, Al 2 O 3, is dissolved in molten synthetic cryolite, Na 3 AlF 6, to lower its melting point for easier electrolysis. [1]
Molten cryolite is used as a solvent for aluminium oxide (Al 2 O 3) in the Hall–Héroult process, used in the refining of aluminium. It decreases the melting point of aluminium oxide from 2000–2500 °C to 900–1000 °C, and increases its conductivity [18] thus making the extraction of aluminium more economical. [19]
Aluminium(I) oxide (Al 2 O) Aluminium(II) oxide ( AlO ) (aluminium monoxide) Aluminium(III) oxide (aluminium oxide), ( Al 2 O 3 ), the most common form of aluminium oxide, occurring on the surface of aluminium and also in crystalline form as corundum , sapphire , and ruby .
The Gmelin rare earths handbook lists 1522 °C and 1550 °C as two melting points given in the literature, the most recent reference [Handbook on the chemistry and physics of rare earths, vol.12 (1989)] is given with 1529 °C.
Aluminium nitride (Al N) is a solid nitride of aluminium. It has a high thermal conductivity of up to 321 W/(m·K) [ 5 ] and is an electrical insulator. Its wurtzite phase (w-AlN) has a band gap of ~6 eV at room temperature and has a potential application in optoelectronics operating at deep ultraviolet frequencies.
Triple point? K (? °C), ? Pa Critical point? K (? °C), ? Pa Std enthalpy change of fusion, Δ fus H o? kJ/mol Std entropy change of fusion, Δ fus S o? J/(mol·K) Std enthalpy change of vaporization, Δ vap H o? kJ/mol Std entropy change of vaporization, Δ vap S o? J/(mol·K) Solid properties Std enthalpy change of formation, Δ f H o solid ...
For example, the melting point of silicon at ambient pressure (0.1 MPa) is 1415 °C, but at pressures in excess of 10 GPa it decreases to 1000 °C. [13] Melting points are often used to characterize organic and inorganic compounds and to ascertain their purity. The melting point of a pure substance is always higher and has a smaller range than ...