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The field of aluminium oxide ceramics has a long history. Aluminium salts were widely used in ancient and medieval alchemy. Several older textbooks cover the history of the field. [11] [12] A 2019 textbook by Andrew Ruys contains a detailed timeline on the history of aluminium oxide from ancient times to the 21st century. [13]
Aluminium (or aluminum) metal is very rare in native form, and the process to refine it from ores is complex, so for most of human history it was unknown. However, the compound alum has been known since the 5th century BCE and was used extensively by the ancients for dyeing .
The Hall–Héroult process is the major industrial process for smelting aluminium.It involves dissolving aluminium oxide (alumina) (obtained most often from bauxite, aluminium's chief ore, through the Bayer process) in molten cryolite and electrolyzing the molten salt bath, typically in a purpose-built cell.
The names aluminium and aluminum are derived from the word alumine, an obsolete term for alumina, [j] the primary naturally occurring oxide of aluminium. [118] Alumine was borrowed from French, which in turn derived it from alumen, the classical Latin name for alum, the mineral from which it was collected. [119]
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 Bayer process is the principal industrial means of refining bauxite to produce alumina (aluminium oxide) and was developed by Carl Josef Bayer.Bauxite, the most important ore of aluminium, contains only 30–60% aluminium oxide (Al 2 O 3), the rest being a mixture of silica, various iron oxides, and titanium dioxide. [1]
Aluminium smelting is the process of extracting aluminium from its oxide, alumina, generally by the Hall-Héroult process. Alumina is extracted from the ore bauxite by means of the Bayer process at an alumina refinery .
The melting point of aluminium oxide is 2050°C (2323K), much higher than pure aluminium's 658°C (931K). [6] This and the insulativity of aluminium oxide can make welding more difficult. In typical commercial aluminium anodizing processes, the aluminium oxide is grown down into the surface and out from the surface by equal amounts. [7]