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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 ...
The porous nature of anodic alumina films was discovered in the 1930s [1] and further elaborated in the 1950s–1970s. [2] [3] Processes for producing anodic aluminum oxide membranes using chromic acid, sulfuric acid, oxalic acid, or phosphoric acid appear in a patent attributed to Alan W. Smith of the Boeing Company in 1974. [4]
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 .
During atomic layer deposition, a film is grown on a substrate by exposing its surface to alternate gaseous species (typically referred to as precursors or reactants). In contrast to chemical vapor deposition, the precursors are never present simultaneously in the reactor, but they are inserted as a series of sequential, non-overlapping pulses.
For example, in the plasma electrolytic oxidation of aluminum, at least 200 V must be applied. This locally exceeds the dielectric breakdown potential of the growing oxide film, and discharges occur. These discharges result in localized plasma reactions, with conditions of high temperature and pressure which modify the growing oxide.
It forms a complex multilayer structured laminate of amorphous, crystalline and porous crystalline aluminum oxide mostly covered with small residual parts of unconverted aluminum hydroxide. For this reason, in the formation of the anode foil, the oxide film is structured by a special chemical treatment so that either an amorphous oxide or a ...
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 difficulty of separating aluminium from oxygen in the oxide ores was overcome by the use of cryolite as a flux to dissolve the oxide mineral(s). Pure cryolite itself melts at 1012 °C (1285 K), and it can dissolve the aluminium oxides sufficiently well to allow easy extraction of the aluminium by electrolysis. Substantial energy is still ...