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Encyclopedia > Aluminum oxide


Name Aluminium oxide
Aluminum oxide (US)
Chemical Formula Al2O3
Appearance White crystalline powder or solid


Formula weight 101.96 amu
Melting point at SP 2303 K
Boiling point at SP 3250 K
Density 3.97 × 103 kg/m3
Crystal structure Trigonal (hex)
Solubility Insoluble


ΔfH0liquid −1620.57 kJ/mol
ΔfH0solid −1675.69 kJ/mol
S0liquid, 1 bar 67.24 J/mol·K
S0solid 50.9 J/mol·K


Ingestion Low hazard
Inhalation May cause irritation or lung damage
Skin Low hazard
Eyes Low hazard

SI units were used where possible.

Aluminium oxide (or aluminum oxide) (Al2O3) is a chemical compound of aluminium and oxygen. It is also referred to as alumina for short, a name commonly used in the mining, ceramic and materials science communities.

Aluminium oxide is the main component of bauxite, the principal ore of aluminium. Industrially, bauxite is purified to aluminium oxide via the Bayer process, and then converted to aluminium metal in the Hall_Heroult process.

The gems ruby and sapphire are mostly aluminium oxide, given their characteristic colors by trace impurities.

Aluminium oxide is responsible for metallic aluminium's resistance to weathering. Metallic aluminium is very reactive with atmospheric oxygen, and a thin layer of aluminium oxide quickly forms on any exposed aluminium surface. This layer protects the metal from further oxidation. The thickness and properties of this oxide layer can be enhanced using a process called anodising.

Aluminium oxide is an excellent thermal and electrical insulator. In its crystalline form, called corundum, its hardness makes it suitable for use as an abrasive and as a component in cutting tools.

Powdered aluminium oxide is frequently used as a medium for chromatography.

In August, 2004, scientists in the United States working for 3M developed a technique for making an alloy of alumina and rare earth elements to produce a strong glass.

Aluminium oxide was taken off the EPA's chemicals lists in 1988.

See also

  • Transparent alumina
  • PhysicsWeb article on Transparent alumina (http://physicsweb.org/article/news/8/8/9)

  Results from FactBites:
Sandblasting Media, Grit Blasting, Abrasive Sandblasting, Abrasive Blasting Media, Abrasive Blast Media (453 words)
Aluminum Oxide is a sharp, long-lasting abrasive sandblasting cutting media that can be re-used many times for grit blasting.
White Aluminum Oxide is a 99.5% ultra-pure grade of blasting media.
White Aluminum Oxide is increasingly being used in critical, high performance processes such as microdermabrasion.
Aluminum - MSN Encarta (857 words)
For example, when thermite (a mixture of powdered iron oxide and aluminum) is heated, the aluminum rapidly removes the oxygen from the iron; the heat of the reaction is sufficient to melt the iron.
Aluminum is never found as a free metal; commonly as aluminum silicate or as a silicate of aluminum mixed with other metals such as sodium, potassium, iron, calcium, and magnesium.
Bauxite, an impure hydrated aluminum oxide, is the commercial source of aluminum and its compounds.
  More results at FactBites »



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