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Encyclopedia > Alumina
Properties

General

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

Physical

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

Thermochemistry

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

Safety

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:
 
The Chemistry and Processing of Jamaican Bauxite (891 words)
In the same year, 2500 tonnes of ore was shipped to the USA for process investigation and it was realised that the bauxite was suitable for processing using Bayer technology.
The alumina plants were said to be working at 96% capacity for the first time in many years and for the first quarter (1997) produced 816,999 tonnes.
Hall process for electrolytic reduction of alumina to aluminum is appropriately provided at Oberlin College, from where Charles Hall had graduated only eight months prior to his successful experiment.
Arctic Silver, Inc. - Arctic Alumina Thermal Adhesive (165 words)
Arctic Alumina Thermal Adhesive IS NOT intended to be used between a CPU and the CPU heatsink.
Arctic Alumina Thermal Adhesive is a permanent adhesive.
Arctic Alumina Thermal Adhesive should be kept cold and away from UV light (sunlight and florescent lighting).
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