Aluminium oxide

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Aluminium oxide (also known as alumina) is a chemical compound of aluminium and oxygen with the chemical formula Al₂O₃. It is the most commonly occurring of several aluminium oxides and specifically identified as aluminium(III) oxide. It is commonly referred to as alumina and may also be called aloxide, aloxite, or alundum depending on particular forms or applications.

Properties

Aluminium oxide is a white, crystalline powder with a melting point of 2,072 °C (3,762 °F) and a boiling point of 2,977 °C (5,391 °F). It is insoluble in water but soluble in some acids and alkalis. It is known for its hardness and strength, making it a useful material in various industrial applications.

Occurrence

Aluminium oxide occurs naturally in its crystalline polymorphic phase α-Al₂O₃ as the mineral corundum, which is the base component of ruby and sapphire. These gemstones owe their characteristic colors to trace impurities.

Production

Aluminium oxide is produced from bauxite through the Bayer process. Bauxite is refined to produce alumina, which is then used in the Hall-Héroult process to produce aluminium metal.

Applications

Industrial Uses

Aluminium oxide is used extensively in various industries. It serves as an abrasive due to its hardness and is used in sandpaper, grinding wheels, and cutting tools. It is also used as a refractory material due to its high melting point and thermal stability.

Electronics

In the electronics industry, aluminium oxide is used as an insulator and as a substrate for semiconductor devices. It is also used in the production of integrated circuits and microelectronic devices.

Medical Applications

Aluminium oxide is used in the medical field for its biocompatibility. It is used in hip replacements, dental implants, and other prosthetic devices.

Catalysis

Aluminium oxide is used as a catalyst and as a catalyst support in various chemical reactions, including the Claus process for sulfur recovery and in the production of polyethylene.

Safety

While aluminium oxide is generally considered non-toxic, inhalation of fine particulate matter can cause respiratory issues. Proper safety measures should be taken when handling the material in powder form.

See also

• Aluminium
• Bauxite
• Corundum
• Ruby
• Sapphire
• Bayer process
• Hall-Héroult process