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What is Aluminum Oxide?

2023-02-11

Alumina is a compound of aluminum and oxygen with the chemical formula Al 2 O 3 . It is the most common of several types of alumina, especially aluminum oxide. Commonly known as Alumina (Al2O3), it can also be known as Aluminum Oxide, Aluminum Oxide, or Corundum in various forms and applications.

Alumina (Al2O3) ceramic

It occurs naturally in its crystalline polycrystalline phase α-Al 2 O 3 as the mineral corundum, various of which form the precious gemstones ruby and sapphire. Al2O3 is important in the production of aluminum metal, used as an abrasive due to its hardness, and as a refractory due to its high melting point.

Al 2 O 3 is an electrical insulator, but has a relatively high thermal conductivity (30 Wm -1 K -1 ) for Ceramic Tools. Aluminum oxide is insoluble in water. Its most common crystalline form is called corundum or alpha-alumina, and its hardness makes it suitable for use as a component in abrasives and cutting tools.

Alumina is responsible for the weather resistance of metallic aluminum. Metallic aluminum is highly reactive with atmospheric oxygen and within hundreds of picoseconds any exposed aluminum surface forms a thin passivation layer of aluminum oxide (4 nanometers thick) that protects the metal from further oxidation.

The thickness and properties of this oxide layer can be enhanced using a process called anodizing. Some alloys, such as aluminum bronze, take advantage of this property by adding a certain percentage of aluminum to the alloy to enhance corrosion resistance.

Alumina (Al2O3)

The alumina produced by anodizing is usually amorphous, but discharge-assisted oxidation processes such as plasma electrolytic oxidation can result in a coating with a large amount of crystalline alumina, which increases its hardness.

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