Material Review: Alumina (Al2O3)

Alumina (Al2O3( or Aluminum Oxide is the only oxide formed by the metal aluminum and occurs in nature as the minerals corundum (Al2O3); diaspore (Al2O3·H 2O(; gibbsite (Al2O3·3H2O); and most commonly as bauxite, which is an impure form of gibbsite. The precious stones ruby and sapphire are composed of corundum (and thus also natural forms of alumina(- getting their colors by small amounts of impurities. The importance of alumina is two-fold; it is used as a starting material for the smelting of aluminum metal, and used as a raw material for a broad range of advanced ceramic products and as an active agent in chemical processing. ("Alumina" Britannica) Although the naturally occurring corundum, ruby and sapphire are sometimes also referred to as alumina, but the proper use of the term is limited to the material that is derived from bauxite and employed in the production of aluminum, industrial ceramics, and chemical processing. In this paper, besides briefly covering the background information/history of the material, we will describe its chemical and physical properties, its manufacturing process (the Bayer process) and its applications or uses.