The principal raw material for the production of aluminum trihydrate and ultimately alumina, or aluminum oxide, is yellow-brown bauxite. Depending on the quality of the ore, two to four tons of bauxite are needed per ton of alumina production.
Alumina is most widely known and used as the starting material for the production of aluminum. However, there is a wide range of specialty aluminas for non-metallic applications. Due to its physical and chemical properties, so-called synthetic aluminum oxide plays an important role as an essential raw material for many market applications.
Aluminum oxide is highly heat resistance (fusion point 2050°C (3725°F)) and 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. Corundum is the second hardest material after a diamond. Aluminum oxide adds great mechanical strength, has excellent resistance to corrosion and wear, and is a nontoxic material.
Among the main criteria for the selection of specialty aluminas are chemical purity—predominantly the level of soda—and the primary crystal size.
The conversion of alumina to specialty alumina passes various transition phases depending on the product's application. Among these are:
- Sintering / Calcination