Alumina

Alumina

Fig.1 Dehydration sequence of hydrated alumina in air

`Formula`	`Al₂O₃`
`Molecular mass`	`101.96 g/mol`
`Density`	`3.98 g/cm³`
`Hardness`	`9`
`Melting point`	`2053°C`
`CAS-No.`	`1344-28-1`
`EINECS-No.`	`2156916`

Aluminium oxide appears in nature as a-Al₂O₃ (=Corundum). The hexagonal a-Al₂O₃ is the only thermodynamically stable modification. Besides there is the cubic face-centered g-Al₂O₃, which develop from aluminium hydroxide at 400-800°C and is finaly converted to a-Al₂O₃ at 1100°C. Chemical data of calcinated aluminas are given on a separate page.

Technically corundum is manufactured today by electric melting of bauxite, which is the starting material for refractory products. Thus, for example crucibles, protective tubes and refractory bricks are produced as sintered corundum by pressing a-Al₂O₃ with bonding agents such as clays, which are fired at approx 1300°C. Alumina coatings are available as Aluminium-Oxide-Coating AA and Aluminium-Oxide-Coating AW.

These recommendations are believed to be correct. However, no guarantee of their accuracy is given. Therefore, purchasers shall make their own tests to determine suitability for their use. These products are offered for industrial and related uses (e.g. research and development) only. However the user must take the necessary precautions appropriate for products containing chemicals. This description does not imply the absence of any patents, the responsibility whatsoever solely rests with the user.