Alumina
Description
Common name for natural or synthetic Aluminum oxide. It is a white, hard, insoluble powder. Aluminum oxide naturally occurs in some feldspars, Alumina trihydrate, Corundum, gibbsite, Bauxite, Ruby, and Sapphire. It was first extract commercially from bauxite in 1888 using the Bayer process. Aluminum oxide is extremely hard and is used as an abrasive both in its natural (corundum, Emery) and synthetic (Alundum) forms. Synthetic alumina is prepared primarily in three forms: activated alumina, smelter-grade alumina, and calcined alumina. The porous, granular activated alumina aggressively absorbs liquid water and water vapor. The fine-grain calcined alumina is a dense impermeable ceramic material used for abrasives, refractories, electrical insulation, high temperature crucibles, and dental restoration. It is also used as a filler for paints, glass, and ceramics. When added to glaze mixtures, aluminum oxide increases viscosity during firing, prevents devitrification during cooling, and adds durability to the final surface.
See also Alpha alumina and Gamma alumina.
Synonyms and Related Terms
aluminum oxide; aluminium oxide; almina (Esp.); alumine (Fr.); alumina (Port.); xido de alumnio (Port.); activated alumina; Alundum; Aloxite; Bausilite; White Bauxilite; corundum
Applications
Risks
- Fire retardant.
- Dust may cause irritation with skin contact or inhalation.
- ThermoFisher: SDS
Physical and Chemical Properties
Soluble in mineral acids and strong alkali. Insoluble in water.
| Composition | Al2O3 |
|---|---|
| CAS | 1344-28-1 |
| Mohs Hardness | 9.0 |
| Melting Point | 2040 C |
| Molecular Weight | mol. wt. = 101.96 |
Comparisons
Properties of Common Abrasives
Resources and Citations
- G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 34
- Encyclopedia Britannica, http://www.britannica.com Comment: alumina" [Accessed May 8, 2003].
- Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979
- Robert Fournier, Illustrated Dictionary of Practical Pottery, Chilton Book Company, Radnor, PA, 1992
- R.M.Organ, Design for Scientific Conservation of Antiquities, Smithsonian Institution, Washington DC, 1968