Aluminium oxide and aluminium hydroxide are two vastly different things. The melting point of aluminium oxide (aka 'alumina') is
about 2072 C.
Aluminium hydroxide doesn't really 'melt': as you heat it, it gradually loses water until you end up with anhydrous alumina. To obtain truly anhydrous
alumina may take some time, even at 900 C or above. The lower the temperature the higher the chances the material will retain small amounts of water.
To obtain annealed alumina you would need to heat well above 2072 C, then allow to cool. What's obtained that way is equivalent to Corundum, the
extremely hard (Mohs 9) mineral. Like the mineral form, annealed alumina is extremely hard and very resistant to chemical attack.
What is your purpose with the 'aluminium oxide cake'?
[Edited on 27-8-2013 by blogfast25] |