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• Aluminium is the third most abundant element in
  the earth's crust after oxygen
• and silicon. Because of its chemical reactivity,
  aluminium is never found in nature
• as an element but always in its oxidised form.

• Bauxite occurs in three main forms depending on
  a) the number of molecules of
• water of hydration and b) the crystalline
  structure. The three structural forms of
• bauxite are Gibbsite, Böhmite and Diaspore.
  Gibbsite is a true aluminium hydroxide
• and Böhmite and Diaspore are both
  aluminium-oxide-hydroxides.

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Extraction Gibbsite Al(OH)3 Na OH- ---gt
Al(OH)4- NaBöhmite and Diaspore AlO(OH)
Na OH - H2O ---gt Al(OH)4- Na
Precipitation Crystalline aluminium trihydroxide
(Gibbsite), conveniently named "hydrate", is
then precipitated from the digestion
liquor Al(OH)4- Na ---gt Al(OH)3 Na OH-
Calcination "Hydrate", is calcined to form
alumina for the aluminium smelting process. In
the calcination process water is driven off to
form alumina 2Al(OH)3 ---gt Al2O3 3H2O The
calcination process must be carefully controlled
since it dictates the properties of the final
product.
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Applications A series of powders with mean
particle size ranged from 18 to 60 nm can be
offered to various applications, particularly in
advanced nanoceramics manufacturing.
Specifications for the powder Phase 100 a-Al2O3

Main chemical impurities (wt.)

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