alumina

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alumina

(əlo͞o`mĭnə) or

aluminum oxide,

Al2O3, chemical compound with m.p. about 2,000°C; and sp. gr. about 4.0. It is insoluble in water and organic liquids and very slightly soluble in strong acids and alkalies. Alumina occurs in two crystalline forms. Alpha alumina is composed of colorless hexagonal crystals with the properties given above; gamma alumina is composed of minute colorless cubic crystals with sp. gr. about 3.6 that are transformed to the alpha form at high temperatures. Alumina powder is formed by crushing crystalline alumina; it is white when pure. Alumina is widely distributed in nature. Combined with silica and other minerals it occurs in clays, feldspars, and micas. It is the major component of bauxitebauxite
, mixture of hydrated aluminum oxides usually containing oxides of iron and silicon in varying quantities. A noncrystalline substance formerly thought to be a mineral, bauxite is claylike and earthy and ranges in color from white to deep brown or red according to the
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 and occurs in an almost pure form as corundumcorundum
, mineral, aluminum oxide, Al2O3. The clear varieties are used as gems and the opaque as abrasive materials. Corundum occurs in crystals of the hexagonal system and in masses. It is transparent to opaque and has a vitreous to adamantine luster.
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. Alumina is commercially important. A major use is in the production of aluminumaluminum
, called in British countries aluminium
, metallic chemical element; symbol Al; at. no. 13; at. wt. 26.98154; m.p. 660.37°C;; b.p. 2,467°C;; sp. gr. 2.6989 at 20°C;; valence +3.
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 metal. It is also used for abrasives; corundum and emery are widely used, as are artificially prepared alumina abrasives. Trade names for alumina abrasives include Alundum and Aloxite. Alumina is also used in ceramics, in pigments, and in the manufacture of chemicals. Clays containing alumina are used in porcelain, pottery, and bricks. Pure alumina is used in making crucibles and other refractory apparatus. Hydrated alumina is used in mordant dyeing to make lake pigments; it is also used in glassmaking, in cosmetics, and in medicine as an antacid.

alumina

[ə′lüm·ə·nə]
(inorganic chemistry)
Al2O3 The native form of aluminum oxide occurring as corundum or in hydrated forms, as a powder or crystalline substance.

alumina

The oxide of aluminum; an important constituent of the clays used in brick, tile, and refractories.
References in periodicals archive ?
The plant produces aluminium oxide from dross under Taha's mechanical separation process at the site of the New Zealand Aluminium Smelters (NZAS) plant.
This plant uses aluminium oxide produced from the Taha metal separation process in Tiwai to make the fertiliser.
However the more plants Taha signs up for recovering metal and aluminium oxide the more fertiliser it will be able to produce.
On the other hand, printing process can cause mechanical, physical and chemical changes of the aluminium oxide film as well.
In this paper, change of the aluminium oxide surface is characterized by application and contact angle measurement of different defined solutions on printing plate samples.
Limited Tenders are invited for 1)Abrasive Aluminium Oxide Industrial Cloth Buffing Wheel Size Od60 Mm X Width 60 Mm X Shank 6 Mm 80 Grit Qty: 1000 No 2)Abrasive Aluminium Oxide Industrial Cloth Buffing Wheel Size Od80 Mm X Width 80 Mm X Shank 6 Mm 80 Grit.
8 Mm (Id) - Aluminium Oxide Vitrified Equivalent To A 46 N5 V30.