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Al(OH)3 A white or tinted mineral, crystallizing in the monoclinic system; a principal constituent of bauxite. Also known as hydrargillite.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(also hydrargillite), a mineral with the chemical composition Al[OH]3. It contains 65.4 percent alumina (A1203); admixtures of Fe3+ and Ga3+ that replace Al3+ in the structure are known. Gibbsite crystallizes in a monoclinic system. Its crystalline structure is of the layer type and consists of bifoliate (OH) packets, in the midst of which Al3+ ions are distributed. Good cleavage occurs along weak interpacket bonds. Gibbsite forms small laminar crystalline particles, usually colorless with a pearly luster, as well as powdery aggregates and incrustations with a radiated or imbricate microstructure. Its hardness on the mineralogical scale is 2.5-3.5; its density is 2,300-2,400 kg/m3. It usually forms upon weathering of alumina-rich rocks. Together with the other hydroxides of aluminum (diaspore and boehmite) and iron, gibbsite is found in bauxite ores. Gibbsite bauxites are among the best aluminum ores.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
This setting was not sufficient to achieve the full conversion of bayerite to boehmite for the powder milled under acidic-basic condition.
This feature was taken as an indication that the conversion of bayerite into boehmite would be controlled by dissolution-reprecipitation mechanism, since the topotactic phase transformation is not likely to occur due to different structural forms, a and [gamma], of these compounds [42].
In the present work, the hydrothermal treatment of mechanochemically formed bayerite resulted in boehmite nanoparticles with isometric shape (Figure 5(d)).
For the powder milled under acidic-basic condition, which had bayerite and boehmite, the weight loss gradually increased during the initial heating, achieving 0.14 wt% at 238[degrees]C, as a result of water desorption (TGA curve, Figure 6(b)).
Considering the predicted weight loss of 34.6 wt% for the water evaporation in (2), the weight loss of 0.43 wt% between 238 and 445[degrees]C corresponded to a bayerite content of 1.2 wt%.
In summary, thermal analyses indicated the formation of 1.7 wt% of aluminum hydroxides (1.2% bayerite and 0.5% boehmite) in the powder milled under acidic-basic condition and 3.2 wt% of boehmite in the powder milled under basic pH condition, both after the hydrothermal treatment.
This result indicated the beneficial effect of the presence of nanoparticles (1.2 wt% bayerite and 0.5 wt% boehmite) on decreasing the friction between the extruded alumina rod and the die surface.
When the milling medium naturally changed from acidic (pH 4.1) to basic (pH 8.4) during milling, bayerite [Al[(OH).sub.3]] nanoparticles were formed, of which only a small fraction was converted to boehmite (AlOOH) during the hydrothermal treatment; thermal analyses indicated formation of 1.2 wt% of bayerite and 0.5 wt% of boehmite.
Tanaka, "Preparation and thermal decomposition of synthetic bayerite," Journal of Thermal Analysis and Calorimetry, vol.
Ichikawa, "Mechanochemical phenomena of gibbsite, bayerite and boehmite by grinding," Reactivity of Solids, vol.

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