Aluminum hydroxide oxide

The term alumina hydrates or hydrated aluminas is used in industry and commerce to designate aluminum hydroxides. These compounds are tme hydroxides and do not contain water of hydration. Several forms are known a general classification is shown in Figure 1. The most weU-defined crystalline forms ate the trihydroxides, Al(OH) gibbsite [14762-49-3], bayerite [20257-20-9], and nordstrandite [13840-05-6], In addition, two aluminum oxide—hydroxides, AIO(OH), boelimite [1318-23-6] and diaspote [14457-84-2], have been clearly defined. The existence of several other forms of aluminum hydroxides have been claimed. However, there is controversy as to whether they ate truly new phases or stmctures having distorted lattices containing adsorbed or intedameUar water and impurities. 

Boehmite (OC-Aluminum Oxide-Hydroxide). Boehmite, the main constituent of bauxite deposits in Europe, is also found associated with gibbsite in tropical bauxites in Africa, Asia, and Austraha. Hydrothemial transformation of gibbsite at temperatures above 150 °C is a common method for the synthesis of weU-cry stalhzed boehmite. Higher temperatures and the presence of alkali increase the rate of transfomiation. Boehmite ciy stals of 5—10 ]liii size (Fig. 3) are produced by tliis method. Fibrous (acicular) boehmite is obtained under acidic hydrothemial conditions (6). Excess water, about 1% to 2% higher than the stoichiometric 15%, is usually found in hydrothemiaHy produced boehmite. 

Fig. 3. Aluminum oxide—hydroxide hydrothemiaHy prepared boehmite, x2,000.

Diaspore (P-Aluminum Oxide Hydroxide). Diaspore, found in bauxites of Greece, Cliina, and the USSR, can also be obtained by hydrothemial transfomiation of gibbsite and boehmite. Higher (>200°) temperatures and pressure (>15 AlPa-150bar) are needed for synthesis and the presence of diaspore seed cry stals helps to avoid boehmite fomiation. 

The Synthesis and Structural Properties of Aluminum Oxide, Hydroxide and... 

Alumina - Alumina forms a variety of oxides and hydroxides whose structures have been characterized by X-ray diffraction (16). From the catalytic viewpoint y-alumina is the most important. This is a metastable phase that is produced from successive dehydration of aluminum trihydroxide (gibbsite) to aluminum oxide hydroxide (boehmite) to y-alumina, or from dehydration of boehmite formed hydrothermally. y-alumina is converted into a-alumina (corundum) at temperatures around 1000 C. 

The mechanism of adsorption of drugs by montmorillonite has been studied using infrared (IR) spectroscopy and XPD [68,69]. X-ray diffractometry and a host of other techniques were used to study the interaction of bovine serum albumin with the surface of a microcrystalline aluminum oxide hydroxide compound [70]. 

Af-dipropyl-p- toluidine, 2 550t a, a -dinitroanthraquinones, 9 315—316 a-alumina, 2 406t 14 103. See also Corundum transition to, 2 403 a-aluminum-iron—silicon alloys, 2 317 intermetallic phases, 2 316t a-aluminum oxide-hydroxide. 

P-Aluminum oxide-hydroxide. See Diaspore Aluminum oxide-hydroxides, 2 421. 

P-aluminum-iron-silicon alloys, 2 317 intermetallic phases, 2 316t P-aluminum oxide-hydroxide. 

WohlfartP, WeiB J, Kashammer J, Kreiter K, Winter C, Fischer RA, Mittler-Neher S (1999) MOCVD of aluminum oxide/hydroxide onto organic self-assembled monolayers. Chem Vap Deposition 5(4) 165-170... 

Tamura, T. and Jackson, M.L., 1953. Structural and energy relationships in the formation of iron and aluminum oxides, hydroxides and silicates. Science, 117 331-383. 

There are two main types of alumina (bauxite) ores used as the primary sources for aluminum metal and aluminum chemicals aluminum hydroxide [Al(OH)3] (gibbsite) and a mixed aluminum oxide hydroxide [AIO(OH)] (boehmite). Thus, bauxite is a term for a family of ores rather than a substance of one definite composition. An average composition of the ores used by industry today would be alumina (A1203), 35 to 60% silica (Si02), 1 to 15% ferric oxide (Fe203), 5 to 40% and titanium dioxide (Ti02), 1 to 4%. 

Figure 7. Sequence of phases formed after thermal treatment of aluminum hydroxides and aluminum oxide hydroxides. Pathway (a) is favored by pressures exceeding 1 bar, moist air, heating rates higher than IK min-1 and particle sizes higher than 100 fim. Pathway (b) is favored by pressures of 1 bar, dry air, heating rates below 1 Kmin-1 and particle sizes below 10 pm.

PZCs/IEPs of aluminum oxide hydroxides (nominally AIOOH) are presented in Tables 3.182 through 3.209. 

Chemical Names Boehmite alumina, alumina monohydrate, aluminum oxide hydroxide Trade Name Dispal Alumina Function in Formula Thickener... 

The commercial sources of most metals are not silicates, however, because generally metals are not easily obtained from them. Despite the abundance and avail-abihty of clay, an economical method of producing aluminum from clay has yet to be discovered. The usual compounds from which metals are obtained are oxides (and hydroxides), sulfides, and carbonates. Aluminum, for example, is produced from bauxite, which is a material containing aluminum oxide hydroxide, AIO(OH), and aluminum hydroxide, Al(OH)3, along with iron oxides and silicates. 

Zeolites are aluminosilicates, and considering this, an aluminosilicate composed of silica sheets (SiaOs) bonded to aluminum oxide/hydroxide layers [Al2(OH)4] (China clay with kaolinite composition) is compared with zeolites in LRAM3.56-PP/PER formulations (Figure 6.6). The curves exhibit the same... 

Aluminum oxide/hydroxide phases, such as gibbsite [Al(OH)3], accumulate from the dissolution of kaolin phases [equation (2)] during ihe final stages of weathering. 

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