Aluminum-titanium oxide

Aluminum. All primary aluminum as of 1995 is produced by molten salt electrolysis, which requires a feed of high purity alumina to the reduction cell. The Bayer process is a chemical purification of the bauxite ore by selective leaching of aluminum according to equation 35. Other oxide constituents of the ore, namely siUca, iron oxide, and titanium oxide remain in the residue, known as red mud. No solution purification is required and pure aluminum hydroxide is obtained by precipitation after reversing reaction 35 through a change in temperature or hydroxide concentration the precipitate is calcined to yield pure alumina. 

The vapor-phase conversion of aniline to DPA over a soHd catalyst has been extensively studied (18,22). In general, the catalyst used is pure aluminum oxide or titanium oxide, prepared under special conditions (18). Promoters, such as copper chromite, nickel chloride, phosphoric acid, and ammonium fluoride, have also been recommended. Reaction temperatures are usually from 400 to 500°C. Coke formed on the catalyst is removed occasionally by burning. In this way, conversions of about 35% and yields of 95% have been reported. Carba2ole is frequently a by-product. 

A wide variety of greens ranging from blue to yellow in shade ate based on cobalt in combination with chromium, aluminum, titanium, nickel, magnesium, antimony, or zinc. These are brighter than the chromium oxides. 

An especially insidious type of corrosion is localized corrosion (1—3,5) which occurs at distinct sites on the surface of a metal while the remainder of the metal is either not attacked or attacked much more slowly. Localized corrosion is usually seen on metals that are passivated, ie, protected from corrosion by oxide films, and occurs as a result of the breakdown of the oxide film. Generally the oxide film breakdown requires the presence of an aggressive anion, the most common of which is chloride. Localized corrosion can cause considerable damage to a metal stmcture without the metal exhibiting any appreciable loss in weight. Localized corrosion occurs on a number of technologically important materials such as stainless steels, nickel-base alloys, aluminum, titanium, and copper (see Aluminumand ALUMINUM ALLOYS Nickel AND nickel alloys Steel and Titaniumand titanium alloys). 

In general, the stability of titanium oxide surfaces in moist environments is less of a concern than it is for aluminum oxide surfaces. For example, an FPL or PAA oxide on aluminum would be completely converted to hydroxide in less than 5 min after exposure to boiling water, whereas even after 24 h only slight changes such as crystallite formation and reduction in density of the cell structure occur for... 

In order to understand the general behavior of the tested materials, scoping tests were conducted in 25 mg/L gold(III)-chloride solutions at 25°C and 80°C with different initial pH values, namely 1.5, 4 and 8. After the start of the experiment the pH was not further adjusted, i.e., it could change freely. It remained similar to the initial pH in all cases. From these tests it was found that, in the case of the iron-oxide based adsorbents, dissolution of the solid took place at pHaluminum oxides and titanium oxide was observed at this pH. At pH>2 all adsorbents were found to be stable and did not dissolve during the experiment. 

Rates of sorption and desorption of phosphate. Eur. J. Soil Sd. 48 101-114 Strens, R.G.S. Wood, B.J. (1979) Diffuse reflectance spectra and optical properties of some iron and titanium oxides and oxyhydr-oxides. Min. Mag. 43 347—354 Stumm, W. Eurrer, G. (1987) The dissolution of oxides and aluminum silicates Examples of surface-coordination-controlled kinetics. 

Iron(III) oxide or alumina is refined from bauxite. Approximately 175 million tons of bauxite are mined annually worldwide, with virtually all of this processed into alumina. Alumina is a white crystalline substance that resembles salt. Approximately 90% of all alumina is used for making aluminum, with the remainder used for abrasives and ceramics. Alumina is produced from bauxite using the Bayer process patented in 1887 by Austrian Karl Josef Bayer (1847-1904). The Bayer process begins by grinding the bauxite and mixing it with sodium hydroxide in a digester. The sodium hydroxide dissolves aluminum oxide components to produce aluminum hydroxide compounds. For gibbsite, the reaction is Al(OH)3 + NaOH —> Al(OH)4 + Na+. Insoluble impurities such as silicates, titanium oxides, and iron oxides are removed from the solution while sodium hydroxide is recovered and recycled. Reaction conditions are then... 

Lightfast chrome yellow pigments that are coated with metal oxides (e.g., of aluminum, titanium, manganese) are produced by Du Pont [3.135]. 

In the following sections some examples are given of the ways in which these principles have been utilized. The first example is the use of these techniques for the low temperature preparation of oxide ceramics such as silica. This process can also be used to produce alumina, titanium oxide, or other metal oxides. The second example describes the conversion of organic polymers to carbon fiber, a process that was probably the inspiration for the later development of routes to a range of non-oxide ceramics. Following this are brief reviews of processes that lead to the formation of silicon carbide, silicon nitride, boron nitride, and aluminum nitride, plus an introduction to the synthesis of other ceramics such as phosphorus nitride, nitrogen-phosphorus-boron materials, and an example of a transition metal-containing ceramic material. 

Active metals such as aluminum, titanium, and high-chromium steels become corrosion resistant under oxidizing conditions because of a very adherent and impervious surface oxide film that, although one molecule thick, develops on the surface of the metal. This film is stable in a neutral medium, but it dissolves in an acid or alkaline environment. In a few cases, such as certain acid concentrations, metals can be kept passive by applying a carefully controlled potential that favors the formation of the passive surface film. The ability to keep the desired potential over the entire structure is very critical in anodic control. If a higher or lower potential is applied, the metal will corrode at a higher rate, possibly higher than if it is not protected at all. 

The direct condensation of ethanol to form n-butanol was investigated by Dolgov and Vol nov in 1933, using titanium oxide promoted with iron-aluminum oxides on charcoal as the catalyst (71). They suggest, with insufficient proof, that ethanol is dehydrated to form ethylene which then reacts with more ethanol to form the butanol. 

Hydrofluoric acid — (HF) A solution of hydrogen fluoride in water. The pure hydrogen fluoride is characterized by Mw of 20.0063 gmol-1 m.p. -83.55 °C (1 atm) b.p. 19.5 °C (latm). When concentrated, this colorless fuming liquid is extremely corrosive and can dissolve almost all inorganic oxides such as silicate compounds or oxides of metals like stainless steel, aluminum, and uranium however, it can be stored in casted iron bottles because a corrosion-resistant iron fluoride layer protects the metal. It is used for several purposes such as the preparation of titanium oxide nano tube arrays [i], silicon nanoparticles [ii] and electrochemical etching of silicon [iii], electrochemical deposition of lithium [iv], etc. 

Although a valence-type force field of the type illustrated by Eq. [1] is most suitable for modeling molecular systems, the electronegativity equalization approach to treating polarization can be coupled equally well to other types of potentials. Streitz and Mintmire used an EE-based model in conjunction with an embedded atom method (EAM) potential to treat polarization effects in bulk metals and oxides. The resulting ES + EAM model has been parameterized for aluminum and titanium oxides, and has been used to study both charge-transfer effects and reactivity at interfaces. 

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