Titanium dioxide rutile form

Titanium dioxide (rutile form) the anatase form is photoactive. Zinc oxide, barium sulphate, iron oxide (red), chromium oxide, lead oxide and cadmium sulphide (can be photoactive) [1,2,5]. 

The possibility of the existence of two forms of titanium dioxide, rutile and anatase, is evident from the identity of their Coulomb energies taking the energy of the repulsive forces and of possible deformation into account, it is seen that the choice between the two structures would depend on the thermodynamic environment during crystallization. In... 

Titanium dioxide (E171, Cl white 6) is a white, opaque mineral occurring naturally in three main forms rutile, anatase, and brookite. More than 4 million tons of titanium dioxide are produced per year and it is widely used for industrial applications (paints, inks, plastics, textiles) and in small amounts as a food colorant. ° "° Production and properties — Titanium oxide is mainly produced from ilmenite, a titaniferous ore (FeTiOj). Rutile and anatase are relatively pure titanium dioxide (Ti02) forms. Titanium oxide pigment is produced via chloride or sulfate processes via the treatment of the titanium oxide ore with chlorine gas or sulfuric acid, followed by a series of purification steps. High-purity anatase is preferred for utilization in the food industry. It may be coated with small amounts of alumina or silica to improve technological properties. 

Examples of dimorphism were known in the cases of calcite and aragonite (see p. 203), the two forms of titanium dioxide (rutile and anatase), and iron disulphide in the forms of bronze-yellow pyrites and silver-white marcasite. Mitscherlich refers to groups of isomorphous elements , such as phosphorus and arsenic. He then thought ... 

Physical and Chemical Properties. Titanium dioxide [13463-67-7] occurs in nature in three crystalline forms anatase [1317-70-0] brookite [12188-41 -9] and mtile [1317-80-2]. These crystals are essentially pure titanium dioxide but contain small amounts of impurities, such as iron, chromium, or vanadium, which darken them. Rutile is the thermodynamically stable form at all temperatures and is one of the two most important ores of titanium. 

Chloride process. This process requires a high titanium feedstock. Rutile is reacted with hydrochloric acid to produce titanium tetrachloride, which can be hydrolyzed with steam or oxidized with air to render the dioxide. A rutile form of titanium dioxide is obtained. 

The main oxides are the dioxides. In fact, Ti02 is by far the most important compound formed by the elements of this group, its importance arising predominantly from its use as a white pigment (see Panel, p. 959). It exists at room temperature in three forms — rutile, anatase and brookite, each of which occurs naturally. Each contains 6-coordinate titanium but rutile is the most common form, both in nature and as produced commercially, and the others transform into it on heating. The rutile... 

Pressure-induced phase transitions in the titanium dioxide system provide an understanding of crystal structure and mineral stability in planets interior and thus are of major geophysical interest. Moderate pressures transform either of the three stable polymorphs into the a-Pb02 (columbite)-type structure, while further pressure increase creates the monoclinic baddeleyite-type structure. Recent high-pressure studies indicate that columbite can be formed only within a limited range of pressures/temperatures, although it is a metastable phase that can be preserved unchanged for years after pressure release Combined Raman spectroscopy and X-ray diffraction studies 6-8,10 ave established that rutile transforms to columbite structure at 10 GPa, while anatase and brookite transform to columbite at approximately 4-5 GPa. 

General Titanium is intrinsically very reactive, so that whenever the metal surface is exposed to air, or to any environment containing available oxygen, a thin tenacious surface film of oxide is formed. This oxide, which is present on fabricated titanium surfaces at normal or slightly elevated temperatures, has been identified as rutile, a tetragonal form of titanium dioxide, and it is the presence of this surface film which confers upon titanium excellent corrosion resistance in a wide range of corrosive media. 

Titanium Dioxide (Titania, Titanium White, Rutile, Anatase, Brookite, Titanic Anhydride, Titanic Acid Anhydride, Titanic Oxide). Ti02, mw 79.90, Selected Parameters of the Allotropic Forms of Ti02... 

The structures of rutile and anatase, the two tetragonal forms of titanium dioxide, have been determined by rigorous methods (Figs. 1 and 2). They seem at first sight to have little in common beyond the fact... 

Three forms of titanium dioxide, Ti02, are known. Of these the crystal structures of the two tetragonal forms, rutile and anatase, have been thoroughly investigated2) in each case only one parameter is involved, and the atomic arrangement has been accurately determined. The third form, brookite, is orthorhombic, with axial ratios... 

The coordination theory, which has been applied successfully2 to brook-ite, the orthorhombic form of titanium dioxide, is based on the assumption that the anions in a crystal are constrained to assume positions about the cations such that they indicate the corners of polyhedra of which the cations mark the centers. These polyhedra are the fundamentally important constituents of the crystal retaining their form essentially, they are combined by sharing corners, edges, and faces in such a way as to build up a crystal with the correct stoichiometrical composition. Thus in rutile, anatase, and brookite there occur octahedra of oxygen ions about titanium ions in rutile each octahedron shares two edges with adjoining octahedra, in anatase four, and in brookite three. 

This process involves the reaction of dried rutile ore and coke with chlorine in the chlorinator to produce titanium tetrachloride. The liquefied titanium tetrachloride is sent to the distillation unit to remove impurities and then to a fluidized bed reactor to react with oxygen to form titanium dioxide and chlorine. Solid titanium dioxide formed at this stage is vacuum degassed before being treated... 

Although, because of its cost, titanium dioxide is usually only used as a whitening agent for rubber compounds, it is in fact a reinforcing agent comparable on a volume basis with the reinforcement found with zinc oxide. There are two forms anatase, which has the greatest whitening power, and rutile, which is somewhat creamier in colour. The rutile form is more thermally stable. 

This feature can be illustrated with respect to frequently observed twinning that occurs on 101 planes in the rutile form of titanium dioxide. Large numbers of... 

Titanium dioxide crystallizes in several forms. The most important is the rutile form. This structure is also adopted by S11O2, MgF2, and ZnF2. A number of oxides that show metallic or metal-insulator transitions, for example, VO2, NbC>2, and Cr02, have a slightly distorted form of the structure. 

In the chloride process, developed in about 1960, the titanium in the ore is converted to titanium(IV) chloride by heating it to 800 °C with chlorine in the presence of carbon, which combines with the released oxygen. The purified chloride is then oxidised to titanium dioxide at 1000 °C and the chlorine formed is recycled. Technical problems arise because the oxidation of titanium(IV) chloride is not sufficiently exothermic to make the reaction self-sustaining but these can be overcome by pre-heating the reactants and by burning carbon monoxide in the reactor to raise the temperature. By careful control of the conditions, it is possible to produce pure rutile particles of a mean size of 200 nm. 

This chapter has been concerned mainly with the chemistry of making pigments but has also stressed the importance of preparing them in the correct physical form. In the case of those pigments which can be made in more than one crystal form, such as the anatase and rutile forms of titanium dioxide, this may mean that all the pigment should be in one form only. In others, a mixture of polymorphic forms may be required, and it is then necessary to ensure that the desired ratio of these forms is present. 

Titanium is not a rare material and it ranks as number four in abundance in the earth s crust. Deposits in the form of rutile are spread all over the world and more than 95% of purified titanium dioxide is used in pigments, where its extraordinary stability justifies use for most qualified applications in the paint and paper industry. 

Different crystal forms of titanium dioxide are known rutile (tP6), anatase (til2) brookite (oP24). Rutile is the most common form (the others, metastable, transform into it on heating). The ideal structure of rutile can be described as ... 

Titanium dioxide occurs in three crystalline modifications anatase, rutile, and brookite. In all three forms, each Ti + ion is surrounded by six 0 ions and each ion has three Ti + neighbors. Both anatase and rutile are important white pigments which are produced on a large scale. Even though their surface chemistry is very important for their technological application, astonishingly little has been published in the chemical literature on this subject. However, it is very likely that many investigations have been undertaken in industrial laboratories. 

Precipitated titanium dioxide is partly hydrated and amorphous. Only after heating to sufficiently high temperatures are crystallographi-cally pure anatase or rutile formed (309a). Very small anatase crystallites were detected by X-ray and electron diffraction in hydrated titanium dioxide (309b). 

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