Titanium dioxide brookite

Anatase titanium dioxide brookite titanium dioxide color index number 77891 E171 Kronos 1171 pigment white 6 rutile titanium dioxide Tioxide TiPure titanic anhydride Tronox. 

Besides anatase and rutile nanoparticles, brookite phase Ti02 nanoparticles have also been synthesized by sol-gel method [157-161]. Lee and Bhave [157] reported the preparation of nanocrystalline brookite titanium dioxide particles by sol process under ambient condition. Titanium tetrachloride was the precursor in water with isopropanol as the co-solvent in hydrochloric acid. The formed gel mass was peptized and crystallized under refluxing condition. The effect of various parameters. 

Titanium dioxide has three crystal stractures, i.e., anatase, rutile and brookite. Titanium dioxide of the anatase type generally shows the highest photoactivity compared... 

Titanium dioxide itself is found in three crystalline forms rutile, anatase, and brookite. Titanium dioxide as a final product for use in rubber is commonly used in the rutile form where no chalking is desired and in the anatase form where chalking characteristics are desired, as with a tire white sidewall application. 

A significant advantage of the PLM is in the differentiation and recognition of various forms of the same chemical substance polymorphic forms, eg, brookite, mtile, and anatase, three forms of titanium dioxide calcite, aragonite and vaterite, all forms of calcium carbonate Eorms I, II, III, and IV of HMX (a high explosive), etc. This is an important appHcation because most elements and compounds possess different crystal forms with very different physical properties. PLM is the only instmment mandated by the U.S. Environmental Protection Agency (EPA) for the detection and identification of the six forms of asbestos (qv) and other fibers in bulk samples. 

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. 

Anatase and mtile are produced commercially, whereas brookite has been produced by heating amorphous titanium dioxide, which is prepared from an alkyl titanate or sodium titanate [12034-34-3] with sodium or potassium hydroxide in. an autoclave at 200—600°C for several days. Only mtile has been synthesized from melts in the form of large single crystals. More recentiy (57), a new polymorph of titanium dioxide, Ti02(B), has been demonstrated, which is formed by hydrolysis of K Ti O to form 20, followed by subsequent calcination/dehydration at 500°C. The relatively open stmcture... 

It is accepted that, at normal pressures, mtile is the thermodynamically stable form of titanium dioxide at all temperatures. Calorimetric studies have demonstrated that mtile is more stable than anatase and that brookite and Ti02 (ii) have intermediate stabiHties, although the relative stabiHties of brookite and Ti02(ii) have not yet been defined. The transformation of anatase to mtile is exothermic, eg, 12.6 KJ/mol (9), although lower figures have also been reported (63). The rate of transformation is critically dependent on the detailed environment and may be either promoted or retarded by the presence of other substances. For example, phosphoms inhibits the transformation of anatase to mtile (64). 

Titanium Dioxide. The specifications of titanium dioxide have been given previously. Titanium dioxide exists ia nature ia three crystalline forms anatase, brookite, and mtile, with anatase as the commonly available form. Anatase has a high refractive iadex (2.52) and excellent stabiUty toward light, oxidation, changes ia pH, and microbiological attack. Titanium dioxide is virtually iasoluble ia all common solvents. 

Titanium dioxide exists in nature as three different polymorphs rutile, anatase and brookite. This material has been extensively studied during the last few decades due to its interesting physical properties and numerous technological applications. Rutile and anatase (a popular white pigment) are widely used in photocataly s and as sensors. Both of them have had new structural and electronic applications suggested recently (see for a review). 

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. 

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 elucidation of the factors determining the relative stability of alternative crystalline structures of a substance would be of the greatest significance in the development of the theory of the solid state. Why, for example, do some of the alkali halides crystallize with the sodium chloride structure and some with the cesium chloride structure Why does titanium dioxide under different conditions assume the different structures of rutile, brookite and anatase Why does aluminum fluosilicate, AljSiCV F2, crystallize with the structure of topaz and not with some other structure These questions are answered formally by the statement that in each case the structure with the minimum free energy is stable. This answer, however, is not satisfying what is desired in our atomistic and quantum theoretical era is the explanation of this minimum free energy in terms of atoms or ions and their properties. 

During the investigation of the structure of brookite, the orthorhombic form of titanium dioxide, another method of predicting a possible structure for ionic compounds was developed. This method, which is described in detail in Section III of this paper, depends on the assumption of a coordination structure. It leads to a number of possible simple structures, for each of which the size of the unit of structure, the space-group symmetry, and the positions of all ions are fixed. In some cases, but not all, these structures correspond to closepacking of the large ions when they do, the method further indicates... 

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. 

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. 

There are three crystal structures of titanium dioxide rutile, anatase, and brookite. The most active phase is rutile, which has a tetragonal structure [133], as shown in Figure 8.5 [134],... 

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. 

Rutile structure (Fig. 4-15). Titanium dioxide occurs naturally as ana-tase, brookite, and rutile, all of which contain octahedral TiC>68 units. The coordination number of the central Ti4+ is very obviously six, and a little thought confirms that the same is true of the Ti4+ ions at the corners. That the coordination number of the O2- ions is three is seen from the nearest... 

The same phenomenon is shown also by anatase and brookite, two additional crystal modifications of titanium dioxide. In these crystals also the minimum O——O— distances have the low value 2.50 A. A theoretical treatment like that described above has been carried out for anatase, with results in good agreement with experiment. 

Double hexagonal closest packing (Sec. 11-5) was first found62 for the oxygen ions in brookite, the orthorhombic form of titanium dioxide, and for the oxygen and fluoride ions in topaz 63 AUSiC F2. It has since been reported for the halogens in one modification of cadmium iodide,64 in mercuric bromide,66 and in mercuric chloride6 and for chloride and... 

It is interesting that rutile, with only two shared edges per octahedron, is reported to be more stable than brookite and anatase, and, moreover, that many substances MXa have the rutile structure, whereas only titanium dioxide has been reported to have the brookite and anatase structures. 

Titanium dioxide [13463-67-7], Ti02, Mr 79.90, occurs in nature in the modifications rutile, anatase, and brookite. Rutile and anatase are produced industrially in large quantities and are used as pigments and catalysts, and in the production of ceramic and electronic materials. 

The rutile structure. Titanium dioxide crystallizes tn three crystal forms at utmospheric pressure anatase, brookite, and rutile (Fig. 4.4a). Only the last (tetragonal P42/mnin) will be considered here. The coordination numbers are 6 for the cation (six oxide anions arranged approximately octahedrally about the titanium ions) and 3 for the anion (three tiianium ions trigonally about the oxide ions). The rutile structure is also found in the dioxides of Cr, Mn, Ge, Ru, Rh, Sn, Os. Ir, Pt. and Pb. 

Experiments in the artificial preparation of titanium dioxide appear to show that rutile is the most stable form and produced at the highest temperature, brookite at a lower temperature, and octahedrite (anatase) at a still lower temperature. 

RUTILE. A mineral, composed of titanium dioxide, which occurs in three distinct forms as rutile, a tetragonal mineral usually of prismatic habit, often twinned as octahedrite (anatase), a tetragonal mineral of psendo-octahedra] habit and as brookite. an orthorhombic mineral. Bolh octahedrite (anatase) and brookite are relatively rare minerals. 

Titanium dioxides The most common forms of titanium dioxide (TiCL) are rutile, anatase, and brookite. Brookite is orthorhombic, whereas rutile and anatase are tetragonal (PAflmnm and lAfamd space groups, respectively) (Klein, 2002, 383-384). Titanium dioxides may sorb both As(III) and As(V) from water. The compounds are also important photocatalysts in the oxidation of As(III), MMA(V), and DMA(V) to inorganic As(V) in water (Nakajima et al., 2005 Xu, Cai and O Shea, 2007). 

Ti02 is an important oxide with a broad range of applications in catalysis (as a catalyst or a support) (6), photocatalysis (35, 36), and sensor technology it is also used as a pigment. Of the three titanium dioxide polymorphs (rutile, anatase, and brookite), rutile and anatase have been most widely investigated they are the only ones reviewed here. 

Titanium dioxide Ti02 occurs in three crystalline modifications, i.e., anatase, rutile, and brookite. Anatase and rutile are important as adsorbents, white pigments, and catalysts. In both modifications, the Ti4+ ions are octahedrally coordinated by oxygen O2", and each O2- has three Ti4+ neighbors. The structural unit in both forms is the Ti06 octahedron with similar Ti—O bond length in each case. The difference between the two structures is due to the different packing of these octahedra (131). 

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