Titanium monoxide structure

Titanium Monoxide. Titanium monoxide [12137-20-1 /, TiO, has a rock-salt structure but can exist with both oxygen and titanium vacancies. For stoichiometric TiO, the lattice parameter is 417 pm, but varies from ca 418 pm at 46 atom % to 4162 pm at 54 atom % oxygen. Apparently, stoichiometric TiO has ca 15% of the Ti and O sites vacant. At high temperatures (>900° C), these vacancies are randomly distributed at low temperatures, they become ordered. Titanium monoxide may be made by heating a stoichiometric mixture of titanium metal and titanium dioxide powders at 1600°C... 

Many of the oxides, carbides, and nitrides with the NaCl structure tend to be nonstoichiometric. Titanium monoxide exists over the range Tio.ssO to TiO, while FeO never occurs it is always nonstoichiometric with a composition ranging from Feo.goO to Feo.geO. As a consequence of these vacancies, the transition metal exists in two valence states, causing the oxide to exhibit semiconductor properties (as for NiO). 

D. Watanabe, O. Terasaki, A. Jostsons, and J. R. Castles, Electron microscope study on the structure of low-temperature modification of titanium monoxide phase, in The Chemistry of Extended Defects in Non-Metallic Solids (L. Eyring and M. O Keeffe, eds.), pp. 238-256, North-Holland, Amsterdam (1970). 

As discussed in Chapter 4, unusually for a transition metal monoxide, TiCi.oo demonstrates metallic conductivity. The existence of the vacant sites within the TiO structure is thought to permit sufficient contraction of the lattice that the 3 c/ orbitals on titanium overlap, thus broadening the conduction band and allowing electronic conduction. 

Ti407 is one of a wide range of defined compositions TiOx (0.5 < X < 2) those between that of Ebonex (x = 1.75) and x = 1.9 have a triclinic crystal structure and are known as Magneli phases Ti 02n i. Titanium dioxide cannot be reduced to the metal with hydrogen, carbon, or carbon monoxide but is reduced to TiOx suboxides at 1,200-1,300 °C, usually with hydrogen. 

The practically most important copolymer is made from ethene and propene. Titanium- and vanadium-based catalysts have been used to synthesize copolymers that have a prevailingly random, block, or alternating structure. Only with Ziegler or single site catalyst, longer-chain a-olefins can be used as comonomer (e.g., propene, 1-butene, 1-hexene, 1-octene). In contrast to this, by radical high-pressure polymerization it is also possible to incorporate functional monomers (e.g., carbon monoxide, vinyl acetate). The polymerization could be carried out in solution, slurry, or gas phase. It is generally accepted [173] that the best way to compare monomer reactivities in a particular polymerization reaction is by comparison of their reactivity ratios in copolymerization reactions. 

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