Titanium dioxide, TiC

The presence of mica in pearlescent pigments only partly accounts for the appearance of the pigment. A very thin layer of the inorganic oxide titanium dioxide (TiC>2) or iron oxide (Fe2C>3) or both is coated on the mica platelets. The various colors and pearlescent effects are created as light is both refracted and reflected from the titanium dioxide layers. The very thin platelets are highly reflective and transparent. With their plate-like shape, the platelets are easily oriented into parallel layers as the paint medium is applied. Some of the incident light is reflected... 

In crystals of more complex formula, such as titanium dioxide, TiC>2, a Schottky defect will consist of two anion vacancies and one cation vacancy. This is because it is necessary to counterbalance the loss of one Ti4+ ion from the crystal by the absence of two O2- ions in order to maintain composition and electroneutrality. This ratio of two anion vacancies per one cation vacancy will hold in all ionic compounds of formula MX2. In crystals like A1203, two Al3+ vacancies must be balanced by three O2- vacancies. Thus, in crystals with a formula M2X3, a Schottky defect will consist of two vacancies on the cation sublattice and three vacancies on the anion sublattice. These vacancies are not considered to be clustered together but are distributed... 

The conductivity of titanium dioxide, TiC>2, at 1166 K was found to depend upon the oxygen partial pressure as in the following table. Assuming that oxygen vacancies are introduced into the oxide as the main point defect, is the vacancy more likely to be doubly or singly charged ... 

The absorptive properties of commonly used powders such as titanium dioxide (TiC>2), zinc oxide (ZnO), kaolin, cornstarch, and methylcellulose were shown to differ considerably when evaluated under standardized conditions (Figure 22.2). The highest water absorption was shown with ZnO and kaolin, followed by cornstarch and Ti02. Methylcellulose formed a gel with water that prevented the entire soaking of the powder, and thus water absorption remained low. 

The DSA-type anodes are inert , coated anodes made of a valve metal (titanium, niobium, or tantalum) base coated with an electrochemically active coating. The active coating is made either of noble metals or of mixed metal oxides. Noble metals in active coatings are usually platinum or platinum alloys. Mixed metal-oxide coatings contain active oxides and inert oxides the active components are usually ruthenium dioxide (R.UO2) and iridium dioxide (IrC>2) and the inert components are mostly titanium dioxide (TiC>2) and other oxides such as tantalum... 

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... 

We saw in Section 6.5.2 that ultraviolet irradiation of titanium dioxide promotes electrons into its conduction band and leaves reactive holes in the valence band with a band gap of 3 V (more, for very small TiC>2... 

Titanium carbide, TiC, is made by the action of carbon black on titanium dioxide at 2000 °C. It is the most important hard metallic material after tungsten carbide, and in fact is the hardest of all the metal carbides with a hardness rating of 9 on the Mohs scale - diamond is 10. In itself it is too brittle to be used pure but when mixed with the carbides of tungsten, tantalum and niobium it delivers great strength. 

TiCl4 can be formed by reacting titanium dioxide (TiQ2) with hydrochloric acid. Ti02 is available as an ore containing 78 % Ti02 and 22 % inerts. The HC1 is available as 45 wt% solution (the balance is water). The per pass conversion of TiOz is 75 %. The HC1 is fed into the reactor in 20 % excess based on the reaction. Pure unreacted TiC is recycled back to mix with the TiC feed. 

Abstract This article updates the one on the same topic published in this series in 1999. The photochemistry of PAHs and PCBs in liquid water and on ice and other solids such as silica, soil and titanium dioxide continues to be actively studied. The photochemistry of PAHs in all phases continues to be dominated by oxidation by O2, with superoxide (O2- ), excited singlet oxygen (102), and hydroxyl radical ( OH) being the active agents. The recent photochemistry of PCBs has been dominated by practical considerations, i.e. how to use photochemistry to clean up environmental problems involving PCBs. The use of surfactants, the semiconductor TiC>2, and various sources of the powerful oxidant, the hydroxyl radical, in this regard has received considerable attention. 

Titanium dioxide, Ti02, reacts with carbon and chlorine to give gaseous TiC ... 

TiC>2 Degussa P25 (presently Evonik) is the most used material for CO2 reduction, normally used as a standard reference material in thermodynamically downhill photocatalytic processes. It is a mixture of two polymorphs of titanium dioxide, namely anatase (80%) and rutile (20%) and the particle size up to some nanometers. Recently, Ohtani et al found that Degussa P25 also contains trace amount of amorphous titanium dioxide [165]. 

A review of the literature showed that the nanoparticles used in the production of nanofluids were aluminum oxide (AI2O3), titanium dioxide (Ti02), nitride ceramics (AIN, SiN), carbide ceramics (SiC, TiC), copper (Cu), copper oxide (CuO), gold (Au), silver (Ag), silica (Si02) nanoparticles and carbon nanotubes (CNT). The base fluids used were water, oil, acetone, decene and ethylene glycol. Modem technology allows the fabrication of materials at the nanometer scale, they are usually available in the market under different particle sizes and purity conditions. They exhibit... 

Semiconductor Electrodes 1. The Chemical Vapor Deposition and Application of Polycrystalline n-Type Titanium Dioxide Electrodes to the Photosensitized Electrolysis of Water Comparison of the behavior of CVD and single crystal n-TiC>2 presented. 229... 

A.R. Khataee, M.B. Kasiri, Photocatal3 tic degradation of organic dyes in the presence of nanostructured titanium dioxide Influence of the chemical structure of dyes . Journal of Molecular Catalysis A Chemical, 328, 8-26, (2010). 

The other important process for production of titanium dioxide is termed the chloride process [7]. The raw material used in this process is natural rutile, which is first heated at 9S0°C in the presence of carbon (in the form of coke) and chlorine. This produces crude TiC, and this product is heated at l(XX) C in the presoice of oxygen to produce the final titanium dioxide product. Under these conditions, the final product is the rutile phase. 

When zirconium silicate (ZrSi04) or a mixture of Z1O3 and SiOj is reacted with aluminum in the presence of aluminum oxide and then rdieated, zirconium silicide (ZrSi ) becomes the major product. Titanium dioxide (TiOs) and boron (111) oxide (BgO,) with aluminum similarly form titanium boride (TiBs). If the reduction of the oxides such as TiOg or Si02 with aluminum is performed in the presence of carbon black, the carbides TiC and SiC are formed embedded in aluminum oxide. This subject is also treated in a British patent titled Autothermic Fired Ceramics. ... 

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