Other Titanates

However, besides lanthanum other rare earth elements showed photocatalytic activity after their incorporation in titanates. Among them, neodymium incorporated in different perovskite-like structures (e.g., NaNdTi04 [86,87], LiNd-TiP4 [87], HNdTi04 [ ] Bi345Ndo.85Ti30i2 [8 ], and A2Nd2Ti30io —Ei, Na, 

K) [89]) showed promising photocatalytic behavior. Other examples are Gd and Er (Ln2Ti20y (Ln = Gd or Er)) [90]. The insertion of yttrium in titanate perov-skites behaves very close to rare earth elements (R3MO7 and R2Ti207 (R=Y or Gd M = Nbor Ta)) [91]. 

Ferrites are ABO3 perovskite-type oxides with high catalytic activity due to optimal defect structure [96]. 

Rutile titanates represent by far the largest commercial class of CICPs. Chromium antimony titanate yellows (C.I. Pigment Brown 24) are the most widely used, followed by nickel antimony titanate yellows (C.I. Pigment Yellow 53). Manganese antimony titanate browns (C.I. Pigment Yellow 164) occupy a much smaller market share, and the other rutile grades a significantly smaller fraction still. 

It is well known that pure rutile titanium dioxide has a photoactive surface [5, 6]. When irradiated with UV light, highly reactive 0x0 radicals are formed that can photocatalytically degrade organic materials in contact with the pigment s surface. Commercial grades of rutile TiOj are passivated with coatings of other metal oxides such as those of aluminum, silicon, or zirconium to suppress this effect. 

Rutile CICPs do not exhibit photocatalytic activity as do pure titanium dioxides. The act of doping the rutile structure with the transition metal and other ions 

Titanate spinels form a much smaller class of pigments than the rutiles. The M3O4 stoichiometry of spinel is met by reacting two units of +2 metal oxide with one unit of Ti02, according to Eq. (5-1). 

Titanates are inverse spinels, where a number of the +2 ions occupy octahedral coordination sites in the lattice. Commercially important grades are the cobalt titanate greens and iron titanate browns. 

---

PEAT-EXCHANGE TECHNOLOGY - HEAT-TRANSFERTffiDIA OTHER TITAN WATER] (Vol 12)... 

Alkali Metal Titanates. Alkali metatitanates may be prepared by fusion of titanium oxide with the appropriate alkah metal carbonate or hydroxide. Representative alkah metal titanates ate hsted in Table 14. The alkah metal titanates tend to be more reactive and less stable than the other titanates, eg, they dissolve relatively easily in dilute acids. 

Radiation other titan radon Estimated 360 eaneers per year. Mostly from building materials. Medieal exposure and natural baekground levels not ineluded. 

This reaction is significant for sodium titanate (Keq — 10 moles /l ) and sodium zirconate, but is negligible for sodium niobate and some other "titanates" such as Mg(Ti205H)2. Gelatinous hydroxide precipitates which would appear likely based on Eq. 3 were not observed in the reaction of sodium titanate with aqueous waste, and stoichiometric loading was achieved with polyvalent cations which form insoluble hydroxides as well as for those forming soluble hydroxides. 

When the specific gravity is determined at a temperature other titan 15, the necessary corrections are obtained from tables given by G. Tommasi (Ann. R. star, chtm. agr. spertrn. di Roma, 1913, VI, p. 157). 

A further simplification of stereochemical notation for saturated carbon centers is to stretch out the carbon skeleton in the plane of the paper (blackboard, computer screen). Valences of atoms or groups other titan hydrogen are indicated by a bold line if they project into the space in front of the plane and with a dashed line if they project into the space behind the paper (blackboard, computer screen). 

It is also known that once the tributyltin radical adds to the sulfur of N-hydroxypyridine-2-thione, breakage of the N-0 bond and decarboxylation are very fast and probably concerted. They are driven energetically by formation of the very stable carbon dioxide molecule. It comes as no surprise that if atoms other titan carbon are attached to the carboxyl group, then they would also end up as free radicals after decarboxylation. This is shown for a urethane analog as a source of nitrogen-centered free radicals. A wide variety of other free-radical species can be produced by this strategy, and it is thus quite useful. 

Ancillary equipment consists of the support equipment, other titan process equipment, needed for a plant to function properly. Pipes, valves, and primary movers (e.g., pumps) are included in this category. 

Table 31.2 lists K for a range of materials. Many ceramics and glasses have k in the range of 4-10. Polarization is electronic only in covalent ceramics such as diamond and is a combination of electronic and ionic in materials such as MgO. Some ceramics, in particular BaTiOs and other titanates and zirconates, have very large k due to their permanent dipole moments. 

Titanates are double oxides of the form MeTiOa or Me2Ti04. Barium titanate BaTiOa and its solid solution crystals with other titanates are especially well-known. BaTiOs crystallizes in the perovskite structure. Its technical importance results from its ferroelectric and associated piezoelectric properties, its high dielectric constant at room temperature, and the interesting semiconducting properties which it exhibits when doped [13]. The remarkable temperature dependence of the electrical resistance of such doped material (the temperature coefficient can be metal-like) is used to advantage in control and circuit devices. 

Magnesium Titanates. Three compounds exist. Mg2Ti04, m.p. 1730 C this has a spinel structure and has been proposed for use as a resistor. MgTi03, m.p. 1630°C ilmenite structure. MgTi205, m.p. 1650°C has a low dielectric constant and has been added to other titanate bodies to reduce their dielectric constants. 

---