Titanium distribution

Treatment with a deficient quantity of chlorobis(cyclooctene)rhodium(I) dimer (Scheme 3) after 12 h gave a shell of rhodium near the surface. With excess reagent after 4 days the rhodium was incorporated uniformly. Cyclopentadienyltitanium catalysts bound to 2% and 20% cross-linked macroporous polystyrenes had uniform titanium distribution when initially functionalized by chloromethylation (22). Surface binding of Pd from (PhCN)2PdCl2 on 2% cross-linked, tertiary amine-substituted polystyrene was found by X-ray photoelectron spectroscopy (2S). 

Comparison of Gale s work with experimental results suggests that the titanium distribution in TS-1 is substantially in agreement with the site preferences expected from thermodynamics, as had been proposed previously on the basis of theoretical investigations (118). 

Nanoscale titanium dioxide (Ti02) is massively produced and widely used in the living environment, which may lead to a potential risk to human health. The central nervous system (CNS) is the potential susceptible target of inhaled nanoparticles, but related studies have been limited so far. Wang et reported the accumulation and toxicity results in vivo of two crystalline phases of Ti02 nanoparticles (80 nm rutile and 155 nm anatase purity > 99%). The female mice were intranasally instilled with 500 pg of Ti02 nanoparticles suspension every other day for 30 days. Synchrotron radiation X-ray fluorescence analysis (SRXRF) was used to determine titanium distribution in the murine brain. 

Fig. 2 Osteoclasts were cultured for 2 weeks on titanium foil before stained with Newport Green DCF and documented with confocal fluores-cence microscopy [14]. Note the green stained granular areas in the cyto-plasm as well as in the nucleus representing titanium distribution in the bi-nucleated cell (blue nuclear stain)...

Titanium is not a rare element it is the most abundant transition metal after iron, and is widely distributed in the earth s surface, mainly as the dioxide TiOj and ilmenite FeTi03. It has become of commercial importance since World War II mainly because of its high strength-weight ratio (use in aircraft, especially supersonic), its... 

The bimetallic mechanism is illustrated in Fig. 7.13b the bimetallic active center is the distinguishing feature of this mechanism. The precise distribution of halides and alkyls is not spelled out because of the exchanges described by reaction (7.Q). An alkyl bridge is assumed based on observations of other organometallic compounds. The pi coordination of the olefin with the titanium is followed by insertion of the monomer into the bridge to propagate the reaction. 

Fig. 7. The effect of preparation on the pore size distribution (a), titanium dispersion (b), and the activity for epoxidation of cyclohexene (c) of titania—siUca containing 10 wt % titania and calcined in air at 673 K. Sample A, low-temperature aerogel Sample B, high-temperature aerogel Sample C, aerogel.

Fig. 1. Global distribution of seabed mineral deposits, where x represents chromite + barite titanium, zirconium, hafnium, and thorium tin I gold, platinum, and silver 3 sand and gravel shell, calcium carbonate gems marine polymetaUic sulfides phosphorites Cl cobalt cmsts S sulfur and B...

The U.S. titanium market distribution is shown in Table 18. Before 1970, more than 90% of the titanium produced was used for aerospace, which feU to ca 70—80% by 1982. Mihtary use has continually decreased from nearly 100% in the early 1950s to 20% in the 1990s. In contrast to the United States, aerospace uses in Western Europe and Japan account for only 40—50% of the demand (58). The CIS s consumption of titanium metal prior to the breakup was about one-half of the world consumption. In the 1980s, considerable amounts were used for submarine constmction. Since the breakup of the former Soviet Union, the internal consumption of titanium in the CIS is beheved to be a modest fraction of its former capacity, thus leaving a large capacity available for export. The world production faciUties for titanium metal and extraction are given in Table 19. 

Titanium, Ti, atomic number 22, relative atomic mass 47.90, is the ninth most common element (ca 0.6% by weight) and is widely distributed in the earth s cmst. It is found particularly in the ores mtile, Ti02, and ilmenite, FeTiO. ... 

The resulting titanium nitride forms a sintered mass, which must be subsequently milled to form a powder having a wide size distribution. The powders produced by these routes ate typically 0.5—10 )Tm, with a wide size distribution. Very fine powders (0.005—0.5 -lm) have been prepared at pilot-plant scale... 

Titanium Monoxide. Titanium monoxide [12137-20-17, TiO, has a rock-salt stmcture 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 4I62 pm at 54 atom % oxygen. Apparendy, 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... 

Table 13. Distribution of U.S. Titanium Dioxide Pigment Shipments and Production ...

Cocatalysts, such as diethylzinc and triethylboron, can be used to alter the molecular-weight distribution of the polymer (89). The same effect can also be had by varying the transition metal in the catalyst chromium-based catalyst systems produce polyethylenes with intermediate or broad molecular-weight distributions, but titanium catalysts tend to give rather narrow molecular-weight distributions. 

Mechanical properties depend on the alloying elements. Addition of carbon to the cobalt base metal is the most effective. The carbon forms various carbide phases with the cobalt and the other alloying elements (see Carbides). The presence of carbide particles is controlled in part by such alloying elements such as chromium, nickel, titanium, manganese, tungsten, and molybdenum that are added during melting. The distribution of the carbide particles is controlled by heat treatment of the solidified alloy. 

Titanium-Based Casting and Wrought Alloys. Titanium-based alloys offer an attractive alternative to gold alloys and to the base-metal alloys that contain nickel or chromium. On a volume basis the cost of titanium is roughly comparable to that of the chromium-containing alloys, but the price of titanium tends to be more stable because its ores are abundant and widely distributed (see Titaniumand titanium alloys). 

Specify stabilized grades of stainless steel. An alternative method to prevent chromium carbide formation is to charge the alloy with substances whose affinity for carbon is greater than that of chromium. These substances will react preferentially with the carbon, preventing chromium carbide formation and thereby leaving the chromium uniformly distributed in the metal. The carbon content of the alloy does not have to be reduced if sufficient quantities of these stabilizing elements are present. Titanium is used to produce one stabilized alloy (321) and niobium is used to provide another (347). Note the cautions below. 

Good results are obtained with oxide-coated valve metals as anode materials. These electrically conducting ceramic coatings of p-conducting spinel-ferrite (e.g., cobalt, nickel and lithium ferrites) have very low consumption rates. Lithium ferrite has proved particularly effective because it possesses excellent adhesion on titanium and niobium [26]. In addition, doping the perovskite structure with monovalent lithium ions provides good electrical conductivity for anodic reactions. Anodes produced in this way are distributed under the trade name Lida [27]. The consumption rate in seawater is given as 10 g A ar and in fresh water is... 

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