Carbon-titanium system

Bigger clusters have been formed, for instance, by the expansion of laser evaporated material in a gas still under vacuum. For metal-carbon cluster systems (including M C + of Ti, Zr and V), their formation and the origin of delayed atomic ions were studied in a laser vaporization source coupled to a time-of-flight mass spectrometer. The mass spectrum of metal-carbon cluster ions (TiC2 and Zr C j+ cluster ions) obtained by using a titanium-zirconium (50 50) mixed alloy rod produced in a laser vaporization source (Nd YAG, X = 532 nm) and subsequently ionized by a XeCl excimer laser (308 nm) is shown in Figure 9.61. For cluster formation, methane ( 15% seeded in helium) is pulsed over the rod and the produced clusters are supersonically expanded in the vacuum. The mass spectrum shows the production of many zirconium-carbon clusters. Under these conditions only the titanium monomer, titanium dioxide and titanium dicarbide ions are formed. 

However, until recently no complexes clearly showed interactions of single C-C bonds with M because of steric interference of the substituents on tetrahedral carbon and the presence of more accessible C-H bonds that can give competing agostic interactions. The first example of well-characterized agostic C-C interactions is present in a 14e titanium system (23).55 The saturated carbon C7 is only 2.293(7) A from Ti (and even less for , C6, and C8). Remarkably these carbons are closer to Ti than any of the bound olefinic carbons C4 and C5 (2.30-2.34 A) and Cp carbons, clearly indicative of several C-C bond interactions. The Ti-C2 distance of 2.579(7) A also indicates that this carbon is involved in the agostic C-C interactions, which are verified by DFT calculations to occur for C2-C7 and even more strongly for the C2-C3, C6-C7, and C7-C8 bonds. Bond indexes of 0.168 for the Ti-C7... 

Another system in which metal-carbon bond strengths have been investigated in detail is the titanium system (silox)2Ti(NHSiBu 3)R. These complexes lose hydrocarbon RH to generate transient [Ti(silox)2(=NSiBu 3)], which then adds a C-H bond from the solvent across the Ti=N bond (Equation (2)). The equilibrium activation between two hydrocarbons could be directly measured in this system (AG ), and construction of a ladder of stabilities was established for some 15 substrates. In this system, relative metal carbon bond strengths could be directly obtained... 

Vog] Vogel, R., About the Influence of the Titanium on the Perlit Creation in Carbon Steel , Ferrum, 14(11-12), 177-195 (1917) (Experimental, Phase Diagram, Phase Relations, 9) [1925Tam] Tamaru, K., On the Equilibrium Diagram of the System Iron-Carbon-Titanium , Sci. Rep. 

Maz] Mazumdar, S., Ramaswamy, V, The Carbon-Iron-Titanium System , J. Alloys Phase Diagrams, 1, 27-38 (1985) (Phase Diagram, Phase Relations, Crys. Structure, Review, 26)... 

Guo] Guo, Y., Wang, C., Yu, H., Interaction Coefficients in the hon-Carbon-Titanium and Titanium-Silver Systems , Metall. Trans. B, 21B, 537-541 (1990) (Phase Relations, Ther-modyn.. Experimental, 33)... 

Natta and a great many others have described the addition step as anionic coordinated. The term anionic is used because, for example, the reaction of tritiated alcohol with the system gives radioactive polymer. Mechanistically, the term anionic seems plausible because the polarization of the carbon-titanium bond should favor a partial negative charge on carbon. The Cossee-Arlman theory suggests, however, that the electronic rearrange-... 

Bipc4ar or separatum I ate Fourfold rc4e -Mechanical rigidity in a filter-press stack - Conduit of water for an aiK de - Evacuatic i of gas f x an aiK de (cell N) and a cathode (cell N+1) - Electrical serializatic i of the cells - Solid titanium - Carbon-based systems (less sturdy). A metal reinforcement is needed on the anode side They include channels to decrease the charge losses in the stack... 

We have used a rat traeheal explant system to examine the role of AOS in particle uptake. When traeheal explants are briefly immersed in a suspension of a mineral dust, dust partieles adhere to the epithelial cell surfaces if the explants are then maintained in organ eulture in air, the epithelial cells slowly take up particles from the apical surface (see Fig. 1). The relative basal level of uptake of different types of particles is quite different (see Table 3), but every type of mineral particle thus far examined (asbestos, carbon, titanium dioxide, iron oxide, talc, wollastonite, or silicon carbide) enters the epithelial cells (3,4,51-54). This system offers several simplifying advantages for studying particle uptake, ineluding lack of airspace inflammatory cells, maintenance of normal levels of intraeel-lular antioxidant defense (Churg A, unpublished data), and retention of a polarized cell structure with normal apical differentiation. 

Color Concentrates. Color concentrates have become the method of choice to incorporate colorants into resins. Color concentrates have high ratios of colorant to a compatible vehicle. The colorant may be added at 70% colorant to 30% vehicle in a titanium dioxide mixture whereas the ratio may be 15% colorant to 85% vehicle in a carbon black mixture. The amount of colorant that can be added is dependent on the surface area and the oil absorption of the colorant and the wetting abiHty of the vehicle. The normal goal is to get as much colorant in the concentrate as possible to obtain the greatest money value for the product. Furthermore, less added vehicle minimizes the effect on the physical or chemical properties of the resin system. 

Mineral fillers are used for light-colored compounds. Talc has a small particle size and is a semireinforcing filler. It reduces air permeabihty and has htde effect on cure systems. Calcined clay is used for halobutyl stoppers in pharmaceutical appHcations. Nonreinforcing fillers, such as calcium carbonate and titanium dioxide, have large particle sizes and are added to reduce cost and viscosity. Hydrated siUcas give dry, stiff compounds, and their acidity reduces cure rate hence, their content should be minimized. 

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