Carbon growth

First Carbonation. The process stream OH is raised to 3.0 with carbon dioxide. Juice is recycled either internally or in a separate vessel to provide seed for calcium carbonate growth. Retention time is 15—20 min at 80—85°C. OH of the juice purification process streams is more descriptive than pH for two reasons first, all of the important solution chemistry depends on reactions of the hydroxyl ion rather than of the hydrogen ion and second, the nature of the C0 2 U20-Ca " equiUbria results in a OH which is independent of the temperature of the solution. AH of the temperature effects on the dissociation constant of water are reflected by the pH. 

In Chapter 2 (Section VI. C) of this volume, Hansen et al. also discuss detailed TEM results that show how the steps of a supported nickel cluster play an important role as centers for carbon growth in a real supported catalyst (73). 

Although fractionations of 60-80%o are theoretically possible under equilibrium conditions at very low temperatures ( 0 °C), they are not observed on Earth. Urey (1967) therefore proposed that the two types of carbon came from two unrelated reservoirs, whereas Arrhenius and Alfven (1971) suggested fractionation during carbonate growth from the gas phase, involving multiple desorption or metastable molecules. 

R.J. Reeder, Carbonates Growth and alteration microstructures, in Minerals and Reactions at the Atomic Scale Transmission Electron Microscopy (ed. 

Therefore, it is seen that rates of both reactions depend on temperature only, not on the carbon content. Zero order kinetics of CF is consistent with whisker carbon growth at constant whisker density[l]. Zero order kinetics of GAS correspond to whisker gasification. 

Inhibition of filamentous carbon growth on metal surfaces by addition of titanium oxide has been reported previously (10). In these experiments the titanium oxide was in the fully oxidized state and was an effective physical barrier toward filament formation, provided that the temperature was kept below 920 K. Above this temperature, the oxide tended to spall, and as bare metal was exposed to the gas phase, prolific filament growth occurred. In the present study we have combined electron microscopy studies with... 

Rare two-phase fluid inclusions e found in anker-ite and in calcite (Fig. 6H). They occur as isolated inclusions or in groups of a few inclusions with a random distribution. Owing to the scarcity of inclusions and to the lack of visible intracrystalline growth features in the carbonate cements, relationships between fluid inclusions and carbonate growth could not be evaluated. As a result, the primary or secondary origin of the inclusions studied cannot be ascertained. Microthermometric measurements are summarized in Table 2 and Fig. 7. 

The most common technique used to grow epitaxial SiC is CVD. The standard gas chemistry used is hydrogen-propane-silane, or TG-CsHs-SiEG, respectively. In this chemistry, C3H8 is the carbon growth precursor while SiTC is the silicon precursor. 

Other mechanisms have been proposed for filamentous carbon growth, and other filament structures have been observed. One of the most common variations in the basic filament type is the spiral conformation, examples of which are shown in Figure 3. 

Baker, R.T.K. Chludzinski, Jr., J.J. "Filamentous Carbon Growth on Nickel-Iron Surfaces The Effect of Various Oxide Additives" J. Catalysis 1980, 64 464. 

Figure 6. Mound-type carbon growths formed by precipitation at 620°C after prior methane exposure of 12 torr h at 750°C. Key a, surface after JO min and...

Figure 4. C-H-O phase diagram showing points/regions of gas compositions suitable for diamond growth as well as non-diamond carbon growth region and no-growth region. (Reproduced with permission.)...

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