Carbon core radius

Figure 11-15 Sphere with un reacted carbon core cf radius ft.

Figure 1 presents a comparison of the measured and calculated core length hydrogen reactivity worths (nor-mialized to PERT-ID calculation near the center of the Cpre) as a function of relative core radius. Table I summarizes the calculated and measured reactivity worths of carbon, uranium, and polyethylene. The agree-meht between the calculations and the experiment is good. 

Note that although the production of carbon nanotubes does not lend itself to an easy scale-up, the tunability of the carbon nanotube radii and the perfection of its structure could be important for their use as a template for the growth of inorganic nanotubes with a controlled radius. This property can be rather important for the selective catalysis of certain reactions, where either the reaction precursor or the product must diffuse through the (inorganic) nanotube inner core. 

In clusters with octahedrally encapsulated carbon atoms, the observed values for the radius of the interstitial atom are much smaller. An illuminating comparison is provided by contrasting the optimum carbon radius in [Co8C(CO)l8]2- (0.74 A) with that for Co6C(CO)fr (0.56 A) 63), which has an octahedral core. Indeed all the octahedral carbido clusters have similarly compressed interstitial cavities (Table IV) and as has been pointed out previously, this fact militates against invoking minimum steric requirements of the carbon atom to explain distortions in octahedral carbido clusters. 

Fig. 3.5. Structure of hard-core carbonate-benzenesulfonate RMs. The mineral core is mainly made up of amorphous carbonate. The carbonate colloidal core has a radius of about 3 nm and the surfactant layer thickness is about 2 nm...

This summarizes the present state of our knowledge about Triton, hi size, mass, and mean density, Triton appears to be a larger and more massive variant of Pluto, since their mean densities are both nearly 2.1 grams/ cm. A plausible model for Triton s interior is one with a rocky core of about 621 mi (1,000 km) radius surrounded by a 217 mi (350 km) thick water ice mantle, above which there is a crust of nitrogen, methane, carbon monoxide, and carbon dioxide ices which is only a few miles thick. 

To illustrate the principles of the shrinking core model, we shall consider the removal of carbon from the catalyst particle just discussed. In Figure 11-15 a core of unreacted carbon is contained between r = 0 and r = R. Carbon has been removed from the porous matrix between r = R arid r = R. Oxygen diffuses from the outer radius Ro to the radius R, where it reacts with carbon to form carbon dioxide, which then diffuses out of the porous matrix. The reaction... 

The data in Table 4.3 correspond to a radius for the octahedrally coordinated carbon atom that Ues in the range 0.59-0.69 A. We noted earlier that the radius of the core carbon in osmium, rhenium, and rhodium clusters lie in the range 0.59-0.62 A. It appears likely that the enthalpy change ZE(M-C), needed to cleave the six M-C bonds in these molecular carbonyl clusters, will lie in the same range (239-306 kcal moT i.e., 38-51 kcal mol per MC link) that we have now calculated for the similarly coordinated carbon atoms in these extended lattice binary carbides MC or M2C. 

Where n represents the number of moles remaining in the ungasified core, s is the cross-sectional area of gasifying mineral (carbon) on the solid sphere, r is the radius of the sphere, is a rate constant, t is time, and C, is the concentration of a gasification agent (such as oxygen). Assuming V is the molar volume, the number of moles, n, is defined as... 

---