Surface structures, carbon/graphite

Fig. 3.1 A schematic representation of the structure of a bulk hexagonal graphite crystal showing the bulk unit cell. Side insets. Top view of the basal plane of graphite and a schematic representation of the surface structure (carbon atoms) of graphite, where every other atom is enhanced (right-side inset) and viewed under ideal conditions, and where every single atom is seen (left-side inset). Figure reproduced from Ref. [3]...

Graphite was tised as substrate for the deposition of carbon vapor. Prior to the tube and cone studies, this substrate was studied by us carefully by STM because it may exhibit anomalotis behavior w ith unusual periodic surface structures[9,10]. In particular, the cluster-substrate interaction w as investigated IJ. At low submonolayer coverages, small clusters and islands are observed. These tend to have linear struc-tures[12j. Much higher coverages are required for the synthesis of nanotubes and nanocones. In addition, the carbon vapor has to be very hot, typically >3000°C. We note that the production of nanotubes by arc discharge occurs also at an intense heat (of the plasma in the arc) of >3000°C. 

In Fig. 4 we show an atomic resolution image of a carbon tube. The structure imaged at the upper right corner of the picture comes from another tube. Both of them were —1000 A long. A perfect honeycomb surface structure is observed. By taking into account the curvature of the tube surface and the STM imaging profile, we find the same lattice parameter as that of. graphite (1.42 A). This directly proves that the tubu-... 

The surface structure has a strong influence on the corrosion rate of carbon in both acid and alkaline electrolytes. Studies by Kinoshita [33] clearly showed that the specific corrosion rate mAcm"2 of carbon black in 96 wt% H3P04 at 160 °C was affected by heat treatment. A similar trend in the corrosion rate in alkaline electrolyte was observed by Ross [30c], as shown in Fig. 4. It is evident that the corrosion rates of the nongraphitized carbons are higher than those of the corresponding graphitized carbons. Their study further indicated that some types of carbon blacks (e.g., semi... 

The effect of oxidation pretreatment and oxidative reaction on the graphitic structure of all CNF or CNF based catalysts has been studied by XRD and HRTEM. From the diffraction patterns as shown in Fig. 2(a), it can be observed the subsequent treatment do not affect the integrity of graphite-like structure. TEM examination on the tested K(0.5)-Fe(5)/CNF catalysts as presented in Fig.2(b), also indicates that the graphitic structure of CNF is still intact. The XRD and TEM results are in agreement with TGA profiles of fi-esh and tested catalyst there is no obviously different stability in the carbon dioxide atmosphere (profiles are not shown). Moreover, TEM image as shown in Fig. 2(b) indicates that the iron oxide particle deposited on the surface of carbon nanofibcr are mostly less than less than 10 nm. 

It is known that some spinel-structured 3d-metal oxides are good catalysts for many processes involving electron transfer [12]. However, their low conductivity does not allow for the direct use in the electrode of the battery, and grafting them onto the carbon matrix is also very difficult technical problem. It was found recently that this problem could be solved indirectly, creating the spinel catalytic centers on the surface of carbon by means of adsorption of some 3d-metal complexes on the graphite surface followed by subsequent pyrolysis at certain temperatures [13,14],... 

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