Graphene internal

Fig. 24. Adsorption of lithium on the internal surfaces of micropores formed by single, bi, and trilayers of graphene sheets in hard carbon.

The detailed analysis of the way in which the overall and internal structure of PCNTs apparently arise is discussed elsewhere[20j. Here, we draw attention to some particularly interesting and unusual structures which occur in the body of the nanotubes. An expansion of the section of the central core which lies ca. 5 below the tip of the nanotube in Fig. 1 is shown in Fig. 2. Loop structures occur at points a-d and a -d in the walls in directly opposing pairs. This parallel behaviour must, on the basis of statistical arguments, be related and we interpret the patterns as evidence for a hemi-toroidal connection between the inner and outer adjacent concentric graphene tubes (i.e., turnovers similar to a rolled-over sock). That the loops, seen in the HRTEM, are evidence for very narrow single-walled closed-ended tubes trapped within the walls can be discounted, also on statistical grounds. 

Fig. 19.1 Creation of three internal edge sites, or a (mono)vacancy, by removal of one basal-plane carbon atom in graphene.

Fig. 19.7 Illustration of the fate of an internal edge (vacancy) (a) schematic representation of graphene cluster C65H20 (b) optimized geometry of C65H20 singlet when C38-C39 bond is formed (c) optimized geometry of C65H20 singlet when C25-C38 bond is formed.

Hybrid models are usuaDy used to study defective surfaces. In these models the internal surfaces of a slit pore, defined by a stack of mean-field layers, are coated by one or more graphene layers with explicit atomic structure. To generate defects one or more carbon atoms are removed from one or more explicit graphene layers [19, 20]. 

Recently, considerable advances have been made in the production of a different class of nanoscopic carbon structures, namely, carbon nanotubes, which stimulated fundamental research exploring the structure-property relationship of these materials [227]. In their simplest form carbon nanotubes are composed of only a single cylindrieal graphene shell with a central hollow internal cavity. These structurally imiform cylinders are invariably sealed at both ends by bended carbon caps, which contain both five- and six-membered rings similar to the struetures of fullerenes. Based on their similarity with highly graphitized carbonaceous materials, nanotubes have low ehemieal reaetivity. Therefore, the chemistry of earbon nanotubes is mainly focused on opening reaetions at its... 

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