6.1 Introduction

The carbon nanotube which is formed by rolling the graphite sheet has a seamless tube structure.1 Figure 6.1 is the structure model, in which a ₁ and a ₂ are the unit vectors of the two-dimensional lattice of a nanolayer of graphite, and O is the origin. The OAB'B rectangle on the graphite sheet can be rolled up through the overlapping of O with A and B with B' to form the carbon nanotube. Two ends of the carbon nanotube are often closed by half a fullerene sphere. The axis of this carbon nanotube is parallel to OB, and the circumference length is OA. This carbon nanotube can be represented by a vector C _h (the connective line of O and A).

(6.1)

Figure 6.1: Schematic representation of a unit cell OAB'B, which can form the CNT on a nanolayer of graphite.

Here, both m and n are integers, and they can be used to characterize the structure of carbon nanotubes. The diameter d ₁ of carbon nanotubes and the chiral angle ? which is the angle formed from C _h and a ₁ are also often used to characterize the structure of carbon nanotubes. The parameters, including C _h, m, n, ? and d _l, can be related by the following expressions:

(6.2)

(6.3)

where, a _c-c is the neighboring carbon atom distance on the graphite sheet.

The carbon nanotubes include single-walled...