Carbon Nanotube Mats and Fibers with Irradiation-Improved Mechanical Characteristics: A Theoretical Model

We employ a theoretical model to calculate mechanical characteristics of macroscopic mats and fibers of single-walled carbon nanotubes. We further investigate irradiation-induced covalent bonds between nanotubes and their effects on the tensile strength of nanotube mats and fibers. We show that the stiffness and strength of the mats can be increased at least by an order of magnitude, and thus small-dose irradiation with energetic particles is a promising tool for making macroscopic nanotube materials with excellent mechanical characteristics.

Figure 1

Typical structure of the nanotube mats used in simulations (a). Schematic representation of a bundle (b). The scale free area coverage is $q=57$ (see text for details). Schematic representation of bundle branching (c) and crossing (d).

Figure 2

Molecular models of nanotubes with irradiation-induced covalent bonds. The bond between two parallel nanotubes in the bundle (a), (b). The bond between two crossed nanotubes (c), (d).

Figure 3

Stiffness of nanotube mats (i.e., spring constant $E_{m}A$ where $A$ is the effective thickness of a mat) as functions of coverage $q$ compared with the semitheoretical estimate through Eq. (3). (a) $w=10\mathrm{n}\mathrm{m}$, $\rho \approx 0.8$, $E=600\mathrm{G}\mathrm{P}\mathrm{a}$ and $L=5\mu \mathrm{m}$. (b) $w=40\mathrm{n}\mathrm{m}$, $\rho \approx 0.3$, $E=600\mathrm{G}\mathrm{P}\mathrm{a}$ and $L=5\mu \mathrm{m}$. Note that the semitheoretical model cannot be expected to work well close to the percolation critical coverage $q=q_c$. Symbols are conjugate gradient results for different mats and the lines are obtained using Eq. (3).