ABSTRACT
Carbon nanotubes (CNTs) are one-dimensional carbon-based nanomaterials discovered by Iijima (1991) that possess very large aspect ratio (>1000), high ‰exibility, low density (~1.8 g/cm3), and exceptional mechanical, thermal, and electrical properties (Popov 2004; Thostenson et al. 2001), which make them ideal candidates for the fabrication of multifunctional nanocomposites. Their extraordinary high Young’s modulus (up to 1.2 TPa) and tensile strength (ca. 50-200 GPa) make them one of the strongest and stiffest materials on earth and, in principal, ideal candidates for polymer reinforcement. There are two main types of CNTs: those consisting of a single graphite sheet wrapped into a cylindrical tube with a diameter in the range of 0.7-3 nm, the single-walled carbon nanotubes (SWCNTs), and those composed of more than two coaxial cylinders, each rolled out of single sheets, with diameters between 2 and 40 nm, the multiwalled carbon nanotubes (MWCNTs). Both types of CNTs can be synthesized using different routes (Dervishi et al. 2009), including high-temperature evaporation using arc-discharge or laser ablation and gas-phase catalytic growth from carbon monoxide or chemical vapour deposition (CVD) from hydrocarbons. CVD materials generally contain residual catalyst particles, while the main contaminants in the products of hightemperature reactions are carbonaceous impurities. The laser process generates CNTs of the highest quality (few defects, high crystallinity, extremely high aspect ratio) compared to other synthesis methods (Díez-Pascual et al. 2009), while nanotubes produced by the CVD technique present a larger number of defects as a result of the lower growth temperature. The purity, quality, aspect ratio, and the nature of impurities, hence the source of the CNTs, can have a strong in‰uence on the nal properties of CNT-reinforced composites.
