Strong carbon-nanotube fibers spun from long carbon-nanotube arrays.

The superior mechanical properties of carbon nanotubes (CNTs) mean they have been regarded as a new material with the potential to revolutionize and enable many advanced technologies. CNTs have extremely high tensile strength ( 150 GPa), high modulus ( 1 TPa), large aspect ratio, low density, good chemical and environmental stability, and high thermal and electrical conductivity. These superior and unique properties make CNTs very attractive for many structural applications such as aerospace structures, body armors, and sporting goods. Early studies of CNT-reinforced nanocomposites showed that CNTs were effective fillers to enhance the mechanical properties of polymer matrices, but the reinforcement was limited by the quality of dispersion, CNT alignment, and load-transfer efficiency between the CNT and the matrix. The full reinforcement potential of CNTs has not yet been utilized in CNT composites. It has been a challenge to make macroscale CNT structures and to fully utilize the outstanding mechanical properties of CNTs. The first macroscale CNT structure was in the form of a film called buckypaper, which displayed relatively high electrical and thermal conductivity, but low mechanical properties. For the purpose of obtaining superior mechanical performance, researchers have recently focused on CNT fibers. The first CNT fiber was successfully prepared through spinning a CNT homogeneous dispersion into a polyvinyl alcohol (PVA) coagulation bath. This approach was modified by Baughman s group to make single-walled (SW) CNT composite fibers with very high strength. 8] The major issues with this approach include a relatively high fraction of remaining polymer volume and short individual CNTs, which limits the fiber s strength, electrical and thermal conductivity. Recently, new approaches have been reported in which pure CNT fibers were spun without a matrix. For example, pure CNT fibers were spun from a CNT-fuming sulfuric acid solution. A continuous multi-walled (MW) CNT yarn was pulled from a high-quality array without twisting. SWCNT fibers were spun from an aerogel in the chemical vapor deposition synthesis zone, and MWCNT fibers were spun from CNT arrays. 15] These CNT fibers usually have a strength of 1.5 GPa and a Young s modulus of 30 GPa. Here, we report the spinning of CNT fibers from relatively long CNT arrays (0.65 mm). The influence of post-spin twisting on the mechanical performance of these fibers is also discussed. Figure 1a shows a scanning electron microscopy (SEM) image of the 0.65-mm CNT array, which is synthesized by