The synergetic relationship between the length and orientation of carbon nanotubes in direct spinning of high-strength carbon nanotube fibers

Floating catalytic chemical vapor deposition (FCCVD) is an attractive method for synthesizing carbon nanotube (CNT) fibers of high strength, toughness and electrical conductivity. During the process of CNT fibers synthesis, the assembly structure, such as the CNT orientation, CNT length, and the inter-tube particle impurity inside the CNT fibers, are key factors to determine the mechanical properties of CNT fibers. However, the regulation mechanism of the assembly structure during the process of CNT fiber synthesis is still unclear. Herein, in order to obtain high-strength CNT fibers, we demonstrated the synergistic relationship between the orientation and length of CNT inside the CNT fibers during the FCCVD growth process by adjusting the winding rate (5–30 m/min) and the length of the high-temperature reaction zone (660–1060 mm). It also revealed that the particle impurities inside the fibers could greatly reduce mechanical strength of CNT fibers. By optimizing the assembly structure of CNT fibers, the stable and continuous synthesis was realized, with the specific tensile strength of 3.1 N/tex (~ 3.5 GPa) without any post-treatment process.