A comparison of the mechanical properties of fibers spun from different carbon nanotubes

Spinnable carbon nanotube (CNT) arrays with different CNT structures have been synthesized using different growth methods and carbon sources, and long and stable fibers have been produced. Parameters of the nanotubes such as tube diameter, wall thickness, tube length and level of defects were found to play a more important role in the mechanical properties of the fibers than did the initial tube arrangement. To improve the fiber strength, as well as the modulus, the tubes must be long and have a small diameter and thin walls. The strongest fiber from double- and triple-walled CNTs is 1.23 GPa in strength, and 32% and 221% higher than those from CNTs with ∼6 and ∼15 walls (932 and 383 MPa), respectively. The fiber strength can be improved by 25%, up to 1.54 GPa, after poly(vinyl alcohol) infiltration with volume fraction of ∼20%. Our study also shows that C2H4 is superior to C2H2 as the carbon source for the growth of mainly double- and triple-walled CNTs, and therefore the spinning of high-strength fibers.