Slippage-inhibiting effect of interfacial cross-linking of nanotubes by defluorination on the mechanical properties of free-standing multi-walled carbon nanotube yarns: Comparison with individual multi-walled carbon nanotubes

Abstract

Carbon nanotube yarns (CNTYs) spun only by twisting have a low mechanical strength due to the slippage of individual CNTs. This hinders the practical applications of CNTYs. Here, we studied the slippage-inhibiting effect of the interfacial cross-linking of the nanotubes by defluorination on the mechanical properties of free-standing MWCNTYs and compared with the fracture tensile strength of the individual defluorinated MWCNTs. The mechanical properties of defluorinated MWCNTYs increased with increasing annealing temperature, and MWCNTYs defluorinated at 800 °C under a pressure of 76 Pa (p-deF800-MWCNTYs) exhibited an average specific fracture strength of 0.69 N/tex and an average specific fracture stiffness of 103.2 N/tex, with high flexibility. As the fracture tensile strength of individual defluorinated MWCNTs was low, the high strength of the p-deF800-MWCNTYs was attributed to the cross-linking of the active carbon atoms in the outer nanotubes with those of the adjacent nanotubes through sp2C and sp3C bonds, which led to the transfer of load to the yarns. Thus, the results of our study highlight the importance of good balance between the defects of CNTs and cross-linking between CNTs.