Enhancement of the Mechanical Properties of Directly Spun CNT Fibers by Chemical Treatment

Abstract

Translating the remarkable mechanical properties of individual carbon nanotubes to macroscopic assemblies presents a unique challenge in maximizing the potential of these remarkable entities for new materials. Infinitely long individual nanotubes would represent the ideal molecular building blocks; however, in the case of length-limited nanotubes, typically in the range of micro- and millimeters, an alternative strategy could be based on the improvement of the mechanical coherency between bundles assembling the macroscopic materials, like fibers or films. Here, we present a method to enhance the mechanical performance of fibers continuously spun from a CVD reactor, by a postproduction processing methodology utilizing a chemical agent aided by UV irradiation. The treatment results in an increase of 100% in specific strength and 300% in toughness of the fibers with strength values rocketing to as high as 3.5 GPa SG(-1). An attempt has been made to explore the nature of the chemical modifications introduced in the fiber and the consequential effects on its properties.

High-strength carbon nanotube fibre-like ribbon with high ductility and high electrical conductivity

“…To narrow the gap further, the structural parameters such as length, diameter and alignment of CNTs should be better controlled. For strength improvement, the intertube load transfer may be manipulated by already reported methods such as electron irradiation 31,32 , chemical treatment 33 and polymer impregnation [34][35][36] , forming primary bonds between CNTs, which are much stronger than Van der Waals interactions. For conductivity improvement, tube chirality should be particularly tailored 37 , and iodine doping 13,38 and metal coating 39,40 may be imposed.…”

Aligned carbon nanotube–epoxy composites: the effect of nanotube organization on strength, stiffness, and toughness

“…However, at the same time, an approach to enhance their packing density may have sense, as it was shown above that even the simple densification by acetone spraying may increase the tensile strength and stiffness of the as-spun materials. Some reported treatments, such as UV [39] or electron-beam irradiation [40], twisting, and infiltration with polymeric compounds [41][42][43][44] appear to affect lateral interactions between nanotube bundles, as well as molecular level couplings between nanotubes and polymer chains [43], thus amplifying the mechanical performance of CNT fibres or yarns [44] (supplementary materials, S10). Remembering the hierarchical structure of the CNT fibres, upon polymer infiltration, a fibre itself can be regarded as a nanostructural composite [13,43] with 50-70 % of a fibre occluded with a polymer depending on the fibre's internal porosity.…”

Mechanical properties of carbon nanotube fibres: St Venant’s principle at the limit and the role of imperfections

“…We suggest that this material is effective in mitigating the deleterious effect of the longitudinal crack-like defects. We have previously observed [31] that the back diffusion of a monomer into the fibre, followed by its UV initiated polymerization could double the observed strength. There have also been reports of carbonaceous deposit seen on the bundles in direct spun fibres, which have been associated with an influence on mechanical properties.…”