Carbon Nanotube Wires Sheathed by Aramid Nanofibers

Abstract

Coaxial fibers are the key elements in many optical, electrical, and biomedical applications. Recent success in materials synthesis has provided versatile choices for the core part, but the search of high‐performance sheath materials remains much less productive. These surface coatings are however as important as the core for their role as protection layers and interaction medium with the externals, thereby critically affecting the real performance of coaxial fibers. Here it is shown that aramid nanofibers (ANFs) with exceptional environmental stability and mechanical properties can be advanced coating materials for both wet‐ and dry‐spun carbon nanotube (CNT) wires. Co‐wet‐spinning ANFs with CNT aqueous dispersion can produce coaxial fibers with a compact sheath comprised of aligned ANFs, showing much enhanced mechanical properties by transferring stress to the sheath without sacrificing the conductivity. On the other hand, an immersion‐precipitation process is used to prepare a porous sheath made from randomly distributed nanofibers on dry‐spun CNT wires, which can be combined with ionic conductive gel electrolyte as a strong packaging layer for flexible solid‐state supercapacitors. The excellent intrinsic characteristics as well as variable ways of structural organizations make ANF‐based coatings an attractive tool for the design of multifunctional high‐performance hybrid materials.

Fabrication, Applications, and Prospects of Aramid Nanofiber

“…Such an ANF layer could play the role of a coating on a polymer matrix, which could be a good material for designing multifunctional high‐performance hybrid structures because of its outstanding intrinsic characteristics and variable routes of preparation. [ 70 ]…”

“…[ 79 ] Interestingly, a coaxial ANF fiber with a core–sheath structure could be prepared by wet spinning. [ 70 ] As illustrated in Figure 12B 1 , an aqueous solution of polystyrene sulfonate‐wrapped CNT and an 8 wt% ANF/DMSO dispersion were designed as the sources for the core and sheath materials, respectively. Both the dispersions were wet spun by a bicomponent spinning technique into a coagulation bath, achieving a coaxial CNT@ANF fiber with enhanced mechanical performance.…”

“…It is noteworthy that a dense ANF sheath could be obtained during wet spinning due to the shear‐induced alignment of nanofibers and the presence of a liquid crystal phase at a high concentration of ANF. [ 70 ] In addition, as illustrated in Figure 12B 2 , a CNT wire was impregnated in a 4 wt% ANF/DMSO dispersion, and then it was immersed in water to accomplish the protonation process and then subjected to freeze drying to obtain a coaxial CNF@ANF fiber with a porous sheath.…”

“…Reproduced with permission. [ 70 ] Copyright 2017, Wiley‐VCH. B 2 ) Schematic illustration of preparation of ANF sheath on the surface of dry‐spun CNT wires.…”

“…Reproduced with permission. [ 70 ] Copyright 2017, Wiley‐VCH. C) Schematic diagram of symbiotic PAO@ANF aerogel fiber preparation by wet spinning.…”