Strong Carbon Nanotube Fibers by Drawing Inspiration from Polymer Fiber Spinning

Abstract

We present a method to spin highly oriented continuous fibers of adjustable carbon nanotube (CNT) type, with mechanical properties in the high-performance range. By lowering the concentration of nanotubes in the gas phase, through either reduction of the precursor feed rate or increase in carrier gas flow rate, the density of entanglements is reduced and the CNT aerogel can thus be drawn (up to 18 draw ratio) and wound at fast rates (>50 m/min). This is achieved without affecting the synthesis process, as demonstrated by Raman spectroscopy, and implies that the parameters controlling composition in terms of CNT diameter and number of layers are decoupled from those fixing CNT orientation. Applying polymer fiber wet-spinning principles then, strong CNT fibers (1 GPa/SG) are produced under dilute conditions and high draw ratios, corresponding to highly aligned fibers (from wide- and small-angle X-ray scattering). This is demonstrated for fibers either made up of predominantly single-wall CNTs (SWCNTs) or predominantly multiwall CNTs (MWCNTs), which surprisingly have very similar tensile properties. Finally, we show that postspin densification has no substantial effect on either alignment or properties (mechanical and electrical). These results demonstrate a route to control CNT assembly and reinforce their potential as a high-performance fiber.

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

“…In comparison with carbon fibre production, which relies on the special grades of polymer precursors and requires several technological steps, including high-temperature treatment at up to 3000°C in the inert atmosphere 3,4 ; synthesis of CNT fibres by this one-step process is more favorable in terms of energy and time consumption and related costs. The required synthesis temperature (1300°C) is similar to that of the conventional carbon black, 5 which is one of the cheapest products produced in millions of tons and used in industry worldwide. In addition, the system can be potentially run using natural gas or CO 2 6 as the major carbon source, with the possibility of recycling both carrier gas and any unreacted hydrocarbon to reduce financial costs and make the production to be more environmentally friendly.…”

“…Assembling of CNT into fibrous materials has been successfully realized through a range of methods, including wet-spinning technique [1], spinning from their liquid crystalline solutions [2], spinning from dry arrays [3], or direct spinning from the gas phase during the floating catalyst CVD synthesis, as described elsewhere [4,5]. High-performance carbon nanotube fibres (CNTF) possess high thermal conductivity and outstanding electrical conductivity able to compete with metals [1,6], and thus they have been recognized as promising materials for cost-effective electronics and electrical wiring [7].…”

Toward High Performance Nanocarbon Fibers

“…42 Figure 11 depicts how lower concentrations of CNTs and higher flow rates can reduce entanglements allowing the aerogel fiber or yarn to be drawn at higher rates. 42 The fast drawing of the fiber or yarn allows the CNTs to be highly aligned with respect to the fiber axis. 42 Highly oriented CNT fibers produced using this method have a reported tensile strength of 1…”

“…42 The fast drawing of the fiber or yarn allows the CNTs to be highly aligned with respect to the fiber axis. 42 Highly oriented CNT fibers produced using this method have a reported tensile strength of 1…”

“…42 Another report indicated CNT fibers with a maximum tensile strength of 1.46 GPa when hexane was used as the hydrocarbon source. 43 Lower results were achieved when EtOH and ethylene glycol were used, demonstrating the impact the CVD synthesis factors can have on the resulting CNT fibers.…”