RESUMO
Spinning fibers from carbon nanotube (CNT)/superacid dispersions has emerged as a promising strategy for industrial-scale production of high-performance CNT fibers (CNTFs). The oxygen content and types of functional groups on CNT surfaces significantly influence dispersion, assembly processes, and fiber properties. In this study, Tuball-SWCNTs were purified and oxidized at varying levels. The dispersion behavior of CNTs with different oxidation levels in chlorosulfonic acid was systematically observed, and the mechanical properties of fibers spun from these dispersions were compared. By adjusting the dispersion concentration, highly oriented CNTFs were produced with a specific strength of 1.03 N/tex, a tensile strength of 1.59 GPa, and an electrical conductivity of 3.58 MS/m. Further investigations indicated that oxygen-containing functional groups decrease the coagulation rate, increasing the maximum draw ratio during spinning and improving CNT alignment in the fibers. Molecular dynamics simulations demonstrated that these functional groups (-OH, -COOH) enhance load transfer between CNTs through hydrogen bonding. This specific strength is the highest achieved using Tuball-SWCNTs for superacid-spun fibers, surpassing previous works due to the oxidation-controlled coagulation rate, enhanced fiber orientation, and improved load transfer via hydrogen bonding. This study provides insights for designing and optimizing high-performance CNTFs.
RESUMO
Surface engineering is effective for developing materials with novel properties, multifunctionality, and smart features that can enable their use in emerging applications. However, surface engineering of carbon nanotubes (CNTs) to add color properties and functionalities has not been well established. Herein, a new surface engineering strategy is developed to achieve rainbow-colored CNTs with high chroma, high brightness, and strong color travel for visual hydrogen sensing. This approach involved constructing a bilayer structure of W and WO3 on CNTs (CNT/W/WO3 ) and a trilayer structure of W, WO3 , and Pd on CNTs (CNT/W/WO3 /Pd) with tunable thicknesses. The resulting CNT/W/WO3 composite film exhibits a wide range of visible colors, including yellow, orange, magenta, violet, blue, cyan, and green, owing to strong thin-film interference. This coloring method outperforms other structural coloring methods in both brightness and chroma. The smart CNT/W/WO3 /Pd films with porous characteristics quickly and precisely detect the hydrogen leakage site. Furthermore, the smart CNT/W/WO3 /Pd films allow a concentration as low as 0.6% H2 /air to be detected by the naked eye in 58 s, offering a very practical and safe approach for the detection and localization of leaks in onboard hydrogen tanks.
RESUMO
Various preforms of carbon nanotubes (CNTs), such as fibers, yarns, or buckypapers (BP), have been developed over the last few years in order to fabricate advanced nanocomposites containing a high volume fraction of the reinforcing phase. However, a homogeneous dispersion and an even isolation of CNTs during the fabrication process of many preforms such as BP is often challenging, while the poor interaction between CNTs and the matrix also limits the final performance of the nanocomposites. Herein, a new route to overcome these two challenges simultaneously has been demonstrated based on an active dispersant (noted as Py-PEI) developed through the quaternization reaction of pyrene derivatives (Py-Br) and polyethylenimine (PEI). The existence of pyrene groups leads to the formation of π-π stacking with CNTs, successfully hindering the re-aggregation of dispersed CNTs. Meanwhile, the amine groups of Py-PEI can establish covalent bonds with epoxy, leading to an enhanced load transfer efficiency between CNTs and epoxy in the composites. Systematic characterization of both fabricated BP and BP-reinforced nanocomposites have been performed, with significantly enhanced CNT dispersion stability in water together with improved mechanical performance of the as-obtained BP/epoxy nanocomposites. This study provides a new strategy in fabricating high performance nanocomposites with the ease of nanofiller dispersion and enhanced reinforcing efficiency.
