Insights into the Nucleation and Structure of Lignin-Based Carbon Nanotubes Synthesized Using Iron via Floating Catalyst Chemical Vapor Deposition

Lignin is an abundant biomass resource that can be converted to carbon nanotubes (CNTs) via floating catalyst chemical vapor deposition (FCCVD). This study investigates how Fe catalyst properties impact the synthesis, structure, and properties of lignin-derived CNTs. During CNTs synthesis via FCCVD, increasing the ferrocene concentration yields more CNT products, but the catalyst efficiency declines, as evidenced by the appearance of shorter CNTs and more Fe residue in the product. Transmission electron microscopy reveals that the size and morphology of Fe nanoparticles strongly influence CNT structure, defects, and graphene layer alignment in the nanotube sidewalls during growth. High-temperature graphitization effectively removes residual catalysts from the CNTs and improves their crystallinity and conductivity. During graphitization from 1600 to 2800 °C, the graphene interlayer spacing decreases, while the Raman IG/ID ratio increases from 3.16 to 8.08, electrical conductivity increases from 4.05 × 104 to 5.92 × 104 S m–1, and thermal conductivity can be enhanced from 31.20 to 50.49 W m–1 K–1. Correlating catalyst characteristics with CNT structure evolution provides insights into the controlled synthesis of tailored biomass-derived CNTs with specific structures and properties

Continuous Preparation of a Flexible Carbon Nanotube Film from Lignin as a Sulfur Host Material for Lithium–Sulfur Batteries

Lignin is an abundant natural polymer and a green biomass precursor containing over 60% carbon. However, high-value and sustainable material production from lignin remains underutilized. Here, a flexible carbon nanotube (CNT) film is continuously fabricated via floating catalyst chemical vapor deposition (FCCVD) using lignin as the carbon source. The as-prepared CNT film exhibits high conductivity (4.19 × 104 S m–1) and can directly serve as an electrode material without further processing. Moreover, the adaptable CNT film displays strong mechanical properties (54.53 MPa) and fatigue resistance, making it an excellent flexible host for lithium–sulfur (Li–S) batteries. The intertwined CNTs provide efficient electron transport, accelerating the reaction kinetics. Consequently, the Li–S cells with CNT film-based cathodes maintained capacities of 706.1 and 435.3 mA h g–1 after 200 cycles at 0.5 and 1.0 C, respectively. Foldable Li–S pouch cells with CNT film-based cathodes also powered LED lights. This green, low-cost, straightforward fabrication of lignin-based CNT films as sulfur hosts provides an attractive alternative for valorizing abundant lignin into high-value materials at scale

Electromechanical Properties and Resistance Signal Fatigue of Piezoresistive Fiber-Based Strain Gauges

Piezoresistive nanocomposite fibers are essential elements for smart wearables and have recently become a research hotspot because of their high sensitivities at large deformations in the plastic regime. However, little attention has been paid to the electromechanical properties of such fibers at low strains where the resistance–strain (R–ε) relationship is reliably linear. In addition, prediction of the resistance signal stability for these materials during cyclic loading remains unreported. Here, we studied these two aspects using wet-spun piezoresistive nanocomposite fibers from polyether block amide (PEBA) composed of a hybrid conductive filler network of carbon black (CB) and carbon nanotubes (CNTs) in which the CB loading in the PEBA matrix was varied at a constant volume fraction of CNTs. We found the R–ε linear relationship (working factor, W) to increase with CB filler loading from 0.01 to 0.058. In addition, the gauge factors of these fibers varied inversely with W from 16.89 to 3.81. Using fatigue theory, we predicted the endurance limit of PEBA/CB-CNT fibers in the elastic regime to be ∼34.9 cycles. Although our fibers were extremely deformable, up to 500% strain, as is the case for most piezoresistive nanocomposite fibers, this work reveals the working range to be actually very small, comparable to rigid conventional strain gauges. We believe with PEBA/CB-CNT fibers’ robust mechanical properties and the ease with which the electromechanical signal can be quantified with the fatigue model, they would be ideal materials to be integrated into textiles to perform as tough, finely tuned strain sensors for a range of rigorous bodily monitoring such as low-strain impacts and joint movements