Multi-property enhancement of aligned carbon nanotube thin films from floating catalyst method

Highlights: • Strong and highly conductive carbon nanotube thin films are successfully fabricated by the floating catalyst method • The combined mechanical and chemical treatments significantly enhance the multi-properties of the carbon nanotubes films • The mechanical condensation on the carbon nanotube films eliminates the intertube spacing and reduces the nanotube waviness • The purification and densification effects of the acid treatment make the films more compacted and less defective The carbon nanotube (CNT) thin film synthesized by the floating catalyst method has attracted increasing attention because of the easy fabrication process and promising mass production at low cost. However, the limited morphology-controlled structure and the loose CNT arrangement make CNT films show relatively low mechanical and electrical properties. In this work, highly dense CNT films with controllable density have been successfully fabricated by a fast two-step post treatment technique combining mechanical condensation and acid treatment. Multiple fracture mechanisms have been identified and analyzed to explain the mechanical performance of these CNT films, including the load transfer efficiency between CNTs, alignment and waviness of CNT films, as well as the effects of CNT qualities. Benefited from the stronger intertube interaction and better CNT quality, the combined post treatment method is found to have dramatically enhanced the mechanical and electrical properties of the CNT films, with tensile strength up to 243 ± 16 MPa (by 101%), modulus up to 2.5 ± 0.1 GPa (by 32%) and electrical conductivity up to 4990 ± 636 S/cm (by 254%) compared to the as-prepared ones. This work proposes a route to fabricate high-quality CNT films on a large scale as promising multifunctional engineering materials.