Achieving Both Ultrahigh Electrical Conductivity and Mechanical Modulus of Carbon Films: Templating‐Coalescing Behavior of Single‐Walled Carbon Nanotube in Polyacrylonitrile

Abstract Promoting the feasibility of carbon films as electrode applications requires sufficient performances in view of both electrical and mechanical properties. Herein, carbon films with ultrahigh electrical conductivity and mechanical modulus are prepared by high temperature carbonization of polyacrylonitrile (PAN)/single‐walled carbon nanotube (SWNT) nanocomposites. Achieving both performances is ascribed to remarkable graphitic crystallinity, resulting from the sequential templating–coalescing behavior of concentrated SWNT bundles (B‐CNTs). While well‐dispersed SWNTs (WD‐CNTs) facilitate radial templating according to their tubular geometry, flattened B‐CNTs sandwiched between carbonized PAN matrices induce vertical templating, where the former and latter produce concentric and planar crystallizations of the graphitic structure, respectively. After carbonization at 2500 °C with the remaining WD‐CNTs as microstructural defects, the flattened B‐CNTs coalesce into graphitic crystals by zipping the surrounding matrix, resulting in high crystallinity with the crystal thicknesses of 27.4 and 39.4 nm for the (002) and (10) planes, respectively. For comparison, the graphene oxide (GO) containing carbon films produce a less‐ordered graphitic phase owing to irregular templating, despite the geometrical consistency. Consequently, PAN/B‐CNT carbon films exhibit exceptional electrical conductivity (40.7 × 10⁴ S m⁻¹) and mechanical modulus (38.2 ± 6.4 GPa). Thus, controlling the templating−coalescing behavior of SWNTs is the key for improving final performances of carbon films.