Exploiting Low Dimensional Properties of Carbon Nanotubes in Macroscopic Yarns for Charge Transfer and Storage(NANOYARN)

This final report covers work performed between August 2018 and August 2022 for the project 'Exploiting low-dimensional properties of carbon nanotubes in macroscopic yarns for charge transfer and storage', funded by the Air Force Office of Scientific Research (AFOSR). Overall, the project has led to a new family of continuous intercalation compounds with unprecedented long-range order, a combination of bulk mechanical and electrical properties beyond those of traditional high-performance materials, and the prospect of realising new physical properties in macroscopic fibres of metamaterials beyond the carbon nanotube intercalation compounds studied in NANOYARN. Through study of different carbon nanotube fibre model systems we were able to clarify the role of the structure of constituent CNTs and their macromolecular organisation in the formation of intercalation compounds with acceptor materials (Fe3Cl and Br). A revised method is proposed to determine charge transfer between host and intercalate, and estimate its spatial distribution in the CNT layers based on Raman spectroscopy using multiple laser lines. The project also studied the relation between bulk tensile properties and electrical conductivity (including at cryogenic temperatures), and the structure of the intercalation compound in terms of inter-tube separation and the supramolecular arrangement of the intercalate. Provided the intercalate preserves the structure of constituent bundles, tensile properties remain largely unaltered, which fundamentally contrast with conventional layered intercalation graphite compounds. Intercalate charged species (e.g. tribromide ion) reduce resistance for transverse electron transfer between adjacent CNTs, increasing overall conductivity to the level approaching Cu. Details of the results of the project are included mainly in five scientific publications and a PhD thesis.