Neutron scattering and flow processing of carbon nanotube solutions for high performance transparent electrodes and data cables
Doctor of Philosophy
Since their discovery, carbon nanotubes (CNTs) have received increasing attention due to their outstanding mechanical, thermal, and electrical properties. In particular, research efforts have focused on transferring the properties of single CNT molecules to macroscopic objects that exhibit similar features through controlled processes. The most industrially scalable way to process CNTs is by dispersing/dissolving them into a liquid phase. Chlorosulfonic acid (CSA) has been shown to be a true solvent for CNTs and it is able to spontaneously dissolve CNTs even at high concentrations (few % by mass), allowing the fluid phase processing of CNTs for the production of fibers and films. Despite many years of research that proved the superior qualities of CSA among other solvents for CNT fluid processing, much remains unknown on the local assembly of CNTs in CSA. In this thesis, we show how small-angle neutron scattering (SANS), combined with supporting polarized optical microscopy and cryogenic transmission electron microscopy, can be used to identify the local structure of CNT-CSA solutions. At very low concentrations, the SANS data show rod-like scattering patterns and confirm the efficacy of CSA as a super solvent for CNTs, whereas at high concentrations, neutron scattering allows for the determination of the local spacing of CNTs in the liquid crystalline phase. The use of CSA to dissolve CNTs opens a new route for the fabrication of CNT coatings. In this thesis we show how thin conductive CNT films from CSA solutions can be produced by scalable dip coating. This process is inherently scalable and no damage to the CNTs is induced, therefore, it is able to produce CNT films with excellent electrical properties, among the best in the literature. Dip coating of CNT-CSA solution is also a viable technique to produce the outer conductor of coaxial data cables by directly coating a solution of CNTs in CSA onto the cable inner dielectric. The high conductivity of the CNT coatings makes CNT coaxial cables an attractive alternative to commercial cables with a metal outer conductor, providing comparable cable attenuation, shielding effectiveness, and mechanical durability with a 97 % lower component mass.
carbon nanotube; solutions