Studying the effects of acid treatments on the electrical behaviors of CNT wires

Abstract

This thesis presents the results of chemically treated carbon nanotube (CNT) yarn in a non-stretched or non-compressed condition. Chemical treatment has been proven to increase the tensile strength and conductivity of CNT wire while under tensile load. In this study, chemical treatment was administered to the CNT wire by emersion without stretching it and simultaneously measuring conductivity. Chemical treatment significantly changed the physical dimensions of the CNT wire, including an increase in diameter and a decrease in length. Physical dimensional changes were not measured, but they did result in changes to conductivity, which were recorded as they occurred. It is obvious that after a period of time, the acid treatment caused separation of individual CNT fibers, which resulted in an overall decrease in conductivity. The acid bath created covalent bonds between the carbon nanotubes and oxides and hydroxyls, while ionic bonds, which presented as increased conductivity, were established. In most test cases, the original conductivity was regained, but then appeared as if the CNT wire lost conductivity to the point of an open circuit. While this study seemingly yielded inconsistent conductivity results between different plies tested, it could be assumed that the inconsistent conductivity is the result of varying tension in the test specimen. One conclusion of this study is that in order to make a direct conductivity comparison between different sized CNT yarns there needs to be a definable consistent tension applied to the CNT wire being tested. Another conclusion is that once a higher-ply CNT wire has begun to un-wind, hand spinning the wire will not recover the conductivity. The final conclusion of this study is that the current spinning technology coupled with acid treating will not permit CNT wire to be used as a direct replacement for copper wire.