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Sustaining Enhanced Electrical Conductivity in KAuBr4‑Doped Carbon Nanotube Wires at High Current Densities

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journal contribution
posted on 24.10.2019, 19:42 by Karen J. Soule, Colleen C. Lawlor, Andrew R. Bucossi, Cory D. Cress, Ivan Puchades, Brian J. Landi
Densification and chemical doping with KAuBr4 are shown to improve the electrical conductivity of commercially scaled CNT wires by a factor of 6 to values greater than 1 MS/m, while increasing the failure current density by 67% to 35 ± 3 MA/m2. The electrical conductivity retention is quantified via measuring changes in the conductivity during increasing applied current densities (working conductivity) and at room temperature after current exposure (resting conductivity). CNT wires doped with KAuBr4 exhibit no change in resting conductivity after application of current densities up to 32 MA/m2, which exceeds that of the as-received material by more than 3 times. The mechanism by which KAuBr4 doping improves the electrical stability of CNT conductors at higher current densities was probed via analysis of CNT wires treated with various thermal oxidation and doping procedures. Energy-dispersive X-ray spectroscopy was used to determine the elemental composition of KAuBr4-doped CNT wires after thermal oxidation to 400 °C, demonstrating the presence of residual chemical dopants near the onset temperature of CNT conductor failure. Therefore, enhanced KAuBr4-doped and densified CNT wire performance is attributed to the inherent thermal stability of KAuBr4 and its decomposition cascade into other chemically active dopants. Overall, the thermal stability of the chemical dopant is a critical factor for high current CNT conductor applications.