Electrical performance of lightweight CNT-Cu composite wires impacted by surface and internal Cu spatial distribution.

We report ultralong conducting lightweight multiwall carbon nanotube (MWCNT)-Cu composite wires with MWCNTs uniformly distributed in a continuous Cu matrix throughout. With a high MWCNT vol% (40-45%), the MWCNT-Cu wire density was 2/3(rd) that of Cu. Our composite wires show manufacturing potential because we used industrially compatible Cu electrodeposition protocols on commercial CNT wires. Further, we systematically varied Cu spatial distribution on the composite wire surface and bulk and measured the associated electrical performance, including resistivity (ρ), temperature dependence of resistance, and stability to current (measured as current carrying capacity, CCC in vacuum). We find that a continuous Cu matrix with homogeneous MWCNT distribution, i.e., maximum internal Cu filling within MWCNT wires, is critical to high overall electrical performances. Wires with maximum internal Cu filling exhibit (i) low room temperature ρ, 1/100th of the starting MWCNT wires, (ii) suppressed resistance-rise with temperature-increase and temperature coefficient of resistance (TCR) ½ that of Cu, and (iii) vacuum-CCC 28% higher than Cu. Further, the wires showed real-world applicability and were easily soldered into practical circuits. Hence, our MWCNT-Cu wires are promising lightweight alternatives to Cu wiring for weight-reducing applications. The low TCR is specifically advantageous for stable high-temperature operation, e.g., in motor windings.