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

Rajyashree Sundaram,Kenji Hata,Atsuko Sekiguchi,Takeo Yamada

doi:10.1038/s41598-017-09279-x

Abstract

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 2/3rd 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.

Highlights

Substituting Cu wires with a lighter material in aerospace and automobile applications is expected to immensely impact fuel savings and reduce CO2 emissions
We demonstrate the fabrication of lightweight multiwall carbon nanotube (MWCNT)-Cu wires with uniform CNT distribution in a continuous Cu matrix throughout the wire length
We report conducting MWCNT-Cu composite wires with 2/3rd the density of Cu containing nanotubes distributed uniformly throughout a continuous Cu matrix all along the wire length

Summary

Introduction

Substituting Cu wires with a lighter material in aerospace and automobile applications is expected to immensely impact fuel savings and reduce CO2 emissions. Shuai et al.[17] and Jin et al.[18] prepared CNT-Cu sheets with high internal Cu penetration by repeated Cu electrodeposition into superaligned MWCNT sheets from aqueous CuSO4/H2SO4 solutions containing glucose Their composites contain low CNT fractions of ~1-5 vol%. With 45 vol% CNTs, the density of our MWCNT-Cu wires is 2/3rd that of Cu. The composite wires exhibit promising electrical performances, including low ρRT (1/100th that of the starting MWCNT wires), lower resistance-change with increasing temperature than Cu, and high CCCs (in vacuum) exceeding that of Cu. Further, we controllably varied the Cu spatial distribution in the CNT-Cu wires and evaluated the corresponding electrical properties. Our results demonstrate that maximizing the Cu content in the bulk to achieve a continuous Cu matrix throughout is vital to overall high electrical performances

Methods

Results

Conclusion