Electrical and mechanical properties of high electrical conductivity CNT/Cu-yarns with Br doping and Cu encapsulation

Abstract Carbon nanotubes (CNTs) are an ideal starting material for the development of strong, light‐weight conductors. In this work, we pursued the development of high specific electrical conductivity and high specific strength CNT/metal composites. We started with CNT yarns which had an initial electrical conductivity, σe, of 3.14 MS m‐1 and a density of 1.32 g cm‐3. We brominated the yarns, demonstrating increases in σe, with our best samples reaching σe = 7.00 MS m‐1. To increase the stability of the bromination, we electroplated a Cu layer onto the Br‐doped yarn which led to a stabilization of the conductivity improvement. This was quantified by monitoring periodically the σe of a Br‐doped and metallized CNT yarn over a period of 69 days, during which time the sample was otherwise exposed to ambient conditions. Analysis gives a value 6.15 MS m‐1 for the brominated yarn after metallization which is excellent for CNT yarns. Tensile tests on these Cu/CNT composites showed tensile strengths reaching 700 MPa, Young's modulus values of 22.8 GPa, and specific tensile strength values of 146 kN*m kg‐1 (this latter is 6X that of Cu). Our best CNT‐Cu composites show specific conductivity values comparable with that of Cu but with much higher specific tensile strengths.