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

• Published in: Nano select Vol. 3; no. 1; pp. 129 - 139
• Main Authors: Xue, Shengchen, Kovacs, Chris, Sumption, Michael, Collings, Edward, Thong, C. J., Philips, John, Tomsic, Michael, Mao, Yu
• Format: Journal Article
• Language: English
• Published: Weinheim John Wiley & Sons, Inc 01-01-2022; Wiley-VCH
• Subjects: Aircraft; Bromination; carbon nanotube; Carbon nanotubes; composite conductor; Composite materials; dopants stabilization; Electrical resistivity; Electrons; high specific conductivity; high specific strength; Manufacturers; Measurement techniques; Mechanical properties; Metallizing; Modulus of elasticity; Temperature; Tensile strength; Tensile tests; Weight reduction; Wire; Yarn; Yarns
• ISSN: 2688-4011; 2688-4011
• DOI: 10.1002/nano.202000279

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.
Br2 treatment doubled the conductivity of CNT yarn (7 MS/m), and CU‐plating stabilized bromination effect at room temperature. Also Cu‐plating provided better conductivity raging from 20–40 MS/m. Bromination did not affect the mechanical property of the yarn. Composite of Cu‐CNT showed wide range of UTS ranging from 400 MPa to 700 Mpa and Yong's modulus from 11 GPa to 22 GPa. In conclusing, the Cu‐CNT composites have conductivity that is comparable with copper and much higher UTS.