Continuous electrodeposition for lightweight, highly conducting and strong carbon nanotube-copper composite fibers

Abstract

Carbon nanotube (CNT) fiber is a promising candidate for lightweight cables. The introduction of metal particles on a CNT fiber can effectively improve its electrical conductivity. However, the decrease in strength is observed in CNT-metal composite fibers. Here we demonstrate a continuous process, which combines fiber spinning, CNT anodization and metal deposition, to fabricate lightweight and high-strength CNT-Cu fibers with metal-like conductivities. The composite fiber with anodized CNTs exhibits a conductivity of 4.08 × 10(4)-1.84 × 10(5) S cm(-1) and a mass density of 1.87-3.08 g cm(-3), as the Cu thickness is changed from 1 to 3 μm. It can be 600-811 MPa in strength, as strong as the un-anodized pure CNT fiber (656 MPa). We also find that during the tensile tests there are slips between the inner CNTs and the outer Cu layer, leading to the drops in electrical conductivity. Therefore, there is an effective fiber strength before which the Cu layer is robust. Due to the improved interfacial bonding between the Cu layer and the anodized CNT surfaces, such effective strength is still high, up to 490-570 MPa.

Carbon Nanotube Fiber Pretreatments for Electrodeposition of Copper

“…e results are in line with the previously published values of CNT-Cu wires [7,9,10] e speci c conductivity reported here decreases less as the weight percentage of CNTs increases compared with thinner bers [10].…”

“…e copper deposition rate was enhanced considerably by Ni and B doping from Watts bath without the need for harsh treatments, such as oxidation, that are known to deteriorate the nanotube properties [29]. Previously, similar improvements in enhancing the copper deposition rate on CNT macrostructures have been attained by utilizing harsh oxidation as a pretreatment method [7,16]. In this case, we used a "soft" doping method, which had a positive e ect on the CNT material conductivity.…”

“…Previously, Xu et al [7] reported using anodization as a pretreatment method for producing functionalized CNTCu composites.…”

“…Low-density CNT composites with significantly increased conductivity, current-carrying capacity, and mechanical properties could revolutionize many different industry sectors with applications in electrical wiring, microelectronics, and power transfer [4][5][6]. Such composites can be formed by utilizing carbon nanotube wires, such as fibers or films, as the base material [7][8][9][10].…”

High-strength carbon nanotube fibre-like ribbon with high ductility and high electrical conductivity

“…For strength improvement, the intertube load transfer may be manipulated by already reported methods such as electron irradiation 31,32 , chemical treatment 33 and polymer impregnation [34][35][36] , forming primary bonds between CNTs, which are much stronger than Van der Waals interactions. For conductivity improvement, tube chirality should be particularly tailored 37 , and iodine doping 13,38 and metal coating 39,40 may be imposed. However, it should be noted that all these modifications may result in gain of one property but loss of another, and the theoretical properties may not be reachable because of the inevitable presence of defects within CNTs and between their surfaces.…”