Toward Scalable Manufacturing of Carbon Nanotube Coated Conductors

Abstract

Here, we report our understanding of carbon nanotube (CNT) solution coating and wire drawing processes toward fabricating high conductivity coated conductors from millimeters long CNTs. The approach studied here enables the formation of dense and aligned coatings of CNTs on various substrate wires. To achieve the coating, millimeters long and vertically aligned multiwalled carbon nanotube arrays were first dispersed in diluted sulfuric acid via mild shear mixing, forming mesoscale CNT fibrils. The resulting fibrils were solution coated onto a substrate wire (i.e., nylon or copper here) and the coating was subsequently wire drawn. During each drawing step, the CNT coated wire was passed through a die to decrease the coating thickness and to coax the CNTs to pack. Effects of various key processing parameters on the structure and resulting electrical conductivity of the coated wires were investigated. Especially, it was shown that the coating quality was strongly controlled by the surface characteristics of the wire former, where both a rough and hydrophobic surface were required. Microscopy and Raman spectroscopy were utilized to probe the structure of CNTs in the coatings. The continuous coating process discussed here can be used to manufacture high conductivity coatings for applications such as electrical wiring, electromagnetic and radio frequency shielding, electrostatic dissipation, and radar absorption. This approach holds the promise for the scalable manufacturing of lightweight CNT-based conductors.

Advanced Electrical Conductors: An Overview and Prospects of Metal Nanocomposite and Nanocarbon Based Conductors

“…Novel approaches for fabricating CNT conductor wires have been also investigated. [29,30] In general, electrical conductivity of CNT fibers can be improved by up to ten times via acid, [31] iodine, [32] or metal nanoparticle [24] doping. Doped nanocarbon fibers contain only a few weight percent of a metal or metal halide, [18] in contrast to metal-carbon nanocomposites that are largely metal-based.…”

“…A plethora of work has been published on mechanical properties of nanocarbon-metal composites; however, their electrical conductivity has been less explored, possibly due to the degradation of the metal's conductivity upon addition of nanocarbons via conventional processing methods. Analysis of the number of patents since 2012 shows an overall growth trend on the number of published patents, on nanocarbon-metal composites mentioning electrical conductivity as a characteristic: 30 There will be more government initiatives on green energy in the coming years, especially with the increasing concerns with global warming. The need to eliminate and reduce the carbon footprint and machinery run on gas/diesel will force the transportation industry toward electromobility in sea, air, and land.…”