Toward Scalable Manufacturing of Carbon Nanotube Coated Conductors

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.