The chemical vapour deposition (CVD) method for growing carbon nanotubes (CNTs) is now well studied and reaching industrial-scale commercialisation. Variations of this process can not only produce CNTs in different external morphologies, such as powders, random forests and aligned structures, but also with a fair degree of diameter and chirality control. However, in its original form using a fixed substrate as catalyst template, it is inherently slow; the nanotubes produced are limited by low aspect ratio, larger diameters and often need post-processing steps. To answer this limitation, some 10 years ago, a one-step continuous process for producing CNT yarns was pioneered and developed in Cambridge. This process, often referred to as the Cambridge direct spinning process essentially produces CNTs from an elastic ‘smoke’ that can be directly wound up as films or condensed into microfibres. The as-produced microfibers produced exhibit excellent specific electrical conductivity (~ 950 S m² kg⁻¹) with a slight dependence on carbon precursor used, can carry more current per weight than copper (~ 600 A m g⁻¹ in vacuum), and are strength-wise on a par with Kevlar (~ 2 N tex⁻¹). With applications such as electrical wiring, body and vehicular armour in prospect, various methods to assemble CNT fibres/films into macroscopic hierarchical structures will be described. The effect of these structural configurations on scaling of specific electrical conductivity with size will also be presented. The talk will conclude with a discussion on current challenges in the manufacturing process such as yield, diameter control and general directions towards achieving these goals.   

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By: Sean Paul Ogilvie
Last updated: Monday, 8 January 2018