Manufacturing Lightweight Carbon Nanotube Electrical Cables: Increasing the Conductivity

Individual Carbon nanotubes (CNT) are as conductive as copper, they can carry more current and have ~7 times smaller density. They also perform better at high frequency, because they have a significantly-reduced skin effect, where the higher the frequency, the thinner the layer at the surface that can carry the current is, leading to increased resistance. Mechanically, CNTs are more stable as electrical conductors, as they do not suffer from creep, a phenomenon where metals deform, in time, under stress and which leads to electrical failures in wires and printed circuit boards. An electrical CNT wire that is as conductive as an aluminium or copper one will be lighter, tougher, able to carry more current and perform better at higher frequencies. Lift a power drill or a vacuum cleaner and imagine that their weight is cut in half, without losing power. The problem when going to a large scale is how to pass the current between individual nanotubes. The structure of graphite is that of individual sheets of sp2-bonded carbon, held together by weak van der Waals forces in directions perpendicular to the individual sheets; these weak forces are the reason why these planes slip across each other and the graphite lead in the pencil works. Conductivity in the plane is very high, but out of plane is much smaller; this means that if we put two nanotubes together, the electrons find a barrier between the nanotubes that they must tunnel through, reducing the conductivity. What we propose to do is to effectively weld nanotubes, by introducing defects in the nanotubes in a controlled way and then healing them together, such that the defects migrate and cancel each other between the tubes, leading to cross-linking of the CNTs in the area of contact. Therefore, our challenge is to discover a manufacturing solution for CNT wires and cables, and we are best placed to do this because we start from our proven method for getting CNTs aligned by electrospinning and we have the right expertise in the management of defects in materials, from introduction/implantation to self-healing.

The proposed research is supported by T Swan Ltd, a premier independent manufacturer of performance and speciality chemicals located in Consett, County Durham. Their company is set up to produce tens of kg of CNTs and can upscale to the level of Nanocyl-Belgium and Cnano and Timesnano in China, to tonnes-per-year, if a significant application breakthrough is found, such as being able to produce lightweight conductors. This will impact significantly not only the company, but also the local economy in the North of England, creating new high-skilled jobs and wealth. The prospect is of interest also to one of the major manufacturers of electrospun fibres, Revolution Fibres, in New Zealand, who have offered their worldwide contacts and resources to help deliver the impact of a breakthrough in increasing the conductivity of carbon nanotube wires. Revolution Fibres are also looking to open a subsidiary in the UK, as a result of this, adding value to the local economy. Lightweight conductors for space and robotics applications are of interest to BAE Systems, as they will result in lighter, more powerful electrical motors that will increase the autonomy and reliability of such systems. Electrical motors will be redesigned to work at higher rpm and have higher torque than possible, which will impact throughout from the academic research and prototype design level, to the application of such motors, including for quality-of-life, such as in bionic prosthetics or for people who are immobile or mobility-impaired. The knowledge gained in this research is transferable to the class of novel 2D materials, such as graphene, where the materials are now being produced in kg quantities but with small micron-sizes and their incorporation into conductive layers requires overcoming the interface barriers. Carbon nanotubes and their fantastic possibilities have now been expounded all the way to GCSE-level textbooks; with this proposal we can deliver on some of those promises and enthuse a new generation of scientists and engineers, increasing the UKs position and reputation in the global research and market.