This image shows two crossed carbon nanotubes and the conductivity as a function of angle. Image: Swansea University.
This image shows two crossed carbon nanotubes and the conductivity as a function of angle. Image: Swansea University.

Scientists at Swansea University in the UK have reported a new approach to measuring the conductivity between identical carbon nanotubes, which could be used to help improve the efficiency of electrical power cables in the future. In a paper in Nano Letters, the scientists at Swansea University’s Energy Safety Research Institute (ESRI), together with researchers at Rice University, report making real physical measurements of carbon nanotubes’ conductivity.

Carbon nanotubes are tiny molecules with incredible physical properties. These cylindrical molecules are filled with hexagonal carbon atoms that look a little like chicken wire wrapped into a graphene tube. They can be used to produce lightweight wires, which can be made into strong, efficient electrical power cables. These cables have the potential to replace existing metal cables, which often overheat and fail – and can lose about 8% of electricity in transmission and distribution.

The new study represents a significant step forward, as previous studies examining conductivity levels could only use theoretical calculations in their measurements. Another limitation was that theoretical studies looked at nanotubes that were similar in diameter. In reality, however, the diameters of nanotubes vary, and it is this variation that makes theoretical models impossible to prove and leads to real practical issues when measuring conductivity in carbon nanotubes.

ESRI director Andrew Barron, who is also a professor at Rice University, and his research team noticed that if two carbon nanotubes of different diameters were laid across each other, the resistance at the point of contact was higher than if the nanotubes were similar in diameter. When the team passed a large voltage through one of the crossed carbon nanotubes, it broke the nanotube in two and welded the two halves to the probes.

By then manipulating these two identical halves of the original carbon nanotube, the scientists were able to measure the conductivity between them. Once this was discovered, the team set about experimentally reproducing measurements that were previously only theoretical.

The team also found that through their practical experiments they were able to prove some key theories. One was that varying the angle of overlap between the two halves of the original carbon nanotube produces a variation in electrical conductivity. Another was that measuring conductivity between two parallel halves of a cut carbon nanotube leads to results that are consistent with the theoretical concept of atomic scale registry.

"This is the first time that it has been possible to make experimental measurements to confirm theoretical models. While it is nice to confirm theory with a real experiment, our methodology now opens up a myriad of possibilities for measurements not previously possible," said Barron. "We are looking forward to expanding the basic knowledge of carbon nanotubes that will help us in the production of efficient electrical cabling and a myriad of other technologies in the future."

This story is adapted from material from Swansea University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.