October 07, 2020 by Luke James
Researchers at Oak Ridge National Laboratory have created a composite material that they claim increases the electrical capacity of copper wires.
Copper (Cu) is ubiquitous in electrical wiring and is the metal of choice for several reasons. In addition to being highly conductive and capable of efficiently carrying electrical current, it is, due to its resistivity, safer to use than wires made out of most other conductive metals. Cu is also ductile, thermally resistant, and inexpensive.
Copper’s electrical resistance, however, can also prove inefficient due to the power losses that the metal can allow, and this has created a great deal of interest in the development of advanced conductors that incorporate carbon nanotubes into the copper matrix. Known as ultra-conductive copper composites, they have the potential to improve energy efficiency in various industrial, commercial, and even residential applications.
In recent research published in the journal Applied Nano Materials, a research team at Oak Ridge National Laboratory (ORNL) presented a new technique for creating a composite material that increases the electrical current capacity of copper wires.
According to the research team, the new technique, described as an ‘electrospinning-based polymer nanofiber templating strategy’, results in a novel material that’s perfect for use at scale in ultra-efficient, power-dense electric vehicle applications (like traction motors), as well as in a multitude of industrial—and other—applications.
To produce the composite material, which is lightweight and features enhanced performance metrics, the researchers used carbon nanotubes (CNTs) which they aligned on flat copper substrates to create a metal matrix conductive material with better current handling and mechanical characteristics than copper alone.
Of course, anybody who has been following this area of research with interest will know that incorporating CNTs into a copper matrix is something that has been explored before. However, previous attempts have resulted in limited scalability and short material lengths. Whereas in this study, the ORNL researchers managed to overcome this problem by experimenting with a new technique.
A close-up of Oak Ridge National Laboratory (ORNL) researchers’ ultra-conductive copper composite. Image Credit: Andy Sproles/ORNL.
Here, the scientists deposited single-wall CNTs using an electrospinning method. This process creates fibres using a liquid jet that flies through an electric field, providing full control over the structure and orientation of the CNTs. In this case, the researchers were able to orient the CNTs in a single general direction to improve the flow of electricity.
A vacuum coating technique was then used to add thin layers of copper film on top of the CNT-coated copper substrates. These samples were then annealed in a vacuum furnace to produce a copper carbon nanotube (Cu-CNT) network that consisted of a dense, uniform copper layer through which copper can diffuse into the CNT matrix.
The result of this technique was a Cu-CNT composite material measuring 10cm by 4cm with hugely enhanced properties. Upon analysis of the material, the researchers found that the material yielded 14% greater current capacity with up to 20% improved mechanical properties in comparison to pure copper.
According to the Oak Ridge National Laboratory researchers, the goal of this study was to mitigate existing barriers to the widespread adoption of electric vehicles, or EVs (the cost of ownership and component life cycles being two examples of which) by using a material that has “better mechanical strength, lighter weight, and higher current capacity”, says Tolga Aytug, the project’s lead investigator.
And, according to the study, this has been comfortably achieved. The Cu-CNT composite material is, when compared to other solutions, a much better conductor of electricity—with less power loss, better efficiency, and increased performance characteristics. This makes it suitable for applications in EVs, such as advanced motor systems, which will naturally benefit from such a rise in power density.
The Cu-CNT composite material could also be used to improve electrification in applications where metrics like size and efficiency are important by creating—to quote ORNL’s paper—“new possibilities for designing advanced conductors for a broad range of systems and industrial applications”.
