Researchers have created a composite material that increases the electrical current capacity of copper wires. The research is aimed at reducing barriers to wider electric vehicle adoption including cutting the cost of ownership and improving the performance and life of components such as electric motors and power electronics. The material can be deployed in any component that uses copper including more efficient bus bars and smaller connectors for electric vehicle traction inverters, as well as for applications such as wireless and wired charging systems.
To produce a lighter-weight conductive material with improved performance, the researchers deposited and aligned carbon nanotubes on flat copper substrates, resulting in a metal-matrix composite material with better current handling capacity and mechanical properties than copper alone.
Incorporating carbon nanotubes (CNTs) into a copper matrix to improve conductivity and mechanical performance is not a new idea. CNTs are an excellent choice due to their lighter weight, high strength, and conductive properties. But past attempts at composites have resulted in very short material lengths — only micrometers or millimeters — along with limited scalability or in longer lengths that performed poorly.
The researchers deposited single-wall CNTs using electrospinning, a commercially viable method that creates fibers as a jet of liquid speeds through an electric field. The technique provides control over the structure and orientation of deposited materials. In this case, the process allowed scientists to successfully orient the CNTs in one general direction to facilitate enhanced flow of electricity.
The team then used magnetron sputtering, a vacuum coating technique, to add thin layers of copper film on top of the CNT-coated copper tapes. The coated samples were then annealed in a vacuum furnace to produce a highly conductive Cu-CNT network by forming a dense, uniform copper layer and to allow diffusion of copper into the CNT matrix. Using this method, the scientists created a copper-carbon nanotube composite 10 centimeters long and 4 centimeters wide with exceptional properties. The composite reached 14% greater current capacity, with up to 20% improved mechanical properties compared with pure copper.
While the composite has direct implications for electric motors, it also could improve electrification in applications where efficiency, mass, and size are a key metric. The improved performance characteristics, accomplished with commercially viable techniques, means new possibilities for designing advanced conductors for a broad range of electrical systems and industrial applications.
The team also is exploring the use of double-wall CNTs and other deposition techniques, such as ultrasonic spray coating coupled with a roll-to-roll system, to produce samples of 1 meter in length.