Copper (Cu) combines many favorable attributes in electrochemical applications: it is abundant, inexpensive, easy to refine and an excellent conductor of electricity with high current-carrying capacity. However, it also has a relatively high electrical resistance compared to its conductivity, which reduces the amount of power that can be transmitted.
Carbon nanotubes (CNT) can provide a huge boost in current-carrying capacity by providing up to five times the electrical conductivity of copper and significantly lower resistance, especially at higher temperatures. Nevertheless, their current-carrying capacity is greatly diminished when millions of CNTs are woven together to form wires.
To improve the performance of CNT-based devices, a multidisciplinary research team at Oak Ridge National Laboratory has developed a new fabrication method for vertically aligned CNTs decorated and even completely encapsulated with a dense network of Cu. The process consists of the conformal deposition of pyrolytic carbon onto a pre-fabricated array of vertically aligned CNTs to stabilize them, followed by mild functionalization and infiltration with an aqueous supersaturated Cu salt solution.
The resulting Cu/CNT composites exhibit superior mechanical properties compared to those of molecularly mixed CNT/Cu and demonstrate room temperature electrical conductivities up to 40% higher than those of conventional Cu. The results obtained from this work suggest that the improved mechanical performance and electrical conductivity can be further enhanced by optimizing CNT and Cu interfacial interactions. A number of issues hinder the development of such interfaces: (1) phase separation; (2) the poor adsorption of Cu to the surface of CNTs; (3) the influence of CNT chirality and crystallinity on composite performance.