Reduction of electrical resistance on suspended glassy carbon nanofibers by localized thermal annealing

Glassy carbon nanofibers (CNF) can be fabricated with relative ease through electrospinning of a polymeric ink—a carbon precursor—followed by a pyrolysis step. These fibers have found applications in fields as diverse as electrochemical sensing, nanoelectronics and energy storage. A critical step for using this type of carbon fibers in such applications is to thermally anneal them. Annealing reduces the variations in electrical resistance inherent to this type of disordered non-graphitizing carbon. In this work, the thermal annealing process was done by exploiting the local Joule heating experienced by the fibers upon application of a voltage. The effect of this annealing process on the CNFs was studied, finding that more than half of the fibers experience a reduction above 90% in their electrical resistance. This decrease was found to be related to the volume of the fibers, with the lesser-volume CNFs experiencing a much more significant reduction in their resistance (thus, indicating a larger graphitization level). The preliminary results presented in this work can serve as the basis for a detailed study on the effect that extreme temperatures have on glassy carbon nanofibers.