Nano Lett. 16, 7282–7289 (2016)

Carbon-based materials have been rapidly adopted in real-world applications. However, many of their outstanding electrical and mechanical properties only occur at the nanoscale, which imposes constraints on the design of macro-sized devices. In order to explore the potential of carbon nanomaterials, 2D building blocks have to be assembled into 3D nanostructures, ideally without compromising the nanoscale performance.

Liangbing Hu and co-workers at the University of Maryland have now proposed a route to bulk materials with enhanced electrical conductivity and tensile strength from carbon nanofibre networks. In the pristine matrix, amorphous interweaved nanofibres interact with one another via weak van der Waals forces. High temperature Joule heating induced by ultrafast electric current pulses enables the gradual merging of adjacent carbon nanofibres where they intersect. The heating effect also leads to further carbonization of the nanofibres, and the resulting 3D matrix has high crystallinity and strong chemical and physical bonding. Compared to the amorphous nanofibres, the electrical conductivity of the covalently interconnected carbon network was more than four orders of magnitude higher. Interestingly, the same conditions didn't prove successful when applied to other carbon-based nanostructures. In highly crystalline carbon nanotubes, Joule heating resulted in deformation of the strong C–C bonds and overall deterioration of their electronic properties.