AC arc discharge synthesis of single-walled nanohorns and highly convoluted graphene sheets

In this paper we report the synthesis of single-walled carbon nanohorns (SWNHs) and highly convoluted graphene sheets by AC powered arc discharge in air. The experimental strategy was based on the design of an experimental set-up able to enhance the synthesis of these compounds at the expense of the usually found cathode crust where multi-walled nanotubes are often found. In this set-up the arc discharge is ignited between pure graphite electrodes experiencing a symmetrical situation as far as the heat generation by the arc and the heat dissipation at the heat sinks is concerned. This is achieved by AC powering two electrodes of the same size and length. A cylindrical steel collector able to control the heat exchange with the surroundings completes the experimental set-up. The yield of the device, in terms of synthesis rate and of fraction of sublimated carbon converted to nanostructures, has been evaluated, and it resulted in being particularly high, indicating that AC powering can represent a key factor in the large-scale synthesis of SWNHs and highly convoluted graphene sheets by arc discharge. The structure of the synthesized powder has been determined by transmission electron microscopy.