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

Abstract

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. Theexperimental strategy was based on the design of an experimental set-up able toenhance the synthesis of these compounds at the expense of the usually foundcathode crust where multi-walled nanotubes are often found. In this set-up the arcdischarge is ignited between pure graphite electrodes experiencing a symmetricalsituation as far as the heat generation by the arc and the heat dissipation atthe heat sinks is concerned. This is achieved by AC powering two electrodes ofthe same size and length. A cylindrical steel collector able to control the heatexchange with the surroundings completes the experimental set-up. The yieldof the device, in terms of synthesis rate and of fraction of sublimated carbonconverted to nanostructures, has been evaluated, and it resulted in being particularlyhigh, indicating that AC powering can represent a key factor in the large-scalesynthesis of SWNHs and highly convoluted graphene sheets by arc discharge. Thestructure of the synthesized powder has been determined by transmission electronmicroscopy.