Energy considerations regarding pulsed arc production of nanomaterials

Abstract

Atmospheric arc discharge volumes have been estimated from the light distribution emitted during evaporation of graphite and molybdenum disulphide (MoS2) anodes. These data have been correlated to the peak power in the case of pulsed arc discharge held at different frequencies (1, 2, and 5 Hz). The measured power density values and the corresponding specific energies per particle have been compared to DC values and showed that pulsed arc discharges deliver electrical power more efficiently than DC arc discharges do with yet lower thermal loads. In particular, the power density of approximately 1 kW/cm3 characteristic of pulsed arcs (10–20 kW/cm3 in DC) suffices to provide 15 eV/particle to the arc plasma (approximately 10 eV/particle or less in DC). Such an energy balance resulted in high ionization rates of the ablated material and production yields of carbon nanotubes around 1011 cm−2 kW h−1. Finally, in situ probe experiments showed that pulsed arcs enhance the transport to the substrate of the generated nanoparticles, such as graphene and MoS2 monolayers. Pulsed anodic arcs open the possibility to generate further nanomaterials thanks to a more rational power investment and a better control of the discharge region.