Reducing dimensions of nanocarbons in electric arc plasma via rapid flow treatment

The pressure of buffer gas and external fields (e.g. temperature field, magnetic field) significantly influence the non-equilibrium deposition process of nanocarbons in electric arc plasma, resulting in the changes of structure and morphology of arc products. By introducing an external rapid-flow field, the influences of pressures and flow speeds on the dimensions of nanocarbons, including amorphous carbon particles (3-D), graphene sheets (2-D) and carbon nanotubes (CNTs) (1-D), have been investigated under respective conditions. With increased flow speeds, a general trend of reduction in dimension has been observed regardless of the specific type of product. Thus the tubular diameter of CNTs could be controllable by adjusting the flow speed, and, more importantly, single-layer graphene sheets can be readily obtained by introducing high-speed flow under optimized condition of buffer gas. This improvement for arc synthesis may facilitate industrial production of various arc nanocarbons for dimensional requirements. Based on these findings, the possible reasons for the dimensional reduction of arc nanocarbons are discussed on two aspects of material growth and fluid dynamics.