Numerical and Experimental Study of the Multichannel Nature of the Synthesis of Carbon Nanostructures in DC Plasma Jets

Abstract

Wide spectrum of carbon nanostructures was synthesized by means of simple plasma chemistry using DC plasma torch: carbon nanotubes, nanowalls, graphene, hydrogenated graphene and a mixture of nanotubes with graphene. The synthesis was performed in the plasma-chemical reactor under the pressure varying in the close range 350–710 Torr with different types of hydrocarbon as an admixture to the helium plasma. Aliphatics (propane, butane methane and acetylene) were used providing a variation of C:H ratio. The plasma-chemical pyrolysis of hydrocarbons in the temperature range 1000–8000 K was analyzed using the thermodynamic and gas dynamic characteristics. It is determined that the main contribution to the formation of predecessors of solid carbon makes the composition of plasma jet in the temperature range 2500–3500 K. In this range the interrelation between atomic hydrogen H and hydrocarbon molecules CH varies dramatically, and the mole fraction of solid carbon Cgr goes upward. The C:H ratio in the carbon feedstock is shown to have an influence on the particularity of processes of formation of condensed carbon.