Synthesis of thermally stable carbon nanostructures via ethanol pyrolysis in DC plasma jets

Thermostable graphene and carbon nanotubes (CNTs) obtained by the plasma-chemical method were stable when heated to 1300 K. The peculiarity of the obtained materials is associated with the nature of the precursor (ethanol) containing oxygen. It is shown that the composition of the gas phase and the temperature interval for the formation of gaseous precursors depends on the plasma-forming gas used for the pyrolysis of ethanol in a plasma jet: helium, argon, or nitrogen. According to the results of plasma flow simulation, the temperatures of the onset of carbon condensation for helium plasma (2900–2950 K) and argon plasma (2980–3010 K) are quite close, and in the corresponding gas phase the main components are H, H2 and CO, and at lower concentrations there are radicals COOH and OH and HCO+. The nitrogen plasma contains well-represented cyanopolyins responsible for the rearrangement of the gas phase at lower temperatures of 2240–2250 K. It seems that these temperatures are too low for CNT synthesis, so only graphene is formed here. The influence of the combination of H and O in the high-temperature region of plasma flow on the mechanism of formation of precursors of carbon nanostructures has been found.