1D modeling of the equilibrium plasma flow in the scope of direct current plasma torch assisted graphene synthesis

Abstract

Results of experimental study of the one-step plasma-based process of the synthesis of unsupported graphene and hydrogenated graphene are presented. A direct current (DC) plasma torch is used, the pressure is held at 350 Тоrr, and the flow rates of plasma forming gas (helium) and carbon source (propane-butane mixture) are kept constant. An influence of reactor geometry on the properties of synthesized product is investigated. Graphene and hydrogenated graphene were synthesized in an appreciable rate in the plasma jet volume under equal conditions using cylindrical and conical reactors accordingly. Synthesized graphene materials are characterized using electron microscopy, Raman spectroscopy, x-ray, and XPS analysis, confirming the existence of graphene and of hydrogenated graphene (graphane). In order to examine an influence of input parameters on the process of the synthesis of graphene materials, the quasi-1D numerical flow model is used to calculate the distributions of temperature and velocity within the reactor channel. The key role of the temperature distribution within the reactor in the synthesis of graphene materials is established. Cylindrical flow channel provides higher temperatures compared with the conical channel. It affects the flow composition at the outlet. Under lower temperature, the flow contains in addition to condensed carbon a great amount of hydrocarbons CH, which is favorable for the production of hydrogenated graphene. Under higher temperature, the pure graphene is synthesized, since the outlet flow has the carbon mainly in the condense phase, the quantity of CH being insignificant.

Distinctive Features of Graphene Synthesized in a Plasma Jet Created by a DC Plasma Torch

“…Differences in the cases of helium and argon are investigated using equilibrium plasma composition as a function of temperature in the range 2000-4000 K. As a matter of fact just in this range the precursor turns into molecular hydrogen and condensed phase of carbon, identified in the database IVTANTERMO [36] as graphite. Modeling of the plasma flow in the reactor is made using quasi-one-dimensional approach under the local thermodynamic equilibrium [28,[37][38][39].…”

“…The peculiarity is the synchronous input of plasma forming gas and carbon precursor into discharge gap of the plasma torch and the arrangement of the collector of the end product. DC plasma torch with power input up to 40 kW was used as a generator of plasma jet [28]. Its original features are an expanding channel of the outlet electrode and the swirling-type stabilization of plasma jet.…”

Graphene Flakes for Electronic Applications: DC Plasma Jet-Assisted Synthesis

“…The design feature of the plasma torch (expanding channel of the output electrode) and the tangential input make it possible to obtain stable plasma jets within a wide range of parametric studies [ 31 ]. A more detailed description of the installation is given in [ 31 , 32 ]. The task of the present experiment was to synthesize the small-size monolayer carbon nanoparticles.…”

Applicability of Atmospheric Pressure Plasma Jet (APPJ) Discharge for the Reduction in Graphene Oxide Films and Synthesis of Carbon Nanomaterials

“…The results are commendable, but the approach needs further development to operate at lower temperatures suited for sensitive (e.g., flexible) substrates. Researchers have also synthesized GSG using high-power APPJ (30-40 kW power, 300-400 A) fixed and enclosed in a reactor with graphitic walls [24,[32][33][34]. The reactor was further enclosed in a vacuum chamber with helium or argon feed-through.…”

“…Crumbled graphene sheets of various sizes (up to a few hundred nanometers) with the number of layers in the range of 1-10 have been obtained. Although this technique is attractive, some of the downsides are [32][33][34]: (i) a very high power consumption; (ii) the necessity of special auxiliary systems including a vacuum chamber with cooling; and (iii) the crumbled nature of graphene, and the need for a post-synthesis solution process to realize particular applications such as transparent conductive layers, sensors, and other functional coatings.…”