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

Abstract

Synthesis of graphene materials in a plasma stream from an up to 40 kW direct current (DC) plasma torch is investigated. These materials are created by means of the conversion of hydrocarbons under the pressure 350–710 Torr without using catalysts, without additional processes of inter-substrate transfer and the elimination of impurities. Helium and argon are used as plasma-forming gas, propane, butane, methane, and acetylene are used as carbon precursors. Electron microscopy and Raman imaging show that synthesis products represent an assembly of flakes varying in the thickness and the level of deformity. An occurrence of hydrogen in the graphene flakes is discovered by X-ray photoelectron spectroscopy, thermal analysis, and express-gravimetry. Its quantity depends on the type of carrier gas. Quasi-one-dimensional approach under the local thermodynamic equilibrium was used to investigate the evolution of the composition of helium and argon plasma jets with hydrocarbon addition. Hydrogen atoms appear in the hydrogen-rich argon jet under higher temperature. This shows that solid particles live longer in the hydrogen-rich environment compared with the helium case providing some enlargement of graphene with less hydrogen in its structure. In conclusion, graphene in flakes appears because of the volumetric synthesis in the hydrogen environment. The most promising directions of the practical use of graphеne flakes are apparently related to structural ceramics.

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

“…Analysis of electrical properties and the search for electronic applications are very poorly represented in the available literature. The exception is an electrochemical application in fuel cells [ 46 ], lithium-ion batteries [ 47 ], and supercondensators [ 30 ]. Electrical properties are a key issue for a wide spectrum of applications.…”

“…Electrical properties are a key issue for a wide spectrum of applications. Generally, it should be mentioned that the plasma synthesized materials, including graphene, are characterized by the standpoint of their structural properties, and chemical content of flakes [ 30 , 48 , 49 , 50 , 51 ]. Here, we study the plasma jet-assisted synthesized graphene materials aimed at the development of electronic devices fabricated by printing techniques on a flexible substrate, providing pervasive, light-weight, and cost-effective devices.…”

“…The authors of [ 27 ] show that with the application of plasma, the small-layer flakes are formed without using substrates, and the synthesis process itself is fast and controlled [ 28 ]. A feature of the plasma synthesis is as follows: when there are cheap gaseous sources of carbon or alcohols, the carbon particle fragments are formed in the gas phase of the plasma stream [ 29 , 30 ]. The synthesized flakes might contain from 1 to 10 and more layers with the different defect density depending on the conditions.…”

“…Application of the direct current (DC) arc torch plasma jets provides the advantages of the property controllability. The experimental and the theoretical studies of the graphene synthesis process show that it is possible to control not only the geometry (thickness, lateral size) of the graphene flakes but also their shape varying the carbon-to-hydrogen ratio in the gas phase [ 30 ]. We apply the carbon nanostructures synthesized using this approach to fabricate the supercapacitor electrodes [ 31 ].…”

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.…”