Publication details

Graphene nanosheet synthesis by oxygen and hydrogen enriched decomposition of ethanol in microwave plasma torch discharge

Authors

TOMAN Jozef JAŠEK Ondřej ŠNÍRER Miroslav KUDRLE Vít JURMANOVÁ Jana

Year of publication 2019
Type Conference abstract
MU Faculty or unit

Faculty of Science

Citation
Description In the present work, a decomposition of ethanol vapours in microwave plasma torch discharge at atmospheric pressure conditions was investigated. The discharge was driven by a microwave generator set to standard frequency of 2.45 GHz, using microwave power from 140 to 350 W. Microwave line was terminated with an exchangeable dual channel carbon nozzle, allowing us to separately sustain the plasma by argon gas (220 - 920 sccm) flowing through the central (axial) channel and initiate synthesis by introduction of ethanol vapours (4 - 20 sccm) carried by argon (300 – 1400 sccm) through secondary channel (annulus). Ethanol molecule provides appropriate ratio of C, H and O atoms for graphene nanosheet synthesis. Disrupting the balance by addition of small amount (1 – 10 sccm) of molecular admixtures (O2 and H2), we were able to study the crucial parameters governing the assembly of carbon species into preferred graphene nanosheet structures. Optical emission spectroscopy (OES) was used to identify the nucleation density of active species such as C2 and C in the plasma and determination of neutral gas temperature approximated from rotational temperatures obtained by simulation of CN rotational spectra. To obtain more detailed information about the material structure Raman spectroscopy and XPS were used. The morphology of synthesized nanostructures was studied by SEM. Addition of oxygen to the process of ethanol decomposition has led to minor effect on the properties of graphene material however, hydrogen admixture had more significant impact on the plasma chemistry of MW discharge and synthesized carbon nanomaterial. Amount of graphene nanopowder decreases with oxygen admixture due to formation of CO in plasma.
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