Investigation of growth mechanism of graphene nanosheets in microwave plasma torch at atmospheric pressure and their properties
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| Year of publication | 2019 |
| Type | Conference abstract |
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| Description | Free-standing graphene nanosheets synthesis by ethanol decomposition in microwave plasma represents simple and environmentally friendly way of graphene production in the form of powder [1]. In our work microwave plasma torch (2.45 GHz, 200-1000 W) at atmospheric pressure was used to synthesize graphene nanosheets consisting of 1 or several graphene layers in Ar (250-1000 sccm) discharge and ethanol (1-30 sccm) mixture Fig 1.. We used dual channel configuration of nozzle electrode with central Ar flow and precursor/Ar flow in secondary channel. During the synthesis well-balanced reaction scheme of C, O, H species was achieved leading to the growth of graphene nanosheets. We investigate the growth mechanism of graphene nanosheets in this plasma chemical reaction scheme by addition of O2 and H2 admixtures. The different amount of oxygen and hydrogen species led to the change of equilibrium between formation of graphene sheets, gaseous byproducts such as H, CO and CHxOy, and an amorphous phase. The amount of C and C2 species was identified as key parameter leading to the formation of graphitic and amorphous phase. We also investigated the possibility of graphene nucleation and growth directly on a dielectric substrate at atmospheric pressure by insertion of Si/SiO2 substrate near the plasma discharge. The homogeneity and quality of graphene layer was investigated in dependence of substrate temperature and precursor flow. Prepared samples are analyzed by scanning and transmission electron microscopy, Raman spectroscopy (Figure 2).and X-ray photoelectron spectroscopy. We investigated functional properties of synthesized nanosheets as well. The electrical conductivity of graphene nanosheets layer was strongly correlated with amount of defects in their structure as proved by Raman spectroscopy and XPS analysis. We also demonstrate very good performance of ammonia gas sensors and electrochemical sensors based on graphene nanosheets. |
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