On the gas-phase graphene nanosheet synthesis in atmospheric microwave plasma torch: Upscaling potential and graphene nanosheet‑copper nanocomposite oxidation resistance

Efficient gas-phase synthesis of few-layer graphene nanosheets (GNS) is based on the controlled formation of the high-temperature environment and the reaction pathway of gas-phase species formed by the decomposition of organic precursors. Such a process results in the formation of high-quality carbon nanomaterial and hydrogen while the concentration of other gaseous by-products is minimized. In this work, the main factors affecting the efficiency of such processes in the TIAGO microwave plasma torch were investigated using detailed material analysis and mass spectrometry of the gas-phase products during the synthesis process. The results showed a limiting effect of increasing the microwave power (MW) on both the product yield as well as material quality, as shown by Raman and x-Ray photoelectron spectroscopy. The change in the reaction pathway increased the formation of C2H4, resulting in the upper limit of the achievable nanopowder yield. The prepared material showed a decrease in its high oxidation resistance, with increasing the delivered MW power as determined by thermogravimetry analysis. This behavior was related to the formation of GNS-Cu nanoparticles composite due to the presence of copper nanoparticles originating from erosion of the electrode of the TIAGO torch during the synthesis process at high MW powers.