Structural characterization of graphene nanostructures produced via arc discharge method

Few-layered graphene (FLG) was produced via substrate-free direct current arc discharge between pure graphite electrodes in an originally designed reactor chamber. Previously, parameters influencing the synthesis condition and properties of graphene-like discharge density, precursor composition, electrode diameter/length, reactor design and type and pressure of buffer gases were optimized. In this study, it was observed that carbon structures with different properties deposited in the different regions of the DC arc reactor. The mechanism of graphene formation by the arc discharge method was investigated in terms of the collection side and distance to the arc region. Variations in the distance to arc region result in dissimilar temperature gradients in the reactor chamber, thereby the deposition mechanism of carbon clusters differs with regard to reactor zones. The products collected from the different regions of the reactor were characterized via Raman Spectroscopy and integrated intensity ratio (I-D/I-G and I-G/I-2D), full width half at maximum (FWHM), crystallite size (L-a), defect density (eta(D)) values were examined. The crystallite size (L-002) and average number of graphene layers (N) were determined by X-Ray diffraction (XRD) analyses. In addition, their morphological properties were investigated with scanning electron microscopy (SEM) and transmission electron microscope (TEM). As a result, the carbon nanostructures with high purity and few-layered morphology collected on the anode region of the reactor. While, the purity of few-layered graphene decreased as moving away from the anode region of the chamber. Therefore, it was determined that the properties of graphene were influenced greatly by the temperature distribution and its gradient around the arc plasma.