Graphite oxidation and SEM as a tool for microstructural investigation

Abstract

The microstructure of graphite and its oxidation have been individually investigated at length. When any catalytic impurities are removed from graphite, oxidative attack takes place preferentially from the exposed edges, or active sites of graphite crystallites. This provides valuable insights regarding the underlying crystallography and fundamental structure of graphite which are not immediately evident from a raw topographical examination using, for example, microscopy. Using new techniques, such as field emission guns and sensitive detectors, modern scanning electron microscopes are capable of operating down to a few hundred volts. When surface features and effects are being considered this is absolutely critical as the low voltages imply low sample penetration of the electrons, thus the true surface morphology of the material can be resolved. In combination, these methods provide a valuable technique for investigating the microstructures found in graphite. The approach has been applied to natural but is even more relevant to synthetic graphite and therefore nuclear materials, which have an exceedingly complex microstructure. The revealed structural qualities can be related to the manufacturing processes in order to gain additional insights into the material and uncover potential options for improving the properties.

Optimization of graphene oxide through various Hummers' methods and comparative reduction using green approach

“…This confirmed that graphene oxide had been reduced. Similar result was obtained by Badenhorst (2017) [43]. Moreover, in all the RGO samples, corrugated surface was observed.…”

“…Each sheet can also be identified from their edges. A similar observation was also reported by Badenhorst (2017), [43]. For GO12H in Figure 4b, there is an ultra-thin layer with folded edges, showing a surface which appeared to be continuous.…”

“…Figures 5b -5d show the spectra of GO12H, GONP and GOSIM respectively. Each spectrum shows the presence of carbon and oxygen atoms in various proportion depending on the level of oxidation, thereby confirming the synthesis of GO [43]. From the spectrum in Figure 5b, GO12H contained 43.03% of oxygen to 55.78% of carbon.…”

Report on initial development of a database of nuclear graphite characteristics based on microstructural characterization

“…Table 2 summarizes the most relevant publication on SEM for nuclear graphite characterization. Badenhorst 2017 [23] This publication provides a comparison between SEM micrographs of oxidized surfaces of a natural graphite and NBG-18.…”