Microwave exfoliated graphite oxide (MEGO) heat treatment: Transformation and stability

• Published in: Diamond and related materials Vol. 120; p. 108654
• Main Authors: Chilingarov, Norbert S., Knot'ko, Alexander V., Skokan, Eugene V., Khavrel, Pavel A., Levanov, Alexander V., Isaikina, Oksana Ya, Shulga, Yury M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.12.2021; Elsevier BV
• Subjects: Bends; Crystal defects; Crystallinity of graphene oxide; Defect annealing; Exfoliation; Graphene; Graphene oxide; Graphite; Heat treatment; Interlayers; Materials substitution; Microstructure; Raman spectroscopy; Raman spectroscopy of graphene oxide; Thermal treatment; Raman spectroscopy of graphene oxide; Graphene oxide; Microstructure; Crystallinity of graphene oxide; Thermal treatment
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2021.108654

Graphene oxide (GO) is actively used in modern material science as a substitute for graphene, which is due to the presence of graphene regions in the GO structure. The setting and tuning of graphene unique properties are largely determined by the type of GO processing. Here, the composition, and microstructure of graphene oxide MEGO (microwave exfoliated graphite oxide) and products of MEGO thermal treatment (MEGO/573 and MEGO/1073) are determined. MEGO family particles are considered as consisting of bundles of oxidized graphene connected by numerous deformation defects of the layers – bends, folds, twists. For prolonged annealing of MEGO in vacuum, the disordered state of the GO bundles is preserved, partial exfoliation of graphene oxide bundles occurs, and holes are formed in the graphene oxide layers. The joint analysis of Raman spectroscopy data for MEGO's and for GO samples studied in a number of works was carried out. The stable minor crystallinity of MEGO samples is determined by small blocks of coherent diffraction (BCD), in which the interlayer distance deviates in both the larger and smaller sides from the characteristic value of graphite. The found features give reasons to believe that the graphene regions availability increases with a given MEGO annealing mode, and GO with similar properties can be used to develop “dry” methods for the synthesis of composites. [Display omitted] •MEGO particles consist of graphene oxide bundles connected by bends, folds, twists.•Holes' formation and partial bundles' exfoliation occur in MEGO annealing up to 1073 K.•MEGO's Raman spectra are consistent with the data for graphene oxides.•Expected the D** line origin is the bundles of weakly ordered graphene oxide layers.•MEGO's includes crystal blocks with interlayer distances more/less than in graphite.