INFLUENCE OF THERMAL OXIDATION PROCESSES ON THE MECHANICAL PROPERTIES OF GRAPHITE FOIL

In this work, graphite foil was obtained from thermally expanded graphite based on intercalated compounds of graphite with nitric acid of stages IV, III, II. The foil was obtained using standard technological operations, including intercalation of nitric acid into graphite, hydrolysis of interstitial compounds, exfoliation of oxidized graphite using thermal shock and rolling of thermally expanded graphite into graphite foil. The structure of the obtained intercalated compounds of graphite and the formation of a certain stage were confirmed by X-ray phase analysis. The morphology and elemental analysis for intermediate products (oxidized graphite and thermally expanded graphite) and the final graphite foil were studied by scanning electron microscopy. It was demonstrated that there are no traces of nitric acid in the products after thermal exfoliation. It has been established that during oxidation of graphite foil, its surface becomes more defective, and graphite foil based on intercalated compounds of stage IV graphite exhibits greater thermal resistance than lower stages of intercalation. Mechanical tests have shown greater tensile strength of graphite foil based on intercalated compounds of graphite with nitric acid of stage II, as well as a decrease in the strength of graphite foil during oxidation. Tests of the tightness of seals made of graphite foil have shown a decrease in the tightness level of a flange gasket made of graphite foil during its oxidation at elevated temperatures in an air atmosphere. In addition, it has been shown that the required compression force to ensure a given tightness level increases with an increase in the number of the stage of intercalation of nitric acid into graphite. For citation: Efimov D.V., Ivanov A.V., Mukhanov V.A., Lukyantsev M.I., Maksimova N.V., Avdeev V.V. Influence of thermal oxidation processes on the mechanical properties of graphite foil. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2025. V. 68. N 9. P. 83-89. DOI: 10.6060/ivkkt.20256809.2y.