Hydrogen isotopic effect during the graphite high-temperature corrosion in water vapours

Abstract

This paper presents the results on a study the processes of physicochemical interactions of water with graphite. The main regularities of the formation of H2, HD and D2 molecules on the graphite surface were determined. It was shown that the fraction of D2 and HD in the gaseous outcome increases in the process of heating, and the quasi-equilibrium state of the graphite's absorption of hydrogen isotopes at the initial stages of interaction is significant: the flow of dissolved atoms into the sample volume is higher than the desorption flow. We suppose that this is due to the higher rate of dissolution of hydrogen atoms in the volume of graphite. We also estimated also the separation factor for the graphite surface-volume system for hydrogen atoms, which was 1.53 for the selected experimental conditions. The temperature dependence of the effective rate constant Ks for the formation of hydrogen isotope molecules in the interaction of graphite with water vapour in the range of 1100 °C–1200 °C was determined. It turned out that KS(D2) > KS(HD) > KS(H2).