Carbon segregation on a tungsten surface |
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Authors: | N. D. Potekhina N. R. Gall’ E. V. Rut’kov A. Ya. Tontegode |
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Affiliation: | (1) Ioffe Physicotechnical Institute, Russian Academy of Sciences, Politekhnicheskaya ul. 26, St. Petersburg, 194021, Russia |
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Abstract: | New measurements are performed and a comprehensive analysis of experimental data is made on the dependence of equilibrium carbon coverage θ on a tungsten surface on its temperature and the degree of carbon loading. It is shown that if the volume is free of carbon, the variation of θ for T≥1400 K can be approximately described by the balance between the carbon flows through the boundary with the activation energy for transition into the bulk E1=4.6 eV and the segregation energy ΔE=1.7 eV. For tungsten loaded preliminarily with carbon to a content of ≈10?2 at. %, the θ(T) relation cannot be described in terms of the equilibrium conditions with constant E1 and ΔE, because these quantities depend on the degree of carbon loading; E1 grows from 4.6 to 6.8 eV and ΔE grows from 1.7 to 2.3 eV with an increase in carbon content from 0 to 10?2 at. %. These variations are attributed to the bonds becoming stronger in carbon-loaded tungsten with increasing carbon content. |
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