THE ROLES OF OXIDE INTERFACES AND GRAIN BOUNDARIES IN HELIUM MANAGEMENT IN NANO-STRUCTURE FERRITIC ALLOYS:A FIRST PRINCIPLES STUDY

摘要

We report a theoretical study for assessing the possible roles of oxide interfaces in managing helium in nano-structured ferritic alloys (NFAs). Various candidate structures of the ferrite/Y_2Ti_2O_7 interfaces are constructed and the associated energies are carefully evaluated. The calculated interface phase diagram predicts the interfaces to be Y/Ti-rich, for the wide temperature range of interest. Vacancies and helium both segregate to the interfaces, in preference to grain boundaries. Combined with our previous results on bulk-phase Y_2Ti_2O_7, the profound implication of helium management in NFAs is discussed.