Evolution of mechanical properties in ErT2 thin films

J. A. Knapp, J. F. Browning, G. M. Bond

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24 Scopus citations

Abstract

The mechanical properties of rare earth tritide films evolve as tritium decays into H3 e, which forms bubbles that influence long-term film stability in applications such as neutron generators. Ultralow load nanoindentation, combined with finite-element modeling to separate the mechanical properties of the thin films from their substrates, has been used to follow the mechanical properties of model ErT2 films as they aged. The size of the growing H3 e bubbles was followed with transmission electron microscopy, while ion beam analysis was used to monitor total T and H3 e content. The observed behavior is divided into two regimes: a substantial increase in layer hardness but elasticity changed little over ∼18 months, followed by a decrease in elastic stiffness and a modest decease in hardness over the final 24 months. We show that the evolution of properties is explained by a combination of dislocation pinning by the bubbles, elastic softening as the bubbles occupy an increasing fraction of the material, and details of bubble growth modes.

Original languageEnglish
Article number053501
JournalJournal of Applied Physics
Volume105
Issue number5
DOIs
StatePublished - 2009

Funding

Discussions with D. M. Follstaedt, S. M. Myers, D. F. Cowgill, and C. S. Snow, ion beam analysis by J. C. Banks, x-ray diffraction by M. A. Rodriguez, sample preparation by L. I. Espada, G. L. Bryant, and M. B. Ritchey, and technical assistance with radiation safety issues by E. A. Staab are all gratefully acknowledged. Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Co., for the National Nuclear Security Administration of the United States Department of Energy under Contract No. DE-AC04-94AL85000. Oak Ridge National Laboratory is managed for the United States Department of Energy (DOE), Office of Basic Energy Sciences-Materials Science under Contract No. DE-AC05-00OR22725 with UT-Battelle LLC.

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