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In-situ time-of-flight neutron diffraction of ErD2 (beta phase) formation during D2 loading

Rodriguez, Marko A.; Snow, Clark S.; Wixom, Ryan R.

In an effort to better understand the structural changes occurring during hydrogen loading of erbium target materials, we have performed D{sub 2} loading of erbium metal (powder) with simultaneous neutron diffraction analysis. This experiment tracked the conversion of Er metal to the {alpha} erbium deuteride (solid-solution) phase and then on to the {beta} (fluorite) phase. Complete conversion to ErD{sub 2.0} was accomplished at 10 Torr D{sub 2} pressure with deuterium fully occupying the tetrahedral sites in the fluorite lattice. Increased D{sub 2} pressure (up to 500 Torr at 450 C) revealed {approx}10 % deuterium occupation of the octahedral sites. Subsequent vacuum pumping of the sample at 450 C removed octahedral site occupancy while maintaining tetrahedral deuterium occupancy, thereby yielding stoichiometric ErD{sub 2.0} {beta} phase.

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TYPE SAND Report YEAR 2008
OSTIDOI

Summary of Sandia research on metal tritides : FY 2007

Snow, Clark S.; Kammler, Daniel K.; Ferrizz, Robert F.; Espada Castillo, Loren I.; Wixom, Ryan R.; Rodriguez, Marko A.

Sandia National Laboratories has cradle to grave responsibility for all neutron generators in the US nuclear weapons stockpile. As such, much research effort is exerted to develop a comprehensive understanding of all the major components of a neutron generator. One of the key components is the tritium containing target. The target is a thin metal tritide film. Sandia's research into metal tritides began in the early 1960's with a collaboration with the Denver Research Institute (DRI) and continues to this day with a major in house research effort. This document is an attempt to briefly summarize what is known about the aging of erbium tritide and to review the major publications conducted at Sandia in FY 07. First, a review of our knowledge of helium in erbium tritide will be presented. Second, executive summaries of the six major SAND reports regarding neutron tube targets published in FY07 by Department 2735, the Applied Science and Technology Maturation Department, and research partners are presented.

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TYPE SAND Report YEAR 2008
OSTIDOI

Helium release and microstructural changes in Er(D,T)2-x3Hex films)

Snow, Clark S.; Brewer, Luke N.; Rodriguez, Marko A.; Kotula, Paul G.; Banks, J.C.; Mangan, Michael M.

Er(D,T){sub 2-x} {sup 3}He{sub x}, erbium di-tritide, films of thicknesses 500 nm, 400 nm, 300 nm, 200 nm, and 100 nm were grown and analyzed by Transmission Electron Microscopy, X-Ray Diffraction, and Ion Beam Analysis to determine variations in film microstructure as a function of film thickness and age, due to the time-dependent build-up of {sup 3}He in the film from the radioactive decay of tritium. Several interesting features were observed: One, the amount of helium released as a function of film thickness is relatively constant. This suggests that the helium is being released only from the near surface region and that the helium is not diffusing to the surface from the bulk of the film. Two, lenticular helium bubbles are observed as a result of the radioactive decay of tritium into {sup 3}He. These bubbles grow along the [111] crystallographic direction. Three, a helium bubble free zone, or 'denuded zone' is observed near the surface. The size of this region is independent of film thickness. Four, an analysis of secondary diffraction spots in the Transmission Electron Microscopy study indicate that small erbium oxide precipitates, 5-10 nm in size, exist throughout the film. Further, all of the films had large erbium oxide inclusions, in many cases these inclusions span the depth of the film.

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TYPE SAND Report YEAR 2007
OSTIDOI
Results 51–73 of 73
Results 51–73 of 73