In situ observation of γ-ZrH formation by X-ray diffraction

Abstract

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. g-ZrHSynchrotron X-ray diffraction Hydrogen charging a b s t r a c tWe report on the measurement of the formation of g-ZrH during in situ gaseous charging. The measurements were undertaken using high-energy synchrotron X-ray diffraction. Experimental observation shows that g-ZrH can form at 180 C from a mixture of aþd while dehydrogenating at slow cooling rates.The observation is further supported by ex situ laboratory X-ray diffraction on deuterated Zr powder that has undergone a similar heat-treatment cycle. The crystal structure of g-ZrH refinement agrees with the reported P4 2 /n structure found in the literature.

The preparation of Zr-deuteride and phase stability studies of the Zr-D system

“…According to Figure 7, the formation and growth of γ-ZrD is compensated for by dissolution of δ-Zr deuterides. This observation supports the existing observation of slow γ Zr deuteride formation by δ→γ transformation at 180°C proposed by Root et al [31] and a recent report [22,39]. In line with in-situ neutron diffraction studies, the laboratory X-ray data also did not…”

“…Nevertheless, this new phase has not been confirmed or observed in this neutron diffraction or other in-situ neutron diffraction [22] and in-situ synchrotron X-ray diffraction studies [26,39].…”

“…Some researchers suggest that γ-ZrD is the stable room temperature phase [30][31][32][33] with a δ to γ transition at 180°C [31] or transforms by a peritectoid reaction α+δ↔γ below ≈255°C [30], while others claim it is a metastable phase [13,34,35,36,37,38]. Additionally, several studies [1][2][3][4]22,39] propose that the γ-phase is a tetragonal phase with the P42/n space group (Figure 2), but Kolesnikov et al [40] reported that the structure of the γ-ZrD is orthorhombic, belonging to the space group Cccm. Many research findings report that the γ-ZrD phase occurs after rapid quenching, while the δ-ZrDx is often found after annealing [1,2,3,4].…”

“…Thus, knowledge of the precise structure, stability, formation and transformation behaviour of various ZrDx phases in the Zr-D system is essential for ensuring integrity of the Zr-based materials in power plant. The discrepancy concerning ZrDx phase stability, crystal structure and transformation may arise because of: the high diffusivity of deuterium at low temperature (<600°C) [26,50]; close structural similarities between relevant phases [26,50]; non-stoichiometry (0<x≤2) of deuteride phases [1][2][3][4]17,[25][26][27]; the strong influence of other impurity elements in the Zr-D system [1,4,27]; an unclear deuteride preparation route [1,4,26,27,30] and the sensitivity of experimental methods [39]. Therefore, to overcome experimental complications arising from the sample and instrument, high resolution in-situ experiments of high purity samples is essential.…”

Residual Lattice Strain and Phase Distribution in Ti-6Al-4V Produced by Electron Beam Melting

“…In addition, they are non-destructive, have a high spatial resolution (ranging in the order if μm to mm depending on the radiation source)), almost no specimen geometry restrictions, and can be applied to all types of crystalline material. Furthermore, with the high-energy synchrotron X-ray diffraction setup used in this work, it is possible to characterize and conduct quantitative studies on multi-component systems containing phase quantities as low as 0.1–0.7% [ 29 , 30 , 31 ] with a high temporal resolution (0.2 s) [ 31 ]. This means that phase specific RS in the target system can be determined dynamically with high accuracy.…”