title: Three-dimensional imaging of dislocation dynamics during the hydriding phase transformation.
abstract: Crystallographic imperfections significantly alter material properties and their response to external stimuli, including solute-induced phase transformations. Despite recent progress in imaging defects using electron and X-ray techniques, in situ three-dimensional imaging of defect dynamics remains challenging. Here, we use Bragg coherent diffractive imaging to image defects during the hydriding phase transformation of palladium nanocrystals. During constant-pressure experiments we observe that the phase transformation begins after dislocation nucleation close to the phase boundary in particles larger than 300 nm. The three-dimensional phase morphology suggests that the hydrogen-rich phase is more similar to a spherical cap on the hydrogen-poor phase than to the core-shell model commonly assumed. We substantiate this using three-dimensional phase field modelling, demonstrating how phase morphology affects the critical size for dislocation nucleation. Our results reveal how particle size and phase morphology affects transformations in the PdH system.
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: A
authors.identifier: 0000-0003-4611-2561
authors.initials: A
authors.lastname: Ulvestad
authors.affiliation: Fuel &Fuel Channel Safety Branch, Canadian Nuclear Laboratories, Chalk River, Ontario K0J 1J0, Canada.
authors.forename: M J
authors.identifier: 0000-0002-7683-6213
authors.initials: MJ
authors.lastname: Welland
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: W
authors.initials: W
authors.lastname: Cha
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Kim
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: R
authors.initials: R
authors.lastname: Harder
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: E
authors.initials: E
authors.lastname: Maxey
authors.affiliation: Stanford PULSE Institute, SLAC National Accelerator Laboratory Menlo Park, California 94025, USA.
authors.forename: J N
authors.initials: JN
authors.lastname: Clark
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Highland
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: H
authors.initials: H
authors.lastname: You
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: P
authors.identifier: 0000-0003-0570-9169
authors.initials: P
authors.lastname: Zapol
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: S O
authors.initials: SO
authors.lastname: Hruszkewycz
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: G B
authors.initials: GB
authors.lastname: Stephenson