Three-dimensional imaging of dislocation dynamics during the hydriding phase transformation

Journal Article · 16 January 2017 · Nature Materials

DOI: https://doi.org/10.1038/nmat4842 · OSTI ID:1352877

Ulvestad, A.  ^[1]; Welland, M. J.  ^[2]; Cha, W. ^[1]; Liu, Y. ^[1]; Kim, J. W. ^[3]; Harder, R. ^[3]; Maxey, E. ^[3]; Clark, J. N. ^[4]; Highland, M. J. ^[1]; You, H. ^[1]; Zapol, P.  ^[1]; Hruszkewycz, S. O. ^[1]; Stephenson, G. B. ^[1]

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1. Argonne National Lab. (ANL), Argonne, IL (United States). Materials Science Division
2. Canadian Nuclear Lab., Chalk River, ON (Canada). Fuel & Fuel Channel Safety Branch
3. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
4. SLAC National Accelerator Lab., Menlo Park, CA (United States). Photon Ultrafast Laser Science and Engineering Inst. (PULSE)

Crystallographic imperfections can significantly alter material properties and responses to external stimuli, including solute induced phase transformations and crystal growth and dissolution . Despite recent progress in imaging defects using both electron and x-ray techniques, in situ three-dimensional imaging studies of defect dynamics, necessary to understand and engineer nanoscale processes, remains challenging. Here, we report in situ three-dimensional imaging of defect dynamics during the hydriding phase transformation of individual palladium nanocrystals by Bragg Coherent Diffractive Imaging (BCDI) . During constant pressure experiments, we observed that the phase transformation begins after the nucleation of dislocations in large (300 nm) particles. The 3D dislocation network shows that dislocations are close to the phase boundary. The 3D phase morphology resolved by BCDI suggests that the hydrogen-rich phase is more similar to a spherical cap on the hydrogen-poor phase than the core-shell model commonly assumed. We substantiate this conclusion using 3D phase field modeling and demonstrate how phase morphology affects the critical size for dislocation nucleation. We determine the size dependence of the transformation pressure for large (150-300 nm) palladium nanocrystals using variable pressure experiments. Our results reveal a pathway for solute induced structural phase transformations in nanocrystals and demonstrate BCDI as a novel method for understanding dislocation dynamics in phase transforming systems at the nanoscale.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1352877
• Journal Information: Nature Materials, Vol. 16, Issue 5; ISSN 1476-1122
• Publisher: Nature Publishing GroupCopyright Statement
• Country of Publication: United States
• Language: English