Formation of self-assembled nanoplates via hydrogenation of epitaxial Pd film.

Boyerinas, Brad M; Roytburd, Alexander L; Bruck, Hugh A · Nano Lett · 2014

basic_science · Level V

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Abstract

Understanding the relationship between the uptake of hydrogen gas and hydride phase formation and evolution in metal solids is a phenomenon of significant technological importance due to current development of hydrogen storage devices, sensors, and membranes. The performance of these devices is degraded by structural defect formation during incoherent metal-hydride phase transformation. In this work, atomic force and scanning electron microscopy reveal formation of nanoplates along the ⟨111⟩ directions in a (111) epitaxial Pd film. These nanostructures are observed after high temperature and high pressure gas phase hydrogenation and cooling in ambient temperature. Transmission electron microsocpy (TEM) analysis of a posthydrogenated film did not show considerable plastic deformation. The size of the nanoplates increased with increasing Pd film thickness. A formation mechanism of nanoplates is proposed: cooling the sample reactor in ambient temperature after hydrogen loading induced formation of coherent or partially coherent β-phase plates along {100} planes corresponding to minimum elastic energy of interaction between metal and hydride phases.