Hydrogen effects on the mechanical properties of nanocrystalline free-standing Palladium thin films

Abstract

Pd membranes are used both in hydrogen detection and hydrogen separation devices. Their properties can be improved at the nanometer scale. We simulate atomistically the tensile properties of Pd mono and polycrystalline free-standing nanofilms of 7 and 10 nm thicknesses with different H concentrations at 300 K. We use Monte Carlo to place H atoms in the Pd membranes. H segregates to the surfaces and subsurfaces of all films and to the grain boundaries (GBs) in the poly-crystalline films. We perform molecular dynamics uniaxial tensile tests. For all pure Pd nanomembranes the Young's modulus and yield strength are substantially reduced compared with the bulk ones, and decrease with increasing H concentration. Dislocations and twin formation are the main deformation mechanisms. Polycrystalline samples also show GB deformation. Wrinkling of the surfaces increase with strain, enhanced by the presence of hydrogen. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Pd membranes are used both in hydrogen detection and hydrogen separation devices. Their properties can be improved at the nanometer scale. We simulate atomistically the tensile properties of Pd mono and polycrystalline free-standing nanofilms of 7 and 10 nm thicknesses with different H concentrations at 300 K. We use Monte Carlo to place H atoms in the Pd membranes. H segregates to the surfaces and subsurfaces of all films and to the grain boundaries (GBs) in the poly-crystalline films. We perform molecular dynamics uniaxial tensile tests. For all pure Pd nanomembranes the Young's modulus and yield strength are substantially reduced compared with the bulk ones, and decrease with increasing H concentration. Dislocations and twin formation are the main deformation mechanisms. Polycrystalline samples also show GB deformation. Wrinkling of the surfaces increase with strain, enhanced by the presence of hydrogen. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.