Deformation Mechanisms in Pd Nanowhiskers
type: CreativeWork
description: The reduced length scales inherent in nanoscale materials enable access to properties that are otherwise not achievable in bulk. The application of their novel structural and functional responses however is hindered by a lack of understanding of their mechanical behavior, which affects their assimilation into device fabrication as well as their reliability during performance. In contrast to bulk materials, nanoscale materials possess a non-negligible proportion of surface atoms, which can exert significant influence on the overall mechanical response. In addition, structures with small volumes can possess much lower defect densities, which could potentially be driven out of the volume instead of interacting and promoting traditional deformation behavior. Systematic experimental investigations will be crucial to developing the necessary understanding, although they remain challenging due to limited access to suitable test specimens and testing methodologies for directly extracting pertinent results. By employing a MEMS-based tensile testing system and a temperature-controlled cryostat configuration to test defect-free and -scarce Pd nanowhiskers, we have been able to systematically investigate some of the important deformation mechanisms in nanoscale single crystals. We first address the elastic behavior in nanoscale crystals, which is predicted to differ from bulk behavior due to the reduced coordination of surface atoms. We measured size-dependent deviations from bulk elastic behavior in nanowhiskers with diameters as small as ~30 nm. In addition to size-dependent variations in Young's modulus in the small strain limit, we measured nonlinear elasticity at strains above ~1%. In addition to providing the first measurements of higher-order elasticity in Pd, our study shows that the elasticity response in Pd nanowhiskers can be attributed to higher-order elasticity in the bulk-like core upon being biased from its equilibrium configuration due to the role of surface str…
abstract: The reduced length scales inherent in nanoscale materials enable access to properties that are otherwise not achievable in bulk. The application of their novel structural and functional responses however is hindered by a lack of understanding of their mechanical behavior, which affects their assimilation into device fabrication as well as their reliability during performance. In contrast to bulk materials, nanoscale materials possess a non-negligible proportion of surface atoms, which can exert significant influence on the overall mechanical response. In addition, structures with small volumes can possess much lower defect densities, which could potentially be driven out of the volume instead of interacting and promoting traditional deformation behavior. Systematic experimental investigations will be crucial to developing the necessary understanding, although they remain challenging due to limited access to suitable test specimens and testing methodologies for directly extracting pertinent results. By employing a MEMS-based tensile testing system and a temperature-controlled cryostat configuration to test defect-free and -scarce Pd nanowhiskers, we have been able to systematically investigate some of the important deformation mechanisms in nanoscale single crystals. We first address the elastic behavior in nanoscale crystals, which is predicted to differ from bulk behavior due to the reduced coordination of surface atoms. We measured size-dependent deviations from bulk elastic behavior in nanowhiskers with diameters as small as ~30 nm. In addition to size-dependent variations in Young's modulus in the small strain limit, we measured nonlinear elasticity at strains above ~1%. In addition to providing the first measurements of higher-order elasticity in Pd, our study shows that the elasticity response in Pd nanowhiskers can be attributed to higher-order elasticity in the bulk-like core upon being biased from its equilibrium configuration due to the role of surface str…
author: Chen, Lisa YingYing
language: en
date published: 2014-01-01
date modified: 2026-07-24T03:47:40Z
provider: University of Pennsylvania
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Pennsylvania