Size-dependent elastic modulus of nanoporous Au nanopillars

S Mathesan and D Mordehai, ACTA MATERIALIA, 185, 441-452 (2020).

DOI: 10.1016/j.actamat.2019.12.018

The deformation response of nanoporous gold nanopillars under compression, with varying nanopillar and ligament diameters, is analyzed from a series of molecular dynamics simulations. We have measured the ligament size-dependent elastic modulus of nanoporous nanopillars from the elastic region of stress-strain curves, showing that the elastic modulus at a given solid fraction depends on both the geometrical characteristics of the nanopillars and topology of the ligament structure. We modified the Gibson-Ashby scaling law for nanopillars, to predict the size-dependency found in the simulations. To compare the modified model and the simulation results, we have developed a method to estimate the average number of load-bearing ligaments by employing a unique post-processing technique. The comparison between the scaling law and the simulation results lead us to the conclusion that the elastic response of the nanopillars is predominantly due to the compression of ligaments. The size effect due to the new dimensionality vanishes at larger nanopillar diameter and eventually, the scaling laws resemble the classical laws, which is a function of solid fraction only. Besides the size effect, the need to generate nanoporous nanopillars with different topologies and to ensemble average over the various topologies is discussed. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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