Stiffening of nanoporous gold: experiment, simulation and theory

By combining electron microscopy measurements, atomistic simulations and elastic homogenization theory, we theoretically investigate the Young's modulus of nanoporous Au structures. Based on atomistic replicas generated starting from experimental tomographic evidence, atomistic simulations reveal that nanoporous Au stiffens as ligaments become finer, reproducing experimental findings obtained by nanoindentation of dealloyed samples. We argue that such a stiffening is neither due to surface stress nor to grain boundaries. Instead, we observe a direct quantitative correlation between the density of dislocations found in the material phase of the nanoporous structures and their Young's modulus and we propose a microscopic explanation of the observed stiffening. In particular, we show that local stress and strain fields in the neighborhood of dislocation cores allow dislocations to work as reinforcing solutes.