Stiffening of nanoporous Au as a result of dislocation density increase upon characteristic length reduction

TL;DR

This study investigates how the stiffness of nanoporous gold increases as ligament size decreases, linking the phenomenon to dislocation density growth rather than surface stress effects, supported by atomistic simulations and experimental data.

Contribution

It provides new insights into the size-dependent mechanical stiffening of nanoporous gold, emphasizing the role of dislocation density increase over surface stress effects.

Findings

Nanoporous Au stiffens with decreasing ligament size.

Dislocation density increase explains the stiffening effect.

Atomistic simulations match experimental nanoindentation results.

Abstract

Structure is the most distinctive feature of nanoporous metals. The intricate maze of rounded shapes, where ligaments and pores run after each other disorderly, strikes imagination no less than it imparts properties that, tuned by size effects, have no counterpart in the bulk form. Indisputably, nanoporous Au has been the absolute protagonist of the field of study, unveiling the disrupting potential of nanoporous metals in areas ranging from catalysis to energy and sensing. Here, we still focus on nanoporous Au, addressing the long-standing issue of mechanical properties in nanoporous metals. In particular, we investigate how Young's modulus changes with ligament size, being the porosity the same. 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. Ruled out surface stress effects, theoretical considerations relate stiffening to the dislocation density increase.