Mechanical properties and scaling laws of nanoporous gold

Abstract

Nanoporous metals are a class of novel nanomaterials with potential applications in many fields such as sensing, catalysis, and fuel cells. The present paper is aimed to investigate atomic mechanisms associated with the uniaxial tensile deformation behavior of nanoporous gold. A phase field method is adopted to generate the bicontinuous open-cell porous microstructure of the material. Molecular dynamics simulations then reveal that the uniaxial tensile deformation in such porous materials is accompanied by an accumulation of stacking faults in ligaments along the loading direction and their junctions with neighboring ligaments, as well as the formation of Lomer–Cottrell locks at such junctions. The tensile strain leads to progressive necking and rupture of some ligaments, ultimately resulting in failure of the material. The simulation results also suggest scaling laws for the effective Young's modulus, yield stress, and ultimate strength as functions of the relative mass density and average ligament size in the material.

Nanoporous Gold—Testing Macro-scale Samples to Probe Small-scale Mechanical Behavior

“…Several numerical simulation studies have used that process to create microstructures that closely resemble experimental NPG. [25,36,48] It is therefore remarkable that spinodal structures with unequal phase fractions are known to disintegrate during coarsening. [49,50] For NPG this implies that networks with low ϕ may exhibit a reduced connectivity density of their load-bearing paths, which would make them anomalously weak and compliant.…”

“…Several of these studies even either report or even presuppose agreement, [2,5,7,12,13,16] while others discuss corrections. [22,23,36,37] Thus, even though it is now widely realized that the Gibson-Ashby scaling relations are not designed for network structures such as NPG, these relations remain indispensable as a starting point for discussing scaling in that material.…”

Mechanical Properties of Nanoporous Au: From Empirical Evidence to Phenomenological Modeling

“…where C2 and C3 are proportionality constants [6]. Along a different line, Liu and Antoniou demonstrated that mass agglomeration at ligament junctions can remarkably affect elastic behavior, inducing a stiffening of the NP metal foam [7].…”

“…In this case, the model exhibited clear limitations, which gave rise to various attempts of modifying the functional dependence of model equations on experimental variables without changing fundamental assumptions [3][4][5][6]. However, recent experimental and theoretical work has definitely shown that limitations arise exactly in connection with the fundamental assumptions of Gibson and Ashby's model, namely the negligible aggregation of mass at ligament junctions and the identification of ligaments with thin beams [7].…”

“…The same conceptual framework has been subsequently used to explain deformation processes involving nanometer-sized ligaments and ligament junctions in NP metals [3][4][5][6]. In this case, the model exhibited clear limitations, which gave rise to various attempts of modifying the functional dependence of model equations on experimental variables without changing fundamental assumptions [3][4][5][6].…”