(9h) Coarsening by Network Restructuring in Model Nanoporous Gold
Nanoporous metals are sponge-like metallic structures with open-cell network structures. They are comprised of interconnected ligaments of nanometer-scale characteristic dimensions. Nanoporous metals have attracted attention both for their intrinsic scientific interest and due to their potential use as actuators, biosensors, fuel cell electrodes and in bone tissue engineering. To realize these promising uses, a fundamental understanding of the stability and morphological evolution of nanoporous metals is necessary. Using atomistic modeling, we show that restructuring of the network of interconnected ligaments causes coarsening in a model of nanoporous gold. The restructuring arises from the collapse of some ligaments onto neighboring ones and is enabled by localized plasticity at ligaments and nodes. This mechanism may explain puzzling experimental observations of occurrence of enclosed voids and reduction in volume in nanoporous metals during their synthesis. An expression is developed for the critical ligament radius below which coarsening by network restructuring may occur spontaneously, setting a lower limit to the ligament dimensions of nanofoams.