Shear-induced Failure in Jammed Nanoparticle Assemblies

摘要

The state of stress during the bottom-up assembly of nanoparticles strongly correlates with the micro structure of dense nanoparticle aggregates therein. A range of interaction length scales exists in these dry granular systems spanning from particle-scale elastic repulsion to aggregate van der Waals cohesion; the competition among these interactions dominates athermal micro structural evolution under applied stress. In this work, structural optimization is employed to simulate the nano-mechanical physics of athermal densification and jamming. The translational and rotational motions of nanoparticles are optimized to static equilibrium. An initially sparse and random configuration of particles is compacted into a mechanically stable (i.e., jammed) state by densifying the system under various external-loading paths (e.g., hydrostatic, uniaxial, and shear). The resultant jammed structures and their responses to shear exhibit strong correlation with the strength of interactions in addition to particle shape [see Smith et al., Phys. Rev. E. 82, 051304 (2011)]. The structural information, such as particle-particle contact types and pore geometry of the heterogeneous media in these densified systems will aid in understanding energy transport for functional applications such as thermoelectric elements and battery electrodes.