Nanostructures such as nanowires and nanotubes are envisioned to play a critical role in the next generation of advanced materials for energy, electronic devices, and nano-electromechanical systems. This broad technological applicability has elicited a demand for extensive characterization of the fundamental properties of nanostructures, yet previous studies have neglected to characterize these materials under high strain-rate conditions. This project involves characterizing the mechanical properties of metallic nanowires at high strain rates using transmission electron microscopy and developing new theoretical models to understand the relationship between the structure of the nanowires and their mechanical properties. This fundamental research provides opportunities to develop new educational modules on the subject of mechanical properties testing and stimulates new innovations in the design and manufacture of high performing robust nanoscale devices. As well, training of a graduate student and post-doctoral associate is an inherent part of this research.

TECHNICAL DETAILS: The goal of this research project is to explore for the first time the mechanical response of sub-150 nm-diameter metallic nanowires at high strain rates (up to 10^5 /s) to elucidate the structure-property relationships of nanostructures at high strain rates. To this end, nanowires are experimentally characterized by augmenting microelectromechanical systems (MEMS) mechanical characterization platforms with capabilities for in situ transmission electron microscopy (TEM) testing. The newly designed MEMS platforms with piezoelectric-based actuation and reduced mass are designed to attain strain rates up to 10^5/s. This testing is coupled to dynamic, high-speed TEM (DTEM) in order to obtain high speed imaging of the deformation and failure processes. These state-of the-art experimental techniques yield significant insights toward the understanding of high-strain rate mechanical behavior of metallic nanowires, dislocation processes in confined geometries, and validation of interatomic potentials for molecular dynamics (MD)-based modeling of metals. This validation is extremely beneficial to atomistic modeling, not only for mechanical characterization, but for a breadth of scientific disciplines where MD simulations are used to gain insights into chemical, electrical, and thermal material behavior.

National Science Foundation (NSF)
Division of Materials Research (DMR)
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Judith Yang
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Northwestern University at Chicago
United States
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