Browsing by Author "Lu, Yang"

Now showing 1 - 4 of 4
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    In Situ Quantitative Mechanical Characterization and Integration of One Dimensional Metallic Nanostructures
    (2011) Lu, Yang; Lou, Jun
    One dimensional (1-D) metallic nanostructures (e.g. nanowires, nanorods) have stimulated great interest recently as important building blocks for future nanoscale electronic and electromechanical devices. In this thesis work, gold and nickel nanowires with various diameters were successfully fabricated, and two dedicated platforms, based on (1) a novel micro mechanical device (MMD) assisted with a quantitative nanoindenter and (2) a TEM-AFM sample holder system, were developed and adopted to perform in situ tensile tests inside SEM and TEM on samples with diameter ranging from a few nanometers to hundreds nanometers. Size-dependent mechanical behavior and different fracture mechanisms of gold nanowires had been revealed and discussed. In addition, we discovered cold welding phenomenon for ultrathin gold nanowires (diameter < 10nm), which is anticipated to have potential applications in the future bottom-up integration of metallic 1-D nanostructures and next-generation interconnects for extremely dense logic circuits.
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    Micromechanical devices for materials characterization
    (2011-11-15) Lou, Jun; Ganesan, Yogeeswaran; Lu, Yang; Peng, Cheng; Rice University; United States Patent and Trademark Office
    The present disclosure describes micromechanical devices and methods for using such devices for characterizing a material's strength. The micromechanical devices include an anchor pad, a top shuttle platform, a nanoindenter in movable contact with the top shuttle platform and at least two sample stage shuttles. The nanoindenter applies a compression force to the top shuttle platform, and the at least two sample stage shuttles move apart in response to the compression force. Each of the at least two sample stage shuttles is connected to the top shuttle platform and to the anchor pad by at least one inclined beam. Methods for using the devices include connecting a sample between the at least two sample stage shuttles and applying a compression force to the top shuttle platform. Application of the compression force to the top shuttle platform results in a tensile force being applied to the sample. Measuring a tip displacement of the nanoindenter is correlated with the sample's strength. Illustrative materials that can be studied using the micromechanical devices include, for example, nanotubes, nanowires, nanorings, nanocomposites and protein fibrils.
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    Strain rate dependent mechanical properties in single crystal nickel nanowires
    (American Institute of Physics, 2013) Peng, Cheng; Zhong, Yuan; Lu, Yang; Narayanan, Sankar; Zhu, Ting; Lou, Jun
    We measure the strain rate dependence of 0.2% offset yield stress in single-crystal nickel nanowires with diameters ranging from 80 to 300 nm. In situ tensile experiments with strain rates from 10 4 s 1 to 10 2 s 1 were conducted, and the small activation volume ( 10b3, where b is the Burgers vector length) and high strain-rate sensitivity ( 0.1) were obtained. These results agreed with atomistic simulations. Our work provides insights into the strength-limiting and rate-controlling mechanism of plasticity at the nanoscale.
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    ‘Unzipping’ of twin lamella in nanotwinned nickel nanowires under flexural bending
    (Taylor & Francis, 2018) Wang, Binjun; Zhang, Hongti; Lou, Jun; Lu, Yang
    We report the fabrication of nickel nanowires with parallel growth-twin structures (‘twin lamella’ along the wire axis) by electrochemical deposition, and demonstrate an interesting twin ‘unzipping’ phenomenon in such nanotwinned nanowires under bending. Through in situ TEM, we found that ‘unzipping’ of twin lamella was achieved by gradually increasing twin spacing along the wire axis via a layer-by-layer twin boundary migration process. Molecular dynamics simulations suggest that partial dislocation slip is responsible for activating the ‘unzipping’, with a multi-step-process involving dislocation loop initiation, expansion and partially annihilation. Our work could provide new insights into the deformation mechanisms of nanotwinned 1-D metallic nanostructures.