Browsing by Author "Peng, Cheng"

Now showing 1 - 4 of 4
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    Fracture toughness of the sidewall fluorinated carbon nanotube-epoxy interface
    (AIP Publishing LLC., 2014) Ganesan, Yogeeswaran; Salahshoor, Hossein; Peng, Cheng; Khabashesku, Valery; Zhang, Jiangnan; Cate, Avery; Rahbar, Nima; Lou, Jun
    The effects ofﾠcarbon nanotubeﾠ(CNT)ﾠsidewall fluorination on theﾠinterfaceﾠtoughness of theﾠCNTﾠepoxyﾠinterfaceﾠhave been comprehensively investigated. Nanoscale quantitative single-CNT pull-out experiments have been conducted on individual fluorinatedﾠCNTsﾠembedded in an epoxy matrix,ﾠin situ, within aﾠscanning electron microscopeﾠ(SEM)ﾠusing an InSEMﾮﾠnanoindenter assisted micro-device. Equations that were derived using a continuum fracture mechanics model have been applied to compute theﾠinterfacialﾠfracture energy values for the system. Theﾠinterfacialﾠfracture energy values have also been independently computed by modeling the fluorinated graphene-epoxyﾠinterfaceﾠusingﾠmolecular dynamics simulationsﾠandﾠadhesionﾠmechanisms have been proposed.
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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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    Nanomechanical and Electro-mechanical Characterization of Materials for Flexible Electrodes Applications
    (2013-09-16) Peng, Cheng; Lou, Jun; Dick, Andrew J.; Xu, Qianfan
    Flexible electronics attract research and commercial interests in last 2 decades for its flexibility, low cost, light weight and etc. To develop and improve the electro-mechanical properties of flexible electrodes is the most critical and important step. In this work, we have performed nanomechanical and electro-mechanical characterization of materials for flexible electrode applications, including metallic nanowires (NWs), indium tin oxide (ITO)-based and carbon nanotube (CNT)-based electrodes. First, we designed and developed four different testing platforms for nanomechanical and electro-mechanical characterization purpose. For the nano/sub-micro size samples, the micro mechanical devices can be used for uni-axial and bi-axial loading tests. For the macro size samples, the micro tester will be used for in situ monotonic tensile test, while the fatigue tester can be used for in situ cyclic tensile or bending testing purpose. Secondly, we have investigated mechanical behaviors of single crystalline Ni nanowires and single crystalline Cu nanowires under uni-axial tensile loading inside a scanning electron microscope (SEM) chamber. We demonstrated both size and strain-rate dependence on yield stress of single-crystalline Ni NWs with varying diameters (from 100 nm to 300 nm), and themolecular dynamics (MD) simulation helped to confirm and understand the experimental phenomena. Also, two different fracture modes, namely ductile and brittle-like fractures, were found in the same batch of Cu nanowire samples. Finally, we studied the electro-mechanical behaviors of flexible electrodes in macro scale. We reported a coherent study integrating in situ electro-mechanical experiments and mechanics modeling to decipher the failure mechanics of ITO-based and CNT-based electrodes under tension. It is believed that our combined experimental and simulation results provide some further insights into the important yet complicated deformation mechanisms for nanoscale metals and fracture mechanism for flexible electrodes applications.
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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.