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Discrete plasticity in sub-10-nm-sized gold crystals

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      Abstract

      Although deformation processes in submicron-sized metallic crystals are well documented, the direct observation of deformation mechanisms in crystals with dimensions below the sub-10-nm range is currently lacking. Here, through in situ high-resolution transmission electron microscopy (HRTEM) observations, we show that (1) in sharp contrast to what happens in bulk materials, in which plasticity is mediated by dislocation emission from Frank-Read sources and multiplication, partial dislocations emitted from free surfaces dominate the deformation of gold (Au) nanocrystals; (2) the crystallographic orientation (Schmid factor) is not the only factor in determining the deformation mechanism of nanometre-sized Au; and (3) the Au nanocrystal exhibits a phase transformation from a face-centered cubic to a body-centered tetragonal structure after failure. These findings provide direct experimental evidence for the vast amount of theoretical modelling on the deformation mechanisms of nanomaterials that have appeared in recent years.

      Abstract

      Deformations in nanocrystals smaller than 10 nm are not well understood. The authors perform compression high-resolution transmission electron microscopy studies of gold nanoparticles, and determine that the nanoparticles deform through the emission of partial dislocations from free surfaces.

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      Most cited references 16

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      Sample dimensions influence strength and crystal plasticity.

      When a crystal deforms plastically, phenomena such as dislocation storage, multiplication, motion, pinning, and nucleation occur over the submicron-to-nanometer scale. Here we report measurements of plastic yielding for single crystals of micrometer-sized dimensions for three different types of metals. We find that within the tests, the overall sample dimensions artificially limit the length scales available for plastic processes. The results show dramatic size effects at surprisingly large sample dimensions. These results emphasize that at the micrometer scale, one must define both the external geometry and internal structure to characterize the strength of a material.
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        Radiation damage in the TEM and SEM.

        We review the various ways in which an electron beam can adversely affect an organic or inorganic sample during examination in an electron microscope. The effects considered are: heating, electrostatic charging, ionization damage (radiolysis), displacement damage, sputtering and hydrocarbon contamination. In each case, strategies to minimise the damage are identified. In the light of recent experimental evidence, we re-examine two common assumptions: that the amount of radiation damage is proportional to the electron dose and is independent of beam diameter; and that the extent of the damage is proportional to the amount of energy deposited in the specimen.
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          Plastic Deformation of Nanometer-Scale Gold Connective Necks.

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            Author and article information

            Affiliations
            [1 ]simpleDepartment of Mechanical Engineering & Materials Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, USA.
            [2 ]simpleSchool of Physics and Technology, Center for Electron Microscopy and MOE Key Laboratory of Artificial Micro- and Nano-structures, Wuhan University , Wuhan 430072, China.
            [3 ]simpleDepartment of Civil and Environmental Engineering, Northwestern University , Evanston, Illinois 60208, USA.
            [4 ]simpleMaterials Science and Engineering Center, Sandia National Laboratories , Albuquerque, New Mexico 87185, USA.
            [5 ]simpleCenter for Integrated Nanotechnologies, Sandia National Laboratories , Albuquerque, New Mexico 87185, USA.
            [6 ]simpleShenyang National Laboratory for Materials Science, Institute of Metal Research, CAS , 72 Wenhua Road, Shenyang 110016, China.
            [7 ]simpleDepartment of Biomedical Engineering, Washington University , Saint Louis, Missouri 63130, USA.
            Journal
            Nat Commun
            Nature Communications
            Nature Publishing Group
            2041-1723
            21 December 2010
            : 1
            : 144
            3105591
            ncomms1149
            10.1038/ncomms1149
            21266994
            Copyright © 2010, Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.

            This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/

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