An analytical model for the critical shell thickness in core/shell nanowires based on crystallographic slip |
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Authors: | HJ Chu CZ Zhou J Wang IJ Beyerlein |
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Institution: | 1. Department of Mechanics, College of Science, Shanghai University, Shanghai 200444, China;2. MST Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA;3. Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA;4. Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO 65409, USA |
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Abstract: | Employing crystal plasticity theory and micromechanics inclusion theory, we developed a full-strain relaxation model under isotropic assumption of materials properties to predict the dependence of the critical shell thickness (CST) for defect-free core/shell nanowires (NWs) on their growth direction. Unlike prior models, we consider three important factors in the energetic analysis (1) the self-energy of a dislocation loop in a finite domain, (2) the three-dimensional mismatch strains that develop in core/shell NWs (axial, radial and tangential directions) as a result of the finite NW geometry and the lattice mismatch between the core and shell materials, and (3) the three-dimensional plastic strains from misfit dislocations that nucleate to relax the mismatch strains. With these, the full-relaxation model is able to reveal that (i) the variation of the CST with growth direction depends on the core radius, (ii) misfit dislocations will not nucleate when the core radius falls below a critical value, (iii) the CST tends to a constant as the core radius increases, and (iv) the CST predicted by prior uniaxial-strain relaxation models is a lower bound. |
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Keywords: | Critical shell thickness Crystalline slip Dislocations Core/shell nanowires Green's function |
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