Mechanical properties of ceria nanorods and nanochains; the effect of dislocations, grain-boundaries and oriented attachment

    Authors

    T. X. T. Sayle; B. J. Inkson; A. Karakoti; A. Kumar; M. Molinari; G. Mobus; S. C. Parker; S. Seal;D. C. Sayle

    Comments

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    Abbreviated Journal Title

    Nanoscale

    Keywords

    MOLECULAR-DYNAMICS SIMULATION; AUGMENTED-WAVE METHOD; LOW-TEMPERATURE; STRUCTURAL STABILITY; MATERIALS SCIENCE; SURFACES; NANOPARTICLES; DEFORMATION; OXIDES; TRANSITION; Chemistry, Multidisciplinary; Nanoscience & Nanotechnology; Materials; Science, Multidisciplinary; Physics, Applied

    Abstract

    We predict that the presence of extended defects can reduce the mechanical strength of a ceria nanorod by 70%. Conversely, the pristine material can deform near its theoretical strength limit. Specifically, atomistic models of ceria nanorods have been generated with full microstructure, including: growth direction, morphology, surface roughening (steps, edges, corners), point defects, dislocations and grain-boundaries. The models were then used to calculate the mechanical strength as a function of microstructure. Our simulations reveal that the compressive yield strengths of ceria nanorods, ca. 10 nm in diameter and without extended defects, are 46 and 36 GPa for rods oriented along [ 211] and [ 110] respectively, which represents almost 10% of the bulk elastic modulus and are associated with yield strains of about 0.09. Tensile yield strengths were calculated to be about 50% lower with associated yield strains of about 0.06. For both nanorods, plastic deformation was found to proceed via slip in the {001} plane with direction < 110 > - a primary slip system for crystals with the fluorite structure. Dislocation evolution for the nanorod oriented along [ 110] was nucleated via a cerium vacancy present at the surface. A nanorod oriented along [ 321] and comprising twin-grain boundaries with {111} interfacial planes was calculated to have a yield strength of about 10 GPa (compression and tension) with the grain boundary providing the vehicle for plastic deformation, which slipped in the plane of the grain boundary, with an associated < 110 > slip direction. We also predict, using a combination of atomistic simulation and DFT, that rutile-structured ceria is feasible when the crystal is placed under tension. The mechanical properties of nanochains, comprising individual ceria nanoparticles with oriented attachment and generated using simulated self-assembly, were found to be similar to those of the nanorod with grain-boundary. Images of the atom positions during tension and compression are shown, together with animations, revealing the mechanisms underpinning plastic deformation. For the nanochain, our simulations help further our understanding of how a crystallising ice front can be used to 'sculpt' ceria nanoparticles into nanorods via oriented attachment.

    Journal Title

    Nanoscale

    Volume

    3

    Issue/Number

    4

    Publication Date

    1-1-2011

    Document Type

    Article

    Language

    English

    First Page

    1823

    Last Page

    1837

    WOS Identifier

    WOS:000289306900069

    ISSN

    2040-3364

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