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1 Apr 2012

Volume 111, Issue 7, Articles (07xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 111, 071101 (2012); http://dx.doi.org/10.1063/1.3694674 (23 pages)

Shunfeng Li and Andreas Waag
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back to top Structural, Mechanical, Thermodynamic, and Optical Properties of Condensed Matter

A formation mechanism for ultra-thin nanotwins in highly textured Cu/Ni multilayers

Y. Liu, D. Bufford, S. Rios, H. Wang, J. Chen, J. Y. Zhang, and X. Zhang

J. Appl. Phys. 111, 073526 (2012); http://dx.doi.org/10.1063/1.3702461 (7 pages) | Cited 3 times

Online Publication Date: 13 April 2012

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High density nanotwins with average twin thickness varying from 3 to 6 nm are formed in sputtered highly (111) textured Cu/Ni multilayers, when individual layer thickness is 25 nm or less. Twin interfaces are normal to growth direction. Both maximum twin thickness and volume fraction of twins vary with the individual layer thickness. Coherency stress plays an important role in tailoring the formation of nanotwins. Nanotwins compete with misfit dislocations in accommodating elastic strain energy in epitaxial Cu/Ni multilayers.
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68.65.Ac Multilayers
68.55.jd Thickness
68.55.jm Texture
61.72.Mm Grain and twin boundaries
68.60.Bs Mechanical and acoustical properties

Configurational effects on shock wave propagation in Ni-Al multilayer composites

Paul E. Specht, Naresh N. Thadhani, and Timothy P. Weihs

J. Appl. Phys. 111, 073527 (2012); http://dx.doi.org/10.1063/1.3702867 (12 pages) | Cited 1 time

Online Publication Date: 13 April 2012

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The shock compression response of cold-rolled Ni and Al multilayered composites at various angles of inclination are investigated by employing meso-scale simulations. The orientation of the laminate layers in the multilayered composite is varied at 0°, 45°, and 90° to the direction of shock front propagation to determine and understand the resulting changes in the shock compression response. Real, heterogeneous microstructures, obtained from optical micrographs of the multilayered composite cross-section, are incorporated into the Eulerian, finite volume code, CTH. The simulations are performed to establish the role that the orientation of material interfaces plays in the dispersion and dissipation of the shock wave as well as the US-UP relationship for each configuration. Noticeable differences are observed at the meso-scale in the pressure, temperature, and strain response, as a function of the underlying microstructure. Geometric dispersion is seen to alter the shape of the resulting pressure pulse and inhibit the development of a steady-state shock wave in the laminate geometry. This effect is heightened by the extensive non-uniformities of the layering caused by cold-rolling. Additionally, two-dimensional effects of strain are seen to increase the dissipation of the shock wave through interfacial heating and shearing, resulting in high levels of viscosity and attenuation. While the effects of dispersion are minimal on the bulk response of the multilayered composite, the high rate of dissipation is seen to change the dependence of the shock velocity on the particle velocity, making dissipation a major contributor to the bulk response of these composites under shock compression.
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62.50.Ef Shock wave effects in solids and liquids
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
68.35.Ja Surface and interface dynamics and vibrations

Interface-controlled thermal transport properties in nano-clustered phase change materials

Dongbok Lee, Stephen Dongmin Kang, Hyun-Mi Kim, Dae-Hwan Kang, Ho-Ki Lyeo, and Ki-Bum Kim

J. Appl. Phys. 111, 073528 (2012); http://dx.doi.org/10.1063/1.3703071 (6 pages) | Cited 1 time

Online Publication Date: 13 April 2012

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We measured the thermal conductivity of nano-clustered Ge2Sb2Te5(GST)–TiOx films in situ upon annealing from room temperature to 200 °C by the time-domain thermoreflectance method. The nano-clustered structure was found to significantly reduce the thermal conductivity of the crystallized GST–TiOx films. The reduction is attributed to the thermal resistance provided by the TiOx boundaries, of which the impact is identified by estimating the apparent interfacial thermal conductance of the embedded GST/TiOx interfaces. We suggest how to deal with the electronic contribution to thermal transport for this procedure. The apparent interfacial thermal conductance of the embedded GST/TiOx interfaces was found to tune closer to the intrinsic value 30 MW/m2 K as the microstructure of the films evolved into a distinctly clustered structure.
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66.70.Lm Other systems such as ionic crystals, molecular crystals, nanotubes, etc.
61.46.Bc Structure of clusters (e.g., metcars; not fragments of crystals; free or loosely aggregated or loosely attached to a substrate)
81.40.Gh Other heat and thermomechanical treatments
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