The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
Junyu Ou - One of the best experts on this subject based on the ideXlab platform.
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low loss plasmonic metamaterial based on epitaxial gold Monocrystal film
Optics Express, 2012Co-Authors: V A Fedotov, T Uchino, Junyu OuAbstract:We demonstrate high-finesse plasmonic metamaterial with strong resonant response in the near-IR spectral range fabricated using a thin low loss film of gold Monocrystal. The Monocrystal was grown using specially formulated simplified crystal growth procedure based on epitaxial deposition, which makes it readily accessible to both plasmonics and metamaterials communities.
Tane Remington - One of the best experts on this subject based on the ideXlab platform.
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spall strength dependence on grain size and strain rate in tantalum
Acta Materialia, 2018Co-Authors: Tane Remington, Eric N Hahn, Shiteng Zhao, R Flanagan, J C E Mertens, Shima Sabbaghianrad, Terence G Langdon, C E WehrenbergAbstract:Abstract We examine the effect of grain size on the dynamic failure of tantalum during laser-shock compression and release and identify a significant effect of grain size on spall strength, which is opposite to the prediction of the Hall-Petch relationship because spall is primarily intergranular in both poly and nanocrystalline samples; thus, Monocrystals have a higher spall strength than polycrystals, which, in turn, are stronger in tension than ultra-fine grain sized specimens. Post-shock characterization reveals ductile failure which evolves by void nucleation, growth, and coalescence. Whereas in the Monocrystal the voids grow in the interior, nucleation is both intra - and intergranular in the poly and ultra-fine-grained crystals. The fact that spall is primarily intergranular in both poly and nanocrystalline samples is a strong evidence for higher growth rates of intergranular voids, which have a distinctly oblate spheroid shape in contrast with intragranular voids, which are more spherical. The length of geometrically-necessary dislocations required to form a grain-boundary (intergranular) void is lower than that of grain-interior (intragranular) void with the same maximum diameter; thus, the energy required is lower. Consistent with prior literature and theory we also identify an increase with spall strength with strain rate from 6 × 106 to 5 × 107 s−1. Molecular dynamics calculations agree with the experimental results and also predict grain-boundary separation in the spalling of polycrystals as well as an increase in spall strength with strain rate. An analytical model based on the kinetics of nucleation and growth of intra- and intergranular voids and extending the Curran-Seaman-Shockey theory is applied which shows the competition between the two processes for polycrystals.
Hassel Ledbetter - One of the best experts on this subject based on the ideXlab platform.
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Elastic-Stiffness Coefficients of Titanium Diboride.
Journal of Research of the National Institute of Standards and Technology, 2009Co-Authors: Hassel Ledbetter, Takaho TanakaAbstract:Using resonance ultrasound spectroscopy, we measured the Monocrystal elastic-stiffness coefficients, the Voigt C ij, of TiB2. With hexagonal symmetry, TiB2 exhibits five independent C ij: C 11, C 33, C 44, C 12, C 13. Using Voigt-Reuss-Hill averaging, we converted these Monocrystal values to quasiisotropic (polycrystal) elastic stiffnesses. Briefly, we comment on effects of voids. From the C ij, we calculated the Debye characteristic temperature, the Gruneisen parameter, and various sound velocities. Our study resolves the enormous differences between two previous reports of TiB2's C ij.
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Elastic constants of body-centered-cubic titanium Monocrystals
Journal of Applied Physics, 2004Co-Authors: Hassel Ledbetter, Masahiko HiraoAbstract:We report estimates of body-centered-cubic titanium’s Monocrystal elastic constants C11, C12, and C44. Two constants resulted from measuring a pure-titanium polycrystal at high temperatures using resonant-ultrasound spectroscopy. The third constant resulted from assuming a Zener elastic anisotropy and using inversely Kroner’s Monocrystal–polycrystal elastic-constant relationship. Our values are C11=97.7, C12=82.7, and C44=37.5 GPa at 1000 °C.
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Beryllium's Monocrystal and polycrystal elastic constants
Journal of Applied Physics, 2004Co-Authors: Albert Migliori, Hassel Ledbetter, Dan J. Thoma, Timothy W. DarlingAbstract:Using resonant-ultrasound spectroscopy, we measured beryllium’s elastic constants for both a Monocrystal and a polycrystal. Thus, we consider the Monocrystal–polycrystal elastic-constant relationship for hexagonal symmetry. Beside the Cij, we report the Debye characteristic temperature Θ and the Gruneisen parameter γ. We comment on beryllium’s chemical bonding and its remarkably low Poisson ratio.
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Predicted Monocrystal elastic constants of 304-type stainless steel
Physica B-condensed Matter, 2002Co-Authors: Hassel LedbetterAbstract:Abstract The three Monocrystal elastic constants - C 11 , C 12 , C 44 - of 304-type stainless steel are estimated from the polycrystalline bulk and shear moduli together with an empirical C 12 / C 11 value, which is discussed theoretically. The estimate involves a reverse Kroner method for relating Monocrystal and polycrystal elastic constants.
C E Wehrenberg - One of the best experts on this subject based on the ideXlab platform.
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spall strength dependence on grain size and strain rate in tantalum
Acta Materialia, 2018Co-Authors: Tane Remington, Eric N Hahn, Shiteng Zhao, R Flanagan, J C E Mertens, Shima Sabbaghianrad, Terence G Langdon, C E WehrenbergAbstract:Abstract We examine the effect of grain size on the dynamic failure of tantalum during laser-shock compression and release and identify a significant effect of grain size on spall strength, which is opposite to the prediction of the Hall-Petch relationship because spall is primarily intergranular in both poly and nanocrystalline samples; thus, Monocrystals have a higher spall strength than polycrystals, which, in turn, are stronger in tension than ultra-fine grain sized specimens. Post-shock characterization reveals ductile failure which evolves by void nucleation, growth, and coalescence. Whereas in the Monocrystal the voids grow in the interior, nucleation is both intra - and intergranular in the poly and ultra-fine-grained crystals. The fact that spall is primarily intergranular in both poly and nanocrystalline samples is a strong evidence for higher growth rates of intergranular voids, which have a distinctly oblate spheroid shape in contrast with intragranular voids, which are more spherical. The length of geometrically-necessary dislocations required to form a grain-boundary (intergranular) void is lower than that of grain-interior (intragranular) void with the same maximum diameter; thus, the energy required is lower. Consistent with prior literature and theory we also identify an increase with spall strength with strain rate from 6 × 106 to 5 × 107 s−1. Molecular dynamics calculations agree with the experimental results and also predict grain-boundary separation in the spalling of polycrystals as well as an increase in spall strength with strain rate. An analytical model based on the kinetics of nucleation and growth of intra- and intergranular voids and extending the Curran-Seaman-Shockey theory is applied which shows the competition between the two processes for polycrystals.
V A Fedotov - One of the best experts on this subject based on the ideXlab platform.
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low loss plasmonic metamaterial based on epitaxial gold Monocrystal film
Optics Express, 2012Co-Authors: V A Fedotov, T Uchino, Junyu OuAbstract:We demonstrate high-finesse plasmonic metamaterial with strong resonant response in the near-IR spectral range fabricated using a thin low loss film of gold Monocrystal. The Monocrystal was grown using specially formulated simplified crystal growth procedure based on epitaxial deposition, which makes it readily accessible to both plasmonics and metamaterials communities.
