Y. Ren | Argonne National Laboratory (original) (raw)
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Papers by Y. Ren
The Journal of Physical Chemistry C, 2013
ABSTRACT The generation and growth of nanoparticles by thermal decomposition of organo-Pd precurs... more ABSTRACT The generation and growth of nanoparticles by thermal decomposition of organo-Pd precursors in toluene solution has been studied using in situ small-angle X-ray scattering. The results show that detectable concentrations of particles begin to form at solution temperatures above 130 °C, and both the size and volume of the particles increase with heating temperature and time. The radius of the particles detected ranges from 0.5 ± 0.1 nm to a few nanometers, depending on the temperature and heating time. The structure of the particles was probed by measurement of pair distribution functions, which demonstrated that the particles have structure identical to bulk metallic Pd. The identification of the particles as metallic Pd was confirmed by X-ray absorption near-edge structure spectroscopy, and transmission electron microscopy.
Physical Review B, 2011
The glass transition involves only a minor change in the internal energy, and yet the physical an... more The glass transition involves only a minor change in the internal energy, and yet the physical and mechanical properties of the glass change dramatically. Atomic bonding behavior is critical to understanding these interesting changes. In order to determine the evolution of the atomic structure through the glass transition, we employed in situ synchrotron x-ray scattering measurements as a function of temperature on a model material-Zr-Cu-Al metallic glass. Based upon the study of pair distribution function and the characterization of the free volume in terms of atomic bonding lengths, we found that the relative change of the quantity, N/N (N represents the number of atom pairs), with significantly longer interatomic distances for the nearest atomic pairs, increases abruptly above the glass transition temperature (T g ). These phenomena are interpreted in terms of the tight-bond cluster model developed recently.
Physical Review B, 2010
High-pressure and variable temperature single crystal synchrotron X-ray measurements combined wit... more High-pressure and variable temperature single crystal synchrotron X-ray measurements combined with first-principles based molecular dynamics simulations study diffuse scattering in the relaxor ferroelectric system PSN (PbSc 1/2 Nb 1/2 O3). Constant temperature experiments show pressure induced transition to the relaxor phase at different temperatures characterized by butterfly and rod shaped diffuse scattering around the {h00} and {hh0} Bragg spots, respectively. The simulations reproduce the observed diffuse scattering features as well as their pressure-temperature behavior, and show that they arise from polarization correlations between chemically-ordered regions, which in previous simulations were shown to behave as polar nanoregions. Simulations also exhibit radial diffuse scattering (elongated towards and away from Q=(000)), that persists even in the paraelectric phase, consistent with previous neutron experiments on (PbMg 1/3 Nb 2/3 O3) (PMN).
Journal of Animal Science, 2011
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Acta Materialia, 2010
Using high-energy X-ray diffraction we examined the atomic structure in bulk metallic glass sampl... more Using high-energy X-ray diffraction we examined the atomic structure in bulk metallic glass samples which underwent severe plastic deformation by the high-pressure torsion (HPT) technique. We obtained the atomic pair distribution function (PDF) and determined the changes in the PDFs due to deformation. The observed changes in the PDF clearly show structural disordering, which suggests structural rejuvenation by heavy deformation. However, the changes cannot be explained simply in terms of creating excess free volume, and they indicate that much more extensive atomic rearrangements take place as a consequence of deformation. Also, we suggest that the observed structural change may well be an outcome of local heating due to deformation and may not directly provide the knowledge of the atomistic mechanism of strain localization.
The microstructural characterization of the Zr 60.0 Ti 14.7 Nb 5.3 Cu 5.6 Ni 4.4 Be 10.0 bulk-met... more The microstructural characterization of the Zr 60.0 Ti 14.7 Nb 5.3 Cu 5.6 Ni 4.4 Be 10.0 bulk-metallicglass-matrix composites is investigated using high-energy synchrotron x-ray diffraction. The convoluted diffraction-intensity distribution in the azimuthal direction is naturally yielded from the spatial arrangements of the crystalline dendrites and their amorphous matrix. We facilitate the area selection and the intensity integration of the diffraction collected from a two-dimensional detector to characterize the diffraction intensity of the amorphous matrix. The results enable us to apply the modified Williamson-Hall plots for using the peak width to study the microstrain and micromechanism of the deformation of the crystalline phase.
The Journal of Physical Chemistry C, 2013
ABSTRACT The generation and growth of nanoparticles by thermal decomposition of organo-Pd precurs... more ABSTRACT The generation and growth of nanoparticles by thermal decomposition of organo-Pd precursors in toluene solution has been studied using in situ small-angle X-ray scattering. The results show that detectable concentrations of particles begin to form at solution temperatures above 130 °C, and both the size and volume of the particles increase with heating temperature and time. The radius of the particles detected ranges from 0.5 ± 0.1 nm to a few nanometers, depending on the temperature and heating time. The structure of the particles was probed by measurement of pair distribution functions, which demonstrated that the particles have structure identical to bulk metallic Pd. The identification of the particles as metallic Pd was confirmed by X-ray absorption near-edge structure spectroscopy, and transmission electron microscopy.
Physical Review B, 2011
The glass transition involves only a minor change in the internal energy, and yet the physical an... more The glass transition involves only a minor change in the internal energy, and yet the physical and mechanical properties of the glass change dramatically. Atomic bonding behavior is critical to understanding these interesting changes. In order to determine the evolution of the atomic structure through the glass transition, we employed in situ synchrotron x-ray scattering measurements as a function of temperature on a model material-Zr-Cu-Al metallic glass. Based upon the study of pair distribution function and the characterization of the free volume in terms of atomic bonding lengths, we found that the relative change of the quantity, N/N (N represents the number of atom pairs), with significantly longer interatomic distances for the nearest atomic pairs, increases abruptly above the glass transition temperature (T g ). These phenomena are interpreted in terms of the tight-bond cluster model developed recently.
Physical Review B, 2010
High-pressure and variable temperature single crystal synchrotron X-ray measurements combined wit... more High-pressure and variable temperature single crystal synchrotron X-ray measurements combined with first-principles based molecular dynamics simulations study diffuse scattering in the relaxor ferroelectric system PSN (PbSc 1/2 Nb 1/2 O3). Constant temperature experiments show pressure induced transition to the relaxor phase at different temperatures characterized by butterfly and rod shaped diffuse scattering around the {h00} and {hh0} Bragg spots, respectively. The simulations reproduce the observed diffuse scattering features as well as their pressure-temperature behavior, and show that they arise from polarization correlations between chemically-ordered regions, which in previous simulations were shown to behave as polar nanoregions. Simulations also exhibit radial diffuse scattering (elongated towards and away from Q=(000)), that persists even in the paraelectric phase, consistent with previous neutron experiments on (PbMg 1/3 Nb 2/3 O3) (PMN).
Journal of Animal Science, 2011
the World Wide Web at:
Acta Materialia, 2010
Using high-energy X-ray diffraction we examined the atomic structure in bulk metallic glass sampl... more Using high-energy X-ray diffraction we examined the atomic structure in bulk metallic glass samples which underwent severe plastic deformation by the high-pressure torsion (HPT) technique. We obtained the atomic pair distribution function (PDF) and determined the changes in the PDFs due to deformation. The observed changes in the PDF clearly show structural disordering, which suggests structural rejuvenation by heavy deformation. However, the changes cannot be explained simply in terms of creating excess free volume, and they indicate that much more extensive atomic rearrangements take place as a consequence of deformation. Also, we suggest that the observed structural change may well be an outcome of local heating due to deformation and may not directly provide the knowledge of the atomistic mechanism of strain localization.
The microstructural characterization of the Zr 60.0 Ti 14.7 Nb 5.3 Cu 5.6 Ni 4.4 Be 10.0 bulk-met... more The microstructural characterization of the Zr 60.0 Ti 14.7 Nb 5.3 Cu 5.6 Ni 4.4 Be 10.0 bulk-metallicglass-matrix composites is investigated using high-energy synchrotron x-ray diffraction. The convoluted diffraction-intensity distribution in the azimuthal direction is naturally yielded from the spatial arrangements of the crystalline dendrites and their amorphous matrix. We facilitate the area selection and the intensity integration of the diffraction collected from a two-dimensional detector to characterize the diffraction intensity of the amorphous matrix. The results enable us to apply the modified Williamson-Hall plots for using the peak width to study the microstrain and micromechanism of the deformation of the crystalline phase.