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120 results on '"Duffy, T. S."'

7. X-ray source characterization and sample heating on x-ray diffraction experiments at the National Ignition Facility

Author

Krygier, A., primary, Wehrenberg, C. E., additional, Bernier, J. V., additional, Clarke, S., additional, Coleman, A. L., additional, Coppari, F., additional, Duffy, T. S., additional, Gorman, M. G., additional, Hohenberger, M., additional, Kalantar, D., additional, Kemp, G. E., additional, Khan, S. F., additional, Krauland, C., additional, Kraus, R. G., additional, Lazicki, A., additional, MacDonald, M. J., additional, MacPhee, A. G., additional, Marley, E., additional, Marshall, M. C., additional, May, M., additional, McNaney, J. M., additional, Millot, M., additional, Ping, Y., additional, Poole, P. L., additional, Rygg, J. R., additional, Schneider, M., additional, Sio, H., additional, Stoupin, S., additional, Swift, D., additional, Yeamans, C., additional, Zobrist, T., additional, Smith, R. F., additional, and Eggert, J. H., additional

Published
2022
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8. Hugoniot states and optical response of soda lime glass shock compressed to 120 GPa.

Author

Renganathan, P., Duffy, T. S., and Gupta, Y. M.

Subjects
*FUSED silica, *GLASS, *LASER interferometry, *REFRACTIVE index, *SHOCK waves, *INTERFEROMETRY, MECHANICAL shock measurement
Abstract

In contrast to relatively pure silica glass (fused silica—FS), commercial silica-rich glasses contain significant fractions of additional oxide components. In particular, soda-lime glass (SLG) consists of approximately 71% SiO2 by weight, which raises the question: what is the effect of additional cations on the shock compression response of silica-rich glasses? To address this question, plate impact experiments were conducted to determine the high-pressure Hugoniot states for shocked SLG (37 to 120 GPa) and compared with recently reported results on FS. Using laser interferometry, particle velocity profiles were measured at the impact surface and at the SLG/LiF window interface. In all experiments, the transmitted profiles show a single shock wave, with no features indicative of a phase transformation. The Hugoniot states determined from the wave profiles are described well using a linear shock velocity–particle velocity relation. Interferometry measurements (using 1550-nm wavelength laser) at the impact surface show that SLG is transparent when shocked to 55 GPa, transparent for tens of nanoseconds after impact between 55 and 81 GPa, and opaque beyond 81 GPa. From impact surface measurements, a linear relationship between the apparent and true particle velocity was observed, resulting in a linear relationship between the refractive index (at 1550 nm) and density. At 120 GPa, the SLG density is nearly twice its ambient value, indicating that SLG can achieve highly dense amorphous states. When compared to FS, shocked SLG is much less compressible and likely does not transform to a crystalline phase. A plausible explanation for this difference is suggested. [ABSTRACT FROM AUTHOR]

Published
2020
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11. Ramp compression of diamond to five terapascals

Author

Smith, R. F., Eggert, J. H., Jeanloz, R., Duffy, T. S., Braun, D. G., Patterson, J. R., Rudd, R. E., Biener, J., Lazicki, A. E., Hamza, A. V., Wang, J., Braun, T., Benedict, L. X., Celliers, P. M., and Collins, G. W.

Published
2014
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15. Structure of boron carbide under laser-based shock-compression at 51 GPa

Author

Glam, B., primary, Tracy, S. J., additional, Smith, R. F., additional, Wicks, J. K., additional, Fratanduono, D. E., additional, Gleason, A. E., additional, Bolme, C. A., additional, Prakapenka, V. B., additional, Speziale, S., additional, Appel, K., additional, Lee, H. J., additional, Mac Kinnon, A., additional, Tavella, F., additional, Eggert, J. H., additional, and Duffy, T. S., additional

Published
2020
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17. In situ observation of a phase transition in silicon carbide under shock compression using pulsed x-ray diffraction

Author

Tracy, S. J., primary, Smith, R. F., additional, Wicks, J. K., additional, Fratanduono, D. E., additional, Gleason, A. E., additional, Bolme, C. A., additional, Prakapenka, V. B., additional, Speziale, S., additional, Appel, K., additional, Fernandez-Pañella, A., additional, Lee, H. J., additional, MacKinnon, A., additional, Tavella, F., additional, Eggert, J. H., additional, and Duffy, T. S., additional

Published
2019
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20. Hydrogen and related materials at high density: Physics, chemistry and planetary implications

Author

Hemley, R. J, Mao, H. K, Duffy, T. S, Goncharov, A, Vos, W, Zha, C. S, Eggert, J. H, Li, M, and Hanfland, M

Subjects
Geophysics
Abstract

Recent studies of low-Z molecular materials including hydrogen to multimegabar pressures (less than 300 GPa) have uncovered a range of phenomena relevant to understanding the nature of the interiors of the outer planets and their satellites. Synchrotron x ray diffraction measurements (to 42 GPa) have been used to determine the crystal structure of the solid (hexagonal-close packed) and equation of state. Sound velocities in fluid and solid hydrogen (to 24 GPa) have been inverted to obtain elastic constants and aggregate bulk and shear moduli. In addition, an improved intermolecular potential has been determined which fits both static and shock-wave data. Use of the new potential for the molecular envelope of Jupiter suggests the need for major revisions of existing Jovian models or a reanalysis of reported free oscillations for the planet. Studies at higher pressures (greater than 100 GPa) reveal a sequence of pressure-induced symmetry-breaking transitions in molecular hydrogen, giving rise to three high-pressure phases (1, 2, and 3). Phase 1 is the rotationally disordered hcp phase which persists from low pressure to well above 100 GPa at high temperature (e.g., 300 K). Phase 2 is a low-temperature, high-pressure phase (transition at 100 GPa and 77 K in H2) with spectral features indicative of partial rotational ordering and crystallographic distortion. The transition to Phase 3 at 150 GPa is accompanied by a weakening of the molecular bond, gradual changes in orientational ordering, strong enhancement of the infrared intramolecular vibrational absorption, and strong intermolecular interactions similar to those of ambient-pressure network solids. Studies of the phase diagram reveal a triple point near 130 K and 160 GPa. Higher pressure measurements of vibrational spectra place a lower bound of approximately 250 GPa on the predicted transition pressure for dissociation of molecular hydrogen to form a monatomic metal.

Published
1994

21. Structure and stability of hydrous minerals at high pressure

Author

Duffy, T. S, Fei, Y, Meade, C, Hemley, R. J, and Mao, H. K

Subjects
Geophysics
Abstract

The presence of even small amounts of hydrogen in the Earth's deep interior may have profound effects on mantle melting, rheology, and electrical conductivity. The recent discovery of a large class of high-pressure H-bearing silicates further underscores the potentially important role for hydrous minerals in the Earth's mantle. Hydrogen may also be a significant component of the Earth's core, as has been recently documented by studies of iron hydride at high pressure. In this study, we explore the role of H in crystal structures at high pressure through detailed Raman spectroscopic and x ray diffraction studies of hydrous minerals compressed in diamond anvil cells. Brucite, Mg(OH)2, has a simple structure and serves as an analogue for the more complex hydrous silicates. Over the past five years, this material has been studied at high pressure using shock-compression, powder x ray diffraction, infrared spectroscopy, Raman spectroscopy, and neutron diffraction. In addition, we have recently carried out single-crystal synchrotron x-ray diffraction on Mg(OH)2 and Raman spectroscopy on Mg(OD)2 at elevated pressure. From all these studies, an interesting picture of the crystal chemical behavior of this material at high pressure is beginning to emerge. Some of the primary conclusions are as follows: First, hydrogen bonding is enhanced by the application of pressure. Second, layered minerals which are elastically anisotropic at low pressure may not be so at high pressure. Furthermore, the brucite data place constraints on the effect of hydrogen on seismic velocities and density at very high pressure. Third, the stability of hydrous minerals may be enhanced at high P by subtle structural rearrangements that are difficult to detect using traditional probes and require detailed spectroscopic analyses. Finally, brucite appears to be unique in that it undergoes pressure-induced disordering that is confined solely to the H-containing layers of the structure.

Published
1994

24. Strain relaxation of SiGe islands on compliant oxide.

Author

Yin, H., Huang, R., Hobart, K. D., Suo, Z., Kuan, T. S., Inoki, C. K., Shieh, S. R., Duffy, T. S., Kub, F. J., and Sturm, J. C.

Subjects
THIN films, EPITAXY
Abstract

The relaxation of patterned, compressively strained, epitaxial Si[sub 0.7]Ge[sub 0.3] films transferred to borophosphorosilicate (BPSG) glass by a wafer-bonding and etch-back technique was studied as an approach for fabricating defect-free Si[sub 1-x]Ge[sub x] relaxed films. Both the desired in-plane expansion and undesired buckling of the films concurrently contribute to the relaxation. Their relative role in the relaxation process was examined experimentally and by modeling. Using x-ray diffraction, Raman scattering and atomic force microscopy, the dynamics of in-plane expansion and buckling of Si[sub 0.7]Ge[sub 0.3] islands for island sizes ranging from 10 µm × 10 µm to 200 µm × 200 µm for anneal temperatures between 750 and 800 °C was investigated. Lateral relaxation is favored in small and thick islands, and buckling is initially dominant in large and thin islands. Raising the temperature to lower viscosity of the oxide enhances the rate of both processes equally. For very long annealing times, however, the buckling disappeared, allowing larger, flat, and relaxed islands to be achieved. Cross-sectional transmission electron microscopy observation on a relaxed Si[sub 0.70]Ge[sub 0.30] island revealed no dislocations, confirming that SiGe relaxation on BPSG is a good approach to achieve high quality relaxed SiGe. [ABSTRACT FROM AUTHOR]

Published
2002
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26. Phase stability of iron germanate, FeGeO3, to 127 GPa.

Author

Dutta, R., Tracy, S. J., Stan, C. V., Prakapenka, V. B., Cava, R. J., and Duffy, T. S.

Subjects
PHASE transitions, IRON, HIGH pressure (Science), X-ray diffraction, LASER heating
Abstract

The high-pressure behavior of germanates is of interest as these compounds serve as analogs for silicates of the deep Earth. Current theoretical and experimental studies of iron germanate, FeGeO3, are limited. Here, we have examined the behavior of FeGeO3 to 127 GPa using the laser-heated diamond anvil cell combined with in situ synchrotron X-ray diffraction. Upon compression at room temperature, the ambient-pressure clinopyroxene phase transforms to a disordered triclinic phase [FeGeO3 (II)] at ~ 18 GPa in agreement with earlier studies. An additional phase transition to FeGeO3 (III) occurs above 54 GPa at room temperature. Laser-heating experiments (~ 1200-2200 K) were conducted at three pressures (33, 54, and 123 GPa) chosen to cover the stability regions of different GeO2 polymorphs. In all cases, we observe that FeGeO3 dissociates into GeO2 + FeO at high pressure and temperature conditions. Neither the perovskite nor the post-perovskite phase was observed up to 127 GPa at ambient or high temperatures. The results are consistent with the behavior of FeSiO3, which also dissociates into a mixture of the oxides (FeO + SiO2) at least up to 149 GPa. [ABSTRACT FROM AUTHOR]

Published
2018
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50. STRENGTH OF MATERIALS UNDER STATIC LOADING IN THE DIAMOND ANVIL CELL.

Author

Duffy, T. S.

Subjects
*STRENGTH of materials, *DEAD loads (Mechanics), *DIAMOND anvil cell, *MAGNETIC properties of metals, *X-ray diffraction, *HYDROSTATICS, *ELASTICITY, *SILICON nitride
Abstract

Strength properties of materials under static and dynamic loading are essential quantities for characterizing mechanical behavior. Quantitative measurements of static strengths achieved in the diamond anvil cell can be made using x-ray diffraction in a radial geometry for samples under non-hydrostatic compression. Results for several metals up to 68 GPa show that the ratio of yield strength to shear modulus ranges from 0.01–0.03 and increases weakly with compression. Trends at lower pressure for Re, W, and [variant_greek_epsilon]-Fe are consistent with available data above 1 Mbar. Strong ceramics such as B6O, c-Si3N4, and TiB2 achieve yield strengths as large at 10% of the shear modulus at pressures up to ∼70 GPa. Strengths of materials used as pressure media are quantitatively compared and evaluated. [ABSTRACT FROM AUTHOR]

Published
2007
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