Bulletin of the American Physical Society
15th APS Topical Conference on Shock Compression of Condensed Matter
Volume 52, Number 8
Sunday–Friday, June 24–29, 2007; Kohala Coast, Hawaii
Session H5: X-ray Diffraction/Scattering II |
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Chair: Reed Patterson, Lawrence Livermore National Laboratory Room: Fairmont Orchid Hotel Plaza III |
Tuesday, June 26, 2007 1:45PM - 2:00PM |
H5.00001: A Geometry for Sub-Nanosecond X-Ray Diffraction from Laser-Shocked Polycrystalline Foils Justin Wark, Andrew Higginbotham, Giles Kimminau, William Murphy, Bob Nagler, Thomas Whitcher, James Hawreliak, Dan Kalantar, Hector Lorenzana, Bruce Remington, Huw Davies, Lee Thornton, Nigel Park, Stan Lukezic In situ picosecond X-ray diffraction has proved to be a useful tool in furthering our understanding of the response of shocked crystals at the lattice level. To date the vast majority of this work has used single crystals as the shocked samples, owing to their diffraction efficiency, although the study of the response of polycrystalline samples is clearly of interest for many applications. We present here the results of experiments to develop sub-nanosecond powder/polycrystalline diffraction using a cylindrical pinhole camera. By allowing the incident X-ray beam to impinge on the sample at non-normal angles, the response of grains making a variety of angles to the shock propagation direction can potentially be interrogated. [Preview Abstract] |
Tuesday, June 26, 2007 2:00PM - 2:15PM |
H5.00002: High pressure X-ray diffraction studies on Bi$_{2-x}$Sb$_{x}$Te$_{3}$ (x=0,1,2) materials Matthew Jacobsen, Ravhi Kumar, Andrew Cornelius Recently Bi$_{2}$Te$_{3}$ based thermoelectric materials have gained importance due to their high thermoelectric figure of merit in thin films [3]. Pressure tuning of the thermoelectric figure of merit has been reported for several materials [1],[2]. In order to investigate the bulk properties of Bi$_{2}$Te$_{3}$, Sb$_{2}$Te$_{3}$, and their solid solution in detail, we have performed structural studies up to 20 GPa. Our diffraction results show that all three compounds transform from the ambient pressure structure to a high pressure phase between 5 and 7 GPa. Details of the results will be discussed in this presentation. [1]Chen, G., Dresselhaus, M.S., Dresselhaus, G., Fleurial, J.-P., and Caillat, T. \emph{Recent developments in themoelectric materials}. International Materials Reviews, \textbf{48}, 45-66 (2003). [2]Rowe, D.M. \emph{CRC Handbook of Thermoelectric Materials}. CRC Press, 1995. [3]Venkatasubramanian, R., Silvola, E., Colpitts, T., and O'Quinn, B. \emph{Thin-film thermoelectric devices with high room-temperature figures of merit}. Nature, \textbf{413}, 597-602, 2001. [Preview Abstract] |
Tuesday, June 26, 2007 2:15PM - 2:30PM |
H5.00003: Static High Pressure X-ray Diffraction of Ti-6Al-4V Gary Chesnut, Nenad Velisavljevic, Lilliana Sanchez Ti-6Al-4V was examined under static-high pressure conditions using a diamond anvil cell. The angle-dispersive x-ray diffraction experiments were performed at the Advanced Photon Source, Argonne National Laboratory. Radial and axial geometry were used to examine multiple samples. The purpose of the experiment was to generate pressure-volume data at room temperature (which is non-existent in literature) and to examine deviatoric stress effects on such a hard alloy. [Preview Abstract] |
Tuesday, June 26, 2007 2:30PM - 2:45PM |
H5.00004: Radiation-induced damage studies of energetic materials. Michael Pravica, Hubertus Giefers, Zachary Quine, Edward Romano, Sean Bajar, Brian Yulga, Wenge Yang, Hans Peter Liermann, Daniel Hooks We present studies of synchrotron radiation-induced decomposition of PETN and TATB under conditions of high pressure, high temperature, and crystalline orientation. We have found that the decomposition rate varies dramatically under all three of these variables. The experiments were performed using white beam synchrotron radiation at the 16 BM-B and 16 BM-D sectors of the HP-CAT beamline at the Advanced Photon Source. Diffraction line intensities were measured as a function of time using energy-dispersive methods and angular-dispersive methods TATB showed dramatic slowing of the decomposition rate with pressure implying a positive activation volume of the activated complex whereas PETN showed little change in decomposition rate with pressure. Increased temperature increased the radiation-induced decomposition rate of TATB. Finally, we found dramatic differences in the radiation-induced decomposition rate for single crystals of explosives depending upon their orientation relative to the polarized x-ray beam. [Preview Abstract] |
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