Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session O3: NT.1 Novel Techniques: XRD |
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Chair: Kyle Ramos, Los Alamos National Laboratory Room: Fifth Avenue |
Wednesday, July 10, 2013 9:15AM - 9:30AM |
O3.00001: In-situ x-ray diffraction, electrical resistivity and thermal conductivity measurements using a Paris-Edinburgh cell Jason Baker, Ravhi Kumar, Nenad Velisavljevic, Changyong Park, Curtis Kenney-Benson, Yoshio Kono, Andrew Cornelius We have designed a special sample cell assembly for simultaneous and in-situ x-ray diffraction, electrical resistance, and thermal conductivity measurements with Paris-Edinburgh type large volume press. Initial measurements have been performed on bismuth (Bi) to up to 7 GPa and 1000$^{\circ}$C. Using Bi, which has a number of well-investigated solid-solid and solid-melt transitions, we have been able to demonstrate the feasibility of performing in-situ measurements and correlating the measured electrical-thermal-structural properties over a broad range of P-T conditions. The goal of developing this new multi-probe measurement capability is to further improve detection of the onset of solid-solid/melt transitions, relate structural and electrical properties of materials, determine changes in thermal conductivity at high P-T, and ultimately extend the technique for investigating other parameters, such as the Seebeck coefficient of thermoelectric materials. [Preview Abstract] |
Wednesday, July 10, 2013 9:30AM - 9:45AM |
O3.00002: Impact Surface X-ray Diffraction Measurements in Shocked Solids Stefan Turneaure, Y.M. Gupta X-ray diffraction (XRD) measurements at the impact surface, rather than the rear surface, of a shocked crystal have two important advantages: time-dependent material response can be directly monitored without the complications arising from wave reflections, and the shocked crystal may be examined in a constant state over a continuous range of peak stresses. Methods for obtaining XRD data at the impact surface of crystals impacting an X-ray window will be presented. An optical beam parallel to and passing in front of the impact surface is blocked by the projectile several hundred ns before impact providing a trigger (about 10 ns jitter) for the X-ray source and detector. The quantitative accuracy of the impact surface XRD method was established using Si(100) shocked elastically to 5.4 GPa. Impact surface XRD measurements are expected to play an important role at the Dynamic Compression Sector at the Advanced Photon Source. Work supported by DOE/NNSA. [Preview Abstract] |
Wednesday, July 10, 2013 9:45AM - 10:15AM |
O3.00003: X-ray diffraction of shock driven phase transitions at the Linac Coherent Light Source Invited Speaker: Cynthia Bolme The Linac Coherent Light Source provides a brilliant ultrafast pulse of hard x-rays that can be used to probe shock compressed material dynamics. In recent experiments, we have employed a nanosecond laser to shock compress single crystal and polycrystalline silica and silicon, while examining the resulting material dynamics with x-ray diffraction using this x-ray free electron laser. Experimental results on phase transition dynamics will be presented. [Preview Abstract] |
Wednesday, July 10, 2013 10:15AM - 10:30AM |
O3.00004: X-ray diffraction study of ramp-compressed Fe and MgO Federica Coppari, Raymond Smith, Jon Eggert, Ryan Rygg, Amy Lazicki, James Hawreliak, Damien Hicks, Jue Wang, Thomas Duffy, Gilbert Collins The study of Fe and MgO under extreme conditions of pressure and temperature is of great relevance for a variety of fields ranging from basic science and high-pressure condensed matter to geophysics and planetary science. We used laser-driven ramp-compression to achieve 5 and 9 Mbar in Fe and MgO respectively and the structural evolution and transformations were documented by in-situ x-ray diffraction. Velocity interferometry was used to infer the pressure. We found that the hexagonal close-packed (hcp) structure of iron remains stable up to 5 Mbar with no significant change in the c/a ratio. A new phase of MgO was observed above 6 Mbar and it is consistent with the CsCl (B2) structure. The new polymorph remains stable up to 9 Mbar, the highest pressure reached in our experiments. [Preview Abstract] |
Wednesday, July 10, 2013 10:30AM - 10:45AM |
O3.00005: Femtosecond x-ray probes of shock-driven phase transitions in nanocrystals Aaron Lindenberg, Josh Wittenberg, Timothy Miller, Elizabeth Szailgyi We have utilized laser-generated shock waves to induce the wurtzite to rock salt structural phase transformation in cadmium sulfide nanorods, and have probed the resulting dynamics and transition state using femtosecond hard x-rays at the Linac Coherent Light Source (LCLS) in diffraction. Colloidally grown nanocrystals are an ideal model system with which to study phase transformations because they are defect-free single crystalline domains. Simulations of this transformation at the nanoscale have suggested a two--stage model consisting of a compression along the c-axis to form a 5 coordinate h-MgO intermediate followed by compressive shear along the a-axis, with the transformation rate limited by the shear step. We observe a stress-dependent transition path: At higher peak stresses, the majority of the sample is converted directly into the rock salt phase, with no evidence of an h-MgO intermediate prior to rock salt formation. At lower peak stresses, an h-MgO structure is observed. Additionally, the observed transformation stress is $\sim$3GPa, significantly below the $\sim$7GPa required under hydrostatic compression, confirming previous observations of shear catalyzed structural transformation under shock compression. [Preview Abstract] |
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