Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session P5: Phase Transitions V |
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Chair: Geoffrey Cox, AWE Room: Regency Ballroom B |
Wednesday, July 12, 2017 11:15AM - 11:30AM |
P5.00001: Results of investigations of phase transitions of shock compressed metals. Mikhail Zhernokletov, Alexey Kovalev, Alexey Podurets, Vladimir Simakov Formations of new crystalline modifications in compressed substances are undeniably among interesting phenomena in physics of shock waves. Since the early 2000, experts from IPE RFNC-VNIIEF have been actively involved in efforts aimed to determine ranges of melting and recording phase transitions at shock adiabats of metals and organic substances by measuring sound velocities with use of the rarefaction overtake technique, which employs indicator liquids and pressure profiles by manganine and PVDF pressure gauges. In the pressure range from 4 to 12~GPa, a two-wave structure was recorded in cerium. Analysis of structures of the shock wave and rarefaction wave in the range (0.6-6.0)~GPa points to the fact that a rarefaction shock wave is formed in the release phase in cerium. Post-test investigations of the cerium samples by the X-ray structural analysis have not revealed changes in cerium phase structure. Basing on our investigations, cerium starts melting at shock adiabat at the pressure of \textasciitilde ~13~GPa. Jumps of sound velocities, which were revealed in tin and zinc at the pressures of (60~-~90) GPa and (105~-~130)~GPa, can be respectively associated with the beginning and completion of melting at their shock adiabats. [Preview Abstract] |
Wednesday, July 12, 2017 11:30AM - 11:45AM |
P5.00002: Isentropic compression of liquid metals near the melt line. Christopher Seagle, Andrew Porwitzky A series of experiments designed to study the liquid metal response to isentropic compression have been conducted at Sandia's Z Pulsed Power Facility. Cerium and Tin have been shock melted by driving a quasi-ballistic flyer into the samples followed by a ramp compression wave generated by an increased driving magnetic field. The sound speed of the liquid metals has been investigated with the purpose of exploring possible solidification on ramp compression. Additional surface sensitive diagnostics have been employed to search for signatures of solidification at the window interface. Results of these experiments will be discussed in relation to the existing equation of state models and phase diagrams for these materials as well as future plans for exploring the response of liquid metals near the melt line. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Wednesday, July 12, 2017 11:45AM - 12:00PM |
P5.00003: Shock driven melting and resolidification upon release in cerium Cindy Bolme, Curt Bronkhorst, Don Brown, Frank Cherne, Jason Cooley, Michael Furlanetto, Arianna Gleason, Brian Jensen, Charles Owens, Suzanne Ali, Dayne Fratanduono, Eric Galtier, Eduardo Granados, Hae Ja Lee, Bob Nagler The temperature rise due to increasing entropy during shock compression and the corresponding temperature decrease due to isentropic expansion upon release cause the physics of melting and solidification under dynamic pressure changes to differ fundamentally from the more common liquid-solid transitions governed by thermal diffusion. We investigated laser shock driven melting and resolidification during release in cerium to examine the dynamics of these processes. Cerium was selected as the material of study due to the low pressure at which $\gamma$-cerium melts along the principle Hugoniot and due to cerium's anomalous melt boundary at low pressure, which facilitates its transition from liquid to solid during isentropic release. The structural phase of cerium was probed with X-ray diffraction using the LCLS X-ray free electron laser, which provided \textit{in situ} measurements of the transition dynamics. The experimental results will be presented showing the resolidification occurring over 10s of ns. [Preview Abstract] |
Wednesday, July 12, 2017 12:00PM - 12:15PM |
P5.00004: Technique in analyzing experimental double shock data to infer a solid-solid phase transition within cerium Frank Cherne, Brian Jensen In the past decade many experiments have been performed looking at various aspects of the dynamic response of cerium metal. Recent experiments looking at off-principle hugoniot have been made and here we present an approach for interpreting the results of these double shock experiments. Double shock experiments are difficult to analyze with the potential of being nearly intractable due to the construction of the experiments. Using a simple one dimensional hydrodynamic code, calculations are performed to match the first and second shock states and the times of arrival. Upon matching velocity time history at the sample window interface, a $U_s$ was determined from the calculation. A two state linear $U_s-u_p$ model with a transitional density switch was developed to best model the experimental data set. The best parameter set shows an inflection point around 12-13 GPa which is near where the $\alpha-\epsilon$ phase transition has been observed in static compression experiments at a temperature. [Preview Abstract] |
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