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 L5: GP1: Geophysics III |
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Chair: Zsolt Jenei, Lawrence Livermore National Laboratory Room: Cascade I |
Tuesday, July 9, 2013 3:30PM - 3:45PM |
L5.00001: Pressure-induced structural change in molten basalt Chrystele Sanloup, James Drewitt, Phillip Dalladay-Simpson, Donna Morton, Nachiketa Rai, Zuzana Konopkova, Wim van Westrenen, Wolfgang Morgenroth Magmas are produced at depth in the Earth, and occurrences of their presence at greater depths are reported based on seismological information, such as the 410 discontinuity or atop the core-mantle boundary. Understanding the presence and eventual stability of magmas in the deep mantle requires a knowledge of their physical properties. However, this has been impeded for a long time due to the challenging nature of the experiments. In the recent years, structural and density information on silica glass have been obtained up to record pressures of up to 100 GPa, a first major step towards obtaining data on the molten state. Here, the structure of molten basalt is reported up to 60 GPa by means of in situ x-ray diffraction, and structural changes are evidenced. Silicon coordination increases from 4 at ambient conditions to 6 at 35 GPa, similarly to what has been reported in silica glass. Compressibility of the melt above completion of Si coordination change is lower than at lower pressure ($P$) conditions, implying that a single equation of state can not accurately describe density evolution of silicate melts over the whole mantle $P$-range. It also implies that melts can be buoyantly stable circa 35-40 [Preview Abstract] |
Tuesday, July 9, 2013 3:45PM - 4:00PM |
L5.00002: Ultrafast x-ray studies on the dynamics of structural transitions in amorphous and crystalline SiO2 Arianna Gleason, Cindy Bolme, Wendy Mao, Wenge Yang, Hae Ja Lee, Bob Nagler, Eric Galtier, Despina Milathianaki, Richard Sandberg Silica (SiO2) and its phase transitions at high pressure and temperature are of paramount importance to geophysics as it is the dominant chemical constituent of the Earth's mantle. Knowledge of its properties and behavior under pressure is essential to interpretation of seismic studies, high velocity cratering impact events, and to understanding the dynamics and evolution of the terrestrial planetary interiors. Here we present unprecedented experimental results on the phase transition kinetics of amorphous and crystalline SiO2 with sub-nanosecond resolution. These novel experiments, performed at LCLS, SLAC are the first ever measurements of a non-metal showing transitions from amorphous SiO$_{\mathrm{2}}$ and single crystal -quartz to polycrystalline coesite and/or stishovite. X-ray diffraction patterns were collected with varied time delays and optical laser powers to achieve a wide sampling of pressure-temperature-time-phase space. Our datasets include information on time-resolved phase growth, grain size and texture development/evolution. [Preview Abstract] |
Tuesday, July 9, 2013 4:00PM - 4:15PM |
L5.00003: Dynamic dehydration processes of porous antigorite by impact Toshimori Sekine, Tomoaki Kimura, Tutomu Mashimo, Takamichi Kobayashi Antigorite Hugoniot indicates that it is stable up to a pressure of $\sim$50 GPa. When antigorite is under a circumstance surrounding pores in natural meteorite, the stability may change with local temperature rising effects. Since antigorite acts a potential carrier of water in the solar system, the dynamic dehydration process is a key to understand the ability of carrier. We carried out shock recovery experiments in a pressure range between 5 GPa and 60 GPa. The recovered samples were investigated using XRD, TEM, and TG-DTA. In order to recover samples, it was found that the amount of sample was critical. There seems to be two steps of dehydration processes; limited dehydration below 20 GPa and violent dehydrations above 20 GPa. The violent reaction depends on the porosity of a sample. The TG-DTA results couples with XRD indicate that dehydration products are forsrerite and enstatite without their high-pressure forms and hydrous minerals. The amount of amorous phase was only a trace based on the TEM observations, implying that dehydration reaction may have occurred at high temperatures for the crystals to grow during pressure release. [Preview Abstract] |
Tuesday, July 9, 2013 4:15PM - 4:30PM |
L5.00004: Shock compression of geological materials Simon Kirk, Chris Braithwaite, David Williamson, Andrew Jardine Understanding the shock compression of geological materials is important for many applications, and is particularly important to the mining industry. During blast mining the response to shock loading determines the propagation speed and resulting fragmentation of the rock. The present work has studied the Hugoniot of two geological materials; Lake Quarry Granite and Gosford Sandstone. For samples of these materials, the composition and microstructure was characterised in detail. The Hugoniot of Lake Quarry Granite was predicted from this information, as the material is fully dense, in good agreement with the measured Hugoniot. Gosford Sandstone is porous and undergoes compaction during shock loading. Such behaviour is similar to a granular material and we show how it can be described using shock compaction models. [Preview Abstract] |
Tuesday, July 9, 2013 4:30PM - 5:00PM |
L5.00005: Structure of multi-component oxide glasses under static and shock compression Invited Speaker: Sung Keun Lee The structures of multi-component oxide glasses (quaternary and beyond) under both static and dynamic compression have not been well understood as most of the previous studies focused on the pressure-induced bonding transition in rather simple model melts (e.g., from single-component, to ternary) that are subjected to less inhomogeneous broadening. Recent advances in element-specific experimental probe of local structures including non-resonant synchrotron inelastic x-ray scattering (IXS) and multi-dimensional solid-state NMR unveil previously unknown structural details of the structural changes in the diverse multi-component oxide glasses under static and dynamic compression. Here, we provide an overview of the recent progress and insights by IXS and NMR into electronic structures of oxide glasses at high pressure. Contrary to an expected complexity in densification for multi-component oxide glasses, experimental results for multi-component amorphous oxide at high pressure demonstrate that the pressure-induced changes in melt structures show a simplicity where the effect composition can be somewhat predicted and quantified [1, 2]. The pronounced simplicity in the melt-densification provides useful atomistic link between the macroscopic properties and the nature of changes in the melt structure at high pressures, such as those deep within the magma ocean [3].\\[4pt] [1] Lee, Proc. Nat. Aca. Sci. (2011), 108, 6847; Sol. St. NMR. (2010), 38, 45\\[0pt] [2] Lee, Park, Kim, Tschauner, Asimow, Bai, Xiao, {\&} Chow, Geophys. Res. Letts. (2012) 39 5306\\[0pt] [2] Lee, Mosenfelder, Park, Asimow (2013) in preparation [Preview Abstract] |
Tuesday, July 9, 2013 5:00PM - 5:15PM |
L5.00006: Deformation response of rocky material for a range of stress states and strain rates Angela Stickle, K.T. Ramesh The failure of rocky materials under impact conditions will occur in a rapidly evolving, multi-axial stress state. Significant improvements in understanding impact processes, then, can come from physically-based models for the dynamic response of materials under general stress states. To provide insight into the deformation response of geologic materials under impact conditions, we present results from a suite of failure experiments on basalt under general stress states. Compression and tension/torsion Kolsky bars are used to illustrate the dynamic (100-1000 1/s) compressive, tensile, and shear responses of the material. Quasi-static compression experiments are used to determine deformation mechanisms at low rates (10$^{-3}$-10$^{-4}$ 1/s). Using results from these experiments, the evolution of strength and damage mechanisms with strain rate can be examined. High-speed imaging (frames every 2-4 $\mu $sec) is used to illustrate crack speeds and failure processes during experiments, while post-mortem SEM analysis provides information about fracture surfaces and relevant damage mechanisms across strain rates. [Preview Abstract] |
Tuesday, July 9, 2013 5:15PM - 5:30PM |
L5.00007: Anisotropic elastic-plastic transition of MgO under shock compression Xun Liu, Kenichi Ogata, Xianming Zhou, Williams J. Nellis, Toshimori Sekine, Tsumoto Mashimo The failure of brittle materials under uniaxial shock-loading has been the subject of many discussions. But the physical explanation of the yield behavior remains poorly understood. In this study, we focus on the elastic-plastic transition of MgO single crystal, which is the simplest metal oxide with a cubic structure, and can be studied as a prototype. Otherwise, the equation of state (EOS) of MgO is also a key problem because of its geophysical importance and its application as pressure scale in static compression experiments. The interface particle velocity profile between MgO single crystal and LiF window was measured by a VISAR system. The Hugoniot elastic limits (HELs) along \textless 100\textgreater\ direction are measured to be around 4.2 GPa, and keep constant under different loading pressure, while the HELs along \textless 110\textgreater\ direction is much higher, with a minimum value of 10GPa and increase with final pressure. When shock along \textless 100\textgreater\ direction, MgO suffers a catastrophically loss of shear strength, while along \textless 110\textgreater\ direction, the deformation is more close to ideal elastic-plastic change. These differences indicate different deformation mechanism along different loading direction, which will be discussed later. [Preview Abstract] |
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