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 R4: NM.3 Novel Properties II |
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Chair: Daniel Eakins, Imperial College London Room: Vashon |
Wednesday, July 10, 2013 3:30PM - 4:00PM |
R4.00001: Recent Studies in Electrical Transport Properties at Extreme Pressures Invited Speaker: Takahiro Matsuoka High pressure plays important roles in expanding our understanding of materials. Electrical transport properties significantly change as pressure brings atoms and molecules close together. For example, O2, which is insulator at ambient pressure, becomes metallic and even a superconductor under high pressures exceeding 95 GPa [1, 2]. Recently, conductive H2 has been reported at near around 220 GPa and room temperature [3]. On the other hand, Li and Na have been found to become a semiconductor and an insulator in dense conditions that ion core-valence overlap becomes significant [4,5]. The number of elemental superconductors is increasing with the development of high-pressure techniques. Currently 22 of 52 elemental superconductors are known to superconduct only at high pressures. In this talk we discuss very recent experiments that revealed re-entrant metallic and superconducting phase of Li at above 100 GPa. In addition, the simultaneous measurement system of X-ray diffraction, Raman scattering and electrical resistance in BL10XU/SPring-8 is presented. In order to study electrical properties, including superconductivity in detail, and reveal underlying physics, it is very important to observe crystal structures and electrical resistance simultaneously at high pressures. Li becomes a semiconductor at above 80 GPa accompanied with structural transformation [4]. Recently we have observed experimentally that Li reverts to a metal accompanied with oC40$\to $oC24 structural transition at 120 GPa at 50 K. Simultaneous with re-metallization, superconductivity also reemerges with Tc above 10 K. High electrical resistivity value and abrupt appearance of superconductivity may indicate that Li in oC24 is a poor metal with atypical electronic states. The present study found a phase diagram, a semiconductor phase between superconducting phases, not previously observed for any materials.\\[4pt] [1] S. Desgreniers et al., J. Phys. Chem. 94, 1117 (1990).\\[0pt] [2] K. Shimizu et al., 393, 767 (1998).\\[0pt] [3] M. Eremets {\&} I. Troyan, Nature Phys. 10, 927 (2011).\\[0pt] [4] T. Matsuoka {\&} K. Shimizu, Nature 458, 186 (2009).\\[0pt] [5] Y. Ma et al., Nature 458, 182 (2009). [Preview Abstract] |
Wednesday, July 10, 2013 4:00PM - 4:15PM |
R4.00002: Strain Rate Behavior of HTPB-Based Magnetorheological Materials Chad Stoltz, Kenneth Seminuk, Vasant Joshi It is of particular interest to determine whether the mechanical properties of binder systems can be manipulated by adding ferrous or Magnetostrictive particulates. Strain rate response of two HTPB/Fe (Hydroxyl-terminated Polybutadiene/ Iron) compositions under electromagnetic fields has been investigated using a Split Hopkinson Pressure bar arrangement equipped with aluminum bars. Two HTPB/Fe compositions were developed, the first without plasticizer and the second containing plasticizer. Samples were tested with and without the application of a 0.01 Tesla magnetic field coil. Strain gauge data taken from the Split Hopkinson Pressure bar has been used to determine what mechanical properties were changed by inducing a mild electromagnetic field onto each sample. The data reduction method to obtain stress-strain plots included dispersion corrections for deciphering minute changes due to compositional alterations. Data collected from the Split Hopkinson Pressure bar indicate changes in the Mechanical Stress-Strain curves and suggest that the impedance of a binder system can be altered by means of a magnetic field. [Preview Abstract] |
Wednesday, July 10, 2013 4:15PM - 4:30PM |
R4.00003: Brazilian Disc Experiments on a Cold Spray Material C.H. Braithwaite, B. Aydelotte, A.P. Jardine Characterisation of novel materials presents a number of unique difficulties to the experimenter, however these are problems which must be overcome in order to effectively utilise such materials in systems level applications. A series of experiments were performed to probe the tensile behaviour of a two cold sprayed composite materials containing a mixture of nickel, aluminium, tungsten and zirconium. Data were acquired at two different strain rates and collected using high speed photography, strain gauges, force-extension measurements and digital image correlation techniques. Comparisons were made with modelling on representative microstructural elements in the CTH code. [Preview Abstract] |
Wednesday, July 10, 2013 4:30PM - 5:00PM |
R4.00004: Polycrystalline solids under nonhydrostatic compression: Determination of strength from x-ray diffraction data Invited Speaker: Anil Singh A polycrystalline sample compressed in a diamond anvil cell (DAC) without any pressure transmitting medium develops a stress state at the center of the sample that is axially symmetric about the load axis. The axial stress component is larger than the radial component and the difference between the two is taken as a measure of compressive strength of the sample material at a confining pressure that equals the mean normal stress. The diffraction data taken from a sample under such a stress sate contain a range of information that is absent in the hydrostatic pressure data. A proper analysis of the data using the lattice strain theory yields compressive strength. The data taken with the radial diffraction geometry wherein the incident x-ray beam is perpendicular to the load axis of the DAC gives reliable estimates of strength. The diffraction data obtained with the conventional geometry wherein the incident x-ray beam passes parallel to the DAC axis are not suitable for a full range of analysis. However, reliable estimates of the strength can be obtained by combining the measured pressure-volume data under nonhydrostatic compression and the hydrostat derived from an independent source. The broadening of diffraction lines under nonhydrostatic compression has been also used to estimate the strength of crystalline solids. The effect of elasto-plastic deformation on the strength estimates will be discussed. [Preview Abstract] |
Wednesday, July 10, 2013 5:00PM - 5:15PM |
R4.00005: ABSTRACT WITHDRAWN |
Wednesday, July 10, 2013 5:15PM - 5:30PM |
R4.00006: Response to Stress in Molecular Loops probed by Raman Spectroscopy M. Pena-Alvarez, M. Taravillo, E. del Corro, V.G. Baonza, M. Kertesz, S. Yamago, P. Mayorga, J.T. Lopez-Navarrete, J. Casado CycloParaPhenylenes (CPPs) are cyclic molecules formed by \textit{para}-substituted benzenes. They are in the spot-light of chemistry because, in addition to their simple hoop-shaped $\pi $-conjugated structure, CPPs are thought of as building blocks for the controlled synthesis of carbon nanotubes (CNTs). Although they were firstly synthesized in 2008, their physico-chemical behavior is still poorly known, despite the interest in their optical properties, reactivity and their use as host agents in supramolecular chemistry. Studies about their possible analogies/differences with CNTs and other sp$^{2}$-carbon structures are still lacking. Pressure-dependent Raman experiments provide key information about all the above properties, so here we present a Raman study on CPPs ranging from [6]CPP to [12]CPP. The pressure-induced changes in their vibrational spectra are analyzed in order to check whether pressure induces conformational changes and how these compare to those previously reported in their linear oligophenylenes analogs. To explore their ability to form host-guest complexes with other carbon species, CPP$+$fullerene mixtures subjected to stress and their recovered samples are studied, concluding that the complex C$_{60}$@[10]CPP has been formed. [Preview Abstract] |
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