Bulletin of the American Physical Society
17th Biennial International Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 56, Number 6
Sunday–Friday, June 26–July 1 2011; Chicago, Illinois
Session S4: Experimental Developments III |
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Chair: Daniel Eakins, Imperial College Room: Renaissance Ballroom C |
Thursday, June 30, 2011 9:15AM - 9:30AM |
S4.00001: A thin-film Hugoniot measurement using a laser-driven flyer plate Hiroki Fujiwara, Kathryn Brown, Dana Dlott A laser-driven flyer plate and a high-speed 8 GHz all-fiber displacement interferometer (DISAR) were used to measure the Hugoniot of polymer thin films (a few micrometers thick) such as PMMA (polymethyl methacrylate) under steady-state shockwave propagation. Results were obtained using conventional methods such as measuring the impact velocity and knowing the Hugoniot of the flyer-plate material, but these were inaccurate. Instead we incorporated nanometer-thick gauge layers in the thin film, whose locations were precisely known. This material is based on work supported by the US Army Research Office under grant W911NF-10-0072, and the US Air Force Office of Scientific Research under award number FAA9550-09-1-0163. [Preview Abstract] |
Thursday, June 30, 2011 9:30AM - 9:45AM |
S4.00002: Use of a fast near-infrared spectrometer for absorption and emission measurements within the expanding blast wave of a high explosive Jon Koch, Scott Piecuch, James Lightstone, Joel Carney We demonstrate the use of a fast InGaAs array and spectrometer to measure properties related to near-infrared absorption and emission (750 nm -1500 nm) following a high explosive detonation. Using a broadband light source and a rigid absorption gauge, gas temperatures are measured at a rate of 20 kHz for a period of several milliseconds behind the blast wave from a 20 g PETN detonation. The temperature and concentration of water vapor is determined by fitting experimental transmission spectra to a simulated database. Strong emission signatures obtained during the breakout event (integrated over approximately the first 20 microseconds) indicate the presence of high energy nitrogen atoms with temperatures as high as 9700 K. Measurements from water absorption at a distance of 23 cm from the charge indicate temperatures decaying from 1600 K to 600 K during the first few milliseconds. These measurements are intended to aid the development of detonation and explosive simulations. [Preview Abstract] |
Thursday, June 30, 2011 9:45AM - 10:15AM |
S4.00003: Dynamic compression of semiconductors: deformation potentials to new phenomena Invited Speaker: Semiconductors are central to technological applications, including optoelectronic devices such as solar cells and light emitting diodes. These multilayered devices experience strains up to 1{\%} due to lattice mismatch at different material interfaces; strains as large as 10{\%} are anticipated in future devices based on semiconductor quantum structures. Although large strains are expected to alter properties of operating devices, definite predictions of these changes are difficult due to the inherent limitations of static compression methods. Recent studies at the Institute for Shock Physics have demonstrated that uniaxial strain conditions during dynamic compression can overcome these limitations and reveal important electronic structure changes in semiconductors. Several examples will be presented, including the accurate determination of deformation potentials in GaN and GaP at high strains, the transformation of GaAs from a direct to an indirect gap semiconductor, the different nature of impurities under compression in GaP, and the dramatic reduction of carrier lifetimes in compressed GaAs. In the future, dynamic compression studies are expected to shed light on a range of time-resolved phenomena in bulk and nanoscale materials. [Preview Abstract] |
Thursday, June 30, 2011 10:15AM - 10:30AM |
S4.00004: Pressure-driven assembly of nanoparticle arrays and nanostructures Hongyou Fan Due to the size- and shape-dependent properties, nanoparticles have been successfully used as functional building blocks to fabricate multi-dimensional (D) ordered assemblies for applications in nanoelectronic and optic devices. To date, fabrications of ordered nanoparticle assemblies have been performed only at ambient pressure through specific interparticle chemical or physical interactions such as van der Waals interactions, dipole-dipole interaction, chemical reactions, etc. Recently we have discovered that an external pressure can be utilized to engineer nanoparticle assembly and to fabricate new nanoparticle architectures without relying on specific nanoparticle interactions. We show that under a hydrostatic pressure field, the unit cell dimension of a 3D ordered nanoparticle arrays can be manipulated to reversibly shrink, allowing fine-tuning of interparticle separation distance. Moreover, under a uniaxial pressure field, nanoparticles are forced to contact and coalesce, forming 1D nanostructures (nanorods or nanowires) and ordered ultrahigh density arrays. This mechanical compression process opens up a new pathway to the engineering and fabrication of nanoparticle architectures. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corp., a wholly owned subsidiary of Lockheed Martin Corp., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Thursday, June 30, 2011 10:30AM - 10:45AM |
S4.00005: Formation of nanostructured arrays through magnetic ramp compression Randy J. Hickman, Tommy Ao, Jack L. Wise, Hongyou Fan Recently, pressure-driven assembly of spherical nanoparticles and formation of one to three dimensional, nanostructured arrays have been demonstrated using diamond anvil cells. Extending the pressure-driven assembly of nanostructured arrays from static diamond anvil cells to dynamic compression techniques has been studied. Shock compression would be unsuitable for synthesis of nanostructures because the evaluated temperatures of shock states would induce melting of nanoparticles. However, magnetic ramp compression has been demonstrated to produce smooth, shockless loading with low temperature states suitable for nanostructure synthesis. Experiments have been performed on the Veloce pulsed power generator to ramp compress nanoparticles into nanostructured arrays, which utilizes a soft-recovery assembly to retrieve formed nanostructure samples. Sandia National Laboratories is a multi-program laboratory 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] |
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