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 T2: Detonation and Shock Induced Chemistry: Photo-interactions and Initiation |
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Chair: Paulus Grivickas, Lawrence Livermore National Laboratory Room: Grand Ballroom AB |
Thursday, July 13, 2017 11:15AM - 11:45AM |
T2.00001: Laser-induced air shock from energetic materials (LASEM) method for estimating detonation performance: challenges, successes and limitations. Invited Speaker: Jennifer Gottfried Recently, a laboratory-scale method for measuring the rapid energy release from milligram quantities of energetic material has been developed based on the high-temperature chemistry induced by a focused, nanosecond laser pulse. The ensuing exothermic chemical reactions result in an increase in the laser-induced shock wave velocity compared to inert materials; a high-speed camera is used to record the expansion of the shock wave into the air above the sample surface. A comparison of the characteristic shock wave velocities for a wide range of energetic materials revealed a strong linear correlation between the laser-induced shock velocity and the reported detonation velocities from large-scale detonation testing. This has enabled the use of the laser-induced air shock from energetic materials (LASEM) method as a means of estimating the detonation performance of novel energetic materials prior to scale-up and full detonation testing. Here, we report new applications of the LASEM method and discuss the challenges and limitations of the technique. While the extension of LASEM to novel high-nitrogen energetic materials and aged conventional energetic material samples has been quite successful, non-organic and other highly reactive samples present some unique challenges. [Preview Abstract] |
Thursday, July 13, 2017 11:45AM - 12:00PM |
T2.00002: Photoinitiation of energetic materials: New ways to achieve tunable sensitivity Maija Kuklja, Roman Tsyshevsky, Sergey Rashkeev, Fenggong Wang, Anton Zverev, Anatoly Mitrofanov Sensitivity to initiation of detonation of energetic materials (EM) is a complex process detailed mechanisms of which have yet to be established. Laser irradiation opens up new opportunities in triggering and controlling explosive decomposition of EM. It has been long realized that electronically excited states play a key role in explosive chemistry, but only recent studies demonstrated an actual laser-stimulated photochemical initiation of EM. Precise tuning of sensitivity to initiation via photo-excitation appears challenging because all secondary explosives are insulators with band gaps of 4-8 eV. We will discuss feasible mechanisms of photocatalytic decomposition of explosives triggered by the laser excitation with low energies (1.17-2.5 eV). The key in tuning the sensitivity of EM to initiation of chemistry is in the controlled modification of the electronic structure of the explosive-metal oxide interfaces. We will explain how the morphology of metal oxide additives or photoactive organic molecules, their interactions with EM crystalline matrix and laser excitation serve to generate a high density of excited and charged states in the EM composites. -/abstract- Authors: M.M. Kuklja, R. Tsyshevsky, S.N. Rashkeev, F. Wang, A.S. Zverev, A.Y. [Preview Abstract] |
Thursday, July 13, 2017 12:00PM - 12:15PM |
T2.00003: Electronic Properties of Energetic Molecules Under Compression Jeffrey Kay Understanding how the electronic structure of energetic materials change under compression is important for understanding the shock response of materials and mechanisms of shock-induced chemical reactions. In this presentation, changes in the electronic structure of prototypical energetic crystals under high degrees of compression are examined \textit{from the molecule's point of view}, \quad using quantum chemical calculations. The effects of compression on the electronic structure of, and interactions between, the constituent molecules are examined in particular. The insights these results provide into previous experimental observations and theoretical predictions of energetic materials under high pressure are discussed. [Preview Abstract] |
Thursday, July 13, 2017 12:15PM - 12:30PM |
T2.00004: Wavelength-Dependence on the Initiation of Iron-Based Photoactive Explosives Kathryn Brown, Thomas Myers, Steven Clarke Photoactive explosives show promise to be relatively insensitive to impact and friction compared to PETN and other detonator materials, but can be more easily initiated with laser light. Metal-ligand charge transfer (MLCT) complexes have been shown to have tunable explosive properties and absorption profiles, making them strong candidates for laser detonator material. Here, we discuss the synthesis and characterization of several iron-based MLCT complexes, as well as results from recent experiments on their sensitivity to initiation from different wavelengths of laser light. [Preview Abstract] |
Thursday, July 13, 2017 12:30PM - 12:45PM |
T2.00005: Explosively Generated Plasmas: Measurement and Models of Shock Generation and Material Interactions Samuel Emery, Mark Elert, Paul Giannuzzi, Ryan Le, Daniel McCarthy, Igor Schweigert Explosively generated plasmas (EGPs) are created by the focusing of a shock produced from an explosive driver via a conical waveguide. In the waveguide, the gases from the explosive along with the trapped air are accelerated and compressed (via Mach stemming) to such extent that plasma is produced. These EGPs have been measured in controlled experiments to achieve temperatures on the order of 1 eV and velocities as high as 25 km/s. We have conducted a combined modeling and measurement effort to increase the understanding for design purposes of the shock generation of EGPs and the interaction of EGP with explosive materials. Such efforts have led to improved measures of pressure and temperature, spatial structure of the plasma, and the decomposition/deflagration behavior of RDX upon exposure to an EGP. [Preview Abstract] |
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