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 B2: Energetic and Reactive Materials: Films |
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Chair: Michael Armstrong, Lawrence Livermore National Laboratory Room: Grand Ballroom AB |
Monday, July 10, 2017 9:15AM - 9:30AM |
B2.00001: Quasi-Isentropic Compression of Vapor Deposited Hexanitroazobenzene (HNAB): Experiments and Analysis Cole Yarrington, Alexander Tappan, Paul Specht, Robert Knepper Vapor-deposited hexanitroazobenzene (HNAB) is an explosive with unique physical characteristics resulting from the deposition process that make it desirable for the study of microstructure effects. A relatively understudied high explosive (HE), few data are available on the equation of state (EOS) of HNAB reactants or products. HNAB samples exhibiting high density and sub-micron porosity and grain size were prepared using physical vapor deposition onto polymethyl methacrylate (PMMA) and lithium fluoride (LiF) substrates. The samples were quasi-isentropically ramp compressed using VELOCE, a compact pulsed power generator. Evidence of a low pressure phase transition was observed in HNAB. Interferometric measurements of reference and sample interface velocities enabled inference of the unreacted EOS for HNAB using DAKOTA, an optimization toolkit. Initial simulations of the HNAB critical thickness experiment have been carried out using the parameterized EOS, and a products EOS from thermal equilibrium calculations. [Preview Abstract] |
Monday, July 10, 2017 9:30AM - 9:45AM |
B2.00002: Ultrafast Shock Compression Hugoniot Data of beta-CL-20 and TATB Thin Films Joseph Zaug, Michael Armstrong, Paulius Grivickas, Alexander Tappan, Ian Kohl, Mark Rodriguez, Robert Knepper, Jonathan Crowhurst, Elissaios Stavrou, Sorin Bastea The shock induced initiation threshold of two energetic materials, CL-20 and TATB are remarkably different; CL-20 is a relatively shock sensitive energetic material and TATB is considered an insensitive high explosive (IHE). Here we report ultrafast laser-based shockwave hydrodynamic data on the 100 ps timescale with 10 ps time resolution to further develop density dependent unreacted shock Hugoniot equations of state (UEOS) and to elucidate ultrafast timescale shock initiation processes for these two vastly different HEs. Thin film samples were made by vacuum thermal evaporation of the explosive on a deposited aluminum ablator layer. The deposited explosives were characterized by scanning electron microscopy, surface profilometry, and x-ray diffraction. Our preliminary UEOS results (u$_{\mathrm{p}}$ range of 1.3 -- 1.8 km/s) from shock compressed beta-CL-20 agree reasonably well with extrapolated pseudo-velocities computed from epsilon-CL-20 isothermal diamond-anvil cell EOS measurements. [Preview Abstract] |
Monday, July 10, 2017 9:45AM - 10:00AM |
B2.00003: Comparison of detonation spreading in pressed ultra-fine and nano-TATB Joseph Olles, Ryan Wixom, Robert Knepper, Cole Yarrington, Rajen Patel, Victor Stepanov Detonation spreading behavior in insensitive high explosives is an important performance characteristic for initiation-train design. In the past, several variations of the floret test have been used to study this phenomenon. Commonly, dent blocks or multi-fiber optical probes were employed for reduced cost and complexity. We devised a floret-like test, using minimal explosive material, to study the detonation spreading in nano-TATB as compared to ultra-fine TATB. Our test uses a streak camera, combined with photonic Doppler velocimetry, to image the breakout timing and quantify the output particle velocity. The TATB acceptor pellets are initiated using an explosively-driven aluminum flyer with a well characterized velocity. We characterized the two types of TATB by assessing purity, particle morphology, and the microstructure of the consolidated pellets. Our results align with published data for ultra-fine TATB, however the nano-TATB shows a distinct difference where output has a strong dependence on density. The results indicate that control over pellet pore size and pressing density may be used to optimize detonation spreading behavior. [Preview Abstract] |
Monday, July 10, 2017 10:00AM - 10:15AM |
B2.00004: Effect of microstructure on the near-failure detonation behavior of vapor-deposited pentaerythritol tetranitrate (PETN) films Robert Knepper, Eric Forrest, Michael Marquez, Alexander Tappan Physical vapor deposition is an attractive method to produce sub-millimeter explosive samples with precisely controlled microstructure and geometry for studying detonation behavior at near-failure conditions. Pentaerythritol tetranitrate (PETN) is particularly interesting, as the microstructure of vapor-deposited films can be varied substantially by altering the surface energy of the substrate. In this work, we examine PETN films deposited in a sandwich structure with aluminum confinement, elucidating the effect of the confinement layers on the explosive thickness needed to sustain a propagating detonation. The interface energy between the PETN and aluminum can be altered depending on whether the aluminum is exposed to atmosphere prior to PETN deposition, which results in significant changes in density, preferred crystal orientation, and porosity distribution in the films. The resulting microstructures are characterized using scanning electron microscopy and x-ray diffraction. The effects of these changes in microstructure on detonation velocity and failure thickness as a function of confinement thickness are determined, providing an estimate of changes in detonation reaction kinetics with variation in microstructure. SAND2017-1750 A [Preview Abstract] |
Monday, July 10, 2017 10:15AM - 10:30AM |
B2.00005: High-throughput shock investigation of thin film thermites and thermites in fluoropolymer binder Sergey Matveev, Will Basset, Dana Dlott, Evyn Lee, Jon-Paul Maria Investigation of nanofabricated thermite systems with respect to their energy release is presented. The knowledge obtained by utilization of a high-throughput tabletop shock-system provides essential information that can be used to tune properties of reactive materials towards a desired application. Our shock system launches 0.25-0.75 mm flyer plates, which can reach velocities of 0.5-6 km s-1 and shock durations of 4 -- 16 ns. In current studies, emission was detected by a home-built pyrometer. Various reactive materials with differing composition (Al/CuO and Zr/CuO nanolaminates; Al/CuO/PVDF); Al, Zr, CuO standards) and varying interfacial area, were impacted at velocities spanning the available range to ascertain reaction thresholds. Our results show that reaction-impact threshold for the thermite systems under consideration is \textless 1 km/s and that reaction starts at a time as short as 20 ns. Utilization of graybody approximation provides temperature profiles along the reaction time. In future, our goal is to expand detection capabilities utilizing infrared absorption to analyze formation of the products after the shock. [Preview Abstract] |
Monday, July 10, 2017 10:30AM - 10:45AM |
B2.00006: Fabrication and Characterization of Thermite Reactive Nano-Laminates Evyn Lee, Jon-Paul Maria, Sergey Matveev, Dana Dlott, Christina Rost, Patrick Hopkins Results of fabrication and characterization of thermite reactive nano-laminates (RNLs) via magnetron sputtering will be presented. The samples were created in a bilayer geometry of a metal and metal oxide at varied thicknesses to alter the amount of interfacial area readily available to participate in the reaction. Two systems were investigated to characterize the RNL system: Al/CuO and Zr/CuO. The Al/CuO system was fabricated at a constant overall stack thickness of nearly one micron with varied numbers of bilayers (one to seven). Thermal conductivity and interface conductance of the Al/CuO system were investigated via time-domain thermoreflectance (TDTR). The Zr/CuO system was also fabricated at varying bilayer thickness and was characterized via high throughput shock studies to characterize the oxygen transfer process at short time scales. Emissions were obtained via a flyer plate impact at velocities ranging 0.5- 2 km s$^{\mathrm{-1\thinspace }}$at durations of 4-16 ns. The reaction impact threshold was found to be at velocities lower than 0.7($+$/-0.05) km s$^{\mathrm{-1}}$. At impact velocities above the threshold, the reaction onset is seen at approximately 1 $\mu $s. [Preview Abstract] |
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