Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session K2: ERM: Reactive powders and nanoenergetics |
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Chair: Robert Knepper, SNL Room: Grand Ballroom II |
Tuesday, June 18, 2019 2:00PM - 2:15PM |
K2.00001: Combined fragment recovery and overpressure measurements from a reactive material cased charge Joseph Hooper, Jacob Kline The fragmentation of a reactive material on impact or explosive launch has proven challenging to model but critical to understanding its lethality. Here we fabricate simple, pure metal reactive cases made from isostatically pressed aluminum powder, and directly measure their fragmentation and combustion via three combined tests. In the first, the charge is detonated in an artificial snow medium to recover all debris produced by explosive launch. Second, an identical charge is detonated in an argon-filled chamber and the debris is again recovered, to measure fragmentation after both explosive launch and impact on the walls. Finally, a third identical charge is detonated in an air-filled chamber and allowed to burn. We present trends in the fragment distribution and simple analytic models for predicting the breakup and subsequent combustion energy release. Particular focus is given to the question: what is the main factor that limits how much aluminum can combust? [Preview Abstract] |
Tuesday, June 18, 2019 2:15PM - 2:30PM |
K2.00002: Shock initiation of reactive nanolaminates Sergey Matveev, Dana Dlott, Petra Hanusova, Jon-Paul Maria In this study, reactivity at the fuel-oxidizer interface under shock compression is studied. We studied the model system consisting of only one metal/metal oxide bilayer, in this case Zr/CuO. The samples were fabricated via magnetron sputtering with a mask to make 50 individual 3-mm sample spots on 2''-square glass substrates. Magnetron sputtering provides a nearly-perfect planar interface between the thermite components that is ideal for further shock compression study. High-throughput tabletop shock-system launches 500 \textmu m-diameter flyer plates with velocities of 0.5-4.6 km s$^{\mathrm{-1}}$. High-speed nanosecond-gated photography and optical pyrometry were utilized to detect regions of intense thermal emission and indicate temperatures of these areas respectively. This work demonstrates that RNLs show almost no reactivity under planar shock, whereas the shear wave spreading radially-out from the center of impact starts the reaction between metal and metal oxide. The brightest, and therefore hottest, thermal emission was observed at about 80 ns. Temporal and spatial reaction propagation was shown to depend on amount of metal fuel and number of interfaces. [Preview Abstract] |
Tuesday, June 18, 2019 2:30PM - 3:00PM |
K2.00003: Effect of liquid process control agent on structure and morphology of reactive materials prepared by high-energy milling Invited Speaker: Edward L. Dreizin High-energy milling has been used to prepare a broad range of reactive material powders, including thermites, metal-metalloid, and intermetallic compositions capable of highly exothermic reactions. Such reactions can involve both condensed components of the prepared powders and external oxidizers. Previous work focused on achieving nano-scale mixing of material components in the prepared, nearly fully dense composite powders. Additionally, control of powder microstructure and morphology, including particle sizes and shapes might be of critical importance in applications. In this talk, effect of polar and non-polar liquid process control agents (PCA) on properties of the prepared reactive material powders will be discussed. It has been shown to be possible to fine tune the powder particle size distributions using staged milling, involving different PCA in different stages. The particle size can be reduced effectively without detrimental effect on the reactivity of the prepared powders. Further, staged milling enables one to modify the chemistry of interfaces formed in the reactive composites, altering their initiation kinetics. It was also shown that spherical powders with narrow size distributions can be prepared using a broad range of starting material powders when PCA comprises two immiscible fluids. Such spherical powders were prepared using elemental Al and B as well as several Al-based thermites and B-metal composites. The mechanisms of formation of spherical powders remain unclear; it is hypothesized that they form from Pickering emulsions formed in the milling vial. Such emulsion interact at high stress and shear with the high-density powder suspension; this interaction is proposed to yield filled spherical particles, which can be recovered, characterized and used for preparing energetic formulations.\\ \\ In collaboration with: Mehnaz Mursalat (NJIT) and Mirko Schoenitz (NJIT) [Preview Abstract] |
Tuesday, June 18, 2019 3:00PM - 3:15PM |
K2.00004: Numerical simulation of explosively-dispersed reactive powder Ryan Houim The ignition and combustion of reactive powders dispersed by shock waves, blasts, and high-speed gas-dynamics flows are important to many scenarios related to national security, explosion safety, and even space exploration. The processes that couple the gas dynamics, particle dispersal of compacted granular media, and combustion are not well understood. Our previous work developed a kinetic-theory granular multiphase flow model and numerical method for simulating layered dust explosions. Here we demonstrate that this approach can be used to simulate the dispersal and combustion of reactive particles by a high-explosive charge. The geometrical configuration of the simulations consists of a high-pressure gas at 1.4 GPa that is surrounded by an annular layer of densely-packed reactive particles. The simulation results show many features observed in experiments of explosively-dispersed reactive particles including the formation of particle fingers. The dispersed particles ignite and burn in a non-premixed combustion mode where the mixing of fuel and oxidizer is performed by velocity slip between the particles and the shock-compressed air. The results also show that the burning of the particles produce acoustic waves that increase the pressure and impulse of the blast. [Preview Abstract] |
Tuesday, June 18, 2019 3:15PM - 3:30PM |
K2.00005: Helium Droplet Mediated Cluster Assembly as a Tool to Probe the Limits of Energy Storage in Metastable Nanomaterials Claron Ridge, Kyle Overdeep, Robert Buszek, Jerry Boatz, Michael Lindsay The recent efforts of our laboratory have been focused on helium droplet mediated deposition as a tool to synthesize novel materials in a pre-reactive, metastable state. We have fabricated a range of materials by varying the composition, cluster size, stoichiometry, and cluster film thickness. Cluster films have been characterized via transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and temperature programed desorption/reaction (TPD/R). The results have been surprising and raise questions about the fundamental behavior of cluster behavior during and after deposition onto a surface. In particular the unusual inversion of core/shell Mg/Cu clusters, which has motivated further density functional theory (DFT) calculations investigating the formation and stability of composite nanoclusters. [1,2] While Helium droplet deposition has proved to be an attractive technique for investigating a wide variety of research areas, from catalysis[3] to quantum superfluidity,[4] our goal remains probing the limits of metastability in reactive nanomaterials (e.g. nanothermites). [1] J. Chem. Phys., 2015, 142 (8) 084307 [2] J.Phys.Chem.A, 2016, 120 (48), 9612 [3] J.Phys.Chem.Lett., 2016, 7 (15), 2910 [4] Phys.Rev.Lett., 2012, 108, 155302 [Preview Abstract] |
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