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 S1: DSIC: Detonation Soot |
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Chair: Robert Reeves, LLNL Room: Grand Ballroom I |
Thursday, June 20, 2019 11:00AM - 11:15AM |
S1.00001: Characterization of Detonation and Partial Detonation of PBX 9501, PBX 9502, and TATB Christopher Freye, Patrick Bowden, Hiro Teshima, Devin Cardon, Elizabeth Francois, C.J. Rosales To further our understanding of chemical reaction pathways occurring during shock loading (sub-detonative and detonative) of plastic bonded explosives (PBXs), post-shock/detonation product species were investigated. Using a contained firing vessel, charges of PBX 9501, PBX 9501/9502 and PBX 9501/TATB were detonated producing gaseous products as well as solid carbonaceous species. Gaseous samples were transferred to a collection vessel which were then analyzed by gas chromatography (GC) with a thermal conductivity detector (TCD) or mass spectrometer (MS). Identification and quantification of gases will be presented. Solid samples collected from detonation of PBX 9502 and TATB were analyzed by liquid chromatography coupled to ultraviolet-visible absorbance and mass spectrometery (LC-UVVis-MS) and gas chromatography with time-of-flight mass spectrometry (GC-TOFMS). Additionally, solid samples from sub-detonatively shocked PBX 9502 were also analyzed via LC-UVVis-MS and GC-TOFMS. Identification of these solids will be reported and potential decomposition pathways to observed intermediate products will be presented. LA-UR-21708 [Preview Abstract] |
Thursday, June 20, 2019 11:15AM - 11:30AM |
S1.00002: The Velocity of Detonation and Reaction Zone Profile in PBX 9502 as a Function of Initial Density Christopher Armstrong, Philip Rae It is known that PBX 9502 changes sensitivity\footnote{Shock Initiation of Energetic Materials at Different Initial Temperatures (Review), P. A. Urtiew, \& C. M. Tarver. Combustion, Explosion, and Shock Waves, (2005)} and performance\footnote{The effect of density on the detonation response of a TATB-based explosive, P.J. Rae, C. L. Armstrong, \& E. H. Haroz. International Detonation Symposium, (2018)} as a function of temperature. Presumably, due to void morphologically driven change in density. These experiments will examine both the velocity of detonation (VOD) and reaction zone profile (particle velocity vs. time) as a function of pressed density. The rate sticks are 2 inches in diameter with an aspect ratio of 1:8. The reaction zone profile is characterized by photonic Doppler velocimetry (PDV) at an aluminized lithium fluoride window and VOD is measured by both piezoelectric pins, and time domain reflectometry (TDR). The density range examined is 1.700 - 1.895 g/cc (1.895 is production density). The results obtained are compared to those of in-situ heated rate stick experiments, and the void structure characterized by small-angle neutron scattering (SANS) methods in order to elucidate the differences in detonation performance as influenced by thermal insult and compaction. [Preview Abstract] |
Thursday, June 20, 2019 11:30AM - 12:00PM |
S1.00003: Frontiers in Experimental Observations of Detonation Properties with X-rays Invited Speaker: Trevor Willey Existing and emerging pulsed X-ray sources have the potential to resolve longstanding mysteries in detonation physics. In recent years, X-ray experimental capabilities have been developed and are beginning to interrogate fundamental physical and chemical kinetic properties on atomic to millimeter length scales over sub-nanosecond to microsecond timescales. Such phenomena include mechanisms of initiation, chemical kinetics, generated solid particulates including their morphologies and agglomeration kinetics, and void collapse with associated hot-spot formation; in most cases, theory and modeling have long preceded experimental capabilities. X-rays have {\AA}ngstr\"{o}m wavelengths capable of probing crystal and molecular structure through diffraction, nano- and mesoscale morphology through scattering, and have the potential to image at sub-micron or even nanometer resolution, well beyond diffraction limited capabilities of, for example, optical imaging. X-rays \textasciitilde 10 keV, or higher, penetrate relatively deeply into the bulk of low-Z, CHNO materials, making interrogation of self-propagating detonation fronts in centimeter-scale charges feasible. This talk will present an overview of the development of X-ray techniques implemented to experimentally observe detonation phenomena. We will highlight various results: imaging of operating detonators and initiation of detonation; characterization of the wide variety of carbonaceous particulates that form behind detonation fronts and their unexpected agglomeration kinetics, and frontier work interrogating chemistry and phase with, for example, dynamic diffraction and other techniques. [Preview Abstract] |
Thursday, June 20, 2019 12:00PM - 12:15PM |
S1.00004: Insights into organic chemistry at extreme conditions through evaluation of recovered carbon products produced by detonations Millicent Firestone, Sokhna Diouf, John Bowlan, Soenke Siefert The direct evaluation of chemical reactions that occur behind the detonation front is challenging due to the extreme conditions produced. Thus, details of the primary carbon fragments (i.e., reactive species) generated by the detonation of an explosive and the operative synthetic pathways for carbon framework extension are not well described. Late time events, such as framework coalescence into nanoparticles and nanoparticle assembly into mesoscale architectures is also not well understood. To further advance our understanding of the chemical and physical events occurring post-detonation, we have sought to evaluate the carbon products recovered from a range of explosives (e.g., nitromethane). Post-event X-ray scattering on the unpurified recovered soot determines nanoparticle morphology and mesoscale aggregate architecture. Isolation, fractionation, and purification of all carbon products contained within the soot are achieved through a multi-step separation protocol. The separation scheme allows for recovery of both soluble (e.g., fullerenes and diamondoids) and nanophase carbons. Based upon these studies, operative mechanisms regulating framework growth are postulated and tested through adjustment of detonation conditions (closed chamber atmosphere and CJ conditions). Understanding the correlation between detonation conditions and carbon product formation is important for achieving greater accuracy in predicting explosive performance. [Preview Abstract] |
Thursday, June 20, 2019 12:15PM - 12:30PM |
S1.00005: Microscopic and Spectroscopic Analysis of Recovered Detonation Soots Michael Nielsen, Michael Bagge-Hansen, Joshua Hammons, Lisa Lauderbach, Shaul Aloni, Sorin Bastea, Larry Fried, Jonathan Lee, Tony van Buuren, Trevor Willey Synchrotron-based, ultrafast measurements provide insight into early events in carbon condensation from detonating high explosives. However, data interpretation is often difficult absent additional information about the nature of the nanoscopic constituents of the produced soot. Detonating similar explosive charges and capturing the early particulates in ice allows for clean (minimal environmental carbon) recovery and mitigates potential changes induced by prolonged particulate burn in atmosphere. Comparisons of small-angle X-ray scattering (SAXS) data collected from recovered soots to time-resolved SAXS collected during the first few microseconds of nanoparticle formation suggest that the products recovered from ice are similar to those formed during experiments at the synchrotron. Transmission electron microscopy and X-ray spectroscopies yield insight into the morphology, phase, and chemistry of the recovered carbonaceous soots. We present and compare these data for a range of high explosive materials and explore the differences in the carbon phase and morphology in relation to the initial chemistry and calculated C-J point and subsequent evolution through the carbon phase diagram. [Preview Abstract] |
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