Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session T3: EM.1 Energetic Materials Equation of State I |
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Chair: Richard Lee, Naval Surface Warfare Center - Indian Head Room: Fifth Avenue |
Thursday, July 11, 2013 9:15AM - 9:45AM |
T3.00001: High-pressure and temperature investigations of energetic materials Invited Speaker: Jared Gump Static high-pressure measurements are extremely useful for obtaining thermodynamic and phase stability information from a wide variety of materials. However, studying energetic materials can be challenging when extracting information from static high-pressure measurements. Energetic materials are traditionally C, H, N, O compounds with low crystalline symmetry, producing weak signal in commonly performed x-ray diffraction measurements. The small sample volume available in a static high-pressure cell exacerbates this issue. Additionally, typical hydrostatic compression media, such as methanol/ethanol, may react with many energetic materials. However, characterization of their thermodynamic parameters and phase stability is critical to understanding explosive performance and sensitivity. Crystalline properties, such as bulk modulus and thermal expansion, are necessary to accurately predict the behavior of shocked solids using hydrodynamic codes. In order to obtain these values, equations of state of various energetic materials were investigated using synchrotron angle-dispersive x-ray diffraction experiments at static high-pressure and temperature. Intense synchrotron radiation overcomes the weak x-ray scattering of energetic materials in a pressure cell. The samples were hydrostatically compressed using a non-reactive hydrostatic medium and heated using a heated diamond anvil cell. Pressure -- volume data for the materials were fit to the Birch-Murnaghan and Vinet formalisms to obtain bulk modulus and its first pressure derivative. Temperature -- volume data at ambient pressure were fit to obtain the volume thermal expansion coefficient. Data from several energetic materials will be presented and compared. [Preview Abstract] |
Thursday, July 11, 2013 9:45AM - 10:00AM |
T3.00002: The high pressure-temperature phase behavior of 2,4,6-trinitrotoluene (TNT) Patrick Bowden, Raja Chellappa, Dana Dattelbaum, Virginia Manner, Nathan Mack, Zhenxian Liu 2,4,6-trinitrotoluene (TNT) is a widely used explosive that is relatively insensitive to initiation by shock loading. While the detonation properties of TNT have been extensively reported, the high pressure-temperature ($P-T)$ stability of TNT has not been investigated in detail. In addition, there are no studies that have determined the effects of pressure on the stability of the liquid phase. At ambient conditions, TNT crystallizes in a monoclinic lattice (space group \textit{P2}$_{1}/a)$, and our previous x-ray diffraction (XRD) measurements at room temperature suggested a phase transition to orthorhombic (space group \textit{Pca2}$_{1})$ at $\sim$20 GPa. In this work, we have performed \textit{in situ} synchrotron XRD and vibrational spectroscopy measurements at various $P-T$ conditions along isothermal and isobaric pathways to confirm previously reported phase transitions, and investigate phase stabilities up to 30 GPa and 500$^{\circ}$C. Using all the available data, we have established the first comprehensive high $P-T$ phase diagram of TNT, including the melting line as a function of pressure. While our synchrotron IR and Raman spectroscopy measurements indicate spectral changes at $\sim$2 GPa, careful XRD measurements (hydrostatic, He medium and non-hydrostatic) reveal that the monoclinic phase is likely stable up to 20 GPa. We will present a self-consistent $P-V-T$ equation of state derived from the reported structural and vibrational data. [Preview Abstract] |
Thursday, July 11, 2013 10:00AM - 10:15AM |
T3.00003: High Pressure-Temperature Phase Diagram of 1,1-diamino-2,2-dinitroethylene Matthew Bishop, Raja Chellappa, Zhenxian Liu, Daniel Preston, Mary Sandstrom, Dana Dattelbaum, Yogesh Vohra, Nenad Velisavljevic 1,1-diamino-2,2-dinitroethelyne (FOX-7) is a less sensitive energetic material with performance comparable to commonly used secondary explosives such as RDX and HMX. At ambient pressure, FOX-7 exhibits complex polymorphism with at least three structurally distinct phases ($\alpha $, \quad $\beta $, and $\gamma )$. In this study, we have investigated the high P-T stability of FOX-7 polymorphs using synchrotron mid-infrared (MIR) spectroscopy. At ambient pressure, our MIR spectra confirmed the known $\alpha \quad \to \quad \beta $ (110 $^{\circ}$C) and $\beta \quad \to \quad \gamma $ (160 $^{\circ}$C) phase transitions; as well as, indicated an additional phase transition, $\gamma \quad \to \quad \delta $ (210$^{\circ}$C), with the $\delta $ phase being stable up to 250 $^{\circ}$C prior to melt/decomposition. In situ MIR spectra obtained during isobaric heating at 0.9 GPa revealed that the $\alpha \quad \to \quad \beta $ transition occurs at 180$^{\circ}$C, while $\beta $ $\to \quad \beta +\delta $ phase transition shifted to 300$^{\circ}$C with suppression of $\gamma $ phase. Decomposition was observed above 325$^{\circ}$C. Based on multiple high P-T measurements, we have established the first high P-T phase diagram of FOX-7. [Preview Abstract] |
Thursday, July 11, 2013 10:15AM - 10:30AM |
T3.00004: High pressure stability of hydrazine (H$_{2}$N-NH$_{2})$: Implications for energetic hydronitrogen compounds Raja Chellappa, Dana Dattelbaum, Zhenxian Liu Hydrazine (H$_{2}$N-NH$_{2})$ is a metastable, high energy density molecule that is relevant to planetary physics and plays an important role in industrial synthesis and propellant applications. Theoretical calculations have predicted the existence of ``hydronitrogen'' extended solids that hold great potential as a high energy density material (HEDM). Exploring the high pressure-temperature ($P-T)$ stability of hydrazine will provide crucial insights into hydrogen bonded -N-H networks under these conditions. Further, related simple molecules such as CH$_{4}$, NH$_{3}$, CO, and CO$_{2}$ have been shown to have rich high $P-T$ phase diagrams, often forming extended amorphous solids. Here, we report the first comprehensive study of hydrazine to 50 GPa at ambient temperature, using both \textit{in situ} vibrational spectroscopy and synchrotron x-ray diffraction to elucidate structural changes driven by compression. Liquid hydrazine solidifies into a monoclinic structure at 0.5 GPa that is isomorphous with the low-$T$ solid phase. Further compression drives structural re-ordering and at least 2 phase transformations to 20 GPa, with complex anisotropic hydrogen bonding interactions. Surprisingly, no evidence for the formation of extended amorphous solids was observed to the highest pressure studied. [Preview Abstract] |
Thursday, July 11, 2013 10:30AM - 10:45AM |
T3.00005: Double Shock Experiments and Reactive Flow Modeling on LX-17 to Understand the Reacted Equation of State Kevin S. Vandersall, Frank Garcia, Laurence E. Fried, Craig M. Tarver Experimental data from measurements of the reacted state of an energetic material are desired to incorporate reacted states in modeling by computer codes. In a case such as LX-17 (92.5{\%} TATB and 7.5{\%} Kel-F by weight), where the time dependent kinetics of reaction is still not fully understood and the reacted state may evolve over time, this information becomes even more vital. Experiments were performed to measure the reacted state of LX-17 using a double shock method involving the use of two flyer materials (with known properties) mounted on the projectile that send an initial shock through the material close to or above the Chapman-Jouguet (CJ) state followed by a second shock at a higher magnitude into the detonated material. By measuring the parameters of the first and second shock waves, information on the reacted state can be obtained. The LX-17 detonation reaction zone profiles plus the arrival times and amplitudes of reflected shocks in LX-17 detonation reaction products were measured using Photonic Doppler Velocimetry (PDV) probes and an aluminum foil coated LiF window. A discussion of this work will include the experimental parameters, velocimetry profiles, data interpretation, reactive CHEETAH and Ignition and Growth modeling, as well as possible future experiments. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
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