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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Phase diagram and decomposition of 1,1-diamino-2,2-dinitroethene single crystals at high pressures and temperatures

The high pressure-high temperature (HP-HT) phase diagram and decomposition of FOX-7, central to understanding its stability and reactivity, were determined using optical spectroscopy and imaging measurements in hydrostatically compressed and heated single crystals. Boundaries between various FOX-7 phases (α, α’, β, γ, and ε) and melting/decomposition curves were established up to 10 GPa and 750 K. Main findings are: (i) a triple point is observed between α, β, and γ phases ~ 0.6 GPa and ~ 535 K, (ii) previously suggested δ phase is not a new phase but is partly decomposed γ phase, (iii) the α-α’ transition takes place along an isobar, whereas the α’-ε transition pressure decreases with increasing temperature, and (iv) melting/decomposition temperatures increase rapidly with pressure, with an increase in the slope at the onset of the α’-ε transition. Our results differ from the recently reported HP-HT phase diagram for nonhydrostatically compressed polycrystalline FOX-7. In addition, the observed interplay between melting and decomposition suggests the suppression of melting with pressure. Our FTIR measurements at different pressures to 3.5 GPa showed similar decomposition products, suggesting similar decomposition pathways irrespective of the pressure. Lastly, the present results provide new insights into the structural and chemical stability of an important insensitive high explosive (IHE) crystal under well-defined HP-HT conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Comprehensive End-To-End Design of Novel High Energy Density Materials: III. Fused Heterocyclic Energetic Compounds

In contrast to synthesis and experimental characterization that are usually expensive and time-consuming, a coupled combination of ab initio and group additive theoretical methods represents a powerful alternative to computationally design and characterize new materials with targeted properties. Heterocyclic energetic materials are considered attractive candidates to replace conventional high explosives, such as PETN, RDX, HMX, and TNT. Heterocycles enable an intriguing opportunity for combinatorial design of new classes of energetic materials with targeted performance and sensitivity properties and offer ways for an accurate analysis of structure–property correlations of the materials. By using a computational strategy that links methods of quantum chemistry and semiempirical statistical analysis, we designed, modeled, and characterized a series of novel linear and fused explosive compounds. Proposed materials with best combinations of performance and sensitivity parameters can be now considered as potential candidates for synthesis and experimental characterization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Investigation into the Synthesis of Several TATB-Inspired Energetic Materials

The synthesis and characterization of several TATB-inspired energetic materials was explored. Despite their structural similarity to TATB, their behavior toward traditional synthetic pathways deviates significantly from that of the parent material. This change in expected reactivity is discussed and an efficient alternative synthesis is reported. The development of a simple and effective route to these TATB-type compounds opens the door to a potential new class of insensitive high explosives.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

High pressure suppression of plasticity due to an overabundance of shear embryo formation

Abstract High pressure shear band formation is a critical phenomenon in energetic materials due to its influence on both mechanical strength and mechanochemical activation. While shear banding is known to occur in a variety of these materials, the governing dynamics of the mechanisms are not well defined for molecular crystals. We conduct molecular dynamics simulations of shock wave induced shear band formation in the energetic material 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) to assess shear band nucleation processes. We find, that at high pressures, the initial formation sites for shear bands, “embryos”, form in excess and rapidly lower deviatoric stresses prior to shear band formation and growth. This results in the suppression of plastic deformation. A local cluster analysis is used to quantify and contrast this mechanism with a more typical shear banding seen at lower pressures. These results demonstrate a mechanism that is reversible in nature and that supersedes shear band formation at increased pressures. We anticipate that these results will have a broad impact on the modeling and development of high-strain rate application materials such as those for high explosives and hypersonic systems.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Magnetised quark nuggets in the atmosphere

A search for magnetised quark nuggets (MQN) is reported using acoustic signals from hydrophones placed in the Great Salt Lake (GSL) in the USA. No events satisfying the expected signature were seen. This observation allows limits to be set on the flux of MQNs penetrating the Earth’s atmosphere and depositing energy in the GSL. The expected signature of the events was ​derived from pressure pulses caused by high-explosive cords between the lake surface and bottom at various locations in the GSL. The limits obtained from this search are compared with those obtained from previous searches and are compared to models for the formation of MQNs.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

The Role of Viscosity in TATB Hot Spot Ignition

The role of dissipative effects, such as viscosity, in the ignition of high explosive pores is investigated using a coupled chemical, thermal, and hydrodynamic model. Chemical reactions are tracked with the Cheetah thermochemical code coupled to the ALE3D hydrodynamic code. We perform molecular dynamics simulations to determine the viscosity of liquid TATB. We also analyze shock wave experiments to obtain an estimate for the shock viscosity of TATB. Using the lower bound liquid-like viscosities, we find that the pore collapse is hydrodynamic in nature. Using the upper bound viscosity from shock wave experiments, we find that the pore collapse is closest to the viscous limit.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Spatiotemporal temperature and density characterization of high-power atmospheric flashover discharges over inert poly(methyl methacrylate) and energetic pentaerythritol tetranitrate dielectric surfaces

A flashover arc source that delivered up to 200 mJ on the 100s-of-ns time-scale to the arc and a user-selected dielectric surface was characterized for studying high-explosive kinetics under plasma conditions. The flashover was driven over thin pentaerythritol tetranitrate (PETN) and poly(methyl methacrylate) (PMMA) dielectric films and the resultant plasma was characterized in detail. Time- and space-resolved temperatures and electron densities of the plasma were obtained using atomic emission spectroscopy. The hydrodynamics of the plasma was captured through fast, visible imaging. Fourier transform infrared spectroscopy (FTIR) was used to characterize the films pre- and post-shot for any chemical alterations. Time-resolved infrared spectroscopy (TRIR) provided PETN depletion data during the plasma discharge. For both types of films, temperatures of 1.6-1.7 eV and electron densities of {approx}7-8 x 10{sup 17}/cm{sup 3}{approx}570 ns after the start of the discharge were observed with temperatures of 0.6-0.7 eV persisting out to 15 {mu}s. At 1.2 {mu}s, spatial characterization showed flat temperature and density profiles of 1.1-1.3 eV and 2-2.8 x 10{sup 17}/cm{sup 3} for PETN and PMMA films, respectively. Images of the plasma showed an expanding hot kernel starting from radii of {approx}0.2 mm at {approx}50 ns and reaching {approx}1.1 mm at {approx}600 ns. The thin films ablated or reacted several hundred nm of material in response to the discharge. First TRIR data showing the in situ reaction or depletion of PETN in response to the flashover arc were successfully obtained, and a 2-{mu}s, 1/e decay constant was measured. Preliminary 1 D simulations compared reasonably well with the experimentally determined plasma radii and temperatures. These results complete the first steps to resolving arc-driven PETN reaction pathways and their associated kinetic rates using in situ spectroscopy techniques.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Fission-suppressed fusion breeder on the thorium cycle and nonproliferation

Fusion reactors could be designed to breed fissile material while suppressing fissioning thereby enhancing safety. The produced fuel could be used to startup and makeup fuel for fission reactors. Each fusion reaction can produce typically 0.6 fissile atoms and release about 1.6 times the 14 MeV neutron's energy in the blanket in the fission-suppressed design. This production rate is 2660 kg/1000 MW of fusion power for a year. The revenues would be doubled from such a plant by selling fuel at a price of 60/g and electricity at $0.05/kWh for Q=P{sub fusion}/P{sub input}=4. Fusion reactors could be designed to destroy fission wastes by transmutation and fissioning but this is not a natural use of fusion whereas it is a designed use of fission reactors. Fusion could supply makeup fuel to fission reactors that were dedicated to fissioning wastes with some of their neutrons. The design for safety and heat removal and other items is already accomplished with fission reactors. Whereas fusion reactors have geometry that compromises safety with a complex and thin wall separating the fusion zone from the blanket zone where wastes could be destroyed. Nonproliferation can be enhanced by mixing {sup 233}U with {sup 238}U. Also nonproliferation is enhanced in typical fission-suppressed designs by generating up to 0.05 {sup 232}U atoms for each {sup 233}U atom produced from thorium, about twice the IAEA standards of 'reduced protection' or 'self protection.' With 2.4%{sup 232}U, high explosive material is predicted to degrade owing to ionizing radiation after a little over 1/2 year and the heat rate is 77 W just after separation and climbs to over 600 W ten years later. The fissile material can be used to fuel most any fission reactor but is especially appropriate for molten salt reactors (MSR) also called liquid fluoride thorium reactors (LFTR) because of the molten fuel does not need hands on fabrication and handling.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2013

Applications of the associated-particle neutron-time-of-flight interrogation technique - From sheep to unexploded ordnance

The associated-particle technique (APT) will be presented for some diverse applications that include on the one hand, analyzing the body composition of live sheep and on the other, identifying the fillers of unexploded ordnance (UXO). What began with proof-of-concept studies using a large laboratory based 14 MeV neutron generator of the 'associated-particle' type, soon became possible for the first time to measure total body protein, fat and water simultaneously in live sheep using a compact field deployable associated-particle sealed-tube neutron generator (APSTNG). This non-invasive technique offered the animal physiologist a tool to monitor the growth of an animal in response to new genetic, nutritional and pharmacologic methods for livestock improvement. While measurement of carbon (C), nitrogen (N) and oxygen (O) determined protein, fat and water because of the fixed stoichiometric proportions of these elements in these body components, the unique C/N and C/O ratios of high explosives revealed their identity in UXO. The algorithm that was developed and implemented to extract C, N and O counts from an APT generated gamma-ray spectrum will be presented together with the UXO investigations that involved preliminary proofof-concept studies and modeling with Monte Carlo produced synthetic spectra of 57-155 mm projectiles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

A reactive flow model for heavily aluminized cyclotrimethylene-trinitramine

An accurate and reliable prediction of reactive flow is a challenging task when characterizing an energetic material subjected to an external shock impact as the detonation transition time is on the order of a micro second. The present study aims at investigating the size effect behavior of a heavily aluminized cyclotrimethylene-trinitramine (RDX) which contains 35% of aluminum by using a detonation rate model that includes ignition and growth mechanisms for shock initiation and subsequent detonation. A series of unconfined rate stick tests and two-dimensional hydrodynamic simulations are conducted to construct the size effect curve which represents the relationship between detonation velocity and inverse radius of the charge. A pressure chamber test is conducted to further validate the reactive flow model for predicting the response of a heavily aluminized high explosive subjected to an external impact.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Structural evolution of detonation carbon in composition B by X-ray scattering

Products evolved during the detonation of high explosives are primarily a collection of molecular gases and solid carbon condensates. Electron microscopy studies have revealed that detonation carbon (soot) can contain a variety of unique carbon particles possessing novel morphologies, such as carbon onions and ribbons. Despite these observations very little is known about the conditions that leads to the production of these novel carbon nanoparticles. A fuller understanding on conditions that generate such nanoparticles would greatly benefit from time-resolved studies that probe particle formation and evolution through and beyond the chemical reaction zone. Herein, we report initial results employing time-resolved X-ray scattering (TRSAXS) measurements to monitor nanosecond time-scale carbon products formed from detonating Composition B (60% TNT, 40% RDX). These studies were performed at the Dynamic Compression Sector (DCS, Sector 35) at the Advanced Photon Source (Argonne National Laboratory). Lastly, analysis of the collected scattering patterns reveals the presence of fractal multi-layered carbon condensates.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Dynamic Exploding Foil Initiator Imaging at the Advanced Photon Source

Recent advances in diagnostics coupled with synchrotron sources have allowed the in-situ investigation of exploding foil initiators (EFI) during flight. Herein, we present the first images of EFIs during flight utilizing x-ray phase contrast imaging at the Advanced Photon Source (APS) located in Argonne National Laboratory. These images have provided the DOE/DoD community with unprecedented images resolving details on the micron scale of the flyer formation, plasma instabilities and in-flight characteristics along with the subsequent interaction with high explosives on the nanosecond time scale. Phase contrast imaging has allowed the ability to make dynamic measurements on the length and time scale necessary to resolve initiator function and provide insight to key design parameters. These efforts have also probed the fundamental physics at “burst” to better understand what burst means in a physical sense, rather than the traditional understanding of burst as a peak in voltage and increase in resistance. This fundamental understanding has led to increased knowledge on the mechanisms of burst and has allowed us to improve our predictive capability through magnetohydrodnamic modeling. This manuscript presents results from several EFI designs along with a look to the future for upcoming work.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Automated Fitting of a Semi-empirical Multiphase Equation of State for Carbon

The equation of state (EOS) of carbon is important in high explosive, geophysical, and inertial confinement fusion applications. Within the semi-empirical Sesame framework, the EOS of each phase is represented by a sum of cold, vibrational, and thermal electronic Helmholtz free energy contributions. Each phase has ~5-10 independent parameters that are adjusted to reproduce single-phase data (e.g., thermal expansion, isothermal compression) as well as experimentally- and computationally- derived phase boundaries. Manual calibration of the full multiphase EOS is arduous. We present our progress in development of automated EOS parameterization based on minimization of an objective function. Here, this function encodes deviation of model EOS results from experimental/computational benchmarks. Optimization is implemented as a combination of global (particle swarm) and local optimization techniques.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Predicting the effects of thermally-induced density gradients on the hydrodynamic behavior of PBX 9502

High explosives are often exposed to thermal and mechanical stimuli within normal and abnormal environments. These stimuli can introduce density gradients in the explosive charge but the effect of such gradients is not well-understood. The goal of this work is to develop a comprehensive methodology to model the evolution of density gradients under various thermal conditions and then to predict shock initiation and detonation behavior of the gradated sample. PBX 9502 was chosen for these scoping studies because it has a large coefficient of thermal expansion and because the available shock initiation data indicates that initial temperature strongly affects the shock-to-detonation transition (SDT). The multiphysics code COMSOL was first used to model induced density gradients in a slab of PBX 9502 with asymmetric heating. Then, the gradated sample was constructed in the Pagosa hydrocode to simulate steel flyer impact scenarios, with SDT and detonation propagation following a calibrated Scaled Uniform Reactive Front (SURF) burn model. Furthermore, the gradated material exhibited very different initiation and corner turning behavior compared to homogeneous materials, and the orientation of the gradation was also found to have some effect. The methodology used here can estimate thermomechanical response of the material for non-uniform thermal environments and compute the resulting detonation properties of the PBX.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Microstructural investigation of PBX 9501: Comparing wet slurry and resonant acoustic mixing techniques

The microstructure of a high explosive (HE) material directly influences the reactive behavior under a variety of insults. Furthermore, the preparation method of polymer-bonded explosives (PBX), as well as the constituent material particle size distribution and consolidation parameters, will dominate the microstructural features that are observed. Here, we compare batches of PBX 9501 prepared by the typical wet slurry process and those prepared by resonant acoustic mixing. The “prills” produced by the wet slurry process leads to an inherently different microstructure than the coated powder produced by resonant acoustic mixing. Additionally, we observed that the conditions required to consolidate (press) the material to the nominal PBX 9501 density varied depending on the preparation technique, which also dictates the observed binder distribution. Furthermore, X-ray microcomputed tomography and ultra-small-angle X-ray scattering analyses revealed distinct differences in the void structure and distribution.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Improving manganin gauge measurements near radiographic fiducials

In dynamic experiments diagnosed with radiography and stress gauges, the gauges are often placed adjacent to radio-graphic fiducials, such as Ta foil, which perturbs the stress measurement. We conducted experiments to test the performance of different arrangements of manganin stress gauges and Ta foils. Three different gauge/foil configurations were tested, as well as a solitary gauge as control. Gauge/foil layers were placed between high-density polyethylene (HDPE) discs and impacted by a projectile in a gas gun, a simplification of a dynamic, high explosive experiment configuration. The stress measurements were minimally perturbed when a section of foil was removed near the active element of the gauge, as expected. In conclusion, a follow-up experiment showed that the modification to the foil has minimal impact on the radiographic measurement of the dynamic flow.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Numerical simulations of the Los Alamos gapstick experiment

The gapstick is a high explosive (HE) sensitivity test recently developed at Los Alamos. The experiment design was motivated by the traditional gap test and consists of a series of HE and inert pellets in a rate stick configuration. The inert pellets are made increasingly longer so that eventually the attenuated shock is unable to initiate the next HE pellet. While the gapstick is a mechanically simple experiment it poses several challenges for numerical simulation. In particular, accurately modeling the HE initiation and detonation phenomena requires a reactive burn model with sufficient mesh resolution to capture the reaction scales. In this work, the Scaled Uniform Reactive Front (SURF) and Arrhenius Wescott-Stewart-Davis (AWSD) burn models are used for simulations of a PBX 9501 (95 wt% HMX, 5% binder) gapstick. Furthermore, the material model for the inert pellet material, Polyvinylidene Fluoride (PVDF), has a direct influence on the shock propagation and a new equation of state (EOS) calibration for PVDF is developed using available Hugoniot data. Despite some challenges, the simulations are able to reasonably predict shock transit velocities and detonation failure in the gapstick.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗