Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session B27: Matter at Extreme Conditions: Energetic Materials IFocus Recordings Available
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Sponsoring Units: GSCCM Chair: Belinda Pacheco, Lawrence Livermore National Laboratory Room: McCormick Place W-187C |
Monday, March 14, 2022 11:30AM - 12:06PM |
B27.00001: Tuning Physical and Chemicalproperties of explosives through Synthetic Modifications Invited Speaker: Nicholas Lease When handling explosives one of the most important factors to consider is the sensitivity of the material towards common stimuli such as impact, friction, electrostatic discharge and temperature. Explosive handling sensitivity is dictated by numerous molecular and physical properties Chemical effects such as thermodynamics, decomposition pathways and bond dissociation energies correlate with handling sensitivity. In addition it is possible that macroscale factors such as crystal structure, crystal packing, hydrogen bonding and electrostatic effects can also play a role in a materials handling sensitivity. Understanding how these molecular properties influence explosive safety is key to developing a blueprint for designing energetics with specific properties and sensitivities. We have been making selective modifications to specific molecular backbones in order to control properties without changing the entire molecule. Specifically, we have focused on the handling sensitivity of three molecular systems: (1) the explosive erythritol tetranitrate (ETN) in both the solid and liquid state, (2) stereochemical isomers, sorbitol hexanitrate and mannitol hexanitrate, which have distinct physical properties such as crystal packing and melting point, and lastly (3) a modified erythritol molecular backbone with systematically varied energetic functional groups. Results from these studies have shown that physical characteristics such as material phase and melting point play large roles in explosive sensitivity. Additionally these studies have demonstrated that through selective modification, explosive sensitivity can be tuned though manipulation of various explosive functional groups. |
Monday, March 14, 2022 12:06PM - 12:18PM |
B27.00002: Prediction of structure of CON and NaN crystals under high pressure. Iskander G Batyrev Structure of CON and NaN crystals under pressure is predicted using evolutionary algorithm and |
Monday, March 14, 2022 12:18PM - 12:30PM |
B27.00003: EVALUATION OF PRECURSOR SHOCK EVOLUTION IN ADDITIVE-MANUFACTURED HIGH EXPLOSIVESTRUCTURES Cameron Brown, Alexander Mueller, Andrew Schmalzer, Bryce C Tappan, Joe Lichthardt, Maria Campbell, Sridhar Seetharaman Cracks, voids, and channels can strongly influence detonation wave propagation in a high explosive (HE) structure. Air gaps between adjacent regions of HE or between the HE and an external confining material may cause precursor shock waves to form which run ahead of the detonation wave and pre- compress or "dead-press" the HE leading to detonation failure. Additive manufacturing allows for the fabrication of HE structures with geometries that are not reproducible with conventional casting, pressing or extrusion methods, and enables the production of samples with controlled void channels via selective control of inter-strand gaps. Precursor shock evolution is herein evaluated by high speed imaging and detonation velocity measurements to determine the relationship to inter-strand gaps and the degree of support from the detonation wave. Recent results for the ongoing research project will be presented. |
Monday, March 14, 2022 12:30PM - 12:42PM |
B27.00004: Molecular Ferroelectrics as Chemically Driven Energetics Yong Hu, Chi-Chin Wu, Jennifer L Gottfried, Rose A Pesce-Rodriguez, Zhiyu Liu, Scott D Walck, Peter W Chung, Shenqiang Ren This work designs and explores energetic molecular ferroelectrics using imidazolium perchlorate (ImClO4) as an example. The material integrates uniquely the covalent bond energetic imidazolium cations as fuel and the perchlorate anions as oxidizer with spontaneous polarization in one molecular crystal. Changes in the structure, composition and energetic properties were studied as function of polarization through thermal heating. High-resolution transmission electron micrographs prior to heating showed distinct moiré fringes revealed self-polarization induced ferroelectric domains. Low temperature heating at 150 °C led to depolarization and desorption of the imidazole rings with significant morphological changes in the crystal without significant influence in the microsecond-timescale energy release. Higher temperature pyrolysis at 350 °C produced a large exotherm and gas combustion products including H2O, CO/N2, and CO2. Via the laboratory-scale energetic test technique - laser-induced air shock from energetic materials (LASEM), the detonation velocity of ImClO4 was estimated at 7.2 ± 0.27 km/s, which is comparable to military explosives 2,4,6-trinitrotoluene (TNT) and hexanitrostilbene (HNS). The electron-phonon interactions were also demonstrated by polarization-dependent heat transfer and specific power. These results unvail the potential of a new class of molecular ferroelectrics for energetic applications. |
Monday, March 14, 2022 12:42PM - 12:54PM |
B27.00005: Influence of Microballoon Additives on the Shock Initiation Behavior of HMX-Silicone Formulations Christopher M Miller, H. Keo Springer Novel manufacturing methods enable tailoring of mesoscale-level heterogeneities in solid high explosives (HEs). These heterogeneities influence the shock initiation behavior of HEs and may be used to meet desired safety and performance metrics. The inclusion of microscopic additives, such as microballoons, is of great interest in the HE community; however, the current influence of these components on shock initiation response is not well characterized. In this work, two-dimensional (2D), microstructure-explicit shock loading simulations are performed on HMX/silicone formulations with microballoons present in the silicone binder. The simulations are carried out using a multi-physics Arbitrary Lagrangian-Eulerian code (ALE3D). The influence of these additives on the rate of chemical reaction in HMX is analyzed as a function of microballoon size, material, thickness, and interior contents. The microballoons are represented by gas-filled glass and polymer beads and results are compared to their solid counterparts. We find that the inclusion of microballoons increases the sensitivity of the HE formulation and heat transfer plays a significant role in the development of hotspots in the HMX. |
Monday, March 14, 2022 12:54PM - 1:06PM |
B27.00006: Development of Predictive Multiscale Constitutive Models for Pressed Energetic Materials to Resolve the Shock to Detonation Transition Michael Sakano, Judith A Brown, Mitchell A Wood Predicting the initiation of energetic materials (EM) under a variety of stimuli and thermodynamic conditions will result in much needed insight into the connection between basic chemical and microstructural properties and the detonation performance. Current experimental characterization of novel energetic materials can be both costly and time-consuming, thus resulting in a lack of materials property data necessary to deploy accurate constitutive models into existing simulation methods. These poorly constrained simulations can only provide a qualitative understanding of the shock-to-detonation process. We propose a multiscale framework that leverages different computational methods to study materials behavior across a variety of shock conditions and length- and time-scales. Parameterization of continuum-scale chemical kinetics and strength models are derived directly from higher fidelity simulation codes to efficiently study hotspot dynamics in pressed EMs. This talk will detail our computational approach for generating training as well as validating continuum predictions with available experiments. We will demonstrate the viability for this multiscale approach to provide rapid progress toward accurate strength and reaction kinetic models beyond what is experimentally capable. |
Monday, March 14, 2022 1:06PM - 1:18PM |
B27.00007: Shock Induced Virtual Glass Transition to Rapidly Reduce Deviatoric Stress in Polystyrene Jalen Macatangay, Brenden W Hamilton, Alejandro H Strachan Shock compression introduces a near-instantaneous increase in temperature and deviatoric stress as the shockwave propagates within a condensed matter system. When polymers are subjected to strong shocks, relaxation mechanisms, such as cooperative intramolecular motion and chain rearrangements, operate to reduce deviatoric stress towards a hydrostatic equilibrium state. However, these mechanisms and their associated rates are poorly understood, especially challenging are the initial response following shock loading. Therefore, we simulate shock loading on glassy polystyrene using molecular dynamic simulations with the multiscale shock technique (MSST) and characterize the stress relaxation processes. For strong shocks, the relaxation of deviatoric (Von Mises) stress exhibits two regimes: i) an initial fast relaxation lasting 2-5 ps, ii) followed by a more gradual process. Analysis of the torsional transition events in the polymer backbone bonds (dihedral angles switching between low-energy states) indicate that the fast relaxation is associated with shock-induced virtual melting. The second regime corresponds to glassy dynamics. |
Monday, March 14, 2022 1:18PM - 1:30PM |
B27.00008: Modeling of PBX 9501 High Explosive Arc Experiments Marvin A Zocher Circular arc experiments have been recently employed at Los Alamos National Laboratory (LANL) for the purpose of evaluating reactive burn in plastic bonded explosives. The circular arc configuration is attractive in that it is perhaps the simplest configuration that allows for an evaluation of the influence of diffraction upon detonation front curvature. In the present work several arc experiments are modeled using the LANL finite volume continuum mechanics code FLAG. Constitutive behavior is modeled using Wescott-Steward-Davis (WSD) models for both reactants and products. Reactive burn is modeled using Arrhenius-WSD (AWSD). Comparisons of simulation prediction to empirical data are made for detonation velocity as well as the shape of the detonation front. |
Monday, March 14, 2022 1:30PM - 1:42PM |
B27.00009: Hydride- and Boron-free Solid Hypergolic H2O2-Ignitophores. Michael Gozin The race and competition in aerospace technologies based on environmentally friendly green propulsion systems with green fuels and oxidizers are attracting significant attention. The development of hybrid propulsion systems that use a hypergolic fuel and green H2O2 oxidizer, capable of deep throttling and restarting from “cold”, is a very challenging task. Here, we describe a new synthetic approach for the synthesis and characterization of conceptually new hydride- and boron-free, and air/moisture stable solid H2O2-hypergols, based on Cu and Co complexes of bis(5-tetrazolyl) amine (H2BTA) ligand. Among prepared and evaluated materials, the best performing compound [K2(H2O)2Cu(BTA)2]n (JD-4) was found to exhibit a short ignition delay time of 7 ms (with H2O2, 97%), and a high thermostability of 343 °C. Based on obtained ignition results, X-ray crystallography, and HASEM software calculations, structure-hypergolic activity-relationship studies were conducted. We found that the electron density difference between Cu and BTA units should be in a specific range (~2) for these compounds to ignite, providing a valuable tool for further development of novel, green, solid fuels for propulsion systems. |
Monday, March 14, 2022 1:42PM - 1:54PM |
B27.00010: The Behavior of Phase Transition and Thermal Decomposition on CL-20/DNB Cocrystals under Extreme Conditions Xiaoyu Sun, Zengming Zhang CL-20/DNB cocrystal has been discovered as a promising explosive owing to its excellent comprehensive performance. The cocrystal molecular formula is C12H10N14O16, and its unit cell structure belongs to the orthorhombic system with space group Pbca. The cocrystal has a unique structure formed by orderly arrangement of CL-20 and DNB molecules through hydrogen bonds and nitro-aromatic interactions, which makes it effectively achieve a fine balance between energy and sensitivity. In this work, the thermal decomposition behavior and structural evolution of CL-20/DNB cocrystal under high temperature and high pressure were studied by means of thermogravimetric differential heating, Raman spectroscopy and X-ray diffraction. The study found that the process of decomposition on sample can be divided into three stages, namely an endothermic melting stage and two exothermic decomposition stages. It can be concluded that the co-crystallization can adjust the explosive melting point and improve its thermal stability. And the stability of cocrystal under compression is also significantly higher than that of CL-20. Additionally, there is a structural phase transition at the pressure range of 13-14 GPa, which is accompanied by a color change of the sample and a red shift of the absorption edge. |
Monday, March 14, 2022 1:54PM - 2:30PM |
B27.00011: Quantum mechanics studies on the stability mechanism and detonation performance of high-energy-density materials Invited Speaker: Lei Zhang We developed a couple of quantum mechanics methods specialized for simulating crystal-level high-energy-density materials (HEDMs). Using these methods, we first studied how nitrogen-aromatics are stabilized under various surroundings. We discovered the presence of dual-aromaticity in five-membered systems like pentazole and C-N heterocycles. Later, anions of these dual-aromatics were found to have abnormal reactivity in acidic surroundings due to a competition between their basicity and dual-aromaticity. At lower acidity, basicity overcomes dual-aromaticity and the heterocyclic anions undergo acid-base neutralization. When the acidity becomes sufficiently high, dual-aromaticity defeats basicity. These anions turn to resist protonation and violate acid-base neutralization, earning extra stability and enhanced firmness through intermolecular interactions with surrounding acidic ions. No such anomaly was observed in organic solutions like benzene and THF, and these solvents present little influence on stability of the heterocyclic anions. This acid-trapping strategy, a promising strategy for facilitating nitrogen-aromatics to productive yielding, was found also applicable to five-membered pnictogen heterocycles and square tetranitrogen. Second, we focused on how various physicochemical characteristics of HEDMs affecting their power level and their stability. High-throughput calculations were conducted for hundreds of HEDMs. Based on the statistical analysis of calculated data and the machine-learning techniques, in-crystal interspecies interactions were identified to be the one that provokes the performance stability contradiction of HEDMs. The optimal range of key features for efficient rational design of advanced HEDMs was delivered. Based on proposed guidelines, three new thermostable HEDMs containing bridged, 3,5-dinitropyrazole moieties were successfully synthesized, characterized, and evaluated. |
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