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 H2: ERM: Synthesis and sensitivity of energetic materials |
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Chair: Timothy Jenkins, ARL Room: Grand Ballroom II |
Tuesday, June 18, 2019 9:15AM - 9:30AM |
H2.00001: Examining Different Regimes of Explosives Handling Sensitivity Virginia Manner, Nicholas Lease, Marc Cawkwell, Clayton Tiemann, Geoffrey Brown, John Yeager, Lisa Kay, David Chavez The handling sensitivity of explosives is controlled by factors that span from fundamental intramolecular effects to mesoscale structure and defects. Although the drop-weight impact test has been used to characterize energetic material sensitivity for over 50 years, there is still very limited understanding on which features of explosives influence or control impact sensitivity. It is critical to understand and mitigate for explosive sensitivity, from applications related to stockpile maintenance and development, to law enforcement safety, to basic research. We have developed derivatives of common explosives such as pentaerythritol tetranitrate (PETN), erythritol tetranitrate (ETN), and trinitrobenzene (TNB), and examined them experimentally and theoretically in order identify correlations between their properties and sensitivity. Because previous results have indicated that different size regimes appear to influence important properties, we will discuss how factors such as basic chemistry of functional groups, intermolecular interactions like hydrogen bonding and crystal packing characteristics, and larger-scale effects such as particle size contribute to the overall picture of handling sensitivity within an explosive system. [Preview Abstract] |
Tuesday, June 18, 2019 9:30AM - 9:45AM |
H2.00002: Synthesis of Heterocyclic Primary Explosives David Chavez, Ellen Denning Primary explosives serve a critical role in the initiation train for many explosive applications. Importantly, primary explosive must possess certain sensitivity properties in order to function in the appropriate manner. Unfortunately, some materials, such as PETN, have issues that may make function and lifetimes challenging in certain applications. This creates this need for novel primary explosives that alleviate these issues. This presentation will describe the synthesis of several new high nitrogen heterocyclic compounds with applications as energetic materials. We have combined the tetrazine ring system with the triazine ring system, and subsequently attached energetic functional groups, such as the azido group, to the rings to prepared novel polycyclic ring systems. The characterization data of these materials will also be presented. [Preview Abstract] |
Tuesday, June 18, 2019 9:45AM - 10:00AM |
H2.00003: Synthesis and Sensitivity Studies of PETN and ETN Derivatives Nicholas Lease, Virginia W. Manner, David E. Chavez, David Robbins, Lisa Kay Nitrate ester explosives are a historic class of explosives first discovered in 19$^{\mathrm{th}}$ century. Explosives such as pentaerythritol tetranitrate (PETN) are still commonly used in explosive stockpiles, while other nitrate ester explosives such as erythritol tetranitrate (ETN) have shown increased interest due to ease of synthesis and melt-castability. While both PETN and ETN have been studied extensively, derivatives of PETN and ETN with various explosive functional groups have not. Herein we discuss the synthesis of PETN and ETN derivatives with varied energetic functional groups. Studying functional group effects on material sensitivity can lead to key insights for tuning sensitivity of explosives, for developing new energetic materials. These materials will be fully characterized and studied for impact, spark and friction sensitivity, in addition to determining thermal and melting point behavior. [Preview Abstract] |
Tuesday, June 18, 2019 10:00AM - 10:15AM |
H2.00004: Data-Driven Retrosynthetic Predictions for Energetic Materials Michael Fortunato, Connor Coley, Brian Barnes, Igor Schweigert, Ariana Beste, Klavs Jensen We present recent work in computer-aided synthesis planning strategies of interest to synthetic chemists, and demonstrate the utility of a new neural network for predicting synthetic pathways to energetic material precursors. These data-driven machine learning techniques have shown great promise in the pharmaceutical industry, and are poised to have a dramatic impact on the research and development process for novel materials. This work expands on previously developed techniques by addressing the ``rare template" problem. Although there is an abundance of computationally accessible reaction data, a significant data imbalance can make models less inclined to recommend energetically relevant reaction templates. A data augmentation strategy leveraging cheminformatics toolkits and high performance computing was used to train a deep neural network to restore fidelity to the rare, energetically relevant templates. The performance of this new neural network is compared to the previous one to highlight its enhanced predictive power for new synthetic routes for energetic materials. A web application created for transitioning this new model to synthetic chemists for everyday use will also be demonstrated. [Preview Abstract] |
Tuesday, June 18, 2019 10:15AM - 10:45AM |
H2.00005: High Pressure Chemistry as a Route Toward Novel Energetic Materials Using First Principles Crystal Structure Prediction Invited Speaker: Brad Steele At high pressures the underlying chemical bonding in materials can change compared to ambient pressure. This can result in stochiometric changes and novel compounds that are otherwise unstable at ambient pressure. For energetic materials, it is one possible route towards synthesis of high-energy high-density materials, extended solids, as well as energetic salts that more stable at high pressure than ambient pressure. In this talk I will discuss our recent discovery of alkali pentazolates at high pressures consisting of high energy all-nitrogen 5-membered rings (cyclo-N5-). I will also talk about other interesting high-energy materials predicted to exist at high-pressures using first-principles crystal structure prediction. I will discuss the method of crystal structure prediction including its successes, limitations, and challenges when attempting to guide experimental synthesis. I will also discuss more recent results on novel high energy materials at high pressures to motivate future areas of research in this field. [Preview Abstract] |
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