Class Of Energetic Materials Research Articles

Construction of energetic metal-organic frameworks based on 5-aminotetrazole

Metal-Organic Frameworks (MOFs) have recently gained prominence as a novel class of energetic materials, owing to their systematic design and the ability to fine-tune properties such as energy content, sensitivity, and thermal stability. In this study, two new MOFs namely Cd(5-AT)3NH2(CH3)2+(1) and Zn(5-AT)(AMP) (2) (5-HAT = 5-aminotetrazole) were prepared under solvothermal conditions using 5-aminotetrazole as the high-nitrogen energetic ligand. X-ray single crystal diffraction analysis revealed that compound 1 possess an ABX3-type perovskite-like structure, whereas compound 2 forms a two-dimensional layer. The high thermal stability of both compounds were confirmed through thermogravimetry (TG) and differential scanning calorimetry (DSC). Their constant-volume combustion heat (ΔcU) was first determined by oxygen-bomb calorimetry and then the standard molar enthalpy of formation (ΔfHo) was calculated. Furthermore, both compounds demonstrated great detonation properties and low sensitivity, showing their potential application as new explosive materials (EMs).

Method and apparatus for automatic high-throughput synthesis of energetic salts

Energetic materials can instantly combust and release a large amount of energy in responding external impulses. Due to its energy characteristics, it has a wide range of practical applications: military and civilian. Designing high-energy-density materials with better performance, lower sensitivity, and more environmental friendliness has become a hotspot in the field of energetic materials in recent years. Energetic salts are formed by acid-base or metathesis reactions of different types of anions and cations. Energetic salts are a new class of energetic materials which were developed in recent years. Usually, they have high nitrogen content, high enthalpy of formation, high detonation performance, are relative stable to external stimuli, and have a wide range of application prospects in the fields of new explosives: low characteristic signal propellants, gas generators, low smoke or smokeless pyrotechnics. The synthesis method of energetic salts is simple, and the types of energetic materials are greatly enriched. This research takes energetic salts as the synthesis target and adopts multi-channel automation technology for high-throughput synthesis, which can improve the efficiency, reduce labor costs, and greatly increase the synthesis speed, which is of great significance for accelerating the synthesis of new energetic salts.

Rapid and On-Scene Chemical Identification of Intact Explosives with Portable Near-Infrared Spectroscopy and Multivariate Data Analysis.

There is an ongoing forensic and security need for rapid, on-scene, easy-to-use, non-invasive chemical identification of intact energetic materials at pre-explosion crime scenes. Recent technological advances in instrument miniaturization, wireless transfer and cloud storage of digital data, and multivariate data analysis have created new and very promising options for the use of near-infrared (NIR) spectroscopy in forensic science. This study shows that in addition to drugs of abuse, portable NIR spectroscopy with multivariate data analysis also offers excellent opportunities to identify intact energetic materials and mixtures. NIR is able to characterize a broad range of chemicals of interest in forensic explosive investigations, covering both organic and inorganic compounds. NIR characterization of actual forensic casework samples convincingly shows that this technique can handle the chemical diversity encountered in forensic explosive investigations. The detailed chemical information contained in the 1350-2550 nm NIR reflectance spectrum allows for correct compound identification within a given class of energetic materials, including nitro-aromatics, nitro-amines, nitrate esters, and peroxides. In addition, the detailed characterization of mixtures of energetic materials, such as plastic formulations containing PETN (pentaerythritol tetranitrate) and RDX (trinitro triazinane), is feasible. The results presented illustrate that the NIR spectra of energetic compounds and mixtures are sufficiently selective to prevent false-positive results for a broad range of food-related products, household chemicals, raw materials used for the production of home-made explosives, drugs of abuse, and products that are sometimes used to create hoax improvised explosive devices. However, for frequently encountered pyrotechnic mixtures, such as black powder, flash powder, and smokeless powder, and some basic inorganic raw materials, the application of NIR spectroscopy remains challenging. Another challenge is presented by casework samples of contaminated, aged, and degraded energetic materials or poor-quality HMEs (home-made explosives), for which the spectral signature deviates significantly from the reference spectra, potentially leading to false-negative outcomes.

Leveraging high heating rates to attain desirable reaction products in Al/Zr/C nanocomposites

Reactive nanolaminates are a class of energetic materials which store significant chemical energy in their heterogeneous microstructure that comprises alternating nano-scaled layers of two or more reactants which can undergo self-propagating exothermic reactions to form stable compound phases. We previously observed that the products of self-propagating formation reactions in Al/Zr/C nanolaminates differ dramatically from those obtained after heating slowly to any temperatures up to 1450 °C. Here we explore this heating-rate dependent phase formation in Al/Zr/C reactive nanolaminates through a combination of nanocalorimetry coupled with in situ synchrotron X-ray diffraction, as well as a suite of ex situ analyses. Specifically, we show that forming a cermet of ZrC + Al requires either a sufficiently high heating rate (such as is present during a self-propagating reaction) or quenching from high temperatures (≈ 1600 °C), demonstrating the utility of high heating rates to produce desirable phases.

PH-Controlled forms of 1-amino-1-hydrazino-2,2-dinitroethylene (HFOX): selective reactivity of amine and hydrazinyl groups with aldehydes or ketones

1-Amino-1-hydrazino-2,2-dinitroethylene (HFOX) is a potential reactive intermediate for a new class of energetic materials.

Energetic azide-based coordination polymers: Sensitivity tuning through diverse structural motifs

Energetic coordination polymers (ECPs), as a new class of energetic materials (EMs), have attracted extensive attention in recent years. However, controllable modulation of mechanical sensitivities and the establishment of structure-function theoretical models of ECPs to meet different applications remain great challenges. Herein, we designed and synthesized four azide-based ECPs, [Cd2(N3)2(datz)2]n1 (Hdatz = 3,5-diamino-1,2,4-triazole), [Cd(N3)2(brt)2]n2 (brt = 4,4′-bi-1,2,4-triazole), [Cd(N3)2(btzp)]n3 (btzp = 1,3-di(tetrazol-1-yl)propane), and [Cd2(N3)4(btzb)]n4 (btzb = 1,4-bis(tetrazol-1-yl)butane). Because of the existence of consolidated network structures, high-energy linkers, and diverse structural motifs, compounds 1–4 exhibit reliable thermal stabilities, tunable mechanical sensitivities, and considerable heats of detonation (ΔHdet) with the ΔHdet values of 3.390, 3.412, 3.947 and 4.504 kJ·g−1, respectively, which are two times higher than those of commercial LA (lead azide) and the reported AgMtta (AgMtta = [Ag(Mtta)]n, HMtta = 5-methyl-1H-tetrazole). The sensitivity measurements demonstrate that the sensitivity toward impact of 1–4 displays in the following order: 1 (>40 J) ≪ 2 (8 J) < 3 (2.5 J) < 4 (2 J). In particular, compound 1 features scarce insensitivity compared with sensitive 2, 3, 4 and most of known azide-based EMs. Furthermore, theoretical calculations, structural analyses, and experimental results revealed that the different sensitivities of the four ECPs are mainly dependent on two different structure models for the first time. The insensitive 1 is “body frame structure” model, while the sensitive 2–4 belong to “non-body frame structure” model. Our study enlightens new insights into structures behind mechanical sensitivities for optimizing advanced EMs.

Theoretical design of bis-azole derivatives for energetic compounds.

Bis-azole derivatives are a new class of energetic materials with features that include high nitrogen content, high heat of formation (HOF), high detonation performance and insensitivity to external stimuli. In this paper, 599 new bis-azole compounds were designed in a high-throughput fashion using bis-azole molecules of high density and high thermal decomposition temperature as the basic structure, and high energy groups such as nitro (–NO2) and amino groups (–NH2) as substituents. The molecular geometry optimization and vibration frequency analysis were performed using the DFT-B3LYP/6-311++G(d,p) method. The calculation results show that none of bis-azole derivatives exhibit a virtual frequency. Additionally, the density, heat of formation and characteristic height (h50) of the above compounds were obtained. Detonation performances were predicted by the Kamlet–Jacobs equations, and their structures and performances were studied. Furthermore, correlations between the performance parameters and the parent structure of the molecule, the number of substituting group and configuration were summarized, revealing promising potential candidates for high-energy density materials (HEDMs).

ADN and HAN‐Based Monopropellants – A Minireview on Compatibility and Chemical Stability in Aqueous Media

AbstractThis article gives a short review on compatibility and chemical stability of selected aqueous ADN and HAN‐based energetic formulations. A brief introduction will outline Energetic Ionic Liquids (EILs) as a new class of energetic materials with beneficial physical‐chemical properties which make them valuable for application in propulsion technologies. EILs combine the advantages of e. g. low toxicity, showing equal or superior propulsion power compared to the state‐of‐the‐art monopropellant hydrazine. Focus is set on open access ADN and HAN‐based monopropellant formulations that are e. g. realized in the advanced blends LMP‐103S, FLP‐106 or LGP 1845.

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 poten...

Multipurpose Energetic Materials by Shuffling Nitro Groups on a 3,3'-Bipyrazole Moiety.

A family of 3,3'-bipyrazole-based energetic compounds having C-NO2 /N-NO2 functionalities was synthesized by using various nitrating conditions. These nitro derivatives of bipyrazole are significantly more dense and energetic compared to the corresponding nitropyrazole analogues while maintaining the desired thermal stability and sensitivity. Depending on the number and nature of energetic nitro groups (C-NO2 /N-NO2 ), different classes of energetic materials, such as green primary explosives, high-performance secondary explosives and heat-resistant explosives, were obtained. All the compounds were thoroughly characterized by IR, NMR [1 H, 13 C{1 H}, 15 N], elemental analysis, and differential scanning calorimetry (DSC). Four were also structurally characterized with single-crystal X-ray diffraction studies. Heats of formation and detonation performance were calculated using Gaussian 03 and EXPLO5 v6.01 programs, respectively.

Bulk detection of explosives and development of customized metal oxide semiconductor gas sensors for the identification of energetic materials

Based on previous work, a setup allowing discrimination between energetic and non-energetic materials was developed. In order to cover novel materials not yet included in databases, a library free approach was chosen. The evaluation of explosion hazards for solid and liquid samples in the lowest milligram range was carried out by relying on the response of the substances towards thermal activation rather than on their chemical nature. The reaction was monitored by a combination of metal oxide semiconductor (MOX) gas sensors, photodiodes and a pressure sensor. Utilization of ambient air as a carrier gas and indirect control over sample weight by the geometry of the heater allow uncomplicated handling under real working conditions. In the first phase readily available physical and chemical sensors were applied. The rate of correct assignments was 99.8% with no false negatives and only 1 false positive out of 475 experiments. The possibility of library free operation was also confirmed by an additional series of experiments on materials not used for training the system. In the second phase the readily available MOX gas sensors were replaced by custom designed ones, which allowed single substances and classes of energetic materials by means to be discriminated by means of principal component analysis (PCA).

Experimental investigation on impact ignition of Al/PTFE reactive materials

Reactive materials are a new class of energetic materials that extremely and efficiently release energy under the influence of high impact loading. An impact tester is used in the present study to explore the impact ignition characteristics of Al/PTFE reactive materials and the impact ignition pressure of Al/PTFE reaction materials under different conditions. The experimental result shows that the critical ignition pressure is approximately 1.44 GPa. Meanwhile, it also shows that the material compactness has a much less pronounced effect on the impact ignition pressure for this reactive material if the loading time scales are of the order of several milliseconds. Plastic work and viscous heat both play a significant role in impact ignition. Finally, it is shown that impact ignition ensures a higher energy release rate than surface ignition.

ChemInform Abstract: Reactive Multilayers Fabricated by Vapor Deposition: A Critical Review

AbstractReview: 252 refs.

Nitroalkynes: A Unique Class of Energetic Materials

Forty-five years after their first preparation, nitroalkynes retain interest for their unique chemical behavior and their potential as energetic materials. This review encompasses the physical and spectral properties, synthesis, reactivity, metal complexes, and theoretical studies of nitroalkynes not previously reviewed, and those prepared after 1973. 1 Introduction 2 Physical Properties of Nitroalkynes 3 Spectral Properties of Nitroalkynes 4 Syntheses of Nitroalkynes 4.1 Unsuccessful Attempts 4.1.1 Nitration 4.1.2 Elimination 4.1.3 Retrocycloaddition 4.2 Successful Strategies 4.2.1 Nitration 4.2.2 Elimination 4.2.3 Nucleophilic Displacement 4.2.4 From Triazoles 4.3 Attempts at the Synthesis of Dinitroacetylene 5 Reactions of Nitroalkynes 5.1 Thermal Decomposition 5.2 Nucleophilic Addition 5.3 Cycloaddition 6 Metal Complexes 7 Theoretical Studies 8 Conclusion

ChemInform Abstract: 1,2,3‐Triazolo[4,5‐e]furazano[3,4‐b]pyrazine 6‐Oxide — A Fused Heterocycle with a Roving Hydrogen Forms a New Class of Insensitive Energetic Materials.

The straightforward synthesis and energetic properties of a new class of energetic materials, 1,2,3-triazolo- [4,5-e]furazano[3,4-b]pyrazine 6-oxide and its energetic salts are described. They were characterized by IR and multinuclear NMR spectroscopy, elemental analysis, differential scanning calorimetry, and single-crystal X-ray diffraction are given. The X-ray structures show that in the title compound, the hydrogen atom is bonded to the nitrogen in the pyrazine ring; however, in the salts, the negative charge is associated with the triazole nitrogen. Heats of formation for all compounds were calculated with the G2 method and then combined with experimentally determined densities to obtain detonation pressures (P) and velocities (D) by using EXPLO5 program. These new materials exhibit good densities and thermal stabilities, high heats of formation, acceptable detonation properties, and are insensitive to impact.

1,2,3‐Triazolo[4,5,‐e]furazano[3,4,‐b]pyrazine 6‐Oxide—A Fused Heterocycle with a Roving Hydrogen Forms a New Class of Insensitive Energetic Materials

The straightforward synthesis and energetic properties of a new class of energetic materials, 1,2,3-triazolo- [4,5-e]furazano[3,4-b]pyrazine 6-oxide and its energetic salts are described. They were characterized by IR and multinuclear NMR spectroscopy, elemental analysis, differential scanning calorimetry, and single-crystal X-ray diffraction are given. The X-ray structures show that in the title compound, the hydrogen atom is bonded to the nitrogen in the pyrazine ring; however, in the salts, the negative charge is associated with the triazole nitrogen. Heats of formation for all compounds were calculated with the G2 method and then combined with experimentally determined densities to obtain detonation pressures (P) and velocities (D) by using EXPLO5 program. These new materials exhibit good densities and thermal stabilities, high heats of formation, acceptable detonation properties, and are insensitive to impact.

Experimental study on impact-initiated characters of multifunctional energetic structural materials

Multifunctional energetic structural materials (MESMs) are a new class of energetic materials, which release energy due to exothermic chemical reactions initiated under shock loading conditions. In order to analyze the impact-initiated process of MESMs, a quasi-sealed test chamber, which was originally developed by Ames [“Vented chamber calorimetry for impact-initiated energetic materials,” in AIAA (American Institute of Aeronautics and Astronautics, 2005), p. 279], is used to study on shock-induced chemical reaction characters at various impact velocities. The impact initiated experiments are involving two typical MESMs, Al/PTFE (polytetrafluoroethylene), W/Zr and inert 2024 Al fragment. The video frames recorded from reactive and inert material impact events have shown the process of late-time after burn phenomena. The total pressure and shock wave reflection at the wall of the test chamber are measured using high frequency gauges. The quasi-pressures inside the test chamber, which is fitting from the total pressure curves, are used to determine the impact initiated reaction efficiencies of MESMs at different impact velocities. A thermochemical model for shock-induced reactions, in which the reaction efficiency is considered, is validated against the experimental data from impact initiation. The results show that the impact velocity plays a significant role in chemical reaction and the energy release characteristics of MESMs. The theoretical calculations correlate reasonably well to the corresponding experimental results, which can be used to predict the reaction results of MESMs over a wide range of pressure satisfactorily.

Structural Characterization of RDX‐Based Explosive Nanocomposites

AbstractRecently developed cyclotrimethylene trinitramine (RDX)‐based nanostructured explosive compositions were shown to exhibit greatly reduced initiation sensitivity as compared to conventional compositions prepared with coarser, micrometer‐scale RDX. In particular, improvements were shown in the sensitivity towards shock and impact stimuli, key sources of inadvertent initiation. Such an improved response to mechanical stimuli is believed to be largely a result of smaller crystal and void sizes. Characterization of these structural parameters is therefore necessary in order to construct a meaningful physical description of these novel explosive compositions. Herein, we report the results of a detailed structural characterization of these novel RDX‐based nanocomposites. The analyzed specimens were in pellet form with nominally 10 % porosity. These results constitute an unprecedentedly complete structural picture of this new class of energetic materials.

Thermochemical modeling of temperature controlled shock-induced chemical reactions in multifunctional energetic structural materials under shock compression

Multifunctional energetic structural materials (MESMs) are a new class of energetic materials which release energy due to exothermic chemical reactions initiated under shock loading conditions. In order to analyze shock-induced chemical reactions (SICR) for MESMs, theoretical models have been developed to calculate the Hugoniot data which include the heat released by shock temperature controlled reactions. The temperature rise of porous materials due to shock compression is first calculated using a constant volume and pressure adjustment. Then the Arrhenius reaction rate and Avrami-Erofeev kinetic models are used to calculate the extent of reaction of MESMs under shock compression. Thermochemical models for shock-induced reactions, in which the reaction efficiency is considered, are given by combining the shock temperature rise with the chemical reaction kinetics. The Hugoniot relations and temperatures are calculated by using the proposed method. The models developed have been validated against the experimental SICR data involving Fe2O3/Al, Al/Ni, and Ti/Ni mixtures. It has been shown that the theoretical calculations correlate reasonably well with the corresponding experimental and simulation results. The models presented can be used to predict the reaction results of MESMs over a wide range of pressure satisfactorily.

Quantum-Chemical Studies on Hexaazaisowurtzitanes

Highly nitrated cage molecules constitute a new class of energetic materials that have received a substantial amount of interest. Among them 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is a powerful explosive with poor impact and friction characteristics. In the present study we aim to design novel energetic materials by tailoring the molecular structure of CL-20. Important characteristics such as the heat of formation and density have been predicted using density functional theory and packing calculations, respectively. Sensitivity correlations have been established for model compounds by analyzing the charge on the nitro groups. Molecules IDX1, IDX4, and IDX7 have been found to have comparable performance with better insensitivity characteristics and may be explored as CL-20 substitutes in defense applications.