Search

Recently, because of the complex international situation and combat environment in the future, the development and application of new concept weapons have raised higher performance requirements for manufacturing technologies. However, at present, most weapons are still prepared using traditional charging methods (cast curing, pressure casting, and melt casting), which require subtractive manufacturing (SM) treatments before use. At present, the demand for weapon products is shifting towards reactive micro structures, high preparation efficiency, miniaturization, and controllable energy release. Besides, the modern "energetic-on-a-chip" trend was expected to reduce size and cost while increasing safety and maintaining performance. In this case, the traditional charging methods were not preferred due to their inherent drawbacks, such as being limited to the model, requiring long solvent drying times and recycling required and pores/cracks caused by the shrinkage of slurry, and so on. Therefore, it is necessary to innovate the processing and manufacturing technology of weapons and address the boundaries of existing charging methods, and this will enable the precise customization of high-quality energetic materials and avoid many defects. Additive manufacturing (AM), or 3D printing technology, has been booming recently. The application of additive manufacturing technology in the field of energetic materials (EMs) can promote the innovation of manufacturing technology for EMs and regulate the microstructure. Additionally, 3D printing technology can break through the existing design and development mode, expand explosive charging technology, and enable the distribution of different types of explosives and explosive density in a specific space area. Besides, 3D printing can fabricate "reactive microstructures" (RMS), which offer a deeper understanding of the EMs' combustion and detonation phenomena at the micro- and nanoscale. Thus, the explosive/propellant grains with multiple damage modes can be designed and manufactured. This paper aims to summarize the current progress in the 3D printing of EMs, analyze the corresponding mechanisms, and provide guidance for future research. [ABSTRACT FROM AUTHOR]

Multiscale methods that are systematic, computationally efficient, and applicable to a wide range of materials are needed to complement experimental research in the development of improved explosives and propellants. Recent research has developed a new unified discrete Hamiltonian approach to multiscale simulation of reacting shock physics using a nonholonomic modeling methodology. The method incorporates the first extension of hybrid particle-element methods to reacting media, the first computational development of an ignition and growth model for condensed phase explosives, and the first use of temperature-parameterized recombination reactions, allowing reacting molecular dynamics derived chemical kinetics to be directly incorporated into the macroscale thermomechanical model. The formulation includes general material and geometric nonlinearities and both Lagrangian and Eulerian reference frames and has been validated in multiscale simulations of shock to detonation in two nitramine explosives. [ABSTRACT FROM AUTHOR]

The use of fluorinated binders can enhance the combustion properties of Al in energetic materials. The underlying mechanism is under investigation and a rational strategy in terms of application has yet to be fully developed. In this study, we have investigated the effect of using a fluorine‐modified hydroxy‐terminated polyether (HTPE) binder to cast aluminized propellants and explosives. We have focused on the combustion behavior and energy release characteristics of Al particles with and without the fluorinated binder during propellant combustion and explosive detonation. The propellants combustion process was recorded using a high‐speed camera and an infrared thermometer. The heat of detonation, detonation velocity and thermal stability of the explosives were investigated using a constant temperature calorimeter, an electrometric method and a small‐scale thermal cook‐off test, respectively. The fluorine‐modified HTPE propellant has exhibited a higher flame temperature and greater energy release efficiency than the HTPE propellant. Moreover, the fluorine‐modified HTPE propellant is characterized by smaller particle agglomerates, leading to a reduction in the mass percentage of agglomerates from 73 wt% to 42 wt%. The detonation heat of fluorine‐modified HTPE explosive increases from 75.2 % to 81 %, but the detonation velocity decreased from 7745 m/s to 7622 m/s. In addition, the fluorine‐modified HTPE binder maintained the thermal stability of explosives due to a milder decomposition before thermal runaway. [ABSTRACT FROM AUTHOR]

From three aspects of principle, qualitative analysis and quantitative analysis, the application research progress of five kinds of spectroscopy techniques, namely ultraviolet absorption spectroscopy, near-infrared spectroscopy, infrared spectroscopy, Raman spectroscopy and terahertz spectroscopy for explosives, were reviewed, and he application direction, advantages, and limitations of these five technologies were summarized. Moreover, the application of machine teaming in the analysis of explosive spectral data has been discussed. it is found that spectral analysis technologies ate wide! used in the field of explosive with their characteristics of safely, speed and accuracy, and they have great potential and application prospects. Finally, some suggestion for future research and development are shown. Spectral analysis technologies should not stay in the laboratory stage, but their advantages should give full pay, and then expand the application range of spectral analysis technology in the field of explosives. The future development direction includes multispectral, artificial intelligence, miniaturization and online monitoring technologies. 101 References are attached. [ABSTRACT FROM AUTHOR]

In response to the problem of the high friction sensitivity of 3,4-bis(3-nitrofurazan-4-yl) furoxan (DNTF) in solid propellants, the inherent component of solid propellants, nitrocellulose (NC), was used to coat DNTF explosives via the water suspension method. The coated samples were characterized by scanning electron microscopy (SEM) and friction sensitivity tests at a fixed 66° swing angle, and molecular dynamics calculations were performed to study the friction sensitivity and desensitization mechanism of NC-based DNTF coatings. The results show that NC, when used as a coating layer, can form a white gel on the surface of DNTF crystals, which can effectively reduce the friction sensitivity of DNTF. The coating effect becomes more obvious as the NC content increases. When the NC content is 5%, the friction sensitivity decreases by 72%, and a prediction formula for the exponential decay of DNTF friction sensitivity is obtained. MD calculation data show that NC can weaken the stiffness, enhance the elastic-plastic properties, increase the ductility and toughness of DNTF materials, and effectively improve the mechanical properties of DNTF. By combining experiments and simulation calculations, while considering the compatibility of new components and changes in propellant energy and other unpredictable new issues, NC can be referred to as a better coating layer for DNTF, as it has a certain feasibility for improving the friction sensitivity of DNTF. [ABSTRACT FROM AUTHOR]

Separation Distances are used throughout the world to protect people and assets from the potential hazardous effects from propellants, explosives, and pyrotechnics. The current separation distances for Hazard Division (HD) 1.3 substances and articles used in the United States, in some cases, may not adequately protect against the effects from heat flux and debris when those substances and articles are ignited in a confined structure. Multiple tests in such a confined scenario with HD 1.3 substances have shown that the heat flux and debris hazards could result in injury at distances beyond the current specified explosives safety separation distance (ESSD). Herein are the recommended ESSDs for confined as well as unconfined HD 1.3 articles and substances based on the analysis of hundreds of tests. Recommended ESSDs include a smaller value for unconfined quantities less than 145 kg and ESSDs that are consistent with NATO distances for confined substances and articles. [ABSTRACT FROM AUTHOR]

We apply the Green–Kubo (G–K) approach to obtain the thermal conductivity tensor of β‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazoctane (β‐HMX) as a function of pressure and temperature from equilibrium molecular dynamics (MD) simulations. Direct application of the G–K formula exhibits slow convergence of the integrated thermal conductivity values even for long (120 ns) accumulated simulation times. To partially mitigate this slow convergence, we apply a recently implemented numerical procedure that involves physically justified filtering of the MD‐calculated G–K heat current and fitting the integrated time‐dependent thermal conductivity to a physically motivated double‐exponential function. The thermal conductivity tensor was determined for pressures 0.1 MPa≤P≤ ${\le P\le }$ 30 GPa and temperatures 300 K≤T≤ ${\le T\le }$ 900 K. The thermal conductivity καβT,P ${{\kappa }^{\alpha \beta }\left(T,P\right)}$ increases with increasing pressure, by approximately an order of magnitude over the interval considered, and decreases with increasing temperature. The MD predictions are compared to experimental and other theoretically determined values for the thermal conductivity of β‐HMX. A simple, semi‐empirical fitting form is proposed that captures the behavior of κααT,P ${{\kappa }^{\alpha \alpha }\left(T,P\right)}$ over the pressure and temperature intervals studied. [ABSTRACT FROM AUTHOR]

Investigations of the detonation characteristics of a new aluminized DNAN‐based melt‐cast explosive RMA‐2X (containing 30 wt.% DNAN (2,4‐dinitroanisole), 30 wt.% NTO (3‐nitro‐1,2,4‐triazol‐5‐one), 10 wt.% HMX (1,3,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane) and 30 wt.% aluminum) were undertaken, as well as a lithium fluoride (LiF) substituted explosive RMF‐2X (containing 30 wt.% DNAN, 30 wt.% NTO, 10 wt.% HMX and 30 wt.% LiF). The interfacial velocity experiment was carried out to measure the reaction zone parameters (including the CJ pressure, the pressure at the Von Neumann spike, and the reaction zone length) of RMA‐2X. The cylinder test was also performed, and employing the test data, the detonation velocity, the Gurney energy, and the detonation energy of RMA‐2X were calculated. Investigation results are analyzed and some conclusions are drawn. The role of aluminum in the detonation characteristics are also discussed. Finally, parameters of the Jones‐Wilkins‐Lee equation of state of the detonation products were confirmed. [ABSTRACT FROM AUTHOR]

An Al-Ni alloy system with excellent energy density and mechanical performance is regarded as a novel high-energy–density material to enhance the energy emission of explosives or propellants. In this study, we explored the influence of a process control agent (PCA) varying from 0, 0.1, 0.25, 0.5, to 1.0 (wt.%) on the cryomilling of Al and Ni powder mixtures. The structural and morphological evolution of cryomilled Al-Ni powder was determined by X-ray diffraction, scanning electron microscopy, particle size distribution analysis, and transmission electron microscopy. Differential thermal analysis was used to study the exothermic reaction temperature, and activation energy calculations were performed using Kissinger plots. The results indicated that the addition of PCA changed the Al-Ni aggregate shape from oval to granular. The lamellar size also became finer after adding PCA up to 0.25 wt.% but the lamellar shape changed to granular at 1 wt.% PCA. These nanoscale lamellae serve as nuclei to produce Al-Ni reaction compounds, which gradually decrease the activation energy. The optimal concentration of PCA was determined to be 0.25 wt.% as this concentration decreased the activation energy of the Al-Ni alloy because of the fine, homogeneous, and alternate Al-Ni lamellae in the alloy when cryomilled. [ABSTRACT FROM AUTHOR]

Aluminum (Al) has been widely used in micro-electromechanical systems (MEMS), polymer bonded explosives (PBXs) and solid propellants. Its typical core-shell structure (the inside active Al core and the external alumina (Al2O3) shell) determines its oxidation process, which is mainly influenced by oxidant diffusion, Al2O3 crystal transformation and melt-dispersion of the inside active Al. Consequently, the properties of Al can be controlled by changing these factors. Metastable intermixed composites (MICs), flake Al and nano Al can improve the properties of Al by increasing the diffusion efficiency of the oxidant. Fluorine, Titanium carbide (TiC), and alloy can crack the Al2O3 shell to improve the properties of Al. Furthermore, those materials with good thermal conductivity can increase the heat transferred to the internal active Al, which can also improve the reactivity of Al. Now, the integration of different modification methods is employed to further improve the properties of Al. With the ever-increasing demands on the performance of MEMS, PBXs and solid propellants, Al-based composite materials with high stability during storage and transportation, and high reactivity for usage will become a new research focus in the future. [ABSTRACT FROM AUTHOR]

A computational and theoretical study of highly filled propellants was made. The dependences of the most important characteristics of propellant formulations (powder power, amount of gaseous products formed, combustion temperature) on the degree of filling with powerful explosives such as hexogen (RDX) and hexanitrohexaazaisowurtzitane (HNIW) were determined. The energy characteristics of promising propellants based on cellulose nitrates with the nitrogen content of 11.5% to 13.2% and a technological fluoropolymer additive F-42 were calculated using the REAL software. The calculated data allow choosing propellant compositions from a variety of formulation options with the set of thermodynamic characteristics (Tcomb from 1959 to 4327 K, FP from 443.7 to 1335 kJ/kg, with Mg from 27.2 to 46.4 mol/kg) required for solving a wide range of problems. [ABSTRACT FROM AUTHOR]

Total electronic energies and frequencies predicted using the deep learning models ANI‐1x and ANI‐1ccx are converted to gas‐phase formation enthalpies ΔfH0 using an atom equivalent (AE) scheme for a database of CHNO compounds. As expected from the accuracy of those models in predicting reference DFT frequencies and DLPNO‐CCSD(T)/CBS energies, this procedure usually outperforms DFT‐based AE schemes. However, for some compounds, including energetic molecules, significant deviations from experiment are observed, larger than obtained using DFT procedures. A close examination of the GDB‐11 database from which the training data was drawn reveals that many structures of interest in the energetic materials community are excluded from this extensive compilation primarily focused on drug discovery and designed with stability constraints in mind. This points to the urgent need to set up a comparable database including energetic species of interest for the design of energetic materials such as propellants or explosives. [ABSTRACT FROM AUTHOR]

Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] Novel efficient synthetic strategies, including green methodologies, to basic and perspective high-energy density compounds, bearing active oxygen sources (C -, N - and O -nitro groups and N -oxide fragments) and high-enthalpy polynitrogen heterocycles, are briefly overviewed. Recently developed synthetic approaches to nitro group-free hypergolic ionic liquids (HILs) and strained 1,5-diaza- bicyclo[3.1.0]hexane derivatives capable of ultrafast ignition upon mixing with an oxidizer, and to high-energy liquid hydrocarbons with strained cyclopropane fragments are also considered. Physicochemical properties, energetic performances and potential applications of energetic compounds and composites as key components of explosives, powders and solid or liquid rocket propellants are critically discussed with a focus on original reports published in the period 2016–2021. [ABSTRACT FROM AUTHOR]

High Energy Materials (HEMs) is a generic/umbrella term which is used for explosives, propellants & pyrotechnics and form an integral part of almost all weapon systems. A large number of HEMs have been reported in the literature in last few decades. This review paper discusses these HEMs in the light of a new classification of explosives proposed by Agrawal: Thermally stable or Heat‐resistant explosives, High performance (high density & high velocity of detonation) explosives, Melt‐Castable explosives, Insensitive high explosives (IHEs), Energetic binders & plasticizers and Novel energetic materials synthesized with the use of dinitrogen pentoxide (N2O5) technology. This review also critically examines these HEMs from the angles of scalability, processability, safety, reliability and performance in order to ascertain their potential for applications. In the end, problems associated with the use of currently available energetic materials & their likely solutions and areas for further research are also highlighted. [ABSTRACT FROM AUTHOR]

In this study, a novel three‐dimensional (3D) porous cross‐link network structure of nitrated bacterial cellulose (NBC) nano‐gel, as an energetic gel matrix for fabrication of nanocomposite energetic materials, (nEMs) was synthesized by sol‐gel synthetic and the freeze‐drying technology. The analysis results revealed that the unique network structure with abundant of nano‐porous, which made the thermal behaviour of the NBC gel different from that of raw NBC. The thermal decomposition kinetic and mechanism of the NBC gel indicated that the exothermic peak temperature of the gel matrix decreased at low concentration, and the activation energy (Ea) of the gel0.5 (150000 J ⋅ mol−1) was much lower than that of raw NBC (223510 J ⋅ mol−1). However, the decomposition kinetic parameters of this study were not enough to illustrate the thermal properties, and which needs more effort to study them and complete. Furthermore, the initial reaction of gel decomposition was the splitting of urethane bond, and then the scission of −O−NO2 bonds happened, and the macromolecular chains' breakage site of gel first occurred at −C−O−C− in the ring. After then, the chains of NBC break at −C−O−C− between the rings; notably, the heat‐release of gel was several times than that of raw NBC, which was liberated during the process of thermal decomposition. This promising research may provide potential application in preparing binder‐based nEMs and the basic theory of thermo‐analysis used in propellants and explosives. [ABSTRACT FROM AUTHOR]

Over the last decade, resonant acoustic mixing (RAM) technology has rapidly matured for use in the defense sector. Its ability to rapidly mix even highly viscous substances through application of acoustic energy while avoiding the use of traditional blades has provided substantial leaps forward in both safety and efficiency. To date, RAM has been applied by the energetics community to a variety of secondary explosive and propellant formulations with no reported incidents; however, the technology has never been rigorously evaluated with highly sensitive energetic materials, such as primary explosives. The work described in this report was performed to facilitate the establishment of safe operating procedures for the RAM mixing of primary explosives and primary explosive formulations. Through a Design of Experiments (DOE) approach, an analysis of mixing conditions that produce an initiation event was performed, which were used to set boundaries for the safe mixing of primary explosives and primary explosive formulations. For initial trials, uncoated copper (I) 5‐nitrotetrazolate (DBX‐1) was utilized, and boundaries were set for the results of this material only. [ABSTRACT FROM AUTHOR]

The research of all-nitrogen compounds has always been a hot topic in nitrogen chemistry and high-energy-density material communities. This research mainly focuses on acyclic and monocyclic all-nitrogen derivatives, while the bicyclic systems of all-nitrogen materials have been rarely investigated. In this study, four bicyclic all-nitrogen derivatives, viz bridged N10 and N12, and caged N10 and N12, are presented. Caged-N10 and caged-N12 exhibit much higher density (d: 1.84 and 1.89 g cm−3) and higher heats of formation (Hf: 15.19 and 16.41 kJ g−1) than bridged-N10 and bridged-N12 (d: 1.71 and 1.72 g cm−3; Hf: 7.64 and 10.24 kJ g−1), respectively. All these materials exhibit remarkable detonation performance (D: 9.87–12.29 km s−1; P: 39.41–72.26 GPa) and excellent specific impulses (Isp: 325.00–434.60 s), which is superior to the state-of-art CL-20 (D: 9.40 km s−1; P: 44.60 GPa; Isp: 272.61 s), endowing these materials with great potential as promising explosives and propellants. In addition, molecular electrostatic potentials, frontier molecular orbitals, and noncovalent interactions were studied to investigate their structure–property relationship. [ABSTRACT FROM AUTHOR]

The research of all-nitrogen compounds has always been a hot topic in nitrogen chemistry and high-energy-density material communities. This research mainly focuses on acyclic and monocyclic all-nitrogen derivatives, while the bicyclic systems of all-nitrogen materials have been rarely investigated. In this study, four bicyclic all-nitrogen derivatives, viz bridged N10 and N12, and caged N10 and N12, are presented. Caged-N10 and caged-N12 exhibit much higher density (d: 1.84 and 1.89 g cm−3) and higher heats of formation (Hf: 15.19 and 16.41 kJ g−1) than bridged-N10 and bridged-N12 (d: 1.71 and 1.72 g cm−3; Hf: 7.64 and 10.24 kJ g−1), respectively. All these materials exhibit remarkable detonation performance (D: 9.87–12.29 km s−1; P: 39.41–72.26 GPa) and excellent specific impulses (Isp: 325.00–434.60 s), which is superior to the state-of-art CL-20 (D: 9.40 km s−1; P: 44.60 GPa; Isp: 272.61 s), endowing these materials with great potential as promising explosives and propellants. In addition, molecular electrostatic potentials, frontier molecular orbitals, and noncovalent interactions were studied to investigate their structure–property relationship. [ABSTRACT FROM AUTHOR]

Owing to its simple preparation and high oxygen content, nitroformate [−C(NO2)3, NF] is an extremely attractive oxidant component for propellants and explosives. However, the poor thermostability of NF-based derivatives has been an unconquerable barrier for more than 150 years, thus hindering its application. In this study, the first example of a nitrogen-rich hydrogen-bonded organic framework (HOF-NF) is designed and constructed through self-assembly in energetic materials, in which NF anions are trapped in pores of the resulting framework via the dual force of ionic and hydrogen bonds from the strengthened framework. These factors lead to the decomposition temperature of the resulting HOF-NF moiety being 200 °C, which exceeds the challenge of thermal stability over 180 °C for the first time among NF-based compounds. A large number of NF-based compounds with high stabilities and excellent properties can be designed and synthesized on the basis of this work. Nitroformate is an attractive oxidant compound in propellants and explosives but its poor thermostability prevents it from application. Here, the authors demonstrate that incorporation of nitroformate in a hydrogen-bonded organic framework increases the thermostability of nitroformate. [ABSTRACT FROM AUTHOR]

Nitrogen-rich compounds are promising candidates for preparing high energetic density materials (HEDMs) and show the potential in the application of propellants, explosives, and pyrotechnics. Two kinds of typical nitrogen-rich compounds, such as tetrazine and triazole, have attracted the attentions in recent years owing to their high densities, good thermal stabilities, and excellent energetic performances. In this work, four series of innovative energetic compounds based on the conjugates of tetrazine and triazole bearing various substituents (–NH2, –NO2, and –NHNO2) were designed. The optimized structures, crystal densities, heats of formation (HOFs) in gas phase and in condensed phase, detonation properties, bond dissociation energies (BDEs), and impact sensitivity (h50) of these compounds were studied systematically via density functional theory (DFT) method. The detonation velocities of four series of compounds are in the range between 7.03 and 8.59 km s−1 and their detonation pressures are in the range between 20.6 and 33.1 GPa. Results indicated that the linkage of –N=N– bond contributed significantly to HOFs and energy density of the energetic molecules, and 1,2,3-triazole showed better performances than 1,2,4-triazole slightly. As for the same series compounds with different substituents, the compounds with –NHNO2 possessed the highest HOFs (such as A6, B6, C6, D6). In terms of the energetic properties (D and P), four compounds (A7, B7, C7, and D7) exhibited the comparable performance with the widely used hexa-hydro-1,3,5-trinitro-1,3,5-triazine (RDX) and in the meanwhile displayed superior thermal stability and sensitivity to RDX, which indicated their potential application in the insensitive energetic materials. [ABSTRACT FROM AUTHOR]

This paper reviews the ballistic properties, stability and vulnerability of gun propellants, gas generators and rocket propellants containing nitroguanidine (NGu), CAS−No [556‐88‐7] as an energetic filler. Nitroguanidine and its formulations burn stable over a broad pressure regime extending from subatmospheric to high pressures (0.1 kPa–400 MPa). Its high nitrogen content (53.83 %) and oxygen balance (Ω=‐30.75 %) effects a high gas pressure in gun propellants combined with low explosion temperature and consequently low signature and reduced erosion. NGu is an effective stabilizer for a broad array of energetic materials encountered in gun and rocket propellants including AP, ADN, HMX, RDX, NGl and also materials with low thermal stability such as NC, HNF, TNAZ and ADN. Finally, the low vulnerability of NGu‐based propellant formulations makes them taylor made to serve insensitive munitions. This review covers 31 NGu‐based rocket and gas generating propellant formulations, 44 gun propellants, five of which contain guanylurea dinitramide, (GuDN, FOX‐12), CAS−No [217464‐38‐5] for comparison, four reference propellants containing neither of the aforementioned ingredients and six combustible cartridge case formulations based on NGu. In addition, the combustion properties of pure NGu, pure GUDN and NGu modified with 17 different catalysts are revised. The review contains 142 references from the public domain. [ABSTRACT FROM AUTHOR]

A novel energetic material based on nanoporous carbons as main ingredient is herein reported for the first time. Prepared by filling the pores of nanoporous carbons with an oxidizer, its energetic character is demonstrated. The decomposition of the oxidizer confined in the nanopores of the carbon renders a material capable to sustain a detonation. The energetic character -temperature and reactivity- seems to be promoted by the nanoconfinement of the salts. The safety properties of such materials are in line with the requirements for application as high explosives or propellants. [ABSTRACT FROM AUTHOR]

The sensitivity of heterogeneous energetic (HE) materials (propellants, explosives, and pyrotechnics) is critically dependent on their microstructure. Initiation of chemical reactions occurs at hot spots due to energy localization at sites of porosities and other defects. Emerging multi-scale predictive models of HE response to loads account for the physics at the meso-scale, i.e. at the scale of statistically representative clusters of particles and other features in the microstructure. Meso-scale physics is infused in machine-learned closure models informed by resolved meso-scale simulations. Since microstructures are stochastic, ensembles of meso-scale simulations are required to quantify hot spot ignition and growth and to develop models for microstructure-dependent energy deposition rates. We propose utilizing generative adversarial networks (GAN) to spawn ensembles of synthetic heterogeneous energetic material microstructures. The method generates qualitatively and quantitatively realistic microstructures by learning from images of HE microstructures. We show that the proposed GAN method also permits the generation of new morphologies, where the porosity distribution can be controlled and spatially manipulated. Such control paves the way for the design of novel microstructures to engineer HE materials for targeted performance in a materials-by-design framework. [ABSTRACT FROM AUTHOR]

Simultaneous numerical solutions of the second and first order partial differential equations describing the first order decomposition of seven explosives are presented. The solutions were used to compare the critical rates of heat production per unit mass of each material. The lower such a rate is the more sensitive is the explosive. The relative sensitivities of Tetryl, PETN, RDX, TNT, HMX and TATB are as might have been predicted. However, PBX9404 shows apparently enhanced thermal sensitivity compared with these six explosives. This provides a warning that some modern low vulnerability composite explosives based partly on propellant ingredients might constitute enhanced thermal threats. [ABSTRACT FROM AUTHOR]

The rise of additive manufacturing has led to the development of new architectures and allowed researchers to 3D-print a variety of energetic composites with different formulations. However, reactive sintering within the composites can negatively impact overall performance of nanoenergetic or reactive materials via the loss of nanostructure. It has been previously proposed that the addition of a gas generator could reduce the impact of reactive sintering while enhancing reactivity. Iodine pentoxide (I 2 O 5) is an extremely powerful oxidizer and a strong gas generator which has been proposed as an efficient source of molecular iodine for biocidal applications. However, fabricated Al/I 2 O 5 nanocomposite propellants are unable to propagate. In this study, we demonstrate that the addition of small quantities of CuO enables consistent propagation. Employing high-speed pyrometry and microscopy, we estimate advective heat transfer in the system and demonstrate that the addition of CuO offers a pathway for enhanced energy-transfer by metal condensation that is not available when I 2 O 5 is the sole oxidizer. Elimination of condensing metal vapor as a participant in energy transfer increased the reliance of the system on particle advection. Small additions of CuO yield a condensable product vapor which can effectively eliminate the reliance on heat transfer via advection, enabling consistent propagation in reactive solid materials. We conclude with a general comment that where reliable propagation is critical, such as a stable burn of a solid propellant or delivery of a biocide, small additions of an oxidizer with a condensable metal vapor could be the difference between guaranteed performance and critical failure. [ABSTRACT FROM AUTHOR]

Ammonium nitrate (AN, NH 4 NO 3) constitutes the key ingredient of monofuels and civilian-grade explosives, attracting scientific interests aimed at improving their operational and safety performance. This study investigates the combustion properties of redox crystals comprising ammonium nitrate and simple saccharides, with the infrared spectroscopy, X-ray diffraction and molecular modelling. Furthermore, the thermogravimetric measurements afford the isoconversional analysis that yields the overall activation energies of the decomposition process. In addition, the synthesised samples are subjected to elemental and sorption analyses. The results outline (i) the molecular inclusion of the solid fuels within the lattice clusters of AN, (ii) a comparable hygroscopicity behaviour, i.e., a minor increase in affinity towards the absorption of moisture, and (iii) an energetically improved decomposition (and regression) rate, relatively to pristine AN. These features manifest themselves in lower activation energies of redox crystals that enhance the deflagrating properties of these materials for possible application in aviation propellants, and minimise the environmental footprint, especially the emission of nitrogen oxide to the atmosphere, which arises because of inhomogeneities in AN-fuel mixtures commonly used in civilian explosives. [ABSTRACT FROM AUTHOR]

The nitramines 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane (HMX), and 1,3,5-trinitro-1,3,5-triazinane (RDX) are energetic materials commonly used in solid propellants and explosives. In order to predict ignition and deflagration of propellants containing these ingredients, their thermal decomposition behaviors must be thoroughly understood. In this study, the thermal decomposition of HMX was investigated using synergetic application of experimental and computational methods. Mole fraction profiles of the gaseous decomposition products evolving from the liquid-phase HMX were obtained using Fourier transform infrared (FTIR) spectroscopy for two types of thermolysis experiments – thermogravimetric analysis (TGA) and confined rapid thermolysis (CRT). Four heating rates (5, 10, 15, and 20 K/min) in TGA experiments and four set temperatures (290, 300, 310 and 320°C) in CRT experiments were considered. In the TGA and differential scanning calorimetry (DSC) results, steep mass loss and rapid decomposition were observed after the melting of the HMX at 280°C. CH 2 O and N 2 O were identified as the major decomposition products. Smaller quantities of H 2 O, HCN, NO and NO 2 , CO and CO 2 were also formed. In the complementary computational study, liquid-phase elementary reactions were investigated using quantum mechanics calculations at B3LYP/6-311++G(d,p) level of theory with the conductor-like polarizable continuum model (CPCM). A zero-dimensional model was developed to simulate the TGA and CRT experiments based on conservation of mass and species in the condensed-phase and the gas-phase control volumes. The predicted mass loss and gas-phase mole fraction profiles of the decomposition products are in good agreements with the corresponding experimental results, indicating that the comprehensive mechanism proposed here captures the important reactions occurring during liquid-phase decomposition of HMX. [ABSTRACT FROM AUTHOR]

The supercritical CO2 foaming process is a preferable way to treat deserted SF‐3 propellants and solves problems of environmental pollution and waste of resources related to conventional treatment methods, and this process is an environmentally friendly method. In this paper, the effect of process conditions, including the immersion time of deserted SF‐3 propellants in the supercritical CO2 fluid, on the appearance of SF‐3 propellants and detonation performance of the perfusion explosive made from SF‐3 propellants are mainly studied. The results show that the diameter of foamed SF‐3 propellants increases with the immersion time when the immersion time is less than 60 min. When the immersion time is 60 min, the performance of the perfusion explosive made from foamed SF‐3 propellants is the best. The highest detonation velocity is 6683 m s−1, and the corresponding shock wave energy is 1.02 kJ g−1. When the immersion time is more than 60 min, the detonation velocity and the shock wave energy of the perfusion explosive made from foamed SF‐3 propellants decreases with the increase of the immersion time. [ABSTRACT FROM AUTHOR]

Smalls arms propellants (SAP) also known as canister powders are readily accessible and cost-effective materials that firearms enthusiasts can acquire for the legitimate assembly of ammunition. These attributes also make SAPs advantageous for the construction of improvised explosive devices (IEDs). Thus, there is a need to develop robust metrics for the characterization of propellants to provide investigative leads as well as for comparisons between known and recovered residues. The goal of this research was to investigate the utility of a high-throughput, non-destructive, and low-cost quantitative automated image analysis routine for the characterization and discrimination of SAP. For this project, 204 one-pound canisters of smokeless propellant (powder) were acquired from local and online sources. These samples represent nine manufacturers and 154 unique brands. From this set, five brands were selected to assess the intra- and inter-lot variability. Eight parameters, which encompass size- and shape-dependent metrics were measured for each sample. A total of ∼85,000 granules (∼680,000 measurements) were analyzed using linear discriminant analysis. A detailed assessment of the variables shows that the size-dependent metrics provide the greatest amount of sample discrimination. Overall accuracy of the method to correctly classify a test subset of data to the brand level is ∼84.72%. The results from this study provide a framework in which to interpret smokeless propellant micromorphometry in the context of intelligence purposes for initial stages of criminal investigations, and for traditional comparisons between known and unknown samples. • We show an automated image analysis routine for the examination of smokeless powder. • We present a framework in which to interpret smokeless propellant micromorphometry. • The method is high-throughput, non-destructive, and low-cost. • The overall accuracy of the method to identify the brand of propellant is ∼85%. [ABSTRACT FROM AUTHOR]

It is important to understand the mechanical behavior of polymeric materials that have a range of industrial and defence applications. In particular, several are used as the binder phase in plastic bonded explosives and propellants. Binder materials used in energetics need to be understood first to ensure their long-term, high-temperature stability when cycled during service, and second to ensure that the accidental loading of such materials leaves the explosives crystals within safe to handle. This work presents experimental data on equation-of-state and shock-induced damage evolution of the polymers teflon, estane™ and Kel-F-800™. The tensile (spall) strength at high rate was quantified using real-time laser interferometric techniques on each polymer as a function of impact stress. Measurements were made of the lateral stress under impact using manganin gauges, which, when combined with longitudinal data, allowed investigation of the shear strength of each polymer. An increase of shear strength, determined in this manner, was noted for two polymers and comparisons are drawn with others investigated using the same technique. A discussion of the mechanical response of these polymers is presented. [ABSTRACT FROM AUTHOR]

The dynamic compaction of granular beds of the propellant cyclotetramethylene tetranitramine (HMX) has been investigated using a modified split Hopkinson pressure bar system. Intergranular stress and bed porosity were simultaneously measured during controlled loading. The importance of grain size was investigated by comparing conventional HMX (mean particle size ∼260 μm) to microfine HMX (<5 μm). Samples were radially confined and compression was predetermined using special end caps. Initial porosity was varied by hydraulically pressing the beds prior to testing. With large grains, resistance to compaction increased with the solid volume fraction. Microfine HMX behaved like low porosity conventional HMX beds in all cases. Porosity was typically reduced by 5%–10% during compaction and intergranular stresses below the yield stress were ensured. Energy dissipation to plastic flow and fracture were largely eliminated. Optical particle size analysis and electron microscopy support the experimental observations. [ABSTRACT FROM AUTHOR]

Fluorine-containing explosives have potential applications in rocket propellant and explosive formulations because they produce a large number of products with a smaller molecular weight and high detonation performance when they are detonated. Here we synthesize a multifluorine substituted energetic compound: 1,3-bis(3,4,5-trifluoro-2,6-dinitrophenyl)urea (ZXC-19). ZXC-19 was synthesized by a simple, efficient and two-step reaction method with commercial reagents for the first time. ZXC-19 was characterized by means of mass spectrometry, multinuclear (1H, 13C, 19F) NMR spectroscopy, single-crystal X-ray diffraction, elemental analysis and DSC. The sensitivities were determined by BAM methods (a drop hammer and a friction tester). The heats of formation were calculated by using CBS-4M electronic enthalpies and an atomization method. Various detonation parameters such as detonation velocity and pressure were computed by using the Kamlet procedure. And the results showed that ZXC-19 has a poor solubility in water, a good solubility in most organic solvents, a surprisingly high density (1.899 g cm−3 at 298 K), a decent thermal stability, a positive and high heat of formation, and good detonation properties. [ABSTRACT FROM AUTHOR]

• Heat flow calorimetry allows chemical compatibility of propellants to be determined. • The absolute and relative assessment criteria can give contradictory results. • After 7 days at 85 °C an absolute heat flow of <15 J g−1 confirms compatibility. • Both assessment methods allowed very incompatible materials to be identified. • The relative assessment method generally gives a more lenient assessment. To ensure safety and reliability, it is important that the explosives and other materials used in munitions do not interact adversely either physically or chemically. Data obtained by heat flow calorimetry on nitrocellulose-based propellants have been reviewed with the aim of identifying improved chemical compatibility assessment criteria. It was shown that relative and absolute assessment techniques could give contrary sentencing. It was concluded that basing the assessment on the absolute criteria would have the advantage that alternative test temperatures and durations could be utilised. After 7 days at 85 °C the increase in the absolute heat flow of the mixture should be <15 J g−1 in order to be assessed as compatible. The assessment of compatibility is complex and improved sentencing results from additional testing at different temperatures to establishing the Arrhenius data and/or chemical analysis to understand the reactions contributing to the heat flow. [ABSTRACT FROM AUTHOR]

The syntheses and characterizations of two new energetic compounds based on a bis‐isoxazole scaffold are presented. The syntheses employ a metal‐free [3+2] cycloaddition of an alkyne and a nitrile oxide. In addition, we report the molecular structure of these compounds as determined by single crystal x‐ray diffractometry. Both materials have favourable sensitivity properties and low melting points. Their energetic properties indicate potential use as propellant plasticizers. [ABSTRACT FROM AUTHOR]