Energetic Materials Research Articles

A study on the isothermal decomposition kinetics of energetic cellulose-rich materials using a vacuum stability test

A study on the isothermal decomposition kinetics of energetic cellulose-rich materials using a vacuum stability test

Trailblazing 3D MOFs Featuring 1,2,4‐Dinitrimino Triazole: Redefining Energetic Materials and Iodine Encapsulation

AbstractThe quest for high‐performance energetic materials for defense and aerospace has intensified, focusing on balancing energy output and safety. This study presents the synthesis of 3D energetic metal‐organic frameworks (EMOFs) [Na3(DNT)(H2O)]n (Na‐MOF), [K2(DNT)2(H2O)]n (K‐MOF), and [Cs2(DNT)]n (Cs‐MOF) using 1,2,4‐dinitrimino triazole (DNT) through a hydrothermal process. The synthesized EMOFs are characterized using infrared spectroscopy, powder X‐ray diffraction, scanning electron microscopy (SEM), elemental analysis, and thermogravimetric analysis and differential scanning calorimetry, and structures confirmed via single‐crystal X‐ray diffraction, revealing 3D frameworks with crystal densities of 2.15, 2.16, and 2.86 g cm−3, respectively. Among them, Na‐MOF exhibits excellent detonation performance (VOD = 8900 m s−1, DP = 26.21 GPa), high thermal stability (Td = 369 °C), and insensitivity to impact and friction (IS = 40 J, FS = 360 N). K‐MOF displays balanced energetic and mechanical properties, while Cs‐MOF, though moderate in energetic performance, shows significant potential in pyrotechnic applications, producing a bright red flame. Intermolecular interactions are analyzed through Hirshfeld surface, 2D fingerprint, and SEM analyses, enhancing the understanding of particle size and morphology. Na‐MOF also demonstrates high iodine encapsulation capacity, positioning it as a potential replacement for traditional materials like RDX and heat‐resistant explosives such as HNS, with comparability to PYX.

Aging mechanisms and kinetics of bis(2,2 dinitropropyl) formal facilitated by transition state bifurcation and HONO catalysis

Serving as energetic plasticizer, revealing the aging mechanisms and kinetics of bis(2,2-dinitropropyl) formal is helpful to remove the safety hazards. Here, based on the DFT barrier of methylene-H abstraction by nitro group (HONO elimination) and the continuous reaction model, an experimentally comparable half-life of BDNPF is reported by transition state theory simulation. Rather than the HONO elimination-addition reactions, HONO bimolecular decompositions are preferred, where the energetically preferred pathway involves formation of N2O3, and generation of N2O4 and HNO catalyzed by HONO. Interestingly, newly reported transition state bifurcations lower the barriers and accelerate HONO decomposition, which also leads to the rate constant of generating HNO consistent with experiments. Moreover, HNO undertakes hydrogen transferred bimolecular pathway and HONO-catalyzed pathway to decompose into N2O and H2O. This work clarifies the degradation pathways and species, and is helpful to the deep understanding of the aging procedures of energetic materials.

Electroless Deposition of Ni Nanoparticles on Boron Particles: Physicochemical and Oxidation Properties

Elemental boron also has a high volumetric heat of combustion (136 kJ/cm3), the third highest gravimetric heat of combustion (58.5 MJ/kg) and its oxidation is a highly exothermic process. All these features make boron an attractive constituent of propellants, explosives, and high energy density solid fuels for air-breathing propulsion as an energetic material. Given these uses, researchers have worked on the ignition and combustion processes of boron. However, boron has several serious issues that limit its practical use, including large ignition delay, inefficient combustion, and a complex burning process in solid propellants due to the formation of a defensive boron oxide (B2O3) layer on the boron surface. Previous studies have found that the ignition and combustion performance of boron can be improved by coating it with metal particles, metal oxides, or organic materials, as well as by removing the boron oxide layer.In the literature, there are limited studies on metal particle coating of a boron surface using the electroless Ni plating method. The electroless coating has several impressive advantages over conventional electrolytic coating. The prime advantage is that electroless plating does not require any electricity to operate and is a low-cost process. Among other advantages, it provides a uniform coating and can be used with all kinds of substrates with complex shapes. Conductive and non-conductive materials/powders can be coated with constant thickness with good adhesion.The present work investigated Ni nanoparticle coating on irregularly shaped/non-spherical boron particles using the electroless Ni-plating method at room temperature to prevent the oxidation of boron particles. This is preferable since it is very difficult to coat large quantities at relatively high temperatures. The four different simple paths were chosen during the electroless Ni plating to coat Ni on boron particles: no rinsing and no drying (Path A), only drying (Path B), both rinsing and drying (Path C) and only rinsing (Path D). Previous studies have explored the effect of bath concentration, pH, and temperature on the Ni coating. However, the influence of the four different paths mentioned above on Ni coating with boron particles or any other materials has rarely been investigated. Surface morphology confirmed the Ni nanoparticles coating on the surface of boron particles. The size of the Ni nanoparticles varied between 10 and 120 nm concerning the chosen paths used for preparation using TEM. XRD characterization results of the Ni coated boron particles showed the formation of crystalline Ni nanoparticles. EDAX and XPS results showed the presence of the primary B and Ni elements in samples synthesized in the present study. Thermogravimetric analysis conducted in air atmosphere found the boron particles coated with Ni nanoparticles had enhanced oxidation resistance compared to bare boron particles. Also, the Ni coated boron particles showed a shift in exothermic peak to a lower temperature and higher heat evolution than the bare boron particles.Acknowledgements:This work was supported by the National Research Foundation (NRF) of Korea grant funded by the Korea government (MSIT) No. 2019R1A2C1010862, 2022R1A2C2013508

Expanding the π -conjugate structures: Synthesis of high-energy and insensitive Tricyclic fused energetic material

In order to meet the growing demand for different applications, great efforts have been made to develop new energetic materials with high energy and good safety. Fused cyclic energetic material, a special category of π-conjugate structures containing two or more rings, typically exhibits excellent performance and is currently a key focus of research. In this paper, we have designed and synthesized a new tricyclic, fused energetic material: 5-amino-[1,2,5]oxadiazolo[3,4-e]tetrazolo[1,5-c]pyrimidine 1-oxide (3). The reaction mechanism of the one-step reaction, including nucleophilic substitution and cyclization, has been theoretically investigated. Notably, compound 3 has a high density (1.864 g cm−3) at room temperature and good detonation properties (Dv: 8391 m s−1 and P: 28.2 GPa). Compound 3 has a relatively low impact and friction sensitivity (IS > 40 J, FS > 300 N), and acceptable thermal stability (Td: 175 °C), demonstrating the great potential of compound 3 as a high-energy, insensitive tricyclic fused energy-containing material.

A high-precision and near-zero residue laser-controlled gel propellant

Micro-nano satellites, with their advantages of small size, low power consumption, short development cycles, and capability for formation flying and networking, play a significant role in scientific research, national defense, and commercial applications. However, currently developed micro-nano satellites globally possess very limited maneuverability and lack effective attitude and orbit propulsion control. Solid propellants can offer some advantages such as high energy density and low cost, and they are extensively used in micro-and nano satellite propulsion systems. However, most of these propellants exhibit poor controllability and produce massive amounts of residual by-products. Laser-controlled gel propellants have been confirmed to be the most effective solution to address these issues in this study. The present study exhibits the preparation of ADN-based laser-controlled gel propellants using the freeze–thaw method and their controllable combustion characteristics under laser irradiation. The results show that the ignition delay time of gel propellants decreases from 93.0 ms to 34.6 ms, the extinction delay time is stable at around 2 ms, and the average burning rate increases from 0.6 mm/s to 1.5 mm/s under continuous laser irradiation with the power density ranging from 0.6 to 1.3 W/mm2. The average utilization rate of gel propellant is as high as 99.2 %. Upon testing, the residual solid matter was identified as unreacted propellant that had not been irradiated by the laser. Laser-controlled gel propellants represent a new type of energetic material that can be modulated to control its ignition, extinction, and burning rate. These capabilities overcome the challenges associated with the inability of traditional chemical propellants to extinguish and restart, thereby fulfilling the propulsion system requirements of micro-nano satellites.

Influence of high-reactivity energetic materials on microstructure and performance on iron-based cladding layer under low laser power

Abstract Under low laser power conditions, the cladding layer is constrained by inadequate energy density, resulting in incomplete melting of certain powder particles and the occurrence of defects such as cracks and pores within the layer. This paper utilizes a QT500 substrate and synergistically integrates high-reactivity energetic materials (H-REMs) with metal powder. By external laser energy ignition, the localized combustion of the H-REMs (Al + Fe2O3) is induced, thereby providing additional heat input during the laser cladding process. Through in-depth analysis of extensive experimental data, the influence of H-REMson microstructure and performance of alloy cladding layerhas beenrevealed. The research results demonstrate that the inclusion of H-REMs leads to a 450 K increase in the maximum temperature of the molten pool. By incorporating high-reactivity energetic materials, the energy density utilization of the composite material increased from 0.2663 to 0.7375. The combustion wave generated by H-REMs induces mixing in the molten pool, resulting in cladding layer grain refinement and an average hardness increase of 80 HV1. The friction coefficient decreases from 0.71024 (prior to the addition of H-REMs) to 0.35809, representing a reduction of approximately 49 %.

Insights into the Mechanical-Structural-Energetic Responses of RDX Nanoparticles from Molecular Dynamics Simulation.

When the particle size of energetic materials is reduced to the nanoscale, significant changes occur in their properties and behavior. In this work, compression processes of three RDX nanoparticles (A, B, and C) were simulated using ReaxFF-lg. The mechanical, structural, and energetic responses of RDX nanoparticles during compression were revealed and characterized. Simulations reveal that the compression process of the nanoparticles can be divided into three stages: elastic stage, primary damage stage, and sustained damage stage. The temperature increase rate in the elastic phase is much lower than in the primary damage phase. In addition, we found that the smaller nanoparticle B presents a smaller elastic modulus and compressive strength, and it has a slower rate of temperature increase during the primary damage phase. Compared to cuboidal nanoparticles (A and B), the spherical nanoparticle C tends to absorb less energy during the elastic stage and exhibits slower damage rate during the primary damage stage. This is a key factor contributing to the low sensitivity of spherical nanoparticles.

In-situ high pressure study of hydrogen-bonded energetic material N-nitropyrazole

The study investigated the behavior of N-nitropyrazole (1-NP, C3H3N3O2) under high pressure using a diamond anvil cell, Raman spectroscopy, and simulation calculations. The pressure–volume relationship of the sample, molecular interactions, and changes in optical Raman were analyzed. The Raman experiments revealed abnormal vibration intensities and a discontinuity in peak position at 2.2 GPa. For instance, the C-H stretching vibration produces a new vibration peak under pressure, and the NO2 torsion mode continues to red shift beyond 2.2 GPa. These observations suggest that the crystal’s phase transition results from the distortion of its hydrogen-bonded network structure. The pressure relief experiment confirms the reversibility of the phase transition.

Ti/CuO Nanothermite Doped with Secondary Energetic Materials: A Study of Combustion Parameters.

Nanothermites have found broad applications; however, due to being systems largely reacting in condensed phases, their performance is somewhat limited by heat and mass transfer. In order to alleviate this issue, nanothermites doped with gas-generating energetic materials have been developed. In this work, we present an investigation of a model Ti/CuO nanothermite doped by four classical energetic materials and investigate their properties and combustion performance. Mechanical and laser irradiation sensitivity, as well as ignition/explosion temperatures have been determined for the studied systems to establish their safety features. In terms of combustion performance, thrust force parameters and linear combustion velocity have been determined and the structure of the evolving flame front was recorded during open-air combustion experiments. The obtained results indicate that the developed doped nanothermite formulations are extremely promising materials for future applications.

Symmetric Refunctionalization of Diaminodinitropyrazine with Hydrazine and Aminotetrazole: Strategy for Enhancing Detonation Performance and Safety in Energetic Materials.

Two novel nitrogen-rich green energetic compounds were synthesized for the first time from readily available and cost-effective pyrazine starting materials. All newly synthesized molecules were comprehensively characterized, including infrared spectroscopy, nuclear magnetic resonance, elemental analysis, mass spectrometry, and thermogravimetric analysis-differential scanning calorimetry. All compounds have additionally been validated by single-crystal X-ray diffraction analysis. The physicochemical properties of compounds 2, 4, and 5 were thoroughly investigated. Notably, all compounds exhibit remarkable performance, such as a high density (>1.84 g cm-3), excellent detonation properties (VOD > 8582 m s-1, and DP > 31.3 GPa), outstanding thermostability (>205 °C), and high insensitivity (IS > 35 J, and FS = 360 N). These attributes are quite comparable to those of secondary benchmark explosives such as TATB, RDX, LLM-105, and FOX-7. This tuned performance evidences that the incorporation of hydrazine, nitro, and aminotetrazole into the pyrazine framework fosters robust nonbonded interactions, ultimately enhancing thermal stability and reducing sensitivity. The findings of this study not only signify that compounds 2 and 5 have excellent detonation properties and stability but also prove that the strategy of replacing amino groups with hydrazine and aminotetrazole is a practical means of developing new insensitive energetic materials.

Preparation, characterization and thermal properties of nitrographene coated aluminum powder

AbstractAluminum powder is commonly used as a metal fuel additive in composite solid propellants. However, its tendency to agglomerate during combustion can lead to two‐phase flow losses, negatively impacting its energy performance. To address this issue and enhance the combustion performance of aluminum powder, nitrated graphene oxide (NGO) was developed to improve aluminum dispersion and optimize its energy characteristics. Various analytical techniques were employed to examine its properties, including Fourier‐transform infrared spectroscopy (FT‐IR), scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), elemental analysis (EA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TG). Al/NGO composite was prepared using a solution‐assisted method in N, N‐dimethylformamide (DMF) and characterized by SEM, XPS and X‐ray diffraction (XRD). The ignition characteristics and heat of combustion of Al/NGO powder were measured using a laser igniter and an oxygen bomb calorimetry. The appropriate mass ratios of NGO coating had positive effects on the ignition and combustion of Al. Specially, 4 % NGO coating reduced Al ignition energy by 46.5 % and increased the Al combustion efficiency by 22.0 %. Moreover, the catalytic effect of Al/NGO on the thermal decomposition of ammonium perchlorate (AP) was investigated using differential thermal analysis (DTA). Results showed that two‐stage pyrolysis paths of AP tended to merge into a single pyrolysis process when Al/NGO4 % was added. The most favorable catalytic effect on AP′s thermal decomposition process was produced with the addition of 10 % Al/NGO4 %, reducing the activation energy by Kissinger equation for high‐temperature decomposition to 107.7 kJ mol−1. These findings may provide valuable insight for enhancing the performance of aluminum powder in energetic materials through NGO modification.

1-Trinitromethyl-3,5-dinitro-4-nitroaminopyrazole: Intramolecular Full Nitration and Strong Intermolecular H-Bonds toward Highly Dense Energetic Materials.

Full nitration is one of the most effective strategies used in synthesizing high-density energetic materials, but this strategy has reached its limit because the resultant compounds cannot be further functionalized. To overcome this limitation, we present the synergistic action of full nitration and strong intermolecular H-bonding in designing and synthesizing 1-trinitromethyl-3,5-dinitro-4-nitroaminopyrazole (DNTP) with a density that exceeds those of the reported monocyclic CHON compounds. The detonation velocity and specific impulse of DNTP exceed those of 1-trinitromethyl-3,4,5-trinitropyrazole (TTP), HMX, and ADN.

Fabrication and performance characterization of NTO/HMX spherical composite explosives with improved safety performance.

AbstractImproving the energy density and safety of explosives are crucial for developing composite energetic materials. In this study, a facile and continuous spray drying granulation technique was used to obtain NTO/HMX composite explosives with insensitive NTO as coating material. The micro‐morphology, particle size, crystallographic structure, exothermic decomposition, impact sensitivity, and detonation performance of NTO/HMX composite explosives with different NTO contents were investigated by various experimental methods. The test results indicate that the higher the NTO content, the better the crystal integrity of HMX and the lower the mechanical sensitivity of NTO/HMX composite explosives. When the mass ratio of NTO and HMX is 25 : 75, NTO/HMX composite explosives have a good spherical density structure formed by the aggregation of nanoparticles, small particle sizes with a median size of 1.22 μm, and a uniform distribution of particle sizes in the range of 0.3–2.8 μm. The addition of NTO not only enhances the thermal decomposition of HMX but also significantly decreases mechanical sensitivity. The composite explosives had not altered the raw NTO and HMX crystallographic structures (β‐type). With the same ratio (25 : 75), NTO/HMX composite explosives (25 : 75) possess higher impact energy and friction force, better safety, and better thermal stability than physical mixtures. Additionally, the high‐energy insensitive composite microspheres preserve the important high‐energy properties of HMX while effectively enhancing its safety characteristics, which have the advantages of controllable crystallographic micromorphology, high energy, and excellent impact sensibility and could be broadly applicable in the field of munitions.

Micron-sized aluminum particle combustion under elevated gas condition: Equivalence ratio effect

Micron-sized aluminum (Al) particle combustion under elevated gas condition is critical for improving energetic material performance, impacting propulsion and explosives technology. This study utilizes Eulerian-Lagrangian method to investigate Al particle combustion dynamics, encompassing both heterogeneous reaction (HTR) and homogeneous reaction (HMR). It focuses on the critical role of the equivalence ratio in single Al particle combustion, highlighting the interplay between HTR and HMR, aiming to optimize energy release and emission control. Our study identifies four stages in the combustion of a single Al particle, where the highest heat release is attributed to HTR, succeeded by HMR, and the minimal from unburned Al vapor. We observe a decline in the total heat release rate with an increasing equivalence ratio, primarily due to the differential impacts of heterogeneous and homogeneous reactions. The thermal-runaway stage in HTR is governed by the particle temperature, while the subsequent decaying stage is influenced by either the diminishing effective Al droplet diameter or the availability of oxygen, contingent upon the fuel conditions. Utilizing Cantera software to analyze HMR allows us to elucidate the thermal effects of elementary reactions and the key reaction pathways. These findings underscore the complex interactions between Al particles and the surrounding gas, providing insights into optimizing the conditions for Al-containing reaction systems.

Simulation and fabrication of reactive metamaterials for controllable energy response

AbstractSimulations and experiments were conducted to control the shock‐to‐detonation transition by energy trapping in localized regions of nitromethane that contained arrays of embedded dense particles (tantalum rods). The localizations were additively manufactured and designed with simulations carried out with ALE3D, that used the ignition and growth reactive flow model for the explosive. Modelling demonstrated enhanced reactivity when the tantalum rods were present, leading to a detonation that otherwise did not occur for the same strength shock without rods. Experiments that confirmed predictions of the simulation were conducted using Fritz plane wave lenses to drive various input shocks into the system. Photon doppler velocimetry was the primary diagnostic used to measure shock input and reaction progression. These results suggest that it is possible design explosives to localize sensitivity to shock loading within an insensitive material increasing the overall safety of fielded energetic materials.

Nitrogen-rich skeleton reassembled ECOFs as energetic materials with low sensitivities and good corrosion resistance

Corrosion between energetic materials and metal containers can accelerate material aging and failure, significantly affecting the safety, reliability, and lifespan of ammunition systems. To address this challenge, we propose the construction of energetic covalent organic frameworks (ECOFs) as a promising solution. We introduce a straightforward method for synthesizing nitrogen-rich ECOFs. The synthesized ECOFs were characterized through powder X-ray diffraction (PXRD), solid-state nuclear magnetic resonance (ssNMR), and Fourier-transform infrared spectroscopy (FTIR). These frameworks exhibit remarkable thermal stability, with decomposition temperatures above 285 °C. Notably, they display low sensitivity to non-explosive stimuli, as evidenced by impact sensitivity over 60 J and friction sensitivity over 360 N. The anti-rust properties of the ECOFs were further evaluated using Tafel curve analysis, highlighting their exceptional resistance to metal corrosion. Particularly, ECOF-3, synthesized from triaminoguanidine nitrate and 5-nitro-1,3-benzenedicarboxaldehyde, stands out for its superior steel corrosion resistance. These ECOFs have potential applications as high-energy, anti-corrosion coatings materials.

Low-sensitivity energetic material based on 1,2,4-oxadiazole

In this work, a new series of monocyclic compounds based on 1,2,4-oxadiazol-5(4H)-one was synthesized. The molecular structure, thermal stability and sensitivity to external stimuli for these compounds were characterized by X-ray diffraction analysis, NMR (1H and 13C) spectroscopy, IR spectroscopy, differential scanning calorimetry (DSC) and the standard BAM method. Compound 3-((2,2,2-trinitroethyl) amino)-1,2,4-oxadiazol (3) with trinitromethyl exhibits a higher decomposition temperature (Td = 143 °C) than that of 3-(dinitromethyl)-1,2,4-oxadiazol-5-one (4) (Td = 76 °C) reported in the literature. In addition, compound 3 exhibits lower impact sensitivities (IS) (IS = 10 J) than 4, N3-(2,2,2-Trinitroethyl)-1,2,4-oxadiazole-3,5-diamine (5) and RDX (4: 6 J; 5: 6 J; RDX: 7.4 J). Charge distribution and Hirshfeld surface were calculated to make further research on the intermolecular interaction of 3 with trinitromethyl. The difference in stability of these compounds is mainly due to the existence of intermolecular hydrogen bonds. These results indicate that compound 3 has promising application prospects as the energetic material.

First Comprehensive Study of Energetic (Methoxy-NNO-azoxy)furazans: Novel Synthetic Route, Characterization, and Property Analysis

This paper provides the first in-depth study of energetic methoxy-NNO-azoxy compounds. 3-Amino-4-(methoxy-NNO-azoxy)furazan (7) is a useful precursor to a number of high-enthalpy substituted (methoxy-NNO-azoxy)furazans enriched with explosophoric functionalities (azofurazan 8, nitrofurazan 9, azoxyfurazan 10 and methylene dinitramine 11). It was shown for the first time that the interaction of nitroso compounds with salts of O-substituted N-nitrohydroxylamines leads to the formation of corresponding azoxy-oxy [N(O)=N–O] compounds, as exemplified by the reaction of 3-amino-4-nitrosofurazan (15) with the ammonium salt of O-methyl-N-nitrohydroxylamine (16) to give 3-amino-4-(methoxy-NNO-azoxy)furazan (7). This novel approach turned out to be the most suitable for the multigram synthesis of aminofurazan 7. The resulting (methoxy-NNO-azoxy)furazans 7–11 have good thermal stability (onset decomposition temperatures 148–238 °C), high experimental enthalpies of formation (1435–2750 kJ∙kg–1) and acceptable densities (1.57–1.75 g∙cm–3). In terms of detonation performance, all synthesized compounds (detonation velocities D = 7.9–8.5 km·s–1, detonation pressures PC–J = 26–32 GPa) lie between 1,3,5-trinitro-1,3,5-triazinane (RDX) (D = 8.9 km·s–1, PC–J = 36 GPa) and N-methyl-N-(2,4,6-trinitrophenyl)nitramide (Tetryl) (D = 7.6 km·s–1, PC–J = 26 GPa). The sensitivity study was performed and the results were compared to those for prevalent energetic materials. We have shown the extent to which introduction of the methoxy-NNO-azoxy group into a molecule can be used to tune the crucial properties of energetic materials (enthalpy of formation and thermal stability).

Decomposition products of tetrazoles as starting reagents of secondary chemical and biochemical reactions

Rapid processes of tetrazole decomposition serve as sources of chemical energy stored in the five-membered ring, as well as gaseous products, primarily molecular nitrogen. Due to these properties, energetic tetrazole derivatives have found applications in various fields of science, engineering and technology, for example as components of energetic materials and products, as well as in emergency rescue equipment. The review presents an alternative view of the processes of tetrazoles decomposition, focusing on the diversity, differences, and similarities of the mechanisms and degradation products formed under the action of external energy sources. Some of these products are valuable reagents for the synthesis of previously inaccessible substances, as well as promising objects of analytical, medical, and bioorthogonal chemistry.<br> Bibliography includes 140 references.