Insensitive Energetic Materials Research Articles

Sequential, Electrochemical-Photochemical Synthesis of 1,2,4-Triazolo-[4,3-a]pyrazines.

1,2,4-triazolo-[4,3-a]pyrazine was prepared via a two-step electrochemical, photochemical process. First, a 5-substituted tetrazole is electrochemically coupled to 2,6-dimethoxypyrazine to yield 1,5- and 2,5- disubstituted tetrazoles. Subsequent photochemical excitation of the 2,5-disubstituted tetrazole species using an ultraviolet lamp releases nitrogen gas and produces a short-lived nitrilimine intermediate. Subsequent cyclization of the nitrilimine intermediate yields a 1,2,4-triazolo-[4,3-a]pyrazine backbone. The scope of this reaction was explored using various tetrazoles and pyrazines. Materials produced were identified using chemical analytical techniques and computationally studied for potential application as an insensitive energetic material.

Improvement of Thermal Stability and Sensitivity of Furazan/Furoxan via Ring Closure Generation of Vicinal Amino-Nitro Structure.

Energetic compounds that display high thermal stability and insensitivity properties are essential for applications in mining, gas drilling, etc. In this work, a novel 4-nitro-5-aminoisoxazole energetic moiety oriented to enhance thermal stability and decrease the sensitivity of furazan/furoxan analogues was constructed. The generation of a vicinal amino-nitro structure can be effectively realized in one step by a green and mild ring-closing reaction of nitroacetonitrile potassium salt with chloroxime in aqueous solution. Seven new energetic compounds with good thermal stability (Td: 155.8∼270.3 °C) and low sensitivity (IS: >40 J, FS: 96∼192 N) were synthesized. The nitro-furazan and isoxazole combined product exhibits the advantages of both skeletons, with energetic properties (Dv = 8350 m s-1, P = 30.1 GPa) that may find value in insensitive energetic materials. This strategy promises to achieve a balance between energy levels and stability of furazan/furoxan analogues and offers a new way for the design and synthesis of highly thermally stable compounds that meet special applications.

Nitrate anions embedded in rigid and cationic 3D energetic MOFs constructed by the chelating ligand towards insensitive energetic materials

A rigid cationic 3D EMOF was prepared by a simple hydrothermal method using a nitrogen-rich chelating ligand, and a strong hydrogen bond interaction was formed to stabilize NO3− anions with high energy and low mechanical stimulation.

3-(3,5-Dinitrophenyl)-5-amino-1,2,4-oxadiazole：Synthesis, Structure and Properties of a Novel Insensitive Energetic Material

Safety and thermal stability of energetic materials are of increasing concern, while simpler synthesis routes are also a major goal for researchers in the field of energetic materials. To meet...

Synthetic manifestation of trinitro-pyrazolo-2H-1,2,3-triazoles (TNPT) as insensitive energetic materials.

This study showcases the design and development of a facile method for synthesizing trinitro-pyrazolo-triazole (TNPT) and its derivatives. The synthesized compounds are analysed using multinuclear NMR [1H, 13C, and 15N] and HRMS analyses. Furthermore, X-ray diffraction studies confirm the structure of some TNPT derivatives. Notably, compounds 8, 9, 11, and 12 exhibit good thermal stability with a decomposition threshold above 250 °C, and show a high level of insensitivity towards impact and friction [impact sensitivity (IS) is more than 25 J and friction sensitivity (FS) is above 180 N]. Compound 12, in particular, displays excellent performance characteristics [density 1.76 g cc-1 (at 298 K), a high detonation velocity (Dv = 8550 m s-1), and good thermal stability (Td = 280 °C), with high insensitivity towards impact and friction (IS = 35 J; FS = 180 N)]. The Hirshfeld surface analysis study provides further insight into the sensitivity of the TNPT derivatives.

The structural and electronic properties of (001) surface of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) with first-principles calculations.

1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is a typical insensitive energetic material. It can be used in explosive formulations, such as PBX-9502 and LX-17-0. TATB is an intriguing and unusual explosive for another reason: it crystallizes into a wide array of planar hydrogen bonds, forming a graphite-like layered structure. Therefore, TATB is one of the important research objects, and its surface structure needs to be deeply understood. In this research work, the electronic and energetic properties of TATB (001) surface are explored. In this paper, the structural, electronic, energetic properties and impact sensitivity of TATB (001) surface structure at 0 and -3 GPa along with x-axis were calculated in this study using the first-principles calculations. The calculations in this paper are performed in the CASTEP code, which is based on the density functional theory with the first-principles calculation method using the plan-wave pseudopotential approach. The exchange-correlation interaction was adopted by the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional. The DFT-D method with the Grimme correction accurately models van der Waals interactions. To model the surface structures of TATB, the planar slab method was employed. We constructed TATB (001) periodic slabs including three layers with a 15-Å vacuum layer.

An aldehyde-group-containing energetic ZIF with unprecedented “negative” catalytic properties for seven different energetic materials

Energetic materials possessing high energy content, exceptional heat resistance, and insensitivity have long been recognized as a significant and prominent subject of academic debate. In this study, the necessity for high-energy explosives in both military and civilian domains prompted the introduction of the concept of an “energetic negative-burning rate catalyst” in heat-resistant and insensitive energetic materials. Therefore, a typical and effective catalyst (ZIF-90) was discovered. ZIF-90, which can be easily synthesized and features a large specific surface area and regular pore structure, contributes to molecular-scale changes in the pyrolysis process of energetic materials. Additionally, the presence of surface aldehyde groups facilitates the partial absorption of heat, thereby collectively contributing to the augmentation of pyrolysis peak temperatures for seven distinct energetic materials (RDX, HMX, CL-20, LLM-105, LLM-126, AlH3, and DAP-4). Specifically, the pyrolysis peak temperatures were elevated by 6.6 ​°C, 1.7 ​°C, 1.6 ​°C, 6.4 ​°C, 1.4 ​°C, 13.1 ​°C, and 7.0 ​°C, respectively. Moreover, the highly stable ZIF-90, functioning as an intrinsically insensitive Energetic Metal-Organic Framework (EMOF), not only effectively mitigates the sensitivity of energetic materials but also ensures minimal energy loss. Notably, the incorporation of a mere 5 ​wt% of ZIF-90 resulted in a significant enhancement of over one-fold in the heat resistance of LLM-105-based explosive cylinders, thereby validating the practical applicability of ZIF-90 in energetic materials. Moreover, the efficacy of ZIF-90 in solid propellant formulations was corroborated through flame experiments conducted on solid propellants. The development of such a pragmatic and universally applicable energetic negative-burning rate catalyst presents a promising strategy for the future advancement of high-performance, heat-resistant, and insensitive energetic materials.

Synthesis and characterization of 2-amino-4,5-bis(tetrazol-5-yl)-1,2,3-triazole: A high-nitrogen energetic material with low sensitivities and high thermal stability

In this study, a high-nitrogen insensitive energetic material, 2-amino-4,5-bis(tetrazole-5-yl)-1,2,3-triazole (H2ABTT), was successfully synthesized by introducing the N-amino group on the 1,2,3-triazole ring. This compound exhibits excellent properties in many aspects. Compared to 4,5-bis(tetrazol-5-yl)-1,2,3-triazole (H3BTT), which has a decomposition temperature (Td) of 277 °C, nitrogen content of 75.11 %, density of 1.69 g cm−3, a detonation velocity of 8630 m s−1, a detonation velocity of 26.3 GPa, an impact sensitivity (IS) of 2 J, and a friction sensitivity (FS) of 240 N, H2ABTT exhibits higher thermal stability of Td:303 °C, higher nitrogen content of N%:76.35 %, higher density of 1.86 g cm−3, more desirable detonation properties (detonation velocity Dv: 9185 m s−1; detonation pressure p: 31.7 GPa), and lower mechanical sensitivities (IS > 100 J; FS > 360 N). Furthermore, H2ABTT outperforms insensitive explosive TATB (Dv = 8179 m s−1; p = 30.5 GPa; IS = 50 J; FS > 360 N) in some properties, making it a potential high-performance insensitive explosive. Besides, energetic salts 4–6 were successfully synthesized based on H2ABTT. The calculated results show that some of these salts even possess higher detonation performance compared to H2ABTT.

Assembling Nitroamino and Amino Groups on a Pyrazolyl-1,3,4-Oxadiazole Framework for the Construction of High-Performance and Insensitive Energetic Materials

AbstractThe introduction of nitroamino groups onto a nitrogen-rich heterocyclic skeleton is an efficient method for constructing high-performance energetic compounds. In this work, the nitroamino-functionalized compound 4-(5-amino-1,3,4-oxadiazol-2-yl)-N,N′-dinitro-1H-pyrazole-3,5-diamine was synthesized in yields of up to 83%. In addition, its energetic salts were also prepared. All these compounds were characterized by NMR and IR spectroscopy and, in two cases, by single-crystal X-ray diffraction. In addition, the difference in the reactivities of the three amino groups on the pyrazolyloxadiazole system was analyzed by an average local ionization energy analysis. The hydrazinium salt of the diamine exhibits promising detonation properties and good molecular stability, suggesting it has good application potential. Compared with previous works, this strategy gives an improved isolated yield and provides a promising method for the construction of nitroamino-functionalized 1,3,4-oxadiazole derivatives.

Thermostable Insensitive Energetic Materials Based on a Triazolopyridine Fused Framework with Alternating Nitro and Amine Groups

AbstractIn this work, we designed and synthesized a series of novel triazolopyridine fused-ring compounds with alternating nitro and amine groups. Three compounds showed remarkable thermal stability at 256, 310, and 294 °C, respectively, and a low mechanical sensitivity [impact sensitivity (IS) = 40 J, friction sensitivity (FS) = 324 N; IS = 35 J, FS = 240 N; and IS > 40 J, FS = 324 N, respectively]. Significantly, two of these compounds exhibited a better detonation performance [detonation velocity (D) = 8200 and 8335 m s–1, Detonation pressure (P) = 25.6 and 27.2 GPa, respectively] than the widely used heat-resistant explosive hexanitrostilbene (HNS; D = 7612 m s–1, P = 24.3 GPa). Additionally, a nitramine derivative displayed a detonation performance (D = 8569 m s–1, P = 31.3 GPa) similar to that of the high-energy explosive RDX. The superior properties of the materials were further confirmed by X-ray diffraction analysis and by several theoretical calculations (ESP, LOL–π, Hirshfeld surfaces, RDG, and NCI analyses). These results indicated that the three compounds might be potential candidates for use as heat-resistant energetic materials.

Enhancement of laser ignitibility of insensitive energetic materials (FOX‐7)

AbstractExperimental investigation into the feasibility of optically sensitising an insensitive explosive, FOX‐7 (1,1‐Diamino‐2,2‐dinitroethene) by the doping of gold nanoparticles (GNPs) has been conducted. The commercially available GNPs were specifically designed in their particle shape and size to strongly absorb at the wavelength of the igniting laser (808 nm). The laser ignitibility of FOX‐7 was significantly increased as the GNPs efficiently converted the absorbed energy into the heat. The laser ignitibility of such optically sensitised FOX‐7 and the detonation capability of the laser initiator devices designed for the study were evaluated. Based on the evaluation of the initiator's output in term of impact pressure, it was shown that an GNPs doped FOX‐7 based laser slapper initiator was able to detonate a secondary explosive.

A Dihydrazone as a Remarkably Nitrogen-Rich Thermostable and Insensitive Energetic Material.

Hydrogen bonds (H-bonds) in energetic compounds have a very pronounced effect on physicochemical properties such as density, thermal stability, sensitivity, and solubility. Now a strategy to synthesize nitrogen-rich energetic materials with overall good properties, which stem from the synergetic effects of inter- or intramolecular H-bonds, is reported. 1,2-Dihydrazono-1,2-di(1H-tetrazol-5-5-yl)ethane (4), a new thermostable and insensitive material, is obtained from the reaction of dioxime (2) with hydrazine hydrate. The exchange of the oxime (NOH) with the hydrazone (NNH2) functionality results in the reduced acidic character and low solubility in water, which make it remarkably suitable for practical use. While the detonation velocity of 4 is comparable with RDX, it has an advantage of high nitrogen content (76%) and high thermal stability (275 °C) and is insensitive toward external stimuli.

Pressure-Modulated Dissolution Behavior of LLM-105 Crystals in High-Temperature Water.

The exploration of the microstructural evolution and reaction kinetics of energetic materials with high-temperature and high-pressure water contributes to the understanding of their microscopic physicochemical origin, which can provide critical experimental data for the use of energetic materials. As a promising high-energy and insensitive energetic material, LLM-105 has been investigated under extreme conditions such as high pressure and high temperature. However, little information is available about the effect of water on LLM-105 under high pressure and high temperature. In this work, the interaction between LLM-105 and water under HP-HT was investigated in detail. As a result, the dissolving behavior of LLM-105 in water under high pressure and high temperature is related to the initial pressure. When the initial pressure is less than 1 GPa, LLM-105 crystals are dissolved in high-temperature water; when the initial pressure is above 1 GPa, LLM-105 particles are only decomposed in high-temperature water. When the solution is saturated at a high temperature, recrystallization of the LLM-105 sample appears in the solution. High pressure hindered the dissolution process of the sample in HP-HT water because the interaction between the solute and the solvent was weakened by high pressure. The initial pressure is one of the significant parameters that determines whether LLM-105 crystals can be dissolved in high-temperature water. More importantly, water under high pressure and high temperature can not only act as a solvent when dissolving the samples but also act as a catalyst to accelerate the decomposition process. In addition, the HP-HT water reduced the decomposition temperature of the LLM-105 crystal to a large extent. The research in this paper not only provides insights into the interaction between LLM-105 and water but also contributes to the performance of energetic materials under extreme conditions and their practical applications in complex conditions.

Scaled-up production and quality controlling techniques of energetic cocrystals: challenges and prospects

Cocrystallization techniques have become extremely important methods for obtaining novel high-energy insensitive energetic materials, and it has attracted great attention for the development of high-energy explosives and propellants, etc. in recent years. Several scale-up cocrystallization techniques including solvent-nonsolvent, semibatch reaction, bead milling, and spray drying methods et al. have been applied for obtaining the energetic cocrystals, and the preparation processes of these methods were also shown. The types and quality of raw materials and solvents, the synthetic times, morphology, and size of these cocrystals were described and compared by using different synthetic techniques in the review. Moreover, the principle, advantages and disadvantages of scale-up preparation methods were shown. More importantly, the preparation efficiency, the ratio between the quality of raw materials and the volume of solvent, and yield of different methods were also exhibited and discussed, which can provide key information and experiences for the future application of the materials. Finally, future research trends are suggested from different perspectives involving the formation mechanisms in the preparation process by using intermolecular interaction simulation, experimental study, and thermodynamic calculations, the optimization of traditional scale-up techniques, and the exploitation of novel methods for the energetic cocrystals.

Synthesis of Two Series of Isomeric Triazolo-Triazine Fused Energetic Salts: High Thermal Stability, Insensitivity, and High Performances

In recent years, the safety of energetic materials has attracted more and more attention. How to design and synthesize heat-resistant and insensitive energetic materials has become an urgent problem to be solved. In this work, two series of energetic salts based on isomeric triamino triazolo-triazine fused-ring compounds were designed and synthesized by incorporating oxygen-rich anions (such as NO3– or ClO4–) with nitrogen-rich energetic cations. All of the new compounds were fully characterized by infrared (IR) spectroscopy, nuclear magnetic resonance (NMR), elemental analysis, and differential scanning calorimetry (DSC). Decomposition temperatures (Td) of isomeric perchlorate salts 3 and 9 are 315 and 364 °C, respectively. Their different properties, densities and molecular stabilities are rationally explained based on crystal structures and packing patterns. Meanwhile, perchlorate 9 has the highest decomposition temperature and good detonation performance (D = 8485 m s–1, P = 27.7 GPa), which is superior to HNS and PYX and suggests that it could be applied as a heat-resistant insensitive explosive.

A new CL‐20/1,4‐DNP cocrystal explosive with good comprehensive performance

AbstractA new energetic cocrystal of 2,4,6,8,10,12‐hexanitrohexaazaisowurtzitane (CL‐20) and 1,4‐dinitropyrazole (1,4‐DNP) with a 1 : 1 molar ratio was prepared by slow solvent evaporation. This cocrystal belongs to monoclinic system with P21/c space group formed mainly by the CH−O, CH−N, and NO2−π interactions through analyzing the structures and interactions. CL‐20/1,4‐DNP cocrystal has a melting point of 132 °C with a decomposition temperature of 253 °C, showing an excellent stability. Moreover, the impact sensitivity of the cocrystal (13.5 J) is similar to that of 1,1‐diamino‐2,2‐dinitroethene (FOX‐7, 14 J), a typical insensitive energetic material, indicating a favorable low sensitivity. Furthermore, the detonation performances of the cocrystal (8954 m/s, 35.90 GPa) are slightly superior to that of 1,3,5‐trinitro‐1,3,5‐ triazacyclohexane (RDX, 8877 m/s, 34.94 GPa), suggesting that CL‐20/1,4‐DNP cocrystal has an excellent detonation property. Therefore, the CL‐20/1,4‐DNP cocrystal may be an attractive new explosive with a good comprehensive performance and thus, may be used as a promising candidate instead of RDX for safety ammunitions in future.

Increasing the limits of energy and safety in tetrazoles: dioximes as unusual precursors to very thermostable and insensitive energetic materials

Unusual thermostable and insensitive high-energy compounds which contain dioximes with donor–acceptor H-bond sites, were synthesized from glyoxal (40% in water) in straightforward steps.

Obtaining advanced insensitive energetic materials by regioselectively introducing N-oxide groups onto 6-trifluoromethyl-1,2,4,5-tetrazine-3-amine

Three N-oxide energetic compounds were selectively obtained from 6-trifluoromethyl-1,2,4,5-tetrazin-3-amine using four kinds of oxidation systems. Their structures were verified through 1H NMR, 13C NMR, IR, single-crystal X-ray diffraction, and elemental analysis, and their thermal properties were studied through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Moreover, their heats of formation and detonation properties were obtained using the Gaussian 09 and EXPLO5 v6.01 programs, respectively. Among them, compound 5 had excellent mechanical sensitivities (IS ​> ​60 ​J, FS ​> ​360 ​N) and high detonation performance (vD ​= ​7351 ​m ​s−1, p ​= ​23.9 ​GPa), which were comparable to those of TNT. Compound 7 was more sensitive (IS ​= ​27 ​J, FS ​> ​360 ​N) than compound 5, which was the isomer of compound 7. The mechanism for regioselectively introducing N-oxide was deeply investigated through the natural bond orbital (NBO) charge analysis. Furthermore, the relationships between the sites of N-oxides and the sensitivities were investigated using Hirschfeld surfaces, electrostatic potential, and 2D fingerprint plots, This study can be used as a reference for the development of the next generation of N-oxide-containing explosives.

Boosting Laser-Ignited Combustion Performance of Energetic Materials with Low Sensitivity: Integration of Triazene-Bridged Triazole with Oxygen-Rich Moieties via Noncovalent Self-Assembly

It has long been a driving force in the development of energetic materials to hunt for novel high-energy density materials (HEDMs) with high energy and good stability. Recently, the noncovalent self-assembly strategy of energetic anions and cations to generate HEDMs is an effective strategy for introducing an oxidizer and fuel separately into the energy system. In this study, bis(1,2,4-triazolyl)triazene containing triazene (−N═N═NH−) and oxidant molecules (i.e., HNO3 and HClO4) were selected as high-energy ions to develop new high energy materials by using noncovalent self-assembly. The experimental results showed that three exemplary compounds possess excellent detonation pressure and detonation velocity (PC–J: 22.8–29.3 GPa and D: 7425–8135 m s–1), which are comparable to the classical explosive trinitrotoluene (TNT) (PC–J: 19.5 GPa and D: 6881 m s–1) as well as 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) (PC–J: 34.9 GPa and D: 8795 m s–1). Moreover, 1 and 3 exhibit low mechanical sensitivities (IS: 40 J and IS: 70 J). Thus, 1 and 3 have great potential as insensitive energetic materials. Especially, these energetic assemblies have excellent laser-ignited combustion properties and can be used as candidates for low sensitivity propellants.

Lithium-Promoted Formation of M-2AZTO-Li (M = N2H5+ or NH3OH+ and AZTO = Anion of 1-Hydroxytetrazole-5-hydrazide)-Type “Quaternary” Complexes with Nitrogen-Rich Characteristics: Construction of Novel Insensitive Energetic Materials

Lithium-based nitrogen-rich complexes are important research objects in the field of high-energy materials. However, the weak coordination abilities of lithium ions relative to those of other metal ions with greater atomic numbers have hindered their applications in the field of nitrogen-rich complexes. Herein, we successfully prepared novel lithium-based nitrogen-rich complexes (N2H5-2AZTO-Li and NH3OH-2AZTO-Li) by exploiting the structural properties of 1-hydroxytetrazolium-5-hydrazine (HAZTO). Both N2H5-2AZTO-Li and NH3OH-2AZTO-Li were found to exhibit physicochemical parameters (including the density, stability, and energetic properties) that were intermediate between those of the simple ionic compounds (3 and 4) and the complexes (5) that formed them, enabling a favorable balance between high energy, high stability, and environmental friendliness (for N2H5-2AZTO-Li: detonation velocity (D) = 9005 m s-1, detonation pressure (P) = 35.5 GPa, decomposition temperature (Tdec) = 238.1 °C, impact sensitivity (IS) = 24 J, friction sensitivity (FS) = 210 N, and detonation product (DP) (CO) < 2%; for NH3OH-2AZTO-Li: D = 9028 m s-1, P = 35.7 GPa, Tdec = 211.2 °C, IS = 20 J, FS = 180 N, and DP (CO) < 2%). This study transcends the conventional structural forms of nitrogen-rich complexes, opening new horizons for the design of novel insensitive energetic materials.