Energetic Materials Frontiers最新文献

This review provides numerous studies on nitrogen-rich tetracyclic-based heterocyclic energetic materials including oxadiazole, tetrazole, triazole, pyrazole, imidazole and tetrazine. The article mainly describes the construction method of energetic skeleton, explosive modification, and properties of tetracyclic energetic materials. The structure-property relationship was obtained by comparing the properties of a series of nitrogen-rich energetic materials. Finally, authors summarize the synthesis laws of energetic skeletons, which provides reference for the development of energetic materials in the future.

As a full nitrogen energetic anion, pentazolate (cyclo-N₅ˉ) holds great promise in the fields of propellants and explosives. Nowadays, nonmetallic pentazolate salts have received extensive attention as excellent nitrogen-rich energetic materials for their high enthalpies of formation, good oxygen balance, and eco-friendly decomposition products. In this study, a 1,4,5-triaminotetrazolium-based pentazolate salt (TATe⁺N₅ˉ, 8) with a nitrogen content of up to 90.30% was designed and synthesized. Its crystal structure indicates that a large number of hydrogen bonds form a hydrogen-bonded network, and the crystal has a mixed stacking pattern. TATe⁺N₅ˉ, which has a relatively high density (1.64 ​g·cm⁻³), high heat of formation (861.9 ​kJ·mol⁻¹), and excellent detonation performances (detonation velocity: 9487 ​m·s⁻¹, detonation pressure: 32.5 ​GPa), provides new insights into the stability of ultrahigh-nitrogen compounds.

Two new tetrazole ligands were designed and synthesized using simple methods in this study, namely 1H-tetrazole-5-carbohydrazide (HCHT, 1) and 2-amino-5-(1H-tetrazol-5-yl)-1,3,4-oxadiazole (HAOT, 2). Their solvent-free potassium salts [K(CHT)]_n (3) and [K(AOT)]_n (4) are new two-dimensional energetic metal-organic frameworks (EMOFs), and their structures were characterized using nuclear magnetic resonance (NMR), infrared spectroscopy (IR), mass spectrometry (MS), elemental analysis (EA), and single-crystal X-ray diffraction (SXRD). Both compounds 3 and 4 exhibit high decomposition temperatures (T_d) of 314 ​°C and 310 ​°C, respectively and are highly insensitive to impact and friction stimuli (IS ​> ​40 ​J, FS ​> ​360 ​N). The detonation velocity and pressure of 3 were calculated at 9141 ​m ​s⁻¹ and 29.0 ​GPa, respectively, and those of 4 were determined at 8423 ​m ​s⁻¹ and 24.5 ​GPa, respectively. Furthermore, intermolecular interactions in 3 and 4 were analyzed using 2D fingerprint plots with associated Hirshfeld surfaces. In this manner, two thermally stable and insensitive EMOFs were developed based on two new tetrazole ligands.

The equation of state (EOS) for energetic structural materials (ESMs) has been drawn a great attention due to the absent comprehensive understanding on the effect of the shock-induced chemical reaction. In this paper, the shock compression behavior of Ni/Al ESM is investigated by developing the EOS, which mainly considers the effects of the chemical reaction and the reaction products. The chemical reaction is based on the Avram-Erofeev kinetic law and the Arrhenius equation. The study concerns the shock pressure, the relative volume, the temperature, and the chemical reaction during the shock compression. The effects of the initial porosities, the stoichiometric ratios and inert additives were mainly discussed. The results showed that high porosity would induce high temperature rise. Different stoichiometric ratios would produce different temperature rise. When the stoichiometric ratio Ni: Al ​= ​1:1, the temperature rise is highest. In addition, the inert additive material would obviously reduce the temperature rise. Finally, the developed model improved the temperature calculation, compared with the existing model.

This study prepared a series of novel hypergolic fluids based on borohydride ionic liquids and organic superbase using an in situ synthetic method. In these hypergolic fluids, ionic liquids in 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) acted as triggers for the self-ignition of DBN and DBU upon contact with high-concentration hydrogen peroxide (H₂O₂). These hypergolic fluids had high densities (>1.000 ​g ​cm⁻³), low viscosities (as low as 34.03 ​cP), and acceptable ignition delay times (IDT). The ignition processes of the hypergolic fluids with 90% H₂O₂ as an oxidizer were first investigated in this study, and they differed from the previously reported ignition phenomena. Different from the case with white fuming acid (WFNA) as an oxidizer, the ignition processes of hypergolic fluids with 90% H₂O₂ as an oxidizer did not exhibit secondary rebound and splashing and formed a homogeneous mixed layer when the droplets were in contact with 90% H₂O₂. The different ignition processes significantly influenced the properties of hypergolic fluids. Compared with the hypergolic fluids with WFNA as an oxidizer, those with 90% H₂O₂ as an oxidizer showed a shorter IDT (IDT_{min[90% H2O2]=}28.3 ​ms, IDT_min[WFNA]=126 ​ms) and formed stable flames without secondary combustion. These results demonstrate that the in-situ synthesized fuels in this study hold great promise as green fuels in hypergolic propulsion systems.

To improve the mechanical properties of 2,4,6-trinitrobenzene-1,3,5-triamine (TATB)-based polymer bonded explosives (PBXs), four kinds of polythiourea binders, namely the polyetherthiourea (P1), aliphatic polythiourea (P2), aromatic polythiourea (P3) and silane polythiourea (P4), were prepared and used in the PBXs. These four polythioureas were synthesized via the copolymerization of carbon disulfide (CS₂) and diamines with various structures under mild conditions. They were then characterized using nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FTIR). The interfacial binding energy between polythioureas and TATB was calculated via molecular dynamics simulations. The tensile and compression mechanical properties of various PBXs (PBX-Pn, n ​= ​1–4) were studied through Brazilian and compression tests and were then compared with those of the PBX with a conventional fluoro polymer binder (PBX-FP). The results show that the PBX-P1 possessed the strongest interfacial interaction energy and the best mechanical properties among all the prepared PBXs. Its Brazilian strength and strain was 11.0 ​MPa and 0.56%, which was 89% and 256% higher than those of the PBX-FP with the same binder proportion, respectively. Furthermore, PBX-P1 showed excellent compression mechanical properties, with a compression strength of 40.7 ​MPa and a compression strain of 3.53%. Moreover, its Brazilian and compression fracture energy was 600% and 101% higher than those of PBX-FP, respectively, which was beneficial for improving the PBX stability. The results of this study provide a new idea for designing TATB-based PBX with improved mechanical properties using polyetherthiourea binders.

Micro-sized aluminum (m-Al) has been widely applied in explosives as fuel additives. Unfortunately, m-Al displays long ignition delay and insufficient combustion, making it fail to fully release its energy in aluminized explosives. In this work, fluoropolymer-coated m-Al composites were prepared using the solvent evaporation method. Then, the surface state of the m-Al composites was determined based on scanning electron microscopy (SEM) images, and their thermal behavior was investigated through thermogravimetric analysis (TGA) at a temperature range of 30–1200 ​°C. Moreover, the reactivity and combustion kinetics of aluminum were explored using laser ignition experiments. To evaluate the metal acceleration ability and detonation performance of CL-20-based explosives containing fluoropolymer-coated m-Al composites, the disc acceleration experiment (DAX) was specially designed taking into account the influence of aluminum particle size. The results of this study show that fluoropolymers were uniformly distributed on the surface of m-Al, and most of the as-prepared particles were microspheres without apparent agglomeration. The presence of fluoropolymers is beneficial to the oxidation of aluminum particles. The explosive sample containing fluoropolymer-coated aluminum composites exhibited shortened ignition delay and an increase in the burning speed from 3.3 ​mm·s⁻¹ to 7.9 ​mm·s⁻¹ compared to the sample with uncoated Al. Most especially, its specific kinetic energy increased from 8.45 ​kJ·g⁻¹ to 9.29 ​kJ·g⁻¹, its detonation velocity increased from 7.75 ​km·s⁻¹ to 7.82 ​km·s⁻¹, and its detonation pressure increased from 25.57 ​GPa to 30.89 ​GPa.

Formazans, containing the characteristic chain of atoms –NN-CRN–NH- (R ​= ​–CN or tetrazyl) are nitrogen-rich and conjugated compounds exhibiting unique properties. In this work, new cyano and tetrazylformazans and their series of nitrogen-rich energetic salts were synthesized via base-promoted gem-diazo coupling reaction. The resulting derivatives were well characterized, and their performances were further investigated. The experimental results indicated that the decomposition temperatures of 1–12 lie between 159 ​°C and 279 ​°C. All of them are much less impact sensitive (≥20 ​J) than trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). They have relatively high positive heats of formation between 987.7 and 1457.3 ​kJ ​mol^-1, which are much higher than those of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), RDX and HMX. The calculated detonation pressures (p) range between 23.2 and 30.2 ​GPa and calculated detonation velocities (D) between 7480 and 8274 ​m ​s^-1. Interestingly, compound 4 shows excellent laser ignition combustion performance.