ABSTRACTIn this work, two TNBA-based low eutectic mixtures, TNBA/TNAZ (TZ) and TNBA/DNTF (TD), as well as eight TNBA-based melt-cast explosives, TNBA/TNAZ/RDX (TZR), TNBA/TNAZ/HMX (TZH), TNBA/TNAZ/TKX-50 (TZT), TNBA/TNAZ/CL-20 (TZC), TNBA/DNTF/RDX (TDR), TNBA/DNTF/HMX (TDH), TNBA/DNTF/TKX-50 (TDT) and TNBA/DNTF/CL-20 (TDC), were developed as structural models. A molecular dynamics approach was used to model the cohesive energy density, binding energy, and mechanical properties of these explosives. Moreover the thermal decomposition properties and mechanical sensitivity were characterized via DSC and mechanical sensitivity tests. Finally, the EXPLO-5 software predicted the detonation properties and detonation products of the aforementioned 10 mixed explosive systems. The results showed that the four mixed explosives of TDT, TDH, TZC, and TDR had excellent performance in cohesive energy density, binding energy, and material rigidity, respectively. The temperature difference was comparatively significant between the melting temperature and decomposition temperature of the eight types of mixed explosives, up to 170.60 K, with TDH and TZH having the highest thermal decomposition temperature at approximately 520 K. The six kinds of mixed explosives of TZR, TZH, TZT, TDR, TDH, and TDT had moderate mechanical sensitivities. . The five types of mixed explosives, TZT, TZC, TDH, TDT, and TDC, had the greatest detonation velocity.

ABSTRACTPresent work demonstrates the effect of in tandem application of chemo-mechanical methods on physio-chemical and thermo-sensitive properties of HMX. Solvent-antisolvent recrystallization produced γ-polymorph of HMX with mean diameter ~7 μm and ~8 μm when acetone and DMF were used as solvent respectively, whereas with γ-butyrolactone, β-HMX with larger particle size (mean diameter ~24 μm) was produced. Ultrasonication initially (1 h) resulted in increase in particle size but with increase in duration (24 h) particles size decreased to (~4 μm) whereas, ball milling resulted in decrease in average particle size to ~1 μm with β-polymorphic form with reduced impact sensitivity.

ABSTRACTAluminized explosives are widely used in underwater explosives, and their energy release follows a typical time-varying process involving two stages: explosive detonation and afterburning of aluminum powder. Simulated deep-water explosion experiments of hexanitrohexaazaisowurtzitane (CL-20)-based explosives were conducted using a deep-water explosion pressure tank to study the effect of aluminum powder combustion on the shockwave propagation and bubble pulsation of deep-water explosions. The distribution mechanism of aluminum powder afterburning energy in the process of shockwave propagation and bubble pulsation under a high hydrostatic pressure was clarified, and the effect of aluminum contents on the bubble behavior of deep-water explosion was obtained by the proposed calculation method of bubble behavior. The results showed that the pressure of the shockwave of the CL-20-based aluminized explosive was lower, and the energy released by the combustion of aluminum powder increased the pressure in the middle and end of the shockwave’s trailing edge, reduced the shockwave attenuation rate, and increased the first bubble pulse pressure and pulse period. The afterburning phenomenon of aluminum powder in the CL-20 aluminized explosive in explosion bubbles under high hydrostatic pressures was captured in the simulated deep-water explosion experiment for the first time. It was proven that the combustion time of the micro-aluminum powder was at the millisecond level, and the maximum radius of the bubble increased with the afterburning of aluminum powder. The characteristic parameters of the first pulsation of the CL-20-based explosive with different aluminum content in deep-water explosions calculated by the second-order Mach accuracy bubble dynamics equation and the equation of state of the explosion products were within 7% of the experimental values. The change of the afterburning process of the aluminum powder caused by the aluminum content has a great influence on the bubble behavior, and through the design of aluminum content, ideal deep-water explosion bubble characteristic parameters can be obtained.

ABSTRACTThe energetic characteristics of a novel ionic cocrystal composed of 1H-tetrazole/sodium perchlorate and differences of properties between the cocrystal and simple mixture are reported herein. Cocrystals containing reductants and oxidizers exhibit enhanced energy release rate compared with their simple mixture owing to their short molecular distances. Differential scanning calorimetry, thermogravimetric analysis, sensitivity tests and humidity tests are performed to clarify the properties of the cocrystals and simple mixture. The calculated detonation velocity of the cocrystal was higher than that of 1H-tetrazole. The cocrystal achieves high deflagration performance, as evaluated via a pressure vessel test.

ABSTRACTTKX-50, as a representative of a new nitrogen-rich energetic compound, has attracted extensive interests due to its high energy and low sensitivity properties. As an important energetic material, combustible agent has great influence on improving the energy level of explosives and propellants. Boron powder has become the most potential combustible agent in energetic fields because of its unique performances. In this work, nano-boron-based microspheres containing TKX-50 are directly fabricated by electrospray deposition. The prepared microspheres showed high monodispersity with particle size ranging from ~1–3 μm. Thermal behavior results show that the mass gain of the electrostatically sprayed sample is 163.3%, which is much higher than that of pure boron and physically mixed samples. Combustion behavior tests show that electrosprayed microspheres exhibit outstanding performance in comparison to physical mixed sample, the peak pressure improved by 85%, the burning time decreased by 21% and the pressurization rate improved by 136%. These excellent properties are probably related to their uniform microstructure. Therefore, electrospray preparation of microspheres with controllable structure has a good application prospect in energetic materials.

ABSTRACTThe efficient design and synthesis of energetic compounds with the highest possible energy and chemical stability has attracted enormous attention due to their high-tech applications. Here we show an energetic compound, 3,5-difluoro-2,4,6-trinitroaniline (8), the relationship between structure and properties is discussed based on the single-crystal diffraction data and several theoretical techniques. It exhibits exceptionally outstanding combination properties, high density (1.861 g cm−3 at 273 K), poor water solubility, high thermal stability (Td = 243°C), superior mechanical sensitivity (IS = 35 J, FS = 360 N), and acceptable detonation properties (VD = 8331 m s−1, P = 31.1 GPa), make it the potential candidate of insensitive high-energy material.

ABSTRACTThis paper presents a comprehensive analysis of the effects of water content and ambient temperature on the mechanical stimulation threshold of hydroxylammonium nitrate (HAN) based liquid propellant. Based on the stability analysis of slow cook-off test for HAN-based liquid propellant, the mechanical sensitivity of the liquid propellant with different water content was evaluated at different ambient temperatures in detailed. Differential scanning calorimetry was employed to investigate the influence of water content on the stability, demonstrating a significant dependence on water content. Additionally, the impact sensitivity of liquid propellant, which is strongly influenced by the variation of initiating bond length with the ambient temperature, was investigated using large scale atomic/molecular massively parallel simulator (LAMMPS), highlighting a notable correlation between the impact sensitivity and ambient temperature. The findings of this research contribute towards understanding the hazard level associated with HAN-based liquid propellant, providing crucial guidance for its formulation design, practical application and safety management.

ABSTRACTDue to safety requirements, insensitive behavior under slow cook-off conditions is the desirable behavior for HTPE propellant. As a low sensitivity oxidant, PSAN is used to partially replace for AP in HTPE propellant formulation to improve the slow cook-off behavior further. But the effect of PSAN on the slow cook-off behavior of propellant is inconclusive. So, in this paper, two kinds of HTPE composite propellant contained either AP as oxidant or a mixture of AP and PSAN were manufactured, named HTPE/AP/Al propellant and HTPE/AP/PSAN/Al propellant respectively. Then the slow cook-off behavior of the two propellants were tested. The results indicated that the slow cook-off response of HTPE/AP/PSAN/Al propellant was much more violent than the response of HTPE/AP/Al propellant. Then the possible mechanism was proposed. It expressed that, during the slow cook-off test, the PSAN decomposed much more than AP, the crack and hole produced in propellant grain; meanwhile the decomposition of PSAN also accelerated the decomposition of HTPE binder, the the crack and hole or AP particles could not be covered effectively by the liquefied decomposition product of HTPE binder; if the ignition occurred, the combustion of thermal damaged propellant was sensitive to pressure, leading a violent response to slow cook-off.

ABSTRACTIn recent years, hollow cage-type molecular structures have attracted much scientific attention and have unique properties due to their structure. One of these mentioned compounds and most interesting high energetic molecules developed in recent years is the polycyclic nitramine, 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane or (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo dodecane, HNIW or CL-20).CL-20 is a new explosive that is 14~20% more powerful than HMX (tetranitrotetraazacyclooctane). CL-20 has a cage structure in polycyclic nitramine class with interest high density (ρ>2 g/cm3) and heat of formation (∆Hf = 100 kcal/mol). Also, CL-20 has several polymorphs such as α, β, γ, and ε. Its high detonation velocity and pressure make it a suitable candidate for replacing HMX. CL-20 has numerous military and commercial applications. Many reports have been published on the chemical and physicals characteristics of this energetic compound. In recent years, continuous advances in this field have established various methods for synthesizing CL-20.In this review article, various techniques and strategies to achieve CL-20 were studied, comprehensively.

ABSTRACTThis study reported the valorization of various alternative lignocellulosic feedstocks including giant reed (GR), palm fronds (PF) and esparto grass (EG) for the development of promising nitrated structurally modified cellulosic biopolymers (NNCs). The extracted nanostructured cellulose precursors and their nitrated derivatives were analyzed for their physicochemical properties, chemical structure, crystallinity and thermal stability. Experimental findings confirmed the successful formation of the desired energetic NNCs polymers with increased densities (1.698–1.711 g/cm3) and high nitrogen contents (13.10–13.26%) followed the order NNC-EG>NNC-PF>NNC-GR, which are greater than those of the commonly used nitrocellulose (1.650–1.670 g/cm3 and 12.50–12.70%). Furthermore, isoconversional integral models (TAS, it-KAS and VYA/CE) were exploited based on non-isothermal DSC data to investigate their thermal decomposition kinetics. The predicted kinetic parameters displayed that the synthesized energy-rich NNCs presented close values of Arrhenius parameters within the range of 156 ≤ Eα (kJ/mol) ≤163 and 14.7 ≤ Log(A(s−1) ≤ 15.6, and decomposed following diverse reaction mechanisms. Consequently, the explored lignocellulosic biomasses could be considered as valuable alternative non-woody resources for the production of advanced high-energy dense cellulosic biopolymers for potential application in the next generation of solid propellant formulations and composite explosives.

ABSTRACTA comprehensive study on the surface morphologies and element distributions of Mg–Al alloy particles and Mg–Al alloy/Teflon/Viton composite (MATV) during oxidation was conducted via scanning electronic microscopy and energy-dispersive X-ray spectroscopy. The formations of the reaction products of MATV were further analyzed via X-ray diffraction. By the temperature of 600°C, a fluorination reaction between Teflon and the alloy underwent on the alloy surface, involving the reaction of the αMg prime phase at lower temperature. A MgF2–AlFx shell surrounding the alloy particle was also generated simultaneously. This shell could elevate the oxidation temperature from the melting point of the alloy to 600~859°C. Furthermore, this shell could also severely decrease the oxidation rate of the exceeded alloy with O2. As the slower oxidation of the homogeneous liquid alloy began at higher temperature, a different mechanistic reaction from that of the pure alloy underwent. MgO particles rather than MgO ridges on the pure alloy surface were generated.

ABSTRACTIn order to balance the contradiction between safety and performance of energetic compounds, a novel approach known as cocrystallization has been widely utilized. In this work, a novel cocrystal of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) and ammonium perchlorate (AP) was successfully synthesized and characterized. The SEM images, PXRD spectra, and FT-IR spectrum confirmed the varied crystal structure of the cocrystal in comparison to the raw materials. In addition, the density of the cocrystal was measured to be 1.90 g.cm−3, and the detonation velocity and detonation pressure were calculated to be (8.53) km.s−1 and (35.21) GPa, respectively.

ABSTRACTAn analytical model for calculating the pressure of detonation product on the liner surface was presented. Calculation results show that when the liner structure is the same, increasing the inscribed circle diameter of the charge cross section can reduce the influence of the charge nonaxisymmetry, when it is greater than the critical value, that is, 1.66× liner diameter, the pressure on liner surface is distributed axisymmetrically. Therefore, the jet of the shaped charge with isosceles trapezoidal cross section can be prevented from having an offset velocity by the above-mentioned method. This finding is verified through numerical simulation.

ABSTRACTAiming at the influence of the embedded gap on the impact initiation of the flat flyer of PBX-9502, the finite element simulation software LS-DYNA and the I-G model are used to establish the numerical calculation model of the cylindrical PBX-9502 with the embedded gap for the impact initiation of flat flyer, and analyze the influence of different impedance. The effect of the thickness and position of the large impedance gap on the reduction of the flyer initiation threshold is studied, the initiation velocity thresholds under different conditions are obtained, and the causes of abnormal detonation at the threshold velocity are analyzed. The results show that, under certain conditions, the small impedance gap will increase the impact initiation velocity threshold while the large impedance gap will decrease; the reduction effect of the position and thickness of the large impedance gap on the detonation velocity increased first and then decreased; both embedded gaps and deformed flying plates will produce Irregular reflection waves that affect the explosive initiated at a critical speed.

ABSTRACTThe solid–liquid equilibrium and thermodynamic properties of FOX-7 in three binary mixed solvents (N-methyl pyrrolidone-water, N,N-dimethylacetamide-water and 1,4-Butyrolactone-water) are studied by focused beam reflectance measurement (FBRM) dynamic detection method and the solubility is predicted by conductor-like screening model for real solvents (COSMO-RS) under atmospheric pressure from 298.15 to 343.15 K. The results show that the solubility of FOX-7 increase with the increasing temperature and the mole fraction of N-methyl pyrrolidone, N,N-dimethylacetamide and 1,4-Butyrolactone. The solubility data can be well correlated by Apelblat, van’t Hoff and Yaws equation. The data of hybrid thermodynamic parameters (including the hybrid enthalpy, entropy, and Gibbs energy) show that the dissolution process is endothermic, non-spontaneous and enthalpy driven. In addition, COSMO-RS can accurately predict the increasing trend of solubility with increasing of temperature and mole fraction of solvent. However, the COSMO-RS overestimates solubility in three binary solvents except for xNMP = 0.1575, the average mean squared quadratic error becomes larger with an increasing mole fraction of water. Solubility data and thermodynamic parameters can lay a foundation for the crystallization and spheroidization modification of FOX-7.

ABSTRACTIn this laboratory, FOX-7@Al composites were developed by spray-drying technique. The effects of inlet temperature, feed rate and nitrogen flow rate and their interactions on the morphology and yield of FOX-7@Al were investigated by response surface methodology (RSM). Corresponding empirical equations were derived to show these interactions. The optimum process conditions determined by RSM were as follows: inlet temperature of 90°C, nitrogen flow rate of 450 L·h−1 and feed rate of 4.25 mL·min−1. The crystal structure, surface element distribution and thermal decomposition performance of FOX-7@Al in optimal condition were researched. Small crystallinity and low crystallinity of FOX-7 were observed in the XRD pattern, which were caused by the recrystallization of FOX-7 during the spray drying process. FOX-7@Al exhibited a concentrated energy release efficiency and a uniformed component distribution. The surface of aluminum nanoparticle was covered by FOX-7 and Viton, which effectively suppressed the agglomeration of aluminum nanoparticles and enhanced the heat and mass transfer properties. The work present here not only gives information for predicting, optimizing and improving the preparation conditions of energetic composites, but also provides a spray drying method for dealing with the materials distribution and thermal decomposition performance of composite aluminized explosives.

ABSTRACTA simple correlation between the resulting volume in the Trauzl-test and the heat of detonation, density and volume of detonation gases is given in this paper. This universally applicable correlation could be used as an alternative to the Trauzl-test to determine the strength of an energetic material.

ABSTRACTThe explosive 2,4,6-trinitrophenol (picric acid) was prepared by five different methods using laboratory-grade chemicals as well as consumer-available chemicals in order to establish background forensic information. Nitrate sources were altered by using three concentrations of nitric acid or nitrate salts; an over-the-counter source of sulfuric acid was also investigated. Recovered products were identified using spectroscopic and thermal techniques. Impurities caused by over-the-counter starting materials were carried throughout the synthesis process to the crude recovered products and were detected by infrared and Raman spectroscopy and differential scanning calorimetry. In cases where nitrate salts were used; potassium picrate was recovered.

ABSTRACTTATB and TATB-d6 were synthesized using phloroglucinol as raw material. Their molecular structure and micromorphology of them were well characterized by FTIR, NMR spectroscopy, XRD and FE-SEM. The thermal behaviors of these compounds were studied with TG-DSC, and the non-isothermal kinetic decomposition parameters of the two compounds were gained using the method of Friedman (FM). The apparent activation energy value of TATB-d6 was larger than that of TATB, which indicated the heat stabilization of deuterated TATB particles was improved. Finally, the thermal detonation critical temperatures of these two products were also calculated and discussed.

ABSTRACTThe pressure-time relation in the shock flow field of a near-earth air blast is complex. The triple point (TP) path is the physical boundary between the free and non-free shock flow fields. Accurately predicting the TP path is the basis for studying the evolution law of the reflection flow field and the guarantee of effectively assessing the damage power of the warhead. Based on the assumption that the Mach stem center is on the projection point of the blast center on the ground, the TP path calculation method was constructed by the geometric relationship. The unknown coefficients were solved using the existing TP data and the least square method. The TP prediction model proposed was compared with the existing ones on the calibration, new numerical simulation TP, and the measured real blast datasets. The error of the new numerical simulation TP data is within ±15% of the real value. The results show that the TP path prediction model proposed performs better. Most of its prediction results are within ±20% of three datasets compared to other models for the working conditions with the scaled height of burst from 0.397 to 2.777 m/kg1/3 and the horizontal scaled distance within 10 m/kg1/3 in the conventional cylindrical TNT explosion with the length-diameter of 1 in the air. The reliability of the prediction model is verified.