Hasil untuk "Explosives and pyrotechnics"

Zhen ZOU, Fengxiang XU, Tengyuan FANG et al.

The catenary reinforced method can enhance the crashworthiness of re-entrant honeycomb (RH) by avoiding hollow structural characteristics, strengthening negative Poission’s ratio effect, and utilizing the high load-bearing effectiveness of catenary structures. Based on the above effects the sandwich beam with reinforced RH (RRH) was proposed. The metallic specimens from the proposed structure were fabricated for three-point bending tests. Results show that the introduced catenary structure can limit the rotation deformation of inclined cell walls around vertices, and the drop in load-bearing force after initial plastic deformation is reduced from 29.3% to 6.6%. Compared to classical RH cored beams, the maximum load-bearing force and energy absorption of RRH ones can be improved by 26.7% and 8.9%, respectively. A parametric analysis was conducted to reveal that the thicknesses of front facesheet, back facesheet, and core had a significant effect on deformation behavior and energy absorption of RRH cored sandwich beams. The thickness of front facesheets, cores, and back facesheets was employed as optimization variables, and the mass, maximum load-bearing force, and energy absorption were used as optimization objectives to perform the multi-objective optimization of RRH cored sandwich beams. The optimized sandwich beam exhibits increases of 64.9% in maximum load-bearing capacity and 46.9% in energy absorption. The impact resistance of conventional honeycomb sandwich beams under in-plane and out-of-plane loading was compared at identical wall thickness and mass, respectively. Analysis demonstrated the superior energy-absorbing protective performance of the proposed RRH sandwich beams. The research results can provide useful guidance for the reinforcement design of honeycomb cored sandwich beams.

Teng LI, Yang QIU, Weiguang YAO et al.

During the underwater launch of multiple projectiles, each projectile operates within a highly complex and dynamic flow field, where its trajectory deflection is influenced by a combination of factors. These factors include initial conditions such as the projectile’s velocity and the presence of crossflow, as well as the mutual interference effects among the projectiles. To gain a deeper understanding of the cavitation evolution and trajectory interference characteristics during the underwater launch of multiple projectiles, this study develops a comprehensive numerical simulation model. The model integrates the overlapping grid technique and the finite volume method and is coupled with a six-degree-of-freedom (6-DOF) motion model. Through this model, the influence mechanisms of spatial arrangement, launch velocity, and crossflow on trajectory deflection are systematically analyzed. The results of this study reveal several important findings. First, the spatial arrangement of the projectiles has a relatively minor impact on trajectory deflection. An equilateral triangular configuration is found to be an optimal choice for practical applications, as it maximizes the efficient utilization of the launch space. Second, as the launch velocity increases, the wake interference between projectiles becomes more pronounced. This intensified interference leads to significant disturbances in the flow field and stronger mutual trajectory interference among the projectiles. Third, higher crossflow velocities exacerbate the asymmetric development of cavitation near the projectile shoulders. When the crossflow velocity exceeds 0.75 m/s, it becomes the dominant factor influencing trajectory deflection. These research findings provide a robust theoretical foundation for trajectory prediction and layout optimization in the underwater launch of multiple projectiles.

Danillo Fernando Vianna Cantini, Vojtech Pelikan, Jiri Pachman

This study focuses on optimizing pyrotechnic compositions containing boron (B) and boron carbide (B4C) as fuels and bismuth oxide (Bi2O3) as the oxidizer. A Central Composite Design (CCD) and Response Surface Methodology (RSM) were employed to screen and evaluate the effects of component concentrations on combustion parameters, specifically adiabatic temperature and constant-volume pressure. Simulations using REAL WIN provided the necessary data, which were analyzed to derive predictive models. Optimization was conducted for various purposes, including matching specific targets, maximizing or minimizing outputs, and balancing performance criteria, demonstrating the flexibility and utility of the approach. Results obtained for the optimal compositions showed excellent agreement with the simulation, with prediction errors below 2% in most cases. For instance, an optimized composition (9.53% B, 3.91% B4C, 86.56% Bi2O3) matched a target temperature of 2000 K with an error between RSM prediction and REAL WIN simulation lower than 1.4% for the constant-volume pressure. The study further explores the limitations and opportunities for improving the model by expanding the experimental range and incorporating additional data points. This investigation highlights the potential for refining predictive accuracy while addressing challenges associated with nonlinear behaviors and extrapolation. By combining DoE approaches with simulation tools, this work offers reliable guidance for formulation and experimental planning in energetic materials development.

Rui Wu, Yi-jie Xiao, Zhi-gang Guo et al.

To study the erosion behavior of azidonitramine propellant on gun barrel material, a high-energy component-based azidonitramine gun propellant was prepared by using NC (Nitrocellulose), NG (Nitroglycerin), and RDX (Hexogen). The erosion characteristics of the propellants were determined using a vented vessel method. The erosion behavior of the gun barrel material was investigated through morphological and element analysis. And the erosion characteristics of the gun barrel material under different propellant flame temperatures and loading densities were analyzed. The results indicated that the erosion degree of the gun barrel material samples intensified with increasing flame temperature and loading density. SEM (Scanning Electron Microscope) observations showed that the surface flatness of the erosion samples decreased with higher propellant flame temperature and decreased followed by an increase with varying propellant loading densities. The surfaces of samples under different loading conditions exhibited various typical features, including solid particles, clusters, erosion pits, erosion marks, and rod-like solids. EDS (Energy Dispersive Spectrometer) testing revealed that, compared to the pre-erosion samples, the content of C and Fe on the surface of the erosive samples decreased, while the content of elements such as Mn, Ni, and Mo increased. The content of C, O, and Cr elements increased in the erosion pits, along with the detection of V. Finally, based on the experimental results, the morphological and elemental distribution characteristics of the gun barrel material after erosion were summarized.

Prawal P.K. Agarwal, Themis Matsoukas

Boron (B) is desirable for energetic applications due to high gravimetric and volumetric energy densities. However, their use is limited because the native oxide shells on their surfaces limit oxidation and heat release by acting as a diffusion barrier and dead weight that does not contribute to heat release during oxidation. This paper reports a facile and efficient method of blending B with perfluoro additives to obtain materials with augmented heat release. We use polytetrafluoroethylene (PTFE) as a fluorine source that reacts with the oxide layer exothermally and use thermochemical analysis to identify the optimum composition of PTFE to extract high energy from B as a result of synergistic oxidation and fluorination reactions. The reduction in ignition temperatures of B is also observed due to its blending with PTFE. In this work, we determined B/PTFE blends with lower ignition temperature and higher oxidative heat release. These effects are due to the gasification of native surface oxide by fluorine via exothermic reactions that facilitate the enhanced reactions in the exposed metal core by eliminating the kinetic/thermodynamic barrier in the diffusion of the oxidizer to the B particle core. The study demonstrates the optimized formulation of highly energetic blends of B/PTFE for energetic applications.

Fateh Chalghoum, Ahmed Fouzi Tarchoun, Amir Abdelaziz et al.

The present work investigated the effect of moisture content on the thermal decomposition of two smokeless powders. First, the main ingredients of the studied gunpowder formulations were identified using gas chromatography-mass spectrometry (GC-MS) and Fourier Transform Infrared (FTIR) spectroscopy. The investigated gunpowders were stored in three different humid environments and then analyzed using a C80 microcalorimeter and a thermogravimetric analyzer. The obtained heat flow curves showed a major exothermic peak within the 140–230 °C temperature range, corresponding to the main gunpowder thermal decomposition. This degradation phase shifted to lower temperatures as the sample moisture content increased. Based on non-isothermal TG experiments, two model-free iterative methods (it-KAS and it-FWO) were applied to estimate the kinetic triplet of this main degradation phase for the stored specimens. It was found that the mean value of the activation energy decreased as the water content of the sample increased. This finding may be explained by the accelerated hydrolysis process of water on the thermal degradation of nitrocellulose-based smokeless powders.

Zhenmin LUO, Fan NAN, Yali SUN et al.

Hydrogen-doped natural gas technology has been gradually used in pipeline transportation, but hydrogen-doped natural gas is suspectible to leakage and explosion accidents. The study used a 20-L spherical device to investigate the effects of hydrogen doping ratio and CO2 addition on the explosion pressure and flame propagation characteristics of hydrogen-doped natural gas，and the chemical reaction kinetics method was used to analyze the explosion mechanism. The results showed that the hydrogen doping ratio has a promoting effect on the pressure parameters of hydrogen-doped natural gas explosion and flame propagation speed. As the hydrogen doping ratio increases, the maximum explosion pressure gradually increases，while both the rapid burn time and sustained burn time decrease progressively. The maximum rise rate of explosion pressure and flame propagation speed gradually increase when the hydrogen doping ratio is lower than 0.5. When the hydrogen doping ratio is greater than 0.5, the maximum rise rate of explosion pressure and flame propagation speed rise rapidly. The addition of CO2 has an inhibitory effect on the explosion pressure and flame propagation speed of the mixed gas, but the suppression effect on pressure parameters with high hydrogen doping ratio is weak. Through reaction kinetic analysis, it can be seen that as the hydrogen doping ratio increases, the laminar burning velocity and adiabatic flame temperature gradually increase. Meanwhile the concentration of active free radicals and the product formation rate increase significantly, and the mixing of hydrogen changes the reaction path of methane. When the hydrogen doping ratio is greater than 0.5, reactions R84, R46 and R3 enter the top ten steps of the reaction, producing H and OH radicals, which promotes the reaction. CO2 can reduce the laminar burning velocity, adiabatic flame temperature, active free radical concentration and product formation raten of the mixed gas, but adding CO2 does not change the reaction path of methane.Hydrogen-doped natural gas technology has been gradually used in pipeline transportation, but hydrogen-doped natural gas is prone to leakage and explosion accidents. The study used a 20L spherical device to investigate the effects of hydrogen blending ratio and CO2 addition on the explosion pressure and flame propagation characteristics of hydrogen-doped natural gas，and the chemical reaction kinetics method was used to analyse the explosion mechanism. The results showed that the hydrogen doping ratio has a promoting effect on the hydrogen-doped natural gas explosion pressure parameters and flame propagation speed. As the hydrogen doping ratio increases, the maximum explosion pressure gradually increases，the rapid burn time and sustained burn time are gradually decreasing. The maximum explosion pressure rise rate and flame propagation speed gradually increase when the hydrogen doping ratio is less than 0.5. When the hydrogen doping ratio is greater than 0.5, the maximum explosion pressure rise rate and flame propagation speed rise rapidly. The addition of CO2 has an inhibitory effect on the explosion pressure and flame propagation speed of the mixed gas, but the suppression effect on pressure parameters with high hydrogen doping ratio is poor. Through reaction kinetic analysis, it can be seen that as the hydrogen doping ratio increases, the laminar burning velocity and adiabatic flame temperature gradually increase, the mole fraction of active free radicals and the rate of product increase significantly, and the mixing of hydrogen changes the reaction path of methane. When the hydrogen doping ratio is greater than 0.5, reactions R84, R46 and R3 enter the top ten steps of the reaction, producing H and OH radicals, which promotes the reaction. CO2 can reduce the laminar burning velocity, adiabatic flame temperature, active free radical mole fraction and rate of production of the mixed gas, but adding CO2 does not change the reaction path of methane.

Zhenhua LIU, Xiangzhen KONG, Jian HONG et al.

To accurately predict the dynamic tensile fracture in concrete materials subjected to impact and blast loadings, this study first establishes a modified Monaghan artificial bulk viscosity computation method within the framework of a non-ordinary state-based peridynamics (NOSB-PD) theory to eliminate numerical oscillations. Subsequently, the corrected strain-rate computation method, previously developed, is integrated into the Kong-Fang concrete material model, which was proposed earlier by the research group to calculate accurately the strain-rate effect during sudden changes. Based on the two methods above, numerical simulations of elastic wave propagation in a one-dimensional rod are conducted, and the results demonstrate that the additional inclusion of the modified Monaghan artificial bulk viscosity force vector state into the original force vector state can effectively suppress the non-physical numerical oscillations caused by the deformation gradient approximation. The superiority of the modified Monaghan artificial bulk viscosity is validated through comparative analysis with the original Monaghan artificial bulk viscosity. Furthermore, the influence of the modified Monaghan artificial bulk viscosity parameters is investigated, and recommended values for these parameters are provided. Finally, the aforementioned model is used to numerically simulate the spall test in concrete specimens, where the effects of including or excluding the modified Monaghan artificial bulk viscosity and different strain-rate computation methods on the prediction results of dynamic tensile fracture are compared and analyzed. The numerical simulation results demonstrate that accurately predicting the dynamic tensile fracture in concrete materials requires simultaneous consideration of the modified Monaghan artificial bulk viscosity and corrected strain-rate computation. The established non-ordinary state-based peridynamics model that accounts for both the modified Monaghan artificial bulk viscosity and corrected strain-rate computation demonstrates strong capabilities in predicting crack locations and quantities based on both qualitative and quantitative analysis metrics. This work provides new insights into the numerical simulation of dynamic tensile fracture in concrete materials under impact and blast loadings.

Hani Boukeciat, Ahmed Fouzi Tarchoun, Amir Abdelaziz et al.

This study reports the successful preparation of an energetic composite consisting of ammonium perchlorate (AP), nitrated microcrystalline cellulose carbamate (M3CN), and diethylene glycol dinitrate (DEGDN). The optimal composition was determined by theoretical performance calculations using the NASA-CEA2 program prior to preparation. Characterization techniques, including Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), confirmed the uniform dispersion of AP within the M3CN/DEGDN matrix without altering its chemical structure. Thermal analysis revealed that the incorporation of AP facilitated the decomposition of both components, as indicated by shifts to lower decomposition peak temperatures. This suggests a catalytic interaction that enhances heat release and combustion energy. Kinetic models using isoconversional methods revealed a significant reduction in activation energy, further supporting the observed catalytic effects in the AP@M3CN/DEGDN composite during different stages of decomposition.

Feixiang CHEN, Guokai ZHANG, Yong HE et al.

To investigate the propagation characteristics of blast shock waves and the thermal effects of fireballs in tunnel explosions involving thermobaric explosives, numerical simulations were conducted using OpenFOAM. The simulation accuracy was validated through comparative analysis with experimental data from tunnel explosion tests. The effects of axial distance along the tunnel and explosive mass on shock wave propagation characteristics and fireball thermal effects were systematically studied. The results demonstrate that under identical charge mass conditions when the axial distance exceeds 1/3 of the equivalent tunnel diameter, the attenuation of shock wave overpressure peak and planar wave formation distance remain independent of axial position. After planar wave formation, the impulse increases with axial distance before stabilizing. At the same axial explosion distances, the planar wave formation distance increases with explosive mass. Post planar wave formation, the attenuation pattern of the shock wave overpressure peak remains unaffected by charge mass. In contrast, the impulse exhibits a growth trend proportional to the increase in charge mass. Under the influence of the tunnel portal energy dissipation effect (tunnel effect), explosion-induced fireballs exhibit a consistent propagation tendency toward the proximal tunnel portal. The confinement imposed by tunnel walls restricts the lateral expansion of the fireball perpendicular to the tunnel axis while facilitating the formation of a high-temperature tip along the longitudinal axis. Especially, the temperature distribution along the tunnel axis maintains axial symmetry despite directional propagation biases. A fitting formula was established to characterize the relationship between the maximum axial propagation distance of explosion fireballs at different temperatures and the explosive mass, enabling the prediction of axial spread limits for fireballs at specific temperatures in typical thermobaric explosive detonations within tunnel-confined environments.

Y. Raj Alexander, Nikunj Rathi, P.A. Ramakrishna

For aerospace vehicles, notably missiles or satellites for attitude and divert control, impulsive thrusters are most desirable if they are quantized as exact instantaneous pulses available over and after extended periods of inactive storage. These thrusters operate for a few milliseconds (ms), typically between 10 ms to 100 ms duration. Compared to its liquid or gaseous counterpart, an impulsive thruster powered by solid propellants is a simple, and reliable solution. Therefore, they are suitable as reaction control systems and divert thrusters for satellite and unmanned aerial vehicle applications.A typical solid propellant would need an extremely thin web thickness for port burning arrangement due to its brief burn duration, which makes propellant manufacturing and its structural anchoring in motor challenging. A high burn rate and high-density propellant based on ammonium perchlorate, aluminum, and Teflon is processed to enable end-burning configuration thus solving the problems, simplifying propellant manufacturing, structural design and integration. It also permits stacking propellants for multi-pulse applications. The high burn rate (40 mm/s at 120 bar pressure) propellant is formulated and tested for ballistic performance evaluation in proof motor configuration, and evaluation of its advantages over conventional propellant. A case of identical design requirements with both double base propellant and high burn rate pressed propellant is compared, tested and evaluated to compare the relative performance merits. The volumetric load is increased from 47% to 82% due to the development and adoption of high burn rate propellant. The overall weight of the thruster is also reduced by 20%.

Xiaodong Yu, Hongsheng Yu, Hongwei Gao et al.

The advent of various additive manufacturing technologies, such as 3D printing, has changed the structural design and preparation process of rocket fuels. In order to investigate the combustion properties of various common polymer materials that can be additively manufactured by fused deposition, the combustion tests of hybrid rocket fuels prepared by 3D printing were carried out. These materials include polylactic acid (PLA), wood-like polylactic acid (Wood), acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-acrylate (ASA), copolymers of nylon 6 and nylon 6,6 (CoPA), polycarbonate-polybutylene terephthalate (PC-PBT), flame retardant polycarbonate (PC-FR) and polyethylene terephthalateco-1,4-cylclohexylenedimethylene terephthalate (PETG). Thermogravimetric-differential scanning calorimetry (TG-DSC) analysis was carried out on these materials, the printing effect of the fuel grains was observed by three-dimensional X-ray microscopy (µCT) and the combustion performance of these fuels in gaseous oxygen flow (GOX) was recorded by high-speed photography at a constant pressure of 1 MPa. The results show that ASA and ABS exhibit good printing results. The regression rates of PC-PBT, PETG, ABS, ASA, CoPA and PLA are 0.792 mm/s, 0.592 mm/s, 0.536 mm/s and 0.477 mm/s, 0.368 mm/s, 0.339 mm/s (AtGOX=220kg/(m2·s)), respectively.

Xinyi Li, Yuangang Xu, Jianxin Zhou et al.

As an important intermediate in the synthesis of most energetic pentazole compounds, the reaction system of sodium pentazole is complex and has many by-products, but there is no suitable HPLC analysis method. Based on the study of ultraviolet absorption peak of sodium pentazole aqueous solution, the HPLC purity analysis method of sodium pentazole was successfully established and its sensitivity, accuracy and repeatability were verified. When the detection wavelength was 192 nm, the chromatographic column was Agilent WondaSil C18 Superb (4.6 × 250 mm, 5 μm), the mobile phase was 95% water and 5% acetonitrile mixed solution, the flow rate was 0.8 ml/min, the analysis time was 8 min, the sample size was 1 μL and the column temperature was 40 °C, a liquid phase map of sodium pentazole was obtained. The analysis results showed that the retention time of pentazole sodium was 3.76 min, and showed a good linear relationship in the range of 0.3068–0.3288 g/L. The linear equation is y = -217447.64+835837.85x, the correlation coefficient R2 is 0.99997, and it has good sensitivity, accuracy and repeatability. In addition, three by-products from the synthesis of sodium pentazole were simply separated.

Lan Jiang, Ruibing Lv, Jinxing Wang et al.

In this work, four energetic nitrates, i.e., 4,7-diamino-1H-[1,2,3]triazolo[4,5-d]pyridazin-5-ium nitrate (1), 2,6-diamino-1‑hydroxy-9H-purine-1,7-diium nitrate (2), 6-amino-[1,2,4]triazolo[4,3-b][1,2,4,5]tetrazin-2-ium nitrate (3) and 3,6-diamino-[1,2,4]triazolo[4,3-b][1,2,4,5]tetrazin-2-ium nitrate (4), were prepared and comprehensively characterized. The X-ray diffraction results indicated that compounds 1–4 had different layered structures with the densities in the range of 1.616–1.805 g/cm3. The highest density value of 1.805 g/cm3 was represented in compound 2, which was higher than that of most other nitrates. Moreover, compounds 1–4 had good thermal stabilities, the decomposition temperatures were in the ranged of 165–181 °C, which made them have great potential to further develop. The calculated detonation velocities and detonation pressures of these compounds were in the range of 7678–8925 m/s, and 21.96–32.39 GPa, respectively. The greatest detonation velocity and detonation pressure were observed in compound 3. The specific impulses of these compounds were in the range of 199.8–244.9 m/s. Notably, compound 1 had near infrared laser (λ = 1064 nm) ignition capacity, which was the first example of CHNO based energetic compound with near infrared laser ignition performance.

Yong Kou, Yi Wang, Jun Zhang et al.

Barium sulfate has been widely used in different fields due to its excellent physical and chemical properties, but its application in solid propellants has not yet been explored. In this work, novel microreactor was used to prepare the barium sulfate nanoparticles. Then the barium sulfate nanoparticles were characterized by Scanning electron microscopy (SEM), Transmission electron microscope (TEM), Energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET). The results show that the barium sulfate nanoparticles are almost spherical with a diameter of 54.34 nm. More, it also has a larger specific surface area. Then 3% barium sulfate nanoparticles were mixed with AP, AN and CL-20 respectively. The results shows that the decomposition peaks of AP and AN are significantly advanced, indicating that nano-barium sulfate has a significant catalytic effect on AP and AN. Nano barium sulfate also has the characteristics of eliminating secondary flames and absorbing harmful radiation, so it is expected to be widely used in solid propellants.

Weiqiang Pang, Luigi T. DeLuca

Xiaofeng Huang, Zhaohui Liu, Chunying Li et al.

The endothermic hydrocarbon fuel is used as a coolant to realize active cooling for the high-heat-flux components of air-breathing hypersonic vehicles. Because of its complex composition and severe thermal boundary conditions, the unstable heat transfer and coking are usually the major problems. Flow boiling heat transfer of a kind of endothermic hydrocarbon fuel named EHF-204 and its visualization were experimentally investigated in mini-channels with 2.0 mm internal diameter at heat flux of 250 kW/m2 and 500 kW/m2. It is found that the heat transfer enhancement and heat transfer deterioration would occur obviously during the flow boiling heat transfer process at subcritical and near-critical pressures of 1.0 MPa and 2.5 MPa. After the fuel was completely vaporized, the heat transfer coefficient would slowly increase again with the increasing fuel temperature. The heat transfer enhancement and heat transfer deterioration process at subcritical temperatures were not existed at the supercritical pressure of 4.0 MPa. The flow patterns of bubbly flow, slug flow, and churn flow were clearly observed at the subcritical pressures. Flow pattern visualization proved that the constant wall temperature heat transfer processes at subcritical pressures were subcooled boiling and saturation boiling flow. The bigger bubbles were formed at lower pressures, which caused higher heat transfer coefficient. The bubbly flow, slug flow caused the heat transfer enhancement, and the appearance of churn flow was a feather that made the boiling heat transfer transition from heat transfer enhancement to heat transfer deterioration. Some interesting visualization phenomena were observed in this study including the twice vaporization during flow boiling.

Yu-long Men, Peng Liu, Xin-yu Meng et al.

Carbon-based materials, metal oxides and metal nanoparticles have been widely used in propellants, explosives and pyrotechnics. Cold plasma technique has been developed for material fabrication and modification at temperatures lower than 200 ⁰C. Due to the low temperatures, cold plasma can efficiently modify material surface properties, and simultaneously maintain material structures well, especially for temperature-sensitive materials. Cold plasma applies gas, e.g. Ar, N2, O2, H2 and air, as working gas, without any harmful substance like acid, alkali and organic solvent. Moreover, material surface properties can be efficiently tuned by simply changing plasma properties, e.g. power, time and working gas. The present review discusses recent progresses in using cold plasma to fabricate carbon-based materials, metal oxides and metal nanoparticles, and to modify surface properties of carbon-based materials, metal oxides and metal nanoparticles. Future research opportunities and challenges are also proposed. It is believed that the present review will stimulate more studies on material fabrication and modification by cold plasma, and help to construct more efficient materials for propellants, explosives and pyrotechnics.

Kai Zhong, Liangliang Niu, Chaoyang Zhang

The addition of active metallic particles to common explosives can greatly extend high-temperature and high-pressure time of explosion, as the so-called thermobaric effect. However, the atomic details for this effect remain unclear. This work presents an atomic insight into the thermobaric explosion including anaerobic and aerobic stages by molecular dynamics simulations with a thermobaric explosive (TBX) model consisting of Al@Al2O3 nanoparticle and RDX. It is found that the thermobaric effect is originated from the Al oxidation by the intermediates and products of the RDX decomposition in the first anaerobic stage with a lot of Al-O, Al-H, Al-C and Al-N bonds formed, and the further oxidation by O2 in the aerobic stage with many C, H and N atoms extruded from the Al clusters. Interestingly, in terms of the components and structures of the final products, as well as the total heat release, the whole thermobaric explosion of the RDX-Al system can be regarded as the sum of the RDX decomposition and the Al oxidation in O2. Thereby, the energy design of a TBX can be simplified by considering the sum of the decomposition heat of the energetic compound involved and the combustion heat of the active metal. Regarding RDX, it plays a role in forming a high temperature and high pressure environment to promote the dispersion and combustion of Al particles. This work presents the atomic details responsible for the thermobaric effect and it is expected to pave a way to understand this effect.

Chao Chen, Haijian Li, Jianhua Yi et al.

Two novel heterobimetallic metal-organic frameworks (MOFs), Ba4Pb4(CH3CO2)8[(CH6CO2)4Pb](CH3CO2)4 (PbBa-MOFs) and Ba2Ni(CO2H)6(OH2)4 (NiBa-MOFs), were prepared via the solvothermal method, and their structures were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. The pyrolysis behavior of the two MOFs and their catalytic performances on the dihydroxylammonium-5,5’-bistetrazole-1,1’-diolate (TKX-50) pyrolysis were studied by thermogravimetric-differential scanning calorimetry (TG-DSC) and thermogravimetric-fourier transform infrared spectroscopy-mass spectrum (TG-FTIR-MS) methods. Compare with the pure TKX-50, the pyrolysis peak temperature and apparent activation energy (Ea) of the TKX-50/PbBa-MOFs mixture were decreased by 3.2°C and 13.47 kJ‧mol−1 respectively. The Ea of TKX-50/NiBa-MOFs was decreased by 9.35 kJ‧mol−1. And the second pyrolysis peak disappeared in the DSC curves of TKX-50 after the addition of the two MOFs, due to that the products from MOFs pyrolysis suppress the chemical reaction pathway on the production of 5,5′-bis (2-hydroxytetrazole) (ABTOX) and accelerate the direct decomposition of 1,1’-bistetrazole diol (BTO). This resulted in the percentage of H2O decreased greatly and the percentage of NO/CH2O, CO2/N2O, NH2+/O• and NH3/OH increased during the pyrolysis of TKX-50. Finally, the relation between the pyrolysis and ignition characteristics was discussed and described. The two MOFs reduced the ignition delay time of the TKX-50 at the high power density region, and the flame becomes more luminous due to the formation of metal oxides and active free radical.