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The laser-ablated reaction process of two aluminized cyclotrimethylene-trinitramine (RDX) explosives with additives is presented, one formulation is RDX/aluminum (Al) /ammonium perchlorate (AP) and named AH, the other is RDX/Al/AP/Boron (B)/magnesium hydride (MgH 2) and named BH. Laser ablation combined with a high-speed photography and an emission spectrometer in this paper provides a high time-resolution observation of the reaction process of energetic materials in laboratory scale. A sample plate with an array of cylindrical holes was used to load the explosive powders for high-throughput studies, and a complete fresh sample was ablated each time to ensure the consistency of the sample status. From the laser-ablated images, AH exhibits a longer combustion duration than aluminized RDX with no additional additives, and BH has an even longer combustion duration than AH. Both AH and BH show a monotonic decreasing trend in luminous intensities, but AH has higher intensities than BH from 3 to 30 µs. In addition to the observation of AlO molecular emission lines in the spectra of AH and BH, neutral magnesium (Mg I) emission lines were observed in the spectra of BH. The spectral distribution with time indicates that the oxidation reaction of Al is the main reason leading to persistent combustion in AH and BH. Overall analysis directly reveals that AP promotes the combustion of AH and makes the afterburning of Al with ambient air less significant, and B/MgH 2 prolongs the combustion duration of BH. [ABSTRACT FROM AUTHOR]

Detonation performance is fundamental to the power evaluation of high explosives (HEs). This paper assesses the detonation performance (including detonation velocity D , detonation pressure P , detonation heat Q , specific kinetic energy E k , detonation products, working capacity, etc.) of HEs by an optimized method. Firstly, "exp-six" intermolecular potential function was used to optimize the theoretical VLW (Virial-Wu) EOS (equation of state), which exhibits a good precision in calculations of detonation performance. Then, the detonation performance of three new HEs (LLM-105, FOX-7, and TKX-50) was calculated and compared with traditional HEs (TATB, HMX, and CL-20). The results indicate that, for D and P , LLM-105, FOX-7, and TKX-50 are superior to TATB, but inferior to HMX and CL-20 except for D of TKX-50. The descending order for Q and E k is CL-20, HMX, TKX-50, FOX-7, LLM-105, and TATB. By analyzing detonation product components, more gaseous products with a higher proportion of heavy and medium molecules favor better detonation performance. Finally, the JWL (Jones-Wilkins-Lee) EOS was fitted by theoretically acquired isentropic expansion process of detonation products and cylinder test was simulated by the hydrodynamic program LS-DYNA. An increasing sequence of working capacity is TATB, LLM-105, FOX-7, TKX-50, HMX and CL-20. [ABSTRACT FROM AUTHOR]

Boron (B) has potential applications in energetic materials as additive fuel. In order to understand the combustion mechanism of B with various scales, the ignition and combustion characteristics of micro- and nano-sized B under different pressures (0.4 MPa, 0.8 MPa and 1.2 MPa) and atmospheres (60% O 2 + 40% N 2 , 80% O 2 + 20% N 2 and 100% O 2) were studied by a laser ignition and combustion experimental system. The evolution images and specialized parameters of ignition and combustion under different conditions were obtained, and the effects of atmosphere and pressure on the ignition and combustion characteristics of micro- and nano-sized B were discussed. Meanwhile, the crystal structure and morphology of condensed combustion products were observed by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM), and then the compositions in micro-areas were analyzed by energy dispersive X-ray spectroscopy (EDX). The results show that, the burning of micro-sized B is relatively slow, while the burning of nano-sized B is intensified, and a deflagration-like phenomenon is observed for nano-sized B in pure oxygen with pressures of 0.8 and 1.2 MPa. The ignition delay time, combustion time and maximum flame temperature of nano-sized B are smaller than those of micro-sized B, while the maximum characteristic spectral intensity of nano-sized B is stronger. Besides, B 2 O 3 , B 6 O and BN exist in condensed combustion products of micro-sized B, but only B 2 O 3 is detected for nano-sized B, and products agglomerating is observed for nano-sized B. In general, nano-sized B has significant advantages than micro-sized B in the ignition and combustion characteristics, especially under conditions of high oxygen concentrations and high pressures. [ABSTRACT FROM AUTHOR]

Reactive materials consisting of aluminum (Al) and fluorine-containing oxidizers have been extensively developed owing to high energy density and potential applications in propellants and explosives. Herein, graphite fluoride (CF) as a new fluorine-containing oxidizer was introduced to construct nano-Al based reactive materials. Systematic investigation and comparison were executed on exothermic reaction behavior and combustion performance of nano-Al/CF and nano-Al/polytetrafluoroethylene (PTFE) based reactive materials. The energy output and exothermic peak of nano-Al/CF were approximately 2367 J/g and 641 °C, which were 300 J/g and 85 °C higher than those of nano-Al/PTFE, respectively. The effects of nano-Al/CF mass ratio and packing density on burning rates were examined to fully understand combustion reaction and flame propagation behavior. Nano-Al/CF exhibited excellent burning rate (1670 m/s), much higher than that of nano-Al/PTFE (930 m/s). More interestingly, flame splitting phenomenon including three distinct flame regions was observed on the critical position with the highest burning rate for nano-Al/CF with the mass ratios of 25/70 and 30/75. The burning rate of nano-Al/CF increased and then decreased with the packing densities ranging from 20.87% to 53.47% TMD. The dominating combustion reaction products (AlF 3 and C) were further determined to figure out the reaction mechanism. These results demonstrated that CF as fluorine-containing oxidizer to construct reactive materials has potential applications in propellants, explosives and pyrotechnics. [ABSTRACT FROM AUTHOR]

The incorporation of aluminum (Al) into explosives represents a facility and efficient way to enhance the energy output through the secondary reaction between Al and the detonation products of explosive. The Al/O ratio and microstructure of HMX/Al play critical roles in combustion performance and energy output. Herein, a gradient structured HMX/Al composite has been designed and fabricated via 3D printing technology using well-dispersed HMX/Al-based ink. For HMX/Al lines, the second reaction heat increases from 196.5 J/g to 1644.8 J/g and the burning rate would decrease from 14.6 to 12.0 mm/s with Al content increased from 10 to 30 wt%. For gradient structured HMX/Al, the burning rate could be controlled by varying the component ratio and the burning rate of each component in the gradient structure was higher than that of the normal HMX/Al counterpart. Furthermore, a gradient evolution of pressure output was monitored for gradient structured HMX/Al cylinder ignited by the laser. These results indicate that the gradient structure as an effective approach can tune combustion performance and energy output of HMX/Al. [ABSTRACT FROM AUTHOR]

To improve and adjust the combustion and energy output of HMX/Al, graphite fluoride (CF) as oxidizer was introduced in HMX/Al and gradient structured HMX/Al/CF was prepared by additive manufacturing technology. For HMX/Al added with CF, a significantly exothermic peak is observed ranging from 860 to 950 °C due to the reaction of Al and fluorine derived from CF decomposition, and the heat release increases by 106.63% compared to that of HMX/Al. The fourth exothermic heat increases from 161.48 to 955.25 J/g with the increased Al content from 10 to 30 wt%. Moreover, the combustion rate and pressure output of HMX/Al have been improved by introducing CF. For HMX/Al added with CF, the combustion time decreases from 10.3 to 2.5 s, which is dependent on the Al content from 10 to 30 wt%. And the highest peak pressure is 1712.2 kPa when Al content is 20 wt% in HMX/Al/CF composites. Furthermore, gradient structured HMX/Al/CF consisting of three layers with Al content of 10, 20 and 30 wt% was prepared to improve combustion and pressure output. The combustion rate and peak pressure of gradient structured HMX/Al/CF are higher than those of single structured HMX/Al/CF. The highest peak pressure (∼2.24 MPa) is obtained when the Al content of the middle layer and outer layer is 30 wt% and 20 wt% in the gradient structured HMX/Al/CF cylinder, respectively. Finally, the reaction intermediates and combustion reaction products were fully characterized to understand the enhanced effect of CF in HMX/Al. This work provides a promoting way to improve and regulate the combustion reaction performance and pressure output of HMX/Al. [ABSTRACT FROM AUTHOR]