Search Results (5)

Crystalline poly-para-xylylene (parylene) has the potential for use as a protective membrane to delay the nucleation of explosives by separating the explosives and their decomposition products to decrease the explosive sensitivity. Here, molecular dynamics (MD) and density functional theory (DFT) techniques were used to calculate the dissociative adsorption configurations of 1,1-diamino-2,2-dinitroethylene (FOX-7) on (001)- and (101)-oriented crystalline parylene membranes. Based on the results of the calculations, this work demonstrates that the -NO₂–π electrostatic interactions are the dominant passivation mechanism of FOX-7 on these oriented surfaces. FOX-7 can dissociatively adsorb on oriented parylene membranes due to the interactions between the LUMO of the toluene (or methyl) groups on parylene and the HOMO of the -NO₂ (or -NH₂) groups on FOX-7. The formation of a new intermolecular H-bond with the ONO group leads to FOX-7 decomposition via intramolecular C-NO₂ bond fission and nitro-to-nitrite rearrangement. The most likely adsorption configurations are described in terms of the decomposition products, surface active groups of parylene, binding behaviors, and N charge transfer. Importantly, the (001)-oriented parylene AF8 membrane is promising for use as a protective membrane to passivate the high-energy -NO₂ bonds during the dissociative adsorption of FOX-7. This study offers a new perspective on the development of protective membranes for explosives. Full article

1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) is a type of high energy explosive, its application in weapon systems is limited by its high mechanical sensitivity. At the same time, 1,1-diamino-2,2-dinitroethylene (FOX-7) is a famous insensitive explosive. The preparation of RDX@FOX-7 composites can meet the requirements, high energy and low sensitivity, of the weapon systems. It is difficult for the reactor to achieve uniform quality of composite material, which affects its application performance. Based on the principle of solvent-anti-solvent, the recrystallization process was precisely controlled by microfluidic technology. The RDX@FOX-7 composites with different mass ratios were prepared. At the mass ratio of 10%, the RDX@FOX-7 composites are ellipsoid of about 15 μm with uniform distribution and quality. The advantages of microscale fabrication of composite materials were verified. The results of structure characterization showed that there is no new bond formation in RDX@FOX-7, but the distribution of two components on the surface of the composite was uniform. Based on the structure characterization, we established the structure model of RDX@RDX-7 and speculated the formation process of the composites in microscale. With the increase of FOX-7 mass ratios, the melting temperature of RDX was advanced, the thermal decomposition peak of RDX changed to double peaks, and the activation energy of RDX@FOX-7 composite decreased. These changes were more pronounced between 3 and 10% but not between 10 and 30%. The ignition delay time of RDX@FOX-7 was shorter than that of RDX and FOX-7. RDX@FOX-7 burned more completely than RDX indicating that FOX-7 can assist heat transfer and improve the combustion efficiency of RDX. Full article

We report a reactive molecular dynamic (ReaxFF-MD) study using the newly parameterized ReaxFF-lg reactive force field to explore the initial decomposition mechanism of 3-Nitro-1,2,4-triazol-5-one (NTO) under shock loading (shock velocity >6 km/s). The new ReaxFF-lg parameters were trained from massive quantum mechanics data and experimental values, especially including the bond dissociation curves, valence angle bending curves, dihedral angle torsion curves, and unimolecular decomposition paths of 3-Nitro-1,2,4-triazol-5-one (NTO), 1,3,5-Trinitro-1,3,5-triazine (RDX), and 1,1-Diamino-2,2-dinitroethylene (FOX-7). The simulation results were obtained by analyzing the ReaxFF dynamic trajectories, which predicted the most frequent chain reactions that occurred before NTO decomposition was the unimolecular NTO merged into clusters ((C₂H₂O₃N₄)_n). Then, the NTO dissociated from (C₂H₂O₃N₄)_n and started to decompose. In addition, the paths of NO₂ elimination and skeleton heterocycle cleavage were considered as the dominant initial decomposition mechanisms of NTO. A small amount of NTO dissociation was triggered by the intermolecular hydrogen transfer, instead of the intramolecular one. For α-NTO, the calculated equation of state was in excellent agreement with the experimental data. Moreover, the discontinuity slope of the shock-particle velocity equation was presented at a shock velocity of 4 km/s. However, the slope of the shock-particle velocity equation for β-NTO showed no discontinuity in the shock wave velocity range of 3–11 km/s. These studies showed that MD by using a suitable ReaxFF-lg parameter set, could provided detailed atomistic information to explain the shock-induced complex reaction mechanisms of energetic materials. With the ReaxFF-MD coupling MSST method and a cheap computational cost, one could also obtain the deformation behaviors and equation of states for energetic materials under conditions of extreme pressure. Full article

To achieve a uniform distribution of the components and a better performance of aluminized composite explosives, Viton (dipolymers of hexafluoropropylene and vinylidene fluoride) @ FOX-7 (1,1-diamino-2,2-dinitroethylene) @Al microspheres and FOX-7/Viton@Al were synthesized by spray-drying strategy contrastively. Viton@FOX-7@Al owned porous and loose morphology and good sphericity with a retained crystal phase of FOX-7 and aluminum. The 23.56% fluorine content on Viton@FOX-7@Al surface indicated that Viton was completely coated on the surface of the particles. Nanosized aluminum (nAl) in Viton@FOX-7@Al had a certain catalytic activity on the thermal decomposition process of FOX-7 resulting in a depressed exothermic peak temperature and reduced apparent activation energy relative to nAl in FOX-7/Viton@Al. Because of the specific structure and the synergies between each individual component, Viton@FOX-7@Al showed reduced impact sensitivity and friction sensitivity than those of FOX-7/Viton@Al. In brief, Viton@FOX-7@Al with multilevel coating structure possessed comparatively low thermal decomposition energy requirement and improved safety performance. Full article

Metal hydrides are regarded as promising hydrogen-supplying fuel for energetic materials while CL-20 (Hexanitrohexaazaisowurtzitane) and FOX-7 (1,1-Diamino-2,2-dinitroethylene) are typical principal components commonly used in energetic materials. Hence, it is interesting to explore the interactions between them for development of new energetic systems. In this paper, the adsorption and decomposition of CL-20 or FOX-7 molecules on the MgH₂ (110) crystal surface were investigated by employing the First-Principles. In total, 18 adsorption configurations for CL-20/MgH₂ (110) and 12 adsorption configurations for FOX-7/MgH₂ (110) were considered. The geometric parameters for the configurations, adsorption energies, charge transfer, density of states, and decomposition mechanism were obtained and analyzed. In most of the configurations, chemical adsorption will occur. Moreover, the orientation of the nitro-group in CL-20 or FOX-7 with regard to the MgH₂ (110) surface plays an important role on whether and how the energetic molecule decomposes. The adsorption and decomposition of CL-20 or FOX-7 on MgH₂ could be attributed to the strong charge transfer between Mg atoms in the first layer of MgH₂ (110) surface and oxygen as well as nitrogen atoms in the nitro-group of CL-20 or FOX-7 molecules. Full article