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Abstract:To enhance practical values and improve safety and mechanical properties of 2, 4, 6, 8, 10, 12-hexanitrohexaazaisowurtzitane /1, 3-dinitrobenzene (CL-20/DNB) cocrystal explosive, two polymer binders, hydroxyl-terminated polybutadiene (HTPB) and polyethylene glycol (PEG), were respectively added along its crystalline surface (0 0 1) and the models of two kinds of CL-20/DNB cocrystal based polymer-bonded explosives (PBXs), CL-20/DNB/HTPB and CL-20/DNB/PEG were constructed. Under the COMPASS force field, the 295 K-NPT molecular dynamics simulation (MD) study for cocrystal explosive and two kinds of PBXs models was conducted. The interface interaction between binder and explosives was explored using the pair correlation function (g(r)). Results show that the binding energy of CL-20/DNB/PEG is larger than that of CL-20/DNB/HTPB, predicting that the stability and compatibility of former is better than those of latter. In comparison with CL-20/DNB cocrystal explosive, adding of small amount of binder (HTPB or PEG) makes the elastic constants (C_ij), tensile modulus (E), bulk (K) and shear (G) modulus decrease, while Cauchy pressure (C₁₂-C₄₄) and K/G value increase, showing that the stiffness of the PBXs system is weaker, and its ductibility is better. The values of (C₁₂-C₄₄) and K/G of CL-20/DNB/HTPB system are larger than those of PBX CL-20/DNB/PEG, indicating that the ductibility of former is better that of latter, predicting that the desensitizing effect of HTPB by improving the cocrystal explosive's mechanical properties is better than that of PEG.

Abstract:To design the formulation of energetic polymer bonded explosives, the energetic binder with different hard and soft segments proportions of 3-azidomethyl-3-methyl oxetane(AMMO): 3, 3-diazidomethyl oxetane(BAMO) was added into the high energy density compound hexanitrohexaazaisowurtzitane (ε-CL-20) used as main body of formulation, forming PBX. The binding energy, the interaction modes between the energetic binder and ε-CL-20 and the mechanical properties of ε-CL-20/energetic binder mixed systems were simulated by molecular dynamic (MD) method. The enthalpies of formation of the energetic binders with different hard and soft segments proportions were calculated by a group additive method. Results show that the compatibility and stability of PBXs predicted by binding energy decrease in the order of ε-CL-20/PBAMO(9)-g-PAMMO(2)>ε-CL-20/PBAMO(5)-g-PAMMO(7)> ε-CL-20/PAMMO (17)>ε-CL-20/PBAMO (12), PBAMO interacts with ε-CL-20 mainly in van der Waals force. PAMMO interacts with ε-CL-20 in van der waals force, electrostatic interaction and other forces. The energetic binders can effectively reduce the rigidity of ε-CL-20, wherein the thermoplastic elastomer can enhance the ductility of ε-CL-20 effectively. The unit mass enthalpy of formation of energetic binder increases gradually with the increase of BAMO content.

Abstract:In order to study dispersal characteristics for sector cross-section structure, the processes of fuel dispersion and shell breakage driven by central explosive were simulated by LS-DYNA code, and the simulated and experimental results were compared. The variation of fuel velocity with time was obtained. The effects of explosive types, groove spacing and groove depth on dispersion were analyzed. Results show that the maximum dispersal velocity of fuel shows up at 180° direction, while the earliest time for the maximum dispersal velocity is at 0° direction. Compared with RDX, HMX exacerbates the extension of shell breakage due to higher explosion pressure and velocity. Thus, dispersal velocity of fuel reduces by 18% averagely. As for location of central explosive, lower dispersal velocity of fuel and radical breakage of shell would occur when central explosive deviates overly from the center of shell cross-section. With 40 mm groove spacing and 2 mm groove depth, simulation reveals fewer shell stress concentration and higher dispersal velocity (283 m·s^-1) at 180° direction.

Abstract:The influence of decouple coefficient(De), the center charge offset and shell weakening in one side on non-ideal characteristics of fuel dispersal were studied by using LS-DYNA. The calculation results show that the optimum value of De is 2 in this study. When the negative offset of center charge is 2 mm, the dispersal velocity in positive direction increases 6 m·s^-1 and decreases 13 m·s^-1 in negative direction. The more the negative offset of center charge increases, the more obvious the velocity increases in positive direction and decreases in negative direction, which indicates that the offset of center charge has inhibition effect at the same direction and promotion effect at the inverse direction on fuel dispersal. And when unilateral weakening occurs, the dispersal velocity of fuel in both sides decrease and the decrease of dispersal velocity in both sides of the Fuel-Air-Explosive (FAE) device using PVC shell is less than that of steel shell, which suggests the decrease of velocity is obvious when using high strength shell and slight with low strength shell.

Abstract:To simplify the calculation of ignition characteristic parameters of solid propellant under laser action, the laser ignition process for solid propellant was divided into three steps, the thermal decomposition, boundary layer gas mixing and rapid chemical reaction by analyzing on the mechanics of laser ignition for solid phase reaction model. The prediction model for ignition delay time and ignition temperature of laser ignition was built, and a laser ignition process of HMX monopropellant was calculated under laser incident intensity of 45, 76, 170 W·cm^-2. The differences of delay time and temperature of ignition between phase-ignition model and prediction model are 3.8%, 8.1%, 11.5% and 1.23%, 0.87%, 0.98%, respectively, which demonstrating that this method is simple and could be used in engineering application.

Abstract:Genetic algorithm for the calculation of combustion equilibrium composition was proposed based on the principles of chemical equilibrium and the method of minimum free energy. By determining the independent variables and its range, the fitness function was confirmed. To validate the accuracy of the genetic algorithm, the calculation results were compared with the data from references experiment. Results show that the calculation values agree well with the reference data with error less than 1% and 1.5% for combustion equilibrium composition and combustion temperature of negative-oxygen compounds, and less than 7.7% and 5% for that of oxygen-enriched compounds. And the theoretic calculations are well coincident with those obtained by tests of hydroxyl-terminated polybutadiene solid Propellants. The maximum error between them is 4.27%, which demonstrates that the genetic algorithm can be used in compound design, performance prediction and combustion products confirming.

Abstract:Using density functional theory (DFT), the reaction of chlorine trifluoride oxide with water was studied. At the B3PW91/6-31++G(d, p) level of DFT, the geometries of reactants, transition states, and products were optimized and the vibration frequencies and zero point vibrational energies (ZPVE) were calculated. Their energies were obtained with the correction of ZPVE. Results show that the energy barriers of the reaction of chlorine trifluoride oxide and water are very low, and a plenty of water is in favor of producing HF, HClO₂ and HClO₄, however, insufficient water is in favor of producing HF and ClFO₂.

Abstract:The impact toughness(A_k) and the fracture toughness(K_ⅠC) are main parameters to characterize the fracture toughness of the engineering materials. In order to solve the the limits of A_k and K_ⅠC in characterization of explosive fracture toughness, the tensile fracture energy W_t and the compress fracture energy W_c based on the stress-strain curve were put forward. The similarity between the physical meanings of the fracture energy parameters (W_t, W_c)and the impact toughness A_k, was found via analyzing the test principle although they could not be directly measured. W_t, W_c and K_ⅠC for different explosives HMX-P1, HMX-P2, TATB-P3 at room temperature were studied by experiments as well as for HMX-P2 at 20, 35, 45 ℃ and 60 ℃. Results show that the W_t, W_c and K_ⅠC of explosives have the same change trend whether for different type explosives or at different temperatures, which indicates they can be used to characterize the toughness of explosive materials.

Abstract:To study the response characteristics of polymer bonded explosive (PBX) under the effect of compression and shear, the response test for PBX-932 and PBX-C43 with same dimension of Φ20 mm×40 mm in the impact velocity of 22-57 m·s^-1 were performed by a designed compression / shear test device. The pressure change process in the experiments was measured by pressure gauges. The impact process was analyzed by high-speed motion pictures. The reaction overpressure of explosive was measured by shock wave overpressure sensor. The response characteristics for two explosive were analyzed. Results show that the damage of PBX increases with impact velocity rising. The impact velocity threshold of PBX-C43 and PBX-932 under the action of pressure range of 160-400 MPa and pulse width of 1.5 ms is 25.5-27.7 m·s^-1 and 22.7-24.4 m·s^-1, respectively. The reaction degree for two explosive is basically identical.

Abstract:Combined with the calculation results of combustion products and correlative thermodynamic properties of fog aerosol by CEA(Chemical Equilib rium and Application), the influence of Mg on combustion reaction and visibility light shielding performance was studied. The combustion temperature, linear burning velocity and combustion residue of fog aerosol with different Mg content were tested by infrared radiation thermometer, high-speed camera and X-ray diffraction. The theoretical calculation results show that the composition of equilibrium products includes gas state such as CO₂, CO, H₂O, H₂ and condensed state such as MgO. The experiment results show that Mg plays an important role in the combustion performance and the nucleation process of the coagulant nucleus by control of combustion temperature and linear burning velocity of fog aerosol. The combustion temperature and burning rate increases as the increasing of Mg. The combustion temperature reaches almost 2000 K and burning rate is 1.26 mm·s^-1 as the content of Mg is 8%. When the combustion temperature beyond 1773 K, the nucleation process of chloride finishes thoroughly and the visibility light shielding performance of artificial fog get better gradually. The experiment results are consistent with the theoretical calculation results on the variation tendency of combustion temperature and composition of combustion products, but the combustion residue is much different from the theoretical condensed phase faction.

Abstract:To improve the infrared radiation intensity of KNO₃/Mg-Al decoy, the combustion and infrared radiation characteristics of the decoy were experimentally studied via the method of adding boron powder in the decoy by a far infrared thermal imager. Results show that the mass burning rate, combustion temperature and radiation radiance of the decoy increase by adding boron powder. With the content of boron powder increases from 0% to 2%, the mass burning rate of the decoy increaseing from 0.390 g·s^-1 to 0.564 g·s^-1. When the content of boron powder increases from 0% to 4%, the combustion temperature and radiation radiance increase from 727.71 ℃, 995.68 W·m^-2·sr^-1 to 1046.19 ℃, 1681.59 W·m^-2·sr^-1 respectively. With increasing the content of boron powder, the radiation intensity reveals the trend to increase firstly and then decrease. When the content of boron powder is 4%, the radiation intensity increases to the maximum of 2.64 W·sr^-1, revealing that adding a certain proportion of boron powder can effectively improve the mass burning rate, combustion temperature and infrared radiation characteristics of the decoy.

Abstract:In order to study the bubble pulsation characteristics of low energy detonating cord, an underwater explosion experiment was carried out by high-speed photography technology.The experimental results show that the bubble pulse shape in the shooting section remains a clindricclity at the first bubbles pulsing tirme, and iregular cylinder from the second bubbles pulsing tirme. The outside edge of bubbles is blurry because of the efect from shell fragments.The first bubble pulsation period is 21.5 ms and the second is 15.5 ms.The maximum diameter of bubble is 11.2 cm in the first bubble pulsation period.In addition, the bubble growth time is 15 ms while the contraction time is 6.5 ms in the first bubble pulsation period.The bubble growth time is longer than the contraction time.

Abstract:Synthesis and properties of 10 kinds of nitroimidazoles energetic materials were reviewed, including 1, 4-dinitroimidazole (1, 4-DNI), 2, 4-dinitroimidazole(2, 4-DNI), 4, 5-dinitroimidazole (4, 5-DNI), 2, 4, 5-trinitroimidazole (2, 4, 5-TNI), 1-methyl-2, 4-dinitroimidazole (2, 4-MDNI), 1-methyl-4, 5-dinitroimidazole (4, 5-MDNI), 1-methyl-2, 4, 5-trinitroimidazole (MTNI), 1-picryl-2, 4-dinitroimidazole (2, 4-PDNI), 1-carboethoxy-2, 4, 5-trinitroimidazole (CTNII), 1-picryl-2, 4, 5-trinitroimidazole (PTNI). The high energy and insensitive explosives, such as 1, 4-DNI, 2, 4-DNI and MTNI, were summarized in detail and the disadvantages in the synthesis of these materials were pointed out. And a new synthetic route of MTNI was designed in theory, using N-methylimizole as starting material via iodination by iodination agent aqueous solution and nitration by super solid acidic.

Abstract:The progress in synthesis and performance of nitrourea energetic materials such as five-membered ring nitroureas, especially glycoluril was systematically reviewed. The nitrourea energetic materials have better thermal stability, higher density and higher energy level, but bisnitrourea-compounds have the poor hydrolytic stability, which restricts their application. Pointed out that the studies on glycoluril derivatives and seven-membered ring and eight-membered ring nitrourea energetic materials are less relatively. To improve actual application values of nitrourea energetic materials, the synthesis of new compounds by designing good nitrogen heterocyclic molecular skeleton and introducing nitroform group (—C(NO₂)₃), nitro group (—NO₂), amino(—NH₂) group and nitramino group(N—NO₂) etc energetic groups into the molecular skeleton may be considered. A research direction in design and synthesis for new nitrourea energetic materials is proposed with 52 references.

Abstract:Five novel 2-dinitromethyl-5-alkoxytetrazole compounds, 2-dinitromethyl-5-methoxytetrazole(DNMMOT), 2-dinitromethyl-5-ethoxytetrazole (DNMEOT), 2-dinitromethyl-5-isopropoxytetrazole (DNMPOT), 2-(2-dinitromethyl tetrazole-5-yloxy)ethanol (SDEH)and 1, 2-bis (2-dinitromethyl tetrazol-5-yloxy)ethane (DEH)were synthesized from the reaction of 2-dinitromethyl-5-nitrotetrazole (HDNMNT)with sodium alkoxide with yields of 91.6%, 92.1%, 91.70%, 31.7%, 57.4%, respectively. Their structures were characterized by IR, NMR, elemental analysis and HPLC-MS, and their detonation performances were predicted by B3LYB method. Results show that reaction mechanism is nucleophilic substitution between HDNMNT and sodium alkoxide. The detonation velocity and pressure of DEH estimated are 8676 m·s^-1 and 34.39 GPa, which can be compared to RDX.

Abstract:An energetic plasticizer 6b-nitrohexahydro-2H-1, 3, 5-trioxacyclopenta[cd]-pentalene-2, 4, 6-tryl trinitrate(2) was synthesized from glyoxal and nitromethane via the condensation and nitration reactions with a total yield of 40.90%, and its structure was characterized by elemental analysis, IR, NMR.The single crystal of compound 2 was obtained firstly.It was found that its crystal belongs to the monoclinic system, and its space group is P2₁/n with a=7.792(9)Å, b=8.534(9)Å, c=19.41(2) Å, β=117.624(4)°, M_r=370.16, V=1305(2) ų, Z=4, D_c=1.884 g·cm^-3, λ=0.71073 Å, F(000)=752, μ=0.189 mm^-1, S=1.097, the final R₁=0.0488, and wR₂=0.1289.

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