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Abstract:Aiming at the problem about early blasting of the detonating network in industry, a type of irreversible detonation explosive diode was designed and develop by numerical simulation method. Using the combination of ignition and growth model and ANSYS/LS-DYNA finite element software are transmitting positive detonation was simulated by various mass of the firing charge and the stopping backward detonation was simulated by various length of the delay element. Then the feasibility was validated by the positive and negative symmetry experiment and the velocity measurement of flying plane. Results show that the explosive diode can achieve the aims of successful transmitting positive detonationsignal and stopping backward detonation signal and that the mass of firing charge and the length of linear delay elements must be limited. The least mass of firing charge is 30 mg and the minimum length of delay elements is 4 mm at 30 mg firing charge.

Abstract:The geometrical structures, front orbital energies and enthalpies of formation (ΔH_f) of 14 kinds of 1, 2, 4, 5-tetrazine polycyclic ring derivatives were studied using density functional theory (DFT) and wB97/6-31+G^** basis set level. The detonation performances of these derivatives were estimated by Kamlet-Jacobs equation. The thermodynamic properties of these compounds at different temperatures from 200K to 800K were obtained by statistic thermodynamics. The detonation properties and heat of formation of these 1, 2, 4, 5-tetrazine derivatives were also compared. Results show that the detonation velocity (D) and detonation pressure (p) have good linear correlation with the numbers of nitrogen, and their ΔH_f are between 527.49 kJ·mol^-1and 1122.53 kJ·mol^-1 and the detonation velocities are between 5.59 and 8.65 km·s^-1. The values of the standard heat capacity (C_{p, m}), standard molar entropy (S_m) and the standard enthalpy (H_m) gradually increase with the temperature. The compounds T7(C₂N₇H₂) and T72(C₂N₁₀H₂) may be considered as potential candidates for energetic materials.

Abstract:When the projectile was launched by a barrel weapon, the precursor flow field had greater impact on the development of combustion gas flow of subsequent propellant and the movement of projectile. To analyze the effect of precursor flow field on the structure of combustion gas jet and movement of projectiles, based on the finite volume method, two different 2-d axisymmetric numerical models with and without the precursor flow field were established using the Whole Zone Movement Method for block grid division and Realizable k-ε turbulence Model and coupling the interior ballistic process and the Six-DOF equations. Taking the 300 mm counter-mass propelling gun as example, the muzzle flow field characteristics at the ejection speed of 1730 m·s^-1 were studied. The results show that when there is no precursor flow field, the wavefront of propellant combustion gas is approximately spherical, and the propellant combustion gas is unable to catch up with the projectile. But under the interference of precursor flow field, the ejectingn velosity of propellant combustion gas increases by about 200 m·s^-1, and the combustion gas catches up with and surrounds the projectile, the maximum pressure in the flow field decreases by a half, the temperature increases by more than 1000 K and the projectile base pressure decreases by about 1.3 MPa.

Abstract:In order to search new high-energy density materials, 2, 3, 4, 5-tetranitropyrrole (TNP) and its methyl-, amino-, nitro-substituted derivatives were designed. Their structures were optimized at the DFT-B3LYP/6-31G^* level. Heats of formation, detonation properties were calculated at the DFT-B3LYP/6-311++G^** level. Nature Bond Orbital (NBO) analysis was carried to understanding the strength of trigger bond and further to access the thermal stability of the model compounds. The calculated results are as follows: the density, detonation velocity and detonation pressure of 1-methyl-2, 3, 4, 5-tetranitropyrrloe are 1.88 g·cm^-3, 8.66 km·s^-1 and 34.10 GPa, respectively, which is comparable to the detonation properties of 1, 3, 5-trinitro-1, 3, 5-triaza-cyclohexane (RDX). The densities of 2, 3, 4, 5-tetranitropyrrole and 1-amino-2, 3, 4, 5-tetranitropyrrole are 1.93 g·cm^-3 and 2.04 g·cm^-3, respectively; the detonation velocities are both 9.01 km·s^-1, and detonation pressures are 37.54 GPa and 38.73 GPa, which suggests that the detonation properties of TNP and ATNP are both comparable to that of 1, 3, 5, 7-tetranitro-1, 3, 5, 7-tetraza-cyclooctcme (HMX). With containing five nitro groups, the BDE of nitro group N (5)—NO₂ is 60.8 kJ·mol^-1, suggesting that pentanitropyrrole has the poorest thermal stability in all five model compounds. The calculated results and previous experimental work agree reasonably well one another, showing values in this paper are reasonable.

Abstract:4, 4′, 5, 5′-Tetranitro-2, 2′-biimidazole (TNBI) was synthesized using ammonium acetate and glyoxal as starting materials by the reactions of cyclic condensation and nitration. A series of 4, 4′, 5, 5′-tetranitro-2, 2′-biimidazolate energetic ion salts were prepared with the cations as 3, 4-diaminofurazan (DAFTNBI), oxalyl dihydrazide (ODTNBI), 3, 6-dihydrazino-1, 2, 4, 5-tetrazine (HTTNBI), biguanide (DBGTNBI), gunanyl urea (DGUTNBI), 4-amino-1, 2, 4-triazole (DATTNBI), urea (DUTNBI). The structures of all compounds were confirmed by IR, ¹H NMR, ¹³C NMR and elemental analysis. The single crystal of TNBI·H₂O was obtained in the water system.The crystal of TNBI·H₂O belongs to monoclinic system, space group P2(1)/n, cell parameters: a=0.5051(17) nm, b＝0.8528(3) nm, c=1.5270(5) nm, β=96.948(6)°, V＝0.6529(4) nm³, Z＝4, D_c＝1.781 g·cm^-3. The thermal properties of seven energetic ion salts were studied by differential scanning calorimetry (DSC) and thermogravimetric (TG). Results show that the thermal decomposition peaks of these energetic ionic salt are at 199.23, 204.52, 230.13, 266.96, 240.63, 187.98 ℃ and 260.19 ℃, respectively, which indicates that their thermal stability is good.

Abstract:By underwater explosion and brisance experiments, the effects of titanium powder with different content on the detonation properties of emulsion explosive were tested and compared with aluminized emulsion explosive. The kinetic parameters of thermal decomposition were calculated using thermal analysis data measured by the C80 calorimeter. Results show that compared with emulsion explosive without additive, the explosion impulse, shock wave energy and bubble energy of emulsion explosives with 5% titanium powder are increased 14.95%, 21.74% and 19.90%. With increasing titanium powder, shock wave parameters increase first and then decrease, it reaches maximum when the mass fraction of titanium powder is 10%, and its brisance is increased 17.65%, which means that titanium powder have remarkable impact on the detonation capability of emulsion explosive. The influence of titanium powder on thermal stability of emulsion explosive is least than aluminum powder and boron powder, whose apparent activation energy is 193.48 kJ·mol^-1.

Abstract:To meet the demand of high ignition energy in narrow space, a new energetic composite was prepared compounding high-energy Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane(HNIW) into macroporous polyacrylonitrile(PAN) fibrosa by electrostatic spinning(ES) method and self-assembly method. The morphology, thermal property and combustion behavior of as-prepared composite were analyzed by SEM, FT-IR, thermal analysis and combustion residues analysis. Results show that HNIW is uniformly distributed on the fibrosa; their compound is a physical process; there is no chemical change. Compared with pure PAN fibrosa, the addition of HNIW enhances the combustion performance of fibrosa, and initial exothermic temperature of HNIW shifts about 38 ℃ downwards because of the existence of fiber. The fiber and HNIW can completely react in a particular proportion.

Abstract:Using diaminomaleonitrile as starting material, a novel energetic compound 5, 5′-(2-(trifluoromethyl)-1H-imidazole-4, 5-diyl) bis (1H-tetrazole) was synthesized by condensation cyclization reaction with trifluoroacetic anhydride and the second condensation cyclization reaction with NaN₃ in the yield of 61.3%; based on acidity of the compound, two energetic ionic salts of hydroxylamine and guanidine of 5, 5′-(2-(trifluoromethyl)-1H-imidazole-4, 5-diyl) bis (1H-tetrazole) were designed and synthesized. The structures of products and intermediates were characterized by IR, NMR and elemental analysis. Key factors affecting the cyclization reaction for tetrazole in the formation process of 5, 5′-(2-(trifluoromethyl)-1H-imidazole-4, 5-diyl) bis (1H-tetrazole) were discussed, the optimum reaction conditions were determined as: H₂O as reaction medium, n(2-(trifluoromethyl)-1H-imidazole-4, 5-dicarbonitrile):n(NaN₃)=1:2.4, reaction temperature 98 ℃, reaction time 4 h, yield up to 86.3%. The thermal decomposition of 5, 5′-(2-(trifluoromethyl)-1H-imidazole-4, 5-diyl) bis (1H-tetrazole) was studied by DSC-TG, which shown the compound decomposition starts at 223.65 ℃, and the whole decomposition process undergos two main exothermic decomposition stages and weight loss stages, the maximum exothermic peak temperature is 285.78 ℃, the structure of the compound is relatively stable.

Abstract:Four kinds of hexanitrohexaazaisowurtzitane (CL-20) based composite particles were prepared by slurry method using CL-20 as filler, wax and Estane5703 as desensitizers. The crystal form, state of coatiing, thermal decomposition temperature of samples before and after coating were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), differential scanning calorimeter (DSC), and the mechanical sensitivity was tested. Results show that CL-20 is coated by wax and Estane5703 perfectly, and the ε crystal form of CL-20 was not changed. The impact sensitivity and friction sensitivity of CL-20 decrease from 100% to 40% and 48%, and thermal decomposition peak temperature increases by 5.4 ℃ compared with raw material when the wax and Estane5703 content are all 2%.

Abstract:To investigate the effect of additives on the impact sensitivity and power of Comp.B, modified Comp.B was prepared by adding 123 resin, polyester fibre and thermoplastic elastomer VP-401, respectively. Big-bill hammer impact sensivity test, Susan test and cylinder test of the samples were conducted. The changes in the impact sensitivitly and power of Comp.B were obtained. The effects of compressive elasticity and toughness on the impact sensitivity as well as content of additives on the power for modified Comp.B were discussed. Results show that by adding 1% 123 resin, the compressive elasticity and toughness of Comp.B can be obviously improved, and the height of the threshold of deflagration reaction is enhanced by 3 m, and the impact sensitivity is obviously reduced. The modified Comp.B with 123 resin still belongs to a kind of explosive with lower strength, the fragmentation of the explosive has occured in the process of plastic deformation occured with the shell within the time range of several hundred microseconds from the Susan projectile′s impact on the target to explosion of fragmentated explosive. The fragmentation degree of the explosive greatly affects the percentage of deflagration, i.e. the relative energy is released. Compared with the power capability of Comp.B, the power of Comp.B with 1% 123 resin is decreased by 4.6% and 1.24%, respectively at radial distance of 5 mm and 19 mm.

Abstract:The uncertainties of model parameters, structural geometry, material property, and external force of the polymer bonder explosive, were quantified with probability box and propagated with nested sampling method in order to separate the different effect of aleatory uncertainty and epistemic uncertainty on response of interest. Moreover, numerical error and model form error were also quantitatively superposed to acquire the response uncertainty and the reliability interval of the polymer bonder explosive (PBX) structure consequently. In addition, the results of proposed method in this paper were compared with the determinate checking method and the probabilistic reliability method. It is indicated that the reliability assessment with the consideration of uncertainty can reduce the engineering risk than the determinate method. Furthermore, the reliability interval obtained by the proposed method covers the reliability calculated by probabilistic method, and can narrow down to the true reliability as the epistemic uncertainty decreases.

Abstract:In order to investigate the temporal and spatial distribution characteristics of gelled kerosene, a high speed camera was used to shoot the breakup process. The breakup characteristics of gelled kerosene at various gas velocities, the effects of flow parameters on breakup time and breakup region were obtained. Results indicate that the same breakup morphology as kerosene (Newtonian fluid) droplet occurs to gelled kerosene droplet with the increase of Weber number (We) and the transition We elevates with the increase of gellant content. For each kind of gelled kerosene, the ratio of total breakup time and initial breakup time (T_tot/T_ini) decreases with the increase of Ohnesorge number (Oh) and tends towards the value of Newtonian fluid (3.125). At the end of breakup, streamwise breakup region widens with the increase of We and the region is wider with the lower gellant content. Cross-stream breakup region widens to a maximum value with the increase of We number. The ratio of cross-stream breakup region and initial diameter tends towards 20 for the gelled kerosene of 1% and 2% gellant content, while the value tends to 17 when gellant content is 3%.

Abstract:2, 3-Bis (hydroxylmethyl)-2, 3-dinitrobutane-1, 4-diol tetranitrate (SMX) was synthesized via. ketal reaction, oxidative coupling, ketal deprotection and nitration etc. four step reaction using 2-(hydroxymethyl)-2-nitro-1, 3-propanediol as starting material. The structure of SMX was characterized by elemental analyses, infrared spectroscopy and nuclear magnetic resonance spectroscopy. The crystal growth morphology and crystallization behavior of SMX were simulated by using Growth Morphology methods in Materials Studio Modeling softwar, the structure features of important crystal facets were analyzed, and the solvent effect on the crystal morphology was discussed. The recrystallization of SMX was carried out by using the mixed solution of ethyl acetate and petroleum ether. The compatibilities of SMX with hydroxy-terminated-polybutadiene (HTPB) propellant components, including HTPB, ammonium perchlorate (AP), aluminum powder, (Al powder) cyclotetramethylenetetramine (HMX), cyclotrimethylenetrinitramine (RDX), tolylene diisocyanate (TDI) were investigated by differential scanning calorimetry (DSC).Results show that the crystal morphology of the product was improved by the ethyl acetate/petroleum ether system. The theoretical predictions are in agreement with the experimental results. The mixed system of SMX with HMX, RDX and Al powder is compatible, with AP is slightly sensitive, and with HTPB and TDI is incompatible.

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