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Abstract:To investigate the intermolecular interactions between insensitive explosive 3, 4-dinitropyrazole (DNP) and high-energy explosive hexaazaisowurtzitane (CL-20), the structure of DNP/CL-20 complex was optimized based on a density functional theory (DFT), six kinds of stable configurations were obtained. The types of intermolecular interaction in complexes were analyzed by natural bond orbital (NBO), electron density topology and reduced density gradient (RDG). The effects of intermolecular interactions on the sensitivity of CL-20 were analyzed from the bond length, bond dissociation energy, bond order of CL-20 trigger bond and the relative charges of nitro group and electron density difference of complex. Results show that the intermolecular hydrogen bond and van der Walls force, including the interactions of N—H…O, C—H…O and N…O, O…O exist in DNP/CL-20 complexes. The analysis of nitro charges and electron density difference show that these intermolecular effects affect the charge distribution and electron density distribution of CL-20 molecules and change the stability of CL-20 trigger bond, resulting in a decrease of its sensitivity. There are good liner relationships among the variations of the bond length, bond dissociation energy, bond order of CL-20 trigger bond and electron density at the bond critical point. The interaction energy of six configurations in the text increases in the order of structure Ⅰ < structure Ⅲ < structure Ⅳ < structure Ⅱ < structure Ⅵ < structure Ⅴ.

Abstract:To accurately predict the crystal morphologies of dihydroxylammonium 5, 5′-bistetrazole-1, 1′-diolate (HATO, also known as TKX-50) under different growth conditions, the PCFF force field parameters were systematically validated and modified. The attachment energies of HATO crystal surface were calculated by the molecular simulation method. The crystal morphologies of HATO in vacuum, in seven solvents (water, dimethyl sulfoxide, methanol, ethanol, ethyl acetate, tetrahydrofuran and trichloromethane), and in three additives (sodium laurylsulfonate, sodium dodecyl benzene sulfonate and dextrin) were obtained. Results show that the crystal morphology of HATO in a vacuum is long flaky, consisting of five cryatal faces, (0 2 0), (1 1 -1), (0 1 1), (1 1 0) and (1 0 0), among them, cryatal face (0 2 0) is the most important, occupying the 53.97% of total surface area. In the polar solvents, including dimethyl sulfoxide, methanol, and ethanol, the morphological importance of (0 2 0) cryatal face decreases, the crystal morphology of HATO is improved. In the three additives, the crystal morphology of HATO is still long flaky. The predicted structure of crystal morphology of HATO is in good agreement with the experiments, it can provide theoretical guidance for the crystal morphology control of HATO.

Abstract:Four kinds of gas clusters of 1, 1-diamino-2, 2-dinitroethene (FOX-7) were obtained by using RI-B2PLYP-D3 and PW6B95-D3 methods with dispersion correction density functional theory. On this account, the existing state of FOX-7 molecules in the crystal structures was simulated. The electron density difference of the neighboring molecules in the process of cluster formation was plotted, and the formation and origin of intermolecular interactions were explained from the point of view of electron density change. The effect of intermolecular interaction of condensed phase FOX-7 on the dissociation mechanism of FOX-7 was investigated. Results show that the intermolecular interactions are due to the partial intermolecular sharing of electrons formed by electron offsets in the FOX-7 clusters. The formation of intermolecular interactions also weakens the chemical bonds in some molecules, resulting in a change in the cleavage channel of FOX-7. Compared with the unimolecule state, the intermolecular interaction makes the cleavage activation energy of C—NO₂ bond in FOX-7 clusters reduce generally when PW6B95-D3 theory is used. Because of different angles of molecular interaction in different clusters, the process of nitro isomer has changed, compared with the unimolecule, the activation energy of nitro isomer channels of cluster Ⅱ decreases by 210.9 kJ·mol^-1, and the activation energy of nitro nitro isomer channel of cluster Ⅳ increases by 39.4 kJ·mol^-1.

Abstract:Toughened paraffin wax applied in polymer bonded explosives(PBXs) is mainly to improve its mechanical properties. In this paper, based on the study of toughened paraffin, four kinds of formulations of toughened paraffin and plasticizers were designed. The blending models of styrene-butadiene-styrene block copolymer(SBS) toughened paraffin Wax with dibutyl phthalate(DBP), dioctyl sebacate(DOS), nitroglycerin(NG) and acetyl tributyl citrate(ATBC) were established. The compatibility of the toughened Wax with plasticizers and the nature of the intermolecular interactions in the blend systems were simulated and studied by molecular dynamics method. Results show that the compatibility of SBS toughened Wax with plasticizers can be comprehensively evaluated by the four criteria of solubility parameter, miscibility simulation, binding energy and intermolecular radial distribution function. In which, the relative error between the simulated value and the experimental one of solubility parameter is within 3% and the miscibility simulation can quickly predict the compatibility between two substances. The binding energy of ATBC and SBS toughened Wax is the largest, which is 2.7 kJ·g^-1. The essence of the interaction between SBS toughened Wax and plasticizers is van der Waals force and electrostatic force, mainly to van der Waals. The compatibility sequence of the three plasticizers with SBS toughened Wax is ATBC> DOS> DBP, NG is incompatible with SBS toughened Wax.

Abstract:To study the effect of Sauter diameter(D₃₂) of droplets on the explosion parameters, the effect of the droplets size of n-heptane (C₇H₁₆) on the explosion parameters in explosion vessel was numerically simulated, while controlling the total concentration of droplets of 80 g·m^-3, when changing the droplet size. Results show that when D₃₂ of n-heptane droplets is between 0-18.1 μm, the maximum explosion pressure p_max decreases gradually with the increase of D₃₂, the maximum value is 1.01 MPa and the minimum value is 0.9015 MPa. The maximum explosion pressure rise rate reveals an overall downward trend with the increase of D₃₂, which reaches the maximum value of 0.37571 MPa·ms^-1 at 0 μm, and the minimum value of 0.18439 MPa·ms^-1 at 18.1 μm. But in the range of 6.81-12 μm, the reverse mutation occurs, reaching the maximum value of 0.34217 MPa·ms^-1 at 10.1 μm, and then restoring the downward trend. The radial flame propagation velocity of droplets suddenly increases near the radial distance of 15 cm, and then decreases sharply after 16 cm. The maximum flame velocity varies with D₃₂ of droplets. Under the conditions of D₃₂=10.1, 12.9, 18.1, 6.81 μm and 0 μm, the maximum flame velocity of droplets field decreases successively. The maximum value is 5.714 m·s^-1, followed by 1.737, 1.36, 1.34 m·s^-1 and 1.27 m·s^-1.

Abstract:To simulate the impact response characteristics effectively and provide reliable data for the safety prediction of explosives, the numerical simulations of the drop test and the Steven test of explosive were performed by the finite element method (FEM) and the coupling algorithm of FEM and smoothed particale hydrodynamics (FEM-SPH) and the discussion and comparative analysis for the advantages and disadvantages of all kinds of algorithms were carried out. Results show that the FEM-SPH coupling algorithm can more effectively simulate the mechanical response problem of viscous explosives after being impacted and the accuracy is higher. In the simulation of drop test, the ascending rates of pressure curve and overloading curve obtained by FEM-SPH coupling algorithm are closer to the measured values. The maximum pressure error is approximately 4%, while the error of FEM is 16%. In the simulation of Steven test, the pressure history curve obtained by FEM-SPH coupling algorithm is more consistent with the testing value. The deviation of the pressure integral value and the experimental value is approximately 10.7%, whereas the deviation of FEM is 29%, and the phenomenon after being impacted is more similar to real test situation. FEM-SPH coupling algorithm can show the relative slippage and flow characteristic of viscous materials and granular ones in the process of impact loading in a certain degree, the problems of simulating large deformation of viscous explosives after being impacted have certain advantages.

Abstract:The wall slip is one of the important factors affecting the quality of gun propellant extrusion molding. To improve the accuracy of numerical simulation of the seven-hole nitroguanidine gun propellant extrusion molding, the wall slip mechanism of nitroguanidine gun propellant dough was studied, the mathematical model of gun propellant flow considering the wall slip correction was established. The finite element method was used to simulate the forming process of seven-hore nitroguanidine gun propellant. The pressure field, the velocity field and the velocity vector distribution at the junction of the segment and the forming section were compared and analyzed at cases whether considering the wall slip. The simulation was validated by the gun propellant extrusion test. Results show that the wall slip reduces the forming pressure of gun propellant and improves the uniformity of gun propellant exit rate, which is beneficial to the forming of gun propellant. The error between the actual size and the simulation size of the gun propellant is less than 2.0% in which, the outer diameter error is 0.59%, and the outer arc error 0.36%, the inner arc error 1.80%, the aperture error 1.67%, and the center aperture error 1.72%. The simulation process is in line with the actual processing.

Abstract:To study the influence of the transducer component composed of bridge foil, flyer and accelerating chamber on the exploding foil initiator (EFI) ignition performance and achieve the goal of reducing the ignition threshold, ANSYS/AUTODYN software was used to simulate the process that bridge foil driven flyer to detonate HNS-Ⅳ. The influence of bridge foil thickness on flyer speed was studied, and the influences of bridge area width, flyer material(organic glass, ceramic and polyimide), flyer thickness and accelerating chamber length on EFI ignition threshold were investigated. Results show that reducing the width of bridge area is helpful to reduce the ignition threshold of exploding foil initiator. Under the same input voltage, the speed of flyer driven by bridge foil with thickness of 2 μm is maximum. The ignition voltage of exploding foil initiator decreases firstly and then increases with the increase of flyer thickness, and the ignition voltage is lowest when the thickness is 10 μm. Compared with 0.225 mm, 0.250 mm and 0.275 mm accelerating chamber, ignition voltage of 0.125 mm one is lowest, so reducing the acceleration chamber length is beneficial for reducing ignition threshold of exploding foil initiator. Under the condition of determinig the accelerating bore aperture, "infinite" accelerating chamber is better than "finite" accelerating chamber for reducing firing voltage of EFI. Polyimide has better mechanical properties, lower ignition voltage and lower kinetic energy compared with other two materials (organic glass and ceramic).

Abstract:To study the effective regulation and control technology of the deflagration to detonation transition (DDT) process for DNTF-based composite explosive, the effect of ignition charge mass, DDT tube wall thickness constraint and molding way etc. on the performance of DDT for DNTF-based composite explosive was investigated by the coaxial ionization probe test technology. The test results were analyzed from the view of the change in rupture state of DDT tube, wave front velocity at different location of DDT process and inducement detonation distance etc. Results show that the DDT tube wall thickness constraint has no significant effect on the inducement detonation distance of DDT for DNTF-based composite explosive, which is at about 375 mm, but decreasing wall thickness can make the duration time of deflagration stage increase and the initial velocity to detonation reduce to 5515 m·s^-1. Increasing ignition charge mass has no significant effect on the reaction violence of DDT for DNTF-based composite explosive, but it can reduce the duration time of initial combustion and detonation induced distance. The duration time of initial combustion, duration time of deflagration and detonation induced distance of the pressed molding specimen are greater than those of the cast specimen, but there is no obvious difference in the violence of the reaction.

Abstract:To prepare ultrafine and high-quality octogen(HMX) and study its crystal types, superfine HMX was prepared by an ultrasonic assisted spray recrystallization refinement method. The effects of atomization rates, solvent and non-solvent type and temperature etc. on the particle morphology and crystal types of HMX were studied. The crystal morphology, particle size and crystal type of HMX were characterized by scanning electron microscopy (SEM) and X-ray diffractometer (XRD). The thermal decomposition properties of HMX were measured by differential scanning calorimetry (DSC). The impact sensitivity of raw HMX and superfine HMX was measured by an impact sensitivity tester. Results show that the ultrafine HMX prepared by ultrasonic assisted spray recrystallization refining has a great influence on the atomization rates, solvent and non solvent type, temperature etc. The morphology of HMX crystals prepared by an ultrasonic frequency of 40 kHz, stirring speed of 400 r·min^-1, atomization rate of 20 mL·min^-1, acetone as solvent, absolute alcohol as non-solvent and temperature of 30 ℃ is the best, the crystal type is β-type. Compared with the raw material of HMX, the apparent activation energy of thermal decomposition reaction of ultrafine HMX increases by 17. 94 kJ·mol^-1 and its characteristic drop height of impact sensitivity increases by 29. 6 cm.

Abstract:To meet the development requirements of miniaturization and high reliability of weapon and ammunition safety system, a safe and arming device of pyrotechnical micro-electro-mechanical system(PyroMEMS) based on silicon double solid beams was designed. The compressive strength and overload strength of the solid beam in the safe and arming mechanism layer were simulated by using ABAQUS software. The principle prototype of safe and arming device of PyroMEMS was fabricated using micro-electro-mechanical system(MEMS) technology according to the simulation results. In order to study its actuation performance, the Si/Pb₃O₄ mixture of mass ratio as 1:9 was selected as ignition powder and the C₆H₂(NO₂)₃OK/KClO₄ mixture of mass ratio as 1:1 was selected as gas generator. Results show that the compressive strength is 310.03 MPa and the overload strength is 47.31 g as the boh length size and width size of silicon double solid beams in the safe and arming device are 300 μm.The designed PyroMEMS S & A device can successfully realize safe and arming functions.

Abstract:The integrated fabrication of exploding foil initiator was realized by micro-electromechanical system manufacturing technology. Bridge foil of Cu with 0.4 mm×0.4 mm×4.6 μm(L×W×H) and poly(monochloro-p-xylylene)(Parylene C) a thickness of 25 μm/Cu with a thickness of 2 μm multilayer flyer were prepared by magnetron sputtering process and chemical vapor deposition technology. The preparation of SUEX dry film barrel was realized by ultraviolet lithography technology. Three kinds of barrels with a thickness of 0.395 mm and diameters of 0.40 mm, 0.56 mm and 1.00 mm were obtained and their wall verticalities were good. The influence of firing voltage and barrel size on the velocity of multilayer flyer were studied by photonic doppler velometer(PDV) measurement system. The detonation tests of HNS explosives were carried out. Results show that the velocity of the multilayer flyer gradually increases with increasing the firing voltage. Under the same firing condition, on the contrary, the velocity of the multi-layer flyer gradually increases with decreasing the diameter of the barrel, i.e. under the same firing condition, the velocity of the multilayer flyer for the barrel with a diameter of 0.40 mm is the maximum. Results of initiating HNS explosives reveal that the firing voltage gradually decreases with decreasing the diameter of the barrel. Compared with the barrel with a diameter of 1.00 mm, the firing voltage of barrel with a diameter of 0.40 mm reduces by about 200 V under the capacitor discharge condition of 0.22 μF.

Abstract:To explore the change trend of intermediate products in biotransformation of 2, 4-dinitrotoluene (2, 4-DNT) and properties of nitroreductase produced by Rhodobacter sphaeroides, the effect of different combination of nitrogen sources on the efficiency of biotransformation 2, 4-DNT by Rhodobacter sphaeroides and the growth of Rhodobacter sphaeroides cells was studied. The concentration changes of 2, 4-DNT and biotransformation products of 2, 4-DNT were measured at different time. The patterns of isoenzymes of nitroreductase was analyzed using native-polyacrylamide gel elecrophoresis (native-PAGE) method, and kinetic parameters of the nitroreductase were measured and obtained. Results show that the optimum combination of nitrogen sources to biotransformation of 2, 4-DNT by Rhodobacter sphaeroides is complex nitrogen sources composed of yeast extract and (NH₄)₂SO₄. Using Rhodobacter sphaeroides, 2, 4-DNT can efficiently reduced as 4-amino-2-nitrotoluene(4A2NT) and 2-amino-4-nitrotoluene(2A4NT). However, the content of 4A2NT is far greater than that of 2A4NT, they have not been futher reduced to 2, 4-diaminotoluene (2, 4-DAT). When the initial concentration of 2, 4-DNT is 20, 40 and 60 mg·L^-1, there is an obvious promoting effect on the actiyity of nitroreductas produced by Rhodobacter sphaeroides. While, when the initial concentration of 2, 4-DNT is 80 mg·L^-1, the actiyity of nitroreductase is inhibited. The activity of nitroreductas produced by Rhodobacter sphaeroides is the highest at the initial pH=7. The kinetic parameters, the maximum reaction rate V_max and Michaelis constant K_m, for the nitroreductase in Rhodobacter sphaeroides are 0.0507 mmol·(L·min) ^-1 and 0.1772 mmol·L^-1, respectively.

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