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Abstract:The wet composite gel of RDX/B/Fe₂O₃ was prepared by adding RDX and B powder into the gel template of Fe₂O₃ which was prepared by sol-gel process. And then it was dried by supercritical CO₂ fluid drying technology to get RDX/B/Fe₂O₃ Nano-composite energetic material. The factors influencing the gel structure and particle size during both the preparation and drying processes of wet gel were investigated. And the optimum condition is as follows: the concentration of Fe³⁺ 0.20 mol·L^-1, n(Fe³⁺):n(C₃H₆O)=1:15, the temperature of the supercritical CO₂ 40 ℃, the pressure of the supercritical CO₂ 10 MPa, the flow rate of CO₂ 15 L·h^-1 when the drying kettle is pressurized and flow rate of CO₂ was 12 L·h^-1 when the drying kettle is pressure balance. Under this condition, the nano-composite energetic material of RDX/B/Fe₂O₃ (mass ratio 90:2:8) was prepared. Scanning electron microscope and differential scanning calorimetry analysis were employed to characterize its microstructure and thermal reactions. Meanwhile, its mechanical sensitivity was measured. Results show that the particle size of nano-composite energetic material was 30-50 nm. Compared with the raw RDX, the thermal decomposition onset point of RDX/B/Fe₂O₃ increases by 7 ℃, the reaction heat improves by 885 J·g^-1 and H₅₀ is 40.8 cm.

Abstract:In order to investigate thermal decomposition properties and thermal stability of high energy density energy materials 2, 4, 6-triamino-3, 5-dinitropyridine-1-oxide(TANPyO), the adiabatic decomposition process of TANPyO was studied by accelerating rate calorimeter(ARC). Temperature rise rate, temperature and pressure versus time curves, pressure and temperature rise rate versus temperature curves were obtained, respectively. Results show that adiabatic decomposition process of TANPyO can be divided into two exothermic stages. The second stage is the main thermal decomposition process with a great change in temperature rise rate. The initial decomposition temperature of TANPyO is 252.7 ℃, which proves that TANPyO has good heat stability. Kinetic and thermodynamic parameters were calculated by temperature rise rate equation and Arrhenius equation are as follows: apparent activation energy 476.96 kJ·mol^-1, pre-exponential factor 6.920×10⁴² min^-1, reaction heat 930.84 J·g^-1, respectively.

Abstract:Sodium dichloroisocyanurate was replaced by sodium hypochlorite as the oxidant for improving the synthetic method of 4, 4′-azobis (1, 2, 4-triazole). Three different factors, the illumination time, the molar ratio available chlorine to acetic acid and the reaction temperature, were studied for the influence of the reaction process. The structure and properties of the product obtained were compared with literature ones. Results show that under the condition of dark (0h illumination time), the molar ratio available chlorine to acetic acid 1:2.5 and 7 ℃, the yield is 78%. Compared with sodium dichloroisocyanurate, sodium hypochlorite used as the oxidizing agent to synthesize 4, 4′-azobis(1, 2, 4-triazole) can not only omit the separation and purification of 4, 4′-azobis(1, 2, 4-triazole), but also solve the problem of processing the isocyanuric acid.

Abstract:The dihydroxylammonium 5, 5′-bistetrazole -1, 1′-diolate(TKX-50) was synthesized using solution glyoxal (40% w/w in H₂O) and hydroxylammonium as starting materials by substitution, chloration, nitrine reaction, ring formation reaction, and salt formation reaction. Its structure was characterized by elemental analysis and NMR, and its impact sensitivity and friction sensitivity were studied. The effects of reaction temperature, holding time and holding temperature on yield of 5, 5′-bistetrazole -1, 1′-diolate (BTO), and the effect of concentration of hydroxylamine on yield of TKX-50 were discussed. Results show that the impact sensitivity H₅₀ for TKX-50 is 41 cm, and its friction sensitivity is 0%.The optimal reaction condition are as following: reaction temperature 0-5 ℃, holding time 12 h, holding temperature 20-25 ℃, when the concentration of hydroxylamine is 50%(w/w in H₂O).

Abstract:Using nitrocotton (NC) as a binder, RDX/NC ultrafine composite energetic microspheres were prepared by spray drying, and was characterized by Scanning Electron Microscope (SEM), X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC). The impact sensitivity of several different samples, including raw RDX, RDX/NC and refined RDX obtained by spray drying, refined RDX obtained by solvent-nonsolvent and RDX/NC obtained by water suspension, were also measured. Results show that compared with raw RDX, the morphology of RDX/ NC composite energetic microspheres changes from block to spherical. The particle size changes from 50-200 μm to 0.5-7 μm. The crystal type is unchanged but the X-ray diffraction peaks weaken obviously. The activation energy decreases from 200.11 kJ·mol^-1 to 186.87 kJ·mol^-1, The critical temperature of thermal explosion increases from 504.98 K to 507.70 K. The sensitivity of RDX/NC and refine RDX prepared by spray drying decrease compared with that of raw RDX.

Abstract:4, 6-Dinitro-7-hydroxybenzofuroxan sodium salt(NaDNP)was synthesized via nitration, substitution and annulation using 3-bromoanisole, etc. as materials in yield of 45.6%. Its purity, morphology and structure were confirmed by high performance liquid chromatography, Na elemental analysis, video microscope, ¹H NMR, ¹³C NMR, FT-IR spectra. Its thermal behavior was studied by DSC and 5 s delay time deflagration point. Its sensitivity properties was studied by impact, flame, hot wire and electrostatic spark sensitivity. Results show that the thermal decomposition peak temperature of NaDNP at a heating rate of 20 ℃·min^-1 is 283.11 ℃ and 5 s delay time deflagration point is 300.3 ℃, revealing that NaDNP has good heat resistance. Its impact sensitivity H₅₀ is 37.4 cm, flame sensitivity H₅₀ 18.5 cm, hot wire sensitivity E₅₀ 1.278 mJ, electrostatic spark sensitivity E₅₀ 4.3 mJ, which is more insensitive than lead 2, 4, 6-trinitroresorcinate (LTNR). NaDNP can be used as an intermediate of primary explosive.

Abstract:Glycocluril (GU) was prepared in the presence of hydrochloric acid by microwave heating with urea and glyoxal as raw materials. Through fuming nitric acid and acetic anhydride, tetranitroglycoluril (TNGU) was synthesized from nitration of GU. The effects of reaction temperature, reaction time and dosage of fuming nitric acid on the nitration were investigated. The structure of TNGU was characterized by IR, ¹H NMR, ¹³C NMR and elemental analysis. Thermal analysis of TNGU was studied by DSC, and thermal decomposition kinetics parameters such as E_K, A and E_o were respectively calculated with Kissinger and Ozawa, and E_K and E_o were significantly consistent. The critical temperature of thermal explosion (T_b), the entropy of activation (ΔS^≠), enthalpy of activation (ΔH^≠) and free energy of activation (ΔG^≠) of thermal decomposition were calculated. Results show that the optimal technological conditions for synthesizing TNGU were as follows: urea 5 g, fuming nitric acid 70 mL and acetic anhydride 35 mL, reaction temperature between 25~30 ℃, reaction time 4 h, the yield of tetranitroglycoluril was 84% (according to GU). Under these conditions, the amount of waste acid was 30 mL, less than that in literature, and nitration time was shortened by 4hs. T_b of TNGU is 465.34 K, and its ΔS^≠, ΔH^≠ and ΔG^≠ are 171.46 J·mol^-1, 195.00 kJ·mol^-1 and 194.99kJ·mol^-1 respectively. The thermal decomposition of TNGU was exothermic with increasing entropy.

Abstract:To understand the crystal structure and crystal growth process of 1-methyl-2, 4, 5-trinitroimidazole (MTNI), the crystal morphology of MTNI in vacuum was predicted using the BFDH(Bravais-Friede Ⅰ Donnay-Harker), growth morphology, and equilibrium morphology methods in molecular simulation software Materials Studio (MS) and important growth crystal planes in morphology were obtained. The analyses show that the (012) crystal plane is of a strong polarity, the (110) and (111) planes are of polarity and the (010) crystal plane is of a weak polarity. The growth of the (012), (110) and (111) crystal planes is inhibited in strong polarity solvents, the planes become appearance face, whereas the (010) crystal plane will gradually become smaller or even disappear. In weak polarity solvents, the growth situation of crystal plane is just the opposite. The predicted crystal morphology of MTNI in seven solvents, such as ethanol, acetone, ether, ethyl acetate, dichloromethane, dimethyl formamide (DMF) and methanol is in agreement with the crystal morphology obtained by experiment. After interreaction of MTNI with ethanol, dichloromethane and DMF, the crystal morphology of MTNI is spherical and the relative spherical degree is 1.12, 1.11 and 1.12, respectively.

Abstract:Polynitroadamantanes are the precursors both in pharmaceutical synthesis and energetic material preparation. In this paper, the determination method of 2, 2-nitroadamantane and 2, 2, 4, 4, 8, 8-hexanitroadamantane was established by High Performance Liquid Chromatography (HPLC) with optimal chromatographic conditions including the detector, mobile phase and stationary phase. The Ultraviolet detector and DIONEX C18 column (5 μm, 120 A, 4.6 mm×250 mm) were confirmed to get base line separation and high limit of detection for these two compounds mixture. The acetonitrile/water (80/20, V/V) was employed as mobile phases, which presented exceptional separation effect on these two targets when the flow rate was 1.0 mL·min^-1. Results show that the detection limit, linear range, the linear correlation coefficient and precision of 2, 2-nitroadamantane are 0.003 mg·mL^-1, 0.005-1.000 mg·mL^-1, 0.9987 and 1.382%, respectively. Correspondingly, the same parameters of 2, 2, 4, 4, 8, 8 -hexanitroadamantane are 0.001 mg·mL^-1, 0.005-1.000 mg·mL^-1, 0.9984 and 1.300%, respectively

Abstract:To improve the characterization of the polycrystalline HMX spectroscopy, the terahertz spectrum experiment and analysis study of α-HMX were carried out using a terahertz time-domain spectroscopy. The terahertz absorption spectrum and characteristic absorption peaks of α-HMX were obtained. Based on a variety of function model of density functional theory, the calculation work of the molecular vibration frequency of α-HMX was performed. The consistency of calculated result under the various function models with the experimental data was compared. Results show that the 0.82 THz absorption frequency of α-HMX crystal is formed by the symmetrical swing of a pair of nitro groups. The 1.51 THz absorption frequency is formed by the symmetrical swing of another pair of nitro groups. The formation of 1.93 THz absorption frequency is derived from the swing and twisting of nitro groups, and a twisting of the C—H group etc. behaviors

Abstract:To explore the effects of the H₂O and Fe(NO₃)₃ on the thermal stablility of NH₄NO₃, thermal analysis for different concentrations of NH₄NO₃(100%, 95%, 90%) solution and 95% NH₄NO₃ solution with different content of Fe(NO₃)₃ (1%, 2%, 3%, 4%)were studied by C80 micro thermal instrument in closed environment. Results show that the NH₄NO₃ solution activation energy rises with the decrease of the concentration of NH₄NO₃, and the difficulty degree of the thermal decomposition decrease. H₂O depresses the decomposition of NH₄NO₃, and increase its self-reaction. The onset temperature(T_onset) of 95%NH₄NO₃ solution is 238.89℃, and with the increase of ferric nitrate, its T_onset decreases. Fe(NO₃)₃ has a catalysis effects on the thermal decomposition of 95% NH₄NO₃ solution. T_onset of 95% NH₄NO₃ with 2% Fe(NO₃)₃ solution is 201.13 ℃.

Abstract:On the basis of the mechanical properties of polymer bonded explosive (PBX), the linear Drucker-Prager model was introduced into the elastic-plastic deformation study of the PBX material. Based on the linear Drucker-Prager model, combined with the classical plasticity theory, the quasi static elastic-plastic deformation process of the PBX was analyzed. The subsequent yield surface characteristics were cleared. Its stiffness algorithm was derived. The elastoplastic constitutive model was constructed. The relationship of stress and strain under the conditions of uniaxial compression state and biaxial compression state was analyzed in theory. The unit characteristics of PBX material were simulated by the linear Drucker-Prager model. Results show that the uniaxial compression simulation results are consistent with theoretical analysis ones and experimental data. The biaxial compression simulation results are consistent with the theoretical analysis ones. By contrast, the ultimate strength of the biaxial compression is 1.16 times greater than that of the uniaxial compression. Corresponding plastic strain is 0.5 times greater than that of the uniaxial compression.

Abstract:In order to assess the safety of a electric squib in different electrostatic discharge(ESD) environments, Human-Body model(HBM), Body-Machine model(BMM) and Machine model(MM) were used to study the safety of the electric squib using two discharge ways of pin-pin and pin-shell with 25 kV discharge voltage. Results show that the decrease of bridge wire resistance is less than 2.1% when ESD is applied to pin-pin, and none of the 40 electric squib samples is ignited. The calculated discharge power of MM model is 104.17 MW, and 6 of 10 samples are ignited when ESD is applied to pin-shell. The analysis indicates that the safety of electric squib in different ESD models is determined by the power and the electric current of ESD, and the open circuit of varistor is the main reason for electric squib samples igniting.

Abstract:Aiming at the problem of the large mass of the powder, the long ignition/flame spreading distance along axis and many complex ignition/flame spreading conditions in the large caliber balance guns with long-chamber charges, a two-phase flow model was developed for the designed multi-point ignition/flame spreading construction. By controlling the number of the igniters, the flow process and rules of gas releasing in the igniter tube with different numbers of igniter were obtained. A comparison of characteristic quantity of ignition characteristics including ignition/flame spreading time, ignition/flame spreading pressure and void ratio etc obtained by the single-point ignition, the two-point ignition and the multi-point ignition in the same specification igniters under the same amount of charge was performed. Combined with the test results of multi-point ignition in large caliber balance gun, the calculated results of the multi-point technology were verified. Results show a lot of gunpowder still do not burnt and appear an obvious accumulation phenomenon at about 3.3 ms when the single-point ignition or two-point ignition is used, but almost all the propellants are burned out at about 2.43 ms when the multi-point ignition is used and the distribution of the characteristic quantity is relatively uniform. Therefore, use of the multi-point ignition technology in the large caliber balance guns with long-chamber charges and the other big charges with heavy propellant can effectively improve the ignition/flame spreading time, increase the ignition/ flame spreading stability and restrain the gunpowder accumulation.

Abstract:To study the distribution characteristics of explosion overpressure field for non-circular cross-section cloud, the numerical simulation of overpressure process of cloud explosion was performed by LS-DYNA program. Comparison between the simulated overpressure values with experimental was carried out. The changing rule of overpressure with distance, as well as of different ignition height on overpressure field distribution was studied at four directions, including 0°, 90°, 135° and 180°. Results show that: ignited cloud shows up as an ellipsoidal detonation fireball in experiment. The peak overpressure value measured at the position of 5 m from explosion center at four directions is from 2.9 MPa to 5.2 MPa. In the range of 5 m to 50 m from explosion center, a shock wave oval trajectory on ground was revealed. Shock wave propagated at 90° direction has lower velocity than others. In the range of 5 m to 15 m, the ground peak overpressure enhances by 8% averagely when ignited height increases from 0.5 m to 2.5 m.

Abstract:In order to evaluate the effectiveness in flame retardant and explosion suppression of the infill, a comparative study of the fast cook-off performances in terms of destructive consequences was carried out between the fuel tanks with spherical explosion suppression infill (or explosion suppression balls for short) and those without. Cook-off experiments were performed on tanks with diesel fuel (-10PD) and jet fuel (RP-5), respectively, simulating the situation of fuel tanks of vehicles or aircrafts being cooked off. The sizes of the fireballs, the surface temperatures, and the parameters of heat radiation were recorded respectively with a video camera, a high-speed camera, an infrared thermal imager, and a heat flux meter. Results show that jet fire or even explosion of vapor cloud would occur while fuel tanks being cooked off so that the primary destructive activities are the thermal effect of jet fireball. The fuel tanks with explosion suppression balls out-performed those without for -10PD as well as for RP-5 in terms of the postpones of the initial combustions for 48 s and 121 s, the reduction in maximal cross-sectional areas for 65.72% and 42.44%, the decrease in the surface temperatures for 26.13% and 12.66%, respectively, and apparent decrease in heat flux damage consequences.

Abstract:Nitrogen-rich compounds without hydrogen have attracted special attention these years. Because these compounds do not contain hydrogen atom without water vapor in their combustion products, and easy to achieve oxygen balance. The synthesis, characterization, performance and research progress of nitrogen-rich compounds without hydrogen(furazan type nitrogen-rich compounds without hydrogen, nitro type nitrogen-rich compounds without hydrogen, nitrogen-rich compounds without hydrogen and oxygen, and compounds with only nitrogen in molecule) are summarized, and their developing trend in the future was analyzed. So far, the nitrogen-rich compounds without hydrogen and all-nitrogen compounds are expected to have practical application, and they are focus of application researchers.

Abstract:A new compound N-(6-azido-3, 5-dinitropyridin-2-yl)-2, 6-diamine-3, 5-dinitropyridine(3) was designed and synthesized via C—N cross-coupling reaction and azide substitution reaction, using 2-amine-6-chloro-3, 5-dinitropyridine as a primary material with a total yield of 69%.Its structure was confirmed by ¹H NMR, ¹³C NMR, MS and elemental analysis. Theoretical calculations at DFT-B3LYP/6-31G^** level were performed. Results show that the detonation performance of compound 3 are detonation velocity D=7.89 km·s^-1 and detonation pressure p=28.37 GPa, revealing that its detonation performance is better than that of 2, 4, 6-trinitrotoluene (TNT).

Abstract:To accurately determine the assignments of IR absorption peaks for 2, 6-diamino-3, 5-dinitropyrazine-1-oxide (LLM-105), the process of change in IR absorption peaks of LLM-105 under the heating conditions was investigated by temperature-dependent FT-IR spectroscopy. The positions of various IR absorption peaks at different temperatures were determined. Results show that with increasing the temperature, the strength of intermolecular hydrogen bond for LLM-105 is significantly weakened. IR absorption peak positions of amino group (—NH₂) and nitro group (—NO₂) participated in forming hydrogen bonds shift at least 4 cm^-1. The pyrazine ring and C—N bond do not participate in the formation of hydrogen bonds, their peak positions shift about 1 cm^-1.

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