Abstract:Molecular surface electrostatic potentials V_S(r) (ESP) of seventeen nitramines have been calculated. As a criterion of the imbalance between the maximum positive, V_S,max and minimum negative, V_S,min, values of molecular surface electrostatic potentials their sum was derived and used as a new simple characteristic for ESPs-V_S,Σ. These V_S,Σ values have close relationships with the Arrhenius parameters, activation energy E_a and preexponent log A, of thermal decomposition of the nitramines studied. The correlation between the V_S,Σ values and heats of fusion of the nitramines studied is described. These findings suggested analyzing the physico-chemical behavior of the nitramine crystals during this decomposition; in this connection an investigation was carried out using isothermal thermogravimetry and scanning electron microscopy of thermally exposed crystals of cis-1, 3, 4, 6-tetranitrooctahydroimidazo-[4, 5-d]imidazole (sintering of its crystal surfaces), of β-1, 3, 5, 7-tetranitro-1, 3, 5, 7-tetrazocane (cracking of its crystals during β→δ transition) and of 2, 4, 6, 8, 10, 12-hexanitro-2, 4, 6, 8, 10, 12-hexaazaisowurtzitane. The results suggest a need to study the pre-decomposition states on thermal decomposition of the nitramines′ molecule′s crystals.

Abstract:An energetic Pb(Ⅱ) complex (Pb(TANPyO)) of 2, 4, 6-triamino-3, 5-dinitropyridine-1-oxide (TANPyO) was synthesized. The structure and properties were characterized by FT-IR spectroscopy, elemental analysis, TG-DTG and DSC, and the impact sensitivity, friction sensitivity and shock wave sensitivity were studied as well. The catalytic effect of Pb(TANPyO) on the thermal decomposition of ammonium perchlorate (AP) was analyzed by TG-DTG and DSC. Results show that the molecular formula of Pb(TANPyO) is Pb(C₅H₄N₆O₅). The impact sensitivity, friction sensitivity and shock wave sensitivity are 305 cm, 36 kg and 4.9 mm, respectively. Pb(TANPyO) has an exothermic peak with summit peak at 329.0 ℃ in the temperature range of 50-500 ℃ with 23.8% residues. Its apparent activation energy of exothermic decomposition reaction is 331.9 kJ·mol^-1. The Pb(TANPyO) has significant catalytic effect on the thermal decomposition of AP.

Abstract:N, N-bis((3, 5-dinitro-1H-1, 2, 4-triazol-1-yl)methyl)nitramine (BDNTMN) was synthesized via diazotization, nitration and N-alkylation etc reactions using 3, 5-diamino-1, 2, 4-triazole (DAT) as starting material. The structures of each compound were characterized by means of ¹H NMR, ¹³C NMR, IR, MS and elemental analysis etc means. The main thermal properties of BDNTMN were analyzed by DSC and TG. The physicochemical property and detonation performance of BDNTMN were predicted by Gaussian 09 and Kamlat-Jacbos equations. Results show that BDNTMN has two thermal decomposition peaks at 170.4 ℃ and 254.1 ℃, respectively. The density, detonation velocity and detonation pressure of BDNTMN are 1.95 g·cm^-3, 9.03 km·s^-1 and 38.7 GPa, respectively, which are better than those of RDX.

Abstract:3, 4-Bis(1H-5-tetrazolyl)furoxan was synthesized via cyclization reaction using 3, 4-dicyanofuroxan and sodium azide as raw materials and water as solvent under the ZnCl₂ catalysis with a total yield of 91.0%. The structure was fully characterized by IR, NMR, elemental analysis, and X-ray single-crystal diffraction. Results show that the crystal belongs to the orthorhombic system, and space group is P2₁2₁2₁ with crystal parameters of a=6.1172(14)Å, b=9.657(2)Å, c=14.220(3)Å, V=840.0(3)ų, Z=4, D_c=1.76 g·cm^-3, F(000)=448, μ=0.147 mm^-1, S=1.031, the final R=0.0800 and wR=0.2523. The structure of 3, 4-bis(1H-5-tetrazolyl) furoxan is almost in one plane, indicating that a strong conjugation effect exists in the molecules. At the same time, lots of weak bonds among nitrogen atoms in the molecules can improve the density of compounds and thermal stability.

Abstract:A new azo-bridged pyridine derivative (E)-1, 2-bis(2-chloro-3-nitropyridin-4-yl) diazene (3) and 2-chloro-4-amine-3, 5-dinitropyridine (2) were synthesized through a direct nitration reaction using 2-chloro-4-aminopyridine(1) as a primary material, followed by a simple amination reaction to give (E)-1, 2-bis(2-amino-3-nitro-pyridin-4-yl)diazene(5) and 2, 4-diamino-3, 5-dinitropyridine(4), with a total yield of 69% and 18%, respectively. Red colored crystals of compound 3 growing from CHCl₃ solvent at room temperature were used for X-ray diffraction analysis. The detonation performances of compounds 4 and 5 were calculated by Kamlet-Jacobs empirical equations. The results show that the crystal of compound 3 is monoclinic, space group P2₁/N with crystal parameters of a=9.965(2) Å, b=6.3190(13) Å, c=10.737(2) Å, β= 93.75(3)°, V=674.6(2) ų, D_c=1.689 g·cm^-3, C₁₀H₄Cl₂N₆O₄, M_r=171.55, F(000)=344, μ(Mo K_α)=0.510 mm^-1, and Z=4. The detonation performance of compound 4 is similar to 2, 4, 6-trinitrotoluene (TNT), whereas the detonation performance of compound 5 is poor.

Abstract:The energetic complex [Cu(pn)₂(FOX-7)₂] (pn=1, 3-diaminopropane) was synthesized by the reaction of K(FOX-7)·H₂O and Cu(NO₃)₂·3H₂O in 1, 3-diaminopropane solution. The thermal decomposition behavior was studied by differential scanning calorimetry (DSC) and thermogravimetry/derivative thermogravimetry (TG/DTG), the specific heat capacity was determined with a micro-DSC and the adiabatic time-to-explosion and the impact sensitivity were studied as well. Results show that the non-isothermal decomposition kinetic equation of the first decomposition process is dα/dT=(10^17.83/β)3α^2/3exp(-1.635×10⁵/RT). The self-accelerating decomposition temperature and critical temperature of t hermal explosion are 145.6 ℃ and 146.7 ℃, respectively. The molar heat capacity is 653.79 J·mol^-1·K^-1 at 298.15 K. Adiabatic time-to-explosion is about 77 s, and the characteristic drop height (H₅₀) of Cu(pn)₂(FOX-7)₂ is 71 cm (>14 J) (RDX, >7.5 J), which indicating Cu(pn)₂(FOX-7)₂ is relatively less sensitive.

Abstract:The relationship between the crystal lattice free volume, ΔV, and impact sensitivity, E_dr, of ten nitramines has been analyzed. It was found that this relationship is not uniquely determined, i.e. it is not given only by their own ΔV values but fundamentally by the type and intensity of the intermolecular forces in the nitramine crystals. Also, relationships between the E_dr values, on the one hand, and bulk modulus, K, and shear modulus, G, on the other, have been the subject of discussion not only for pure cyclic nitramines but also for their PBXs, bonded by a poly-fluoro binder. The closest linear correlation exists between the E_dr values and dimensionless K·G^-1 ratio which indicates the plasticity range. A similar relationship is valid also for the ΔV values. Relationships of the E_dr and/or ΔV values with the shear modulus or to the K·G^-1 ratio reflect an unusual behavior of ε-HNIW to which the published morphological instability of this particular HNIW version might also be related.

Abstract:The void defect evolvement and molecular conformational transition in crystalline δ-HMX were simulated applying molecular dynamics (MD) method and a compared research with β phase was performed. The simulated system contains a void defect with size of 30 HMX molecules, corresponding to 10% concentration of vacancies. The energy barriers for molecular conformation conversions in vacuum were calculated by the QST3 method. Results show that all the conformation transitions have low activation energy. At the simulation temperature of 500 K, whether the δ phase or β phase, the whole crystal completely collapses into liquid state and is accompanied by a large lattice expansion. In the collapsed liquid molecules, four kinds of molecular conformations, α, β, BB(boat-boat) and BC(boat-chair), can be observed. A large number of transition states and intermediate structures coexist with four kinds of molecular conformations. Tracing the evolvement of single molecule with time during MD simulation can find the frequent transition between different conformations due to low conversion energy barriers. When simulated temperature decreases to 300 K and 200 K, two crystalline phases present different evolvement trends. For δ-HMX system, the void collapse occurs and the whole lattice loses strict periodic structure, but the void inserted into β-HMX is still hold on and there only occur the shrink of void and shift of a few molecules toward the center of void. In addition, in contrary to the lattice shrink of δ-HMX, the volume of β-HMX continuously expands with rising the simulated temperature.

Abstract:Two superfine particles of 1, 3, 5-triamino-2, 4, 6-trinitrobenzene (TATB), 2, 2′, 4, 4′, 6, 6′-hexanitrostilbene(HNS) were prepared respectively and their particle conglomeration′s microstructures were studied by SEM method, gas sorption method, and fractal method. Results show that the HNS conglomeration consists of cashew-like nanometer crystals which piles up tightly here or loose somewhere else with surface area of 11.8 m²·g^-1, and the TATB conglomeration consists of nanometer crystals which connect mutually with surface area of 24.77 m²·g^-1. Both samples show Ⅳ type desorption isotherms with hysteresis loop ranged in high relative pressure 0.8-1. Barrett-Joyner-Halenda (BJH) analysis and Horvaih-Kawazoe (HK) analysis indicates that TATB conglomeration has the higher pore volume and higher surface area than HNS conglomeration before 12 Å and after 80 Å, while it is reverse within 12-80Å, which indicate that the microspore contributes to pore volume more than mesopores. In addition, the fractal microstructure are found from the desorption isotherm of both samples. The fractal dimension behaves low in range of relative pressure p/p₀ of 0.00-0.04, medium in 0.04-0.10, and high in 0.1-0.2. TATB conglomeration has higher fractal dimension than HNS in every similar range. BJH data, HK data, and fractal analysis disclose more details of microstructure than surface area and the textual discussion should be expected beneficial to comprehension of microstructure and microstructure -performance relationship.

Abstract:To understand the effects of slow heating on the safety of explosive components, the differential scanning calorimeter (DSC) analyses of powder PBX-6 explosives under various pressures and heating rates were conducted, and accelerated aging tests of SR50 mm hemispherical PBX-6 explosive components under 55 ℃ for 140 days were carried out. The device was designed for the slow cook-off tests of Φ100 mm explosive sphere, and the slow cook-off tests at heating rates of 2 ℃·min^-1 and 5 ℃·min^-1 were carried out for spherical specimens S-1^# and S-2^#, respectively. Through analysis of the temperature history at measuring positions recorded by thermoelectric couples and temperature measuring system, combined with the comparison of the shock wave overpressure and the residues after deflagration, the relations between the slow cook-off behaviors and the thermal decomposition characteristics were studied, and the safety of PBX-6 explosive components under slow heating conditions was evaluated. The experimental results show that the specimen S-1^# moderately deflagrates after heating 8373 s with deflagration temperature of 218.5 ℃ at heating rate of 2 ℃·min^-1, and the specimen S-2^# violently deflagrates after heating 4074 s with deflagration temperature of 224.9 ℃ at heating rate of 5 ℃·min^-1 and the shock wave overpressure is 21.8 kPa. It indicates that, as the heating rate rises, the explosive components will deflagrate with shorter heating time, higher deflagration temperature and a higher grade of deflagration.

Abstract:Gelled propellant simulant containing 5 wt% carbon particles with an average diameter of 5 μm was prepared, and the atomization characteristics was investigated. The rheology properties of the simulant were measured. Under the conditions of jet velocity of 10-22 m·s^-1, impingement angle of 60°-90°, injector orifice diameter of 0.5-1.5 mm and ratio of injector orifice length to diameter of 3.5-8, atomization experiments were carried out. The breakup characteristics of liquid sheet were studied by the linear stability theory. Results show that the addition of carbon particles makes the simulants consistency coefficient increase and flow index decrease. Within the investigation conditions, the simulant is atomized into ligaments and large drops, and the atomization quality improves with the increases of jet velocity and impingement angles. The changes in ratio of injector length to diameter and the injector orifice diameters have little influences on the atomization patterns. The relative error between the predicted breakup lengths and measured values is about 14.9%-24%, but the tendency of the breakup lengths predicted by the linear stability theory agrees well with the experimental results.

Abstract:More and more attention has been paid to the micromixer as its unique mixed features. In recent years, the micromixer has been applied to the preparation of the emulsion matrix. Two kinds of micromixers were used to complete separately the first emulsification and the second emulsification of emulsion matrix. Both of the emulsion principle of the split-recombine micromixer for high viscosity fluid and the influence of the width, length of the microchannel and fluid flow velocity on the emulsification effect were discussed. Results show that different types of micromixers are suitable for different stages of the emulsification. Under the conditions of the total fluid flow of 40 mL·min^-1, a good quality emulsion matrix with viscosity of 38000 cP and average granularity of aqueous phase of 1.895 μm is prepared by the micromixers. The dissolution loss rate of ammonium nitrate (AN) was 0.2497% after 30 days storage at room temperature. The emulsification principle of the caterpillar split-recombine micromixer for high viscosity fluids is the shear effect of the microchannel to the fluids. The width of the microchannel affects the pressure of emulsification significantly. The longer the length of microchannel is, the larger the flow velocity of fluid is and the better the quality of emulsification is.

Abstract:To research the dispersion properties and infrared (IR) interference efficiency of graphite flake particulates modified by hydrophobic nano-silica, the flowability of graphite flake particles before and after modification was measured by a powder property tester. The smoke was formed by dispersing the graphite flake particles into the smoke box using air flow dispersion way. The mass concentration and IR spectrum transmission of the smoke were measured. On the basis of stir settlement model, the settling velocity of smoke was calculated. Results show that the Carr′s flowability index of graphite flake particulates modified with hydrophobic nano-silica in mass ratio of 4.0 % is the highest, reaching 61 and at the same time, the settling velocity decreases from 2.288×10^-3 m·s^-1 before modification to 1.125×10^-3 m·s^-1 after modification. Average IR spectrum transmission of the smoke formed in the wave band range of 3-5 μm and 8-12 μm decreases from 0.3895 % and 0.7288% to 0.072% and 0.176%. The physical modification of hydrophobic nano-SiO₂ on graphite flake surface effectively improves the flowability and dispersion properties and significantly increases the duration of the smoke formed by graphite flake particles and IR interference performance.

Abstract:The two kinds of energetic ionic salts IMI·TNR and 4-AT·TNR (IMI=imidazolium, 4-AT=4-amino-1, 2, 4-triazolium, TNR=2, 4, 6-trinitro resorcinol) were synthesized. The crystal structures were determined by IR, elemental analysis and X-ray single crystal diffraction. The thermal decomposition mechanisms were investigated with DSC and TG. The non-isothermal reaction kinetic parameters were researched by Kissinger′s method and Ozawa′s method on the basic of DSC results. The mpact sensitivity, friction sensitivity and flame sensitivity for two ionic salts was measured. Results show that the crystal of IMI·TNR is monoclinic, space group P2₁/c with a density of 1.779 g·cm^-3 and decomposition temperature of 223.4 ℃ and 4-AT·TNR is triclinic, space group P-1 with a density of 1.772 g·cm^-3 and decomposition temperature of 259.8 ℃. The values of T_b, ΔS^≠, ΔH^≠ and ΔG^≠ are 222.4 ℃, -213.06 J·K^-1·mol^-1, 302.89 kJ·mol^-1and 407.10 kJ·mol^-1 for IMI·TNR and 257.3 ℃, -221.31 J·K^-1·mol^-1, 129.66 kJ·mol^-1 and 243.24 kJ·mol^-1, respectively. They are insensitive to impact, friction and flame stimuli.

Abstract:A novel cocrystal explosive composed of benzotrifuroxan (BTF) and 2, 4-dinitroanisole (DNAN) in a 2:1 molar ratio was prepared by an evaporation solvent method, its structure was characterized by the single crystal X-ray diffraction (SXRD) and the impact sensitivity was studied as well. Results show that the cocrystal explosive belongs to monoclinic system with P21/c space group. The cocrystal displays an H₅₀ of above 112 cm, indicating lower sensitivity compared to pure BTF.

Abstract:The thermal expansion of nitroguanidine (NQ) crystal was investigated by means of in situ powder X-ray diffraction method and in situ FTIR spectra method. Results show that the average thermal expansion coefficients of the a-, b-, c-axis at 30-160 ℃ for NQ are 12.9×10^-6℃^-1, -10.1×10^-6℃^-1 and 145.5×10^-6℃^-1, respectively, revealing that the thermal expansion of NQ is obviously anisotropic and thermal expansion along the b -axis is negative. The anisotropic thermal expansion of NQ is caused by the anisotropic intermolecular interaction. The intermolecular hydrogen bond decreases with the increase of temperature, and the intermolecular distance increases, and the space hindrance of the molecules along the b axis is reduced, which leads to a negative expansion along the b axis.

Abstract:The single crystal of 1-amino-1-ethylamino-2, 2-dinitroethylene (AEFOX-7) was obtained. The crystal structure of AEFOX-7·H₂O is orthorhombic, space group Pna2(1)/m with crystal parameters of a=1.3692(3) nm, b=0.71240(16) nm, c=0.9024(2) nm, β=90°, V＝0.8802(4) nm³, Z＝4, μ＝0.133 mm^-1, F(000)＝408, D_c ＝1.465 g·cm^-3, R₁＝0.0306 and wR₂＝0.0855. Enthalpies of combustion of AEFOX-7, AMFOX-7 (1-amino-1-methylamino-2, 2-dinitroethylene) and FOX-7 at 298.15 K were determined, and the corresponding enthalpies of combustion were -(2347.83±4.84), -(1819.96±5.94) kJ·mol^-1and -(1159.77±1.30) kJ·mol^-1, respectively.

Abstract:The title compound, 5-azido-1, 2, 4-triazolyl-5-acetic acid (ATAA), was synthesized for the first time by Sandmeyer-reaction in a mixed system (including sodium nitrite, sulfuric acid and sodium azide) from 5-amino-1, 2, 4-triazolyl-5-acetic acid. Its chemical structure was fully characterized via NMR, IR, MS and elemental analyses. Typical TG and DSC curves indicate the thermal behavior of ATAA includes one dehydrating crystal water stage, one melting stage and one obvious melting decomposition stage. The peak temperatures at each stage are 85.6 ℃, 168.0 ℃ and 177.9 ℃, respectively. In addition, a novel polynitro-azole energetic compound (5-azido-3-trinitromethyl-1H-1, 2, 4-triazole) was designed and calculated. The standard enthalpy of formation, the calculated density as well as the detonation velocity are 449.62 kJ·mol^-1, 1.91 g·cm^-3 and 9096 m·s^-1, respectively.

Abstract:We have suggested two empirical nitrogen equivalent equations for predicting the detonation velocity (D) and detonation pressure (p) of CHNO explosives with more approaching the results of Kamlet-Jacobs equations than common used nitrogen equivalent equations

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