Abstract:

Abstract:Uniaxial tensile testing and short-term tensile creep testing within several hours for a long-term thermally aged polymer bonded explosive (PBX) within years were conducted to evaluate the aging effects in terms of mechanical properties. Dumbbell specimens were thermally aged at 45, 55, 65 ℃ and 75 ℃ respectively for 36 months. The quasi-static tensile strength testing was conducted at 45 ℃. The tensile creep testing for 6 month and 36 month thermally stored specimens were carried out at controlled temperature of 45 ℃. The results show that the tensile mechanical properties, such as tensile strength and elastic modulus essentially keep unchanged compared to the pristine specimens, but the creep time to rupture (TTR) of the thermally treated specimen becomes much longer than the pristine specimens except for 75 ℃. Combining scanning electronic microscope(SEM) observation and contacted angle analysis, we proposed that the mechanical failure for the targeted PBX was controlled by the thermal rheological mechanism of the ingredients when aged temperature is below 55 ℃, but when temperature is above 55 ℃; the failure was controlled by thermal stresses mismatch around the interface between the binder and the explosive crystals in the formulation. The long-term thermally storage below 75 ℃ for this PBX can improve the creep performance in terms of TTR.

Abstract:Polymer bonded explosive (PBX) is a typical particle-filled elastic material, and its mechanical properties are closely associated to the loading rate and strain history. The cyclic loading and unloading stress-strain curves of cast PBX in the quasi-static strain rate range of 10^-4-10^-2/s were obtained by a material testing machine. The constitutive behavior of the PBX was analyzed by Dorfmann and Ogden′s model. Results show that the PBX has loading rate effect, there are stress softening and hysteresis phenomena during cyclic loading, and residual strain phenomenon exists in the unloading process. Material damage can be characterized by hysteresis and the size of residual strain, and the damage extent is mainly affected by the maximum loading strain control. In the Dorfmann and Ogden′s model, the shear modulus μ is only affected by loading rate. The values of μ at 10^-4, 10^-3/s and 10^-2/s are 43.94, 56.92 MPa and 71.93 MPa, respectively. The model can better describe the stress softening and residual strain behavior of the PBX. The prediction results are in good agreement with the experimental data.

Abstract:Energies of combustion and specific heat capacities of diaminofurazan(DAF), dinitrofurazan(DNF) and diaminoazofurazan(DAAzF) were determined. Energies of combustion for the three compounds are (-13043±119), (-6863±37) J·g^-1 and (-12661±54) J·g^-1, respectively. The corresponding standard molar enthalpies of formation (Δ_fH_m^Θ) were obtained with the different combustion products. The values of specific heat capacities for the three compounds are (140.8±0.1), (236.8±0.2), (216.9±0.2) J·mol^-1·K^-1, respectively. Energy of combustion tends to rise with the decrease of oxygen content in molecule (DAF>DAAzF>DNF). Amino group contributes to increase energy of combustion, but nitro group has the opposite effect. As for the specific heat capacity, the change rule is opposite to energy of combustion.

Abstract:To find the relationship between the structures and thermochemical properties of energetic compounds, the structures and thermochemical properties of 15 kinds of azo-bridged azoles were studied by density functional theory. Their structures were optimized at B3LYP/6-311+G (d, p) level, their entropies and constant-pressure specific heat capacity were calculated and their enthalpies of formation were estimated via design of the isodesmic reaction. Results show that the N atom and C atom on the heterocyclic ring are sp² heterocyclic atoms. All heterocyclic rings are nearly in the same plane. The enthalpy of formation of the compound is proportional to the number of nitrogen atom. For compounds with the same number of nitrogen atoms, the enthalpy of formation of the compound decreases with increasing the distances from the azo-bridge to nitrogen atom on heterocyclic ring and the distances between the nitrogen atoms on heterocyclic ring. The constant pressure specific heat capacity at different temperatures are inversely proportional to the nitrogen content (the number of nitrogen atom on the heterocyclic ring).

Abstract:To evaluate the thermal stability of 1-amino-2-nitroguanidine(ANQ) and investigate the potential application value of ANQ as energetic material, thermal behaviors, specific heat capacity and adiabatic time-to-explosion of ANQ were studied by DSC, micro-DSC and TG/DTG methods. Results show that thermal behavior of ANQ can be divided into two coterminous intense exothermic decomposition processes. The peak temperatures of the two decomposition processes at the heating rate of 5 ℃·min^-1 are 192.5 ℃ and 196.2 ℃, respectively, and the whole decomposition enthalpy is -2075 J·g^-1. The apparent activation energy and pre-exponential constant of the first decomposition process are 224.3 kJ·mol^-1 and 10^23.15 s^-1, respectively. The self-accelerating decomposition temperature and critical temperature of thermal explosion for ANQ are 184.5 ℃ and 192.7 ℃, respectively. The molar heat capacity of ANQ is 145.5 J·mol^-1·K^-1 at 298.15 K. Adiabatic time-to-explosion was estimated to be about 60 s. The thermal stability of ANQ is good.

Abstract:1, 1′-Dioxide-5, 5′-azotetrazole dipotassium salt was synthesized via two-step reactions of azido-cyclization and oxidation-coupling using cyanogen bromide, sodium azide and 50% solution of hydroxylamine as raw materials. The yields of two-step reactions were 78% and 82%, respectively. The structure of 1, 1′-dioxide-5, 5′-azotetrazole dipotassium salt was characterized by infrared spectrum (IR), nuclear magnetic resonance (NMR), elemental analysis and thermal properties were studied by differential scanning calorimetry (DSC) and thermogravimetry-derivative thermogravimetry (TG-DTG). Results show that there were two thermal decompositon peaks at 271.0 ℃ and 328.0 ℃ under heating condition, respectively, while possess a total mass loss of 37.5% before 320 ℃ for 1, 1′-dioxide-5, 5′-azotetrazole dipotassium salt.

Abstract:Using picryl chloride and hydrazine hydrate as the starting materials, an insensitive energetic compound 5, 7-diamino-4, 6-dinitrobenzotriazol-3-ium-1-oxide(2) was synthesized through cyclization and vicarious nucleophilic substitution(VNS) reactions with a total yield of 31.0%. The structures of the title compound and its intermediate were characterized by ¹H NMR, ¹³C NMR, FT-IR and elementary analysis. The reaction condition of VNS was optimized. A cyclization reaction mechanism of 4, 6-dinitrobenzotriazol-3-ium-1-oxide(1) was speculated. The calculations of electrostatic potential(ESP) and molecular orbital of the title compound were performed by quantum chemical method. The detonation properties and thermal property of the titled compound and its intermediate 4, 6-dinitrobenzotriazol-3-ium-1-oxide were studied. Results show that the optimal reaction conditions of VNS were determined as the VNS reagent is NH₂OH·HCl, the reaction time at room temperature is 5 h. The titled compound has insensitive characteristic and good thermal stability. The density and thermal stability of compound 2 formed after introducing the two amino groups in compound 1 are improved. Thermal decomposition temperature, density and detonation velocity of two kinds of compounds are 201.3 ℃, 1.73 g·cm^-3 and 7371.13 m·s^-1 for compound 1 and 248.5 ℃, 1.76 g·cm^-3 and 7396.7 m·s^-1 for compound 2.

Abstract:5-(3-Amino-1, 2, 5-oxadiazol-4-yl)tetrazol-1-ol (4) as well as its ammonium salt (5), and hydroxylammonium salt (6) were synthesized with high yield from malononitrile as raw material via diazotization, addition, and cyclization reactions. Their structures were characterized by infrared (IR) spectra, nuclear magnetic resonance (NMR), elemental analyses, and X-ray single-crystal diffraction(XRD). The impact and friction sensitivities of compounds 4, 5 and 6 were tested using the drop hammer method and friction sensitivity tester. The thermal stabilities of compounds 4, 5 and 6 were studied by DSC. Results show that a large number of intramolecular and intermolecular hydrogen bonds for compounds 4, 5 and 6 are formed. These hydrogen bonds have an important influence on their structure, density, thermal properties and sensitivities, especially all hydrogens in the molecule of compound 6 participate in hydrogen bond formation, resulting in compound 6 has a relatively high density (1.786 g·cm^-3). Compounds 4, 5 and 6 exhibit low impact and friction sensitivity and good thermal stabiliy and can be used as environmentally friendly and new-generation insensitive energetic materials.

Abstract:To improve the storage stability of potassium borohydride(KBH₄), sodium borohydride(NaBH₄) and lithium aluminum hydride(LiAlH₄), KBH₄ and NaBH₄ were coated by paraffin via solvent-nonsolvent method and LiAlH₄ was coated by naphthalene via recrystallization. The surface coating stafas of the samples was studied by SEM, FTIR and XRD and the combustion properties of the propellants added into coated sample were tested by an Infrared Thermometer. Results show that KBH₄, NaBH₄ and LiAlH₄ are completely coated and the coating stafas of NaBH₄ is the best. The combustion properties of propellant added with coating-NaBH₄ sample are significantly improved and the burning rate is increased by more than 5%.

Abstract:Potassium dinitromethane {K[CH(NO₂)₂]}_n was synthesized. The single-crystal structure of {K[CH(NO₂)₂]}_n was determined, which is triclinic, space group P-1 with crystal parameters of a=4.5285(11)Å, b=7.0377(17)Å, c=7.8543(19)Å, α=70.671(3)°, β= 88.557(3)°, γ=75.818(4)°, V=228.58(10)ų, Z=2, D_c =2.094 g·cm^-3, F(000)=144, S=1.060, μ (Mo K_α)=1.077 mm^-1, R₁=0.0457, wR₂=0.1399, (Δp)_max=0.484 e·Å^-3 and (Δp)_min=-1.278 e·Å^-3. Thermal behavior of {K[CH(NO₂)₂]}_n was studied by DSC and TG-DTG methods. DSC result presented two exothermic processes. The self-accelerating decomposition temperature and critical temperature of thermal explosion of {K[CH(NO₂)₂]}_n are 161.0 ℃ and 162.8 ℃, respectively. {K[CH(NO₂)₂]}_n presents lower thermal stability than K(DNDZ) and K(AHDNE), but higher thermal stability than K(NNMPA). {K[CH(NO₂)₂]}_n is relatively insensitive.

Abstract:Two kinds of phase transitions (α→β and β→γ) of the insensitive high explosive, 1, 1-diamino-2, 2-dinitroethylene(FOX-7), have been investigated by temperature-dependent Fourier transform infrared(FTIR) spectroscopy, and the effects of intermolecular H-bonding interactions and molecular structure in the phase transitions of FOX-7 were discussed. The frequency of ν₁₁ [NH₂ (ν_as)] and ν₁₀ [NO₂ (ν_s)] shifts about 20 cm^-1, together with the loss of ν₁₈ [C—NO₂ (ν)] in the range of 55 ℃ to 122 ℃, while ν₁₂ [C—NH₂(ν)] disappears and ν₂₀[NO₂(ω)] transforms to another broad peaks in the range of 122 ℃ to 190 ℃. The analytical results of the IR spectra indicate that intermolecular hydrogen bonding interactions change in the phase transitions of the FOX-7, which cause the changes of the molecular structure. Moreover, in the process of α→β transition, the changes of H-bonding length with increasing temperature are not consistent with the linear thermal expansion formula, and ν₁₁、ν₄[Fermi resonance between the NH₂ (ν_as) and the overtone mode of the NH₂ scissor (2ν₅)]、ν₇ and ν₁₀[NO₂(ν_as)] show special frequencies, which are different from those of α and β-FOX-7. The results confirm the transition state in the α→β transition.

Abstract:The solubility data of 3, 4-bis(3-nitrofurazan-4-yl)furoxan (DNTF) in binary system ethanol-water at temperatures ranging from 298.15 to 338.15 K were determined by using a laser monitoring system under atmospheric pressure. The van′t Hoff plot, modified Apelblat equation, R-K model and Jouyban-Acree model were adopted to fit the experimental solubility data. Since the correlation coefficients (R²) of the four correlation equations are greater than 0.99 and the Root-mean-square deviations (RMSD) are close to 0, four correlation equations can be adopted to correlate the solubility data. The standard enthalpy of dissolution, standard entropy of dissolution and the Gibbs free energy were calculated based on the experimental solubility data, from which we conclude that the dissolution of DNTF is an endothermic and non-spontaneous process.

Abstract:An integrated exploding foil initiator(EFI) based on a parylene-C flyer and Su8 photo-resist barrel was fabricated using magnetron sputtering, photolithography, and chemical vapor deposition(CVD). The effect of structure parameters of exploding foil, flyer and barrel on the loading capability of flyer was investigated by photonic Doppler. Results show that under the conditions of initiation voltage 2.6 kV, capacitance 0.2 μF, and discharge duration 1.2 μs, through the test, finding that the change of part of materials for EFI caused by integrated fabricating dose not significantly influence the loading capability of flyer. The EFI′s driving process of parylene-C and polyimide flyer with identical dimension are similar to each other. The flyer driving capability of integrated EFI was consistent with that of classic EFI with same structure parameters. The HNS-Ⅳ can successfully be detonated by the integrated EFI.

Abstract:Two-dimensional numerical simulation of the impact process for drop hammer on granular HMX was carried out by using ANSYS/AUTODYN software. The temperature rise generated in particles was estimated via the principle converted from plastic work to heat energy based on the calculated values of stress and plastic work. The HMX particles was geometrical shapes and round, assuming that the particles had elastic-plastic deforming properties. Particle stack form had two kinds of situations of regular and irregular arrangement. The initial velocity of the drop weight was calculated through setting the drop height and the formula of free fall. For different drop heights and the calculation of different yield stress values of sample particle material, the temperature rise changes in particles under drop hammer impact were obtained. The results showed that the regular arrangement produces low temperature (37.2 ℃) rise, whereas the irregular arrangement produces higher temperature (142.9 ℃) rise. In irregular arrangement, the local plastic deformation work of particles can lead to higher temperature rise, causing particle ignition. At the same time, considering the uncertainty of the yield stress value of HMX, the calculation of temperature rise is performed taking the smaller yield stress value(0.13 GPa), while the other calculation conditions are the same, and the temperature rise obtained is 83.2 ℃, which got 59.7 ℃ lower than the yield stress value of 0.26 GPa.

Abstract:To study the influence extent and law of near-ambient temperature changes on shock initiation characteristics of explosives, an experimental device with local heating and cooling to explosive was designed and established. Combined with Lagrangian analysis method, the growth process of shock initiation pressure at the near room temperature from 5 ℃ to 75 ℃ for two explosives (PBX-1: a HMX/TATB composite explosive; PBX-2: a TATB based IHE) was studied. Based on the experimental results, numerical simulation of the shock initiation process for two kinds of explosives was performed by the model of ignition growth. The results show that as temperature changing from 5 ℃ to 75 ℃, the growth of shock-initiation pressure of two kinds of explosives is gradually changing fast, the run distance to detonation becomes shorter and the reaction rate parameter G₁ in the ignition growth model becomes larger, indicating that the two explosives become more sensitive to shock as near-ambient temperature increasing, the effects of near-ambient temperature changes on safety of explosives can not be ignored.

Abstract:The two types of flyer were designed to study short duration pulse shock initiation characteristics of ultrafine 2, 6-diamino-3, 5-dinitro-pyrazine-1-oxide(LLM-05). The firing testing of ultrafine LLM-105 is implemented by D-optimal method based on analysis of flyer velocity. It is found that the flyer velocity is increasing as increasing pulse current. The velocity is sensitive to current variety for large dimension flyer by contrasting small dimension flyer. The inferior velocity consistency for large flyer exists, which has the relationship with air resistance. The air resistance is increasing with improvement of flyer dimension. The 50% firing current, of ultrafine LLM-105 is 2.14 kA by small dimension flyer, which is almost equal to initiating threshold of HNS-Ⅳ. It is indicated that ultrafine LLM-105 would be used for initiation explosive at slapper detonator. The LLM-105 explosion system will satisfy the development trend of slappde detonator, namely, desensitization, low input energy, and so on.

Abstract:To optimize the performance of the detonation wave aiming warhead, the different forms of asymmetrical initiations were studied. The fluid dynamic simulation model verified by experiment was used to research the effects of asymmetrical one initiation line with different initiation points, asymmetrical two initiation lines with different central angles, and the asymmetrical three initiation lines with different central angles of the adjacent lines on warhead fragment velocity and scattering. The results show that for the researched object, 4 initiation points are adequate in one initiation line; in the asymmetrical two lines initiation, the central angle of 60° may produce the highest velocity enhancement 38.37% in the aiming direction side, so do the asymmetrical three initiation lines with central angle of 45°, with an enhancement of 39.36%. The velocity enhancement of the fragments in the aiming direction is the interacting results of detonation transfer length (time) and the detonation pressure.

Abstract:A new fluorodinitromethyl-containing energetic plasticizer 3, 4-bis (3-fluorodinitromethylfurazan-4-oxy)furazan was self-designed and synthesized. Its structure was characterized by FT-IR, ¹³C NMR, ¹⁹F NMR, elemental analysis, DSC and TG-DTG. Based on the calculated standard enthalpy of formation and the measured density, the detonation properties of 3, 4-bis(3-fluorodinitromethylfurazan-4-oxy)furazan were estimated by Kamlet-Jacobs equations and compared with those of commonly used plasticizing agents, nitroglycerine(NG), bis(2-fluoro-2, 2-diniroethyl)formal (FEFO), and 3, 3′-dinitrodifurazanyl ether (FOF-1). Results show that 3, 4-bis(3-fluorodinitromethylfurazan-4-oxy)furazan has good thermal stability (decomposition temperature of 197.8 ℃), high density(1.88 g·cm^-3), low melting point(50 ℃), which indicates that 3, 4-bis(3-fluorodinitromethylfurazan-4-oxy)furazan is an energetic plasticizer with excellent comprehensive performance.

Abstract:A novel energetic inner-salt 5, 5′-bis(3-diazo-1, 2, 4-triazole)(BDTZ) was firstly designed and synthesized via two-step reactions of cyclodehydration and diazotization using oxalic acid and aminoguanidinium bicarbonate as starting materials with a total yield of 53.0%, and its structure was characterized by the means of IR spectrum, NMR and elemental analysis. Based on 3LYP/6-311G+(d, p) level, the estimated density of BDTZ is 1.73 g·cm^-3, its detonation velocity is 7780 m·s^-1 and the detonation pressure is 26.72 GPa. The nitrogen content of BDTZ is 74.47%, which contains no toxic heavy metals, showing that BDTZ is a green primary explosive with good detonation performance.

Abstract:

Abstract:

Abstract: