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Abstract:Bu-NENA (N-butyl-N-nitratoethylnitramine)/NC (nitrocellulose) double-base propellant was formulated with Bu-NENA as a replacement for NG (nitroglycerin) and the NG/NC propellant was also prepared as a control. The sensitivity, evaporation, thermal decomposition and mechanical properties of the double-base propellants were investigated. Results show that the friction sensitivity of the Bu-NENA/NC propellant drops to 18% from 94%, and the H₅₀ of the impact sensitivity enhances to 27.1 cm from 8.1 cm. Thermogravimetric analysis of Bu-NENA/NC propellant reveals that the onset temperature and the peak temperature of first decomposition stage reach to 144.6℃ and 179.5℃ from 120.3℃ and 151.5℃, respectively. The value of evaporation rate for Bu-NENA/NC propellant at 80, 90, 100℃ is lower than that of NG/NC propellant, which indicates that the volatility of the Bu-NENA/NC propellant decreases. Bu-NENA/NC double-base propellant has better mechanical property than NG/NC propellant and the low temperature elongation at break point rises to 13.63%, which is 1.63 times to that of the NG/NC propellant.

Abstract:To investigate the effect of aluminum (Al) powder with different surface morphology on the burning rate of hydroxyl-terminated polybutadiene(HTPB) propellant, based on the formulation of HTPB four component propellant, the morphologys of two kinds of Al (5-10 μm) powder were observed by scanning electron microscopy (SEM) and laser particle size distribution instrument, and the burning rate of HTPB propellant with different Al powders was measured by underwater acoustic emission method, and the pressure exponent was also calculated. Results show that the surface morphology of Al powder can be distinguished from adhered with Al spot particles and smooth, which have influence on the burning rate of HTPB propellant. At the low pressure stage (3-5 MPa), the burning rate of HTPB propellant increased by 1.33 mm·s^-1 and the pressure exponent is 0.36, when the surface morphology of Al powder adhered with Al spot particles. Correspondingly, it is 1.29 mm·s^-1 and 0.34, when the surface morphology of Al powder is smooth. At the high pressure stage (12-20 MPa), the burning rate of HTPB propellant increased by 4.47 mm·s^-1 and the pressure exponent is 0.67, when the surface morphology of Al powder adhered with Al spot particles, and it is 2.48 mm·s^-1 and 0.40, when the surface morphology of Al powder is smooth.

Abstract:To analye the decomposition mechanism of nitroglycerin (NG) during storage in detail, the change in the concentrations of three kinds of gases, including CO, NO, NO₂ released by NG decomposition at 55℃ and 60℃ was monitored by thermal decomposition experiment.The rate constants of four kinds of initial reactions including the hemolytic cleavage reaction of O-NO₂ group, HONO elimination reaction, hydrogen abstraction reaction at α-position and hydrogen abstraction reaction at β-position at 20-60℃ were calculated by the density functional theory and canonical variational transition state theory. Results show that 90 days and 70 days respectively are two important time points at 55℃ and 60℃.With increasing the decomposition time gradually, the concentrations of CO and NO increase, but the concentration of NO₂ increases first and then decreases. At 20-60℃, the rate constant of autocatalytic reaction of hydrogen abstraction at β-position is the fastest, which is 10²-10¹¹ times greater than those of the other three kinds of reactions and the rate of HONO elimination reaction is smallest which is 1/10¹¹-1/10⁵ times of the rate constants of the other three kinds of reactions. The rate of hydrogen abstraction reaction at α-position is about two orders of magnitude more than the rate of the hemolytic cleavage reaction of O—NO₂ group. On basis of the double attribute of NO₂ molecules as the decomposition reaction product and the reactants of catalytic reaction, taking NO₂ gas concentration reaching the highest point in time as benchmark, the process of NG decomposition during storage can be divided into two stages. The hemolytic cleavage of O—NO₂ is the main reaction channels of the first stage, and the rates of autocatalytic reaction of hydrogen abstraction at α=position and β-position increase with the NO₂ concentration increasing. The autocatalytic reaction of hydrogen abstraction at β-position is main reaction channel of the second stage. The autocatalytic reaction of hydrogen abstraction at α-position is secondary reaction channel of the second stage. HONO elimination reaction has minimum effects to NG decomposition throughout the entire process.

Abstract:A comparative assessment of three different methods used for estimating and generating the relaxation modulus master curves of ammonium perchlorate-hydroxyl-terminated polybutadiene (AP-HTPB) solid propellant was carried out. These methods are the Williams-Landel-Ferry (WLF) method, the Arrhenius method, and the basic time-temperature superposition (TTS) method. The experimental data of the relaxation modulus for composite solid propellant were gathered by performing stress relaxation tests at constant strain level 10% for 1380 s at several temperature(-40, +20, +76℃). The procedures and steps for evaluating the three methods was based on the same experimental data obtained for relaxation modulus to estimate the shift factors and then to generate the master curves of relaxation modulus and finally comparing the best fit method through the determination coefficient (R²). The corresponding results indicate that the basic TTS method generated the best fit curve relative to the experimental data because this method is independent of external material constants and empirical equations in its application and it can be generally applicable to any viscoelastic material. However, in the applications of finite element software, the material constants are usually required to define the non-linear viscoelastic material model, in this case, the result of the present work demonstrates that both WLF and Arrhenius methods can produce satisfactory results, when appropriate constants are used, and the WLF method has proven to be more accurate and would be preferred in finite element analysis of AP-HTPB solid propellant.

Abstract:In order to study the effect of subatmospheric pressures on the ignition and combustion characteristics of Al/Mg fuel-rich propellant, the propellant was ignited by CO₂ laser with different heat fluxes (1.26, 1.86, 2.23, 2.79 W·mm^-2) at subatmospheric pressures (0.01, 0.02, 0.04, 0.06, 0.08, 0.1 MPa). The ignition and combustion process of propellant was recorded by a high speed camera. The ignition delay time was obtained by two photodiodes which monitor the laser signal and flame signal. The effect of subatmospheric pressures on the ignition delay time, combustion process and linear burning rate of the propellant was discussed. Results show that the pressure influences the diffusion of the pyrolytic gases. The initial flame forms the shape of a cylinder when pressure is 0.08 MPa, as pressure decreases to 0.02 MPa, the shape of initial flame changes to be spherical. The reduction in pressure causes a longer ignition delay time, however, as the heat flux increases, the effect of pressure on the ignition delay time is significantly reduced. The burning rate decreases with the reduction of pressure and it decreases by 47% when the pressure drops from 0.1 MPa to 0.01 MPa. The Vielle burning rate formula shows a good agreement with burning rate data. Therefore, the Vielle burning rate formula is more suitable for characterization of Al/Mg fuel-rich propellant burning rate characteristics at subatmospheric pressures environment.

Abstract:To improve the efficiency of ultrasonic testing for plastic bonded explosive(PBX) materials, and ensure the reliability and safety of the final product, a non-contact and nondestructive testing method of internal defects in PBX based on laser ultrasonic technique was studied. Based on thermo-elastic mechanism, a finite element numerical calculation method and model for the laser ultrasound of PBX material were established. The distribution of internal transient temperature and ultrasound fields of PBX material under the pulsed laser irradiation was obtained.The interaction between the laser ultrasound with the internal hole and crack defects of PBX was simulated. The numerical results show that using 5 laser beam to stimulate simultaneously, it can greatly improve the detection ability of laser ultrasound on internal defect within the safety temperature range of PBX. The detection of the cracks with length of more than 0.5 mm and the holes with diameter of more than 0.2 mm can be realized. The feasibility of laser ultrasound for the internal defect detection of PBX materials is preliminarily validated

Abstract:A nitrogen-rich energetic compound-triaminoguanidinium 2, 4, 6-trioxo-1, 3, 5-triazinan-1-ide (1) was prepared with a yield of 91% via one-step metathesis reaction using triaminoguanidinium hydrochloride (TAG-HCl) and sodium cyanurate (CANa) as raw materials. The structure of the product was characterized by X-ray single-crystal diffraction, UV-Vis, FT-IR, ¹H NMR, mass spectrometry and elemental analysis. The enthalpy of formation and detonation parameters of the product were calculated. Its thermal stability, non-isothermal reaction kinetics and decomposition process were studied by differential scanning calorimetry(DSC) at a heating rate of 10 K·min^-1 and thermogravimetric (TG) analysis coupled with Fourier transform infrared spectroscopy (FTIR). The impact sensitivity of the product was determined by the drop hammer test. Results show that the crystal of compound 1 is monoclinic, space group P2₁/n with a calculated density of 1.676 g·cm^-3. Its enthalpy of formation is 327.9 kJ mol^-1, the detonation velocity 7900 m·s^-1, and the detonation pressure 26.5 GPa. Probable thermal decomposition mechanism of 1 under N₂ atmosphere as shown in the text is proposed. Compound 1 is very insensitive to impact, and the impact sensitivity is greater than 60 J, which is better than that of TATB (50 J).

Abstract:3, 4-Diaminofurazan (DAF) was synthesized from glyoxal and hydroxylamine by one step with yield of 48.0% and purity of 99.8%. 3, 3'-Diamino-4, 4'-azoxyfurazan (DAOAF) was successfully obtained through the reaction of DAF and potassium monopersulfate triple salt (KHSO₅·0.5KHSO₄·0.5K₂SO₄) as oxidant in the buffer system of NaHCO₃ solution. Its structure was characterized by IR, ¹H NMR and MS spectra. The purity of DAOAF was determined by HPLC and the impurities contained were also qualitatively and quantitatively analyzed. The optimum synthesis conditions are determined as follows:the molar ratio of n(DAF):n(NaHCO₃):n(KHSO₅·0.5KHSO₄·0.5K₂SO₄) is 1:6:4 for 5 h at 20-25℃, the yield and purity of crude product are 84.1% and 98.2%, respectively. The impurities contained in the crude DAOAF are DAF, DAAF and ANF. The impurities can be removed effectively by recrystallizing from DMF at 95℃, thus producing high-purity DAOAF (99.6%), with a total recovery rate of 86.6%.

Abstract:4, 4'-Bis(dinitromethyl)-3, 3'-azofurazan (4) and potassium 4, 4'-bis(dinitromethyl)-3, 3'-azofurazanate (3) were synthesized from 4, 4'-dicyano-3, 3'-azofurazan through addition, diazotization and nitration with yield for each step reaction of 93.3%, 91.2%, 24.5% and 63.1%, respectively. In addition, a new furazan, 4, 4'-aminoxim-3, 3'-hydrazinefurazan (1), was obtained in the synthesis process of 4. This synthesis of 1 may proceed first with hydroxylamine addition of 4, 4'-dicyano-3, 3'-azofurazan followed by reduction of excessive hydroxylamine. The intermediates and product were analyzed by ¹H NMR, ¹³C NMR, IR and mass spectrum. The thermal behavior of 1, 3 and 4 were studied by DSC-TG method. The thermal behavior of 1 includes one dehydration endothermal stage and two obvious decomposition stages with mass loss of 5.1%, 53.5% and 36.3%, respectively. The peak temperature of each stage is 83.7℃, 241.1℃ and 336.2℃. The thermal behavior of 3 and 4 include only one obvious decomposition stage. The mass loss and the peak temperature are 86.6% and 258.1℃, 71.8%156.0℃, respectively.

Abstract:Using 3, 3'-dinitro-5, 5'-bis-1, 2, 4-triazole-1, 1'-diolate(DNOBT) as starting material, three energetic ionic salts (DNOBT-3-AT, DNOBT-ODH, DNOBT-DHT)were synthesized by reaction with 3-amino-1, 2, 4-triazole, oxalyl dihydrazide, 3, 6-dihydrazine-1, 2, 4, 5-tetrazine, respectively, and their structures were characterized by FT-IR, NMR and elementary analysis. The single crystal of DNOBT-3-AT was cultivated, and its crystal structure was determined by X-ray crystallography. It is found that DNOBT-3-AT crystallizes in monoclinic system, space group P2(1)/c. Their physico-chemistry and detonation properties were calculated by Gaussian 09 program and Kamlet-Jacobs formula. Meanwhile, the thermal behaviors of the three compounds were studied with differential scanning calorimetry (DSC). Results show that the detonation velocities are 7736.4, 7729.56, 7974.64 m·s^-1, and the detonation pressures are 26.8, 26.74, 28.56 GPa, respectively. The first exothermic decomposition peak temperatures of DNOBT-3-AT, DNOBT-ODH and DNOBT-DHT are 276.54, 257.02, 154.15℃, respectively, which shows that DNOBT-3-AT has better thermal stability than DNOBT-ODH and DNOBT-DHT.

Abstract:To identify the shock generated sources of shear type explosive bolt, four kinds of explosive bolts with different states including preload, no preload, no piston shear and only propellant combustion, were designed. The decoupling of four kinds of shock sources including the collision of propellant combustion, piston shear weak surface, end of piston stroke and preload release, was realized. Their acceleration response at 15 cm from the shock source center on 60 cm×60 cm×1 cm equivalent aluminum plate were measured by using the piezoresistive accelerometer. On this account, the shock response spectrum of various source was calculated and compared with the overall shock response spectrum. Results show that the characteristics of different shock sources are different, the shock induced by propellant combustion is mainly caused by high frequency, while the shock caused by the collision of the piston shear weak surface and the end of piston stroke is concentrated in medium and low frequency. The preload release is major contributor to the overall shock response output, accouunting for approximately 57.51%, while the contributions of three shock sources of propellant combustion, piston shear and piston impact are equivalent.

Abstract:Internal stress of 1, 3, 5-triamino-2, 4, 6-trinitrobenzene (TATB) based polymer bonded explosive (PBX) is an important cause of its cracking and low stress damage. For verifying the feasibility of analyzing the internal stress of TATB based PBX by neutron diffraction, 2 kN dual leadscrew was mounted horizontally on the Residual Stress Neutron Diffractometer (RSND), and the internal stress alterations were measured by the in-situ neutron stress measurement technique under different load status. Results show that the(002) crustal plane (diffraction angle 29°) and(412) crustal plane (diffraction angle 75°) of TATB crystal can be used as a neutron stress observation surface. The changes in lattice spacing measured by neutron diffraction (lattice strain) is approximately linearly increased with the applied stress on it, and the lattice strain increases with the increase of stress. In the process of more complex in-situ compressive loading/unloading, the lattice strain result is basically consistent with the complex stress change process. The neutron diffraction signal intensity decreases exponentially with the path and the neutron diffraction depth is 6 mm.

Abstract:Aiming at the problem that in the degradation of phenol wastewater by Electro-Fenton, Fe of Fe anode is easily dissolved, which affects the degradation efficiency, the study on the degradation of phenol wastewater by Electro-Fenton was carried out using ghe dimensionally stable anode of Ti/IrO₂-Ta₂O₅. The degradation intermediate products and degradation process of phenol wastewater of Ti/IrO₂-Ta₂O₅ anode and Fe anode for Fenton degradation of phenol were detected by high performance liquid chromatography(HPLC). Results show that when FeSO₄·7H₂O dosage is 0.1 g·L^-1, H₂O₂ dosage is 2.94 mmoL·L^-1, initial pH is 3.5, voltage is 5 V and degradation time is 2 min, by using Ti/IrO₂-Ta₂O₅ anode, the removal efficiency of phenol and COD can reach 94.14% and 40.74%, respectively. When Fe anode is used, at the same initial pH, voltage and degradation time, the removal efficiencies of phenol and COD are 40.74% and 26.41%, respectively. Compared with the Electro-Fenton process of Fe anode, the Electro-Fenton method of Ti/IrO₂-Ta₂O₅ anode has the advantages of less acid consumption, less H₂O₂ dosage, shorter reaction time, lower electrolysis votage, lower consumption of electrode and better treatment effect for degradating phenol wastewater. The degradation process of phenol wastewater of Ti/IrO₂-Ta₂O₅ anode and Fe anode for Fenton degradation of phenol are the same, but the degradation efficiency of phenol wastewater by Electro-Fenton method with Ti/IrO₂-Ta₂O₅ anode is higher in the same degradation time. This is because the electrocatalysis reaction using Ti/IrO₂-Ta₂O₅ anod and Electro-Fenton reaction can form a synergisic effect, the synergistic degradation of wastewater is more than that of alone Electro-Fenton reaction using Fe anode.

Abstract:Aromatic structures exhibit high stabilities and most of the heat-resistant energetic compounds are constructed with aromatic moieties. Based on the differences in the ring skeleton, the aromatic heat-resistant energetic compounds were divided into single, fused and coupling aromatic ring systems, and their synthesis and performance were reviewed. On the basis of overall summary for the research progress in the synthesis of heat-resistant aromatic energetic compounds with single, fused and polycyclic structures, the synthesis of some conjugate energetic compounds with good heat resistance were emphatically introduced. Structure activity relationship between molecular structure and thermostability were also discussed. The outlook of prospect on the aromatic heat-resistant energetic compounds were also carried out.

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