Abstract:

Abstract:To study the influence law of purified cotton quality and nitrification process on the nitrification uniformity of nitrocellulose (NC) with high-nitrogen content, purified cottons with different maturity were nitrified via H₂SO₄-HNO₃-H₂O system, and NC with high-nitrogen content was prepared by changing sulfuric acid-nitric acid ratio and nitrification time. The nitrogen content and nitrification uniformity of NC were measured by polarizing microscope. The influence law of different maturity and nitrification processes on the nitrogen content and nitrification uniformity of NC with high-nitrogen content was discussed. At the same time, typical gun propellants were suppressed via. gelatinization of NC with different uniformity, and the microstructure of the lateral cross sections of the corresponding granules was compared. Results show that the nitrification uniformity of NC prepared from purified cottons with high maturity is better than that of low maturity products. NC prepared by low sulfuric acid-nitric acid ratio as 2.7 has higher nitrogen content and better nitrification uniformity. Using purified cotton of maturity as more than 70% as raw material, the nitrification uniformity index-variance of prepared NC is about 2.3. When nitrification time is about 30 mins, the nitrification effect is the best, the prolongation of nitrification time only has a little effect on the nitrogen content, but the uniformity decreases. So through the control of sulfuric acid-nitric acid ratio in the nitrification system and nitrification time, using purified cotton of high maturity as raw material, the NC with better uniformity can be obtained and the gelatinized extrusion molding quality of high-uniformity NC-pressed single-base propellant is significantly improved.

Abstract:To improve the mechanical properties of high-energy TEGDN gun propellants, based on high-energy TEGDN gun propellant formulations, adding a small amount (mass fraction of 0.5%, 1.0%, 1.5%, 2.0%) of cellulose nanofibers (CNFs) obtained from lignocellulose, high-energy TEGDN gun propellants containing CNFs were prepared. The surface structure and thermal decomposition property of high-energy TEGDN gun propellants before and after adding CNFs were studied by scanning electron microscopy, thermogravimetric analyzer and differential scanning calorimeter. The impact strength and energy performance of high-energy TEGDN gun propellants containing CNFs were studied by the Charpy impact testing machine and closed bomb vessel test. The results show that adding a small amount of CNFs can obviously improve the low-temperature impact strength of high-energy TEGDN gun propellants and very little on thermal decomposition performance. Compared with the original high-energy TEGDN gun propellant (reference sample), the impact strength of high-energy TEGDN gun propellant of adding 0.5% CNFs increases by 30.4% under the low temperature of -40 ℃ and increases by 8.9% under the room temperature of 20 ℃. With increasing the content of CNFs, the powder force decreases gradually, the covolume increases gradually, the burning rate decreases gradually, and the pressure exponent increases slightly. When the dosage of CNFs is 0.5%, the powder force, covolume and pressure exponent of high-energy TEGDN gun propellant are 1191.91 kJ·kg^-1, 0.870 L·kg^-1 and 1.06, respectively, compared with the reference sample, they have a reduce of 1.9%, an increase of 5.1% and an increase of 4.2%. respectively

Abstract:In order to study the mechanical mechanism and movement characteristics of the projectile′s dynamic engraving rifling with serial launch method at different initial velocities, the internal ballistic physics process with serial launch method was analyzed based on the 30 mm caliber artillery. The finite element models of the projectile and barrel were established and the finite element simulation of the engraving process was carried out with LS-DYNA. The results show that the initial engraving velocity has no influence on the deformation of the ammunition belt. The ammunition belt is grooved by the rifling gradually and the plastic deformation occurs. When the initial engraving velocity increases from 5 m·s^-1 to 400 m·s^-1, the equivalent stress of the ammunition belt increases from 611.8 MPa to 717.5 MPa, the plastic strain peak of the ammunition belt decreases from 0.89 to 0.75, the engraving resistance peak increases from 20.3 kN to 22.9 kN and the friction resistance after the engraving process is completed increased from 0 to 3.5 kN. When the initial engraving velocity increases, the strain rate of the ammunition belt material, the plastic flow stress and the engraving resistance change, which have great influence on the following ballistic process of the projectile after the engraving process. When three projectiles are launched with serial method in turn, the standard deviation of axial velocity of the first projectile is 8.3 m·s^-1, and the subsequent two are 18.2 m·s^-1 and 26.7 m·s^-1 respectively. The vibration shock effects of the subsequent projectiles are more significant than the first one at high engraving velocity.

Abstract:To investigate the effect of mold inner flow channel structure on the forming process of nitroguanidine gun propellant, the mold inner flow channel model of 11/7 nitroguanidine gun propellant was established. The numerical simulation of nine schemes of different combinations of shrinkage angle as 30°, 45° and 60° and forming section length as 25, 30 mm and 45 mm was performed. The effect of shrinkage angle and forming section length on the shear rate, pressure and velocity distribution in the extrusion process were analyzed. Results show that the shrinkage angle has similar effects on the interfaces of different contraction sections and forming section and nearing-outlet etc.sections, and it shows that the shear rate of the propellant dough near the center of mold needle and the wall surface is higher than that of the surrounding pare. The sectional pressure distribution is uniform and the flow velocity distribution of the dough has the characteristics of large middle parts and small two sides. The length of forming section has a great influence on the shear rate distribution during the extrusion process of dough. The smaller the length of the forming section, the more likely the sudden change of shear rate, which may lead to the unsteady flow. At the same time, it can be determined that the optimal inner flow channel parameter scheme is the shrinkage angle of 45° and the forming section length of 30 mm.

Abstract:Using 2, 3, 5, 6-tetraamineopyridine hydrochloride and triethoxy methane as starting materials, N-heterocyclic nitramine precursor 1, 5-2H-diimidazo [4, 5-b:4′, 5′-e] pyridine was prepared by condensation reactions. The optimum molar ratio of triethoxy methane/2, 3, 5, 6-tetraamineopyridine hydrochloride was indentified to be 4.5. The yield was 56.5%. 2, 9-Dialdehyde-5, 13-dithio-2, 4, 6, 7, 9, 11, 12, 14-octaaza-tricyclo[8.4.0.0^{3, 8}]tetradecane was synthesized using thiosemicarbazide and 1, 4-diformyl-2, 3, 5, 6-tetrahydroxylpiperazine as raw materials. The optimum molar ratio of thiosemicarbazide/1, 4-diformyl-2, 3, 5, 6-tetrahydroxylpiperazine was indentified to be 2.2. The yield was 46.0%. Their structures were characterized by ¹H NMR, IR, MS and elemental analyses. The geometry optimization and frequency vibration analysis of two N-heterocyclic nitramine precursors were performed by density functional theory DFT-B3LYP/6-311+G(d) method. Thermodynamic properties of two precursors in the temperature range of 200 K to 800 K were investigated. Results show that the constant pressure molar capacity, standard molar entropy and standard molar enthalpy of two N-heterocyclic nitramine precursors increase with the increase of temperature.

Abstract:An energetic compound 5, 10-bis(dinitromethyl)-furazan[3, 4-e]bis([1, 2, 4]triazolo)[4, 3-a:3′, 4′-c] pyrazine (BOBTP, total yield of seven-step synthesis as 10%) was synthesized using diaminofurazan (DAF) as raw material. Its corresponding energetic ion compounds were synthesized via. neutralization reaction collocated with a series of nitrogen-rich cations. Its structure was characterized by single-crystal X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FT-IR), nuclear magnetic resonance (¹H NMR and ¹³C NMR) and elemental analyses. Its thermal decomposition temperature was measured by thermogravimetry(TG) and differential scanning calorimetry(DSC). Its detonation performance were calculated with Explore 5 v6.02 software. Results show that the crystal of dipotassium salt of BOBTP belongs to monoclinic system and C2/c space group with cell parameters of a=1.9913(3) nm, b=0.93491(12) nm, c=1.6807(2) nm, β=90.160(3)°, V=3129.0(7) nm³, Z=8, D_c =2.103 g·cm^-3, M=1.752 mm^-1, F(000) =1976. For energetic ion compounds obtained based on BOBTP, the measured densities at 25 ℃ are in the range of 1.62-1.75 g·cm^-3 and the onset temperatures of thermal decomposition reaction are in the range of 186-232 ℃. The calculated detonation velocities and pressures are higher than 7500 m·s^-1 and 20 GPa, respectively. The measured impact and friction sensitivities are relatively low. In which, the impact sensitivity of dihydroxylamine salt of BOBTP is 18 J and the friction sensitivity is 240 N.

Abstract:To obtained the influence of high temperature and mechanical stress on the mechanical behaviors of polymer bonded explosive(PBX), the response of HMX-based PBX-1 and TATB-based PBX-2 under the action of different high temperature and mechanical stress were obtaitned based on the results of matrerial testing machine, and their change mechanism of mechanical properties are analyzed by dynamic mechanical analyzer (DMA) and scanning electron microscopy (SEM). Results show that the tensile strength and compressive strength of the two PBXs decrease with temperature increasing under coupled high temperature-mechanical stress loading at 25-90 ℃, but the failure strain undergos saltation at some temperature point, which is about 65 ℃ for PBX-1 and 35 ℃, about 55 ℃ and 75 ℃ for PBX-2. The response rule of PBX-1 subjected to sequence high temperature-mechanical stress loading contains two temperature ranges, 25-150 ℃ for the first stage, the compressive strength and failure strain of materials under the action of the high temperature in the range almost do not change, 150-200 ℃ for second stage, the failure strain increases with the increase of temperature, the compressive strength first decreases and then increases, which is lowest at 180 ℃. Under coupled high temperature-mechanical stress action, the phase change of binder and its change of viscoelastic characteristics is the main reason affecting the high temperature softening and deterioration of machanical properties of PBX. The deformation behaviors of PBX, especially its saltation of tensile failure strain and compressive failure strain are caused by softening-flow-viscous flow. At the same time, the failure mode of PBX changes from brittle fracture to debonding failure and the saltation temperature of PBX corresponds to the transition temperature of the state of matter for binder. For sequence high temperature-mechanical stress loading, the elastic recovery of binder and explosive crystal without damage is the main reason for no change of the mechanical properties of PBX-1 at 25-150 ℃. The crushing of explosive crystals occurs at high temperature around 180 ℃, leading to the compressive strength of PBX-1 reaches the minimum at around 180 ℃.

Abstract:To investigate the effect of thermal aging on the overloading safety of explosive charge, the accelerating aging of RDX-based aluminized and pressed explosive charge was performed at high temperature of 71 ℃ for 39 days. The launching safety of charge before and after aging were checked by drop hammer loading device and the effect of explosive grain structure, deterrent and binder content and quality of RDX crystal on the launching safety of charge was analyzed. Results show that under the same drop hammer loading condition, the probability of occurring combustion and explosion of unaged sample is larger than aged sample, after aging, the structure of explosive grain of aged sample is completer, the binder of explosive grain is softened and migrated, micro pore is reduced and closed, the content of deterrent and binder of explosive grain surface increases from 5.90% to 6.20%. Compared with the RDX crystal particles before aging, the half width of Raman charavteristic peak of the RDX crystal particles after aging decreases, especially full width at half maxima for charavteristic peak at 345 cm^-1 decreases by 42.2%. Showing that in the aging process, the softening and migration of deterrent and binder in explosive grain, micro defect repair, surface passivation and improvement of quality of RDX crystal etc. factors are the main reasons of lanching safety of aged charge is better than that of unaged charge.

Abstract:To explore the crystal habits of β-HMX in acetone, we prepared β-HMX single crystals by solvent evaporation method and applied powder X-ray diffractions to determine all the crystal surfaces, using powder GeO₂ as the internal standard sample for the refinement and the zero shift correction. A model was established for the crystal habit of β-HMX in acetone and compared to those reported in literature. The crystal surface of β-HMX are indexed as (1 0 0), (0 1 1), (-1 1 1) and (0 2 0). Among them, the (1 0 0) crystal face is the largest one, following by (1 1 0) and (-1 1 1) and (0 2 0), which consists with the theoretical calculated AE model with solvent effect correction. Because of the weak interactions with acetone molecules, (1 1 0) and (0 2 0) crystal faces disappeared gradually during the crystal growth process, which indicates the solvent environment has significant effect on the morphology of β-HMX.

Abstract:In order to study the feasibility of fast neutron radiography technology(FNR) in weapon quality detection, the research object was established on the basis of the open hypothetical weapon model, and the MC method was used to evaluate the safety of the fast neutron radiography in the weapon quality detection. Results showed that the fissile materials of uranium and plutonium have minimal damage under 14.1 MeV fast neutron irradiation with a total dose of 2×10⁸ n. On the basis of referring to the foreign research model and the default defects, the author designed and manufactured the experimental samples, and studied the internal slit, round hole and center displacement which may appear in the weapon inspection by means of both experiments and simulations. The experiment results show that FNR can identify the defects of 1-mm-thick slits inside a steel block of 5 mm thickness. The simulations further show that FNR is able to diagnose the center displacement with certain thicknesses for particular materials. Therefore, our results suggest FNR could be a feasible and potential technique in weapon quality testing.

Abstract:To accurately determine the purity of 3, 4-dinitropyrazole product, a high performance liquid chromatography (HPLC) method for the determination of 3, 4-dinitropyrazole and possible impurities, 3-nitropyrazole and 1, 3-dinitropyrazole, occurring in its synthetic process was established. The effect of different mobile phase system, mobile phase ratio and flow rate etc. conditions on the separation effect of high performance liquid chromatography for 3, 4-dinitropyrazole was discussed. The quantitative analysis was carried out by an external standard method. Results show that The optimal chromatographic conditions obtained are as follows: hypersil ODS2 chromatographic column (250 mm×4.6 mm, 5 μm), UV detection wavelength 260 nm, acetonitrile/0.1% acetic acid with a volume ratio of 35:65 as mobile phase, flow rate 1.0 mL·min^-1, column temperature 25 ℃, injection volume 10 μL. Under the above-mentioned conditions, the retention factors of 3-nitropyrazole, 3, 4-dinitropyrazole and 1, 3-dinitropyrazole are 0.41, 1.20, 1.52, respectively. The resolution between 3-nitropyrazole and 3, 4-dinitro-pyrazole is 9.42, and the resolution of 3-nitropyrazole with 1, 3-dinitrazole is 3.16. 3, 4-Dinitropyrazole, 3-nitropyrazole and 1, 3-dinitropyrazole show a good linear relationship in the concentration range of 5-500 mg·L^-1, 5-250 mg·L^-1 and 5-250 mg·L^-1, respectively. The detection limits of 3, 4-dinitropyrazole, 3-nitropyrazole and 1, 3-dinitropyrazole are 1.19, 0.73, 1.04 mg·L^-1, respectively. The standard recovery rates are 98.17%-104.84% with the relative standard deviations of 1.39%-2.08%.

Abstract:Aiming at whether there are interaction problem among various operating factors in the degradation of wastewater with nitrobenzene (NB) via an ultrasonic enhanced iron-carbon micro-electrolysis method, the process conditions were optimized by response surface methodology (RSM). In experiments, selecting 29 representative groups as the test points, taking ultrasonic (US) power, zero valent iron (Fe⁰) dosage, activated carbon (GAC) dosage, initial pH value of wastewater as main factors, removal efficiency of NB as response value, the response surface experiments of four factors and three levels were designed and the optimum process conditions were obtained. The results show that there is a significant interaction between Fe⁰ dosage and initial pH value, and initial pH value and ultrasonic power and predicted value of the removal efficiency of NB is 98.50% when the Fe⁰ dosage is 20.7 g·L^-1, the GAC dosage is 13.19 g·L^-1, the initial pH value is 2.08, the ultrasonic power is 175.96 W. A difference of 1.23%(< 2%)is observed with the measured value. Therefore, the obtained secondary mathematical model for the degradation of NB via ultrasonic enhanced iron-carbon micro-electrolysis has a good reliability for the optimization of process conditions and the prediction of removal efficiency of NB.

Abstract:

Abstract:

Abstract:

Abstract:Laser Raman spectroscopy is an in-situ non-destructive fast detection technology, which has significant application prospects in the field of explosives analysis and detection. Research progress on the applications of conventional laser Raman spectroscopy and its derivative techniques including Fourier transform Raman spectroscopy (FT-Raman), confocal micro Raman, surface enhanced Raman scattering(SERS), portable Raman and remote Raman in the field of explosives analysis were reviewed. The advantages and limitations of different type of laser Raman spectroscopic techniques were analyzed. The laser Raman spectra data of several typical explosives such as TNT, CL-20, HMX, PETN and RDX were compared. It is considered that the future research should focus on the establishment of Raman quantitative analysis methods for explosives, the preparation of high-performance substrate materials for surface enhanced Raman and the improvement of portable Raman spectroscopy.