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Abstract:The impact load was applied to azido polyether propellant by the instrumented drop hammer device at -40 ℃. The impact damage of the sample was characterized by X-ray micro-tomography (X-μCT), and the dynamic mechanical properties of the propellant sample were studied by dynamic mechanical analyzer at different loading frequencies. Results show that the dynamic mechanical properties of azido polyether propellant exhibit obviously loading frequency-dependent and the glass transition temperature increases from -38.1 ℃ to -23.1 ℃ when the loading frequency varies from 1 Hz to 20 Hz. The propellant samples have no macroscopic crack with the impact energy below 2 J, but part of the perchlorate amine(AP) particles inside have been broken; and the propellant samples break with the impact energy increasing. The test curves of broken samples contain unstable crack growth which indicates the partial brittle material character of azido polyether propellant. The whole process of the fracture of azido polyether propellant is that the initial micro cracks was formed in the AP particles with defects, extend to large macroscopic cracks in the basal body, and then the propellant samples broke.

Abstract:To understand the curing process of hydroxy-terminated polybutadiene(HTPB)/isophorone diisocyanate(IPDI) binder system under the conditions of different catalysts [dibutyltin dilaurate(DBTDL), ferric acetylacetonate(FeAA), tin (ii) ethyethylhexanoate(TECH), diazabicyclooctane(DABCO), triphenylbismuth(TPB) and nano zinc oxide (nano-ZnO)], the relationship of viscosity vs. time for HTPB/IPDI system under the action of different catalysts at 45 ℃ was studied by viscosity method, and the changes in curing reaction rate were discussed. Results show that the rheological reaction rate constant for HTPB/IPDI system without catalyst and under the action of different catalysts at 45 ℃ is determined as k_blank=0.002, k_DBTDL=0.045, k_FeAA=0.0439, k_TECH=0.0335, k_DABCO=0.0051, k_TPB=0.0036 and k_nano-ZnO=0.0034. The effect of different catalysts on the curing reaction rate of HTPB/IPDI binder system decreases in the order of DBTDL > FeAA > TECH > DABCO > TPB > nano-ZnO. In the HTPB/IPDI system, when DBTDL, FeAA, TECH, DABCO, TPB and nano-ZnO are used as catalyst, the pot-life of the binder system is 0.3, 0.7, 1.9, 6.7, 16, 18 h, respectively. Through the change situation analyses of the pot life and the reacon rate constant k for sulrry during the curing process, considering that TPB is more suitable to be used as the curing catalyst of HTPB/IPDI system. The trend of the logarithm of viscosity increases with time reveals the phenomenon of two defined stages, fast early stage and slow later period, and deviation from the bottom right of graph line. The main reason for this phenomenon is due to the obvious reactive differences of NCO groups in IPDI. Science the steric effect of the methyl group and the cyclohexane ring, the reactivity of prim NCO group is significantly lower than the secondary NCO group.

Abstract:To improve the mechanical properties of ammonium perchlorate(AP)/ hydroyl-terminated polybutadiene(HTPB) base bleed propellants, the 2 mm short carbon fibers of mass fraction as 0.3% and 0.5% respectively were added in the original AP/HTPB base bleed propellant formulation. The static uniaxial compression and tensile tests for AP/HTPB base bleed propellants containing short carbon fibers were conducted. The microscopic analysis of fracture surface for specimens was performed by SEM. Experimental results show that the tensile strength of AP/HTPB base bleed propellants of adding 2 mm short carbon fibers of mass fraction as 0.3% and 0.5% increases by 11.7% and 33.0% respectively and their compression strength increases by 2.1% and 7.8% respectively. The short carbon fibers are distributed in the HTPB matrix. The bonding property between short carbon fibers and HTPB matrix is good. The damage of new AP/HTPB base bleed propellants containing short carbon fibers is mainly caused by debonding of the AP particles. The short carbon fibers in AP/HTPB base bleed propellants have an inhibitory effect on microcrack development, which demonstrates the short carbon fiber is a good reinforcement material for AP/HTPB base bleed propellants.

Abstract:To explore the changing rule of morphology and physical quantity of the droplet in the micro-explosion process of single gelled fuel droplet, numerical simulation study of the micro-explosion process of JP-8 metally gelled fuel droplet was carried out by smoothed particle hydrodynamics (SPH) method. The problem of severe changes of density gradient and smoothing length gradient in the process of bubble expansion was solved by introducing the full variable smoothing lengths SPH method. The elastic gelatinizer membrane was simulated by the modified JCD (Johnson-Cook Damage) strength model. The growth, expansion, broken shell, jet etc.processes for internal bubble in the micro-explosion process of gelled droplet were simulated. The variation characteristics of internal pressure of droplet and stress of gelatinizer membrane in the bubble deformation process were obtained. The changing rules of droplet′s radius, pressure, tensile stress and surface tension etc. physical quantities in the micro-explosion process of gelled fuel droplet were explored. The numerical simulation results show that the droplet′s volume expands gradually and pressure increases in pulse as time goes, and gelatinizer membrane breaks and the droplet′s volume decreases rapidly when diameter ratio D/D₀ reaches 1.4; For the multi-bubble gel droplet, the large bubble expands faster than the small bubble, and generates larger pressure on the wall, leading to the gelatinizer membrane fractures near the big bubble, and the rupture time is shortened compared with the single bubble. The numerical simulation results are in agreement with the experimental ones, which reveals the inherent mechanism of the droplet micro explosion process and verifies the effectiveness of the SPH algorithm in solving such problems.

Abstract:In the process of fitting the constitutive equations, the Bagley correction method was brought in to obtain the correction parameters to refit the constitutive equation and reduce experimental errors caused by the viscosity of paste propellant. The experimental errors were reduced from 8% to less than 2% by using the Bagley correction method. The obtained curve of the constitutive equations were consistent with the experimental data. The results showed that the Bagley correction method had an obvious effect in improving the accuracy of the equation to a certain extent.

Abstract:Octagon (HMX) based metalized explosive containing boron (B)/aluminum(Al) compound powder, oxidizer ammonium perchlorate(AP) and binder hydroxyl-terminated polybutadiene(HTPB) was designed and prepared. The appearance morphology of B powder, Al powder and B-Al compound powder were observed by SEM. The effects of HMX and AP on the thermal oxidation characteristics of B and Al powder were investigated by TG-DSC. A deeper understanding of reaction kinetic mechanism of the B and Al powder was made. The sensitivities(impact sensitivity, friction sensitivity, electrostatic spark sensitivity, cap initiation sensitivity) and ignition and propagation properties for metalized containing B/Al were measured, which made a fully acknowledge of the safety under different external energy stimuli and ability of detonation propagation. The results show that there are many small particles of B powder on the surface of spherical Al powder in the B-Al compound powder. From room temperature(25 ℃) to 1000 ℃ under N₂ atmosphere, although the pressures have an effect on the thermal decomposition peak temperature of HMX and AP, however partial oxidation of Al powder and B powder only occurs, whereas the combustion does not occur. The impact sensitivity, friction sensitivity and electrostatic spark sensitivity of the metalized explosives containing B and Al powder are 40%-80%, 100% and 3.83-6.40 kV respectively, and all the metalized explosives designed can be intiated by 8^# industrial detonator, which indicates that the mechanical sensitivity of the metalized explosive containing B and Al powder without binder is high. The mechanical sensitivity is obviously lowered by adding desensitized HMX and AP, and it can be further lowered by adding polyurethane binder. By increasing the 20% content of polyurethane binder HTPB, the impact sensitivity and friction sensitivity of the HMX based metalized explosive containing B powder can be reduced less than 10% and 30%, respectively, revealing that the safety requirements for preparation and processing technology of mixed explosive can be satisfied. Additionally, the metalized explosive of Ф 50 mm can be intiated by 8^# industrial detonator and can propagate stable detonation, showing a strong after-effect power ability.

Abstract:N-(1, 4, 6-trinitrohexahydroimidazo[4, 5-d]imidazol-2(1H)-ylidene)nitramide(TNINA), a energetic nitrogenous poly-heterocyclic compound, was synthesized with a total yield of 47% by three stages of nitration reaction using hexahydroimidazo[4, 5-d]imidazol-2(1H)-imine as raw material. The factors affecting the third nitration reactions such as reaction time, reaction tempterature and volume ratio of acetic anhydride to nitric acid were investigated as well. The title compound and its intermediates were characterized by IR, NMR and MS. Its thermal stability was analyzed by DSC and TG and the temperature of decomposition was 214.4 ℃, and exothermic process was finished instantly. The theoretical density of TNINA after optimizing predicted by Monte-Carlo method is 1.91 g·cm^-3, and experimental value is 1.89 g·cm^-3. The heat of detonation, detonation velocity and detonation pressure predicted by Kamlet-Jacobs formula are 5513.26 kJ·kg^-1, 8.836 km·s^-1, 35.80 GPa, and the theoretical and experimental impact sensitivity(H₅₀) is 41 cm and 53 cm. All the results show that TNINA have better detonation performance and more insensitive than RDX.

Abstract:In order to investigate the effect of fine zirconium powder with diameter of 1 μm on the reaction mechanism of KClO₄ during thermal decomposition, TG/DTG and X-ray photoelectron spectroscopy (XPS) analysis were applied to determine the thermal behavior of KClO₄ and Zr/KClO₄ (50:50). The result of XPS shows that the addition of KClO₄ promoted the reversible chemical reaction equilibrium of KClO₄. Linear regression was used to determine the kinetic triplet. The calculation result shows that the activation energy declined while the pre-exponential factor increased and the mechanism function shifted from G(α)=[-ln(1-α)]^3/4 to G(α)=-ln(1-α), the critical temperature of thermal explosion declined from 587.7 ℃ to 516.9 ℃ for the first decomposition stage. As for the second one, the activation energy increased while the pre-exponential factor hardly changed and the mechanism function remains G(α)=-ln(1-α). Thus it can be inferred that zirconium accelerated the first thermal decomposition step of KClO₄, increased the number of active sites and made it easier to happen, but became inert substance since it was oxidized to ZrO₂ and that was the reason of the increment of the activation energy and the invariant of the mechanism function.

Abstract:In order to control the structure of ball propellant with micro-pores, the factors affecting the particles diameter, surface porosity, particles surface state were explored by adjusting the process parameters and adding alkane solvents. As a result, the viscosity of NC collosol and the emulsion decrease with the solvent dosage increasing, the average particles diameter decrease apparently. When alkane is drawn into emulsion process as pore-forming agent, the ball propellant with open pores at the surface will be obtained. With the increase of alkane dosage, the surface porosity gradually increases, meanwhile. When the leaching method is used to separate solvent, the high particles sphericity will be gotten through decreasing the speed of adding water. The structures of ball propellant with micro-pores can be controlled effectively by adjusting the process parameter and adding alkane into emulsion.

Abstract:To study the effect of recrystallization process on fhe thermal properties and mechanical sensitivity of dihydroxylammonium 5, 5′-bistetrazole-1, 1′-diolate(HATO, TKX-50), Six kinds of HATO samples with different particle size and morphology were prepared using falling temperature method and solvent-nonsolvent method respectively. The particle size and morphology of HATO samples obtained by different recrystallization process were characterized by laser granularity instrument and scanning electron microscope(SEM). The thermal decomposition properties was analyzed by means of differential scanning calorimeter(DSC). Its impact and friction sensitivities were were measured by GJB772A-97 method. The results show that HATO samples without addition of surfactnt obtained by falling temperature method have maximum particle sizes(d₅₀=196.5 μm), the crystal surface is smooth and the shape is regular, showing the highest decomposition temperature and the lowest mechanical sensitivity. Its decomposition peak is 249.1 ℃. The impact and friction sensitivities are 8% and 20% respectively.

Abstract:To understand the salt-forming reaction process of urotropine(HA) and nitric acid (NA) system and clear the salt-forming mechanism, the change in characteristic absorption peak of main fuctional groups with time in the process of forming mononitrate of HA (HAMN) and dinitrate of HA (HADN) was tracked, monitored and analyzed by on-line infrared spectroscopy technology and the interaction between HA and NA was studied by computational chemistry method. Results show that in the salt-forming process of HA, the reaction of forming HAMN by NA with HA is quick, but the reaction of HAMN to HADN is relatively low. When NA reachs 5.97 mol·L^-1, HADN is only formed. In the IR spectra of HAMN, the inverted peaks appear at 1002, 1236, 690, 806 cm^-1, which are the characteristic absorpption peak of C—N bond in HA. Due to the HAMN is formed, the C—N bond force constant of HA is changed, the absorption peaks at 979, 1024, 1219 cm^-1 and 1259 cm^-1 were appeared on the left and right sides of the inverted peak.When there is HADN precipitation, without adding NA, there are still HADN formation and precipitation and the amount of NA in the solution shows a slow upward trend. In the process of HAMN formation, HAMN adsorbs the NA molecules around it. When the HADN is formed, the NA molecules are released into the solution, and the HAMN molecules are supplied to continue to form new HADN molecule. The optimized structure of HA and NA, HA and H₂O obtained by Gaussian software and calculated binding energy values are obtained, revealling that the NA system of HA is more stable. The results are in agreement with the experimental ones.

Abstract:Based on the relation of thermal conductivity and thermal resistance, the interface-resistance-baseed thermal conductivity model was established to predicet the PBX thermal conductivity. The interface-contained samples were prepared by coating fluorine rubber on the surface of TATB pill. The conductivitys of as-repared samples and TATB pills and fluorine rubbers pills were measured by using the flash diffusivity method. The coefficient of thermal conductivity of TATB/fluorine rubber layer are 6.18×10^-3, 6.53×10^-3, 9.87×10^-3, 2.16×10^-2, 7.72×10^-3 W·m^-1·K^-1, respectively at 293-333 K. The thermal conductivity of the TATB-based PBX was obtained by using the thermal condctivity model. The results of caculation were well agreed with the test value.

Abstract:The energy conversion components as the core parts of initiating explosive device are an important factors affecting the safety and reliability of micro electro-mechanical systems(MEMS) initiating explosive device, and the effect on the whole weapon system also can not be ignored. Materials research and structure design of the energy conversion components are one of research hotspots in recent years. From the perspective of substrate material and resistance material research, structure design and so one of energy conversion components, the latest research development of energy conversion components of MEMS initiating explosive device over the past few years was reviewed in this paper. Two key technologies for energy conversion components of MEMS initiating explosive device: design/preparation method of the energy conversion components of MEMS initiating explosive device and measurement and characterization for performance parameters of the energy conversion components, were introduced Pointing out that the energy conversion component of MEMS initiating explosive device with miniaturization, integration, multi function and high reliability is a hot point of research in the future. To provide theoretical support for design and research of the energy conversion component of of MEMS initiating explosive device, the study on heat dissipation characteristics and bridge resistance characteristics under micro scale should be strengthened. Considering that the composite energetic thin film bridge energy conversion component is an important development direction of energy conversion component of MEMS initiating explosive device.

Abstract:To get the crystal structure of 1-trinitromethyl-3-nitro-1, 2, 4-triazole(TNMNT) and estimate its properties, using 3-nitro-1, 2, 4-triazole as starting material, TNMNT was synthesized via substitution reaction and nitration reaction with total yield of 62%. The pure single crystal of TNMNT was cultured and obtained by solvent evaporation method using absolute ethyl alcohol as solvent. Its structure was characterized by NMR spectrometry, IR spectrometry, and single crystal X-ray diffractometer. The thermal stability was analyzed by the DSC-TG method. The enthalpy of formation and detonation parameters were calculated with Gaussian 09 and EXPLO5(V6.02) program, respectively. Results show that the crystal of TNMNT belongs to monoclinic system, space group is P21/c with crystal parameters of a=6.643(3)Å, b=20.494(7)Å, c=6.698(3)Å, β=94.225(9)°, V=909.4(6)Å, Z=4, D_c=1.922 g·cm^-3, μ=0.190 mm^-1, F(000)=528.0. The thermal decomposition peak temperature of TNMNT at a heating rate of 5 ℃·min^-1 is 158.3 ℃. Its standard enthalpy of formation is 210.9 kJ·mol^-1, detonation velocity 9023 m·s^-1, and detonation pressure 35.5 GPa. The existence of numerous intermolecular and intramolecular hydrogen bonds makes the TNMNT molecule stably exist, and the introduction of the trinitromethyl moeity makes the energy of TNMNT molecule enhance.

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