Abstract:To evaluate the energy potential of new oxidation high nitrogen heterocycle hydroxylammonium salts as composite solid propellant components, the energy effects after replacing AP in two kinds of composite solid propellant systems AP/Al/HTPB and AP/Al/GAP+NE with dihydroxylammonium 5, 5′-bistetrazole-1, 1′-diolate(TKX-50), dihydroxylammonium 3, 3′-dinitro-bis-(1, 2, 4-triazole)-1, 1′-diolate(DHDNBT) and dihydroxylammonium 5, 5′-azo-bis(1-oxidotetrazolate)(DHABT)were calculated by using propellant performance evaluation program(PEP)and was compared with HMX. Results show that in the high solid content AP/Al/HTPB system, the energy characteristics of the formula obtained by partly replacing AP with TKX-50 AND DHABT in a wide formula range are equivalent to those of the formula obtained by replacing AP with HMX. The energy characteristics of the formula obtained by replacing AP with DHDNBT are equivalent to those of the formula obtained by replacing AP with the same content HMX. In AP /Al/GAP+NE system, the energy characteristics of the formula with DHDNBT are the same with those of the formula with HMX, but the energy performances of the formula with TKX-50 and DHABT are better than those of formula with HMX. The highest freezing specific impulse of the formula with TKX-50 and DHABT are 2662.7 N·s·kg^-1(TKX-50)and 2696.0 N·s·kg^-1(DHABT)respectively and 40.2 N·s·kg^-1(TKX-50) and 73.5 N·s·kg^-1(DHABT)higher than the highest freezing specific impulse of the formula obtained by replacing AP in the same system with HMX(2622.5 N·s·kg^-1). Replacing AP in AP/Al/GAP+NE with the assumed dihydoxylammonium bis(oxidotetrazol-5-yl)amine(DHBTA)can make the highest freezing specific impulse achieve 2708.7 N·s·kg^-1, 86.2 N·s·kg^-1 higher than the highest freezing specific impulse obtained by replacing AP in the same system with HMX and in a wide range of adjustment formula has a higher energy characteristics than HMX formula.

Abstract:To research the thermal safety problem of AP/HTPB composite solid propellant under the action of thermal loading, a two-dimensional simplified model about cook-off of solid rocket motor was established. Among them, the process of slow cook-off for AP/HTPB propellant was described by using two-step global reactions. The theoretical calculation results were in good agreement with the experimental data. On this basis, the numerical predictions of slow cook-off behavior for the motor were conducted at heating rates of 1.8, 3.6 K·h^-1 and 7.2 K·h^-1, respectively. Results show that with different of heating rates, the initial ignition locations of AP/HTPB propellant are occurred in the annular region on the inner wall of the propellant at the longitudinal distance of about 1mm, and the initial ignition location moves from the central to the grain shell end surface with the increase of heating rate. When the heating rate increases from 1.8 K·h^-1 to 7.2 K·h^-1, the ignition temperature increases from 592 K to 595 K, revealing a little temperature change, but the ignition delay time shortens from 31.48 h to 14.87 h.

Abstract:The heats of formation for poly(3, 3′-bisazidomethyl oxetane-3-azidomethyl-3′-methyl oxetane) (P(BAMO/AMMO)) based energetic thermoplastic polyurethane elastomers (ETPE) with different content of poly(3, 3′-bisazidomethyl oxetane) (PBAMO) and hard segment were estimated by group additivity method and combustion heats method. The effect of contents of PBAMO and hard segment on the heat of formation of ETPE. A group of P(BAMO/AMMO) ETPE-based propellants were selected by the least free energy method. The theoretical specific impulse was calculated. The maximum static state tensile stress, breaking elongation, impact sensitivity, friction sensitivity, burning rate of P(BAMO/AMMO) ETPE based propellant formulation were measured. Results show that the heat of formation of P(BAMO/AMMO) ETPE decreases as the mass of PBAMO increases or the content of hard segment decreases. The theoretical specific impulse of the preferred 15/5/20/38.5/18/3.5-P(BAMO/AMMO)/Bu-NENA/RDX/AP/Al/catalyst propellant is 2699.51 N·s·kg^-1 under the combustion chamber pressure of 10 MPa. The maximum tensile stress of the propellant is 1.22 MPa. The breaking elongation is 11.37%.The coated-solid filler can significantly reduce the mechanical sensitivity of premixed materials, making impact sensitivity H₅₀ increase by 37 cm, friction sensitivity P decrease by 36%, and burning rate pressure exponent (n) be 0.37 in the pressure range of 6 to 15 MPa.

Abstract:To study the mechanical properties of polyvinyl butyral(PVB)-based high solid content propellant, the effect of PVB with various viscosity, PVB blended with viscosity of 45 mPa·s and 300 mPa·s and plasticizers 1, 2-dibutylphthalate (DBP) and acetyl tributylcitrate (ATBC) on the PVB-based high solid content propellant was analyzed by a static mechanical test. The effect of PVB with various viscosity and two plasticizers on the dynamic mechanical property of PVB-based propellant was studied by dynamic thermomechanical analysis (DMA). Results show that with the increase of the viscosity of PVB, the high temperature tensile stress of the propellant increases, the normal temperature and high temperature elongation decrease. The PVB blended with mass ratio of 1:3 with viscosity of 45 mPa·s and 300 mPa·s can make the tensile mechanical properties of the propellant achieve the average value of these two kinds of single viscosity propellant. Replacing DBP with ATBC decreases low and normal temperature tensile elongation slightly The PVB based propellant with PVB of viscosity of 45 mPa·s has stronger α-transformation and the propellant with plasticizer DBP has stronger β-transformation.

Abstract:The mechanical properties, physical crosslinking degree, crosslinking network structure integrity and tenacity of hydroxyl-terminated epoxy ethane/tetrahydrofuran random copolyether (PET)/polyfuctional isocyanate (N-100) binder films were analyzed by the uniaxial tensile test, infrared spectrum testing and equilibrium swelling methods. Results show that with increasing curing parameter (R), the crosslink density of PET/N-100 binder films increases gradually, the average molecular weight of chain segment between crosslink points decreases gradually, the maximum tensile strength and elastic modulus increases gradually, while the elongation at break decreases gradually. The crosslinking network structure integrity of PET/N-100 binder system is directly proportional to the ratio of hydrogen bonding, and is inversely proportional to the content of N-100. When the R value is 1.2, the correction factor of shear modulus of PET/N-100 binder films is the maximum, the crosslinking network structure is most complete, and the mechanical property is the better, the same as the tenacity of PET/N-100 binder film.

Abstract:Nano β-Cu(copper β-resorcylate) were prepared via a facile wet mechanical grinding method, and were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). Meanwhile, the catalytic properties of nano β-Cu were investigated. Results reveal that the nano β-Cu is semi-spherical and homogeneous with a fairly uniform size of 100 nm. DSC results show that the nano β-Cu has significant catalytic effects on ultra-fine AP with different particle size. The peak temperature of decomposition in the high temperature range for 6 μm and 1 μm AP decreases to 373.1 ℃ and 351.2 ℃, respectively, and the apparent decomposition heat increases to 1529 J·g^-1 and 1513 J·g^-1, respectively. And the reaction rate constant increases about 10 times. Compared with 6 μm AP, nano β-Cu makes the peak temperature of the high temperature decomposition of 1 μm AP obviously lower, and the reaction rate constant much higher, indicating nano β-Cu exhibits much better catalytic efficiency for accelerating the thermal decomposition of 1 μm AP.

Abstract:A series of bis(imidazole)dihydroboronium ionic liquids with dicyanamide and nitrocyanamide anions were prepared by two-step synthetic method using trimethylamine borane as reaction substrate. Their structures and compositions were confirmed by ¹H NMR and ¹³C NMR, infrared and high resolution mass spectrometry, and properties were measured and calculated. The results show that resulting ionic liquids have good performances: decomposition temperature up to 150 ℃, densities from 1.04 to 1.27 g·cm^-3 and specific impulses from 173.8 to 202.1 s. With the increase of hydrocarbon side chains in imidazolium cations, densities of ionic liquids decrease while heats of formation increase. The dicyanamide ionic liquids show shorter ignition delay times than the corresponding nitrocyanamide ionic liquids. Among the ionic liquids, bis(1-allyl-1H-imidazole-3-yl)dihydroboronium dicyanamide possesses good comprehensive properties such as viscosity 69 mPa·s, decomposition temperature 180 ℃, heat of formation 753.6 kJ·mol^-1, ignition delay time 18 ms and specific impulse 176.7 s, therefore exhibiting application potential as the green fuel of hypergolic bipropellants.

Abstract:Quadricyclane (QC) possessing high strain and caged structure is a very promoting spontaneous ignition type hydrocarbon fuel. The synthesis process of QC in kilogram scale was studied under the condition of no solvent. The spontaneous ignition performance of QC/ white fuming nitric acid (WFNA) and QC/N₂O₄ was measured. After 16 h-reaction and further purification, the purity and yield of QC product can reach 99.5% and 96.2%, respectively. The batch production is 2 kg. The ignition delay time of QC/WFNA and QC/N₂O₄ are 98 ms and 29 ms, respectively. The addition of boron, carbon and aluminum nanoparticles can improve the spontaneous ignition performance. The boron, carbon and aluminum nanoparticles can shorten the ignition delay time. After adding the 0.25% mass fraction of boron/alumium/carbon nanoparticles, the ignition delay time is 68/73/75 ms (WFNA) and 18/27/33 ms (N₂O₄), respectively, proving that QC can be used as a kind of high-energy liquid propellant.

Abstract:Exo-tetrahydrodicyclopentadiene (exo-THDCPD) is an important high density liquid hydrocarbon fuel. To improve the synthesis efficiency of exo-THDCPD, a new process of continuous preparation of exo-THDCPD, including the cascade of two reactors (continuous-flow bubbling hydrogenation reactor and continuous-flow isomerization tank reactor), namely the cascade of two processes (dicyclopentadiene (DCPD) was hydrogenated to endo-THDCPD over Pd/C catalyst and the endo-THDCPD was isomerized to exo-THDCPD over AlCl₃ catalyst) was studied. The liquid-phase continuous-flow preparation of exo-THDCPD was realized. Results show that the optimum liquid-phase continuous-flow process conditions of preparing exo-THDCPD are determined as: weight hourly space velocity(WHSV), 2.4 h^-1; hydrogenation pressure(p_H), 0.1 MPa; H₂ gas flow rate, 80 mL·min^-1; DCPD concentration (C_DCPD), 0.76 mol·L^-1; hydrogenation reaction temperature: 30 ℃; isomerization; reaction temperature, 70 ℃; conversion of DCPD, 100% and yield of exo-THDCPD, 92.5%.

Abstract:The ignition delay times of toluene/O₂/N₂ and n-decane/O₂/N₂ were obtained in a reflection type shock tube, via measuring the shock pressure signal and the OH radical emission intensity signal using a measurement system consisting of pressure sensors, photomultiplier tubes and an oscilloscope. The experiment conditions are over the temperature range from 1175 K to 2023 K, pressure at 0.1 MPa and equivalence ratio of 0.5, 1.0 and 2.0. In the experiment, liquid fuel was atomized into fuel aerosol by the supersonic atomizer. Long shock tube dwell time (about 15 ms) was achieved by tailored contact surface operation under such conditions. Results show that the ignition delay times of toluene is longer than that of n-decane at the same ignition pressure and ignition temperature. With the increase in initial reaction temperature, the ignition delay times of toluene and n-decane shorten. The logarithm of ignition delay times is directly proportional to the reciprocal of temperature. The fluorescence intensity of OH radical in ignition process reveals different change rule at different temperature.

Abstract:Aiming at the problems on high toxic and hard degradable intermediates existing in unsymmetrical dimethylhydrazine (UDMH) degradation method at present, a detection method of ultraviolet(UV) spectroscopy to trace and analyze the oxidative degradation products of UDMH wastewater was established. The assignation of product peaks in UDMH wastewater degradation process was determined. The degradation products of two oxidation systems Cu²⁺/H₂O₂ system and Fenton system were analyzed. The degradation mechanism was deduced. Results show that the UV peaks of UDMH and unsymhydrazone(FDMH) are at 200 nm and 235 nm, respectively. Two systems can effectively degrade UDMH wastewater, but Cu²⁺/H₂O₂ system has more intermediate products and higher toxicity. The addition of H₂O₂ before adding Cu²⁺can reduce intermediates. The addition of iron powder is beneficial to decrease intermediates. Fenton system can effectively inhibit the producing of toxic intermediate products.

Abstract:The triamino trinitrobenzene(TATB)granule deformation and structural evolution during compaction process were studied by x-ray tomography technology and deformation characteristics of deformable material. The CT images show that the deformation orientations of granules in the central part are mostly downwards. In the meanwhile, there are arching between the granules near the edge of mould. The porosity changing mainly happens in the initial stage of compaction with the forming pressures of 0 MPa to 10 MPa, and the porosity of each part(5, 20, 35 mm away from the top surface) decreases 73%, 62% and 58%, respectively. During each compaction process, the porosity increases from the top down and the displacements mainly take place along the axial direction. Friction between the mould and granule is greater than that between the granules, which makes the displacements of the granules in the central part larger than granules at other parts. Results show that X-ray tomography can nondestructively characterize inner structural evolution of TATB granules during compaction. Morphology changes and contact relations of granules reveal the interaction mode between the granules. The displacements of granules indirectly reflect the internal stress transfer in the explosive.

Abstract:To study the energy releasing characteristics of aluminum powder in HMX based explosives, the quasi-static pressure of HMX/HTPB 88/12 and HMX/Al/HTPB 53/35/12 explosives containing aluminum powder with granularity of 13 μm and 130 μm respectively after explosion in an enclosed space was measured by pressure sensor. Results show that the quasi-static pressure after explosion of HMX /HTPB 88/12 and HMX/Al/HTPB 53/35/12 explosives in an enclosed condition can be produced. The quasi-static pressure of the HMX/Al/HTPB 53/35/12 explosive is 1.24 times greater than that of the HMX/HTPB 88/12 explosive. The quasi-static pressure of HMX/Al/HTPB 53/35/12 explosives containing aluminum powder with granularity of 13 μm and 130 μm respectively, produced by explosion in an enclosed space is 378 kPa and 347 kPa, respectively, meaning that under implosion condition when the content of aluminum powder is 35%, compared with the explosive with the large particle aluminum powers, the explosive with small particle aluminum powder can release more energy and improve the quasi-static pressure in an enclosed space.

Abstract:Friction sensitivity tests were conducted on the PBX-923 and PBX-2 tablets to study their reaction characteristics under compressed friction. The reaction overpressures of the explosive were obtained by blast pressure gauges to evaluate the reaction degree. Based on the data of overpressures and the recovered samples, reaction characteristics of these two explosives were analyzed. The ignition thresholds of friction work and corresponding friction powers were calculated and the ignition mechanism under compressed friction was analyzed. Results initially show that the ignition thresholds of friction work of PBX-923 and PBX-2 using smooth steel strip were more than 515.9 J and 583.2 J, respectively. And the corresponding friction powers were more than 10115 W and 11435 W, respectively. They were much higher than the ignition thresholds of friction work and the corresponding friction powers using sandy abrasive strip, which were between 294.7-368.3 J and 7.80-9.75 kW for PBX-923, and between 147.3-191.5 J and 3.90-5.07 kW for PBX-2, respectively. It confirms that the ignition of PBX is not directly caused by overall uniformly temperature rise during friction. Instead, shear induced ignition is probably the main ignition mechanism under compressed friction using sandy abrasive strap.

Abstract:In order to characterize the dynamic mechanical behavior of polymer bonded explosives (PBX), a macroscopic elastic-viscoplastic constitutive relation has been developed, coupled by the micromechanical damage mechanism based on the macro crack statistical method. Dynamic compressive and fracture test of the PBX(64%RDX and 20%Al and 16%HTPB) have been carried out, and the material contants and algorithm for the model have been presented. By comparing with the dynamic compressive test data and simulation results of PBX, this model can predict the mechanical deformation process under different loading conditions, so that it can be spread for the deformation analysis of heterogeneous explosives.

Abstract:With Fe₂O₃、CuO、Fe₃O₄、MoO₃ as oxidants, 50 nm or 5μm aluminum particle as reducer, twelve thermites were prepared by mixing them under ultrasonic shock. Structure and morphology of the thermites were studied by scanning electron microscope (SEM). The effects of oxidizer agent species and particle size of the materials on the reaction activity of thermites were studied by differential scanning calorimetry (DSC) and laser ignition. Results show that the dispersion of nanometer aluminum particle in MoO₃ is the best. The reaction order from high to low is Al/MoO₃ > Al/Fe₂O₃ > Al/CuO > Al/Fe₃O₄. When using nanometer aluminum particle, the critical reaction temperature of super thermites decreases 200-400 ℃, lower than that of micrometer aluminum particle. The critical reaction temperature decreases only 10-30 ℃ using nanometer oxidants, lower than that using corresponding micrometer materials. All the results indicate that particle size of aluminum particle is the key factor effecting the reaction activity of thermites, and ultra-refinement of oxidizer is only supplementary for the reaction activity of thermites. When the aluminum particle size locates on the same order, the reaction activity of thermites mainly depend on the species of oxidants.

Abstract:For the real evaluation of the bubble energy and the accurate calculation of bubble oscillation period of underwater explosion, according to the existing research payoffs of underwater explosion and the similarity law, a method of accurately estimating the bubble oscillation period of underwater explosion was presented. The formula estimating the bubble oscillation period of TNT explosive was obtained via three calibration experiments of TNT explosion in sea, and the error of calculated and the experimental one is smaller than -1.34%. The formula estimating the bubble oscillation period of Al/RDX/TNTT explosive was obtained via three calibration experiments of Al/RDX/TNTT explosion in sea, and the error of calculated and the experimental one is smaller than 1.45%. The bubble oscillation period is proportional to the 1/3 powers of explosive equivalent and is inversely proportional to the 5/6 powers of summation of the converted water depth of atmospheric pressure and water depth over explosion. The bubble oscillation period is badly affected by the types of explosives. The chemical characteristics of explosive and formulas used to calculate the bubble oscillation period have strong correlation. Use of calibration method in sea can accurately estimate the bubble oscillation period of underwater explosion. The error of the estimated value and the experimented one is smaller than 2.54%. The method is suitable for estimation of the bubble oscillation period value of underwater explosion of explosive.

Abstract:Based on the traditional shock absorption technology of air bubbles curtain, a new energy attenuation idea about air bubbles curtain generated by blasting was put forward. According to the conditions in the paper, the experiment was carried on to test this energy attenuation idea. Results showed that the explosion air bubbles curtain can reduce the peak pressure of shock wave, and the signal attenuation is as high as 60%, the specific impulse of shock wave by 62.2%. When wavelet packet decomposition technique is adopted to judge the attenuate effect of explosion air bubbles curtain, it can be concluded that explosion air bubbles curtain can attenuate different frequency shock wave effectively. Most shock waves of different frequency can be attenuated by more than 50%. Explosion air bubbles curtain can eliminate the high frequency part of the underwater explosion shock wave effectively. Only the low frequency part can pass the explosion air bubbles curtain, but the energy of it can be also weakened greatly.

Abstract:The thermal decomposition process of lead azide (LA) and carboxymethylcellulose lead azide (CMC-LA) was studied by dynamic vacuum stability test (DVST) method. The test data were analyzed by differential method. The reaction mechanism function and apparent activation energy of CMC-LA and LA were obtained. The influence rule of sodium carboxymethyl cellulose crystal control agent on the stability and kinetic parameters of the thermal decomposition reaction of LA was analyzed. Results show that in the non-isothermal stage, the mechanism function of the thermal decomposition reaction of LA in the temperature range from 60 ℃ to 100 ℃ is the Zhuralev-Lesokin-Tempelman equation, the apparent activation energy(E_a)is 86.53, 42.26, 39.43, 38.09 kJ·mol^-1 and 10.84 kJ·mol^-1, while thermal decomposition mechanism function of CMC-LA in the temperature range from 60 ℃ to 70 ℃ is the Avrami-Erofeev equation with E_a of 133.02 kJ·mol^-1 and 41.87 kJ·mol^-1 and thermal decomposition reaction mechanism of CMC-LA in the temperature range from 80 ℃ to 100 ℃ is the deceleration type α-t curve with E_a of 43.07, 34.34 kJ·mol^-1 and 33.46 kJ·mol^-1. Addding sodium carboxymethylcellulose changes the reaction mechanism function of LA, leading the gas production of CMC-LA smaller at 60 ℃ to 70 ℃, and with a better thermal stability.

Abstract:The optical properties: dielectric function, refractive coefficients, absorption and reflection spectra, etc. for NH₄ClO₄ crystal were calculated by the first principle method based on the density functional theory (DFT). The relationship between peaks in the dielectric function pictures and the inter-bands transitions in the band structures was analyzed. Results show that the static dielectric function ε₁(0) is 1.10, and the static reflectivity n₀ is 1.05, and the maximum absorption coefficient is 1.91×10⁵ cm^-1 corresponding to peak energy of 10.88 eV. The calculation results are in good agreements with experimental ones.

Abstract:The progress on research methods, influential factors and mechanisms of the deflagration-to-detonation transition(DDT) of energetic materials were summarized. The research methods for DDT mainly include experimental research and numerical simulation method.The influential factors for DDT are loading density, confinement condition, ignition ways and strength, physicochemical characters of material, etc The mechanisms of DDT mainly include "the shockwave grown-up theory" and "the locative heat explosive theory". The research on DDT in the future should be in accompany with the study on the safety of new high energy propellant and explosives. The three-dimension mathematical model of the border issues caused by energetic materials reaction, physicochemical characters and geometry effect of energetic materials should be considered for numerical simulation.

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