Abstract:

Abstract:To study the change rule of mesoscopic interface performance of HTPB/IPDI (hydroxyl-terminated polybutadiene/isophorone diisocyanate) composite solid propellant with the loading rate, based on the molecular dynamics algorithm, the mesoscopic particles packing model of HTPB/IPDI composite solid propellant was generated. Bonding effect between particles and binder was modeled by a rate-dependent cohesive zone model constructed via combining viscoelastic standard mechanical units and exponential type rate-independent cohesion zone model(CZM). The relaxation parameters of the matrix material in the meso-scle finite element model were obtained through stress-relaxation tests of HTPB/IPDI curing films. The macroscopic mechanical response of HTPB/IPDI propellant at different loading rates of 0.1, 5 mm·min^-1 and 20 mm·min^-1 was simulated and calculated based on the model. The inversion analysis of rate-dependent cohesive zone model parameters was performed through Hooke-Jeeves optimization algorithm using numerical simulation results and the uniaxial tensile test results curve of of HTPB/IPDI propellant. The optimized values of interface parameters were obtained. The macroscopic mechanical behavior of HTPB/IPDI composite solid propellant at the loading rates of 50 mm·min^-1 and 100 mm·min^-1 was predicted using the established model. Results show that the predicted results are consistent with the actual experimental ones.

Abstract:To solve the problem that the Hydroxyl-Terminated Polybutadiene(HTPB) propellant aging characteristics at different storage stages cannot be described by commonly used aging models accurately, the segmented aging model was proposed. The high temperature accelerated life test of the HTPB propellant was carried out, and the aging mechanism of HTPB propellant was analyzed in three stages by using the maximum elongation as the characteristic parameter. According to the correlation analysis results of different aging stages, the segmented aging model was established. The time conversion relationship between high temperature (60 ℃) accelerated aging and room temperature (25 ℃) effective storage was obtained by using the time-temperature equivalence principle, and the storage life of HTPB propellant at room temperature (25 ℃) is predicted for 11.60 years by combing with the segmented aging model. The correlation coefficient R of the segmented aging model is more than 0.95, and the standard deviation R_std is less than 0.015.

Abstract:To investigate the thermal safety of the base bleeding projectile, based on the two-step chemical reaction mechanism of ammonium perchlorate(AP)/hydroxyl-terminated polybutadiene(HTPB) base bleeding propellant, a two-dimensional unsteady state cook-off model of the base bleeding unit is built. The fast cook-off response characteristics of the base bleeding unit were analyzed under the conditions of the external heating rates of 1, 5 K·min^-1 and 10 K·min^-1, respectively. The results show that at heating rates of 1, 5 K·min^-1 and 10 K·min^-1, the first ignition points of the base bleeding propellant all occur near the outside end surface wall of the base bleeding propellant. The change in external heating rates has little impact on the ignition position of base bleeding propellant. With increasing the heating rate, the ignition time occurring cook-off response of base bleeding propellant reveals an exponential decay. At heating rates of 1, 5 K·min^-1 and 10 K·min^-1, the temperatures occurring cook-off response of AP/HTPB base bleeding propellant are 579.4, 574.0 K and 573.5 K, respectively. The effect of heating rateson the ignition temperature of base bleeding propellant is small.

Abstract:In order to reduce the glass temperature of star type energetic thermoplastic elastomers(SETPE) and enhance its pliability, a novel A_nB star type energetic thermoplastic elastomers(TSETPE) based on PBAMO/APP was prepared via a urethane reaction of functional prepolymers, using UPBAMO (monofunctionality poly(3, 3-bis-azidomethyl oxetane)) as hard blocks, APP (trifunctionality glycidyl azide polymer modified by polytetrahydrofuran with the number average molecular mass(M_n)of 4000~6000) as soft blocks, toluene 2, 4-diisocyanate as linking compound. The optimized time of blocking reaction of UPBAMO was determined as 2 h. Its performance were characterized by Flourier transform infrared spectroscopy, nuclear magnetic resonance, gel permeation chromatograph and mechanical property test. The number average molecular mass (M_n) of synthesized TSETPE was 15000~19000, the glass temperature of TSETPE decreased from -16.9 ℃ to -24.3 ℃ and the elongation (20 ℃) of TSETPE improved from 44.5% to 652%~919% as compared with SETPE which had similar M_n. The application study show that the TSETPE has good compatibility with commonly used energetic materials such as hexogen, aluminum powder, nitroglycerine, etc. The melt cast PBX explosive based on the TSETPE holds high energetic characteristics, and its heat of detonation can reach 7411 J·g^-1.

Abstract:A new energetic ionic salt bis-1, 2, 4-triazolium 1H, 1′H-5, 5′-bistetrazole-1, 1′-diolate (T₂BTO) was synthesized by using 1H, 1′H-5, 5′-bistetrazole-1, 1′-diol dihydrate (BTO) and 1, 2, 4-triazole as starting materials. Its structure was characterized by X-ray single crystal diffraction, FT-IR, ¹H NMR, ¹³C NMR and elemental analyses. Its thermal behavior was studied by differential scanning calorimetry(DSC) and thermogravimetry-derivative thermogravimetry(TG-DTG). Its kinetic parameters of thermal decomposition(activation energy E_a、E_O and pre-exponential factor A)were calculated by Kissinger′s and Ozawa′s method. The characteristic drop height of impact sensitivity (H₅₀) was determined by WL-1 type impact sensitivity test instrument. Its detonation velocity (D) and detonation pressure (p) were calculated by Kamlet-Jacobs empirical formula. Results show that the crystal of T₂BTO is monoclinic, space group C2/c with crystal parameters of a=15.2410(12) Å, b=10.5185(8) Å, c=7.7546(7) Å, V=1221.26(18) Å ³, ρ=1.688 g·cm^-3, Z=8. Its thermal decomposition temperature on DSC curve at 10 K·min^-1 is 519.9 K, there is only one stage on TG curve with a mass loss of 90.8 % between 453.2 K and 523.2 K, revealing a better thermal stability. E_K=144.39 kJ·mol^-1, E_O=145.52 kJ·mol^-1, ln(A/s^-1)=32.99, H₅₀>61.0 cm, D=7579 m·s^-1, p=24.49 GPa.

Abstract:Five kinds of composite explosives containing 1, 1-diamino-2, 2-dinitroethene(FOX-7) were prepared by mixing FOX-7 with five kinds of commonly used single-compound explosives, cyclotrimethylenetrinitramine(RDX), triaminotrinitrobenzene(TATB), 2, 6-diamino-3, 5-dinitropyrazine-1-oxide (LLM-105), cyclotetramethylene tetranitramine(HMX), hexanitrohexaazaisowurtzitane(CL-20) in the mass ratio of 1:1 respectively. Effect of temperature on the crystal phase transformation of FOX-7 in the composite exposives were studied by a variable X-ray powder diffraction technique. In the process of temperature increasing, the α→β crystal phase transformation of FOX-7 in five kinds of composite explosives occurs at 105-125 ℃. The β→γ crystal phase transformation of FOX-7 in FOX-7/HMX and FOX-7/LLM-105 composite explosives does not occur. In the process of temperature decreasing, the γ→α crystal phase transformation of FOX-7 in FOX-7/RDX composite explosive occurs directly. The crystal phase transformation of FOX-7 in other three kinds of composite explosives is reversible in the cooling and heating process, i.e. in the cooling process, the crystal phase transformation occurs from γ or β to α.

Abstract:To obtain the solvent-free single crystal of 3, 4-dinitropyrazole (DNP) structure, DNP was synthesized by a 3-step method using pyrazole as raw material. The single crystal of DNP was cultured by solvent evaporation method using ether as solvent. Its single crystal structure was determined by a X-ray single-crystal diffractometer. Results show that the crystal is monoclinic, space group is P2₁/c, with cell parameters of a=9.9801(8)Å, b=11.9959(9)Å, c=9.7192(7)Å, β=94.232(1)°, V=1160.41(15)ų, F(000)= 640, Z=8, D_c=1.80969 g·cm^-3.The existence of numerous intermolecular hydrogen bonds and the π-π stacking interaction existed between the DNP molecules make the DNP molecules stably exist.

Abstract:To obtain nano-1, 3, 5-triamino-2, 4, 6-trinitrobenzene(TATB) with controllable particle size and higher purity, nano-TATB was prepared by a spraying recrystallization method with trifluoromethanesulfonic acid as solvent and deionized water as non-solvent. The influence of preparation technology and pH on the particle size and purity of nano-TATB was studied. The morphology, specific surface area, crystal structure, purity and thermal decomposition characteristics of nano-TATB were characterized by field emission scanning electron microscopy(FE-SEM), BET(brunauer-emmett-teller) specific surface area test, high performance liquid chromatography(HPLC) and differential scanning calorimetry(DSC), etc. Results show that the volume ratio of solvent to non-solvent can affect the morphology and particle size of nano-TATB. With the decreasing volume ratio of solvent to non-solvent, the particle size of the sample becomes smaller and the size distribution is more uniform. Under the condition of volume ratio 1:50 and pH=7, nano-TATB particles with the size of 60 nm, uniform particles and specific surface area of 31.6 m²·g^-1 are obtained. The effect of pH value on the purity of nano-TATB is very important, with water washing to pH=7, the purity of the sample can reach 98.1%.

Abstract:To study luminous intensity of pyrotechnics composites containing nano composite material and aluminum powder, a nano composite material KClO₄/CNTs was prepared based on double decomposition reaction of NH₄ClO₄ and KOH. Its structure was characterized by fourier transform infrared spectrometer(FTIR) and X-radiffraction. The component contents of KClO₄/CNTs were analyzed by adopting chemical analysis method. The luminous intensity of different pyrotechnic composites, such as KClO₄/CNTs-Al and KClO₄-CNTs-Al and KClO₄-Al, was determined. Results show that KClO₄ can effectively be loaded on the surface of CNTs and is completely coated. The average diameter of the prepared KClO₄/CNTs composite material is 74.0 nm. The mass ratio of the two substances measured by chemical analysis method is 78:22. Compared with the KClO₄-CNTs-Al and KClO₄-Al pyrotechnic composites, the luminous intensities of KClO₄/CNTs-Al (its proportion by weight is 77:23) pyrotechnic composite are separately improved by 39.4% and 88.2%. The improvements of luminous intensity result from nanocrystallization of potassium perchlorate and the catalysis and combustion of carbon nanotubes, among them, the contribution of potassium perchlorate nanocrystallization to the luminous intensity is better than the carbon nanotubes.

Abstract:To explore the effect of HMX gradation on the rheological properties of the aldol based polymer bonded explosive, the material state under different HMX particle gradation ratio was investigated by power law model and Casson model. The results show that the material is a pseudoplastic fluid with thixotropy. The non-Newtonian index (n value) is negatively correlated with the content of small particles. The viscosity of the material has the maximum value at low shear rate of 2.15 s^-1 and positive linear relationship at high shear rate of 53.85 s^-1 with the small particles content. The yield value of the material is negatively correlated with the content of small particles. Moreover, the content of the middle particles has the greatest effect on the yield value. Considering that the material with higher n value, lower viscosity and lower yield value has the better rheological properties.

Abstract:To reasonably evaluate the thermal safety of explosive, the cook-off process for RDX-based polymer bonded explosive (PBX) cylinder was numerically simulated using self-written finite element software—dynamic response simulation package for energetic materials. The kinetic process of multi-step thermal decomposition reaction for explosive was realized. Change rule of the mass fraction of each components with temperature in the ignition area was explored. Results show that the primary thermal decomposition reaction at 400 K begins to accelerate. At 450 K, the secondary decomposition reaction occurs obviously. At 460 K, the third step reaction begins to accelerate, the final gas product gradually accumulates. When the mass fraction of final gas product is 0.006%, the ignition occurs. In addition, with the increase of heating rate, the ignition time of explosive is rapidly decayed and the temperature of the center is decreased.

Abstract:In order to improve the mechanical property of combustible cartridge case and adapt the feature of unit cartridge case charge, a kind of new combustible cartridge case(NCCC) was designed and manufactured. The mechanical property and combustion performance of NCCC and suction molding combustible cartridge case(SMCCC) were studied by experiment measurement. The burning-off property of NCCC in mixed charge with main charge was analyzed. Results show that compared with SMCCC, the tensile strength of NCCC increases from 32.68 MPa to 94.18 MPa and the compressive strength increases from 7.79 MPa to 11.78 MPa, revealing that its mechanical properties are significantly improved. But NCCC exists about 8ms ignition delay phenomenon and the pressure rises slowly, the burning rate is low in combustion process. When the percentage of NCCC is from 0% to 60% in mixed charge composed of NCCC and AGu-15 7/7H, the combustion residues in closed bomb are mainly from AGu-15 7/7H. The ballistic test of NCCC charge shows that it can meet the requirements of ballistic performance of unit cartridge case charge.

Abstract:To study the influence of porous copper dimension on its azide reaction, according to the different solubleness of copper azides and copper at 50 ℃ in 0.5 mol·L^-1 diluted hydrochloric acid, the reaction characteristics of copper particles with different sizes and monolithic porous copper with particle size of about 200 nm, thickness of 0.2-0.3 mm and density of 1.51 g·cm^-3 with gaseous diazoimide were analyzed by an ICP spectrometer. Results show that when the size of copper particle is about 0.5 μm, the average conversion of copper particle can reach 95.64%, the copper particle can react with gaseous diazoimide completely. When the thickness of porous copper is 0.2 mm, the conversion of the azide is greater than 97%.

Abstract:The effect of solvent volume ratio of dinitrogen pentoxide/nitric acid/acetic anhydride system on the synthesis of cyclotetramethylenetetramine (HMX) via the nitration of 3, 7-dinitro-1, 3, 5, 7-tetrazabicyclo[3.3.1]nonane (DPT) was investigated. Results show that the highest yield of HMX is 87.9% when the volume ratio of nitric acid/acetic anhydride is 3:2. Raman spectra reveals that, the concentration of nitronium ion in the system gradually decreases with increasing the ratio of acetic anhydride and the significant red-shift of the vibration frequency of nitronium ion occurs, revealing that the trend of the concentration of the nitronium ion with bending deformation in dinitrogen pentoxide ion pairs is increases first and then decreases. The dinitrogen pentoxide which is between the range of certain ion pairs and free ions, as well as certain electron donating effect for solvent system, may have appropriate nitrification ability and high reactiviy, and be conducive to the synthesis of HMX.

Abstract:In order to improve the function reliability of explosive null gate, the traditional and weak gap explosive null gate whose charge size are 0.8 mm×0.8 mm with different gap thicknesses are simulated by ANSYS/LS-DYNA software, and the simulation results are verified through experiments. The simulation results and experimental results show that an additional round air groove on the basis of traditional gap explosive null gate could contribute to shock attenuation and gap breakage. Gap window of the null gate for reliable action is increased from 0.6-0.7 mm to 0.7-1.0 mm, which improve the function reliability of gap null gate.

Abstract:Aim at the problem of easily passivation and poorly continuous usability of iron and carbon packings in iron carbon micro-electrolysis treatment of organic wastewater, the ultrasound (US)-zero valent iron/granular active carbon (Fe⁰/GAC) micro-electrolysis was used to degrade nitrobenzene wastewater. The continuous usability of Fe⁰ and GAC was studied. The effect of Fe⁰ dosage, GAC dosage and initial pH value of wastewater on nitrobenzene degradation by US-Fe⁰/GAC were investigated. The results show that, when Fe⁰/GAC is not changed, the removal efficiency of four batches of same nitrobenzene wastewater treated by US-Fe⁰/GAC is all about 90%, whereas under Fe⁰/GAC treatment, 4 times of nitrobenzene removal efficiencies are 48%, 36%, 25% and 17%, respectively. The ultrasound can not only maintain the high activety of iron and carbon packings to use them continuously, but also can effectively improve the removal efficiency of nitrobenzene treated by Fe⁰/GAC. The suitable operating parameters of degrading nitrobenzene obtained are Fe⁰ dosage 20 g·L^-1, GAC dosage 10 g·L^-1, initial pH=4 for wastewater. Under these conditions, after 80 min, the removal efficiency of nitrobenzene reaches 93% and the biochemical coefficient BOD₅/COD_cr of effluent reaches 0.32, which can meet the requirement of biochemical treatment.

Abstract:Hypergolic ionic liquids exhibit a potential application prospect in the field of green hypergolic propellents. The research progress in synthesis and performance of seven kinds of hypergolic ionic liquids, including dicyanamide, nitrocyanamide, borohydride, HP-cation, boronium, alminium, hydrazinium-based hypergolic ionic liquids were systematically reviewed. The initial combustion mechanism of dicyanamide-babed hypergolic ionic liquids was introduced. Combining the structure-activity relationship of hypergolic ionic liquids, pointing out that new hypergolic ionic liquids with the advantages of low vapor pressure, short ignition delay time, non-toxic, low characteristic signature, good thermal stability and green environmental protection are the focus of future research. In addition, the research of combustion mechanism for hypergolic ionic liquids could be done through detecting the highly active gaseous intermediate (HNCO etc) by using in situ IR spectroscopy in two stages of hypergolic process, and determining highly active gaseous species source. Based on the above technics, the accurate combustion mechanism of hypergolic ionic liquids can be finally deduced by means of quantum chemical calculation.

Abstract:

Abstract:

Abstract: