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Abstract:Quadricyclane is a liquid fuel with high strain caged structure.The gas chromatography mass spectrometer, fourier transform infrared spectroscopy and nuclear magnetic resonance spectrometer were used to characterize the molecular structure of quadricyclane, which was synthesized by photoisomerization. The pyrolysis products of quadricyclane at 300-800 ℃ were analyzed by pyrolysis gas chromatography mass spectrometer. Results show that the molecular structure of the synthesized quadricyclane is consistent with theoretical structure. The purity of quadricyclane is 94%, calculated by gas chromatography normalization. Some gasification products and their isomers are founded when the temperature is below 400 ℃. When the temperature is 500-650 ℃, the pyrolysis products are mostly cyclic olefins. With the increase of temperature, the pyrolysis products turn from cyclic olefins to benzene homologues. When the temperature is above 750 ℃, the pyrolysis products change to biphenyls and polycyclic aromatic hydrocarbon compounds.

Abstract:The ammonium perchlorate (AP) powder was coated and agglomerated to improve the powder propellant surface properties, which provided the conditions for Al/AP propellant long-term storage and high efficiency combustion. The energy characteristics of Al/AP powder rocket motor were calculated by Gibbs minimum free energy method, and the effects of the hydroxyl-terminated polybutadiene(HTPB) to AP powder on the loading density, hygroscopicity, and thermal decomposition were analyzed by pretreatment experiments. The ignition tests were conducted in the closed burner to study the effect laws of O/F and packing quality to the energy characteristic parameters of Al/AP powder propellant. The results show that, the optimal material ratio of AP pretreatment is 10%HTPB, and in this circumstance, the theoretical specific impulse of Al/AP powder rocket engine can be up to a maximum of 262.1 s at 3:1 of O/F. The energy characteristic parameters of powder propellant will increase with the growth of O/F in a certain rage; the gas generating quality of powder propellant per unit mass is basically equal at the same O/F, and both combustion temperature and velocity characteristics will increase with the growth of packing quality.

Abstract:Paraffin fuels are ideal energy for hybrid rocket engine owing to the characteristics of high regression rate. In order to study the relationship between the combustion characteristics and chemical components of paraffin fuel, the gas chromatography was carried out for 54^#, 58^#, 62^# and 66^# 4 kinds of macrocrystalline paraffin fuels, and measured the combustion heat and the regression rate in the oxygen flow rate of these 4 kinds of macrocrystalline paraffin fuels. In addition, the energy characteristics of these macrocrystalline paraffin fuels at different oxygen fuel ratio were calculated using NASA-CEA software. The results show that the average molecular formulas of the 54^#, 58^#, 62^# and 66^# 4 kinds of macrocrystalline paraffin were C_26.40H_54.80, C_27.59H_57.18, C_28.02H_58.04 and C_32.11H_66.22, respectively, and the percentage contents of the n-alkanes of the 54^#, 58^#, 62^# and 66^# 4 kinds of macrocrystalline paraffin were 92.79%, 89.44%, 88.36% and 84.55%, respectively. The bigger the carbon number as well as the less the percentage content of n-alkanes, the smaller the combustion heat of paraffin fuel. And the regression rates of paraffin fuels were reduced along with the increase of carbon number. According to the calculated results of NASA-CEA software, the theoretical specific impulse of paraffin fuels were decreased with the carbon number of paraffin increasing, and the adiabatic flame temperatures were increased with the carbon number of paraffin increasing, but these influences of the chemical components of paraffin fuels on the energy characteristics were insignificant. The optimum oxygen fuel ratio of 4 kinds of macrocrystalline paraffin were all 2.7, the theoretical specific impulse were all about 354 s more than HTPB, and the adiabatic flame temperature were all about 3600 K less than HTPB.

Abstract:The migrating components in the interface of the bonded samples of glycidyl azide polymer(GAP) based propellant/Hydroyl-Terminated Polybutadiene(HTPB) based liner/Ethylene-Propylene-DieneMischpolymere(EPDM) based insulation were determined by high performance liquid chromatography(HPLC) after aged at 50, 60 ℃ and 70 ℃. The apparent migration activation energy(E_a) and the average diffusion coefficients (D) of the migrating components were determined. The results show that during aging nitrate ester plasticizers of nitroglycerine(NG) and 1, 2, 4-Butanetriol Trinitrate(BTTN) migrated from propellant to liner and insulation. The E_a values of NG and BTTN were among 43-121 kJ·mol^-1 and their average diffusion coefficients were in the range of 10^-19-10^-16 m²·s^-1. The amine stabilizers of AD1 and AD2 were found to migrate during curing of the samples, while during storage, consumption of them was the main phenomenon. It could also be concluded that the content of AD1 had correlation with the mechanic property of the bonding system. When content of AD1 was less than 40%, the tensile strength of the samples decreased sharply.

Abstract:A new energetic compound 5-methyl-4-nitro-1H-pyrazol-3-(2H)-one (MNPO) was synthesized with total yield of 68%, using ethyl 3-oxobutanoate as raw material. Corresponding ion salts were prepared via. metathesis reaction and neutralization reaction by the reactions of MNPO with a series of high nitrogen cation. Their structures were characterized by single-crystal X-ray diffraction, Fourier transform infrared(FT-IR) spectroscopy, nuclear magnetic resonance(¹H NMR、¹³C NMR)spectrometry, elemental analyses and other means. Their thermal decomposition temperatures were measured by thermogravimetry(TG) and differential scanning calorimetry(DSC). Their detonation performances were calculated with Explo5 v6.02 software. Results show that the crystal of MNPO belongs to orthorhombic system, and its space group is Pbca with crstal parameters of a=71495(18) nm, b=1.1639(3) nm, c=1.3834(3) nm, V=1.1512(5) nm³ and Z=8. For energetic ion salts of MNPO with densities of 1.62-1.74 g·cm^-3, their decomposition temperatures are in the range of 181-272 ℃, theoretical detonation velocities are greater than 7000 m·s^-1 and detonation pressures are greater than 15 GPa. The measured impact and friction sensitivities are low, in which, the impact sensitivity of ammonium salt of MNPO is 28 J and the friction sensitivity 240 N.

Abstract:The fluorine-containing 3-azidomethyl-3-Methyloxetane (PAMMO) based thermoplastic elastomers were developed using PAMMO and the poly[3, 3-bis(2, 2, 2-trifluoro-ethoxymethyl)oxetane] glycol (PBFMO)preparing from a cationic polymerization as the raw materials, toluene-2, 4-diisocyanate (TDI) as the coupling agent to enhance its comprehensive properties. The molecular structure, relative molecular mass and mechanical properties of thermoplastic elastomers were confirmed by FT-IR, NMR, GPC, DSC, TG/DTG and universal testing machine respectively. The results show that the number average relative molecular mass of the thermoplastic elastomers was 38200, the decomposition temperature(T_d) was found to be 220 ℃, the tensile strength at break was 15 MPa, and the corresponding elongation was 700%. Therefore, the thermoplastic elastomers exhibited good thermal stability and mechanical properties.

Abstract:To reduce the mechanical sensitivity of RDX and improve its thermal decomposition performance, three kinds of RDX/Al/SiO₂ nano-composite energetic materials of RDX/Al mass fraction as 30%, 50% and 70% respectively (the mass ratio of RDX to Al is 6:1) were prepared by sol-gel method using tetramethoxysilane as precursor and fluorine boric acid as catalyst. Their morphology and structurre were characterized by scanning electron microscopy(SEM), energy dispersive spectrometer(EDS) and X-ray diffraction(XRD). Thermal performances of the samples were investigated by thermogravimetric analysis(TG) and differential scanning calorimetry(DSC). The mechanical sensitivity of the samples was measured according to GJB772A-1997 method. The results show that the RDX/Al/SiO₂ is the nano-composite energetic material formed by the Al and RDX into the skeletonn of gel as SiO₂. The minimum particle size of RDX in composite material is 65.09 nm, with increasing the RDX-Al content, its average particle size increases.When the mass fraction of RDX-Al is 30%, compared with the pure RDX, the decomposition temperature of RDX in the composite material decreases by 22.4 ℃, compared with the raw material RDX, the characteristic drop height (H₅₀) of the sample increases by 108.6 cm and the percentage of explosion decreases by 60%.

Abstract:In order to understanding the influence of binder content on residual stress and mechanical performance of polymer bonded explosive(PBX), the residual stress of warm compacted 1, 3, 5-triamino-2, 4, 6-trinitrobenzene (TATB) based PBX, with binder content ranging from 0 to 11%, were measured by VKα based X-ray diffraction method and mechanical properties were measured by Brazilian test. A simplified model of TATB crystal packed with binder structure was introduced for verifying the experiment results only in one condition of temperature. Results show that: the residual stress in PBX without any binder exhibits tensile mode is tension stress, with the binder content increasing, the residual stress reduces gradually. While the content of the binder is added more than 5%, the tensile residual stress reduces seriously. While the content is added from 7% to 9%, the residual stress turns to performing as compressive mode, the mechanical strength increases gradually with the more binder. The calculated residual stress of PBX agrees well with the experimental results. The experiment results can provide a reference for the formula design of reducing residual stress in TATB based PBX.

Abstract:The thermal oxidation characterization and its dynamic mechanism of micron-Al powders in air were investigated by simultaneous thermal analysis. Three kinds of micron-sized aluminum powders were heated up to 1110 ℃ at 10 K·min^-1 heating rate in air. The kinetic parameters of the oxidation reaction were calculated by Satava-Sestak integral method. By analyzing the obtained TG-DTG-DTA curves and using SEM and XRD to observe the oxidation products of different stages, it can be found the thermal reactivity of aluminum has size effect: the smaller the particle size is, the deeper the degree of oxidation is. The oxidation process of micron-Al powder is divided into three distinct stages. During stage Ⅰ, below 550 ℃, the oxidation rate is the lowest, the natural amorphous alumina layer on the particle surface grow slowly. During stage Ⅱ, 550-670 ℃, the oxide transformed into γ-Al₂O₃ which can′t form a continuous shell on the surface of Al particles completely, the oxidation rate increases rapidly at the beginning of the stage Ⅱ, but decreases to the minimum when γ-Al₂O₃ layer completely covers the particle surface again. During stage Ⅲ, 670-1110 ℃, because of the volume expansion of molten Al and the shrinkage of the surface area caused by the transition from γ-Al₂O₃ to α-Al₂O₃, the alumina layer produces cracks or breaks, the oxidation reaction is the most dramatic and produced only α-Al₂O₃ finally. Calculations prove that the smaller the particle size is, the lower the apparent activation energy of the oxidation reaction is, and the easier the reaction is. The most probable mechanism functions of thermal oxidation of the samples is the boundary control model function R₃: G(α)=G(α)=1-(1-α)^1/3 in the temperature range from 550 ℃ to 1110 ℃.

Abstract:To obtain the time windows of reliable effect for explosive null gate under the different gap thickness, the numerical simulation and the experimental research of improved explosive null gate with round air groove of charge size of 0.6 mm×0.6 mm and gap thickness of 0.6-1.1 mm were carried out through LS-DYNA software and test. The numerical simulation results show that when the gap thickness is less than 1.0mm, the closing time of explosive null gate dose not exceed 0.9 μs. However, with the further increase of the gap thickness, the success probability of explosive null gate will be significantly reduced. The explosive null gate fails even at 1.1 mm. The test results and simulation ones have a consistent regularity. When the gap thickness reaches 1.0 mm, the reliability time window of explosive null gate is [4.0 μs, + ∞). When the gap thickness is 1.1 mm, the success probability of explosive null gate is low.

Abstract:To investigate the response characteristic of PBX-2 explosive under projectile impact at ambient temperature and 75 ℃, the projectile impact tests of PBX-2 explosive were conducted by a high temperature impact test device. The reaction overpressure of the explosive was measured by the shock-wave overpressure sensor and the response characteristics of the explosive at ambient temperature and 75 ℃ were comprehensively analyzed using recovered samples. The stress variation of PBX-2 at ambient temperature and 75 ℃ at different impact velocities was calculated and analyzed using finite element program LS-DYNA. The results show that the threshold velocity of ignition reaction for PBX-2 explosive at ambient temperature is from 263.5 m·s^-1 to 269.9 m·s^-1, while the threshold velocity of ignition reaction for PBX-2 heated to 75 ℃ is from 316 m·s^-1 to 367 m·s^-1. Compared with ambient temperature state, when the projectile velocity is less than 800 m·s^-1, the reaction degree of PBX-2 at 75 ℃ obviously decreases. However, when the projectile velocity is higher than 800 m·s^-1, the impact pressure of about 1.54 GPa can make the PBX-2 at 75 ℃ occur violent reaction.

Abstract:In the tension and compression tests under quasi-static loading, almost all polymer bonded explosives (PBXs) reflect obviously nonlinear constitutive behavior, now commonly used constitutive model in the description of the nonlinear adaptability is not ideal. Aimming at the nonlinearity and asymmetry of stress-strain curves for five typical PBXs (PBX-X, PBX-9502, LX-17, PBX-9501, and EDC-37), a quasi-static constitutive model with four parameters that considers both tension and compression was deduced based on Boltzmann function. Based on the discussion of the physical meaning of undetermined parameters for the model, on account of determined method of undetermined parameters proposed in this paper, the stress-strain curves for five kinds of typpical PBXs were fitted by the constitutive model. Results show that the constitutive model can well describe the constitutive behavior at different temperatures and strain rates for typpical PBXs. The constitutive model of tension and compression based on the Boltzmann function is expected to be widely used as a universal quasi-static constitutive model for different PBX materials.

Abstract:The extended finite element method(XFEM) is applied to analyze the cracking failure mechanism of the whole process from local crack initiation to crack growth, in the PBX-9502 platelike specimen with cavity subjected to overall compression. The nonlinear constitutive behaviors and failure of PBX under complex stress states were described by means of stress state dependent strength surface, non-associated flow rule and cohesive model. Comparison between the numerical simulation results and Los Alamos National Laboratory (LANL) test ones was carried out. Results show that the plate with cavity produce local tensile stress around cavity in the overall compression environment and this tension condition leads to local cracking initiation. The overall development trend of numerical simulation for cracking is in agreement with experimental results, including overall trend of crack history, feature of crack-time curve, crack initiation moment, crack initial speed, etc. Based on the XFEM and cohesive model method, the crack initiation and growth of PBX energetic materials can be simulated.

Abstract:Using 3, 3′-bis(nitromethyl ONN azoxy)azoxyfurazan(BNMAF) as starting material, an excellent energetic compound 3, 3′-bis(trinitromethyl ONN azoxy)azoxyfurazan(BTNAF) was synthesized via two steps (nitration and second nitration)with a total yield of 68.7%. The thermal behavior of BTNAF was investigated by differential scanning calorimetry(DSC) for the first time (melting point: 59-61 ℃, decomposition point: 183.6 ℃, decomposition heat: 1989 J·g^-1) The physicochemistry and detonation performances of 3, 3′-bis(nitromethyl ONN azoxy)azoxyfurazan(BNMAF), 3, 3′-bis(dinitromethyl ONN azoxy)azoxyfurazan(BDNAF) and BTNAF were fully analyzed and compared by Gaussian, which revealed that BDNAF (detonation velocity: 9560 m·s^-1; detonation pressure: 42.40 GPa)and BTNAF (detonation velocity: 8944 m·s^-3; detonation pressure: 38.48 GPa)were two promising energetic compounds with outstanding performances.

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