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Abstract:The energy performances of glycidyl azide polymer (GAP)/ nitrocellulose(NC) cross-linked modified double-base propellant, in which GAP modified nitrocellulose powders was used as binder, were calculated by a propellant energy characteristic calculation program. The smoke signature of the propellant was evaluated by the content of Al₂O₃ and HCl in combustion products. Results show that with increasing the content of plasticizer glycidyl azide polymer azide (GAPA), the theory specific impulse increases first and then decreases. With increasing the content of GAP in binder, the theory specific impulse decreases and combustion temperature decreases. And the smaller the plasticizing ratio is, the larger the decreasing amplitude will be. The content of GAPA and GAP has little effect on the smoke signature of the propellant. Replaced ammonium perchlorate (AP) with 4, 4-dinitro-3, 3-diazenofuroxan(DNAF), when the content of solids is 60%, and the theory specific impulse is 2600 N·s·kg^-1, compared with the combustion products of AP formulation, the combustion products of GAP/NC propellant don't contain HCl, while the content of N₂ increases by 44% and the content of Al₂O₃ decreases by 67%, indicating that GAP/NC propellant is a prominent propellant with high energy and low characteristic signal.

Abstract:To compare the properties of the hexanitrohexaazaisowurtzitane (CL-20)/ cyclotetramethylenete-tranitramine (HMX) cocrystal and CL-20/HMX blends, the cocrystal structure and blending structure with the molar ratio of CL-20 and HMX as 2：1 were constructed respactively. The mechanical properties,structure stability and radial distribution function of the cocrystal system and blending system were simulated by molecular dynamics (MD) method. Simulation and calculation results show that the cocrystal process of CL-20/HMX can significantly improve the antideformation ability and ductility of the system. The tensile modulus of the cocrystal structure is greater than that of blending structure. The maximum bond length(L_max)decreases in the order CL-20/HMX blends＞ε-CL-20＞β-HMX＞CL-20/HMX cocrystal. The structure of CL-20/HMX blends is sensitized by the interaction in which Van der Waals force predominate. The cohesive energy density (CED) value of CL-20/HMX cocrystal structure is far greater than that of CL-20/HMX blends structure. The low sensitivity of CL-20/HMX cocrystal system is caused by the existence of hydrogen bond CH…O with relatively short length.

Abstract:GAP-ETPE/NC polymer blends were prepared using glycidyl azide polymer(GAP) based energetic thermoplastic elastomer(ETPE) and nitrocellulose(NC) with different mass ratios by solution blending process. The structure of the GAP-ETPE/NC polymer blends was characterized by fourier transform infrared spectroscopy(FT-IR) and wide X-ray diffraction(WXRD). The thermal and mechanical properties were investigated by dynamic mechanic analysis(DMA), universal testing machine, shore durometer, and thermogravimetric(TG) analysis. Results show that the prepared GAP-ETPE/NC polymer blends have typical features of azido-typed polyether-based polyurethane and nitrocellulose. Compared to NC, their structural compatibility and thermal stability are certainly improved. Besides, the degree of crystallinity and orientation is promoted with increasing of NC content, which increase the strength and modulus of polymer blends. Meanwhile, there are significant improvements of elongation and low-temperature mechanical properties with the increasing of the GAP-ETPE content. When the mass fraction between GAP-ETPE and NC decreases from 5/5 to 3/7, the tensile strength increases from 20.7 MPa to 39.2 MPa, while breaking elongation decreases from 141% to 40.6% for GAP-ETPE/NC polymer blends.

Abstract:The thermal decomposition behavior of hydroxyl-termined polyether(HTPE)/ 1, 1-diamino-2, 2-dinitroethene (FOX-7) and HTPE/N-guanylurea-dinitramide(FOX-12) mixed systems under different heating rates(2.5, 5.0, 10.0 ℃·min^-1 and 20.0 ℃·min^-1)were investigated by differential scanning calorimetry(DSC) and thermogravimetry-derivative thermogravimetry(TG-DTG)analysis. The thermal decomposition apparent activation energy of HTPE, HTPE/FOX-7 and HTPE/FOX-12 mixed system were calculated by Kissinger′s and Ozawa′s methods. Results show that the thermal decomposition apparent activation energy of HTPE by Kissinger′s is 127.45 kJ·mol^-1. Thermal decomposition of HTPE is a mass loss process. Apparent activation energy of HTPE/FOX-7 mixed system calculated by the two methods are 288.16 kJ·mol^-1 and 270.85 kJ·mol^-1, respectively, and 179.50 kJ·mol^-1 and 170.35 kJ·mol^-1 for HTPE/FOX-12 mixed system.Compared with FOX-7 and FOX-12, the apparent activation energy of mixed systems decrease by 17.1-34.5 kJ·mol^-1 and 78.8-87.9 kJ·mol^-1, respectively. The main decomposition peak temperature for insensitive energetic components (FOX-7 and FOX-12) are decreased by HTPE with 14.4 ℃ and 17.4 ℃. The heat release during decomposition process for HTPE/FOX-7 mixed system increases 196.2 J·g^-1 and decreases 275.2 J·g^-1 for HTPE/FOX-12 mixed system.

Abstract:To establish a rapid quantitative test method of blending uniformity of modified double-base propellant components, a near infrared (NIR) spectrometer was adopted to test the double-base absorbed sample and to quantitatively analyze the contents of each component and their dispersion uniformity. Firstly, based on sample testing, the quantitative calibration models of the components: nitrocellulose(NC), nitroglycerine(NG), cyclotrimethylenetrinitramine(RDX) and water were established and the correlation coefficients of each component model are more than 0.98, and the mean values of components′ absolute errors obtained by internal validation are less than 2%. Then NIR spectra of samples in the blending process were continually collected. The component contents of sample were predicted by the established models. The absolute errors of the predicted results and the actual values are less than 2%. The blending uniformity of sample was analyzed by coefficient of variation (CV) method for the contents of each component and and moving block standard deviation (MBSD) method for the original spectra of samples. The CV values of each component are less than 1.5%, while MBSD value of the sample is less than 0.001. Two kinds of evaluation indexes have reached steady state after 2.5 min, indicating that sample components had uniform distribution. Results show that it is feasible to use near infrared (NIR) spectroscopy to test the blending uniformity of modified double-base propellant components.

Abstract:A novel high energetic density compound 2, 6-dinitro-3, 7-dis(nitroimino)-2, 4, 6, 8-tetrazabicyclo[3.3.0]octane (TNGG)was synthesized using 3, 7-bis(nitroimino)-2, 4, 6, 8-tetraazabicyclo[3.3.0]octane as raw material and acetic anhydride as acylation reagent by acylation reaction and nitration reaction.Its structure was characterized.The factors affecting the yield of TNGG were investigated.Its thermal decomposition behavior was studied by thermogravimetric-differential scanning calorimetry(TG-DSC)analysis.Based on the density, the detonation performance of TNGG were obtained by isodesmic reaction and Kamlet-Jacobs formula.Results indicate that the yield of TNGG is up to 31.3% under the optimum synthetic conditions of reaction time 15 min, reaction temperature 25 ℃ and 98% fuming nitric acid/phosphorus pentoxide as nitrating system.The TG-DSC curves show that the thermal decomposition of the compound is completed within 700 ℃, with the mass loss about 100%.The thermal decomposition peak temperature of TNGG is 182.6 ℃, indicating that it has a good thermal stability.Theoretical calculations show that the hydrolysis stability of TNGG is better than that of tetranitroglycoluril (TNGU).The theoretical detonation velocity and detonation pressure of TNGG are 9.76 km·s^-1 and 44.0 GPa, respectively, better than those of HMX and RDX.

Abstract:5, 5′-Dinitramino-3, 3′-bi[1.2.4-triazolate] carbohydrazide salt(CBNT)was synthesized via ring formation reaction, nitration reaction and salt formation reaction using oxalic acid and aminoguanidinium bicarbonate as starting materials.Its structure was characterized by IR, NMR and elemental analysis.The thermal behavior of CBNT was studied by differential thermal analysis /thermogravimetry (DTA-TG)and its impact sensitivity and friction sensitivity were measured.Results show that the temperature of exothermic decomposition peak for CBNT is 229 ℃.Its impact sensitivity (H₅₀)is 89 cm, and friction sensitivity in explosion percentage is 4%-8%.

Abstract:The composite energetic material nPS/NaClO₄ was prepared by using nano porous silicon (nPS) as reducing agent and sodium perchlorate (NaClO₄) as oxidizer. And its thermal decomposition was analyzed by differential scanning calorimetry (DSC)-thermogravimetric (TG) analysis in a wide temperature range from 25 ℃ to 1200 ℃. To better understand the properties of nPS/NaClO₄, the thermal decomposition of nPS, NaClO₄, Si/NaClO₄, nPS/NaCl were analyzed, respectively. Results show that the Si—H bonds was broken around 400.0 ℃ in the oxygen atmosphere, and 820.0 ℃ in the argon atmosphere. The exothermic decomposition peak for NaClO₄ was 587.8 ℃ with the total mass loss of 68.31%. The exothermic decomposition peak for nPS/NaCl composite material was 883.3 ℃ with heat release of 567.0 J·g^-1. The heat releasing for nPS/NaClO₄ reached 359.5 J·g^-1, 15.3 J·g^-1 more than that of Si/NaClO₄ under the same condition, which may be due to the existence of Si—H bonds. Based on the analysis of thermal test results, thermal decomposition mechanism for nPS/NaClO₄ composite energetic material may be as follows: the cleavage of the Si—H bonds is in advance for the existence of O₂, which participates in the exothermic reaction. The remaining Si—H bonds after 800 ℃ react with NaCl and generate Si. The XRD spectra of solid combustion product of nPS/NaClO₄ allow a convincing check of the validity of the mechanistic assumptions.

Abstract:The crystal structure of the solvate formed by explosive and solvent is very unstable, and it is easy to transfer to explosive crystal with the removal of the solvent molecules under certain conditions.To investigate the changes of microstructure and properties of hexanitrostilbene(HNS)/1, 4-dioxane(Dioxane) solvate in the process of rapid desolvation, the desolvation way of in-situ pyrolysis to sovent by in-situ X-ray powder diffraction(XRD) made the solvate decompose and a preliminary study of the micro-structure change and macro performance were performed.Results show that the desolvation of HNS/Dioxane solvate can be realized by in-situ XRD technique and the obtained HNS has microcrystal cluster and fine porous structure.Compared with conventional HNS, the surface area of desolvated HNS significantly increases from 1.6 m²·g^-1(raw HNS) to 3.7 m²·g^-1.The value of characteristic drop height H₅₀ of impact sensitivity decreases from 109.3 cm for raw HNS to 28.9 cm for desolvated HNS, and the value of energy required for initiation E₅₀ of electrostatic spark sensitivity decreases from 0.896 J for raw HNS to 0.413 J for desolvated HNS.The value of explosion probability point P of friction sensitivity decreases from 36% for raw HNS to 12% for desolvated HNS, revealing that the fast desolvation method of explosive of the solvate not only can obtain micro/nano porous HNS but also can effectively improve the response to different stimuli.

Abstract:To study the effect of hole structure on tensile behavior of polymer-bonded explosive(PBX), a plate specimen with-hole was designed and digital image correlation method (DICM) was applied for strain analysis. The quasi-static tension results show that brittle fracture occurs at the edge of hole. Moreover, as the main characteristic failure parameter, the strain component ε_yy, reaches the critical value at the horizontal edge of the hole, and then cracks initiates and propagates to failure. Except for the significant heterogeneity and asymmetry, the strain distribution agrees well with the theoretical analysis. The inhomogeneity and microscopic defects of the materials may take a major responsibility for the imperfect distribution of the strain field. The defects near the hole may remarkably deteriorate the strength of the structure, even though the strain concentration around the hole is the critical reason of specimen failure.

Abstract:Using N, N-dimethylformamide (DMF) as solvent, nitrated bacterial cellulose (NBC) solutions with different nitrogen contents were prepared according to a certain proportion. The effects of solution concentrations and nitrogen contents of NBC on the viscosities of NBC solutions and the dependence relationship of concentrations and viscosities of the solutions were studied by a HAAKE rotational rheometer, and the viscoelasticity of NBC solution was analyzed through its stress scanning and frequency scanning. Results show that the solution system is the Newtonian-fluid when the concentration of NBC solution is in the range of 0.5%-5.0%, and the viscosity increases as the increase of the solution concentration, meeting an exponential function growth relation. When the concentration of NBC solution is 5.5%, NBC solution is the non-Newtonian fluid, showing a shear thinning effect, and the shear stress and shear rate meet a power function growth relation. The viscosities of NBC solutions increase with the increase of NBC molecular weight. NBC with high molecular weight helps to improve the stability of the solution system and makes it less response to external stimulus.

Abstract:In order to study the relationship between the heating rate and the critical temperature of thermal initiation of cook-off bomb in defined conditions, experiments were carried out with a self-designed test setup. Cook-off bomb with RDX based high energy explosives was heated at a heating rate of 1 ℃·min^-1 and then makes the outer wall temperature of case keep at 160, 170, 180, 185 ℃ and 195 ℃ respectively for 50 min and then the response of cook-off bomb was observed. The critical temperature of thermal initiation of cook-off bomb at different heating rates was simulated by FLUENT software. Results show that explosive in constant high temperature environment is more dangerous than slow heating. The environment temperature of the reaction is lower and the response is more intense. When heating rate is 1 ℃·min^-1, the critical temperature of thermal initiation of cook-off bomb is 194.8 ℃. In addition, the critical temperature of thermal initiation increases slowly with the increasing of heating rate. When heating rate is larger than 10 ℃·min^-1, the critical temperature of thermal initiation is 197 ℃. When cook-off bomb is heated to its critical temperature of thermal initiation at different heating rates and then the temperature is kept constant until the response, the heating rate has no influence on the ignition position of cook-off bomb under the given conditions. Ignition point is always in the center of explosives.

Abstract:Carbon nanotubes (CNTs) array confined with nano copper was prepared by electrochemical deposition method with CNTs array as working electrode. The effect of electrodeposition parameters on deposition of copper nanoparticle filled on CNTs array was studied. CNTs array confined with copper azide was obtained by gas-solid in-situ reaction. Scanning electron microscope, X ray diffracmeter and differential scanning calorimetry were used to characterize the structures and thermal properties of CNTs array confined with copper azide and nano copper. Results show that CNTs array confined with nano copper can be obtained at 1 mA and 10 mA. CNTs is not react wiht HN₃ during the in-situ process. CNTs array confined with copper azide can be initiated by thermal stimulus reliably. The 50% fire energy by Langlie method is 3.09 mJ.

Abstract:To promote the research on curtain damping technology of explosion bubble and reveal the pulsation rule of underwater explosion bubble with low energy detonating cord(LEDC), an experimental research on the pulsation characteristics of underwater explosion bubble with single or two horizontal and vertical placed LEDC was carried out by a high-speed photography system. The pulsation characteristics of bubble under different placement of LEDC were obtained. The results show that the shape of the bubble pulsation at the first time is cylindrical when the single horizontal LEDC is exploded under water. The first period of the bubble pulsation is 11.5 ms, and the maximum diameter reaches to 6.9 cm. Under the conditions of two horizontal LEDC, the first period of the bubble pulsation is 14 ms and two bubbles begin to merge with each other and form a bubble curtain layer at 22 ms. The first period of the bubble pulsation of two horizontal LEDC is longer than that of one horizontal LEDC. Under the conditions of two vertical LEDC, the first period of the bubble pulsation is 27.5 ms. The first period of the bubble pulsation of two vertical LEDC is also longer than that of one vertical LEDC and a fully integrated bubble curtain is formed at 79.5 ms which is still visible at 323 ms. When the vertical placed LEDC are wrapped into a network, the bubble pulse duration is longer, and it was conducive to the formation of the explosion bubble curtain.

Abstract:To study the cracking phenomenon at the end of Al/steel clad pipe by interior explosive expansion under water and interface bonding form, a reliable polyvinyliene fluoride(PVDF) piezoelectric film sensor was first used for testing the impact pressure of Al/Steel coaxial pipe by interior explosive expansion under water, and the pressure history curves were obtained and compared. Results show that the impact pressure peak of base pipe and flyer pipe along the detonation wave transmission direction of metal detonating cord reveals an increasing trend, indicating that the direct cause of the cracking phenomenon at the end is an increase in pressure. The calculated mean of peak pressure is 532.9 MPa. According to the relationship between the impact velocity and the impact pressure of explosive cladding, the impact velocity obtained in the case of the known impact pressure is 52.57 m·s^-1. From the explosive welding interface bonding mechanism and the metallography knowledge, the impact temperature produced by the interface impact is not high enough to make the interface melt. The metallographic photos of interface reveals that its way of combination is direct bonding between metal without the transition layer and melting phenomenon, showing that measuring the impact pressure of interior explosive expansion under water by PVDF piezoelectric film sensor and inferring the interface bonding form by the obtained data are feasible.

Abstract:Mechanical properties and constitutive models of solid propellants were reviewed from experimental techniques, mechanical parameters determination and developing constitutive models. Based on that, the current shortage and future research contents were also proposed. Firstly, up to now, experimental techniques of mechanical properties on solid propellants is still difficult under dynamic loading conditions and multiaxial stress conditions. Solving this problem can refer to the test methods for other strain-rate sensitive materials. Secondly, there is limited information available on the relationship of the mechanical parameters for solid propellants under different stress conditions. To solve this problem, it is necessary to refer to the research methods or means and basic conclusions of other nonmetal materials. Finally, there is a great gap between the practical need and the current studies on the constitutive models of solid propellants, especially the large deformation nonlinear viscoelastic constitutive models under dynamic loading conditions. The method of developing integral-type nonlinear viscoelastic constitutive models incorporating the damage on a macro-scale can be suggested to establish the constitutive models. However, the main emphasis is to derive and solve the damage function, which should be properly selected based on the deformation of solid propellants under dynamic loading conditions.

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