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Abstract:To develop new series of tetrazole energetic materials， two new compounds， magnesium and calcium salts of 1，2-bis（tetrazol-5-yl）ethane （［Mg（BTE）（H₂O）₄］_n·nH₂O and ［Ca（BTE）（H₂O）₅］_n） were prepared. Their single crystals were obtained by solvent evaporation method. The structures were fully characterized by X-ray single crystal diffraction， elemental analysis and FT-IR method. The thermal decomposition behavior of two compounds were studied by DSC and TG-DTG methods Their non-isothermal kinetic parameters were calculated by the Kissinger method and Ozawa method. Results show that ［Mg（BTE）（H₂O）₄］_n·nH₂O belongs to monoclinic system，space group P2₁/c，cell parameters：a=9.0367（18） Å，b=9.1427（18） Å，c=7.4491（15） Å，β=103.51（3）°，Z=2. ［Ca（BTE）（H₂O）₅］_n belongs to orthorhombic system， space group Pnnm， cell parameters： a=11.205（2） Å，b=13.605（3） Å，c=7.1415（14） Å，Z=4.The temperatures of first exothermic peak for ［Mg（BTE）（H₂O）₄］_n·nH₂O and ［Ca（BTE）（H₂O）₅］_n are 387.7℃ and 415.8℃， respectively.

Abstract:A new seven-membered cyclic compound 7-hydroxytrifurazano［3，4-b：3′，4′-f：3″，4″-d］azepine （HYTF） was synthesized using bis（3-nitrofurazan-4-yl）furazan and hydroxylamine solution as starting materials. The structure of HYTF was characterized by IR， ¹³C and ¹⁵N NMR and elemental analysis. The chemical shifts of ¹³C and ¹⁵N NMR for HYTF were assigned based on the experimental results and theoretical simulation （Gauge Independent Atomic Orbital）. 7-Hydroxytrifurazano［3，4-b：3′，4′-f：3″，4″-d］azepine （HYTF） and 7H-trifurazano［3，4-b：3′，4′-f：3″，4″-d］azepine （HATF） could be synthesized by controlling the reaction temperature， and their formation mechanism were proposed and illuminated. Based on the experimental density （ρ=1.86 g·cm^-3） and calculated enthalpy of formation（Δ_fH（s）=573.8 kJ·mol^-1）， the detonation velocity （8181 m·s^-1） and detonation pressure （28.0 GPa） of HYTF were calculated by Explo5 （V6.04）. In addition， the thermal stability （T_dec=161.8 ℃） was analyzed by differential scanning calorimetry （DSC）.

Abstract:In order to obtain a CL-20 based energetic film that can be reliably detonated at the micrometer scale， hexanitrohexaazaisowurtzitane （CL-20）， ethyl cellulose （EC） and poly azido-glycidyl ether （GAP） are selected as the main explosive and bonding system respectively， two ink formulations suitable for the micro-spray direct writing process have been designed and formulated with adding an appropriate amount of low-boiling solvent. The two ink materials are directly written by a double-nozzle microjet direct writing device. The molded samples were characterized by scanning electron microscope， MZ-220SD electron density meter and X-ray diffractometer. The impact sensitivity， thermal decomposition performance and critical thickness of the entrapped film were investigated. Results show that CL-20 based energetic film has a smooth surface and many tiny pores inside， the microstructure size is about 1 μm. The crystal form of CL-20 in membrane is ε type. The forming density of the energetic film is 1.547 g·cm^-3， reaching 79.2% of the maximum theoretical density. The apparent activation energy of thermal decomposition and drop height （impact sensitivity） of CL-20 based energetic film is 241.21 kJ·mol^-1 and 65.7 cm apart， which are both improved compared with raw material CL-20. The critical detonation thickness of the energetic film is 1.0 mm×0.045 mm， demonstrating excellent microscale detonation capability.

Abstract:To improve the catalytic effect of nano metal oxides on the thermal decomposition of AP， butterfly wing-shaped titanium dioxide （BW-TiO₂） has been prepared by impregnation-calcination method based on the template of a natural Morpho Butterfly wing. Field emission scanning electron microscope（FESEM）， transmission electron microscope（TEM）， X-ray diffraction （XRD）， and X-ray photoelectron spectroscopy （XPS） were used to characterize its morphology， structure， and composition. The catalytic performance of BW-TiO₂ for the thermal decomposition of ammonium perchlorate（AP） was studied using the differential scanning calorimetry（DSC）. The results show that the as-prepared BW-TiO₂ owns a anatase phase with a size of 8~12 nm， accompanying with small amount of amorphous carbon and Ti. BW-TiO₂ tightly resembles into a parallel grid skeleton structure， containing well-connected nano tubular channels and a large number of micro-pores. BW-TiO₂ illustractes excellent catalytic activity for AP thermal decomposition. Adding 5% BW-TiO₂ can reduce the high-temperature decomposition peak temperature from 429.1 to 374.1 ℃， increase the exothermic heat from 255 to 1323 J∙g^-1， and decrease the active energy from 190 to 130.9 kJ∙mol^-1.

Abstract:To explore the effect of polytetrafluoroethylene（PTFE） content and sintering temperature on the morphology and combustion performances of aluminum powder （Al）/PTFE composites， the ball mill-sintering process was used to prepare Al/PTFE samples. These samples have been characterized by scanning electron microscopy（SEM） and X-ray diffractometer （XRD）， and the effect of PTFE content and sintering temperature on the microscopic morphology of the composites has been studied. The combustion processes have been analyzed using a confined combustion chamber， coupled with a high-speed camera and infrared thermal imager. The effects of PTFE content and sintering temperature on the combustion performances of the composites have been explored. The results show that sintering at 340 ℃ can make the composites form a regular core-shell structure. When the PTFE content is less than 35%， the integrity of the particle coating optimizes with the increasing of the PTFE content. However， when the PTFE content continues to increase， the shape of the composite particles becomes irregular， and the condensed products begin to agglomerate. With the increase of PTFE content and sintering temperature， the burning rate， radiation intensity， and the flame temperature of the samples all show a trend of first increase and then decrease. Compare the samples prepared under the optimal conditions （35% PTFE content， sintering temperature 340 ℃） with the ones prepared under other conditions， the combustion pressure can be increased by 16%， whereas the combustion time is shortened by up to 37%， so that the central flame temperature increases by 317.1 ℃. This indicates that the appropriate amount （35% optimal） of PTFE content and proper sintering temperature （340 ℃ optimal） will significantly improve the combustion performances of the composite particles.

Abstract:In order to accurately describe the shape of behind-armor debris cloud from vertical penetration of a finite-thickness target plate by an explosively formed projectile（EFP），the dimensional analysis and the theory of orthogonal design were used as bases in this work. The effect of EFP molding parameters and the material parameters of projectile and target plate on the shape of behind-armor debris cloud were studied using SPH algorithm in AUTODYN software. A mathematical description model of the debris cloud shape behind armor from vertical penetration by an EFP was established. The shape parameter of major semi-axis of behind-armor debris cloud from a vertical EFP penetration was calculated using that model and compared with the simulated and related experimental results. It is proved that the error between the calculated major semi-axis result of debris cloud by that model and the related experimental result is controlled within 3%，and the shape of behind-armor debris cloud formed by an vertical EFP penetration can be described accurately with this model.

Abstract:In order to obtain propagation laws of shock wave inside the bunker under different working conditions, 48 explosion tests at various buried depths were carried out using an underground engineering model that could be assembled by steel structural units. Waveforms of shock waves were measured by piezoresistive pressure sensors mounted on the sidewall of the structures. From the measured data, distribution formulas on positive pressure impulse and action time of shock wave in the underground bunker under deep drilling explosion conditions were studied. The results show that values of representing characteristic parameters of shock waves are mainly related to the reinforcement ratio of the covering layer, the proportional blast height of the charge, the proportional blast distance and the proportional diameter of the cross section of the structure. Correlation coefficients of fitted algorithms are greater than 0.8, and average errors are less than 20%; therefore the engineering models can provide load basis for analysis and design of underground structures against blast damage.

Abstract:In order to further study the detonation growth characteristics of main explosive shocked by booster in detonation sequence， the high speed scanning camera was used to capture the propagation trajectory of the detonation wave in the main explosive along the lateral axis， and the detonation propagation process was analyzed by means of numerical simulation. The results show that compared with the HMX-based ideal explosive， the charge of booster plays a greater impact on the development of the detonation wave in TATB-based non-ideal explosive. The detonation wave growth distance becomes longer and the stable detonation occurs at the distance 40mm， when the booster size reduces to Φ10 mm×5 mm. Different from 1D shock ignition test， the initiation process in main charge shocked by the smaller diameter booster has the two-dimensional effects. Thus， the difference of detonation chemical reaction rate along axis and radial direction plays an important roles on the detonation transfer reliability.

Abstract:The output pressure is one of the most important feature of detonators. Using photonic doppler velocimetry （PDV） and impedance matching technique， a reliable measurement method for output pressure was carried out. The interface particle velocities between slapper detonators and optic windows were measured by PDV for three kind of detonators. The calculation results show the output pressures are 7.64， 7.29， 6.71 GPa， respectively. The PBX-RDX content has certain influence on the output pressure. As the PBX-RDX content decreases， the output pressure decreases. The output pressure of the three detonators were simulated by Ansys/Ls-Dyna. The simulated output pressures are 7.7， 7.1， 6.4 GPa， respectively. Comparing to the simulation， the pressure difference is less than 6.5%， which validates the method effective. The shell material has significant influence to detonator output pressure. For higher shock impedance， the output pressure is lower. Especially， the peak pressure for steel shell case is undistinguishable.

Abstract:In order to obtain the thermal cycling properties of octogen（HMX） and triaminotrinitrobenzene（TATB） based polymer bonded explosive （PBX） ， the thermal cycling tests of HMX- and TATB-based PBX were carried out under the condition of -40—75 ℃. P-wave and S-wave velocity of explosive specimens with 3N （N=0，1，2，…，9） cycles were measured by ultrasonic echo method. The dynamic elastic modulus （Young"s modulus， shear modulus） and dynamic Poisson"s ratio were calculated by ultrasonic measurement method. The static elastic modulus was measured directly through the tensile property test， while the ratio of dynamic and static elastic modulus was calculated. Results show that the density of HMX-based PBX decreases and later the decrease rate slows down with the increase of the cycle number during the thermal cycling test. The density of TATB-based PBX decreases first， then the decrease rate slows down， and finally has a slight upward trend. The change trend of P-wave velocity， S-wave velocity and dynamic elastic modulus of HMX- and TATB-based PBX are consistent with the change trend of their density respectively. Their corresponding dynamic Poisson"s ratio is basically unchanged. There is a positive linear relationship between P-wave ， S-wave velocity and its density. The static elastic modulus first decreases and then increases， the dynamic and static elastic modulus first increases and then decreases， where the inflexion point of HMX-based PBX is in its 15st thermal cycle， and that of TATB-based PBX is in its 21st thermal cycle. The results show that the damage quantity of PBX during thermal cycling is closely related to its density change and internal micro damage. All these phenomenon demonstrate that the ultrasonic longitudinal and shear wave velocities can be used to quantitatively evaluate the thermal fatigue damage of PBX in thermal cycling test. The change trend of the dynamic and static elastic modulus of PBX is related to its micro structure evolution including internal micro-cracks and binder flow in micro-pores.

Abstract:In order to study the effect of the crystal microscopic properties of elemental explosives on their macro-mechanical behavior and impact sensitivity of composite explosives， the micro-plastic characterization methods of TNT， RDX and HMX were studied. And the correlation analysis between the micro-plasticity of the explosive crystals and their impact sensitivities of the elemental explosive was carried out. Nano-indentation technology was used to test and calculate the micro-elasticity and micro-plasticity of TNT， RDX and HMX explosive crystals， and a calculation method based on the ratio of plastic energy and indentation energy （η_P） was proposed to quantify the micro-plastic properties of explosive crystals. The results showed that， compared with the micro-plasticity （δ_h） calculated by the indentation depth， the linear correlation coefficient between the micro-plastic properties （η_P） of the explosives crystals obtained in this research and impact sensitivities （P） of explosives in simple powders reached 95.8%， or micro-plastic properties of simple explosives were highly related to their impact sensitivities on the micro-characterization method of plastic properties of explosives crystals proposed in this paper. This research provided a micro- characterizing method for evaluating safety levels of explosives.

Abstract:As the most widely used military composite explosive， the performance of melt-cast explosives is closely related to the choice of carrier explosive. The current research advances of melt-cast explosives were reviewed. The physicochemical properties and detonation performances of 13 representative melt-cast carrier explosives （such as 2，4，6-trinitrotoluene （TNT）， 2，4-dinitroanisole （DNAN）， etc） were discussed. The molecular structures， synthesis methods， physicochemical properties and detonation performances of 16 newly synthesized melt-cast explosives were introduced （such as bis（1，2，4-oxadiazole）bis（methylene） dinitrate （BOM）， etc）. Their advantages and shortcomings as melt-cast explosives were analyzed. The effects of different functional groups and molecular structures on the properties of the compounds were discussed. The future development direction of melt-cast carrier explosive is to understand the effects of molecular structure on performance of explosives， and to design and synthesize a series of new compounds with excellent comprehensive performance， in order to meet the application requirements of melt-cast explosives.

Abstract:Due to the superior thermal stability， good modification and appropriate ring tension of imidazole based energetic compounds， they were considered as an important research direction of high energy materials. This review summaries recent progresses of synthesis， property and application of energetic imidazole-bridged azoles， such as bisimidazoles， triazolyl imidazoles and tetrazolyl imidazoles and their energetic salt derivatives. It was found that single or double bond linked bisimidazoles had better thermal stabilities and mechanical sensitivities， higher densities and donation properties than their mono-cyclic imidazole analogs， and could realize the balance between energy and safety which is difficult to be realized by introducing nitrogen-rich energetic groups， connecting groups and formation of energetic salts into mono imidazolyl rings. On the other hand， bicyclic azoles with two different nitrogen heterocyclic structures linked by C─C bond or C─N bond usually has the advantages of combing the good properties of their related structure characteristics， making it an important direction for development of novel high nitrogen and high energy compounds in the future. This review summarizes the recent advances in energetic imidazole-bridged azoles and proposes an efficient construction strategy for designing high nitrogen content， high energy and good safety based on triazolyl imidazole and tetrazolyl imidazole building blocks.

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