Abstract:

Abstract:In order to solve the problems of long time consumption， high cost and low material utilization in the deposition and forming methods of commonly used thin-film energy conversion component， silver film bridge were prepared by inkjet printing. The morphology and thickness of the silver film bridge were test by scanning electron microscopy （SEM） and atomic mechanics microscopy （AFM）， and the ignition performance was studied. The results show that the thickness of the silver film bridge is 2.1 μm， and the surface roughness is good. The performance test results show that the silver film bridge has two situations of electric heating and electric explosion under different input energy. Under 47 μF pulse discharge， the 50% ignition voltage of the silver film bridge dipped with lead stiphenate （LTNR） is 6.65 V. and the foot-to-foot can withstand 25 kV electrostatic discharge （discharge capacitance is 500 pF， 5 kΩ resistor in series）， which can pass the 1A1W5min test of insensitive electric initiating device.

Abstract:The planar thin film transducer chip was designed with longitudinally integrated PN junction structure diode， and integrated through microelectronics technology for excellent security performance and high integration characteristics. Each of three different-sized chips with 1.0 mm×1.0 mm，1.5 mm×1.5 mm and 2.0 mm×4.0 mm， were designed under four breakdown voltages of 8， 18， 28， 34 V， and two kinds of resistance ，3 Ω and 4 Ω. The ignition tests were carried out on the integrated chip to study the impact of the integrated structure on the burst performance of the transducer. Results from the static electricity of these chips show that the larger the size of the integrated thin film chip is， the stronger the antistatic ability， the greater the resistance in the bridge area of the chip， and the more vulnerable to electrostatic interference are. The electrostatic protection performance of designed chip can reach 500 pF/500 Ω/25 kV. The smaller the breakdown voltage is， the greater the bypass current capacity， the greater the impact on the burst performance of the transducer， and the greater the breakdown voltage， but the smaller the electrostatic protection effect are on the energy converter. For initiating explosive devices to be ignited under 33 μF/16 V， the integrated chip with an 18V breakdown voltage should be selected. Therefore， when the integrated thin film chip is applied， it is necessary to select an appropriate breakdown voltage according to the working voltage of the transducer for both a protection against static interference and a necessary avoidance in failure of its normal function.

Abstract:In order to achieve the high safety of ignition device and micro package volume， a MEMS ignition device has been designed with a double-layer barrier electro-thermal safety and arming device in this work. The device is of three core components including an igniter， a safety and arming device， and an ignition powder， all of which are assembled linearly within an overall size of Φ10 mm×3.3 mm. The S&A device has a double-layer structure with bistable function. The frontend initiator， which is fabricated on a ceramic circuit board， is a NiCr bridge foil to be covered with an Al/CuO energetic film. The two pads from the circuit board lead the bridge foil electrode to the backend device， there by reducing the package volume of the sequence. BPN is selected as the ignition powder in the device. According to the safety and arming function test， the ignition device can prevent the igniter from lighting the ignition powder in safety condition， when the size of the Al/CuO is set to Φ800 μm×30 μm. Otherwise， the BPN ignition powder can be ignited in arming condition.

Abstract:To investigate the effects of temperature on the electrical explosion and ignition of semiconductor bridge （SCB）， the electrical explosion characteristics and ignition performance of SCB with the ambient temperature of 25 ℃ and -40 ℃ were studied by a capacitive discharge method， and a mathematical model was established. The ignition temperature of Al/CuO nanothermite was tested at ambient temperature of 25 ℃ and -40 ℃， respectively. The ignition sensitivity of SCB was measured by the D-optimization method. When the charging voltage increases from 30 to 50V， the difference of critical initiation time reduced from 0.47 to 0.25 μs. The difference of critical initiation energy increased from 0.16to 0.65 mJ. Results shown that with the increase of charging voltage， the influence of ambient temperature on the critical initiation time decreased， and the influence on the critical initiation energy increased. Both the ignition temperatures of Al/CuO nanothermite at 25 ℃ and -40 ℃ are 740.7 ℃. The 50% ignition voltage at ambient temperature of 25 ℃ is 0.6 V lower than that at -40 ℃.

Abstract:In order to explore the influence of temperature impact and cycling on ignition time of laser pyrotechnics，the laser initiators with carbon doped tetraammine bis（5-nitrotetrazolato） cobalt（Ⅲ） perchlorate （BNCP） as primary explosive and fiber-window structure were employed to study performance of BNCP， structure change of laser initiators and structural constraint between fiber and explosive under different temperature alternating experiments （47 h and 94 h）. The experiment results show that the ignition time can reach less than 0.2 ms indicating a great ignition performance before temperature alternating experiment. However， the ignition time delayed more than 0.5 ms after 47 h temperature alternating experiment and some initiators delayed more than 1 ms even misfired after 94 h temperature alternating experiment. The crystal grains of BNCP broke up and the bulk density decreased from 0.43 g·cm^-3 to 0.32 g·cm^-3 after alternating temperature experiment. However， the change of bulk density has no influence on thermal decomposition and ignition performance. The difference of expansion coefficient between ceramic fiber optic components and igniter shell leads to a gap between fiber and doped BNCP during alternating temperature experiment. The gap has a great influence on both laser spot intensity and hot spot diffusion. With structural constraints of fiber and explosive increasing， the ignition gap can decrease effectively during alternating temperature environment and the environment adaptability of laser initiators can be improved.

Abstract:As the core components of electrical initiators， transducers are essential for the safety and reliability of electrical initiators. The development trends of miniaturization of the structure of electrical initiators， informatization the transducing process and integration of the firing sequence have put forward higher requirements for transducers. How to realize reliable ignition under low energy stimulation and enhance the ignition output capacity has become one of the major issues for the current research of transducers. To this end， this review summarized the latest research progress on the low-energy firing and output efficiency enhancement of electrical initiator transducers in recent years from the perspectives of the preferential selection of transducer substrate and resistive materials， the optimal design of firing structure， the efficiency enhancement of self-contained energetic integration and energetic film composite. On this basis， the focuses of future research on the efficiency enhancement of transducer are discussed： establishing a gene pool of transducer material parameters， improving the efficiency of transducer firing structure optimization design by means of machine learning algorithms， conducting basic research on novel transducer systems such as wide-bandgap semiconductor materials， and exploring the integration of novel energetic films such as energetic Metal-Organic Frameworks （MOFs） and chalcogenide on transducers.

Abstract:Copper（Ⅰ） 5-Nitrotetrazolate （DBX-1） is a green primary explosive without toxic heavy metal， which has been always attracted much attention since its discovery. DBX-1 is considered to be the most likely to replace lead azide （LA） as a result of its suitable ignition sensitivity， excellent detonation ability and output ability， good compatibility and temperature resistance. Sodium 5-nitrotetrazolium （5-NaNT） is the starting material for the preparation of DBX-1. This work addresses the synthesis problems of 5-NaNT based upon the review on the research progress of DBX-1. This work introduces both the development process of DBX-1 from laboratory synthesis to 100-gram preparation and the synthetic path evolution of 5-NaNT. Here is mainly focused on the synthesis method， performance evaluation and verification of DBX-1.Finally， it points out that some key issues must be cracked before application， such as the synthesis of 5-NaNT with safety and efficiency， the optimal technology of preparation， the sensitivity adjustment of DBX-1.

Abstract:Molecular dynamics simulations were used to investigate the effects of a series of vacancy defect concentrations （0%， 1.56%， 6.25% and 12.5%） on the sensitivities， mechanical properties and bursting properties of dihydroxylammonium 5，5"-bistetrazole-1，1"-diolate （TKX-50）. Firstly， perfect crystal model and vacancy defect models were first constructed， and the correctness and validity of the Dreiding force field used in the study were verified. Then the models were geometrically optimized and molecular dynamics simulated， and the trajectory files to reach thermodynamic equilibrium were statistically and analytically analyzed. It was found that vacancy defects lead to decreases in the cohesion energy density and in the number of total hydrogen bonds of TKX-50， indicating that TKX-50 containing vacancy defects has increased susceptibility and decreased safety. And with the increase of vacancy defects， the number of hydrogen bonds between hydroxylamine cations remains almost constant， and the number of hydrogen bonds whose hydrogen bond acceptor is oxygen atom on bitetrazolium anion is significantly reduced compared with other hydrogen bonds. Besides， the vacancy defects reduce the bulk modulus （K）， elastic modulus （E）， and shear modulus （G） of TKX-50 by 1.530-4.122 GPa， 3.066-10.652 GPa， 1.216-4.202 GPa， respectively. It indicates that the stiffness of TKX-50 crystal decreases with the increase of vacancy defect concentration. The positive Cauchy pressure （C₁₂-C₄₄） of all models indicates that all models exhibit ductility， and the values of K/G and Poisson"s ratio （γ） increase with the increase of vacancy defect concentration， indicating that the toughness and plasticity of TKX-50 are enhanced by the increase of vacancy defects. In addition， the vacancy defects also reduce the detonation velocity and detonation pressure of TKX-50 by 93-317 m·s^-1 and 1.0~3.5 GPa， respectively， indicating that the damage power of defect crystals is reduced.

Abstract:Energetic molecules with cage-like backbones， owning additional strain energy and stability， are potential candidates for optimizing the long-known contradiction between high energy density and low sensitivity of energetic materials. However， the reaction mechanism of caged energetic materials under shock compression is still unclear. Here， a series of ab initio molecular dynamics calculations were conducted to simulate the early decay of typical caged energetic compounds when compressed by shock waves of 8 to 11 km·s^-1，and the studied compounds included octanitrocubane （ONC）， hexanitrohexaazaisowoodethane （CL-20）， 4，10-dinitro-2，6，8，12-tetraoxa-4，10-diazatetracyclododecane （TEX）， and the reference plane system triaminotrinitrobenzene （TATB）. The shock sensitivity of the four studied systems was calculated as ONC > CL-20 > TEX > TATB， which is in good agreement with reference experimental shock/impact sensitivity tests. The reaction initiation mechanism was revealed （i） the presence of electron-rich oxygen/nitrogen elements increases electron delocalization over the cage and the proper degree of freedom of the covalent bonds confers them additional elastic deformation capacity upon shock stimulus， both enhance the structural stability of hetero-cage， （ii） the dissociation of the nitro groups takes precedence over the collapse of the hetero-cage， which can delay the reaction process and reduce the shock sensitivity， and （iii） intermolecular hydrogen bonds （HB） is highly plastic deformable and enriched HB can delay the onset of reactions by buffering shocks. The current study proposed that the hetero-cage backbone with enhanced electron delocalization effect and proper degree of freedom， and the enriched intermolecular hydrogen bonding interactions could reduce the shock wave sensitivity， thereby providing theoretical guidance for the rational design of novel insensitive energetic materials.

Abstract:The Laser-induced Air Shock from Energetic Materials （LASEM）， a laser-induced air shock performance test method based on milligram-scale energetic materials on microsecond time scales， was combined with a pulsed laser system and high-speed ripple shadowing. The effects of different particle sizes and different stacking densities on the characteristic velocities of shock waves from five energetic materials （CL-20， HMX， RDX， FOX-7， LLM105） were investigated. The results show that when the particle size is less than 75 μm， the measurement results deviation is large. When the particle size is in the range of 75-500 μm， the measurement results are less volatile and consistent with the order of the burst pressure value， which can be used as reference data to assess the actual burst performance. When the bulk density is less than 0.7 g·cm^-3， the measurement results fluctuate in a wide range. When the bulk density is in the range of 0.7-1.35 g·cm^-3， the measurement results are more stable and consistent with the order of the burst pressure value， and thus the measurement value is more valuable.

Abstract:In order to study the safety protection issues and explosion characteristics of colloidal charge structure under high temperature environment， the charge structure consisting of a thermally insulating outer layer， an endothermic colloid and an emulsion explosive was designed. The effects of three colloid proportions and two sensitizing modes （emulsion explosives were sensitized by sodium nitrite and expanded perlite respectively） of explosive in the charge structure on thermal insulation and explosion performance were studied by physical property measurement， thermometric analysis， explosion testing technology （underwater explosion， detonation velocity experiment， near-field detonation pressure measurement） and field experiment （sympathetic detonation， blasthole blasting）. The results show that the colloidal material containing 0.5% high molecular water-absorbent resin is suitable for the charge structure， attributing to the fire resistance， high specific heat and low thermal conductivity， which extends the thermally insulating protection time to 55 min. In underwater explosion and detonation velocity experiments， as the heating time of 100 ℃ water bath increases， all detonation parameters （peak shock wave pressure， specific impulse， detonation velocity， and total explosive energy） of the charge of two sensitizing modes decrease. Affected by the demulsification of emulsion explosive and the reduction of sensitization hot spots， the detonation performance of emulsion explosive sensitized by sodium nitrite （EE-SN） is attenuated greater than that of emulsion explosive sensitized by expanded perlite （EE-EP）. After heating for 2 hours， the total explosive energy loss of EE-EP and EE-SN is 4.76% and 17.62%， respectively. In the near-field explosion pressure measurement of colloidal medium， the colloidal layer in charge structure will weaken the strength of explosion shock wave. However， the blasting effect is good in the field experiment， and the charge structure has realized the 30 mm sympathetic detonation and the stable detonation propagation in the blast hole， indicating that the colloidal charge structure has a good application prospect for high-temperature blasting.