Abstract:As information， intelligence and miniaturization progresses in ammunitions， Micro-Electrical-Mechanical System （MEMS） based initiator was derived to meet the need of the information of energy-transferring， miniaturization on structure and integration of energy sequence. As one kind of a system-level MEMS initiator， the present micro fire-train was integrated based on initiation detonation mechanism of the flyer impacting the next booster explosive. By focusing on the application and technical requirements of micro fire-train， the state-of-art of the fire-train was reviewed from five aspects， including the micro-heater design and firing energy control， microscale detonation energy control and devitrization， energy transmission and safety control， micro fire-train design and integration， and reliability evaluation of the fire-train. Based on the analysis of state-of-art of micro fire-train， some suggestions for future development were proposed， and the key points for the further development of micro fire-train are discussed： strengthen the basic research of initiation and detonation mechanism under micro scale； promote digital engineering and improve forward-design capability； build mass production capacity including element-level， component-level and system-level of the micro fire-train； enhance the qualification and improve technology maturity of micro fire-train. It is vital useful for the peers to pay more attention on the design， fabrication， test and evaluation of the micro fire-train.

Abstract:In order to investigate the pulse laser action process of the explosives doped with nano-aluminum powder， the plasma expansion and shock wave characteristics of single-pulse laser ablation of the PETN explosives doped with 1% nano-aluminum powder were studied by shadow measurement system， while the characteristic spectra of the explosives after laser ablation were investigated by laser induced breakdown spectroscopy （LIBS）. The results showed that when laser pulses irradiate the surface of PETN explosive doped with nano-aluminum powder， high temperature and high density plasma was formed， which expanded continuously and compressed the surrounding air to form shock wave. At 50 ns， the velocity of shock wave was 12500 m•s^-1. With the increase of time， the plasma continued to expand， the shock wave advanced forward and the velocity decreased. At 800 ns， a large number of ejection materials were observed in the shock wave. The maximum strength of the spectral lines of Al atom and AlO gas phase molecule were achieved at 1 μs， and disappeared at 10 μs， indicating that the interaction time between nano-aluminum powder and explosive was less than 10 μs. The spectral lines of C atom and CN were not detected at 20 mJ laser energy. When the laser energy increased to 30 mJ， the spectral lines of C atom and CN group were observed in the spectrum of PETN explosive doped with nano-aluminum powder， and the spectral intensity increased with the increase of laser energy. Moreover， the laser energy required for the decomposition of the PETN explosives doped with nano-aluminum powder should not be less than 30 mJ.

Abstract:To study the safety of pulse excitation of hot bridge wire EED， we established a numerical model for the temperature rise of the hot bridge wire EED， and the ignition criterion of hot bridge wire EED was obtained. Based on the above， we designed the calculation procedure for the critical ignition current of the hot bridge wire EED and revealed the influence of single pulse and pulse train current excitation parameters on the critical ignition current of hot bridge wire EED. The results showed that under single pulse excitation and when the pulse width was less than 5 μs， the ignition energy of the hot bridge wire EED was fixed， which suggested that the bridge wire-reagent system was in an adiabatic state. So the ignition state was related to the energy input to the bridge wire. However， when the pulse width was greater than 15 ms， the critical ignition current of the hot bridge wire EED was fixed. So the ignition state was related to the electric power of the bridge wire. Another difference was that under narrow pulse train current excitation， the time constant of the curve for critical ignition current with repetition period was independent of the pulse width. Furthermore， when the repetition period was greater than 1.25 ms， the bridge wire-reagent system exhibited no thermal accumulation effect， and the critical ignition current was the same as the single pulse current excitation. However， when the repetition period was lower than 1.25 ms， the bridge wire-reagent system exhibited the thermal accumulation effect， which resulted in rapid decrease of the critical ignition current as the repetition period decreased.

Abstract:In order to demonstrate the feasibility of amorphous alloy as a new type of micro-heater material， the amorphous alloy bridge wire micro-heater was designed and fabricated， and the influence of constituent components on the energy release effect of amorphous alloy material was studied by DSC thermal analysis. On this basis， the electrothermal temperature response， change in temperature coefficient of resistance and the electro-explosive characteristics of the amorphous alloy bridge wire micro-heater were investigated. Results show that the amorphous alloy is regarded as a metastable energetic material when it releases energy， and exhibits negative temperature coefficient of resistance during crystallization process， leading to that relative change in resistance is 6.38%， and the electrothermal energy transfer power is increased by 17.5%. Compared to the Ni-Cr bridge wire micro-heater with linear temperature coefficient of resistance， amorphous alloy bridge wire micro-heater characterizes a better energy release effect. These preliminarily demonstrate the feasibility of amorphous alloy as a promising initiator micro-heater material， and expand the approach on efficiency improvement of electrical initiator micro-heater.

Abstract:In order to explore the effect of microstructure and crystal organization of copper （Cu） foil on the performance of exploding foil initiator（EFI）， three Cu foils with different crystal morphologies were prepared through the closed-field non-equilibrium magnetron sputtering ion plating technique and Lift-Off etching method under the sputtering power of 150， 450 W and 800 W. Experimental characterizations of the electrical explosion performance and flyer velocity of exploding foil （EF）， and the ignition performance of EFI were conducted subsequently. Average grain size of the samples fabricated at 150， 450 W and 800 W are 19.6-36.7nm， 41.5-62.9 nm and 58.6-80.2 nm， surface average roughness are in turn 6.7， 16.9 nm and 46.2 nm， and the adhesion force are 42.436， 55.569 mN， and 71.135 mN， respectively. Of which， the Cu foil prepared at 800 W exhibits the largest and the most uniform grain size， the densest and smoothest grain， the fewest grain boundaries， the largest surface roughness and the strongest adhesion force. The corresponding EF has the smallest resistance and inductance， highest energy conversion efficiency and flyer velocity. The 50% firing sensitivity of the integrating EFI sputtered at 800 W are 19.1% and 22.6% higher than the samples sputtered at 450 W and 150 W， respectively.

Abstract:In order to enhance the energy-release efficiency of aluminum powder， the inert alumina layer of micron-sized aluminum was replaced by cobalt layer with higher thermal conductivity via combining the replacement and subsequent electroless plating methods. Thus the Al@Co core-shell particles were obtained. The cobalt shell thickness was respectively confirmed as 90， 150， 200 and 250 nm. Scanning electron microscopy， transmission electron microscopy， energy dispersion spectrum， vibrating-sample magnetometer， and thermal tests were conducted. The results show that the cobalt shell is dense and uniform with controllable thickness， and the natural oxidation resistance of the particles rises with the increasing shell thickness. And the particles exhibit typical ferrohysteresis loops， further confirming the presence of ferromagnetic cobalt. Al@Co core-shell particle with 200 nm-cobalt coating can fully overcome the endotherm resulting from the melting of aluminum， showing sharp exothermic with the enthalpy energy of 521.40 J·g^-1， which is a promising selection of fuel component in novel green primary explosives.

Abstract:In order to solve the problems of crystal transformation and low forming efficiency of the main explosive in hexanitrohexaazaisowurtzitane （CL-20） based all-liquid explosive ink micro-jet printing， suspension explosive ink compatible with 3D micro-jet printing was designed and prepared by using polyvinyl alcohol （PVA） aqueous solution as colloidal suspension and micro-nano CL-20 particles as suspension particles. 3D micro-jet technology was used for printing the explosive ink. The properties of the samples were characterized by densitometer， laser confocal microscope， scanning electron microscope， X-ray diffractometer and nano-indentation instrument， respectively. The impact sensitivity， friction sensitivity， and detonation velocity of the samples were also tested， which was used for the study of the relationship between the content of CL-20 and the properties of micro-detonation agent. The results showed that the "coffee ring" phenomenon became more obvious with the increasing content of micro-nano CL-20 particles in the explosive ink， and the thickness of the single layer deposition of the powder line became thicker， while the density decreased gradually. The main explosive CL-20 exhibited no crystal transformation in the 3D microjet printing process and was ε type. When the ratio of micro-nano CL-20 particles to binder was 9∶1， the measured density of the sample was 1.638 g·cm^-3 （86.19% TMD）， and the elastic modulus was 5.43 GPa. The impact sensitivity， friction sensitivity and detonation velocity were 4 J， 240 N and 7689 m·s^-1， respectively， showing better safety performance and micro-scale detonation transmission ability.

Abstract:In order to obtain a fully solution-based explosive ink that was compatible with inkjet printing technology and stably detonated at the microscale， an energetic ink was designed by exploiting 3，4-dinitrofurazanfuroxan （DNTF） as the main explosive and polydimethylsiloxane （PDMS）/nitrocellulose （NC） as the composite binder. The rheological properties and printability of energetic inks were explored by viscometer， electron densitometer， and high-speed photographic instrument. The microscopic morphology， mechanical properties， and safety performance of inkjet-deposited samples were characterized using scanning electron microscopy， nanoindenter， and BAM impact sensitivity tester. The results show that the DNTF-based energetic ink is compatible with inkjet printing technology. The composite bonding system could bind the explosive particles tightly. The maximum elastic modulus of DNTF-based composites reaches up to 6.438 GPa； Compared with the raw DNTF， the impact sensitivity and friction sensitivity of DNTF-based composites increase by 6.5 J and 24 N， respectively. In the groove with 100 mm length， 1 mm width， and 1 mm depth， the detonation velocity of sample reaches 7927 m·s^-1.

Abstract:In view of the urgent demand for high-temperature resistant initiators for pyrogenic products in complex application environments in deep space， primary explosive based on composite films of MXene/Cd（N₃）₂ with high-temperature resistant was prepared by surface self-assembly of electrostatic interaction. The morphology and structure of the composite film primary explosive were characterized by scanning electron microscopy， energy dispersive X-ray spectroscopy， X-ray diffraction and infrared spectroscopy. The thermal properties were studied by differential scanning calorimetry and thermogravimetry， and the detonation process was recorded by high-speed photography. The results show that cadmium azide was evenly distributed on the MXene layer， and there was no deposition and stacking in the large gap. The introduction of MXene can effectively promote the thermal decomposition rate of cadmium azide. The combination of MXene material and cadmium azide didn’t affect the crystal form and detonation performance of cadmium azide. The prepared MXene/Cd （N₃）₂ composite film primary explosive can realize ignition and detonation with less charge.

Abstract:To search green， low-toxicity lead-free primary explosive， a new tetrazole derivative ligand 1H-5-acylhydrazide tetrazole （TZCA） and its complex Ni（TZCA）₂（ClO₄）₂ （ECCs-1） were synthesized by hydrazinolysis and coordination reactions using ethyl 1H-tetrazole-5-carboxylate as the raw material. The molecular structure and thermal decomposition properties of the title complex were tested by X-ray single crystal diffraction， IR diffraction， NMR， elemental analysis， thermogravimetric and simultaneous thermal analyzers. The heat of combustion of ECCs-1 was tested by oxygen bomb calorimetry and its energy parameters were predicted based on Hess law and K-J equation. Sensitivities of ECCs-1 were tested by BAM test methods. The results show that the density of TZCA is 1.83 g·cm^-3， monoclinic crystal system， C2/c space group， the stacking mode is V-staggered stacking. The density of ECCs-1 powder is 1.90 g·cm^-3， impact sensitivity is 17 J， friction sensitivity is 72 N， thermal decomposition temperature is 336 ℃， activation energy of the thermal decomposition reaction is 183.3 kJ·mol^-1， thermal explosion critical temperature is 309.8 ℃， activation entropy is 46.745 J·K^-1·mol^-1， and the activation enthalpy is 178.563 kJ·mol^-1. The hot baking and lead plate tests both show that ECCs-1 has a good detonation performance.

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