Abstract:

Abstract:As a ideal alloy fuel， Al-5Li alloy can significantly improve the combustion efficiency of propellant with the characteristics of high heat release and micro-explosion during combustion compared with Al. However， Al-5Li alloy powders have high reactivity which is easier to react with the components of propellant， preventing it from being used in propellants directly with some structure related defects， such as pores and cracks. In order to improve the stability and compatibility of Al-5Li alloy， the Al-5Li@7PA samples with high stability and compatibility were obtained through the coating treatment of 7% long-chain alkanoic acid （PA）. The surface is dense and crack-free， and PA molecules adhere to the alloy surface through chemical bonding. The coated samples can be stable in hot water for 30 min. It"s worth noting that the heat of combustion of Al-5Li@7PA samples has an increase of 4.55% compared with the raw Al-5Li. At the aspects of compatibility and chargeability， the compatibility level with HTPB of Al-5Li@7PA samples has increased from level 5 to level 1， and there are no defects such as pores and cracks in the grain column， indicating that the coated Al-5Li alloy meets the propellant charging requirements. Propellant combustion performance test shows that the combustion rate and temperature of Al-5Li@7PA have increased by 10.28% and 45.41% compared with Q3 Al propellant respectively， and the particle size of the combustion product residue is smaller.

Abstract:To improve the combustion efficiency of aluminum powders， Al-LiH composite fuels with mass contents of 3%， 5%， 10%， and 15% were prepared using the ball milling method， respectively. The sample structure， morphology， and particle size are characterized by X-ray diffraction （XRD）， scanning electron microscopy （SEM）， and particle size analyzer. The thermal oxidation performance was characterized using the DSC-TG. Finally， their combustion performance was investigated using the CO₂ laser ignition device， high-speed camera， and oxygen bomb calorimeter. The results show that LiH can be embedded into Al powder through the ball milling method， and the LiH content is a key factor affecting its microstructure， particle size， and particle size distribution. The addition of LiH increases the mass calorific value of fuel. At the same time， with the increase of LiH content， the combustion flame intensity of Al-LiH composite fuel increases and the ignition delay time significantly decreases. Among them， Al-3LiH and Al-10LiH composite fuels achieve second oxidation after the first oxidation. The analysis suggests that the second oxidation phenomenon is caused by the microexplosion phenomenon of Al-LiH composite fuel at high temperatures.

Abstract:To elucidate the promotion mechanism of the oxidation performance of the Al-W alloy fuel， Al-20W and Al-30W alloy fuels were prepared by the aluminum thermal reduction and the ultra-high temperature gas atomization， and their oxidation process were studied by thermogravimetric/differential thermal analysis， X-ray diffractometer， and scanning electron microscope/energy dispersive spectrometer. The results indicate that Al-20W and Al-30W alloy fuels both contain metastable Al/W alloy phases， and the types and morphology of the Al/W alloy phases transform with increasing temperature. Al-20W and Al-30W alloy fuels have better thermal oxidation performance than pure Al fuel， with complete oxidation at 1300 ℃ and 1500 ℃， respectively， and all oxidation products WO₃ volatilizing. The presence of W enhances the oxidation performance of the Al-W alloy fuels. The promotion mechanism includes： the volatilization of WO₃ provides channels for O₂ to diffuse into the interior of the particles. As an “O atoms transport ship”， WO₃ transports O atoms to the pure Al phase， promoting the oxidation of the pure Al phase. WO₃ undergoes further chemical reactions and ultimately volatilize in a gaseous form， promoting the oxidation of the phase containing W.

Abstract:The achievement of rapid energy release at a low activation energy is vital for the improvement of the thermal decomposition characteristics of 1，1-diamino-2，2-dinitroethylene （FOX-7）. Herein， MoS₂ doped FOX-7 （FOX-7/MoS₂） energetic composites were prepared by the solvent-antisolvent method. Scanning electron microscopy （SEM）， energy dispersive spectrometer （EDS）， X-ray powder diffraction （XRD）， X-ray photoelectron spectroscopy （XPS）， thermogravimetric-differential scanning calorimeter （TG-DSC） were employed to investigate the morphology， phase composition， thermal decomposition characteristics， and decomposition activation energy of composites. The doped FOX-7/MoS₂ energetic composites displayed improved decomposition temperature at low temperatures and fastened decomposition heat release at high temperatures. Compared with the raw material FOX-7， the decomposition temperature and activation energy of FOX-7/MoS₂-5% during the low-temperature stage increased by 6.8 ℃ and 78.6 kJ·mol^-1， respectively. The decomposition temperature and activation energy at the high temperature decreased by 23.4 ℃ and 340.4 kJ·mol^-1， respectively. The TG-MS results showed that the proportion of CO₂ in the FOX-7/MoS₂-5% increased from 7.3% to 16.8% at the high-temperature stage， indicating a promoted and completed decomposition of FOX-7 using the MoS₂ dopant.

Abstract:Isomerism is common in energetic compounds. Isomers may have differences in energy and safety performance. Investigating the mechanisms in these differences contributes to a deeper understanding of the structure-performance relationship of energetic compounds. The thermal decomposition mechanisms of three isomeric energetic compounds， 2，6-diamino-3，5-dinitro-1-oxide pyrimidine （LLM-105）， 3，5-diamino-4，6-dinitro-1-oxide diazine， and 1，4-dinitrofurazan ［3，4-b］ pyrazine （DNFP）， were studied using the self-consistent-charge density-functional tight-binding method （SCC-DFTB） under program heating and isothermal heating conditions. The results show that there is a strong hydrogen bond network in the LLM-105 crystal， enabling a molecular hydrogen transfer reaction accounting for 68.75% in the early stage of decomposition， which plays an important role in its high thermal stability； The skeleton structure of 3，5-diamino-4，6-dinitro-1-oxide diazine was prone to ring-opening through N─N bond cleavage under heating， resulting in lower thermal stability compared to LLM-105； The bond dissociation energy of DNFP for nitro group cleavage is 172.3 kJ·mol^-1， which is significantly lower than the other two isomers. Additionally， its fused-ring skeleton was also susceptible to ring-opening through C─C and N─O bond cleavage， resulting in the lowest thermal stability. In summary， the bond dissociation energy of the weakest bond in the molecule， the stability of the ring skeleton structure， and the hydrogen bond network of the crystal are important structural factors that determine the thermal stability of energetic compounds.

Abstract:Co-crystal technology is one of the effective methods to reduce the sensitivity of CL-20. Studying the chemical reaction of CL-20 co-crystal under shock is helpful to understand the shock reaction mechanism of CL-20 co-crystal， which is of great significance to the safety evaluation and analysis of explosives. In this study， the molecular dynamics method of ReaxFF-lg reaction force field and the non-equilibrium loading method were used to simulate the shock compression process of CL-20/DNT， CL-20/DNB and CL-20/MDNT co-crystals at 2-5 km·s^-1 shock velocity. The thermodynamic evolution characteristics， initial chemical reaction path and product information of energetic co-crystals after shock are obtained and compared with those of CL-20. It’s discovered that the three co-crystals of CL-20/DNT， CL-20/DNB and CL-20/MDNT have a certain degree of shock sensitivity reduction， and the order of shock sensitivity of the three co-crystals is CL-20/MDNT>CL-20/DNB>CL-20/DNT. The decomposition reaction of the three co-crystals all starts from the decomposition of CL-20， and the decomposition rate of CL-20 is faster than that of DNT， DNB and MDNT. At the shock velocity of 2 km·s^-1， the polymerization reaction of CL-20 co-crystal occurs first. The polymerization reaction between CL-20 and co-crystal ligand molecules is earlier than that between CL-20 molecules， and the reaction frequency is much higher than that between CL-20 molecules. At the shock velocity of 3 km·s^-1， the N─N and C─N bonds of CL-20 are first broken， and the cage structure is destroyed. At the same time， NO₂ is generated. NO₂ generated by the initial bond breaking of CL-20 further combines with the eutectic ligand molecules DNT， DNB and MDNT to reduce the concentration of the intermediate products of CL-20 reaction， so as to achieve the desensitization effect. At the shock velocity of 4 or 5 km·s^-1， the ring skeleton structure in CL-20 is directly destroyed， the C-N bond is broken， generating small molecular fragments， including N_2， NO₂， H₂， CO₂， H₂O and other products.

Abstract:The relationship between crystal defects and hotspots formation of explosives under dynamic loading is a hot research topic in energetic materials. Understanding the mechanism of hotspots formation and its role in the ignition and sensitivity of high explosives are of great importance due to the needs of safety assessment of explosives and developing insensitive munitions. In this work， the ReaxFF reactive force field and molecular dynamics method were applied to investigate the dynamic responses of single crystal cyclotetramethylene tetranitramine （HMX） explosive with cylindrical voids under shock loading. Moreover， the effect of void size and double voids were studied. It is found that the shock induced collapse of voids includes three stages， namely， the plastic deformation on the upstream of the void， the movement of upstream atoms towards the centerline and the downstream of the void forming flowing atoms， and the collision of flowing atoms on the downstream. The main mechanism of hotspots formation is the collision of flowing atoms on the downstream that transforms kinetic energy into thermal energy leading to rapid temperature rise. The high temperature of hotspots initiates local chemical reactions， and the breaking of N─NO₂ bond in HMX molecule with NO₂ formation is the principal initial reaction mechanism. The void collapse process and hotspots formation mechanism of cylindrical void is similar to spherical void， while the convergence effect is weaker and the velocity of formed flowing atoms is lower for cylindrical void， resulting in significantly low hotspot temperature and weak chemical reactions. Besides， the collapse of cylindrical void forms shear bands around， which was not observed for spherical void. With the increase of void size， the velocity of flowing atoms goes up， the shear bands are wider， and the hotspot temperature is higher and hotspot area is larger， leading to more violent chemical reactions. For the sample with two voids that are aligned along the shock direction with a distance of void radius， the collapse of voids is similar to single void. The shock pressure reduces when the shock wave propagates through the upstream void due to the reflected rarefaction wave. Therefore， the velocity of the flowing atoms formed during the collapse of the downstream void is smaller， and the temperature of the second hotspot is lower. The current findings are beneficial to comprehend the effects of crystal defects on hotspots formation and subsequent ignition of explosives and can provide physical mechanism and laws cognition to construct macro-theoretical models.

Abstract:In order to explore the electromagnetic field safety threshold of electro-explosive devices（EEDs） and provide a sensitivity evaluation benchmark for the study of electromagnetic compatibility and electromagnetic environmental effects of EEDs， based on the electromagnetic thermal coupling model of EEDs， white light interference method was used to test the electromagnetic field response characteristics of No.14 EED. The effect relationship between electromagnetic field coupling， self sensitivity， and electromagnetic response of EEDs was studied， a test method and calculation method for the electromagnetic field safety threshold of EEDs have been developed， and the electromagnetic field safety threshold of No.14 EED has been obtained within the frequency range of 10 kHz-18 GHz. The results indicate that the sensitive frequency range of No.14 EED is between 40 MHz and 1 GHz.

Abstract:In complex environment， the micro safety and arming （S&A） device of initiating explosive device needs to have recoverable and anti-overload characteristics. Therefore， this study designed a metal-based electrothermal-driven micro S&A device based on laser processing. The finite element simulation was used to analyze the action characteristics of the nickel-based micro-electrothermal actuator. By adjusting the length and width of the hot arm and the cold arm of the double-arm U-shaped electrothermal actuator and the gap between the arms， the influence of them on the output displacement was explored. Through orthogonal experiments， the optimized ultra-fast laser processing parameters were obtained as follows： frequency 100 kHz， energy 113 μJ， and cutting speed 100 mm·s^-1， respectively. The ultra-fast pulse laser precision manufacturing of nickel-based electrothermal micro S&A device was realized. Finally， the performance verification platform of the micro S&A device was built， the driving displacement and explosion-proof performance of the mechanism under different current excitations were verified. The results show that the driving displacement of the processed micro S&A device can reach 1084 μm under the excitation current of 8 A， and the assembled micro S&A device of initiating explosive device can effectively isolate the explosion in the explosive sequence.

Abstract:In order to study the effects of boundary constraint and separation surface width on separation performance of lead linear shaped charge， numerical simulation was used to analyze the factors affecting the separation of cast aluminum target plate after the explosion of lead linear shaped charge. The effects of free boundary constraint， fixed boundary constraint and slot width of separation surface on separation performance of lead linear shaped charge were obtained. Results show that the separation of brittle materials such as cast aluminum from lead linear shaped charge is the result of the joint action of jet penetration and high pressure detonation products. The boundary constraint has little influence on jet penetration and the deviation is generally less than 5%， but it has a great influence on the cracking process of the target plate. The strong fixed boundary constraint will limit the deformation and displacement of the material during the separation of the cutting cable， and then limit the cracking effect of high-pressure detonation products on brittle materials such as cast aluminum， which will increase the difficulty of subsequent separation. By appropriately increasing the width of the separation interface， the effect of boundary constraints on the separation performance of the cutting cable can be effectively reduced， and the separation reliability of the cutting cable can be improved. The 2.7 g·m^-1 lead linear shaped charge can reliably separate the ZL114A material with a thickness of 4.5 mm when the width of the weakening groove is ≥12 mm.

Abstract:This review summarizes the development and application status of explosive network multi-point initiation technology and in-line multi-point initiation technology. The application status of multi-point synchronous explosive network and multi-point logical explosive network were introduced respectively， and their advantages and disadvantages were analyzed. The research status of in-line multi-point initiation technology at home and abroad was compared， and the gaps in the current in-line multi-point initiation technology were pointed out. The influence of parameters such as the number of initiation points， initiation position on the output of the multi-point initiation system were summarized. The future research directions of multi-point initiation technology were pointed out： precise control of multi-point initiation， modularization and integration of multi-point initiation devices， low-cost multi-point initiation technology， and safety and reliability of multi-point initiation devices in complex environments.