Abstract:

Abstract:In order to clarify the influence mechanism of H₂O and H₂O₂ molecules on the thermal stability of energetic cocrystals， molecular dynamics （MD） simulation method was employed to analyze the diffusion behavior and thermal decomposition mechanism of solvent molecules in α-CL-20 and CL-20/H₂O₂ （orthogonal/monoclinic）. The results show that both H₂O and H₂O₂ will diffuse out of the cell as the temperature rises， among which H₂O molecules diffuse faster； when the temperature is lower than 500 K， the monoclinic CL-20/H₂O₂ lattice framework has the ability to hinder the diffusion of H₂O₂ molecules. When the temperature rises above 500 K， this hindering effect no longer exists. In the process of thermal decomposition， α-CL-20 releases energy the slowest， and the decomposition of CL-20 also proceeds the slowest； when the temperature is lower than 1500 K， the solvent exhibits a certain stabilizing effect on the thermal decomposition of energetic components， but this effect disappears as the temperature rises. In addition， the presence of solvents can increase the lattice energy significantly.

Abstract:Pentazoles are currently a research hotspot in the field of energetic materials， however， the stability of existing pentazoles is generally not high. In order to develop new pentazoles with better properties， based on the analyses of the available structures， 20 substituted derivatives of HN₅ with the electron-withdrawing groups， i.e.，N₅（CH₂）_x-1R（R=—NO₂，—CF₃，—CN， —CHO， —COOH； x=1， 2， 3， 4）， were designed and studied by using the density functional theory method. The bond dissociation energy （E_BD） of the bonds linked with the N₅ ring and the activation energy （E_a） of the cracking of the N₅ ring were calculated and compared with that of some pentazoles substituted by the electron-donating groups， and the effects of substituents on E_BD and E_a were discussed. Results show that the E_a of all molecules is much smaller than E_BD， indicating that the stability of the N₅ ring is the key factor to determine the stability of the pentazoles. When R is directly connected to the N₅ ring （N₅R）， the E_a of N₅R with R being an electron-withdrawing group is smaller than that of N₅R with R being an H or an electron-donating group. The N₅ ring is a strong electron-withdrawing group， and bearing too much or too little negative charges is not conducive to the stability of the N₅ ring.

Abstract:In order to investigate the thermal decomposition mechanism of the energetic cocrystal TKX-55 and the effect of solvent component dioxane （1，4-dioxane， DIO） on the decay of the energetic component 5，5´-bis（2，4，6-trinitrophenyl）-2，2´-bis（1，3，4-oxadiazole） （BTNPBO）， the molecular dynamics simulations on TKX-55 and pure solvent component DIO were carried out with the ReaxFF-lg （Reactive Force Field-Low Gradients） force field. The results show that the initial decomposition reaction of TKX-55 includes the dimerization of energetic molecules， the hydrogen transfer between energetic and solvent components， the ring-opening reaction of 1，3，4-oxadiazole in energetic components， and the dissociation of nitro group. The dimerization reaction facilitates the rapid growth of the subsequent clusters， and the release of the heat and the stable small molecule products are restricted by the formation of a large number of clusters. It is one essential reason for the high heat resistance of TKX-55. For the pure solvent， the heat release and clustering are constrained at low temperatures； while enhanced at elevated temperatures. The main role of DIO molecules in TKX-55 is thought-to adsorb small reactive intermediates （such as OH， NO， NO₂， etc.） and thereby inhibit the decomposition of BTNPBO.

Abstract:In order to ensure the safety of the incineration process， the incinerator must be able to withstand the impact of accidental explosion when the waste energetic materials are incinerated. The dynamic coefficient method and the method proposed by Atomic Weapons Establishment （AWE Method） were used to design the shell of vertical incinerator for waste energetic materials. Then， three-dimensional numerical simulation of the shell stress of the designed incinerator under detonation of energetic materials was carried out using AUTODYN software. The influence of exhaust gas outlet， outlet position and detonation position of energetic materials on the anti-explosion performance of the incinerator was analyzed. Numerical simulation results show that the existence of the outlet destroys the continuity of the shell， therefore， the stress concentration occurs near the outlet， and the maximal stress appears at the upper edge of the outlet. Besides， as the diameter of the outlet increases， as the center of the outlet is closer to the shell cover， and as the detonation position of energetic materials is closer to the outlet， the stress concentration at the upper edge of the outlet becomes more serious. When the energetic material is close to the incinerator shell， the explosion will cause plastic deformation of the shell. Hence， when the diameter of outlet is determined， some measures can be taken to ensure the safety of the incineration process， such as keeping the outlet away from the seal plate， setting a stiffening ring at the outlet and keeping a certain distance between energetic materials and the shell.

Abstract:In order to determine the parameters of the JWL equation of state for unreacted explosives， a method to determine the JWL parameters by using the BP neural network-Genetic Algorithm （BP-GA Algorithm） and the shock Hugoniot was proposed. Firstly， BP neural network is trained to fit the nonlinear system composed of different JWL parameters， and then Genetic Algorithm is used to search the set of JWL parameters with the largest fitness value. The results show that the JWL parameters can be determined by the BP-GA Algorithm when the initial density， detonation velocity， Hugoniot parameters C₀ and S are known. The p-v curves of eight kinds of unreacted explosives determined by BP-GA Algorithm are consistent with those determined by test data， and the R² of eight p-v curves are not less than 0.9995， which proves the high accuracy of BP-GA algorithm.

Abstract:In order to study the influence of structural parameters on characteristics of fragments from warheads with a composite charge， AUTODYN-3D finite element calculation software was used. Next the propagation of detonation waves and shell breaking process of warheads were compared and analyzed， under the central single-point initiation and the internal and external simultaneous initiation. Then the influence of shell thicknesses and central charge diameters on the average mass and velocity of fragments from warheads was obtained. The calculation results show that， with the increase of shell thicknesses or the decrease of central charge diameters， the average mass of fragments under single-point initiation increases more times than that under internal and external simultaneous initiation， and the difference in power output of warheads between those two initiation modes becomes more significant. The static explosion test results show that the average velocity of fragments， shock wave overpressure， and the number of witness target holes under internal and external simultaneous initiation increase 27.1%， 31.4%， and 39.3%， respectively， compared with those under single initiation. The test results are in good agreement with the calculation results.

Abstract:The hydrodynamic software FLUENT was used to study the drag coefficient of fragments with different initial velocities （≤2500 m·s^-1） and altitudes （≤20 km）， and the velocity attenuation model of fragments with different altitudes was corrected Then the accuracy of the corrected model was verified by the corresponding velocity attenuation characteristic tests with low atmospheric pressures. The results show that the calculated results of spherical fragments with an initial velocity of 700 m·s^-1 and cuboid fragments with an initial velocity of 1000 m·s^-1 using the corrected velocity attenuation model are in good agreement with the experimental results that the errors are less than 5%， and the calculation accuracy of the modified velocity attenuation model is about 10% higher than that of the original model. The corrected velocity attenuation model of fragments can be used to calculate the influence of the drag coefficient， which is varied with the altitude， on the velocity attenuation coefficient of fragments， to improve the calculation accuracy of the fragment velocity， and to further improve the accuracy of the power evaluation of the fragment warhead.

Abstract:To obtain the reaction characteristics of tetraethylammonium decahydrodecaborate （（C₂ H₅）₄N］₂B₁₀H₁₀，BHN-10） under explosion and shock， the reaction pathways and decomposition products of BHN-10 under shock were studied by electrically exploded plasma shock and explosive blast shock. Results show that the gaseous decomposition products of BHN-10 under electrically exploded plasma shock are organic combustible gases， such as carbon alkanes， alkenes， alkynes， and etc. BHN-10 has good stability under explosive blast shock. The shock wave of 25 GPa magnitude generated by explosive blast cannot promote the decomposition of BHN-10， while the explosion heat is a main factor leading to the reaction of BHN-10. The combustion of BHN-10 occurs under explosive blast shock after 8 ms， and the combustion appears from the central position， lasting for more than 200 ms. The mixture of HMX and BHN-10 has an accelerated diffusion speed of fireball under explosive blast shock， and its combustion time is equivalent to that of BHN-10.

Abstract:Iodine-rich compounds are a new type of bactericidal materials developed in recent years. Gaseous products comprised of large amounts of iodine or iodine-containing components are released can be used as strong biocides during the progress of decomposition or explosion of iodine-rich compounds. It has the advantages of short response time， good flexibility， high sterilization efficiency， and can adapt to the needs of complex environment. In this review， we summarized the iodination methods of preparing five-member or six-member nitrogen heterocycles by using I₂/KI， I₂/oxidants， NIS or ICl， and the range of application， advantages and disadvantages of different iodide methods were compared and analyzed， It is pointed out that the preparation of iodine-rich energetic compounds in the future should focus on improving the atom economy of iodine and the green and friendly synthesis process. It is hoped that this review will provide guidance for the design， synthesis and large-scale preparation of new iodine-rich energetic compounds in the future.

Abstract:Initiating explosive devices are the first component of the weapon system， their safety and reliability directly affect the safety and reliability of the weapon system. In order to meet the development requirements of miniaturization and integration of ammunition， the fuze is needed to integrate with initiator to form a micro-initiation system with high safety， high reliability， and multi-functional integration. MEMS （Micro-Electro-Mechanical System） safety and arming device （S&A device） is one of the key technologies. The development of MEMS S&A device used in micro-fuze and micro-initiation system in recent years was summarized， and the device material， device size， driven mechanisms， driven conditions， output efficiency， application platforms， and other aspects were compared and analyzed. Combined with the structure and size of the initiating device， the working principle of micro-initiation system with built-in MEMS S&A device was proposed. This MEMS initiator with built-in S&A device meets the development requirements of the next generation initiator， and it is also one of the main development directions of initiator in the future.