Abstract:

Abstract:

Abstract:The study of polynitrogen pentazolate salts， which are usually achieved from the precursors of N₅ covalent compounds， is the hotspot of research in the field of new energetic materials. In most cases， the stability of N₅ covalent compounds will significantly affect the possibility of successful preparations of pentazolate salts. Herein， the calculations of dissociation energy （E_BD） of the bonds in the straight side chain and activation energy （E_a） of the N₅ ring were carried out for the selected eighteen non-aryl substituted N₅ compounds （R—N₅ or N₅—R—N₅） by using the B3LYP/6-31G** method of density functional theory， and meanwhile the influence of the side chain on their stabilities and pyrolysis mechanism were investigated. When R is the hydroxyl or amino group， the side chain and the N₅ ring are more prone to break， making it difficult to obtain the N₅^- ring. When R is alkyl， the E_a of the N₅ ring cleavage is relatively larger， making it more likely to produce the N₅^- ring， and the stability of the side chain′s C—N bond as well as the N₅ ring will be little affected by the length of the alkyl chain. The sequential cleavage of two N₅ rings occurs in the bicyclic molecular structures and the energy barrier of the second ring is higher than that of the first one， resulting in the formation of N₂ and azide. The C—C bond on the side chain of the molecule will be broken before the break of C—N bond， which may significantly reduce the E_BD of the C—N bond but have little effect on the E_a of the N₅ ring. Therefore， for the preparations of pentazolate salts from covalent pentazoles， cutting off the C—C bond first may be more conducive to obtaining N₅^- ring.

Abstract:To study the influence of crystal defects on the initial reaction of hexanitrohexaazaisowurtzitane （CL-20）， molecular dynamic simulation and ReaxFF-lg reactive force field are used to study the initial reaction path， thermal decomposition products， and reaction kinetics of CL-20 with vacancy defects at high temperature （1500-3500 K）. The results show that the initial decomposition path of CL-20 with vacancy is the breaking of N─NO₂ bond， the same as that of perfect crystal. The vacancy defects prove to increase the frequency of ring-opening reactions and the production of NO₂. Compared with perfect CL-20， it can be seen that the vacancy defects would reduce the CL-20 activation energy barrier and accelerate its thermal decomposition process. The reaction rate constants of CL-20 with 16.7% vacancies are 1.7 and 1.4 times higher than that of perfect CL-20 at 2000 K and 3000 K， respectively. The CL-20 molecules around the vacancy are easier to decompose， leading to the increase of the sensitivity of CL-20.

Abstract:In order to investigate the mechanical response process of porous propellant under impact loading and the effect of geometric parameter changes on the mechanical properties of the particles， ANSYS/LS-DYNA was used to establish the numerical models of seven-hole and nineteen-hole propellants to simulate the force of the particles under impact loading. Then， the models of single-hole propellant， seven-hole and nineteen-hole propellants with aspect ratios of 1∶1 and 2∶1， and lace-shaped seven-hole and nineteen-hole propellants were established to study the influence of the number of holes， aspect ratios and shape on propellant stress. The results show that the particles rebound after being compressed， the stress on the surface in contact with the drop hammer increased gradually from the center to the boundary， and the middle of the particles expanded. The increase of the number of holes will change the continuity of the stress distribution on the end surface due to the stress concentration at the hole. Compared with the single-hole propellant， the duration under stress and the maximum compressive displacement of the seven-hole propellant are increased by 3.39% and 3.76%， respectively， whereas the duration under stress and the maximum compressive displacement of the nineteen-hole propellant are increased by 10.17% and 15.05%， respectively. When the number of holes remains constant and the aspect ratio increases from 1∶1 to 2∶1， the peak stress decreases and the peak compressive displacement increases. The lace-shaped particles were more prone to cause stress concentration in the concave of lace than the cylindrical ones. The study of the stress response process of the propellant and its influencing factors provides fundamental data to study the mechanical properties of the propellant.

Abstract:In order to explore the solid propellant combustion catalyst， a new type of bi-ligand containing energy complex ［Cu（MIM）₂（AIM）₂］（DCA）₂ was synthesized from 1-methylimidazole （MIM）， 1-allyl imidazole （AIM）， copper nitrate and NaDCA， and its structure was characterized by infrared spectroscopy， X-ray single crystal diffraction and powder diffraction. The thermal decomposition process of the energetic complex was analyzed by DSC and TGA. Within the temperature range of 40-500 ℃， there is a melting peak （peak temperature is 93.5 ℃） and an exothermic decomposition peak （peak temperature is 199.4 ℃） in DSC curve. The sensitivity test of the complex shows that the friction sensitivity and impact sensitivity are low and the operation process is safe. Comparing the bi-ligand ［Cu（MIM）₂（AIM）₂］（DCA）₂ with ［Cu（MIM）₄］（DCA）₂ and ［Cu（AIM）₄］（DCA）₂ catalyses on the thermal decomposition of AP， the results show that the bi-ligand complex has better catalytic effect， which advanced the exothermic peak temperature of AP by 88.8 ℃， increased the heat release from 782 J·g^-1 to 2458 J·g^-1， and lowered the thermal decomposition activation energy by 47.1 KJ·mol^-1， implying the potential application as a composite propellant catalyst .

Abstract:To study the synthetic mechanism and properties of 3，7-dinitro-［1，2，4］triazolo［5，1-c］［1，2，4］triazine-4-amine （TTX），the synthetic mechanism of TTX was studied by density functional theory （DFT）， and the influence of pH value on the cyclization reaction was investigated. Thermal properties and impact sensitivity were studied by differential scanning calorimetry （DSC） and BAM drophammer apparatus， respectively. TTX was synthesized by the coupling reaction of sodium cyanonitromethanide and azo salt of 5-amino-3-nitro-1，2，4-triazole （ANTA）， following by intramolecular cyclization reaction. TTX showed a decomposition temperature of 281.8 ℃ and a apparent activation energy of 356.7 kJ·mol^-1. The impact sensitivity of TTX was measured to be 60 J. Moreover， the compatibility of TTX with HMX， RDX， Al powder and NC was studied. TTX had a good compatibility with Al powder， but a fair compatibility with HMX and a poor compatibility with RDX and NC. Therefore， adding RDX or NC into TTK would apparently increase its sensitity.

Abstract:The accommodation of liquid propellant in current-used weapons and equipment makes it important for expanding its application field in various existing weapon systems in the form of general solid propellant. In the current paper， a nitrocellulose-based energetic hollow spherical shell that can be used to encapsulate the liquid propellant is designed. The preparation method is based on the spherical propellant prepared by the internal solution method and on the principle of double emulsification， using W/O type Pickering emulsifier active calcium phosphate and O/W type emulsifier sodium carboxymethyl cellulose to make the emulsion containing nitrocellulose emulsify into a monodisperse W/O/W type emulsion， then evaporate the solvent to obtain the shell. The feasibility of activated calcium phosphate on the W/O type emulsifier has been examined through triple contact angle technique using a contact angle meter. Besides， the basic morphology and particle size， as well as packing density have been characterized using a ultra-depth-of-field electron microscopy system and mass-volume method， respectively. Results show that the three-phase contact angle of activated calcium phosphate is 121.80°. The shell has a large cavity structure with a particle size of 0.7-1.1 mm and a bulk density of 0.1-0.2 g·mL^-1. The microstructure demonstrated a majority of white fiber structure. In addition， embedded white particles in the fiber could also been observed. The optimized ratio of sodium carboxymethyl cellulose to active calcium phosphate， and active calcium phosphate to nitrocellulose should be 1∶1-1.25∶1 and 0.16∶1-0.24∶1， respectively.

Abstract:In order to further improve the compactness of energetic powder materials， an ultrasonic-assisted isostatic pressing method is proposed， and an experimental prototype is designed and produced. The simulation software COMSOL is used to analyze the sound field of a single ultrasonic vibrator and the whole isostatic ultrasonic assisted molding system， and the influence of the cover thickness， 10 MPa pre-pressure and ultrasonic power voltage amplitude on the sound field distribution is studied. The simulation results show the rationality and feasibility of the ultrasonic-assisted isostatic pressing. The press molding experiments of polymer-bonded explosive（PBX） simulants are carried out whether to consider ultrasonic-assisted and 10 MPa pre-pressure conditions. The computed tomography（CT） and scanning electron microscope（SEM） are used to test and analyze the samples. The results show that the internal uniformity and compactness of the materials with ultrasonic-assisted and 10 MPa pre-pressure are better than those materials without， and their internal grains are finer and the grain distribution is more uniform.

Abstract:With extrusion deposition technology as the core， based on the features of high viscosity and no-resistant to high temperature for propellant， the extrusion deposition rapid prototyping system for propellant was designed and a complete prototype was built. Using a certain ZY propellant as raw material， different materials with concentrations of 27.3%， 33.3%， 38.5%， 42.9%， 46.7% and 50% were prepared. Through 3D printing extrusion experiments， it is found that there is a polynomial function relationship between the inner diameter of the needle and the material concentration. The filling speed range is 2-4 mm·s^-1， the filling rate range is 70%-90%， and the temperature range of the bottom plate is 25-45 ℃. On this basis， the propellant 3D printer was used to print the propellant， and the compression test was carried out. The results showed that the compression strength of the propellant could reach up to 230 MPa.

Abstract:In order to prevent the spacecraft from being damaged due to the high pyroshock of the separation nut， an orifice is used to suppress the pyroshock response of the separation nut during separation. Throttle holes with three diameters of Φ2 mm， Φ4 mm and Φ6 mm are set on the powder gas channel of the separation nut. The pressure， acceleration and preload of the separation nuts of different orifices in the separation process are tested simultaneously， so as to analyze the separation process of the separation nuts. According to the sequence of movement， the pyroshock load is decoupled into three types of pyroshock sources： powder combustion， preload release and piston impact. The time-acceleration （a-t） curve is transformed into a shock response spectrum （SRS）， and the contribution of each shock source is calculated. The relationship between the orifice diameter and the shock response is obtained. The results show that in the frequency domain of 500 to 10000 Hz， the contribution of gunpowder action is 8.3% to 11.0%； the contribution of preload release is 44.0% to 51.5%； and the contribution of piston impact is 40.2% to 45.0%. The maximum pyroshock response during the separation process is： 1416 g （Φ6 mm）， 1251 g （Φ4 mm） and 852 g （Φ2 mm）. It can be seen that the use of the orifice can effectively suppress the impact response of the separation nut.

Abstract:It was designed that an airtight planar triggered spark-gap switch （PTS） with parallel three-electrode structure based on printed circuit board （PCB） technology， aiming to improve the working probability of exploding foil initiator systems （EFIs）， as well as to reduce the size and cost of the system. The PTS was batched-prepared with PCB technology according to the structural parameters of three electrodes， and the outline of a single parallel PCB-PTS （P³） was 13.5 mm（l）×7.5 mm（w）×2.5 mm （h）. The 3D and sectional appearances of the P³ were reconstructed via a micro computed tomography， which indicated that PCB technology could meet the machining precision. We simulated the electrostatic field distribution among the switch gap to explain the conduction process， and the theoretical self-breakdown voltage （U_SB） was figured out based on the simulation results. Most importantly， the test results of electrical performance of the switch show that （1） the about 2000 V U_SB derived from real-world measurements was slightly lower than the calculated value； （2） P³ switched reliably at 50%-95% U_SB， and there was a constant risetime of about 121.8 ns and a peak current more than 1500 A， which fit the characteristic requirements of EFIs. Finally， P³ was applied to exploding foil initiator （EFI） to verify its practicability， and it was found that HNS-IV pellets were reliably detonated under the ignition condition of 0.22 μF/1400 V.

Abstract:To select an optimum treatment technology to solve the TNT red water contaminated soil problem in explosive industry， the high temperature sintering resourcing technology was developed. Contaminated soil and clay soil were mixed in a volume ratio of 4∶6， dried for 26 h in the drying section of a tunnel kiln by residual heat from the roasting section， and then roasted for 24 h in the roasting section at 1100 ℃. Sintering tail gas of the tunnel kiln was emitted into ambient air from its 43 m high funnel after treatment of desulfurization and denitrification facilities. Finished bricks were cooled down naturally out of the kiln. The featured pollutant-dinitrotoluene sulfonate in contaminated soil is completely decomposed， sintering tail gas reaches the emission standards， resource-based products meet the quality standard of building material bricks without any featured pollutant residue， and soil restoration target （the content of dinitrotoluene sulfonate in soil less than 100 mg·kg^-1） is met. The effectiveness and practicability of the high temperature sintering resourcing technology in TNT red water contaminated soil restoration was verified through engineering application.

Abstract:As the most commonly used primary explosives， lead azide and lead styphnate are widely used in military and civilian applications. However， they are harmful to the environment and human body. Therefore， the research of new green primary explosives is an important trend. This paper reviews the synthesis and performances of six new types of initiating agents， including tetrazole， furazan， fused-ring， coordination compound， copper azide， and nano-thermite. Among of these initiating agents： （1） tetrazoles have excellent detonation performance but low safety performance； （2） furazans have higher density and good oxygen balance； （3） fused ring compounds have high thermal stability， low sensitivity and good safety； （4） the sensitivity and energy can be tailored by changing the metal ions， ligands and anions； （5） copper azide has strong detonation ability while its electrostatic sensitivity is extremely high； （6） nano-thermite has the merits of high energy density， ease of synthesis， and environment friendly， but it is difficult to achieve rapid combustion to detonation. Except for copper azide and nano-thermite， the other four types of primary explosives have complex synthesis processes and low yields. Therefore， the decreasing of sensitivity and process feasibility should be emphasized with the consideration of detonation ability for the further research of primary explosives.

Abstract:Due to conjugated planar molecular structure and additional N-oxide bonds， nitrogen-rich fused-ring N-oxides usually exhibit the advantages of high density， good detonation performances and good sensitivity and they have gradually become a research hotspot of energy materials. This article reviewed molecular structure， synthesis method and physical and chemical properties of twenty nitrogen-rich fused-ring N-oxides that were synthesized in the last decade. At the same time， this article compared some main physical and chemical properties between nitrogen-rich fused-ring N-oxides and their precursors. This review will provide some references for the synthesis and property investigation of new nitrogen-rich fused-ring N-oxides.