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Determination of Parameters of JWL Equation of State for Unreacted Explosives based on BP-GA Algorithm
Online:September 30, 2021 DOI: 10.11943/CJEM2021133
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.
Online:September 29, 2021 DOI: 10.11943/CJEM2021118
Abstract:Energy Coordination Compound （ECC） has become one of the research hotspots in recent years because of its diverse Coordination modes between different metal elements and ligands， and it is expected to obtain energetic materials with highly adjustable properties. In this paper， the ways and types of assembling ECC with different ligands are reviewed， and the applications of ECC and its functional materials as initiators， propellant catalysts， flammable agents and oxidants of thermite， pyrotechnics colorants are reviewed. Studies have shown that the energetic complexes formed after the coordination of different metal ions and nitrogen-rich ligands show great potential in the field of new energetic materials， and can meet the requirements of energy， sensitivity and other properties through the change of the type and number of ligands. The law of ECC synthesis is summarized and how to improve the energy characteristics and expand the application in the future is prospected.
Online:September 15, 2021 DOI: 10.11943/CJEM2021103
Abstract:The thermal decomposition characteristics and thermal safety of methylhydrazine （MMH） were studied by means of differential scanning calorimetry （DSC）. The kinetics， thermodynamics and thermal safety parameters of MMH were calculated， respectively. The thermal explosion delay period of MMH of ball shaped with radius of 1 m at different supercritical ambient temperatures were also obtained. Based on the isoconversion rate method， the adiabatic induction period and self-accelerating decomposition temperature of MMH were further evaluated by using AKTS software. The results show that the thermal decomposition process of MMH has only one strong exothermic peak. The apparent activation energy values of MMH calculated by Kissinger and Ozawa methods are 159.13 and 158.89 kJ·mol-1， respectively. The values of Tbp0 of MMH is 469.55 K. The values of entropy of activation （
）， enthalpy of activation （ ）， and free energy of activation （ ） are 73.93 J·mol-1，155.32 and 121.46 kJ·mol-1， respectively. The corresponding temperatures for adiabatic induction period at 8， 24 h and 168 h are 429.55， 424.05 K and 414.95 K， respectively. When the packing mass was 5， 25， 50 kg and 100 kg， the self-accelerating decomposition temperatures of MMH are 415.15， 414.15， 413.15 K and 412.15 K in turn. The results provide the necessary theoretical basis for evaluating the thermal safety of MMH in the processes of production， storage， transportation and use.
Online:September 13, 2021 DOI: 10.11943/CJEM2021102
Abstract:Composite solid propellant contains more solid particles， so it is difficult to accurately simulate the extrusion process of the propellant in twin-screw extruder with traditional finite element analysis method. Whereas， the coupling of discrete element method （DEM） and computational fluid dynamics （CFD） is an effective method for simulation the production process of composite solid propellant， but it is very difficult to implement. In this paper， based on the calibrated contact model parameters， the simulation of solid particles in solid propellant with aluminum powder and ammonium perchlorate as main components in twin-screw extrusion process was realized with DEM， and then the DEM-CFD coupling calculation of the solid propellant solid particles and the liquid phase was realized. The results show that the transportation of solid propellant particles in twin-screw calculated by DEM is consistent with the experimental law. Comparing the results between DEM-CFD coupled simulation and DEM for solid particles， it can be seen that the fluidity of materials was significantly improved by adding the liquid phase The filling rate of materials in the screw conveying section increases from 20% to 40%， and the average conveying speed of solid particles increases by 150%， but the stress of screw does not change much.
Online:September 26, 2021 DOI: 10.11943/CJEM2021159
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.
Online:September 14, 2021 DOI: 10.11943/CJEM2021170
Abstract:A 1，3，5-trinitrobenzene /1，4-dinitroimidazole （TNB/1，4-DNI） cocrystal explosive was prepared by solvent evaporation. The crystal structure was characterized by single crystal X-ray diffraction analysis. Results shows that the cocrystal crystallizes in the orthorhombic space group P212121 with crystal parameters of a = 6.4068（5） ?，b = 10.4569（8） ?， c = 20.7164（17） ?， α = β = γ = 90°， ρ = 1.776 g·cm-3， Z = 4. The differential scanning calorimetry （DSC） was used to analyze the thermal properties of the TNB/1，4-DNI cocrystal explosive. The melting point is 84.4 ℃， which is significantly lower than that of both TNB （123.5 ℃） and 1，4-DNI （91 ℃）. The TNB/1，4-DNI cocrystal explosive can be re-formed into pure cocrystal explosive after melting and cooling. The detonation velocity and pressure of TNB/1，4-DNI cocrystal explosive were also calculated to be 7704 m·s-1 and 26.08 GPa by the empirical nitrogen equivalent equations， which are significantly higher than those of the commonly used melt-cast explosive TNT. Therefore， TNB/1，4-DNI cocrystal explosive could be used as a new type of melt-cast explosive.
Online:August 23, 2021 DOI: 10.11943/CJEM2021052
Abstract:In order to study the laser radiation effect on Octogen （HMX） crystal， various technical methods were used to characterize the microstructure evolution of HMX crystal under 360 nm ultraviolet laser. By optical microscope， the process from accumulation of defects to cracking under laser irradiation was observed in HMX crystals. In-situ Raman spectroscopy demonstrated that the absorption of UV photons would stimulate HMX molecules， causing the ring vibration. In-situ wide-angle X-ray scattering （WAXS）， single crystal X-ray diffraction （SCXRD） and in-situ small-angle X-ray scattering （SAXS） were also adopted to study the crystal changes and defects evolution of HMX under UV laser irradiation. It is found that phase transformation does not happen but some new defects generate in HMX. The in-situ SAXS results show that the pores in HMX increase continuously after 1170 minutes of laser irradiation and a bimodal distribution exists in the region ranging from 10 to 20 nm and 30 to 40 nm， respectively. During the laser irradiation process， small pores in HMX keep accumulating and gradually merge into larger pores. Due to the accumulation of defects， the microcosmic pores extend into micro-cracks， and then expand into macro-cracks.
Online:August 27, 2021 DOI: 10.11943/CJEM2020307
Abstract:It is reported herein that the interfacial adhesion between binder and filler has distinct effect on mechanical properties of propellant. The tensile fracture progress of propellant （nitrate ester plasticized glycidyl azide polymer （GAP） / hexanitrohexaazaisowurtzitane （ε-CL-20） polyether propellant and polyethylene glycol （PEG） / octogen （β-HMX） polyether propellant） was monitored by in-situ tensile scanning electron microscope. In addition， the interaction strength between binder matrices and solid fillers was characterized by adhesion work and binding energy. The adhesion work was studied by inverse gas chromatography （IGC） and contact angle method， and the binding energy was calculated via molecular dynamics （MD）. Results shows that the dehumidification and fracture expanding progress of GAP/ε-CL-20 propellant are more serious than these of PEG/β-HMX propellant during stretching progress. GAP/ε-CL-20 propellant breaks when ε is more than 60% while PEG/β-HMX propellant breaks when ε is more than 80%. Besides， the adhesion work 70.69 mJ·m-2 and binding energy 259.90 kJ·mol-1 between GAP matrix and ε-CL-20 are both lower than the adhesion work 98.61 mJ·m-2 and binding energy 335.65 kJ·mol-1 for PEG/β-HMX system， suggesting that the poor interfacial adhesion between GAP binder matrix and ε-CL-20 is one of main reasons for inferior mechanical properties of GAP/ε-CL-20 propellant.
Preparation， Crystal Structure and Performance Characterization of NTO·（3，5-DATr） Energetic Ionic Salt and NTO/IMZ Energetic Co-crystal
Online:August 13, 2021 DOI: 10.11943/CJEM2021094
Abstract:In order to decrease the acidity of insensitive explosive 3-nitro-1，2，4-triazol-5-one （NTO）， NTO·（3，5-DATr） energetic ionic salt （
Ⅰ） and NTO/IMZ energetic co-crystal （ Ⅱ） were prepared by the reactions of NTO with 3，5-diamino-1，2，4-triazole （3，5-DATr） and imidazole （IMZ）. The single crystals were obtained by solvent volatilization， and the crystal structures were measured by single crystal X-ray diffraction. Crystal Ⅰbelongs to monoclinic crystal system， space group P21/c， with Mr= 229.19， a= 3.5687（7） ?， b=17.245（3） ?， c=14.655（3） ?， β=93.79（3）°， V=899.9（3） ?3， Z=4， Dc=1.692 g·cm-3； Crystal Ⅱbelongs to orthorhombic crystal system， space group Pbcn， with Mr=207.17， a=16.9398（16） ?， b=5.6802（5） ?， c=17.9111（19） ?， V=1723.4（3） ?3， Z=8， Dc=1.597 g·cm-3. Differential scanning calorimetry （DSC） and thermal weight loss method （TG） were used to test their thermal decomposition properties， and the results show that both Ⅰand Ⅱhave good thermal stability. The Gaussian 09 program was used to optimize the molecular structures and calculate their enthalpy of formation. Software EXPLO 5 was used to calculate the detonation velocity and pressure of Ⅰ（D=7662.3 m·s-1， p = 21.0 GPa） and Ⅱ（D=6490.2 m·s-1， p= 14.6 GPa）. The mechanical sensitivity was tested by the BAM method. Results show that both of them are insensitive towards impact and friction （IS > 40 J， FS > 360 N）. The pH value of standard samples were measured by pH meter. The pH values of NTO， Ⅰ，and Ⅱin 0.01 mol·L-1 standard solution are 2.92 （22.8 ℃）， 4.10 （22.7 ℃）， and 4.98 （22.8 ℃）， respectively， indicating that the formation of salt and co-crystal significantly decrease the acidity of NTO.
Online:August 24, 2021 DOI: 10.11943/CJEM2021082
Abstract:In order to enhance the comprehensive properties of glycidyl azide polymer （GAP）， the fluorine-containing GAP copolymer-based thermoplastic elastomers were developed using fluorine-containing GAP copolymer as prepolymer， butylene glycol （BDO） as chain extender and the toluene diisocyanate （TDI） as the curing agent. The molecular structure， relative molecular mass， glass transition temperature， thermally stability and mechanical properties of thermoplastic elastomers were explored via FT-IR， NMR， GPC， DSC， TG/DTG， tensile test and SEM characterizations， respectively. The number-average molecular weight of the thermoplastic elastomers was determined to be 33520 g·mol-1. The glass transition temperature （Tg） and decomposition temperature （Td） were found to be -33.3 ℃ and 220 ℃， respectively. The tensile strength at break was 5.94 MPa， and the corresponding elongation was 886%. Therefore， the thermoplastic elastomers exhibited good thermal stability and mechanical properties. Cook-off test was employed to investigate the thermal decomposition characteristics of the fluorine-containing GAP copolymer-based elastomers/Al composite， the response temperature peak of the composite was 301 ℃，suggesting an enhanced exothermal process.
Online:August 18, 2021 DOI: 10.11943/CJEM2021031
Abstract:In order to analyze the factors affecting the ignition delay time in the gas phase reaction process between hydrazine fuel and NO2， the reaction process was simulated by using density functional theory. The reaction activities， active sites， potential energy surfaces and reaction rate constants in hydrogen extraction reaction process of hydrazine （N2H4）， methyl hydrazine （MMH） and unsymmetrical dimethyl hydrazine （UDMH） were calculated. The results showed that the energy difference between the highest occupied orbital and the lowest vacant orbital of UDMH was the smallest among the three hydrazine fuels， which was 0.20522 eV， indicating that UDMH had the highest activity， so it has the fastest reaction rate with NO2， which in line with the characteristic of the shortest ignition delay time. The active sites of three hydrazine fuels were identified， N（1） or N（4） for N2H4， N（1） for MMH and N（1） for UDMH. The active sites of hydrogen extraction reaction of three hydrazine fuels were calculated， it was found that the reaction barrier of UDMH is the smallest， which is 3.589 kJ ·mol-1， and the reaction rate constant is the largest， which is 9.81×105 L·s-1·mol-1， which is consistent with the shortest ignition delay time， it is concluded that in hydrazine fuel， the smaller the hydrogen extraction reaction barrier with NO2， the larger the reaction rate constant， and the shorter the ignition delay time.
Online:August 18, 2021 DOI: 10.11943/CJEM2021056
Abstract:In order to realize the non-destructive measurement when predicting the storage life of nitrate ester plasticized polyether （NEPE） propellant， the high temperature accelerated aging， gas content monitoring and uniaxial tensile mechanical property experiment were carried out on NEPE propellant with 10% constant compression strain . The non-destructive storage life prediction model based on characteristic gas contents was proposed through correlation analysis and remaining life prediction model. The results show that during the storage and aging processes， the total amount of CO gas is the largest， reaching more than 1300 mg at different temperatures. The generating rates of NO and CO are growing slowly in the early aging period， and growing faster in the late period. The generating rate of HCl increases rapidly during the eraly and late aging period and slowly in the middle. Maximum tensile strength σm and maximum elongation εm increase slightly in the early aging period， the former oscillates slightly and the latter gradually increases in the middle period， and both of them decrease sharply in the late period. The correlation between the contents of CO and the maximum tensile strength is largest and there is a single correlation between them at different temperatures. The maximum correlation value reaches about 0.93-0.95. Four life prediction methods of NEPE propellant are established based on traditional and improved aging life prediction model， tensile strength and CO content. The maximum correlation coefficient and estimation results show that the improved prediction model based on the content of CO gas release is most effective.
Influence of the Pitch Angular Velocity on the Ballistic Trajectory of Projectiles Penetrating into Multi-layered Target
Online:August 09, 2021 DOI: 10.11943/CJEM2021033
Abstract:In order to investigate the influence of the pitch angular velocity on the penetration trajectory of projectile penetrating into multi-layered target， a large amount of experimental and simulation from literature was analyzed. In the paper， LS-DYNA finite element software was used to simulate the projectile penetrating into multi-layered slabs with or without considering the pith angle velocity. Data obtained in the simulations， like the paper studied the pith angle， landing time， landing speed， landing offset， angle of attack，landing angle， fuse overloading and etc.， were compared with the experimental results. The results show that the numerical simulation was agreed well with the corresponding experimental data， when the pitch was taken into consideration. The influences of pitch with different values and directions on the trajectory of projectile penetration into multi-layered reinforced concrete slabs were analyzed. It shows that， under the same value， the positive pith angular velocity had a greater influence than the negative one. Secondly， in order to ensure that the projectile explode in the target building， the value of the pith angular velocity and direction of the projectile must be controlled between -627°·s-1 and 427°·s-1.
Effect of Graphene Oxide on Thermal Expansion Coefficient of GAP Modified Spherical Propellant Composites
Online:August 10, 2021 DOI: 10.11943/CJEM2021099
Abstract:In order to investigate the effects of graphene oxide （GO） on the thermal expansion coefficient of GAP modified spherical propellant composites， GAP modified spherical propellant composites containing GO with 0%， 0.5%， 1%， 1.5% were prepared， respectively. Fourier transform infrared spectroscopy （FTIR）， scanning electron microscopy （SEM） and differential scanning calorimetry （DSC） were used to investigate the structure， morphology and thermal properties of the composites， respectively. The effect of GO content on thermal expansion coefficient and glass transition temperature was investigated using a static thermomechanical tester （TMA）. The results showed that the addition of GO had no significant effect on the structure and thermal properties of the cured system and no chemical reaction occurred. The addition of GO resulted in a reduction to the expansion coefficient of the composites. When the content of GO is 1%， the expansion coefficient presents the greatest reduction， decreasing from 3.236×10-4 K-1 to 2.692×10-4 K-1. The glass transition temperature increased from 20.8 ℃ to 25.1 ℃ with the addition of GO content relative to the pure GAP modified spherical propellant composite.
Online:July 23, 2021 DOI: 10.11943/CJEM2021101
Abstract:In this work， the auto-ignition behaviors of FOX-7/NC/NG powder were investigated by using rapid compression machine （RCM） under a high temperature environment. High speed images and pressure evolutions were used to record the responses of FOX-7/NC/NG samples under high temperature and pressure conditions. Results show that the samples were not able to ignite at 3.0 MPa and 598.1 K， with the heating rate of about 1.2×104 K·s-1. With the temperature increasing to 913.1 K （the heating rate is about 2.5×104 K·s-1）， the auto-ignition was observed. In addition， the validated tests of FOX-7/NC/NG samples were conducted. Results show that the experiment has a good repeatability. The uncertainties of ignition delay times （IDTI） and burning duration are less than 20% and 5%， respectively. Lastly， the auto-ignition behaviors of FOX-7/NC/NG samples were studied at different thermal loading rates. It was found that the higher thermal loading rate， the faster ignition and the shorter burning duration.
Online:August 08, 2021 DOI: 10.11943/CJEM2021104
Abstract:The effects of four typical stabilizers （DPA， C2， AKⅡ， MNA） on the thermal decomposition behavior of nitrocellulose， the thermal decomposition parameters of nitrocellulose samples under different conditions are obtained by DTA， DSC and ARC. The results of non-isothermal calorimetry showed that the critical temperature of thermal explosion of nitrocellulose was increased by 0.06， 0.82， 1.00 and 1.56 K， respectively， after adding four typical stabilizers. The adiabatic thermal test showed that the stabilizers had limited effect on the initial temperature rise rate and pressure of nitrocellulose at the initial stage， but reduced the maximum temperature rise rate of nitrocellulose by 0.39， 0.64， 0.70 and 0.65 K·min-1. The effects of thermal history on the thermal decomposition of nitrocellulose samples are investigated by DSC interruption and re-scanning method. The results show that four typical stabilizers have good thermal stability. Although the initial thermal decomposition of nitrocellulose was less affected by stabilizers， but with the progress of thermal decomposition reaction， the severe autocatalytic decomposition caused by nitrocellulose thermal decomposition products could be alleviated by rapid reaction with stabilizers， and the influence of thermal history on the thermal decomposition of nitrocellulose could be reduced. N-methyl-4-nitroaniline has the most obvious inhibition effect on the autocatalytic decomposition of nitrocellulose.
Online:August 17, 2021 DOI: 10.11943/CJEM2021055
Abstract:Numerical simulation was carried out to study the reaction evolution of explosive charge under weak stimulation and the effect of confinement conditions on its explosion reaction. Based on the multi-media arbitrary Lagrangian-Eulerian method and fluid-structure coupling technique， the numerical simulation of the reaction evolution growth of constrained charge and its interaction with the shell after local ignition were realized. In order to simulate the process from slow burning to violent explosion， a phenomenological model of explosion evolution growth was established. Based on the central ignition experiment of the strongly constrained spherical charge， a series of simulations were conducted and the influence of confinement conditions on the reaction pressure growth process of PBX-2 explosive was analyzed. The results show that the peak value of reaction pressure increases with the increase of shell strength or thickness. When the thickness of the steel shell increases from 5 mm to 20 mm， the peak value of the pressure increases from 163 MPa to 1357 MPa， and the process of pressure increase varies greatly. However， with the fracture and disintegration of the shell， the transformation from explosion to detonation of the explosive charge is restrained.
Online:August 09, 2021 DOI: 10.11943/CJEM2021098
Abstract:The attachment energy （AE） model and molecular dynamics （MD） methods were used to predict the crystal morphology of 1，1-diamino-2，2-dinitroethylene （FOX-7） under vacuum condition and in eight solvent systems including dimethylsulfoxide （DMSO）， acetone， methanol， N-methylpyrrolidone （NMP）， N，N-Dimethylacetamide （DMAC）， ethylacetate （EA）， water （H2O）， and DMSO/H2O （V/V=2/1）. By calculating the interaction energies between the solvent and crystal plane， and the attachment energies under the influence of the solvent， the simulated crystal habit and its aspect ratio were obtained. The results show that FOX-7 crystal has six important growth planes under vacuum： （1 0
）， （1 0 1）， （0 1 1）， （0 0 2）， （1 1 0）， （1 1 ）. Among them， the area of （0 1 1） plane accounts for the largest proportion， which is the most important crystal plane affecting the crystal morphology of FOX-7. The influence degree of solvent on the aspect ratio of crystal is in the following order： DMSO 2O 2O. By recrystallization experiments， FOX-7 crystals have a bulk-like shape in DMSO， methanol， and DMSO/H2O； a rod-like shape in acetone and NMP； a needle-like shape in DMAC and H2O； a flake-like shape in EA. The theoretical prediction results are in good agreement with the experimental results， which proves that the simulation of the crystal habit of FOX-7 based on the AE model can provide better guidance for the crystallization experiment. Results in thermal properties show that the crystal surface morphology and internal defects affect the phase transition temperature and thermal decomposition temperature of FOX-7. The fewer the crystal defects， the higher the α→β transformation temperature. The larger the crystal aspect ratio， the smaller the particle size， and the lower the first decomposition temperature.
Molecular Simulation of Three Kinds of Amine Antioxidants on the Aging Protection Mechanism of Hydroxyl-terminated Polybutadiene Polyurethane
Online:July 07, 2021 DOI: 10.11943/CJEM2021036
Abstract:To explore the aging mechanism and performance of antioxidants N-（1，3-dimethyl）butyl-N"-phenyl-p-phenylenediamine （4020）， N-isopropyl-N"-phenyl-p-phenylenediamine （4010NA）， N-phenyl-2-naphthylamine （D） in hydroxyl-terminated polybutadiene polyurethane （HTPB-TDI） system， quantum mechanics （QM） simulation， molecular dynamics （MD） simulation， monte carlo （MC） simulation were used to calculate the dissociation free energy， diffusion coefficient， solubility parameter and permeability coefficient of the HTPB-TDI system and each component. Results show that the order of the bond dissociation free energy of the three antioxidants is ΔGD>ΔG4010NA>ΔG4020， and they are all less than the minimum free energy of dissociation of HTPB-TDI （345.63 kJ·mol-1）， indicating that the three antioxidants can preferentially react with the active free radicals in HTPB-TDI and slow down the progress of the free radical chain reaction in HTPB-TDI； The difference of diffusion coefficient and solubility parameter between antioxidant 4020 and HTPB-TDI is the smallest， which indicates that antioxidant 4020 has poor diffusion ability and good compatibility with HTPB-TDI， so it can exist in HTPB-TDI stably and uniformly. The order of the permeability coefficient of oxygen in the three kinds of hydroxyl-terminated polybutadiene polyurethane antioxidant systems is PHTPB-TDI/D＞PHTPB-TDI/4010NA＞PHTPB-TDI/4020， which indicates that D has the worst oxygen barrier ability. According to the chemical reaction difficulty， mobility， compatibility and oxygen permeability of the three kinds of antioxidants， the order of antiaging properties of the three kinds of antioxidants is 4020>4010NA>D.
Preparation， Characterization and Plasticizing GAP-ETPE Propellants of Azide Hyperbranched Copolymer
Online:June 24, 2021 DOI: 10.11943/CJEM2021116
Abstract:A mixture of 3，3-bis（chloromethyl）oxetane （BCMO） and 3-ethyl-3-oxetane methanol （EHO） were used to synthesis the azide hyperbranched copolymers （r-POB-m） via cationic ring-opening polymerization and azidation reaction with different monomer molar ratio （BCMO/EHO=m）. The chemical structures were characterized with Infrared spectroscopy （FT-IR）， nuclear magnetic resonance （NMR）， gel permeation chromatography （GPC） and elemental analysis. The results showed that the copolymer has high molecular weight （>4400 g·mol-1）， high nitrogen content （up to 43%） and controllable branching structure. X-ray diffractometer （XRD）， Hacker rheometer and differential scanning calorimeter （DSC） were utilized to characterize crystallinity， viscosity and chemical compatibility respectively. When m=4， r-POB-4 is amorphous， possesses the lowest process viscosity and has good compatibility with the main components of the propellant， indicating that it is a potential candidate for plasticizer. In addition， compared with the GAPA plasticizer， the energetic thermoplastic elastomer （ETPE）-based propellant with r-POB-4 plasticizer exhibits higher elongation at break， lower consistency coefficient and lower viscous flow activation energy， suggesting that the azide hyperbranched copolymer could be applied as the plasticizer to effectively improve the mechanical properties and processing properties of the propellant.
Online:March 31, 2021 DOI: 10.11943/CJEM2020247
Abstract:In order to improve the combustion efficiency of Al powder， Al/modified fluororubber composite fuel（FKM-GW@Al） was prepared with the self-made silane modified fluororubber（FKM-GW） using the sol-gel method. The stability of FKM-GW@Al in solvent was studied， and the results show it is difficult to peel off the FKM-GW with functional groups， while the FKM-GW@Al has strong stability in ethyl acetate. The application of FKM-GW@Al in NEPE high-energy and low burning rate solid propellant formula was studied. Results show that after replacing Al powder by FKM-GW@Al （fluorine mass fraction 2.58%）， the heat of explosion of the propellant increased from 6348.8 J·g-1 to 6831.6 J·g-1， the content of activated aluminum in residuesdecreased from 1.02% to 0.06%， and both the static and dynamic burning rates of the propellant containing FKM-GW@Al decreased. The thermal decomposition properties of FKM-GW@Al and the propellant containing FKM-GW@Al were studied by DSC-TG， and the influence mechanism of FKM-GW@Al on combustion characteristics of the propellant was analyzed.
Online:April 20, 2021 DOI: 10.11943/CJEM2021007
Abstract:In order to study the aging migration process and influencing factors of deterred DB propellants，a theoretical model on the deterrent distribution and the change of combustion performance caused by aging migration was established based on the normal distribution characteristics of deterrent and the inference of Fickian second diffusion law. Six kinds of propellants with different contents of nitroglycerin（NG）and dibutyl phthalate（DBP）were treated by accelerated aging experiments at different temperatures and times，and the combustion performances of propellants were tested by closed bomb vessel. The kinetic process and thermodynamic influence of aging migration for propellants were analyzed. Theoretical analysis shows that the integral value growth rate of the dynamic vivacity for deterred spherical propellants presents a good linear growth relationship with aging time. The results of the closed bomb vessel show that the percentage increase of the maximum dynamic activity for the six propellants after accelerated aging also gives a good linear relationship with aging time，which is consistent with the theoretical research results. The established thermodynamic equation of aging migration for deterred propellants is basically consistent with the experimental results，and the logarithm of migration driving factor and the reciprocal of temperature present an obvious linear negative correlation. When the total content of NG and DBP in propellants is greater than 15%，the migration driving factor is more susceptible to the influence of temperature，leading to migration invalidation. When the total content of NG and DBP is less than 15%，the invalidation rate caused by deterrent migration is relatively slow，which is more conducive to the use and shooting safety after the storage of propellants.
Numerical Simulation Analysis of Irreversible Deformation Mechanism Caused by Thermal Cycling of PBX?9502
Online:May 12, 2021 DOI: 10.11943/CJEM2020091
Abstract:Aiming at the problem of the irreversible deformation mechanism caused by thermal cycling in PBX-9502 （a type of TATB based polymer bonded explosive）， a three-phase microstructure model and an extended finite element method （XFEM） are used to establish a calculation model. The model takes into account the anisotropy of the TATB grains， the local differences in the thermodynamic properties of the bonding agent and its interface. Using the established model， the phenomenon and mechanism of irreversible deformation caused by thermal cycling of PBX-9502 are numerically analyzed. The results show that due to the severe anisotropy of TATB grains in PBX-9502 and the differences in the thermodynamic properties of TATB grains and binders， PBX-9502 specimens have internal deformation and stress concentration during thermal cycling. Resulting in the destruction of the bonding agent and the debonding of the interface and other internal damage to the material， which in turn led to the irreversible deformation of the PBX-9502 specimen under thermal cycling. At the end of the calculation， the axial strain of the PBX-9502 specimen reached 0.2%.
Online:May 20, 2021 DOI: 10.11943/CJEM2021047
Abstract:High tension bonds or high-energy bonds are important elements in the formation of disruptive energetic materials， but it"s hard to form and easy to break，. Their construction has always been a difficult problemin the field of chemistry and energetic materials. By using the unique internal space of molecular cages to “assist” the construction of such chemical bonds provides a feasible route for related research， and has been put into practice. This review summarized “confinement effect”， weak interaction， electron transport and other characteristics of molecular cages. It is discussed that it can prevent oxygen oxidation of P4 and other high-tension materials， stabilize aryl pentazoles and other high active substances， reactants such as NaN3 to accelerate the reaction， change the reaction path. The roles of molecular cages in these processes， such as “firewall”， “stabilizer”， “accelerator”， “channel remover” and others， were reviewed， which provided references for the preparation of novel energetic compounds such as TdN4 and the study of controllable energy release . At the same time， it also points out the key direction of future research： design and synthesis of new and efficient molecular cages. developing good characterization methods and means of molecular cage complex. Enhance the composite and release of multi-environment responsive molecular cages and energetic materials.
Online:June 10, 2021 DOI: 10.11943/CJEM2021069
Abstract:In order to ensure the safety of field mixed emulsion explosive， dynamic extrusion was used to simulate the charging process of explosive. The stability of field mixed emulsion explosive prepared at different rotating speed was studied by laser particle sizer， microscope， water-soluble ammonium nitrate precipitation test and digital viscometer. The experimental results show that crystallization instability in the emulsion matrix will occur in some extent under dynamic extrusion when the particle size is larger than 5 μm.After 10 times of dynamic extrusion， the amount of ammonium nitrate released from the emulsion matrix is 5.14 times of that before compression， the viscosity increases by 43%， and the W/O structure has been completely destroyed.When the particle size is smaller than 5 μm， the dynamic extrusion resistance of emulsion matrix is improved，after 10 times of dynamic extrusion， the particle size of emulsion matrix increased by 2.16 times， the amount of ammonium nitrate released from the emulsion matrix is only 2.14 times of that before compression， the viscosity increased by 10%， and the microstructure remained stable.The dynamic extrusion process will accelerate the crystallization instability of matrix， change the physicochemical properties， reduce the performance of emulsion explosive， and is not conducive to the loading process. In production practice， it is necessary to reasonably control the particle size D≤5 μm.
Preparation and Oxidation Characteristics of Micron Aluminum Powder Interface Structure Based on Focused Ion Beam
Online:July 14, 2021 DOI: 10.11943/CJEM2020323
Abstract:In order to study the interface structure of aluminum core/oxide layer intuitively， the slicing method of aluminum powders （2-8 μm） were successfully established based on FIB micro and nano processing technology. The slices were obtained by combining FIB direct cutting with profile thinning. The interface structure of the prepared slice samples was clear and intact， and the oxide layers were not damaged. The microstructure， crystallinity and element distribution of “Al core/oxide layer” under different ageing conditions were obtained were characterized by SEM， HRTEM and EDS. The stoichiometric ratio of Al and O elements in the oxide layer of aluminum particles deviated from the standard Al2O3， showing a gradient distribution. The positive correlation between the oxide layer thickness of aluminum particles and the aging temperature has been quantitatively obtained. The oxide layer thickness of the samples without thermal aging was ~5.4 nm， and the oxide layer thickness of the samples aged at 75 ℃ and 95 ℃ increased to （34.1±2.1） nm and （51.3±2.2） nm， respectively.
Online:July 20, 2021 DOI: 10.11943/CJEM2021071
Abstract:In order to study the influence of aluminum powder on the mechanical property， interface， combustion， safety， energy， density and other performance of propellants， the glycidyl azide polymer （GAP） propellants with 5%， 10%， 15% and 18% aluminum powder were evaluated by tensile testing machine， dynamic thermomechanical analysis （DMA）， calculation program and etc. Results show that， with the replacement of 320 μm AP with 30 μm aluminum powder and the increase of aluminum powder contents， the propellant has increasing maximal tensile strength and maximal elongation， and improving interface performance. The burning rates change scarcely but the pressure indexes drop down from 0.43 to 0.40 under the pressure of 3-9 MPa. The hazard grades of propellants with 5% and 18% aluminum powder are 1.3 both. The friction and impact sensitivities of propellant with 18% aluminum powder are 44% and 0%， respectively， which are lower than the formulation with 5% aluminum powder （48% and 4%， respectively）. At last， the calculation result shows that with the increase of aluminum powder， the energy and density of propellants grow up， but the standard specific impulse levels off to moderate pace of growth.
Rheological Behavior of the Compound Mixed with Metastable Aluminum-based Composites and Typical Binders
Online:August 13, 2021 DOI: 10.11943/CJEM2021077
Abstract:The dispersion characteristics of metal additives in binders might tremendously affect the processing properties of propellants and explosives. Rheological properties of the two metastable intermolecular composites （QAlPV and PAlPV） mixed with hydroxyl-terminated polybutadiene （HTPB）， glycidyl azide polymer （GAP） or poly （ethyleneoxide-co-teterafuran） （PET） separately were investigated by RS-300 rheometer respectively. Results show that all the six sorts of suspensions exhibited pseudoplastic fluid characteristics， and their apparent viscosity decreases with the increase of temperature between 20 ℃ and 60 ℃. In the systems containing GAP and PET， the flow activation energy of the suspensions with PALPV is greater than those containing QALPV. The results present that the suspensions filled with the lamellar aluminum-based composite exhibites more rigidity， meanwhile their apparent viscosity are more sensitive to temperature. Therefore， the dispersion of PALPV in binders could be improved by increasing the temperature. The dispersion and homogeneity of the suspensionsformed by QALPV， GAP or PET separately could be improved by accelerating the shear rate.
Online:July 15, 2021 DOI: 10.11943/CJEM2021079
Abstract:In order to explore the detonation law of α-AlH3 in condensed phase explosive， the safety features of α-AlH3 were characterized. The results indicated that α-AlH3 had poor thermal stability due to its sensitivity to temperature and humidity. The operational condition for α-AlH3 samples should not exceed 30℃ RT and 60% RH. HMX was selected as the main high explosive to develop a formulation containing α-AlH3 with a self-designed technology namely direct method of step temperature control and cooling. The safety， detonation performance， work capacity and explosion reaction process of the explosive were studied. The molding powder had low mechanical sensitivity and good moldability. When the α-AlH3 content exceeded 10%， the relative density of the grain decreased with increasing content of α-AlH3. The characteristic detonation velocity of α-AlH3 was 6078 m·s-1. Compared with an HMX based explosive formulation containing aluminum， the counterpart with α-AlH3 had an equivalent work capacity. But its work capacity was poor at the high and medium pressure stage of the expansion process of the detonation products. The hydrogen element in α-AlH3 mainly existed in the form of hydrogen in the detonation products.
Online:July 14, 2021 DOI: 10.11943/CJEM2021080
Abstract:A 20 L explosion device was used to study the explosion characteristics of fuel-air explosive containing micro/nano-aluminum powder. Results indicated that when adding 5% and 10% nano-aluminum to micro-aluminum， the maximum pressure of mixed powder increased by 24.2% and 58.5%， respectively. The maximum rate of pressure rise increased by 80.6% and 103.4%. The nano-aluminum would not have any contribution to the explosion effect while its content was more than 10%. For the fuel with a solid/liquid ratio of 30/70， while the ignition energy increased from 11.83 J to 28 J， the explosion pressure consequently increased from 0.28 MPa to 0.52 MPa， meanwhile the explosion temperature increased from 834 ℃ to 1118 ℃，indicating that the explosion parameters of FAE could be improved by increasing the ignition energy. Increasing the content of micro/nano aluminum powders could effectively increase the explosion pressure and temperature of FAE.
Online:September 01, 2021 DOI: 10.11943/CJEM2021081
Abstract:In order to improve the reactivity of submicron aluminum powder， Al-Cu composite metal powder was prepared by means of electric explosion with composite wires. The preparation parameters were determined by monitoring the waveform with oscilloscope in the electric explosion process. The structure and morphology of the composite was characterized by XRD， SEM， TEM-MAPPING and XPS. The Al-Cu composites powder was consisted of CuAl2 and Al. The morphology of the material was sphere with an average size 150 nm. The forming mechanism of the morphology of the as-prepared composite particles was analyzed. Both DSC and aluminum-water reaction methods were employed to evaluate the reactivity of the material. The first oxidation peak temperature of Al-Cu composite metal powder was 550 ℃， as shown in its DSC curve. This parameter was decreased by 50 ℃ comparing with Al prepared with the same parameters. This results indicated that as-prepared composite particles had better reactivity. The first oxidation process of Al-Cu composite metal powder lasted from 500 ℃ to 600 ℃ within 5 mins， while the counterpart lasted from 500 ℃ to 650 ℃ within 7.5 min. Comparing with Al， the heat release rate of Al-Cu composite metal powder was increased by 33% during the first oxidation process. The reaction completeness of the as-prepared composite particles was 0.88 tested by aluminum-water reaction method， but it was only 0.73 for the counterpart. During the first 10 mins of Al-H2O reaction， the reaction completeness of Al-Cu composite powder was 0.36 which was as much as ten times that of the counterpart. The result suggested that the reactivity of the composite was improved a lot.
Online:August 24, 2021 DOI: 10.11943/CJEM2021087
Abstract:Aiming at the development and problems of high-strength energetic structural materials （ESMs）， the characteristics， static mechanical behaviors and dynamic mechanical behaviors of high-entropy alloys （HEAs） were summarized and analyzed. The assumptions， potential and challenges of HEAs as high-strength ESMs were proposed and verified from the perspective of both theoretical and experimental aspects. It was found that HEAs had the basic features of “free composition design”， “simple crystal structure with strong lattice distortion” and “high strength and hardness”. At the same time， both static and dynamic mechanical behaviors of HEAs can be adjusted in a wide range by means of process adjustment and composition design. All the above features indicated that HEAs had the potential advantages to be used as high-strength ESMs in terms of workability， high strength， and rapid oxidation to release energy. Existing experimental results also confirmed the application potential of high-entropy alloy ESMs. Finally， the challenges faced by the research of high-entropy alloy ESMs and the priorities of future research， such as high-throughput experiments and simulations， researches on dynamic mechanical behaviors and preparation for large-scale samples， were raised based on the intrinsic features of HEAs and previous experimental results.
Energy Output Characteristics of RDX-based Composite Explosives Containing Hydrogen Storage Materials
Online:August 23, 2021 DOI: 10.11943/CJEM2021126
Abstract:In order to study the energy output characteristics of three composite explosives containing Mg-based hydrogen storage materials， Ti-based hydrogen storage materials and ZrH2 hydrogen storage materials respectively， a constant temperature detonation heat calorimeter and an underwater explosion system were used to study the detonation heat and underwater energy characteristics of the explosives. The results illustrated an order of the detonation heat in terms of a thermobaric formulation of RDX/hydrogen storage material/AP/others， which was Mg-based sample>Ti-based sample?ZrH2-based sample. Accordingly， the detonation heat for the three explosives were 7587.0606 kJ·kg-1， 6416.4741 kJ·kg-1 and 3950.6279 kJ·kg-1. It was indicated that the detonation heat of the explosives containing hydrogen storage materials was positively correlated with the chemical potential of each hydrogen storage material. In underwater explosions， the explosion parameters including peak pressure， impulse， energy flow density and shock wave energy of the composite explosives presented a similar order， that the Mg-based sample was the best and the ZrH2-based sample was the worst. Accordingly， the shock wave energy was 1.41 times， 1.26 times and 0.97 times of TNT equivalent for each formula. It was showed that hydrogen storage materials with much higher activity and potential energy could be beneficial for the shock wave in underwater explosion. The contribution to the energy released in underwater explosion of hydrogen storage materials was mainly in the form of bubble pulsation. The bubble energy of the composite explosives containing Mg-based， Ti-based and ZrH2 hydrogen storage materials were 2.17 times， 1.78 times， and 0.86 times of TNT equivalent respectively， indicating that Mg-based hydrogen storage material had the best energy releasing performance in the secondary reaction， followed by Ti-based hydrogen storage material and ZrH2was the worst The trends of the explosion parameters of the composite explosives in detonation heat test and underwater explosion test were consistent. The overall energy level of the explosives was in the order of Mg-based sample>Ti-based sample>ZrH2-based sample. The explosive containing Mg-based hydrogen storage material had the largest energy in underwater explosion， reaching up to 2.02 times of TNT equivalent. The applicability of the ZrH2 in thermobaric formulation was not strong for both of the energy tested in detonation heat and underwater explosion was lower than TNT.
Preparation and Characterization of Thermal Oxidation and Pressurization of Al/Mo/PMF （Graphite Fluoride） Composite Powder
Online:September 07, 2021 DOI: 10.11943/CJEM2021148
Abstract:In order to obtain the metal alloy composite fuel with pressurization effect， Al/Mo/PMF composite powder was prepared by a combination of vacuum suspension smelting， ultra-high temperature gas atomization and mechanical alloying. The phase， morphology and thermal properties of the composite powder were analyzed by XRD， SEM， TG/DTA. The combustion enthalpy and pressurization properties of the composite powder was measured by oxygen bomb calorimeter and constant volume isothermic combustion experiments. Results show that PMF distributes homogeneously in the composite particles after mechanical ball milling， which is helpful to improve the thermal reactivity of the powder and advance the initial reaction temperature. The extra pressurization effect was obvious due to the production of AlF3 and MoO3 with low boiling point. The extra pressurization generated by the combustion of Al/Mo/PMF 64/16/20 composite powder was 4.49% higher than that of pure Al powder. With the increase of PMF in the composite， the combustion enthalpy and combustion completeness of the composite powder decreased. The measured combustion enthalpy of Al/Mo/PMF 76/19/5 composite powder was 22541.8 J?g-1， while the measured combustion enthalpy of Al/Mo/PMF 64/16/20 composite powder was 16788.5 J?g-1. When the PMF content was 5%， the composite can burn completely， meanwhile the extra pressurization can be presented effectively. The corresponding maximum pressure was 3.430 MPa. In addition， the oxidation process and the mechanism of Al/Mo/PMF 76/19/5 composite powder were also studied.
Ignition and Explosion Characteristics of Modified Magnesium Hydride Based Hydrogen Storage Materials
Online:August 16, 2021 DOI: 10.11943/CJEM2021163
Abstract:In order to study the influence of modification technology on the ignition and explosion characteristics of the composite hydrogen storage materials， the combustion heat of Al， MgH2， Hydrogen storage material CM and hydrogen storage material CM-H coated with hydroxyl terminated polybutadiene （HTPB） was measured by an oxygen bomb calorimeter， and the mass change of the four samples within 48 h was test as well. Results show that CM-H has the highest combustion heat for 30.5633 MJ·kg-1. Meanwhile its mass gained within 48 h in air is the least for 0.46%. Result show that the modification can effectively prevent the performance degradation of the materials so that they can maintain a high combustion heat. The minimum ignition energy， flame propagation characteristics and explosion pressure of the four samples were studied by an 1.2 L Hartmann tube， a high-speed camera and a 20 L ball explosion test device respectively. Results show that the minimum ignition energy of CM is 50-60 mJ， which was only a half of the critical ignition energy of aluminum powder （100-150 mJ）. It indicated that the addition of MgH2 into metal materials can effectively reduce the ignition energy. The minimum ignition energy of CM-H dramatically increased to 700-750 mJ after coating. The test results of flame propagation speed， explosion pressure and explosion index presented the performance order of MgH2 > CM > CM-H > Al. Results indicat that the modified composite hydrogen storage material has lower electric spark sensitivity， higher safety and better explosion performance.
Online:August 13, 2021 DOI: 10.11943/CJEM2021165
Abstract:How to improve the explosion energy and power ability of explosive by applying reactive metal particles effectively is the key problem for the design of metalized explosive. To explore the application of the micro-B/Al composite powder in enhance blast explosive （EBX） and thermobaric explosive （TBX）， three HMX-based explosives containing B/Al particles were designed and prepared. The energy output characteristics of the samples with a dimension Φ100 mm×105 mm was studied by air blast and underwater explosion test， meanwhile the power abilities were evaluated by a Φ50 mm cylinder test. The effect of the content of micro-metal on energy output process and power ability of metalized explosives was discussed. Results show that in the air blast and underwater explosion tests， initiated by the detonation of HMX， the combustion of micro-Al can promote the afterburning effect of micro-Boron resulting in releasing a great amount of combustion heat to generate expansible products with high temperature and high pressure， finally increase the sustained duration of fireball and total energy in underwater explosion. In the cylinder test， there was not enough oxygen to react with micro-B before the cooper cylinder burst， accordingly the advantage of combustion energy of micro-boron in explosives containing B/Al could not present. However， after the cooper cylinder burst， the oxygen in the air can oxide B/Al composite powder to release a large amount of combustion heat， which can enhance the power ability of aftereffect.
Online:August 16, 2021 DOI: 10.11943/CJEM2021178
Abstract:To study the energy output law of the suspended AlH3 dust in explosion and release process， a modified 20 L ball explosion test system was used to study the explosion pressure and flame propagation law in closed and venting conditions alternately. The results showed that the lower explosion limit concentration of suspended AlH3 in a closed system decreased from 40 g·m-3 to 30 g·m-3 comparing with aluminum powder， indicating that the hydrogen released by the burning AlH3 accelerated the entire chemical reaction process. In addition， both the maximum explosion pressure and explosion pressure rise rate of AlH3 dust explosion in a closed system were higher than that of the aluminum powder. The maximum explosion pressure rose from 1.02 MPa to 1.15 MPa， indicating that a combustible gas-dust composite system was formed due to the release of hydrogen to exacerbate the violence of the explosion energy release process. Under venting conditions， when the concentration of AlH3 dust was 500 g·m-3， the explosion pressure （p） and pressure rise rate （dp/dt） decreased the most， reaching 43% and 30% respectively， indicating explosion venting can effectively reduce explosion damage. Moreover， it was concluded that the length and speed of the explosion vent flame reached the peak values when the concentration of AlH3 was 750 g·m-3， meanwhile the probability and frequency of multiple flames presented a positive correlation with the concentration.
Online:August 21, 2021 DOI: 10.11943/CJEM2021180
Abstract:Aluminum powder was widely used to improve the energy characteristics of explosives and solid propellants due to its excellent properties, such as high activity, high density, high combustion enthalpy and low oxygen consumption. The transition metal Cu had a good catalytic effect on the combustion of aluminum powder and could make the aluminum powder burn more completely. As a binder component of solid propellant, hydroxy-terminated polybutadiene (HTPB) was beneficial to prevent the oxidation and agglomeration of aluminum particles, accordingly in favor of the press-packing and curing while uniformly coating on the surface of aluminum particles. Using the copper acetylacetonate as copper source, formaldehyde and hydrazine as reducing agent, HTPB/Cu/μAl composite particles were prepared by one-pot liquid phase reduction. The structure and morphology of the samples were characterized by IR, XRD, SEM and EDS. Meanwhile, the catalytic performance of HTPB/Cu/μAl on the decomposition of AP was studied. The results showed that the reduced Cu particles were scattered on the surface of aluminum particles, and HTPB was evenly coating on the surface of Cu/μAl. In the DSC curve of HTPB/Cu/μAl, the oxidation exothermic peak of transition metal Cu and the decomposition exothermic peak of HTPB appeared simultaneously between 150~350 °C. However, the coating had almost no effect on the oxidation exothermic peak of micron aluminum powder at 550 °C. The average activation energy of HTPB/Cu/μAl was 287.2 kJ·mol-1, which was 36.35 kJ·mol-1 lower than that of μAl (323.55 kJ·mol-1). Both of the decomposition peaks of AP at high temperature and low temperature had changes when HTPB/Cu/μAl composites were added. Compared with pure AP, the exothermic decomposition peak at high temperature of HTPB/Cu/μAl/AP was reduced by 127 °C, indicating that the HTPB/Cu/μAl composites could promote the thermal decomposition behavior of AP.
Influence of Magnesium Content on Reactive Performance of Centrifugal Atomized Aluminum-Magnesium Alloy Powder
Online:September 03, 2021 DOI: 10.11943/CJEM2021197
Abstract:To investigate the effect of Mg content on the properties of centrifugal atomized aluminum-magnesium （Al-Mg） alloy powders， Al-Mg alloy powders with different mass ratios （70∶30， 50∶50， 30∶70） were prepared by centrifugal atomization. The particle size， morphology， physical phase， and kinetics parameters of the samples were characterized via the particle size distribution meter， scanning electron microscope （SEM）， X-ray powder diffractometer （XRD） and TG-DSC. The effect of different Mg content on the activity of the alloy was also studied by thermal oxidation at 71 ℃. Results showed that all Al-Mg alloy powders had a good size distribution， regular morphology and high sphericity. The metallographic structure demonstrated that Al-Mg30 and Al-Mg50 had a dendritic structure， and Al-Mg70 was composed of α-solid solution and dendritic precipitates. The main phase of the alloy was α-Al， β-Al3Mg2 and γ-Al12Mg17. The β-Al3Mg2 phase gradually decreased and the γ-Al12Mg17 phase increased with the increasement of Mg content. Moreover， the deactivation rate of Al-Mg alloy powders was found to increase with the increasement of Mg content. The activity of alloy powders remained basically constant after 48 h. The TG-DSC results indicated that both the initial exothermic temperature and the activation energy of the alloys were gradually reduced as the Mg content increased， but the reactive speed was accelerated. The increasement ratio of weight of all Al-Mg alloys was greater than that of micron Mg （53.06%） and Al （8.63%）. The results of Laser ignition showed that the ignition delay of Al-Mg alloy was much shorter than monolithic aluminum， as well as the combustion duration. The microburst phenomenon was observed in the test.
2021,29(9):781-789, DOI: 10.11943/CJEM2020234
Abstract:In order to study the performance of 3，3''-bi（1，2，4-oxadiazole）-5，5''-diylbis（methylene）dinitrate （BOM）， the sample was prepared by using the melting casting process and its the detonation velocity was measured. The thermal safety of the BOM casting process was studied by the thermal decomposition and constant temperature test. The solidification properties of BOM were studied by macroscopic solidification molding and microscopic solidification crystallization test. The mechanical properties of the BOM casting were studied by compressive and tensile tests. The detonation velocity and detonation heat properties of BOM/HMX/Al melt-cast explosive system were analyzed by detonation performance calculation. The results show that the natural solidification density of BOM is 1.726 g·cm-3 and the detonation velocity is 7679 m·s-1. The peak temperature of BOM decomposition is 213.8 ℃， and the calculated critical temperature of thermal explosion is 190.7 ℃. There is no discoloration and smoke during the constant temperature heating， which shows satisfactory thermal safety of the melt-casting process. The solidification defects of BOM were concentrated in the feeding area at the top of the casting， The volume shrinkage rate of natural solidification was 15.7%， and the forming density was 94.7% of the theoretical density， indicating good solidification and forming performance. The compressive strength of the casting is 6.21 MPa and the tensile strength is 1.89 MPa. In the BOM/HMX/Al melt-cast explosive system， the detonation velocity decreases linearly with the increase of Al content. When the Al content is less than 24%， the detonation heat increases gradually with the increase of Al content. When the Al content is more than 24%， the detonation heat is related to the ratio of BOM and HMX in the formula， and the ratio of BOM and HMX system needs to be adjusted to meet the optimal Al/O ratio of the formula.
2021,29(9):790-797, DOI: 10.11943/CJEM2020226
Abstract:The co-crystal of hexanitrohexaazaisowurtzitane （CL-20） and 2，4-dinitro-2，4-diazapentane （DMMD） was prepared by co-crystallization in solution. It was characterized by single crystal X-ray diffraction（SCXRD）， scanning electron microscopy（SEM）， powder X-ray diffraction（PXRD）， and fourier transform infrared （FT-IR）， and differential scanning calorimetry （DSC）. The results show that CL-20/DMMD co-crystal belongs to monoclinic system with space P21/c. Analysis of interactions in co-crystal shows that the main forces between two kinds of molecule in co-crystal are hydrogen bonds and features a layered motif. There is new crystal phase in the XRD pattern. The shift of peaks for CL-20/DMMD attributes to the formation of C─H…O hydrogen bonding in FT-IR pattern. Results of DSC show that the melting point of co-crystal is 180.8 ℃， which is 21.5 ℃ and 120.9 ℃ higher than that of CL-20 and DMMD. The main thermal decomposition peak temperature of CL-20/DMMD co-crystal is 240.1 ℃， which increases by 3.5 ℃ compared with CL-20. The predicted detonation velocity and detonation pressure of CL-20/DMMD co-crystal are 9386 m·s-1 and 45.09 GPa according to the theories of Rothstein and Petersen， respectively. They are slightly lower than that of CL-20 and higher that of DMMD（D=7287 m·s-1，P=21.79 GPa），HMX（D=9048 m·s-1，P=40.55 GPa）， RDX（D=8945 m·s-1， P=37.28 GPa）， and TNT（7042 m·s-1， P=21.44 GPa）.
A Novel Melt-Cast Explosive Bis（dinitromethyl-ONN-azoxyfurazanyl）trifurazan（BDNAF）： Synthesis and Characterization
2021,29(9):798-802, DOI: 10.11943/CJEM2021001
Abstract:A novel melt-cast energetic compound bis（dinitromethyl-ONN-azoxyfurazanyl）furazan （BDNAF） was synthesized using 3，4-bis （3′-aminofurazal-4′-yl）furazan （BATF） and 2，2-dimethyl-5-nitro-5-nitroso-1，3-dioxane （DMNNDO） as starting materials via oxidation coupling， hydrolysis， bromization， reduction and nitration five-step reactions. The structures of the intermediates and the target material were fully characterized by infrared spectrum（IR）， nuclear magnetic resonance（NMR） and elemental analysis（EA）. The thermal behaviors of intermediate compound 3，3''-bis（nitromethyl-ONN-azoxyfurazanyl）furazan （BNAAF） and target compound BDNAF were investigated based on differential scanning calorimetry（DSC） measurement， and the physicochemical properties and detonation performances of BNAAF and BDNAF were estimated by Gaussian 09 program and Explo 5（v. 6.04）. Results show that the intermediate compound BNAAF directly decomposed at 106.4 ℃ without melting process， and the calculated density of BNAAF is 1.82 g·cm-3， the detonation velocity is 8298 m·s-1， and the detonation pressure is 29.0 GPa. The melting point of the target compound BDNAF is 95.4 ℃， the first decomposition point is 170.5 ℃ at the heating rate of 10 ℃·min-1， and the theoretical density of BDNAF is 1.91 g·cm-3， the detonation velocity is 9005 m·s-1 and the detonation pressure 35.9 GPa， which revealed that BDNAF is a promising melt-cast explosive.
2021,29(9):803-810, DOI: 10.11943/CJEM2021074
Abstract:In order to study the problem of impact strength and rheological properties of propellant substitutes （Cellulose Acetate， CA） assisted with supercritical carbon dioxide （SC-CO2）， the in-line slit rheometer， drop hammer impact test machine， SEM were used， and the rheological properties， impact strength and cell morphology of product were characterized in varied experiment conditions. Research results prove that， when process temperature is 50 ℃， solvent ration is 1.2 mL·g-1， flowability of CA is optimized evidently as injection speed of CO2 increasing. However， impact strength of extrusion product only account for nearly 53.11% of those products prepared without SC-CO2（when injected mass fraction of SC-CO2/CA is 0.173%， screw speed is 10 r·min-1）； SEM results prove that， quantities of irregular foam structure exist in product prepared with SC-CO2， foam size are both over 2 μm， some of them even reach at 15-25 μm. Impact strength and product appearance could be modified as screw speed increase， product prepared in 14 r·min-1 attain higher impact strength （nearly 170.33%） than 6 r·min-1. During the process of propellant substitutes assisted with supercritical carbon dioxide， rheological properties of CA in barrel could be optimized as injection speed， solvent ratio， process temperature and screw speed increase， however， impact strength of CA could be positively modified as screw speed increase.
Preparation of High Loading Cu1/Al2O3 Single-Atom Catalyst and its Effect on the Thermal Decomposition of AP
2021,29(9):811-818, DOI: 10.11943/CJEM2020266
Abstract:To improve the thermal decomposition performance of ammonium perchlorate （AP）， Cu1/Al2O3 single-atom catalyst was prepared through the evaporation induced self-assembly （EISA） method. The morphology and structure of prepared Cu1/Al2O3 single-atom catalyst were characterized by X-ray diffractometer （XRD）， inductively coupled plasma （ICP-OES）， transmission electron microscopy （TEM）， X-ray absorption spectroscopy （XAS） and X-ray photoelectron spectrometer （XPS）. The effect on the thermal decomposition of ammonium perchlorate（AP）was also investigated by differential scanning calorimetry （DSC） and thermal gravimetry （TG）. Results show that Cu atoms were dispersed and stabilized through oxygen bridge bonds on the Al2O3 supporter. The Cu loading was determined to be 8.7%. When the content of Cu1/Al2O3 single-atom catalyst is 5%， the high-temperature exothermic decomposition peak temperature of AP decreases to 319 ℃， which was 85 ℃ lower than that of pure AP. This Cu1/Al2O3 single-atom catalyst exhibits superior catalytic performance on the thermal decomposition of AP， which was more effective than Cu（NO3）2·3H2O and nano-CuO catalyst.
2021,29(9):819-826, DOI: 10.11943/CJEM2021004
Abstract:To investigate the quasi-static tensile mechanical properties of aging high solid content modified double-base propellants （CMDB）， the uniaxial tensile tests of CMDB propellant were carried out at four different temperatures （323， 293， 273， 253 K） and different strain rates （3.3×10-5， 3.3×10-4， 3.3×10-3， 3.3×10-2 s-1）. The CMDB propellant samples with different aging time （0，10，20，35，50，65，80，100 d） were tested by gas chromatography. The mechanical properties of CMDB propellant and the change of stabilizer content after aging were studied. The results show that the maximum elongation and the content of stabilizer decrease significantly during the aging process， which can be used as the failure criterion of the aging CMDB propellant. By using the time-temperature superposition principle （TTSP）， the maximum tensile strength curve of CMDB propellant was obtained， and the aging strength main curve equation was established， which could be used to predict the maximum tensile strength of CMDB propellant with different aging time in the range of quasi-static strain rate.
2021,29(9):827-832, DOI: 10.11943/CJEM2020084
Abstract:In order to realize the efficient application of TKX-50 in field of solid propellants， the energy performance of poly（glycidylaminopropyl ether） （GAP）-based solid propellants containing TKX-50， CL-20， and TKX-50/CL-20 was calculated using the minimum free energy method， and the feasibility of TKX-50 and CL-20 combination application was analyzed. The application efficiency of TKX-50/CL-20/GAP-based solid propellant was also estimated. The results show that when TKX-50 content increases， balance combustion temperature of propellant in combustion chamber（Tc） and combustion gas average relative molecular mass（
） of propellant decrease at the same time， and the theoretical ratio of impulse was first increased and then decreased. The compatibility of TKX-50 and CL-20 was moderate compatibility. It has good thermal stability and safety performance of the TKX-50/CL-20 mixture propellant. It can significantly broaden the choice of the content of each component of the formulation with TKX-50/CL-20 mixture propellant. The lower limit of CL-20 content in the compound propellant with theoretical specific impulse greater than 272 s was only 40% of pure CL-20 propellant. At the same energy level， TKX-50/CL-20 mixture has the characteristics of low cost and low characteristic signal， and has the potential of engineering application.
2021,29(9):833-839, DOI: 10.11943/CJEM2020303
Abstract:3， 4-dinitropyrazole（DNP）， a new type of smelt-cast matrix explosive， is a kind of high energy matrix with great application potential. The impact Hugoniot relationship of explosive is the basis to investigate its impact initiation characteristics. For this reason， the pressure comparison method was adopted in this study. Plane wave generators were selected to act the designed loading. The post-shock pressure of DNP explosive and LY12 aluminum samples under nine shock pressures were measured by manganese-copper piezoresistivity gauges. By calculating the experimental data， the velocity （D） of the shock wave and the velocity u of the particle under different pressures were obtained. The D-U relationship of the DNP explosive in the range of 3.7~14.4 GPa was obtained by fitting. The results showed that the Hugoniot relationship of the DNP explosive in the range of 3.7~14.4 GPa could be approximated as a straight line in the D-U plane. The post-wave state of DNP explosive under the action of shock wave was defined， which provided a reference for further study of impact ignition and initiation of DNP explosives. In addition， the influence of polytetrafluoroethylene packaging of manganese-copper piezoresistance gauges on the experimental test results was analyzed. The systematic error caused by packaging was effectively eliminated through theoretical analysis and reasonable interpretation of test signals.
2021,29(9):840-847, DOI: 10.11943/CJEM2020217
Abstract:To study the correlation between the packed density of nonmetallic spherical spacers （NSS） and its suppression of propane explosion， a newly designed constant-volume combustion cylinder combined with high-speed schlieren photography was employed. The explosion experiments of propane-oxygen pre-mixtures with different equivalence ratios（1，1.5 and 2） were conducted in cylinders with different packed densities of NSS （21.9 kg·m-3，38.7 kg·m-3 and 45.1 kg·m-3）. The effect of packed densities of NSS on maximum explosion pressures， total heat loss， flame tip velocities， flame propagation characteristics and turbulence in cylinders with different equivalence ratios of propane-oxygen were analyzed in detail. The results show that NSS has suppression effect on the maximum explosion pressure， and has promotion effect on the flame propagation process. When the packed density of NSS is 45.1 kg·m-3， the maximum explosion descending rate and heat loss in cylinders reach maxima， while the peak flame tip velocity ， the maximum tip velocity difference between two points and the turbulence enhancement factor in cylinders are relatively small， which indicates the best explosion suppression performance of NSS.
2021,29(9):848-854, DOI: 10.11943/CJEM2020141
Abstract:In order to prevent the spacecraft from being damaged by the high pyroshock during the action of the pyrotechnic separation nuts， a metal rubber vibration isolator（MRVI） was used to suppress the pyroshock response caused by the impact of the piston in the separation nut. Three kinds of MRVIs with different stiffness were installed at the end of the piston movement in the separating nut， and the shock response spectrum（SRS） in the frequency domain of 500 Hz to 10000 Hz was analyzed. The results show that the pyroshock suppression effect of the MRVI mainly occurs in the frequency band above 3000 Hz， and the pyroshock suppression effect in the frequency band above 5000 Hz is the most significant. The maximum acceleration response after installing a small-stiffness MRVI is reduced from 1330 g to 852 g， and the maximum reduction in analysis frequency domain is 675 g@5993 Hz. The maximum acceleration response after installing a medium-stiffness MRVI is reduced from 1530 g to 1251 g， and the maximum reduction in analysis frequency domain is 539 g@9514 Hz. The maximum acceleration response after installing a large-stiffness MRVI is reduced from 1697 g to 1416 g， and the maximum reduction in analysis frequency domain is 538 g@8476 Hz. The use of MRVI achieves a better pyroshock suppression effect， and provides a viable method for the pyroshock reduction design of the pyrotechnical actuation devices.
2021,29(9):855-870, DOI: 10.11943/CJEM2020322
Abstract:Cocrystal is composed of different neutral components through intermolecular non-bond interactions at molecular level and it has fixed ratio and particular structure. Cocrystallization technology is a novel method for ameliorating properties of energetic materials and it has wide development prospect and application value. It can decrease the sensitivity， improve the mechanical properties， thermal performance， and energy density of energetic materials. The research progress of preparation and application of energetic cocrystals was summarized， including the current research status， preparation method， characterization methods， and formation mechanism. The existing problems of energetic cocrystals were introduced： first， the properties of some cocrystal explosives need to be further improved； second， the preparation of cocrystal requires harsh conditions with low product yield； third， the characterization and test methods lack variety. The further development direction of cocrystal explosives were pointed out： strengthen the research of multiple components energetic cocrystals， improve the technologies to increase the yield， investigate the crystallization dynamics behavior to seek for the best cocrystallization conditions， and look for effective means to characterize the cocrystal structure.
2021,29(9):871-882, DOI: 10.11943/CJEM2020311
Abstract:As a new generation of rapid prototyping technology， direct writing technology has the advantages of fast molding speed， good molding consistency， and high preparation accuracy. It has certain advantages in the preparation of MEMS energetic devices. In this paper， the common direct writing technologies of MEMS energetic devices were described. On this basis， according to the research status of direct writing technology in micro-nano energetic devices， the direct writing technologies used in micro-scale charges of MEMS energetic devices， ignition circuit and transducer element， and packaging materials were summarized. The future research directions were proposed： preparing energetic ink with high solid content and stable performance， increasing the charge density of energetic ink， preparing silver ink circuit with low sintering temperature， and at the same time developing direct writing technology for MEMS energetic device transducers and packaging materials， exploring the influencing factors and laws of direct writing accuracy， breaking through the application bottleneck of direct writing technology， and promoting the progress of engineering application of this technology.
Vol, 29, No.9, 2021
>Preparation and Property
>Propulsion and Projection
>Explosion and Damage
客座编审 程广斌 教授
客座编审 韩 勇 研究员
客座编审 焦清介 教授