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HE Xu-dong, ZHANG Zeng-ming, ZHANG Chao-yang, XUE Xiang-gui
Online:March 18, 2024 DOI: 10.11943/CJEM2023263
Abstract:The packing structure of energetic crystals is one of the important factors affecting their sensitivity. A crucial mechanism for reducing the sensitivity of energetic materials is buffering external stimuli through the slipping between molecular layers within the crystal. It is very important to understand the inherent relationship between the geometric shape of energetic molecules and their crystal properties for the better design of low sensitivity high energetic materials (LSHEs). This study used neutral CHNO molecules containing nitro from the Cambridge Structural Database as samples. Hypothesis testing methods (including Z-, t-, and χ2 tests) were employed to investigate the correlation between the geometric shape of molecules and their crystal density, packing coefficient, and slipping ability. The study shows that among spherical, planar and linear molecules: spherical molecules have the highest crystal density and packing coefficient, but weaker slipping ability; planar molecules with high planarity achieve a crystal density comparable to spherical molecules by a high packing coefficient, while also exhibiting stronger crystal slipping ability, its confidence level of the χ2 test is close to 1; linear molecules perform less well than the former two. Though some crystals with high crystal density and packing coefficient do not have slipping ability, general speaking, the crystal density and packing coefficient of the crystals with slipping ability are higher than those without. Both Z-tests and t-tests indicate a confidence level exceeding 0.95, suggesting that designing crystal structures conducive to intermolecular-layer slipping is not contradictory to reduceing their sensitivity and increasing crystal density. Planar molecules have a higher crystal density than average, and it is strongly associated with crystal slipping ability, making them the preferred choice for designing LSHEs.
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WU Rui, XIAO Yi-jie, LI Qiang, YUAN Mao-bo, LIU Bo, ZHANG Yu-cheng
Online:March 07, 2024 DOI: 10.11943/CJEM2024033
Abstract:In order to investigate the thermal erosion characteristics and variation law of triple base propellant, various kinds of gun propellants with different components content were prepared. The erosion characteristics were determined through simulated test in a semi-closed bomb. The analysis reveals the impact of energy component and plasticizer content on gun propellant explosion temperature, and the impact of explosion temperature on erosion characteristics. The results indicate that changes in the explosion temperature of gun propellant, attributed to variations in cyclotrimetheylenetrinitramine (RDX), nitroguanidine (NQ) and dioctyl phthalate (DOP) content, significantly affect erosion characteristics. An increase of 1% in RDX content results in an increase in explosion temperature by 0.59% and an increase in erosion rate by 1.23%. Compared with the absence of RDX, the erosion rate of 2% RDX-containing propellant increase 23.38%. Notably, an increase of 1% in NQ content reduces the explosion temperature by 0.23% and the erosion rate by 0.56%. An increase of 1% in DOP content reduces the explosion temperature by 2.99% and the erosion rate by 7.01%. For the triple base propellants within the range of explosion temperature from 2600-3100 K, an exponential relationship between the rate of erosion mass and explosion temperature is established, and characteristic coefficients of RDX, NQ, DOP system is given respectively, which is 0.106, 0.101, 0.163.
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WANG Zhe-jun, QIANG Hong-fu, WANG Jia-xiang, PEI Shu-di, LI Shi-qi, GENG Ting-jing, HAN Yong-heng
Online:March 02, 2024 DOI: 10.11943/CJEM2024014
Abstract:The damage behaviors of composite solid propellants were reviewed from four aspects: micro scale, meso scale, macro scale and cross scale. During this process, the observation and characterization methods of damage at different scales, determination methods for damage thresholds, construction methods for damage evolution models, numerical simulation methods for damage, and macro-mesoscopic cross-scale analysis methods were summarized. Based on this, to several shortcomings in current research, the future research directions that need to be further focused on are as follows: expanding the range of influencing factors to be considered in numerical simulation of damage behaviors for composite solid propellants at the microscale, and strengthening the verification of simulation results with experimental research conclusions from multiple aspects; improve the ability of damage observation experiments at the meso scale, the characterization level of damage evolution models, and the computational accuracy of damage numerical simulations; improve the detection accuracy of damage identification testing at the macro scale, the accuracy of determination methods for damage thresholds, and the predictive ability of damage evolution models; further establishing a theoretical method system for cross-scale study of the propellant damage behaviors based on the developed standard specification for the study of damage behaviors for composite solid propellants in single-scale.
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HU Li-jing-cao, SUN Huan-yu, AN Zi-wei, ZHAO Zi-chang, HUANG Wei, LIU Yu-ji
Online:February 29, 2024 DOI: 10.11943/CJEM2023270
Abstract:5-amino-2H-pyrazol-3,4-dione-3-oxime-4-hydrazone (
3 ) and its perchlorate (4 ), nitrate (5 ) and 5,5′-dinitramino-3,3′-azo-1,2,4-oxadiazolate salts (6 ) were prepared from 4-chloro-3,5-dinitro-1H-pyrazole via amination and substitution/reduction reactions. The single crystals of3 and4 were obtained by solvent evaporation method and the crystals were characterized by single crystal X-ray diffraction. The structures of energetic compounds3 -6 were characterized by nuclear magnetic resonance spectroscopy and infrared spectroscopy. Moreover, the capacities of those compounds were confirmed by gas pycnometer, differential scanning calorimetry, impact and friction sensitivity testers. Their enthalpies of formation and detonation parameters were estimated using theoretical calculation methods. The results show that3 has a planar molecular configuration. The ketone oxime and ketone hydrazone have unique double bond characteristics, reducing the conjugation of the pyrazole ring and making it easier to form salts. After salt formation, different anions have various effects on the performance of the neutral compound. Among those examined anions, the perchlorate anion not only improves the oxygen balance, but also increases the density, resulting in the detonation velocity and pressure of4 (8499 m·s-1 and 30.2 GPa) higher than3 (8072 m·s-1 and 22.5 GPa). In addition, 5,5′-dinitramino-3,3′-azo-1,2,4-oxadiazole significantly increases the decomposition temperature of3, rising from 135 ℃ to 285 ℃. These results indicate that a rational combination of anions and cations can effectively regulate the performances of target energetic compound. -
LIU Jun, LIANG Shuang, LIU Xiang-yang, GAO Jie
Online:February 26, 2024 DOI: 10.11943/CJEM2023236
Abstract:To reveal the relationship between the evolutions of polymer chains within the NEPE propellant matrix and the hyperelastic mechanical behavior, a multiscale approach was adopted to investigate the evolution behavior and characterization model of polymer chains under different deformation states. Firstly, based on the microscopic models of components such as matrix adhesives, curing agents, and plasticizers, a dynamic model describing the evolution of cross-linked and free chain configurations under complex deformation states was developed through molecular dynamics simulation of the matrix system Subsequently, the free energy contributed bycrosslinked and free chains was quantitatively characterized based on statistical mechanics, and a hyperelastic constitutive model considering the cross-linking and entanglement effects was established. Finally, the developed constitutive model was validated by using the quasi-static tensile experimental data of NEPE propellant matrix samples. Compared with the classical Arruda-Boyce model, the constitutive parameters in the present model have real physical significances and can be obtained by experimental methods, which enables the present model to better predict the hyperelastic behavior of the propellant matrix under different deformation states, and thus provide model for the regulation of mechanical properties and component optimization of propellant matrix.
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XUE Hui-hui, HUANG Juan, ZHANG A-lei, CHEN Ke-quan, ZHOU Jie, DING Ya-jun, XIAO Zhong-liang
Online:February 03, 2024 DOI: 10.11943/CJEM2023203
Abstract:A green non-toxic, easy and accuracy analysis method of the nitrogen content in nitrocellulose (NC) was investigated by using ultraviolet spectrophotometer, which was based on a linear relationship between the nitrogen content of NC and the molar ratio of nitrite-to-nitrate ions released after alkaline hydrolysis. Under the same reaction condition, five NC standard samlpes with known nitrogen contents were hydrolyzed. The concentrations of NO2- and NO3- in the hydrolysate were measured by the ultraviolet spectrophotometer, and the reaction condition of measuring system was optimized. The linear relationship between the nitrogen content of NC standards (x) and the molar ratio of nitrite-to-nitrate ions (y) was determined by the least squares method. Finally, three NC samples were used to evaluate the proposed method. Results show that the concentration of NO2- and NO3- in alkaline hydrolysate can be measured simultaneously by ultraviolet spectrophotometer, and the most suitable reaction condition is as follows: the concentration of sulfamic acid of 20 g·L-1, and the process time of 30 min. Under the optimal reaction condition, the linear relationship between x and y is obtained, and the R2 is 0.9893. The verification results of NCA, NCB and NCC reveal that the nitrogen content determined by ultraviolet spectrophotometer and actual nitrogen contents are in good agreement. The relative standard deviation (n=4) values are all less than 0.150%.
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YANG Ya-lin, QIN Yi-feng, XIA Jiang-lu, DU Hui-ying, LI Xin-yu, WU Bo, MA Cong-ming
Online:January 30, 2024 DOI: 10.11943/CJEM2024006
Abstract:Polycyclic energetic compounds with high nitrogen content have attracted much attention owing to their distinctive advantages in constructing novel energetic molecules with low mechanical sensitivity, good thermal stability and high density. The construction of polycyclic skeletons involves the incorporation of tetrazole into fused heterocycle, serving as high-energy organic fuel and hydrogen bond donors. Three self-assembled non-hydrated energetic compounds, namely 7-amino-6-(2H-tetrazol-5-yl)-pyrazolo[1,5-a]pyrimidine (
1 ), 7-diamino-6-(2H-tetrazol-5-yl)-[1,2,4]triazolo[1,5-a]pyrimidine perchlorate(2) , and 2,7-diamino-6-(2H-tetrazol-5-yl)-[1,2,4]triazolo[1,5-a]pyrimidine perchlorate(3), were synthesized through noncovalent self-assembly of polycyclic skeleton with the oxidizing structural unit HClO4 rich in hydrogen bond acceptors. The structural characterization employed Nuclear Magnetic Resonance Spectroscopy and single crystal X-ray diffraction, while thermal behaviors and mechanical sensitivities were determined by differential scanning calorimetry-thermogravimetry and BAM methods. Detonation performances were predicted utilizing the Gaussian 09 program and EXPLO5 V6.05.02. The results show that three compounds exhibit high crystal densities (ρ: 1.75-1.86 g·cm-3), good thermal stabilities (decomposition temperature (onset): 184-260 ℃), and good detonation performances (detonation velocity: 7343-7570 m·s-1; detonation pressure: 21.1~22.8 GPa), surpassing those of traditional explosives trinitrotoluene (TNT). Both compound1 (impact sensitivity (IS) > 40 J, friction sensitivity (FS)=216 N) and compound3 (IS=25 J, FS = 240 N) exhibit low mechanical sensitivity. -
WEN Yi-meng, MAO Jun-qing, MA Song-yu-chen, DI Yang, LIU Tao, LIU Jie
Online:January 25, 2024 DOI: 10.11943/CJEM2023200
Abstract:Due to contacts with additives or changes of environmental conditions (temperature or pressure), the polymorphism hexanitrohexaazaisowurtzitane (CL-20) is easy to transform into mixed crystal form in propellant system, which leads to structural damage and performance degradation of the propellant. In order to hinder the contact between the solvent and CL-20, then inhibit the crystal transformation of CL-20, the polyphenol amine (PCHA) film was prepared based on the oxidative self-polymerization of hexamethylenediamine (HMDA) and catechol (CCh). The surface of CL-20 crystal was modified by water suspension method under mild conditions. The scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (RAMAN), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to study the morphology, coating content, thermal properties, and stability in ethylene glycol solution for the composite particles. The results show that HMDA and CCh can modify the surface of CL-20 crystal under mild conditions and form a dense PCHA coating layer. The content of PCHA is about 1% measured by dissolution weighing method and high performance liquid chromatography (HPLC). The PCHA coating layer increases the crystal transition and thermal decomposition temperature by 16 ℃ and 7 ℃, respectively. The thermal decomposition activation energy Ea at different heating rates was calculated by Kissinger method. The activation energy of CL-20@PCHA is about 8 kJ·mol-1 higher than that of CL-20, and the thermal stability is greatly improved. The XRD test results indicate that the PCHA film can effectively prevent the contact between the solvent and CL-20, slow down the dissolution rate of CL-20 in the solvent, and effectively inhibit the crystal transformation of CL-20.
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XIA Wen-tao, DU Fang, LI Yi-heng, LIN Li-yun, QU Wei-chen, QIN Rui, TAO Bo-wen, GU Jian
Online:January 24, 2024 DOI: 10.11943/CJEM2023230
Abstract:In order to investigate the combustion characteristics of Al powders in NOx, the reaction mechanism of Al with three nitrogen oxides (NO2, NO and N2O) was studied by means of density functional theory ωB97X. Firstly, the geometries of reactants, intermediates, transition states and products were optimized with all parameters. The authenticity of intermediates and transition states was confirmed by frequency analysis. The transition states were further determined by intrinsic reaction coordinates (IRC) calculation, and then the detailed reaction paths and mechanisms were obtained. High precision single-point energy of each structure was obtained by using the double hybrid functional PWPB95 combined with DFT-D3 correction and def2-TZVPP basis set. The rate constants of the related reactions were calculated by using the variational interpolation transition state theory, and the Arrhenius expressions for each reaction are obtained. The results show that the reaction process of Al with NO and NO2 is that Al and O atoms join together to form the intermediate of the complex, and then break the N─O bond through the ternary ring transition state to form the product. When Al reacts with N2O, Al reacts with N atoms to form a complex and then the elimination reaction takes place through the ring transition states. The activation energies of the reaction of Al with NO2, NO and N2O are 4.3 kJ·mol-1,249 kJ·mol-1 and 13.4 kJ·mol-1, respectively. From 2400 K to 4100 K, the reaction rate of Al with NO2 and N2O is higher than 106 m3·mol-1·s-1, which indicates that the reaction is easy to take place and the reaction rate is very fast, and the reaction rate of Al with NO is about 1/10000 of that of Al with NO2 and N2O.
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PAN Chang-xin, LIU Feng, BI Ru-jie, DAI Wei, ZHU Zheng-de, CHENG Yu-hang
Online:January 17, 2024 DOI: 10.11943/CJEM2023219
Abstract:In order to study the effect of high pressure from screw pumping and medium deep hole charging on the microstructure and thermal stability of the on-site mixed emulsion explosive matrix, the microstructure, particle size distribution, crystallization content, thermal decomposition process, thermal decomposition reaction activation energy, thermal decomposition mechanism function and rate equation of the matrix under atmospheric and high pressures were studied by optical microscope, laser particle size analyzer, water solubility experiment, thermogravimetry and derivative thermogravimetry (TG-DTG) couple method, Kissinger method and Ozawa method, Coats-Redfern method and ?atava method. The results show that from atmospheric pressure to high pressure, polymerization, demulsification and crystallization of the intra-matrix phase droplets appeared, the particle size increased from 3.717 μm to 4.474 μm, the precipitation amount of ammonium nitrate crystals increased from 0.0530 g to 0.0640 g, and the uniformity of the emulsion system was weakened. The average thermal decomposition onset temperature of the matrix Tonset increased from 157.4 ℃ to 184.0 ℃, the average first-order derivative thermogravimetric peak temperature Tp increased from 262.6 ℃ to 281.8 ℃, the average mass loss rate increased from 0.1454 %·s-1 to 0.1476 %·s-1, and the reaction activation energy decreased from 108.49 kJ·mol-1 to 84.74 kJ·mol-1. The free water released by evaporative demulsification under high pressure might cause the rise of Tonset and Tp, and the thermal decomposition reaction was more likely to occur. The activation energy calculated by the Ozawa method had a different trend with the increase of conversion rate, and the thermal decomposition reaction mechanism function changed from Valensi equation to inverse Jinder equation and the rate equation also changed. The high pressure promotes the process of droplet polymerization, demulsification and crystallization of the intra-matrix phase, reduces the activation energy of the thermal decomposition reaction, and weakens the homogeneity and thermal stability of the system.
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LI Si-han, WANG Ke-jian, NIU Yu-lei, HUANG Han-zhe, MA Zi-yu
Online:January 11, 2024 DOI: 10.11943/CJEM2023209
Abstract:In order to study the quasi-static compression behavior of polymer bonded explosive (PBX), the uniaxial quasi-static compression tests were carried out on two typical PBX substitute materials (with and without aluminum powder) at different strain rates, and their mechanical properties were compared and analyzed. Based on the Zu-Wang-Tang (ZWT) model, a new model was proposed to describe the quasi-static compression behavior of materials. The constitutive model parameters were obtained by genetic algorithm, and the model was developed by using Fortran language in the User Material (UMAT) subroutine interface of Abaqus finite element analysis software. Results show that the quasi-static compression process of casting PBX substitute materials can be divided into three stages: elastic compression, stress decay and instability failure. The mechanical behavior of quasi-static compression is obviously correlated with the strain rate. With the increase of the strain rate, the effective compressive strain of the material is basically unchanged, while the logarithms of compression modulus, yield strength and compressive strength are linearly related to the logarithm of strain rate. The addition of aluminum powder can improve the compression modulus, yield strength and compression strength of casting PBX substitute materials. The newly constructed constitutive model can better describe the quasi-static compression behavior of casted PBX substitute materials, and its universality is validated by the finite element analysis software. The coefficients of determination (R2) between the simulated and experimental results are higher than 0.98, indicating a high level of consistency.
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LIU Rui, LIU Jian, TANG Yue-chuan, ZHANG Chao-yang, HUANG Jing, HUANG xin
Online:January 08, 2024 DOI: 10.11943/CJEM2023226
Abstract:The explore of energetic molecules faces multiple challenges, and the traditional design method are inefficient. The emergence of computer-aided molecular design has changed the research and development model. This review provides an overview of the development of energetic molecular design and introduces the current research status of computer-aided energetic molecular design. By summarizing the latest advancements in Artificial Intelligence (AI) technology across various design aspects, including performance prediction, molecular generation, retrosynthetic reaction prediction, and reaction condition prediction, we discussed the existing gap between the current approaches in energetic molecular design and other materials design methods. By thinking about the causes of the gap, we present an outlook on the future developmental directions of AI-assisted energetic molecular design. Research indicates that AI has already been applied in property prediction and molecular generation of energetic molecular design, but requires further exploration in retrosynthetic reaction prediction, and reaction conditions prediction. AI-assisted design of energetic molecules holds broad promising application prospects. Data enhancement, transfer learning and high-throughput computing are expected to solve the problem of weak data of energetic molecules. Enhancing AI-assisted prediction of synthesis routes and reaction conditions for energetic molecules shows promise for achieving the automatic molecular design via whole process of “design-evaluation-preparation-verification”. AI-assisted energetic molecular design provides new possibilities for improving the level of energetic molecular design and helps to improve the efficiency of energetic molecule research and development.
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Online:January 05, 2024 DOI: 10.11943/CJEM2023206
Abstract:In order to understand the ignition process of plasma jet in the liquid propellant electrothermal chemical gun, the spreading characteristics of plasma jet in simulative liquid propellant LP1846 were studied. A two-dimensional axisymmetric unsteady mathematical model of plasma jet spreading in the liquid was established, and the model was validateded with the experiments based on the liquid working medium of water. On this basis, the spreading process of plasma jet in the simulative liquid propellant LP1846 was numerically simulated. The morphological changes of plasma jet and the distribution characteristics of pressure, velocity and temperature in the jet field were analyzed. Results show that when the plasma jet expands in the simulative liquid propellant LP1846, there is turbulent mixing phenomenon due to Taylor-Helmholtz instability, and it becomes more and more intense. It is manifested by the protruding head of the jet and the axial elongation to form a tip, and the jet entrains the simulative liquid propellant medium to produce droplets in Taylor cavity, and the number of droplets gradually increases. At the same time, the necking phenomenon occurs near the nozzle hole during the expansion of plasma jet due to the simulative liquid propellant backflow. The jet field fluctuates due to the alternating action of expansion and compression waves, especially near the nozzle hole. The pressure field shows alternating distribution of high and low pressures, and the velocity field also shows similar distribution.
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HUANG Qi, LIU Li, JIN Bo, PENG Ru-fang
Online:December 31, 2023 DOI: 10.11943/CJEM2023169
Abstract:A new energetic iron-oxygen cluster, [Fe2Ⅲ(μ2-CH3O)(μ3-OH)(μ2-O)(BODTO2-)(H2O)]4 (
1 ), was synthesized by solvothermal method using 5,5"-{[3,3"-bis(1,2,4-oxadiazole)]-5,5"-yl}-bis(1-hydroxytetrazole) as ligand. The structure and thermal stability of compound1 were studied by single-crystal X-ray diffraction, differential scanning calorimetry and thermogravimetric analysis. The catalytic performance of compound1 on the thermal decomposition of ammonium perchlorate (AP) was also investigated by differential thermal analyzer. Compound1 crystallizes in cubic I-43d space group with a density of 1.506 g·cm-3. In the crystal structure, the nearby Fe3+ cations are interconnected to each other by bridging oxygen atoms. Through those connections, the iron(Ⅲ) cluster cages are formed. The peak thermal decomposition temperatures of compound1 are 513.9 K, 617.6 K and 669.4 K, respectively. The detonation velocity and detonation pressure of compound1 are 6.94 km·s-1 and 19.09 GPa, respectively. In addition, the impact sensitivity and friction sensitivity of compound1 are 15 J and 360 N, respectively. After adding 10% compound1 to AP, the high temperature decomposition temperature of AP decreases by 65 K, and the decomposition activation energy decreases by 82.2 kJ·mol-1, demonstrating the high catalytic activity of compound1 for the thermal decomposition of AP and the great potential of compound1 for application in energetic combustion catalysts. -
LIANG Peng-fei, CHEN Jin-fang, ZHAO Mei-ling, ZHANG Guo-hui, WANG Ya-li
Online:December 26, 2023 DOI: 10.11943/CJEM2023078
Abstract:Atomization performance of free impinging jets with unequal nozzle diameter of 60% Glycerol-water (60G) solution was investigated using PIV technique. The liquid sheet breakup characteristics and droplet behaviors were studied under different Weber numbers (51≤We≤1605), jet velocities (2.12 m·s-1≤u≤6.37 m·s-1) and nozzle diameters (nozzle 1: D1(left nozzle diameter)-D2(right nozzle diameter)=1.5-2 mm and nozzle 2: D1-D2=2-3 mm). The droplet distribution of the composite energetic material binder solvent diethylene glycol-water solution was also investigated. The results show that, as We number increases, liquid sheet breakup length increases first and then decreases from M3 beginning, the liquid sheet thickness and droplet diameter decrease while the droplet velocity increases. Nevertheless, as the nozzle diameter increases, changes in liquid sheet breakup mode are insignificant, and the liquid sheet breakup length, thickness and droplet diameter all increase, while the droplet velocity decreases. At the same time, the empirical correlation equations are obtained between liquid sheet breakup length, liquid sheet thickness, Sauter mean diameter D[3,2] and nozzle diameter, We number. After validation using the diethylene glycol-water solution, it reveales that with the increase of jet velocity, the droplet diameter decreases and the distribution becomes narrow after the impinging of diethylene glycol-water solution. The error range of D[3,2] values is within ±15% of the empirical correlation equation, which is consistent with the theoretical prediction results.
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DU Hui-ying, QU Zhi-hui, XIA Jiang-lu, YANG Ya-lin, LI Xin-yu, QIN Yi-feng, WU Bo, MA Cong-ming
Online:December 26, 2023 DOI: 10.11943/CJEM2023201
Abstract:1,3,5,5-Tetranitro-hexahydropyrimidine (DNNC) and 1,4,6,6-tetranitro-1,4-diazepane (TNDA) were synthesized from the reaction of 2,2-dinitropropane-1,3-diol with tert-butylamine and ethylenediamine, respectively. Their structures were characterized by nuclear magnetic resonance (NMR), fourier infrared spectroscopy(FT-IR), and single crystal X-ray diffraction. Meanwhile, their thermal behaviors and mechanical sensitivities were determined by differential scanning calorimetry-thermogravimetry(DSC-TG) and the BAM methods. Furthermore, isodesmic reactions and EXPLO5 were used to predict detonation parameters. The crystal structures indicate that the cyclohexane skeleton in DNNC and the cycloheptane skeleton in TNDA are both chair conformations. Both of them have extensive intermolecular and intramolecular non-classical hydrogen bonds. The results of DSC-TG show that the phase transition temperatures of DNNC and TNDA are 155.0 ℃ and 154.5 ℃, respectively. Furthermore, their peak decomposition temperatures are 215.3 ℃ and 205.9 ℃. In addition, DNNC and TNDA possess good mechanical sensitivity. Their impact sensitivities are 25 J and 17.5 J, and friction sensitivities are 144 N and 240 N. Besides, their theoretical detonation velocities are 8772 m·s-1 and 7828 m·s-1, and detonation pressures are 34.8 GPa and 25.0 GPa.
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Gan Ren-jie, YU Li-da, LI Hai-ning, ZHANG Wei-bin, LI Wei-bin, YANG Zhan-feng
Online:December 25, 2023 DOI: 10.11943/CJEM2023198
Abstract:The internal crack detection of polymer bonded explosive (PBX) is of great significance and engineering application value for its safety and structural integrity evaluation. In order to improve the imaging detection accuracy and image quality of PBX internal crack defects, the curved surface modified water immersion ultrasonic total focusing imaging method was proposed. On this basis, the delay multiply and sum (DMAS) technology was further combined. The ultrasonic imaging detection of the bottom crack defects of the Φ100.0 mm semi-cylindrical PBX was studied by water immersion method, and high-precision imaging characterization and high signal-to-noise ratio imaging of this bottom crack defect of the curved PBX was realized. The experimental results show that the crack defect height measurement error of the traditional TFM imaging algorithm is 12.0%, and the image signal-to-noise ratio is 1.37 dB. The height measurement error of this crack defect after surface correction is 3.6%, and the image signal-to-noise ratio is 2.13 dB. The crack defect height measurement error of the surface correction algorithm combined with DMAS is only 0.4%, and the image signal-to-noise ratio is 5.32 dB.
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LV Liang-liang, ZHANG Wei-bin, LI Gong-ping, PAN Xiao-dong, ZHANG Cai-xin, YANG Ya-fei, ZHANG Cui
Online:December 12, 2023 DOI: 10.11943/CJEM2023212
Abstract:The performance and dependability of PBX are significantly impacted by internal cracks. Accurate crack identification and quantitative analysis are crucial to evaluate the performance of PBX. Currently, the ability to identify and quantitatively analyze internal cracks of PBX needs to be further improved. Consequently, research on a deep learning-based method for PBX crack identification was conducted. Based on the popular deep learning networks, five different deep learning network structures were designed. This study aimed to compare the effects of network type, connection style, and pre-trained models on the recognition of PBX cracks. Internal crack images of PBX were obtained by CT technique. The training dataset of network was constructed using these crack images. The crack dataset was used to train five different types of networks. The performance of five networks was assessed based on Accuracy, F1, and MIoU. Select an outstanding network for PBX crack recognition and training based on the findings. The results indicate that, U-Net outperforms Seg-Net in pixel-level crack recognition and the Concatenate operation preserves more features compared to the Pooling Indices method. The pre-trained model (MobileNet and ResNet) can improve the training speed of the network, but its crack pixel-level recognition performance is reduced. The proposed method was applied to identify PBX crack, achieving pixel-level recognition. The results include a crack detection rate of 0.9570, a single pixel recognition accuracy of 0.9936, an MIoU of 0.9873, and a relative crack area of 0.7585, demonstrating superiority over traditional image segmentation methods.
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CAI Jing-jing, XU Xuan, CHEN Zhan-yang, YANG Jun
Online:December 07, 2023 DOI: 10.11943/CJEM2023196
Abstract:In order to explore the influence of the radial air gap in the hole on the directional penetration effect of shaped charge with/without metal liner and the detonation energy transfer process of explosive, ANSYS/LS-DYNA software was used to carry out the numerical simulation study when the air gap of the charge in the hole was 6, 8, 10, 12, 14 cm. The process of centralized release of energy from the shaped charge with metal liner forming an EFP and without metal liner forming concentrated detonation product flow as well as the depth of directional penetration into the borehole wall, was analyzed. The results show that when the air gap is less than 10 cm, the penetration depth of concentrated detonation product flow into the hole wall is increased by 53% (6 cm) and 29% (8 cm), respectively, compared with the average penetration depth of EFP. When the air gap was greater than 10 cm, the average penetration depth of EFP increased by 26% (12 cm and 14 cm) compared with the concentrated detonation product flow. The kinetic energy of EFP and concentrated detonation product flow per unit area through the hole wall on the shaped energy axis was calculated, it is found that when the air gap is small, the energy dissipation of concentrated detonation product flow in the air is less than that of EFP plastic deformation, and the penetration effect of concentrated detonation product flow on the hole wall is better. When the air gap is large, the density and kinetic energy at the axis of the concentrated detonation product flow are significantly reduced due to the spatial expansion of detonation products, while the EFP has high density and incompressibility, small energy dispersion and slow decay of kinetic energy, so the penetration effect of EFP on the hole wall is better than that of the concentrated detonation product flow.
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DING Zhi-hao, YANG Wei-tao, GAO Yu-chen, YANG Jian-xing, KONG Xin, YANG Bin
Online:December 05, 2023 DOI: 10.11943/CJEM2023110
Abstract:To study the effects of extrusion system nozzle runner structural parameters (cone angle, outlet diameter, and molding section length) on the fluid flow of energy-containing material extrusion process in the direct-in-writing-forming (DIW) technology, an extrusion model of high-viscosity energy-containing materials based on the Polyflow Extrusion module was established, and the model was verified by extrusion experiments under the working conditions of direct-write 3D printing. The study analyzed the effects of cone angle range (90°-130°), outlet diameter (0.75-2 mm), and molding section length (5-20 mm) on the extrusion process of high-viscosity energy-containing materials through the established model. The results show that the Polyflow Extrusion module can accurately simulate the flow behavior of composite energy-containing materials. When the cone angle is 100°, and the nozzle outlet diameter is between 1.5 mm and 1.75 mm, the extrusion process is relatively stable with small extrusion expansion. Additionally, as the length of the molding section grows, the required inlet pressure increases while the outlet expansion effect decreases.
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YUE Hong-li, ZHANG Cui, ZHANG Wei-bin
Online:November 03, 2023 DOI: 10.11943/CJEM2023157
Abstract:The molding granule is an intermediate for polymer-bonded explosive (PBX) components. Characterization of the physical parameters of granular system is of great significance to understanding the influence of different granule structure on the performance of PBX components. X-ray computed micro-tomography (XCT) and CT image processing were used to non-destructively characterize physical parameters (including granule diameter, volume fraction, porosity, sphericity and intrinsic density) of the granular random packing systems. The average granule diameter of granular systems is up to 1.04 mm, the volume fraction is up to 68.7%, the lowest porosity is 1.04%, the highest average sphericity is 0.93, and the highest density is 1.44 g·cm-3. Results show that the type of binder, explosive crystal composition, explosive crystal ratio and granulation process in the formulation of molding granules have important influences on the physical parameters of the granular system. Moreover, there is a correlation between physical parameters of granular systems. The more dispersed diameter distribution of granular system leads to the larger the average surface area of granules. The larger average granule diameter and lower average sphericity of granular system result in the higher porosity of the granules. The volume fraction of granular systems with larger average granule diameter is higher, and the volume fraction of the granule accumulation is independent of the sphericity when the average sphericity is large. This work provides a basis for understanding the physical parameters of random packing system of modeling granules and the in-depth study of the relationship between granular structure and material properties.
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CHEN Rong, MA Rong, WANG Zheng, REN Ke-rong, ZHANG Si-yuan, TIAN zhan-dong
Online:October 23, 2023 DOI: 10.11943/CJEM2023133
Abstract:The cast TiZrNbV refractory high entropy alloy (RHEA) has high structural strength and good energy release characteristics. As an energetic structural material, it needs to withstand complex dynamic load environments in engineering applications. Studying the spalling behavior of TiZrNbV refractory high entropy alloy and obtaining accurate dynamic constitutive parameters are vital for its engineering application. The spalling characteristics of TiZrNbV RHEA were studied by flat plate impact experiment using a 20mm light gas gun. Parameters such as spalling strength, Hugoniot elastic limit (HEL), and plastic strain rate were obtained, based on the free surface velocity history. The recycled specimens were analyzed using scanning electron microscopy (SEM), and the spalling characteristics of TiZrNbV RHEA at different strain rates were analyzed from both macro and micro perspectives. It was shown that the geometrically necessary dislocation of the samples significantly increased with the increase of loading velocity. The spalling strength of TiZrNbV RHEA increases with the loading strain rate and the loading stress, with values ranging from 0.93 GPa to 2.23GPa. The GTN-JC constitutive model parameters of TiZrNbV RHEA were obtained by calibrating the free surface velocity history of the spallation experiment with a flyer velocity of 580 m·s-1. The spallation behavior of the sample under 610 m·s-1 flyer velocity loading was calculated by using the fitted parameters. It was indicated that the free surface velocity curve of the spallation experiment performed well in simulating the spallation behavior of coarse-grained TiZrNbV RHEA. The simulation results show that the free surface velocity curve is consistent before the first tensile stage, which can be used for the dynamic analysis of sample spalling failure. The obtained parameters can provide reference for the engineering application of TiZrNbV RHEA.
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ZHAO Yang, JIN bo, PENG Ru-fang
Online:November 10, 2023 DOI: 10.11943/CJEM2023177
Abstract:In order to utilize the performance advantages of carbon nanomaterials, this article summarizes the application of carbon nanomaterials in the desensitizing technology of energetic materials. The effects of typical carbon nanomaterials, such as graphite, carbon nanotubes, graphene and its derivatives, fullerene and its derivatives, on the reduction of impact, shock wave, and friction sensitivity of energetic materials, and explored the desensitization mechanism of different carbon nanomaterials was discussed. Finally, the development prospect of carbon nanomaterials in this field of desensitizing technique of energetic materials is forecasted. It is considered that optimizing the preparation process of carbon nanomaterials and energetic materials, deeply understanding the properties of carbon nanomaterials and conducting functional modification, regulating the interface interaction between carbon nanomaterials and energetic materials and further exploring the desensitization mechanism of carbon nanomaterial will be the focus of future research.
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YAO Chao-qun, LIU Xuan, ZHANG De-wang, ZHAO Shuai-nan, GUO Xiao-ni, CHEN Guang-wen
Online:February 01, 2024 DOI: 10.11943/CJEM2024017
Abstract:Energetic materials are widely applied in the area of weaponry industry, aerospace and civil construction. The synthesis of energetic materials is very complex and of great danger in the conventional stirred tank, which can no longer fulfill the requirement of product quality and process safety. The microreaction technology, which has significant advantages of fast heat/mass transfer and excellent safety, has great potential in the synthesis of energetic materials. This review introduces the progress from four aspects, namely the principle of microreaction technology, energetic compound synthesis, production of energetic particles and ultrasonic microreactors. It aims to elaborate the application characteristics of microreaction technology in the area of energetic materials based on the viewpoint of chemical engineering. Finally, the challenges and future direction are summarized and outlooked, including reaction kinetics/thermal kinetics, mixing intensification of viscous and solid‐involved fluids, reaction scale‐up and intelligent system, waste treatment and how to embrace emerging technologies such as artificial intelligence.
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QIAO De-qian, WENG Shi-chun, GUO Zi-chao, RAO Guo-ning
Online:March 04, 2024 DOI: 10.11943/CJEM2023247
Abstract:Currently, microchannel reactors are extensively employed in the synthesis of energetic materials, significantly enhancing the safety of the synthesis process. However, it is still crucial to consider the thermal stability of these materials. Two important parameters that characterize the risk of thermal decomposition for hazardous chemicals and energetic materials are the time to maximum rate under adiabatic conditions(TMRad) and the initiation temperature(TD24), which corresponds to the time to maximum rate within 24 hours. The traditional calculation methods for these two parameters are the single-step N-order method and numerical calculations, which have drawbacks such as being time-consuming and labor-intensive during analysis. To address this issue, this study proposes a method for calculating characteristic parameters of thermal runaway decomposition based on the first peak observed after splitting a multi-peak curve in dynamic test curves obtained from Differential Scanning Calorimeter(DSC). Furthermore, a comparison between this paper’s method and a modeling method using an exhaustive approach was conducted by evaluating TD24 deviation. Numerical simulation was employed for verification purposes, enabling calculation of thermal runaway characteristic parameters of four substances, namely 1,8-dinitroanthraquinone, M-NQ, 1,5-dinitroanthraquinone, and DNTF based on literature experiments. The results indicate that numerical simulations demonstrate a maximum percentage TD24 deviation of 2.88% and 6.9% for two-step and three-step consecutive reactions respectively. The maximum deviation observed was 6.41 ℃; for three-step continuous reactions, the TD24 exhibited a maximum deviation of 5.39 ℃. Furthermore, experimental results employing the methodology proposed in this study demonstrated that the TD24 values for four energetic materials were calculated with the deviations of -4.55 ℃, 0.71 ℃, 3.16 ℃, and -0.84 ℃ respectively; all absolute percentage deviations were less than 2% when compared to TD24 obtained through model calculations. These findings validate the effectiveness of the proposed TD24 calculation method presented in this paper as it exhibits minimal deviation during calculation while offering a straightforward computational process capable of accurately determining thermal decomposition runaway characteristic parameters.
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LIU Xuan, YAO Chao-qun, LIAN Ying-jiang, HAN Mei, CHEN Guang-wen
Online:January 22, 2024 DOI: 10.11943/CJEM2023256
Abstract:The study investigated the nitration of 2-methyl-4,6-pyrimidinone (MPO) with nitrate sulfur mixed acid in a microchannel reactor, and further prepared 1,1-diamino-2,2-dinitroethylene (FOX-7) through hydrolysis reaction. N-octane was introduced as an inert solvent to generate slug flow for the reaction system. The reaction occurred inside disperse droplets, thus solving the problem of clogging of nitration intermediates in the microchannel reactor and achieving process intensification and continuous operation. The effects of reaction temperature, residence time, material ratio, and hydrolysis conditions on the product yield were investigated. The combination of microreactor and stirred reactor was proposed. At the molar ratio of nitric acid to MPO of 4.4, reaction temperature of 30 ℃, and residence time of 3 min in the microreactor followed by a 30 min insulation reaction in a stirred kettle, and the ring-opening realized by the hydrolysis with ice water for 2 h, the yield of FOX-7 could reach 90.1%, with a purity of over 99%.
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LI Jia-wei, LI Jia-fei, ZHANG Dong-xu, XUE Zhi-hua, LI Zhe-qiang, LEI Jin-shan, WANG Jing-yu, WU Bi-dong
Online:January 30, 2024 DOI: 10.11943/CJEM2023264
Abstract:To improve the safety of the charging process of molecular perovskite energetic material (DAP-4), spherical granulation of DAP-4-based energetic composite microspheres was realized by altering the composite ratio of the bonding agents, Glycidyl Azide Polymer (GAP) and nitrocellulose (NC) (constituting 2% of the mass of DAP-4) using the coaxial droplet microfluidic technology. The macro and micro morphology, crystal structure, thermal properties, combustion properties, and mechanical sensitivity of the samples were tested and analyzed by scanning electron microscope, X-ray diffractometer, differential thermal scanning calorimeter, thermogravimetric analyzer, high-speed photography, impact sensitivity tester and friction sensitivity tester. The results indicate that DAP-4 has the best sphericity when the ratio of GAP to NC is 4∶1. The crystal structure of DAP-4 is not changed after spheroidizing granulation, and the peak temperature of thermal decomposition is slightly advanced. The combustion time of DAP-4 microspheres is slightly longer than that of raw materials, and the overall performance is still very stable and continuous combustion, retaining its excellent combustion performance. The GN41 microspheres can significantly improve fluidity while reducing mechanical sensitivity and improve the safety of the charging process.
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ZHOU Lin, YANG Wei, LU Yang-cheng
Online:February 07, 2024 DOI: 10.11943/CJEM2023267
Abstract:Nowadays, the conventional batch preparation process is difficult to achieve accurate control of process parameters, product structure and properties due to the macro scale, resulting in poor product uniformity and significant safety risk in the preparation process. Therefore, how to achieve safe, controllable, and efficient preparation of energetic materials has become a popular research topic. Microreactors are well-suited for preparing energetic materials due to their advantages of miniaturization, integration, high safety, and excellent mass and heat transfer efficiencies. Consequently, microreactor technology has gradually attracted the wide attention of researchers and emerged in the preparation of energetic materials.. This paper provides a detailed overview of the domestic and international research progress on the application of microreactors in hazardous chemical synthesis processes and the preparation of energetic materials. Special attention is given to the potential application of microreactors in the preparation of monolithic and composite energetic materials. The future research direction was prospected, and the future development needs of microreactor technology were emphasized, including large-scale production, three wastes treatment and intelligent platform construction.
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XIA Hao-xuan, SHI Jin-yu, LIU Jin-bo, ZHOU Xing-yi, FEI Yi-peng, Ning-Jue-yong, LIU Li, ZHU Peng, SHEN Rui-qi
Online:February 29, 2024 DOI: 10.11943/CJEM2023276
Abstract:To achieve the crystallization regulation and batch production of explosives at the safety-critical scale, the ZS-1 microfluidic crystallization system was established based on the microfluidic technology. The experiments were carried out with DMSO as the solvent and deionized water as the anti-solvent. By changing the crystallization process parameters such as the two-phase flow rate ratio, explosive concentration and total flow rate, the particle size control of RDX and the polymorphic transformation of HMX at the microscale was studied, and high-throughput screening of crystallization parameters was explored. Batch preparation experiment of micron RDX was carried out on the ZS-1 microfluidic system. The results show that the average paritcle size of RDX is deduced by 22.2 times after recrystallization. Specifically, the D50 of RDX samples is 3.35 μm, the SPAN number is 0.956 and the purity is 99.80%, and the hourly output of single system reaches 207.7 g. The ZS-1 microfluidic crystallization system verifies the feasibility of batch preparation of narrow size-distributed micron explosives at the microscale.
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LI Yu-guang, YUAN Fei, ZHAO Shuang-fei, NIE Ying-ying, ZHAO Yue, HE Wei, GUO Kai
Online:March 04, 2024 DOI: 10.11943/CJEM2024004
Abstract:To enhance the thermal safety of microreactors utilized for preparing energetic materials, a computational fluid dynamics simulation based on the finite volume method was employed to investigate the impact of structural parameters on flow and heat transfer in a spiral microreactor. The findings reveal that centrifugal force induces continuous directional secondary flow disturbance within the spiral channel, thereby augmenting fluid heat transfer performance. Increasing the curvature of the spiral microreactor, reducing the dimensionless pitch value, and elevating fluid velocity effectively enhance Nusselt number while controlling drag coefficient along the reactor path. Notably, scaling up beyond a radius of 2.5 mm leads to a significant decline in heat transfer performance of a spiral microreactor exhibits a scale-up effect, with a significant decrease in heat transfer performance for spiral microreactors. By maintaining a controlled radius at 2.5 mm, high heat transfer performance can be sustained even with a 25 times increase in heat transfer fluid flux and an impressive 98.9% reduction in pressure drop.
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HAN Rui-shan, WANG Yan-lan, LU Fei-peng, ZHANG Song, ZHANG Fang, LI Jiao, CHU En-yi
Online:March 04, 2024 DOI: 10.11943/CJEM2024012
Abstract:To meet the demand for rapid mixing of the reaction solution in the synthesis of silver azide (AgN3, SA) primary explosives, a continuous reverse-rotating T-shaped micro-mixing chip was designed and fabricated. The influence of chip structure and reactant flow rates on mixing efficiency was investigated using Ansys Fluent simulation software, leading to optimization of an efficient micro-hybrid chip structure. This optimized chip was employed for the continuous synthesis of SA primary explosives. The morphology, compositional structure, and thermal properties of the resulting SA primary explosives were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). It was observed that a near 100% mixing efficiency could be achieved when employing a micro-mixing chip with a channel size of 1 mm, collision angle of 180°, and reactant flow rate above 4 mL·min-1. By adjusting the flow rate, concentration, and surfactant content of the reactants, uniform morphology with narrow particle size distribution could be obtained for the SA primary explosives; their main component consisted of AgN3 crystals exhibiting an orthorhombic crystal system. Compared to the conventional methods, the exothermic peak temperature decreased from 365.2 ℃ to 358.2 ℃ (a reduction by 7 ℃) while the exothermic amount increased from 851.6 kJ·kg-1 to 976.7 kJ·kg-1 (an increase by 14.7%) when utilizing microfluidic preparation techniques for SA primary explosives, indicating enhanced reactivity and energy.
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SHENG Min, TIAN Jun-jun, WANG Fang-fang, LI Wei-ye, WU Zhan-hua
Online:February 07, 2024 DOI: 10.11943/CJEM2024018
Abstract:To better evaluate the thermal safety risk of continuous flow reactions, a study was conducted using a tubular reactor as an example. By constructing a reaction system model based on heat balance and material balance, the actual heat transfer and thermal safety risk of continuous flow reaction systems were investigated. To address the adiabatic temperature rise reaction phenomenon at the inlet end of a channel reactor, a method based on the critical reaction half-life was proposed as a criterion for thermal safety assessment. Two major reaction conditions with high thermal safety risk were identified: when the total heat release of the target reaction is greater than 800 J·g-1, and the reaction half-life of the reaction at the reaction temperature is less than the critical reaction half-life; when the total heat release of the decomposition reaction is greater than 800 J·g-1, and the reaction half-life of the target reaction at the reaction temperature is less than the critical reaction half-life, while the reaction half-life of the decomposition reaction at 100% MTSR (maximum temperature that the process reaction can reach) is also less than the critical reaction half-life. Furthermore, the accuracy and practicality were verified through the nitration reaction of chlorobenzene, and the results show that an explosively decomposition reaction could occur in the channel reactor under these conditions, thus confirming the high-risk thermal safety conditions of continuous flow reactions determined by this evaluation method.
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YANG Wei, ZHAO Deng-peng, LU Huan-chang, ZHANG Zhen-qi, MA Qing, HUANG Jing-lun, TIAN Jun-jun, JING Su-ming, FAN Gui-juan
Online:February 29, 2024 DOI: 10.11943/CJEM2024035
Abstract:To improve the thermal safety and synthetic efficiency during the synthesis process of 3-Nitro-1,2,4-triazol-5-one (NTO) by conventional methods, a continuous flow reaction system was designed and prepared based on the solid contents and kinetics at different reaction stages of nitration. The continuous flow synthesis of NTO was realized by combining microfluidic reaction technology with tubular reaction technology, using 2,4-dihydro-1,2,4-triazol-5-one (TO) and 85% nitric acid as the main raw materials. The reaction conditions and continuous flow system were optimized. NTO with a purity of 99.53% and a yield of 81.4% was achieved at a reaction temperature of 45 ℃, a nitration residence time of 9 min, a molar ratio of n(TO)∶n(NTO) equals 1∶6. The chemical structure of NTO synthesized by the continuous flow method was characterized by 1H and 13C NMR, element analysis (EA), infrared spectroscopy (FT-IR). In addition, the crystal form, particle morphology, thermal stability and mechanical sensitivity were characterized by the powder X-ray diffraction (XRD), thermal analyzer (DSC-TG), optical microscope and BAM technology. The results show that NTO grows into stable β-form. At the heating rate of 10 ℃·min-1, the thermal decomposition peak temperature is 276.23 ℃ and the mass loss rate during thermal decomposition is 85.12%. The impact sensitivity is over 40 J, and the friction sensitivity is over 360 N. Compared with NTO synthesized by the flask method, the thermal decomposition peak temperature is increased by 2.95 ℃, and the mass loss rate is elevated by 4.44%. The mechanical sensitivities is similar, the crystal morphology is regular and the particle size distribution range is narrowed. The continuous flow synthesis time is 90% shorter than that of the flask process, with 3.4% higher of the yiel , and the preparation efficiency and safety are improved.
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LI Yong-qiang, LI Gao-chun, LIN Ming-liang
2024,32(2):124-132, DOI: 10.11943/CJEM2023225
Abstract:As a composite material composed of fillers and matrix, the damage of hydroxylated polybutadiene (HTPB) propellant mainly involves particle breakage, matrix fracture, and debonding of the bonding interface layer. To further explore its structural damage and mechanical performance evolution under external loading, a combination of micro CT, high-speed CCD camera, and all atom molecular dynamics simulation was used to analyze the multi-scale damage of the propellant under in-situ loading. The results indicate that the typical damage process of the propellant begins with the failure of the bonding interface layer, extends to the growth of debonding pores, evolves through the merging of pores, accelerates the collection of local large deformations, and terminates at the fracture of the matrix. Meanwhile, the interface binding energy and stress concentration degree cause the large ammonium perchlorate (AP) particles to debond first, and the porosity and strain exhibit an exponential function relationship. Furthermore, the traction separation curve of the micro interface layer conforms to an exponential cohesive force model, where the initiation and expansion of micro voids disrupt their cohesion, while the molecular spacing affects the evolution of stress.
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MAIMAITITUERSUN Wubuliaisan, ZHOU Tao, WU Yan-qing, HOU Xiao, ZHOU Cheng-zhe
2024,32(2):133-141, DOI: 10.11943/CJEM2023220
Abstract:In order to study the damage evolution and mechanical properties of solid propellants, uniaxial tensile and stress relaxation tests were performed on NEPE propellant. The resulting stress-strain curves and relaxation master modulus curves were obtained. A nonlinear viscoelastic constitutive model considering microscopic damage was developed under finite deformation. This model enables multiscale analysis of the mechanical response of propellants by incorporating the evolution of microvoids with various factors, including temperature, strain rate, confining pressure, and cyclic stress softening. The model was then implemented into ABAQUS with the parameters determined based on experimental data. Subsequently, the model was employed to predict the mechanical response of NEPE propellant under different loading conditions. The results demonstrate that the model accurately predicts the uniaxial tensile response of propellants under wide temperature ranges (223-333 K) and loading rates (1-200 mm·min-1). Moreover, the model exhibits reasonable predictability in cyclic loading, confining pressure tests, and biaxial tensile tests, thereby validating its effectiveness under complex stress conditions. Notably, the model necessitates only a small set of model parameters and can be easily programmed into commercial software, providing theoretical guidance for the multiscale analysis of the structural integrity of solid rocket motors.
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WANG Gui-jun, ZHOU Tao, WU Yan-qing, HOU Xiao, HUANG Feng-lei
2024,32(2):142-151, DOI: 10.11943/CJEM2023218
Abstract:To accurately predict the cracking of propellant grain during ignition at low temperatures, a cross-scale analysis method coupled with global-local unidirectional contracting was proposed. For Nitrate Ester Plasticized Polyether (NEPE) propellant, uniaxial tensile tests at low temperature and intermediate strain rate were carried out, and the typical failure modes of the propellant were obtained. The results show that the ignition of solid rocket motor grain at low temperature can be analyzed successfully with macroscope method based on the developed nonlinear viscoelastic constitutive model, and the location of the dangerous point for propellant grain was obtained. Meanwhile, a mesoscopic particle filling model considering the particle-matrix interfacial debonding and particle fracture was established, and the analysis results on a macro scale were applied to the corresponding mesoscopic representative volume element (RVE). Finally, based on the established mesoscopic failure criteria of the propellant, it is shown that the structural integrity of the propellant grain meets the requirements under low-temperature ignition conditions. Furthermore, the proposed contracting cross-scale analysis method can be used as an effective method to predict the cracking behaviors of the propellant grain during ignition at low temperature.
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PEI Shu-di, QIANG Hong-fu, WANG Xue-ren, WANG Zhe-jun
2024,32(2):152-161, DOI: 10.11943/CJEM2023231
Abstract:In order to study the effect of loading Angle on the failure mechanism of HTPB propellant bonding interface, microCT was used to scan and reconstruct the bonding interface in-situ during uniaxial tensile process, and the damage evolution process was characterized. Then, the meso-structural parameters and damage variables were introduced into the cohesive force model, and the meso-damage evolution process of the adhesive interface under different loading angles was obtained. The results show that the initial dehumidification of AP particles at the bonding interface mainly starts from the weak interface layer near the interface, and the direction is along the shear component direction of the interface. The fracture pattern of the interface is related to the shear Angle. The smaller the resultant force and the Angle of the interface, the easier the crack propagation to the propellant/liner interface, whereas the crack propagation is more likely to occur between AP particles. Finally, compared with the experimental results, the accuracy of the calculated results is verified, and the damage evolution law of the propellant bonding interface structure under different loading angles is revealed.
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ZENG Yi, HUANG Wei, CHEN Jia-xing, XU Jin-sheng, CHEN Xiong, WU Rui
2024,32(2):162-174, DOI: 10.11943/CJEM2023248
Abstract:This research investigates the mesoscopic damage mechanisms in hydroxyl-terminated polybutadiene (HTPB) propellants under thermal-mechanical coupling. Experimental characterization and theoretical analysis were employed to analyze these mechanisms at different environmental temperatures (50, 70, and 90 ℃) and loading cycles. At 50 ℃, the propellants underwent approximately 3000 and 10800 loading cycles; at 70 ℃, 1800, 3600, and 7030 cycles; and at 90 ℃, around 1800 cycles. The findings indicate that the mesoscopic damage in HTPB propellants, exacerbated by thermomechanical coupling, is more pronounced than that caused by a single aging factor. This damage primarily results from two processes: thermal degradation of the matrix, diminishing both its load-bearing capacity and adhesion to particles, leading to particle dewetting; and the subsequent exacerbation of the matrix"s thermal degradation by this dewetting. The above interaction makes the mesoscopic damage more severe. Moreover, the damage intensifies with increasing aging temperature, but extremely high temperatures modify the mesoscopic damage mechanism. Furthermore, the study emphasizes the importance of selecting an appropriate number of loading cycles to assess significant mesoscopic damage in HTPB propellants. Notably, substantial damage occurs when the loading cycle ratio (
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LI Shi-qi, QIANG Hong-fu, CHEN Tie-zhu, WANG Xue-ren, WANG Zhe-jun, WANG Guang
2024,32(2):175-182, DOI: 10.11943/CJEM2023232
Abstract:To analyze the mesostructure evolution behavior of nitrate ester plasticized polyether (NEPE) propellants under uniaxial quasi-static tensile load, in-situ observation test was conducted on NEPE propellants during the tensile process using Micro CT. The size and an shape of ammonium perchlorate (AP) particles and initial defects in NEPE propellants were characterized. The failure process of the mesostructure in the propellant during uniaxial tensile process was obtained, and the quantitative analysis of the changes in meso-damage of NEPE propellants was carried out using porosity. The reason for the changes of macro-mechanical properties is explained based on the evolution laws of the structure of NEPE propellant on the mesoscale. The results indicate that the initial defects size of NEPE propellant is small and the volume ratio is low, with an average value of 0.12%. In the process of uniaxial quasi-static tension, the meso-failure process of NEPE propellant mainly includes three stages, pores nucleation, growth and convergence. Although the volume fraction of AP particles is low, it is often the start of meso-damage because of easy debonding. HMX particles will also debonding after a certain degree of debonding of AP. The influence of HMX debonding behavior should be considered when analyzing the macro-mechanical properties of NEPE propellant. The nucleation and growth of a large number of mesoscopic defects is the reason why the macro-mechanical properties properties of NEPE propellant enter the nonlinear section. The phenomenon that the increase of macroscopic stress lags behind the increase of strain is more and more obvious because of the continuous convergence of mesoscopic defects. During the loading process, the porosity shows a change trend of slowly increasing first, then sharply increasing and finally increasing tends to be gentle. The change law of porosity can not only quantitatively reflect the evolution stages of the mesoscopic defects of NEPE propellant, but also have a certain corresponding relationship with the changes of the macroscopic mechanical properties of NEPE propellant.
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WANG Ran, WU Yi, BAI Long, ZHANG Yi-ming, WANG Ning-fei
2024,32(2):183-192, DOI: 10.11943/CJEM2023119
Abstract:In order to investigate the uniaxial compression mechanical behavior of four-component HTPB propellant under wide temperature and wide strain rate ranges, uniaxial compressive mechanical performance tests of propellant were conducted under wide temperature and strain rate ranges based on universal material testing machine, high-speed hydraulic servo testing machine, split Hopkinson pressure bar, and programmatic constant temperature and humidity testing machine. Stress-strain curves of HTPB propellant under 10-4-103 s-1 at -40, -25, -10, 20 ℃ and 50 ℃ were obtained, and the segmented uniaxial compression rate-temperature constitutive relationship of HTPB propellant was established. The results indicate that the mechanical response of HTPB propellant exhibits a significant rate-temperature correlation. At any strain rate, its mechanical response undergoes staged changes, i.e., linear elastic stage-nonlinear yield stage-strain softening or strain hardening stage. Moreover, at high strain rates, the strain softening phenomenon after the nonlinear yield behavior is significantly weaker than that at low and medium strain rates. In addition, at high strain rates, as the temperature decreases, the changing rate of the stress-strain curve gradually slows down; while at low and medium strain rates, the changing rate of the stress-strain curve gradually increases as the temperature decreases. The mechanical strength of HTPB propellant increases significantly with decreasing temperature. When the temperature drops from 50 ℃ to -40 ℃, the maximum stress under wide strain rate increases from about 2.2-8.8 MPa to 11-22 MPa. The segmented rate-temperature constitutive relationship constructed based on the experimental data has a better fitting effect at higher temperatures, which can better predict the mechanical behavior of HTPB propellant.
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ZHOU Dong-mo, XIE Xu-yuan, WANG Rui-min, LIU Xiang-yang, HUI Bu-qing
2024,32(2):193-203, DOI: 10.11943/CJEM2023224
Abstract:To study the formation mechanism of residual stress/strain of the nitrate ester plasticized polyether (NEPE) propellant grain during the curing and cooling stages, the temperature field, curing degree field and stress/strain field of the propellant were numerically analyzed via ABAQUS finite element software. The results show that there are temperature gradient and curing rate gradient in the NEPE propellant grain during the curing process at 50 ℃. The temperature and the curing rate are notably higher at the center of the grain, and they eventually reach a consensus at the end of curing. The temperature difference in the propellant does not affect the final residual stress/strain. The total residual stress/strain during curing and cooling obey the principle of stress/strain superposition, and they are mainly composed of the curing shrinkage stress/strain and thermal stress/strain during cooling. For the total residual stress, the proportions of the two stages are approximately 20% and 80%, respectively, and for the total residual strain, the proportions are about 30% and 70%, respectively. Compared with the traditional method, the residual stress/strain calculated in this study have the same distribution characteristics, but the values are smaller.
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WANG Yao-xiao, WANG Xiao-ying, CHEN Chen, TAN Zhu-yun, ZHOU Xing
2024,32(2):204-210, DOI: 10.11943/CJEM2023178
Abstract:To establish the correlation between the microstructure and mechanical properties of high nitrate plasticized polyethylene glycol (PEG) based polyurethane in nitrate ester plasticized polyether (NEPE) propellant, biuret triisocyanate (N-100) was used as a multifunctional curing agent and mixed with nitrate ester plasticized PEG for curing to prepare PEG elastomers with curing parameters ranging from 1.2 to 1.7. The microstructure of PEG elastomer crosslinked network was studied by uniaxial tension, X-ray diffraction, low field nuclear magnetic resonance and equilibrium swelling test methods. Furthermore, the effects of different network chain structures on the mechanical properties of PEG elastomer were analyzed. The results show that the PEG elastomer is amorphous due to its high plasticized properties. Meanwhile, the total ratio of suspended tail chains to free chains is more than 85%, the structural integrity of the crosslinked network is low, and the elastomer exhibits high elongation, low tensile strength and low initial modulus. Secondly, all the tensile strength and initial modulus of elastomer are positively correlated with the crosslinked chain density. The maximum elongation increases first and then decreases with the increase of physical temporary entanglement chain density. CU-5 elastomer with a curing parameter of 1.6 has the most complete cross-linked network. At the same time, the corresponding tensile strength is 0.80 MPa, and the maximum elongation is 1456%, which indicates that the mechanical properties are the best. Finally, the chain density measured by equilibrium swelling method and low field nuclear magnetic resonance satisfy the magnitude relationship of νL,A<νs<νL,A+B.
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DUAN Lei-guang, WANG Xue-ren, QIANG Hong-fu, WANG Zhe-jun
2024,32(2):211-229, DOI: 10.11943/CJEM2023252
Abstract:The health condition of solid rocket motors largely depends on the real-time status of the propellant. Therefore, monitoring the propellant status is an important foundation for ensuring the structural integrity and reliability of solid rocket motors. We provides a comprehensive review of research progress in the monitoring of propellant status from four aspects: environmental status monitoring, chemical status monitoring, mechanical status monitoring, and integrated application of monitoring data. The necessity of propellant status monitoring is highlighted, and the research achievements and shortcomings in propellant status monitoring are summarized from multiple perspectives. Furthermore, development ideas are proposed for monitoring technology and the application of monitoring data. The analysis suggests that real-time monitoring technology should focus on embedded sensor compatibility, new sensing technology, and long-life technology. In terms of the application of monitoring data, efforts should be made to establish databases, diagnostic and predictive health management systems, in order to promote the development of digital twin technology for the full life of solid rocket motors using finite element model updating methods.
Vol, 32, No.2, 2024 Multiscale Mechanical Behaviors of Solid Propellant
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Eco-friendly technology
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Initiating explosive device technology
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Damage and ignition
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Preparation and performance—Study on synthesis and performance
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High efficiency destruction technology
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Propulsion and projection—Preparation and performance about propulsion materials
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Damage and Ignition
2020
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Detonation Physics
2020
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Crystal and microscopic analysis
2020-2022 发表
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Chemical Propellant
2021-2022 Collection
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