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    • Preparation and Thermal Decomposition Properties of Mesoporous Carbon Nanospheres /RDX Host-guest Energetic Composites

      2023, 31(1):18-25. DOI: 10.11943/CJEM2022169

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      Abstract:To investigate the effect of mesoporous carbon nanospheres (MCS) on the thermal decomposition properties of cyclotrimethylenetrinitramine(RDX), MCS was prepared by double template method with the particle size of about 350 nm. RDX crystals were introduced into the pore and surface of MCS by host-guest chemistry technology. The morphology and structure of MCS and MCS/RDX composite were characterized by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The interface interaction between MCS and RDX was studied by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry-thermogravimetry (DSC-TG). Compared with pure RDX, the decomposition temperature of MCS/RDX composite decreased by 13 ℃ and the heat release increased. The apparent activation energy decreased from 234.87 kJ·mol-1 to 126.48 kJ·mol-1. The sensitivity tests were carried out by the drop hammer impact sensitivity instrument and the electrostatic spark device. Compared with the pure RDX, the impact sensitivity and electrostatic spark sensitivity of the obtained MCS/RDX composite are apparently reduced. Therefore, the obtained MCS has good catalytic performance for the thermal decomposition of RDX and can reduce the sensitivity of RDX.

    • Preparation and Properties of TNBA/TNAZ Lowest Eutectic Mixture

      2023, 31(2):130-141. DOI: 10.11943/CJEM2022059

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      Abstract:The eutectic mixtures of 2,4,6-trinitro-3-bromoanisole (TNBA) and 1,3,3-trinitroazetidine (TNAZ) with different mass ratios were prepared by the electrostatic spray method. T-X and H-X phase diagrams were drawn according to the differential scanning calorimetry (DSC) curves of the eutectic mixtures to obtain the mass ratio of the lowest eutectic. Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), High Performance Liquid Chromatography (HPLC), X-ray Powder Diffraction (XRD), Infrared (IR), X-ray Photoelectron Spectroscopy (XPS), DSC, and thermogravimetry-mass (TG-MS) spectrometry were used to determine the morphology, component content, element distribution, crystal structure and thermal decomposition properties of the lowest eutectic. And the mechanical sensitivity, thermal sensitivity and detonation performances of the lowest eutectic were tested and theoretically calculated. The results showed that 60.95∶39.05 is the optimal mass ratio of TNBA/TNAZ lowest eutectic mixture; the microscopic morphology has no sharp edges and corners; the component proportion is the same as before electrostatic spraying; the surface elements are evenly distributed; and the crystal structure is basically the same as that of the raw materials. The eutectic temperature is 350.18 K, which is 22.72 K and 24.82 K lower than that of raw materials TNBA and TNAZ. The thermal decomposition reaction rate constant (k), activation enthalpy (ΔH), activation energy (EK), activated Gibbs free energy (ΔG), and activation entropy (ΔS) of the lowest eutectic are 0.33 s-1, 60.10 kJ·mol-1, 64.44 kJ·mol-1, 135.21 kJ·mol-1, and -143.78 J·(mol∙K)-1, respectively. The impact sensitivity (H50), friction sensitivity (FS), and 5s explosion temperature of the lowest eutectic mixture are 42 cm, 20%, and 558 K, respectively. Its detonation performance (OB=-34.83%,Q=5101.78 kJ·kg-1VD=7598.37 m·s-1) is between TNBA and TNAZ. The main detonation products are N2、C(d)、CO、CO2 and H2O.

    • Preparation of TKX-50/KH550 Composites and their Compatibility with Nitrocellulose

      2022, 30(12):1197-1204. DOI: 10.11943/CJEM2022165

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      Abstract:To improve the compatibility of dihydroxylammonium 5,5′-bitetrazole-1,1′-diolate(TKX-50) with nitrocellulose(NC), silane coupling agent (KH550) was used as the coating agent and three TKX-50/KH550 composites (TK1, TK2, TK3) were obtained.The morphology, structure and thermal stability of the composites were studied by using scanning electron microscopy (SEM), Fourier infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Accelerating rate calorimeter (ARC) and DSC were used to examine the compatibility of TKX-50/KH550 composites with NC. The results show that the apparent activation energy of thermal decomposition of the prepared TKX-50/KH550 composites are 190.03, 195.82 and 194.42 kJ·mol-1 respectively higher than that of TKX-50 (138.86 kJ·mol-1), indicating the thermal stability of TKX-50 is improved by KH550 coating. In adiabatic conditions, the initial thermal decomposition temperature of the mixtures of TKX-50/KH550 composites and NC are 14.93, 18.18 and 17.90 ℃ respectively higher than that of TKX-50 and NC. After coated with KH550, the compatibility of TKX-50 and NC is improved, and the compatibility level of TKX-50/KH550 composites and NC is raised from Level 3 to Level 2.

    • Preparation of Zr/Pb3O4 Microencapsulation and Its Property

      2022, 30(4):301-308. DOI: 10.11943/CJEM2021284

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      Abstract:The mixing uniformity and processing safety of widely used zirconium/lead tetroxide (Zr/Pb3O4) composites are indispensable. In the current paper, a Zr/Pb3O4 microcapsule bonded with the adhesive alginate was prepared by crosslinking the liquid phase with sodium alginate(SA) and Ca2+ in aqueous phase to form calcium alginate (CA) gel. The morphology, particle size, sphericity, fluidity and apparent density of CA/Zr/Pb3O4 microcapsules and the traditional-made NC/Zr/Pb3O4 controlled sample were evaluated. The average particle size, variance, sphericity and repose angle of CA/Zr/Pb3O4 microcapsules is measured to 517.10 μm, 44.21 μm, 0.90, and 27.44°, respectively. The flame sensitivity, burning rate, flame length and sensitivity of CA/Zr/Pb3O4 microcapsules were tested to 65.38 mm, which was lower than that of Zr/Pb3O4 powder (81.83 mm). Besides, the combustion rate deviation of CA/Zr/Pb3O4 microcapsules and Zr/Pb3O4 powder is 6.86 and 12.04, respectively, implying an excellent combustion consistency. Furthermore, much more flame length of 17.1 mm and burning particles than Zr/Pb3O4 were obtained in of CA/Zr/Pb3O4 microcapsules. In addition, a reduced the electrostatic sensitivity of CA/Zr/Pb3O4 microcapsules (156.25 mJ) and Zr/Pb3O4 powder (0.71 mJ) were realized. More importantly, the water-phase preparation carried out in the current paper may pave a high-safety and universal way for a variety of pyrotechnic agents.

    • Preparation and Characterization of nAl@PVDF@CL-20 Composite Energetic Particles Assembled via Microfluidic Method

      2022, 30(4):341-348. DOI: 10.11943/CJEM2021317

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      Abstract:The explosives and propellants containing hexanitrohexaazaisowurtzitane (CL-20) and aluminum (Al) powders show excellent energy properties, and Al/CL-20-based energetic materials have become the focus of research. By using polyvinylidene fluoride (PVDF) as binder combined with nano-aluminum (nAl) powders and CL-20, the nAl@PVDF and nAl@PVDF@CL-20 composite energetic particles could be prepared via microfluidic technology. The morphology, internal structure, and particle size of two composite particles were observed by scanning electron microscope (SEM) and laser particle size analyzer. Chemical structure of composite particles was analyzed by Fourier transform infrared spectrometer (FTIR). Thermogravimetry-differential scanning calorimetry (TG-DSC) was used for thermal analysis. The results show that the as-prepared composite particles exhibit high sphericity, good dispersibility, and uniform particle size distribution with the particle size of 10-20 μm. The components of composite particles are well-distributed, and there is no chemical bond between the components. Thermal analysis results display that both nAl@PVDF and nAl@PVDF@CL-20 composite particles exhibit pre-ignition reaction between PVDF and surface oxidation layer of nAl. The heat released from the pre-ignition reaction could promote the decomposition of PVDF. The decomposition reaction of CL-20 could be accelerated by combining with nAl and PVDF. Compared with nAl/PVDF/CL-20 material acquired by mechanical mixing, nAl@PVDF@CL-20 composite particles prepared by microfluidic method possess homogeneous component distribution.

    • Calculated Thermodynamic Properties of Energetic 1,1-Diamino-2, 2-dinitroethene (FOX-7) at the Finite Temperature

      2022, 30(12):1245-1251. DOI: 10.11943/CJEM2022137

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      Abstract:To study the fundamental physical properties and intermolecular interaction of energetic materials under the loading temperature, the first-principle calculation was performed combined with zero-point energy and temperature effect corrections. The accuracy of lattice parameters at experiment temperature (173 K) can be significantly improved, and the deviations between the calculated lattice parameters and available experimental data are within 1%. The unit cell volume change with temperature is relatively reasonable compared with the experimental value at 0-500 K, and their deviation is mainly from the lack of interactions between phonons. Furthermore, the basic thermodynamic properties such as heat capacity, entropy and bulk modulus were predicted, and the results indicate that the lattice parameters and thermal expansion coefficient of FOX-7 have strong anisotropy in 0-500 K. Especially, the thermal expansion coefficient of interlayer direction is higher than that of inner layer direction, which is closely related to the molecular configuration and stacking. Importantly, when the temperature reaches 200 K, the shrinkage of thermal expansion coefficient of FOX-7 is related to the rotation of NO2 group. The NO2 group would regulate the intermolecular interaction by changing the dihedral angle with the molecular plane, thereby triggering potential phase transformation of FOX-7. In addition, the bulk modulus under the adiabatic conditions is consistent with the experimental values reasonably, and the evolution of adiabatic bulk modulus with temperature reflects the softening behavior of FOX-7 at the finite temperature. With the increase of temperature, the calculated heat capacity and entropy increase gradually, showing obvious numerical differences under the constant volume and pressure due to the anharmonic effect.

    • Preparation and Characterization of FOX-7 Explosives with Different Shapes

      2022, 30(7):659-665. DOI: 10.11943/CJEM2021330

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      Abstract:The particle size and morphology of energetic material crystal have a great influence on its performance. In order to study the relationship between crystal morphology, particle size and thermal decomposition performance of 1,1-diamino-2,2-dinitroethylene (FOX-7) explosive, FOX-7 explosive particles with different morphologies and particle sizes were prepared according to solvent/non-solvent method. Scanning electron microscope (SEM), X-ray diffractometer (XRD), differential scanning calorimeter (DSC) and impact sensitivity tester were used to investigate the crystal morphology and particle size, crystal form, thermal decomposition property and safety property of FOX-7 explosives, respectively. The results show that by changing the cooling rate, stirring rate and other process conditions, FOX-7 explosive particles with different morphologies such as sea urchin shape, spherical shape, flower shape and block shape can be obtained. The crystal form of prepared FOX-7 explosive is consistent with that of raw material as α-form. The crystal morphology and particle size of FOX-7 have a great influence on the breaking of intramolecular hydrogen bonds and the destruction of the conjugated system, and the spherical shape is beneficial to increase the thermal decomposition temperature. For the FOX-7 sample with a same shape, the larger the particle size, the better the thermal stability. Among the FOX-7 samples with diameters of tens of microns, the sample with spherical morphology has the best safety performance.

    • Research Progress and Applications of Energetic Coordination Compounds

      2022, 30(3):276-288. DOI: 10.11943/CJEM2021118

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      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.

    • Ultrasonic Detection and Imaging of Metal-explosive Interface Debonding Defects Using Multiple Pulse-echoes

      2022, 30(9):952-958. DOI: 10.11943/CJEM2021035

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      Abstract:The structural integrity evaluation of the metal-explosive bonding interface is of great importance and engineering value. To realize high sensitivity detection of interfacial debonding defects in the metal-explosive structure, the ultrasonic detection and imaging methods based on multiple pulse-echoes was proposed. The acoustic impedance and reflection characteristics at bonding interface of aluminum, shellac, and RDX were calculated and analyzed. For specimens with different adhesive layer thickness and artificial prefabricated debonding defects, debonding information were extracted from the captured multiple echoes. The influence of adhesive layer with different thickness on the amplitude of multiple echoes was discussed and analyzed. Results show that dramatical amplitude difference exists in the reflected waves between the aluminum-adhesive and the aluminum-water interface. Both the first echo and multiple echoes could effectively distinguish the area with and without adhesive layer. The acoustic attenuation caused by the aluminum-adhesive interface keeps accumulating in high order echoes. As the thickness of the adhesive layer increases, the cumulative effect of the acoustic attenuation difference in the multiple ultrasonic echoes between aluminum-adhesive and aluminum-water interfaces gradually weakens. Experimental results show that the minimum debonding defects with Φ1.5 mm circular and 1 mm wide rectangular shape could be detected using multiple ultrasonic echoes method.

    • Stabilizing Modifications of α-AlH3 by Acidic and Organic Solution Treatment

      2022, 30(8):779-786. DOI: 10.11943/CJEM2021142

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      Abstract:In order to improve the stability of α-AlH3, acidic and organic solutions were used as modifiers to treat α-AlH3. Through structural characterization, stability test, and mechanical sensitivity test, the properties of samples before and after the treatment were compared and analyzed. The performance on hydrogen release and the corresponding modification mechanisms were compared, and the modifier with a better stabilizing effect was obtained. The experimental results show that the proposed modification methods are effective and have a negligible effect on the hydrogen release properties of the studied samples. The weight loss associated with hydrogen release observed for the modified α-AlH3 does not exceed by 1%, and the changes in initial temperature and peak temperature of hydrogen release are less than ±3 ℃, the maximum hydrogen release rate is not affected by more than 20%. Treatment by hydrobromic acid solution exhibited the best effect on enhancing the storage stability of α-AlH3, and the amount of hydrogen release for the studied samples during the storage was found to decrease from 0.87% to 0.02%. It suggests that the acidic and organic solution treatment can reduce the impurities and defects on the surface of α-AlH3 sample, and the amorphous alumina or aluminum hydroxide are likely to be formed on the surface of α-AlH3 after the acidic solution treatment which enhances the stability of α-AlH3. Compared with organic solutions, the acidic solution treatment shows a better ability to maintain the hydrogen release properties of α-AlH3, enhance its storage stability, and reduce mechanical sensitivity, which can be used as a promising modifier in practical applications.

    • Uniaxial Tensile Properties of Butadiol Quaternary Propellant under Confining Pressure and Wide Temperature

      2022, 30(8):793-803. DOI: 10.11943/CJEM2022032

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      Abstract:In order to study the uniaxial tensile mechanical properties of hydroxyl tetrade propellant under wide temperature and confining pressure, the mechanical properties of propellants under different temperatures(-50 ℃, 20 ℃ and 70 ℃), confining pressures(0.1, 2 MPa and 8 MPa) and tensile rates(100, 1000 mm·min-1 and 4200 mm·min-1) experiments were conducted by using a wide-temperature-confining pressure gas test system. The internal microscopic reasons for the development of macroscopic mechanical properties were analyzed by means of scanning electron microscopy (SEM) and micron CT, with the main of revealing the influence mechanism of external load on mechanical properties of high solid content propellants. The results show that the damage of propellant is mainly attribute to“de-wetting” at room temperature and high temperature. At low temperature and atmospheric pressure, the particles suffer the "de-wetting" and ductile fracture. When the confining pressure increasing, it would change to brittle fracture of particles. Nevertheless, the elongation still increases with the increase of confining pressure. Under high confining pressure and different tensile rates, the mechanical properties of the propellant at room temperature and high temperature are similar. Because at this conditions, high temperature weakens the interaction between binder matrix and solid filler, and the “de-wetting” of the propellant are more seriously, but high confining pressure inhibits the “de-wetting” and weakens the influence of temperature. When the time-pressure equivalent superposition principle (TPSP) is used to carry out the fitting analysis of the principal curve of the maximum tensile strength, at low of -50 ℃, the relationship between the time-pressure displacement factor and the corresponding confining pressure does not conform to the standard form, and the superposition principle of TPSP has certain limitations for the use of high solid content propellants.

    • Aluminum/water Reaction Mechanism of Aluminum-based Hydrogels

      2022, 30(6):557-563. DOI: 10.11943/CJEM2021273

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      Abstract:In order to study the aluminum-water reaction characteristics of PVA-nAl/HTPB, the PVA-nAl/HTPB composites were prepared by dispersing nAl/HTPB in the polyvinyl alcohol (PVA), which was obtained by physical cross-linking method. In order to explore the aluminum-water reaction mechanism, the aluminum-water reaction characteristics of the polyvinyl alcohol-nAl/HTPB with 0.1 mol·L-1 NaOH solution at different temperatures (25, 40, 55, 70, 85 ℃ and 100 ℃))were investigated and the residue after the aluminum-water reaction were characterized. The results show that the maximum hydrogen production and rate of PVA-nAl/HTPB is 76 mL·g-1 and 80 mL·g-1·min-1, respectively, which is higher than that of PVA-nAl. The product of the aluminum-water reaction is aluminium oxyhydroxide (AlO(OH)).

    • Slow Cook-off Characteristics of HTPB SRM with Different Structural Sizes

      2022, 30(2):155-162. DOI: 10.11943/CJEM2021097

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      Abstract:Slow cook-off test is one of the key tests of low vulnerability assessment for solid rocket motor. In order to study the influence of the charge size of HTPB composite propellant on the slow cook-off characteristics, slow cook-off tests and numerical simulation were carried out to compare and analyze the ignition growth laws of solid rocket motor under slow cook-off tests, with charge dimensions of Φ100 mm × 200 mm, Φ160 mm × 400 mm and Φ522 mm × 887 mm. Their corresponding ignition temperatures, ignition positions and response levels were determined. Results show that the ignition temperature of specimens of Ф100 mm×200 mm, Ф160 mm×400 mm and Ф522 mm×887 mm of solid rocket motors are 244 ℃, 172 ℃ and 155 ℃, respectively. Taking test data as inputs, the calculated ignition temperature is 250, 269, 154℃, and their corresponding calculation errors and response levelsare 2.88%, 1.17%, 0.64%, and explosion, explosion and deflagration. The calculated cloud diagram shows that the ignition position of medium and small test pieces is located in the center of charge cylinders, and the ignition position of full-scale solid motor is in the center of meat thickness of solid propellant front-end, which is a ring shape area.

    • A Correction Method for the Velocity Attenuation Model of Fragments Based on Altitudes

      2022, 30(1):58-63. DOI: 10.11943/CJEM2021150

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

    • Interface Structure and Stability of Al/Fe2O3 Nano-thermite: A Periodic DFT Study

      2022, 30(3):197-203. DOI: 10.11943/CJEM2021224

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      Abstract:Nano-thermites, as one kind of energetic composites, have wide applications. A systematic study on the relationship between the interface structures and properties has great significance for the preparation of the new nano-thermites with excellent performance. The structures and energies of Fe2O3(104) and Fe2O3(110) surfaces and the structures, bonding properties, and adhesion work of Al(111)/Fe2O3(104) and Al(111)/Fe2O3(110) interfaces (AFS1, AFS2, AFS3, AFS4 and AFS5) were studied with the periodic density functional theory in this work. Results show that O-terminated Fe2O3(104) and Fe2O3(110) surfaces and the interfaces formed by these surfaces with Al(111) are more stable than those of the (104) and (110) surfaces of Fe2O3 respectively. Among 5 of the Al/Fe2O3 interfaces, the interfaces composed by the O-terminated Fe2O3(104) and Fe2O3(110) surfaces with Al(111), i.e., AFS1 and AFS5, have the maximum adhesion work (3.92 J·m-2 and 3.02 J·m-2, respectively), and AFS1 is more stable than AFS5. In these two most stable interfaces, the Al atoms stack on the top position of the O atoms of the Fe2O3 surfaces and the binding of Al and Fe2O3 surfaces is mainly through the Al-O ionic bonds.

    • Molecular Dynamics Simulation of the Compatibility of DNTF With Polymers

      2023, 31(1):61-69. DOI: 10.11943/CJEM2022163

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      Abstract:To determine the compatibility of 3,4-Dinitrofurazanfuroxan (DNTF) with different polymeric passivators, models of fusion-cast explosives were constructed. These fusion-cast explosives were mixtures of DNTF with polymethyl methacrylate(PMMA), fluororubber (F2603), cis-butadiene rubber (BR), or polyvinylidene fluoride (PVDF). The molecular dynamics (MD) simulation method was used to study the compatibility between DNTF and the above-mentioned four polymer passivators from the radial distribution function, solubility parameter and Flory-Huggins interaction parameter under the COMPASS force field. The nature of the intermolecular interaction force in the blends was revealed. The compatibility of the four blend systems was further experimentally verified by using the vacuum stability tests (VST). The results show that the intermolecular radial distribution function values for individual components are lower than that between two different components in the blends. The solubility parameters of these systems are less than 3 J1/2·cm-3/2. The interaction parameter values of the systems are less than the critical interaction parameter value. The outgassing volume of these systems are all less than 0.6ml, indicating that DNTF is compatible with PMMA, F2603, BR and PVDF. The numerical simulation results are well consistent with the experimental results.

    • Flow and Casting Process Simulation of Unsaturated Polyester Coating Layer

      2022, 30(11):1106-1127. DOI: 10.11943/CJEM2022045

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      Abstract:The new challenge to the existing coating layer process was put forward by the development of solid rocket motor technology. In recent years, thermosetting resin as the matrix was used, combined with continuous automatic coating technology, the popular coating production method of coating layer lies in whether complete molding and excellent performance can be obtained quickly. The flow properties and casting condition of unsaturated polyester (UPR) coating layer were studied. The chemical rheological model of the UPR coating layer during continuous automatic manufacturing is obtained by introducing exponential function based on Kinua-Fontana model. The functional relationship of viscosity versus time and temperature of cured UPR is established. The suitable temperature for casting operation was obtained. The filling volume fraction distribution, flow rate distribution and weld line position of coating layer were predicted by introducing of POLYFLOW simulation software, which the constitutive equations is established on the base of Bird-Carrea power-law equation. The casting process was simulated at the constant rate and pressure, respectively. The results show that the casting temperature is below 35 ℃, the casting pressure is more than 1 MPa, and the inlet flow rate is more than 150 mm3·s-1 and less than 175 mm3·s-1 in the coating layer casting process.

    • Molecular Dynamics Simulations for Interfacial Interactions of TATB with AOT

      2022, 30(6):597-603. DOI: 10.11943/CJEM2021311

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      Abstract:The crystallization process of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) will be affected by dioctyl sulfosuccinate sodium salt (AOT) and the molecular dynamics (MD) method was used to study this crystallization process in this work. The crystal morphologies of TATB crystal in vacuum were predicted by Bravis-Friedel-Donnary-Harker (BFDH) and attachment energy (AE) models. Seven important crystal planes of TATB were determined, which are (0 0 1), (1 0 -1), (1 -1 0), (1 0 0), (1 -1 1), (0 1 -1) and (0 1 0). The interface model for TATB with AOT was established and performed the molecular dynamics simulation. The modified AE model was used to analysis simulation data. After calculation, we found that the crystallization rate of TATB was improved under the influence of AOT solution. After analyzing the molecular structure and the intermolecular interaction of TATB, it is considered that because of the special plane structure, the intermolecular interaction between (0 0 1) plane and AOT is weak and the attachment energy (119.832 kJ·mol-1) of (0 0 1) plane is low. So, the growth rate of (0 0 1) plane is relatively slow. The attachment energies of (1 0 -1), (1 -1 0), (1 0 0), (1 -1 1), (0 1 -1) and (0 1 0) planes are all higher than (0 0 1) and they all grow faster than (0 0 1). Therefore, in the experimental process, a leaf-like TATB structure formed first. With the reaction time was further, the (0 0 1) plane gradually grows, the leaves become longer.

    • A Theoretical Study on the Stability of Electron Withdrawing Group Substituted Pentazoles

      2022, 30(1):12-19. DOI: 10.11943/CJEM2021192

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      Abstract:Pentazoles are currently a research hotspot in the field of energetic materials, however, the stability of existing pentazoles is generally not high. In order to develop new pentazoles with better properties, based on the analyses of the available structures, 20 substituted derivatives of HN5 with the electron-withdrawing groups, i.e.,N5(CH2x-1R(R=—NO2,—CF3,—CN, —CHO, —COOH; x=1, 2, 3, 4), were designed and studied by using the density functional theory method. The bond dissociation energy (EBD) of the bonds linked with the N5 ring and the activation energy (Ea) of the cracking of the N5 ring were calculated and compared with that of some pentazoles substituted by the electron-donating groups, and the effects of substituents on EBD and Ea were discussed. Results show that the Ea of all molecules is much smaller than EBD, indicating that the stability of the N5 ring is the key factor to determine the stability of the pentazoles. When R is directly connected to the N5 ring (N5R), the Ea of N5R with R being an electron-withdrawing group is smaller than that of N5R with R being an H or an electron-donating group. The N5 ring is a strong electron-withdrawing group, and bearing too much or too little negative charges is not conducive to the stability of the N5 ring.

    • Molecular Dynamics Study on the Pyrolysis Mechanisms of TKX-55 and Dioxane

      2022, 30(1):20-33. DOI: 10.11943/CJEM2021067

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

    • Isolation and Identification of a Highly Efficient Strain of Aniline Degrading Bacterium Q6 and Degradation Characteristics

      2022, 30(10):1004-1012. DOI: 10.11943/CJEM2022168

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      Abstract:The production and processing of pyrotechnics produce aniline wastewater, which causes a great pollution to the environment. To provide an efficient strain resource for aniline degradation, a strain Q6 with aniline as the only carbon source and energy growth was isolated from the activated sludge in the aerobic aeration tank of the chemical wastewater treatment plant. Through morphological observation, physiological and biochemical characteristics and 16S rDNA gene sequence phylogeny analysis, the strain was identified as Acidovorax sp. The effects of inoculum amount, temperature, pH value and additional carbon and nitrogen sources on aniline degradation by strain Q6 were studied. Meanwhile, the degradation kinetics of aniline at different initial concentrations and the growth kinetics of strain Q6 were fitted. The results showed that under the conditions of temperature 23-37 ℃ and pH 5-8, strain Q6 could degrade aniline efficiently, and ammonium chloride was the best co-metabolizing nitrogen source to promote the degradation of aniline.The optimum conditions of 33 ℃, pH 7 and inoculation amount of 10%, the degradation rate of aniline at different initial concentrations (200-3000 mg·L-1) was above 95.0%, and the degradation process of aniline showed first-order and zero-order kinetics. The growth process of Q6 conformed to the Haldane equation with a maximum specific growth rate μmax of 0.130 h-1, a half-satiation constant Ks of 190 mg·L-1 and the inhibition constant Ki of 8497 mg·L-1. The results show that strain Q6 has unique potential in the treating industrial wastewater containing high concentration of aniline.

    • Determination of Hydrazine, Monomethylhydrazine, and Unsymmetrical Dimethylhydrazine in Water by Hydrophilic Interaction Chromatography Coupled with Mass Spectrometry

      2022, 30(10):1022-1029. DOI: 10.11943/CJEM2021220

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      Abstract:A method of determination of hydrazine, monomethylhydrazine (MMH), and unsymmetrical dimethylhydrazine (UDMH) in water by hydrophilic interaction chromatography (HILIC) coupled with mass spectrometry (MS) was developed. Sample preparation, composition of mobile phase and parameters of MS detection were investigated for optimization for HILIC-MS analysis of hydrazine compounds. 80% isopropanol-0.1% formic acid was used as sample solvent, and injection volume was 10 μL. Composition of mobile phase was 70% acetonitrile-10 mmol·L-1 ammonium formate, pH=3.5. Hydrophilic interaction chromatographic column was utilized for separation. Protonated non-covalent adduct of hydrazine and acetonitrile, protonated MMH and protonated UDMH were selected as detection ions, and post-source collision energy were 50, 100, 100 eV, respectively. Good linearity between MS response intensity and analyte concentration for quantitative analysis was obtained in certain range of analyte concentration. The limits of detection for hydrazine, MMH and UDMH were 0.04, 0.005, 0.025 mg·L-1, respectively. Recovery of spiked water sample was determined as 92%-115%.

    • Advances in Biosensors-based Trace Explosives Detection

      2022, 30(10):1047-1054. DOI: 10.11943/CJEM2021277

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      Abstract:Explosive TNT is the most important weapon energy source in military activities. It not only has a powerful damaging effect, but also has chemical toxicity. Even a trace amount of TNT will pose a serious threat to the natural environment and human health. Therefore, the development of trace explosive detection technology with high sensitivity, high accuracy and fast response has far-reaching research significance for protecting the ecological environment and maintaining human health. Among many trace detection technologies, biosensing technology has the advantages of good selectivity, simple synthesis, fast response and high sensitivity, and has good application prospects. This paper reviews the research progress of biosensor technology in the detection of trace explosives in recent years, focusing on the advantages and limitations of five types of biosensors: antibody immunity, peptides, aptamers, enzymes and multi-parameter loading. Among them, the sensor prepared based on aptamer has good affinity and specificity for explosive molecules, the detection limit is 1000 times lower than other types of sensors, and has good stability, easy modification and modification, and strong structural expansion ability. Future research will focus on the construction of high-throughput trace explosives sensing systems based on bioreceptor components such as aptamers, combined with neural network algorithms and machine learning to construct biosensors with multiple detection and bionic remote sensing properties.

    • Progress Progess on Detection Methods of UDMH and Its Transformation Products in Water

      2022, 30(6):611-621. DOI: 10.11943/CJEM2021154

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      Abstract:Rapid detection of unsymmetrical dimethylhydrazine (UDMH) and its transformation products in water is of great significance for its pollution control. This paper reviewsthe research progress of chromatographic methods (including gas chromatography, high performance liquid chromatography, and ion chromatography) and non-chromatographic methods (including the electrochemical method, spectrophotometry and chemiluminescence) in the detection of UDMH in water. Then, application of chromatography in in the detection of UDMH conversion products in water was briefly introduced. The advantages and disadvantages of different detection methods in the detection concentration range, sample pretreatment and anti-interference ability, etc.,were pointed out. It was suggested that the design of efficient automatic chromatographic pretreatment device and the combination of various separation and detection technologies would be the future development direction to solve the detection problem of UDMH and its transformation products in water.

    • Experiment and Simulation of Flow Field Characteristics for Single Modular Artillery Charge System

      2023, 31(1):70-82. DOI: 10.11943/CJEM2022198

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      Abstract:Modular artillery charge system (MACS) is one of the main charge structures for large-caliber howitzers. To accurately study the interior ballistic characteristics of single modular artillery charge system and analyze the variation law of gas flow and pressure wave in the chamber, a combustion experiment platform for MACS was designed to carry out the combustion experiment of single modular artillery charge system. According to the characteristics of modular artillery charge system, the axisymmetric two-dimensional two-phase flow interior ballistic model of modular charge was constructed in different regions. Based on the high-order accurate Monotonic Upstream-centered Scheme for Conservation Laws (MUSCL), the numerical simulation of the ignition process of single-module charge was carried out. The results show that the calculated results are in good agreement with the experimental results. The calculated maixmum errors of the pressures at different test points are less than 4%, indicating that the mathematical model established and calculation method used can describe the combustion process of single modular artillery charge system well. The results also show that before t=5.0 ms, the combustion of the module cartridge has little effect on the internal flow field of the module. The gas of main propellant can"t diffuse into the charge chamber in time due to the obstruction of the end cover of the cartridge.Only the gas of the ignition tube has a certain effect on the flow field in the chamber. The maximum pressure in the chamber during this period is about 4.3% higher than that before the right end of the fire tube is not broken. After the rupture of the cartridge, there is a pressure difference of 3.05 MPa at the boundary between the cartridge and the chamber, so that the propellant gas and solid particles flow rapidly along the axial direction to the free space of the chamber. A strong reflection of the pressure wave is formed at the bottom of the projectile. After that, the pressure wave oscillates repeatedly and gradually weakens.