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Abstract:In order to study the safety performances of the mixed explosives of 3,4-dinitrofurazanfuroxan (DNTF) and dihydroxylammonium 5,5´-bistetrazole-1,1´-diolate (HATO), the sensitivity of DNTF/HATO with different proportions were studied. The critical diameter of DNTF explosive was about 0.2 mm. When the HATO content was less than 55%, the mechanical sensitivity of DNTF/HATO decreased linearly with the increasing HATO content. The shock wave sensitivity of DNTF/HATO was similar to that of DNTF when the HATO content was no more than 50%, and only decreased when the HATO content was 55%. The thermal decomposition temperature of HATO decreased from 243 ℃ to 230 ℃ for DNTF/HATO. The molecular dynamics of DNTF/HATO was simulated by Dreiding force field. With the increasing HATO content, the bond length of C—N and C—O which connected NO₂ and the ring in the DNTF molecule showed decreasing trend for DNTF/HATO, suggesting the enhanced structural stability of DNTF/HATO.

Abstract:In order to study the detonation and safety performances of dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) based polymer bonded explosives (PBX), the TKX-50 based PBX was prepared by a slurry kneading method, using fluororesin F2314 as the polymer binder. The detonation performance (detonation velocity, detonation pressure, detonation heat and cylinder expansion tests) and safety performance (impact sensitivity, shock wave sensitivity and thermal sensitivity) were carried out according to the National Military Standard (GJB-772A-1997) and self-built standard test method, and the results were compared with PBX-9501, etc. The results showed that, comparing with PBX-9501, the detonation velocity of TKX-50 based PBX was as high as 9037 m·s^-1 (density of 1.860 g·cm^-3), while the detonation heat (5055 J·g^-1), detonation pressure (26.4 GPa) and the work capacity (1.377 kJ·g^-1) were lower. For the safety performances, the minimum impact energy of raw TKX-50 was only 5 J, while that of recrystallized product was 32 J. The shock wave sensitivity of TKX-50 based PBX was lower (L₅₀=15.1 mm) than that of HMX-based PBX (L₅₀=22.6 mm). Besides, the thermal decomposition temperature (240 ℃) and 5 s explosion temperature (277 ℃) of TKX-50 was lower than HMX (285 ℃, 327 ℃). In this case, TKX-50 based PBX would react more violently under thermal stimulation.

Abstract:To systematically understand the effect of ammonium perchlorate (AP) on the thermal decomposition mechanism of 5,5'-bitetrazole-1,1'-dioxadihydroxyammonium(HATO), the thermal decomposition characteristics, gas products and condensed phase change of HATO and HATO/AP blends were analyzed by combination of thermogravimetry-mass spectrometry-Fourier transform infrared spectroscopy (TG-MS-FTIR), differential scanning calorimetry(DSC) and Fourier transform infrared spectroscopy (FTIR). HATO had two consecutive thermal decomposition stages,while HATO/AP blends had three. For HATO/AP blends, the melting profile of AP disappeared; the thermal decomposition of HATO showed an advanced initial temperature, prolonged decomposition time and unchanged completeness of HATO decomposition. The gas products from the thermal decomposition of HATO were CO₂, N₂O, HCN, NH₃, NO, N₂ and H₂O; whereas CO₂, N₂O, HCN, NH₃, NO, N₂, H₂O, HCl and NOCl were detected for HATO/AP blends. The activation energy of HATO and HATO/AP blends tetrazole ring, which was calculated by equal conversion rate method was 53.38kJ·mol^-1 and 60.69 kJ·mol^-1,respectively. By comparing the thermal decomposition process of HATO and HATO/AP blends and the change of characteristic groups of condensed phase, the advancement of thermal decomposition temperature of HATO can be attributed to the proton transfer between the ammonium ion of AP and HATO. The prolonged decomposition time for HATO/AP blends might be explained by following mechanism: NH₃ was produced from the HATO and AP, which further reacted with the thermal decomposition intermediate 1,1'-dihydroxy-5,5'-tetrazolium (BTO) to form Diammonium 5,5'-bistetrazole-1,1'-diolate (ABTOX).

Abstract:In order to obtain castable explosive with high energy and high mechanical strength, CL-20/DNAN/TNT castable explosive was successfully prepared by casting process with 2,4-dinitroanisole (DNAN) and trinitrotoluene (TNT) as low eutectic carriers and hexanitrohexaazoisowurtziane (CL-20) as high energy component. The effects of micro-nano CL-20 particle grading and three functional assistants of N-methyl-4-nitroaniline, tris-(2-chloroethyl) phosphate and catechol on the properties of CL-20/DNAN/TNT castable explosives were investigated. The prepared CL-20-based castable explosives were characterized by SEM, viscosity, density, XRD, mechanical sensitivity, mechanical properties and detonation speed. When the mass ratio of bulk CL-20 to 100 nm CL-20 was 70:30 and 0.5% tri-(2-chloroethyl) phosphate was added, the castable explosive had smooth surface, no obvious internal defects and good density uniformity. Compared with the castable explosive with coarse CL-20, the impact and friction sensitivity was reduced by 32.7% and 57.1%, respectively. The compressive and tensile strength was increased from 7.93 MPa and 3.48 MPa to 33.74 MPa and 4.94 MPa, respectively. The detonation speed was increased by 37.0 m·s^-1 from 8188 m·s^-1 to 8225 m·s^-1.

Abstract:In order to compare the comprehensive properties of 2,4-dinitroanisole(DNAN)-based and 2,4,6-trinitrotoluene（TNT） -based melt-cast explosives, the suspension rheology, performance, safety and mechanical properties of typical TNT-based and DNAN-based explosives were systematically investigated by experiment tests. The viscosity of DNAN(6.87 mPa·s) was lower than that of TNT(9.05 mPa·s), which made the limit solid content of the DNAN/HMX melt-cast system (about 80%) higher than that of the TNT/HMX melt-cast system (about 75%). The detonation velocity and detonation pressure was 8336 m·s^-1 and 31.03 GPa, 8452 m·s^-1 and 31.44 GPa, for DNAN/HMX(20/80) and TNT/HMX(25/75), respectively. The response level of DNAN/HMX(20/80) and TNT/HMX(25/75) was burning and explosion, respectively under 1 K·min^-1 slow cook-off. Under 4.51 GPa incident shock wave pressure, TNT/HMX(25/75）achieved complete detonation within 8-12 mm, whereas DNAN/HMX(20/80) failed to achieve complete detonation within 12 mm; tensile and compressive strength of DNAN/HMX(20/80) was higher than that of TNT/HMX(25/75).With basically equal energy performance, DNAN/HMX(20/80) melt-cast explosives have better safety and mechanical properties than TNT/HMX（25/75） melt-cast explosives.

Abstract:In order to enhance the safety and energy of the explosive charge, three new composite charge structures were designed and prepared by 3D printing technology. 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and 2,4,6-triamino-1,3,5-trinitrobenzene (TATB) were chosen as the main explosive due to high energy density of CL-20 and high safety of TATB. Glycidyl azide polymer binder (GAP) and polyisocyanate (N-100) were used as binders to prepare two energetic formulations TATB/GAP/N-100 and CL-20/GAP/N-100 for 3D printing. Three new structures were constructed by 3D printing based on the two formulations. The effects of the binder contents and printed parameters on microstructure of the energetic charges were studied. Stable charge structure was obtained when the content of the binder, printed speed and the nozzle diameter was 20%, 3 mm·s^-1 and 0.25 μm, respectively. The impact sensitivity of three new structures was studied by GJB772A-1997 method 601.2. The H₅₀ for the axial/radial composite charge structure was about 72.00 cm, which was three times higher than that of raw CL-20.

Abstract:In order to study the properties of 3,3'-diamino-4,4'-azoxyfurazan (DAAF)-based insensitive high polymer bonded explosives (PBX), three kinds of DAAF-based PBXs (DAAF/EVA (95/5), DAAF/Viton A (95/5) and DAAF/F₂₃₁₁ (95/5)) were prepared by water suspension coating technique. The morphology structure, crystal form, thermal decomposition characteristic and mechanical sensitivity were analyzed by scanning electron microscopy (SEM), X-ray diffractometer (XRD), differential scanning calorimeter (DSC), impact and friction sensitivity apparatus. The fast and slow cook-off behaviors were examined. The DAAF/F₂₃₁₁ was well coated which had a smooth spherical shape with 450 μm in diameter, while DAAF/EVA and DAAF/VitonA were poorly coated with rough surface. The exothermic peak temperature of DAAF/F₂₃₁₁ was 0.9 ℃ lower than that of DAAF (when the heating rate was 10 ℃·min^-1). The activation energy and the critical temperature of thermal explosion of DAAF/F₂₃₁₁ was 12.14 kJ·mol^-1 and 8.29 ℃ higher than that of the raw DAAF, respectively. According to the GJB772A-1997 method, the impact sensitivity H₅₀ of the three DAAF-based PBXs were greater than 100 cm, and the friction sensitivity was 0. The response level of the fast and slow cook-off tests was burning, which satisfied the safety requirements for insensitive ammunition.

Abstract:In order to improve the safety performance of cyclotetramethylenetetranitramine (HMX) based cast polymer bonded explosive (PBX), a certain amount of 1,1-diamino-2,2-dinitroethylene (FOX-7) was substituted for HMX in the formulation. The influence of FOX-7 on the thermal stability, mechanical sensitivity, shock wave sensitivity and electrostatic spark sensitivity of the formulation was studied. The friction sensitivity of the formulation GOXL-A was lower than that of the HMX based cast PBX formulation GO-1 after the introduction of FOX-7. The response time in the fast cook-off and slow cook-off tests was delayed by 58.8% and 18.5%, respectively. The formulation had passed the EIS slow cook-off test with a heating rate of 3.3 ℃·h^-1. The shock wave sensitivity was significantly reduced. The separator thickness (L₅₀) was reduced by 15.7% compared with GO-1, and the 50% critical detonation pressure (p₅₀) was increased by 9.5%. Its static spark sensitivity is significantly reduced. The 50% ignition voltage (V₅₀) and 50% ignition energy (E₅₀) increased by 65.3% and 187.5%, respectively.

Abstract:In order to study the effects of surface modification on the mechanical sensitivity, interfacial mechanical and processing properties of energetic materials, inspired by the mussel adhesion protein, the modified explosives (HMX@PDA, TATB@PDA) and aluminum powder (Al@PDA) were prepared by polymerization of dopamine on the surface of energetic materials with one-step method, in which PDA formed a compact and firm coating film. The surface morphology, grain fracture morphology, element content and surface wettability of the modified energetic materials were characterized by scanning electron microscope, X-ray photoelectron spectroscopy and contact angle test. The mechanical sensitivity and tensile stress-strain curve of the modified energetic materials were measured by national military standard (GJB-772A-1997), Brazil experiment and other standard testing methods. Compared with HMX crystal, the friction sensitivity of HMX@PDA crystal decreased by 30%, and the characteristic drop-off value increased by 100%. The Brazilian tensile strength of TATB@PDA-based PBX cylinders was 15% higher than that of the TATB-based PBX cylinders. After 24 h in HTPB liquid phase, sedimentation was effectively slowed down for Al@PDA, as compared with naked aluminum powders. The characteristic complete and compact coating abilities on the crystal and rich active groups endow polydopamine remarkable interfacial modification effect on sensitivity reduction, interface mechanical properties improvement, processing stability improvement and other aspects of energetic materials.

Abstract:In order to study the response characteristics of cylindrical shelled propellant charges under the impact of the bullet, a kind of 12.7 mm bullet impact test was designed. The high-speed camera recorded the response of the shelled charges under the impact of a 12.7 mm bullet. Shell fragment velocities and air overpressures at different positions and azimuths were measured. Besides, the ideal detonation of the shelled charge was numerically calculated and the relative energy release rate was obtained. Four bullet impact tests of cylindrical shelled charge were carried out totally, in the first three tests, deflagration reaction occurred in the charge, and in the fourth test, almost no reaction occurred in the charge. Results show that the reaction and relative energy release rate are great influenced by the impact position. A time sequence response of ignition, smoking, extinguishment and low-pressure combustion occurred in the propellant when the bullet impacted vertically on the axis of the shelled charge, and its relative energy release rate was 1.146%. When the bullet impact position deviated from the axis by a distance, the propellant almost had no reaction, and its relative energy release rate was only 0.473%. The reaction of propellant can accelerate the shell fragments. When the deflagration reaction occurred in the shelled charge, the fragment velocity could reach 428.6 m·s^-1, while the maximum fragment velocity was only 70.1 m·s^-1 when the propellant almost had no reaction.

Abstract:To decrease the mechanical sensitivity of hydroxyl terminated polybutadiene(HTPB) propellant with high burning rate, the effects of liquid ferrocene combustion catalyst (EMT) content, particle size and ratio of oxidant AP on the mechanical sensitivity of HTPB propellant with high burning rate were studied. The correlation between thermal decomposition property and mechanical sensitivity of AP/EMT system was studied by means of DSC-TG thermal analysis and mechanical sensitivity test. The fraction and impact sensitivity of the propellant slurry increased with the increase of fine AP content or the decrease of fine AP particle size. The decomposition rate constant and heat of AP at high temperature was increased by EMT, which explained the increased mechanical sensitivity of the high burning rate propellants. The mechanical sensitivity of the propellant might be reduced by reducing content of EMT. Synergistic effect was not found between the amine salt desensitizer of GZJ-01 and electronic conductive polyaniline DBJ-01 on decreasing the mechanical sensitivity of high burning rate HTPB propellant. The mechanical sensitivity of the high burning rate propellants can be decreased by coating with fine AP and replacing EMT with GRCJ.

Abstract:To study the relationship between the molecular structure of double-core ferrocene derivatives (DFDs) and mechanical sensitivity of fine AP/DFD, molecular structure of DFD, interaction between AP and DFD, characteristics of thermal decomposition of super fine AP/DFD, and mechanical sensitivity of the mixture were studied by simulation and experiments. The trigger mechanisms of impact and friction sensitivity of the AP/DFD mixture were different. The correlation analysis showed that the thermal decomposition of AP was the dependent factor on the impact sensitivity of the mixture, the closer profiles for the three exothermic reaction processes caused lower impact sensitivity. The friction sensitivity of the mixture was dependent on the reaction between DFD molecule and crystal planes of AP,Higher difference beween the lower thermal decomposition temperature of AP and DFD led to lower friction sensitivity.

Abstract:The mitigation technology of controlling the reaction level of munitions under accidental stimulation is one of the key technologies of insensitive munitions, which plays an important role in improving the safety of munitions. In order to provide reference for improving the comprehensive performance of munitions, the principles and methods for structural mitigation and protection design aiming at reducing the intensity reaction level of munitions under thermal, mechanical and combined stimuli were summarized, based on the analysis of the research progress of mitigation technology abroad. The core ideas of mitigation designs were reducing stimuli energy and controlling the process of reaction evolution of charges. On this basis, three directions were recommended including research in the ignition and mechanism of reaction evolution of charges, the composite shell technology, and the combined design technology for charge-structure-mitigation.

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