Abstract:In order to obtain a CL-20 based energetic film that can be reliably detonated at the micrometer scale， hexanitrohexaazaisowurtzitane （CL-20）， ethyl cellulose （EC） and poly azido-glycidyl ether （GAP） are selected as the main explosive and bonding system respectively， two ink formulations suitable for the micro-spray direct writing process have been designed and formulated with adding an appropriate amount of low-boiling solvent. The two ink materials are directly written by a double-nozzle microjet direct writing device. The molded samples were characterized by scanning electron microscope， MZ-220SD electron density meter and X-ray diffractometer. The impact sensitivity， thermal decomposition performance and critical thickness of the entrapped film were investigated. Results show that CL-20 based energetic film has a smooth surface and many tiny pores inside， the microstructure size is about 1 μm. The crystal form of CL-20 in membrane is ε type. The forming density of the energetic film is 1.547 g·cm^-3， reaching 79.2% of the maximum theoretical density. The apparent activation energy of thermal decomposition and drop height （impact sensitivity） of CL-20 based energetic film is 241.21 kJ·mol^-1 and 65.7 cm apart， which are both improved compared with raw material CL-20. The critical detonation thickness of the energetic film is 1.0 mm×0.045 mm， demonstrating excellent microscale detonation capability.

Abstract:In order to provide the thermodynamic criterion for the cocrystal formation and give theoretical basis for the screening and optimization of crystallization solvents and parameters, the thermodynamic of hexanitrohexaazaisowurtzitane (CL-20)/1,4-dinitroimidazole (1,4-DNI) cocrystal formation has been investigated. Taking acetone, ethyl acetate and methanol as solvents, the solubility data of CL-20, 1,4-DNI in pure solvents and CL-20 in 1,4-DNI solutions with different concentrations (0.04, 0.06, 0.08, 0.10, 0.12, 0.16, 0.20, 0.24 g·mL^-1) were achieved with the help of high performance liquid chromatography. The ternary phase diagrams of CL-20/1,4-DNI solvents were built. The thermodynamic parameters of the solubility product K_sp, the complexation constant K₁₁, and the reaction free energy ΔG⁰ were obtained through fitting the solubility data based on the mathematical models of solution chemistry theory. The results show that if the solubilities of CL-20 and 1,4-DNI are larger and their discrepency is less in a solvent, the cocrystal region is larger and its shape is more symmetrical. The order of the cocrystal regions in the three solvents from large to small is acetone > ethyl acetate > methanol, and the shape of the cocrystal region in the acetone and ethyl acetate is more symmetrical. The calculated thermodynamic parameters indicate that the acetone is the most beneficial to the formation of CL-20/1,4-DNI cocrystal among the three solvents, followed by ethyl acetate. The ternary phase diagram and thermodynamic parameters in acetone solvent at different temperatures show that lowering the crystallization temperature is beneficial to the precipitation of the CL-20/1,4-DNI cocrystal.

Abstract:Hexanitrohexaazaisowurtzitane (CL-20) with a negative oxygen balance, is currently the most powerful commercially available explosive. In this work, the CL-20/H₂O₂ host-guest energetic material (CL-20/H₂O₂) was constructed by using urea hydrogen peroxide (UHP) as raw material through the solvent volatilization at low temperature and negative pressure. The structure of the complex was confirmed through X-ray diffraction (XRD) and Raman spectra. Results indicates that CL-20/H₂O₂ crystallizes in orthorhombic system space group Pbca with a long-range ordered stacked structure. The ratio of CL-20 molecule and H₂O₂ molecule is 2∶1 stoichiometry according to the thermogravimetry and simultaneous differential scanning calorimetry (TG-DSC) analyses. Furthermore, the polymorph transitions of CL-20/H₂O₂ with increasing temperature were investigated by in situ high temperature XRD. Results show that CL-20/H₂O₂ gradually converts to γ-CL-20 with elevated temperature and the rate of transition is faster than that of ε-CL-20. The CL-20 acetonitrile solvate (CL-20/CH₃CN) is a key intermediate via a solid state phase transition to form the CL-20/H₂O₂ host-guest energetic material by tracing the growing process of CL-20/H₂O₂.

Abstract:Phonon spectra play an important role in studying the thermodynamic properties of solids and the microscopic process of initiating chemical decomposition reactions， which can help to reveal the microscopic physical mechanism of initial thermal decomposition mechanism， detonation performance and sensitivity. In this work， the density functional theory with dispersion correction was used to calculate the phonon spectra and thermodynamic properties of 2，4，6，8，10，12-hexanitrohexaazaiso-wurtzitane（CL-20）/1，4-dinitroimidazole（1，4-DNI） cocrystal and co-formers. Through analyzing the phonon density of states， the way in which the phonon mode stores and transfers energy was determined， the direction of thermal energy flow was proposed， and the trigger bond and impact sensitivity order were predicted. The results show that the initial bonds of ε-CL-20 and CL-20/1，4-DNI cocrystal are predicted to be N─NO₂ bonds on CL-20 molecules； the initial thermal decomposition of 1，4-DNI may be related to the ring-opening of imidazole. By comparing the phonon density of states of CL-20 and 1，4-DNI molecules in cocrystal and its pure components. It can be found that the thermal stability of both CL-20 and 1，4-DNI molecules were improved in cocrystal， so that the thermal stability of the cocrystal being superior to the co-formers. According to the "doorway" mode phonon number and characteristic vibration frequency Δω_d， the order of the impact sensitivity is predicted of to be ε-CL-20>CL-20/1，4-DNI>1，4-DNI， completely consistent with the experimental measurement results. The thermodynamic parameters of CL-20/1，4-DNI cocrystal and co-formers have been calculated by phonon spectra， at the same temperature， the order is CL-20/1，4-DNI>ε-CL-20>1，4-DNI. In addition， low-frequency phonons contribute the most to heat capacity（C_V）， and the chemical bond breakage caused by energy transfer may undergo a multi-phonon up-pumping process.

Abstract:Ultrafine hexanitrohexaazaisowurtzitane/cyclotetramethylene tetranitramine(CL-20/HMX)cocrystal explosive was prepared by ultra-highly efficient mixing method. X-ray diffraction and differential scanning calorimetry were utilized to determine whether the cocrystal explosive was prepared. The crystal morphology, particle size, sensitivity of cocrystal explosive were characterized. The prepared samples were regular block-like ultrafine CL-20/HMX cocrystal explosives with uniform particle size of less than 1 μm, which appeared new stronger diffraction peaks at 11.558°, 13.264°, 18.601°, 24.474°, 33.785°, 36.269°. The purity of the CL-20/HMX cocrystal explosive was 92.6%. The thermal decomposition process of cocrystal explosives had only one exothermic decomposition stage with peak temperatures of 248.3 ℃. The enthalpy for the exothermic decomposition of the cocrystal (2912.1 J·g^-1) was remarkable higher than that of the physical mixture of CL-20 and HMX (1327.3 J·g^-1). According to GJB772A-1997《The explosive test method》, the friction sensitivity of CL-20/HMX cocrystal explosive was 84%, which was decreased by 16% compared with original CL-20, the characteristic height of the cocrystal was increased by 28.6 cm and 11.5 cm compared with original CL-20 and HMX, respectively. The compatibility of CL-20/HMX cocrystal with components of solid propellant, including hydroxyl-terminated glycidylazide polymer(HGAP), nitroglycerin/1,2,4-butanetriol trinitrate (NG/BTTN), triisocyanate(N-100), ammonium perchlorate(AP), aluminum powder(Al powder) were investigated by differential scanning calorimetry(DSC). The CL-20/HMX cocrystal was compatible with NG/BTTN, AP and Al powder, while incompatible with HGAP, N-100.

Abstract:In order to study the effect of iron tannate catalyst on thermal decomposition properties of common components in solid propellants, three submicron composite microspheres,tannic acid and iron (Ta-Fe)/ hexanitrohexaazaisowurtzitane (CL-20), Ta-Fe/ cyclotrimethylenetrinitramine (RDX) and Ta-Fe/ cyclotetramethylene tetranitramine (HMX), were prepared by ultrasonic spray drying. The morphology, particle size and composition of these composites were characterized by SEM and granulometer analyser. The effect of Ta-Fe on the thermal decomposition catalytic properties and kinetic parameters of CL-20, RDX and HMX were studied by differential scanning caloriometry (DSC). Results show that Ta-Fe distributes evenly with spherical particles and good dispersibility, and the particle size distribution range is 500-1000 nm. Ta-Fe effectively promotes the thermal decomposition of CL-20, RDX and HMX, whose peak thermal decomposition temperatures decrease by 17.2，8.2 ℃ and 11.5 ℃,respectively. Especially, Ta-Fe/CL-20 has the best catalytic effect, whose activation energy is 9.6 kJ·mol^-1 lower than raw CL-20.

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:To improve the safety performance of hexanitrohexaazaisowurtzitane (CL-20) and maintain its higher energy, three kinds of CL-20/FOX-7 polymer bonded explosives(PBXs) with different formulation proportions were prepared by water suspension coating method using polyurethane polymer Estane as coating agent and 1,1-diamino-2,2-dinitroethene(FOX-7) as energetic sensitivity-reducing component. The morphology structure, crystal form, thermal decomposition characteristic and impact and friction sensitivity of samples were tested and analyzed by scanning electron microscopy (SEM), X-ray diffractometer (XRD), differential scanning calorimeter (DSC), impact sensitivity tester and friction sensitivity tester. The detonation velocity of three kinds of PBXs was tested by an electrical measurement method. The results show that the explosive particles based on CL-20/FOX-7 have better coating effect, and neither CL-20 nor FOX-7 has crystal transformation. The apparent activation energy of three kinds of PBXs are increased by 17.12, 32.87 and 40.24 kJ·mol^-1 compared with refined CL-20. The enthalpies of activation (ΔH) of PBX samples are also significantly improved compared with CL-20. The characteristic drop height increases from 27.5 cm of refine CL-20 to 58.3, 56.5 cm and 54.2 cm， respectively, compared with CL-20. The actual detonation velocities of three kinds of PBXs with different formulation proportions are 8474, 8503 m·s^-1 and 8577 m·s^-1 ，respectively, which is equivalent to the detonation velocity of PBXN-5, but the characteristic drop height increases by more than 48.5% compared with PBXN-5, the safety performance of explosives is significantly improved.

Abstract:To establish a simple, efficient and good reproducible method of measuring the content of γ-crystal form impurities in ε-hexanitrohexaazaisowurtzitane(ε-CL-20), the characteristic parameters for the quantitative characterization of γ-CL-20/ε-CL-20 mixed samples were determined by Raman spectroscopy, and then, the characteristic peak area ratio A₂₃₂/A₅₂₈ of two crystal forms was plotted against γ-CL-20 content. The standard curves in the two sets of concentration ranges of 2%-9% and 10%-90% were obtained respectively and compared with the quantitative results obtained by the peak area method. Results show that when the content of γ-CL-20 is 2%-9%, the relative error of A₂₃₂/A₅₂₈ values for three sets of parallel experiments is not more than 2.2%, and the fitting equation is y=0.0062e^0.2512x with a correlation coefficient of 0.9806. When the content of γ-CL-20 is 10%-90%, the relative error of A₂₃₂/A₅₂₈ is not exceed 2.9%, and the fitting equation is y=0.0822e^0.0596x with a correlation coefficient of 0.9816. Data reproducibility and fitting correlation coefficient of A₂₃₂/A₅₂₈ are far better than the peak are method.

Abstract:To further improve the forming effect of suspended explosive ink, a kind of "O/W" type binder emulsion was designed by using ethyl acetate solution of type 26 fluoroelastomer (Viton) as oil phase, aqueous solution of polyvinyl alcohol (PVA) as water phase, Tween-80 and sodium dodecyl sulfate (SDS) as surfactants. The orthogonal design of L₂₅(5⁶) was designed by SPSS data analysis software. The content of each component and preparation process in emulsion were optimized. The analyzed and optimized results were verified by experiments, and the stability of emulsion was evaluated by the static stability of emulsion as index. The microstructure of emulsion was measured by optical microscope. The suspended explosive ink was prepared using emulsion as binder system，hexanitrohexaazaisowurtzitane(CL-20) as the body explosive. The direct writing pattern and crystal type of the explosive ink were analyzed. The results show that the mass ratio of Tween-80/SDS is 1∶2, The mass fraction of an emulsifier (the total mass of the emulsion) is 2%, the concentration ratio of water phase to oil phase is 2∶1, the stirring time is 30 min, the emulsifying temperature is 20 ℃ and the stirring speed is 350 rpm, are more conducive to maintaining the stability of binder emulsion. The emulsion binder system prepared by optimized experimental conditions can be stable about 360 h. The size of dispersed phase droplet in the emulsion is 20-120 μm, the distribution is uniform and there is no obvious agglomeration phenomenon. The prepared explosive ink writes smoothly without blocking the direct writing needle and the crystal type of CL-20 in explosive ink composite has no change.

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:To further understand the structural evolution law of internal and external groups of ε-phase 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (ε-CL-20) molecule skeleton during the heating process, the temperature response law of internal and external groups of ε-CL-20 skeleton was quantitatively compared and analyzed by in-situ Fourier transform infrared spectroscopy (in-situ FT-IR) and differential scanning calorimetry (DSC). Results show that the infrared absorption peak intensity of external groups (—NO₂, C—H) of ε-CL-20 skeleton undergoes three change stages as temperature increases: linear decrease (Z_Ⅰ), accelerated decrease (Z_Ⅱ), and second accelerated decrease (Z_Ⅲ), which correspond to the thermal expansion, thermally induced phase-transition and thermal decomposition process of CL-20 crystal, respectively. The C—N stretching vibration inside the molecular skeleton also undergoes the above-mentioned three stages,but the initial temperature of Z_Ⅱ and Z_Ⅲ regions are significantly higher than that of the external group, indicating that the external groups are more sensitive to temperature than internal groups, whether thermally induced phase-transition or thermal decomposition, while the internal groups of the skeleton respond to temperature only at higher temperature. The temperature response characteristics of C—C stretching vibration inside molecular skeleton are even more complex. As temperature increases, the peak intensity of C—C stretching only undergoes an accelerated reduction process, and a new characteristic peak of C—C stretching vibration is observed, which is closely related to ε-γ phase transition, illustrating that the phase transition process makes the vibration mode of C—C bond inside the molecular skeleton change significantly. After further heating, the relative proportion of the new characteristic peak area is continuously increasing, showing that the change of the vibration mode inside the skeleton is still ongoing until the end of thermal decomposition.

Abstract:In this paper, based on the mature technical system of hydroxyl terminated polybutadiene（HTPB） composite solid propellants, the new energetic material have been introduced for these formulations to obtain plume with less emission and higher combustion efficiency. According to the literature, in order to achieve the low emission of the combustion plume, high-energy compounds such as hexanitrohexaazaisowurtzitane (CL-20) and polynitrogen compounds can be used to partially replace some ammonium perchlorate (AP), whereas the dinitramide Ammonium (ADN) and nitrous oxide (HNF) are expected to completely replace AP in HTPB propellants. More importantly, in order to improve the combustion efficiency of aluminum (Al) powder, aluminum hydride (AlH₃), nano-Al or various composite Al powder could be used. In general, the development of new energetic ingredients for HTPB propellants should follow the problem-oriented principle. As a result, it′s better to investigate the characteristics of such novel energetic ingredients, and thereby the practical applications of HTPB propellants could be extended, which may promote solid-power technology in both military and civilian applications.

Abstract:Energetic compounds represented by trinitrotoluene (TNT), cyclotrimethylene trinitramine (RDX) and cyclotetramethylene tetranitramine (HMX) are highly toxic. When released into the environment, these energetic compounds will undergo complex redistribution, migration and transformation in soil-water-organism system, and pose hazards to ecosystems and human health. According to the pollution status of energetic compounds in domestic and foreign sites, the environmental behaviors of TNT, RDX and HMX in soil such as dissolution/precipitation, volatilization, adsorption/desorption, photolysis, hydrolysis, reduction, microbial degradation and plant uptake and transformation were reviewed. The physical and chemical properties of explosives and soils, and the effect of on-site environmental conditions on these complex environmental behaviors were also analyzed. The latest research on the environmental behavior of hexanitrohexaazaisowurtzitane (CL-20) and other novel explosives was briefly introduced. Based on the current research status, it is recommended that more attention should be paid to marine environmental ammunition pollution and combined pollution between energetic compounds and heavy metals in the future, and more attention should be paid to the application of the advanced technologies, such as compound-specific stable isotope analysis, to the environmental behavior and fate of explosives.

Abstract:To research the effect of crystal defect on the stability, sensitivity and detonation performance of hexanitrohexaazaisowurtzitane(CL-20) /nitroguanidine(NQ)cocrystal explosive, the"perfect"and defective(adulteration, vacancy and dislocation)CL-20/NQ cocrystal explosive models were established. Molecular dynamics method was applied to predict the properties of various models. The binding energy, trigger bond length distribution, bonding diatomic interaction energy, cohesive energy density and detonation parameters of different models were got and compared. The results show that compared with the"perfect"crystal, the decreasing ampliture of binding energy of defective crystal is 4.29%-24.33%, indicating that the intermolecular interaction energy is weakened and the stability is decreased. The increasing ampliture of trigger bond length of defective crystal is 0.78%-6.04%, while the decreasing ampliture of bonding diatomic interaction energy is 2.86%-20.03% and the decreasing ampliture of cohesive energy density is 2.46%-12.72%, indicating that the sensitivity of explosive is increased and safety is worsened. Owing to the influence of crystal defect, the decreasing ampliture of density, detonation velocity and detonation pressure of explosive is 0.58%-7.57%, 0.43%-5.99%, and 1.19%-15.31%, respectively, indicating that the energy density and power are decreased. Therefore, crystal defect has a negative effect on the stability, sensitivity and energetic characteristics of CL-20/NQ cocrystal explosive, among them, the effect of vacancy defect on the performance of explosive is more significant.

Abstract:In order to improve the safety performance of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), nano CL-20/AP（ammonium perchlorate) energetic composite particles were readily prepared via a one-step ball milling method, a facile, clean, and continuous synthesized strategy. The prepared samples were studied by scanning electron microscopy(SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and impact sensitivity test. The SEM results show that the CL-20/AP composite particles are smooth on surface and nearly spherical with size of 300-500 nm. The XRD peak position of CL-20/AP is obviously deviated and some peaks are even disappeared, which means new crystalline phase may be formed. Due to the preferred orientation of the polycrystalline samples, the XRD peak intensity is reduced. The thermal decomposition peak of CL-20/AP decreases. The impact sensitivity result shows that the H₅₀ of the nano CL-20/AP composite particles is 26.07 cm, which increases by 13.10 cm compared with raw CL-20, indicating a better safety performance.

Abstract:Ab initio molecular dynamics simulations were used to study the decomposition mechanism of 2, 4, 6, 8, 10, 12-hexanitro-2, 4, 6, 8, 10, 12-hexaazaisowurtzitane(CL-20) crystal, an excellent high energy density cage compound, under extreme conditions. It is found that the initiation and subsequent decomposition mechanisms of the CL-20 crystal are diverse at different conditions, and CL-20 is sensitive to both high temperature and pressure. Comparing the numbers of corresponding main products, it is found that the high pressure decelerates the decomposition. While, the appearance of special intermediates R-C_xO_y (x>2, y>5) indicates that the high pressure makes the decomposition much more complex. Among these intermediates, C₃O₆ is proved to be a high energy density compound.

Abstract:Replacing traditional solid propellants with high-energy explosives (such as hexanitrohexaazaisowurtzitane (CL-20)) is an important way to achieve microthrusters with small size and large specific impulse. In order to realize the self-sustaining combustion of CL-20, a composite propellant system with CL-20 nano-microparticles hosted in the rGO three-dimensional network is designed. Ultrafine CL-20 spherical particles (diameter 300 nm-2 μm) have been prepared by a solvent-nonsolvent method firstly, then self-supporting rGO/CL-20 fiber propellant was prepared by a dimensionally confined hydrothermal strategy. Based on the analysis of thermal analysis kinetics and combustion characteristics, it is concluded that the positive feedback mechanism of the combustion heat release of rGO/CL-20 fiber propellant plays a key role in its combustion propagation. Due to the construction of rGO three-dimensional network, the thermal conductivity of the fiber propellant is improved, and the exothermic effect of rGO/KOH can serve as the initial ignition energy for rGO itself and CL-20 microparticles. Once ignited, the combustion of high-energy CL-20 releases more heat energy than rGO, thereby forming the positive feedback mechanism. The combustion propagation speed of the prepared self-supporting rGO/CL-20 fiber propellant is 20.66 mm·s^-1, moreover, the fibrous structure facilitates the rapid modular charge of the microthrusters.

Abstract:To study the influence of particle size on critical detonation performance of hexanitrohexaazaisowurtzitane (CL-20)-based explosives ink by micro-flow direct writing technology, three different particle sizes of CL-20 explosives were prepared by mechanical ball grinding method and solvent-nonsolvent method, respectively. The CL-20-based explosive ink by micro-flow direct writing technology was prepared by a two-component adhesive dispersion system consisting of waterborne polyurethane (WPU) and ethyl cellulose (EC). The particle size distribution and morphology of the prepared CL-20 explosives and the corresponding ink samples were characterized by laser particle size analyzer and scanning electron microscope (SEM), respectively. The crystal type of the CL-20 in ink samples were measured by X-ray diffractometer (XRD). The critical detonation thickness of CL-20 explosive ink samples with different particle sizes were tested by wedge shaped charge test. The results show that the two CL-20 explosives prepared by mechanical ball grinding method have a nearly spherical shape and smooth surface, whose median size are 140 nm and 1.5 μm, respectively. The corresponding ink samples have a honeycomb shape, with good dispersing effect and uniform compact cross-section. The CL-20 explosive prepared by solvent-nonsolvent method has a fusiform shape with a median size of 15 μm. The corresponding ink sample has poor dispersing effect, and the explosive particles and adhesive system are difficult to form a composite structure. The XRD test results indicate that three crystal types of the CL-20 in ink samples are all ε form. The critical detonation thickness of CL-20 explosive ink samples with a charge width of 1 mm is as small as 69 μm, and decreases with the decrease of CL-20 particle size, indicating that reducing the particle size of the CL-20 can significantly enhance its critical detonation performance.

Abstract:A composite sample of CL-20 and dihydroxylammonium 5, 5'-bistetrazole-1, 1'-diolate(TKX-50, HATO)was prepared by in-situ crystallization method in aqueous suspension of CL-20 using 1, 1'-dihydroxy-5, 5'-bitetrazole(H₂DHBT)and hydroxylamine aqueous solution as raw material through neutralization reaction. The morphology and structure of the composite were characterized by scanning electron microscope(SEM), Fourier transform infrared spectroscopy(FT-IR), nuclear magnetic resonance(NMR)and X-ray diffraction(XRD). The effect of different processing conditions on the morphology of the composite was studied. Thermal property was analyzed using DSC. Its impact and friction sensitivity were measured with GJB772A-1997 method. Its detonation velocity was calculated using Urizar 's formula. Results show that the technological conditions for obtaining CL-20/HATO composite sample with uniform adhesion are:reaction temperature 90 ℃, reaction time 10 min and dropping rate 60 mL·min^-1 of NH₂OH aqueous solution. The crystal form of CL-20 in prepared CL-20/HATO composite sample does not change. The mass ratio of CL-20 and HATO in CL-20/HATO composite obtained by quantitative carbon spectroscopy is m(CL-20) :m(HATO) =55:45. The temperature of thermal decomposition of the complete is 238.3 ℃ and 250.7 ℃. Its characteristic drop height is 44.7 cm, the probability of impact explosion is 52% and the probability of friction explosion is 76%. Theoretical detonation velocity of the composite sample is 9516 m·s^-1.

Abstract:To study the underwater explosion process of hexanitrohexaazaisowurtzitane (CL-20)-based polymer bonded explosives (PBXs) with and without aluminum powders, two kinds of explosives with aluminum contents of 0 and 15% were prepared.An underwater explosion experimental device was designed, and the images of pressure histories, bubble periods and bubble pulse of shock wave were obtained.The shock wave energy, bubble energy and total underwater explosion energy of two kinds of explosives were calculated The underwater explosion process was well-simulated by the AUTODYN software.Results show that when aluminum content increases from 0 to 15%, the total underwater explosion energy increases from 1.4 times TNT equivalent to 1.7 times TNT equivalent.In the process of bubble pulsation, the light is produced in the bubble of CL-20 based aluminized explosive when the time is from 49.5 ms to 49.8 ms.The peak pressure of aluminized explosives and nonaluminized explosives are 15.16 MPa and 15.51 MPa.The bubble of secondary pressure wave are 2.25 MPa and 2.35 MPa, 50.20 ms and 46.76 ms for the bubble periods.The maximum bubble radius are 67.87 cm and 60.27 cm.The simulation results of aluminized explosives and non-aluminized explosives overpressure are 14.90 MPa and 15.14 MPa.The bubble of secondary pressure wave are 2.16 MPa and 2.27 MPa, bubble period for 49.32 ms and 45.90 ms, 66.32 cm and 58.89 cm for the maximum bubble radius.The shock wave and bubble parameters obtained by calculation are in good agreement with experimental results.

Abstract:Based on the first-principle software developed by ourselves, the thermodynamic stability, mechanical properties, and detonation performances of structure for hexanitrohexaazaisowurtzitane(CL-20) explosive with five crystallline phase, benzotrifuroxane(BTF) crystal explosive and CL-20/BTF cocrystal explosive were studied. Results show that the electrostatic attraction effect of weak hydrogen bonds makes the intermolecular binding energy of CL-20/BTF cocrystal increase by 39% compared with that of hydrogen-free BTF crystal, which improves thermodynamic stability of cocrystal structure and significantly changes its mechanical properties, such as bulk modulus and sound speed etc. Although the BTF/CL-20 cocrystal and pure BTF crystal have the similar density, but due to the oxygen balance coefficient of the cocrystal has been optimized, so its detonation velocity and detonation pressure are improved by about 11% and 5%, respectively. Compared with the β-CL-20 crystal, the density and oxygen balance of the cocrystal are decreased, the detonation pressure and detonation velocity relatively decrease by about 15% and 6%, respectively. Design of a new type of insensitive cocrystal explosive should avoid the molecule with extremely weak strength covalent bonds and structure with characteristic peaks of high density vibration spectrum, thermodynamic stability effect of hydrogen bond on the molecular space packing should be effectively used, and the hydrogen element content should be moderately controlled to protect the high energy density of explosives.