Abstract:

Abstract:The reaction mechanism of intermediate 3，3′-Bis（1，2，4-oxadiazole）］-5，5′-diyldimethanol acetate （BODM） hydrolyzed to 3，3"-Bi（1，2，4-oxadiazole）-5，5"-diyldimethanol （BOD） was investigated by theoretical calculation. The synthesis process was optimized by single factor experiment and orthogonal experiment. The structure and properties of BOD were analyzed by XRD， FTIR， NMR and DSC. It was found that the reaction mechanism was the lone pair electrons in BODM —［O］— formed an OH…O hydrogen bond with H in H₂O， then the O—C bond in —［O］—［C═O］—broke， and the H and OH bonds in H2O formed —OH and —COOH group in —［O］— and —［C═O］—， respectively. and found that the crystal of BOD belong to the monoclinic system， the space group is C2/c， the cell angle α=90°， β=105.361（7）°， γ=90°， the cell volume v=774.9（2） A³， the density ρ=1.698 g·cm^-3. The melting point and decomposition peak temperature were 197.18 ℃ and 278.37 ℃， respectively. The results of single factor experiment showed that with the increase of reaction time and solvent， the yield of BOD increased at first and then became stable. With the increase of reaction temperature， the yield of BOD increased slowly and then decreased rapidly. With the increase of material ratio， the yield of BOD increased first and then decreased. In addition， the optimal process conditions were obtained by orthogonal experiment： BODM hydrolyzed in potassium carbonate methanol solution at 45 ℃ for 8 h， in which the molar ratio of BODM to potassium carbonate was 15∶1， and the yield was 94%. This study provides theoretical basis and experimental reference for scaling up and large-scale production of BOD.

Abstract:In order to improve the safety performance of hexanitrohexaazaisowurtzitane （CL-20）， the CL-20 with self-assembled stacking structures were prepared by the solvent-nonsolvent method using nitrified graphene （NG） as a crystallization inducer. The morphologies， structures， and thermal properties of the stacking structure CL-20 were characterized by field emission scanning electron microscopy （FE-SEM）， X-ray diffraction （XRD）， fourier transform infrared spectroscopy （FT-IR）， and synchronous thermal analyzer （DSC-TG） respectively， and their mechanical sensitivities were tested and analyzed. The results show that under the induction of different content of NG， CL-20 recrystallizes into square flake crystals， and self-assembles and stacks into petal-shaped， spiral-shaped， tower-shaped， and other structures. During the formation of the self-assembled stacking CL-20， the induction effects of NG are reflected in the adsorption effect of its sheet layer on CL-20 and the formation of hydrogen bonds between NG′s active functional groups with CL-20. Compared with the raw CL-20， the thermal decomposition temperature of the self-assembled stacking CL-20 is reduced by about 5 ℃， the maximum thermal decomposition enthalpy is increased by about 33%， and the mass loss is increased from 81% to 99%. The prepared self-assembled stacking CL-20 has a significantly lower mechanical sensitivity than that of the raw CL-20. When the NG content is 0.5%， the self-assembled petal CL-20 prepared by NG induction has the lowest impact sensitivity of 6 J.

Abstract:Using droplet microfluidics technology， an aqueous solution of the active agent at a concentration of 0.5% was used as the continuous phase， and an ethyl acetate solution of DAAF was employed as the dispersed phase. DAAF/F2602 composite microspheres were prepared by fluid-focused microchanneling. The effects of two-phase flow rate ratio， concentration of dispersed phase， and type of active agent on particle morphology， particle size， and roundness of DAAF/F2602 composite microspheres were investigated. The optimal process conditions， including a suspension concentration of 4%， a two-phase flow rate ratio of 16∶1 and an active agent of CTAB， were obtained and compared with the aqueous suspension method. The results show that the DAAF crystalline shape of the samples obtained from two preparation methods are unchanged， the impact sensitivity is higher than 100 J， and the friction sensitivity is 0% and the friction sensibility are more than 360 N， indicating that the two samples have good safety performance. Among them， the particle sizes of DAAF/F2602 composite microspheres which obtained by the droplet microfluidization method were in the range of 20.22 to 53.85 μm， which were smaller than that obtained by the aqueous suspension method （121-356 μm）.Furthermore， the particle sizes distribution was observed to be more uniform. Thethermal decomposition exhibited a delayed peak temperature by 6.45 ℃， and the activation energy was increased by 6.12 kJ·mol^-1， which lead to improved thermal stability. The cone angle generated by the stacking of DAAF/F2602 composite microspheres which obtained by the droplet microfluidization method， is 34°. This angle is smaller than that of composite particles obtained by the water suspension method （40°）， which indicate better dispersion property.

Abstract:Solubility is an important parameter for the crystallization of molecular perovskite energetic materials （H₆N₂H₁₄）［NH₄（ClO₄）₃］（DAP-4）. In this work， the dissolution behaviors of DAP-4 at different temperatures （288-323 K） and in different solvents （ethanol， ethyl acetate， formic acid， deionized water， acetone， cyclohexane， methanol， acetonitrile， n-propanol） were studied by the gravimetric method. The dissolution models were established by the Apelblat equation and the λh equation， respectively. Meanwhile， the dissolution thermodynamic parameters （ΔH_d， ΔS_d， ΔG_d） were obtained by Van’t Hoff equation based on the thermodynamic principle of solid-liquid equilibrium. Results show that the solubility of DAP-4 is the largest in water and the smallest in ethyl acetate， which are increased with the increasing of temperature in different solvents. The fitting result of dissolution model from the Apleblat equation is better than that of the λh equation. Positive values of ΔH_d， ΔS_d， and ΔG_d indicate that the dissolving process of DAP-4 are non-spontaneous endothermic.

Abstract:In order to characterize the mechanical response of double-base propellant， the viscoelastic properties and constitutive model of double base propellant were studied. Firstly， the viscoelastic properties of double-base propellant were investigated by tensile， compression and stress relaxation experiments with an observation of fracture surface. Then， a hyperelastic-viscoelastic model of double base propellant was established based on the Reduced Polynomial（N=5） model and Prony series. The parameters of the developed model were obtained by the experimental data. Finally， the hyperelastic-viscoelastic model of double base propellant was verified. The relatively error between the results of the simulation calculated by the hyperelastic model and the experiment for uniaxial tensile stress-strain is less than 5.01%. The relatively error between the results of simulation and experiment for stress relaxation is less than 6.49%. The developed hyperelastic-viscoelastic constitutive model of double-base propellant can well describe the mechanical properties of double base propellant， which provides a significant method for the research of mechanical properties of propellant.

Abstract:In response to the serious problems involving large smoke， flame and pungent smell known for a small and medium caliber weapon， the single base seven holes propellants were treated by chemical denitration method to prepare nitro gradiently distributed propellants with different denitration degrees. Their physicochemical， static burning properties， interior ballistic performance and emission hazard phenomenon were investigated. Based on the minimum free energy method， the influence of amount of camphor agent and the denitration degree on the combustion gases （CO， H₂） produced and unoxidized carbon were studied. The results show that with the increase of denitration degree， the explosion heat of propellants decreases from 4001 J·g^-1 to 3517 J·g^-1， the web thickness reduces from 0.92 mm to 0.89 mm， the content of stabilizer declines from 2.60% to 1.95%， the stability remains unchanged， B_m value increases to 0.66， and the progressive burning property enhances gradually； the better progressive burning of propellants， the higher initial velocity of the projectile under the same bore pressure condition was observed， the numerical expression and control method of ballistic performance for this investigated propellant were obtained based on the enantiomorphic coupling relationship established between the mass of charge， bore pressure and initial velocity； in comparison with the camphor-deterred propellants， the nitro gradiently distributed propellants demonstrated the promising characteristics of lower concentration of combustible gas， and less unoxidized carbon； in addition， the small flame， less irritating odour and low emission harmful phenomena are found for nitro gradiently distributed propellants during the firing test.

Abstract:Photoacoustic signals were induced on slices of black powder and its components， which was radiated by 1064 nm laser pulses with 10 ns duration. The laser pulse energies were adjusted by regulating the number of fused silica plates on the laser path as attenuators. An optical fiber-based Michelson interferometer was utilized to detect the generated acoustic signals. Acoustic wave energy was estimated. A primary model was proposed to estimate the reaction rate of black powder. Detected phase changes were similar to each other， but the dimensions varied with laser pulse energy. Thermal reaction of blackpowder was not significant under laser radiation， but other reaction mechanism existed and enhanced the photoacoustic signal. Relationship between laser pulse energy and integration of absolute value of phase change is approximately linear. Reaction rate of black powder is positively related to laser energy， except for high-energy pulse. The maximum of reaction rate was about 20 mmol·s^-1， which was achieved when laser energy is around 10 mJ.

Abstract:In order to rapidly analyze the product quality of 2，6-diamino-3，5-dinitropyrazine-1-oxide （ANPZO） and optimize the synthesis process， high-performance liquid chromatography （HPLC） method was developed to quantitatively analyze the purity of ANPZO. The effects of mobile phase composition， elution mode and detector wavelength on the resolution have been studied. The separation of ANPZO and its intermediate 2，6-diamino-3，5-dinitropyrazine （ANPZ） was accomplished by using C18 analytical column with size of 250×4.6 mm and 5 µm. The initial mobile phase composition was 0.1% trifluoroacetic acid and methanol （95∶5， v/v）. The methanol ratio was increased to 100% from 2 min to 7 min after the sample injection. Gradient elution was performed at a flow rate of 1.0 mL·min^-1， the column oven temperature was set at 30 ℃， and detection wavelength was 425 nm. The validation of the developed methods showed good linearity （R²=0.9996）， repeatability （%Area RSD%=0.30%） over the concentration range of 0.1 mg·mL^-1 to 0.6 mg·mL^-1. The limit of detection（signal/noise=3） and quantitation（signal/noise=10） of ANPZO were found to be 20 ng·g^-1 and 67 ng·g^-1， respectively. Therefore， the reported method is accurate， precise and sensitive， which can be used for the quality control of ANPZO.

Abstract:Fused-ring energetic compounds， composed of two or more rings sharing two atoms and one chemical bond， have sizeable π-π conjugate structures and are a kind of popular new energetic materials. The polycyclic coplanar structure of energetic fused rings shows good molecular stability. Furthermore， the coplanar structure is featured with high heat of formation， significant ring tension， and high energetic performance. It can achieve a balance between high performance and molecular stability. With a C—N bond as the common building block， these nitrogen heterocycles have good density， stability， and numerous modifiable sites， which have become a new class of backbones in the field of energetic fused heterocycles. In this paper， the authors review the recent advance of synthesis， detonation properties， stability， and outlook of C—N type fused-ring energetic materials， which will be useful for the energetic community in future studies.

Abstract:Energetic materials are of great strategic value in both national defense and civil application. The thermal decomposition characteristics are one of the most important characteristics directly related to the effective application of energetic materials. It is of great significance to clarify the thermal decomposition behavior and mechanism of energetic materials for further improving the thermal decomposition efficiency and inhibiting their unstable decomposition. Three typical energetic materials， cyclotetramethylene tetranitramine （HMX）， hexanitrohexaazaisowurtzitane （CL-20） and 3，4-dinitrofurazanofuroxan （DNTF）， were studied. The basic physical and chemical properties related to the thermal decomposition characteristics were present， and the thermal decomposition behavior and mechanism were summarized， with emphasis on the structural characteristics of materials and the types of additives that influence the thermal decomposition. It is found that the removal of nitro group is the key step in the thermal decomposition， and the metallic materials rich in active sites and organic complexes with abundant active groups tend to interact with nitro groups to accelerate the thermal decomposition process. Inorganic non-metallic materials can also contribute to the decomposition behavior due to the large specific surface area and excellent gas diffusion ability. Three methods， including eutectic， coating and adding desensitizing agent， are widely used to improve the thermal stability of these three energetic materials. Based on the research of the thermal decomposition mechanism， the design and development of thermal decomposition accelerators and inhibitors can be carried out， which will effectively promote the innovative development of thermal application of energetic materials and become the focus of future research on the thermal decomposition characteristics of energetic materials.