Abstract:In order to explore new energetic material with both good thermal stability and high safety performance， 4，8-di（2，4，6-trinitro-3，5-diaminophenyl）difurazanopyrazine （NADFP） was synthesized by substitution reaction using 1-chloro-2，4，6-trinitro-3，5-diaminobenzene and 4H，8H-difurazanopyrazine as raw materials. Its structure was characterized by nuclear magnetic resonance （¹H and ¹³C spectrum）， infrared spectroscopy and element analysis. The single crystal of NADFP·DMF was obtained by solvent evaporation method， and the crystal structure was determined by single crystal X-ray diffraction. Results show that NADFP·DMF belongs to monoclinic system， space group P2₁/c， a=7.854（3） Å， b=18.466（6） Å， c=11.093（3） Å， ρ=1.640 g·cm^-3. The inter-/intramolecular interactions were calculated by Hirshfeld surfaces analysis with hydrogen bond interactions accounting for 53.5%. The thermal behavior of NADFP was studied by DSC and TG/DTG methods， which show that its decomposition peaks are 337.2 ℃ and 368.8 ℃. The theoretical detonation performances and mechanical sensitivities of NADFP were investigated. The measured density is 1.81 g·cm^-3， the solid formation enthalpy is 827.1 kJ·mol^-1， the calculated detonation velocity and pressure are 7968 m·s^-1 and 36.0 GPa， respectively. The impact sensitivity is above 40 J， and the friction sensitivity is above 360 N. The overall performance of NADFP is obviously better than that of traditional heat-resistant explosive 2，2′，4，4′，6，6′-hexanitrostilbene.

Abstract:In order to easily synthesize sodium pentazolate， the synthesis method and conditions of sodium pentazolate were studied. Diazoniums 4a-b and sodium pentazolate were characterized by infrared （IR）， nuclear magnetic resonance （NMR）， mass spectrometry （ESI-MS）， or ion chromatography （IC）. Results show that sodium pentazolate can be easily synthesized via the cyclization/C—N cleavage one-pot method； the appropriate reaction conditions for the synthesis of sodium pentazolates from diazonium chloride 4a are as follows： the molar ratio of NaHCO₃ to 2，6-dimethyl-4-aminophenol is 0.6， the cyclization temperature is -45 ℃， the cyclization time is 2 h， the C—N cleavage temperature is -35 ℃， the C—N cleavage reaction time is 24 h， and the molar ratio of m-CPBA to 2，6-dimethyl-4-aminophenol is 3∶1； the suitable reaction conditions for synthesizing sodium pentazolate from diazonium tetrafluoroborate 4b are as follows： the molar ratio of NaHCO₃ to diazonium tetrafluoroborate is 0.3， the cyclization temperature is -45 ℃， the cyclization time is 7 h， the C—N cleavage temperature is -35 ℃， the C—N cleavage reaction time is 24 h， and the molar ratio of m-CPBA to diazonium tetrafluoroborate is 4∶1； sodium pentazolate can be easily isolated by ethanol extraction， of which the purity is up to 98.87 % （area normalization）.

Abstract:In order to obtain spherical granulations with regular shape， good dispersibility and uniform particle size， the effects of different binders on 2，2"，4，4"，6，6"-hexanitrodiphenylethylene （HNS） composite microspheres were studied by using droplet microfluidic technology. Fluoroelastomer （F₂₆₀₄）， nitrocellulose （NC） and glycidyl azide polymer （GAP） were selected to prepare spherical granulation of submicron HNS， and submicron-level HNS/F₂₆₀₄ （95/5）， HNS/NC （95/5） and HNS/GAP （95/5） composite microspheres were successfully prepared. Resultant microspheres were characterized by scanning electron microscope， X-ray diffractometer， specific surface area， thermal analyzer， true density tester and mechanical sensitivity tester. Results indicated that such methods could obtain the HNS composite microspheres with high sphericity， monodisperse， narrow size distribution， good roundness and improved safety performances. The average circularities were 0.934， 0.915 and 0.925 with D₅₀ of 45.39， 58.68 μm and 45.43 μm （the span was less than 0.55）， respectively. Thermal decomposition peak temperatures were 354.44， 349.53 ℃ and 339.37 ℃ for HNS/F₂₆₀₄， HNS/NC and HNS/GAP， respectively. The spheroidization process increases the true density of the microspheres to 1.9408， 1.9383 g·cm^-3 and 1.9204 g·cm^-3， respectively， which can effectively improve the HNS charge performance. The cone angles of 27°， 24.3°， and 24° indicated that microspheres have good dispersion performances. Compared with submicron HNS， the impact sensitivity of the three microspheres was increased by 5.5， 4， 3.5 J， and the friction sensitivity was increased by 52， 36 N and 4 N， respectively， indicating a better safety performance.

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 （E_K）， 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^-1，V_D=7598.37 m·s^-1） is between TNBA and TNAZ. The main detonation products are N₂、C（d）、CO、CO₂ and H₂O.

Abstract:The polymorphic transformation （PT） and control technology of hexanitrohexaazaisowurtzitane （CL‍-20） has been a hot area of research in energetic materials， which is also the key issue must be addressed to promote its application. In order to further understand the PT characteristics and mechanism of ε‍-CL‍-20 with different crystallization characteristics， the PT laws and isothermal PT kinetics of ε‍-CL‍-20 were studied based on in‍-situ X‍-ray powder diffraction （XRD） technology. The effect of surface and internal defects on the ε→γ PT behavior of CL‍-20 was discussed. The isothermal PT kinetics of ε‍-CL‍-20 with different crystallization characteristics was analyzed and the related parameters were calculated. The results show that temperature is the dominant factor affecting the solid‍-solid PT of ε‍-CL‍-20. For the conventional particle ε‍-CL‍-20， with the increase of internal and surface defects in the crystal， the initial temperature of PT decreases and the PT rate increases. Compared with 100 μm CL‍-20， ultrafine （0.5-1 μm） ε‍-CL‍-20 has higher starting temperature of PT， but its PT rate is also faster. The abnormal PT behavior of ultrafine ε‍-CL‍-20 is explained from the two‍-sidedness of crystal defects. When CL‍-20 undergoes ε→γ PT under thermal stimulation， both the surface and internal defects of the crystal have an induction effect on the PT process， and the γ crystal preferentially nucleates at the defects such as vacancies， impurities or dislocations with low nucleation barrier on the ε‍-CL‍-20 crystal， and then gradually grows up at these positions.

Abstract:The research on low-sensitivity gun propellants has a vital impact on the survivability and safety performance of weapon system. Gun propellant （IM） with nitrocellulose （NC） and glycidyl azide polymer （GAP） as binder was prepared. N-butyl-N- nitramine （Bu-NENA） was used as low sensitive energetic plasticizer， hexogen （RDX） was used as high-energy filler and graphite as additive of thermal conductive. The physicochemical， combustion， mechanical， and sensitivity properties of the IM gun propellant were studied， and the insensitivity properties were further studied by slow cook-off， fast cook-off， bullet impact， fragment impact and sympathetic detonation tests. Results showed that the gun propellant had stable combustion performance， and the impetus was1050 kJ·kg^-1. Theoretical explosion temperature was 2677 K. The impact strength and the compressive strength were 8.2 kJ·m^-2 and 131.5 MPa at -40 ℃， respectively. The sensitivity of the gun propellant （H₅₀=62.62 cm，P=28%，V₅₀=1.95 kV） was greatly reduced compared with TEGN gun propellants（H₅₀=16.33 cm，P=100%，V₅₀=2.02 kV）. Moreover， only combustion reactions were observed in slow cook-off， fast cook-off， bullet impact， fragment impact and sympathetic detonation tests. It demonstrated that the prepared gun propellants possessed good low vulnerability characteristics.

Abstract:The polymer bonded explosive （PBX） model containing different coating structures is established based on the peridynamics theory and Voronoi method. The dynamic damage behaviors of PBX under different impact speeds are simulated. The simulation results indicate that double-layer coating structure can better protect HMX crystal compared to single-layer coating structure. For single-layer coating structure， the damage mode is mainly transgranular fracture. By contrast， the damage is dominated by intergranular fracture in the case of double-layer coating structure. Moreover， for double-layer coating structure， the quantitative results on damage ratio of HMX is obtained and the performance of different coating structures is ordered. By analyzing the stress state of HMX， it is found that the coating structure can greatly impact the stress distribution. This study can help better design the coating structures in PBX.

Abstract:The mixture and composite of dihydroxylammonium-5，5"-bistetrazole-1，1"-diolate （HATO） and ammonium perchlorate （AP） were prepared by dry-mixing and solvent-nonsolvent recrystallization， respectively. The microstructure and mechanical sensitivity of HATO， AP， HATO+AP mixture and HATO-AP composite were analyzed by scanning electron microscope （SEM） and military standard methods， and the ignition and combustion pressure characteristics of four materials mentioned above were also compared experimentally. In addition， the reaction characteristics of HATO-AP composite was discussed based on the thermogravimetry-mass spectrometry （TG-MS） results. Results show that HATO and AP may be cocrystal， crystal mixed or coated with each other in HATO-AP composite， which makes the mechanical sensitivity of HATO-AP composite significantly lower than that of HATO+AP mixture. The peak of combustion pressure and pressurization rate of HATO are much higher than that of AP. The HATO-AP composite can eliminate the adverse effects of AP in combustion property， and increase the peak of combustion pressure by 17.3% compared with raw. Because of the intimate contact between HATO and AP on a smaller microscopic scale in the composite， this allows these two molecules to react directly. The N element may directly react to form NH₃， HCN， NO or other NO_x instead of N₂ in the reaction process. The changes in reaction mechanism may make a difference on combustion pressure characteristics of HATO-AP composite.

Abstract:Furoxan is a nitrogen-rich aromatic ring with a potential "nitro" fragment. The compactness of the skeleton and outstanding enthalpy of formation make it an important molecular skeleton for the research of energetic materials. The unique arrangement of nitrogen and oxygen atoms significantly increases the tendency of furoxan to tautomerism， and the presence of tautomers reduces the stability of the furoxan skeleton and increases the difficulty of its synthesis. This account reviews the research on the synthetic methodologies of furoxan based on different strategies. Focusing on the synthetic mechanism of furoxan framework itself， the advantages and disadvantages of different synthetic methodologies are analyzed and compared. Moreover， the progress of energetic materials based on the strategy developed for the synthesis of furoxan is also summarized. Considering the high density， high oxygen balance and high enthalpy of formation of furoxan ring， energetic structures based on the furoxans will still be a key direction of research and development of high energy density materials.

Abstract:Glycidyl azide polymer （GAP） has been considered as excellent energetic binder or plasticizer in high energetic solid propellants because of its high heat of combustion， low burning temperature， good thermal stability， clear exhaust and good compatibility with oxidizers. However， the presence of bulky， polar azide side group and reduced backbone flexibility， causing poor mechanical properties， especially the inferior low-temperature mechanical properties. Owing to chemical modification could better regulate the performance of GAP， it has attracted extensive attention. This paper illustrates the synthetic methods and processes of GAP， such as direct and indirect methods； summarizes various chemical modification methods of GAP and clarifies the relationship between the structures and properties of the GAP-based copolymers. At last， the future development of controllable， facile and green synthesis strategies for high molecular weight GAP， performance research methods and application prospects in high energy thermoplastic elastomers are described and discussed.

Abstract:As a kind of clean energy， microwave is widely used in energetic materials due to its unique penetrability and high safety， which can interact with energetic materials in volume. The application of microwave in the testing of energetic materials， microwave assisted synthesis of energetic materials， excitation of energetic materials and enhancement of propellant combustion were summarized. The mechanism of microwave-assisted synthesis of energetic materials is not clear， the absorption materials introduced in microwave sensitized explosives is relatively single， and the microwave enhanced combustion is only suitable for some propellants were pointed out. The future development directions were put forward： expanding the types of absorbing materials， activating non-metallic energetic materials by microwave ignition of nano-thermites， and realizing the dexterity and convenience of microwave devices.