Abstract:Triaminoguanidinium nitrate （TAGN） was obtained via amination of guanidinium nitrate， and its structure and properties were characterized by elemental analysis， fourier transform infrared spectroscopy （FT-IR）， differential scanning calorimetry （DSC） and scanning electron microscope （SEM）. Short block-like TAGN crystal particles were prepared by ultrasound assissted cooling crystallization in water. The influencing factors of crystal modifier， ultrasonic and cooling process for controlling crystal morphology and particle size， were analyzed by SEM and particle size analysis， and results revealed that ultrasound assissted process can lead to uniform crystalline morphology with narrow particle size distribution. The crystal morphology modifier and temperature control program have a significant effect on the particle size， particle size distribution and crystalline morphology of TAGN. Under the action of ultrasonic （750 W， 20 KHz）， two kinds of high-quality TAGN crystals with uniform crystalline morphology， smooth surface without sharp edge angle， high density and narrow particle size distribution were prepared by using suitable cooling process and PVP K30 （0.03%） as the crystal morphology modifier. Compared with present manufactured raw materials，the comprehensive performance of TAGN have been improved， the characteristic explosion percentage of two kinds of TAGN decreases from 20% to 8% and 4% apart， the characteristic drop height increases 5.9 cm and 3.4 cm apart， the density increases from 1.571 g·cm^-3 to 1.586 g·cm^-3 and 1.589 g·cm^-3 apart， the onset melt point increases from 224.8 ℃ to 227.7 ℃ and 228.2 ℃， respectively. Charging with the prepared product will significantly improve the charging process performance and solid content， so as to improve weapon performance.

Abstract:A rapid and accurate high performance liquid chromatographic method was developed for the simultaneous determination of TATB and HMX in explosive formulations. Dimethyl sulfoxide （DMSO） was used as the solvent and ultrasonic assisted to dissolve the sample. The influences of sample weight， dissolve time， mobile phase type， chromatographic column type and detection wavelength on results were investigated. The results show that HMX and TATB were confirmed to separate within 6.5 min by using C18 chromatographic column with mobile phase of acetonitrile and water at 45/55（V/V）. And the HMX and TATB could be extracted completely at the condition of ultrasonic for 1.0 h and standing at room temperature for more than 4.0 h after they were dissolved in 250 mL DMSO. The relative standard deviation of reproducibility （n=8） was 0.55% and 0.99%， respectively. Linear relationships between values of peak area and mass concentration of TATB and HMX were good in the ranges of 0.032-0.056 mg·mL^-1（R²=1.0000） and 0.011-0.016 mg·mL^-1（R²=0.9999）.

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:Due to the superior thermal stability， good modification and appropriate ring tension of imidazole based energetic compounds， they were considered as an important research direction of high energy materials. This review summaries recent progresses of synthesis， property and application of energetic imidazole-bridged azoles， such as bisimidazoles， triazolyl imidazoles and tetrazolyl imidazoles and their energetic salt derivatives. It was found that single or double bond linked bisimidazoles had better thermal stabilities and mechanical sensitivities， higher densities and donation properties than their mono-cyclic imidazole analogs， and could realize the balance between energy and safety which is difficult to be realized by introducing nitrogen-rich energetic groups， connecting groups and formation of energetic salts into mono imidazolyl rings. On the other hand， bicyclic azoles with two different nitrogen heterocyclic structures linked by C─C bond or C─N bond usually has the advantages of combing the good properties of their related structure characteristics， making it an important direction for development of novel high nitrogen and high energy compounds in the future. This review summarizes the recent advances in energetic imidazole-bridged azoles and proposes an efficient construction strategy for designing high nitrogen content， high energy and good safety based on triazolyl imidazole and tetrazolyl imidazole building blocks.

Abstract:As the most widely used military composite explosive， the performance of melt-cast explosives is closely related to the choice of carrier explosive. The current research advances of melt-cast explosives were reviewed. The physicochemical properties and detonation performances of 13 representative melt-cast carrier explosives （such as 2，4，6-trinitrotoluene （TNT）， 2，4-dinitroanisole （DNAN）， etc） were discussed. The molecular structures， synthesis methods， physicochemical properties and detonation performances of 16 newly synthesized melt-cast explosives were introduced （such as bis（1，2，4-oxadiazole）bis（methylene） dinitrate （BOM）， etc）. Their advantages and shortcomings as melt-cast explosives were analyzed. The effects of different functional groups and molecular structures on the properties of the compounds were discussed. The future development direction of melt-cast carrier explosive is to understand the effects of molecular structure on performance of explosives， and to design and synthesize a series of new compounds with excellent comprehensive performance， in order to meet the application requirements of melt-cast explosives.

Abstract:In order to study the effect of the crystal microscopic properties of elemental explosives on their macro-mechanical behavior and impact sensitivity of composite explosives， the micro-plastic characterization methods of TNT， RDX and HMX were studied. And the correlation analysis between the micro-plasticity of the explosive crystals and their impact sensitivities of the elemental explosive was carried out. Nano-indentation technology was used to test and calculate the micro-elasticity and micro-plasticity of TNT， RDX and HMX explosive crystals， and a calculation method based on the ratio of plastic energy and indentation energy （η_P） was proposed to quantify the micro-plastic properties of explosive crystals. The results showed that， compared with the micro-plasticity （δ_h） calculated by the indentation depth， the linear correlation coefficient between the micro-plastic properties （η_P） of the explosives crystals obtained in this research and impact sensitivities （P） of explosives in simple powders reached 95.8%， or micro-plastic properties of simple explosives were highly related to their impact sensitivities on the micro-characterization method of plastic properties of explosives crystals proposed in this paper. This research provided a micro- characterizing method for evaluating safety levels of explosives.

Abstract:In order to obtain the thermal cycling properties of octogen（HMX） and triaminotrinitrobenzene（TATB） based polymer bonded explosive （PBX） ， the thermal cycling tests of HMX- and TATB-based PBX were carried out under the condition of -40—75 ℃. P-wave and S-wave velocity of explosive specimens with 3N （N=0，1，2，…，9） cycles were measured by ultrasonic echo method. The dynamic elastic modulus （Young"s modulus， shear modulus） and dynamic Poisson"s ratio were calculated by ultrasonic measurement method. The static elastic modulus was measured directly through the tensile property test， while the ratio of dynamic and static elastic modulus was calculated. Results show that the density of HMX-based PBX decreases and later the decrease rate slows down with the increase of the cycle number during the thermal cycling test. The density of TATB-based PBX decreases first， then the decrease rate slows down， and finally has a slight upward trend. The change trend of P-wave velocity， S-wave velocity and dynamic elastic modulus of HMX- and TATB-based PBX are consistent with the change trend of their density respectively. Their corresponding dynamic Poisson"s ratio is basically unchanged. There is a positive linear relationship between P-wave ， S-wave velocity and its density. The static elastic modulus first decreases and then increases， the dynamic and static elastic modulus first increases and then decreases， where the inflexion point of HMX-based PBX is in its 15st thermal cycle， and that of TATB-based PBX is in its 21st thermal cycle. The results show that the damage quantity of PBX during thermal cycling is closely related to its density change and internal micro damage. All these phenomenon demonstrate that the ultrasonic longitudinal and shear wave velocities can be used to quantitatively evaluate the thermal fatigue damage of PBX in thermal cycling test. The change trend of the dynamic and static elastic modulus of PBX is related to its micro structure evolution including internal micro-cracks and binder flow in micro-pores.

Abstract:The output pressure is one of the most important feature of detonators. Using photonic doppler velocimetry （PDV） and impedance matching technique， a reliable measurement method for output pressure was carried out. The interface particle velocities between slapper detonators and optic windows were measured by PDV for three kind of detonators. The calculation results show the output pressures are 7.64， 7.29， 6.71 GPa， respectively. The PBX-RDX content has certain influence on the output pressure. As the PBX-RDX content decreases， the output pressure decreases. The output pressure of the three detonators were simulated by Ansys/Ls-Dyna. The simulated output pressures are 7.7， 7.1， 6.4 GPa， respectively. Comparing to the simulation， the pressure difference is less than 6.5%， which validates the method effective. The shell material has significant influence to detonator output pressure. For higher shock impedance， the output pressure is lower. Especially， the peak pressure for steel shell case is undistinguishable.

Abstract:To explore the effect of polytetrafluoroethylene（PTFE） content and sintering temperature on the morphology and combustion performances of aluminum powder （Al）/PTFE composites， the ball mill-sintering process was used to prepare Al/PTFE samples. These samples have been characterized by scanning electron microscopy（SEM） and X-ray diffractometer （XRD）， and the effect of PTFE content and sintering temperature on the microscopic morphology of the composites has been studied. The combustion processes have been analyzed using a confined combustion chamber， coupled with a high-speed camera and infrared thermal imager. The effects of PTFE content and sintering temperature on the combustion performances of the composites have been explored. The results show that sintering at 340 ℃ can make the composites form a regular core-shell structure. When the PTFE content is less than 35%， the integrity of the particle coating optimizes with the increasing of the PTFE content. However， when the PTFE content continues to increase， the shape of the composite particles becomes irregular， and the condensed products begin to agglomerate. With the increase of PTFE content and sintering temperature， the burning rate， radiation intensity， and the flame temperature of the samples all show a trend of first increase and then decrease. Compare the samples prepared under the optimal conditions （35% PTFE content， sintering temperature 340 ℃） with the ones prepared under other conditions， the combustion pressure can be increased by 16%， whereas the combustion time is shortened by up to 37%， so that the central flame temperature increases by 317.1 ℃. This indicates that the appropriate amount （35% optimal） of PTFE content and proper sintering temperature （340 ℃ optimal） will significantly improve the combustion performances of the composite particles.

Abstract:To improve the catalytic effect of nano metal oxides on the thermal decomposition of AP， butterfly wing-shaped titanium dioxide （BW-TiO₂） has been prepared by impregnation-calcination method based on the template of a natural Morpho Butterfly wing. Field emission scanning electron microscope（FESEM）， transmission electron microscope（TEM）， X-ray diffraction （XRD）， and X-ray photoelectron spectroscopy （XPS） were used to characterize its morphology， structure， and composition. The catalytic performance of BW-TiO₂ for the thermal decomposition of ammonium perchlorate（AP） was studied using the differential scanning calorimetry（DSC）. The results show that the as-prepared BW-TiO₂ owns a anatase phase with a size of 8~12 nm， accompanying with small amount of amorphous carbon and Ti. BW-TiO₂ tightly resembles into a parallel grid skeleton structure， containing well-connected nano tubular channels and a large number of micro-pores. BW-TiO₂ illustractes excellent catalytic activity for AP thermal decomposition. Adding 5% BW-TiO₂ can reduce the high-temperature decomposition peak temperature from 429.1 to 374.1 ℃， increase the exothermic heat from 255 to 1323 J∙g^-1， and decrease the active energy from 190 to 130.9 kJ∙mol^-1.

Abstract:1，3，5-triamino-2，4，6-trinitrobenzene （TATB） has good detonation energy and excellent safety performance， which is the only single explosive meeting the insensitive high energy explosive （IHE） standard. However， TATB has strong intramolecular and intermolecular hydrogen bonding， which makes it difficult to dissolve in common solvents. While improving the solubility of TATB is not only an important prerequisite for product refining， quality control and shape control， but also an important way to reduce the production cost and environmental pollution. Therefore， improving the solubility of TATB is an important basis for engineering application. The research progress of dissolution characteristics of TATB in different solvents are reviewed， including common solvents （e.g. dimethyl sulfoxide）， strong acids and bases （e.g. concentrated sulfuric acid， sodium hydroxide solution）， and ionic liquids （e.g. 1-ethyl-3-methylimidazolium acetate）， et al. The existing advantages and disadvantages of the current solvent systems in dissolving TATB are analyzed. The dissolving solvents and methods of the future are also anticipated， for instance， developing new combination solvents to improve solubility， and studying the dissolution mechanism by using computational chemistry method.

Abstract:To investigate the effect of micro-defects on the shock response， chemical decomposition， and damage evolution of pentazolate salts， ab initio molecular dynamics method is employed to simulate the dynamics evolution and initial chemical reaction mechanisms for perfect Mn（N₅）₂ crystal and the crystal with 3% vacancy defects under different shock velocities （8， 9， 10， 11 km·s^-1 and 12 km·s^-1）. The calculated Hugoniot curves indicate that the vacancy-containing system exhibits a slightly higher compression ratio under high-pressure conditions than the perfect system. The molecular dynamics results indicate that when shock velocity v_shock<10 km·s^-1， perfect and vacancy-containing system only show a slight （<10%） volume compression and neither of them exhibit chemical reactions within 5000 fs. When v_shock=10 km·s^-1， N─N starts to uniformly rupture within the space of perfect crystal at 512.8 fs， whereas the reaction of vacancy-containing system is advanced to 281.6 fs and the N─N is ruptured near the vacancy. When v_shock continually increases to 11 and 12 km·s^-1， the starting time of reaction for two systems is further advanced and the reaction process is further speeded up. The positive effects of the vacancy on shock sensitivity and chemical reaction process are weakened with the increase of v_shock. The simulated results at the atomistic scale reveal that vacancy defect is one of the early nucleation structures of hot spots. The stress near the vacancy promotes the cascade decomposition of the surrounding pentazolate anion， thereby causing the growth and propagation of damage and ignition of energetic materials.

Abstract:The dynamic behavior of Al/Ni energetic structural materials under shock compression loading was investigated by mesoscale simulation. The influence of material composition and manufacturing technique on microstructures were analyzed against the scanning electron micrographs （SEMs） of three typical Al/Ni materials. Two types of mesoscale models were established based on the SEMs and the uniform particle morphologies of Al/Ni material， respectively. The shock responses of Al/Ni material， including particle deformation， pressure， temperature， and propagation of shock waves， were analyzed. The results show that， as for Al/Ni powder composites， Ni particles are the main components of the matrix， and the embedded Al particles gradually reunite with its volume fraction increasing. In contrast， Al layers are the main components of the matrix of Al/Ni multi-layered composites， and Ni particles parallelly distributed in the material. The mesoscale model with the uniform particles could not be used to predict the formations of local high pressure and hot spots， since that such processes are related to the heterogeneous microstructure of Al/Ni materials.

Abstract:When polymer-bonded explosives （PBX） charges are rapidly extruded in a crack in the warhead′s case， it′s required to accurately predict unexpected ignition of cased PBX for safety reasons. Using the combined microcrack and microvoid model （CMM）， damage-ignition responses of crack-extruded PBX are investigated in three aspects： （i） interactions between crack and extruded PBX； （ii） mechanical-thermal-chemical responses of PBX at the macroscale； and （iii） underlying mechanisms of damage-ignition at the mesoscale. Meanwhile， the difference between two typical PBXs （pressed PBX-5 and casted GOFL-5） in response to crack-extruded loading is compared. The results show that， under 200 m·s^-1 extruded velocity， pressed PBX-5 exhibits brittle failure （extruded 3 mm at 60 μs） and shows a stress concentration near the crack； microcrack shows a rapid growth along the 45° angle with the extruded surface. In contrast， under the same extruded condition， casted GOFL-5 exhibits a rapid flow rate near the crack； large quantities of material are extruded （extruded 9 mm at 60 μs）. Both pressed and casted PBXs show an ignition near the crack. Shear-crack hotspot is the dominated ignition mechanism for PBX-5， while locally plastic dissipation is a possible dominated ignition mechanism for GOFL-5.

Abstract:In order to study the propagation characteristics of the flame generated by ignition charge combustion in the propellant pellet packed bed under the ignition transmission structure of the central fire tube， a porous media model was used to simulate the gun propellant pellet packed bed in the propellant chamber， the flow and propagation process of high temperature and high speed gas generated by the combustion of ignition charge in the gun propellant pellet bed is simulated by using the N-S equation， the isothermal surface propagation of the temperature field is equivalent to the flame front propagation， and the simulation results were compared with those of experimental data. The results show that in the case of a dense charge bed of propellant， the isothermal surface is equivalent to the flame front in the process of ignition flame propagation， and the simulation value of flame propagation velocity is 91 m·s^-1， which is close to 96 m·s^-1 obtained by experiment；the simulated cloud images of temperature field of high temperature flame gas propagation are consistent with those of the experimental flame propagation images； the pressure data at the three pressure measuring holes in the chamber calculated by the porous media model are in good agreement with those of experimental data.

Abstract:The growth kinetics of PNP degradation by Rhodobacter sphaeroides H strain was analyzed by fitting the Haldane kinetic equation. The effects of nutrition factors (carbon source, metal ions and NaCl concentration) on the degradation of PNP by H strain and the substrate broad spectrum of phenol by H strain were investigated, and the metabolic mechanism of degradation of PNP by H strain was speculated. Results show that the growth kinetics of H strain degrading PNP conforms to Haldane model (R²=0.9990). The most suitable carbon source and metal ions for degrading PNP by strain H are malic acid and Ca²⁺, respectively, and the tolerance value of NaCl concentration is 20 mg·L^-1. Influence of the catechol on PNP degradation is the greatest among phenols. High performance liquid chromatography-mass spectrometry (HPLC-MC) was used to analyze the metabolites of PNP produced by the strain. It is found that the intermediate products are mainly hydroquinone (HQ), 4-hydroxymuconic acid semialdehyde (4-HS) and maleamic acid (MA). Meanwhile, enzyme activity analysis shows that the substrate HQ produces 4-HS under the action of hydroquinone 1,2-dioxygenase in crude enzyme solution, thus suggesting that strain H may utilize the metabolic pathway of hydroquinone.

Abstract:A method based on hydrophilic interaction chromatography (HILIC) coupled with mass spectrometry (MS) was developed for determination of hydroxyethyl hydrazine nitrate (HEHN). The effects of the composition of mobile phase and parameters for MS detection were investigated on the optimization of chromatography separation, time required for analysis, and detection sensitivity. Good linearity is obtained under the concentration range of 0.01-0.1 μg·mL^-1 with R²=0.9991, and the limit of detection of 1.2 ng·mL^-1. Recovery of two HEHN samples with concentration of 0.0250 and 0.0900 μg·mL^-1 is determined as 98.1% and 97.7%, respectively, while relative standard deviation (RSD) is no more than 1.6%, indicating good precision of the method. A real sample of liquid propellant is determined by this method, and the content of HEHN measured as 12.5%±0.3% is in accordance with the prepared concentration of 12.9%.

Abstract:A composite fiber nitrocellulose/glycidyl azide polymer/nanometer 1,3,5-triamino-2,4,6-trinitrobenzene(NC/GAP/nano-TATB) with three-dimensional structure was prepared by electrospinning method. Differential scanning calorimeter(DSC) and online thermal-infrared spectrometry(TG-IR) measurement were conducted to probe the low temperature thermochemical properties of the composite fiber. Result indicates that there is only one exothermic peak existing in its DSC curve, which means that NC, GAP, and nano-TATB decomposed simultaneously rather than decomposed individually. The activation energy (E_a) of NC/GAP/nano-TATB (208.1 kJ·mol^-1) is lower than nano-TATB (228.9 kJ·mol^-1), and the rate constant (k) of NC/GAP/nano-TATB (1.70 s^-1) is higher than nano-TATB (0.92 s^-1). The composite fiber is easier to be activated and will decompose faster than nano-TATB. The main products for thermal decomposition of NC/GAP/nano-TATB include CO₂, N₂O, NO, CO, NO₂ and H₂O, meanwhile, fragments like ─CH─, ─CH₂O, and C─O─C were also detected. Moreover, the energetic performance and sensitivity of the composite fiber have been detailedly evaluated and compared with that of NC/GAP and nano-TATB. Combustion temperature (T_c) of NC/GAP/nano-TATB is up to 1583 ℃ and the addition of nano-TATB is favorable to the reduction of impact sensitivity.

Abstract:Cyclotrimethylenetrinitramine (RDX), Cyclotetramethylenetetranitramine (HMX) and Hexanitrohexaazaisowurtzitane (CL-20) own abundant phase transition behavior and characteristics under high pressure/high-temperature and high-pressure. The phase transition routes of three high explosives under different conditions, part of the phase structures under high pressure and p-T phase diagrams were summarized. These researches have provided effective references for the study of detonation behavior and theoretical analysis of energetic materials. Based on current works, there still exist some problems in this area. For example, some divergences still exist about the study of the complex phase transitions, most of the new structures under high pressure are not confirmed and the p-T diagrams are incomplete. In addition, the profound theoretical mechanism of the phase transition has not been sufficiently revealed. Therefore, it will serve as a main tendency to explore the mechanism of transformation between different crystal phases and obtain more information of phase structures in the future research.

Abstract:Explosive crystal characteristics essentially influence physic-chemical properties, functions and applications, including safety, thermal stability and compatibility with other chemical substances, mechanical properties, initiation and detonation performances. Based on the properties and shortages of current high energy explosives, regulation and control of the explosive crystal characteristics to improve the performances of explosives and expand their applications has achieved increasing research attention and become a significant branch of energetic materials. This review summarized the current development of the control principle and process methods of explosive crystal characteristics including polymorph, crystal quality, particle shape and aggregated structure, and focused on the analysis and discussion of crystal characteristics, property and performance, and application and prospects of high quality reduced sensitivity explosive, explosive spherulite and explosive with hierarchical micro-nanostructure. Additionally, considering the current major problems, several developing suggestions based on explosive crystal engineering are proposed. All these investigations may guide the production, process and application of explosive.

Abstract:In order to study the effect of formic acid/water mixed solvent on the growth morphology of energetic ionic salt dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50), interaction energy between TKX-50 faces and formic acid/water mixed solvent was calculated using molecular dynamics method. The growth morphology of TKX-50 in formic acid/water mixed solvent with different volume ratios (1/4, 1/3, 1/2, 1/1 and 2/1) was predicted by modified attachment energy model, and the effect of temperature on the crystal morphology of TKX-50 was simulated. The results show that changing the volume ratio of formic acid/water in the mixed solvent can significantly change the crystal morphology of TKX-50. When the volume ratio of formic acid/water is 1/2 and the temperature is 298 K, the crystal morphology of TKX-50 is relatively closer to spherical shape. Radial distribution function analysis shows that hydrogen bonds, van der Waals forces and electrostatic forces exist between the (1 1 0) crystal face of TKX-50 and the mixed solvent molecules.

Abstract:In order to study the formation mechanism of 2,4,6-trinitrotoluene (TNT)/ 1-nitronaphthalene (NNAP) cocrystal, powder XRD, FTIR and DSC were used to study the TNT / NNAP samples after grinding at 0 s, 10 s, 20 s, 30 s, 40 s, 50 s and 2 mins. The XRD patterns showed that the new diffraction peak, corresponded to (2 -1 1) plane of TNT/NNAP cocrystal, appeared at 2θ=25.8° and gradually increased its intensity. FTIR spectrum illuminated that the C—N—O bending vibration peak (716 cm^-1) of TNT had a blue-shift and became sharp. At the same time, due to π-π stacking, the C—C bending vibration peak (734 cm^-1) of TNT benzene ring exhibited a red-shift. The DSC curves indicated there were three endotherm peaks during the formation of cocrystal. These results showed that cocrystal packed at (2 -1 1)) plane firstly. H-bond and π-π stacking played important roles in the formation of TNT/NNAP cocrystal. TNT and NNAP firstly generated two eutectics, then transferred into TNT/NNAP cocrystal. The melting point of this cocrystal is 65 ℃.

Abstract:The microstructure of HMX (Octogen) crystal particles with average sizes of 5 and 20 μm was studied by in situ variable-temperature small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The WAXS results showed that the initial β→δ phase transition temperature of HMX (5 μm) is 194 ℃, which is 8 ℃ higher than that of the HMX (20 μm). Guinier law modelling analysis of SAXS measurements revealed the presence of defects with gyration radii between 0.6~0.9 nm will occur in HMX when above 150 ℃. The volume ratio of the defects irreversibly increases with temperature. The number of defects in HMX (20 μm) was found to be higher than that of HMX (5 μm). SAXS, WAXS and scanning electron microscopy all indicate that the thermal stability of HMX (5 μm) is better than that of HMX (20 μm). Finally, the mechanism of defects formation and their effect on the structural integrity and sensitivity of HMX were discussed.

Abstract:In order to study the crystal nucleation process of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105), the CrystlScan multi-channel crystallizer was used to measure the crystallization nucleation induction period of LLM-105 in antisolvent system. The influence of supersaturation on the nucleation of LLM-105 was studied by using the induction period measurement method, and the important nucleation parameters were calculated by the classic nucleation theory. The results show that the induction period of anti-solvent crystallization of LLM-105 decreases with increasing supersaturation. When the supersaturation ratio S<2.53, heterogeneous nucleation was mainly observed, the interfacial tension γ value is 6.67717×10^-23 J·m^-2, and the surface entropy factor f value is 1.49; when S>2.53, the homogeneous nucleation was mainly achieved, the interfacial tension γ value is 9.89842×10^-23 J·m^-2 and the surface entropy factor f value is 2.23. The surface entropy factor values were all less than 3, indicating that the growth mode of LLM-105 in ethyl acetate as an anti-solvent crystal is a continuous growth mechanism, the nucleation rate increases as the supersaturation ratio increases, and the critical nucleus radius and the number of critical nucleation decrease as the supersaturation ratio increases.

Abstract:To facilitate the crystallization of spherical FOX-7, a laser dynamic method was performed to determine the solubility of FOX-7 in the solvent mixtures of DMSO-EAC with different volume ratio in the temperature range of 298.15~333.15 K. The solubility equation was established and the crystallization thermodynamic parameters were estimated. The cooling crystallization experiment was carried out in DMSO-EAC mixed solvent. The results show that the solubility of FOX-7 in mixed solvents increases with increasing temperature and DMSO content. All models fit well with experimental data, of which the CNIBS/R-K model has the best correlation. The crystals of FOX-7 obtained by cooling crystallization in V_DMSO∶V_EAC=1∶3 system are regular, ellipsoidal and uniform in particle size.