Abstract:In order to study the performance of 3，3''-bi（1，2，4-oxadiazole）-5，5''-diylbis（methylene）dinitrate （BOM）， the sample was prepared by using the melting casting process and its the detonation velocity was measured. The thermal safety of the BOM casting process was studied by the thermal decomposition and constant temperature test. The solidification properties of BOM were studied by macroscopic solidification molding and microscopic solidification crystallization test. The mechanical properties of the BOM casting were studied by compressive and tensile tests. The detonation velocity and detonation heat properties of BOM/HMX/Al melt-cast explosive system were analyzed by detonation performance calculation. The results show that the natural solidification density of BOM is 1.726 g·cm^-3 and the detonation velocity is 7679 m·s^-1. The peak temperature of BOM decomposition is 213.8 ℃， and the calculated critical temperature of thermal explosion is 190.7 ℃. There is no discoloration and smoke during the constant temperature heating， which shows satisfactory thermal safety of the melt-casting process. The solidification defects of BOM were concentrated in the feeding area at the top of the casting， The volume shrinkage rate of natural solidification was 15.7%， and the forming density was 94.7% of the theoretical density， indicating good solidification and forming performance. The compressive strength of the casting is 6.21 MPa and the tensile strength is 1.89 MPa. In the BOM/HMX/Al melt-cast explosive system， the detonation velocity decreases linearly with the increase of Al content. When the Al content is less than 24%， the detonation heat increases gradually with the increase of Al content. When the Al content is more than 24%， the detonation heat is related to the ratio of BOM and HMX in the formula， and the ratio of BOM and HMX system needs to be adjusted to meet the optimal Al/O ratio of the formula.

Abstract:The co-crystal of hexanitrohexaazaisowurtzitane （CL-20） and 2，4-dinitro-2，4-diazapentane （DMMD） was prepared by co-crystallization in solution. It was characterized by single crystal X-ray diffraction（SCXRD）， scanning electron microscopy（SEM）， powder X-ray diffraction（PXRD）， and fourier transform infrared （FT-IR）， and differential scanning calorimetry （DSC）. The results show that CL-20/DMMD co-crystal belongs to monoclinic system with space P2₁/c. Analysis of interactions in co-crystal shows that the main forces between two kinds of molecule in co-crystal are hydrogen bonds and features a layered motif. There is new crystal phase in the XRD pattern. The shift of peaks for CL-20/DMMD attributes to the formation of C─H…O hydrogen bonding in FT-IR pattern. Results of DSC show that the melting point of co-crystal is 180.8 ℃， which is 21.5 ℃ and 120.9 ℃ higher than that of CL-20 and DMMD. The main thermal decomposition peak temperature of CL-20/DMMD co-crystal is 240.1 ℃， which increases by 3.5 ℃ compared with CL-20. The predicted detonation velocity and detonation pressure of CL-20/DMMD co-crystal are 9386 m·s^-1 and 45.09 GPa according to the theories of Rothstein and Petersen， respectively. They are slightly lower than that of CL-20 and higher that of DMMD（D=7287 m·s^-1，P=21.79 GPa），HMX（D=9048 m·s^-1，P=40.55 GPa）， RDX（D=8945 m·s^-1， P=37.28 GPa）， and TNT（7042 m·s^-1， P=21.44 GPa）.

Abstract:A novel melt-cast energetic compound bis（dinitromethyl-ONN-azoxyfurazanyl）furazan （BDNAF） was synthesized using 3，4-bis （3′-aminofurazal-4′-yl）furazan （BATF） and 2，2-dimethyl-5-nitro-5-nitroso-1，3-dioxane （DMNNDO） as starting materials via oxidation coupling， hydrolysis， bromization， reduction and nitration five-step reactions. The structures of the intermediates and the target material were fully characterized by infrared spectrum（IR）， nuclear magnetic resonance（NMR） and elemental analysis（EA）. The thermal behaviors of intermediate compound 3，3'-bis（nitromethyl-ONN-azoxyfurazanyl）furazan （BNAAF） and target compound BDNAF were investigated based on differential scanning calorimetry（DSC） measurement， and the physicochemical properties and detonation performances of BNAAF and BDNAF were estimated by Gaussian 09 program and Explo 5（v. 6.04）. Results show that the intermediate compound BNAAF directly decomposed at 106.4 ℃ without melting process， and the calculated density of BNAAF is 1.82 g·cm^-3， the detonation velocity is 8298 m·s^-1， and the detonation pressure is 29.0 GPa. The melting point of the target compound BDNAF is 95.4 ℃， the first decomposition point is 170.5 ℃ at the heating rate of 10 ℃·min^-1， and the theoretical density of BDNAF is 1.91 g·cm^-3， the detonation velocity is 9005 m·s^-1 and the detonation pressure 35.9 GPa， which revealed that BDNAF is a promising melt-cast explosive.

Abstract:In order to study the problem of impact strength and rheological properties of propellant substitutes （Cellulose Acetate， CA） assisted with supercritical carbon dioxide （SC-CO₂）， the in-line slit rheometer， drop hammer impact test machine， SEM were used， and the rheological properties， impact strength and cell morphology of product were characterized in varied experiment conditions. Research results prove that， when process temperature is 50 ℃， solvent ration is 1.2 mL·g^-1， flowability of CA is optimized evidently as injection speed of CO₂ increasing. However， impact strength of extrusion product only account for nearly 53.11% of those products prepared without SC-CO₂（when injected mass fraction of SC-CO₂/CA is 0.173%， screw speed is 10 r·min^-1）； SEM results prove that， quantities of irregular foam structure exist in product prepared with SC-CO₂， foam size are both over 2 μm， some of them even reach at 15-25 μm. Impact strength and product appearance could be modified as screw speed increase， product prepared in 14 r·min^-1 attain higher impact strength （nearly 170.33%） than 6 r·min^-1. During the process of propellant substitutes assisted with supercritical carbon dioxide， rheological properties of CA in barrel could be optimized as injection speed， solvent ratio， process temperature and screw speed increase， however， impact strength of CA could be positively modified as screw speed increase.

Abstract:To improve the thermal decomposition performance of ammonium perchlorate （AP）， Cu₁/Al₂O₃ single-atom catalyst was prepared through the evaporation induced self-assembly （EISA） method. The morphology and structure of prepared Cu₁/Al₂O₃ single-atom catalyst were characterized by X-ray diffractometer （XRD）， inductively coupled plasma （ICP-OES）， transmission electron microscopy （TEM）， X-ray absorption spectroscopy （XAS） and X-ray photoelectron spectrometer （XPS）. The effect on the thermal decomposition of ammonium perchlorate（AP）was also investigated by differential scanning calorimetry （DSC） and thermal gravimetry （TG）. Results show that Cu atoms were dispersed and stabilized through oxygen bridge bonds on the Al₂O₃ supporter. The Cu loading was determined to be 8.7%. When the content of Cu₁/Al₂O₃ single-atom catalyst is 5%， the high-temperature exothermic decomposition peak temperature of AP decreases to 319 ℃， which was 85 ℃ lower than that of pure AP. This Cu₁/Al₂O₃ single-atom catalyst exhibits superior catalytic performance on the thermal decomposition of AP， which was more effective than Cu（NO₃）₂·3H₂O and nano-CuO catalyst.

Abstract:To investigate the quasi-static tensile mechanical properties of aging high solid content modified double-base propellants （CMDB）， the uniaxial tensile tests of CMDB propellant were carried out at four different temperatures （323， 293， 273， 253 K） and different strain rates （3.3×10^-5， 3.3×10^-4， 3.3×10^-3， 3.3×10^-2 s^-1）. The CMDB propellant samples with different aging time （0，10，20，35，50，65，80，100 d） were tested by gas chromatography. The mechanical properties of CMDB propellant and the change of stabilizer content after aging were studied. The results show that the maximum elongation and the content of stabilizer decrease significantly during the aging process， which can be used as the failure criterion of the aging CMDB propellant. By using the time-temperature superposition principle （TTSP）， the maximum tensile strength curve of CMDB propellant was obtained， and the aging strength main curve equation was established， which could be used to predict the maximum tensile strength of CMDB propellant with different aging time in the range of quasi-static strain rate.

Abstract:In order to realize the efficient application of TKX-50 in field of solid propellants， the energy performance of poly（glycidylaminopropyl ether） （GAP）-based solid propellants containing TKX-50， CL-20， and TKX-50/CL-20 was calculated using the minimum free energy method， and the feasibility of TKX-50 and CL-20 combination application was analyzed. The application efficiency of TKX-50/CL-20/GAP-based solid propellant was also estimated. The results show that when TKX-50 content increases， balance combustion temperature of propellant in combustion chamber（T_c） and combustion gas average relative molecular mass（） of propellant decrease at the same time， and the theoretical ratio of impulse was first increased and then decreased. The compatibility of TKX-50 and CL-20 was moderate compatibility. It has good thermal stability and safety performance of the TKX-50/CL-20 mixture propellant. It can significantly broaden the choice of the content of each component of the formulation with TKX-50/CL-20 mixture propellant. The lower limit of CL-20 content in the compound propellant with theoretical specific impulse greater than 272 s was only 40% of pure CL-20 propellant. At the same energy level， TKX-50/CL-20 mixture has the characteristics of low cost and low characteristic signal， and has the potential of engineering application.

Abstract:3， 4-dinitropyrazole（DNP）， a new type of smelt-cast matrix explosive， is a kind of high energy matrix with great application potential. The impact Hugoniot relationship of explosive is the basis to investigate its impact initiation characteristics. For this reason， the pressure comparison method was adopted in this study. Plane wave generators were selected to act the designed loading. The post-shock pressure of DNP explosive and LY12 aluminum samples under nine shock pressures were measured by manganese-copper piezoresistivity gauges. By calculating the experimental data， the velocity （D） of the shock wave and the velocity u of the particle under different pressures were obtained. The D-U relationship of the DNP explosive in the range of 3.7~14.4 GPa was obtained by fitting. The results showed that the Hugoniot relationship of the DNP explosive in the range of 3.7~14.4 GPa could be approximated as a straight line in the D-U plane. The post-wave state of DNP explosive under the action of shock wave was defined， which provided a reference for further study of impact ignition and initiation of DNP explosives. In addition， the influence of polytetrafluoroethylene packaging of manganese-copper piezoresistance gauges on the experimental test results was analyzed. The systematic error caused by packaging was effectively eliminated through theoretical analysis and reasonable interpretation of test signals.

Abstract:To study the correlation between the packed density of nonmetallic spherical spacers （NSS） and its suppression of propane explosion， a newly designed constant-volume combustion cylinder combined with high-speed schlieren photography was employed. The explosion experiments of propane-oxygen pre-mixtures with different equivalence ratios（1，1.5 and 2） were conducted in cylinders with different packed densities of NSS （21.9 kg·m^-3，38.7 kg·m^-3 and 45.1 kg·m^-3）. The effect of packed densities of NSS on maximum explosion pressures， total heat loss， flame tip velocities， flame propagation characteristics and turbulence in cylinders with different equivalence ratios of propane-oxygen were analyzed in detail. The results show that NSS has suppression effect on the maximum explosion pressure， and has promotion effect on the flame propagation process. When the packed density of NSS is 45.1 kg·m^-3， the maximum explosion descending rate and heat loss in cylinders reach maxima， while the peak flame tip velocity ， the maximum tip velocity difference between two points and the turbulence enhancement factor in cylinders are relatively small， which indicates the best explosion suppression performance of NSS.

Abstract:In order to prevent the spacecraft from being damaged by the high pyroshock during the action of the pyrotechnic separation nuts， a metal rubber vibration isolator（MRVI） was used to suppress the pyroshock response caused by the impact of the piston in the separation nut. Three kinds of MRVIs with different stiffness were installed at the end of the piston movement in the separating nut， and the shock response spectrum（SRS） in the frequency domain of 500 Hz to 10000 Hz was analyzed. The results show that the pyroshock suppression effect of the MRVI mainly occurs in the frequency band above 3000 Hz， and the pyroshock suppression effect in the frequency band above 5000 Hz is the most significant. The maximum acceleration response after installing a small-stiffness MRVI is reduced from 1330 g to 852 g， and the maximum reduction in analysis frequency domain is 675 g@5993 Hz. The maximum acceleration response after installing a medium-stiffness MRVI is reduced from 1530 g to 1251 g， and the maximum reduction in analysis frequency domain is 539 g@9514 Hz. The maximum acceleration response after installing a large-stiffness MRVI is reduced from 1697 g to 1416 g， and the maximum reduction in analysis frequency domain is 538 g@8476 Hz. The use of MRVI achieves a better pyroshock suppression effect， and provides a viable method for the pyroshock reduction design of the pyrotechnical actuation devices.

Abstract:Cocrystal is composed of different neutral components through intermolecular non-bond interactions at molecular level and it has fixed ratio and particular structure. Cocrystallization technology is a novel method for ameliorating properties of energetic materials and it has wide development prospect and application value. It can decrease the sensitivity， improve the mechanical properties， thermal performance， and energy density of energetic materials. The research progress of preparation and application of energetic cocrystals was summarized， including the current research status， preparation method， characterization methods， and formation mechanism. The existing problems of energetic cocrystals were introduced： first， the properties of some cocrystal explosives need to be further improved； second， the preparation of cocrystal requires harsh conditions with low product yield； third， the characterization and test methods lack variety. The further development direction of cocrystal explosives were pointed out： strengthen the research of multiple components energetic cocrystals， improve the technologies to increase the yield， investigate the crystallization dynamics behavior to seek for the best cocrystallization conditions， and look for effective means to characterize the cocrystal structure.

Abstract:As a new generation of rapid prototyping technology， direct writing technology has the advantages of fast molding speed， good molding consistency， and high preparation accuracy. It has certain advantages in the preparation of MEMS energetic devices. In this paper， the common direct writing technologies of MEMS energetic devices were described. On this basis， according to the research status of direct writing technology in micro-nano energetic devices， the direct writing technologies used in micro-scale charges of MEMS energetic devices， ignition circuit and transducer element， and packaging materials were summarized. The future research directions were proposed： preparing energetic ink with high solid content and stable performance， increasing the charge density of energetic ink， preparing silver ink circuit with low sintering temperature， and at the same time developing direct writing technology for MEMS energetic device transducers and packaging materials， exploring the influencing factors and laws of direct writing accuracy， breaking through the application bottleneck of direct writing technology， and promoting the progress of engineering application of this technology.