Abstract:In order to study the performance of aluminum-based composite fuel in NEPE solid propellant， the aluminum-base composite fuel（Al@AP） was used in the NEPE solid propellant instead of aluminum powder， and the effects of Al@AP on the combustion， mechanics， and process performance of NEPE propellant were studied by explosion heat test， engine test， residual active aluminum test， high-speed photography， unidirectional tensile test and process properties test. And the combustion mechanism of Al@AP in NEPE propellant was derived. Results shows that by replacing FLQT-3 Al powder with 19.5% Al@AP， the explosion heat of NEPE propellant increased from 6029.4 J·g^-1 to 6924.8 J·g^-1， and the mass of residue decreased from 28.91 g to 7.64 g， and the active aluminum content of residue decreased from 14.64% to 0.37%， and the particle size of residue decreased from 94.12 μm to 24.21 μm. The injection efficiency of NEPE propellant with Al@AP is improved. The residence time of aluminum powder at the burning surface decreased from 55 ms to 40 ms， and there was no obvious agglomeration phenomenon. Al@AP powder has little effect on the dynamic burning rate， mechanics and process properties of NEPE propellant.

Abstract:The Arrhenius equation has been widely used as kinetics model for predicating aging property and shelf life of polymer materials by extrapolating high temperature accelerated test data. However， the suitability of the equation to composite solid propellants was questioned. Therefore the application history of the Arrhenius equation on aging of composite solid propellants has been reviewed. By combing the theoretical evolution process of Arrhenius equation， physical meaning of the equation parameters was clarified， and the misunderstanding on the equation was revealed. Theoretical analysis shows that only one of the two parameters （frequency factor and activation energy） is relative to temperature in the Arrhenius equation， and the parameters can be regarded as constants to solid propellants aged between the highest acceleration temperature allowed by current industry-standard and room temperature. The following conditions should be met to apply the Arrhenius equation： 1） it can be considered as the same aging mechanism in the range of temperatures involved in， 2） it has similar aging levels at the deadline of different acceleration temperatures， and 3） it has a parameter k with physical meaning of rate constant exactly. Mathematical models with logarithmic time are unsuitable to fit performance-time relationship， while those with logarithmic performance are suitable.

Abstract:The aim of this study is to explore the effect of absorption coefficient on propulsion performance of the laser ablated ammonium dinitramide （ADN）-acetone based liquid propellant. ADN and absorbent were mixed with different proportions in the range of 0-80% and a proportional distance of 10% to form ADN-acetone based liquid propellants. The absorption coefficients of propellants with different proportions were measured and calculated using a near-infrared spectrometer. Under the laser energy of 60 mJ and liquid film thickness of 300 μm condition， the impulses generated by laser ablation of propellants with different proportions were measured using a high-precision torsion pendulum. Results show that the absorption coefficient decreased with the increase of ADN content. In addition， the impulse decreased after peaking at ADN content of 30%， but increased again at ADN content of 80% sharply. The decrease of impulse in the ADN content range of 30%-70% is mainly caused by the decrease of absorption coefficient which leads to the decrease of laser energy deposited by the propellant. The impulse increase at ADN content of 80% is caused by the propellant whose absorption coefficient approaches to 0 and constitutes a “water cannon target” with the container. After the container is ablated by the laser， the propellant will act as a constraint， and result in the increase of impulse.

Abstract:Addition of high energy boron into the liquid fuel is an effective method to improve the energy density of the blended fuel. However， the added content of boron is limited， due to the dramatic increase in the viscosity of the blended fuel. So it is important to increase the boron content as much as possible without obvious viscosity increase. Four organosilanes including propyltrimethoxysilane （C3-silane）， octyltrimethoxysilane （C8-silane）， dodecyltrimethoxysilane （C12-silane） and hexadecyltrimethoxysilanes （C16-silane） were used to modify boron particles. First， the modified boron particles were characterized by scanning electron microscopy， contact angle measurement， X-ray diffraction， particle size analysis （using dynamic laser scattering） and thermogravimetric analysis. Then the rheological properties of organosilane modified boron/JP-10 blend fuels were investigated. Finally， the effect of temperature on the apparent viscosities at different shear rates was studied. The results show that boric acid on the boron surface was removed upon surface modification with organosilanes and the surface characteristics of boron powder were transformed from hydrophilicity to hydrophobicity. The content of organosilane was less than 1.5% in the organosilane modified boron particles， which would have marginal effect on the total heat value. Organosilane modified boron/JP-10 blend fuels with solids content of 50% showed good fluidity and their apparent viscosities were lower than 0.3 Pa·s at 25 ℃ and 100 s^-1 of shear rate. Keeping other conditions the same， the apparent viscosity of blend fuels depends on the length of side chain alkyl group of organosilane： C3-silane>C8-silane≈C12-silane≈C16-silane. Organosilane modified boron/JP-10 blend fuels showed shear-thinning characteristics and the relationship between the apparent viscosity and the shear rate could be well fitted by power-law equation. The apparent viscosity of blend fuels depends strongly on the temperature and their relationship could be well expressed by Arrhenius equation. The shear activation energy of blend fuels increases with increasing the length of side chain alkyl group of organosilane coated on the boron.

Abstract:To improve the hazard classification of anhydrous hydrazine， the extremely insensitive detonating substance （EIDS） gap test and external fire test were conducted for the standard packaging anhydrous hydrazine （18 kg and 120 kg） in accordance with the United Nations “Recommendations on the Transport of Dangerous Goods， Manual of Tests and Criteria”. The deflagration process， the highest temperature of the fireball surface and shock wave effect of samples were obtained by a high-speed camera， an infrared thermal imaging and a shock wave pressure acquisition system. The experimental results show that， under external fire conditions， the TNT equivalence of the anhydrous hydrazine-18 kg was 0.724， which was 1930.67 times that of anhydrous hydrazine-120 kg. Under certain conditions， anhydrous hydrazine has obvious explosive properties and can be assigned to Division 1.1 C or Division 1.3 C for different packaging design pressures. The hazard class of anhydrous hydrazine is closely related to the standard packaging design pressure. For safety purposes， the design pressure of packaged anhydrous hydrazine should be properly reduced within the allowable range to effectively reduce its hazard.

Abstract:The ignition and combustion characteristics of NEPE propellant were studied based on a CO₂ laser ignition test platform established， in which the combustion processes of NEPE propellant in different gas environments were photographed using a high-speed camera and the ignition delay times of NEPE propellant were measured under the pressure of 0.1-3.0 MPa in nitrogen and air through a signal acquisition system. The results show that the ambient pressure and gas environment strongly affect the ignition and combustion process of NEPE propellant. The combustion of NEPE propellant becomes more intense as the increase of ambient pressure， and the burning of NEPE propellant appears more violent in air as compared to that in nitrogen. The ignition delay time of NEPE propellant decreases with the ambient pressure increases in the range of 0.1 MPa to 3.0 MPa. Specifically， the reduction in ignition delay time of NEPE propellant is observed from 0.51 s to 0.29 s in nitrogen and from 0.32 s to 0.18 s in air. However， when the ambient pressure exceeds 0.5 MPa， the influence of the ambient pressure on the ignition delay time becomes insignificant. In addition， the burning rate of NEPE propellant is also found to be effectively affected by the ambient pressure. With the ambient pressure increases from 0.1 MPa to 3.0 MPa， the enhancement in burning rate of NEPE propellant can be seen from 1.71 mm·s^-1 to 4.54 mm·s^-1 in nitrogen and from 2.51 mm·s^-1 to 11.4 mm·s^-1 in air， and thus a stronger increase in the burning rate is observed in air. Finally， the experimental data of burning rate were fitted by an empirical formula， which indicates the Vielle burning rate formula is more suitable for reproducing the burning rate characteristics of NEPE propellant especially at 0.1-3.0 MPa.

Abstract:As an energetic material， octogen（HMX） is widely used in solid propellants. While improving the energy performance of the propellant， it also changes the combustion process of the propellant. To study the effect of HMX content on the ignition， combustion， and agglomeration properties of propellant and its condensed phase combustion products （CCPs）， burning surface photography， laser ignition and collection of the CCPs were used for testing and studying typical AP/HTPB/Al/HMX propellants with HMX contents ranging 0%-10%. Results show that as the HMX content increases from 0 to 10%， the ignition delay time increases from 191 ms to 286 ms， and both the burning rate and pressure exponent of the propellent decreases. The volume average particle size of the CCPs increased from 48.1 μm to 138.3 μm. The propellent with 10% HMX has the highest agglomeration degree on the burning surface， while the propellent with 8% HMX has the highest active aluminum content in the CCPs.

Abstract:To study the mechanical properties of Hydroxyl-Terminated Polybutadience （HTPB） propellant/liner bonding interface for solid rocket motor at different temperatures accurately， the model-Ⅰ fracture properties of the interface were studied with experimental method and simulation. Firstly， the load-displacement curves of the test samples at different temperatures were obtained through uniaxial tensile tests and the failure process of the samples were also recorded with the high-speed cameras. It was found that the failure form of HTPB propellant/liner interface was cohesive failure of HTPB propellant， which indicated that the strength of bonding interface was higher than that of the propellant. From -40 ℃ to 60 ℃， the critical displacement first increased and then decreased， indicating that the effect of temperature on this parameter is obvious. And then a cohesion model with polynomial damage variable was developed， based on the bilinear cohesion law. According to the simulation data， the effects of the interface parameters on the predicted results of the interface properties at different temperatures were analyzed. Moreover， the load-displacement curves of the bonding interface at different temperatures were predicted with the critical displacement as a known parameter. It found that the predicted results by simulation were in agreement with the experimental results， which indicates that the developed interface model can more accurately reflect the temperature-dependent behavior of model-Ⅰfracture of the debonding interface for solid rocket motor than the bilinear cohesion model.

Abstract:In order to improve the safety performance of potassium perchlorate （KClO₄）， KClO₄/ Silver （KClO₄/Ag） composite particles were prepared by chemical reaction of glucose and silver ammonia on the surface of KClO₄ particles. The particle morphology， phase composition， thermal decomposition temperature and mechanical sensitivity of the modified particles were analyzed by means of scanning electron microscope （SEM）， X-ray diffraction （XRD）， differential scanning calorimeter （DSC）， et al. The results show that KClO₄/Ag composite particles have obvious spherification effect， smooth surface and no obvious edges and corners. On the basis of retaining the original good stability and high decomposition temperature of KClO₄， it also has the characteristics of silver metal. Compared with the initial raw KClO₄， the mechanical sensitivity of KClO₄/Ag composite particles decreased significantly， the friction sensitivity explosion probability decreased from 90% to 50%， and the impact sensitivity explosion probability decreased from 70% to 40%. At the same time， the thermal decomposition performance of KClO₄/Ag composite particles is obviously different from that of raw KClO₄. The exothermic peak of KClO₄/Ag composite particles is 12 ℃ earlier and the decomposition efficiency is higher than that of raw KClO₄.

Abstract:In order to realize the non-destructive measurement when predicting the storage life of nitrate ester plasticized polyether （NEPE） propellant， the high temperature accelerated aging， gas content monitoring and uniaxial tensile mechanical property experiment were carried out on NEPE propellant with 10% constant compression strain . The non-destructive storage life prediction model based on characteristic gas contents was proposed through correlation analysis and remaining life prediction model. The results show that during the storage and aging processes， the total amount of CO gas is the largest， reaching more than 1300 mg at different temperatures. The generating rates of NO and CO are growing slowly in the early aging period， and growing faster in the late period. The generating rate of HCl increases rapidly during the eraly and late aging period and slowly in the middle. Maximum tensile strength σ_m and maximum elongation ε_m increase slightly in the early aging period， the former oscillates slightly and the latter gradually increases in the middle period， and both of them decrease sharply in the late period. The correlation between the contents of CO and the maximum tensile strength is largest and there is a single correlation between them at different temperatures. The maximum correlation value reaches about 0.93-0.95. Four life prediction methods of NEPE propellant are established based on traditional and improved aging life prediction model， tensile strength and CO content. The maximum correlation coefficient and estimation results show that the improved prediction model based on the content of CO gas release is most effective.

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:To study the biaxial compressive mechanical properties of solid propellantn， it is necessary to determine the optimal propellant specimen configuration. This configuration should be compatible with the testing machine and test fixture and meetthe requirements of biaxial deformation characteristics. Based on the finite element numerical simulation calculation， the deformation stress contour of the three-component HTPB composite solid propellant specimens with eight different configurations under biaxial compression loading were obtained. Moreover， the optimal propellant specimen configuration was verified by conducting the dynamic biaxial compressive mechanical properties test on the corresponding specimen. Results show that the stress contour of all specimens under small deformation （strain within 10%） is uniform overall. However， the requirement of the plane stress does not meet during deformation of the specimens with an aspect ratio greater than 1. Furthermore， the average value of plane stress， dispersion of plane stress， the whole stress stability factor and the stress concentration factor were selected as the optimizing objective function of the propellant specimen configuration. The contrastive analysis shows that the optimal configuration is a 25 mm cube. Finally， the validity of the above determinated optimal configuration was verified by analyzing the characteristics of stress-strain curves of the propellant specimens obtained under dynamic biaxial compressive loading condition

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:To study the rheological properties and to cure the reaction process of branched polyglycidyl azide （B-GAP）-based propellent， the slurries were tested by rheological research methods， and the changes of viscosity with shear rate and modulus with time at 50， 55， 60 ℃ and 65 ℃ were studied. The results indicate： B-GAP propellant slurry has a shear thinning properties and belongs to pseudoplastic non-Newtonian fluid； The curing reaction rate of the propellant slurry increases as the curing reaction progresses， reaching a maximum value when the curing degree is 0.3， and then the reaction rate begins to decrease until zero； Temperature has a great influence on the kinetics of propellant curing reaction. Within a certain temperature range， the peak value of the curing reaction rate increases with the increase of temperature， and the maximum value of storage modulus decreases with the increase of temperature； Based on the power law equation and Arrhenius equation， the constitutive equation and curing kinetic reaction equation of B-GAP slurry was obtained.

Abstract:Energetic burning rate catalyst is a hot research direction in the field of solid propellant in recent years. The application research progress and development trend of energetic combustion-rate catalysts in solid propellants were reviewed from the following four categories： monometal-organic framework type， bimetal based multi-functional type， molecular supported type and other types. It was pointed out that the catalytic effect of mono-metal-organic frame type burning rate catalyst is relatively simple， and the catalytic effect is better when combined with other metal salts. Bimetal based multi-functional combustion rate catalysts have excellant catalytic performance and potential application prospects. Molecular supported burn rate catalysts are still in the preliminary exploration stage， and their preparation and application have become one of the development directions of burning rate catalysts. The application of other new energetic burning rate catalysts should be strengthened. Finally， the main research directions in the future were suggested as following： green and environmental protection， high energy and low sensitivity， and nano and multi-functional composite. Burning rate catalysts containing heavy metals will have adverse effects on the environment， and the development of green and environmental protection burning rate catalysts has become an inevitable trend. The energy loss of propellant can be reduced by giving certain energy characteristics to burning rate catalysts. High energy and low sensitivity have become an important direction of burning rate catalysts. Nanocrystallization of energetic burning rate catalysts is always an effective way to improve the catalytic activity of catalysts. Burning rate catalysts with multiple functions will be the development trend in the future.

Abstract:The agglomeration of condensed phase during the combustion process of propellant is one of the main reasons for energy loss and nozzle ablation， and the introduction of fluorine into propellant is considered to be an effective way to solve the agglomeration. In order to solve the condensed phase agglomeration of aluminum， a fluoroalcohol compound was introduced into the traditional HTPE propellant， and it was integrated into the binder cross-linked network through the curing reaction to form a solid propellant based on a novel fluorocarbon binder. Thermogravimetric （TG） and laser ignition were used to characterize the thermal decomposition and the burning intensity of the propellant. The combustion surface flame morphology and particle size distribution of combustion condensed phase products were characterized by scanning electron microscope （SEM） and EDS. The results show that the weight loss of the propellant after adding PFD still includes three main stages， but PFD will cause the decomposition of RDX in the propellant to be delayed by 15-20 ℃.Moreover， the fluorine-containing segment will completely decompose and lose weight before 250 ℃. Compared with the blank propellant sample， the propellant containing PFD has higher burning brightness at the same ignition time. With the increase of PFD， the intensity of the combustion flame of the propellant sample increases significantly， and the flame jet is more intense. The average particle size of condensed phase products decreased gradually from 5.13 μm （1%PFD） to 1.04 μm（5%PFD）.

Abstract:The rapid development of additive manufacturing technology provides an effective way for the flexibility and adaptability of traditional solid propellant casting molding， however， to meet the requirements of the casting， the thermosetting solid propellants with good fluidity could not deposite layer by layer. In order to realize the additive manufacturing， the hydroxyl-terminated polybutadiene （HTPB） was modified by adding a small amount of styling aids. The rheological properties of the modified-HTPB and slurry made by using the modified-HTPB were studied. The rheological curve test results show that apparent viscosity and viscous flow activation energy of the modified-HTPB increase significantly with the decrease of temperature. The rheological property of the modified-HTPB solid propellant slurry is consistent with Herschel-Bulkley equation， and the fluidity of modified-HTPB solid propellant slurry increases with the increment of temperature. Besides， the slurry possesses high storage modulus（G′＞10⁴ Pa） and small loss tangent（ω＜10 rad·s^-1，G″/G′＜0.5） at ambient temperature， showing a low fluidity. A small amount of styling aids has little effect on the thermal decomposition behavior of the propellant， which promotes the 3D printing of the modified-HTPB solid propellant .

Abstract:Composite solid propellant contains more solid particles， so it is difficult to accurately simulate the extrusion process of the propellant in twin-screw extruder with traditional finite element analysis method. Whereas， the coupling of discrete element method （DEM） and computational fluid dynamics （CFD） is an effective method for simulation the production process of composite solid propellant， but it is very difficult to implement. In this paper， based on the calibrated contact model parameters， the simulation of solid particles in solid propellant with aluminum powder and ammonium perchlorate as main components in twin-screw extrusion process was realized with DEM， and then the DEM-CFD coupling calculation of the solid propellant solid particles and the liquid phase was realized. The results show that the transportation of solid propellant particles in twin-screw calculated by DEM is consistent with the experimental law. Comparing the results between DEM-CFD coupled simulation and DEM for solid particles， it can be seen that the fluidity of materials was significantly improved by adding the liquid phase The filling rate of materials in the screw conveying section increases from 20% to 40%， and the average conveying speed of solid particles increases by 150%， but the stress of screw does not change much.

Abstract:The thermal decomposition characteristics and thermal safety of methylhydrazine （MMH） were studied by means of differential scanning calorimetry （DSC）. The kinetics， thermodynamics and thermal safety parameters of MMH were calculated， respectively. The thermal explosion delay period of MMH of ball shaped with radius of 1 m at different supercritical ambient temperatures were also obtained. Based on the isoconversion rate method， the adiabatic induction period and self-accelerating decomposition temperature of MMH were further evaluated by using AKTS software. The results show that the thermal decomposition process of MMH has only one strong exothermic peak. The apparent activation energy values of MMH calculated by Kissinger and Ozawa methods are 159.13 kJ·mol^-1 and 158.89 kJ·mol^-1， respectively. The values of T_bp0 of MMH is 469.55 K. The values of entropy of activation （ΔS≠）， enthalpy of activation （ΔH≠）， and free energy of activation （ΔG≠） are 73.93 J·mol^-1， 155.32 kJ·mol^-1 and 121.46 kJ·mol^-1， respectively. The corresponding temperatures for adiabatic induction period at 8， 24 h and 168 h are 429.55， 424.05 K and 414.95 K， respectively. When the packing mass was 5， 25， 50 kg and 100 kg， the self-accelerating decomposition temperatures of MMH are 415.15， 414.15， 413.15 K and 412.15 K in turn. The results provide the necessary theoretical basis for evaluating the thermal safety of MMH in the processes of production， storage， transportation and use.

Abstract:Improving the reaction performance of traditional binary thermites is one of the research hotspots in the field of energetic materials in recent years. The introduction of additives to form composite thermite is an effective method. According to the application fields and the different effects of additives， the composite thermites were divided into fuel-enhanced type， gas-producing type and modified additive type. The research status of composite thermite and its related engineering applications were reviewed， and then the new research directions and ideas for composite thermite were proposed， including the use and preparation of new alloy fuels and alloy hydrides， the combined use of non-azide gas generating agents and thermite， the influence of the types and amounts of inert additives， and the coating technology of the binder on the surface of the thermite， etc.

Abstract:It is reported herein that the interfacial adhesion between binder and filler has distinct effect on mechanical properties of propellant. The tensile fracture progress of propellant （nitrate ester plasticized glycidyl azide polymer （GAP） / hexanitrohexaazaisowurtzitane （ε-CL-20） polyether propellant and polyethylene glycol （PEG） / octogen （β-HMX） polyether propellant） was monitored by in-situ tensile scanning electron microscope. In addition， the interaction strength between binder matrices and solid fillers was characterized by adhesion work and binding energy. The adhesion work was studied by inverse gas chromatography （IGC） and contact angle method， and the binding energy was calculated via molecular dynamics （MD）. Results shows that the dehumidification and fracture expanding progress of GAP/ε-CL-20 propellant are more serious than these of PEG/β-HMX propellant during stretching progress. GAP/ε-CL-20 propellant breaks when the elongation is more than 60% while PEG/β-HMX propellant breaks when the elongation is more than 80%. Besides， the adhesion work 70.69 mJ·m^-2 and binding energy 259.90 kJ·mol^-1 between GAP matrix and ε-CL-20 are both lower than the adhesion work 98.61 mJ·m^-2 and binding energy 335.65 kJ·mol^-1 for PEG/β-HMX system， suggesting that the poor interfacial adhesion between GAP binder matrix and ε-CL-20 is one of main reasons for inferior mechanical properties of GAP/ε-CL-20 propellant.

Abstract:To explore the aging mechanism and performance of antioxidants N-（1，3-dimethyl）butyl-N"-phenyl-p-phenylenediamine（4020）， N-isopropyl-N"-phenyl-p-phenylenediamine （4010NA）， N-phenyl-2-naphthylamine （D） in hydroxyl-terminated polybutadiene polyurethane （HTPB-TDI） system， quantum mechanics （QM） simulation， molecular dynamics （MD） simulation， monte carlo （MC） simulation were used to calculate the dissociation free energy， diffusion coefficient， solubility parameter and permeability coefficient of the HTPB-TDI system and each component. Results show that the order of the bond dissociation free energy of the three antioxidants is ΔG_D>ΔG_4010NA>ΔG₄₀₂₀， and they are all less than the minimum free energy of dissociation of HTPB-TDI （345.63 kJ·mol^-1）， indicating that the three antioxidants can preferentially react with the active free radicals in HTPB-TDI and slow down the progress of the free radical chain reaction in HTPB-TDI. The difference of diffusion coefficient and solubility parameter between antioxidant 4020 and HTPB-TDI is the smallest， which shows that antioxidant 4020 has poor diffusion ability and good compatibility with HTPB-TDI， so it can exist in HTPB-TDI stably and uniformly； The order of the permeability coefficient of oxygen in the three kinds of hydroxyl-terminated polybutadiene polyurethane antioxidant systems is P_HTPB-TDI/D＞P_{HTPB-TDI/4010NA}＞P_{HTPB-TDI/4020}， which manifests that D has the worst oxygen barrier ability. According to the chemical reaction difficulty， mobility， compatibility and oxygen permeability of the three kinds of antioxidants， the order of antiaging properties of the three kinds of antioxidants is 4020>4010NA>D.

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:In order to obtain accurate and reliable physicochemical properties of condensed phase combustion products （CCPs） of composite propellants， a method of ethylenediamine tetraacetic acid （EDTA） titration based on microwave digestion was proposed to achieve the quantitative analysis of the total components of condensed phase combustion products. Four groups of condensed phase combustion products of propellant were obtained by using self-developed condensed phase combustion products collection system. The determination accuracy of EDTA titration， inductively coupled high frequency plasma emission spectrometry （ICP）， gas volumetric method and potassium dichromate titration were compared and analyzed for the content of active Al. The results show that the EDTA titration method based on microwave digestion can accurately determine the contents of Al， Al₂O₃， AlN， Fe₂O₃ and C in the condensed phase combustion products of composite propellants. Microwave digestion can effectively dissolve the Al₂O₃ shell coating on the surface of active Al. The optimal parameters of microwave digestion is supposed to be V_H3PO4∶V_H2SO4∶V_HNO3=10∶2∶1. The temperature was 240 ℃， and the digestion time was 150 min. ICP spectroscopy can also detect all component contents of condensed combustion products， with a precision slightly lower than EDTA titration. The content of active Al in condensed phase combustion products determined by gas volumetric method and potassium dichromate titration was significantly lower than that determined by EDTA titration and ICP spectrometric method. EDTA titration is the most accurate method to determine the content of active Al. Compared with gas volumetric method， potassium dichromate titration method and ICP spectrometric method， the accuracy of EDTA titration is improved by 60%， 40% and 22%， respectively.

Abstract:A high-speed camera， a high-precision pressure sensor， an R-type thermocouple and a micro-thrust test bench has been used to investigate the controllable combustion behaviors and thrust performance of the laser-controlled solid propellant （LCSP） under laser irradiation. The burning rate， ignition delay time， chamber pressure， combustion flame temperature and micro-thrust under different laser power densities were obtained. The results showed that the burning rate and chamber pressure increased linearly， while the ignition delay time decreased with increasing laser power density. Combining the thermocouple temperature curves， it was concluded that the combustion process of LCSP might be divided into five zones： pre-heating zone， condensed phase zone， triple zone， gas phase zone and flame zone. Meanwhile， the combustion flame temperature of the LCSP was 1202.3 ℃ under the laser power density of 1.343 W·mm^-2. Dependence of the combustion status on laser power density makes sense to realize the accurate adjustment of micro-thrust. In the experiment， the thrust control of LCSP is successfully realized by changing the laser power density. As the laser power density increased from 0.344 W·mm^-2 to 1.343 W·mm^-2， thrust of the LCSP increased from 1.58 mN to 2.28 mN.

Abstract:In order to improve the combustion efficiency of Al powder， Al/modified-fluororubber composite fuel（FKM-GW@Al） was prepared with the silane modified-fluororubber（FKM-GW） by sol-gel method. The stability of FKM-GW@Al in solvent was studied， and the results show that with functional groups， the FKM-GW@Al is stabile in ethyl acetate. The application of FKM-GW@Al in NEPE high-energy and low burning-rate solid propellant was studied. Results show that compared with Al powder， FKM-GW@Al with fluorine mass fraction 2.58%， make the explosion heat of the propellant increase from 6348.8 J·g^-1 to 6831.6 J·g^-1， the content of activated aluminum in residues decreased from 1.02% to 0.06%， and both the static and dynamic burning rates of the propellant containing FKM-GW@Al decrease. The thermal decomposition properties of FKM-GW@Al and the propellant containing FKM-GW@Al were studied by DSC-TG， and the influence mechanism of FKM-GW@Al on combustion characteristics of the propellant was analyzed.

Abstract:ResoDyn Acoustic Mixers Incorporation developed a mixing technique known as Resonant Acoustic® Mixing （RAM） in the early 21st century. This technology uses acoustic waves to create multiple micro-mixing zones within a material rather than the bulk mixing generated by traditional impeller or rotor agitation or planetary mixer. RAM technology can be used for the large-scale production of pharmaceuticals， cosmetics， and bulk powder mixing. For energetic materials， RAM is considered to have potential advantages over traditional high-shear processing methods （e.g. planetary mixing）， including shorter time scales， improved mix homogeneity， reduced waste output， absence of moving parts （an ignition source）， and the potential to mix higher viscosity， ‘unmixable’ compositions （compared to planetary mixers）. RAM has become the processing technology of choice in the development and production of propellants， explosives， and pyrotechnics. A summary of applications of RAM in the field of energetic materials， including the formation of co-crystal explosives and nano thermites and the processing of propellants and PBXs， is detailly overviewed in this text.

Abstract:In order to explore the solid propellant combustion catalyst， a new type of bi-ligand containing energy complex ［Cu（MIM）₂（AIM）₂］（DCA）₂ was synthesized from 1-methylimidazole （MIM）， 1-allyl imidazole （AIM）， copper nitrate and NaDCA， and its structure was characterized by infrared spectroscopy， X-ray single crystal diffraction and powder diffraction. The thermal decomposition process of the energetic complex was analyzed by DSC and TGA. Within the temperature range of 40-500 ℃， there is a melting peak （peak temperature is 93.5 ℃） and an exothermic decomposition peak （peak temperature is 199.4 ℃） in DSC curve. The sensitivity test of the complex shows that the friction sensitivity and impact sensitivity are low and the operation process is safe. Comparing the bi-ligand ［Cu（MIM）₂（AIM）₂］（DCA）₂ with ［Cu（MIM）₄］（DCA）₂ and ［Cu（AIM）₄］（DCA）₂ catalyses on the thermal decomposition of AP， the results show that the bi-ligand complex has better catalytic effect， which advanced the exothermic peak temperature of AP by 88.8 ℃， increased the heat release from 782 J·g^-1 to 2458 J·g^-1， and lowered the thermal decomposition activation energy by 47.1 KJ·mol^-1， implying the potential application as a composite propellant catalyst .

Abstract:In order to analyze the factors affecting the ignition delay time in the gas phase reaction process between hydrazine fuel and NO₂， the reaction process was simulated by using density functional theory. The reaction activities， active sites， potential energy surfaces and reaction rate constants in hydrogen extraction reaction process of hydrazine （N₂H₄）， methyl hydrazine （MMH） and unsymmetrical dimethyl hydrazine （UDMH） were calculated. The results showed that the energy difference between the highest occupied orbital and the lowest vacant orbital of UDMH was the smallest among the three hydrazine fuels， which was 0.20522 eV， indicating that UDMH had the highest activity， so it has the fastest reaction rate with NO₂， which in line with the characteristic of the shortest ignition delay time. The active sites of three hydrazine fuels were identified， N（1） or N（4） for N₂H₄， N（1） for MMH and N（1） for UDMH. The active sites of hydrogen extraction reaction of three hydrazine fuels were calculated， it was found that the reaction barrier of UDMH is the smallest， which is 3.589 kJ ·mol^-1， and the reaction rate constant is the largest， which is 9.81×10⁵ L·s^-1·mol^-1， which is consistent with the shortest ignition delay time， it is concluded that in hydrazine fuel， the smaller the hydrogen extraction reaction barrier with NO₂， the larger the reaction rate constant， and the shorter the ignition delay time.

Abstract:Meriting in green and pollution-free combustion products， large specific surface area， insensitive-safety ， large contact area with reactants and easy modification， nanocarbon has been widely focused on tuning the performances of energetic materials （EMs） such as high explosives， propellants and thermites. This work reviews the effects of nanocarbon on the decomposition characteristics， sensitivity， mechanical performances and combustion properties of EMs. In addition， it discloses the progresses in the detection， adsorption and degradation of EMs conducted by nanocarbon. The interaction mechanisms of typical nanocarbon materials （nano-diamond， fullerene， nanocarbon fiber， carbon nanotube and graphene） in EMs have been analyzed. Within this review， issues， challenges and promising research directions existing in the application of nanocarbon in EMs are highlighted and presented. （1） Optimizing the high-cost preparation processes of nano carbon. Easy agglomeration and large batch differences of nanocarbon. （2） Expanding the application scope of nanocarbon. Exploring the effects of new-type nanocarbon such as onion carbon and modified nanocarbon on the properties of energetic materials. （3） According to the specific environment and nanocarbon regulation mechanism， the application conditions of nanocarbon in improving the properties of energetic materials are optimized. It is expected that nanocarbon materials will provide a forum for future advancement in the modifications of multifunctional EMs.

Abstract:In order to study the influence of aluminum powder on the mechanical property， interface， combustion， safety， energy， density and other performance of propellants， the glycidyl azide polymer （GAP） propellants with 5%， 10%， 15% and 18% aluminum powder were evaluated by tensile testing machine， dynamic thermomechanical analysis （DMA）， calculation program and etc. Results show that， with the replacement of 320 μm AP with 30 μm aluminum powder and the increase of aluminum powder contents， the propellant has increasing maximal tensile strength and maximal elongation， and improving interface performance. The burning rates change scarcely but the pressure indexes drop down from 0.43 to 0.40 under the pressure of 3-9 MPa. The hazard grades of propellants with 5% and 18% aluminum powder are 1.3 both. The impact and friction sensitivities of propellant with 18% aluminum powder are 0% and 44%， respectively， which are lower than the formulation with 5% aluminum powder （4% and 48%， respectively）. At last， the calculation result shows that with the increase of aluminum powder， the energy and density of propellants grow up， but the standard specific impulse levels off to moderate pace of growth.

Abstract:Slow cook-off test is one of the key tests of low vulnerability assessment for solid rocket motor. In order to study the influence of the charge size of HTPB composite propellant on the slow cook-off characteristics， slow cook-off tests and numerical simulation were carried out to compare and analyze the ignition growth laws of solid rocket motor under slow cook-off tests， with charge dimensions of Φ100 mm × 200 mm， Φ160 mm × 400 mm and Φ522 mm × 887 mm. Their corresponding ignition temperatures， ignition positions and response levels were determined. Results show that the ignition temperature of specimens of Ф100 mm×200 mm， Ф160 mm×400 mm and Ф522 mm×887 mm of solid rocket motors are 244 ℃， 172 ℃ and 155 ℃， respectively. Taking test data as inputs， the calculated ignition temperature is 250， 269， 154℃， and their corresponding calculation errors and response levelsare 2.88%， 1.17%， 0.64%， and explosion， explosion and deflagration. The calculated cloud diagram shows that the ignition position of medium and small test pieces is located in the center of charge cylinders， and the ignition position of full-scale solid motor is in the center of meat thickness of solid propellant front-end， which is a ring shape area.

Abstract:A mixture of 3，3-bis（chloromethyl）oxetane （BCMO） and 3-ethyl-3-oxetane methanol （EHO） were used to synthesis the azide hyperbranched copolymers （r-POB-m） via cationic ring-opening polymerization and azidation reaction with different monomer molar ratio （BCMO/EHO=m）. The chemical structures were characterized with Infrared spectroscopy （FT-IR）， nuclear magnetic resonance （NMR）， gel permeation chromatography （GPC） and elemental analysis. The results showed that the copolymer has high molecular weight （>4400 g·mol^-1）， high nitrogen content （up to 43%） and controllable branching structure. X-ray diffractometer （XRD）， Hacker rheometer and differential scanning calorimeter （DSC） were utilized to characterize crystallinity， viscosity and chemical compatibility respectively. When m=4， r-POB-4 is amorphous， possesses the lowest process viscosity and has good compatibility with the main components of the propellant， indicating that it is a potential candidate for plasticizer. In addition， compared with the GAPA plasticizer， the energetic thermoplastic elastomer （ETPE）-based propellant with r-POB-4 plasticizer exhibits higher elongation at break， lower consistency coefficient and lower viscous flow activation energy， suggesting that the azide hyperbranched copolymer could be applied as the plasticizer to effectively improve the mechanical properties and processing properties of the propellant.

Abstract:In order to improve the stability of α-AlH₃， acidic and organic solutions were used as modifiers to treat α-AlH₃. Through structural characterization， stability test， and mechanical sensitivity test， the properties of samples before and after the treatment were compared and analyzed. The performance on hydrogen release and the corresponding modification mechanisms were compared， and the modifier with a better stabilizing effect was obtained. The experimental results show that the proposed modification methods are effective and have a negligible effect on the hydrogen release properties of the studied samples. The weight loss associated with hydrogen release observed for the modified α-AlH₃ does not exceed by 1%， and the changes in initial temperature and peak temperature of hydrogen release are less than ±3 ℃， the maximum hydrogen release rate is not affected by more than 20%. Treatment by hydrobromic acid solution exhibited the best effect on enhancing the storage stability of α-AlH₃， and the amount of hydrogen release for the studied samples during the storage was found to decrease from 0.87% to 0.02%. It suggests that the acidic and organic solution treatment can reduce the impurities and defects on the surface of α-AlH₃ sample， and the amorphous alumina or aluminum hydroxide are likely to be formed on the surface of α-AlH₃ after the acidic solution treatment which enhances the stability of α-AlH₃. Compared with organic solutions， the acidic solution treatment shows a better ability to maintain the hydrogen release properties of α-AlH₃， enhance its storage stability， and reduce mechanical sensitivity， which can be used as a promising modifier in practical applications.

Abstract:In order to improve the adaptability of bonding agent to various energy-containing fillers and modify the interfacial bonds of solid propellants， a kind of multifunction telechelic bonding agent was designed and prepared. The bonding effectiveness was studied by molecular dynamics simulations and experimental evaluations. The results show that this bonding agent can show decent interactions with various energy-containing fillers. By altering the molecule backbone of this bonding agent， it can adapt to different adhesive systems. As compared to the three-claw bonding agent， the two-claw one has fewer branches， better diffusivity in adhesive， higher transferability toward interface， and better bonding effectiveness.

Abstract:Starting from the multi-amine， hydroxy polybutadienes （AEHTPB）， multi-cyano， amine polybutadiene （AEHTPB-CN） was synthesized through appropriate synthesis strategies. The structure of the product was characterized via FT-IR and ¹H NMR， and its physicochemical properties such as viscosity， glass-transition temperature， hydroxyl value， and amine value were also determined. The effect of AEHTPB-CN on the mechanical properties of binder system was investigated via tensile tests， and the performance of the resultant propellant with AEHTPB-CN/HTPB mixture as a binder was explored. The results showed that the cyano groups in the AEHTPB-CN molecule could form hydrogen bonds with the urethane groups， which increased the physical crosslinking density of the elastomer and effectively improved the tensile strength. The propellant level study indicated that the AEHTPB-CN had a good bonding and burning rate inhibition effect on HTPB propellant. At room temperature， compared to HTPB-based propellant， the propellant containing AEHTPB-CN （5-8wt.%） were 35.4%-43.3% larger in tensile strength， 62.0%-91.3% higher in elongation， and the burning rate was reduced by 10.5%-11.4%.

Abstract:Compared with traditional casting method， composite solid propellant manufactured by additive manufacturing （commonly known as “3D printing”） technology exhibits a series of technical advantages， such as arbitrary grain configuration without mold limitation and continuously controllable formulation as well as performance. In order to improve printing effect， printing formulation and technical parameters of composite solid propellant based on light-curing molding were studied， and the performance of printed propellant samples was evaluated. In addition， comprehensive additive manufacturing of composite solid propellant and resistive temperature sensor was achieved by integrating resistive temperature sensor into the printed propellant samples， and the resistance values of temperature sensor at different temperatures were examined. The results show that solid propellant slurry with 83% solid content displays a good pre-curing effect by adding no less than 3% ultraviolet （UV）-curable resin. The slurry with 77% or 80% solid content can be extruded through a 0.26 mm diameter needle， while solid content reaching 81% or above requires a 0.5 mm diameter needle. The printed propellant sample comprising 81% solid content possesses good dimensional stability and unconspicuous appearance defects， but computed tomography （CT） results reveal the existence of lamellar pores inside the sample. The tensile strength and elongation at break of printed propellant sample are equal to 0.94 MPa and 15.63% at 20 ℃， respectively. At 60 ℃， the tensile strength and elongation at break of sample are 0.70 MPa and 14.63%， respectively. The printed propellant owns comparable tensile strength and reduced elongation at break compared to conventional casting propellant. The bonding strength between temperature sensor and propellant is 0.21 MPa， showing favourable bonding effect. The resistance of temperature sensor varies linearly with temperature within testing temperature range （20-60 ℃）， demonstrating good temperature monitoring capability.

Abstract:Boron-based hypergolic ionic liquids， which exhibited low viscosity， short ignition delay time and low cost， were considered as the powerful candidate for conventional liquid propellants. Here， the research progress of design， synthesis and physical chemical properties on boronium-anion-based HILs were systematically reviewed. The theoretical and applied studies including thermal decomposition， hypergolic reaction， combustion mechanism and relationship between structure and performance were briefly summarized. The practical application and development tendency of boronium-anion-based HILs were also discussed．

Abstract:In order to study the uniaxial tensile mechanical properties of hydroxyl tetrade propellant under wide temperature and confining pressure， the mechanical properties of propellants under different temperatures（-50 ℃， 20 ℃ and 70 ℃）， confining pressures（0.1， 2 MPa and 8 MPa） and tensile rates（100， 1000 mm·min^-1 and 4200 mm·min^-1） experiments were conducted by using a wide-temperature-confining pressure gas test system. The internal microscopic reasons for the development of macroscopic mechanical properties were analyzed by means of scanning electron microscopy （SEM） and micron CT， with the main of revealing the influence mechanism of external load on mechanical properties of high solid content propellants. The results show that the damage of propellant is mainly attribute to“de-wetting” at room temperature and high temperature. At low temperature and atmospheric pressure， the particles suffer the "de-wetting" and ductile fracture. When the confining pressure increasing， it would change to brittle fracture of particles. Nevertheless， the elongation still increases with the increase of confining pressure. Under high confining pressure and different tensile rates， the mechanical properties of the propellant at room temperature and high temperature are similar. Because at this conditions， high temperature weakens the interaction between binder matrix and solid filler， and the “de-wetting” of the propellant are more seriously， but high confining pressure inhibits the “de-wetting” and weakens the influence of temperature. When the time-pressure equivalent superposition principle （TPSP） is used to carry out the fitting analysis of the principal curve of the maximum tensile strength， at low of -50 ℃， the relationship between the time-pressure displacement factor and the corresponding confining pressure does not conform to the standard form， and the superposition principle of TPSP has certain limitations for the use of high solid content propellants.

Abstract:The development of new combustion catalysts plays a key role in high performance propellants. Herein， the metal-organic complexes Mg（Salen） and Pb（Salen） were synthesized and characterized using X-ray diffraction， fourier transform infrared， and scanning electron microscope. Their catalytic effects on the thermal decomposition of 1，3，5，7-tetranitro-1，3，5，7-tetrazolidine （HMX） were further investigated by differential scanning calorimetry. The results indicate that the thermal decomposition of HMX is evidently enhanced by the introduction of Mg（Salen） and Pb（Salen）. Compared with HMX， the decomposition peak temperatures of HMX/Mg（Salen） and HMX/Pb（Salen） dropped by 3.0 ℃ and 34.0 ℃， and theoretical apparent activation energies decreased by 7.7 kJ·mol^-1 and 34.4 kJ·mol^-1， respectively. The catalytic decomposition mechanisms of Mg（Salen） and Pb（Salen） are also elucidated by exploring the decomposition kinetics and the reaction function models.

Abstract:High-energy-density hydrocarbon fuels are important aerospace power source， which mainly developing direction is high-energy and green， especially under the requirements of low carbon and sustainable development， the green synthesis of high-energy-density hydrocarbon fuel becomes essential. The green synthesis technology of high-energy-density hydrocarbon fuel has been reviewed. Compared with traditional synthesis of JP-10 （exo-THDCPD） and Adamantane， the advanced synthesis for fuel is improved by changing the synthesis route or using green catalysts such as solid acids and ionic liquids. Using biomass as feedstock is another strategy for green synthesis， covering terpenoids and lignocellulose-derived platform molecules such as cyclic ketones/alcohols， furanic aldehydes/alcohols， etc.， and the alternative fuels such as bio-based RJ-4（endo-THDMCPD and exo-THDMCPD） and JP-10 have been synthesized. In addition， the photocatalytic technology is used to synthesis of fuel with high tension and polycyclic structures from the perspective of green synthesis process view point， an outlook on further development of high-energy-density hydrocarbon fuel is also given. This review article will be helpful to explore and develop better approach and process for the synthesis of high-energy-density hydrocarbon fuel and upgrade for advanced aerospace vehicles.

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.