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:In order to study the aging migration process and influencing factors of deterred DB propellants， a theoretical model on the deterrent distribution and the change of combustion performance caused by aging migration was established based on the normal distribution characteristics of deterrent and the inference of Fickian second diffusion law. Six kinds of propellants with different contents of nitroglycerin（NG） and dibutyl phthalate（DBP） were treated by accelerated aging experiments at different temperatures and times， and the combustion performances of propellants were tested by closed bomb vessel. The kinetic process and thermodynamic influence of aging migration for propellants were analyzed. Theoretical analysis shows that the integral value growth rate of the dynamic vivacity for deterred spherical propellants presents a good linear growth relationship with aging time. The results of the closed bomb vessel show that the percentage increase of the maximum dynamic activity for the six propellants after accelerated aging also gives a good linear relationship with aging time， which is consistent with the theoretical research results. The established thermodynamic equation of aging migration for deterred propellants is basically consistent with the experimental results， and the logarithm of migration driving factor and the reciprocal of temperature present an obvious linear negative correlation. When the total content of NG and DBP in propellants is greater than 15%， the migration driving factor is more susceptible to the influence of temperature， leading to migration invalidation. When the total content of NG and DBP is less than 15%， the invalidation rate caused by deterrent migration is relatively slow， which is more conducive to the use and shooting safety after the storage of propellants.

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:The effects of four typical stabilizers （DPA， C2， AKⅡ， MNA） on the thermal decomposition behavior of nitrocellulose， the thermal decomposition parameters of nitrocellulose samples under different conditions are obtained by DTA， DSC and ARC. The results of non-isothermal calorimetry show that the critical temperature of thermal explosion of nitrocellulose increases by 0.06， 0.82， 1.00 and 1.56 K， respectively， after adding four typical stabilizers. The adiabatic thermal test show that the stabilizers have limited effect on the initial temperature rise rate and pressure of nitrocellulose at the initial stage， but reduces the maximum temperature rise rate of nitrocellulose by 0.39， 0.64， 0.70 and 0.65 K·min^-1. The effects of thermal history on the thermal decomposition of nitrocellulose samples are investigated by DSC interruption and re-scanning method. The results show that four typical stabilizers have good thermal stability. Although the initial thermal decomposition of nitrocellulose is less affected by stabilizers， but with the progress of thermal decomposition reaction， the severe autocatalytic decomposition caused by nitrocellulose thermal decomposition products could be alleviated by rapid reaction with stabilizers， and the influence of thermal history on the thermal decomposition of nitrocellulose could be reduced. N-methyl-4-nitroaniline has the most obvious inhibition effect on the autocatalytic decomposition of nitrocellulose.

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: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: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 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 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 understand the constant volume combustion performance of single charge and the mixed charge（MC+B） of 37-hole nitroguanidine propellant， a lace-shaped 37-hole triguanidine-15 propellant is used as the main charge （MC）， and the lace-shaped 19-hole triguanidine-15 coated propellant is used as the auxiliary charge（B）. The packing density is 0.20 g·cm^-3， under 50 ℃， 20 ℃， -40 ℃， the effect of arc thickness on the combustion performance of single main charge and the effect of the mixing mass ratios on the combustion performance of the mixed charge （MC+B） were studied through constant volume closed-bomb test. The results show that the lower the temperature， the more obvious the erosion and combustion phenomenon of the 37-hole single main charge. At the same temperature， the greater the arc thickness of the main charge， the less obvious the erosion and combustion phenomenon， the stronger the progressive combustion， and the better the combustion performance. The higher the temperature， the greater the value of ΔL， L_m/L₀ of the mixed charge of the same mixing ratio， the better the progressive combustion； At the same temperature， the progressive combustion of the mixed charge is stronger than that of the single main charge， and as the ratio of the coated propellant increases， the erosion combustion peak gradually decreases， indicating that the addition of the coated propellant significantly improves the progressive combustion and reduces the erosion combustion peak of the mixed charge， and at 50 ℃， 20 ℃， -40 ℃， the mixing ratio of the mixed charge to obtain better progressive combustion is 7∶3.