Abstract:

Abstract:4H-［1，2，3］Triazolo［4，5-c］［1，2，5］oxadiazole 5-oxide （TODO）hydroxylamine salts and TODO amine salts were synthesized via nitration， cyclization and salt-forming reaction using 3，4-diaminofuran. At the same time， an energetic eutectic（HATODO/ATODO cocrystal） was synthesized by TODO hydroxylamine salts（NH₃OH⁺C₂H₅O^-）and TODO amine salts（NH₄⁺C₂H₅O^-）as raw materials. Its structure was characterized by SXRD，FT-IR and NMR， and the thermal decomposition was studied by TG-DSC. The mechanical sensitivities were tested according to the GJB772A-97 method and the detonation performance was calculated. Results show that the structure of the HATODO/ATODO cocrystal belongs to the monoclinic crystal system， the P2₁/c space group， a=8.5202（3） Å， b=10.3870（4） Å，c=13.4481（4）Å， α=90°， β=102.0510（10）， γ=90°， V=1163.92（7） ų， Z=4.TODO hydroxylamine salts initial decomposition temperature is about 147.9 ℃， TODO amine salts initial decomposition temperature was about 181.3 ℃， whereas the initial decomposition temperature of energetic HATODO/ATODO cocrystal is about 151.2 ℃. The sensitivities of HATODO/ATODO cocrystal is comparable to ADN. The calculated detonation velocity and pressure of HATODO/ATODO cocrystal is 8462 m·s^-1 and 32.07 GPa.

Abstract:In order to study the effect of Mg（BH₄）₂ on thermal stability of nitramine explosives， the thermal decomposition properties of Mg（BH₄）₂/RDX， Mg（BH₄）₂/HMX and Mg（BH₄）₂/CL-20 were investigated by differential scanning calorimetry （DSC）. Thermal decomposition products of three mixtures were analyzed by Thermogravimetric analysis-Fourier transform infrared spectroscopy coupling technique （TG-FTIR）. Results show that Mg（BH₄）₂ has different effects on the thermal decomposition and apparent activation energy of three kinds of nitramine explosives， in which the heat release of RDX and CL-20 increases by 14.7% and 32.1% respectively， and but that of HMX decreases by 45.8%. The apparent activation energies of RDX decreases by 15.8 kJ·mol^-1， while that of HMX and CL-20 increases by 19.7 kJ·mol^-1 and 11.5 kJ·mol^-1， respectively. The thermal decomposition products of three kinds of nitramine explosives are the same （mainly NO₂ and N₂O） whether there is Mg（BH₄）₂ or not. Mg（BH₄）₂ has little effects on the thermal decomposition products and the contents of HMX and RDX， but caused the apparent water peak of CL-20. The concentration ratio of NO₂ to N₂O decreased by 89.2%， indicating that Mg（BH₄）₂ promotes the thermal decomposition of RDX and CL-20， and inhibits the thermal decomposition of HMX.

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:The effect of crosslinking catalyst Copper 2，4-glutarate-cyclooctadiene complex dosage on the properties of polytriazole-crosslinked solid elastomer was studied. Propargyl-terminated ethylene oxide-tetrahydrofuran copolymer （PTPET）was used as an adhesive and polyazide compound as an curing agent， a series of polytriazole-crosslinked solid elastomers S1-S4 were prepared by adding crosslinked catalysts of 0.01%， 0.02%， 0.05% and 0.10%. The chemical structure， thermal stability， mechanical properties and network structure of polytriazole-crosslinked solid elastomers were characterized by FTIR， TG， equilibrium swelling method and DMA. It was found that PTPET elastomer is more stable than PET elastomer， the dosage of the catalyst did not influence the thermal stability of the elastomer， and the decomposition temperature for all samples is at 405 ℃. The elastomer S2 with 0.02% crosslinking catalyst has the most perfect network structure and the best mechanical properties， and the glass transition temperature is -67.4 ℃.

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 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 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: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 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: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 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 bonding interface of solid rocket motor will be damaged due to the creep effect from long-term vertical storage. This paper reviews the relevant research progress from three perspectives as the influencing factors of interface damage under creep condition， interface damage test， and numerical simulation of interface damage. It emphasizes that the cumulative damage of bonding interface under creep condition cannot be ignored， summarizes the shortcomings of test and numerical simulation research， and makes a prospect. According to the findings， the most difficult aspect of experimental research is devising reasonable tests and selecting variables that effectively characterize the timeliness of damage. The focus of numerical simulation research is to build a creep interface cohesion model with damage， in order to provide some reference for the performance evaluation of bonding interface under storage conditions.