Abstract:For achieving engineering application of pentazolium anionic energetic materials， it is necessary to realize large-scale production of 3，5-dimethyl-4-hydroxyphenylpentazole （HPP） as the precursor of pentazole. The pilot synthesis techniques of HPP were performed based on accessibly lab-leveled method using 10 L and 100 L reactors for scale-up experiments. The dropping time of aqueous solutions of sodium nitrite and sodium azide， the purity and the feeding mass of 3，5-dimethyl-4-hydroxyaniline hydrochloride （DAC）， on the production of HPP were investigated. Results indicate that HPP production increases with the increasing of the total dropping time of sodium nitrite aqueous solution and sodium azide aqueous solution. After a certain value， the production of HPP remains. The purity of DAC affects the HPP production significantly that the production increases with the increasing of purity. With the scale up， HPP production increases along with the reducing of production ratio. With the feeding mass of DAC reached to 6 kg， a batch of product increased to 11.5 kg as well as the production rate decreased to 1.91.

Abstract:In order to synthesize high-purity 3，5-diamino-2，4，6-trinitrochlorobenzene （DATNCB）， the synthesis route screening and process optimization of DATNCB were studied with 1，3，5-trichloro-2，4，6-trinitrobenzene （TCTNB） or picric acid （2） as raw materials， respectively. The structure of the product was characterized by IR， NMR and MS； the thermal behavior of DATNCB was studied by DSC-TG； the purity of DATNCB was analyzed by HPLC. The results show that： the best synthetic route of DATNCB is starting from picric acid， then by via VNS amination followed by chlorination. The total yield is 39.2%. The highest yield of 3，5-diamino-2，4，6-trinitrophenol （3） was 74.8% when VNS amination temperature was 90 ℃ and post-treatment pH value was 3； the highest yield of DATNCB was 52.4% when phosphorus oxychloride/N，N-dimethylaniline was used as the chlorination reagent， the reaction temperature was 80 ℃ and the reaction time was 10 h. The melting point of DATNCB is 224.0 ℃. There is only one weight loss stage in the range of 179.7-270.9 ℃ and the weight loss rate is 91.6%； the peak decomposition temperature is 256.1 ℃. The purity of DATNCB reach 97.09% without further purification， and up to 99.8% after recrystallization with ethyl acetate/petroleum.

Abstract:To improve the compatibility of dihydroxylammonium 5，5′-bitetrazole-1，1′-diolate（TKX-50） with nitrocellulose（NC）， silane coupling agent （KH550） was used as the coating agent and three TKX-50/KH550 composites （TK1， TK2， TK3） were obtained.The morphology， structure and thermal stability of the composites were studied by using scanning electron microscopy （SEM）， Fourier infrared spectroscopy （FTIR）， and differential scanning calorimetry （DSC）. Accelerating rate calorimeter （ARC） and DSC were used to examine the compatibility of TKX-50/KH550 composites with NC. The results show that the apparent activation energy of thermal decomposition of the prepared TKX-50/KH550 composites are 190.03， 195.82 and 194.42 kJ·mol^-1 respectively higher than that of TKX-50 （138.86 kJ·mol^-1）， indicating the thermal stability of TKX-50 is improved by KH550 coating. In adiabatic conditions， the initial thermal decomposition temperature of the mixtures of TKX-50/KH550 composites and NC are 14.93， 18.18 and 17.90 ℃ respectively higher than that of TKX-50 and NC. After coated with KH550， the compatibility of TKX-50 and NC is improved， and the compatibility level of TKX-50/KH550 composites and NC is raised from Level 3 to Level 2.

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:In order to investigate the infrared extinction performance of nickel-plated graphene and explore the best formulation， nickel-plated graphene was prepared by the redox and chemical plating methods. The influence of various factors on the extinction performance of nickel-plated graphene was analyzed by designed orthogonal experiments with the infrared decay rate as the evaluation index， and the optimal formulation was determined. The infrared transmittance of nickel-plated graphene was measured in a smoke-screen chamber test. The average mass extinction coefficient of nickel-plated graphene was calculated by linear fitting according to the “Lambert-Beer” law. The results showed that the optimal process parameters for the preparation of nickel-plated graphene were： c（NiSO₄·6H₂O）=20 g·L^-1， c（NaH₂PO₂·H₂O）=24 g·L^-1， c（C₆H₅Na₃O₇·2H₂O）=10 g·L^-1， c（NH₄Cl）=30 g·L^-1， pH=8-9， and plating temperature of 65 ℃. The nickel-plated graphene prepared under the optimal conditions exhibited good infrared extinction in both mid- and far-infrared wavelengths. The average mass extinction coefficients of the nickel-plated graphene in the infrared bands of 3-5 μm and 8-14 μm were 2.38 m²·g^-1 and 2.19 m²·g^-1， respectively. Compared with the modified graphene， the average mass extinction coefficients of nickel-plated graphene in the mid-infrared bands were improved by 30% and 35%， respectively， which have broader application prospects.

Abstract:In order to obtain the gun propellant with progressive combustion characteristics and corresponding control methods at multi-dimensions， according to the principle of internal ballistics， the concept of the pre-grooved gun propellant was proposed. The physical and mathematical models of the combustion process were established， and the Г-Ψ relationship was deduced. The principle of progressive combustion and multi-dimensional control methods were demonstrated. The method used for the preparation of the pre-grooved gun propellant was described. The pre-grooved gun propellant structured with a center opening was designed， and propellants having different groove numbers and various length/outside diameter ratios were prepared. In order to compare with the seven-hole propellants with and without coating ， the combustion performance of the pre-grooved gun propellant was characterized by the closed bomb test. The experimental results show that the pre-grooved gun propellant has the progressive combustion behavior as theoretically designed. Compared with the seven-hole propellant， the combustion enhancement value（ΔL） value obtained by using this method is increased by 2 folds， the progressive combustion characteristic（L_m/L₀） value is increased by 24.4%， and the relative pressure at the split point（B_m） value is increased by 32.4%. The progressive combustion feature exhibited by pre-grooved gun propellants outperforms that of the seven-hole propellant， and was comparable to that of the coated seven-hole propellant.

Abstract:The design efficiency of energetic compounds depends on many factors， such as the proportion of potential high performance samples in the screening space and the accurate prediction method of key properties. In this study， we proposed a scheme to improve the overall performance of virtual screening space by pre-screening molecular skeletons， and a method combining high-throughput computing and deep learning is applied to the design of energetic compounds. It was found that there is a moderate positive correlation between crystal density molecular skeleton density of energetic molecules， and the overall density of virtual screening space can be effectively improved by pre-screening high-density molecular skeletons. Based on the density data-set of energetic crystals collected from the crystallography database CCDC， a new density prediction model of energetic crystals was obtained via deep learning， with reliable accuracy and generalization. We took fused-ring energetic molecules as the research object， obtained high-density fused-ring skeletons through skeleton pre-screening， and then the virtual screening space composed of potential high-density molecules was constructed through fragment docking. The formation enthalpy， detonation performance and chemical stability were predicted by quantum chemical calculation and the equation of state of detonation products. Finally， 6 novel energetic molecules with energy level better than RDX and stability better than TNT were selected by performance ranking. This study shows that the overall performance of virtual screening space can be effectively improved by pre-screening molecular skeletons， and on this basis， high-throughput computing and deep learning can be used to achieve efficient design of energetic molecules.

Abstract:The preparations of high-energy pentazolate salts is a research hotspot in the field of energetic materials. The preparation of pentazolate anion is a key step in the preparations of high-energy pentazolate salts. However， as the important precursors for pentazolate anion， the stability of existing arylpentazoles is generally not high. In order to develop new precursors of pentazolate anion with better properties， 18 substituted derivatives of PyN₅ with the electron-withdrawing and electron-donating groups， i.e.， R-PyN₅ （R=－NO₂， －CN， －NF₂， －OH， －OMe， －N（Me）₂）， were designed and studied by using the density functional theory method. The bond dissociation energy（E_BD）， and the activation energy（E_a1） of the bridged C—N bond and the activation energy（E_a2） of the cracking of the N₅ ring were calculated， and the stability of the bridged C—N bond and pentazolate ring were discussed. E_a1 of all molecules is smaller than E_BD， indicating that the breakage of the bridged C—N bond is more likely to follow the path 2 rather than path 1. E_a2 of all molecules is smaller than E_a1， indicating that the stability of the N₅ ring is the key factor to determine the stability of the arylpentazoles. Compared with PhN₅， —N（Me）₂ meta-substituted and bis-substituted compounds have lower E_a1， higher E_a2 and lower ΔE （E_a2－E_a1）. Therefore，—N（Me）₂ meta-substituted and bis-substituted compounds are the most potential precursors of N₅ˉ ion for replacing PhN₅.

Abstract:To study the fundamental physical properties and intermolecular interaction of energetic materials under the loading temperature， the first-principle calculation was performed combined with zero-point energy and temperature effect corrections. The accuracy of lattice parameters at experiment temperature （173 K） can be significantly improved， and the deviations between the calculated lattice parameters and available experimental data are within 1%. The unit cell volume change with temperature is relatively reasonable compared with the experimental value at 0-500 K， and their deviation is mainly from the lack of interactions between phonons. Furthermore， the basic thermodynamic properties such as heat capacity， entropy and bulk modulus were predicted， and the results indicate that the lattice parameters and thermal expansion coefficient of FOX-7 have strong anisotropy in 0-500 K. Especially， the thermal expansion coefficient of interlayer direction is higher than that of inner layer direction， which is closely related to the molecular configuration and stacking. Importantly， when the temperature reaches 200 K， the shrinkage of thermal expansion coefficient of FOX-7 is related to the rotation of NO₂ group. The NO₂ group would regulate the intermolecular interaction by changing the dihedral angle with the molecular plane， thereby triggering potential phase transformation of FOX-7. In addition， the bulk modulus under the adiabatic conditions is consistent with the experimental values reasonably， and the evolution of adiabatic bulk modulus with temperature reflects the softening behavior of FOX-7 at the finite temperature. With the increase of temperature， the calculated heat capacity and entropy increase gradually， showing obvious numerical differences under the constant volume and pressure due to the anharmonic effect.

Abstract:To explore the effect of magnetic field on the explosion characteristics of premixed gas and its mechanism， taking ethylene as an example， the influence law of magnetic field on the explosion characteristics of premixed ethylene/air was experimentally studied. The chain reaction process of ethylene explosion was numerically simulated. The influence of magnetic field force on key free radicals was theoretically analyzed. The transient pressure of ethylene explosion was measured by pressure sensors and the flame propagation velocities were measured by explosion velocity apparatus. Results show that under the maximum magnetic field intensity of 3300 Gs， the maximum explosion pressure of 6.5% ethylene decreased by 18.18% and the explosion pressure rise rate reduced by 17.33%. Along the flame propagation direction， the magnetic field firstly promoted and then suppressed the flame propagation speed of ethylene explosion， in which the suppression effect was greater than the promotion effect. The ethylene explosion was simulated by Chemkin-pro software， and the key free radicals in ethylene explosion were obtained. Different types of free radicals have different intensities of magnetization. Force of free radical under magnetic field is proportional to magnetization of free radical. The magnetic field force has a greater impact on free radicals with high magnetization， and no impact on anti-magnetic substances. Different types of free radicals appear stratification phenomenon under magnetic field. The collisions between different types of free radicals were reduced， and the elementary reaction rate was decreased， which suppressed the ethylene explosion.

Abstract:In order to study the law of crack initiation， growth and evolution of explosives under weak load. The numerical simulation of crack initiation and evolution of explosives was carried out by using the material model considering the phenomena of tensile and compressive anisotropy with strain rate effect. The numerical results are in good agreement with the test data， and the applicability of the numerical model is verified. The typical characteristic images of crack generation and evolution of explosives were obtained through a series of numerical simulations， and the effects of initial crack size， loading rate and loading position on the crack propagation process of explosives were also analyzed， which can provide reference for the analysis of damage and fracture process as well as the dynamic response of explosives.

Abstract:In order to evaluate the output energy characteristics of the ignition cap， it was proposed to conduct the ignition cap firing test in an open burster container and use a high-speed mid-wave infrared thermal imager to capture the whole process of the ignition cap firing. Since it was difficult to measure the output flame temperature of ignition cap， the drop weight instrument was used to give the corresponding initial firing energy of ignition cap. At the same time， the infrared thermal imager was triggered to collect flame information. The experimental data and infrared images of ignition cap under three test conditions of normal（25 ℃）， heated（50 ℃） and frozen（-49 ℃） temperature were processed. The results show that the output flame maximum temperature can reach up to 1204 ℃， and the flame duration is about 3-4 ms. The whole process of the flame with time can be divided into four stages： firing， diffusion， forming and dissipation， and the temperature in the top and bottom area of flame is much higher than in other areas. Through calculation and software correction， the measurement error of this test is below 6.6%， which can prove the reliability of the method and provide a new way for evaluating the output energy characteristics of ignition cap.

Abstract:In order to accurately understand the mechanical characteristic of 1，3，5-triamino-2，4，6-trinitrobenzene （TATB）-based polymer bonded explosive （PBX） under compressive loading， an in-situ measurement technique based on micro X-ray computed tomography （μ-CT） imaging and digital volume correlation （DVC） was proposed. The in-situ scanning for TATB based PBX sample under uniaxial compression was carried out by using μ-CT and the three-dimensional digital volume images of the samples under different loading were obtained. Then， two sets of digital volume images obtained before and after loading respectively were analyzed by using local DVC method based on the Inverse Compositional Gauss-Newton （IC-GN） algorithm and the three-dimensional internal displacement and strain fields with sub-voxel accuracy were obtained. The internal stress fields were finally rebuilt according to the elastic Hook’s rule. The results show that the generation and development process of the strain localization zone inside the sample could be directly revealed based on the internal measurement technique combining DVC and μ-CT. In addition， the Zero-mean Normalized Cross-Correlation （ZNCC） coefficients are commonly lower at the microcracks. In practical applications， the location of sub-voxel microcracks could be identified by the distribution of ZNCC coefficients.

Abstract:To study the relationship between shear band and brittle-ductile transition behavior of typical polymer bonded explosives（PBX） under the influence of temperature， the mechanical response of PBX at 323-363 K was tested by using DIC digital image technology， in-depth analysis of shear band evolution law and failure mode. At the same time， the brittle-ductile transition mechanism of PBX under temperature effect was analyzed based on the theoretical model of crack slip. And the critical conditions of wing crack development and plastic slip area were obtained by considering the effect of temperature. The results showed that at 323-363 K， the variation of the shear band width of the PBX depended on the competition mechanism of dilation and shrinkage. There are four main mechanisms： Ⅰ. Dilatation and shrinkage reach equilibrium； Ⅱ. Shrinkage is dominant； Ⅲ. Dilatation is the main controlling factor； Ⅳ. Dilatation dominates intermittently. Combined with the principle of Griffith energy release， it is found that the shear strength， cohesion and fracture toughness of the specimen are the key controlling factors of the brittle-ductile transition. Under the condition， the judging basis of PBX brittle-ductile transition was obtained. When the condition of wing crack instability was met， the macroscopic failure mode tends to split failure； and when the critical condition of the plastic slip area was achieved， the multiple slip zones are connected to each other to form a plastic slip surface， and the macroscopic failure mode was dominated by the ductile fracture of shear crack slip.