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Abstract:To obtain the influence rule of different crystallization conditions on the quality and morphology of 1, 1-diamino-2, 2-dinitroethylene(FOX-7)crystals and realize the control of its crystal morphology, the solubility of FOX-7 in dimethyl sulfox- ide(DMSO), water(H₂O)and its binary mixed solvent in the range of 20-95 ℃ and the metastable zone width of binary sol- vent mixtures DMSO / H₂O=2:1(in volume ratio) were measured by turbidimetric method using a CrystalSCAN multi-channel crystallizer. The crystal morphology of FOX-7 under various crystallization conditions was investigated by cooling method, and the mechanical sensitivity and thermal performance of FOX-7 were tested. Results show that the solubility of FOX-7 increases with the increase of temperature and DMSO content in binary mixed solvent. The width of metastable zone becomes narrower with the increase of temperature, decrease of cooling rate and increase of stirring rate. In the process of cooling crystallization, the crystal morphology of FOX-7 is significantly affected by solvent ratio, starting temperature and cooling rate of crystallization. In the range of 50-80 ℃, at the cooling rate of higher than 2 ℃ ·min^-1, the cube-like high-quality FOX-7 crystal with almost the same aspect ratio and regular morphology can be obtained, and particle size is controllable in the range of 20-150 μm. At the same time, the better crystal quality of FOX-7, the higher crystal density and the higher thermal decomposition temperature. The impact sensitivity of FOX-7 is lower and small affected by the crystal morphology, but the friction sensitivity is greatly affected by parti- cle morphology, the frictional sensitivity value of columnar-like crystals is the smallest and that of plate-like crystals is the largest.

Abstract:Aiming at the problem of leading to explosive structure damage, performance reduction and safety descending due to the polymorphic transformation of hexanitrohexaazaisowurtzitane(HNIW)was easily occurred in complex environment, the effects of additives on the heat-induced polymorphic transformation(PT)behavior of ε-HNIW in composite explosives were stud- ied by the in-situ X-ray powder diffraction(in-situ XRD)technology. The change rule of heat-induced PT rate of HNIW in com - posite explosives with temperature were calculated and obtained by means of in-situ XRD non-standard quantitative phase analy - sis. The heat-induced PT characteristic parameters and PT rules of HNIW in composite explosives were analyzed and obtained. It was proposed to divide the additive into three species, including promote PT system, intermediate PT system and suppress PT system. Results show that the additives used in promote PT system have the tittle dissolution on HNIW, the interface micro-disso- lution layers were formed on the HNIW crystal surfaces, which makes the heat- induced PT route change from solid - solid PT to solid -solution -solid PT and reduces the PT activity barrier energy, thus the heat-induced PT of ε→γ is obviously promoted. The additives used in the suppress and intermediate PT system have strong coating effect on the HNIW crystals. The preliminary heat- induced PT temperature is improved through altering the thermal transfer mode and surface heat insulation, and the inhibition ef- fect on the heat-induced PT of HNIW is realized to a certain extent.

Abstract:To further evaluate the thermal stability of bis (nitroguanidine) methane (BNGM) and explore its potential application as energetic material, the thermal behavior, specific heat capacity, adiabatic time-to-explosion and impact sensitivity of BNGM were studied by differential scanning calorimetry (DSC), micro-DSC, thermogravimetry /differential thermogravimetry (TG/DTG) and impact experiment. Results show that the thermal behavior of BNGM can be divided into two exothermic decomposition processes. The peak temperatures of the two decomposition processes at a heating rate of 10 ℃·min^-1 are 208.1 ℃ and 292.5 ℃, respectively. Its self-accelerating decomposition temperature (T_SADT) and critical temperature of thermal explosion (T_b) are 189.6 ℃ and 190.9 ℃, respectively. Its molar heat capacity at 298.15 K is 251.9 J·mol^-1·K^-1. Adiabatic time-to-explosion is estimated to be about 280 s. BNGM has a low impact sensitivity, which is higher than 23.5 J. The thermal stability of BNGM is good.

Abstract:A highly active 1, 2‐bis(trimethylsilyl)diimine(BSD)was synthesized using lithium tris(trimethylsilyl)hydrazine and p‐toluenesulfonylazide as starting materials. 1, 1, 4, 4‐Tetra(trimethylsilyl)tetrazene(TST)was then synthesized further via dimerization reaction of 1, 2‐bis(trimethylsilyl)diimine. The total yield was about 5.0%. The structures of BSD and TST were characterized by means of NMR, FT‐IR, UV‐Vis absorption spectra and element analyses. The mechanism of the dimerization reaction was then studied by quantum chemical calculation method. Results show that BSD firstly is isomerized to 1, 1‐bis (trimethylsilyl)diimine intermediate, and then two 1, 1‐bis(trimethylsilyl)diimine intermediates interact to form TST. Two processes require up to 103.0 kJ·mol^-1 and 114.3 kJ·mol^-1 activation energies, respectively. The theoretical results are consistent with the experimental phenomenon that high temperature condition is favorable for the conversion of BSD to TST.

Abstract:To increase the anti-oxidized properties of the micron-sized aluminum powder with shell-core structure, four kinds of micron-sized aluminum powder with different granularity(2.51, 5.20, 13.35, 24.02 μm)were slowly heated to 650 ℃ by a synchronous thermal analyzer at a heating rate of 20 ℃·min^-1 in the oxygen atmosphere to realize the enhancement of the alumina shell of micron-sized aluminum powder. The thermal response behavior of micron-sized aluminum powder before and after treating in slowly heating condition was investigated by the thermogravimetric analysis technique. The oxidation products at different stages were analyzed by scanning electron microscopy(SEM)and X-ray diffraction(XRD). Results show that after the the alumina shell is strengthened, the alumina shell of the micron-sized aluminum powder changes from amorphous state to γ state and the compactness increases. At the same time, the thickness of alumina shell of four kinds of micron-sized aluminum powder samples increases to 3.3-5.9 times of the original thickness. Under the condition of maintaining the high activity of micron-sized aluminum powder, the phase change and thickening of the alumina shell make the aluminum powder do not oxidize in the oxidative environment during slowly heating process below 1350 ℃, still maintain higher activity and increase the antioxidized properties greatly. The mechanism of slow oxidation of the micron-sized aluminum powder is changed from"shell broken"reaction mechanism with weight gain in stages to oxidation inhibition mechanism after the the alumina shell is strengthened.

Abstract:To investigate the reaction process of aluminized explosives, the rapid reaction in RDX based aluminized explosive powder was stimulated by means of laser ablation, and the emission spectrum distribution in the reaction process was monitored in real time, and the transient temperature of the reaction region was calculated based on the molecular spectrum of AlO. Results show that there are obvious differences in the spectrum distribution and reaction behavior between the early and late stages of aluminized explosives. The early stage is mainly the plasma cooling and the dissipation process of RDX and air formed under la ser ablation.The emission spectrum from the O/H/N element is dominant in this stage, and its spectral line height is exponentially attenuated. The oxidation reaction of Al element is dominant in the late stage, and the reaction has a certain self-sustaining. The spectra of the corresponding intermediates AlO molecules have typical characteristics of persistent and non-monotonic changes. The trend of temperature change is closely related to the development trend of the whole reaction. The temperature of the severe reaction in the early stage is higher and decreases as the reaction continues to weaken.

Abstract:To explore the influence rule of octogen (HMX) solid content, system temperature, HMX particle size, HMX particle gradation and functional additives etc.on the rheological properties of 2, 4-dinitroanisole (DNAN)/HMX suspensions, the apparent viscosity of DNAN/HMX suspensions under different material state conditions was investigated by a digital viscometer.Results show that the suspension presents Newtonian fluid characteristics when the solid content is 3%.Apparent viscosity of the suspension can be described with Ostwald-deWaele model when the HMX solid content is 12%-30%, and the value of nonNewton index n is decreased from 0.842 to 0.374.The influence of temperture on the apparent viscosity can be described by the Arrhenius equation when the temperture is in the range of 95-116℃, and the activation energy E_a increases from 25.97 kJ·mol^-1 to 30.17 kJ·mol^-1.The apparent viscosity decrases as the particle size increases.When the particle gradation ratio of 999.5 μm particle size to 132.6 μm is 2:1, the apparent viscosity reaches the minimum and the solid content is up to 80%.Functional additives N-methyl-4-nitroaniline (MNA) and tri (β chloroethyl) phosphate (CEF) make the apparent viscosity of the suspensions decrease, while dehydrated sorbitol monostearate polyoxyethylene ether (Tween 60), microcrystalline wax-80(MV80), cellulose acetate butyrate (CAB), and thermoplastic polyurethane-5720(TPU 5720) make the the apparent viscosity of the suspensions increase.

Abstract:To study the underwater explosion process of hexanitrohexaazaisowurtzitane (CL-20)-based polymer bonded explosives (PBXs) with and without aluminum powders, two kinds of explosives with aluminum contents of 0 and 15% were prepared.An underwater explosion experimental device was designed, and the images of pressure histories, bubble periods and bubble pulse of shock wave were obtained.The shock wave energy, bubble energy and total underwater explosion energy of two kinds of explosives were calculated The underwater explosion process was well-simulated by the AUTODYN software.Results show that when aluminum content increases from 0 to 15%, the total underwater explosion energy increases from 1.4 times TNT equivalent to 1.7 times TNT equivalent.In the process of bubble pulsation, the light is produced in the bubble of CL-20 based aluminized explosive when the time is from 49.5 ms to 49.8 ms.The peak pressure of aluminized explosives and nonaluminized explosives are 15.16 MPa and 15.51 MPa.The bubble of secondary pressure wave are 2.25 MPa and 2.35 MPa, 50.20 ms and 46.76 ms for the bubble periods.The maximum bubble radius are 67.87 cm and 60.27 cm.The simulation results of aluminized explosives and non-aluminized explosives overpressure are 14.90 MPa and 15.14 MPa.The bubble of secondary pressure wave are 2.16 MPa and 2.27 MPa, bubble period for 49.32 ms and 45.90 ms, 66.32 cm and 58.89 cm for the maximum bubble radius.The shock wave and bubble parameters obtained by calculation are in good agreement with experimental results.

Abstract:To evaluate the vulnerability of explosive charge, a roast bomb structure with different sealing conditions (state 1:the end cover is 2 steel plugs and 2 pressure membranes.state 2:the end cover is 4 pressure membranes) and thermal conductivity of coating layer (state 3:the end cover is 4 pressure membranes, hollow glass microspheres (HGMs) partially instead of the silicone rubber in the coating layer) was designed.The response characteristics of octogen (HMX)-based aluminized explosive (HAE) under the condition of external fire with liquid fuel were studied.Results show that the pressure membrane of end cover and HGMs coating layer can achieve the purpose of reducing the vulnerability of explosive charge.The effect of pressure relief area and thermal conductivity of coating layer on the fast cook-off characteristics of explosive charge is different.The response level of roast bomb of decreasing the thermal conductivity of coating layer (projectile body is complete, charge and end cover sprayed, and the charge is not steady combustion) is lower than that of roast bomb with the change of sealing conditions (projectile body is complete, the charge is steady combustion).When the ratio of pressure relief area to the surface area of HAE charge is greater than 0.015, the explosive charge reveals in steady combustion state.When the content of the HGMs exceeds 5%, the end cover of roast bomb and explosive charge are sprayed out, and the structure of the explosive charge is integrated and the combustion state does not occur.

Abstract:The stress-strain curves of polymer bonded explosives (PBXs) are generally nonlinear and poorly unsymmetric.The construction of constitutive model is a difficult problem in the research of mechanical properties of explosives.In this paper, tak-ing PBX-901 as the research object, the uniaxial tension and compression experiments at different temperatures were carried out firstly.Then, a four-parameter and a two-parameter constitutive model were respectively established and the relative undeter-mined parameters were determined based on the Boltzmann function according to S-shaped stress-strain curves obtained.The parameters of two-parameter constitutive model can be determined only using analytical solution including the compression strength and initial segment elastic modulus, and its description error is less than 5%, while the parameters of the four-parameter model though parameter fitting.Finally the second development module of ANSYS software was adopted to realize the numerical application of the two -parameter constitutive model for the Brazilian disk tests.Through comparison with the experimental re-sults, the relative error of numerical results only is about 5.11%.The description precision of the nonlinear two-parameter consti-tutive model established in the text is satisfactory and it meets the needs of engineering

Abstract:The synthetic methods of five classes of azole-and azine-based nitrogen-rich energetic compounds with oxygen (including nitroxide, hydroxyl oxygen, ligand oxygen, carbonyl oxygen and composite oxygen) in recent years were summarized, in which, studies on the synthesis of nitrogen-rich compounds with nitroxide and composite oxygen are the most active.Considering that the following points are the focus of future research.Studies on the scale-up synthesis and practical application for the excellent nitrogen-rich energetic compounds containing oxygen with simple synthetic process and readily available raw materials are carried out.The process improvement for the excellent nitrogen-rich energetic compounds containing oxygen with high synthesis difficulty and high cost is carried out.When designing a novel nitrogen-rich energetic compound containing oxygen, the introduction of azo group and fused ring should be considered.49 references are attached.

Abstract:To study the mechanical properties and reaction characteristics of aluminum/titanium hydride/polytetrafluoroethylene (Al/TiH₂/PTFE) reaction materials, four kinds of specimens with different content of TiH₂(0%, 5%, 10%, 20%) were prepared by cold isostatic pressing and vacuum sintering process.At the same time, TiH₂/PTFE specimens without active Al particles were also prepared as the control group, then all the specimens were subjected to quasi-static compression experiments. The stress-strain curves and the reaction rate data of the specimens with different TiH₂ content were obtained, and the reaction phenomena of the specimens were recorded.Moreover, the phase analyses of reaction residues were performed by XRD and the reaction mechanism of the materials was discussed.Results show that the content of TiH₂ has a significant effect on the material properties and the reaction rate.When the content of TiH₂ is 5%, the reaction rate is 90% and the material strength reaches the maximum value of 108 MPa, which is 15.1% higher than that of Al/PTFE type material.When the content of TiH₂ and Al is the same, the reinforcing effect of TiH₂ particles on PTFE matrix is greater than that of Al particles.Compared with Al/PTFE material, a special combustion flaming phenomenon appears in the reaction of TiH₂-containing samples, and the phenomenon gradually is obvious with the increasing of TiH₂ content.The high temperature of the crack tip of materials causes the reaction between Al and PTFE, which makes TiH₂ activate, hydrogen release and TiC generate, the energy of TiH₂ fully release and the purpose of using as a high-energy additive reach.

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