Abstract:Different types of equipments are installed in the warship cabins according to their functions. However, present research of cabin internal blast damage mainly focuses on the effects of damage elements on vacant cabin, and the effects of the equipments installed in the cabin are seldomly considered. By using the finite element software LS-DYNA, three types of rib-reinforced cabin models, including the one installed with no equipment, the one with one equipment, and the one with two equipments, were built. The analysis of the damage of cabin structure and equipments caused by the internal blast of warhead charge and the comparative analysis of the influence of equipments on the damage effect were conducted. The comparative analysis results show that, because of the obstruction of the equipments, different arrangements of equipments affect the internal flow field distribution of shock waves in a cabin and convergence of shock waves in corners, reduce the maximum overpressure value and change its location, which finally lead to the change of the cabin structure′s damage process .

Abstract:In order to study the catalytic performance of bimetallic oxides in solid propellants, the honeycombs ZnCo₂O₄（ZnCo₂O₄(HCs)） particles grown on nickel foam (NF) were successfully prepared by solvothermal method and the subsequent thermal annealing process. Its phase composition and morphology structure were systematically characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopic(FT-IR), scanning electron microscopy (SEM) and N₂ adsorption-desorption test. The thermal behavior of ammonium perchlorate (AP) and hexanitrohexaazaisowurtzane (CL-20) catalyzed by ZnCo₂O₄(HCs) were investigated by differential scanning calorimetry (DSC). Results showed that when 20% ZnCo₂O₄(HCs) is added, the thermal decomposition peak temperatures of ZnCo₂O₄(HCs)/AP and ZnCo₂O₄(HCs)/CL-20 decreased most which were 575.01 K and 521.55 K, respectively. Compared with pure AP and CL-20, the exothermic decomposition peak temperatures of ZnCo₂O₄(HCs)/AP and ZnCo₂O₄(HCs)/CL-20 were decreased by 101.87 and 3.73 K and the apparent activation energies calculated by thermal analysis kinetics were reduced by 17.88 and 6.23 kJ·mol^-1. Furthermore, the as-prepared ZnCo₂O₄(HCs) exhibited good catalytic activity comparing with ZnCo₂O₄ nanocrystallites (NCs), nanowires (NWs) and nanospheres (NSs). This can be attributed to the porous structure and large specific surface area of ZnCo₂O₄(HCs), which can provide rich active sites as a catalyst for the thermal decomposition reaction.

Abstract:In the preparation of new heat-resisting energetic materials, two new polynitroazobenzene energetic compounds,2,2′,4,4′,6,6′-hexachloro-3,3′,5,5′-tetranitroazobenzene (HCTNAB) and 4,4′-dichloro-2,2′,3,3′,5,5′-hexanitro-6,6′-dimethoxy- azobenzene (DCHNDOCAB), were prepared and their structures were determined by elemental analyses, FTIR, single-crystal X-ray diffraction analysis. Meanwhile, the thermal decomposition temperature was determined by differential scanning calorimetry (DSC) and TG-DTG, the thermal decomposition temperature of HCTNAB is 266.8 ℃, and the thermal decomposition temperature of DCHNDOCAB is 269 ℃. To accomplish the performance prediction of DCHNDOCAB, we used the calculations that based upon the B3LYP (Becke three-parameter Lee-Yang-Parr)/6-311++G^** method gain optimized structure using Gaussian 09. Our research shows that HCTNAB can be seen as a vital energetic intermediate containing active chlorine. The calculated detonation velocity of DCHNDOCAB is 7117 m·s^-1, and the detonation pressure is 21.0 GPa, show that the DCHNDOCAB is hopeful to become a new heat-resisting azo aromatic energetic materials.

Abstract:Endothermic hydrocarbon fuels undergo thermal cracking before entering the combustion chamber and can produce a mixture of unreacted fuels and pyrolysis products (i.e. cracked fuels). The objective of this work is to investigate the effects of pyrolysis conversions, pyrolysis pressures, ignition pressures and free radicals on ignition characteristics of cracked n-decane over temperature of 1300-1800 K, pressure of 0.1-3.0 MPa and equivalence ratio of 1.0. Components of the thermally cracked n-decane at 3.0 and 5.0 MPa in a flow reactor were calculated theoretically using an accurately combined mechanism, which are in good agreement with the experimental results in literature. The results showed the conversion rates of n-decane cracking at 3 and 5 MPa are 46.2% and 58.8%, respectively. The distribution of cracking products is consistent, but the ethylene content decreases with the increase of pressure, while the alkane content increases with the increase of pressure. Meanwhile, the content of free radicals at 3 MPa is slightly higher than that at 5 MPa, but the content of free radicals is very low. Ignition delay time increases with the decreasing of n-decane conversion and pyrolysis pressure, while higher ignition pressure can shorten it significantly. Furthermore, the presence of free radicals in cracked n-decane could accelerate the ignition process with ignition delay time shortening more than 15% when the conversion was less than 40%, compared with that of cracked n-decane without radicals.

Abstract:In order to obtain the characteristics of electromagnetic radiation signals during the explosion of RDX and RDX-based aluminized explosives, the broadband antenna measurement system is utilized in explosion experiments. The experimental results show that the electromagnetic radiation signal of the RDX and RDX-based aluminized explosives has a significant delay compared with the detonation time. At 2 m distance, the field strength of the explosive electromagnetic radiation signal is 1.8-15.2 V·m^-1 and decreases with the increase in the explosive distance. When the aluminum content is from 0% to 20%, the field strength of the electromagnetic radiation signal generated by the explosion increases with the increase of aluminum content. When the aluminum content is from 20% to 30%, the field strength of the electromagnetic radiation signal generated by the explosion decreases as the aluminum content increases. The frequency of electromagnetic radiation signals generated by the explosion of RDX and RDX based aluminized explosives is mainly distributed within 500 MHz. The addition of aluminum changes the frequency component of the electromagnetic radiation signal, and the spectrum of the electromagnetic radiation signal of different aluminized explosives is different.

Abstract:New energetic materials with molecular perovskite structure (H₂dabco[NH₄(ClO₄)₃](DAP, dabco =N(CH₂CH₂)₃N) were prepared from ammonium perchlorate, 1, 4-diazoxane[2.2.2]octane and perchloricacid, and its crystal structure and morphology were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy(EDS). The thermal decomposition properties of the DAP and AP were studied by thermo gravimetric (TG) and differential scanning calorimetry (DSC). And the hygroscopicity of DAP and AP was measured by weight gain method. Results show that DAP is a new crystal different from AP in structure and morphology. It exhibited the exothermic peak temperature of 385 ℃ and apparent decomposition heat of 3157 J·g^-1.Compared with the AP after the recrystallization, the exothermic peak temperature delayed 19 ℃, apparent decomposition heat increased by 2221.9 J·g^-1. The hygroscopicity of AP is determined to be 0.560%, while the hygroscopicity of (H₂dabco)[NH₄(ClO₄)₃] is only 0.044%, indicating that this method effectively reduce the hygroscopicity of AP.

Abstract:To establish the relationship between the microscopic chemical reaction mechanism and the macroscopic explosion pressure in the initial stage of methane explosion, the coupling relationship between content changes of key free radicals or molecules (such as CO₂, C₂, CHO•, OH•, C₃) and explosion pressure was investigated experimentally. The flame emission spectrum explosion pressure were obtained by a 20-Litre standard spherical explosion container and a grating spectrometer. Studies show that large amounts of CO₂ are produced during the pressure rising period, while the formation of C₂ and CHO• are primarily in the explosion induction period and they are consumed rapidly when explosion pressure rises. The content of OH• is at a high level throughout the methane explosion. The rapid increase of CO₂ accompanies with pressure rising, which reveals a positive correlation. On the contrary, the consumption of C₂ and CHO• accelerates when explosion pressure rises, revealing that they are correlated negatively. Formation reduction of C₂ and CHO• and their corresponding contents during the explosion induction period, suppression on OH• production during the whole methane explosion and decrease or inhibition in CO₂ formation can slow down or inhibit the explosion process and effectively reduce the methane explosion pressure. The result shows that it is possible to inhibit explosion and reduce the pressure efficiently through the manipulation of decreasing the production of C₂ and CHO• in the induction period, reducing the content of OH• throughout methane explosion and suppressing the formation of CO₂.

Abstract:Cracks in polymer bonded explosives (PBXs) may occur during manufacturing, transportation and storage stages. The surface crack of explosives has an important influence on their mechanical properties and detonation performance. Quantitative detection of the depth of the surface crack is of great significance to the process of surface crack removal. The numerical simulation of surface crack depth estimation was investigated by using Rayleigh surface waves which propagate along the cylindrical and spherical surfaces of PBXs. The propagation patterns of surface waves were studied on these two types of surfaces. The reflection and transmission of surface waves at different frequencies in PBXs with crack of varied depth were simulated through the finite element method (FEM).The FEM results indicate that the depth of crack in curved surfaces can be deduced according to the amplitude variations of reflected and transmitted waves.

Abstract:The detection of trace trinitrotoluene (TNT) explosives by Surface Enhanced Raman Scattering (SERS) was studied. A novel organic metal framework ZIF-8@Ag composites material prepared by in situ growth was used as SERS substrates. Meanwhile, the structure and properties of the composites were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy(TEM) and X-ray powder diffraction(XRD). Results show that the ZIF-8@Ag composites material has good SERS activity, and the enhancement factor is calculated as 8.84×10³. The probe 4-ATP is self-assembled on the surface of AgNPs. And it could selectively recognize TNT by the interaction of probe 4-ATP and TNT molecules. The detection limit is as low as 10^-9 mol·L^-1. In addition, the mechanism of the interaction between the probe 4-ATP and TNT was studied by ultraviolet spectroscopy, which found that TNT and 4-ATP formed Meisenheimer complex.