Nitro-tetrazole based high performing explosives: Recent overview of synthesis and energetic properties

Heterocyclic skeleton (Azoles) and different energetic groups containing high performing explosives are highly emerged in recent years to meet the challenging requirements of energetic materials in both military and civilian applications with improved performance. For this purpose tetrazole (Azole) is identified as an attractive heterocyclic backbone with energetic functional groups nitro (-NO₂), nitrato (-ONO₂), nitrimino (-NNO₂), and nitramino (–NH–NO₂) to replace the traditionally used high performing explosives. The tetrazole based compounds having these energetic functional groups demonstrated advanced energetic performance (detonation velocity and pressure), densities, and heat of formation (HOF) and became a potential replacement of traditional energetic compounds such as RDX. This review presents a summary of the recently reported nitro-tetrazole energetic compounds containing poly-nitro, di/mono-nitro, nitrato/nitramino/nitrimino, bridged/bis/di tetrazole and nitro functional groups, describing their preparation methods, advance energetic properties, and further applications as high-performing explosives, especially those reported in the last decade. This review aims to provide a fresh concept for designing nitro-tetrazole based high performing explosives together with major challenges and perspectives.     

基于黏度和介电常数的柴油机机油质量监测研究

对某重型柴油机机油在使用过程中混入柴油、冷却液、烟炱等污染的情况进行模拟试验,在纯净的机油中分别混入柴油、冷却液和烟炱并搅拌均匀,配成不同百分比的模拟污染油液,利用油品传感器FPS(Fluid PropertySensor)测量模拟污染油液的黏度、介电常数和温度。试验表明:当机油中混入柴油、冷却液和烟炱时,机油的黏度或介电常数随着混入的百分比变化而变化;试验得出了它们之间的定量关系式。通过实车机油质量的检测认为:该方法可以用于机油的在线监测,为机油的按质换油提供监测方法和手段。     

电磁屏蔽混凝土性能的数值模拟

从理论上探讨混凝土对电磁波屏蔽效能的潜在规律，旨在为提高我军营房综合防护能力提供参考数据。研究结果显示：复介电常数、复磁导率虚部对混凝土屏蔽效能的改善在高频波段均明显好于实部；与复介电常数相比复磁导率在低频波段的防护效能则更为突出；而单一组分手性物质对混凝土电磁屏蔽效能的提高作用有限。     

Thermal and combustion behavior of Al-MnO2 nanothermite with poly(vinylidene fluoride -co- hexafluoropropylene) energetic binder

Fluoropolymers get increasing attention in energetic materials application due to the high fluorine content. To explore the effect of poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) on Al/MnO2 nanothermite, the samples with different contents are prepared and characterized by SEM, TG-DSC, XRD, and their ignition and combustion behavior are tested and recorded. The results show that P(VDF-HFP) as an energetic binder can combine the nanothermite components together, even exist in the gaps. The integrity of energetic materials has been improved. Thermal analysis shows that the addition of P(VDF-HFP) greatly changes the thermal reaction processes, and the exothermic peaks appear early, but the utilization of fuel and oxidizer is not efficient from the XRD results. Furthermore, the appropriate addition of P(VDF-HFP) can directly reduce the ignition energy threshold and increase the combustion time, which is necessary for the potential ignition charge application. The possible reasons for above phenomena are discussed and analyzed. This research provides a reference for improvement of thermite-based ignition charge formulation.     

Vapor-phase decomposition of dimethyl methylphosphonate (DMMP), a sarin surrogate,in presence of metal oxides

Chemical warfare agents (CWA) are stockpiled in large quantities across the globe. Agents stored in inaccessible facilities need to be destroyed rapidly without dispersing the compounds to surrounding areas. Metal-based energetic formulations are used in such prompt defeat applications to rapidly decompose the CWA by generating a high temperature environment. An alternate, and possibly a more effective decomposition pathway could be provided by chemicidal action of aerosolized condensed combustion products, which typically consist of metal oxides. Toxic fumes that escape the high tem-perature blast zone can be neutralized by smoke generated during combustion, depending on the par-ticle size, surface characteristics, chemical properties, and concentration of this smoke. This review considers relevant experimental and modeling studies quantifying decomposition of CWA comprising organophosphorus compounds and their surrogates on the surface of various metal oxides. Dimethyl methylphosphonate (DMMP), a sarine surrogate, was used most commonly for such experiments. Many reported efforts focused on the mechanisms of adsorption of DMMP to various metal oxides and initial reaction steps cleaving various bonds from the chemisorbed molecules. For selected oxides, these ex-periments were supported by quantum-mechanical calculations. In other studies, the capacity of oxide surfaces to adsorb and decompose DMMP was quantified. In most cases, porous catalysts were used although limited experimental data are available for aerosolized nonporous oxide particles. The reported experimental data applicable to scenarios involving prompt decomposition of CWA are summarized. It is noted that information is lacking describing respective heterogeneous reaction kinetics. Preliminary estimates of aerosolized smoke particle concentrations required to destroy CWA are made considering gas phase diffusion rates and reported values of the oxide capacity to decompose CWA or their surrogates.     

Construction and Properties of Structure-and Size-controlled Micro/Nano-energetic Materials

The recent research progress of structure- and size-controlled micro/nano-energetic materials is reviewed, which properties are fundamentally different from those of their corresponding bulk materials. The development of the construction strategies for achieving zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) micro/nanostructures from energetic molecules is introduced. Also, an overview of the unique properties induced by micro/nanostructures and size effects is provided. Special emphasis is focused on the size-dependent properties that are different from those of the conventional micro-sized energetic materials, such as thermal decomposition, sensitivity, combustion and detonation, and compaction behaviors. A conclusion and our view of the future development of micro/nano-energetic materials and devices are given.     

Nitrogen analogs of TEX – A computational study

TEX, a well-known nitramine type explosive, has been subjected to centric perturbations by replacing its etheric (acetal) oxygens with nitrogen atoms one by one. The structural features, stabilities and IR and UV-VIS spectra of new structures formed are investigated. For this purpose, density functional theory has been employed at the B3LYP/6-31G (d,p) and B3LYP/6-311G(d) levels. In general the calculations revealed that the oxygen–nitrogen replacement resulted in more energetic but less sensitive structures than TEX.     

BST组分对介电可调性的影响

从钛酸锶钡（BST）相变行为出发,指出在外加电场的作用下,氧八面体中心的Ti4＋偏离在零场中氧八面体的位置,可使介电常数降低,并讨论了组分对介电性的影响。结果表明,在居里点以上50-100 K的范围内具有介电可调性,并且越接近居里点可调性越强。     

制冷系统节能目标函数的研究

本文分析传统采用制冷系数(EER)作为节能指标的不准确性,提出采用(?)效率作为衡量制冷装置在不同工况下运行的节能指标。从(?)效率定义出发推导出带回热的制冷系统的(?)效率关系式,这为寻找装置最佳运行工况提供理论依据,并通过实验证实了理论的分析。     

分布式计算环境下的栅格数据存储策略

针对传统的栅格数据存储策略不能满足分布式计算环境下粗粒度数据访问需求,应对海量栅格数据计算时效率低下的问题,结合分布式文件系统的存储特点,同时考虑地图代数算子在Map/Reduce阶段以栅格瓦片为单位的计算特点,提出一种基于Hadoop分布式文件系统的栅格瓦片存储策略。围绕栅格数据瓦片分割、压缩瓦片数据组织与存储、分布式文件输入输出接口改进等方面对该存储策略加以实现,并使用基于该存储策略的地图代数局部算子的分布式计算流程加以验证。理论分析与实验结果表明,该策略能够显著提高分布式计算环境下空间分析算子的运算速度。     

Insensitive energetic microspheres DAAF/RDX fabricated by facile molecular self-assembly

Insensitive energetic materials are promising in the defense weapons field. However, energetic materials still suffer from great challenges and the concern about their safety limits their utilization. In this work, insensitive energetic explosive 3,3′-diamino-4,4′-azoxyfurazan/hexahydro-1,3,5-trinitro-1,3,5-triazine (DAAF/RDX) microspheres were fabricated by self-assembly method. Rod-like DAAF/RDX was prepared by mechanical ball milling for comparison. DAAF/RDX composites with different mass ratios (90:10, 80:20, and 70:30) were obtained. The morphologies and structures of as-obtained DAAF/RDX composites were characterized by scanning electron microscopy (SEM), powder x-ray diffraction (PXRD) and fourier transform infrared spectroscopy (FT-IR). The results showed that DAAF/RDX microspheres exhibited regular shaped microspheres with sizes from 0.5 to 1.2 μm. There was no crystal transition during the modification process. The thermal properties of as-obtained materials were then evaluated by differential scanning calorimetry (DSC) and materials studio software. DAAF/RDX microspheres showed an advanced decomposition peak temperature compared with rod-like DAAF/RDX. The binding energy and peak temperature values at zero β_i (T_P0) of DAAF/RDX (90:10) increased by 36.77 kJ/mol, 1.6 °C, and 58.11 kJ/mol, 12.3 °C compared to DAAF/RDX (80:20) and DAAF/RDX (70:30), indicating the better thermal stability of DAAF/RDX (90:10). The characteristic drop height (H₅₀) of DAAF/RDX (higher than 100 cm) composites was higher than that of raw RDX (25 cm), suggesting significant improvements in mechanical safety. The preparation of DAAF/RDX microspheres is promising for the desensitization of RDX and useful for the formation of other materials and future wide applications.     

Fabrication and characterization of mussel-inspired layer-by-layer assembled CL-20-based energetic films via micro-jet printing

Three-dimensional (3D) micro-jet printing is a droplet deposition technique based on liquid-phase materials. To improve the deposition density and performance of energetic films with micro/nanoscale on an energetic chip, polydopamine (PDA) was utilized as a linker bridge to induce the in-situ self-assembly of CL-20-based energetic film via 3D micro-jet printing. The self-assembly was extensively characterized by confocal laser scanning microscopy (CLSM), SEM, power-XRD, XPS, and DSC. The performance of the self-assembled film was verified by the mechanical properties and detonation properties, and a possible self-assembly mechanism in the layer-by-layer micro-jet printing process was proposed. The results indicated PDA-induced self-assembly enhanced the physical entanglement between the binders and energetic crystal, reduced the porosity from 15.87% to 11.28%, and improved the elastic modulus and the detonation performance of the CL-20-based energetic film. This work proposes a novel and promising energetic film design and fabrication strategy to enhance the interaction between the energetic composite layers in the micro-jet printing process.     

Investigation on the foaming behaviors of NC-based gun propellants

To prepare the porous NC-based (nitrocellulose-based) gun propellants, the batch foaming process of using supercritical CO₂ as the physical blowing agent is used. The solubilities of CO₂ in the single-base propellants and TEGDN (trimethyleneglycol dinitrate) propellants are measured by the gravimetric method, and SEM (scanning electron microscope) is used to observe the morphology of foamed propellants. The result shows that a large amount of CO₂ could be dissolved in NC-based propellants. The experimental results also reveal that the energetic plasticizer TEGDN exerts an important influence on the pore structure. The triaxial tensile failure mechanism for solid-state nucleation is used to explain the nucleation of NC-based propellants in the solid state. Since some specific foaming behaviors of NC-based propellants can not be explained by the failure mechanism, a solid-state nucleation mechanism which revises the triaxial tensile failure mechanism is proposed and discussed.     

基于空频域信息的单站无源定位可观测分析

对利用空频域信息的单站无源定位方法进行可观测性分析。针对非线性系统的可观测性理论需要计算复杂的雅克比矩阵的问题,提出把观测方程先经过伪线性化处理,然后运用线性系统的可观测性分析的理论,对匀速、匀加速直线运动进行了具体分析,得出只要目标不朝观测站作径向运动都是可以对其进行观测的。实验结果也验证了分析结论的正确性。     

北斗全球系统导航信号恒包络调制和复用技术

出于以导频通道为代表的北斗全球导航卫星系统现代化信号结构升级以及后向兼容的需求,北斗系统近几年提出了多种新型恒包络调制和复用技术,包括适用于北斗系统B1频点的正交复用二进制偏移载波(QMBOC)调制和非对称双正交相移键控(ADualQPSK)调制,适用于B2频点的时分复用AltBOC(TDAlt BOC)调制与非对称恒包络二进制偏移载波(ACE-BOC)调制,适用于B3频点的双正交相移键控(DualQPSK)调制,适用于双边带任意信号路数、任意功率配比的广义恒包络二进制偏移载波(GCE-BOC)调制。本文系统性地论述了北斗全球系统中提出的多种新型恒包络调制和复用技术,在此基础上基于GCEBOC调制总结出了一种恒包络调制的统一解析表示形式,对全面理解北斗全球系统信号设计思路及在此基础上发展设计新型的恒包络调制和复用技术均能提供重要的借鉴。     

多孔介质中气体流量对流动阻力影响的实验研究

对空气在多孔介质(Pd/SiO2颗粒催化剂)中的流动阻力特性进行了冷态实验,研究了气体流量对流动阻力的影响.结果表明:催化剂厚度一定时,随着气体流量增大,多孔介质中的流动阻力也逐渐增大.经过与经典阻力计算公式对比,分析了偏差影响因素.最后,结合实验数据拟合出了适合管式反应器中流动阻力计算的半经验公式,能精确地预测颗粒填...     

潜艇螺旋桨区域腐蚀电场模型特征及奇异峰成因分析

针对边界元法推算潜艇腐蚀电场分布时边界条件影响电场信号特征,导致螺旋桨区域产生奇异峰现象的问题,以实测船用921合金钢和镍青铜螺旋桨材料极化曲线作为建模边界条件,重点对比分析了恒电位和非线性边界条件下的电场特征,并通过建立阻抗谱参数下的船壳-螺旋桨电化学阻抗等效电路,分析了潜艇腐蚀电场螺旋桨区域产生奇异峰的原因。仿真结果表明:潜艇电场特征分布及螺旋桨区域奇异峰现象与船体材料电化学极化状态有关,合理设定非线性极化边界参数可达到削弱奇异峰现象、平滑腐蚀电场模型的效果。     

Experimental and numerical study of the blast wave decrease using sandwich panel by granular materials core

Among the intrinsic properties of some materials, e.g., foams, porous materials, and granular materials, are their ability to mitigate shock waves. This paper investigated shock wave mitigation by a sandwich panel with a granular core. Numerical simulations and experimental tests were performed using Autodyn hydro-code software and a shock tube, respectively. The smoothed particle hydrodynamics (SPH) method was used to model granular materials. Sawdust and pumice, whose properties were determined by several compression tests, were used as granular materials in the sandwich panel core. These granular materials possess many mechanisms, including compacting (e.g., sawdust) and crushing (e.g., pumice) that mitigate shock/blast wave. The results indicated the ineffectiveness of using a core with low thickness, yet it was demonstrated to be effective with high thickness. Low-thickness pumice yielded better results for wave mitigation. The use of these materials with a core with appropriate core reduces up to 88% of the shock wave. The results of the experiments and numerical simulations were compared, suggesting a good agreement between the two. This indicates the accuracy of simulation and the ability of the SPH method to modeling granular material under shock loading. The effects of grain size and the coefficient of friction between grains have also been investigated using simulation, implying that increasing the grain size and coefficient of friction between grains both reduce overpressure.     

基于ANSYS软件的管道漏磁场分析

介绍了漏磁场分析的基本理论以及由麦克斯韦方程导出的泊松方程对应的能量泛函,利用基于此理论基础的ANSYS有限元分析软件的ANSYS Multiphysics软件包对管道漏磁场进行模拟仿真,能得出大量缺陷漏磁场数据,这为缺陷漏磁检测定量化打下基础.     

Formulation development and characterization of cellulose acetate nitrate based propellants for improved insensitive munitions properties

Cellulose acetate nitrate (CAN) was used as an insensitive energetic binder to improve the insensitive munitions (IM) properties of gun propellants to replace the M1 propellant used in 105 mm artillery charges. CAN contains the energetic nitro groups found in nitrocellulose (NC), but also acetyl functionalities, which lowered the polymer's sensitivity to heat and shock, and therefore improved its IM properties relative to NC. The formulation, development and small-scale characterization testing of several CAN-based propellants were done. The formulations, using insensitive energetic solid fillers and high-nitrogen modifiers in place of nitramine were completed. The small scale characterization testing, such as closed bomb testing, small scale sensitivity, thermal stability, and chemical compatibility were done. The mechanical response of the propellants under high-rate uni-axial compression at, hot, cold, and ambient temperatures were also completed. Critical diameter testing, hot fragment conductive ignition (HFCI) tests were done to evaluate the propellants' responses to thermal and shock stimuli. Utilizing the propellant chemical composition, theoretical predictions of erosivity were completed. All the small scale test results were utilized to down-select the promising CAN based formulations for large scale demonstration testing such as the ballistic performance and fragment impact testing in the 105 mm M67 artillery charge configurations. The test results completed in the small and large scale testing are discussed.