Effect of the Al/O ratio on the Al reaction of aluminized RDX-based explosives

Aluminum(Al) powders are used in composite explosives as a typical reducing agent for improving explosion performance. To understand energy release of aluminum in aluminized RDX-based explosives, a series of thermal measurements and underwater explosion(UNDEX) experiments were conducted. Lithium fluoride(LiF) was added in RDX-based explosives, as a replacement of aluminum, and used in constant temperature calorimeter experiments and UNDEXs. The influence of aluminum powder on explosion heat(Qv) was measured. A rich supply of data about aluminum energy release rate was gained. There are other oxides(CO_2, CO, and H_2O) in detonation products besides alumina when the content of RDX is maintained at the same levels. Aluminum cannot fully combine with oxygen in the detonation products. To study the relationship between the explosive formulation and energy release, pressure and impulse signals in underwater experiments were recorded and analyzed after charges were initiated underwater. The shock wave energy(Esk), bubble energy(Eb), and total energy(Et) monotony increase with the Al/O ratio, while the growth rates of the shock wave energy,bubble energy, and total energy become slow.     

含铝炸药水下爆炸性能的实验研究

对RS211、HL-1、HL-2这3种含铝炸药和TNT炸药进行了水下爆炸实验,测量了4种炸药水下爆炸冲击波压力剖面和气泡脉动周期,获得了4种炸药水下爆炸冲击波的峰值超压、冲量、能量和气泡能。实验结果表明,在所研究的范围内,与TNT炸药相比,含铝炸药的冲击波能量有明显增加,约为TNT炸药的1.20～1.35倍,气泡能有显著增加,约为TNT炸药的1.50～2.30倍,表明在炸药中加入铝粉对于提高炸药水中爆炸威力是有益的。     

Macrokinetics of the retention of condensed carbon and detonation diamond in a hermetic explosion chamber

The effect of the thermophysical parameters of a cooling medium on the macrokinetics of secondary physicochemical processes that occur in a hermetic chamber after the explosion of a solid explosive charge is studied. The yields of condensed carbon and the content of the diamond phase in it are mainly determined by the temperature of the medium in the chamber after explosion. The maximum yield of detonation diamond synthesized from a trinitrotoluene-hexogen TG50/50 alloy is equal to ～10% of the initial explosive mass and is achieved when the steady-state temperature of the medium in the chamber does not exceed T_m=550±50 K. As this temperature increases, the yield of detonation diamond decreases approximately in inverse proportion to the temperature, and, at T_m>2800 K, there is virtually no diamond phase in the explosion products. The conversion of condensed carbon due to the presence of the oxygen-containing components of the explosion products (CO₂, H₂O) begins at a temperature of the medium of above 1550±150 K. The decrease in the final energy release that is experimentally detected in calorimetric studies in the case of an explosion of solid explosives with a negative oxygen balance in an inert gaseous medium or in the case where explosives are surrounded by massive shells results from the endothermic conversion of condensed carbon, which absorbs a significant portion of the explosion energy.     

Heat of explosion and acceleration ability of explosive–inorganic oxidizer mixtures

Experimental results have shown that the use of inorganic oxidizers (ammonium nitrate, ammonium perchlorate, and ammonium dinitramide) as additives does not lead to a considerable increase in the heat of explosion and acceleration ability of HMX. Ammonium perchlorate does not have an effect on the acceleration ability; however, it leads to an increase in the heat of explosion of triaminotrinitrobenzene. Calculations have shown that the acceleration ability of explosives with a low oxygen ratio can be increased through the formation of nanostructured composites with inorganic oxidizers. Calculations suggest that the addition of the studied oxidizers to CL-20 leads to a decrease in the acceleration ability of this promising explosive.     

气相/凝聚炸药爆轰合成的碳包铜纳米颗粒特征

采用凝聚炸药爆轰和气相爆轰分别制备碳包铜纳米颗粒,并利用XRD,Raman和TEM等方法对合成纳米产物进行对比分析。其中凝聚炸药爆轰法以柠檬酸铜干凝胶、油酸和黑索金为原料按照一定比例配成爆炸源,在氮气的保护氛围中引爆；而气相爆轰法以乙酰丙酮铜为原料,分别以H2和O2,H2和空气为爆炸源,在负氧条件下引爆。通过XRD,Raman和TEM分析结果表明,两类爆轰法均可得到分散性良好的碳包覆铜纳米颗粒,碳壳石墨化程度较高。气相爆轰可以合成10 nm以下的纳米晶粒,而凝聚炸药爆轰合成的晶粒尺寸在20~40 nm,且存在较多空壳结构；气相爆轰产物其碳壳尺寸在2~3 nm,凝聚炸药爆轰产物其碳壳尺寸在2~5 nm。     

Surface‐enhanced Raman spectroscopy for trace‐level detection of explosives

The detection of explosives and their associated compounds for security screening is an active area of research and a wide variety of detection methods are involved in this very challenging area. Surface‐enhanced Raman scattering (SERS) spectroscopy is one of the most sensitive tools for the detection of molecules adsorbed on nano‐scale roughened metal surface. Moreover, SERS combines high sensitivity with the observation of vibrational spectra of species, giving complete information on the molecular structure of material under study. In this paper, SERS was applied to the detection of very small quantities of explosives adsorbed on industrially made substrates. The spectra were acquired with a compact Raman spectrometer. Usually, a high signal‐to‐noise (S/N) spectrum, suitable for identification of explosive molecules down to few hundreds of picograms, was achieved within 30 s. Our measurements suggest that it is possible to exploit SERS using a practical detection instrument for routine analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

“最小键级原理”的从头算证实———苯和苯胺类硝基衍生物

感度是爆炸物对外界刺激的敏感程度 ,是火药、炸药和起爆药的基本属性 .在外界撞击作用下炸药发生爆炸的难易程度即该炸药的撞击感度 .感度通常依靠实测 ,从理论上加以判别是人们追求的目标 ,故研究炸药感度与结构的关系一直是该领域的热点 .根据撞击引起热解、热解引起爆炸、撞击感度主要与热解引发步骤相关联等思想 ,我们建议了“最小键级原理 (PSBO)”[1- 4] :对系列结构相似爆炸物 ,其热解引发键键级 (或重叠布居 )越小 ,则撞击感度越大 ;热解引发键键级越大 ,则撞击感度越小 .该判据已在多系列炸药中获得证实和应用[1- 4] .“热解引…     

Sensitivities of ionic explosives

ABSTRACT

We have investigated the relevance for ionic explosive sensitivity of three factors that have been demonstrated to be related to the sensitivities of molecular explosives. These are (1) the maximum available heat of detonation, (2) the amount of free space per molecule (or per formula unit) in the crystal lattice and (3) specific features of the electrostatic potential on the molecular or ionic surface. We find that for ionic explosives, just as for molecular ones, there is an overall tendency for impact sensitivity to increase as the maximum detonation heat release is greater. This means that the usual emphasis upon designing explosives with large heats of detonation needs to be tempered somewhat. We also show that a moderate detonation heat release does not preclude a high level of detonation performance for ionic explosives, as was already demonstrated for molecular ones. Relating the free space per formula unit to sensitivity may require a modified procedure for ionic explosives; this will continue to be investigated. Finally, an encouraging start has been made in linking impact sensitivities to the electrostatic potentials on ionic surfaces, although limited so far to ammonium salts.     

Silicon photonic structures with embedded polymers for novel sensing methods

At present time research and development of a new generation of optical sensors using conjugated polymers, in particular sensors of explosives are actively underway. Nevertheless, the problems of the sensitivity, selectivity, and stability of such sensors are still of great interest. One of the ways to solve the problem is the creation of luminescence sensors based on photonic crystals with a high specific surface area, which have significant sorption ability and allow to effective modulate emission properties of luminophores. In this paper, porous silicon microcavities with embeded organic polyphenylenevinylene- (PPV) and polyfluorene- (PF) type polymers were created. It was shown that polymer infiltration in porous silicon microcavities leads to modification of their luminescence properties, which is expressed in narrowing of the emission spectrum and changing of its directional pattern. It was demonstrated that such structures exhibit sensitivity to saturated vapors of trinitrotoluene. The structures proposed can be treated as a basis for development of new type of sensors used for detection of vapors of nitroaromatic compounds.     

Thermal cook-off of an HMX based explosive: Pressure gauge experiments and modeling

Safety issues related to thermal cook-off are important for handling and storing explosive devices. Violence of an event as a function of confinement is important for prediction of collateral events. There are major issues which require an understanding of the following events: (1) transit to detonation of a pressure wave from a cook-off event, (2) sensitivity of changes in HMX-based explosives with thermally induced phase transitions, and (3) the potential danger of neighboring explosive devices being affected by a cook-off reaction. Results of cook-off events of known size, confinement, and thermal history allow for development and/or calibration of computer models for calculating events that are difficult to measure experimentally. The text was submitted by the authors in English.     

Underwater explosion research using small amounts of chemical explosives

Underwater explosions have found extensive application in technology, acoustics and physics. Most investigations using underwater explosions are performed as full-scale tests, this is mainly due to the widely held view that reliable measurements of pressure waves taken at a short range from the detonation of small amounts of chemical explosives are extremely difficult, if not impossible, to perform. On the basis of a number of tests where small amounts of explosives, ranging from 0.2 to 6 g were detonated, the scaling law for underwater explosion shock waves was generalized and includes short distances and very small charge weights typical of laboratory conditions. Empirical expressions for the peak pressure, time constant, impulse and energy flux density as a function of charge weight and distance have been worked out. Excellent agreement was found between the peak pressures calculated using the empirical expression and the corresponding values calculated using Kirkwood - Bethe's theory for underwater shock waves. Various scaling effects, which if not realized may lead to erroneous results, are emphasized. It is concluded that small scale (laboratory) underwater explosion tests, give valid useful results and may be used instead of traditional full scale tests in a number of fields.     

Detection of explosives on human nail using confocal Raman microscopy

Trace amounts of explosives were detected on human nail using confocal Raman microscopy. Contamination of the nail can result from the manual handling, packaging or transportation of explosive substances. Raman spectra were obtained from pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT), ammonium nitrate and hexamethylenetetramine (HMTA) particles on the surface of the nail with dimensions in the range 5–10 µm. An added difficulty in an analytical procedure is the presence of a nail varnish coating that has been applied, which traps the particulate matter between the coating and nail. Using confocal Raman microscopy, interference‐free spectra could be acquired from particles of explosives visually masked by the nail varnish. Spectra of the explosives could be readily obtained in situ within 90 s without alteration of the evidential material. Acquisition of a Raman point map of a PETN particle under the nail varnish coating is also reported. Copyright © 2008 John Wiley & Sons, Ltd.     

Development of an explosion from an initiation source in a liquid high explosive

A numerical analysis of the development of combustion and explosion from a reaction hotspot in the bulk and in a thin layer of a liquid explosive placed between two flat solid surfaces is performed. A comparison of the theoretical results with experimental data shows that a satisfactory agreement between the measured and calculated flame speeds is possible only under the assumption of a multifold increase in the burning surface area due to its instability. An estimate of the parameters of the shock wave generated by an accelerating flame shows that the mechanisms of shock-wave and cavitation initiation of detonation cannot be ignored in analyzing the regimes of unsteady combustion of liquid explosives.     

Combustion and explosion of hydrogen-air mixtures under conditions imitating elements of gas-laden rooms

The time evolution of the processes of combustion and explosion with regard to safety problems in handling reactive gas mixtures was studied. The explosion safety for reaction volumes and gas-laden rooms can be assessed only if data on the possible consequences of the emergencies under conditions close to real ones or modeling them are available. The propagation of nonplanar explosion waves with a short positive phase in volumes with variable cross section is an essentially unsteady process. Until recently, the regularities of the evolution of the characteristics of such waves during their propagation in a reactive mixture with heat release virtually have not been studied. At the same time, these processes determine the character of combustion, and, therefore, the possibility of their formalization provides the opportunity to treat the entire variety of combustion regimes. Only a knowledge of general laws of the interaction of unsteady gasdynamic processes and gaskinetic processes in a reactive medium makes it possible to control combustion regimes purposefully and effectively. The present work is devoted to studying the propagation of combustion in cavities with a geometry imitating elements of reaction volumes and rooms filled with a hydrogen-air mixture. Results for a pyramid-shaped cavity capable of cumulating flows and waves are considered and compared to those obtained using a conical cavity [1–5].     

爆炸丝线起爆装置研制及应用

为实现低密度粉末炸药的线同步起爆,研制了一种爆炸丝线起爆系统。储能装置采用3个低感电容并联,总容量为12μF;采用200kV/100kA场畸变开关作为放电开关;触发器产生1.5kV脉冲经过高压脉冲变压器输出幅度大于40kV的高压脉冲触发开关。在储能电容器充电40kV下,电爆炸丝负载上获得了73kA的脉冲电流。采用高速分幅相机观测了爆炸丝爆炸过程图像,结果表明爆炸丝膨胀过程的同步性较好。该线起爆系统已成功应用于爆炸膨胀环实验。     

Development and evaluation of magnetic resonance technologies, particularly NMR, for detection of explosives

Beginning in 1972 nuclear magnetic resonance (NMR) technologies for detecting explosives and illegal contraband were developed and evaluated at the Southwest Research Institute. Fullscale systems on the basis of hydrogen transient NMR were developed and evaluated in laboratory and field tests with generally favorable results but with some limitations. These included (1) an experimental, mobile system for detecting buried, nonmetallic land mines; (2) an instrument for inspection of letters and small parcels for small quantities of explosives or illegal drugs; (3) a system for inspection of checked airline baggage and air cargo for concealed explosives and illegal drugs; and (4) a system for rapid inspection of quantities of mail for illegal drugs.¹H NMR offers high sensitivity and detects high-energy explosives such as RDX, TNT, and PETN, as well as nitroglycerine and ammonium-nitrate-based explosives and illegal drugs. Challenges in both physics and engineering were successfully addressed to achieve the goals of rapid inspection with low false-alarm and high detection probability. Electron paramagnetic resonance was found suitable for detecting black powder in laboratory tests as was nuclear quadrupole resonance for a few high-energy explosives. Low-field¹H NMR was also explored in the laboratory to make it practical for explosives detection and found to have potential, but numerous implementation problems must be overcome.     

Effects and phenomena in filamentary heavy-metal azide crystals exposed to heat, light, and electric and magnetic fields

Heavy-metal azides (lead, silver, and thallium azides) attract attention of scientists not only because they are common initiating explosives whose nature of explosion is still discussed, but also because their properties are close (on a number of parameters) to those of halogenides whose physical properties are well studied. In the present work, based on the analysis and correlations of polarization-and magnetostrictive effects found in heavy-metal azides, an attempt is made to substantiate the physical-chemical mechanism of detonation initiation as ionization induced by the electric field. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 96–102, January, 2006.     

TNT炸药和乳化炸药驱动飞板的通用状态方程特征线法研究

 在爆炸气体动力学的基础上,利用特征线差分法,对飞板的运动规律进行研究。差分过程中,基于稳定爆轰的基本假设,根据二维定常流理论,推导了通用状态方程的特征线相容关系。利用爆轰气体密度取代特征线相容关系中的马赫数,导出了与物质物态无关的通用状态方程特征线法,编写了爆轰产物作用下飞板内部和边界的差分计算程序。利用该程序计算了飞板在TNT炸药和乳化炸药爆轰作用下的运动参数,研究了在不同质量比下TNT炸药和乳化炸药爆轰驱动飞板的抛掷姿态曲线,并与Richter公式计算结果进行了对比研究。     

氢化镁储氢型乳化炸药的爆炸特性研究

 通过理论计算和水下爆炸实验,初步研究了MgH₂敏化储氢型乳化炸药的爆炸特性和爆轰反应机理。结果表明：与玻璃微球敏化的乳化炸药相比,MgH₂敏化的乳化炸药水下爆炸的冲击波超压、比冲量、比冲击波能、比气泡能及水下爆炸比总能量显著增加,其中冲击波超压和水下爆炸总能量分别增加了20.5%和31.0%。MgH₂储氢型乳化炸药的爆轰机理与玻璃微球敏化乳化炸药不同,MgH₂在乳化炸药中起到了敏化剂和含能材料的双重作用,即MgH₂在乳化基质中水解产生均匀分布的氢气泡,起到了敏化作用,同时氢气参与爆炸反应,提高了炸药的爆炸能量和做功能力。     

UV and 532 nm Photo-Dissociation of 2-Nitrotoluene: Observation of Electronically-Excited NO; Emission from Carbon (I); N2–NO Energy Transfer; and Stabilization of 2-Nitrotoluene-Ar Clusters

2-nitrotoluene is a taggant used in explosive compounds and also often used as a simulant for nitro-based high explosives. Various spectroscopic techniques focus on the detection of vibrationally excited NO as an indicator for the presence of explosives. We report on the photo-dissociation of 2-nitrotoluene using UV and 532 nm wavelengths. We not only observe vibrationally excited NO in its electronic ground state, but also vibrationally excited NO in its electronic excited state. The photo-dissociation of 2-nitrotoluene leads to the formation of atomic carbon and its emission, overlapping the NO emission, is observed. Energy transfer from laser-excited nitrogen to NO leads to NO emission with long lifetimes. Argon atoms stabilize 2-nitrotoluene molecules and delay their photo-dissociation.