Method for estimating the acceleration ability of aluminized high explosives

A semiempirical method for calculating the acceleration ability of aluminized high explosives was developed using experimental data. The method is based on the assumption that the coefficient of transformation of chemical energy into the kinetic energy of the flyer depends on the number of moles of gaseous detonation products. The model takes into account the effective extent of oxidation of aluminum at various stages of motion of the flyer. Calculations were performed for compositions containing a number of new explosives. The calculation results show that nanostructured aluminized composite can be superior to mechanical mixture in acceleration ability if the main explosive has a highly negative oxygen balance or contains and enhanced amount of hydrogen.     

Acceleration ability of high explosives and their mixtures with fuel additives. 1. Assessment by the M-40 method

The relationship between the chemical composition of the detonation products and the acceleration ability of explosives is considered. Based on theoretical and experimental studies, it is concluded that, at volumetric energy content, the most important parameter is the average atomicity of the molecules constituting the detonation products. Among the CHNOF-containing explosives, groups with high acceleration ability were identified. The experimental results on the acceleration ability obtained using the M-40 method are reported for mixtures of dispersed Al with HEs with different oxygen balance and for mixtures of HMX-based HE with Al, Mg, Y, Ta, ZrH₂. An analysis of the acceleration ability on the charge density for BTNEN and mixtures thereof with Al made is possible to estimate the degree of conversion of the energy of combustion of Al under the gasdynamic conditions typical of the M-40 method, which turned out to be 20–40%.     

Heat of explosion and acceleration ability of aluminized hexanitrohexaazaisowurtzitane-based compositions

Measurements and calculations of the heat of explosion and acceleration ability of aluminized compositions based on hexanitrohexaazaisowurtzitane, a promising high explosive, showed that the indicated parameters of such mixtures substantially exceed those of HMX-based counterparts. Creating aluminized nanocomposites to improve the acceleration ability is advantageous only if the content of the oxide film in the nanoaluminum powder is minimized by coating the particles with a protective layer of an active material. According to calculations, nanocomposites containing hexanitrohexaazaisowurtzitane and aluminum with active coating should have a record acceleration ability.     

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.     

Influence of the particle size of the components on the mechanical sensitivity of metallized high explosives

The results of experimental studies of the mechanical initiation of compositions of explosives (HMX, RDX) with aluminum powder at various component and granulometric compositions are presented. It is shown that nanocomposites and mechanical mixtures of explosives with nanoscale aluminum are characterized by extremely high sensitivity in comparison with compositions containing micron-sized aluminum powder. The results are explained based on the assumption that an increase in the sensitivity is caused by an additional heat release in the course of chemical interaction of components at mechanically induced hot spots. Data on the effect of passivating coating and aging of the particles of nanoscale aluminum on the sensitivity of binary compositions are obtained and analyzed.     

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。     

Initial stage of the explosion of ammonium nitrate and its powder mixtures

There is an obvious contradiction between the statistics of the devastating explosions that take place with the participation of ammonium nitrate and explosive properties of this material determined in standard tests. Pure ammonium nitrate does not burn under normal conditions and has a very low sensitivity to conventional mechanical and thermal stimuli. So far, ammonium nitrate has been detonated only by using high explosives. Causes of accidental explosions involving large masses of ammonium nitrate are likely to be found in a nonconventional behavior of ammonium nitrate. These changes may arise due to different chemical or physical factors, such as those associated with the presence of active additives, crushing of particles, etc., and lead to acceleration of the process at the initial stage of explosion. This work is devoted studying the convective burning and the initial stage of deflagration-to-detonation transition in dry and wet mixtures of ammonium nitrate with various, largely combustible additives. Experiments were conducted on loose-packed charges in a constant-volume bomb and by using the method of the critical bed height with recording pressure-time diagrams by a piezoelectric sensor. Ammonium nitrate of two different types was used: granular and powdered. The fuel additives were charcoal and aluminum powder, whereas the additives inhibiting the combustion of ammonium nitrate were water and monosodium salt of phosphoric acid. In addition, finely dispersed mixture of four components (ammonium nitrate, aluminum, powdered sugar, and TNT in a proportion of 76: 8: 12: 4) was used. The experiments in the constant-volume bomb were supplemented by numerical simulations, which made it possible to obtain a better understanding of the convective burning of the test mixtures and to evaluate the possibility of using a constant-volume bomb to collect quantitative information on the intensity of the combustion of the mixture at the initial stage of the explosion.     

Acceleration ability of high explosives and their mixtures with fuel additives. 2. Activated and ultrafine aluminum powders

The acceleration ability of high explosives containing additives of activated and ultrafine aluminum was considered. It was demonstrated that different methods of activation of Al oxidation that make it possible to increase the rate of this process in air severalfold produce little or no effect on the acceleration ability of aluminized high explosives. The basic features of the behavior of Al in detonation waves that explain the results are formulated.     

利用单色谱仪研究炸药粉快速反应产物发射谱

利用作者研制的快速反应（爆轰）光谱探测技术研究了五种常用猛炸药快速反应最终产物光谱。研究表明，随着炸药负氧平衡值的影响，最终产物Ｈ２Ｏ的含量也增加，同样随着炸药中碳含量的增加ＣＯ２量增加，固体Ｃ２也明显增多，它能为爆轰产物合成金刚石选用主炸药提供有参考价值的数据，实验值与ＢＫＷ方程计算进行了比较，其趋势是一致的，为微观研究炸药粉快速反应提供了一个较简便而行之有效的方法。     

Studies on 2,4-DNT Mixtures Using Reflection Terahertz Time Domain Spectroscopy for Explosives Detection

Absorption spectra （0.2-1.8 THz） of the mixtures of explosive 2,4-DNT and polyethylene（PE） at different ratios are obtained using reflection terahertz time domain spectroscopy （THz-TDS）. The pronounced absorption peak of 2,4-DNT at 1.08 THz is always observed for the mixtures with 2,4-DNT ratios above 20%. Experimental results demonstrate that more applicable and realistic THz-TDS in reflection geometry can be used to distinguish explosive mixed with other material having no THz fingerprints, and has a high potential in the detection of explosives.     

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.     

Particle size and gas environment effects on blast and overpressure enhancement in aluminized explosives

Aluminized RDX-based explosives were detonated under controlled conditions while varying particle size and atmosphere in an effort to quantify the contribution of aerobic and anaerobic Al reaction to blast and overpressure. Early time reaction of aluminum acts to enhance the primary explosive blast, and this reaction is approximately half aerobic and half anaerobic (i.e. oxidation by detonation products and/or nitridation), suggesting that very rapid early-time mixing occurs in explosive fireballs. Particle size effects are surprisingly negligible over the range of 3–40 μm, which implies that conventional scaling laws for aluminum combustion provide less insight than previously assumed. Quasi-static pressures obtained in the time period from 5 to 10 microns after detonation suggest that oxidation of aluminum is complete in the presence of 20% oxygen. However, for nitrogen environments, oxidation only proceeds to half its theoretical maximum, except for the smallest (3 μm particles) for which oxidation was nearly complete. These results demonstrate that oxidation of aluminum in aluminized explosives is robust in anaerobic environments, and that simulation efforts cannot neglect anaerobic channels, even though aerobic oxidation provides the greatest energy release.     

Towards optoelectronic detection of explosives

Detection of explosives is an important challenge for contemporary science and technology of security systems. We present an application of NOx sensors equipped with concentrator in searching of explosives. The sensors using CRDS with blue — violet diode lasers (410 nm) as well as with QCL lasers (5.26 μm and 4.53 μm) are described. The detection method is based either on reaction of the sensors to the nitrogen oxides emitted by explosives or to NOx produced during thermal decomposition of explosive vapours. For TNT, PETN, RDX, and HMX the detection limit better than 1 ng has been achieved.     

Demixing of a binary mixture in slit-like pores at high temperatures

We investigate the fluid—fluid demixing transitions in the case of adsorption of so-called symmetric binary mixtures in slit-like pores at temperatures higher than the bulk gas—liquid critical temperature. The aim of the study is to determine how the demixing of such mixtures in the pores depends on the bulk phase composition and on the parameters characterizing the pore. The calculations have been carried out by means of a density functional theory. In the case of an equimolar bulk mixture, the demixing transition inside the pore occurs only when the adsorption potentials of both species are identical. The occurrence of this transition is manifested by a cusp in the adsorption isotherm. For nonequimolar bulk phase compositions, the transition can also take place if the adsorption energies of both components are different. However, the difference in the adsorption energies should be small enough, otherwise a continuous demixing takes place. For non-equimolar compositions two branches of the grand canonical potential intersect, whereas for equimolar bulk composition they meet tangentially. We have determined phase behaviour for several model systems.     

炸药颗粒压制成型数值模拟

 分析炸药压药过程中细观的力学行为,能够为改进压药工艺和提高炸药元件质量提供理论依据。建立了模压条件下炸药颗粒压制成型的计算模型。模型中炸药颗粒被认为是直径相同的球形颗粒,并按一定规律排列。利用非线性有限元计算方法,对炸药颗粒压制成型过程进行了数值模拟计算,分析了压制过程中炸药颗粒变形、受力和温度变化情况。结果表明：药粒在压缩中存在运动和变形两个阶段。在药粒运动阶段,应力集中主要出现在颗粒与约束面的接触部分;药粒进入了塑性变形后,药粒内部压力迅速升高且压力趋于一致。压缩过程中药粒温度升高,药床接近密实状态时,药床中心处药粒温度最高。     

Concurrent Detection of Protein Adsorption on Mixed Nanoparticles by Differential Centrifugal Sedimentation

In mixtures of nanoparticles of various sizes or compositions, monitoring protein partitioning on their surfaces provides important information about particle–protein interactions during competitive adsorption. Utilizing the size‐resolving capability of differential centrifugal sedimentation, the adsorption of bovine serum albumin on multisize gold nanoparticles with diameters ranging from 20 to 100 nm or gold, silver, and silica nanoparticles with similar diameter can be concurrently observed. This method can be used to gain insight into nanoparticle–protein interactions based on analyses of curvature and relative abundance.     

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。     

核四极共振隐藏炸药探测信息库设计

利用核四极共振(Nuclear Quadrupole Resonance, 简称NQR)技术探测炸药时,实验复杂,参数繁多. 原子核参数、脉冲参数、环境参数等各参数对炸药共振频率及探测信噪比都有不同程度的影响. 针对长期以来国内外一直没有统一的炸药信息库,测试数据无法有效记录和管理的现象,在全面分析各参数与共振频率之间关系的基础上,设计并实现了隐藏炸药探测信息库. 该信息库能有效的收集和记录炸药参数信息,为今后炸药测试数据的统计分析提供统一规范的数据支持.      

A method for the determination of the viscoelastic relaxation function of reactive materials

Modern insensitive high explosives HE are heterogeneous materials consisting of a mixture of explosive grains within a polymeric binder matrix [1]. The mechanical material behaviour is strongly determined by this heterogeneous structure. The stiffness and strength comes mainly from the explosive grains whereas the softer polymeric binder is responsible for the viscoelastic behaviour. Depending on the mechanical loading regime different mechanisms are present and must be taken into account for the material modelling.