A study of the interaction between the components of heterogeneous explosives by the electrical-conductivity method

The detonation of TNT/RDX alloys is studied by the electrical-conductivity method. The measurement technique is developed with correction for the deformation of electrodes in the explosion. The maximum electrical conductivity of pure TNT was ≈25 Ω⁻¹·cm⁻¹. The addition of RDX decreases the electrical conductivity and width of the conducting zone, which, is, apparently, connected with the formation of diamond. It is shown that the RDX particle size plays an important role. With equal mass fraction, the conductivity of the sample is several times smaller for micron particles than for millimeter particles. This fact is explained by the different degree of mixing of the detonation products of the heterogeneous-explosive components. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 5, pp. 97–108, September–October, 2000. This work was supported by the Russian Foundation for Fundamental Research (Grant Nos. 99-03-32336 and 96-15-96264).     

Specific Features of Synthesis of Detonation Nanodiamonds

It is demonstrated that the Chapman-Jouguet parameters for high explosives used in nanodiamond synthesis are located in the region of liquid nanocarbon; therefore, the chemical reaction zone of the detonation wave involves formation of carbon nanodroplets, which are later crystallized into nanodiamonds on the segment of the isentrope of expansion of detonation products, passing through the region of stability of nanodiamonds in the pressure range of 16.5–10 GPa and the temperature range of 3400–2900 K. Soot in the resultant mixture is the product of amorphization of nanodroplets rather than graphitization of ultrafine diamonds. The influence of detonation conditions of high-explosive charges in an explosive chamber on nanodiamond synthesis is analyzed. __________ Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 5, pp. 104–116, September–October, 2005.     

On the presence of states with a negative Grüneisen parameter in overdriven explosion products

Experimental data on the properties of explosion products in overdriven detonation for 50/50 TNT/RDX and PBX-9502 explosives indicate conditions characterized by a negative Grüneisen parameter. Given a possible relationship of this anomaly with the properties of explosion product components, available experimental data for nitrogen, carbon monoxide, carbon dioxide, and water are analyzed. The first three of these (carbon dioxide specifically) are capable of manifesting a negative Grüneisen parameter at pressures and temperatures characteristic of the anomaly of overdriven explosion products.     

Analysis of Post Detonation Products of Different Explosive Charges

High explosive charges containing TNT, Comp. B, PBXN-106, TNT/TATB and the aluminium containing charges TNT/AN/Al, Comp. B/Al and a PBX high explosive with polyurethane binder, RDX, AP and Al have been initiated in a containment of 1.5 m³ in argon atmosphere. The gaseous and solid products were analyzed by mass spectrometry and other techniques. From the reaction products, the completeness of the Al reaction under different conditions was evaluated. The heat of detonation was calculated from the heat of formation of the products and the components of the explosive charges. The method described is suitable for studying the reaction behavior of components in composite explosives, especially of less sensitive high explosives.     

Influence of the molecular structure of explosives on the rate of formation,yield, and properties of ultradisperse diamond

The dependence of the detonation rate and electrical resistance of the detonation products on the initial density of 2,4-dinitro-2,4-diazapentane is recorded. Investigation of the solid detonation products of DNP and its alloys with hexogen shows that the content of diamond in these products and the dimensions of its particles and microcrystallites are considerably smaller than for alloys of TNT with hexogen.Institute of Chemical Physics, 142432 Chernogolovka. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 2, pp. 102–106, March–April, 1994.     

Detonation synthesis of nanoscale silicon carbide from elemental silicon

Direct reaction of precursors with the products of detonation remains an underexplored area in the ever-growing body of detonation synthesis literature. This study demonstrated the synthesis of silicon carbide during detonation by reaction of elemental silicon with carbon products formed from detonation of RDX/TNT mixtures. Continuum scale simulation of the detonation showed that energy transfer by the detonation wave was completed within 2–9 μs depending on location of measurement within the detonating explosive charge. The simulated environment in the detonation product flow beyond the Chapman-Jouguet condition where pressure approaches 27 GPa and temperatures reach 3300 K was thermodynamically suitable for cubic silicon carbide formation. Carbon and added elemental silicon in the detonation products remained chemically reactive up to 500 ns after the detonation wave passage, which indicated that the carbon-containing products of detonation could participate in silicon carbide synthesis provided sufficient carbon-silicon interaction. Controlled detonation of an RDX/TNT charge loaded with 3.2 wt% elemental silicon conducted in argon environment lead to formation of ～3.1 wt% β-SiC in the condensed detonation products. Other condensed detonation products included primarily amorphous silica and carbon in addition to residual silicon. These results show that the energized detonation products of conventional high explosives can be used as precursors in detonation synthesis of ceramic nanomaterials.     

老化对TNT基熔铸炸药性能的影响

为了研究老化对炸药性能的影响,对自然贮存的3种熔铸炸药TNT／RDX、TNT／RDX／Al和 TNT／HMX／Al进行了加速老化试验。通过扫描电镜、真空安定性试验研究了老化前后3种炸药的微观形貌和安全性能,并测试了老化前后3种炸药的感度和爆速。结果表明,老化后炸药颜色变深,体积膨胀,质量变轻。样品的放气量小于2 mL／g ,热感度变化也较小。机械感度的变化与炸药组分和老化方式有关。TNT／RDX的爆速随着贮存时间的增加而降低,与整体加速老化情况一致,TNT／RDX／Al和 TNT／HMX／Al的爆热随贮存时间的增加变化趋势相反,说明两者老化机理可能不同。     

Isotope studies of detonation mechanisms of TNT,RDX, and HMX

An analysis is performed of experimental data from isotopic tracer studies of the detonation mechanism and formation of the diamond phase of carbon in the detonation products of TNT, RDX, HMX, and their mixtures. Dependences of the relative yield and phase composition of carbon in the detonation products of components of composite explosives on the particle sizes of the explosives are given. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 5, pp. 96–103, September–October, 2007.     

Modification of W/O Emulsions by Demilitarized Composition B

A series of W/O emulsion explosives containing 30–50 wt‐% of the demilitarized mixture RDX/TNT (Composition B 50/50) was prepared. Detonation velocities and relative explosive strengths of these mixtures were determined and their detonation characteristics were calculated according to the EU standard methods for commercial explosives. Thermal reactivities of the most reactive components of these W/O mixtures were examined by means of differential thermal analysis and outputs were analyzed according to the Kissinger method. The reactivities, expressed as the E_a ⋅ R⁻¹ slopes of the Kissinger relationship, correlate with the squares of the detonation velocities of the corresponding explosive mixtures. It was found that fortification of the W/O emulsions by the demilitarized mixture RDX/TNT allows modification of detonation velocities of the resulting emulsion explosives within relatively broad limits. However, the effect of this admixture on the relative explosive strength is not well defined. Nevertheless, fortification in this sense can give rock‐blasting explosives with a performance on the level of industrial powdered amatols.     

Using the tracer method to study detonation processes

The tracer method was used to study the synthesis of nanodiamonds during detonation of composite explosives. Alloys of TNT with RDX, HMX, PETN, and benzotrifuroxan were studied. It was shown that, in all cases, most nanodiamonds were formed from TNT carbon. It was concluded that during the chemical reaction in the detonation wave propagating in heterogeneous explosives, equilibrium parameters were not established. In homogeneous TNT/PETN mixtures, individual components react with each other to form common products. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 6, pp. 92–98, November–December, 2008.     

空爆圆柱型药柱二维图像的实时分析

为了实时分析圆柱型药柱空中爆炸火团的持续时间和大小,拓展圆柱型药柱空中爆轰参数的研究领域,在质量相同、试验条件相同和拍摄参数相同的条件下,采用高速动态分析仪,以4 000 f/s的拍摄速度获取了3种类型(即RDX型、HMX型和TNT型)各3发圆柱型药柱的空中爆炸图像,并计算出其空中爆炸火团的平均持续时间分别为:122.08 ms、164.50 ms和238.92 ms.应用ACDsee和AutoCAD工具软件,用尺寸标注的方法分别测算出各个爆炸火团的水平和垂直最大半径,结果是HMX型最大,分别为10.36 m和9.42 m;从图像中还可以观察到各类爆炸火团具有不同的几何形状.     

Detonation Products as a Function of Initiation Strength,ambient gas and binder systems of explosives charges

The way of initiating an insensitive high explosive can influence the start of a detonation reaction remarkably. In order to study the extent of this influence, different boosters and different booster structures for the initiation of explosive mixtures containing TNT and nitroguanidine (NQ) have been used. The experiments have been conducted in a 1.5 m³ containment from which the detonation products could be taken and analyzed. In those cases where we only used a 10 g RDX booster together with a detonation cap no. 8, we had not a complete detonation reaction by initiating cylindrical charges of TNT/NQ and TNT/AN. This means that unreacted TNT was analyzed in the solid residue, mainly consisting of carbon soot. On the other hand, we had a complete detonation using an additional booster of about 18 g detonation sheet, placed on the front side of the cylindrical explosive, having the same diameter as the explosive charge. Another part of the investigations deals with the determination of the influence of different argon pressures on the composition of the detonation gas and the solid residue. Between vacuum and one bar argon a strong change not only of the gas but also of the soot residue was measured. A stronger influence on the products was found using a confinement with glass tubes. The investigation of Al-containing charges exhibited a very different behavior compared with charges without Al. No more influence of vaccum or of different ambient gas pressure could be observed. By investigation of two composite explosive charges (PBX) containing binder systems of different energies and different oxygen balances, a great influence on the reaction of Al was found. The PBX charges with the better O₂-balance containing the energetic GAP-binder reacted nearly completely with the Al, opposite to the charge containing the polyisobutylene (PIB) binder system.     

Correlation of electrical conductivity in the detonation of condensed explosives with their carbon content

This paper presents the comparative analysis of the results of more than fifty experiments on measuring the electrical conductivity of detonation products of RDX, HMX, PETN, TNT, and TATB-based explosives. It is revealed that there is a correlation between the electrical conductivity and the mass fraction of carbon both in the chemical spike and at the Chapman–Jouguet point.     

Combustion heat of the Al/B powder and its application in metallized explosives in underwater explosions

An underwater explosion test is used to determine the detonation properties of metallized explosives containing aluminum and boron powders. An oxygen bomb calorimeter (PARR 6200 calorimeter, Parr Instrument Company, USA) is used to obtain the heat of combustion of the metal mixtures. As the content of boron powders is increased, the heat of combustion of the metal mixtures increases, and the combustion efficiency of boron decreases. The highest value of the combustion heat is 38.2181 MJ/kg, with the boron content of 40%. All metallized explosive compositions (RDX/Al/B/AP) have higher detonation energy (including higher shock wave energy and bubble energy) in water than the TNT charge. The highest total useful energy is 6.821 MJ/kg, with the boron content of 10%. It is 3.4% higher than the total energy of the RDX/Al/AP composition, and it is 2.1 times higher than the TNT equivalent.     

A Low‐Sensitivity Composition Based on FOX‐7

1,1‐Diamino‐2,2‐dinitroethene (DADNE, FOX‐7) is considered to be an explosive combining comparatively high performance and low sensitivity. In the present study, FOX‐7 has been evaluated as a possible replacement of RDX in TNT‐based melt‐cast compositions. A composition containing FOX‐7, TNT, Al and wax, and a method of preparing it were proposed. Its sensitivity to impact, friction, shock wave, jet impact, fast heating, and its thermal stability were tested. Some detonation parameters like the detonation pressure, velocity and heat were measured. Moreover, the Gurney velocity, the so‐called effective exponent of the expansion isentrope and the JWL equation of state of the detonation products were determined from the results of a cylinder test. The detonation characteristics were compared with that obtained for cast TNT.     

Effective Detonation Synthesis of Cubic Boron Nitride

Successful realization of detonation‐induced h‐BN→c‐BN phase transition requires that a hydrolysis of BN by water from the detonation products is suppressed. For this two kinds of experiments for synthesis of c‐BN were attempted: using benzo‐trifuroxan (with no water in products) as an explosive, in 80% yield; and using the cast 50% TNT+50% RDX charges containing 5–25 wt.‐% of h‐BN powder in order to expend water from the detonation products by a part of BN, and to realize the phase transition in the rest, in 10% yield.     

Where and when are nanodiamonds formed under explosion?

The formation of nano-sized diamonds during the detonation of a TNT/RDX explosive with 50/50 composition was investigated experimentally in situ by means of small-angle X-ray scattering using synchrotron radiation with nanosecond time resolution. No nanodiamonds were observed immediately after the detonation front, as only the nucleation of nanodiamonds takes place at this moment. The increase in small-angle X-ray scattering which was observed during 2 μs was the cause of the dynamic growth of nanodiamonds. The inclusion of a very thin shell around the explosive causes a significant increase in this time, because the kinetic of nanodiamonds growth was changed.

In another set of experiments, the nanodiamonds were artificially introduced into different explosives before explosion. The nanodiamonds were not destroyed in RDX immediately after the detonation front, but burned in an oxidants with some delay. In TNT, the nanodiamonds were not destroyed at all.     

Density distribution at the detonation front of cylindrical charges of small diameter

A synchrotron radiation based technique is use to study the density distribution at the detonation front and its neighborhood for condensed explosives. Particular data are obtained on the structure of the detonation front in TNT, RDX, and an alloy of TNT with RDX; a comparison of the data with those obtained using different techniques confirms the correctness of the technique. It is concluded that adequate information on the structure of the chemical-reaction zone can be obtained for charges of small diameter. At the same time, it is shown that the Chapman-Jouguet parameters for such charges are far from their predicted values for an infinite medium. The results of the work, including those on the curvature of the detonation front in charges of small diameter, supplement the existing knowledge of the detonation transformation in condensed explosives. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 2, pp. 91–99, March–April, 2007.     

The Influence of Temperature in the Range from 77 k to 338 k on the Detonation Velocity of RDX/TNT 60/40

The detonation velocity of rods made of RDX/TNT 60/40 was determined with high accuracy in the temperature range from 77 K to 338 K. It was found out that the detonation velocity decreases with increasing temperature. To explain this thermodynamically unusual behaviour it is assumed that the effect of the increase of the detonation velocity with increasing temperature is superposed on the decrease caused by the simultaneous decreasing density of the explosive.     

Synthesis of ultrafine diamonds from alloys of TNT with polycyclic nitramines

The synthesis of ultrafine diamonds from alloys of TNT with new polycyclic nitramines was studied experimentally. The use of nitramines with an oxygen balance smaller than that of RDX increases the yield of ultrafine diamonds. An increase in the particle size of the sensitizer in the TNT alloys was shown to result in a higher yield of diamonds. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 4, pp. 131–134, July–August, 2006.