Shock Initiation Characteristics of an Aluminized DNAN/RDX Melt-Cast Explosive

Shock sensitivity is one of the key parameters for newly developed, 2,4-dinitroanisole (DNAN)-based, melt-cast explosives. For this paper, a series of shock initiation experiments were conducted using a one-dimensional Lagrangian system with a manganin piezoresistive pressure gauge technique to evaluate the shock sensitivity of an aluminized DNAN/cyclotrimethylenetrinitramine (RDX) melt-cast explosive. This study fully investigated the effects of particle size distributions in both RDX and aluminum, as well as the RDX’s crystal quality on the shock sensitivity of the aluminized DNAN/RDX melt-cast explosive. Ultimately, the shock sensitivity of the aluminized DNAN/RDX melt-cast explosives increases when the particle size decreases in both RDX and aluminum. Additionally, shock sensitivity increases when the RDX’s crystal quality decreases. In order to simulate these effects, an Ignition and Growth (I&G) reactive flow model was calibrated. This calibrated I&G model was able to predict the shock initiation characteristics of the aluminized DNAN/RDX melt-cast explosive.     

Thermokinetic decomposition and sensitivity studies of 4,4ˊ-diamino-3,3ˊ-azoxy furazan (DAAF)-based melt cast explosive formulations

4,4ˊ-diamino-3,3ˊ-azoxy furazan (DAAF) is an insensitive high explosive. DAAF has safety characteristics (impact, friction) similar to triaminotrinitrobenzene and shock sensitivity similar to HMX. The present article describes the thermal analysis and sensitivity study of DAAF with RDX and 2,4,6-trinitrotoluene (TNT). DAAF has been evaluated as a possible replacement for RDX in TNT-based, aluminized as well as nonaluminized melt cast formulation. DAAF-based melt cast formulations were characterized for their sensitivity to mechanical stimuli, bomb calorimetric analysis, and thermal decomposition behavior. The thermal analysis reveals the compatibility of DAAF with benchmark explosives like RDX and TNT in explosive formulations. The composition DT (DAAF + TNT) and DTA (DAAF + TNT+ Al) is more friction and impact insensitive as compared to RT (RDX + TNT) and RTA (RDX + TNT+ Al) compositions. The bomb calorimetric values of DT composition as well as DTA composition are higher than RT and RTA compositions. The result shows that DAAF can be effectively used as a RDX replacement in melt cast explosive formulations. DT-based aluminized composition showed more thermal stability than RT- and RTA-based control compositions, which clearly revealed the usefulness of DAAF for enhanced blast effect.     

Oxalylhydrazinium Nitrate and Dinitrate—Efficiency Meets Performance

Oxalylhydrazinium nitrate (OHN) and dinitrate (OHDN) were synthesized by protonation of oxalyldihydrazide with nitric acid. The synthesis is extremely cost effective (～$40/kg at the lab scale) and can be carried out in large scales and very good yields. OHN and OHDN were intensively characterized by low-temperature X-ray diffraction (XRD), nuclear magnetic resonance (NMR) and vibrational spectroscopy. These new organic nitrate salts could be used as powerful ingredients in energetic formulations due to their low sensitivities (measured by Bundesanstalt für Materialforschung und Pröfung methods). Their thermal stability was investigated by differential scanning calorimetry (DSC) measurements. Further thermal studies of OHN showed compatibility with TNT (2,4,6-trinitrotoluene), DNAN (2,4-dinitroanisole), and RDX (1,3,5-trinitro-1,3,5-triazinane). The theoretical detonation and propulsion parameters of OHN and OHDN were calculated with the EXPLO5.5 code and compared to well-known insensitive explosives. The aquatic toxicity of OHN was determined by the luminescent bacteria inhibition test, yielding a much lower toxicity than RDX.     

Thermal conductivity of energetic materials

ABSTRACT

Thermal conductivity has been determined for a variety of energetic materials (EMs) using finite element analysis (FEA) and cookoff data from the Sandia Instrumented Thermal Ignition (SITI) experiment. Materials studied include melt-cast, pressed, and low-density explosives. The low-density explosives were either prills or powders with some experiments run at pour density (not pressed). We have compared several of our thermal conductivities with those in the literature as well as investigated contact resistance between the confining aluminum and explosive, multidimensional heat transfer effects, and uncertainty in the thermocouple bead positions. We have determined that contact resistance is minimal in the SITI experiment, the heat transfer along the midplane is one-dimensional, and that uncertainty in the thermocouple location is greatest near the heated boundary. Our values of thermal conductivity can be used with kinetic mechanisms to accurately predict thermal profiles and energy dissipation during the cookoff of explosives.     

Numerical study of countermeasure against thermal stimuli for HMX-based polymer-bonded explosives

ABSTRACT

An accurate thermal decomposition model of Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)-based polymer-bonded explosives is indispensable to the design of countermeasure against environmental thermal stimuli for certain explosive devices. However, the complicated chemical reactions occurring in decomposition of HMX-based polymer-bonded explosives pose great challenge to scientists. In this study, the thermal ignition kinetic model proposed by Tarver is implemented to study thermal decomposition of HMX-based polymer-bonded explosives using commercial software Abaqus, which does not only consider the thermal decomposition of HMX but also the polymer binders. The simulation results are compared to ODTX and Scaled Thermal Explosion Experiment (STEX) and reasonably good agreements are achieved. Then the thermal decomposition model is applied to analyze an explosive device exposed to environmental thermal stimuli. Furthermore, countermeasure against environmental thermal stimuli is suggested and analyzed quantitatively for the explosive device. The time to explosion and environmental temperature before ignition is calculated and analyzed for the explosive device under various heating rates.     

Heteropolyacids: An Efficient Catalyst for Synthesis of CL-20

CL-20, a high-energy material with a cage-like structure, is considered the most powerful explosive today. It is usually prepared via nitration with concentrated nitric and sulfuric acid, but this technique pollutes the environment. In this article, CL-20 was synthesized by nitration of 2,6,8,12-tetraacetyl 2,4,6,8,10,12-hexaazatetracyclo[5,5,0,0^3,11,0^5,9]dodecane (TAIW) using a clean nitrating agent, heteropolyacids. Using the new nitrating agent caused the elimination of concentrated sulfuric acid during the reaction. This is an environmentally friendly technique.     

Shock initiation of TATB/FEFO formulations

Abstract

The shock initiation properties of transferable insensitive explosive (TIE) formulations based on the solid high explosive, triaminotrinitrobenzene (TATB), and the liquid explosive, bis(2-fluoro-2,2-dinitroethyl) formal (FEFO), are measured by wedge test, embedded particle velocity gauge and embedded manganin pressure gauge techniques and calculated using the Ignition and Growth reactive flow model. These extrudable formulations are demonstrated to be slightly more shock sensitive than the TATB/inert binder explosive, LX-17. However, the TIE formulations are much less sensitive than HMX-based explosives and still qualify as insensitive explosives in safety and hazard tests. The wedge tests showed a very steep dependence of run distance to detonation on the input shock pressure. Embedded gauge and reactive flow modeling results imply that shock initiation begins when a small amount of the solid TATB decomposes rapidly enough to heat the surrounding FEFO to decomposition temperature. The FEFO then reacts rapidly, raising the pressure and temperature sufficiently to cause surface decomposition of the TATB particles at rates comparable to those measured in other TATB-based explosives. An Ignition and Growth reactive flow model for TIE based on these assumptions yields reasonable agreement with the experimental shock initiation data.     

A comparative study of performance between TKX-50-based composite explosives and other composite explosives

Dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) is a promising candidate for high-energy explosive (e.g. HMX), which can be used as the main component in composite explosive formulations processed through a melting method. In the present study, TKX-50-based explosive composites were prepared using 2,4,6-Trinitrotoluene (TNT) or TNT/wax as the carrier, and were compared with HMX-, 3-nitro-1,2,4-triazol-5-one (NTO)-, and hexahydro-1,3,5-trinitro-1,3,5-s-triazine (RDX)-based formulations. Crystal stability, surface micro-topography, thermal decomposition performance, mechanical property, thermal sensitivity, and mechanical sensitivity of the composites were comprehensively investigated. Overall, TKX-50-based formulations exhibited improved properties with a superior safety performance compared to HMX- and RDX-based formulations and better mechanical properties than NTO-based formulations.     

Effect of Pressure of the Casting Vessel on the Solidification Characteristics of a DNAN/RDX Melt-Cast Explosive

This study experimentally and numerically investigated the effect of pressure of the casting vessel on the solidification characteristics of a DNAN (2,4-dinitroanisole)/RDX(cyclotrimethylenetrinitramine) melt-cast explosive. The solidification and cooling time was recorded by a thermocouple, the distribution of the shrinkage porosity was observed and analyzed, and the density of the explosive charge was measured. The primary solidification characteristics were verified by numerical simulation achieved with ProCAST casting software, and results were in qualitative agreement with experimental results. Both the experimental and numerical results demonstrate that increasing pressure of the casting vessel can effectively diminish the shrinkage porosity, reduce the solidification time, and increase the relative density of the DNAN/RDX melt-cast explosive.     

一种新型地震专用炸药震源

激发效果的优劣是影响地震资料采集效果的重要因素。在陆地地震勘探中，炸药震源激发是主要激发方式之一。采用的炸药和激发点的地质条件决定了采集的地震资料信噪比和带宽。常规炸药与地震专用炸药（dBX）的对比试验结果表明，在相同的表层地质条件下，采用dBX型炸药激发获得的地震数据的质量明显优于用常规炸药获得的地震数据。     

Thermal Behaviors and Their Correlations of Mg(BH4)2-Contained Explosives

In order to explore the effect of metal hydride on energetic materials’ thermal behaviors and their correlations, we studied the heats of combustion and detonation of RDX, TNT, and Mg(BH₄)₂-containing explosives both theoretically and experimentally. The results showed that Mg(BH₄)₂ can significantly improve the energy of explosive. As the mass fraction of Mg(BH₄)₂ increases, the combustion heat of composite explosives increases gradually, while the combustion efficiency decreases. When its mass fraction is about 30%, the theoretical heats of detonation of RDX/Mg(BH₄)₂ and TNT/Mg(BH₄)₂ reach maximum, which are 7418.47 and 7032.46 kJ/kg, respectively. When we compared the errors between calculation and experimental values, we found that L-C method is more accurate in calculating oxygen-enriched and oxygen-balanced explosives, and that minimum free energy method is more suitable for seriously negative oxygen-balanced explosive. For single explosive, there are three kinds of relationships between heat of combustion and detonation according to the oxygen balance. For Mg(BH₄)₂-containing explosives, the relationship is in accordance with Boltzmann function.     

Mass spectral and thermal studies on explosion of lead salts of picramic acid and 2,4-dinitro phenol

Abstract

The mass speotral studies on the slow decomposition and explosion of lead salts of 2,4 -dinitrophenol and 2-amino-4, 6-dinitrophenol show distinct differences in the reaction pathways of the two salts. The low temperature decomposition occurs in two stages of an explosion following a slow decomposition, where as both salts explode in an overlapping complex pattern at high temperatures. The decomposition pathways are predicted by unalysing the fragmentation patterns. The results are suggestive of first step of the reaction to be a rupture of the Pb-O linkage. Thermal studies supplementing the mass spectral data show that lead pioramato is more belsant than leud salt of 2,4 dinitrophenol. This is attributed to a higher degree of covalency of the Pb-O bond in picramate relative to dinitro phenolate.     

两步法合成2-氨基-5-硝基苯酚

以邻氨基苯酚和尿素为原料,将传统环合-硝化-水解三步法工艺改为环合硝化-水解两步法合成了2-氨基-5-硝基苯酚(ANP);研究了影响环合硝化反应和水解反应的因素;优化了反应条件。环合硝化反应的最优条件为:n(邻氨基苯酚)∶n(尿素)=1.00∶1.20、环合时间6h、硝酸用量40.2g、硫酸用量20g、硝化时间3h、硝化温度70℃,在此条件下中间产物6-硝基苯并噁唑酮的收率为90.2%;水解反应的最优条件为:体积分数95%的乙醇为溶剂、n(6-硝基苯并噁唑酮)∶n(氢氧化钠)=1.0∶3.3、水解温度80℃、水解时间15h,在此条件下ANP收率为81.2%。两步反应ANP的总收率为73.2%。对产品进行了元素分析和红外光谱表征,确认终产物为ANP。该方法成本低,ANP总收率高,溶剂可回收,三废量少。     

Mechanochemical Nitration of Aromatic Compounds

Nitration of organic compounds is necessary to produce many energetic materials, such as TNT and nitrocellulose. The conventional nitration process uses a mixture of concentrated sulfuric and nitric acids as nitrating agents and multiple solvents. The chemicals are corrosive and require special handling and disposal procedures. In this study, aromatic nitration has been achieved using solvent-free mechanochemical processing of environmentally benign precursors. Mononitrotoluene was synthesized by milling toluene with sodium nitrate and molybdenum trioxide as a Lewis acid catalyst. Several parameters affecting the desired product yield were identified and varied. A number of byproducts, i.e., dimers of toluene were also produced, but the selectivity was observed to increase with increasing mononitrotoluene yield. Both absolute mononitrotoluene yields and selectivity of its production increased with the increase in the energy transferred to the material from the milling tools.     

水平井液体炸药爆炸压裂裂缝模型计算方法研究

针对水平井开发及生产后期油层改造存在的工艺复杂、成本高、有效率低等问题,开展了液体炸药在水平井油层爆炸压裂的试验研究。基于层内爆炸技术及液体炸药在水平井油层的爆炸试验应用,探讨了深层岩石水平井液体炸药爆炸产生裂缝体系的计算模型及方法,分析了爆炸弹性地震波的作用,结合CZ44-58水平井液体炸药爆炸压裂的现场工艺试验进行了主要参数计算和分析。现场试验证明了液体炸药在水平井试验应用的安全可靠性及现场使用的可操作性,该计算方法为进一步开展水平井液体炸药爆炸压裂现场应用研究提供了设计参考和指导。     

Shock sensitivity of blasting explosive cartridges

Abstract

The undersand variable gap–initiator test was applied to most Japanese blasting explosive cartridges and found useful as the sensitivity test for the cartridges. The recent Japanese watergel and emulsion explosives were shown to be more shock–sensitive than previous ones. The blast noise in the undersand explosion was shown to decrease when the depth of sand cover the cartridge was increased. For 100g of explosive, a sand layer 20cm deep was effective in reducing the blast noise, when the depth of the sand layer was increased, there was no additional effect. All blasting explosives excluding Kuro Carlit were not ignited by a small gas flame. A cartridge of 100g Kuro Carlit was ignited undersand but did not show the phenomenon of deflagration to detonation     

Explosive Detection by Microthermal Analysis

Differential scanning microcalorimetry at high heating rates of ～ 300°C/s was performed on 30- to 100-µm-size explosive particles using two MEMS-based thermal conductivity gauges in air and under N₂. The gauges consist of a thin-film Si₃N_x membrane with a centrally located Al thin-film heater, which is surrounded by six thin-film Si/Al junctions, creating a temperature-sensitive thermopile (～ 1.3 mV/K) with an effective sensitive area of ca. 200 × 200 µm. Heating was carried out by applying a linear voltage ramp during 1.6 s. The measurements were performed in a specially designed exposure chamber having a transparent glass lid that enabled optical observation of the thermal process.

Besides explosives (TNT, RDX, picric acid, urea nitrate, and TATP) we have studied nonexplosive materials, organic and inorganic, in order to see whether the explosives have a unique response. The materials we studied were oxygen-poor and -rich organic compounds (polyethylene and sugars, respectively), sea sand, and iron flakes.

Clear, well-resolved exotherms were obtained at moderated temperatures (～ 250°C) for all types of explosive materials tested by us. In addition, all explosives exhibited a melting endotherm preceding the exotherm. Sea sand and iron showed no peaks at the heating temperature range. Polyethylene showed an endotherm representing its melting. The sugars showed an endotherm but also an exotherm when heated to elevated temperatures (> 370°C). The thermogram of each material depends on its properties and is characterized by a unique pattern. This pattern may enable the detection and identification of explosive particles using this technology.     

NTO-Picryl Constitutional Isomers—A DFT Study

The quantum chemical properties and the detonation performance of some new explosives, 5-nitro-4-picryl-2,4-dihydro-3H-1,2,4-triazol-3-one (class A) and 5-nitro-2-picryl-2,4-dihydro-3H-1,2,4-triazol-3-one (class B), and their constitutional isomers have been investigated theoretically using the density functional theory (DFT) 6-31G(d,p) method.

All of the constitutional isomers were found to be more sensitive than 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO) and TNT but more insensitive than RDX and HMX. Their detonation performance is higher than that of NTO and TNT and all except two had lower detonation performance than RDX and HMX.     

Improved synthetic routes to polynitroheterocycles

Abstract

The preparations of several explosive precursors utilizing oxidative nitration are described. These include 1,3-di-t-butyl-5,5-dinitrohexahydropyrimidine, 3-t-butyl-5,5-dinitrotetrahydro-1,3-oxazine, 2,2-dinitro-1,3-propanediol (ADIOL) and potassium aci-2,2-dinitroethanol. The former pyrimidine and oxazine precursors were nitrolyzed to 1,3,5,5-tetranitrohexahydropyrimidine (DNNC) and 3,5,5-trinitrotetrahydro-1,3-oxazine (TriNOx). ADIOL, a widely used reagent in explosives preparation, was prepared by the trans-ketalization of 2,2-dimethyl-5,5-dinitro-1,3-dioxane. The dioxane was prepared in high yield by the oxidative nitration of 5-hydroxymethyl-2,2-dimethyl-5-nitro-1,3-dioxane. The little known explosive, 1,3,3,5,5-pentanitro-piperidine (PNP), has been prepared from potassium aci-2,2,4,4-tetranitrobutanol and t-butylamine hydrochloride. The vacuum thermal stabilities of DNNC, TriNOx and PNP at 100°C are reported.     

Measurements of reaction zone and determination of the equation of state parameters of DNAN-based melt-cast aluminized explosive

ABSTRACT

To investigate the detonation characteristics and the detonation wave profiles of the melt-cast aluminized explosive RBOL-2 (DNAN/HMX/aluminum/other additives), the particle velocity of the interface between the explosive and the Lithium-Fluoride (LiF) window and the free-surface velocity of the copper plate accelerated are measured by using the DISAR interferometer system. It is found that, for RBOL-2 explosive, the reaction zone length is 202 ± 2.5 ns/1.073 ± 0.013 mm, the particle velocity and the pressure at the Von Neumann spike are 2364 ± 3 m/s and 41.80 ± 0.07 GPa, respectively, and the particle velocity and the pressure at the Chapman-Jouguet point are 1564 ± 3 m/s and 25.42 ± 0.05 GPa, respectively. Moreover, the parameters of the Jones-Wilkins-Lee (JWL) equation of state of the RBOL-2 explosive are also determined by the genetic optimization algorithm and the measured free surface velocity of the copper plate.