Explosive Compositions Research Articles

Microstructure and formation of melting zone in the interface of Ti/NiCr explosive cladding bar

The tube of titanium and the bar of NiCr alloy were bonded through explosive cladding technique; a good quality bonding was obtained. Melting zones are encountered in sections of the explosive cladding interface, and they serious affect the properties of the explosive cladding composite. Microstructure of melting zone in the interface of Ti/NiCr explosive cladding bar were investigated by means of optical microscope (OM), scanning electron microscope (SEM) and microhardness as well as using micro-focus X-ray diffraction and electron probe analyses. The results show that the melting zone is composed of intermetallics of brittle and stiff, and there is no element diffusion during explosive cladding process. The tendency of composition segregation of melting zone is decreased. The solidification rate and the actual distribution coefficient of solute in the melting zone of Ti/NiCr explosive cladding interface are not less than 0.1×108k/s and 1 respectively. The formation of microstructure in the melting zone is result from the high solidification rate in the explosive cladding interface.

Structural Characterization of RDX‐Based Explosive Nanocomposites

AbstractRecently developed cyclotrimethylene trinitramine (RDX)‐based nanostructured explosive compositions were shown to exhibit greatly reduced initiation sensitivity as compared to conventional compositions prepared with coarser, micrometer‐scale RDX. In particular, improvements were shown in the sensitivity towards shock and impact stimuli, key sources of inadvertent initiation. Such an improved response to mechanical stimuli is believed to be largely a result of smaller crystal and void sizes. Characterization of these structural parameters is therefore necessary in order to construct a meaningful physical description of these novel explosive compositions. Herein, we report the results of a detailed structural characterization of these novel RDX‐based nanocomposites. The analyzed specimens were in pellet form with nominally 10 % porosity. These results constitute an unprecedentedly complete structural picture of this new class of energetic materials.

Effect of aluminum on the acceleration ability of composite formulations based on regular high explosives

The effect of addition of aluminum powders, including nanosized powders, on the acceleration ability of explosive compositions as studied by standard methods is examined. The analysis is based both on literature data and results obtained at the Semenov Institute of Chemical Physics RAS. A brief description of the methods and criteria for evaluating the acceleration ability, including the Gurney velocity, is presented. It is shown that the addition of highly dispersed aluminum can increase the acceleration ability of compositions as compared to that of individual HEs. Nanosized aluminum also improves the acceleration ability, but the observed increase is somewhat lower than for micron-sized aluminum because of a high content of alumina in nanoparticles. The possibility of increasing the acceleration ability by adding nanosized aluminum to CL-20 powerful HE is considered.

Nanoindentation of explosive polymer composites to simulate deformation and failure

Crack initiation and propagation is a common concern for molecular composites such as plastic bonded explosives (PBXs) and pharmaceutical tablets. Under compressive stresses, cracks form at contacts between crystals and propagate along crystal-binder interfaces, causing composite failure. To investigate this process, crystal-binder interfaces have been characterised and their mechanical properties tested. Here, samples were created with interfaces representative of those in PBXs and characterised with surface energy measurements and neutron reflectometry (NR). Nanoindentation was performed to simulate the deformation and cracking that occurs at crystal–crystal contacts through the binder. NR revealed that use of a plasticiser disrupts typical crystal–binder intermixing and results in a mechanically weaker interface. During nanoindentation, a plasticised binder was observed by atomic force microscopy to delaminate around indentation impressions, whereas a non-plasticised binder did not. Differences in interfacial adhesion and incompatible strain, dictated by the elastic–plastic film compliances, were used to explain the contrasting delamination behaviours.

Detection of unexploded ordnance by PGNAA based borehole-logging

The performance of a borehole-logging system, based on prompt-gamma-neutron-activation-analysis (PGNAA), for explosive detection was studied by Monte-Carlo simulations. The prompt gamma of nitrogen, which is a constituent of common explosive, was used to identify the unexploded ordnance (UXO). Our results show that the minimum counting time depends on the soil moisture, the cladding thickness and the explosive composition. In conjunction with the standard detection by magnetometry, the PGNAA is a promising analytical technique for definitive identification of deep buried UXOs.

Dissolution kinetics of sub-millimeter Composition B detonation residues: Role of particle size and particle wetting

The dissolution of the 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) from microscale particles (<250μm) of the explosive formulation Composition B was examined and compared to dissolution from macroscopic particles (>0.5mm). The dissolution of explosives from detonation soot was also examined. The measured mass transfer coefficients for the microscale particles were one to two orders of magnitude greater than the macroscopic particles. When normalized to particle surface area, mass transfer coefficients of microscale and macroscale particles were similar, indicating that the bulk dissolution processes were similar throughout the examined size range. However, an inverse relationship was observed between the particle diameter and the RDX:TNT mass transfer rate coefficient ratio for dry-attritted particles, which suggests that RDX may be more readily dissolved (relative to TNT) in microscale particles compared to macroscale particles. Aqueous weathering of larger Composition B residues generated particles that possessed mass transfer coefficients that were on the order of 5- to 20-fold higher than dry-attritted particles of all sizes, even when normalized to particle surface area. These aqueous weathered particles also possessed a fourfold lower absolute zeta-potential than dry-attritted particles, which is indicative that they were less hydrophobic (and hence, more wettable) than dry-attritted particles. The increased wettability of these particles provides a plausible explanation for the observed enhanced dissolution. The wetting history and the processes by which particles are produced (e.g., dry physical attrition vs. aqueous weathering) of Composition B residues should be considered when calculating mass transfer rates for fate and transport modeling.

Fate Dynamics of Environmentally Exposed Explosive Traces

The chemical and physical fates of trace amounts (<50 μg) of explosives containing 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and pentaerythritol tetranitrate (PETN) were determined for the purpose of informing the capabilities of tactical trace explosive detection systems. From these measurements, it was found that the mass decreases and the chemical composition changes on a time scale of hours, with the loss mechanism due to a combination of sublimation and photodegradation. The rates for these processes were dependent on the explosive composition, as well as on both the ambient temperature and the size distribution of the explosive particulates. From these results, a persistence model was developed and applied to model the time dependence of both the mass and areal coverage of the fingerprints, resulting in a predictive capability for determining fingerprint fate. Chemical analysis confirmed that sublimation rates for TNT were depressed by UV (330-400 nm) exposure due to photochemically driven increases in the molecular weight, whereas the opposite was observed for RDX. No changes were observed for PETN upon exposure to UV radiation, and this was attributed to its low UV absorbance.

High-speed synchrotron X-ray phase contrast imaging for analysis of low-Z composite microstructure

The study of high performance composites such as plastic-bonded explosives under extreme conditions often requires innovative experimental techniques. Here, static synchrotron X-ray phase-contrast imaging (PCI) of simulated explosive materials has been performed at high speed in an effort to determine feasibility of imaging material response to dynamic, high-strain rate events (102–107s−1). The microstructure of pristine materials, idealized composites and simulated explosive composites has been characterized with synchrotron PCI at the Advanced Photon Source. High spatial resolution (2μm) of the microstructure was achieved with 5μs exposures, and features such as interfaces, cracks, voids, and bubbles were clearly observed. The likelihood of obtaining sufficient phase information at even faster exposures (e.g., 0.2–0.5μs) is shown to be high.

Spectrophotometric and chromatographic determination of insensitive energetic materials: HNS and NTO, in the presence of sensitive nitro-explosives

As there are no molecular spectroscopic determination methods for the most widely used insensitive energetic materials, 2,2′,4,4′,6,6′-hexanitrostilbene (HNS) and 3-nitro-1,2,4-triazole-5-one (NTO), in the presence of sensitive nitro-explosives, two novel spectrophotometric methods were developed. For HNS and TNT mixtures, both analytes react with dicyclohexylamine (DCHA) forming different colored charge-transfer complexes, which can be resolved by derivative spectroscopy. The spectrophotometric method for NTO measures the 416-nm absorbance of its yellow-colored Na+NTO− salt formed with NaOH. TNT, if present, is pre-extracted into IBMK as its Meisenheimer anion forming an ion-pair with the cationic surfactant cetyl pyridinium (CP+) in alkaline medium, whereas the unextracted NTO is determined in the aqueous phase. The molar absorptivity (ɛ, Lmol−1cm−1) and limit of quantification (LOQ, mgL−1) are as follows: for HNS, ɛ=2.75×104 and LOQ=0.48 (in admixture with TNT); for NTO, ɛ=6.83×103 and LOQ=0.73. These methods were not affected from nitramines and nitrate esters in synthetic mixtures or composite explosives. The developed methods were statistically validated against HPLC, and the existing chromatographic method was modified so as to enable NTO determination in the presence of TNT. These simple, low-cost, and versatile methods can be used in criminology, remediation/monitoring of contaminated sites, and kinetic stability modeling of munitions containing desensitized energetic materials.

Energetic materials for nanocrystalline stainless steel production

Austenitic stainless steel is one of the most common classes of metallic alloys sintered by powder metallurgy processing routes. However, the uncontrolled grain growth induced by the temperature used in conventional sintering must be avoided. The increase in specific surface together with the decrease in particle/grain size accelerates the kinetics of grain growth. Dynamic densification is a physical process in which the energy is transmitted to the powder at high pressure during an extremely reduced time period, which leads to interparticle bonding without significant thermal effects.In this study nanocrystalline stainless steel powders were densified by explosives and compared with microcrystalline powder. Nanocrystalline stainless steel powders were produced by mechanical milling and sputtering. In both cases, the densification by explosive composition with a detonation velocity of 4mm/μs leads to the formation of nanocrystalline bulk stainless steel, with the same chemical and structural compositions as the starting powders.

Detonation pressure of explosive charges applied in spacecraft division systems

We present findings of experimental investigations of polytropic exponents of explosion products and the detonation pressure of explosive compositions with organic and inorganic inert components, including elastic explosives, which are used in spacecraft division systems. We have developed the calculation procedure for the detonation pressure and polytropic exponents of explosion products of charges made of the mentioned compositions.

Scaling of light emission from detonating bare Composition B, 2,4,6-trinitrotoluene [C7H5(NO2)3], and PE4 plastic explosive charges

It is well known that an intense flash of light is emitted when an explosive charge is detonated. The light emission continues well beyond the actual detonation process due to shock excitation of the air molecules around the charge, as well as post-detonation reactions in the expanding products of the detonation. Various researchers have studied these emissions, and it has been established that there are features in such emission spectra that can be regarded as characteristic for a specific explosive composition and configuration. In this study, the emission characteristics at wavelengths between 650 and 940 nm were experimentally investigated for cylindrical bare Composition B, 2,4,6-trinitrotoluene [C7H5(NO2)3], and PE4 plastic explosive charges in the mass (M) range of 0.5 kg to 4 kg. The results show that the light emission parameters scale to M1/3 consistent with other explosive blast parameters such as pressure and impulse (so-called Hopkinson’s scaling). It is also shown that for bare charges, two distinct regions in time can be distinguished for the light emission, namely, light from the early time frame, while the charge is detonating (and slightly beyond), and light from the expanding products of the explosive (the “fireball”). It is argued that in the first region, ionization effects and shock excitation of the air molecules around the charge dominate the light emission. The dominance of these effects fizzles out rapidly as the blast wave expands from the charge, leaving only light emission from the expanding products of the detonation.

Investigation on the Novel Technology of the Fine Inclusion Removal due to the Dispersed &lt;i&gt;In Situ&lt;/i&gt; Phase Induced by the Composite Ball Explosive Reaction

The production of high purity steel is a major task for the iron and steel enterprises in the 21st century. To improve the quality of steel products and produce the cleanness steel, the key technique is to control inclusions in the molten steel. In the present investigation, a novel fine inclusion removal technology due to the dispersed in-situ phase induced by the composite ball explosion reaction was put forward. A composite ball with this function has been designed and the industrial experimental investigation was also carried out. The results indicate that feeding composite ball in RH ladle is a novel technology and the inclusion in the molten steel can be removed effectively. Compared with conventional inclusion removal technology, the number of the oxide inclusion can be decreased to a lower level and the inclusion size becomes much finer. Using this novel technology, the total oxygen in the as-cast slab can approach to 6ppm. This novel technology can be achieved without special facility and be realized in most steelmaking plant.

Investigation on Cleansing the if Molten Steel with the Dispersed &lt;i&gt;In Situ&lt;/i&gt; Phase Induced by the Composite Ball Explosive Reaction in RH Ladles

A novel fine inclusion removal technology due to the dispersed in-situ phase induced by the composite ball explosive reaction was put forward. A composite ball with this function has been designed and prepared using a laboratory model batch type balling disc (at 12 rpm) and the composite ball has been fed at the end of RH refining. The results indicate that feeding composite ball in RH ladle is a novel technology and the inclusion in the IF molten steel can be removed effectively. Compared with conventional inclusion removal technology, the number of the oxide inclusion can be decreased to a lower level and the inclusion size becomes finer. Using this novel technology, the total oxygen in the as-cast slab can approach to 5ppm and the steel production cost for per ton can be reduced by 5 ~12 RMB.

Production and Sensitivity Evaluation of Nanocrystalline RDX‐based Explosive Compositions

AbstractThe initiation sensitivity of cyclotrimethylenetrinitramine (RDX) was investigated as a function of crystal size. For this study, RDX powders with mean crystal sizes of ca. 200 and 500 nm were prepared by rapid expansion of supercritical solutions (RESS) with carbon dioxide as the solvent. Initiation sensitivity testing to impact, sustained shock, and electrostatic discharge stimuli was performed on uncoated as well as wax‐coated specimens. The test data revealed that in a direct comparison to coarser grades the nanocrystalline RDX‐based samples were substantially less sensitive to shock and impact stimuli. Furthermore, the 500 nm RDX‐based specimens exhibited the lowest sensitivity values, an indication that minima in shock and impact sensitivities with respect to crystal size exist.

Novel Concept of Cleansing the Liquid Steel by the Fine &lt;i&gt;In-Situ&lt;/i&gt; Phase due to the Composite Ball Explosion Reaction in RH Ladle

The production of high purity steel is a major task for the iron and steel enterprises in the 21st century. To improve the quality of steel products and produce the cleanness steel, the key technique is to control inclusions in the molten steel. In the present investigation, a novel fine inclusion removal technology due to the dispersed in-situ phase induced by the composite ball explosion reaction was put forward. A composite ball with this function has been designed and the industrial experimental investigation was also carried out. The results indicate that feeding composite ball in RH ladle is a novel technology and the inclusion in the molten steel can be removed effectively. Compared with conventional inclusion removal technology, the number of the oxide inclusion can be decreased to a lower level and the inclusion size becomes much finer. Using this novel technology, the total oxygen in the as-cast slab can approach to 6ppm. This novel technology can be achieved without special facility and be realized in most steelmaking plant.

Numerical Simulation of Explosively Compacted Powder-in-Tube MgB&lt;sub&gt;2&lt;/sub&gt; Superconductor

High Tc MgB2 superconductors were fabricated using the ex-situ and in-situ powder in tube (PIT) technique. During treatment, the precursor materials were shock consolidated under high strain-rates using PETN as the explosive medium. After compaction, the superconducting properties of the steel-sheathed MgB2 samples were examined by means of magnetization measurements using a SQUID magnetometer. Bean’s critical state model was applied to investigate the critical current density characteristics of the samples at fields up to 5T. The superconducting transition temperature of the specimens was determined by examining the material temperature dependence of magnetisation in zero field cooled (ZFC) and field cooled (FC) states. An assessment of the explosive compaction technique was carried out by simulating the procedure using the LS-DYNA explicit finite element code. The sample is modelled as a porous soil-like material with a customised yield surface. The numerically estimated final product dimensions, porosity and hardness are compared to the experimental results; furthermore, the numerically obtained pressure, temperature and strain rate profiles are used to assess the efficiency of the compaction process for different explosive quantities and powder compositions.

Laser-induced breakdown method for code detection (identification) in explosion products of coded explosives

The results of a study on the development of a method for coding explosives are presented. As coding additives (CAs), it is proposed to use aluminum alloy powders with dosed amounts of rare-earth coding elements (CEs). This choice is dictated by the fact that aluminum alloys are commonly used as efficient additives in explosive compositions, while rare-earth elements are used as additives in technological operations, but are absent in the composition of standard explosives. In this case, the key to information on a given explosive and its manufacturer is the ratio of CE concentrations determined when analyzing explosives, e.g., when investigating an act of terrorism. Examples of explosion product decoding using a LIES laser-spark express analyzer.

Toward a Thermal Disequilibrium Multiphase Model for High Explosives Containing Metallic Particles

To investigate the effects of explosive composition on Al combustion, in particular regarding its oxygen balance, several liquid mixtures are experimentally studied with varying oxygen balance. They are then loaded with Al particles and the velocity of detonation (VOD) is recorded. Computational results with the help of conventional Chapman Jouguet (CJ) codes are compared but fail to reproduce experimental observations. A new multiphase flow model out of thermal equilibrium is then considered. Two options are considered as limiting cases: stiff thermal relaxation and vanishing heat exchange between Al and detonation products. With this last option, predictions are in excellent agreement with the experiments. This suggests that temperature disequilibrium plays a major role in heterogeneous explosives detonation dynamics.

Influence of Dense Inert Additives (W and Pb) on Detonation Conditions and Regime of Condensed Explosives

Results of experimental and theoretical studies of the unusual detonation properties of mixtures of high explosives (HEs) with high-density inert additives W and Pb were analyzed and systematized. Typical examples of the nonideal detonation of composite explosives for which the measured detonation pressure is substantially lower and the detonation velocity is higher than the values calculated within the framework of the hydrodynamic model, with the specific heat ratio for the detonation products of ∼6–8, are presented. Mechanisms of formation of anomalous pressure and mass velocity profiles, which explain the correlation between the Chapman-Jouguet pressure for HE–W and HE–Pb mixtures, the velocity of the free surface of duralumin target, and the depth of the dent imprinted in steel witness plates, are described.