Low Explosives Research Articles

Facile fabrication of porous CL-20 for low sensitivity high explosives.

A facile solvent/non-solvent co-crystallization technology is applied to fabricate porous CL-20, which exhibits interesting morphologies and low sensitivity with β-cyclodextrin as a crystal modifier.

Direct Real-Time Detection of Vapors from Explosive Compounds

The real-time detection of vapors from low volatility explosives including PETN, tetryl, RDX, and nitroglycerine along with various compositions containing these substances was demonstrated. This was accomplished with an atmospheric flow tube (AFT) using a nonradioactive ionization source coupled to a mass spectrometer. Direct vapor detection was accomplished in less than 5 s at ambient temperature without sample preconcentration. The several seconds of residence time of analytes in the AFT provided a significant opportunity for reactant ions to interact with analyte vapors to achieve ionization. This extended reaction time, combined with the selective ionization using the nitrate reactant ions (NO3(-) and NO3(-)·HNO3), enabled highly sensitive explosives detection from explosive vapors present in ambient laboratory air. Observed signals from diluted explosive vapors indicated detection limits below 10 ppqv using selected ion monitoring (SIM) of the explosive-nitrate adduct at m/z 349, 378, 284, and 289 for tetryl, PETN, RDX, and NG, respectively. Also provided is a demonstration of the vapor detection from 10 different energetic formulations sampled in ambient laboratory air, including double base propellants, plastic explosives, and commercial blasting explosives using SIM for the NG, PETN, and RDX product ions.

Upgraded Analytical Model of the Cylinder Test

AbstractA Gurney‐type equation was previously corrected for wall thinning and angle of tilt, and now we have added shock wave attenuation in the copper wall and air gap energy loss. Extensive calculations were undertaken to calibrate the two new energy loss mechanisms across all explosives. The corrected Gurney equation is recommended for cylinder use over the original 1943 form. The effect of these corrections is to add more energy to the adiabat values from a relative volume of 2 to 7, with low energy explosives having the largest correction. The data was pushed up to a relative volume of about 15 and the JWL parameter ω was obtained directly. The total detonation energy density was locked to the v=7 adiabat energy density, so that the Cylinder test gives all necessary values needed to make a JWL.

Shear Waves from Explosions in Granite Revisited: Lessons Learned from the New England Damage Experiment

Abstract We studied seismic‐wave generation from five small (60–122 kg) fully contained explosions detonated in Barre Granite as a part of the New England Damage Experiment (NEDE). The explosions were conducted using three types of explosives with different velocities of detonation (VOD): black powder, ammonium nitrate fuel oil (ANFO) emulsion, and composition B (COMP‐B). Empirical evidence suggests that the low VOD explosives produce more shear‐wave energy than high VOD explosives. The proposed mechanisms to explain this effect include: (a) inhibition of gas‐driven fracture propagation by thicker pulverized zone for high VOD explosions, and (b) fracture toughness increase at higher loading rate. The main objective of the experiment was to study differences in shear‐wave generation between different types of explosives, and to determine the likely mechanism responsible for these differences. Seismic amplitude analysis revealed that COMP‐B releases more energy and larger amplitude P waves for the same weight of explosives, while producing smaller amplitude S waves. Furthermore, large radial cracks were observed on the surface after the ANFO and black powder shots, while there was no surface fracturing after the COMP‐B shots. Thus, longer fractures correlate with higher S ‐wave amplitudes. However, drilling into the source region indicates that high VOD explosions may actually produce a smaller pulverized zone, which means that fracture inhibition is a less plausible explanation. Therefore we hypothesize that increase in loading rate, in combination with shorter impulse duration for high VOD explosives, inhibits fracture processes, and subsequently reduced S ‐wave radiation.

Study of Low Detonation Velocity Explosives Used in Explosion Welding

In order to solve a series of questions on low detonation velocity explosives used in explosion welding which was added into lots of salt, for example hand mixing is heterogeneous, low velocity detonation is unstable, moisture absorption and agglomeration of explosive is easy, ammonium nitrate (AN), wax, diluent, surfactant, gelling agent were mixed into slurry liquid when water temperature was controlled within 105-115°C, and after this liquid was dried, sieved, and cooled at the pressure between -0.07and -0.09Mpa, it can made low detonation velocity explosives used in explosion welding. The microstructure and moisture absorption of the explosive was analyzed, the influence of the charge layout density and thickness on detonation velocity was researched. The results show that each component of the explosives is homogeneous, and is not easy to absorb moisture. When the density is 0.71-0.74g﹒cm-3, the detonation velocity is 2300-2380m﹒s-1,which can satisfy the requirement of explosion welding of mental plate.

Development of pressure and temperature gauges to monitor in situ performance of commercial explosives

A better understanding of the detonation performance of an explosive charge can be gained by directly measuring pressure, temperature and velocity of detonation (VOD). This is particularly important with explosives used in the mining industry because their performance is directly influenced by the degree of confinement given by the borehole diameter and the surrounding rock mass. A project funded by the Australian Coal Association Research Program (ACARP) was initiated in early 2009 with the view to design and build cost effective prototype instrumentation to measure the relative differences in detonation pressures and temperatures of commercial mining explosives. The project’s primary focus was on low density explosives. Low density (also referred to as low shock) explosives have been available in various forms for nearly 20 years. There have been significant advances in the availability, reliability and flexibility of these explosives which now offer a range of densities and degrees of water resistance. Their detonation performance is not well understood and cannot be accurately predicted with current ideal and non-ideal detonation codes. It was therefore viewed as important to be able to directly measure pressure and temperature during the detonation process of these complex mixtures in production blastholes. Identifying the pressure release patterns of both conventional and low density explosives under different geotechnical conditions should provide the necessary information to both validate detonation codes and better define input parameters for breakage and fragmentation models. This paper gives a general description of the prototype instrumentation developed and reports on the results obtained to date in both laboratory and full scale conditions.

Negative Ion Formation of Pentaerythritol Tetranitrate in Atmospheric Pressure Chemical Ionization-Mass Spectrometry and in Corona Discharge Ionization-Ion Mobility Spectrometry

Wooju Communication & Technology Co., Seoul 150-732, KoreaReceived October 15, 2010, Accepted January 4, 2011Key Words : APCI-MS, IMS, Pentaerythritol tetranitrate, Negative ion, Detection limitExplosives have been divided into high and low ex-plosives, the former used as detonating charges and thelatter as propellants. Explosives have also been classifiedaccording to their chemical structures. Most organic ex-plosives contain nitro groups and are subdivided into nitro-aromatic compounds, nitrate esters, and nitroamines.

Highly Sensitive and Selective Explosive Detector Based on Nanoporous Silicon Photonic Crystal Infiltrated with Emissive Organics [Nanoproducts

Emitech Inc. (www.emitechinc.com) is developing a porous silicon (PSi) microcavity (MC)-based fluorescent detector for explosives. It was initially funded by the Army Small Business Innovation Research Phase II contract (Figure 1). The sensory part of the device is composed of a nano-PSi photonic crystal with MC, infiltrated with fluorescent organics that are specific to target explosive vapors and particulates. It is important that the nanodevice structure provides an extremely large interfacial area between the sensory material and the analyte vapors leading to its highest sensitivity, which is critical for fast trace detection of low vapor pressure explosives. An important feature of the nanodevice is the real-time sampling system (integrated with sensory head) based on the proprietary thermal air-jet technology.

Evaluation of Plastic Bonded Explosive (PBX) Formulations Based on RDX, Aluminum, and HTPB for Underwater Applications

AbstractAluminized high explosives are known to give better underwater performance. All explosive formulations for underwater targets are filled into warheads and shells by casting method. TNT, a high explosive is used as casting medium due to its lower melting point. Plastic bonded explosives are fast replacing TNT‐based high explosive formulations for the reasons that they are more insensitive and low vulnerable explosives with better shelf life. Few aluminized plastic bonded explosive formulations based on RDX, aluminum, and HTPB have been processed, varying the aluminum content from 0 to 35% and evaluated underwater. The present paper discusses the experimental methodology adopted to evaluate the above formulations for their ballistic parameters, viz., peak over pressure and impulse. Explosion bulge tests have been conducted with each explosive formulation and extent of bulge in test plates is presented and compared with a standard underwater explosive, viz., HBX‐3.

Investigation of 4-year-old stabilised/solidified and accelerated carbonated contaminated soil

The investigation of the pilot-scale application of two different stabilisation/solidification (S/S) techniques was carried out at a former fireworks and low explosives manufacturing site in SE England. Cores and granular samples were recovered from uncovered accelerated carbonated (ACT) and cement-treated soils (S/S) after 4 years to evaluate field-performance with time. Samples were prepared for microstructural examination and leaching testing. The results indicated that the cement-treated soil was progressively carbonated over time, whereas the mineralogy of the carbonated soil remained essentially unchanged. Distinct microstructures were developed in the two soils. Although Pb, Zn and Cu leached less from the carbonated soil, these metals were adequately immobilised by both treatments. Geochemical modeling of pH-dependent leaching data suggested that the retention of trace metals resulted from different immobilisation mechanisms operating in the two soils examined.

Tunable Generation and Adsorption of Energetic Compounds in the Vapor Phase at Trace Levels: A Tool for Testing and Developing Sensitive and Selective Substrates for Explosive Detection

Among various methods for landmine detection, as well as soil and water pollution monitoring, the detection of explosive compounds in air is becoming an important and inevitable challenge for homeland security applications, due to the threatening increase in terrorist explosive bombs used against civil populations. However, in the last case, there is a crucial need for the detection of vapor phase traces or subtraces (in the ppt range or even lower). A novel and innovative generator for explosive trace vapors was designed and developed. It allowed the generation of theoretical concentrations as low as 0.24 ppq for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in air according to Clapeyron equations. The accurate generation of explosive concentrations at subppt levels was verified for RDX and 2,4,6-trinitrotoluene (TNT) using a gas chromatograph coupled to an electron capture detector (GC-ECD). First, sensing material experiments were conducted on a nanostructured tungsten oxide. The sensing efficiency of this material determined as its adsorption capacity toward 54 ppb RDX was calculated to be five times higher than the sensing efficiency of a 54 ppb TNT vapor. The material sensing efficiency showed no dependence on the mass of material used. The results showed that the device allowed the calibration and discrimination between materials for highly sensitive and accurate sensing detection in air of low vapor pressure explosives such as TNT or RDX at subppb levels. The designed device and method showed promising features for nanosensing applications in the field of ultratrace explosive detection. The current perspectives are to decrease the testing scale and the detection levels to ppt or subppt concentration of explosives in air.

Dynamic Planar Solid Phase Microextraction−Ion Mobility Spectrometry for Rapid Field Air Sampling and Analysis of Illicit Drugs and Explosives

A preconcentration device that targets the volatile chemical signatures associated with illicit drugs and explosives (high and low) has been designed to fit in the inlet of an ion mobility spectrometer (IMS). This is the first reporting of a fast and sensitive method for dynamic sampling of large volumes of air using planar solid phase microextraction (PSPME) incorporating a high surface area for absorption of analytes onto a sol-gel polydimethylsiloxane (PDMS) coating for direct thermal desorption into an IMS. This device affords high extraction efficiencies due to strong retention properties at ambient temperature, resulting in the detection of analyte concentrations in the parts per trillion range when as low as 3.5 L of air are sampled over the course of 10 s (absolute mass detection of less than a nanogram). Dynamic PSPME was used to sample the headspace over the following: 3,4-methylenedioxymethamphetamine (MDMA) tablets resulting in the detection of 12-40 ng of piperonal, high explosives (Pentolite) resulting in the detection of 0.6 ng of 2,4,6-trinitrotoluene (TNT), and low explosives (several smokeless powders) resulting in the detection of 26-35 ng of 2,4-dinitrotoluene (2,4-DNT) and 11-74 ng of diphenylamine (DPA).

The Analysis of Black Powder Substitutes Containing Ascorbic Acid by Ion Chromatography/Mass Spectrometry*†

Black powder substitutes containing ascorbic acid are a group of low explosives that utilize ascorbic acid as the fuel. The analysis of these powders is complicated by the degradation of ascorbic acid which occurs rapidly in solution and may also occur as the powder ages. Aqueous extracts of both intact powders and postblast residues were analyzed by an existing ion chromatography/mass spectrometry (IC/MS) method used at the Bureau of Alcohol, Tobacco, Firearms and Explosives. Results have shown that while ascorbic acid itself is not detected in this method, its diagnostic degradation products (threonic acid, monohydrated diketogulonic acid, and oxalic acid) can be identified. In addition, anions from the inorganic oxidizers (perchlorate and nitrate) and combustion products such as chloride, chlorate, and nitrite, can be identified within the same experiment. While this IC/MS method shows promise, future modifications are necessary because of limitations in identifying threonate in postblast residues, as well as coeluting compounds observed in postblast residues.

Investigation of low detonation velocity emulsion explosives

Emulsion explosives (EEs) with detonation velocity up to 2–3 km/sec are considered. The compositions contain a large amount of hollow glass microspheres. Examples are given of the use of low detonation velocity EEs to clad metal plates with foils up to 0.1 mm thick and to weld a small-diameter tube to a steel collar in a parallel explosive welding arrangement.

Detection and discrimination of low concentration explosives using MOS nanoparticle sensors

In the present study, four explosives of NH 4NO 3, mineral explosives (ME), picric acid (PA) and 2,6-dinitrotoluene (2,6-DNT) have been investigated by using ZnO-doped nanoparticle sensors with additives of Sb 2O 3, TiO 2, V 2O 5 and WO 3. Firstly, eighteen ZnO-doped nanoparticle sensors were optimized and selected six best sensors to compose a new optimized array. Then, the detection capability of the sensor array was studied by using static sampling method. The results showed that with the increase in concentration of samples, the sensitivities of the sensors also increased, and the lowest detection limit of the four samples were low to 3.34 μg/L. At last, for the sake of approaching closer practical application, these four explosives were also studied with full dynamic sampling method and the results demonstrated that all the samples could be well identified completely at the concentration of 15.4 μg/L when maximum values of slope were extracted as the feature parameters to DFA analysis.

A Survey of Background Levels of Explosives and Related Compounds in the Environment*

In this paper, swabbings from various public areas in 28 different cities throughout the United States were collected. A wide variety of objects were tested, ranging from park benches and telephones to sign posts and mailboxes. Inorganic anions and cations common in low explosives were detected simultaneously using capillary zone electrophoresis. Organic high explosives including nitroaromatics, nitramines, and nitrate esters were detected using gas chromatography with a pulsed-discharge electron capture detector. Confirmation of selected results was performed by ion chromatography and negative ion chemical ionization GC/MS. In general the results provide two major conclusions: (i) with the exception of nitrate, most low explosive oxidizers are rare in the environment; (ii) no organic explosives or significant interferences to these explosives were detected.

Fluorescence Detection and Identification of Tagging Agents and Impurities Found in Explosives

The detection and identification of 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), and pentaerythritol tetranitrate (PETN) vapors have proven to be difficult and challenging due to the low vapor pressures of these high explosives. Detecting higher vapor pressure impurity compounds found in TNT and possible tagging agents mandated to be added to plastic explosives (RDX and PETN) would allow for easier vapor detection. The higher vapor pressure nitro compounds of interest are considered to be non-fluorescent; however, once reduced to their amino analogs, they have relatively high quantum yields. The standard reduction products, the reduction products obtained in solution, and the reduction products obtained in vapor phase were analyzed by conventional fluorescence, synchronous luminescence, and derivative spectroscopy. The nitro analogs of the isomers 1,3-diaminobenzene, 1,2-diaminobenzene, and 1,4-diaminobenzene are found as impurities in TNT. We provide for the first time the synchronous luminescence derivative spectra of these isomers; including their individual spectra and a spectrum of an isomeric mixture of the three. Using the standard reduction products associated with these isomers and other aromatic amines, our data suggest that the vapors of two signature impurities, 1,3-dinitrobenzene and 2,4-dinitrotoluene (2,4-DNT), minor impurity compounds, and two possible tagging agents, 2-nitrotoluene (2-NT) and 4-nitrotoluene (4-NT), can be detected and selectively identified using our fluorescence approach. To prove our methodology, we show that we were able to generate, collect, and reduce 2-NT, 4-NT, and 2,4-DNT vapors to their amino analogs. Using our fluorescence approach, these vapors could be detected and selectively identified both individually and in a mixture. Collectively, our data indicate that our method of detecting and identifying higher vapor pressure explosive-like compounds could potentially be used to detect and identify low vapor pressure explosives such as TNT, RDX, and PETN.

Estimating Total Effective Dose Equivalents from Terrorist Use of Radiological Dispersion Devices

ABSTRACT Radiological dispersion devices (RDDs), commonly called “dirty bombs,” utilize a conventional explosive to deliberately disperse non-fissile material as an aerosol. This analysis models total effective dose equivalent (Sv) at various locations down-wind from the detonation site subsequent to terrorists detonating a 241Am, 137Cs, 60Co, 192Ir, or90Sr RDD. A source term for each isotope equaling 3.7 × 1013 Bq with an instantaneous release by either high explosives or low explosives at street level is assumed in order to evaluate total effective dose equivalent (TEDE) under various meteorological scenarios for intentional releases of non-fissile materials by terrorists. The inhalation pathway on average contributes most to TEDE. The inhalation pathway accounts for 96% (0.22 Sv) of the mean exposure estimate of 0.2321 Sv and occurs over an extremely short time frame (i.e., a few minutes). Ground shine, on average, contributes the second most to TEDE estimates accounting for approximately 4% (0.009 Sv) of the estimate. A cautionary note with regard to ground shine is warranted, however, because Hotspot estimates for this pathway are based on the assumption that a person is exposed for 4 days (96 hours). The TEDE for submersion (i.e., passing through the plume without inhaling particles) is negligible for the scenarios evaluated contributing less than 1% (5.2 × 10−6 Sv) to the TEDE estimate averaged across all 140 model runs (5 nuclides × 2 rainfall scenarios × 2 explosive scenarios × 7wind and atmospheric stability scenarios). The TEDE value for 241Am from inhalation is much greater, on average, than the inhalation TEDE value for 60Co, 137Cs, 192Ir, or 90Sr. This underscores the potentially high risk to human health posed by exposure to 241Am. Ground shine is the primary exposure pathway for 60Co and 137Cs due to the energetic and penetrating gamma rays those radionuclides emit. 192Ir and 90Sr have relatively low mean TEDE values for all of the pathways examined.

Things That Go Boom: Injuries From Explosives

Abstract : Explosive agents are materials that undergo rapid exothermic reaction when appropriately stimulated. The degree to which this reaction occurs is dependent upon the characteristics of the explosive agent. Low order explosives react by rapid burning or conflagration. On the other hand, high order explosives produce extreme heat and energy and result in the formation of a pressure wave or blast wave. This supersonic, superheated wave, known as over-pressure comprises the blast front (Fig. 1). The blast wave is reflected and sustained by fixed structures and confined environments such as rooms, vehicles, etc., and may portend the effects of blast-related injury. By the same mechanism, water, which is a relatively noncompressible medium, sustains more of the energy from the blast energy and as such blast waves in water have a greater injurious effect propagated over a greater distance. The three main factors which characterize the blast wave are peak rate of pressure rise, peak pressure, and duration of the pressure rise.

Fluorescent polymer-porous silicon microcavity devices for explosive detection

Conjugated polymers entrapped in porous silicon microcavity have been studied as optical sensors for low volatility explosives such as trinitrotoluene. The fluorescence spectra of entrapped polymers were modulated by the microcavity via a spectral “hole” that matches the resonance peak of the microcavity reflectance. Exposure of the porous silicon microcavity containing entrapped polymer to explosives vapor results in a red shift of the resonance peak and the spectral hole, accompanied by the quenching of the fluorescence. This multiplexed response provides multiple monitoring parameters, enabling the development of an optical sensor array for the detection of target explosive vapor.