Primary Explosives Research Articles

Tetrazole Azasydnone (C2 N7 O2 H) And Its Salts: High-Performing Zwitterionic Energetic Materials Containing A Unique Explosophore.

This work reports the first compound containing both a tetrazole and an azasydnone ring, a unique energetic material. Several energetic salts of the tetrazole azasydnone were synthesized and characterized, leading to the creation of new secondary and primary explosives. Molecular structures are confirmed by 1 H and 13 C NMR, IR spectroscopy, and X-ray crystallographic analysis. The high heats of formation, fast detonation velocities, and straight-forward synthesis of energetic azasydnones should capture the attention of future energetics research.

Presence of mercury and methylmercury in Baltic Sea sediments, collected in ammunition dumpsites

Methylmercury (MeHg) is the most toxic and dangerous form of mercury occurring in the environment. MeHg is highly bioaccumulative in organisms and undergoes biomagnification via the food chain. In the Baltic Sea munition dumpsites, methylmercury can be formed from mercury fulminate contained in primary explosives, as environmental conditions there favour methylation. MeHg in analysed sediments ranged from 19 to 2362 pg g−1d.w., the concentration of mercury (HgTOT) ranged from 4 to 294 ng g−1 d.w., and the values of MeHg/Hg ratio ranged from 0.1 to 2.0%. The obtained results confirmed that munition dumpsites are a source of mercury. The concentration of MeHg is elevated in a wider area than immediately next to dumped munitions. Presented results suggest that physical processes responsible for sediment and near-bottom water movement are diffusing MeHg signal, making munition dumpsites rather a diffuse source of MeHg than a number of point sources associated with particular munitions.

Synthesis of 5‐Nitrotetrazolates by the Direct Oxidation of 5‐Aminotetrazole in a Single‐Pot Synthesis without Isolation of Explosive Intermediates

A readily available oxidizer, potassium superoxide can be used for the oxidation of 5-amino-1H-tetrazole (5-AT) to 5-nitrotetrazole (5-NT) in high yields in a single-pot synthesis. This strategy reduces the synthesis of this important energetic material down to a single step and eliminates highly sensitive diazonium and copper salt primary explosive intermediates. Use of dimethyl sulfoxide along with molecular sieves and 18-crown-6 as phase transfer catalyst promoted faster reaction rates and greater yield. The overall yield of this process is 48-53 % and the resultant aqueous solution of product was effectively used for the preparation of nitrotetrazole-containing primary explosive DBX-1. Unlike current methods of nitrotetrazole preparation, this entirely solution-based route results in a final solution of sodium nitrotetrazolate, without the need to handle energetic intermediates or products, making it the safest method of nitrotetrazole preparation reported to date.

Charged Charges: Zwitterionic Primary Explosives

Key words high-energy materials - mesoionic heterocycles - zwitterions

Time Delay of Initiation of some Primary Explosives and Initiating Mixtures when Exposed to Continuous IR Laser Radiation

AbstractLaser initiation of energetic materials is a topic of significant interest. An extremely important parameter of initiation for numerous applied tasks is the time delay of initiation from the beginning of laser exposure. Experimental studies of the process of initiation of a number of primary explosives (lead styphnate (LS), lead azide, (LA)) and initiating mixtures (potassium perchlorate and potassium hexacyanoferrate (III) (PP/PH), bismuth oxide and aluminum ‐ nanothermite (NT)) under the exposure of a continuous IR (0.915 μm) laser with a power of up to 10 W were carried out. The time delay of initiation of these explosives was measured. It is shown that nanothermite (NT) has the lowest time delays and minimal initiation thresholds. At a laser power of 1 W and a light spot diameter of 0.5 mm (intensity 0.5 kW / cm2) the time delay of NT initiation was 1.2–1.8 ms. For other explosives with such a laser spot diameter, the initiation threshold was 2–3 W (1–1.5 kW/cm2). It is shown that mixtures of these explosives photosensitized by 0.5 % nanoaluminum have an initiation threshold ten times lower than for pure materials. For such compositions, the initiation time delay was 2–10 ms at the laser radiation intensity of 0.5 kW/cm2. It was found that for the PP/PH material there is a certain limit on the minimum time delay of initiation, which was 0.1–0.15 ms. It is suggested that this effect is associated with the micro‐hotspot nature of laser initiation of EM and the presence of a critical zone of initiation.

Pentazolate Anion Cyclo-N5−: Development of a New Energetic Material

Abstract The pentazolate anion cyclo-N5- has received considerable attention from researchers, most metallic and non-metallic salts synthesized from pentazole have decomposition temperatures exceeding 100 °C. The author thinks, anhydrous metallic pentazolates provides prospects for wide application in the field of green, non-toxic, high-energy primary explosives. Hydrazine pentazolate and hydroxylamine pentazolate which have nitrogen contents of 95% are regarded as non-metallic pentazolates with the best performance and application prospects. Optimize synthesis processes of pentazole and functional group-modified pentazolate compounds will be the key direction in pentazole chemistry.

High-Pressure Structural and Electronic Properties of Potassium-Based Green Primary Explosives

Recently synthesized green primary explosives potassium 4,4′-bis(dinitromethyl)-3,3′-azofurazanate (K2BDAF) and potassium 1,1′-dinitramino-5,5′-bistetrazolate (K2DNABT) offer fast, powerful initiation capacity and high-performance detonation characteristics to replace the long-standing toxic primary explosives. In the present study, we report the structural and electronic properties of the emerging green primary explosives K2BDAF and K2DNABT under hydrostatic pressure up to 10 GPa. We observed that dispersion correction methods are important for capturing weak intermolecular interactions in order to accurately describe the geometries of the primary explosives. The computed ground state structural properties using optB86b-vdW method are in good agreement with the experimental results. The pressure-dependent lattice constants and bond parameters show anisotropic nature and also a sharp discontinuity around 4–5 GPa. The obtained equilibrium bulk modulus shows that K2BDAF is softer than K2DNABT. Bonding analysis revealed that the C-NO2 energetic functional groups are more sensitive than the stable ring structure under hydrostatic pressure. The calculated electronic structure of K2BDAF using the Tran–Blaha-modified Becke–Johnson (TB-mBJ) potential shows a direct-to-indirect band gap transition around 5 GPa, which is consistent with the aforementioned discontinuity of the structure, while K2DNABT is found to be a direct-band-gap insulator in the studied pressure range of 1–10 GPa. The abnormal trends in the structural and electronic properties suggest that K2BDAF may undergo a structural transition/distortion around 4–5 GPa of pressure.

Comparison of explosion models for detonation onset estimation in large-scale unconfined vapor clouds

Although industrial denotations in semi-open and congested geometries are often neglected by many practitioners during risk assessment, recent studies have shown that industrial detonations might be more common than previously believed. Therefore, from the explosion safety perspective, it becomes imperative to better assess industrial detonation hazards to improve robustness of explosion mitigation design, emergency response procedures, and building siting evaluation. Having that in mind, this study aims to review current empirical vapor cloud explosion models, understand their limitations, and assess their capability to indicate detonation onset for elongated vapor clouds. Six models were evaluated in total: TNO Multi-Energy, Baker-Strehlow-Tang (BST), Congestion Assessment Method (CAM), Quest Model for Estimation of Flame Speed (QMEFS), Primary Explosion Site (PES), and Confinement Specific Correlation (CSC). Model estimations were compared with large-scale test data available in the open literature. The CAM model demonstrated good performance in indicating deflagration-to-detonation transition (DDT) for test conditions experiencing detonation onset without any modification in the methodology. Some suggestions are provided to improve simulation results from PES, BST and QMEFS.

Sensitive Energetics from the N-Amination of 4-Nitro-1,2,3-Triazole.

Energetic N‐amino‐C‐nitro compounds 1‐amino‐4‐nitro‐1,2,3‐triazole and 2‐amino‐4‐nitro‐1,2,3‐triazole are characterized for the first time as energetic materials. These compounds were characterized chemically by nuclear magnetic resonance (NMR), Infrared spectroscopy and X‐ray crystallography. Compounds were also characterized energetically by differential scanning calorimetry (DSC), impact, and friction and found to possess sensitivities and performances classifying them as primary explosives with PETN‐like performance.

Study on Synthesis and Characterization of Primary Explosive KDNBF with Different Morphologies

AbstractTraditional primary explosives are usually heavy metal salts, especially salts of lead, such as lead azide (LA) and lead styphnate (LS), which can cause environmental pollution problems. The potassium salt of 4,6‐dinitrobenzofuroxan (KDNBF) has attracted more and more attention due to its advantages of no heavy metal pollution to the environment and appropriate sensitivity. There are many reports on the thermal properties and applications of KDNBF, but few reports on the morphological properties. In addition, little is known about the optimal synthesis conditions of KDNBF with different morphologies in the preparation process. In this study, Taguchi's experimental design method was used to determine the optimal experimental conditions for obtaining the maximum yields of KDNBF with different morphologies. The synthesized KDNBF was identified by means of SEM, NMR, FTIR, EA, and TG‐DSC, and its sensitivity was measured using BAM fallhammer, BAM friction tester, and electrostatic spark sensitivity tester. The experimental results indicated that the maximum yields of flaky and spherical KDNBFs could reach 85.6 % and 82.6 % after purification under the optimal experimental condition, respectively. The spherical KDNBF powder had a relatively denser structure than the flaky KDNBF powder. The thermal analyses showed that the activation energies of the decomposition reaction of the flaky and spherical KDNBF powders calculated by the Kissinger method were 171.5 and 188.5 kJ mol−1, respectively, and the Ozawa method were 170.7 and 186.9 kJ mol−1, respectively. The thermal stability of spherical KDNBF powder was higher than that of flaky KDNBF powder. In addition, the sensitivity tests showed that the spherical KDNBF powder was less sensitive than the flaky KDNBF powder.

Study on Pressure Characteristics and Its Evolution Law at the Ellipsoidal End Cover Pole of Cylindrical Explosion Containment Vessels

To explore the postposition of the maximum pressure at the pole of the ellipsoidal end cover of cylindrical explosion containment vessels and to reveal the mechanism of the load evolution, the experimental method was used to measure the pressure curve at the pole under different charges, and the numerical simulation method was used to analyze the evolution law of the explosion flow field within the end cover. The results show that the end cover pole was subjected to three types of pressure: the primary explosion wave, the secondary shock wave and the convergence wave. In addition, the pressure peaks increased in sequence. The evolution of the flow field in the end cover was affected by the amount of charge and the aspect ratio of the vessel. When the scaled distance due to a small charge increased, or when the aspect ratio of the vessel was reduced, the time interval between the convergence wave and the secondary shock wave at the end cover pole decreased gradually. When the scaled distance increased to 4.05 m·kg−1/3, the convergence wave at the pole superimposed on the secondary shock wave. As the aspect ratio of the vessel ranged from 1.75 to 2.50, the time interval between the two peaks was about 150 μs. However, if the aspect ratio was less than 1.40, the convergence wave and the secondary shock wave were fused through complex interaction.

Theoretical study of the reduction in sensitivity of copper azide following encapsulation in carbon nanotubes.

Research aimed at reducing the sensitivity of primary explosives with excellent ignition performance is of great significance for their practical application. In this work, we theoretically studied the effect of inserting the primary explosive copper azide (Cu(N3)2) into single-walled carbon nanotubes (SWCNTs) on the sensitivity of the explosive to changes in hydrostatic pressure. The electronic structure of Cu(N3)2 was found to be more sensitive to external pressure than lead azide, which is consistent with their experimental impact sensitivities. A composite of Cu(N3)2 molecules and SWCNTs (Cu(N3)2/CNTs) was prepared in which the components mainly interacted electrostatically and the Cu(N3)2 molecules formed semi-arc structures along the nanotube walls, rather than exhibiting their usual planar structure. The electrostatic potential and electronic structure of the composite indicate that it is more stable than crystalline Cu(N3)2. Notably, combining the Cu(N3)2 with the SWCNTs reduces the sensitivity of the Cu(N3)2 to external pressure, implying that carbon nanotubes can reduce the sensitivity of Cu(N3)2. This work should aid the development of highly efficient green primary explosives.

Numerical analysis of the interaction of two underwater explosion bubbles using the compressible Eulerian finite-element method

This paper presents numerical investigations of the nonlinear interactions between two underwater explosion (UNDEX) bubbles using the compressible Eulerian finite-element method (EFEM). The volume of fluid method is applied to capture the multi-fluid interface. In this model, the high-temperature and high-pressure gaseous products inside the UNDEX bubble are described by the equation of state for Jones–Wilkins–Lee, which allows us to consecutively simulate the propagation of the primary explosion shock wave and multi-period bubble pulsations. To verify the efficiency and accuracy of the present model, comparisons with experimental data are performed, showing that both the dynamic behaviors of oscillating bubbles and the pressure profiles of primary shock waves, bubble pulsations, and jetting loads are highly consistent. In addition, it is found that the EFEM model can satisfactorily reproduce the complex characteristics of interacting bubbles, such as the coalescence and splitting that occur during later pulsating cycles in bubbles. On this basis, the effects of the initial bubble–bubble distance γbb and buoyancy parameter δ on the features of bubble interactions and the corresponding pressure loads in the flow field are analyzed and discussed. In particular, the pressure induced by two identical UNDEX bubbles (each generated by detonation of an explosive with weight W) is compared to that induced by a single bubble generated by an explosive with weight W or 2W to provide the basic technical support and reference for the design of multiple-weapon attacks in military engineering applications.

Molecular design of nitro-oxide-substituted cycloalkane derivatives for high-energy-density materials

High-energy-density materials in which cycloalkane hydrogens (cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, and cyclooctane) were replaced with -N-NO2 and –NO functional groups were designed and evaluated with regard to their explosive characteristics by using density functional theory calculations in combination with the Kamlet-Jacobs equations and an atoms-in-molecules analysis. Improved detonation properties with a higher sensitivity than conventional explosives such as 1,3,5-trinitro-1,3,5-triazinane and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane were predicted. Interestingly, NO-substituted structures showed substantial detonation properties with very low sensitivities. This method of substituting –NO groups on cycloalkanes supplies a firm basis for further studies on the design of new explosives. Moreover, the newly found structures may be promising candidates for developing primary explosives.

Comparison of 1-Propyl-5H-tetrazole and 1-Azidopropyl-5H-tetrazole as Ligands for Laser Ignitable Energetic Materials

Laser ignitable explosives are potential candidates in future applications for replacing toxic and very sensitive primary explosives, which are used in current devices. In this study, the literatur...

High-performance primary explosives derived from copper thiolate cluster-assembled materials for micro-initiating device

As an important primary explosive, copper azide is attractive for its outstanding detonation power, but it is limited by high electrostatic sensitivity and inferior ignition ability for use in micro-initiating device. In this work, we report the first copper thiolate cluster-assembled material (Cu12bpy, bpy = 4,4′-bipyridine) and successfully employ it as a precursor to prepare copper azide-heteroatoms doped porous carbon hybrids (denoted as CA-HPCH). Given the dense copper content, abundant heteroatoms and periodic structure of Cu12bpy, as-obtained CA-HPCH exhibits high copper azide content (89.43%), excellent flame ignition capability (H50 ≥ 60 cm) and reduced electrostatic sensitivity (E50 = 1.1 mJ). The performance is superior to pristine copper azide and surpasses that of most reported primary explosives. Furthermore, the micro-initiating device fabricated by CA-HPCH displays relatively short ignition time (7.0 µs) and low input ignition energy (0.106 mJ). These findings provides new sight to develop high-performance primary explosives for use in micro-initiators.

Functionalized carbon fibers assembly with Al/Bi2O3: A new strategy for high-reliability ignition

Carbon fiber is used to construct an energy conversion component with the purpose of high reliability, safety and potential application in micro size. The carbon fiber oxidant (CFO) is endowed as the carrier for the assembly of CFO/Al/Bi2O3 while long-range electrostatic force and covalent interactions are analyzed as the main force. The self-assembly can function with a voltage as low as 15.34 V and can detonate RDX successfully without using primary explosives and traditional bridge film unit. The ignition mechanism is deduced that carbon fibers have a transient high conductivity when the voltage is charged. The one-dimensional structure and micro-size make the puncture easily and reliably. Moreover, the integration of Al/Bi2O3 enhanced its initiation power and reliability. The research broadens the understanding of carbon fiber as one-dimensional material, and more applications are expected in this new field by considering the variety of carbon fiber size, different sorts of reactive materials and so on.

Nitrogen-Rich Tetrazolo[1,5-b]pyridazine: Promising Building Block for Advanced Energetic Materials.

Two metal-free explosives, tetrazolo[1,5-b]pyridazine-containing molecules [6-azido-8-nitrotetrazolo[1,5-b]pyridazine-7-amine (3at) and 8-nitrotetrazolo[1,5-b]pyridazine-6,7-diamine (6)], were obtained via straightforward two-step synthetic routes from commercially available reagents. Compound 3at displays an excellent detonation performance (Dv = 8746 m s-1 and P = 31.5 GPa) that is superior to commercial primary explosives such as lead azide and diazodinitrophenol (DDNP). Compound 6 has superior thermal stability, remarkable insensitivity, and good detonation performance, strongly suggesting it as an acceptable secondary explosive. The initiating ability of compound 3at has been tested by detonating 500 mg of RDX with a surprisingly low minimum primary charge of 40 mg. The extraordinary initiating power surpasses conventional primary explosives, such as commercial DDNP (70 mg) and reported 6-nitro-7-azido-pyrazol[3,4-d][1,2,3]triazine-2-oxide (ICM-103) (60 mg). The outstanding detonation power of 3at contributes to its future prospects as a promising green primary explosive. In addition, the environmentally benign methodology for the synthesis of 3at effectively shortens the time from laboratory-scale research to practical applications.

Pulsed laser irradiation of a nanoparticles sensitised RDX crystal

The laser initiation of secondary explosives presents tactical, safety and environmental advantages over traditional ignition systems utilising primary explosives. In this paper, direct ignition or initiation by pulsed laser was investigated of cyclotrimethylenetrinitramine (RDX) crystals doped with gold nanoparticles (GNPs) for the first time. A nano-seconds pulsed laser was used for direct irradiation of the crystals at the GNP's surface-plasmon-resonance wavelength of 532 nm. RDX crystals were recrystallised from a solution containing GNPs and characterised by visual microscopy for surface coating and subsurface doping. A high-speed camera was used to observe and capture the modes of interaction between the GNPs-doped RDX crystals and pulsed laser irradiation with a new classification method. Laser fluence thresholds for ignition and initiation were established. The GNPs sensitized RDX to pulsed laser irradiation at this selected wavelength is 3 orders of magnitude more sensitive than pure RDX. Direct initiation of the GNPs doped RDX crystal at laser fluence of 0.04 J/cm2 led to the total consumption of a crystal sample, which was unreproducible with pure RDX. The results show that GNPs are effective optical sensitizers for direct initiation of RDX crystal by low-power pulsed laser.

Hydrogen peroxide (H2O2): a review of its use in homemade explosives

This article presents an overview of hydrogen peroxide and its use in the illicit production of homemade explosives. Hydrogen peroxide is used extensively around the world in many industries, including aerospace. It is also used as the main ingredient in some household cleaning products. However, it has been illicitly used to create both primary and secondary homemade explosives in recent numerous terrorist attacks across Europe. In this article, we describe the historical background and the characteristics of the substance, the aspects concerning its manufacture and present-day use as a main explosive component or direct chemical precursor of homemade explosives, and the options for detection.