1,5‐Di(nitramino)tetrazole: High Sensitivity and Superior Explosive Performance

Highly energetic 1,5‐di(nitramino)tetrazole and its salts were synthesized. The neutral compound is very sensitive and one of the most powerful non‐nuclear explosives to date. Selected nitrogen‐rich and metal salts were prepared. The potassium salt can be used as a sensitizer in place of tetracene. The obtained compounds were characterized by low‐temperature X‐ray diffraction, IR and Raman spectroscopy, multinuclear NMR spectroscopy, elemental analysis, and DSC. Calculated energetic performances using the EXPLO5 code based on calculated (CBS‐4M) heats of formation and X‐ray densities support the high energetic performances of the 1,5‐dinitraminotetrazolates as energetic materials. The sensitivities towards impact, friction, and electrostatic discharge were also explored.     

Thermal decomposition properties and compatibility of CL-20, NTO with silicone rubber

The new polycyclic nitramine 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW) has been focused as a considerable amount of research recently on investigating its polymorphs, relative stability, and respective reaction chemistry. It is known as CL-20 popularly, CL-20 is a very high-energy and relatively high oxygen balance value crystalline compound whose method of synthesis and detailed performance data are still classified. 5-oxo-3-nitro-1,2,4-triazole (NTO, or nitrotriazolone) was an insensitive molecule comparison general explosives, and the NTO based polymer bonded explosives (PBX) was a low vulnerability explosive. Both energetic materials are all very important high explosives, which is used in a variety of military formulations widely owing to the properties of high energy and desensitization of PBX, many researchers have demonstrated the usefulness of above two energetic materials in explosive component. In this work, the thermal decomposition characteristics of explosives CL-20 and NTO were studied using thermal analytical techniques (TG, DSC), then the compatibility of above two explosives with silicone rubber, and the decomposition kinetic parameters such as activation energies of decomposition, the frequency factor of the decompose reaction are also evaluated by non-isothermal DSC techniques.     

Theoretical evaluation of sensitivity and thermal stability for high explosives based on quantum chemistry methods: A brief review

Over the past 20 years, a number of scientists have conducted numerous fundamental investigations based on quantum chemistry theory into various mechanistic processes that seems to contribute to the sensitivity of energetic materials. A large number of theoretical methods that have been used to predict their mechanical and spark sensitivity are summarized in this article, in which the advantages and disadvantages of these methods, together with their scope of use are clarified. In addition, the theoretical models for thermal stability of explosives are briefly introduced as a supplement. It has been concluded that the current ability to predict sensitivity is merely based on a series of empirical rules, such as simple oxygen balance, molecular properties, and the ratios of C and H to oxygen for different classes of explosive compounds. These are valid only for organic classes of explosives, though some special models have been proposed for inorganic explosives, such as azides. An exact standard for sensitivity should be established experimentally by some new techniques for both energetic compounds and their mixtures. © 2013 Wiley Periodicals, Inc.     

Nitrato Functionalized Polymers for High Energy Propellants and Explosives: Recent Advances

Future propellants and explosive research focus on developing compositions with less vulnerability without compromising performance. This has provided impetus for research in the area of high energy materials and compounds free from pollution, for safe handling, high performance, reliability and reproducibility. The energetic oxidizers and energetic binders are being developed in this scenario for use in composite propellants and explosives. In a propellant, the binder holds together the matrix containing solid oxidizer particles and finely divided metal particles. It provides structural integrity and aid the combustion of the propellant. Any new development in this area wherein the binder can contribute to the energetic is of immense importance. This can be achieved by incorporation of energetic groups such as nitrato (?ONO₂), azide (?N₃) or flurodinitro CF(NO₂)₂ as side chain or on to the existing polymer backbone. Among these, nitrato functionalized energetic binders can find application in myriad areas like boosters, plastic bonded explosives, gas generators and pyrogen igniters. The present article is a concise review on various types of nitrato binders; their synthesis, properties and their propellant studies. Copyright © 2017 John Wiley & Sons, Ltd.     

Energetic materials based on poly furazan and furoxan structures

Furazan and furoxan represent fascinating explosophoric units with intriguing structures and unique properties. Compared with other nitrogen-rich heterocycles, most poly furazan and furoxan-based heterocycles demonstrate superior energetic performances due to the higher enthalpy of formation and density levels. A large variety of advanced energetic materials have been achieved based on the combination of furazan and furoxan moieties with different kinds of linkers and this review provides an overview of the development of energetic poly furazan and furoxan structures during the past decades, with their physical properties and detonation characteristics summarized and compared with traditional energetic materials. Various synthetic strategies towards these compact energetic structures are highlighted by covering the most important cyclization methods for construction of the hetercyclic scaffolds and the following modifications such as nitrations and oxidations. Given the synthetic availabilities and outstanding properties, energetic materials based on poly furazan and furoxan structures are undoubtedly listed as a promising candidate for the development of new-generation explosives, propellants and pyrotechnics.     

1,1′‐Nitramino‐5,5′‐bitetrazoles

1,1′‐Dinitramino‐5,5′‐bitetrazole and 1,1′‐dinitramino‐5,5′‐azobitetrazole were synthesized for the first time. The neutral compounds are extremely sensitive and powerful explosives. Selected nitrogen‐rich salts were prepared to adjust sensitivity and performance values. The compounds were characterized by low‐temperature X‐ray diffraction, IR and Raman spectroscopy, multinuclear NMR spectroscopy, elemental analysis, and DTA/DSC. Calculated energetic performances using the EXPLO5 code based on calculated (CBS‐4M) heats of formation and X‐ray densities support the high performances of the 1,1′‐dinitramino‐5,5′‐bitetrazoles as energetic materials. The sensitivities toward impact, friction, and electrostatic discharge were also explored. Most of the compounds show sensitivities in the range of primary explosives and should only be handled with great care!     

Reactive characterization of nanothermites

Conventional thermal analysis techniques (TG and DSC) give valuable information on the activation energy and the reactivity of energetic materials such as organic explosives. Here, we discuss the use of these methods for characterizing nanothermites, energetic compositions made of metallic oxides and a fuel (often a reducing metal). The experimental limitations of these analysis techniques are identified. It is difficult to ignite nanothermites with slow heating rates as those used in DSC. This is due to the inorganic nature of the thermite components and because the reaction involves interparticular heat and matter transfers. In addition, during the progressive decomposition of nanothermites, there is no change in mass, so it cannot be observed by thermogravimetric analysis. The use of laser ignition to prime the abrupt combustion of nanothermite pellets allows determining the ignition energy and analyzing the propagation of the combustion front. It also provides qualitative data that can be used to understand the combustion mechanism and to correlate it to the microstructure of the nanothermites. By analyzing several examples, we will show that the coupling of high speed video to existing thermal analysis techniques could significantly extend their utilization range for the characterization of new energetic materials.     

A Facile and Versatile Synthesis of Energetic Furazan-Functionalized 5-Nitroimino-1,2,4-Triazoles

An analogue-oriented synthetic route for the formulation of furazan-functionalized 5-nitroimino-1,2,4-triazoles has been explored. The process was found to be straightforward, high yielding, and highly efficient, and scalable. Nine compounds were synthesized and the physicochemical and energetic properties, including density, thermal stability, and sensitivity, were investigated, as well as the energetic performance (e.g., detonation velocities and detonation pressures) as evaluated by using EXPLO5 code. Among the new materials, compounds 4 – 6 and 11 possess high densities, acceptable sensitivities, and good detonation performances, and thereby demonstrate the potential applications as new secondary explosives.     

Amination of energetic anions: high-performing energetic materials

The new energetic materials 2-amino-5-nitrotetrazole (ANT, 1), 1-amino-3,4-dinitro-1,2,4-triazole (ADNT, 2), and both 1,1'-diamino-5,5'-bistetrazole and 1,2'-diamino-5,5'-bistetrazole (11DABT, 3 and 12DABT, 4) have been prepared by the amination of the parent anion with O-tosylhydroxylamine. The 5-H-tetrazolate anion has also been aminated using hydroxylamine O-sulfonic acid to both 1-aminotetrazole and 2-aminotetrazole (1AT, 5 and 2AT, 6). The prepared materials have been characterized chemically (XRD (1-4, 6·AtNO(2), 8), multinuclear NMR, IR, Raman) and as explosives (mechanical and electrostatic sensitivity) and their explosive performances calculated using the EXPLO5 computer code. The prepared N-amino energetic materials, which can also be used as new ligands for high energy-capacity transition metal complexes, exhibit high explosive performances (in the range of hexogen and octogen) and a range of sensitivities from low to extremely high.     

Energetic Salts Based on Tetrazole N‐Oxide

Energetic materials (explosives, propellants, and pyrotechnics) are used extensively for both civilian and military applications and the development of such materials, particularly in the case of energetic salts, is subject to continuous research efforts all over the world. This Review concerns recent advances in the syntheses, properties, and potential applications of ionic salts based on tetrazole N‐oxide. Most of these salts exhibit excellent characteristics and can be classified as a new family of highly energetic materials with increased density and performance, alongside decreased mechanical sensitivity. Additionally, novel tetrazole N‐oxide salts are proposed based on a diverse array of functional groups and ions pairs, which may be promising candidates for new energetic materials.     

Detonation Properties of High Explosives Containing Ammonia Borane

Ammonia borane (AB) is used as a combustion agent to improve the properties of high explosives. The detonation velocity (D_v) and detonation pressure (P) of raw high explosives and of samples containing AB were calculated and compared. The detonation properties, impact sensitivities, thermal sensitivities, and thermal decomposition characteristics of high explosives containing AB were also measured. The results indicated that when the AB content was 20 wt‐%, the optimal detonation velocity and detonation pressure were achieved. Both the detonation velocity and detonation pressure of the high explosives containing AB were clearly increased compared with those of the raw high explosives. Moreover, the detonation velocities of high explosives containing AB were 7078 to 7423 m · s^–1 and their density ranged from 1.570 to 1.589 g · cm^–3. The detonation pressure ranged from 34.5 to 37 GPa and the average heat of detonation was 6688 J · g^–1. Furthermore, the impact and thermal sensitivities were 170 cm and 613 K, respectively, whereas a slight change occurred in the thermal decomposition characteristics. These results suggest that AB can serve as a powerful combustible agent in energetic materials and improve the detonation properties and sensitivities of high explosives.     

Assembly of Tetrazolylfuroxan Organic Salts: Multipurpose Green Energetic Materials with High Enthalpies of Formation and Excellent Detonation Performance

A series of highly energetic organic salts comprising a tetrazolylfuroxan anion, explosophoric azido or azo functionalities, and nitrogen-rich cations were synthesized by simple, efficient, and scalable chemical routes. These energetic materials were fully characterized by IR and multinuclear NMR (¹H, ¹³C, ¹⁴N, ¹⁵N) spectroscopy, elemental analysis, and differential scanning calorimetry (DSC). Additionally, the structure of an energetic salt consisting of an azidotetrazolylfuroxan anion and a 3,6,7-triamino-7H-[1,2,4]triazolo[4,3-b][1,2,4]triazolium cation was confirmed by single-crystal X-ray diffraction. The synthesized compounds exhibit good experimental densities (1.57–1.71 g cm⁻³), very high enthalpies of formation (818–1363 kJ mol⁻¹), and, as a result, excellent detonation performance (detonation velocities 7.54–8.26 kms⁻¹ and detonation pressures 23.4–29.3 GPa). Most of the synthesized energetic salts have moderate sensitivity toward impact and friction, which makes them promising candidates for a variety of energetic applications. At the same time, three compounds have impact sensitivity on the primary explosives level (1.5–2.7 J). These results along with high detonation parameters and high nitrogen contents (66.0–70.2 %) indicate that these three compounds may serve as potential environmentally friendly alternatives to lead-based primary explosives.     

Developing small-scale tests to predict explosivity

Materials which release significant heat upon decomposition are energetic materials. Some of these are also explosives. Seeking a correlation with detonability of large quantities of energetic materials, four laboratory tests were used. The characteristics considered indicative of detonability were ability to fragment a metal casing, when initiated by a detonator, and ability to produce large quantities of gas and heat. The best developed of these tests is differential scanning calorimetry. It has already been pioneered by other researchers. A limitation of this study is that large-scale detonability remains unknown for a number of materials examined; thus, it is difficult to sufficiently evaluate the success of the small-scale analyses.     

Corrosion resistance of cement mortars containing spent catalyst of fluidized bed cracking (FBCC) as an additive

Compatibility is an important property for energetic materials and their additives such as a casing material or a binder. If these substances are incompatible an extra risk is introduced in handling and storage of ammunition and explosives. As part of a co-operation program between the Dutch TNO-PML and the Polish MIAT several compatibility tests are performed and compared with each other. All tests are performed according to a NATO Standard in which several tests are described which can be used to determine the compatibility of an energetic material and an additive. These tests were performed on a huge set of energetic materials e.g. propellants (single and double base), explosives (RDX, PETN, HMX and TNT) and several additives like Teflon, polypropylene, self-burning case, inhibitors etc. The results of pressure vacuum stability tests, dynamic thermogravimetry measurements and differential scanning calorimetry tests with several combinations of energetic materials and additives used during the co-operation program are presented and discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Manipulating sensitivities of planar oxadiazole-based high performing energetic materials

Nitrogen-rich energetic materials based on five-membered azoles, such as tetrazoles, triazoles, oxadiazoles, pyrazoles, and imidazoles, have garnered significant attention in recent years due to their environmental compatibility while maintaining high performance. These materials, including explosives, propellants, and pyrotechnics, are designed to release energy rapidly and efficiently while minimizing the release of toxic or hazardous byproducts and have attracted potential applications in the defense and space industries. The presence of extensive N C, N N, and NN high energy bonds in azoles provides high enthalpies of formation and facilitates intermolecular interactions through π-stacking which may help with reducing sensitivity to external stimuli. Now, we report on the synthesis and energetic properties of N-(5-(1H-tetrazol-5-yl)-1,3,4-oxadiazol-2-yl)nitramide ( 5 ) and its energetic salts. These new high nitrogen–oxygen-containing materials have attractive feature applications of insensitivity and increased performance.     

三、四唑高能离子盐的研究概况

为满足火炸药等领域对多功能含能材料的需求,高生成焓、高密度、钝感、稳定和环境友好的三、四唑高能离子盐的研究受到广泛关注。 本文综述了10年来三唑和四唑高能离子盐的合成及性能研究概况,为含能离子盐的研究提供参考。     

Nitro-, Cyano-, and Methylfuroxans,and Their Bis-Derivatives: From Green Primary to Melt-Cast Explosives

In the present work, we studied in detail the thermochemistry, thermal stability, mechanical sensitivity, and detonation performance for 20 nitro-, cyano-, and methyl derivatives of 1,2,5-oxadiazole-2-oxide (furoxan), along with their bis-derivatives. For all species studied, we also determined the reliable values of the gas-phase formation enthalpies using highly accurate multilevel procedures W2-F12 and/or W1-F12 in conjunction with the atomization energy approach and isodesmic reactions with the domain-based local pair natural orbital (DLPNO) modifications of the coupled-cluster techniques. Apart from this, we proposed reliable benchmark values of the formation enthalpies of furoxan and a number of its (azo)bis-derivatives. Additionally, we reported the previously unknown crystal structure of 3-cyano-4-nitrofuroxan. Among the monocyclic compounds, 3-nitro-4-cyclopropyl and dicyano derivatives of furoxan outperformed trinitrotoluene, a benchmark melt-cast explosive, exhibited decent thermal stability (decomposition temperature >200 °C) and insensitivity to mechanical stimuli while having notable volatility and low melting points. In turn, 4,4′-azobis-dicarbamoyl furoxan is proposed as a substitute of pentaerythritol tetranitrate, a benchmark brisant high explosive. Finally, the application prospects of 3,3′-azobis-dinitro furoxan, one of the most powerful energetic materials synthesized up to date, are limited due to the tremendously high mechanical sensitivity of this compound. Overall, the investigated derivatives of furoxan comprise multipurpose green energetic materials, including primary, secondary, melt-cast, low-sensitive explosives, and an energetic liquid.     

3,6‐Dinitropyrazolo[4,3‐c]pyrazole‐Based Multipurpose Energetic Materials through Versatile N‐Functionalization Strategies

A family of 3,6‐dinitropyrazolo[4,3‐c]pyrazole‐based energetic compounds was synthesized by using versatile N‐functionalization strategies. Subsequently, nine ionic derivatives of the N,N′‐(3,6‐dinitropyrazolo[4,3‐c]pyrazole‐1,4‐diyl)dinitramidate anion were prepared by acid‐base reactions and fully characterized by infrared, multinuclear NMR spectra, and elemental analysis. The structures of four of these compounds were further confirmed by single‐crystal X‐ray diffraction. Based on their different physical and detonation properties, these compounds exhibit promising potential as modern energetic materials and can be variously classified as green primary explosives, high‐performance secondary explosives, fuel‐rich propellants, and propellant oxidizers.     

Synthesis of 5‐Aminotetrazole‐1 N‐oxide and Its Azo Derivative: A Key Step in the Development of New Energetic Materials

1‐Hydroxy‐5‐aminotetrazole ( 1 ), which is a long‐desired starting material for the synthesis of hundreds of new energetic materials, was synthesized for the first time by the reaction of aqueous hydroxylamine with cyanogen azide. The use of this unique precursor was demonstrated by the preparation of several energetic compounds with equal or higher performance than that of commonly used explosives, such as hexogen (RDX). The prepared compounds, including energetic salts of 1‐hydroxy‐5‐aminotetrazole (hydroxylammonium ( 2 , two polymorphs) and ammonium ( 3 )), azo‐coupled derivatives (potassium ( 5 ), hydroxylammonium ( 6 ), ammonium ( 7 ), and hydrazinium 5,5′‐azo‐bis(1‐N‐oxidotetrazolate ( 8 , two polymorphs)), as well as neutral compounds 5,5′‐azo‐bis(1‐oxidotetrazole) ( 4 ) and 5,5′‐bis(1‐oxidotetrazole)hydrazine ( 9 ), were intensively characterized by low‐temperature X‐ray diffraction, IR, Raman, and multinuclear NMR spectroscopy, elemental analysis, and DSC. The calculated energetic performance, by using the EXPLO5 code, based on the calculated (CBS‐4M) heats of formation and X‐ray densities confirm the high energetic performance of tetrazole‐N‐oxides as energetic materials. Last but not least, their sensitivity towards impact, friction, and electrostatic discharge were explored. 5,5′‐Azo‐bis(1‐N‐oxidotetrazole) deflagrates close to the DDT (deflagration‐to‐detonation transition) faster than all compounds that have been investigated in our research group to date.     

Double-pulse standoff laser-induced breakdown spectroscopy for versatile hazardous materials detection

We have developed a double-pulse standoff laser-induced breakdown spectroscopy (ST-LIBS) system capable of detecting a variety of hazardous materials at tens of meters. The use of a double-pulse laser improves the sensitivity and selectivity of ST-LIBS, especially for the detection of energetic materials. In addition to various metallic and plastic materials, the system has been used to detect bulk explosives RDX and Composition-B, explosive residues, biological species such as the anthrax surrogate Bacillus subtilis, and chemical warfare simulants at 20 m. We have also demonstrated the discrimination of explosive residues from various interferents on an aluminum substrate.