Promising Thermally Stable Energetic Materials with the Combination of Pyrazole–1,3,4-Oxadiazole and Pyrazole–1,2,4-Triazole Backbones: Facile Synthesis and Energetic Performance

Abstract

Thermally stable energetic materials have broad applications in the deep mining, oil and natural exploration, and aerospace industries. The quest for thermally stable (heat-resistant) energetic materials with high energy output and low sensitivity has fascinated many researchers worldwide. In this study, two different series of thermally stable energetic materials and salts based on pyrazole–oxadiazole and pyrazole–triazole (3–23) with different explosophoric groups have been synthesized in a simple and straightforward manner. All the newly synthesized compounds were fully characterized by IR, ESI-MS, multinuclear NMR spectroscopy, elemental analysis, and thermogravimetric analysis–differential scanning calorimetry measurements. The structures of 3, 7, and 22 were supported by single-crystal X-ray diffraction studies. The density, heat of formation, and energetic properties (detonation velocity and detonation pressure) of all the compounds range between 1.75 and 1.94 g cm–3, 0.73 to 2.44 kJ g–1, 7689 to 9139 m s–1, and 23.3 to 31.5 GPa, respectively. All the compounds are insensitive to impact (>30 J) and friction (>360 N). In addition, compounds 4, 6, 10, 14, 17, 21, 22, and 23 show high onset decomposition temperature (T d between 238 and 397 °C) than the benchmark energetic materials RDX (T d = 210 °C), HMX (279 °C), and thermally stable HNS (318 °C). It is noteworthy that the pyrazole–oxadiazole and pyrazole–triazole backbones greatly influence their physicochemical and energetic properties. Overall, this study offers a perspective on insensitive and thermally stable nitrogen-rich materials and explores the relationship between the structure and performance.

Thermally Stable and Insensitive Energetic Cocrystals Comprising Nitrobarbituric Acid Coformers

“…The onset decomposition temperature of all the cocrystals is >222 °C, which is far better than that of NBA (∼173 °C) and the benchmark explosive RDX (210 °C). Among them, NBA:DAG melts (onset: 185 °C; peak: 196 °C) before decomposition and shows excellent thermal stabilities (310 °C), which is better than the heat-resistant explosive HMX (279 °C) and close to HNS (318 °C) . Additionally, the thermal stabilities of NBA/AmTz and NBA/DAG were determined at various heating rates 5, 10, 15, and 20 °C (Figure ).…”

“… a Onset decomposition temperature (DSC, 5 °C/min). b Crystal density. c Computed HOF. d Detonation pressure. e Detonation velocity. f Impact sensitivity. g Friction sensitivity. h Ref . i Ref . …”

“…Among them, NBA:DAG melts (onset: 185 °C; peak: 196 °C) before decomposition and shows excellent thermal stabilities (310 °C), which is better than the heat-resistant explosive HMX (279 °C) and close to HNS (318 °C). 32 Additionally, the thermal stabilities of NBA/AmTz and NBA/DAG were determined at various heating rates 5, 10, 15, and 20 °C (Figure 9). The calculated density of all the cocrystals ranges between 1.71 and 1.80 g cm −3 , which is better than the benchmark explosive TNT (1.65 g cm −3 ) and some of them are close to RDX (1.80 g cm −3 ).…”

“…In this work, we have studied the cocrystallization of nitrobarbituric acid (NBA) 30 coformer with four energetic materials, namely, 1H-tetrazol-5-amine (AmTz), 7H- [1,2,4]triazolo [4,3-b][1,2,4]triazole-3,6,7-triamine (TATOT), 31 5-(4nitro-1H-pyrazol-3-yl)-4H-1,2,4-triazol-3-amine (NPTA), 32 and 1,3-diaminoguanidinehydrochloride (DAG), which possess high nitrogen content in their molecular backbone as shown in Figure 1. AmTz, TATOT, and DAG have also been reported as nitrogen-rich cationic species in secondary energetic salts.…”

Facile synthesis of thermally stable tetrazolo[1,5-b][1,2,4]triazine substituted energetic materials: synthesis and characterization

“…[1][2][3] Fused heterocycles constitute a large variety of structural scaffolds and recent accomplishments of several research groups globally confirmed that the presence of fused backbones in energetic materials usually enhances the energy and nitrogen content, detonation performance, insensitivity and thermal stability, which enhances their practical applicability. [4][5][6][7][8] Nitrogen-rich fused heterocycles have more extensive N-C, N-N and NvN high-energy bonds in the structure than single-ring heterocycles, which provide high energy content to these compounds. A few combinations of strained fused catenated heterocyclic compounds have also been synthesized and their energetic properties were examined, which showed good thermal stability and insensitivity towards external stimuli such as impact and friction.…”