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Cocrystals of hexanitrohexaazaisowurtzitane (CL-20) and 7H-trifurazano[3,4-b:3′,4′-f:3′′,4′′-d]azepine (TFAZ) in a 1 : 1 molar ratio were prepared by both slow evaporation and self-assembly methods. Structure determination showed that they belong to the monoclinic system (space group P21) with a crystal density of 1.932 g cm−3. The intermolecular hydrogen bonds and N–O⋯NO2 type interactions are demonstrated as the predominant driving forces in the cocrystal formation. Furthermore, the cocrystals were successfully synthesized by a self-assembly method using only water as a solvent under mild conditions and the product yield was up to 92.3%. The two types of cocrystals were fully characterized by powder X-ray diffraction, infrared spectroscopy and scanning electron microscopy. Moreover, the thermal behavior, sensitivity, and calculated detonation performance of the cocrystals were evaluated. The cocrystals exhibit good thermal stability (Td = 242.8 °C), low impact sensitivity (H50 = 42 cm) and friction sensitivity (Pf = 38%), high crystal density, and high calculated detonation velocity (9103 m s−1). This work opens up a new perspective in the environment-friendly preparation of energetic cocrystals on a large-scale, as well as providing potential low-sensitivity and high-energy explosives. [ABSTRACT FROM AUTHOR]

Cocrystals of 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20) and 2,4-dinitro-2,4-diazapentane (DNDAP) in a 2 : 1 molar ratio were prepared by both slow evaporation and spray drying methods. The structure of the cocrystals was characterized using single crystal X-ray diffraction and it showed evidence of hydrogen bonds between HCL-20 and ODNDAP to the primary stabilizing force in cocrystal formation. Infrared spectroscopy and powder X-ray diffraction analysis indicated that the polycrystalline product from the spray drying method is consistent with the single crystals from solution crystallization. DSC and TG tests revealed that the exothermic decomposition of the cocrystal occurs via two main continuous steps with peak maxima at 223.5 °C and 254.1 °C and largely increases the melting point of DNDAP by 129.9 °C. The cocrystal possesses high detonation velocity and detonation pressure (8997 m s−1 and 37.5 GPa, respectively); meanwhile it features significantly reduced impact and friction sensitivities relative to those of CL-20. These results demonstrate that the CL-20/DNDAP cocrystal can be utilized as a promising ingredient in explosive applications. [ABSTRACT FROM AUTHOR]