A CL-20/DNDAP cocrystal explosive prepared by a spray drying method exhibited a small particle size with a narrow size distribution and good comprehensive performance.
CL-20/TFAZ cocrystal explosives were prepared by a self-assembly method under aqueous conditions with both low sensitivity and high detonation performances.
Achieving
high thermal stability and low mechanical sensitivity
are two major goals in the development of energetic compounds. Six
highly stable insensitive polynitrophenyl-substituted furazan (furoxan)-annelated
azepines have been prepared and characterized in this work. All the
involved compounds were characterized by 1H and 13C NMR spectroscopy, IR spectroscopy, and elemental analysis, and
four of them were further supported by single-crystal X-ray diffraction
investigations. Moreover, their thermal stabilities and mechanical
sensitivities were evaluated. All energetic compounds exhibited excellent
thermal stabilities with decomposition temperatures ranging from 290
to 333 °C. Compounds 1c and 2c exhibit
extremely low mechanical sensitivity (IS >40 J and FS > 360
N). Based
on experimental densities and calculated heat of formation, the detonation
velocities and pressures for the energetic compounds were calculated
using EXPLO5 (V6.04) with the corresponding results in the range of
26.4 to 29.9 GPa and 7979 m s–1 to 8356 m s–1. The detailed study based on Hirshfeld surfaces and
electrostatic potential (ESP) analysis was used to illustrate the
relationship between molecular structures and sensitivity of these
compounds. The comprehensive performances of these materials are superior
to those of the widely used heat-resistant explosive HNS (2,2′,4,4′,6,6′-hexanitrostilbene).
In this paper, twelve 1,3-dinitrohexahydropyrimidine-based energetic compounds were designed by introducing various explosopheres into hexahydropyrimidine skeleton. Their geometric and electronic structures, heats of formation (HOFs), energetic performance, thermal stability and impact sensitivity were discussed. It is found that the incorporation of electron-withdrawing groups (–NO2, –NHNO2, –N3, –CH(NO2)2, –CF(NO2)2, –C(NO2)3) improves HOFs of the derivatives and all the substituents contribute to enhancing the densities and detonation properties (D, P) of the title compounds. Therein, the substitution of –C(NO2)3 features the best energetic performance with detonation velocity of 9.40 km s−1 and detonation pressure of 40.20 GPa. An analysis of the bond dissociation energies suggests that N–NO2 bond may be the initial site in the thermal decompositions for most of the derivatives. Besides, –ONO2 and –NF2 derivatives stand out with lower impact sensitivity. Characters with striking detonation properties (D = 8.62 km s−1, P = 35.08 GPa; D = 8.81 km s−1, P = 34.88 GPa), good thermal stability, and acceptable impact sensitivity (characteristic height H50 over 34 cm) lead novel compounds 5,5-difluoramine-1,3-dinitrohexahydropyrimidine (K) and 5-fluoro-1,3,5-trinitrohexahydropyrimidine (L) to be very promising energetic materials. This work provides the theoretical molecular design and a reasonable synthetic route of L for further experimental synthesis and testing.
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