Abstract
Design and synthesis of new compounds with both high detonation performances and good safety properties have always been a formidable task in the field of energetic materials. By introducing -ONO2 and -NHNO2 moieties into 1,2,4-oxadiazole- and 1,2,5-oxadiazole-based backbones, a new family of energetic materials, including ammonium 3-nitramino-4-(5-hydroxymethyl-1,2,4-oxadiazol-3-yl)-furazan (4), 3,3′-bis[5-nitroxymethyl-1,2,4-oxadiazol-3-yl]-4,4′-azofuroxan (6), [3-(4-nitroamino-1,2,5-oxadiazol-3-yl)-1,2,4-oxadiazol-5-yl]-methylene nitrate (8), and its energetic ionic salts (10–12), were synthesized and fully characterized. The energetic and physical properties of the materials were investigated through theoretical calculations and experimental determination. The results show that the oxadiazole-based compounds exhibit high enthalpy of formations, good detonation performances, and extraordinary insensitivities. In particular, the hydrazinium salt (11) shows the best energetic properties (11: d = 1.821 g cm−3; P = 35.1 GPa, vD = 8,822 m s−1, IS = 40 J, FS > 360N). The ESP and Hirshfeld surface analysis indicated that a large number of hydrogen bonds as well as π-π stacking interactions within molecules might be the key reason for their low sensitivities and high energy-density levels.
Highlights
Nitrogen-rich azoles are widely applied heterocyclic frameworks in the design of energetic materials, among which 1,2,5-oxadiazole is lucubrated due to its high heat of formation and good oxygen balance (Zheng et al, 2010; Wang et al, 2011; Fischer et al, 2014; Tsyshevsky et al, 2015; Liu et al, 2018)
The design and synthesis of new structures with optimal balance between high detonation performances and good safety properties have become a formidable task in the research field of energetic materials (Fischer et al, 2014; Wei et al, 2015). 3,4-Bis(nitramino)furazan (Scheme 1A), a typical example that has a high density of 1.899 g cm−3, is impossible to be applied due to its high sensitivities (IS < 1 J and FS < 5 J) (Figure 1A) (Tang et al, 2015)
The construction of N-heterocyclic skeleton is the core of energetic materials (Xue et al, 2019)
Summary
Nitrogen-rich azoles are widely applied heterocyclic frameworks in the design of energetic materials, among which 1,2,5-oxadiazole (furazan) is lucubrated due to its high heat of formation and good oxygen balance (Zheng et al, 2010; Wang et al, 2011; Fischer et al, 2014; Tsyshevsky et al, 2015; Liu et al, 2018). The replacement of a nitramino group with a 5-methyl1,2,4-oxadiazole (Scheme 1B) moiety can improve the insensitivity (IS = 37.8 J and FS > 360 N), the energetic level of 3-nitramino-4-(5-methyl-1,2,4-oxadiazol-3-yl)furazan methyl(CH3) becomes much lower (ρ = 1.65 cm−1 and vD = 7,810 m s−1) due to the existence of non-energetic methyl group (Yu et al, 2017) (Figure 1B).
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