Determination of detonation characteristics by laser-induced plasma spectra and micro-explosion dynamics

Determination of macroscale detonation parameters of energetic materials (EMs) in a safe and rapid way is highly desirable. However, traditional experimental methods suffer from tedious operation, safety hazards and high cost. Herein, we present a micro-scale approach for high-precision diagnosis of explosion parameters based on radiation spectra and dynamic analysis during the interaction between laser and EMs. The intrinsic natures of micro-explosion dynamics covering nanosecond to millisecond and chemical reactions in laser-induced plasma are revealed, which reveal a tight correlation between micro-detonation and macroscopic detonation based on laser-induced plasma spectra and dynamics combined with statistic ways. As hundreds to thousands of laser pulses ablate on seven typical tetrazole-based high-nitrogen compounds and ten single-compound explosives, macroscale detonation performance can be well estimated with a high-speed and high-accuracy way. Thereby, the detonation pressure and enthalpies of formation can be quantitatively determined by the laser ablation processes for the first time to our knowledge. These results enable us to diagnose the performance of EMs in macroscale domain from microscale domain with small-dose, low-cost and multiple parameters.

Energetic isomers of bridged oxadiazole nitramines: the effect of asymmetric heterocyclics on stability and energetic properties

Energetic isomers often exhibit different properties. To understand the effect of arrangement and connection of isomers on energetic properties and sensitivity, in this study, we designed and synthesized a series of oxadiazole nitramine compounds including N-(5-(5-(nitramino)-1,3,4-oxadiazol-2-yl)-1,2,4-oxadiazol-3-yl)nitramide (NOON) and its ionic derivatives. NOON exhibits comparable performance (D = 8888 m s^-1, P = 34.1 GPa) to highly explosive RDX. A comparative study of detonation properties, sensitivity, and thermal stability of the three oxadiazole nitramine isomers (NOON, ICM-101, and DNBO) is carried out. The results show that due to the proton transformation, strong intramolecular hydrogen bonding interaction, and formation of six-membered ring conformation, the 2-nitramino-1,3,4-oxadiazole building block exhibits better detonation properties and higher thermal stability than its isomer 2-nitramino-1,2,4-oxadiazole.

Density Functional Theory (DFT) Study on the Structures and Energetic Properties of Isomers of Tetranitro-bis-1,2,4-triazoles

A series of isomers of tetranitro-bis-1,2,4-triazoles were designed, and their electronic structures, heats of formation, densities, detonation performances, thermal stabilities, and impact sensitivities were investigated by density functional theory (DFT). The structure and energetic properties of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) were also calculated at the same level. On comparing with the detonation velocity and pressure and bond dissociation energy (BDE) of HMX, it was found that four isomers (BT2, BT5, BT6, BT7) have higher detonation performances than HMX and three isomers (BT5, BT6, BT7) have better thermal stabilities than HMX. The calculated results of impact sensitivities indicated that all of the designed isomers have more sensitivity than HMX. The calculated results of energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) indicated that all of the designed isomers were more easily excited than HMX in the chemical reaction process. In particular, 3,3',5,5'-tetranitro-1,1'-bis-1,2,4-triazoles (BT5) exhibited excellent detonation performances (9464 m s^-1, 39.44 GPa) and good thermal stability (BDE 256.81 kJ mol^-1). The results indicated that the isomerization of tetranitro-bis-1,2,4-triazoles could improve their detonation performance or thermal stability and might lead to a promising isomer possessing both good performance and high thermal stability.