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Ultra‐High Fidelity Laser‐Induced Air Shock from Energetic Materials
摘要： Recent interest in the implementation of the Laser-induced Air Shock from Energetic Materials (LASEM) technique prompted an investigation using ultra-high-speed imaging diagnostics to provide early-time (sub-μs) shock-wave-radius-versus-time data necessary to accurately determine the characteristic laser-induced-shock velocity (y-intercept) for high explosives (HE) of interest. Ultra-high-speed focused-shadowgraphy images were collected from nanosecond-pulsed laser-ablated samples of HE similar to those in the published literature. Shadowgraphy images were collected using interframe times ranging from 50–750 ns, with exposure times of 5 ns. Acquired shock-wave-radius-versus-time data permitted a high-fidelity assessment of the shock wave velocity produced at the characteristic radius of the generated laser-plasma pulse. The resulting data from eight different HE indicated that early-time energy contributions and the resulting laser-induced shock velocity profiles produced from ablation of the HE material were indistinguishable amongst the explosives tested for the majority of the time domain characterized (0–12 μs).
关键词： laser-induced shock wave,shock physics,energetic-material characterization,detonation performance,laser-induced plasma
更新于2025-09-11 14:15:04
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Optimizing the oxygen balance by changing the A-site cations in molecular perovskite high-energetic materials
摘要： We presented two new members of molecular perovskite high-energetic materials, (H2pz)[Na(ClO4)3] (PAP-1) and (H2dabco-O)[K(ClO4)3] (DAP-O2), in which H2pz2+ (piperazine-1,4-diium) and H2dabco-O2+ (1-hydroxy-1,4-diazabicyclo[2.2.2]octane-1,4-diium) act as A-site fuel cations, respectively. Compared with their H2dabco2+ analogues, (H2dabco)[M(ClO4)3] (M = Na+ for DAP-1 and K+ for DAP-2, respectively), PAP-1 and DAP-O2 exhibit optimized oxygen balance by employing two strategies to change the A-site cations, i.e., “trimming the C and H atoms” of H2dabco2+ by using H2pz2+ to form PAP-1 and adding an O atom into H2dabco2+ by using H2dabco-O2+ to form DAP-O2, respectively. As suggested by DFT calculations and the K–J equation, the smaller H2pz2+ cation in PAP-1 gives a significantly-optimized oxygen balance from ?22.0% to ?3.9% and an increased crystal density from 2.02 to 2.07 g cm?3, resulting in a better detonation performance for PAP-1. Meanwhile the larger H2dabco-O2+ cation gives a slightly-optimized oxygen balance from ?21.3% to ?17.1% but a decreased crystal density from 2.04 to 1.98 g cm?3, leading to a decreased detonation performance from DAP-2 to DAP-O2. This study demonstrated how to rationally choose the A-site cations in a perovskite structure for modulating the properties of molecular perovskite high-energetic materials, providing important clues for designing more advanced energetic materials for practical use.
关键词： high-energetic materials,oxygen balance,molecular perovskite,detonation performance,A-site cations
更新于2025-09-04 15:30:14