Challenges in Evaluating the Energetic Properties of Aluminum Nanoparticles Through Laser-Induced Air Shock from Energetic Materials (LASEM)

This study examines the application of the Laser-Induced Air Shock from Energetic Materials (LASEM) technique to characterize the energetic properties of aluminum nanoparticles. We investigated the shock wave velocities generated during the nanosecond laser ablation of aluminum and aluminum oxide particles by utilizing high-speed schlieren imaging. Additionally, we studied the time scale of AlO formation in the plasma plume following ablation through optical emission spectroscopy. The results obtained from the LASEM measurements are found to be inconsistent across four common analysis methods and mostly incompatible with the expected energetic behavior of the material. This is explained by the observation that exothermic oxidation reactions of aluminum do not occur within the initial 0–10 µs timeframe, suggesting that the shock wave propagation velocity is likely not connected to the reactivity of the material under test. This research underscores the complexities involved in the interpretation of LASEM results for evaluating and contrasting the energetic properties of metal nanoparticles, particularly aluminum.