Interplay of shell evolution and oxidation depth on the ignition and combustion behavior of aluminum nanoparticles

Abstract

Shell morphology and oxidation depth can significantly affect the combustion effectiveness of aluminum nanoparticles (ANPs). This study presents an approach to dynamically detect and reconstruct irregular ANP surfaces using the Alpha Shape algorithm. We also introduce a visualization technique to observe nanoscale density, per-atom stress, charge, and temperature distribution of ANPs. Our findings reveal a striking phenomenon where a transitory cavity forms in the particle center during ignition, playing a significant role in the overall ignition and combustion process of ANPs. The reaction rate is found to be closely associated with the formation and collapse of the cavity, with over half of the energy being released in this process. Furthermore, the study highlights the impact of oxidation depth on ANP combustion behavior. In cases of mild oxidation, a breach in the weak area of the shell leads to the leakage of aluminum atoms from the core and the eventual shell collapse. The duration of physiochemical stages during ignition and combustion varies with oxidation depth but generally conforms to established principles. This study is expected to offer valuable insight into the interplay between shell morphology and oxidation depth on the ignition and combustion behavior of ANPs for researchers and engineers in the field of material science and combustion technology.