Responses of Core-Shell Al/Al2O3 Nanoparticles to Heating: ReaxFF Molecular Dynamics Simulations

HD Zeng and XL Cheng and CY Zhang and ZP Lu, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 9191-9197 (2018).

DOI: 10.1021/acs.jpcc.8b01088

Molecular dynamics simulations combined with the ReaxFF reactive force field were implemented to detailedly study the atomic diffusion behaviors of core-shell Al/Al2O3 nanoparticles. According to atomic mean square displacements, the reaction initialization of core-shell Al/Al2O3 nanoparticles substantially resulted from the inward diffusion of shell oxygen atoms. In particular, the effect of shell thickness on the atomic diffusivities of the system was investigated. The results demonstrated that the diffusivities of core Al atoms and shell O atoms at the core- shell interfaces were irrelevant to the shell thickness during heating process; however, corresponding atomic diffusivities decreased as increasing the shell thickness after heating. A majority of distorted (AlO)(n) (n = 3, 4, and 5) clusters were ejected from the system surface at later stages, suggesting the detonation of the nanoparticles. The presence of a significant void space was observed when the alumina shell melted, which was in agreement with the experimental evidence. The alumina shell with 1 nm melts at 1153 K, and the melting point enhances with the augment of shell thickness. Furthermore, the electric field- induced atomic diffusion mechanisms of core-shell Al/Al2O3 nanoparticles are obtained as is reported, further providing extensive insights into the ignition mechanisms of passivated aluminum nanoparticles.

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