Correction to “Oxidation of Aluminum Particles from 1 to 10 nm in Diameter: The Transition from Clusters to Nanoparticles”

Micrometer- and nanometer-scale aluminum (nAl) particles are often considered attractive choices for fuels in energetic materials. In general, reaction rates increase as particle size decreases because of the increased surface area and reduced diffusion lengths between reactants. The oxidation behavior for aluminum nano-particles >10 nm in diameter has been widely studied, and so has the oxidation behavior of clusters <1 nm in diameter (primarily for catalysis applications). These two regimes exhibit vastly different reaction mechanisms, but there is no experimental work observing the oxidation behavior for intermediate size particles with diameters from 1 to 10 nm. The present study investigates this transition regime by producing unpassivated aluminum particles in this size range using superfluid helium droplet assembly (SHeDA) and then oxidizing the particles by rapidly transferring them from ultrahigh vacuum (UHV) to ambient air. Scanning transmission electron microscopy with energy dispersive spectroscopy (STEM/EDS) and X-ray photoelectron spectroscopy (XPS) showed that particles <4 nm in diameter vaporize upon oxidation while particles >4 nm in diameter do not. We have hypothesized that this is a critical diameter and is the threshold between the oxygen-etching mechanism of clusters and the heterogeneous oxidation of nanoparticles.