Oxidation Kinetics of Aluminum Nanoparticles Goal:Understand the nature of single nanoparticle reactivity. A. How reactive are nanoparticles ? B. How can we moderate there reactivity through changes in composition, size, morphology ? Technical Approach: 1. Develop reproducible aluminum sources. 2. Develop the necessary methods, including tools to study reactivity at the single-particle level. 3. Compare reactivity with atomistic and phenomenological models. Zachariah

Progress 1.Developed two reliable and reproducible sources of nanoaluminum: laser ablation DC arc: more reactive nanoparticles because smaller 2.Measured the composition of individual nanoparticles using single- particle mass spectrometry. 3.Measured rates of aluminum nanoparticle oxidation. 4.Studied the internal pressure and surface tension of bare and oxide coated aluminum. 5.Developed a connection between the melting of aluminum and the onset of oxidation Zachariah (cont.)

Developed a phenomenological model for how the internal pressure of oxide coated nanoparticles can retard the oxidation rate. Developed method for coating aluminum with carbon and studied the oxidative and thermal stability as a function of size. Results from this year 20 nm Carbon-coated aluminum Zachariah (cont.) Completed determination of size-dependent kinetics for aluminum nanoparticle oxidation ( K). less than 50 nm — fast, low activation energy nm — slow, high activation energy Developed a plasma-hydrodynamics model for the interaction for an intense laser pulse with a single nanoparticle, for application to quantification of single particle mass-spectrometry.