Nanostructured highly-exothermic reactive mixtures, referred to as Nanoenergetic Materials (NM) or Metastable Intermolecular Composites (MIC), may release energy much faster than conventional energetic materials. The size reduction of reactant powders such as aluminum from micro- to nano-size increases the reaction front propagation velocity in some systems by two to three orders of magnitude. Our recent experiments suggest that oxidation of nanoparticles of aluminum proceeded in a few microseconds. In this report, we present a rapid oxidation model of spherical aluminum nanoparticles surrounded by oxygen, using Cabrera-Mott oxidation model with self-consistent potential, and taking self-heating into account. In this model, aluminum ions are helped to escape aluminum surface (overcoming ionization potential Wi), and to move through oxide layer to its outer part with the help of self-consistent electric field potential (V) created by the imbalance between excess positive aluminum ions and electrons. Excess concentrations of electrons and ions in oxide layer in turn are dependent on electric field potential via appropriate Gibbs factors, leading to a self-consistent version of Poisson equation. In contrast with Coulomb potential, our result shows that for aluminum nanoparticles (20-100 nm), a double layer potential leads to enhanced oxidation rates throughout the oxidation process.
Journal: TechConnect Briefs
Volume: 2, Nanotechnology 2012: Electronics, Devices, Fabrication, MEMS, Fluidics and Computational (Volume 2)
Published: June 18, 2012
Pages: 649 - 652
Industry sector: Advanced Materials & Manufacturing
Topics: Informatics, Modeling & Simulation