Overview of Nanoscale Energetic Materials Research at Los Alamos
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Overview of Nanoenergetic Material Research at Los Alamos Steven F. Son, Timothy J. Foley, V. Eric Sanders, Alan M. Novak, Douglas G. Tasker, and Blaine W Asay, Los Alamos National Laboratory Los Alamos, New Mexico 87545 USA [email protected] ABSTRACT Metastable Intermolecular Composite (MIC) materials are comprised of a mixture of oxidizer and fuel with particle sizes in the nanometer range. Characterizing their ignition and combustion is an ongoing effort at Los Alamos. In this paper we will present some recent studies at Los Alamos aimed at developing a better understanding of ignition and combustion of MIC materials. Ignition by impact has been studied using a laboratory gas gun using nano-aluminum (Al) and nano-tantalum (Ta) as the reducing agent and bismuth (III) oxide (Bi2O3) as the oxidant. As expected from the chemical potential, the Al containing composites gave higher peak pressures. It was found, for the Al/Bi 2O3 system, that impact velocity under observed conditions plays no role in the pressure output until approximately 100 m/s, below which speed, impact energy is insufficient to ignite the reaction. This makes the experiment more useful in evaluating the reactive performance. Replacing the atmosphere on impact with an inert gas reduced both the amount of light produced and the realized peak pressure. The combustion of low-density MIC powders has also been studied. To better understand the reaction mechanisms of burning MIC materials, dynamic electrical conductivity measurements have been performed on a MIC material for the first time. Simultaneous optical measurements of the wave front position have shown that the reaction and conduction fronts are coincident within 160 µm. INTRODUCTION Novel properties associated with nanostructured materials, including nanoenergetic materials, have attracted a great deal of interest recently. Some thermite reactions offer energy release on a mass or volume basis that exceeds classical energetic materials. However, broad application is limited because the energy release rate is generally slow 1. Employing reactants on the nano-scale reduces the diffusion barrier sufficiently to dramatically increase the energy release rate2. These materials have been termed metastable intermolecular composites (MIC). Here we use this term to refer to any composite energetic material utilizing nano-scale energetic constituents. Our baseline composite material is prepared from nano-scale aluminum and molybdenum trioxide. The Al/MoO3 composite, for example, is prepared by immersing the powders in a solvent and then mixing the two powders using an ultrasonic mixer. The particles become suspended in the solvent and once thoroughly mixed, the mixture is
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poured into a pan and heated to a few degrees above ambient, allowing the solvent to evaporate. These nano-scale thermites are generally very spark and friction sensitive. Consequently, only very small samples are handled and appropriate personal protection is used. In this paper we will present an overview of o
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