Metal-based reactive nanomaterials

Recent developments in materials processing and characterization resulted in the discovery of a new type of reactive materials containing nanoscaled metal components. The well-known high oxidation energies of metallic fuels can now be released very rapidly because of the very high reactive interface areas in such metal-based reactive nanomaterials. Consequently, these materials are currently being examined for an entire range of applications in energetic formulations inappropriate for conventional, micron-sized metal fuels having relatively low reaction rates. New application areas, such as reactive structural materials, are also being explored. Research remains active in manufacturing and characterization of metal-based reactive nanomaterials including elemental metal nanopowders and various nanocomposite material systems. Because of the nanometer scale of the individual particles, or phase domains, and because of the very high enthalpy of reaction between components of the nanocomposite materials, the final phase compositions, morphology, and thermodynamic properties of the reactive nanocomposite materials may be different from those of their micron-scaled counterparts. Ignition mechanisms in such materials can be governed by heterogeneous reactions that are insignificant for materials with less developed reactive interface areas. New combustion regimes are being observed that are affected by very short ignition delays combined with very high metal combustion temperatures. Current progress in this rapidly growing research area is reviewed and some potential directions for the future research are discussed. (C) 2008 Elsevier Ltd. All rights reserved.