Nano-scale reactants in the self-propagating high-temperature synthesis of nickel aluminide

The ignition and combustion behaviors of nickel (Ni) and aluminum (Al) thermites were studied as a function of Al particle size. In particular, nano-scale Ni/Al composites were compared to micron-scale Ni/Al composites. Laser ignition experiments were performed on pressed Ni/Al pellets to determine ignition time and temperature as a function of Al particle size. Flame propagation behavior and burn rates were also examined using high-speed diagnostics. Results show that nano-scale composites have significantly reduced ignition times over micron-scale composites owing primarily to the unique thermal properties associated with nanoparticles. Flame propagation and overall burn rate was also influenced by Al particle size and physical properties. Electron micrographs of the products reveal the formation of whiskers in nano-scale composites but not in micron-scale composites. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.