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 nano-particles. 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.