Ni/Al Energetic Nanocomposites and the Solid Flame Phenomenon

Reactive nanocomposites (RNCs), which are comprised of stochastically layered metals, were fabricated using short-term high-energy ball milling of nickel and aluminum powders. By varying the milling conditions, the internal nanostructure of the RNCs can be controlled. Utilizing the slice and view methodology by use of a dual beam scanning electron/ion microscope, 3D reconstruction of the RNC particles was accomplished and their nanostructures were quantitatively and statistically analyzed. The reactivity, including ignition and combustion parameters, as well as microstructure of the combustion wave, for different RNCs was analyzed using high-speed infrared imaging and high-speed micro video recording. The direct relationships between the 3D structural characteristics and reactivity parameters have been determined. A comparison with existing theoretical models allows us to conclude that, for specially designed RNCs, the reaction can be initiated and self-propagates solely due to solid-state mechanisms, i.e., in the solid flame mode. In addition, a novel nano quasi-homogeneous reaction regime was discovered. It was directly demonstrated that, by understanding the fundamental quantitative relationship between the structure and properties of RNCs, unprecedented control over the reaction can be achieved. (Graph Presented).