The Kinetics of Ni/Al Reactive Intermetallic Composites

Molecular dynamics (MD) simulations have been used to study the underlying physics and atomistic mechanisms of the reaction progression in Ni/Al reactive intermetallic composites. Preparation of these composites, either through deposition techniques or through the process of mechanical ball milling, gives rise to a periodic ordered, nanolaminated structure and in the first part of this thesis, the effects of this laminate period, ignition temperature and volumetric defects are studied. The presence of defects not only speeds up the reaction by as much as 5 times, but changes the nature of mass transport from diffusive to partly ballistic. Subsequently, the feasibility of using amorphous energetic materials is studied. The use of amorphous precursors is found to speed up the reaction as well as increase the heat of reaction, starting as it does from a higher energy state. Amorphous Ni recrystallizes at elevated temperatures and this process has been investigated (both thermal and shock induced recrystallization). The results presented herein, hint at the possibility of nanostructural tiling and the building of hierarchal nanostructures, starting from amorphous rather than liquid or chemical precursors