(749b) Nanoscale Aluminum, Silicon, and Aluminum/Silicon Mixture Formation For Use In Pyrotechnic Applications

The incorporation of nanoscale materials into pyrotechnic, energetic, and explosive formulations has fostered the development of a variety of novel tunable materials with controllable combustion characteristics.  The addition of metallic nanoparticles to energetic formulations has been shown to modify burn rates and reaction propagation in a variety of pyrotechnic formulations.  Specifically, high surface area nanoscale metals with large combustion enthalpies can be used as fuels to enhance energetic reactions.  Silicon and aluminum are both highly combustible additives of interest to the Department of Defense.  While nano-scale silicon and aluminum are both readily combustible in their unpassivated state, it is important to note that their ignition and oxidation behaviors are different.  Silicon has a higher ignition temperature than aluminum, and it is believed silicon it is less susceptible to oxidation.  Therefore, combining these two fuels into a single heterogeneous nanoscale composite in variaous stoichiometric ratios is advantageous for tuning properties. In order to maximize the chemical reactivity of these fuels premature oxidation during nanoscale synthesis must be prevented.

The top-down synthesis of heterogeneous aluminum-silicon nanoscale composites was undertaken using inert gas high energy milling and cryogenic milling.  The effect of milling parameters (e.g. time, intensity, temperature, and use of a process control agent) on the specific surface area, morphology, intermixedness, and reactive content of these composites will be discussed.  Finally, the oxidative properties of these composites will also be presented.