(655d) Oxidation Behavior of Milled Aluminum, Silicon, and Aluminum/Silicon Nanocomposites for Pyrotechnic Applications

The use of nano-scale materials with high specific surface area has been of recent interest in pyrotechnic, energetic, and explosive chemistry as a means of tuning combustion properties of novel formulations.  Incorporating high surface area fuels such as aluminum (5-25 m²/g), silicon (20-100 m²/g), and nano-composites thereof (30-50 m²/g) can alter the burn rates and detonation velocities of energetic formulations.  Inert gas condensation (IGC) techniques have proven capable of producing large quantities of high purity nano-scale fuels; however, the high cost of these nano-fuels remains a limiting factor in their successful incorporation into pyrotechnic formulations.   Therefore, the ability to produce low-cost nano-scale materials is of great interest.  Low-cost synthesis can be accomplished using wet and dry attrition methodologies, but oftentimes the nano-fuels pick up a detrimental amount of oxygen during attrition thereby reducing their effective combustion enthalpy. 

Aluminum and silicon are of interest because of their high energy densities.  But, because these two elements have significantly different ignition temperatures, combustion enthalpies, and oxidation behaviors they can each be incorporated alone as nano-scale elemental powders or together as a heterogeneous nano-composite powder depending on the application of interest.  By changing the specific surface area, and composition of these nano-scale aluminum and silicon additives one can tune the performance of the formulation.  Herein, the surface area and reactive content of dry and wet milled aluminum, silicon, and composite powders will be presented.  The amount of premature oxidation that occurs during various low-cost synthesis routes will be compared and discussed with respect to the energetic performance of these milled fuel mixtures.