(663b) Aluminum-Based Ternary Reactive Composite Powders

Adding aluminum to propellants, pyrotechnics, and explosives is a common way to boost their energy density. A number of approaches have been investigated that shorten aluminum ignition delay, increase combustion rate, and decrease the tendency of aluminum droplets to agglomerate.  Boron as an additive to energetic formulations is also of interest, but due to kinetic barriers in boron combustion, aluminum is the more widely used additive.  However, aluminum can potentially be used to enhance boron combustion, making use of the higher volumetric and gravimetric enthalpy of boron.  Two composite powders of Al-B-X, where X is a halogen-containing additive of elemental iodine or PTFE (Teflon), are explored in this work.  Both materials are prepared by mechanical milling.  For halogen-containing composites, an added objective is the ability to release combustion products that help defeat biological agents.  Recently it was shown that composite materials of aluminum and elemental iodine, prepared by mechanical milling have enhanced oxidation rates and generate combustion products substantially improving prompt inactivation of bioaerosols.  Biocidal effectiveness of other halogens, such as fluorine or fluorinated combustion products expected in presence of Teflon is also of interest.  In addition, Al-Teflon composites are known to be highly reactive.  Finally, both Teflon and iodine serve as effective surfactants during mechanical milling, assisting formation of the composites with desired particle sizes and morphologies.  In this work, composites containing elemental iodine and Teflon are produced using mechanical milling and characterized.  Oxidation, ignition, and combustion of the prepared powders are studied experimentally.