(599b) Preparation, Ignition and Combustion of Metal-Sulfur Nanocomposite Thermites with Biocidal Properties

Research is currently active in preparing reactive materials as components to advanced munitions, capable of eliminating or inactivating stockpiles of biological weapons.  Previously, it was shown that a range of iodine-bearing metal fuels, including Al-I₂, Al-CHI₃, Al-B-I₂ and Mg-B-I₂, can be prepared by mechanical milling.  Milling was shown to be a versatile and scalable technique used to stabilize and incorporate biocidal component, i.e. iodine (up to 20 wt. %), in the fuel’s metal matrices.  Current focus is geared towards preparing new materials capable of undergoing highly exothermic reactions with greater concentrations of biocidal components in the starting powder mixtures.  The prepared materials must be compatible with common binders and insensitive to spark, impact, friction and other common ignition stimuli for conventional processing and material handling.

Sulfur is a moisture and air stable compound capable of undergoing thermite reactions when mixed with metals, Zn, Hf, Ti, Mg, etc.  It is also known to have biocidal properties. In this study, preparation of nanocomposite thermites under ambient and liquid nitrogen temperatures by mechanical alloying (or ball milling) of starting metal powder, i.e. Mg, or Al, with elemental sulfur is explored.  Combustion in oxidative environments is expected to form gaseous products with active antimicrobial/biocidal properties.  Stoichiometric ratios of the starting materials are used to increase the concentration of biocidal component, 57 – 64 wt. % of sulfur, in these thermites.  Nanocomposites and their combustion products are characterized using scanning electron microscopy and x-ray diffraction.  The spark sensitivity of the prepared material is tested and compared to conventional thermite systems, i.e. Al-CuO and Al-MoO₃.  An electrically heated filament experiment is used to study the ignition of the powders.  Combustion dynamics of the powders is tested by feeding them into a hydrocarbon flame and measuring intensities and durations of the emission pulses produced by particles.  Both, combustion times and combustion temperatures are identified.