Iodine-Rich Biocidal Reactive Materials
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Iodine-Rich Biocidal Reactive Materials Curtis E. Johnson and Kelvin T. Higa NAVAIR, Research Division, 1900 N Knox Rd, Stop 6303 China Lake, CA 93555, U.S.A. ABSTRACT The objectives of this work are to prepare and characterize iodine-rich thermites and reactive materials for potential application in bio-agent defeat. Iodine-rich compositions were prepared using metal iodate oxidizers in combination with aluminum fuel. Higher iodine contents were achieved using iodine-rich additives, tetraiodoethylene and tin tetraiodide. Reactivity during rapid combustion was evaluated for both nanoscale and micron-scale materials. The nanoscale materials were evaluated directly using a spark-initiated pan dent test. The micron-scale materials were mixed with 50% of nano Al/MoO3 and also evaluated with the pan dent test. The results for the mixed material were shown to fit well to a linear combination of the expected dent for each component, based on a rapid reaction. Results of the pan dent test were used to down-select micron thermites for further testing. Bismuth iodate was synthesized by precipitation from nitric acid solutions. The average particle size was controlled by the addition rate, and sizes included 95 nm (amorphous structure), and 330 nm and 3 micron (both crystalline). Additional sizes were produced by ball milling the 3 micron material, giving 1 micron and 350 nm sizes. Fluoropolymers were included in some compositions to provide additional biocidal products, namely HF, that could be produced from reaction of AlF3 product with water. INTRODUCTION Iodine-producing reactive materials have potential application in the destruction of biological warfare agents, such as Bacillus anthracis (anthrax) spores. Iodine is an established spore-killing agent at elevated temperatures [1], and near room temperature [2-5]. Extremely high heat outputs are achievable with Al/iodine oxide thermites. Due to the high moisture sensitivity of the binary iodine oxides (I2O5 and I2O6), the present work is concentrated on nonhygroscopic metal iodate oxidizers. Additives to the formulations can be designed to generate specific additional sporicidal compounds, including HX (X = halogen). EXPERIMENT Commercial reagents: Al powders (80 nm, Novacentrix, metallic Al content ~74%; ~2 μm and ~5 μm, Valimet H-2 and H-5), MoO3 (45 nm, Climax; 1.6 μm, Matheson, Coleman & Bell), Bi2O3 (320 nm and 10 μm, Aldrich; 2.5 μm, Skylighter), AgIO3 (1.6 μm, Noah Technologies). Silver iodate (160-320 nm) [6] and bismuth iodate (62 nm to 3 μm) were prepared by aqueous precipitation. Some Valimet Al powders were coated with 5% K2AlF5 hydrate to enhance reactivity. Particle sizes are from surface area analysis, SEM, or manufacturer’s specification. Thermite composites were prepared by sonicating hexane suspensions [7], or by a milling process [8]. Micron thermites were generally prepared by dry mixing powders. Thermodynamic calculations were conducted on pure Al/oxidizer mixtures [9].
RESULTS AND DISCUSSION Table I lists some of the component reactions that are of
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