Reaction kinetics of nanometric aluminum and iodine pentoxide

Owing to increasing threats of biological attacks, new methods for the neutralization of spore-forming bacteria are currently being examined. Thermites may be an effective method to produce high-temperature reactions, and some compositions such as aluminum (Al) and iodine pentoxide (I₂O₅) also have biocidal properties. This study examines the thermal degradation behavior of I₂O₅ mixed with micron and nanometer scale aluminum (Al) particles. Differential scanning calorimetry (DSC) and thermogravimetric (TG) analyses were performed in an argon environment on both particle scales revealing a non-reaction for micron Al and a complex multistep reaction for the nanometer scale Al. Results show that upon I₂O₅ decomposition, iodine ion sorption into the alumina shell passivating Al particles is the rate-controlling step of the Al–I₂O₅ reaction. This pre-ignition reaction is unique to nano-Al mixtures and attributed to the significantly higher specific surface area of the nanometric Al particles which provide increased sites for I⁻ sorption. A similar pre-ignition reaction had previously been observed with fluoride ions and the alumina shell passivating Al particles.