Performance of iodine oxides/iodic acids as oxidizers in thermite systems

Iodine oxides are of interest as biocidal components in energetic application such as thermites due to their high energy release and biocidal agent delivery. In this study, various iodine oxides/iodic acids, including I2O5, HI3O8 and HIO3, were employed as oxidizers in thermite systems. Their decomposition behaviors were studied using a home-made time resolved temperature-jump/time-of-flight mass spectrometer (T-Jump/TOFMS), which identified a single step decomposition for all oxides at high heating rates (∼105 K/s). In addition, both nano-aluminum (nAl, ∼80 nm) and nano-tantalum (nTa, <50 nm) were adopted as the fuel in order to fully understand how iodine containing oxidizers react with the fuel during ignition. The ignition and reaction process of nAl-based and nTa-based thermites were characterized with T-Jump/TOFMS, and their combustion properties were evaluated in a constant-volume combustion cell and compared to a traditional thermite system (nAl/CuO). The ignition temperatures of nAl-based thermites using these oxidizers were all very close to the melting point of aluminum (∼660 °C), which suggests that the mobility of the aluminum core dominats the ignition/reaction and the gaseous oxygen released from the decomposition of the oxidizer does not participate in the ignition until the molten aluminum is available. Unlike nAl-based thermites, the ignition temperatures of nTa-based thermites are lower than the oxygen release temperatures from the corresponding bare oxidizers. All nTa-based thermites ignited prior to the release of gas phase oxygen. In this case, a condensed phase reaction mechanism is proposed to dominate the ignition process. Moreover, combustion cell tests results show that nAl/a-HI3O8 has the highest pressurization rate and peak pressure and shortest burn time, and since it also has an iodine content of ∼75% as high as I2O5 on a per mass basis, this material may be a very promising candidate in biocidal application.