Thermite reactions with high energy release and biocidal agents' production are of interest for their potential applications in bio-agent defeat. In this work, we investigated the ignition and combustion of nano-Al/micro-I_2O_5 thermite, and studied its potential use in biocidal applications. Cyro-milling technique was used to produce micro-sized I_2O_5 (～2-4 μm) which were used as the oxidizer in this study. The ignition and reaction of the prepared nano-Al/micro-I_2O_5 thermite were systematically studied by a rapid fine wire heating technique using a high speed digital camera and a temperature-jump/time-of-flight (T-Jump/TOF) mass spectrometer. The ignition temperature of nano-Al/micro-I_2O_5 thermite in air at atmospheric pressure was found to be ～810 K, lower than ignition temperature ～940 K in vacuum. Time-resolved mass spectra results confirmed that nano-Al/micro-I_2O_5 thermite reaction can produce a lot of iodine species which were suggested to be good biocidal agents. Thermal decomposition of the I_2O_5 oxidizer under rapid heating conditions were investigated by T-Jump/TOF mass spectrometer, and was found to release significant O_2 before its thermite ignition. Constant-volume combustion cell tests were carried out to characterize the pressure rise and optical emissions during the thermite combustion events, and the performance of the I_2O_5 containing thermites was compared with other metal oxides thermite systems. The results show that Al/I_2O_5 thermite composite outperform the traditional Al/CuO and Al/Fe_2O_3 thermite systems in terms of peak pressure, pressurization rate and burning time. Additionally, we observed the concurrent pressure and optical rising for all nano-Al/micro-oxidizer thermites in this study. The results indicate that the pressure rise in nano-Al/micro-I_2O_5 thermite reaction should be from the produced hot biocidal species by very exothermic thermite reactions other than from the decomposition of oxidizers, suggesting the beneficial of using microsized I_2O_5 as the biocidal oxidizer. Transmission electron microscope with X-ray compositional microanalysis characterization was performed to analyze the post-combustion products and the production of iodine and aluminum oxides were found as main products. Additional studies of hygroscopic properties of I_2O_5 on its thermite reaction will also be discussed. Our study of Al/I_2O_5 thermites show that these I_2O_5 containing thermite reactions are very reactive and suggested to effectively produce iodine gas which can be used in microbial agent defeat applications.
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