Persulfate salt as an oxidizer for biocidal energetic nano-thermites

Nanoscale potassium persulfate (K2S2O8) was evaluated as an alternative to other peroxy salts, such as periodates (KIO4), in aluminum-fueled energetic nano-composite formulations. High speed imaging coupled with temperature jump (T-jump) ignition found the nano-Al/K2S2O8 reaction to have an ignition temperature of 600 degrees C which is comparable to nano-Al/KIO4 and lower than nano-Al/K2SO4. The results from constant-volume pressure cell experiments further show that nano-Al/K2S2O8 releases more gas and has a longer burn time than nano-Al/KIO4. Thermal analyses at low heating rates (10 degrees C min(-1)) by coupled differential scanning calorimetry (DSC), thermal gravimetric analysis (TG) and mass spectrometry (MS) show that there are three main steps of thermal decomposition for nano-K2S2O8, with initial exothermic decomposition to release O-2 at 270 degrees C, and following endothermic decomposition to release both O-2 and SO2 at higher temperatures. The heat of formation of K2S2O8 was measured to be -1844.5 kJ mol(-1) based on the DSC results. Experiments performed at ultrafast heating rates (similar to 10(5) degrees C s(-1)) using temperature-jump time-of-flight (T-jump/TOF) MS show that the low O-2 generation temperature of nano-K2S2O8 contributes to its high reactivity in nano-thermite compositions. An ignition mechanism involving gaseous oxygen was proposed for nano-thermite compositions containing reactive oxysalts such as nano-K2S2O8. In contrast, a condense phase ignition mechanism was proposed for nano-thermites involving less reactive oxysalts such as nano-K2SO4. Given that the nano-Al/K2S2O8 system is highly exothermic in addition to generating a considerable amount of SO2, it may be a candidate for use in energetic biocidal applications.