Ignition and combustion behaviors of nano-composite energetic materials
Granier, John Joseph
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Advances in material processing have created nano-sized fuel particles with enhanced properties ideal for exothermic reactions compared with those of larger particles of the same material. As a result the combustion associated with nano-scale particles has recently shown the potential for enhanced energetic behavior of thermites. In this study, the ignition sensitivity of an aluminum molybdenum-trioxide (AI/M0O3) composite mixture was examined. Laser ignition experiments were performed to determine the ignition time and burn rates of newly developed nano-Al mixed with M0O3. The scope of this work can best be summarized in two stages: first, the ignition time and bum rates for three nano-regime Al mixtures were studied over a varied composition range, the results were then used to further study ignition time and bum rate as a function of Al particle diameter, which ranged from 17.4 nm to 20 µm at the optimum stoichiometric composition. A 50-W CO2 laser provided the ignition source and high-speed digital images were used to determine ignition time and bum rates. Results indicate that a slightly fuel rich (equivalence ratio of 1.2) mixture presents the earliest ignition times and fastest burn rates for the nano Al particle diameters. Experiments using a slightly fuel rich mixture for ten Al particle diameters show an increased sensitivity to ignition with decreasing particle size, a decreased bum rate with decreasing particle size and less variability of ignition times and burn rates for nano-regime Al.