Combustion behavior of highly energetic thermites: Nano versus micron composites

Combustion behavior of energetic composite materials was experimentally examined for the purpose of evaluating the unique properties of nano-scale compared with traditional micron-scale particulate media. Behavior of composite systems composed of aluminum (Al) and molybdenum trioxide (MoO3) were studied as a function of Al particle size, equivalence ratio and bulk density. Samples were prepared by mechanically mixing individual fuel and oxidizer particles and combustion experiments included measurements of ignition and flame propagation behavior. Ignition was achieved using a 50-W CO2 laser and combustion velocities were measured from photographic data. Reaction kinetics were studied with differential scanning calorimetry (DSC). Results indicate that the incorporation of nano-Al particles (1) significantly reduces ignition temperatures and (2) produces unique reaction behavior that can be attributed to a different chemical kinetic mechanism than observed with micron-Al particles.