Speaker: Swati Umbrajkar

Advisor: Dr. Edward L. Dreizin

Nanocomposite reactive materials comprising various Al-metal oxide (Me_xO_y) systems are being developed for advanced propellants and other energetic compositions. Heterogeneous reactions in such materials were investigated using differential scanning calorimetry combined with structural and phase analyses of partially reacted samples recovered at different temperatures. The dense nanocomposite powders used in this study were prepared by arrested reactive milling. Specifically reactions in the 2Al+3CuO and 2Al+MoO₃ material systems were investigated in detail. Ignition experiments with the nanocomposite powders heated at different rates were also performed and compared to the results of thermal analysis. The results of thermal analysis measurements were processed using isoconversion techniques. Multi-step reaction mechanisms were proposed to describe the experiments. The kinetic descriptions of individual steps are determined by activation energies, which should remain valid for any material with the same bulk composition, and by the frequency factors depending on the available reactive interface or degree of compositional refinement achieved. The reaction mechanisms describing each reaction step were tentatively assigned considering specific processes of metal oxide decomposition followed by diffusion of reacting species through amorphous and then crystalline Al₂O₃ polymorphs. Ignition of these nanocomposite materials was shown to be driven primarily by the lower-temperature oxidation processes. The developed technical approach enables quantitative description of the ignition kinetics for novel energetic materials based on the combined processing of thermal analysis and ignition experiments.