Aluminum powders with modified morphology and enhanced reactivity prepared by emulsion-assisted milling

Emulsion-assisted milling was used to prepare micron-sized aluminum powders with irregular and spherical particle shapes. These powders were compared to the similarly sized starting atomized aluminum. For both milled powders, particles consist of closely packed, flattened refined primary particles. The size of these primary particles is smaller for the spherical powder. In thermo-analytical experiments, milled powders oxidize faster and more completely than the atomized powder. Milled powders coated on an electrically heated filament ignite at lower temperatures than atomized aluminum. In constant volume explosion tests, milled powders exhibit shorter ignition delays, greater combustion rates, and greater combustion heat release compared to the reference atomized aluminum. The spherical milled powder consistently outperforms the irregularly shaped powder in both the ignition and combustion experiments. The results suggest that the milled powders, especially the powder with spherical particle sizes, oxidize, ignite, and burn as fast as a much finer (nano-sized) aluminum powder. Unlike nanopowder, the milled powder has a reactive aluminum content as great as the atomized, micron-sized aluminum.