Improving the Morphology and Reactivity of Ball-Milled Aluminum Powders using Liquid Metal Embrittlement

Liquid Metal Embrittlement (LME) is a process of modifying normally ductile/malleable solid metals, such as aluminum, with the help of liquid metals, such as gallium, in order to limit their elongation to failure. Recent studies have shown improvements in reactivity of aluminum-based thermites by mixing aluminum powder with a gallium alloy, galinstan, liquid at room temperature. Here, the LME approach serves to change not only the reactivity but also the morphology of aluminum powders used as fuels. Aluminum powders with tunable particle sizes and shapes are prepared by ball-milling. A Retsch PM 400 planetary mill is used. Emulsion-assisted milling is used to prepare porous spherical aluminum powders with narrow particle size distributions. Thin foils of gallium serve as additives mixed with the starting Al powder in a milling vial. Less than 5 % of gallium are added and milling is performed in agate vials with agate milling balls to minimize interaction of gallium with the milling media and vials. Powders prepared with and without addition of gallium are recovered and characterized using scanning electron microscopy, thermal analysis, and x-ray diffraction. Effect of gallium additives and milling conditions on the structure, morphology, and reactivity of the prepared powders will be discussed.