Activation of micro aluminum particles with non-thermal plasma for reaction with compressed water

Oxidation of aluminum powder with water cogenerates hydrogen, heat, and valuable aluminum (hydr)oxides. However, initiating the oxidation reaction is inhibited by the protective aluminum oxide shell. In this work, non-thermal hydrogen and argon plasmas are used to activate the surface of 45 μm spherical aluminum particles prior to oxidation in compressed water at 1500 psig. It was found that non-thermal plasma treatment enhanced the oxidation kinetics such that ignition delay decreased by 45 % and rate of temperature increase at thermal runaway increased by 50 % compared to the untreated powders. Surface characterization of the aluminum powders via X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy showed that oxygen-to-aluminum atomic concentration ratio decreased after plasma treatment, which indicates that the thickness of the aluminum oxide shell on the particle surface was reduced. Non-thermal plasma treatment is a chemical activation that improves the reactivity of aluminum powders in water instead of classical methods such as particle size reduction and oxidation in alkaline solutions. Figure shows the interaction between excited hydrogen species (e.g., H radicals, H 2 molecules) and the native aluminum oxide shell of the aluminum particle. The reactive hydrogen species react with aluminum oxide through chemical reduction pathways that decrease the shell thickness. A thinner alumina shell reduces the ignition delay when the aluminum particle oxidizes in water because the diffusion path for hydrating the alumina shell is reduced. • Hydrogen, heat and alumina are cogenerated from reaction of aluminum with water. • Non-thermal hydrogen and argon plasmas activate the surface of aluminum particles. • Surface treatment via non-thermal plasmas improve the reaction kinetics of aluminum oxidation in water. • Plasma activation is a chemical activation method instead of classical methods such as size reduction or alkaline media.