Highly stable functionalized aluminum nanoparticles for magneto-energetic composite fabrication

An effective coating strategy is employed to functionalize and protect the surfaces of aluminum (Al) nanoparticle (NPs) from oxidation and aggregation using silanization of the oxide surface with (3-aminopropyl) triethoxysilane (Al@APTES), followed by an amine/carboxylic exchange using glutaric anhydride (Al@APTES@GA). The stability of the two types of functionalized Al NPs in aqueous solution is studied using dynamic light scattering and x-ray diffraction phase/composition identification. It is found that Al@APTES NPs transform into bayerite (β-Al(OH)3) after storage for a short period of time, while Al@APTES@GA NPs exhibit long-term stability. Hydration of Al results in micro-sized aggregates and a large proportion of dead weight, which reduces the particles' energetic properties. Al-Fe3O4 magnetic-energetic (Magnerg) composites are fabricated via the electrostatic interaction of oppositely charged NPs in an aqueous solution. The high dispersity and stability of Al@APTES@GA NPs assure their intimate arrangement with oxidizing Fe3O4 NPs that facilitates mass transport between reactants.