Self-stabilization of aqueous suspensions of alumina nanoparticles obtained by electrical explosion

The particle-size distribution, electrooptical potential, and acid properties of the surface of Al₂O₃ nanoparticles in aqueous media were studied by dynamic light scattering, electroacoustic spectral analysis, and potentiometric titration. The nanopowder with the mean particle size 22 nm was obtained by the oxidation of aluminum wire in the vapor phase using electrical explosion in oxygen-argon mixture. In spite of the presence of aggregates, aqueous suspensions of nanoparticles, as distinct from suspensions of micropowders, are stable without the addition of special stabilizers because of the spontaneous formation of a double electrical layer on their surface, the electrokinetic potential of which is positive and exceeds 30 mV. The most probable reason for electrostatic self-stabilization of suspensions of nanopowders is the adsorption of Al ions formed in the hydrolysis of aluminum nitrates, small amounts of which are produced in electrical discharges during preparation.