Micro- and nano-spheres of low melting point metals and alloys, formed by ultrasonic cavitation

Metals and alloys of low melting points (<430 °C) can be melted in hot silicone oil to form two immiscible liquids. Irradiation of the system with ultrasonic energy induces acoustic cavitation in the oil, which disperses the molten metals into microspheres that solidify rapidly upon cooling. This method has been applied to seven pure metals (Ga, In, Sn, Bi, Pb, Zn, Hg) and two eutectic alloys of gold (Au–Ge and Au–Si). The morphology and composition of the resulting microspheres were examined by SEM and EDS. Eutectic Au–Si formed also crystalline Au nanoparticles, which were separated and studied by HRTEM.