Alloying nanoparticles by discharges in liquids: a quest for metastability

摘要: The use of ultrafast processes to synthesize alloy nanoparticles far from thermodynamic equilibrium is subject to phase transformations that keep particles at a given temperature for periods of time that are usually long with respect to the process pulse durations. Reaching non-equilibrium conditions is then not straightforwardly associated with this process, as fast as it can be, but rather with heat transfer mechanisms during phase transformations. This latter aspect is dependent on nanoparticle size. Furthermore, other important phenomena such as chemical ordering are essential to explain the final structure adopted by an alloy nanoparticle. In this work, specific attention is paid to suspensions submitted to either electrical discharges or to ultrashort laser excitations. After discussing the thermodynamic considerations that give the frame beyond which non-equilibrium alloys form, a description of the heating processes …