Phase Transformations in Nanostructures

Reactive diffusion in stressed nanostructures

In nanoscaled objects, reaction-induced elastic stress and non-equilibrium vacancies can hardly relax. As a result, stresses may become outstandingly high, even approaching the theoretical strength of the material. A better understanding of the interrelation between diffusion, reaction and stress may lead to a perfect control of, for instance, the formation of hollow nanoparticles or hollow nanowires with a wide range of potential applications ranging from photonics to drug delivery.In order to accurately describe these phenomena we are developing a set of analytical equations solved numerically.

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Fig. 1: Kirkendall voiding during the oxidation of a metallic nanoparticle

Self-assembling nanowires

We are exploring alternative synthesis routes in order to find a new self-ordering way of producing multilayered or core-shell nanowires which would be only based on diffusion processes and phase separation. Simply put, we would like to create a plain alloyed nanowire and provoke the formation of layers just by a well-designed heat treatment.

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Fig. 2: Nickel nanowires coated with a copper layer, depending on the coating technique, the wires form different shapes (packages, nano-cactuses…)