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Role of oxidation of the melting transition of metallic nanoparticles

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Owing to their valuable size- and shape-dependent properties, metallic nanoparticles play an increasingly vast role in scientific areas as diverse as catalysis, magnetic information storage, or for optical and electronic sensors with further use in nanomedicine. In many applications the nanoparticles need to be exposed to conventional media such as air or water and can become oxidized. Oxidation can modify the properties, and it is essential to understand these processes in order to control them and prevent extensive degradation of the material under the desired working conditions. This internship aims to address one specific property, namely the thermal stability, and determine by molecular simulation the dual influence of nanoparticle size and the amount of oxygen absorbed on its melting temperature, and compare the results of the simulations to the prediction of simple thermodynamical models based on the Gibbs-Thomson equation that relates the depression in the melting point to the size and interfacial energies.

The simulations will be carried out for the specific case of aluminum particles, for which atomistic models have already been successfully implemented in our lab. Oxidation of the particles proceeds on the surface, with an oxide shell surrounding a metallic core. Of special interest will be the characterization of the melting mechanisms and the interplay between the earlier thermal destabilization of the metallic core and the pressure exerted by the still solid shell. Comparison with existing recent measurements will also be attempted.

Florent Calvo, 04 76 51 45 92
Universite Joseph Fourier Grenoble 1, BP 87
St Martin d’Heres