Influencing the room temperature oxidative stability of nanoclusters by alloying with more oxophilic elements

Abstract

Oxidative stabilities of single component nanoclusters are studied in the presence of an oxophilic element. Atomistic simulations are used to study the early stages of heterogeneous oxidation of a representative binary alloy nanoclusters such as Ni–Al. The role of oxophilic Al atoms in enhancing the oxidation of Ni atoms in the Ni–Al alloy is highlighted. The simulated trajectories are used to better elucidate the mechanism of oxidation for two elements with distinct oxidation rates. Increased oxidation kinetics for particles with higher Al content is consistent with higher oxophilicity of Al atoms in comparison with Ni atoms. Ni rich alloys are found to be least oxidized with significant phase segregation between the Ni and Al phases. Furthermore, the oxides formed were found to be non-stoichiometric for Ni rich alloys and near stoichiometric for Al rich alloys. Phase segregation for the alloys is also found to be induced, resulting from the relative differences in the atom mobilities during the oxidation process. Thermodynamic and kinetic considerations are used to understand the higher degree of oxidation of Ni atoms in the presence of a higher composition of Al oxides. The simulations suggest a general strategy that allows for tuning the room temperature oxidative stability of single component nanoclusters by alloying with a higher oxophilic element.