Thermostructural Behaviour of Ni-Cr Materials: Modelling Bulk and Nanoparticle Systems

Abstract

The thermostructural properties of Ni-Cr materials, as bulk and nanoparticle (NP) systems, have been predicted with a newly developed interatomic potential, for Ni/Cr ratios from 100/0 to 60/40. The potential, which has been fitted using experimental data and further validated using Density Functional Theory (DFT), describes correctly the variation with temperature of the lattice parameters and the coefficient of thermal expansion, from 100 K to 1000 K. Using this potential, we have performed Molecular Dynamics (MD) simulations on bulk Ni-Cr alloys of various compositions, for which no experimental data are available. Similarly, NPs with diameters of 3, 5, 7, 10 nm were studied. We found a very rapid convergence of NP properties with the size of the systems, showing already the 5 nm NPs a thermostructural behaviour similar to that the bulk. MD simulations of two 5 nm NPs show very little sintering and thermally-induced damage, for temperatures between 300 K and 1000 K, suggesting that materials formed by agglomeration of Ni-Cr NPs meet the thermostructural stability requirements for catalysis applications.