Thermal stability of CoNiPtCuAu nanoalloys: from segregation to melting properties.

Abstract

Recent breakthroughs in the field of high-entropy alloy nanoparticles (HEA NPs) have significantly expanded their potential applications (such as catalysis or energy storage) making them promising candidates for use over a wide temperature range. However, their thermal stabilities are not yet fully understood, which is crucial to their future development. To better understand these phenomena and the underlying mechanisms, we performed molecular dynamics simulations by adopting an incremental approach to investigate the structural and thermal stability of CoNiPtCuAu HEA NPs, as well as their ternary and quaternary sub-alloys. More precisely, CoNiPt ternary system is first considered and then Cu and Au atoms are progressively introduced with the aim to analyse and quantify the thermal stability of HEA NPs in terms of their melting temperature and segregation mechanisms. Through our atomic-scale simulations, we demonstrate the negative impact of Au and Cu atoms on thermal stabilisation, whose presence at the surface tends to favour melting of the NPs because of their low melting point. These detailed analyses provide a robust and relevant research approach for identifying the key parameters influencing the thermal stability of HEA NPs, which is essential for obtaining such nano-objects with optimised structural and thermal properties.