From "Passive Response" to "Controllable Design": The Evolution of Crystal Structure and Morphology of Hollow FePt Nanochains by Annealing Treatment.

Atomic migration behavior in reactive atmospheres, especially the competitive mechanism between short- and long-range transport, is vital to determine the stability and performance of alloy nanomaterials. In this work, taking hollow Fe3Pt7 nanochains as a model system, in situ scanning electron microscopy and molecular dynamics simulations were combined to reveal the effects of annealing temperature and reaction atmosphere on the structure evolution. Vacuum annealing from room temperature to 900 °C results in size compression, pore formation, collapse of the hollow structure, and phase transition to L12-phase Pt3Fe. In contrast, annealing in air not only causes compression and pore formation but also induces Pt segregation and formation of Pt/Fe2O3 heterostructures. Molecular dynamics simulations provide qualitative atomistic insight into how effective metal-oxygen interactions modify the structural-reconstruction pathway and elemental redistribution. This work provides atomic-scale mechanistic support for transitioning binary alloy materials from "passive response" to "controllable design".