Laser-induced metastable mixed phase of AuNi nanoparticles: a coherent X-ray diffraction imaging study

Abstract

The laser annealing process for AuNi nanoparticles has been visualized using coherent X-ray diffraction imaging (CXDI). AuNi bimetallic alloy nanoparticles, originally phase separated due to the miscibility gap, transform to metastable mixed alloy particles with rounded surface as they are irradiated by laser pulses. A three-dimensional CXDI shows that the internal part of the AuNi particles is in the mixed phase with preferred compositions at ∼29 at% of Au and ∼90 at% of Au.

Phase separated bi-metallic PtNi nanoparticles formed by pulsed laser dewetting

“…In a tomographic transmission CXDI, the small angle x-ray diffraction (XRD) profile (magnitude) of an isolated object satisfying the oversampling condition are recorded at various incident x-ray beam directions and, used to reconstruct its 3D electron density quantitatively with a nm scale resolution utilizing a phase retrieval algorithm [39][40][41][42][43][44][45]. Similar to a recent CXDI report on pulsed laser dewetted AuNi NPs [46], interesting 3D morphology of Pt-and Ni-rich regions was observed.…”

Oxidation-induced three-dimensional morphological changes in Ni nanoparticles observed by coherent X-ray diffraction imaging

“…In most cases, the spatial resolution of the 3D CXDI is still limited to tens of nanometres which is far from resolving individual atoms (Gallagher-Jones et al, 2016). However, 3D CXDI has demonstrated great potential in investigating materials processes involved in catalytic reactions, alloying, dewetting and so forth in a non-destructive manner (Robinson et al, 2016;Liu et al, 2018;Kim et al, 2019Kim et al, , 2020.…”