Laser Generation\nof AlCrCuFeNi High-Entropy Alloy\nNanocolloids

We\nreport on the synthesis of AlCrCuFeNi high-entropy\nalloy (HEA)\nnanoparticles (NPs) using pulsed laser ablation of the AlCrCuFeNi\ntarget in two different solvents, deionized water (DIW) and anhydrous\nethanol (EtOH). The laser-generated AlCrCuFeNi HEA NPs in DIW and\nEtOH show a bimodal size distribution of the NPs. The compositional,\nphase, and structural analysis using microscopic and spectroscopic\ntechniques reveals the formation of different phases and nanostructures\nof AlCrCuFeNi NPs in these solvents. In DIW, the formation of a core–shell\nstructure in which the shell is rich in Al and O and the core is rich\nin Cu–Ni was observed. However, in EtOH, the formation of solid\nsolution AlCrCuFeNi HEA NPs was observed. The scanning transmission\nelectron microscopy–EDS analysis revealed that the segregation\nof Al is driven by the formation of an oxide. The statistical analysis\nof the chemical composition of the particles revealed the different\ntrends as a function of particle size. Larger NPs show variation in\ntheir composition, and the content of O plays a crucial role in the\nphase segregation of HEA NPs, leading to compositional variation in\nthe oxide layer and the core of the HEA NPs. However, in small NPs,\nthe homogeneous variation of all the elements in HEA was observed.\nFurther, the calculation of physiochemical and thermodynamic parameters\nindicates the formation of a solid solution with a mixture of face-centered\ncubic and body-centered cubic phases in HEA NPs. Based on the experimental\nresults, a possible growth mechanism of different morphologies and\nphases of these NPs during pulsed laser ablation in liquid is discussed.