Synthesis of High Entropy Alloy Nanoparticles by Pulsed Laser Ablation in Liquids: Influence of Target Preparation on Stoichiometry and Productivity

Abstract

High entropy alloys (HEAs) have a wide range of applications across various fields, including structural engineering, biomedical science, catalysis, magnetism, and nuclear technology. Nanoscale HEA particles show promising catalytic properties. Nevertheless, attaining versatile composition control in nanoparticles poses a persistent challenge. This study proposes the use of pulsed laser ablation in liquids (PLAL) for synthesizing nanoparticles using equiatomic CoCrFeMnNi targets with varied preparation methods. We evaluate the impact of target preparation method on nanoparticle yield and composition as well as the magnetic properties of the nanoparticles. The elemental powder‐pressed heat‐treated target (HEA‐PP), identified as the most time‐efficient and cost‐effective, exhibits noticeable segregation and non‐uniform elemental distribution compared to ball milled hot‐pressed powder (HEA‐BP) and face‐centered cubic (FCC) single crystal (HEA‐SX) alloy targets. From all targets, nanoparticles (sizes from 2 to 120 nm) can be produced in ethanol with a nearly equiatomic CoCrFeMnNi composition and a FCC structure, showing oxidation of up to 20 at.%. Nanoparticles from HEA‐PP exist in a solid solution state, while those from HEA‐BP and HEA‐SX form core‐shell structures with a Mn shell due to inhomogeneous material expulsion, confirmed by mass spectrometry. HEA‐PP PLAL synthesis demonstrates 6.8 % and 15.1 % higher productivity compared to HEA‐BP and HEA‐SX, establishing PLAL of elemental powder‐pressed targets as a reliable, time‐efficient, and cost‐effective method for generating solid solution HEA nanoparticles.

Laser Precise Synthesis of Oxidation-Free High-Entropy Alloy Nanoparticle Libraries

“…Carbon thermal shock, fast-moving bed pyrolysis, laser-assisted photothermal reduction, liquid metal-assisted reduction, hydrogen spillover-driven strategies, and traditional wet-chemistry techniques have been used to prepare HEA-NPs with strict preparation environments (vacuum or an inert atmosphere). ,,, Although some methods can also achieve the preparation of single-phase solid solution alloys in air, it is necessary to include at least one noble metal component (Pd, Pt, Ir, Au, Rh, etc. ), which further decreases the composed element inclusiveness. ,− The laser ablation in liquid method developed in recent years can synthesize HEA-NPs with high element inclusivity, but it also requires the complex preparation process of alloy targets in an inert atmosphere or vacuum. − Moreover, preparing HEA-NPs with tunable composition in a precisely controllable manner is daunting work using traditional routes. This is particularly problematic in the synthesis of HEA-NPs containing elements with significant differences in vapor pressure.…”