Kinetically Controlled Synthesis of Non-Noble Metal Based High-Entropy Alloy Nanoparticles via...

The scalable synthesis of high-entropy alloy nanoparticles (HEA NPs) with atomic-level elemental homogeneity still remains a significant challenge, particularly for systems with high binary mixing enthalpies. Here, we demonstrate continuous, high-volume (∼5 g/h) synthesis of compositionally uniform, single-phase HEA NPs with average sizes around 30 nm using a supersonic-nozzle-assisted thermal plasma jet. The nozzle provides significantly enhanced jet velocities up to the supersonic regime (M_a > 1) with highly directional flow to achieve uniform, ultrafast cooling rates of up to 10⁸ K/s. This ultrafast quenching effectively limits atomic diffusion, thereby suppressing elemental segregation even in systems with high binary mixing enthalpies (e.g., Cu-Cr: 12 kJ/mol). The extreme cooling rates also impact the growth of HEA NPs, resulting in crystallite size reduction and lattice parameter contraction. Finally microstructural analysis reveals that the supersonic nozzle leads to a distinct nanostructure transition from long-range, uniform to nonuniform nanotwins, providing a mechanism for tuning the structure of HEA NPs at nanoscales.