Electron Radiation-Induced Nickel Nanoparticle Formation in KCl-ZnCl₂ Eutectic Molten Salt Using X-ray Absorption Spectroscopy

Understanding the speciation and local structure of metal solutes in molten salts is essential for predicting thermal properties and the redox and corrosion potentials of molten salts for next-generation nuclear reactors and concentrated solar power plant applications. We employ X-ray absorption spectroscopy combined with electron paramagnetic resonance (EPR) measurements to investigate the effects of electron irradiation on 0.1 wt % NiCl₂ dissolved in molten eutectic KCl-ZnCl₂ salt. Radiation-driven reduction of Ni²⁺ leading to nucleation and growth of Ni nanoparticles is studied as a function of electron dose (3-15 MGy) and temperature. Quantitative X-ray absorption near edge structure and linear combination fitting are utilized to investigate the extent of reduction as a function of the electron dose and temperature. A multiple-scattering (MS) approach is used for extended X-ray absorption fine structure analysis to deduce the size of the Ni nanoparticles formed and to understand the effect of the dose on the local structure of the nanoparticles. EPR studies on solidified NiCl₂ dissolved in molten eutectic KCl-ZnCl₂ salt show the formation of magnetic Ni nanoparticles.