High-Temperature\nFerrofluids Based on Molten Salts

Molten metal chloride salts are promising candidates\nfor advanced\nheat transfer fluids in generation IV nuclear reactors and beyond.\nHowever, research on the magnetic properties of suspended metallic\nnanoparticles at elevated temperatures is scarce, and there have been\nno attempts to develop a high-temperature, molten salt based ferrofluid.\nSuch a ferrofluid would enable in situ manipulation of both the physical\nand thermal properties of the fluid via an external magnetic field.\nThis study examines molten salt based ferrofluids comprised of metallic\ncobalt nanoparticles dispersed in molten metal chloride salts. High-temperature\nmagnetometry and magneto-thermogalvometric measurements were conducted\nto evaluate the magnetic characteristics of the ferrofluid. Further\nanalysis was conducted through a combination of microscopy, spectroscopy,\nsolubility tests, and diffraction measurements. The metallic cobalt\nnanoparticles exhibited a notable degree of chemical stability and\nsustained magnetism from 25 to 800 °C when suspended in NaCl–MgCl<sub>2</sub> and KCl–ZnCl<sub>2</sub> mixtures.