Molten-salt synthesis of manganese-doped intermetallic TiFexMn(1−x) nanoparticles from oxide precursors

Abstract

Manganese-doped intermetallic TiFexMn(1−x) nanoparticles (NPs) were synthesized by a molten-salt synthesis method using TiO2, FeSO4•7H2O, and Mn(NO3)2•6H2O as the raw materials. The Ti–Fe–Mn oxide precursors prepared from the raw materials were efficiently reduced at temperatures as low as 600 °C in molten LiCl in the presence of CaH2 as the reducing agent. This resulted in the formation of TiFexMn(1−x) NPs exhibiting few impurities (e.g., TiFe2 or/and TiFe39). Increase in the Mn content led to peak shifts in the X-ray diffraction (XRD) patterns, indicating good incorporation of Mn into the cubic CsCl-type structure of intermetallic TiFe to form a solid solution. Nano-sized particles of< 100 nm were clearly observed in the obtained powders by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moreover, homogeneous distribution of the constituent elements (i.e., Ti, Fe, and Mn) was confirmed by energy dispersive X-ray (EDX) spectroscopy. Finally, the hydrogen absorption properties of the prepared TiFe0.7Mn0.3 NPs were analyzed. Notably, with the exception of micron-sized TiFe0.7Mn0.3 prepared by common arc melting, the generated NPs exhibited almost no hydrogen absorption. The results obtained herein demonstrated the importance of particle size in activating TiFe-based hydrogen absorption materials.