Towards a sustainable technology for production of extra-pure Ti metal: Electrolysis of sulfurized Ti(C,N) in molten CaCl₂

A new concept for producing highly pure Ti metal powder from ilmenite (FeTiO₃) is proposed in this article. Titanium nitride (TiN) or titanium oxycarbonitride (TiO_xC_yN_z) could be synthesized in the first step via the simultaneous carbothermal reduction and nitridation (CTRN) of FeTiO₃ to remove oxygen roughly. To separate oxygen completely, high-quality TiS₂ samples were then synthesized from TiN and TiC using S₂ gas, and the clean sulfides were finally reduced to α-Ti powders with spherical morphology using electrolysis in molten CaCl₂. X-ray diffraction (XRD), scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDS), and elemental LECO analysis were used to study the phases and microstructures of the sulfides and the electrochemically reduced powders. The Ti powder showed no carbon contamination and consisted of high-purity foil-like Ti sheets with very low oxygen, carbon, and nitrogen contents of less than 0.15wt% O, 0.02wt% C, and 0.003wt% N, respectively. The quality of the Ti powder was much higher than that of the powder obtained using the conventional OS process (proposed by K. Ono and R.O. Suzuki) starting directly from the oxides.