An approach to prepare high-purity TiSi2 for clean utilization of Ti-bearing blast furnace slag

Abstract

The large amounts of accumulated titanium (Ti)-bearing blast furnace slag are not only an industrial waste but also an important Ti resource. TiSi₂ is widely used in high-tech industries and is normally prepared using high-purity Ti and Si as the raw materials. In this study, a new approach, Si–Ti solvent refining, has been proposed to prepare high-purity TiSi₂ using Ti-bearing blast furnace slag and low-purity Si as raw materials. First, TiO₂ in Ti-bearing blast furnace slag was reduced by low-purity Si to form a raw Si–Ti alloy. Then, different amounts of low-purity Si were added to the raw Si–Ti alloys to obtain three different Si–Ti solvents (Si–39.6 wt% Ti, Si–35 wt% Ti, and Si–30 wt% Ti), which were used for the solvent refining of TiSi₂. The three Si–Ti solvents were then separated into TiSi₂, eutectic Si–Ti alloy, and agglomerated impurities via electromagnetic directional crystallization to obtain pure TiSi₂ crystals. The results showed that the removal ratios of impurities were significantly enhanced by Si–Ti solvent refining. When using the Si–30 wt%Ti% solvent, the largest removal ratios of Fe, Mn, Ni, Mg, Al, and Ca impurities in the region of agglomerated TiSi₂ crystals were 76.5 ± 0.5%, 62 ± 0.5%, 80 ± 0.5%, 94.5 ± 0.5%, 86 ± 1%, and 93 ± 1%, respectively. The purity of the region containing agglomerated TiSi₂ crystals was 99.32 ± 0.01%. Finally, the purification mechanism of TiSi₂ crystals by Si–Ti solvent refining is discussed in terms of thermodynamics. This study provides a new technical route for the green, efficient, and economical utilization of Ti-bearing blast furnace slag. It also provides a new method for preparing high-purity TiSi₂ alloy using low-purity raw materials.