A novel approach to prepare high-purity Si and Si/TiSi2 materials simultaneously using Ti-bearing blast furnace slag

• Published in: Journal of alloys and compounds 2019-08, Vol.798, p.333-341
• Main Authors: Lei, Yun, Wang, Chao, Ma, Wenhui, Wu, Jijun, Wei, Kuixian, Li, Shaoyuan, Lv, Guoqiang, Morita, Kazuki
• Format: Article
• Language: English
• Subjects: Acid leaching; Bearing; Blast furnace gas; Blast furnace slags; Directional solidification; Leaching; Metallurgy; Purity; Si powders; Si/TiSi2; Silicon; Solar cells; Steel industry; Ti-bearing slag; Titanium base alloys; Titanium dioxide; Waste treatment
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2019.05.291

A new approach was proposed to prepare multi-products, high-purity Si powders, bulk Si, and Si/TiSi2 materials (eutectic Si-Ti), simultaneously using inexpensive low-purity Si (99.3%) and metallurgical waste—Ti-bearing blast furnace slag. TiO2 in Ti-bearing blast furnace slag was first reduced by Si to form a Si-Ti alloy which was then separated into high-purity bulk Si (99.97%) and Si/TiSi2 materials (99.4%) using directional solidification. The bulk Si could be repeatedly recycled as a reductant, or further upgraded to prepare super-pure Si powders (99.995%) after acid leaching. The new approach shows many sustainable and economic benefits, such as no carbon gas emission, low acid consumption and Si loss, recyclable Si reductant, widely-used multi-products employing one approach, and rapid consumption of accumulated Ti-bearing blast furnace slag. •A new approach was proposed to clean up the Ti-bearing blast furnace slag.•Multi-products could be prepared simultaneously throughout one approach.•Most of Si could be recycled as reductant repeatedly.•Most of impurities could be removed to obtain high-purity Si and Ti materials.•Si-Ti alloy could be separated into bulk Si and eutectic Si-Ti alloy.