Yonghui Yang,Hengwei Yan,Pengchen Yang,Zhanwei Liu,Guang Yang
The segregation of aluminum-silicon alloys directly impacts the mechanical and chemical properties of the alloys, Therefore, homogenization of alloys is of great significance for alloys. This study initially investigated the electrochemical behavior of aluminum (III) and silicon (IV) during the preparation of aluminum-silicon (Al-Si) alloys in NaF-AlF 3 -Al 2 O 3 -SiO 2 molten salts through cyclic voltammetry and steady-state polarization. The results revealed that Al 2 O 3 underwent one-step reduction to Al, whereas SiO 2 underwent a two-step reduction process to Si. In addition, electrolysis experiments were carried out in a NaF-AlF 3 -Al 2 O 3 -SiO 2 -5wt%CaF 2 -1wt%MgF 2 -2wt%LiF molten salt system with molecular ratio of 2.4. These experiments involved variations in current density, electrolysis time, Al 2 O 3 and SiO 2 additions. It is worth noting that under the conditions of current density of 0.7 A/cm 2 , electrolysis time of 2 h, and silica addition of 2 %, the reduction rate of silicon reached a maximum value of 72.57 %, at which time the silicon in the aluminum-silicon alloys showed a dendritic structure, which was uniformly distributed throughout the entire alloy, and the segregation of the alloy was effectively avoided.
Yun Li,Zelong Huang,Liyuan Chai,Yunyan Wang,Xin Wang,Yong Ke,Cong Peng,Xiaobo Min
High-silica-calcium oxygen-sulfur mixed lead-zinc (HSC-PbZnOS) ore is a complex and refractory resource. This study proposed a novel and cleaner process to extract zinc and conserve sulfur and calcium in CaS form from HSC-PbZnOS concentrate. After mineral composition characterization of HSC-PbZnOS concentrate, thermodynamic and experimental investigations reveal that zinc oxides can be directly reduced by carbon, ZnS first reacted with CaO above 770 ℃ to form a stable intermediate CaZnSO (CaO + ZnS → CaZnSO), which is subsequently reduced above 1126 ℃ to Zn(g) and CaS (CaZnSO + C → Zn(g) + CO + CaS). Thus sulfur was fixed as CaS and SO₂ emission was avoided. SiO₂ tended to react with CaO to form silicates, partially inhibiting sulfur-fixation. However, under reducing conditions around 1300 ℃, silicate decomposed to release CaO, allowing it to regain reactivity with ZnS. In addition, pilot tests show that adding 10 wt% limestone increased the Zn reduction rate to 98.9% and the sulfur fixation rate to 98.1%. The gaseous product was ZnO, and the residue mainly consisted of individual SiO₂ and CaS. This work provides a clean, short-process route for efficient utilization of complex HSC-PbZnOS resources with industrial potential.
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