基于Al-Si合金精炼硅技术的微量金属添加剂对硼的捕获行为及其热力学研究

项目名称： 基于Al-Si合金精炼硅技术的微量金属添加剂对硼的捕获行为及其热力学研究

项目编号： No.51504118

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 矿业工程

项目作者： 雷云

作者单位： 昆明理工大学

项目金额： 20万元

中文摘要： 如何深度去除硅中B（硼）是Al-Si合金电磁凝固精炼技术需突破的难题。由于V、Zr和Ti与B的亲和力强，本课题提出往Al-Si合金中添加微量的V、Zr和Ti强化除B的方法：B在精炼时先被V、Zr和Ti捕获（形成硼化物）而更容易往硅晶界和液相迁移（降低B的分凝系数），再用湿法除去硅晶界和液相的硼化物而达到强化除B的目的，添加的V、Zr和Ti因分凝系数小可被轻易地去除。本课题将通过热力学数据的测定（溶解度、活度系数、相互作用系数），从理论上预测V、Zr和Ti捕获B的能力及计算相应的硼化物在Al-Si合金中稳定存在时的热力学条件。同时，以热力学预测结果为理论根据，研究Al-Si合金电磁凝固精炼过程的冷却速度、熔体成分、感应热场等因素对Zr、V和Ti捕获B行为的影响规律，结合微观观察和分析手段，揭示影响捕获B过程的关键因素和限制性环节。本课题研究成果将为冶金法制备太阳能级多晶硅提供新方法。

中文关键词： 金属凝固；电磁冶金；迁移规律；固液界面

英文摘要： How to deeply remove B (boron) from silicon is the difficult problem that the technology of electromagnetic solidification refining with Al-Si alloy has to break through. As V, Zr and Ti have strong affinity for B, we propose a method of strengthening B removal process by adding tiny amount of V, Zr and Ti to the Al-Si alloy: B is firstly captured by V, Zr and Ti (form borides) in the refining process which makes it easier to move to the silicon grain boundaries and liquid phase (because the segregation coefficient of B decreases); thereafter, the borides in grain boundaries and liquid phase are removed by hydrometallurgy. The added V, Zr and Ti can be easily removed in this process because of their small segregation coefficients. This study will theoretically predict the ability of V, Zr and Ti capture boron and the thermodynamic conditions to form their borides in Al-Si alloy by measuring the thermodynamic data (solubilities, activity coefficients, and interaction coefficients). Meanwhile, using the thermodynamic prediction results as theoretical basis, this work will study the effects of cooling rate, melt composition and induction heating field on the behavior of V, Zr and Ti capture B in the electromagnetic solidification refining with Al-Si alloy. Combined with microscopic observation and analysis, the key factor and the restrictive links which influence the process of V, Zr and Ti capture B will be revealed. The research results will provide new metallurgical methods for solar-grade polysilicon production.

英文关键词： solidification of metal;electromagnetic metallurgy;migration;solid/liquid interface