物理法制备高纯铝的基础研究

High purity aluminum (Al) is mainly used for preparation of electrolytic condenser, special alloy, etc. It is the critical material in the high-tech area. The traditional method such as three-layer liquid electrolysis, segregation has many problems, e.g., high energy consumption, in preparation of high purity Al. The physical methods such as vacuum volatilization, liquation are the important approach for clean purification of metals. The technology development for physical purification of Al, however, is seriously hindered due to lack of the research on the basic thermodynamic data of Al-based melt and the regularities of migration and distribution of impurities in Al melt. The physical method for preparation of high purity Al, therefore, is proposed in this program based on the phase change of solid-liquid-gas. High purity Al will be prepared while the impurities with low boiling point (lead, zinc, etc.) were removed by vacuum volatilization, the impurities with high melting point (silicon, iron, etc.) removed by liquation and cooling liquation and the others removed by zone refining. To realize the above objective, the research on the occurrence state of impurities in the Al melt, the distribution characteristics and microscopic interaction of impurities between the solid-liquid phase，the diffusion and migration behavior and the distribution character of impurities in the solid-liquid-gas phase will be carried out. The experimental study such as vacuum volatilization, liquation and cooling liquation and zone refining will also be carried for purification of crude Al. The regularities of migration and distribution of impurities in the solid-liquid-gas phase will be revealed. The regulatory mechanism for removing of impurities from Al melt will be obtained. The coordination and coupling of vacuum volatilization, liquation and cooling liquation and zone refining will be realized. Finally, Al with the purity larger than 5N will be prepared from crude Al (99%), the prototypes for physical preparation of high purity Al will be proposed in this program, which will open up a new avenue for development of new technology of preparing high purity metals.

高纯铝主要用于电解电容器、特种合金等，是电子信息、航空航天等高技术领域关键材料。传统三层液电解法、偏析法制备高纯铝存在能耗高、效率低等问题。真空挥发、熔析凝析等物理法是清洁提纯金属的重要手段，但相关铝基熔体基础热力学数据以及铝中杂质元素的迁移分布规律研究薄弱，阻碍了物理法提纯铝的技术发展。本项目提出基于固-液-气相变（物理法）制备高纯铝。真空挥发脱除铅、锌等低沸点杂质，熔析凝析脱除硅、铁等高熔点杂质，区域熔炼制备高纯铝。研究铝中杂质元素赋存状态，杂质组元在固-液相间分布特征及微观相互作用，杂质组元在固-液-气相间扩散迁移行为和分布特性。开展真空挥发-熔析凝析-区域熔炼实验研究。揭示铝中杂质元素在固-液-气相间的迁移分布规律，获得杂质脱除调控机制，实现真空挥发、熔析凝析和区域熔炼协同耦合，由99%的原铝制备纯度大于5N的金属铝，形成物理法制备高纯铝技术原型，为高纯金属制备开辟新途径。

高纯铝是电子信息、航空航天、精密仪器等高新技术领域的关键基础材料，其传统制备方法存在能耗高、效率低等问题。项目围绕铝中杂质元素气-液、固-液相间分布特性与迁移规律，开展了杂质元素在铝基体中的赋存状态及杂质含量检测方法、杂质元素气-液相间平衡及逸散规律、杂质元素强制迁移机理及固-液相间扩散迁移规律以及真空挥发-旋转结晶-区域熔炼制备高纯铝实验研究。研究了不同铝原料中Si、Fe、Cu、Zn、Mg、Ti、V等杂质元素的存在形式，揭示了铝基体中杂质元素的赋存状态及元素间相互作用规律，形成了铝中不同含量杂质元素的检测方案；获得了铝基合金组元的活度等热力学数据和预测模型，建立了定量预测铝基合金组元相间分布的气液平衡理论，阐明了铝中杂质元素气-液相间分布特性和迁移分布规律，实现了原铝中镁、锌、铅等低沸点杂质的真空挥发深度脱除；探究了铝与钛、钒、硼等杂质元素的微观相互作用机制，开展了硼化物脱除铝熔体中钒、钛等杂质元素的实验研究，阐明了钒、钛、铁等杂质元素强制迁移机理；开展了固液界面特性和原铝、3N精铝旋转结晶法提纯实验研究，实现了铝中硅、铁等杂质元素的高效脱除；确定了区域熔炼制备高纯铝过程中温度场分布的影响因素及设定条件，揭示了常压、真空区域熔炼过程中杂质元素的分配规律和迁移机理，实现了4N铝中硅、铁等杂质元素的深度脱除，由99.8%的原铝成功制备了5N以上的高纯铝，形成了真空挥发-旋转结晶-区域熔炼为主的物理法制备高纯铝技术原型。项目执行期内，发表学术论文33篇，被SCI、EI收录30篇；申请国家发明专利11项，授权5项；出版著作1部；项目负责人首批成为云南省科学家工作室首席科学家，入选全国高校黄大年式教师团队负责人；项目组入选省部级人才计划8人次，获云南省青年科技奖等人才奖励3人次；培养博士、硕士研究生13人；组织召开全国学术会议2次，参加国内外学术会议31人次。