【作者】 杨昇；

【导师】 顾松青； 杨冠群； 刘凤琴；

【作者基本信息】 郑州大学 ， 凝聚态物理， 2003， 博士

【摘要】 本文介绍了金属钪的基本性质、制造方法以及铝钪合金的优异性能，综述了铝钪合金在国内外的研究近况，分析了目前影响铝钪合金大规模应用的主要问题。首次提出了通过铝土矿或赤泥提取含钪氧化物，利用未经高度提纯的含钪氧化物，在铝电解槽中直接电解铝钪合金的新的技术思路和工艺方案。通过这一工艺方案的实施，可使钪资源得以有效利用，缩短铝钪合金的生产流程，降低合金的生产成本，促进铝钪合金的大规模应用。 为了论证用电解法生产铝钪合金的可行性，分别对氧化钪在炼铝用电解质中的溶解性能，含钪电解质的物理化学性质，电解铝钪合金的平衡过程的热力学和电化学过程进行了研究。 通过对氧化钪在Na₃AlF₆—3％MgF₂—3％CaF₂体系电解质中溶解特性的研究，得到氧化钪溶解度随分子比、温度和氧化铝添加量变化的函数关系。研究表明，减少氧化铝添加量和升高温度均有利于氧化钪在熔盐中的溶解。通常情况下，分子比对氧化钪溶解度的影响不大，主要体现在与氧化铝添加量的交互作用。在现代点式下料电解槽的操作条件下，氧化钪的溶解度可以达到3～5％，完全能够满足直接电解铝钪合金的需要。 通过对含钪电解质的初晶温度、电导率、密度以及热失重率等物理化学性质的研究，得出如下规律和结论：在电解质中添加氧化钪有助于降低电解温度，从而起到节能降耗的作用；在通常铝电解控制的氧化物添加范围内，氧化钪对电解质电导率和密度的影响较小，不会影响电解过程的稳定运行；在正常电解过程控制的过热度下（10K～40K），在电解质中添加氧化钪有助于减小电解质的挥发损失，减少对环境的污染；同时氧化钪本身不会因挥发而造成损失。含钪电解质的初晶温度、电导率、密度以及热失重率等物理化学性质，均可以满足电解铝钪合金的工艺需要。用含钪的电解质进行电解直接生产铝钪合金是可行的。 采用循环伏安法、稳态极化法和线性伏安法对Sc³⁺在冰晶石熔盐体系中铝电极上的电化学还原过程及氧化钪在石墨电极上的分解电压进行研究。研究结果表明：Sc³⁺在熔盐中电解还原过程为一步获得三个电子的简单电荷传递过程。因此，用电解法生产铝钪合金，不会因为生成低价钪中间产物，造成较多的二次反应而使电流效率大幅降低。同时，由于氧化钪的分解电压为1.2V，与同温度下氧化郑州大学博士论文摘要铝的分解电压（l.巧V，CO:=70%）十分接近。因而在直接电解铝抗合金时，氧化杭不致在电解质中产生大量积累，保证电解过程能够顺利稳定运行。 采用差热分析法，对铝抗二元相图富铝区的液相线进行了测试。并对铣在合金液中能否生成A13Sc进行了讨论，认为在合金液中抗含量小于2.5%时，通常铝电解所采用的温度超过合金液相线30K以上，合金液中不会有A13Sc金属间化合物生成;对铝抗合金电解过程的热力学平衡进行了研究，得到了电解铝杭合金的平衡常“K的表达式‘类六老分;‘”用Mie^模”“漩铝龄“中的活度系数进行了近似计算，得到的结论为，当合金中抗的浓度不大时，铣的活度系数近似为10一3数量级。对氧化抗在冰晶石系电解质中的浓度与活度的关系进行了研究，得到电解质中氧化铣的活度近似与其浓度的4.3次方成正比的结论，即ascZo3喇scZo夕;通过本章的研究工作，最终得到了用浓度表示的铝抗合金电解过程近似的热力学平衡关系式:、_<sub>厂.些退‘’改一Y lj J·月12伪 该式对于指导实际电解工艺参数的选择，具有重要的指导意义。由该式可见，保持电解质中的氧化杭含量在较高水平，同时控制电解质中的氧化铝含量在较低水平，对电解生产杭含量较高的铝杭合金是至关重要的。 在热力学研究证明直接电解法生产铝抗合金可行的基础上，对电解铝抗合金的工艺操作参数进行了研究。研究结果表明，电解过程中，合金中抗含量随电解质中氧化抗含量的增加和氧化铝含量的减少而升高;并随电解温度、电极距离以及阴极电流密度的增加而提高。但温度、极距和电流密度对合金含抗量的影响不显著。电解质中氧化抗含量的增加有助于提高电流效率，而氧化铝的作用则相反。采用较低的电解温度可以使电流效率有所提高。电极距离对电流效率的影响较为显著，保持较高的极距可以得到较高的电流效率。阴极电流密度对电流效率的影响不十分显著，但过大的电流密度，会使电流效率有所降低。 对电解法生产的铝抗合金和热还原的铝杭合金进行了金相比较和扫描电镜研究。研究表明:含杭量为0.5%的铝抗合金，A13Sc相晶粒细小、弥散，有利于发挥铝抗合金的优异性能。当含杭量达到0.7%时，A13Sc相明显变得粗大，特别是还原法的铝抗合金，不但有粗大的原晶，而且有明显的聚集倾向，并相互结合成更加粗大的二次晶。当含抗量达到2%，电解法合金的A13S。相晶粒大小变化不大，但还原法合金的A13Sc相晶粒则变得十分巨大。用电解法生产铝杭合金，不但可以得到结晶形态比还原法更好的产品，而且可以得到较高的电流效率。 为了得到高含抗量的合金，在电解工艺参数的控制上，除了可以沿用现代大型铝电解的控制?更多还原

【Abstract】 The basic properties, extracting methods of Scandium and its superior application performances are introduced briefly in this article. The latest research status on Al-Sc alloys is reviewed. The main obstacles and problems for application of Al-Sc alloys on a large scale are analyzed. A technology development project and its scheme are proposed firstly in this paper that the Sc oxide with not high purity is extracted from bauxite or red mud in alumina production, then the direct molten salt electrolysis process is applied to produce Al-Sc alloys by using the Sc oxide as electrolysis raw material. After the technology is developed and applied , the Sc containing resources will be utilized effectively, the Al-Sc alloy production process will be simplified, the production cost will be greatly reduced and a large-scale application of Al-Sc alloy will be promoted.The research work on solubility of Sc2O3 in the electrolyte for Al electrolysis, some important physical-chemical properties of the Sc containing electrolyte and thermodynamics and the electro-chemical process of direct electrolysis of Al-Sc alloy is carried out to evaluate the feasibility of industrial application of direct electrolysis for Al-Sc alloys.The relationship of solubility of Sc2O3 in Na3AlF6-3%MgF2-3%CaF2 electrolyte with CR, temperature and addition of A12O3 during Al-Sc alloys direct electrolysis has been revealed by the research work. The results show that reducing the addition of Al2O3 and temperature rising can increase the solubility. CR has little influence on the solubility. Under normal operation conditions of the modern Al electrolysis cells with point feeding the solubility of Sc2O3 in the electrolyte can reach up to 3-5%, which meets the need for direct electrolysis of Al-Sc alloy.The conclusions can be obtained from the research results on physical chemistry properties (such as liquidus temperature, electrical conductivity, density and thermo-lost weight rate etc.) that the electrolysis temperature can be reduced to save energy by addition of Sc2O3; existing and normal addition range of Sc2O3 in Al electrolysis has a little influence on the density and electrical conductivity of electrolyte and consequently on the stability of the cell as well; addition of Sc2O3 into the electrolyte can decrease the volatile loss from the electrolyte and reduced environment pollution under the normal superheat (20K-40K) in the electrolysis process, and at the same time Sc2O3 won’t be lostthrough volatilization. The properties such as liquidus temperature, electrical conductivity, density and thermo-lost weight rate of the Sc containing electrolyte can satisfy the need of direct electrolysis process for Al-Sc alloys so that Al-Sc alloys direct electrolysis is feasible.The electro-chemical reduction process of Sc3+ on Al pole and decompositionvoltage of Sc2O3 on graphite pole in cryolite melt have been investigated by using cycling volt-current analysis, steady-state polarized method and linear volt-current analysis. The results show that the electrolysis reduction process of Sc3+ in melts is a simple electron transferring process by obtaining 3 electrons in one step, as a result of which the direct electrolysis process to produce Al-Sc alloys will reach a high current efficiency because of no creation of low valent Sc ions and secondary reactions as well. The decomposition voltage of Sc2O3 is 1.2V which is close to that of Al2O3 under the same temperature (1.15V, CO2=70%) so that the SciOs will not be accumulated in melts during electrolysis which keeps the process stable.The equilibrium constant K of the reaction of A1-SC2O3 under the electrolysis conditions is calculated. It is found by thermodynamics analysis that there is no possibility to form Al3Sc in liquid alloys under normal electrolysis conditions. The activity coefficient of Sc in liquid Al is approximately calculated and found to be far smaller than 1 if Sc content is very low in the alloys by use of the Miedema model. It is shown from the experiments results and thei更多还原