KF-NaF-AlF3体系结构性质的分子动力学模拟
Molecular Dynamics Simulation for the Structural Properties of the KF-NaF-AlF3 System
DOI: 10.12677/MEng.2021.82009, PDF,  被引量   
作者: 陈应斌, 陈金辉*：吉利百矿铝业有限公司，广西 百色；胡 博, 陈 昌*, 官朝红：中南大学冶金与环境学院，湖南 长沙
关键词: nKF-2.2NaF-AlF3；结构性质；输运性质；分子动力学；nKF-2.2NaF-AlF3； Structural Properties； Transport Properties； Molecular Dynamics
摘要: 近年来低温铝电解质的研究已成为铝电解工业上节能减排的热点问题，对其基本物理化学性质的探索是一个必然的过程。本文运用密度泛函理论与经典分子动力学方法相结合的方法系统研究了1100 K下xKF-2.2NaF-AlF3熔盐体系的结构性质和输运性质。研究结果表明在平衡的高温钾冰晶石熔盐体系中六配位[AlF6]3−、五配位[AlF5]2−、四配位[AlF4]−络合离子共同存在，且六配位铝氟离子集团占主导地位(70%以上)，并会发生部分的离解，生成五配位或者四配位离子团；当KF浓度增大时，电解质体系中游氟原子含量会增加，桥氟含量逐渐降低，体系的聚合程度也会随之下降。此外，KF的加入使得桥氟离子解离，Na、Al的自扩散系数会先增大后降低，体系显示出低粘度高电导率的特性，但当KF浓度达到2%后，电导率会逐渐降低。
Abstract: The study of low temperature aluminium electrolytes has become a hot issue for energy saving and emission reduction in the aluminium electrolysis industry in recent years, and the exploration of their basic physicochemical properties is an inevitable process. In this paper, the structural and transport properties of the nKF-2.2NaF-AlF3 molten salt system at 1100 K have been systematically investigated using a combination of density flooding theory and classical molecular dynamics methods. The results show that in the equilibrium high-temperature potassium cryolite molten salt system, hexacoordinated [AlF6]3-, pentacoordinated [AlF5]2- and tetracoordinated [AlF4]- complex ions co-exist, and the hexacoordinated aluminium-fluorine ion group dominates (more than 70%) and undergoes partial dissociation to produce pentacoordinated or tetracoordinated ion groups; As the KF concentration increases, the amount of free fluorine atoms in the electrolyte system increases, the bridge fluorine content gradually decreases and the degree of polymerisation of the system decreases. In addition, the addition of KF causes the dissociation of the bridging fluorine ions, the self-diffusion coefficients of Na and Al will first increase and then decrease, and the system shows the characteristics of low viscosity and high conductivity, but when the KF concentration reaches 2%, the conductivity will gradually decrease.
文章引用：陈应斌, 陈金辉, 胡博, 陈昌, 官朝红. KF-NaF-AlF3体系结构性质的分子动力学模拟[J]. 冶金工程, 2021, 8(2): 67-75. https://doi.org/10.12677/MEng.2021.82009

参考文献

[1] Cassayre, L., Palau, P., Chamelot, P. and Massot, L. (2010) Properties of Low-Temperature Melting Electrolytes for the Aluminum Electrolysis Process: A Review. Journal of Chemical & Engineering Data, 55, 4549-4560. [Google Scholar] [CrossRef] 
[2] Danielik, V. and Gabcova, J. (2004) Phase Diagram of the System NaF-KF-AlF3. Journal of Thermal Analysis and Calorimetry, 76, 763-773. [Google Scholar] [CrossRef] 
[3] Hıves, J., Fellner, P. and Thonstad, J. (2013) Transport Numbers in the Molten System NaF-KF-AlF3-Al2O3. Ionics, 19, 315-319. [Google Scholar] [CrossRef] 
[4] Redkin, A.A. and Tkacheva, O.Y. (2010) Electrical Conductivity of Molten Fluoride Oxide Melts. Journal of Chemical & Engineering Data, 55, 1930-1939. [Google Scholar] [CrossRef] 
[5] Apisarov, A.P., Dedyukhin, A.E. and Red’kin, A.A. (2010) Physicochemical Properties of KF-NaF-AlF3 Molten Electrolytes. Russian Journal of Electrochemistry, 46, 633-639. [Google Scholar] [CrossRef] 
[6] Yang, J., Yan, H. and Li, W. (2011) Surface Tension and Density in the KF-NaF-AlF3. Journal of Chemical & Engineering Data, 56, 4147-4151. [Google Scholar] [CrossRef] 
[7] Yang, J., Li, W., Yan, H. and Liu, D. (2016) Light Metals 2013. Springer International Publishing, Cham, 689-693. [Google Scholar] [CrossRef] 
[8] Akdeniz, Z. and Madden, P.A. (2006) Raman Spectra of Ionic Liquids: A Simulation Study of AlF3 and Its Mixtures with NaF. The Journal of Physical Chemistry B, 110, 6683-6691. [Google Scholar] [CrossRef] [PubMed]
[9] Bessada, C., Rakhmatullin, A., Rollet, A.L. and Zanghi, D. (2009) High Temperature NMR Approach of Mixtures of Rare Earth and Alkali Fluorides: An Insight into the Local Structure. Journal of Fluorine Chemistry, 130, 45-52. [Google Scholar] [CrossRef] 
[10] Klix, A., Suzuki, A. and Terai, T. (2006) Study of Tritium Migration in Liquid Li2BeF4 with ab Initio Molecular Dynamics. Fusion Engineering and Design, 81, 713-717. [Google Scholar] [CrossRef] 
[11] 徐驰, 陈念贻, 等. 冰晶石熔体结构的计算机模拟研究[J]. 金属学报, 1986, 22(2): 112-118.
[12] 侯怀宇, 谢刚, 陈书荣, 等. NaF-AlF3系熔盐结构的分子动力学计算[J]. 中国有色金属学报, 2000, 10(6): 914-918.
[13] Belashchenke, D.K., Saposznikova, S.Y., et al. (1998) Computer Study of Structure, Thermodynamic, and Electrical Transport Properties of Na3AlF6-Al2O3 and CaF2-Al2O3 Melts. Metallurgical and Materials Transactions B, 29, 105-110. [Google Scholar] [CrossRef] 
[14] 赵婷, 尤静林, 等. NaF-AlF3二元系铝氟四面体团簇结构的拉曼光谱表征与量子化学从头计算[J]. 光散射学报, 2012, 24(1): 1-7.
[15] 颜恒维, 邱仕麟, 等. NaF-KF-AlF3电解质体系的研究[J]. 轻金属, 2009(5): 32-34.
[16] Yan, H., Yang, J. and Li, W. (2011) Surface Tension and Density in the KF-NaF-AlF3-Based Electrolyte. Journal of Chemical & Engineering Data, 56, 4147-4151. [Google Scholar] [CrossRef] 
[17] Matsui, M. (1996) Molecular Dynamics Study of the Structures and Bulk Moduli of Crystals in the System CaO-MgO-Al2O3-SiO2. Physics and Chemistry of Minerals, 23, 345-353. [Google Scholar] [CrossRef] 
[18] 孙小伟. 高温高压下ZnO和GaN材料热力学特性的分子动力学研究[D]: [硕士学位论文]. 兰州: 西北师范大学, 2005.
[19] Kubo, R. (1966) The Fluctuation-Dissipation Theorem. Reports on Progress in Physics, 29, 255-284. [Google Scholar] [CrossRef] 
[20] Lv, X., Han, Z., Chen, J., Jiang, L., Xu, Z. and Liu, Q. (2018) First-Principles Molecular Dynamics Study of Ionic Structure and Transport Properties of LiF-NaF-AlF3 Molten Salt. Chemical Physics Letters, 706, 237-242. [Google Scholar] [CrossRef] 
[21] Lv, X., Xu, Z., Li, J., Chen, J. and Liu, Q. (2016) Molecular Dynamics Investigation on Structural and Transport Properties of Na3AlF6-Al2O3 Molten Salt. Journal of Molecular Liquids, 221, 26-32. [Google Scholar] [CrossRef] 
[22] Wu, T., He, S., Liang, Y. and Wang, Q. (2015) Molecular Dynamics Simulation of the Structure and Properties for the CaO-SiO2 and CaO-Al2O3 Systems. Journal of Non-Crystalline Solids, 411, 145-151. [Google Scholar] [CrossRef] 
[23] Lv, X., Xu, Z. and Li., J. (2016) First-Principles Molecular Dynamics Investigation on Na3AlF6 Molten Salt. Journal of Fluorine Chemistry, 185, 42-47. [Google Scholar] [CrossRef] 

为你推荐