SmF_3-LiF-Sm_2O_3体系熔盐电解Al-Sm中间合金的研究
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摘要
在SmF_3-Li F-Sm_2O_3熔盐体系中,以金属Al棒和氧化钐为原料,在不同工艺条件(温度、熔盐配比、阴极电流密度)下,采用液态阴极电解法制备Al-Sm中间合金。采用X射线衍射(XRD)、带能谱(EDS)的扫描电镜(SEM),分析了Al-Sm中间合金的物相组成、微观组织以及微区成分含量;通过热力学吉布斯自由能的计算,研究了铝热还原Sm F3和Sm_2O_3的可能性,分析了电流效率的组成情况;研究了电解温度、阴极电流密度、熔盐配比对电解Al-Sm中间合金电流效率的影响;结果表明,Al-Sm中间合金中除了Al、Sm相外,还存在Al4Sm和Al3Sm相;AlSm中间合金的相由三部分组成:灰色部分的Al相,分布在灰色组织上的细小波浪状的Al3Sm相,错综排列的白色条状物的Al4Sm相;在1200 K、1400 K下,两个铝热还原反应的吉布斯自由能△rGm1θ(1200 K)、△rGm1θ(1400 K)、△rGm2θ(1200 K)、△rGm2θ(1400 K)均大于0,正反应不能自发发生,故计算所得的电流效率为纯的熔盐电解效率,并不包括铝热还原效率;所得Al-Sm中间合金中Sm含量最低为21.49%,最高为32.8%;在Sm F3∶Li F=80∶20、1020℃、100 A、30 min下,电流效率为最高(62.17%);电流效率最低为49.45%。
The Al-Sm master alloy was prepared by liquid cathode electrolysis under different technology conditions such as temperature,ratio of molten salt,cathodic current density in SmF_3-Li F-Sm_2O_3 molten salt system with Al rod and samarium oxide as raw materials. Phase composition,microstructure and micro zone component contents of Al-Sm master alloy were analyzed by XRD,SEM with EDS.The possibility of aluminium thermal reduction of SmF_3 and Sm_2O_3 was studied and the composition of current efficiency was analyzed through Gibbs free energy calculation. The influence of electrolytic temperature,cathodic current density,ratio of molten salt on Al-Sm current efficiency was studied. The results show that the phase compositions of Al-Sm master alloy are Al,Sm,Al4 Sm and Al3 Sm. The phases of Al-Sm master alloy are consists of three parts,including grey Al phase,tiny wavy material Al3 Sm distributed in the grey part,and criss-crossing string Al4 Sm phase. Gibbs free energy △rGm1θ(1200 K),△rGm1θ(1400 K),△rGm2θ(1200 K)and △rGm2θ(1400 K)of two aluminium thermal reduction reactions are all greater than zero under the temperatures of 1200 K and 1400 K,showing reactions are not going to happen,so current efficiency is pure efficiency. The lowest and highest contents of Sm in Al-Sm master alloy are 21. 49% and 32. 8% respectively. The highest current efficiency is 62. 17% in the best condition of SmF_3∶ Li F = 80 ∶20,temperature 1020 ℃,current intensity 100 A and time 30 min. The lowest current efficiency is 49. 45%.
The Al-Sm master alloy was prepared by liquid cathode electrolysis under different technology conditions such as temperature,ratio of molten salt,cathodic current density in SmF_3-Li F-Sm_2O_3 molten salt system with Al rod and samarium oxide as raw materials. Phase composition,microstructure and micro zone component contents of Al-Sm master alloy were analyzed by XRD,SEM with EDS.The possibility of aluminium thermal reduction of SmF_3 and Sm_2O_3 was studied and the composition of current efficiency was analyzed through Gibbs free energy calculation. The influence of electrolytic temperature,cathodic current density,ratio of molten salt on Al-Sm current efficiency was studied. The results show that the phase compositions of Al-Sm master alloy are Al,Sm,Al4 Sm and Al3 Sm. The phases of Al-Sm master alloy are consists of three parts,including grey Al phase,tiny wavy material Al3 Sm distributed in the grey part,and criss-crossing string Al4 Sm phase. Gibbs free energy △rGm1θ(1200 K),△rGm1θ(1400 K),△rGm2θ(1200 K)and △rGm2θ(1400 K)of two aluminium thermal reduction reactions are all greater than zero under the temperatures of 1200 K and 1400 K,showing reactions are not going to happen,so current efficiency is pure efficiency. The lowest and highest contents of Sm in Al-Sm master alloy are 21. 49% and 32. 8% respectively. The highest current efficiency is 62. 17% in the best condition of SmF_3∶ Li F = 80 ∶20,temperature 1020 ℃,current intensity 100 A and time 30 min. The lowest current efficiency is 49. 45%.
引文
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[2]庞思明,颜世宏,李宗安,等.我国熔盐电解法制备稀土金属及其合金工艺技术进展[J].稀有金属,2011,35(3):440-450.Pang S M,Yan S H,Li Z A,et al.Development on molten salt electrolytic methods and technology for preparing rare earth metals and alloys in china[J].Chinese Journal of Rare Metals,2011,35(3):440-450.
[3]徐光宪.稀土(下册)[M].北京:冶金工业出版社,1995.89.Xu G X.Rare Earths(VolumeⅡ)[M].Beijing:Metallurgical Industry Press,1995.89.
[4]陈宇昕.氟化物体系电解稀土氧化物制备稀土金属研究[J].稀土,2014,35(2):99-107.Chen Y X.Research progress of preparation of rare earth metals by electeolysis in fluoride salt system[J].Chinese Rare Earths,2014,35(2):99-107.
[5]郝占忠,姜银举,秦凤启,等.用富镧合金做还原剂制取金属钐[J].稀土,1992,13(1):47-49.Hao Z Z,Jiang Y J,Qin F Q,et al.The metal samarium is made from lanthanum alloy[J].Chinese Rare Earths,1992,13(1):47-49.
[6]林河成.金属钐材料的生产应用及市场[J].四川稀土,2007,(2):17-20.Lin H C.Application and market of metallic samarium materials[J].Sichuan Rare Earths,2007,(2):17-20.
[7]薛云,王倩,颜永得,等.在Li Cl-KCl-Al Cl3熔盐中直接电化学还原Sm2O3及得Al-Sm合金的形成[J].无机化学学报,2013,29(9):1947-1951.Xue Y,Wang Q,Yan Y D,et al.Direct electrochemical reduction of Sm2O3and formation of Al-Sm alloys in Li ClKCl-Al Cl3melts[J].Chinese Journal of Inorganic Chemistry,2013,29(9):1947-1951.
[8]Che N Q,Han W,Yang Y S,et al.A new electrochemical preparation method for formation Sm-Al alloys on inert Mo electrode from Sm2O3in Li Cl-KCl-Mg Cl2-KF molten salts[J].ACTA Metallurgica Sinica,2012,25(2):102-110.
[9]张清,李全安,陈君,等.Mg-5Y-3Sm-0.8Ca-0.5Sb合金的组织和力学性能[J].稀土,2015,36(5):97-101.Zhang Q,Li Q A,Chen J,et al.Microstructure and mechanical properties of Mg-5Y-3Sm-0.8Ca-0.5Sb alloy[J].Chinese Rare Earths,2015,36(5):97-101.
[10]姜银举,郭海涛,谢萍,等.氧化铈熔盐电解过程预还原反应的冶金热力学分析[J].稀土,2010,31(2):24-27.Jiang Y J,Guo H T,Xie P,et al.Thermodynamics analysis of pre-reduction of cerium oxide in fused-salt electrolysis process[J].Chinese Rare Earths,2010,31(2):24-27.
[11]梁英教,车萌昌.无机物热力学数据手册[M].沈阳:东北大学出版社,1993.43-44,49,339,341.Liang Y J,Che M C.Thermodynamic Data Manual[M].Shenyang:Northeastern University Press,1993.43-44,49,339,341.
[12]傅献彩.物理化学[M].北京:高等教育出版社,1990.62-65.Fu X C,Physical and Chemica[M].Beijing:Higher Education Press,1990.62-65.
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[14]赵义发.氯化稀土熔盐电解的热力学分析[J].中国稀土学报,1984,2(l):54-58.Zhao Y F.Thermodynamic analysis of the electrolytic electrolysis of rare earth chloride[J].Journal of the Chinese Society of Rare Earths,1984,2(l):54-58.
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[16]陈国华,王小青,刘玉宝,等.熔盐电解法制备镨钕镝合金的研究[J].稀土,2015,36(1):80-84.Chen G H,Wang X Q,Liu Y B,et al.Preparation of Pr-Nd-Dy alloys by molten salt electrolysis[J].Chinese Rare Earths,2015,36(1):80-84.
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