Double Peak Effect Of Lns And Electrolysis Mechanism Of Al-Li-Y Alloys In Molten Salts

Aluminium-lithium alloys as new type metal materials have attracted extensive attention inaerospace, weapons and other areas because of light weight, high specific strength and goodcorrosion resistant performance. With the development and application of lanthanides in thefields of laser, superconduction, luminescence, magnetism, semiconductor, alloy, nucleartechnology and so on, it is becoming more and more important to study the performance andstructural regularity of lanthanide elements and their compounds.This thesis researched the reduction mechanism, transport parameters and reversibilityproperties of yttrium in LiCl–KCl–YCl₃melts firstly. At773K, Y（III） ions would be reduced tometal yttrium in one step at2.06V （vs Ag⁺/Ag） in molybdenum electrode. The reductionprocess of Y（III） is reversible in low scanning speed and irreversible in high scanning speed.Furthermore, the incovertibility of Y（III） reduction process increases with the increase ofscanning speed. Then the solubility of Y₂O₃was studied. Y₂O₃powder is nearly insoluble inLiCl–KCl melts, and can be chloridized into YCl₃by adding AlCl₃. The electrochemicalmeasurements show that yttrium co-electrodeposits with aluminum in LiCl–KCl–AlCl₃–Y₂O₃melts at773K, and forms α-Al3Y and Al₂Y intermetallic compounds at–1.45and–1.49V,respectively. Al–Li–Y alloys with different intermetallic compounds were prepared bygalvanostatic electrolysis. The results of XRD, SEM and EDS indicate that the Al–Li–Y alloysare mainly composited by Al₂Y and α-Al3Y. The ICP results show that the composition ofAl–Li–Y alloys can be controlled by the AlCl₃concentration of the melts.At last, we investigated the regularity of deposition potentials and depolarization values oflanthanides in LiCl–KCl–AlCl₃–Ln₂O₃and LiCl–KCl–ZnCl₃–LnCl₃melts, respectively. Thedeposition potentials of Lns in LiCl–KCl–AlCl₃–Ln₂O₃melts were investigated at773K. Lnsdeposit on more positive potential than their electrode potential, and form Al–Lns intermetalliccompounds. With respect to Eu and Yb, the deposition potentials of the Al-rich Al–Lnsintermetallics suddenly shift very negative, and appear two extreme values. It shows a doublepeak effect. Moreover, the discrepancy between the potential of Ln（III）/Ln（0） couples anddeposition potentials of Al-rich Al–Lns intermetallics also shows double peak effect. Similarly,the deposition potentials of Lns in LiCl–KCl–ZnCl₃–LnCl₃melts also appear two extreme valueson Eu and Yb, and show a double peak effect. The depolarization values of Lns in this system also show a double peak effect.In this thesis, the reduction mechanism of Y（III） was studied in LiCl–KCl–YCl₃melts.Co–electrodeposition mechanism of ternary Al–Li–Y alloys from RE oxides in the molten saltswas investigated. It provides a reliable theoretical basis and technical routine for the preparationof new alloy materials. The regularities of the characteristics of Lns in molten salts weresystematic investigated. This is advantageous for the research on dry reprocessing technology ofspent nuclear fuel.