Cathode for rare earth molten salt electrolysis and an electrolysis system comprising the same

Abstract

A cathode for rare earth molten salt electrolysis is provided. The cathode includes a column. The bottom of the column includes a cone. The peak of the cone includes a sharp tip or a flat surface. When the peak of the cone is the sharp tip, an opening angle of the sharp tip is between 5 degree and 175 degree. An electrolysis system having a cathode is also provided.

What is claimed is: 
     
         1 . A cathode for rare earth molten salt electrolysis, comprising:
 a column, wherein the bottom of the column comprises a cone, wherein the peak of the cone comprises a sharp tip or a flat surface, wherein when the peak of the cone is a sharp tip, an opening angle of the sharp tip is between 5 degree and 175 degree.   
     
     
         2 . The cathode for rare earth molten salt electrolysis as claimed in  claim 1 , wherein the cathode comprises tungsten, molybdenum, tantalum or alloy thereof. 
     
     
         3 . The cathode for rare earth molten salt electrolysis as claimed in  claim 1 , wherein when the peak of the cone is a sharp tip and the slant lengths of the cone are the same, an opening angle of the sharp tip is calculated by formula (I): 
       
         
           
             
               
                 
                   
                     
                       
                         c 
                         2 
                       
                       = 
                       
                         2 
                         ⁢ 
                         
                           
                             a 
                             2 
                           
                           ( 
                           
                             1 
                             - 
                             
                               cos 
                               ⁡ 
                               ( 
                               γ 
                               ) 
                             
                           
                           ) 
                         
                       
                     
                     , 
                   
                 
                 
                   
                     ( 
                     I 
                     ) 
                   
                 
               
             
           
         
         wherein c is a diameter of the column, a is a slant length of the cone, and γ is an opening angle of the sharp tip. 
       
     
     
         4 . The cathode for rare earth molten salt electrolysis as claimed in  claim 1 , wherein the slant lengths of the cone are different. 
     
     
         5 . An electrolysis system, comprising:
 a cathode;   at least one anode; and   an electrolyte containing rare earth oxides,   wherein the cathode and the at least one anode are disposed in the electrolyte, and   wherein a ratio of a surface area of the cathode to a surface area of the at least one anode is between 1:100 and 1:1.   
     
     
         6 . The electrolysis system as claimed in  claim 5 , wherein the cathode comprises a column. 
     
     
         7 . The electrolysis system as claimed in  claim 6 , wherein the bottom of the column comprises a plane, an arc or a cone. 
     
     
         8 . The electrolysis system as claimed in  claim 7 , wherein the peak of the cone comprises a sharp tip or a flat surface. 
     
     
         9 . The electrolysis system as claimed in  claim 8 , wherein when the peak of the cone is a sharp tip, an opening angle of the sharp tip is between 5 degree and 175 degree. 
     
     
         10 . The electrolysis system as claimed in  claim 8 , wherein when the peak of the cone is a sharp tip and the slant lengths of the cone are the same, an opening angle of the sharp tip is calculated by formula (I): 
       
         
           
             
               
                 
                   
                     
                       
                         c 
                         2 
                       
                       = 
                       
                         2 
                         ⁢ 
                         
                           
                             a 
                             2 
                           
                           ( 
                           
                             1 
                             - 
                             
                               cos 
                               ⁡ 
                               ( 
                               γ 
                               ) 
                             
                           
                           ) 
                         
                       
                     
                     , 
                   
                 
                 
                   
                     ( 
                     I 
                     ) 
                   
                 
               
             
           
         
         wherein c is a diameter of the column, a is a slant length of the cone, and γ is an opening angle of the sharp tip. 
       
     
     
         11 . The electrolysis system as claimed in  claim 8 , wherein the peak of the cone is the sharp tip, and the slant lengths of the cone are different. 
     
     
         12 . The electrolysis system as claimed in  claim 5 , wherein the at least one anode surrounds the cathode. 
     
     
         13 . The electrolysis system as claimed in  claim 5 , wherein the cathode comprises tungsten, molybdenum, tantalum or alloy thereof. 
     
     
         14 . The electrolysis system as claimed in  claim 5 , wherein the at least one anode comprises graphite. 
     
     
         15 . The electrolysis system as claimed in  claim 5 , wherein the rare earth oxides comprise neodymium oxide, praseodymium oxide or dysprosium oxide.