Method for preparing tantalum or niobium powders used for manufacturing capacitors

Abstract

Disclosed relates to a method for preparing tantalum or niobium powders used for manufacturing capacitors in an electrolytic reducing reactor including an anode, a cathode and a molten salt, the method comprising: obtaining a tantalum or niobium oxide, expressed by Ta 2 O (5-y) or Nb 2 O (5-y) where y=2.5 to 4.5, from a tantalum pentoxide Ta 2 O 5 or a niobium pentoxide Nb 2 O 5 generated partially by an alkaline metal electrolytically reduced via a first electrolytic reducing reaction that reduces an alkaline metal oxide from a molten salt comprising at least one metal halogen compound, selected from the group consisting of alkaline metal and alkaline earth metal, and an alkaline metal oxide on the cathode; and preparing a tantalum or niobium powder by a first electrolytic reducing reaction that reduces at least one metal halogen compound selected from the group consisting of the alkaline metal oxide and the alkaline earth metal on the cathode and by a second reducing reaction with the tantalum or niobium oxide, represented by Ta 2 O (5-y) or Nb 2 O (5-y) where y=2.5 to 4.5.

1 . A method for preparing tantalum or niobium powders used for manufacturing capacitors in an electrolytic reducing reactor including an anode, a cathode and a molten salt, the method comprising:
 obtaining a tantalum or niobium oxide, expressed by Ta 2 O (5-y)  or Nb 2 O (5-y)  where y=2.5 to 4.5, from a tantalum pentoxide Ta 2 O 5  or a niobium pentoxide Nb 2 O 5  generated partially by an alkaline metal electrolytically reduced via a first electrolytic reducing reaction that reduces an alkaline metal oxide from a molten salt comprising at least one metal halogen compound, selected from the group consisting of alkaline metal and alkaline earth metal, and an alkaline metal oxide on the cathode; and   preparing a tantalum or niobium powder by a first electrolytic reducing reaction that reduces at least one metal halogen compound selected from the group consisting of the alkaline metal oxide and the alkaline earth metal on the cathode and by a second reducing reaction with the tantalum or niobium oxide, represented by Ta 2 O (5-y)  or Nb 2 O (5-y)  where y=2.5 to 4.5.   
     
     
         2 . The method for preparing tantalum or niobium powders used for manufacturing capacitors as recited in  claim 1  further comprising:
 leaching and washing the tantalum or niobium powder, obtained during the second reducing reaction, in an inorganic acid.   
     
     
         3 . The method for preparing tantalum or niobium powders used for manufacturing capacitors as recited in  claim 1 ,
 wherein the tantalum or niobium powder obtained during the second reducing reaction has a mesh structure.   
     
     
         4 . The method for preparing tantalum or niobium powders used for manufacturing capacitors as recited in  claim 1 ,
 wherein the tantalum pentoxide Ta 2 O 5  or the niobium pentoxide Nb 2 O 5  is used in the form of powder or porous pellet.   
     
     
         5 . The method for preparing tantalum or niobium powders used for manufacturing capacitors as recited in  claim 4 ,
 wherein the tantalum pentoxide Ta 2 O 5  or the niobium pentoxide Nb 2 O 5  porous pellet is prepared by molding the tantalum pentoxide Ta 2 O 5  or the niobium pentoxide Nb 2 O 5  powders to form a molded pellet and sintering the molded pellet.   
     
     
         6 . The method for preparing tantalum or niobium powders used for manufacturing capacitors as recited in  claim 4  or  5 ,
 wherein the tantalum pentoxide Ta 2 O 5  or the niobium pentoxide Nb 2 O 5  powders have a content of metal impurities of 150 ppm or less and a carbon content of 50 ppm or less.   
     
     
         7 . The method for preparing tantalum or niobium powders used for manufacturing capacitors as recited in  claim 4 ,
 wherein the tantalum pentoxide Ta 2 O 5  or the niobium pentoxide Nb 2 O 5  in the form of powder is charged into a porous cathode basket.   
     
     
         8 . The method for preparing tantalum or niobium powders used for manufacturing capacitors as recited in  claim 4 ,
 wherein a single type cathode including a high-conductive conductor and a non-conductive ceramic filter having a porosity of 10 to 60% and charged with Ta 2 O 5  or Nb 2 O 5  powders is used as a cathode.   
     
     
         9 . The method for preparing tantalum or niobium powders used for manufacturing capacitors as recited in  claim 8 ,
 wherein the high-conductive conductor is made of one selected from the group consisting of SUS, copper, titanium and tantalum.   
     
     
         10 . The method for preparing tantalum or niobium powders used for manufacturing capacitors as recited in  claim 8 ,
 wherein the non-conductive ceramic filter is made of one selected from the group consisting of magnesia, alumina, magnesium aluminate and zirconia.   
     
     
         11 . The method for preparing tantalum or niobium powders used for manufacturing capacitors as recited in  claim 4 ,
 wherein the Ta 2 O 5  or Nb 2 O 5  porous pellet has a plurality of perforations.   
     
     
         12 . The method for preparing tantalum or niobium powders used for manufacturing capacitors as recited in  claim 1 ,
 wherein reduction temperatures of Ta 2 O 5  or Nb 2 O 5  is controlled by an applied voltage.   
     
     
         13 . The method for preparing tantalum or niobium powders used for manufacturing capacitors as recited in  claim 1 ,
 wherein platinum, pyro-carbon, or Fe 3 O 4  is used as an anode.   
     
     
         14 . A method for preparing tantalum or niobium powders used for manufacturing capacitors in an electrolytic reducing reactor including an anode, a cathode and a molten salt,
 wherein the molten salt is composed of an alkaline metal halogen compound and an alkaline earth metal halogen, the alkaline earth metal halogen compound is first electrolytically reduced on the cathode, the electrolytically reduced alkaline earth metals reduce tantalum pentoxide Ta 2 O 5  or niobium pentoxide Nb 2 O 5  indirectly, and local sinterings are induced via controlling potentials.