Method for forming titanium oxide film and titanium electrolytic capacitor

Abstract

A compact type large capacity titanium electrolytic capacitor having minimized leakage current is provided by forming a stable oxide film having a large dielectric constant on a titanium surface, wherein a titanium substrate having a titanium oxide film thereon having a thickness of 50 nm or more is subjected to calcination in vacuum or an inert gas atmosphere, thereby reducing the thickness of said oxide film to less than 50 nm and the calcined surface of said metal titanium substrate is subjected to oxidation, thereby re-forming an oxide film on the surface of said metal titanium substrate. The metal titanium substrate having the re-formed oxide film obtained by such method can be used as an anode for a titanium electrolytic capacitor.

1 . A method for forming a titanium oxide film on a metal titanium substrate characterized in that a metal titanium substrate having on the surface thereof an oxide film having a thickness of at least 50 nm is subjected to calcination in vacuum or an inert gas atmosphere, thereby reducing the thickness of said oxide film to less than 50 nm, and the calcined surface of said metal titanium substrate is subjected to oxidation, thereby re-forming an oxide film on the surface of said metal titanium substrate.  
     
     
         2 . The method according to  claim 1 , wherein said metal titanium substrate having on the surface thereof the oxide film having the thickness of at least 50 nm is prepared by applying titanic acid or an organic titanium compound to the surface of said metal titanium substrate.  
     
     
         3 . The method according to  claim 2 , wherein said titanic acid is peroxotitanic acid.  
     
     
         4 . The method according to  claim 2 , wherein said organic titanium compound is an alkoxy titanium.  
     
     
         5 . The method according to  claim 1 , wherein said metal titanium substrate having on the surface thereof the oxide film having the thickness of at least 50 nm is prepared by subjecting a metal titanium substrate to heat treatment in the presence of oxygen.  
     
     
         6 . The method according to  claim 5 , wherein said heat treatment in the presence of oxygen is conducted at 500-900° C.  
     
     
         7 . The method according to  claim 1 , wherein said calcination is conducted at 500-900° C.  
     
     
         8 . The method according to  claim 1 , wherein said oxidation is conducted by anodic oxidation.  
     
     
         9 . The method according to  claim 1 , wherein said oxidation is conducted by heat treatment in oxygen or an oxygen-containing atmosphere.  
     
     
         10 . The method according to  claim 1 , wherein said oxidation is conducted by heat treatment in oxygen or an oxygen-containing atmosphere, and by anodic oxidation.  
     
     
         11 . The method according to  claim 10 , wherein said heat treatment in oxygen or an oxygen-containing atmosphere is conducted at 500-900° C.  
     
     
         12 . A titanium electrolytic capacitor wherein a metal titanium substrate having an oxide film obtained by the method according to any one of claims  1 - 11  is used as an anode.  
     
     
         13 . A method for forming an oxide film on a metal titanium substrate characterized in that titanic acid or an organic titanium compound is applied to the surface of the metal titanium substrate to forme an oxide film on the surface, the metal titanium substrate having the oxide film is subjected to calcination, and the calcined substrate is subjected to anodic oxidation in an electrolyte-containing solution, thereby re-forming an oxide film on the surface of said metal titanium substrate.  
     
     
         14 . The method according to  claim 13 , wherein said titanic acid is peroxotitanic acid.  
     
     
         15 . The method according to  claim 13 , wherein said organic titanium compound is alkoxy titanium.  
     
     
         16 . The method according to  claim 13 , wherein said calcination is conducted in vacuum, an inert gas atmosphere, oxygen or an oxygen-containing atmosphere at 500-900° C.  
     
     
         17 . A titanium electrolytic capacitor wherein a metal titanium substrate having an oxide film obtained by the method according to any one of claims  13 - 16  is used as an anode.