Method of anodizing valve metal derived anode bodies and electrolyte therefore

Abstract

An electrolyte solution for anodizing a metal and a capacitor comprising the anodized metal. The electrolyte comprises more than about 5%, by weight, and less than about 30%, by weight, water; about 0.1 to 20%, by weight, ionogen and an aprotic polar solvent. The ionogen comprises phosphoric acid and an alkanol amine in an amount, and ratio, sufficient to maintain a pH of about 4 to about 9.

Claimed is:  
     
         1 . An electrolyte solution for anodizing a metal comprising: 
 more than about 5%, by weight, and less than about 30%, by weight, water;    about 0.1 to 20%, by weight, ionogen comprising: 
 phosphoric acid; and  
 an alkanol amine wherein the amount of ionogen is sufficient to maintain a pH of about 4 to about 9; and  
   an aprotic polar solvent.    
     
     
         2 . The electrolyte of  claim 1  wherein said alkanol amine is selected from monoethanol amine, diethanol amine, triethanol amine, ethyl diethanolamine, diethyl ethanolamine, dimethyl ethanolamine and dimethyl ethoxy ethanolamine.  
     
     
         3 . The electrolyte of  claim 2  wherein said alkanol amine is selected from dimethyl ethanolamine and dimethyl ethoxy ethanolamine.  
     
     
         4 . The electrolyte of  claim 1  wherein said aprotic polar solvent comprises an N-alkyl amide.  
     
     
         5 . The electrolyte of  claim 4  wherein said N-alkyl amide is selected from dimethyl formamide and dimethyl acetamide.  
     
     
         6 . The electrolyte of  claim 1  wherein said aprotic polar solvent comprises dimethyl sulfoxide.  
     
     
         7 . The electrolyte of claim I comprising about 0.1 to about 15%, by weight, said ionogen.  
     
     
         8 . The electrolyte of  claim 7  comprising about 0.5 to about 5%, by weight, phosphoric acid.  
     
     
         9 . The electrolyte of  claim 7  comprising about 0.5 to about 7%, by weight, alkanol amine.  
     
     
         10 . An anode anodized by the electrolyte of  claim 1 .  
     
     
         11 . An anode of  claim 10  comprising a valve metal selected from titanium, tungsten, chromium, aluminium, zirconium, hafnium, zinc, vanadium, niobium, tantalum, bismuth, antimony and mixtures, alloys and metallic glass compositions thereof.  
     
     
         12 . The anode of  claim 11  wherein said anode comprises tantalum.  
     
     
         13 . A capacitor comprising the anode of  claim 12 .  
     
     
         14 . A method for anodizing an anode comprising the steps of: 
 providing a valve metal;    placing said valve metal in an electrolyte comprising: 
 more than about 5%, by weight, and less than about 30%, by weight, water;  
 about 0.1 to 20%, by weight, ionogen comprising:  
 phosphoric acid; and  
 an alkanol amine wherein the amount of ionogen is sufficient to maintain a pH of about 4 to about 9; and  
 an aprotic polar solvent; and  
   subjecting said valve metal to an anodizing voltage.    
     
     
         15 . The method for anodizing an anode of  claim 14  wherein said alkanol amine is selected from monoethanol amine, diethanol amine, triethanol amine, ethyl diethanolamine, diethyl ethanolamine, dimethyl ethanolamine and dimethyl ethoxy ethanolamine.  
     
     
         16 . The method for anodizing an anode of  claim 15  wherein said alkanol amine is selected from dimethyl ethanolamine and dimethyl ethoxy ethanolamine.  
     
     
         17 . The method for anodizing an anode of  claim 14  wherein said aprotic polar solvent comprises an N-alkyl amide.  
     
     
         18 . The method for anodizing an anode of  claim 17  wherein said N-alkyl amide is selected from a group consisting of dimethyl formamide and dimethyl acetamide.  
     
     
         19 . The method for anodizing an anode of  claim 14  wherein said aprotic polar solvent comprises dimethyl sulfoxide.  
     
     
         20 . The method for anodizing an anode of  claim 14  comprising about 0.1 to about 15%, by weight, said ionogen.  
     
     
         21 . The method for anodizing an anode of  claim 20  comprising about 0.5 to about 5%, by weight, said phosphoric acid.  
     
     
         22 . The method for anodizing an anode of  claim 20  comprising about 0.5 to about 7%, by weight, said alkanol amine.  
     
     
         23 . An anode anodized by the method of  claim 14 .  
     
     
         24 . The anode of  claim 23  wherein said valve metal is selected from titanium, tungsten, chromium, aluminium, zirconium, hafiium, zinc, vanadium, niobium, tantalum, bismuth, antimony and mixtures, alloys and metallic glass compositions thereof.  
     
     
         25 . The anode of  claim 24  wherein said valve metal comprises tantalum.  
     
     
         26 . A capacitor comprising the anode of  claim 25 .  
     
     
         27 . A capacitor formed by the process of: 
 providing a valve metal;    placing said valve metal in an electrolyte comprising: 
 more than about 5%, by weight, and less than about 30%, by weight, water;  
 about 0.1 to 20%, by weight, ionogen comprising:  
 phosphoric acid; and  
 an alkanol amine wherein the amount of ionogen is sufficient to maintain a pH of about 4 to about 9; and  
 an aprotic polar solvent; and  
   subjecting said valve metal to an anodizing voltage to form an anodized anode;    forming a capacitor with said anodized anode.    
     
     
         28 . The capacitor of  claim 27  wherein said alkanol amine is selected from monoethanol amine, diethanol amine, triethanol amine, ethyl diethanolamine, diethyl ethanolamine, dimethyl ethanolamine and dimethyl ethoxy ethanolamine.  
     
     
         29 . The capacitor of  claim 28  wherein said alkanol amine is selected from dimethyl ethanolamine and dimethyl ethoxy ethanolamine.  
     
     
         30 . The capacitor of  claim 27  wherein said aprotic polar solvent comprises an N-alkyl amide.  
     
     
         31 . The capacitor of  claim 30  wherein said N-alkyl amide is selected from dimethyl formamide and dimethyl acetamide.  
     
     
         32 . The capacitor of  claim 31  wherein said aprotic polar solvent comprises dimethyl sulfoxide.  
     
     
         33 . The capacitor of  claim 27  wherein said electrolyte comprises about 0.1 to about 15%, by weight, ionogen.  
     
     
         34 . The capacitor of  claim 33  wherein said electrolyte comprises about 0.5 to about 5%, by weight, phosphoric acid.  
     
     
         35 . The capacitor of  claim 33  wherein said electrolyte comprises about 0.5 to about 7%, by weight, said alkanol amine.  
     
     
         36 . The capacitor of  claim 27  wherein said valve metal is selected from titanium, tungsten, chromium, aluminium, zirconium, hafnium, zinc, vanadium, niobium, tantalum, bismuth, antimony and mixtures, alloys and metallic glasses thereof.  
     
     
         37 . The capacitor of  claim 36  wherein said valve metal comprises tantalum.