Valve metal ribbon type fibers for solid electrolytic capacitors

Abstract

A method for making superconducting material useful for forming electrolytic devices comprising the steps of establishing multiple valve metal rods in a primary billet of a ductile material; working the primary billet to a series of reduction steps to form said valve metal rods into a plurality of elongated elements surrounded at least in part by the ductile material; cutting the elongated elements from step (b) and bundling the cut elements to form a secondary billet; working the secondary billet through a series of reduction steps followed by rolling to final thickness; removing the ductile material, whereby to leave valve metal elongated fibers; and sintering the elongated fibers from step (e) under vacuum.

1 . A method for making valve metal fibers useful for forming electrolytic capacitors comprising the steps of 
 (a) establishing multiple valve metal rods in a primary billet of a ductile material;    (b) working the primary billet to a series of reduction steps to form said valve metal rods into a plurality of elongated elements surrounded at least in part by the ductile material;    (c) cutting the elongated elements from step (b) and bundling the cut elements to form a secondary billet;    (d) working the secondary billet through a series of reduction steps followed by rolling to the elongated elements into flattened fibers having a width to thickness aspect ratio of at least about 10 to 1;    (e) removing the ductile material, whereby to leave valve metal elongated flattened fibers; and    (f) sintering the elongated flattened fibers from step (e) under vacuum.    
   
   
       2 . The method of  claim 1 , wherein the ductile material comprises a ductile metal.  
   
   
       3 . The method of  claim 2 , wherein the ductile metal comprises copper.  
   
   
       4 . The method of  claim 1 , wherein the sintering is conducted at a temperature in the range of 1300° C. to 1800° C. for a time period of 10 to 60 minutes.  
   
   
       5 . The method of  claim 4 , wherein the sintering is conducted at a temperature in the range of 1300° C. to 1500° C. for a period of 10 to 50 minutes.  
   
   
       6 . The method of  claim 5 , wherein the sintering is conducted at a temperature of about 1500° C. for about 50 minutes.  
   
   
       7 . The method of  claim 1 , including the step of anodizing the sintered flattened fibers from step (g).  
   
   
       8 . The method of  claim 1 , including the step of twisting the flattened filaments before sintering.  
   
   
       9 . The method of  claim 1 , wherein the valve metal comprises tantalum.  
   
   
       10 . The method of  claim 1 , wherein the valve metal comprises niobium.  
   
   
       11 . The method of  claim 1 , wherein the valve metal comprises aluminum.  
   
   
       12 . The method of  claim 1 , wherein the valve metal comprises vanadium.  
   
   
       13 . An electrolytic capacitor comprising an anode formed of valve metal filaments of substantially uniform thickness within a range of 0.3-1.0 microns, and having a specific capacitance in excess of about 10,000 CV/g.  
   
   
       14 . The capacitor of  claim 13 , wherein the valve metal comprises tantalum.  
   
   
       15 . The capacitor of  claim 13 , wherein the valve metal comprises niobium.  
   
   
       16 . The capacitor of  claim 13 , wherein the valve metal comprises aluminum.  
   
   
       17 . The capacitor of  claim 13 , wherein the valve metal comprises vanadium.  
   
   
       18 . The capacitor of  claim 13 , wherein the filaments comprise ribbon-like fibers.  
   
   
       19 . The capacitor of  claim 18 , wherein the ribbon-like fibers have a width to thickness aspect ratio of at least about 10 to 1.