Metallization of carbon nanotubes for field emission applications

Abstract

The present invention is directed towards metallized carbon nanotubes, methods for making metallized carbon nanotubes using an electroless plating technique, methods for dispensing metallized carbon nanotubes onto a substrate. The present invention is also directed towards cold cathode field emitting materials comprising metallized carbon nanotubes, and methods of using metallized carbon nanotubes as cold cathode field emitters.

What is claimed is:  
     
         1 . A metallized carbon nanotube material comprising carbon nanotubes which have a metal coating on them.  
     
     
         2 . The material of  claim 1 , wherein the carbon nanotubes are selected from the group consisting of single-wall carbon nanotubes, multi-wall carbon nanotubes, buckytubes, carbon fibrils, derivatized carbon nanotubes, chemically-modified carbon nanotubes, metallic carbon nanotubes, semiconducting carbon nanotubes, and combinations thereof.  
     
     
         3 . The material of  claim 1 , wherein the metal coating is uniformly distributed over an exterior surface of said carbon nanotubes.  
     
     
         4 . The material of  claim 1 , wherein the metal is selected from the group consisting of nickel, iron, copper, silver, zinc, rhodium, tin, cadmium, chromium, beryllium, palladium, indium, platinum, gold, and combinations thereof.  
     
     
         5 . The method of  claim 1 , wherein the metal coating has a thickness which ranges from at least about 0.1 nanometers to at most about 1 micrometer.  
     
     
         6 . A method of making metallized carbon nanotubes comprising the steps of: 
 a) providing a plurality of carbon nanotubes;    b) preparing an electroless metal plating solution;    c) adding said carbon nanotubes to said electroless plating solution;    d) subjecting said electroless plating solution to a reducing condition which causes metal ions in solution to be reduced to metal and nucleate on the carbon nanotubes to produce metallized carbon nanotubes; and    e) removing said metallized carbon nanotubes from solution.    
     
     
         7 . The method of  claim 6 , further comprising the step washing the metallized carbon nanotubes.  
     
     
         8 . The method of  claim 6 , further comprising the step of drying the metallized carbon nanotubes.  
     
     
         9 . The method of  claim 6 , wherein the carbon nanotubes are selected from the group consisting of single-wall carbon nanotubes, multi-wall carbon nanotubes, buckytubes, carbon fibrils, derivatized carbon nanotubes, chemically-modified carbon nanotubes, metallic carbon nanotubes, semiconducting carbon nanotubes, and combinations thereof.  
     
     
         10 . The method of  claim 6 , further comprising the step of treating the carbon nanotubes with hydrochloric acid prior to their metallization.  
     
     
         11 . The method of  claim 6 , wherein the electroless plating solution comprises a solvent, a metal salt, and a reducing agent.  
     
     
         12 . The method of  claim 11 , wherein the electroless plating solution further comprises an optional component selected from the group consisting of a promoter species, an inhibiting agent, a balancing agent, and combinations thereof.  
     
     
         13 . The method of  claim 11 , wherein the metal salt comprises a metal selected form the group consisting of nickel, iron, copper, silver, zinc, rhodium, tin, cadmium, chromium, beryllium, palladium, indium, platinum, gold, and combinations thereof.  
     
     
         14 . The method of  claim 6 , wherein the step of adding said carbon nanotubes to said electroless plating solution further comprises ultrasonicating the carbon nanotubes in a solvent just prior to addition.  
     
     
         15 . The method of  claim 6 , wherein the step of removing said metallized carbon nanotubes from solution further comprises a separation technique selected from the group consisting of filtration, centrifugation, and combinations thereof.  
     
     
         16 . Metallized carbon nanotubes made by a process comprising the steps of: 
 a) providing a plurality of carbon nanotubes;    b) preparing an electroless metal plating solution;    c) adding said carbon nanotubes to said electroless plating solution;    d) subjecting said electroless plating solution to a reducing condition which causes metal ions in solution to be reduced to metal and nucleate on the carbon nanotubes to produce metallized carbon nanotubes; and    e) removing said metallized carbon nanotubes from solution.    
     
     
         17 . A cathode for field emission applications comprising: 
 a) a substrate; and    b) metallized carbon nanotubes.    
     
     
         18 . A method of making cathodes for field emission applications comprising the steps of: 
 a) providing a suitable substrate; and    b) dispensing metallized carbon nanotubes onto said substrate using an applicator means.    
     
     
         19 . The method of  claim 18 , wherein the applicator means comprises a spraying technique whereby a suspension of metallized carbon nanotubes suspended in a suitable solvent is sprayed onto said substrate.  
     
     
         20 . The method of  claim 19 , wherein the suspension of metallized carbon nanotubes is generated using ultrasonic assistance.  
     
     
         21 . A field emission display device comprising: 
 a) an anode which includes a phosphor deposited on a substrate; and    b) a cathode comprising a layer of metallized carbon on a substrate.    
     
     
         22 . A field emission display device comprising: 
 a) an anode assembly; and    b) a cathode assembly, wherein the cathode assembly comprises: 
 1) a substrate;  
 2) an electically conducting layer deposited on the substrate; and  
 3) a layer of metallized carbon nanotubes deposited over the electrically conducting layer.  
   
     
     
         23 . The field emission display device of  claim 22 , wherein the metallized carbon nanotubes comprise single-wall carbon nanotubes.