Methods for synthesizing carbon nanotubes

Abstract

A catalyst material for carbon nanotube synthesis includes a uniform dispersion of host particles on a substrate. The host particles themselves include catalyst nanoparticles that are effective to catalyze nanotube syntheses reactions and provide nucleation sites. Methods for preparing catalyst materials include co-sputtering a catalytic species and a host species to form a precursor thin film on a substrate, followed by an oxidation reaction of the precursor thin film in air. The precursor thin film can be patterned on the substrate to limit the locations of the catalyst material to well-defined areas. Methods for nanotube synthesis employ CVD in conjunction with the catalyst materials of the invention. During the synthesis, the catalyst nanoparticles catalyze carbon nanotubes to grown from a carbon-containing gas.

1 . A method for synthesizing carbon nanotubes, comprising:
 forming a precursor layer on a substrate by co-sputtering a catalytic species and a host species;   transforming the precursor layer to form a uniform dispersion of host particles including catalyst nanoparticles; and   passing a carbon-containing gas over the substrate in a reactor at a first elevated temperature for a period of time.   
     
     
         2 . The method of  claim 1  wherein transforming the precursor layer is performed in air. 
     
     
         3 . The method of  claim 1  wherein the period of time is in a range of about 5 minutes to about 30 minutes. 
     
     
         4 . The method of  claim 1  wherein the carbon-containing gas includes a hydrocarbon. 
     
     
         5 . The method of  claim 4  wherein the hydrocarbon includes methane, ethylene, or acetylene. 
     
     
         6 . The method of  claim 1  wherein the host species includes a metal oxide. 
     
     
         7 . The method of  claim 1  wherein the reactor is a tube reactor. 
     
     
         8 . The method of  claim 1  wherein transforming the precursor layer is performed at a second elevated temperature. 
     
     
         9 . The method of  claim 8  wherein the first and second temperatures are the same. 
     
     
         10 . The method of  claim 8  wherein the second elevated temperature is in a range of about 400° C. to about 900° C. 
     
     
         11 . The method of  claim 1  wherein transforming the precursor layer, and passing the carbon-containing gas over the substrate, are performed in the same reactor. 
     
     
         12 . A method for synthesizing carbon nanotubes, comprising:
 forming a precursor layer on a substrate by co-evaporating a catalytic species and a host species;   transforming the precursor layer to form a uniform dispersion of host particles including catalyst nanoparticles; and   passing a carbon-containing gas over the substrate in a reactor at a first elevated temperature for a period of time.   
     
     
         13 . The method of  claim 12  wherein transforming the precursor layer is performed in air. 
     
     
         14 . The method of  claim 12  wherein the host species includes a metal oxide. 
     
     
         15 . The method of  claim 12  wherein transforming the precursor layer, and passing the carbon-containing gas over the substrate, are performed in the same reactor. 
     
     
         16 . A method for synthesizing carbon nanotubes, comprising:
 forming a precursor layer on a substrate by electro-depositing, laser ablating, or arc evaporating a catalytic species and a host species;   transforming the precursor layer to form a uniform dispersion of host particles including catalyst nanoparticles; and   passing a carbon-containing gas over the substrate in a reactor at a first elevated temperature for a period of time.   
     
     
         17 . The method of  claim 16  wherein transforming the precursor layer is performed in air. 
     
     
         18 . The method of  claim 16  wherein the host species includes a metal oxide. 
     
     
         19 . The method of  claim 16  wherein transforming the precursor layer, and passing the carbon-containing gas over the substrate, are performed in the same reactor.