Supported metal catalyst for synthesizing carbon nanotubes by low-temperature thermal chemical vapor deposition and method of synthesizing carbon nanotubes using the same

Abstract

The present invention discloses a supported metal catalyst useful in synthesizing carbon nanotubes by low-temperature (<600° C.) thermal chemical vapor deposition (CVD), which contains particles of a noble metal having a diameter of 0.1-10 microns as a support and a metal catalyst deposited on the support. The metal catalyst is iron, cobalt, nickel or an alloy thereof. The weight ratio of the metal catalyst to the support ranges from 0.1:100 to 10:100. The present invention also discloses a method of synthesizing carbon nanotubes directly on a substrate by low-temperature thermal CVD, wherein the support is not needed to be removed from the substrate after growth of carbon nanotubes.

What is claimed is:  
     
         1 . A supported metal catalyst for synthesizing carbon nanotubes by low-temperature thermal chemical vapor deposition (CVD) comprising: 
 particles of a noble metal with diameters of 0.01-10 microns; and    a metal catalyst deposited on the noble metal particles, wherein said metal catalyst is selected from the group consisting of iron, cobalt, nickel and their alloys, and the weight ratio of said metal catalyst to said noble metal particles ranges from 0.1:100 to 10:100.    
     
     
         2 . The supported metal catalyst as claimed in  claim 1 , wherein said noble metal particles are selected from the group consisted of silver, gold, platinum, palladium, copper, and their alloys.  
     
     
         3 . The supported metal catalyst as claimed in  claim 2 , wherein said noble metal particles are silver.  
     
     
         4 . The supported metal catalyst as claimed in  claim 1 , which is prepared by mixing said noble metal particles with a solution of a salt of said metal catalyst; and heating the resulting mixture to evaporate solvent therein, so that said metal catalyst is deposited on said noble metal particles.  
     
     
         5 . The supported metal catalyst as claimed in  claim 4 , wherein said salt solution of the metal catalyst is a nitrate solution or a sulfate solution.  
     
     
         6 . The supported metal catalyst as claimed in  claim 5 , wherein said salt solution of the metal catalyst is an aqueous or an alcohol solution.  
     
     
         7 . The supported metal catalyst as claimed in  claim 1 , which is prepared by a deposition precipitation method comprising the following steps: 
 a) dispersing said noble metal particles in a solvent;    b) adding a salt solution of said metal catalyst to the resulting dispersion of said noble metal particles from Step (a);    c) heating the resulting mixture from Step (b) and adding a precipitation agent to the heated mixture, so that said metal catalyst is deposited on said noble metal particles; and    d) adding a reducing agent to the resulting mixture from Step (c) to reduce ions of said metal catalyst.    
     
     
         8 . The supported metal catalyst as claimed in  claim 7 , wherein said solvent in Step (a) is water or an alcohol.  
     
     
         9 . The supported metal catalyst as claimed in  claim 7 , wherein the precipitation agent in Step (c) is ammonia or sodium hydrocarbonate.  
     
     
         10 . The supported metal catalyst as claimed in  claim 7 , wherein the reducing agent in Step (d) is hydrazine, formaldehyde, phosphite, or benzaldehyde.  
     
     
         11 . A method of synthesizing carbon nanotubes by low-temperature thermal CVD, which comprises the following steps: 
 A) dispersing the supported metal catalyst of  claim 1  on a substrate; and    B) growing carbon nanotubes on said supported metal catalyst by using a carbon source gas and through a thermal CVD.    
     
     
         12 . The method as claimed in  claim 11 , wherein said substrate in Step (A) is selected from the group consisting of ITO conductive glass, reinforced glass, sodium glass, quartz, silicon oxide, silicon wafer, aluminum, and metal sheets.  
     
     
         13 . The method as claimed in  claim 11 , wherein said thermal CVD in Step (B) is carried out at a reaction temperature of 400-600° C.  
     
     
         14 . The method as claimed in  claim 11 , wherein said thermal CVD in Step (B) is carried out at a pressure of 0.5-2 atm for a reaction time of 1-120 minutes; and said carbon source gas comprises a hydrocarbon or carbon monoxide.  
     
     
         15 . The method as claimed in  claim 14 , wherein said hydrocarbon contains 1-6 carbons.  
     
     
         16 . The method as claimed in  claim 14 , wherein said carbon source gas is methane, acetylene, or carbon monoxide.  
     
     
         17 . The method as claimed in  claim 11 , wherein the thermal CVD in Step (B) is carried out in the presence of hydrogen gas; and said carbon source gas comprises a hydrocarbon or carbon monoxide.