Synthesis Of High Quality Carbon Single-Walled Nanotubes

Abstract

Methods and processes for synthesizing high quality carbon single-walled nanotubes (SWNTs) are provided. A carbon precursor gas at reduced concentration (pressure) is contacted with a catalyst deposited on a support and at temperature about 10° C. above the SWNT synthesis onset temperature, but below the thermal decomposition temperature of the carbon precursor gas for given growth conditions. The concentration (pressure) of the carbon precursor gas can be controlled by reducing the total pressure of the gas, or by diluting with an inert carrier gas, or both. The methods produce SWNTs with the ratio of G-band to D-band in Raman spectra (I G :I D ) of about 5 to about 200.

We claim: 
     
         1 . A method for synthesizing carbon single-walled nanotubes (SWNTs), the method comprising:
 contacting supported metal catalyst with a carbon precursor gas at a partial pressure of about 0.01 torr to about 200 torr and a temperature between about 600° C. and 1200° C. wherein SWNTs are synthesized with a ratio of G-band to D-band in Raman spectra (I G :I D ) of greater than about 100.   
     
     
         2 . The method of  claim 1 , wherein the metal catalyst comprises a Group V metal, a Group VI metal, a Group VII metal, a Group VIII metal, a lanthanide, a transition metal, or a mixture thereof. 
     
     
         3 . The method of  claim 2 , wherein the metal catalyst comprises Fe and a second metal, wherein the second metal is V, Nb, Cr, W, Mo, Mn, Re, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, Ce, Eu, Er, Yb, Ag, Au, Zn, Cd, Sc, Y, La, or a mixture thereof. 
     
     
         4 . The method of  claim 3 , wherein the second metal comprise Fe and Ni, Co, Cr, Mo, and a combination thereof. 
     
     
         5 . The method of  claim 4 , wherein the metal catalyst is Fe—Mo. 
     
     
         6 . The method of  claim 1 , wherein the support is a powdered oxide. 
     
     
         7 . The method of  claim 6 , wherein the powdered oxide is oxide selected from the group consisting of Al 2 O 3 , SiO 2 , MgO, and zeolites. 
     
     
         8 . The method of  claim 7 , wherein the powdered oxide is Al 2 O 3 . 
     
     
         9 . The method of  claim 1 , wherein the catalyst and the support are in a ratio of about 1:1 to about 1:500. 
     
     
         10 . The method of  claim 9 , wherein the ratio of about 1:10 to about 1:20. 
     
     
         11 . The method of  claim 1 , wherein the carbon precursor gas is selected from the group consisting of methane, ethane, propane, butane, pentane, hexane, ethylene, acetylene, propylene, acetone, and methanol. 
     
     
         12 . The method of  claim 11 , wherein the carbon precursor gas comprises methane. 
     
     
         13 . The method of  claim 11 , wherein the carbon precursor gas further comprises an inert gas and the total pressure is about 740 torr to about 780 torr. 
     
     
         14 . The method of  claim 13 , wherein the inert gas is argon, helium, nitrogen, or combinations thereof. 
     
     
         15 . The method of  claim 11 , wherein the synthesis is under reduced pressure. 
     
     
         16 . The method of  claim 1 , wherein the ratio of I G :I D  is less than 100. 
     
     
         17 . The method of  claim 16 , wherein the ratio of I G :I D  is about 5 to about 30. 
     
     
         18 . A method for synthesizing carbon single-walled nanotubes (SWNTs), the method comprising:
 contacting metal catalyst on a support in a ratio of about 1:10 to about 1:40 with a carbon precursor gas at a pressure of about 0.01 torr to about 200 torr and a temperature between about 600° C. and 900° C., wherein SWNTs are synthesized with a ratio of G-band to D-band in Raman spectra (I G :I D ) of greater than 5, and wherein the metal catalyst is Fe—Mo.   
     
     
         19 . The method of  claim 18 , wherein the support is a powdered oxide. 
     
     
         20 . The method of  claim 19 , wherein the powdered oxide is oxide selected from the group consisting of Al 2 O 3 , SiO 2 , MgO, and zeolites. 
     
     
         21 . The method of  claim 20 , wherein the powdered oxide is Al 2 O 3 . 
     
     
         22 . The method of  claim 18 , wherein the carbon precursor gas is selected from the group consisting of methane, ethane, propane, butane, pentane, hexane, ethylene, acetylene, propylene, acetone, and methanol. 
     
     
         23 . The method of  claim 22 , wherein the carbon precursor gas is methane. 
     
     
         24 . The method of  claim 22 , wherein the carbon precursor gas further comprises an inert gas and the total pressure is about 740 torr to about 780 torr. 
     
     
         25 . The method of  claim 24 , wherein the inert gas is argon, helium, nitrogen, hydrogen, or combinations thereof. 
     
     
         26 . The method of  claim 18 , wherein the ratio of I G :I D  is less than 100. 
     
     
         27 . The method of  claim 26 , wherein the ratio of I G :I D  is about 5 to about 30.