Method and apparatus for synthesizing filamentary structures

Abstract

Method and apparatus for producing filamentary structures. The structures include single-walled nanotubes. The method includes combusting hydrocarbon fuel and oxygen to establish a non-sooting flame and providing an unsupported catalyst to synthesize the filamentary structure in a post-flame region of the flame. Residence time is selected to favor filamentary structure growth.

1 . Method for producing filamentary structures comprising:
 combusting hydrocarbon fuel and oxygen to establish a non-sooting flame; and   providing an unsupported catalyst to synthesize the filamentary structures in a post-flame region of the flame.   
     
     
         2 . The method of  claim 1  wherein residence time of the structures in the post-flame region extends up to 200 milliseconds. 
     
     
         3 . The method of  claim 1  further including a diluent. 
     
     
         4 . The method of  claim 1  further including quenching the filamentary structures. 
     
     
         5 . The method of  claim 4  wherein quenching includes injection of an inert fluid to quench by sensible energy, latent energy or chemical reaction. 
     
     
         6 . The method of  claim 1  wherein the filamentary structures comprise single-walled nanotubes. 
     
     
         7 . The method of  claim 1  wherein the filamentary structures comprise multi-walled nanotubes. 
     
     
         8 . The method of  claim 1  wherein the filamentary structures comprise fullerenic structures. 
     
     
         9 . The method of  claim 1  wherein the filamentary structures comprise carbon nanofibers. 
     
     
         10 . The method of  claim 1  wherein the filamentary structures comprise carbon structures decorated or in close association with metallic particles. 
     
     
         11 . The method of  claim 1  wherein the catalyst is a metal catalyst. 
     
     
         12 . The method of  claim 1  wherein the catalyst is a mixture of different metals. 
     
     
         13 . The method of  claim 11  wherein the metal catalyst includes iron. 
     
     
         14 . The method of  claim 13  wherein the metal catalyst precursor is iron pentacarbonyl. 
     
     
         15 . The method of  claim 1  wherein the hydrocarbon fuel is acetylene. 
     
     
         16 . The method of  claim 3  wherein the diluent is argon. 
     
     
         17 . The method of  claim 1  wherein the flame is a premixed flame. 
     
     
         18 . The method of  claim 1  wherein the flame is a non-premixed flame. 
     
     
         19 . The method of  claim 1  further including the step of withdrawing post-flame gases at locations corresponding to selected residence times to control the filamentary structure morphology. 
     
     
         20 . The method of  claim 1  wherein the filamentary structures are nanotubes having a diameter in the range 0.4 nm-100 nm. 
     
     
         21 . The method of  claim 1  wherein the filamentary structures have substantially metallic chirality. 
     
     
         22 . The method of  claim 1  wherein the filamentary structures have substantially semiconductor chirality. 
     
     
         23 . The method of  claim 1  further including co-injection of modifying agents. 
     
     
         24 . The method of  claim 23  wherein the modifying agents are selected from the group consisting of ammonia, thiophene, hydrogen and carbon monoxide. 
     
     
         25 . The method of  claim 1  further including injecting a secondary oxidant in the post-flame region so as to preferentially oxidize carbon and/or metallic contamination. 
     
     
         26 . The method of  claim 1  further including injecting a secondary reagent in the post-flame region so as to preferentially open, alter and/or functionalize the filamentary structures. 
     
     
         27 . The method of  claim 1  wherein equivalence ratio, catalyst type, and catalyst concentration are selected to establish the non-sooting flame. 
     
     
         28 . The method of  claim 1  wherein the hydrocarbon fuel and oxygen are in an equivalence ratio in the range 1.0-1.7. 
     
     
         29 . Method for producing filamentary structures comprising:
 combusting hydrocarbon fuel and oxygen to establish a flame under conditions that result in yields of the filamentary structures of greater than 1% with respect to non-structured material; and   providing an unsupported catalyst to synthesize the filamentary structures in a post-flame region of the flame.   
     
     
         30 . Apparatus for synthesis of filamentary structures comprising:
 a burner system;   a source of hydrocarbon fuel and oxygen delivered to the burner to establish a non-sooting flame; and   a source of an unsupported catalyst delivered to the burner system.   
     
     
         31 . The apparatus of  claim 30  wherein the burner system is designed to provide a selected residence time in a post-flame region in the burner system.