Crystalline graphite nanofibers and a process for producing same

Abstract

A carbon nanofiber having substantially graphite sheets that are substantially parallel to the longitudinal axis of the nanofiber and a produce for producing same. The carbon nanofibers are produced by contacting an iron, or an iron:copper bimetallic, or an iron:nickel bimetallic bulk catalyst with a mixture of carbon monoxide and hydrogen at temperatures from about 625° C. to about 725° C. for an effective amount of time.

What is claimed is:  
     
         1 . A substantially crystalline graphitic carbon nanofiber comprised of substantially graphite sheets that are substantially parallel to the longitudinal axis of the nanofibers, wherein the distance between graphite sheets is from about 0.335 nm to about 0.67 nm, and having a crystallinity greater than about 95%.  
     
     
         2 . The nanofiber of  claim 1  wherein said substantially graphite sheets are separate and non-continuous sheets.  
     
     
         3 . The nanofiber of  claim 1  which is characterized as having continuous substantially graphite sheets forming a non-cylindrical multifaceted tubular structure.  
     
     
         4 . The nanofiber of the  claim 1  wherein the distance between the graphite sheets is from about 0.335 and 0.40 nm.  
     
     
         5 . The nanofiber of  claim 1  wherein at least a portion of the edge regions of the nanofiber contain a functional group selected from the group consisting of basic groups, acidic groups, and oxygenated groups.  
     
     
         6 . The nanofiber of  claim 5  wherein the functional group is a basic group that is a NH 4 + group.  
     
     
         7 . The nanofiber of  claim 5  wherein the functional group is an acid group which is a COOH -  group.  
     
     
         8 . The nanofiber of  claim 5  wherein the functional group is an oxygenated group selected from the group consisting of hydroxyl, peroxide, ether, keto, and aldehyde.  
     
     
         9 . A substantially crystalline graphitic carbon nanofiber comprised of substantially graphite discontinuous sheets that are substantially parallel to the longitudinal axis of the nanofibers, wherein the distance between graphite sheets is from about 0.335 nm to about 0.67 nm, and having a crystallinity greater than about 95%.  
     
     
         10 . The nanofiber of the  claim 9  wherein the distance between the graphite sheets is from about 0.335 and 0.40 nm.  
     
     
         11 . The nanofiber of  claim 9  wherein at least a portion of the edge regions of the nanofiber contain a functional group selected from the group consisting of basic groups, acidic groups, and oxygenated groups.  
     
     
         12 . The nanofiber of  claim 11  wherein the functional group is a basic group that is a NH 4 + group.  
     
     
         13 . The nanofiber of  claim 11  wherein the functional group is an acid group which is a COOH -  group.  
     
     
         14 . The nanofiber of  claim 11  wherein the functional group is an oxygenated group selected from the group consisting of hydroxyl, peroxide, ether, keto, and aldehyde.  
     
     
         15 . A substantially crystalline graphitic carbon nanofiber comprised of continuous substantially graphite sheets that are substantially parallel to the longitudinal axis of the nanofibers and which has a substantially non-cylindrical multifaceted tubular structure, wherein the distance between graphite sheets is from about 0.335 nm to about 0.67 nm, and having a crystallinity greater than about 95%.  
     
     
         16 . The nanofiber of the  claim 15  wherein the distance between the graphite sheets is from about 0.335 and 0.40 nm.  
     
     
         17 . The nanofiber of  claim 15  wherein at least a portion of the edge regions of the nanofiber contain a functional group selected from the group consisting of basic groups, acidic groups, and oxygenated groups.  
     
     
         18 . The nanofiber of  claim 17  wherein the functional group is a basic group that is a NH 4 + group.  
     
     
         19 . The nanofiber of  claim 17  wherein the functional group is an acid group which is a COOH group.  
     
     
         20 . The nanofiber of  claim 17  wherein the functional group is an oxygenated group selected from the group consisting of hydroxyl, peroxide, ether, keto, and aldehyde.  
     
     
         21 . A process for producing a substantially crystalline graphitic nanofiber wherein at least a portion of which are comprised of graphite sheets that are substantially parallel to the longitudinal axis of the nanofiber, which process comprises reacting a mixture of CO/H 2  in the presence of a catalyst selected from the group consisting of Fe, Fe:Cu bimetallic, and Fe:Ni bimetallic powder catalysts for an effective amount of time at a temperature from about 625° C. to about 725° C.  
     
     
         22 . The process of  claim 21  wherein said nanofibers are characterized as having separate and non-continuous substantially graphite sheets.  
     
     
         23 . The process of  claim 21  wherein said nanofibers are characterized as having continuous substantially graphite sheets forming a non-cylindrical multifaceted tubular structure.  
     
     
         24 . The process of  claim 21  wherein the catalyst is an Fe:Cu bimetallic wherein the ratio of Fe to Cu is from about 1:99 to about 99:1.  
     
     
         25 . The process of  claim 24  wherein the ratio of Fe to Cu is from about 3:7 to about 7:3  
     
     
         26 . The process of  claim 21  wherein the catalyst is an Fe:Ni bimetallic wherein the ratio of Fe to Ni is from about 1:99 to about 99:1.  
     
     
         27 . The process of  claim 26  wherein the ratio of Fe to Ni is from about 3:7 to about 7:3  
     
     
         28 . The process of  claim 21  wherein the ratio of CO to H 2  is from about 95:5 to about 5:95.  
     
     
         29 . The process of  claim 28  wherein the ratio of CO to H 2  is from about 80:20 to about 20:80.  
     
     
         30 . The process of  claim 25  wherein the ratio of CO to H 2  is from about 80:20 to about 20:80.  
     
     
         31 . The process of  claim 21  wherein the crystallinity of the nanofiber is greater than about 98%.  
     
     
         32 . The process of  claim 25  wherein the crystallinity of the nanofiber is greater than about 98%.  
     
     
         33 . The process of  claim 21  wherein the particle size of the bimetallic powder is from about 0.25 nanometer to about 5 micrometer.  
     
     
         34 . The process of  claim 33  wherein the particle size of the bimetallic powder is from about 2.5 nanometers to about 1 micrometer.