Carbon nanotube particulates, compositions and use thereof

Abstract

A method for making carbon nanotube particulates involves providing a catalyst comprising catalytic metals, such as iron and molybdenum or metals from Group VIB or Group VIIIB elements, on a support material, such as magnesia, and contacting the catalyst with a gaseous carbon-containing feedstock, such as methane, at a sufficient temperature and for a sufficient contact time to make small-diameter carbon nanotubes having one or more walls and outer wall diameters of less than about 3 nm. Removal of the support material from the carbon nanotubes yields particulates of enmeshed carbon nanotubes that retain an approximate three-dimensional shape and size of the particulate support that was removed. The carbon nanotube particulates can comprise ropes of carbon nanotubes. The carbon nanotube particulates disperse well in polymers and show high conductivity in polymers at low loadings. As electrical emitters, the carbon nanotube particulates exhibit very low “turn on” emission field.

1 . A method for producing carbon nanotube particulates, comprising: 
 (a) providing a catalyst comprising catalytic metal on a particulate support, wherein the particulate support has a cross-sectional dimension of less than about 1000 microns,    (b) contacting the catalyst with a gaseous stream comprising a carbon-containing feedstock at a sufficient temperature and for a contact time sufficient to make a carbon product on the catalyst wherein the carbon product comprises carbon nanotube particulates, wherein the particulates comprise small-diameter carbon nanotubes, wherein the small-diameter carbon nanotubes have a outer diameter in the range of about 0.5 nm and about 3 nm, and    (c) removing the particulate support from the carbon product comprising the carbon nanotube particulates, wherein the carbon nanotube particulates retain a macroscopic morphology of an approximate shape and an approximate cross-sectional dimension as before removal of the particulate support.    
     
     
         2 . The method of  claim 1  wherein the small-diameter carbon nanotubes are selected from the group consisting of single-wall carbon nanotubes, double-wall carbon nanotubes, triple-wall carbon nanotubes, quadruple-wall carbon nanotubes and combinations thereof.  
     
     
         3 . The method of  claim 1  wherein the particulate support comprises a material selected from the group consisting of zeolite, silica, alumina, zirconia, magnesia and combinations thereof.  
     
     
         4 . The method of  claim 1  wherein the particulate support comprises magnesia.  
     
     
         5 . The method of  claim 1  wherein the catalytic metal comprises at least one element selected from the group consisting of chromium, molybdenum, tungsten, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, a lanthanide series element, an actinide series element, and combinations thereof.  
     
     
         6 . The method of  claim 1  wherein the catalytic metal comprises iron.  
     
     
         7 . The method of  claim 1  wherein the catalytic metal comprises iron and molybdenum.  
     
     
         8 . The method of  claim 1  wherein the small-diameter carbon nanotube particulates have a bulk density in a range of about 0.01 g/cm 3  and about 0.5 g/cm 3 .  
     
     
         9 . The method of  claim 1  wherein the particulate support has a cross-sectional dimension in a range of about 0.1 micron and about 1000 microns.  
     
     
         10 . The method of  claim 1  wherein the particulate support has a cross-sectional dimension in a range of about 1 micron and about 100 microns.  
     
     
         11 . The method of  claim 1  wherein the carbon nanotube particulates have a cross-sectional dimension in the range of about 0.1 micron and about 1000 microns.  
     
     
         12 . The method of  claim 1  wherein the carbon nanotube particulates have a cross-sectional dimension in the range of about 1 micron and about 100 microns.  
     
     
         13 . The method of  claim 1  wherein the small-diameter carbon nanotubes are present in the small-diameter carbon nanotube particulates in an amount greater than about 50 wt % of a total weight of the carbon product.  
     
     
         14 . The method of  claim 1  wherein the small-diameter carbon nanotubes are present in the small-diameter carbon nanotube particulates in an amount greater than about 80 wt % of a total weight of the carbon product.  
     
     
         15 . The method of  claim 1  wherein the small-diameter carbon nanotubes are present in the small-diameter carbon nanotube particulates in an amount greater than about 90 wt % of a total weight of the carbon product.  
     
     
         16 . The method of  claim 1  wherein the small-diameter carbon nanotubes span between more than one carbon nanotube particulate.  
     
     
         17 . The method of  claim 1  wherein the carbon particulates have a surface area in the range of about 10 m 2 /g and about 1000 m 2 /g.  
     
     
         18 . The method of  claim 1  wherein the carbon particulates have a surface area in the range of about 100 m 2 /g and about 1000 m 2 /g.  
     
     
         19 . The method of  claim 1  wherein the small-diameter carbon nanotubes in the carbon nanotube particulates comprise ropes of small-diameter carbon nanotubes.  
     
     
         20 . The method of  claim 19  wherein the ropes have a cross-sectional dimension in the range of about 10 nm and about 50 nm.  
     
     
         21 . The method of  claim 19  wherein the ropes have a cross-sectional dimension of less than 10 nm.  
     
     
         22 . The method of  claim 1  wherein the carbon nanotube particulates comprise small-diameter carbon nanotubes having more than about 10 small-diameter carbon nanotubes/μm surface area of the carbon nanotube particulates.  
     
     
         23 . The method of  claim 1  further comprising annealing the carbon nanotube particulates to form annealed carbon nanotube particulates.  
     
     
         24 . The method of  claim 23  wherein the annealing is done by heating the carbon nanotube particulates in nitrogen or an inert gas environment at a temperature between about 800° C. and 1500° C. for a time in the range of about 1 and about 24 hours.  
     
     
         25 . The method of  claim 23  wherein the annealed carbon nanotube particulates are stable in air at a temperature greater than about 400° C.  
     
     
         26 . The method of  claim 23  wherein the annealed carbon nanotube particulates are stable in air at a temperature greater than about 450° C.  
     
     
         27 . The method of  claim 23  wherein the annealed carbon nanotube particulates are stable in air at a temperature greater than about 500° C.  
     
     
         28 . The method of  claim 23  wherein the annealed carbon nanotube particulates are stable in air at a temperature greater than about 550° C.  
     
     
         29 . The method of  claim 1  wherein the carbon nanotube particulates are blended with a matrix material selected from the group consisting of thermoplastic polymers, thermoset polymers, metals, ceramics, and combinations thereof.  
     
     
         30 . The method of  claim 1  wherein the carbon nanotube particulates are blended with a matrix material that comprises a polymer.  
     
     
         31 . The method of  claim 1  further comprising derivatizing the carbon nanotubes to form derivatized carbon nanotubes.  
     
     
         32 . The method of  claim 31  wherein the derivatized carbon nanotubes are fluorinated carbon nanotubes.  
     
     
         33 . The method of  claim 31  wherein the derivatized carbon nanotubes comprise one or more functional groups.  
     
     
         34 . The method of  claim 31  wherein the carbon nanotube particulates comprising the derivatized carbon nanotubes are blended with a matrix material selected from the group consisting of thermoplastic polymers, thermoset polymers, metals, ceramics, and combinations thereof  
     
     
         35 . The method of  claim 32  wherein the carbon nanotube particulates comprising the fluorinated carbon nanotubes are blended with a matrix material selected from the group consisting of thermoplastic polymers, thermoset polymers, metals, ceramics, and combinations thereof  
     
     
         36 . The method of  claim 33  wherein the carbon nanotube particulates comprising the derivatized carbon nanotubes comprising one or more functional groups are blended with a matrix material selected from the group consisting of thermoplastic polymers, thermoset polymers, metals, ceramics, and combinations thereof.  
     
     
         37 . A carbon nanotube particulate comprising a plurality of small-diameter carbon nanotubes arranged in a 3-dimensional network in the carbon nanotube particulate, wherein the carbon nanotube particulate has a cross-sectional dimension of less than about 1000 microns and wherein the small-diameter carbon nanotubes have a diameter in the range of about 0.5 nm and about 3 nm.  
     
     
         38 . The carbon nanotube particulate of  claim 37  wherein the small-diameter carbon nanotubes are selected from the group consisting of single-walled carbon nanotubes, double-walled carbon nanotubes, triple-walled carbon nanotubes, quadruple-walled carbon nanotubes and combinations thereof.  
     
     
         39 . The carbon nanotube particulate of  claim 37  wherein the carbon nanotube particulate has a bulk density in a range of about 0.01 g/cm 3  and about 0.5 g/cm 3 .  
     
     
         40 . The carbon nanotube particulate of  claim 37  wherein the carbon nanotube particulate has a cross-sectional dimension in the range of about 0.1 micron and about 1000 microns.  
     
     
         41 . The carbon nanotube particulate of  claim 37  wherein the carbon nanotube particulate has a cross-sectional dimension in the range of about 1 micron and about 100 microns.  
     
     
         42 . The carbon nanotube particulate of  claim 37  wherein the small-diameter carbon nanotubes span between more than one carbon nanotube particulate.  
     
     
         43 . The carbon nanotube particulate of  claim 37  wherein the carbon nanotube particulate has a surface area in the range of about 100 m2/ g and about 1000 m 2 /g.  
     
     
         44 . The carbon nanotube particulate of  claim 37  wherein the carbon nanotube particulate comprises ropes of small-diameter carbon nanotubes.  
     
     
         45 . The carbon nanotube particulate of  claim 44  wherein the ropes have a cross-sectional dimension in a range of about 10 nm and about 50 nm.  
     
     
         46 . The carbon nanotube particulate of  claim 44  wherein the ropes have a cross-sectional dimension less than 10 nm.  
     
     
         47 . The carbon nanotube particulate of  claim 37  wherein the carbon nanotube particulate is annealed to form an annealed carbon nanotube particulate.  
     
     
         48 . The carbon nanotube particulate of  claim 47  wherein the annealed carbon nanotube particulate is stable in air at a temperature greater than about 400° C.  
     
     
         49 . The carbon nanotube particulate of  claim 47  wherein the annealed carbon nanotube particulate is stable in air at a temperature in excess of about 450° C.  
     
     
         50 . The carbon nanotube particulate of  claim 47  wherein the annealed carbon nanotube particulate is stable in air at a temperature in excess of about 500° C.  
     
     
         51 . The carbon nanotube particulate of  claim 47  wherein the annealed carbon nanotube particulate is stable in air at a temperature in excess of about 550° C.  
     
     
         52 . The carbon nanotube particulate of  claim 37  wherein a plurality of carbon nanotube particulates are present in a matrix material, wherein the plurality of carbon nanotube particulates is present at a concentration in the range of about 0.001 wt % and about 50 wt %.  
     
     
         53 . The carbon nanotube particulate of  claim 52  wherein the matrix material is selected from the group consisting of thermoplastic polymers, thermoset polymers, metals, ceramics, and combinations thereof  
     
     
         54 . The carbon nanotube particulate of  claim 37  wherein a plurality of carbon nanotube particulates are present in a matrix material comprising a polymer, wherein the plurality of carbon nanotube particulates is present at a concentration in a range of about 0.001 wt % and about 50 wt %.  
     
     
         55 . The carbon nanotube particulate of  claim 37  wherein the carbon nanotubes are derivatized carbon nanotubes.  
     
     
         56 . The carbon nanotube particulate of  claim 37  wherein the carbon nanotubes are fluorinated carbon nanotubes.  
     
     
         57 . The carbon nanotube particulate of  claim 55  wherein the derivatized carbon nanotubes comprise one or more functional groups.  
     
     
         58 . The carbon nanotube particulate of  claim 55  wherein the carbon nanotube particulates comprising the derivatized carbon nanotubes are in a composite material comprising a matrix material selected from the group consisting of thermoplastic polymers, thermoset polymers, metals, ceramics, and combinations thereof.  
     
     
         59 . The carbon nanotube particulate of  claim 56  the carbon nanotube particulates comprising the fluorinated carbon nanotubes are in a composite material comprising a matrix material selected from the group consisting of thermoplastic polymers, thermoset polymers, metals, ceramics, and combinations thereof.  
     
     
         60 . The carbon nanotube particulate of  claim 57  wherein the carbon nanotube particulates comprising the derivatized carbon nanotubes comprising one or more functional groups are in a composite material comprising a matrix material selected from the group consisting of thermoplastic polymers, thermoset polymers, metals, ceramics, and combinations thereof.  
     
     
         61 . The carbon nanotube particulate of  claim 37  wherein the particulate is present in a field emission device.  
     
     
         62 . The carbon nanotube particulate of  claim 37  wherein the particulate is present in a cathode of a field emission device.  
     
     
         63 . A method for producing carbon nanotube particulates, comprising: 
 (a) providing a catalyst comprising catalytic metal on a particulate support, wherein the particulate support has a cross-sectional dimension of less than about 1000 microns, and    (b) contacting the catalyst with a gaseous stream comprising a carbon-containing feedstock at a sufficient temperature and for a contact time sufficient to make a carbon product on the catalyst wherein the carbon product comprises carbon nanotube particulates wherein the carbon nanotube particulates comprise small-diameter carbon nanotubes, wherein the small-diameter carbon nanotubes have a outer diameter in the range of about 0.5 nm and about 3 nm.    
     
     
         64 . The method of  claim 63  further comprising removing the particulate support from the carbon product comprising the carbon nanotube particulates wherein the carbon nanotube particulates have a macroscopic morphology of an approximate shape as the particulate support and an approximate cross-sectional dimension as the particulate support.  
     
     
         65 . The method of  claim 63  wherein the small-diameter carbon nanotubes are selected from the group consisting of single-wall carbon nanotubes, double-wall carbon nanotubes, triple-wall carbon nanotubes, quadruple-wall carbon nanotubes and combinations thereof.  
     
     
         66 . The method of  claim 63  wherein the particulate support comprises a material selected from the group consisting of zeolite, silica, alumina, zirconia, magnesia and combinations thereof.  
     
     
         67 . The method of  claim 63  wherein the particulate support comprises magnesia.  
     
     
         68 . The method of  claim 63  wherein the catalytic metal comprises at least one element selected from the group consisting of chromium, molybdenum, tungsten, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, a lanthanide series element, an actinide series element, and combinations thereof.  
     
     
         69 . The method of  claim 63  wherein the catalytic metal comprises iron.  
     
     
         70 . The method of  claim 63  wherein the catalytic metal comprises iron and molybdenum.  
     
     
         71 . The method of  claim 63  wherein the particulate support has a cross-sectional dimension in a range of about 0.1 micron and about 1000 microns.  
     
     
         72 . The method of  claim 63  wherein the particulate support has a cross-sectional dimension in a range of about 1 micron and about 100 microns.  
     
     
         73 . The method of  claim 63  wherein the small-diameter carbon nanotubes are present in the small-diameter carbon nanotube particulates in an amount greater than about 50 wt % of a total weight of the carbon product.  
     
     
         74 . The method of  claim 63  wherein the small-diameter carbon nanotubes are present in the small-diameter carbon nanotube particulates in an amount greater than about 80 wt % of a total weight of the carbon product.  
     
     
         75 . The method of  claim 63  wherein the small-diameter carbon nanotubes are present in the small-diameter carbon nanotube particulates in an amount greater than about 90 wt % of a total weight of the carbon product.  
     
     
         76 . The method of  claim 63  wherein the small-diameter carbon nanotubes span between more than one carbon nanotube particulate.  
     
     
         77 . The method of  claim 63  wherein the small-diameter carbon nanotubes in the carbon nanotube particulates comprise ropes of small-diameter carbon nanotubes.  
     
     
         78 . The method of  claim 78  wherein the ropes have a cross-sectional dimension in the range of about 10 nm and about 50 nm.  
     
     
         79 . The method of  claim 78  wherein the ropes have a cross-sectional dimension of less than 10 nm.  
     
     
         80 . The method of  claim 64  further comprising annealing the carbon nanotube particulates to form annealed carbon nanotube particulates.  
     
     
         81 . The method of  claim 80  wherein the annealing is done by heating the carbon nanotube particulates in nitrogen or an inert gas environment at a temperature between about 800° C. and 1500° C. for a time in the range of about 1 hour and about 24 hours.  
     
     
         82 . The method of  claim 80  wherein the annealed carbon nanotube particulates are stable in air at a temperature greater than about 400° C.  
     
     
         83 . The method of  claim 80  wherein the annealed carbon nanotube particulates are stable in air at a temperature greater than about 450° C.  
     
     
         84 . The method of  claim 80  wherein the annealed carbon nanotube particulates are stable in air at a temperature greater than about 500° C.  
     
     
         85 . The method of  claim 80  wherein the annealed carbon nanotube particulates are stable in air at a temperature greater than about 550° C.  
     
     
         86 . The method of  claim 64  wherein the carbon nanotube particulates are blended with a matrix material selected from the group consisting of thermoplastic polymers, thermoset polymers, metals, ceramics, and combinations thereof.  
     
     
         87 . The method of  claim 64  wherein the carbon nanotube particulates are blended with a matrix material that comprises a polymer.  
     
     
         88 . The method of  claim 64  further comprising derivatizing the carbon nanotubes to form derivatized carbon nanotubes.  
     
     
         89 . The method of  claim 88  wherein derivatized carbon nanotubes are fluorinated carbon nanotubes.  
     
     
         90 . The method of  claim 88  wherein the derivatized carbon nanotubes comprise one or more functional groups.  
     
     
         91 . The method of  claim 88  wherein the carbon nanotube particulates comprising the derivatized carbon nanotubes are blended with a matrix material selected from the group consisting of thermoplastic polymers, thermoset polymers, metals, ceramics, and combinations thereof  
     
     
         92 . The method of  claim 89  wherein the carbon nanotube particulates comprising the fluorinated carbon nanotubes are blended with a matrix material selected from the group consisting of thermoplastic polymers, thermoset polymers, metals, ceramics, and combinations thereof  
     
     
         93 . The method of  claim 90  wherein the carbon nanotube particulates comprising the derivatized carbon nanotubes comprising one or more functional groups are blended with a matrix material selected from the group consisting of thermoplastic polymers, thermoset polymers, metals, ceramics, and combinations thereof.  
     
     
         94 . A product of the process, comprising: 
 (a) providing a catalyst comprising catalytic metal on a particulate support, wherein the particulate support has a cross-sectional dimension of less than about 1000 microns,    (b) contacting the catalyst with a gaseous stream comprising a carbon-containing feedstock at a sufficient temperature and for a contact time sufficient to make a carbon product on the catalyst wherein the carbon product comprises small-diameter carbon nanotubes, wherein the small-diameter carbon nanotubes have a outer diameter in the range of about 0.5 nm and about 3 nm, and    (c) removing the particulate support from the carbon product to form carbon nanotube particulates, wherein the carbon nanotube particulates retain a macroscopic morphology of an approximate shape and an approximate cross-sectional dimension as before removal of the particulate support.    
     
     
         95 . The product of  claim 94  further comprising annealing the carbon nanotube particulates.  
     
     
         96 . The product of  claim 94  wherein the small-diameter carbon nanotubes are selected from the group consisting of single-walled carbon nanotubes, double-walled carbon nanotubes, triple-walled carbon nanotubes, quadruple-walled carbon nanotubes and combinations thereof.