Carbon nanotube particulates, compositions and use thereof

a carbon nanotube and particulate technology, applied in the manufacture of electrode systems, metal/metal-oxide/metal-hydroxide catalysts, electric discharge tubes/lamps, etc., can solve the problems of increasing defects, -wall carbon nanotubes, 4 nm, and the lik

Inactive Publication Date: 2005-01-06
UNIDYM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0015] In another embodiment, an carbon nanotube particulate electron emitter comprises a carbon nanotube particulate on a surface wherein the carbon nanotube particulate comprises entangled small-diameter carbon nanotubes wherein the small-diameter nanotubes have an outer diameter in a range of about 0.5 nm and about 3 nm, wherein the carbon nanotube particulate has a cross-sectional dimension in a range of about 0.1 micron and about 100 microns, preferably in the range of about 0.1 micron and about 3 microns. The 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. The carbon nanotube particulate emitter is suitable for use as a cathode component in field emission devices.

Problems solved by technology

However, as the number of walls increases, so does the number of defects.
Because single-wall carbon nanotubes generally cannot accommodate defects during growth, they typically have very few defects.
Large multi-wall carbon nanotubes, with diameters greater than about 4 nm, tend to have an increasing number of defects and decreasing electrical conductivity and tensile strength.

Method used

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  • Carbon nanotube particulates, compositions and use thereof
  • Carbon nanotube particulates, compositions and use thereof
  • Carbon nanotube particulates, compositions and use thereof

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0099] 0.40 g iron (III) nitrate nonahydrate, (Fe(NO3)3·9H2O) (Mol. Wt. 404.02), 0.0365 g ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O24·4H2O), 10 g magnesium nitrate hexahydrate (Mg(NO3)2·6H2O), and 4 g anhydrous citric acid were dissolved in a 500-ml beaker with 10 mls deionized water. As soon as a clear solution was formed, the beaker was placed in a high temperature furnace preheated at 650° C. A sudden drop in furnace temperature was observed. In a few minutes the solution foamed and a large quantity of light yellow fluffy flakes filled the beaker. The furnace temperature was reduced to 550° C. and the catalyst was held at 550° C. for 60 minutes. The catalyst was removed from the furnace and placed in a desiccator. With aid of a blender, the catalyst flakes were readily ground to fine flowing powder. The physical characteristics of the catalyst powder were small primary particle size (3). The chemical composition of the resulting catalyst was: 3.5 wt % Fe and 1.3 wt % Mo. I...

example 2

[0103] This example demonstrates the production of small-diameter carbon nanotubes using the catalyst of Example 1 treated with a sulfur-containing compound.

[0104] 1 g catalyst, as prepared in Example 1, was placed in a fluidized bed reactor. The reactor was purged with argon gas (flow rate: 150 sccm) and the temperature was increased at a rate of 20° C. / min to 500° C. At 500° C., thiophene (C4H4S, Acros) was introduced to the catalyst by passing the argon through thiophene held at room temperature for 10 minutes. After thiophene treatment, the reactor temperature was raised to 850° C. under an argon purge. At 850° C., the argon was turned off and methane (CH4. Matheson) was introduced for 10 minutes to grow nanotubes. After the 10 minutes of growth reaction, the methane was turned off and argon was turned on. The reactor was cooled to room temperature under an argon purge. The resulting material retrieved from the reactor was dark black powder. The growth of SWNT, as measured by T...

example 3

[0108] This example demonstrates the growth of small-diameter carbon nanotubes using a catalyst with a different iron and molybdenum composition. 1.1 g iron nitrate nonahydrate (Fe(NO3)3·9H2O), 0.028 g ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O24·4H2O), 20 g magnesium nitrate hexahydrate (Mg(NO3)2·6H2O). and 6 g anhydrous citric acid were dissolved in 20 ml deionized water in a 500-ml beaker. The rest of the preparation procedure was identical to Example 1. The catalyst metal composition of the resulting catalyst was 4.8 wt % Fe and 0.48 wt % Mo. The physical properties were similar those of the catalyst in Example 1.

[0109] 1 g catalyst was placed in a fixed fluidized bed reactor. The reactor was first purged with argon gas (flow rate: 150 sccm) and the temperature was increased at a rate of 20° C. / min to 850° C. At 850° C., the argon was turned off and methane (CH4) was turned on for 10 minutes and then turned off. The reactor was cooled to room temperature under an argon pu...

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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.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priority from United States provisional application, Ser. Nos. 60 / 429,233 and 60 / 429,264, both filed Nov. 26, 2002, which applications are both incorporated herein by reference.FIELD OF THE INVENTION [0002] This invention relates generally to a method for making carbon nanotube particulates, compositions and uses thereof. BACKGROUND OF THE INVENTION [0003] Carbon nanotubes are a novel form of carbon. Single-wall carbon nanotubes are hollow, tubular fullerene molecules consisting essentially of sp2-hybridized carbon atoms typically arranged in hexagons and pentagons. Single-wall carbon nanotubes typically have diameters in the range between about 0.5 nanometers (nm) and about 3.5 nm, and lengths usually greater than about 50 nm. They are known for their excellent electrical and thermal conductivity and high tensile strength. Since their discovery in 1993, there has been substantial research to describe their proper...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B01J23/881B01J23/887B01J35/00B01J35/02C01B31/02C23C16/26C23C16/44D01F9/12H01J1/00H01J1/304H01J9/02H01J29/48
CPCB01J23/881Y10S977/752B01J35/0026B01J35/023B82Y10/00B82Y30/00B82Y40/00C01B31/0233C01B31/0253C01B2202/02C01B2202/04C01B2202/06C01B2202/34C01B2202/36C23C16/26C23C16/4417H01J1/3048H01J9/025H01J29/481H01J2201/30469B01J23/8872C01B32/162C01B32/168
Inventor MCELRATH, KENNETH O.YANG, YUEMEISMITH, KENNETH A.HU, XIAODONG
Owner UNIDYM
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