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Methods of oxidizing multiwalled carbon nanotubes

a carbon nanotube and multi-walled technology, applied in carbon nanotubes, inorganic chemistry, electrolytic capacitors, etc., can solve the problems of graphite and carbon black poor predictors of nanotube chemistry, fibrils have also been oxidized non-uniformly, and no practical significance, etc., to achieve enhanced electrochemical characteristics

Inactive Publication Date: 2005-01-06
HYPERION CATALYSIS INT
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0052] Electrochemical capacitors assembled from electrodes made from the oxidized multiwalled carbon nanotubes of the invention exhibit enhanced electrochemical characteristics, such as specific capacitance.

Problems solved by technology

The differences make graphite and carbon black poor predictors of nanotube chemistry.
Fibrils have also been oxidized non-uniformly by treatment with nitric acid.
These compounds were not isolated and are, unlike the derivatives described herein, of no practical significance.
There are many drawbacks associated with the methods now available to provide oxidized carbon nanotubes.
For example, one disadvantage of using strong acid treatment is the generation of environmentally harmful wastes.
Treating such wastes increases the production costs of the products in which oxidized nanotubes can be used, such as electrodes and capacitors.

Method used

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  • Methods of oxidizing multiwalled carbon nanotubes
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  • Methods of oxidizing multiwalled carbon nanotubes

Examples

Experimental program
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Effect test

example 1

Oxidation of Carbon Nanotubes With Gas Phase CO2

[0150] Oxidized carbon nanotubes were prepared by using CO2 in the gaseous phase. About 10 grams of carbon nanotubes were placed into a reactor as shown in FIG. 1. The reactor was a heated quartz tube having a reacting chamber connected at each end to a side tube. The reacting chamber had an outside diameter of about 3 inches and each side tube has an outside diameter of about 1 inch. Between the side tube at the bottom side and the reacting chamber there was a gas permeable porous quartz plate, which supports a bed of carbon nanotubes prepared as described in U.S. application Ser. No. 08 / 459,534 filed on Jun. 2, 1995.

[0151] A stream of gaseous CO2 was continuously passed down through the bed of carbon nanotubes at a rate of about 120 cc / min for 2 hours at about 800° C.

[0152] The degree of oxidation was measured by the weight loss exhibited by the carbon nanotubes; a weight loss of about 10% was recorded. The carbon nanotubes oxidiz...

example 2

Oxidation of Carbon Nanotubes With Wet-air

[0153] Carbon nanotubes were oxidized by using wet air. About 10 grams of carbon nanotubes prepared according to U.S. application Ser. No. 08 / 459,534 filed on Jun. 2, 1995 were charged into the reactor described in Example 1.

[0154] Air saturated with water vapor at room temperature was continuously passed down through the bed of carbon nanotubes at a rate of about 120 cc / min. The temperature of the reactor, measured by a k-type thermocouple positioned inside the bed of carbon nanotubes, was set at 530° C. The degree of oxidation was controlled by variation of the reaction duration and monitored by weight loss, compared to the initial weighted unoxidized carbon nanotubes. Three samples with weight losses of 7.1, 12.4, and 68% corresponding to 4, 5, and 8 hr oxidation, respectively, were prepared.

example 3

Oxidation of Carbon Nanotubes With Oxygen

[0155] Carbon nanotubes are oxidized by using oxygen in the gas phase. About 10 grams of carbon nanotubes prepared according to U.S. Ser. No. 08 / 459,534 filed on Jun. 2, 1995 are charged into a reactor as described in Example 1.

[0156] A stream of gaseous oxygen is continuously passed down through the bed of carbon nanotubes at a rate of about 120 cc / min for 2 hours at 600° C. The temperature of the reactor is measured by a k-type thermocouple positioned inside the bed of carbon nanotubes. The degree of oxidation is controlled by variation of the reaction duration and monitored by weight loss as compared to the initial weight of unoxidized carbon nanotubes. The resulting weight loss is about 10%. The carbon nanotubes oxidized in this manner disperse in water quite easily whereas they hardly do so prior to treatment with gaseous oxygen.

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Abstract

Methods of oxidizing multiwalled carbon nanotubes are provided. The multiwalled carbon nanotubes are oxidized by contacting the carbon nanotubes with gas-phase oxidizing agents such as CO2, O2, steam, N2O, NO, NO2, O3, and ClO2. Near critical and supercritical water can also be used as oxidizing agents. The multiwalled carbon nanotubes oxidized according to methods of the invention can be used to prepare rigid porous structures which can be utilized to form electrodes for fabrication of improved electrochemical capacitors.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of Invention [0002] The invention relates broadly to methods of oxidizing the surface of multiwalled carbon nanotubes. The invention also encompasses methods of making aggregates of surface-oxidized nanotubes, and using the same. The invention also relates to complex structures comprised of such surface-oxidized carbon nanotubes linked to one another. [0003] 2. Description of the Related Art [0004] Carbon Nanotubes [0005] This invention lies in the field of submicron graphitic carbon fibrils, sometimes called vapor grown carbon fibers or nanotubes. Carbon fibrils are vermicular carbon deposits having diameters less than 1.0μ, preferably less than 0.5μ, and even more preferably less than 0.2μ. They exist in a variety of forms and have been prepared through the catalytic decomposition of various carbon-containing gases at metal surfaces. Such vermicular carbon deposits have been observed almost since the advent of electron microscopy. (Baker...

Claims

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Application Information

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IPC IPC(8): C01B31/02D01F11/12H01G9/00H01G9/058H01G9/155H01M4/96
CPCB82Y30/00Y10T428/292C01B31/0233C01B31/0253C01B31/0273C01B2202/06C01B2202/28C01B2202/34C01B2202/36C04B35/6265C04B35/83C04B2235/5252C04B2235/5264C04B2235/5288D01F11/12D01F11/122D01F11/123H01G11/36H01M4/583H01M4/96Y02E60/50Y02E60/13Y10S977/847Y10T428/30B82Y40/00C01B32/162C01B32/168C01B32/174Y02P20/54Y02E60/10C01B2202/10
Inventor NIU, CHUNMINGMOY, DAVIDCHISHTI, ASIFHOCH, ROBERT
Owner HYPERION CATALYSIS INT
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