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Catalyst system for producing carbon fibrils
Inactive Publication Date: 2003-06-05
SUN XIAO DONG +2
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[0061] Once the above-mentioned catalysts are created, the catalysts may be used to synthesize carbon fibrils. The method commonly used to synthesize carbon fibrils may be a solid state reaction. The catalysts on the substrate are typically placed in a reaction chamber, such as a quartztube reactor, at a temperature in a range between about 300.degree. C. and about 1000.degree. C., and preferably in a range between about 400.degree. C. and about 700.degree. C. The elevated temperature in the reactor facilitates the synthesis of the carbon fibrils.
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However, Mandeville et al. and Moy et al. are ostensibly limited to iron catalysts and their binary alloys.
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example2
[0092] Catalysts were fabricated with six metals: iron, cobalt, aluminum, zinc, chromium, and yttrium on a quartz substrate. Solutions of high purity metal nitrates were used as metal precursors (the concentration of all nitrate solutions used herein was 1 molar). Once the precursors were deposited on the substrate, the precursors were annealed at 200.degree. C. for greater than 24 hours in a vacuum oven (pressure about 10 torr) to form catalysts. The catalysts were then loaded into a chemical vapor deposition reactor which was free of any volatile materials, pumped to high vacuum (less than 1 torr), and the reactor was flushed with a mixture of high purity (greater than 99.9%) hydrogen and high purity (greater than 99.9%) argon into the tube wherein the argon to hydrogen volume ratio was about 5:1. The flow rate was such that it took about 8 minutes to refresh the gas in the tube. The temperature was slowly ramped up from room temperature to 500.degree. C. The catalysts were anneal...
example 3
[0094] Using the method of Example 2, catalysts were fabricated with eight metals: copper, iron, zinc, nickel, aluminum, cobalt, yttrium, and chromium on a quartz substrate. The following catalysts were shown to produce carbon fibrils: copper and iron; and aluminum and cobalt.
example 4
[0095] Using the method of Example 2, catalysts were fabricated with eight metals: copper, iron, zinc, nickel, aluminum, cobalt, yttrium, and chromium on a quartz substrate. The following catalysts produced carbon fibrils: cobalt, iron and copper; nickel, iron and yttrium; copper, iron, cobalt, and aluminum; cobalt and copper; zinc, cobalt, chromium, and copper; yttrium, cobalt, nickel, and copper; cobalt, nickel and copper; nickel, chromium, and yttrium; cobalt, zinc and copper; zinc, yttrium, chromium, and nickel; aluminum, iron, and nickel; nickel, iron, yttrium, and aluminum; chromium and zinc; nickel and yttrium; and chromium, aluminum, and iron.
[0096] It is evident that with the vast array of elemental metals and metal alloys, there is a multitude of possible catalyst combinations. However, it was unexpectedly found that some iron combinations were ineffective catalysts for the production of carbon fibrils.
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Abstract
A catalyst system and method for making carbon fibrils is provided which comprises a catalytic amount of an inorganic catalyst comprising nickel and one of the following substances selected from the group consisting of chromium; chromium and iron; chromium and molybdenum; chromium, molybdenum, and iron; aluminum; yttrium and iron; yttrium, iron and aluminum; zinc; copper; yttrium; yttrium and chromium; and yttrium, chromium and zinc. In a further aspect of the invention, a catalyst system and method is provided for making carbon fibrils which comprises a catalytic amount of an inorganic catalyst comprising cobalt and one of the following substances selected from the group consisting of chromium; aluminum; zinc; copper; copper and zinc; copper, zinc, and chromium; copper and iron; copper, iron, and aluminum; copper and nickel; and yttrium, nickel and copper.
Description
[0001] This application claims priority from Provisional Application No. 60 / 127,038 entitled "New Catalysts for Synthesis of Carbon Fibrils," filed on Mar. 31, 1999 which is incorporated herein by reference.[0002] The present invention is related to a catalyst system for preparing carbon fibrils. More specifically, the invention is related to carbon fibrils and new catalysts which have been found useful for the synthesis of carbon fibrils.[0003] Carbon fibrils, also known as carbon nanotubes, are microscopic fibers of carbon which are either tubes or dense fibers (i.e. not hollow) with a typical diameter in a range between about 1 nanometer and about 500 nanometers. In particular, it is often preferable to synthesize carbon fibrils with a diameter in a range between about 10 nanometers and about 50 nanometers. The aspect ratio of length of the carbon fibril to the diameter of the carbon fibril is typically greater than about 100.[0004] Production of carbon fibrils is a well known sy...
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