# US 7,744,843 B2 · Methods for bulk synthesis of carbon nanotubes

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- Number: US 7,744,843 B2
- Document ID: US7744843B2
- Status: Granted
- Kind: B2
- Application number: 11/571,104
- Filed: 2005-06-15
- Published: 2008-09-11
- Granted: 2010-06-29
- Earliest claimed: 2004-06-21
- Assignees: Drexel University
- Inventors: Yury Gogotsi
- Web page: https://patentgrep.com/patent/US7744843B2

## CPC

- C01B 32/162: characterised by catalysts
- B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites
- B82Y 40/00: Manufacture or treatment of nanostructures
- C01B 2202/02: Single-walled nanotubes
- C01B 2202/34: Length
- C01B 2202/36: Diameter
- Y10S 977/842: for carbon nanotubes or fullerenes
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

Methods for synthesizing single-wall carbon nanotubes by extracting metals from a carbide by halogen treatment at a temperature ranging between 700 to 1700° C. at ambient or low pressure are provided.

## Claims

### Claim 1

A method for synthesizing single-wall carbon nanotubes comprising extracting metals from a carbide by halogen treatment at a temperature ranging between 700 to 1700° C. at ambient or low pressure.

### Claim 2 (depends on 1)

The method of claim 1 wherein the carbide does not comprise aluminum.

### Claim 3 (depends on 1)

The method of claim 1 wherein the carbide is a SiC.

### Claim 4 (depends on 1)

The method of claim 1 further comprising adding a platinum catalyst to the carbide during halogen treatment.

### Claim 5

A method for synthesizing carbon nanotubes, comprising:
extracting metal from a carbide substrate using one or more halogens at a temperature in the range of from about 700° C. to about 2000° C.; and
growing carbon nanotubes in a non-vacuum pressure environment on the substrate upon conversion of the carbide substrate into carbon.

### Claim 6 (depends on 5)

The method of claim 5, wherein the carbide substrate comprises a metal carbide.

### Claim 7 (depends on 5)

The method of claim 5, wherein the metal carbide comprises SiC, TiC, B4C, ZrC, YC2, Fe3C, or any combination thereof.

### Claim 8 (depends on 5)

The method of claim 5, wherein the halogen comprises Cl2, HCl, Br2, I2 , HBr, HI, or any combination thereof.

### Claim 9 (depends on 5)

The method of claim 5, wherein the concentration of the halogen in the non-vacuum pressure environment is in the range of from about 0.01% to about 100%.

### Claim 10 (depends on 5)

The method of claim 5, wherein the metal comprises Si, Ti, B, Zr, Y, Fe, or any combination thereof.

### Claim 11 (depends on 5)

The method of claim 5, wherein the metal is dissociated from the carbide substrate under equilibrium.

### Claim 12 (depends on 5)

The method of claim 5, wherein the metal carbide does not include aluminum.

### Claim 13 (depends on 5)

The method of claim 5, wherein the metal does not include aluminum.

### Claim 14 (depends on 5)

The method of claim 5, wherein extraction of the metal from the carbide substrate is performed by subjecting the carbide substrate to a flow of halogen.

### Claim 15 (depends on 14)

The method of claim 14, wherein the flow of halogen further comprises an inert carrier gas.

### Claim 16 (depends on 5)

The method of claim 5, wherein the substrate is heated to a temperature in the range of from about 700° C. to about 2000° C. in an inert gas environment, and the halogen is introduced to the inert gas environment when the temperature is reached.

### Claim 17 (depends on 5)

The method of claim 5, wherein the carbide substrate comprises TiC or ZrC, and the halogen comprises iodine.

### Claim 18 (depends on 5)

The method of claim 5, wherein the step of extracting metal gives rise to a porous carbon layer on the carbide substrate.

### Claim 19 (depends on 18)

The method of claim 18, wherein formation of the porous carbon layer gives rise to one-dimensional growth of the carbon nanotubes.

### Claim 20 (depends on 19)

The method of claim 19, wherein carbon nanotubes grow at a temperature in the range of from 800° C. to 2000° C.

### Claim 21 (depends on 20)

The method of claim 20, wherein the carbon nanotubes grow at a temperature in the range of from 800° C. to 1700° C.

### Claim 22 (depends on 21)

The method of claim 21, wherein the carbon nanotubes comprise single-wall carbon nanotubes.

### Claim 23 (depends on 20)

The method of claim 20, wherein the carbon nanotubes grow at a temperature in the range of from 1700° C. to 2000° C.

### Claim 24 (depends on 21)

The method of claim 21, wherein the carbon nanotubes comprise multi-wall carbon nanotubes.

### Claim 25 (depends on 5)

The method of claim 5, wherein the carbide substrate comprises metal impurities in ppm amounts, the metal impurities capable of catalyzing the growth of the carbon nanotubes.

### Claim 26 (depends on 5)

The method of claim 5, further comprising the step of removing all of the extracted metal.

### Claim 27 (depends on 5)

The method of claim 5, wherein the method further comprises the presence of a secondary catalyst.

### Claim 28 (depends on 27)

The method of claim 27, wherein the secondary catalyst comprises platinum, palladium, or any combination thereof.

### Claim 29 (depends on 27)

The method of claim 27, wherein the secondary catalyst is supplied through the gas phase to the growing nanotubes.

### Claim 30 (depends on 27)

The method of claim 27, wherein the secondary catalyst becomes positioned at the interface between the carbide substrate and the growing carbon nanotubes.

### Claim 31 (depends on 27)

The method of claim 27, wherein the carbon nanotubes grow at a temperature of less than 1500° C.

### Claim 32 (depends on 5)

The method of claim 5, wherein the growing carbon nanotubes gives rise to an ordered array of carbon nanotubes.

### Claim 33 (depends on 32)

The method of claim 32, wherein the ordered array of carbon nanotubes comprise an ordered array of single-wall carbon nanotubes.

### Claim 34 (depends on 33)

The method of claim 33, wherein each of the single-wall carbon nanotubes is characterized as ranging in size from about 0.7 nm to 1.7 nm.