LOW TEMPERATURE CNT GROWTH USING GAS-PREHEAT METHOD

• US 20100221424A1
• Filed: 02/26/2010
• Published: 09/02/2010
• Est. Priority Date: 02/27/2009
• Status: Active Grant

• Current Assignee: Applied NanoStructured Solutions, LLC (Cabot Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: MALECKI, Harry C., Shah, Tushar K.
• Granted Patent: US 8,580,342 B2
• Time in Patent Office: Days
• US Class Current: 427/249.100
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: C01B 2202/04 Nanotubes with a specific amount of walls
• CPC Class Codes: C01B 32/164 involving continuous processes

Abstract

A method for synthesizing carbon nanotubes (CNT) comprises the steps of providing a growth chamber, the growth chamber being heated to a first temperature sufficiently high to facilitate a growth of carbon nanotubes; and passing a substrate through the growth chamber; and introducing a feed gas into the growth chamber pre-heated to a second temperature sufficient to dissociate at least some of the feed gas into at least free carbon radicals to thereby initiate formation of carbon nanotubes onto the substrate.

Claims

1. A method for synthesizing carbon nanotubes (CNT) comprising the steps of:

providing a growth chamber, the growth chamber being heated to a first temperature sufficiently high to facilitate a growth of carbon nanotubes;

passing a substrate through the growth chamber; and

introducing a feed gas into the growth chamber pre-heated to a second temperature sufficient to dissociate at least some of the feed gas into at least free carbon radicals to thereby initiate formation of carbon nanotubes onto the substrate.

2. The method of claim 1 wherein the second temperature is higher than the first temperature.

3. The method of claim 1, further comprising controlling the first temperature in a range of from about 450°

C. to about 650°

C.

4. The method of claim 1, further comprising controlling the second temperature in a range of from about 550°

C. to about 1000°

C.

5. The method of claim 1 wherein the substrate is comprises at least one material selected from the group consisting of:

a carbon fiber, a graphite fiber, a cellulosic fiber, a glass fiber, a metal fiber, a ceramic fiber, an aramid fiber, and any combination thereof.

6. The method of claim 1 wherein the substrate is coated with at least one material selected from the group consisting of:

a catalyst, and a sizing.

7. The method of claim 1, further comprising introducing into the growth chamber a process gas along with the feed gas.

8. The method of claim 7, wherein the process gas and the feed gas are mixed and the mixture is heated to the second temperature before introduction into the growth chamber.

9. The method of claim 8, further comprising diffusing the heated mixture into the growth chamber.

10. The method of claim 7, wherein the feed gas is heated by heating the process gas to a temperature exceeding that of the second temperature T2, and then mixing with the feed gas at a temperature below T2 to raise the temperature of the feed gas to the second temperature.

11. A method for synthesizing carbon nanotubes (CNT) comprising the steps of:

providing a growth chamber, the growth chamber being heated to a first temperature;

passing a substrate through the growth chamber;

providing a feed gas pre-heated to a second temperature; and

introducing into the growth chamber the pre-heated feed gas wherein the second temperature is selected to achieve a desired temperature profile within the growth chamber to allow for the formation of carbon nanotubes on the substrate.

12. The method of claim 11 wherein the second temperature is within about 40% of the first temperature.

13. The method of claim 11 further comprising:

introducing into the growth chamber a process gas along with the feed gas.

14. The method of claim 13, wherein the process gas and the feed gas are mixed and the resulting mixture is heated to the second temperature before introduction into the growth chamber.

15. The method of claim 14, further comprising diffusing the heated mixture into the growth chamber.

16. The method of claim 13, wherein the feed gas is pre-heated by pre-heating the process gas to a temperature exceeding that of the second temperature T2, and then mixing with the feed gas to raise the temperature of the feed gas to the second temperature.

17. A system for synthesizing carbon nanotubes (CNT) comprising:

a growth chamber that receives a substrate having a catalyst disposed thereon;

a heater for heating the growth chamber to a first temperature, the first temperature sufficiently high to facilitate a growth of carbon nanotubes on the substrate; and

a gas pre-heater that heats a feed gas to a second temperature and introduces the feed gas into the growth chamber to synthesize carbon nanotubes on the substrate.

18. The system of claim 17 wherein the second temperature is sufficient to dissociate at least some of the feed gas into at least free carbon radicals.

19. The system of claim 17 wherein the second temperature is within about 40% of the first temperature and is sufficient to achieve a desired temperature profile within the growth chamber.

20. The system of claim 17, wherein the gas pre-heater comprises a heater external to the growth chamber that controllably heats the feed gas to the second temperature.

21. The system of claim 17, wherein the gas pre-heater comprises a heater external to the growth chamber that controllably heats a process gas to a temperature exceeding the second temperature;

and a diffuser having an input for receiving the heated process gas and an input for receiving the feed gas at a lower temperature and combining the heated process gas and the feed gas to provide a diffused output into the growth chamber including feed gas at the second temperature.

22. The system of claim 17, wherein the substrate comprises at least one material selected from the group consisting of:

a carbon fiber, a graphite fiber, a cellulosic fiber, a glass fiber, a metal fiber, a ceramic fiber, an aramid fiber, and any combination thereof.

23. The system of claim 17, further comprising a controller for controlling one or more of the rate at which the growth chamber receives the substrate, the first temperature, the second temperature, and the feed gas supply.

24. The system of claim 17, wherein the first temperature is in a range of from about 450°

C. to about 650°

C.

25. The method of claim 17, wherein the second temperature is in a range of from about 550°

C. to about 1000°

C.

26. The system of claim 17, wherein the substrate is a fiber tow having a sizing and an iron based catalyst thereon.

27. The system of claim 17, wherein the feed gas comprises at least one gas selected from the group consisting of:

acetylene, methanol, ethylene, methane, propane, benzene, and natural gas.

28. The system of claim 21, wherein the process gas comprises at least one gas selected from the group consisting of:

nitrogen, helium and argon.