Apparatus and method for manufacturing carbon nanotubes

Abstract

An apparatus for manufacturing carbon nanotubes is provided. The apparatus includes a reaction chamber having a first inlet configured for introducing a carbon-containing gas thereinto and a first outlet; a heater for elevating an interior temperature of the reaction chamber, wherein the reaction chamber is configured for accommodating a substrate and the first inlet defines a route for channeling the introduced carbon-containing gas toward the substrate, the route being substantially perpendicular to a main plane of the substrate.

Description

BACKGROUND

1. Technical Field

The present invention relates to carbon nanotubes, and more particularly to an apparatus and method for manufacturing carbon nanotubes by chemical vapor deposition (CVD).

2. Discussion of Related Art

Generally, it has been known that carbon nanotubes can be manufactured by methods including resistance heating, plasma discharge such as arc discharge with a carbon rod as a raw material, laser ablation, and chemical vapor deposition using acetylene gas.

Chemical vapor deposition is a method of generating carbon nanotubes by a chemical decomposition reaction of the carbon-containing gas, using acetylene gas, methane gas, or the like containing carbon as a raw material. The chemical vapor deposition depends on a chemical reaction occurring in the carbon-source gas as part of a thermal decomposition process, thereby enabling the manufacture of high-purity carbon nanotubes. As shown in FIG. 3, a typical CVD apparatus 10 includes a horizontally disposed quartz tube 30 configured to accommodate a substrate 20, upon which nanotubes can be grown. The quartz tube 30 has an inlet 32 and a corresponding outlet 34. The substrate 20 has a catalyst layer 22 formed on a top surface thereof. During nanotube growth, a flow of carbon-containing gas is horizontally provided to move along and inside the quartz tube 30, thereby bringing carbon elements contained in the gas to the substrate 20.

However, carbon nanotubes formed by the above-mentioned apparatus have shortcomings. During the manufacturing process, the direction of the gas flow is substantially parallel with the surface of the catalyst layer, while the nanotubes grow upwardly perpendicular to the catalyst layer 22. As such, although rather slow, the horizontal movement of the flow disturbs the growing process of the nanotubes and alters the vertical alignment of the carbon nanotubes.

Therefore, what is needed in the art is to provide an apparatus for manufacturing vertically aligned carbon nanotubes.

SUMMARY

In one aspect of the present invention, an apparatus for manufacturing carbon nanotubes is provided. The apparatus includes: a reaction chamber having a first inlet configured for introducing a carbon-containing gas thereinto, a first outlet, a heater for elevating an interior temperature of the reaction chamber, wherein the reaction chamber is configured for accommodating a substrate and the first inlet defines a route for channeling the introduced carbon-containing gas toward the substrate, the route being substantially perpendicular to a main plane of the substrate.

In another aspect of the present invention, a method for manufacturing carbon nanotubes is provided. The method includes the steps of: placing a substrate with a catalyst layer formed thereon in to a reaction chamber; introducing a carrier gas into the reaction chamber; heating the reaction chamber to a predetermined temperature; introducing a carbon-containing gas into the reaction chamber and directing the carbon-containing gas to flow toward to the substrate along a direction that is substantially perpendicular to a main plane of the substrate.

Detailed features of the present carbon nanotubes manufacturing apparatus will become more apparent from the following detailed description and claims, and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present apparatus and method can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present apparatus and method. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views, wherein:

FIG. 1A is a schematic cross-sectional view of an apparatus for manufacturing carbon nanotubes according to a first exemplary embodiment.

FIG. 1B is a schematic cross-sectional view of a substantially cube-shaped reaction chamber of the apparatus illustrated in FIG. 1A.

FIG. 1C is a schematic cross-sectional view of a semi-cone reaction chamber of an apparatus for manufacturing carbon nanotubes according to a second embodiment.

FIG. 1D is a schematic cross-sectional view of a hemispherical reaction chamber of an apparatus for manufacturing carbon nanotubes according to a third embodiment.

FIG. 2A is a schematic cross-sectional view of an apparatus for manufacturing carbon nanotubes according to a fourth exemplary embodiment.

FIG. 2B is a schematic cross-sectional view of a reaction chamber with a inverted-funnel shaped gas guiding member of the apparatus illustrated in FIG. 2A.

FIG. 2C is a schematic cross-sectional view of a reaction chamber with a hemispherical gas guiding member of an apparatus for manufacturing carbon nanotubes according to a fifth embodiment.

FIG. 3 is a schematic cross-sectional view of a typical apparatus for manufacturing carbon nanotubes.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made to the drawings to describe the preferred embodiments of the present apparatus for manufacturing carbon nanotubes, in detail.

Referring now particularly to FIG. 1A, where an apparatus 40 for manufacturing carbon nanotubes according to a first embodiment of the present invention is shown. The apparatus 40 mainly includes a reaction chamber 60 and a heater 70. A substrate 50 is disposed in the reaction chamber 60. The heater 70 is configured for heating the interior of the reaction chamber 60.

The substrate 50 has a catalyst layer 52 formed on a top surface thereof. The substrate 50 is made of a material selected from a group consisting of quartz, silicon, and magnesium oxide. The material of the catalyst layer 52 is selected from a group consisting of cobalt, nickel, iron, and any appropriate alloy of them.

In the first embodiment, the reaction chamber 60 is a cubic chamber as shown in FIG. 1B. Alternately, the reaction chamber 60 could have other shapes, i.e., substantially semi-conical in a second embodiment or hemispheric in a third embodiment, as shown in FIG. 1C and FIG. 1D respectively. Referring to FIG. 1B, the reaction chamber 60 has a first inlet 62 and a first outlet 64. The first inlet 62 is configured in a top of the reaction chamber 60 spatially corresponding to the substrate 50. The first outlet 64 is configured to be adjacent to a bottom of the reaction chamber 60. Alternately, the first outlet 64 could also be formed at the bottom of the reaction chamber 60.

Additionally, the reaction chamber 60 is received in a quartz tube 80 that has a second inlet 82 at one end portion and a second outlet 84 at another end portion. The second inlet 82 is in communication with the first inlet 62 and the second outlet 84 is in communication with the first outlet 64. In the illustrated exemplary embodiment, the second inlet 82 is in communication with the first inlet 62 via a gas guiding pipe 86.

The heater 70 can be any type of heating device that is adapted for heating the reaction chamber 60, for example a high temperature furnace or a high frequency induction heating furnace can be used.

In another aspect of the present invention, a method for manufacturing carbon nanotubes comprises the steps in no particular order of:

• (1) placing a substrate 50 that with has a catalyst layer 52 formed thereon in to a reaction chamber 60;
• (2) introducing a carrier gas into the reaction chamber 60;
• (3) heating the reaction chamber 60 to a predetermined temperature;
• (4) introducing a carbon-containing gas into the reaction chamber 60 and directing the carbon-containing gas to flow toward to the substrate 50 along a direction that is substantially perpendicular to a main plane of the substrate 50.

In step (1), the substrate 50 with a catalyst layer 52 formed thereon is fed into the reaction chamber 60.

In step (2), a carrier gas is introduced into the reaction chamber 60. In the illustrated exemplary embodiment, the carrier gas is supplied to the second inlet 82, then the carrier gas is transported successively passing through the gas guiding pipe 86, the first inlet 62. Thereafter, the carrier gas is discharged into the reaction chamber 60. The carrier gas is selected from the group consisting of hydrogen gas, nitrogen gas, ammonia gas, and similarly inert gases.

In step (3), the reaction chamber 60 is heated to a predetermined temperature by the heater 70. Specifically, the predetermined temperature is in the range from 500° C. to 900° C.

In step (4), the carbon-containing gas is introduced through the second inlet 82 for a certain time so as to grow carbon nanotubes on the substrate 50. The carbon-containing gas is selected from a group consisting of methane, ethane, ethylene, acetylene and similar carbon containing gases.

During the above-described process of manufacturing carbon nanotubes, the moving direction of the flow of carbon-containing gas is generally perpendicular to the surface of the catalyst layer, and is thus greatly advantageous for the vertical growth of carbon nanotubes. So the apparatus provided in the exemplary embodiment can be used to manufacture carbon nanotubes with high vertically oriented alignment.

An apparatus 400 according to the fourth embodiment, as shown in FIG. 2A, is described as follows. The apparatus 400 mainly includes a reaction chamber 600 and a heater 700. A substrate 500 is received and disposed in the reaction chamber 600. The heater 700 is configured for heating the interior of the reaction chamber 600.

Similar to the substrate 50 shown in FIG. 1A, the substrate 500 shown in FIG. 2A has a catalyst layer 520 formed on a top surface thereof. The substrate 500 is made of a material selected from a group consisting of quartz, silicon, and magnesium oxide. The material of the catalyst layer 520 is selected from a group consisting of cobalt, nickel, iron, and any appropriate alloy of them.

The reaction chamber 600 is a substantially cube-shaped chamber as shown in FIG. 2B. The reaction chamber 600 has a first inlet 620, a first outlet 640 and a gas guiding member 660. The first inlet 620 is configured at a top of the reaction chamber 600 and spatially corresponding to the substrate 500. The first outlet 640 is configured adjacent to a bottom of the reaction chamber 600. Alternately, the first outlet 640 can also be formed at the bottom of the reaction chamber 600. The gas guiding member 660 is a shell portion that has a shape of inverted-funnel as shown in FIG. 2B. The gas guiding member 660 comprises a narrow opening coupled to the first inlet 620 and an opposite wide opening spatially corresponding to the substrate 500. Alternately, the gas guiding member 660 could also be a shell portion having other shapes, for example, hemispherical in a fifth embodiment as shown in FIG. 2C.

Additionally, the reaction chamber 600 is received in a quartz tube 800 that has a second inlet 820 at one end portion and a second outlet 840 at another end portion. The second inlet 820 is in communication with the first inlet 620 and the second outlet 840 is in communication with the first outlet 640. In the illustrated exemplary embodiment, the second inlet 820 is in communication with the first inlet 620 via a gas guiding pipe 860.

The heater 700 can be any type of heating device that is adapted for heating the reaction chamber 600, for example, a high temperature furnace or a high frequency induction heating furnace.

While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Claims

1. An apparatus for manufacturing carbon nanotubes, the apparatus comprising:

a reaction chamber having a first inlet configured for introducing a carbon-containing gas thereinto, and a first outlet; and

a heater for elevating an interior temperature of the reaction chamber, wherein the reaction chamber is configured for accommodating a substrate and the first inlet defines a route for channeling the introduced carbon-containing gas toward the substrate, the route being substantially perpendicular to a main plane of the substrate.

2. The apparatus for manufacturing carbon nanotubes according to claim 1, wherein the reaction chamber has a shape selected from a group consisting of substantially semi-conical and hemispheric.

3. The apparatus for manufacturing carbon nanotubes according to claim 1, wherein the first inlet is configured at a top of the reaction chamber and spatially corresponding to the substrate, and the first outlet is configured adjacent to a bottom of the reaction chamber.

4. The apparatus for manufacturing carbon nanotubes according to claim 1, further comprising a gas guiding member for guiding the gas to flow perpendicularly toward the substrate.

5. The apparatus for manufacturing carbon nanotubes according to claim 4, wherein the gas guiding member comprises a inverted-funnel portion having

a narrow opening coupled to the first inlet and an opposite wide opening spatially corresponding to the substrate.

6. The apparatus for manufacturing carbon nanotubes according to claim 4, wherein the gas guiding member comprises a hemispherical portion having a narrow opening coupled to the first inlet and an opposite wide opening spatially corresponding to the substrate.

7. The apparatus for manufacturing carbon nanotubes according to claim 1, further comprising a quartz tube, wherein the reaction chamber is received in the quartz tube, the quartz tube has a second inlet in communication with the first inlet and a second outlet in communication with the first outlet.

8. The apparatus for manufacturing carbon nanotubes according to claim 7, further comprising a gas guiding pipe, wherein the second inlet is in communication with the first inlet via the gas guiding pipe.

9. The apparatus for manufacturing carbon nanotubes according to claim 7, wherein the quartz tube is received in the heater.

10. A method for manufacturing carbon nanotubes, the method comprising the steps of:

placing a substrate with a catalyst layer formed thereon in to a reaction chamber;

introducing a carrier gas into the reaction chamber;

heating the reaction chamber to a predetermined temperature;

introducing a carbon-containing gas into the reaction chamber and directing the carbon-containing gas to flow toward to the substrate along a direction that is substantially perpendicular to a main plane of the substrate.

11. The method for manufacturing carbon nanotubes according to claim 10, wherein the carrier gas is selected from the group consisting of hydrogen gas, nitrogen gas, ammonia gas, and the like inert gases.

12. The method for manufacturing carbon nanotubes according to claim 10, wherein the predetermined temperature is in the range from 500° C. to 900° C.

13. The method for manufacturing carbon nanotubes according to claim 10, wherein the carbon-containing gas is selected from a group consisting of methane, ethane, ethylene, acetylene and a combination thereof.