WO2004035881A2

WO2004035881A2 - Single-walled carbon nanotube synthesis method and apparatus

Info

Publication number: WO2004035881A2
Application number: PCT/KR2003/002114
Authority: WO
Inventors: Jeong-Ku Heo; Young-Hee Lee; Chan Kim; Cheol-Min Yang; Kay-Hyeok An; Seong-Chu Lim; Young-Sang Jo
Original assignee: Jeong-Ku Heo; Young-Hee Lee; Chan Kim; Cheol-Min Yang; Kay-Hyeok An; Seong-Chu Lim; Young-Sang Jo
Priority date: 2002-10-18
Filing date: 2003-10-14
Publication date: 2004-04-29
Also published as: AU2003269531A8; KR20030013351A; KR100733482B1; WO2004035881A3; AU2003269531A1; KR20050062775A

Abstract

Disclosed is a single-walled carbon nanotube synthesis method and apparatus, characterized in that a synthesis chamber of the carbon nanotube is divided into at least one first reaction chamber where a transition metal compound and hydrocarbon are fed and pyrolyzed, and a second reaction chamber where the pyrolyzed transition metal is dispersed, in which the second reaction chamber has a cross section wider than that of the at least one first reaction chamber, whereby the transition metal is rapidly dispersed from the first reaction chamber to the second reaction chamber. Thus, excessive growth of a catalytic transition metal due to re-combination of the transition metal is restrained, resulting in continuously preparing the single-walled carbon nanotube on a large scale.

Description

SINGLE- WALLED CARBON NANOTUBE SYNTHESIS METHOD AND

APPARATUS

Technical Field

The present invention relates to a method and apparatus for synthesizing a single- walled carbon nanotube by thermal decomposition.

Background Art

In general, a carbon nanotube (hereinafter, abbreviated to 'CNT') is composed of a graphite plate having a hexagonal honeycomb structure wound in the form of a tube, comprising only carbon atoms. The CNT has a diameter that can be up to tens of nm, and a length that can be up to hundreds of μm. When the tube is a single layer, such a tube is referred to as a single-walled CNT. Also, the tube having ones of to tens of layers is referred to as a multi-walled CNT. Such a nanotube was first discovered by S. Iihjima, Nature 354, 56 (1991). The CNT is advantageous in terms of long length, thin diameter, dynamic stability and high electroconductivity, and thus can be applied for field emission devices, high capacitors, secondary electrodes, etc. Further, it is easy to employ the CNT as a composite additive suitable for the increase of conductivity and tensile strength and the decrease of weight. Further, the CNT has an empty inner chamber, and thus research on gas adsorption and applications as storing materials using such a

CNT has been intensively performed.

The single-walled CNT has both properties as semiconductors and conductors according to chiral angles wound by the graphite plate, and therefore utilized as tera bite-grade memory materials. As the preparation methods of the CNT, there are techniques for arc- discharge and laser ablation experimented at laboratory level to study the characteristics and applications of the CNT, and pyrolysis of hydrocarbon for mass preparation of the CNT.

As for the arc-discharge method, the arc-discharge is caused by use of two carbon rods having different diameters, thus synthesizing the CNT.

However, since larger amounts of nano-materials and graphite fractions are produced as impurities, together with the CNT, the prepared CNT has low purity

(Y. H. Lee et al./Carbon Science Vol. 2, No. 2(2001) 122 and 123).

As for the laser ablation method, a test piece made by mixing a transition metal with graphite powders at a predetermined ratio is introduced into a quartz tube, and vaporized by an external laser, to synthesize the CNT. Such a laser ablation method is advantageous of the synthesis of the CNT having high purity, but suffers from low productivity (Y. H. Lee et al./Carbon Science Vol. 2, No. 2(2001) 123).

As for the pyrolysis method, liquid or gas hydrocarbon is fed into the heated reaction tube, along with the transition metal, after which the hydrocarbon is decomposed, to continuously synthesize the CNT in the gas state (Y. H. Lee et al./Carbon Science Vol. 2, No. 2(2001) 127). As such, the size of the transition metal is reported to determine the diameter of the CNT. Generally, in cases of the single-walled CNT, the diameter thereof is known to be not more than 5 nm (the multi-walled CNT has a diameter exceeding 5 nm). To synthesize the single- walled CNT, the size of a catalytic transition metal crystal should be in the range of about 10 nm. The size of the transition metal crystal depends on the dispersion rate of the decomposed transition metal atoms and the concentration of the transition metal decomposed per unit volume concentrated in the reaction chamber. However, it is difficult to control the dispersion rate and the concentration.

A conventional method of synthesizing the single-walled CNT by the pyrolysis is classified into a method of using a cooling rod schematically shown in FIG. 1 so that cooling water is passed through the inside of the reaction chamber, and a method of preparing a carbon nanotube by pyrolyzing carbon monoxide (CO) and pentacarbonyl, instead of hydrocarbon, disclosed in Korean Patent Application No. 10-2001-7003540 (hereinafter, called 'HIPCO process').

As for the using method of the cooling rod shown in FIG. 1 , when the transition metal compound is continuously fed into a reaction chamber 12 through a feeding nozzle 11, since the reaction chamber 12 is wholly heated by a heater 13, the decomposed transition metal is rapidly re-combined while the transition metal compound is decomposed at high temperatures (by increasing the density according to continuous feeding). Thus, it is difficult to maintain the size of the transition metal crystal at the level of 10 nm, thus decreasing the yield of the single-walled CNT. As well, with the intention of recovering the single- walled CNT collected on the cooling rod 14, there is required a separation and combination process of the cooling rod 14. Hence, technical limitations are imposed on mass production and continuous preparation process of the single- walled CNT.

In the HIPCO process, high pressure (5-10 atm) of carbon monoxide is used to disperse the transition metal (Y. H. Lee et al./Carbon Science Vol. 2, No.

2(2001) 128). However, such a HIPCO process is disadvantageous in that a device required for feeding the above carbon monoxide is difficult to manufacture, and such manufacturing costs are high, thus not realizing mass production of the single-walled CNT.

Disclosure of the Invention

Therefore, it is an object of the presenfinvention to solve the problems encountered in the related art and to provide a single-walled carbon nanotube synthesis method.

Another object of the present invention is to provide a single- walled carbon nanotube synthesis apparatus.

To achieve the above objects of the present invention, there is provided a single-walled carbon nanotube synthesis method, comprising feeding a transition metal compound and hydrocarbon into a reaction chamber; decomposing the transition metal compound and hydrocarbon by heating to induce synthesis of a single-walled carbon nanotube; dispersing the decomposed transition metal to induce continuous synthesis of the single-walled carbon nanotube; cooling the dispersed transition metal to be inactivated; and collecting the inactivated transition metal and the synthesized single-walled carbon nanotube.

The transition metal compound and hydrocarbon are heated at 1200- 2500°C, whereby they can be sufficiently decomposed even in a short period, thus increasing the synthesis yield of the single-walled carbon nanotube, which is related to decreasing a length of a first reaction chamber in the apparatus realizing the above method.

Preferably, the transition metal is dispersed under pressure lower than atmospheric pressure (760 Torr), and more preferably under pressure of 200-400 Torr. Thereby, the dispersion rate of the transition metal is properly controlled. In addition, the above synthesis method further includes the step of recovering the collected single-walled carbon nanotube, thus supporting the continuous synthesis of the single- alled carbon nanotube.

Further, a single-walled carbon nanotube synthesis apparatus for use in realizing the above synthesis method comprises a cylinder block, including at least one first reaction chamber to pyrolyze a transition metal compound and hydrocarbon, and a second reaction chamber having a cross section wider than that of the at least one first reaction chamber to disperse the pyrolyzed transition metal; a feeding nozzle to feed the transition metal compound and hydrocarbon into the first reaction chamber; a heater to heat the first reaction chamber; and a cooling unit to cool the second reaction chamber so that the transition metal is inactivated in the second reaction chamber, characterized in that the whole reaction chambers are not heated, and the dispersion of the pyrolyzed transition metal is induced, resulting in a continuously synthesized single-walled carbon nanotube.

The cooling unit functions to cool a wall of the second reaction chamber of the cylinder block, so that the inactivated transition metal and the synthesized single-walled carbon nanotube are attached to the wall of the second reaction chamber to be collected.

The cross section of the second reaction chamber is 1.5-1000 times as large as that of the first reaction chamber, therefore easily performing the dispersion of the transition metal.

The length of the first reaction chamber is not more than 50 cm, to restrain the synthesis of a multi-walled carbon nanotube in the first reaction chamber. This is concerned with the heating temperature of the first reaction chamber. That is, the length of the first reaction chamber is shortened and the heating temperature thereof is increased, whereby the transition metal compound and hydrocarbon minimally reside in the first reaction chamber while they are sufficiently decomposed therein. Thus, the synthesis of the multi-walled carbon nanotube due to the re-combination of the transition metal in the first reaction chamber is restrained, and the synthesis yield of the single-walled carbon nanotube increases.

Moreover, the above apparatus further includes a recovery unit to recover the single-walled carbon nanotube collected in the second reaction chamber.

Since the single-walled carbon nanotube is recovered immediately after being synthesized by the recovery unit, the apparatus acts to support the continuous synthesis of the single-walled carbon nanotube.

In addition, the apparatus has a pressure pump to maintain the pressure of the second reaction chamber to be lower than atmospheric pressure.

Brief Description of the Drawings

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic sectional view showing a conventional carbon nanotube synthesis apparatus; FIG. 2A is a schematic sectional view showing a single-walled carbon nanotube synthesis apparatus according to a first embodiment of the present invention;

FIG. 2B is a schematic sectional view showing a single- walled carbon nanotube synthesis apparatus according to a second embodiment of the present invention;

FIG. 2C is a schematic sectional view showing a single-walled carbon nanotube synthesis apparatus according to a third embodiment of the present invention; FIG. 3 is a flow chart showing a single-walled carbon nanotube synthesis method by use of the synthesis apparatus of FIG. 2C;

FIG. 4 is a graph showing a Raman spectrum data image of the single- walled carbon nanotube synthesized according to the present invention; and

FIG. 5 is a HRTEM photograph of the single-walled carbon nanotube synthesized according to the present invention.

Best Mode for Carrying Out the Invention

Reference should now be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components. FIG. 2A shows a single- walled carbon nanotube synthesis apparatus according to a first embodiment of the present invention, comprising a cylinder block 21 including a first reaction chamber 21a to pyrolyze a transition metal compound and hydrocarbon and a second reaction chamber 21b having a cross section wider than that of the first reaction chamber 21a to disperse the pyrolyzed transition metal. Further, the above apparatus includes a feeding nozzle 22 to feed the transition metal compound and hydrocarbon into the first reaction chamber 21a, a heater 23 to heat the first reaction chamber 21a, and a cooling unit 24 to cool a wall of the second reaction chamber 21b. In addition, a pressure pump 25 is contained to maintain the pressure in the second reaction chamber 21b to be lower than atmospheric pressure. The wall of the second reaction chamber 21b is cooled by the cooling unit 24, and thus acts as a collecting portion to collect the single-walled carbon nanotube attached thereto while the transition metal in the second reaction chamber 2 lb is inactivated.

The cooling unit 24 is used to circulate cooling water toward an outer surface of the wall of the second reaction chamber 21b. In the present embodiment, the cooling unit 24 functions to cool the entire wall of the second reaction chamber 21b of the cylinder block 21. Alternatively, the cooling unit 24 may act to cool the partial wall of the second reaction chamber 21b.

The cross section of the second reaction chamber 21b is 1.5-1000 times as large as that of the first reaction chamber 21a. Thus, it is easy to move and disperse the pyrolyzed hydrocarbon and transition metal compound and the re- combined materials in the first reaction chamber 21a into the second reaction chamber 21b.

A total length (A) of the first reaction chamber 21a is not more than 50 cm. While the fed transition metal compound and hydrocarbon are decomposed at high temperatures, such decomposed materials are quickly removed from the first reaction chamber 21a. Thereby, the synthesis of a multi-walled carbon nanotube due to re-combination of the transition metal in the first reaction chamber 21a is prevented. Hence, it is preferable that the first reaction chamber 21a is maintained at sufficiently high temperatures so that the transition metal compound and hydrocarbon fed through the feeding nozzle 22 are sufficiently decomposed in a short period. This principle remains the same as other embodiments described in FIGS. 2B and 2C, below.

FIG. 2B shows a single-walled carbon nanotube synthesis apparatus according to a second embodiment of the present invention. A cylinder block 31 includes two first reaction chambers 31a and one second reaction chamber 31b. As such, such two first reaction chambers 31a are connected in parallel to the second reaction chamber 31b. For mass synthesis, the above single-walled carbon nanotube synthesis apparatus includes a plurality of the first reaction chambers. That is, the first reaction chamber may be provided in at least one. As shown in FIG. 2B, the above apparatus further has a recovery unit to recover the carbon nanotube collected on the wall of the second reaction chamber 31b. The upper portion of the cylinder block 31 is structured to allow a piston 32 to move up and down, and the lower portion of the cylinder block 31 is provided with a recovery drum 33. When the piston 32 is moved downwardly, the carbon nanotube collected on the wall of the second reaction chamber 3 lb' is recovered into the recovery drum 33 by the piston 32. In FIG. 2B, the reference numeral 34 designates a heater to heat the first reaction chambers 31a, and the reference numeral 35 designates a feeding nozzle to feed the transition metal compound and hydrocarbon into the first reaction chambers 31a. Additionally, the numerals 36 and 37 indicate a pressure pump to maintain the pressure of the second reaction chamber 31b at a predetermined level, and a cooling unit to cool the wall of the second reaction chamber 31b of the cylinder block 31 , respectively.

FIG. 2C shows a single-walled carbon nanotube synthesis apparatus according to a third embodiment of the present invention. To recover the synthesized single-walled carbon nanotube, a rotary drum 42 is provided into a second reaction chamber 41b. While the rotary drum 42 is rotated about a rotating axis positioned to be vertical with respect to a paper surface of the drawing, it is structured to circulate cooling water therein. Thereby, an outer surface of the rotary drum 42 functions as a collecting portion to collect the inactivated transition metal and the synthesized single-walled carbon nanotube while cooling the second reaction chamber 41b. The carbon nanotube synthesized in the first reaction chamber 41a and the second reaction chamber 41b (as mentioned above, if the temperature of the first reaction chamber is sufficient high, the synthesis of the carbon nanotube is restrained in the first reaction chamber) is attached to the outer surface of the rotary drum 42, and then collected. In addition, a scrapper 32 is separately provided to separate the single- walled carbon nanotube from the outer surface of the rotary drum 42. Further, a recovery drum 44 to recover the single-walled carbon nanotube, which is separated by the scrapper 43 and then dropped downwards, is provided below the second reaction chamber 41b. In FIG. 2C, the reference numeral 41 indicates a cylinder block constituting the first reaction chamber 41a and the second reaction chamber 41b, and the reference numeral 45 indicates a feeding nozzle to feed hydrocarbon and a transition metal compound into the first reaction chamber 41a. In addition, the reference numeral 46 indicates a heater to heat the first reaction chamber 41a, and the numeral 47 indicates a pressure pump to maintain the pressure of the second reaction chamber 41b at a predetermined level.

The recovery unit shown in FIGS. 2B or 2C (32 and 33 of FIG. 2B, and 42, 43 and 44 of FIG. 2C) acts to continuously recover the collected single- walled carbon nanotube during the operation of the apparatus, thus supporting the continuous synthesis of the single-walled carbon nanotube.

FIG. 3 is a flow chart showing the method of synthesizing the single- walled carbon nanotube using the apparatus of FIG. 2C. Hereinafter, a detailed description will be given of the method of synthesizing the single-walled carbon nanotube with reference to FIGS. 2C and 3. In the present embodiment, iron (II) pentacarbonyl (Fe(CO)₅) and sulfur-containing thiophene (C₄H₄S) which serves to improve the synthesis yield of the carbon nanotube are used as a transition metal source and an additive, respectively. The above materials are mixed together at a predetermined ratio by weight (transition metahsulfur = 5:1-10:1), and then utilized in the form of solution. The mixed solution in the state of being vaporized through a bubbler along with C₂H₂ gas and inert Ar (or He gas) is fed into the first reaction chamber 41a by means of the feeding nozzle 45, in the operation 301.

The catalytic transition metal, the additive, and the C H₂ gas fed together are heated and decomposed while passing through the first reaction chamber 41a heated to 1200-2500°C by the heater 46, in the operation 302. Naturally, a predetermined amount of the single-walled carbon nanotube may be synthesized even in the first reaction chamber 41a.

While the decomposed catalytic transition metal atoms are moved from the first reaction chamber 41a to the second reaction chamber 41b, they are dispersed by the differences of, the cross section and the pressure between the first and second reaction chambers 41a and 41b, in the operation 303.

The transition metal compound and hydrocarbon fed through the feeding nozzle 45 are decomposed in the, first reaction chamber 41a, and the decomposed transition metal is re-combined in the first reaction chamber 41a and the second reaction chamber 41b, and thus recrystallized to the catalytic transition metal.

As such, the single-walled carbon nanotube is synthesized. As mentioned above, although the single- walled carbon nanotube may be synthesized in the first reaction chamber 41a, if the temperature of the first reaction chamber 41 is sufficiently high, the re-combination of the transition metal or the synthesis of the carbon nanotube in the first reaction chamber 41a are prevented. Thus, such recombination or synthesis is allowed to generate mainly in the second reaction chamber 41b.

More specifically, the catalytic transition metal grows to the size suitable for the synthesis of the single-walled carbon nanotube, that is, about 10 nm or less, by the re-combination. Thereby, carbon atoms decomposed from the carbon source are synthesized to the single-walled carbon nanotube.

The temperature required for complete decomposition of the hydrocarbon and transition metal compound is 600°C. Thus, if the temperature of the first reaction chamber 41a is at least 600°C, the feeding materials are decomposed. However, at the temperatures below 1200°C, the transition metal moved to the second reaction chamber 41b is quickly cooled and inactivated, thus decreasing the synthesis yield of the single-walled carbon nanotube in the second reaction chamber 41b. Hence, the temperature of the first reaction chamber 41a should be preferably maintained at 1200°C or higher. The higher the temperature of the first reaction chamber 41 a, the more favorable the synthesis of the single-walled carbon nanotube. However, it is difficult to prepare the heater 46 for use in heating the first reaction chamber 41a to high temperatures, and the apparatus may disorder due to expansion of a conductor. In cases of using a heater using tungsten, the temperature of the first reaction chamber 41a may be maintained up to about 2500°C.

The catalytic transition metal concerned with the synthesis of the carbon nanotube _k continuously grows in proportion to the concentration of the decomposed transition metal. If the transition metal grows to exceed 10 nm, the multi-walled carbon nanotube may be synthesized. Thus, the synthesis yield of the desired single-walled carbon nanotube may decrease. The size of the catalytic transition metal is in proportion to the concentration of the transition metal in the reaction chamber. Hence, the cross section when the transition metal is moved from the first reaction chamber 41a to the second reaction chamber 41b is enlarged, whereby the concentration of the transition metal may decrease in the reaction chamber. That is, when the materials in the first reaction chamber 41a are moved to the second reaction chamber 41b, the concentration decreases while the dispersion occurs by the difference of the cross section of the two reaction chambers. Thereby, the growth of the catalytic transition metal is restrained, and the continuous synthesis of the single-walled carbon nanotube results. As such, the dispersion rate of the transition metal should be sufficiently fast to restrain the growth. Thus, a cross section ratio of the first reaction chamber 41a to the second reaction chamber 41b ranges from 1:1.5 to 1 :1000.

The dispersion rate of the transition metal and the concentration of transition metal per unit volume are determined by the amount of the transition metal moved into the second reaction chamber 41b (adjustable by the bubbler), the moving rate (adjustable by the amount of gas-C₂H₂+Ar-), the heating temperature of the first reaction chamber 41a (adjustable by the temperature of the heater), the pressure of the second reaction chamber 41b (adjustable by the pressure pump), and the inner diameter ratio of the first reaction chamber 41a to the second reaction chamber 41b.

To rapidly disperse the transition metal in the second reaction chamber 41b, preference is given to maintaining the pressure of the second reaction chamber 41b to be lower than atmospheric pressure. If the pressure is close to atmospheric pressure, the transition metal is not rapidly dispersed and thus the synthesis possibility of the multi-walled carbon nanotube increases. Meanwhile, if the pressure is too low, the transition metal is very instantly dispersed up to the outer surface of the rotary drum 42 of the second reaction chamber 41b (in FIG. 2B, the inner wall of the second reaction chamber 31b), and thus inactivated due to the cooling, thereby decreasing the synthesis yield of the single-walled carbon nanotube. Hence, the pressure of the second reaction chamber 41b is preferably maintained in the range of 10-700 Torr.

Further, if the cross section ratio of the first reaction chamber 41a to the second reaction chamber 41b is too low, it is difficult to disperse the transition metal moved to the second reaction chamber 41b. Thus, it is preferable that the cross section ratio of the first reaction chamber 41a to the second reaction chamber 41b is 1 :1.5 or more. Whereas, if the cross section of the second reaction chamber 41b is at least 1000 times as large as that of the first reaction chamber 41a, the apparatus has an excessive occupation area and thus it is difficult to install such an apparatus.

The length of the first reaction chamber 41a indicates the period required for heating the transition metal compound and hydrocarbon fed into the first reaction chamber 41a. When the temperature of the first reaction chamber 41a is low, the length of the first reaction chamber 41a should be long so that the fed transition metal compound and hydrocarbon are sufficiently heated and decomposed. However, in such a case, the decomposed transition metal is re- combined and grows to exceed 10 nm. Thus, the multi-walled carbon nanotube may be synthesized in the first reaction chamber 41a. With the aim of increasing the synthesis yield of the single-walled carbon nanotube, the temperature of the first reaction chamber 41a is increased and the length of the first reaction chamber 41a is shortened. Meanwhile, if the length of the first reaction chamber 41a exceeds 50 cm, the multi-walled carbon nanotube may be synthesized in the first reaction chamber 41a. Therefore, it is preferable that the length of the first reaction chamber 41a is not more than 50 cm. While the catalytic transition metal dispersed in the second reaction

^' chamber 41b is moved to the recovery drum 42, it is cooled, in the operation 304. Then, since such a transition metal is inactivated, the synthesis of the carbon nanotube is stopped. Consequently, the inactivated transition metal is attached to the outer surface of the rotary drum ^'42, along with the synthesized single- walled carbon nanotube, and then collected,, in the operation 305. Further, transition metals remaining after the carbon nanotube is synthesized are cooled, inactivated and then attached to the outer surface of the rotary drum 42. Thereby, the concentration of the transition metal in the second reaction chamber 41b is restrained in the predetermined level or less. The single-walled carbon nanotube and transition metal collected to the outer surface of the rotary drum 42 are separated from the outer surface of the rotary drum 42 by the scrapper 43 according to rotating the rotary drum 42, and then dropped downwards, thereby being recovered to the recovery drum 44, in the operation 306. That is, since the single-walled carbon nanotube is continuously recovered immediately after being collected to the outer surface of the recovery drum 44, the continuous synthesis of the single-walled carbon nanotube can be realized.

From FIGS. 4 and 5, it can be seen that the single- walled carbon nanotube is synthesized according to the present invention. FIG. 4 is a Raman spectrum data graph of the single- walled carbon nanotube, and FIG. 5 is a flHRTEM photograph of the single-walled carbon nanotube. In FIG. 4, there are two peaks at 400 cm^"1 or less. Such peaks are produced by the a and b points of the single- walled carbon nanotube of FIG. 5. Also, the diameter of the single- walled carbon nanotube is calculated from the data of FIG. 4 and the equation determining diameter of the tube, w_r = (223.75 cm^'1.nm/dt(nm) + 14 cm^"1). From this, it can be found that the a and b points of the single- walled carbon nanotube have the diameter of 0.85 and 0.90 nm, respectively.

Industrial Applicability

As described above, the present invention provides a method and apparatus for synthesizing a single-walled carbon nanotube synthesis by thermal decomposition, characterized by mass production of the single-walled carbon nanotube and low preparation costs, attributable to the inexpensive single-walled carbon nanotube synthesis apparatus and the continuous synthesis of the single- walled carbon nanotube. Although the preferred embodiments of the present invention have been disclosed in conjunction with FIGS. 1 to 5, a further understanding can be obtained by reference to the embodiments which are provided herein for purposes of illustration only and are not intended to be limiting unless otherwise specified. Further, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. A method of synthesizing single-walled carbon nanotubes, comprising the following steps of: feeding transition metal compounds and hydrocarbon into a reaction chamber; decomposing the transition metal compound and hydrocarbon by heating to induce synthesis of the single-walled carbon nanotube, to prepare a decomposed transition metal; dispersing the decomposed transition metal to induce continuous synthesis of the single-walled carbon nanotube, to prepare a dispersed transition metal; cooling the dispersed transition metal to be inactivated, to prepare inactivated transition metals and synthesized single-walled carbon nanotubes; and collecting the inactivated transition metal and the synthesized single- walled carbon nanotube .

2. The method as defined in claim 1, further comprising the step of recovering the collected single-walled carbon nanotube.

3. The method as defined in claim 1, wherein the decomposing step is performed by heating the transition metal compound and hydrocarbon at 1200- 2500°C.

4. The method as defined in claim 1, wherein the dispersing step is performed under pressure not exceeding atmospheric pressure (760 Torr).

5. The method as defined in claim 4, wherein the dispersing step is performed under pressure of 200-400 Torr.

6. An apparatus for synthesizing single-walled carbon nanotubes, comprising: a cylinder block, including at least one first reaction chamber to thermally decompose transition metal compounds and hydrocarbons, and a second reaction chamber having a cross section wider than that of the at least one first reaction chamber to disperse a thermally decomposed transition metal; a feeding nozzle to feed the transition metal compound and hydrocarbon into the first reaction chamber; a heater to heat the first reaction chamber; and a cooling unit to cool the second reaction chamber so that the transition metal is inactivated in the second reaction chamber.

7. The apparatus as defined in claim 6, wherein the cooling unit functions to cool a wall of the second reaction chamber of the cylinder block.

8. The apparatus as defined in claim 6, wherein the cross section of the second reaction chamber is 1.5-1000 times as large as that of the first reaction chamber.

9. The apparatus as defined in . claim 6, wherein a length of the first reaction chamber is not longer than 50 cm.

10. The apparatus as defined in claim 6, further comprising a recovery unit to recover the single-walled carbon nanotube collected on a collecting portion.

1 1. The apparatus as defined in claim 10, wherein the recovery unit includes a water cooled spimiing dram positioned in the second reaction chamber , a scrapper to separate synthesized single-walled carbon nanotube on the surface of the spinning drum, and a recovery box positioned below the second reaction chamber to recover the single-walled carbon nanotubes separated by the scrapper.

12. The apparatus as defmed in claim 6, further comprising a pressure pump to maintain the pressure of the second reaction chamber lower than atmospheric pressure.