Carbon nanotube preparation method and carbon nanotube prepared using same

Abstract

The present invention relates to a carbon nanotube preparation method and carbon nanotubes prepared using same, the method comprising the steps of: (a) preparing a composition comprising 5-100 parts by weight of a carbon nitride precursor, 0.2-10 parts by weight of a salt of a metal that forms a solid solution with carbon, and 1-50 parts by weight of a denitrifying agent; (b) performing first firing on the composition at a temperature of 300-700°C, thereby obtaining graphitized carbon nitride; (c) performing second firing on the graphitized carbon nitride at a temperature higher than the first firing temperature, thereby preparing carbon tubes in which nanoparticles of the metal are dispersed on the surface thereof; and (d) charging a reactor with the carbon tubes in which nanoparticles of the metal are dispersed on the surface thereof, and then injecting a carbon source or the carbon source and H2 and / or N2 gas into the reactor and performing third firing on same at a temperature higher than the second firing temperature, thereby growing the carbon nanotubes.

Description

Method for manufacturing carbon nanotubes and carbon nanotubes manufactured thereby

[0001] The present invention relates to a method for manufacturing carbon nanotubes and carbon nanotubes manufactured thereby, and more particularly, to a method for manufacturing carbon nanotubes capable of controlling diameter and length using graphitized carbon nitride and carbon nanotubes manufactured thereby.

[0002] Carbon nanotubes (CNTs) are nanoscale carbon materials formed by rolling graphene sheets into a cylindrical shape. They exist in single-wall and multi-wall forms and have high utility in electronics, energy, and various other fields due to their unique physicochemical properties.

[0003] Carbon nanotubes are manufactured using a variety of methods. Examples include chemical vapor deposition (CVD), which deposits carbon atoms by exposing a gaseous carbon source to a catalytic metal surface at high temperatures; arc discharge, which utilizes carbon vapor generated by passing a high current between two carbon electrodes; and laser deposition, which irradiates a carbon target with a high-power laser.

[0004] However, conventional methods have been known to struggle to achieve the right ratio of catalyst to carbon source, and to control the diameter, length, and structural uniformity of carbon nanotubes. In particular, the commonly used chemical vapor deposition method requires expensive equipment such as plasma reactors and consumes significant energy, making it inefficient for mass production. Furthermore, introducing catalyst precursors such as metals in a plasma environment is challenging, and the carbon source can crack and agglomerate.

[0005] Meanwhile, carbon nitride is a compound formed from carbon and nitrogen. Graphitized carbon nitride, in particular, possesses a layered structure similar to graphene. Due to its structural characteristics, it exhibits excellent thermal stability and unique electronic and optical properties, leading to various studies utilizing it.

[0006] The purpose of the present invention is to provide a method for manufacturing carbon nanotubes with controllable diameter and length using graphitized carbon nitride; and

[0007] Another object of the present invention is to provide a carbon nanotube having excellent thermal stability and electrical conductivity using the above method.

[0008] However, it is not limited thereto, and includes parts that can be clearly understood by a person having ordinary knowledge in the technical field to which the present invention belongs from the description of the present invention.

[0009] The present invention,

[0010] (a) a step of preparing a composition comprising 5 to 100 parts by weight of a carbon nitride precursor, 0.2 to 10 parts by weight of a metal salt forming a solid solution with carbon, and 1 to 50 parts by weight of a denitrifying agent;

[0011] (b) a step of first calcining the composition at a temperature of 300 to 700°C to obtain graphitized carbon nitride;

[0012] (c) a step of firing the graphitized carbon nitride a second time at a temperature higher than the first firing temperature to produce a carbon tube having nanoparticles of the metal dispersed on the surface; and

[0013] (d) a step of loading a carbon tube having nanoparticles of the metal dispersed on the surface into a reactor, and then injecting a carbon source or at least one gas selected from the carbon source and H2 or N2 into the reactor to perform a third firing at a temperature higher than the second firing to grow carbon nanotubes; a method for manufacturing a carbon nanotube is provided.

[0014] The above carbon nitride precursor may be at least one selected from the group consisting of melamine, urea, thiourea, cyanamide, and dicyandiamide.

[0015] The salt of the metal forming the above carbon and solid solution may be a nitrate of one or more metals selected from the group consisting of Fe, Ni, and Co.

[0016] The above denitrifying agent may contain a carbonyl group.

[0017] The composition may include 5 to 100 parts by weight of a carbon nitride precursor, 0.2 to 10 parts by weight of a metal salt forming a solid solution with carbon, and 1 to 50 parts by weight of a denitrifying agent.

[0018] The above first firing can be performed at 400 to 600°C for 30 to 240 minutes.

[0019] The above graphitized carbon nitride may be g-C3N4 in the form of nanosheets.

[0020] The above second firing can be performed at 800 to 1100°C for 20 to 120 minutes.

[0021] The above carbon tube has a density of 0.1 to 10 g / cm 3 , and the porosity can be 10 to 50%.

[0022] The pressure inside the reactor may be 1.5 to 3 atm.

[0023] The above third firing can be performed at 1100 to 1500°C for 1 to 30 minutes.

[0024] The above carbon source and gas can be injected into the reactor at a flow rate ratio of 1:2.

[0025] When the above gas is injected, a plasma reaction can be performed to induce cracking of the above gas.

[0026] The present invention provides a carbon nanotube manufactured using the above method.

[0027] The above carbon nanotubes may have an average diameter of 10 to 500 nm and an average length of 1 to 30 μm.

[0028] According to the present invention, a carbon nanotube having excellent thermal stability and electrical conductivity while being controllable in diameter and length can be manufactured with excellent processability using a carbon tube having a predetermined nano metal particle manufactured using graphitized carbon nitride dispersed on the surface.

[0029] However, the effects of the present invention are not limited thereto, and may include effects expected from the technical features of the present invention by a person having ordinary knowledge in the technical field to which the present invention pertains.

[0030] Figures 1 to 4 are the results of SEM and / or EDS analysis of carbon tubes in Experimental Example 1; and

[0031] Figure 5 is an SEM photograph of a carbon nanotube in Experimental Example 2.

[0032] The present invention

[0033] (a) a step of preparing a composition comprising 5 to 100 parts by weight of a carbon nitride precursor, 0.2 to 10 parts by weight of a metal salt forming a solid solution with carbon, and 1 to 50 parts by weight of a denitrifying agent;

[0034] (b) a step of first calcining the composition at a temperature of 300 to 700°C to obtain graphitized carbon nitride;

[0035] (c) a step of firing the graphitized carbon nitride a second time at a temperature higher than the first firing temperature to produce a carbon tube having nanoparticles of the metal dispersed on the surface; and

[0036] (d) a step of loading a carbon tube having nanoparticles of the metal dispersed on the surface into a reactor, and then injecting a carbon source or at least one gas selected from the carbon source and H2 or N2 into the reactor to perform a third firing at a temperature higher than the second firing to grow carbon nanotubes; a method for manufacturing a carbon nanotube is provided.

[0037] According to the present invention, a carbon nanotube having excellent thermal stability and electrical conductivity while being controllable in diameter and length can be manufactured with excellent processability using a carbon tube having a predetermined nano metal particle manufactured using graphitized carbon nitride dispersed on the surface.

[0038] Specifically, the inventors of the present invention, after numerous studies, have confirmed that when a graphitized carbon nitride is obtained through a first calcination of a carbon nitride precursor and a second calcination is performed consecutively, the graphitized carbon nitride is decomposed, nitrogen in the graphitized carbon nitride is removed by a denitrifying agent, and at the same time, a certain amount of carbon is inserted into the metal forming a solid solution with the carbon, and after reaching a saturation state, the existing carbon is pushed out to form a tube shape, and in the process of the metal being discharged to the surface in a nano form, a carbon tube having metal nanoparticles dispersed on the surface can be manufactured. Furthermore, the carbon tube having metal nanoparticles dispersed on the surface has a form in which nano metal catalyst particles are supported on a carbon tube support, and through this, carbon nanotubes having excellent thermal stability and electrical conductivity while allowing control of the diameter and length can be manufactured with excellent processability.

[0039] In step (a), a composition is prepared comprising 5 to 100 parts by weight of a carbon nitride precursor, 0.2 to 10 parts by weight of a metal salt forming a solid solution with carbon, and 1 to 50 parts by weight of a denitrifying agent.

[0040] The above carbon nitride precursor is not limited as long as it forms graphitized carbon nitride through a polymerization reaction when heated above a certain temperature, including a cyanide (CN) bond, but may be, for example, one or more selected from the group consisting of melamine, urea, thiourea, cyanamide, and dicyandiamide.

[0041] If the above carbon nitride precursor is less than 5 parts by weight, it is difficult to obtain a sufficient amount of graphitized carbon nitride, and if it exceeds 100 parts by weight, an excessive amount of graphitized carbon nitride is formed, which is decomposed in the subsequent reaction, making it difficult to sufficiently remove nitrogen, which is not preferable. Specifically, it may be 10 to 80 parts by weight, or 20 to 60 parts by weight, or 30 to 50 parts by weight.

[0042] The above carbon and metal forming a solid solution are metals in which carbon atoms are inserted between the crystal lattices of the metal or alloy at a certain temperature to form a single solid phase, and in the formed solid solution of carbon and metal, the physical and chemical properties of the carbon or metal can change significantly.

[0043] There is no limitation on the metal known in the art as forming the above carbon and solid solution, but it may be, for example, one or more selected from the group consisting of Fe, Ni, and Co.

[0044] Fe, Ni, and Co each have crystal lattice structures flexible enough to accommodate carbon atoms, and the carbon atoms can interact with each other through their electronic structure and chemical properties to form stable solid solutions.

[0045] On the other hand, metals such as Pt and Mg do not form a direct solid solution with carbon, so they do not participate in the formation of carbon tubes through the process of insertion and discharge of the metal, and they do not form a bond with carbon and exist separately, so they ultimately cannot form carbon nanotubes.

[0046] The salt of the metal forming the above carbon and solid solution may be in the form of one or more salts selected from the group consisting of nitrate, nitrite, sulfate, thiosulfate, carbonate, chloride, halide, formate and mixtures thereof of the metal, and specifically may be a nitrate.

[0047] If the metal salt forming the above carbon and solid solution is less than 0.2 parts by weight, it is difficult for a sufficient amount of metal to be discharged in a nano form onto the surface of the graphitized carbon nitride, and the carbon volatilizes during the reaction, making it difficult to form carbon tubes. If it exceeds 10 parts by weight, an excessive amount of metal may be discharged onto the surface of the graphitized carbon nitride, causing the carbon tubes to form a film, which is not preferable. Specifically, it may be 0.3 to 5 parts by weight, or 0.5 to 3 parts by weight, or 0.6 to 1.5 parts by weight.

[0048] In the present invention, the denitrifying agent refers to a substance that induces a denitrification reaction of another compound participating in the reaction. The denitrifying agent can induce the formation of carbon tubes by removing nitrogen from graphitized carbon nitride in the second calcination process. The denitrifying agent is not limited as long as it contains a carbonyl group, and may be, for example, at least one selected from the group consisting of acetic acid, butanoic acid, citric acid, formic acid, gluconic acid, glycolic acid, malonic acid, oxalic acid, pentanoic acid, methanesulfonic acid, sulfobenzoic acid, sulfosuccinic acid, sulfophthalic acid, salicylic acid, sulfosalicylic acid, benzoic acid, lactic acid, glyceric acid, succinic acid, malic acid, tartaric acid, isocitric acid, and propenoic acid, but is not limited thereto.

[0049] If the amount of the denitrifying agent is less than 1 part by weight, it is difficult to sufficiently remove nitrogen from the graphitized carbon nitride, and if it exceeds 50 parts by weight, side reactions may occur due to substances formed by the decomposition of the carbonyl group, which is not preferable. Specifically, the amount of the denitrifying agent may be 3 to 40 parts by weight, or 6 to 30 parts by weight, or 10 to 20 parts by weight.

[0050] The form of the above composition is not limited, but may be, for example, a solution, a suspension or a powder, and more specifically, may be a powder form from which moisture has been removed through vacuum drying.

[0051] In step (b), the composition can be first calcined with a carbon nitride precursor at a temperature of 300 to 700°C to obtain graphitized carbon nitride (g-C3N4) in the form of nanosheets.

[0052] If the above first firing condition is less than 300°C or less than 30 minutes, it is difficult to sufficiently carbonize the carbon nitride precursor, and if it exceeds 700°C or more than 240 minutes, structural deformation of the graphitized carbon nitride may occur or volatilization may occur, which is not preferable. Specifically, the reaction may be performed at 400 to 600°C. Specifically, the reaction may be performed for 60 to 180 minutes, or 90 to 150 minutes.

[0053] In step (c), when the graphitized carbon nitride obtained through the first calcination is subsequently calcined a second time at a temperature higher than the first calcination temperature, the graphitized carbon nitride is decomposed, and nitrogen in the graphitized carbon nitride is removed by the denitrifying agent. At the same time, as a certain amount of carbon is inserted into the metal forming the carbon and solid solution, it becomes saturated, and then the existing carbon is pushed out to form a tube shape. In the process of the metal being discharged to the surface in a nano form, a carbon tube in which metal nanoparticles are dispersed on the surface can be manufactured. Such a metal forms a carbide bond rather than a simple physical bond with the carbon tube, so that the carbon tube can serve as a support for the metal catalyst, as will be described below.

[0054] The above second calcination can be performed at a temperature of 800 to 1100°C for 20 to 120 minutes. If it is less than 800°C or less than 30 minutes, it is difficult for the metal to be discharged from the graphitized carbon nitride surface in a nano form, and if it exceeds 1100°C or more than 120 minutes, the carbon tube may volatilize or structural deformation may occur, which is not preferable. Specifically, the reaction can be performed at 850 to 1000°C. Specifically, the reaction can be performed for 30 to 100 minutes, or 50 to 80 minutes.

[0055] The metal formed in the above carbon tube may be nano-sized, for example, having an average particle diameter of 1 to 1000 nm, or 10 to 100 nm.

[0056] The above carbon tube has a density of 0.1 to 10 g / cm 3 , and the porosity may be 10 to 50%. If the density and porosity are outside this range, the subsequent carbon nanotube formation and growth may not occur smoothly, which is not desirable. Specifically, the density is 1 to 5 g / cm 3 , or 1.5 to 3 g / cm 3, and the porosity can be 20 to 40%.

[0057] The diameter of the above carbon tube may be 0.1 to 50 μm, and the length may be 1 to 300 μm. If the diameter and length are outside these ranges, the formation and growth of the carbon nanotube may not occur smoothly, which is undesirable. Specifically, the diameter may be 1 to 30 μm, or 3 to 20 μm, and the length may be 10 to 200 μm, or 20 to 150 μm.

[0058] In step (d), carbon tubes having metal nanoparticles dispersed on the surface, manufactured through the second firing, are loaded into a reactor, and then a carbon source or at least one gas selected from the carbon source and H2 or N2 is injected into the reactor to perform a third firing at a temperature higher than the second firing to grow carbon nanotubes.

[0059] Metal nanoparticles easily aggregate, making size control impossible, and their high price makes them uneconomical. In the present invention, carbon tubes having metal nanoparticles dispersed on their surfaces serve as a supported catalyst for the nano metal, with the nano metal catalyst particles supported on a carbon tube support, thereby suppressing the generation of amorphous carbon at a predetermined temperature while controlling the diameter and length according to the particle size of the nano metal used, thereby increasing the predictability of the shape of the resulting carbon nanotube.

[0060] First, carbon tubes with metal nanoparticles dispersed on their surfaces are loaded into the reactor. This pre-injection of carbon tubes with metal nanoparticles dispersed on their surfaces into the reactor forms a catalyst layer, minimizing reaction catalyst loss and enhancing process efficiency.

[0061] A porous tube may be installed inside the reactor to maintain a pressure of 1.5 to 3 atmospheres (atm). The porous tube can control the volume within the reactor, thereby increasing the uniformity of the growing carbon nanotubes, and can also control the residence time of materials within the reactor, thereby improving the efficiency and completeness of the reaction. Materials that can be used for the porous tube include, for example, SiC, which has excellent high-temperature chemical resistance. Specifically, the porous tube can be used to maintain a pressure of 1.8 to 2.3 atmospheres (atm).

[0062] The above reactor may be, but is not limited to, a fixed bed reactor or a fluidized bed reactor.

[0063] The third calcination may be performed at a temperature of 1100 to 1500°C for 1 to 30 minutes. The supported catalyst calcined within this temperature and time range can control the diameter and length of the carbon nanotubes while minimizing the generation of amorphous carbon. If the temperature is lower than 1100°C or for less than 1 minute, it is difficult to secure the intended effect of the present invention, and if the temperature exceeds 1500°C or for more than 20 minutes, the carbon nanotubes may volatilize or undergo structural deformation during the growth process, which is undesirable. Specifically, the reaction may be performed at 1200 to 1400°C, or 1250 to 1350°C. Specifically, the reaction may be performed for 5 to 20 minutes, or 5 to 15 minutes.

[0064] The above carbon source may be one or more selected from, but is not limited to, low-carbon substances such as methane, ethane, propane, and butane, and highly volatile alcohols such as acetylene, methanol, ethanol, and propanol.

[0065] The carbon nanotube reaction can be promoted by injecting the above carbon source and at least one gas selected from H2 and N2. The gas may be H2, N2, or a mixture of H2 and N2.

[0066] The carbon source and gas may be injected into the reactor at a flow rate ratio of 1:1 to 1:3. If the flow rate exceeds this range, the carbon nanotube growth time may become excessively long or it may be difficult to secure an appropriate length, which is undesirable. Specifically, the carbon source and gas may be injected into the reactor at a flow rate ratio of 1:1.5 to 1:2.5.

[0067] The above carbon source or gas can induce cracking by using plasma or a heat source when introduced into the reactor, and more specifically, plasma can be used.

[0068] Plasma can be performed in the form of applying 1 to 100 Kw DC plasma, and specifically, 10 to 50 Kw DC plasma can be applied.

[0069] Afterwards, depending on the case, acid washing can be performed to remove impurities on the surface of the carbon nanotube and increase its purity.

[0070] The present invention provides a carbon nanotube manufactured using the above method.

[0071] These carbon nanotubes can be used in various fields such as electricity, electronics, and energy because they can control their diameter and length while also having excellent thermal stability and electrical conductivity.

[0072] The above carbon nanotubes may have an average diameter of 10 to 500 nm and an average length of 1 to 30 μm. Specifically, the average diameter may be 20 to 100 nm.

[0073] Hereinafter, the present invention will be described in detail with reference to examples. However, the following examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples.

[0074] <Example 1-1>

[0075] Melamine (37.8 g), Ni(NO3) (20.78 g), and benzoic acid (12.2 g) were dissolved in 200 ml of distilled water at 80°C, and the mixture was stirred for about 4 hours. The temperature was then raised to 100°C and the distilled water was removed. The remaining solid was then finely powdered using a ball mill, and vacuum-dried to remove moisture to obtain graphitized carbon nitride.

[0076] The powder obtained above was reacted at 550°C for 2 hours in a normal pressure furnace under a N2 atmosphere, then the temperature was raised to 900°C, the reaction was carried out for 1 hour, and then cooled to produce a carbon tube with nickel dispersed on the surface.

[0077] <Example 1-2>

[0078] The carbon tube powder with nickel dispersed on the surface, manufactured in Example 1-1, was introduced into the reactor. To maintain the reactor pressure at approximately 700 to 1520 torr (2 atm), a porous tube made of SiC was installed.

[0079] 10 slm of methane as a carbon source and 20 slm of N2 and H2 gas diluted with 24% H2 as reaction gases were injected into the reactor after cracking using a 30 kW DC plasma. The inside of the reactor was maintained at 1300°C, and the reaction was performed for 10 minutes to grow carbon nanotubes.

[0080] <Example 2>

[0081] In Example 1, a carbon tube was manufactured in the same manner as in Example 1 except that Co(NO3)2 was used instead of Ni(NO3)2.

[0082] <Comparative Example 1>

[0083] A carbon tube was manufactured in the same manner as in Example 1, except that Mg(NO3)2 was used instead of Ni(NO3)2.

[0084] Comparative Example 2

[0085] A carbon tube was manufactured in the same manner as in Example 1, except that H2PtCl6 was used instead of Ni(NO3)2.

[0086] <Comparative Example 3>

[0087] In Example 1, a carbon tube was manufactured in the same manner as in Example 1 except that 0.1 g of Ni(NO3)2 was used.

[0088] Experimental Example 1

[0089] SEM and / or EDS analyses of the carbon tubes manufactured in Examples 1-1 and 2 and Comparative Examples 1 to 3 are shown in Fig. 1 (Example 1-1), Fig. 2 (Example 2), Fig. 3 (Comparative Example 1), and Fig. 4 (Comparative Example 2).

[0090] According to the SEM analysis of Fig. 1, tubes with an average diameter of 5 μm and an average length of 50 μm, and a white component dispersed on the surface of the tubes can be confirmed. According to the EDM analysis, the tubes are carbon tubes from which N has been removed from g-C3N4, and it can be confirmed that the white component of 10 to 100 nm ejected on the surface is nickel particles.

[0091] Similarly, according to Fig. 2, cobalt particles of 10 to 100 nm in size can be observed discharged onto the surface of a carbon tube having an average diameter of 5 μm and an average length of 50 μm. Compared to nickel, the amount of cobalt discharged onto the surface of the carbon tube is small, due to the relatively high proportion of Co-Carbide bonds present.

[0092] According to Fig. 3, it can be confirmed that magnesium particles discharged on the surface of carbon tubes with an average diameter of 5 μm and an average length of 50 μm are hardly observed. This is because magnesium does not form a solid solution with carbon and therefore exists separately from the carbon tube.

[0093] According to Fig. 4, it can be confirmed that the carbon tube itself is not formed, and the platinum particles are evenly distributed even in areas without carbon. This is because the platinum particles do not participate in the formation of the carbon tube and are distributed separately from the carbon.

[0094] In the case of Comparative Example 3, carbon tubes were not formed and there was almost no residue, so it could not be confirmed in the photograph.

[0095] Experimental Example 2

[0096] The average diameter and average length of the carbon nanotubes manufactured in Example 1-2 were confirmed and shown in Fig. 5.

[0097] According to Fig. 5, it can be confirmed that the average diameter of the carbon nanotube is 20 to 50 nm, and the average length is 1 ㎛ or more, with an average length of 15 ㎛.

Claims

1. (a) a step of preparing a composition comprising 5 to 100 parts by weight of a carbon nitride precursor, 0.2 to 10 parts by weight of a metal salt forming a solid solution with carbon, and 1 to 50 parts by weight of a denitrifying agent; (b) a step of first calcining the composition at a temperature of 300 to 700°C to obtain graphitized carbon nitride; (c) a step of producing a carbon tube having nanoparticles of the metal dispersed on the surface by performing a second firing of the graphitized carbon nitride at a temperature higher than the first firing temperature; and (d) After loading the carbon tube with the metal nanoparticles dispersed on the surface into the reactor, the carbon source or the carbon source and H 2 or N 2 A method for manufacturing carbon nanotubes, comprising: a step of injecting at least one gas into the reactor and performing a third firing at a temperature higher than the second firing to grow carbon nanotubes; 2. In paragraph 1, A method for manufacturing a carbon nanotube, wherein the carbon nitride precursor is at least one selected from the group consisting of melamine, urea, thiourea, cyanamide, and dicyandiamide.

3. In paragraph 1, A method for manufacturing a carbon nanotube, wherein the salt of the metal forming the above carbon and solid solution is a nitrate of at least one metal selected from the group consisting of Fe, Ni, and Co.

4. In paragraph 1, A method for producing a carbon nanotube, wherein the above denitrifying agent contains a carbonyl group.

5. In paragraph 1, A method for producing a carbon nanotube, wherein the composition comprises 5 to 100 parts by weight of a carbon nitride precursor, 0.2 to 10 parts by weight of a metal salt forming a solid solution with carbon, and 1 to 50 parts by weight of a denitrifying agent.

6. In paragraph 1, A method for manufacturing a carbon nanotube, wherein the first firing is performed at 400 to 600°C for 30 to 240 minutes.

7. In paragraph 1, The above graphitized carbon nitride is gC in the form of nanosheets. 3 N 4 A method for manufacturing carbon nanotubes.

8. In paragraph 1, A method for manufacturing a carbon nanotube, wherein the second firing is performed at 800 to 1100°C for 20 to 120 minutes.

9. In paragraph 1, The above carbon tube has a density of 0.1 to 10 g / cm 3 A method for manufacturing a carbon nanotube having a porosity of 10 to 50%.

10. In paragraph 1, A method for manufacturing carbon nanotubes, wherein the inside of the reactor is at a pressure of 1.5 to 3 atm.

11. In paragraph 1, A method for manufacturing a carbon nanotube, wherein the third firing is performed at 1100 to 1500°C for 1 to 30 minutes.

12. In paragraph 1, A method for manufacturing carbon nanotubes, wherein the above carbon source and gas are injected into a reactor at a flow rate ratio of 1:

2.

13. A method for manufacturing carbon nanotubes in claim 1, wherein the gas is injected and a plasma reaction is performed to induce cracking of the gas.

14. A carbon nanotube manufactured using the method according to paragraph 1.

15. In paragraph 14, The above carbon nanotube is a carbon nanotube having a diameter of 10 to 500 nm and an average length of 1 to 30 ㎛.

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