Method for manufacturing single-walled carbon nanotubes using thermal plasma

Abstract

A method for manufacturing single-walled carbon nanotubes according to one embodiment comprises the steps of: generating plasma in a plasma arc region; introducing a catalyst precursor and a carbon raw material into the plasma arc region through a central inlet; pyrolyzing the catalyst precursor; and synthesizing carbon nanotubes by reacting the pyrolyzed catalyst precursor and the carbon raw material.

Description

Method for manufacturing single-walled carbon nanotubes using thermal plasma

[0001] The various embodiments below relate to a method for manufacturing single-wall carbon nanotubes (SWCNTs) using thermal plasma, and more specifically, to a method for manufacturing a catalyst suitable for manufacturing single-wall carbon nanotubes using thermal plasma and synthesizing single-wall carbon nanotubes using the same.

[0002] Carbon nanotubes (CNTs) are nanometer-sized materials in which carbon atoms are arranged in a hexagonal lattice to form a cylindrical structure, possessing unique electrical, mechanical, and chemical properties. Single-walled carbon nanotubes (SWCNTs) are cylindrical structures composed of a single layer of graphene sheet, exhibiting a more uniform structure and superior electronic properties compared to multi-walled carbon nanotubes (MWCNTs). However, it is difficult to maintain a constant temperature of over 1,000°C during the synthesis of single-walled carbon nanotubes, which limits the size of reactors suitable for mass production; furthermore, the synthesis of single-walled carbon nanotubes is impossible without promoters such as S, Mo, and V.

[0003] Chemical Vapor Deposition (CVD), Floating Catalyst Chemical Vapor Deposition (FCCVD), Arc Discharge, and Laser Ablation are widely used for the synthesis of conventional single-walled carbon nanotubes (SWCNTs). In particular, while CVD is widely used commercially because it allows for the growth of carbon nanotubes on various substrates at low temperatures, it presents difficulties in obtaining single-walled carbon nanotubes of uniform quality. Additionally, although Arc Discharge and Laser Ablation can produce high-quality single-walled carbon nanotubes, they face limitations in large-scale production and suffer from high process costs.

[0004] As such, a new synthesis technology using thermal plasma is required to overcome the limitations of existing single-walled carbon nanotube synthesis methods, such as low quality, low production efficiency, and high cost.

[0005] A method for manufacturing single-walled carbon nanotubes according to one embodiment is devised to solve the problems described above. It aims to provide a method for manufacturing single-walled carbon nanotubes with improved selectivity and yield compared to existing manufacturing methods by controlling the input temperature of the catalyst and reaction gas using plasma and manufacturing a catalyst suitable for the synthesis of single-walled carbon nanotubes.

[0006]

[0007] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0008] A method for manufacturing a single-walled carbon nanotube according to one embodiment may include the steps of: generating plasma in a plasma arc region; introducing a catalyst precursor and a carbon raw material into the plasma arc region through a central inlet; thermally decomposing the catalyst precursor; and reacting the thermally decomposed catalyst precursor with the carbon raw material to synthesize a carbon nanotube.

[0009] A method for manufacturing a single-walled carbon nanotube according to one embodiment may utilize a plasma device, wherein the plasma device may include a cathode and an anode forming a plasma arc region, a central inlet connected to the center of the plasma arc region, and a side inlet connected to the side of the plasma arc region.

[0010]

[0011] The above anode includes a first anode and a second anode located at the bottom of the first anode, and may additionally include an insulator between the first anode and the second anode.

[0012] The step of generating plasma in the plasma arc region may include the step of injecting process gas into the plasma arc region; and the step of supplying power to the plasma arc region, wherein the power may be 1 kW to 30 kW.

[0013] The step of generating plasma in the above plasma arc region may include a step of generating plasma by an electric discharge of the cathode and the first anode, and a step of extending the length of the plasma arc by the cathode and the second anode.

[0014] The above process gas may include one or more of nitrogen (N2), hydrogen (H2), argon (Ar), and helium (He).

[0015] The catalyst precursor may include one or more of ferrocene, nickelocene, cobaltocene, osmocene, ruthenocene, iron (Fe), nickel (Ni), cobalt (Co), chromium (Cr), tungsten (W), titanium (Ti), ruthenium (Ru), rhodium (Rh), palladium (Pd), platinum (Pt), copper (Cu), yttrium (Y), zirconium (Zr), and silicon (Si).

[0016] The above carbon raw materials are methane (CH4), ethane (C2H6), acetylene (C2H2), ethylene (C2H4), propane (C3H8), and butane (C4H 10 ), pentane (C5H 12 ), hexane (C6H 14 It may include one or more of ) and ferrocene (Fe(C5H5)2).

[0017] In a method for manufacturing a single-walled carbon nanotube according to one embodiment, the step of thermally decomposing the catalyst precursor may be to thermally decompose the catalyst precursor into a catalyst of less than 10 nm in size at a high temperature of 3,000°C to 20,000°C.

[0018] The catalyst formed by thermally decomposing the above catalyst precursor may satisfy the following Equation 1.

[0019]

[0020] I α : Intensity of the α-phase peak in X-ray diffraction (XRD)

[0021] I γ : Intensity of the γ-phase peak in X-ray diffraction

[0022] In a method for manufacturing a single-walled carbon nanotube according to one embodiment, the step of synthesizing a carbon nanotube by reacting the pyrolyzed catalyst precursor with a carbon raw material may be carried out at a high temperature of 3,000°C to 20,000°C.

[0023] A method for manufacturing a single-walled carbon nanotube according to one embodiment may not use a promoter comprising one or more of S, Mo, and V.

[0024] In a method for manufacturing a single-walled carbon nanotube according to one embodiment, a carrier gas and a carbon raw material may be introduced through the central inlet. The carrier gas may include one or more of nitrogen (N2), hydrogen (H2), argon (Ar), and helium (He).

[0025] A method for manufacturing a single-walled carbon nanotube according to one embodiment may introduce a sheath gas through the side inlet, and the sheath gas may include one or more of nitrogen (N2), hydrogen (H2), argon (Ar), and helium (He).

[0026]

[0027] A single-walled carbon nanotube according to one embodiment may be manufactured by the method for manufacturing the single-walled carbon nanotube.

[0028] The carbon nanotubes manufactured above can satisfy the following Equation 2.

[0029]

[0030] I G : Intensity of the G-peak in the Raman spectrum

[0031] I D : Intensity of the D-peak in the Raman spectrum

[0032] A method for manufacturing single-walled carbon nanotubes according to one embodiment enables mass production of single-walled carbon nanotubes because the decomposition and synthesis of precursors are carried out within a short time without a promoter at ultra-high temperatures. Furthermore, the selectivity and yield of single-walled carbon nanotubes can be improved by controlling the catalyst size according to the temperature at which the gas and catalyst precursors are introduced. In addition, it has the advantage of being environmentally friendly as no harmful gases, such as hydrogen sulfide (H2S), are present in the exhaust gas.

[0033] FIG. 1 is a cross-sectional view of a plasma device used in a method for manufacturing single-walled carbon nanotubes according to one embodiment.

[0034] FIG. 2 is a flowchart of a method for manufacturing single-walled carbon nanotubes according to one embodiment.

[0035] Figure 3 is a diagram showing the distribution of catalyst sizes generated according to the input location of the raw material and plasma power.

[0036] Figure 4 is a diagram showing the TEM image and XRD analysis results of the catalyst produced according to Example 1.

[0037] Figure 5 is a diagram showing the TEM image and XRD analysis results of the catalyst produced according to Comparative Example 1.

[0038] Figure 6 is a diagram showing the distribution of carbon nanotubes produced according to the input location of the raw material and plasma power.

[0039] Figure 7 is a diagram showing the TEM image and XRD analysis results of carbon nanotubes produced according to Example 1.

[0040] FIG. 8 is a TEM image of carbon nanotubes produced according to Comparative Example 1 and This is a diagram showing the values.

[0041] Hereinafter, embodiments will be described in detail with reference to the attached drawings. In the description with reference to the attached drawings, identical components are given the same reference numeral regardless of the drawing number, and redundant descriptions thereof will be omitted.

[0042] The terms used in the embodiments are for illustrative purposes only and should not be interpreted as intended to be limiting. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0043] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the embodiments pertain. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0044] In addition, when describing with reference to the attached drawings, identical components are assigned the same reference numeral regardless of drawing symbols, and redundant descriptions thereof are omitted. In describing the embodiments, if it is determined that a detailed description of related prior art could unnecessarily obscure the essence of the embodiments, such detailed description is omitted.

[0045] Additionally, terms such as first, second, A, B, (a), (b), etc., may be used when describing the components of the embodiments. These terms are intended merely to distinguish the components from other components, and the nature, order, or sequence of the components is not limited by these terms. Where it is stated that a component is "connected," "combined," or "joined" to another component, it should be understood that the component may be directly connected or joined to the other component, but that another component may also be "connected," "combined," or "joined" between each component.

[0046] Components included in any one embodiment and components having common functions shall be described using the same names in other embodiments. Unless otherwise stated, the descriptions given in any one embodiment may also apply to other embodiments, and specific descriptions shall be omitted to the extent of overlap.

[0047] It is understood that the term “about” refers to a range of numbers that a person skilled in the art would consider equivalent to the stated value in terms of achieving the same function or result. When the term “about” is used with a number or value, the term “about” refers to ±20% of the number or value, primarily ±10% of the number or value, often ±5% of the number or value, or ±2% of the number or value. In some modalities, the term “about” may refer to the number or value itself.

[0048] In this document, each of the phrases such as "A or B", "at least one of A and B", "at least one of A or B", "A, B or C", "at least one of A, B and C", and "at least one of A, B, or C" may include any one of the items listed together in the corresponding phrase, or all possible combinations thereof.

[0049]

[0050] [Method for manufacturing carbon nanotubes]

[0051] Carbon nanotubes are nanometer-sized structures made by rolling graphene sheets, in which carbon atoms are arranged in a hexagonal structure, into a cylinder.

[0052] Carbon nanotubes can be single-wall carbon nanotubes (SWCNT), multi-wall carbon nanotubes (MWCNT), or thin-wall carbon nanotubes (TWCNT).

[0053] A method for manufacturing carbon nanotubes according to one embodiment is specifically for mass-producing single-walled carbon nanotubes with high selectivity and high yield, and may comprise the steps of: generating plasma in a plasma arc region using a plasma device according to one embodiment (S1); introducing a catalyst precursor and a carbon raw material into the plasma arc region through a central inlet (S2); thermally decomposing the catalyst precursor (S3); and reacting the thermally decomposed catalyst precursor with the carbon raw material to synthesize carbon nanotubes (S4).

[0054] The specific method for manufacturing the carbon nanotubes described above will be described together with a plasma device, which will be described in detail below.

[0055]

[0056] - Plasma device

[0057] FIG. 1 shows a cross-sectional view of a plasma device used in a method for manufacturing single-walled carbon nanotubes according to one embodiment.

[0058] Referring to FIG. 1, a plasma device (1000) may include a plasma torch (1100) and a heater (1200). Specifically, for example, the plasma device (1000) may include a plasma torch (1100), which is a high-temperature reaction zone located at the top, and a heater (1200), which is a relatively low-temperature reaction zone located at the bottom. The plasma torch (1100) corresponds to the place where plasma is generated, and examples of the heater (1200) may include FCCVD, CVD, etc.

[0059] A plasma torch (1100) according to one embodiment may include a cathode (1103) and an anode (1104, 1105) that form a plasma arc region (1108), a central inlet (1101) connected to the center of the plasma arc region (1108), and a side inlet (1110) connected to the side of the plasma arc region (1108). In this case, the cathode (1103) may include tungsten, copper, iron, nickel, gold, silver, etc. Additionally, the anode (1104, 1105) may include a first anode (1104) and a second anode (1105) located at the bottom of the first anode (1104), and may additionally include an insulator (1111) between the first anode (1104) and the second anode (1105). In this case, the anode (1104, 1105) may include a carbon-based material or a material constituting the cathode (1103) listed above, and the insulator (1111) may include aluminum, silicon oxide, epoxy, rubber-based materials, etc. Additionally, a cooling water (1102) to prevent unnecessary overheating may be located on the outside surrounding the cathode (1103), the first anode (1104), the insulator (1111), and the second anode (1105). A process gas inlet (1109) connected to a plasma arc region (1108) between the cathode (1103) and the first anode (1104) may be included, and plasma is generated by the electric discharge of the cathode (1103) and the first anode (1104), and the arc length of the generated plasma may be extended by the cathode (1103) and the second anode (1105). An insulator (1111) is included between the first anode (1104) and the second anode (1105), thereby increasing the length of the plasma arc. This allows the time for the thermal decomposition of the catalyst precursor and the synthesis of carbon nanotubes to be sufficiently extended, which has the advantage of enabling sufficient thermal decomposition and synthesis reactions to occur within the plasma region.If such an insulator (1111) does not exist and the second anode (1105) is located at the bottom of the first anode (1104), a problem arises where plasma adheres to the first anode (1104), and thus the length of the plasma arc cannot be increased.

[0060] Meanwhile, a sheath gas containing one or more of nitrogen (N2), hydrogen (H2), argon (Ar), and helium (He) can be introduced through the side inlet (1110).

[0061] A heater (1200) according to one embodiment may include a heater reaction zone inlet (1201) and a heater reaction zone (1202), and a carrier gas including one or more of nitrogen (N2), hydrogen (H2), argon (Ar) and helium (He) may be introduced through the heater reaction zone inlet (1201).

[0062]

[0063] To specifically describe the step (S1) of generating plasma in the plasma arc region (1108), the step may include the step of injecting process gas into the plasma arc region (1108) and the step of supplying power to the plasma arc region (1108).

[0064] In the step of injecting a process gas into the plasma arc region (1108), the process gas is a gas capable of generating plasma and may include one or more of nitrogen (N2), hydrogen (H2), argon (Ar), and helium (He). For example, it may be injected through a process gas inlet (1109) connected to the plasma arc region (1108) between the cathode (1103) and the first anode (1104).

[0065] In the step of supplying power to the plasma arc region (1108), the supplied power may be 1 kW to 30 kW, and preferably 5 kW to 20 kW. The power supplied to the plasma arc region (1108) can maintain the temperature of the plasma center generated in the plasma arc region (1108) at a high temperature of 3,000°C to 20,000°C, and the thermal decomposition of the catalyst precursor to be subsequently introduced can be effectively carried out, or the synthesis reaction of carbon nanotubes can be synthesized in large quantities in a short period of time.

[0066]

[0067] Next, regarding the step (S2) of introducing a catalyst precursor and a carbon raw material into the plasma arc region through a central inlet, in this step, the catalyst precursor may correspond to the types mentioned earlier and may be introduced via a ball feeder or screw feeder, etc., at a rate of 0.01 g / min to 1 g / min. In addition, the carbon raw material is a material that can serve as a raw material for carbon nanotube formation and may be introduced, for example, at a flow rate of 0.1 to 20 LPM, and its types include methane (CH4), ethane (C2H6), acetylene (C2H2), ethylene (C2H4), propane (C3H8), and butane (C4H 10 ), pentane (C5H 12 ), hexane (C6H 14 It may include one or more of ) and ferrocene (Fe(C5H5)2), but is not limited thereto.

[0068] Additionally, the catalyst precursor and carbon raw material may be introduced through a central inlet (1101) connected to the center of the plasma arc region (1108) within the plasma device (1000).

[0069] A plasma device (1000) according to one embodiment includes a central inlet (1101) connected to the center of a plasma arc region (1108) within a plasma torch (1100), and a side inlet (1110) connected to the side of a plasma arc region (1108). However, if the catalyst precursor and carbon raw material are introduced into the plasma arc region (1108) through the side inlet (1110) instead of through the central inlet (1101) of the plasma device (1000), it is difficult to achieve an appropriate plasma temperature even if the power supplied to the plasma arc region (1108) is set to more than double, so that relatively large catalyst particles may be formed. As a result, most of the carbon nanotubes finally synthesized may be multi-wall carbon nanotubes (MWCNT) or thin-wall carbon nanotubes (TWCNT), which is undesirable in terms of selectivity and synthesis rate.

[0070] Meanwhile, when the catalyst precursor and carbon raw material are introduced through the central inlet (1101), they may be introduced together with a carrier gas having a flow rate of, for example, 5 to 100 LPM. The carrier gas facilitates the smooth introduction of raw materials such as the catalyst precursor and serves to protect the cathode. Specific types may include one or more of nitrogen (N2), hydrogen (H2), argon (Ar), and helium (He), but are not limited thereto.

[0071]

[0072] Next, regarding the step (S3) of thermally decomposing the catalyst precursor, the catalyst precursor may be thermally decomposed at a high temperature in the center of the previously generated plasma, thereby forming a catalyst with a size of 10 nm or less, preferably 5 nm or less, more preferably 3 nm or less. In this case, the catalyst precursor may specifically include metallocenes such as ferrocene, nickelocene, cobaltocene, osmocene, and ruthenocene, or iron (Fe), nickel (Ni), cobalt (Co), chromium (Cr), tungsten (W), titanium (Ti), ruthenium (Ru), rhodium (Rh), palladium (Pd), platinum (Pt), copper (Cu), yttrium (Y), zirconium (Zr), silicon (Si), or a combination thereof.

[0073] For example, since high temperatures of 3,000°C to 20,000°C are higher than the boiling point of iron (Fe) used as a catalyst, iron (Fe) can be thermally decomposed into very small and even gaseous states, it is desirable to provide power as described above.

[0074] The crystal phase of iron (Fe) changes with temperature; the gamma phase is formed at high temperatures, while the alpha phase is formed at medium or low temperatures, which can be confirmed through X-ray diffraction (XRD).

[0075] As an example, a catalyst formed by thermally decomposing a catalyst precursor through the above range of power may satisfy the following Equation 1, in which the ratio of the intensity of the α-phase peak to the intensity of the γ-phase peak in X-ray diffraction satisfies the following Equation 1.

[0076]

[0077] I α : Intensity of the α-phase peak in X-ray diffraction (XRD)

[0078] I γ: Intensity of the γ-phase peak in X-ray diffraction

[0079] If the ratio of the intensity of the α-phase peak to the intensity of the γ-phase peak satisfies Equation 1 above, then 70% or more, preferably 80% or more, more preferably 90% or more, and most preferably 99% or more of the carbon nanotubes synthesized through the catalyst may correspond to single-walled carbon nanotubes (SWCNT).

[0080]

[0081] Finally, the step (S4) of synthesizing carbon nanotubes by reacting the pyrolyzed catalyst precursor with the carbon raw material can be carried out at a high temperature of 3,000°C to 20,000°C, which is the center of the plasma arc region (1108), similar to the pyrolyzed reaction of the catalyst precursor mentioned earlier. Accordingly, the carbon nanotubes produced may correspond to single-walled carbon nanotubes (SWCNT) in an amount of 70% or more, preferably 80% or more, more preferably 90% or more, and most preferably 99% or more. In this case, based on single-walled carbon nanotubes, the ratio of the intensity of the G-peak to the intensity of the D-peak in the Raman spectrum ( ) can be 20 to 200, specifically 35 to 100, more specifically 40 to 80, or 45 to 50.

[0082] According to the method for manufacturing single-walled carbon nanotubes according to the embodiment described in detail above, by introducing a catalyst precursor and a carbon raw material into the center of a plasma obtained through specific power, single-walled carbon nanotubes with high yield and selectivity can be manufactured without using a promoter containing one or more of S, Mo, and V, and harmful gases such as H2S can not be generated.

[0083]

[0084] Hereinafter, the structure of the present invention and the resulting effects are to be explained in more detail through examples and comparative examples. However, these examples are intended to explain the present invention more specifically, and the scope of the present invention is not limited to these examples.

[0085]

[0086] Examples

[0087] 1. Preparation Example: Preparation of Carbon Nanotubes (CNT)

[0088] (1) Example 1

[0089] When the chemical vapor deposition (CVD) reactor is set to 1,100°C and the temperature is reached, the plasma torch is prepared for operation. After introducing carrier gas N25 LPM into the center of the cathode, process gas N230 LPM between the cathode and the anode, and sheath gas N220 LPM into the bottom of the anode, the plasma torch is operated at 5 kW. Subsequently, carbon nanotubes are manufactured by introducing CH45 LPM along with the carrier gas and ferrocene in powder form at a rate of 0.5 g / min using a ball feeder through the central inlet at the center of the cathode.

[0090]

[0091] (2) Example 2

[0092] Carbon nanotubes are prepared by introducing only ferrocene at a central inlet at 0.5 g / min, excluding CH4, in Example 1 above.

[0093]

[0094] (3) Comparative Example 1

[0095] When the chemical vapor deposition (CVD) reactor is set to 1,100°C and the temperature is reached, the plasma torch is prepared for operation. After introducing carrier gas N25 LPM into the center of the cathode, process gas N230 LPM between the cathode and the anode, and sheath gas N220 LPM into the bottom of the anode, the plasma torch is operated at 5 kW. Subsequently, carbon nanotubes are manufactured by introducing CH45 LPM along with the process gas and ferrocene in powder form at a rate of 0.5 g / min using a ball feeder through a side inlet, which is a side part of the plasma arc region.

[0096]

[0097] (4) Comparative Example 2

[0098] Carbon nanotubes are prepared by excluding CH4 from Comparative Example 1 above and introducing only ferrocene at a rate of 0.5 g / min through a side inlet.

[0099]

[0100] (5) Comparative Example 3

[0101] When the chemical vapor deposition (CVD) reactor is set to 1,100°C and the temperature is reached, the plasma torch is prepared for operation. After introducing carrier gas N25 LPM into the center of the cathode, process gas N230 LPM between the cathode and the anode, and sheath gas N220 LPM into the bottom of the anode, the plasma torch is operated at 10 kW. Subsequently, carbon nanotubes are manufactured by introducing CH45 LPM along with the process gas and ferrocene in powder form at a rate of 0.5 g / min using a ball feeder through a side inlet, which is a side part of the plasma arc region.

[0102]

[0103] (6) Comparative Example 4

[0104] Carbon nanotubes are prepared by excluding CH4 in Comparative Example 3 above and introducing only ferrocene at 0.5 g / min through a side inlet.

[0105]

[0106] (7) Comparative Example 5

[0107] A chemical vapor deposition (CVD) reactor is set to 1,100°C, and when the temperature is reached, preparations are made to operate the plasma torch. After introducing carrier gas N25 LPM into the center of the cathode, process gas N230 LPM between the cathode and the anode, and sheath gas N220 LPM into the bottom of the anode, the plasma torch is operated at 5 kW. Subsequently, carbon nanotubes are manufactured by introducing CH45 LPM and ferrocene in powder form at a rate of 0.1 g / min using a ball feeder through the heater reaction zone inlet at the top of the CVD reactor.

[0108]

[0109] (8) Comparative Example 6

[0110] Carbon nanotubes are prepared by excluding CH4 in Comparative Example 5 above and introducing only ferrocene at 0.5 g / min through the heater reaction zone inlet.

[0111]

[0112] 2. Experimental Example 1: Analysis of Catalyst Size Distribution

[0113] During the carbon nanotube manufacturing process of Examples 1 and 2 and Comparative Examples 1 to 6 above, a catalyst formed from ferrocene was obtained and analyzed as follows:

[0114]

[0115] (1) Transmission Electron Microscopy (TEM) Analysis

[0116] The catalyst samples of Examples 1 and 2 and Comparative Examples 1 to 6 obtained above were dispersed in ethanol by ultrasonic treatment, and then coated onto a Lacey carbon grid to prepare analysis samples. Subsequently, the analysis samples were observed using a transmission electron microscope (TEM). Among them, the TEM images of the catalysts in Example 1 and Comparative Example 1 are shown in Figures 4 and 5, respectively.

[0117]

[0118] (2) X-ray Diffraction (XRD) Analysis: Fe Phase Analysis and Crystal Size Calculation

[0119] X-ray diffraction analysis was performed on 500 of the catalysts obtained in Examples 1 and 2 and Comparative Examples 1 to 6, and the catalyst size distribution for each of the catalysts in Examples 1 and 2 and Comparative Examples 1 to 6 is shown in FIG. 3. In addition, the Fe phase and crystal size of the catalyst in Example 1 and Comparative Example 1 are shown in FIG. 4 and FIG. 5, respectively.

[0120]

[0121] 3. Experimental Example 2: Analysis of Single-Walled Carbon Nanotube Selectivity

[0122] The carbon nanotubes prepared in Examples 1 and 2 and Comparative Examples 1 to 6 above were analyzed as follows:

[0123]

[0124] (1) TEM analysis

[0125] 500 carbon nanotubes prepared in Examples 1 and 2 and Comparative Examples 1 to 6 were observed using a transmission electron microscope (TEM). The distribution ratio of carbon nanotubes for each of Examples 1 and 2 and Comparative Examples 1 to 6 is shown in FIG. 6.

[0126] Among them, the TEM images of carbon nanotubes in Example 1 and Comparative Example 1 are shown in Figs. 7 and 8, respectively.

[0127]

[0128] (2) XRD analysis

[0129] X-ray diffraction analysis was performed on the carbon nanotubes prepared in Examples 1 and 2 and Comparative Examples 1 to 6 above, and the distribution ratio of carbon nanotubes according to the Fe crystal phase for each of the carbon nanotubes of Examples 1 and 2 and Comparative Examples 1 to 6 is shown in FIG. 6. In addition, the catalytic Fe crystal phase in Example 1 and Comparative Example 1 ( ) is shown in Fig. 7 and Fig. 8, respectively.

[0130]

[0131] 4. Experimental Example 3: Crystallinity Analysis (Raman Spectroscopy Analysis)

[0132] Raman spectroscopy analysis was performed on the carbon nanotubes prepared in Examples 1 and 2 and Comparative Examples 1 to 6 above, and I for each of the carbon nanotubes of Examples 1 and 2 and Comparative Examples 1 to 6 G / D The values ​​are shown in Fig. 6.

[0133]

[0134] As shown in the drawings of the results of the above manufacturing and experimental examples, when comparing Examples 1 and 2, in which the catalyst precursor and carbon raw material were introduced through the central inlet and the plasma power was 5 kW, with Comparative Examples 1 to 6, in which they were introduced through the side inlet or the heater reaction zone, the Raman spectrum I of the synthesized carbon nanotubes G / D The value has a range of 35 to 100, and of the formed catalyst It can be seen that the value is greater than 0.01 and less than 2, and it can be confirmed that the ratio of manufactured single-walled carbon nanotubes is 80% or more. In addition, when the catalyst precursor was introduced through the side inlet, catalysts of various sizes in a wide range of 2 to 200 nm were formed, whereas when introduced through the center inlet, catalysts of less than 10 nm were formed.

[0135] Meanwhile, looking at Figures 3 and 6, it can be seen that in the case of Example 1 and Comparative Example 1, where CH4 and ferrocene were added simultaneously, the catalyst size is smaller and distributed within a narrower range compared to the case of Example 2 and Comparative Example 2, where only ferrocene was added without CH4, while all other conditions were identical, and the CNT distribution also shows a higher proportion of SWCNT. This can be seen as a result that occurs when the amount of carbon added increases as the ferrocene decomposes and Fe aggregates, causing a portion of the Fe surface to be encapsulated with carbon, thereby preventing the increase in Fe particle size.

[0136]

[0137] Although the embodiments have been described above with reference to limited drawings, those skilled in the art will readily understand that various technical modifications and variations can be applied based on the above, and that the various embodiments described above can be combined with one another without contradiction. For example, appropriate results can be achieved even if the described techniques are performed in a different order than described, and / or the components of the described system, structure, device, circuit, etc. are combined or combined in a form different from the described method, or are replaced or substituted by other components or equivalents.

[0138] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims set forth below.

[0139]

[0140] Explanation of the symbols

[0141] 1000 : Plasma device

[0142] 1100 : Plasma torch

[0143] 1101 : Center input

[0144] 1102 : Coolant

[0145] 1103 : Cathode

[0146] 1104: First anode

[0147] 1105 : Second anode

[0148] 1106 : 1st Arc

[0149] 1107 : 2nd Arc

[0150] 1108 : Plasma arc region

[0151] 1109: Process gas inlet

[0152] 1110: Side input

[0153] 1111 : Insulator

[0154] 1200 : Heater

[0155] 1201: Heater reaction zone inlet

[0156] 1202 : Heater reaction zone

Claims

1. A method for manufacturing single-walled carbon nanotubes using a plasma device, A step of generating plasma in a plasma arc region; A step of introducing a catalyst precursor and a carbon raw material into a plasma arc region through a central inlet; A step of thermally decomposing the above catalyst precursor; and A step of synthesizing carbon nanotubes by reacting the above-mentioned pyrolyzed catalyst precursor with a carbon raw material. Includes, The above plasma device is, A cathode and an anode forming a plasma arc region, A central inlet connected to the center of the plasma arc region, and including a side inlet connected to the side of the plasma arc region, Method for manufacturing single-walled carbon nanotubes.

2. In Paragraph 1, The above anode is, First anode, and It includes a second anode located at the bottom of the first anode, and A further comprising an insulator between the first anode and the second anode, Method for manufacturing single-walled carbon nanotubes.

3. In Paragraph 2, The step of generating plasma in the above plasma arc region is, Step of injecting process gas into the plasma arc region; and Step of supplying power to the above plasma arc region Includes, The above power is 1 kW to 30 kW, Method for manufacturing single-walled carbon nanotubes.

4. In Paragraph 2, The step of generating plasma in the above plasma arc region is, A step of generating plasma by electric discharge of the above-mentioned cathode and first anode; and Step in which the length of the plasma arc is increased by the above-mentioned cathode and second anode including, Method for manufacturing single-walled carbon nanotubes.

5. In Paragraph 3, The above process gas comprises one or more of nitrogen (N2), hydrogen (H2), argon (Ar), and helium (He). Method for manufacturing single-walled carbon nanotubes.

6. In Paragraph 1, The above catalyst precursor is, One or more of ferrocene, nickelocene, cobaltocene, osmocene, ruthenocene, iron (Fe), nickel (Ni), cobalt (Co), chromium (Cr), tungsten (W), titanium (Ti), ruthenium (Ru), rhodium (Rh), palladium (Pd), platinum (Pt), copper (Cu), yttrium (Y), zirconium (Zr), and silicon (Si), Method for manufacturing single-walled carbon nanotubes.

7. In Paragraph 1, The above carbon raw material is, Methane (CH4), Ethane (C2H6), Acetylene (C2H2), Ethylene (C2H4), Propane (C3H8), Butane (C4H 10 ), pentane (C5H 12 ), hexane (C6H 14 ) and one or more of ferrocene (Fe(C5H5)2), Method for manufacturing single-walled carbon nanotubes.

8. In Paragraph 1, The step of thermally decomposing the above catalyst precursor is, The above catalyst precursor is thermally decomposed into catalysts smaller than 10 nm in size at a high temperature of 3,000°C to 20,000°C, Method for manufacturing single-walled carbon nanotubes.

9. In Paragraph 8, The catalyst formed by thermally decomposing the above catalyst precursor satisfies the following Equation 1, Method for manufacturing single-walled carbon nanotubes. I α : Intensity of the α-phase peak in X-ray diffraction (XRD) I γ : Intensity of the γ-phase peak in X-ray diffraction 10. In Paragraph 1, The step of synthesizing carbon nanotubes by reacting the above-mentioned pyrolyzed catalyst precursor with a carbon raw material is, Synthesis reaction carried out at a high temperature of 3,000℃ to 20,000℃, Method for manufacturing single-walled carbon nanotubes.

11. In Paragraph 1, Not using a promoter that includes one or more of S, Mo, and V, Method for manufacturing single-walled carbon nanotubes.

12. In Paragraph 1, Through the central inlet above, a carrier gas and a carbon raw material are introduced, and The above carrier gas comprises one or more of nitrogen (N2), hydrogen (H2), argon (Ar), and helium (He). Method for manufacturing single-walled carbon nanotubes.

13. In Paragraph 1, Through the above-mentioned side inlet, sheath gas is introduced, and The above sheath gas comprises one or more of nitrogen (N2), hydrogen (H2), argon (Ar), and helium (He). Method for manufacturing single-walled carbon nanotubes.

14. Carbon nanotubes produced by the method for producing single-walled carbon nanotubes described in claim 1.

15. In Paragraph 14, The carbon nanotubes manufactured above satisfy the following Equation 2, Carbon nanotubes. I G : Intensity of the G-peak in the Raman spectrum I D : Intensity of the D-peak in the Raman spectrum

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