KR101252333B1 - A controllable fabrication method of graphene sheets using the thermal plasma chemical vapor deposition method - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing graphene by thermal plasma chemical vapor deposition, wherein a long carbon rod is attached to an anode end of a plasma apparatus, and the graphite plate is slightly removed from the rod. After positioning vertically, thermally decompose liquid and gaseous carbon source materials such as ethanol and methane, using the high temperature of thermal plasma, and atomize the carbon atom beam, which is piggybacked on the thermal plasma flame, through a long tube. Reducing the energy of the beam and simultaneously stabilizing and uniformizing the beam to impinge on the graphite plate to produce graphene; Since the carbon source material can be continuously supplied, it is possible to continuously and mass produce graphene, and since graphene is synthesized by epitaxial growth by the surface structure of the graphite plate (graphene structure), pure crystals having high crystallinity can be produced. Graphene sheets can be prepared, the number of layers of graphene sheets can be adjusted by adjusting the injection rate of the carbon source to be injected, and the distance between the rods attached to the anode and the graphite plate is controlled. The size of the graphene can be adjusted, and a long graphene sheet in the shape of a band is produced by passing a long graphite plate through a carbon atom beam at a constant speed while maintaining a constant gap between the rod attached to the anode and the graphite plate. If the graphite plate is rotated, the number of layers of the graphene sheet can be adjusted according to the rotational speed. If the graphite plate is rotated at a high speed, the injection speed of the carbon source can be increased. It can increase the amount of graphene produced per unit time.

Graphene Sheet, Thermal Plasma Chemical Vapor Deposition, Carbon Atom Beam

Description

A controllable fabrication method of graphene sheets using the thermal plasma chemical vapor deposition method}

The present invention relates to a method for producing graphene by thermal plasma chemical vapor deposition, and more particularly, to injecting carbon source materials, such as alcohol and hydrocarbons, into a thermal plasma flame at a constant rate. When the carbon atoms generated by pyrolysis are carried on the thermal plasma flame, the carbon atom beam passes through the carbon atom beam by attaching a long carbon rod to the anode, which reduces the energy of the beam and at the same time stabilizes and makes the beam uniform. A graphene sheet is produced by impinging a graphite plate positioned perpendicular to the rod at a distance from the end of the carbon rod, or a long strip of graphene sheet is produced by passing a long graphite plate through a carbon atom beam at a constant speed, or To adjust the number of layers of the graphene sheet according to the rotation speed, or to rotate the graphite plate at high speed Books to be produced per unit time by increasing the infusion rate of the carbon source So by thermal plasma chemical vapor deposition to increase the amount of pin Yes relates to a process for preparing a pin.

Graphene [ Nature Mater 6, 18319 (2007)] is a perfect 2-D material of atomic thickness in which the hexagonal rings made by sp2 bonds with only carbon atoms are honeycomb-shaped. That is, it is a substance corresponding to one layer of graphite which is a layer structure. Recently, the graphene has a very high electrical conductivity at room temperature, the unusual physical properties such as the quantum Hall effect at room temperature, the behavior of electrons like massless dirac fermion, and the possibility of various applications such as electronic devices, transparent electrodes, gas sensors, etc. It becomes the target of. In order to study and apply the physical properties of graphene, it is essential to develop a technique for producing a large amount of controlled high crystalline graphene.

A method of copying a layer of graphite by a method of producing a small amount of graphene [Science 306, 666 (2004)], a method of epitaxial growth on a substrate by a chemical vapor deposition (CVD) method [Surf. Sci. 264 , 261 (1992)], and methods for producing silicon carbide by pyrolysis [Science 312 , 1191 (2006)]. A method for mass production of graphene is a method of oxidizing graphite to disperse in a solvent and to reduce the dispersed graphene oxide [J Am. Chem. Soc. 128, 7720 (2006)] and a method for producing graphene by reacting ethanol with Na [Nature Nanotech. 4, 30 (2008)], the crystallinity of graphene may be affected by chemical reactions in the manufacturing process. Pyrolysis of ethanol into microwave plasma [Nano letters 8 , 2012 (2008)] is a continuous process, but graphene is released by gas collisions for a short time through the plasma region without the aid of catalysts or other materials. The disadvantage is that the yield is relatively low because it is made. In addition, these methods cannot artificially control the number or size of graphene sheets.

Pyrolyze and atomize alcohols or hydrocarbon-based materials under a specific temperature implemented by thermal plasma flames, and then piggyback them onto thermal plasma flames to form carbon atom beams, and attach long rods to the anode to stabilize the beams by flowing them into the rods. And made uniform, and then impinged on a graphite plate perpendicular to the rod to produce a graphene. Since the present invention can continuously supply a carbon source, it is possible to continuously and mass-produce graphene. Since the generated thermal plasma can realize high temperature of thousands to tens of thousands, it is possible to manufacture high quality graphene having high crystallinity. , The number of layers of the graphene sheet can be adjusted by adjusting the injection speed of the carbon source, the size of the graphene can be adjusted by adjusting the inner diameter and length of the carbon rod attached to the anode and the distance between the graphite plates, and the long graphite The long band-shaped graphene sheet can be manufactured by passing the carbon atom beam at a constant speed, and the graphene sheet can be adjusted according to the rotational speed by rotating the graphite plate, and the graphite plate is rotated at high speed. In addition, by increasing the injection speed of the carbon source material can be increased the amount of graphene sheet produced per unit time. Therefore, it is believed that the above problems can be solved through the present invention.

As described above, the graphene sheet manufacturing method using the thermal plasma chemical vapor deposition method according to the present invention comprises the steps of forming a high temperature thermal plasma flame by injecting plasma gas; Injecting a gaseous or liquid carbon source material into the plasma flame into the formed high temperature thermal plasma flame to form a carbon atom beam in which atomized carbon atoms are piggybacked on the thermal plasma flame; Attaching an elongated tube to the anode to allow the formed carbon atom beam to flow into the rod, thereby reducing energy of the carbon atom beam and simultaneously stabilizing and making the beam uniform; Impinging the carbon atom beam exiting the rod onto a graphite plate positioned vertically at a suitable distance from the end of the rod; Adjusting the number of layers of the graphene sheet by adjusting the injection rate (mL / min) of the carbon source material; Adjusting the size of the graphene sheet by attaching rods with different inner diameters and adjusting the gap between the attached rods and graphite plates according to the inner diameters of the rods; Instead of fixing the graphite plate, passing the long graphite plate through a carbon atom beam at a constant speed to produce a long strip-shaped graphene sheet; Instead of fixing the graphite plate, the graphite plate is rotated and the rotational speed is controlled to adjust the time at which the carbon atom beam hits the graphite plate, thereby controlling the number of colliding carbon atoms. By producing a graphene by performing a process including the step of increasing the amount of graphene produced per unit time by increasing the speed, due to the epitaxial growth by the surface structure (graphene structure) of the graphite plate It is possible to produce high purity and high crystalline graphene, to control the number of layers of graphene sheets, to control the size of graphene sheets, to produce long strip-shaped graphene sheets, and to continuously It is possible to supply graphene continuously and in mass production.

In order to achieve the above object, the graphene manufacturing method using the thermal plasma chemical vapor deposition method according to the present invention comprises the steps of: (a) injecting Ar, which is a plasma gas, into a plasma gas inlet to form a thermal plasma flame of 1000 to 20000 degrees; (B) Inject the carbon source material into the plasma frame continuously through the carbon source material inlet by using a syringe pump or a gas flow control device to atomize the carbon source material using the high temperature of the plasma, and then piggyback on the thermal plasma to attach it to the anode. Flowing along the rod of carbon or ceramic material; (C) colliding the carbon atom beam with the plate by placing a metal plate such as graphite or copper perpendicularly to the rod slightly away from the end of the rod attached to the anode; It includes, (D) step (b) to adjust the number of layers of the graphene sheet by adjusting the injection rate (mL / min) of the carbon source; (E) adjusting the size of graphene in step (b) and (c) by attaching rods with different inner diameters to the anode and manufacturing graphene by varying the distance between the rods and the plates according to the inner diameter of the rods; (F) a step of producing a long strip-shaped graphene sheet by passing a carbon atom beam while moving the strip-shaped long plate at a constant speed in step (c); (G) How to control the number of layers of the graphene sheet by rotating the plate in step (c) and the amount of graphene made per unit time by increasing the injection speed of carbon source while rotating the plate at high speed It includes a method of increasing.

In the present invention, in the step (a), the high temperature thermal plasma flame is formed using a non-feeding or transporting thermal plasma torch, and the diameter of the anode nozzle of the plasma torch is 2 to 15 mm in size. 4-6 mm is preferable. Suitable temperatures of the plasma flame formed are 1000 to 20000 oC, with 5000 to 10000 oC being preferred. In addition, in the present invention, the injection hole for injecting a carbon source material such as ethanol into the plasma frame in the step (b) is located between the plasma cathode and 0 to 10 mm distance, preferably between 0 and 5 mm. The carbon source materials used are alcohol liquids such as ethanol, gas such as hydrocarbon-based methane, ethylene, acetylene, and CO gas. The rod attached to the anode may use a ceramic rod that can withstand high temperatures, but a carbon rod that is resistant to high temperatures and is easy to process is preferable.As a carbon atom beam flows along the rod, the energy of the beam is reduced while stabilizing and uniformizing. Rod to make can be used a rod of 10 ~ 100 cm long, but the length is preferably between 10 ~ 30 cm and the inner diameter is preferably between 0.5 ~ 5 cm.

In the step (c), the plate placed in front of the rod to which the carbon atom beam collides may be used if it is a plate of all heat-resistant materials, but a graphite plate capable of epitaxial growth of graphene is preferable, and the graphite plate is formed from the end of the rod. It may be located 0.5 to 20 cm away but preferably 3 to 10 cm away, preferably perpendicular to the rod.

In the method (d), the graphene sheet is synthesized by controlling the injection rate of the carbon source. When the carbon source is a liquid such as ethanol, the syringe pump is used at a rate of 0.001 to 1 mL / min and the gaseous state is methane. In this case, when the gas flow control device is injected at a rate of 10 to 1000 sccm, graphene sheets are produced between 1 and several tens of layers.

In the method (E), the rods having different inner diameters are attached to the anodes, and the graphene is manufactured by varying the distance between the rods and the graphite plates according to the inner diameter of the rods. By attaching a carbon rod of 2 cm and adjusting the distance between the graphite plate and the carbon rod at intervals of 3 to 10 cm, a graphene sheet having a size between 100 nm and several tens of μm is produced.

In the method (bar), a carbon atom beam is formed at a constant speed (1 mm / s to 1 m / s) using a linear motor while maintaining a constant distance between the rod and the plate attached to the anode. When passing through, the carbon atom beam strikes the plate at the position passing through the atomic beam for a certain time, and the plate moves sideways at a constant speed, so that the graphene sheet grows to the side to produce a long strip of graphene sheet.

In the method (g), the plate is rotated instead of being fixed. When the carbon source material is injected at a constant speed while rotating the plate at a constant speed (1 to 3000 rpm), the amount of carbon atoms that collide with a specific portion of the plate will be constant at each rotation, and as the rotation speed increases, the amount of carbon atoms that collide will decrease. will be. If the graphene made in the collision is removed from the plate before the next collision, the layers of the graphene sheet can be adjusted by controlling the rotation speed. In addition, since the time required for the graphene to stay in the reaction zone is shortened when rotating, thin graphene is produced even if the carbon source injection rate is greatly increased. Therefore, increasing the injection rate of the carbon source increases the amount of graphene produced per unit time. .

Hereinafter, a method of preparing graphene using thermal plasma chemical vapor deposition according to the present invention will be described in detail with reference to the accompanying drawings.

According to the present invention, a carbon atom beam produced by piggybacking carbon atoms produced by thermal decomposition of a carbon source material such as alcohol such as ethanol, hydrocarbons such as methane and carbon such as CO at a high temperature of thermal plasma is applied to an anode. Graphite or copper, which is attached to a tube and flows into the rod, reduces the energy of the carbon atom beam, stabilizes it, makes it uniform and places it perpendicular to the rod some distance (3 to 10 cm) from the rod, Graphene is produced by colliding with a metal plate such as zinc. That is, carbon source materials such as ethanol are atomized using thermal plasma, and the rods are attached to the anodes to flow into the rods, thereby reducing the energy of the carbon atom beams and at the same time stabilizing and uniformizing the carbon atom beams. Since the carbon atom beam exiting the beam rapidly decreases energy, the carbon atom beam with appropriate energy is collided with the plate by adjusting the distance from the end of the rod to the plate, and thus the surface structure of the plate is momentarily affected, namely epitaxial growth. Graphene is synthesized. In this case, when the rod having a large inner diameter is attached, the kinetic energy of the carbon atom beam is greatly reduced in the rod, thereby allowing the plate to be positioned relatively close to the rod. The size of the graphene sheet is influenced by the uniformity of the carbon atom beam and the surface roughness of the plate, and the carbon atom beam exits the rod end and spreads laterally as it moves away from the end of the rod. The further away it decreases. Therefore, by attaching a long rod with a large inner diameter to sufficiently reduce the kinetic energy of the carbon atom beam in the rod, the larger graphene sheet is produced as the graphene is manufactured by placing the plate close to the rod. In the graphene manufacturing method as described above, since the carbon source is pyrolyzed at high temperature, pure graphene having high crystallinity may be prepared by fully atomizing and epitaxial growth caused by the graphene structure as the carbon atom beam collides with the plate. It can control the number of layers of graphene sheet by adjusting the rate of injecting carbon source material, and can control the size of graphene by adjusting the gap between the rod and the plate, The long band-shaped graphene sheet can be manufactured by passing the beam, and when the plate is rotated, the number of layers of the graphene sheet can be adjusted by controlling the rotational speed. Can increase the amount of graphene produced per unit time, and can continuously supply carbon source materials. Graphene on the door can enable continuous and mass production.

Referring to the graphene manufacturing method using the thermal plasma chemical vapor deposition method in detail step by step as follows.

First, a high temperature thermal flame is formed using a thermal plasma torch. At this time, as shown in Figure 1, the thermal plasma torch is formed using a non-feeding or transfer thermal plasma torch, the diameter of the anode nozzle of the plasma torch is 2 to 15 mm in size, 4 to 6 mm desirable. Suitable temperatures of the plasma flame formed are 1000 to 20000 oC, with 5000 to 10000 oC being preferred.

Next, a liquid or gaseous carbon source material is continuously injected into the plasma flame at a constant rate, pyrolyzed to high temperature of the plasma, atomized, and then piggybacked on a thermal plasma. In this process, the injection hole for injecting the carbon source material into the plasma flame is located between 0 and 10 mm distance from the plasma cathode, preferably between 0 and 5 mm. As the carbon source material used, alcohols such as liquid ethanol, hydrocarbon gases such as methane, ethylene and acetylene, and CO are used. The injection rate of the carbon source material is controlled according to the number of layers of the graphene sheet to be synthesized.

Next, as shown in FIG. 1, a rod is attached to the end of the anode and the plate is positioned perpendicular to the rod slightly away from the end of the rod to impinge the carbon atom beam with the appropriate energy onto the plate. Rods attached to the anode for the purpose of reducing the energy of the carbon atom beams formed in this process and at the same time stabilizing and making them uniform can be made of rods such as ceramics and carbon, but carbon rods that can withstand high temperatures and are easily processed are preferred. . The rod can be used with rods of various lengths between 5 and 50 cm, but is preferably between 15 and 25 cm. When a carbon atom beam hits a plate with too high energy, carbon nanotubes are made instead of graphene. The energy of the carbon atom beam decreases little by little as it flows along the rod, but rapidly decreases as it exits the rod end and reaches the plate, and the beam spreads rapidly, so the distance from the end of the rod to the plate is very important. The inner diameter of the rod and the length of the rod and the distance between the end of the rod are related to each other. If the rod has an inner diameter of 0.5 cm and a length of 20 cm, it is preferable to place the plate at a distance of about 10 cm.

Next, the number of layers of the graphene sheet is adjusted by adjusting the injection rate (mL / min) of the carbon source material. If the carbon source is a liquid such as ethanol is injected at a rate of 0.001 ~ 1 mL / min, in the case of gaseous phase, such as methane is injected at a rate of 10 ~ 5000 sccm, graphene sheets of between 1 to several dozen graphene is prepared.

Next, the size of the graphene sheet is adjusted by attaching a rod having a different inner diameter to the anode and adjusting the distance between the rod and the plate according to the inner diameter. A carbon rod with an inner diameter of 0.5 to 2 cm is attached, and the gap between the rod and the plate is adjusted to 3 to 10 cm, and a graphene having a size of 100 nm to several tens of μm is prepared.

Next, when a long graphite plate (10 cm to 1 m) is passed through a carbon atom beam at a constant speed (1 mm / s to 1 m / s) using a linear motor, a long strip-shaped graphene sheet is produced. The width of the graphene sheet is adjusted by adjusting the size of the inner diameter of the carbon rod (0.5 ~ 50 cm) and the number of layers of the graphene sheet is controlled by controlling the moving speed of the graphite plate.

Next, when the plate is rotated at a constant speed (1 to 3000 rpm), the time that the carbon atom beam impinges on a specific portion of the plate is constant every revolution, and the time becomes shorter as the rotation speed is increased. Adjusting the rotational speed controls the number of layers of graphene sheets, and increasing the injection rate of carbon source (1 to 60 mL / min) increases the amount of graphene produced per unit time.

The graphene thus prepared is analyzed by SEM (scanning electron microscopy) method and the results are shown in FIGS. 2, 3, and 4. As shown in FIG. 3, when the amount of carbon source injected per unit time is small, very thin transparent graphene is prepared, and when the amount is large, thick opaque graphene is prepared. This shows that the number of layers of the graphene sheet varies depending on the injection speed of the carbon source. As shown in FIG. 4, the size of the graphene sheet is changed according to the distance between the carbon rods attached to the graphite plate and the graphite plate. In addition, as shown in Figures 2, 3, 4, the product produced through the above process is present as a very pure graphene does not contain other impurities.

1 is a view schematically showing the configuration of a thermal plasma chemical vapor deposition apparatus.

≪ Description of reference numerals &

1. Power supply.

2. Plasma gas inlet.

3. Plasma cathode.

4. Plasma anode.

5. Carbon source inlet.

6. Thermal Plasma Flame.

7. Carbon rods.

8. Graphite plate.

9. Air vents.

Figure 2 is a scanning electron microscopy (SEM) photograph of the high magnification (top) and low magnification (bottom) of the graphene sheet prepared by thermal plasma chemical vapor deposition according to the present invention.

3 is a graphene sheet (top) and a large number of layers (graph) of the graphene sheet prepared by thermal plasma chemical vapor deposition method by varying the ethanol injection rate of 0.05 mL / min and 0.1 mL / min according to the present invention A picture of a graphene sheet (below).

4 is attached to a small diameter carbon rod (inner diameter: 0.5 cm, length: 20 cm) and a large diameter carbon rod (inner diameter: 1.5 cm, length: 20 cm) according to the present invention and the gap between the carbon rod and the graphite plate is small diameter This is a picture of a small graphene sheet (top) and a large graphene sheet (bottom) produced by thermal plasma chemical vapor deposition, differing from 10 cm for carbon rods and 3.5 cm for large diameter carbon rods.

Claims (10)

(A) injecting the plasma gas into the plasma gas injection hole to form a thermal plasma flame of 1000 ~ 20000 degrees Celsius; (B) injecting carbonaceous material of gaseous or liquid phase into the plasma flame through the carbon source material injection hole into the formed thermal plasma flame to atomize the carbon atoms onto the thermal plasma flame to form a carbon atom beam; (C) stabilizing and uniformizing the beam while simultaneously reducing the energy of the carbon atom beam by attaching a tube of 10 to 100 cm length to the anode by attaching a tube of 10 to 100 cm in length to the anode; ; (D) impinging the carbon atom beam exiting the rod onto a plate positioned perpendicularly at a distance of 0.5-20 cm from the end of the rod; Graphene manufacturing method using a thermal plasma chemical vapor deposition method comprising a. The method of claim 1, In the step (a), the thermal plasma flame of 1000 to 20000 degrees Celsius is formed using a non-feedable or transferable thermal plasma torch, and the diameter of the anode nozzle of the plasma torch is 2 to 15 mm and the Graphene manufacturing method using the thermal plasma chemical vapor deposition method, characterized in that the temperature is 1000 ~ 20000 degrees Celsius. The method of claim 1, The method of manufacturing graphene using the thermal plasma chemical vapor deposition method characterized in that the (b) injecting the gaseous or liquid carbon source material specified in the step (b) using a syringe pump or a gas flow control device. The method of claim 1, In order to reduce the energy of the carbon atom beam generated in the step (c) and stabilize the beam and to make the beam uniform, attaching a rod having an inner diameter of 0.5 to 5 cm to the anode is made of carbon that is well tolerated at high temperature. Method for producing graphene using thermal plasma chemical vapor deposition method, characterized in that. The method of claim 3, The method of manufacturing graphene using the thermal plasma chemical vapor deposition method characterized in that in the step (b) by controlling the injection rate of the carbon source material to control the number of layers (layer) of the graphene sheet.        The method of claim 1,        Thermal plasma chemical vapor phases characterized in that to control the width of the graphene sheet (synthesizing) by attaching a rod having a different inner diameter in the step (d) and synthesizing by varying the distance between the rod and the plate according to the attached rod. Graphene manufacturing method using the deposition method        The method of claim 1,        Instead of fixing the plate in the step (d), the strip-shaped plate is maintained at a constant speed of 1 mm / s to 1 m / s using a linear motor while maintaining a constant gap between the attached rod and the plate. Graphene manufacturing method using thermal plasma chemical vapor deposition, characterized in that to produce a strip-like long graphene sheet through the atomic beam        The method of claim 1,        In the step (d), instead of fixing the plate, the plate is rotated and the carbon source material is injected at a constant speed, thereby controlling the rotation speed of the plate to control the number of layers of the graphene sheet and increasing the amount of the carbon source to be injected. Method for producing graphene using thermal plasma chemical vapor deposition, characterized in that to increase the amount of graphene produced per unit time delete delete

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