KR20180065424A - Graphene Fabricating Method - Google Patents

Abstract

According to an embodiment of the present invention, provided is a graphene production method comprising the following steps: forming graphene oxide by mixing graphite, sulfuric acid (H_2SO_4), and potassium permanganate (KMnO_4); and undergoing heat treatment using the graphene oxide produced in the previous step at a temperature exceeding a decomposition temperature for sulfur (S) and at a temperature below a decomposition temperature for carbon (C). According to the present invention, it is possible to effectively reduce a production time.

Description

[0001] Graphene Fabricating Method [

Embodiments of the present invention relate to a method of manufacturing a graphene.

Generally, graphite has a structure in which a plate-shaped two-dimensional graphene sheet in which carbon atoms are connected in a hexagonal shape is laminated. Recently graphene was stripped from graphite and its properties were investigated.

The most notable feature is that when electrons move from graphene, the mass of electrons flows like zero. This means that the electrons flow at the speed at which the light travels in the vacuum, that is, the light flux. Graphene also has an unusual half-integer quantum Hall effect on electrons and holes. Also, to date, the electron mobility of graphene is known to have a high value of about 20,000 to 50,000 cm 2 / Vs.

As a method for synthesizing graphene, a layer of graphite can be separated to form graphene, and methods such as mechanical peeling, chemical peeling and non-oxidative peeling are used. When chemical stripping is used, graphene oxide graphene is produced using strong acid. In order to remove the sulfur component of sulfuric acid used, it is generally repeated several times using deionized water. However, it is difficult to completely remove sulfur by only cleaning using ultrapure water, and there is a problem that the amount of generated wastewater increases.

Korean Patent Laid-Open Publication No. 2015-0021897 (2015.03.03) "Method for producing graphene, graphene, and manufacturing apparatus"

It is an object of the present invention to provide a graphene manufacturing method capable of manufacturing high quality graphene with minimal cleaning.

One embodiment of the present invention is a method of manufacturing a semiconductor device, comprising: mixing graphene, sulfuric acid (H2SO4), and potassium permanganate (KMnO4) to form an oxidized graphene; And heat treating the formed graphene grains at a temperature not lower than a decomposition temperature of sulfur (S) and not higher than a decomposition temperature of carbon (C).

In one embodiment of the present invention, the annealing step may heat the graphene oxide using radiant heat.

In one embodiment of the present invention, the heat-treating step may be heat-treated for 30 seconds to 20 minutes.

In one embodiment of the present invention, the heat-treating step may be heat-treated in a vacuum or an inert gas atmosphere.

In one embodiment of the present invention, the heat treatment may be performed in a gas atmosphere containing a reducing gas of 0% or more and 5% or less.

In one embodiment of the present invention, the heat treatment may be performed at a temperature ranging from 200 ° C to 2500 ° C.

In one embodiment of the present invention, the method may further include forming the graphene grains to an arbitrary size by milling the graphene grains.

Another embodiment of the present invention is a method of manufacturing a semiconductor device, comprising: mixing graphite, sulfuric acid (H2SO4), and potassium permanganate (KMnO4) to form oxidized graphene; And heat treating the formed graphene grains by using radiant heat at a temperature ranging from 250 ° C to 300 ° C for 1 minute to 10 minutes.

In one embodiment of the present invention, the method may further include forming the graphene grains to an arbitrary size by milling the graphene grains.

In one embodiment of the present invention, the step of heat-treating may be performed under an inert gas atmosphere containing a vacuum or 0% to 5% reducing gas.

An embodiment of the present invention provides a graphene produced by any one of claims 1 to 10 and comprising 0 to 2 atomic percent oxygen.

Other aspects, features, and advantages other than those described above will be apparent from the following detailed description, claims, and drawings.

According to the embodiments of the present invention as described above, it is possible to remove impurity sulfur by heat-treating the graphene oxide formed by chemical stripping at a temperature lower than the decomposition temperature of carbon above the decomposition temperature of sulfur, Graphene can be produced by reducing oxidized graphene. Particularly, in the method of manufacturing graphene according to an embodiment of the present invention, sulfur can be removed quickly in a predetermined temperature range by heat-treating the graphene grains using radiant heat, thereby shortening the processing time effectively.

1 is a perspective view schematically illustrating the graphene referred to herein.
FIG. 2 is a flowchart sequentially illustrating a method of manufacturing graphene according to an embodiment of the present invention.
Fig. 3 is a conceptual view schematically showing a method of heat treatment using radiant heat in the graphene manufacturing method of Fig. 2;

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. The effects and features of the present invention and methods of achieving them will be apparent with reference to the embodiments described in detail below with reference to the drawings. However, the present invention is not limited to the embodiments described below, but may be implemented in various forms.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals refer to like or corresponding components throughout the drawings, and a duplicate description thereof will be omitted .

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. As used in the specification, "comprises" and / or "comprising" do not exclude the presence or addition of the stated components, steps, operations, and / or elements. The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by terms. Terms are used only for the purpose of distinguishing one component from another.

In the present specification, when various components such as layers, films, regions, plates, and the like are referred to as being "on" another component, it is to be understood that not only is there a " . Also, for convenience of explanation, the components may be exaggerated or reduced in size. For example, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, and thus the present invention is not necessarily limited to those shown in the drawings.

1 is a perspective view schematically illustrating the graphene referred to herein.

As used herein, the term "graphene" refers to a graft in which a plurality of carbon atoms are covalently linked to one another to form a polycyclic aromatic molecule, A 6-membered ring is formed as a repeating unit, but it is also possible to further include a 5-membered ring and / or a 7-membered ring. Thus, the graphene film forms a single layer of carbon atoms (C) (usually sp2 bonds) covalently bonded to each other. The graphene film may have various structures, and such a structure may vary depending on the content of the 5-membered ring and / or the 7-membered ring which may be contained in the graphene.

The graphene film may be formed of a single layer of graphene as shown in the figure, but it is also possible to form a plurality of layers by stacking a plurality of the graphene films. Usually, the lateral end portions of the graphene film may be saturated with hydrogen atoms (H) .

Graphene is a two-dimensional planar nanomaterial that can have various physical, chemical, electrical, and optical properties. In particular, it can have a charge mobility of about 100 times that of silicon (Si) and about 150 times that of copper (Cu), and can have an allowable current density of about 100 times that of copper (Cu).

Also, since graphene is a nanomaterial having a two-dimensional planar structure in structure, it can be used in various forms.

FIG. 2 is a flowchart sequentially illustrating a method of manufacturing graphene according to an embodiment of the present invention.

Referring to FIG. 2, a method of manufacturing a graphene according to an embodiment of the present invention includes preparing graphite (S10), mixing graphite with sulfuric acid (H2SO4) and potassium permanganate (KMnO4) Thereby forming oxidized graphene GO (S20). The graphene manufacturing method according to an embodiment of the present invention uses chemical exfoliation, and graphene can be produced by separating a layer of graphite.

Here, the chemical exfoliation is a method of peeling off based on a solvent, which can be accomplished by simple ultrasonic pulverization after insertion of the graphene interlayer oxygen functional group through the production of graphite oxide. At this time, the interlayer spacing of the graphite is increased, and the peeling can be induced by decreasing the interlayer π-π interaction and the van der Waals force. Here, the strong acid sulfuric acid (H2SO4) functions as an oxidizing agent, and the potassium permanganate (KMnO4) functions as a catalyst. The oxidizing agent does not necessarily have to be solely sulfuric acid (H2SO4). In another embodiment, the oxidant may be comprised of a mixture comprising sulfuric acid (H2SO4) and nitric acid (HNO3). On the other hand, the solvent to be mixed with the sulfuric acid and the potassium permanganate in the graphite may include at least one selected from the group consisting of distilled water, ethanol, methanol, ethylene glycol, and glycerin . These solvents can be dried naturally or can be dried using filters and vacuum ovens.

In some embodiments, graphite powder and sulfuric acid are mixed and potassium permanganate is slowly added at below 10 占 폚, raised to room temperature after 2 hours, and then maintained at a temperature for 5 days. In this process, there can be a gap between graphene and graphene. The graphite is then oxidized by adding it to a solution containing 5 wt% sulfuric acid and a small amount of hydrogen peroxide. Then, washing and centrifugation are carried out using an acid solution and DI water to remove impurities. Then, centrifugation is carried out using DI water to remove the acid solution. Finally, the graphene oxide can be obtained by drying using a vacuum oven.

Meanwhile, the method of fabricating a graphene according to an embodiment of the present invention may further include milling an oxide graphene (GO) to form the graphene grains to an arbitrary size. Concretely, a ball having a diameter of 1 to 50 mm to be used for graining oxide, solvent and ball milling obtained through the above-described process can be placed in a reactor and ball milled. The solvent may be selected from the group consisting of distilled water, methanol and ethanol. The material of the ball may be glass, zirconia, alumina, or nylon. The reactor can be mounted on a ball milling machine and ball milling can be performed for 3 to 50 hours at a rotational speed of the ball milling machine of 50 to 5,000 rpm. The size of the graphene grains is controlled according to the ball milling process time, and the size of the graphene grains to be peeled may have a certain size. For example, the longer the ball milling process time, the smaller the size of the oxidized grains. The size of the graphene oxide can be adjusted to a size between 50 nm and 300 um according to the ball milling process time.

On the other hand, graphene oxide (GO) containing an oxygen functional group may contain sulfur (S) by sulfuric acid used for separating the layer. Sulfur (S) is unintentionally included in the manufacturing process, and sulfur (S), which is an impurity, must be removed to form a high quality graphene. Conventionally, sulfur (S) was removed from the graphene by several rinses using DI water, but it was difficult to completely remove sulfur (S). Also, since the amount of wastewater formed in the washing process is large, environmental pollution is also a problem. In the present invention, graphene oxide (GO) can be heat-treated to solve this problem.

Specifically, the formed graphene grains are subjected to heat treatment at a temperature equal to or higher than the melting point of sulfur (S) and below the decomposition temperature of carbon (C) (S30). Here, the decomposition temperature means a temperature at which the molecules or atoms constituting the substance can be disconnected from each other. In other words, the bond between the sulfur (S) and the oxide graphene (GO) can be separated by heat-treating the oxide graphene (GO) at a temperature equal to or higher than the decomposition temperature of the sulfur (S). At this time, the separated sulfur (S) is combined with oxygen (O2) of the oxidized graphene (GO) to become sulfur dioxide (SO2), and the oxidized graphene (GO) can be reduced. However, when a temperature higher than the decomposition temperature of carbon (C) is applied, the carbon (C) in the graphene (GO) is separated, so that the heat treatment can be performed at a temperature lower than the decomposition temperature of carbon (C). In one embodiment, the graphene oxide (GO) can be heat treated at a temperature in the range of 200 ° C to 2500 ° C.

Fig. 3 is a conceptual view schematically showing a method of heat treatment using radiant heat in the graphene manufacturing method of Fig. 2; 3, the case where the graphene oxide is disposed in the chamber using the radiant heat has been described. However, the present invention is not limited thereto, and various methods for heating the graphene oxide may be used, for example, Conductive heat or the like may be used. Hereinafter, for convenience of explanation, the case of heat treatment using radiant heat will be mainly described.

Referring to FIG. 3, in the graphene manufacturing method, graphene oxide may be disposed in the chamber 100 to perform heat treatment using radiant heat.

The chamber 100 may be of a substantially hexahedral shape, but is not limited thereto. The chamber 100 may be made of a material such as SUS. A gas supply unit 110 for supplying gas into the chamber 100 may be provided at one side of the chamber 100. In addition, the gas discharge unit 120, which is capable of discharging gas, may be provided on the opposite side of the gas supply unit 110, that is, on the other side of the chamber 100. Although one gas supply unit 110 and a gas discharge unit 120 are illustrated as being disposed in the chamber 100, the present invention is not limited thereto.

A predetermined gas may be supplied to the inner space of the chamber 100 through the gas supply unit 110. [ The graphene manufacturing method according to an embodiment of the present invention can heat-treat the graphene oxide (GO) under an ordinary atmosphere. As another embodiment, the graphene manufacturing method can heat-treat graphene oxide (GO) under a vacuum or an inert gas atmosphere. At this time, the inert gas may be argon (Ar). In addition, the inert gas gas atmosphere may contain no reducing gas such as hydrogen (H2) or a reducing gas in the range of 0% to 5%. In the present invention, it is possible to induce the bond between sulfur (S) and oxygen (O) through heat treatment to form reduction grains simultaneously with the removal of sulfur, so that it is not necessary to include a reducing gas.

The chamber 100 may have the heating unit 130 disposed therein. The heating unit 130 can heat the graphene grains GO using radiant heat. The heating unit 130 may include a lamp 131 that emits light including a near-infrared wavelength band. The reflecting surface 132 may be provided on one side of the lamp 131 so that most of the light emitted from the lamp 131 can be directed to the seating part 150 on which the graphene oxide GO is placed. The heating unit 130 can heat the graphene grains GO to a desired constant temperature by controlling the output of the plurality of lamps 131. [

The chamber 100 is disposed to face the graphene graphene G0 so as to face away from the graphene graphene GO and to absorb the heat radiated from the heating portion 130 to discharge the graphene GO to the seating portion 150 on which the graphene graphene GO is placed And may further include a suscepter unit 140. The susceptor 140 can prevent a sudden temperature rise of the graphene grains GO due to the light emitted from the heating unit 130 and plays a role of keeping the temperature around the graphene GO The environment necessary for heat-treating the graphene oxide GO can be maintained.

The above-described chamber 100 may be a chamber used for synthesizing graphene using chemical vapor deposition (CVD). The annealing process of the oxidized graphene GO can be rapidly performed through the chamber 100 using radiant heat. In one embodiment, the graphene fabrication method can remove sulfur (S) by performing heat treatment on the oxidized graphene (GO) for 30 seconds to 20 minutes. The heat treatment time may depend on the heat treatment temperature, and if the heat treatment temperature is increased, the heat treatment time may be reduced. For example, in the graphene manufacturing method, heat treatment can be performed on graphene oxide (GO) at a temperature ranging from 250 ° C to 300 ° C for 1 minute to 10 minutes using radiant heat. Here, when the heat treatment is performed at a temperature lower than 250 캜, the time of the heat treatment process may be increased. In the case where the heat treatment is performed at a temperature higher than 300 캜, the time required for raising the temperature to the set temperature is long.

Hereinafter, effects of the graphene manufacturing method according to one embodiment of the present invention will be described with reference to Tables 1 and 2.

Table 1 shows the atomic percentages of the three major components before heat treatment of the oxidized graphene (GO) formed by the chemical stripping method. Table 2 shows the atomic percentages of the three major components after the heat treatment of the oxidized graphene (GO) Table.

main ingredient Atom percent (at%) Carbon (C) 62.02 Oxygen (O) 37.51 Sulfur (S) 0.47

Referring to Table 1, it can be seen that the main components before the heat treatment are carbon, oxygen, and sulfur, and sulfur is contained as an impurity. It is also seen that oxygen forms graphene oxide (GO) at 30 at% or more.

main ingredient Atom percent (at%) Carbon (C) 97.5 Oxygen (O) 1.4 Nitrogen (N) 1.1

Referring to Table 2, it can be confirmed that the main components after the heat treatment are carbon, oxygen and nitrogen, and sulfur is removed. Particularly, graphene after heat treatment contains 0 to 2 atomic percent (at%), and in the example of Table 2 contains 1.4 atomic percent (at%), it can be confirmed that oxidized graphene (GO) is reduced.

As described above, in the method of manufacturing graphene according to an embodiment of the present invention, impurity sulfur can be removed by performing heat treatment of the oxidized graphene formed by chemical stripping at a temperature below the decomposition temperature of carbon above the decomposition temperature of sulfur In addition, graphene can be produced by reducing graphene oxide. Particularly, in the method of manufacturing graphene according to an embodiment of the present invention, sulfur can be removed quickly in a predetermined temperature range by heat-treating the graphene grains using radiant heat, thereby shortening the processing time effectively.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art . Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

100: chamber
110: gas supply part
120: gas discharge portion
130:
131: Lamp
132: On one side,
140: susceptor portion
150:

Claims (11)

Mixing graphite, sulfuric acid (H2SO4) and potassium permanganate (KMnO4) to form oxidized graphene; And
Heat treating the formed graphene grains at a temperature not lower than a decomposition temperature of sulfur (S) and not higher than a decomposition temperature of carbon (C). The method according to claim 1,
Wherein the heat treatment step comprises heat treating the graphene oxide using radiant heat. 3. The method of claim 2,
Wherein the heat treatment step is a heat treatment for 30 seconds to 20 minutes. The method according to claim 1,
Wherein the heat treatment is a heat treatment in a vacuum or an inert gas atmosphere. 5. The method of claim 4,
Wherein the heat treatment is performed in a gas atmosphere containing a reducing gas of not less than 0% and not more than 5%. The method according to claim 1,
Wherein the heat treatment is performed in a temperature range of 200 DEG C to 2500 DEG C. The method according to claim 1,
And milling the oxidized graphene to form the graphene grains to an arbitrary size. Mixing graphite, sulfuric acid (H2SO4) and potassium permanganate (KMnO4) to form oxidized graphene; And
And heat treating the formed graphene grains by using radiant heat at a temperature ranging from 250 ° C to 300 ° C for 1 minute to 10 minutes. 9. The method of claim 8,
And milling the oxidized graphene to form a graphene graphene graft having an arbitrary size. 9. The method of claim 8,
Wherein the heat treatment is performed in an atmosphere of an inert gas containing vacuum or 0 to 5% of reducing gas. 11. A composition according to any one of claims 1 to 10,
Graphene comprising 0 to 2 atomic percent oxygen.

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