WO2020130658A1 - Tungsten-doped graphene oxide film, method for manufacturing same, and electron emitter including same - Google Patents

Tungsten-doped graphene oxide film, method for manufacturing same, and electron emitter including same Download PDF

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WO2020130658A1
WO2020130658A1 PCT/KR2019/018062 KR2019018062W WO2020130658A1 WO 2020130658 A1 WO2020130658 A1 WO 2020130658A1 KR 2019018062 W KR2019018062 W KR 2019018062W WO 2020130658 A1 WO2020130658 A1 WO 2020130658A1
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tungsten
graphene oxide
doped graphene
doped
film
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Korean (ko)
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박건식
사토로프맛랍전
홍동표
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서울대학교산학협력단
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/182—Graphene
    • C01B32/198—Graphene oxide
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
    • C04B35/52—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbon, e.g. graphite
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/62218—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products obtaining ceramic films, e.g. by using temporary supports
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
    • C04B2235/96—Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance

Definitions

  • the present invention relates to a graphene oxide film doped with tungsten, a method for manufacturing the same, and an electron emitter including the same. More specifically, the present invention relates to a method for manufacturing tungsten-doped graphene oxide capable of stably emitting electrons having a high current density and an electron emitter including the same.
  • Efficient electron sources are essential in a variety of applications, such as large energy accelerators, X-ray tubes, electron microscopes, microwave amplifiers, and more.
  • the electron source emits electrons to a thermal ion cathode or a large electrostatic field that needs to be released at high temperatures.
  • Field emission is a quantum mechanical phenomenon that tunnels through the potential-energy barrier between the solid emitter and the vacuum interface and escapes into vacuum due to the influence of an externally applied electric field.
  • the electric field is zero, the potential barrier of the solid becomes lower in the presence of the external electric field E, allowing tunneling of electrons.
  • the emission current density (J) is exponentially dependent on the work function ( ⁇ ) and electric field (E) as given by the Fowler-Nordheim (F-N) equation.
  • the field emission device is formed so that the emission tip has a sharp needle shape to obtain a large local field.
  • carbon-based materials with nanometer-sized, sharp tips can provide large-scale field enhancements, resulting in large electron emission.
  • Examples of such newly developed materials include carbon nanotubes, graphene, graphene oxide (rGO), and carbon nanosheets.
  • graphene and graphene oxide (rGO) have attracted attention due to their unique properties.
  • Graphene is a two-dimensional planar nanostructure composed of single-layer sp2 bonded carbon atoms.
  • the electric field required for the field emission of the graphene sheet is about 108V/m.
  • the work function of the graphene sheet is about 5 eV, so when an electric field is applied along the sheet, a large field enhancement is caused at the sharp tip, and a significant amount of electrons can be obtained only at the sharp edge of the graphene.
  • the multi-layer rGO sheet has a carbon structure similar to graphene defects and can be easily peeled from graphite by chemical methods. Likewise, the rGO sheet must be oriented to align the energy with the applied electric field for electron emission.
  • the rGO sheet can be used as an electron source for high power terahertz vacuum electronic devices (VEDs) requiring very high density uniform sheet beams from relatively small size emitters (emitters).
  • VEDs high power terahertz vacuum electronic devices
  • a recent study showed that a current density of 10 A/cm 2 can be achieved using a vertically aligned graphene oxide sheet sandwiched on a wafer.
  • VED it is necessary to further increase the current density along with the emission current. There is.
  • Technical problem to be achieved by the present invention is to provide a graphene oxide film doped with tungsten, a method for manufacturing the same, and an electron emitter including the same. More specifically, it is to provide a method for manufacturing tungsten-doped graphene oxide capable of stably emitting electrons having a high current density and an electron emitter including the same.
  • a method of preparing tungsten-doped graphene oxide comprises mixing a graphene oxide solution and a WO 3 solution to prepare a mixed solution, and hydrothermally treating the mixed solution to tungsten doping. And forming the oxidized graphene, and heat-treating the tungsten-doped graphene oxide at a temperature of 800°C to 1200°C.
  • the WO 3 solution may include WO 3 in the form of nanoparticles dissolved in a solvent.
  • the manufacturing method further includes a step of molding the prepared tungsten-doped graphene oxide, and the tungsten-doped graphene oxide may be formed into a film having a thickness of 100 nm to 200 nm.
  • the graphene oxide solution may be prepared by mixing graphite powder and KMnO 4 in a specific ratio (1:6).
  • the step of hydrothermal treatment of the mixed solution in the production method may be performed for 2 hours to 4 hours at a temperature of 150 °C to 200 °C.
  • the mixing may include sonication.
  • the tungsten-doped graphene oxide film according to an embodiment of the present invention has an oxygen content of 20 at% or less, and a tungsten/carbon ratio of 0.010 or more.
  • the tungsten-doped graphene oxide film may have a thermal conductivity of 150 W/mK or higher at a temperature of 20°C to 100°C.
  • the tungsten-doped graphene oxide film may have a Young's modulus of 100 GPa to 400 GPa.
  • the electrical conductivity of the tungsten-doped graphene oxide film may be 6 * 10 6 S/m or more.
  • the thickness of the tungsten-doped graphene oxide film may be 100 nm to 200 nm.
  • the electron emitter according to an embodiment of the present invention includes one of the tungsten-doped graphene oxide films described above.
  • the tungsten-doped graphene oxide film in the electron emitter may be positioned in a flat or circular shape.
  • the present invention provides a tungsten-doped graphene oxide film capable of stably producing electron emission with a high current density, a method for manufacturing the same, and an electron emitter comprising the same.
  • the manufacturing method overcomes the current density limitation for high-frequency electronic devices by improving the physical properties of graphene oxide, thereby improving the overall current capacity.
  • WO 3 nanoparticle doping can be used to reduce oxygen and other contaminants, and since tungsten has a high melting point and strong mechanical strength, it can keep the film stable during high release.
  • FIG. 1 is a view schematically showing a method of manufacturing an rGO film doped with tungsten according to an embodiment of the present invention.
  • FIG. 2 is a view showing a tungsten-doped GO solution (left), an unmolded tungsten-doped rGO film (center), and a molded tungsten-doped rGO film (right) according to an embodiment of the present invention. .
  • Fig. 3 shows cross sections of tungsten-doped rGO films (a, b) and tungsten-doped rGO films (c, d).
  • FIG. 4 is a diagram showing the results of Raman spectroscopy analysis on a tungsten doped rGO film and an undoped rGO film according to the present invention.
  • FIG. 5 is a diagram schematically showing electrical conductivity and thermal conductivity measured in comparison with tungsten-doped rGO film and other samples according to the present invention.
  • FIG. 6 is a graph showing a graph of emission patterns and electric field emission of a graphene sheet.
  • FIG. 7 is a photograph of (a) a tungsten-doped rGO thin film associated with a tungsten-doped rGO film according to the present invention, (b) a schematic view of manufacturing a cylindrical graphene sheet emitter, (c) a photograph of a cylindrical graphene sheet emitter, and (d) It is a diagram showing a circular radiation pattern of a cylindrical graphene sheet emitter.
  • FIG. 8 is a diagram showing a schematic diagram of a field emission test setup related to a tungsten-doped rGO film according to the present invention.
  • FIG. 9 is a graph showing data of a field emission test related to a tungsten-doped rGO film according to the present invention.
  • (c) is the I-V curve
  • (d) is the E-J curve
  • (e) is the F-N curve
  • (f) is the stability test result.
  • FIG 10 is a view of the emission pattern observed with the phosphor screen associated with tungsten-doped rGO film according to the present invention.
  • the present invention relates to a graphene oxide film doped with tungsten and a method for manufacturing the same.
  • the present invention relates to a method of manufacturing graphene oxide doped with tungsten capable of stably emitting electrons having a high current density.
  • the tungsten-doped graphene oxide film manufactured according to an embodiment of the present invention may have high electrical conductivity, thermal conductivity, and high Young's modulus. Although it will be described in detail later, the tungsten-doped graphene oxide film according to an embodiment of the present invention may have an oxygen content of 20 at% or less, and a tungsten/carbon ratio of 0.010 or more. This oxygen content and the ratio of tungsten/carbon can be achieved by the heat treatment temperature to be described later.
  • the tungsten-doped graphene oxide film having such a composition may have a thermal conductivity of 150 W/mK or higher at a temperature of 20°C to 100°C.
  • Young's modulus is 100 GPa to 400 GPa, and the electrical conductivity may be 6 * 10 6 S/m or more.
  • the tungsten-doped graphene oxide film may be manufactured by a manufacturing method to be described later, and may have high electrical conductivity and thermal conductivity, and may have a Young's modulus, such as an electron emitter.
  • a method for preparing tungsten-doped graphene oxide according to an embodiment of the present invention comprises mixing a graphene oxide solution and a WO 3 solution to prepare a mixed solution, and the tungsten-doped graphene oxide is subjected to hydrothermal treatment of the mixed solution. Forming, and heat-treating the tungsten-doped graphene oxide.
  • Tungsten has a very high melting point and strong mechanical strength, so it can keep the graphene oxide film stable during high electron emission. In the manufacturing process, the reduction of oxygen must occur to the maximum. And the tungsten nanoparticles must be uniformly mixed with the graphene oxide solution and dissolved.
  • the tungsten doped graphene oxide (W-rGO) produced by the present invention may have lower heat generation and higher heat transport than undoped graphene oxide (rGO).
  • FIG. 1 shows a process of manufacturing tungsten-doped graphene oxide according to an embodiment of the present invention.
  • a method of manufacturing tungsten-doped graphene oxide includes: 1) graphite oxidation, 2) production of graphene oxide solution, 3) production of tungsten nanoparticles using a sol-gel method, 4 ) WO 3 solution preparation, 5) Preparation of W-GO solution by liquid-liquid mixing of GO and WO 3 solution, 6) Reduction of hydrothermal to obtain W-rGO film, 7) High temperature treatment to obtain high conductivity (> It may include a forming step to obtain a 1000°C W-rGO film and 8) a uniform film for cathodic application.
  • Graphene oxide can be prepared using a modified Hummer method.
  • graphite powder and KMnO 4 are added to a bottle at a weight ratio of 1:6 and mixed.
  • the bottle is transferred to a rotary heating mantle and mixed at 45° C. for 6 hours.
  • the solution is then neutralized with distilled water. Thereafter, the solution is washed with H 2 O 2 for precipitation and distilled water is added for cleaning.
  • the solution is oxidized for 1 week. During this period, distilled water can be changed every 24 hours.
  • the solution is then filtered using a vacuum filter to obtain a bucky paper/high cake. The obtained cake was dried in a vacuum environment inside the vacuum chamber for 24 hours, and an ultrasonic treatment bath was used for 6 hours to prepare an aqueous graphene oxide solution.
  • WO 3 solution for example, 0.038 mg of WO 3 in the form of nanoparticles can be dissolved in 0.5 ml of NH 4 OH solution.
  • the prepared WO 3 when the WO 3 nanoparticles are prepared, the prepared WO 3 can be dissolved homogeneously and rapidly in NH 4 OH.
  • the amount of NH 4 OH required for dissolution may be small.
  • NH 4 OH when the WO 3 nanoparticle is 0.038 mg, NH 4 OH may be used in less than 0.5 ml. therefore. The overall pH of the solution can be maintained unchanged.
  • a step of preparing a mixed solution by mixing the graphene oxide solution and the WO 3 solution will be described.
  • ultrasonic treatment can be performed.
  • the WO 3 solution can be mixed with the previously prepared graphene oxide solution to significantly improve the mixing rate and the homogeneity of the solution.
  • the hydrothermal treatment may be performed at 180° C. for 3 hours as shown in FIG. 1. However, this is an example, and is not limited thereto. In one example, the hydrothermal treatment may be performed at 150°C to 200°C for 2 hours to 4 hours.
  • the heat treatment may be performed under a nitrogen atmosphere at a temperature of 800°C to 1200°C.
  • the electrical conductivity of tungsten-doped graphene oxide prepared according to the heat treatment temperature may vary. If the heat treatment temperature is less than 800 °C, there may be a problem that the conductivity is lowered because the oxygen functional group is not sufficiently removed. If the heat treatment temperature is 1200 °C or higher, there may be a problem such as crack due to excessive structural change of the film.
  • FIG. 2 is a view showing a tungsten-doped GO solution (left), an unmolded tungsten-doped rGO film (center), and a molded tungsten-doped rGO film (right) according to an embodiment of the present invention.
  • the tungsten-doped graphene oxide film produced through molding may be applied to an electron emitter or the like.
  • the film thickness of the tungsten-doped graphene oxide film prepared according to the amount of the mixed solution (mixed graphene oxide solution and WO 3 solution) used in the hydrothermal treatment process can be adjusted.
  • Fig. 3 shows cross sections of tungsten-doped rGO films (a, b) and tungsten-doped rGO films (c, d).
  • FIG. 3 (a) and (b) are tGO doped tGO, and when they have a thin edge (100 nm to 200 nm) as in (a), rGO peeling occurs as shown in (b). You can confirm that.
  • (C) and (d) in FIG. 3 are tungsten-doped W-rGO, which shows that peeling does not occur as shown in (d) even if it has a thin edge (100 nm to 200 nm) as in (c). Can be confirmed.
  • the elements present in the film were analyzed using energy dispersive X-ray spectroscopy (EDA), which is shown in FIG. 4.
  • EDA energy dispersive X-ray spectroscopy
  • FIG. 4 it was confirmed that the wt% of C and W maintained a ratio of 1:0.01.
  • the presence of oxygen groups was significantly reduced to over 60% compared to the film without W doping.
  • the elemental data of the X-ray photoelectron spectroscopy was verified by EDS.
  • the XRD pattern of the collected W-rGO complex is shown in Figure 4. It was confirmed that the characteristic peak corresponding to the (002) plane of graphene appears at about 23.58°C after heat reduction of rGO and W-rGO at 800°C.
  • the distance of the W-rGO thin film layer was calculated based on the peak position.
  • the heat reduction temperature was 800°C
  • the distance was 0.369 nm
  • the heat reduction temperature was 1200°C
  • the distance was reduced to 0.351 nm.
  • This reduction in distance (d) means that the functional groups were effectively removed from the W-rGO film.
  • the derived d value is similar to the graphite value ( ⁇ 0.334 nm).
  • FIG. 5 is a diagram schematically showing a value for electrical conductivity measured in comparison to tungsten-doped rGO film and other samples according to the present invention.
  • the electrical sheet resistance of the annealed rGO and W-rGO membranes at different temperatures was measured using a 4-probe method. Accuracy was verified by examining three different samples prepared using similar parameters for each point. The sample size was 5000 ⁇ m in length, 5000 ⁇ m in width, and 0.1 ⁇ m in thickness.
  • FIG. 5(a) is a graph showing the conductivity of the W-rGO film versus the annealing temperature. It can be seen from FIG. 5(b) that the conductivity of the W-rGO film annealed at 1200°C was significantly improved compared to the rGO film annealed at 800°C.
  • the W-rGO film annealed at high temperature shows much improved electrical conductivity than other rGO thin films produced by chemical or thermal reduction.
  • the W-rGO film exhibits the best results when annealed at 1200°C through electrical conductivity measurement. 5 (c) and (d) together, it can be seen that the thermal conductivity of the W-rGO film is relatively much higher than that of the tungsten undoped rGO film due to the sp2 bond and the restoration of the relatively dense layer. there was.
  • the thermal conductivity increases according to the annealing temperature.
  • it is 120 W/mK at room temperature, and when the temperature is 150° C., it increases to 140 W/mK.
  • W-rGO films annealed at temperatures of 800° C. and 1200° C. show improved conductivity of 170 W/mK and 260 W/mK, respectively, compared to undoped rGO films.
  • the W-rGO thin film heat-treated at 1200°C shows an improvement of about 200%. This is due to the doping of tungsten, because tungsten doping simultaneously reduced oxygen in the structure and restored the sp2 bonded carbon network. Therefore, it can be confirmed that the tungsten doped graphene film has improved electrical conductivity and thermal conductivity.
  • thermal conductivity and the like were measured for an undoped rGO film annealed at 800°C and a tungsten doped rGO film annealed at 800°C and 1200°C.
  • 5(e) shows a stress versus strain graph. As can be seen from the graph, it can be seen that mechanical properties are significantly improved when doping tungsten.
  • the tensile strength of W-rGO was higher than that of rGO heat-treated at 800°C.
  • the W-rGO film annealed at 1200°C has a tensile strength of about 941 MPa, and it can be confirmed that Young's modulus (see FIG. 5(f)) is improved by about 20 times or more compared to the undoped rGO.
  • the tungsten-doped graphene film produced by the manufacturing method according to an embodiment of the present invention has an oxygen content of 20 at% or less and a tungsten/carbon ratio of 0.010 or more.
  • the tungsten doped graphene film may have high electrical conductivity, thermal conductivity, and high Young's modulus.
  • the tungsten-doped graphene oxide film according to an embodiment of the present invention may have a thermal conductivity of 150 W/mK or higher at a temperature of 20°C to 100°C.
  • Young's modulus is 100 GPa to 400 GPa, and the electrical conductivity may be 6 * 10 6 S/m or more.
  • the tungsten-doped graphene oxide film has high electrical conductivity and thermal conductivity, and can be used as an electron emitter since it has Young's modulus.
  • the electron emitter according to this embodiment may include the above-described tungsten-doped graphene film.
  • the tungsten-doped graphene film may be positioned in a flat or circular shape.
  • Cold cathode electron emitters can be used as a source of high-density electron beams that cannot be currently achieved with thermal ion cathodes.
  • the field emission source is required to have a high aspect ratio emission surface such as a lightning rod to avoid destruction. It is important to form a sharp, high aspect ratio emitting surface for field enhancement in these electron emitters. Non-uniform field emission points can inevitably cause local field emission accompanied by local evaporation of the emission source and thus electrical damage due to poor vacuum.
  • the tungsten-doped graphene film according to this embodiment may be applied as an electron emission source.
  • FIG. 6 shows a graph of the emission pattern and field emission of the graphene film. If the graphene sheets are overlapped horizontally and the edges are cut evenly, release occurs only at the edges of the graphene sheets.
  • the emission pattern in FIG. 6 (left) indicates that the graphene film is an excellent sheet electron emitter. The electrons coming from the edge of the graphene sheet induce a phosphor with a sheet electron beam and create a streamlined emission pattern.
  • the FE test of the graphene sheet shown on the right side of FIG. 6 shows that the on field is 2V/ ⁇ m, the FE current density is about 10A/cm 2 and the current is 2mA. In this case, the maximum value of the current was about 6 mA, and the film deterioration was about 6% for 6 hours.
  • FIG. 7 is a photograph of (a) a tungsten-doped rGO film associated with a tungsten-doped rGO film according to the present invention, (b) a schematic view of the manufacture of a cylindrical graphene sheet emitter, (c) a photograph of a cylindrical graphene sheet emitter, and (d) It is a diagram showing a circular radiation pattern of a cylindrical graphene sheet emitter.
  • the tungsten-doped graphene film according to this embodiment may function as an electron emission source in a circular shape as shown in FIG. 7.
  • FIG. 8 is a diagram showing a schematic diagram of a field emission test setup related to a tungsten-doped rGO film according to the present invention.
  • 9 is a graph showing data of a field emission test related to a tungsten-doped rGO film according to the present invention.
  • (c) is the I-V curve
  • (d) is the E-J curve
  • (e) is the F-N curve
  • (f) is the stability test result.
  • 10 is a view of the emission pattern observed with the phosphor screen associated with tungsten-doped rGO film according to the present invention.
  • the field emission test results show a stable and reproducible current density and emission current compared to an undoped film.
  • 9(e) shows the FN plot for each cycle confirming the field emission tendency of the undoped rGO film.
  • 9(d) and (f) show the highest current density achieved at an applied electric field of 7.4 V/ ⁇ m, which was confirmed to be the highest in tGO doped with tungsten at 6000 A/cm 2 .
  • the amount of variation was less than 1%, which confirmed excellent stability. This is due to the doping of tungsten nanoparticles during the synthesis process.
  • FIG. 10(a) shows the emission pattern of the rGO film doped with tungsten observed with a phosphor screen.
  • a phosphor screen is placed instead of the anode.
  • a square sheet type beam pattern is observed, which means that the emitted electron beam is essentially sheet type and can be precisely shaped for focusing.
  • 10(b) and 10(c) show the rGO and W-rGO films, respectively, after the field emission experiment. 10(b), it can be seen that the rGO film edges were completely destroyed after the experiment. However, in the case of W-rGO film, it can be seen that the edge of the film is kept in a solid shape.
  • the W-rGO film does not deteriorate even after a long field emission operation, and when it is used as an electron emission cathode, it can be seen that it has an improved effect.

Abstract

A method for producing a tungsten-doped graphene oxide according to an embodiment of the present invention comprises: a step for mixing a graphene oxide solution and a WO3 solution to prepare a mixed solution; a step for performing a hydrothermal treatment on the mixed solution to form a tungsten-doped graphene oxide; and a step for heat-treating the tungsten-doped graphene oxide at a temperature of 800-1200°C. The production method according to the present embodiment improves the physical properties of graphene oxide, thereby overcoming the current density limitation of high-frequency electronic devices and improving the overall current capacity, and can reduce oxygen and other contaminants by using WO3 nanoparticle doping. In addition, since tungsten has a high melting point and high mechanical strength, a graphene oxide film can be kept stable during very high emission.

Description

텅스텐이 도핑된 산화 그래핀 필름 및 이의 제조 방법, 이를 포함하는 전자 방출기Tungsten doped graphene oxide film and method for manufacturing same, electron emitter comprising same
본 발명은 텅스텐이 도핑된 산화 그래핀 필름 및 이의 제조 방법, 이를 포함하는 전자 방출기에 대한 것이다. 보다 구체적으로, 본 발명은 높은 전류 밀도의 전자 방출을 안정적으로 할 수 있는 텅스텐 도핑된 산화 그래핀의 제조 방법 및 이를 포함하는 전자 방출기에 대한 것이다. The present invention relates to a graphene oxide film doped with tungsten, a method for manufacturing the same, and an electron emitter including the same. More specifically, the present invention relates to a method for manufacturing tungsten-doped graphene oxide capable of stably emitting electrons having a high current density and an electron emitter including the same.
효율적인 전자 소스는 대형 에너지 가속기, X선관, 전자 현미경, 마이크로 웨이브 증폭기 등과 같은 다양한 응용 분야에서 필수적이다. 전자 소스는 고온에서 방출이 필요한 열 이온 음극 또는 큰 정전기장으로 전자를 방출한다. Efficient electron sources are essential in a variety of applications, such as large energy accelerators, X-ray tubes, electron microscopes, microwave amplifiers, and more. The electron source emits electrons to a thermal ion cathode or a large electrostatic field that needs to be released at high temperatures.
전계 방출은 고체 이미터와 진공 계면 사이의 전위-에너지 장벽을 통해 터널링되고 외부에서 인가된 전계의 영향으로 인해 진공으로 탈출하는 양자 역학 현상이다. 전계가 제로일 때 고체의 잠재적 장벽은 외부 전계 E의 존재 하에서 보다 낮아지고, 전자의 터널링을 가능하게 한다. 방출 전류 밀도 (J)는 Fowler-Nordheim(F-N) 방정식에 의해 주어진 것처럼 일 함수 (φ) 및 전기장 (E)에 기하 급수적으로 의존한다.Field emission is a quantum mechanical phenomenon that tunnels through the potential-energy barrier between the solid emitter and the vacuum interface and escapes into vacuum due to the influence of an externally applied electric field. When the electric field is zero, the potential barrier of the solid becomes lower in the presence of the external electric field E, allowing tunneling of electrons. The emission current density (J) is exponentially dependent on the work function (φ) and electric field (E) as given by the Fowler-Nordheim (F-N) equation.
그러나, 대부분의 금속은 4eV 내지 5eV 범위의 일 함수(φ)를 가지며, 평면 기하학적으로 109V/m 정도의 큰 전계 하에서만 전자 방출이 일어난다. 이 정전기 장은 상당히 높으며 종종 고장을 일으킨다. 해결책으로서, 전계 방출 장치는 방출 팁이 큰 국부적인 장을 얻기 위해 날카로운 바늘 형상을 갖도록 형성된다.However, most metals have a work function φ in the range of 4 eV to 5 eV, and electron emission occurs only under a large electric field of 109 V/m in planar geometry. This electrostatic field is quite high and often fails. As a solution, the field emission device is formed so that the emission tip has a sharp needle shape to obtain a large local field.
최근 나노미터 크기의 날카로운 팁을 가진 탄소 기반의 재료가 대규모의 필드 향상을 제공하여 큰 전자 방출을 할 수 있음이 밝혀졌다. 이러한 새로 개발된 재료로는 탄소 나노 튜브, 그래핀, 산화 그래핀(grapheneoxide, rGO), 탄소 나노 시트 등이 있다. 이러한 나노 구조 중에서 특히 그래핀과 산화 그래핀(rGO)은 독특한 특성 때문에 주목을 받았다. 그래핀(Graphene)은 단일층 sp2 결합된 탄소 원자로 구성된 2차원 평면 나노 구조이다. 그래핀 시트의 전계 방출을 위하여 필요한 전계는 108V/m 정도이다. 그래핀 시트의 일함수는 약 5eV이므로 전기장이 시트를 따라 가해지면 날카로운 팁에서 큰 필드 향상이 유발되고 그래핀의 날카로운 모서리에서만 상당한 양의 전자를 얻을 수 있다.It has recently been discovered that carbon-based materials with nanometer-sized, sharp tips can provide large-scale field enhancements, resulting in large electron emission. Examples of such newly developed materials include carbon nanotubes, graphene, graphene oxide (rGO), and carbon nanosheets. Among these nano-structures, graphene and graphene oxide (rGO) have attracted attention due to their unique properties. Graphene is a two-dimensional planar nanostructure composed of single-layer sp2 bonded carbon atoms. The electric field required for the field emission of the graphene sheet is about 108V/m. The work function of the graphene sheet is about 5 eV, so when an electric field is applied along the sheet, a large field enhancement is caused at the sharp tip, and a significant amount of electrons can be obtained only at the sharp edge of the graphene.
그러나, 전체 전류가 기대치보다 훨씬 낮기 때문에 그래핀 시트의 비균일 에너지로부터 전류를 추출하는 것은 비효율적이다. 다중층 rGO 시트는 그래핀 결함과 유사한 탄소 구조를 가지며 화학적 방법으로 흑연으로부터 쉽게 박리될 수 있다. 마찬가지로, rGO 시트는 전자 방출을 위해 인가된 전기장과 에너지를 정렬하도록 배향되어야 한다.However, it is inefficient to extract current from the non-uniform energy of the graphene sheet because the total current is much lower than expected. The multi-layer rGO sheet has a carbon structure similar to graphene defects and can be easily peeled from graphite by chemical methods. Likewise, the rGO sheet must be oriented to align the energy with the applied electric field for electron emission.
또한, rGO 시트로부터의 방출 전류가 매우 크기 때문에 rGO 시트는 비교적 작은 크기의 방출기(에미터)로부터 매우 고밀도의 균일한 시트빔이 요구되는 고출력 테라 헤르츠 진공 전자 장치(VEDs)용 전자 소스로 사용될 수 있다. 최근 연구는 웨이퍼에 샌드위치된 수직 정렬 그래핀 산화물 시트를 사용하여 10A/cm2의 전류 밀도가 달성될 수 있음을 보여주었다 그러나, VED에서 실제 적용을 위해서는, 방출 전류와 함께 전류 밀도를 더 높일 필요가 있다.In addition, since the emission current from the rGO sheet is very large, the rGO sheet can be used as an electron source for high power terahertz vacuum electronic devices (VEDs) requiring very high density uniform sheet beams from relatively small size emitters (emitters). have. A recent study showed that a current density of 10 A/cm 2 can be achieved using a vertically aligned graphene oxide sheet sandwiched on a wafer. However, for practical application in VED, it is necessary to further increase the current density along with the emission current. There is.
그러나, 산소 작용기 및 다른 불순물로 인해 산화 그래핀은 제조 공정 중에 오염될 수 있고, 특성을 상실할 수 있다. 또한, 매우 높은 전류를 생성하는 동안, rGO 시트는 광범위한 발열 및 불량한 열 발산율, 과도한 줄 가열으로 인한 열 파괴 경향을 나타낸다. 이 문제를 극복하기 위해 rGO 필름의 열 전도성 및 전기 전도성을 기계적 강도와 함께 향상시킬 필요가 있다. 이를 위해서 오염을 제어하고 산소 또는 기타 불순물을 감소시킬 수 있는 제조 방법이 요구된다.However, due to oxygen functional groups and other impurities, graphene oxide can be contaminated during the manufacturing process and lose its properties. In addition, while generating very high currents, the rGO sheet exhibits a wide range of heat generation and poor heat dissipation, and a tendency to heat breakdown due to excessive joule heating. In order to overcome this problem, it is necessary to improve the thermal conductivity and electrical conductivity of the rGO film along with the mechanical strength. To this end, there is a need for a manufacturing method that can control contamination and reduce oxygen or other impurities.
본 발명이 이루고자 하는 기술적 과제는 텅스텐이 도핑된 산화 그래핀 필름 및 이의 제조 방법, 이를 포함하는 전자 방출기를 제공하는 것이다. 보다 구체적으로, 높은 전류 밀도의 전자 방출을 안정적으로 할 수 있는 텅스텐 도핑된 산화 그래핀의 제조 방법 및 이를 포함하는 전자 방출기를 제공하기 위한 것이다.Technical problem to be achieved by the present invention is to provide a graphene oxide film doped with tungsten, a method for manufacturing the same, and an electron emitter including the same. More specifically, it is to provide a method for manufacturing tungsten-doped graphene oxide capable of stably emitting electrons having a high current density and an electron emitter including the same.
이러한 과제를 해결하기 위하여 본 발명의 실시예에 따른 텅스텐 도핑된 산화 그래핀의 제조 방법은 산화 그래핀 용액과 WO3 용액을 혼합하여 혼합 용액을 제조하는 단계, 상기 혼합 용액을 수열처리하여 텅스텐 도핑된 산화 그래핀을 형성하는 단계, 상기 텅스텐 도핑된 산화 그래핀을 800℃ 내지 1200℃의 온도에서 열처리하는 단계를 포함한다. In order to solve this problem, a method of preparing tungsten-doped graphene oxide according to an embodiment of the present invention comprises mixing a graphene oxide solution and a WO 3 solution to prepare a mixed solution, and hydrothermally treating the mixed solution to tungsten doping. And forming the oxidized graphene, and heat-treating the tungsten-doped graphene oxide at a temperature of 800°C to 1200°C.
상기 WO3 용액은 용매에 용해된 나노 입자 형태의 WO3를 포함할 수 있다. The WO 3 solution may include WO 3 in the form of nanoparticles dissolved in a solvent.
상기 제조 방법은 상기 제조된 텅스텐 도핑된 산화 그래핀을 성형하는 단계를 더 포함하고, 상기 텅스텐 도핑된 산화 그래핀은 두께가 100㎚ 내지 200㎚인 필름 형태로 성형될 수 있다.The manufacturing method further includes a step of molding the prepared tungsten-doped graphene oxide, and the tungsten-doped graphene oxide may be formed into a film having a thickness of 100 nm to 200 nm.
상기 산화 그래핀 용액은 흑연 분말 및 KMnO4를 특정 비율(1:6)로 혼합하여 이용하여 제조될 수 있다.The graphene oxide solution may be prepared by mixing graphite powder and KMnO 4 in a specific ratio (1:6).
상기 제조 방법 중 상기 혼합 용액을 수열처리하는 단계는 150℃ 내지 200℃ 온도에서 2시간 내지 4시간 동안 수행될 수 있다.The step of hydrothermal treatment of the mixed solution in the production method may be performed for 2 hours to 4 hours at a temperature of 150 ℃ to 200 ℃.
상기 산화 그래핀 용액과 WO3 용액을 혼합하여 혼합 용액을 제조하는 단계에서 상기 혼합은 초음파 처리를 포함할 수 있다.In the step of preparing a mixed solution by mixing the graphene oxide solution and the WO 3 solution, the mixing may include sonication.
본 발명의 일 실시예에 따른 텅스텐 도핑된 산화 그래핀 필름은 산소 함량이 20at% 이하이고, 텅스텐/탄소의 비율은 0.010 이상이다.The tungsten-doped graphene oxide film according to an embodiment of the present invention has an oxygen content of 20 at% or less, and a tungsten/carbon ratio of 0.010 or more.
상기 텅스텐 도핑된 산화 그래핀 필름은 20℃ 내지 100℃의 온도에서 열전도도가 150W/mK 이상일 수 있다.The tungsten-doped graphene oxide film may have a thermal conductivity of 150 W/mK or higher at a temperature of 20°C to 100°C.
상기 텅스텐 도핑된 산화 그래핀 필름은 영 모듈러스가 100GPa 내지 400GPa일 수 있다.The tungsten-doped graphene oxide film may have a Young's modulus of 100 GPa to 400 GPa.
상기 텅스텐 도핑된 산화 그래핀 필름의 전기 전도도는 6 * 106S/m 이상일 수 있다.The electrical conductivity of the tungsten-doped graphene oxide film may be 6 * 10 6 S/m or more.
상기 텅스텐 도핑된 산화 그래핀 필름의 두께는 100㎚ 내지 200㎚일 수 있다.The thickness of the tungsten-doped graphene oxide film may be 100 nm to 200 nm.
본 발명의 일 실시예에 따른 전자 방출기는 전술한 텅스텐 도핑된 산화 그래핀 필름 중 하나를 포함한다. The electron emitter according to an embodiment of the present invention includes one of the tungsten-doped graphene oxide films described above.
상기 전자 방출기에서 상기 텅스텐 도핑된 산화 그래핀 필름은 평면 또는 원형으로 위치할 수 있다.The tungsten-doped graphene oxide film in the electron emitter may be positioned in a flat or circular shape.
이상과 같이 본 발명은 높은 전류 밀도의 전자 방출을 안정적으로 생산할 수 있는 텅스텐 도핑된 산화 그래핀 필름 및 이의 제조 방법, 이를 포함하는 전자 방출기를 제공한다. As described above, the present invention provides a tungsten-doped graphene oxide film capable of stably producing electron emission with a high current density, a method for manufacturing the same, and an electron emitter comprising the same.
상기 제조 방법은 산화 그래핀의 물리적 특성을 향상시킴으로써 고주파 전자 장치에 대한 전류 밀도 제한을 극복하여 전반적인 전류 용량을 향상시킨다. 또한 WO3 나노 입자 도핑을 사용하여 산소 및 기타 오염 물질을 감소시킬 수 있고, 텅스텐은 융점이 높고 기계적 강도가 강하기 때문에 높은 방출 동안 필름을 안정적으로 유지할 수 있다.The manufacturing method overcomes the current density limitation for high-frequency electronic devices by improving the physical properties of graphene oxide, thereby improving the overall current capacity. In addition, WO 3 nanoparticle doping can be used to reduce oxygen and other contaminants, and since tungsten has a high melting point and strong mechanical strength, it can keep the film stable during high release.
도 1은, 본 발명의 실시예에 따른 텅스텐이 도핑된 rGO막의 제조방법을 개략적으로 나타낸 도이다.1 is a view schematically showing a method of manufacturing an rGO film doped with tungsten according to an embodiment of the present invention.
도 2는, 본 발명의 일 실시예에 따른 텅스텐이 도핑된 GO 용액(왼쪽), 성형되지 않은 텅스텐이 도핑된 rGO 필름(중앙) 및 성형된 텅스텐이 도핑된 rGO 필름(오른쪽)을 나타낸 도이다.2 is a view showing a tungsten-doped GO solution (left), an unmolded tungsten-doped rGO film (center), and a molded tungsten-doped rGO film (right) according to an embodiment of the present invention. .
도 3은, 텅스텐이 도핑되지 않은 rGO 필름(a, b) 및 텅스텐이 도핑된 rGO 필름(c, d)의 단면을 도시한 것이다. Fig. 3 shows cross sections of tungsten-doped rGO films (a, b) and tungsten-doped rGO films (c, d).
도 4는, 본 발명에 따른 텅스텐이 도핑된 rGO 필름 및 도핑되지 않은 rGO 필름에서의 라만 분광 분석 결과를 나타낸 도이다.4 is a diagram showing the results of Raman spectroscopy analysis on a tungsten doped rGO film and an undoped rGO film according to the present invention.
도 5는, 본 발명에 따른 텅스텐이 도핑된 rGO 필름 및 다른 샘플들과 비교하여 측정한 전기 전도도 및 열 전도도를 도식화하여 나타낸 도이다.FIG. 5 is a diagram schematically showing electrical conductivity and thermal conductivity measured in comparison with tungsten-doped rGO film and other samples according to the present invention.
도 6은, 그래핀 시트의 방출 패턴 및 전계 방출에 대한 그래프를 나타낸 도이다.6 is a graph showing a graph of emission patterns and electric field emission of a graphene sheet.
도 7은, 본 발명에 따른 텅스텐이 도핑된 rGO 필름과 관련된 (a) 텅스텐 도핑된 rGO 박막의 사진, (b) 원통형 그래핀 시트 방출기의 제조 개략도, (c) 원통형 그래핀 시트 방출기의 사진 및 (d) 원통형 그래핀 시트 방출기의 순환 방사 패턴을 나타낸 도이다.FIG. 7 is a photograph of (a) a tungsten-doped rGO thin film associated with a tungsten-doped rGO film according to the present invention, (b) a schematic view of manufacturing a cylindrical graphene sheet emitter, (c) a photograph of a cylindrical graphene sheet emitter, and (d) It is a diagram showing a circular radiation pattern of a cylindrical graphene sheet emitter.
도 8은, 본 발명에 따른 따른 텅스텐이 도핑된 rGO 필름과 관련된 전계 방출시험 설정의 개략도를 나타낸 도이다.8 is a diagram showing a schematic diagram of a field emission test setup related to a tungsten-doped rGO film according to the present invention.
도 9는, 본 발명에 따른 따른 텅스텐이 도핑된 rGO 필름과 관련된 전계 방출시험의 데이터를 그래프화 하여 나타낸 도이다. (c)는 I-V 곡선이고, (d)는 E-J 곡선이며, (e)는 F-N 곡선이고 (f)는 안정성 시험 결과이다. 9 is a graph showing data of a field emission test related to a tungsten-doped rGO film according to the present invention. (c) is the I-V curve, (d) is the E-J curve, (e) is the F-N curve, and (f) is the stability test result.
도 10은, 본 발명에 따른 따른 텅스텐이 도핑된 rGO 필름과 관련된 형광체 스크린으로 관찰한 방출 패턴에 대한 도이다.10 is a view of the emission pattern observed with the phosphor screen associated with tungsten-doped rGO film according to the present invention.
이하, 첨부된 도면을 참조하면서 본 발명에 따른 바람직한 실시예를 상세히 설명한다. 이에 앞서, 본 명세서 및 청구범위에 사용된 용어나 단어는 통상적이거나 사전적인 의미로 해석되어서는 아니되며, 발명자는 그 자신의 발명을 가장 최선의 방법으로 설명하기 위해 용어의 개념을 적절하게 정의할 수 있다는 원칙에 입각하여, 본 발명의 기술적 사상에 부합되는 의미와 개념으로 해석되어야만 한다Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in the specification and claims should not be interpreted in a conventional or lexical sense, and the inventor may properly define the concept of terms in order to best describe his or her invention. Based on the principle that it can be, it should be interpreted as meanings and concepts consistent with the technical spirit of the present invention.
따라서, 본 명세서에 기재된 실시예와 도면에 도시된 구성은 본 발명의 가장 바람직한 일 실시에 불과할 뿐이고 본 발명의 기술적 사상을 모두 대변하는 것은 아니므로, 본 출원시점에 있어서, 이들을 대체할 수 있는 다양한 균등물과 변형예들이 있을 수 있음을 이해해야 한다.Therefore, the embodiments shown in the embodiments and the drawings described in this specification are only the most preferred implementation of the present invention and do not represent all of the technical spirit of the present invention, and at the time of this application, they can replace various It should be understood that there may be equivalents and variations.
본 발명은 텅스텐이 도핑된 산화 그래핀 필름 및 이의 제조 방법에 관한 것이다. The present invention relates to a graphene oxide film doped with tungsten and a method for manufacturing the same.
보다 구체적으로, 본 발명은 높은 전류 밀도의 전자 방출을 안정적으로 할 수 있는 텅스텐이 도핑된 산화 그래핀의 제조 방법에 대한 것이다. More specifically, the present invention relates to a method of manufacturing graphene oxide doped with tungsten capable of stably emitting electrons having a high current density.
본 발명의 일 실시예에 따라 제조되는 텅스텐 도핑된 산화 그래핀 필름은 높은 전기 전도도, 열 전도도 및 높은 영 모듈러스를 가질 수 있다. 이후 별도로 상세하게 설명하겠으나 본 발명의 일 실시예에 따른 텅스텐 도핑된 산화 그래핀 필름은 산소 함량은 20at% 이하이고, 텅스텐/탄소의 비율이 0.010 이상일 수 있다. 이러한 산소 함량 및 텅스텐/ 탄소의 비율은 후술할 열처리 온도에 의해 달성될 수 있다. 이러한 조성을 갖는 텅스텐 도핑된 산화 그래핀 필름은 20℃ 내지 100℃의 온도에서 열전도도가 150W/mK 이상일 수 있다. 또한, 영 모듈러스가 100GPa 내지 400GPa이고, 전기 전도도는 6 * 106 S/m 이상일 수 있다. 이러한 텅스텐 도핑된 산화 그래핀 필름은 후술할 제조 방법으로 제조될 수 있으며, 높은 전기 전도도 및 열 전도도, 영 모듈러스를 갖는바 전자 방출기 등으로 사용할 수 있다.The tungsten-doped graphene oxide film manufactured according to an embodiment of the present invention may have high electrical conductivity, thermal conductivity, and high Young's modulus. Although it will be described in detail later, the tungsten-doped graphene oxide film according to an embodiment of the present invention may have an oxygen content of 20 at% or less, and a tungsten/carbon ratio of 0.010 or more. This oxygen content and the ratio of tungsten/carbon can be achieved by the heat treatment temperature to be described later. The tungsten-doped graphene oxide film having such a composition may have a thermal conductivity of 150 W/mK or higher at a temperature of 20°C to 100°C. In addition, Young's modulus is 100 GPa to 400 GPa, and the electrical conductivity may be 6 * 10 6 S/m or more. The tungsten-doped graphene oxide film may be manufactured by a manufacturing method to be described later, and may have high electrical conductivity and thermal conductivity, and may have a Young's modulus, such as an electron emitter.
이하, 본 발명의 일 실시예에 따른 텅스텐 도핑된 산화 그래핀의 제조 방법에 대하여 설명한다.Hereinafter, a method of manufacturing tungsten-doped graphene oxide according to an embodiment of the present invention will be described.
본 발명의 일 실시예에 따른 텅스텐 도핑된 산화 그래핀의 제조 방법은 산화 그래핀 용액과 WO3 용액을 혼합하여 혼합 용액을 제조하는 단계, 상기 혼합 용액을 수열처리하여 텅스텐 도핑된 산화 그래핀을 형성하는 단계, 상기 텅스텐 도핑된 산화 그래핀을 열처리하는 단계를 포함한다.A method for preparing tungsten-doped graphene oxide according to an embodiment of the present invention comprises mixing a graphene oxide solution and a WO 3 solution to prepare a mixed solution, and the tungsten-doped graphene oxide is subjected to hydrothermal treatment of the mixed solution. Forming, and heat-treating the tungsten-doped graphene oxide.
텅스텐은 융점이 매우 높고 기계적 강도가 강해 전자의 높은 방출 동안 산화 그래핀 필름을 안정적으로 유지할 수 있다. 제조 과정에서 산소의 환원은 최대로 일어나야 하며. 하고 텅스텐 나노 입자는 산화 그래핀 용액과 균일하게 혼합되어 용해되어야 한다. Tungsten has a very high melting point and strong mechanical strength, so it can keep the graphene oxide film stable during high electron emission. In the manufacturing process, the reduction of oxygen must occur to the maximum. And the tungsten nanoparticles must be uniformly mixed with the graphene oxide solution and dissolved.
본 발명에 의해 제조된 텅스텐 도핑된 산화 그래핀(W-rGO)은 도핑되지 않은 산화 그래핀(rGO)에 비하여 발열이 낮고 열 수송은 더 높을 수 있다. The tungsten doped graphene oxide (W-rGO) produced by the present invention may have lower heat generation and higher heat transport than undoped graphene oxide (rGO).
이하, 본 발명의 일 실시예에 따른 텅스텐이 도핑된 산화 그래핀의 제조 방법에 대하여 구체적으로 설명한다. Hereinafter, a method of manufacturing tungsten-doped graphene oxide according to an embodiment of the present invention will be described in detail.
도 1은, 본 발명의 일 실시예에 따른 텅스텐 도핑된 산화 그래핀의 제조 과정을 도시한 것이다. 1 shows a process of manufacturing tungsten-doped graphene oxide according to an embodiment of the present invention.
도 1을 참고로 하면 본 실시예에 따른 텅스텐 도핑된 산화 그래핀의 제조 방법은, 1) 흑연 산화, 2) 산화 그래핀 용액의 제조, 3) 졸-겔법을 이용한 텅스텐 나노 입자의 제조, 4) WO3 용액 제조, 5) GO 및 WO3 용액의 액체-액체 혼합에 의한 W-GO용액의 제조, 6) W-rGO 필름을 얻기 위한 수열 감소, 7) 높은 전도성을 얻기 위한 고온 처리 (>1000℃ W-rGO 필름 수득 및 8) 음극 적용을 위해 균일한 필름을 수득하기 위한 성형 단계를 포함할 수 있다. Referring to FIG. 1, a method of manufacturing tungsten-doped graphene oxide according to this embodiment includes: 1) graphite oxidation, 2) production of graphene oxide solution, 3) production of tungsten nanoparticles using a sol-gel method, 4 ) WO 3 solution preparation, 5) Preparation of W-GO solution by liquid-liquid mixing of GO and WO 3 solution, 6) Reduction of hydrothermal to obtain W-rGO film, 7) High temperature treatment to obtain high conductivity (> It may include a forming step to obtain a 1000°C W-rGO film and 8) a uniform film for cathodic application.
각 단계에 대한 내용은 하기에서 상세히 설명한다.Details of each step are described in detail below.
먼저, 산화 그래핀 용액을 준비하는 단계에 대하여 설명한다. 산화 그래핀은 변형된 허머 방법을 사용하여 준비할 수 있다.First, a step of preparing a graphene oxide solution will be described. Graphene oxide can be prepared using a modified Hummer method.
일례로 병에 흑연 분말 및 KMnO4를 1:6의 중량% 비율로 넣고 혼합한다. 다음, 병을 회전 가열 맨틀로 옮기고 45℃에서 6시간 동안 혼합한다. 다음 증류수를 사용하여 용액을 중화한다. 이후 침전을 위해 H2O2와 함께 용액을 세척하고 세정하기 위해 증류수를 첨가한다. 다음, 용액을 1주일 동안 산화시킨다. 이 기간 동안 증류수는 매 24시간마다 교체될 수 있다. 그 후 용액을 진공 필터를 사용하여 여과하고 버키 페이퍼/고 케익을 수득한다. 수득된 케익을 진공 챔버 내부의 진공 환경에서 24시간 동안 건조하고, 초음파 처리 욕조를 6시간 동안 사용하여 산화 그래핀 수용액을 제조한다. For example, graphite powder and KMnO 4 are added to a bottle at a weight ratio of 1:6 and mixed. Next, the bottle is transferred to a rotary heating mantle and mixed at 45° C. for 6 hours. The solution is then neutralized with distilled water. Thereafter, the solution is washed with H 2 O 2 for precipitation and distilled water is added for cleaning. Next, the solution is oxidized for 1 week. During this period, distilled water can be changed every 24 hours. The solution is then filtered using a vacuum filter to obtain a bucky paper/high cake. The obtained cake was dried in a vacuum environment inside the vacuum chamber for 24 hours, and an ultrasonic treatment bath was used for 6 hours to prepare an aqueous graphene oxide solution.
다음, WO3 용액을 준비하는 단계에 대하여 설명한다. WO3 용액을 준비하기 위해 일례로 나노 입자 형태의 WO3 0.038㎎을 0.5㎖의 NH4OH 용액에 용해시킬 수 있다. Next, steps for preparing the WO 3 solution will be described. To prepare a WO 3 solution, for example, 0.038 mg of WO 3 in the form of nanoparticles can be dissolved in 0.5 ml of NH 4 OH solution.
본 실시예에서, WO3 나노 입자를 준비하였을 때, 준비된 WO3는 NH4OH에 빠른 속도로 균질하게 용해될 수 있다. 또한, WO3가 나노 입자이기 때문에 용해에 요구되는 NH4OH의 양이 적을 수 있다. 일례로, WO3 나노 입자가 0.038㎎인 경우 NH4OH는 0.5㎖ 미만으로 사용될 수 있다. 따라서. 용액의 전반적인 pH를 변경하지 않고 유지할 수 있다. In this embodiment, when the WO 3 nanoparticles are prepared, the prepared WO 3 can be dissolved homogeneously and rapidly in NH 4 OH. In addition, since WO 3 is a nanoparticle, the amount of NH 4 OH required for dissolution may be small. For example, when the WO 3 nanoparticle is 0.038 mg, NH 4 OH may be used in less than 0.5 ml. therefore. The overall pH of the solution can be maintained unchanged.
다음, 산화 그래핀 용액과 WO3 용액을 혼합하여 혼합 용액을 제조하는 단계에 대하여 설명한다. 혼합 과정에서 초음파 처리를 할 수 있다. 초음파 처리를 통해 WO3 용액은 이전에 준비된 산화 그래핀 용액과 혼합되어 혼합 속도 및 용액의 균질성을 현저하게 향상시킬 수 있다.Next, a step of preparing a mixed solution by mixing the graphene oxide solution and the WO 3 solution will be described. In the mixing process, ultrasonic treatment can be performed. Through sonication, the WO 3 solution can be mixed with the previously prepared graphene oxide solution to significantly improve the mixing rate and the homogeneity of the solution.
다음, 혼합 용액을 수열처리하여 텅스텐 도핑된 산화 그래핀 필름을 형성하는 단계에 대하여 설명한다. 수열처리는 도 1에 도시된 바와 같이 180℃에서 3시간 동안 이루어질 수 있다. 그러나 이는 일 예시이며, 이에 제한되는 것은 아니다. 일례로, 수열 처리는 150℃내지 200℃에서 2시간 내지 4시간 동안 수행될 수 있다. Next, a step of forming a tungsten-doped graphene oxide film by hydrothermal treatment of the mixed solution will be described. The hydrothermal treatment may be performed at 180° C. for 3 hours as shown in FIG. 1. However, this is an example, and is not limited thereto. In one example, the hydrothermal treatment may be performed at 150°C to 200°C for 2 hours to 4 hours.
다음, 텅스텐 도핑된 산화 그래핀 필름을 열처리하는 단계에 대하여 설명한다. 열처리는 800℃ 내지 1200℃의 온도로 질소 분위기하에서 이루어질 수 있다. 이후 보다 상세하게 설명하겠으나, 열처리 온도에 따라 제조되는 텅스텐 도핑된 산화 그래핀의 전기 전도도가 달라질 수 있다. 열처리 온도가 800℃ 미만이면, 산소 관능기가 충분히 제거되지 않아 전도도가 낮아지는 문제가 있을 수 있고, 열처리 온도가 1200℃ 이상이면 필름의 과도한 구조 변화로 크랙(crack) 등의 문제가 있을 수 있다. Next, a step of heat-treating the tungsten-doped graphene oxide film will be described. The heat treatment may be performed under a nitrogen atmosphere at a temperature of 800°C to 1200°C. Hereinafter, it will be described in more detail, but the electrical conductivity of tungsten-doped graphene oxide prepared according to the heat treatment temperature may vary. If the heat treatment temperature is less than 800 °C, there may be a problem that the conductivity is lowered because the oxygen functional group is not sufficiently removed. If the heat treatment temperature is 1200 °C or higher, there may be a problem such as crack due to excessive structural change of the film.
이후, 제조된 산화 그래핀 필름을 성형하는 과정 등을 더 포함할 수 있다. Thereafter, a process of forming the prepared graphene oxide film may be further included.
도 2는, 본 발명의 일 실시예에 따른 텅스텐이 도핑된 GO 용액(왼쪽), 성형되지 않은 텅스텐이 도핑된 rGO 필름(중앙) 및 성형된 텅스텐이 도핑된 rGO 필름(오른쪽)을 나타낸 도이다. 성형을 통해 제조된 텅스텐 도핑된 산화 그래핀 필름은 이후 전자 방출기 등에 적용될 수 있다. 2 is a view showing a tungsten-doped GO solution (left), an unmolded tungsten-doped rGO film (center), and a molded tungsten-doped rGO film (right) according to an embodiment of the present invention. . The tungsten-doped graphene oxide film produced through molding may be applied to an electron emitter or the like.
본 제조 방법에서, 수열처리 공정에서 사용되는 혼합 용액(산화 그래핀 용액과 WO3 용액의 혼합)의 양에 따라 제조되는 텅스텐 도핑 산화 그래핀 필름의 막 두께를 조절할 수 있다. In this manufacturing method, the film thickness of the tungsten-doped graphene oxide film prepared according to the amount of the mixed solution (mixed graphene oxide solution and WO 3 solution) used in the hydrothermal treatment process can be adjusted.
이하에서 텅스텐 도핑의 효과에 대하여 상세하게 설명한다. Hereinafter, the effect of tungsten doping will be described in detail.
도 3은, 텅스텐이 도핑되지 않은 rGO 필름(a, b) 및 텅스텐이 도핑된 rGO 필름(c, d)의 단면을 도시한 것이다. Fig. 3 shows cross sections of tungsten-doped rGO films (a, b) and tungsten-doped rGO films (c, d).
도 3에서 (a) 및 (b)은 텅스텐이 도핑되지 않은 rGO로, (a)에서와 같이 얇은 가장자리(100㎚ ~ 200㎚)를 갖는 경우 (b)에 도시된 바와 같이 rGO의 박리가 일어나는 것을 확인할 수 있다. 도 3에서 (c) 및 (d)은 텅스텐이 도핑된 W-rGO로, (c)와 같이 얇은 가장자리(100㎚ ~ 200㎚)를 갖더라도 (d)에 도시된 바와 같이 박리가 일어나지 않는 것을 확인할 수 있다. In FIG. 3, (a) and (b) are tGO doped tGO, and when they have a thin edge (100 nm to 200 nm) as in (a), rGO peeling occurs as shown in (b). You can confirm that. (C) and (d) in FIG. 3 are tungsten-doped W-rGO, which shows that peeling does not occur as shown in (d) even if it has a thin edge (100 nm to 200 nm) as in (c). Can be confirmed.
도 4는, 본 발명에 따른 텅스텐이 도핑된 rGO 필름(W-rGO) 및 도핑되지 않은 rGO 필름에서의 라만 분광 분석 결과를 나타낸 것이다. 4 shows the results of Raman spectroscopy analysis on tungsten-doped rGO film (W-rGO) and undoped rGO film according to the present invention.
도 4를 참고하면, 도핑되지 않은 rGO 필름의 경우 라만 분광 분석 결과 sp2 영역의 고온 어닐링 결함이 나타난다. 그러나 W-rGO 필름의 경우 800℃에서 sp2 도메인의 복원이 증가하기 시작하는 것을 확인할 수 있다. 이는 텅스텐의 도핑에 의해 탄소와 텅스텐 사이의 강력한 공유 결합이 형성되어, 탄소의 증발이 제한되었기 때문이다. Referring to FIG. 4, in the case of an undoped rGO film, a Raman spectroscopy analysis shows a high temperature annealing defect in the sp2 region. However, in the case of the W-rGO film, it can be confirmed that the restoration of the sp2 domain starts to increase at 800°C. This is because doping of tungsten forms a strong covalent bond between carbon and tungsten, which limits evaporation of carbon.
이를 확인하기 위하여 에너지 분산형 X선 분광법(EDA)을 사용하여 필름에 존재하는 원소를 분석하여 이를 도 4에 나타내었다. 도 4를 참고로 하면 C와 W의 wt%는 1:0.01의 비율을 유지하는 것이 확인되었다. 산소 그룹의 존재는 W 도핑이 없는 필름과 비교하여 60% 이상으로 현저하게 감소되었다. 또한, X선 광전자 분광기의 원소 데이터를 EDS로 검증하여 도시하였다. 수집된 W-rGO 복합체의 XRD 패턴이 도 4에 도시되었다. 그래핀의 (002)면에 해당하는 특성 피크는 800℃에서 rGO 및 W-rGO의 열 환원 후 약 23.58℃부근에 나타나는 것을 확인할 수 있었다. 피크 위치를 기준으로 W-rGO 박막층 거리를 계산하였다. 열 환원 온도가 800℃일 때는 거리가 0.369㎚였으나, 열 환원 온도가 1200℃인 경우 거리가 0.351㎚로 감소하는 것을 확인할 수 있었다. 이러한 거리(d) 감소는 W-rGO 필름에서 작용기가 효과적으로 제거되었음을 의미한다. 이때 도출되는 d값은 흑연 값(~0.334㎚)과 유사하다. To confirm this, the elements present in the film were analyzed using energy dispersive X-ray spectroscopy (EDA), which is shown in FIG. 4. Referring to Figure 4, it was confirmed that the wt% of C and W maintained a ratio of 1:0.01. The presence of oxygen groups was significantly reduced to over 60% compared to the film without W doping. In addition, the elemental data of the X-ray photoelectron spectroscopy was verified by EDS. The XRD pattern of the collected W-rGO complex is shown in Figure 4. It was confirmed that the characteristic peak corresponding to the (002) plane of graphene appears at about 23.58°C after heat reduction of rGO and W-rGO at 800°C. The distance of the W-rGO thin film layer was calculated based on the peak position. When the heat reduction temperature was 800°C, the distance was 0.369 nm, but when the heat reduction temperature was 1200°C, it was confirmed that the distance was reduced to 0.351 nm. This reduction in distance (d) means that the functional groups were effectively removed from the W-rGO film. At this time, the derived d value is similar to the graphite value (~0.334 nm).
또한, W-rGO 박막의 경우 31℃ 부근의 피크가 WC의 (001)면을 나타내므로 텅스텐이 탄소 네트워크에 도핑된 것을 확인할 수 있었다. 나머지 얕은 피크는 명확하게 관찰되었고 전형적인 텅스텐의 평면 반사를 확인할 수 있었다. 패턴에서 확인할 수 있는 바와 같이 모든 샘플은 고도로 결정화 되었으며, 그래핀과 W의 회절 피크가 동시에 존재하는 것을 통해 텅스텐이 탄소 네트워크 내에 성공적으로 도핑된 것을 확인할 수 있었다. In addition, in the case of the W-rGO thin film, since the peak near 31°C represents the (001) plane of WC, it was confirmed that tungsten was doped into the carbon network. The rest of the shallow peaks were clearly observed and the plane reflection of typical tungsten could be confirmed. As can be seen from the pattern, all the samples were highly crystallized, and it was confirmed that tungsten was successfully doped in the carbon network through the simultaneous presence of the diffraction peaks of graphene and W.
화학 상태를 더 분석하기 위해 XPS 표면 분석을 두 필름에서 모두 수행하고 그 결과를 도 4에 나타내었다. XPS 스펙트럼은 합성된 복합 재료에서 C, W 및 O가 나타남을 확인하였다. To further analyze the chemical state, XPS surface analysis was performed on both films and the results are shown in FIG. 4. XPS spectrum confirmed that C, W and O appeared in the synthesized composite material.
도 4는, 1200℃에서 열처리한 W-rGO 박막으로부터 얻은 XPS 스펙트럼을 도시한다. 이 스펙트럼에서, 283.3eV를 중심으로 하는 SP3- 하이브리드화된 C, 284.3eV를 중심으로 하는 평면형 SP2-하이브리드화된 C가 나타난다. 284.6eV에서의 결합 에너지는 그래핀의 C1s 코어 레벨에 대응한다. W의 피크는 36.5eV로 O의 피크는 531.8eV에서 나타났다. 이는 O가 관능기 및 그래핀의 오염으로 인한 것임을 나타낸다. XPS 측정을 통해 텅스텐 나노 입자가 rGO 필름에 도핑되었음을 확인할 수 있다. 284.6eV에서의 C1s 피크는 두 필름 모두 높은 온도 감소 후 강도가 증가했다. 그러나 W-rGO는 rGO와 비교하여 산소 그룹(O1s)에서 강한 C1s 피크를 나타냈다. 이러한 피크는 sp2 하이브리드화의 높은 비율과 W-rGO의 산소 그룹의 효율적인 감소를 의미한다. 4 shows the XPS spectrum obtained from the W-rGO thin film heat-treated at 1200°C. In this spectrum, SP3-hybridized C centered at 283.3 eV, and planar SP2-hybridized C centered at 284.3 eV are shown. The binding energy at 284.6 eV corresponds to the C1s core level of graphene. The peak of W was 36.5eV and the peak of O was 531.8eV. This indicates that O is due to contamination of functional groups and graphene. XPS measurement confirms that the tungsten nanoparticles are doped into the rGO film. The C1s peak at 284.6 eV increased in strength after both films had a high temperature decrease. However, W-rGO showed a strong C1s peak in the oxygen group (O1s) compared to rGO. These peaks indicate a high rate of sp2 hybridization and efficient reduction of the oxygen group of W-rGO.
또한, 도 4는 어닐링 온도의 함수로 플롯된 EDS를 사용하여 측정된 C:W 비율과 O의 at%를 나타낸다. 해당 그래프에서 나타난 바와 같이 O at%는 현저히 감소하고 C at%는 감소함을 확인할 수 있다.4 also shows the C:W ratio and at% of O measured using EDS plotted as a function of annealing temperature. As shown in the graph, it can be seen that O at% is significantly decreased and C at% is decreased.
도 5는, 본 발명에 따른 텅스텐이 도핑된 rGO 필름 및 다른 샘플들과 비교하여 측정한 전기 전도도에 대한 값을 도식화하여 나타낸 도이다. 상이한 온도에서 어닐링된 rGO 및 W-rGO 막의 전기 시트 저항을 4-탐침법을 사용하여 측정하였다. 각각의 점에 대해 유사한 매개 변수를 사용하여 준비된 3개의 다른 샘플을 검사하여 정확성을 검증했다. 표본 크기는 길이가 5000㎛, 너비가 5000㎛, 두께가 0.1㎛였다. FIG. 5 is a diagram schematically showing a value for electrical conductivity measured in comparison to tungsten-doped rGO film and other samples according to the present invention. The electrical sheet resistance of the annealed rGO and W-rGO membranes at different temperatures was measured using a 4-probe method. Accuracy was verified by examining three different samples prepared using similar parameters for each point. The sample size was 5000 μm in length, 5000 μm in width, and 0.1 μm in thickness.
도 5의 (a)는 W-rGO막의 전도율 대 어닐링 온도를 나타낸 그래프이다. 도 5의 (b)에서 1200℃에서 어닐링된 W-rGO 필름의 전도도는 800℃에서 어닐링된 rGO 필름과 비교하여 현저히 개선되었음을 확인할 수 있다. 5(a) is a graph showing the conductivity of the W-rGO film versus the annealing temperature. It can be seen from FIG. 5(b) that the conductivity of the W-rGO film annealed at 1200°C was significantly improved compared to the rGO film annealed at 800°C.
W-rGO 필름에 대하여 세 가지 다른 샘플에서 실험을 수행하였고, 평균 전도도 값은 660,000 ± 48,000S/m로 나타났다. 전기 전도도의 큰 증가는 라만 분광법(도 4 참조)과 EDS 분광학 (EDS spectroscopy)에 의해 확인된 고온 어닐링 후 도핑에 의해 달성된 산소 관능기의 제거 및 구조 개선로 인한 것이다. Experiments were conducted on three different samples of W-rGO film, and the average conductivity value was 660,000 ± 48,000 S/m. The large increase in electrical conductivity is due to the removal of oxygen functional groups achieved by doping after high temperature annealing confirmed by Raman spectroscopy (see FIG. 4) and EDS spectroscopy (EDS spectroscopy) and structural improvement.
도 5의 (b)에 도시된 바와 같이, 고온에서 어닐링된 W-rGO 막은 화학적 또는 열 환원에 의해 제조된 다른 rGO 박막보다 훨씬 향상된 전기 전도도를 나타낸다. As shown in Fig. 5(b), the W-rGO film annealed at high temperature shows much improved electrical conductivity than other rGO thin films produced by chemical or thermal reduction.
도 5의 (a) 및 (b)을 참고로 하면, 전기 전도도 측정을 통해 W-rGO 필름이 1200℃에서 어닐링된 경우 최상의 결과를 나타냄을 확인할 수 있다. 도 5의 (c) 및 (d)을 함께 참고하면, sp2 본드 및 상대적으로 밀도가 높은 층의 복원으로 인해 W-rGO 필름의 열전도도는 텅스텐 도핑되지 않은 rGO 필름보다 상대적으로 훨씬 크다는 것을 확인할 수 있었다. Referring to (a) and (b) of FIG. 5, it can be confirmed that the W-rGO film exhibits the best results when annealed at 1200°C through electrical conductivity measurement. 5 (c) and (d) together, it can be seen that the thermal conductivity of the W-rGO film is relatively much higher than that of the tungsten undoped rGO film due to the sp2 bond and the restoration of the relatively dense layer. there was.
도 5를 통해 어닐링 온도에 따라 열전도도가 증가하는 것을 확인할 수 있다. 도 5의 (d)를 참고로 하면 도핑되지 않은 rGO 필름의 경우 상온에서 120W/mK이고, 온도가 150℃인 경우 140W/mK로 증가한다. 그러나 800℃ 및 1200℃의 온도에서 어닐링된 W-rGO 필름은 도핑되지 않은 rGO 필름과 비교하여 각각 170W/mK 및 260W/mK의 향상된 전도도를 보여준다. 특히, 1200℃에서 열처리된 W-rGO 박막은 약 200%의 향상을 보여준다. 이것은 텅스텐의 도핑에 의한 것으로, 텅스텐 도핑이 구조 내 산소의 감소 및 sp2 결합된 탄소 네트워크의 복원을 동시에 가능하게 하였기 때문이다. 따라서 텅스텐 도핑된 그래핀 필름이 개선된 전기 전도도 및 열 전도도를 가진다는 것을 확인할 수 있다. It can be seen through FIG. 5 that the thermal conductivity increases according to the annealing temperature. Referring to (d) of FIG. 5, in the case of an undoped rGO film, it is 120 W/mK at room temperature, and when the temperature is 150° C., it increases to 140 W/mK. However, W-rGO films annealed at temperatures of 800° C. and 1200° C. show improved conductivity of 170 W/mK and 260 W/mK, respectively, compared to undoped rGO films. In particular, the W-rGO thin film heat-treated at 1200°C shows an improvement of about 200%. This is due to the doping of tungsten, because tungsten doping simultaneously reduced oxygen in the structure and restored the sp2 bonded carbon network. Therefore, it can be confirmed that the tungsten doped graphene film has improved electrical conductivity and thermal conductivity.
마찬가지로, 800℃에서 어닐링된 도핑되지 않은 rGO 필름 및 800℃ 및 1200℃ 온도에서 어닐링된 텅스텐 도핑 rGO 필름에 대하여 열 전도율 등을 측정하였다. 도 5의 (e)는 응력 대 변형률 그래프를 보여준다. 그래프로부터 확인할 수 있는 바와 같이, 텅스텐 도핑시 기계적 성질이 현저하게 향상됨을 알 수 있다. 800℃에서 열처리된 rGO 보다 W-rGO의 인장 강도가 더 높게 나타났다. 특히 1200℃에서 어닐링된 W-rGO 필름은 약 941MPa의 인장 강도를 지니고 있으며, 영 모듈러스(도 5의 (f) 참조)가 도핑되지 않은 rGO과 비교하여 약 20배 이상 향상된 것을 확인할 수 있었다. Similarly, thermal conductivity and the like were measured for an undoped rGO film annealed at 800°C and a tungsten doped rGO film annealed at 800°C and 1200°C. 5(e) shows a stress versus strain graph. As can be seen from the graph, it can be seen that mechanical properties are significantly improved when doping tungsten. The tensile strength of W-rGO was higher than that of rGO heat-treated at 800℃. In particular, the W-rGO film annealed at 1200°C has a tensile strength of about 941 MPa, and it can be confirmed that Young's modulus (see FIG. 5(f)) is improved by about 20 times or more compared to the undoped rGO.
이를 통해 본 실시예에 따른 제조 방법으로 텅스텐을 도핑하는 경우 텅스텐이 고르고 균일하게 잘 도핑되며, 이렇게 제조된 텅스텐 도핑된 산화 그래핀의 물리적 특성이 우수함을 확인할 수 있었다.Through this, when doping tungsten by the manufacturing method according to the present embodiment, it was confirmed that tungsten is evenly and well doped, and the physical properties of the tungsten-doped graphene oxide thus prepared are excellent.
즉, 상기 측정 결과를 통해 본 발명의 일 실시예에 따른 제조 방법으로 제조된 텅스텐 도핑된 그래핀 필름이 산소 함량은 20at% 이하이고, 텅스텐/탄소의 비율이 0.010 이상임을 확인할 수 있었다. 텅스텐 도핑에 의해 그래핀 내부의 산소 비율이 감소하는 바, 텅스텐 도핑된 그래핀 필름은 높은 전기 전도도, 열 전도도 및 높은 영 모듈러스를 가질 수 있다. 전술한 측정 결과와 같이 본 발명의 일 실시예에 따른 텅스텐 도핑된 산화 그래핀 필름은 20℃ 내지 100℃의 온도에서 열전도도가 150W/mK 이상일 수 있다. 또한, 영 모듈러스가 100GPa 내지 400GPa이고, 전기 전도도는 6 * 106 S/m 이상일 수 있다. 이러한 텅스텐 도핑된 산화 그래핀 필름은 높은 전기 전도도 및 열 전도도, 영 모듈러스를 갖는바 전자 방출기 등으로 사용할 수 있다.That is, through the measurement results, it was confirmed that the tungsten-doped graphene film produced by the manufacturing method according to an embodiment of the present invention has an oxygen content of 20 at% or less and a tungsten/carbon ratio of 0.010 or more. As the oxygen ratio inside the graphene decreases due to tungsten doping, the tungsten doped graphene film may have high electrical conductivity, thermal conductivity, and high Young's modulus. As described above, the tungsten-doped graphene oxide film according to an embodiment of the present invention may have a thermal conductivity of 150 W/mK or higher at a temperature of 20°C to 100°C. In addition, Young's modulus is 100 GPa to 400 GPa, and the electrical conductivity may be 6 * 10 6 S/m or more. The tungsten-doped graphene oxide film has high electrical conductivity and thermal conductivity, and can be used as an electron emitter since it has Young's modulus.
이하, 본 발명의 다른 일 실시예에 따른 전자 방출기에 대하여 설명한다. 본 실시예에 따른 전자 방출기는 전술한 텅스텐 도핑된 그래핀 필름을 포함할 수 있다. 이때 텅스텐 도핑된 그래핀 필름은 평면 또는 원형으로 위치할 수 있다. Hereinafter, an electron emitter according to another embodiment of the present invention will be described. The electron emitter according to this embodiment may include the above-described tungsten-doped graphene film. At this time, the tungsten-doped graphene film may be positioned in a flat or circular shape.
냉음극 전자 방출기는 현재 열 이온 음극으로는 달성할 수 없는 고밀도 전자빔의 공급원으로 이용할 수 있다. 이때 파괴를 피하기 위해 전계 방출원은 피뢰침과 같은 높은 종횡비의 방출면을 가질 것이 요구된다. 이러한 전자 방출기에서 필드 향상을 위해 날카롭고 높은 종횡비의 방출 표면을 형성하는 것이 중요하다. 불균일한 전계 방출 지점은 필연적으로 방출원의 국부적인 증발을 수반하는 국부적인 전계 방출 및 그에 따른 열악한 진공으로 인한 전기 파손을 야기할 수 있다. Cold cathode electron emitters can be used as a source of high-density electron beams that cannot be currently achieved with thermal ion cathodes. At this time, the field emission source is required to have a high aspect ratio emission surface such as a lightning rod to avoid destruction. It is important to form a sharp, high aspect ratio emitting surface for field enhancement in these electron emitters. Non-uniform field emission points can inevitably cause local field emission accompanied by local evaporation of the emission source and thus electrical damage due to poor vacuum.
본 실시예에 따른 텅스텐 도핑된 그래핀 필름은 전자 방출원으로 적용될 수 있다. The tungsten-doped graphene film according to this embodiment may be applied as an electron emission source.
도 6은, 그래핀 필름의 방출 패턴 및 전계 방출에 대한 그래프를 나타낸 것이다. 그래핀 시트를 수평으로 겹치고 가장자리를 균일하게 절단하면 그래핀 시트의 가장자리에서만 방출이 일어난다. 도 6의 방출 패턴(왼쪽)은 그래핀 필름이 우수한 시트 전자 방출기임을 나타낸다. 그래핀 시트의 가장자리에서 나오는 전자는 시트 전자선으로 인광체를 유발하고 유선형 방출 패턴을 만든다. 도 6의 오른쪽에 표시된 그래핀 시트의 FE 테스트는 켜짐 필드가 2V/㎛이고 FE 전류 밀도가 약 10A/cm2 이고 전류가 2㎂임을 나타낸다. 이 경우 전류의 최대 값은 약 6mA였고, 6시간 동안 필름의 열화는 6% 정도였다. 6 shows a graph of the emission pattern and field emission of the graphene film. If the graphene sheets are overlapped horizontally and the edges are cut evenly, release occurs only at the edges of the graphene sheets. The emission pattern in FIG. 6 (left) indicates that the graphene film is an excellent sheet electron emitter. The electrons coming from the edge of the graphene sheet induce a phosphor with a sheet electron beam and create a streamlined emission pattern. The FE test of the graphene sheet shown on the right side of FIG. 6 shows that the on field is 2V/µm, the FE current density is about 10A/cm 2 and the current is 2mA. In this case, the maximum value of the current was about 6 mA, and the film deterioration was about 6% for 6 hours.
도 7은, 본 발명에 따른 텅스텐이 도핑된 rGO 필름과 관련된 (a) 텅스텐 도핑된 rGO 필름의 사진, (b) 원통형 그래핀 시트 방출기의 제조 개략도, (c) 원통형 그래핀 시트 방출기의 사진 및 (d) 원통형 그래핀 시트 방출기의 순환 방사 패턴을 나타낸 도이다. 본 실시예에 따른 텅스텐 도핑된 그래핀 필름은 도 7과 같이 원형의 형상으로 전자 방출원으로 기능할 수 있다.FIG. 7 is a photograph of (a) a tungsten-doped rGO film associated with a tungsten-doped rGO film according to the present invention, (b) a schematic view of the manufacture of a cylindrical graphene sheet emitter, (c) a photograph of a cylindrical graphene sheet emitter, and (d) It is a diagram showing a circular radiation pattern of a cylindrical graphene sheet emitter. The tungsten-doped graphene film according to this embodiment may function as an electron emission source in a circular shape as shown in FIG. 7.
도 8은, 본 발명에 따른 따른 텅스텐이 도핑된 rGO 필름과 관련된 전계 방출시험 설정의 개략도를 나타낸 도이다. 도 9는, 본 발명에 따른 따른 텅스텐이 도핑된 rGO 필름과 관련된 전계 방출시험의 데이터를 그래프화 하여 나타낸 도이다. (c)는 I-V 곡선이고, (d)는 E-J 곡선이며, (e)는 F-N 곡선이고 (f)는 안정성 시험 결과이다. 도 10은, 본 발명에 따른 따른 텅스텐이 도핑된 rGO 필름과 관련된 형광체 스크린으로 관찰한 방출 패턴에 대한 도이다.8 is a diagram showing a schematic diagram of a field emission test setup related to a tungsten-doped rGO film according to the present invention. 9 is a graph showing data of a field emission test related to a tungsten-doped rGO film according to the present invention. (c) is the I-V curve, (d) is the E-J curve, (e) is the F-N curve, and (f) is the stability test result. 10 is a view of the emission pattern observed with the phosphor screen associated with tungsten-doped rGO film according to the present invention.
도 8 내지 도 10을 참고로 하면, 전계 방출 시험 결과는 도핑되지 않은 막과 비교하여 안정적이며 재현 가능한 전류 밀도 및 방출 전류를 보여준다. 8-10, the field emission test results show a stable and reproducible current density and emission current compared to an undoped film.
도 9의 (e)는 도핑되지 않은 rGO 필름의 전계 방출 경향을 확인하는 각 사이클에 대한 F-N 플롯을 나타낸 것이다. 도 9의 (d) 및 (f)은 7.4V/㎛의 적용 전계에서 달성된 최고 전류 밀도를 보여주며, 이는 6000A/cm2로 텅스텐이 도핑된 rGO에서 가장 높게 나타나는 것을 확인할 수 있었다. 또한, 도 9의 (f)를 참고로 하면, 6.6V/㎛로 192시간 테스트했을 때, 변동량이 1% 미만으로 탁월한 안정성을 확인할 수 있었다. 이는 합성 과정에서 텅스텐 나노 입자의 도핑에 기인하는 것이다. 9(e) shows the FN plot for each cycle confirming the field emission tendency of the undoped rGO film. 9(d) and (f) show the highest current density achieved at an applied electric field of 7.4 V/µm, which was confirmed to be the highest in tGO doped with tungsten at 6000 A/cm 2 . In addition, referring to FIG. 9(f), when tested at 6.6 V/µm for 192 hours, the amount of variation was less than 1%, which confirmed excellent stability. This is due to the doping of tungsten nanoparticles during the synthesis process.
도 10(a)는 텅스텐이 도핑된 rGO 필름을 형광체 스크린으로 관찰한 방출 패턴을 나타낸 것이다. 도 10(a)에서는 양극 대신에 형광체 스크린이 놓여있다. 사각 시트 타입의 빔 패턴이 관찰되는데, 이는 방출된 전자빔이 본질적으로 시트 타입이고 포커싱을 위해 정확하게 성형될 수 있음을 의미한다. 도 10의 (b)와 (c)는 전계 방출 실험 후 각각 rGO와 W-rGO 막을 나타낸 것이다. 도 10의 (b)는 실험 후 rGO 필름 모서리가 완전히 파괴된 것을 확인할 수 있다. 그러나 W-rGO 필름의 경우 필름 모서리가 단단한 형태로 유지되는 것을 확인할 수 있다.FIG. 10(a) shows the emission pattern of the rGO film doped with tungsten observed with a phosphor screen. In Fig. 10(a), a phosphor screen is placed instead of the anode. A square sheet type beam pattern is observed, which means that the emitted electron beam is essentially sheet type and can be precisely shaped for focusing. 10(b) and 10(c) show the rGO and W-rGO films, respectively, after the field emission experiment. 10(b), it can be seen that the rGO film edges were completely destroyed after the experiment. However, in the case of W-rGO film, it can be seen that the edge of the film is kept in a solid shape.
이로부터 W-rGO 필름이 장시간의 전계 방출 작업 후에도 열화되지 않음을 확인할 수 있으며, 이를 전자 방출 음극 등으로 사용하는 경우 개선된 효과를 가지는 것을 확인할 수 있다. From this, it can be confirmed that the W-rGO film does not deteriorate even after a long field emission operation, and when it is used as an electron emission cathode, it can be seen that it has an improved effect.
이상에서는 실시예들을 참조하여 설명하였지만, 해당 기술 분야의 숙련된 통상의 기술자는 하기의 특허 청구의 범위에 기재된 본 발명의 사상 및 영역으로부터 벗어나지 않는 범위 내에서 본 발명을 다양하게 수정 및 변경시킬 수 있음을 이해할 수 있을 것이다.Although described above with reference to embodiments, those skilled in the art can variously modify and change the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand that there is.

Claims (13)

  1. 산화 그래핀 용액과 WO3 용액을 혼합하여 혼합 용액을 제조하는 단계;Preparing a mixed solution by mixing a graphene oxide solution and a WO 3 solution;
    상기 혼합 용액을 수열처리하여 텅스텐 도핑된 산화 그래핀을 형성하는 단계;Forming a tungsten-doped graphene oxide by hydrothermal treatment of the mixed solution;
    상기 텅스텐 도핑된 산화 그래핀을 800℃ 내지 1200℃의 온도에서 열처리하는 단계를 포함하는 텅스텐 도핑된 산화 그래핀의 제조 방법. Method of manufacturing a tungsten-doped graphene oxide comprising the step of heat-treating the tungsten-doped graphene oxide at a temperature of 800 ℃ to 1200 ℃.
  2. 제1항에 있어서,According to claim 1,
    상기 WO3 용액은 용매에 용해된 나노 입자 형태의 WO3를 포함하는 것을 특징으로 하는 텅스텐 도핑된 산화 그래핀의 제조 방법.The WO 3 solution is a method for producing tungsten doped graphene oxide, characterized in that it comprises WO 3 in the form of nanoparticles dissolved in a solvent.
  3. 제1항에 있어서,According to claim 1,
    상기 제조된 텅스텐 도핑된 산화 그래핀을 성형하는 단계를 더 포함하고,Further comprising the step of forming the prepared tungsten doped graphene oxide,
    상기 텅스텐 도핑된 산화 그래핀은 두께가 100㎚ 내지 200㎚인 필름 형태로 성형되는 것을 특징으로 하는 텅스텐 도핑된 산화 그래핀의 제조 방법.The tungsten-doped graphene oxide is a method of manufacturing a tungsten-doped graphene oxide characterized in that it is molded into a film having a thickness of 100 nm to 200 nm.
  4. 제1항에 있어서,According to claim 1,
    상기 산화 그래핀 용액은, 흑연 분말 및 KMnO4를 1:6의 중량% 비율로 혼합하여 제조되는 것을 특징으로 하는 텅스텐 도핑된 산화 그래핀의 제조 방법. The graphene oxide solution, a method for producing tungsten doped graphene oxide, characterized in that the graphite powder and KMnO 4 is prepared by mixing in a weight ratio of 1:6.
  5. 제1항에 있어서,According to claim 1,
    상기 혼합 용액을 수열처리하는 단계는, 150℃ 내지 200℃의 온도에서 2시간 내지 4시간 동안 수행되는 것을 특징으로 하는 텅스텐 도핑된 산화 그래핀의 제조 방법. The step of hydrothermal treatment of the mixed solution is a method for producing tungsten-doped graphene oxide, which is performed for 2 hours to 4 hours at a temperature of 150°C to 200°C.
  6. 제1항에 있어서,According to claim 1,
    산화 그래핀 용액과 WO3 용액을 혼합하여 혼합 용액을 제조하는 단계에서 상기 혼합은 초음파 처리를 포함하는 것을 특징으로 하는 텅스텐 도핑된 산화 그래핀의 제조 방법.In the step of preparing a mixed solution by mixing a graphene oxide solution and a WO 3 solution, the mixing comprises a sonication treatment method of manufacturing tungsten doped graphene oxide.
  7. 텅스텐 도핑된 산화 그래핀 필름으로서,A tungsten doped graphene oxide film,
    상기 텅스텐 도핑된 산화 그래핀 필름은, 산소 함량이 20at% 이하이고,The tungsten doped graphene oxide film, the oxygen content is 20at% or less,
    상기 텅스텐/탄소의 비율은 0.010 이상인 텅스텐 도핑된 산화 그래핀 필름.The tungsten / carbon ratio is 0.010 or more tungsten doped graphene oxide film.
  8. 제7항에 있어서,The method of claim 7,
    상기 텅스텐 도핑된 산화 그래핀 필름은 20℃ 내지 100℃의 온도에서 열전도도가 150W/mK 이상인 것을 특징으로 하는 텅스텐 도핑된 산화 그래핀 필름.The tungsten-doped graphene oxide film is a tungsten-doped graphene oxide film, characterized in that the thermal conductivity at a temperature of 20 ℃ to 100 ℃ 150W / mK or more.
  9. 제7항에 있어서,The method of claim 7,
    상기 텅스텐 도핑된 산화 그래핀 필름은 영 모듈러스가 100GPa 내지 400GPa인 것을 특징으로 하는 텅스텐 도핑된 산화 그래핀 필름.The tungsten doped graphene oxide film is a tungsten doped graphene oxide film, characterized in that the Young's modulus is 100GPa to 400GPa.
  10. 제7항에서,In claim 7,
    상기 텅스텐 도핑된 산화 그래핀 필름의 전기 전도도는 6 * 106 S/m 이상인 것을 특징으로 하는 텅스텐 도핑된 산화 그래핀 필름.The tungsten-doped graphene oxide film is characterized in that the electrical conductivity of the tungsten-doped graphene oxide film is 6 * 10 6 S / m or more.
  11. 제7항에서,In claim 7,
    상기 텅스텐 도핑된 산화 그래핀 필름의 두께는 100㎚ 내지 200㎚인 텅스텐 도핑된 산화 그래핀 필름.The tungsten-doped graphene oxide film has a thickness of 100 nm to 200 nm.
  12. 제7항 내지 제11항 중 어느 한 항에 따른 텅스텐 도핑된 산화 그래핀 필름을 포함하는 전자 방출기.An electron emitter comprising the tungsten-doped graphene oxide film according to claim 7.
  13. 제12항에 있어서,The method of claim 12,
    상기 텅스텐 도핑된 산화 그래핀 필름은 평면 또는 원형으로 위치하는 전자 방출기. The tungsten-doped graphene oxide film is a flat or circular electron emitter.
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