CN105244249A - Graphene sheet-carbon nanotube film flexible composite material, preparation method and application thereof - Google Patents

Abstract

The invention discloses a graphene sheet-carbon nanotube film flexible composite material, a preparation method and an application. It uses microwave plasma enhanced chemical vapor deposition to prepare graphene sheets on carbon nanotube films, and uses the obtained graphene sheet-carbon nanotube film flexible composite materials as cathodes to assemble field emitters. The graphene sheet-carbon nanotube film flexible composite material prepared by this method has the characteristics of flexibility, and the graphene sheet is distributed on the carbon nanotube in an array state, and the number of layers of the graphene sheet is 1-10 layers. The distribution density on the surface is 8-12 pieces/square micron, and the width is 0.5-1.2 micron. Compared with graphene sheets grown on planar silicon substrates, the graphene sheet-carbon nanotube film flexible composite material prepared by this method has a lower turn-on electric field and a larger field emission current density, and can It works stably under the field emission current density and has high application value.

Description

A flexible composite material of graphene sheet-carbon nanotube film and its preparation method and application

This invention is funded by the National Natural Science Foundation of China-Youth Fund Project (Project No. 51302187). This work was supported by the Key Project of Tianjin Applied Basic and Frontier Technology Research Program (Project No. 14JCZDJC32100).

technical field

The invention belongs to the technical field of preparation and application of nanomaterials, and relates to the preparation of a flexible composite nanomaterial with a unique structure using a plasma-enhanced chemical vapor deposition method on a commercially available carbon nanotube film as a substrate, and using it for vacuum field electron emission Device fabrication method.

Background technique

Since its discovery in 2004, graphene has shown good application prospects in many aspects due to its excellent electrical, mechanical properties and chemical stability, including the development of vacuum field electronic devices. Graphene has sharp edges at the atomic scale and unparalleled excellent electrical conductivity. Under the action of an external electric field, it can form a huge local electric field at the edge, which makes it easier for electrons to escape into the vacuum. In addition, compared with the traditional one-dimensional field emission materials such as carbon nanotubes, the unique two-dimensional structure of graphene is conducive to the rapid dissipation of Joule heat generated in the field emission on its surface, effectively avoiding the effective field emission point due to Joule heat. Accumulation and burning, so that the graphene-based field emission cathode material has better field emission stability than carbon nanotubes. Studies have shown that the traditional graphene epitaxially grown by depositing catalysts generally lies flat on the substrate, and its atomic-scale sharp edges cannot become efficient field emission points in the field emission process, which requires the prepared graphene to be in an array The states are distributed on the substrate, that is, arrayed graphene sheets are prepared. Plasma-enhanced chemical vapor deposition is the mainstream method for preparing arrayed graphene sheets today. This method does not require the introduction of catalysts, and the growth of graphene sheets is less dependent on the substrate, so that graphene sheets on various substrates growth becomes possible. At present, the substrates that have been used for the growth of graphene sheets are mainly hard substrates such as silicon wafers and metal sheets, which limits the application of field emitters to a certain extent, and field electron emission devices with flexible substrates can make up for this. 1. Defects in the field of application. The development of field emission electronic components on flexible substrates is currently a hot topic, which may bring about a revolution in the field of high-performance displays. Just imagine that a mobile phone or computer is flexible and can be folded and put into a pocket at will, which requires its display device to be flexible and foldable (which of course also requires the flexibility and miniaturization of the corresponding hardware equipment). This prospect Undoubtedly charming. In the current research on flexible substrate field emitters, such as graphene/carbon nanotube composite materials and ZnO nanowire/graphene composite materials, graphene is only used as a flexible substrate with excellent electrical conductivity and foldability. However, the advantage of its sharp edge as a highly efficient field emission point has not been exploited. The present invention is proposed based on the development of high-performance graphene-based field emission cathode materials. We use the carbon nanotube film as the substrate, and the graphene sheet grown on it as the field emission main body, and make full use of the conductivity of the carbon nanotube film Good, flexible, uneven surface (field emission points are less affected by electric field shielding) and good structural advantages of graphene sheet field emission stability, so that the prepared composite material has more advantages than graphene sheets prepared on general hard flat materials. Low operating voltage and good field emission stability at high current density, which greatly enhances its application value.

Contents of the invention

The purpose of the present invention is to overcome the limitation in application of existing hard flat panel field emitter, the deficiency that the field emission cathode material of planar substrate graphene sheet field emission is higher deficiency, utilize a kind of simple plasma-enhanced chemical vapor deposition process in Densely distributed graphene sheets are prepared on the carbon nanotube film substrate, which effectively integrates the advantages of carbon nanotube film such as good conductivity, flexibility and foldability, uneven surface and good field emission stability of graphene sheets, thus providing a low operating voltage, Large field emission current density, high field emission stability, flexible field emission cathode material.

To achieve the above object, the present invention discloses the following technical contents:

A graphene sheet-carbon nanotube film flexible composite material, which is composed of graphene sheets with 1-10 layers of deposited edge layers on the carbon nanotube film; wherein the distribution density of the deposited graphene sheets on the carbon nanotube film 8-12 sheets/square micron, and the width of the graphene sheet is 0.5-1.2 micron.

The present invention further discloses a preparation method of a graphene sheet-carbon nanotube film flexible composite material, which is characterized in that the steps are as follows:

(1) Put the commercially available carbon nanotube film on the graphite sample stage of the microwave plasma enhanced chemical vapor deposition device, feed 15sccm high-purity hydrogen (5N), adjust the air pressure to 1.5kPa, and carry the carbon nanotube film The sample stage is heated to a stable temperature of 600°C, and the carbon nanotube film is heat-treated for 30 minutes;

(2) On the basis of step (1), increase the temperature of the sample stage to a stable temperature of 750°C, and adjust the air pressure to 1kPa;

(3) Start the microwave source on the basis of step (2), adjust the microwave power to 200-300W, and feed 1-3sccm high-purity acetylene gas (5N), quickly adjust the pressure of the reaction chamber to 1kPa, and start the graphene sheet Deposition, the deposition time is 2 hours, the distribution density of the deposited graphene sheets is 8-12 sheets/square micron, and the width of the graphene sheets is 0.5-1.2 microns. The method for preparing the graphene sheet may be microwave plasma enhanced chemical vapor deposition, radio frequency sputtering deposition, radio frequency plasma enhanced chemical vapor deposition and other methods.

The present invention further discloses the application of the graphene sheet-carbon nanotube film flexible composite material in the preparation of vacuum field electron emission devices, and the experimental results show that:

(1) The open electric field of the graphene sheet-carbon nanotube film flexible composite material prepared by the present invention is only 1.78-3.38V/μm;

(2) The maximum field emission current density of the graphene sheet-carbon nanotube film flexible composite material prepared by the present invention can reach 7.10 mA/cm ² ;

(3) The graphene sheet-carbon nanotube film flexible composite material prepared by the present invention exhibits good field emission when the average field emission current density is as high as 3.62mA/cm ² and the corresponding applied electric field strength is only 2.30V/μm Stability: within 20 hours, the field emission current density does not decrease significantly, and the current fluctuation is less than 3%.

Compared with the prior art, the graphene sheet-carbon nanotube film flexible composite material disclosed by the present invention and its preparation method and application have positive effects:

The carbon nanotube film has excellent conductivity, which is conducive to the flow of electrons from the carbon nanotube film to the graphene sheet; the carbon nanotube film has the characteristics of flexibility, which makes the prepared field emission cathode material have the advantages of flexibility and foldability; Compared with planar structure substrates such as sheets and metal sheets, the surface of carbon nanotube film is uneven, which can effectively reduce the influence of electric field shielding effect on the field emission of graphene sheet, thereby reducing the working voltage of graphene sheet-carbon nanotube film flexible composite material; The thickness of graphene sheets can be controlled by experimental parameters, and the prepared graphene sheets with sharp edges (1-10 layers) can promote field electron emission; the above structural advantages of carbon nanotube films and graphene sheets make all The prepared graphene sheet-carbon nanotube film flexible field emission cathode material has a low turn-on field (1.78-3.38V/μm) and a large field emission current density (7.10mA/cm ² ), while also retaining graphite Graphene materials have good field emission stability, and these indicators are improved compared with graphene sheets prepared on planar silicon substrates. In addition, the microwave plasma enhanced chemical vapor deposition method adopted in the present invention has a simple process, does not introduce impurities into the prepared material, and has high practical value.

Description of drawings:

Fig. 1 is the schematic diagram of the technological process of preparing graphene sheet-carbon nanotube film flexible composite material of the present invention, and its core step is to prepare graphene sheet on carbon nanotube film by microwave plasma enhanced chemical vapor deposition method;

Fig. 2 is the optical and scanning electron microscope picture of carbon nanotube film used in the present invention, comprises: 21. the optical picture of carbon nanotube film; 22. the low magnification scanning electron microscope top view of carbon nanotube film;

Fig. 3 is the structural representation of the reaction chamber of the microwave plasma enhanced chemical vapor deposition device used in the present invention; The purity of acetylene gas and hydrogen used is 5N, and the substrate is heated with a self-made graphite heater, and "mechanical pump+molecular pump" is used The combined device evacuates the reaction chamber;

Fig. 4 is the scanning electron microscope and transmission electron microscope pictures of the graphene sheet-carbon nanotube film flexible composite material prepared in embodiment 1, comprising:

41. The low magnification scanning electron microscope top view of the graphene sheet-carbon nanotube film flexible composite material prepared according to the conditions of Example 1 (microwave power: 200W; acetylene gas flow rate: 2 sccm);

42. The high-magnification scanning electron microscope top view of the graphene sheet-carbon nanotube film flexible composite material prepared according to the conditions of Example 1 (microwave power: 200W; acetylene gas flow rate: 2 sccm);

43. The low magnification transmission electron microscope picture of the graphene sheet-carbon nanotube film flexible composite material prepared according to the conditions of Example 1 (microwave power: 200W; acetylene gas flow rate: 2 sccm);

44. The high-magnification transmission electron microscope picture of the graphene sheet-carbon nanotube film flexible composite material prepared according to the conditions of Example 1 (microwave power: 200W; acetylene gas flow rate: 2 sccm);

Fig. 5 shows the structural representation of the high vacuum field emission tester used in the present invention, for testing the field emission performance of the graphene sheet-carbon nanotube film flexible composite material gained in each embodiment; This device is a field emission test routine The device uses the prepared graphene sheet-carbon nanotube film flexible composite material as the cathode, and the corresponding anode is a stainless steel plate with a diameter of about 10 cm, and the distance between the cathode and the anode is kept at 1 mm; during the test, the anode load is 0-10kV Adjustable positive bias, and the cathode is grounded, and the test results are automatically recorded by the computer;

Fig. 6 is the field emission performance diagram of the graphene sheet-carbon nanotube film flexible composite material prepared under different conditions. Field emission properties of four types of samples such as graphene sheets prepared in example 3-carbon nanotube film flexible composites and graphene sheets prepared on planar silicon substrates;

Fig. 7 is the field emission stability diagram when the field emission current density is about 1/2 of the maximum field emission current density within 20 hours of the graphene sheet-carbon nanotube film flexible composite material prepared in embodiment 1, characterized in Field emission current density as a function of time under constant applied electric field.

detailed description

The present invention will be further described in detail below with reference to the drawings and embodiments, but the present invention is not limited to these embodiments. The carbon nanotube film, silicon single wafer, high-purity hydrogen gas, high-purity acetylene gas, microwave plasma-enhanced chemical vapor deposition device, and field emission tester used therein are all commercially available.

Figure 1 is a schematic diagram of the process flow for preparing graphene sheet-carbon nanotube film flexible composite material according to the present invention, the core step of which is the preparation of graphene sheet on carbon nanotube film by microwave plasma enhanced chemical vapor deposition.

Shown in Figure 2 is the optical picture and scanning electron microscope picture of the carbon nanotube film (commercially available) used in the present invention; wherein Figure 21 shows the optical picture of the carbon nanotube film, it can be seen that the carbon nanotube film is flexible and Free bending; Figure 22 shows the top view of the low-magnification scanning electron microscope of the carbon nanotube film. It can be seen that the carbon nanotubes are densely distributed, with few impurities on the surface, and the surface of the film is uneven due to the uneven distribution of carbon nanotubes.

Example 1

Heat treatment of carbon nanotube film in hydrogen atmosphere:

Cut the carbon nanotube film into 1cm×1cm pieces with a blade and place them on the graphite sample stage of a microwave plasma-enhanced chemical vapor deposition device (commercially available). Figure 3 is a schematic diagram of the reaction chamber of the device; Vacuum system, vacuumize the reaction chamber to about 1.0×10 ^-3 Pa, then inject 15sccm hydrogen (purity 5N), adjust the air pressure to 1.5kPa, heat the sample stage with a self-made graphite heater until the temperature is stable at 600°C, and continue Treat for 30 minutes to remove adsorbates and pollutants on the surface of the carbon nanotube film.

Graphene sheets prepared by microwave plasma enhanced chemical vapor deposition:

After heat-treating the carbon nanotube film in a hydrogen atmosphere, immediately raise the temperature of the substrate to 750°C, and adjust the air pressure to 1kPa. After the temperature and air pressure are stable, start the microwave source, set the microwave power to 200W, and immediately inject 2 sccm of acetylene gas (purity is 5N), and quickly adjust the air pressure to be stable at 1kPa, that is, the growth of graphene sheets is started, and the growth time is 2 hours; Figure 41 and Figure 42 in Figure 4 are respectively the prepared graphite in this embodiment Low-magnification and high-magnification scanning electron microscope top views of flexible composites of olefin sheet-carbon nanotube film. It can be seen that graphene sheets are densely distributed on the surface of carbon nanotubes. The distribution density is about 10 sheets/square micron, and the width of graphene sheets is 0.7-1.1 micron, the uneven surface of the carbon nanotube film causes the surface of the composite material to be uneven; Figure 43 in Fig. 4 shows the prepared graphene sheet-carbon nanotube film flexible composite material in the present embodiment It can be seen that the graphene sheets are densely distributed on the carbon nanotubes, and the non-overlapping parts of the graphene sheets are almost transparent, indicating that the thickness of the prepared graphene sheets is small, and the thickness of the graphene sheets can be Further, it can be seen from the high-magnification transmission electron microscope picture shown in Figure 44 in Figure 4 that there are only 3-4 layers at the edge of the graphene sheet shown. The number of layers of graphene sheets obtained in this embodiment is 1-7 layers.

Field emission performance test:

A high vacuum field emission tester (commercially available) is used to test the field emission performance of the graphene sheet-carbon nanotube film flexible composite material prepared in this embodiment, as shown in Fig. 5 is the structural representation of the device, the The device is a conventional field emission performance testing device. The vacuum in the test chamber was maintained at about 1×10 ^-7 Pa by a titanium ion pump. The graphene sheet-carbon nanotube film flexible composite material prepared in this example is glued on the copper sample stage with conductive adhesive as the cathode, and a stainless steel plate with a diameter of about 10 cm is used as the anode, and the distance between the cathode and the anode is 1 mm ; During the test, the 0-10kV adjustable positive bias load is placed on the anode, and the bias voltage increases at a constant speed (500V/min), and the cathode is grounded, and the test results are automatically recorded by the computer. Figure 6 is the field emission performance diagram of graphene sheet samples with different morphologies, which characterizes the relationship between the field emission current density and the applied electric field strength, specifically including the graphite prepared in Example 1, Example 2, and Example 3. Field emission properties of four types of samples, including flexible composites of olefin sheets-carbon nanotube films and graphene sheets prepared on planar silicon substrates. It can be seen that the open field and maximum field emission current density of the graphene sheet-carbon nanotube film flexible composite material prepared in this example are 1.78V/μm and 7.10mA/cm ² , which are far superior to those of silicon 4.29 V/μm and 1.67 mA/cm ² for graphene sheets prepared on a single wafer. The main reason for the enhanced field emission performance is that the carbon nanotube film has better conductivity than the silicon single wafer, and the uneven surface reduces the influence of the electric field shielding effect. Figure 7 shows that the graphene sheet-carbon nanotube film flexible composite material prepared in this embodiment is within 20 hours, when the field emission current density is about 1/2 of the maximum field emission current density (average field emission current density (3.62mA/cm ² ) field emission stability graph, which characterizes the relationship of the field emission current density with time under the action of a constant external electric field. It can be seen that the field emission current density changes very little within 20 hours without a significant drop, the fluctuation is less than 3%, and the working electric field is only 2.30V/μm. These results show good application prospects.

Field emitter assembly (conventional assembly method):

Adhere the prepared graphene sheet-carbon nanotube film flexible composite material with a conductive adhesive on a copper electrode with a thickness of 2 mm as the cathode, and the anode is a copper plate with a thickness of about 2 mm, and the thickness of the passage between the two electrodes is 200 microns The ring-shaped polytetrafluoroethylene film is isolated; during the field emission process, the positive bias is applied to the anode and the cathode is grounded to obtain stable field electron emission. The field emission current can be controlled by adjusting the anode bias.

Example 2

Heat treatment of carbon nanotube film in hydrogen atmosphere:

Cut the carbon nanotube film into 1cm×1cm pieces with a blade and place them on the graphite sample stage of a microwave plasma-enhanced chemical vapor deposition device (commercially available). Figure 3 is a schematic diagram of the reaction chamber of the device; Vacuum system, vacuumize the reaction chamber to about 1.0×10 ^-3 Pa, then inject 15sccm hydrogen (purity 5N), adjust the air pressure to 1.5kPa, heat the sample stage with a self-made graphite heater until the temperature is stable at 600°C, and continue Treat for 30 minutes to remove adsorbates and pollutants on the surface of the carbon nanotube film.

Graphene sheets prepared by microwave plasma enhanced chemical vapor deposition:

After heat-treating the carbon nanotube film in a hydrogen atmosphere, immediately raise the temperature of the substrate to 750°C, and adjust the air pressure to 1kPa. After the temperature and air pressure are stable, start the microwave source, set the microwave power to 200W, and immediately inject 1 sccm of acetylene gas (purity is 5N), and quickly adjust the air pressure to a stable 1kPa, that is, the growth of graphene sheets starts, and the growth time is 2 hours. The distribution density of the obtained graphene sheets is about 8 sheets/square micrometer, the width is 0.6-0.9 micrometers, and the number of layers is 1-6 layers.

Field emission performance test:

A high vacuum field emission tester (commercially available) is used to test the field emission performance of the graphene sheet-carbon nanotube film flexible composite material prepared in this embodiment, as shown in Fig. 5 is the structural representation of the device, the The device is a conventional field emission performance testing device. The vacuum in the test chamber was maintained at about 1×10 ^-7 Pa by a titanium ion pump. The graphene sheet-carbon nanotube film flexible composite material prepared in this example is glued on the copper sample stage with conductive adhesive as the cathode, and a stainless steel plate with a diameter of about 10 cm is used as the anode, and the distance between the cathode and the anode is 1 mm ; During the test, the 0-10kV adjustable positive bias load is placed on the anode, and the bias voltage increases at a constant speed (500V/min), and the cathode is grounded, and the test results are automatically recorded by the computer. It can be seen from Figure 6 that the open field and maximum field emission current density of the graphene sheet-carbon nanotube film flexible composite material prepared in this example are 2.80V/μm and 4.16mA/cm ² , which are far It is better than 4.29V/μm and 1.67mA/cm ² of the graphene sheet prepared on the silicon single wafer. The main reason for the enhanced field emission performance is that the carbon nanotube film has better conductivity than the silicon single wafer, and the uneven surface reduces the influence of the electric field shielding effect.

Field emitter assembly (conventional assembly method):

Adhere the prepared graphene sheet-carbon nanotube film flexible composite material with a conductive adhesive on a copper electrode with a thickness of 2 mm as the cathode, and the anode is a copper plate with a thickness of about 2 mm, and the thickness of the passage between the two electrodes is 200 microns The ring-shaped polytetrafluoroethylene film is isolated; during the field emission process, the positive bias is applied to the anode and the cathode is grounded to obtain stable field electron emission. The field emission current can be controlled by adjusting the anode bias.

Example 3

Heat treatment of carbon nanotube film in hydrogen atmosphere:

Cut the carbon nanotube film into 1cm×1cm pieces with a blade and place them on the graphite sample stage of a microwave plasma-enhanced chemical vapor deposition device (commercially available). Figure 3 is a schematic diagram of the reaction chamber of the device; Vacuum system, vacuumize the reaction chamber to about 1.0×10 ^-3 Pa, then inject 15sccm hydrogen (purity 5N), adjust the air pressure to 1.5kPa, heat the sample stage with a self-made graphite heater until the temperature is stable at 600°C, and continue Treat for 30 minutes to remove adsorbates and pollutants on the surface of the carbon nanotube film.

Graphene sheets prepared by microwave plasma enhanced chemical vapor deposition:

After heat-treating the carbon nanotube film in a hydrogen atmosphere, immediately raise the temperature of the substrate to 750°C, and adjust the air pressure to 1kPa. After the temperature and air pressure are stable, start the microwave source, set the microwave power to 200W, and immediately inject 3 sccm of acetylene gas (purity is 5N), and quickly adjust the air pressure to a stable 1kPa, that is, the growth of graphene sheets starts, and the growth time is 2 hours. The distribution density of the obtained graphene sheets is about 12 sheets/square micrometer, the width is 0.9-1.2 micrometers, and the number of layers is 1-10 layers.

Field emission performance test:

A high vacuum field emission tester (commercially available) is used to test the field emission performance of the graphene sheet-carbon nanotube film flexible composite material prepared in this embodiment, as shown in Fig. 5 is the structural representation of the device, the The device is a conventional field emission performance testing device. The vacuum in the test chamber was maintained at about 1×10 ^-7 Pa by a titanium ion pump. The graphene sheet-carbon nanotube film flexible composite material prepared in this example is glued on the copper sample stage with conductive adhesive as the cathode, and a stainless steel plate with a diameter of about 10 cm is used as the anode, and the distance between the cathode and the anode is 1 mm ; During the test, the 0-10kV adjustable positive bias load is placed on the anode, and the bias voltage increases at a constant speed (500V/min), and the cathode is grounded, and the test results are automatically recorded by the computer. It can be seen from Figure 6 that the open field and maximum field emission current density of the graphene sheet-carbon nanotube film flexible composite material prepared in this example are 2.33V/μm and 6.99mA/cm ² , which are far It is better than 4.29V/μm and 1.67mA/cm ² of the graphene sheet prepared on the silicon single wafer. The main reason for the enhanced field emission performance is that the carbon nanotube film has better conductivity than the silicon single wafer, and the uneven surface reduces the influence of the electric field shielding effect.

Field emitter assembly (conventional assembly method):

Adhere the prepared graphene sheet-carbon nanotube film flexible composite material with a conductive adhesive on a copper electrode with a thickness of 2 mm as the cathode, and the anode is a copper plate with a thickness of about 2 mm, and the thickness of the passage between the two electrodes is 200 microns The ring-shaped polytetrafluoroethylene film is isolated; during the field emission process, the positive bias is applied to the anode and the cathode is grounded to obtain stable field electron emission. The field emission current can be controlled by adjusting the anode bias.

Example 4

Heat treatment of carbon nanotube film in hydrogen atmosphere:

Cut the carbon nanotube film into 1cm×1cm pieces with a blade and place them on the graphite sample stage of a microwave plasma-enhanced chemical vapor deposition device (commercially available). Figure 3 is a schematic diagram of the reaction chamber of the device; Vacuum system, vacuumize the reaction chamber to about 1.0×10 ^-3 Pa, then inject 15sccm hydrogen (purity 5N), adjust the air pressure to 1.5kPa, heat the sample stage with a self-made graphite heater until the temperature is stable at 600°C, and continue Treat for 30 minutes to remove adsorbates and pollutants on the surface of the carbon nanotube film.

Graphene sheets prepared by microwave plasma enhanced chemical vapor deposition:

After heat-treating the carbon nanotube film in a hydrogen atmosphere, immediately raise the temperature of the substrate to 750°C, and adjust the air pressure to 1kPa. After the temperature and air pressure are stable, start the microwave source, set the microwave power to 250W, and immediately inject 1 sccm of acetylene gas (purity is 5N), and quickly adjust the air pressure to a stable 1kPa, that is, the growth of graphene sheets starts, and the growth time is 2 hours. The distribution density of the obtained graphene sheets is about 8 sheets/square micron, the width is 0.5-0.9 micron, and the number of layers is 1-5.

Field emission performance test:

A high vacuum field emission tester (commercially available) is used to test the field emission performance of the graphene sheet-carbon nanotube film flexible composite material prepared in this embodiment, as shown in Fig. 5 is the structural representation of the device, the The device is a conventional field emission performance testing device. The vacuum in the test chamber was maintained at about 1×10 ^-7 Pa by a titanium ion pump. The graphene sheet-carbon nanotube film flexible composite material prepared in this example is glued on the copper sample stage with conductive adhesive as the cathode, and a stainless steel plate with a diameter of about 10 cm is used as the anode, and the distance between the cathode and the anode is 1 mm ; During the test, the 0-10kV adjustable positive bias load is placed on the anode, and the bias voltage increases at a constant speed (500V/min), and the cathode is grounded, and the test results are automatically recorded by the computer. The open field and maximum field emission current density of the graphene sheet-carbon nanotube film flexible composite material prepared in this example are 3.38V/μm and 3.35mA/cm ² , which are far superior to those produced on silicon single wafers. 4.29 V/μm and 1.67 mA/cm ² for the prepared graphene sheet. The main reason for the enhanced field emission performance is that the carbon nanotube film has better conductivity than the silicon single wafer, and the uneven surface reduces the influence of the electric field shielding effect.

Field emitter assembly (conventional assembly method):

Adhere the prepared graphene sheet-carbon nanotube film flexible composite material with a conductive adhesive on a copper electrode with a thickness of 2 mm as the cathode, and the anode is a copper plate with a thickness of about 2 mm, and the thickness of the passage between the two electrodes is 200 microns The ring-shaped polytetrafluoroethylene film is isolated; during the field emission process, the positive bias is applied to the anode and the cathode is grounded to obtain stable field electron emission. The field emission current can be controlled by adjusting the anode bias.

Example 5

Heat treatment of carbon nanotube film in hydrogen atmosphere:

Cut the carbon nanotube film into 1cm×1cm pieces with a blade and place them on the graphite sample stage of a microwave plasma-enhanced chemical vapor deposition device (commercially available). Figure 3 is a schematic diagram of the reaction chamber of the device; Vacuum system, vacuumize the reaction chamber to about 1.0×10 ^-3 Pa, then inject 15sccm hydrogen (purity 5N), adjust the air pressure to 1.5kPa, heat the sample stage with a self-made graphite heater until the temperature is stable at 600°C, and continue Treat for 30 minutes to remove adsorbates and pollutants on the surface of the carbon nanotube film.

Graphene sheets prepared by microwave plasma enhanced chemical vapor deposition:

After heat-treating the carbon nanotube film in a hydrogen atmosphere, immediately raise the temperature of the substrate to 750°C, and adjust the air pressure to 1kPa. After the temperature and air pressure are stable, start the microwave source, set the microwave power to 250W, and immediately inject 3 sccm of acetylene gas (purity is 5N), and quickly adjust the air pressure to a stable 1kPa, that is, the growth of graphene sheets starts, and the growth time is 2 hours. The distribution density of the obtained graphene sheets is about 11 sheets/square micrometer, the width is 0.8-1.1 micrometers, and the number of layers is 1-8 layers.

Field emission performance test:

A high vacuum field emission tester (commercially available) is used to test the field emission performance of the graphene sheet-carbon nanotube film flexible composite material prepared in this embodiment, as shown in Fig. 5 is the structural representation of the device, the The device is a conventional field emission performance testing device. The vacuum in the test chamber was maintained at about 1×10 ^-7 Pa by a titanium ion pump. The graphene sheet-carbon nanotube film flexible composite material prepared in this example is glued on the copper sample stage with conductive adhesive as the cathode, and a stainless steel plate with a diameter of about 10 cm is used as the anode, and the distance between the cathode and the anode is 1 mm ; During the test, the 0-10kV adjustable positive bias load is placed on the anode, and the bias voltage increases at a constant speed (500V/min), and the cathode is grounded, and the test results are automatically recorded by the computer. The open field and maximum field emission current density of the graphene sheet-carbon nanotube film flexible composite material prepared in this example are 2.00V/μm and 6.16mA/cm ² , which are far superior to those produced on silicon single wafers. 4.29 V/μm and 1.67 mA/cm ² for the prepared graphene sheet. The main reason for the enhanced field emission performance is that the carbon nanotube film has better conductivity than the silicon single wafer, and the uneven surface reduces the influence of the electric field shielding effect.

Field emitter assembly (conventional assembly method):

Adhere the prepared graphene sheet-carbon nanotube film flexible composite material with a conductive adhesive on a copper electrode with a thickness of 2 mm as the cathode, and the anode is a copper plate with a thickness of about 2 mm, and the thickness of the passage between the two electrodes is 200 microns The ring-shaped polytetrafluoroethylene film is isolated; during the field emission process, the positive bias is applied to the anode and the cathode is grounded to obtain stable field electron emission. The field emission current can be controlled by adjusting the anode bias.

Example 6

Heat treatment of carbon nanotube film in hydrogen atmosphere:

Cut the carbon nanotube film into 1cm×1cm pieces with a blade and place them on the graphite sample stage of a microwave plasma-enhanced chemical vapor deposition device (commercially available). Figure 3 is a schematic diagram of the reaction chamber of the device; Vacuum system, vacuumize the reaction chamber to about 1.0×10 ^-3 Pa, then inject 15sccm hydrogen (purity 5N), adjust the air pressure to 1.5kPa, heat the sample stage with a self-made graphite heater until the temperature is stable at 600°C, and continue Treat for 30 minutes to remove adsorbates and pollutants on the surface of the carbon nanotube film.

Graphene sheets prepared by microwave plasma enhanced chemical vapor deposition:

After heat-treating the carbon nanotube film in a hydrogen atmosphere, immediately raise the temperature of the substrate to 750°C, and adjust the air pressure to 1kPa. After the temperature and air pressure are stable, start the microwave source, set the microwave power to 300W, and immediately inject 2 sccm of acetylene gas (purity is 5N), and quickly adjust the air pressure to a stable 1kPa, that is, the growth of graphene sheets starts, and the growth time is 2 hours. The distribution density of the obtained graphene sheets is about 10 sheets/square micron, the width is 0.6-1.0 micron, and the number of layers is 1-7.

Field emission performance test:

A high vacuum field emission tester (commercially available) is used to test the field emission performance of the graphene sheet-carbon nanotube film flexible composite material prepared in this embodiment, as shown in Fig. 5 is the structural representation of the device, the The device is a conventional field emission performance testing device. The vacuum in the test chamber was maintained at about 1×10 ^-7 Pa by a titanium ion pump. The graphene sheet-carbon nanotube film flexible composite material prepared in this example is glued on the copper sample stage with conductive adhesive as the cathode, and a stainless steel plate with a diameter of about 10 cm is used as the anode, and the distance between the cathode and the anode is 1 mm ; During the test, the 0-10kV adjustable positive bias load is placed on the anode, and the bias voltage increases at a constant speed (500V/min), and the cathode is grounded, and the test results are automatically recorded by the computer. The open field and maximum field emission current density of the graphene sheet-carbon nanotube film flexible composite material prepared in this example are 2.97V/μm and 3.74mA/cm ² , which are far superior to those produced on silicon single wafers. 4.29 V/μm and 1.67 mA/cm ² for the prepared graphene sheet. The main reason for the enhanced field emission performance is that the carbon nanotube film has better conductivity than the silicon single wafer, and the uneven surface reduces the influence of the electric field shielding effect.

Field emitter assembly (conventional assembly method):

Adhere the prepared graphene sheet-carbon nanotube film flexible composite material with a conductive adhesive on a copper electrode with a thickness of 2 mm as the cathode, and the anode is a copper plate with a thickness of about 2 mm, and the thickness of the passage between the two electrodes is 200 microns The ring-shaped polytetrafluoroethylene film is isolated; during the field emission process, the positive bias is applied to the anode and the cathode is grounded to obtain stable field electron emission. The field emission current can be controlled by adjusting the anode bias.

Example 7

Heat treatment of carbon nanotube film in hydrogen atmosphere:

Cut the carbon nanotube film into 1cm×1cm pieces with a blade and place them on the graphite sample stage of a microwave plasma-enhanced chemical vapor deposition device (commercially available). Figure 3 is a schematic diagram of the reaction chamber of the device; Vacuum system, vacuumize the reaction chamber to about 1.0×10 ^-3 Pa, then inject 15sccm hydrogen (purity 5N), adjust the air pressure to 1.5kPa, heat the sample stage with a self-made graphite heater until the temperature is stable at 600°C, and continue Treat for 30 minutes to remove adsorbates and pollutants on the surface of the carbon nanotube film.

Graphene sheets prepared by microwave plasma enhanced chemical vapor deposition:

After heat-treating the carbon nanotube film in a hydrogen atmosphere, immediately raise the temperature of the substrate to 750°C, and adjust the air pressure to 1kPa. After the temperature and air pressure are stable, start the microwave source, set the microwave power to 300W, and immediately inject 3 sccm of acetylene gas (purity is 5N), and quickly adjust the air pressure to a stable 1kPa, that is, the growth of graphene sheets starts, and the growth time is 2 hours. The distribution density of the obtained graphene sheets is about 9 sheets/square micron, the width is 0.7-1.0 micron, and the number of layers is 1-8.

Field emission performance test:

A high vacuum field emission tester (commercially available) is used to test the field emission performance of the graphene sheet-carbon nanotube film flexible composite material prepared in this embodiment, as shown in Fig. 5 is the structural representation of the device, the The device is a conventional field emission performance testing device. The vacuum in the test chamber was maintained at about 1×10 ^-7 Pa by a titanium ion pump. The graphene sheet-carbon nanotube film flexible composite material prepared in this example is glued on the copper sample stage with conductive adhesive as the cathode, and a stainless steel plate with a diameter of about 10 cm is used as the anode, and the distance between the cathode and the anode is 1 mm ; During the test, the 0-10kV adjustable positive bias load is placed on the anode, and the bias voltage increases at a constant speed (500V/min), and the cathode is grounded, and the test results are automatically recorded by the computer. The open field and maximum field emission current density of the graphene sheet-carbon nanotube film flexible composite material prepared in this example are 2.27V/μm and 5.65mA/cm ² , which are far superior to those produced on silicon single wafers. 4.29 V/μm and 1.67 mA/cm ² for the prepared graphene sheet. The main reason for the enhanced field emission performance is that the carbon nanotube film has better conductivity than the silicon single wafer, and the uneven surface reduces the influence of the electric field shielding effect.

Field emitter assembly (conventional assembly method):

Adhere the prepared graphene sheet-carbon nanotube film flexible composite material with a conductive adhesive on a copper electrode with a thickness of 2 mm as the cathode, and the anode is a copper plate with a thickness of about 2 mm, and the thickness of the passage between the two electrodes is 200 microns The ring-shaped polytetrafluoroethylene film is isolated; during the field emission process, the positive bias is applied to the anode and the cathode is grounded to obtain stable field electron emission. The field emission current can be controlled by adjusting the anode bias.

Finally, it should be noted that the above only exemplifies typical embodiments of the present invention. But obviously the present invention is not limited to above-mentioned embodiment, also has many other experimental parameter combination methods, the related situation that those of ordinary skill in this research field can directly derive or associate from the disclosed content of the present invention, all should be considered as protection scope of the present invention.

Claims (4)

1. A graphene sheet-carbon nanotube film flexible composite material is characterized in that it is made up of graphene sheets with 1-10 layers of deposited edge layers on the carbon nanotube film; wherein graphite is deposited on the carbon nanotube film The distribution density of the olefin sheets is 8-12 pieces/square micrometer, and the width of the graphene sheets is 0.5-1.2 micrometers. 2. Graphene sheet-carbon nanotube film flexible composite material described in claim 1 is used for preparing vacuum field electron emission device. 3. the preparation method of graphene sheet-carbon nanotube membrane flexible composite material described in claim 1 is characterized in that carrying out as follows: (1) Put the commercially available carbon nanotube film on the graphite sample stage of the microwave plasma enhanced chemical vapor deposition device, feed 15sccm high-purity hydrogen (5N), adjust the air pressure to 1.5kPa, and carry the carbon nanotube film The sample stage is heated to a stable temperature of 600°C, and the carbon nanotube film is heat-treated for 30 minutes; (2) On the basis of step (1), increase the temperature of the sample stage to a stable temperature of 750°C, and adjust the air pressure to 1kPa; (3) Start the microwave source on the basis of step (2), adjust the microwave power to 200-300W, and feed 1-3sccm high-purity acetylene gas (5N), quickly adjust the pressure of the reaction chamber to 1kPa, and start the graphene sheet Deposition, the deposition time is 2 hours, the distribution density of the deposited graphene sheets is 8-12 sheets/square micron, and the width of the graphene sheets is 0.5-1.2 microns. 4. the preparation method of graphene sheet-carbon nanotube film flexible composite material described in claim 3, wherein the method for preparing graphene sheet is microwave plasma enhanced chemical vapor deposition, radio frequency sputter deposition or radio frequency plasma enhanced chemical vapor phase deposition.