CN102674321B - Graphene foam with three dimensional fully connected network and macroscopic quantity preparation method thereof - Google Patents

Abstract

The invention relates to a graphene-based new material and its chemical vapor deposition preparation technology, specifically a graphene foam with a three-dimensional fully connected network and a macro-scale preparation method thereof, which is suitable for mass production of high-quality graphene foam. The three-dimensional interconnected graphene is grown on the surface of three-dimensional porous metal by catalytic cracking of carbon source gas by chemical vapor deposition technology, and the porous foam-like three-dimensional graphene macroscopic body can be obtained after subsequent dissolution of the porous metal substrate. The invention prepares a three-dimensional continuous graphene macrobody by a simple template replication method, and has the characteristics of simple operation, high yield and easy structure regulation. Graphene foam is a fully connected network in a seamless connection, with low density, high porosity, high specific surface area, excellent charge conduction and heat conduction capabilities. It lays the foundation for applications in fields such as electromagnetic shielding, microwave absorption, catalysis, sensing and energy storage materials.

Description

A graphene foam with a three-dimensional fully connected network and its macro-preparation method

Technical field:

The present invention relates to a graphene-based new material and its chemical vapor deposition (CVD) preparation technology, specifically a graphene foam with a three-dimensional fully connected network and its macro-preparation method, which is suitable for mass production of high-quality graphene macro-body .

Background technique:

Graphene is a two-dimensional honeycomb crystal structure formed by densely packing a single layer of carbon atoms, and is the basic structural unit for constructing other dimensional carbon materials (zero-dimensional fullerene, one-dimensional carbon nanotubes, and three-dimensional graphite). The unique crystal structure of graphene makes it have excellent electrical, thermal and mechanical properties, such as its electron mobility up to 200,000cm ² /V·s at room temperature, and its thermal conductivity up to 5300W/m·k. Electronic devices, transparent conductive films, composite materials, catalytic materials, energy storage materials, field emission materials, gas sensors and gas storage and other fields have been widely used. In order to make comprehensive use of the many excellent properties of graphene, the mass preparation of high-quality graphene and the assembly of single-sheet graphene into multifunctional macroscopic bulk materials will become crucial. Since 2004, when the research group of the University of Manchester used the tape stripping method (or micromechanical stripping method) to separate and obtain stable graphene for the first time, many methods for preparing graphene have been developed, including SiC substrate surface epitaxial growth method, chemical Oxidation stripping method, high energy ultrasonic solution stripping method and chemical vapor deposition method. Due to the relatively simple preparation process and large output, graphene prepared by chemical oxidation exfoliation has been widely used in composite materials and assembled into various two-dimensional macroscopic structures, such as super strong graphene paper materials, flexible transparent conductive graphene films, etc. However, these composite materials and macrostructures have poor electrical properties. On the one hand, the graphite raw materials are strongly oxidized and peeled off during the chemical exfoliation process, and the obtained graphene has a large number of structural defects and poor electrical conductivity. On the other hand, it is due to Graphene prepared by chemical exfoliation has a small size, and there is a large contact resistance between sheets when assembled into a macroscopic structure. Recently, people have developed a CVD method to successfully prepare large-area high-quality graphene transparent conductive films, which show better transparent conductive properties than films prepared by chemical exfoliation of graphene. However, the current CVD method uses planar metals such as metal foil as the growth substrate, and the yield of graphene prepared is low, and only two-dimensional planar graphene films can be obtained, which can only meet the needs of graphene in the fields of electronic devices and transparent conductive films. Applications.

Three-dimensional objects are the most common form of existence and application of materials in human life. In addition to two-dimensional films, porous materials such as foams and sponges with three-dimensional network structures are another important macroscopic body, which can combine the high electrical conductivity, thermal conductivity, high strength, low density, and high gas permeability of materials. Physical and chemical properties. Wood, cork, sponge, coral, and bone are common macroscopic materials with network structure in nature. The development of modern science and technology has made polymers, metals, ceramics, glass, etc. Every aspect of human life has gained practical application. Compared with two-dimensional graphene films, three-dimensional graphene network materials have extremely low density and high porosity. In addition to making full use of graphene's excellent electrical, thermal, and mechanical properties, it can also take advantage of its large specific surface area. . Therefore, the development of a graphene foam with a three-dimensional network structure and its macro-scale preparation method can expand the physical properties and application space of graphene, which will greatly promote the use of graphene in electrical conduction, heat conduction composite materials, thermal management materials, electromagnetic shielding, Applications in the fields of microwave absorption, catalysis, sensing and energy storage materials have a huge industrial application background and broad market prospects.

Invention content:

The purpose of the present invention is to provide a graphene foam with a three-dimensional fully connected network and its macro-preparation method, give full play to the excellent performance of graphene and expand the application of graphene, and solve the problem of low graphene output in the prior art , and can only obtain two-dimensional planar graphene films and other problems, it has the characteristics of simple operation, low cost, high yield and easy structure regulation.

Technical scheme of the present invention is:

A graphene foam with a three-dimensional fully connected network and its macro-scale preparation method. The method adopts CVD technology to catalytically crack carbon source gas on the surface of a three-dimensional porous metal template to grow three-dimensional connected graphene, which can be obtained after subsequent dissolution of the metal porous substrate. A porous foam-like three-dimensional fully connected graphene macrobody is obtained. Specific steps are as follows:

(1) Chemical vapor deposition growth of graphene: using porous metal as a template, a layer of graphene film is grown on the surface of foamed metal by chemical vapor deposition, with an average thickness of 0.34-5nm;

(2) Coating of polymer protective layer: evenly coat a layer of polymer on the surface of the grown graphene to prevent the graphene network from being damaged in subsequent processing;

(3) Dissolving of the foamed metal template: dissolve and remove the porous metal template skeleton with a solution of porous metals such as acid or ferric chloride;

(4) Removal of the polymer protective layer: dissolve and remove the polymer protective layer covering the surface of the graphene network with an organic solvent.

In the present invention, the porous metal template used is foamed nickel, foamed copper, foamed iron or foamed cobalt, etc., and its pore size distribution is 50-200PPI, preferably 90-120PPI; surface density is 50-1000g/m ² , preferably The range is 250-400 g/m ² .

In the present invention, the porous metal template used can be put into the reaction zone by curling, so as to realize the macro preparation of large-area three-dimensional fully connected graphene network.

In the present invention, the CVD cracking carbon source used is one or more of hydrocarbon methane, ethane, ethylene, acetylene, benzene, toluene, cyclohexane and ethanol, methanol, acetone, carbon monoxide, and the carbon source flow rate 1-100 ml/min, preferably in the range of 2-20 ml/min. The carrier gas is hydrogen or a mixture of hydrogen and inert gas, wherein the volume ratio of hydrogen is ≥ 1/10, and the total flow rate of the carrier gas is 1-5000 ml/min, preferably in the range of 100-1000 ml/min.

In the present invention, the number of graphene layers can be controlled by the carbon source concentration.

In the present invention, the CVD growth temperature is 500-1100°C, preferably in the range of 700-1000°C; the growth time is 1-60 minutes, preferably in the range of 2-15 minutes; the cooling rate after the reaction is 10-600°C/min, The preferred range is 50-200°C/min.

In the present invention, one or more polymers are used to consolidate and protect the graphene network to prevent the graphene network from being damaged during the process of dissolving the porous metal skeleton. These polymers are one or more of polymethyl methacrylate, polyethylene, polystyrene and polypropylene.

In the present invention, the solution for removing foam metal is one or more of sulfuric acid, hydrochloric acid, nitric acid, and ferric chloride aqueous solution, with a concentration of 0.1-5mol/L, preferably in the range of 0.5-3mol/L; the dissolution reaction temperature is at 0-100°C, preferably in the range of 20-80°C.

In the present invention, an organic solvent is used to remove the polymer protective layer, and the organic solvent used is acetone, ethyl lactate, ethylene dichloride, trichloroethylene, chloroform and other ketones, chlorinated hydrocarbons, halogenated hydrocarbons, aromatic hydrocarbons One or more than two reagents. The dissolution temperature is in the range of 0-200°C, preferably in the range of 25-100°C.

The graphene foam obtained in the present invention is a three-dimensional fully connected network structure formed by graphene in a seamless connection, with a density of 0.1mg/cm ³ -100mg/cm ³ , a porosity of 60%-99.9%, and a specific surface area of 130 -2600m ² /g, conductivity 0.5S/cm-1000S/cm.

The beneficial effects of the present invention are:

1. The present invention proposes a new graphene material-graphene foam with a three-dimensional fully connected network and a simple CVD template method to realize the macro-preparation of graphene foam.

2. The graphene in the graphene foam obtained by the present invention constitutes a fully connected network in a seamlessly connected manner, so that the graphene foam macroscopic body has low density, high porosity, high specific surface area, excellent The ability of charge conduction and heat conduction has laid the foundation for the application of graphene in the fields of electrical conduction, heat conduction composite materials, thermal management materials, electromagnetic shielding, wave absorption, catalysis, sensing and energy storage materials.

3. The present invention has the characteristics of simple operation, low cost and easy structure regulation, and is expected to produce high-quality graphene foam on a large scale.

4. The density of the three-dimensional fully connected graphene foam obtained by the present invention can be as low as 0.1 mg/cm ³ , the porosity can be as high as 99.9%, the specific surface area can be as high as 2600 m ² /g, and the electrical conductivity can be as high as 1000 S/cm or more.

Description of drawings:

Figure 1 is a schematic diagram of the experimental device for growing graphene foam by CVD method. In the figure, 1 gas inlet; 2 porous metal; 3 thermocouple; 4 gas outlet.

Figure 2 is a scanning electron micrograph of nickel foam coated with graphene on the surface after CVD growth; wherein, (a) is a low-magnification scanning electron micrograph; (b-d) is a high-magnification scanning electron micrograph.

Figure 3 is a characterization of a graphene foam with a three-dimensional fully connected network. Wherein, (a) is the optical photograph of graphene foam; (b) is the scanning electron microscope photograph of graphene foam; (c) is the low power transmission electron microscope photograph of graphene foam; (d) is the high power transmission electron microscope of graphene foam Photo; (e) is the resonance laser Raman spectrum of graphene foam.

Figure 4 shows the variation trend of the average number of layers of graphene grown by CVD with the concentration of methane. The larger the concentration of methane used, the thicker the number of graphene layers obtained.

Fig. 5 (a)-(b) is the influence of the change of graphene average number of layers on the thickness, quality, density and specific surface area of graphene foam; Wherein, Fig. 5 (a) figure is thickness, quality and graphene average layer Number relationship curve; Fig. 5 (b) figure is density, specific surface area and graphene average layer number relationship curve.

Detailed ways:

The present invention is further described in detail below by way of examples and accompanying drawings.

Example 1

At first, as shown in Figure 1, the present invention adopts horizontal type reaction furnace to grow graphene, and the two ends of horizontal type reaction furnace are respectively provided with gas inlet 1 and gas outlet 4, and foamed nickel 2 is placed in the high temperature zone of horizontal type reaction furnace, and thermocouple 3 Located in the high temperature zone of the horizontal reactor to monitor the reaction temperature in real time. Place nickel foam (70 mm x 300 mm x 1.2 mm, with a pore size distribution of about 110PPI and a surface density of about 300g/m ² ) in the central area of a horizontal reactor (tube diameter 75 mm, reaction zone length 300 mm) (reaction zone, there is a thermocouple at this position to monitor the furnace temperature in real time); heated to 1000°C in an atmosphere of hydrogen and argon (during the heating process, the flow rates of hydrogen and argon were 200 and 500 ml/min respectively, and the temperature rise rate was 33 °C/min), heat treatment for 10 minutes after the furnace temperature rises to 1000 °C; after the heat treatment is completed, a mixed gas of methane, hydrogen and argon is introduced (gas flow rates are respectively 5 ml/min of methane, 200 ml/min of hydrogen and 200 ml/min of argon) 500 ml/min), start to grow graphene, the growth time is 5 minutes, after the growth is finished, it is cooled rapidly with the speed of 100 ℃ of minutes, to obtain the nickel foam whose surface is coated with graphene, and the average thickness of the graphene film is about 1.7nm.

Then, the ethyl lactate solution of polymethyl methacrylate (PMMA) (polymethyl methacrylate accounts for 4wt%) is added dropwise to the nickel foam surface that surface is coated with graphene, bakes 30 minutes at 180 ℃ of temperature Then put it into 3mol/L hydrochloric acid solution, and react at 80°C for 3 hours to dissolve the foamed nickel template. PMMA was dissolved and removed with acetone at a temperature of 55 °C, and finally a graphene foam with a three-dimensional interconnected network was obtained.

Scanning electron microscopy, transmission electron microscopy and resonance laser Raman spectroscopy observations show that the obtained graphene foam completely replicates the shape and structure of the metal foam template, with a size of 70 mm × 300 mm × 0.2 mm, and the graphene structure is continuous and complete without damage , with high quality, the average number of layers is about 5 layers, the density of graphene foam is about 5mg/cm ³ , the porosity is about 99.7%, the specific surface area is about 520m ² /g, and the electrical conductivity is about 10S/cm.

Example 2

At first, as shown in Figure 1, the present invention adopts horizontal type reaction furnace to grow graphene, and the two ends of horizontal type reaction furnace are respectively provided with gas inlet 1 and gas outlet 4, and foamed nickel 2 is placed in the high temperature zone of horizontal type reaction furnace, and thermocouple 3 Located in the high temperature zone of the horizontal reactor to monitor the reaction temperature in real time. Place nickel foam (70 mm x 300 mm x 1.2 mm, with a pore size distribution of about 110PPI and a surface density of about 300g/m ² ) in the central area of a horizontal reactor (tube diameter 75 mm, reaction zone length 300 mm) (reaction zone, there is a thermocouple at this position to monitor the furnace temperature in real time); heated to 1000°C in an atmosphere of hydrogen and argon (during the heating process, the flow rates of hydrogen and argon were 200 and 500 ml/min respectively, and the temperature rise rate was 33 °C/min), heat treatment for 10 minutes after the furnace temperature rises to 1000 °C; after the heat treatment is completed, a mixed gas of methane, hydrogen and argon is introduced (gas flow rates are respectively 2 ml/min of methane, 200 ml/min of hydrogen and 200 ml/min of argon) 500 milliliters/minute), start to grow graphene, growth time is 5 minutes, grows and cools rapidly with the speed of 100 ℃/minute after the end, obtains the nickel foam of surface coating graphene, and the average thickness of graphene film is about 1nm.

Then, the ethyl lactate solution of polymethyl methacrylate (PMMA) (polymethyl methacrylate accounts for 4wt%) is added dropwise to the nickel foam surface that surface is coated with graphene, bakes 30 minutes at 180 ℃ of temperature Then put it into 3mol/L hydrochloric acid solution, and react at 80°C for 3 hours to dissolve the foamed nickel template. PMMA was dissolved and removed with acetone at a temperature of 55 °C, and finally a graphene foam with a three-dimensional interconnected network was obtained.

Scanning electron microscopy, transmission electron microscopy and resonance laser Raman spectroscopy observations show that the obtained graphene foam completely replicates the shape and structure of the metal foam template, with a size of 70 mm × 300 mm × 0.1 mm, and the graphene structure is continuous and complete without damage , with high quality, the average number of layers is about 3 layers, the density of graphene foam is about 6mg/cm ³ , the porosity is about 99.6%, the specific surface area is about 850m ² /g, and the electrical conductivity is about 7S/cm.

Example 3

At first, as shown in Figure 1, the present invention adopts horizontal type reaction furnace to grow graphene, and the two ends of horizontal type reaction furnace are respectively provided with gas inlet 1 and gas outlet 4, and foamed nickel 2 is placed in the high temperature zone of horizontal type reaction furnace, and thermocouple 3. Located in the high temperature zone of the horizontal reactor to monitor the reaction temperature in real time. Place nickel foam (70 mm x 300 mm x 1.2 mm, with a pore size distribution of about 110PPI and a surface density of about 300g/m ² ) in the central area of a horizontal reactor (tube diameter 75 mm, reaction zone length 300 mm) (reaction zone, there is thermocouple real-time monitoring furnace temperature at this position); Heating to 900 ℃ in the atmosphere of hydrogen and argon (hydrogen and argon flow rate are respectively 200 and 500 milliliters/minute in the heating process, and the heating rate is 33 °C/min), heat treatment for 10 minutes after the furnace temperature rises to 900 °C; after the heat treatment is completed, a mixed gas of methane, hydrogen and argon is introduced (gas flow rates are respectively 5 ml/min of methane, 200 ml/min of hydrogen and 200 ml/min of argon) 500 ml/min), start to grow graphene, and the growth time is 5 minutes. After the growth, it is cooled rapidly at a speed of 100 ° C/min to obtain the nickel foam with graphene on the surface. The average thickness of the graphene film is about 1.7nm .

Then, the ethyl lactate solution of polymethyl methacrylate (PMMA) (polymethyl methacrylate accounts for 4wt%) is added dropwise to the nickel foam surface that surface is coated with graphene, bakes 30 minutes at 180 ℃ of temperature Then put it into 3mol/L hydrochloric acid solution, and react at 80°C for 3 hours to dissolve the foamed nickel template. PMMA was dissolved and removed with acetone at a temperature of 55 °C, and finally a graphene foam with a three-dimensional interconnected network was obtained.

Scanning electron microscopy, transmission electron microscopy and resonance laser Raman spectroscopy observations show that the obtained graphene foam completely replicates the shape and structure of the metal foam template, with a size of 70 mm × 300 mm × 0.2 mm, and the graphene structure is continuous and complete without damage , with high quality, the average number of layers is about 5 layers. The graphene foam has a density of about 5 mg/cm ³ , a porosity of about 99.7%, a specific surface area of about 520 m ² /g, and an electrical conductivity of about 8 S/cm.

Example 4

At first, as shown in Figure 1, the present invention adopts horizontal type reaction furnace to grow graphene, and horizontal type reaction furnace two ends are respectively provided with gas inlet 1 and gas outlet 4, foam copper 2 is placed in the high temperature zone of horizontal type reaction furnace, thermocouple 3. Located in the high temperature zone of the horizontal reactor to monitor the reaction temperature in real time. Place copper foam (70 mm x 300 mm x 1.2 mm, with a pore size distribution of about 110PPI and a surface density of about 300g/m ² ) in the central area of a horizontal reactor (tube diameter 75 mm, reaction zone length 300 mm) (reaction zone, there is a thermocouple at this position to monitor the furnace temperature in real time); heated to 1000°C in an atmosphere of hydrogen and argon (during the heating process, the flow rates of hydrogen and argon were 200 and 500 ml/min respectively, and the temperature rise rate was 33 °C/min), heat treatment for 10 minutes after the furnace temperature rises to 1000 °C; after the heat treatment is completed, a mixed gas of methane, hydrogen and argon is introduced (gas flow rates are respectively 5 ml/min of methane, 200 ml/min of hydrogen and 200 ml/min of argon) 500 milliliters/minute), start to grow graphene, growth time is 10 minutes, grows and cools rapidly with the speed of 100 ℃ of minutes after the end, obtains the nickel foam of surface coating graphene, and the average thickness of graphene film is about 0.34nm.

Then, the ethyl lactate solution of polymethyl methacrylate (PMMA) (polymethyl methacrylate accounts for 4wt%) is added dropwise to the copper foam surface that the surface is coated with graphene, bakes 30 minutes at 180 ℃ of temperature Then put it into the mixed solution of ferric chloride and hydrochloric acid (concentrations of ferric chloride and hydrochloric acid are both 1mol/L), and react at 80° C. for 3 hours to dissolve the foamed copper template. PMMA was dissolved and removed with acetone at a temperature of 55 °C, and finally a graphene foam with a three-dimensional interconnected network was obtained.

Scanning electron microscopy, transmission electron microscopy and resonance laser Raman spectroscopy observations show that the obtained graphene foam completely replicates the shape and structure of the metal foam template, with a size of 70 mm × 300 mm × 0.05 mm, and the graphene structure is continuous and complete without damage , with high quality, the average number of layers is about 1 layer, the density of graphene foam is about 4mg/cm ³ , the porosity is about 99.8%, the specific surface area is about 2600m ² /g, and the electrical conductivity is about 5S/cm.

Example 5

At first, as shown in Figure 1, the present invention adopts horizontal type reaction furnace to grow graphene, and the two ends of horizontal type reaction furnace are respectively provided with gas inlet 1 and gas outlet 4, and foamed nickel 2 is placed in the high temperature zone of horizontal type reaction furnace, and thermocouple 3 Located in the high temperature zone of the horizontal reactor to monitor the reaction temperature in real time. Place nickel foam (1000mm×300mm×1.2mm, pore size distribution about 110PPI, surface density about 300g/m ² ) in the center of a horizontal reactor (tube diameter 75mm, reaction zone length 300mm) Area (reaction zone, there is thermocouple real-time monitoring furnace temperature at this position); Heating to 1000 ℃ in the atmosphere of hydrogen and argon (hydrogen and argon flow rate are respectively 200 and 500 milliliters/minute in the heating process, and the heating rate is 33°C/min), heat treatment for 10 minutes after the furnace temperature rises to 1000°C; after the heat treatment is completed, a mixed gas of methane, hydrogen and argon is introduced (the gas flow rates are respectively 5 ml/min of methane, 200 ml/min of hydrogen and 200 ml/min of argon gas 500 ml/min), start to grow graphene, the growth time is 5 minutes, after the growth is finished, it is cooled rapidly at a speed of 100 ℃ minutes, and the nickel foam whose surface is coated with graphene is obtained, and the average thickness of the graphene film is about 1.7 nm.

Then, the ethyl lactate solution of polymethyl methacrylate (PMMA) (polymethyl methacrylate accounts for 4wt%) is added dropwise to the nickel foam surface that surface is coated with graphene, bakes 30 minutes at 180 ℃ of temperature Then put it into 3mol/L hydrochloric acid solution, and react at 80°C for 3 hours to dissolve the foamed nickel template. PMMA was dissolved and removed with acetone at a temperature of 55 °C, and finally a graphene foam with a three-dimensional interconnected network was obtained.

Scanning electron microscopy, transmission electron microscopy and resonance laser Raman spectroscopy observations show that the obtained graphene foam completely replicates the shape and structure of the metal foam template, with a size of 1000 mm × 300 mm × 0.2 mm, and the graphene structure is continuous and complete without damage , with high quality, the average number of layers is about 5 layers, the density of graphene foam is about 5mg/cm ³ , the porosity is about 99.7%, the specific surface area is about 520m ² /g, and the electrical conductivity is about 10S/cm.

Example 6

At first, as shown in Figure 1, the present invention adopts horizontal type reaction furnace to grow graphene, and the two ends of horizontal type reaction furnace are respectively provided with gas inlet 1 and gas outlet 4, and foamed nickel 2 is placed in the high temperature zone of horizontal type reaction furnace, and thermocouple 3 Located in the high temperature zone of the horizontal reactor to monitor the reaction temperature in real time. Place nickel foam (70 mm x 300 mm x 1.2 mm, with a pore size distribution of about 110PPI and a surface density of about 300g/m ² ) in the central area of a horizontal reactor (tube diameter 75 mm, reaction zone length 300 mm) (reaction zone, there is a thermocouple at this position to monitor the furnace temperature in real time); heated to 10000°C in an atmosphere of hydrogen and argon (during the heating process, the flow rates of hydrogen and argon were 200 and 500 ml/min respectively, and the heating rate was 33 °C/min), heat treatment for 10 minutes after the furnace temperature rises to 1000 °C; after heat treatment is completed, ethanol is brought in by argon bubbling (wherein, the flow rate of argon is 50 ml/min, and the ethanol is placed at a constant temperature at 0 °C In the Montess washing bottle), feed hydrogen simultaneously as buffer gas (gas flow rate is 200 milliliters/minute), start to grow graphene, growth time is 5 minutes, grows and cools rapidly with the speed of 100 ℃/minute after the end, obtains Nickel foam coated with graphene on the surface, the average thickness of the graphene film is about 1.7nm.

Then, the ethyl lactate solution of polymethyl methacrylate (PMMA) (polymethyl methacrylate accounts for 4wt%) is added dropwise to the nickel foam surface that surface is coated with graphene, bakes 30 minutes at 180 ℃ of temperature Then put it into 3mol/L hydrochloric acid solution, and react at 80°C for 3 hours to dissolve the foamed nickel template. PMMA was dissolved and removed with acetone at a temperature of 55 °C, and finally a graphene foam with a three-dimensional interconnected network was obtained.

Scanning electron microscopy, transmission electron microscopy and resonance laser Raman spectroscopy observations show that the obtained graphene foam completely replicates the shape and structure of the metal foam template, with a size of 70 mm × 300 mm × 0.2 mm, and the graphene structure is continuous and complete without damage , with high quality, the average number of layers is about 5 layers, the density of graphene foam is about 5mg/cm ³ , the porosity is about 99.7%, the specific surface area is about 520m ² /g, and the electrical conductivity is about 10S/cm.

As shown in Figure 1, there are four mass flow meters at one end of the gas inlet 1 in the figure, which can selectively control the introduction of gases such as argon, helium, hydrogen, methane, ethane or carbon monoxide. Liquid carbon sources (such as ethanol, methanol, benzene, toluene, or cyclohexane, etc.) are placed in a Montessori bottle at 0°C, and brought in by bubbling argon or a mixture of argon and helium.

As shown in Figure 2, it can be seen from the scanning electron microscope photos of nickel foam coated with graphene on the surface after CVD growth that the surface of nickel foam is evenly coated with a layer of graphene film after CVD reaction, and this layer of graphene film is uniform and continuous No damage.

As shown in Figure 3, it can be seen from the characterization of graphene foam that the size of the graphene foam obtained by this method can reach 170×220mm ² . The scanning electron microscope photos show that the network in the graphene foam is uniform and continuous without damage. The transmission electron microscope photos show The number of graphene layers includes single layer and few layers, and the resonance laser Raman spectrum shows that graphene has very high quality (D mode intensity is almost zero).

As shown in Figure 4, it can be seen from the variation trend of the average layer number of graphene grown by CVD with the methane concentration that the average layer number of graphene can be controlled by adjusting the methane concentration of the CVD reaction.

As shown in Figure 5, it can be seen from the influence of the change of the average number of layers of graphene on the thickness, quality, density and specific surface area of graphene foam that adopting this method gained graphene foam has extremely low density (as low as 3mg/ cm ³ ) and extremely high specific surface area (up to 850m ² /g).

The above results show that the present invention realizes a new graphene material --- the macro-preparation of graphene foam with a three-dimensional fully connected network with a simple method of CVD template replication, which is easy to operate, low in cost and easy to use. Features of structural regulation. In such a three-dimensional macroscopic body, graphene constitutes a fully connected network in a seamless manner, so that the graphene foam macroscopic body has low density, high porosity, high specific surface area, excellent charge conduction and Thermal conductivity lays the foundation for the application of graphene in the fields of electrical conduction, heat conduction composite materials, thermal management materials, electromagnetic shielding, wave absorption, catalysis, sensing and energy storage materials.

Claims (7)

1. A macro-preparation method of a graphene foam with a three-dimensional fully connected network, characterized in that: the graphene foam forms a three-dimensional fully connected network structure for graphene in a seamlessly connected manner, and the density is ^0.1mg /cm -100mg/cm ³ , porosity 60%-99.9%, specific surface area 130-2600m ² /g, electrical conductivity 0.5S/cm-1000S/cm; the graphene foam with three-dimensional fully connected network The preparation method is as follows: use chemical vapor deposition technology to catalytically crack carbon source gas on the surface of a three-dimensional porous metal template, grow three-dimensional connected graphene, and evenly coat a layer of high molecular polymer on the surface of the grown graphene to prevent graphene from The network is destroyed in the subsequent processing; after the metal porous substrate is subsequently dissolved, the polymer protective layer covering the surface of the graphene network is dissolved and removed with an organic solvent to obtain a graphene foam with a three-dimensional fully connected network; The macro-preparation method of the graphene foam with three-dimensional fully connected network, the specific steps are as follows: (1) Chemical vapor deposition growth of graphene: using porous metal as a template, a layer of graphene film is grown on the surface of foamed metal by chemical vapor deposition; (2) coating of high molecular polymer protective layer: evenly coat one deck high molecular polymer on the graphene surface of growing, to prevent that graphene network from being destroyed in follow-up processing; Described high molecular polymer is poly One or more of methyl methacrylate, polyethylene, polystyrene and polypropylene; (3) Dissolution of the foamed metal template: dissolve and remove the porous metal template skeleton with a porous metal solution; (4) Removal of the polymer protective layer: dissolve and remove the polymer protective layer covering the surface of the graphene network with an organic solvent. 2. according to the macro preparation method of the graphene foam with three-dimensional fully connected network according to claim 1, it is characterized in that, the porous metal template that adopts is foamed nickel, foamed copper, foamed iron or foamed cobalt, and its aperture is distributed in 50-200PPI, surface density 50-1000g/m ² . 3. according to the macro preparation method of the graphene foam with three-dimensional fully connected network according to claim 1, it is characterized in that, in chemical vapor deposition reaction process, carbon source is hydrocarbon methane, ethane, ethylene, acetylene, One or more of benzene, toluene, cyclohexane, ethanol, methanol, acetone, and carbon monoxide, and the carbon source flow rate is 1-100 ml/min. 4. according to the macro-preparation method of the graphene foam with three-dimensional fully connected network according to claim 1, it is characterized in that, in chemical vapor deposition reaction process, carrier gas is hydrogen or is the mixed gas of hydrogen and inert gas, wherein The hydrogen volume ratio is ≥1/10, and the total flow rate of the carrier gas is 1-2000 ml/min. 5. according to the macro-preparation method of the graphene foam with three-dimensional fully connected network according to claim 1, it is characterized in that, chemical vapor deposition growth graphene temperature is 500-1100 ℃, and growth time is 1-60 minute, reaction After finishing, the cooling rate is 5-600°C/min. 6. according to the macro-preparation method of the graphene foam with three-dimensional fully connected network according to claim 1, it is characterized in that the solution of porous metal is one or both of sulfuric acid, hydrochloric acid, nitric acid, ferric chloride aqueous solution Above, the concentration is 0.1-5mol/L, and the dissolution reaction temperature is 0-100°C. 7. according to the macro-preparation method of the graphene foam with three-dimensional fully connected network according to claim 1, it is characterized in that, after removing porous metal skeleton, remove polymer protective layer with organic solvent, the organic solvent that adopts is One or more of ketones, chlorinated hydrocarbons, halogenated hydrocarbons, and aromatic hydrocarbons, the dissolution temperature is 0-200°C.