Graphene and preparation method and preparation device thereof

Abstract

The invention belongs to the technical field of graphene, and provides graphene and a preparation method and device thereof.The preparation method comprises the steps that first graphene and process airflow are mixed in a reaction chamber to form a continuously rotating first airflow mixture, and the process airflow comprises carbon source gas and plasma source gas; and then carrying out plasma enhanced growth reaction on the first airflow mixture to enable the first graphene to grow into second graphene with increased transverse width. The large-size graphene is prepared by taking the small-size graphene as a seed, the problems of high cost, pollution and the like of a traditional preparation method of the large-size graphene are solved, a plasma enhanced growth reaction is carried out in a continuous rotating airflow mode, the dispersity and the growth uniformity can be enhanced, and efficient and large-scale preparation of the large-size graphene is facilitated.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of graphene preparation, and relates to graphene and a preparation method and device thereof. BACKGROUND

[0002] As a two-dimensional carbon material with a single atomic layer thickness, graphene exhibits a broad application prospect in the fields of flexible electronics, high-thermal-conductivity interface materials, transparent conductive films and three-dimensional functional network structures due to its excellent electrical, thermal, mechanical and optical properties.

[0003] The lateral size (i.e. the unfolding scale of the sheet layer in the two-dimensional plane direction) of graphene is one of the key structural parameters determining its macroscopic properties. Generally, the larger the size of the graphene sheet layer is, the fewer the number of joint nodes between the sheet layers is, thereby significantly reducing the interface contact resistance and improving the overall electrical conductivity; meanwhile, the large-size sheet layer is conducive to reducing the interface between the sheet layers in the graphene film, and is conducive to achieving better heat transport. Therefore, large-sheet graphene with a lateral size of tens of microns or even hundreds of microns has an irreplaceable advantage in high-end application scenarios such as high-thermal-conductivity films, transparent electrodes of high-frequency optoelectronic devices and low-impedance three-dimensional conductive networks.

[0004] At present, the mainstream technology for preparing large-size graphene is the chemical vapor deposition (CVD) method. This method can grow continuous, high-quality and large-lateral-size single-layer or multi-layer graphene films at high temperatures by catalytically cracking carbon source gas (such as methane) on the surface of a metal substrate (such as a copper foil or a nickel foil). The graphene obtained by the CVD method has a low defect density and a high carrier mobility, and is the main source of graphene for current high-performance electronic devices. However, this process has significant limitations: first, the CVD process needs to be carried out at high temperature (usually > 1000℃), high vacuum or precise atmosphere control conditions, which requires large equipment investment and high energy consumption, and it is difficult to realize low-cost large-scale production; second, the obtained graphene is firmly attached to the metal substrate, and the metal substrate must be removed by wet etching in the subsequent process, which not only introduces a large amount of chemical waste liquid and causes environmental pollution, but also easily causes the graphene to wrinkle, tear or be contaminated by residual metal ions, thereby affecting its intrinsic properties; in addition, the graphene film after transfer often introduces impurities due to the residual polymer support layer, which easily further deteriorates the electrical and thermal properties.

[0005] In addition to the CVD method, physical exfoliation methods (such as mechanical exfoliation, liquid shear exfoliation) and chemical oxidation-reduction methods are also widely used for graphene preparation. The former can obtain high-quality graphene, but has extremely low yield, wide size distribution, and is difficult to control the lateral size, and is usually only suitable for laboratory research; the latter generates graphene oxide (GO) by treating natural graphite with a strong oxidizing agent (such as concentrated sulfuric acid, potassium permanganate), and then obtains graphene by reduction, which has solution processability and certain production capacity, but the resulting product has many structural defects, the conjugate network is severely damaged, and the lateral size is generally smaller (usually <5 μm), with much lower electrical and thermal conductivity than CVD graphene. Although in recent years some studies have tried to improve the size of graphene prepared by chemical method through optimization of oxidation conditions, use of mild exfoliation methods or template-assisted growth, etc., in the pursuit of large lateral size, there are often problems such as harsh requirements for raw material purity, severe reaction conditions, complex post-processing, and poor batch consistency, leading to rising costs, narrow process window, and difficulty in balancing size, quality and yield. Especially in the face of high thermal conductivity or high-frequency electronic applications, small-size graphene cannot meet the performance threshold due to a large number of interface scattering. 2 Although the above-mentioned methods can be used to prepare graphene, they still have some problems. For example, the CVD method has high cost and is difficult to scale up; the physical exfoliation method has low yield and wide size distribution; and the chemical oxidation-reduction method has many structural defects and a conjugate network that is severely damaged.

[0006] In summary, there is still a need for a solution that can have large size, high purity, and scalability. SUMMARY

[0007] In view of the problems in the prior art, the purpose of the present application is to provide a graphene and a preparation method and device thereof. The preparation method comprises mixing first graphene and a process gas flow in a reaction chamber to form a continuously rotating first gas flow mixture, the process gas flow comprising a carbon source gas and a plasma source gas, and then performing a plasma-enhanced growth reaction on the first gas flow mixture to grow the first graphene into second graphene with increased lateral width. By using small-size graphene as a seed to prepare large-size graphene, the problems of high cost and pollution in traditional preparation methods of large-size graphene can be solved. The plasma-enhanced growth reaction in a continuously rotating gas flow can enhance the dispersibility and growth uniformity, which is beneficial to the efficient mass production of large-size graphene.

[0008] To achieve this purpose, the present application adopts the following technical solutions:

[0009] In a first aspect, the present application provides a preparation method of graphene, comprising: mixing first graphene and a process gas flow in a reaction chamber to form a continuously rotating first gas flow mixture, the process gas flow comprising a carbon source gas and a plasma source gas, and then performing a plasma-enhanced growth reaction on the first gas flow mixture to grow the first graphene into second graphene with increased lateral width.

[0010] The plasma method for growing graphene can improve production efficiency with the assistance of plasma, but there are still problems of difficult nucleation and different growth forms. Therefore, the small-size graphene provided as the nucleus can not only solve the nucleation problem, but also provide a template for subsequent graphene growth, so that the small-size graphene grows into large-size graphene along the edge. In addition, the source of small-size graphene is abundant, which can be waste of graphene production or product screened to ensure the quality of graphene product, which has important significance for turning waste into treasure. At the same time, the preparation method can also solve the high cost and pollution problems caused by traditional thermal CVD. It is also worth emphasizing that the first graphene in the application is subjected to a plasma-enhanced growth reaction in the case that the first graphene and the process gas flow form a continuously rotating first gas mixture. In this way, compared with flat production of samples, the dispersibility and growth uniformity can be effectively improved, and continuous production is beneficial, so as to facilitate the improvement of production efficiency and yield.

[0011] The following is a preferred technical solution of the application, but not as a limitation of the technical solution provided by the application. Through the following technical solution, the technical purpose and beneficial effect of the application can be better achieved and realized.

[0012] As a preferred technical solution of the application, the vacuum degree of the reaction chamber is ≤60kPa, such as 60kPa, 50kPa, 40kPa, 30kPa, 20kPa, 10kPa or 5kPa, etc. before the mixing is performed.

[0013] Preferably, after the gas mixture is formed, the working pressure of the reaction chamber is ≤500kPa, such as 500kPa, 400kPa, 300kPa, 200kPa, 100kPa or 80kPa, etc.

[0014] Preferably, the carbon source gas includes methane.

[0015] Preferably, the plasma source gas includes hydrogen.

[0016] Preferably, the flow ratio of the carbon source gas to the plasma source gas is (0.2~4):1, such as 0.2:1, 0.3:1, 0.5:1, 0.8:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1, etc.

[0017] Preferably, the total flow rate of the carbon source gas and the plasma source gas is 1 sccm to 500 sccm, such as 1 sccm, 3 sccm, 5 sccm, 8 sccm, 10 sccm, 50 sccm, 100 sccm, 150 sccm, 200 sccm, 250 sccm, 300 sccm, 350 sccm, 400 sccm, 450 sccm, or 500 sccm, etc.

[0018] Preferably, the feeding speed of the first graphene is 10 g / min to 100 g / min, such as 10 g / min, 30 g / min, 50 g / min, 80 g / min, 90 g / min, or 100 g / min, etc.

[0019] Preferably, the lateral size of the first graphene ranges from 1 nm to 1 μm, such as 1 nm, 35 nm, 10 nm, 30 nm, 50 nm, 80 nm, 100 nm, 300 nm, 500 nm, 800 nm, or 1 μm, etc. Further, the median lateral size of the first graphene is ≤ 1 μm.

[0020] As a preferred technical solution of the present application, the preparation method further comprises providing an auxiliary rotating gas flow, the flow direction of the auxiliary rotating gas flow is tangent to the flow direction of the process gas flow, for assisting in forming the continuously rotating first gas flow mixture.

[0021] Preferably, the composition of the auxiliary rotating gas flow is the same as that of the process gas flow.

[0022] Preferably, the flow ratio of the auxiliary rotating gas flow to the process gas flow is 1: (1.5-3), such as 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, or 1:3, etc. Thereby, the first gas flow mixture formed has a spiral rotating structure, improving the rotating effect; if the auxiliary rotating gas flow is too small, it may result in weak spiral, but if it is too large, it may also cause the rotating flow to stagnate, so the flow ratio should be reasonably adjusted to make the first gas flow mixture rotate stably and continuously.

[0023] Preferably, the flow rate of the auxiliary rotating gas flow is 1 sccm to 200 sccm, such as 1 sccm, 3 sccm, 10 sccm, 30 sccm, 50 sccm, 100 sccm, 130 sccm, 150 sccm, 180 sccm, or 200 sccm, etc.

[0024] Preferably, the discharge mode of the plasma-enhanced growth reaction comprises radio frequency or dielectric barrier discharge.

[0025] Preferably, the discharge power of the plasma enhanced growth reaction is 1 kW to 10 kW, such as 1 kW, 3 kW, 5 kW, 8 kW or 10 kW, etc.

[0026] Preferably, the reaction time of the plasma enhanced growth reaction is 10 min to 100 min, such as 10 min, 30 min, 50 min, 80 min or 100 min, etc.

[0027] As a preferred technical solution of the present application, the preparation method further comprises, after the plasma enhanced growth reaction, obtaining a second gas flow mixture, cooling the second gas flow mixture, and then collecting the second graphene.

[0028] Preferably, the cooling temperature is 30°C to 50°C, such as 30°C, 35°C, 40°C, 45°C or 50°C, etc.

[0029] Preferably, the ratio of the lateral size of the second graphene to the lateral size of the first graphene is ≥ 2, such as 2, 3, 5, 8, 10, etc. This ratio value can refer to the ratio of the median lateral size, i.e. 50% of the particles are greater than and less than the value.

[0030] In a second aspect, the present application provides a graphene preparation device, which is used to perform the preparation method of the first aspect; the preparation device comprises a reaction chamber, which is provided with a process gas flow inlet, an auxiliary rotating gas flow inlet and a discharge outlet; the spraying direction of the process gas flow inlet to the inside of the reaction chamber is parallel to the axial direction of the reaction chamber, and the spraying direction of the auxiliary rotating gas flow inlet to the inside of the reaction chamber is tangent to the spraying direction of the process gas flow inlet; the inside of the reaction chamber is further provided with a plasma generating device.

[0031] As a preferred technical solution of the present application, the preparation device further comprises a gas supply unit, which comprises a carbon source gas storage device and a plasma source gas storage device, both of which are in communication with the process gas flow inlet of the reaction chamber, and are used to provide process gas flow.

[0032] Preferably, the gas supply unit further comprises a gas control device, and the carbon source gas storage device and the plasma source gas storage device are in communication with the gas inlet of the gas control device, and the gas outlet of the gas control device is in communication with the process gas flow inlet of the reaction chamber.

[0033] Preferably, the gas outlet of the gas control device is also in communication with the auxiliary rotating gas flow inlet of the reaction chamber, and is used to provide auxiliary rotating gas flow.

[0034] Preferably, the preparation device further comprises a feeding unit, the feeding unit comprises a first graphene feeding device, the first graphene feeding device is connected with the process gas inlet of the reaction chamber, and the first graphene feeding device is used for providing the first graphene.

[0035] Preferably, the feeding unit further comprises a powder controller, the first graphene feeding device is connected with the feeding port of the powder controller, and the discharging port of the powder controller is connected with the process gas inlet of the reaction chamber.

[0036] Preferably, the preparation device further comprises a vacuum device, the vacuum device is connected with the reaction chamber, and the vacuum device is used for forming a vacuum environment.

[0037] Preferably, along the flow direction of the material, the reaction chamber comprises a reaction zone, a cooling zone and a discharging port; the plasma reaction device is arranged in the reaction zone, and the cooling zone is provided with a cooling device.

[0038] Preferably, the cooling device comprises a water cooling instrument, and the water cooling instrument is connected with a water cooling pipe, and the water cooling pipe is arranged outside the cooling zone of the reaction chamber.

[0039] Preferably, the preparation device further comprises a powder collecting device, the feeding port of the powder collecting device is connected with the discharging port of the reaction chamber, the powder collecting device is used for collecting the generated second graphene, the discharging port of the powder collecting device is used for discharging the second graphene, and the powder collecting device further has an exhaust port used for exhausting gas.

[0040] Preferably, the preparation device further comprises a gas dust removal device, the gas dust removal device is connected with the gas outlet of the powder collecting device, and the gas outlet of the gas dust removal device is further connected with a gas recovery device.

[0041] Preferably, the gas outlet of the gas recovery device is connected with a gas recycling pipeline, and the gas recycling pipeline is connected with the process gas inlet and / or the auxiliary rotating gas inlet.

[0042] In a third aspect, the present application provides a graphene, which is obtained by using the preparation method of the first aspect or using the preparation device of the second aspect.

[0043] It should be noted that, due to the limitation of the length and in order to avoid redundancy, the present application does not exhaustively list all point values in the above numerical range, but is not limited to the listed values, and other unlisted values in the above numerical range are also applicable.

[0044] Compared with the prior art, the present application has at least the following beneficial effects:

[0045] The preparation method comprises mixing first graphene and a process gas flow in a reaction chamber to form a first gas flow mixture in continuous rotation, the process gas flow comprising a carbon source gas and a plasma source gas, and then performing a plasma enhanced growth reaction on the first gas flow mixture to grow the first graphene into second graphene with increased lateral width. By using small-size graphene as seeds to prepare large-size graphene, the problems of high cost and pollution in the traditional preparation method of large-size graphene can be solved. The plasma enhanced growth reaction is performed in the form of continuous rotation of the gas flow, which can strengthen the dispersibility and growth uniformity, and is conducive to efficient and large-scale preparation of large-size graphene. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a schematic diagram of a preparation device of graphene in Example 1.

[0047] In the figure: 10-reaction chamber, 11-process gas flow inlet, 12-assisted rotating gas flow inlet, 13-reaction zone, 14-cooling zone, 20-plasma generating device, 31-carbon source gas storage device, 32-plasma source gas storage device, 33-gas control device, 40-first graphene feeding device, 50-vacuum device, 60-cooling device, 70-powder collecting device, 80-gas dust removal device, 90-gas recovery device.

[0048] Figure 2 is an AFM test diagram of the first graphene in Example 1.

[0049] Figure 3 is an AFM test diagram of the second graphene in Example 1. DETAILED DESCRIPTION

[0050] The technical solutions of the present application will be further described below through specific embodiments.

[0051] Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations of the present application.

[0052] Example 1

[0053] This embodiment provides a preparation method of graphene, which is implemented by a preparation device as shown in Figure 1 The preparation device comprises:

[0054] The reaction chamber 10 includes a reaction zone 13, a cooling zone 14 and a discharge port along the flow direction of the material; the front end of the reaction zone 13 is provided with a process gas inlet 11 and an auxiliary rotating gas inlet 12; the spraying direction of the process gas inlet 11 to the inside of the reaction chamber 10 is parallel to the axial direction of the reaction chamber 10, and the spraying direction of the auxiliary rotating gas inlet 12 to the inside of the reaction chamber 10 is tangent to the spraying direction of the process gas inlet 11; the reaction zone 13 of the reaction chamber 10 is further provided with a plasma generating device 20 (including a dielectric barrier discharge power supply); the cooling zone 14 is provided with a water cooling instrument of a cooling device 60, and the water cooling instrument is connected with a water cooling pipe which is arranged outside the cooling zone 14 of the reaction chamber 10;

[0055] A gas supply unit includes a carbon source gas storage device 31 and a plasma source gas storage device 32, and a gas control device 33, the carbon source gas storage device 31 and the plasma source gas storage device 32 are connected with the gas inlet of the gas control device 33, and the gas outlet of the gas control device 33 is connected with the process gas inlet 11 of the reaction chamber 10; at the same time, the gas outlet of the gas control device 33 is also connected with the auxiliary rotating gas inlet 12 of the reaction chamber 10, for providing auxiliary rotating gas flow;

[0056] A material supply unit includes a first graphene feeding device 40 and a powder controller, the first graphene feeding device 40 is connected with the feeding port of the powder controller, and the discharge port of the powder controller is connected with the process gas inlet 11 of the reaction chamber 10, for providing first graphene;

[0057] A vacuum device 50 connected with the reaction chamber 10 for forming a vacuum environment;

[0058] A powder collecting device 70 which is a cyclone separator, the feeding port of the powder collecting device 70 is connected with the discharge port of the reaction chamber 10 for collecting generated second graphene, and the discharge port of the powder collecting device 70 is used for discharging second graphene, and the powder collecting device 70 further has an exhaust port for discharging gas;

[0059] A gas dust removal device 80 connected with the exhaust port of the powder collecting device 70;

[0060] A gas recovery device 90, the exhaust port of the gas dust removal device 80 is also connected with the gas recovery device 90;

[0061] A gas recycling pipeline is connected to the gas outlet of the gas recycling device 90, and is connected to the process gas inlet 11 and / or the auxiliary rotating gas inlet 12, so as to recycle the residual gas.

[0062] The preparation method of the graphene comprises the following steps:

[0063] S1, start the vacuum pump, reduce the air pressure in the reaction chamber 10 to below 60 kPa, and introduce the process gas flow, the gas composition is carbon source gas CH4 and plasma source gas H2, the flow ratio is 1:1, the total flow is 260 sccm, and the pressure in the reaction chamber 10 is controlled to be lower than 500 kPa;

[0064] S2, a certain amount of small-size first graphene (lateral size range is 250 nm-1 μm, and the median lateral size is 0.5 μm) is put into the first graphene feeding device 40, and is fed into the reaction chamber 10, the feeding speed is controlled to be 50 g / min, the first graphene powder is taken into the reaction chamber 10 by the process gas flow, and at the same time, the auxiliary rotating gas flow is added into the reaction chamber 10, the composition is the same as that of the process gas flow, the powder is dispersed, and the process gas flow containing the first graphene forms a continuously rotating first gas mixture in the reaction zone 13, and the flow of the rotating auxiliary gas flow is 130 sccm;

[0065] S3, the power of the dielectric barrier discharge power supply is set to 5 kW, the first gas mixture is subjected to a plasma enhanced growth reaction, the reaction time is 60 min, the first graphene is grown into second graphene with increased lateral width, the product after the reaction forms a second gas mixture, and enters the cooling zone 14 for rapid cooling, and the temperature of the cooling zone 14 is controlled to be 40℃;

[0066] S4, the large-size second graphene generated by the reaction is collected by the cyclone separator, and the gas after recycling can continue to be recycled.

[0067] Example 2

[0068] The difference between this embodiment and example 1 is that in step S1, the flow ratio of the carbon source gas to the plasma source gas is adjusted from 1:1 to 0.2:1, and other conditions are the same as those in example 1.

[0069] Example 3

[0070] The difference between this embodiment and example 1 is that in step S1, the flow ratio of the carbon source gas to the plasma source gas is adjusted from 1:1 to 0.5:1, and other conditions are the same as those in example 1.

[0071] Example 4

[0072] The difference between this embodiment and embodiment 1 is that, in step S1, the flow ratio of the carbon source gas to the plasma source gas is adjusted from 1:1 to 4:1, and other conditions are the same as those in embodiment 1.

[0073] Embodiment 5

[0074] The difference between this embodiment and embodiment 1 is that, in step S1, the flow ratio of the carbon source gas to the plasma source gas is adjusted from 1:1 to 5:1, and other conditions are the same as those in embodiment 1.

[0075] Embodiment 6

[0076] The difference between this embodiment and embodiment 1 is that, in step S2, the flow of the auxiliary rotating gas is adjusted from 130 sccm to 30 sccm, and other conditions are the same as those in embodiment 1.

[0077] Embodiment 7

[0078] The difference between this embodiment and embodiment 1 is that, in step S2, the flow of the auxiliary rotating gas is adjusted from 130 sccm to 300 sccm, and other conditions are the same as those in embodiment 1.

[0079] Embodiment 8

[0080] The difference between this embodiment and embodiment 1 is that, in step S3, the power of the dielectric barrier discharge power supply is adjusted from 5 kW to 1 kW, and other conditions are the same as those in embodiment 1.

[0081] Embodiment 9

[0082] The difference between this embodiment and embodiment 1 is that, in step S3, the power of the dielectric barrier discharge power supply is adjusted from 5 kW to 10 kW, and other conditions are the same as those in embodiment 1.

[0083] Embodiment 10

[0084] The embodiment provides a preparation method of graphene. The preparation device used in the preparation method is different from that in embodiment 1 in that the power supply of the plasma generating device is adjusted from a dielectric barrier discharge power supply to a radio frequency power supply, and other conditions are the same as those in the preparation device in embodiment 1. The preparation method comprises the following steps.

[0085] S1, start the vacuum pump, reduce the gas pressure in the reaction chamber 10 to below 60 kPa, and introduce a process gas flow. The gas composition is a carbon source gas CH4 and a plasma source gas H2, the flow ratio is 1:1, the total flow is 260 sccm, and the pressure of the reaction chamber 10 is controlled to be lower than 500 kPa;

[0086] S2, a certain amount of small size first graphene (lateral size range of 1 nm-100 nm, median lateral size of 50 nm) is put into the first graphene feeding device 40, and is fed into the reaction chamber 10, the feeding speed is controlled to be 100 g / min, the first graphene powder is taken into the reaction chamber 10 by using the process gas flow, and at the same time, an auxiliary rotating gas flow with the same composition as the process gas flow is added into the reaction chamber 10, so that the powder is dispersed and the process gas flow containing the first graphene forms a continuously rotating first gas flow mixture in the reaction zone 13, and the flow rate of the rotating auxiliary gas flow is 130 sccm;

[0087] S3, the power of the radio frequency power supply is set to 6 kW, and the first gas flow mixture is subjected to a plasma enhanced growth reaction, the reaction time is 60 min, the first graphene is grown into second graphene with increased lateral width, the product after the reaction forms a second gas flow mixture, and enters the cooling zone 14 for rapid cooling, and the temperature of the cooling zone 14 is controlled to be 40℃;

[0088] S4, the large size second graphene generated by the reaction is collected by the cyclone separator, and the gas after recovery can be recycled.

[0089] Example 11

[0090] The embodiment provides a preparation method of graphene, wherein in a preparation device used in the preparation method, the power supply of a plasma generating device is adjusted from a dielectric barrier discharge power supply to a radio frequency power supply, and other conditions are the same as those of the preparation device in Example 1; and the preparation method comprises the following steps:

[0091] S1, the vacuum pump is started, the gas pressure in the reaction chamber 10 is reduced to below 60 kPa, and the process gas flow is introduced, the gas composition is carbon source gas CH4 and plasma source gas H2, the flow rate ratio is 1:1, the total flow rate is 260 sccm, and the pressure in the reaction chamber 10 is controlled to be lower than 500 kPa;

[0092] S2, a certain amount of small size first graphene (lateral size range of 1 nm-100 nm, median lateral size of 50 nm) is put into the first graphene feeding device 40, and is fed into the reaction chamber 10, the feeding speed is controlled to be 100 g / min, the first graphene powder is taken into the reaction chamber 10 by using the process gas flow, and at the same time, an auxiliary rotating gas flow with the same composition as the process gas flow is added into the reaction chamber 10, so that the powder is dispersed and the process gas flow containing the first graphene forms a continuously rotating first gas flow mixture in the reaction zone 13, and the flow rate of the rotating auxiliary gas flow is 130 sccm;

[0093] S3, set the power of the radio frequency power supply to 3kW, and perform a plasma enhanced growth reaction on the first gas mixture, with a reaction time of 60min, so as to grow the first graphene into a second graphene with an increased lateral width, and the product after the reaction forms a second gas mixture and enters the cooling area 14 for rapid cooling, with the temperature of the cooling area 14 being controlled to be 40℃;

[0094] S4, collect the large-size second graphene generated by the reaction through a cyclone separator, and the gas after recovery can continue to be recycled.

[0095] Comparative Example 1

[0096] The difference between this comparative example and Example 1 is that in step S2, the flow rate of the auxiliary rotating gas flow is adjusted from 120sccm to 0sccm, i.e., no auxiliary rotating gas flow is introduced, and other conditions are the same as those in Example 1.

[0097] Comparative Example 2

[0098] The difference between this comparative example and Example 1 is that in step S1, the first graphene is pre-laid in the reaction chamber without being fed through the first graphene feeding device, and the flow rate of the auxiliary rotating gas flow is adjusted from 120sccm to 0sccm, i.e., no auxiliary rotating gas flow is introduced, and other conditions are the same as those in Example 1.

[0099] Characterization and testing:

[0100] The first graphene and the obtained second graphene of Example 1 were subjected to lateral size testing, and the samples were tested using an atomic force microscope (AFM), and the widest size in a plurality of samples in the field of view was taken as the lateral size, wherein the median lateral size was the median of a plurality of lateral sizes counted in the field of view of the AFM. Figure 2 The AFM graph of the first graphene of Example 1 is shown in FIG. 1. Figure 3 The AFM graph of the second graphene of Example 1 is shown in FIG. 2, and it can be clearly seen from the graph that the lateral size of the graphene after treatment has been increased.

[0101] The results of Examples 1-11 and Comparative Examples 1-2 are shown in Table 1 below.

[0102] Table 1

[0103]

[0104] It can be seen from Table 1 that:

[0105] Compared with Comparative Example 1 and Comparative Example 2, Example 1 is conducive to high dispersibility, uniform growth and lateral size growth of small-size graphene by matching the auxiliary rotating gas flow with the process gas flow, so as to obtain large-size graphene. The preparation method of graphene provided by the application is suitable for lateral growth of small-size graphene of various scales. For example, the lateral size of the second graphene obtained by the preparation method is 6.7 times that of the first graphene, the lateral size of the second graphene obtained by the preparation method is about 14 times that of the first graphene, and the lateral size of the second graphene obtained by the preparation method is 20 times that of the first graphene, that is, the ratio of the lateral size of the second graphene to the lateral size of the first graphene is all greater than or equal to 2, and the target growth size can be obtained by optimizing and controlling the experimental conditions.

[0106] Compared with Example 1 and Example 2 to Example 5, when the proportion of the carbon source gas is small and the proportion of hydrogen is too large, the growth of graphene is inhibited, and the size of the obtained product is small. At the same time, the low hydrogen content also affects the growth of graphene, because hydrogen has two main functions, one is to participate in the construction of the carbon grid, and the other is to terminate the grain edge growth by etching. Therefore, it is necessary to control the reasonable ratio of carbon source gas to hydrogen, for example, the ratio can be further selected to be 1:(0.8-3), and more preferably 1:(1-2).

[0107] Compared with Example 1 and Example 6 and Example 7, when the proportion of the auxiliary rotating gas flow is too small, the rotating effect of the first gas mixture is not enough, the reaction is not sufficient, and the sample size increases little. When the proportion of the auxiliary rotating gas flow is too large, the gas flow stagnates, causing part of the sample to remain in the reaction zone, and the yield of the second graphene meeting the target size decreases. Therefore, it is necessary to control the reasonable proportion of the auxiliary rotating gas flow and the process gas flow, for example, the ratio can be further selected to be 1:(1.5-3).

[0108] Compared with Example 1 and Example 8 and Example 9, when the power of the power supply is too small, the plasma density is affected, the reaction is not sufficient, and when the power of the power supply is too large, the plasma is too active, which may cause the etching effect to be enhanced and affect the growth of graphene. Therefore, the power can be controlled to be 2kW-7kW.

[0109] The above describes the preferred embodiments of the application, but the application is not limited to the specific details in the above embodiments. Within the technical concept of the application, various simple modifications can be made to the technical solutions of the application, and these simple modifications all belong to the protection scope of the application.

[0110] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the application will not describe various possible combinations again.

[0111] Furthermore, the various embodiments can also be combined, if not in contradiction, as long as they do not deviate from the spirit of the present application, which should be considered as disclosed.

Claims

1. A method of producing graphene, characterized by, The preparation method comprises the following steps: mixing the first graphene with a process gas flow in a reaction chamber to form a first gas flow mixture in continuous rotation, the process gas flow comprising a carbon source gas and a plasma source gas, and then performing a plasma enhanced growth reaction on the first gas flow mixture to grow the first graphene into second graphene with increased lateral width.

2. The method of claim 1, wherein the graphene is prepared by the method of claim 1. The vacuum degree of the reaction chamber is ≤60 kPa before the mixing is performed; Preferably, the working pressure of the reaction chamber is ≤500 kPa after the gas flow mixture is formed; Preferably, the carbon source gas comprises methane; Preferably, the plasma source gas comprises hydrogen; Preferably, the flow rate ratio of the carbon source gas to the plasma source gas is (0.2-4):1; Preferably, the total flow rate of the carbon source gas and the plasma source gas is 1-500 sccm; Preferably, the feeding speed of the first graphene is 10-100 g / min; Preferably, the lateral size of the first graphene ranges from 1 nm to 1 μm.

3. The method of claim 1 or 2, wherein the graphene is prepared by the method of claim 1 or 2. The preparation method further comprises providing an auxiliary rotating gas flow, the flow direction of the auxiliary rotating gas flow being tangential to the flow direction of the process gas flow, for assisting in forming the first gas flow mixture in continuous rotation; Preferably, the auxiliary rotating gas flow has the same composition as the process gas flow; Preferably, the flow rate ratio of the auxiliary rotating gas flow to the process gas flow is 1:(1.5-3); Preferably, the flow rate of the auxiliary rotating gas flow is 1-200 sccm; Preferably, the discharge mode of the plasma enhanced growth reaction comprises radio frequency or dielectric barrier discharge; Preferably, the discharge power of the plasma enhanced growth reaction is 1-10 kW; Preferably, the reaction time of the plasma enhanced growth reaction is 10-100 min.

4. The method for preparing graphene according to any one of claims 1-3, characterized in that, The preparation method further comprises, after the plasma enhanced growth reaction is performed, obtaining a second gas flow mixture, cooling the second gas flow mixture, and then collecting the second graphene; Preferably, the cooling temperature is 30-50 °C; Preferably, the ratio of the lateral size of the second graphene to the lateral size of the first graphene is ≥2.

5. An apparatus for producing graphene, characterized by comprising: The preparation device is used to perform the preparation method of any one of claims 1-4; the preparation device comprises a reaction chamber, the reaction chamber being provided with a process gas flow inlet, an auxiliary rotating gas flow inlet and a discharge outlet; the spray direction of the process gas flow inlet to the inside of the reaction chamber is parallel to the axial direction of the reaction chamber, and the spray direction of the auxiliary rotating gas flow inlet to the inside of the reaction chamber is tangential to the spray direction of the process gas flow inlet; the inside of the reaction chamber is further provided with a plasma generating device.

6. The apparatus according to claim 5, wherein The preparation device further comprises a gas supply unit, the gas supply unit comprising a carbon source gas storage device and a plasma source gas storage device, both being in communication with the process gas flow inlet of the reaction chamber, for providing the process gas flow; Preferably, the gas supply unit further comprises a gas control device, the carbon source gas storage device and the plasma source gas storage device are in communication with the gas inlet of the gas control device, and the gas outlet of the gas control device is in communication with the process gas inlet of the reaction chamber. Preferably, the gas outlet of the gas control device is also in communication with the auxiliary rotating gas inlet of the reaction chamber, for providing an auxiliary rotating gas flow.

7. The apparatus according to claim 5 or 6, wherein The preparation device further comprises a feeding unit, the feeding unit comprises a first graphene feeding device, the first graphene feeding device is in communication with the process gas inlet of the reaction chamber, for providing a first graphene; Preferably, the feeding unit further comprises a powder controller, the first graphene feeding device is in communication with the feeding inlet of the powder controller, and the discharging outlet of the powder controller is in communication with the process gas inlet of the reaction chamber, Preferably, the preparation device further comprises a vacuum device, the vacuum device is in communication with the reaction chamber, for forming a vacuum environment.

8. The apparatus of any one of claims 5-7, wherein the graphene is prepared by a method comprising: In the flow direction of the material, the reaction chamber comprises a reaction zone, a cooling zone and a discharging outlet; the plasma reaction device is arranged in the reaction zone, and the cooling zone is provided with a cooling device; Preferably, the cooling device comprises a water cooling instrument, and the water cooling instrument is in communication with a water cooling pipe, which is arranged outside the cooling zone of the reaction chamber.

9. The apparatus according to any one of claims 5 to 8, wherein the apparatus is configured to produce graphene by the method according to any one of claims 1 to 4. The preparation device further comprises a powder collecting device, the feeding inlet of the powder collecting device is in communication with the discharging outlet of the reaction chamber, for collecting the generated second graphene, the discharging outlet of the powder collecting device is used for discharging the second graphene, and the powder collecting device further has an exhaust outlet, for exhausting gas; Preferably, the preparation device further comprises a gas dust removal device, the gas dust removal device is in communication with the exhaust outlet of the powder collecting device, and the gas outlet of the gas dust removal device is also in communication with a gas recovery device; Preferably, the gas outlet of the gas recovery device is in communication with a gas recycling pipeline, and the gas recycling pipeline is in communication with the process gas inlet and / or the auxiliary rotating gas inlet.

10. Graphene, characterized in that, The preparation method of claims 1-4 is used, or the preparation device of any one of claims 5-9 is used.

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