High-performance graphene heat-conducting film and preparation method thereof

Abstract

The application relates to a preparation method of a high-performance graphene heat-conducting film, which comprises the following steps: providing a low-defect-concentration graphene film with a heat-conducting coefficient not lower than 1200 W / mK; fixing the low-defect-concentration graphene film in a plasma device in a double-side clamping mode of a heat insulation layer so that the plasma directly acts on the low-defect-concentration graphene film; initiating an ultrahigh-temperature plasma in an inert or reducing atmosphere, and performing plasma treatment on the low-defect-concentration graphene film from the side to obtain a high-quality graphene expansion film; and performing densification treatment on the high-quality graphene expansion film to obtain the high-performance graphene heat-conducting film. The application also relates to the high-performance graphene heat-conducting film obtained by the above preparation method. According to the high-performance graphene heat-conducting film and the preparation method thereof, the low-defect-concentration graphene film is treated by plasma from the side by using ultrahigh temperature formed by plasma, and the bottleneck of improving the heat-conducting coefficient of the current graphene heat-conducting film is broken through.

Description

Technical Field

[0001] This invention relates to plasma ultra-high temperature heat treatment of graphene films, and more specifically to a high-performance graphene thermally conductive film and its preparation method. Background Technology

[0002] Graphene, a two-dimensional material composed of a single layer of tightly packed carbon atoms, has attracted widespread attention from the global academic and industrial communities since its discovery in 2004 due to its excellent thermal conductivity [Nature Materials 6, 183 (2007)]. Graphene has an extremely high thermal conductivity (~5000 W / mK), far exceeding that of metals and other carbon materials, making it an ideal thermal conductive medium [Nano Lett. 8, 902–907 (2008)]. Thanks to its superior thermal conductivity, graphene has shown great application potential in the field of electronic devices [Adv. Mater. 29, 1–8 (2017)]. Currently, graphene thermal conductive films have been applied to the heat dissipation systems of smartphones and tablets from Huawei, Xiaomi, and other electronic devices. By placing the graphene thermal conductive film on the back of heat-generating components such as processors and batteries, heat can be effectively and quickly conducted to the heat dissipation device, thereby improving the stability and lifespan of the device. Graphene thermal conductive films, as an innovative heat dissipation solution, have significant application potential in the thermal management of high-power-density systems such as 5G communication base stations, new energy batteries, and insulated-gate bipolar transistor devices. However, the fabrication of graphene thermal conductive films with higher thermal conductivity currently faces enormous technical challenges.

[0003] Graphene films are generally assembled from graphene materials such as graphene oxide and reduced graphene oxide. Due to the microstructural defects of the graphene sheets themselves and the macroscopic defects such as wrinkles and inconsistencies in orientation formed by the stacking of the sheets, graphene films generally have a large number of structural defects. High-temperature heat treatment is required to reduce structural defects in order to give full play to the thermal conductivity advantages of graphene. According to research reports, increasing the graphitization temperature in the graphene film preparation process is a feasible approach. By increasing the heat treatment temperature, structural defects in graphene films can be reduced, and the thermal conductivity advantages of graphene can be fully utilized [Small 10(23),4839–4844(2014).]. Currently, graphitization furnaces are generally used to perform long-term (2-4 hours) graphitization heat treatment on graphene oxide or reduced graphene oxide films at a high temperature of about 3000℃. However, traditional high-temperature graphitization furnaces have many problems, such as slow heating and cooling rates, long processing time, and high energy consumption, which makes the process cost of heat treatment account for more than 50% of the preparation cost of graphene thermal conductive films. More importantly, due to the limitations of induction heating, the temperature limit of traditional graphitization furnaces is generally around 3200℃. The processed graphene film still has a large number of structural defects, making it difficult to further improve the thermal conductivity, which has become a bottleneck for improving the performance of graphene thermal conductive films. Summary of the Invention

[0004] To address the problems of slow heating and cooling rates, long processing times, high energy consumption, and high costs associated with traditional graphitization equipment and processes in the prior art, this invention provides a high-performance graphene thermal conductive film and its preparation method.

[0005] The method for preparing a high-performance graphene thermal conductive film according to the present invention includes the following steps: S1, providing a low-defect-concentration graphene film with a thermal conductivity of not less than 1200 W / mK; S2, fixing at least one layer of low-defect-concentration graphene film in a plasma device by double-sided covering and clamping with a heat insulation layer so that the plasma can directly act on the low-defect-concentration graphene film; S3, initiating ultra-high temperature plasma in an inert or reducing atmosphere to perform plasma treatment on the low-defect-concentration graphene film from the side to obtain a high-quality graphene expanded film; S4, densifying the high-quality graphene expanded film to obtain a high-performance graphene thermal conductive film.

[0006] Preferably, in step S1, the carbon content of the low-defect-concentration graphene film is greater than 95 at.%, and the intensity of the defect characteristic peak (I) in its Raman spectrum is... D ) and intrinsic characteristic peak intensity (I G (less than 0.05)

[0007] Preferably, the thermal conductivity of the low-defect-concentration graphene film is between 1200-1500 W / mK. It should be understood that although the thermal conductivity of low-defect-concentration graphene films prepared by existing technologies is typically no higher than 1500 W / mK, low-defect-concentration graphene films with thermal conductivity higher than 1500 W / mK can obviously also be used in this invention.

[0008] Preferably, the thickness of the low-defect-concentration graphene film is not less than 100 μm. It should be understood that the thinner the thermally conductive film, the easier it is to obtain high thermal conductivity, and the present invention has obvious advantages in being used for low-defect-concentration graphene films with a thickness of not less than 100 μm.

[0009] Preferably, in step S2, the double-sided covering and clamping method of the heat insulation layer is to completely cover the surface of the low-defect-concentration graphene film with a porous graphite plate as the heat insulation layer and press it tightly together.

[0010] Preferably, 5-20 layers of low-defect-concentration graphene film are stacked and fixed in the plasma device by a double-sided insulating layer clamping method.

[0011] Preferably, the plasma device is an arc plasma device or an inductively coupled plasma device.

[0012] Preferably, in the arc plasma equipment, the low-defect-concentration graphene film is fixed to the cathode position in the arc plasma furnace by a double-sided insulating layer clamping method, so that the side of the low-defect-concentration graphene film is placed facing the anode graphite rod.

[0013] Preferably, the parameters for arc plasma treatment include: gas pressure in the reaction chamber of 5-15 kPa, arc current of 50-200 A, and treatment time of 2-10 min.

[0014] Preferably, in an inductively coupled plasma (ICP) device, a low-defect-concentration graphene film is fixed to the sample mounting stage at the bottom of the ICP torch device by means of a double-sided heat insulation layer, so that the side of the low-defect-concentration graphene film faces the plasma torch nozzle.

[0015] Preferably, the parameters for inductively coupled plasma treatment include: plasma power supply frequency of 27.12MHz, power supply of 30-100KW, gas inlet speed of 10-30L / min, and treatment time of 5-20min.

[0016] Preferably, in step S3, the inert or reducing atmosphere is one of argon, nitrogen, hydrogen, or a combination thereof.

[0017] Preferably, in step S4, the densification process is performed by roller pressing or flat pressing.

[0018] The present invention also relates to a high-performance graphene thermal conductive film obtained by the above preparation method, which has a thermal conductivity greater than 1800 W / mK.

[0019] Preferably, the thickness of the high-performance graphene thermal conductive film is not less than 100 μm.

[0020] The present invention relates to a high-performance graphene thermal conductive film and its preparation method. By utilizing the ultra-high temperature generated by plasma to treat a low-defect-concentration graphene film from the side, this invention overcomes the current bottleneck in improving the thermal conductivity of graphene thermal conductive films, thereby meeting the increasing demand for heat dissipation performance due to the improvement in the performance of electronic products. Specifically, the present invention employs a thermally insulating laminated method to sandwich the graphene film, fully utilizing the local ultra-high temperature generated by plasma. This promotes the repair of defects and grain growth in the graphene film structure, improving the thermal conductivity of the graphene thermal conductive film and efficiently preparing a high-performance graphene thermal conductive film. Compared with traditional high-temperature heat treatment methods, plasma generates higher temperatures. Fully utilizing the ultra-high temperature of plasma not only significantly improves the thermal conductivity of the graphene thermal conductive film but also greatly reduces the energy consumption and cost of preparing high-performance graphene thermal conductive films, making it very suitable for the mass production of high-performance graphene thermal conductive films. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the electric arc plasma furnace used in Examples 1 and 2.

[0022] Figure 2 This is a schematic diagram of the inductively coupled plasma torch device used in Examples 3 and 4.

[0023] Figure 3 This is a schematic diagram of the structure of the electric arc plasma furnace used in Comparative Example 3.

[0024] Figure 4 This is a schematic diagram of the structure of the electric arc plasma furnace used in Comparative Example 4.

[0025] Figure 5 These are photographs and Raman spectra of the high-quality graphene film in Example 1 before and after plasma heat treatment.

[0026] Figure 6 These are photographs and Raman spectra of the high-quality graphene film in Example 2 before and after plasma heat treatment.

[0027] Figure 7 These are photographs and Raman spectra of the high-quality graphene film in Example 3 before and after plasma heat treatment.

[0028] Figure 8 These are photographs and Raman spectra of the high-quality graphene film in Example 4 before and after plasma heat treatment.

[0029] Figure 9 These are Raman spectra of the graphene oxide film in Comparative Example 1 and photographs before and after plasma heat treatment.

[0030] Figure 10 These are Raman spectra of the reduced graphene oxide film in Comparative Example 2 and photographs before and after plasma heat treatment.

[0031] Figure 11 These are photographs and Raman spectra of the high-quality graphene film in Comparative Example 3 before and after plasma heat treatment.

[0032] Figure 12 These are photographs and Raman spectra of the high-quality graphene film in Comparative Example 4 before and after plasma heat treatment.

[0033] Figure 13 These are photographs and Raman spectra of the high-quality graphene film in Comparative Example 5 before and after heat treatment in a graphitization furnace. Detailed Implementation

[0034] The preferred embodiments of the present invention are given below with reference to the accompanying drawings and described in detail.

[0035] This invention proposes to utilize high-temperature plasma to treat graphene films composed of graphene sheets. By employing methods such as external heat insulation encapsulation and side heat absorption with in-plane conduction, the ultra-high temperature characteristics of plasma are fully utilized, while avoiding the adverse effects of localized ultra-high temperature plasma. This promotes the repair of structural defects and grain size growth in the graphene film, improves the thermal conductivity of the graphene film, and efficiently prepares high-performance graphene thermal conductive films.

[0036] Plasma is a unique state of matter, characterized by an ionized gas composed of atoms with some electrons stripped and positive and negative electrons produced by ionized atoms. It is considered the fourth state of matter, after solid, liquid, and gas, and is also known as the "supergas." Plasma is renowned for its extremely high temperature, typically ranging from several thousand to tens of thousands of degrees Celsius [Thin Solid Films 520, 4219–4236 (2012)]. Furthermore, thanks to the large number of free electrons and ions within plasma, these particles can move rapidly and transfer energy under the influence of an electric field. Therefore, plasma exhibits extremely rapid heating and cooling rates. This characteristic enables plasma processing technology to quickly heat and cool materials, improving production efficiency and reducing energy consumption. Thus, plasma's ultra-high temperature characteristics and rapid heating and cooling rates significantly distinguish it from traditional graphitization furnaces. However, the ultra-high temperature region of plasma is limited to a very small spatial range, and the films assembled from two-dimensional sheets such as graphene oxide and reduced graphene oxide have low thermal conductivity due to numerous structural defects. Therefore, if plasma directly acts on these films, it will cause the local temperature of the film to rise sharply and instantaneously. Defects such as oxygen-containing functional groups in the film structure will form a large amount of gas at high temperatures, which will impact the film from the inside, causing structural damage and generating more macroscopic defects, which will have an adverse effect on thermal conductivity.

[0037] This invention addresses the localization characteristics of ultra-high temperature plasma by proposing the use of graphene films with low defect concentration (carbon content > 95 at.%) as raw materials. Utilizing the high lateral thermal conductivity (1200-1500 W / mK) of the graphene film itself, a thermally insulating encapsulation method is used to clamp the graphene film and plasma treatment is performed from its side. This avoids the disadvantage of localized plasma temperature, not only improving the thermal conductivity of the graphene thermal conductive film but also significantly reducing the manufacturing cost of high-performance graphene thermal conductive films.

[0038] To make the technical means, creative features, achieved objectives and effects of this invention readily understandable, the invention will be further described in detail below through embodiments. Obviously, the embodiments described below are merely some examples of this invention, and those skilled in the art can obtain other embodiments based on these embodiments without any creative effort.

[0039] Example 1

[0040] Heat treatment of multiple low-defect-concentration graphene films using electric arc plasma

[0041] 1.1 Preparation of graphene films with low defect concentration

[0042] (1) A graphene oxide (GO) slurry (2% solid content) was uniformly coated onto a polyethylene terephthalate (PET) substrate using a blade coater to obtain a graphene oxide wet film with a thickness of 50 mm.

[0043] (2) The graphene oxide wet film obtained in step (1) is placed in a forced-air drying oven and heated at 50°C for 12 hours to dry, resulting in a graphene oxide dry film with a thickness of 0.5 mm.

[0044] (3) The graphene oxide dry film obtained in step (2) is placed in a graphitization furnace for high-temperature graphitization treatment. The high-temperature graphitization process is divided into four stages: the first stage is to raise the temperature from room temperature to 1000℃ at a heating rate of 5.5℃ / min; the second stage is to raise the temperature from 1000℃ to 3150℃ at a heating rate of 1.9℃ / min; the third stage is the heat preservation stage, which is to keep the temperature at 3150℃ for 2 hours; the fourth stage is the cooling stage, in which heating is stopped and the sample is allowed to cool to room temperature with the graphitization furnace after standing for 15-20 hours to obtain a porous graphene film. Throughout the graphitization heat treatment process, argon gas is kept flowing in the graphitization furnace at a flow rate of 10L / min to ensure an inert gas environment inside the furnace.

[0045] (4) The porous graphene film obtained in step (3) is placed in a calender for calendering. The calendering pressure is 5 MPa, and finally a low defect concentration graphene film with a thickness of about 0.1 mm is obtained.

[0046] 1.2 Arc plasma thermal treatment of graphene films with low defect concentration

[0047] (1) Cut five sheets of low-defect-concentration graphene film (100mm×100mm×0.1mm) prepared in step 1.1 and wrap them between two porous graphite insulation plates (100mm×100mm×1.5mm). Then, fix them as a whole at the cathode position in the arc plasma furnace, with the side of the low-defect-concentration graphene film facing the anode graphite rod (e.g., Figure 1 (As shown).

[0048] (2) Adjust the distance between the anode and cathode so that the distance between the anode graphite rod and the side end of the low-defect-concentration graphene film is about 1 mm.

[0049] (3) Evacuate the inside of the electric arc plasma furnace to a vacuum, and then fill it with nitrogen. After filling, the gas pressure inside the furnace is 5 kPa.

[0050] (4) Cooling water is introduced into the furnace cavity wall at a temperature of 20°C.

[0051] (5) Apply voltage to the anode and cathode of the arc plasma furnace to induce a plasma arc ignition reaction between them. Control the arc current to be 50A and the heat treatment time to be 2min. Obtain a high-quality graphene expanded film.

[0052] (6) After plasma heat treatment, a high-quality graphene expanded film was removed from the electric arc furnace cavity and calendered using a roll calender at a pressure of 5 MPa to obtain a high-performance graphene thermally conductive film. Raman spectroscopy and thermal conductivity tests were then performed on the film, and the results are as follows: Figure 5 As shown in Table 1.

[0053] Example 2

[0054] Heat treatment of multiple low-defect-concentration graphene films using electric arc plasma

[0055] (1) Cut 10 sheets of low-defect-concentration graphene film (100mm×100mm×0.1mm) prepared in step 1.1, stack them neatly, and wrap them between two porous graphite insulation plates (100mm×100mm×1.5mm). Then, press and fix them as a whole at the cathode position in the arc plasma furnace, so that the side of the low-defect-concentration graphene film faces the anode graphite rod (e.g., Figure 1 (As shown).

[0056] (2) Adjust the distance between the anode and cathode so that the distance between the anode graphite rod and the side end of the low-defect-concentration graphene film is about 1 mm.

[0057] (3) The inside of the electric arc plasma furnace is evacuated to a vacuum, and then hydrogen is introduced. After the introduction is completed, the gas pressure inside the furnace is 15 kPa.

[0058] (4) Cooling water is introduced into the furnace cavity wall at a temperature of 20°C.

[0059] (5) Apply voltage to the anode and cathode of the arc plasma furnace to induce a plasma arc ignition reaction between the anode and cathode. Control the arc current to be 200A and the heat treatment time to be 10min. Obtain a high-quality graphene expanded film.

[0060] (6) After plasma heat treatment, a high-quality graphene expanded film was removed from the electric arc furnace cavity and calendered using a vacuum flat-press calender at a pressure of 15 MPa to obtain a high-performance graphene thermally conductive film. Raman spectroscopy and thermal conductivity tests were then performed, and the results are as follows: Figure 6 As shown in Table 1.

[0061] Example 3

[0062] Thermal treatment of multiple low-defect-concentration graphene films using inductively coupled plasma

[0063] (1) A low-defect-concentration graphene film was prepared according to the method in Example 1.

[0064] (2) Cut 20 sheets of low-defect-concentration graphene film (100mm×100mm×0.1mm) obtained in step (1), stack them neatly, and wrap them between two porous graphite heat insulation plates (100mm×100mm×1.5mm). Then, press and fix them as a whole onto the sample clamping stage at the bottom of the inductively coupled plasma torch device, so that the side of the low-defect-concentration graphene film faces the plasma torch nozzle (e.g., Figure 2 (As shown).

[0065] (3) Evacuate the inside of the plasma furnace to a vacuum, and then fill it with argon gas. After filling, the gas pressure inside the furnace is 5 kPa.

[0066] (4) Cooling water is introduced into the furnace cavity wall at a temperature of 20°C.

[0067] (5) Low-defect-concentration graphene films were heat-treated using an inductively coupled plasma torch. The plasma source was argon, with an argon inlet rate of 10 L / min. The distance between the plasma torch nozzle and the side end of the low-defect-concentration graphene film was 50 mm. The plasma power supply was 30 kW, and the heat treatment time was 20 min. During the heat treatment, a gas pump was used to evacuate the furnace through a evacuation valve to maintain the furnace pressure at approximately 5 kPa. High-quality expanded graphene films were obtained.

[0068] (6) After plasma heat treatment, a high-quality graphene expanded film was removed from the sample clamping stage in the furnace and calendered using a flat press at a pressure of 15 MPa to obtain a high-performance graphene thermally conductive film. Raman spectroscopy and thermal conductivity tests were then performed on the film, and the results are as follows: Figure 7 As shown in Table 1.

[0069] Example 4

[0070] Thermal treatment of multiple low-defect-concentration graphene films using inductively coupled plasma

[0071] (1) A low-defect-concentration graphene film was prepared according to the method in Example 1.

[0072] (2) Cut 20 sheets of low-defect-concentration graphene film (100mm×100mm×0.1mm) obtained in step (1), stack them neatly, and wrap them between two porous graphite heat insulation plates (100mm×100mm×1.5mm). Then, press and fix them as a whole onto the sample clamping stage at the bottom of the inductively coupled plasma torch device, so that the side of the low-defect-concentration graphene film faces the plasma torch nozzle (e.g., Figure 2 (As shown).

[0073] (3) Evacuate the inside of the plasma furnace to a vacuum, and then fill it with argon gas. After filling, the gas pressure inside the furnace is 5 kPa.

[0074] (4) Cooling water is introduced into the furnace cavity wall at a temperature of 20°C.

[0075] (5) Low-defect-concentration graphene films were heat-treated using an inductively coupled plasma torch. The plasma source was argon, with an argon inlet rate of 30 L / min. The distance between the plasma torch nozzle and the side end of the high-quality graphene film was 120 mm. The plasma power supply was 100 kW, and the heat treatment time was 5 min. During the heat treatment, a gas pump was used to evacuate the furnace through a evacuation valve to maintain the furnace pressure at approximately 5 kPa. High-quality expanded graphene films were obtained.

[0076] (6) After plasma heat treatment, a high-quality graphene expanded film was removed from the sample clamping stage in the furnace and calendered using a flat press at a pressure of 15 MPa to obtain a high-performance graphene thermally conductive film. Raman spectroscopy and thermal conductivity tests were then performed on the film, and the results are as follows: Figure 8 As shown in Table 1.

[0077] Comparative Example 1

[0078] The plasma heat treatment process in this comparative embodiment is the same as in Example 1, but the sample treated is a graphene oxide film with very low carbon content, high oxygen content, and many structural defects; that is, the graphene oxide film is directly subjected to arc plasma heat treatment. The preparation method of the graphene oxide film is as follows:

[0079] (1) A graphene oxide (GO) slurry (2% solid content) was uniformly coated onto a polyethylene terephthalate (PET) substrate using a blade coater to obtain a graphene oxide wet film with a thickness of 50 mm.

[0080] (2) The graphene oxide wet film obtained in step (1) is placed in a forced-air drying oven and heated at 50°C for 12 hours to dry it, so as to obtain a graphene oxide dry film with a thickness of 0.5 mm.

[0081] The electric arc plasma heat treatment method is as follows:

[0082] (1) Cut five pieces of the above graphene oxide film (100mm×100mm×0.1mm in size) and wrap them between two porous graphite heat insulation plates (100mm×100mm×1.5mm in size). Then fix them as a whole in the cathode position of the electric arc plasma furnace, so that the side of the graphene oxide film faces the anode graphite rod.

[0083] (2) Adjust the distance between the anode and cathode so that the distance between the anode graphite rod and the side end of the graphene oxide film is about 1 mm.

[0084] (3) Evacuate the inside of the electric arc plasma furnace to a vacuum, and then fill it with nitrogen. After filling, the gas pressure inside the furnace is 5 kPa.

[0085] (4) Cooling water is introduced into the furnace cavity wall at a temperature of 20°C.

[0086] (5) Apply voltage to the anode and cathode of the electric arc plasma furnace, and a plasma arc ignition reaction occurs between the anode and cathode. Control the arc current to 50A and the heat treatment time to 2min.

[0087] (6) After the heat treatment was completed, it was found that the graphene oxide film had been burned and cracked. Figure 9 ).

[0088] Comparative Example 2

[0089] The plasma heat treatment process in this comparative embodiment is the same as that in Example 1, but the sample being treated is a reduced graphene oxide film with low carbon content, high oxygen content, and many structural defects. That is, the reduced graphene oxide film is directly subjected to arc plasma heat treatment.

[0090] The method for preparing the reduced graphene oxide film is as follows:

[0091] (1) A graphene oxide (GO) slurry (2% solid content) was uniformly coated onto a polyethylene terephthalate (PET) substrate using a blade coater to obtain a graphene oxide wet film with a thickness of 50 mm.

[0092] (2) The graphene oxide wet film obtained in step (1) is placed in a forced-air drying oven and heated at 50°C for 12 hours to dry it, so as to obtain a graphene oxide dry film with a thickness of 0.5 mm.

[0093] (3) The graphene oxide film obtained in step (2) is reduced in a high temperature environment of 1000℃ and argon atmosphere, and after being kept at the temperature for 10h, it is naturally cooled to room temperature to obtain the reduced graphene oxide film.

[0094] (4) The reduced film obtained in step (3) is placed in a calender for rolling and calendering to remove the bubbles generated during the reduction process. The calendering pressure is 2 MPa, and a reduced graphene oxide film with a thickness of about 0.1 mm is obtained.

[0095] The electric arc plasma heat treatment method is as follows:

[0096] (1) Cut five pieces of the above-mentioned reduced graphene oxide film (100mm×100mm×0.1mm in size) and wrap them between two porous graphite heat insulation plates (100mm×100mm×1.5mm in size). Then fix them as a whole in the cathode position of the electric arc plasma furnace, so that the side of the reduced graphene oxide film faces the anode graphite rod.

[0097] (2) Adjust the distance between the anode and cathode so that the distance between the anode graphite rod and the side end of the reduced graphene oxide film is about 1 mm.

[0098] (3) Evacuate the inside of the electric arc plasma furnace to a vacuum, and then fill it with nitrogen. After filling, the gas pressure inside the furnace is 5 kPa.

[0099] (4) Cooling water is introduced into the furnace cavity wall at a temperature of 20°C.

[0100] (5) Apply voltage to the anode and cathode of the electric arc plasma furnace, and a plasma arc ignition reaction occurs between the anode and cathode. Control the arc current to 50A and the heat treatment time to 2min.

[0101] (6) After the heat treatment was completed, it was found that the reduced graphene oxide film had been partially ablated and destroyed. Figure 10 ).

[0102] Comparative Example 3

[0103] Compared to Example 1, this comparative example removes the porous graphite plate covering the low-defect-concentration graphene film during the arc plasma heat treatment process, allowing the low-defect-concentration graphene film to be directly exposed to the arc plasma field (e.g., ...). Figure 3 (As shown). The preparation method of the low defect concentration graphene film is exactly the same as in Example 1. The arc plasma heat treatment and rolling method for the low defect concentration graphene film are as follows:

[0104] (1) Cut five sheets of low-defect-concentration graphene film (100mm × 100mm × 0.1mm in size) prepared in step 1.1 and fix them at the cathode position in the arc plasma furnace, so that the side of the high-quality graphene film faces the anode graphite rod (e.g., Figure 3 (As shown).

[0105] (2) Adjust the distance between the anode and cathode so that the distance between the anode graphite rod and the side end of the low-defect-concentration graphene film is about 1 mm.

[0106] (3) Evacuate the inside of the electric arc plasma furnace to a vacuum, and then fill it with nitrogen. After filling, the gas pressure inside the furnace is 5 kPa.

[0107] (4) Cooling water is introduced into the furnace cavity wall at a temperature of 20°C.

[0108] (5) Apply voltage to the anode and cathode of the arc plasma furnace to induce a plasma arc ignition reaction between them. Control the arc current to be 50A and the heat treatment time to be 2min. Obtain a high-quality graphene expanded film.

[0109] (6) After plasma heat treatment, a high-quality graphene expanded film was removed from the electric arc furnace cavity and calendered using a roll calender at a pressure of 5 MPa to obtain a high-performance graphene thermally conductive film. Raman spectroscopy and thermal conductivity tests were then performed on the film, and the results are as follows: Figure 11 As shown in Table 1.

[0110] Comparative Example 4

[0111] Compared to Example 1, this comparative example adjusts the clamping and fixing direction of the low-defect-concentration graphene film during the arc plasma heat treatment process. The fixing direction was changed from the side of the low-defect-concentration graphene film facing the anode graphite rod in Example 1 to the front of the low-defect-concentration graphene film facing the anode graphite rod. Furthermore, the porous graphite plate covering the low-defect-concentration graphene film was removed, allowing the low-defect-concentration graphene film to be directly exposed to the arc plasma field (e.g., ...). Figure 4 (As shown). The preparation method of the low defect concentration graphene film is exactly the same as in Example 1. The arc plasma heat treatment and rolling method for the low defect concentration graphene film are as follows:

[0112] (1) Cut five low-defect-concentration graphene films (100mm × 100mm × 0.1mm in size), place and fix them on a porous graphite plate (100mm × 100mm × 1.5mm in size), and then fix them at the cathode position in the arc plasma furnace. The front side of the low-defect-concentration graphene film should face the anode graphite rod (e.g., Figure 4 (As shown).

[0113] (2) Adjust the distance between the anode and cathode so that the distance between the anode graphite rod and the front side of the low-defect-concentration graphene film is about 1 mm.

[0114] (3) Evacuate the inside of the electric arc plasma furnace to a vacuum, and then fill it with nitrogen. After filling, the gas pressure inside the furnace is 5 kPa.

[0115] (4) Cooling water is introduced into the furnace cavity wall at a temperature of 20°C.

[0116] (5) Apply voltage to the anode and cathode of the arc plasma furnace to induce a plasma arc ignition reaction between them. Control the arc current to be 50A and the heat treatment time to be 2min. Obtain a high-quality graphene expanded film.

[0117] (6) After plasma heat treatment, a high-quality graphene film was removed from the electric arc furnace chamber and calendered using a roll calender at a pressure of 5 MPa to obtain a high-performance graphene thermally conductive film. Raman spectroscopy and thermal conductivity tests were then performed on the film, and the results are as follows: Figure 12 As shown in Table 1.

[0118] Comparative Example 5

[0119] Compared to Example 1, this comparative example does not use arc plasma to heat-treat the low-defect-concentration graphene film. Instead, it uses a conventional graphitization furnace to perform high-temperature heat treatment on the low-defect-concentration graphene film. The preparation method of the low-defect-concentration graphene film is exactly the same as in Example 1. The high-temperature heat treatment and calendering methods for the low-defect-concentration graphene film are as follows:

[0120] (1) Cut a low-defect-concentration graphene film (100mm×100mm×0.1mm in size) and place it in a graphite boat and put it into a graphitization furnace.

[0121] (2) The furnace temperature was raised from room temperature to 1000℃ at a heating rate of 5.5℃ / min, then raised to 2700℃ at a heating rate of 1.9℃ / min, and finally raised to 3150℃ at a heating rate of 1.5℃ / min, and held at that temperature for 2 hours. Throughout the heat treatment process, argon gas was kept flowing through the graphitization furnace at a flow rate of 10L / min to ensure an inert gas environment inside the furnace.

[0122] (3) After the graphitization heat treatment is completed, the power to the graphitization furnace is turned off. The sample is removed from the furnace when it cools to 200°C. It is then calendered using a roll calender at a pressure of 5 MPa. The resulting graphene film is subjected to Raman spectroscopy and thermal conductivity tests. The results are as follows: Figure 13 As shown in Table 1.

[0123] Test methods

[0124] The thermal conductivity of the graphene film was measured using a Netzsch LFA 467 thermal conductivity meter via laser scintillation.

[0125] Table 1 shows the thermal conductivity test data of the graphene films in Examples 1-4 and Comparative Examples 1-5. According to the data in the table, both arc plasma heat treatment and inductively coupled plasma heat treatment can significantly improve the thermal conductivity of graphene films with low defect concentration (Examples 1-4), with the lowest improvement approaching 40% (38.81%, Example 1) and the highest reaching 47.64% (Example 2). The thermal conductivity of the treated graphene films all exceed 1800 W / mK, which is a leading level in the industry. In stark contrast, the thermal conductivity improvement of graphene films heat-treated in a conventional graphitization furnace is only 10.67% (Comparative Example 5). Furthermore, Raman spectroscopy tests reveal ( Figure 5-8 After plasma heat treatment, the structure of graphene films undergoes significant changes. The ratio of the intensities of the D peak to the G peak in the Raman spectrum is I. D / I G The significant reduction after heat treatment indicates that the effective utilization of ultra-high temperatures in plasma heat treatment can effectively reduce the defect concentration of high-quality graphene films, thereby improving the thermal conductivity of the graphene films. Comparative test results show that when directly treating graphene oxide and reduced graphene oxide films with many defects, the localization of ultra-high plasma temperatures, coupled with the low thermal conductivity of these films, leads to heat accumulation and the generation of large amounts of gas, damaging the film structure. Therefore, it is impossible to directly prepare high-performance graphene thermally conductive films. In avoiding the disadvantages of plasma ultra-high temperature localization and fully utilizing the characteristics of ultra-high plasma temperatures, the comparative results show that the clamping method of the graphene film and the plasma heat treatment process are crucial. Thermal insulation and side heat treatment of low-defect-concentration graphene films are key to preparing high-performance graphene thermally conductive films. Thermal insulation can concentrate the heat of the plasma on the sample to be treated, reducing heat loss to the environment. Side-mounted plasma heat treatment fully utilizes the high lateral thermal conductivity of the low-defect-concentration graphene film to transfer heat to all parts of the sample. It also avoids the problem of insufficient heat transfer to all samples when front-mounted plasma heat treatment of low-defect-concentration graphene films due to low longitudinal thermal conductivity. Comparative Example 5 shows that plasma heat treatment is significantly superior to traditional graphitization furnaces. Furthermore, plasma heat treatment reduces the heat treatment time from tens of hours required in conventional graphitization furnaces to minutes, and can simultaneously process dozens of high-quality graphene films, significantly reducing energy consumption and cost, making it ideal for the industrial production of high-performance graphene thermally conductive films.

[0126] Table 1. Comparison of thermal conductivity of graphene films in Examples 1-4 and Comparative Examples 1-5

[0127] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-performance graphene thermally conductive film, characterized in that, The preparation method includes the following steps: S1 provides a low-defect-concentration graphene film with a thermal conductivity of not less than 1200 W / mK, wherein the carbon content of the low-defect-concentration graphene film is greater than 95 at.%, and the intensity of the defect characteristic peak (I) in its Raman spectrum is... D ) and intrinsic characteristic peak intensity (I G The ratio of () is less than 0.05; S2, at least one layer of low-defect-concentration graphene film is fixed in the plasma device by a double-sided covering and clamping method with a heat insulation layer so that the plasma can directly act on the low-defect-concentration graphene film. S3, in an inert or reducing atmosphere, an ultra-high temperature plasma is induced to treat a graphene film with low defect concentration from the side, thereby obtaining a high-quality graphene expanded film. S4, densification treatment is performed on a high-quality graphene expanded film to obtain a high-performance graphene thermal conductive film.

2. The preparation method according to claim 1, characterized in that, In step S2, the double-sided covering and clamping method of the heat insulation layer is to completely cover the surface of the low-defect-concentration graphene film with a porous graphite plate as the heat insulation layer and press it tightly together.

3. The preparation method according to claim 1, characterized in that, In step S2, the plasma device is an arc plasma device or an inductively coupled plasma device.

4. The preparation method according to claim 3, characterized in that, In an arc plasma device, a low-defect-concentration graphene film is fixed to the cathode position in the arc plasma furnace with a double-sided heat insulation layer, so that the side of the low-defect-concentration graphene film faces the anode graphite rod; or in an inductively coupled plasma device, the low-defect-concentration graphene film is fixed to the sample clamping stage at the bottom of the inductively coupled plasma torch device with a double-sided heat insulation layer, so that the side of the low-defect-concentration graphene film faces the plasma torch nozzle.

5. The preparation method according to claim 3, characterized in that, The parameters for arc plasma treatment include: gas pressure in the reaction chamber 5-15 kPa, arc current 50-200 A, and treatment time 2-10 min; or the parameters for inductively coupled plasma treatment include: plasma power supply frequency 27.12 MHz, power supply power 30-100 KW, gas inlet speed 10-30 L / min, and treatment time 5-20 min.

6. The preparation method according to claim 1, characterized in that, In step S3, the inert or reducing atmosphere is one of argon, nitrogen, hydrogen, or a combination thereof.

7. The preparation method according to claim 1, characterized in that, In step S4, the densification process is performed by roller pressing or flat pressing.

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