High-thermal-conductivity graphene heat dissipation film and preparation method thereof

Abstract

The application relates to the technical field of heat-conducting materials, in particular to a high-heat-conducting graphene heat-dissipation film and a preparation method thereof. The heat-dissipation film comprises the following raw materials: graphene oxide; an interlayer bridging agent for combining graphene layers; a special reagent for improving surface tension and pre-dissolving the interlayer bridging agent; and a pH regulator for adjusting the pH of the solution to 6-7. The application improves the heat-conducting performance of the heat-dissipation film by introducing the interlayer bridging agent, and improves the order and integrity of the interlayer arrangement through a preparation method of lower-temperature graphitization treatment, lower-pressure calendering, higher-temperature graphitization treatment and higher-pressure calendering, thereby improving the heat-conducting rate of the heat-dissipation film and the heat-dissipation performance of the graphene heat-dissipation film.

Description

Technical Field

[0001] This invention relates to the field of thermal conductive materials technology, and in particular to a high thermal conductivity graphene heat dissipation film and its preparation method. Background Technology

[0002] With the continuous development and progress of science and technology and the continuous improvement of people's living standards, all kinds of consumer electronics products (smartphones, tablets, and various wearable smart devices, etc.) have entered the daily lives of ordinary people. Consequently, people's requirements for electronic products are also gradually upgrading, such as higher screen display fidelity, faster operating response speed, higher component packaging density, and faster heat dissipation.

[0003] Regarding the technical challenges of heat dissipation, on the one hand, reducing the weight of mobile terminals is essential for improving the user experience. Manufacturers are making every effort to "slim down" bulky heat sinks and develop fanless cooling devices. On the other hand, multi-core chips have become mainstream, leading to a surge in heat dissipation. Effective heat dissipation plays a crucial role in operating speed, but the contact gaps between heat sinks and component surfaces create significant thermal resistance, becoming a bottleneck for heat dissipation in most devices. For electronic products, effective chip heat dissipation allows them to maintain lower operating temperatures, thereby significantly increasing lifespan and operating speed. Research shows that for every 2°C increase in electronic component temperature, reliability decreases by 10%; the lifespan at a 50°C temperature rise is only 1 / 6 of that at a 25°C temperature rise. Therefore, how to quickly dissipate heat in a confined space is a pressing issue for current mobile smart terminal electronic products, and the advent of the 5G era has exacerbated this problem. Researchers have tried numerous materials, such as thermal grease, carbon nanotubes, and carbon nanofibers, but none have yet provided a truly effective solution.

[0004] The emergence of graphene heat dissipation films has further solved this problem. Graphene heat dissipation films are high-performance heat dissipation films derived from the heat treatment of graphene oxide. They possess excellent mechanical properties, high thermal conductivity, light weight, thin material, and good flexibility, providing high-quality and economical complete heat dissipation solutions for industries such as electronics, aerospace, and medical. Furthermore, pure graphene heat dissipation films have significant advantages in thermal conductivity and heat flux, making them more suitable for the heat dissipation requirements of smartphones in the 5G era.

[0005] Existing graphene heat dissipation films typically involve first preparing graphene oxide into a slurry, coating it into a film, and then subjecting it to heat treatment and post-treatment. For example, Chinese invention patent application number 201910429144.1 provides a pre-reduced graphene oxide film and its preparation method, as well as a graphene thermally conductive film and its preparation method. This method involves adding a chemical reducing agent to the graphene oxide slurry to prepare a pre-reduced graphene oxide film, and then further treating the graphene oxide film using a thermal reduction method to obtain the graphene thermally conductive film. Another Chinese invention patent application number 201910404255.7 provides a graphene oxide composite carbon source mixture and its preparation method, as well as a graphene thermally conductive film and its preparation method. This invention introduces a carbon source dispersion during the preparation of graphene oxide, allowing the carbon source to be uniformly and stably inserted into the interlayer of graphene oxide and enabling the graphene oxide to be fully exfoliated, thereby improving the thermal conductivity of the graphene thermally conductive film.

[0006] Thermal conductivity is a key performance indicator of graphene heat dissipation films. The formula for calculating the thermal conductivity of graphene heat dissipation films is K=αρC. p Where α is the thermal diffusivity, ρ is the density, and C is the thermal diffusivity. p To achieve isobaric specific heat capacity, improving the thermal conductivity of a heat dissipation film mainly involves increasing α and ρ through appropriate methods. Current preparation techniques typically employ only one ultra-high temperature (≥3000℃) treatment and one high-pressure equalization to improve α and ρ respectively. This heavily relies on the processing capabilities of the equipment, which has essentially reached its limits. The resulting heat dissipation films exhibit suboptimal thermal conductivity, making further performance improvements impossible, and also suffer from excessive energy consumption. Summary of the Invention

[0007] Based on the above-mentioned technical problems, the present invention provides a high thermal conductivity graphene heat dissipation film and its preparation method. On the one hand, the microstructure of the heat dissipation film is improved by introducing an interlayer bridging agent. On the other hand, the preparation method of lower temperature graphitization treatment → lower pressure calendering → higher temperature graphitization treatment → higher pressure calendering improves the orderliness and integrity of the interlayer arrangement, thereby improving the thermal conductivity of the heat dissipation film and thus improving the heat dissipation performance of the graphene heat dissipation film.

[0008] The first technical problem solved by this invention is to provide a high thermal conductivity graphene heat dissipation film, comprising the following raw materials:

[0009] Graphene oxide;

[0010] Interlayer bridging agent, used for interlayer bonding of graphene sheets;

[0011] Special reagents for improving surface tension and pre-dissolving interlayer bridging agents;

[0012] pH adjuster, used to adjust the pH of a solution to 6-7.

[0013] Furthermore, the amount of graphene oxide added is 3-10 wt% of the total raw materials, the amount of special reagent added is 0.5-5.5 wt% of the total raw materials, and the amount of interlayer bridging agent added is 1 / 40 to 1 / 10 of the amount of graphene oxide.

[0014] Preferably, the interlayer bridging agent is a compound of silicate esters and inorganic acids in a mass ratio of 4 to 12:1.

[0015] Preferably, the interlayer bridging agent is a compound of silicate esters and inorganic acids.

[0016] Preferably, the silicate ester is one of tetraethyl orthosilicate, methyl orthosilicate, and propyl orthosilicate.

[0017] Preferably, the inorganic acid is boric acid.

[0018] In a preferred embodiment, the interlayer bridging agent is a compound of tetraethyl silicate and boric acid in a mass ratio of 5 to 10:1.

[0019] In a more preferred embodiment, the interlayer bridging agent is a compound of tetraethyl silicate and boric acid in a mass ratio of 8.4:1.

[0020] Preferably, the pH adjuster is ammonia water with a concentration of 22-25%.

[0021] Preferably, the special reagent is one or more of ethanol, PEG200, diethyl ether, acetone, ethyl acetate, and isopropanol.

[0022] The second technical problem solved by this invention is to provide a method for preparing a high thermal conductivity graphene heat dissipation film, comprising the following steps:

[0023] (1) Add the interlayer bridging agent to the special reagent and mix thoroughly to obtain a premixed solution for later use;

[0024] (2) Add water, graphene oxide and premixed liquid to a mixer in sequence and mix thoroughly. Stir at low speed for more than 60 minutes. Add pH adjuster to the mixer and mix to obtain a mixture.

[0025] (3) The mixture is transferred to a high-pressure homogenizer for homogenization. After homogenization, the mixture is degassed and then coated and dried to form a film.

[0026] (4) After cutting the dried film, put it into the carbonization furnace and process it at 300-350℃ for 4.5-7.5h under nitrogen protection. Then, continue to heat it to 2100-2200℃ for 2h under argon protection to perform the first graphitization. Cool it to room temperature to obtain a first pre-made rough film.

[0027] (5) The first preformed rough film is subjected to the first calendering treatment to obtain the first graphene film. The first graphene film is placed in the graphitization furnace and heated to 2600-2800℃ under argon protection. It is held for 1 hour for the second graphitization and then cooled to room temperature to obtain the second preformed rough film.

[0028] (6) The pre-fabricated coarse film is subjected to a second calendering process to obtain a graphene heat dissipation film.

[0029] Furthermore, in step (2), the mixing time of water and graphene oxide in the mixer shall not be less than 30 min, and the interval between adding pH adjuster and premixed liquid to the mixer shall not be less than 10 min.

[0030] Furthermore, the low-speed stirring in step (2) uses a double planetary mixer with a planetary speed of 20-50 rpm and a dispersion disc speed of 800-1200 rpm.

[0031] Preferably, the pressure of the homogenization process in step (3) is 600~900 bar and the rotation speed is 35~40 Hz.

[0032] This invention creatively employs a silicate ester and boric acid complex as an interlayer bridging agent. Utilizing the hydrolysis reaction of boric acid and silicate esters, it condenses with hydroxyl groups in graphene oxide in the presence of concentrated ammonia. During heat treatment, it tightly bonds with the graphene sheet framework, acting as a bridging agent to improve interlayer heat transfer and enhance the heat dissipation effect of the heat dissipation film. Furthermore, existing technologies mostly use organic bridging agents, which inevitably carbonize at high temperatures and eventually rearrange into the graphene framework's chemical structure, thus not being present in the final product. The interlayer bridging agent used in this invention not only exists in the product but also further performs functions beyond bridging.

[0033] Taking boric acid and tetraethyl silicate as an example: boric acid and tetraethyl silicate condense with hydroxyl groups in graphene oxide in the presence of concentrated ammonia water. After low-temperature heat treatment to remove SiO2 and B2O3, they undergo a high-temperature treatment above 2100℃ to produce SiC and B4C by C substitution of oxygen in SiO2 and B2O3. The presence of these two substances acts as a bridge between layers, improving the heat dissipation performance between graphite layers. Finally, after high-temperature treatment above 2600~2800℃, the carbon elements after SiC decompose are used to repair defects in the graphene sheets, while B4C exists in the material. Due to the further repair of the structure and the presence of the highly thermally conductive B4C, its overall thermal conductivity is further improved.

[0034] Its high thermal conductivity can further improve heat dissipation.

[0035] In addition, special reagents are used, such as ethanol, PEG200, diethyl ether, acetone, ethyl acetate, or isopropanol. These special reagents not only improve surface tension to ensure smooth and uniform mixing of the mixture, thus playing a pre-dispersion role, preventing agglomeration, and ensuring a good forward reaction, but also effectively alleviate the problem of polarity mismatch between water and graphene oxide by using a solvent with lower polarity than water for mixing.

[0036] In terms of preparation method, this invention uses a process of "lower temperature graphitization treatment → lower pressure calendering → higher temperature graphitization treatment → higher pressure calendering". After graphitization occurs naturally at a lower temperature (2100-2200℃), it is pressed using a flat press. Under the action of external force, the layers are brought closer together, making it easier to improve the graphitization effect again. Then, it is graphitized again at a higher temperature (2600-2800℃) using the graphitization reaction that occurs at high temperature. This method improves the orderliness and integrity of the interlayer arrangement, which can significantly improve the thermal conductivity of the heat dissipation film in the horizontal direction, thereby obtaining an ultra-high performance graphene heat dissipation film.

[0037] The beneficial effects of this invention are:

[0038] By introducing interlayer bridging agents to alter the interlayer structure of graphene, and by employing a preparation method involving lower-temperature graphitization → lower-pressure calendering → higher-temperature graphitization → higher-pressure calendering, the orderliness and integrity of the interlayer arrangement are improved, thereby increasing the thermal conductivity of the heat dissipation film and thus enhancing its heat dissipation performance. Attached Figure Description

[0039] Figure 1 Here is a SEM image of the graphene heat dissipation film obtained in Example 3;

[0040] Figure 2 The image shows a SEM image of the graphene heat dissipation film obtained in Comparative Example 2. Implementation

[0041] A high thermal conductivity graphene heat dissipation film comprises the following raw materials:

[0042] Graphene oxide, a core raw material for high thermal conductivity graphene heat dissipation films;

[0043] Interlayer bridging agent, used for interlayer bonding of graphene sheets;

[0044] Special reagents for improving surface tension and pre-dissolving interlayer bridging agents;

[0045] pH adjuster, used to adjust the pH of a solution to 6-7.

[0046] The amount of graphene oxide added is 3 to 10 wt% of the total amount of raw materials, preferably 4 to 8 wt% of the total amount of raw materials, and more preferably 4.5 to 6.5 wt% of the total amount of raw materials.

[0047] The amount of special reagent added is 0.5 to 5.5 wt% of the total amount of raw materials, preferably 1.0 to 2.5 wt% of the total amount of raw materials, and even more preferably 1.0 to 2.0 wt% of the total amount of raw materials.

[0048] The amount of interlayer bridging agent added is 1 / 40 to 1 / 10 of the graphene oxide, preferably 1 / 30 to 1 / 10 of the graphene oxide.

[0049] Preferably, the interlayer bridging agent is a compound of silicate esters and inorganic acids in a mass ratio of 4-12:1.

[0050] Furthermore, the silicate ester is one or more of tetraethyl orthosilicate, methyl orthosilicate, propyl orthosilicate, and water-soluble silicone oil.

[0051] Preferably, the silicate ester is tetraethyl silicate.

[0052] Preferably, the inorganic acid is boric acid.

[0053] In a preferred embodiment, the interlayer bridging agent is a compound of tetraethyl silicate and boric acid in a mass ratio of 5 to 10:1.

[0054] In a specific preferred embodiment, the interlayer bridging agent is a compound of tetraethyl silicate and boric acid in a mass ratio of 8.4:1.

[0055] Preferably, the pH adjuster is ammonia water with a concentration of 22-25%.

[0056] Preferably, the special reagent is one or more of ethanol, PEG200, diethyl ether, acetone, ethyl acetate, and isopropanol.

[0057] A method for preparing a high thermal conductivity graphene heat dissipation film includes the following steps:

[0058] (1) Add the interlayer bridging agent to the special reagent and mix thoroughly to obtain a premixed solution for later use;

[0059] (2) Add water, graphene oxide and premixed liquid to a mixer in sequence and mix thoroughly. Stir at low speed for more than 60 minutes. Add pH adjuster to the mixer and mix to obtain a mixture.

[0060] (3) The mixture is transferred to a high-pressure homogenizer for homogenization. After homogenization, the mixture is degassed and then coated and dried to form a film.

[0061] (4) After cutting the dried film, put it into the carbonization furnace and process it at 300-350℃ for 4.5-7.5h under nitrogen protection. Then, continue to heat it to 2100-2200℃ for 2h under argon protection to perform the first graphitization. Cool it to room temperature to obtain a first pre-made rough film.

[0062] (5) The first preformed rough film is subjected to the first calendering treatment to obtain the first graphene film. The first graphene film is placed in the graphitization furnace and heated to 2600-2800℃ under argon protection. It is held for 1 hour for the second graphitization and then cooled to room temperature to obtain the second preformed rough film.

[0063] (6) The pre-fabricated coarse film is subjected to a second calendering process to obtain a graphene heat dissipation film.

[0064] Furthermore, there are certain restrictions on the order and timing of the raw materials being added to the mixer in step (2). Specifically, the mixing time of water and graphene oxide in the mixer shall not be less than 30 minutes, and the interval between adding the pH adjuster and the premixed liquid to the mixer shall not be less than 10 minutes.

[0065] Preferably, the low-speed stirring in step (2) is carried out using a double planetary mixer with a planetary speed of 20-50 rpm and a dispersion disc speed of 800-1200 rpm.

[0066] In one specific embodiment, the rotation speed of the dual planetary mixer is set to 45 rpm, and the rotation speed of the dispersion disc is set to 1000 rpm. First, water is added to the mixer, then graphene oxide is added to the mixer containing water and mixed evenly for 35 minutes. Then, the premixed liquid is added to the mixer and stirred for another 35 minutes. Concentrated ammonia is added and stirred for another 15 minutes to obtain the final mixture.

[0067] Preferably, the homogenization process in step (3) is performed at a pressure of 1000-1200 bar, a rotation speed of 35-40 Hz, and a homogenization time of 20-30 min.

[0068] Furthermore, in step (3), two homogenization processes are performed. Specifically, the same pressure and speed parameters are used to perform two consecutive homogenization processes without adding any liquid components or adjusting the flow rate.

[0069] Furthermore, the coating in step (3) adopts the industry's traditional coating method, and the coating process is dried at 75~95℃. The coating thickness is 1~3mm, and the width is 650~1200mm.

[0070] Preferably, the drying film is cut to a size of 300mm*300mm in step (4).

[0071] Preferably, the pressure of the first rolling in step (5) is 20-30 MPa.

[0072] Preferably, the pressure of the secondary rolling in step (6) is 40-45 MPa.

[0073] In comparison, the graphene film obtained from the first calendering process is 105-110% thicker than the graphene heat dissipation film obtained from the second calendering process; its density is 90-98% of that of the graphene heat dissipation film; its thermal conductivity is 75-92% of that of the graphene heat dissipation film; and its flatness is also higher. In other words, the product performance is improved after the second calendering process.

[0074] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0075] The following describes the types of raw materials used in the examples. All examples use raw materials of the same specifications.

[0076] Graphene oxide: Changzhou Sixth Element Technology Materials Co., Ltd., model SE243EW;

[0077] Boric acid: Chengdu Kelong Chemical Co., Ltd., AR grade;

[0078] Tetraethyl silicate: Chengdu Kelong Chemical Co., Ltd., AR grade, liquid;

[0079] Methyl orthosilicate: Guangzhou Longkai Chemical Co., Ltd., AR grade, liquid;

[0080] Propylene orthosilicate: Guangzhou Longkai Chemical Co., Ltd., AR grade, liquid.

[0081] Unless otherwise specified, all "%" in this application refers to mass percentage, and all ratios mentioned in this application refer to mass ratio.

[0082] Example 1

[0083] A method for preparing a high thermal conductivity graphene heat dissipation film

[0084] 1. Raw material preparation

[0085] Graphene oxide, added at 8 wt% of the total raw material;

[0086] Interlayer bridging agent, the amount added is 1 / 30 of the amount of graphene oxide added; the interlayer bridging agent is a compound of methyl orthosilicate and boric acid in a mass ratio of 7.5:1;

[0087] Ethanol, added at a rate of 1.5 wt% of the total raw materials;

[0088] Concentrated ammonia solution with a concentration of 25%;

[0089] The remainder is water.

[0090] 2. Preparation of high thermal conductivity graphene heat dissipation film

[0091] (1) Add the interlayer bridging agent to ethanol and mix thoroughly to obtain a premixed solution for later use.

[0092] (2) Set the speed of the double planetary mixer to 45 rpm and the speed of the dispersion disc to 1000 rpm.

[0093] First, put water into the mixer and turn on the mixer. Then, add graphene oxide into the mixer and mix evenly for 35 minutes. Next, add the premixed solution into the mixer and continue mixing for 35 minutes. Add concentrated ammonia to adjust the pH of the solution to 6.5 and continue mixing for 15 minutes to obtain the mixture.

[0094] (3) Set the pressure of the high pressure homogenizer to 800 bar and the speed to 40 Hz.

[0095] The mixture was transferred to a high-pressure homogenizer for homogenization for 60 minutes. After degassing, the homogenized mixture was coated with a coating thickness of 3±0.2 mm and a width of 700±5 mm to obtain a dried film.

[0096] (4) Cut the dried film into 300mm*300mm pieces and put them into a carbonization furnace. Under nitrogen protection, the temperature is programmed to rise to 350℃ for 7 hours. Under argon protection, the temperature is further raised to 2200℃ and held for 2 hours for graphitization. The film is then cooled to room temperature to obtain a pre-made rough film.

[0097] (5) The first preformed rough film is subjected to the first calendering process with a calendering pressure of 25 MPa to obtain a first graphene film. The first graphene film is placed in a graphitization furnace and heated to 2700℃ under argon protection. It is held for 1 hour for the second graphitization and then cooled to room temperature to obtain a second preformed rough film.

[0098] (6) The pre-fabricated rough film is subjected to a second calendering process with a calendering pressure of 40 MPa to obtain a graphene heat dissipation film. Example

[0099] A method for preparing a high thermal conductivity graphene heat dissipation film

[0100] 1. Raw material preparation

[0101] Graphene oxide, added at 6 wt% of the total raw materials;

[0102] Interlayer bridging agent, the amount added is 1 / 30 of the amount of graphene oxide added; the interlayer bridging agent is a compound of tetraethyl silicate and boric acid in a mass ratio of 8:1;

[0103] PEG200, added at a rate of 3.2 wt% of the total raw material;

[0104] Concentrated ammonia solution with a concentration of 25%;

[0105] The remainder is water.

[0106] 2. Preparation of high thermal conductivity graphene heat dissipation film

[0107] (1) Add the interlayer bridging agent to ethanol and mix thoroughly to obtain a premixed solution for later use.

[0108] (2) Set the speed of the double planetary mixer to 45 rpm and the speed of the dispersion disc to 1000 rpm.

[0109] First, put water into the mixer and turn on the mixer. Then, add graphene oxide into the mixer and mix evenly for 30 minutes. Next, add the premixed solution into the mixer and continue mixing for 40 minutes. Add concentrated ammonia to adjust the pH of the solution to 6.5 and continue mixing for 10 minutes to obtain the mixture.

[0110] (3) Set the pressure of the high pressure homogenizer to 900 bar and the speed to 40 Hz.

[0111] The mixture was transferred to a high-pressure homogenizer for homogenization for 60 minutes. After degassing, the homogenized mixture was coated with a coating thickness of 3±0.2 mm and a width of 700±5 mm to obtain a dried film.

[0112] (4) Cut the dried film into 300mm*300mm pieces and put them into a carbonization furnace. Under nitrogen protection, the temperature is programmed to rise to 350℃ for 7 hours. Under argon protection, the temperature is further raised to 2200℃ and held for 2 hours for graphitization. The film is then cooled to room temperature to obtain a pre-made rough film.

[0113] (5) The first preformed rough film is subjected to a first calendering process with a calendering pressure of 25 MPa to obtain a first graphene film. The first graphene film is placed in a graphitization furnace and heated to 2800℃ under argon protection. It is held for 1 hour for a second graphitization and then cooled to room temperature to obtain a second preformed rough film.

[0114] (6) The pre-fabricated rough film is subjected to a second calendering process with a calendering pressure of 40 MPa to obtain a graphene heat dissipation film.

[0115] Example 3

[0116] A method for preparing a high thermal conductivity graphene heat dissipation film

[0117] 1. Raw material preparation

[0118] Graphene oxide, added at a rate of 5.5 wt% of the total raw material;

[0119] Interlayer bridging agent, the amount added is 1 / 10 of the amount of graphene oxide added; the interlayer bridging agent is a compound of tetraethyl silicate and boric acid in a mass ratio of 8.4:1;

[0120] Ethanol, added at a rate of 1.5 wt% of the total raw materials;

[0121] Concentrated ammonia solution with a concentration of 25%;

[0122] The remainder is water.

[0123] 2. Preparation of high thermal conductivity graphene heat dissipation film

[0124] (1) Add the interlayer bridging agent to ethanol and mix thoroughly to obtain a premixed solution for later use.

[0125] (2) Set the speed of the double planetary mixer to 45 rpm and the speed of the dispersion disc to 1000 rpm.

[0126] First, put water into the mixer and turn on the mixer. Then, add graphene oxide into the mixer and mix evenly for 35 minutes. Next, add the premixed solution into the mixer and continue mixing for 35 minutes. Add concentrated ammonia to adjust the pH of the solution to 6.5 and continue mixing for 15 minutes to obtain the mixture.

[0127] (3) Set the pressure of the high pressure homogenizer to 800 bar and the speed to 40 Hz.

[0128] The mixture was transferred to a high-pressure homogenizer and homogenized for 30 minutes. The homogenized mixture was then degassed. After degassed, it was homogenized again for 30 minutes. The high-pressure homogenizer parameters remained unchanged for both homogenization processes; no liquid components were added or the flow rate was adjusted. The homogenized mixture was then degassed again. The mixture was then removed and coated with a coating to a thickness of 3 ± 0.2 mm and a width of 700 ± 5 mm to obtain a dried film.

[0129] (4) Cut the dried film into 300mm*300mm pieces and put them into a carbonization furnace. Under nitrogen protection, the temperature is programmed to rise to 350℃ for 7 hours. Under argon protection, the temperature is further raised to 2200℃ and held for 2 hours for graphitization. The film is then cooled to room temperature to obtain a pre-made rough film.

[0130] (5) The first preformed rough film is subjected to a first calendering process with a calendering pressure of 25 MPa to obtain a first graphene film. The first graphene film is placed in a graphitization furnace and heated to 2800℃ under argon protection. It is held for 1 hour for a second graphitization and then cooled to room temperature to obtain a second preformed rough film.

[0131] (6) The pre-fabricated rough film is subjected to a second calendering process with a calendering pressure of 40 MPa to obtain a graphene heat dissipation film.

[0132] The obtained graphene heat dissipation film was scanned using a scanning electron microscope to observe its microstructure. The results are as follows: Figure 1 As shown.

[0133] Example 4

[0134] A method for preparing a high thermal conductivity graphene heat dissipation film

[0135] 1. Raw material preparation

[0136] Graphene oxide, added at 10 wt% of the total raw material;

[0137] Interlayer bridging agent, the amount added is 1 / 30 of the amount of graphene oxide added; the interlayer bridging agent is a compound of tetraethyl silicate and boric acid in a mass ratio of 5:1;

[0138] Ethanol, added at a rate of 1.5 wt% of the total raw materials;

[0139] Concentrated ammonia solution with a concentration of 25%;

[0140] The remainder is water.

[0141] 2. Preparation of high thermal conductivity graphene heat dissipation film

[0142] (1) Add the interlayer bridging agent to ethanol and mix thoroughly to obtain a premixed solution for later use.

[0143] (2) Set the speed of the double planetary mixer to 45 rpm and the speed of the dispersion disc to 1000 rpm.

[0144] First, put water into the mixer and turn on the mixer. Then, add graphene oxide into the mixer and mix evenly for 35 minutes. Next, add the premixed solution into the mixer and continue mixing for 35 minutes. Add concentrated ammonia to adjust the pH of the solution to 6.5 and continue mixing for 15 minutes to obtain the mixture.

[0145] (3) Set the pressure of the high pressure homogenizer to 800 bar and the speed to 40 Hz.

[0146] The mixture was transferred to a high-pressure homogenizer and homogenized for 30 minutes. The homogenized mixture was then degassed. After degassed, it was homogenized again for 30 minutes. The high-pressure homogenizer parameters remained unchanged for both homogenization processes; no liquid components were added or the flow rate was adjusted. The homogenized mixture was then degassed again. The mixture was then removed and coated with a coating to a thickness of 3 ± 0.2 mm and a width of 700 ± 5 mm to obtain a dried film.

[0147] (4) Cut the dried film into 300mm*300mm pieces and put them into a carbonization furnace. Under nitrogen protection, the temperature is programmed to rise to 350℃ for 7 hours. Under argon protection, the temperature is further raised to 2200℃ and held for 2 hours for graphitization. The film is then cooled to room temperature to obtain a pre-made rough film.

[0148] (5) The first preformed rough film is subjected to a first calendering process with a calendering pressure of 25 MPa to obtain a first graphene film. The first graphene film is placed in a graphitization furnace and heated to 2800℃ under argon protection. It is held for 1 hour for a second graphitization and then cooled to room temperature to obtain a second preformed rough film.

[0149] (6) The pre-fabricated rough film is subjected to a second calendering process with a calendering pressure of 40 MPa to obtain a graphene heat dissipation film.

[0150] Comparative Example 1:

[0151] The raw materials and amounts used in this comparative example are the same as those in Example 3.

[0152] Preparation of high thermal conductivity graphene heat dissipation film

[0153] (1) Add the interlayer bridging agent to ethanol and mix thoroughly to obtain a premixed solution for later use.

[0154] (2) Set the speed of the double planetary mixer to 45 rpm and the speed of the dispersion disc to 1000 rpm.

[0155] First, put water into the mixer and turn on the mixer. Then, add graphene oxide into the mixer and mix evenly for 35 minutes. Next, add the premixed solution into the mixer and continue mixing for 35 minutes. Add concentrated ammonia to adjust the pH of the solution to 6.5 and continue mixing for 15 minutes to obtain the mixture.

[0156] (3) Take out the mixture and coat it with a coating thickness of 3±0.2mm and a width of 700±5mm to obtain a dry film.

[0157] (4) Cut the dried film into 300mm*300mm pieces and put them into a carbonization furnace. Under nitrogen protection, the temperature is programmed to rise to 350℃ for 7 hours. Under argon protection, the temperature is further raised to 2200℃ and held for 2 hours for graphitization. The film is then cooled to room temperature to obtain a pre-made rough film.

[0158] (5) The first preformed rough film is subjected to a first calendering process with a calendering pressure of 25 MPa to obtain a first graphene film. The first graphene film is placed in a graphitization process and heated to 2800℃ under argon protection. It is held for 1 hour for a second graphitization process and then cooled to room temperature to obtain a second preformed rough film.

[0159] (6) The pre-fabricated rough film is subjected to a second calendering process with a calendering pressure of 40 MPa to obtain a graphene heat dissipation film.

[0160] The obtained graphene heat dissipation film was scanned using a scanning electron microscope to observe its microstructure. The results are as follows: Figure 2 As shown.

[0161] Comparative Example 2:

[0162] The raw materials and amounts used in this comparative example are the same as those in Example 3.

[0163] Preparation of high thermal conductivity graphene heat dissipation film

[0164] (1) Add the interlayer bridging agent to ethanol and mix thoroughly to obtain a premixed solution for later use.

[0165] (2) Set the speed of the double planetary mixer to 45 rpm and the speed of the dispersion disc to 1000 rpm.

[0166] First, put water into the mixer and turn on the mixer. Then, add graphene oxide into the mixer and mix evenly for 35 minutes. Next, add the premixed solution into the mixer and continue mixing for 35 minutes. Add concentrated ammonia to adjust the pH of the solution to 6.5 and continue mixing for 15 minutes to obtain the mixture.

[0167] (3) Set the pressure of the high pressure homogenizer to 800 bar and the speed to 40 Hz.

[0168] The mixture was transferred to a high-pressure homogenizer and homogenized for 60 minutes. After homogenization, the mixture was degassed without adding any liquid components or adjusting the flow rate. The mixture was then removed and coated to a thickness of 3±0.2 mm and a width of 700±5 mm to obtain a dried film.

[0169] (4) Cut the dried film into 300mm*300mm pieces and put them into a carbonization furnace. Under nitrogen protection, the temperature is programmed to rise to 350℃ for 7 hours. Under argon protection, the temperature is further raised to 2800℃ and held for 1 hour for graphitization. The film is then cooled to room temperature to obtain a pre-made rough film.

[0170] (5) The pre-fabricated rough film is calendered at a pressure of 40 MPa to obtain a primary graphene film.

[0171] The obtained primary graphene film was scanned using a scanning electron microscope to observe its microstructure. The results are as follows: Figure 2 As shown.

[0172] Comparative Example 3:

[0173] The raw materials and amounts used in this comparative example are the same as those in Example 3.

[0174] Preparation of high thermal conductivity graphene heat dissipation film

[0175] (1) Set the speed of the double planetary mixer to 45 rpm and the speed of the dispersion disc to 1000 rpm.

[0176] First, put water into the mixer and start stirring. Then, add graphene oxide into the mixer and mix evenly for 10 minutes. Next, add ethanol and interlayer bridging agent into the mixer and continue stirring for 10 minutes. Add concentrated ammonia to adjust the pH of the solution to 6.5 and continue stirring for 10 minutes to obtain the mixture.

[0177] (2) Set the pressure of the high pressure homogenizer to 800 bar and the speed to 40 Hz.

[0178] The mixture was transferred to a high-pressure homogenizer and homogenized for 30 minutes. The homogenized mixture was then degassed. After degassed, it was homogenized again for 60 minutes. The high-pressure homogenizer parameters remained unchanged for both homogenization processes; no liquid components were added or the flow rate was adjusted. The homogenized mixture was then degassed again. The mixture was then removed and coated to a thickness of 3 ± 0.2 mm and a width of 700 ± 5 mm to obtain a dried film.

[0179] (3) After cutting the dried film into 300mm*300mm pieces, put it into a carbonization furnace and process it at 350℃ for 7 hours under nitrogen protection. Then, under argon protection, continue to heat it to 2200℃ and hold it for 2 hours to graphitize it. Cool it to room temperature to obtain a pre-made rough film.

[0180] (5) The first preformed rough film is subjected to the first calendering process with a calendering pressure of 25 MPa to obtain the first preformed rough film. The first preformed rough film is placed in a graphitization furnace and heated to 2800℃ under argon protection. It is held for 1 hour for the second graphitization and then cooled to room temperature to obtain the second preformed rough film.

[0181] (6) The pre-fabricated rough film is subjected to a second calendering process with a calendering pressure of 40 MPa to obtain a graphene heat dissipation film.

[0182] Comparative Example 4:

[0183] A method for preparing a high thermal conductivity graphene heat dissipation film

[0184] 1. Raw material preparation

[0185] Graphene oxide, added at 8 wt% of the total raw material;

[0186] The interlayer bridging agent is added at 1 / 10 of the amount of graphene oxide added; the interlayer bridging agent is oxalic acid.

[0187] Ethanol, added at a rate of 1.5 wt% of the total raw materials;

[0188] Concentrated ammonia solution with a concentration of 25%;

[0189] The remainder is water.

[0190] 2. Preparation of high thermal conductivity graphene heat dissipation film

[0191] (1) Set the speed of the double planetary mixer to 45 rpm and the speed of the dispersion disc to 1000 rpm.

[0192] First, put water into the mixer and start stirring. Then, add graphene oxide into the mixer and mix evenly for 10 minutes. Next, add ethanol and interlayer bridging agent into the mixer and continue stirring for 10 minutes. Add concentrated ammonia to adjust the pH of the solution to 6.5 and continue stirring for 10 minutes to obtain the mixture.

[0193] (2) Set the pressure of the high pressure homogenizer to 800 bar and the speed to 40 Hz.

[0194] The mixture was transferred to a high-pressure homogenizer and homogenized for 60 minutes. The homogenized mixture was then degassed. After degassed, it was homogenized again for 60 minutes. The high-pressure homogenizer parameters remained unchanged for both homogenization processes; no liquid components were added or the flow rate was adjusted. The homogenized mixture was then degassed again. The mixture was then removed and coated with a coating thickness of 3±0.2 mm and a width of 700±5 mm to obtain a dried film.

[0195] (3) After cutting the dried film into 300mm*300mm pieces, put it into a carbonization furnace and process it at 350℃ for 7 hours under nitrogen protection. Then, under argon protection, continue to heat it to 2200℃ and hold it for 2 hours to graphitize it. Cool it to room temperature to obtain a pre-made rough film.

[0196] (4) The first preformed rough film is subjected to the first calendering process with a calendering pressure of 25 MPa to obtain a first graphene film. The first graphene film is placed in a graphitization furnace and heated to 2800℃ under argon protection. It is held for 1 hour for the second graphitization and then cooled to room temperature to obtain a second preformed rough film.

[0197] (5) The pre-fabricated rough film is subjected to a second calendering process with a calendering pressure of 40 MPa to obtain a graphene heat dissipation film.

[0198] The graphene heat dissipation films obtained in Examples 1-4 and Comparative Examples 1-4 were tested, and their thermal diffusivity, thermal conductivity, and density were measured respectively. The results are shown in Table 1.

[0199] The test method for thermal diffusivity is as follows: the test instrument is the Netzsch LFA467 thermal conductivity meter (using the ASTM E1461-2013 standard), the test temperature is 25°C, the test humidity is 60% RH, and the test environment is constant temperature and humidity.

[0200] The thermal conductivity test method is as follows: the ASTM E1461-2014 standard is adopted, the instrument is the German Netzsch flash thermal conductivity meter LFA467, the test humidity is 60%RH, and the test environment is constant temperature and humidity.

[0201] The density test method is as follows: the ADTM D792 standard is adopted, the instrument is the American AccuPyc II 1340 density meter, the test temperature is room temperature of 25℃, the test humidity is 60%RH%, and the test environment is constant temperature and humidity.

[0202] Table 1. Performance Test Results

[0203]

[0204] from Figure 1 It can be seen that the graphene heat dissipation film prepared using Example 3 has a uniform and dense interlayer distribution, ensuring its good thermal conductivity; from Figure 2 It can be seen that the graphene heat dissipation film prepared in Comparative Example 2 is disordered and loose, with low flatness. The density of Comparative Example 2 also shows that its material is loose, so its thermal conductivity cannot be guaranteed and it cannot dissipate heat well.

[0205] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high thermal conductivity graphene heat dissipation film, characterized in that, Including the following raw materials: Graphene oxide; Interlayer bridging agent, used for interlayer bonding of graphene sheets, wherein the interlayer bridging agent is a compound of silicate ester and boric acid; Special reagents are used to improve surface tension and as pre-dissolved interlayer bridging agents. The special reagents are one or more of ethanol, PEG200, diethyl ether, acetone, ethyl acetate, and isopropanol. pH adjuster, used to adjust the pH of the solution to 6-7; The amount of graphene oxide added is 3 to 10 wt% of the total raw materials, the amount of special reagent added is 0.5 to 5.5 wt% of the total raw materials, and the amount of interlayer bridging agent added is 1 / 40 to 1 / 10 of the amount of graphene oxide. The high thermal conductivity graphene heat dissipation film is prepared by the following method: (1) Add the interlayer bridging agent to the special reagent and mix thoroughly to obtain a premixed solution for later use; (2) Add water, graphene oxide and premixed liquid to a mixer in sequence and mix thoroughly. Stir at low speed for more than 60 minutes. Add pH adjuster to the mixer and mix to obtain a mixture. (3) The mixture is transferred to a high-pressure homogenizer for homogenization. After homogenization, the mixture is degassed and then coated and dried to form a film. (4) After cutting the dried film, put it into the carbonization furnace and process it at 300-350℃ for 4.5-7.5h under nitrogen protection. Then, continue to heat it to 2100-2200℃ for 2h under argon protection to perform the first graphitization. Cool it to room temperature to obtain a first pre-made rough film. (5) The first preformed rough film is subjected to the first calendering treatment to obtain the first graphene film. The first graphene film is placed in the graphitization furnace and heated to 2600-2800℃ under argon protection. It is held for 1 hour for the second graphitization and then cooled to room temperature to obtain the second preformed rough film. (6) The pre-fabricated coarse film is subjected to a second calendering process to obtain a graphene heat dissipation film.

2. The high thermal conductivity graphene heat dissipation film according to claim 1, characterized in that, The silicate ester is one of tetraethyl orthosilicate, methyl orthosilicate, or propyl orthosilicate.

3. The method for preparing a high thermal conductivity graphene heat dissipation film according to claim 1, characterized in that, Includes the following steps: (1) Add the interlayer bridging agent to the special reagent and mix thoroughly to obtain a premixed solution for later use; (2) Add water, graphene oxide and premixed liquid to a mixer in sequence and mix thoroughly. Stir at low speed for more than 60 minutes. Add pH adjuster to the mixer and mix to obtain a mixture. (3) The mixture is transferred to a high-pressure homogenizer for homogenization. After homogenization, the mixture is degassed and then coated and dried to form a film. (4) After cutting the dried film, put it into the carbonization furnace and process it at 300-350℃ for 4.5-7.5h under nitrogen protection. Then, continue to heat it to 2100-2200℃ for 2h under argon protection to perform the first graphitization. Cool it to room temperature to obtain a first pre-made rough film. (5) The first preformed rough film is subjected to the first calendering treatment to obtain the first graphene film. The first graphene film is placed in the graphitization furnace and heated to 2600-2800℃ under argon protection. It is held for 1 hour for the second graphitization and then cooled to room temperature to obtain the second preformed rough film. (6) The pre-fabricated coarse film is subjected to a second calendering process to obtain a graphene heat dissipation film.

4. The method for preparing a high thermal conductivity graphene heat dissipation film according to claim 3, characterized in that, In step (2), the mixing time of water and graphene oxide in the mixer shall not be less than 30 min, and the interval between adding pH adjuster and premixed liquid to the mixer shall not be less than 10 min.

5. A method for preparing a high thermal conductivity graphene heat dissipation film according to claim 3, characterized in that, The low-speed mixing in step (2) uses a double planetary mixer with a planetary speed of 20-50 rpm and a dispersion disc speed of 800-1200 rpm.

6. The method for preparing a high thermal conductivity graphene heat dissipation film according to claim 3, characterized in that, The homogenization process in step (3) involves a pressure of 600-900 bar and a rotation speed of 35-40 Hz.

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