A method for preparing graphene film and graphene thermal pad

Abstract

This invention relates to a method for preparing graphene film and a graphene thermal conductive pad, comprising the following steps: preparing a graphene oxide slurry with a solid content of 3%; pouring the graphene oxide slurry and a foaming agent into a container that provides centripetal force through rotation; rapidly freezing and solidifying the materials in the container to obtain a first substrate intermediate with oriented alignment; slicing the graphene oxide film along its thickness direction under low temperature conditions and performing low-temperature drying to obtain a dried second substrate intermediate; after drying, heating to foam the foaming agent to obtain a third substrate intermediate with pores evenly distributed on the surface and inside; and performing thermal reduction and calendering treatments to obtain a porous graphene film. The graphene thermal conductive pad is obtained by vacuum injection of silicone oil into the pores of the graphene film using the above substrate, followed by curing. It exhibits strong interlayer bonding and can simultaneously achieve in-plane and longitudinal thermal conductivity.

Description

Technical Field

[0001] This invention belongs to the field of graphene technology, and more specifically, relates to a method for preparing vertically arranged graphene films and graphene thermal pads. Background Technology

[0002] With the continuous development and breakthroughs in 5G technology, transistor size has been shrinking exponentially. The increased heat generated by the increased number of transistors and power consumption has seriously affected product stability and lifespan, leading to higher requirements for heat dissipation. Graphene, due to its extremely high in-plane thermal conductivity and good mechanical properties (high Young's modulus and elongation at break), has become a research hotspot for heat dissipation materials. Compared to traditional metal thermal conductive materials, which suffer from high density and easy oxidation, graphene materials have significant advantages in heat dissipation performance. However, graphene's carbon atoms are sp2 hybridized, resulting in a honeycomb-like two-dimensional planar structure. While the prepared graphene thermal conductive film possesses extremely high planar thermal conductivity (≥1600), its longitudinal thermal conductivity is very low (5-10) compared to planar thermal conductivity. Furthermore, due to its interlayer structure, delamination occurs during longitudinal cutting. Developing and designing a TIM material with high interlayer bonding strength and the ability to balance in-plane and longitudinal thermal conductivity has become a pressing technical problem for those skilled in the art. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method for preparing vertically aligned graphene films and a graphene thermal pad. The method involves providing centripetal force to allow graphene oxide to adhere to the substrate wall and grow in an aligned manner, while rapid freezing maintains this adherent growth state, thus constructing a graphene film with a longitudinally oriented thermally conductive network. Adding a foaming agent during the process creates a porous structure on both the surface and interior of the substrate, resulting in a graphene film that combines in-plane and longitudinal thermal conductivity. Because the preparation process eliminates the need for a post-lamination slitting step, the interlayer bonding of the thermal pad is stronger.

[0004] The first objective of this invention is to provide a method for preparing graphene film, comprising the following steps: preparing a graphene oxide slurry with a solid content of 3%; pouring the graphene oxide slurry and a foaming agent into a container that provides centripetal force through rotation; rapidly freezing and solidifying the material in the container to obtain a first substrate intermediate with oriented alignment; slicing the graphene oxide film along its thickness direction under low temperature conditions and performing low-temperature drying to obtain a dried second substrate intermediate; after drying, heating treatment to foam the foaming agent to obtain a third substrate intermediate with pores evenly distributed on its surface and inside; and performing thermal reduction and calendering treatments to obtain a porous graphene film.

[0005] In a further technical solution, the addition ratio of the foaming agent to the graphene oxide slurry is 1-20:100 by weight.

[0006] In a further technical solution, the foaming agent is selected from one of ADC foaming agent, OBSH foaming agent, or DPT foaming agent. Preferably, the foaming agent is OBSH foaming agent. All of the above foaming agents decompose in the 100-200℃ range. The main reason for using these foaming agents is that graphene oxide undergoes reduction at certain temperatures, affecting its self-assembly and making it difficult to form a thermally conductive network. Foaming at lower temperatures allows for the simultaneous creation of a thermally conductive network on the surface and in the internal cavities. OBSH foaming agent is preferred because its decomposition products have a smaller impact on graphene oxide.

[0007] In a further technical solution, the container is a jacketed reactor. The reason for using a jacketed reactor is to facilitate rapid freezing and shaping. Liquid nitrogen or liquid helium can be directly introduced through the jacket layers, and the materials inside the reactor can be uniformly and rapidly frozen, allowing the materials to cool simultaneously and thus preserving their directional arrangement more intact.

[0008] In a further technical solution, the specific method of rapid freezing and shaping is to introduce liquid nitrogen or liquid helium into the container to rapidly freeze and shape the material inside the container.

[0009] In a further technical solution, the temperature of the low-temperature drying process is maintained below 0°C.

[0010] In a further technical solution, in the heating process after drying, the temperature is increased to above 150°C at a rate of 10-20°C / min.

[0011] In a further technical solution, the thermal reduction treatment step includes carbonization treatment and graphene treatment, wherein the carbonization treatment temperature is 800-2000℃ and the graphene treatment temperature is 2000-3200℃.

[0012] Another objective of this invention is to provide a graphene thermal pad. The graphene film material with pores evenly distributed on the surface and inside obtained by the above method is injected with silicone oil into the pores of the graphene film material by vacuum injection, and then cured to obtain the graphene thermal pad.

[0013] In a further technical solution, the longitudinal thermal conductivity of the thermal pad is 20-100 W / (mk). Beneficial effects

[0014] This invention employs rotation to provide centripetal force. Under the action of centripetal force, the side with more oxygen-containing functional groups tends to move outward, while the corresponding graphene oxide will align vertically, resulting in oriented graphene oxide. Simultaneously, rapid freezing is used to instantly solidify the oriented graphene oxide, ensuring that the graphene oxide matrix maintains its oriented state. After low-temperature drying, an oriented matrix is ​​obtained. Furthermore, a foaming agent is used to create a porous structure on the surface and inside, making the bond between the matrix and silicone oil tighter. According to the method of this invention, a TIM material with strong interlayer bonding and beneficial longitudinal thermal conductivity can be prepared. Implementation

[0015] The present invention will be further described below with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field, and there are no specific restrictions on their sources; they can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0016] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0017] The technical solution of the present invention is illustrated below through specific embodiments. It should be understood that the one or more steps mentioned in the present invention do not preclude the existence of other methods and steps before or after the combined steps, or that other methods and steps may be inserted between these explicitly mentioned steps. It should also be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Unless otherwise stated, the numbering of each method step is only for the purpose of identifying each method step, and not for limiting the order of each method or limiting the scope of the present invention. Changes or adjustments to their relative relationships, without substantial changes to the technical content, can also be considered as within the scope of the present invention.

[0018] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents. Example 1

[0019] Preparation of graphene oxide slurry:

[0020] Flake graphite and 98% concentrated sulfuric acid were mixed in a certain proportion and stirred rapidly to obtain pre-oxide A after oxidation. After a period of time, 3% sulfuric acid with a lower concentration was added and stirring was continued to assist in intercalation oxidation to obtain pre-oxide B. Sufficient ultrapure water was added to pre-oxide B for filtration and washing until the solution was close to neutral. Then, it was vacuum dried at 60°C for 24 hours to obtain pre-oxide C. An appropriate amount of 98% concentrated sulfuric acid was added to pre-oxide C and mixed evenly. Potassium permanganate was added for oxidation, and the mixture was stirred continuously and heated to 40°C for constant temperature reaction. Hydrogen peroxide was added dropwise until the color of the mixture no longer changed to obtain graphene oxide solution. After settling for 24 hours, the supernatant was removed. The precipitate was repeatedly washed with dilute hydrochloric acid and ultrapure water until neutral to obtain graphene oxide slurry with a solid content of 3%.

[0021] Preparation of oriented substrates

[0022] The graphene oxide slurry A with a solid content of 3% obtained in the previous step was poured into a reaction vessel, which was a rotatable hopper equipped with a jacket. The foaming agent and graphene oxide slurry were added and mixed at a ratio of 1:24 by mass. In this embodiment, OBSH foaming agent was selected.

[0023] After thorough mixing, the hopper is rotated at a speed of 1000 r / min for 8 hours. Liquid nitrogen is then rapidly introduced into the jacket of the hopper to quickly freeze and shape the oriented graphene oxide, resulting in the first substrate intermediate. The shaped graphene oxide is then sliced ​​into 1.0 mm thick sheets along the direction perpendicular to its thickness, maintaining a low temperature below -100°C, to obtain the second substrate intermediate. The second substrate intermediate is then dried at a low temperature below 0°C for 72 hours, heated to above 150°C and held at that temperature for 6 hours to allow the foaming agent in the second substrate intermediate to foam, resulting in the third substrate intermediate with open surfaces. The obtained third substrate intermediate is then subjected to carbonization at 1400°C and graphitization at 2800°C for high-temperature heat treatment and reduction, followed by mechanical calendering at 100 MPa to prepare a graphene film.

[0024] Preparation of high thermal conductivity graphene pads

[0025] Add a curing agent to the silicone oil and stir quickly until uniform. In this embodiment, the curing agent is selected by adding the graphene film material to the silicone oil containing the curing agent and placing it in a vacuum pouring machine. The silicone oil is poured into the pores of the graphene film material by vacuum pouring. The reduced graphene film material is filled with silicone oil and cured at a constant temperature of 80-150℃ to obtain a graphene pad with high thermal conductivity. Example 2

[0026] Preparation of graphene oxide slurry: This step is the same as in Example 1, and will not be repeated here.

[0027] Preparation of the oriented substrate: The graphene oxide slurry A with a solid content of 4% obtained in the previous step is poured into a reaction vessel, which is a rotatable hopper equipped with a jacket. The foaming agent and graphene oxide slurry are added and mixed at a ratio of 1:36 by mass. In this embodiment, OBSH foaming agent is selected.

[0028] After thorough mixing, the hopper is rotated at a speed of 1200 r / min for 8 hours. Liquid nitrogen is then rapidly introduced into the jacket of the hopper to quickly freeze and shape the oriented graphene oxide, resulting in the first substrate intermediate. Maintaining a low temperature of -100℃, the shaped graphene oxide is sliced ​​into 1.0 mm thick sheets along the direction perpendicular to its thickness, yielding the second substrate intermediate. The second substrate intermediate is then dried at 0℃ for 72 hours, heated to above 150℃ and held at that temperature for 4 hours to allow the foaming agent in the second substrate intermediate to foam, resulting in the third substrate intermediate with open surfaces. The obtained third substrate intermediate is then subjected to carbonization at 1400℃ and graphitization at 2800℃ for high-temperature heat treatment reduction, followed by mechanical calendering at 100 MPa to prepare a graphene film.

[0029] Preparation of high thermal conductivity graphene gasket: Add curing agent to silicone oil and stir quickly until uniform. Add graphene film to silicone oil containing curing agent and place it in a vacuum casting machine. Use vacuum casting to pour silicone oil into the pores of the graphene film. Fill the reduced graphene film with silicone oil and cure at a constant temperature of 80°C to obtain a high thermal conductivity graphene gasket. Example 3

[0030] Preparation of graphene oxide slurry: This step is the same as in Example 1, and will not be repeated here.

[0031] Preparation of the oriented substrate: The graphene oxide slurry A with a solid content of 4% obtained in the previous step is poured into a reaction vessel, which is a rotatable hopper equipped with a jacket. The foaming agent and graphene oxide slurry are added and mixed at a ratio of 1:58 according to mass parts. In this embodiment, OBSH foaming agent is selected.

[0032] After thorough mixing, the hopper is rotated at a speed of 1200 r / min for 8 hours. Liquid nitrogen is then rapidly introduced into the jacket of the hopper to quickly freeze and shape the oriented graphene oxide, resulting in the first substrate intermediate. Maintaining a low temperature of -100℃, the shaped graphene oxide is sliced ​​into 1.0 mm thick sheets along the direction perpendicular to its thickness, yielding the second substrate intermediate. The second substrate intermediate is then dried at 0℃ for 72 hours, heated to above 150℃ and held at that temperature for 4 hours to allow the foaming agent in the second substrate intermediate to foam, resulting in the third substrate intermediate with open surfaces. The obtained third substrate intermediate is then subjected to carbonization at 1400℃ and graphitization at 2800℃ for high-temperature heat treatment reduction, followed by mechanical calendering at 100 MPa to prepare a graphene film.

[0033] Preparation of high thermal conductivity graphene gasket: Add curing agent to silicone oil and stir quickly until uniform. Add graphene film to silicone oil containing curing agent and place it in a vacuum casting machine. Use vacuum casting to pour silicone oil into the pores of the graphene film. Fill the reduced graphene film with silicone oil and cure at a constant temperature of 80°C to obtain a high thermal conductivity graphene gasket. Example 4

[0034] Preparation of graphene oxide slurry: This step is the same as in Example 1, and will not be repeated here.

[0035] Preparation of the oriented substrate: The graphene oxide slurry A with a solid content of 4% obtained in the previous step is poured into a reaction vessel, which is a rotatable hopper equipped with a jacket. The foaming agent and graphene oxide slurry are added and mixed at a ratio of 1:100 by mass. In this embodiment, OBSH foaming agent is selected.

[0036] After thorough mixing, the hopper is rotated at a speed of 1200 r / min for 8 hours. Liquid nitrogen is then rapidly introduced into the jacket of the hopper to quickly freeze and shape the oriented graphene oxide, resulting in the first substrate intermediate. Maintaining a low temperature of -100℃, the shaped graphene oxide is sliced ​​into 1.0 mm thick sheets along the direction perpendicular to its thickness, yielding the second substrate intermediate. The second substrate intermediate is then dried at 0℃ for 72 hours, heated to above 150℃ and held at that temperature for 4 hours to allow the foaming agent in the second substrate intermediate to foam, resulting in the third substrate intermediate with open surfaces. The obtained third substrate intermediate is then subjected to carbonization at 1400℃ and graphitization at 2800℃ for high-temperature heat treatment reduction, followed by mechanical calendering at 100 MPa to prepare a graphene film.

[0037] Preparation of high thermal conductivity graphene gasket: Add curing agent to silicone oil and stir quickly until uniform. Add graphene film to silicone oil containing curing agent and place it in a vacuum casting machine. Use vacuum casting to pour silicone oil into the pores of the graphene film. Fill the reduced graphene film with silicone oil and cure at a constant temperature of 80°C to obtain a high thermal conductivity graphene gasket.

[0038] Comparative Example

[0039] A graphene thermal pad with a thickness of 1.0 mm was prepared using the method disclosed in the Chinese invention patent with announcement number CN114801421A.

[0040] The graphene thermal conductive pads obtained in Examples 1-4 and the comparative examples were tested for their longitudinal thermal conductivity according to the ASTM-E1461 standard. The test results are shown in the table below:

[0041] Experimental group <![CDATA[Graphene density (g / cm 3 )]]> Longitudinal thermal conductivity (W / mk) Example 1 0.964 22.56 Example 2 1.245 38.67 Example 3 1.434 54.22 Example 4 1.625 83.68 Comparative Example 1 0.944 6.44

[0042] The test results above show that the addition ratio of foaming agent and graphene oxide slurry results in graphene films with different densities. The densities of Example 1 and Comparative Example 1 are both 0.9 g / cm³. 3 The longitudinal thermal conductivity of Example 1 is 22.56 W / mK, while that of Comparative Example 1 is 6.44 W / mK. The longitudinal thermal conductivity of Example 1 is approximately three times that of the thermal pad prepared in Comparative Example 1 using existing technology. Analysis suggests that the centripetal force stage allows for directional alignment of the graphene film during construction. Rapid freezing then maintains the oriented structure of the graphene, preventing it from losing its alignment due to gravity. Furthermore, the foaming agent creates pores within and on the surface of the graphene film, allowing for more complete silicone oil filling and reducing residual gas within the pores. Therefore, the graphene thermal pad prepared according to this invention achieves higher longitudinal thermal conductivity.

[0043] In addition, Examples 2-4 changed the proportion of foaming agent. As the proportion of foaming agent decreased, the density of the graphene film increased. The higher the density, the more its compression and resilience performance would be sacrificed, but the thermal conductivity would be improved with the increase of density. By adjusting its density, the thermal pad can be adapted to more products and usage environments, and customized product preparation can also be achieved.

[0044] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing a graphene film, characterized in that, Includes the following steps: A graphene oxide slurry with a solid content of 3% was prepared; the graphene oxide slurry and a foaming agent were poured into a container that was rotated to provide centripetal force; the materials in the container were rapidly frozen and shaped to obtain a first substrate intermediate with oriented arrangement; The graphene oxide film was sliced ​​along its thickness direction under low temperature conditions and then dried at low temperature to obtain a dried second substrate intermediate. After drying, the material is heated and foamed with a foaming agent to obtain a third substrate intermediate with pores evenly distributed on the surface and inside. After thermal reduction and calendering, a porous graphene film is obtained.

2. The method for preparing a graphene film according to claim 1, characterized in that: The foaming agent and graphene oxide slurry are added in a ratio of 1-20:100 by weight.

3. The method for preparing a graphene film according to claim 1, characterized in that: The foaming agent is selected from one of ADC foaming agent, OBSH foaming agent, or DPT foaming agent.

4. The method for preparing a graphene film according to claim 3, characterized in that: The foaming agent used is OBSH foaming agent.

5. The method for preparing a graphene film according to claim 1, characterized in that: The container is a jacketed reactor.

6. The method for preparing a graphene film according to claim 5, characterized in that: The specific method for rapid freezing and shaping is to introduce liquid nitrogen or liquid helium into the container to rapidly freeze and shape the material inside the container.

7. The method for preparing a graphene film according to claim 1, characterized in that: In the low-temperature drying process, the temperature is maintained below 0°C.

8. The method for preparing a graphene film according to claim 1, characterized in that: After drying, in the heating process, the temperature is increased to above 150℃ at a rate of 10-20℃ / min.

9. The method for preparing a graphene film according to claim 1, characterized in that: The thermal reduction process includes carbonization and graphene treatment, wherein the carbonization temperature is 800-2000℃ and the graphene treatment temperature is 2000-3200℃.

10. A graphene thermally conductive pad, characterized in that: A graphene film with pores evenly distributed on its surface and inside, prepared according to any one of claims 1-9, is used to inject silicone oil into the pores of the graphene film using a vacuum infusion method, and then cured to obtain a graphene thermal pad.

11. The thermally conductive pad according to claim 10, characterized in that: The longitudinal thermal conductivity of the thermal pad is 20-100 W / (mk).