High vertical thermal conductivity graphene heat conduction film and preparation method thereof

Abstract

The application provides a high-vertical-thermal-conductivity graphene heat-conducting film and a preparation method thereof, and a specific construction method is as follows: after graphene oxide slurry is continuously coated into a relatively thick first graphene oxide film and a relatively thin second graphene oxide film and dried, the second graphene oxide film which is preferentially dried is trimmed and then folded and laid flat on a wet surface of the first graphene oxide film, then a third graphene oxide film is supplemented and coated on the original position of the second graphene oxide film, after the first graphene oxide film, the second graphene oxide film and the third graphene oxide film are completely dried, an overall continuous graphene oxide film with uniform thickness is obtained, and then carbonization, graphitization and calendering treatment are carried out to obtain the high-vertical-thermal-conductivity graphene heat-conducting film. The graphene heat-conducting film has not only a relatively high in-plane thermal conductivity, but also a relatively high vertical thermal conductivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of graphene heat-conducting film, in particular to a high vertical thermal conductivity graphene heat-conducting film and a preparation method thereof. BACKGROUND

[0002] The graphene oxide slurry can be coated on a substrate to self-assemble into a highly oriented graphene oxide film, and the graphene film with extremely high in-plane thermal conductivity (the theoretical thermal conductivity of single-layer graphene is as high as 5300 W / mK) can be obtained through carbonization and graphitization, however, the vertical thermal conductivity is generally lower than 10 W / mK, because the film forming process forms sp2 hybridization plane in the plane which is conducive to phonon conduction, and the connection between layers in the vertical direction mainly relies on van der Waals force, which is weak and not conducive to heat conduction.

[0003] As a new material encouraged by the Ministry of Industry and Information Technology for the first batch of demonstration applications, the graphene heat-conducting film is one of the most promising new heat dissipation materials in the current heat management field, which can be used as an important component for terminal product heat dissipation, mainly playing a role in dissipating the heat of components and devices through its high thermal conductivity to prevent equipment overheating and reduce work efficiency or even damage the equipment. With the continuous growth of global internet data traffic, the demand for ICT equipment is increasing, and the continuous improvement of chip power density has led to the demand for high thermal conductivity interface materials; the current in-plane thermal conductivity of the graphene heat-conducting film has exceeded 2000 W / mK, and it is difficult to continuously improve the in-plane thermal conductivity, if the vertical thermal conductivity is improved, the double heat dissipation paths of in-plane heating and out-of-plane heat conduction are constructed, which is very beneficial to the stable position of the graphene heat-conducting film in the heat management field, and even can be far ahead of other interface heat dissipation materials.

[0004] Based on this, the present application is proposed. SUMMARY

[0005] The present application aims to provide a high vertical thermal conductivity graphene heat-conducting film and a preparation method thereof, and the preparation method is as follows:

[0006] After the graphene oxide slurry is continuously coated into a relatively thick first graphene oxide film and a relatively thin second graphene oxide film and dried, the second graphene oxide film which is preferentially dried is trimmed and folded and laid flat on the wet surface of the first graphene oxide film, then a third graphene oxide film is supplemented and coated at the original position of the second graphene oxide film, the third graphene oxide film is overlapped with the folded part of the second graphene oxide film, the thickness of the third graphene oxide film is equal to the total thickness of the first graphene oxide film and the second graphene oxide film, after the first graphene oxide film, the second graphene oxide film and the third graphene oxide film are completely dried, an overall continuous graphene oxide film with uniform thickness is obtained, then carbonization, graphitization and calendering treatment are performed to obtain a high vertical thermal conductivity graphene heat-conducting film.

[0007] It is worth mentioning that the first graphene oxide film and the second graphene oxide film are continuously coated, that is, the bottom edges of the first graphene oxide film and the second graphene oxide film are continuously connected.

[0008] Preferably, the whole continuous and uniform-thickness graphene oxide film further comprises a soaking treatment before the carbonization treatment.

[0009] Preferably, the whole continuous and uniform-thickness graphene oxide film further comprises an edge cutting treatment before the carbonization treatment. The purpose of the edge cutting treatment is to cut off the non-overlapping part of the first graphene oxide film and the second graphene oxide film, and to cut off the collapsed part of the whole continuous and uniform-thickness graphene oxide film after coating, so that the overall thickness of the finished product of the high vertical thermal conductivity graphene heat conduction film is more uniform.

[0010] Preferably, the solid content of the graphene oxide slurry is 2.5-8%. This solid content can coat a graphene oxide film with a wide range of thickness. If the solid content is too low, only a thin graphene oxide film can be coated, and it is impossible to form a graphene oxide film with a large thickness difference between the two sections and a significant drying time difference. If the solid content is too high, the slurry is thick and not conducive to coating.

[0011] Preferably, the coating thickness of the first graphene oxide film is 3-5mm, and the coating thickness of the second graphene oxide film is 1-2mm. A certain thickness difference causes a certain drying time difference. The second graphene oxide film dries first and then bends and lays flat on the wet surface of the first graphene oxide film. In addition, the purpose of controlling the thickness of the second graphene oxide film to be 1-2mm is that the smaller the thickness, the weaker the interlayer force, and the lower the bending stiffness, which is more conducive to bending. However, if the thickness is too small, it will increase the difficulty of coating. In addition, over-thick graphene oxide slurry coating will cause edge collapse.

[0012] Preferably, the length and width of the second graphene oxide film after trimming are not greater than those of the first graphene oxide film, and the laying and overlapping operation should be completed before the first graphene oxide film is dry. Before trimming, the two can be the same width and length. After bending, the second graphene oxide film should be in full contact with the wet surface of the first graphene oxide film. The purpose is to eliminate the edge effect, promote the wet fusion of the two, and enhance the bonding force.

[0013] The coating thickness of the third graphene oxide film is the total thickness of the first graphene oxide film and the second graphene oxide film, and the purpose is to finally obtain a continuous and uniform-thickness graphene heat conduction film.

[0014] Preferably, the second graphene oxide film serves to connect the upper and lower surfaces of the main graphene oxide film, and the water immersion treatment allows for more thorough bonding of the various graphene oxide film segments. The second graphene oxide film plays a core role in ultimately improving the vertical thermal conductivity of the finished graphene thermal conductive film. After immersion in water, the various graphene oxide film segments undergo wet fusion, and the second graphene oxide film crosslinks with both the first and third graphene oxide films in the thickness direction. Ultimately, the finished graphene thermal conductive film forms several I-shaped networks in terms of thickness for its thermal conductivity path.

[0015] Preferably, the graphene oxide slurry used for the first, second, and third graphene oxide films is from the same batch, in order to make it easier to control the thickness uniformity.

[0016] Preferably, the high thermal conductivity graphene thermal conductive film is obtained by heat treatment reduction and defect repair of the integrally continuous graphene oxide film with uniform thickness. The carbonization temperature is 1000~2000℃, the carbonization time is 1~3h, the heating rate from room temperature to 500℃ is 0.1~1℃ / min, and the rate for other stages is 2~10℃ / min; the graphitization temperature is 2000~3300℃, the graphitization time is 6~20h, the heating rate from room temperature to 500℃ is 0.1~1℃ / min, and the rate for other stages is 2~10℃ / min. The carbonization and graphitization annealing processes are slow to avoid rapid release of mixed gas and impurities during rapid annealing, which could cause the film to burn out. The high-temperature annealing for a certain period of time ensures that the functional groups are fully removed, causing the carbon atoms to transform from sp³ hybridization to sp² hybridization, thereby improving the thermal conductivity.

[0017] Preferably, the carbonization and graphitization processes require inert gas protection; further, the inert gas is one or more of argon, nitrogen, helium, etc.

[0018] Preferably, the graphene oxide film with uniform thickness and continuous overall structure usually needs to be calendered after graphitization to make the graphene thermal conductive film relatively uniform in thickness and reduce the interlayer spacing, which helps to improve the vertical thermal conductivity. More importantly, calendering further bonds the first, second and third graphene films together.

[0019] The high vertical thermal conductivity graphene thermal conductive film prepared by the method described in this invention has a density of 1.8~2.2 g / cm³, an in-plane thermal conductivity of 1000~1900 W / mK, a vertical thermal conductivity of 150~400 W / mK, a peel strength of >30 g / 25 mm, and no delamination problem. Attached Figure Description

[0020] Figure 1 A schematic cross-sectional view of the high vertical thermal conductivity graphene thermal conductive film provided in Example 1, which is composed of first, second, and third graphene oxide films.

[0021] Figure 2 Schematic diagram of the planar view of the continuous and uniform-thickness graphene oxide film before edge cutting for Example 1.

[0022] Figure 3 Schematic diagram of the interface fusion of the continuous and uniform-thickness graphene oxide film after water soaking treatment for Example 1.

[0023] Figure 4 Schematic diagram of the heat conduction model of the high-vertical-thermal-conductivity graphene heat conduction film provided by the present application.

[0024] Explanation of reference signs:

[0025] 1-first graphene oxide film; 2-second graphene oxide film; 3-third graphene oxide film; 4-bending site of the second graphene oxide film. Embodiment

[0026] The following detailed description of the exemplary embodiments of the present application refers to the accompanying drawings that form a part of this description, in which are shown, by way of example, exemplary embodiments in which the present application can be practiced. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application as claimed, but merely to provide examples of how the present application can be practiced by one of ordinary skill in the art. It should be understood that various modifications and variations can be made to the embodiments described herein without departing from the scope of the present application as defined by the appended claims. The detailed description and accompanying drawings are therefore to be taken in a illustrative sense, and not in a restrictive sense, if any such modifications and variations are made to the embodiments described herein, they will fall within the scope of the present application as described herein. Furthermore, the background art is provided to illustrate the state of the art and its significance to the present application, and is not intended to limit the scope of the present application or the application of the present application.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terminology used in the description of the present application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application; the use of the term "and / or" herein includes any and all combinations of one or more of the associated listed items.

[0028] Unless otherwise specified, the examples were carried out under conventional conditions or under the conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used were conventional products that can be obtained commercially.

[0029] In order to make the technical problems, technical solutions and advantages of the present application more clear, the following will be described in detail with reference to the accompanying drawings and specific examples.

[0030] The following are specific examples and comparative examples: Example 1

[0031] A graphene oxide cake (purchased from Yuntian Mo Rui Technology Co., Ltd.) was prepared into a slurry with a solid content of 5%, and was coated on a PET substrate to form two continuous graphene oxide films with different thicknesses. One was a first graphene oxide film with a coating thickness of 3 mm, and the other was a second graphene oxide film with a coating thickness of 1 mm. The widths and lengths of the two coatings were the same. The graphene oxide films were placed in a 60°C environment for drying. The 1 mm second graphene oxide film was dried first. After trimming, the 1 mm graphene oxide film was bent and completely laid on the wet surface of the 3 mm first graphene oxide film. The 1 mm graphene oxide film was then coated with the 5% slurry to form a third graphene oxide film with a coating thickness of 4 mm. The coating width and length were consistent with those of the two graphene oxide films. The additional graphene oxide film was connected to the 1 mm and 3 mm graphene oxide films. The graphene oxide films were continuously dried at 60°C. After the entire graphene oxide film was dried, the non-overlapping parts of the 3 mm and 1 mm graphene oxide films were cut off. A graphene oxide film with uniform thickness composed of three graphene oxide films was obtained. The graphene oxide film was treated in water for 1 min, and then dried at 60°C. After drying, the graphene oxide film was carbonized, graphitized, and calendered to obtain a graphene heat conduction film with high vertical thermal conductivity.

[0032] The carbonization temperature was 1300°C, the carbonization time was 3 h, the heating rate was 0.5°C / min from room temperature to 500°C, and the other segments were 3°C / min. The graphitization temperature was 3000°C, the graphitization time was 14 h, the heating rate was 0.5°C / min from room temperature to 500°C, and the other segments were 3°C / min. Nitrogen was used as a protective gas during the heat treatment process. The calendering pressure was 200 MPa.

[0033] The obtained graphene heat conduction film was tested for thickness, density, peel, in-plane and vertical thermal conductivity. The peel test was based on the enterprise standard Q / GDMR 07-2023, and the in-plane and vertical thermal conductivity was determined by the laser scattering method according to the standard ASTM E1461-2014. Example 2

[0034] Referring to Example 1, the thicknesses of the first and third graphene oxide films were adjusted to 3.5 mm and 4.5 mm, respectively, and the other steps remained unchanged. Example 3

[0035] Referring to Example 1, the solid content of the graphene oxide slurry was adjusted to 6.5%, and the thicknesses of the first and third graphene oxide films were adjusted to 4 mm and 5 mm, respectively. The other steps remained unchanged. Example 4

[0036] Referring to Example 3, the second graphene oxide film thickness was adjusted to 1.5 mm, and other steps were unchanged. Example 5

[0037] Referring to Example 1, the graphene oxide slurry solid content was adjusted to 8%, the first, second and third graphene oxide film thicknesses were adjusted to 5 mm, 1.5 mm and 6.5 mm respectively, and other steps were unchanged. Comparative Example 1

[0038] Referring to Example 1, the 5% graphene oxide slurry was coated into a continuous 4 mm graphene oxide film without thicker and thinner sections, without overlapping operation, without additional coating of graphene oxide film, without water soaking treatment, and other steps were unchanged. Comparative Example 2

[0039] Referring to Example 1, the graphene oxide slurry solid content was adjusted to 7%, and the first and second graphene oxide film thicknesses were adjusted to 5 mm and 3 mm respectively, and other steps were unchanged. Comparative Example 3

[0040] Referring to Example 1, the uniform thickness graphene oxide film composed of three graphene oxide films was not subjected to water soaking treatment, and other steps were unchanged. Comparative Example 4

[0041] Referring to Example 1, the first and second graphene oxide film thicknesses were adjusted to 2.5 mm and 2 mm respectively, and other steps were unchanged. Comparative Example 5

[0042] Referring to Example 1, the second graphene oxide film coating length was greater than the first graphene oxide film, and after trimming, the length was still greater than the first graphene oxide film, and other steps were unchanged.

[0043] The main experimental parameters and test results of Examples 1-5 and Comparative Examples 1-5 are summarized in Table 1.

[0044] Table 1

[0045]

[0046] As can be seen from the examples and comparative example 1 in Table 1, the graphene heat-conducting film with high vertical thermal conductivity provided by the present application has higher in-plane and vertical thermal conductivity, and has comparable peeling strength to the graphene heat-conducting film prepared by conventional method. It is worth mentioning that the graphene heat-conducting film prepared in each example is uniformly layered after peeling test, indicating that the second graphene oxide film is well integrated into the main graphene oxide film, which is the key basis for improving the vertical thermal conductivity of the graphene heat-conducting film. Comparative example 2 is broken when bending due to the relatively large thickness of the second graphene oxide film and the relatively weak flexibility after drying; comparative example 3 has poor in-plane thermal conductivity, vertical thermal conductivity and peeling strength due to the existence of obvious interface between the graphene oxide films in each segment because the main graphene oxide film is not subjected to water soaking treatment; comparative example 4 cannot perform the operation of stacking the dry film on the wet film because the two segments of the graphene oxide film do not have obvious difference in thickness and the wet films in the two segments do not have obvious difference in drying time; and comparative example 5 has poor bonding force and uneven layering after peeling test because the second graphene oxide film does not completely fall on the first graphene oxide wet film.

[0047] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the above examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of producing a high vertical thermal conductivity graphene thermal film, characterized by, The graphene oxide slurry is continuously coated into a first graphene oxide film with a coating thickness of 3-5 mm and a second graphene oxide film with a coating thickness of 1-2 mm, the second graphene oxide film is preferentially dried, trimmed and folded and laid on the wet surface of the first graphene oxide film, then a third graphene oxide film is coated on the original position of the second graphene oxide film, the third graphene oxide film overlaps the folded part of the second graphene oxide film, and the thickness of the third graphene oxide film is equal to the sum of the thicknesses of the first graphene oxide film and the second graphene oxide film, after the first graphene oxide film, the second graphene oxide film and the third graphene oxide film are completely dried, a whole continuous graphene oxide film with uniform thickness is obtained, then the whole continuous graphene oxide film with uniform thickness is subjected to water soaking, edge cutting, carbonization, graphitization and calendering treatment to obtain a high vertical thermal conductivity graphene heat conducting film.

2. A method of producing a high vertical thermal conductivity graphene thermal film as claimed in claim 1, characterized by, The length and width of the second graphene oxide film after trimming are not greater than those of the first graphene oxide film, and the folding and laying operation should be completed before the first graphene oxide film is dried.

3. A method of producing a high vertical thermal conductivity graphene thermal film as claimed in claim 1, characterized by, The solid content of the graphene oxide slurry is 2.5-8%.

4. A method of producing a high vertical thermal conductivity graphene thermal film as claimed in claim 1, characterized by, The carbonization temperature is 900-1400℃, the graphitization temperature is 2000-3300℃, and inert gas protection is required during the carbonization and graphitization processes.

5. A method of producing a high vertical thermal conductivity graphene thermal film as claimed in claim 1, characterized by, The calendering pressure is 100-300MPa.

6. A high vertical thermal conductivity graphene thermal film prepared according to the method of any one of claims 1 to 5, wherein, The density of the graphene heat-conducting film is 1.8-2.2 g / cm 3 , the in-plane heat-conducting coefficient is 1000-1900 W / mK, the vertical heat-conducting coefficient is 150-400 W / mK, the peeling strength is >30 g / 25 mm, and there is no delamination problem.

Images