Preparation method of graphene heat-conducting film

Abstract

The invention provides a preparation method of a graphene heat-conducting film. An efficient longitudinal heat conduction channel is constructed in the Z-axis direction of the graphene heat conduction film mainly through a rapid pulling heat setting strategy, efficient heat conduction is achieved on the bottom face and the surface of the graphene film, and graphene oxide sheet layers are induced to be arranged in order in the Z-axis direction through longitudinal friction force of longitudinal rapid pulling. The graphene oxide slurry is prevented from flowing back and collapsing to the constructed longitudinal heat conduction channel through rapid heat setting, and rapid setting and construction of the heat conduction channel with efficient heat conduction from the bottom surface to the surface of the graphene heat conduction film are maintained. By constructing a Z-axis efficient heat-conducting channel, the heat source temperature can be quickly conducted to the surface of the graphene heat-conducting film from the bottom surface of the graphene heat-conducting film, a Z-axis heat-conducting mode that the heat source temperature of the graphene heat-conducting film is diffused and conducted layer by layer is replaced, and scattering of hot carriers among graphene film layers is greatly avoided. The preparation method is a preparation method of the graphene heat-conducting film compatible with longitudinal and planar heat-conducting properties.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of graphene heat conduction application, in particular to a method for improving the thickness direction heat conduction performance of graphene heat conduction film by constructing Z-axis high heat conduction channel through fast heat lifting shaping. BACKGROUND

[0002] With the advent of the 5G era, the heat dissipation problem of highly integrated electronic chips has put forward new demands for thermal management engineering materials, and it is urgent to find a heat conduction material with high efficient heat conduction performance in Z-axis and X-Y direction. Graphene is an extremely advantageous heat conduction material, which presents excellent heat conduction performance of 1000W / mk-1800W / mk in X-Y direction, and its heat conduction performance in X-Y direction is extremely competitive among traditional thermal management engineering materials. However, its heat conduction performance in Z-axis direction still needs to be further improved, which is mainly due to the two-dimensional characteristics of graphene sheet layer, which causes serious phonon scattering in the heat conduction mode of layer-by-layer diffusion conduction in Z-axis direction, resulting in that the heat conduction performance in Z-axis direction is far less than that in X-Y direction. Although there are many explorers in the improvement of the heat conduction performance of graphene heat conduction film in Z-axis direction, there are few outstanding research results. At present, the improvement strategies for the heat conduction performance of graphene heat conduction film in Z-axis direction can be basically summarized into three kinds, the first is to improve the paving order of graphene sheet layer in Z-axis direction of graphene heat conduction film; the second is to construct a high-entropy chaotic system to improve the heat conduction performance of graphene heat conduction film in Z-axis direction relying on the high intrinsic heat conduction performance of graphene; the third is to fill high heat conduction filler in graphene film to improve the heat conduction performance of graphene heat conduction film in Z-axis direction relying on the heat conduction performance of the filler. Although these improvement strategies improve the heat conduction performance of graphene heat conduction film in Z-axis direction to some extent, they are basically based on sacrificing the heat conduction performance of graphene heat conduction film in X-Y direction, which does not meet the demand and idea of the 5G era for new heat dissipation materials with high efficient heat conduction performance in Z-axis and X-Y direction. Therefore, it is particularly important to improve the heat conduction performance in Z-axis direction while maintaining or slightly sacrificing the heat conduction performance in X-Y direction of graphene heat conduction film.

[0003] The information disclosed in this Background section is only for the purpose of increasing the understanding of the background of the application and should not be taken as an acknowledgement or any form of suggestion that this information forms prior art that is already known in this field. SUMMARY

[0004] The application aims to provide a graphene heat-conducting film with a Z-axis high-heat-conducting channel constructed by fast pulling and heat setting and a preparation method thereof, and the Z-axis high-heat-conducting channel is constructed in the Z-axis direction of the graphene heat-conducting film by the strategy of fast pulling and heat setting, so that the bottom surface and the surface of the graphene film realize efficient heat conduction. The longitudinal friction force of fast pulling can induce the highly ordered arrangement of graphene oxide layers in the Z-axis direction, and fast heat setting avoids the backflow and collapse of the graphene oxide coating slurry to the constructed longitudinal heat-conducting channel, the fast setting and construction of the efficient heat-conducting channel in the Z-axis direction realize the fast conduction of the heat source temperature from the bottom surface to the surface of the graphene heat-conducting film, avoid the serious scattering of phonons in the layer-by-layer heat conduction process of the graphene film, and realize the smooth heat conduction of the graphene heat-conducting film in the Z-axis direction. The construction of the Z-axis high-heat-conducting channel greatly retains the heat conduction performance of graphene in the X-Y direction, and is a graphene heat-conducting film preparation method compatible with longitudinal and planar heat conduction performance.

[0005] The preparation method of the graphene heat-conducting film with a Z-axis high-heat-conducting channel constructed by fast pulling and heat setting provided by the application specifically comprises the following steps. S1, preparing graphene oxide water slurry with a solid content of 4%-9%: under stirring, add ammonia water with a mass concentration of 25%-28% to deionized water, and the amount of ammonia water added is 5%-10% of the mass of the graphene oxide cake, to obtain an alkaline mixed water solvent containing ammonia water. The graphene oxide cake is weighed according to the designed solid content; the graphene oxide cake is added to the mixed water solvent in small pieces under stirring and fully stirred and dispersed to obtain a dispersed graphene water slurry. According to the solid content design of the graphene oxide water slurry, the graphene oxide cake is dissolved in deionized water; the solid content of the graphene oxide cake is 30-60%, and the oxygen content is 60%-62% (XPS characterization). The solid content of the graphene oxide water slurry is adjusted according to the oxidation degree of the graphene oxide, and the higher the oxidation degree, the greater the designed solid content. The graphene oxide cake is an oxide of graphene obtained by chemical oxidation and exfoliation of flake graphite, and its surface contains abundant hydroxyl, carboxyl, epoxy and other oxygen-containing functional groups.

[0006] S2, homogenization and defoaming treatment: the graphene oxide water slurry prepared in S1 is subjected to homogenization treatment using a high-pressure homogenizer, the discharge particle size of the homogenized graphene oxide water slurry is controlled in the range of 0.3-2.0 μm, and a homogenized graphene oxide water slurry is obtained; the homogenized graphene oxide water slurry is transferred to a double-planetary defoaming machine for defoaming treatment, and the viscosity of the homogenized and defoamed graphene oxide water slurry is controlled within the range of 2000-10000 mpa.s, if the slurry viscosity is too low, it can be appropriately placed for a period of time to improve the viscosity of the graphene oxide water slurry, and a graphene oxide water slurry to be coated is obtained.

[0007] S3, coating: design 0.2mm-2mm diameter holes on the coating substrate and punch holes with a density of 1-20 holes / 100cm 2 The edge burrs of the through holes are polished to ensure the flatness of the through hole position; a graphene oxide coating layer with a thickness of 2000-10000 microns is coated on the coating substrate, and the coating speed is 10-40mm / s.

[0008] S4, Z-axis heat conduction channel construction: select a heating wire smaller than the hole diameter as the pulling wire, and select a 5V-36V low-voltage power supply as the heating power; the heating wire can be selected from a metal wire; the metal wire is passed through the through hole of the coating substrate, through the substrate and the graphene oxide coating layer, and is vertically fixed, the heating power is connected to the metal wire at both ends of the coating film, and a communication switch is designed; within the range of the mass of the graphene oxide coating film / mass at the time of coating being greater than 30%, the heating power is started to heat the metal wire, and the metal wire is vertically pulled upward at a speed of 5-200mm / s, the rapid pulling heat setting time is 10-120s, and the metal wire is taken out after the end; then natural air drying, air drying or heat drying drying treatment is carried out to obtain a graphene oxide heat conduction film with a Z-axis (thickness direction) heat conduction channel. The graphene oxide coating layer obtained after coating has good flowability, and it is relatively easy to pass the heating wire at this time. With the passage of time, the graphene oxide coating layer will backfill the passage, making it difficult to pass the heating wire, so it is necessary to limit the mass of the graphene oxide coating layer when the hole is punched: the mass of the graphene oxide coating layer when coating is >30%, which is the appropriate condition for passing the heating wire.

[0009] S5, thermal reduction treatment: the graphene oxide film with Z-axis heat conduction channel obtained in S4 after drying treatment is subjected to 200-300℃ heat pretreatment, 800-1500℃ carbonization treatment and 2800-3200℃ graphitization treatment according to the conventional thermal reduction treatment process, to obtain a graphene heat conduction film with Z-axis heat conduction channel, and each heat treatment link is carried out under a load of 10-80kg.

[0010] Compared with the prior art, the technical effects achieved by the present application are as follows: The graphene heat conduction film with Z-axis high heat conduction channel constructed by the fast heating and pulling setting strategy avoids the backflow and collapse of the graphene oxide slurry to the constructed longitudinal heat conduction channel, realizes the rapid setting and construction of the Z-axis heat conduction channel, and realizes the high heat conduction performance of the graphene heat conduction film in the Z-axis direction by the longitudinal friction and interfacial shear force of the rapid pulling, which is a simple and efficient Z-axis direction paving order self-sufficient construction strategy. Unlike the traditional graphene heat conduction film with high heat conduction performance in the X-Y direction and low heat conduction performance in the Z-axis direction, the graphene heat conduction film has high heat conduction performance in the Z-axis and X-Y directions and other physical properties are basically not attenuated.

[0011] By constructing the Z-axis efficient heat conduction channel, the heat source temperature can be rapidly conducted from the bottom surface of the graphene heat conduction film to the surface, realizing efficient heat conduction in the Z-axis direction, avoiding the serious scattering of heat carrier phonons caused by the traditional layer-by-layer diffusion type heat conduction, and only a small amount of Z-axis heat conduction channels need to be constructed to realize efficient heat conduction of the heat source in the Z-axis direction. The construction of a small amount of Z-axis heat conduction channels will not affect the ordered self-assembly and long-range order in the X-Y direction, will not cause irreversible damage to the microstructure in the X-Y direction, and will not need to be assisted by heat-conducting fillers and construct a high-entropy chaotic system. It is a strategy for improving the Z-axis heat conduction performance without damaging the X-Y direction heat conduction performance. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 XPS spectrum of the GO cake selected for Example 1.

[0013] Figure 2 Particle size test curve of the homogeneous slurry of step S2 of Example 1.

[0014] Figure 3 SEM image of the Z-axis heat conduction channel constructed by heat fixation type pulling of Example 1.

[0015] Figure 4 SEM image of the edge area of the Z-axis heat conduction channel constructed by heat fixation type pulling of Example 1.

[0016] Figure 5 SEM image of the cross section of the Z-axis heat conduction channel constructed by heat fixation type pulling of Example 1.

[0017] Figure 6 Z-axis direction heat conduction performance test curve of the sample of Example 1.

[0018] Figure 7 SEM image of the Z-axis heat conduction channel constructed by pulling without heat fixation of the sample of Example 2.

[0019] Figure 8 SEM image of the Z-axis heat conduction channel constructed by heat fixation type pulling of Example 3.

[0020] Figure 9 SEM image of the inner wall of the Z-axis heat conduction channel constructed by heat fixation type pulling of Example 3.

[0021] Figure 10 Z-axis direction heat conduction performance test curve of the sample of Example 4.

[0022] Figure 11 Z-axis direction heat conduction performance test curve of the sample of Example 5.

[0023] Figure 12Z-axis direction thermal conductivity test curve of Example 6 sample.

[0024] Figure 13 Z-axis direction thermal conductivity test curve of Example 7 sample.

[0025] Figure 14 Z-axis direction thermal conductivity test curve of Example 8 sample.

[0026] Figure 15 Z-axis direction thermal conductivity test curve of Example 9 sample. DETAILED DESCRIPTION

[0027] The present application is further described in the following Examples, but it should be understood that these Examples do not limit the scope of the application. Unless otherwise indicated, the techniques employed in the Examples are conventional techniques well known in the art. Unless otherwise indicated, the reagents, methods and equipment employed in the present application are conventional reagents, methods and equipment in the art, and there is no specific limitation on their sources, which can be purchased on the market or prepared according to conventional methods well known to those skilled in the art.

[0028] Unless otherwise indicated, the terms "comprise" or variations such as "comprises" or "comprising" will be understood to imply the inclusion of a stated element or group of elements but not the exclusion of any other element or group of elements.

[0029] The technical solutions of the present application are described below through specific examples. It should be understood that the one or more steps mentioned in the present application do not exclude other methods and steps before or after the combination steps, or other methods and steps can be inserted between these explicitly mentioned steps. It should also be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application. Unless otherwise specified, the numbering of each method step is only for the purpose of identifying each method step, and is not intended to limit the arrangement order of each method or to limit the scope of the implementation of the present application. Changes or adjustments of the relative relationship, without substantial changes in technical content, can also be considered as the scope of the implementation of the present application.

[0030] The application discloses a graphene heat-conducting film with a Z-axis high-heat-conducting channel constructed by fast heat drawing and setting and a preparation method thereof. The Z-axis high-heat-conducting channel is constructed in the Z-axis direction of the graphene heat-conducting film by the strategy of fast heat drawing and setting, so that efficient heat conduction is realized between the bottom surface and the surface of the graphene film. The improved strategy is optimized on the basis of the first Z-axis direction heat-conducting performance improvement strategy. The principle is that the longitudinal friction force of fast longitudinal drawing is used to induce the highly ordered arrangement of graphene oxide layers in the Z-axis direction, and the fast heat setting is used to avoid the backflow and collapse of the graphene oxide slurry to the constructed longitudinal heat-conducting channel, so that the fast setting and construction of the heat-conducting channel for efficient heat conduction from the bottom surface to the surface of the graphene heat-conducting film are maintained. By constructing the Z-axis high-heat-conducting channel, the heat source temperature can be quickly conducted from the bottom surface of the graphene heat-conducting film to the surface of the graphene heat-conducting film, the Z-axis heat-conducting mode of layer-by-layer diffusion and conduction of the heat source temperature of the graphene heat-conducting film is replaced, and the scattering of the heat carriers between the graphene film layers is greatly avoided. In addition, the Z-axis high-heat-conducting channel is constructed in a small amount, the fast heat conduction from the bottom surface to the surface of the graphene film and the Z-axis heat conduction are realized, and the construction of the small amount of Z-axis heat-conducting channel does not affect the long-range order of the ordered paving of the graphene film in the X-Y direction, so that the heat-conducting performance of the graphene in the X-Y direction is greatly reserved. This is a graphene heat-conducting film preparation method compatible with longitudinal and planar heat-conducting performance. Example 1

[0031] The present embodiment is a graphene heat-conducting film preparation method provided by the application for constructing a Z-axis high-heat-conducting channel by fast heat drawing and setting, and the specific steps are as follows: S1, preparation of graphene oxide water slurry: the basic parameters of the graphene oxide cake selected in the embodiment are as follows: the solid content of the graphene oxide cake is 44.78%, the S element impurity content ratio is 2.11%, the XPS characterization result is as shown in the figure, the SP Figure 1 / SP 2 / SP 3 C-C ratio is 43.95%, the C-O ratio is 45.03%, and the O-C=O / C=O ratio is 11.02%. The design solid content of the graphene oxide water slurry is 5%. Under the condition of stirring, 9% of the mass of the graphene oxide cake is added into deionized water, and the mass concentration of AR analytical pure ammonia water is 25%, so that an alkaline mixed water solvent with ammonia water is obtained; the graphene oxide cake is weighed according to the design solid content of 5%; the graphene oxide cake is added into the mixed water solvent in small pieces under the condition of stirring and is fully stirred and dispersed, so that a dispersed graphene water slurry is obtained.

[0032] S2, homogenization and defoaming treatment: the graphene oxide water slurry prepared in S1 is treated by using a high-pressure homogenizer, and the particle size D 10 , D 50 , D 90 ​Figure 2 The particle size test curve shows that the GO slurry after small particle size regulation has good liquid crystal arrangement characteristics and good ordered paving characteristics with particle sizes of 0.275 μm, 0.475 μm and 0.784 μm respectively. The well-homogenized graphene oxide water slurry is transferred to a double-planet defoaming machine for defoaming treatment, the stirring speed is controlled at 80 r / min, the dispersion speed is controlled at 2000 r / min, and the vacuum stirring time is 180 min. The viscosity of the homogenized and defoamed graphene oxide water slurry is controlled at 6000 mPa·s, and the graphene oxide water slurry to be coated is obtained.

[0033] S3, coating: a 0.8 mm diameter hole is designed on the coating substrate, and the through hole is punched with a density of 5 holes / 100 cm 2 , and the edge burrs of the through hole are polished to ensure the flatness of the through hole position; a copper heating wire smaller than the hole diameter is selected as the pulling wire, and a 12V low-voltage power supply is selected as the heating power supply; a graphene oxide coating layer with a thickness of 5000 μm is coated on the coating substrate.

[0034] S4, Z-axis heat conduction channel construction: the metal wire is passed through the through hole of the coating substrate, through the substrate and the graphene oxide coating layer, and is vertically fixed, the heating power supply is connected to the metal wires at both ends of the coating film and a communication switch is designed; within the range of more than 30% of the mass of the graphene oxide coating film during coating, the heating power supply is started to heat the metal wire, and the metal wire is vertically pulled up at a speed of 100 mm / s, the rapid pulling heat setting time is 80 s, and the metal wire is taken out after the end; then, drying treatment is carried out by blowing hot air at 45°C to obtain a graphene oxide heat conduction film constructed with a Z-axis heat conduction channel.

[0035] S5, heat treatment: the graphene oxide dry film constructed with a Z-axis heat conduction channel obtained in S4 is subjected to 240°C heat pretreatment, 1200°C carbonization treatment and 3100°C graphitization treatment according to the conventional heat treatment process, to obtain a graphene heat conduction film constructed with a Z-axis heat conduction channel, and each heat treatment link is carried out under a load of 10 kg.

[0036] S6, the Z-axis direction heat conduction performance of the sample obtained in step S5 and the blank control sample is tested and compared horizontally, the test instrument is LFA46700B-0816-L, the test method is 4 samples round, the thermal diffusivity is 108.873 mm 2 / s, and the Z-axis direction heat conduction coefficient is 22.515 W / mk.

[0037] Other embodiments explore the influence of influencing factors on the performance of the material by controlling variables, as shown in the table:

[0038] The difference between Comparative Example 1 and Example 1 is that the coating substrate of S3 is not provided with a hole for passing through the pulling line, and there is no step S4, i.e. no heat pulling shaping treatment, the graphene sheets inside the graphene film are orderly tiled, and no Z-axis longitudinal heat conduction channel is constructed, and the Z-axis direction heat conduction coefficient is 3.207 W / mk, which is much lower than that of other examples, which can be attributed to the fact that the conventional planar coating film has no Z-axis heat conduction channel, and the heat is conducted from the bottom heat source to the surface layer through layer-by-layer heat conduction, and the interlayer gap causes serious phonon scattering, which is not conducive to the heat conduction in the Z-axis direction.

[0039] Example 2 The difference between Example 2 and Example 1 is that no heating pulling is performed in step S4, i.e. no power is turned on, and only pulling is performed without heat fixation treatment, and the obtained graphene heat conduction film is tested for heat conduction performance, and the Z-axis (thickness) direction heat conduction coefficient is 3.578 W / mk, which is similar to that of the sample of the comparative example, which can be attributed to the fact that the heat fixation shaping pulling cannot construct a stable Z-axis heat conduction channel, and the GO slurry is refilled into the gap after pulling under the action of the gravitational field. The SEM graph of the heat conduction channel of the graphene heat conduction film obtained in this example is shown in Figure 7 .

[0040] Example 3 The difference between Example 3 and Example 1 is that the direct current heating voltage in step S3 is 36V, i.e. the temperature of the pulling wire is increased by increasing the heating voltage, and the obtained graphene heat conduction film is tested for heat conduction performance, and the Z-axis (thickness) direction heat conduction coefficient is 6.496 W / mk, which is twice that of the control group, but much lower than that of Example 1 but better than that of the comparative example, which can be attributed to the fact that under the premise of fixed size of the pulling wire, the higher the direct current heating voltage, the higher the temperature of the wire, and excessive heat fixation shaping temperature is easy to cause rapid thermal reduction of GO in the pulling boundary area and accompanied by obvious gas production, and excessive gas production causes the graphene layers arranged in the Z-axis direction to be obviously layered, which is not conducive to the self-assembly of GO sheet layers in the Z-axis direction. The SEM graph of the heat conduction channel of the graphene heat conduction film obtained in this example is shown in Figure 8 . Figure 9 Then it is the SEM graph of the inner wall of the heat conduction channel, and it can be found that it is obviously layered by interlayer separation. According to the results of the heat conduction test and the SEM graph, it is considered that when the heating voltage of the pulling line is high, the heat fixation effect is good, but the inner wall of the Z-axis channel constructed is obviously layered, which can be attributed to the fact that high heat makes the GO sheet layer on the surface of the inner wall rapidly thermally reduced and deoxidized, which is not conducive to the construction of the longitudinal orderly arrangement with good self-assembly film effect on the Z-axis channel.

[0041] Example 4 The difference between Example 4 and Example 1 is that the designed hole density is 1 / 100 cm 2The obtained graphene heat-conducting film was tested for heat-conducting performance, and the Z-axis direction heat-conducting coefficient was 8.192 W / mk, and the heat-conducting performance test curve is shown in Figure 10 The Z-axis direction heat-conducting performance was not as good as that of Example 1 but better than that of the comparative example, which was mainly due to the small hole density in the film, the small cross-sectional area, the insufficient gas leakage cross-sectional area of the gas produced by the heat reduction and deoxidization of the GO film in the heat treatment stage, and the gas accumulation in the film leading to a high degree of expansion. The high degree of expansion caused the graphene layers in the phase to be delaminated, and the Z-axis direction heat-conducting channel was delaminated due to excessive expansion, and the delamination caused the Z-axis direction heat-conducting channel to be cut off.

[0042] Example 5 Example 5 was different from Example 1 in that the designed hole density was 10 / 100 cm 2 , and the Z-axis direction heat-conducting coefficient was 11.535 W / mk, and the heat-conducting performance test curve is shown in Figure 11 The Z-axis direction heat-conducting performance was not as good as that of Example 1 but better than that of the comparative example, which was mainly due to the small hole density in the film, the small cross-sectional area, the insufficient gas leakage cross-sectional area of the gas produced by the heat reduction and deoxidization of the GO film in the heat treatment stage, and the gas accumulation in the film leading to a high degree of expansion. The high degree of expansion caused the graphene layers in the phase to be delaminated, and the Z-axis direction heat-conducting channel was delaminated due to excessive expansion, and the delamination caused the Z-axis direction heat-conducting channel to be cut off.

[0043] Example 6 Example 6 was different from Example 1 in that the pulling speed of step S4 was reduced to 5 mm / s, the Z-axis direction heat-conducting coefficient was 11.393 W / mk, and the heat-conducting performance test curve is shown in Figure 12 The Z-axis direction heat-conducting performance was not as good as that of Example 1. It was analyzed that in the slow pulling process, the GO solidification and shaping interface film at the metal wire interface was easy to be carried out with the treatment by the friction of the metal wire, a new interface was continuously formed at the interface, and the GO slurry was taken out by the friction, the vertical distance of the new interface from the metal wire was increased, the solidification and shaping effect was poor, and the longitudinal ordered arrangement of the graphene layers in the Z-axis direction was not good.

[0044] Example 7 Example 7 was different from Example 1 in that the pulling speed of step S4 was increased to 200 mm / s, the Z-axis direction heat-conducting coefficient was 11.221 W / mk, and the heat-conducting performance test curve is shown in Figure 13The Z-axis direction heat conduction performance is not as good as that of Example 1. This can be attributed to the fact that the pulling speed is too high, which easily causes the GO slurry at the pulling position to be stuck out, resulting in a larger hole at the pulling position, an increased vertical distance between the GO slurry new interface and the metal wire, a poor heat curing and shaping effect of the metal wire, and an unclear longitudinal arrangement of the graphene sheet layer on the Z-axis channel, thereby resulting in a poor Z-axis heat conduction channel construction effect.

[0045] Example 8 Example 8 is different from Example 1 in that the hole diameter designed in step S3 is reduced to 0.2 mm, and the thermal conductivity is 12.893 W / mk. The heat conduction performance test curve is as shown in Figure 14 The Z-axis direction heat conduction performance is not as good as that of Example 1, but is better than that of the comparative example. It is analyzed that the reduction of the pulling hole diameter requires a thinner metal wire to be matched, and the small cross-sectional area of the thin metal wire results in a poor pulling effect of the graphene sheet layer. The thin metal wire is in a submerged state during the pulling process, and after the pulling is completed, the newly constructed Z-axis heat conduction channel is easily squeezed and filled with the GO slurry under the action of the gravity field.

[0046] Example 9 Example 9 is different from Example 1 in that the hole diameter designed in step S3 is expanded to 2 microns, and the thermal conductivity is 11.098 W / mk. The heat conduction performance test curve is as shown in Figure 15 The Z-axis direction heat conduction performance is not as good as that of Example 1, but is better than that of the comparative example. It is analyzed that the expansion of the pulling hole diameter causes the Z-axis heat conduction channel bottom to be filled and buried with the flow-following GO slurry, forming a conical channel, which to some extent destroys the longitudinal arrangement of the graphene sheet layer on the Z-axis. In addition, the larger pulling hole is not conducive to the pulling of the graphene sheet layer in the longitudinal direction by the metal wire, and the heat curing and shaping effect is poor.

[0047] The foregoing description of specific exemplary embodiments of the application is intended to be illustrative only and is not intended to limit the application to the precise forms described. Many modifications and variations are possible in light of the above teachings without departing from the spirit or essential characteristics of the application. The exemplary embodiments were chosen and described in order to explain the principles of the application and its practical application to thereby enable others skilled in the art to best utilize the application and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the application be defined by the claims and their equivalents.

Claims

1. A method for preparing a graphene thermally conductive film, comprising at least the following steps: preparing a graphene oxide aqueous slurry from a graphene oxide cake; homogenizing and degassing the graphene oxide aqueous slurry, adjusting the graphene oxide flake diameter and the viscosity of the graphene oxide aqueous slurry to obtain a coatable slurry; coating the graphene oxide aqueous slurry on a coating substrate to obtain a graphene oxide coating; drying the graphene oxide coating and separating it from the coating substrate to obtain a graphene oxide film; and thermally reducing the graphene oxide film to obtain a graphene thermally conductive film. The method is characterized in that: After the coating step is completed, a heating wire is used to pass through the coated substrate and the graphene oxide coating. When the heating wire is energized, it generates heat and is pulled vertically upward to construct a heat conduction channel along the thickness direction of the graphene oxide coating.

2. The method for preparing a graphene thermally conductive film according to claim 1, wherein: The heating wire is a metal heating wire, which is fixed vertically after passing through the coated substrate and the graphene oxide coating, and is connected to a heating power source at both ends. It is vertically pulled upward at a speed of 5mm / s-200mm / s for heat setting. The pulling and heat setting time is 10s-120s. After the pulling and heat setting treatment, the metal heating wire is taken out.

3. The method for preparing a graphene thermally conductive film according to claim 2, wherein: The coating substrate is provided with through holes with a diameter of 0.2 mm to 2 mm, and the through holes are arranged at a number of 1 to 20 holes per 100 cm².

4. The method for preparing a graphene thermally conductive film according to claim 2, wherein: The heating power supply uses a low-voltage power supply of 5V-36V.

5. The method for preparing a graphene thermally conductive film according to claim 1, wherein: In the step of preparing the graphene oxide water slurry, the solid content of the graphene oxide cake is 30%-60%.

6. The method for preparing a graphene thermally conductive film according to claim 1, wherein: In the step of preparing the coatable slurry, the graphene oxide aqueous slurry is homogenized and degassed, and then the viscosity of the graphene oxide aqueous slurry is adjusted to 2000 mPa.s-10000 mPa.s.

7. The method for preparing a graphene thermally conductive film according to claim 1, wherein: The thickness of the graphene oxide coating is 2000 μm-10000 μm.

8. The method for preparing a graphene thermally conductive film according to claim 1, wherein: The thermal reduction treatment step includes thermal pretreatment, carbonization treatment and graphitization treatment.

9. The method for preparing a graphene thermally conductive film according to claim 8, wherein: The temperature of the heat pretreatment step is 200-300°C, the temperature of the carbonization treatment is 800-1500°C, and the temperature of the graphitization is 2800-3200°C.

10. The method for preparing a graphene thermally conductive film according to claim 9, wherein: The thermal reduction treatment steps are all carried out under the condition of a load of 10kg-80kg.

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