Reduced graphene oxide film as well as preparation method and application thereof

Abstract

According to the reduced graphene oxide film as well as the preparation method and the application thereof provided by the invention, the reduced graphene oxide film with a higher thermal diffusion coefficient in a specific direction can be industrially produced by improving related process parameters such as related performance, coating rate and drying speed of a coating base material; the reduced graphene oxide film can be optimized according to the efficient heat dissipation requirement in the specific direction.

Description

Technical Field

[0001] The present application relates to the field of thermal management, and specifically, to a reduced graphene oxide film and a preparation method and application thereof. Background Art

[0002] Reduced graphene oxide film has important application value in the fields of electronic heat dissipation and flexible devices due to its high thermal conductivity, light weight and flexibility. Traditional reduced graphene oxide films usually exhibit isotropic thermal diffusion characteristics within the plane, that is, the difference in thermal diffusion coefficients in different directions in the same plane is small. In some application scenarios, the material is required to have a higher thermal diffusion coefficient in a specific direction. Traditional reduced graphene oxide films are difficult to optimize for the efficient heat dissipation needs in a specific direction.

[0003] In the prior art, the thermal diffusion coefficient of the reduced graphene oxide film in a certain direction is improved by adding directional fillers or applying magnetic fields, electric fields, etc., but there are problems such as complex processes and poor material uniformity. Summary of the invention

[0004] In a first aspect, the present application provides a reduced graphene oxide film, wherein the reduced graphene oxide film includes a first direction in a plane, and a thermal diffusion coefficient in the first direction is greater than a thermal diffusion coefficient in other directions in the plane.

[0005] Furthermore, the thermal expansion coefficient of the reduced graphene oxide film in the first direction is 1.1 times or more of the thermal diffusion coefficients in other directions within the plane.

[0006] Furthermore, the density of the reduced graphene oxide film is 1.8~2.3g / cm 3 .

[0007] Furthermore, the density of the reduced graphene oxide film is 0.1~0.5g / cm 3 , and there are pores in the reduced graphene oxide film.

[0008] The second aspect of the present application is to provide a method for preparing reduced graphene oxide, comprising the following steps: A graphene oxide slurry is prepared and coated onto a substrate with a scraper, and then dried to form a graphene oxide film. The graphene oxide film is then peeled off from the substrate, heat treated, and rolled to obtain a reduced graphene oxide film. The roughness of the substrate is 5-50 μm, the coating speed is 0.3-2 m / min, and the relative movement direction between the substrate and the scraper is defined as a first direction.

[0009] Furthermore, the roughness of the substrate is 10-30 μm, and the coating speed is 0.5-1.5 m / min.

[0010] Furthermore, the roughness of the substrate in the first direction is 10-20 μm, and the roughness of the substrate perpendicular to the first direction is 15-30 μm.

[0011] Furthermore, the air permeability of the substrate is 80 to 90 cc / min, and the substrate is in a tensioned state during the coating process.

[0012] Furthermore, after the stripping step, the graphene oxide film is chemically reduced, and the reducing agent is at least one of hydrazine hydrate, sodium hydrogen borate, dimethylhydrazine, and thiourea; and / or, the reducing agent concentration is 5% to 80%; And / or, the chemical reduction time is 1 to 200 seconds.

[0013] The third aspect of the present application is to provide an application of a reduced graphene oxide film, comprising the following steps: a) determining a first direction of the reduced graphene oxide film, taking a single reduced graphene oxide film as a heat dissipation unit, or taking two or more reduced graphene oxide films and stacking them in the same first direction as a heat dissipation unit; b) connecting the heat dissipation unit to a heating element, and the reduced graphene oxide film conducts heat generated by the heating element in a first direction.

[0014] The beneficial effect of the present application is to provide an industrial method and product for directionally regulating the thermal properties of reduced graphene oxide films. By improving the relevant process parameters such as the coating substrate performance, coating rate, drying speed, etc., industrial-grade mass production of reduced graphene oxide films with higher thermal diffusion coefficients in specific directions can be achieved. Such reduced graphene oxide films can then be optimized for efficient heat dissipation requirements in specific directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 The reduced graphene oxide film prepared in Example 4 of the present application Figure 2 The reduced graphene oxide film prepared in Example 6 of the present application DETAILED DESCRIPTION

[0017] The following detailed description of the exemplary embodiments of the present application refers to the accompanying drawings, which form a part of the description, and in which the exemplary embodiments that can be implemented by the present application are shown as examples. The following more detailed description of the embodiments of the present application is not intended to limit the scope of the present application as required, but is only for illustration and does not limit the description of the characteristics and features of the present application, so as to propose the best way to perform the present application, and is sufficient to enable those skilled in the art to implement the present application. However, it should be understood that various modifications and variations can be made without departing from the scope of the present application as defined by the appended claims. The detailed description and the accompanying drawings should be considered only as illustrative, not restrictive, and if there are any such modifications and variations, they will all fall within the scope of the present application described herein. In addition, the background technology is intended to illustrate the current status and significance of the research and development of the present technology, and is not intended to limit the present application and the application field of the present application.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the term "and / or" used herein includes any and all combinations of one or more related listed items.

[0019] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0020] The first aspect of the present application is to provide a reduced graphene oxide film, wherein the reduced graphene oxide film includes a first direction in a plane, and the thermal diffusion coefficient of the first direction is greater than the thermal diffusion coefficient of other directions in the plane. The reduced graphene oxide film has better thermal performance in a specific direction in the same plane, and is more capable of matching the high heat dissipation requirements in the specific direction.

[0021] In some embodiments of the first aspect of the present application, the thermal expansion coefficient of the reduced graphene oxide film in the first direction is 1.1 times or more of the thermal diffusion coefficients in other directions within the plane.

[0022] In some embodiments of the first aspect of the present application, the density of the reduced graphene oxide film is 1.8-2.3 g / cm 3 This type of reduced graphene oxide film has good thermal conductivity and heat dissipation performance within the plane.

[0023] In some embodiments of the first aspect of the present application, the density of the reduced graphene oxide film is 0.1-0.5 g / cm 3, and the reduced graphene oxide film has cavities. In addition to having good thermal conductivity and heat distribution performance, this type of reduced graphene oxide film has micro-nano cavities. When subjected to external compressive stress, the pore structure can quickly disperse the stress and be compressed without destroying the film structure. When no longer subjected to external forces, the film rebounds, giving the film the ability to rebound after compression.

[0024] The second aspect of the present application is to provide a method for preparing reduced graphene oxide, comprising the following steps: A graphene oxide slurry is prepared and coated onto a substrate with a scraper, and then dried to form a graphene oxide film. The graphene oxide film is then peeled off from the substrate, heat treated, and rolled to obtain a reduced graphene oxide film. The roughness of the substrate is 5-50 μm, the coating speed is 0.3-2 m / min, and the relative movement direction between the substrate and the scraper is defined as a first direction.

[0025] The inventors found that the selection of the surface roughness of the substrate in conjunction with the coating speed of the graphene oxide slurry can affect the final self-assembly degree of the reduced graphene oxide film. First, the coating speed can directly affect the shear force of the slurry on the substrate surface. When there is a certain coating speed, the relative movement between the scraper and the substrate generates a shear force, which prompts the graphene oxide sheets to be arranged along the shear direction to form an orderly orientation; secondly, the roughness of the substrate can affect the contact angle between the substrate and the graphene oxide slurry, so that the orientation of the graphene oxide sheets on the substrate surface is restricted. When the coating speed is fast, the graphene oxide slurry does not have time to fully spread and adjust the orientation. When the graphene oxide slurry is coated too slowly, the industrial production efficiency is affected. The relative force between the internal flakes of graphene oxide will also cause the orientation distribution of the flakes to deviate from the relative movement direction of the substrate and the scraper. For the substrate, if the substrate is too smooth, the distribution of the graphene oxide flakes on the substrate surface is even more unnecessary due to the castable characteristics of the graphene oxide slurry. The greater the surface roughness of the substrate, the greater the influence of the substrate surface structure on the orientation distribution of the flakes. Based on the influence of the above two factors, the roughness of the substrate is set to 5~50μm, and the coating speed is set to 0.3~2m / min. The prepared reduced graphene oxide film can have a better thermal diffusion coefficient in the first direction of relative movement between the scraper and the substrate. Typically, but not limiting, the roughness of the substrate is 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm; the coating speed is 0.3m / min, 0.4m / min, 0.5m / min, 0.6m / min, 0.7m / min, 0.8m / min, 0.9m / min, 1.0m / min, 1.1m / min, 1.2m / min, 1.3m / min, 1.4m / min, 1.5m / min, 1.6m / min, 1.7m / min, 1.8m / min, 1.9m / min, 2.0m / min.

[0026] In some embodiments of the second aspect of the present application, the inventors found that the roughness of the substrate is 10-30 μm, the coating speed is 0.5-1.5 m / min, and the prepared reduced graphene oxide film can have a better thermal diffusion coefficient. Typically but not limiting, the roughness of the substrate is 10 μm, 15 μm, 20 μm, 25 μm, 30 μm; the coating speed is 0.5 m / min, 0.6 m / min, 0.7 m / min, 0.8 m / min, 0.9 m / min, 1.0 m / min, 1.1 m / min, 1.2 m / min, 1.3 m / min, 1.4 m / min, 1.5 m / min.

[0027] In some embodiments of the second aspect of the present application, the roughness of the substrate in the first direction is 10-20 μm, and the roughness of the substrate perpendicular to the first direction is 15-30 μm. The inventors also found that by controlling the roughness of the coated substrate in different directions, the orientation of the graphene oxide sheets can be further controlled. If the roughness of the substrate in the first direction is small, then the microstructure in the first direction of the substrate has a weaker restrictive effect on the graphene oxide sheets, while the roughness of the substrate perpendicular to the first direction is large, which hinders the graphene oxide sheets from sliding in this direction. The two work together to further enhance the orientation of the graphene oxide slurry in the first direction, and the prepared reduced graphene oxide film can have a better thermal diffusion coefficient in the first direction.

[0028] In some embodiments of the second aspect of the present application, the air permeability of the substrate is 80 to 90 cc / minute, and the substrate is in a tensioned state during the coating process. When the air permeability of the substrate is too high, the slurry sinks and is tightly anchored in the substrate, which will make it difficult to peel off the graphene oxide film in the later stage. If the air permeability of the substrate is low, it will make it difficult to dry the reduced graphene oxide film. At the same time, the slurry is mainly attached to the surface of the substrate with low air permeability, and the contact and bonding between the slurry and the substrate are limited. In the subsequent drying process, the film material may also fall off, causing wrinkles in the product. The substrate is in a tensioned state during the coating process, which can make the coating of the graphene oxide slurry smoother, and the arrangement of the graphene oxide flakes during the coating and drying process is less disturbed.

[0029] In some embodiments of the second aspect of the present application, after the stripping step, the graphene oxide film is further chemically reduced, and the reducing agent is at least one of hydrazine hydrate, sodium hydrogen borate, dimethylhydrazine, and thiourea; and / or, the reducing agent concentration is 5% to 80%; And / or, the chemical reduction time is 1 to 200 seconds.

[0030] Through the action of the reducing agent, cavities are formed inside the original membrane. When subjected to external compressive stress, the three-dimensional pore structure can quickly disperse the stress and be compressed without destroying the membrane structure. When no longer subjected to external forces, the membrane rebounds. Typically but not restrictive, the concentration of the reducing agent is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%; the time of chemical reduction is 1s, 3s, 5s, 10s, 20s, 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s, 120s, 130s, 140s, 150s, 160s, 170s, 180s, 190s, 200s.

[0031] The third aspect of the present application is to provide an application of a reduced graphene oxide film, comprising the following steps: a) determining a first direction of the reduced graphene oxide film, taking a single reduced graphene oxide film as a heat dissipation unit, or taking two or more reduced graphene oxide films and stacking them in the same first direction as a heat dissipation unit; b) connecting the heat dissipation unit to a heating element, and the reduced graphene oxide film conducts heat generated by the heating element in a first direction.

[0032] In some embodiments of the third aspect of the present application, the specific application of the graphene oxide film is as follows: In some embodiments, the heat dissipation unit is a single sheet with a density of 1.8-2.3 g / cm 3 The reduced graphene oxide film is used, and the heating element is a mobile phone chip. A single reduced graphene oxide film is attached to the chip to conduct the heat generated by the chip in the actual required heat dissipation direction.

[0033] In some embodiments, the heat dissipation unit is multiple and has a density of 0.1-0.5 g / cm 3 The reduced graphene oxide film is a plurality of reduced graphene oxide films which are stacked and connected. The heating element is a mobile phone chip. The plurality of stacked and connected reduced graphene oxide films are attached to the chip, and the heat generated by the chip is conducted in the actually required heat dissipation direction.

[0034] The detection methods involved in the embodiments of the present application are as follows: Density: Density = mass / volume Thermal diffusivity test method: The test method in the standard "Q / GDMR 04-2023 Laser Flash Method for Testing Thermal Conductivity" pays attention to distinguishing the sample cutting direction when preparing the test sample: When using the Laminate mode test method, it should be noted that the sample should be cut with the first direction as the length direction or the width direction.

[0035] Among them, when using the In-Plane mode test method, the thermal diffusion coefficient test in a specific direction requires controlling the sensor recognition position of the j detection equipment to be on a diameter consistent with the specific direction, and shielding the sensor recognition position that is not located on the same diameter. Example 1

[0036] A method for preparing a reduced graphene oxide film comprises the following steps: S1. Mix the A52 graphene oxide cake purchased by Yuntian Mo Rui with deionized water and put it into a planetary mixing equipment for stirring to obtain a slurry with a solid content of 5%. Then, the slurry is homogenized and vacuum degassed to obtain a graphene oxide slurry with a solid content of 5%.

[0037] S2. Use commercially available PP as the coating substrate. The product specifications of the PP substrate are selected as follows: roughness is 10~30μm, air permeability is 80~90cc / minute, and the coating substrate is tensioned on the coating line. The coating line is a conveying structure, a scraper is set at the front end of the coating line, and an oven is set at the rear end.

[0038] S3. After the graphene oxide slurry is fed onto the substrate, the substrate is moved at a speed of 1 m / min and passes through a scraper and an oven respectively, that is, the graphene oxide slurry is coated into a graphene oxide film at a coating speed of 1 m / min and then dried, wherein the direction in which the substrate moves is taken as the first direction.

[0039] S4. The obtained graphene oxide film is peeled off from the substrate, and then heat-treated, including pretreatment at 240°C for 1 hour, carbonization treatment at 1200°C for 1 hour in a nitrogen atmosphere, and graphitization treatment at 3000°C for 1 hour in an argon atmosphere, and finally the reduced graphene oxide film is obtained by flat pressing.

[0040] The density of the obtained reduced graphene oxide film is 2.126 g / cm 3 The thermal diffusion coefficient of the reduced graphene oxide film in the first direction was 736.378 mm 2 / s; the thermal diffusion coefficient in the plane perpendicular to the first direction is 639.386mm 2 / s. Example 2-3

[0041] The difference from Example 1 is that in step S3, the coating speed is set to 0.5 m / min and 1.5 m / min respectively, and the other steps are consistent with Example 1.

[0042] The density of the reduced graphene oxide film obtained at a coating speed of 0.5 m / min was 2.109 g / cm 3 The thermal diffusion coefficient of the reduced graphene oxide film in the first direction was 722.960 mm 2 / s; the thermal diffusion coefficient in the plane perpendicular to the first direction is 613.284 mm 2 / s.

[0043] The density of the reduced graphene oxide film obtained at a coating speed of 1.5 m / min was 2.123 g / cm 3 The thermal diffusion coefficient of the reduced graphene oxide film in the first direction was 721.181 mm 2 / s; the thermal diffusion coefficient in the plane perpendicular to the first direction is 630.475mm 2 / s. Example 4

[0044] Different from Example 1, in step S2, the parameters of the substrate are further limited as follows: a commercially available PP substrate is selected, specifically, the substrate roughness is 10-30 μm, wherein the roughness in the longitudinal direction (i.e., the first direction in this embodiment) is 10-20 μm, the substrate weft roughness (perpendicular to the first direction) is 15-30 μm, and the air permeability is 80-90 cc / min. The other steps are consistent with Example 1.

[0045] The obtained reduced graphene oxide film is as follows Figure 1 As shown, the density is 2.201g / cm 3 The thermal diffusion coefficient of the reduced graphene oxide film in the first direction was 761.371 mm 2 / s; the thermal diffusion coefficient in the plane perpendicular to the first direction is 649.847mm 2 / s. Example 5

[0046] Different from Example 1, in step S2 and step S3, the selection of substrate and coating speed are further limited, respectively. The specific preparation method of Example 5 is as follows: S1. Mix the A52 graphene oxide cake purchased by Yuntian Mo Rui with deionized water and put it into a planetary mixing equipment for stirring to obtain a slurry with a solid content of 5%. Then, the slurry is homogenized and vacuum degassed to obtain a graphene oxide slurry with a solid content of 5%.

[0047] S2. Use commercially available PP as the coating substrate. The product specifications of the PP substrate are selected as follows: roughness is 20~50μm, air permeability is 80~90cc / minute, and the coating substrate is tensioned on the coating line. The coating line is a conveying structure, a scraper is set at the front end of the coating line, and an oven is set at the rear end.

[0048] S3. After the graphene oxide slurry is fed onto the substrate, the substrate is moved at a speed of 0.3 m / min and passes through a scraper and an oven respectively, that is, the graphene oxide slurry is coated into a graphene oxide film at a coating speed of 0.3 m / min and then dried, wherein the direction in which the substrate moves is taken as the first direction.

[0049] S4. The obtained graphene oxide film is peeled off from the substrate, and then heat-treated, including pretreatment at 240°C for 1 hour, carbonization treatment at 1200°C for 1 hour in a nitrogen atmosphere, and graphitization treatment at 3000°C for 1 hour in an argon atmosphere, and finally the reduced graphene oxide film is obtained by flat pressing.

[0050] The density of the obtained reduced graphene oxide film is 2.049 g / cm 3The thermal diffusion coefficient of the reduced graphene oxide film in the first direction was found to be 683.557 mm 2 / s; the thermal diffusion coefficient in the plane perpendicular to the first direction is 621.431mm 2 / s. Example 6

[0051] Different from Example 4, in step S4, the peeled graphene oxide film is first chemically reduced, and then heat treated and rolled. The preparation method of step S4 is as follows: The obtained graphene oxide film is peeled off from the substrate, and then chemically reduced. Specifically, the graphene oxide film is immersed in a 30% hydrazine hydrate solution for 10 seconds and then immediately removed, and then dried again and heat treated. The heat treatment includes pretreatment at 240°C for 1 hour, carbonization treatment at 1200°C for 1 hour in a nitrogen atmosphere, and graphitization treatment at 3000°C for 1 hour in an argon atmosphere, and finally the reduced graphene oxide film is obtained by flat pressing. The other steps of Example 6 are consistent with those of Example 4.

[0052] The obtained reduced graphene oxide film is as follows Figure 2 As shown, the density is 0.136g / cm 3 The thermal diffusion coefficient of the reduced graphene oxide film in the first direction was 762.394 mm 2 / s; the thermal diffusion coefficient in the plane perpendicular to the first direction is 629.181mm 2 / s. Example 7

[0053] The difference from Example 6 is that in step S4, the type, concentration and treatment time of the reducing agent are different, specifically, the graphene oxide film is immersed in a 5% dimethylhydrazine solution for 200 seconds and then immediately removed. The other steps of Example 7 are consistent with those of Example 6.

[0054] The density of the obtained reduced graphene oxide film is 0.106 g / cm 3 The thermal diffusion coefficient of the reduced graphene oxide dimethyl ethylene film in the first direction was 751.869 mm 2 / s; the thermal diffusion coefficient in the plane perpendicular to the first direction is 625.425mm 2 / s. Example 8

[0055] The difference from Example 6 is that in step S4, the type, concentration and treatment time of the reducing agent are different, specifically, the graphene oxide film is immersed in a 60% hydrazine hydrate solution for 2 seconds and then immediately removed. The other steps of Example 7 are consistent with those of Example 6.

[0056] The density of the obtained reduced graphene oxide film is 0.235 g / cm 3 The thermal diffusion coefficient of the reduced graphene oxide dimethyl ethylene film in the first direction was 753.629 mm 2 / s; the thermal diffusion coefficient in the plane perpendicular to the first direction is 628.924mm 2 / s. Example 9

[0057] The single reduced graphene oxide film prepared in Example 4 is attached to the mobile phone chip to efficiently conduct the heat generated by the chip in the first direction. Example 10

[0058] The five reduced graphene oxide films prepared in Example 6 are stacked and connected, and the five stacked and connected reduced graphene oxide films are attached to a mobile phone chip to efficiently conduct the heat generated by the chip in a first direction.

[0059] The above is a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A reduced graphene oxide film, characterized in that: The reduced graphite oxide film includes a first direction in a plane, and a thermal diffusion coefficient in the first direction is greater than a thermal diffusion coefficient in other directions in the plane.

2. A reduced graphene oxide membrane according to claim 1, characterized in that: The thermal expansion coefficient in the first direction is 1.1 times or more of the thermal diffusion coefficients in other directions in the plane.

3. A reduced graphene oxide film according to claim 1, characterized in that: The density of the reduced graphene oxide film is 1.8-2.3 g / cm 3 .

4. A reduced graphene oxide film according to claim 1, characterized in that: The density of the reduced graphene oxide film is 0.1-0.5 g / cm 3 , and, the reduced graphene oxide film has pores.

5. A method for preparing a reduced graphene oxide film according to any one of claims 1 to 4, characterized in that: The reduced graphene oxide film is obtained by coating graphene oxide slurry onto a substrate with a scraper, drying it to form a graphene oxide film, and then peeling off, heat treating, and rolling the graphene oxide film. The roughness of the substrate is 5-50 μm, the coating speed is 0.3-2 m / min, and the relative movement direction of the substrate and the scraper is a first direction.

6. A method for preparing a reduced graphene oxide film according to claim 5, characterized in that: The roughness of the substrate is 10-30 μm, and the coating speed is 0.5-1.5 m / min.

7. A method for preparing a reduced graphene oxide film according to claim 6, characterized in that: The roughness of the substrate in the first direction is 10-20 μm, and the roughness of the substrate perpendicular to the first direction is 15-30 μm.

8. A method for preparing a reduced graphene oxide film according to claim 5, characterized in that: The air permeability of the substrate is 80 to 90 cc / min, and the substrate is in a tensioned state during the coating process.

9. A method for preparing a reduced graphene oxide film according to claim 5, characterized in that: After the stripping step, the method further comprises chemically reducing the graphene oxide film, wherein the reducing agent is at least one of hydrazine hydrate, sodium hydrogen borate, dimethylhydrazine, and thiourea; And / or, the reducing agent concentration is 5% to 80%; And / or, the chemical reduction time is 1 to 200 s.

10. A use of the reduced graphene oxide film according to any one of claims 1 to 4 or the reduced graphene oxide film prepared by the method according to any one of claims 5 to 9, characterized in that: The following steps are involved: a) determining a first direction of the reduced graphene oxide film, taking a single reduced graphene oxide film as a heat dissipation unit, or taking two or more reduced graphene oxide films and stacking them in the same first direction as a heat dissipation unit; b) connecting the heat dissipation unit to a heating element, and the reduced graphene oxide film conducts heat generated by the heating element in a first direction.

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