Preparation method of graphene film, graphene heat conduction piece and preparation method of graphene heat conduction piece

Abstract

The invention discloses a preparation method of a graphene film, a graphene heat conduction piece and a preparation method of the graphene heat conduction piece. The preparation method of the graphene film comprises the steps that S1, a periodic fold template is obtained, the wavelength of folds in the periodic fold template ranges from 1 micrometer to 100 micrometers, and the amplitude of the folds in the periodic fold template ranges from 5 micrometers to 200 micrometers; s2, coating the periodic fold template with the graphene oxide aqueous slurry to a predetermined thickness, and stripping the periodic fold template after drying treatment to obtain a graphene oxide film; the mass percentage content of graphene oxide in the graphene oxide water slurry is 1-15 wt%; s3, performing thermal reduction treatment on the graphene oxide film to obtain a graphene film; the preparation method of the graphene heat conduction piece comprises the following steps: immersing graphene films in an adhesive, and laminating and curing a plurality of graphene films infiltrated with the adhesive to obtain a graphene block; cutting the graphene block body to obtain a graphene heat conduction piece; the graphene heat conduction piece is provided with periodic wrinkles. The graphene heat-conducting piece has excellent mechanical property and heat-conducting property.

Description

Technical Field

[0001] The present invention relates to the technical field of heat-conducting materials, and in particular to a method for preparing a graphene film, a graphene heat-conducting component and a method for preparing the same. Background Art

[0002] As the integration of chips increases, the heat flux density of chips continues to rise. If the excess heat is not conducted away in time, it will greatly affect the performance of the chip. Thermal interface materials are a type of material used to fill the gap between the chip and the heat sink and conduct heat away, including thermal pads, thermal grease, thermal gel and thermal adhesive. The thermal conductivity of traditional thermal interface materials is 1-10W / mK, which is difficult to meet the thermal conductivity requirements of existing high heat flux density chips.

[0003] Graphene is a sp2 hybridized two-dimensional carbon material with excellent electrical and thermal conductivity. Its in-plane thermal conductivity can theoretically reach 5300W / mK. Under the current process level, the in-plane thermal conductivity of mass-produced graphene films can reach 2000W / mK, which is much higher than traditional metals. However, the z-direction thermal conductivity of graphene is relatively low, generally less than 10W / mK. The graphene thermal pads prepared under the current process are difficult to take into account both low contact thermal resistance and high thermal conductivity. The main reason is that the graphene thermal pads with a thermal conductivity greater than 70W / mK generally have a solid content of ≥50wt%. At this time, the graphene thermal pad has a large compressive stress and is difficult to form a good contact with the device surface. The contact thermal resistance between thermal grease and liquid metal and the device surface can be ignored, and their interface thermal resistance is basically equal to the thermal resistance of the material body. However, for graphene thermal pads, the contact thermal resistance ≥ the body thermal resistance, and the interface thermal resistance = contact thermal resistance + body thermal resistance. In the industry, 130W / mK graphene thermal pads have been mass-produced, but due to the high contact thermal resistance, their interface thermal resistance is still higher than that of liquid metal and some high-performance silicone greases, resulting in their actual effect being less than theoretical expectations. Therefore, reducing the contact thermal resistance of graphene thermal pads is the key to improving their practical application performance. The thermal resistance of graphene thermal pads prepared by existing methods is greater than 0.2K·cm 2 / W, much higher than most silicone greases on the market, such as Dow Corning 5888 (thermal resistance ≈ 0.05K·cm 2 / W) and Shin-Etsu 8117 (thermal resistance ≈ 0.05K·cm 2 / W). Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a graphene film, a graphene thermal conductor and a method for preparing the same.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a method for preparing a graphene film, comprising the following steps:

[0006] S1. Obtain a periodic fold template, wherein the wavelength of the folds in the periodic fold template is 1 μm to 100 μm, and the amplitude is 5 μm to 200 μm;

[0007] S2, coating a graphene oxide water slurry on a periodic wrinkle template to a predetermined thickness, peeling off the periodic wrinkle template after drying, and obtaining a graphene oxide film; the mass percentage of graphene oxide in the graphene oxide water slurry is 1wt% to 15wt%;

[0008] S3. Performing thermal reduction treatment on the graphene oxide film to obtain a graphene film.

[0009] In some embodiments, in step S1, the periodic pleated template is polypropylene, polyethylene, polyethylene terephthalate, polytetrafluoroethylene or polyphenylene phthalamide.

[0010] In some embodiments, in step S2, the predetermined thickness is 0.5 mm to 1 mm; and / or the thickness of the graphene oxide film is 50 μm to 1000 μm.

[0011] In some embodiments, in step S2, the drying temperature of the drying treatment is 25°C to 100°C, and the drying time is 4h to 48h.

[0012] In some embodiments, in step S3, the thermal reduction temperature of the thermal reduction treatment is higher than 2400° C., and the thermal reduction time is greater than 4 hours.

[0013] The present invention also proposes a method for preparing a graphene thermal conductor, comprising the following steps: immersing any of the above-mentioned graphene films in an adhesive, stacking and solidifying a plurality of graphene films soaked in the adhesive to obtain a graphene block; and cutting the graphene block to obtain a graphene thermal conductor.

[0014] In some embodiments, the adhesive is a silicone resin, and the silicone resin includes hydrogen siloxane and vinyl silicone oil;

[0015] The hydrogen-containing siloxane comprises at least one of terminal hydrogen-containing polysiloxane, pendant hydrogen-containing polysiloxane and terminal side hydrogen-containing polysiloxane, the viscosity of the hydrogen-containing siloxane is 10mPa·s to 100mPa·s, and the mass percentage of hydrogen in the hydrogen-containing siloxane is 0.1wt% to 1wt%; and / or, the viscosity of the vinyl silicone oil is 40mPa·s to 500mPa·s, and the mass percentage of vinyl in the vinyl silicone oil is 0.2wt% to 1.5wt%.

[0016] In some embodiments, the curing temperature of the curing molding is 85° C. to 125° C., and the curing time is 4 h to 12 h.

[0017] In some embodiments, the mass percentage of graphene in the graphene thermal conductor is 40 wt % to 80 wt %.

[0018] The present invention also provides a graphene thermal conductive member, which is obtained by using any of the above-mentioned methods for preparing a graphene thermal conductive member, and the graphene thermal conductive member has periodic wrinkles.

[0019] Beneficial effects of the present invention:

[0020] In the preparation method of the graphene film of the present invention, a graphene oxide film is first prepared by coating on a periodic wrinkle template by a coating method, and then a graphene film with periodic wrinkles is obtained by thermal reduction treatment. The preparation method is simple and easy to implement, and can be applied to large-scale production.

[0021] In the preparation method of the graphene heat conductive member of the present invention, a graphene film with periodic wrinkles is used to prepare a graphene heat conductive member with periodic wrinkles. The preparation method is simple and easy, and the consistency and stability of the graphene heat conductive member can be guaranteed in mass production. The introduction of wrinkles can significantly reduce the compressive stress of the graphene heat conductive member, increase the compression rate of the graphene heat conductive member, and reduce the application thermal resistance of the graphene heat conductive member, thereby greatly enhancing the heat conduction effect of the graphene heat conductive member.

[0022] The graphene thermal conductive part prepared by the invention has excellent mechanical properties and thermal conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0024] Figure 1 is a schematic diagram of the structure of the graphene film in Example 1 of the present invention;

[0025] Figure 2 is a schematic structural diagram of a graphene block in Example 1 of the present invention;

[0026] Figure 3 is a schematic diagram of the structure of the graphene block after cutting in Example 1 of the present invention;

[0027] Figure 4 It is a schematic diagram of the structure of the graphene heat conductor in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the present invention will be further described in detail below in conjunction with embodiments. The embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0029] The present invention provides a method for preparing a graphene film, which comprises the following steps:

[0030] S1. Obtain a periodic wrinkle template, in which the wavelength of wrinkles is 1 μm to 100 μm and the amplitude is 5 μm to 200 μm.

[0031] In some embodiments, the periodic pleated template may be polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), or polyphenylene phthalamide.

[0032] The periodic pleated template can be made by 3D printing or injection molding. The mold used for injection molding can be made by CNC processing. The preparation process conditions can be selected according to actual needs and will not be repeated here. The wavelength and amplitude of the pleats in the periodic pleated template are adjustable, wherein the wavelength of the pleats is 1μm to 100μm, for example, 1μm, 10μm, 30μm, 50μm, 80μm, 100μm, etc. can be selected. If the wavelength of the pleats is less than 1μm, the preparation accuracy of the periodic pleated template is insufficient, and the difficulty of the subsequent adhesive being immersed in the surface of the graphene film is increased; if the wavelength of the pleats is greater than 100μm, the number of pleats in the graphene thermal conductive sheet is too small to exert the effect. The amplitude of the pleats in the periodic pleated template is 5μm to 200μm, for example, 5μm, 10μm, 50μm, 100μm, 150μm, 200μm, etc. can be selected. If the amplitude of the wrinkles is less than 5 μm, the wrinkles will have little effect on the stress of the graphene thermal conductor and it will be difficult to reduce its stress; if the amplitude of the wrinkles is higher than 200 μm, it will make it difficult for the subsequent adhesive to penetrate into the surface of the graphene film.

[0033] S2. Applying graphene oxide water slurry on the periodic wrinkle template to a predetermined thickness, peeling off the periodic wrinkle template after drying, and obtaining a graphene oxide film; the mass percentage of graphene oxide in the graphene oxide water slurry is 1wt% to 15wt%.

[0034] The mass percentage of graphene oxide in the graphene oxide water slurry can be selected from 1wt%, 3wt%, 5wt%, 10wt%, 15wt%, etc. If the mass percentage of graphene oxide in the graphene oxide water slurry is lower than 1wt%, the slurry is too thin to be applied, and if the mass percentage of graphene oxide is higher than 15wt%, the slurry is too thick to be applied. Preferably, the mass percentage of graphene oxide is 2wt% to 10wt%, for example, 2wt%, 4wt%, 6wt%, 8wt%, 10wt%, etc. can be selected.

[0035] The coating can be processed by a precision coating machine, and the predetermined coating thickness can be 0.5 mm to 1 mm, for example, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, etc. can be selected.

[0036] The drying temperature of the drying treatment is 25°C to 100°C, for example, 25°C, 45°C, 65°C, 80°C, 100°C, etc. can be selected; the drying time is 4h to 48h, for example, 4h, 18h, 24h, 36h, 48h, etc. can be selected. The thickness of the graphene oxide film obtained after drying is 50μm to 1000μm, for example, 50μm, 100μm, 300μm, 500μm, 1000μm, etc. can be selected, preferably 200μm to 1000μm, for example, 200μm, 400μm, 600μm, 800μm, 1000μm, etc. can be selected. If the thickness of the graphene oxide film is less than 200μm, it is difficult to accurately control the thickness; if the thickness of the graphene oxide film is too high, the contact area between the graphene film and the adhesive in the later stage will be reduced, resulting in problems such as cracking and high hardness of the graphene thermal conductor.

[0037] In some embodiments, the periodic wrinkle template in step S1 is replaced with a heat-shrinkable film, the material of which may be PE, PP or PET, etc. In step S2, a water slurry of graphene oxide is coated on the film to a predetermined thickness, and the temperature is rapidly raised to 180°C to 220°C for 20s to 40s to cause the film to shrink, thereby obtaining a graphene oxide film with periodic wrinkles.

[0038] S3. Performing thermal reduction treatment on the graphene oxide film to obtain a graphene film.

[0039] In this step, the thermal reduction temperature of the thermal reduction treatment is higher than 2400°C, preferably higher than 2800°C, such as 2900°C; the thermal reduction time is greater than 4 hours, preferably greater than 5 hours, such as 5 hours. Thermal reduction is to reduce graphene oxide to graphene by high temperature heating, and the temperature and time of thermal reduction can be selected according to actual needs. The graphene film finally obtained has a loose structure and periodic wrinkles.

[0040] The present invention also proposes a method for preparing a graphene thermal conductor, which comprises the following steps: immersing the above-mentioned graphene film in an adhesive, stacking and solidifying a plurality of graphene films soaked in the adhesive to obtain a graphene block; and cutting the graphene block to obtain a graphene thermal conductor.

[0041] Among them, the adhesive is preferably an organic silicone resin, and the organic silicone resin includes hydrogen-containing siloxane and vinyl silicone oil. Among them, the hydrogen-containing siloxane includes at least one of terminal hydrogen-containing polysiloxane, side hydrogen-containing polysiloxane and end hydrogen-containing polysiloxane. The viscosity of the hydrogen-containing siloxane is 10mPa·s to 100mPa·s, for example, 10mPa·s, 30mPa·s, 50mPa·s, 70mPa·s, 100mPa·s, etc. can be selected; the mass percentage of hydrogen in the hydrogen-containing siloxane is 0.1wt% to 1wt%, for example, 0.1wt%, 0.2wt%, 0.5wt%, 0.8wt%, 1wt%, etc. can be selected. The viscosity of vinyl silicone oil is 40mPa·s~500mPa·s, for example, 40mPa·s, 100mPa·s, 150mPa·s, 300mPa·s, 500mPa·s, etc. can be selected; the mass percentage of vinyl in vinyl silicone oil is 0.2wt%~1.5wt%, for example, 0.2wt%, 0.5wt%, 1.0wt%, 1.2wt%, 1.5wt%, etc. can be selected.

[0042] The graphene film is immersed in an adhesive so that the surface of the graphene film is coated with the adhesive and the pores inside the graphene film are also filled with the adhesive. Several graphene films with the surface and the interior soaked with the adhesive are stacked, and the thickness of the adhesive between two adjacent graphene films is 2μm to 8μm, such as 5μm. The total thickness of the graphene film stack obtained by stacking several graphene films is ≥90mm, and the total thickness is not specifically limited, as long as it reaches 90mm.

[0043] Further, the graphene film stack is cured and formed, the curing temperature is 85°C to 125°C, and the curing time is 4h to 12h. For example, the curing temperature can be 85°C, 95°C, 100°C, 115°C, 125°C, etc., and the curing time can be 4h, 6h, 8h, 10h, 12h, etc. The cured graphene block is cut along its thickness direction (i.e., the graphene film stacking direction) to obtain a graphene thermal conductor, which can be further cut to obtain a smaller graphene thermal conductor. The graphene thermal conductor is rotated 90 degrees, and its flat surface is in contact with the surface of the electronic device to form a good contact.

[0044] The mass percentage of graphene in the graphene heat conducting member is 40wt% to 80wt%, for example, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, etc. can be selected, and the mass percentage of graphene is preferably 50wt% to 70wt%. If the mass percentage of graphene is lower than 40wt%, the thermal conductivity of the obtained heat conducting member is lower due to less thermal conductive material; if the mass percentage of graphene is higher than 80wt%, the content of the adhesive silicone resin is lower, resulting in a larger hardness and easy cracking of the heat conducting member.

[0045] The present invention also provides a graphene thermal conductor, which is obtained by using the above-mentioned method for preparing the graphene thermal conductor, and the prepared graphene thermal conductor has periodic wrinkles.

[0046] The main reason for the high contact thermal resistance of graphene thermal conductors (such as graphene thermal pads) is that compared with thermal interface materials (TIM) such as silicone grease and gel, the hardness of graphene thermal conductors is relatively large, and they cannot completely fill the gap when in contact with chips and heat sinks. The application thermal resistance of TIM material = body thermal resistance + contact thermal resistance. For graphene thermal conductors, the contact thermal resistance is greater than the body thermal resistance, while for silicone grease, the contact thermal resistance can be ignored. Therefore, although the thermal conductivity of the graphene thermal conductor itself is much greater than that of silicone grease, its application thermal resistance is greater than that of some silicone greases, resulting in that in actual applications, the thermal conductivity of the graphene thermal conductor is not as good as that of silicone grease. The graphene thermal conductor of the present invention is composed of a graphene film and a silicone resin (adhesive), wherein silicone is a common matrix of TIM materials, which can achieve low hardness and low stress. The high stress of the graphene thermal conductor mainly comes from the graphene film. If the graphene membrane with periodic wrinkles is compared to a spring, according to Hooke's law, the force F given to the object by the spring is -kx, and the stiffness coefficient of the compression spring is k = (G*d^4) / (8*D^3*N), where x is the deformation, G is the shear modulus of the spring material, d is the wire diameter of the spring, D is the diameter of the spring, and N is the number of turns of the spring. For graphene thermal conductors with few wrinkles and many wrinkles, the shear modulus of the material and the spring wire diameter of the two are the same, while the spring of the multi-wrinkled graphene thermal conductor has more turns and a larger spring diameter, so the stiffness coefficient is smaller. Therefore, under the same deformation, the compressive stress of the multi-wrinkled graphene thermal conductor is smaller.

[0047] The following is described by specific examples:

[0048] Example 1

[0049] A method for preparing a graphene film comprises the following steps:

[0050] S1. Obtain a periodic fold template, wherein the wavelength of the folds in the periodic fold template is 50 μm, the amplitude is 25 μm, and the material of the periodic fold template is PE.

[0051] S2, coating the graphene oxide water slurry on the periodic fold template to a predetermined thickness, peeling off the periodic fold template after drying, and obtaining a graphene oxide film; the mass percentage of graphene oxide in the graphene oxide water slurry is 10wt%. The predetermined coating thickness is 800μm, the drying temperature of the drying treatment is 100°C, the drying time is 24h, and the thickness of the graphene oxide film obtained after drying is 500μm.

[0052] S3, thermally reducing the graphene oxide film to obtain a graphene film. The thermal reduction temperature of the thermal reduction treatment is 2900°C and the thermal reduction time is 5 hours. The graphene film finally obtained is as follows Figure 1 As shown, it has periodic folds.

[0053] The present invention also proposes a method for preparing a graphene thermal conductor, which comprises the following steps: immersing the above-mentioned graphene film in an adhesive, stacking and solidifying a plurality of graphene films soaked in the adhesive to obtain a graphene block; and cutting the graphene block to obtain a graphene thermal conductor.

[0054] The adhesive is an organic silicone resin, the organic silicone resin includes hydrogen-containing siloxane and vinyl silicone oil, the hydrogen-containing siloxane includes terminal hydrogen-containing polysiloxane, the viscosity of the hydrogen-containing siloxane is 50 mPa·s, the mass percentage of hydrogen in the hydrogen-containing siloxane is 0.5 wt%, the viscosity of the vinyl silicone oil is 300 mPa·s, and the mass percentage of vinyl in the vinyl silicone oil is 0.8 wt%.

[0055] During lamination, the thickness of the adhesive between two adjacent graphene films was 5 μm. The total thickness of the graphene film laminate obtained by laminating a plurality of graphene films reached 90 mm.

[0056] Further, the graphene film stack is cured and formed at a curing temperature of 85° C. and a curing time of 12 h. The graphene block obtained after curing and forming is as follows: Figure 2 As shown in FIG. 1 , the graphene block is composed of a plurality of graphene films impregnated with an adhesive, and the size of the graphene block is 90 mm*90 mm*90 mm. Figure 3 As shown, the graphene block is cut along the graphene film stacking direction and then rotated 90 degrees to obtain the following Figure 4 The graphene heat conducting member shown has an upper surface and / or a lower surface in contact with the surface of the electronic device when in use. The mass percentage of graphene in the graphene heat conducting member is 60wt%.

[0057] The present invention also provides a graphene thermal conductor, which is obtained by using the above-mentioned method for preparing the graphene thermal conductor, and the prepared graphene thermal conductor has periodic wrinkles.

[0058] Example 2

[0059] The graphene film preparation method, graphene heat conductive member and preparation method thereof of this embodiment are different from those of embodiment 1 in that, in the preparation process of the graphene film, the amplitude of the wrinkles in the periodic wrinkle template used in step S1 is 50 μm. The rest is the same as embodiment 1 and will not be described again.

[0060] Example 3

[0061] The graphene film preparation method, graphene heat conductive member and preparation method thereof of this embodiment are different from those of embodiment 1 in that, in the preparation process of the graphene film, the amplitude of the wrinkles in the periodic wrinkle template used in step S1 is 75 μm. The rest is the same as embodiment 1 and will not be repeated here.

[0062] Example 4

[0063] The graphene film preparation method, graphene heat conductive member and preparation method thereof of this embodiment are different from those of embodiment 1 in that, in the preparation process of the graphene film, the amplitude of the wrinkles in the periodic wrinkle template used in step S1 is 100 μm. The rest is the same as embodiment 1 and will not be repeated here.

[0064] Example 5

[0065] The graphene film preparation method, graphene heat conductive member and preparation method thereof of this embodiment are different from those of embodiment 1 in that, in the process of preparing the graphene film, the wavelength of the wrinkles in the periodic wrinkle template used in step S1 is 100 μm and the amplitude is 100 μm. The rest is the same as embodiment 1 and will not be described again.

[0066] Example 6

[0067] A method for preparing a graphene film comprises the following steps:

[0068] S1. Obtain a periodic fold template, wherein the wavelength of the folds in the periodic fold template is 1 μm, the amplitude is 5 μm, and the material of the periodic fold template is PP.

[0069] S2, coating the graphene oxide water slurry on the periodic fold template to a predetermined thickness, peeling off the periodic fold template after drying, and obtaining a graphene oxide film; the mass percentage of graphene oxide in the graphene oxide water slurry is 1wt%. The predetermined coating thickness is 0.5mm, the drying temperature of the drying treatment is 25°C, the drying time is 48h, and the thickness of the graphene oxide film obtained after drying is 200μm.

[0070] S3, performing thermal reduction treatment on the graphene oxide film to obtain a graphene film, wherein the thermal reduction temperature of the thermal reduction treatment is 2600° C. and the thermal reduction time is 7 hours. Finally, the obtained graphene film has periodic wrinkles.

[0071] The present invention also proposes a method for preparing a graphene thermal conductor, which comprises the following steps: immersing the above-mentioned graphene film in an adhesive, stacking and solidifying a plurality of graphene films soaked in the adhesive to obtain a graphene block; and cutting the graphene block to obtain a graphene thermal conductor.

[0072] The adhesive is an organic silicone resin, the organic silicone resin includes hydrogen-containing siloxane and vinyl silicone oil, the hydrogen-containing siloxane includes side hydrogen-containing polysiloxane and end hydrogen-containing polysiloxane. The viscosity of the hydrogen-containing siloxane is 10 mPa·s, the mass percentage of hydrogen in the hydrogen-containing siloxane is 0.1 wt%, the viscosity of the vinyl silicone oil is 40 mPa·s, and the mass percentage of vinyl in the vinyl silicone oil is 0.2 wt%.

[0073] During lamination, the thickness of the adhesive between two adjacent graphene films was 3 μm. The total thickness of the graphene film laminate obtained by laminating a plurality of graphene films reached 90 mm.

[0074] Further, the graphene film stack is cured and formed at a curing temperature of 125° C. for 4 hours. The graphene block obtained after curing is cut along the graphene film stacking direction and then rotated 90 degrees to obtain a graphene thermal conductive member. The mass percentage of graphene in the graphene thermal conductive member is 40wt%.

[0075] The present invention also provides a graphene thermal conductor, which is obtained by using the above-mentioned method for preparing the graphene thermal conductor, and the prepared graphene thermal conductor has periodic wrinkles.

[0076] Example 7

[0077] A method for preparing a graphene film comprises the following steps:

[0078] S1. Obtain a periodic fold template, wherein the wavelength of the folds in the periodic fold template is 100 μm and the amplitude is 200 μm. The material of the periodic fold template is PET.

[0079] S2, coating the graphene oxide water slurry on the periodic fold template to a predetermined thickness, peeling off the periodic fold template after drying, and obtaining a graphene oxide film; the mass percentage of graphene oxide in the graphene oxide water slurry is 1wt%. The predetermined coating thickness is 1mm, the drying temperature of the drying treatment is 100°C, the drying time is 4h, and the thickness of the graphene oxide film obtained after drying is 1000μm.

[0080] S3, performing thermal reduction treatment on the graphene oxide film to obtain a graphene film, wherein the thermal reduction temperature of the thermal reduction treatment is 3000° C. and the thermal reduction time is 4 hours. Finally, the obtained graphene film has periodic wrinkles.

[0081] The present invention also proposes a method for preparing a graphene thermal conductor, which comprises the following steps: immersing the above-mentioned graphene film in an adhesive, stacking and solidifying a plurality of graphene films soaked in the adhesive to obtain a graphene block; and cutting the graphene block to obtain a graphene thermal conductor.

[0082] The adhesive is an organic silicone resin, the organic silicone resin includes hydrogen-containing siloxane and vinyl silicone oil, the hydrogen-containing siloxane includes side hydrogen-containing polysiloxane and end hydrogen-containing polysiloxane. The viscosity of the hydrogen-containing siloxane is 100 mPa·s, the mass percentage of hydrogen in the hydrogen-containing siloxane is 1wt%, the viscosity of the vinyl silicone oil is 500 mPa·s, and the mass percentage of vinyl in the vinyl silicone oil is 1.5wt%.

[0083] When stacking, the thickness of the adhesive between two adjacent graphene films is 8 μm. The total thickness of the graphene film stack obtained by stacking several graphene films reaches 90 mm.

[0084] Further, the graphene film stack is cured and formed, the curing temperature is 100° C., and the curing time is 8 hours. The graphene block obtained after curing is cut along the graphene film stacking direction, and then rotated 90 degrees to obtain a graphene thermal conductive member. The mass percentage of graphene in the graphene thermal conductive member is 80wt%.

[0085] The present invention also provides a graphene thermal conductor, which is obtained by using the above-mentioned method for preparing the graphene thermal conductor, and the prepared graphene thermal conductor has periodic wrinkles.

[0086] Example 8

[0087] The preparation method of the graphene film, the graphene heat conductive member and the preparation method thereof of this embodiment are different from those of Embodiment 1 in that, in the preparation process of the graphene film, in steps S1 and S2, a heated shrinkable PE film is used as a wrinkle template, a graphene oxide water slurry is coated on the PE film to a predetermined thickness, the temperature is rapidly raised to 200° C. after 30 seconds to shrink the PE film, and the PE film is peeled off after drying to obtain a graphene oxide film with periodic wrinkles. The rest is the same as Embodiment 1 and will not be repeated here.

[0088] Comparative Example 1

[0089] The graphene film preparation method, graphene heat conductive member and preparation method thereof of this embodiment are different from those of embodiment 1 in that a flat template is used for coating during the preparation of the graphene film, and the surface of the graphene film obtained is flat and has no wrinkles. The rest is the same as embodiment 1 and will not be described again.

[0090] Comparative Example 2

[0091] The graphene film preparation method, graphene heat conductive part and preparation method thereof of this embodiment are different from those of embodiment 4 in that, in the preparation process of the graphene film, a pressure of 40 MPa is applied while performing thermal reduction treatment in step S3 to obtain a flat and dense graphene film, and a graphene heat conductive part with a flat surface is obtained by using the graphene film. The rest is the same as embodiment 4 and will not be repeated here.

[0092] Performance test:

[0093] The long-term compressive stress, compression rate and applied thermal resistance of the graphene thermal conductors prepared in Examples 1 to 5 and Comparative Examples 1 and 2 were tested, wherein the compressive stress and compression rate were tested by an MTS mechanical machine, and different compression rates were set by displacement. The pressing rate was 25.4 mm / min, and the pressure head stayed for 10 minutes after contacting the graphene thermal conductor. The stress at this time was recorded as the long-term compressive stress; the applied thermal resistance was tested by a longwin thermal resistance meter, the test temperature was 80°C, and the pressure was 40 psi. The test results are shown in Table 1.

[0094] Table 1 Performance test results of Examples 1 to 5 and Comparative Examples 1 and 2

[0095]

[0096]

[0097] According to Table 1, the graphene thermal conductors of Examples 1 to 5 of the present invention have smaller long-term compressive stress, higher compression rate and lower application thermal resistance; the graphene thermal conductor of Comparative Example 1 has no wrinkles, and its compressive stress is larger, its compression rate is lower, and its application thermal resistance is also larger; the graphene film subjected to high-temperature hot pressing of Comparative Example 2 has no periodic wrinkles, and the graphene thermal conductor finally obtained also has no periodic wrinkles, and the graphene thermal conductor has relatively large compressive stress, relatively low compression rate, and relatively large application thermal resistance. It can be seen that the introduction of wrinkles into the graphene thermal conductor of the present invention can significantly reduce the compressive stress of the graphene thermal conductor, so that its long-term compressive stress is reduced from 50psi to 10psi; increase the compression rate of the graphene thermal conductor, and the compression rate increases from 10% to 70%; the application thermal resistance of the graphene thermal conductor increases from 0.25K·cm 2 / W is reduced to 0.038K·cm 2 / W, therefore, the graphene thermal conductor prepared by the present invention has excellent mechanical properties and thermal conductivity.

[0098] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0099] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the scope covered by the claims of the present invention.

Claims

1. A method for preparing a graphene film, characterized in that: The following steps are involved: S1, obtaining a periodic wrinkle template, wherein the wavelength of wrinkles in the periodic wrinkle template is 1 μm to 100 μm, and the amplitude is 5 μm to 200 μm; S2, coating a graphene oxide water slurry on the periodic fold template to a predetermined thickness, peeling off the periodic fold template after drying, and obtaining a graphene oxide film; the mass percentage of graphene oxide in the graphene oxide water slurry is 1wt% to 15wt%; S3. Performing thermal reduction treatment on the graphene oxide film to obtain the graphene film.

2. The method for preparing a graphene film according to claim 1, characterized in that: In the step S1, the periodic pleat template is polypropylene, polyethylene, polyethylene terephthalate, polytetrafluoroethylene or polyphenylene phthalide.

3. The method for preparing a graphene film according to claim 1, characterized in that: In the step S2, the predetermined thickness is 0.5 mm to 1 mm; and / or the thickness of the graphene oxide film is 50 μm to 1000 μm.

4. The method for preparing a graphene film according to claim 1, characterized in that: In the step S2, the drying temperature of the drying treatment is 25°C to 100°C, and the drying time is 4h to 48h.

5. The method for preparing a graphene film according to claim 1, characterized in that: In the step S3, the thermal reduction temperature of the thermal reduction treatment is higher than 2400° C., and the thermal reduction time is greater than 4 hours.

6. A method for preparing a graphene thermal conductive member, characterized in that: The method comprises the following steps: immersing the graphene film according to any one of claims 1 to 5 in an adhesive, stacking and solidifying a plurality of the graphene films soaked in the adhesive to obtain a graphene block; and cutting the graphene block to obtain a graphene thermal conductor.

7. The method for preparing a graphene heat conducting member according to claim 6, characterized in that: The adhesive is an organic silicone resin, and the organic silicone resin includes hydrogen-containing siloxane and vinyl silicone oil; The hydrogen-containing siloxane comprises at least one of terminal hydrogen-containing polysiloxane, pendant hydrogen-containing polysiloxane and terminal side hydrogen-containing polysiloxane, the viscosity of the hydrogen-containing siloxane is 10mPa·s to 100mPa·s, and the mass percentage of hydrogen in the hydrogen-containing siloxane is 0.1wt% to 1wt%; and / or, the viscosity of the vinyl silicone oil is 40mPa·s to 500mPa·s, and the mass percentage of vinyl in the vinyl silicone oil is 0.2wt% to 1.5wt%.

8. The method for preparing a graphene heat conducting member according to claim 6, characterized in that: The curing temperature of the curing molding is 85° C. to 125° C., and the curing time is 4 h to 12 h.

9. The method for preparing a graphene heat conducting member according to claim 6, characterized in that: The mass percentage of graphene in the graphene heat conducting member is 40wt% to 80wt%.

10. A graphene heat conducting member, characterized in that: The graphene thermal conductor is obtained by the preparation method of any one of claims 6 to 9, wherein the graphene thermal conductor has periodic wrinkles.

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