Graphene heat-conducting thick film material based on high heat conductivity coefficient

Abstract

The invention discloses a graphene heat-conducting thick film material based on a high heat conductivity coefficient, and belongs to the technical field of heat-conducting thick films. Silicon carbide / aluminum oxide ceramic fibers, polyvinyl butyral and dimethyl sulfoxide are subjected to ultrasonic treatment, and bottom layer slurry is obtained; the coated liquid alloy, polyurethane acrylate and benzoyl peroxide are stirred, and middle layer slurry is obtained; performing ultrasonic treatment on the aminated graphene grafted ceramic fiber, flake graphene and cyclohexanone to obtain top layer slurry; sequentially coating the bottom layer slurry, the middle layer slurry and the top layer coating in a mold layer by layer through a sandwich method, spraying a 1H, 1H, 2H, 2H-perfluorodecyl triethoxy silane solution, drying and curing to obtain the graphene heat-conducting thick film material based on the high heat conductivity coefficient. The high in-plane horizontal and vertical heat conduction efficiency, the high mechanical strength and the low interface thermal resistance of the graphene heat conduction thick film are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal conductive thick films, and in particular relates to a graphene thermal conductive thick film material with high thermal conductivity. Background Art

[0002] With the rapid development of consumer electronic products such as mobile phones, tablets and smart wearables in the 5G era, the high-density functions and lightweight design have made the heat dissipation problem of electronic devices increasingly prominent. The demand for the heat diffusion capacity of heat dissipation components is getting higher and higher. Therefore, it is necessary to replace traditional heat-conducting metal materials with materials that have both high thermal conductivity and light weight to achieve efficient heat dissipation of electronic products.

[0003] Graphene is composed of sp 2 Hybridized carbon atoms are tightly arranged to form a single-layer honeycomb crystal structure. The thermal conductivity of graphene at room temperature can reach 5000W / mK, which is 10 times higher than the thermal conductivity of copper at room temperature. It is the material with the highest thermal conductivity known to mankind. Graphene thermal conductive thick film is a new type of thermal conductive material. It mainly dissipates the heat of components and equipment through its own high heat dissipation performance to prevent equipment from overheating and causing reduced work efficiency or even equipment damage. It combines the excellent thermal conductivity of graphene with the light and thin characteristics of film. It has the characteristics of high thermal conductivity, light weight, and good flexibility. It is widely used in the heat dissipation field of mid-to-high-end smartphones, tablets and other consumer electronic products.

[0004] A Chinese invention patent application with publication number CN 115784220A discloses a thickened graphene oxide film, a graphene thermally conductive film, and a preparation method thereof. A graphene oxide cake having a solid content greater than 40% is mixed and extruded into a thin sheet by a roller process. The sheet is folded in half and extruded into a sheet while the surface is wetted. This process is repeated multiple times while gradually reducing the thickness of the sheet to obtain a thickened graphene oxide film. The graphene oxide film is then carbonized and graphitized, and then calendered to obtain a graphene thermally conductive film. Although this preparation method significantly optimizes the horizontal thermal conductivity of the thick film and enhances the interlayer bonding strength through repeated physical folding, the hydrogen bonding strength between the graphene oxide sheets is weak, and micro-voids and phonon scattering barriers exist, resulting in high interlayer interface thermal resistance and poor vertical thermal conductivity. Furthermore, the carbonized and graphitized graphene oxide film has limited mechanical properties, leading to stress concentration and cracking, further shortening the material's service life. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems of the limited thermal conductivity of graphene thermal conductive thick film in the vertical direction and poor interlayer bonding strength, limited mechanical properties, easy cracking and reduced service life, and to provide a graphene thermal conductive thick film material based on high thermal conductivity.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A graphene-based thermally conductive thick film material with high thermal conductivity is prepared by the following steps:

[0008] Step 1: Add silicon carbide / alumina ceramic fiber, polyvinyl butyral and dimethyl sulfoxide into a reactor and ultrasonicate for 30-40 minutes to obtain a bottom slurry;

[0009] Add the coated liquid alloy, polyurethane acrylate and benzoyl peroxide into a reaction kettle and stir at 3000-4000 rpm for 5-10 minutes to obtain a middle layer slurry;

[0010] Aminated graphene grafted ceramic fiber, flake graphene and cyclohexanone were added into a reactor and ultrasonicated for 15-30 minutes to obtain a top layer slurry.

[0011] Step 2: Wipe the mold clean with anhydrous ethanol and dry it for later use; apply the bottom layer slurry, middle layer slurry and top layer coating in sequence in the mold through the sandwich method and solidify them. After demolding, spray 1wt% 1H,1H,2H,2H-perfluorodecyltriethoxysilane solution on the surface, dry and solidify it to obtain a graphene-based thermal conductive thick film material with high thermal conductivity.

[0012] Furthermore, the mass ratio of silicon carbide / alumina ceramic fiber, polyvinyl butyral and dimethyl sulfoxide is 10-14:1.2-1.6:15-19; the usage ratio of coated liquid alloy, polyurethane acrylate and benzoyl peroxide is: 8-12g:10-14mL:0.12-0.16g; the mass ratio of amino graphene grafted ceramic fiber, flaky graphene and cyclohexanone is: 10-14:0.5-0.9:5-9.

[0013] Furthermore, the silicon carbide / alumina ceramic fiber is specifically prepared by the following steps: adding silicon carbide whiskers, silane coupling agent KH-550 and anhydrous ethanol to a reactor, ultrasonicating for 30-40 minutes, then adding alumina powder and anhydrous ethanol, ultrasonicating for 30-40 minutes, ball milling at 400-500 rpm for 8-9 hours, transferring to a water bath, stirring and evaporating at 90-100°C until viscous, vacuum drying at 70-80°C for 10-12 hours, grinding, and passing through a 40-mesh sieve to obtain a mixed powder; the mixed powder is loaded into a mold, transferred to a vacuum hot pressing furnace, kept warm and pressurized at 1540-1580°C, 80-90 MPa of argon and 3% hydrogen for 1-2 hours, cooled with the furnace, and wire-cut to a thickness of 1 mm to obtain the silicon carbide / alumina ceramic fiber.

[0014] Furthermore, the usage ratio of silicon carbide whiskers, silane coupling agent KH-550, anhydrous ethanol, aluminum oxide powder and anhydrous ethanol is 2.4-2.8 g: 0.12-0.16 g: 100-120 mL: 16-20 g: 100-120 mL.

[0015] Furthermore, the coated liquid alloy is prepared by the following steps:

[0016] Glycidyl methacrylate, silane coupling agent KH-560, divinylbenzene, oxidized carbon nanotubes and gallium-indium alloy are added to a reactor, followed by sodium dodecylbenzenesulfonate, baking soda and deionized water. The mixture is stirred at 1200-1300 rpm for 10-20 minutes and ultrasonicated in an ice bath for 15-30 minutes to obtain a monomer emulsion. The monomer emulsion is added to a reactor, nitrogen is introduced and stirred for 30-40 minutes, potassium persulfate is added at 70-80°C, and the mixture is reacted for 6-8 hours to obtain a coated liquid alloy.

[0017] Furthermore, the usage ratio of glycidyl methacrylate, silane coupling agent KH-560, divinylbenzene, oxidized carbon nanotubes, gallium-indium alloy, sodium dodecylbenzenesulfonate, baking soda and deionized water is 20-24 g: 0.8-1.2 g: 3.2-3.6 g: 1.2-1.6 g: 8-10 g: 0.6-0.8 g: 1.2-1.4 g: 600-700 mL; the usage ratio of monomer emulsion and potassium persulfate is 600-700 mL: 1.2-1.4 g.

[0018] Furthermore, the amino graphene grafted ceramic fiber is specifically prepared by the following steps: adding amino graphene powder, silane coupling agent KH-560 and anhydrous ethanol to a reactor, ultrasonicating for 45-60 minutes to obtain an amino graphene dispersion, then adding silicon carbide / alumina ceramic fiber, ultrasonicating for 20-30 minutes, taking out, and vacuum drying at 100-110°C for 6-8 hours to obtain the amino graphene grafted ceramic fiber.

[0019] Furthermore, the usage ratio of the amino graphene powder, the silane coupling agent KH-560, the anhydrous ethanol and the silicon carbide / alumina ceramic fiber is 1.76-1.80 g: 0.05-0.09 g: 500-600 mL: 10-12 g.

[0020] Furthermore, the sandwich method specifically includes the following steps: pouring the bottom layer slurry into the mold, scraping it with a scraper, curing it at 65-75°C for 15-25 minutes, drying it at 120-140°C for 30-40 minutes, and drying it at 200-210°C for 10-20 minutes to obtain a bottom layer film, scraping the middle layer slurry on the bottom layer film, curing it at 80-90°C for 10-20 minutes, and then scraping the top layer coating, and hot pressing it at 150-160°C and 0.5-0.7MPa for 15-25 minutes.

[0021] Furthermore, the blade coating was used to control the thickness of the bottom layer to be 0.8 mm, the thickness of the middle layer to be 0.3 mm and the thickness of the top layer to be 100 μm.

[0022] Beneficial effects of the present invention:

[0023] 1. The present invention significantly improves tensile strength and crack resistance by designing a layered structure and functionalizing the core material, adding silicon carbide whiskers, and reinforcing alumina ceramic fibers. The coated liquid alloy forms a continuous metal thermal conductive chain during solidification and hot pressing, achieving efficient vertical thermal conduction. The amino-grafted graphene ceramic fibers construct a horizontal continuous thermal conductive network, improving the in-plane thermal diffusion efficiency. The rough surface of the fibers is embedded in the middle layer polymer to form a physical anchor. The amino groups are covalently bonded to the middle layer -NCO, strongly bridging the interlayer interface and significantly reducing thermal resistance. The graphene thermal conductive thick film achieves high in-plane horizontal and vertical thermal conductivity, high mechanical strength, and low interface thermal resistance.

[0024] 2. The present invention achieves ultra-high thermal conductivity by constructing a sandwich structure with a dense ceramic matrix at the bottom, a liquid alloy coating for thermal conductivity in the middle layer, and a high-conductivity graphene reinforcement at the top layer. By combining ceramic fiber reinforcement, graphene reinforcement and a polymer matrix, the interface treatment is optimized to obtain excellent mechanical strength, toughness, thermal stability and low thermal expansion coefficient. The layered preparation process and interface treatment improve the strong bonding force within and between layers while also achieving low thermal resistance. The surface hydrophobic treatment further improves environmental tolerance. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] Example 1: A graphene-based thermally conductive thick film material with high thermal conductivity is prepared by the following steps:

[0027] S1: 10 g of silicon carbide / alumina ceramic fiber, 1.2 g of polyvinyl butyral, and 15 g of dimethyl sulfoxide were added to a reactor and ultrasonicated for 30 min to obtain a bottom slurry;

[0028] 8 g of coated liquid alloy, 10 mL of polyurethane acrylate, and 0.12 g of benzoyl peroxide were added to a reactor and stirred at 3000 rpm for 5 min to obtain a middle layer slurry;

[0029] 10 g of amino-modified graphene-grafted ceramic fiber, 0.5 g of flake graphene and 5 g of cyclohexanone were added into a reactor and ultrasonicated for 15 min to obtain a top slurry.

[0030] The bottom slurry uses the adhesive properties of polyvinyl butyral to bond silicon carbide / alumina ceramic fibers to form a high-strength ceramic fiber skeleton; the middle slurry uses benzoyl peroxide to initiate the cross-linking and curing of polyurethane acrylate to form a flexible thermal conductive layer; in the top slurry, flaky graphene and amino-graphene grafted ceramic fibers work together to form a high thermal conductivity layer of graphene.

[0031] S2: Wipe the mold clean with anhydrous ethanol, ventilate and dry it for later use; pour the bottom layer slurry into the mold, apply it with a scraper, cure it at 65°C for 15 minutes, dry it at 120°C for 30 minutes, and dry it at 200°C for 10 minutes to obtain a bottom layer film, apply the middle layer slurry on the bottom layer film, cure it at 80°C for 10 minutes, and then apply the top layer coating, hot press it at 150°C and 0.5MPa for 15 minutes, demould, spray the surface with a 1% mass fraction of 1H,1H,2H,2H-perfluorodecyltriethoxysilane solution, and cure it at 120°C for 30 minutes to obtain a graphene-based thermal conductive thick film material with high thermal conductivity.

[0032] Through a three-layer composite construction process, the bottom layer utilizes a hot-pressed, dense silicon carbide / alumina ceramic fiber skeleton, providing high mechanical strength and basic thermal diffusion capabilities. The middle layer incorporates a gallium-indium alloy-coated thermally conductive powder, which achieves a low-resistance thermal network through polymer interfacial grafting. The top layer utilizes amino-graphene-grafted ceramic fibers and flake graphene to synergistically construct a high-thermal conductivity surface layer, significantly improving vertical / in-plane heat transfer efficiency. Silane coupling agents are used to modify the fiber / filler surface in multiple steps to enhance interfacial compatibility between layers. A layered curing process ensures tight interlayer bonding and avoids thermal expansion mismatch. Fluorosilane spraying enhances the hydrophobicity and stability of the material, achieving high thermal conductivity, strong interfacial bonding, and high stability.

[0033] Specifically, in step S1, the silicon carbide / aluminum oxide ceramic fiber in the bottom slurry is prepared by the following steps:

[0034] 2.4 g of silicon carbide whiskers, 0.12 g of silane coupling agent KH-550 and 100 mL of anhydrous ethanol were added to a reactor, ultrasonicated for 30 minutes, and then 16 g of alumina powder and 100 mL of anhydrous ethanol were added, ultrasonicated for 30 minutes, ball-milled at 400 rpm for 8 hours, transferred to a water bath, stirred and evaporated at 90°C until viscous, vacuum-dried at 70°C for 10 hours, ground, and passed through a 40-mesh sieve to obtain a mixed powder; the mixed powder was loaded into a mold and transferred to a vacuum hot pressing furnace, kept warm and pressurized at 1540°C, 80 MPa of argon and 3% hydrogen for 1 hour, cooled with the furnace, and wire-cut to a thickness of 1 mm to obtain silicon carbide / alumina ceramic fiber.

[0035] By combining ball milling and vacuum hot pressing sintering, silicon carbide whiskers are used as a high-strength skeleton to provide mechanical support and thermal conduction path. Alumina powder fills the gaps between the whiskers to form a continuous thermal conduction network. Silane coupling agent preferentially modifies the surface of silicon carbide whiskers to form active groups, enhance chemical bonding with alumina, and suppress interfacial thermal resistance.

[0036] Specifically, in step S1, the coated liquid alloy in the middle layer slurry is prepared by the following steps:

[0037] 20 g of glycidyl methacrylate, 0.8 g of silane coupling agent KH-560, 3.2 g of divinylbenzene, 1.2 g of oxidized carbon nanotubes and 8 g of gallium-indium alloy were added to a reactor, and then 0.6 g of sodium dodecylbenzenesulfonate, 1.2 g of baking soda and 600 mL of deionized water were added. The mixture was stirred at 1200 rpm for 10 min and ultrasonicated in an ice bath for 15 min to obtain a monomer emulsion. 600 mL of the monomer emulsion was added to a reactor, nitrogen was introduced and stirred for 30 min, and 1.2 g of potassium persulfate was added at 70°C. The mixture was reacted for 6 h to obtain a coated liquid alloy.

[0038] Using sodium dodecylbenzenesulfonate and baking soda as emulsifiers, the monomer mixture of the oil phase is dispersed in the water phase to form a stable emulsion; under nitrogen protection and heating conditions, potassium persulfate is used as an initiator to trigger free radical polymerization of monomers such as glycidyl methacrylate, and the double bonds in the monomer molecules are opened and connected to each other to form polymer chains, which wrap the gallium-indium alloy and oxidized carbon nanotubes in the polymer matrix, providing a high thermal conductivity, leakage resistance, and easy-to-process composite filler for the middle layer.

[0039] Specifically, in step S1, the amino-graphene-grafted ceramic fiber in the top slurry is prepared by the following steps:

[0040] 1.76 g of amino graphene powder, 0.05 g of silane coupling agent KH-560 and 500 mL of anhydrous ethanol were added to a reactor and ultrasonicated for 45 min to obtain an amino graphene dispersion. Then 10 g of silicon carbide / alumina ceramic fiber was added, ultrasonicated for 20 min, and then taken out and vacuum dried at 100 ° C for 6 h to obtain amino graphene grafted ceramic fiber.

[0041] Aminated graphene is chemically grafted onto the surface of ceramic fibers to form a fiber-graphene composite structure. The ceramic fibers act as channels to quickly conduct heat in the longitudinal direction, while the graphene sheets expand the heat conduction path for lateral heat conduction, achieving bidirectional heat conduction enhancement and improved structural stability.

[0042] It should be noted that the silicon carbide / alumina ceramic fibers in the bottom layer provide mechanical support and basic thermal diffusion for the thick film, and the silicon carbide / alumina ceramic fibers in the top layer are efficiently loaded with amino-treated graphene. The fibers serve as a dispersed skeleton and help inhibit graphene agglomeration while building a three-dimensional thermal conductive network, further improving thermal conductivity.

[0043] Example 2: A graphene-based thermally conductive thick film material with high thermal conductivity is prepared by the following steps:

[0044] S1: 12 g of silicon carbide / alumina ceramic fiber, 1.4 g of polyvinyl butyral, and 17 g of dimethyl sulfoxide were added to a reactor and ultrasonicated for 35 min to obtain a bottom slurry;

[0045] 10 g of coated liquid alloy, 12 mL of polyurethane acrylate, and 0.14 g of benzoyl peroxide were added to a reactor and stirred at 3500 rpm for 7.5 min to obtain a middle layer slurry;

[0046] 12 g of amino-modified graphene-grafted ceramic fiber, 0.7 g of flake graphene and 7 g of cyclohexanone were added into a reactor and ultrasonicated for 22.5 min to obtain a top layer slurry.

[0047] S2: Wipe the mold clean with anhydrous ethanol, ventilate and dry it for later use; pour the bottom layer slurry into the mold, apply it with a scraper, cure it at 70°C for 20 minutes, dry it at 130°C for 35 minutes, and dry it at 205°C for 15 minutes to obtain a bottom layer film, apply the middle layer slurry on the bottom layer film, cure it at 85°C for 15 minutes, and then apply the top layer coating, hot press it at 155°C and 0.6MPa for 20 minutes, demould, spray the surface with a mass fraction of 1H,1H,2H,2H-perfluorodecyltriethoxysilane solution, and cure it at 125°C for 35 minutes to obtain a graphene-based thermal conductive thick film material with high thermal conductivity.

[0048] Specifically, in step S1, the silicon carbide / aluminum oxide ceramic fiber in the bottom slurry is prepared by the following steps:

[0049] 2.6 g of silicon carbide whiskers, 0.14 g of silane coupling agent KH-550 and 110 mL of anhydrous ethanol were added to a reactor, ultrasonicated for 35 minutes, and then 18 g of alumina powder and 110 mL of anhydrous ethanol were added, ultrasonicated for 35 minutes, ball-milled at 450 rpm for 8.5 hours, transferred to a water bath, stirred and evaporated at 95°C until viscous, vacuum-dried at 75°C for 11 hours, ground, and passed through a 40-mesh sieve to obtain a mixed powder; the mixed powder was loaded into a mold and transferred to a vacuum hot pressing furnace, kept warm and pressurized at 1560°C, 85 MPa of argon and 3% hydrogen for 1.5 hours, cooled with the furnace, and wire-cut to a thickness of 1 mm to obtain silicon carbide / alumina ceramic fiber.

[0050] Specifically, in step S1, the coated liquid alloy in the middle layer slurry is prepared by the following steps:

[0051] 22 g of glycidyl methacrylate, 1.0 g of silane coupling agent KH-560, 3.4 g of divinylbenzene, 1.4 g of oxidized carbon nanotubes and 9 g of gallium-indium alloy were added to a reactor, and then 0.7 g of sodium dodecylbenzenesulfonate, 1.3 g of baking soda and 650 mL of deionized water were added. The mixture was stirred at 1250 rpm for 15 min and ultrasonicated in an ice bath for 22.5 min to obtain a monomer emulsion. 650 mL of the monomer emulsion was added to a reactor, nitrogen was introduced and stirred for 35 min, and 1.3 g of potassium persulfate was added at 75°C. The mixture was reacted for 7 h to obtain a coated liquid alloy.

[0052] Specifically, in step S1, the amino-graphene-grafted ceramic fiber in the top slurry is prepared by the following steps:

[0053] 1.78 g of amino graphene powder, 0.07 g of silane coupling agent KH-560 and 550 mL of anhydrous ethanol were added to a reactor and ultrasonicated for 52.5 min to obtain an amino graphene dispersion. Then, 11 g of silicon carbide / alumina ceramic fiber was added, ultrasonicated for 25 min, and then taken out and vacuum dried at 105 ° C for 7 h to obtain amino graphene grafted ceramic fiber.

[0054] Example 3: A graphene-based thermally conductive thick film material with high thermal conductivity is prepared by the following steps:

[0055] S1: 14 g of silicon carbide / alumina ceramic fiber, 1.6 g of polyvinyl butyral, and 19 g of dimethyl sulfoxide were added to a reactor and ultrasonicated for 40 min to obtain a bottom slurry;

[0056] 12 g of coated liquid alloy, 14 mL of polyurethane acrylate, and 0.16 g of benzoyl peroxide were added to a reactor and stirred at 4000 rpm for 10 min to obtain a middle layer slurry;

[0057] 14 g of amino-modified graphene-grafted ceramic fiber, 0.9 g of flake graphene and 9 g of cyclohexanone were added into a reactor and ultrasonicated for 30 min to obtain a top slurry.

[0058] S2: Wipe the mold clean with anhydrous ethanol, ventilate and dry it for later use; pour the bottom layer slurry into the mold, apply it with a scraper, cure it at 75°C for 25 minutes, dry it at 140°C for 40 minutes, and dry it at 210°C for 20 minutes to obtain a bottom layer film, apply the middle layer slurry on the bottom layer film, cure it at 90°C for 20 minutes, and then apply the top layer coating, hot press it at 160°C and 0.7MPa for 25 minutes, demould, spray the surface with a mass fraction of 1H,1H,2H,2H-perfluorodecyltriethoxysilane solution, and cure it at 130°C for 40 minutes to obtain a graphene-based thermal conductive thick film material with high thermal conductivity.

[0059] Specifically, in step S1, the silicon carbide / aluminum oxide ceramic fiber in the bottom slurry is prepared by the following steps:

[0060] 2.8 g of silicon carbide whiskers, 0.16 g of silane coupling agent KH-550 and 120 mL of anhydrous ethanol were added to a reactor, ultrasonicated for 40 minutes, and then 20 g of alumina powder and 120 mL of anhydrous ethanol were added, ultrasonicated for 40 minutes, ball-milled at 500 rpm for 9 hours, transferred to a water bath, stirred and evaporated at 100° C. until viscous, vacuum-dried at 80° C. for 12 hours, ground, and passed through a 40-mesh sieve to obtain a mixed powder; the mixed powder was loaded into a mold and transferred to a vacuum hot pressing furnace, kept warm and pressurized at 1580° C., 90 MPa of argon and 3% hydrogen for 2 hours, cooled with the furnace, and wire-cut to a thickness of 1 mm to obtain silicon carbide / alumina ceramic fiber.

[0061] Specifically, in step S1, the coated liquid alloy in the middle layer slurry is prepared by the following steps:

[0062] 24 g of glycidyl methacrylate, 1.2 g of silane coupling agent KH-560, 3.6 g of divinylbenzene, 1.6 g of oxidized carbon nanotubes and 10 g of gallium-indium alloy were added to a reactor, followed by 0.8 g of sodium dodecylbenzenesulfonate, 1.4 g of baking soda and 700 mL of deionized water. The mixture was stirred at 1300 rpm for 20 min and ultrasonicated in an ice bath for 30 min to obtain a monomer emulsion. 700 mL of the monomer emulsion was added to a reactor, nitrogen was introduced and stirred for 40 min, 1.4 g of potassium persulfate was added at 80°C, and the mixture was reacted for 8 h to obtain a coated liquid alloy.

[0063] Specifically, in step S1, the amino-graphene-grafted ceramic fiber in the top slurry is prepared by the following steps:

[0064] 1.80 g of amino graphene powder, 0.09 g of silane coupling agent KH-560 and 600 mL of anhydrous ethanol were added to a reactor and ultrasonicated for 60 min to obtain an amino graphene dispersion. 12 g of silicon carbide / alumina ceramic fiber was then added and ultrasonicated for 30 min before being taken out and vacuum dried at 110 °C for 8 h to obtain amino graphene grafted ceramic fiber.

[0065] The diameter of the silicon carbide whiskers is 0.2 μm and the length is 10 μm. The thickness of the bottom layer, the middle layer and the top layer are controlled by blade coating to be 0.8 mm, 0.3 mm and 100 μm respectively.

[0066] The flake graphene described in Examples 1 to 3 is selected from LT-C-015-1 of Shanghai Liantian Materials Technology Co., Ltd.; the silicon carbide whiskers are selected from Shanghai Naionami Technology Co., Ltd. Naionami; the gallium-indium alloy is selected from Elysium of Tongxiang Metal Materials (Shanghai) Co., Ltd.; the amino graphene powder is selected from szbknm2010 of Suzhou Kaifa New Materials Technology Co., Ltd.; and the remaining raw materials are all commercially available products.

[0067] Comparative Example 1: The difference from Example 1 is that silicon carbide whiskers are not added in the specific preparation of silicon carbide / alumina ceramic fibers, alumina ceramic fibers are used to replace silicon carbide / alumina ceramic fibers in the preparation of the base slurry in S1, and the other steps remain unchanged to prepare a graphene thermal conductive thick film material.

[0068] Comparative Example 2: The difference from Example 1 is that the coated liquid alloy is not prepared, and the coated liquid alloy is replaced by graphene oxide in the middle layer slurry prepared in S1, and the other steps remain unchanged to prepare a graphene thermal conductive thick film material.

[0069] Comparative Example 3: The difference from Example 1 is that the amino-treated graphene grafted ceramic fiber is not prepared, and the amino-treated graphene grafted ceramic fiber is replaced by amino-treated graphene in the top layer slurry prepared in S1, and the other steps remain unchanged to prepare the graphene thermal conductive thick film material.

[0070] The graphene thermally conductive thick film materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were placed in an argon atmosphere and heated to 3000° C. at a heating rate of 10° C. / min for thermal reduction and graphitization. Then, a hydraulic press was used to apply 20 tons of pressure to the surface of the graphene thick film in a vacuum environment and maintained for 30 minutes to obtain a graphene thermally conductive thick film with high thermal conductivity. The thermal conductivity was tested by a laser scattering method, the tensile strength was tested by a universal material testing machine, and the thermal resistance of GaN at 5-10 W / mm was measured by infrared microscopy. The results are shown in Table 1:

[0071] Table 1: Performance test results of graphene thermal conductive thick film

[0072]

[0073]

[0074] As can be seen from Table 1, the performance of a graphene thermal conductive thick film material based on high thermal conductivity prepared in Examples 1 to 3 of the present invention is significantly better than that of the comparative example; the present invention significantly improves the tensile strength and crack resistance by adding silicon carbide whiskers and reinforcing alumina ceramic fibers. The coated liquid alloy forms a continuous metal thermal conductive chain during solidification and hot pressing, thereby achieving efficient thermal conduction in the vertical direction. The amino-grafted graphene ceramic fibers construct a horizontal continuous thermal conductive network, thereby improving the in-plane thermal diffusion efficiency. The rough surface of the fibers is embedded in the middle layer polymer to form a physical anchor, and the amino group is covalently bonded to the middle layer -NCO, strongly bridging the interlayer interface and significantly reducing the thermal resistance; the high in-plane horizontal and vertical thermal conductivity efficiency, high mechanical strength, and low interface thermal resistance of the graphene thermal conductive thick film are achieved.

[0075] The tensile strength in Comparative Example 1 is significantly reduced, which may be because silicon carbide whiskers as the key reinforcing phase are not added in the preparation of the base slurry. The strength, stiffness and toughness of the pure alumina base are much lower than those of the alumina composite material reinforced with silicon carbide whiskers, and it cannot effectively assume the mechanical support in the multi-layer structure, resulting in uneven internal microstructure, concentrated stress points, and a decrease in the mechanical properties of the base material, which in turn causes a significant decrease in the tensile strength of the entire thick film material.

[0076] The vertical thermal conductivity coefficient in Comparative Example 2 is significantly reduced, which may be because the coated liquid alloy is not added in the preparation of the middle layer slurry, which loses its role as a bridge for efficient thermal conduction in the vertical direction. The addition of the graphene oxide substitute, its inherent properties and parallel stacking, form a thermal resistance barrier layer in the thickness direction, which seriously blocks the heat flow path in the vertical direction and reduces the vertical thermal conductivity of the material.

[0077] In Comparative Example 3, the horizontal thermal conductivity coefficient decreased significantly and the interface thermal resistance increased significantly, which may be because the amino-treated graphene was not grafted onto ceramic fibers in the top slurry. The ceramic fibers serve as a thermal conductive skeleton, and their long diameter provides a low-resistance path for heat. The mixed system of amino-treated graphene and flaky graphene lacks fiber support, and forms a disordered stacked two-dimensional sheet structure after curing and hot pressing. The huge contact thermal resistance between the sheets and the broken thermal conductive network hinder the horizontal heat transfer in the plane; after removing the ceramic fibers, the difference in thermal expansion coefficient between the top and middle layer polymers increases, and the interface microcracks increase under thermal cycling, further increasing the thermal resistance.

[0078] While the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A graphene thermal conductive thick film material with high thermal conductivity, characterized in that: Prepared by the following steps: Step 1: Add silicon carbide / alumina ceramic fiber, polyvinyl butyral and dimethyl sulfoxide into a reactor and ultrasonicate for 30-40 minutes to obtain a bottom slurry; Add the coated liquid alloy, polyurethane acrylate and benzoyl peroxide into a reaction kettle and stir at 3000-4000 rpm for 5-10 minutes to obtain a middle layer slurry; Add amino graphene grafted ceramic fiber, flake graphene and cyclohexanone into a reactor and ultrasonicate for 15-30 minutes to obtain a top slurry; Step 2: Wipe the mold clean with anhydrous ethanol and dry it for later use; apply the bottom layer slurry, middle layer slurry and top layer coating in sequence in the mold through the sandwich method and solidify them. After demolding, spray 1wt% 1H,1H,2H,2H-perfluorodecyltriethoxysilane solution on the surface, dry and solidify it to obtain a graphene-based thermal conductive thick film material with high thermal conductivity.

2. The graphene-based thermally conductive thick film material with high thermal conductivity according to claim 1, characterized in that: The mass ratio of the silicon carbide / alumina ceramic fiber, polyvinyl butyral and dimethyl sulfoxide is 10-14:1.2-1.6:15-19; the usage ratio of the coated liquid alloy, polyurethane acrylate and benzoyl peroxide is: 8-12g:10-14mL:0.12-0.16g; the mass ratio of the amino-grafted graphene ceramic fiber, flaky graphene and cyclohexanone is: 10-14:0.5-0.9:5-9.

3. The graphene-based thermally conductive thick film material with high thermal conductivity according to claim 1, characterized in that: The silicon carbide / aluminum oxide ceramic fiber described in step 1 is specifically prepared by the following steps: Silicon carbide whiskers, silane coupling agent KH-550 and anhydrous ethanol are added to a reactor, ultrasonicated for 30-40 minutes, and then alumina powder and anhydrous ethanol are added, ultrasonicated for 30-40 minutes, ball-milled at 400-500 rpm for 8-9 hours, transferred to a water bath, stirred and evaporated at 90-100° C. until viscous, vacuum-dried at 70-80° C. for 10-12 hours, ground, and passed through a 40-mesh sieve to obtain a mixed powder; the mixed powder is loaded into a mold, transferred to a vacuum hot pressing furnace, kept warm and pressurized at 1540-1580° C., 80-90 MPa of argon and 3% hydrogen for 1-2 hours, cooled with the furnace, and wire-cut to a thickness of 1 mm to obtain silicon carbide / alumina ceramic fiber.

4. The graphene-based thermally conductive thick film material with high thermal conductivity according to claim 3, characterized in that: The usage ratio of the silicon carbide whisker, the silane coupling agent KH-550, the anhydrous ethanol, the aluminum oxide powder and the anhydrous ethanol is 2.4-2.8 g: 0.12-0.16 g: 100-120 mL: 16-20 g: 100-120 mL.

5. The graphene-based thermally conductive thick film material with high thermal conductivity according to claim 1, characterized in that: The coated liquid alloy in step 1 is specifically prepared by the following steps: Glycidyl methacrylate, silane coupling agent KH-560, divinylbenzene, oxidized carbon nanotubes, and gallium-indium alloy were added to a reaction kettle, followed by sodium dodecylbenzenesulfonate, baking soda, and deionized water. The mixture was stirred at 1200-1300 rpm for 10-20 minutes, and ultrasonicated in an ice bath for 15-30 minutes to obtain a monomer emulsion. The monomer emulsion is added into the reaction kettle, nitrogen is introduced and stirred for 30-40 minutes, potassium persulfate is added at 70-80° C., and the reaction is carried out for 6-8 hours to obtain a coated liquid alloy.

6. The graphene-based thermally conductive thick film material with high thermal conductivity according to claim 5, characterized in that: The usage ratio of glycidyl methacrylate, silane coupling agent KH-560, divinylbenzene, oxidized carbon nanotubes, gallium-indium alloy, sodium dodecylbenzenesulfonate, baking soda and deionized water is 20-24 g: 0.8-1.2 g: 3.2-3.6 g: 1.2-1.6 g: 8-10 g: 0.6-0.8 g: 1.2-1.4 g: 600-700 mL; The usage ratio of the monomer emulsion and potassium persulfate is 600-700 mL: 1.2-1.4 g.

7. The graphene-based thermally conductive thick film material with high thermal conductivity according to claim 1, characterized in that: The amination-treated graphene-grafted ceramic fiber in step 1 is prepared by the following steps: Aminated graphene powder, silane coupling agent KH-560 and anhydrous ethanol were added to a reactor and ultrasonicated for 45-60 minutes to obtain an aminated graphene dispersion. Silicon carbide / alumina ceramic fiber was then added and ultrasonicated for 20-30 minutes. The dispersion was taken out and vacuum dried at 100-110°C for 6-8 hours to obtain an aminated graphene grafted ceramic fiber.

8. The graphene-based thermally conductive thick film material with high thermal conductivity according to claim 7, characterized in that: The usage ratio of the amino graphene powder, the silane coupling agent KH-560, anhydrous ethanol and the silicon carbide / alumina ceramic fiber is 1.76-1.80 g: 0.05-0.09 g: 500-600 mL: 10-12 g.

9. The graphene-based thermally conductive thick film material with high thermal conductivity according to claim 1, characterized in that: The sandwich method described in step 2 specifically includes the following steps: Pour the bottom layer slurry into the mold, apply it with a scraper, cure it at 65-75℃ for 15-25min, dry it at 120-140℃ for 30-40min, and dry it at 200-210℃ for 10-20min to obtain the bottom layer film, apply the middle layer slurry on the bottom layer film, cure it at 80-90℃ for 10-20min, then apply the top layer coating, and hot press it at 150-160℃ and 0.5-0.7MPa for 15-25min.

10. The graphene-based thermally conductive thick film material with high thermal conductivity according to claim 9, characterized in that: The blade coating controlled the bottom layer thickness to be 0.8 mm, the middle layer thickness to be 0.3 mm and the top layer thickness to be 100 μm.

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