Composite thermal conductive fillers, in-situ modified thermal conductive gels with graphene, and their manufacture and use.

Abstract

The present invention discloses a graphene oxide-coated aluminum oxide composite thermally conductive filler, in which aluminum oxide is grown in situ on the surface of graphene oxide, followed by a special drying technique to form a microspherical structure in which graphene oxide is coated on the aluminum oxide surface. The present invention also discloses a thermally conductive gel in situ modified with graphene, which contains the composite thermally conductive filler. The present invention also discloses its production and use. In the product manufactured in the present invention, graphene is coated on the surface of aluminum oxide, and the two particles contact and cooperate with each other to form a special compounding action of two-dimensional and zero-dimensional spheres, building a three-dimensional extensive thermally conductive network structure, achieving high thermal conductivity and high extrusion speed at a low loading.

Description

[Technical Field]

[0001] This invention relates to a composite thermally conductive filler, a thermally conductive gel modified in situ with graphene, and the production and use of the same. [Background technology]

[0002] In the heat dissipation process of a device, it is necessary to transfer heat from the inside of the device to the external environment through the interface between the device package material and the heat sink, via the heat sink. Because solid surfaces are microscopically rough, the actual contact area between the two solid surfaces accounts for only 1-2% of the apparent contact area, even at a high contact pressure of 10 MPa, with the remaining portion being tiny voids filled with air. To reduce interfacial thermal resistance, thermally conductive interface materials have been developed. By filling the space between the contact surfaces with a thermally conductive interface material, the air in the voids at the contact interface is removed, a continuous heat conduction path is formed across the contact interface, and heat dissipation efficiency can be improved.

[0003] Thermally conductive gels are a novel thermally conductive interface material. Conventional thermally conductive gel materials are typically composite materials in which thermally conductive particles are directly mixed with organic polymer materials such as silicone oil. Adding large amounts of thermally conductive fillers not only increases the cost and weight of the thermally conductive gel, but also leads to a decrease in the interfacial wettability of the material, an increase in viscosity, and an increase in hardness, making it difficult to significantly improve thermal conductivity. [Overview of the project] [Problems that the invention aims to solve]

[0004] This invention was made to further improve the thermal conductivity of a thermally conductive gel. [Means for solving the problem]

[0005] In one aspect, the present invention relates to a graphene oxide-coated aluminum oxide composite thermal conductive filler, wherein aluminum oxide is grown in-situ on the surface of graphene. Generally, in the process of realizing the present invention, first, spherical aluminum oxide is grown in-situ on the surface of two-dimensional graphene oxide. During the in-situ growth process, the aluminum oxide tends to be unevenly distributed, growing on the same side of the graphene and less on the other side. Subsequently, during the spray drying process, it curls to form a form in which the aluminum oxide is coated with graphene oxide, often becoming microsphere-like, and in the final product, the aluminum oxide is basically located on the inner surface of the graphene.

[0006] Preferably, the microspheres have a diameter of 5 to 20 μm and a specific surface area of ​​1 to 5.1 m². 2 / g (more preferably 1-5m 2 It is / g).

[0007] Preferably, the graphene oxide is graphene modified with a coupling agent. In specific examples, the coupling agent is γ-aminopropyltriethoxysilane, boronate coupling agent, titanate coupling agent, or aluminate coupling agent.

[0008] In another aspect, the present invention relates to a graphene-modified in-situ thermal conductive gel containing the above-mentioned graphene oxide-coated aluminum oxide composite thermal conductive filler.

[0009] In yet another aspect, the present invention relates to a method for producing the graphene oxide-coated aluminum oxide composite thermal conductive filler, comprising the following steps.

[0010] 1) Preparation of graphene oxide dispersion: The process involves dispersing graphite oxide in deionized water, adjusting the pH to 4-7 (preferably 6-7) by adding ammonia water, preparing a graphite oxide suspension with a mass concentration of 1-20 g / L (preferably 5-10 g / L), removing the graphite oxide suspension with a high-pressure homogenizer, homogenizing it at a pressure of 30-80 MPa (preferably 40-60 MPa) (1-6 times), and obtaining a uniform and stable graphene oxide dispersion with a single layer of size of 5-20 μm.

[0011] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: The aluminum salt is dissolved in the graphene oxide dispersion, where the amount of aluminum salt used is 2 to 15 times the mass of the graphene oxide. The pH of the system is adjusted to 8 to 12, and aluminum oxide particles are nucleated and grown in situ on the surface of the graphene oxide. After spray drying, the particles have a size of 5 to 20 μm and a specific surface area of ​​1 to 5 m². 2 Steps to obtain a graphene oxide-coated aluminum oxide composite thermal conductive filler at a concentration of / g.

[0012] In a specific example, in step 1), a graphite oxide suspension is prepared with a pH of 6-7 and a mass concentration of 5-10 g / L, and then homogenized at a pressure of 40-60 MPa.

[0013] In specific examples, the aluminum salt is one of aluminum chloride, aluminum nitrate, aluminum sulfate, ammonium aluminum sulfate, and sodium methaluminate.

[0014] In a specific example, in step 2), before spray drying, the coupling agent is added in a mass ratio of 1:5 to 1 with the graphene oxide, and the mixture is reacted at 40 to 100°C for 0.5 to 10 hours. In a specific example, the coupling agent is γ-aminopropyltriethoxysilane, boronate coupling agent, titanate coupling agent, or aluminate coupling agent.

[0015] In a specific embodiment, in step 2), the spray air pressure range for the spray drying is 2 to 20 MPa, and the outlet temperature range is 80 to 110 °C.

[0016] In yet another aspect, the present invention relates to a method for manufacturing the graphene in-situ modified thermally conductive gel, including the following.

[0017] Disperse the platinum catalyst in the silicone oil base such that the mass percentage of the platinum catalyst and the silicone oil is 0.1 to 2.0%. Disperse the graphene oxide-coated aluminum oxide composite thermally conductive filler in the silicone oil base such that the mass ratio of the graphene oxide-coated aluminum oxide thermally conductive filler to the silicone oil base is 10 to 15:1 (stir until a uniform mixture is obtained at 1000 to 3000 rpm). While mechanically stirring, perform heat vulcanization crosslinking and reduction of graphene oxide under vacuum conditions.

[0018] In yet another aspect, the present invention relates to the use of the above-mentioned graphene in-situ modified thermally conductive gel in the manufacture of the above-mentioned composite thermally conductive filler.

[0019] In yet another aspect, the present invention relates to the use of the above-mentioned graphene in-situ modified thermally conductive gel in the manufacture of electronic products (such as mobile phones, communication base stations, new energy battery vehicles, LED chips, IGBTs and other power modules, high-power semiconductors, aerospace, etc.).

[0020] In yet another aspect, the present invention relates to an electronic product including the graphene in-situ modified thermally conductive gel according to claim 13.

[0021] The product manufactured in the embodiment of the present invention has graphene tightly coating aluminum oxide spheres. The present invention realizes the in-situ growth of aluminum oxide on the surface of graphene oxide by reacting an aluminum salt and aqueous ammonia in a graphene oxide dispersion liquid, and effectively suppresses the aggregation of graphene oxide. In the drying stage, by means of spray drying, the production of spherical composite thermal conductive fillers coated with aluminum oxide by graphene oxide is achieved, and the optimal spray droplet size is realized by precisely controlling the spray air pressure and outlet temperature range. At a small spray pressure, the size of the droplets is too large, and the size of the final composite thermal conductive filler exceeds 20 μm, making it difficult to completely coat aluminum oxide with graphene. The thermal conductive gel obtained with such fillers has a low thermal conductivity and a high hardness. At a large spray pressure, aluminum oxide detaches from the surface of graphene oxide, and the composite of graphene and aluminum oxide in the obtained composite filler becomes non-uniform. The special spherical graphene structure can effectively reduce the specific surface area of graphene (1 - 5 m 2 / g) and suppress the problem that the adsorption amount of graphene with a large specific surface area (theoretical specific capacity ~ 2600 m 2 / g) on the silicone oil base is large.

[0022] In the present invention, regarding the principle of in-situ growth of aluminum oxide on the surface of graphene oxide, the aluminum salt exists as anionic Al 3+ in an aqueous solution, and since graphene oxide is negatively charged on the surface in an aqueous dispersion liquid, Al 3+ is adsorbed on the surface of the graphene oxide lamella by the interaction force of positive and negative charges. Next, by adjusting the pH of the solution system to 8 - 12, Al 3+ reacts with OH - to crystallize and nucleate, and grows in-situ on the surface of graphene oxide.

[0023] The product manufactured according to the embodiment of the present invention has a graphene coating on the surface of aluminum oxide. Through mutual contact and cooperation between the two, a special two-dimensional and zero-dimensional spherical compounding action is formed, creating a broad three-dimensional heat conduction network structure, thereby achieving high thermal conductivity and high extrusion speed with a low filler amount.

[0024] Products manufactured according to the embodiments of the present invention can achieve a thermal conductivity of 8-12 W / (m·K) or higher, and the extrusion speed often exceeds 60 g / min. The present invention is simple and easy to implement, suitable for industrial mass production, and improves upon the conventional technical shortcoming that even when manufactured using complex processes, the thermal conductivity of graphene thermal conductive gel still does not reach 8 W / (m·K). [Modes for carrying out the invention]

[0025] The inventors manufactured heat dissipation gels by referring to several prior art documents, including CN108148558A, CN110003438A, CN105754350A, and CN111471305A. However, none of the manufactured products achieved a thermal conductivity exceeding 8 W / (m·K), thus failing to meet the inventors' expectations. Through further research and development, the inventors completed the present invention. The present invention develops a simple and easy process suitable for industrial mass production, and the manufactured high-performance graphene thermal conductive gel can achieve a thermal conductivity of 8 to 12 W / (m·K).

[0026] The present inventors attempted to mechanically mix graphene powder and aluminum oxide powder based on prior art, but because the density of graphene powder (0.003 g / mL) and the density of aluminum oxide (3.96 g / mL) are significantly different, it was difficult to uniformly mix graphene and aluminum oxide. Furthermore, graphene was extremely prone to aggregation, making it difficult to form effective pathways in the thermally conductive gel using graphene.

[0027] Based on the above, the inventors conducted further research and development to complete the present invention.

[0028] Raw materials and equipment origins: Graphite oxide: The graphite oxide paste used is SE2430W-N, a product of Changzhou Sixth Element Materials Science and Technology Co., Ltd., with a solid content of 43±5 wt%, a pH of 1.8~2.3, a particle size of 100 μm or less, a carbon content of 51±5 wt%, and a sulfur content of 2 wt% or less.

[0029] Evaluation and analysis method: Test equipment - DRL thermal conductivity meter, Test method - ASTM D5470 Thermal resistance thermal conductivity test standard

[0030] Example 1: 1) Preparation of graphene oxide slurry Graphite oxide was dispersed in deionized water to prepare 1 L of graphite oxide suspension with a mass concentration of 10 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 5, and the mixture was uniformly stirred to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphene oxide dispersion. The size of the graphene oxide in the dispersion was 5 μm.

[0031] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 100 g of aluminum chloride was weighed and dissolved in 1 L of graphene oxide dispersion with a mass concentration of 10 g / L, and mechanically stirred until completely dissolved. Then, ammonia water was added to adjust the pH to 9, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Subsequently, 2 g of γ-aminopropyltriethoxysilane was added and the reaction was carried out at 50°C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was dried by spray drying with a spray air pressure of 20 MPa and an outlet temperature of 110°C, resulting in a particle size of 5 μm and a specific surface area of ​​5.1 m². 2 A modified graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained using a coupling agent at a concentration of / g.

[0032] 3) Manufacturing of thermally conductive gels: First, 0.01 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 10 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler prepared in step 2 was weighed and dispersed in vinyl silicone oil, and the thermal conductive filler was uniformly dispersed in the vinyl silicone oil under high-speed stirring at 1000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 40 rpm / min, and heated to 120°C for 5 hours to obtain a high-performance thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 8.3 W / (m·K) and the extrusion rate was 82 g / min.

[0033] Example 2: 1) Preparation of graphene oxide slurry Graphite oxide was dispersed in deionized water to prepare 1 L of graphite oxide suspension with a mass concentration of 10 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 5, and the mixture was uniformly stirred to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphene oxide dispersion. The size of the graphene oxide in the dispersion was 5 μm.

[0034] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 100 g of aluminum chloride was weighed and dissolved in 1 L of graphene oxide dispersion with a mass concentration of 10 g / L, and mechanically stirred until completely dissolved. Then, ammonia water was added to adjust the pH to 9, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Subsequently, 2 g of γ-aminopropyltriethoxysilane was added and the reaction was carried out at 50°C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was dried by spray drying with a spray air pressure of 20 MPa and an outlet temperature of 110°C, resulting in a particle size of 5 μm and a specific surface area of ​​5.1 m². 2 A modified graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained using a coupling agent at a concentration of / g.

[0035] 3) Manufacturing of thermally conductive gels: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of dimethyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 12 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in dimethyl silicone oil, and the thermal conductive filler was uniformly dispersed in the dimethyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 80 rpm / min, and heated to 200°C for 0.5 hours to obtain a high-performance thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 9.5 W / (m·K) and the extrusion rate was 72 g / min.

[0036] Example 3: 1) Preparation of graphene oxide slurry Graphite oxide was dispersed in deionized water to prepare 1 L of graphite oxide suspension with a mass concentration of 10 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 5, and the mixture was uniformly stirred to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphene oxide dispersion. The size of the graphene oxide in the dispersion was 5 μm.

[0037] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 100 g of aluminum chloride was weighed and dissolved in 1 L of graphene oxide dispersion with a mass concentration of 10 g / L, and mechanically stirred until completely dissolved. Then, ammonia water was added to adjust the pH to 9, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Subsequently, 2 g of γ-aminopropyltriethoxysilane was added and the reaction was carried out at 50°C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was dried by spray drying with a spray air pressure of 20 MPa and an outlet temperature of 110°C, resulting in a particle size of 5 μm and a specific surface area of ​​5.1 m². 2A modified graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained using a coupling agent at a concentration of / g.

[0038] 3) Manufacturing of thermally conductive gels: First, 0.01 g of platinum catalyst was weighed and dispersed in 1 g of methylphenyl silicone oil, and mechanically stirred until uniform dispersion was achieved. Then, 13 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in methylphenyl silicone oil, and the thermal conductive filler was uniformly dispersed in the methylphenyl silicone oil under high-speed stirring at 3000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 60 rpm / min, and heated to 160°C for 2 hours to obtain a high-performance thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 10.6 W / (m·K) and the extrusion rate was 69 g / min.

[0039] Example 4: 1) Preparation of graphene oxide slurry Graphite oxide was dispersed in deionized water to prepare 1 L of graphite oxide suspension with a mass concentration of 10 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 5, and the mixture was uniformly stirred to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphene oxide dispersion. The size of the graphene oxide in the dispersion was 5 μm.

[0040] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 100 g of aluminum chloride was weighed and dissolved in 1 L of graphene oxide dispersion with a mass concentration of 10 g / L, and mechanically stirred until completely dissolved. Then, ammonia water was added to adjust the pH to 9, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Subsequently, 2 g of γ-aminopropyltriethoxysilane was added and the reaction was carried out at 50°C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was dried by spray drying with a spray air pressure of 20 MPa and an outlet temperature of 110°C, resulting in a particle size of 5 μm and a specific surface area of ​​5.1 m². 2 A modified graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained using a coupling agent at a concentration of / g.

[0041] 3) Manufacturing of thermally conductive gels: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of methylchlorophenyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 15 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in methylchlorophenyl silicone oil, and the thermal conductive filler was uniformly dispersed in the methylchlorophenyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 80 rpm / min, and heated to 200°C for 1 hour to obtain a high-performance thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 12.1 W / (m·K) and the extrusion rate was 63 g / min.

[0042] Example 5: 1) Preparation of graphene oxide slurry Graphite oxide was dispersed in deionized water to prepare 1 L of graphite oxide suspension with a mass concentration of 10 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 5, and the mixture was uniformly stirred to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphene oxide dispersion. The size of the graphene oxide in the dispersion was 5 μm.

[0043] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 100 g of aluminum chloride was weighed and dissolved in 1 L of graphene oxide dispersion with a mass concentration of 10 g / L, and mechanically stirred until completely dissolved. Then, ammonia water was added to adjust the pH to 9, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Subsequently, 2 g of γ-aminopropyltriethoxysilane was added and the reaction was carried out at 50°C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was dried by spray drying with a spray air pressure of 20 MPa and an outlet temperature of 110°C, resulting in a particle size of 5 μm and a specific surface area of ​​5.1 m². 2 A modified graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained using a coupling agent at a concentration of / g.

[0044] 3) Manufacturing of thermally conductive gels: First, 0.001 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 15 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in vinyl silicone oil, and the thermal conductive filler was uniformly dispersed in the vinyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 10 rpm / min, and heated to 200°C for 2 hours to obtain a high-performance thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 12.3 W / (m·K) and the extrusion rate was 68 g / min.

[0045] Example 6: 1) Preparation of graphene oxide slurry Graphite oxide was dispersed in deionized water to prepare 1 L of graphite oxide suspension with a mass concentration of 10 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 5, and the mixture was uniformly stirred to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphene oxide dispersion. The size of the graphene oxide in the dispersion was 5 μm.

[0046] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 100 g of aluminum chloride was weighed and dissolved in 1 L of graphene oxide dispersion with a mass concentration of 10 g / L, and mechanically stirred until completely dissolved. Then, ammonia water was added to adjust the pH to 9, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Subsequently, 2 g of γ-aminopropyltriethoxysilane was added and the reaction was carried out at 50°C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was dried by spray drying with a spray air pressure of 20 MPa and an outlet temperature of 110°C, resulting in a particle size of 5 μm and a specific surface area of ​​5.1 m². 2 A modified graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained using a coupling agent at a concentration of / g.

[0047] 3) Manufacturing of thermally conductive gels: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 15 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in vinyl silicone oil, and the thermal conductive filler was uniformly dispersed in the vinyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 10 rpm / min, and heated to 200°C for 2 hours to obtain a high-performance thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 12.1 W / (m·K) and the extrusion rate was 65 g / min.

[0048] Example 7: 1) Preparation of graphene oxide slurry Graphite oxide was dispersed in deionized water to prepare 1 L of graphite oxide suspension with a mass concentration of 10 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 5, and the mixture was uniformly stirred to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphene oxide dispersion. The size of the graphene oxide in the dispersion was 5 μm.

[0049] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 100 g of aluminum chloride was weighed and dissolved in 1 L of graphene oxide dispersion with a mass concentration of 10 g / L, and mechanically stirred until completely dissolved. Then, ammonia water was added to adjust the pH to 9, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Subsequently, 2 g of γ-aminopropyltriethoxysilane was added and the reaction was carried out at 50°C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was dried by spray drying with a spray air pressure of 20 MPa and an outlet temperature of 110°C, resulting in a particle size of 5 μm and a specific surface area of ​​5.1 m². 2 A modified graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained using a coupling agent at a concentration of / g.

[0050] 3) Manufacturing of thermally conductive gels: First, 0.003 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 15 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in vinyl silicone oil, and the thermal conductive filler was uniformly dispersed in the vinyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 10 rpm / min, and heated to 200°C for 2 hours to obtain a high-performance thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 12.2 W / (m·K) and the extrusion rate was 58 g / min.

[0051] Example 8: 1) Preparation of graphene oxide slurry Graphite oxide was dispersed in deionized water to prepare 1 L of graphite oxide suspension with a mass concentration of 10 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 5, and the mixture was uniformly stirred to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphene oxide dispersion. The size of the graphene oxide in the dispersion was 5 μm.

[0052] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 100 g of aluminum chloride was weighed and dissolved in 1 L of graphene oxide dispersion with a mass concentration of 10 g / L, and mechanically stirred until completely dissolved. Then, ammonia water was added to adjust the pH to 9, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Subsequently, 2 g of γ-aminopropyltriethoxysilane was added and the reaction was carried out at 50°C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was dried by spray drying with a spray air pressure of 20 MPa and an outlet temperature of 110°C, resulting in a particle size of 5 μm and a specific surface area of ​​5.1 m². 2 A modified graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained using a coupling agent at a concentration of / g.

[0053] 3) Manufacturing of thermally conductive gels: First, 0.005 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 15 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in vinyl silicone oil, and the thermal conductive filler was uniformly dispersed in the vinyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 10 rpm / min, and heated to 200°C for 2 hours to obtain a high-performance thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 12.1 W / (m·K) and the extrusion rate was 55 g / min.

[0054] Example 9: 1) Preparation of graphene oxide slurry Graphite oxide was dispersed in deionized water to prepare a 5 L graphite oxide suspension with a mass concentration of 1 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 7, and the mixture was uniformly stirred to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized three times under a pressure of 30 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphite oxide dispersion. The size of the graphene oxide in the dispersion was 10 μm.

[0055] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 140 g of aluminum sulfate was weighed and dissolved in 5 L of graphene oxide dispersion with a mass concentration of 1 g / L, and mechanically stirred until completely dissolved. Then, ammonia water was added to adjust the pH to 12, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Subsequently, 5 g of boronate coupling agent was added and the reaction was carried out at 90°C for 0.5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was dried by spray drying with a spray air pressure of 20 MPa and an outlet temperature of 100°C, resulting in a particle size of 5 μm and a specific surface area of ​​4.9 m². 2 A modified graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained using a coupling agent at a concentration of / g.

[0056] 3) Manufacturing of thermally conductive gels: First, 0.01 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 15 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in vinyl silicone oil, and the thermal conductive filler was uniformly dispersed in the vinyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 10 rpm / min, and heated to 200°C for 2 hours to obtain a high-performance thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 11.6 W / (m·K) and the extrusion rate was 65 g / min.

[0057] Example 10: 1) Preparation of graphene oxide slurry Graphite oxide was dispersed in deionized water to prepare a 5 L graphite oxide suspension with a mass concentration of 2 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 6, and the mixture was uniformly stirred to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 60 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphite oxide dispersion. The size of the graphene oxide in the dispersion was 15 μm.

[0058] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 300g of aluminum nitrate was weighed and dissolved in 5L of graphene oxide dispersion with a mass concentration of 2g / L, and mechanically stirred until completely dissolved. Then, ammonia water was added to adjust the pH to 11, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Subsequently, 5g of titanate coupling agent was added and the reaction was carried out at 80°C for 1 hour to modify the aluminum oxide and graphene oxide. Finally, the mixture was dried by spray drying with a spray air pressure of 12MPa and an outlet temperature of 100°C, resulting in a particle size of 10μm and a specific surface area of ​​2.3m². 2 A modified graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained using a coupling agent at a concentration of / g.

[0059] 3) Manufacturing of thermally conductive gels: First, 0.01 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 15 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in vinyl silicone oil, and the thermal conductive filler was uniformly dispersed in the vinyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 10 rpm / min, and heated to 200°C for 2 hours to obtain a high-performance thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 11.7 W / (m·K) and the extrusion rate was 61 g / min.

[0060] Example 11: 1) Preparation of graphene oxide slurry Graphite oxide was dispersed in deionized water to prepare a 5 L graphite oxide suspension with a mass concentration of 4 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 7, and the mixture was uniformly stirred to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 50 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphite oxide dispersion. The size of the graphene oxide in the dispersion was 20 μm.

[0061] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 400g of ammonium aluminum sulfate was weighed and dissolved in 5L of graphene oxide dispersion with a mass concentration of 4g / L, and mechanically stirred until completely dissolved. Then, aqueous ammonia was added to adjust the pH to 10, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Subsequently, 5g of aluminate coupling agent was added and the reaction was carried out at 60°C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was dried by spray drying with a spray air pressure of 2MPa and an outlet temperature of 80°C, resulting in a particle size of 20μm and a specific surface area of ​​1m². 2A modified graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained using a coupling agent at a concentration of / g.

[0062] 3) Manufacturing of thermally conductive gels: First, 0.01 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 15 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in vinyl silicone oil, and the thermal conductive filler was uniformly dispersed in the vinyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 10 rpm / min, and heated to 200°C for 2 hours to obtain a high-performance thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 11.9 W / (m·K) and the extrusion rate was 63 g / min.

[0063] Example 12: 1) Preparation of graphene oxide slurry Graphite oxide was dispersed in deionized water to prepare a 2 L graphite oxide suspension with a mass concentration of 5 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 7, and the mixture was uniformly stirred to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized twice under a pressure of 30 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphite oxide dispersion. The size of the graphene oxide in the dispersion was 12 μm.

[0064] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 300g of sodium metaaluminate was weighed and dissolved in 2L of graphene oxide dispersion with a mass concentration of 5g / L, and mechanically stirred until completely dissolved. Then, ammonia water was added to adjust the pH to 12, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Subsequently, 5g of aluminate coupling agent was added and the reaction was carried out at 50°C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was dried by spray drying, with a spray air pressure range of 12MPa and an outlet temperature of 90°C, resulting in a particle size of 10μm and a specific surface area of ​​3.2m². 2 A modified graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained using a coupling agent at a concentration of / g.

[0065] 3) Manufacturing of thermally conductive gels: First, 0.01 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 15 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in vinyl silicone oil, and the thermal conductive filler was uniformly dispersed in the vinyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 10 rpm / min, and heated to 200°C for 2 hours to obtain a high-performance thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 11.7 W / (m·K) and the extrusion rate was 65 g / min.

[0066] Comparative Example 1 3g of intercalated graphene powder, 400g of spherical alumina filler with an average particle size of 50μm, 50g of spherical alumina filler with an average particle size of 3μm, viscosity of 6000mm 2100g of dimethyl silicone oil (1 / s) was placed in a ball mill pot and stirred at 100 rpm for 10 minutes. 200g of zirconia balls were added to the ball mill pot. The mixture was ball milled at 500 rpm for 20 hours. After ball milling was complete, the mixture was removed to obtain a graphene-containing thermally conductive gel composite material. Tests showed that the thermal conductivity of the thermally conductive gel was 5 W / (m·K), but the extrusion rate was not measured.

[0067] Comparative Example 2 1) Preparation of graphene oxide slurry: Graphite oxide was dispersed in deionized water to prepare a 5 L graphite oxide suspension with a mass concentration of 4 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 7, and the mixture was uniformly stirred to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 50 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphite oxide dispersion. The size of the graphene oxide in the dispersion was 20 μm.

[0068] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 400g of ammonium aluminum sulfate was weighed and dissolved in 5L of a graphene oxide dispersion with a mass concentration of 4g / L, and mechanically stirred until completely dissolved. Then, aqueous ammonia was added to adjust the pH to 10, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Subsequently, 5g of aluminate coupling agent was added and the reaction was carried out at 60°C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was dried by freeze-drying, resulting in a specific surface area of ​​155m². 2 A lamellar composite thermal conductive filler was obtained in which aluminum oxide was supported on graphene oxide at a concentration of / g.

[0069] 3) Manufacturing of thermally conductive gels: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of methylchlorophenyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 15 g of the lamellar composite thermal conductive filler, in which aluminum oxide was supported on graphene oxide produced in step 2, was weighed and dispersed in methylphenyl silicone oil, and the thermal conductive filler was uniformly dispersed in the methylchlorophenyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 80 rpm / min, and heated to 200°C for 1 hour to obtain a thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 6 W / (m·K) and the extrusion rate was 5 g / min.

[0070] Comparative Example 3 1) Preparation of graphene oxide slurry: Graphite oxide was dispersed in deionized water to prepare a 5 L graphite oxide suspension with a mass concentration of 4 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 7, and the mixture was uniformly stirred to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 50 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphite oxide dispersion. The size of the graphene oxide in the dispersion was 20 μm.

[0071] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 400 g of commercially available spherical aluminum oxide particles with a size of 5 μm were weighed and dispersed in 5 L of graphene oxide dispersion with a mass concentration of 4 g / L. The mixture was mechanically stirred until uniform dispersion was achieved. Then, 5 g of aluminate coupling agent was added, and the mixture was reacted at 60°C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was dried by spray drying with a spray air pressure of 2 MPa and an outlet temperature of 80°C, resulting in a particle size of 20 μm and a specific surface area of ​​63 m². 2 A modified graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained using a coupling agent at a concentration of / g.

[0072] 3) Manufacturing of thermally conductive gels: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of methylchlorophenyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 15 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in methylphenyl silicone oil, and the thermal conductive filler was uniformly dispersed in the methylchlorophenyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 80 rpm / min, and heated to 200°C for 1 hour to obtain a thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 7 W / (m·K) and the extrusion rate was 13 g / min.

[0073] Comparative Example 4 1) Preparation of graphene oxide slurry: Graphite oxide was dispersed in deionized water to prepare a 5 L graphite oxide suspension with a mass concentration of 4 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 7, and the mixture was uniformly stirred to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 50 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphite oxide dispersion. The size of the graphene oxide in the dispersion was 20 μm.

[0074] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 400g of ammonium aluminum sulfate was weighed and dissolved in 5L of graphene oxide dispersion with a mass concentration of 4g / L, and mechanically stirred until completely dissolved. Then, aqueous ammonia was added to adjust the pH to 10, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Finally, the mixture was dried by spray drying with a spray air pressure of 2MPa and an outlet temperature of 80°C, resulting in a particle size of 20μm and a specific surface area of ​​1.2m². 2 A graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained at a concentration of / g.

[0075] 3) Manufacturing of thermally conductive gels: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of methylchlorophenyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 15 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in methylphenyl silicone oil, and the thermal conductive filler was uniformly dispersed in the methylchlorophenyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 80 rpm / min, and heated to 200°C for 1 hour to obtain a thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 3 W / (m·K) and the extrusion rate was 11 g / min.

[0076] Comparative Example 5 1) Preparation of graphene oxide slurry: Graphite oxide was dispersed in deionized water to prepare a 5 L graphite oxide suspension with a mass concentration of 4 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 7, and the mixture was uniformly stirred to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 50 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphite oxide dispersion. The size of the graphene oxide in the dispersion was 20 μm.

[0077] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 400g of ammonium aluminum sulfate was weighed and dissolved in 5L of graphene oxide dispersion with a mass concentration of 4g / L, and mechanically stirred until completely dissolved. Then, aqueous ammonia was added to adjust the pH to 10, allowing aluminum ions to combine with hydroxide ions, thus enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Finally, the mixture was dried by spray drying with a spray air pressure of 2MPa and an outlet temperature of 80°C, resulting in a particle size of 20μm and a specific surface area of ​​1.2m². 2 A graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained at a concentration of / g.

[0078] 3) Manufacturing of thermally conductive gels: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of methylchlorophenyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 5 g of aluminate coupling agent was added, and 15 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in methylphenyl silicone oil. The thermal conductive filler was uniformly dispersed in the methylchlorophenyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 80 rpm / min, and heated to 200°C for 1 hour to obtain a thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 4.1 W / (m·K) and the extrusion rate was 26 g / min.

[0079] Comparative Example 6 1) Preparation of graphene oxide slurry: Graphite oxide was dispersed in deionized water to prepare a 5 L graphite oxide suspension with a mass concentration of 4 g / L. A certain amount of aqueous ammonia was added to adjust the pH to 7, and the mixture was uniformly stirred to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 50 MPa to achieve monolayer exfoliation, obtaining a uniform and stable graphite oxide dispersion. The size of the graphene oxide in the dispersion was 20 μm.

[0080] 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: First, 400g of ammonium aluminum sulfate was weighed and dissolved in 5L of graphene oxide dispersion with a mass concentration of 4g / L, and mechanically stirred until completely dissolved. Then, 5g of aluminate coupling agent was added and stirred until dissolved. Subsequently, ammonia water was added to adjust the pH to 10, allowing aluminum ions to bind with hydroxide ions, thereby enabling the nucleation of aluminum oxide particles and their in-situ growth on the graphene oxide surface. Finally, the mixture was dried by spray drying with a spray air pressure of 2MPa and an outlet temperature of 80°C, resulting in a particle size of 20μm and a specific surface area of ​​1.2m². 2 A modified graphene oxide-coated aluminum oxide composite thermal conductive filler was obtained using a coupling agent at a concentration of / g.

[0081] 3) Manufacturing of thermally conductive gels: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of methylchlorophenyl silicone oil, and mechanically stirred until uniform dispersion occurred. Then, 15 g of the graphene oxide-coated aluminum oxide composite thermal conductive filler produced in step 2 was weighed and dispersed in methylphenyl silicone oil, and the thermal conductive filler was uniformly dispersed in the methylchlorophenyl silicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, vacuumed at 80 rpm / min, and heated to 200°C for 1 hour to obtain a thermal conductive gel. Tests showed that the thermal conductivity of the thermal conductive gel was 3.5 W / (m·K) and the extrusion rate was 13 g / min.

[0082] Comparing the properties of the graphene thermal conductive gels produced in Examples 1-12 with those of the graphene thermal conductive gel produced in Comparative Example 1, the thermal conductivity of the thermal conductive gel produced in Example 4 can reach 12 W / (m·K), which is significantly higher than the 5 W / (m·K) of Comparative Example 1. At the same time, the extrusion rate in each example mostly exceeds 60 g / min, and can reach a maximum of 82 g / min.

[0083] Comparing the properties of the graphene thermal conductive gels produced in Examples 1-12 with those of the graphene thermal conductive gel produced in Comparative Example 2, the thermal conductivity of the thermal conductive gel produced in Example 4 can reach 12 W / (m·K), which is far higher than the 6 W / (m·K) of Comparative Example 2. At the same time, the extrusion rate exceeds 60 g / min, which is far higher than the 5 g / min of Comparative Example 2. Comparative Example 2 differs from the examples mainly in that freeze-drying was used instead of spray drying. Freeze-drying is a method that perfectly preserves the two-dimensional lamellar structure of graphene by freezing the system into a solid state and then sublimating the ice under extremely low pressure. Therefore, the specific surface area of ​​the aluminum oxide-supported graphene oxide composite filler obtained in Comparative Example 2 is 155 m². 2 The value is large at / g, and in Example 4 it is 5.1m 2The concentration is much larger than per gram, and when dispersed in methylphenyl silicone oil over such a large specific surface area, the methylphenyl silicone oil rapidly adsorbs to the surface of the large area of ​​graphene, making it difficult for the silicone oil to uniformly wet the entire filler and form a uniform, highly extruded, thermally conductive gel.

[0084] Comparing the properties of the graphene thermal conductive gels produced in Examples 1-12 with those of the graphene thermal conductive gel produced in Comparative Example 3, the thermal conductivity of the thermal conductive gel produced in Example 4 can reach 12 W / (m·K), which is far higher than the 7 W / (m·K) of Comparative Example 3. At the same time, the extrusion rate exceeds 60 g / min, which is far higher than the 13 g / min of Comparative Example 3. Comparative Example 3 differs from the examples in that it mainly uses commercially available micrometer aluminum oxide. However, the density of the aluminum oxide is high at 3.96 g / mL, making it difficult to uniformly disperse in the graphene oxide dispersion by mechanical stirring. As a result, it is difficult to uniformly disperse on the surface of the graphene oxide, and in the composite filler obtained by spray drying, most of the aluminum oxide particles do not composite with the graphene. The graphene oxide coats and dries alone to form a sphere, but the aluminum oxide dries in its initial state and becomes a powder. Therefore, the specific surface area of ​​the composite filler remains 63 m². 2 The large value per gram makes it difficult for the silicone oil to uniformly wet the entire filler and form a uniform, highly extruded, heat-conductive gel.

[0085] Comparing the properties of the graphene thermal conductive gels produced in Examples 1-12 with those of the graphene thermal conductive gel produced in Comparative Example 4, the thermal conductivity of the thermal conductive gel produced in Example 4 can reach 12 W / (m·K), which is far higher than the 3 W / (m·K) of Comparative Example 4. At the same time, the extrusion rate exceeds 60 g / min, which is far higher than the 11 g / min of Comparative Example 4. Comparative Example 4 differs from the Examples mainly in that the composite thermal conductive filler was not modified with a coupling agent. However, in the manufacturing process of the thermal conductive gel, the compatibility between the graphene-coated aluminum oxide thermal conductive filler and the silicone oil is poor, and it is difficult to uniformly disperse it in the silicone oil. As a result, it is difficult to form a thermal conductive network structure, resulting in low thermal conductivity and a low extrusion rate.

[0086] Comparing the properties of the graphene thermal conductive gels produced in Examples 1-12 with those of the graphene thermal conductive gel produced in Comparative Example 5, the thermal conductivity of the thermal conductive gel produced in Example 4 can reach 12 W / (m·K), which is far higher than the 4.1 W / (m·K) of Comparative Example 5. At the same time, the extrusion rate exceeds 60 g / min, which is far higher than the 26 g / min of Comparative Example 5. Comparative Example 5 differs from the examples mainly in that a silane coupling agent is added to the silicone oil base along with the thermal conductive filler during the thermal conductive gel production process, and the thermal conductive filler was not exclusively modified beforehand. While coupling agent modification requires a reaction at a constant temperature, the mixing process between the thermally conductive filler and silicone oil is carried out under room temperature conditions. This makes it difficult to effectively graft the coupling agent onto the surface of the thermally conductive filler, resulting in poor compatibility between the thermally conductive filler and silicone oil. The filler is not uniformly dispersed in the silicone oil, making it difficult to form a thermally conductive network structure, resulting in low thermal conductivity and a low extrusion rate.

[0087] Comparing the properties of the graphene thermal conductive gels produced in Examples 1-12 with those of the graphene thermal conductive gel produced in Comparative Example 6, the thermal conductivity of the thermal conductive gel produced in Example 4 can reach 12 W / (m·K), which is far higher than the 3.5 W / (m·K) of Comparative Example 6. At the same time, the extrusion rate exceeds 60 g / min, which is far higher than the 13 g / min of Comparative Example 6. Comparative Example 6 differs from the examples mainly in that the silane coupling agent was added before the formation of aluminum oxide. However, the modification of the coupling agent requires a reaction at a constant temperature, and there is no high-temperature process in the subsequent aluminum oxide production and graphene coating process. Furthermore, in the subsequent drying process, some of the coupling agent is adsorbed on the surface of the aluminum oxide, but none is adsorbed on the surface of the graphene. Therefore, it is difficult to effectively graft the coupling agent onto the surface of the thermally conductive filler, the compatibility between the thermally conductive filler and the silicone oil is poor, and it is difficult to uniformly disperse it in the silicone oil. Consequently, it is difficult to form a thermally conductive network structure, resulting in low thermal conductivity and a low extrusion rate.

Claims

1. A method for producing a composite thermally conductive filler, 1) Preparation of graphene oxide dispersion: The process involves dispersing graphite oxide in deionized water, adjusting the pH to 4-7, preparing a graphite oxide suspension with a mass concentration of 1-20 g / L, detaching the graphite oxide suspension using a high-pressure homogenizer, homogenizing it at a pressure of 30-80 MPa, and obtaining a uniform and stable graphene oxide dispersion with a single-layer detachment size of 5-20 μm. 2) Manufacturing of graphene oxide-coated aluminum oxide composite thermal conductive fillers: An aluminum salt is dissolved in the graphene oxide dispersion, where the amount of aluminum salt used is 2 to 15 times the mass of the graphene oxide, and the pH of the system is adjusted to 8 to 12. Aluminum oxide particles are nucleated and grown in situ on the graphene oxide surface, then spray-dried, resulting in a size of 5 to 20 μm and a specific surface area of ​​1 to 5 m². ２ Steps to obtain a graphene oxide-coated aluminum oxide composite thermal conductive filler at a concentration of / g. A method characterized by including the following.

2. The method according to claim 1, characterized in that, in step 1), a graphite oxide suspension is prepared with a pH of 6 to 7 and a mass concentration of 5 to 10 g / L, and then homogenized at a pressure of 40 to 60 MPa.

3. The method according to claim 1, characterized in that the aluminum salt is any of aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum ammonium sulfate, and sodium methaluminate.

4. The method according to claim 1, characterized in that, in step 2), before spray drying and after aluminum oxide particles have nucleated and grown in-situ on the surface of graphene oxide, the coupling agent is added in a mass ratio of 1:5 to 1 of the coupling agent to the graphene oxide, and the reaction is carried out at 40 to 100°C for 0.5 to 10 hours.

5. The method according to claim 4, characterized in that the coupling agent is γ-aminopropyltriethoxysilane, a boronate coupling agent, a titanate coupling agent, or an aluminate coupling agent.

6. The method according to claim 1, characterized in that, in step 2), the spray air pressure range for the spray drying is 2 to 20 MPa and the outlet temperature range is 80 to 110°C.

7. A method for producing a thermally conductive gel, A composite thermally conductive filler is prepared by the method described in any one of claims 1 to 6, and A method comprising dispersing a platinum catalyst in a silicone oil base, dispersing a thermally conductive filler in the silicone oil base such that the mass ratio of the composite thermally conductive filler to the silicone oil base is 10 to 15:1, and performing thermal vulcanization crosslinking and reduction of graphene oxide under vacuum conditions while mechanically stirring.

8. The method according to 7, characterized in that the mass percentage of the platinum catalyst and the silicone oil is 0.1 to 2.0%.