Thermally conductive gel in-situ modified with composite thermally conductive filler, graphene, and its preparation 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] The present invention relates to a composite thermally conductive filler, a thermally conductive gel in-situ modified with graphene, and its preparation and use. [Background technology]

[0002] In the heat dissipation process of a device, heat must be transferred from inside the device through the interface between the device packaging material and the heat sink, and then through the heat sink to the external environment. Because solid surfaces are microscopically rough, the actual contact area between the two solid surfaces only accounts for 1-2% of the apparent contact area, even at high contact pressures of 10 MPa; the remainder is made up of tiny air-filled voids. Thermally conductive interface materials have been developed to reduce interfacial thermal resistance. Filling the contact surfaces with thermally conductive materials removes the air from the voids at the contact interface, forming a continuous heat conduction path across the contact interface and improving heat dissipation efficiency.

[0003] Thermally conductive gel is a novel thermally conductive interface material. Conventional thermally conductive gel materials are typically composites in which thermally conductive particles are directly mixed into organic polymers such as silicone oil. Adding a large amount of thermally conductive filler not only increases the cost and weight of the thermally conductive gel, but also reduces the interfacial wettability of the material, increases its viscosity, and increases its hardness, making it difficult to significantly improve its thermal conductivity. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to further improve the thermal conductivity performance of thermally conductive gel. [Means for solving the problem]

[0005] In one aspect, the present invention relates to a graphene oxide-coated aluminum oxide composite thermally conductive filler, in which aluminum oxide is grown in situ on the surface of graphene. Generally, in the process of realizing the present invention, spherical aluminum oxide is first grown in situ on the surface of two-dimensional graphene oxide. During the in situ growth process, the aluminum oxide is unevenly distributed and tends to grow on the same side of the graphene, with less growth on the other side. Subsequently, during the spray-drying process, the graphene oxide is curled to form a microsphere-like shape, with the aluminum oxide coated on the graphene. In the final product, the aluminum oxide is primarily 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 m. 2 / g (more preferably, 1 to 5 m 2 / g).

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

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

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

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

[0011] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: An aluminum salt is dissolved in the graphene oxide dispersion, and the amount of the aluminum salt used is 2 to 15 times the mass of the graphene oxide in terms of aluminum. The pH of the system is adjusted to 8 to 12, and aluminum oxide particles nucleate and grow in situ on the surface of the graphene oxide. The dispersion is spray-dried to produce a dispersion with a size of 5 to 20 μm and a specific surface area of 1 to 5 m. 2 / g of graphene oxide-coated aluminum oxide composite thermally conductive filler

[0012] In a specific example, in step 1), the pH is adjusted to 6 to 7, a graphite oxide suspension having a mass concentration of 5 to 10 g / L is prepared, and the suspension is homogenized under a pressure of 40 to 60 MPa.

[0013] In a specific embodiment, the aluminum salt is any one of aluminum chloride, aluminum nitrate, aluminum sulfate, ammonium aluminum sulfate, and sodium metaaluminate.

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

[0015] In a specific embodiment, in step 2), the atomizing air pressure range of 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 producing the above-mentioned thermally conductive gel in-situ modified with graphene, the method comprising:

[0017] The platinum catalyst is dispersed in a silicone oil base so that the mass percentage of the platinum catalyst and silicone oil is 0.1-2.0%. The graphene oxide-coated aluminum oxide thermally conductive filler is dispersed in a silicone oil base so that the mass ratio of the graphene oxide-coated aluminum oxide composite thermally conductive filler to the silicone oil base is 10-15:1 (stirring at 1000-3000 rpm until uniformly mixed). While mechanically stirring, thermal vulcanization crosslinking and reduction of the graphene oxide are carried out under vacuum conditions.

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

[0019] In yet another aspect, the present invention relates to use of the thermally conductive gel in-situ modified with graphene in the manufacture of electronic products (e.g., 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 comprising the in-situ graphene-modified thermally conductive gel according to claim 13.

[0021] In the products manufactured in the examples of the present invention, graphene tightly coats aluminum oxide spheres. The present invention achieves in-situ growth of aluminum oxide on the surface of graphene oxide by reacting aluminum salt with aqueous ammonia in a graphene oxide dispersion, while also effectively suppressing graphene oxide aggregation. In the drying step, a spherical composite thermally conductive filler coated with graphene oxide is produced using a spray-drying method. The optimal spray droplet size is achieved by precisely controlling the spray air pressure and outlet temperature range. At low spray pressures, the droplet size is too large, resulting in a final composite thermally conductive filler exceeding 20 μm, making it difficult to completely coat the aluminum oxide with graphene. The thermally conductive gel obtained using such fillers has low thermal conductivity and high hardness. At high spray pressures, aluminum oxide detaches from the surface of graphene oxide, resulting in non-uniform graphene-aluminum oxide composites in the resulting composite filler. The special spherical graphene structure is achieved by controlling the specific surface area (1-5 m) of graphene. 2 / g), and the large specific surface area of graphene (theoretical specific capacity ~2600 m 2 This can alleviate the problem of the large adsorption amount (1 / g) of silicone oil base.

[0022] In the present invention, the principle of in-situ growth of aluminum oxide on the surface of graphene oxide is that aluminum salt is in an anionic state in an aqueous solution. 3+ Since graphene oxide exists as a negatively charged surface in aqueous dispersion, Al 3+ is adsorbed on the surface of the graphene oxide lamellae due to the interaction force of positive and negative charges, and then the pH of the solution is adjusted to 8–12, whereby Al 3+ OH - The reaction occurs with the SiO2, causing crystallization, nucleation, and growth in situ on the surface of graphene oxide.

[0023] The product manufactured in the embodiment of the present invention has graphene coated on the surface of aluminum oxide, and the two come into contact and cooperate with each other to form a special two-dimensional and zero-dimensional spherical compounding action, building a three-dimensional extensive heat-conducting network structure, and achieving high thermal conductivity and high extrusion speed with a low filling amount.

[0024] The products manufactured in the examples of the present invention can achieve thermal conductivities of 8-12 W / (m·K) or more, often at extrusion rates exceeding 60 g / min. The present invention overcomes the drawback of the conventional graphene thermal conductive gel, which, despite being manufactured through complicated processes, still has a thermal conductivity of less than 8 W / (m·K). DETAILED DESCRIPTION OF THE INVENTION

[0025] The inventors have produced heat-dissipating gels by referring to several prior art documents, including CN108148558A, CN110003438A, CN105754350A, and CN111471305A. However, none of the products produced had a thermal conductivity of more than 8 W / (m·K), which did not meet the inventors' expectations. After further research and development, the inventors have completed the present invention. The present invention develops a simple and easy process suitable for industrial mass production, resulting in a high-performance graphene thermal conductive gel with a thermal conductivity of 8-12 W / (m·K).

[0026] The inventors attempted to mechanically mix graphene powder and aluminum oxide powder based on conventional techniques, but because the density of graphene powder (0.003 g / mL) and the density of aluminum oxide (3.96 g / mL) differ greatly, it was difficult to uniformly mix the graphene and aluminum oxide, and the graphene was extremely prone to agglomeration, making it difficult for the graphene to form effective passages in the thermally conductive gel.

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

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

[0029] Evaluation and analysis method: Test equipment - DRL thermal conductivity meter, Test method - ASTM D5470 Thermal resistance and 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 ammonia water was added to adjust the pH to 5, and the mixture was stirred uniformly to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphene oxide dispersion with a size of 5 μm.

[0031] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: 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. The solution was mechanically stirred until completely dissolved. Subsequently, aqueous ammonia was added to adjust the pH to 9, allowing aluminum ions to bond with hydroxide ions, resulting in the nucleation of aluminum oxide particles and their in-situ growth on the surface of graphene oxide. Then, 2 g of γ-aminopropyltriethoxysilane was added and reacted at 50 °C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was spray-dried at a spray air pressure of 20 MPa and an outlet temperature of 110 °C to obtain a 5 μm particle size and a specific surface area of 5.1 m. 2 / g of a modified graphene oxide-coated aluminum oxide composite thermally conductive filler with a coupling agent was obtained.

[0032] 3) Preparation of thermally conductive gel: First, 0.01 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil. This was mechanically stirred until a uniform dispersion was achieved. Next, 10 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in vinyl silicone oil. The thermally 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, evacuated at 40 rpm / min, heated to 120 °C, and reacted for 5 hours to obtain a high-performance thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 ammonia water was added to adjust the pH to 5, and the mixture was stirred uniformly to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphene oxide dispersion with a size of 5 μm.

[0034] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: 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. The solution was mechanically stirred until completely dissolved. Subsequently, aqueous ammonia was added to adjust the pH to 9, allowing aluminum ions to bond with hydroxide ions, resulting in the nucleation of aluminum oxide particles and their in-situ growth on the surface of graphene oxide. Then, 2 g of γ-aminopropyltriethoxysilane was added and reacted at 50 °C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was spray-dried at a spray air pressure of 20 MPa and an outlet temperature of 110 °C to obtain a 5 μm particle size and a specific surface area of 5.1 m. 2 / g of a modified graphene oxide-coated aluminum oxide composite thermally conductive filler with a coupling agent was obtained.

[0035] 3) Preparation of thermally conductive gel: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of dimethylsilicone oil. This was mechanically stirred until a uniform dispersion was achieved. Next, 12 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in dimethylsilicone oil. The thermally conductive filler was uniformly dispersed in the dimethylsilicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, evacuated at 80 rpm / min, heated to 200 °C, and reacted for 0.5 hours to obtain a high-performance thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 ammonia water was added to adjust the pH to 5, and the mixture was stirred uniformly to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphene oxide dispersion with a size of 5 μm.

[0037] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: 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. The solution was mechanically stirred until completely dissolved. Subsequently, aqueous ammonia was added to adjust the pH to 9, allowing aluminum ions to bond with hydroxide ions, resulting in the nucleation of aluminum oxide particles and their in-situ growth on the surface of graphene oxide. Then, 2 g of γ-aminopropyltriethoxysilane was added and reacted at 50 °C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was spray-dried at a spray air pressure of 20 MPa and an outlet temperature of 110 °C to obtain a 5 μm particle size and a specific surface area of 5.1 m. 2 / g of a modified graphene oxide-coated aluminum oxide composite thermally conductive filler with a coupling agent was obtained.

[0038] 3) Preparation of thermally conductive gel: First, 0.01 g of platinum catalyst was weighed and dispersed in 1 g of methylphenylsilicone oil, followed by mechanical stirring until uniform dispersion was achieved. Next, 13 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in methylphenylsilicone oil. The thermally conductive filler was uniformly dispersed in the methylphenylsilicone oil under high-speed stirring at 3000 rpm / min. Finally, the system was transferred to a planetary mixer, evacuated at 60 rpm / min, heated to 160 °C, and reacted for 2 hours to obtain a high-performance thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 ammonia water was added to adjust the pH to 5, and the mixture was stirred uniformly to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphene oxide dispersion with a size of 5 μm.

[0040] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: 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. The solution was mechanically stirred until completely dissolved. Subsequently, aqueous ammonia was added to adjust the pH to 9, allowing aluminum ions to bond with hydroxide ions, resulting in the nucleation of aluminum oxide particles and their in-situ growth on the surface of graphene oxide. Then, 2 g of γ-aminopropyltriethoxysilane was added and reacted at 50 °C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was spray-dried at a spray air pressure of 20 MPa and an outlet temperature of 110 °C to obtain a 5 μm particle size and a specific surface area of 5.1 m. 2 / g of a modified graphene oxide-coated aluminum oxide composite thermally conductive filler with a coupling agent was obtained.

[0041] 3) Preparation of thermally conductive gel: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of methylchlorophenyl silicone oil, followed by mechanical stirring until uniform dispersion was achieved. Next, 15 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in methylchlorophenyl silicone oil. The thermally 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, evacuated at 80 rpm / min, heated to 200 °C, and reacted for 1 hour to obtain a high-performance thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 ammonia water was added to adjust the pH to 5, and the mixture was stirred uniformly to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphene oxide dispersion with a size of 5 μm.

[0043] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: 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. The solution was mechanically stirred until completely dissolved. Subsequently, aqueous ammonia was added to adjust the pH to 9, allowing aluminum ions to bond with hydroxide ions, resulting in the nucleation of aluminum oxide particles and their in-situ growth on the surface of graphene oxide. Then, 2 g of γ-aminopropyltriethoxysilane was added and reacted at 50 °C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was spray-dried at a spray air pressure of 20 MPa and an outlet temperature of 110 °C to obtain a 5 μm particle size and a specific surface area of 5.1 m. 2 / g of a modified graphene oxide-coated aluminum oxide composite thermally conductive filler with a coupling agent was obtained.

[0044] 3) Preparation of thermally conductive gel: First, 0.001 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil. This was mechanically stirred until a uniform dispersion was achieved. Next, 15 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in vinyl silicone oil. The thermally 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, evacuated at 10 rpm / min, heated to 200 °C, and reacted for 2 hours to obtain a high-performance thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 ammonia water was added to adjust the pH to 5, and the mixture was stirred uniformly to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphene oxide dispersion with a size of 5 μm.

[0046] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: 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. The solution was mechanically stirred until completely dissolved. Subsequently, aqueous ammonia was added to adjust the pH to 9, allowing aluminum ions to bond with hydroxide ions, resulting in the nucleation of aluminum oxide particles and their in-situ growth on the surface of graphene oxide. Then, 2 g of γ-aminopropyltriethoxysilane was added and reacted at 50 °C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was spray-dried at a spray air pressure of 20 MPa and an outlet temperature of 110 °C to obtain a 5 μm particle size and a specific surface area of 5.1 m. 2 / g of a modified graphene oxide-coated aluminum oxide composite thermally conductive filler with a coupling agent was obtained.

[0047] 3) Preparation of thermally conductive gel: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil. This was mechanically stirred until a uniform dispersion was achieved. Next, 15 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in vinyl silicone oil. The thermally 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, evacuated at 10 rpm / min, heated to 200 °C, and reacted for 2 hours to obtain a high-performance thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 ammonia water was added to adjust the pH to 5, and the mixture was stirred uniformly to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphene oxide dispersion with a size of 5 μm.

[0049] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: 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. The solution was mechanically stirred until completely dissolved. Subsequently, aqueous ammonia was added to adjust the pH to 9, allowing aluminum ions to bond with hydroxide ions, resulting in the nucleation of aluminum oxide particles and their in-situ growth on the surface of graphene oxide. Then, 2 g of γ-aminopropyltriethoxysilane was added and reacted at 50 °C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was spray-dried at a spray air pressure of 20 MPa and an outlet temperature of 110 °C to obtain a 5 μm particle size and a specific surface area of 5.1 m. 2 / g of a modified graphene oxide-coated aluminum oxide composite thermally conductive filler with a coupling agent was obtained.

[0050] 3) Preparation of thermally conductive gel: First, 0.003 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil. This was mechanically stirred until a uniform dispersion was achieved. Next, 15 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in vinyl silicone oil. The thermally 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, evacuated at 10 rpm / min, heated to 200 °C, and reacted for 2 hours to obtain a high-performance thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 ammonia water was added to adjust the pH to 5, and the mixture was stirred uniformly to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 80 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphene oxide dispersion with a size of 5 μm.

[0052] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: 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. The solution was mechanically stirred until completely dissolved. Subsequently, aqueous ammonia was added to adjust the pH to 9, allowing aluminum ions to bond with hydroxide ions, resulting in the nucleation of aluminum oxide particles and their in-situ growth on the surface of graphene oxide. Then, 2 g of γ-aminopropyltriethoxysilane was added and reacted at 50 °C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was spray-dried at a spray air pressure of 20 MPa and an outlet temperature of 110 °C to obtain a 5 μm particle size and a specific surface area of 5.1 m. 2 / g of a modified graphene oxide-coated aluminum oxide composite thermally conductive filler with a coupling agent was obtained.

[0053] 3) Preparation of thermally conductive gel: First, 0.005 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil. This was mechanically stirred until uniform dispersion was achieved. Next, 15 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in vinyl silicone oil. The thermally 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, evacuated at 10 rpm / min, heated to 200 °C, and reacted for 2 hours to obtain a high-performance thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 5 L of graphite oxide suspension with a mass concentration of 1 g / L. A certain amount of ammonia water was added to adjust the pH to 7, and the mixture was stirred uniformly to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized three times under a pressure of 30 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphite oxide dispersion with a graphene oxide size of 10 μm.

[0055] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: 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. The mixture was mechanically stirred until completely dissolved. Subsequently, aqueous ammonia was added to adjust the pH to 12, allowing aluminum ions to bond with hydroxide ions, resulting in the nucleation of aluminum oxide particles and their in-situ growth on the surface of graphene oxide. 5 g of boronate coupling agent was then added and reacted at 90 °C for 0.5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was spray-dried at a spray air pressure of 20 MPa and an outlet temperature of 100 °C to obtain a particle size of 5 μm and a specific surface area of 4.9 m. 2 / g of a modified graphene oxide-coated aluminum oxide composite thermally conductive filler with a coupling agent was obtained.

[0056] 3) Preparation of thermally conductive gel: First, 0.01 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil. This was mechanically stirred until uniform dispersion was achieved. Next, 15 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in vinyl silicone oil. The thermally 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, evacuated at 10 rpm / min, heated to 200 °C, and reacted for 2 hours to obtain a high-performance thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 5 L of graphite oxide suspension with a mass concentration of 2 g / L. A certain amount of ammonia water was added to adjust the pH to 6, and the mixture was stirred uniformly to obtain a graphite oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 60 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphite oxide dispersion. The graphene oxide size in the dispersion was 15 μm.

[0058] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: First, 300 g of aluminum nitrate was weighed and dissolved in 5 L of graphene oxide dispersion with a mass concentration of 2 g / L. The mixture was mechanically stirred until completely dissolved. Subsequently, aqueous ammonia was added to adjust the pH to 11, allowing aluminum ions to bond with hydroxide ions, resulting in the nucleation of aluminum oxide particles and their in-situ growth on the surface of graphene oxide. 5 g of titanate coupling agent was then added and reacted at 80 °C for 1 hour to modify the aluminum oxide and graphene oxide. Finally, the mixture was spray-dried at a spray air pressure of 12 MPa and an outlet temperature of 100 °C to obtain a particle size of 10 μm and a specific surface area of 2.3 m. 2 / g of a modified graphene oxide-coated aluminum oxide composite thermally conductive filler with a coupling agent was obtained.

[0059] 3) Preparation of thermally conductive gel: First, 0.01 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil, followed by mechanical stirring until uniform dispersion was achieved. Next, 15 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in vinyl silicone oil. The thermally 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, evacuated at 10 rpm / min, heated to 200 °C, and reacted for 2 hours to obtain a high-performance thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 5 L of graphite oxide suspension with a mass concentration of 4 g / L. A certain amount of ammonia water was added to adjust the pH to 7, and the mixture was stirred uniformly to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 50 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphite oxide dispersion with a graphene oxide size of 20 μm.

[0061] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: First, 400 g of aluminum ammonium sulfate was weighed and dissolved in 5 L of graphene oxide dispersion with a mass concentration of 4 g / L. The mixture was mechanically stirred until completely dissolved. Then, ammonia water was added to adjust the pH to 10, allowing aluminum ions to bond with hydroxide ions, resulting in the nucleation of aluminum oxide particles and their in-situ growth on the surface of graphene oxide. 5 g of an aluminate coupling agent was then added and reacted at 60 °C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was spray-dried at a spray air pressure of 2 MPa and an outlet temperature of 80 °C to obtain a particle size of 20 μm and a specific surface area of 1 m. 2 / g of a modified graphene oxide-coated aluminum oxide composite thermally conductive filler with a coupling agent was obtained.

[0062] 3) Preparation of thermally conductive gel: First, 0.01 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil, followed by mechanical stirring until uniform dispersion was achieved. Next, 15 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in vinyl silicone oil. The thermally 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, evacuated at 10 rpm / min, heated to 200 °C, and reacted for 2 hours to obtain a high-performance thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 2 L of graphite oxide suspension with a mass concentration of 5 g / L. A certain amount of ammonia water was added to adjust the pH to 7, and the mixture was stirred uniformly to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized twice under a pressure of 30 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphite oxide dispersion. The graphene oxide size in the dispersion was 12 μm.

[0064] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: First, 300 g of sodium metaaluminate was weighed and dissolved in 2 L of graphene oxide dispersion with a mass concentration of 5 g / L. The mixture was mechanically stirred until completely dissolved. Subsequently, aqueous ammonia was added to adjust the pH to 12, allowing aluminum ions to bond with hydroxide ions, resulting in the nucleation of aluminum oxide particles and their in-situ growth on the surface of graphene oxide. 5 g of an aluminate coupling agent was then added and reacted at 50 °C for 5 hours to modify the aluminum oxide and graphene oxide. Finally, the mixture was spray-dried at a spray air pressure of 12 MPa and an outlet temperature of 90 °C to obtain a particle size of 10 μm and a specific surface area of 3.2 m. 2 / g of a modified graphene oxide-coated aluminum oxide composite thermally conductive filler with a coupling agent was obtained.

[0065] 3) Preparation of thermally conductive gel: First, 0.01 g of platinum catalyst was weighed and dispersed in 1 g of vinyl silicone oil. This was mechanically stirred until uniform dispersion was achieved. Next, 15 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in vinyl silicone oil. The thermally 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, evacuated at 10 rpm / min, heated to 200 °C, and reacted for 2 hours to obtain a high-performance thermally conductive gel. Testing showed that the thermal conductivity of the thermally conductive gel was 11.7 W / (m·K) and the extrusion rate was 65 g / min.

[0066] Comparative Example 1 3 g of intercalated graphene powder, 400 g of spherical alumina filler with an average particle size of 50 μm, 50 g of spherical alumina filler with an average particle size of 3 μm, and a viscosity of 6000 mm 2100 g of dimethyl silicone oil (1 / s) was placed in a ball mill pot and stirred at 100 rpm for 10 minutes. 200 g 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 and a graphene-containing thermally conductive gel composite was obtained. Testing 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 5 L of graphite oxide suspension with a mass concentration of 4 g / L. A certain amount of ammonia water was added to adjust the pH to 7, and the mixture was stirred uniformly to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 50 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphite oxide dispersion with a graphene oxide size of 20 μm.

[0068] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: First, 400 g of aluminum ammonium sulfate was weighed and dissolved in 5 L of graphene oxide dispersion with a mass concentration of 4 g / L. The mixture was then mechanically stirred until completely dissolved. Subsequently, aqueous ammonia was added to adjust the pH to 10, allowing aluminum ions to bond with hydroxide ions, resulting in the nucleation of aluminum oxide particles and their in-situ growth on the surface of graphene oxide. Five grams of an aluminate coupling agent was then added, and the reaction was carried out at 60°C for five hours, resulting in the modification of aluminum oxide and graphene oxide. Finally, the mixture was freeze-dried to obtain a mixture with a specific surface area of 155 m. 2 A lamellar composite thermally conductive filler was obtained in which aluminum oxide was supported on graphene oxide at 1000 nm / g.

[0069] 3) Preparation of thermally conductive gel: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of methylchlorophenylsilicone oil, followed by mechanical stirring until uniform dispersion was achieved. Next, 15 g of the lamellar composite thermally conductive filler (aluminum oxide supported on graphene oxide) prepared in step 2 was weighed and dispersed in methylchlorophenylsilicone oil. The thermally conductive filler was uniformly dispersed in the methylchlorophenylsilicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, evacuated at 80 rpm / min, heated to 200 °C, and reacted for 1 hour to obtain a thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 5 L of graphite oxide suspension with a mass concentration of 4 g / L. A certain amount of ammonia water was added to adjust the pH to 7, and the mixture was stirred uniformly to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 50 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphite oxide dispersion. The size of the graphene oxide in the dispersion was 20 μm.

[0071] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: First, 400 g of commercially available aluminum oxide spherical 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 dispersion was mechanically stirred until uniform. 5 g of an aluminate coupling agent was then added and reacted at 60 °C for 5 hours to achieve the modification of aluminum oxide and graphene oxide. Finally, the mixture was dried by spray drying at a spray air pressure of 2 MPa and an outlet temperature of 80 °C. The particles were dispersed to a size of 20 μm and a specific surface area of 63 m. 2 / g of a modified graphene oxide-coated aluminum oxide composite thermally conductive filler with a coupling agent was obtained.

[0072] 3) Preparation of thermally conductive gel: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of methylchlorophenyl silicone oil, followed by mechanical stirring until uniform dispersion was achieved. Next, 15 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in methylchlorophenyl silicone oil. The thermally 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, evacuated at 80 rpm / min, heated to 200 °C, and reacted for 1 hour to obtain a thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 5 L of graphite oxide suspension with a mass concentration of 4 g / L. A certain amount of ammonia water was added to adjust the pH to 7, and the mixture was stirred uniformly to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 50 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphite oxide dispersion with a graphene oxide size of 20 μm.

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

[0075] 3) Preparation of thermally conductive gel: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of methylchlorophenyl silicone oil, followed by mechanical stirring until uniform dispersion was achieved. Next, 15 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in methylchlorophenyl silicone oil. The thermally 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, evacuated at 80 rpm / min, heated to 200 °C, and reacted for 1 hour to obtain a thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 5 L of graphite oxide suspension with a mass concentration of 4 g / L. A certain amount of ammonia water was added to adjust the pH to 7, and the mixture was stirred uniformly to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 50 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphite oxide dispersion with a graphene oxide size of 20 μm.

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

[0078] 3) Preparation of thermally conductive gel: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of methylchlorophenylsilicone oil, followed by mechanical stirring until uniform dispersion was achieved. Next, 5 g of aluminate coupling agent was added, and 15 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in methylchlorophenylsilicone oil. The thermally conductive filler was uniformly dispersed in the methylchlorophenylsilicone oil under high-speed stirring at 2000 rpm / min. Finally, the system was transferred to a planetary mixer, evacuated at 80 rpm / min, heated to 200 °C, and reacted for 1 hour to obtain a thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 5 L of graphite oxide suspension with a mass concentration of 4 g / L. A certain amount of ammonia water was added to adjust the pH to 7, and the mixture was stirred uniformly to obtain a graphene oxide dispersion. The graphene oxide dispersion was homogenized once under a pressure of 50 MPa to achieve monolayer exfoliation, resulting in a uniform and stable graphite oxide dispersion with a graphene oxide size of 20 μm.

[0080] 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: First, 400 g of aluminum ammonium sulfate was weighed and dissolved in 5 L of graphene oxide dispersion with a mass concentration of 4 g / L. The mixture was mechanically stirred until completely dissolved. 5 g of aluminate coupling agent was then added and stirred until dissolved. Ammonia water was then added to adjust the pH to 10, allowing aluminum ions to bond with hydroxide ions, resulting in the nucleation of aluminum oxide particles and their in-situ growth on the surface of graphene oxide. Finally, the mixture was dried by spray drying at 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 1.2 m. 2 / g of a modified graphene oxide-coated aluminum oxide composite thermally conductive filler with a coupling agent was obtained.

[0081] 3) Preparation of thermally conductive gel: First, 0.02 g of platinum catalyst was weighed and dispersed in 1 g of methylchlorophenyl silicone oil, followed by mechanical stirring until uniform dispersion was achieved. Next, 15 g of the graphene oxide-coated aluminum oxide composite thermally conductive filler prepared in step 2 was weighed and dispersed in methylchlorophenyl silicone oil. The thermally 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, evacuated at 80 rpm / min, heated to 200 °C, and reacted for 1 hour to obtain a thermally conductive gel. Testing showed that the thermal conductivity of the thermally 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 to 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 much higher than the 5 W / (m K) of Comparative Example 1. At the same time, the extrusion speed of each example mostly exceeds 60 g / min, reaching a maximum of 82 g / min.

[0083] Comparing the properties of the graphene thermal conductive gels prepared in Examples 1 to 12 with those prepared in Comparative Example 2, the thermal conductivity of the thermal conductive gel prepared in Example 4 reached 12 W / (m·K), significantly higher than the 6 W / (m·K) of Comparative Example 2. At the same time, the extrusion rate exceeded 60 g / min, significantly higher than the 5 g / min of Comparative Example 2. Comparative Example 2 differs from the Examples primarily in the use of freeze-drying instead of spray-drying. Freeze-drying involves freezing a system into a solid and then sublimating the ice under extremely low pressure, thereby completely preserving the two-dimensional lamellar structure of graphene. Therefore, the specific surface area of the aluminum oxide-loaded graphene oxide composite filler obtained in Comparative Example 2 was 155 m. 2 / g, which is large, and 5.1m in Example 4 2 / g, and when dispersed in methylphenylsilicone oil with such a large specific surface area, the methylphenylsilicone oil quickly adsorbs onto the large-area surface of graphene, making it difficult for the silicone oil to uniformly wet the entire filler and form a uniform, highly extrudable thermally conductive gel.

[0084] Comparing the properties of the graphene thermal conductive gels prepared in Examples 1 to 12 with those prepared in Comparative Example 3, the thermal conductivity of the thermal conductive gel prepared in Example 4 reached 12 W / (m K), much higher than the 7 W / (m K) of Comparative Example 3. At the same time, the extrusion rate exceeded 60 g / min, much higher than the 13 g / min of Comparative Example 3. Comparative Example 3 differs from the Examples mainly in that commercially available micrometer aluminum oxide was used. However, the density of aluminum oxide was high at 3.96 g / mL, making it difficult to uniformly disperse it in the graphene oxide dispersion by mechanical stirring. Therefore, in the composite filler obtained by spray drying, most of the aluminum oxide particles were not composited with graphene. The graphene oxide was coated and dried alone to form a sphere, while the aluminum oxide dried in its original state to form a powder. Therefore, the specific surface area of the composite filler was still 63 m. 2 / g, making it difficult for the silicone oil to uniformly wet the entire filler to form a uniform, highly extrudable thermally conductive gel.

[0085] Comparing the properties of the graphene thermal conductive gels prepared in Examples 1 to 12 with those prepared in Comparative Example 4, the thermal conductivity of the thermal conductive gel prepared in Example 4 reached 12 W / (m·K), significantly higher than the 3 W / (m·K) of Comparative Example 4. At the same time, the extrusion rate exceeded 60 g / min, significantly higher than the 11 g / min of Comparative Example 4. Comparative Example 4 differs from the Examples primarily in that the composite thermal conductive filler was not modified with a coupling agent. However, during the thermal conductive gel preparation process, the graphene-coated aluminum oxide thermal conductive filler had poor compatibility with silicone oil and was difficult to disperse uniformly in the silicone oil. This made it 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 to 12 with those produced in Comparative Example 5, the thermal conductivity of the thermal conductive gel produced in Example 4 reached 12 W / (m·K), much higher than the 4.1 W / (m·K) of Comparative Example 5. At the same time, the extrusion rate exceeded 60 g / min, much higher than the 26 g / min of Comparative Example 5. Comparative Example 5 differs from the Examples mainly in that a silane coupling agent was added to the silicone oil base together with the thermal conductive filler during the thermal conductive gel production process, and the thermal conductive filler was not modified prior to that. Coupling agent modification requires a reaction at a certain temperature. However, the mixing process of the thermally conductive filler and silicone oil is carried out under room temperature conditions, making it difficult to effectively graft the coupling agent onto the surface of the thermally conductive filler. The thermally conductive filler has poor compatibility with silicone oil and is difficult to disperse uniformly in the silicone oil. As a result, it is difficult to form a thermally conductive network structure, resulting in low thermal conductivity and a slow extrusion speed.

[0087] Comparing the properties of the graphene thermal conductive gels prepared in Examples 1 to 12 with those prepared in Comparative Example 6, the thermal conductivity of the thermal conductive gel prepared in Example 4 reached 12 W / (m·K), significantly higher than the 3.5 W / (m·K) of Comparative Example 6. At the same time, the extrusion rate exceeded 60 g / min, significantly higher than the 13 g / min of Comparative Example 6. Comparative Example 6 differs from the Examples primarily in that a silane coupling agent was added before aluminum oxide formation. However, the coupling agent modification required a reaction at a certain temperature, eliminating the need for high-temperature processes in the subsequent aluminum oxide production and graphene coating processes. Furthermore, during the subsequent drying process, some of the coupling agent adsorbed onto the aluminum oxide surface, but none of it adsorbed onto the graphene surface. Therefore, it is difficult to effectively graft the coupling agent onto the surface of the thermally conductive filler, and the thermally conductive filler has poor compatibility with the silicone oil, making it difficult to disperse uniformly in the silicone oil. As a result, it is difficult to form a thermally conductive network structure, resulting in low thermal conductivity and a low extrusion speed.

Claims

1. A graphene oxide-coated aluminum oxide composite thermally conductive filler, Aluminum oxide is grown in-situ on the surface of graphene oxide. A composite thermally conductive filler characterized in that the composite thermally conductive filler is a microsphere of a graphene oxide-coated aluminum oxide composite thermally conductive filler.

2. 2. The composite thermally conductive filler according to claim 1, wherein the aluminum oxide is grown in-situ on the inner surface of the graphene oxide.

3. The microspheres have a diameter of 5 to 20 μm and a specific surface area of 1 to 5.1 m ２ 2. The composite thermally conductive filler according to claim 1, wherein the filler has a viscosity of 1000 MPa.

4. The composite thermally conductive filler according to any one of claims 1 to 3, characterized in that the graphene oxide is coupling agent-modified graphene.

5. 5. The composite thermally conductive filler according to claim 4, wherein the coupling agent is γ-aminopropyltriethoxysilane, a boronate coupling agent, a titanate coupling agent, or an aluminate coupling agent.

6. A method for producing the composite thermally conductive filler according to any one of claims 1 to 5, comprising: 1) Preparation of graphene oxide dispersion: A process of dispersing graphite oxide in deionized water, adjusting the pH to 4 to 7, and preparing a graphite oxide suspension with a mass concentration of 1 to 20 g / L, exfoliating the graphite oxide suspension with a high-pressure homogenizer, and homogenizing it at a pressure of 30 to 80 MPa to obtain a uniform and stable dispersion of exfoliated graphene oxide particles with a size of 5 to 20 μm. 2) Preparation of graphene oxide-coated aluminum oxide composite thermally conductive filler: An aluminum salt is dissolved in the graphene oxide dispersion, and the amount of the aluminum salt used is 2 to 15 times the mass of the graphene oxide in terms of aluminum. The pH of the system is adjusted to 8 to 12. Aluminum oxide particles nucleate and grow in situ on the surface of the graphene oxide. The aluminum salt is spray-dried to produce a graphene oxide dispersion having a size of 5 to 20 μm and a specific surface area of 1 to 5 m. ２ / g of a graphene oxide-coated aluminum oxide composite thermally conductive filler A method comprising:

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

8. 7. The method of claim 6, wherein the aluminum salt is any one of aluminum chloride, aluminum nitrate, aluminum sulfate, ammonium aluminum sulfate, and sodium metaaluminate.

9. The method according to claim 6, wherein in step 2), a coupling agent is added to the graphene oxide in a mass ratio of 1:5 to 1:1 before spray drying, and the reaction is carried out at 40 to 100°C for 0.5 to 10 hours.

10. 10. The method of claim 9, wherein the coupling agent is γ-aminopropyltriethoxysilane, a boronate coupling agent, a titanate coupling agent, or an aluminate coupling agent.

11. The method according to claim 6, wherein in step 2), the atomizing air pressure range of the spray drying is 2 to 20 MPa and the outlet temperature range is 80 to 110°C.

12. A thermally conductive gel in-situ modified with graphene, comprising the composite thermally conductive filler according to any one of claims 1 to 5.

13. A method for producing the in-situ graphene modified thermally conductive gel of claim 12, comprising: A method comprising dispersing a platinum catalyst in a silicone oil base, dispersing a thermally conductive filler in the silicone oil base so 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.

14. 14. The method of claim 13, wherein the mass percentage of the platinum catalyst and the silicone oil is 0.1 to 2.0%.

15. An electronic product comprising the in-situ graphene-modified thermally conductive gel of claim 12.

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