Preparation method of high-elasticity carbon-based thermal interface material

Abstract

This invention discloses a method for preparing a highly elastic carbon-based thermal interface material. The method utilizes centrifugal filtration technology to prepare a highly oriented substrate, employs interface fusion technology to achieve dimensional control of the thermal interface, utilizes high-temperature annealing to achieve a high-speed heat conduction pathway, and adjusts the elasticity and density of the thermal interface material by controlling the substrate composition, structure, and pressure. The carbon-based thermal interface prepared by this method exhibits controllable three-dimensional dimensions, a simple operation, low interfacial thermal resistance, and excellent elasticity, making it widely applicable for vertical heat dissipation in high-power heat sources.

Description

Technical Field

[0001] This invention belongs to the field of thermal management and relates to a method for preparing a highly elastic carbon-based thermal interface material. Background Technology

[0002] With the widespread application of 5G technology, information content and data traffic have increased significantly, leading to increasingly higher requirements for the integration density, operating frequency, and power density of electronic devices. However, as these requirements increase, the thermal dissipation problem of electronic devices has become increasingly prominent, thus intensifying the demand for efficient thermal management materials.

[0003] These materials are primarily responsible for filling the gaps between rough heat sources and heat sinks, ensuring heat transfer area and heat transfer capacity, thereby effectively reducing the temperature of the heat source and ensuring the stable and long-term operation of electronic devices. Currently, thermal interface materials are widely used in new energy batteries, automotive electronic equipment, smart terminals (mobile phones, computers, etc.), 5G base stations, data centers, and other fields.

[0004] Meanwhile, with the rapid growth of emerging technologies and applications, higher requirements are being placed on the performance indicators of thermal interface materials. For example, there is a need to improve thermal conductivity, enhance heat resistance, increase lateral dimensions, reduce costs, and extend service life.

[0005] Currently, the main high thermal interface materials on the market (thermal conductivity greater than 10 W / mK) include: composite thermally conductive silicone (10-20 W / mK), liquid gallium alloy (73 W / mK), indium-based alloy, composite oriented carbon fiber (25-150 W / mK), vertical graphene (100 W / mK), and diamond (300-600 W / mK). However, these materials all have certain limitations in application: for example, thermally conductive silicone has poor heat resistance and is prone to curing and failure; liquid gallium alloy is corrosive; indium metal is too rare and non-renewable; diamond is expensive and lacks flexibility (mainly used in the aerospace field). In particular, in the field of extreme thermal conductivity, there is currently no material that can simultaneously meet the requirements of high thermal conductivity, high interface flexibility, high heat resistance, and renewability.

[0006] In contrast, carbon materials have seen rapid development due to their advantages such as good stability, ease of processing, physical or chemical modification capabilities, and high flexibility. In recent years, vertically oriented carbon fibers, graphene, graphite, and carbon nanotubes have demonstrated high cost-effectiveness. However, these materials have failed to achieve a synergistic improvement in thermal stability, thermal conductivity, density, and elasticity, significantly hindering the performance of carbon-based thermal interface materials and limiting their application areas. Summary of the Invention

[0007] This invention addresses the shortcomings of existing technologies by providing a method for preparing a highly elastic carbon-based thermal interface material. The method utilizes centrifugal filtration to prepare a highly oriented substrate, interface fusion technology to achieve dimensional control of the thermal interface, high-temperature annealing to create a high-speed heat conduction pathway, and adjustment of the substrate composition, structure, and pressure to regulate the elasticity and density of the thermal interface material. Under pressure, the heat dissipation interface is compacted, while the flexible thermal interface can fully fill the interface gaps, resulting in a sharp reduction in interface thermal resistance. The carbon-based thermal interface prepared by this method exhibits controllable three-dimensional dimensions, a simple operation, low interface thermal resistance, and excellent elasticity, making it widely applicable for vertical heat dissipation of high-power heat sources.

[0008] Specifically, the present invention adopts the following technical solution:

[0009] (1) Disperse 0.5 to 1 part by mass of graphene oxide and 2 to 20 parts by mass of polymer carbon source evenly in 100 parts by mass of solvent to form a composite dispersion.

[0010] (2) The composite dispersion obtained in step (1) is placed in a cylinder with a filter membrane as the inner layer and a porous filter screen as the outer layer. The central axis of the cylinder is parallel to the ground. The cylinder rotates under the drive of the motor to generate centrifugal force, so that the mixture of graphene oxide and polymer carbon source is separated from the solvent under centrifugal action, forming a graphene oxide-based composite membrane with a thickness of more than 50 μm on the filter membrane. The graphene oxide-based composite membrane is then peeled off.

[0011] (3) Spray a polar solvent on the surface of the graphene oxide-based composite film obtained in step (2) until the surface is wetted, and stack them layer by layer until the thickness is greater than 1 cm. Then keep it at 60-180℃ and 1-60MPa static pressure for 5-30 min to obtain a graphene oxide-based composite thick film.

[0012] (4) Cut the graphene oxide-based composite thick film obtained in step (3) along a direction perpendicular to the film surface, with a cutting spacing of 50 to 500 μm, to obtain graphene oxide-based composite slices.

[0013] (5) The graphene oxide-based composite slices obtained in step (4) are heated to 250-350°C in air and held for 5-60 min. Then, they are chemically reduced at 60-100°C for 5-60 min in a hydrogen iodide atmosphere. Finally, they are placed in a container that restricts the edges of the slices and heat-treated at 2700°C in an argon atmosphere for 2-12 h to obtain a highly elastic carbon-based thermal interface material.

[0014] Furthermore, the polymer carbon source mentioned in step (1) includes polyacrylonitrile, pitch, polyimide, soluble lignin, etc. The solvent includes water, DMF, DMSO, NMP.

[0015] Further, in step (2), the pore size of the outer filter screen is no greater than 100 μm, and the pore size of the inner filter membrane is 0.2–1 μm. The cylinder rotates at a speed of 500–6000 r / min, and the inner diameter of the cylinder is greater than 20 cm.

[0016] Furthermore, the polar solvent mentioned in step (3) includes water, DMF, DMSO, and NMP.

[0017] Furthermore, the cutting methods described in step (4) include laser cutting, diamond wire cutting, and blade circular cutting.

[0018] In this invention, the thermal conductivity test employs a vertical equivalent thermal conductivity test, referencing the standard ASTM D5470, to determine the material's thermal conductivity under actual application conditions. Unlike the thermal conductivity in this invention, the equivalent heat loss rate fully considers interfacial thermal resistance, providing feedback on the overall interfacial thermal conductivity effect under real-world conditions.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) The strategy of “centrifugal filtration + interface fusion + vertical cutting” achieves the synergistic orientation of graphene oxide and polymer and the preparation of large-area, size-controllable materials. First, the orientation structure enhances the graphitization ability of the polymer itself and reduces the amount of graphene oxide used. Second, centrifugal filtration enables graphene oxide and polymer molecules to be aligned in a direction parallel to the film. After stacking and cutting, a graphene alignment structure with vertical orientation can be obtained, which allows the prepared film to maintain better vertical thermal conductivity and elasticity after subsequent high-temperature sintering. Third, the orientation of the polymer increases the high-temperature graphitization ability of the polymer, which in turn allows for the addition of more polymer to reduce costs.

[0021] (2) The solvent permeation rate of centrifugal filtration is fast, which enables rapid drying of the film and controllable recovery of the solvent without high temperature heating, significantly improving the preparation efficiency. During this process, under the action of centrifugal force, the material is uniform and tightly stacked, without skin effect and stress concentration, which helps to prepare thick and highly oriented films, reduces the number of film stacking interfaces, and is more conducive to the structural integrity of thermal interface materials.

[0022] (3) The ultra-high polymer content reduces the preparation cost on the one hand, and the graphitized part provides a heat conduction channel at high temperature, while the non-graphitized part provides additional elasticity to the material as a whole; at the same time, the increase in polymer content provides more channels for gas escape, which can suppress film foaming and indirectly increase the material density.

[0023] (4) Applying a certain pressure to the thermal interface sheet during the high-temperature process can suppress material foaming and improve the orientation of the thermal interface material; at the same time, it can promote the fusion of the sheets and increase the density. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the production equipment used in the preparation method of a highly elastic carbon-based thermal interface material according to the present invention. 1 is a filter membrane, 2 is a cylinder composed of a porous filter screen, 3 is the holes on the cylinder, and 4 is the central axis of the cylinder.

[0025] Figure 2 This is a top view of the thermal interface material of Example 1;

[0026] Figure 3 This is a cross-sectional scanning electron microscope image of the thermal interface material in Example 1;

[0027] Figure 4 The image shows the Raman spectrum of the thermal interface material in Example 1. Detailed Implementation

[0028] The present invention will be specifically described below through embodiments. These embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential changes and adjustments made by those skilled in the art based on the above-described invention shall fall within the scope of protection of the present invention.

[0029] Example 1

[0030] (1) Disperse 1 part by mass of graphene oxide and 10 parts by mass of polyacrylonitrile in 100 parts by mass of DMF to form a composite dispersion.

[0031] (2) The composite dispersion obtained in step (1) is placed in a cylinder with an inner layer of filter membrane with a pore size of 1 μm and an outer layer of porous filter screen with a pore size of 80 μm. The inner diameter of the cylinder is 30 cm and the central axis of the cylinder is parallel to the ground. The cylinder rotates under the drive of a motor to generate centrifugal force at a speed of 6000 r / min, so that the mixture of graphene oxide and polyacrylonitrile is separated from the solvent under centrifugal action, forming a graphene oxide-based composite membrane with a thickness of 65 μm on the filter membrane. The graphene oxide-based composite membrane is then peeled off.

[0032] (3) Spray DMF onto the surface of the graphene oxide-based composite film obtained in step (2) until the surface is wetted, stack the layers until the thickness is greater than 1 cm, and then keep it at 180°C and 1 MPa static pressure for 10 min to obtain a graphene oxide-based composite thick film.

[0033] (4) The graphene oxide-based composite thick film obtained in step (3) is laser-cut along a direction perpendicular to the film surface, with a cutting spacing of 50 μm, to obtain graphene oxide-based composite slices.

[0034] (5) The graphene oxide-based composite slices obtained in step (4) are heated to 250°C in air and held for 60 min. Then, they are chemically reduced at 60°C for 60 min in a hydrogen iodide atmosphere. Finally, they are placed in a container that restricts the edges of the slices and heat-treated at 2700°C in an argon atmosphere for 2 h to obtain a highly elastic carbon-based thermal interface material.

[0035] The appearance of the obtained highly elastic carbon-based thermal interface material is as follows: Figure 2 As shown, the material surface is smooth and shiny, with a high degree of graphitization. The microstructure is as follows: Figure 3 As shown, its interior can be found to consist of highly oriented sheet-like units. Raman spectroscopy results are as follows... Figure 4 As shown, certain defect structures (D peak) can be observed inside the material, originating from sp peaks formed after partial polymer carbonization. 3 Carbon provides elasticity to the material. Tests show that the high orientation and elasticity resulting from centrifugal shear force lead to low interfacial thermal resistance in this material, with a vertical equivalent thermal conductivity of 23 W / mK.

[0036] Example 2

[0037] (1) Disperse 1 part by mass of graphene oxide and 20 parts by mass of asphalt in 100 parts by mass of NMP to form a composite dispersion.

[0038] (2) The composite dispersion obtained in step (1) is placed in a cylinder with an inner layer of filter membrane with a pore size of 1 μm and an outer layer of porous filter screen with a pore size of 70 μm. The inner diameter of the cylinder is 30 cm and the central axis of the cylinder is parallel to the ground. The cylinder rotates under the drive of a motor to generate centrifugal force at a speed of 6000 r / min, so that the mixture of graphene oxide and asphalt is separated from the solvent under centrifugal action, forming a graphene oxide-based composite membrane with a thickness of 80 μm on the filter membrane. The graphene oxide-based composite membrane is then peeled off.

[0039] (3) Spray water on the surface of the graphene oxide-based composite film obtained in step (2) until the surface is wet, stack the layers until the thickness is greater than 1 cm, and then keep it at 180°C and 10 MPa static pressure for 5 min to obtain a graphene oxide-based composite thick film.

[0040] (4) The graphene oxide-based composite thick film obtained in step (3) is laser-cut along a direction perpendicular to the film surface with a cutting spacing of 100 μm to obtain graphene oxide-based composite slices.

[0041] (5) The graphene oxide-based composite slices obtained in step (4) are heated to 300°C in air and held for 30 min. Then, they are chemically reduced at 60°C for 60 min in a hydrogen iodide atmosphere. Finally, they are placed in a container that restricts the edges of the slices and heat-treated at 2700°C in an argon atmosphere for 6 h to obtain a highly elastic carbon-based thermal interface material.

[0042] The vertical equivalent thermal conductivity of the obtained highly elastic carbon-based thermal interface material is 34 W / mK.

[0043] Example 3

[0044] (1) Disperse 0.5 parts by mass of graphene oxide and 2 parts by mass of soluble lignin in 100 parts by mass of water to form a composite dispersion.

[0045] (2) The composite dispersion obtained in step (1) is placed in a cylinder with an inner layer of a filter membrane with a pore size of 0.2 μm and an outer layer of a porous filter screen with a pore size of 70 μm. The inner diameter of the cylinder is 30 cm and the central axis of the cylinder is parallel to the ground. The cylinder rotates under the drive of a motor to generate centrifugal force at a speed of 500 r / min, so that the mixture of graphene oxide and soluble lignin is separated from the solvent under centrifugal action, forming a graphene oxide-based composite membrane with a thickness of 50 μm on the filter membrane. The graphene oxide-based composite membrane is then peeled off.

[0046] (3) Spray water on the surface of the graphene oxide-based composite film obtained in step (2) until the surface is wet, stack the layers until the thickness is greater than 1 cm, and then keep it at 60°C and 60 MPa static pressure for 30 min to obtain a graphene oxide-based composite thick film.

[0047] (4) Cut the graphene oxide-based composite thick film obtained in step (3) along a diamond wire perpendicular to the film surface, with a cutting spacing of 500 μm, to obtain graphene oxide-based composite slices.

[0048] (5) The graphene oxide-based composite slices obtained in step (4) are heated to 350°C in air and held for 5 min. Then, they are chemically reduced at 100°C for 5 min in a hydrogen iodide atmosphere. Finally, they are placed in a container that restricts the edge of the slices and heat-treated at 2700°C in an argon atmosphere for 2 h to obtain a highly elastic carbon-based thermal interface material.

[0049] The vertical equivalent thermal conductivity of the obtained highly elastic carbon-based thermal interface material is 41 W / mK.

[0050] Example 4

[0051] (1) Disperse 0.8 parts by mass of graphene oxide and 15 parts by mass of soluble lignin in 100 parts by mass of water to form a composite dispersion.

[0052] (2) The composite dispersion obtained in step (1) is placed in a cylinder with an inner layer of a filter membrane with a pore size of 0.5 μm and an outer layer of a porous filter screen with a pore size of 60 μm. The inner diameter of the cylinder is 50 cm and the central axis of the cylinder is parallel to the ground. The cylinder rotates under the drive of a motor to generate centrifugal force at a speed of 2000 r / min, so that the mixture of graphene oxide and soluble lignin is separated from the solvent under centrifugal action, forming a graphene oxide-based composite membrane with a thickness of 80 μm on the filter membrane. The graphene oxide-based composite membrane is then peeled off.

[0053] (3) Spray DMSO onto the surface of the graphene oxide-based composite film obtained in step (2) until the surface is wetted, stack the layers until the thickness is greater than 1 cm, and then keep it at 100°C and 10 MPa static pressure for 20 min to obtain a graphene oxide-based composite thick film.

[0054] (4) Cut the graphene oxide-based composite thick film obtained in step (3) into a circular cut with a blade perpendicular to the film surface, with a cutting spacing of 200 μm, to obtain graphene oxide-based composite slices.

[0055] (5) The graphene oxide-based composite slices obtained in step (4) are heated to 350°C in air and held for 20 min. Then, they are chemically reduced at 80°C for 15 min in a hydrogen iodide atmosphere. Finally, they are placed in a container that restricts the edge of the slices and heat-treated at 2700°C in an argon atmosphere for 12 h to obtain a highly elastic carbon-based thermal interface material.

[0056] The vertical equivalent thermal conductivity of the obtained highly elastic carbon-based thermal interface material is 52 W / mK.

Claims

1. A method for preparing a highly elastic carbon-based thermal interface material, characterized in that, Includes the following steps: (1) Disperse 0.5 to 1 part by mass of graphene oxide and 2 to 20 parts by mass of polymer carbon source evenly in 100 parts by mass of solvent to form a composite dispersion. (2) The composite dispersion obtained in step (1) is placed in a cylinder with a filter membrane as the inner layer and a porous filter screen as the outer layer. The central axis of the cylinder is parallel to the ground. The cylinder rotates under the drive of the motor to generate centrifugal force, so that the mixture of graphene oxide and polymer carbon source is separated from the solvent under centrifugal action, forming a graphene oxide-based composite membrane with a thickness of more than 50 μm on the filter membrane. The graphene oxide-based composite membrane is then peeled off. (3) Spray a polar solvent on the surface of the graphene oxide-based composite film obtained in step (2) until the surface is wetted, stack them layer by layer until the thickness is greater than 1 cm, and then keep it at 60-180℃ and 1-60MPa static pressure for 5-30 min to obtain a graphene oxide-based composite thick film. (4) Cut the graphene oxide-based composite thick film obtained in step (3) along a direction perpendicular to the film surface, with a cutting spacing of 50 to 500 μm, to obtain graphene oxide-based composite slices. (5) The graphene oxide-based composite slices obtained in step (4) are heated to 250-350°C in air and held for 5-60 min. Then, they are chemically reduced at 60-100°C for 5-60 min in a hydrogen iodide atmosphere. Finally, they are placed in a container that restricts the edges of the slices and heat-treated at 2700°C in an argon atmosphere for 2-12 h to obtain a highly elastic carbon-based thermal interface material.

2. The method according to claim 1, characterized in that, The polymer carbon source mentioned in step (1) includes polyacrylonitrile, pitch, polyimide, and soluble lignin.

3. The method according to claim 1, characterized in that, The solvents mentioned in step (1) include water, DMF, DMSO, and NMP.

4. The method according to claim 1, characterized in that, The outer filter screen in step (2) has a pore size of no more than 100 μm, and the inner filter membrane has a pore size of 0.2 to 1 μm.

5. The method according to claim 1, characterized in that, The cylinder rotation speed in step (2) is 500-6000 r / min, and the inner diameter of the cylinder is greater than 20 cm.

6. The method according to claim 1, characterized in that, The polar solvents mentioned in step (3) include water, DMF, DMSO, and NMP.

7. The method according to claim 1, characterized in that, The cutting methods described in step (4) include laser cutting, diamond wire cutting, and blade circular cutting.

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