Carbon nanotube heat dissipation layer, preparation method and application thereof

Abstract

The application discloses a carbon nanotube heat dissipation layer and a preparation method and application thereof. The carbon nanotube heat dissipation layer comprises a bottom heat dissipation layer and a surface heat dissipation layer. The bottom heat dissipation layer comprises alumina modified carbon nanotube powder, a dispersing agent, water, a leveling agent, an adhesion promoter and polyurethane resin. The surface heat dissipation layer comprises alumina modified carbon nanotube powder, a dispersing agent, water, a leveling agent, polyurethane resin and a thickening agent. The alumina modified carbon nanotube powder is uniformly grown with alumina particles on the surface of carbon nanotubes. The alumina particles on the surface not only enhance the dispersion capacity of the carbon nanotubes, but also enhance the heat conductivity between the carbon nanotubes, thereby improving the heat dissipation capacity of the coating. The carbon nanotube heat dissipation layer is suitable for aluminum or aluminum alloy materials, can be directly coated on the surface of aluminum or aluminum alloy, does not need any pretreatment on the surface of aluminum or aluminum alloy, has excellent adhesion and is suitable for popularization and use.

Description

Technical Field

[0001] This invention relates to the field of heat dissipation layers, and particularly to a carbon nanotube heat dissipation layer, its preparation method, and its application. Background Technology

[0002] With the increasing integration and miniaturization of electronic products, heat dissipation becomes slower during operation. Low heat dissipation efficiency can significantly affect product stability and lifespan, thus placing higher demands on the thermal management of electronic products and equipment. The solution of attaching heat sinks to the surface of electronic products and equipment and installing fans, using a combination of heat conduction and convection to improve heat dissipation, has been widely adopted in the industry.

[0003] Coating the surface of a heat sink with a carbon nanotube heat dissipation layer can further improve its infrared radiation heat dissipation capability, enhancing the heat dissipation capacity of electronic products and equipment. This solution is low-cost, and for irregularly shaped materials, spraying or dip coating processes can be used, unaffected by the material's shape and size. Due to its light weight and good thermal conductivity, aluminum is currently the most common material for heat sinks. However, aluminum oxide forms on the surface, and oil, dirt, and other contaminants adhere to it. Therefore, pretreatment of the aluminum surface is an essential and crucial step. Conventional methods involve mechanically grinding the surface and using acidic or alkaline cleaning agents to remove oil stains. However, this method can create white spots on the aluminum surface and even cause the aluminum to yellow or blacken. Furthermore, this method generates a large amount of acidic or alkaline wastewater, increasing wastewater treatment costs and polluting the environment.

[0004] Carbon nanotubes are sp 2 One-dimensional tubular nanomaterials composed of hybrid C-C bonds possess superior mechanical, electrical, and thermal properties. Their axial thermal conductivity is 2000-3000 W / mK, about 10 times that of copper, far exceeding that of other metallic materials. They also have high thermal radiation and stronger heat dissipation capabilities. However, carbon nanotubes have poor radial thermal conductivity, which limits their application in the field of heat dissipation.

[0005] Invention patent 202210749264.1 discloses a method for preparing heat-dissipating coatings by physical ball milling and blending of graphene, carbon nanotubes and alumina. However, this method cannot ensure that the thermally conductive filler alumina adheres evenly to the surfaces of carbon nanotubes and graphene, resulting in an insignificant heat dissipation effect of the final coating.

[0006] Invention patent 202211230726.5 discloses a graphene heat dissipation coating and its preparation method. The coating is prepared with a pleated graphene oxide heat dissipation coating. The coating has a balanced thermal conductivity and emissivity, which can improve the heat dissipation capacity of electronic components in low-temperature environments. Before the coating is applied to the aluminum plate, the aluminum plate needs to be sanded with sandpaper and the surface oil stains need to be cleaned with sodium hydroxide solution. The process is relatively cumbersome. Summary of the Invention

[0007] The main objective of this invention is to provide a heat dissipation layer that can be directly coated on the surface of aluminum or aluminum alloy and its preparation method, so as to overcome the shortcomings of the poor radial thermal conductivity of existing carbon nanotubes and the need for surface pretreatment of aluminum or aluminum alloys before use.

[0008] To achieve the aforementioned objective, the technical solution adopted by the present invention includes: a carbon nanotube heat dissipation layer, which comprises: a carbon nanotube heat dissipation bottom layer and a carbon nanotube heat dissipation surface layer; wherein the thickness of the carbon nanotube heat dissipation bottom layer is 1-3 μm, and the thickness of the carbon nanotube heat dissipation surface layer is 10-15 μm.

[0009] Furthermore, the components of the carbon nanotube heat dissipation bottom layer, by weight percentage, include: 4%-8% alumina-modified carbon nanotube powder, 1%-5% dispersant, 1%-3% leveling agent, 0.5%-2% adhesion promoter, 15%-25% polyurethane resin, and the remainder is water.

[0010] The components of the carbon nanotube surface layer, by weight percentage, include: 3%-8% alumina-modified carbon nanotube powder, 1%-5% dispersant, 0.5%-1% leveling agent, 19%-25% polyurethane resin, 0.5%-1% thickener, and the remainder is water.

[0011] Furthermore, the alumina-modified carbon nanotube powder is made by coating a layer of alumina powder onto the surface of carbon nanotubes.

[0012] The carbon nanotubes are multi-walled carbon nanotubes with a diameter of 9-80 nm and a length of 1-20 μm.

[0013] Furthermore, the dispersant is one or more of the following: sodium methylene bisnaphthalene sulfonate, octylphenol polyoxyethylene ether, sodium polyacrylate, and sodium poly(p-styrene sulfonate);

[0014] The leveling agent is one or more of Tego500, Tego450, BYK345, BYK333, SN4763, and Capstone FS-31;

[0015] The adhesion promoter is one of Lubrizol R2063, AddBond DS1300, and MOAP1708;

[0016] The polyurethane resin is one or more of Eterane 8925B, Eterane 89252, ETERSOL 61325B, and Bayhydrol XP 2592;

[0017] The thickener is a water-based thickener; the water-based thickener is one of Rheovis AS1130 and Rheovis HS1169.

[0018] Another object of the present invention is to provide a method for the above-mentioned carbon nanotube heat dissipation layer, the method specifically including the following steps:

[0019] S1) Prepare alumina-modified carbon nanotube powder for later use;

[0020] S2) Weigh out each component according to the designed proportions;

[0021] S3) Alumina-modified carbon nanotube powder, dispersant, and water are mixed to prepare an aqueous carbon nanotube slurry;

[0022] S4) The carbon nanotube aqueous slurry obtained in S3) is mixed with the remaining components and then magnetically stirred at a certain speed to obtain carbon nanotube heat dissipation bottom coating and carbon nanotube heat dissipation top coating, respectively.

[0023] S5) First, apply a dry film of the carbon nanotube heat dissipation bottom layer coating obtained in S4) onto the carrier. After curing, the carbon nanotube heat dissipation bottom layer is obtained. Then, apply the carbon nanotube heat dissipation top layer coating obtained in S4) onto the carbon nanotube heat dissipation bottom layer. After curing, the carbon nanotube heat dissipation top layer is obtained, thus obtaining the carbon nanotube heat dissipation layer.

[0024] Furthermore, the specific steps of S1) are as follows:

[0025] S1.1) First, add carbon nanotubes to KMnO4 / H2SO4 solution, sonicate the mixture in an ultrasonic microwave chemical synthesizer for 30 min, filter the treated carbon nanotubes, wash the carbon nanotubes with deionized water until the washed deionized water is neutral, and obtain carboxylated carbon nanotubes.

[0026] S1.2) Carboxylated carbon nanotubes are then added to deionized water and neutralized with NaOH aqueous solution. Aluminum chloride powder is then added and stirred evenly under magnetic stirring. NaOH aqueous solution is then added while stirring to obtain aluminum hydroxide-coated carbon nanotubes. The aluminum hydroxide-coated carbon nanotubes are filtered and washed with deionized water until the washed deionized water is neutral. The washed aluminum hydroxide-coated carbon nanotubes are then freeze-dried to obtain aluminum hydroxide-coated carbon nanotube powder.

[0027] S1.3) The aluminum hydroxide-coated carbon nanotube powder was calcined at 950-1050℃ for 30 min under a flowing nitrogen atmosphere to obtain alumina-modified carbon nanotube powder.

[0028] Furthermore, the specific steps of S3) are as follows:

[0029] S3.1) Mix alumina-modified carbon nanotube powder, dispersant, and water, and then mechanically stir for 10-20 minutes to mix evenly at a speed of 500-800 r / min to obtain a mixed liquid;

[0030] S3.2) The mixed liquid obtained in S3.1) is homogenized in a high-pressure homogenizer for 3-6 minutes at a homogenization pressure of 500-700 bar, and then filtered through a 500-mesh filter bag to obtain a carbon nanotube aqueous slurry.

[0031] Furthermore, the specific steps of S4 are as follows:

[0032] S4.1) The carbon nanotube aqueous slurry, leveling agent, adhesion promoter and polyurethane resin obtained in S3) are mixed evenly by stirring with a magnetic stirrer for 5-10 minutes at a speed of 200-500 r / min to obtain the bottom heat dissipation layer.

[0033] S4.2) The carbon nanotube aqueous slurry, leveling agent, polyurethane resin and thickener obtained in S3) are mixed evenly by stirring with a magnetic stirrer for 5-10 minutes at a speed of 200-500 r / min to obtain the surface heat dissipation layer.

[0034] Furthermore, the specific process in S5) is as follows:

[0035] The curing temperature of the bottom heat dissipation layer is 140-160℃, and the baking time is 5-10 minutes.

[0036] The curing temperature of the surface heat dissipation layer is 110-120℃, and the baking time is 5-10 minutes.

[0037] The carbon nanotube heat dissipation layer prepared by the above method is applied to the heat dissipation of aluminum or aluminum alloy surfaces.

[0038] This invention utilizes interionic interaction forces to uniformly grow alumina particles on the surface of carbon nanotubes, improving the dispersibility and radial thermal conductivity of carbon nanotubes and enhancing the heat dissipation capacity of the coating. A bottom heat dissipation layer with a dry film thickness of 1-3 μm is first coated on the surface of the aluminum sheet, followed by a top heat dissipation layer with a dry film thickness of 10-15 μm. The heat dissipation layer has excellent adhesion and requires no pretreatment of the aluminum sheet, thus improving production efficiency and the heat dissipation capacity of the aluminum sheet.

[0039] The beneficial technical effects of this invention are: due to the adoption of the above technical solution, the preparation method of this invention utilizes Al 3+ With COO - The interaction between ions allows for the uniform growth of alumina particles on the surface of carbon nanotubes. Compared with the direct physical blending of alumina and carbon nanotube powder, this method results in better compatibility and more uniform distribution of alumina and carbon nanotubes. It can also improve the thermal conductivity between carbon nanotubes and the dispersion ability of carbon nanotubes, and the coating has better heat dissipation.

[0040] The two-coating scheme of primer and topcoat can be directly applied to the surface of aluminum or aluminum alloy without any pretreatment of aluminum or aluminum alloy, including grinding, pickling / alkaline washing and other processes. This scheme improves production efficiency and avoids subsequent acid / alkaline wastewater treatment, making it more environmentally friendly. Attached Figure Description

[0041] Figure 1 This is a flowchart of a method for preparing a carbon nanotube heat dissipation layer according to the present invention.

[0042] Figure 2 This is a schematic diagram of the carbon nanotube heat dissipation layer of the present invention coated on an aluminum sheet.

[0043] Figure 3 This is a schematic diagram showing the adhesion test results of the carbon nanotube heat dissipation layer on the heat dissipation aluminum fin.

[0044] Figure 4 The graph shows the heat dissipation capacity test curve of the carbon nanotube heat dissipation layer. Detailed Implementation

[0045] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0046] like Figure 1 As shown, the present invention discloses a method for preparing a carbon nanotube heat dissipation layer, which specifically includes the following steps:

[0047] S1) Prepare alumina-modified carbon nanotube powder for later use;

[0048] The specific steps are as follows:

[0049] S1.1) First, add carbon nanotubes to KMnO4 / H2SO4 solution, sonicate the mixture in an ultrasonic microwave chemical synthesizer for 30 min, filter the treated carbon nanotubes, wash the carbon nanotubes with deionized water until the washed deionized water is neutral, and obtain carboxylated carbon nanotubes.

[0050] S1.2) Carboxylated carbon nanotubes are then added to deionized water and neutralized with NaOH aqueous solution. Aluminum chloride powder is then added and stirred evenly under magnetic stirring. NaOH aqueous solution is then added while stirring to obtain aluminum hydroxide-coated carbon nanotubes. The aluminum hydroxide-coated carbon nanotubes are filtered and washed with deionized water until the washed deionized water is neutral. The washed aluminum hydroxide-coated carbon nanotubes are then freeze-dried to obtain aluminum hydroxide-coated carbon nanotube powder.

[0051] S1.3) The aluminum hydroxide-coated carbon nanotube powder was calcined at 950-1050℃ for 30 min under a flowing nitrogen atmosphere to obtain alumina-modified carbon nanotube powder.

[0052] S2) Weigh out each component according to the designed proportions;

[0053] S3) Alumina-modified carbon nanotube powder, dispersant, and water are mixed to prepare an aqueous carbon nanotube slurry;

[0054] The specific steps are as follows:

[0055] S3.1) Mix alumina-modified carbon nanotube powder, dispersant, and water, and then mechanically stir for 10-20 minutes to mix evenly at a speed of 500-800 r / min to obtain a mixed liquid;

[0056] S3.2) The mixed liquid obtained in S3.1) is homogenized in a high-pressure homogenizer for 3-6 minutes at a homogenization pressure of 500-700 bar, and then filtered through a 500-mesh filter bag to obtain a carbon nanotube aqueous slurry.

[0057] S4) The carbon nanotube aqueous slurry obtained in S3) is mixed with the remaining components and then magnetically stirred at a certain speed to obtain carbon nanotube heat dissipation bottom coating and carbon nanotube heat dissipation top coating, respectively.

[0058] The specific steps are as follows:

[0059] S4.1) The carbon nanotube aqueous slurry, leveling agent, adhesion promoter and polyurethane resin obtained in S3) are mixed evenly by stirring with a magnetic stirrer for 5-10 minutes at a speed of 200-500 r / min to obtain the bottom heat dissipation layer.

[0060] S4.2) The carbon nanotube aqueous slurry, leveling agent, polyurethane resin and thickener obtained in S3) are mixed evenly by stirring with a magnetic stirrer for 5-10 minutes at a speed of 200-500 r / min to obtain the surface heat dissipation layer.

[0061] S5) First, apply a dry film of the carbon nanotube heat dissipation bottom layer coating obtained in S4) onto the carrier. After curing, the carbon nanotube heat dissipation bottom layer is obtained. The curing temperature of the bottom heat dissipation layer is 140-160℃, and it is baked for 5-10 minutes. Then, apply the carbon nanotube heat dissipation top layer coating obtained in S4) onto the carbon nanotube heat dissipation bottom layer. The curing temperature of the top layer heat dissipation layer is 110-120℃, and it is baked for 5-10 minutes. After curing, the carbon nanotube heat dissipation top layer is obtained, which is the carbon nanotube heat dissipation layer.

[0062] The carrier is made of aluminum or aluminum alloy.

[0063] Example 1

[0064] Preparation of alumina-modified carbon nanotube powder: 5g of multi-walled carbon nanotubes GT210 (diameter 8-15nm, length 20-50μm) and 3g of multi-walled carbon nanotubes TNIM8 (diameter 30-80nm, length <10μm) were added to 200ml of KMnO4 (3mol / L) / H2SO4 (1mol / L) aqueous solution and magnetically stirred until homogeneous. The mixture was poured into a 500ml three-necked flask and ultrasonicated for 30min at 800W in an ultrasonic microwave chemical synthesizer. The carboxylated carbon nanotubes were filtered and washed with deionized water until the deionized water was neutral, yielding carboxylated carbon nanotubes. The carboxylated carbon nanotubes were added to 150ml of deionized water and magnetically stirred until homogeneous. Then, 0.5mol / L NaOH aqueous solution was added until the pH was neutral. Finally, 3g of aluminum chloride was added and magnetically stirred until completely dissolved. While stirring, 0.5mol / L NaOH aqueous solution was added. NaOH aqueous solution was used until most of the carbon nanotubes settled to the bottom to obtain aluminum hydroxide-coated carbon nanotubes. The aluminum hydroxide-coated carbon nanotubes were filtered and washed with deionized water until the deionized water was neutral. The washed aluminum hydroxide-coated carbon nanotubes were freeze-dried to obtain aluminum hydroxide-coated carbon nanotube powder. The aluminum hydroxide-coated carbon nanotube powder was calcined at 1000℃ for 30 min under a flowing nitrogen atmosphere to obtain alumina-modified carbon nanotube powder.

[0065] Preparation of the bottom heat dissipation layer: 21g of alumina-modified carbon nanotube powder, 6.5g of sodium methylene bis(naphthalene) sulfonate, 3.5g of octylphenol polyoxyethylene ether, and 269g of water were stirred at 500r / min for 20min, and then homogenized for 3min at a high pressure of 500bar to obtain an aqueous carbon nanotube slurry. 80g of the aqueous carbon nanotube slurry, 17.5g of polyurethane resin Eternal8925B, 1.5g of MOAP1708, 0.6g of Capstone FS-31, and 0.4g of Tego450 were mixed evenly under magnetic stirring for 6min at a stirring speed of 500r / min to obtain the bottom heat dissipation layer. The surface tension of the coating was 17.3mN / m, and the viscosity was 34mPa·s.

[0066] Preparation of the surface heat dissipation layer: Take 78g of carbon nanotube aqueous slurry, 20.5g of polyurethane resin Eternal89252, 0.5g of BYK333, 0.2g of SN4763, and 0.8g of thickener Rheovis AS1130 and stir them under magnetic stirring for 6 minutes to mix them evenly. The stirring speed is 500r / min to obtain the surface heat dissipation layer. The surface tension of the coating is 26.5mN / m and the viscosity is 91mPa·s.

[0067] A bottom heat dissipation layer is coated onto an aluminum sheet and baked at 160℃ for 5 minutes, resulting in a dry film thickness of 1.5 μm. A top heat dissipation layer is then coated and baked at 120℃ for 5 minutes, resulting in a total heat dissipation coating thickness of 12.8 μm, thus obtaining the heat dissipation aluminum sheet. Figure 2 As shown.

[0068] Example 2

[0069] Preparation of alumina-modified carbon nanotube powder: The preparation method is basically the same as that in Example 1, except that the amount of carbon nanotubes GT210 and TNIM8 added is 6.5g and 2g, respectively.

[0070] Preparation of the bottom heat dissipation layer: 21g of alumina-modified carbon nanotube powder, 4.5g of sodium methylene bis(naphthalene) sulfonate, 3.5g of octylphenol polyoxyethylene ether, 2g of sodium polyacrylate, and 269g of water were stirred at 500r / min for 20min and homogenized for 3min at 500bar to obtain an aqueous carbon nanotube slurry. 80g of the aqueous carbon nanotube slurry, 17.5g of polyurethane resin Eternal8925B, 1.5g of MOAP1708, 1g of Capstone FS-31, and 0.3g of Tego450 were stirred under magnetic stirring for 6min to mix evenly at 500r / min to obtain the bottom heat dissipation layer. The surface tension of the coating was 16.4mN / m, and the viscosity was 51mPa·s.

[0071] Preparation of the surface heat dissipation layer: Take 78g of carbon nanotube aqueous slurry, 20.5g of polyurethane resin Eternal89252, 0.5g of BYK333, 0.4g of SN4763, and 0.8g of thickener Rheovis AS1130 and stir them under magnetic stirring for 6 minutes to mix them evenly. The stirring speed is 500r / min to obtain the surface heat dissipation layer. The surface tension of the coating is 24.9mN / m and the viscosity is 100mPa·s.

[0072] The bottom heat dissipation layer is coated onto the oil-stained aluminum sheet and baked at 160℃ for 5 minutes, resulting in a dry film thickness of 1.5μm. Then, the top heat dissipation layer is coated and baked at 120℃ for 5 minutes, resulting in a total heat dissipation coating thickness of 12.7μm, thus obtaining the heat dissipation aluminum sheet.

[0073] Example 3

[0074] Preparation of alumina-modified carbon nanotube powder: The preparation method is basically the same as that in Example 1, except that GT210 carbon nanotubes are replaced with NC7000 (9.5 nm diameter, 1.5 μm length), and the calcination temperature is 1030 °C.

[0075] Preparation of the bottom heat dissipation layer: 26g of alumina-modified carbon nanotube powder, 8.5g of sodium methylene bis(naphthalene) sulfonate, 3.5g of sodium poly(p-styrene) sulfonate, and 262g of water were stirred at 500r / min for 20min, and then homogenized in a high-pressure homogenizer for 4min at a homogenization pressure of 500bar to obtain an aqueous carbon nanotube slurry. 78g of the aqueous carbon nanotube slurry, 20.3g of polyurethane resin Eternal8925B, 0.7g of AddBond DS1300, 0.6g of Capstone FS-31, and 0.4g of Tego450 were mixed evenly under magnetic stirring for 6min at a stirring speed of 500r / min to obtain the bottom heat dissipation layer. The surface tension of the coating was 16.2mN / m, and the viscosity was 29mPa·s.

[0076] Preparation of surface heat dissipation layer: Take 73g of carbon nanotube aqueous slurry, 24.5g of polyurethane resin ETERSOL 61325B, 0.7g of BYK333, and 0.8g of thickener Rheovis AS1130 and stir under magnetic stirring for 6min to mix evenly. The stirring speed is 500r / min to obtain the surface heat dissipation layer. The surface tension of the coating is 27.9mN / m and the viscosity is 127mPa·s.

[0077] The bottom heat dissipation layer is coated onto the aluminum sheet and baked at 160℃ for 8 minutes, resulting in a dry film thickness of 1.5μm. Then, the top heat dissipation layer is coated and baked at 120℃ for 5 minutes, resulting in a total heat dissipation coating thickness of 12.8μm, thus obtaining the heat dissipation aluminum sheet.

[0078] Comparative Example 1

[0079] The method for preparing the heat dissipation layer in this comparative embodiment is basically the same as that in Example 3, except that only the surface heat dissipation layer is prepared.

[0080] The heat dissipation layer was coated onto the aluminum sheet and baked at 120℃ for 5 minutes. The total thickness of the dry film of the heat dissipation coating was 11.2 μm, thus obtaining the heat dissipation aluminum sheet.

[0081] Comparative Example 2

[0082] The preparation method of the heat dissipation layer in this comparative embodiment is basically the same as that in Example 1. The main difference is that when preparing the bottom heat dissipation layer, no adhesion promoter MOAP1708 is added, and the surface tension of the coating is 17.5 mN / m.

[0083] The bottom heat dissipation layer is coated onto the aluminum sheet and baked at 160℃ for 5 minutes. The dry film thickness of the heat dissipation coating is 1.3μm, thus obtaining the heat dissipation aluminum sheet.

[0084] Comparative Example 3

[0085] The method for preparing the heat dissipation layer in this comparative embodiment is basically the same as that in Example 2, except that only the surface heat dissipation layer is prepared.

[0086] The heat dissipation layer was applied to an oil-stained aluminum sheet and baked at 120°C for 5 minutes to obtain a heat dissipation aluminum sheet. The surface of the heat dissipation aluminum sheet had shrinkage cavities, exposing the substrate. The dry film thickness of the coating could not be measured.

[0087] Table 1 Performance of the heat dissipation layer in the examples and comparative examples

[0088]

[0089] Figure 3 The figures show the adhesion test results, where (a), (b), (c), and (d) are Comparative Example 1, Example 3, Comparative Example 3, and Example 2, respectively. As can be seen from the figures, by using the method of coating a bottom heat dissipation layer + a top heat dissipation layer, the coating did not have leveling problems on either clean or oily aluminum sheets, and the adhesion of the coating on the aluminum sheet after drying can reach level 0. Figure 4 The figure shows a comparison of the heat dissipation capabilities of carbon nanotube heat dissipation layers. The heat dissipation aluminum sheet in the figure is from Example 1. As can be seen from the figure, the pure aluminum sheet has a certain heat dissipation capability, but the surface temperature is still relatively high. After coating with the carbon nanotube heat dissipation layer, the surface temperature drops by more than 8°C, and the heat dissipation capability is significantly improved. Table 1 summarizes the experimental results of all cases. As can be seen from the table, the prepared heat dissipation aluminum sheet can reduce the temperature by 10-14°C, and the heat dissipation layer has good adhesion and hardness. However, when only the bottom heat dissipation layer or the top heat dissipation layer is coated, the adhesion or heat dissipation effect of the heat dissipation layer is poor, and it even fails to level on the aluminum sheet with oil stains, resulting in pinholes.

[0090] In this embodiment, an oil-stained aluminum sheet was used, and its preparation method is as follows:

[0091] The aluminum sheet was cleaned with 100% anhydrous ethanol, baked at 100°C for 1 minute, and then a layer of mechanical lubricating oil was evenly coated on its surface and baked at 100°C for 1 minute to obtain an oil-stained aluminum sheet.

[0092] In the implementation method, the surface tension and viscosity of the coating are measured using a surface tension tester and a rotational viscometer, respectively.

[0093] In this implementation, the coating adhesion test standard is determined according to GB / T 9286-1998.

[0094] In this implementation, the hardness test standard for coated pencils is determined according to GB / 6739-1996.

[0095] In this implementation method, the coating heat dissipation capacity testing method includes the following steps:

[0096] The heat dissipation layer is coated on the surface of an aluminum sheet or an aluminum sheet containing oil. After drying and curing, the sample is cut into 5cm×5cm sizes to obtain a heat dissipation aluminum sheet.

[0097] A layer of thermally conductive silicone grease is applied to the constant temperature electric heating plate, and the heat dissipation aluminum fins and aluminum sheets are attached to the surface of the thermally conductive silicone grease. Temperature measuring electrodes are attached to each heat dissipation aluminum fin and aluminum sheet.

[0098] The constant temperature electric heating plate is set to 100℃. After the temperature stabilizes, the temperature of each heat dissipation aluminum sheet and aluminum surface is collected for 60 seconds, with one temperature data point collected every second. Finally, the average value of all temperature data for each sample is taken as the temperature of each heat dissipation aluminum sheet or aluminum sheet surface.

[0099] The foregoing has provided a detailed description of a carbon nanotube heat dissipation layer and its preparation method according to the embodiments of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this application; furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

[0100] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0101] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0102] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0103] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or the technology or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be considered in accordance with the appended claims.

Claims

1. A carbon nanotube heat dissipation layer, characterized in that, The carbon nanotube heat dissipation layer includes: a carbon nanotube heat dissipation bottom layer and a carbon nanotube heat dissipation surface layer; wherein, the thickness of the carbon nanotube heat dissipation bottom layer is 1-3 μm, and the thickness of the carbon nanotube heat dissipation surface layer is 10-15 μm. The components of the carbon nanotube heat dissipation bottom layer, by weight percentage, include: 4%-8% alumina-modified carbon nanotube powder, 1%-5% dispersant, 1%-3% leveling agent, 0.5%-2% adhesion promoter, 15%-25% polyurethane resin, and the remainder is water. The components of the carbon nanotube surface layer, by weight percentage, include: 3%-8% alumina-modified carbon nanotube powder, 1%-5% dispersant, 0.5%-1% leveling agent, 19%-25% polyurethane resin, 0.5%-1% thickener, and the remainder is water. The alumina-modified carbon nanotube powder is composed of carbon nanotubes coated with a layer of alumina powder; the specific preparation process is as follows: First, carbon nanotubes are added to a KMnO4 / H2SO4 solution. The mixture is then sonicated in an ultrasonic microwave chemical synthesizer for 30 min. The treated carbon nanotubes are then filtered and washed with deionized water until the washed deionized water is neutral, thus obtaining carboxylated carbon nanotubes. Next, carboxylated carbon nanotubes are added to deionized water and neutralized with NaOH aqueous solution. Then, aluminum chloride powder is added and stirred evenly under magnetic stirring. NaOH aqueous solution is added while stirring to obtain aluminum hydroxide-coated carbon nanotubes. The aluminum hydroxide-coated carbon nanotubes are filtered and washed with deionized water until the washing deionized water is neutral. The washed aluminum hydroxide-coated carbon nanotubes are freeze-dried to obtain aluminum hydroxide-coated carbon nanotube powder. Finally, the aluminum hydroxide-coated carbon nanotube powder was calcined at 950-1050 °C for 30 min under a flowing nitrogen atmosphere to obtain alumina-modified carbon nanotube powder. The carbon nanotubes are multi-walled carbon nanotubes with a diameter of 9-80 nm and a length of 1-20 μm. The multi-walled carbon nanotubes are combinations of GT210 and TNIM8, or combinations of NC7000 and TNIM8.

2. The carbon nanotube heat dissipation layer according to claim 1, characterized in that, The dispersant is one or more of the following: sodium methylene bis(naphthalene) sulfonate, octylphenol polyoxyethylene ether, sodium polyacrylate, and sodium poly(p-styrene) sulfonate; The leveling agent is one or more of Tego500, Tego450, BYK345, BYK333, SN4763, and Capstone FS-31; The adhesion promoter is one of Lubrizol R2063, AddBond DS 1300, and MOAP1708; The polyurethane resin is one or more of Eterane 8925B, Eterane 89252, ETERSOL 61325B, and Bayhydrol XP2592; The thickener is a water-based thickener; the water-based thickener is one of Rheovis AS 1130 and Rheovis HS 1169.

3. A method for preparing a carbon nanotube heat dissipation layer as described in any one of claims 1-2, characterized in that, The method specifically includes the following steps: S1) Prepare alumina-modified carbon nanotube powder for later use; S2) Weigh out each component according to the designed proportions; S3) Alumina-modified carbon nanotube powder, dispersant, and water are mixed to prepare an aqueous carbon nanotube slurry; S4) The carbon nanotube aqueous slurry obtained by S3) is mixed with the remaining components and then magnetically stirred at a certain speed to obtain carbon nanotube heat dissipation bottom coating and carbon nanotube heat dissipation top coating, respectively. S5) First, apply a dry film of the carbon nanotube heat dissipation bottom layer coating obtained in S4) onto the carrier. After curing, the carbon nanotube heat dissipation bottom layer is obtained. Then, apply the carbon nanotube heat dissipation top layer coating obtained in S4) onto the carbon nanotube heat dissipation bottom layer. After curing, the carbon nanotube heat dissipation top layer is obtained, which is the carbon nanotube heat dissipation layer.

4. The method according to claim 3, characterized in that, The specific steps of S3 are as follows: S3.1) Mix alumina-modified carbon nanotube powder, dispersant, and water, and then mechanically stir for 10-20 min to mix evenly at a speed of 500-800 r / min to obtain a mixed liquid; S3.2) The mixed liquid obtained in S3.1) is homogenized in a high-pressure homogenizer for 3-6 min at a homogenization pressure of 500-700 bar, and then filtered with a 500-mesh filter bag to obtain a carbon nanotube aqueous slurry.

5. The method according to claim 3, characterized in that, The specific steps of S4 are as follows: S4.1) The carbon nanotube aqueous slurry, leveling agent, adhesion promoter and polyurethane resin obtained in S3) are mixed evenly by stirring with a magnetic stirrer for 5-10 min at a speed of 200-500 r / min to obtain the bottom heat dissipation layer. S4.2) The carbon nanotube aqueous slurry, leveling agent, polyurethane resin and thickener obtained in S3) are mixed evenly by stirring with a magnetic stirrer for 5-10 min at a speed of 200-500 r / min to obtain the surface heat dissipation layer.

6. The method according to claim 3, characterized in that, The specific process in S5 is as follows: The curing temperature of the bottom heat dissipation layer is 140-160 ℃, and the baking time is 5-10 min; The curing temperature of the surface heat dissipation layer is 110-120 ℃, and the baking time is 5-10 min.

7. A carbon nanotube heat dissipation layer prepared by the method according to any one of claims 3-6 is used in the field of heat dissipation on the surface of aluminum or aluminum alloy materials.

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