A heat-conducting film for reinforcing longitudinal heat conductivity and its application

Abstract

The application relates to the field of interface heat-conducting materials, and specifically provides a heat-conducting film for reinforcing longitudinal heat conductivity, and a preparation method thereof, which comprises the following steps: S1, mixing an oxidized graphite solution and an additive solution according to a certain mass ratio to prepare mixed slurry; coating the mixed slurry on a substrate to dry to obtain a film piece, and cutting the film piece; S2, stacking a specified number of the cut film pieces according to the thickness of the heat-conducting film; S3, pre-treating the stacked film pieces at 50-250 DEG C for 30-100 h; S4, carbonizing the film pieces; S5, graphitizing the film pieces; and S6, calendering the film pieces into finished products. By optimizing the types and dosages of the additives and optimizing the preparation method, the prepared heat-conducting film has excellent longitudinal heat conductivity, up to 30 W / m.k, far higher than the industry level, and can be used on a heat dissipation device.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive interface materials, C01B32 / 184, and particularly to a thermally conductive film with enhanced longitudinal thermal conductivity and its application. Background Technology

[0002] As a novel two-dimensional material, graphene has been widely used in thermal conductivity and heat dissipation due to its unique single-atom-layer structure. Graphene thermal conductive films are commonly used as heat dissipation devices in electronic products. Although graphene thermal conductive films have extremely high in-plane thermal conductivity, with a theoretical lateral thermal conductivity as high as 5300 W / m·K, their longitudinal thermal conductivity is relatively low, typically only 10-20 W / m·K, due to the limited intermolecular structure in the vertical direction. Improving the longitudinal thermal conductivity of graphene thermal conductive films has always been a hot research topic in the industry.

[0003] Existing technologies employ CVD (Continuous Chemical Vapor Deposition) to prepare vertically oriented graphene on a substrate surface to increase longitudinal thermal conductivity. However, this method requires sophisticated equipment and stringent preparation conditions, hindering large-scale industrial application. Chinese patent CN115092915B discloses a fiber array-reinforced graphene product, device, and preparation method. This patent first arranges a fiber array vertically on a substrate, then coats the substrate with graphene oxide slurry, and finally heat-treats to create a fiber array-reinforced graphene thermal pad, improving the pad's longitudinal thermal conductivity. However, the longitudinal thermal conductivity in this patent depends on the longitudinal arrangement of the fibers, making it difficult to control its stability. Furthermore, cracking easily occurs between the fibers and graphene, leading to a decrease in longitudinal thermal conductivity. Chinese patent CN113148986A discloses a method for preparing a high thermal conductivity self-supporting vertically oriented graphene film. This patent mixes graphene oxide and modified single-walled carbon nanotubes and then performs electrochemical deposition and graphitization treatment to obtain a vertically oriented graphene film, which improves the thermal conductivity of the graphene film; however, its longitudinal thermal conductivity is only 2.214-5.729 W / m·k, which is still at a very low level. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention first provides a thermally conductive film with enhanced longitudinal thermal conductivity, the preparation method of which includes the following steps:

[0005] S1. Mix graphite oxide solution and additive solution in a certain mass ratio to prepare a mixed slurry; coat the mixed slurry onto a substrate and dry it to obtain a film, which is then cut.

[0006] S2. Stack the cut film sheets according to the specified number of thicknesses of the thermal conductive film;

[0007] S3. Pre-treat the stacked membranes at 50-250℃ for 30-100 hours.

[0008] S4. Carbonization treatment of the diaphragm;

[0009] S5. Graphitization treatment of the diaphragm;

[0010] S6. Calender into finished product.

[0011] Further, the mass fraction of the graphite oxide solution in S1 is 1-15%, preferably 2-10%, and more preferably 3-8%. Unless otherwise specified, all solutions mentioned in this application are aqueous solutions.

[0012] Furthermore, the pH value of the graphite oxide solution is 5.5-9.

[0013] Preferably, the pH value of the graphite oxide solution is 6-8.

[0014] Furthermore, the additive is selected from at least one of chopped carbon fibers, carbon nanotubes, graphene, and fullerene.

[0015] Furthermore, the carbon nanotubes include at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, and double-walled carbon nanotubes.

[0016] Furthermore, the mass fraction of the additive in the additive solution is 20-70 wt%.

[0017] Preferably, the mass fraction of the additive in the additive solution is 30-50 wt%.

[0018] Furthermore, the mass ratio of graphite oxide to additives in the mixed slurry of S1 is 100:5-30. This application utilizes a mixture of additives and graphite oxide, interspersed with a certain amount of additives within the graphite layer, which exhibits superior lateral thermal conductivity, to increase the longitudinal distribution of molecular structures in the graphene film. Such additives, such as carbon nanotubes, can utilize their unique structure for ballistic and diffusion transport, thereby improving the longitudinal thermal conductivity of the thermally conductive film. However, the amount of additives needs to be controlled to avoid affecting the continuity of the two-dimensional layered structure of graphene and causing a decrease in lateral thermal conductivity.

[0019] Preferably, the mass ratio of graphite oxide to additives in the mixed slurry of S1 is 100:5-20.

[0020] In a preferred embodiment, the mass ratio of graphite oxide to additives in the mixed slurry of S1 is 100:5-15.

[0021] Furthermore, the thickness of the wet film coated in S1 is 1-10 mm, preferably 2-8 mm, and more preferably 2-6 mm.

[0022] Furthermore, the length × width of the cut membrane in S1 is 10-50cm × 10-50cm. The specifications of the membrane in this application are not strictly defined and can be adjusted according to the actual needs of the thermally conductive film.

[0023] In one embodiment, the length × width of the diaphragm after cutting in S1 is 30 × 30 cm.

[0024] Furthermore, this application does not have strict requirements on the thickness of the thermally conductive film, which can be adjusted as needed.

[0025] In one embodiment, the thickness of the thermally conductive film is 20-1500 μm.

[0026] Furthermore, in S2, a certain gap needs to be reserved between adjacent membranes when the membranes are stacked.

[0027] Furthermore, in S2, the ratio of the total thickness of the diaphragm to the total reserved gap is 100:20-90, preferably 100:30-80.

[0028] Furthermore, the pretreatment in S3 is as follows: sintering at 50-65℃ for 3-8 hours, sintering at 70-90℃ for 6-15 hours, sintering at 100-160℃ for 30-60 hours, and sintering at 210-270℃ for 5-15 hours.

[0029] Furthermore, the pretreatment in S3 is as follows: sintering at 50-65℃ for 3-8 hours, sintering at 70-90℃ for 6-15 hours, sintering at 100-140℃ for 40-60 hours, and sintering at 230-260℃ for 5-15 hours.

[0030] Preferably, the pretreatment in S3 is as follows: sintering at 50-60℃ for 4-6 hours, sintering at 75-85℃ for 8-12 hours, sintering at 110-130℃ for 40-60 hours, and sintering at 240-255℃ for 8-15 hours.

[0031] Furthermore, the carbonization treatment is as follows: sintering at 300-600℃ for 1-5 hours, sintering at 650-1100℃ for 2-6 hours, and sintering at 1300-1700℃ for 1-6 hours.

[0032] Furthermore, the carbonization treatment is as follows: sintering at 400-600℃ for 1-3 hours, sintering at 700-1000℃ for 3-6 hours, and sintering at 1400-1600℃ for 3-5 hours.

[0033] In a preferred embodiment, the carbonization treatment is: sintering at 500°C for 1-3 hours, sintering at 800°C for 3-5 hours, and sintering at 1500°C for 3-5 hours.

[0034] Furthermore, the graphitization treatment temperature is set as follows: from room temperature to 1000℃ within 1-3 hours, from 1000℃ to 2000℃ within 4-7 hours, from 2000℃ to 2800℃ within 5-8 hours, and held at that temperature for 2-10 hours.

[0035] This application optimizes the pretreatment temperature conditions specifically based on the type of membrane raw material. This not only allows the membrane to expand and fill the gaps, but also ensures that more regularly arranged microcrystals can be generated at this temperature. This ensures that the growth size of microcrystals is more suitable during the pretreatment and carbonization processes, thereby improving the thermal conductivity of the thermal conductive film. When the pretreatment temperature is too high, it will cause intergranular defects in the graphite in the thermal conductive film, resulting in a decrease in thermal conductivity. It may even cause the membrane to crack during graphitization or produce an uneven surface. In addition, a suitable graphitization temperature can further optimize the development of microcrystals and improve the thermal conductivity of the thermal conductive film.

[0036] Secondly, this application also provides the application of the thermally conductive film with enhanced longitudinal thermal conductivity in a heat dissipation device.

[0037] Furthermore, the thermally conductive film with enhanced longitudinal thermal conductivity is used in heat dissipation devices for pads, IGBTs, laptop speakers, industrial LED lights, or drone laser locators.

[0038] Beneficial effects

[0039] 1. This application adds additives to graphene oxide and simultaneously performs pretreatment, carbonization, graphitization and other operations, so that the longitudinal distribution of additives and the lateral generation of graphite occur simultaneously and coexist, which improves the compatibility between the two and avoids the phenomenon of film cracking or performance instability caused by material incompatibility in traditional solutions.

[0040] 2. This application optimizes the types and relative amounts of additives, which can ensure that the transverse thermal conductivity of the thermal conductive film does not decrease, while also having excellent longitudinal thermal conductivity, which is as high as 30W / m·k, far superior to the general level in the industry.

[0041] 3. This application optimizes the processing of the thermal conductive film, so that the thermal conductive film has regularly arranged crystals of appropriate size, thereby further improving the thermal conductivity of the thermal conductive film. Attached Figure Description

[0042] Appendix Figure 1 Temperature test results of the aluminum heat sink surface after 2 hours of LED illumination;

[0043] Appendix Figure 2 Temperature test diagram of the surface of the thermal conductive film in Example 1 after 2 hours of LED lamp irradiation;

[0044] Appendix Figure 3Temperature test diagram of the surface of the thermal conductive film in Comparative Example 1 after 2 hours of LED irradiation. Detailed Implementation

[0045] In the following examples and comparative examples, unless otherwise specified, all solutions are aqueous solutions.

[0046] Example 1

[0047] This embodiment provides a thermally conductive film with enhanced longitudinal thermal conductivity. The preparation method of the thermally conductive film includes the following steps:

[0048] S1. Mix 5 wt% graphite oxide solution (pH 7.0) and 45 wt% additive solution at a mass ratio of graphite oxide to additive of 100:10, and homogenize using a high-pressure homogenizer to prepare a mixed slurry; coat the mixed slurry onto a substrate with a wet film thickness of 5 mm, and dry to obtain a film sheet, which is then cut into film sheets with a length × width of 30 cm × 30 cm.

[0049] The additives mentioned above are a mixture of multi-walled carbon nanotubes and single-walled carbon nanotubes in a mass ratio of 1:2, and are all purchased from Zhongke Times Nano.

[0050] S2. Stack the 30-layer cut film according to the thickness of the thermal conductive film. A certain gap needs to be reserved between adjacent films during stacking. The ratio of the total thickness of the film to the total gap is 100:50.

[0051] S3. Pre-treat the stacked films according to the following temperatures: 50℃ for 5 hours, 80℃ for 10 hours, 120℃ for 50 hours, and 250℃ for 10 hours.

[0052] S4. Carbonize the membrane of S3 at the following temperatures: 500℃ for 2 hours, 800℃ for 4 hours, and 1500℃ for 4 hours.

[0053] S5. Graphitize the film of S4 at the following temperatures: 2h from room temperature to 1000℃, 5h from 1000℃ to 2000℃, 6h from 2000℃ to 2800℃, and hold for 5h.

[0054] S6. Calender into a finished thermal conductive film with a thickness of 200μm.

[0055] Example 2

[0056] This embodiment provides a thermally conductive film with enhanced longitudinal thermal conductivity. The preparation method of the thermally conductive film includes the following steps:

[0057] S1. Mix 8 wt% graphite oxide solution (pH 8) and 50 wt% additive solution at a mass ratio of graphite oxide to additive of 100:5, and homogenize using a high-pressure homogenizer to prepare a mixed slurry; coat the mixed slurry onto a substrate with a wet film thickness of 6 mm, and dry to obtain a film sheet, which is then cut into film sheets with a length × width of 30 cm × 30 cm.

[0058] The additives mentioned above are a mixture of multi-walled carbon nanotubes and single-walled carbon nanotubes in a mass ratio of 1:2, and are all purchased from Zhongke Times Nano.

[0059] S2. Stack the 30-layer cut film according to the thickness of the thermal conductive film. A certain gap needs to be reserved between adjacent films during stacking. The ratio of the total thickness of the film to the total gap is 100:80.

[0060] S3. Pre-treat the stacked films at the following temperatures: sintering at 60℃ for 4 hours, sintering at 85℃ for 8 hours, sintering at 110℃ for 40 hours, and sintering at 240℃ for 8 hours.

[0061] S4. Carbonize the membrane of S3 at the following temperatures: 600℃ for 1 hour, 1000℃ for 3 hours, and 1600℃ for 3 hours.

[0062] S5. Graphitize the film of S4 according to the following temperatures: increase the temperature from room temperature to 1000℃ within 3 hours, increase the temperature from 1000℃ to 2000℃ within 7 hours, increase the temperature from 2000℃ to 2800℃ within 8 hours, and hold at that temperature for 2 hours.

[0063] S6. Calender into a finished thermal conductive film with a thickness of 450μm.

[0064] Example 3

[0065] This embodiment provides a thermally conductive film with enhanced longitudinal thermal conductivity. The preparation method of the thermally conductive film includes the following steps:

[0066] S1. Mix 3 wt% graphite oxide solution (pH 6) and 30 wt% additive solution at a mass ratio of graphite oxide to additive of 100:15, and homogenize using a high-pressure homogenizer to prepare a mixed slurry; coat the mixed slurry onto a substrate with a wet film thickness of 2 mm, and dry to obtain a film sheet, which is then cut into film sheets with a length × width of 30 cm × 30 cm.

[0067] The additive, a mixture of multi-walled carbon nanotubes and single-walled carbon nanotubes, is purchased from Zhongke Times Nano in a mass ratio of 1:1.

[0068] S2. Stack the 30-layer cut film according to the thickness of the thermal conductive film. A certain gap needs to be reserved between adjacent films during stacking. The ratio of the total thickness of the film to the total gap is 100:30.

[0069] S3. Pre-treat the stacked films at the following temperatures: 50℃ for 6 hours, 75℃ for 12 hours, 110℃ for 60 hours, and 240℃ for 15 hours.

[0070] S4. Carbonize the membrane of S3 at the following temperatures: 400℃ for 1 hour, 700℃ for 6 hours, and 1400℃ for 5 hours.

[0071] S5. Graphitize the film of S4 according to the following temperatures: increase the temperature from room temperature to 1000℃ within 1 hour, increase the temperature from 1000℃ to 2000℃ within 4 hours, increase the temperature from 2000℃ to 2800℃ within 5 hours, and hold for 8 hours.

[0072] S6. Calender into a finished thermal conductive film with a thickness of 50μm.

[0073] Example 4

[0074] It is basically the same as Example 1, except that the additive is fullerene.

[0075] Example 5

[0076] It is basically the same as Example 1, except that: the additive is fullerene; the mass ratio of graphite oxide to additive in the mixed slurry is 100:3; and the volume of the mixed slurry is the same as in Example 1.

[0077] Comparative Example 1

[0078] This comparative example provides a commercially available ordinary graphene thermal conductive film with a thickness of 200 μm.

[0079] Comparative Example 2

[0080] It is basically the same as Example 1, except that: the additive is short-cut carbon fiber, which was purchased from Shaanxi Tianze New Material Technology Co., Ltd., and the mass ratio of graphite oxide to additive is 10:5.

[0081] Comparative Example 3

[0082] It is basically the same as Example 1, except that: the additive is multi-walled carbon nanotubes, which were purchased from Zhongke Times Nano, and the mass ratio of graphite oxide to additive is 100:5.

[0083] Performance testing methods:

[0084] Heat dissipation experiment: An LED lamp (65W) with an aluminum lampshade heat sink was placed in a 25℃ constant temperature chamber and subjected to stable irradiation for 2 hours. The highest surface temperature of the aluminum lampshade was measured to be 86.3℃. Afterwards, the aluminum lampshade heat sink was removed, and the thermally conductive film from the above embodiment was used to replace the aluminum heat sink in the LED lamp. The highest surface temperature of the thermally conductive film was measured under the same test conditions. The results are shown in Table 1.

[0085] Performance test results:

[0086] Table 1

[0087]

Claims

1. A thermally conductive film with enhanced longitudinal thermal conductivity, characterized in that, The method for preparing the thermally conductive film includes the following steps: S1. Mix graphite oxide solution and additive solution in a certain mass ratio to prepare a mixed slurry; coat the mixed slurry onto a substrate and dry it to obtain a film, which is then cut. S2. Stack the cut film sheets according to the specified number of thicknesses of the thermal conductive film; S3. Pre-treat the stacked membranes at 50-250℃ for 30-100 hours. S4. Carbonization treatment of the diaphragm; S5. Graphitization treatment of the diaphragm; S6. Calendering into finished products; The additive is a mixture of multi-walled carbon nanotubes and single-walled carbon nanotubes in a mass ratio of 1:

2. The pretreatment in S3 is as follows: sintering at 50-65℃ for 3-8 hours, sintering at 70-90℃ for 6-15 hours, sintering at 100-160℃ for 30-60 hours, and sintering at 210-270℃ for 5-15 hours. The mass ratio of graphite oxide to additives in the mixed slurry of S1 is 100:5-30; In S2, a certain gap needs to be reserved between adjacent membranes when stacking them. The carbonization treatment is as follows: sintering at 300-600℃ for 1-5 hours, sintering at 650-1100℃ for 2-6 hours, and sintering at 1300-1700℃ for 1-6 hours; The processing temperature for the graphitization treatment is set as follows: from room temperature to 1000℃ within 1-3 hours, from 1000℃ to 2000℃ within 4-7 hours, from 2000℃ to 2800℃ within 5-8 hours, and then held at that temperature for 2-10 hours.

2. The thermally conductive film according to claim 1, characterized in that, The ratio of the total thickness of the diaphragm to the total reserved gap in S2 is 100:20-90.

3. The application of the thermally conductive film according to any one of claims 1-2 in a heat dissipation device, characterized in that, The thermally conductive film with enhanced longitudinal thermal conductivity is used in heat dissipation devices for pads, IGBTs, laptop speakers, industrial and mining LED lights, or drone laser locators.

Images