Heat-conducting silica gel sheet and preparation method thereof

Abstract

The invention belongs to the technical field of heat-conducting silica gel, and particularly relates to a heat-conducting silica gel sheet and a preparation method thereof. The invention relates to a heat-conducting silica gel sheet which is prepared by the following steps: carrying out surface activity modification on carbon fibers through polymer deposition, then growing zinc oxide nanoflowers in situ, finally adding aluminum oxide and modified carbon fibers into a silica gel matrix consisting of vinyl silicone oil, hydrogen-containing silicone oil, a catalyst and an inhibitor, and carrying out synergistic modification on silica gel through an extrusion orientation method. And forming an intercommunicated heat-conducting network to prepare the heat-conducting silica gel sheet. The prepared heat-conducting silica gel sheet has high heat conductivity and excellent mechanical property, and the insulating property of the heat-conducting silica gel sheet is also improved.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal conductive silicone rubber, and in particular relates to a thermal conductive silicone rubber sheet and a preparation method thereof. Background Art

[0002] The rapid development of electronic information technology is driving the miniaturization, integration, and intelligence of electronic components, leading to difficulties dissipating heat during operation. Thermal interface materials (TIMs) serve as an effective heat transfer medium, filling the gap between heat-dissipating and heat-generating components to dissipate heat promptly. Silicone materials, with their excellent chemical stability, weather resistance, and high-temperature resistance, hold great promise for their application in the field of TIMs.

[0003] Carbon fiber plays an important role in polymer-based composite materials such as silicone due to its superior mechanical and thermal conductivity. However, during its preparation, carbon fiber needs to undergo high-temperature carbonization and graphitization treatment. Its surface is very smooth and chemically inert, with only a very small number of active groups. This directly affects the interfacial bonding strength between the carbon fiber and the polymer matrix, thereby affecting its performance. In addition, carbon fiber has high thermal conductivity as well as high electrical conductivity. The volume resistivity of carbon fiber is only 10 -2 Ω·cm, which greatly limits its scope of application. Therefore, it is also necessary to ensure its insulation properties through modification.

[0004] At present, there are many methods for carbon fiber surface modification, such as oxidation treatment, plasma treatment, chemical vapor deposition, chemical grafting modification, etc., but many of them are completed under highly toxic, high energy consumption, and harsh treatment conditions. For example, the oxidation treatment method will destroy the internal structure of the carbon fiber and may cause the mechanical properties of the carbon fiber body to deteriorate. The plasma modification method has expensive equipment investment and high cost. Summary of the Invention

[0005] In view of the above problems, the present invention proposes a thermally conductive silicone sheet and a preparation method thereof, which effectively solves the problem of carbon fiber in the thermally conductive silicone adhesive material.

[0006] In order to achieve the above objectives, in a first aspect, the present invention provides a thermally conductive silicone sheet.

[0007] A thermally conductive silicone sheet comprises the following components in parts by weight: 10-12 parts of vinyl silicone oil, 1.4-1.6 parts of hydrogenated silicone oil, 20-30 parts of aluminum oxide, 15-18 parts of modified carbon fibers, 0.1-0.2 parts of a catalyst, and 0.015-0.018 parts of an inhibitor.

[0008] Through the above technical solution, alumina and modified carbon fibers are added to a silicone matrix composed of vinyl silicone oil, hydrogenated silicone oil, catalysts and inhibitors, and the silicone is synergistically modified by extrusion orientation to form an interconnected thermal conductive network, thereby obtaining a thermally conductive silicone sheet with high thermal conductivity and excellent mechanical properties. In addition, the insulation performance of the thermally conductive silicone sheet is also improved.

[0009] Furthermore, the modified carbon fiber is prepared by the following steps: S1, carbon fiber pretreatment to obtain P-CF; S2, P-CF is treated with dihydroxyphenylpropionic acid and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane successively to obtain CF@DA / NSi; S3, CF@DA / NSi is treated with zinc nitrate and sodium hydroxide to obtain modified carbon fiber.

[0010] Through the above technical scheme, the carbon fiber is pretreated to remove impurities, and then dihydroxyphenylpropionic acid and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane are reacted and deposited on the carbon fiber surface to generate a copolymer, thereby increasing the activity of the carbon fiber surface and improving its interfacial bonding strength with the silica gel matrix. On this basis, evenly distributed nanoflower-shaped zinc oxide is deposited on the carbon fiber surface by in situ growth, which not only increases the volume resistivity of the carbon fiber, but also avoids the presence of small pores between the carbon fiber and the silica gel matrix, and enhances the mechanical properties of the thermally conductive silicone sheet through mechanical engagement with the silica gel matrix.

[0011] Furthermore, the S1 is specifically as follows: immersing 10-12 g of carbon fiber in 200-300 mL of anhydrous ethanol, stirring uniformly at room temperature for 10-20 min, washing with distilled water, and drying at 60-65° C. to obtain P-CF.

[0012] Through the above technical solution, the carbon fiber is pretreated to remove impurities, which is more conducive to subsequent coating modification.

[0013] Furthermore, S2 is specifically as follows: 10-12 g of P-CF is added to 100-150 mL of a Tris-HCl buffer solution containing 0.1-0.12 mol / L dihydroxyphenylpropionic acid, stirred until the reaction is complete, washed with distilled water, and dried at 60-65°C to obtain CF@DA; then 10-12 g of CF@DA is added to 100-150 mL of a buffer solution containing 0.1-0.12 mol / L N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, stirred until the reaction is complete, washed with distilled water, and dried at 60-65°C to obtain CF@DA / NSi.

[0014] Furthermore, the pH of the Tris-HCl buffer solution is 8.5-9.5.

[0015] Through the above technical scheme, dihydroxyphenylpropionic acid and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane are reacted and deposited on the P-CF surface to generate a copolymer, thereby increasing the activity of the carbon fiber surface and improving its interfacial bonding strength with the silica gel matrix.

[0016] Furthermore, the S3 is specifically as follows: dissolving 12-18 mmol zinc nitrate in 100-120 mL deionized water, adding 4-6 g of CF@DA / NSi, ultrasonically dispersing the mixture evenly, then adding 20-30 mmol sodium hydroxide, reacting at 85-90 ° C for 20-24 hours, then washing with deionized water until neutral, and drying at 60-65 ° C to obtain modified carbon fiber.

[0017] Furthermore, the alumina is spherical alumina with a particle size of 5-10 microns.

[0018] Through the above technical solution, the selection of spherical alumina of this particle size is conducive to filling between the modified carbon fibers and the modified carbon fibers, and the alumina is tightly connected to the alumina, thereby constructing a good thermal conductivity path.

[0019] Furthermore, the catalyst is a platinum catalyst.

[0020] Through the above technical solution, the use of platinum catalyst can reduce the occurrence of side reactions, thereby improving the quality and performance of the silica gel matrix.

[0021] Furthermore, the inhibitor is ethynyl cyclohexanol.

[0022] Through the above technical solution, ethynyl cyclohexanol forms a coordination bond with the platinum catalyst, effectively inhibiting the reaction between the vinyl and silicon hydrogen components, prolonging the cross-linking time, keeping the system in a stable state, and precisely controlling the reaction process.

[0023] In a second aspect, the present invention proposes a method for preparing the above-mentioned thermally conductive silicone sheet, comprising the following steps: (1) adding all the aluminum oxide, vinyl silicone oil, half of the hydrogen-containing silicone oil and half of the catalyst, stirring and degassing, and then adding the remaining half of the hydrogen-containing silicone oil, all the modified carbon fibers and the inhibitor in batches, stirring and degassing to obtain a mixed silicone material; (2) applying external force to extrude the mixed silicone material into a mold to obtain a thermally conductive silicone sheet precursor; (3) vacuum drying and curing the thermally conductive silicone sheet precursor to obtain a thermally conductive silicone sheet.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention adds alumina and modified carbon fibers to a silicone matrix composed of vinyl silicone oil, hydrogenated silicone oil, a catalyst, and an inhibitor, and synergistically modifies the silicone through an extrusion orientation method to form an interconnected heat-conducting network, thereby obtaining a thermally conductive silicone sheet with high thermal conductivity and excellent mechanical properties. In addition, the insulation performance of the thermally conductive silicone sheet is also improved.

[0026] The present invention pre-treats the carbon fiber to remove impurities, and then uses dihydroxyphenylpropionic acid and N-(β-aminoethyl)

[0027] -γ-aminopropyltriethoxysilane reacts and deposits on the surface of carbon fiber to generate a copolymer, thereby increasing the activity of the carbon fiber surface and improving its interfacial bonding strength with the silicone matrix. On this basis, evenly distributed nanoflower-shaped zinc oxide is deposited on the carbon fiber surface by in situ growth, which not only increases the volume resistivity of the carbon fiber, but also avoids the existence of small pores between the carbon fiber and the silicone matrix, and enhances the mechanical properties of the thermal conductive silicone sheet through mechanical meshing with the silicone matrix. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Infrared spectra of CF, P-CF, CF@DA, CF@DA / NSi and modified carbon fiber, where a is CF, b is P-CF, c is CF@DA, d is CF@DA / NSi, and e is modified carbon fiber;

[0029] Figure 2 SEM images of CF, P-CF, CF@DA, and CF@DA / NSi, where (a) is CF, (b) is P-CF, (c) is CF@DA, and (d) is CF@DA / NSi.

[0030] Figure 3 is the XRD pattern of modified carbon fiber;

[0031] Figure 4 SEM and EDS images of modified carbon fibers, where (a) and (b) are from Example 1, (c) is from Comparative Example 3, and (d) is from CF@DA / NSi.

[0032] Figure 5 This is the SEM image of the modified carbon fiber prepared in Comparative Example 1.

[0033] Figure 6 These are SEM images of the thermally conductive silicone sheets of Example 1, Comparative Example 5, and Comparative Example 6 parallel to the orientation direction, (a) is Comparative Example 5, (b) is Comparative Example 6, and (c) is Example 1. DETAILED DESCRIPTION

[0034] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] Example 1

[0036] A thermally conductive silicone sheet comprises the following components in parts by weight: 10 parts of vinyl silicone oil, 1.4 parts of hydrogenated silicone oil, 20 parts of aluminum oxide, 15 parts of modified carbon fibers, 0.1 parts of a catalyst, and 0.015 parts of an inhibitor.

[0037] The aluminum oxide is spherical aluminum oxide with a particle size of 5 microns.

[0038] The catalyst is a platinum catalyst.

[0039] The inhibitor is ethynylcyclohexanol.

[0040] The modified carbon fiber is prepared by the following steps:

[0041] S1, carbon fiber pretreatment: 10 g of carbon fiber (denoted as CF) was soaked in 200 mL of anhydrous ethanol, stirred at room temperature for 10 min, washed with distilled water, and dried at 60 °C to obtain P-CF;

[0042] S2, add 10g of P-CF to 100mL of Tris-HCl buffer solution containing 0.1mol / L dihydroxyphenylpropionic acid, stir until the reaction is complete, wash with distilled water, and dry at 60°C to obtain CF@DA; then add 10g of CF@DA to 100mL of buffer solution containing 0.1mol / L N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, stir until the reaction is complete, wash with distilled water, and dry at 60°C to obtain CF@DA / NSi; the pH of the Tris-HCl buffer solution is 8.5.

[0043] S3, 12 mmol zinc nitrate was dissolved in 100 mL deionized water, 4 g CF@DA / NSi was added, and ultrasonic dispersion was performed uniformly. Then 20 mmol sodium hydroxide was added and reacted at 85 °C for 20 h. Then, the modified carbon fiber was washed with deionized water until neutral and dried at 60 °C.

[0044] Figure 1 The infrared spectra of CF, P-CF, CF@DA, CF@DA / NSi and modified carbon fiber are shown in Figure 2. Figure 1 It can be seen that CF at 3400cm -1The stretching vibration peaks of -OH and NH bonds are at 2941-2852 cm -1 The stretching vibration peak of the C-H bond appears in the range of 1682 cm -1 Nearby is the stretching vibration peak of C=O, 1401cm -1 is the stretching vibration peak of the OH bond in the carboxyl group, 1252 cm -1 The stretching vibration peak corresponding to the CN bond. Compared with CF, the intensity of the above characteristic peaks of P-CF is enhanced. CF@DA at 3400cm -1 The hydroxyl peak of CF@DA / NSi is significantly enhanced, which is related to the chemical structure of hydroxyl and carboxyl groups in dihydroxyphenylpropionic acid. -1 and 781cm -1 The stretching vibration peak and bending vibration peak of Si-O bond appeared respectively, indicating that N-

[0045] (β-aminoethyl)-γ-aminopropyltriethoxysilane reacted with dihydroxyphenylpropionic acid on the surface of CF@DA, and the copolymer was deposited on the surface of carbon fiber. The infrared spectrum of modified carbon fiber is at 3400cm -1 The broad peak becomes larger, which corresponds to the stretching vibration peak of the surface hydroxyl groups in zinc oxide. The results of infrared spectroscopy show that zinc oxide is successfully coated on the surface of carbon fiber.

[0046] Figure 2 The SEM images of CF, P-CF, CF@DA, and CF@DA / NSi are shown in Figure 2. Figure 2 As can be seen in the figure, the CF surface is covered with fragmented impurities formed during industrial production, and several grooves are distributed along the longitudinal direction of the carbon fiber. However, the fragmented impurities on the P-CF surface are significantly removed, and the longitudinal grooves remain unchanged. The CF@DA surface remains unchanged, while some fine particles can be seen on the CF@DA / NSi surface. These fine particles are believed to be a copolymer of dihydroxyphenylpropionic acid and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane.

[0047] Figure 3 is the XRD pattern of modified carbon fiber. Figure 3 It can be seen that the XRD of P-CF shows a 2θ value of 26.5°.

[0048] The diffraction peaks at 2θ and 55° correspond to the (002) and (004) crystal planes of the graphite structure on the carbon fiber surface, respectively. In addition, the diffraction peak of the (002) crystal plane is very strong, which indicates that the graphite crystal structure on the P-CF surface is relatively complete. In addition to the carbon fiber diffraction peaks, the modified carbon fiber also has diffraction peaks of 2θ of 31.8°, 34.4°, 36.3°, 47.5°, 56.6°, 62.9°, 66.5°, 67.9, and 72.6°, which correspond to the (100), (002), (101), (102), (110), (103), (200), (112), and (201) crystal planes in zinc oxide, respectively. This shows that zinc oxide is in situ grown on the carbon fiber and this method has no effect on the structure of the carbon fiber itself.

[0049] Figure 4 The SEM and EDS images of modified carbon fibers are shown in Figure 2. Figure 4 It can be seen that the zinc oxide on the surface of the modified carbon fiber is a nanoflower-like structure, and the zinc oxide nanoflowers grow evenly on the surface of the carbon fiber.

[0050] Example 2

[0051] A thermally conductive silicone sheet comprises the following components in parts by weight: 11 parts of vinyl silicone oil, 1.5 parts of hydrogenated silicone oil, 25 parts of aluminum oxide, 17 parts of modified carbon fibers, 0.15 parts of a catalyst, and 0.017 parts of an inhibitor.

[0052] The aluminum oxide is spherical aluminum oxide with a particle size of 5 microns.

[0053] The catalyst is a platinum catalyst.

[0054] The inhibitor is ethynylcyclohexanol.

[0055] The modified carbon fiber is prepared by the following steps:

[0056] S1, carbon fiber pretreatment: 11 g of carbon fiber was immersed in 250 mL of anhydrous ethanol, stirred at room temperature for 15 min, washed with distilled water, and dried at 63 °C to obtain P-CF;

[0057] S2, add 11 g of P-CF to 125 mL of Tris-HCl buffer solution containing 0.11 mol / L dihydroxyphenylpropionic acid, stir until the reaction is complete, wash with distilled water, and dry at 63°C to obtain CF@DA; then add 11 g of CF@DA to 125 mL of a buffer solution containing 0.11 mol / L N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, stir until the reaction is complete, wash with distilled water, and dry at 63°C to obtain CF@DA / NSi; the pH of the Tris-HCl buffer solution is 9.0.

[0058] S3, 15mmol zinc nitrate was dissolved in 110mL deionized water, 5g CF@DA / NSi was added, and ultrasonic dispersion was uniform. Then 25mmol sodium hydroxide was added and reacted at 88℃ for 22h. Then, it was washed with deionized water until neutral and dried at 63℃ to obtain modified carbon fiber.

[0059] Example 3

[0060] A thermally conductive silicone sheet comprises the following components in parts by weight: 12 parts of vinyl silicone oil, 1.6 parts of hydrogenated silicone oil, 30 parts of aluminum oxide, 18 parts of modified carbon fibers, 0.2 parts of a catalyst, and 0.018 parts of an inhibitor.

[0061] The aluminum oxide is spherical aluminum oxide with a particle size of 10 microns.

[0062] The catalyst is a platinum catalyst.

[0063] The inhibitor is ethynylcyclohexanol.

[0064] The modified carbon fiber is prepared by the following steps:

[0065] S1, carbon fiber pretreatment: 12 g of carbon fiber was immersed in 300 mL of anhydrous ethanol, stirred at room temperature for 20 min, washed with distilled water, and dried at 65 °C to obtain P-CF;

[0066] S2, add 12g of P-CF to 150mL of Tris-HCl buffer solution containing 0.12mol / L dihydroxyphenylpropionic acid, stir until the reaction is complete, wash with distilled water, and dry at 65°C to obtain CF@DA; then add 12g of CF@DA to 150mL of buffer solution containing 0.12mol / L N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, stir until the reaction is complete, wash with distilled water, and dry at 65°C to obtain CF@DA / NSi; the pH of the Tris-HCl buffer solution is 9.5.

[0067] S3, 18 mmol zinc nitrate was dissolved in 120 mL deionized water, 6 g CF@DA / NSi was added, and ultrasonic dispersion was performed uniformly. Then 30 mmol sodium hydroxide was added and reacted at 90 °C for 24 h. Then, the modified carbon fiber was washed with deionized water until neutral and dried at 65 °C.

[0068] The thermally conductive silicone sheet is prepared by the following method: (1) all the aluminum oxide, vinyl silicone oil, half of the hydrogenated silicone oil and half of the catalyst are added, stirred and degassed, and then the remaining half of the hydrogenated silicone oil, all the modified carbon fibers and the inhibitor are added in batches, stirred and degassed to obtain a mixed silicone material; (2) external force is applied to extrude the mixed silicone material into a mold to obtain a thermally conductive silicone sheet precursor; (3) the thermally conductive silicone sheet precursor is vacuum dried and cured at 65°C to obtain a thermally conductive silicone sheet.

[0069] Comparative Example 1

[0070] The same as Example 1, except that the modified carbon fiber was prepared by the following steps: S1, carbon fiber pretreatment: 10 g of carbon fiber was soaked in 200 mL of anhydrous ethanol, stirred at a constant speed for 10 min at room temperature, washed with distilled water, and dried at 60° C. to obtain P-CF;

[0071] S2, dissolve 12mmol zinc nitrate in 100mL deionized water, add 4g P-CF, disperse evenly by ultrasonication, then add 20mmol sodium hydroxide, react at 85℃ for 20h, then wash with deionized water until neutral, and dry at 60℃ to obtain modified carbon fiber.

[0072] Figure 5 The SEM image of the modified carbon fiber prepared in Comparative Example 1. Figure 5 It can be seen that the growth of zinc oxide on the carbon fiber surface is small, and the growth of zinc oxide nanoflowers on the carbon fiber surface is very uneven. Figure 4 It can be seen that the pre-construction of a copolymer of dihydroxyphenylpropionic acid and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane on the carbon fiber surface plays a very critical role in the in situ growth of zinc oxide.

[0073] Comparative Example 2

[0074] The same as Example 1, except that no alumina was added.

[0075] Comparative Example 3

[0076] The same as Example 1, except that the amount of sodium hydroxide added is 15 mmol.

[0077] Figure 4 (c) is the SEM image of the modified carbon fiber of Comparative Example 3. Figure 4 (c) It can be seen that the amount of sodium hydroxide has a greater effect on the structure of zinc oxide. When the amount is small, zinc oxide is in the form of nanoparticles.

[0078] Comparative Example 4

[0079] The same as Example 1, except that 3-aminopropyltriethoxysilane was used instead of N-(β-aminoethyl)-γ-aminopropyltriethoxysilane.

[0080] Comparative Example 5

[0081] The same as Example 1, except that the modified carbon fiber is replaced with carbon fiber for preparing the thermal conductive silicone sheet.

[0082] Comparative Example 6

[0083] The same as Example 1, except that the modified carbon fiber is replaced with CF@DA / NSi for preparing the thermal conductive silicone sheet.

[0084] Performance Testing

[0085] The thermal conductivity, electrical insulation performance and tensile properties parallel to the orientation direction of the thermally conductive silicone sheets prepared in Examples 1 to 5 and Comparative Examples 1 to 6 were tested. The results are shown in Table 1:

[0086] Table 1. Thermal conductive silicone sheet performance test results

[0087]

[0088] As can be seen from Table 1, the thermally conductive silicone sheets prepared in Examples 1 to 3 of the present application have high thermal conductivity, tensile strength, elongation at break, and volume resistivity.

[0089] Figure 6 The SEM images of the thermally conductive silicone sheets of Example 1, Comparative Example 5 and Comparative Example 6 are parallel to the orientation direction. Figure 6 It can be seen that there are many obvious small pores between the carbon fiber and the silicone matrix in the thermal conductive silicone sheet of comparative example 5, indicating that the wetting effect between the carbon fiber and the silicone matrix is very poor. The presence of pores will greatly weaken the thermal conductivity of the thermal conductive silicone sheet. In comparative example 6, the thermal conductive gasket prepared by coating the carbon fiber with a copolymer of dihydroxyphenylpropionic acid and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane has no pores, and the CF@DA / NSi is tightly bonded to the silicone matrix. This shows that this modification method improves the chemical environment of the carbon fiber surface and improves its wettability with the matrix. On this basis, in Example 1, the thermal conductive silicone sheet in which the modified carbon fiber is prepared by in-situ growth of zinc oxide on the carbon fiber surface is also not observed to have pores, and the zinc oxide nanoflowers can be well embedded in the silicone matrix. Zinc oxide nanoflowers coated carbon fiber can not only increase the volume resistivity of the carbon fiber, but also avoid the problem of reduced thermal conductivity due to the presence of a large number of pores between the carbon fiber and the matrix, and can also physically improve the mechanical properties of the thermal conductive silicone sheet by increasing the mechanical engagement between the carbon fiber and the silicone matrix.

[0090] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A thermally conductive silicone sheet, characterized by: The invention comprises the following components in parts by weight: 10-12 parts of vinyl silicone oil, 1.4-1.6 parts of hydrogenated silicone oil, 20-30 parts of aluminum oxide, 15-18 parts of modified carbon fiber, 0.1-0.2 parts of catalyst and 0.015-0.018 parts of inhibitor.

2. The thermally conductive silicone sheet according to claim 1, characterized in that: The modified carbon fiber is prepared by the following steps: S1, pretreatment of carbon fiber to obtain P-CF; S2, treating P-CF with dihydroxyphenylpropionic acid and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane in sequence to obtain CF@DA / NSi; S3, treating CF@DA / NSi with zinc nitrate and sodium hydroxide to obtain modified carbon fiber.

3. The thermally conductive silicone sheet according to claim 2, characterized in that: The S1 is specifically as follows: immersing 10-12 g of carbon fiber in 200-300 mL of anhydrous ethanol, stirring uniformly at room temperature for 10-20 minutes, washing with distilled water, and drying at 60-65° C. to obtain P-CF.

4. The thermally conductive silicone sheet according to claim 2, wherein: The S2 is specifically as follows: 10-12 g of P-CF is added to 100-150 mL of a Tris-HCl buffer solution containing 0.1-0.12 mol / L dihydroxyphenylpropionic acid, stirred until the reaction is complete, washed with distilled water, and dried at 60-65°C to obtain CF@DA; then 10-12 g of CF@DA is added to 100-150 mL of a buffer solution containing 0.1-0.12 mol / L N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, stirred until the reaction is complete, washed with distilled water, and dried at 60-65°C to obtain CF@DA / NSi.

5. The thermally conductive silicone sheet according to claim 3, characterized in that: The pH of Tris-HCl buffer solution is 8.5-9.

5.

6. The thermally conductive silicone sheet according to claim 2, characterized in that: The S3 is specifically as follows: 12-18 mmol of zinc nitrate is dissolved in 100-120 mL of deionized water, 4-6 g of CF@DA / NSi is added, and ultrasonic dispersion is performed uniformly. Then, 20-30 mmol of sodium hydroxide is added, and the mixture is reacted at 85-90° C. for 20-24 hours. The mixture is then washed with deionized water until neutral, and dried at 60-65° C. to obtain the modified carbon fiber.

7. The thermally conductive silicone sheet according to claim 1, characterized in that: The aluminum oxide is spherical aluminum oxide with a particle size of 5-10 microns.

8. The thermally conductive silicone sheet according to claim 1, characterized in that: The catalyst is a platinum catalyst.

9. The thermally conductive silicone sheet according to claim 1, characterized in that: The inhibitor is ethynylcyclohexanol.

10. A method for preparing a thermally conductive silicone sheet according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) adding all the aluminum oxide, vinyl silicone oil, half of the hydrogenated silicone oil and half of the catalyst, stirring and degassing, and then adding the remaining half of the hydrogenated silicone oil, all the modified carbon fibers and the inhibitor in batches, stirring and degassing to obtain a mixed silicone material; (2) applying external force to extrude the mixed silicone material into a mold to obtain a thermally conductive silicone sheet precursor; (3) vacuum drying and solidifying the thermal conductive silicone sheet precursor to obtain a thermal conductive silicone sheet.

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