Ultrathin heat dissipation composite coating, preparation thereof and ultrathin heat dissipation metal plate comprising ultrathin heat dissipation composite coating

Abstract

The invention provides an ultrathin heat dissipation composite coating, preparation of the ultrathin heat dissipation composite coating and an ultrathin heat dissipation metal plate comprising the ultrathin heat dissipation composite coating. The preparation method comprises the following steps: preparing a silicon dioxide precursor sol and a titanium dioxide precursor sol by a sol-gel method, adding the silicon dioxide precursor sol and the titanium dioxide precursor sol into a solvent to obtain composite slurry, coating the surface of a substrate with the composite slurry, and drying to obtain the ultrathin heat dissipation composite coating. The thickness of the ultra-thin heat dissipation composite coating is 50-100 nm, and the ultra-thin heat dissipation composite coating has super-hydrophilicity and super-lipophilicity, so that the contact area between a cooling working medium and the ultra-thin heat dissipation metal plate is increased, and the comprehensive heat dissipation capacity is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and specifically includes an ultra-thin heat dissipation composite coating, its preparation, and an ultra-thin heat dissipation metal plate containing the same. Background Art

[0002] With the emergence and rapid development of the fifth-generation mobile communication technology, high performance, high integration, lightweight, and miniaturization have become the development trends of electronic products such as smartphones and tablets. To meet the requirements of product performance and small size, people have increasingly strict requirements for the area of chips and the transistor density, which leads to the generation of excessive working temperatures when the chips are working, affecting the use performance of electronic products and thus restricting their further development. Ultra-thin vapor chambers solve the heat dissipation problem by the phase change of the internal cooling working fluid and become key devices for electronic products. Compared with copper materials commonly used in current vapor chambers, aluminum materials have the characteristics of light weight, high thermal conductivity, wide material sources, low cost, and easier processing, so they have become a research hotspot in recent years.

[0003] Currently, the research on aluminum materials for vapor chambers, especially ultra-thin vapor chambers, mainly focuses on the design of the wick. Since the metal surface is relatively smooth, its wettability to the cooling working fluid is poor, resulting in low capillary performance of the wick. The most effective method is to perform surface modification treatment on it to improve its surface hydrophilicity and thus increase the capillary force. The methods for hydrophilic modification of metal aluminum materials mainly include electrochemical deposition, anodic oxidation, etc., but the main disadvantages are high process difficulty and manufacturing cost, and the preparation process is relatively cumbersome. Therefore, there is an urgent need to develop a new method to improve the heat dissipation performance of ultra-thin vapor chambers by increasing the wettability to the cooling working fluid. Summary of the Invention

[0004] Aiming at the above problems existing in the prior art, the first object of the present invention is to provide a preparation method of an ultra-thin heat dissipation composite coating. By compounding and using a silica precursor sol and a titanium dioxide precursor sol, after coating on the surface of a metal substrate, it endows the substrate with excellent hydrophilicity and lipophilicity, and the water contact angle ≤ 4°, thereby increasing the heat dissipation area between the metal substrate and the cooling working fluid to improve the heat dissipation effect, and there is also extremely strong adhesion between the ultra-thin heat dissipation composite coating and the metal substrate, meeting the application requirements of high-integration ultra-thin and light electronic devices.

[0005] The second object of the present invention is to provide an ultra-thin heat dissipation composite coating prepared by the above-mentioned preparation method.

[0006] The third object of the present invention is to provide an ultra-thin heat dissipation metal plate.

[0007] To achieve the above first object, the technical solutions adopted by the present invention include:

[0008] The present invention discloses a preparation method of an ultra-thin heat dissipation composite coating, comprising the following steps:

[0009] 1) Mix tetraethyl orthosilicate and a part of absolute ethanol to obtain a first solution; mix an acid catalyst, water and the remaining absolute ethanol to obtain a second solution; add the second solution to the first solution, stir at room temperature for 2-4 h, and then transfer to 50-60 °C for aging for 3-4 days to obtain a silica precursor sol;

[0010] 2) Mix tetra-isopropyl titanate and a part of absolute ethanol, and then add a mixed solution prepared by mixing an acid catalyst, water and the remaining absolute ethanol to obtain a titanium dioxide mother liquor; add the titanium dioxide mother liquor to water, heat and reflux for 4-6 h, after the reflux ends, exchange with absolute ethanol to remove water, and then heat and concentrate by 10 times to obtain a titanium dioxide precursor sol;

[0011] 3) Mix the silica precursor sol, the titanium dioxide precursor sol and a solvent uniformly to obtain a composite slurry;

[0012] 4) Coat the composite slurry on the surface of a substrate, and obtain an ultra-thin heat dissipation composite coating after drying.

[0013] Further, in the composite slurry, the silica precursor sol accounts for 1-4 wt%, the titanium dioxide precursor sol accounts for 1-4 wt% and the solvent accounts for 90-95 wt%.

[0014] In the present invention, it aims to provide a preparation method of a heat dissipation coating with super-hydrophilicity and super-lipophilicity. By controlling the usage amounts of the raw materials in the silica precursor sol, the hydrolysis condition of the silica precursor sol and the control of the generated silica are realized, such as the solid content of the silica precursor sol, the morphology of silica, the particle size of silica, the dispersibility of silica, etc., so as to be matched with the titanium dioxide precursor sol. After introducing the silica precursor sol, the hydroxyl content on the surface of the ultra-thin heat dissipation composite coating can be increased, and excellent hydrophilic and lipophilic properties can be obtained; by controlling the usage amounts of the raw materials in the titanium dioxide precursor sol, the hydrolysis condition of the titanium dioxide precursor sol and the control of the generated titanium dioxide are realized, such as the solid content of the titanium dioxide precursor sol, the morphology of titanium dioxide, the particle size of titanium dioxide, the dispersibility of titanium dioxide, etc., so as to be matched with the silica precursor sol. After introducing the silica precursor sol, the flexibility of the silica precursor sol can be increased to enhance the adhesion; by further controlling the ratio relationship between the silica precursor sol and the titanium dioxide precursor sol and the proportion in the composite slurry, an ultra-thin heat dissipation composite coating with excellent heat dissipation performance and good adhesion can be obtained.

[0015] Further, in the composite slurry, the mass ratio of the silica precursor sol to the titanium dioxide precursor sol is 3:2.

[0016] Further, in the composite slurry, the silica precursor sol accounts for 3 wt%, the titanium dioxide precursor sol accounts for 2 wt%, and the solvent accounts for 95 wt%.

[0017] Further, the solvent is selected from one or more of water, alcohol solvents, ketone solvents, and alcohol ether solvents.

[0018] Exemplarily, the alcohol solvents are selected from one or more of methanol, ethanol, propanol, butanol, butanediol, and propylene glycol; the ketone solvent is selected from acetone; the alcohol ether solvents are selected from ethylene glycol ether solvents and / or ethylene glycol butyl ether, etc.

[0019] Further, in step 1, the molar ratio of tetraethyl orthosilicate, acid catalyst, absolute ethanol, and water is 0.2 - 3:0.005 - 0.02:5 - 15:6 - 15; preferably 1:0.01:10:10; the solid content of the silica precursor sol is 2 - 10 wt%; exemplarily, the solid content of the silica precursor sol can be 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%, etc.

[0020] Further, in step 2, the molar ratio of titanium isopropoxide, acid catalyst, absolute ethanol, and water in the titanium dioxide mother liquor is 0.6 - 2.5:0.08 - 0.16:40 - 60:0.56 - 1.2; preferably 1:0.13:50:0.82; the solid content of the titanium dioxide precursor sol is 0.1 - 2 wt%; exemplarily, the solid content of the titanium dioxide precursor sol can be 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, or 2 wt%, etc.

[0021] Further, the acid catalyst is selected from one or more of nitric acid, hydrochloric acid, acetic acid, sulfuric acid, hypochlorous acid, and hydrofluoric acid; preferably nitric acid with a concentration of 1 - 2 M.

[0022] Further, in step 2, when adding the titanium dioxide mother liquor to water, the molar ratio of the final water to titanium isopropoxide should be controlled to be 90.

[0023] Further, the coating method is spraying or dipping. The spraying speed is 1-20 cm / s, preferably 5-10 cm / s. When the dipping method is adopted, the common dipping method in the art can be referred to. One dipping cycle includes four steps: descending for coating, immersion, ascending for pulling, and staying. The rate of descending for coating is 4000-6000 μm / s. After the substrate is completely immersed in the composite slurry, the immersion time is 10-30 s. After the immersion ends, the rate of ascending for pulling is 1000-3000 μm / s. After the substrate completely leaves the composite slurry, it stays for 10-30 s. A total of 3-6 coating processes are required to complete the coating process.

[0024] Further, before coating, it also includes plasma treatment of the substrate to activate the surface of the substrate. By plasma treatment, the active groups on the surface of the substrate are increased, thereby increasing the bonding force between the coating and the substrate, increasing the adhesion of the coating, enhancing the durability, reducing the occurrence of coating peeling, and further prolonging its service life. For the selection of the plasma treatment instrument during the plasma treatment process, vacuum plasma or atmospheric plasma can be used to treat the surface of the substrate to enhance the adhesion between the film layer and the substrate. Preferably, vacuum plasma is used for surface treatment. The treatment time and power are based on the substrate surface reaching a super-hydrophilic state. The surface plasma treatment time is 50-600 s, and the treatment power is 20-300 W. Preferably, the surface plasma treatment time is 100-300 s, and the treatment power is 100-200 W.

[0025] To achieve the above second object, the technical solution adopted by the present invention includes:

[0026] The present invention discloses an ultra-thin heat dissipation composite coating prepared by the preparation method as described above.

[0027] Further, the thickness of the ultra-thin heat dissipation composite coating is 50-100 nm, preferably 70-90 nm.

[0028] To achieve the above third object, the technical solution adopted by the present invention includes:

[0029] The present invention discloses an ultra-thin heat dissipation metal plate, which includes a metal substrate and an ultra-thin heat dissipation composite coating formed thereon by the preparation method described above;

[0030] The material of the metal substrate is selected from one or more of copper, aluminum, titanium, silver, copper alloy, aluminum alloy, silver alloy, titanium alloy, and stainless steel.

[0031] Advantages of the present invention:

[0032] The present invention provides an ultra-thin heat-dissipating composite coating that can be coated on a metal substrate, and further obtains an ultra-thin heat-dissipating metal plate that can be used in high-integration ultra-thin and light electronic devices. By plasma treatment, the active groups on the surface of the metal substrate are increased, which can increase the bonding force between the coating and the metal substrate, increase the adhesion of the coating, enhance the durability, thereby reducing the occurrence of coating peeling, and further extending its service life. By controlling the proportion of raw materials in the ultra-thin heat-dissipating composite coating, the prepared coating has a nano-interface structure, and at the same time has super-hydrophilicity and super-lipophilicity, and the water contact angle ≤ 4°, thereby increasing the contact area between the cooling working fluid and the ultra-thin heat-dissipating metal plate and obtaining a higher heat-dissipating effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The following further elaborates on the specific embodiments of the present invention in conjunction with the drawings.

[0034] Figure 1 The structural diagram of the ultra-thin heat-dissipating composite coating of Example 1 of the present invention observed by SEM is shown.

[0035] Figure 2 The test diagram of the contact angle of water on the super-ambiphilic interface of the ultra-thin heat-dissipating composite coating of Example 1 of the present invention is shown.

[0036] Figure 3 The test diagram of the contact angle of toluene on the super-ambiphilic interface of the ultra-thin heat-dissipating composite coating of Example 1 of the present invention is shown.

[0037] Figure 4 The test diagram of testing the film adhesion of the ultra-thin heat-dissipating composite coating of Example 1 of the present invention by the cross-cut method is shown.

[0038] Figure 5 The comparison diagram of the heat-dissipating effects between the ultra-thin heat-dissipating aluminum sheet of Example 1 of the present invention and the aluminum sheet only subjected to cleaning treatment is shown.

[0039] Figure 6 The test diagram of the contact angle of water on the interface of the ultra-thin heat-dissipating composite coating prepared in Comparative Example 1 of the present invention is shown.

[0040] Figure 7 The test diagram of the contact angle of water on the interface of the titanium dioxide coating in Comparative Example 2 of the present invention is shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] To more clearly illustrate the present invention, the present invention will be further described below in conjunction with preferred embodiments and the drawings. It should be clear that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0042] In addition, unless otherwise specified, the raw materials used in the present invention can be obtained commercially, and any range recorded in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0043] Example 1

[0044] 1) Pretreatment of substrate: A 20 mm × 20 mm aluminum sheet was used as the substrate, and the aluminum sheet was ultrasonically cleaned with acetone, ethanol, and deionized water for 10 min respectively, and the cleaned substrate was blown dry with a nitrogen air gun for later use. The surface of the cleaned aluminum sheet was activated by vacuum plasma to obtain a hydrophilic aluminum sheet, and the treatment time was 100 s and the treatment power was 200 W.

[0045] 2) Preparation of composite slurry:

[0046] 2-1) Preparation of solvent: At room temperature, 1 gram of water, 50 grams of anhydrous ethanol and 11 grams of butanol were stirred evenly to obtain a solvent.

[0047] 2-2) Preparation of silica precursor sol: Prepare according to the ratio of tetraethyl silicate (TEOS): HNO3: H2O: EtOH = 1: 0.01: 10: 10. First, mix TEOS and half of the anhydrous ethanol, stir magnetically for 30 minutes to obtain a first solution, and then mix HNO3, H2O and the other half of the anhydrous ethanol to obtain a second solution. At room temperature, add the second solution dropwise to the first solution while stirring continuously. After stirring for 3 hours, turn to 60°C for aging for 3 days to obtain a silica precursor sol with a solid content of 5wt%.

[0048] 2-3) Preparation of titanium dioxide precursor sol: Prepare according to the ratio of tetraisopropyl titanate (TIPT): H2O: HNO3: anhydrous ethanol = 1: 0.82: 0.13: 50. First, TIPT and half of the anhydrous ethanol are mixed evenly and magnetically stirred for 30 minutes. Then, a mixture of the other half of the anhydrous ethanol, water, and nitric acid is added dropwise under stirring. Continue stirring for 2 hours after addition and age at room temperature for 2 days to obtain a titanium dioxide mother liquor. Add the titanium dioxide mother liquor dropwise to water under stirring, control the final H2O / TIPT molar ratio to 90, and then heat and reflux for 6 hours. After the reflux is completed, exchange with anhydrous ethanol to remove water, and then concentrate 10 times under heating to obtain a titanium dioxide precursor sol with a solid content of 1wt%.

[0049] 2-4) Preparation of composite slurry: Mix silica precursor sol, titanium dioxide precursor sol and solvent in mass percentages of 3%, 2% and 95%, and stir them thoroughly to obtain composite slurry required for coating.

[0050] 3) Coating: Spray the composite slurry on the surface of the hydrophilically treated aluminum sheet, and after drying, obtain an ultra-thin heat-dissipating aluminum sheet coated with an ultra-thin heat-dissipating composite coating. The thickness of the ultra-thin heat-dissipating composite coating is 80 nm. Among them, the spraying speed is 10 cm / s.

[0051] Performance Test

[0052] Perform SEM characterization on the ultra-thin heat-dissipating aluminum sheet prepared in Example 1. As Figure 1 shown, the silica and titanium dioxide nanoparticles are evenly distributed on the surface of the substrate, the particle diameter is about 10 nm, and the surface of the film is flat.

[0053] Drop 2 μl of water on the ultra-thin heat-dissipating aluminum sheet prepared in Example 1 to test the wettability of the interface to water. After testing, the contact angle is about 4°, indicating that the ultra-thin heat-dissipating composite coating has superhydrophilicity (see Figure 2 ).

[0054] Drop 2 μl of toluene on the ultra-thin heat-dissipating aluminum sheet prepared in Example 1 to test the wettability of the interface to oily substances. After testing, the contact angle is 0°, indicating that the ultra-thin heat-dissipating composite coating has superoleophilicity (see Figure 3 ).

[0055] Refer to the coating film adhesion test method of GB / T 9286, and use the cross-cut method to test the adhesion of the composite film on the ultra-thin heat-dissipating aluminum sheet prepared in Example 1. After testing, the film adhesion rating is 0 level, indicating that the ultra-thin heat-dissipating composite coating has strong adhesion (see Figure 4 ).

[0056] Drop a drop of water at about 65 °C on the aluminum sheet that has only been cleaned and the ultra-thin heat-dissipating aluminum sheet prepared in Example 1 respectively, and record and observe the temperature change trend of the water drop on the surface of the aluminum sheet through an infrared thermal imaging camera to study the overall heat dissipation process of the water drop. As Figure 5 shown, by comparison, it is found that the ultra-thin heat-dissipating aluminum sheet prepared in Example 1 has better heat dissipation effect.

[0057] Example 2

[0058] 1) Pretreatment of the substrate: Use an aluminum sheet of 20 mm × 20 mm as the substrate. Ultrasonically clean the aluminum sheet with acetone, ethanol, and deionized water in sequence for 10 min, and dry the cleaned substrate with a nitrogen air gun for standby. Use vacuum plasma to activate the surface of the cleaned aluminum sheet to obtain a hydrophilically treated aluminum sheet. The treatment time is 100 s, and the treatment power is 200 W.

[0059] 2) Preparation of the composite slurry:

[0060] 2-1) Preparation of solvent: At room temperature, 1 gram of water, 50 grams of anhydrous ethanol and 11 grams of butanol were stirred evenly to obtain a solvent.

[0061] 2-2) Preparation of silica precursor sol: Prepare according to the ratio of tetraethyl silicate (TEOS): HNO3: H2O: EtOH = 1: 0.01: 10: 10. First, mix TEOS and half of the anhydrous ethanol, stir magnetically for 30 minutes to obtain a first solution, and then mix HNO3, H2O and the other half of the anhydrous ethanol to obtain a second solution. At room temperature, add the first solution dropwise to the second solution while stirring continuously. After stirring for 3 hours, turn to 60°C for aging for 3 days to obtain a silica precursor sol.

[0062] 2-3) Preparation of titanium dioxide precursor sol: Prepare according to the ratio of tetraisopropyl titanate (TIPT): H2O: HNO3: anhydrous ethanol = 1: 0.82: 0.13: 50. First, TIPT and half of the anhydrous ethanol are mixed evenly and magnetically stirred for 30 minutes. Then, a mixture of the other half of the anhydrous ethanol, water, and nitric acid is added dropwise under stirring. Continue stirring for 2 hours after addition and age at room temperature for 2 days to obtain a titanium dioxide mother liquor. Add the titanium dioxide mother liquor dropwise to water under stirring, control the final molar ratio of H2O / TIPT to 90, and then heat and reflux for 6 hours. After the reflux is completed, exchange with anhydrous ethanol to remove water, and then concentrate 10 times under heating to obtain a titanium dioxide precursor sol.

[0063] 2-4) Preparation of composite slurry: SiO2 precursor sol, TiO2 precursor sol and solvent are mixed in mass percentages of 3%, 2% and 95%, and stirred sufficiently to obtain composite slurry required for coating.

[0064] 3) Coating: The composite slurry is coated on the surface of the hydrophilic aluminum sheet by a pull-up coating method, and after drying, an ultra-thin heat dissipation aluminum sheet coated with an ultra-thin heat dissipation composite coating is obtained, and the thickness of the ultra-thin heat dissipation composite coating is 80nm, wherein the drop speed of the pull-up coating is 6000μm / s, the immersion time is 15s, the pull-up speed is 1500μm / s, the residence time is 15s, and the number of coatings is 5 times. The obtained ultra-thin heat dissipation aluminum sheet is subjected to performance testing, and the test results are equivalent to those of Example 1.

[0065] Comparative Example 1

[0066] 1) Pretreatment of substrate: A 20 mm × 20 mm aluminum sheet was used as the substrate, and the aluminum sheet was ultrasonically cleaned with acetone, ethanol, and deionized water for 10 min respectively, and the cleaned substrate was blown dry with a nitrogen air gun for later use. The surface of the cleaned aluminum sheet was activated by vacuum plasma to obtain a hydrophilic aluminum sheet, and the treatment time was 100 s and the treatment power was 200 W.

[0067] 2) Preparation of composite slurry:

[0068] 2-1) Preparation of solvent: At room temperature, 1 gram of water, 50 grams of anhydrous ethanol and 11 grams of butanol were stirred evenly to obtain a solvent.

[0069] 2-2) Preparation of silica precursor sol: Prepare according to the ratio of tetraethyl silicate (TEOS): HNO3: H2O: EtOH = 0.5: 0.01: 8: 12. First, mix TEOS and half of the anhydrous ethanol, stir magnetically for 30 minutes to obtain a first solution, and then mix HNO3, H2O and the other half of the anhydrous ethanol to obtain a second solution. At room temperature, add the second solution dropwise to the first solution while stirring continuously. After stirring for 3 hours, turn to 60°C for aging for 3 days to obtain a silica precursor sol with a solid content of 3wt%.

[0070] 2-3) Preparation of titanium dioxide precursor sol: Prepare according to the ratio of tetraisopropyl titanate (TIPT): H2O: HNO3: anhydrous ethanol = 0.8: 0.80: 0.08: 40. First, TIPT and half of the anhydrous ethanol are mixed evenly and magnetically stirred for 30 minutes. Then, a mixture of the other half of the anhydrous ethanol, water, and nitric acid is added dropwise under stirring. After adding, stirring is continued for 2 hours, and the mixture is aged at room temperature for 2 days to obtain a titanium dioxide mother liquor. The titanium dioxide mother liquor is added dropwise to water under stirring, and the final molar ratio of H2O / TIPT is controlled to be 90, and then heated to reflux for 6 hours. After the reflux is completed, it is exchanged with anhydrous ethanol to remove water, and then concentrated 10 times under heating conditions to obtain a titanium dioxide precursor sol with a solid content of 0.5wt%.

[0071] 2-4) Preparation of composite slurry: SiO2 precursor sol, TiO2 precursor sol and solvent are mixed in mass percentages of 3%, 2% and 95%, and stirred sufficiently to obtain composite slurry required for coating.

[0072] 3) Coating: spraying the composite slurry on the surface of the hydrophilic treated aluminum sheet, and obtaining an ultra-thin heat dissipation aluminum sheet coated with an ultra-thin heat dissipation composite coating after drying, wherein the thickness of the ultra-thin heat dissipation composite coating is 80 nm, wherein the spraying speed is 10 cm / s.

[0073] Performance Testing

[0074] 2 μl of water was dripped onto the ultra-thin heat dissipation aluminum sheet prepared in Comparative Example 1. After testing, the contact angle was about 10.9°, indicating that the ultra-thin heat dissipation composite coating did not have super hydrophilicity (see Figure 6 ).

[0075] Comparative Example 2

[0076] 1) Pretreatment of substrate: A 20 mm × 20 mm aluminum sheet was used as the substrate, and the aluminum sheet was ultrasonically cleaned with acetone, ethanol, and deionized water for 10 min respectively, and the cleaned substrate was blown dry with a nitrogen air gun for later use. The surface of the cleaned aluminum sheet was activated by vacuum plasma to obtain a hydrophilic aluminum sheet, and the treatment time was 100 s and the treatment power was 200 W.

[0077] 2) Preparation of composite slurry:

[0078] 2-1) Preparation of solvent: At room temperature, 1 gram of water, 50 grams of anhydrous ethanol and 11 grams of butanol were stirred evenly to obtain a solvent.

[0079] 2-2) Preparation of titanium dioxide precursor sol: Prepare according to the ratio of tetraisopropyl titanate (TIPT): H2O: HNO3: anhydrous ethanol = 1: 0.82: 0.13: 50. First, TIPT and half of the anhydrous ethanol are mixed evenly and magnetically stirred for 30 minutes. Then, a mixture of the other half of the anhydrous ethanol, water, and nitric acid is added dropwise under stirring. Continue stirring for 2 hours after addition and age at room temperature for 2 days to obtain a titanium dioxide mother liquor. Add the titanium dioxide mother liquor dropwise to water under stirring, control the final H2O / TIPT molar ratio to 90, and then heat and reflux for 6 hours. After the reflux is completed, exchange with anhydrous ethanol to remove water, and then concentrate 10 times under heating to obtain a titanium dioxide precursor sol with a solid content of 1wt%.

[0080] 2-3) Preparation of slurry: Mix the titanium dioxide precursor sol and the solvent in a mass percentage of 5% and 95%, and stir them thoroughly to obtain the slurry required for coating.

[0081] 3) Coating: spraying slurry on the surface of the hydrophilic aluminum sheet, and obtaining a heat dissipation aluminum sheet coated with a titanium dioxide coating after drying, wherein the thickness of the ultra-thin heat dissipation coating is 80 nm, wherein the spraying speed is 10 cm / s.

[0082] Performance Testing

[0083] 2 μl of water was dripped onto the heat dissipation aluminum sheet prepared in Comparative Example 2. After testing, the contact angle was about 44°, indicating that the titanium dioxide coating did not have super hydrophilicity (see Figure 7 ).

[0084] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation manners here. Any obvious changes or modifications derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A preparation method of an ultra-thin heat dissipation composite coating, characterized in that It includes the following steps: 1) Mix tetraethyl orthosilicate and part of absolute ethanol to obtain a first solution; mix an acid catalyst, water and the remaining absolute ethanol to obtain a second solution; add the second solution to the first solution, stir at room temperature for 2 - 4 h, and then transfer to 50 - 60 °C for aging for 3 - 4 days to obtain a silica precursor sol; 2) Mix tetra-isopropyl titanate and part of absolute ethanol, and then add a mixed solution prepared by mixing an acid catalyst, water and the remaining absolute ethanol to obtain a titanium dioxide mother liquor; add the titanium dioxide mother liquor to water, heat and reflux for 4 - 6 h, after the reflux ends, exchange with absolute ethanol to remove moisture, and then heat and concentrate by 10 times to obtain a titanium dioxide precursor sol; 3) Mix the silica precursor sol, the titanium dioxide precursor sol and a solvent evenly to obtain a composite slurry; 4) Coat the composite slurry on the surface of a substrate, and obtain an ultrathin heat dissipation composite coating after drying.

2. The preparation method according to claim 1, characterized in that, In the composite slurry, the silica precursor sol accounts for 1 - 4 wt%, the titanium dioxide precursor sol accounts for 1 - 4 wt% and the solvent accounts for 90 - 95 wt%; Preferably, in the composite slurry, the silica precursor sol accounts for 3 wt%, the titanium dioxide precursor sol accounts for 2 wt% and the solvent accounts for 95 wt%.

3. The preparation method according to claim 1, characterized in that, The solvent is selected from one or more of water, alcohol solvents, ketone solvents, and alcohol ether solvents.

4. The preparation method according to claim 1, characterized in that In step 1, the molar ratio of the tetraethyl orthosilicate, the acid catalyst, the absolute ethanol and the water is 0.2 - 3:0.005 - 0.02:5 - 15:6 - 15; preferably 1:0.01:10:10; The solid content of the silica precursor sol is 2 - 10 wt%.

5. The preparation method according to claim 1, characterized in that, In step 2, the molar ratio of the tetra-isopropyl titanate, the acid catalyst, the absolute ethanol and the water in the titanium dioxide mother liquor is 0.6 - 2.5:0.08 - 0.16:40 - 60:0.56 - 1.2; preferably 1:0.13:50:0.82; The solid content of the titanium dioxide precursor sol is 0.1 - 2 wt%.

6. The preparation method according to claim 1, characterized in that, The coating method is spraying or dipping, and the spraying speed is 1 - 20 cm / s; The dipping includes four steps of descending film coating, dipping, upward pulling and staying.

7. The preparation method according to claim 1, wherein Before coating, it also includes plasma treatment of the substrate to activate the surface of the substrate.

8. An ultra-thin heat dissipation composite coating, characterized in that, It is prepared by using the preparation method described in any one of claims 1 - 7.

9. The ultra-thin heat dissipation composite coating according to claim 8, characterized in that The thickness of the ultrathin heat dissipation composite coating is 50 - 100 nm, preferably 70 - 90 nm.

10. An ultra-thin heat dissipation metal plate, characterized in that, The ultrathin heat dissipation metal plate includes a metal substrate and an ultrathin heat dissipation composite coating formed thereon by using the preparation method described in any one of claims 1 - 7; The material of the metal substrate is selected from one or more of copper, aluminum, titanium, silver, copper alloy, aluminum alloy, silver alloy, titanium alloy and stainless steel.

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