A high thermal conductivity radiative cooling coating material and its preparation method

Abstract

The present invention discloses a high thermal conductivity radiative cooling coating material and a preparation method thereof, belonging to the technical field of coating materials. The preparation method of the high thermal conductivity radiative cooling coating material of the present invention includes the following steps: coating hBN nanosheets with surface hydroxylation on the surface of amino-functionalized SiO2 hollow sphere particles to obtain hollow SiO2@hBN composite particles; adding hBN micron sheets with surface hydroxylation and hollow SiO2@hBN composite particles into a solvent containing a dispersant, dispersing uniformly to obtain a raw material solution, and then adding a solution of a polymer substrate into the raw material solution, dispersing uniformly and then coating to obtain the high thermal conductivity radiative cooling coating material. The high thermal conductivity radiative cooling coating material prepared by the present invention has a high thermal conductivity and excellent radiative cooling effect, and is suitable for the field of thermal management of electronic devices.

Description

Technical Field

[0001] The present invention relates to the technical field of coating materials, and particularly to a high thermal conductivity radiative cooling coating material and a preparation method thereof. Background Art

[0002] With the gradual miniaturization and high integration of electronic devices, the problems of extremely high heat flux density and hot spots have become one of the important reasons restricting the further development of microelectronic devices. There is an urgent need to find new and low-energy-consuming efficient cooling technologies to ensure the stable operation of electronic devices. Radiative cooling technology transfers heat to the low-temperature environment of outer space through thermal radiation to achieve the purpose of passive cooling of objects. This technology does not require any additional energy consumption, is conducive to energy conservation and carbon reduction, and has great application potential in the field of electronic device thermal management.

[0003] However, the materials currently applied to radiative cooling generally have extremely low thermal conductivity, and the multi-layer, porous and other structures used to improve the radiation performance of the materials lead to a further reduction in thermal conductivity. The low thermal conductivity characteristic of radiative cooling materials is not conducive to the heat dissipation of electronic devices, greatly affects the normal operation of electronic devices, and limits the application and development of radiative cooling materials in this field. Therefore, it is particularly important to develop a radiative cooling coating material with high thermal conductivity. Summary of the Invention

[0004] The purpose of the present invention is to provide a high thermal conductivity radiative cooling coating material and a preparation method thereof to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above purpose, the present invention provides the following scheme:

[0006] One of the technical solutions of the present invention: A preparation method of a high thermal conductivity radiative cooling coating material, comprising the following steps:

[0007] Coat hBN nanosheets with surface hydroxylation on the surface of surface-aminated SiO2 hollow sphere particles to obtain hollow SiO2@hBN composite particles;

[0008] Add hBN microsheets with surface hydroxylation and hollow SiO2@hBN composite particles into a solvent containing a dispersant, disperse evenly to obtain a raw material solution, and then add a solution of a polymer matrix into the raw material solution, disperse evenly and then coat to obtain the high thermal conductivity radiative cooling coating material.

[0009] Further, the preparation method of the hollow SiO2@hBN composite particles specifically includes:

[0010] The SiO2 hollow sphere particles are added to an organic solvent solution and dispersed evenly, and the pH is adjusted to acidic to obtain a mixed solution. A silane coupling agent containing amino groups is added to the mixed solution, and the reaction is carried out with heating and stirring to obtain SiO2 hollow sphere particles with surface amination;

[0011] The hBN nanosheets are heat-treated at a high temperature in an air atmosphere to obtain hBN nanosheets with surface hydroxylation;

[0012] The surface-aminated SiO2 hollow sphere particles and the surface-hydroxylated hBN nanosheets are added to a solvent and dispersed evenly, and then the pH is adjusted to acidic, and the reaction is stirred to obtain the hollow SiO2@hBN composite particles.

[0013] Furthermore, the particle size of the SiO2 hollow sphere particles is 0.5 - 5 μm; the dosage ratio of the SiO2 hollow sphere particles to the organic solvent in the organic solvent solution is 2 - 3.5 g:250 - 450 mL; the pH of the mixed solution is 5; the volume ratio of the silane coupling agent containing amino groups to the mixed solution is (0.5 - 0.8):(60 - 100); the temperature of the heating and stirring reaction is 60 °C, and the time is 6 h;

[0014] The temperature of the high-temperature heat treatment is 1000 °C, and the time is 3 h;

[0015] The mass ratio of the surface-aminated SiO2 hollow sphere particles to the surface-hydroxylated hBN nanosheets is (9 - 12):(5 - 6); the total dosage of the surface-aminated SiO2 hollow sphere particles and the surface-hydroxylated hBN nanosheets and the dosage of the solvent are in the ratio of 0.7 - 0.8 g:100 - 120 mL; the stirring reaction time is 4 h.

[0016] Furthermore, the dosage ratio of the solvent containing a dispersant, the surface-hydroxylated hBN micro-sheets, and the hollow SiO2@hBN composite particles is 20 - 55 mL:0.72 - 1.92 g:0.36 - 0.96 g;

[0017] In the solution of the polymer substrate, the dosage ratio of the polymer substrate to the solvent is 2 - 4.5 g:12 - 25 mL;

[0018] In the solvent containing a dispersant, the dosage ratio of the dispersant to the solvent is 0.08 - 0.2 g:20 - 55 mL.

[0019] Furthermore, the mass ratio of the total mass of the surface-hydroxylated hBN micro-sheets and the hollow SiO2@hBN composite particles to the mass of the polymer substrate is 1.08 - 2.88 g:2 - 4.5 g.

[0020] Furthermore, the preparation method of the surface-hydroxylated hBN micro-sheets includes the following steps:

[0021] The hBN micro-sheets are heat-treated at high temperature in an air atmosphere to obtain surface-hydroxylated hBN micro-sheets;

[0022] The temperature of the high-temperature heat treatment is 1000 °C and the time is 3 h.

[0023] The second technical solution of the present invention: A high thermal conductivity radiative cooling coating material prepared by the above preparation method.

[0024] The third technical solution of the present invention: An application of the above high thermal conductivity radiative cooling coating material in the preparation of electronic devices.

[0025] The present invention discloses the following technical effects:

[0026] (1) The high thermal conductivity radiative cooling coating material prepared by the present invention has a high thermal conductivity and excellent radiative cooling effect (i.e., high solar band reflectivity and infrared band emissivity), and is suitable for the field of electronic device thermal management.

[0027] (2) The present invention performs multi-shape co-doping on the polymer substrate with boron nitride micro-sheets (surface-hydroxylated hBN micro-sheets) and hollow spherical particles with boron nitride coated on the surface (hollow SiO2@hBN composite particles), so that the coating material has a good radiative cooling effect and a high thermal conductivity. Specifically:

[0028] Coat a layer of hBN nano-sheet particles on the surface of the SiO2 hollow particles, and improve the scattering of incident light through the multi-layer structure, thereby optimizing the reflection performance of the coating material, increasing the reflectivity of the coating material to sunlight, and reducing the absorption of solar radiation.

[0029] Use SiO2 hollow particles with boron nitride coated on the surface (hollow SiO2@hBN composite particles) and surface-hydroxylated hBN micro-sheet particles for multi-shape co-doping. The hollow SiO2@hBN composite particles have a high reflectivity in the ultraviolet and visible light bands, and couple with the high reflectivity of the surface-hydroxylated hBN micro-sheet particles in other bands to achieve an improvement in the reflection performance in the entire solar radiation band and optimize the reflectivity of the coating material to the greatest extent. At the same time, the PVDF-HFP polymer substrate used has an extremely high emissivity in the atmospheric window band, and the particle doping has a weak influence on the infrared emissivity. Therefore, the coating material prepared by the present invention has excellent reflectivity and emissivity, and can achieve a good radiative cooling effect.

[0030] In the present invention, by coating boron nitride on the surface of SiO2 hollow particles, due to the high thermal conductivity of the boron nitride material, the thermal conductivity of the filler is greatly improved. In addition, the multi-shape co-doping strategy adopted can form a thermal conduction network inside the coating material, which is conducive to the formation of thermal conduction channels, thereby greatly improving the thermal conductivity of the material. The high thermal conductivity of the coating material is conducive to the heat generated by the operation of electronic devices being transferred outward through heat conduction and heat convection, coupled with radiative cooling, to achieve efficient cooling of electronic devices. Brief Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 FTIR diagrams of the raw material SiO2 hollow sphere particles used in Example 1 of the present invention, the surface amino-functionalized SiO2 hollow sphere particles prepared in Example 1, and the hollow SiO2@hBN composite particles prepared in Example 1;

[0033] Figure 2 SEM diagram of the hollow SiO2@hBN composite particles prepared in Example 1 of the present invention;

[0034] Figure 3 Cross-sectional view of the high thermal conductivity radiative cooling coating material prepared in Example 1 of the present invention. Detailed Embodiments

[0035] Now, the various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0036] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0037] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0038] Without departing from the scope or spirit of this invention, various improvements and variations can be made to the specific embodiments of the description of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of this invention are obvious to those skilled in the art. The description of this invention and the examples are merely exemplary.

[0039] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0040] One of the technical solutions of this invention: provides a preparation method of a high thermal conductivity radiative cooling coating material, comprising the following steps:

[0041] (1) Preparation method of hollow SiO2@hBN composite particles:

[0042] S1. Preparation of surface-aminated SiO2 hollow sphere particles: Add SiO2 hollow sphere particles into an organic solvent solution (deionized water and absolute ethanol with a volume ratio of 1:19), ultrasonically disperse (10 - 30 min) evenly, adjust the pH to 5 by dropwise adding concentrated hydrochloric acid while stirring to obtain a mixed solution, add a silane coupling agent containing an amino group into the mixed solution, heat and stir for reaction, then wash and dry to obtain surface-aminated SiO2 hollow sphere particles;

[0043] In a specific embodiment of this invention, the particle size of the SiO2 hollow sphere particles is 0.5 - 5 μm, and the shell thickness is 50 - 100 nm; the dosage ratio of the SiO2 hollow sphere particles to the organic solvent in the organic solvent solution is 2 - 3.5 g:250 - 450 mL; the volume ratio of the silane coupling agent containing an amino group to the mixed solution is (0.5 - 0.8):(60 - 100); the temperature of the heating and stirring reaction is 60 °C, and the time is 6 h;

[0044] In a specific embodiment of this invention, the washing is specifically: repeatedly wash 2 - 3 times with absolute ethanol and deionized water; the drying is vacuum drying, and the temperature is 60 - 70 °C.

[0045] S2. Preparation of surface-hydroxylated hBN nanosheets: The hBN nanosheets (commercially available, with a particle size of 50 - 100 nm) were heat-treated at a high temperature (1000 °C, for 3 h) in an air atmosphere to obtain surface-hydroxylated hBN nanosheets.

[0046] S3. Preparation of hollow SiO2@hBN composite particles: The surface-aminated SiO2 hollow sphere particles and the surface-hydroxylated hBN nanosheets were added to deionized water and ultrasonically dispersed (for 10 - 30 min) evenly, and then concentrated hydrochloric acid was added dropwise while stirring to adjust the pH to 4. After stirring and reacting, they were washed and dried to obtain hollow SiO2@hBN composite particles.

[0047] In a specific embodiment of the present invention, the mass ratio of the surface-aminated SiO2 hollow sphere particles to the surface-hydroxylated hBN nanosheets is (9 - 12):(5 - 6); the total amount of the surface-aminated SiO2 hollow sphere particles and the surface-hydroxylated hBN nanosheets and the amount of deionized water used are in a ratio of 0.7 - 0.8 g:100 - 120 mL; the stirring reaction time is 4 h;

[0048] In a specific embodiment of the present invention, the washing is specifically: repeatedly washed 2 - 3 times with absolute ethanol and deionized water; the drying is vacuum drying at a temperature of 60 - 70 °C.

[0049] (2) Preparation method of surface-hydroxylated hBN micro-sheets:

[0050] The hBN micro-sheets (commercially available, with a particle size of about 1 μm) were heat-treated at a high temperature (1000 °C, for 3 h) in an air atmosphere to obtain surface-hydroxylated hBN micro-sheets.

[0051] (3) Preparation method of high thermal conductivity radiative cooling coating material (hollow SiO2@hBN / hBN-PVDF-HFP composite material):

[0052] S1. Take a polymer substrate (PVDF-HFP, with a weight-average molecular weight of M w 400,000) and dissolve it in NMP by mechanical stirring at room temperature to obtain a solution of the polymer substrate.

[0053] In a specific embodiment of the present invention, the usage ratio of the polymer substrate to NMP is 2 - 4.5 g:12 - 25 mL.

[0054] S2. Add a dispersant to NMP and stir at room temperature for 20 - 30 min to obtain a solvent containing the dispersant; add the hollow SiO2@hBN composite particles prepared in step (1) and the surface-hydroxylated hBN micro-sheets prepared in step (2) to the solvent containing the dispersant and ultrasonically disperse (for 10 - 30 min) evenly to obtain a raw material solution.

[0055] In a specific embodiment of the present invention, the dosage ratio of the dispersant to NMP in the solvent containing the dispersant is 0.08 - 0.2 g: 20 - 55 mL; the dosage ratio of the solvent containing the dispersant, the surface-hydroxylated hBN microflakes, and the hollow SiO2@hBN composite particles is 20 - 55 mL: 0.72 - 1.92 g: 0.36 - 0.96 g.

[0056] S3. Mix the solution of the polymer substrate prepared in step S1 and the raw material solution prepared in step S2, perform ultrasonic dispersion (30 - 60 min) until uniform, then defoam in a vacuum environment, and then uniformly coat and dry to obtain a high thermal conductivity radiative cooling coating material.

[0057] In a specific embodiment of the present invention, the mass ratio of the total mass of the surface-hydroxylated hBN microflakes and the hollow SiO2@hBN composite particles to the mass of the polymer substrate is 1.08 - 2.88 g: 2 - 4.5 g.

[0058] In a specific embodiment of the present invention, the drying temperature is 50 °C and the time is 16 - 24 h.

[0059] In the second aspect of the present invention, there is provided a high thermal conductivity radiative cooling coating material prepared by the above preparation method.

[0060] In the third aspect of the present invention, there is provided an application of the above high thermal conductivity radiative cooling coating material in the preparation of electronic devices.

[0061] Example 1

[0062] A preparation method of a high thermal conductivity radiative cooling coating material:

[0063] (1) Preparation of hollow SiO2@hBN composite particles:

[0064] S1. Prepare surface-aminated SiO2 hollow sphere particles

[0065] Mix 12.5 mL of deionized water and 237.5 mL of absolute ethanol, add 2 g of SiO2 hollow sphere particles (commercially available, particle size 1 - 5 μm, shell thickness 50 - 100 nm), ultrasonically disperse for 20 min, then while stirring, dropwise add concentrated hydrochloric acid to adjust the pH of the system to 5 to obtain a mixed solution; add 2 mL of KH550 to the mixed solution, magnetically stir for 6 h under a water bath at 60 °C, then perform vacuum filtration, wash repeatedly 3 times with absolute ethanol and deionized water, and dry in vacuum at 60 °C to obtain surface-aminated SiO2 hollow sphere particles.

[0066] S2. Prepare surface-hydroxylated hBN nanosheets

[0067] Take 1 g of hBN nanosheets (commercially available, particle size 50 - 100 nm) and place them in a tube furnace. Heat at 1000 °C for 3 h in an air atmosphere to obtain surface-hydroxylated hBN nanosheets.

[0068] S3. Preparation of hollow SiO2@hBN composite particles

[0069] Take 1.6 g of the surface-aminated SiO2 hollow sphere particles prepared in step S1 and 0.8 g of the surface-hydroxylated hBN nanosheets prepared in step S2, add them to 350 mL of deionized water, ultrasonically disperse for 20 min, then while stirring, dropwise add concentrated hydrochloric acid to adjust the pH of the system to 4. Continue to stir at room temperature for 4 h for the self-assembly process. Finally, perform vacuum filtration, wash repeatedly 3 times with absolute ethanol and deionized water, and dry in vacuum at 60 °C to obtain hollow SiO2@hBN composite particles.

[0070] (2) Preparation of surface-hydroxylated hBN micro-sheets

[0071] Take 1.5 g of hBN micro-sheets (commercially available, particle size about 1 μm) and place them in a tube furnace. Heat at 1000 °C for 3 h in an air atmosphere to obtain surface-hydroxylated hBN micro-sheets.

[0072] (3) Preparation of high thermal conductivity radiative cooling coating material

[0073] S1. Take 3 g of PVDF-HFP (weight average molecular weight M w 400,000) and dissolve it in 18 mL of NMP by mechanical stirring at room temperature to obtain a solution of the polymer substrate.

[0074] S2. Add 0.12 g of a dispersant (polyvinylpyrrolidone) to 30 mL of NMP, stir at room temperature for 30 min to obtain an NMP mixed solution. Take 1.2 g of the surface-hydroxylated hBN micro-sheets prepared in step (2) and 0.6 g of the hollow SiO2@hBN composite particles prepared in step (1), add them to the NMP mixed solution, and ultrasonically disperse for 20 min to obtain a raw material solution.

[0075] S3. Mix the solution of the polymer substrate prepared in step S1 and the raw material solution prepared in step S2, ultrasonically disperse for 40 min, then defoam in a vacuum environment, and then uniformly coat it on the electronic device with a scraper and dry at 50 °C for 18 h to obtain a high thermal conductivity radiative cooling coating material (i.e., hollow SiO2@hBN / hBN-PVDF-HFP composite material).

[0076] Take the composite material prepared in this example for radiative property characterization, and it is found that the solar band reflectivity of the composite material prepared in this example is as high as 89.7%, and the infrared band emissivity is as high as 93.1%.

[0077] The thermal conductivity of the composite material prepared in this example was compared with that of the pure PVDF-HFP coating material, and it was found that the thermal conductivity increased from 0.146 W·m -1 ·K -1 to 0.88 W·m -1 ·K -1 . Therefore, the composite material (coating material) prepared in this example has more excellent radiative cooling characteristics and thermal conductivity, which is beneficial to the heat dissipation of electronic devices.

[0078] The preparation method of the pure PVDF-HFP coating material is as follows: Take 3 g of PVDF-HFP and dissolve it in 18 mL of NMP by mechanical stirring at room temperature. After defoaming in a vacuum environment, it is directly coated evenly on the electronic device with a scraper and dried at 50 °C for 18 h to obtain the pure PVDF-HFP coating material.

[0079] The FTIR spectra of the raw material SiO2 hollow sphere particles (SiO2), the surface-aminated SiO2 hollow sphere particles (SiO2-KH550) prepared in this example, and the hollow SiO2@hBN composite particles (SiO2@hBN) prepared in this example are shown in Figure 1 .

[0080] As can be seen from Figure 1 , compared with the SiO2 hollow particles, the absorption peaks of the SiO2-KH550 hollow particles appear at 3438 cm -1 and 1635 cm -1 , which are caused by the vibration of -NH2. New absorption peaks appear at 2985 cm -1 and 1392 cm -1 , corresponding to the vibration of -CH2 in KH550. The results show that the surface amination treatment of the hollow sphere particles with KH550 is successful. By comparing the infrared spectral curves of the hollow particles before and after coating, it can be found that the B-N characteristic peaks at 1409 cm -1 and 814 cm -1 indicate that the coating of hBN on the surface of the SiO2 hollow particles has been achieved.

[0081] The SEM image of the hollow SiO2@hBN composite particles (SiO2@hBN) prepared in this example is shown in Figure 2 .

[0082] As can be seen from Figure 2 , the hBN nanosheets have been successfully coated on the surface of the SiO2 hollow particles.

[0083] The cross-sectional view of the high-thermal-conductivity radiative cooling coating material prepared in this example is shown in Figure 3 .

[0084] It can be seen from Figure 3 that the particles are uniformly dispersed in the polymer substrate material, and the hBN micron sheets are dispersed between the hollow SiO2@hBN composite particles, forming a heat conduction network, which is beneficial to the improvement of the thermal conductivity of the coating material.

[0085] Example 2

[0086] A preparation method of a high thermal conductivity radiative cooling coating material:

[0087] (1) Preparation of hollow SiO2@hBN composite particles:

[0088] S1. Preparation of surface-aminated SiO2 hollow sphere particles

[0089] Mix 20 mL of deionized water and 380 mL of absolute ethanol, add 3 g of SiO2 hollow sphere particles (particle size 1 - 5 μm, shell thickness 50 - 100 nm), ultrasonically disperse for 30 min, then while stirring, dropwise add concentrated hydrochloric acid to adjust the pH of the system to 5 to obtain a mixed solution; add 3 mL of KH550 to the mixed solution, magnetically stir for 6 h under a water bath at 60 °C, then perform vacuum filtration, wash repeatedly 3 times with absolute ethanol and deionized water, and dry in vacuum at 60 °C to obtain surface-aminated SiO2 hollow sphere particles.

[0090] S2. Preparation of surface-hydroxylated hBN nanosheets

[0091] Take 1.5 g of hBN nanosheets (commercially available, particle size 50 - 100 nm) and place them in a tube furnace, heat at 1000 °C for 3 h in an air atmosphere to obtain surface-hydroxylated hBN nanosheets.

[0092] S3. Preparation of hollow SiO2@hBN composite particles

[0093] Take 2 g of the surface-aminated SiO2 hollow sphere particles prepared in step S1 and 1 g of the surface-hydroxylated hBN nanosheets prepared in step S2.1, add them to 450 mL of deionized water, ultrasonically disperse for 30 min, then while stirring, dropwise add concentrated hydrochloric acid to adjust the pH of the system to 4, continue to stir at room temperature for 4 h for the self-assembly process, finally perform vacuum filtration, wash repeatedly 3 times with absolute ethanol and deionized water, and dry in vacuum at 60 °C to obtain hollow SiO2@hBN composite particles.

[0094] (2) Preparation of surface-hydroxylated hBN micron sheets

[0095] Take 2.5 g of hBN micron sheets (commercially available, particle size about 1 μm) and place them in a tube furnace, heat at 1000 °C for 3 h in an air atmosphere to obtain surface-hydroxylated hBN micron sheets.

[0096] (3) Preparation of a High Thermal Conductivity Radiative Cooling Coating Material

[0097] S1. Take 2 g of PVDF-HFP (weight-average molecular weight is M w 400,000) and dissolve it in 12 mL of NMP by mechanical stirring at room temperature to obtain a solution of the polymer substrate.

[0098] S2. Add 0.18 g of a dispersant (polyvinylpyrrolidone) to 55 mL of NMP, stir at room temperature for 30 min to obtain an NMP mixed solution. Take 1.92 g of the surface-hydroxylated hBN microflakes prepared in step (2) and 0.96 g of the hollow SiO2@hBN composite particles prepared in step (1), add them to the NMP mixed solution, and ultrasonically disperse for 30 min to obtain a raw material solution.

[0099] S3. Mix the solution of the polymer substrate prepared in step S1 and the raw material solution prepared in step S2, ultrasonically disperse for 50 min, then defoam in a vacuum environment, and then uniformly coat it on the electronic device with a scraper and dry at 50 °C for 24 h to obtain a high thermal conductivity radiative cooling coating material (i.e., a hollow SiO2@hBN / hBN-PVDF-HFP composite material).

[0100] Take the composite material prepared in this example for radiative property characterization, and it is found that the solar band reflectivity of the composite material prepared in this example is as high as 94.9%, and the infrared band emissivity is as high as 91.2%.

[0101] Compare the thermal conductivity of the composite material prepared in this example with that of the pure PVDF-HFP coating material, and it is found that the thermal conductivity increases from 0.146 W·m -1 ·K -1 to 1.32 W·m -1 ·K -1 . Therefore, the composite material (coating material) prepared in this example has more excellent radiative cooling characteristics and thermal conductivity, which is beneficial to the heat dissipation of electronic devices.

[0102] Comparative Example 1

[0103] The same as Example 1, the difference is only that the hollow SiO2@hBN composite particles doped in the coating material are replaced with the same amount of surface-hydroxylated hBN microflakes (i.e., only surface-hydroxylated hBN microflakes are used for doping, keeping the total amount of particles unchanged), and the solar band reflectivity of the coating material is reduced from 89.7% to 83.0%.

[0104] Comparative Example 2

[0105] Same as Example 1, with the only difference being that the surface-hydroxylated hBN micron sheets doped in the coating material are replaced with the same amount of hollow SiO2@hBN composite particles (i.e., only using hollow SiO2@hBN composite particles for doping while keeping the total amount of particles unchanged). The solar-band reflectivity of the coating material decreases from 89.7% to 78.1%, and the thermal conductivity decreases from 0.88 W·m -1 ·K -1 to 0.469 W·m -1 ·K -1 .

[0106] Comparative Example 3

[0107] Same as Example 1, with the only difference being that the hollow SiO2@hBN composite particles doped in the coating material are replaced with the same amount of SiO2 hollow particles. The solar-band reflectivity of the coating material decreases from 89.7% to 79.6%, and the thermal conductivity decreases from 0.88 W·m -1 ·K -1 to 0.693 W·m -1 ·K -1 .

[0108] Comparative Example 4

[0109] Same as Example 1, with the only difference being that the polymer substrate (PVDF-HFP, weight-average molecular weight M w 400,000) in the coating material is replaced with the same amount of polymethyl methacrylate PMMA (weight-average molecular weight M w of 350,000). The infrared-band emissivity of the coating material decreases from 93.1% to 91.1%.

[0110] Comparative Example 5

[0111] Same as Example 1, with the only difference being that the polymer substrate (PVDF-HFP) in the coating material is replaced with the same amount of polydimethylsiloxane PDMS (weight-average molecular weight M w of ~25,000). The emissivity of the coating material decreases from 93.1% to 91.9%.

[0112] The above-described embodiments are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a high thermal conductivity radiation cooling coating material, characterized in that: The following steps are involved: The surface of SiO2 hollow sphere particles with surface amino groups was coated with hBN nanosheets with surface hydroxylation to obtain hollow SiO2@hBN composite particles. Adding surface hydroxylated hBN micron sheets and hollow SiO2@hBN composite particles into a solvent containing a dispersant, dispersing them evenly to obtain a raw material solution, then adding a polymer base solution into the raw material solution, dispersing them evenly and coating them to obtain the high thermal conductivity radiation cooling coating material; the polymer base solution is PVDF-HFP; The preparation method of the hollow SiO2@hBN composite particles specifically comprises: The SiO2 hollow sphere particles are added to an organic solvent solution and dispersed uniformly, the pH is adjusted to acidic to obtain a mixed solution, a silane coupling agent containing an amino group is added to the mixed solution, and the mixture is heated and stirred for reaction to obtain SiO2 hollow sphere particles with surface amino groups; The hBN nanosheets are subjected to high temperature heating treatment in an air atmosphere to obtain surface hydroxylated hBN nanosheets; The SiO2 hollow sphere particles with surface amino groups and the hBN nanosheets with surface hydroxy groups are added into a solvent and dispersed evenly, and then the pH is adjusted to acidic, and the reaction is stirred to obtain the hollow SiO2@hBN composite particles; The particle size of the SiO2 hollow sphere particles is 0.5-5 μm; the amount ratio of the SiO2 hollow sphere particles to the organic solvent in the organic solvent solution is 2-3.5 g: 250-450 mL; the pH of the mixed solution is 5; the volume ratio of the amino-containing silane coupling agent to the mixed solution is (0.5-0.8): (60-100); the temperature of the heating and stirring reaction is 60° C. and the time is 6 hours; The mass ratio of the SiO2 hollow sphere particles with surface amino groups to the hBN nanosheets with surface hydroxylation is (9-12):(5-6); the stirring reaction time is 4 hours; The method for preparing the surface hydroxylated hBN micron sheet comprises the following steps: The hBN microsheets are subjected to high temperature heating treatment in an air atmosphere to obtain surface hydroxylated hBN microsheets; The high temperature heating treatment is performed at a temperature of 1000°C and a time of 3 hours; The usage ratio of the surface hydroxylated hBN micron sheets and hollow SiO2@hBN composite particles is 0.72-1.92 g:0.36-0.96 g; the mass ratio of the total mass of the surface hydroxylated hBN micron sheets and hollow SiO2@hBN composite particles to the mass of the polymer substrate is 1.08-2.88 g:2-4.5 g.

2. A high thermal conductivity radiation cooling coating material prepared by the preparation method according to claim 1.

3. Use of the high thermal conductivity radiation cooling coating material according to claim 2 in the preparation of electronic devices.

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