Silica-coated barium sulfate filler with radiation refrigeration effect and preparation method of silica-coated barium sulfate filler

Abstract

The invention discloses a silicon dioxide coated barium sulfate filler with a radiation refrigeration effect and a preparation method thereof, and belongs to the technical field of building coatings. According to the silicon dioxide coated barium sulfate filler with the radiation refrigeration effect and the preparation method of the silicon dioxide coated barium sulfate filler, provided by the invention, SiO2 nanoparticles formed by hydrolytic condensation of tetraethyl silicate form a full-coating or semi-coating effect on BaSO4 (particularly micron-sized BaSO4) particles, so that the reflecting capacity and scattering capacity of barium sulfate particles are improved; and when the coating is applied to the radiation refrigeration coating, the solar radiation power can be reflected more efficiently, so that the radiation refrigeration power of the coating is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building coatings, and particularly relates to a silica-coated barium sulfate filler with a radiation refrigeration effect and a preparation method thereof. BACKGROUND

[0002] At present, radiation refrigeration coatings show great application prospects in reducing refrigeration costs. In contrast to active refrigeration which needs to be driven by electricity to circulate refrigeration, radiation refrigeration coatings directly emit heat radiation to deep space through the atmospheric window ("sky window") without consuming any energy. Its passivity can alleviate the phenomenon that the air temperature in the city is significantly higher than that in the surrounding suburbs by reducing the temperature of the building, and reduce the emission of CO2 in active refrigeration applications to slow down global warming. This not only meets the requirements of the "double carbon" target, but also is a long-term embodiment of the sustainable development strategy of energy saving and emission reduction to protect the ecological environment.

[0003] Patent application publication CN114231073A discloses a core-shell structure reflective matrix, a daytime radiation refrigeration coating, a coating and a preparation method. The technical path disperses micron-sized inorganic materials in an ethanol-ammonia solution; after sufficient stirring, the ammonium ionized micron-sized inorganic materials are obtained by centrifugal drying; the ammonium ionized micron-sized inorganic materials are added to a binder solution, and ball milling is performed to obtain a mixed solution A; nanometer-sized inorganic materials are added to the mixed solution A, and ball milling is performed to obtain the daytime radiation refrigeration coating. The technical solution coats the nanoparticles on the large particles by simple bonding, but the obtained coating structure is not firm and has poor mechanical resistance. The particle size of the core-shell structure prepared by bonding is not uniform. The technical solution needs to be subjected to a long ball milling process, and the preparation process is complicated and energy-consuming.

[0004] Patent application publication CN117567877A discloses a slurry for a rare earth-based reflective filler for radiation refrigeration coatings and a preparation method thereof. The raw materials of the slurry include, by weight, germanium oxide 20-35 parts, niobium oxide 25-36 parts, rare earth oxide 13-20 parts, and selenium oxide 16-35 parts. The preparation method of the slurry includes: mixing the raw materials, crushing, sintering, then quenching the molten liquid with cold water to obtain a coarse product powder and grinding to obtain A1, A2 and A3 slurries with different particle sizes; another coarse product powder is taken and ground with water, then atomized and dried, and then sintered again to obtain a powder which is dispersed in a solvent to obtain A4 slurry; the A1, A2, A3 and A4 slurries are mixed to obtain the slurry. The slurry has high window emissivity and reflectivity, but the preparation process is complex, energy-consuming and not environmentally friendly.

[0005] Patent application publication CN116947095A discloses a high-solar reflectivity bismuth oxychloride microsphere and its preparation method and application. A bismuth-containing solution is mixed with a chlorine-containing solution to perform a hydrolysis reaction to obtain a precursor, wherein the chlorine-containing solution is prepared by dissolving a chlorine salt into a structural inducer aqueous solution with a mass fraction of <12%, and the bismuth-containing solution is prepared by dissolving a bismuth salt into an acetic acid solution, and the molar ratio of the bismuth salt to the chlorine salt is <1:0.4. Then, the precursor is calcined at a temperature of <500°C to obtain bismuth oxychloride microspheres with an average reflectivity of >85%, and the microspheres prepared by the method have uniform particle sizes. However, the raw materials used are toxic and are not conducive to production and application, and the reflectivity cannot meet the requirements of the required reflectivity of the radiation cooling coating.

[0006] Patent application publication CN113372740A discloses an environmentally friendly high-reflectivity coating material and a preparation method thereof. The invention is prepared by melting, quenching, drying, and ball milling an inorganic environmentally friendly flux, mixing, ball milling, and dispersing titanium dioxide, calcium sulfate, inorganic environmentally friendly flux, zirconium silicate, tin oxide, barium sulfate, high-reflectivity filler, and high-temperature binder, and then performing precipitation, dehydration, drying, and powdering to obtain a blended material. After modification by porosification, the high-reflectivity filler powder is obtained. However, the preparation process is complex, and the raw materials used are expensive. Although the reflectivity of the material can be improved after porosification, the application of the radiation cooling coating will increase the bubbles of the coating, affecting the workability of the coating. SUMMARY

[0007] The purpose of the present application is to overcome the problem of insufficient reflectivity of existing radiation cooling fillers, thereby reducing the cooling power of the coating, and to provide a silica-coated barium sulfate filler with radiation cooling effect and a preparation method thereof, further improving the reflectivity of barium sulfate in the infrared wave band, thereby improving the cooling power of the radiation cooling coating. The present application develops a new coating process and synthesizes a new inorganic hybrid material, without the need for additional binder or calcination. The prepared material has uniform particle size, and the reflectivity of barium sulfate in the ultraviolet and far infrared wave bands is strengthened.

[0008] To solve the above problems, the present application realizes the following technical scheme:

[0009] The first invention of the present application is to:

[0010] A preparation method of a silica-coated barium sulfate filler with radiation cooling effect is provided, which comprises the following preparation steps:

[0011] S1. Pour anhydrous ethanol 50-70 parts by mass, deionized water 10-40 parts by mass, sodium hexametaphosphate 4-10 parts by mass, and BaSO4 4-10 parts by mass into a three-necked flask, and perform ultrasonic dispersion to uniformly disperse the BaSO4;

[0012] S2. Then add the mixed tetraethyl orthosilicate 4-10 parts by mass and anhydrous ethanol 60-80 parts by mass into the constant pressure funnel, then add it to the three-necked flask described in step S1, and continue to stir the reaction;

[0013] S3. After the reaction is completed, the anhydrous ethanol is centrifuged three times, and finally dried in a vacuum drying box to obtain the silica-coated barium sulfate filler (SiO2@BaSO4 material);

[0014] S4. The silica-coated barium sulfate filler obtained after drying in step S3 is ground and used.

[0015] The further optimization of the preparation method of the silica-coated barium sulfate filler with radiation refrigeration effect of the present application is:

[0016] The BaSO4 is micron-sized BaSO4; and / or

[0017] The volume ratio of anhydrous ethanol and deionized water in step S1 is 7:1-8:3; and / or

[0018] The frequency of ultrasonic dispersion in step S1 is 26-28 kHz, and the ultrasonic dispersion time is 10-20 min.

[0019] The further optimization of the preparation method of the silica-coated barium sulfate filler with radiation refrigeration effect of the present application is:

[0020] The molar ratio of tetraethyl orthosilicate and anhydrous ethanol in step S2 is 1:10-1:2; and / or

[0021] The molar ratio of tetraethyl orthosilicate in step S2 and BaSO4 in step S1 is 1:1-3:1.

[0022] The further optimization of the preparation method of the silica-coated barium sulfate filler with radiation refrigeration effect of the present application is:

[0023] The stirring reaction temperature in step S2 is 25-60℃.

[0024] The further optimization of the preparation method of the silica-coated barium sulfate filler with radiation refrigeration effect of the present application is:

[0025] The speed of dropwise addition in step S2 is 50-70 drops / min, the stirring speed of uniform stirring is 200-300 r / min, and the reaction time is 6-12 h.

[0026] The further optimization of the preparation method of the silica-coated barium sulfate filler with radiation refrigeration effect of the present application is:

[0027] The drying temperature in step S3 is 70-90 DEG C, and the drying time is 8-10 hours.

[0028] The further optimization of the preparation method of the silica-coated barium sulfate filler with the radiation refrigeration effect of the application is that:

[0029] The morphology of the BaSO4 includes one or a combination of several of the following: spherical, angular, rod-shaped, flaky, cubic, layered, and spheroidal.

[0030] The further optimization of the preparation method of the silica-coated barium sulfate filler with the radiation refrigeration effect of the application is that:

[0031] The whiteness of the BaSO4 is 90-98%, the brightness is 98-100, and the particle size is 2-10 microns.

[0032] The second invention object of the application is that:

[0033] The silica-coated barium sulfate filler with the radiation refrigeration effect is prepared by the preparation method of the silica-coated barium sulfate filler with the radiation refrigeration effect described above.

[0034] The silica-coated barium sulfate filler with the radiation refrigeration effect of the application is further optimized in that:

[0035] The silica-coated barium sulfate filler with the radiation refrigeration effect is an inorganic particle with a particle size distribution of 3-10 microns, wherein:

[0036] D50 is 2-3 microns, D90 is 3-6 microns; the main component of the inner core is barium sulfate, the main component of the outer shell is silicon dioxide, the coating rate is 5-100%, the size ratio of the core-shell is 15:16-3:11, the blue-white brightness of the particle is 95-97%, the brightness is 98-100; the total solar reflectance (TSR) is 0.96-0.99, the near-infrared reflectance (NIR) is 0.89-0.96, and the ultraviolet reflectance (NUV) is 0.98-1.

[0037] The main technology of the application is that the SiO2 nanoparticles formed by the hydrolysis and condensation of tetraethyl silicate fully or semi-coat the BaSO4 (especially micron-sized BaSO4) particles, thereby improving the reflection and scattering capabilities of the barium sulfate particles, and the application in the radiation refrigeration coating can more efficiently reflect the solar radiation power, thereby improving the radiation refrigeration power of the coating.

[0038] The silica-coated barium sulfate filler with a radiation refrigeration effect (a core-shell structure reflective matrix) of the present application can form a multi-stage scattering structure by forming a composite structure by coating a nanoscale inorganic material on the outer surface of a microscale inorganic material, so as to obtain high-efficiency wide-spectrum sunlight reflection efficiency.

[0039] The silica-coated barium sulfate filler with a radiation refrigeration effect of the present application has the following characteristics and advantages:

[0040] The filler is more hydrophilic after being coated with silica, and has good dispersibility in paint.

[0041] The filler is coated with silica, and the absorption of silica in the ultraviolet band is basically 0, which helps to improve the weather resistance of the coating.

[0042] The filler is coated with silica, and the light-shielding index of silica is high, which improves the whiteness of the filler and helps to improve the hiding power of the coating.

[0043] At room temperature, electromagnetic waves in the atmospheric window band (8-13 μm) are less reflected, absorbed and scattered when passing through the atmosphere. The present application utilizes this characteristic to bring the thermal radiation energy of the ground to outer space as much as possible. The energy distribution of solar photons is 0.49-4.13 eV, and high-quality dielectric particles should have a larger band gap than the energy of solar photons to avoid sunlight absorption. The electron band gap of barium sulfate is as high as 7.2417 eV, which is higher than the photon energy in the solar spectrum, and the barium sulfate particles can avoid the transition phenomenon of photon absorption, and have high reflection ability for different wave bands of solar radiation. And barium sulfate raw materials are cheap and easy to obtain, making it a popular material in radiation refrigeration applications, especially in the field of radiation refrigeration coatings. The band gap of silica is 7.5387 eV, which is higher than the photon energy in the solar spectrum, effectively avoiding the absorption of solar radiation, and silica has high emissivity in the atmospheric window region (8-13 μm). The extinction coefficient of silica in visible light is low, indicating that silica has high reflectivity in the solar radiation band. The present application utilizes the characteristics of barium sulfate and silica to grow silica nanoparticles on the surface of barium sulfate microparticles, thereby improving the reflectivity of the particles in the near-infrared region. At the same time, the special composite structure of silica and barium sulfate makes the light form a multi-stage scattering effect when passing through the particles, further improving the reflectivity of the particles. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 The present application relates to a preparation method of a silica-coated barium sulfate filler with a radiation refrigeration effect;

[0045] Figure 2Reflectivity graphs of the silica powder, alumina powder, barium sulfate powder, and silica-coated barium sulfate powder (SiO2@BaSO4) in the range of 200-2500 nm. DETAILED DESCRIPTION

[0046] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application is described in detail below with specific examples. It should be understood that the specific examples described herein are only used to explain the present application and are not limited to the present application. Any simple improvement to the preparation method of the present application under the concept of the present application falls within the scope of protection of the present application.

[0047] The raw material information involved in the following examples and comparative examples is as follows:

[0048] The tetraethyl orthosilicate solution is provided by Shanghai Maikelin Biochemical Technology Co., Ltd., AR 99%, CAS number 78-10-4, which can be used directly without further treatment.

[0049] The anhydrous ethanol is provided by Shanghai Titan Science and Technology Co., Ltd., AR 99.9%, CAS number 64-17-5.

[0050] The barium sulfate, silicon oxide and alumina powder are provided by Shanghai Aladdin Biochemical Technology Co., Ltd., AR 99.9%.

[0051] The sodium hexametaphosphate is provided by Shanghai Aladdin Biochemical Technology Co., Ltd., AR 99%, CAS number 10124-56-8.

[0052] Example 1

[0053] A preparation method of a silica-coated barium sulfate filler with a radiation refrigeration effect, comprising the following preparation steps:

[0054] S1. uniformly dispersing barium sulfate in anhydrous ethanol and water as solvents:

[0055] According to the proportion, pour 700 mL of anhydrous ethanol, 200 mL of deionized water, 4 g of sodium hexametaphosphate and 8 g of BaSO4 into a three-necked flask, and perform ultrasonic dispersion to uniformly disperse BaSO4 in the solvent;

[0056] The frequency of ultrasonic dispersion in step S1 is 28 kHz, and the ultrasonic dispersion time is 20 min;

[0057] S2. Then add uniformly mixed tetraethyl orthosilicate 4 g and anhydrous ethanol 800 mL into a constant pressure funnel, then drop it into the three-necked flask described in step S1, and continuously stir the reaction;

[0058] The dropping speed in step S2 is 50 drops / min, the stirring speed for uniform stirring is 200 r / min, and the reaction time is 10 h.

[0059] The stirring reaction temperature in step S2 is 25℃.

[0060] S3. After the reaction is completed, the silica-coated barium sulfate filler (SiO2@BaSO4 material) is obtained by centrifugal washing with anhydrous ethanol three times and finally drying in a vacuum drying oven.

[0061] The centrifugal speed is 8000 r / min, and the centrifugal time is 5 min.

[0062] The drying temperature in step S3 is 70℃, and the drying time is 8 h.

[0063] S4. The silica-coated barium sulfate filler obtained after step S3 is dried and then used after being ground.

[0064] Example 2

[0065] The difference between Example 2 and Example 1 is only that:

[0066] The amount of tetraethyl orthosilicate added in step S2 is 8 g (the mass ratio of BaSO4 to tetraethyl orthosilicate is 1:1).

[0067] The stirring reaction temperature in step S2 is 50℃.

[0068] The dropping speed in step S2, the stirring speed for uniform stirring, and the reaction time are the same as in Example 1, and the reaction time is 6 h.

[0069] The drying temperature in step S3 is 80℃.

[0070] Example 3

[0071] The amount of tetraethyl orthosilicate added in step S2 is 12 g (the mass ratio of BaSO4 to tetraethyl orthosilicate is 2:3).

[0072] The stirring reaction temperature in step S2 is 60℃.

[0073] The dropping speed in step S2 is 30 drops / min, and the stirring speed for uniform stirring and the reaction time are the same as in Example 1.

[0074] The drying temperature in step S3 is 80℃.

[0075] Comparative Example 1

[0076] The difference between Example 1 and Comparative Example 1 is that:

[0077] The SiO2@BaSO4 material was used in Example 1.

[0078] Comparative Example 1 is a barium sulfate powder without coating modification according to the present application.

[0079] Comparative Example 2

[0080] The difference between Example 1 and Comparative Example 2 is that:

[0081] The SiO2@BaSO4 material was used in Example 1.

[0082] Comparative Example 2 is an alumina powder without coating modification according to the present application.

[0083] Comparative Example 3

[0084] The difference between Example 1 and Comparative Example 3 is that:

[0085] The SiO2@BaSO4 material was used in Example 1.

[0086] Comparative Example 3 is a silica powder.

[0087] Comparative Example 4

[0088] The difference between Example 1 and Comparative Example 4 is that:

[0089] The SiO2@BaSO4 material was used in Example 1.

[0090] Comparative Example 4 is a physical mixture powder of silica and barium sulfate.

[0091] The performance tests of the above examples and comparative examples are as follows:

[0092] 1. The whiteness of the examples and comparative examples was tested on a whiteness meter according to the standard method of GB / T 23774-2009;

[0093] 2. The particle size of the examples and comparative examples was tested by laser particle size according to the standard method of GB / T 19077-2016;

[0094] 3. The solar reflectance of the powder was tested by UV-Vis ultraviolet spectrophotometer, and the solar reflectance (TSR), infrared band reflectance (NIR), visible light band reflectance (VIS), and ultraviolet reflectance (NUV) were calculated;

[0095] 4. The coating rate of the powder was tested and calculated by X-ray fluorescence spectrometer (XRF);

[0096] 5. The core-shell ratio of the powder was tested and calculated by SEM (scanning electron microscope)-EDS (energy dispersive spectrometer);

[0097] 6. The lightness of the powder was tested by Datacolor colorimeter.

[0098] 7. The oil absorption of the powder was tested by GB / T 5211.15-2014 "Pigments and Extenders-General Test Methods-Part 15: Determination of Oil Absorption", unit: ml / 100g.

[0099] The data obtained from the above performance tests are recorded in Table 1.

[0100]

[0101] The D50 of the SiO2@BaSO4 material described in Example 1 was 2-3 μm, and the D90 was 3-5 μm;

[0102] The D50 of the SiO2@BaSO4 material described in Example 2 was 2-3 μm, and the D90 was 3-6 μm;

[0103] The D50 of the SiO2@BaSO4 material described in Example 3 was 2-3 μm, and the D90 was 3-6 μm;

[0104] The D50 of the powder described in Comparative Example 1 was 3-5 μm, and the D90 was 5-7 μm;

[0105] The D50 of the powder described in Comparative Example 2 was 0.3-0.6 μm, and the D90 was 0.6-0.9 μm;

[0106] The D50 of the powder described in Comparative Example 3 was 2-3 μm, and the D90 was 3-7 μm;

[0107] The D50 of the powder described in Comparative Example 4 was 2-5 μm, and the D90 was 5-7 μm.

[0108] From the results of the above examples and comparative examples, it can be seen that Comparative Example 1 is uncoated barium sulfate, which has poor reflectivity in the infrared part, and the energy of the infrared band accounts for a very high proportion in sunlight, which will cause it to absorb a large amount of solar radiation and cause heating, which is not conducive to its use in radiative cooling coatings. The barium sulfate coated with silicon dioxide has a significant improvement in reflectivity in the infrared part, and when used in radiative cooling coatings, it will exhibit better daytime cooling effect.

[0109] Comparative Example 2 is an alumina powder, which, although close to the example in various optical properties, must reach the nanometer level in particle size to achieve the same effect, so the oil absorption is extremely high, which may cause the viscosity to be too high in the paint, or other problems such as not being able to be added, and cannot be used. The example can achieve the effect at the micron level, and even if a large amount is added in the paint, it will not have a negative effect such as too high viscosity.

[0110] Comparative Example 3 is a silica powder, which has a higher reflectivity in the infrared, but has a lower reflectivity in the visible light range and a lower whiteness. If used in paint, on the one hand, it will absorb more energy in the visible light band (related to visible light reflectivity), and on the other hand, it will cause the paint hiding power and whiteness to be insufficient (related to whiteness). When used in paint, the example can ensure a higher visible light reflectivity, i.e., a refrigeration effect, and can also ensure a higher paint hiding power and whiteness, which is more practical in designing paint formulations.

[0111] Comparative Example 4 is a physically blended powder of silica and barium sulfate, which does not improve the solar reflectivity and whiteness.

[0112] In summary, the above is only a preferred example of the present application, and does not limit the present application in any form; any skilled person in the art can make some changes, modifications and equivalent changes to the disclosed technical content without departing from the scope of the technical solutions of the present application, and all equivalent examples of the present application are considered to be equivalent examples of the present application; at the same time, any equivalent changes, modifications and evolution of the above examples according to the essential technology of the present application are still within the protection scope of the technical solutions of the present application.

[0113] The technical features of the above-described examples can be combined in any way. To make the description concise, not all possible combinations of the technical features in the above examples are described, but as long as the combinations of the technical features do not exist, they should be considered as the scope of the description.

[0114] Unless otherwise specified, the experimental methods in the present application are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0115] Unless otherwise specified, the various optimized technical solutions in the present application can be combined with each other.

[0116] Unless otherwise specified, percentages and parts are weight percentages and weight parts.

[0117] Unless otherwise specified, the experimental methods in the present application are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0118] Various starting materials, reagents, components, and the like, used in the present application are those known in the art and are commercially available unless otherwise indicated.

[0119] Unless otherwise defined, 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 application belongs. Furthermore, all methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application.

Claims

1. A method for preparing a silica-coated barium sulfate filler with a radiative refrigeration effect, the method comprising the following preparation steps: S1.pouring anhydrous ethanol 50-70 parts by mass, deionized water 10-40 parts by mass, sodium hexametaphosphate 4-10 parts by mass, and BaSO4 4-10 parts by mass into a three-necked flask, and performing ultrasonic dispersion to uniformly disperse the BaSO4; S2.subsequently adding uniformly mixed tetraethyl orthosilicate 4-10 parts by mass and anhydrous ethanol 60-80 parts by mass into a constant pressure funnel, and then dropping the mixture into the three-necked flask of step S1, and continuously stirring and reacting; S3.after the reaction is completed, washing the product with anhydrous ethanol by centrifugation three times, and finally drying in a vacuum drying oven to obtain the silica-coated barium sulfate filler; and S4.after the silica-coated barium sulfate filler obtained in step S3 is dried, grinding the filler and using the ground filler. 2.The method for preparing a silica-coated barium sulfate filler with a radiative refrigeration effect according to claim 1, wherein: the BaSO4 is micron-sized BaSO4; and / or the volume ratio of the anhydrous ethanol and the deionized water in step S1 is 7:1-8:3; and / or the ultrasonic dispersion in step S1 is performed at a frequency of 26-28 kHz for 10-20 min. 3.The method for preparing a silica-coated barium sulfate filler with a radiative refrigeration effect according to claim 1, wherein: the molar ratio of the tetraethyl orthosilicate and the anhydrous ethanol in step S2 is 1:10-1:2; and / or the molar ratio of the tetraethyl orthosilicate and the BaSO4 in step S1 in step S2 is 1:1-3:

1. 4.The method for preparing a silica-coated barium sulfate filler with a radiative refrigeration effect according to claim 1, wherein: the stirring and reaction temperature in step S2 is 25-60℃. 5.The method for preparing a silica-coated barium sulfate filler with a radiative refrigeration effect according to claim 1, wherein: the dropping speed in step S2 is 50-70 drops / min, the stirring speed is 200-300 r / min, and the reaction time is 6-12 h. 6.The method for preparing a silica-coated barium sulfate filler with a radiative refrigeration effect according to claim 1, wherein: the drying temperature in step S3 is 70-90℃, and the drying time is 8-10 h. 7.The method for preparing a silica-coated barium sulfate filler with a radiative refrigeration effect according to claim 1, wherein: the morphology of the BaSO4 includes one or a combination of spherical, angular, rod-shaped, flaky, cubic, layered, and spheroidal shapes. 8.The method for preparing a silica-coated barium sulfate filler with a radiative refrigeration effect according to claim 1, wherein: the whiteness of the BaSO4 is 90-98%, the brightness is 98-100, and the particle size is 2-10 μm. 9.A silica-coated barium sulfate filler with a radiative refrigeration effect, wherein: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The silica-coated barium sulfate filler with the radiation refrigeration effect is prepared by the preparation method of the silica-coated barium sulfate filler with the radiation refrigeration effect according to any one of claims 1-8.

10. The silica-coated barium sulfate filler with the radiation refrigeration effect according to claim 9, wherein: The inorganic particles have a particle size distribution of 3-10 μm, wherein: The D50 is 2-3 μm, the D90 is 3-6 μm, the main component of the core is barium sulfate, the main component of the shell is silica, the coating rate is 5-100%, the size ratio of the core-shell is 15:16-3:11, the blue-white brightness of the particles is 95-97%, the brightness is 98-100, the total solar reflectance is 0.96-0.99, the near-infrared reflectance is 0.89-0.96, and the ultraviolet reflectance is 0.98-1.

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