Low-melting-point rare-earth glass microspheres, radiation-cooling coatings and their preparation methods

Abstract

This invention provides low-melting-point rare-earth glass microspheres, a radiation-cooling coating, and a preparation method. The glass microspheres can be prepared by direct vitrification sintering, a simple method requiring minimal materials and suitable for mass production. The introduction of high-performance rare-earth oxides and other materials during preparation results in higher emission and reflection properties compared to existing silica microspheres. Using these rare-earth glass microspheres instead of silica microspheres as fillers further enhances heat dissipation.

Description

Technical Field

[0001] This invention belongs to the field of glass microspheres, and in particular relates to a low melting point rare earth glass microsphere, a radiation cooling coating, and a preparation method thereof. Background Technology

[0002] Silica microspheres are a commonly used filler to achieve high heat dissipation performance by enhancing emission. Due to the Furlich effect, silica microspheres exhibit significant emission performance at a wavelength of 9 μm. In existing technologies, silica microspheres are often prepared using the sol-gel method, which is complex and has low yield, thus limiting the production and application of silica microspheres. Summary of the Invention

[0003] In view of this, the present invention aims to propose a low-melting-point rare-earth glass microsphere, a radiation cooling coating, and a preparation method. The glass microsphere can replace the commonly used silica microsphere as a high-emission filler, and has the advantages of simple process, suitability for mass production, and excellent thermal conductivity and emission performance. It represents a further metamaterialization of silica microspheres. It can also be used as a filler in heat dissipation materials or coatings to enhance heat dissipation.

[0004] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0005] A low-melting-point rare-earth glass microsphere is prepared from raw materials comprising the following parts by weight: 40-65 parts bismuth oxide, 15-30 parts lanthanum cerium oxide, 7-10 parts tellurium-doped boron oxide, 2-5 parts silicon dioxide, 7-10 parts selenium-doped aluminum hydroxide, and 1-3 parts alkali metal; the alkali metal being one of Na2O and K2O.

[0006] Furthermore, lanthanum cerium oxide is prepared by the following method:

[0007] S11. Weigh cerium chloride and lanthanum chloride, add deionized water, and prepare a lanthanum chloride and cerium chloride solution.

[0008] S12. Heat and stir the lanthanum chloride and cerium chloride solution, add ammonia water until precipitation is complete, and continue the reaction for 3-8 hours, then allow it to settle at room temperature for 10-20 hours.

[0009] S13. The precipitate is filtered, washed and dried to obtain lanthanum cerium hydroxide powder;

[0010] S14. Calcining lanthanum cerium hydroxide yields lanthanum cerium oxide powder.

[0011] Furthermore, in step S11, the molar ratio of cerium chloride to lanthanum chloride is 80:1-10:1, and the concentration of the prepared lanthanum chloride-cerium solution is 0.3-1 mol / L;

[0012] In step S12, the heating temperature is 60-100℃;

[0013] In step S14, the calcination temperature is 400-900℃ and the time is 3-6h.

[0014] Furthermore, tellurium-doped boron oxide is prepared by the following method:

[0015] S21. Dissolve telluric acid in deionized water to prepare a telluric acid solution;

[0016] S22. Dissolve boric acid in anhydrous ethanol to prepare a boric acid solution;

[0017] S23. Add a small amount of 65% nitric acid to the boric acid solution as a hydrolysis catalyst to maintain pH=2-3;

[0018] S24. Add the telluric acid solution obtained in step S21 dropwise to the boric acid solution obtained in step S23.

[0019] S25. Transfer the reacted solution to a sealed container and let it stand at 40-80℃ for 24-48 hours to complete gelation.

[0020] S26. The system after the above reaction is separated by filtration. The solid component is dried overnight at 100-160℃ and then calcined at 400-550℃ under nitrogen protection for 4-6 hours with the heating rate controlled at 2-5℃ / min. After calcination, it is cooled in the furnace to obtain tellurium-doped boron oxide.

[0021] Furthermore, in step S21, the concentration of the telluric acid solution is 0.05 mol / L;

[0022] In step S22, the concentration of the boric acid solution is 0.5 mol / L, and after adding the boric acid, it is placed in a water bath at 80°C and magnetically stirred to ensure complete dissolution.

[0023] In step S24, the amount of telluric acid solution used is 80-150 mL, the amount of boric acid solution used is 150 mL, the dropping rate is controlled at 0.5-2 mL / min, and the mixture is stirred at a constant temperature of 80℃ for 3-5 hours.

[0024] Furthermore, selenium-doped aluminum hydroxide was prepared by the following method:

[0025] S31. Dissolve AlCl3·6H2O in deionized water to prepare an AlCl3 solution, and dissolve Na2SeO3 in water to prepare a Na2SeO3 solution.

[0026] S32. Mix the above AlCl3 solution and Na2SeO3 solution, and stir in a water bath at 40-80℃.

[0027] S33. Add NaOH solution dropwise to the mixed solution, control the pH to 9.0±0.2, and a white gelatinous precipitate will form. Continue stirring for 2-4 hours.

[0028] S34. Wash the precipitate with deionized water at 60-90℃ until the conductivity of the filtrate is <50μS / cm, and then wash it with ethanol three times or more.

[0029] S35. Freeze-dry for 20-36 hours to obtain a white powder—selenium-doped aluminum hydroxide.

[0030] Furthermore, the concentration of the AlCl3 solution prepared in step S31 is 0.2 mol / L, and the concentration of the Na2SeO3 solution is 0.02 mol / L;

[0031] In step S32, the volume ratio of AlCl3 solution to Na2SeO3 solution is 1:1-2.

[0032] The present invention also provides a method for preparing low-melting-point rare-earth glass microspheres as described above, the method comprising the following steps:

[0033] S41. Weigh and mix the low-melting-point rare earth glass microsphere raw materials according to the proportion to obtain a mixed powder.

[0034] S42. Place the mixed powder obtained in step S41 into a furnace with stirring, heat it to 1000~1200℃ to make glass melt, continue heating and stirring for 3-6 hours.

[0035] S43. Pour the glass melt into a mold and cast it into shape, and anneal it at 400-500℃ for 2-4 hours to obtain a glass ingot;

[0036] S44. After the glass frit is initially crushed, it is poured into a ball mill jar and ground thoroughly to obtain glass powder;

[0037] S45. The obtained glass powder is made into glass microspheres by floating electrothermal beading method. The furnace temperature is 700-800℃, the heating time is 20-40s, and the dust-carrying airflow pressure is 0.5-3MPa.

[0038] Furthermore, in step S42, the furnace temperature is 1050-1080℃, and the heating time is 4.5-5 hours; preferably, the heating temperature and time can make the glass molten block reach a denser state;

[0039] In step S44, the particle size D of the glass powder after ball milling 90 The thickness is below 4μm, thus ensuring that the glass powder can quickly form a molten state at the melting temperature;

[0040] In step S45, when the heating time is 40s and the dust-carrying gas pressure is 2.6-3MPa, primary distribution rare earth glass microspheres with a particle size of 0.8-1.2μm are prepared; when the heating time is 34s and the dust-carrying gas pressure is 1.8-2.2MPa, secondary distribution rare earth glass microspheres with a particle size of 1.8-2.2μm are prepared; when the heating time is 20s and the dust-carrying gas pressure is 0.5-1MPa, tertiary distribution rare earth glass microspheres with a particle size of 3.8-4.2μm are prepared.

[0041] The present invention also provides a radiation cooling coating, which comprises the following raw materials in parts by weight: 82-88 parts of styrene-acrylic emulsion, 8-10 parts of rare earth glass microsphere heat dissipation filler, 1-2 parts of silane coupling agent, 0.5-1 parts of wetting agent, 0.2-0.4 parts of dispersant, 0.1-0.15 parts of film-forming agent, 0.1-0.25 parts of defoamer, 0.1-0.5 parts of thickener, 1-3 parts of ultraviolet absorber, and 0.5-1 parts of antioxidant; wherein, the rare earth glass microsphere heat dissipation filler comprises three types of rare earth glass microspheres with different particle size distributions, namely primary distribution 0.8~1.2μm, secondary distribution 1.8~2.2μm, and tertiary distribution 3.8~4.2μm, the primary, secondary, and tertiary distributions are mixed in a mass ratio of 1:1:1, and the rare earth glass microspheres are the low melting point rare earth glass microspheres described above.

[0042] Rare earth glass microsphere heat dissipation fillers require narrow particle size distributions within different ranges. Therefore, by adjusting the dust-carrying airflow pressure and heating time according to different particle size requirements, microspheres of different sizes can be obtained. To ensure narrow particle size, the obtained glass microspheres are further sorted.

[0043] Furthermore, the silane coupling agent is one or more of Momentive A-1706, A-187, 1170, Huitu H-6042, and KH450;

[0044] The wetting agent is one or more of CF-10, X-405, PE-100, YMY-670 and TEGO Twin 4100;

[0045] The dispersant is one or more of CD-904, KYC-917, DISPERBYK-180, DISPERBYK-182, DISPERBYK-190, and DISPERBYK-199;

[0046] The film-forming agent is one or more of Fexanol 1951, sc-34, dodecyl alcohol ester, V-216 and N138;

[0047] The defoamer is one or more of TEGO 810, DF-2665, DF-2854, BYK-011 and BYK-021;

[0048] The thickener is one or more of CO-1358, CO-1059, 350D, PTF R-024, and Zhongwan R-725;

[0049] The ultraviolet absorber is one or more of UV-1300, UV-106, UV-400, Tinuvin 123, and Tinuvin 400-DW(N);

[0050] The antioxidant is one or more of pownox-138, YOUNGING BHT, Irganox EL 1291, JADEWIN TNPP, and KYJ-101.

[0051] The preparation method of the radiation cooling coating is as follows:

[0052] The above raw materials are mixed sequentially and subjected to rapid and thorough mechanical stirring. The resulting coating is sprayed onto the substrate using a spray gun and left overnight to obtain a radiation cooling coating containing rare earth glass microsphere heat dissipation filler.

[0053] Compared with existing technologies, the low-melting-point rare-earth glass microspheres, radiation-cooling coating, and preparation method described in this invention have the following advantages:

[0054] (1) The low-melting-point rare-earth glass microspheres described in this invention have low melting point characteristics compared to ordinary silica microsphere fillers. Therefore, they can be prepared by the floating electrothermal bead formation method, which is simpler and suitable for mass production. At the same time, the rare-earth glass microspheres have better performance than silica microspheres. They are a further metamaterialization of silica microspheres and have better emission performance, thus the heat dissipation effect is more obvious.

[0055] (2) The low-melting-point rare-earth glass microspheres of the present invention contain rare-earth components lanthanum and cerium oxide, as well as alkali metals for fluxing and Al(OH)3 for inhibiting crystallization. In the synthesis composition, B2O3 is doped with Te and Al(OH)3 is doped with Se. These two elements can introduce a large number of non-bridging oxygen bonds into the system, reducing the overall network connectivity and rigidity, which helps to reduce phonon scattering at the interface and improve the overall thermal conductivity of the glass.

[0056] (3) The rare earth glass microspheres described in this invention are made of low melting point glass with a melting temperature of 1000~1200℃. Therefore, they can be directly prepared by vitrification sintering without the need for the complex sol-gel method. The preparation method is simpler, and the yield is high and the process is stable, which improves production efficiency.

[0057] (4) The rare earth glass microspheres described in this invention are used as fillers to make coatings with an emissivity of ≥95%. Attached Figure Description

[0058] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0059] Figure 1 Evaluation of the heat dissipation performance of the cooling radiation coatings prepared for the examples and comparative examples;

[0060] Figure 2 This is a heat dissipation evaluation system. Detailed Implementation

[0061] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0062] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0063] Example 1

[0064] A low-melting-point rare-earth glass microsphere is prepared from raw materials comprising the following parts by weight: 60 parts bismuth oxide, 20 parts lanthanum cerium oxide, 8 parts tellurium-doped boron oxide, 4 parts silicon dioxide, 7 parts selenium-doped aluminum hydroxide, and 1 part alkali metal Na2O.

[0065] I. Preparation of Lanthanum-Cerium Oxide:

[0066] S11. Weigh cerium chloride and lanthanum chloride at a molar ratio of 50:1, add deionized water, and prepare a 0.5 mol / L lanthanum chloride solution.

[0067] S12. The lanthanum chloride solution was heated and stirred at 80°C, and ammonia was added until precipitation was complete. The reaction was continued for 4 h, and then the solution was allowed to settle at room temperature for 12 h.

[0068] S13. The precipitate is filtered, washed and dried to obtain lanthanum cerium hydroxide powder;

[0069] S14. Lanthanum cerium hydroxide is calcined at 500℃ for 3 hours to obtain lanthanum cerium oxide powder with a La / Ce (molar ratio) of 0.02.

[0070] II. Preparation of tellurium-doped boron oxide

[0071] S21. Dissolve telluric acid in deionized water to prepare a 0.05 mol / L telluric acid solution;

[0072] S22. Dissolve boric acid in anhydrous ethanol to prepare a 0.5 mol / L boric acid solution. Heat the solution in a water bath at 80°C with magnetic stirring until it is completely dissolved.

[0073] S23. Add a small amount of 65% nitric acid to the boric acid solution as a hydrolysis catalyst to maintain pH=2-3;

[0074] S24. Add 150 mL of telluric acid solution dropwise to 150 mL of boric acid solution, controlling the dropping rate to about 1 mL / min, and stir at 80 °C for 4 hours.

[0075] S25. Transfer the reacted solution to a sealed container and let it stand at 40°C for 48 hours to complete gelation.

[0076] S26. The system after the above reaction is separated by filtration. The solid component is dried at 150°C overnight and then calcined at 450°C under nitrogen protection for 4 hours. The heating rate is controlled at 3°C / min. After calcination, the system is cooled in the furnace to obtain tellurium-doped boron oxide.

[0077] III. Preparation of selenium-doped aluminum hydroxide

[0078] S31. Dissolve AlCl3·6H2O in deionized water to prepare a 0.2 mol / L AlCl3 solution, and dissolve Na2SeO3 in water to prepare a 0.02 mol / L Na2SeO3 solution.

[0079] S32. Mix the above AlCl3 solution and Na2SeO3 solution at a volume ratio of 1:2 and stir in a water bath at 60°C.

[0080] S33. Add NaOH solution dropwise to the mixed solution, control the pH to 9.0±0.2, and a white gel-like precipitate will form. Continue stirring for 2 hours.

[0081] S34. The precipitate is washed with deionized water at 60℃ until the conductivity of the filtrate is <50μS / cm, and then washed with ethanol three or more times.

[0082] S35. After freeze-drying for 24 hours, a white powder—selenium-doped aluminum hydroxide—is obtained.

[0083] IV. Preparation of low-melting-point rare-earth glass microspheres

[0084] S41. Weigh the above glass microsphere raw materials according to the proportion and mix them thoroughly to obtain a mixed powder;

[0085] S42. Place the mixed powder in a furnace with stirring, heat it to 1060℃ to form a glass melt, continue heating and stirring for 4.5 hours.

[0086] S43. Pour the glass melt into a mold and cast it into shape, and anneal it at 500°C for 2 hours to obtain a glass molten block;

[0087] S44. After initially breaking the glass frit, pour it into a ball mill jar and grind it thoroughly until D. 90 <4μm, glass powder is obtained;

[0088] S45. The obtained glass powder is used to form glass microspheres by floating electrothermal beading method. The furnace cavity is heated to 800℃, and the heating time is controlled at 40s, 34s ​​and 20s respectively. The corresponding dust-carrying gas flow pressure is 3 MPa, 2 MPa and 0.75 MPa respectively. The corresponding glass microsphere particle sizes are 0.8-1.2μm, 1.8-2.2μm and 3.8-4.2μm respectively, which correspond to primary distribution rare earth glass microspheres, secondary distribution rare earth glass microspheres and tertiary distribution rare earth glass microspheres respectively.

[0089] V. Preparation of rare earth glass microsphere heat dissipation filler

[0090] Three rare earth glass microspheres with different particle size distributions were mixed in a mass ratio of 1:1:1 to obtain rare earth glass microsphere heat dissipation filler.

[0091] A radiation-cooling coating containing rare-earth glass microspheres, the coating comprising the following raw materials in parts by weight:

[0092] 87 parts of styrene-acrylic emulsion;

[0093] Eight parts of rare earth glass microsphere heat dissipation filler;

[0094] One part of Momentive A-1706 silane coupling agent;

[0095] Wetting agent CF-10 0.6 parts;

[0096] 0.2 parts of dispersant KYC-917;

[0097] Film-forming agent Fexanol 1951, 0.12 parts;

[0098] 0.2 parts of defoamer TEGO 810;

[0099] Thickener CO-1358 0.2 parts;

[0100] UV absorber UV-1300, 2 parts;

[0101] Antioxidant Pownox-138, 0.68 parts.

[0102] In preparing the radiation cooling coating, the above raw materials are mixed in the order of weight parts and subjected to rapid and thorough mechanical stirring. The resulting coating is sprayed onto the substrate with a spray gun to a thickness of about 20 μm. After being left overnight, a radiation cooling coating containing rare earth glass microsphere heat dissipation filler is obtained.

[0103] Example 2

[0104] A low-melting-point rare-earth glass microsphere is prepared from raw materials comprising the following parts by weight: 45 parts bismuth oxide, 30 parts lanthanum cerium oxide, 9 parts tellurium-doped boron oxide, 5 parts silicon dioxide, 9 parts selenium-doped aluminum hydroxide, and 2 parts alkali metal Na2O.

[0105] I. Preparation of lanthanum cerium oxide:

[0106] S11. Weigh cerium chloride and lanthanum chloride at a molar ratio of 20:1, add deionized water, and prepare a 0.8 mol / L lanthanum chloride solution.

[0107] S12. The lanthanum chloride solution was heated and stirred at 100°C, and ammonia was added until precipitation was complete. The reaction was continued for 6 h, and then the solution was allowed to settle at room temperature for 15 h.

[0108] S13. The precipitate is filtered, washed and dried to obtain lanthanum cerium hydroxide powder;

[0109] S14. Lanthanum cerium hydroxide is calcined at 800℃ for 3 hours to obtain lanthanum cerium oxide powder with a La / Ce (molar ratio) of 0.05.

[0110] II. Preparation of tellurium-doped boron oxide

[0111] S21. Dissolve telluric acid in deionized water to prepare a 0.05 mol / L telluric acid solution;

[0112] S22. Dissolve boric acid in anhydrous ethanol to prepare a 0.5 mol / L boric acid solution. Incubate the solution in a water bath at 80°C with magnetic stirring until completely dissolved.

[0113] S23. Add a small amount of 65% nitric acid to the boric acid solution as a hydrolysis catalyst to maintain pH=2-3;

[0114] S24. Add 80 mL of telluric acid solution dropwise to 150 mL of boric acid solution, controlling the dropping rate to about 1 mL / min, and stir at 80 °C for 4 hours.

[0115] S25. Transfer the reacted solution to a sealed container and let it stand at 40°C for 48 hours to complete gelation.

[0116] S26. The system after the above reaction is separated by filtration. The solid component is dried at 150°C overnight and then calcined at 450°C under nitrogen protection for 4 hours. The heating rate is controlled at 3°C / min. After calcination, the system is cooled in the furnace to obtain tellurium-doped boron oxide.

[0117] III. Preparation of selenium-doped aluminum hydroxide

[0118] S31. Dissolve AlCl3·6H2O in deionized water to prepare a 0.2 mol / L AlCl3 solution, and dissolve Na2SeO3 in water to prepare a 0.02 mol / L Na2SeO3 solution.

[0119] S32. Mix the above AlCl3 solution and Na2SeO3 solution at a volume ratio of 1:1 and stir in a water bath at 60°C.

[0120] S33. Add NaOH solution dropwise to the mixed solution, control the pH to 9.0±0.2, and a white gelatinous precipitate will form. Continue stirring for 4 hours.

[0121] S34. The precipitate is washed with deionized water at 60℃ until the conductivity of the filtrate is <50μS / cm, and then washed with ethanol three or more times.

[0122] S35. After freeze-drying for 24 hours, a white powder—selenium-doped aluminum hydroxide—is obtained.

[0123] IV. Preparation of low-melting-point rare-earth glass microspheres

[0124] S41. Weigh the above glass microsphere raw materials according to the proportion and mix them thoroughly to obtain a mixed powder;

[0125] S42. Place the mixed powder in a furnace with stirring, heat it to 1070°C to form a glass melt, continue heating and stirring for 5 hours.

[0126] S43. Pour the molten glass into a mold and cast it into shape, then anneal it at 500°C for 3.5 hours to obtain a glass molten block;

[0127] S44. After initially breaking the glass frit, pour it into a ball mill jar and grind it thoroughly until D. 90 <4μm, glass powder is obtained;

[0128] S45. The obtained glass powder is used to form glass microspheres by floating electrothermal beading method. The furnace cavity is heated to 800℃, and the heating time is controlled at 40s, 34s ​​and 20s respectively. The corresponding dust-carrying gas flow pressure is 2.7 MPa, 1.8 MPa and 1 MPa respectively. The corresponding glass microsphere particle sizes are 0.8-1.2μm, 1.8-2.2μm and 3.8-4.2μm respectively, which correspond to primary distribution rare earth glass microspheres, secondary distribution rare earth glass microspheres and tertiary distribution rare earth glass microspheres respectively.

[0129] V. Preparation of rare earth glass microsphere heat dissipation filler

[0130] Three rare earth glass microspheres with different particle size distributions were mixed in a mass ratio of 1:1:1 to obtain rare earth glass microsphere heat dissipation filler.

[0131] A radiation-cooling coating containing rare-earth glass microspheres, the coating comprising the following raw materials in parts by weight:

[0132] 83 parts of styrene-acrylic emulsion;

[0133] 10 parts of rare earth glass microsphere heat dissipation filler;

[0134] 2 parts of silane coupling agent KH450;

[0135] 0.75 parts of TEGO Twin 4100 wetting agent;

[0136] Dispersant DISPERBYK-180 0.35 parts;

[0137] Film-forming agent: 0.15 parts of dodecyl alcohol ester;

[0138] Defoamer BYK-011 0.25 parts;

[0139] Thickener PTF R-024 0.2 parts;

[0140] 2.5 parts of Tinuvin 123, an ultraviolet absorber;

[0141] Antioxidant Irganox EL 1291 0.8 parts.

[0142] In preparing the radiation cooling coating, the above raw materials are mixed in the order of weight parts and subjected to rapid and thorough mechanical stirring. The resulting coating is sprayed onto the substrate with a spray gun to a thickness of about 35 μm. After being left overnight, a radiation cooling coating containing rare earth glass microsphere heat dissipation filler is obtained.

[0143] Comparative Example 1

[0144] This comparative example follows the same steps as Example 1, except that boron oxide without tellurium doping was used when preparing the glass microspheres.

[0145] Comparative Example 2

[0146] This comparative example follows the same steps as Example 1, except that undoped aluminum hydroxide was used when preparing the glass microspheres.

[0147] Comparative Example 3

[0148] This comparative example follows the same steps as Example 1, except that lanthanum oxide and cerium oxide are not added during the preparation of glass microspheres.

[0149] Comparative Example 4

[0150] This comparative example uses 4μm SiO2 microspheres as filler, and the method for preparing the coating is the same as in Example 1, except that 4μm SiO2 microspheres are used instead of rare earth glass microsphere heat dissipation filler.

[0151] Comparative Example 5

[0152] This comparative example follows the same steps as Example 1, except that when preparing lanthanum cerium oxide, cerium chloride and lanthanum chloride are weighed in a molar ratio of 5:1, that is, the final synthesized lanthanum cerium oxide has a La / Ce (molar ratio) of 0.2.

[0153] Comparative Example 6

[0154] The steps in this comparative example are the same as in Example 1, except that the amount of telluric acid used is reduced to 40 mL when preparing tellurium-doped boron oxide, resulting in a lower tellurium content.

[0155] Comparative Example 7

[0156] This comparative example follows the same steps as Example 1, except that AlCl3 solution and Na2SeO3 solution are mixed at a volume ratio of 2:1 when preparing selenium-doped aluminum hydroxide.

[0157] Comparative Example 8

[0158] This comparative example follows the same steps as Example 1, except that it uses low-melting-point rare-earth glass microspheres with a particle size of 1.8-2.2 μm as the coating filler.

[0159] Comparative Example 9

[0160] This comparative example follows the same steps as Example 1, except that low-melting-point rare-earth glass microspheres with particle sizes of 0.8-1.2 μm and 1.8-2.2 μm are mixed at a mass ratio of 1:1 as coating fillers.

[0161] Comparative Example 10

[0162] This comparative example follows the same steps as Example 1, except that when preparing the rare earth glass microsphere heat dissipation filler, three different rare earth glass microspheres with different particle size distributions are mixed in a mass ratio of 1:2:1.

[0163] The heat dissipation performance evaluation of the glass microsphere-containing coatings prepared in the above embodiments and comparative examples was conducted under outdoor sunlight, and the temperature change of the coating substrate steel plate was recorded in real time. The evaluation system is shown in [link to evaluation system]. Figure 2 Multiple coatings were placed simultaneously in an unobstructed outdoor environment, with a patch thermocouple attached to the center of each coating and connected to a temperature measuring instrument to measure temperature changes in real time.

[0164] Figure 1 This describes the process of applying the coating obtained in the examples and comparative examples to the surface of a steel plate and then placing it outdoors to allow it to heat up. From Figure 1 It can be found that the surface temperature of Examples 1-2 is significantly lower than that of the comparative examples, while the surface temperature of Comparative Examples 3-5 is significantly higher than that of the other groups. This proves that lanthanum oxide and its proportion play a decisive role in the heat dissipation performance of the coating. At the same time, the rare earth glass microsphere heat dissipation filler provided by the present invention has good substitutability for SiO2 microspheres.

[0165] The emissivity of the embodiments and comparative examples provided by the present invention was measured, and the results are shown in Table 1.

[0166] Table 1 Comparison of performance parameters

[0167]

[0168] As shown in Table 1, Examples 1-2 exhibit excellent emission performance and strong thermal conductivity. When the raw material of the glass microsphere filler is free of tellurium / selenium doping (Comparative Examples 1-2) or has a low doping amount (Comparative Examples 6-7), the thermal conductivity of the coating decreases significantly, further illustrating the key role of tellurium / selenium doping in improving thermal conductivity. When lanthanum cerium oxide is not added to the glass microspheres (Comparative Example 3) or the lanthanum ratio is too high (Comparative Example 5), both the emission performance and thermal conductivity of the coating decrease to varying degrees, indicating the decisive role of lanthanum cerium oxide and the appropriate lanthanum-cerium ratio in coating performance. When the filler is replaced with SiO2 microspheres, all properties also decrease, indicating that the present invention is a substitute for SiO2 microspheres. When the particle size distribution of the glass microsphere filler differs (Comparative Examples 8-10), all coating properties decrease slightly, indicating that the coating prepared according to the particle size distribution ratio provided by the present invention has the best effect.

[0169] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-melting-point rare-earth glass microsphere, characterized in that: The glass microspheres are prepared from the following raw materials in parts by weight: 40-65 parts bismuth oxide, 15-30 parts lanthanum cerium oxide, 7-10 parts tellurium-doped boron oxide, 2-5 parts silicon dioxide, 7-10 parts selenium-doped aluminum hydroxide, and 1-3 parts alkali metal; the alkali metal is one of Na2O and K2O.

2. The low-melting-point rare-earth glass microspheres according to claim 1, characterized in that: Lanthanum cerium oxide is prepared by the following method: S11. Weigh cerium chloride and lanthanum chloride, add deionized water, and prepare a lanthanum chloride and cerium chloride solution. S12. Heat and stir the lanthanum chloride and cerium chloride solution, add ammonia water until precipitation is complete, and continue the reaction for 3-8 hours, then allow it to settle at room temperature for 10-20 hours. S13. The precipitate is filtered, washed and dried to obtain lanthanum cerium hydroxide powder; S14. Calcining lanthanum cerium hydroxide yields lanthanum cerium oxide powder.

3. The low-melting-point rare-earth glass microspheres according to claim 2, characterized in that: In S11, the molar ratio of cerium chloride to lanthanum chloride is 80:1-10:1, and the concentration of the prepared lanthanum chloride-cerium solution is 0.3-1 mol / L. In S12, the heating temperature is 60-100℃; In S14, the calcination temperature is 400-900℃ and the time is 3-6h.

4. The low-melting-point rare-earth glass microspheres according to claim 1, characterized in that: Tellurium-doped boron oxide was prepared by the following method: S21. Dissolve telluric acid in deionized water to prepare a telluric acid solution; S22. Dissolve boric acid in anhydrous ethanol to prepare a boric acid solution; S23. Add 65% nitric acid to the boric acid solution as a hydrolysis catalyst to maintain pH=2-3; S24. Add the telluric acid solution obtained in step S21 dropwise to the boric acid solution obtained in step S23. S25. Transfer the reacted solution to a sealed container and let it stand at 40-80℃ for 24-48 hours to complete gelation. S26. The system after the above reaction is separated by filtration. The solid component is dried overnight at 100-160℃ and then calcined at 400-550℃ under nitrogen protection for 4-6 hours with the heating rate controlled at 2-5℃ / min. After calcination, it is cooled in the furnace to obtain tellurium-doped boron oxide.

5. The low-melting-point rare-earth glass microspheres according to claim 4, characterized in that: In S21, the concentration of telluric acid solution is 0.05 mol / L; In S22, the concentration of boric acid solution is 0.5 mol / L, and after adding boric acid, it is completely dissolved in a water bath at 80°C with magnetic stirring. In S24, the volume of telluric acid solution is 80-150 mL, the volume of boric acid solution is 150 mL, the dropping rate is controlled at 0.5-2 mL / min, and the mixture is stirred at a constant temperature of 80℃ for 3-5 hours.

6. The low-melting-point rare-earth glass microspheres according to claim 1, characterized in that: Selenium-doped aluminum hydroxide is prepared by the following method: S31. Dissolve AlCl3·6H2O in deionized water to prepare an AlCl3 solution, and dissolve Na2SeO3 in water to prepare a Na2SeO3 solution. S32. Mix the above AlCl3 solution and Na2SeO3 solution, and stir in a water bath at 40-80℃. S33. Add NaOH solution dropwise to the mixed solution, control the pH to 9.0±0.2, and a white gelatinous precipitate will form. Continue stirring for 2-4 hours. S34. Wash the precipitate with deionized water at 60-90℃ until the conductivity of the filtrate is <50μS / cm, and then wash it with ethanol three times or more. S35. Freeze-dry for 20-36 hours to obtain a white powder—selenium-doped aluminum hydroxide.

7. The low-melting-point rare-earth glass microspheres according to claim 6, characterized in that: The concentration of the AlCl3 solution prepared in S31 is 0.2 mol / L, and the concentration of the Na2SeO3 solution is 0.02 mol / L. The volume ratio of AlCl3 solution to Na2SeO3 solution in S32 is 1:1-2.

8. A method for preparing low-melting-point rare-earth glass microspheres as described in any one of claims 1-7, characterized in that: The method includes the following steps: S41. Weigh and mix the low-melting-point rare earth glass microsphere raw materials according to the proportion to obtain a mixed powder. S42. Place the mixed powder obtained in step S41 into a furnace with stirring, heat it to 1000~1200℃ to make glass melt, continue heating and stirring for 3-6 hours. S43. Pour the glass melt into a mold and cast it into shape, and anneal it at 400-500℃ for 2-4 hours to obtain a glass ingot; S44. After the glass frit is initially crushed, it is poured into a ball mill jar and ground thoroughly to obtain glass powder; S45. The obtained glass powder is made into glass microspheres by floating electrothermal beading method. The furnace temperature is 700-800℃, the heating time is 20-40s, and the dust-carrying airflow pressure is 0.5-3MPa.

9. The method for preparing low-melting-point rare-earth glass microspheres according to claim 8, characterized in that: In step S42, the furnace temperature is 1050-1080℃, and the heating time is 4.5-5 hours; In step S44, the particle size D of the glass powder after ball milling 90 Below 4μm; In step S45, when the heating time is 40s and the dust-carrying gas pressure is 2.6-3MPa, primary distribution rare earth glass microspheres with a particle size of 0.8-1.2μm are prepared; when the heating time is 34s and the dust-carrying gas pressure is 1.8-2.2MPa, secondary distribution rare earth glass microspheres with a particle size of 1.8-2.2μm are prepared; when the heating time is 20s and the dust-carrying gas pressure is 0.5-1MPa, tertiary distribution rare earth glass microspheres with a particle size of 3.8-4.2μm are prepared.

10. A radiation-cooling coating, characterized in that: The coating comprises the following raw materials in parts by weight: 82-88 parts of styrene-acrylic emulsion, 8-10 parts of rare earth glass microsphere heat dissipation filler, 1-2 parts of silane coupling agent, 0.5-1 parts of wetting agent, 0.2-0.4 parts of dispersant, 0.1-0.15 parts of film-forming agent, 0.1-0.25 parts of defoamer, 0.1-0.5 parts of thickener, 1-3 parts of ultraviolet absorber, and 0.5-1 parts of antioxidant; wherein, the rare earth glass microsphere heat dissipation filler comprises three types of rare earth glass microspheres with different particle size distributions, namely, primary distribution 0.8-1.2μm, secondary distribution 1.8-2.2μm, and tertiary distribution 3.8-4.2μm, wherein the primary, secondary, and tertiary distributions are mixed in a mass ratio of 1:1:1, and the rare earth glass microspheres are the low melting point rare earth glass microspheres described in any one of claims 1-7.

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