Waste glass / alpha-Al2O3 composite radiation refrigeration material and preparation method thereof

Abstract

The invention belongs to the technical field of radiation refrigeration materials, and discloses a waste glass / alpha-Al2O3 composite radiation refrigeration material and a preparation method thereof, and the material is composed of 40-60 wt% of waste glass powder, 40-60 wt% of alpha-Al2O3 powder and 1-10 wt% of a sintering aid. The components of the waste glass powder need to meet the following requirements: 65 to 75 weight percent of SiO2, 13 to 17 weight percent of Na2O / K2O, 6.9 to 9.0 weight percent of CaO, 1.0 to 5.0 weight percent of MgO, 1.0 to 3.5 weight percent of Al2O3, less than or equal to 0.3 weight percent of Fe2O3 and less than or equal to 2.0 weight percent of total impurities. The sintering aid is selected from low-melting-point oxides such as P2O5 and B2O3. The preparation method comprises the following steps: respectively carrying out ball milling on the waste glass and alpha-Al2O3 to D50lt; 10 [mu] m and lt; and after being mixed with an auxiliary agent to form slurry, the slurry is coated on a base material, and the base material is sintered and molded at a low temperature of 500-600 DEG C. The solar reflectivity of the material is greater than or equal to 92% (0.3-2.5 [mu] m), the atmospheric window emissivity is greater than or equal to 94% (8-13 [mu] m), and the performance of the material is attenuated by 1t after the material is subjected to ultraviolet aging for 1000 hours; 5%. According to the invention, the waste glass is used as a low-cost binding phase and an infrared emission reinforcing phase, so that the coating has excellent weather resistance, environmental benefits and process compatibility, and is suitable for building tiles and metal roof coatings.

Description

Technical Field

[0001] This invention belongs to the field of radiation cooling materials technology, specifically relating to a composite radiation cooling material using waste glass and α-Al2O3 as the main raw materials and its preparation method. Background Technology

[0002] Under the dual pressures of global warming and accelerated urbanization, the demand for space cooling is experiencing explosive growth. Related carbon emissions have doubled in the past three decades, creating a vicious cycle of "the hotter it gets, the more air conditioning is used, and the more air conditioning is used, the hotter it gets." Given the difficulty of widely replacing the existing energy structure with renewable energy, passive radiative cooling technology has attracted widespread attention due to its "zero energy consumption and zero emissions" characteristics. Existing technologies have developed highly manufacturable radiative cooling materials, including polymer porous coatings, polymer-dielectric coatings, and multilayer polymer films. However, polymer-based materials generally suffer from insufficient weather resistance, easily aging and degrading under environmental factors such as ultraviolet radiation and temperature changes, leading to a significant reduction in service life and severely hindering their large-scale application. Although micro- and nano-ceramic materials with excellent environmental stability (such as SiO2, SiC, and Al2O3) have been proven suitable for radiative cooling, their high cost and lack of effective binding phases limit their widespread application in fields such as construction. Therefore, developing high-performance radiative cooling materials that are both cost-effective and weather-resistant is key to achieving the large-scale application of passive radiative cooling. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention proposes a waste glass / α-Al₂O₃ composite radiative cooling material and its preparation method. This invention not only reduces the preparation cost of radiative cooling materials and realizes the resource utilization of solid waste, but also effectively solves the problem of poor weather resistance in existing radiative cooling materials.

[0004] Waste glass, mainly composed of 65-75 wt% SiO2, 1-3 wt% Al2O3, and 10-15 wt% Na2O / K2O, has the following characteristics:

[0005] (1) High durability and environmental stability;

[0006] (2) Lower softening temperature, which facilitates low-temperature processing;

[0007] (3) Abundant infrared active vibrational modes (such as Al-O, Si-O, PO and other chemical bonds) can effectively enhance infrared emission performance in the atmospheric window band;

[0008] (4) The global annual output of waste glass exceeds 150 million tons, with a utilization rate of less than 30% and a raw material cost of less than 5 yuan / kg.

[0009] This invention includes the following technical solutions:

[0010] A waste glass / α-Al2O3 composite radiative cooling material is composed of the following components by mass percentage:

[0011] Waste glass powder of 40-60 wt% has the following composition: SiO2 65-75 wt%, Na2O / K2O 13-17 wt%, CaO 6.9-9.0 wt%, MgO 1.0-5.0 wt%, Al2O3 1.0-3.5 wt%, Fe2O3 ≤0.3 wt%, and the remainder being impurities with a total amount ≤2.0 wt%.

[0012] 40-60 wt% α-Al₂O₃ powder;

[0013] 1-10 wt% of sintering aids, selected from at least one of P2O5, B2O3, ZnO, CaO, MgO, BaO, and Li2O.

[0014] In the above scheme, waste glass powder provides the binder phase and infrared emission function, α-Al2O3 powder enhances the solar reflection and infrared reflection function, and sintering aids are used to reduce the sintering temperature (P2O5 and B2O3 are optimal).

[0015] Furthermore, in the aforementioned composite radiative cooling material, the content of waste glass powder is 45-55 wt%, the content of α-Al2O3 powder is 45-55 wt%, and the content of sintering aid is 3-8 wt%.

[0016] Furthermore, in the aforementioned composite radiative cooling material, the sintering aid is P2O5 and / or B2O3.

[0017] Furthermore, the aforementioned composite radiative cooling material has a solar reflectivity ≥92% (0.3-2.5μm band);

[0018] Atmospheric window emissivity ≥94% (8-13μm band);

[0019] After 1000 hours of UV aging, the optical performance degradation is less than 5%.

[0020] Furthermore, in the aforementioned composite radiative cooling material, the waste glass powder is selected from construction waste glass or packaging waste glass, and the Fe2O3 content is confirmed to be ≤0.3wt% by XRF composition analysis before use.

[0021] This invention also discloses a method for preparing the above-mentioned composite radiative cooling material, comprising the following steps:

[0022] (1) Raw material processing:

[0023] Waste glass is washed, crushed, and then ball-milled to D. 50 <10μm;

[0024] α-Al2O3 was ball-milled to D 50 <1μm;

[0025] (2) Preparation of composite slurry:

[0026] Waste glass powder, α-Al2O3 powder, and sintering aids are added to water or ethanol solvent in a certain proportion, with a solid-liquid ratio of 0.6-1.2 g / mL.

[0027] Add 0.5-5 wt% of an auxiliary agent, which includes at least one of a dispersant, a pH adjuster, and a leveling agent.

[0028] (3) Shaping and sintering:

[0029] The slurry is coated onto the substrate surface to form a 200-1000μm wet film;

[0030] Heat to 500-600℃ at a rate of 5-20℃ / min, hold for 5-20 minutes, and then cool with the furnace.

[0031] Furthermore, in the above preparation method, the solid-liquid ratio in step (2) is 0.7-1.1 g / mL, and the amount of the additive is 1-3 wt% of the total mass of the powder.

[0032] Furthermore, in the above preparation method, the substrate in step (3) is a building ceramic tile or a metal plate, and the coating method is spraying or brushing.

[0033] Furthermore, in the above preparation method, the dispersant in step (2) is sodium polyacrylate or sodium lignosulfonate, and the leveling agent is polyvinyl butyral.

[0034] In this invention, the waste glass powder, α-Al2O3 powder, and sintering aids in the slurry can be expressed as follows by mass percentage: the amount of waste glass powder can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, or 60%, etc.

[0035] In this invention, the amount of waste glass powder, α-Al2O3 powder, and sintering aid in the slurry can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, or 60% by mass percentage.

[0036] In this invention, the waste glass powder, α-Al2O3 powder and sintering aid in the slurry are expressed as a percentage by mass, and the amount of sintering aid can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc.

[0037] In this invention, the amount of solvent water or alcohol in the slurry is added according to the solid / liquid ratio of waste glass powder, α-Al2O3 powder and sintering aid in the solvent. The solid / liquid ratio can be 0.6g / mL, 0.65g / mL, 0.7g / mL, 0.75g / mL, 0.8g / mL, 0.85g / mL, 0.9g / mL, 0.95g / mL, 1g / mL, 1.05g / mL, 1.1g / mL, 1.15g / mL or 1.2g / mL, etc.

[0038] In this invention, other additives in the slurry, such as dispersants, pH adjusters, leveling agents, etc., can be added in addition to those mentioned above. The amount added can be based on the total mass of waste glass powder, α-Al2O3 powder and sintering aids. The total amount of other additives can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc.

[0039] Preferably, the amount of waste glass powder can be 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, or 55%, etc.

[0040] Preferably, the amount of α-Al2O3 powder can be 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, or 55%, etc.

[0041] Preferably, the amount of sintering aid can be 3%, 4%, 5%, 6%, 7% or 8%, etc.

[0042] Preferably, the solid-liquid ratio can be 0.7 g / mL, 0.75 g / mL, 0.8 g / mL, 0.85 g / mL, 0.9 g / mL, 0.95 g / mL, 1 g / mL, 1.05 g / mL, or 1.1 g / mL, etc.

[0043] The present invention also discloses the application of the above-mentioned composite radiative cooling material in the preparation of radiative cooling coatings on the surface of building exterior wall ceramic tiles or metal roofs.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. Breakthrough improvement in weather resistance

[0046] Optical performance degradation <3% after 600 hours of UV aging.

[0047] 2. Reduced preparation costs and significant environmental benefits.

[0048] Waste glass is used as an inexpensive binder phase (cost < 5 yuan / kg), and its infrared vibrational peaks, such as Si-O, Al-O, and PO bonds, can effectively enhance infrared emission performance in the atmospheric window band, while reducing the application of α-Al2O3. Based on this, high-value utilization of solid waste is also achieved.

[0049] 3. Strong process compatibility

[0050] The sintering temperature (500-600℃) is compatible with the production process of building ceramics and can be directly implemented on the tile glaze production line without the need for additional equipment; the coating thickness is adjustable from 200-1000μm and is suitable for various construction methods such as spraying and roller coating, adapting to complex building curved surfaces. Attached Figure Description

[0051] Figure 1 Here is a SEM image of the composite radiation cooling material prepared in Example 3;

[0052] Figure 2 The ultraviolet-visible absorption spectrum of the composite radiative cooling material prepared in Example 3 (Note: The solar reflectance obtained at wavelengths exceeding 1600 nm has a value exceeding 100%, so it is replaced with 99%).

[0053] Figure 3 The image shows the long-wave infrared spectrum of the composite radiative cooling material prepared in Example 3. Detailed Implementation

[0054] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0055] The waste glass powder used in this invention comes from construction waste glass and packaging glass. The α-Al₂O₃ powder used is from Shandong Aluminum Industry and needs to be finely ground before use. The additives used, including sintering aids and other additives, come from Beijing Honghu Chemical Co., Ltd.

[0056] The composition of the waste glass powder of the present invention is defined as shown in Table 1 below.

[0057] Table 1. Composition Limitations of Waste Glass Powder

[0058]

[0059] Note: Other components, including P2O5, Cr2O3, and SO3, must have a total content of ≤2.0%. Waste glass powder must undergo XRF composition analysis before use to ensure that each component meets the range in the table above, especially Fe2O3 ≤0.3% (to avoid light absorption).

[0060] Example 1

[0061] (1) Raw material processing

[0062] Waste glass pretreatment

[0063] Waste construction glass was selected, ultrasonically cleaned with deionized water, and then crushed to a particle size ≤5mm. It was then subjected to planetary ball milling (zirconia balls, ball-to-material ratio 10:1, speed 300rpm) for 4 hours to obtain D. 50 =8μm glass powder.

[0064] α-Al2O3 treatment

[0065] Industrial-grade α-Al₂O₃ (purity ≥ 99%) was also ball-milled to D. 50 =0.6μm.

[0066] (2) Preparation of composite slurry

[0067] Weigh the raw materials according to the ratio of waste glass powder: α-Al2O3: sintering aid (P2O5) = 11:8:1 (mass ratio). Use water as a solvent (solid / liquid ratio 0.8g / mL). Mix in a mixer at 2000rpm for 10 minutes. Add 1% sodium polyacrylate dispersant (based on the total weight of the powder). Mix in a mixer at 2000rpm for 30 minutes. Add a certain amount of ammonia to adjust the pH value to form a uniform slurry.

[0068] (3) Shaping and sintering

[0069] Coating

[0070] The slurry was sprayed onto the surface of the pretreated 304 stainless steel plate, with the wet film thickness controlled at 500 μm, and dried at room temperature for 12 hours.

[0071] sintering

[0072] The temperature is increased to 500°C in a box furnace at 5°C / min, held for 10 minutes, and then cooled with the furnace to obtain the coating.

[0073] Example 2

[0074] (1) Raw material processing

[0075] Waste glass pretreatment

[0076] Waste construction glass was selected, ultrasonically cleaned with deionized water, and then crushed to a particle size ≤5mm. It was then subjected to planetary ball milling (zirconia balls, ball-to-material ratio 10:1, speed 300rpm) for 4 hours to obtain D. 50 =7μm glass powder.

[0077] α-Al2O3 treatment

[0078] Industrial-grade α-Al₂O₃ (purity ≥ 99%) was also ball-milled to D. 50 =0.7μm.

[0079] (2) Preparation of composite slurry

[0080] Weigh the raw materials according to the ratio of waste glass powder: α-Al2O3: sintering aid (B2O3) = 10:9:1 (mass ratio). Use ethanol as solvent (solid / liquid ratio 0.9 g / mL) and mix in a mixer at 2000 rpm for 10 minutes. Then add 2% polyvinyl butyral (leveling agent) (based on the total weight of powder) and mix in a mixer at 2000 rpm for 30 minutes. Add a certain amount of ammonia water to adjust the pH value to form a uniform slurry.

[0081] (3) Shaping and sintering

[0082] Coating

[0083] The slurry was applied to the surface of the tile, with a wet film thickness of 800 μm, and dried at room temperature for 12 hours.

[0084] sintering

[0085] The coating is obtained by heating to 550°C in a box furnace at a rate of 10°C / min, holding at that temperature for 10 minutes, and then cooling with the furnace.

[0086] Example 3

[0087] (1) Raw material processing

[0088] Waste glass pretreatment

[0089] Waste construction glass was selected, ultrasonically cleaned with deionized water, and then crushed to a particle size ≤5mm. It was then subjected to planetary ball milling (zirconia balls, ball-to-material ratio 10:1, speed 300rpm) for 4 hours to obtain D. 50 =9μm glass powder.

[0090] α-Al2O3 treatment

[0091] Industrial-grade α-Al₂O₃ (purity ≥ 99%) was also ball-milled to D. 50=0.6μm.

[0092] (2) Preparation of composite slurry

[0093] Weigh the raw materials according to the ratio of waste glass powder: α-Al2O3: sintering aid (mixture of B2O3 and P2O5) = 9:10:1 (mass ratio). Use ethanol as solvent (solid / liquid ratio 1.0 g / mL) and mix in a mixer at 2000 rpm for 10 minutes. Then add 2% sodium lignosulfonate (based on the total weight of the powder) and mix in a mixer at 2000 rpm for 30 minutes. Add a certain amount of ammonia water to adjust the pH value and form a uniform slurry.

[0094] (3) Shaping and sintering

[0095] Coating

[0096] The slurry was sprayed onto the surface of the pretreated 304 stainless steel plate, with the wet film thickness controlled at 500 μm, and dried at room temperature for 12 hours.

[0097] sintering

[0098] The temperature was increased to 600℃ in a box furnace at a rate of 10℃ / min, held for 5 minutes, and then cooled with the furnace to obtain the coating. The resulting photograph after sintering is shown below. Figure 1 As shown, the performance test is as follows Figure 2-3 As shown.

[0099] Test case

[0100] Test method description:

[0101] Solar reflectance: Reflectance in the 0.3-2.5 μm band was measured using an ultraviolet-visible-near-infrared spectrophotometer (ASTM E903 standard);

[0102] Atmospheric window emissivity: Emissivity in the 8-13 μm band was measured using a Fourier transform infrared spectrometer (ASTM E408 standard);

[0103] Change rate of reflectance after pollution: Refer to GB / T 9780 standard to measure the attenuation of reflectance after simulating dust pollution;

[0104] Artificial weathering resistance: The appearance and performance stability of the coating were tested in a QUV ultraviolet aging chamber according to ISO 4892-3 standard.

[0105] Washability: The number of brushing cycles before coating damage is determined using a brushing tester according to GB / T 9266 standard.

[0106] Temperature resistance test: According to JG / T 25 standard, thermal cycling is performed in the range of -30℃ to 80℃, and the coating cracking or peeling is observed.

[0107] The performance comparison of the radiation cooling coatings obtained in Examples 1-3 is shown in Table 2 below.

[0108] Table 2 Comparison of the performance of radiation-cooling coatings

[0109]

[0110]

[0111] Test results show that all embodiments achieved high optical performance with solar reflectivity ≥94% and atmospheric window emissivity ≥97%. Embodiment 3 performed best, with reflectivity and emissivity both reaching 98%, but its wash resistance (1600 cycles) and temperature change resistance (30 cycles) were slightly lower than other embodiments, possibly related to increased coating brittleness due to the higher sintering temperature (600℃). Regarding weather resistance, all three samples passed 600 hours of UV aging without abnormalities, far exceeding industry standards; wash resistance was ≥1600 cycles, meeting the durability requirements of architectural coatings. Pollution tests showed a reflectivity decay of 13-16%, requiring further optimization of surface hydrophobicity. Overall, Embodiment 2 achieves the best balance between optical performance, weather resistance, and mechanical strength, making it suitable for outdoor architectural applications.

[0112] The above are some limited preferred embodiments of the present invention, described in a relatively specific and detailed manner, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A waste glass / α-Al₂O₃ composite radiative cooling material, characterized in that, It consists of the following components by mass percentage: Waste glass powder of 40-60 wt% has the following composition: SiO2 65-75 wt%, Na2O / K2O 13-17 wt%, CaO 6.9-9.0 wt%, MgO 1.0-5.0 wt%, Al2O3 1.0-3.5 wt%, Fe2O3 ≤0.3 wt%, and the remainder being impurities with a total amount ≤2.0 wt%. 40-60 wt% α-Al₂O₃ powder; 1-10 wt% of sintering aids, selected from at least one of P2O5, B2O3, ZnO, CaO, MgO, BaO, and Li2O.

2. The composite radiative cooling material according to claim 1, characterized in that: The waste glass powder content is 45-55 wt%, the α-Al2O3 powder content is 45-55 wt%, and the sintering aid content is 3-8 wt%.

3. The composite radiative cooling material according to claim 1 or 2, characterized in that: The sintering aid is P2O5 and / or B2O3.

4. The composite radiative cooling material according to any one of claims 1-3, characterized in that, Its performance meets the following requirements: Solar reflectivity ≥92% (0.3-2.5μm band); Atmospheric window emissivity ≥94% (8-13μm band); After 1000 hours of UV aging, the optical performance degradation is less than 5%.

5. The composite radiative cooling material according to claim 1, characterized in that: The waste glass powder is selected from construction waste glass or packaging waste glass, and the Fe2O3 content is confirmed to be ≤0.3wt% by XRF composition analysis before use.

6. The method for preparing the composite radiative cooling material according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Raw material processing: Waste glass is washed, crushed, and then ball-milled to D. 50 <10μm; α-Al2O3 was ball-milled to D 50 <1μm; (2) Preparation of composite slurry: Waste glass powder, α-Al2O3 powder, and sintering aids are added to water or ethanol solvent in a certain proportion, with a solid-liquid ratio of 0.6-1.2 g / mL. Add 0.5-5 wt% of an auxiliary agent, which includes at least one of a dispersant, a pH adjuster, and a leveling agent. (3) Shaping and sintering: The slurry is coated onto the substrate surface to form a 200-1000μm wet film; Heat to 500-600℃ at a rate of 5-20℃ / min, hold for 5-20 minutes, and then cool with the furnace.

7. The preparation method according to claim 6, characterized in that: In step (2), the solid-liquid ratio is 0.7-1.1 g / mL, and the amount of the additive is 1-3 wt% of the total mass of the powder.

8. The preparation method according to claim 6, characterized in that: The substrate mentioned in step (3) is a building ceramic tile or a metal sheet, and the coating method is spraying or brushing.

9. The preparation method according to claim 6, characterized in that: The dispersant in step (2) is sodium polyacrylate or sodium lignosulfonate, and the leveling agent is polyvinyl butyral.

10. The application of the composite radiative cooling material as described in any one of claims 1-5 in the preparation of a radiative cooling coating on the surface of building exterior wall tiles or metal roofs.

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