A full-dimensional hydrophobic radiation refrigeration cement coating and a preparation method thereof

Abstract

The present disclosure provides a full-dimensional hydrophobic radiation refrigeration cement coating and a preparation method thereof. The main raw materials of the coating are cement, functional fillers, micron / nanofibers, hydrophobic components and water. Unlike conventional hydrophobic surface paint which only has surface hydrophobic self-cleaning function, the full-dimensional hydrophobic radiation refrigeration cement coating of the present disclosure integrates radiation refrigeration and full-dimensional hydrophobicity, and can still maintain excellent self-cleaning and radiation refrigeration performance even after abrasion. The coating has a contact angle with water greater than 150°, and the overall reflectivity and overall infrared emissivity of the atmospheric window are both above 90%.

Description

Technical Field

[0001] This invention relates to the field of passive energy utilization, specifically to a multidimensional hydrophobic radiation-cooling cement coating and its preparation method. Background Technology

[0002] Cooling is ubiquitous in modern society, ensuring environmental comfort. In recent decades, rapid population growth and intensive industrial development have led to global warming, further increasing the demand for cooling, especially during hot summers. It is reported that building energy consumption accounts for 40% of the total global energy cost today, with over 44% used for building thermal management, significantly exacerbating the global energy crisis. However, traditional compression-based cooling systems, such as air conditioning, consume vast amounts of energy while generating excessive CO2 and ozone depletion, contributing to both energy crises and environmental problems. Therefore, seeking energy-efficient and environmentally friendly cooling strategies has become extremely urgent.

[0003] As an alternative, passive diurnal radiative cooling has emerged as a highly attractive technology, capable of reducing the surface temperature of terrestrial objects (300K) by sending excess heat into space (3K) through atmospheric transparency windows (8–13 μm), with zero energy consumption. These windows overlap with the peak thermal radiation spectrum region of objects on Earth at typical ambient temperatures (close to 300K). Therefore, any object on Earth can radiate heat into outer space through atmospheric transparency windows, thus utilizing the coldness of space to lower its temperature.

[0004] Solar radiation is a significant heat source affecting the temperature of any exposed surface. While most sunlight intensity comes from photons in the visible light region, ultraviolet (UV) and near-infrared (NIR) photons also contribute significantly to solar radiation. Although specular reflectivity can be used to suppress sunlight, most research on radiative cooling employs diffuse reflection for this purpose. Diffuse reflection typically occurs in media whose components have varying refractive indices and exhibit a degree of disorder, leading to multiple scattering of incident light within the structure. Coatings, with their relatively simple preparation processes, offer a straightforward method for achieving light scattering because the arrangement of components within the coating is naturally disordered.

[0005] Because white surfaces have the highest solar reflectivity, which helps reduce heat absorption within the solar spectrum, existing passive radiative cooling technologies for daytime use are mostly white. However, the solar reflectivity of white surfaces typically decreases due to dust and other contaminants, leading to a loss of cooling performance. Research indicates that dust accumulation is the primary factor causing this decrease in solar reflectivity. A conventional solution to maintain the solar reflectivity of white surfaces is to apply a hydrophobic topcoat, but this suffers from reduced hydrophobicity or loss of self-cleaning properties after wear. To further maintain the coating's solar reflectivity and infrared emissivity over a longer period, the coating should integrate multi-dimensional hydrophobicity, self-cleaning, and radiative cooling, ensuring excellent cooling performance even after surface wear. Summary of the Invention

[0006] To address the aforementioned technical problems, this disclosure provides a low-cost, multi-dimensional hydrophobic radiation-cooling cement coating and its preparation method. This coating can be applied to surfaces such as buildings, oil and gas storage tanks, grain silos, substations, and tents, providing an integrated solution for zero-energy radiation cooling during the day, hydrophobic self-cleaning, and waterproofing. The multi-dimensional hydrophobic radiation-cooling cement coating provided in this application has a water contact angle of not less than 150°, exhibiting excellent superhydrophobic self-cleaning capabilities. Furthermore, the coating retains its excellent hydrophobic self-cleaning function even after wear, maintaining high solar reflectivity and infrared emissivity for a long time. This multi-dimensional hydrophobic radiation-cooling cement coating has a solar reflectivity of not less than 90% and an infrared emissivity of not less than 90%, demonstrating excellent zero-energy radiation cooling performance.

[0007] Therefore, this application provides the following aspects:

[0008] <1> A multidimensional hydrophobic radiation-cooling cement coating, comprising cement, functional fillers, admixtures, and water, wherein...

[0009] The functional filler includes a main filler and optional auxiliary fillers. The main filler is selected from one or more of micron-sized hollow glass microspheres, micron-sized silica, and ceramic powder, and the mass fraction of the main filler relative to the total solids content in the all-dimensional hydrophobic radiation-cooling cement coating is 20-40%.

[0010] The admixture comprises micro / nanofibers and hydrophobic components, and the mass fraction of each of the micro / nanofibers and hydrophobic components relative to the solid content in the all-dimensional hydrophobic radiation-cooling cement coating is less than 3.0%.

[0011] The cement accounts for 40%-80% of the total solids content in the all-dimensional hydrophobic radiation-cooling cement coating.

[0012] The amount of water accounts for 40%-70% of the total solids content in the all-dimensional hydrophobic radiation-cooled cement coating.

[0013] <2> .according to <1> The aforementioned all-dimensional hydrophobic radiation-cooled cement coating, wherein the micron / nanofiber is obtained by peeling off bagasse.

[0014] <3> According to any one of the above claims, the auxiliary filler is selected from at least one of nano-silica, nano-calcium carbonate and nano-alumina, and the mass fraction of the auxiliary filler relative to the solid content in the all-dimensional hydrophobic radiation-cooling cement coating is less than 10%.

[0015] <4> .according to <1> The aforementioned all-dimensional hydrophobic radiation-cooling cement coating, wherein the main filler and auxiliary filler are spherical in shape, the average particle size of the main filler is 0.2-100μm, and the particle size of the auxiliary filler is 20-800nm.

[0016] <5> According to claim 1, the mass fraction of each of the micro / nano fibers and the hydrophobic component relative to the solid content in the all-dimensional hydrophobic radiation-cooling cement coating is less than 2.0%.

[0017] <6> The all-dimensional hydrophobic radiation-cooling cement coating according to any one of the above claims further includes a defoamer, and the mass fraction of the defoamer relative to the solid content in the all-dimensional hydrophobic radiation-cooling cement coating is less than 2.0%.

[0018] <7> According to any one of the above claims, the contact angle between the coating formed by the all-dimensional hydrophobic radiation-cooling cement coating and water is greater than 150°.

[0019] <8> A multidimensional hydrophobic radiation-cooling cement coating, comprising the following components in the following mass percentage range:

[0020] Micron-sized hollow glass microspheres account for 5%-40%

[0021] Micron-sized silica 5%-20%,

[0022] Nano-calcium carbonate or nano-silica 2%-15%,

[0023] Hydrophobic component 1.0%-3%,

[0024] Micron / nano bagasse fiber 0.3%-3%,

[0025] Cement 40%-80%, and

[0026] Water 40%-70%,

[0027] The mass percentages mentioned above refer to the mass fractions of each component relative to the solid content in the all-dimensional hydrophobic radiation-cooled cement coating.

[0028] <9> A multidimensional hydrophobic radiation-cooling cement coating, comprising the following components in the following mass percentage range:

[0029] Micron-sized hollow glass microspheres account for 5%-40%

[0030] Micron-sized silica 5%-20%,

[0031] Ceramic powder 5%-20%,

[0032] Nano-calcium carbonate or nano-silica 2%-15%,

[0033] Nano aluminum oxide 3%-10%,

[0034] Hydrophobic component 1.0%-3%,

[0035] Micron / nano bagasse fiber 0.3%-3%,

[0036] Cement 40%-80%, and

[0037] Water content: 40%-70%.

[0038] The mass percentages mentioned above are all mass fractions relative to the solid content in the all-dimensional hydrophobic radiation-cooled cement coating.

[0039] <10> A method for preparing a multidimensional hydrophobic radiation-cooled cement coating according to any one of the preceding claims, the method comprising the following steps:

[0040] A) Weigh the additive and water according to the formula, disperse them evenly at high speed, and then slowly add the main filler and optional auxiliary filler according to the formula while stirring at low speed. Continue to disperse and set aside.

[0041] B) Add the functional filler dispersion obtained in step A) to the cement powder weighed according to the formula, and mix and disperse the components thoroughly to obtain the all-dimensional hydrophobic radiation cooling cement coating.

[0042] <11> .according to <10> The method wherein step B) uses a planetary rotation and revolution mixing to mix and disperse, and the planetary rotation and revolution mixing adopts a low-speed and high-speed gradient mixing method, with the rotation and revolution speed increasing from 200 RPM to 2500 RPM, and the mixing time is 3-10 minutes. Attached Figure Description

[0043] Figure 1A digital photograph of the all-dimensional hydrophobic radiation-cooled cement coating prepared in Example 1 of the present invention;

[0044] Figure 2 A microscopic photograph of the surface of the all-dimensional hydrophobic radiation-cooled cement coating prepared in Example 1 of the present invention, observed under a field emission scanning electron microscope.

[0045] Figure 3 The full-dimensional hydrophobic radiation-cooled cement coating prepared in Example 1 of this invention was observed under a field emission scanning electron microscope. Figure 2 Magnified microscopic photograph;

[0046] Figure 4 Microscopic images of the coating surface of the all-dimensional hydrophobic radiation-cooled cement coating prepared in Example 1 of the present invention under a polarizing microscope.

[0047] Figure 5 Photograph of the contact angle between the surface of the all-dimensional hydrophobic radiation-cooled cement coating prepared in Example 1 of the present invention and water;

[0048] Figure 6 Photograph of the contact angle between the all-dimensional hydrophobic radiation-cooled cement coating prepared in Example 1 of the present invention and water after it has been sanded down to half its thickness;

[0049] Figure 7 This is a schematic diagram of the reflectance of the all-dimensional hydrophobic radiation-cooled cement coating prepared in Example 1 of the present invention at different wavelengths. The overall solar reflectance of the coating is 92.7%.

[0050] Figure 8 This is a schematic diagram of the emissivity of the all-dimensional hydrophobic radiation-cooled cement coating prepared in Example 1 of the present invention at different wavelengths. The average emissivity of the coating in the atmospheric window is 94.11%.

[0051] Figure 9 This is a schematic diagram showing the temperature of the lower surface of the substrate and the light intensity at different times for the full-dimensional hydrophobic radiation-cooling cement coating and the uncoated coating prepared in Example 2 of the present invention.

[0052] Figure 10 This is a schematic diagram of the reflectance of the all-dimensional hydrophobic radiation-cooled cement coating of Embodiment 3 of the present invention at different wavelengths. The overall solar reflectance of the coating is 94.4%.

[0053] Figure 11 This is a digital photograph of the all-dimensional hydrophobic radiation-cooled cement coating after a cross-cut test in Embodiment 3 of the present invention.

[0054] Figure 12 This is a schematic diagram of the reflectance of the all-dimensional hydrophobic radiation-cooled cement coating in Example 4 at different wavelengths. The overall solar reflectance of the coating is 93.7%.

[0055] Figure 13 This is a schematic diagram of the reflectance of the cement coating prepared in Comparative Example 1 of the present invention at different wavelengths. The overall solar reflectance of the coating is 76.95%.

[0056] Figure 14 Photographs showing the contact angle between the radiation-cooled cement coating prepared in Comparative Example 2 of this invention and water;

[0057] Figure 15 This is a schematic diagram of the reflectance of the radiation-cooled cement coating prepared in Comparative Example 2 of the present invention at different wavelengths. The overall solar reflectance of the coating is 93.4%. Detailed Implementation

[0058] The features and advantages of the present invention are described in detail below.

[0059] The term "infrared emissivity of the atmospheric window" refers to the ratio of the energy emitted by a surface object through a mid-infrared atmospheric transparent window of 8-13 μm to the energy of blackbody radiation at the same temperature. The testing and calculation process is described in the Examples section.

[0060] The term "total solar reflectivity" refers to the ability of an object's surface to reflect light within the solar spectrum, and its testing and calculation process is described in the Examples section.

[0061] In view of the high energy consumption and significant environmental pollution caused by building thermal management in summer, this application provides a multidimensional hydrophobic radiation cooling cement coating and its preparation method.

[0062] In this invention, the term "all-dimensional hydrophobicity" means that, unlike preparing a hydrophobic topcoat on the coating surface, a hydrophobic component is added during the in-situ hydration of cement, thereby achieving hydrophobic self-cleaning in all parts of the coating. This allows the coating to retain its self-cleaning ability even after wear, thus maintaining good radiative cooling performance over a long period. Examples of hydrophobic components include one or more of dimethylpolysiloxane, methylvinylpolysiloxane, and methylphenylpolysiloxane.

[0063] On the one hand, this application provides a full-dimensional hydrophobic radiation-cooling cement coating, which comprises cement, functional filler, admixture and water.

[0064] The functional filler includes a main filler and optional auxiliary fillers. The main filler is selected from one or more of micron-sized hollow glass microspheres, micron-sized silica, and ceramic powder. The mass fraction of the main filler relative to the total solids content in the all-dimensional hydrophobic radiation-cooling cement coating is 20-40%, preferably 22-38%, and more preferably 25-35%. The morphology of the main filler and auxiliary filler is preferably spherical. The average particle size of the main filler is 0.2-100 μm, and the particle size of the auxiliary filler is 20-800 nm. The mass fraction of the auxiliary filler relative to the total solids content in the all-dimensional hydrophobic radiation-cooling cement coating is preferably less than 10%, more preferably less than 5%, and more preferably 1%-5%.

[0065] The admixture comprises micro / nanofibers and a hydrophobic component, and the mass fraction of each admixture relative to the solid content in the all-dimensional hydrophobic radiation-cooled cement coating is less than 3.0%. For example, the hydrophobic component is preferably 1.0%-3%, and the micro / nanofiber component is preferably 0.3%-3%. The amount of water used is 40%-70% of the solid mass, and includes the water contained in the micro / nano bagasse fiber aqueous dispersion.

[0066] Preferably, the micro / nanofibers are obtained by peeling bagasse. Specifically, the micro / nanofiber fibers are obtained by peeling bagasse after chemical and mechanical treatment, with a diameter of several nanometers to tens of nanometers and a length of several hundred nanometers to several micrometers.

[0067] Preferably, the main filler is selected from one or more of the following: micron hollow microspheres, micron silica, ceramic powder, etc.

[0068] Preferably, examples of the auxiliary filler include one or more selected from nano-silica, nano-calcium carbonate, nano-alumina, etc.

[0069] Preferably, the additive further includes an antifoaming agent.

[0070] Preferably, the mass fraction of the additives in the coating is less than 1.0%.

[0071] According to the present invention, the all-dimensional hydrophobic radiation-cooling cement coating uses cement as the main raw material, which is low in cost and has a relatively simple preparation process. By introducing hydrophobic components during the in-situ hydration of cement, the radiation-cooling cement coating can have the ability to be all-dimensionally hydrophobic and self-cleaning. On the one hand, it can effectively prevent rainwater from soaking and causing the coating to fall off. On the other hand, it can enable the radiation-cooling cement coating to maintain high solar reflectivity and high-to-medium far-infrared emissivity for a long time.

[0072] As an example, according to one embodiment of the present invention, a multidimensional hydrophobic radiation-cooled cement coating is provided, comprising the following components in the following mass percentage ranges: 5%-40% micron hollow glass microspheres, 5%-20% micron silica, 2%-15% nano-calcium carbonate or nano-silica, 1.0%-3% hydrophobic component, 0.3%-3% micron / nano bagasse fiber, 40%-80% cement, and 40%-70% water, wherein the mass percentages are the mass fractions of each component relative to the solid content in the multidimensional hydrophobic radiation-cooled cement coating.

[0073] As another example, according to another embodiment of the present invention, a multidimensional hydrophobic radiation-cooled cement coating is provided, comprising the following components in the following mass percentage ranges: 10%-40% micron hollow glass microspheres, 5%-20% micron silica, 5%-20% ceramic powder, 2%-10% nano-calcium carbonate or nano-silica, 3%-10% nano-alumina, 1.0%-3% hydrophobic component, 0.3%-2.0% micron / nano bagasse fiber, 40%-80% cement, and 40%-70% water, wherein the mass percentages are the mass fractions of each component relative to the solid content in the multidimensional hydrophobic radiation-cooled cement coating.

[0074] On the other hand, this application also provides a method for preparing a multidimensional hydrophobic radiation-cooled cement coating, comprising the following steps:

[0075] A) Weigh the additives according to the formula, disperse them evenly at high speed, stir at low speed, and slowly add the main filler and auxiliary filler according to the formula. Continue to disperse and set aside.

[0076] B) Add the functional filler dispersion obtained in step A) to the cement powder weighed according to the formula, and use a planetary rotation and revolution stirring to mix and disperse the components to obtain the all-dimensional hydrophobic radiation cooling cement coating.

[0077] The planetary rotation and revolution mixing adopts a low-speed and high-speed gradient speed-increasing mixing method, with the rotation and revolution speed increasing from 200 RPM to 2500 RPM, and the mixing time being 3-10 minutes.

[0078] In the preparation method of the present invention, the main filler is preferably selected from one or more of micron-sized hollow microspheres, micron-sized silica, ceramic powder, etc. Preferably, the auxiliary filler is selected from one or more of nano-silica, nano-calcium carbonate, nano-alumina, etc. Preferably, the additive is one or more of an defoamer, a hydrophobic component, and micron / nanofiber obtained from bagasse peeling.

[0079] In the preparation process of the aforementioned all-dimensional hydrophobic radiation-cooled cement coating, nano / micro fibers (e.g., nano / micro fibers obtained by peeling bagasse) are first introduced. On the one hand, biomass nano / micro fibers can increase the viscosity of the slurry, thereby improving workability, and their excellent water retention can provide moisture for cement hydration, thus improving the strength of the coating. On the other hand, the multi-level network structure of biomass nano / micro fibers can connect the cement hydration products, thereby improving the toughness of the coating and preventing shrinkage cracking of the cement coating. Then, functional fillers and hydrophobic components are added during the in-situ cement hydration process. Among them, nano-calcium carbonate and micro-hollow glass microspheres, as white pigments, can increase the reflective area of ​​the coating, thereby improving the reflectivity of the coating. The phonon polaron resonance exhibited by micro- and nano-silica can improve the infrared emissivity of the coating at atmospheric windows.

[0080] In summary, this disclosure provides a multidimensional hydrophobic radiation-cooled cement coating, comprising cement, functional fillers, micro / nanofibers, hydrophobic components, and water. Without being bound by any theoretical constraints, the applicant believes that: the multidimensional hydrophobic radiation-cooled cement coating firstly introduces nano / microfibers, such as those obtained by stripping bagasse. On the one hand, biomass nano / microfibers can increase the viscosity of the slurry, thereby improving workability, and the excellent water retention provided by the numerous active groups on the fiber surface can provide moisture for cement hydration, thus improving the coating strength. On the other hand, the multi-level network structure of biomass nano / microfibers can connect the cement hydration products, thereby improving the coating's toughness and preventing shrinkage cracking of the cement coating; then, functional fillers and hydrophobic components are added during the in-situ cement hydration process. Nano-calcium carbonate and micron-sized hollow glass microspheres, as white pigments, can increase the reflective area of ​​the coating, thereby improving its reflectivity, while silica can increase the infrared emissivity of the coating at atmospheric windows.

[0081] Example

[0082] To enable those skilled in the art to further understand, implement, or use the present invention, the following detailed description of the all-dimensional hydrophobic radiation-cooling cement coating provided by the present invention is provided in conjunction with embodiments. Therefore, these embodiments are not intended to limit the scope of protection of the present invention, which is defined by the appended claims.

[0083] All reagents used in the following examples are commercially available and were used directly without special treatment. The micron / nano bagasse fibers were obtained in the laboratory through peeling, specifically, bagasse fibers with diameters ranging from several nanometers to tens of nanometers and lengths ranging from hundreds of nanometers to several micrometers obtained through chemical and mechanical treatment. Specifically, the peeling method involved first thoroughly washing the bagasse with clean water, then immersing it in a 3%-8% sodium chlorite solution with 3-5 ml of acetic acid added, reacting it in an 80°C oven for 6 hours, washing it again, and then mechanically dispersing and peeling it using high-pressure homogenization.

[0084] The prepared all-dimensional hydrophobic radiation-cooled cement coating was applied to a 5cm×5cm cement substrate. The spectral reflectance, total solar reflectance, and infrared emissivity of the coating were measured using a UV / Vis / Near-Infrared spectrophotometer (Pekin-Elmer Lambda950) and a Fourier transform infrared spectrometer (Nicolet iS50), respectively.

[0085] The prepared all-dimensional hydrophobic radiation-cooling cement coating was applied to a cement substrate measuring 20cm long × 20cm wide × 1cm thick. The substrate was placed in a sample chamber exposed to air and insulated at the bottom. A thermal resistor in a nearby Stevenson screen was used to measure the ambient air temperature, and a thermal resistor inserted into the central hole at the bottom of the cement substrate was used to measure the surface temperature beneath the coating. An anemometer was used to measure wind speed and the conduction and convection non-radiative heat transfer coefficients, and an irradiance meter was used to measure solar irradiance. All the measured data were wirelessly transmitted to a computer terminal.

[0086] The formula for calculating total solar reflectance is as follows:

[0087]

[0088] Where λ is the incident light wavelength in the range of 0.3-2.5 μm, and I solar It is the standardized ASTM G173 global solar intensity spectrum, ρ solar (λ,θ) is the spectral reflectance of the surface.

[0089] The formula for calculating the infrared emissivity of the atmospheric window is as follows:

[0090]

[0091] Among them, I BB (λ) is the spectral intensity of the blackbody, ε LWIR (λ,θ) is the spectral thermal emissivity of the surface in the range of 8-13 μm.

[0092] Example 1

[0093] A) Weigh the additives (1.0% hydrophobic component (dimethyl polysiloxane) and 1.2% micron / nano bagasse fiber) according to the formula, disperse them at high speed, add water (60% by mass of solids) and stir at low speed. Slowly add the main filler and auxiliary filler (20% micron hollow glass microspheres, 5% micron silica, and 2% nano calcium carbonate) according to the formula, continue to disperse and set aside.

[0094] B) Add the functional filler dispersion obtained in step A) to the cement powder weighed according to the formula amount (70.8%), and use a planetary rotation and revolution stirring to mix and disperse the components to obtain the all-dimensional hydrophobic radiation cooling cement coating.

[0095] C) Apply the all-dimensional hydrophobic radiation cooling cement coating obtained in step B) to the cement substrate by scraping and brushing, and cure it under natural conditions (temperature 25℃±3℃, humidity 50%±10%).

[0096] Figure 1 The photograph shows the all-dimensional hydrophobic radiation-cooling cement coating prepared for this embodiment coated on a cement substrate. Due to its strong diffuse reflection of sunlight, the coating appears white.

[0097] Figure 2 This is a microscopic photograph of the surface of the all-dimensional hydrophobic radiation-cooling cement coating prepared in this embodiment. It can be seen that the inorganic functional filler is uniformly dispersed in the coating, and the regular particles are beneficial for improving solar reflectivity.

[0098] Figure 3 The surface of the all-dimensional hydrophobic radiation-cooled cement coating prepared in this embodiment Figure 2 More detailed microscopic images were obtained under a field emission scanning electron microscope.

[0099] Figure 4 The microscopic photographs of the all-dimensional hydrophobic radiation-cooled cement coating prepared in this embodiment, observed under a polarizing microscope, show that the inorganic filler is uniformly dispersed in the cement matrix.

[0100] Figure 5 This is a schematic diagram of the contact angle between the all-dimensional hydrophobic radiation-cooled cement coating prepared in this embodiment and water. The contact angle between the coating and water is 152.6°, and the roll-off angle is less than 5°, indicating that it has obvious hydrophobic self-cleaning ability.

[0101] Figure 6 This is a schematic diagram of the contact angle between the all-dimensional hydrophobic radiation-cooling cement coating prepared in this embodiment and water after it has been sanded down to half its thickness. Even after sanding, the contact angle with water is still greater than 147°, demonstrating excellent self-cleaning ability and the ability to maintain high solar reflectivity and infrared emissivity for a long time.

[0102] Figure 7This diagram illustrates the reflectance of the all-dimensional hydrophobic radiation-cooled cement coating prepared in this embodiment at different wavelengths. The overall solar reflectance of the coating is 92.7%.

[0103] Figure 8 This diagram illustrates the emissivity of the all-dimensional hydrophobic radiation-cooled cement coating prepared in this embodiment at different wavelengths. The average emissivity of the coating within the atmospheric window is 94.11%.

[0104] Example 2

[0105] A) Weigh out the additives (1.0% hydrophobic component (dimethyl polysiloxane) and 1.5% micron / nano bagasse fiber) and water (70% by mass of solids) according to the formula. After high-speed dispersion, stir at low speed and slowly add the main filler and auxiliary filler (30% micron hollow glass microspheres, 5% micron silica, and 2% nano silica) according to the formula. Continue to disperse and set aside.

[0106] B) Add the functional filler dispersion obtained in step A) to the cement powder weighed according to the formula amount (60.5%), and use a planetary rotation and revolution stirring to mix and disperse the components to obtain the all-dimensional hydrophobic radiation cooling cement coating.

[0107] C) Apply the all-dimensional hydrophobic radiation-cooling cement coating obtained in step B) onto the cement substrate by scraping and brushing, and cure it under natural conditions (temperature 25℃±3℃, humidity 50%±10%).

[0108] Figure 9 This diagram illustrates the surface temperature and light intensity of the substrate's lower surface at different times for the all-dimensional hydrophobic radiation-cooled cement coating and the uncoated coating obtained in this embodiment. Figure 9 It can be seen that during a relatively sunny winter midday period (when the light intensity is below 600W / m²), 2 The temperature of the lower surface of the cement substrate coated with the full-dimensional hydrophobic radiation-cooling cement coating is consistently lower than that of the cement substrate without the radiation-cooling coating, with an average difference of 11.7°C.

[0109] Example 3

[0110] A) Weigh out the additives (1.0% hydrophobic component (dimethyl polysiloxane) and 2.0% micron / nano bagasse fiber) and water (70% by mass of solids) according to the formula. After high-speed dispersion, stir at low speed and slowly add the main filler and auxiliary filler (40% micron hollow glass microspheres and 2% nano silica) according to the formula. Continue to disperse and set aside.

[0111] B) Add the functional filler dispersion obtained in step A) to the cement powder weighed according to the formula amount (55%), and use a planetary rotation and revolution stirring to mix and disperse the components to obtain the all-dimensional hydrophobic radiation cooling cement coating.

[0112] C) Apply the all-dimensional hydrophobic radiation-cooling cement coating obtained in step B) onto the cement substrate by scraping and brushing, and cure it under natural conditions (temperature 25℃±3℃, humidity 50%±10%).

[0113] Figure 10 This diagram illustrates the reflectance of the all-dimensional hydrophobic radiation-cooled cement coating at different wavelengths in this embodiment. The overall solar reflectance of the coating is 94.4%.

[0114] Figure 11 This is a digital photograph of the all-dimensional hydrophobic radiation-cooled cement coating after a 100-cross cross-cut adhesion test in this embodiment. Even with a high concentration of inorganic fillers, the coating still maintains good adhesion to the cement substrate.

[0115] Example 4

[0116] A) Weigh out the additives (1.0% hydrophobic component (dimethyl polysiloxane) and 1.5% micron / nano bagasse fiber) and water (70% by mass of solids) according to the formula. After high-speed dispersion, stir at low speed and slowly add the main filler and auxiliary filler (10% micron hollow glass microspheres, 10% micron silica, 8% ceramic powder, and 3% nano alumina) according to the formula. Continue to disperse and set aside.

[0117] B) Add the functional filler dispersion obtained in step A) to the cement powder weighed according to the formula amount (66.5%), and use a planetary rotation and revolution stirring to mix and disperse the components to obtain the all-dimensional hydrophobic radiation cooling cement coating.

[0118] C) Apply the all-dimensional hydrophobic radiation-cooling cement coating obtained in step B) onto the cement substrate by scraping and brushing, and cure it under natural conditions (temperature 25℃±3℃, humidity 50%±10%).

[0119] Figure 12 This diagram illustrates the reflectance of the all-dimensional hydrophobic radiation-cooled cement coating at different wavelengths in this embodiment. The overall solar reflectance of the coating is 93.7%.

[0120] Comparative Example 1

[0121] A) Weigh out 1.2% aqueous dispersion of micron / nano bagasse fiber according to the formula and add it to 100% cement powder. Use a planetary stirring machine to mix and disperse the components.

[0122] B) Apply the comparative cement coating obtained in step A) to the cement substrate by scraping and brushing, and cure it under natural conditions (temperature 25℃±3℃, humidity 50%±10%).

[0123] Figure 13 This is a schematic diagram showing the reflectance of the cement coating prepared in this comparative example at different wavelengths. The overall solar reflectance of the coating is 76.95%, which fails to meet the basic requirement of >80% reflectance for building reflective thermal insulation coatings.

[0124] Comparative Example 2

[0125] No hydrophobic components were used in this comparative example.

[0126] A) Weigh 1.2% of micron / nano bagasse fiber according to the formula and add it to water (mass fraction of solid mass). Disperse at high speed and stir at low speed. Slowly add the main filler and auxiliary filler (20% micron hollow glass microspheres, 5% micron silica, and 2% nano calcium carbonate) according to the formula. Continue to disperse and set aside.

[0127] B) Add the functional filler dispersion obtained in step A) to the cement powder weighed according to the formula amount (71.8%), and use a planetary rotation and revolution stirring to mix and disperse the components to obtain the all-dimensional hydrophobic radiation cooling cement coating.

[0128] C) Apply the radiation-cooled cement coating obtained in step B) to the cement substrate by scraping and brushing, and cure it under natural conditions (temperature 25℃±3℃, humidity 50%±10%).

[0129] Figure 14 The contact angle between the radiation-cooled cement coating prepared for this comparative example and water is less than 90°, indicating that it does not possess hydrophobic properties.

[0130] Figure 15 This is a schematic diagram showing the reflectance of the radiation-cooled cement coating prepared in this comparative example at different wavelengths. The overall solar reflectance of the coating is 93.4%, which is basically consistent with the solar reflectance of the all-dimensional hydrophobic radiation-cooled cement coating, indicating that the hydrophobic treatment did not significantly affect the solar reflectance of the coating.

[0131] Industrial applicability

[0132] Unlike conventional hydrophobic topcoats that only possess surface hydrophobic self-cleaning functions, the all-dimensional hydrophobic radiation-cooling cement coating of this invention integrates radiation cooling and all-dimensional hydrophobicity, maintaining excellent self-cleaning and radiation cooling performance even with wear. The coating obtained by this invention has a water contact angle greater than 150°, and both its overall reflectivity and overall infrared emissivity at the atmospheric window are above 90%. Therefore, the all-dimensional hydrophobic radiation-cooling cement coating of this invention is expected to have broad application prospects in industry.

Claims

1. A multidimensional hydrophobic radiation-cooling cement coating, comprising cement, functional fillers, admixtures, and water, wherein... The functional filler includes a main filler and an auxiliary filler. The main filler includes micron-sized hollow glass microspheres and optionally contains one or more selected from micron-sized silica and ceramic powder. The main filler accounts for 20-40% of the total solid content in the all-dimensional hydrophobic radiation-cooling cement coating by mass fraction. The auxiliary filler is selected from at least one of nano-silica, nano-calcium carbonate and nano-alumina. The admixture comprises micro / nanofibers and hydrophobic components, and the mass fraction of each of the micro / nanofibers and hydrophobic components relative to the solid content in the all-dimensional hydrophobic radiation-cooled cement coating is less than 3.0%. The hydrophobic component is selected from one or more of dimethylpolysiloxane, methyl vinyl polysiloxane, and methyl phenyl polysiloxane. The cement accounts for 40%-80% of the total solids content in the all-dimensional hydrophobic radiation-cooling cement coating; and The amount of water accounts for 40%-70% of the total solids content in the all-dimensional hydrophobic radiation-cooled cement coating. The average particle size of the main packing is 0.2-100 μm, while the particle size of the auxiliary packing is 20-800 nm. The contact angle between the coating formed by the all-dimensional hydrophobic radiation-cooled cement coating and water is greater than 150°.

2. The all-dimensional hydrophobic radiation-cooling cement coating according to claim 1, wherein the micron / nanofiber is obtained by peeling from bagasse.

3. The all-dimensional hydrophobic radiation-cooling cement coating according to claim 1, wherein the mass fraction of the auxiliary filler relative to the solid content in the all-dimensional hydrophobic radiation-cooling cement coating is less than 10%.

4. The all-dimensional hydrophobic radiation-cooling cement coating according to claim 1, wherein the morphology of the main filler and the auxiliary filler is spherical.

5. The all-dimensional hydrophobic radiation-cooling cement coating according to claim 1, wherein, The mass fraction of each of the micro / nano fibers and the hydrophobic component relative to the solid content in the all-dimensional hydrophobic radiation-cooled cement coating is less than 2.0%.

6. The all-dimensional hydrophobic radiation-cooling cement coating according to claim 1 further includes a defoamer, and the mass fraction of the defoamer relative to the solid content in the all-dimensional hydrophobic radiation-cooling cement coating is less than 2.0%.

7. A multidimensional hydrophobic radiation-cooling cement coating, comprising the following components in the following mass percentage range: Micron-sized hollow glass microspheres account for 5%-40% Micron-sized silica 5%-20%, Nano-calcium carbonate or nano-silica 2%-15%, Hydrophobic component 1.0%-3%, Micron / nano bagasse fiber 0.3%-3%, Cement 40%-80%, and Water 40%-70%, The mass percentages mentioned above refer to the mass fraction of each component relative to the solid content in the all-dimensional hydrophobic radiation-cooled cement coating. The hydrophobic component is selected from one or more of dimethylpolysiloxane, methylvinylpolysiloxane, and methylphenylpolysiloxane. The micron-sized hollow glass microspheres and micron-sized silica are the main fillers, and the nano-calcium carbonate or nano-silica is the auxiliary filler. The average particle size of the main filler is 0.2-100 μm, while the particle size of the auxiliary filler is 20-800 nm. The contact angle between the coating formed by the all-dimensional hydrophobic radiation-cooled cement coating and water is greater than 150°.

8. A multidimensional hydrophobic radiation-cooling cement coating, comprising the following components in the following mass percentage range: Micron-sized hollow glass microspheres account for 10%-40% Micron-sized silica 5%-20%, Ceramic powder 5%-20%, Nano-calcium carbonate or nano-silica 2%-10%, Nano aluminum oxide 3%-10%, Hydrophobic component 1.0%-3%, Micron / nano bagasse fiber 0.3%-2.0%, Cement 40%-80%, and Water 40%-70%, The mass percentages mentioned above refer to the mass fraction of each component relative to the solid content in the all-dimensional hydrophobic radiation-cooled cement coating. The hydrophobic component is selected from one or more of dimethylpolysiloxane, methylvinylpolysiloxane, and methylphenylpolysiloxane. The micron-sized hollow glass microspheres, micron-sized silica, and ceramic powder are the main fillers, while the nano-alumina is the auxiliary filler. The average particle size of the main filler is 0.2-100 μm, and the particle size of the auxiliary filler is 20-800 nm. The contact angle between the coating formed by the all-dimensional hydrophobic radiation-cooled cement coating and water is greater than 150°.

9. A method for preparing a multidimensional hydrophobic radiation-cooling cement coating according to any one of claims 1-8, the method comprising the following steps: A) Weigh the additive and water according to the formula, disperse them evenly at high speed, and slowly add the main filler and auxiliary filler according to the formula under low speed stirring. Continue to disperse and set aside. B) Add the functional filler dispersion obtained in step A) to the cement powder weighed according to the formula, and mix and disperse the components thoroughly to obtain the all-dimensional hydrophobic radiation cooling cement coating.

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