Silica composite, method for the production thereof, refrigeration film or coating produced therefrom and use of the refrigeration film or coating

Abstract

The application discloses a kind of silica composite material, its preparation method, the refrigeration film or coating prepared from it and the application of the refrigeration film or coating.The structure of the silica composite material includes silica microspheres and silica nanoclusters combined on the surface of the silica microspheres.In the technical solution, the characteristics of silica at 9.6 μm have significant phonon polarization-phonon resonance, which realizes lower infrared reflectivity and higher solar radiation reflectivity, which is more conducive to radiative cooling. The high roughness of the surface silica particle cluster realizes self-cleaning function.

Description

Technical Field

[0001] This invention relates to the field of radiative cooling technology. More specifically, it relates to a silica composite material, a method for preparing the same, a cooling film or coating obtained therefrom, and the application of the cooling film or coating. Background Technology

[0002] From the perspective of actual car use, it's common for car interiors to overheat, requiring frequent cleaning. Conventional methods for cooling cars include opening windows for ventilation and using air conditioning. However, opening windows is impractical in rainy weather, and air conditioning increases energy consumption. Therefore, finding a type of car window that can cool without consuming energy and has a self-cleaning function is essential.

[0003] Some technical solutions include a composite cooling glass that has a cooling effect, but this type of composite glass is relatively thick and cannot achieve self-cleaning. There is also a radiation-cooling waterproof membrane, but it cannot achieve high light transmittance. Another solution is a radiation-cooling film with self-cleaning function, but this solution involves simultaneously stirring particles of different sizes, which cannot effectively form a composite structure, and the film produced by this solution has poor light transmittance, making it unsuitable for automotive glass. Summary of the Invention

[0004] Based on the above facts, the purpose of this invention is to provide a silica composite material, its preparation method, the cooling film or coating obtained therefrom, and the application of the cooling film or coating, to solve the problem of high internal temperatures in automobiles and the need for regular external cleaning, achieving self-cleaning of automobile glass while simultaneously cooling and dissipating heat without additional energy consumption. It also improves driving safety in rainy and foggy weather and effectively assists air conditioning in winter and summer, achieving energy conservation and consumption reduction.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] On one hand, the present invention provides a silica composite material, wherein the structure of the composite material includes silica microspheres and silica nanoclusters bonded to the surface of the silica microspheres.

[0007] Furthermore, the particle size of the silica microspheres is 1-6 μm.

[0008] Furthermore, in the silica nanoclusters, the silica particles have a particle size of 50-100 nm.

[0009] Furthermore, the volume ratio of the silica microspheres to the silica nanoclusters is 1.5-3:1.

[0010] Furthermore, the composite material is in the form of a gel.

[0011] In another aspect, the present invention provides a method for preparing the silica composite material as described above, comprising the following steps:

[0012] Provides silica nanoclusters;

[0013] Silica microspheres are grown on the silica nanoclusters to obtain the silica composite material.

[0014] Furthermore, the preparation of the silica nanoclusters includes the following steps:

[0015] Nanoscale monodisperse silica powder was prepared by using tetraethyl orthosilicate as the silicon source and ammonia as the catalyst via a sol-gel method.

[0016] The silica powder was surface modified using a silane coupling agent to obtain the silica nanoclusters.

[0017] Furthermore, the method for growing silica microspheres is a seed growth method.

[0018] In another aspect, the present invention provides a cooling film or coating with a self-cleaning function, which is prepared from raw materials comprising the silica composite material described above.

[0019] Furthermore, the thickness of the cooling film or coating is 10-15 μm.

[0020] Furthermore, the preparation of the coating includes the following steps:

[0021] The silica composite material is applied to a substrate and dried to obtain the cooling film or coating.

[0022] Furthermore, the application method is an dip-coating method.

[0023] In another aspect, the present invention provides the application of the cooling film or coating described above in the cooling and self-cleaning of automotive glass.

[0024] The beneficial effects of this invention are as follows:

[0025] In the structure of the silica composite material provided by the present invention, silica nanoparticle clusters are distributed around the silica microspheres. By utilizing the significant phonon polarization-phonon resonance characteristics of silica at 9.6 μm, a lower infrared reflectivity and a higher solar radiation reflectivity are achieved, which is more conducive to radiative cooling. The high roughness of the surface silica particle clusters is used to achieve a self-cleaning function. Attached Figure Description

[0026] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0027] Figure 1 This diagram illustrates the principle of radiation-induced cooling self-cooling of a silica composite material according to a specific embodiment of the present invention.

[0028] Figure 2 A schematic diagram of the structure of a silica composite material according to a specific embodiment of the present invention is shown. Detailed Implementation

[0029] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0030] To address the issue of excessively high interior temperatures in automobiles and the need for regular external cleaning, one specific embodiment of the present invention provides a silica composite material. The composite material comprises silica microspheres and silica nanoclusters bonded to the surface of the silica microspheres.

[0031] In this silica composite material, micron-sized silica microspheres are surrounded by nano-sized clusters of silica particles. This structure combines the roughness of microparticles with the scattering effect of large-particle size. Therefore, when used as a cooling film or coating for automotive glass, it can achieve self-cleaning of the glass while simultaneously providing cooling and heat dissipation without additional energy consumption. It improves driving safety in rainy and foggy weather and effectively assists air conditioning in winter and summer, achieving energy conservation and consumption reduction. An exemplary mechanism of action is as follows... Figure 1 As shown, specifically, when sunlight shines on the SiO2 microsphere structure, due to its significant phonon-polarized phonon resonance at 9.6 μm, exhibits near-perfect absorption in the resonance region when its electromagnetic resonance is concentratedly excited, effectively dissipating heat. When light shines on it, visible light passes through and infrared light is reflected, creating a radiative heat dissipation effect. Because of its relatively large surface roughness and its location within the gaps of the SiO2 microspheres, the SiO2 nanoclusters exhibit a hydrophobic effect when water falls, as the liquid's surface contact area with the nanoclusters is reduced, and the tilted contact allows the liquid to slide directly off.

[0032] For example, the silica microspheres have a particle size of 1-6 μm.

[0033] Compared to non-clustered dispersed silica nanoparticles, silica nanoclusters can impart better self-cleaning properties to materials.

[0034] For example, in the silica nanoclusters, the silica particles have a particle size of 50-100 nm.

[0035] By controlling the particle size of silica ions in silica microspheres and silica nanoclusters, the structure achieves both good roughness and scattering effect.

[0036] For example, the volume ratio of silica microspheres to silica nanoclusters is 1.5-3:1. In this case, the cooling film or coating prepared using this silica composite material has lower infrared reflectivity and higher solar radiation reflectivity, which is more beneficial for radiative cooling and self-cleaning. Preferably, the volume ratio of silica microspheres to silica nanoclusters is 2:1.

[0037] Furthermore, the composite material is in the form of a gel.

[0038] According to another specific embodiment of the present invention, a method for preparing the silica composite material as described above is provided, the method comprising the following steps:

[0039] 1) Provides silica nanoclusters.

[0040] The large surface roughness of clustered silica nanoparticles is beneficial for the hydrophobic properties of the film.

[0041] The preferred particle size of the silica nanoclusters is 50-100 nm.

[0042] For example, the preparation of the silica nanoclusters includes the following steps:

[0043] i) Using tetraethyl orthosilicate as the silicon source and ammonia as the catalyst, nanoscale monodisperse silica powder was prepared by sol-gel method.

[0044] For example, step i) is specifically described as follows:

[0045] (1) Sol-gel: First, measure 18 mL of ethanol (C2H5OH) and 3 mL of distilled water (H2O), and stir at 35°C with a magnetic stirrer at a constant speed for 6 min to ensure thorough mixing. Before stirring, cover the mouth of the beaker with a safety film to prevent the evaporation of ethanol during stirring. Then, add 3 mL of ammonia (NH3·H2O) and stir magnetically for 10 min. The safety film can effectively prevent the volatilization of ammonia (ammonia is highly irritating, so wear a mask, rubber gloves, and goggles, and wear a lab coat). Finally, add 3 mL of tetraethyl orthosilicate (TEOS) and stir at a constant speed with a magnetic stirrer. Note that the stirring speed should be such that the rotor does not touch the beaker wall and a conical vortex just appears in the center of the reaction liquid.

[0046] (2) Centrifugation: After the reaction is complete, remove the reaction solution from the magnetic stirrer, put it into a centrifuge tube, and centrifuge it using a high-speed centrifuge. The purpose is to separate the silica generated by the reaction from the solution. The centrifuge parameters are set as follows: speed 10000 rad / s, time 50s.

[0047] (3) Drying and grinding: After centrifugation, remove the clear part on the top of the centrifuged liquid, retain the solid at the bottom of the tube and the reaction liquid at the bottom, and dry them in an oven at 80°C for 24 hours; collect the powder, grind it with an agate mortar and pestle and set it aside for later use.

[0048] ii) The silica powder was surface modified using a silane coupling agent to obtain the silica nanoclusters.

[0049] For example, in step ii), the specific surface modification method is as follows: the silica powder is added to a mixture of anhydrous ethanol and silane coupling agent, and stirred at room temperature to obtain the silica nanoclusters.

[0050] 2) Silica microspheres are grown on the silica nanoclusters to obtain the silica composite material.

[0051] For example, the method for growing silica microspheres on silica nanoclusters is the seed growth method.

[0052] For example, the growth method specifically includes the following steps:

[0053] a. Preparation of seed solution: Mix the reactants distilled water, ethanol, ammonia and tetraethyl silicate according to the proportions above, and stir in the order listed above. The mixture after stirring is recorded as the seed solution.

[0054] b. Seed growth reaction: The silica nanoclusters are mixed with the seed liquid and reacted at room temperature for 4 hours. The reaction solution obtained after the reaction is completed is called α solution. The seed liquid is added to α solution and the reaction is continued for 4 hours. The reaction solution after the reaction is completed is called β solution. The seed liquid is added to β solution and the reaction is continued for 4 hours. The reaction solution is called γ solution. The seed liquid is added to γ ​​solution and the reaction is continued for 4 hours. The reaction solution is called δ solution. The seed liquid is added to δ solution and the reaction is continued for more than 12 hours. The reaction solution is called ε solution. After the reaction, the mixture is centrifuged and dried.

[0055] In step 2), the resulting silica composite material contains micron-sized silica microspheres surrounded by nano-sized clusters of silica particles. This silica composite material is gel-like.

[0056] According to another specific embodiment of the present invention, a cooling film or coating with a self-cleaning function is provided, which is prepared from raw materials comprising the silica composite material as described above.

[0057] For example, the thickness of the cooling film or coating is 10-15 μm. This allows for a better balance between the transmission of visible light and heat dissipation in the vehicle.

[0058] The cooling film or coating can be prepared using conventional methods in the art. In some examples, the preparation includes the following steps:

[0059] The silica composite material is applied to a substrate and dried to obtain the cooling film or coating.

[0060] The substrate can be automotive glass.

[0061] Furthermore, the application method is dip-coating. Specifically, this can be achieved by immersing the pretreated substrate in the silica composite material, removing it, and drying it to obtain the cooling film or coating.

[0062] According to yet another specific embodiment of the present invention, the application of the cooling film or coating described above in the cooling and self-cleaning of automotive glass is provided.

[0063] Forming this cooling film or coating on automotive glass can give the glass a good self-cleaning effect while providing cooling and heat dissipation capabilities without additional energy consumption.

[0064] In some examples, the application scenarios include, but are not limited to:

[0065] 1) Driving in the rain can affect the driver's vision due to water stains and frequent wiper movements. Using a self-cleaning windshield can help. Because of the superhydrophobic properties of the clustered silica particles on its surface, rainwater is turned into water droplets due to surface tension. When the car is tilted slightly during driving, the water droplets will roll off the window and carry away some dust and dirt particles, achieving a self-cleaning effect. This effectively improves driving safety while keeping the car windows clean.

[0066] 2) Solving the problem of impaired visibility while driving in foggy weather: The main cause of car fogging is the temperature difference between the interior and exterior windows. When the outdoor temperature is lower than the interior temperature of the car, the temperature of the window glass in contact with the outside is low, causing water vapor inside the car to condense on the glass and form fog. Using glass with self-cleaning and radiant cooling properties, the temperature difference can be reduced through a silica composite structure, and the water droplets in the fog can be directly washed away by gravity, thus achieving a fog-free effect.

[0067] 3) It assists in cooling the vehicle in summer and insulating it in winter, thereby achieving energy conservation and consumption reduction. In winter, when the interior temperature of the vehicle is higher than the exterior temperature, far-infrared radiation mainly comes from the interior. Glass with a silica microsphere structure can reflect it back into the interior, preventing heat loss. It allows solar radiation from the outside to enter, and this energy is absorbed and converted into far-infrared radiation that remains inside, thus saving on air conditioning usage. In summer, when the exterior temperature of the vehicle is higher than the interior temperature, glass with a SiO2 microsphere structure can reflect it out, preventing heat from entering the vehicle. It can also reflect most of the direct solar radiation from the outside, thus reducing air conditioning cooling costs.

[0068] The technical solution of the present invention will be described below with reference to some specific embodiments:

[0069] Example 1

[0070] A silica composite material, the structural schematic diagram of which is shown below. Figure 2 As shown, its preparation includes the following steps:

[0071] Sol-gel: Measure 18 mL of ethanol (C2H5OH) and 3 mL of distilled water (H2O), and stir at 35°C with a magnetic stirrer at a constant speed for 6 min to ensure thorough mixing. Before stirring, cover the mouth of the beaker with a plastic film to prevent ethanol evaporation during stirring. Then add 3 mL of ammonia water (NH3·H2O), and stir magnetically for 10 min. Finally, add 3 mL of tetraethyl orthosilicate (TEOS), and stir at a constant speed with a magnetic stirrer. Note that the stirring speed should be such that the rotor does not touch the beaker wall and a conical vortex just appears in the center of the reaction solution.

[0072] Centrifugation: After the reaction is complete, remove the reaction solution from the magnetic stirrer, put it into a centrifuge tube, and centrifuge it using a high-speed centrifuge. The purpose is to separate the silica produced by the reaction from the solution. The centrifuge parameters are set as follows: speed 10000 rad / s, time 50s.

[0073] Drying and grinding: After centrifugation, remove the clear part on the top of the centrifuged liquid, retain the solid at the bottom of the tube and the reaction liquid at the bottom, and dry them in an oven at 80℃ for 24 hours; collect the powder, grind it with an agate mortar and pestle for later use, and obtain nano-sized monodisperse silica powder.

[0074] The silica powder was surface modified using a silane coupling agent: the silica powder was added to a mixture of anhydrous ethanol and a silane coupling agent, and stirred at room temperature to obtain silica nanoclusters; silica microspheres were then grown on the silica nanoclusters using a seed growth method to obtain the silica composite material. The specific method is as follows:

[0075] Preparation of seed culture: Measure 18 mL of ethanol (C2H5OH) and 3 mL of distilled water (H2O), and stir at 35°C with a magnetic stirrer at a constant speed for 6 min to ensure thorough mixing. Before stirring, cover the mouth of the beaker with a plastic film to prevent ethanol evaporation during stirring. Then add 3 mL of ammonia water (NH3·H2O), stir magnetically for 10 min, and finally add 3 mL of tetraethyl orthosilicate (TEOS). Stir at a constant speed with a magnetic stirrer until the seed culture is obtained.

[0076] The silica nanoclusters were mixed with seed solution and reacted at room temperature for 4 hours. Seed solution was then added to the reaction solution after the reaction was complete, and the reaction was continued for another 4 hours. This process was repeated for over 12 hours. After the reaction, the mixture was centrifuged and dried. The morphology of the obtained silica composite material (gel) was characterized (e.g., by SEM). It was found that in the structure of this composite material, silica nanoclusters (with silica particles of 50-100 nm in diameter) were attached to the surface of silica microspheres (1-6 μm in diameter), and the volume ratio of silica microspheres to silica nanoclusters was 2:1.

[0077] Specific application examples:

[0078] The silica composite materials prepared in the above examples and comparative examples are used for refrigeration and self-cleaning of automotive glass. Specifically, the steps include:

[0079] 1) Perform surface cleaning pretreatment on the automotive glass;

[0080] 2) The pretreated automotive glass is immersed in the silica composite material (gel) and coated using the dip-coating method to form a cooling film or coating on the automotive glass, thus obtaining self-cleaning automotive glass that cools and dissipates heat without additional energy consumption.

[0081] After being coated or layered, automotive glass exhibits excellent self-cooling and self-cleaning properties without compromising its mechanical properties. This allows for self-cleaning of the automotive glass while simultaneously cooling and dissipating heat without additional energy consumption. It improves driving safety in rainy and foggy weather and effectively assists air conditioning in winter and summer, achieving energy savings and reduced consumption.

[0082] In this embodiment, no specific requirements are made for the testing method of the coating or coating film performance; any existing corresponding performance testing method can be used.

[0083] In some examples, the self-cooling performance can be tested using the following methods:

[0084] A coating was prepared on a glass water cup, and then water was filled into the cup. At the same time, an uncoated glass water cup was filled with the same volume and temperature of water, and the cups were placed in the sun for temperature comparison. A thermometer was inserted into the mouth of the cups, and the temperature change was monitored from 6 am to 6 pm under exposed air conditions. It was found that the temperature of the water in the coated glass water cup was about 4-5°C lower or more than that in the uncoated glass water cup.

[0085] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A cooling membrane with self-cleaning function, characterized in that, It is prepared from raw materials containing silica composite material, and the preparation includes the following steps: The silica composite material is applied to a substrate and dried to obtain the cooling film. The composite material consists of silica microspheres and silica nanoclusters bonded to the surface of the silica microspheres; The silica microspheres have a particle size of 1-6 μm; In the silica nanoclusters, the silica particles have a particle size of 50-100 nm; The volume ratio of the silica microspheres to the silica nanoclusters is 1.5-3:1; The composite material is in a gel-like state; The preparation method of the silica composite material includes the following steps: Provides silica nanoclusters; Silica microspheres were grown on the silica nanoclusters to obtain the silica composite material; The method for growing silica microspheres is a seed growth method; The preparation of the silica nanoclusters includes the following steps: Nanoscale monodisperse silica powder was prepared by using tetraethyl orthosilicate as the silicon source and ammonia as the catalyst via a sol-gel method. The silica powder was surface modified using a silane coupling agent to obtain the silica nanoclusters.

2. The cooling membrane according to claim 1, characterized in that, The thickness of the cooling film is 10-15 μm.

3. The cooling membrane according to claim 1, characterized in that, The application method is dip-coating.

4. The application of the cooling film as described in any one of claims 1-3 in the cooling and self-cleaning of automotive glass.

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