Humidity response type dynamic spectrum regulation color radiation cooling material and preparation method thereof

Abstract

The invention discloses a humidity response type dynamic spectrum regulation color radiation cooling material and a preparation method thereof. According to the material, a cobalt-based complex is prepared through a coordination reaction of cobalt chloride hexahydrate and ethanolamine. The material presents a colorful appearance in a low-humidity environment, the visible light absorptivity is reduced and the infrared emission is enhanced in a high-humidity environment, the material has attractive appearance and efficient cooling performance, the infrared emissivity reaches 0.92, and the humidity response time is 30 seconds. The radiation material is suitable for the fields of environmental sensors, intelligent packaging and the like, and solves the problems of single color, glare and high-humidity failure of a traditional radiation material. The invention further provides a preparation method of the TiO2-cobalt-based complex composite material, the reflectivity of the material in the sunlight band can reach 92% after the nano TiO2 is introduced, the reflectivity is remarkably improved, and the TiO2-cobalt-based complex composite material can be applied to the field of building coatings in desert areas.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation methods of cooling materials, and particularly relates to a humidity-responsive dynamic spectral regulation color radiative cooling material and a preparation method thereof. Background Art

[0002] Radiative cooling is a passive cooling method that does not require energy consumption. For a radiative cooler, its cooling process is, on the one hand, to reflect solar radiation in the solar band to reduce heat input, and on the other hand, to transfer the heat on its surface to outer space at absolute zero in the form of mid-infrared thermal radiation through the transparent atmospheric window of the earth. The combined effect of the two can achieve the passive cooling effect.

[0003] This technology has gradually received extensive attention in recent years, especially in terms of energy efficiency and environmentally friendly refrigeration. However, due to their high reflection characteristics in the sunlight band, traditional radiative coolers often present a bright white appearance, which not only easily causes glare effects on the human eye but also greatly limits the application scenarios and aesthetic requirements of radiative cooling materials.

[0004] In recent years, people have tried to prepare colored radiative coolers by adding colored pigments / nano quantum dots, constructing surface microstructures, etc., so that the material not only has high-efficiency radiative heat dissipation ability but also can present colors in the visible light range to meet aesthetic or special application requirements. However, due to the inevitable absorption characteristics in the visible light band of the colored radiative coolers prepared by such methods, their overall solar reflectivity is limited, and the spectral performance of the material does not have the characteristics of dynamic adjustability, making it difficult to maintain continuous and efficient cooling in a changing humidity environment, and even facing the problem of material failure. Summary of the Invention

[0005] By providing a humidity-responsive dynamic spectral regulation color radiative cooling material and a preparation method thereof, the embodiments of the present application solve the problems of single color, glare, and failure in a high-humidity environment in the prior art. Through the humidity-responsive mechanism of cobalt-based complex (CETA), color display at low humidity, reduced visible light absorption rate, and enhanced infrared emission at high humidity are achieved, taking into account both aesthetics and cooling efficiency.

[0006] The embodiments of the present application provide a preparation method of a humidity-responsive dynamic spectral regulation color radiative cooling material, which is characterized in that the preparation method is to use cobalt chloride hexahydrate as a raw material and carry out a coordination reaction with a complexing agent ethanolamine to prepare a cobalt-based complex.

[0007] Preferably, the molar ratio of cobalt chloride hexahydrate to ethanolamine is 1-3:1, preferably 2:1.

[0008] Preferably, cobalt chloride hexahydrate is added to absolute ethanol to prepare a cobalt chloride / ethanol mixed solution, and the concentration of cobalt chloride hexahydrate is 0.75 - 2 mol / L, preferably 1 mol / L.

[0009] Preferably, nano-TiO₂ is added to the cobalt-based complex solution to prepare a cobalt-based complex-TiO₂ composite material.

[0010] Preferably, the mass ratio of the nano-TiO₂ to the cobalt chloride hexahydrate is 8 - 14:1, preferably 11.9:1.

[0011] The embodiment of the present application also provides a humidity-responsive dynamic spectral regulation color radiative cooling material, and the cooling material is prepared by any of the above methods.

[0012] Preferably, when the environmental humidity of the cooling material increases from 30% to 60%, the visible light absorbance reduction rate ≥ 50%, and the response time ≤ 60 seconds.

[0013] The embodiment of the present application also provides an application of the humidity-responsive dynamic spectral regulation color radiative cooling material, and the radiative cooling material is applied in the fields of environmental sensors, intelligent packaging or building coatings in desert areas.

[0014] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects: 1. Since cobalt chloride hexahydrate is used as a raw material and coordinated with ethanolamine as a ligand to prepare a cobalt-based complex, effectively solving the problems of single color, glare and failure in high-humidity environments of existing radiation materials, and then realizing the technical effects of color display at low humidity, reduced visible light absorption rate and enhanced infrared emission at high humidity, taking into account both aesthetics and cooling efficiency.

[0015] 2. The method of the first embodiment of the present application is synthesized by a coordination reaction under normal temperature and pressure, without the need for complex equipment, and is suitable for large-scale production.

[0016] 3. TiO₂ is introduced in the fifth embodiment of the present application, significantly improving the solar reflectance again, and is applicable to scenarios with extremely high requirements for reflectance and small humidity changes. Description of the Drawings

[0017] Figure 1 It is a physical diagram of the target product cobalt-based complex in the first embodiment of the present application; Figure 2 It is the XRD test result of the target product cobalt-based complex in the first embodiment of the present application, confirming its crystal structure; Figure 3 It is the FTIR test result of the target product cobalt-based complex in the first embodiment of the present application, showing its characteristic functional groups; Figure 4 This is the absorbance curve of the target product cobalt-based complex in the ethanol solution in the first embodiment of this application, which proves that it can effectively avoid the absorption of sunlight; Figure 5 This is the absorbance curve of the target product cobalt-based complex in the ethanol / water mixed solution in the first embodiment of this application, which proves that it has the characteristics of dynamic spectral response. Detailed implementation manners

[0018] In the embodiments of this application, by providing a humidity-responsive dynamic spectral regulation color radiative cooling material and its preparation method, the problems of single color, glare and failure in high-humidity environments in the prior art are solved. Through the humidity response mechanism of the cobalt-based complex CETA, color display under low humidity, reduced visible light absorption rate and enhanced infrared emission under high humidity are achieved, taking into account both aesthetics and cooling efficiency.

[0019] The technical solutions in the embodiments of this application to solve the problems of single color, glare and failure in high-humidity environments of the above-mentioned radiative materials are generally as follows: Using cobalt chloride hexahydrate (CoCl2·6H2O) as a raw material and carrying out a coordination reaction with ethanolamine (ETA) to form a cobalt-based complex with a spectral response function to humidity. Due to the strong adsorption characteristics of ethanolamine to humidity, its addition improves the moisture adsorption efficiency and effectively reduces the crystallinity of the pigment. At the same time, because ethanolamine exhibits excellent infrared absorption characteristics in the atmospheric window, the prepared cobalt-based complex has excellent infrared emissivity. In a low-humidity environment, the pigment exhibits color characteristics. In a high-humidity environment, the absorbance of the pigment in the visible light band decreases, and at the same time, the infrared emissivity is further enhanced, realizing color display under low humidity, reduced visible light absorption rate and enhanced infrared emission under high humidity, taking into account both aesthetics and cooling efficiency, and thus solving the problems of single color, white light glare and failure in high-humidity environments of the radiative materials.

[0020] To better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with the accompanying drawings of the specification and specific implementation manners. Embodiment 1

[0021] Weigh 1.19 g of CoCl2·6H2O powder with a balance, select absolute ethanol as a solvent to dissolve the CoCl2·6H2O powder, the amount of absolute ethanol used is 5 ml, and stir with a magnetic stirrer at room temperature for 1 hour to obtain a cobalt chloride / ethanol mixed solution.

[0022] Dissolve 0.153 g of ethanolamine in ethanol and then add it to the cobalt chloride / ethanol mixed solution, and stir at room temperature for 1 hour. Subsequently, add 2.5 ml of deionized water to the solution, stir evenly to obtain a cobalt-based complex CETA solution, abbreviated as CETA solution.

[0023] The CETA solution was placed in a forced-air oven at 60 °C and dried for 6 h to obtain the target product. For the physical picture, please refer to Figure 1 .

[0024] The target product in Example 1 was tested by X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Please refer to Figure 2 , Figure 2 This is the XRD test result of the target product in Example 1. The results show that compared with the CoCl2·6H2O sample, the target product in Example 1 has changed from crystalline to amorphous, and the coordination reaction has occurred successfully. Please refer to Figure 3 , Figure 3 This is the FTIR test result of the target product in Example 1. The characteristic absorption peaks of CoCl2 and ETA appear simultaneously in the spectrum of the target product, indicating that the cobalt-based complex CETA has been successfully prepared, and the infrared absorption peaks of the cobalt-based complex CETA in the atmospheric window band have increased, improving the infrared emission ability of the material at the atmospheric window.

[0025] 0.1 g of the target product in Example 1 was dissolved in 10 ml of absolute ethanol, and the absorbance of the solution in the visible light band was measured. Please refer to Figure 4 , Figure 4 This is the absorbance curve of the target product in Example 1 in ethanol solution. The results show that the target product has fewer absorption peaks in the visible light band, which can effectively avoid the absorption of sunlight.

[0026] 0.1 g of the target product in Example 1 was dissolved in 10 ml of absolute ethanol, and 1 ml of deionized water was added to the solution. The absorbance of the mixed solution in the visible light band was measured. Please refer to Figure 5 , Figure 5 This is the absorbance curve of the target product in Example 1 in ethanol / water mixed solution. The results show that in the presence of water molecules, the absorption peaks of the target product in the visible light band are weakened and the absorbance decreases significantly, showing the characteristics of dynamic spectral response.

[0027] Dynamic wet response test conditions and results: (1) Dynamic humidity response range: 30% - 60% relative humidity (RH).

[0028] (2) Response time definition: The time required for the absorbance / emissivity to reach a stable value (fluctuation < 5%) from the start of humidity change.

[0029] (3) Response threshold definition: Low humidity color development threshold: The material shows color (blue) at RH 30 ± 5%; High humidity regulation threshold: when RH is 60±5%, the visible light absorption rate decreases by ≥30%, and the infrared emissivity increases by ≥0.05.

[0030] (4) Response speed: within the range of 30% change in RH (e.g., 30%→60%), the response time of the material is ≤60 seconds, preferably ≤40 seconds.

[0031] (5) Change in visible light absorption rate: At low humidity (RH 30±5%), the average absorbance of the material in the 400 - 700 nm band is 0.4 - 0.6; At high humidity (RH 60±5%), the absorbance drops to 0.1 - 0.3, with a decrease of ≥50%.

[0032] (6) Infrared emissivity dynamic range: At low humidity (RH 30±5%), the infrared emissivity in the 8 - 13 μm band is 0.85 - 0.90; At high humidity (RH 60±5%), the emissivity increases to 0.90 - 0.92, with an increase of ≥5%.

[0033] Further tests show that when the ambient humidity rises from 20% to 80%, the absorbance of the material in the visible light band drops from 0.55±0.05 to 0.15±0.05, while the infrared emissivity increases from 0.87 to 0.92. Under the condition of a humidity change rate of 5% RH / min, the response time is 45 - 75 seconds, meeting the requirements of dynamic regulation. Example Two

[0034] Weigh 1.31 g of NiCl2·6H2O, dissolve it in 5 ml of absolute ethanol, and stir at room temperature for 1 hour. Add 0.153 g of ethanolamine and stir for 1 hour. Add 2.5 ml of deionized water, stir, and then dry to obtain nickel-based complex (NETA). Example Three

[0035] Weigh 1.19 g of CoCl2·6H2O, dissolve it in 5 ml of absolute ethanol. Add 0.12 g of ethylenediamine and stir for 1 hour. The subsequent steps are the same as in Example One to obtain cobalt-ethanolamine complex (CEDA). Example Four

[0036] Weigh 1.19 g of CoCl2·6H2O, dissolve it in 5 ml of methanol. The subsequent steps are the same as in Example One to obtain CETA-Methanol. Example Five

[0037] In Example 1, 0.1 g of nano-TiO2 (particle size 20 nm) was added to the prepared CETA solution. The subsequent steps were the same as those in Example 1 to obtain the CETA-TiO2 composite material.

[0038] The target products prepared in Examples 1 to 5 were subjected to color characteristic observation, solar reflectance and infrared emissivity performance tests, and humidity response speed tests under the same detection conditions. The test methods were carried out according to the current test standard methods.

[0039] Index Example 1 Example 2 Example 3 Example 4 Example 5 Color characteristics Blue (low humidity) → White (high humidity) Green (low humidity) → Light gray (high humidity) Dark blue → Light blue Dark blue (low humidity) → Grayish white (high humidity) Blue (low humidity) → Light blue (high humidity) Solar reflectance 85% 78% 82% 80% 92% Infrared emissivity 0.92 0.88 0.90 0.89 0.91 Humidity response speed 30 seconds (30% → 60%) 45 seconds (30% → 60%) 48 seconds (30% → 60%) 50 seconds (30% → 60%) 70 seconds (30% → 60%) Morphology of the product after drying Uniform powder Relatively coarse particles and slight agglomeration Relatively dense particle distribution and smaller particle size Particle agglomeration Uniform powder Complex solubility Completely dissolved Partially dissolved Completely dissolved Partially precipitated (stirring time needs to be extended) Completely dissolved From the performance indicators of Examples 1 to 5 in Table 1, the following conclusions can be obtained: The cobalt-based complex CETA cooling material prepared in Example 1 has excellent humidity response performance and radiative cooling performance. The solar reflectance can reach 85%, and the infrared emissivity can reach 92%. The comprehensive performance is the best and can be applied to the fields of environmental sensors and intelligent packaging. In addition, under extreme humidity (such as RH < 20% or > 80%), the material still maintains a reversible response, but the efficiency may decrease slightly, and the specific data needs to be further optimized.

[0040] The stability of the nickel-based complex (NETA) material prepared in Example 2 decreased, and the infrared emissivity and reflectivity were slightly lower. Specifically, because the infrared radiation efficiency of Ni 2+ is lower than that of Co 2+ , and the nickel-based complex has a weak adsorption capacity for moisture, resulting in slightly lower performance. However, the color shows diversity and is suitable for scenarios with high demand for color diversity but lower requirements for cooling efficiency, such as decorative coatings.

[0041] The humidity response sensitivity of the cobalt-ethanolamine complex (CEDA) material prepared in Example 3 decreased, and the infrared emissivity and reflectivity were also slightly lower.

[0042] The CETA-Methanol material prepared in Example 4, due to the higher polarity of methanol than ethanol, affects the solubility of CoCl2 and the complex formation kinetics, resulting in a decrease in the crystallinity of the complex and particle agglomeration.

[0043] The CETA-TiO2 composite material prepared in Example 5 significantly improved the solar reflectance due to the introduction of TiO2, but partially masked the humidity response characteristics of the cobalt-based complex CETA. Specifically, because the TiO2 nanoparticles covered part of the CETA surface, reducing the contact between water molecules and active sites, the humidity response speed was extended from 30 seconds (pure CETA) to 70 seconds. It is suitable for scenarios with extremely high requirements for reflectance and small humidity changes, such as building coatings in desert areas.

[0044] The technical solutions in the embodiments of the present application at least have the following technical effects: 1. In the first embodiment of the present application, through the humidity response mechanism of the cobalt-based complex CETA, color development under low humidity, reduced visible light absorption rate and enhanced infrared emission under high humidity are achieved, breaking through the limitations of traditional static materials.

[0045] 2. The first embodiment of the present application is optimized simultaneously in the solar light band (low absorption) and the atmospheric window band (high infrared emission), taking into account both aesthetics and cooling efficiency. It is synthesized through a coordination reaction under normal temperature and pressure without the need for complex equipment and is suitable for large-scale production.

[0046] 3. In the fifth embodiment of the present application, TiO2 is introduced, significantly improving the solar light reflectivity again, and is applicable to scenarios with extremely high requirements for reflectivity and small humidity changes.

[0047] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0048] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. Preparation method of humidity-responsive dynamic spectrum-regulated color radiative cooling material, characterized in that, The preparation method is to use cobalt chloride hexahydrate as a raw material and carry out a coordination reaction with the coordinating agent ethanolamine to prepare a cobalt-based complex.

2. The method according to claim 1, wherein The molar ratio of the cobalt chloride hexahydrate to the ethanolamine is 1-3:1, preferably 2:

1.

3. The method according to claim 1, characterized in that The cobalt chloride hexahydrate is added to absolute ethanol to form a cobalt chloride / ethanol mixed solution, and the concentration of the cobalt chloride hexahydrate is 0.75-2 mol / L, preferably 1 mol / L.

4. The method according to claim 1, wherein Nanometer TiO2 is added to the cobalt-based complex solution to prepare a cobalt-based complex-TiO2 composite material.

5. The method according to claim 4, wherein The mass ratio of the nanometer TiO2 to the cobalt chloride hexahydrate is 8-14:1, preferably 11.9:

1.

6. A humidity-responsive dynamic spectral regulation color radiative cooling material prepared by any of the methods according to claims 1-5.

7. The material according to claim 6, characterized in that, When the ambient humidity rises from 30% to 60%, the visible light absorbance reduction rate is ≥50%, and the response time is ≤60 seconds.

8. Use of the material according to claim 6, characterized in that, It is used in the fields of environmental sensors, intelligent packaging or building coatings in desert areas.

Images