A color dual-mode Janus radiant heat management material and a preparation method and application thereof

Abstract

The application relates to the technical field of thermal management, in particular to a preparation method and application of a Janus radiation thermal management material of a double module, which comprises the following steps: placing a titanium foil serving as an anode and a stainless steel sheet serving as a cathode in an electrolyte H3PO4 solution, adopting an anodic oxidation method to obtain a colored titanium foil; dissolving P(VDF-HFP) in acetone, adding deionized water to obtain a precursor solution; taking the colored titanium foil as a radiation heat preservation film, coating the precursor solution on the back of the colored titanium foil, and drying to form a white radiation cooling surface. The radiation heat preservation layer is prepared based on the film interference principle, the film with structural color is prepared as a radiation heat preservation layer, the radiation heat preservation layer solves the contradiction that color and radiation heat preservation effect cannot be achieved, and the radiation heat preservation layer simultaneously has multiple colors compared with ordinary commercial coatings and radiation heat preservation capacity. The radiation thermal management material can switch the refrigeration / heat preservation mode according to the environment, has huge energy-saving potential, and provides a feasible method for replacing ordinary commercial dyes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermal management, in particular to a preparation method and application of a color dual-mode Janus radiant thermal management material. BACKGROUND

[0002] In the past decade, the demand for cooling and heating in human society has grown rapidly. About 37% of the energy consumption is used for cooling and heating in buildings throughout the year.

[0003] Therefore, it is crucial to explore advanced thermal energy management technologies for sustainable development. Among them, radiant thermal energy management stands out as a technology that can regulate heat exchange processes through infrared (IR) radiation without additional energy consumption. Radiant thermal energy management materials (RTMM) need to be selectively spectrally designed, i.e., high solar reflectance and mid-infrared (MIR) emissivity of materials within the atmospheric transparency window (8-13 μm) will help achieve excellent radiant cooling performance. Conversely, high solar absorptance and low broadband MIR emissivity of materials make them very suitable for radiant heating. However, traditional RTMMs usually present a monochromatic appearance (white, black, or metallic), which hinders their widespread application and severely limits their aesthetic appeal. Therefore, it is urgent to develop color RTMMs.

[0004] In recent years, research has attempted to incorporate color into low-emissivity materials to produce color RTMMs, mainly using IR transparent dyes or photonic structures. However, the dye method has limited color selection and requires low content, while photonic structures are costly and difficult to accurately control layer thickness. Therefore, it is necessary to develop a simple method to produce a variety of color choices of low-emissivity materials. At the same time, climate and seasonal changes pose challenges to single-mode RTMMs, and fixed spectral design cannot cope with temperature fluctuations. Dual-mode RTMMs are more practical in real environments. SUMMARY

[0005] The present application proposes a simple anodization strategy to manufacture dual-mode RTMMs, which solves the contradiction between color and radiant insulation by using structural color based on interference principles and supplemented by a porous P(VDF-HFP) cooling layer. The dual-mode radiant thermal management film realizes bright colors comparable to ordinary commercial dyes while maintaining radiant insulation capacity.

[0006] To achieve the above purpose, on the one hand, the present application provides a preparation method of a color dual-mode Janus radiant thermal management material, which comprises the following steps:

[0007] S1, using H3PO4 solution as an electrolyte, placing a titanium foil as an anode and a stainless steel sheet as a cathode in the electrolyte, and obtaining a colored titanium foil by an anodization method;

[0008] S2, dissolving P(VDF-HFP) powder in acetone and adding deionized water to obtain a P(VDF-HFP)-acetone-water precursor solution;

[0009] S3, using the colored titanium foil as a radiation insulation film, coating the P(VDF-HFP)-acetone-water precursor solution on the back of the colored titanium foil, and drying to form a white radiation cooling surface, thereby obtaining the color dual-mode Janus radiation heat management material.

[0010] As a further preferred technical solution of the present application, the concentration of the H3PO4 solution is 0.1-1 mol / L.

[0011] As a further preferred technical solution of the present application, the process parameters of the anodic oxidation method are as follows: temperature range of 0-60℃, voltage range of 1-60V, and oxidation time of 2-5 minutes. More preferably, the temperature range is 25℃, the oxidation time is 5 minutes, and a series of colored titanium foils with transition colors between brick red and deep purple can be produced by finer modulation of the anodic oxidation voltage interval between 10-20V.

[0012] As a further preferred technical solution of the present application, before step S1, the titanium foil is ultrasonically cleaned multiple times in ethanol and deionized water, respectively, and then dried.

[0013] As a further preferred technical solution of the present application, in step S2, the mass ratio of P(VDF-HFP) powder, acetone, and deionized water is 0.5-1:8:1.

[0014] As a further preferred technical solution of the present application, in step S3, the P(VDF-HFP)-acetone-water precursor solution is coated by scraping.

[0015] As a further preferred technical solution of the present application, in step S3, the thickness of the P(VDF-HFP) layer formed by coating the P(VDF-HFP)-acetone-water precursor solution is 100-300μm. More preferably, the P(VDF-HFP)-acetone-water precursor solution is coated multiple times, and after each coating, the water is completely evaporated. The rapid evaporation of acetone causes the phase separation of the polymer and water, and the slow evaporation of water forms a hierarchical porous morphology of P(VDF-HFP), thereby showing high reflection of visible light.

[0016] According to another aspect of the present application, the present application also provides a color dual-mode Janus radiation heat management material prepared by the above method.

[0017] According to another aspect of the present application, the present application also provides an application of the color dual-mode Janus radiant heat management material as a building wall material in building heat management.

[0018] Compared with the prior art, the present application can achieve the following beneficial effects:

[0019] 1) The preparation method proposed by the present application is simple, easy to prepare in large areas, and suitable for industrial production;

[0020] 2) The color dual-mode Janus radiant heat management material (RTMM) prepared by the anodization strategy has an unprecedented combination of solar absorptance and mid-infrared (MIR) emittance. Specifically, it has a very high solar absorptance and a very low MIR emittance (only 0.07), which significantly improves the heat management performance of the RTMM and makes it perform well in various heat management applications.

[0021] 3) By precisely controlling the voltage and temperature parameters during the anodization process, the present application can easily achieve rich color selection of the RTMM. This feature not only meets the market demand for personalized colors, but also provides more possibilities for the wide application of the RTMM in various fields.

[0022] 4) The present application prepares a thin film with structural color based on the thin film interference principle as a radiant insulation layer, which solves the contradiction between color and radiant insulation effect, and realizes the simultaneous radiant insulation capacity of various colors comparable to ordinary commercial coatings. The color of the radiant insulation film comes from the effect of thin film interference caused by the difference in refractive index between the dense oxide layer and the Ti metal substrate. Based on the different thickness of the oxide layer, the film has rich colors, including: changing the anodization time, voltage and temperature to achieve fine adjustment within the full color range. BRIEF DESCRIPTION OF DRAWINGS

[0023] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0024] Figure 1 The experimental device for outdoor experiments on the heat management film samples of Examples 1 and 2 is shown in the figure, and the dashed line is the position of sealing the upper opening of the foam box with an LDPE film;

[0025] Figure 2 The experimental data and experimental conditions under sealed conditions in the outdoor experiment are shown in the figure, where (a) is the real-time temperature curve of the Janus dual-mode radiant heat management film under the condition of using a polyethylene PE film for sealing, (b) is the corresponding environmental conditions, including solar radiation, humidity and wind speed.

[0026] Figure 3 For the experimental data and experimental conditions of the non-enclosed condition test in the outdoor experiment, (a) the real-time temperature curve of the radiation heating surface (solid line), the cooling surface (dashed line) and the environment (black solid line) of the Janus bimodule radiation heat management film, when not sealed with polyethylene PE film; (b) the corresponding environmental conditions, including solar radiation, humidity and wind speed

[0027] The purposes, functional characteristics and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0028] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0029] Unless otherwise defined, the technical terms used in the following examples have the same meaning as generally understood by those skilled in the art to which the present application belongs. The test reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods, unless otherwise specified, are conventional methods.

[0030] Example 1

[0031] 1) Commercial titanium foil 50μm was sequentially ultrasonically cleaned in ethanol and deionized water for 15 minutes, and then naturally air-dried. Then, the cleaned titanium foil was connected to the positive electrode of the power supply, and a piece of stainless steel foil with the same size was connected to the negative electrode of the power supply, and 0.1mol / L H3PO4 solution was used as the electrolyte. Anodization was carried out by applying a voltage of 10V while controlling the electrolyte temperature to be 25℃, and the oxidation time was 5 minutes to obtain a yellow titanium foil. Finally, the yellow titanium foil was washed with deionized water and naturally air-dried.

[0032] 2) 1 gram of P(VDF-HFP) powder was dissolved in 8 grams of acetone to prepare a P(VDF-HFP) solution, then 1 gram of deionized water was added to obtain a P(VDF-HFP)-acetone-water precursor. After ultrasonic treatment of the precursor for 10 minutes, 1 milliliter of the clear liquid of the precursor was taken and scraped on the back of the yellow titanium foil to form a P(VDF-HFP) layer on the back of the yellow titanium foil as a white radiation cooling surface with a thickness of 300μm. The thickness of the P(VDF-HFP) layer was controlled by the number of scraping times, 1.5mL of the precursor solution was taken each time, and the scraping was performed 14 times, with an interval of 10 minutes between each scraping to ensure complete evaporation of the water. Finally, the obtained Janus radiation heat management film was dried in air for 12 hours.

[0033] Example 2

[0034] The same preparation method as in Example 1 was used, with the only difference being the change in the anodization process parameters: the applied voltage was 20 V, the temperature of the electrolyte was 25 °C, and the oxidation time was 5 minutes, resulting in a deep purple titanium foil, which was finally coated with the P(VDF-HFP)-acetone-water precursor to obtain the Janus radiative heat management film.

[0035] To further demonstrate the beneficial technical effects of the present application, the products of Examples 1 and 2 above were subjected to the following performance tests:

[0036] As shown in Figure 1 , we carried out an outdoor test to verify the radiative cooling and heating performance of the Janus radiative heat management material. In the experiment, samples with a size of 2.5 cm x 2.5 cm were used, and the radiative heat management capability of the samples was tested under two conditions: without the use of low-density polyethylene (LDPE) film and with the use of LDPE film to seal, where the LDPE film serves to reduce the interference of thermal radiation and air convection of the surrounding buildings on the test results of the samples. During the test, the samples were placed in a foam box (porous foam material) with an inner wall covered with aluminum foil to maximize the insulation against thermal convection and thermal radiation. To measure the sample temperature, a layer of 10 pm thick copper foil was fixed to the back of the sample with thermal grease, and a thermocouple was tightly attached to the bottom of the copper foil and connected with thermal silver paste to ensure good thermal conductivity, thereby accurately recording the real-time temperature of the sample and the environment. The copper foil, as an excellent conductor, can reflect the overall temperature of the sample, making the temperature tested by the thermocouple more accurate. The environmental temperature was defined as the temperature inside the incubator at the same level as the sample. At the same time, the comprehensive weather station recorded the weather data including humidity, solar radiation intensity and wind speed Figure 2 b and Figure 3 b).

[0037] As shown in Figure 2 a, when the solar radiation intensity exceeds 1000 W / m 2 , the average temperatures of the yellow and deep purple titanium foils can reach 97 °C and 102 °C, respectively, which are about 25.4 K and 28.2 K higher than the air temperature in a closed environment. In contrast, the temperature of the porous P(VDF-HFP) layer is always 9 K lower than the air temperature.

[0038] As shown in Figure 3 , the real-time temperatures of all samples were measured without the coverage of low-density polyethylene (LDPE) film to set up a more actual environmental condition. In this case, the average temperature on the radiative heating side increased almost 16 K higher than the environmental temperature, while the radiative cooling side was about 5.8 K lower than the environmental temperature.

[0039] The above test results effectively prove that the color double module Janus RTMM radiation heat management film provides a zero energy consumption heat management strategy. Therefore, the Janus radiation heat management material of the present application can switch the refrigeration / heat preservation mode according to the environment, has great energy saving potential, can be used as a building wall material, or as a material such as a refrigeration / protective box. Different thicknesses of the titanium foil oxide layer give the material rich colors, providing a feasible method to replace ordinary commercial dyes, and realizing a variety of colors comparable to ordinary commercial paints while having radiation heat preservation capability.

[0040] Although the specific embodiments of the present application are described above, those skilled in the art should understand that these are only illustrative, and various changes or modifications can be made to the present embodiments without departing from the principles and essence of the present application, and the protection scope of the present application is only limited by the appended claims.

Claims

1. A method for preparing a color dual-mode Janus radiative thermal management material, characterized in that, Includes the following steps: S1. Using H3PO4 solution as electrolyte, titanium foil as anode and stainless steel sheet as cathode are placed in the electrolyte, and colored titanium foil is obtained by anodic oxidation. S2. Dissolve P(VDF-HFP) powder in acetone and add deionized water to mix well to obtain P(VDF-HFP)-acetone-water precursor solution. S3. Using colored titanium foil as a radiation insulation film, P(VDF-HFP)-acetone-water precursor solution is coated on the back of the colored titanium foil and dried to form a white radiation cooling surface, thus obtaining the colored dual-module Janus radiation thermal management material. The concentration of the H3PO4 solution is 0.1~1 mol / L; the process parameters adopted for the anodic oxidation method are: temperature range of 0-60 ℃, voltage range of 1-60 V, oxidation time of 1-5 minutes; the mass ratio of P(VDF-HFP) powder, acetone and deionized water is 0.5-1 : 8 :

1.

2. The method for preparing the Janus radiative thermal management material for a color dual-module according to claim 1, characterized in that, Before step S1, the process also includes ultrasonically cleaning the titanium foil multiple times in ethanol and deionized water, and finally drying it.

3. The method for preparing the Janus radiative thermal management material for a color dual-module according to claim 1, characterized in that, In step S3, the P(VDF-HFP)-acetone-water precursor solution is coated by a scraping method.

4. The method for preparing the Janus radiative thermal management material for a color dual-module according to claim 1, characterized in that, In step S3, the thickness of the P(VDF-HFP) layer formed by coating the P(VDF-HFP)-acetone-water precursor solution is 100-300 μm.

5. The method for preparing the Janus radiative thermal management material for a color dual-mode system according to any one of claims 1-4, characterized in that, In step S3, the P(VDF-HFP)-acetone-water precursor solution is coated multiple times. After each coating is completed, the water is ensured to evaporate completely before the next coating is applied.

6. A color dual-module Janus radiative thermal management material, characterized in that, It is prepared by the method described in any one of claims 1-5.

7. The application of the Janus radiant heat management material with color dual-module as described in claim 6 as a building wall material in building thermal management.

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