A photothermal-radiation cooling bifunctional composite film and a preparation method and application thereof

Abstract

The application provides a photothermal-radiation cooling dual-function composite film and a preparation method and application thereof, and belongs to the technical field of new energy materials and devices. The method comprises the following steps: preparing a PDMS / MWCNTs mixed solution; fully stirring the solution and placing the solution in a vacuum degassing machine for vacuum air extraction; spraying a layer of release agent on a glass sheet; placing the glass sheet on a heating table to heat the release agent to solidify the release agent into a film; uniformly dropping the prepared solution on the glass sheet, using a four-side film applicator to scrape the solution into an unformed film with uniform thickness; placing the glass sheet on the heating table to heat the solution to solidify the solution; and tearing the film from the glass sheet to obtain a PDMS / MWCNTs film. The application further provides the photothermal-radiation cooling dual-function composite film prepared by the method. The preparation method has the characteristics of low manufacturing cost, simple manufacturing process and easy preparation; and the prepared composite film has high solar absorption rate and high atmospheric window emissivity. The prepared composite film can be applied to thermoelectric power generation devices.

Description

Technical Field

[0001] This invention relates to the field of new energy materials and devices, specifically to a photothermal-radiation cooling dual-functional composite thin film, its preparation method, and its application. Background Technology

[0002] Solar absorbers, under sunlight, efficiently absorb solar energy and convert it into heat, increasing surface temperature. An ideal photothermal material is a perfect blackbody, which completely absorbs incident sunlight without reflection or transmission. Multi-scale nanophotonic materials such as carbon nanotubes, graphene, and metal nanoparticles possess extremely high light absorption and photothermal properties.

[0003] Radiation coolers radiate electromagnetic waves to exchange heat with outer space, thereby achieving cooling. Typical radiation coolers have high emissivity in the atmospheric window (8-13 μm).

[0004] The global energy landscape is shifting towards cleaner, newer energy sources, utilizing environmentally friendly technologies such as solar energy and outer space cooling systems. Thermoelectric power generation devices generate electricity based on temperature differences. By integrating solar absorbers and radiant coolers into these devices, the temperature differences between the solar absorber and the surrounding environment, as well as between the radiant cooler and the surrounding environment, can be used to achieve thermoelectric conversion and generate electricity.

[0005] The photothermal-radiative cooling dual-functional composite film can absorb solar energy during the day to achieve a temperature rise, and radiate heat into outer space at night to achieve a temperature drop. Integrating the photothermal-radiative cooling dual-functional composite film into thermoelectric power generation devices can enable 24-hour power generation. The photothermal-radiative cooling dual-functional composite film can also be applied to the field of intelligent temperature control, such as wearable devices and spacecraft thermal management, to achieve adaptive temperature regulation. Summary of the Invention

[0006] The purpose of this invention is to provide a photothermal-radiation cooling dual-functional composite thin film, its preparation method and application, to solve the problems in the prior art that solar absorbers and radiation coolers cannot be integrated at the same time and that the preparation process of solar absorbers and radiation coolers is complicated.

[0007] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows:

[0008] A method for preparing a photothermal-radiative cooling dual-functional composite thin film, characterized by comprising the following steps:

[0009] Step S1: Prepare a PDMS / MWCNTs mixed solution.

[0010] Step S2: Thoroughly stir the PDMS / MWCNTs mixed solution and place it in a vacuum degassing machine to remove air;

[0011] Step S3: Spray a layer of release agent onto the glass slide.

[0012] Step S4: Place the glass sheet on a heating table and heat it to solidify the release agent into a film.

[0013] Step S5: The prepared PDMS / MWCNTs mixed solution is evenly dropped onto the glass slide, and the PDMS / MWCNTs mixed solution is coated into a uniform unformed film using a four-sided coating tool.

[0014] Step S6: Place the glass slide on a heating stage and heat it to solidify the PDMS / MWCNTs mixed solution.

[0015] Step S7: Peel the film off the glass slide to obtain the PDMS / MWCNTs film.

[0016] Further, in step S1, the PDMS / MWCNTs mixed solution is prepared according to the mass ratio of PDMS component: curing agent: MWCNTs of 100 (15g): 10 (1.5g): X (0.15-0.75g).

[0017] Furthermore, in step S2, the PDMS / MWCNTs mixed solution is placed in a vacuum degassing machine for 30 seconds to remove vacuum.

[0018] Furthermore, in step S4, the temperature of the heating platform is set to 110°C and the heating time is set to 3 minutes.

[0019] Furthermore, in step S5, the thickness specifications of the four-sided coating apparatus are 100-200-300-400μm and 250-500-750-1000μm.

[0020] Furthermore, in step S6, the temperature of the heating platform is set to 110°C and the heating time is set to 5 minutes.

[0021] This invention also proposes a photothermal-radiative cooling dual-functional composite film, which is prepared by a photothermal-radiative cooling dual-functional composite film preparation method. The composite film is composed of PDMS and MWCNTs and has flexibility and stretchability.

[0022] Furthermore, the absorption rate of the composite film is determined by the film thickness and the MWCNT doping concentration.

[0023] The present invention also proposes the application of the photothermal-radiation cooling bifunctional composite thin film prepared by the aforementioned photothermal-radiation cooling bifunctional composite thin film preparation method in thermoelectric power generation devices.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] The proposed method for preparing a photothermal-radiative cooling bifunctional composite thin film using a blade coating process is characterized by low manufacturing cost, simple manufacturing process, and ease of preparation. The photothermal-radiative cooling bifunctional composite thin film prepared by this method possesses high solar absorptivity, high atmospheric window emissivity, and high flexibility. The photothermal conversion function enables the thin film to effectively absorb sunlight and convert it into heat energy during the day, increasing the material's surface temperature. At night, the radiative cooling function effectively reduces the material's surface temperature by radiating mid-infrared heat into the atmospheric window. The photothermal-radiative cooling bifunctional composite thin film prepared by this invention has wide applications, including in the field of thermoelectric power generation devices, where it can be used to improve thermoelectric conversion efficiency. Furthermore, this composite thin film can also be used in intelligent temperature control systems for building surfaces, vehicle cooling systems, and thermal management systems in the aerospace field. The photothermal-radiative cooling bifunctional composite thin film preparation method provided by this invention combines the advantages of low cost, ease of operation, and environmental friendliness, and has broad prospects for industrial application. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 Contour plots showing the absorbance of films with a thickness of 100-500 μm and a MWCNT concentration of 1-5%.

[0028] Figure 2 This is a physical image of the bifunctional composite film of Embodiment 1 of the present invention.

[0029] Figure 3 The absorption rate is that of the bifunctional composite film in Embodiment 1 of the present invention.

[0030] Figure 4 This is a temperature variation graph of the bifunctional composite thin film of Embodiment 1 of the present invention under standard solar irradiance.

[0031] Figure 5 The emissivity of the bifunctional composite thin film in the atmospheric window band of Embodiment 1 of the present invention is shown.

[0032] Figure 6 This is a temperature data graph of a bifunctional composite film according to an embodiment of the present invention at night.

[0033] Figure 7 This is a flowchart of the dual-function composite thin-film integrated thermoelectric power generation device of Embodiment 2 of the present invention.

[0034] Figure 8 This is a physical image of a bifunctional composite thin film integrated into a thermoelectric power generation device according to Embodiment 2 of the present invention.

[0035] Figure 9 The IV and IP curves of the thermoelectric power generation device in Example 2 of this invention are shown under standard solar irradiation.

[0036] Figure 10 This is the output voltage of the thermoelectric power generation device in Example 2 of the present invention at night. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] This invention utilizes a blade coating method to prepare a PDMS (polydimethylsiloxane) / MWCNTs (multi-walled carbon nanotubes) composite film with dual photothermal and radiation cooling functions. This film exhibits high light absorption and atmospheric window emissivity, while also possessing flexibility and stretchability. Integrating the film into a thermoelectric power generation device enables 24-hour uninterrupted power generation.

[0039] This invention proposes a method for preparing a photothermal-radiative cooling dual-functional composite thin film, the method comprising the following steps:

[0040] Step S1: Prepare the PDMS / MWCNTs mixed solution;

[0041] Step S2: Thoroughly stir the PDMS / MWCNTs mixed solution and place it in a vacuum degassing machine to remove air;

[0042] Step S3: Spray a layer of release agent onto the glass slide;

[0043] Step S4: Place the glass sheet on a heating table and heat it to solidify the release agent into a film;

[0044] Step S5: The prepared PDMS / MWCNTs mixed solution is evenly dropped onto the glass slide, and the PDMS / MWCNTs mixed solution is coated into a uniform unformed film using a four-sided coating tool.

[0045] Step S6: Place the glass slide on a heating stage and heat it to solidify the PDMS / MWCNTs mixed solution;

[0046] Step S7: Peel the film off the glass slide to obtain the PDMS / MWCNTs film.

[0047] Specifically, in step S1, the PDMS / MWCNTs mixed solution is prepared according to the mass ratio of PDMS component: curing agent: MWCNTs of 100 (15g): 10 (1.5g): X (0.15-0.75g).

[0048] Specifically, in step S2, the PDMS / MWCNTs mixed solution is placed in a vacuum degassing machine for 30 seconds to remove air.

[0049] Specifically, in step S4, the temperature of the heating platform is set to 110°C and the heating time is set to 3 minutes.

[0050] Specifically, in step S5, the thickness specifications of the four-sided coating apparatus are 100-200-300-400μm and 250-500-750-1000μm.

[0051] Specifically, in step S6, the temperature of the heating platform is set to 110°C and the heating time is set to 5 minutes.

[0052] Furthermore, the absorptivity of the PDMS / MWCNTs thin film is determined by the film thickness and the MWCNTs doping concentration. Specifically: the MWCNTs mass percentage is 1%–5%, preferably 3%; the film thickness is 200–500 μm, preferably 300 μm; the average absorptivity in the solar spectral band (300–2500 nm) is ≥99%; and the peak emissivity in the atmospheric window band (8–13 μm) is ≥95%.

[0053] Figure 1 The figure shows contour plots of the absorbance of films with thicknesses of 100-500 μm and MWCNT concentrations of 1-5%. It can be seen that the absorbance of a 100 μm thick film with a 1% concentration is only 50%. Increasing the doping concentration of MWCNTs in the PDMS matrix and the film thickness improves the absorbance. At a certain thickness and doping concentration (e.g., 400 μm thick, 3% concentration), the absorbance of PDMS / MWCNTs reaches nearly 100%. However, beyond a certain threshold, further increasing the doping concentration or thickness does not further improve the absorbance. For example, the absorbance of a 300 μm thick film with a 4% MWCNT concentration is 99%, and increasing the film thickness does not further increase the absorbance.

[0054] The following two embodiments will be used to describe in detail the preparation method of the photothermal-radiation cooling dual-functional composite thin film of the present invention.

[0055] Example 1

[0056] A method for preparing a photothermal-radiative cooling bifunctional composite thin film, the purpose of which in this embodiment is to prepare a thin film with a thickness of 300 μm and a MWCNT concentration of 3%, includes the following steps:

[0057] Step S1: Prepare a PDMS / MWCNTs mixed solution.

[0058] Specifically, the solution was prepared according to the mass ratio of PDMS components: curing agent: MWCNTs of 100 (15g): 10 (1.5g): 3 (0.45g).

[0059] Step S2: Thoroughly stir the PDMS / MWCNTs mixed solution and place it in a vacuum degassing machine to remove air.

[0060] Specifically, the PDMS / MWCNTs mixed solution was placed in a vacuum degassing machine and vacuumed for 30 seconds.

[0061] Step S3: Spray a layer of release agent onto the glass slide.

[0062] Step S4: Place the glass sheet on a heating table and heat it to solidify the release agent into a film.

[0063] Specifically, the temperature of the heating platform is set to 110℃, and the heating time is set to 3 minutes.

[0064] Step S5: The prepared PDMS / MWCNTs mixed solution is evenly dropped onto the glass slide, and the PDMS / MWCNTs mixed solution is coated into a uniform unformed film using a four-sided coating tool.

[0065] Specifically, the four-sided coating tool selects one side with a thickness of 300μm for coating.

[0066] Step S6: Place the glass slide on a heating stage and heat it to solidify the PDMS / MWCNTs mixed solution.

[0067] Specifically, the temperature of the heating platform is set to 110℃, and the heating time is set to 5 minutes.

[0068] Step S7: Peel the film off the glass slide to obtain the PDMS / MWCNTs film.

[0069] A physical image of the photothermal-radiative cooling dual-functional composite thin film prepared by this method is shown below. Figure 2 As shown, the PDMS / MWCNTs film did not crack under hand-held stretching, indicating that the film has a certain degree of stretchability. Figure 3 The figure shows the absorptivity of the bifunctional composite film. The film has a high broadband absorptivity in the solar spectrum (280-2500nm), with an average absorptivity of 99%. Figure 4The figure shows the temperature change of the bifunctional composite film under standard solar irradiance. It can be seen that under standard solar irradiance, the film rapidly rises to 52°C within 60 seconds, reaching a maximum temperature of 55°C. Figure 5 The emissivity of the bifunctional composite thin film in the atmospheric window band shows that the peak emissivity of the film can reach 90% in the infrared band of 8-13 μm. Figure 6 This is a temperature data graph of a bifunctional composite thin film at night. The film radiates heat into outer space through an atmospheric window, achieving a temperature drop of 7.3K compared to the surrounding environment.

[0070] Example 2

[0071] The purpose of this embodiment is to provide the application of a photothermal-radiative cooling dual-functional composite thin film in thermoelectric power generation devices, such as... Figure 7 As shown, the method includes the following steps:

[0072] Step S1: Prepare Ecoflex (environmentally friendly thermoplastic elastomer material) solution.

[0073] Specifically, Ecoflex is a two-component product, and solutions are prepared according to the mass ratio of Ecoflex component A to Ecoflex component B of 1 (2g): 1 (2g).

[0074] Step S2: Thoroughly stir the Ecoflex solution and place it in a vacuum degassing machine to remove air.

[0075] Specifically, the vacuum pumping time is set to 30 seconds.

[0076] Step S3: Spray a layer of release agent onto the glass slide.

[0077] Step S4: Place the glass sheet on a heating table and heat it to solidify the release agent into a film.

[0078] Specifically, the heating table temperature is set to 110℃ and the heating time is 3 minutes.

[0079] Step S5: Place the glass slide on the spin coater, drop the prepared Ecoflex solution onto the center of the glass slide, and spin coat.

[0080] Specifically, the spin coating speed was set to 500 rpm / s, and the spin coating time was 120 seconds.

[0081] Step S6: Place the glass sheet on a heating stage and heat until the film solidifies to obtain the Ecoflex substrate.

[0082] Specifically, the heating table temperature is set to 150℃, and the heating time is 3 minutes.

[0083] Step S7: Adhere the single-sided copper foil with PI (polyimide film) attached to the water-soluble tape, and use ultraviolet laser to etch the designed electrode pattern to obtain PI-Cu-water-soluble tape.

[0084] Step S8: Apply PI-Cu water-soluble tape to the Ecoflex substrate, place it on a heating table, and heat and pressurize it.

[0085] Specifically, the heating table temperature is set to 150℃ and the heating time is 15 minutes.

[0086] Step S9: Dissolve the PI-Cu water-soluble tape in water. The PI-Cu will then adhere to the Ecoflex substrate. Peel off any excess PI-Cu.

[0087] Step S10: Prepare PDMS / MWCNTs mixed solution

[0088] Specifically, a solution was prepared according to the following mass ratio: PDMS components: curing agent: MWCNTs: 100 (15g): 10 (1.5g): 3 (0.45g).

[0089] Step S11: Thoroughly stir the PDMS / MWCNTs mixed solution and place it in a vacuum degassing machine to remove air.

[0090] Specifically, the vacuum pumping time is set to 30 seconds.

[0091] Step S12: Apply double-sided heat release tape to the glass slide and then attach the silver sheet to the other side of the double-sided heat release tape.

[0092] Specifically, the silver sheet is 50 μm thick.

[0093] Step S13: The prepared PDMS / MWCNTs mixed solution is evenly dropped onto the glass slide, and the PDMS / MWCNTs mixed solution is coated into a uniform unformed film using a four-sided coating tool.

[0094] Specifically, the four-sided coating tool selects one side with a thickness of 300μm for coating.

[0095] Step S14: Place the glass slide on a heating stage and heat it to solidify the solution into a film. At the same time, the double-sided heat-release tape becomes ineffective and loses its adhesiveness, causing the Ag-PDMS / MWCNTs film to detach from the tape.

[0096] Specifically, the heating table temperature is set to 110℃ and the heating time is 3 minutes.

[0097] Step S15: Use an ultraviolet laser to cut the Ag-PDMS / MWCNTs film into an electrode pattern.

[0098] Step S16: Align the mask with the electrodes on the Ecoflex substrate, apply a layer of solder paste, and remove the mask.

[0099] Specifically, the melting point of solder paste is 183°C.

[0100] Step S17: Arrange the p-type and n-type thermoelectric particles in sequence, and apply a small amount of solder paste to the top of the p-type and n-type thermoelectric particles.

[0101] Specifically, the melting point of solder paste is 138°C.

[0102] Step S18: Place the glass slide on a heating table and heat it until it cools to room temperature.

[0103] Specifically, the heating table temperature is set to 220℃, and the heating time is 3 minutes.

[0104] Step S19: Apply an appropriate amount of solder paste to the top of the p-type and n-type thermoelectric particles, and place Ag-PDMS / MWCNTs electrodes on the top of the p-type and n-type thermoelectric particles.

[0105] Specifically, the melting point of solder paste is 138°C.

[0106] Step S20: Place the glass plate on a heating stage and heat it. Then cool it to room temperature to obtain a thermoelectric power generation device.

[0107] Specifically, the heating table temperature is set to 180℃, and the heating time is 3 minutes.

[0108] Step S21: Place the thermoelectric generator on the spin coater, drop Ecoflex solution onto the thermoelectric generator, and spin coat it.

[0109] Specifically, the spin coating speed was set to 500 rpm / s, and the spin coating time was 120 seconds.

[0110] Step S22: Place the thermoelectric generator on a heating platform and heat it until the Ecoflex solution solidifies, thus encapsulating and protecting the thermoelectric generator.

[0111] Specifically, the heating table temperature is set to 110℃ and the heating time is 3 minutes.

[0112] A physical image of the thermoelectric generator prepared by this method is shown below. Figure 8 As shown. Figure 9 The figures show the IV and IP curves of a thermoelectric generator under standard solar irradiation. The power output of the thermoelectric generator under standard solar irradiation is 0.006 mW. Figure 10The output voltage of the thermoelectric power generation device at night is approximately 0.4mV. Thermoelectric power generation devices can output a certain amount of electrical energy both day and night, achieving uninterrupted power supply around the clock and providing an all-weather power supply solution for distributed electronic devices. Therefore, integrating a photothermal-radiative cooling dual-functional composite thin film can significantly increase the temperature difference between the hot and cold ends of the thermoelectric power generation device, thereby improving the output voltage and power. This provides a novel and efficient method for improving the efficiency of solar energy utilization and clean energy sources such as outer space cooling sources.

[0113] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A method for preparing a photothermal-radiative cooling bifunctional composite thin film, characterized in that, The method includes the following steps: Step S1: Prepare the PDMS / MWCNTs mixed solution; Step S2: Thoroughly stir the PDMS / MWCNTs mixed solution and place it in a vacuum degassing machine to remove air; Step S3: Spray a layer of release agent onto the glass slide; Step S4: Place the glass sheet on a heating table and heat it to solidify the release agent into a film; Step S5: The prepared PDMS / MWCNTs mixed solution is evenly dropped onto the glass slide, and the PDMS / MWCNTs mixed solution is coated into a uniform unformed film using a four-sided coating tool. Step S6: Place the glass slide on a heating stage and heat it to solidify the PDMS / MWCNTs mixed solution; Step S7: Peel the film off the glass slide to obtain the PDMS / MWCNTs film.

2. The method for preparing a photothermal-radiative cooling dual-functional composite thin film according to claim 1, characterized in that, In step S1, the PDMS / MWCNTs mixed solution is prepared according to the mass ratio of PDMS component: curing agent: MWCNTs of 100 (15g): 10 (1.5g): X (0.15-0.75g).

3. The method for preparing a photothermal-radiative cooling dual-functional composite thin film according to claim 1, characterized in that, In step S2, the PDMS / MWCNTs mixed solution is placed in a vacuum degassing machine and vacuumed for 30 seconds.

4. The method for preparing a photothermal-radiative cooling dual-functional composite thin film according to claim 1, characterized in that, In step S4, the temperature of the heating platform is set to 110℃ and the heating time is set to 3 minutes.

5. The method for preparing a photothermal-radiative cooling dual-functional composite thin film according to claim 1, characterized in that, In step S5, the thickness specifications of the four-sided coating device are 100-200-300-400μm and 250-500-750-1000μm.

6. The method for preparing a photothermal-radiative cooling dual-functional composite thin film according to claim 1, characterized in that, In step S6, the temperature of the heating platform is set to 110℃ and the heating time is set to 5 minutes.

7. A photothermal-radiative cooling dual-functional composite thin film, characterized in that, The composite film is prepared by the photothermal-radiation cooling dual-functional composite film preparation method according to any one of claims 1 to 6, wherein the composite film is composed of PDMS and MWCNTs, and the composite film has flexibility and stretchability.

8. The photothermal-radiative cooling dual-functional composite thin film according to claim 7, characterized in that, The absorption rate of the composite film is determined by the film thickness and the MWCNT doping concentration.

9. The application of the photothermal-radiation cooling bifunctional composite thin film prepared by the photothermal-radiation cooling bifunctional composite thin film preparation method according to any one of claims 1 to 6, or the photothermal-radiation cooling bifunctional composite thin film according to any one of claims 7 to 8, in thermoelectric power generation devices.

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