A method for preparing an aluminum-based inorganic flexible passive daytime radiative cooling material

Abstract

The application discloses a preparation method of an aluminum-based inorganic flexible passive daytime radiative cooling material, and comprises the following steps: S1, preparing a precursor solution; S2, performing electrostatic spinning on the precursor solution to prepare and collect an aluminum-based flexible electrostatic spinning fiber film; and S3, drying the aluminum-based flexible electrostatic spinning fiber film in a vacuum drying box, and placing the dried aluminum-based flexible electrostatic spinning fiber film in a muffle furnace to perform high-temperature calcination to remove organic components, so that the aluminum-based inorganic flexible passive daytime radiative cooling material is obtained. The preparation method of the aluminum-based inorganic flexible passive daytime radiative cooling material is adopted, the flexible inorganic nanofiber film structure prepared based on the electrostatic spinning technology can realize multistage sunlight scattering, so that heat absorption and light emission are reduced, and then the effective passive daytime radiative cooling can be performed. In addition to excellent daytime refrigeration performance, the fiber film also has excellent ultraviolet aging resistance, high-temperature resistance, flexibility and other performances.

Description

Technical Field

[0001] This invention belongs to the field of passive radiation cooling technology, specifically relating to a method for preparing an aluminum-based inorganic flexible passive daytime radiation cooling material. Background Technology

[0002] With the intensification of global warming, high temperatures are becoming increasingly common in summer. Therefore, cooling is becoming more crucial for human life. Current mainstream cooling technologies, such as air conditioning, consume large amounts of electricity and produce greenhouse gases (CO2) and ozone-depleting gases (CCl2F). Furthermore, these cooling technologies only transfer heat to different parts of the Earth; they do not dissipate heat into the atmosphere. Therefore, most cooling technologies have a net heating effect on the atmosphere.

[0003] Passive diurnal radiative cooling achieves passive refrigeration by transferring excess heat to the cold outer space through thermal radiation, based on the large temperature difference between Earth (~300K) and outer space (~3K). This cooling system does not rely on external energy consumption because cooling between the Earth's surface and outer space is achieved through the emission of infrared thermal radiation. This novel and environmentally friendly cooling technology has received considerable attention and extensive research both domestically and internationally in recent years.

[0004] While many materials have proven to possess excellent passive daytime radiative cooling properties, the vast majority of commonly used materials contain organic components. The high-molecular-weight organic materials in passive daytime radiative cooling materials are prone to aging under sunlight, thus easily causing secondary environmental pollution. In contrast, inorganic fiber membranes exhibit superior performance in terms of UV resistance, high-temperature resistance, flexibility, and tensile strength. This indicates that economical and durable inorganic cooling materials offer a sustainable solution to problems such as the greenhouse effect and energy progress. Furthermore, compared to other technologies, electrospinning technology offers numerous advantages, including simple manufacturing, high preparation efficiency, easy control of structural parameters, inexpensive raw materials, and complete manufacturing technology. Therefore, this invention proposes a method for preparing an aluminum-based inorganic flexible passive daytime radiative cooling material. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing an aluminum-based inorganic flexible passive daytime radiation cooling material. The flexible inorganic nanofiber membrane structure prepared by electrospinning technology can achieve multi-level sunlight scattering, thereby reducing heat absorption and light emission, and can be used for effective passive daytime radiation cooling. In addition to excellent daytime cooling performance, the fiber membrane also has excellent resistance to ultraviolet aging, high temperature resistance, and flexibility.

[0006] To achieve the above objectives, the present invention provides a method for preparing an aluminum-based inorganic flexible passive daytime radiation cooling material, comprising the following steps:

[0007] S1. Prepare the precursor solution;

[0008] S11. Dissolve the aluminum-based compound in a two-component solvent and add the acidic mixed solute in small amounts multiple times;

[0009] S12. Add 5 wt% polyvinylpyrrolidone as a spinning aid and stir until homogeneous to obtain a precursor solution.

[0010] S2. Electrospin the precursor solution to prepare and collect aluminum-based flexible electrospun fiber membranes.

[0011] S3. The aluminum-based flexible electrospun fiber membrane is dried in a vacuum drying oven. The dried aluminum-based flexible electrospun fiber membrane is then placed in a muffle furnace for high-temperature calcination to remove organic components, thus obtaining an aluminum-based inorganic flexible passive daytime radiation cooling material.

[0012] Preferably, in step S11, the aluminum-based compound is composed of aluminum chloride hexahydrate and aluminum isopropoxide in a mass ratio of 0.8:2 to 1:2; the two-component solvent is composed of water and anhydrous ethanol in a mass ratio of 0.93:1 to 1:1; and the acidic mixed solute is composed of tartaric acid and glacial acetic acid in a mass ratio of 3.9:50 to 4:50.

[0013] Preferably, in step S12, the mixture is stirred evenly at a temperature of 20°C to 70°C.

[0014] Preferably, in step S2, the electrospinning process conditions are as follows: spinning temperature is 20℃~40℃, spinning humidity is 10%~50%, spinning voltage is 15.5kV~20kV, the propulsion rate of the spinning solution is 0.5ml / h~1.2ml / h, the distance between the spinneret and the collector is 10cm~20cm, and the rotation speed of the roller collector is 200rpm~500rpm.

[0015] Preferably, in step S3, the temperature of the vacuum drying oven is 70℃~90℃, and the drying time is 12h~16h.

[0016] Preferably, in step S3, the muffle furnace is used for high-temperature calcination at 900℃ to 1200℃ with a heating rate of 1℃ / min to 5℃ / min.

[0017] The beneficial effects of this invention are:

[0018] (1) The aluminum-based inorganic flexible passive daytime radiation cooling material prepared by the present invention aims to prepare a flexible pure inorganic nanofiber membrane structure based on electrospinning technology. Compared with common polymer organic materials that are prone to aging and decomposition under long-term solar irradiation, it can effectively extend the service life and reduce environmental pollution from waste polymers, and has practical value.

[0019] (2) The preparation process in this invention is simple and the structural parameters are easy to control, which makes the process capable of mass production.

[0020] (3) The aluminum-based inorganic flexible passive daytime radiation cooling material prepared by the present invention has high reflectivity and high emissivity. In addition to excellent daytime cooling performance, the cooling material also has excellent resistance to ultraviolet aging, high temperature resistance, and flexibility. It can be better assembled on the surface of actual buildings and also has the functions of heat preservation and fire prevention.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 This is a SEM image of the aluminum-based inorganic flexible passive daytime radiation cooling material prepared in Example 1 of the preparation method of the aluminum-based inorganic flexible passive daytime radiation cooling material of the present invention.

[0023] Figure 2 The image shows the spectral curve of the aluminum-based inorganic flexible passive daytime radiation cooling material prepared in Example 1 of the preparation method of the aluminum-based inorganic flexible passive daytime radiation cooling material of the present invention.

[0024] Figure 3 This image shows the actual outdoor cooling effect of the aluminum-based inorganic flexible passive daytime radiation cooling material prepared in Example 1 of the preparation method of the aluminum-based inorganic flexible passive daytime radiation cooling material of the present invention.

[0025] Figure 4 The stress-strain curves of the aluminum-based inorganic flexible passive daytime radiation cooling material prepared in Example 1 of the preparation method of the aluminum-based inorganic flexible passive daytime radiation cooling material of the present invention before and after 72 hours of ultraviolet lamp irradiation are shown.

[0026] Figure 5 The image shows an SEM image of the aluminum-based inorganic flexible passive daytime radiation cooling material prepared in Comparative Example 1 of the preparation method of the aluminum-based inorganic flexible passive daytime radiation cooling material of the present invention.

[0027] Figure 6 This is a SEM image of the aluminum-based inorganic flexible passive daytime radiation cooling material prepared in Comparative Example 2 of the preparation method of the aluminum-based inorganic flexible passive daytime radiation cooling material of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0030] A method for preparing an aluminum-based inorganic flexible passive daytime radiation cooling material includes the following steps:

[0031] S1. Prepare the precursor solution.

[0032] S11. Dissolve the aluminum-based compound in a two-component solvent and add the acidic mixed solute in small amounts multiple times.

[0033] The aluminum-based compound consists of aluminum chloride hexahydrate and aluminum isopropoxide in a mass ratio of 0.8:2 to 1:2. The two-component solvent consists of water and anhydrous ethanol in a mass ratio of 0.93:1 to 1:1. The acidic mixed solute consists of tartaric acid and glacial acetic acid in a mass ratio of 3.9:50 to 4:50.

[0034] S12. Add 5 wt% polyvinylpyrrolidone as a spinning aid, and stir evenly at a temperature of 20℃~70℃ to obtain a precursor solution.

[0035] S2. Electrospin the precursor solution to prepare and collect aluminum-based flexible electrospun fiber membranes.

[0036] The specific process conditions for electrospinning are as follows: spinning temperature is 20℃~40℃, spinning humidity is 10%~50%, spinning voltage is 15.5kV~20kV, the propulsion rate of the spinning solution is 0.5ml / h~1.2ml / h, the distance between the spinneret and the collector is 10cm~20cm, and the rotation speed of the roller collector is 200rpm~500rpm.

[0037] S3. Dry the aluminum-based flexible electrospun fiber membrane using a vacuum drying oven. The temperature of the vacuum drying oven is 70℃~90℃, and the drying time is 12h~16h.

[0038] The dried aluminum-based flexible electrospun fiber membrane is placed in a muffle furnace and calcined at high temperature to remove organic components. The muffle furnace is calcined at a high temperature of 900℃ to 1200℃ with a heating rate of 1℃ / min to 5℃ / min to obtain the aluminum-based inorganic flexible passive daytime radiation cooling material.

[0039] Example 1

[0040] A method for preparing an aluminum-based inorganic flexible passive daytime radiation cooling material includes the following steps:

[0041] S1. Dissolve 10g of aluminum chloride hexahydrate and 20g of aluminum isopropoxide in 60g of a mixed solvent of water and anhydrous ethanol in a mass ratio of 1:1. Add 1.2g of tartaric acid and 15g of glacial acetic acid in small amounts several times. Finally, add 5wt% of polyvinylpyrrolidone as a spinning aid. Stir the mixture at 60℃ to obtain a precursor solution.

[0042] S2. Electrospin the precursor solution to prepare and collect aluminum-based flexible electrospun fiber membranes.

[0043] The specific process conditions for electrospinning are as follows: spinning temperature is 27℃, spinning humidity is 25%, spinning voltage is 19kV, spinning solution propulsion rate is 0.8ml / h, distance between spinneret and collector is 20cm, and roller collector rotation speed is 300rpm.

[0044] S3. The aluminum-based flexible electrospun fiber membrane is dried in a vacuum drying oven at 80℃ for 14 hours. The dried aluminum-based flexible electrospun fiber membrane is then placed in a muffle furnace for high-temperature calcination to remove organic components. The muffle furnace is calcined at 1100℃ with a heating rate of 1℃ / min to obtain the aluminum-based inorganic flexible passive daytime radiation cooling material.

[0045] like Figure 1 As shown, the aluminum-based inorganic flexible passive daytime radiation cooling material prepared in Example 1 is composed of multiple layers of stacked fibers, with numerous nanopores formed between the fibers. The fiber surface is smooth and flat, and the fiber diameter is distributed between 200 nm and 1.1 μm, which is comparable to the wavelength of reflected light. This gives the aluminum-based inorganic flexible passive daytime radiation cooling material a strong ability to reflect sunlight, and the material exhibits a very high solar reflectivity.

[0046] like Figure 2 As shown, this aluminum-based inorganic flexible passive daytime radiation cooling material exhibits strong reflectivity, especially in the solar spectrum, with an average reflectivity of 96.94% in the 0.3μm to 2.5μm band and an average emissivity of 92.85% in the atmospheric window band, particularly in the 8μm to 13μm band.

[0047] like Figure 3 As shown, under direct sunlight, when the ambient temperature reaches 37°C, the flexible inorganic material can achieve a cooling effect of up to 5°C compared to the blank control group (common building materials).

[0048] like Figure 4 As shown, the maximum normal stress of the aluminum-based inorganic flexible passive daytime radiation cooling material is 0.59 MPa, and its mechanical properties do not change significantly after ultraviolet lamp irradiation.

[0049] Example 2

[0050] A method for preparing an aluminum-based inorganic flexible passive daytime radiation cooling material includes the following steps:

[0051] S1. Dissolve 10g of aluminum chloride hexahydrate and 20g of aluminum isopropoxide in 60g of a mixed solvent of water and anhydrous ethanol in a mass ratio of 1:1. Add 1.2g of tartaric acid and 15g of glacial acetic acid in small amounts several times. Finally, add 5wt% of polyvinylpyrrolidone as a spinning aid. Stir the mixture at 60℃ to obtain a precursor solution.

[0052] S2. Electrospin the precursor solution to prepare and collect aluminum-based flexible electrospun fiber membranes.

[0053] The specific process conditions for electrospinning are as follows: spinning temperature is 27℃, spinning humidity is 25%, spinning voltage is 20kV, spinning solution propulsion rate is 0.8ml / h, distance between spinneret and collector is 20cm, and roller collector rotation speed is 300rpm.

[0054] S3. The aluminum-based flexible electrospun fiber membrane is dried in a vacuum drying oven at 80℃ for 14 hours. The dried aluminum-based flexible electrospun fiber membrane is then placed in a muffle furnace for high-temperature calcination to remove organic components. The muffle furnace is calcined at 1100℃ with a heating rate of 1℃ / min to obtain the aluminum-based inorganic flexible passive daytime radiation cooling material.

[0055] The aluminum-based inorganic flexible passive daytime radiation cooling material prepared in Example 2 is composed of multiple layers of stacked fibers, with numerous nanopores formed between the fibers. The fiber surface is smooth and flat, and the fiber diameter is distributed between 200 nm and 900 nm.

[0056] Actual outdoor cooling tests show that the aluminum-based inorganic flexible passive daytime radiation cooling material prepared in Example 2 can achieve a cooling effect of up to 4.8°C compared with the blank control group (common building materials).

[0057] Example 3

[0058] A method for preparing an aluminum-based inorganic flexible passive daytime radiation cooling material includes the following steps:

[0059] S1. Dissolve 10g of aluminum chloride hexahydrate and 20g of aluminum isopropoxide in 60g of a mixed solvent of water and anhydrous ethanol in a mass ratio of 1:1. Add 1.2g of tartaric acid and 15g of glacial acetic acid in small amounts several times. Finally, add 5wt% of polyvinylpyrrolidone as a spinning aid. Stir the mixture at 60℃ to obtain a precursor solution.

[0060] S2. Electrospin the precursor solution to prepare and collect aluminum-based flexible electrospun fiber membranes.

[0061] The specific process conditions for electrospinning are as follows: spinning temperature is 27℃, spinning humidity is 25%, spinning voltage is 19kV, spinning solution propulsion rate is 0.8ml / h, distance between spinneret and collector is 20cm, and roller collector rotation speed is 300rpm.

[0062] S3. The aluminum-based flexible electrospun fiber membrane is dried in a vacuum drying oven at 80℃ for 14 hours. The dried aluminum-based flexible electrospun fiber membrane is then placed in a muffle furnace for high-temperature calcination to remove organic components. The muffle furnace is calcined at 1100℃ with a heating rate of 3℃ / min to obtain the aluminum-based inorganic flexible passive daytime radiation cooling material.

[0063] The aluminum-based inorganic flexible passive daytime radiation cooling material prepared in Example 3 is composed of multiple layers of stacked fibers, with numerous nanopores formed between the fibers. The fiber surface is smooth and flat, and the fiber diameter is distributed between 200 nm and 900 nm.

[0064] Actual outdoor cooling tests show that the aluminum-based inorganic flexible passive daytime radiation cooling material prepared in Example 3 can achieve a cooling effect of up to 4.7°C compared with the blank control group (common building materials).

[0065] Comparative Example 1

[0066] A method for preparing an aluminum-based inorganic flexible passive daytime radiation cooling material includes the following steps:

[0067] S1. Dissolve 10g of aluminum chloride hexahydrate and 20g of aluminum isopropoxide in 60g of a mixed solvent of water and anhydrous ethanol in a mass ratio of 1:1. Add 1.2g of tartaric acid and 15g of glacial acetic acid in small amounts several times. Finally, add 5wt% of polyvinylpyrrolidone as a spinning aid. Stir the mixture at 60℃ to obtain a precursor solution.

[0068] S2. Electrospin the precursor solution to prepare and collect aluminum-based flexible electrospun fiber membranes.

[0069] The specific process conditions for electrospinning are as follows: spinning temperature is 27℃, spinning humidity is 25%, spinning voltage is 19kV, spinning solution propulsion rate is 1.5ml / h, distance between spinneret and collector is 20cm, and roller collector rotation speed is 300rpm.

[0070] S3. The aluminum-based flexible electrospun fiber membrane is dried in a vacuum drying oven at 80℃ for 14 hours. The dried aluminum-based flexible electrospun fiber membrane is then placed in a muffle furnace for high-temperature calcination to remove organic components. The muffle furnace is calcined at 1100℃ with a heating rate of 1℃ / min to obtain the aluminum-based inorganic flexible passive daytime radiation cooling material.

[0071] like Figure 5 As shown, a large number of beads exist in this aluminum-based inorganic flexible passive daytime radiation cooling material. The fiber morphology is closely related to the polymer solution injection rate. For a given electrospinning condition, increasing the injection rate does not significantly change the velocity of the jet in the high-voltage electric field, but the increased flow rate leads to an increase in the charge carried by the jet, thereby enhancing the jet's instability.

[0072] If the entangled molecular chains in the polymer solution cannot effectively overcome the stretching force and orient themselves, the jet is prone to solidify into beads along the axial direction, especially when the injected solution volume is greater than the solution volume forming the jet, beads are more likely to form in the fiber membrane. This bead structure has an adverse effect on the mechanical and other properties of the fiber.

[0073] Actual outdoor cooling tests show that the aluminum-based inorganic flexible passive daytime radiation cooling material prepared in Comparative Example 1 can only achieve a cooling effect of 1.3℃ compared with the blank control group (common building materials).

[0074] Comparative Example 2

[0075] A method for preparing an aluminum-based inorganic flexible passive daytime radiation cooling material includes the following steps:

[0076] S1. Dissolve 10g of aluminum chloride hexahydrate and 20g of aluminum isopropoxide in 60g of a mixed solvent of water and anhydrous ethanol in a mass ratio of 1:1. Add 1.2g of tartaric acid and 15g of glacial acetic acid in small amounts several times. Finally, add 5wt% of polyvinylpyrrolidone as a spinning aid. Stir the mixture at 60℃ to obtain a precursor solution.

[0077] S2. Electrospin the precursor solution to prepare and collect aluminum-based flexible electrospun fiber membranes.

[0078] The specific process conditions for electrospinning are as follows: spinning temperature is 27℃, spinning humidity is 25%, spinning voltage is 19kV, spinning solution propulsion rate is 0.8ml / h, distance between spinneret and collector is 20cm, and roller collector rotation speed is 300rpm.

[0079] S3. The aluminum-based flexible electrospun fiber membrane is dried in a vacuum drying oven at 80℃ for 14 hours. The dried aluminum-based flexible electrospun fiber membrane is then placed in a muffle furnace for high-temperature calcination to remove organic components. The muffle furnace is calcined at 1300℃ with a heating rate of 1℃ / min to obtain the aluminum-based inorganic flexible passive daytime radiation cooling material.

[0080] like Figure 6 As shown, the fiber surface in this aluminum-based inorganic flexible passive daytime radiation cooling material becomes rough and exhibits numerous fiber breaks. During high-temperature calcination, the surface treatment agent volatilizes, gradually revealing fiber defects such as protrusions and cracks, leading to a gradual decrease in mechanical strength.

[0081] The resulting inorganic fiber membrane has poor flexibility and cannot be fully tested in actual outdoor cooling tests.

[0082] Therefore, the present invention adopts the above-mentioned method for preparing an aluminum-based inorganic flexible passive daytime radiation cooling material. The flexible inorganic nanofiber membrane structure prepared by electrospinning technology can achieve multi-level sunlight scattering, thereby reducing heat absorption and light emission, and can be used for effective passive daytime radiation cooling. In addition to excellent daytime cooling performance, the fiber membrane also has excellent resistance to ultraviolet aging, high temperature resistance, and flexibility.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an aluminum-based inorganic flexible passive daytime radiation cooling material, characterized in that, Includes the following steps: S1. Prepare the precursor solution; S11. Dissolve the aluminum-based compound in a two-component solvent, and add the acidic mixed solute in small amounts multiple times; the aluminum-based compound is composed of aluminum chloride hexahydrate and aluminum isopropoxide in a mass ratio of 0.8:2 to 1:2; the two-component solvent is composed of water and anhydrous ethanol in a mass ratio of 0.93:1 to 1:1; the acidic mixed solute is composed of tartaric acid and glacial acetic acid in a mass ratio of 3.9:50 to 4:

50. S12. Add 5 wt% polyvinylpyrrolidone as a spinning aid and stir until homogeneous to obtain a precursor solution. S2. Electrospin the precursor solution to prepare and collect aluminum-based flexible electrospun fiber membranes; the propulsion rate of the spinning solution is 0.5 ml / h~1.2 ml / h; S3. The aluminum-based flexible electrospun fiber membrane is dried in a vacuum drying oven. The dried aluminum-based flexible electrospun fiber membrane is then placed in a muffle furnace for high-temperature calcination to remove organic components, thus obtaining an aluminum-based inorganic flexible passive daytime radiation cooling material. The muffle furnace is calcined at a high temperature of 900℃ to 1200℃ with a heating rate of 1℃ / min to 5℃ / min.

2. The preparation method of an aluminum-based inorganic flexible passive daytime radiation cooling material according to claim 1, characterized in that: In step S12, the mixture is stirred evenly at a temperature of 20℃~70℃.

3. The preparation method of an aluminum-based inorganic flexible passive daytime radiation cooling material according to claim 1, characterized in that: In step S2, the specific process conditions for electrospinning are as follows: spinning temperature is 20℃~40℃, spinning humidity is 10%~50%, spinning voltage is 15.5kV~20kV, the distance between the spinneret and the collector is 10cm~20cm, and the rotation speed of the roller collector is 200rpm~500rpm.

4. The preparation method of an aluminum-based inorganic flexible passive daytime radiation cooling material according to claim 1, characterized in that: In step S3, the temperature of the vacuum drying oven is 70℃~90℃, and the drying time is 12h~16h.

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