CN114713476A - Preparation method of double-sided synergistic functional coating for efficient environmental water vapor capture - Google Patents

Abstract

The invention provides a preparation method of a double-sided synergistic functional coating for high-efficiency environmental water vapor capture, which includes the steps of preparing a water collecting layer, preparing radiative cooling functional particles, and preparing a radiative cooling coating. The Namib desert beetle survives in water-scarce deserts by collecting water droplets in the air, thanks to its unique pattern of alternating patterns on its back. Inspired by this, the present invention uses an aluminum sheet as a substrate to obtain a wettability alternate pattern by mask spraying to improve the water collection efficiency. However, the heat released during condensation of the water droplets reduces the water collection rate. In order to control the re-evaporation rate of water droplets, the present invention adds a radiative cooling layer on the back of the water-collecting layer to rapidly release condensation heat. The radiation cooling layer adopts MgHPO ₄ ·0.78H ₂ O as functional particles and P(VDF-HFP) as binder. The water collecting device with the double-sided synergistic functional structure is simple to manufacture, and the raw materials are green and pollution-free, which provides a new way for the development of a new type of fresh water collecting device.

Description

A preparation method of double-sided synergistic functional coating for efficient environmental water vapor capture

technical field

The invention belongs to the technical field of preparation of gradient wettability surfaces, and particularly relates to a preparation method of a double-sided synergistic functional coating used for efficient environmental water vapor capture on a surface between hydrophilic and hydrophobic phases for freshwater collection.

Background technique

Harvesting water from environmental fog is widely discussed as a solution to the scarcity of freshwater resources in arid and underdeveloped regions. The Namib desert beetle survives in water-scarce deserts by collecting water droplets in the air, thanks to its unique pattern of alternating patterns on its back. Saharan silver ants are able to regulate their body temperature in the extreme heat of the African desert thanks to a series of densely arranged, uniquely shaped triangular hairs that radiate heat to their surroundings in full sun. The hydrophilic-hydrophobic interphase surface combined with backside radiative cooling technology inspired by these two organisms significantly improves the efficiency of water harvesting, providing a new avenue for developing novel freshwater harvesting devices.

Using the method of mask spraying, a hydrophilic and hydrophobic water-collecting layer was prepared on the surface of the aluminum sheet. In order to improve the water collection efficiency, a radiative cooling layer is added on the back of the water collection layer. Using the high reflectivity of MgHPO ₄ ·0.78H ₂ O in the solar spectral band (0.2-2.5 μm) and high emissivity in the atmospheric window band (8-13 μm), the surface is cooled by radiating heat to the external environment. The decrease in temperature helps to reduce the re-evaporation rate of water droplets and increase the condensation rate, which in turn improves the water collection efficiency.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a simple, convenient and economical high-efficiency water collecting device. Combining the advantages of hydrophilic surface and hydrophobic surface, the removal of water droplets is accelerated, and the cooling coating solves the problem of accelerated re-evaporation rate caused by the release of heat during the condensation process of water droplets. The combination of double-sided functional coatings realizes efficient water collection and has certain application potential in solving the problem of shortage of fresh water resources.

The technical scheme that realizes the object of the present invention is:

A preparation method of a double-sided synergistic functional coating for efficient environmental water vapor capture, characterized in that the method comprises the following steps:

A. Preparation of water-collecting layer: Add 1.65-1.69 g of Al ₂ O ₃ powder and 0.31-0.35 g of TiO ₂ powder into 20 mL of ethanol, stir well and add 0.2-0.4 mL of hexadecyltrimethoxysilane Continue stirring for 10min; add 1.3-1.7g epoxy resin and 0.75g curing agent to the system, and finally ultrasonicate the solution for 20min and continue to stir to obtain milky white hydrophobic suspension coating; use aluminum sheet as the base to prepare hydrophobic coating by mask spraying method Coating, use a mask during the spraying process to obtain a patterned surface with hydrophilic and hydrophobic phases. After spraying, the sample is placed in an oven at 60 °C for drying for 4 hours;

B. Preparation of radiation cooling functional particles: Weigh _16.264g of MgCl _{2 · 6H 2} O powder and dissolve it in 100 mL of deionized water _; The magnetic stirrer was stirred at room temperature for 2 hours, during which the rate of addition was controlled with ammonia water, the pH value was slowly adjusted to 8, and then stirred for 4 hours to obtain a precipitate; Dry in an oven at 80°C for 6-8h to obtain MgHPO ₄ ·0.78H ₂ O powder for later use;

C. Preparation of radiation cooling coating: slowly add 0.2 g of P(VDF-HFP) to 10 mL of ethanol one by one and stir until it is clear without bubbles, then weigh 2.9 g of the powder prepared in step B and add it to the ethanol solution one by one; Then add 1.5g epoxy resin and 0.5g curing agent into the solution and stir magnetically for 30min to obtain a white milky viscous liquid; drop the liquid onto the back of the water-collecting layer prepared in step A and then put it in a 60℃ oven to dry for 4- A radiative cooling coating was obtained in 8 hours.

Further, the Al ₂ O ₃ powder in the step A is commercial, and the particle size is 30 nm, and the TiO ₂ powder is commercial, and the particle size is 25 nm.

Further, the modifier hexadecyltrimethoxysilane added in the step A was 0.4 mL.

Further, in the step A, the water collecting layer is prepared by a method of mask spraying, the spraying distance is 20 cm, and the pressure of the nozzle is 0.68 MPa.

Further, in the preparation of the radiation cooling functional particles in the step B, the molar ratio of the Mg element and the P element is configured as 1:1.

The beneficial effects of the present invention are: compared with the prior art, the advantages of the present invention are:

1. The preparation process is simple, the raw materials are readily available, and the cost is low.

2. The special surface pattern of the water collecting device and the cooling effect on the back side increase the water collection efficiency by 67.33%.

3. The contact angle of the hydrophobic region of the water collecting layer is 147°, and the contact angle of the hydrophilic region is 76°.

4. The radiation cooling layer of the water collection device can significantly reduce the temperature.

5. The water collecting device can be recycled many times, and the water soaking does not affect the performance.

Description of drawings

Figure 1: Wetting of water by the water-collecting coating of the water-collecting device obtained in Example 1 and surface morphology (Figure a), XPS spectrum (Figure b) and XPS elemental analysis (Figures c and d).

Figure 2: Solar emissivity and absorptivity (figures a and b), XRD patterns (figure c), surface topography (figures e and f), and radiative cooling functional particles of the radiative cooling layer of the water collecting device obtained in Example 1 The electron microscope photo (Fig. d).

Figure 3: XPS elemental analysis (Figures a, b and c) and infrared absorption spectrum (Figure d) of the radiation cooling layer of the water collecting device obtained in Example 1.

Figure 4: Infrared thermographic image of the radiative cooling layer of the water collecting device obtained in Example 1.

Figure 5: Figure a obtained in Example 1 is an optical image of the water collection device for the water collection experiment, and Figure b is the original aluminum sheet, the aluminum sheet with a fully sprayed hydrophobic coating, the patterned aluminum sheet with a hydrophobic coating, and the addition of the backside Changes in the efficiency of the aluminum sheet after the radiation cooling layer during repeated water collection experiments. Figure c is a schematic diagram of the growth of water droplets on the patterned surface, and Figure d is the corresponding water collection efficiency when the sample is inclined at different angles.

Figure 6: Optical pictures of the four samples obtained in Example 1 for water collection experiments at different times.

Detailed ways

In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples. Those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms are also within the scope defined by the claims listed in this application.

Example 1:

1. Preparation of water-collecting layer A: 1.67 g of Al ₂ O ₃ powder and 0.33 g of TiO ₂ powder were added to 20 mL of ethanol, and after stirring evenly, 0.4 mL of hexadecyltrimethoxysilane was added and the stirring was continued for 10 min. 1.5 g of epoxy resin and 0.75 g of curing agent were added to the system, and finally the solution was ultrasonicated for 20 min and continued to be stirred to obtain a milky white super-hydrophobic suspension coating. The hydrophilic and hydrophobic interphase coating on the patterned surface was prepared by mask spraying method with aluminum sheet as substrate. The spraying distance is 20cm, and the nozzle pressure is 0.68MPa. After spraying, the samples were placed in an oven at 60 °C for drying for 4 h.

2. Synthesis of radiation cooling functional particle B: 16.264 g of MgCl ₂ ·6H ₂ O powder was weighed and dissolved in 100 mL of deionized water. Then weigh 7.84g of H ₃ PO ₄ , add it into the MgCl ₂ ·6H ₂ O aqueous solution, stir with a magnetic stirrer at room temperature for 2 hours, control the dropping rate with ammonia water during this period, slowly adjust the pH value to 8, and stir for another 4 hours to fully react to obtain a precipitate thing. After standing at room temperature for 24 hours, a white solid was obtained by suction filtration and washing, which was dried in a drying oven at 80° C. for 6 hours to obtain MgHPO ₄ ·0.78H ₂ O powder for later use.

3. Preparation of radiation cooling coating C: 0.2 g of P(VDF-HFP) was slowly added to 10 mL of ethanol gradually and stirred until it was clear without bubbles, and then 2.9 g of the previously prepared powder was weighed and added to the ethanol solution in a small amount. Then, 1.5 g of epoxy resin and 0.5 g of curing agent were added to the solution and stirred magnetically for 30 min to obtain a white milky viscous liquid. The liquid was drop-coated on the back of the water-collecting layer and then dried in an oven at 60 °C for 4 h to obtain a radiation cooling coating.

Example 2:

1. Preparation of water-collecting layer A: add 1.67 g of Al ₂ O ₃ powder and 0.33 g of TiO ₂ powder into 20 mL of ethanol, stir evenly, add 0.2 mL of hexadecyltrimethoxysilane, and continue stirring for 10 min. 1.5 g of epoxy resin and 0.75 g of curing agent were added to the system, and finally the solution was ultrasonicated for 20 min and continued to be stirred to obtain a milky white super-hydrophobic suspension coating. The hydrophilic and hydrophobic interphase coating on the patterned surface was prepared by mask spraying method with aluminum sheet as substrate. The spraying distance is 20cm, and the nozzle pressure is 0.2MPa. After spraying, the samples were placed in an oven at 60 °C for drying for 4 h.

2. Synthesis of radiation cooling functional particle B: 16.264 g of MgCl ₂ ·6H ₂ O powder was weighed and dissolved in 100 mL of deionized water. Then weigh 7.84g of H ₃ PO ₄ , add it into the MgCl ₂ ·6H ₂ O aqueous solution, stir with a magnetic stirrer at room temperature for 2 hours, control the dropping rate with ammonia water during this period, slowly adjust the pH value to 8, and stir for another 4 hours to fully react to obtain a precipitate thing. After standing at room temperature for 24 hours, a white solid was obtained by suction filtration and washing, which was dried in a drying oven at 80° C. for 6 hours to obtain MgHPO ₄ ·0.78H ₂ O powder for later use.

3. Preparation of radiation cooling coating C: 0.2 g of P(VDF-HFP) was slowly added to 10 mL of ethanol gradually and stirred until it was clear without bubbles, and then 2.9 g of the previously prepared powder was weighed and added to the ethanol solution in a small amount. Then, 1.5 g of epoxy resin and 0.5 g of curing agent were added to the solution and stirred magnetically for 30 min to obtain a white milky viscous liquid. The liquid was drop-coated on the back of the water-collecting layer and then dried in an oven at 60 °C for 4 h to obtain a radiation cooling coating.

Example 3:

1. Preparation of water-collecting layer A: 1.67 g of Al ₂ O ₃ powder and 0.33 g of TiO ₂ powder were added to 20 mL of ethanol, and after stirring evenly, 0.4 mL of hexadecyltrimethoxysilane was added and the stirring was continued for 10 min. 1.5 g of epoxy resin and 0.75 g of curing agent were added to the system, and finally the solution was ultrasonicated for 20 min and continued to be stirred to obtain a milky white super-hydrophobic suspension coating. The hydrophilic and hydrophobic interphase coating on the patterned surface was prepared by mask spraying method with aluminum sheet as substrate. The spraying distance is 20cm, and the nozzle pressure is 0.68MPa. After spraying, the samples were placed in an oven at 60 °C for drying for 4 h.

2. Synthesis of radiation cooling functional particle B: 16.264 g of MgCl ₂ ·6H ₂ O powder was weighed and dissolved in 100 mL of deionized water. Then weigh 7.84g of H ₃ PO ₄ , add it into the MgCl ₂ ·6H ₂ O aqueous solution, stir with a magnetic stirrer at room temperature for 2 hours, control the dropping rate with ammonia water during this period, slowly adjust the pH value to 8, stir for 4 hours, and fully react to obtain a precipitate thing. After standing at room temperature for 12 hours, a white solid was obtained by suction filtration and washing, which was dried in a drying oven at 80° C. for 8 hours to obtain MgHPO ₄ ·0.78H ₂ O powder for later use.

3. Preparation of radiation cooling coating C: 0.2 g of P(VDF-HFP) was slowly added to 10 mL of ethanol gradually and stirred until it was clear without bubbles, and then 2.9 g of the previously prepared powder was weighed and added to the ethanol solution in a small amount. Then, 1.5 g of epoxy resin and 0.5 g of curing agent were added to the solution and stirred magnetically for 30 min to obtain a white milky viscous liquid. The liquid was drop-coated on the back of the water-collecting layer and then dried in an oven at 60 °C for 8 h to obtain a radiation cooling coating.

Summary: The Namib desert beetle survives by collecting airborne droplets in water-scarce deserts due to its unique alternate pattern on its back. Inspired by this, the present invention uses an aluminum sheet as a substrate to obtain a wettability alternate pattern by mask spraying to improve the water collection efficiency. However, the heat released during condensation of the water droplets reduces the water collection rate. In order to control the re-evaporation rate of water droplets, the present invention adds a radiative cooling layer on the back of the water-collecting layer to rapidly release condensation heat. The radiation cooling layer adopts MgHPO ₄ ·0.78H ₂ O as the functional particle and P(VDF-HFP) as the binder. The water collecting device with the double-sided synergistic functional structure is simple to manufacture, and the raw materials are green and pollution-free, which provides a new way for the development of a new type of fresh water collecting device.

Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, but not to limit the protection scope of the present invention. The essence and scope of the technical solution of the invention.

Claims (5)

1. A preparation method of a double-sided synergistic functional coating for efficient environmental water vapor capture is characterized by comprising the following steps:

A. preparing a water collecting layer: 1.65-1.69g of Al₂O₃Powder and 0.31-0.35g TiO₂Adding the powder into 20mL of ethanol, stirring uniformly, adding 0.2-0.4mL of hexadecyl trimethoxy silane, and continuing stirring for 10 min; adding 1.3-1.7g of epoxy resin and 0.75g of curing agent into the system, finally carrying out ultrasonic treatment on the solution for 20min and continuously stirring to obtain milky hydrophobic suspension coating; preparing a hydrophobic coating by using an aluminum sheet as a substrate and adopting a mask spraying method, obtaining hydrophilic and hydrophobic alternate patterned surfaces by using a mask in the spraying process, and drying the sample in an oven at 60 ℃ for 4 hours after the spraying is finished;

B. preparation of radiation cooling functional particles: 16.264g of MgCl were weighed₂·6H₂Dissolving O powder in 100mL of deionized water; 7.84g of H are then weighed out₃PO₄Adding MgCl₂·6H₂Stirring in an O aqueous solution for 2h at room temperature by using a magnetic stirrer, controlling the dropping speed by using ammonia water during the stirring, slowly adjusting the pH value to 8, stirring for 4h, and fully reacting to obtain a precipitate; standing at room temperature for 12-24h, vacuum filtering, washing to obtain white solid, and drying at 80 deg.C for 6-8h in drying oven to obtain MgHPO₄·0.78H₂O powder is reserved;

C. preparation of radiation cooling coating: gradually and slowly adding 0.2g of P (VDF-HFP) into 10mL of ethanol and stirring until the mixture is clear and free of bubbles, and then gradually adding a small amount of 2.9g of the powder prepared in the step B into the ethanol solution; then adding 1.5g of epoxy resin and 0.5g of curing agent into the solution and magnetically stirring for 30min to obtain white milky viscous liquid; and D, dripping the liquid on the back of the water collecting layer prepared in the step A, and then putting the water collecting layer into an oven at the temperature of 60 ℃ for drying for 4-8 hours to obtain the radiation cooling coating.

2. The method for preparing the double-sided co-functional coating for efficient environmental moisture capture as claimed in claim 1, wherein: al in the step A₂O₃The powder is commercial, and has a particle size of 30nm and TiO₂The powder was commercially available with a particle size of 25 nm.

3. The method for preparing the double-sided co-functional coating for efficient environmental moisture capture as claimed in claim 1, wherein: the modifying agent hexadecyl trimethoxy silane added in the step A is 0.4 mL.

4. The method for preparing the double-sided co-functional coating for efficient environmental moisture capture as claimed in claim 1, wherein: and B, preparing the water collecting layer in the step A by adopting a mask spraying method, wherein the spraying distance is 20cm, and the pressure intensity of a spray head is 0.68 MPa.

5. The method for preparing the double-sided co-functional coating for efficient environmental moisture capture as claimed in claim 1, wherein: and B, in the preparation of the radiation cooling functional particles in the step B, the molar ratio of Mg element to P element is 1: 1 configuration.

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