CN114854307B

CN114854307B - Self-cleaning broadband high-light-absorption coating and preparation method and application thereof

Info

Publication number: CN114854307B
Application number: CN202210503731.2A
Authority: CN
Inventors: 吴晓宏; 崔召奇; 李杨; 卢松涛; 秦伟
Original assignee: Harbin Institute of Technology; Chongqing Research Institute of Harbin Institute of Technology
Current assignee: Harbin Institute of Technology; Chongqing Research Institute of Harbin Institute of Technology
Priority date: 2022-05-10
Filing date: 2022-05-10
Publication date: 2022-11-04
Anticipated expiration: 2042-05-10
Also published as: CN114854307A

Abstract

The invention discloses a self-cleaning broadband high-light-absorption coating as well as a preparation method and application thereof, belonging to the technical field of preparation of high-light-absorption hydrophobic coatings. The invention takes carbon black, resin and the like as raw materials, a first layer coating with stronger covering power is obtained by regulating and controlling the atomization effect, the spraying time and the spraying distance in multiple spraying, a middle layer coating with larger particles and poorer covering power and a third layer coating which is smaller in particles and mainly adhered to the middle layer are combined to form a nano-micron tree-shaped hierarchical structure, the light absorption capacity of the coating in a wider wavelength band range can be improved by the structure, the solar absorption ratio under the AM0 solar spectrum can reach 99.48 percent at most, the reflectivity is generally lower than 0.6 percent in the range of 200-2500nm, the structure also has the function of amplifying the hydrophobic effect, the contact angle of the surface of the coating can reach 154.19 percent at most, and the self-cleaning effect is excellent.

Description

Self-cleaning broadband high-light-absorption coating and preparation method and application thereof

Technical Field

The invention relates to a self-cleaning broadband high-light-absorption coating, and a preparation method and application thereof, and belongs to the technical field of preparation of high-light-absorption hydrophobic coatings.

Background

The high light absorption coating refers to a coating which has very high absorptivity to incident light of a certain wave band on the surface of the coating through material selection or microstructure regulation, and has wide research and application in the fields of stray light inhibition, photothermal conversion and the like. Due to the aggravation of the greenhouse effect and the sharp decrease of the fossil energy reserves, solar energy has the advantages of small land area limitation, large reserves, environmental protection and the like compared with the traditional fossil energy, and becomes an important component of human social energy, but the problem of low efficiency is often accompanied in the common solar energy application field, so that an efficient light absorption mode is urgently needed to solve the problems.

The existing high light absorption coating is composed of carbon black pigment and resin binder, has advantages in cost and process, but is limited by poor intrinsic light absorption performance of the traditional carbon black, the reflectivity of the coating is high (3-5%), the solar absorption ratio is generally lower than 98%, and the high absorption band is narrow. In order to further reduce the reflectivity and enhance the solar absorption ratio, the carbon nano tube is used for replacing carbon black to prepare a high light absorption coating in the prior art, and although the coating has very low reflectivity (1 percent), the coating has the problems of complex preparation process, high price, poor substrate adaptability, difficult construction, poor bonding force and the like, and the coating cannot meet the requirements of modern application scenes. Other black surface treatment processes, such as anodization, have strict requirements on the shape, material, size, etc. of the substrate, and cannot meet the requirements at present. Moreover, when the existing high light absorption coating is exposed in the air, the light absorption performance is degraded because pollutants such as dust and the like are adsorbed by factors such as static electricity and the like to cause the change of surface properties. Therefore, it is necessary to provide a self-cleaning broadband high light absorption coating, and a preparation method and application thereof.

Disclosure of Invention

The invention provides a self-cleaning broadband high-light-absorption coating, and a preparation method and application thereof, aiming at solving the technical problems of poor optical performance, narrow high-light-absorption waveband, complex preparation process, high cost, difficult construction, poor substrate adaptability, easy adsorption of pollutants such as dust and the like to cause performance degradation and the like of the existing high-light-absorption coating.

The technical scheme of the invention is as follows:

a self-cleaning broadband high light absorption coating, the surface of which is a nano-micron multi-scale hierarchical tree structure.

A preparation method of the self-cleaning broadband high light absorption coating comprises the step of coating the spraying liquid on a substrate in a multi-spraying mode.

Further limited, the spraying liquid is prepared from the following raw materials in parts by weight: 1-3 parts of carbon black, 40 parts of a binder and 78-80 parts of a solvent.

More specifically, the binder is one or more of silicone resin, polyurethane and epoxy resin mixed according to any proportion.

More particularly, the solvent is absolute ethanol.

The spraying liquid is further limited to be prepared by mixing the raw materials for preparing the spraying liquid according to the proportion and then sequentially carrying out ultrasonic treatment and magnetic stirring treatment.

More specifically, the ultrasonic treatment time is 20min.

More particularly, the magnetic stirring treatment time is 3 hours.

More particularly, the number of spraying is 3.

More specifically, the operation process of the multiple spraying is as follows:

(1) Pretreating a substrate;

(2) Carrying out first spraying on the substrate by using a spray gun, wherein the spraying parameters are as follows: the pressure is 20psi, and the distance between the nozzle and the matrix is 10cm; after the spraying is finished, drying at room temperature for 0.5h, and then drying at 80 ℃ for 3h;

(3) And (3) carrying out secondary spraying by using a spray gun, wherein the spraying parameters are as follows: the pressure was 10psi and the distance between the nozzle and the substrate was 20cm; after the spraying is finished, drying for 0.5h at room temperature, and then drying for 3h at 80 ℃;

(4) And (3) carrying out third spraying by using a spray gun, wherein the spraying parameters are as follows: the pressure was 30psi and the distance between the nozzle and the substrate was 40cm; after the spraying, the mixture was dried at room temperature for 0.5h and then dried at 120 ℃ for 3h.

More particularly, the matrix pretreatment operation process comprises the following steps: and grinding the sand paper, sequentially soaking the sand paper in an ethanol solution and deionized water, performing ultrasonic treatment for 30min respectively, and drying.

The self-cleaning broadband high light absorption coating is used for stray light inhibition parts of space explorers, surfaces of solar photo-thermal converters, ultraviolet protection surfaces or building surfaces.

The self-cleaning high light absorption coating with the nano-micron tree-shaped hierarchical structure on the surface is obtained by regulating and controlling the atomization effect, the spraying time and the spraying distance in multiple spraying by taking carbon black, resin and the like as raw materials, the coating not only provides the broadband high absorption characteristic, but also provides the super-hydrophobic surface, has excellent self-cleaning characteristic, and has the following specific beneficial effects compared with the prior art:

(1) The invention takes carbon black, resin and the like as raw materials and has the advantage of controllable cost.

(2) According to the invention, by regulating and controlling the atomization effect, the spraying time and the spraying distance in multiple spraying, the first layer of coating with strong covering power is obtained, the middle layer of coating with larger particles and poor covering power and the third layer of coating with smaller particles and mainly adhered to the middle layer are combined to form a nano-micron tree-shaped hierarchical structure, the structure can improve the light absorption capacity of the coating in a wider wavelength band range, the solar absorption ratio of the coating is obviously improved to 99.48% compared with other high light absorption coatings based on traditional carbon black, the high absorption band range of the coating is wider, the reflectivity of the coating is generally lower than 0.6% in the range of 200-2500nm, the structure also has the effect of amplifying the hydrophobic effect, the water drops can realize the conversion from a Wenzel state to a Cassie state on the hydrophobic surface, the contact angle of the coating surface can reach 154.19% to the maximum, and the self-cleaning effect is excellent.

(3) The preparation method of the self-cleaning broadband high light absorption coating provided by the invention is simple and reliable, is easy to construct, and has low requirements on the shape, size and material of a matrix.

Drawings

FIG. 1 is a TEM photograph of the carbon black used in example 1;

FIG. 2 is a SEM photograph of example 1 when only the first coating layer was sprayed;

FIG. 3 is an SEM photograph of the high light absorbing coating after spraying the intermediate layer of example 1;

FIG. 4 is an SEM photograph of example 1 after spray coating a third coating layer;

FIG. 5 is a schematic view of a nano-micron multi-scale hierarchical tree structure of a highly light absorbing coating;

FIG. 6 is a reflectance test at a wavelength of 200 to 2500nm for the highly light absorbing coatings prepared in examples 1 to 5;

FIG. 7 is a graph of the contact angle test results for example 1 when only the first coating layer was sprayed;

fig. 8 is a graph of the contact angle test results of example 1 after spraying all three layers of coating.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The experimental procedures used in the following examples are conventional unless otherwise specified. The materials, reagents, methods and apparatus used, unless otherwise specified, are conventional and commercially available to those skilled in the art.

Example 1:

(1) Mixing 0.125g of carbon black with 2.0g of silicone resin and 4.0g of absolute ethyl alcohol, carrying out ultrasonic treatment for 20min, and then carrying out magnetic stirring treatment for 3h to mix uniformly, thereby obtaining a spray coating liquid, wherein a TEM photograph of the carbon black is shown in FIG. 1, and is known from FIG. 1: the carbon black used is relatively disordered as a whole, has a partial lattice structure only at the edge, has the diameter of primary particles of 30-40 nm, and is aggregated together to form a grape string-shaped structure.

(2) Polishing an aluminum sheet substrate by using 100-mesh sand paper, removing an oxide layer on the surface of the aluminum sheet substrate, then soaking in an ethanol solution for ultrasonic treatment for 30min, finally soaking in deionized water for ultrasonic treatment for 30min, and drying.

(3) Spraying the spraying liquid obtained in the step (1) on the aluminum sheet substrate treated in the step (2) by using a spray gun, wherein the specific spraying process comprises the following steps:

firstly, controlling the spraying pressure to be 20psi, controlling the distance between a nozzle and an aluminum sheet to be 10cm, drying the sprayed aluminum sheet for 0.5 hour at room temperature, and then drying the aluminum sheet for 3 hours in a blast drying 80 ℃ oven to obtain a first layer of coating with strong covering power, wherein the appearance of the first layer of coating is shown in figure 2;

then, controlling the spraying pressure to be 10psi, controlling the distance between a nozzle and the aluminum sheet to be 20cm, drying the sprayed aluminum sheet for 0.5 hour at room temperature, and then drying the aluminum sheet for 3 hours in an air-blast drying 80 ℃ oven to obtain a middle layer coating with larger particles and poorer covering capability, wherein the appearance of the middle layer coating is shown in figure 3;

and finally, controlling the spraying pressure to be 30psi and the distance between the nozzle and the aluminum sheet to be 40cm, drying the sprayed aluminum sheet for 0.5 hour at room temperature, and then drying the aluminum sheet for 3 hours in a blast drying 120 ℃ box to obtain carbon black particles which mainly comprise fine particles and are mainly adhered to the middle layer coating, wherein the appearance of the carbon black particles is shown in figure 4.

The three layers of coatings obtained by spraying according to different processes are combined to form a nano-micron tree-shaped hierarchical coating structure, and the schematic cross-sectional structure diagram is shown in figure 5: the first compact layer ensures that incident light rays cannot directly irradiate on the substrate to generate strong reflection, the tree-shaped structure consisting of the middle layer and the third coating forms light capture structures with different scales, and incident light rays in different directions can be reflected and absorbed on the surface of the tree-shaped structure for multiple times, so that the reflectivity is further reduced.

Example 2:

(1) 0.050g of carbon black, 2.0g of organic silicon resin and 4.0g of absolute ethyl alcohol are mixed, ultrasonic treatment is carried out for 20min, and then magnetic stirring treatment is carried out for 3h to obtain spraying liquid.

(3) And (3) spraying the spraying liquid obtained in the step (1) on the aluminum sheet substrate treated in the step (2) by using a spray gun, wherein the specific spraying process comprises the following steps:

firstly, controlling the spraying pressure to be 20psi, controlling the distance between a nozzle and an aluminum sheet to be 10cm, drying the sprayed aluminum sheet for 0.5 hour at room temperature, and then drying the aluminum sheet for 3 hours in an air-blast drying 80 ℃ oven to obtain a first coating;

then, controlling the spraying pressure to be 10psi, controlling the distance between a nozzle and the aluminum sheet to be 20cm, drying the sprayed aluminum sheet for 0.5 hour at room temperature, and then drying the aluminum sheet for 3 hours in a forced air drying 80 ℃ box to obtain an intermediate layer coating;

and finally, controlling the spraying pressure to be 30psi and the distance between a nozzle and the aluminum sheet to be 40cm, drying the sprayed aluminum sheet at room temperature for 0.5 hour, and then drying the aluminum sheet in a forced air drying 120 ℃ oven for 3 hours to obtain a third coating, wherein the three coatings are combined to form a nano-micron tree-like hierarchical structure.

Example 3:

(1) Mixing 0.075g of carbon black, 2.0g of organic silicon resin and 4.0g of absolute ethyl alcohol, carrying out ultrasonic treatment for 20min, and then carrying out magnetic stirring treatment for 3h to uniformly mix the components to obtain the spraying liquid.

and finally, controlling the spraying pressure to be 30psi, controlling the distance between a nozzle and the aluminum sheet to be 40cm, drying the sprayed aluminum sheet for 0.5 hour at room temperature, and then drying the aluminum sheet for 3 hours in a blast drying 120 ℃ box to obtain a third coating, wherein the three coatings are combined to form a nano-micron tree-shaped hierarchical structure.

Example 4:

(1) Mixing 0.100g of carbon black, 2.0g of organic silicon resin and 4.0g of absolute ethyl alcohol, carrying out ultrasonic treatment for 20min, and carrying out magnetic stirring treatment for 3h to uniformly mix the components to obtain the spray coating liquid.

Example 5:

(1) Mixing 0.150g of carbon black, 2.0g of organic silicon resin and 4.0g of absolute ethyl alcohol, carrying out ultrasonic treatment for 20min, and carrying out magnetic stirring treatment for 3h to uniformly mix the components to obtain the spray coating liquid.

then, controlling the spraying pressure to be 10psi, controlling the distance between a nozzle and the aluminum sheet to be 20cm, drying the sprayed aluminum sheet at room temperature for 0.5 hour, and then drying the aluminum sheet in an air-blast drying 80 ℃ oven for 3 hours to obtain a middle layer coating;

The effect example:

(1) The coatings obtained in examples 1 to 5 were subjected to a reflectance test using an ultraviolet-visible-near infrared spectrophotometer in combination with an integrating sphere unit, and the results of diffuse reflectance spectrum measurement at wavelengths of 200 to 2500nm are shown in fig. 6: as the content of the carbon black increases, the reflectivity of the corresponding coating in the tested wave band is decreased firstly and then increased. When the content of carbon black in the coating is 0.125g, the reflectivity of the corresponding coating in visible light and near infrared bands is lower than 0.6%, and the reflectivity of the corresponding coating in ultraviolet bands is obviously reduced, so that the result shows that the nano-micron multi-scale rough structure can obviously improve the light absorption capacity of the coating in a wider wavelength band range.

(2) The solar absorptance of the coatings with different aspect ratios obtained in examples 1 to 5 in the AM0 solar spectrum was calculated, and the results are shown in table 1 below:

TABLE 1

Carbon Black content (g)	AM0 phaseAbsorption ratio of Yang (%)
		0.050	97.56
0.075	98.91
		0.100	98.94
0.125	99.48
		0.150	99.36

As can be seen from Table 1, with the increase of the content of the carbon black in the coating, the solar absorption ratio of the obtained high-light-absorption coating in the AM0 spectrum shows a trend of increasing firstly and then decreasing, wherein the performance is most excellent when the content of the carbon black is 0.125g, and the solar absorption ratio in the AM0 spectrum reaches 99.48%, so that the solar absorption ratio can meet most application scenes.

(3) The coatings obtained in example 1 were subjected to a water drop contact angle test, the contact angle after spraying only the first layer of coating being 137.25 ° as shown in fig. 7; while the contact angle after spraying the middle and third coating layers reached 154.19 deg., as shown in fig. 8. The result shows that the nano-micron multi-scale rough structure formed by multiple spraying amplifies the hydrophobic effect, and the water drop can realize the conversion from a Wenzel state to a Cassie state on the hydrophobic surface. Cassie state water drops cannot fill microscopic grooves on the rough surface, certain air is trapped under the water drops, composite contact on the surface of the material is presented, contact angle hysteresis is reduced, rolling angle is reduced, and self-cleaning capacity of the surface of the material is enhanced.

The above embodiments are merely preferred embodiments of the present invention, and the present invention is not limited to the above embodiments, and modifications and changes thereof may be made by those skilled in the art within the scope of the claims of the present invention.

Claims

1. A preparation method of a self-cleaning broadband high light absorption coating is characterized in that the surface of the coating is of a nano-micron multi-scale hierarchical tree structure;

the method comprises the steps of coating the spraying liquid on a matrix in a multi-time spraying manner;

the spraying liquid is prepared from the following raw materials in parts by weight: 1-3 parts of carbon black, 40 parts of silicone resin and 78-80 parts of solvent;

the operation process of multiple spraying is as follows:

(1) Matrix pretreatment: grinding the sand paper, sequentially soaking the sand paper in an ethanol solution and deionized water, performing ultrasonic treatment for 30min respectively, and drying;

(2) Carrying out first spraying on the substrate by using a spray gun, wherein the spraying parameters are as follows: pressure of 20psi, nozzle to substrate distance of 10cm; after the spraying is finished, drying for 0.5h at room temperature, and then drying for 3h at 80 ℃;

(3) And (3) carrying out secondary spraying by using a spray gun, wherein the spraying parameters are as follows: the pressure is 10psi, the distance between the nozzle and the matrix is 20cm; after the spraying is finished, drying at room temperature for 0.5h, and then drying at 80 ℃ for 3h;

2. The method of claim 1, wherein the solvent is absolute ethanol.

3. The method for preparing a self-cleaning broadband high light absorption coating according to claim 1, wherein the spraying liquid is prepared by mixing raw materials for forming the spraying liquid according to a ratio, and then sequentially performing ultrasonic treatment and magnetic stirring treatment.

4. The method for preparing a self-cleaning broadband high light absorbing coating according to claim 3, wherein the ultrasonic treatment time is 20min and the magnetic stirring treatment time is 3h.

5. Use of a self-cleaning broad-band highly light absorbing coating obtained by the preparation method according to claim 1 for a space explorer stray light suppressing part, a solar photo-thermal converter surface, a uv protected surface or a building surface.