Gradient composite material with photo-thermal and super-hydrophobic properties as well as preparation method and application of gradient composite material

Abstract

The invention belongs to the technical field of new materials, and relates to a gradient composite material with photo-thermal and super-hydrophobicity as well as a preparation method and application of the gradient composite material. The gradient composite material comprises two or more layers of carbon fiber composite materials, and each layer of carbon fiber composite material comprises a carbon fiber fabric; the surface of the carbon fiber fabric is coated with the photo-thermal coating, and the photo-thermal coating comprises nano carbon powder; the surface of the photo-thermal coating is coated with the hydrophobic coating, and the hydrophobic coating comprises polydimethylsiloxane and nano silicon dioxide; wherein the content of the nano carbon powder in the photo-thermal coating in each layer of the carbon fiber composite material is different, and is gradually reduced layer by layer from top to bottom in the thickness direction of the gradient composite material. The gradient composite material formed through gradient distribution of the content of the nano carbon powder has excellent photo-thermal and super-hydrophobicity, while the photo-thermal performance is maintained, the impact resistance and energy absorption are remarkably improved, and the problem of poor toughness caused by high-content carbon powder is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of new materials, and relates to a gradient composite material with photothermal and superhydrophobic properties, a preparation method thereof, and an application thereof. Background Art

[0002] Due to its unique surface wettability, superhydrophobic materials exhibit great application potential in fields such as self-cleaning, anti-icing, anti-fogging, and anti-corrosion. However, traditional superhydrophobic materials often only focus on surface coatings, and there are problems such as poor erosion resistance and single mechanical properties, which limit their practical applications. In recent years, combining photothermal materials with superhydrophobic materials to develop superhydrophobic composite materials with photothermal properties has become a research hotspot. Such materials not only possess superhydrophobic properties but also can convert light energy into heat energy, and have broad application prospects in fields such as solar interface evaporation, photothermal anti-fogging, and anti-icing.

[0003] Currently, there have been some research reports on photothermal superhydrophobic composite materials. The prior arts CN 117304728 A, CN 118791915 A, CN 115584656 B, and CN 117463994 A respectively adopt methods of surface spraying composite solutions and surface etching micro-nano structures to prepare photothermal superhydrophobic materials, which have problems such as complex preparation processes, high costs, poor wear resistance, and poor erosion resistance. In addition, the method of surface spraying photothermal superhydrophobic materials also has poor interfacial bonding between the surface spray coating and the matrix material, resulting in a decrease in the overall mechanical properties of the material. Summary of the Invention

[0004] To solve the above problems existing in the prior art, the object of the present invention is a gradient composite material with photothermal and superhydrophobic properties, a preparation method thereof, and an application thereof, so as to overcome the deficiencies of the prior art.

[0005] One object of the present invention is achieved by the following technical solutions: A gradient composite material with photothermal and superhydrophobic properties, comprising two or more layers of carbon fiber composite materials. Each layer of carbon fiber composite material includes: Carbon fiber fabric; A photothermal coating coated on the surface of the carbon fiber fabric, and the photothermal coating includes nano-carbon powder; A hydrophobic coating coated on the surface of the photothermal coating, and the hydrophobic coating includes polydimethylsiloxane and nano-silica; Wherein, the content of nano-carbon powder in the photothermal coating of each layer of carbon fiber composite material is different, and decreases layer by layer from top to bottom along the thickness direction of the gradient composite material.

[0006] Preferably, the number of layers of the carbon fiber composite material is 2 - 10 layers; more preferably 3 - 6 layers.

[0007] Preferably, the photothermal coating is formed on the surface of the carbon fiber fabric by impregnating and pre-curing a mixed solution A comprising nano-carbon powder, a curing agent, and a resin.

[0008] Preferably, the hydrophobic coating is formed on the surface of the photothermal coating by impregnating and curing a mixed solution B comprising polydimethylsiloxane, nano-silica, and an organic solvent.

[0009] The second object of the present invention is achieved by the following technical solution: A method for preparing a gradient composite material with photothermal and superhydrophobic properties, comprising the following steps: S1. Disperse the nano-carbon powder in the curing agent, and then add the resin to obtain a mixed solution A; S2. Add polydimethylsiloxane and nano-silica to the organic solvent to obtain a mixed solution B; S3. Immerse the carbon fiber fabric in the mixed solution A, take it out, and perform pre-curing treatment to obtain a carbon fiber prepreg; S4. Immerse the carbon fiber prepreg in the mixed solution B, take it out, and obtain a layer of carbon fiber composite material; S5. Repeat steps S1 - S4 at least once, with the nano-carbon powder content in the mixed solution A being different in each step S1, to obtain at least two layers of carbon fiber composite materials with different nano-carbon powder contents; S6. Lay the carbon fiber composite materials with different nano-carbon powder contents layer by layer in ascending order of nano-carbon powder content, and use the vacuum bag film method for curing and forming to form a gradient composite material.

[0010] In step S1, the nano-carbon powder is dispersed in the curing agent, and ultrasonic assistance is used for dispersion with an ultrasonic time of 5 - 30 min; after adding the resin, ultrasonic assistance is also used for dispersion with an ultrasonic time of 5 - 30 min. In step S2, polydimethylsiloxane and nano-silica are added to the organic solvent, and ultrasonic assistance is used for dispersion with an ultrasonic time of 5 - 30 min. The ultrasonic treatment is carried out in an ultrasonic cleaner with an ultrasonic frequency of 20 - 80 KHz and an ultrasonic power of 50 - 500 W.

[0011] In step S1: Preferably, the nano-carbon powder includes one or more of nano-graphene, carbon nanotubes, nano-carbon black, and nano-activated carbon. Further preferably, it is nano-graphene, and the thickness of the graphene is 0.34 - 10 nm, and the sheet diameter is 100 - 999 nm.

[0012] Preferably, the resin is one or more of epoxy resin, polyurethane resin, phenolic resin, and acrylic resin. Further preferably, the resin is epoxy resin.

[0013] Preferably, the mass ratio of the nano-carbon powder to the curing agent is 0.1-10:100, and more preferably 0.5-6:100.

[0014] Preferably, the mass ratio of the resin to the curing agent is 2-4:1.

[0015] Preferably, the content of the nano-carbon powder in the mixed solution A is 0.1-2 wt%.

[0016] Preferably, in adjacent two layers of carbon fiber composites, the content difference of the nano-carbon powder in the used mixed solution A is 0.1-1 wt%. More preferably, in adjacent two layers of carbon fiber composites, the content difference of the nano-carbon powder in the used mixed solution A is 0.3-0.8 wt%.

[0017] In step S2: The organic solvent is a solvent that will volatilize at the curing temperature and can dissolve polydimethylsiloxane, and examples thereof include one or more of ethyl acetate, methyl acetate, propyl acetate, dimethyl carbonate, n-hexane, and tetrahydrofuran.

[0018] Preferably, the mass ratio of polydimethylsiloxane to nano-silica is 6:1-1:1, and the mass of the organic solvent is 1-10 times the total mass of polydimethylsiloxane and nano-silica.

[0019] There is no order difference between steps S1 and S2, and the order can be adjusted arbitrarily.

[0020] In step S3: Preferably, the impregnation time of the carbon fiber fabric is 5-20 min.

[0021] Preferably, the pre-curing temperature is 60-90 °C and the pre-curing time is 0.5-2 h.

[0022] The impregnation time in step S4 is 10-40 min.

[0023] In step S6, the curing and forming temperature is 100-150 °C and the curing time is 1-5 h.

[0024] The third object of the present invention is achieved by the following technical solutions: An application of a gradient composite material with photothermal and superhydrophobic properties in any one of the following: a. A solar interface evaporation system for seawater desalination or sewage treatment, achieving efficient solar-driven water evaporation through the photothermal performance and surface superhydrophobic performance of the material; b. A photothermal de-icing device for anti-icing and de-icing on the surfaces of aircraft glass, wind turbine blades, etc., accelerating the melting of ice layers and the evaporation of water droplets by converting solar energy into heat energy; c. Self-cleaning surface construction, used in fields such as building facades and solar panels. Through its superhydrophobic surface, it can effectively repel and remove pollutants such as dust and oil stains, achieving self-cleaning of the surface.

[0025] Compared with the prior art, the present invention has the following beneficial effects: 1. The gradient composite material provided by the present invention has excellent photothermal performance and superhydrophobic performance, and good durability, and can withstand long-term rain erosion and ultraviolet irradiation.

[0026] 2. The present invention forms a gradient composite material through the gradient distribution of the nano-carbon powder content. While maintaining the photothermal performance, it significantly improves the impact resistance and energy absorption, and solves the problem of poor toughness caused by high content of carbon powder.

[0027] 3. Compared with the uniform structure, the gradient composite material provided by the present invention can greatly improve the photothermal performance and impact resistance under the condition of equivalent graphene content.

[0028] 4. The preparation process of the present invention does not require complex equipment, and the raw materials are easily available. It adopts conventional processes such as impregnation, ultrasonic dispersion and hot pressing curing, which is easy to realize large-scale production and reduce the preparation cost.

[0029] 5. The composite material prepared by the present invention can be applied to multiple fields such as solar interface evaporation, photothermal de-icing and defogging, and self-cleaning surfaces, and has broad application prospects. Description of the Drawings

[0030] Figure 1 is the contact angle of Examples 1-4 and Comparative Examples 1-3; Figure 2 is the contact angle ° of Examples 1-4 after 1 h of rain and ultraviolet irradiation treatment; Figure 3 is the force-displacement curve in the impact test of Examples 1-4 and Comparative Examples 1-2; Figure 4 is the force-displacement curve in the impact test of Comparative Examples 3-6. Detailed Embodiments

[0031] The technical solutions of the present invention will be further described and illustrated below through specific examples and drawings. It should be understood that the specific examples described herein are only for helping to understand the present invention and are not used for specific limitations of the present invention. And the drawings used in this article are only for better illustrating the content disclosed by the present invention, and do not have a limiting effect on the protection scope. If there is no special description, the raw materials used in the embodiments of the present invention are all common raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0032] In the description of the present invention, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, and includes a and b.

[0033] Graphene: Purchased from Shanghai Macklin Biochemical Co., Ltd., CAS number 1034343-98-0, thickness ~5 nm, conductivity ≥1600 S / cm.

[0034] Epoxy resin AB glue: Yituo Composite Materials YT-CC302, E-51 low-viscosity epoxy resin. In the examples and comparative examples, the epoxy resin refers to the A component in the epoxy resin AB glue, and the curing agent is the B component in the epoxy resin AB glue.

[0035] Carbon fiber fabric: Purchased from Shandong Dingsheng Composite Materials Co., Ltd., domestic model T300, width 1000 mm.

[0036] Average particle size of nano-silica: 7 - 40 nm.

[0037] PDMS: Purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd., model SYLGARD (R) 184.

[0038] In the following examples and comparative examples, an ultrasonic cleaner was used to assist in dispersion, with a power of 100 W and a frequency of 40 KHz.

[0039] Example 1

[0040] The composite material of this example was prepared by the following steps: (1) Add 0.1 g of graphene powder to 10 g of curing agent, ultrasonically disperse for 20 min, then add 30 g of epoxy resin, and ultrasonically disperse for 30 min to obtain a uniformly dispersed mixed solution A; (2) Mix 5 g of PDMS, 2 g of nano-SiO₂ and 20 g of ethyl acetate, ultrasonically disperse for 10 min to obtain a uniformly dispersed mixed solution B; (3) Place the carbon fiber fabric in the mixed solution A, fully impregnate for 10 min and then take it out, then lay it flat and put it into a vacuum oven for pre-curing treatment at a temperature of 70 °C for 1 hour to obtain a carbon fiber prepreg; (4) Place the carbon fiber prepreg in the mixed solution B, impregnate for 10 minutes and then take it out to obtain a layer of carbon fiber composite material; (5) Repeat steps (1)-(4) 2 times, with step (1) being the same each time, to obtain a three-layer carbon fiber composite material with the same nano-carbon powder content; (6) Lay the three-layer carbon fiber composite materials with the same nano-carbon powder content layer by layer, use the vacuum bag film forming process, and then put it into an oven for curing treatment at 120 °C for 2 hours to obtain the composite material.

[0041] Example 2

[0042] The composite material of this example is prepared by the following steps: (1) Add 0.3 g of graphene powder to 10 g of curing agent, ultrasonically disperse for 20 min, then add 30 g of epoxy resin, and ultrasonically disperse for 30 min to obtain a uniformly dispersed mixed solution A; (2) Mix 5 g of PDMS, 2 g of nano-SiO2 and 20 g of ethyl acetate, and ultrasonically disperse for 10 min to obtain a uniformly dispersed mixed solution B; (3) Immerse the carbon fiber fabric in the mixed solution A for 10 min, take it out, then lay it flat and put it into a vacuum oven for pre-curing treatment at a temperature of 70 °C for 1 hour to obtain a carbon fiber prepreg; (4) Immerse the carbon fiber prepreg in the mixed solution B for 10 minutes, take it out to obtain a layer of carbon fiber composite material; (5) Repeat steps (1)-(4) 2 times, with the same step (1) each time, to obtain a three-layer carbon fiber composite material with the same nano-carbon powder content; (6) Lay the three-layer carbon fiber composite materials with the same nano-carbon powder content layer by layer, adopt the vacuum bag molding process, and then put it into an oven for curing treatment at 120 °C for 2 hours to obtain the composite material.

[0043] Example 3

[0044] The composite material of this example is prepared by the following steps: (1) Add 0.5 g of graphene powder to 10 g of curing agent, ultrasonically disperse for 20 min, then add 30 g of epoxy resin, and ultrasonically disperse for 30 min to obtain a uniformly dispersed mixed solution A; (2) Mix 5 g of PDMS, 2 g of nano-SiO2 and 20 g of ethyl acetate, and ultrasonically disperse for 10 min to obtain a uniformly dispersed mixed solution B; (3) Immerse the carbon fiber fabric in the mixed solution A for 10 min, take it out, then lay it flat and put it into a vacuum oven for pre-curing treatment at a temperature of 70 °C for 1 hour to obtain a carbon fiber prepreg; (4) Immerse the carbon fiber prepreg in the mixed solution B for 10 minutes, take it out to obtain a layer of carbon fiber composite material; (5) Repeat steps (1)-(4) 2 times, with the same step (1) each time, to obtain a three-layer carbon fiber composite material with the same nano-carbon powder content; (6) Lay the carbon fiber composites with the same nano-carbon powder content in three layers layer by layer, adopt the vacuum bag film forming process, and then place them in an oven for curing treatment at 120 °C for 2 hours to obtain the composite material.

[0045] Example 4

[0046] The gradient composite material of this example is prepared by the following steps: Obtain the first layer of carbon fiber composite material according to steps (1)-(4) of Example 1, with a low graphene content; Obtain the second layer of carbon fiber composite material according to steps (1)-(4) of Example 2, with a medium graphene content; Obtain the third layer of carbon fiber composite material according to steps (1)-(4) of Example 3, with a high graphene content; First lay the first layer of carbon fiber composite material, then lay the second layer of carbon fiber composite material on top, and then lay the third layer of carbon fiber composite material on the second layer of carbon fiber composite material, so that the nano-carbon powder content in the composite material decreases layer by layer from top to bottom. Adopt the vacuum bag film forming process, and then place it in an oven for curing treatment at 120 °C for 2 hours to obtain the gradient composite material.

[0047] Comparative Example 1 The composite material of Comparative Example 1 is prepared by the following steps: (1) Mix 10 g of curing agent and 30 g of epoxy resin, and disperse them ultrasonically for 30 min to obtain a uniformly dispersed mixed solution C; (2) Place the carbon fiber fabric in the mixed solution C and impregnate it fully for 10 min, then take it out, and then lay it flat and put it into a vacuum oven for pre-curing treatment at a temperature of 70 °C for 1 hour to obtain the carbon fiber prepreg; (3) Repeat steps (1)-(2) 2 times to obtain three layers of carbon fiber prepregs; (4) Lay the three layers of carbon fiber prepregs layer by layer, adopt the vacuum bag film forming process, and then place them in an oven for curing treatment at 120 °C for 2 hours to obtain the ordinary carbon fiber composite material.

[0048] Comparative Example 2 The composite material of Comparative Example 2 is prepared by the following steps: (1) Mix 10 g of curing agent and 30 g of epoxy resin, and disperse them ultrasonically for 30 min to obtain a uniformly dispersed mixed solution C; (2) Mix 5 g of PDMS and 20 g of ethyl acetate, and disperse them ultrasonically for 10 min to obtain a uniformly dispersed mixed solution D; (3) Place the carbon fiber fabric in the mixed solution C and impregnate it fully for 10 minutes, then take it out, lay it flat and put it into a vacuum oven for pre-curing treatment at a temperature of 70 °C for 1 hour to obtain a carbon fiber prepreg; (4) Place the carbon fiber prepreg in the mixed solution D and impregnate it for 10 minutes, then take it out to obtain a layer of carbon fiber composite material; (5) Repeat steps (1)-(4) 2 times to obtain a three-layer carbon fiber composite material; (6) Lay the three-layer carbon fiber composite material layer by layer, adopt the vacuum bag film forming process, and then put it into an oven for curing treatment at 120 °C for 2 hours to obtain a composite material.

[0049] Comparative Example 3 The composite material of Comparative Example 3 was prepared by the following steps: (1) Mix 10 g of curing agent and 30 g of epoxy resin, and disperse them ultrasonically for 30 minutes to obtain a uniformly dispersed mixed solution C; (2) Mix 5 g of PDMS, 2 g of nano-SiO2 and 20 g of ethyl acetate, and disperse them ultrasonically for 10 minutes to obtain a uniformly dispersed mixed solution B; (3) Place the carbon fiber fabric in the mixed solution C and impregnate it fully for 10 minutes, then take it out, lay it flat and put it into a vacuum oven for pre-curing treatment at a temperature of 70 °C for 1 hour to obtain a carbon fiber prepreg; (4) Place the carbon fiber prepreg in the mixed solution B and impregnate it for 10 minutes, then take it out to obtain a layer of carbon fiber composite material; (5) Repeat steps (1)-(4) 2 times to obtain a three-layer carbon fiber composite material; (6) Lay the three-layer carbon fiber composite material layer by layer, adopt the vacuum bag film forming process, and then put it into an oven for curing treatment at 120 °C for 2 hours to obtain a composite material.

[0050] Comparative Example 4 The composite material of Comparative Example 4 was prepared by the following steps: (1) Add 0.5 g of graphene powder to 10 g of curing agent, disperse it ultrasonically for 20 minutes, then add 30 g of epoxy resin and disperse it ultrasonically for 30 minutes to obtain a uniformly dispersed mixed solution A; (2) Mix 5 g of PDMS, 2 g of nano-SiO2 and 20 g of ethyl acetate, and disperse them ultrasonically for 10 minutes to obtain a uniformly dispersed mixed solution B; (3) Place the carbon fiber fabric in the mixed solution A and impregnate it fully for 10 minutes, then take it out, lay it flat and put it into a vacuum oven for pre-curing treatment at a temperature of 70 °C for 1 hour to obtain a carbon fiber prepreg; (4) Immerse the carbon fiber prepreg in the mixed solution B for 10 minutes and then take it out to obtain a layer of carbon fiber composite material; (5) Use the vacuum bag film forming process for a layer of carbon fiber composite material, put it into an oven and cure it at 120 °C for 2 hours to obtain a composite material.

[0051] Comparative Example 5 The gradient composite material of Comparative Example 5 is prepared by the following steps: Obtain the first layer of carbon fiber composite material with low graphene content according to steps (1)-(4) of Example 1; Obtain the second layer of carbon fiber composite material with medium graphene content according to steps (1)-(4) of Example 2; Obtain the third layer of carbon fiber composite material with high graphene content according to steps (1)-(4) of Example 3; Lay the first layer of carbon fiber composite material, the third layer of carbon fiber composite material, and the second layer of carbon fiber composite material in sequence, use the vacuum bag film forming process, and then put it into an oven and cure it at 120 °C for 2 hours to obtain a gradient composite material.

[0052] Comparative Example 6 The gradient composite material of Comparative Example 6 is prepared by the following steps: Obtain the first layer of carbon fiber composite material with low graphene content according to steps (1)-(4) of Example 1; Obtain the second layer of carbon fiber composite material with medium graphene content according to steps (1)-(4) of Example 2; Obtain the third layer of carbon fiber composite material with high graphene content according to steps (1)-(4) of Example 3; Lay the third layer of carbon fiber composite material, the first layer of carbon fiber composite material, and the second layer of carbon fiber composite material in sequence, use the vacuum bag film forming process, and then put it into an oven and cure it at 120 °C for 2 hours to obtain a gradient composite material.

[0053] Performance testing Contact angle test: Use a contact angle measuring instrument OCA25 and the sessile drop method to quickly and accurately measure the contact angle of the composite material.

[0054] Photothermal conversion performance test: Irradiate the composite material with a solar simulator, with a radiation intensity of 600 W / m 2 , after natural sunlight irradiation at room temperature of 9 °C for 5 minutes, use an infrared thermal imager to record the surface temperature change.

[0055] Erosion resistance performance test: An environmental test chamber was used to simulate a humid and hot environment. The composite material was subjected to rainwater scouring and ultraviolet irradiation for 1 h, with a water pressure of 0.12 MPa, a nozzle hole diameter of 0.8 mm, a temperature of 38 °C, and a humidity of 64%. After that, the contact angle of the composite material was measured again.

[0056] Impact performance test: A drop hammer impact testing machine was used to conduct impact experiments on the specimens. The hammer head was hemispherical with a mass of 0.5 kg and an impact velocity of 6 m / s. The boundaries of the specimens were fixed on four sides.

[0057] Table 1 Performance of the composite materials in the examples and comparative examples

[0058] As can be seen from Table 1 and Figure 1 , the contact angles of Examples 1-4 are greater than 150°, indicating that the materials have superhydrophobic properties. The contact angle of Example 3 is the largest, which is attributed to the high graphene content. The composite materials of Examples 1-4 were subjected to rainwater scouring and ultraviolet irradiation tests. Table 1 and Figure 2 show that the materials still maintain good superhydrophobic properties, indicating that the materials have excellent erosion resistance. By comparing Examples 1-4, it can be seen that Example 3 has a higher surface temperature in the photothermal conversion test because the graphene content in Example 3 is the highest. The high graphene content is beneficial to improving the photothermal conversion performance of the materials. Although Example 3 has good photothermal properties, the high content of graphene will lead to poor toughness and easy fracture of the composite materials, and poor impact resistance. The impact performance is only 1642.5 J. Through gradient design (Example 4), the impact resistance of the materials is greatly improved to 2342.9 J (as Figure 3 shown). The graphene content in Example 4 is equivalent to that in Example 2, but Example 4 adopts a gradient structure, which is beneficial to the improvement of photothermal properties, making Example 4 have a higher surface temperature in the photothermal conversion test.

[0059] The material of Comparative Example 4 is a single-layer structure, and its contact angle, photothermal conversion performance, and impact resistance are all very poor. Especially in the impact test, it directly fractures and fails. By comparing Example 4 with Comparative Examples 5-6, it can be seen that laying the layers in the order of decreasing graphene content is more beneficial to performance improvement.

[0060] All aspects, embodiments, and features of the present invention should be considered illustrative in all respects and do not limit the present invention. The scope of the present invention is only defined by the claims. Without departing from the spirit and scope of the claimed invention, those skilled in the art will understand other embodiments, modifications, and uses.

[0061] In the preparation method of the present invention, the order of each step is not limited to the listed order. For those of ordinary skill in the art, without creative efforts, the sequence changes of each step are also within the protection scope of the present invention. In addition, two or more steps or actions can be carried out simultaneously.

[0062] Finally, it should be noted that the specific embodiments described herein are only examples of the present invention and do not limit the implementation manners of the present invention. Those skilled in the technical field to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar ways for substitution. It is not necessary and impossible to list all implementation manners here. And these obvious changes or variations derived from the essential spirit of the present invention still belong to the protection scope of the present invention. Interpreting them as any additional restrictions is contrary to the spirit of the present invention.

Claims

1. A gradient composite material with photothermal and superhydrophobic properties, characterized in that, Comprising two or more layers of carbon fiber composite materials, each layer of carbon fiber composite material comprising: Carbon fiber fabric; A photothermal coating coated on the surface of the carbon fiber fabric, the photothermal coating including nano carbon powder; A hydrophobic coating coated on the surface of the photothermal coating, the hydrophobic coating including polydimethylsiloxane and nano silica; Wherein, the content of nano carbon powder in the photothermal coating of each layer of carbon fiber composite material is different, and decreases layer by layer from top to bottom along the thickness direction of the gradient composite material.

2. The gradient composite material according to claim 1, wherein The number of layers of the carbon fiber composite material is 2 to 10 layers; And / or, the photothermal coating is formed on the surface of the carbon fiber fabric by impregnation and pre-curing with a mixed solution A including nano carbon powder, a curing agent, and a resin; And / or, the hydrophobic coating is formed on the surface of the photothermal coating by impregnation and curing with a mixed solution B including polydimethylsiloxane, nano silica, and an organic solvent.

3. A preparation method of a gradient composite material with photothermal and superhydrophobic properties, characterized in that, Including the following steps: S1. Disperse nano carbon powder in a curing agent, and then add a resin to obtain a mixed solution A; S2. Add polydimethylsiloxane and nano silica to an organic solvent to obtain a mixed solution B; S3. Immerse the carbon fiber fabric in the mixed solution A, take it out, and perform pre-curing treatment to obtain a carbon fiber prepreg; S4. Immerse the carbon fiber prepreg in the mixed solution B, take it out, and obtain one layer of carbon fiber composite material; S5. Repeat steps S1 - S4 at least once, and the content of nano carbon powder in the mixed solution A in each step S1 is different, to obtain at least two layers of carbon fiber composite materials with different nano carbon powder contents; S6. Lay the carbon fiber composite materials with different nano carbon powder contents layer by layer in ascending order of nano carbon powder content, and use the vacuum bag film method for curing and forming to form a gradient composite material.

4. The preparation method according to claim 3, characterized in that The nano carbon powder is one or more of nano graphene, carbon nanotubes, nano carbon black, and nano activated carbon; And / or, the resin is one or more of epoxy resin, polyurethane resin, phenolic resin, and acrylic resin.

5. The preparation method according to claim 3, wherein The mass ratio of the nano carbon powder to the curing agent is 0.1 - 10:100; And / or, the mass ratio of the resin to the curing agent is 2 - 4:1; And / or, the content of the nano carbon powder in the mixed solution A is 0.1 - 2 wt%.

6. The preparation method according to claim 3, characterized in that, In adjacent two layers of carbon fiber composite materials, the content of nano carbon powder in the used mixed solution A differs by 0.1 - 1 wt%.

7. The preparation method according to claim 3, characterized in that, The mass ratio of polydimethylsiloxane to nano silica is 6:1 - 1:1; And / or, the mass of the organic solvent is 1 - 10 times the total mass of polydimethylsiloxane and nano silica.

8. The preparation method according to claim 3, characterized in that In step S3, the impregnation time of the carbon fiber fabric is 5 - 20 min, the pre-curing temperature is 60 - 90 °C, and the pre-curing time is 0.5 - 2 h.

9. The preparation method according to claim 3, characterized in that, The impregnation time in step S4 is 10 - 40 min; And / or, in step S6, the temperature for curing and forming is 100 - 150 °C, and the curing time is 1 - 5 h.

10. Application of the gradient composite material as described in claim 1 or the gradient composite material prepared by the preparation method as described in claim 3 in any of the following: a. Solar interface evaporation system; b. Photothermal de-icing device; c. Self-cleaning surface construction.

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