An ultra-lightweight high infrared emissivity coating on the surface of a carbon / carbon composite material and its preparation method and application

Abstract

The present invention discloses an ultra-lightweight, high-infrared emissivity coating on the surface of a carbon / carbon composite material, its preparation method, and application, and relates to the technical field of infrared radiation coating materials. The coating slurry comprises the following components in parts by weight: 5 to 8 parts of hollow carbon spheres, 0.7 to 1.0 parts of sodium dodecylbenzenesulfonate, 16 to 23 parts of deionized water, 0.8 to 1.0 parts of phenolic resin, and 6006 to 7010 parts of isopropyl alcohol. The present invention selects hollow carbon spheres with a cavity structure and a large specific surface area as the main material of the coating. With the help of a compressed air spraying process, the spheres are evenly sprayed on the surface of the composite material, and an appropriate micro-nano pore structure is constructed, thereby greatly reducing the surface density of the coating while increasing the infrared emissivity, and having a significant weight reduction effect.

Description

Technical Field

[0001] The present invention relates to the technical field of infrared radiation coating materials, and in particular to an ultra-lightweight high infrared emissivity coating on the surface of a carbon / carbon composite material, and a preparation method and application thereof. Background Art

[0002] The rapid development of aerospace technology has placed increasingly stringent demands on thermal management materials for spacecraft, requiring them to combine high-temperature resistance, high thermal conductivity, high heat dissipation, and lightweight design. Carbon fiber-reinforced carbon-based composites (C / C composites) are a key candidate for future high-power spacecraft due to their low density, high specific strength, high thermal conductivity, and excellent high-temperature performance. To fully utilize the thermal management capabilities of C / C composites, a high-emissivity heat-dissipating coating is typically applied to their surface to achieve a "dissipating while conducting" effect during application.

[0003] Based on the principle of matching thermophysical properties, a carbonaceous coating has been developed on the surface of C / C composites, achieving high emissivity while maintaining good interfacial bonding between the coating and the substrate. Nanocarbon materials, due to their large surface area, can provide coatings with more interfaces. These interfaces act as reflection sites, enhancing the reflection of electromagnetic waves within the coating, increasing the absorptivity and, consequently, the emissivity. For example, Krivchenko et al. used plasma etching to fabricate a graphene nanostructure with an emissivity exceeding 0.99 in the near-infrared band of 0.4–2 μm. Yu Gaojie et al. used CVD to fabricate a graphene coating. However, due to the small size of the graphene sheets and the relatively few skeletal pores, they were only able to increase the emissivity to 0.790 in the 1–22 μm band. Finally, Li Wei et al. used commercial spherical carbon black powder and a compressed air spray technique combined with chemical vapor infiltration to fabricate a nanocarbon black coating with an appropriate porosity on the surface of a composite material, achieving an emissivity of 0.95. However, most of these commonly used nanomaterials are solid structures, and in the field of high-performance spacecraft, lightweighting is an eternal theme of development. Therefore, how to structurally design nanophase carbon materials to further reduce weight while obtaining high emissivity is an urgent problem that needs to be solved in this field. Summary of the Invention

[0004] To address the shortcomings of the aforementioned background technology, the present invention utilizes compressed air spray technology to prepare a nanocarbon coating with both high infrared emissivity and ultra-lightweight properties on the surface of a C / C composite material, using hollow carbon spheres as a base material. This coating exhibits high infrared emissivity due to the appropriate pore structure formed by the stacking of hollow carbon spheres. The hollow structure of the hollow carbon spheres reduces the coating's areal density while providing a large specific surface area, achieving excellent weight reduction benefits and providing an important solution for further achieving the goal of lightweighting spacecraft.

[0005] The first object of the present invention is to provide a coating slurry with ultra-lightweight and high infrared emissivity on the surface of a carbon / carbon composite material, wherein the coating slurry comprises the following components in parts by weight:

[0006] 5-8 parts of hollow carbon spheres, 0.7-1.0 parts of sodium dodecylbenzenesulfonate, 16-23 parts of deionized water, 0.8-1.0 parts of phenolic resin, and 6006-7010 parts of isopropyl alcohol.

[0007] Preferably, the outer diameter of the hollow carbon sphere is 150-250 nm, the wall thickness is 5-10 nm, and the OA angle of the hollow carbon sphere wall is 15-35°.

[0008] A second object of the present invention is to provide a method for preparing an ultra-lightweight coating slurry with high infrared emissivity on the surface of a carbon / carbon composite material, comprising the following steps:

[0009] Adding sodium dodecylbenzenesulfonate to deionized water and mixing well to obtain a sodium dodecylbenzenesulfonate solution;

[0010] dispersing phenolic resin in an isopropyl alcohol solution to obtain a phenolic resin solution;

[0011] The sodium dodecylbenzenesulfonate solution was added to isopropyl alcohol and mixed well, and then the hollow carbon spheres were added in multiple times, and each addition was added after the mixture was mixed well to obtain a uniformly dispersed mixed solution;

[0012] The phenolic resin solution is added to the mixed solution and mixed evenly to obtain a coating slurry.

[0013] Preferably, the hollow carbon spheres are added in portions one at a time.

[0014] Preferably, ultrasound is used during the mixing process, and the ultrasound duration is 2 to 5 minutes.

[0015] A third object of the present invention is to provide a method for preparing an ultra-lightweight, high-infrared emissivity coating on a carbon / carbon composite surface, using an ultra-lightweight, high-infrared emissivity coating slurry on a carbon / carbon composite surface, comprising the following steps:

[0016] spraying the coating slurry onto the surface of the carbon / carbon composite material;

[0017] A proper amount of graphene is grown on the surface of the sprayed coating to ensure good bonding strength between the coating and the surface of the carbon / carbon composite material;

[0018] That is, an ultra-light coating with high infrared emissivity is prepared on the surface of the carbon / carbon composite material.

[0019] Preferably, during the spraying process, the discharge port of the spray gun is at an angle of 45 to 60 degrees to the surface of the carbon / carbon composite material, and the distance therebetween is 6 to 10 cm.

[0020] Preferably, the step of growing an appropriate amount of graphene on the sprayed coating surface comprises:

[0021] The chemical vapor deposition method is adopted, with methane as the carbon source, the pressure in the furnace is 5-20 kPa, the deposition temperature is 1050-1150°C, and the time is 4-8 hours.

[0022] A fourth object of the present invention is to provide an ultra-light coating with high infrared emissivity on the surface of a carbon / carbon composite material.

[0023] A fifth object of the present invention is to provide an application of a coating on the surface of a carbon / carbon composite material.

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

[0025] The present invention provides an ultra-lightweight, high-infrared emissivity coating on the surface of a carbon / carbon composite material, as well as its preparation method and application. Hollow carbon spheres with a cavity structure and a large specific surface area are selected as the main material of the coating. With the help of a compressed air spraying process, they are evenly sprayed on the surface of the composite material, and an appropriate micro-nano pore structure is constructed. This improves the infrared emissivity while greatly reducing the surface density of the coating, resulting in a significant weight reduction effect. Subsequently, an appropriate amount of graphene is deposited and grown to reinforce the porous hollow carbon sphere coating and combine it with the surface of the composite material to prepare a high-infrared emissivity, ultra-lightweight coating with good interface bonding. The beneficial effects of the present invention are as follows:

[0026] (1) Hollow carbon spheres are selected as raw materials, and the stacking of spheres is used to construct a rich pore structure with micro-nano dimensions. At the same time, the high specific surface area of ​​hollow carbon spheres can provide more interfaces and sites for the scattering and absorption of infrared rays, greatly improving the infrared emissivity.

[0027] (2) Hollow carbon spheres have a large specific surface area, thin sphere walls, and a cavity structure inside them, making them lightweight. Figure 4 As shown in the figure, the volume of 100 mg of carbon nanotubes, carbon black and hollow carbon spheres. Under the same weight, the volume of hollow carbon spheres is larger, that is, the coating per unit area can be the lightest, which can greatly reduce the weight of the prepared coating and achieve excellent weight reduction effect. The surface density is only 2×10 -6 g / m 3 , while the coating surface density prepared by carbon black balls combined with chemical vapor infiltration is 1×10 -5 g / m 3 In addition, the particle size of hollow carbon spheres can be adjusted according to actual application conditions to meet the needs of different application environments.

[0028] (3) The size structure of the hollow carbon sphere is limited (outer diameter is 200±50nm, wall thickness is 5-10nm, and OA angle of the sphere wall is 15-35°). While achieving the goal of lightweighting, the OA angle of 15-35° can ensure that the sphere wall has few defects and high crystallinity, making the hollow carbon sphere have high structural stability and avoiding structural collapse during subsequent graphene deposition.

[0029] (4) The coating prepared from hollow carbon spheres has good thermal shock resistance because there is a cavity structure inside it. The microcracks generated by stress extend to the hollow structure and terminate there. The stress is released, preventing the microcracks from further expanding to form large cracks, which in turn causes the material to be damaged and fail.

[0030] (5) The raw materials of the coating and the carbon / carbon composite material are both carbonaceous materials with similar thermal expansion coefficients, which effectively alleviate the thermal stress caused by the mismatch of thermophysical properties. Subsequently, an appropriate amount of graphene is deposited on the surface of the coating, which enhances the bonding strength between the coating and the substrate interface, giving it excellent thermal shock resistance. Compared with depositing pyrolytic carbon, growing graphene further reduces weight, ultimately achieving the goal of lightweighting the high infrared emissivity coating.

[0031] (6) The coating is simple to prepare and has strong repeatability. It can be prepared on the surface of C / C composite materials of different sizes. The highest emissivity is 0.98 in the 1-22 μm band. No cracking occurred after 80 thermal cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Scanning electron microscope image of the hollow carbon spheres of the present invention.

[0033] Figure 2 Macroscopic photograph of the spray coating of the present invention.

[0034] Figure 3 Scanning electron microscope image of the spray coating in the present invention.

[0035] Figure 4 Volume images of carbon nanotubes, carbon black and hollow carbon spheres provided by the present invention. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below with reference to specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0037] A first aspect of the present invention provides a coating slurry having an ultra-lightweight and high infrared emissivity on the surface of a carbon / carbon composite material, the coating slurry comprising the following components in parts by weight:

[0038] 5-8 parts of hollow carbon spheres, 0.7-1.0 parts of sodium dodecylbenzenesulfonate, 16-23 parts of deionized water, 0.8-1.0 parts of phenolic resin, and 6006-7010 parts of isopropyl alcohol.

[0039] The present invention uses hollow carbon spheres as raw materials, utilizing stacking of spheres to create a rich micro-nanopore structure. The high specific surface area of ​​the hollow carbon spheres provides more interfaces and sites for infrared scattering and absorption, significantly increasing infrared emissivity. The hollow carbon spheres have an outer diameter of 150 to 250 nm, a wall thickness of 5 to 10 nm, and a wall OA angle of 15 to 35 degrees.

[0040] The present invention limits the size structure of the hollow carbon spheres. The outer diameter of the hollow carbon spheres is 200±50nm, the wall thickness is 5-10nm, and the OA angle of the sphere wall is 15-35°. While achieving the goal of lightweighting, the OA angle of 15-35° can ensure that the sphere wall has few defects and has a high degree of crystallinity, so that the hollow carbon spheres have high structural stability and avoid structural collapse during subsequent graphene deposition.

[0041] Hollow carbon spheres have a large specific surface area and thin sphere walls. The cavity structure inside them greatly reduces the weight of the coating, achieving excellent weight reduction effects. The surface density is only 2×10 -6 g / m 3 The coating surface density prepared by carbon black balls combined with chemical vapor infiltration is 1×10 -5 g / m 3 In addition, the particle size of hollow carbon spheres can be adjusted according to actual application conditions to meet the needs of different application environments.

[0042] A second aspect of the present invention provides a method for preparing an ultra-lightweight coating slurry with high infrared emissivity on the surface of a carbon / carbon composite material, comprising the following steps:

[0043] Adding sodium dodecylbenzenesulfonate to deionized water and mixing well to obtain a sodium dodecylbenzenesulfonate solution;

[0044] dispersing phenolic resin in an isopropyl alcohol solution to obtain a phenolic resin solution;

[0045] The sodium dodecylbenzenesulfonate solution was added to isopropyl alcohol and mixed well, and then the hollow carbon spheres were added in multiple times, and each addition was added after the mixture was mixed well to obtain a uniformly dispersed mixed solution;

[0046] The phenolic resin solution is added to the mixed solution and mixed evenly to obtain a coating slurry.

[0047] The hollow carbon spheres were added in 1 portion each time.

[0048] During the mixing process, ultrasound is used, and the ultrasound duration is 2 to 5 minutes.

[0049] In one embodiment, a method for preparing an ultra-lightweight coating slurry with high infrared emissivity on the surface of a carbon / carbon composite material comprises:

[0050] (1) adding 0.7 to 1.0 parts by weight of sodium dodecylbenzenesulfonate to 16 to 23 parts by weight of deionized water, and ultrasonicating for 5 minutes to completely dissolve it uniformly to obtain a sodium dodecylbenzenesulfonate solution for use;

[0051] (2) dispersing 0.8 to 1.0 parts by mass of a phenolic resin into 6 to 10 parts by mass of an isopropyl alcohol solution to obtain a phenolic resin solution;

[0052] (3) adding the sodium dodecylbenzenesulfonate solution to 6000-7000 parts by mass of isopropanol, ultrasonically mixing for 5 minutes, and then gradually adding the hollow carbon spheres at a rate of 1 part by mass each time. After each addition, ultrasonically mixing for 2 minutes, the next step is added. A total of 5-8 parts by mass of hollow carbon spheres are added to obtain a uniformly dispersed mixed solution;

[0053] (4) Finally, the phenolic resin solution is added to the mixed solution and mixed evenly to obtain a coating slurry.

[0054] A third aspect of the present invention provides a method for preparing an ultra-lightweight, high-infrared emissivity coating on the surface of a carbon / carbon composite material, using the above-mentioned ultra-lightweight, high-infrared emissivity coating slurry on the surface of a carbon / carbon composite material, comprising the following steps:

[0055] spraying the coating slurry onto the surface of the carbon / carbon composite material;

[0056] A proper amount of graphene is grown on the surface of the sprayed coating to ensure good bonding strength between the coating and the surface of the carbon / carbon composite material;

[0057] That is, an ultra-light coating with high infrared emissivity is prepared on the surface of the carbon / carbon composite material.

[0058] During the spraying process, the spray gun outlet is at an angle of 45 to 60 degrees to the surface of the carbon / carbon composite material, and the distance is 6 to 10 cm. The method of growing an appropriate amount of graphene on the sprayed coating surface includes:

[0059] The chemical vapor deposition method is adopted, with methane as the carbon source, the pressure in the furnace is 5-20 kPa, the deposition temperature is 1050-1150°C, and the time is 4-8 hours.

[0060] In one embodiment, a coating preparation method includes:

[0061] (1) Using compressed air spraying technology, spray the slurry onto the surface of the C / C composite material using a spray gun. The spray gun outlet is at an angle of 45-60 degrees to the composite material surface and the distance is 6-10 cm. Spray the material surface multiple times until the surface is completely and evenly covered with the slurry.

[0062] (2) Using chemical vapor deposition, an appropriate amount of graphene is grown on the sprayed coating surface to ensure good bonding strength between the coating and the C / C composite surface. The graphene is grown using methane as the carbon source, a furnace pressure of 5-20 kPa, a deposition temperature of 1100 ± 40°C, and a deposition time of 4-8 hours. It should be noted that the present invention employs deposition in a vacuum furnace.

[0063] The coating prepared from hollow carbon spheres in the present invention has good thermal shock resistance because there is a cavity structure inside it. The microcracks generated by stress extend to the hollow structure and terminate there. The stress is released, preventing the microcracks from further extending to form large cracks, which in turn causes the material to be damaged and fail.

[0064] The coating provided by the present invention is simple to prepare and has strong repeatability. It can be prepared on the surface of C / C composite materials of different sizes. The highest emissivity is 0.98 in the 1-22 μm band. No cracking occurred after 80 thermal cycles.

[0065] A fourth aspect of the present invention provides an ultra-light coating with high infrared emissivity on the surface of a carbon / carbon composite material.

[0066] A fifth aspect of the present invention provides an application of a coating on the surface of a carbon / carbon composite material.

[0067] The coating provided by this invention is made from the same carbonaceous material as the carbon / carbon composite material, sharing a similar thermal expansion coefficient, effectively mitigating thermal stresses caused by mismatched thermophysical properties. Subsequently, an appropriate amount of graphene is deposited on the coating surface, enhancing the interface between the coating and the substrate and imparting excellent thermal shock resistance. Compared to depositing pyrolytic carbon, growing graphene further reduces weight, ultimately achieving the goal of lightweighting the high-infrared emissivity coating.

[0068] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0069] Example 1

[0070] An ultra-lightweight, high-infrared emissivity coating on the surface of a carbon / carbon composite material is prepared by the following method:

[0071] (1) 0.7 parts by mass of sodium dodecylbenzenesulfonate was dissolved in 17 parts by mass of deionized water, and ultrasonicated for 5 minutes to disperse uniformly to obtain a sodium dodecylbenzenesulfonate solution for standby use; then 0.9 parts by mass of phenolic resin was dispersed in 8 parts by mass of isopropanol solution to obtain a phenolic resin solution for standby use.

[0072] (2) The sodium dodecylbenzenesulfonate solution was added to 6000 parts by mass of isopropanol and mixed evenly by ultrasonication for 5 minutes. Subsequently, the hollow carbon spheres were gradually added at a rate of 1 part by mass each time. After each addition, ultrasonication was performed for 2 minutes. It was observed that the hollow carbon spheres were evenly distributed and did not settle. Then, the next step was performed, and a total of 5 parts by mass of hollow carbon spheres were added to obtain a uniformly dispersed mixed solution. Finally, the phenolic resin solution was added to the mixed solution and mixed evenly to obtain a coating slurry.

[0073] (3) Use compressed air spraying technology to spray the slurry onto the surface of the composite material. The spray gun outlet is at a 45-degree angle to the composite material surface and the distance is 8 cm. Spray the material surface multiple times until the surface is completely and evenly covered with the slurry.

[0074] (4) Using chemical vapor deposition, methane is used as the carbon source, the furnace pressure is 7 kPa, the deposition temperature is 1060 ° C, and the time is 5 h, an appropriate amount of graphene is grown on the surface of the sprayed coating, so that the coating has good bonding strength with the surface of the C / C composite material.

[0075] The average emissivity of the prepared coating in the 1-22 μm band is 0.982; after depositing the pyrolytic carbon layer, the average emissivity in the 1-22 μm band is 0.963. No cracking occurred after 80 thermal cycles.

[0076] Example 2

[0077] An ultra-lightweight, high-infrared emissivity coating on the surface of a carbon / carbon composite material is prepared by the following method:

[0078] (1) 0.9 parts by mass of sodium dodecylbenzenesulfonate was dissolved in 20 parts by mass of deionized water, and the mixture was ultrasonically dispersed for 5 minutes to obtain a sodium dodecylbenzenesulfonate solution for standby use; then 0.8 parts by mass of phenolic resin was dispersed in 10 parts by mass of isopropanol solution to obtain a phenolic resin solution for standby use.

[0079] (2) The sodium dodecylbenzenesulfonate solution was added to 6500 parts by mass of isopropanol and ultrasonicated for 5 minutes to mix evenly. Then, the hollow carbon spheres were gradually added at 1 part by mass each time. Ultrasonication was performed for 2 minutes after each addition. It was observed that the hollow carbon spheres were evenly distributed and did not settle. Then, the next step was performed to add a total of 8 parts by mass of hollow carbon spheres to obtain a uniformly dispersed mixed solution. Finally, the phenolic resin solution was added to the mixed solution and mixed evenly to obtain a coating slurry.

[0080] (3) Use compressed air spraying technology to spray the slurry onto the surface of the composite material. The discharge port of the spray gun is at a 50-degree angle to the surface of the composite material and the distance is 6 cm. Spray the material surface multiple times until the surface is completely and evenly covered with the slurry.

[0081] (4) Using chemical vapor deposition, methane is used as the carbon source, the furnace pressure is 5 kPa, the deposition temperature is 1100 ° C, and the time is 6 h, an appropriate amount of graphene is grown on the surface of the sprayed coating, so that the coating has good bonding strength with the surface of the C / C composite material.

[0082] The average emissivity of the prepared coating in the 1-22 μm band is 0.978; after depositing the pyrolytic carbon layer, the average emissivity in the 1-22 μm band is 0.954. No cracking occurred after 80 thermal cycles.

[0083] Example 3

[0084] An ultra-lightweight, high-infrared emissivity coating on the surface of a carbon / carbon composite material is prepared by the following method:

[0085] (1) 1.0 parts by mass of sodium dodecylbenzenesulfonate was dissolved in 18 parts by mass of deionized water, and ultrasonicated for 5 minutes to disperse uniformly to obtain a sodium dodecylbenzenesulfonate solution for standby use; then 0.8 parts by mass of phenolic resin was dispersed in 10 parts by mass of isopropanol solution to obtain a phenolic resin solution for standby use.

[0086] (2) Sodium dodecylbenzenesulfonate solution was added to 7000 parts by mass of isopropanol and mixed evenly by ultrasonication for 5 minutes. Then, hollow carbon spheres were gradually added at a rate of 1 part by mass each time. Ultrasonication was performed for 2 minutes after each addition. It was observed that the hollow carbon spheres were evenly distributed without settling. Then, the next step was performed, and a total of 6 parts by mass of hollow carbon spheres were added to obtain a uniformly dispersed mixed solution. Finally, the phenolic resin solution was added to the mixed solution and mixed evenly to obtain a coating slurry.

[0087] (3) Use compressed air spraying technology to spray the slurry onto the surface of the composite material. The spray gun outlet is at a 60-degree angle to the composite material surface and the distance is 10 cm. Spray the material surface multiple times until the surface is completely and evenly covered with the slurry.

[0088] (4) Using chemical vapor deposition, methane is used as the carbon source, the furnace pressure is 20 kPa, the deposition temperature is 1140 ° C, and the time is 8 h, an appropriate amount of graphene is grown on the surface of the sprayed coating, so that the coating has good bonding strength with the surface of the C / C composite material.

[0089] The average emissivity of the prepared coating in the 1-22 μm band is 0.970; after depositing the pyrolytic carbon layer, the average emissivity in the 1-22 μm band is 0.94. No cracking occurred after 80 thermal cycles.

[0090] Example 4

[0091] An ultra-lightweight, high-infrared emissivity coating on the surface of a carbon / carbon composite material is prepared by the following method:

[0092] (1) 0.7 parts by mass of sodium dodecylbenzenesulfonate was dissolved in 23 parts by mass of deionized water, and the mixture was ultrasonically dispersed for 5 minutes to obtain a sodium dodecylbenzenesulfonate solution for standby use; then 0.9 parts by mass of phenolic resin was dispersed in 8 parts by mass of isopropanol solution to obtain a phenolic resin solution for standby use.

[0093] (2) Sodium dodecylbenzenesulfonate solution was added to 7000 parts by mass of isopropanol and mixed evenly by ultrasonication for 5 minutes. Then, hollow carbon spheres were gradually added at a rate of 1 part by mass each time. Ultrasonication was performed for 2 minutes after each addition. It was observed that the hollow carbon spheres were evenly distributed without sedimentation. Then, the next step was performed, and a total of 8 parts by mass of hollow carbon spheres were added to obtain a uniformly dispersed mixed solution. Finally, the phenolic resin solution was added to the mixed solution and mixed evenly to obtain a coating slurry.

[0094] (3) Use compressed air spraying technology to spray the slurry onto the surface of the composite material. The spray gun outlet is at a 60-degree angle to the composite material surface and the distance is 10 cm. Spray the material surface multiple times until the surface is completely and evenly covered with the slurry.

[0095] (4) Using chemical vapor deposition, methane is used as the carbon source, the pressure in the furnace is 10 kPa, the deposition temperature is 1100 ° C, and the time is 6 h, an appropriate amount of graphene is grown on the surface of the sprayed coating, so that the coating has good bonding strength with the surface of the C / C composite material.

[0096] The average emissivity of the prepared coating in the 1-22 μm band is 0.975; after depositing the pyrolytic carbon layer, the average emissivity in the 1-22 μm band is 0.92. No cracking occurred after 80 thermal cycles.

[0097] In order to illustrate the coating provided by the present invention, it is described with reference to the accompanying drawings.

[0098] Figure 1 is a scanning electron microscope image of the hollow carbon sphere of the present invention; Figure 1 It can be seen that the diameter of the hollow carbon sphere is about 200 nm, with thin walls and a large cavity structure. Figure 2 is a macroscopic photograph of the coating after spraying in the present invention; Figure 2 It can be seen that the hollow carbon spheres are evenly covered on the surface of the composite material. Figure 3 is a scanning electron microscope picture of the spray coating in the present invention; Figure 3 It can be seen that the stacking of hollow carbon spheres constructs a rich pore structure with micro-nano dimensions, which is conducive to the scattering and absorption of infrared rays and the subsequent deposition of graphene.

[0099] Figure 4 Volume images of carbon nanotubes, carbon black, and hollow carbon spheres. Figure 4 This is a volume picture of carbon nanotubes, carbon black and hollow carbon spheres with the same mass of 100 mg. Under the condition of the same mass, hollow carbon spheres have the largest volume and the smallest density, reflecting their lightweight characteristics.

[0100] The present invention describes preferred embodiments and their effects. However, those skilled in the art, once informed of the basic inventive concept, may make additional changes and modifications to these embodiments. Therefore, it is intended that the appended claims be interpreted to include the preferred embodiments as well as all changes and modifications that fall within the scope of the invention.

[0101] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an ultra-lightweight coating with high infrared emissivity on the surface of a carbon / carbon composite material, characterized in that: The following steps are involved: spraying the coating slurry onto the surface of the carbon / carbon composite material; A proper amount of graphene is grown on the surface of the sprayed coating to ensure good bonding strength between the coating and the surface of the carbon / carbon composite material; That is, an ultra-lightweight coating with high infrared emissivity is prepared on the surface of the carbon / carbon composite material; The coating slurry comprises the following components in parts by weight: 5-8 parts of hollow carbon spheres, 0.7-1.0 parts of sodium dodecylbenzenesulfonate, 16-23 parts of deionized water, 0.8-1.0 parts of phenolic resin, 6006-7010 parts of isopropyl alcohol; The outer diameter of the hollow carbon sphere is 150-250 nm, the wall thickness is 5-10 nm, and the OA angle of the hollow carbon sphere wall is 15-35°; The preparation method of the coating slurry comprises: Adding sodium dodecylbenzenesulfonate to deionized water and mixing well to obtain a sodium dodecylbenzenesulfonate solution; dispersing phenolic resin in isopropyl alcohol to obtain a phenolic resin solution; The sodium dodecylbenzenesulfonate solution was added to isopropyl alcohol and mixed well, and then the hollow carbon spheres were added in multiple times, and each addition was added after the mixture was mixed well to obtain a uniformly dispersed mixed solution; Adding the phenolic resin solution to the mixed solution and mixing them evenly to obtain a coating slurry; Add 1 portion of hollow carbon spheres at a time; The method of growing an appropriate amount of graphene on the surface of the sprayed coating comprises: Chemical vapor deposition (CVD) was used with methane as the carbon source, a furnace pressure of 5–20 kPa, a deposition temperature of 1050–1150 °C, and a deposition time of 4–8 h.

2. The method for preparing an ultra-lightweight coating with high infrared emissivity on the surface of a carbon / carbon composite material according to claim 1, characterized in that: During the mixing process, ultrasound is used and the ultrasound duration is 2 to 5 minutes.

3. The method for preparing an ultra-lightweight coating with high infrared emissivity on the surface of a carbon / carbon composite material according to claim 1, characterized in that: During the spraying process, the spray gun outlet is at an angle of 45 to 60 degrees to the surface of the carbon / carbon composite material, and the distance is 6 to 10 cm.

4. An ultra-lightweight coating with high infrared emissivity on the surface of a carbon / carbon composite material prepared by the method according to any one of claims 1 to 3.

5. Use of the coating according to claim 4 on the surface of a carbon / carbon composite material.

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