Method for improving binding force of inorganic thermal control coating on surface of carbon / carbon composite material

Abstract

The invention provides a method for improving the binding force of an inorganic thermal control coating on the surface of a carbon / carbon composite material, which comprises the following steps: placing the carbon / carbon composite material in absolute ethyl alcohol, and carrying out ultrasonic cleaning and drying to finish ultrasonic cleaning; laser is adopted to continuously scan the surface of the carbon / carbon composite material, and laser cleaning is completed; spraying a surface treating agent on the surface of the carbon / carbon composite material subjected to laser cleaning; and spraying the inorganic thermal control coating on the surface of the carbon / carbon composite material sprayed with the surface treating agent, drying in the shade, curing, and forming the inorganic thermal control coating on the surface of the carbon / carbon composite material. According to the method, the binding force of the inorganic thermal control coating on the surface of the carbon / carbon composite material is improved through ultrasonic cleaning, laser cleaning and the bridging effect of the surface treating agent.

Description

Technical Field

[0001] This invention belongs to the field of coating and substrate bonding strength improvement technology, and specifically relates to a method for improving the bonding strength of inorganic thermal control coatings on carbon / carbon composite material surfaces. Background Technology

[0002] Carbon / carbon composites (hereinafter referred to as C / C composites) are carbon fiber reinforced ultra-high temperature ceramic matrix composites with excellent high-temperature strength, high-temperature fracture toughness, and superior thermal shock resistance, oxidation resistance, ablation resistance, and reliability. In recent years, with the increasing demand for lightweight and high-strength materials in the aerospace field, C / C composites have been increasingly used in spacecraft. For example, traditional spacecraft thermal control systems often use metal materials such as copper, which suffer from problems such as high areal density, low modulus, easy deformation, insufficient strength, and low heat transfer efficiency under high-power heat flux, making it difficult to meet future application requirements. High thermal conductivity C / C composites combine excellent properties such as lightweight, high temperature resistance, high specific strength, high specific modulus, and stable physicochemical properties, making them the preferred material for fabricating lightweight and efficient radiators. However, C / C composites are black and have a high solar absorptivity, which severely restricts their radiative heat dissipation capacity. Therefore, it is necessary to prepare a high-temperature resistant, low-absorption, high-emissivity thermal control coating on its surface to adjust the thermal and optical properties of the spacecraft and thus achieve thermal control effects.

[0003] Thermal control coatings are divided into organic and inorganic coatings. Currently, commonly used high-temperature resistant, low-absorption, and high-emissivity thermal control coatings are generally inorganic, such as multi-element doped titanium oxide coatings. However, C / C composites are oleophilic and hydrophobic materials, making it difficult for water-based inorganic coatings to wet and spread on their surface, posing a significant challenge to coating adhesion. Therefore, it is necessary to develop a new surface treatment method for C / C composites to enhance the adhesion of inorganic coatings to the C / C composite surface. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the inventors have conducted intensive research and provided a method to improve the adhesion of inorganic thermal control coatings on the surface of carbon / carbon composite materials, thus solving the problem of poor adhesion of inorganic thermal control coatings on the surface of carbon / carbon composite materials.

[0005] The technical solution provided by this invention is as follows:

[0006] A method for improving the adhesion of inorganic thermal control coatings on carbon / carbon composite surfaces includes:

[0007] The carbon / carbon composite material was placed in anhydrous ethanol, ultrasonically cleaned, and dried to complete the ultrasonic cleaning process.

[0008] Laser cleaning is achieved by continuously scanning the surface of carbon / carbon composite materials with a laser.

[0009] A surface treatment agent is sprayed onto the surface of the carbon / carbon composite material after laser cleaning;

[0010] Inorganic thermal control coating is sprayed onto the surface of carbon / carbon composite material that has been coated with surface treatment agent, air-dried, and cured to form an inorganic thermal control coating on the surface of carbon / carbon composite material.

[0011] The method for improving the adhesion of inorganic thermal control coatings on the surface of carbon / carbon composite materials provided by the present invention has the following beneficial effects:

[0012] (1) In view of the problem that C / C composites are brittle and conventional pretreatment methods such as manual grinding and sandblasting are prone to damage to the material, this invention uses laser cleaning for pretreatment, which effectively avoids the risk of damage to the material by manual operation; laser cleaning can also activate the surface of C / C composites, significantly reduce the contact angle of water on its surface, enhance the wettability of water-based paint, and improve the adhesion of the coating; the laser cleaning process can also have an etching effect, increase the roughness of the C / C composite surface, and further enhance the adhesion of the coating;

[0013] (2) The present invention uses a heat-resistant silane coupling agent solution as a surface treatment agent. On the one hand, the silane coupling agent is an organosilicon compound with a special structure. Its molecules contain groups at both ends that can react with inorganic and organic materials, respectively. Through chemical bonding, it forms a "molecular bridge" at the interface between the two, thereby effectively enhancing the adhesion of the inorganic coating on the C / C composite surface. On the other hand, the present invention selects a heat-resistant silane coupling agent, which can increase the applicable temperature range of the coating.

[0014] (3) This invention selects multi-doped titanium oxide as the effective component of the thermal control coating. By doping titanium oxide with trivalent oxide, oxygen vacancies are introduced while generating lattice distortion, which reduces lattice symmetry, increases carrier concentration, and broadens the infrared absorption band. While obtaining high emissivity, it maintains a low solar absorptivity, thus achieving spectral selective absorption. The infrared emissivity at 600℃ can reach 0.80~0.85, and the solar absorptivity is 0.20~0.35, which has excellent high-temperature heat dissipation effect. Attached Figure Description

[0015] Figure 1 The wettability of deionized water on the surface of carbon / carbon composite material before and after laser cleaning;

[0016] Figure 2 The cross-cut results are for the coating prepared in Example 1;

[0017] Figure 3 The cross-cut results are for the coating prepared in Comparative Example 1;

[0018] Figure 4 The cross-cut results are for the coating prepared in Comparative Example 2;

[0019] Figure 5The cross-cut results are for the coating prepared in Comparative Example 3. Detailed Implementation

[0020] The features and advantages of the present invention will become clearer and more explicit from the following detailed description.

[0021] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0022] This invention provides a method for improving the adhesion of inorganic thermal control coatings on the surface of carbon / carbon composite materials, comprising the following steps:

[0023] (1) Ultrasonic cleaning: Place the C / C composite in anhydrous ethanol and ultrasonically vibrate for 1-2 hours. Then dry it with compressed air and let it stand for 1-2 hours.

[0024] (2) Laser cleaning: A laser is applied to the surface of the C / C composite material, so that the beam continuously sweeps across the surface 2 to 3 times.

[0025] In this step, the laser wavelength is <400nm (ultraviolet laser), such as 355nm, the average laser output power is 500-2000W, the laser pulse frequency is 10-100kHz, the laser output pulse width is 10-50ns, and the laser scanning speed is 5-50mm / s.

[0026] This invention selects ultraviolet laser for laser cleaning. On the one hand, ultraviolet laser has the characteristics of "cold processing" or "cold ablation". During scanning and cleaning, heat does not diffuse, and it will not cause oxidation damage or deformation of C / C composite due to local overheating. On the other hand, ultraviolet photons have high energy and can directly break the chemical bonds of organic materials, rather than relying on heat to melt or vaporize them. The broken chemical bonds have a certain degree of activity and can form chemical bonds with surface treatment agents, effectively improving the adhesion of the coating.

[0027] (3) Spraying surface treatment agent: Use air spraying method to spray the surface treatment agent 2 to 3 times on the C / C composite surface treated in step (2).

[0028] In this step, the surface treatment agent comprises the following components in parts by weight:

[0029] 100 parts of silane coupling agent;

[0030] 50-200 parts of anhydrous ethanol;

[0031] 10-100 parts of deionized water.

[0032] The silane coupling agent is a heat-resistant silane coupling agent selected from at least one of Y-5475 or Y-5669.

[0033] (4) Preparation of thermal control coating: The inorganic thermal control coating is sprayed onto the surface of the C / C composite material treated in step (3) by air spraying.

[0034] In this step, the inorganic thermal control coating comprises the following components in parts by weight:

[0035] 100 parts of thermal control packing;

[0036] 50-200 parts of inorganic binder;

[0037] 100-300 parts of deionized water.

[0038] The inorganic binder is at least one of silicate binders or phosphate binders, such as potassium silicate or potassium phosphate.

[0039] The chemical composition of the thermal control packing is Ti 1-x M x O 2-0.5x M represents one or more of Gd, Yb, and Ga, and 0 < x ≤ 0.5, which is called multi-doped titanium oxide.

[0040] Preferably, the chemical composition of the thermal control filler is Ti. 1-x Gd x O 2-0.5x 0 < x ≤ 0.5. Alternatively, the chemical composition of the thermal control filler is Ti. 1-x Yb x O 2-0.5x 0 < x ≤ 0.5. Alternatively, the chemical composition of the thermal control filler is Ti. 1-x Ga x O 2-0.5x 0 < x ≤ 0.5. Alternatively, the chemical composition of the thermal control filler is Ti. 1-x (Gd y Yb 1-y ) x O 2-0.5x 0 < x ≤ 0.5, 0 < y < 1. Alternatively, the chemical composition of the thermally controlled filler is Ti. 1-x (Gd y Ga 1-y ) x O 2-0.5x 0 < x ≤ 0.5, 0 < y < 1. Alternatively, the chemical composition of the thermally controlled filler is Ti. 1-x (Yb y Ga 1-y ) x O 2-0.5x0 < x ≤ 0.5, 0 < y < 1. Alternatively, the chemical composition of the thermally controlled filler is Ti. 1-x (Gd y Yb z Ga k ) x O 2-0.5x , 0<x≤0.5, 0<y<1, 0<z<1, 0<k<1, y+z+k=1.

[0041] The preparation method of thermally controlled packing includes the following steps:

[0042] (4.1) Take dry titanium dioxide and trivalent oxide powder, weigh them according to the stoichiometric ratio, add them to a ball mill jar, use deionized water as the ball milling medium and zirconia balls as the grinding balls, and ball mill at 300-500 r / min for 8-12 h. Among them, the trivalent oxide powder is one or more of gadolinium oxide (Gd2O3), ytterbium oxide (Yb2O3), and gallium oxide (Ga2O3) powder.

[0043] (4.2) Dry the ball-milled slurry at 90-120℃ for 12-24 hours.

[0044] (4.3) The dried powder is sieved into small particles with uniform particle size using a standard sieve of 100 to 400 mesh.

[0045] (4.4) Place the sieved powder in an alumina crucible and put it into a high-temperature furnace for solid-phase synthesis. Heat the powder to 1300-1600℃ at a heating rate of 1-3℃ / min and hold for 12-24h. Then cool it with the furnace.

[0046] (4.5) Grind the solid-phase synthesized powder with a mortar until the particle size is less than 1-3 mm, add it to a ball mill jar, use deionized water as the ball milling medium and zirconia balls as the grinding balls, and ball mill at 300-500 r / min for 12-24 h to make the particle size of the ball-milled powder 1-5 μm.

[0047] (4.6) Dry the slurry after ball milling at 90-120℃ for 12-24 hours.

[0048] (4.7) The dried powder is sieved into small particles with uniform particle size using a standard sieve of 100-400 mesh to obtain the thermal control filler.

[0049] Doping titanium dioxide with trivalent oxides introduces oxygen vacancies while simultaneously causing lattice distortion, reducing lattice symmetry, increasing carrier concentration, and broadening the infrared absorption band. This achieves high emissivity while maintaining a low solar absorptivity, enabling spectrally selective absorption. The infrared emissivity at 600℃ can reach 0.80–0.85, and the solar absorptivity is 0.20–0.35, exhibiting excellent high-temperature heat dissipation. This solves the problem of high solar absorptivity in traditional high-emissivity coatings, which deteriorates the coating's heat dissipation capacity.

[0050] In this step, the ambient temperature during air spraying of the inorganic thermal control coating is 20–30℃, the relative humidity is 30%–70%, and the coating thickness is 50–200μm.

[0051] (5) Coating curing: Place the inorganic thermal control coating in an environment with a temperature of 20-30℃ and a relative humidity of 40%-70% to air dry for 12-24 hours, and then place the inorganic thermal control coating in an oven at 80-250℃ to dry for 4-12 hours.

[0052] Example

[0053] Example 1

[0054] A method for forming an inorganic thermal control coating on the surface of a carbon / carbon composite material includes the following steps:

[0055] (1) Place the C / C composite material in anhydrous ethanol, ultrasonically vibrate for 2 hours, then dry it with compressed air and let it stand for 2 hours;

[0056] (2) Select an ultraviolet laser cleaning device with an output wavelength of 355nm, an average output power of 1000W, a laser pulse frequency of 50kHz, a laser output pulse width of 10ns, and a laser scanning speed of 10mm / s, so that the laser spot acts on the surface of the C / C composite material and is continuously scanned 3 times.

[0057] (3) Take 100g of heat-resistant silane coupling agent Y-5475, add 50g of anhydrous ethanol and 20g of deionized water, mix them together and stir evenly to make a surface treatment agent; then use air spraying to spray the surface treatment agent twice on the C / C composite surface treated in step (2);

[0058] (4) Take Ti 0.5 Gd 0.5 O 1.75 50g of powder (solar absorptivity 0.30, emissivity 0.81 at 600℃), 50g of potassium silicate solution, and 90g of deionized water were mixed evenly by ball milling to prepare an inorganic thermal control coating. The coating was then sprayed onto the C / C composite surface treated in step (3) using air spraying.0.5 Gd 0.5 O 1.75 Prepared according to the preparation method described above;

[0059] (5) After spraying, place the coating in an environment with a temperature of 25-30℃ and a relative humidity of 40%-45% to air dry for 15 hours. Then place the coating in an oven at 200℃ and dry for 10 hours to obtain an inorganic coating that is well bonded to the C / C composite.

[0060] like Figure 1 As shown, after laser cleaning, the wettability of deionized water on the C / C composite surface significantly increased, and it spread very easily. This indicates that water-based inorganic coatings have good film-forming properties on the C / C composite surface after laser cleaning, which is beneficial to improving coating adhesion. Figure 2 As shown, after laser cleaning and spraying of surface treatment agent, the surface of the C / C composite material prepared in Example 1 has a good, smooth and flat surface, without defects such as cracks or protrusions. The cross-cut test results show that the coating adhesion can reach level 1.

[0061] Examples 2-7

[0062] A method for forming an inorganic thermal control coating on the surface of a carbon / carbon composite material includes the following steps:

[0063] (1) Place the C / C composite material in anhydrous ethanol, ultrasonically vibrate for 2 hours, then dry it with compressed air and let it stand for 2 hours;

[0064] (2) Select an ultraviolet laser cleaning device with an output wavelength of 355nm, an average output power of 1000W, a laser pulse frequency of 50kHz, a laser output pulse width of 10ns, and a laser scanning speed of 10mm / s, so that the laser spot acts on the surface of the C / C composite material and is continuously scanned 3 times.

[0065] (3) Take 100g of heat-resistant silane coupling agent Y-5475, add 50g of anhydrous ethanol and 20g of deionized water, mix them together and stir evenly to make a surface treatment agent; then use air spraying to spray the surface treatment agent twice on the C / C composite surface treated in step (2);

[0066] (4) Take 50g of thermal control filler powder, 50g of potassium silicate solution, and 90g of deionized water, mix them evenly by ball milling to prepare an inorganic thermal control coating. Then, spray the coating onto the C / C composite surface treated in step (3) using air spraying. The thermal control filler powder is Ti. 0.5 Ga 0.5 O 1.75 Powder (solar absorptivity 0.20, emissivity 0.80 at 600℃), Ti 0.5Yb 0.5 O 1.75 Powder (solar absorptivity 0.35, emissivity 0.82 at 600℃), Ti 0.5 (Gd 0.5 Yb 0.5 ) 0.5 O 1.75 Powder (solar absorptivity 0.31, emissivity 0.82 at 600℃), Ti 0.5 (Gd 0.5 Ga 0.5 ) 0.5 O 1.75 Powder (solar absorptivity 0.28, emissivity 0.82 at 600℃), Ti 0.5 (Yb 0.5 Ga 0.5 ) 0.5 O 1.75 Powder (solar absorptivity 0.33, emissivity 0.83 at 600℃), Ti 0.5 (Gd 0.3 Yb 0.3 Ga 0.4 ) 0.5 O 1.75 When the powder (solar absorptivity 0.32, emissivity 0.84 at 600℃) is used, it corresponds to Examples 2-7 respectively; the thermal control filler is prepared according to the preparation method described above;

[0067] (5) After spraying, place the coating in an environment with a temperature of 25-30℃ and a relative humidity of 40%-45% to air dry for 15 hours. Then place the coating in an oven at 200℃ and dry for 10 hours to obtain an inorganic coating that is well bonded to the C / C composite.

[0068] After laser cleaning and spraying of surface treatment agent, the C / C composite material surface prepared in Examples 2-7 has a good surface condition, is flat and smooth, and has no defects such as cracks or protrusions. Cross-cut test results show that the coating adhesion can reach level 1.

[0069] Comparative Example

[0070] Comparative Example 1

[0071] A method for forming an inorganic thermal control coating on the surface of a carbon / carbon composite material includes the following steps:

[0072] (1) Place the C / C composite material in anhydrous ethanol, ultrasonically vibrate for 2 hours, then dry it with compressed air and let it stand for 2 hours;

[0073] (2) Take Ti 0.5 Gd 0.5 O 1.7550g of powder, 50g of potassium silicate solution, and 90g of deionized water were mixed evenly by ball milling to prepare an inorganic thermal control coating. The coating was then sprayed onto the surface of the C / C composite material using an air spraying method.

[0074] (3) After spraying, place the coating in an environment with a temperature of 25-30℃ and a relative humidity of 40%-45% for 15 hours to air dry. Then place the coating in an oven at 200℃ for 10 hours to dry, and obtain an inorganic coating with extremely poor bonding with C / C composite.

[0075] Figure 3 The surface morphology of the inorganic coating prepared on C / C composite material without laser cleaning and surface treatment agent is shown in Comparative Example 1. It can be seen that cracks are formed on the coating surface, and the coating morphology at the edge and inside of the specimen is inconsistent. The edge has raised cracks, indicating that the coating is not spread evenly. The cross-cut test results show that the coating has extremely poor adhesion.

[0076] Comparative Example 2

[0077] A method for forming an inorganic thermal control coating on the surface of a carbon / carbon composite material includes the following steps:

[0078] (1) Place the C / C composite material in anhydrous ethanol, ultrasonically vibrate for 2 hours, then dry it with compressed air and let it stand for 2 hours;

[0079] (2) Set the output wavelength of the laser cleaning equipment to 532nm, the average output power to 1000W, the laser pulse frequency to 50kHz, the laser output pulse width to 10ns, and the laser scanning speed to 10mm / s, so that the laser spot acts on the surface of the C / C composite material and is continuously scanned 3 times.

[0080] (3) Take Ti 0.5 Gd 0.5 O 1.75 50g of powder, 50g of potassium silicate solution, and 90g of deionized water are mixed evenly by ball milling to prepare an inorganic thermal control coating. Then, the coating is sprayed onto the surface of the C / C composite material treated in step (2) by air spraying.

[0081] (4) After spraying, place the coating in an environment with a temperature of 25-30℃ and a relative humidity of 40%-45% for 15 hours to air dry. Then place the coating in an oven at 200℃ for 10 hours to dry, and obtain an inorganic coating that bonds well with the C / C composite.

[0082] Figure 4The surface morphology of the inorganic coating prepared on C / C composite material that has been laser-cleaned but not coated with a surface treatment agent is shown in Comparative Example 2. It can be seen that the coating surface is smooth and flat, indicating that the inorganic coating is well spread and uniformly formed. The cross-cut test results show that the coating adhesion is significantly improved compared with Comparative Example 1, but lower than that of the coating prepared in Example 1.

[0083] Comparative Example 3

[0084] A method for forming an inorganic thermal control coating on the surface of a carbon / carbon composite material includes the following steps:

[0085] (1) Place the C / C composite material in anhydrous ethanol, ultrasonically vibrate for 2 hours, then dry it with compressed air and let it stand for 2 hours;

[0086] (2) Take 100g of heat-resistant silane coupling agent Y-5475, add 50g of anhydrous ethanol and 20g of deionized water, mix them together and stir evenly to make a surface treatment agent; then use air spraying to spray the surface treatment agent twice on the C / C composite surface treated in step (1);

[0087] (3) Take Ti 0.5 Gd 0.5 O 1.75 50g of powder, 50g of potassium silicate solution, and 90g of deionized water are mixed evenly by ball milling to prepare an inorganic thermal control coating. Then, the coating is sprayed onto the surface of the C / C composite material treated in step (3) by air spraying.

[0088] (4) After spraying, place the coating in an environment with a temperature of 25-30℃ and a relative humidity of 40%-45% for 15 hours to air dry. Then place the coating in an oven at 200℃ for 10 hours to dry, and obtain an inorganic coating that bonds well with the C / C composite.

[0089] Figure 5 The surface morphology of the inorganic coating prepared on C / C composite material without laser cleaning but with surface treatment agent is shown in Comparative Example 3. Although the cross-cut test results show that the coating has good adhesion to the C / C composite material, the surface condition of the coating is poor and there are many small protrusions. This is because the inorganic coating on the surface of the C / C composite material without laser cleaning has poor wettability. After spraying, the coating is prone to agglomerate and form small droplets. After drying, the droplets solidify and form protrusions.

[0090] As can be seen from Example 1 and Comparative Examples 1-3, laser cleaning and spraying surface treatment agents can work together from different aspects to improve the adhesion of inorganic coatings on the C / C composite surface.

[0091] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0092] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for improving the adhesion of inorganic thermally controlled coatings on the surface of carbon / carbon composite materials, characterized in that, Includes the following steps: The carbon / carbon composite material was placed in anhydrous ethanol, ultrasonically cleaned, and dried to complete the ultrasonic cleaning process. Laser cleaning is achieved by continuously scanning the surface of carbon / carbon composite materials with a laser. A surface treatment agent is sprayed onto the surface of the carbon / carbon composite material after laser cleaning; Inorganic thermal control coating is sprayed onto the surface of carbon / carbon composite material that has been coated with surface treatment agent, air-dried, and cured to form an inorganic thermal control coating on the surface of carbon / carbon composite material.

2. The method for improving the adhesion of inorganic thermally controlled coatings on the surface of carbon / carbon composite materials according to claim 1, characterized in that, In the laser cleaning step, the laser wavelength is <400nm, the average laser output power is 500-2000W, the laser pulse frequency is 10-100kHz, the laser output pulse width is 10-50ns, and the laser scanning speed is 5-50mm / s.

3. The method for improving the adhesion of inorganic thermally controlled coatings on the surface of carbon / carbon composite materials according to claim 1, characterized in that, The surface treatment agent comprises the following components in parts by weight: 100 parts of silane coupling agent; 50-200 parts of anhydrous ethanol; 10-100 parts of deionized water.

4. The method for improving the adhesion of inorganic thermally controlled coatings on the surface of carbon / carbon composite materials according to claim 3, characterized in that, The silane coupling agent is a heat-resistant silane coupling agent, selected from at least one of Y-5475 or Y-5669.

5. The method for improving the adhesion of inorganic thermally controlled coatings on the surface of carbon / carbon composite materials according to claim 1, characterized in that, The surface treatment agent is sprayed onto the surface of the carbon / carbon composite material 2 to 3 times.

6. The method for improving the adhesion of inorganic thermally controlled coatings on the surface of carbon / carbon composite materials according to claim 1, characterized in that, The inorganic thermal control coating comprises the following components in parts by weight: 100 parts of thermal control packing; 50-200 parts of inorganic binder; 100-300 parts deionized water; The chemical composition of the thermal control filler is Ti. 1-x M x O 2-0.5x M represents one or more of Gd, Yb, and Ga, and 0 < x ≤ 0.

5.

7. The method for improving the adhesion of inorganic thermally controlled coatings on the surface of carbon / carbon composite materials according to claim 6, characterized in that, The method for preparing the thermally controlled packing includes: Weigh dry titanium dioxide and trivalent oxide powder according to stoichiometric ratio, wherein the trivalent oxide powder is one or more of gadolinium oxide, ytterbium oxide, and gallium oxide powder; Titanium dioxide and trivalent oxide powders are added to a ball mill jar, ball milled, and the slurry is dried. The dried powder is then sieved to obtain powder with uniform particle size. The sieved powder was subjected to solid-phase synthesis at high temperature, and then cooled in the furnace after heat preservation. The powder synthesized from solid phase is ground and ball-milled. After ball milling, the slurry is dried and the dried powder is sieved to obtain the spectrally selective absorption thermal control filler.

8. The method for improving the adhesion of inorganic thermally controlled coatings on the surface of carbon / carbon composite materials according to claim 6, characterized in that, The inorganic binder is at least one of silicate binder or phosphate binder.

9. The method for improving the adhesion of inorganic thermally controlled coatings on the surface of carbon / carbon composite materials according to claim 6, characterized in that, The ambient temperature during the spraying of the inorganic thermal control coating is 20-30℃, and the relative humidity is 30%-70%. Preferably, the thickness of the inorganic thermal control coating is 50-200μm.

10. The method for improving the adhesion of inorganic thermally controlled coatings on the surface of carbon / carbon composite materials according to claim 1, characterized in that, The steps of spraying the inorganic thermal control coating onto the surface of the carbon / carbon composite material that has been coated with a surface treatment agent, air-drying, and curing include: placing the inorganic thermal control coating in an environment with a temperature of 20-30°C and a relative humidity of 40%-70% to air-dry for 12-24 hours, and then placing the inorganic thermal control coating in an oven at 80-250°C to dry for 4-12 hours.

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