High-emissivity coating applied to surface of wide-temperature-range anti-oxidation coating of C / C composite material and preparation method of high-emissivity coating

Abstract

The invention discloses a high-emissivity coating applied to the surface of a C / C composite material wide-temperature-range anti-oxidation coating and a preparation method of the high-emissivity coating. A gradient design thought is adopted, namely, an inner layer is a wide-temperature-range compact anti-oxidation layer; the outermost layer is an environmental barrier layer which can resist radiation heat transfer and lattice vibration heat transfer and has a micro-ablation function; a relatively loose stress buffer layer, namely rare earth silicate of which the thermal expansion coefficient is between that of an inner layer and that of an outer layer, is introduced between two relatively compact coatings, so that the reliability of a coating system is improved, and the service life of the coating system is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of C / C composite material anti-oxidation coatings, and in particular relates to a high-emissivity coating applied to the surface of a C / C composite material wide-temperature range anti-oxidation coating and a preparation method thereof. Background Art

[0002] With the advancement of science and technology and the development of industry, the problem of energy shortage has become increasingly prominent. In this context, the application significance of infrared radiation materials has gradually emerged, and people's attention to them has also been increasing. Infrared radiation materials can quickly and efficiently radiate the heat of the substrate in the form of radiation, thereby reducing the temperature of the substrate. In recent years, the application scope of infrared radiation materials has continued to expand, from the initial infrared drying and heating to aerospace, industrial kilns, metallurgical manufacturing, architectural coatings and other fields. Among them, the application in the aerospace field is the most extensive. The fuselage of the aircraft will generate very high heat due to atmospheric friction during high-speed flight. If these high heat cannot be dissipated in time, the performance of the fuselage shell material and internal structural parts will be negatively affected. The use of high-emissivity coatings can dissipate the heat accumulated on the surface of the fuselage through radiation, effectively prevent heat conduction, thereby reducing energy consumption and reducing the deformation of structural parts to increase flight life. In industrial kilns, high-emissivity materials are mainly used for furnace walls. Selecting high-emissivity furnace wall materials is conducive to enhancing radiation heat exchange and accelerating the temperature rise of the heated object, achieving the purpose of energy saving. When the surface of a building is coated with a high-emissivity coating, it can effectively reflect the energy of sunlight and block most of the heat conduction to achieve the effect of thermal insulation, which is of great significance for improving the internal environment.

[0003] In view of the harsh service conditions faced by carbon aerogel composite materials in the application of high-speed equipment thermal protection materials, the protective coating is required to have many functions such as anti-oxidation, inhibition of phonon heat transfer, inhibition of radiation heat transfer, etc., and a multi-layer coating system strategy must be adopted. The design, preparation and synergistic effect of the multi-layer coating system are very important. Summary of the invention

[0004] Aiming at the problem that the prior art lacks an anti-oxidation coating with high heat dissipation and micro-ablation performance requirements on the surface of a wide temperature range anti-oxidation coating of a C / C composite material, the present invention provides a high-emissivity coating applied to the surface of a wide temperature range anti-oxidation coating of a C / C composite material and a preparation method thereof. The high-emissivity coating applied to the surface of a wide temperature range anti-oxidation coating of a C / C composite material comprises a rare earth silicate layer pre-sprayed on the surface of the wide temperature range anti-oxidation coating of the C / C composite material, wherein the rare earth silicate layer comprises ytterbium pyrosilicate, and the high-emissivity coating comprises molybdenum disilicide; the high-emissivity coating applied to the surface of a wide temperature range anti-oxidation coating of a C / C composite material has the following performance indicators: the density range of the C / C composite material matrix is: 0.4 g / cm 3~0.8g / cm 3 The emissivity of the high emissivity coating is 0.925-0.933 in the 1μm~16μm band at room temperature.

[0005] The technical solution of the present invention is as follows: The high emissivity coating applied to the surface of the wide temperature range anti-oxidation coating of the C / C composite material described in the present invention adopts a gradient design concept, that is, the inner layer is a dense anti-oxidation layer with a wide temperature range; and the outermost layer is an environmental barrier layer that can resist radiation heat transfer and lattice vibration heat transfer and has a micro-ablation function; a relatively loose stress buffer layer is introduced between the two relatively dense coating layers, that is, a rare earth silicate with a thermal expansion coefficient between the inner layer and the outer layer, so as to improve the reliability and life of the coating system.

[0006] Rare earth silicates with a medium thermal expansion coefficient are used to transition between the wide temperature range anti-oxidation layer and the environmental barrier layer that inhibits lattice heat transfer, radiation heat transfer and micro-ablation. The loose and porous stress relief layer is prepared by plasma spraying, which also has the function of resisting gas erosion.

[0007] The purpose of the present invention is achieved through the following technical solutions: A method for preparing a high-emissivity coating applied to the surface of a wide-temperature range anti-oxidation coating of a C / C composite material comprises the following steps: S1. Sandblasting is performed on the surface of the wide temperature range anti-oxidation coating of the C / C composite material. The process parameters are as follows: the spray gun pressure is 1 MPa, and the sandblasting time is 1s~3s; S2. Using a plasma spraying process to spray ytterbium pyrosilicate powder on the surface of the wide temperature range anti-oxidation coating of the C / C composite material, the particle size of the sprayed ytterbium pyrosilicate powder is 15 μm-55 μm, and the thickness of the sprayed rare earth silicate coating is 100 μm-150 μm; The plasma spraying process parameters are as follows: spraying distance 120mm~160mm, spraying current 350A~400A, spraying power 22kw~25kw, plasma gas is argon, hydrogen, nitrogen, the gas flow rates of the three are 30L / min~45L / min, 2L / min~3L / min, 1.5L / min~4L / min respectively; S3. Spray molybdenum disilicide powder on the surface of the rare earth silicate coating by plasma spraying, the particle size of the plasma sprayed molybdenum disilicide powder is 30 μm~60 μm, and the thickness of the sprayed high emissivity coating is 60 μm~100 μm; after the spraying is completed, a high emissivity coating applied to the surface of the wide temperature range anti-oxidation coating of the C / C composite material is obtained; The plasma spraying process parameters are as follows: spraying distance 140mm~160mm, spraying current 480A~500A, spraying power 25kw~27kw, plasma gas is argon, hydrogen, nitrogen, the gas flow rates of the three are 30L / min~45L / min, 2L / min~3L / min, 3.5L / min~5L / min respectively; The high-emissivity coating applied to the surface of the wide-temperature-range anti-oxidation coating of the C / C composite material is sprayed with ytterbium pyrosilicate powder on the surface of the wide-temperature-range anti-oxidation coating of the C / C composite material to form a stress buffer layer, and the ytterbium pyrosilicate presents a typical stacked morphology after spraying, and the coating material is sprayed ytterbium pyrosilicate; In the high emissivity coating, the molybdenum disilicide is a stacked morphology formed after spraying, and the coating is sprayed molybdenum disilicide; The high emissivity coating applied to the surface of the wide temperature range anti-oxidation coating of the C / C composite material has the following performance indicators: the density range of the C / C composite material matrix is: 0.4g / cm 3 ~0.8g / cm 3 ; The emissivity of the high emissivity coating is 0.925-0.933 in the 1μm~16μm band at room temperature.

[0008] Furthermore, the plasma spraying process parameters described in step S2 are as follows: spraying distance is 160 mm, spraying current is 400 A, spraying power is 25 kW, plasma gas is argon, hydrogen and nitrogen, and the gas flow rates of the three are 45 L / min, 2.5 L / min and 4 L / min respectively.

[0009] Furthermore, the plasma spraying process parameters described in step S3 are as follows: the spraying distance is 150 mm, the spraying current is 490 A, the spraying power is 26 kW, the plasma gas is argon, hydrogen, and nitrogen, and the gas flow rates of the three are 45 L / min, 2.5 L / min, and 4 L / min, respectively.

[0010] The present invention also relates to a high-emissivity coating applied to the surface of a wide-temperature-range anti-oxidation coating of a C / C composite material, which is obtained by using the above-mentioned method for preparing a high-emissivity coating applied to the surface of a wide-temperature-range anti-oxidation coating of a C / C composite material. The high-emissivity coating applied to the surface of a wide-temperature-range anti-oxidation coating of a C / C composite material comprises a rare earth silicate layer sprayed in advance on the surface of the wide-temperature-range anti-oxidation coating of the C / C composite material, the rare earth silicate layer comprising ytterbium pyrosilicate, and the high-emissivity coating comprising molybdenum disilicide; wherein ytterbium pyrosilicate powder is sprayed on the surface of the wide-temperature-range anti-oxidation coating of the C / C composite material to form a stress buffer layer, ytterbium pyrosilicate presents a typical stacked morphology after spraying, and the coating material is sprayed ytterbium pyrosilicate; in the high-emissivity coating, molybdenum disilicide has a stacked morphology formed after spraying, and the coating is sprayed molybdenum disilicide; the high-emissivity coating applied to the surface of the wide-temperature-range anti-oxidation coating of the C / C composite material has the following performance indicators: the density range of the C / C composite material matrix is: 0.4 g / cm 3 ~0.8g / cm 3 ; The emissivity of the high emissivity coating is 0.925-0.933 in the 1μm~16μm band at room temperature.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention proposes a high-emissivity coating applied to the surface of a wide-temperature-range anti-oxidation coating of a C / C composite material, which is used to solve the problems of thermal radiation and micro-ablation on the surface of the C / C composite material. The present invention uses a plasma spraying method to first prepare a relatively loose stress buffer layer on the surface of the wide-temperature-range anti-oxidation coating of the C / C composite material, that is, a rare earth silicate with a thermal expansion coefficient between the inner layer and the outer layer, to improve the reliability and life of the coating system, and then a high-emissivity coating is prepared on the surface of the rare earth silicate coating using a plasma spraying process. The plasma-sprayed rare earth silicate coating will allow the thermal expansion coefficient of the entire coating to be distributed in a gradient form between the anti-oxidation coating and the high-emissivity coating, alleviating the problem of coating cracking caused by thermal stress.

[0012] 2. The present invention performs sandblasting on the surface of the C / C composite material wide temperature range anti-oxidation coating before spraying the rare earth silicate coating, so that the surface of the C / C composite material wide temperature range anti-oxidation coating has good bonding with the rare earth silicate coating. The present invention selects the plasma spraying process in the preparation of the high emissivity coating to improve the bonding strength between the high emissivity coating and the rare earth silicate coating.

[0013] 3. The present invention proposes a high-emissivity coating applied to the surface of a wide-temperature-range anti-oxidation coating of a C / C composite material. From the perspective of the overall coating of the C / C composite material, the composite multilayer coating can achieve the effect of a multifunctional coating that takes into account anti-oxidation, high emissivity and micro-ablation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] These and / or other aspects and advantages of the present invention will become more clear and easier to understand from the following detailed description of the embodiments of the present invention in conjunction with the accompanying drawings, in which: Figure 1 This is a flow chart for preparing a high-emissivity coating applied to the surface of a wide-temperature-range anti-oxidation coating of a C / C composite material in an embodiment of the present invention; Figure 2 This is a cross-sectional SEM image of the high emissivity coating prepared in Example 2 of the present invention; Figure 3 The thickness diagram of each layer is a cross-sectional SEM image of the high emissivity coating prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] Embodiment 1: A high emissivity coating applied to the surface of a wide temperature range anti-oxidation coating of a C / C composite material comprises the following steps: S1. Pre-sandblasting is performed on the surface of the wide temperature range anti-oxidation coating of the C / C composite material, with the pressure of the sandblasting gun tip at 1 MPa and the time being 1 second; S2. Then, a plasma spraying process is used to spray ytterbium pyrosilicate powder with a particle size of 15 μm to 35 μm on the surface of the wide temperature range anti-oxidation coating of the C / C composite material, wherein the spraying distance is 120 mm, the spraying current is 350 A, the spraying power is 22 kW, and the plasma gas is argon, hydrogen, and nitrogen, and the gas flow rates of the three are 30 L / min, 2 L / min, and 1.5 L / min, respectively; S3. Finally, the plasma spraying method is used again to spray molybdenum disilicide powder with a particle size of 30μm~60μm on the surface of the rare earth silicate coating, wherein the spraying distance is 140mm, the spraying current is 480A, the spraying power is 25kw, and the plasma gas is argon, hydrogen, and nitrogen, and the gas flow rates of the three are 30L / min, 2L / min, and 5 / min respectively; after the spraying is completed, the high emissivity coating is obtained.

[0017] The surfaces of the high-emissivity coating and the mitigation layer prepared by spraying are very dense and free of cracks.

[0018] The obtained high-emissivity coating applied to the surface of the wide temperature range anti-oxidation coating of the C / C composite material has the following performance indicators: Analysis shows that the emissivity of the coating is 0.928 in the 1μm~16μm band at room temperature.

[0019] Embodiment 2: A high emissivity coating applied to the surface of a wide temperature range anti-oxidation coating of a C / C composite material comprises the following steps: S1. Pre-sandblasting is performed on the surface of the wide temperature range anti-oxidation coating of the C / C composite material, with the pressure of the sandblasting gun tip at 1 MPa and the time being 1 second; S2. Then, a plasma spraying process is used to spray ytterbium pyrosilicate powder with a particle size of 30 μm to 55 μm on the surface of the wide temperature range anti-oxidation coating of the C / C composite material, wherein the spraying distance is 150 mm, the spraying current is 350 A, the spraying power is 22 kW, and the plasma gas is argon, hydrogen, and nitrogen, and the gas flow rates of the three are 35 L / min, 3 L / min, and 2.5 L / min, respectively; S3. Finally, the plasma spraying method is used again to spray molybdenum disilicide powder with a particle size of 30μm~60μm on the surface of the rare earth silicate coating, wherein the spraying distance is 160mm, the spraying current is 500A, the spraying power is 27kw, and the plasma gas is argon, hydrogen, and nitrogen, and the gas flow rates of the three are 35L / min, 3.5L / min, and 5L / min, respectively; after the spraying is completed, the high emissivity coating is obtained.

[0020] The surfaces of the high-emissivity coating and the mitigation layer prepared by spraying are very dense and free of cracks.

[0021] The obtained high-emissivity coating applied to the surface of the wide temperature range anti-oxidation coating of the C / C composite material has the following performance indicators: Analysis shows that the emissivity of the coating is 0.925 in the 1μm~16μm band at room temperature.

[0022] like Figure 2 As shown, from bottom to top are the obtained high emissivity coating and rare earth silicate coating. It can be seen that the two coatings are tightly combined without obvious boundaries, and the obtained coating is obviously prepared by plasma spraying. The coating is stacked together in layers; this shows that the prepared high emissivity coating has a dense cross-section and has certain anti-oxidation and micro-ablation properties while taking into account the high emissivity effect; Figure 3 It shows that the thickness of the prepared rare earth silicate coating and high emissivity coating are also within the range provided above.

[0023] Embodiment 3: A high emissivity coating applied to the surface of a wide temperature range anti-oxidation coating of a C / C composite material comprises the following steps: S1. Pre-sandblasting is performed on the surface of the wide temperature range anti-oxidation coating of the C / C composite material, with the pressure of the sandblasting gun tip at 1 MPa and the time being 1 second; S2. Then, a plasma spraying process is used to spray ytterbium pyrosilicate powder with a particle size of 15 μm to 35 μm on the surface of the wide temperature range anti-oxidation coating of the C / C composite material, wherein the spraying distance is 160 mm, the spraying current is 400 A, the spraying power is 25 kW, and the plasma gas is argon, hydrogen, and nitrogen, and the gas flow rates of the three are 45 L / min, 2.5 L / min, and 4 L / min, respectively; S3. Finally, the plasma spraying method is used again to spray molybdenum disilicide powder with a particle size of 30μm~60μm on the surface of the rare earth silicate coating, wherein the spraying distance is 150mm, the spraying current is 490A, the spraying power is 26kw, the plasma gas is argon, hydrogen, and nitrogen, and the gas flow rates of the three are 45L / min, 2.5L / min, and 4L / min, respectively. After the spraying is completed, the high emissivity coating is obtained.

[0024] The surfaces of the high-emissivity coating and the mitigation layer prepared by spraying are very dense and free of cracks.

[0025] The obtained high-emissivity coating applied to the surface of the wide temperature range anti-oxidation coating of the C / C composite material has the following performance indicators: Analysis shows that the emissivity of the coating is 0.933 in the 1μm~16μm band at room temperature.

[0026] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that in step S1, the pressure of the sandblasting gun head is increased to 1.5 MPa and the distance of the spray gun for spraying the high emissivity coating is changed to 120 mm; The high emissivity coating applied to the surface of the wide temperature range anti-oxidation coating of C / C composite materials includes the following steps: The surface of the wide temperature range anti-oxidation coating of the C / C composite material was sandblasted in advance, with the pressure of the sandblasting gun tip at 1.5 MPa and the time at 1 second. Then, the plasma spraying process was used to spray ytterbium pyrosilicate powder with a particle size of 15μm~35μm on the surface of the wide temperature range anti-oxidation coating of the C / C composite material. The spraying distance was 120mm, the spraying current was 350A, the spraying power was 20kw, and the plasma gas was argon, hydrogen, and nitrogen. The gas flow rates of the three were 30L / min, 2L / min, and 1.5L / min respectively. Finally, the plasma spraying method was used again to spray molybdenum disilicide powder with a particle size of 30μm~60μm on the surface of the rare earth silicate coating, wherein the spraying distance was 120mm, the spraying current was 480A, the spraying power was 25kw, the plasma gas was argon, hydrogen, and nitrogen, and the gas flow rates of the three were 30L / min, 2L / min, and 3.5L / min, respectively; after the spraying was completed, the high emissivity coating was obtained.

[0027] The process parameters for preparing the coating are not within the scope of the present patent. The obtained high-emissivity coating has obvious crack stratification on the coating surface. Due to the long sandblasting time, cracks appear in the base coating, which in turn causes cracks in the rare earth silicate layer. In addition, cracks can also be observed macroscopically on the surface of the sprayed high-emissivity coating. Both the high-emissivity coating and the relief layer prepared by spraying have macroscopically visible cracks on their surfaces, which will reduce the overall service life of the composite coating.

[0028] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that the spraying power of S3 spraying high emissivity coating is changed to 28kw; The high emissivity coating applied to the surface of the wide temperature range anti-oxidation coating of C / C composite materials includes the following steps: The surface of the wide temperature range anti-oxidation coating of the C / C composite material is sandblasted in advance, with the pressure of the sandblasting gun tip at 1 MPa and the time being 3 seconds; Then, the plasma spraying process was used to spray ytterbium pyrosilicate powder with a particle size of 15μm~25μm on the surface of the wide temperature range anti-oxidation coating of the C / C composite material. The spraying distance was 120mm, the spraying current was 350, the spraying power was 22kw, and the plasma gas was argon, hydrogen, and nitrogen. The gas flow rates of the three were 30L / min, 2L / min, and 1.5L / min respectively. Finally, the plasma spraying method is used again to spray the molybdenum disilicide powder with a particle size of 30μm~60μm on the surface of the rare earth silicate coating, wherein the spraying distance is 140mm, the spraying current is 500, the spraying power is 28kw, and the plasma gas is argon, hydrogen, and nitrogen, and the gas flow rates of the three are 30L / min, 2.5L / min, and 3.5L / min, respectively. After the spraying is completed, the high emissivity coating is obtained.

[0029] The process parameters of spraying are not within the scope of the present patent, and the surface of the high-emissivity coating produced has macroscopically visible cracks, which will reduce the overall service life of the composite coating.

[0030] Results and Discussion: The high emissivity coating applied to the surface of the wide temperature range anti-oxidation coating of C / C composite material described in the present invention is required to be used in a high temperature air environment, and the surface of the prepared coating needs to be dense and free of cracks; By comparing Examples 1-3 with Comparative Example 1, it can be seen that the ytterbium pyrosilicate layer coating prepared by spraying in Comparative Example 1 has obvious cracks. This is because the coating is cracked due to excessive spray gun pressure during sandblasting, and when spraying the high-emissivity coating, the spray gun distance is too small to the sample distance, resulting in cracks in the high-emissivity coating. These cracks can not only be clearly observed from the macroscopic surface, but also affect the life of the coating when used in a wide temperature range high-temperature oxygen environment. Therefore, the mitigation layer coating prepared using plasma spraying process parameters other than this patent will greatly affect the service life of the coating.

[0031] By comparing Examples 1-3 with Comparative Example 2, it can be seen that after changing the spray gun power for spraying the high-emissivity coating in Comparative Example 2, obvious cracks will be generated in the sprayed high-emissivity coating, which will affect the service life of the coating. Due to the presence of macro cracks on the coating surface, the coating cannot be used in a high-temperature oxygen atmosphere over a wide temperature range. Using plasma spraying process parameters other than those of this patent to prepare a high-emissivity coating will have a great negative impact on the entire composite coating when used in a high-temperature air environment. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the technical content disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a high emissivity coating applied to the surface of a wide temperature range anti-oxidation coating of a C / C composite material, characterized by: The following steps are involved: S1. Sandblasting is performed on the surface of the wide temperature range anti-oxidation coating of the C / C composite material. The process parameters are as follows: the spray gun pressure is 1 MPa, and the sandblasting time is 1s~3s; S2. Using a plasma spraying process to spray ytterbium pyrosilicate powder on the surface of the wide temperature range anti-oxidation coating of the C / C composite material, the particle size of the sprayed ytterbium pyrosilicate powder is 15 μm-55 μm, and the thickness of the sprayed rare earth silicate coating is 100 μm-150 μm; The plasma spraying process parameters are as follows: spraying distance 120mm~160mm, spraying current 350A~400A, spraying power 22kw~25kw, plasma gas is argon, hydrogen, nitrogen, the gas flow rates of the three are 30L / min~45L / min, 2L / min~3L / min, 1.5L / min~4L / min respectively; S3. Spray molybdenum disilicide powder on the surface of the rare earth silicate coating by plasma spraying, the particle size of the plasma sprayed molybdenum disilicide powder is 30 μm~60 μm, and the thickness of the sprayed high emissivity coating is 60 μm~100 μm; after the spraying is completed, a high emissivity coating applied to the surface of the wide temperature range anti-oxidation coating of the C / C composite material is obtained; The plasma spraying process parameters are as follows: spraying distance 140mm~160mm, spraying current 480A~500A, spraying power 25kw~27kw, plasma gas is argon, hydrogen, nitrogen, the gas flow rates of the three are 30L / min~45L / min, 2L / min~3L / min, 3.5L / min~5L / min respectively; The high-emissivity coating applied to the surface of the wide-temperature-range anti-oxidation coating of the C / C composite material is sprayed with ytterbium pyrosilicate powder on the surface of the wide-temperature-range anti-oxidation coating of the C / C composite material to form a stress buffer layer, and the ytterbium pyrosilicate presents a typical stacked morphology after spraying, and the coating material is sprayed ytterbium pyrosilicate; In the high emissivity coating, molybdenum disilicide is a stacked morphology formed after spraying, and the coating is sprayed molybdenum disilicide; the high emissivity coating applied to the surface of the wide temperature range anti-oxidation coating of the C / C composite material has the following performance indicators: the density range of the C / C composite material matrix is: 0.4g / cm 3 ~0.8g / cm 3 ; The emissivity of the high emissivity coating is 0.925-0.933 in the 1μm~16μm band at room temperature.

2. The method for preparing a high-emissivity coating applied to the surface of a wide-temperature range anti-oxidation coating of a C / C composite material according to claim 1, characterized in that: The plasma spraying process parameters described in step S2 are as follows: spraying distance is 160 mm, spraying current is 400 A, spraying power is 25 kW, plasma gas is argon, hydrogen, and nitrogen, and the gas flow rates of the three are 45 L / min, 2.5 L / min, and 4 L / min, respectively.

3. The method for preparing a high-emissivity coating applied to the surface of a wide-temperature-range anti-oxidation coating of a C / C composite material according to claim 1, characterized in that: The plasma spraying process parameters described in step S3 are as follows: the spraying distance is 150 mm, the spraying current is 490 A, the spraying power is 26 kW, the plasma gas is argon, hydrogen, and nitrogen, and the gas flow rates of the three are 45 L / min, 2.5 L / min, and 4 L / min, respectively.

4. A high emissivity coating applied to the surface of a wide temperature range anti-oxidation coating of a C / C composite material, characterized by: The high emissivity coating applied to the surface of the wide temperature range anti-oxidation coating of the C / C composite material is obtained by using the preparation method of any one of claims 1 to 3, wherein the high emissivity coating applied to the surface of the wide temperature range anti-oxidation coating of the C / C composite material is pre-sprayed with a rare earth silicate layer on the surface of the wide temperature range anti-oxidation coating of the C / C composite material, the component of the rare earth silicate layer is ytterbium pyrosilicate, and the component of the high emissivity coating is molybdenum disilicide; Among them, ytterbium disilicate powder is sprayed on the surface of the wide temperature range anti-oxidation coating of the C / C composite material to form a stress buffer layer, and the ytterbium disilicate presents a typical stacked morphology after spraying, and the coating material is sprayed ytterbium disilicate; in the high-emissivity coating, molybdenum disilicide is a stacked morphology formed after spraying, and the coating is sprayed molybdenum disilicide; the high-emissivity coating applied to the surface of the wide temperature range anti-oxidation coating of the C / C composite material has the following performance indicators: the density range of the C / C composite material matrix is: 0.4g / cm 3 ~0.8g / cm 3 ; The emissivity of the high emissivity coating is 0.925-0.933 in the 1μm~16μm band at room temperature.

Images