A high infrared emissivity anti-vacuum volatilization thermal control coating, its preparation method and application

Abstract

This invention provides a high infrared emissivity, vacuum volatilization resistant thermal control coating, its preparation method, and its application, relating to the field of inorganic functional coating materials technology. The aforementioned thermal control coating includes a substrate and an adhesive layer and a functional layer sequentially disposed on the surface of the substrate. The functional layer is made of Al2O3 doped with rare earth ions. By modifying the surface of the substrate using a NiCr-based alloy adhesive layer and an Al2O3 composite ceramic functional layer with a specific molar ratio (99:(1-90)), rare earth ions (such as Sm) can be utilized. 3+ Yb 3+ The solid solution distortion in the crystal lattice and the induction mechanism of the second phase (garnet / perovskite phase) increase the infrared emissivity of the coating to above 0.85. The preparation method proposed in this invention can be achieved by plasma spraying, which is simple and highly reproducible.

Description

Technical Field

[0001] This invention relates to the field of inorganic functional coating materials technology, and in particular to a high infrared emissivity anti-vacuum volatilization thermal control coating, its preparation method and application. Background Technology

[0002] Space nuclear reactors, with their advantages of high energy density, long lifespan, and strong environmental adaptability, have become a strategic technology for overcoming energy bottlenecks in deep space exploration and a core support for my country's future deep space exploration missions. When such reactors are in orbit, core components such as heat pipes and reactor vessels must operate under extreme high temperatures (≥800℃) and ultra-high vacuum (≤10℃) for extended periods. -6 The space reactor operates under a harsh coupling environment (Pa). This environment places extremely high demands on the stability, mechanical properties, and environmental compatibility of structural materials. Among these, the high-temperature volatilization behavior of the materials is directly related to the service safety and mission reliability of the space reactor.

[0003] Nickel-based superalloys (such as Hastelloy 230 and the Inconel series) are important candidate materials for space reactor heat pipes and in-core components due to their excellent high-temperature strength. However, research shows that these alloys exhibit a significant tendency for elemental volatilization at temperatures far below their melting point. Research conducted as early as the 1960s at Oak Ridge National Laboratory in the United States indicated that 316 stainless steel exhibits volatilization at temperatures of 982℃ and 10℃. -6 The volatilization rate under Pa conditions is as high as 6.60 × 10⁻⁶. -3 mg / (cm 2 The volatilization rate is approximately 76 μm / year, accompanied by preferential volatilization of elements such as Cr and Mn, inducing grain boundary porosity and compositional segregation. Although the volatilization rate of nickel-based alloys is better than that of stainless steel, it still remains at a high level (e.g., the volatilization rate of Inconel alloy is approximately 39 μm / year, and that of INOR-8 alloy is approximately 31 μm / year). Domestic research has further confirmed that due to the extremely high saturated vapor pressure of elements such as Mn, Monel alloys and stainless steels experience severe loss of Mn and Cr elements in the 750-900℃ range, leading to decreased material strength, grain boundary deterioration, and even the risk of leakage in thin-walled components. This high-temperature volatilization not only leads to component thinning and performance degradation, but the generated volatiles may also condense on the surface of optical loads or insulating components, causing secondary pollution.

[0004] To suppress substrate volatilization, existing technologies typically employ magnetron sputtering to prepare Ni-W gradient coatings (W content > 60 at.%). While this method can reduce the substrate volatilization rate by more than 85% and effectively block element diffusion, the high-W coating exhibits extremely low thermal conductivity (< 25 W / m·K) and extremely high infrared reflectivity (low emissivity), resulting in a significant reduction in the heat dissipation efficiency of the components covered by the coating. During long-term operation, this heat accumulation effect can cause the actual operating temperature of the components to rise by 50-100°C compared to the design value, which in turn accelerates the high-temperature creep and microstructure degradation of the substrate material, and may even trigger interfacial cracking of the coating due to thermal mismatch, forming a vicious cycle of "thermal runaway - intensified volatilization".

[0005] Therefore, coatings with only a single anti-volatilization function are insufficient to meet the long lifespan requirements of space reactor components in extreme environments.

[0006] In view of this, it is necessary to design an improved high infrared emissivity anti-vacuum volatilization thermal control coating, its preparation method and application, in order to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a high infrared emissivity anti-vacuum volatilization thermal control coating, its preparation method, and its application.

[0008] To achieve the above-mentioned objectives, in a first aspect, the present invention provides a high infrared emissivity anti-vacuum volatilization thermal control coating, comprising:

[0009] substrate;

[0010] An adhesive layer is formed on the surface of the substrate and is tightly bonded to the substrate. The thickness of the adhesive layer is 20-50 µm and the raw material is NiCr-based alloy powder.

[0011] A functional layer, formed on the surface of the adhesive layer, has a thickness of 80-150 µm and is made of Al2O3 composite agglomerated ceramic powder, the raw materials of which include Al2O3, Sm2O3 and Yb2O3.

[0012] Preferably, the NiCr-based alloy powder is a NiCrAlY type alloy powder; when the Al2O3 composite agglomerated ceramic powder uses Al2O3 and Sm2O3 as raw materials, the average particle size of both is 1-5 µm and the molar ratio is 99:(1-90); when the Al2O3 composite agglomerated ceramic powder uses Al2O3 and Yb2O3 as raw materials, the average particle size of both is 1-5 µm and the molar ratio is 99:(1-90).

[0013] Secondly, the present invention provides a method for preparing a high infrared emissivity anti-vacuum volatilization thermal control coating, comprising the following steps:

[0014] S1. Using atmospheric plasma spraying process, NiCr-based alloy powder is sprayed onto the substrate surface to form an adhesive layer.

[0015] S2. Using an atmospheric plasma spraying process, Al2O3 composite agglomerated ceramic powder is sprayed onto the surface of the adhesive layer, thus forming a functional layer on the adhesive layer, and a high infrared emissivity anti-vacuum volatilization thermal control coating is obtained; wherein, the raw materials of the Al2O3 composite agglomerated ceramic powder include Al2O3, Sm2O3 and Yb2O3, and the average particle size of the three is 1-5 µm.

[0016] Preferably, in step S1, the plasma spraying process parameters are as follows: powder feeding rate of 40-60 g / min, argon flow rate of 30-50 L / min, hydrogen flow rate of 5-8 L / min, spraying current of 350-450 A, spraying power of 25-35 kW, spray gun lateral movement speed of 650-850 mm / s, spray gun longitudinal step length of 1-4 mm / step, and spraying distance of 70-140 mm.

[0017] Preferably, in step S2, the plasma spraying process parameters are as follows: powder feeding rate of 40-60 g / min, argon flow rate of 30-50 L / min, hydrogen flow rate of 9-15 L / min, spraying current of 500-600 A, spraying power of 40-50 kW, spray gun lateral movement speed of 650-850 mm / s, spray gun longitudinal step length of 1-4 mm / step, and spraying distance of 70-140 mm.

[0018] Preferably, in step S2, the Al2O3 composite agglomerated ceramic powder is prepared as follows: Al2O3 and Sm2O3, or Al2O3 and Yb2O3 are mixed, and then a dispersant and a binder are added. The resulting mixture is then subjected to ball milling, spray granulation, and high-temperature sintering to obtain Al2O3 composite agglomerated ceramic powder.

[0019] Preferably, the molar ratio of Al2O3 to Sm2O3 is 99:(1-90), and the molar ratio of Al2O3 to Yb2O3 is 99:(1-90).

[0020] Preferably, the dispersant is sodium citrate and the binder is polyvinyl alcohol, and the amount of dispersant and binder added is 1-5% of the total mass of the raw materials used in step S2.

[0021] Preferably, the ball milling time is 12-48 h and the rotation speed is 180-280 r / min; the spray granulation temperature is 100-150℃ and the rotation speed is 20-40 r / min; the high-temperature sintering temperature is 1200-1500℃ and the time is 6-12 h.

[0022] Thirdly, the present invention provides an application of a high infrared emissivity anti-vacuum volatilization thermal control coating in the preparation of heat pipes and reactor vessel surfaces for space nuclear reactor systems.

[0023] The beneficial effects of this invention are:

[0024] 1. The high infrared emissivity anti-vacuum volatilization thermal control coating, its preparation method, and its application provided by this invention modify the substrate surface by using a NiCr-based alloy bonding layer and an Al2O3 composite ceramic functional layer with a specific molar ratio (99:(1-90)), and utilizing rare earth ions (such as Sm) to achieve the desired effect. 3+ Yb 3+ The solid solution distortion in the crystal lattice and the second phase (garnet / perovskite phase) inducement mechanism increase the infrared emissivity of the coating to over 0.85.

[0025] 2. The preparation method provided by the present invention optimizes the preparation process, and the final coating surface has no obvious cracks, and it is tightly bonded to the substrate without peeling. Under the premise of ensuring excellent thermal stability, it achieves a comprehensive improvement in infrared radiation performance and effective suppression of vacuum evaporation rate. Attached Figure Description

[0026] Figure 1 This is a SEM image of the thermal control coating obtained in Example 1 of the present invention;

[0027] Figure 2 The image shows the SEM image of the thermal control coating prepared in Example 1 of this invention after 2000 hours under high temperature and ultra-high vacuum.

[0028] Figure 3 The infrared emissivity in the 2.5-15 µm band of the thermal control coatings prepared in Examples 1 to 2 and Comparative Example 1 of the present invention;

[0029] Figure 4 The bonding strength results of the thermal control coatings obtained in Examples 1 to 2 and Comparative Example 1 of the present invention are shown.

[0030] Figure 5 The images show the XRD patterns of the thermal control coatings obtained in Examples 1 to 2 and Comparative Example 1 of this invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0033] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0034] On one hand, the present invention provides a high infrared emissivity anti-vacuum evaporation thermal control coating, which comprises:

[0035] substrate;

[0036] An adhesive layer is formed on the surface of the substrate and is tightly bonded to the substrate. Its thickness is 20-50 µm and the raw material is NiCr-based alloy powder.

[0037] The functional layer, which is formed on the surface of the adhesive layer, has a thickness of 80-150 µm and is made of Al2O3 composite agglomerated ceramic powder.

[0038] Furthermore, the present invention also provides a method for preparing the above-mentioned high infrared emissivity anti-vacuum volatilization thermal control coating, comprising the following steps:

[0039] S1. Using atmospheric plasma spraying process, NiCr-based alloy powder is sprayed onto the substrate surface to form an adhesive layer.

[0040] S2. Using an atmospheric plasma spraying process, Al2O3 composite agglomerated ceramic powder is sprayed onto the surface of the adhesive layer, thus forming a functional layer on top of the adhesive layer, resulting in a high infrared emissivity anti-vacuum volatilization thermal control coating. The raw materials for the Al2O3 composite agglomerated ceramic powder include Al2O3, Sm2O3, and Yb2O3, with a mesh size of 250-320 mesh, and the average particle size of Al2O3, Sm2O3, and Yb2O3 are all 1-5 µm.

[0041] In the above technical solution, the NiCr-based binder layer possesses both excellent thermal expansion matching and interfacial bonding strength, which not only improves the structural stability of the coating but also effectively extends its service life under high-temperature environments. Ni, as the main component of the binder layer, primarily improves the interfacial bonding of the coating; while the addition of Cr effectively reduces the critical Al content required for the formation of the dense α-Al₂O₃ phase, promoting the formation of this beneficial phase. Furthermore, the functional layer prepared from Al₂O₃ composite agglomerated ceramic powder with a specific ratio undergoes solid solution and second-phase formation mechanisms (such as Sm) during spraying and sintering. 3+ 、or Yb 3+ Al replacement 3+This process leads to lattice distortion and the introduction of oxygen vacancies, inducing the formation of a garnet / perovskite phase with high infrared emissivity. Secondly, by optimizing the preparation process, the final coating surface is free of obvious cracks and exhibits a tight bond with the substrate without peeling. This achieves a comprehensive improvement in infrared radiation performance and effective suppression of vacuum evaporation rate while ensuring excellent thermal stability.

[0042] In some embodiments, in step S1, the substrate includes stainless steel, high-temperature alloys, and other alloys, which need to be cleaned and sandblasted before use. The cleaning process can remove oil and oxides from the substrate surface, which is beneficial to improving the adhesion between the adhesive layer and the substrate. Sandblasting can activate the substrate surface. The cleaning process involves ultrasonically cleaning the substrate with acetone and ethanol in sequence, with each cleaning time being 20-40 minutes.

[0043] In some embodiments, in step S1, the NiCr-based alloy powder is a NiCrAlY type alloy powder, with a Cr content of 20-24%, an Al content of 3-7%, a Y content of 0.5-1%, and the remainder being Ni. It needs to be dried at 80-120°C for 60-120 min before spraying.

[0044] In some embodiments, before plasma spraying NiCrAlY alloy powder in step S1, the substrate is preheated using the generated flame, and then plasma spraying is performed. The specific process parameters are as follows: powder feed rate is 40-60 g / min, argon flow rate is 30-50 L / min, hydrogen flow rate is 5-8 L / min, spraying current is 350-450 A, spraying power is 25-35 kW, spray gun lateral movement speed is 650-850 mm / s, spray gun longitudinal step is 1-4 mm / step, and spraying distance is 70-140 mm.

[0045] In some embodiments, in step S2, the raw material powder used to prepare the Al2O3 composite agglomerated ceramic powder is Al2O3 and Sm2O3, or Al2O3 and Yb2O3. The average particle size of the powder raw material is 1-5 µm, the molar ratio of Al2O3 to Sm2O3 is 99:1-90:10, and the molar ratio of Al2O3 to Yb2O3 is 99:(1-90).

[0046] More specifically, the preparation method of Al2O3 composite agglomerated ceramic powder is as follows: Al2O3 and Sm2O3, or Al2O3 and Yb2O3 are mixed, and then a dispersant and a binder are added. The mixture is then subjected to ball milling, spray granulation, and high-temperature sintering to obtain Al2O3 composite agglomerated ceramic powder. The dispersant is sodium citrate, and the binder is polyvinyl alcohol. The amount of both dispersant and binder added is 1-5% of the total mass of all raw materials in this step. The ball milling process uses zirconia balls and pure water as the medium, with a ball-to-material ratio of 5:1 to 15:1. The ball milling time is 12-48 h, and the rotation speed is 180-280 r / min. The spray granulation temperature is 100-150℃, and the rotation speed is 20-40 r / min. The high-temperature sintering temperature is 1200-1500℃, and the time is 6-12 h.

[0047] In some embodiments, the plasma spraying process parameters in step S2 are as follows: powder feed rate of 40-60 g / min, argon flow rate of 30-50 L / min, hydrogen flow rate of 9-15 L / min, spraying current of 500-600 A, spraying power of 40-50 kW, spray gun lateral movement speed of 650-850 mm / s, spray gun longitudinal step length of 1-4 mm / step, and spraying distance of 70-140 mm.

[0048] The following specific embodiments further illustrate the high infrared emissivity anti-vacuum volatilization thermal control coating proposed in this invention, its preparation method, and its application:

[0049] Example 1

[0050] This embodiment provides a method for preparing a high infrared emissivity anti-vacuum volatilization thermal control coating, comprising the following steps:

[0051] S1. The stainless steel substrate was ultrasonically cleaned with acetone and ethanol, respectively, for 20 min each time. NiCrAlY alloy powder (purchased from Zhongnuo New Materials, with Cr content of 20-24%, Al content of 3-7%, Y content of 0.5-1%, and the remainder Ni) was dried at 80℃ for 120 min, and then plasma spraying was performed. Before spraying, the substrate was preheated appropriately using the flame generated by the plasma. The powder feeding rate was 40 g / min, the argon flow rate was 40 L / min, the hydrogen flow rate was 8 L / min, the spraying current was 350 A, the spraying power was 25 kW, the spray gun lateral movement speed was 650 mm / s, the spray gun longitudinal step length was 2 mm / step, and the spraying distance was 95 mm, thus obtaining an adhesive layer with a thickness of 20 µm on the substrate surface.

[0052] S2. Al2O3 and Yb2O3 with a size of 2 µm were weighed at a molar ratio of 97:3. A dispersant and a binder were added, each amounting to 1% of the sum of the masses of Al2O3, Yb2O3, dispersant, and binder. The dispersant was sodium citrate, and the binder was polyvinyl alcohol. After mixing the raw materials, the mixture was sequentially ball-milled, spray-granulated, and sintered at high temperature to obtain Al2O3 / Yb2O3 composite agglomerated ceramic powder. First, the ball milling time was 24 h, the speed was 260 r / min, zirconia balls were used in the ball milling process, pure water was used as the medium, and the ball-to-material ratio was 8:1. Second, the spray granulation temperature was 120℃, and the speed was 30 r / min. Third, the high-temperature sintering temperature was 1400℃, and the time was 6 h. Finally, the mixture was sieved using a 300-mesh sieve to obtain Al2O3 / Yb2O3 composite agglomerated ceramic powder.

[0053] The Al2O3 / Yb2O3 composite agglomerated ceramic powder was dried at 80℃ for 120 min. The substrate containing the adhesive layer obtained in step S1 was preheated by the flame generated by plasma. Then, the Al2O3 / Yb2O3 composite agglomerated ceramic powder was sprayed onto its surface by plasma spraying to obtain a functional layer with a thickness of 100 µm. A high infrared emissivity anti-vacuum volatilization thermal control coating was obtained. The specific process parameters are as follows: powder feed rate of 40 g / min, argon flow rate of 40 L / min, hydrogen flow rate of 12 L / min, spraying current of 500 A, spraying power of 40 kW, spray gun lateral speed of 680 mm / s, spray gun longitudinal step of 2 mm / step, and spraying distance of 120 mm.

[0054] The thermal control coating prepared in this embodiment has an infrared emissivity of 0.862 in the 2.5-15 µm band, as tested.

[0055] The surface SEM image of the thermal control coating obtained in this embodiment is as follows: Figure 1 As shown, the results indicate that the coating surface is relatively smooth and dense. In this state, molten or incompletely molten powder particles overlap to form a continuous matrix, with almost no obvious macroscopic or microscopic pores on the surface and subsurface. The thermally controlled coating operates at high temperatures (650℃) and ultra-high vacuum (10... -6 The surface SEM image after 2000 hours under the influence of Pa is shown below. Figure 2 As shown, the results indicate that a small number of holes appeared on the coating surface, but the coating as a whole still maintained a high degree of integrity, without large-area cracking or severe peeling. The above results together prove that the thermal control coating provided in this embodiment has excellent anti-vacuum volatilization performance and high-temperature structural stability.

[0056] Example 2

[0057] This embodiment provides a method for preparing a high infrared emissivity anti-vacuum volatilization thermal control coating, comprising the following steps:

[0058] S1. The stainless steel substrate was ultrasonically cleaned successively with acetone and ethanol, with each ultrasonic cleaning lasting 20 min. NiCrAlY alloy powder (purchased from Zhongnuo New Materials, Cr content 20-24%, Al content 3-7%, Y content 0.5-1%, the remainder Ni) was dried at 80℃ for 120 min, and then plasma spraying was performed. Before spraying, the substrate was preheated appropriately using the plasma-generated flame. The powder feed rate was 40 g / min, the argon flow rate was 40 L / min, the hydrogen flow rate was 8 L / min, the spraying current was 350 A, the spraying power was 25 kW, the spray gun lateral speed was 650 mm / s, the spray gun longitudinal step was 2 mm / step, and the spraying distance was 95 mm, thus obtaining a 20 µm thick adhesive layer on the substrate surface.

[0059] S2. Al2O3 and Sm2O3 with a size of 2 µm were weighed at a molar ratio of 97:3. A dispersant and a binder were added, each amounting to 1% of the sum of the masses of Al2O3, Sm2O3, dispersant, and binder. The dispersant was sodium citrate, and the binder was polyvinyl alcohol. All raw materials were mixed and then sequentially ball-milled, spray-granulated, and sintered at high temperature to obtain Al2O3 / Sm2O3 composite agglomerated ceramic powder. The ball milling process used zirconia balls, pure water as the medium, a ball-to-material ratio of 8:1, a ball milling time of 24 h, and a rotation speed of 260 r / min. The spray granulation temperature was 120℃, and the rotation speed was 30 r / min. The high-temperature sintering temperature was 1450℃, and the time was 6 h. Finally, the powder was sieved using a 300-mesh sieve to obtain Al2O3 / Sm2O3 composite agglomerated ceramic powder.

[0060] The Al2O3 / Sm2O3 composite agglomerated ceramic powder was dried at 80℃ for 120 min. The substrate containing the adhesive layer obtained in step S1 was preheated by the flame generated by plasma. Then, the Al2O3 / Sm2O3 composite agglomerated ceramic powder was sprayed onto its surface by plasma spraying to obtain a functional layer with a thickness of 100 µm. A high infrared emissivity anti-vacuum volatilization thermal control coating was obtained. The specific process parameters are as follows: powder feed rate of 40 g / min, argon flow rate of 40 L / min, hydrogen flow rate of 12 L / min, spraying current of 500 A, spraying power of 40 kW, spray gun lateral speed of 680 mm / s, spray gun longitudinal step of 2 mm / step, and spraying distance of 120 mm.

[0061] Tests showed that the thermal control coating prepared in this embodiment has an infrared emissivity of 0.859 in the 2.5-15 µm band.

[0062] Comparative Example 1

[0063] The only difference between this comparative example and Example 1 is that Yb2O3 is not added in step S2; that is, Al2O3 with a size of 2 µm is directly sprayed onto the surface of the adhesive layer to prepare the functional layer. The amount of Al2O3 used in Comparative Example 1 is the same as the total amount of Al2O3 and Yb2O3 in Example 1. The other experimental parameters are the same as those in Example 1, and will not be repeated here.

[0064] The thermal control coating prepared in this comparative example has an infrared emissivity of 0.835 in the 2.5-15 µm band, as tested.

[0065] The infrared emissivity of the thermal control coatings prepared in Examples 1 and 2 and Comparative Example 1 in the 2.5-15 µm wavelength band is as follows: Figure 3 As shown, the emissivity curves of Examples 1 (3Yb) and 2 (3Sm) in the 2.5-6.0 µm band are significantly higher than those of Comparative Example 1. Specifically, the emissivity of Examples 1 and 2 generally maintains a high plateau above 0.80, while the emissivity of Comparative Example 1 only fluctuates around 0.50. This phenomenon confirms that the introduction of rare earth elements greatly optimizes the emission characteristics of the coating in the mid-infrared band, giving it excellent high infrared radiation heat dissipation capability. The bonding strength results of the thermal control coatings prepared in Examples 1 to 2 and Comparative Example 1 are as follows: Figure 4 As shown in the comparative analysis of the embodiments and comparative examples, it can be seen that the doping of rare earth elements did not affect the adhesion between the coating and the substrate. The above results indicate that the thermal control coating proposed in this invention, by introducing rare earth elements, significantly improves infrared emissivity while maintaining high adhesion strength between the coating and the substrate. The XRD pattern of the thermal control coating is shown below. Figure 5 As shown, the results indicate that the thermal control coating prepared in Example 1 ( Figure 5 The right figure shows that Yb was successfully doped, and the thermal control coating of Example 2 ( Figure 5 (Left image) Successfully doped with Sm.

[0066] Comparative Example 2

[0067] The only difference between this comparative example and Example 1 is that in step S2, the hydrogen flow rate is 8 L / min, the spraying current is 400 A, and the spraying power is 30 kW. The other experimental parameters are the same as those in Example 1, and will not be repeated here.

[0068] Tests revealed a large number of unmelted particles on the coating surface, with significant peeling.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high infrared emissivity anti-vacuum volatilization thermal control coating, characterized in that, include: substrate; An adhesive layer is formed on the surface of the substrate and is tightly bonded to the substrate. The thickness of the adhesive layer is 20-50 µm and the raw material is NiCr-based alloy powder. A functional layer, formed on the surface of the adhesive layer, has a thickness of 80-150 µm and is made of Al2O3 composite agglomerated ceramic powder, the raw materials of which include Al2O3, Sm2O3 and Yb2O3.

2. The high infrared emissivity anti-vacuum volatilization thermal control coating according to claim 1, characterized in that, The NiCr-based alloy powder is a NiCrAlY type alloy powder; when the Al2O3 composite agglomerated ceramic powder uses Al2O3 and Sm2O3 as raw materials, the average particle size of both is 1-5 µm and the molar ratio is 99:(1-90); when the Al2O3 composite agglomerated ceramic powder uses Al2O3 and Yb2O3 as raw materials, the average particle size of both is 1-5 µm and the molar ratio is 99:(1-90).

3. A method for preparing a high infrared emissivity anti-vacuum volatilization thermal control coating as described in claim 2, characterized in that, Includes the following steps: S1. Using atmospheric plasma spraying process, NiCr-based alloy powder is sprayed onto the substrate surface to form an adhesive layer. S2. Using an atmospheric plasma spraying process, Al2O3 composite agglomerated ceramic powder is sprayed onto the surface of the adhesive layer, thus forming a functional layer on the adhesive layer, and a high infrared emissivity anti-vacuum volatilization thermal control coating is obtained; wherein, the raw materials of the Al2O3 composite agglomerated ceramic powder include Al2O3, Sm2O3 and Yb2O3, and the average particle size of the three is 1-5 µm.

4. The preparation method according to claim 3, characterized in that, In step S1, the plasma spraying process parameters are as follows: powder feed rate is 40-60 g / min, argon flow rate is 30-50 L / min, hydrogen flow rate is 5-8 L / min, spraying current is 350-450 A, spraying power is 25-35 kW, spray gun lateral movement speed is 650-850 mm / s, spray gun longitudinal step is 1-4 mm / step, and spraying distance is 70-140 mm.

5. The preparation method according to claim 3, characterized in that, In step S2, the plasma spraying process parameters are as follows: powder feed rate is 40-60 g / min, argon flow rate is 30-50 L / min, hydrogen flow rate is 9-15 L / min, spraying current is 500-600 A, spraying power is 40-50 kW, spray gun lateral movement speed is 650-850 mm / s, spray gun longitudinal step is 1-4 mm / step, and spraying distance is 70-140 mm.

6. The preparation method according to claim 3, characterized in that, In step S2, the Al2O3 composite agglomerated ceramic powder is prepared as follows: Al2O3 and Sm2O3, or Al2O3 and Yb2O3 are mixed, and then a dispersant and a binder are added. The resulting mixture is then ball-milled, spray-granulated, and sintered at high temperature to obtain Al2O3 composite agglomerated ceramic powder.

7. The preparation method according to claim 6, characterized in that, The molar ratio of Al2O3 to Sm2O3 is 99:(1-90), and the molar ratio of Al2O3 to Yb2O3 is 99:(1-90).

8. The preparation method according to claim 6, characterized in that, The dispersant is sodium citrate, and the binder is polyvinyl alcohol. The amount of dispersant and binder added is 1-5% of the total mass of the raw materials used in step S2.

9. The preparation method according to claim 6, characterized in that, The ball milling time is 12-48 h, and the rotation speed is 180-280 r / min; the spray granulation temperature is 100-150℃, and the rotation speed is 20-40 r / min; the high-temperature sintering temperature is 1200-1500℃, and the time is 6-12 h.

10. The application of a high infrared emissivity anti-vacuum volatilization thermal control coating as described in any one of claims 1-2 or a high infrared emissivity anti-vacuum volatilization thermal control coating prepared by any one of claims 3-9 in the preparation of heat pipes and reactor vessel surfaces of space nuclear reactor systems.

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