High-emissivity rare earth doped hafnium-based ceramic / silicon carbide composite ultrahigh-temperature thermal protection coating and preparation method thereof
Through rare earth doped hafnium-based ceramics and silicon carbide composites, combined with the vapor-phase silicon permeability process, an ultra-high temperature thermal protection coating with high emissivity was prepared, which solved the problem of insufficient long-term service performance of the existing coating at high temperatures, and achieved excellent high-temperature performance and ablation resistance.
Patent Information
- Application Number
- CN202510235274.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-28
- Publication Date
- 2025-06-06
AI Technical Summary
The thermal protection coatings of existing hypersonic aircraft are insufficient in service at high temperatures. The brittleness of traditional ceramic materials and the loss of ablation materials lead to changes in aerodynamic appearance and high maintenance costs.
A high emissivity ultra-high temperature thermal protection coating is prepared by using rare earth-doped hafnium-based ceramics and silicon carbide composite materials.
The coating is achieved to remain intact under conditions above 1600°C, and the average temperature on the back of the sample is maintained below 910.3°C, which significantly improves the high-temperature long-term service performance and has good thermal shock and ablation resistance.
Smart Images
Figure CN120097724A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of thermal protective coatings, and relates to a high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating and a preparation method thereof, and improves the high-temperature and long-term service performance of the coating through component design and process optimization. Background Art
[0002] The pursuit and research of various countries for higher-speed aircraft have led to the birth of hypersonic aircraft. When an aircraft flies at hypersonic speed near the atmosphere, aerodynamic heating will inevitably occur. At this time, the temperature of the aircraft surface will rise sharply, especially the nose cone and leading edge of the aircraft, which can reach or even exceed 1600°C. Traditional thermal protection systems have obvious disadvantages. The brittleness of high-temperature ceramics, the loss of ablative materials will change the aerodynamic shape, and their high replacement and maintenance costs make traditional thermal protection systems have extremely low application value in hypersonic aircraft.
[0003] SiC ceramics have the characteristics of high specific strength, high specific modulus, high temperature resistance, impact resistance and good mechanical properties. At the same time, they overcome the fatal shortcomings of ceramic materials such as low fracture toughness, poor impact load resistance and thermal shock resistance, and become an important heat protection material for key parts of aircraft. However, many advantages of this material can only be maintained in an inert atmosphere. Although recent studies have shown that SiC generated by oxidation of SiO 2 It can effectively block the diffusion of oxygen, but the SiO 2 It is in a molten amorphous state, and the improvement of high-temperature long-term service performance is limited. Therefore, it is urgent to design the composition and structure of the coating to obtain better high-temperature long-term service performance to solve the thermal barrier coating in the design of hypersonic aircraft. Summary of the invention
[0004] In view of the problem that the existing hypersonic thermal protection coatings have insufficient high-temperature and long-term service performance, the present invention provides a rare earth element-doped hafnium-based ceramic and silicon carbide composite coating and a preparation method thereof. The composite coating achieves excellent high-temperature and long-term service performance through slurry composition design and preparation process optimization. The immersion and pulling combined with vapor phase siliconization process used in the coating preparation has the advantages of simple method, stable forming quality and applicability to complex parts.
[0005] In order to achieve the above purpose, this paper adopts the following technical solutions:
[0006] A high-emissivity rare-earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protection coating, wherein the coating is composited from SiC and rare-earth-doped hafnium-based ceramic.
[0007] Furthermore, the coating is formed by rare earth-doped hafnium-based ceramic particles wrapped by SiC, and the thickness of the coating is 20 μm-200 μm.
[0008] Furthermore, the coating is formed by rare earth-doped hafnium-based ceramic particles wrapped by SiC, and the thickness of the coating is 20 μm-200 μm.
[0009] A method for preparing the high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating as described above comprises the following steps:
[0010] (1) Preparation of rare earth doped hafnium oxide powder: submicron rare earth oxide and HfO 2 ball milling and mixing, treating at 900-2000° C. for 0.5-2 h in an inert atmosphere to obtain rare earth-doped hafnium oxide powder;
[0011] (2) Preparation of slurry: Dissolve the polymer binder in the solvent and stir on a magnetic stirrer for 2 to 4 hours to form a solution. Then, rare earth-doped hafnium oxide powder, HfB 2 , SiC and the solution are mixed by ball milling to obtain a slurry with a certain viscosity;
[0012] (3) immersing the substrate into the slurry prepared in step (2) by an immersion-pulling method, so that the slurry is evenly coated on the surface of the substrate to obtain a coating, and controlling the substrate rising speed to be 30 to 500 μm / s. After the substrate is completely lifted out of the liquid surface, it is naturally dried and placed in a muffle furnace for curing at 100 to 230° C. for 0.5 h to 1.5 h to obtain a cured coating;
[0013] (4) pyrolyzing the cured coating obtained in step (3) at 500 to 900° C. in an inert atmosphere for 0.5 to 2.5 hours to obtain a pretreated coating;
[0014] (5) The pre-treated coating obtained in step (4) is placed in a container containing Si particles and placed in a vacuum induction heating furnace and heated to 1500-2200° C. for 5 min-100 min.
[0015] Furthermore, the rare earth oxide in step (1) and HfO 2 The mass ratio is 1:0.2~5.
[0016] Furthermore, the rare earth oxide in step (1) includes one or a mixture of praseodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, and thulium oxide; and the substrate is one of graphite, C / C composite material, C / Cf composite material, and C / SiC composite material.
[0017] Furthermore, the polymer binder in step (2) includes one or a mixture of phenolic resin, epoxy resin, and polyimide.
[0018] Furthermore, the solvent in step (2) includes one or a mixture of ethanol, propanol, and deionized water.
[0019] Furthermore, in step (2), the ratio of the hafnium-containing compound to SiC is 1:0.5-3, and the solid content ratio in the slurry is 20wt%-60wt%.
[0020] The present invention has the following beneficial effects:
[0021] 1. The present invention provides a new idea of rare earth doping to improve the high temperature and long-term service performance of silicon carbide composite coatings. By synthesizing a solid solution of hafnium oxide and rare earth oxides, rare earth-doped HfC and HfSi are obtained after a gas phase siliconization reaction. 2 . By designing and preparing rare earth doped silicon carbide composite coating, extremely excellent high temperature and long-term service performance was obtained. After the coating after gas phase siliconization was ablated for 3000s under oxyacetylene flame flow above 1600℃, the coating remained intact, and the average temperature on the back of the sample remained below 910.3℃.
[0022] 2. The present invention utilizes the gas phase siliconization method to generate a layer of SiC between the substrate surface and the coating, thereby improving the bonding strength between the coating and the substrate and obtaining good thermal shock resistance.
[0023] 3. The rare earth element doped hafnium-based ceramic and silicon carbide composite coating of the present invention is prepared by a method of gas phase siliconization combined with an impregnation process, which can prepare a thicker coating while ensuring good bonding with the substrate. The preparation process is simple, the operation is convenient, and it can be applied to the surface of parts with complex shapes. It has strong repeatability and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 This is a cross-sectional SEM morphology image of the high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protection coating of Example 2 of the present invention;
[0025] Figure 2 This is the macroscopic morphology of the high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating with a pulling speed of 100 μm / s in Example 1 of the present invention;
[0026] Figure 3 This is the macroscopic morphology of the high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating with a pulling speed of 200 μm / s in Example 2 of the present invention;
[0027] Figure 4 This is the macroscopic morphology of the high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating with a pulling speed of 300 μm / s in Example 3 of the present invention;
[0028] Figure 5 This is a SEM scan of the high-emissivity rare-earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protection coating of Example 2;
[0029] Figure 6 The front and back temperature curves of Example 2 of the present invention during the oxyacetylene flame ablation experiment of the high-emissivity rare-earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating;
[0030] Figure 7 This is a macroscopic comparison of the high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protection coating before and after oxyacetylene flame ablation in Example 2 of the present invention;
[0031] Figure 8 It is the mid-infrared emissivity of the high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating before and after oxyacetylene flame ablation in Example 2 of the present invention. DETAILED DESCRIPTION
[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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.
[0033] Example 1
[0034] A high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating is prepared by the following method:
[0035] 1. Use 1200# sandpaper to grind the graphite substrate flat, and then use ethanol ultrasonic for 10 minutes and then deionize and clean it for use.
[0036] 2. Rare earth oxides and HfO 2 The mixture is weighed in a mass ratio of 1:2, ball-milled and mixed, and then treated at 1400° C. for 0.5 h in an inert atmosphere to obtain rare earth-doped hafnium oxide powder.
[0037] 3. Weigh phenolic resin and ethanol in a mass ratio of 2:13 to prepare an ethanol solution of phenolic resin.
[0038] 4. Rare earth-doped hafnium oxide and silicon carbide were weighed at a mass ratio of 1:0.5, and a phenolic resin ethanol solution was weighed at a solid phase ratio of 30 wt %, and the powder and the solution were ball-milled to obtain a slurry.
[0039] 5. Immerse the substrate in the slurry, set the pulling speed of the pulling machine to 100μm / s, let the coating dry naturally after pulling, cure at 150℃ for 0.5h, put it into a tubular furnace and pyrolyze it at 500℃ in an inert atmosphere for 1h. Finally, put it into a vacuum induction furnace and siliconize it at 1700℃ for 10min.
[0040] Example 2
[0041] A high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating is prepared by the following method:
[0042] 1. Use 1200# sandpaper to grind the graphite substrate flat, and then use ethanol ultrasonic for 10 minutes and then deionize and clean it for use.
[0043] 2. Rare earth oxides and HfO 2 The mixture is weighed in a mass ratio of 1:2, ball-milled and mixed, and then treated at 1400° C. for 0.5 h in an inert atmosphere to obtain rare earth-doped hafnium oxide powder.
[0044] 3. Weigh phenolic resin and ethanol in a mass ratio of 2:15 to prepare an ethanol solution of phenolic resin.
[0045] 4. Hafnium carbide and silicon carbide were weighed at a mass ratio of 1:1, and a phenolic resin ethanol solution was weighed at a solid phase ratio of 30 wt %, and the powder and the solution were ball-milled to obtain a coating slurry.
[0046] 5. Immerse the substrate in the slurry, set the pulling speed of the pulling machine to 200μm / s, let the coating dry naturally after pulling, cure at 150℃ for 0.5h, put it into a tubular furnace and pyrolyze it at 500℃ in an inert atmosphere for 1h. Finally, put it into a vacuum induction furnace and siliconize it at 1700℃ for 10min.
[0047] Example 3
[0048] A high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating is prepared by the following method:
[0049] 1. Use 1200# sandpaper to grind the graphite substrate flat, and then use ethanol ultrasonic for 10 minutes and then deionize and clean it for use.
[0050] 2. Rare earth oxides and HfO 2 The mixture is weighed in a mass ratio of 1:2, ball-milled and mixed, and then treated at 1400° C. for 0.5 h in an inert atmosphere to obtain rare earth-doped hafnium oxide powder.
[0051] 3. Weigh phenolic resin and ethanol in a mass ratio of 2:10 to prepare an ethanol solution of phenolic resin.
[0052] 4. Hafnium boride and silicon carbide were weighed at a mass ratio of 1:1.5, and a phenolic resin ethanol solution was weighed at a solid phase ratio of 40 wt %, and the powder and the solution were ball-milled to obtain a coating slurry.
[0053] 5. Immerse the substrate in the slurry, set the pulling speed of the pulling machine to 300μm / s, let the coating dry naturally after pulling, cure at 150℃ for 0.5h, put it into a tubular furnace and pyrolyze it at 500℃ in an inert atmosphere for 1h. Finally, put it into a vacuum induction furnace and siliconize it at 1700℃ for 10min.
[0054] Reference Figure 1 , Figure 2 , Figure 3 , Figure 4 It can be seen that the coating has good process applicability, and a complete, dense, crack-free high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating can be obtained at different pulling speeds.
[0055] Reference Figure 5 The SEM scan results of the coating cross section show that the coating is mainly composed of hafnium-based ceramic particles wrapped by SiC, and there is diffusion between the C element and the Si element between the coating and the substrate, proving that SiC is generated between the coating and the substrate. At the same time, there is diffusion of rare earth elements on the surface, which makes the surface molten amorphous SiO 2 The increased viscosity makes it less likely to be washed away from the surface during the ablation process, thereby better isolating oxygen and protecting the interior of the coating and the substrate.
[0056] Reference Figure 6 , Figure 7 , the high-emissivity rare earth doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating prepared in Example 2 was subjected to an oxyacetylene flame ablation test. It was found that during ablation, the temperature of the coating surface was always maintained above 1600°C under the action of the oxyacetylene flame, while the highest temperature on the back did not exceed 910.3°C. This shows that the high-emissivity rare earth doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating has obvious thermal insulation capabilities, and the performance remains stable. The coating remains intact after ablation, and there are no defects such as cracks and voids on the surface, which shows that the coating not only has excellent thermal insulation properties, but also has excellent anti-ablation properties.
[0057] Reference Figure 8 It can be found that the average mid-infrared emissivity of the rare earth doped hafnium-based ceramic and silicon carbide composite ultra-high temperature thermal protection coating after ablation is still greater than 0.85. At high temperatures, thermal radiation accounts for a large proportion of heat transfer and can be said to be the main form of heat transfer at high temperatures. Therefore, the high emissivity of the coating can effectively ensure the thermal insulation performance of the coating.
[0058] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.
Claims
1. A high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating, characterized in that: The coating is composited from SiC and rare earth-doped hafnium-based ceramics.
2. The high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating according to claim 1, characterized in that: The coating is formed by rare earth-doped hafnium-based ceramic particles wrapped by SiC, and the thickness of the coating is 20 μm-200 μm.
3. The high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating according to claim 1, characterized in that: The hafnium-based ceramic includes one or a mixture of hafnium oxide, hafnium carbide, hafnium boride and hafnium silicide.
4. A method for preparing a high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating as claimed in any one of claims 1 to 3, characterized in that: The steps include: (1) preparing rare earth doped hafnium oxide powder, mixing submicron rare earth oxide and HfO2 by ball milling, and treating at 900-2000° C. for 0.5-2 h in an inert atmosphere to obtain rare earth doped hafnium oxide powder; (2) preparing a slurry: dissolving a polymer binder in a solvent, stirring on a magnetic stirrer for 2 to 4 hours to form a solution, and then ball-milling a hafnium-containing compound, SiC and the solution to obtain a slurry with a certain viscosity, wherein the hafnium-containing compound is a mixture of rare earth-doped hafnium oxide and one or more of hafnium silicide, hafnium carbide and hafnium boride; (3) immersing the substrate into the slurry prepared in step (2) by an immersion-pulling method, so that the slurry is evenly coated on the surface of the substrate to obtain a coating, and controlling the substrate rising speed to be 30 to 500 μm / s. After the substrate is completely lifted out of the liquid surface, it is naturally dried and placed in a muffle furnace for curing at 100 to 230° C. for 0.5 h to 1.5 h to obtain a cured coating; (4) pyrolyzing the cured coating obtained in step (3) at 500 to 900° C. in an inert atmosphere for 0.5 to 2.5 hours to obtain a pretreated coating; (5) The pre-treated coating obtained in step (4) is placed in a container containing Si particles and placed in a vacuum induction heating furnace and heated to 1500-2200° C. for 5 min-100 min.
5. The method for preparing a high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating according to claim 4, characterized in that: The mass ratio of the rare earth oxide to HfO2 in step (1) is 1:0.2-5.
6. The method for preparing a high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating according to claim 4, characterized in that: The rare earth oxide in step (1) includes one or a mixture of praseodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, and thulium oxide; the substrate is one of graphite, C / C composite material, C / Cf composite material, and C / SiC composite material.
7. The method for preparing a high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating according to claim 4, characterized in that: The polymer binder described in step (2) includes one or a mixture of phenolic resin, epoxy resin, and polyimide.
8. The method for preparing a high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating according to claim 4, characterized in that: The solvent in step (2) includes one or a mixture of ethanol, propanol, and deionized water.
9. The method for preparing a high-emissivity rare earth-doped hafnium-based ceramic / silicon carbide composite ultra-high temperature thermal protective coating according to claim 4, characterized in that: In step (2), the ratio of the hafnium-containing compound to SiC is 1:0.5-3, and the solid content ratio in the slurry is 20wt%-60wt%.