Method for improving uniformity of surface coating composition of curved surface C / C composite material

Abstract

The application discloses a method for improving the uniformity of the surface coating composition of a curved surface C / C composite material, and comprises the following steps: preparing a single-phase / multi-phase ceramic coating on the surface of the curved surface C / C composite material to obtain a test piece; preparing a resin carbon barrier layer on the surface of the test piece; and then performing silicon infiltration treatment on the test piece, so that the phenomenon of the non-uniform coating composition in the corner area of the curved surface C / C composite material can be improved.

Description

Technical Field

[0001] This invention relates to a method for improving the uniformity of coating composition on curved C / C composite material surfaces. Background Technology

[0002] Carbon / carbon (C / C) composites are pure carbon multiphase structures composed of carbon fibers or their fabrics as reinforcement and chemically vapor-infiltrated pyrolytic carbon or liquid-phase impregnated and carbonized resin carbon or pitch carbon as the matrix. C / C composites possess excellent properties such as high specific strength, high specific modulus, low coefficient of thermal expansion, and high temperature resistance. In particular, their mechanical properties do not decrease but rather increase at high temperatures, even maintaining a high mechanical property retention rate above 2000℃, making them promising candidates for high-temperature oxidation-resistant and ablation-resistant materials. However, because C / C composites are entirely carbon-based, when exposed to oxygen-rich atmospheres above 370℃, the carbon fibers and matrix oxidize rapidly. Severe oxidation leads to a rapid decline in the mechanical properties of C / C composites, significantly limiting their application in the aerospace field.

[0003] Currently, the main methods for improving the high-temperature oxidation and ablation resistance of C / C composites are surface coating and matrix modification. High-temperature coating technology can completely isolate oxidizing gases from the matrix material, meeting the requirement for long-term oxidation protection of C / C composites. Coating preparation methods mainly include embedding, spraying, chemical vapor deposition, slurry coating, and gas / liquid phase silicate infiltration. Slurry coating is simple to operate and allows for coating composition and structure design, but it results in numerous internal pores and poor adhesion to the matrix. Currently, slurry coating is often combined with gas / liquid phase silicate infiltration, resulting in a short preparation cycle and applicability to coatings on curved and irregularly shaped components. However, controlling the uniformity of the coating on curved surfaces is extremely difficult, significantly impacting its service life in actual service environments.

[0004] Reference 1, "Yuqi Wang, Lingxiang Guo, Yuyu Zhang, Xuemeng Zhang, Hongkang Ou, Jia Sun*. Ablation behaviors and mechanism of ZrC-SiC-Si / SiC-Si double-layered coatings on C / C composite under plasma flame at 3000℃. Corrosion Science, 2023, 218: 111200", describes the preparation of a ZrC-SiC-Si / SiC-Si double-layered coating using a slurry coating combined with vapor-phase silicon infiltration. However, the scouring effect of silicon vapor on the porous pre-coating at high temperatures leads to the loss of the ultra-high temperature ceramic phase and coating thinning, making it difficult to control the coating uniformity.

[0005] Reference 2, "Ding Wuqing, Zhou Lei, Zhang Jiaping*, Fu Qiangang*. Long-term oxidation of MoSi2-modified HfB2-SiC-Si / SiC-Si coating at 1700℃[J]. Surface Engineering, 2023, 39(3): 315-325", successfully prepared HfB2-SiC-Si / SiC-Si coating by slurry coating combined with vapor phase silicon infiltration. However, severe elemental segregation occurred inside the coating, resulting in uneven coating composition.

[0006] Reference 3, "Li Tao, Zhang Yulei*, Lv Junshuai, Fu Yanqin, Sun Jia, Qiang Xinfa. A novel MoSi2-rich coating on the SiC-Si coated C / C composites for the preparation and antioxidative properties at 1773K and 1973K. Corrosion Science, 2022, 204: 110392," describes a method of applying a slurry and combining it with high-temperature reaction sintering and liquid-phase silicon infiltration to obtain a MoSi2-rich coating with good bonding between the inner and outer layers and a dense structure. However, this method is only applicable to coatings with dimensions of 10×10×10cm. 3 Coating preparation on standard oxide sample surfaces cannot provide strong theoretical support for high-temperature oxidation protection of curved and irregularly shaped components. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for improving the uniformity of coating composition on the surface of curved C / C composite materials. This method can improve the phenomenon of uneven coating composition in the corner areas of curved C / C composite materials.

[0008] To achieve the above objectives, this invention discloses a method for improving the uniformity of coating composition on curved C / C composite surfaces, comprising the following steps:

[0009] Single-phase / multi-phase ceramic coatings were prepared on the surface of curved C / C composite materials to obtain specimens;

[0010] A resin carbon barrier layer was prepared on the surface of the specimen, and then the specimen was subjected to silicon infiltration treatment.

[0011] Furthermore, the process of preparing a single-phase / multi-phase ceramic coating on the surface of the curved C / C composite material is as follows:

[0012] 11) Clean and dry the curved C / C composite material;

[0013] 12) Dissolve resin 1 in anhydrous ethanol A to obtain resin solution A;

[0014] Resin 2 is dissolved in anhydrous ethanol B to obtain resin solution B. One or more of ZrB2 or HfB2, SiC, HfSi2, MoSi2, ZrSi2 and TaSi2 are added to resin solution B, stirred and ultrasonically dispersed to obtain a mixed slurry.

[0015] 13) The mixed slurry is coated onto the surface of the curved C / C composite material and dried to obtain a ceramic coating.

[0016] Furthermore, resin 1 is a mixture of one or more resins selected from phenolic resin, epoxy resin, polyester resin and furan resin.

[0017] Furthermore, the mass ratio of resin 1 to anhydrous ethanol A is 10-30:60-80.

[0018] Furthermore, the mass ratio of the resin 2, anhydrous ethanol, BZrB2 or HfB2, SiC and one or more of HfSi2, MoSi2, ZrSi2 and TaSi2 is 5-20:70-90:20-40:40-60:5-20.

[0019] Furthermore, the process of preparing a resin carbon barrier layer on the surface of the specimen and then performing silicon infiltration treatment on the specimen is as follows:

[0020] 21) Coat the corners of the specimen with resin solution A and then dry it to obtain a resin carbon barrier layer;

[0021] 22) The specimen obtained in step 21) is cured at 150-200°C and then carbonized in an argon atmosphere at 900-1200°C to obtain a ceramic pre-coating with a resin carbon barrier layer at the corners.

[0022] 23) Prepare the mixed powder;

[0023] 24) Place the specimen obtained in step 22) in a graphite crucible with a 5-10 mm thick layer of mixed powder at the bottom, and add more mixed powder to the graphite crucible until the mixed powder covers the specimen by 5-10 mm. Seal the graphite crucible and heat it to 1500-1700℃ at a rate of 4-10℃ / min under vacuum conditions, hold it at that temperature, and then cool it down.

[0024] Furthermore, the operation process of step 23) is as follows:

[0025] Si powder, SiC and C powder are mixed and then ball-milled, and then dried to obtain a mixed powder.

[0026] Furthermore, the mass ratio of Si powder, SiC and C powder is 50-80:5-25:10-25.

[0027] The surface coating of the curved C / C composite material described in this invention is prepared based on the method for improving the compositional uniformity of the surface coating of the curved C / C composite material.

[0028] The present invention has the following beneficial effects:

[0029] The method for improving the compositional uniformity of coatings on curved C / C composite surfaces, as described in this invention, involves constructing a resin-carbon barrier layer. After applying a ceramic outer coating, a resin solution is directly applied to the corners of the curved sample. Through carbonization, a pre-coating with resin carbon is obtained. This method is simple to operate and significantly reduces the preparation time of traditional repeated coating methods. Furthermore, the resin-carbon barrier layer effectively mitigates the erosion of the porous pre-coating by melt flow during silicon infiltration, reduces the loss of ultra-high temperature ceramic phases in localized areas, improves the overall compositional uniformity of the coating, and gives the coating stable high-temperature oxidation resistance, thereby preventing localized coating failure caused by coating inhomogeneity. This invention can further provide a solution to localized damage to the substrate caused by melt infiltration processes, achieving a protective effect where both the substrate and the coating are protected from melt erosion.

[0030] Furthermore, by adjusting the content of each component in the original slurry, a controllable structural design for a uniform coating on the surface of curved samples can be achieved by coating the outer ceramic coating and the carbon resin layer in different areas. Attached Figure Description

[0031] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0032] Figure 1 This is a process flow diagram of the present invention.

[0033] Figure 2 The images show cross-sectional SEM and energy dispersive spectroscopy (EDS) images of the pre-coated samples after carbonization, with pre-coated areas applied in different regions. Figure 2In the image, (a) is a cross-sectional SEM image of the sample coated with 50 wt.% HfB2 at the corner after carbonization in the corner region; (b) is a cross-sectional SEM image and spot scan energy dispersive spectroscopy (EDS) image of the sample coated with 50 wt.% HfB2 at the corner after carbonization in the transition region; (c) is a cross-sectional SEM image of the sample coated with 60 wt.% HfB2 at the corner after carbonization in the corner region; and (d) is a cross-sectional SEM image and spot scan energy dispersive spectroscopy (EDS) image of the sample coated with 60 wt.% HfB2 at the corner after carbonization in the transition region.

[0034] Figure 3 To construct the cross-sectional SEM and energy dispersive spectroscopy (EDS) images of the coated samples after carbonization to construct the resin carbon barrier layer, Figure 3 In Figure 1, (a) is a cross-sectional SEM image of a sample coated with 40 wt.% HfB2 and resin carbon at the corners after carbonization; (b) is a cross-sectional SEM image of a sample coated with 50 wt.% HfB2 and resin carbon at the corners after carbonization; (c) is a cross-sectional SEM image of a sample coated with 60 wt.% HfB2 and resin carbon at the corners after carbonization; (d) is a high-magnification SEM image of the area within the frame in Figure (a); (e) is a high-magnification SEM image of the area within the frame in Figure (b); (f) is a high-magnification SEM image of the area within the frame in Figure (c); and (g) is the area scan energy dispersive spectroscopy (EDS) spectrum of Figure (d).

[0035] Figure 4 The images show cross-sectional SEM images of coated samples after silicon infiltration, including samples with pre-coated areas and samples with resin carbon barrier layers. Figure 4 In the figures, (a) is a cross-sectional SEM image of a sample coated with 40 wt.% HfB2 at the corners after silicon infiltration; (b) is a cross-sectional SEM image of a sample coated with 50 wt.% HfB2 at the corners after silicon infiltration; (c) is a cross-sectional SEM image of a sample coated with 60 wt.% HfB2 at the corners after silicon infiltration; (d) is a cross-sectional SEM image of a sample coated with 40 wt.% HfB2 and resin carbon at the corners after silicon infiltration; (e) is a cross-sectional SEM image of a sample coated with 50 wt.% HfB2 and resin carbon at the corners after silicon infiltration; and (f) is a cross-sectional SEM image of a sample coated with 60 wt.% HfB2 and resin carbon at the corners after silicon infiltration. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0038] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0039] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this invention generally indicates that the preceding and following objects have an "or" relationship.

[0040] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0041] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0043] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0044] The method for improving the uniformity of coating composition on curved C / C composite surfaces according to the present invention includes:

[0045] 1) Prepare single-phase / multi-phase ceramic coatings on the surface of curved C / C composite materials;

[0046] 11) The density of the embedded SiC inner coating is 1.7–1.8 g / cm³. 3 The curved C / C composite material (PC-SiC-C / C) was ultrasonically cleaned with deionized water 4-6 times, with each cleaning time being 20-40 minutes, and then dried in an electric heating drying oven at a temperature of 60-100℃ for 6-10 hours.

[0047] 12) Dissolve 10-30 wt.% of one or more resins selected from phenolic resin, epoxy resin, polyester resin, and furan resin thoroughly in 60-80 wt.% anhydrous ethanol to obtain resin solution A;

[0048] A mixture of one or more resins selected from phenolic resin, epoxy resin, polyester resin, and furan resin, comprising 5-20 wt.%, is fully dissolved in 70-90 wt.% anhydrous ethanol to obtain resin solution B.

[0049] A mixture of one or more of ZrB2 or HfB2, SiC, HfSi2, MoSi2, ZrSi2 and TaSi2 is added to resin solution B in a ratio of 20-40 wt.%: 40-60 wt.%: 5-20 wt.%. After thorough stirring, the mixture is placed in an ultrasonic cleaner for ultrasonic dispersion until there are no obvious agglomerated particles in the slurry, thus obtaining a mixed slurry.

[0050] 13) Apply the mixed slurry to the surface of the curved C / C composite material using a brush, and dry it in an electric heating drying oven at a temperature of 60 to 100°C for 10 to 20 minutes. Repeat the above brushing-drying steps until a ceramic coating of the required thickness is obtained on the surface of the curved C / C composite material.

[0051] 2) Prepare a resin carbon barrier layer on the surface of the specimen obtained in step 1);

[0052] 21) Coat the corners of the specimen obtained in step 1) with resin solution A and dry it in an electric heating drying oven at a temperature of 60-100℃ for 10-20 minutes to obtain a resin carbon barrier layer.

[0053] 22) Place the specimen obtained in step 21) into an Al2O3 boat and place it in a tubular heat treatment furnace. Then cure it at 150-200℃ for 1-2 hours, and then carbonize it in an argon atmosphere at 900-1200℃ for 2-4 hours to obtain a ceramic pre-coating with a resin carbon barrier layer at the corners.

[0054] 23) Mix 50-80 wt.% Si powder, 5-25 wt.% SiC and 10-25 wt.% C powder and pour them into a ball mill jar and ball mill for 5-8 hours. Then place them in an electric heating drying oven at 60-100℃ and dry for 10-16 hours to obtain mixed powder.

[0055] 24) Place the specimen obtained in step 22) in a graphite crucible with a 5-10 mm thick layer of mixed powder at the bottom, and add more mixed powder to the graphite crucible until the mixed powder covers the specimen by 5-10 mm. Seal the graphite crucible and place it in a heat treatment furnace. Then, under vacuum conditions, heat the specimen to 1500-1700℃ at a rate of 4-10℃ / min and hold it for 1-2 hours. Then, turn off the power and cool down to obtain a PC-SiC-C / C curved surface specimen with ceramic coating modification.

[0056] Example 1

[0057] This embodiment includes the following steps:

[0058] 1) The density of the embedded SiC inner coating is 1.7 g / cm³. 3The curved C / C composite material (PC-SiC-C / C) was ultrasonically cleaned with deionized water for 5 times, with each cleaning time lasting 30 minutes, and then dried in an electric heating drying oven at 70℃ for 8 hours.

[0059] 2) Dissolve 23 wt.% phenolic resin completely in 77 wt.% anhydrous ethanol to obtain phenolic resin solution A; dissolve 12 wt.% phenolic resin completely in 88 wt.% anhydrous ethanol to obtain phenolic resin solution B. Then add 40 wt.% SiC, 40 wt.% HfB2, and 20 wt.% MoSi2 to phenolic resin solution B to obtain HfB2-SiC-MoSi2-phenolic resin slurry. After stirring, place the HfB2-SiC-MoSi2-phenolic resin slurry in an ultrasonic cleaner for ultrasonic dispersion until there are no obvious agglomerated particles in the slurry.

[0060] 3) Apply HfB2-SiC-MoSi2-phenolic resin slurry to the surface of the curved PC-SiC-C / C sample using a brush, and dry it in an electric heating drying oven at 70℃ for 20 minutes. Repeat the above brushing-drying steps until the desired thickness of HfB2-SiC-MoSi2 external coating is obtained.

[0061] 4) Coat the corners of the PC-SiC-C / C curved surface sample coated with HfB2-SiC-MoSi2 external coating with phenolic resin solution A, and dry it in an electric heating drying oven at 70℃ for 20 min to obtain a resin carbon barrier layer.

[0062] 5) Place the coated sample into an Al2O3 boat and put it in a tube heat treatment furnace. Cure it at 200℃ for 1 hour, and then carbonize it in an argon atmosphere at 900℃ for 2 hours to obtain an HfB2-SiC-MoSi2 pre-coating with a resin carbon barrier layer at the corners. Figure 3 (a, d, g) are cross-sectional SEM images and energy dispersive spectroscopy (EDS) images of the coated sample after carbonization to construct the resin carbon barrier layer. After carbonization, a resin carbon layer with a thickness of about 6 mm was formed on the outer side of the ceramic coating in the corner area.

[0063] 6) Mix 71 wt.% Si powder, 14 wt.% SiC and 15 wt.% C powder and pour them into a ball mill jar and ball mill for 6 hours. Then place them in an electric heating drying oven at 70°C and dry for 12 hours to obtain mixed powder.

[0064] 7) Place the HfB2-SiC-MoSi2 pre-coated PC-SiC-C / C curved surface sample with a resin carbon barrier layer at the corners, convex side up, in a graphite crucible with a 6mm thick layer of mixed powder at the bottom. Continue adding mixed powder until the mixed powder covers the sample by 6mm. Then, place the sealed graphite crucible in a heat treatment furnace and heat it to 1600℃ at a rate of 10℃ / min under vacuum conditions, hold it at that temperature for 2 hours, and then turn off the power to cool it down, obtaining the HfB2-SiC-MoSi2 coated modified PC-SiC-C / C curved surface sample.

[0065] In this embodiment, the HfB2-SiC-MoSi2 coating exhibited uniform composition in the corner areas of the PC-SiC-C / C curved surface sample, and no loss of the ultra-high temperature ceramic phase was observed. Figure 4 As shown in (d), the resin carbon acts as a barrier layer, effectively mitigating the erosion of the coating at the edges and corners of the sample by the melt.

[0066] Comparative Example 1

[0067] This comparative example includes the following steps:

[0068] 1) The density of the embedded SiC inner coating is 1.7 g / cm³. 3 The curved C / C composite material (PC-SiC-C / C) was ultrasonically cleaned with deionized water for 5 times, with each cleaning time lasting 30 minutes, and then dried in an electric heating drying oven at 70℃ for 8 hours.

[0069] 2) Dissolve 12 wt.% phenolic resin in 88 wt.% anhydrous ethanol to obtain a phenolic resin solution. Add 40 wt.% SiC, 40 wt.% HfB2, and 20 wt.% MoSi2 to the phenolic resin solution to obtain an HfB2-SiC-MoSi2-phenolic resin slurry. After thoroughly stirring the HfB2-SiC-MoSi2-phenolic resin slurry, place it in an ultrasonic cleaner for ultrasonic dispersion until there are no obvious agglomerated particles in the slurry.

[0070] 3) Apply HfB2-SiC-MoSi2-phenolic resin slurry to the cleaned curved PC-SiC-C / C sample surface using a brush, and dry it in an electric heating drying oven at 70℃ for 20 minutes. Repeat the above brushing-drying steps until the desired thickness of HfB2-SiC-MoSi2 external coating is obtained.

[0071] 4) Place the coated sample into an Al2O3 boat and put it in a tube heat treatment furnace. Then cure it at 200℃ for 1 hour and then carbonize it in an argon atmosphere at 900℃ for 2 hours to obtain HfB2-SiC-MoSi2 pre-coating.

[0072] 5) Mix 71 wt.% Si powder, 14 wt.% SiC and 15 wt.% C powder and pour them into a ball mill jar and ball mill for 6 hours. Then place them in an electric heating drying oven at 70°C and dry for 12 hours to obtain mixed powder.

[0073] 6) Place the HfB2-SiC-MoSi2 pre-coated PC-SiC-C / C curved surface sample with the convex side facing up in a graphite crucible with a 6mm thick layer of mixed powder at the bottom. Then continue to add mixed powder until the mixed powder covers the sample by 6mm. Then place the sealed graphite crucible in a heat treatment furnace and heat it to 1600℃ at a rate of 10℃ / min under vacuum conditions. Hold it at this temperature for 2 hours, then turn off the power and cool down. Finally, obtain the HfB2-SiC-MoSi2 coated modified PC-SiC-C / C curved surface sample.

[0074] Because the melt changes its flow direction and increases its flow velocity at the corners of the sample during silicon infiltration, it exacerbates the erosion of the pre-coating in this area. Therefore, the corner areas of the HfB2-SiC-MoSi2 coated PC-SiC-C / C curved surface sample obtained in this comparative example are as follows: Figure 4 As shown in (a), a large amount of ultra-high temperature ceramic phase is lost in the corner area of ​​the curved sample.

[0075] Example 2

[0076] This embodiment includes the following steps:

[0077] 1) The density of the embedded SiC inner coating is 1.7 g / cm³. 3 The curved C / C composite material (PC-SiC-C / C) was ultrasonically cleaned with deionized water for 5 times, with each cleaning time lasting 30 minutes, and then dried in an electric heating drying oven at 70℃ for 8 hours.

[0078] 2) Dissolve 23 wt.% phenolic resin completely in 77 wt.% anhydrous ethanol to obtain phenolic resin solution A; dissolve 12 wt.% phenolic resin completely in 88 wt.% anhydrous ethanol to obtain phenolic resin solution B; add 30 wt.% SiC, 50 wt.% HfB2, and 20 wt.% MoSi2 to phenolic resin solution B to obtain HfB2-SiC-MoSi2-phenolic resin slurry 1; add 40 wt.% SiC, 40 wt.% HfB2, and 20 wt.% MoSi2 to phenolic resin solution B to obtain HfB2-SiC-MoSi2-phenolic resin slurry 2. Place the thoroughly stirred slurry in an ultrasonic cleaner for ultrasonic dispersion until there are no obvious agglomerated particles in the slurry.

[0079] 3) Apply HfB2-SiC-MoSi2-phenolic resin slurry 1 to the corner areas of the cleaned curved PC-SiC-C / C sample using a brush, apply HfB2-SiC-MoSi2-phenolic resin slurry 2 to the remaining areas of the sample surface, and dry in an electric heating drying oven at 70℃ for 20 minutes. Repeat the above brushing-drying steps until the desired thickness of the HfB2-SiC-MoSi2 external coating is obtained.

[0080] 4) Coat the corners of the PC-SiC-C / C curved surface sample coated with HfB2-SiC-MoSi2 external coating with phenolic resin solution A, and dry it in an electric heating drying oven at 70℃ for 20 min to obtain a resin carbon barrier layer.

[0081] 5) Place the coated sample into an Al2O3 boat and put it in a tube heat treatment furnace. Cure it at 200℃ for 1 hour, and then carbonize it in an argon atmosphere at 900℃ for 2 hours to obtain an HfB2-SiC-MoSi2 pre-coating with a resin carbon barrier layer at the corners. Figure 3 (b, e) are cross-sectional SEM images and energy dispersive spectroscopy (EDS) images of the coated sample after carbonization to construct the resin carbon barrier layer. After carbonization, a resin carbon layer with a thickness of about 6 mm was formed on the outer side of the ceramic coating in the corner area.

[0082] 6) Mix 71 wt.% Si powder, 14 wt.% SiC and 15 wt.% C powder and pour them into a ball mill jar and ball mill for 6 hours. Then place them in an electric heating drying oven at 70°C and dry for 12 hours to obtain mixed powder.

[0083] 7) Place the HfB2-SiC-MoSi2 pre-coated PC-SiC-C / C curved surface sample with resin carbon barrier layer at the corners, convex side up, in a graphite crucible with a 6mm thick layer of mixed powder at the bottom. Then continue to add mixed powder until the powder covers the sample by 6mm. Then place the sealed graphite crucible in a heat treatment furnace and heat it to 1600℃ at a rate of 10℃ / min under vacuum conditions. Hold it at this temperature for 2 hours, then turn off the power and cool down to obtain the HfB2-SiC-MoSi2 coated modified PC-SiC-C / C curved surface sample.

[0084] In this embodiment, the HfB2 content at the sample corners was increased to 50 wt.%, and a resin carbon barrier layer was simultaneously coated. The introduction of the resin carbon layer improved the loss of ultra-high temperature ceramic phase in localized micro-regions, and the overall coating was dense and uniform. Figure 4 As shown in (e).

[0085] Comparative Example 2

[0086] This comparative example includes the following steps:

[0087] 1) The density of the embedded SiC inner coating is 1.7 g / cm³. 3 The curved C / C composite material (PC-SiC-C / C) was ultrasonically cleaned with deionized water for 5 times, with each cleaning time lasting 30 minutes, and then dried in an electric heating drying oven at 70℃ for 8 hours.

[0088] 2) Dissolve 12 wt.% phenolic resin in 88 wt.% anhydrous ethanol to obtain a phenolic resin solution; add 30 wt.% SiC, 50 wt.% HfB2, and 20 wt.% MoSi2 to the phenolic resin solution to obtain HfB2-SiC-MoSi2-phenolic resin slurry 1; add 40 wt.% SiC, 40 wt.% HfB2, and 20 wt.% MoSi2 to the phenolic resin solution to obtain HfB2-SiC-MoSi2-phenolic resin slurry 2; place the thoroughly stirred slurry in an ultrasonic cleaner for ultrasonic dispersion until there are no obvious agglomerated particles in the slurry.

[0089] 3) Apply HfB2-SiC-MoSi2-phenolic resin slurry 1 to the corner areas of the cleaned curved PC-SiC-C / C sample using a brush, apply HfB2-SiC-MoSi2-phenolic resin slurry 2 to the remaining areas of the sample surface, and dry in an electric heating drying oven at 70℃ for 20 minutes. Repeat the above brushing-drying steps until the desired thickness of the HfB2-SiC-MoSi2 external coating is obtained.

[0090] 4) The coated sample was placed in an Al2O3 boat and then placed in a tubular heat treatment furnace. It was cured at 200℃ for 1 hour, and then carbonized at 900℃ in an argon atmosphere for 2 hours to obtain an HfB2-SiC-MoSi2 pre-coated layer. The phase distribution in the corner area of ​​the sample after carbonization is shown in the figure. Figure 2 As shown in (a), the phases are uniformly distributed at the corners of the sample, and the energy spectrum of the transition region of the sample after carbonization is as follows. Figure 2 As shown in (b), the gradient change of Hf content is displayed, which realizes the content control in the corner area of ​​the curved sample, and thus realizes the coating preparation of the regional composition of the curved sample.

[0091] 5) Mix 71 wt.% Si powder, 14 wt.% SiC and 15 wt.% C powder and pour them into a ball mill jar and ball mill for 6 hours. Then place them in an electric heating drying oven at 70°C and dry for 12 hours to obtain mixed powder.

[0092] 6) Place the HfB2-SiC-MoSi2 pre-coated PC-SiC-C / C curved surface sample, convex side up, in a graphite crucible with a 6mm thick layer of mixed powder at the bottom. Continue adding mixed powder until the powder covers the sample by 6mm. Then, place the sealed graphite crucible in a heat treatment furnace and heat it to 1600℃ at a rate of 10℃ / min under vacuum conditions, hold it at that temperature for 2 hours, and then turn off the power to cool it down, obtaining the HfB2-SiC-MoSi2 coated modified PC-SiC-C / C curved surface sample.

[0093] This comparative example involves regional pre-coating, increasing the HfB2 content at the corners to 50 wt.%. Appropriately increasing the HfB2 content reduces its loss to some extent and improves the problem of uneven coating composition at the corners. However, localized micro-regions of ultra-high temperature ceramic phase loss still exist, such as... Figure 4 As shown in (b).

[0094] Comparative Example 3

[0095] This comparative example includes the following steps:

[0096] 1) The density of the embedded SiC inner coating is 1.7 g / cm³. 3 The curved C / C composite material (PC-SiC-C / C) was ultrasonically cleaned with deionized water for 5 times, with each cleaning time lasting 30 minutes, and then dried in an electric heating drying oven at 70℃ for 8 hours.

[0097] 2) Dissolve 12 wt.% phenolic resin in 88 wt.% anhydrous ethanol to obtain a phenolic resin solution; add 20 wt.% SiC, 60 wt.% HfB2, and 20 wt.% MoSi2 to the phenolic resin solution to obtain HfB2-SiC-MoSi2-phenolic resin slurry 1; add 40 wt.% SiC, 40 wt.% HfB2, and 20 wt.% MoSi2 to the phenolic resin solution to obtain HfB2-SiC-MoSi2-phenolic resin slurry 2; place the thoroughly stirred slurry in an ultrasonic cleaner for ultrasonic dispersion until there are no obvious agglomerated particles in the slurry.

[0098] 3) Apply HfB2-SiC-MoSi2-phenolic resin slurry 1 to the corner areas of the cleaned curved PC-SiC-C / C sample using a brush, apply HfB2-SiC-MoSi2-phenolic resin slurry 2 to the remaining areas of the sample surface, and dry in an electric heating drying oven at 70℃ for 20 minutes. Repeat the above brushing-drying steps until the desired thickness of the HfB2-SiC-MoSi2 external coating is obtained.

[0099] 4) The coated sample was placed in an Al2O3 boat and then in a tubular heat treatment furnace. It was cured at 200℃ for 1 hour, and then carbonized at 900℃ in an argon atmosphere for 2 hours to obtain the HfB2-SiC-MoSi2 pre-coating. The phase distribution in the corner area of ​​the carbonized sample is shown below. Figure 2 As shown in (c), the phases are uniformly distributed at the corners of the sample, and the energy spectrum of the transition region of the sample after carbonization is as follows. Figure 2 As shown in (d), the gradient change of Hf content is displayed, which realizes the content control in the corner area of ​​the curved sample, and thus realizes the coating preparation of the regional composition of the curved sample.

[0100] 5) Mix 71 wt.% Si powder, 14 wt.% SiC and 15 wt.% C powder and pour them into a ball mill jar and ball mill for 6 hours. Then place them in an electric heating drying oven at 70°C and dry for 12 hours to obtain mixed powder.

[0101] 6) Place the HfB2-SiC-MoSi2 pre-coated PC-SiC-C / C curved surface sample, convex side up, in a graphite crucible with a 6mm thick layer of mixed powder at the bottom. Continue adding mixed powder until the powder covers the sample by 6mm. Then, place the sealed graphite crucible in a heat treatment furnace and heat it to 1600℃ at a rate of 10℃ / min under vacuum conditions, hold it at that temperature for 2 hours, and then turn off the power to cool it down. Finally, obtain the HfB2-SiC-MoSi2 coated modified PC-SiC-C / C curved surface sample.

[0102] In this comparative example, a pre-coating was applied to different areas, increasing the HfB2 content at the corners to 60 wt.%. The ultra-high temperature ceramic phase was preserved in localized micro-regions at the corners of the samples. However, the excessively high HfB2 content caused a severe mismatch in the thermal expansion coefficients between the outer and inner coatings, resulting in the peeling of most of the outer coating. Figure 4 As shown in (c).

[0103] Comparative Example 4

[0104] This comparative example includes the following steps:

[0105] 1) The density of the embedded SiC inner coating is 1.7 g / cm³. 3 The curved C / C composite material (PC-SiC-C / C) was ultrasonically cleaned with deionized water for 5 times, with each cleaning time lasting 30 minutes, and then dried in an electric heating drying oven at 70℃ for 8 hours.

[0106] 2) Dissolve 23 wt.% phenolic resin completely in 77 wt.% anhydrous ethanol to obtain phenolic resin solution A; dissolve 12 wt.% phenolic resin completely in 88 wt.% anhydrous ethanol to obtain phenolic resin solution B; add 20 wt.% SiC, 60 wt.% HfB2, and 20 wt.% MoSi2 to phenolic resin solution B to obtain HfB2-SiC-MoSi2-phenolic resin slurry 1; add 40 wt.% SiC, 40 wt.% HfB2, and 20 wt.% MoSi2 to phenolic resin solution B to obtain HfB2-SiC-MoSi2-phenolic resin slurry 2; place the thoroughly stirred slurry in an ultrasonic cleaner for ultrasonic dispersion until there are no obvious agglomerated particles in the slurry.

[0107] 3) Apply HfB2-SiC-MoSi2-phenolic resin slurry 1 to the corner areas of the cleaned curved PC-SiC-C / C sample using a brush, apply HfB2-SiC-MoSi2-phenolic resin slurry 2 to the remaining part of the sample surface, and dry in an electric heating drying oven at 70℃ for 20 minutes. Repeat the above brushing-drying steps until the desired thickness of HfB2-SiC-MoSi2 external coating is obtained.

[0108] 4) Coat the corners of the PC-SiC-C / C curved surface sample coated with HfB2-SiC-MoSi2 external coating with phenolic resin solution A, and dry it in an electric heating drying oven at 70℃ for 20 min to obtain a resin carbon barrier layer.

[0109] 5) Place the coated sample into an Al2O3 boat and put it in a tube heat treatment furnace. Cure it at 200℃ for 1 hour, and then carbonize it in an argon atmosphere at 900℃ for 2 hours to obtain an HfB2-SiC-MoSi2 pre-coating with a resin carbon barrier layer at the corners. Figure 3 (c, f) are cross-sectional SEM images and energy dispersive spectroscopy (EDS) images of the coated sample after carbonization to construct the resin carbon barrier layer. After carbonization, a resin carbon layer with a thickness of about 6 mm was formed on the outer side of the ceramic coating in the corner area.

[0110] 6) Mix 71 wt.% Si powder, 14 wt.% SiC and 15 wt.% C powder and pour them into a ball mill jar and ball mill for 6 hours. Then place them in an electric heating drying oven at 70°C and dry for 12 hours to obtain mixed powder.

[0111] 7) Place the HfB2-SiC-MoSi2 pre-coated PC-SiC-C / C curved surface sample with a resin carbon barrier layer at the corners, convex side up, in a graphite crucible with a 6mm thick layer of mixed powder at the bottom. Continue adding mixed powder until the mixed powder covers the sample by 6mm. Then, place the sealed graphite crucible in a heat treatment furnace and heat it to 1600℃ at a rate of 10℃ / min under vacuum conditions, hold it at that temperature for 2 hours, and then turn off the power to cool it down, obtaining the HfB2-SiC-MoSi2 coated modified PC-SiC-C / C curved surface sample.

[0112] In this comparative example, the HfB2 content at the sample corners was increased to 60 wt.%, and a resin carbon barrier layer was coated. However, due to the mismatch in thermal expansion coefficients, localized peeling of the outer coating still occurred, such as... Figure 4 As shown in (f).

[0113] Example 3

[0114] This embodiment includes the following steps:

[0115] 1) The density of the embedded SiC inner coating is 1.7 g / cm³. 3 The curved C / C composite material (PC-SiC-C / C) was ultrasonically cleaned with deionized water for 5 times, with each cleaning time lasting 30 minutes, and then dried in an electric heating drying oven at 70℃ for 8 hours.

[0116] 2) Dissolve 23 wt.% phenolic resin completely in 77 wt.% anhydrous ethanol to obtain phenolic resin solution A; dissolve 12 wt.% phenolic resin completely in 88 wt.% anhydrous ethanol to obtain phenolic resin solution B; add 35 wt.% SiC, 45 wt.% HfB2, and 20 wt.% MoSi2 to phenolic resin solution B to obtain HfB2-SiC-MoSi2-phenolic resin slurry 1; add 40 wt.% SiC, 40 wt.% HfB2, and 20 wt.% MoSi2 to phenolic resin solution B to obtain HfB2-SiC-MoSi2-phenolic resin slurry 2; place the thoroughly stirred slurry in an ultrasonic cleaner for ultrasonic dispersion until there are no obvious agglomerated particles in the slurry.

[0117] 3) Apply HfB2-SiC-MoSi2-phenolic resin slurry 1 to the corner areas of the cleaned curved PC-SiC-C / C sample using a brush, apply HfB2-SiC-MoSi2-phenolic resin slurry 2 to the remaining areas of the sample surface, and dry in an electric heating drying oven at 70℃ for 20 minutes. Repeat the above brushing-drying steps until the desired thickness of the HfB2-SiC-MoSi2 external coating is obtained.

[0118] 4) Coat the corners of the PC-SiC-C / C curved surface sample coated with HfB2-SiC-MoSi2 external coating with phenolic resin solution A, and dry it in an electric heating drying oven at 70℃ for 20 min to obtain a resin carbon barrier layer.

[0119] 5) Place the coated sample into an Al2O3 boat and put it in a tube heat treatment furnace. Cure it at 200℃ for 1 hour, and then carbonize it in an argon atmosphere at 900℃ for 2 hours to obtain an HfB2-SiC-MoSi2 pre-coating with a resin carbon barrier layer at the corners.

[0120] 6) Mix 71 wt.% Si powder, 14 wt.% SiC and 15 wt.% C powder and pour them into a ball mill jar and ball mill for 6 hours. Then place them in an electric heating drying oven at 70°C and dry for 12 hours to obtain mixed powder.

[0121] 7) Place the HfB2-SiC-MoSi2 pre-coated PC-SiC-C / C curved surface sample with a resin carbon barrier layer at the corners, convex side up, in a graphite crucible with a 6mm thick layer of mixed powder at the bottom. Continue adding mixed powder until the powder covers the sample by 6mm. Then, place the sealed graphite crucible in a heat treatment furnace and heat it to 1600℃ at a rate of 10℃ / min under vacuum conditions, hold it at that temperature for 2 hours, and then turn off the power to cool it down. Finally, obtain the HfB2-SiC-MoSi2 coated modified PC-SiC-C / C curved surface sample.

[0122] Example 4

[0123] This embodiment includes the following steps:

[0124] 1) The density of the embedded SiC inner coating is 1.7 g / cm³. 3 The curved C / C composite material (PC-SiC-C / C) was ultrasonically cleaned with deionized water for 5 times, with each cleaning time lasting 30 minutes, and then dried in an electric heating drying oven at 70℃ for 8 hours.

[0125] 2) Dissolve 23 wt.% phenolic resin completely in 77 wt.% anhydrous ethanol to obtain phenolic resin solution A; dissolve 12 wt.% phenolic resin completely in 88 wt.% anhydrous ethanol to obtain phenolic resin solution B; then add 35 wt.% SiC, 45 wt.% HfB2, and 20 wt.% MoSi2 to phenolic resin solution B to obtain HfB2-SiC-MoSi2-phenolic resin slurry 1; add 40 wt.% SiC, 40 wt.% HfB2, and 20 wt.% MoSi2 to phenolic resin solution B to obtain HfB2-SiC-MoSi2-phenolic resin slurry 2; place the thoroughly stirred slurry in an ultrasonic cleaner for ultrasonic dispersion until there are no obvious agglomerated particles in the slurry.

[0126] 3) Apply HfB2-SiC-MoSi2-phenolic resin slurry 1 to the corner areas of the cleaned curved PC-SiC-C / C sample using a brush, apply HfB2-SiC-MoSi2-phenolic resin slurry 2 to the remaining areas of the sample surface, and dry in an electric heating drying oven at 70℃ for 20 minutes. Repeat the above brushing-drying steps until the desired thickness of the HfB2-SiC-MoSi2 external coating is obtained.

[0127] 4) Coat the corners of the PC-SiC-C / C curved surface sample coated with HfB2-SiC-MoSi2 external coating with phenolic resin solution A, and dry it in an electric heating drying oven at 70℃ for 20 min to obtain a resin carbon barrier layer.

[0128] 5) Place the coated sample into an Al2O3 boat and put it in a tubular heat treatment furnace. Cure it at 200℃ for 1 hour, and then carbonize it in an argon atmosphere at 900℃ for 2 hours to obtain an HfB2-SiC-MoSi2 pre-coating with a resin carbon barrier layer at the corners.

[0129] 6) Mix 71 wt.% Si powder, 14 wt.% SiC and 15 wt.% C powder and pour them into a ball mill jar and ball mill for 6 hours. Then place them in an electric heating drying oven at 70°C and dry for 12 hours to obtain mixed powder.

[0130] 7) Place the HfB2-SiC-MoSi2 pre-coated PC-SiC-C / C curved surface sample with a resin carbon barrier layer at the corners, convex side up, in a graphite crucible with an 8mm thick layer of Si, SiC, and C powder mixed at the bottom. Continue adding the mixed powder until it covers the sample by 8mm. Then, place the sealed graphite crucible in a heat treatment furnace and heat it to 1600℃ at a rate of 10℃ / min under vacuum conditions, hold it at that temperature for 2 hours, and then turn off the power to cool it down, obtaining the HfB2-SiC-MoSi2 coated modified PC-SiC-C / C curved surface sample.

[0131] Example 5

[0132] The method for improving the uniformity of coating composition on curved C / C composite surfaces according to the present invention includes:

[0133] 1) Prepare single-phase / multi-phase ceramic coatings on the surface of curved C / C composite materials;

[0134] 11) The density of the embedded SiC inner coating is 1.7–1.8 g / cm³. 3 The curved C / C composite material (PC-SiC-C / C) was ultrasonically cleaned with deionized water for 4 times, with each cleaning time lasting 20 minutes, and then dried in an electric heating drying oven at 60℃ for 6 hours.

[0135] 12) Dissolve 10 wt.% of one or more resins selected from phenolic resin, epoxy resin, polyester resin, and furan resin in 60 wt.% anhydrous ethanol to obtain resin solution A;

[0136] A mixture of one or more resins selected from phenolic resin, epoxy resin, polyester resin, and furan resin, containing 5 wt.%, is fully dissolved in 70 wt.% anhydrous ethanol to obtain resin solution B.

[0137] Add one or more of ZrB2 or HfB2, SiC, HfSi2, MoSi2, ZrSi2 and TaSi2 to resin solution B in a ratio of 20wt.%:40wt.%:5wt.% and stir thoroughly. Then place the mixture in an ultrasonic cleaner for ultrasonic dispersion until there are no obvious agglomerated particles in the slurry to obtain a mixed slurry.

[0138] 13) Apply the mixture slurry to the surface of the curved C / C composite material using a brush, and dry it in an electric heating drying oven at 60°C for 10 minutes. Repeat the above brushing-drying steps until a ceramic coating of the required thickness is obtained on the surface of the curved C / C composite material.

[0139] 2) Prepare a resin carbon barrier layer on the surface of the specimen obtained in step 1);

[0140] 21) Coat the corners of the specimen obtained in step 1) with resin solution A and dry it in an electric heating drying oven at 60°C for 10 minutes to obtain a resin carbon barrier layer.

[0141] 22) Place the specimen obtained in step 21) into an Al2O3 boat and place it in a tubular heat treatment furnace. Then cure it at 150°C for 1 hour and then carbonize it in an argon atmosphere at 900°C for 2 hours to obtain a ceramic pre-coating with a resin carbon barrier layer at the corners.

[0142] 23) Mix 50 wt.% Si powder, 5 wt.% SiC and 10 wt.% C powder and pour them into a ball mill jar and ball mill for 5 hours. Then place them in an electric heating drying oven at 60°C and dry for 10 hours to obtain mixed powder.

[0143] 24) Place the specimen obtained in step 22) in a graphite crucible with a 5 mm thick layer of mixed powder at the bottom, and add more mixed powder to the graphite crucible until the mixed powder covers the specimen by 5-10 mm. Seal the graphite crucible and place it in a heat treatment furnace. Then, heat it to 1500℃ at a rate of 4℃ / min under vacuum conditions and hold it for 1 hour. After that, turn off the power and cool down to obtain a PC-SiC-C / C curved surface specimen with ceramic coating modification.

[0144] Example 6

[0145] The method for improving the uniformity of coating composition on curved C / C composite surfaces according to the present invention includes:

[0146] 1) Prepare single-phase / multi-phase ceramic coatings on the surface of curved C / C composite materials;

[0147] 11) The density of the embedded SiC inner coating is 1.7–1.8 g / cm³. 3 The curved C / C composite material (PC-SiC-C / C) was ultrasonically cleaned with deionized water for 6 times, with each cleaning time lasting 40 minutes, and then dried in an electric heating drying oven at 100℃ for 10 hours.

[0148] 12) Dissolve 30 wt.% of a mixture of one or more resins selected from phenolic resin, epoxy resin, polyester resin, and furan resin in 80 wt.% anhydrous ethanol to obtain resin solution A;

[0149] A mixture of one or more resins selected from phenolic resin, epoxy resin, polyester resin, and furan resin, at a concentration of 20 wt.%, is fully dissolved in 90 wt.% anhydrous ethanol to obtain resin solution B.

[0150] A mixture of one or more of ZrB2 or HfB2, SiC, HfSi2, MoSi2, ZrSi2 and TaSi2 is added to resin solution B in a ratio of 40 wt.%: 60 wt.%: 20 wt.%. After thorough stirring, the mixture is placed in an ultrasonic cleaner for ultrasonic dispersion until there are no obvious agglomerated particles in the slurry, thus obtaining a mixed slurry.

[0151] 13) Apply the mixed slurry to the surface of the curved C / C composite material using a brush, and dry it in an electric heating drying oven at 100°C for 20 minutes. Repeat the above brushing-drying steps until a ceramic coating of the required thickness is obtained on the surface of the curved C / C composite material.

[0152] 2) Prepare a resin carbon barrier layer on the surface of the specimen obtained in step 1);

[0153] 21) Coat the corners of the specimen obtained in step 1) with resin solution A and dry it in an electric heating drying oven at 100°C for 20 minutes to obtain a resin carbon barrier layer.

[0154] 22) Place the specimen obtained in step 21) into an Al2O3 boat and place it in a tubular heat treatment furnace. Then cure it at 200℃ for 2 hours and then carbonize it in an argon atmosphere at 1200℃ for 4 hours to obtain a ceramic pre-coating with a resin carbon barrier layer at the corners.

[0155] 23) Mix 80 wt.% Si powder, 25 wt.% SiC and 25 wt.% C powder and pour them into a ball mill jar and ball mill for 8 hours. Then place them in an electric heating drying oven at 100°C and dry for 16 hours to obtain mixed powder.

[0156] 24) Place the specimen obtained in step 22) in a graphite crucible with a 10 mm thick layer of mixed powder at the bottom, and add more mixed powder to the graphite crucible until the mixed powder covers the specimen by 10 mm. Seal the graphite crucible and place it in a heat treatment furnace. Then, heat it to 1700℃ at a rate of 10℃ / min under vacuum conditions and hold it for 2 hours. After that, turn off the power and cool down to obtain a PC-SiC-C / C curved surface specimen with ceramic coating modification.

[0157] Example 7

[0158] The method for improving the uniformity of coating composition on curved C / C composite surfaces according to the present invention includes:

[0159] 1) Prepare single-phase / multi-phase ceramic coatings on the surface of curved C / C composite materials;

[0160] 11) The density of the embedded SiC inner coating is 1.7–1.8 g / cm³. 3The curved C / C composite material (PC-SiC-C / C) was ultrasonically cleaned with deionized water for 4 times, with each cleaning time lasting 30 minutes, and then dried in an electric heating drying oven at 80℃ for 8 hours.

[0161] 12) Dissolve 200 wt.% of one or more resins selected from phenolic resin, epoxy resin, polyester resin, and furan resin in 70 wt.% anhydrous ethanol to obtain resin solution A;

[0162] A mixture of one or more resins selected from phenolic resin, epoxy resin, polyester resin, and furan resin, at a concentration of 10 wt.%, is fully dissolved in 80 wt.% anhydrous ethanol to obtain resin solution B.

[0163] A mixture of one or more of ZrB2 or HfB2, SiC, HfSi2, MoSi2, ZrSi2 and TaSi2 is added to resin solution B in a ratio of 30 wt.%: 50 wt.%: 10 wt.%. After thorough stirring, the mixture is placed in an ultrasonic cleaner for ultrasonic dispersion until there are no obvious agglomerated particles in the slurry, thus obtaining a mixed slurry.

[0164] 13) Apply the mixture slurry to the surface of the curved C / C composite material using a brush, and dry it in an electric heating drying oven at 80°C for 15 minutes. Repeat the above brushing-drying steps until a ceramic coating of the required thickness is obtained on the surface of the curved C / C composite material.

[0165] 2) Prepare a resin carbon barrier layer on the surface of the specimen obtained in step 1);

[0166] 21) Coat the corners of the specimen obtained in step 1) with resin solution A and dry it in an electric heating drying oven at 80°C for 15 minutes to obtain a resin carbon barrier layer.

[0167] 22) Place the specimen obtained in step 21) into an Al2O3 boat and place it in a tubular heat treatment furnace. Then cure it at 180°C for 1.5 hours and then carbonize it in an argon atmosphere at 1000°C for 3 hours to obtain a ceramic pre-coating with a resin carbon barrier layer at the corners.

[0168] 23) Mix 60 wt.% Si powder, 15 wt.% SiC and 15 wt.% C powder and pour them into a ball mill jar and ball mill for 6 hours. Then place them in an electric heating drying oven at 80°C and dry for 11 hours to obtain mixed powder.

[0169] 24) Place the specimen obtained in step 22) in a graphite crucible with an 8 mm thick layer of mixed powder at the bottom, and add more mixed powder to the graphite crucible until the mixed powder covers the specimen by 8 mm. Seal the graphite crucible and place it in a heat treatment furnace. Then, heat it to 1600℃ at a rate of 8℃ / min under vacuum conditions and hold it for 1.5 h. After that, turn off the power and cool down to obtain a PC-SiC-C / C curved surface specimen with ceramic coating modification.

[0170] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and disclosure of the invention. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0171] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

[0172] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for improving the uniformity of coating composition on curved C / C composite surfaces, characterized in that, Includes the following steps: Single-phase / multi-phase ceramic coatings were prepared on the surface of curved C / C composite materials to obtain specimens; A resin carbon barrier layer was prepared on the surface of the specimen, and then the specimen was subjected to silicon infiltration treatment. The process of preparing single-phase / multi-phase ceramic coatings on the surface of curved C / C composite materials is as follows: 11) Clean and dry the curved C / C composite material; 12) Dissolve resin 1 in anhydrous ethanol A to obtain resin solution A; Resin 2 is dissolved in anhydrous ethanol B to obtain resin solution B. One or more of ZrB2 or HfB2, SiC, HfSi2, MoSi2, ZrSi2 and TaSi2 are added to resin solution B, stirred and ultrasonically dispersed to obtain a mixed slurry. 13) The mixed slurry is coated onto the surface of the curved C / C composite material and dried to obtain a ceramic coating; The process of preparing a resin carbon barrier layer on the surface of the specimen and then performing silicon infiltration treatment on the specimen is as follows: 21) Coat the corners of the specimen with resin solution A and then dry it to obtain a resin carbon barrier layer; 22) The specimen obtained in step 21) is cured at 150~200 ℃ and then carbonized in an argon atmosphere at 900~1200 ℃ to obtain a ceramic pre-coating with a resin carbon barrier layer at the corners. 23) Prepare the mixed powder; 24) Place the specimen obtained in step 22) in a graphite crucible with a 5-10 mm thick layer of mixed powder at the bottom, and add more mixed powder to the graphite crucible until the mixed powder covers the specimen by 5-10 mm. Then seal the graphite crucible, and heat it to 1500-1700 ℃ under vacuum conditions, hold it at the temperature, and then cool it down. Resin 1 or Resin 2 is a mixture of one or more resins selected from phenolic resin, epoxy resin, polyester resin and furan resin.

2. The method for improving the uniformity of coating composition on curved C / C composite material surfaces according to claim 1, characterized in that, The mass ratio of resin 1 to anhydrous ethanol A is 10~30:60~80.

3. The method for improving the uniformity of coating composition on curved C / C composite material surfaces according to claim 1, characterized in that, The mass ratio of the resin 2, anhydrous ethanol B, ZrB2 or HfB2, SiC and one or more of HfSi2, MoSi2, ZrSi2 and TaSi2 is 5~20:70~90:20~40:40~60:5~20.

4. The method for improving the uniformity of coating composition on curved C / C composite material surfaces according to claim 1, characterized in that, The operation process of step 23) is as follows: Si powder, SiC and C powder are mixed and then ball-milled, and then dried to obtain a mixed powder.

5. The method for improving the uniformity of coating composition on curved C / C composite material surfaces according to claim 1, characterized in that, The mass ratio of Si powder, SiC and C powder is 50~80:5~25:10~25.

6. The method for improving the uniformity of coating composition on curved C / C composite material surfaces according to claim 1, characterized in that, Heating was carried out under vacuum at a rate of 4–10 °C / min to 1500–1700 °C.

7. A surface coating for curved C / C composite materials, characterized in that, It is prepared based on the method for improving the uniformity of coating composition on the surface of curved C / C composite materials according to any one of claims 1-6.

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