A C / C composite material anti-oxidation ablation coating prepared by polymer-converted ceramics, and its preparation method and application

Abstract

The present invention discloses an anti-oxidation ablation coating for a C / C composite material prepared using polymer-converted ceramics, as well as a preparation method and application thereof, and relates to the technical field of surface coatings. The method comprises preparing polymer-converted ceramic powder; uniformly mixing SiC powder in a phenolic resin ethanol solution to obtain slurry A; uniformly mixing SiC powder and polymer-converted ceramic powder in a phenolic resin ethanol solution to obtain slurry B; sequentially applying slurry A and slurry B to the surface of a C / C composite material; and heat-treating the C / C composite material with a pre-coated layer in an inert atmosphere to obtain an anti-oxidation ablation coating on the surface of the C / C composite material. The present invention introduces polymer-converted ultrahigh temperature ceramics onto the surface of a C / C composite material by slurry coating combined with a high-temperature vapor phase siliconization method to obtain a silicon-rich ceramic coating. The preparation process has low cost, simple process, high quality reliability, and strong designability.

Description

Technical Field

[0001] The present invention relates to the technical field of surface coatings, and in particular to a C / C composite material anti-oxidation ablation coating prepared by polymer-converted ceramics, and a preparation method and application thereof. Background Art

[0002] In recent years, the rapid development of aerospace technology has placed increasingly stringent demands on the ultra-high-temperature structural materials required for thermal protection systems. Aircraft components must not only withstand the erosion of high-speed particles and gas streams, and extreme high temperatures, but also overcome lateral and shear stresses. This demanding service environment requires ultra-high-temperature structural materials to possess high-temperature resistance, oxidation and ablation resistance, excellent mechanical properties, and low density.

[0003] Carbon / carbon (C / C) composites are the only composite materials currently suitable for temperatures above 3000°C due to their low density, high specific strength, low coefficient of thermal expansion, and excellent thermal stability (thermal shock and ablation resistance) and mechanical strength at temperatures exceeding 2000°C. However, like other carbonaceous materials, C / C composites suffer from a critical drawback: high oxidation sensitivity in high-temperature, aerobic environments. Studies have shown that the initial oxidation temperature of C / C composites in air is only 370°C, and rapid oxidation occurs above 500°C. Severe oxidation significantly degrades the mechanical properties of C / C composites, limiting their application in high-temperature, oxidizing environments. Currently, the development of high-temperature oxidation-resistant coatings on the material surface, predicated on preventing contact and diffusion of oxygen-containing gases, is considered an effective means of providing long-term protection for C / C composites at temperatures above 2000°C.

[0004] Slurry coating combined with high-temperature vapor-phase siliconization can produce dense, substrate-bonded silicon-rich coatings on C / C composites. Typically, researchers use inorganic ceramic powders as raw materials and dissolve them in anhydrous ethanol to create the coating slurry. However, neither nano- nor micro-sized powders can be completely dissolved to produce a slurry with uniform solute content and stable suspension. Due to the inhomogeneity and instability of the slurry, achieving a pre-coating with the desired thickness and low porosity is difficult in practice. Summary of the Invention

[0005] In response to the shortcomings of the aforementioned background technology, the present invention primarily addresses the uniformity and stability issues of ceramic slurries, as well as the interfacial compatibility issues between anti-oxidation and ablative coatings and C / C composite materials. The present invention provides an anti-oxidation and ablative coating for C / C composite materials prepared using polymer-converted ceramics, as well as a preparation method and application thereof. This method utilizes slurry coating combined with high-temperature vapor-phase siliconization to introduce polymer-converted ultrahigh-temperature ceramics onto the surface of a C / C composite material to produce a silicon-rich ceramic coating. The preparation process is low-cost, simple, highly reliable, and highly designable.

[0006] The first object of the present invention is to provide a method for preparing a C / C composite material anti-oxidation ablation coating prepared by polymer-converted ceramics, comprising the following steps:

[0007] Preparation of polymer-converted ceramic powder;

[0008] The SiC powder was uniformly mixed in the phenolic resin ethanol solution to obtain slurry A;

[0009] The SiC powder and the polymer-converted ceramic powder are uniformly mixed in the phenolic resin ethanol solution to obtain slurry B;

[0010] After slurry A and slurry B are sequentially applied to the surface of the C / C composite material, they are sequentially cured and carbonized to obtain a pre-coating layer on the surface of the C / C composite material; wherein, after slurry A is applied to the surface of the C / C composite material and dried, slurry B is then applied;

[0011] The C / C composite material with a pre-coating is treated in an inert atmosphere at 1800-2150° C. for 15-30 minutes to obtain an anti-oxidation and ablation coating on the surface of the C / C composite material.

[0012] Preferably, the polymer-converted ceramic powder is prepared according to the following steps:

[0013] Silane polymer and transition metal polymer are mixed in a certain proportion and dissolved in xylene solution. After being evenly mixed at 70-90° C., they are treated in an inert atmosphere at 250-400° C. for 2-4 hours to obtain polymer-converted ceramic powder.

[0014] Preferably, the transition metal element in the transition metal polymer is Hf, Zr, Ti or Ta.

[0015] The mass ratio of the transition metal polymer to the silane polymer is 1:1.5-2.

[0016] Preferably, the curing temperature is 200-300° C., and the curing time is 2-4 hours; the carbonization temperature is 900-1100° C., and the carbonization time is 2-4 hours.

[0017] Preferably, the density of the C / C composite material is 1.60-1.85 g / cm 3 .

[0018] Preferably, the phenolic resin ethanol solution is prepared by mixing phenolic resin and anhydrous ethanol in a mass ratio of 1:5 to 7.

[0019] Preferably, in the slurry A, the mass fraction of the SiC powder is 30 to 50 wt%.

[0020] Preferably, in the slurry B, the mass fraction of the SiC is 10-20 wt %, and the mass fraction of the polymer-converted ceramic powder is 20-40 wt %.

[0021] The second object of the present invention is to provide a C / C composite material anti-oxidation and ablation coating.

[0022] The third object of the present invention is to provide an application of a coating in the anti-oxidation and ablation of C / C composite materials.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention provides a C / C composite material anti-oxidation ablative coating prepared by polymer-to-ceramic conversion, as well as a preparation method and application thereof. The method first uses the Schlenk technique to prepare a silicon-based single-source polymer containing transition metal elements, followed by sequentially obtaining a ceramic powder having a unique "capsule-like" nanostructure through low-temperature crosslinking, cracking, and high-temperature heat treatment. Secondly, an anti-oxidation ablative coating is prepared on the surface of the C / C composite material by slurry coating combined with a high-temperature vapor-phase siliconization method. The slurry coating process regulates the structure and thickness of the anti-oxidation ablative coating by adjusting the slurry components, slurry component content, and number of coatings. With the strong penetrating ability of silicon vapor during the high-temperature vapor-phase siliconization process, it can easily penetrate the pre-coating layer to reach the C / C substrate and react to form a jagged SiC transition layer at the interface, thereby improving the bonding strength between the coating and the C / C substrate and the density of the coating.

[0025] This invention proposes a method for preparing an anti-oxidation and ablative coating for a C / C composite material using polymer-converted ceramics. First, a multi-element single-source polymer is prepared using the Schlenk technique. This is then cross-linked and cured at a specific temperature to produce an amorphous polymer-converted ceramic powder. Next, the polymer-converted ultrahigh-temperature ceramic is introduced onto the surface of the C / C composite material through a slurry coating combined with high-temperature vapor-phase siliconization to produce a silicon-rich ceramic coating.

[0026] The method provided by the invention has low preparation process cost, simple process, high quality reliability and strong designability.

[0027] The present invention utilizes a high-temperature vapor-phase siliconization method to provide a suitable high-temperature environment for converting silicon blocks into silicon vapor. Thanks to its strong penetrability, gaseous silicon can easily penetrate the porous pre-coating layer and reach the C / C substrate for reaction. Simultaneously, the amorphous carbon layer on the exterior of the polymer-converted ceramic powder particles introduced into the pre-coating layer also reacts in situ with the gaseous silicon. This reaction not only resolves the interfacial compatibility issue between the anti-oxidation and ablative coating and the C / C composite material, but also, because these reactions are accompanied by volume expansion of the pre-coating components, facilitates the ultimate production of a dense, anti-ablative coating.

[0028] The present invention leverages the "scab" effect of oxidation expansion of multiple components in the coating to quickly repair defects such as cracks and pores in the coating in a high-temperature aerobic environment, thereby improving the anti-oxidation and ablation performance of the C / C composite material and laying the foundation for stable service in harsh environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The process flow chart of the present invention is as follows: (a) preparing a single-source polymer-converted ceramic powder, (b) preparing a polymer-converted ceramic surface coating on a C / C composite material;

[0030] Figure 2 SEM images of single-source polymer-converted ceramics obtained after heat treatment at different temperatures: (a) 900°C, (b) 1900°C;

[0031] Figure 3 SEM images of the pre-coating sample obtained after curing and carbonization provided in Example 1: (a) surface SEM image, (b) cross-sectional SEM image;

[0032] Figure 4 SEM photos of the coating sample obtained after slurry coating combined with high-temperature vapor siliconization in Example 1: (a) surface SEM photo, (b) cross-sectional SEM photo;

[0033] Figure 5 This is a photograph of the surface macromorphology of the coating provided in Example 1 after plasma ablation. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below with reference to specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0035] Ceramic precursors are typically polymers, which, due to their excellent molecular solubility in solvents and strong liquid suspension stability, can be used to address the uniformity and stability issues of ceramic slurries. Furthermore, pyrolysis after slurry application can convert the polymers into ceramics (PDCs), resulting in a uniformly dispersed nanopowder, making it easy to obtain solid coatings or films with controllable thickness and porosity.

[0036] The polymer conversion to ceramics (PDCs) method involves crosslinking, curing, and then pyrolyzing a synthesized polymer precursor to achieve ceramicization. By introducing heterogeneous elements into organic polymers to synthesize a single-source precursor, nanocomposite ceramics can be prepared using the PDCs method. Unlike directly introducing two or more precursor powders into a slurry and allowing them to react during high-temperature vapor siliconization to form the target ceramic, this method allows for the molecular-level structural design of the polymer precursor introduced into the slurry. By modifying the polymer with organic molecules such as metal alkoxides or acetylacetonates, polycondensation reactions such as dehydration and addition occur, integrating various metal elements into the silane-based polymer structure and improving the polymer's structural stability. After cracking, nanocomposite ceramics with small grain size and low oxygen content are obtained. After further high-temperature annealing, PDCs exhibit a unique microstructure, manifesting as a "capsule-like" core-shell structure with an amorphous carbon shell and a highly crystalline ceramic core. Based on this, if combined with the high-temperature vapor-phase siliconization process, gaseous silicon can react in situ with the PDC amorphous carbon layer in the pre-coating to form SiC, which can not only improve the density of the coating, but also ensure that the coating has excellent anti-oxidation and ablation properties.

[0037] A first aspect of the present invention provides a method for preparing an anti-oxidation ablative coating of a C / C composite material by using polymer-converted ceramics, comprising the following steps:

[0038] Preparation of polymer-converted ceramic powder;

[0039] The SiC powder was uniformly mixed in the phenolic resin ethanol solution to obtain slurry A;

[0040] The SiC powder and the polymer-converted ceramic powder are uniformly mixed in the phenolic resin ethanol solution to obtain slurry B;

[0041] The phenolic resin ethanol solution is prepared by mixing phenolic resin and anhydrous ethanol in a mass ratio of 1:5 to 7;

[0042] Slurry A and slurry B are sequentially applied to the surface of the C / C composite material, and then cured and carbonized to obtain a pre-coating layer on the surface of the C / C composite material; wherein slurry A is applied to the surface of the C / C composite material and dried, and then slurry B is applied; wherein the curing temperature is 200-300°C and the curing time is 2-4 hours; the carbonization temperature is 900-1100°C and the carbonization time is 2-4 hours;

[0043] The C / C composite material with a pre-coating is treated in an inert atmosphere at 1800-2150° C. for 15-30 minutes to obtain an anti-oxidation and ablation coating on the surface of the C / C composite material.

[0044] The present invention introduces polymer-converted ultra-high temperature ceramics onto the surface of a C / C composite material through slurry coating combined with a high-temperature vapor-phase siliconization method to prepare a silicon-rich ceramic coating. The preparation process has low cost, simple process, high quality reliability, and strong designability. The high-temperature vapor-phase siliconization method can make the gaseous silicon have strong penetrability. It can easily penetrate the porous pre-coating layer to reach the C / C matrix to react. At the same time, the amorphous carbon layer on the outside of the polymer-converted ceramic powder particles introduced into the pre-coating layer can also react in situ with the gaseous silicon. The occurrence of this reaction is accompanied by the volume expansion of the components in the pre-coating layer, and can also help to finally prepare a dense anti-ablation coating.

[0045] It should be noted that the density is 1.60-1.85g / cm 3 C / C composite materials are used as matrix materials.

[0046] The polymer-converted ceramic powder is prepared according to the following steps:

[0047] A silane polymer and a transition metal polymer are mixed in a specific ratio and dissolved in a xylene solution. After uniform mixing at 70-90°C, the mixture is treated in an inert atmosphere at 250-400°C for 2-4 hours to obtain a polymer-converted ceramic powder. The polymer-converted ceramic powder is prepared using the Schlenk technique to prepare a multi-element single-source polymer. This is then cross-linked and cured at a specific temperature to produce an amorphous polymer-converted ceramic powder.

[0048] Specifically, the transition metal element in the transition metal polymer is Hf, Zr, Ti or Ta.

[0049] The transition metal polymer may be a hafnium-containing organic polymer such as hafnium acetylacetonate and tetrakis(diethylamide)hafnium, a zirconium-containing organic polymer such as zirconium acetylacetonate and tetrakis(dimethylamino)zirconium, or tetrabutyl titanate.

[0050] The silane polymer may be polycarbosilane (PCS), polysilazane (PSZ), silicon boron carbon nitride (SiBCN), or the like.

[0051] The mass ratio of the transition metal polymer to the silane polymer is 1:1.5-2.

[0052] In the slurry A, the mass fraction of the SiC powder is 30-50 wt%.

[0053] In the slurry B, the mass fraction of the SiC is 10-20 wt %, and the mass fraction of the polymer-converted ceramic powder is 20-40 wt %.

[0054] In one embodiment, a method for preparing a C / C composite anti-oxidation ablation coating by using polymer-converted ceramics is described in Figure 1 As shown, specifically including:

[0055] Step 1: A silane polymer and a transition metal polymer are mixed in a certain proportion and dissolved in a xylene solution, and then stirred thoroughly at 70-90°C for more than 3 hours. Subsequently, the mixture is cross-linked and cured at 250-400°C for more than 2 hours. The treatment is performed in an argon atmosphere in a Schlenk apparatus to obtain a single-source polymer powder that meets coating requirements.

[0056] Step 2: ultrasonically clean the C / C composite material with deionized water and dry it in an electric heated blast drying oven at a temperature of 80-100° C. for more than 4 hours;

[0057] Step 3: Immerse the C / C composite material into slurry A and let it stand for 5 to 10 seconds, then take it out and dry it. Repeat this process several times to obtain the SiC inner coating.

[0058] Step 4: Immerse the C / C composite material with the SiC inner coating into slurry B, let it stand for 5 to 10 seconds, and then dry. Repeat this process several times to obtain the outer coating.

[0059] Step 5: Curing the C / C composite material pre-coated with the above slurry and dried at 200-300° C. for more than 2 hours, and then carbonizing it at 900-1100° C. for more than 2 hours in an argon atmosphere to obtain a pre-coating layer;

[0060] Step 6: Place the C / C composite material with the pre-coating layer on a porous graphite plate, and place the whole into a graphite crucible with a certain number of silicon blocks at the bottom. Perform vapor siliconization treatment under the protection of an argon atmosphere at a temperature of 1800-2150°C for 15-30 minutes to obtain a double-layer anti-oxidation and ablation coating on the surface of the C / C composite material.

[0061] The mixed solution in step 1 comprises a transition metal-containing polymer and a silane-based polymer mixed in a mass ratio of 1:1.5-2, with xylene as the solvent, and the mass concentration of the solute in the mixed solution is 50 wt %. The transition metal element may be Hf, Zr, Ti, or Ta, etc.

[0062] The slurry A in step 3 comprises: mixing phenolic resin and anhydrous ethanol in a mass ratio of 1:6, and obtaining a uniformly stirred phenolic resin solution after ultrasonic treatment; adding SiC powder to the phenolic resin solution, and obtaining SiC-phenolic resin slurry A after sufficient stirring, wherein the mass fraction of SiC powder is 30-50wt%.

[0063] The slurry B in step 4 comprises: adding SiC powder and the single-source polymer powder prepared in step 1 to the phenolic resin solution, stirring evenly to obtain slurry B, wherein the mass fraction of SiC is 10-20wt%, and the mass fraction of the single-source polymer powder is 20-40wt%.

[0064] A second aspect of the present invention provides a C / C composite anti-oxidation ablative coating. The coating has a double-layer structure, comprising a SiC inner coating and an anti-oxidation ablative outer coating. The SiC inner coating is used to mitigate thermal mismatch between the coating and the substrate.

[0065] A third aspect of the present invention provides an application of a coating in the anti-oxidation and ablation of a C / C composite material.

[0066] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0067] Example 1

[0068] A method for preparing a C / C composite material anti-oxidation ablation coating by using polymer-converted ceramics comprises the following steps:

[0069] Step 1, see Figure 1 As shown in (a), a single-source polymer-converted ceramic powder is prepared:

[0070] 1) First, add a magnet and an appropriate amount of zeolite to a three-necked flask. Next, weigh 40g of polysilazane into the flask, then add 20g of the weighed ZrC polymer precursor. Finally, add 60g of xylene to the flask to create a mixed solution. Then, apply vacuum grease to all interfaces of the Schlenk apparatus to ensure a good airtightness after connection.

[0071] 2) Next, open the vacuum pump valve to remove air and residual moisture from the apparatus. When the vacuum gauge indicates a vacuum of -0.9 MPa, turn off the vacuum pump and wait for 5 minutes to maintain pressure. If the vacuum gauge reading does not change during this period, the apparatus is considered airtight and can proceed to the next step. Now, slowly turn the valve on the double-row tube in the Schlenk apparatus to fill with argon for the first purge. Repeat the above vacuum pumping and argon filling steps three times to ensure a water- and oxygen-free environment within the apparatus.

[0072] 3) Increase the argon flow rate and turn on the magnetic stirrer at the bottom of the three-necked flask to heat and stir. The heating and stirring temperature is 80°C and the reaction time is 3 hours.

[0073] 4) After heating and stirring, lower the temperature of the heating platform at the bottom of the three-necked flask to 60°C and maintain it there. Simultaneously, introduce condensed water into the condenser connected to the top of the flask for cooling. Slowly open the vacuum pump valve to remove the remaining solvent in the flask.

[0074] 5) The solvent-removed reactant was taken out from the three-necked flask, placed in a tube furnace at 300° C. for cross-linking and curing, and kept warm for 2 hours in an argon atmosphere. The cured polymer-converted ceramic powder was then collected.

[0075] Step 2, see Figure 1 As shown in (b), the coating is prepared by slurry coating combined with high-temperature vapor siliconization:

[0076] 1) The density is 1.75g / cm 3 The C / C block was processed into a cylindrical sample with a size of φ20mm×5mm, and after ultrasonic cleaning with deionized water and drying in an electric heated forced air drying oven at a temperature of 90℃, a C / C substrate for subsequent coating preparation was obtained.

[0077] 2) 30 wt % of SiC and 10 wt % of phenolic resin were dissolved in 60 wt % of anhydrous ethanol, and slurry A was obtained after sufficient stirring and ultrasonic treatment.

[0078] 3) Immerse the C / C substrate in slurry A and let it stand for 5 seconds. Take it out and dry it. Repeat this process 4 times.

[0079] 4) 15 wt% of SiC, 30 wt% of polymer-converted ceramic powder, and 5 wt% of phenolic resin were dissolved in 50 wt% of anhydrous ethanol, and slurry B was obtained after sufficient stirring and ultrasonic treatment.

[0080] 5) Immerse the C / C substrate coated with slurry A and dried into slurry B and let it stand for 5 seconds. Take it out and dry it. Repeat this process 4 times.

[0081] 6) The coated sample was cured at 300° C. for 2 h, and then carbonized at 900° C. under argon atmosphere for 2 h to obtain a pre-coated sample.

[0082] 7) The C / C composite material with the pre-coating layer was placed on a porous graphite plate and then placed in a graphite crucible with a certain amount of silicon blocks at the bottom. The temperature was then raised to 1880°C under the protection of an argon atmosphere and kept at this temperature for 20 minutes for vapor phase siliconization treatment, thereby obtaining an anti-oxidation and ablation coating on the surface of the C / C composite material.

[0083] Step 3: Plasma flame ablation test coating:

[0084] At a heat flux density of 6.65MW / m 2 The sample was ablated under a plasma flame for 30 seconds, with a linear ablation rate of 0.33 μm / s. During the process, the argon flow rate was 60 slpm, the hydrogen flow rate was 1 slpm, and the vertical distance between the flame spray gun nozzle and the sample surface was 40 mm. The surface temperature of the coating sample exceeded 3000°C.

[0085] Example 2

[0086] A method for preparing a C / C composite material anti-oxidation ablation coating by using polymer-converted ceramics comprises the following steps:

[0087] Step 1: Preparation of single-source polymer-converted ceramic powder:

[0088] 1) First, add a magnet and an appropriate amount of zeolite to a three-necked flask. Next, weigh 40g of polysilazane into the flask, and then add 20g of the weighed HfC polymer precursor. Finally, add 60g of xylene to the flask to create a mixed solution. Then, apply vacuum grease to all interfaces of the Schlenk apparatus to ensure a good airtightness after connection.

[0089] 2) Next, open the vacuum pump valve to remove air and residual moisture from the apparatus. When the vacuum gauge indicates a vacuum of -0.9 MPa, turn off the vacuum pump and wait for 5 minutes to maintain pressure. If the vacuum gauge reading does not change during this period, the apparatus is considered airtight and can proceed to the next step. Now, slowly turn the valve on the double-row tube in the Schlenk apparatus to fill with argon for the first purge. Repeat the above vacuum pumping and argon filling steps three times to ensure a water- and oxygen-free environment within the apparatus.

[0090] 3) Increase the argon flow rate and turn on the magnetic stirrer at the bottom of the three-necked flask to heat and stir. The heating and stirring temperature is 70°C and the reaction time is 3 hours.

[0091] 4) After heating and stirring, lower the temperature of the heating platform at the bottom of the three-necked flask to 60°C and maintain it there. Simultaneously, introduce condensed water into the condenser connected to the top of the flask for cooling. Slowly open the vacuum pump valve to remove the remaining solvent in the flask.

[0092] 5) The solvent-removed reactant was taken out from the three-necked flask, placed in a tube furnace at 250° C. for cross-linking and curing, and kept warm for 2 hours in an argon atmosphere. The cured polymer-converted ceramic powder was then collected.

[0093] Step 2: Slurry coating combined with high temperature vapor phase siliconization to prepare the coating:

[0094] 1) The density is 1.80g / cm 3 The C / C block was processed into a cylindrical sample with a size of φ20mm×5mm, and after ultrasonic cleaning with deionized water and drying in an electric heated blast drying oven at a temperature of 90℃, a C / C substrate for subsequent coating preparation was obtained.

[0095] 2) 30 wt % of SiC and 10 wt % of phenolic resin were dissolved in 60 wt % of anhydrous ethanol, and slurry A was obtained after sufficient stirring and ultrasonic treatment.

[0096] 3) Immerse the C / C substrate in slurry A and let it stand for 5 seconds. Take it out and dry it. Repeat this process 4 times.

[0097] 4) 20 wt% of SiC, 40 wt% of polymer-converted ceramic powder, and 3 wt% of phenolic resin were dissolved in 37 wt% of anhydrous ethanol, and slurry B was obtained after sufficient stirring and ultrasonication.

[0098] 5) Immerse the C / C substrate coated with slurry A and dried into slurry B and let it stand for 5 seconds. Take it out and dry it. Repeat this process 5 times.

[0099] 6) The coated sample was cured at 300° C. for 2 h, and then carbonized at 900° C. under argon atmosphere for 2 h to obtain a pre-coated sample.

[0100] 7) The C / C composite material with the pre-coating layer is placed on a porous graphite plate and then placed in a graphite crucible with a certain amount of silicon blocks at the bottom. The temperature is then raised to 1900°C under the protection of an argon atmosphere and kept at this temperature for 15 minutes for vapor phase siliconization treatment, thereby obtaining an anti-oxidation and ablation coating on the surface of the C / C composite material.

[0101] Step 3: Plasma flame ablation test coating:

[0102] At a heat flux density of 6.65MW / m 2The coating sample was ablated under a plasma flame for 90 seconds, with a linear ablation rate of -0.167 μm / s. During the process, the argon gas flow rate was 60 slpm, the hydrogen gas flow rate was 1 slpm, and the vertical distance between the flame spray gun nozzle and the sample surface was 40 mm. At this time, the surface temperature of the coating sample exceeded 3000°C.

[0103] Example 3

[0104] A method for preparing a C / C composite material anti-oxidation ablation coating by using polymer-converted ceramics comprises the following steps:

[0105] Step 1: Preparation of single-source polymer-converted ceramic powder:

[0106] 1) First, add the magnet and an appropriate amount of zeolite to a three-necked flask. Next, weigh 40g of polysilazane into the flask, add 20g of tetrabutyl titanate, and then add 60g of xylene to the flask to create a mixed solution. Then, apply vacuum grease to all interfaces of the Schlenk apparatus to ensure a good airtightness after connection.

[0107] 2) Next, open the vacuum pump valve to remove air and residual moisture from the apparatus. When the vacuum gauge indicates a vacuum of -0.9 MPa, turn off the vacuum pump and wait for 5 minutes to maintain pressure. If the vacuum gauge reading does not change during this period, the apparatus is considered airtight and can proceed to the next step. Now, slowly turn the valve on the double-row tube in the Schlenk apparatus to fill with argon for the first purge. Repeat the above vacuum pumping and argon filling steps three times to ensure a water- and oxygen-free environment within the apparatus.

[0108] 3) Increase the argon flow rate and turn on the magnetic stirrer at the bottom of the three-necked flask to heat and stir. The heating and stirring temperature is 80°C and the reaction time is 3 hours.

[0109] 4) After heating and stirring, lower the temperature of the heating platform at the bottom of the three-necked flask to 70°C and maintain it there. Simultaneously, introduce condensed water into the condenser connected to the top of the flask for cooling. Slowly open the vacuum pump valve to remove the remaining solvent in the flask.

[0110] 5) The solvent-removed reactant was taken out from the three-necked flask, placed in a tube furnace at 250° C. for cross-linking and curing, and kept warm for 2 hours in an argon atmosphere. The cured polymer-converted ceramic powder was then collected.

[0111] Step 2: Slurry coating combined with high temperature vapor phase siliconization to prepare the coating:

[0112] 1) The density is 1.85g / cm 3The C / C block was processed into a cylindrical sample with a size of φ20mm×5mm, and after ultrasonic cleaning with deionized water and drying in an electric heated blast drying oven at a temperature of 90℃, a C / C substrate for subsequent coating preparation was obtained.

[0113] 2) 30 wt % of SiC and 10 wt % of phenolic resin were dissolved in 60 wt % of anhydrous ethanol, and slurry A was obtained after sufficient stirring and ultrasonic treatment.

[0114] 3) Immerse the C / C substrate in slurry A and let it stand for 5 seconds. Take it out and dry it. Repeat this process 4 times.

[0115] 4) 18 wt% of SiC, 36 wt% of polymer-converted ceramic powder, and 6 wt% of phenolic resin were dissolved in 40 wt% of anhydrous ethanol, and slurry B was obtained after sufficient stirring and ultrasonication.

[0116] 5) Immerse the C / C substrate coated with slurry A and dried into slurry B and let it stand for 5 seconds. Take it out and dry it. Repeat this process 5 times.

[0117] 6) The coated sample was cured at 300° C. for 2 h, and then carbonized at 900° C. under argon atmosphere for 2 h to obtain a pre-coated sample.

[0118] 7) The C / C composite material with the pre-coating layer was placed on a porous graphite plate and then placed in a graphite crucible with a certain amount of silicon blocks at the bottom. The temperature was then raised to 1860°C under the protection of an argon atmosphere and kept at this temperature for 25 minutes for vapor phase siliconization treatment, thereby obtaining an anti-oxidation and ablation coating on the surface of the C / C composite material.

[0119] Step 3: Plasma flame ablation test coating:

[0120] At a heat flux density of 6.65MW / m 2 The sample was ablated under a plasma flame for 120 seconds, with a linear ablation rate of -0.25 μm / s. During the process, the argon flow rate was 60 slpm, the hydrogen flow rate was 1 slpm, and the vertical distance between the flame spray gun nozzle and the sample surface was 40 mm. The surface temperature of the coating sample exceeded 3000°C.

[0121] The coatings in all examples have low linear ablation rates and exhibit excellent anti-ablation performance.

[0122] In order to illustrate the relevant performance of the anti-oxidation and ablation coating obtained on the surface of the C / C composite material provided by the present invention, Example 1 is taken as an example with reference to the accompanying drawings.

[0123] Figure 2 SEM images of single-source polymer-converted ceramics obtained after heat treatment at different temperatures: (a) 900℃, (b) 1900℃; Figure 2 As can be seen, the morphology of the ceramic powders converted from single-source polymers changes significantly with increasing heat treatment temperature. The surface of the ceramic particles changes from a smooth and dense structure to a rough structure with numerous micropores (pore diameter approximately 1 μm). This is caused by the pyrolysis of the single-source polymer within this temperature range, releasing a large number of small molecules and gaseous products.

[0124] Figure 3 SEM photos of the pre-coating sample obtained after curing and carbonization provided in Example 1: (a) surface SEM photo, (b) cross-sectional SEM photo; Figure 3 The pre-coating is approximately 270 μm thick, has a distinct double-layer structure, and is loose and porous. The pre-coating surface is dotted with numerous microcracks and pores, which could provide infiltration pathways for the gaseous silicon densified coating during the subsequent high-temperature vapor siliconization process.

[0125] Figure 4 SEM photos of the coating sample obtained after slurry coating combined with high-temperature vapor siliconization in Example 1: (a) surface SEM photo, (b) cross-sectional SEM photo; Figure 4 It can be seen that after high temperature vapor phase siliconization, Figure 3 The defects found within the pre-coating layer were almost completely eliminated. Simultaneously, the double-layer structure of the coating layer disappeared, and a dense SiC-PDCs coating was formed with the assistance of silicon infiltration. Furthermore, gaseous silicon has a strong permeability, easily penetrating the porous pre-coating layer to the interface between the C / C substrate and the coating layer, where it reacts and ultimately forms a jagged SiC-Si transition layer.

[0126] Figure 5 This is a macroscopic photo of the surface morphology of the coating after plasma ablation provided in Example 1. Figure 5 It can be seen that after plasma ablation for 30s, 90s and 120s, the coating structure on the sample surface is still intact, and no defects such as obvious pits and macro cracks appear on the surface, indicating that the sample has good anti-ablation performance.

[0127] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a C / C composite material anti-oxidation ablative coating by using polymer-converted ceramics, characterized in that: The following steps are involved: Preparation of polymer-converted ceramic powder; The SiC powder was uniformly mixed in the phenolic resin ethanol solution to obtain slurry A; The SiC powder and the polymer-converted ceramic powder are uniformly mixed in the phenolic resin ethanol solution to obtain slurry B; After slurry A and slurry B are sequentially applied to the surface of the C / C composite material, they are sequentially cured and carbonized to obtain a pre-coating layer on the surface of the C / C composite material; wherein, after slurry A is applied to the surface of the C / C composite material and dried, slurry B is then applied; The C / C composite material with a pre-coating layer is placed on a porous graphite plate and then placed in a graphite crucible with a certain amount of silicon blocks at the bottom. The C / C composite material is subjected to a vapor phase siliconization treatment under the protection of an argon atmosphere at a temperature of 1800-2150°C for 15-30 minutes to obtain an anti-oxidation and ablation coating on the surface of the C / C composite material. The polymer-converted ceramic powder is prepared according to the following steps: The silane polymer and the transition metal polymer are mixed in a certain proportion and dissolved in a xylene solution. After being mixed evenly at 70-90°C, the mixture is treated in an inert atmosphere at 250-400°C for 2-4 hours to obtain a polymer-converted ceramic powder. The transition metal element in the transition metal polymer is Hf, Zr, Ti or Ta; The mass ratio of the transition metal polymer to the silane polymer is 1:1.5-2.

2. The method for preparing a C / C composite material anti-oxidation ablation coating by using polymer-converted ceramics according to claim 1, characterized in that: The curing temperature is 200~300℃, and the curing time is 2~4h; the carbonization temperature is 900~1100℃, and the carbonization time is 2~4h.

3. The method for preparing a C / C composite material anti-oxidation ablative coating by using polymer-converted ceramics according to claim 1, characterized in that: The density of the C / C composite material is 1.60-1.85 g / cm 3 .

4. The method for preparing a C / C composite material anti-oxidation ablative coating by using polymer-converted ceramics according to claim 1, characterized in that: The phenolic resin ethanol solution is prepared by mixing phenolic resin and anhydrous ethanol in a mass ratio of 1:5-7.

5. The method for preparing a C / C composite material anti-oxidation ablative coating by using polymer-converted ceramics according to claim 1, characterized in that: In the slurry A, the mass fraction of the SiC powder is 30-50 wt %.

6. The method for preparing a C / C composite material anti-oxidation ablative coating by using polymer-converted ceramics according to claim 1, characterized in that: In the slurry B, the mass fraction of the SiC is 10-20 wt %, and the mass fraction of the polymer-converted ceramic powder is 20-40 wt %.

7. A C / C composite material anti-oxidation and ablation coating prepared by the method according to any one of claims 1 to 6.

8. Use of the coating according to claim 7 in the anti-oxidation and ablation of C / C composite materials.

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