Matrix coating system and method for C / C composite material protection

Abstract

The invention discloses a matrix coating system and method for C / C composite material protection, and belongs to the technical field of ablation resistance of C / C composite materials. According to the preparation method disclosed by the invention, polymer converted ultra-high-temperature ceramic is introduced into a C / C composite material matrix by adopting a precursor impregnation and pyrolysis method, so that the ablation resistance of the matrix is remarkably improved, and a modified coating is prepared on the surface of the modified matrix by combining slurry coating with a high-temperature gas-phase siliconizing process, so that a compact and high-temperature-resistant protective barrier is formed; oxygen, heat and high-speed airflow scouring are effectively isolated, synergistic improvement of the overall ablation resistance is achieved, and the technical problem that due to the fact that the synergistic performance of a modified matrix and coating components is poor, the requirements in an extreme service environment are not met is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of C / C composite material anti-ablation, and in particular relates to a substrate coating system and method for protecting C / C composite materials. Background Art

[0002] In recent years, the continuous pursuit of high thrust-to-weight ratios in aircraft engines has placed higher demands on the performance of engine hot-end components. The surface temperatures of the hot-end components of next-generation high-thrust-to-weight engines will reach over 1700°C, and currently available alloys are unable to withstand such high temperatures. This demanding service environment requires ultra-high-temperature structural materials with high-temperature resistance, oxidation and ablation resistance, excellent mechanical properties, and low density.

[0003] Carbon / carbon (C / C) composites are carbon-based composites reinforced with carbon fibers. They feature low density, high specific strength and modulus, and mechanical properties that increase with increasing temperature. They are considered one of the most ideal thermal structural materials and are widely used in aerospace engine hot-end components. However, C / C composites are highly oxidatively sensitive, leading to oxidative failure in high-temperature (>500°C) aerobic environments, limiting their application.

[0004] Currently, the main technical approaches to improving the high-temperature oxidation and ablation resistance of C / C composites include matrix modification and coating protection. Matrix modification significantly enhances the composite's oxidation and ablation resistance by introducing ultra-high-temperature ceramic components with high melting points and excellent oxidation resistance, such as carbides (HfC, ZrC, TaC, TiC, etc.) and borides (HfB2, ZrB2, TaB2, TiB2, etc.). Coating protection enhances the C / C composite's oxidation and ablation resistance by depositing a coating with excellent ablation resistance on the surface of the composite matrix. This coating isolates the matrix from direct contact between oxygen and flame, inhibiting carbon oxidation reactions, and ultimately improving the composite's oxidation and ablation resistance.

[0005] Prior art researchers have attempted to combine matrix modification and protective coatings to protect C / C composites from high-temperature oxidation and ablation. However, inadequate compositional matching between the modified matrix and the protective coating, particularly when their physical properties, such as thermal expansion coefficients, differ significantly, can lead to reduced coating bond strength, cracking, and even flaking, severely impacting the effectiveness of high-temperature oxidation and ablation protection.

[0006] Furthermore, existing research typically uses a static oxidizing environment at 1700°C as the testing condition, whereas the actual service environment for aircraft engine hot-end components is a dynamic gas-wash environment at 1700°C. Currently, there is limited systematic research on this dynamic environment, and the duration of dynamic gas-wash tests in published literature is typically only around 100 seconds, far below the actual service life requirements for aircraft engine hot-end components and unable to truly reflect the long-term service performance of the material in this environment. Summary of the Invention

[0007] The purpose of the present invention is to provide a substrate coating system and method for protecting C / C composite materials, so as to solve the technical problem that the poor synergistic performance between the modified substrate and the coating components does not meet the requirements of extreme service environments.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a method for preparing a matrix coating system for protecting C / C composite materials, comprising the following steps: S1: immersing the porous low-density C / C composite material in a single-source polymer precursor PCS-Ti solution for vacuum impregnation to obtain a C / C composite material impregnated with the precursor; drying the C / C composite material impregnated with the precursor to obtain a dried C / C composite material impregnated with the precursor; S2: After repeating S1 several times, the obtained dried precursor-impregnated C / C composite is wrapped with graphite paper and then heat-treated; S3: Repeat S1 and S2 several times to obtain matrix-modified C / C composites; S4: Immerse the matrix-modified C / C composite material in slurry A and let it stand, then take it out and dry it. Repeat the above process several times to obtain a modified C / C composite material with a SiC inner coating; S5: Immersing the modified C / C composite material with the SiC inner coating into slurry B and allowing it to stand, then taking it out and drying it, repeating the above process several times, and then sequentially curing and carbonizing it to obtain a modified C / C composite material with a pre-coating layer; S6: performing vapor phase siliconization treatment on the modified C / C composite material with the pre-coating layer to obtain a base coating system for protecting the C / C composite material.

[0009] Furthermore, in S1, the porous low-density C / C composite material is polished, ultrasonically cleaned, and dried in sequence before use; the density of the porous low-density C / C composite material is 1.1-1.3 g / cm 3 .

[0010] Furthermore, in S1, the process parameters of the vacuum impregnation treatment are: vacuuming to -0.08~-0.1MPa, maintaining the pressure for 20~40min; and drying at a temperature of 60~100°C.

[0011] Furthermore, in S2, S1 is repeated 3 to 5 times; the heat treatment is carried out in an inert atmosphere; the process parameters of the heat treatment are: heating to 1400 to 1800°C at a rate of 3 to 5°C / min, keeping warm for 1 to 3 hours, and then cooling to room temperature at a rate of 2 to 4°C / min.

[0012] Furthermore, in S3, S1 and S2 are repeated 10 to 14 times.

[0013] Furthermore, in S4, the preparation process of the slurry A is as follows: Phenolic resin and anhydrous ethanol are mixed in a mass ratio of 1:5-6, and subjected to ultrasonic treatment to obtain a phenolic resin solution. SiC powder is then added to the phenolic resin solution, and stirred to obtain slurry A; the mass fraction of SiC powder in the slurry A is 30-50wt%; The standing time is 5 to 10 seconds; and the number of repetitions is 3 to 4 times.

[0014] Furthermore, in S5, the preparation process of the slurry B is as follows: SiC powder and single-source polymer precursor PSZ-Zr-Ti powder are added to the phenolic resin solution, and the mixture is stirred to obtain slurry B; the mass fraction of SiC in slurry B is 10-20wt%, and the mass fraction of single-source polymer precursor PSZ-Zr-Ti powder is 20-40wt%; The number of repetitions is 6 to 8 times; the curing is performed at 200 to 300° C. for more than 2 hours; the carbonization is performed at 900 to 1100° C. for more than 2 hours; and both the curing and carbonization are performed in an argon atmosphere; The preparation method of the single-source polymer precursor PSZ-Zr-Ti powder is as follows: Polysilazane, zirconium acetylacetonate, and tetrabutyl titanate are mixed and added into xylene to obtain a mixed solution; the mixed solution is reacted under an anhydrous inert atmosphere, and then heated and stirred, and the heating and heat preservation are maintained to a constant temperature, followed by cooling and solvent removal to obtain a single-source polymer precursor PSZ-Zr-Ti; and the single-source polymer precursor PSZ-Zr-Ti is then cross-linked at low temperature to obtain a single-source polymer precursor PSZ-Zr-Ti powder; The mass ratio of the polysilazane, zirconium acetylacetonate and tetrabutyl titanate is (5-6): (2-3): 1; the mass concentration of the mixed solution is 50wt%; the reaction temperature is 60-90°C and the reaction time is 2-4h; the constant temperature is 60°C; and the low-temperature crosslinking temperature is 200-300°C.

[0015] Furthermore, in S6, the vapor phase siliconizing treatment is performed under the protection of an argon atmosphere, with a treatment temperature of 1800-2200° C. and a treatment time of 15-30 min.

[0016] Furthermore, the preparation method of the single-source polymer precursor PCS-Ti solution is: Polycarbosilane and tetrabutyl titanate are mixed and then added into xylene to obtain a mixed solution; the mixed solution is reacted under an anhydrous inert atmosphere, then heated and stirred, and cooled to obtain a single-source polymer precursor PCS-Ti solution; The mass ratio of the polycarbosilane to tetrabutyl titanate is (3-4):1; the mass concentration of the mixed solution is 50 wt %; the reaction temperature is 60-90° C., and the reaction time is 2-4 hours.

[0017] The invention also discloses a base coating system for protecting C / C composite materials, which is prepared by the preparation method.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a method for preparing a substrate coating system for C / C composite material protection, which adopts a precursor impregnation and cracking method to introduce polymer-converted ultra-high temperature ceramics into the interior of the C / C composite material matrix to significantly improve the anti-ablation performance of the matrix itself, and prepares a modified coating on the surface of the modified matrix by slurry coating combined with a high-temperature vapor phase siliconization process to form a dense, high-temperature resistant protective barrier, effectively isolating oxygen, heat and high-speed airflow erosion, and achieving a synergistic improvement in the overall anti-ablation performance; in addition, the double-layer anti-ablation coating of the present invention and the SiC-TiC modified C / C composite material matrix have similar chemical compositions and thermal expansion coefficients, which significantly reduce interfacial thermal stress and avoid the problems in traditional technologies. Problems such as cracking and peeling of the coating caused by thermal mismatch between the coating and the modified substrate are solved; in addition, the high-temperature gas-phase siliconization process adopted in the present invention can convert silicon blocks into silicon vapor during the reaction process. Thanks to its strong penetrability, it can easily penetrate the porous pre-coating layer to reach the surface of the modified substrate and react with it. 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 gaseous silicon. The above reaction can effectively solve the interface compatibility problem between the anti-oxidation ablation coating and the substrate-modified C / C composite material, greatly improve the interface bonding strength between the anti-oxidation ablation coating and the modified substrate, and improve the resistance of the C / C composite material to long-term dynamic gas erosion in extreme service environments.

[0019] Furthermore, the method of the present invention prepares a polymer-converted ZrC-SiC-TiC ceramic-modified SiC-Si coating on the surface of the modified substrate through slurry coating combined with a high-temperature vapor phase siliconizing process, thereby achieving a synergistic improvement in the overall anti-ablation performance; the preparation process is simple and controllable, has strong designability, and low preparation cost. The coating and the modified substrate can be flexibly optimized by adjusting parameters such as the single-source precursor composition and siliconizing parameters, and is suitable for large-scale production of hot-end components of aircraft engines. According to relevant experimental results, the prepared material exhibits excellent long-term anti-oxidation and ablation performance under a dynamic gas scouring environment at 1700°C, which meets the actual service requirements of the hot-end components of aircraft engines and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The process flow chart of the substrate coating system for protection of C / C composite materials is as follows; Figure 2 The following are the surface macroscopic morphology photos of the substrate coating system used for C / C composite material protection after oxyacetylene flame ablation test at different times; Among them: a-0s; b-600s; c-1200s; d-2400s; Figure 3 is the XRD pattern of the substrate coating system used for protection of C / C composite materials; Figure 4 The surface temperature curve of the coating during the oxyacetylene flame ablation test at different times for the substrate coating system used for C / C composite material protection and the linear ablation rate of the coating after ablation; Where: a-coating surface temperature curve; b-line ablation rate; Figure 5 The SEM images of the ablation center area of ​​the sample surface after the substrate coating system for C / C composite material protection was subjected to oxyacetylene flame ablation test for different times; Among them: a-600s; b-1200s; c-2400s. DETAILED DESCRIPTION

[0021] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0022] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0023] All features, such as values, amounts, contents, and concentrations, described herein as numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0024] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0025] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0026] The present invention provides a method for preparing a substrate coating system for protecting C / C composite materials, comprising the following steps: Step 1: preparing a single-source polymer precursor PCS-Ti solution and a single-source polymer precursor PSZ-Zr-Ti powder; The preparation process of the single-source polymer precursor PCS-Ti solution is as follows: polycarbosilane PCS and tetrabutyl titanate TBT are mixed in a mass ratio of 3 to 4:1, xylene is used as a solvent, and the mass concentration of the mixed solution is 50wt%. The mixture is mixed evenly, and the mixture is reacted at 60 to 90°C for 2 to 4 hours under an anhydrous inert atmosphere of a Schlenk system. After heating and stirring, the mixture is cooled to room temperature to obtain the single-source polymer precursor PCS-Ti solution. The preparation process of the single-source polymer precursor PSZ-Zr-Ti powder is as follows: polysilazane PSZ, zirconium acetylacetonate and tetrabutyl titanate TBT are mixed in a mass ratio of (5-6): (2-3): 1, xylene is used as a solvent, and the mass concentration of the mixed solution is 50wt%. The mixture is mixed evenly, and reacted at 60-90°C for 2-4 hours under an anhydrous inert atmosphere of a Schlenk system. After the heating and stirring are completed, the temperature of the heating table is lowered to 60°C and maintained, and condensed water is introduced into the condenser connected to the top for cooling. The vacuum pump valve is slowly opened to remove the remaining solvent in the bottle to obtain the single-source polymer precursor PSZ-Zr-Ti; the single-source polymer precursor PSZ-Zr-Ti is cross-linked at a low temperature of 200-300°C to obtain the corresponding single-source polymer precursor PSZ-Zr-Ti powder; Step 2: Step a, dipping-drying: Immerse the low-density C / C composite material in the single-source polymer precursor PCS-Ti solution obtained in step 1, and place them together in a vacuum impregnation box. Evacuate to 0.08-0.1 MPa and maintain the pressure for 20-30 minutes. Take out the C / C composite material impregnated with the precursor, remove excess solution on the surface of the material, and place it in an oven at a temperature of 60-80°C for drying. Repeat the immersion and drying three times to obtain a dried C / C composite material impregnated with the precursor. Step b, high temperature heat treatment: The dried C / C composite material impregnated with the precursor obtained in step a is tightly wrapped with graphite paper, placed in the constant temperature zone of a high-temperature tube furnace, and heated to 1600-1900°C at a rate of 3-5°C / min using Ar as a protective gas. After holding for 1-3 hours, the temperature is lowered to room temperature at a rate of 2-4°C / min to achieve the introduction of polymer-converted ceramics into the material; Step 3: Repeat the impregnation, drying, and high-temperature heat treatment 10 to 14 times to obtain a C / C-SiC-TiC composite material; Step 4: ultrasonically clean the C / C-SiC-TiC composite material obtained in step 3 with deionized water, and dry it in an electric blast drying oven at a temperature of 80-100° C. for more than 4 hours; Step 5: Immerse the C / C-SiC-TiC composite material into slurry A and let it stand for 5-10 seconds. Take it out and dry it. Repeat this process several times to obtain the SiC inner coating. Step 6: Immerse the C / C-SiC-TiC composite material with the SiC inner coating into slurry B, let it stand for 5-10 seconds, and then dry. Repeat this process several times to obtain the outer coating. Step 7: Curing the C / C-SiC-TiC composite material pre-coated with the above slurry and dried at 200-300° C. for 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; Step 8: Place the C / C composite material with a 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 phase siliconization treatment under the protection of an argon atmosphere at a temperature of 1800~2150℃ and a treatment time of 15~30min to obtain a double-layer anti-oxidation and ablation coating on the surface of the C / C composite material.

[0027] Preferably, the density of the porous low-density C / C composite material is 1.10-1.30 g / cm 3 .

[0028] Preferably, the slurry A in step 5 is: phenolic resin and anhydrous ethanol are mixed in a mass ratio of 1:5-6, and a uniformly dispersed phenolic resin solution is obtained after ultrasonic treatment; SiC powder is added to the phenolic resin solution, and SiC phenolic resin slurry A is obtained after sufficient stirring, wherein the mass fraction of SiC powder is 30-50wt%.

[0029] Preferably, the slurry B in step 6 is prepared by adding SiC powder and the single-source polymer precursor PSZ-Zr-Ti 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 precursor PSZ-Zr-Ti powder is 20~40wt%.

[0030] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0031] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0032] Example 1 A method for preparing a matrix coating system for protecting C / C composite materials comprises the following steps: Step 1: Prepare the precursor 1) First, add the magnet and an appropriate amount of zeolite to a three-necked flask. Then, weigh 40g of polycarbosilane (PCS) into the three-necked flask, and continue to add 10g of tetrabutyl titanate (TBT). Then, add 50g of xylene to the three-necked flask to obtain a mixed solution. Then, apply vacuum grease to all interfaces of the Schlenk apparatus to ensure good airtightness after the device is connected. 2) Next, open the vacuum pump valve to remove air and residual water vapor from the device. When the vacuum gauge shows a vacuum of -0.9 MPa, turn off the vacuum pump and wait for 5 minutes to maintain pressure. If the vacuum pump reading does not change during this period, the device is considered airtight and can proceed to the next step. At this time, slowly turn the valve on the double-row pipe in the Schlenk device to fill with argon gas for the first gas purge. Repeat the above vacuum pumping and argon filling steps three times to ensure that the device is free of water and oxygen. 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 60°C and the reaction time is 3 hours. 4) After heating and stirring, cool to room temperature to obtain a single-source polymer precursor PCS-Ti solution; 5) Replace the polymer precursor solution in 1) with: 30g polysilazane PSZ, 60g zirconium acetylacetonate, and 10g tetrabutyl titanate TBT, using 100g xylene as the solvent. Repeat steps 1) to 4) at a reaction temperature of 80°C. 6) After heating and stirring, lower the temperature of the heating plate at the bottom of the three-necked flask to 60°C and maintain it there. Simultaneously, allow condensed water to cool the condenser connected to the top of the flask. Slowly open the vacuum pump valve to remove the remaining solvent in the flask. 7) The solvent-removed reactants were removed from the three-necked flask and placed in a tube furnace for crosslinking and curing at 300°C for 2 hours in an argon atmosphere. The cured material was collected as the single-source polymer precursor PSZ-Zr-Ti powder. Step 2: Precursor impregnation and cracking matrix modification: 1) The density is 1.10g / cm 3 The porous low-density C / C composite material was processed into a round cake sample with a size of 28 mm × 5 mm, and then ultrasonically cleaned with deionized water and dried in an electric blast drying oven at a temperature of 80 ° C to obtain the matrix modification. 2) Immersing the low-density C / C composite material in the single-source polymer precursor PCS-Ti solution obtained in step 1, placing the composite material in a vacuum drying oven, evacuating to -0.1 MPa, and maintaining the pressure for 30 minutes, taking out the C / C composite material impregnated with the precursor, removing excess solution from the surface of the material, and drying the composite material in an oven at 80°C. Repeat the immersion-drying cycle three times to obtain a dried C / C composite material impregnated with the precursor; 3) The dried precursor-impregnated C / C composite material was tightly wrapped with graphite paper and placed in the constant temperature zone of a high-temperature tube furnace. Using Ar as a protective gas, the temperature was raised to 1600°C at a rate of 5°C / min, maintained at that temperature for 2 hours, and then cooled to room temperature at a rate of 3°C / min to achieve the introduction of polymer-converted ceramics into the material. 4) Repeat the impregnation-drying-high temperature heat treatment 12 times to obtain the C / C-SiC-TiC composite material; Step 3: Slurry coating combined with high temperature vapor phase siliconization process to prepare the coating: 1) The C / C-SiC-TiC composite material sample modified by the matrix in step 2 was ultrasonically cleaned with deionized water and dried in an electric heated blast drying oven at a temperature of 90° C. before being used for subsequent coating preparation.

[0033] 2) 30 wt% SiC and 10 wt% phenolic resin were dissolved in 60 wt% anhydrous ethanol, and slurry A was obtained after thorough stirring and ultrasonication; 3) Immerse the C / C-SiC-TiC composite matrix in slurry A and let it stand for 5 seconds. Take it out and dry it. Repeat this process 4 times.

[0034] 4) 15 wt% SiC and 35 wt% single-source polymer precursor PSZ-Zr-Ti powder were dissolved in 50 wt% anhydrous ethanol, and slurry B was obtained after sufficient stirring and ultrasonication; 5) The C / C-SiC-TiC composite substrate coated with slurry A and dried was immersed in slurry B and allowed to stand for 5 seconds. After removal, it was dried and the process was repeated 4 times.

[0035] 6) The coated sample was cured at 300°C for 2 hours, and then carbonized at 900°C under argon atmosphere for 2 hours to obtain a pre-coated sample.

[0036] 7) The C / C-SiC-TiC composite material with a 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 1850°C under the protection of an argon atmosphere and kept at this temperature for 15 minutes for vapor phase siliconization treatment. Thus, an anti-oxidation and ablation coating was obtained on the surface of the C / C composite material.

[0037] Step 4: Oxyacetylene flame ablation test sample: At a heat flux density of 5MW / m 2 The coating sample was ablated under a plasma flame for 600 seconds, with a linear ablation rate of 0.925 μm / s. The oxygen flow rate was 14.4 L / s, the acetylene flow rate was 10 L / s, and the vertical distance between the flame spray gun nozzle and the sample surface was 31 mm. The surface temperature of the coating sample exceeded 1700°C.

[0038] Example 2 A method for preparing a matrix coating system for protecting C / C composite materials comprises the following steps: Step 1: Prepare the precursor 1) First, add the magnet and an appropriate amount of zeolite to a three-necked flask. Then, weigh 40g of polycarbosilane (PCS) into the three-necked flask, and continue to add 10g of tetrabutyl titanate (TBT). Then, add 50g of xylene to the three-necked flask to obtain a mixed solution. Then, apply vacuum grease to all interfaces of the Schlenk apparatus to ensure good airtightness after the device is connected. 2) Next, open the vacuum pump valve to remove air and residual water vapor from the device. When the vacuum gauge shows a vacuum of -0.9 MPa, turn off the vacuum pump and wait for 5 minutes to maintain pressure. If the vacuum pump reading does not change during this period, the device is considered airtight and can proceed to the next step. At this time, slowly turn the valve on the double-row pipe in the Schlenk device to fill with argon gas for the first gas purge. Repeat the above vacuum pumping and argon filling steps three times to ensure that the device is free of water and oxygen. 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 60°C and the reaction time is 3 hours. 4) After heating and stirring, cool to room temperature to obtain a single-source polymer precursor PCS-Ti solution; 5) Replace the polymer precursor solution in 1) with: 30g polysilazane PSZ, 60g zirconium acetylacetonate, and 10g tetrabutyl titanate TBT, 100g xylene as solvent, reaction temperature 80°C, and repeat steps 1) to 4); 6) After heating and stirring, lower the temperature of the heating plate at the bottom of the three-necked flask to 60°C and maintain it there. Simultaneously, allow condensed water to cool the condenser connected to the top of the flask. Slowly open the vacuum pump valve to remove the remaining solvent in the flask. 7) The solvent-removed reactants were removed from the three-necked flask and placed in a tube furnace for crosslinking and curing at 300°C for 2 hours in an argon atmosphere. The cured material was collected to obtain the single-source polymer precursor PSZ-Zr-Ti powder. Step 2: Precursor impregnation and cracking matrix modification: 1) The density is 1.20g / cm 3 The porous low-density C / C composite material was processed into a round cake sample with a size of 28 mm × 5 mm, and then ultrasonically cleaned with deionized water and dried in an electric blast drying oven at a temperature of 80 ° C to obtain the matrix modification. 2) Immersing the low-density C / C composite material in the single-source polymer precursor PCS-Ti solution obtained in step 1, placing the composite material in a vacuum drying oven, evacuating to -0.1 MPa, and maintaining the pressure for 30 minutes, taking out the C / C composite material impregnated with the precursor, removing excess solution from the surface of the material, and drying the composite material in an oven at 80°C. Repeat the immersion-drying cycle three times to obtain a dried C / C composite material impregnated with the precursor; 3) The dried precursor-impregnated C / C composite material was tightly wrapped with graphite paper and placed in the constant temperature zone of a high-temperature tube furnace. Using Ar as a protective gas, the temperature was raised to 1600°C at a rate of 5°C / min, maintained at that temperature for 2 hours, and then cooled to room temperature at a rate of 3°C / min to achieve the introduction of polymer-converted ceramics into the material. 4) Repeat the impregnation-drying-high temperature heat treatment 12 times to obtain the C / C-SiC-TiC composite material; Step 3: Slurry coating combined with high temperature vapor phase siliconization process to prepare the coating: 1) The C / C-SiC-TiC composite material sample modified by the matrix in step 2 was ultrasonically cleaned with deionized water and dried in an electric heated blast drying oven at a temperature of 90° C. before being used for subsequent coating preparation.

[0039] 2) 30 wt% SiC and 10 wt% phenolic resin were dissolved in 60 wt% anhydrous ethanol, and slurry A was obtained after thorough stirring and ultrasonication; 3) Immerse the C / C-SiC-TiC composite matrix in slurry A and let it stand for 5 seconds. Take it out and dry it. Repeat this process 4 times.

[0040] 4) 15 wt% SiC and 35 wt% single-source polymer precursor PSZ-Zr-Ti powder were dissolved in 50 wt% anhydrous ethanol, and slurry B was obtained after sufficient stirring and ultrasonication; 5) The C / C-SiC-TiC composite substrate coated with slurry A and dried was immersed in slurry B and allowed to stand for 5 seconds. After removal, it was dried and the process was repeated 4 times.

[0041] 6) The coated sample was cured at 300°C for 2 hours, and then carbonized at 900°C under argon atmosphere for 2 hours to obtain a pre-coated sample.

[0042] 7) The C / C-SiC-TiC composite material with a 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 1850°C under the protection of an argon atmosphere and kept at this temperature for 15 minutes for vapor phase siliconization treatment. Thus, an anti-oxidation and ablation coating was obtained on the surface of the C / C composite material.

[0043] Step 4: Oxyacetylene flame ablation test sample: At a heat flux density of 5MW / m 2 The coating sample was ablated under a plasma flame for 1200 seconds, with a linear ablation rate of 0.905 μm / s. The oxygen flow rate was 14.4 L / s, the acetylene flow rate was 10 L / s, and the vertical distance between the flame spray gun nozzle and the sample surface was 31 mm. The surface temperature of the coating sample exceeded 1700°C.

[0044] Example 3 A method for preparing a matrix coating system for protecting C / C composite materials comprises the following steps: Step 1: Prepare the precursor 1) First, add the magnet and an appropriate amount of zeolite to a three-necked flask. Then, weigh 40g of polycarbosilane (PCS) into the three-necked flask, and continue to add 10g of tetrabutyl titanate (TBT). Then, add 50g of xylene to the three-necked flask to obtain a mixed solution. Then, apply vacuum grease to all interfaces of the Schlenk apparatus to ensure good airtightness after the device is connected. 2) Next, open the vacuum pump valve to remove air and residual water vapor from the device. When the vacuum gauge shows a vacuum of -0.9 MPa, turn off the vacuum pump and wait for 5 minutes to maintain pressure. If the vacuum pump reading does not change during this period, the device is considered airtight and can proceed to the next step. At this time, slowly turn the valve on the double-row pipe in the Schlenk device to fill with argon gas for the first gas purge. Repeat the above vacuum pumping and argon filling steps three times to ensure that the device is free of water and oxygen. 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 60°C and the reaction time is 3 hours. 4) After heating and stirring, cool to room temperature to obtain a single-source polymer precursor PCS-Ti solution; 5) Replace the polymer precursor solution in 1) with: 30g polysilazane PSZ, 60g zirconium acetylacetonate, and 10g tetrabutyl titanate TBT, 100g xylene as solvent, reaction temperature 80°C, and repeat steps 1) to 4); 6) After heating and stirring, lower the temperature of the heating plate at the bottom of the three-necked flask to 60°C and maintain it there. Simultaneously, allow condensed water to cool the condenser connected to the top of the flask. Slowly open the vacuum pump valve to remove the remaining solvent in the flask. 7) The solvent-removed reactants were removed from the three-necked flask and placed in a tube furnace for crosslinking and curing at 300°C for 2 hours in an argon atmosphere. The cured material was collected to obtain the single-source polymer precursor PSZ-Zr-Ti powder. Step 2: Precursor impregnation and cracking matrix modification: 1) The density is 1.30g / cm 3 The porous low-density C / C composite material was processed into a round cake sample with a size of 28 mm × 5 mm, and then ultrasonically cleaned with deionized water and dried in an electric blast drying oven at a temperature of 80 ° C to obtain the matrix modification. 2) Immersing the low-density C / C composite material in the single-source polymer precursor PCS-Ti solution obtained in step 1, placing the composite material in a vacuum drying oven, evacuating to -0.1 MPa, and maintaining the pressure for 30 minutes, taking out the C / C composite material impregnated with the precursor, removing excess solution from the surface of the material, and drying the composite material in an oven at 80°C. Repeat the immersion-drying cycle three times to obtain a dried C / C composite material impregnated with the precursor; 3) The dried precursor-impregnated C / C composite material was tightly wrapped with graphite paper and placed in the constant temperature zone of a high-temperature tube furnace. Using Ar as a protective gas, the temperature was raised to 1600°C at a rate of 5°C / min, maintained at that temperature for 2 hours, and then cooled to room temperature at a rate of 3°C / min to achieve the introduction of polymer-converted ceramics into the material. 4) Repeat the impregnation-drying-high temperature heat treatment 12 times to obtain the C / C-SiC-TiC composite material; Step 3: Slurry coating combined with high temperature vapor phase siliconization process to prepare the coating: 1) The C / C-SiC-TiC composite material sample modified by the matrix in step 2 was ultrasonically cleaned with deionized water and dried in an electric heated blast drying oven at a temperature of 90° C. before being used for subsequent coating preparation.

[0045] 2) 30 wt% SiC and 10 wt% phenolic resin were dissolved in 60 wt% anhydrous ethanol, and slurry A was obtained after thorough stirring and ultrasonication; 3) Immerse the C / C-SiC-TiC composite matrix in slurry A and let it stand for 5 seconds. Remove it and dry it. Repeat this process 4 times. 4) 15 wt% SiC and 35 wt% single-source polymer precursor PSZ-Zr-Ti powder were dissolved in 50 wt% anhydrous ethanol, and slurry B was obtained after sufficient stirring and ultrasonication; 5) The C / C-SiC-TiC composite substrate coated with slurry A and dried was immersed in slurry B and allowed to stand for 5 seconds. After removal, it was dried and the process was repeated 4 times.

[0046] 6) The coated sample was cured at 300°C for 2 hours, and then carbonized at 900°C under argon atmosphere for 2 hours to obtain a pre-coated sample.

[0047] 7) The C / C-SiC-TiC composite material with a 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 1850°C under the protection of an argon atmosphere and kept at this temperature for 15 minutes for vapor phase siliconization treatment. Thus, an anti-oxidation and ablation coating was obtained on the surface of the C / C composite material.

[0048] Step 4: Oxyacetylene flame ablation test sample: At a heat flux density of 5MW / m 2 The coating sample was ablated under a plasma flame for 2400 seconds, with a linear ablation rate of 0.763 μm / s. The oxygen flow rate was 14.4 L / s, the acetylene flow rate was 10 L / s, and the vertical distance between the flame spray gun nozzle and the sample surface was 31 mm. The surface temperature of the coating sample exceeded 1700°C.

[0049] Figure 1 This is a flow chart of the present invention. It can be seen from the figure that the low-density C / C composite material is first subjected to precursor impregnation and cracking to prepare a matrix-modified C / C composite material, and then slurries A and B are prepared and two layers of coating are dip-coated on the surface of the matrix-modified C / C composite material, and then cured and carbonized. Finally, the above C / C composite material is subjected to high-temperature vapor phase siliconization treatment to obtain the target sample.

[0050] Figure 2 The surface macroscopic morphology of the substrate coating system used for C / C composite material protection after oxyacetylene flame ablation test at different times is shown in Figure 2. Figure 2 a It can be seen that the surface of the sample is smooth and dense before gas flushing. Figure 2 It can be seen from bd that the oxide layer on the surface of the sample remains relatively intact after gas scouring, and the depth of the erosion pit on the surface of the sample increases continuously with the extension of gas scouring time.

[0051] Figure 3 This is the XRD diagram of the substrate coating system used for protection of C / C composite materials. It can be seen from the figure that the surface of the C / C composite material modified by the substrate coating is mainly composed of three phases: Si, SiC and (Zr-Ti)C.

[0052] Figure 4 The surface temperature curve of the coating in the oxyacetylene flame ablation test of the substrate coating system for C / C composite material protection at different times ( Figure 4 a) and the linear ablation rate of the coating after ablation ( Figure 4 b) Figure 4 It can be seen from a that the temperature of the dynamic gas flushing test of different durations is above 1750℃. Figure 4b It can be seen that the C / C composite material modified by the substrate and coating has excellent resistance to long-term dynamic gas erosion. As the gas erosion time increases, the linear ablation rate gradually decreases. After 2400s of dynamic gas erosion, the linear ablation rate of the sample is only 0.763μm / s.

[0053] Figure 5 The SEM images of the ablation center area of ​​the sample surface after the substrate coating system for C / C composite material protection was subjected to oxyacetylene flame ablation test for different times. Figure 5 It can be seen from a that after 600s of gas flushing, the surface of the sample is uneven and not completely sintered. There are a lot of cracks, holes and exposed fibers. Figure 5 b It can be seen that after 1200s of gas flushing, the surface of the sample becomes dense and there are large molten areas. Figure 5 c It can be seen that after 2400s of gas flushing, the surface of the sample is sintered more densely, the number of surface pores is reduced, and the pore size becomes smaller.

[0054] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a matrix coating system for protecting C / C composite materials, characterized in that: The following steps are involved: S1: immersing the porous low-density C / C composite material in a single-source polymer precursor PCS-Ti solution for vacuum impregnation to obtain a C / C composite material impregnated with the precursor; drying the C / C composite material impregnated with the precursor to obtain a dried C / C composite material impregnated with the precursor; S2: After repeating S1 several times, the obtained dried precursor-impregnated C / C composite is wrapped with graphite paper and then heat-treated; S3: Repeat S1 and S2 several times to obtain matrix-modified C / C composites; S4: Immerse the matrix-modified C / C composite material in slurry A and let it stand, then take it out and dry it. Repeat the above process several times to obtain a modified C / C composite material with a SiC inner coating; S5: Immersing the modified C / C composite material with the SiC inner coating into slurry B and allowing it to stand, then taking it out and drying it, repeating the above process several times, and then sequentially curing and carbonizing it to obtain a modified C / C composite material with a pre-coating layer; S6: performing vapor phase siliconization treatment on the modified C / C composite material with the pre-coating layer to obtain a base coating system for protecting the C / C composite material.

2. The method for preparing a matrix coating system for protecting C / C composite materials according to claim 1, characterized in that: In S1, the porous low-density C / C composite material is polished, ultrasonically cleaned and dried in sequence before use; the density of the porous low-density C / C composite material is 1.1-1.3 g / cm 3 .

3. The method for preparing a matrix coating system for protecting C / C composite materials according to claim 1, characterized in that: In S1, the process parameters of the vacuum impregnation treatment are: vacuuming to -0.08~-0.1MPa, maintaining the pressure for 20~40min; and drying at a temperature of 60~100°C.

4. The method for preparing a matrix coating system for protecting C / C composite materials according to claim 1, characterized in that: In S2, S1 is repeated 3 to 5 times; the heat treatment is carried out in an inert atmosphere; the process parameters of the heat treatment are: heating to 1400 to 1800°C at a rate of 3 to 5°C / min, keeping warm for 1 to 3 hours, and then cooling to room temperature at a rate of 2 to 4°C / min.

5. The method for preparing a matrix coating system for protecting C / C composite materials according to claim 1, characterized in that: In S3, S1 and S2 are repeated 10 to 14 times.

6. The method for preparing a matrix coating system for protecting C / C composite materials according to claim 1, characterized in that: In S4, the preparation process of the slurry A is as follows: Phenolic resin and anhydrous ethanol are mixed in a mass ratio of 1:5-6, and subjected to ultrasonic treatment to obtain a phenolic resin solution. SiC powder is then added to the phenolic resin solution, and stirred to obtain slurry A; the mass fraction of SiC powder in the slurry A is 30-50wt%; The standing time is 5 to 10 seconds; and the number of repetitions is 3 to 4 times.

7. The method for preparing a matrix coating system for protecting C / C composite materials according to claim 1, characterized in that: In S5, the preparation process of the slurry B is as follows: SiC powder and single-source polymer precursor PSZ-Zr-Ti powder are added to the phenolic resin solution, and the mixture is stirred to obtain slurry B; the mass fraction of SiC in slurry B is 10-20wt%, and the mass fraction of single-source polymer precursor PSZ-Zr-Ti powder is 20-40wt%; The number of repetitions is 6 to 8 times; the curing is performed at 200 to 300° C. for more than 2 hours; the carbonization is performed at 900 to 1100° C. for more than 2 hours; and both the curing and carbonization are performed in an argon atmosphere; The preparation method of the single-source polymer precursor PSZ-Zr-Ti powder is as follows: Polysilazane, zirconium acetylacetonate, and tetrabutyl titanate are mixed and added into xylene to obtain a mixed solution; the mixed solution is reacted under an anhydrous inert atmosphere, and then heated and stirred, and the heating and heat preservation are maintained to a constant temperature, followed by cooling and solvent removal to obtain a single-source polymer precursor PSZ-Zr-Ti; and the single-source polymer precursor PSZ-Zr-Ti is then cross-linked at low temperature to obtain a single-source polymer precursor PSZ-Zr-Ti powder; The mass ratio of the polysilazane, zirconium acetylacetonate and tetrabutyl titanate is (5-6): (2-3): 1; the mass concentration of the mixed solution is 50wt%; the reaction temperature is 60-90°C and the reaction time is 2-4h; the constant temperature is 60°C; and the low-temperature crosslinking temperature is 200-300°C.

8. The method for preparing a matrix coating system for protecting C / C composite materials according to claim 1, characterized in that: In S6, the vapor phase siliconizing treatment is performed under the protection of an argon atmosphere, with a treatment temperature of 1800-2200° C. and a treatment time of 15-30 minutes.

9. The method for preparing a matrix coating system for protecting C / C composite materials according to claim 1, characterized in that: The preparation method of the single-source polymer precursor PCS-Ti solution is: Polycarbosilane and tetrabutyl titanate are mixed and then added into xylene to obtain a mixed solution; the mixed solution is reacted under an anhydrous inert atmosphere, then heated and stirred, and cooled to obtain a single-source polymer precursor PCS-Ti solution; The mass ratio of the polycarbosilane to tetrabutyl titanate is (3-4):1; the mass concentration of the mixed solution is 50 wt %; the reaction temperature is 60-90° C., and the reaction time is 2-4 hours.

10. A substrate coating system for protecting C / C composite materials, characterized in that: The method is prepared according to any one of claims 1 to 9.

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