A superstructure coating and its preparation method

Abstract

This invention belongs to the technical field of composite material surface coating preparation, and discloses a superstructure coating and its preparation method. A lattice pattern is etched onto the surface of a composite material to obtain a first composite material; the first composite material is then vacuum-impregnated in a precursor solution to obtain a second composite material; the second composite material is cured and carbonized to prepare a three-dimensional network carbon skeleton on it, resulting in a third composite material; a pyrolytic carbon layer is deposited on the surface of the three-dimensional network carbon skeleton using chemical vapor deposition to obtain a fourth composite material; and an ultra-high temperature ablation-resistant coating is deposited on the fourth composite material using chemical vapor deposition to obtain the superstructure coating. This invention utilizes a laser galvanometer to construct a superstructure array, and the three-dimensional network carbon skeleton and PyC construct multi-level thermal conductivity pathways, strengthening the bonding strength between the CVD coating and the substrate and reducing the interfacial thermal resistance between them, thereby enhancing thermal conductivity and ultimately achieving the preparation of a high-performance ablation-resistant coating.

Description

Technical Field

[0001] This invention belongs to the technical field of composite material surface coating preparation, specifically relating to a superstructure coating and its preparation method. Background Technology

[0002] Carbon / carbon (C / C) composites have become a leading candidate material for aerospace vehicle thermal protection systems due to their advantages such as low density, high specific strength, high thermal conductivity, and excellent high-temperature mechanical properties. However, C / C composites exhibit severe high-temperature oxidation sensitivity, undergoing oxidation in oxygen-containing environments exceeding 450 °C, leading to structural integrity degradation and rapid failure. Therefore, ceramic coatings are typically applied to the surface of the composite material to achieve oxygen isolation and improve its ablation resistance. Among these methods, CVD (Chemical Vapor Deposition) technology is widely used due to its ability to deposit dense coatings, its lack of limitation on sample shape, and its low damage to the substrate. However, because the coating prepared by this technology does not chemically react with the substrate, and there is a continuous heterogeneous interface between the coating and the C / C substrate, the difference in their coefficients of thermal expansion generates strong thermal stress, making the coating prone to peeling off and failing from the substrate. To solve this problem, researchers typically have two approaches: one is to construct a porous surface on the composite material through pre-oxidation / ablation, forming an embedded structure with the coating to improve its adhesion; the other is to grow nanowires on the composite material surface, using the pull-out and bridging mechanism of the nanowires to enhance the bonding strength between the coating and the substrate. However, the pore shape and distribution generated on the composite material surface by pre-oxidation / ablation are highly random, and internal oxidation can also form pores, greatly reducing the mechanical properties of the material itself. Furthermore, the size effect of the nanomaterials and the strengthening effect of a single pull-out mechanism are very limited. In addition, the continuous interface between the coating and the C / C substrate is a strong thermal resistance. During the ablation process, heat accumulates on the coating surface and cannot be efficiently transferred to the substrate, causing the coating to fail prematurely due to the rapid consumption of low-melting-point phases caused by excessively high temperatures. Therefore, in response to the two major challenges faced by the coatings mentioned above, it is urgent to develop a new solution that can improve the bonding strength between the coating and the substrate while reducing the interfacial thermal resistance, so as to prepare high-performance ablation-resistant coatings. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to propose a superstructure coating and its preparation method. The method involves constructing a superstructure array using a laser galvanometer, building a multi-level thermal conductivity pathway with a three-dimensional network carbon skeleton and PyC, strengthening the bond between the CVD coating and the substrate, reducing the interfacial thermal resistance between them, enhancing thermal conductivity, and ultimately achieving the preparation of a high-performance ablation-resistant coating.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a superstructure coating includes the following steps: A lattice pattern is etched on the surface of a composite material to obtain a first composite material, wherein each unit structure in the lattice pattern is a blind hole structure. The first composite material was vacuum impregnated in a precursor solution to obtain the second composite material; The second composite material is cured and carbonized to prepare a three-dimensional network carbon skeleton on the second composite material, thus obtaining the third composite material. The third composite material is subjected to chemical vapor deposition to deposit a pyrolytic carbon layer on the surface of the three-dimensional network carbon skeleton to obtain the fourth composite material; The superstructure coating is obtained by chemical vapor deposition of an ultra-high temperature ablation resistant coating on the fourth composite material.

[0005] Preferably, the composite material has a density of 1.70-1.85 g / cm³. 3 C / C composite materials, or those with a density of 2.3-4.5 g / cm³. 3 The ceramic material includes a composite material of one or more of ZrC, SiC and HfC.

[0006] Preferably, the diameter of the blind hole structure is 200-400μm, the depth is 70-150μm, and the center distance between adjacent blind hole structures is 500-700μm.

[0007] Preferably, the preparation process of the precursor solution includes: By mass, 5-10 parts of resorcinol, 7-12 parts of formaldehyde solution and 5-18 parts of distilled water are mixed evenly to obtain a mixed solution. Then, 0.05-0.15 parts of hexadecyltrimethylammonium bromide are added to the mixed solution as a catalyst and mixed evenly to obtain the precursor solution. The mass concentration of the formaldehyde solution is 36 wt.%-38 wt.%.

[0008] Preferably, when the first composite material is vacuum impregnated in the precursor solution to obtain the second composite material, the impregnation is carried out at a pressure of 0.01-0.09 MPa for 30-50 minutes, and then the first composite material is taken out to obtain the second composite material.

[0009] Preferably, when the second composite material is cured and carbonized to prepare a three-dimensional network carbon skeleton on the second composite material, the third composite material is obtained: The second composite material is cured at 70-100℃ for 24-48 hours, and then carbonized at 900-1000℃ for 2-3 hours in a protective atmosphere to prepare a three-dimensional network carbon skeleton on the second composite material, thus obtaining the third composite material.

[0010] Preferably, when the third composite material is subjected to chemical vapor deposition to deposit a pyrolytic carbon layer on the surface of the three-dimensional network carbon skeleton to obtain the fourth composite material, the deposition temperature is 1000-1100℃, the pressure is 8-12kPa, the natural gas flow rate is 15-18L / min, and the deposition time is 4-6min.

[0011] Preferably, when the fourth composite material is subjected to chemical vapor deposition to obtain an ultra-high temperature ablation resistant coating and the superstructure coating, the deposition temperature is 1000-1200℃, the flow rate of H2 used for deposition is 700-1300 ml / min, the flow rate of trichloromethylsilane is 0.05-0.6 g / min, and the deposition time is 20-30 h.

[0012] Preferably, the ultra-high temperature ablation resistant coating is a SiC coating, a ZrC coating, an HfC coating, or a TaC coating.

[0013] The present invention also provides a superstructure coating, which is prepared by the preparation method of the present invention as described above.

[0014] The present invention has the following beneficial effects: The present invention provides a method for preparing a superstructure coating. This method involves etching a lattice pattern of blind holes on the surface of a composite material, vacuum impregnating it in a precursor solution (to fully fill the blind hole structure with the precursor), and then curing and carbonizing it to prepare a three-dimensional network carbon skeleton. Subsequently, a pyrolytic carbon layer and an ultra-high temperature ablation-resistant coating are formed on the surface of the carbon skeleton through chemical vapor deposition in a continuous process. This method effectively solves the technical problems of low interfacial bonding strength, high interfacial thermal resistance, and easy peeling failure of existing CVD coatings on C / C composite materials. The specific principle of this invention is as follows: the blind hole lattice pattern only acts on the surface of the composite material and does not penetrate into the matrix, thus avoiding damage to the internal fibers and structure of the matrix from the root, thereby ensuring the original mechanical integrity of the matrix. This is different from the defects of traditional pre-oxidation / ablation methods, which are prone to forming pores in the matrix and damaging mechanical properties. At the same time, the lattice structure acts as the "main root" of the plant root system, providing support for the subsequent structure, while the three-dimensional network carbon skeleton and the surface pyrolytic carbon layer filling it act as "lateral roots", forming a tight interlocking with the lattice structure and the subsequently deposited ultra-high temperature ablation resistant coating. Through the meso-micro multi-level pull-out mechanism, that is, when the coating is subjected to peeling force, the three-dimensional network carbon skeleton and the pyrolytic carbon layer will generate pull-out resistance, and the lattice blind hole structure will generate mechanical interlocking resistance. The dual resistance works synergistically to significantly improve the interfacial bonding strength between the coating and the matrix. Compared with the traditional solution without interface modification, the bonding strength is significantly improved. In terms of heat conduction, the three-dimensional network carbon skeleton itself possesses a certain thermal conductivity. Together with the pyrolytic carbon layer, it constructs a multi-level thermal conduction pathway penetrating the coating and substrate, breaking the continuous heterogeneous thermal resistance interface between the traditional CVD coating and substrate. This allows the heat accumulated on the coating surface during ablation to be quickly and efficiently transferred to the substrate, preventing excessive heat buildup on the coating surface and the rapid consumption of the low-melting-point phase, thus preventing premature coating failure. Regarding thermal stress mitigation, the periodic blind hole lattice can divide and redistribute the thermal stress on the coating surface, preventing thermal stress concentration in localized areas and reducing the possibility of crack formation. Simultaneously, the three-dimensional network carbon skeleton is a soft carbon phase, while the ultra-high temperature ablation-resistant coating is a hard ceramic phase. The resulting three-dimensional interpenetrating structure between the soft and hard phases effectively buffers the thermal stress caused by the difference in their thermal expansion coefficients, offsetting some stress through its own deformation, thus preventing cracking and peeling of the coating during preparation (e.g., high-temperature deposition) and service (e.g., cyclic ablation). Furthermore, the etching parameters of the dot matrix pattern can be precisely controlled, allowing for adjustments to the size, spacing, and depth of blind holes according to actual needs, ensuring a good match with the subsequent carbon skeleton and coating. Vacuum impregnation, curing carbonization, and chemical vapor deposition are all mature processes with interconnected and controllable steps. This ensures that the precursor fully fills the blind holes and the carbon skeleton is uniformly formed, while also ensuring that the pyrolytic carbon layer and ultra-high temperature ablation-resistant coating are deposited densely, thereby guaranteeing the consistency of product quality. This provides a feasible path for the large-scale preparation of high-performance ablation-resistant coatings, achieving an overall comprehensive improvement in coating performance. Attached Figure Description

[0015] Figure 1 This is a SEM image of the superstructure array prepared on the surface of the composite material in Example 1 of the present invention.

[0016] Figure 2 This is a SEM image of a three-dimensional network-like carbon skeleton filling the array structure in Embodiment 1 of the present invention.

[0017] Figure 3 This is a SEM image of the SiC coating deposited by CVD in Example 1 of the present invention.

[0018] Figure 4 This is a SEM image of the cross section after CVD deposition of the SiC coating in Example 1 of the present invention.

[0019] Figure 5 This is a SEM image of the carbon skeleton in the array structure of Comparative Example 3 of the present invention.

[0020] Figure 6 This is a SEM image of the carbon skeleton in the array structure of Comparative Example 4 of the present invention.

[0021] Figure 7 This is a SEM image of the cross section after CVD deposition of the SiC coating in Comparative Example 1 of this invention. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] Superstructure materials can endow special mechanical, physical or chemical properties that surpass those of traditional homogeneous materials. They refer to the regular, ordered, multi-level or periodic geometric configurations constructed at the micro / mesoscale through artificial design. This invention applies this design concept to the design of traditional coatings, solving two major problems currently faced by coatings in service. In nature, plant root systems are mainly composed of a hierarchical structure of "taproot-lateral roots". Taproots grow vertically along the direction of gravity, penetrating deep into the soil. By increasing the contact area between the root system and the soil and mechanically interlocking, they stabilize the soil layer and prevent shallow soil from slipping due to concentrated stress. Lateral roots form a network structure in the soil. Through the friction of the root-soil complex, they improve the soil's shear resistance. This invention uses a plant root-inspired superstructure design for the substrate coating interface. A micron-scale (200-400 μm) superstructure array is constructed on the surface of the composite material using a laser galvanometer as the "taproot". Subsequently, a three-dimensional network carbon skeleton structure is prepared in the array structure. A layer of pyrolytic carbon (PyC) is deposited on the surface of the carbon skeleton using chemical vapor infiltration (CVI) technology as the "lateral roots". Finally, a coating is prepared on the surface of the composite material using CVD technology. The bonding strength between the coating and the substrate is enhanced by a multi-level pull-out mechanism that combines macroscopic, mesoscopic, and microscopic elements. A multi-level thermal conduction pathway is constructed using a three-dimensional network carbon skeleton and PyC to reduce the interfacial thermal resistance between the coating and the substrate. This effectively transfers the heat accumulated on the coating surface during ablation to the substrate. At the same time, this biomimetic superstructure design can effectively alleviate the thermal stress during ablation and improve the service stability of the coating.

[0024] Specifically, the preparation method of the superstructure coating of the present invention includes the following steps: Step 1: Fabrication of the superstructure array: A lattice pattern is etched onto the surface of the composite material using a digital laser galvanometer method to obtain the first composite material. For example... Figure 1As shown, the dot pattern is a periodic array structure (i.e., all dots constitute an array). Each unit structure in the dot pattern is a blind hole structure. According to the processing characteristics of the digital laser galvanometer method, the shape of the blind hole structure is cylindrical. In this invention, the diameter of the blind hole structure is 200-400μm, the depth is 70-150μm, and the distance between the centers of adjacent unit structures (i.e., adjacent blind holes) is 500-700μm. In this step, the periodic array pattern is etched on the surface of the composite material using the digital laser galvanometer method. The pattern shape, size, and arrangement are highly designable, the pattern distribution is controllable, the preparation is stable, and it will not damage the interior of the composite material, making it suitable for large-scale applications. The micron-level (200-400μm) array structure divides and redistributes the thermal stress on the coating surface, mitigating the phenomenon of stress concentration on the coating surface. In this invention, the optimal size, depth, and spacing of the unit structure were obtained through experimental optimization: When the unit structure is too large and deep, it causes significant damage to the integrity of the substrate structure, and the coating is not easy to fill completely. When the unit structure is too small and too dense, the small conical holes themselves become the source of microcracks at the interface, and the cracks propagate rapidly along the hole walls when thermal expansion mismatch occurs. When the unit structure is shallow, the mechanical interlocking stroke is short, the bonding strength between the coating and the substrate is only slightly improved, and the difference in thermal expansion coefficients cannot be effectively eliminated, so a deep stress gradient cannot be formed. The thermal mismatch stress between the substrate and the coating is still concentrated at the flat interface, resulting in a high risk of debonding. When the unit structure is sparsely arranged, the stress dispersion is discontinuous, most of the interface is still a flat and weak interface, the stress is only released at a few unit structures, and the rest of the area is still concentrated, resulting in poor interface strengthening effect.

[0025] Specifically, in this step, the composite material can have a density of 1.70-1.85 g / cm³. 3 C / C composite materials can also be made with a density of 2.3-4.5 g / cm³. 3 C / C composite materials modified with ceramics (ceramics include one or more of ZrC, SiC, and HfC). In the technical solution of this invention, it is best to grind the sample surface smooth before etching the pattern; Step Two: Preparation of the Three-Dimensional Networked Carbon Skeleton: The composite material etched in Step One (i.e., the first composite material) is immersed in the precursor solution, and then placed in a vacuum chamber and immersed for 30-50 min at a pressure of 0.01-0.09 MPa to obtain the second composite material; subsequently, the second composite material is cured in an oven at 70-100℃ for 24-48 h, and then carbonized in a tube furnace at 900-1000℃ under an argon atmosphere for 2-3 h to achieve the preparation of a three-dimensional networked carbon skeleton in the array structure, resulting in the third composite material. The third composite material is as follows. Figure 2 As shown; The precursor solution is prepared by stirring 5-10g of resorcinol, 7-12g of formaldehyde solution, and 5-18g of distilled water for 30-50 minutes to obtain a homogeneous mixture. Subsequently, 0.05-0.15g of hexadecyltrimethylammonium bromide (CTAB) is added to the homogeneous mixture as a catalyst, and stirring is continued for 20-40 minutes to obtain a homogeneous mixture. The mass concentration of the formaldehyde solution is 36 wt.%-38 wt.%, and in the following examples and comparative examples of this invention, the mass concentration of the formaldehyde solution used is 37 wt.%.

[0026] Step 3: Deposition of pyrolytic carbon: The sample prepared in Step 2 (i.e., the third composite material) is placed in a chemical vapor deposition furnace to deposit a high-texture PyC shell on the surface of the three-dimensional network carbon skeleton. The deposition temperature is 1000-1100℃, the pressure is 8-12kPa, the natural gas flow rate is 15-18L / min, and the deposition time is 4-6min. This step deposits a high-texture PyC (i.e., pyrolytic carbon layer) on the surface of the three-dimensional network carbon skeleton. On the one hand, it strengthens the original carbon skeleton, and on the other hand, the high-texture PyC has high thermal conductivity, which improves the thermal conductivity of the carbon skeleton. It constructs a multi-level thermal conduction path at the interface between the coating and the substrate, reduces the interfacial thermal resistance, and enables the heat accumulated by the coating during service to be efficiently transferred to the substrate, thereby improving the stability of the oxidation products of the surface coating.

[0027] Step 4: Coating preparation: A SiC coating is deposited on the surface of the sample (i.e., the fourth composite material) prepared in step 3 by CVD (chemical vapor deposition). The deposition temperature is 1000-1200℃, and the flow rates of H2 and trichloromethylsilane (MTS) used for deposition are 700-1300 ml / min and 0.05-0.6 g / min, respectively. The deposition time is 20-30 h.

[0028] In addition to SiC coatings, the deposited coatings (i.e., ultra-high temperature ablation resistant coatings) can also be one or more composite layer structures of ZrC coatings, HfC coatings, and TaC coatings.

[0029] Example 1 The preparation method of the superstructure coating in this embodiment includes the following steps: Step 1: Using a digital laser galvanometer method, at a density of 1.70 g / cm³ 3 The surface of the C / C composite material is polished smooth and then etched with a dot matrix pattern, such as... Figure 1 As shown, the dot pattern is a periodic array structure. The diameter of each unit structure in the dot pattern is 200 μm, the depth is 70 μm, and the distance between the centers of adjacent unit structures is 500 μm. Step Two: The composite material etched in Step One is immersed in the precursor solution, and then the entire assembly is placed in a vacuum chamber and immersed for 30 minutes at a pressure of 0.01 MPa; subsequently, it is cured in an oven at 70°C for 24 hours, and then carbonized in a tube furnace at 900°C under an argon atmosphere for 2 hours to achieve the fabrication of a three-dimensional network carbon framework in the array structure, such as... Figure 2 As shown, the three-dimensional network carbon skeleton is uniformly filled in the array structure, and the carbon skeleton and the array structure are tightly bonded together without large gaps. The precursor solution is prepared by stirring 5g of resorcinol, 7g of formaldehyde solution, and 5g of distilled water for 30 minutes to obtain a homogeneous mixture, then adding 0.05g of CTAB as a catalyst to the mixture and stirring for another 20 minutes to obtain a homogeneous mixture. Step 3: Place the sample prepared in Step 2 in a chemical vapor deposition furnace and deposit a highly textured PyC shell on the surface of the three-dimensional network carbon skeleton. The deposition temperature is 1000℃, the pressure is 8kPa, the natural gas flow rate is 15L / min, and the deposition time is 4min. Step 4: A SiC coating was deposited on the surface of the sample prepared in Step 3 using CVD. The deposition temperature was 1000℃, and the flow rates of H2 and MTS used were 700 ml / min and 0.05 g / min, respectively. The deposition time was 20 h. (Refer to...) Figure 3 and Figure 4 , Figure 3 This is a magnified view of a specific area. Figure 4 These are the overall morphology images after CVD deposition of SiC. In the two images, the black area represents the carbon phase, and the white area represents the SiC phase. Figure 3 It can be seen that the interface between SiC and the carbon framework is well bonded and exhibits a three-dimensional interpenetrating mosaic distribution structure. Figure 4 It can be observed that, with the assistance of the array structure, the SiC phase is pinned in the matrix of the composite material, and a uniformly distributed carbon skeleton can be observed inside the SiC phase.

[0030] Experimental testing showed that the interfacial bonding strength between the SiC coating and the substrate prepared in this embodiment was 18.6 MPa. Comparative Example 1 The preparation method of the comparative coating is as follows: Step 1: [The following appears to be a separate, unrelated sentence:] The density is 1.70 g / cm³. 3 The surface of the C / C composite material is polished smooth; Step 2: A SiC coating was deposited on the surface of the C / C composite sample by CVD at a deposition temperature of 1000℃. The flow rates of H2 and MTS used for deposition were 700 ml / min and 0.05 g / min, respectively, and the deposition time was 20 h.

[0031] like Figure 7 As shown, the interface between the SiC coating and the substrate (i.e., C / C composite material) prepared in this comparative example is flush. Experimental testing showed that the bonding strength between the SiC coating and the substrate was only 11.1 MPa.

[0032] As can be seen from Example 1 and Comparative Example 1, compared with Comparative Example 1 without interface modification, the bonding strength between the SiC coating and the substrate in Example 1 (11.1 MPa) increased by 67.57%, indicating that the superstructure interface design in Example 1 can effectively improve the interfacial bonding strength between the composite material and the coating.

[0033] Example 2 The preparation method of the superstructure coating in this embodiment includes the following steps: Step 1: Using a digital laser galvanometer method, at a density of 1.80 g / cm³ 3 The C / C composite material surface is polished smooth and etched with a dot matrix pattern. The dot matrix pattern is a periodic array structure. Each unit structure in the dot matrix pattern has a diameter of 300μm, a depth of 150μm, and a distance of 600μm between the centers of adjacent unit structures. Step 2: The composite material etched in Step 1 is immersed in the precursor solution, and then the whole thing is placed in a vacuum chamber and immersed for 40 min under a pressure of 0.05 MPa; then cured in an oven at 80℃ for 30 h, and then carbonized in a tube furnace at 950℃ under an argon atmosphere for 2.5 h to achieve the preparation of a three-dimensional network carbon skeleton in the array structure. The precursor solution was prepared by stirring 8g of resorcinol, 10g of formaldehyde solution, and 15g of distilled water for 40 minutes to obtain a homogeneous mixture, and then adding 0.10g of CTAB as a catalyst to the mixture and stirring for another 30 minutes to obtain a homogeneous mixture. Step 3: Place the sample prepared in Step 2 in a chemical vapor deposition furnace and deposit a highly textured PyC shell on the surface of the three-dimensional network carbon skeleton. The deposition temperature is 1100℃, the pressure is 12kPa, the natural gas flow rate is 18L / min, and the deposition time is 5min. Step 4: A SiC coating is deposited on the surface of the sample prepared in Step 3 by CVD. The deposition temperature is 1100℃, the flow rates of H2 and MTS used for deposition are 1000 ml / min and 0.3 g / min, respectively, and the deposition time is 23 h.

[0034] Experimental results show that the SiC-coated C / C composite material prepared in this embodiment has a thermal conductivity of 185.16 W / m·K and a flexural strength of 232.42 ± 3.27 MPa, demonstrating excellent mechanical load-bearing capacity.

[0035] Comparative Example 2 The preparation method of the comparative coating is as follows: Step 1: [The following appears to be a separate, unrelated sentence:] The density is 1.80 g / cm³. 3 The surface of the C / C composite material is polished smooth; Step 2: Place the C / C composite material from Step 1 in a muffle furnace at 800℃ for pre-oxidation treatment for 5 minutes to form a porous structure on the surface of the C / C composite material. Step 3: A SiC coating is deposited on the surface of the sample prepared in Step 2 using a CVD method. The deposition temperature is 1100℃, and the flow rates of H2 and MTS used for deposition are 1000 ml / min and 0.3 g / min, respectively. The deposition time is 23 h.

[0036] Experimental results showed that the SiC-coated C / C composite material prepared in this comparative example had a thermal conductivity of 148.51 W / m·K and a flexural strength of 165.33 ± 5.34 MPa.

[0037] Compared with Comparative Example 2 which was pre-oxidized, Example 2 showed a 24.68% increase in thermal conductivity, indicating that the superstructure interface design of Example 2 can effectively reduce the interfacial thermal resistance between the composite material and the coating and improve the thermal conductivity of the material. In addition, the flexural strength of Example 2 was improved compared with Comparative Example 2.

[0038] Analysis showed that the pre-oxidation treatment in Comparative Example 2 damaged the fibers and pyrolytic carbon of the C / C composite material, which reduced the thermal conductivity and strength of the composite material to a certain extent.

[0039] Example 3 The preparation method of the superstructure coating in this embodiment includes the following steps: Step 1: Using a digital laser galvanometer method, at a density of 1.85 g / cm³ 3 The C / C composite material surface is polished smooth and etched with a dot matrix pattern. The dot matrix pattern is a periodic array structure. Each unit structure in the dot matrix pattern has a diameter of 400μm, a depth of 130μm, and a distance of 700μm between the centers of adjacent unit structures. Step 2: The composite material etched in Step 1 is immersed in the precursor solution, and then the whole thing is placed in a vacuum chamber and immersed for 50 min under a pressure of 0.09 MPa; then cured in an oven at 80℃ for 48 h, and then carbonized in a tube furnace at 1000℃ in an argon atmosphere for 3 h to achieve the preparation of a three-dimensional network carbon skeleton in the array structure. The precursor solution is prepared by stirring 10g of resorcinol, 12g of formaldehyde solution, and 18g of distilled water for 50 minutes to obtain a homogeneous mixed solution, and then adding 0.15g of CTAB as a catalyst to the mixed solution and stirring for another 30 minutes to obtain a homogeneous mixed solution. Step 3: Place the sample prepared in Step 2 in a chemical vapor deposition furnace and deposit a highly textured PyC shell on the surface of the three-dimensional network carbon skeleton. The deposition temperature is 1100℃, the pressure is 10kPa, the natural gas flow rate is 16L / min, and the deposition time is 6min. Step 4: A SiC coating is deposited on the surface of the sample prepared in Step 3 by CVD. The deposition temperature is 1200℃, the flow rates of H2 and MTS used for deposition are 1300 ml / min and 0.6 g / min, respectively, and the deposition time is 30 h.

[0040] Experimental testing showed that the SiC-coated C / C composite material prepared in this embodiment did not peel off after 15s×20 cycles of oxyacetylene ablation. The mass ablation rate and linear ablation rate were only 0.24mg / s and 0.31μm / s, respectively, demonstrating good ablation resistance and thermal shock resistance.

[0041] Example 4 The preparation method of the superstructure coating in this embodiment includes the following steps: Step 1: Using a digital laser galvanometer method at a density of 2.75 g / cm³ 3 The surface of the C / C-ZrC-SiC composite material is polished smooth and etched with a lattice pattern. The lattice pattern is a periodic array structure. The diameter of each unit structure in the lattice pattern is 400μm and the depth is 150μm. The distance between the centers of adjacent unit structures is 600μm. Step 2: The composite material etched in Step 1 is immersed in the precursor solution, and then the whole thing is placed in a vacuum chamber and immersed for 40 min under a pressure of 0.06 MPa; then cured in an oven at 100°C for 36 h, and after being taken out, it is carbonized in a tube furnace at 1000°C under an argon atmosphere for 2 h to achieve the preparation of a three-dimensional network carbon skeleton in the array structure. The precursor solution was prepared by stirring 6g of resorcinol, 8g of formaldehyde solution, and 14g of distilled water for 40 minutes to obtain a homogeneous mixture, and then adding 0.13g of CTAB as a catalyst to the mixture and stirring for another 30 minutes to obtain a homogeneous mixture. Step 3: Place the sample prepared in Step 2 in a chemical vapor deposition furnace and deposit a highly textured PyC shell on the surface of the three-dimensional network carbon skeleton. The deposition temperature is 1070℃, the pressure is 10kPa, the natural gas flow rate is 15L / min, and the deposition time is 4min. Step 4: A SiC coating is deposited on the surface of the sample prepared in Step 3 by CVD. The deposition temperature is 1100℃, the flow rates of H2 and MTS used for deposition are 1200 ml / min and 0.35 g / min, respectively, and the deposition time is 25 h.

[0042] Experimental testing showed that the bonding strength between the SiC coating-coated C / C-ZrC-SiC composite matrix and the coating prepared in this embodiment was 17.2 MPa, indicating that the coating and the matrix have excellent bonding strength.

[0043] Comparative Example 3 The preparation method of the comparative coating is as follows: Step 1: Using a digital laser galvanometer method, at a density of 1.80 g / cm³ 3 The C / C composite material surface is polished smooth and etched with a dot matrix pattern. The dot matrix pattern is a periodic array structure. Each unit structure in the dot matrix pattern has a diameter of 300μm, a depth of 40μm, and a distance of 600μm between the centers of adjacent unit structures. Step 2: The composite material etched in Step 1 is immersed in the precursor solution, and then the whole thing is placed in a vacuum chamber and immersed for 40 min under a pressure of 0.05 MPa; then cured in an oven at 80℃ for 30 h, and then carbonized in a tube furnace at 950℃ under an argon atmosphere for 2.5 h to achieve the preparation of a three-dimensional network carbon skeleton in the array structure. The precursor solution was prepared by stirring 8g of resorcinol, 10g of formaldehyde solution, and 15g of distilled water for 40 minutes to obtain a homogeneous mixture, and then adding 0.10g of CTAB as a catalyst to the mixture and stirring for another 30 minutes to obtain a homogeneous mixture. Step 3: Place the sample prepared in Step 2 in a chemical vapor deposition furnace and deposit a highly textured PyC shell on the surface of the three-dimensional network carbon skeleton. The deposition temperature is 1100℃, the pressure is 12kPa, the natural gas flow rate is 18L / min, and the deposition time is 5min. Step 4: A SiC coating is deposited on the surface of the sample prepared in Step 3 by CVD. The deposition temperature is 1100℃, the flow rates of H2 and MTS used for deposition are 1000 ml / min and 0.3 g / min, respectively, and the deposition time is 23 h.

[0044] like Figure 5 As shown, the carbon skeleton in this comparative example failed to effectively fill the array structure. The thermal conductivity of the SiC-coated C / C composite material prepared was 152.32 W / m·K, and the interfacial bonding strength was 13.28 MPa. Both the thermal conductivity and strength were lower than those in Example 2.

[0045] Comparative Example 4 The preparation method of the comparative coating is as follows: Step 1: Using a digital laser galvanometer method, at a density of 1.80 g / cm³ 3 The C / C composite material surface is polished smooth and etched with a dot matrix pattern. The dot matrix pattern is a periodic array structure. Each unit structure in the dot matrix pattern has a diameter of 300μm, a depth of 150μm, and a distance of 600μm between the centers of adjacent unit structures. Step 2: The composite material etched in Step 1 is immersed in the precursor solution, and then the whole thing is placed in a vacuum chamber and immersed for 40 min under a pressure of 0.05 MPa; then cured in an oven at 80℃ for 30 h, and then carbonized in a tube furnace at 950℃ under an argon atmosphere for 2.5 h to achieve the preparation of a three-dimensional network carbon skeleton in the array structure. The precursor solution was prepared by stirring 8g of resorcinol, 10g of formaldehyde solution, and 15g of distilled water for 40 minutes to obtain a homogeneous mixed solution, and then adding 0.24g of CTAB as a catalyst to the mixed solution and stirring for another 30 minutes to obtain a homogeneous mixed solution. Step 3: Place the sample prepared in Step 2 in a chemical vapor deposition furnace and deposit a highly textured PyC shell on the surface of the three-dimensional network carbon skeleton. The deposition temperature is 1100℃, the pressure is 12kPa, the natural gas flow rate is 18L / min, and the deposition time is 5min. Step 4: A SiC coating is deposited on the surface of the sample prepared in Step 3 by CVD. The deposition temperature is 1100℃, the flow rates of H2 and MTS used for deposition are 1000 ml / min and 0.3 g / min, respectively, and the deposition time is 23 h.

[0046] like Figure 6 As shown, the high CTAB content used in this comparative example resulted in extremely small pore sizes and severe shrinkage of the prepared carbon framework, creating large gaps between it and the array structure. This mismatch with the array structure resulted in a thermal conductivity of only 126.82 W / m·K for the SiC-coated C / C composite material. This demonstrates that the small pore structure is detrimental to SiC deposition, and the presence of numerous pores in the coating reduces its thermal conductivity. This example also illustrates that not all three-dimensional carbon frameworks are suitable; a matching relationship is required.

[0047] As can be seen from the above-described solution of this invention, in the technical solution of this invention, a three-dimensional network-like carbon skeleton is filled in a periodic array pattern. After CVD deposition of the coating, the mesoscopic-microscopic multi-level pull-out mechanism strengthens the interfacial bonding strength between the coating and the composite material; the soft carbon phase and the hard ceramic phase form a three-dimensional interpenetrating structure (e.g., Figure 3As shown, the black phase is the carbon phase and the white phase is the SiC phase, which effectively alleviates the thermal stress level of the coating during preparation and service, and avoids cracking and peeling of the coating due to high thermal stress.

[0048] Furthermore, there is a strong matching relationship between array depth, carbon skeleton size, and CVD coating. When the array depth is too shallow, the carbon skeleton cannot effectively fill the array structure (e.g., Figure 5 As shown); when the skeleton size is too small, the severe shrinkage during carbonization results in a large gap between it and the array structure (e.g. Figure 6 As shown in the figure, an excessively small skeleton structure is not conducive to CVD deposition of coatings.

[0049] Furthermore, this invention employs a plant root-inspired superstructure design at the substrate-coating interface. A micrometer-scale (200-400 μm) superstructure array serves as the "main root," while a PyC-coated three-dimensional network of carbon framework acts as the "lateral roots." After CVD deposition of the SiC coating, the coating and substrate exhibit an "intercalated" structure (e.g., ...). Figure 4 As shown in the figure, reducing interfacial thermal resistance, improving the interfacial bonding strength between the substrate and the coating, and mitigating the thermal stress of the coating, ultimately achieves the preparation of a high-performance ablation-resistant coating.

[0050] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a superstructure coating, characterized in that, The process includes the following: A lattice pattern is etched on the surface of a composite material to obtain a first composite material, wherein each unit structure in the lattice pattern is a blind hole structure. The first composite material was vacuum impregnated in a precursor solution to obtain the second composite material; The second composite material is cured and carbonized to prepare a three-dimensional network carbon skeleton on the second composite material, thus obtaining the third composite material. The third composite material is subjected to chemical vapor deposition to deposit a pyrolytic carbon layer on the surface of the three-dimensional network carbon skeleton to obtain the fourth composite material; The superstructure coating is obtained by chemical vapor deposition of an ultra-high temperature ablation resistant coating on the fourth composite material.

2. The method for preparing a superstructure coating according to claim 1, characterized in that, The composite material has a density of 1.70-1.85 g / cm³. 3 C / C composite materials, or those with a density of 2.3-4.5 g / cm³. 3 The ceramic material includes a composite material of one or more of ZrC, SiC and HfC.

3. The method for preparing a superstructure coating according to claim 1, characterized in that, The diameter of the blind hole structure is 200-400μm and the depth is 70-150μm, and the center distance between adjacent blind hole structures is 500-700μm.

4. The method for preparing a superstructure coating according to claim 1, characterized in that, The preparation process of the precursor solution includes: By mass, 5-10 parts of resorcinol, 7-12 parts of formaldehyde solution and 5-18 parts of distilled water are mixed evenly to obtain a mixed solution. Then, 0.05-0.15 parts of hexadecyltrimethylammonium bromide are added to the mixed solution as a catalyst and mixed evenly to obtain the precursor solution. The mass concentration of the formaldehyde solution is 36 wt.%-38 wt.%.

5. A method for preparing a superstructure coating according to claim 1 or 4, characterized in that, To obtain the second composite material, the first composite material is vacuum impregnated in a precursor solution at a pressure of 0.01-0.09 MPa for 30-50 minutes. After that, the first composite material is removed to obtain the second composite material.

6. A method for preparing a superstructure coating according to claim 1 or 4, characterized in that, When the second composite material is cured and carbonized to prepare a three-dimensional network carbon skeleton on the second composite material, the third composite material is obtained: The second composite material is cured at 70-100℃ for 24-48 hours, and then carbonized at 900-1000℃ for 2-3 hours in a protective atmosphere to prepare a three-dimensional network carbon skeleton on the second composite material, thus obtaining the third composite material.

7. The method for preparing a superstructure coating according to claim 1, characterized in that, When the third composite material is subjected to chemical vapor deposition to deposit a pyrolytic carbon layer on the surface of the three-dimensional network carbon skeleton to obtain the fourth composite material, the deposition temperature is 1000-1100℃, the pressure is 8-12kPa, the natural gas flow rate is 15-18L / min, and the deposition time is 4-6min.

8. The method for preparing a superstructure coating according to claim 1, characterized in that, When the superstructure coating is obtained by chemical vapor deposition of the fourth composite material to form an ultra-high temperature ablation resistant coating, the deposition temperature is 1000-1200℃, the flow rate of H2 used for deposition is 700-1300 ml / min, the flow rate of trichloromethylsilane is 0.05-0.6 g / min, and the deposition time is 20-30 h.

9. A method for preparing a superstructure coating according to claim 1 or 8, characterized in that, The ultra-high temperature ablation resistant coating is a SiC coating, a ZrC coating, an HfC coating, or a TaC coating.

10. A superstructure coating, characterized in that, The superstructure coating is prepared by the preparation method according to any one of claims 1-9.

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