Core-shell structure nanowire reinforced ceramic-based modified composite material with silicon-rich coating on surface and rapid preparation method and application of core-shell structure nanowire reinforced ceramic-based modified composite material

Abstract

The invention discloses a core-shell structure nanowire reinforced ceramic matrix modified composite material containing a silicon-rich coating on the surface and a rapid preparation method and application thereof, and belongs to the technical field of carbon-carbon composite material matrix modification. The method comprises the following steps: dissolving a mixed organic precursor formed by a silicon carbide precursor and an ultra-high temperature ceramic polymer precursor in an organic solvent to form a mixed organic precursor solution, carrying out chemical liquid phase vaporization deposition on a carbon fiber preform in the mixed organic precursor solution, and then cooling to obtain a deposited composite material; performing heat treatment to obtain a silicon carbide nanowire reinforced ceramic matrix modified composite material; performing chemical liquid phase vaporization deposition in an organic solvent, then cooling and then cooling, and depositing pyrolytic carbon on the surface of the silicon carbide nanowire to form a core-shell structure, so as to obtain the core-shell structure nanowire reinforced ceramic matrix modified composite material; and gas-phase siliconizing hole sealing treatment is carried out to form a free silicon coating, and the core-shell structure nanowire reinforced ceramic-based modified composite material with the surface containing the silicon-rich coating is obtained. The ceramic-based modified composite material with low surface porosity is rapidly prepared by adopting a chemical liquid phase vaporizing deposition and chemical vapor siliconizing combined process.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon-carbon composite material matrix modification, and specifically relates to a core-shell structured nanowire-reinforced ceramic-based modified composite material with a silicon-rich coating on the surface, and a rapid preparation method and application thereof. Background Art

[0002] Ultrahigh temperature ceramic modified carbon-carbon composites combine the excellent high temperature resistance of ultrahigh temperature ceramics (UHTC) and the excellent high temperature mechanical properties of C / C composites, and are considered to be one of the most promising structural materials in extreme environments. Matrix modification is one of the common methods for preparing ultrahigh temperature ceramic modified carbon-carbon composites. Common methods include reactive melt infiltration (RMI), precursor impregnation pyrolysis (PIP) and chemical vapor deposition (CVI / CVD). The RMI process uses capillary force to infiltrate the melt into the porous preform, and through its chemical reaction with carbon to generate a modified ultrahigh temperature ceramic phase. Although the densification efficiency is high and the production cycle is short, it will inevitably cause damage to the carbon fiber during the melt infiltration process, resulting in a decrease in the mechanical properties of the composite material. PIP is to infiltrate a polymer organic ceramic polymer precursor into the interior of the carbon fiber preform, and then convert it into a modified ceramic through a high temperature carbon thermal reduction reaction heat treatment pyrolysis. It has the advantage of simple process, but it requires multiple cycles of impregnation and pyrolysis processes, so the preparation cycle is long. The CVI process is a chemical reaction process that converts gaseous raw materials into solid products. It can finely control the material structure and has little damage to the fibers. However, it has a long preparation cycle, high cost, and high requirements for equipment. As an improved process of chemical vapor deposition (CVI / CVD), chemical liquid phase vapor deposition (CLVI / CLVD) has a densification rate that is more than 2 orders of magnitude faster than the reported isothermal CVI process, so it can greatly reduce the preparation cost and shorten the preparation cycle. However, CLVD has the process problems of large pores being difficult to deposit and high-density composite materials being difficult to prepare, and ultra-high temperature ceramics have the inherent disadvantage of brittleness, which greatly limits the application environment of this process. Therefore, it is possible to consider combining the advantages of different processes to quickly prepare modified composite materials, while introducing nano-reinforcements with good chemical stability and excellent mechanical properties to achieve the reinforcement effect on ceramic-based composites.

[0003] Hou et al. (Ablation behaviors and mechanisms of C f / HfC PIP -SiC CVIComposites: From SiO2 nanowires film to HfO2 skeleton[J].Corrosion Science, 2022, 209.) The preparation of ceramics by CVI process can fill the cracks and holes formed by the gas products formed by the carbon thermal reduction reaction during the PIP heat treatment, and connect the HfC ceramic particles prepared by the PIP method. However, in this combined process, due to the introduction of the CVI process, the overall process preparation cycle is further increased, and the process is relatively complicated.

[0004] Zhang et al. (Ablation behavior of C / C-HfC-SiC composites prepared by joint route of precursor infiltration and pyrolysis and gaseous silicon infiltration [J]. Chinese Journal of Aeronautics, 2023, 36 (9): 426-436.) used the gas phase silicon infiltration process (GSI, infiltration of porous C / C with gas phase silicon in a high temperature environment) to fill the defects formed in PIP due to the heat treatment reaction, and the coverage of the surface Si-rich layer increased its ablation resistance. However, although the GSI process was introduced and the heat treatment temperature was increased, PIP is still the main process for preparing composite materials, the overall preparation cycle has not been significantly reduced, and the introduced reinforcing phase SiC nanowires are difficult to stably maintain the nanowire morphology above 1800°C, and its reinforcing effect is weakened.

[0005] He et al. (Microstructure and ablation property of C / C-ZrC-SiC composites fabricated by chemical liquid-vapor deposition combined with precursor infiltration and pyrolysis [J]. Ceramics International, 2019, 45 (3): 3767-3781) found that the CLVD process preferentially fills the small pores within the bundle, while the PIP process preferentially deposits the large pores between bundles and layers. The combined process of CLVD and PIP reduces the porosity of the composite and increases the ceramic content, resulting in improved mechanical properties and ablation properties. However, the intrinsic defects of a large number of pores generated on the surface by high-temperature pyrolysis in both CLVD and PIP are not effectively filled, and the ablation and mechanical properties of the modified composite need to be further improved.

[0006] Therefore, developing a new combined process to achieve the rapid preparation of ceramic-based modified composites and reduce the macroporous defect structure on their surface to obtain high-density, high-performance composites is an urgent problem to be solved. Summary of the invention

[0007] In order to overcome the shortcomings of the above-mentioned prior art, in view of the inherent defects of ultra-high temperature ceramics such as brittleness, the presence of a large number of pore defects on the surface after high-temperature heat treatment and the long preparation cycle, the present invention provides a core-shell structured nanowire-reinforced ceramic-based modified composite material with a silicon-rich coating on the surface, and a rapid preparation method and application thereof, and a ceramic-based modified composite material with low surface porosity is quickly prepared by a combined process of CLVD and GSI.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for rapidly preparing a core-shell structured nanowire-reinforced ceramic-based modified composite material having a silicon-rich coating on the surface, comprising the following steps:

[0010] S1: dissolving a mixed organic precursor formed by a silicon carbide precursor and an ultra-high temperature ceramic polymer precursor in an organic solvent to form a mixed organic precursor solution, subjecting a carbon fiber preform to a first chemical liquid phase vapor deposition in the mixed organic precursor solution, followed by cooling and recooling to obtain a composite material after deposition;

[0011] S2: heat treating the deposited composite material, then cooling it down, and simultaneously forming silicon carbide nanowires, ceramic phase and pyrolytic carbon to obtain a silicon carbide nanowire reinforced ceramic matrix modified composite material;

[0012] S3: subjecting the silicon carbide nanowire reinforced ceramic matrix modified composite material to a second chemical liquid phase vapor deposition in an organic solvent, followed by cooling and then depositing pyrolytic carbon on the surface of the silicon carbide nanowire to form a core-shell structure, thereby obtaining a core-shell structure nanowire reinforced ceramic matrix modified composite material;

[0013] S4: The core-shell structured nanowire reinforced ceramic-based modified composite material is subjected to a gas phase silicon infiltration and pore sealing treatment to form a free silicon coating, thereby obtaining a core-shell structured nanowire reinforced ceramic-based modified composite material having a silicon-rich coating on the surface.

[0014] In one embodiment, in S1, the density of the carbon fiber preform is 0.4-1.2 g / cm 3 The carbon fiber preform has a size of Cylindrical carbon fiber preform.

[0015] In one embodiment, in S1, the ultrahigh temperature ceramic polymer precursor is any one of a hafnium carbide precursor, a zirconium carbide precursor and a tantalum carbide precursor.

[0016] In one embodiment, in S1 and S3, the organic solvent is any one of xylene, toluene, cyclohexane and kerosene.

[0017] In one embodiment, in S1, the mass ratio of the silicon carbide precursor, the ultrahigh temperature ceramic polymer precursor and the organic solvent is 1:(5-10):(1-10).

[0018] In one embodiment, in S1, the process of the first chemical liquid phase vapor deposition is as follows:

[0019] The carbon fiber preform is placed in a liquid phase furnace filled with a mixed organic precursor solution, heated to 800-1200°C at a rate of 10-20°C / min, chemically vaporized for 16-24h, and then cooled to 600°C at a rate of 10-20°C / min;

[0020] In S3, the process of the second chemical liquid phase vapor deposition is as follows:

[0021] The silicon carbide nanowire reinforced ceramic matrix modified composite material is placed in a liquid phase furnace filled with an organic solvent, heated to 800-1200°C at a rate of 10-20°C / min, chemically vaporized for 5-15 hours, and then cooled to 600°C at a rate of 10-20°C / min.

[0022] In one embodiment, in S2, the heat treatment process is as follows:

[0023] Under the protection of argon atmosphere, heat up to 1500-1800°C at a rate of 2-5°C / min and keep warm for 2-4h;

[0024] In S4, the process of the gas phase siliconization sealing treatment is as follows:

[0025] Keep warm at 1800-2150°C for 10-30 minutes.

[0026] The present invention also provides a core-shell structure nanowire reinforced ceramic matrix modified composite material with a silicon-rich coating on the surface prepared by the preparation method, comprising a core-shell structure nanowire reinforced ceramic matrix modified composite material and a free silicon coating; the core-shell structure nanowire reinforced ceramic matrix modified composite material comprises a ceramic phase, carbon fiber, silicon carbide nanowires and pyrolytic carbon;

[0027] The ceramic phase and pyrolytic carbon are co-deposited around the carbon fibers, the silicon carbide nanowires grow in large quantities in the internal voids and on the surface of the core-shell structure nanowire reinforced ceramic matrix modified composite material, pyrolytic carbon is deposited on the surface of the silicon carbide nanowires to form a core-shell structure, and the free silicon coating is deposited on the core-shell structure nanowire reinforced ceramic matrix modified composite material.

[0028] In one embodiment, the core-shell structure divides the macroporous defect structure on the surface of the core-shell structured nanowire-reinforced ceramic-based modified composite material to construct a small grid structure forming a three-dimensional network; the free silicon coating fills and covers the small grid structure.

[0029] The present invention also provides the application of the core-shell structured nanowire reinforced ceramic-based modified composite material with a silicon-rich coating on the surface in the field of thermal protection.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention provides a method for rapidly preparing a core-shell structure nanowire-reinforced ceramic-based modified composite material with a silicon-rich coating on the surface. The method adopts a chemical liquid phase vapor deposition and a gas phase siliconization process to rapidly prepare a high-performance ceramic-based modified composite material with low surface porosity. The method mainly uses a chemical liquid phase vapor deposition process to form silicon carbide nanowires in one step while preparing ultra-high temperature ceramic components, and then deposits pyrolytic carbon on the surface of the nanowires to form a stable reinforcement of the core-shell structure. The structure is used to construct a three-dimensional network space, and the large pores on the surface of the composite material are effectively divided into small grid structures to promote the rapid deposition of free silicon during gas phase siliconization, so as to achieve rapid densification of the surface. The above method can effectively shorten the preparation cycle, reduce the surface porosity, and construct a core-shell structure to effectively enhance the matrix and improve the thermal conductivity, so that the mechanical properties and ablation properties of the composite material are significantly improved, and it has good industrial application prospects and economic benefits.

[0032] The present invention provides a core-shell structured nanowire reinforced ceramic-based modified composite material having a silicon-rich coating on the surface, which is prepared by the above-mentioned preparation method. Ultrahigh temperature ceramics and nanowire reinforcement phases are introduced in a one-step method, pyrolytic carbon is deposited on the surface of SiC nanowires to form a core-shell structure, and a high-stability core-shell structure is constructed by depositing pyrolytic carbon to achieve effective division of large pore defect structures. The formed small grid structure improves the high-temperature stability of the SiC nanowires, reduces structural changes caused by high-temperature treatment of the vapor phase siliconization process, and assists the vapor phase siliconization technology to quickly densify the surface of the composite material. The structure exhibits excellent performance in many aspects such as load-bearing, heat transfer and ablation resistance.

[0033] Furthermore, the core-shell structured nanowire-reinforced ceramic-based modified composite material utilizes the core-shell structure to divide the large surface pores into small grid structures, thereby enabling the filling of the surface pores by free silicon, and finally depositing to form a dense silicon-rich coating.

[0034] The present invention also provides a core-shell structured nanowire-reinforced ceramic-based modified composite material with a silicon-rich coating on the surface, which has excellent mechanical properties and anti-oxidation and ablation properties and can be widely used in the field of thermal protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Figure (a) is a flow chart of the rapid preparation method of the present invention, and Figure (b) is a schematic diagram of the corresponding equipment;

[0036] Figure 2 Figure (a) is a macroscopic morphology of the SiC nanowire-reinforced C / C-HfC-SiC composite material prepared in Example 1; Figure (b) is a macroscopic morphology of the non-SiC nanowire-reinforced ceramic matrix modified composite material prepared in Comparative Example 1;

[0037] Figure 3 Figures (a) and (b) show the microscopic morphology of SiC nanowire-reinforced C / C-HfC-SiC composites before and after polishing; Figures (c) and (d) show the microscopic morphology of the core-shell structure formed by pyrolytic carbon deposited on the surface of SiC nanowires after the second chemical liquid phase vapor deposition process;

[0038] Figure 4 Figure (a) is a TEM image of SiC nanowires in a SiC nanowire-reinforced C / C-HfC-SiC composite material obtained after the first chemical liquid phase vaporization process in Example 1, and Figure (b) is a TEM image of a core-shell structure in a core-shell structure nanowire-reinforced C / C-HfC-SiC composite material obtained after the second chemical liquid phase vaporization process in Example 1;

[0039] Figure 5 Figures (a) and (c) are respectively the cross-section, surface micromorphology, and corresponding energy spectrum and XRD results of the SiC nanowire-reinforced ceramic matrix modified composite material with a silicon carbide-rich coating on the surface obtained in Comparative Example 2 after vapor phase siliconization; Figures (b) and (d) are the cross-section, surface micromorphology, and corresponding energy spectrum and XRD results of the nanowire-reinforced ceramic matrix modified composite material with a silicon-rich coating on the surface obtained in Example 1;

[0040] Figure 6 It is the thermal diffusivity and thermal conductivity obtained by testing the composite material prepared by chemical liquid phase vapor deposition in the present invention. Figure 6HS0 is a SiC-free nanowire-reinforced C / C-HfC-SiC composite material obtained by the first chemical liquid phase vapor deposition process in Example 1, HS1 is a SiC nanowire-reinforced C / C-HfC-SiC composite material obtained by the first chemical liquid phase vapor deposition process in Example 2, and HS2 is a core-shell structure nanowire-reinforced C / C-HfC-SiC composite material obtained by two chemical liquid phase vapor deposition processes in Example 1;

[0041] Figure 7 The heat flux density is 2.38MW / m 2 Macroscopic morphology after 60 seconds of oxyacetylene flame ablation; Figure 7 (a) The sample is a C / C-HfC-SiC composite material without SiC nanowires and reinforced with a silicon carbide-rich coating on the surface obtained by vapor phase siliconization in Comparative Example 1. Figure 7 (b) The sample is a SiC nanowire reinforced C / C-HfC-SiC composite material having a silicon carbide-rich coating on the surface obtained by vapor phase siliconization in Comparative Example 2. Figure 7 (c) The sample is a C / C-HfC-SiC composite material with a core-shell structure nanowire reinforced with a silicon-rich coating on the surface obtained by vapor phase siliconization in Example 1;

[0042] Figure 8 This is the microscopic morphology of the ablation center of the sample after oxyacetylene ablation; Figure 8 (a) is a SiC nanowire-free reinforced C / C-HfC-SiC composite material having a silicon carbide-rich coating on the surface obtained by vapor phase siliconization in Comparative Example 1, Figure 8 (b) is a SiC nanowire reinforced C / C-HfC-SiC composite material having a silicon carbide-rich coating on the surface obtained by vapor phase siliconization in Comparative Example 2, Figure 8 (c) is a core-shell structured nanowire reinforced C / C-HfC-SiC composite material having a silicon-rich coating on the surface obtained by vapor phase siliconization in Example 1. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0044] 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.

[0045] Herein, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0046] In this document, unless otherwise specified, “includes,” “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.”

[0047] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0048] The present invention provides a core-shell structure nanowire reinforced ceramic-based modified composite material with a silicon-rich coating on the surface, and a rapid preparation method and application thereof. The preparation method adopts a chemical liquid phase vapor deposition process to introduce ultra-high temperature ceramics and construct a core-shell structure, which plays a role in strengthening the matrix, filling gaps and improving thermal conductivity; secondly, a surface sealing treatment is performed by combining a gas phase siliconization process to quickly prepare a core-shell structure nanowire reinforced ceramic-based modified composite material with low surface porosity. The chemical liquid phase vapor deposition process regulates the core-shell structure by adjusting the deposition temperature, the composition of the precursor solution and the heat treatment temperature, and regulates the composition and microstructure of the coating formed on the surface of the ceramic-based modified composite material by means of the strong penetration ability of the gas phase silicon in the gas phase siliconization process, thereby improving the density, mechanics and anti-oxidation and ablation properties of the composite material.

[0049] like Figure 1 As shown, the present invention provides a method for rapidly preparing a core-shell structured nanowire-reinforced ceramic-based modified composite material having a silicon-rich coating on the surface, comprising the following steps:

[0050] S1: dissolving a mixed organic precursor formed by a silicon carbide precursor and an ultra-high temperature ceramic polymer precursor in an organic solvent to form a mixed organic precursor solution, wherein the mass ratio of the silicon carbide precursor, the ultra-high temperature ceramic polymer precursor and the organic solvent is 1:(5-10):(1-10), subjecting a carbon fiber preform to a first chemical liquid phase vapor deposition in the mixed organic precursor solution, followed by cooling and recooling to obtain a composite material after deposition;

[0051] Specifically, the process of the first chemical liquid phase vapor deposition is as follows:

[0052] The carbon fiber preform is placed in a liquid phase furnace filled with a mixed organic precursor solution, heated to 800-1200°C at a rate of 10-20°C / min, chemically vaporized for 16-24 hours, and then cooled to 600°C at a rate of 10-20°C / min; by adjusting the chemical liquid phase vaporization deposition process parameters, ultra-high temperature ceramics and nanowire reinforcement phases can be introduced simultaneously, reducing the time for additional introduction of reinforcement phases or matrix densification.

[0053] More specifically, the density of the carbon fiber preform is 0.4 to 1.2 g / cm 3 The carbon fiber preform has a size of The cylindrical carbon fiber preform is preferably a preform of a super high temperature ceramic polymer. More preferably, the ultra-high temperature ceramic polymer precursor is any one of a hafnium carbide precursor, a zirconium carbide precursor and a tantalum carbide precursor. The organic solvent is any one of xylene, toluene, cyclohexane and kerosene.

[0054] S2: heat treating the deposited composite material, then cooling it down, and simultaneously forming silicon carbide nanowires, ceramic phase and pyrolytic carbon to obtain a silicon carbide nanowire reinforced ceramic matrix modified composite material;

[0055] Specifically, the heat treatment process is as follows:

[0056] Under the protection of argon atmosphere, the temperature is raised to 1500-1800°C at a rate of 2-5°C / min and kept at this temperature for 2-4 hours. The heat treatment temperature is 1500-1800°C to avoid the phenomenon that the prepared silicon carbide nanowires will agglomerate or coarsen due to excessively high temperature.

[0057] S3: subjecting the silicon carbide nanowire reinforced ceramic matrix modified composite material to a second chemical liquid phase vapor deposition in an organic solvent, followed by cooling and then depositing pyrolytic carbon on the surface of the silicon carbide nanowire to form a core-shell structure, thereby obtaining a core-shell structure nanowire reinforced ceramic matrix modified composite material;

[0058] Since SiC nanowires have problems such as poor high-temperature structural stability, easy agglomeration and easy decomposition in actual preparation and application, pyrolytic carbon is deposited on their surface to form a core-shell structure. First, its thermal stability is improved; second, this structure can enhance the connection between the nanowires and the matrix, giving full play to the advantages of high elasticity and high modulus of SiC nanowires. At the same time, the multi-stage pull-out phenomenon during fracture can further consume energy and improve the mechanical properties of ceramic materials; third, the intrinsic thermal conductivity of the shell pyrolytic carbon is relatively high, and the nanowires are connected to each other to construct a three-dimensional thermal conductive network, which improves the thermal conductivity of the composite material.

[0059] Specifically, the process of the second chemical liquid phase vapor deposition is as follows:

[0060] The silicon carbide nanowire reinforced ceramic matrix modified composite material is placed in a liquid phase furnace filled with an organic solvent, heated to 800-1200°C at a rate of 10-20°C / min, chemically vaporized for 5-15 hours, and then cooled to 600°C at a rate of 10-20°C / min; this process can utilize the chemical liquid phase vaporization deposition process to grow SiC nanowires under non-catalytic conditions and quickly deposit pyrolytic carbon to construct a core-shell structure.

[0061] More preferably, the organic solvent is any one of xylene, toluene, cyclohexane and kerosene.

[0062] S4: performing a gas phase siliconization and sealing treatment on the core-shell structured nanowire reinforced ceramic matrix modified composite material to form a free silicon coating, thereby obtaining a core-shell structured nanowire reinforced ceramic matrix modified composite material having a silicon-rich coating on the surface;

[0063] Specifically, the process of gas phase siliconization sealing treatment is as follows:

[0064] Keep warm at 1800-2150°C for 10-30 minutes.

[0065] The present invention also provides a core-shell structured nanowire-reinforced ceramic-based modified composite material having a silicon-rich coating on the surface thereof, which is prepared by the above-mentioned preparation method, comprising the core-shell structured nanowire-reinforced ceramic-based modified composite material and a free silicon coating deposited on the surface of the core-shell structured nanowire-reinforced ceramic-based modified composite material;

[0066] The core-shell structure nanowire reinforced ceramic matrix modified composite material comprises a ceramic phase, carbon fiber, silicon carbide nanowires and pyrolytic carbon;

[0067] The ceramic phase and pyrolytic carbon are co-deposited around the carbon fibers, the silicon carbide nanowires grow in large quantities in the internal voids and on the surface of the core-shell structure nanowire reinforced ceramic matrix modified composite material, pyrolytic carbon is deposited on the surface of the silicon carbide nanowires to form a core-shell structure, and the free silicon coating is deposited on the core-shell structure nanowire reinforced ceramic matrix modified composite material;

[0068] The core-shell structure divides the macroporous defect structure on the surface of the core-shell structure nanowire-enhanced ceramic matrix modified composite material to construct a small grid structure forming a three-dimensional network; the free silicon coating fills and covers the small grid structure. Specifically, the core of the core-shell structure is silicon carbide nanowires, and the shell is pyrolytic carbon.

[0069] Through the combined process of rapidly preparing nanowire-reinforced ceramic-based modified composite materials, pyrolytic carbon is deposited on the surface of SiC nanowires to form a core-shell structure, thereby improving the high-temperature stability of the SiC nanowires and reducing the structural changes caused by the high-temperature treatment of the vapor phase siliconization process.

[0070] After constructing the core-shell structure, the macroporous defect structure on the surface of the composite material was effectively divided, and a small grid structure of a three-dimensional network was constructed (such as Figure 3 (c)), which is conducive to the rapid sealing of the surface by vapor phase siliconization (as shown in Figure 5 As shown in Table 1), a dense coating is formed to reduce the porosity. At the same time, the nanomaterial itself has a large specific surface area, and the pyrolytic carbon in the shell of the nanowire can fully react with the silicon vapor to quickly form a high-quality, uniformly distributed SiC coating. Subsequently, due to the low diffusion rate of silicon in the SiC coating, the silicon vapor cannot continue to diffuse into the internal matrix, and the unreacted free silicon can only condense on the SiC coating that has been formed on the surface. Therefore, the surface sealing coating of the core-shell structure nanowire reinforced composite material contains a large amount of free silicon and has a low porosity.

[0071] The flexural strength and flexural modulus of the core-shell structured nanowire reinforced composite material with a silicon-rich coating on the surface reached 138.35MPa and 18.50GPa, respectively, which were 29.5% and 19.4% higher than those of the silicon carbide nanowire reinforced modified composite material with a silicon carbide-rich coating on the surface, as shown in Table 2. 2 After 60s of ablation under oxyacetylene flame, the core-shell structured nanowire reinforced composite material with a silicon-rich coating on the surface has good ablation performance, with a wire ablation rate and a mass ablation rate of 1.02μm / s and 0.25mg / s respectively. The reason is that the surface coating is rich in free silicon (such as Figure 5 The evaporation heat absorption and the improved thermal conductivity due to the core-shell structure (as shown in Figure 6 As shown in Figure 2, the surface temperature of the ablation center decreases, which promotes the formation of a dense oxide layer on the surface (as shown in Figure 2). Figure 8 shown).

[0072] The present invention adopts a combined process of CLVD and GSI to quickly prepare a ceramic-based modified composite material with low surface porosity. The core-shell structure formed by depositing pyrolytic carbon on the surface of silicon carbide nanowires using CLVD can play a role in strengthening the matrix. At the same time, the thermal conductivity is improved due to the filling of the internal voids of the composite material and the heat transfer path provided by the deposited pyrolytic carbon. In addition, the network structure formed by constructing the core-shell structure divides the large pores on the surface of the composite material into small grid structures, and the sealing coating deposited on the surface of the composite material by combining the chemical vapor siliconization process contains a large amount of free silicon. The evaporation and oxidation of free silicon during ablation has the effect of reducing the surface temperature, thereby improving the ablation performance of the composite material. In addition, the preparation method provided by the present invention has a short preparation cycle, a fast deposition rate, uniform distribution of ceramic products, and little damage to the fibers during the preparation process.

[0073] The present invention also provides the core-shell structure nanowire reinforced ceramic matrix modified composite material with a silicon-rich coating on the surface, which has excellent mechanical properties and anti-oxidation and ablation properties and can be widely used in the field of thermal protection.

[0074] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it 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 within the scope limited by the appended claims of the application equally.

[0075] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0076] Embodiment 1:

[0077] (1) Weigh a certain amount of polycarbosilane and ultra-high temperature ceramic hafnium carbide polymer precursor and dissolve them in 10L of xylene (the mass ratio of polycarbosilane, ultra-high temperature ceramic hafnium carbide polymer precursor, and xylene is 1:5:5), and subject them to ultrasonic vibration for 2 hours to obtain a uniformly dispersed mixed organic precursor solution;

[0078] (2) The density is 0.4 g / cm 3 , the preform with a size of φ80 mm×10 mm, the heating elements H1 and H2 and other components are fully assembled, and a uniformly dispersed mixed organic precursor solution is poured into the reaction container so that the upper surface of the heating element H1 is immersed in the mixed organic precursor solution;

[0079] (3) Start the power supply of the equipment and adjust the power so that the temperature of the heating element H2 is raised to 800°C at a rate of 10°C / min and kept at this temperature for 24 hours; when cooling, it is lowered to 600°C at a rate of 10°C / min, and then the power supply is turned off and cooled with the furnace;

[0080] (4) placing the composite material obtained in (3) in an isothermal furnace in a flowing argon environment for heat treatment, heating the temperature to 1500° C. at a heating rate of 2° C. / min, keeping the temperature for 2 h, then turning off the power and cooling the furnace to obtain a SiC nanowire reinforced C / C-HfC-SiC composite material;

[0081] (5) placing the composite material obtained in (4) into a liquid phase furnace filled with an organic solvent, heating it to 800°C at a rate of 10°C / min, and chemically vaporizing and depositing it for 5 hours. Then cooling it to 600°C at a rate of 10°C / min, turning off the power and cooling it with the furnace, to obtain a core-shell structure nanowire reinforced C / C-HfC-SiC composite material;

[0082] (6) The core-shell structured nanowire reinforced C / C-HfC-SiC composite material was subjected to a gas phase siliconization and sealing treatment. Under an argon protection environment, the siliconization temperature was 1800°C and the insulation time was 10 min to obtain a core-shell structured nanowire reinforced C / C-HfC-SiC composite material with a silicon-rich coating on the surface.

[0083] After the introduction of SiC nanowires, pyrolytic carbon is deposited on the surface, which can, firstly, improve its thermal stability. After gas-phase siliconization, its structure changes little. Secondly, it can enhance the connection between the nanowires and the matrix. The multi-stage pull-out phenomenon of pyrolytic carbon and SiC nanowires during fracture can further consume energy and improve the mechanical properties of the composite material. Thirdly, the intrinsic thermal conductivity of the shell pyrolytic carbon is high, and the nanowires are connected to each other to construct a three-dimensional thermal conductive network, which improves the thermal conductivity of the composite material. Fourthly, the core-shell structure divides the large pore defect structure into smaller ones, which is beneficial to the surface sealing after gas-phase siliconization and the rapid deposition of silicon-rich coating, which can greatly reduce the ablation surface temperature. Therefore, the porosity of the C / C-HfC-SiC composite material reinforced with a core-shell structure nanowire having a silicon-rich coating on the surface obtained in Example 1 is 3.93%, and the mechanical properties are significantly improved. The bending strength and bending modulus are 138.35 MPa and 18.50 GPa, respectively. Secondly, the improved thermal conductivity, coupled with the large amount of free silicon contained in the surface sealing coating, plays a role in significantly cooling the surface during ablation (the ablation center temperature is 1885°C), resulting in the formation of a dense oxide layer, and the ablation performance is significantly improved, and the ablation linear ablation rate is 1.02 μm / s (see Table 2 for details).

[0084] Embodiment 2:

[0085] (1) Weigh a certain amount of polycarbosilane and ultra-high temperature ceramic zirconium carbide and tantalum carbide polymer precursors and dissolve them in 10L toluene (the mass ratio of polycarbosilane, ultra-high temperature ceramic zirconium carbide and tantalum carbide to toluene is 1:5:1), and then ultrasonically vibrate for 2 hours to obtain a uniformly dispersed mixed organic precursor solution;

[0086] (2) The density is 0.6 g / cm 3 , the preform with a size of φ80 mm×15 mm, the heating elements H1 and H2 and other components are fully assembled, and a uniformly dispersed mixed organic precursor solution is poured into the reaction container so that the upper surface of the heating element H1 is immersed in the mixed organic precursor solution;

[0087] (3) Start the power supply of the equipment and adjust the power so that the temperature of the heating element H2 is raised to 900°C at a rate of 15°C / min and kept at this temperature for 20 hours; when cooling, it is lowered to 600°C at a rate of 15°C / min, and then the power supply is turned off and cooled with the furnace;

[0088] (4) placing the composite material obtained in (3) in an isothermal furnace in a flowing argon environment for heat treatment, heating the temperature to 1600° C. at a heating rate of 3° C. / min, keeping the temperature for 2 h, then turning off the power and cooling with the furnace to obtain a SiC nanowire reinforced C / C-ZrC-TaC-SiC modified composite material;

[0089] (5) The SiC nanowire-reinforced C / C-ZrC-TaC-SiC modified composite material obtained in (4) was placed in a liquid phase furnace filled with an organic solvent, heated to 900°C at a rate of 15°C / min, and chemically vaporized for 10 hours. Then, the temperature was lowered to 600°C at a rate of 15°C / min, the power was turned off, and the furnace was cooled to obtain a core-shell structure nanowire-reinforced C / C-ZrC-TaC-SiC composite material;

[0090] (6) The core-shell structured nanowire reinforced C / C-ZrC-TaC-SiC composite material was subjected to a gas phase siliconization and sealing treatment. Under an argon protection environment, the siliconization temperature was 1900°C and the insulation time was 15 min to obtain a core-shell structured nanowire reinforced C / C-ZrC-TaC-SiC composite material with a silicon-rich coating on the surface.

[0091] Embodiment 3:

[0092] (1) Weigh a certain amount of polycarbosilane and ultra-high temperature ceramic hafnium carbide and tantalum carbide polymer precursors and dissolve them in 10L of cyclohexane (the mass ratio of polycarbosilane, ultra-high temperature ceramic hafnium carbide and tantalum carbide polymer precursors, and cyclohexane is 1:10:10), and ultrasonically vibrate for 2 hours to obtain a uniformly dispersed mixed organic precursor solution;

[0093] (2) The density is 0.9 g / cm 3 , the preform with a size of φ100mm×20mm, the heating elements H1 and H2 and other components are fully assembled, and a uniformly dispersed mixed organic precursor solution is poured into the reaction container so that the upper surface of the heating element H1 is immersed in the mixed organic precursor solution;

[0094] (3) Start the power supply of the equipment and adjust the power so that the temperature of the heating element H2 is raised to 1000°C at a rate of 20°C / min and kept at this temperature for 16 hours; when cooling, it is lowered to 600°C at a rate of 20°C / min, and then the power supply is turned off and cooled with the furnace;

[0095] (4) placing the composite material obtained in (3) in an isothermal furnace in a flowing argon environment for heat treatment, heating the temperature to 1700° C. at a heating rate of 4° C. / min, keeping the temperature for 3 h, then turning off the power and cooling the furnace to obtain a SiC nanowire reinforced C / C-HfC-TaC-SiC composite material;

[0096] (5) placing the composite material obtained in (4) into a liquid phase furnace filled with an organic solvent, heating it to 1000°C at a rate of 20°C / min, and chemically vaporizing and depositing it for 15 hours. Then cooling it to 600°C at a rate of 20°C / min, turning off the power and cooling it with the furnace, to obtain a core-shell structure nanowire reinforced C / C-HfC-TaC-SiC composite material;

[0097] (6) The core-shell structured nanowire reinforced C / C-HfC-TaC-SiC composite material was subjected to a gas phase siliconization and sealing treatment. Under an argon protection environment, the siliconization temperature was 1900°C and the insulation time was 30 min to obtain a core-shell structured nanowire reinforced C / C-HfC-TaC-SiC composite material with a silicon-rich coating on the surface.

[0098] Embodiment 4:

[0099] (1) Weigh a certain amount of polycarbosilane and ultra-high temperature hafnium carbide, zirconium carbide and tantalum carbide polymer precursors and dissolve them in 10L kerosene (the mass ratio of the ultra-high temperature ceramic polymer precursor composed of polycarbosilane, ultra-high temperature hafnium carbide, zirconium carbide and tantalum carbide polymer precursors to kerosene is 1:10:5), and then ultrasonically vibrate for 2 hours to obtain a uniformly dispersed mixed organic precursor solution;

[0100] (2) The density is 1.2 g / cm 3 , the preform with a size of φ120mm×30mm, the heating elements H1 and H2 and other components are fully assembled, and a uniformly dispersed mixed organic precursor solution is poured into the reaction container so that the upper surface of the heating element H1 is immersed in the mixed organic precursor solution;

[0101] (3) Start the power supply of the equipment and adjust the power so that the temperature of the heating element H2 is raised to 1200°C at a rate of 20°C / min and kept at this temperature for 16 hours; when cooling, it is lowered to 600°C at a rate of 20°C / min, and then the power supply is turned off and cooled with the furnace;

[0102] (4) placing the composite material obtained in (3) in an isothermal furnace in a flowing argon environment for heat treatment, heating the temperature to 1800° C. at a heating rate of 5° C. / min, keeping the temperature for 4 h, then turning off the power and cooling the furnace to obtain a SiC nanowire reinforced C / C-HfC-ZrC-TaC-SiC composite material;

[0103] (5) placing the composite material obtained in (4) into a liquid phase furnace filled with an organic solvent, heating it to 1200°C at a rate of 20°C / min, and chemically vaporizing and depositing it for 15 hours. Then cooling it to 600°C at a rate of 20°C / min, turning off the power and cooling it with the furnace, to obtain a core-shell structure nanowire reinforced C / C-HfC-ZrC-TaC-SiC composite material;

[0104] (6) The core-shell structured nanowire reinforced C / C-HfC-ZrC-TaC-SiC composite material was subjected to vapor phase siliconization and sealing treatment. Under an argon protection environment, the siliconization temperature was 2150°C and the insulation time was 30 min to obtain a core-shell structured nanowire reinforced C / C-HfC-ZrC-TaC-SiC composite material with a silicon-rich coating on the surface.

[0105] Comparative Example 1:

[0106] (1) Weigh a certain amount of polycarbosilane and ultra-high temperature hafnium carbide polymer precursor and dissolve them in 10L of xylene (the mass ratio of polycarbosilane, ultra-high temperature hafnium carbide polymer precursor, and xylene is 1:5:5), and subject them to ultrasonic vibration for 2 hours to obtain a uniformly dispersed mixed organic precursor solution;

[0107] (2) The density is 0.4 g / cm 3 , the preform with a size of φ80 mm×10 mm, the heating elements H1 and H2 and other components are fully assembled, and a uniformly dispersed mixed organic precursor solution is poured into the reaction container so that the upper surface of the heating element H1 is immersed in the mixed organic precursor solution;

[0108] (3) Start the power supply of the equipment and adjust the power so that the temperature of the heating element H2 is raised to 1000°C at a rate of 10°C / min and kept at this temperature for 24 hours; when cooling, it is lowered to 600°C at a rate of 10°C / min, and then the power supply is turned off and cooled with the furnace;

[0109] (4) placing the composite material obtained in (3) in an isothermal furnace in a flowing argon environment for heat treatment, heating the temperature to 1850° C. at a heating rate of 2° C. / min, keeping the temperature for 2 h, then turning off the power and cooling the furnace to obtain a SiC nanowire-free reinforced ceramic matrix modified composite material;

[0110] (5) The composite material obtained in (4) was placed in a liquid phase furnace filled with an organic solvent, and the temperature was raised to 800°C at a rate of 10°C / min, and chemical liquid phase vapor deposition was performed for 5 hours. Then, the temperature was lowered to 600°C at a rate of 10°C / min, and the power was turned off and the furnace was cooled;

[0111] (6) The composite material is subjected to a gas phase siliconization sealing treatment. In an argon protection environment, the siliconization temperature is 1800°C and the holding time is 10 min to obtain a SiC-free nanowire reinforced C / C-HfC-SiC composite material with a silicon carbide-rich coating on the surface.

[0112] Since the heat treatment temperature is relatively high, SiC nanowires are not introduced. Due to the lack of SiC nanowire reinforcement phase with high elasticity and high modulus, energy cannot be further consumed through the pull-out phenomenon at the time of fracture, so the mechanical properties are reduced. In addition, the coating formed by surface deposition after vapor siliconization is mainly SiC, and there is no obvious effect of reducing the ablation temperature. Compared with the C / C-HfC-SiC composite material with a surface containing a silicon carbide-rich coating and no nanowire reinforcement obtained in this comparative example 1, the C / C-HfC-SiC composite material with a core-shell structure nanowire reinforcement containing a silicon-rich coating on the surface obtained in Example 1 has a porosity reduction of 64.3%, a flexural strength improvement of 62.7%, a flexural modulus improvement of 121.0%, ablation center temperature reduction of 397°C, ablation linear ablation rate reduction of 85.0%, and ablation mass ablation rate reduction of 70.9% (see Table 2).

[0113] Comparative Example 2:

[0114] (1) Weigh a certain amount of polycarbosilane and ultra-high temperature ceramic hafnium carbide polymer precursor and dissolve them in 10L of xylene (the mass ratio of polycarbosilane, ultra-high temperature ceramic hafnium carbide polymer precursor, and xylene is 1:5:5), and subject them to ultrasonic vibration for 2 hours to obtain a uniformly dispersed mixed organic precursor solution;

[0115] (2) The density is 0.4 g / cm 3 , the preform with a size of φ80 mm×10 mm, the heating elements H1 and H2 and other components are fully assembled, and a uniformly dispersed mixed organic precursor solution is poured into the reaction container so that the upper surface of the heating element H1 is immersed in the mixed organic precursor solution;

[0116] (3) Start the power supply of the equipment and adjust the power so that the temperature of the heating element H2 is raised to 900°C at a rate of 10°C / min and kept at this temperature for 24 hours; when cooling, it is lowered to 600°C at a rate of 10°C / min, and then the power supply is turned off and cooled with the furnace;

[0117] (4) placing the composite material obtained in (3) in an isothermal furnace in a flowing argon environment for heat treatment, heating the temperature to 1800° C. at a heating rate of 2° C. / min, keeping the temperature for 2 h, then turning off the power and cooling with the furnace to obtain a SiC nanowire reinforced ceramic matrix modified composite material;

[0118] (5) The composite material is subjected to a gas phase siliconization sealing treatment. In an argon protection environment, the siliconization temperature is 1800°C and the holding time is 10 min, thereby obtaining a SiC nanowire reinforced C / C-HfC-SiC composite material with a silicon carbide-rich coating on the surface.

[0119] After the introduction of SiC nanowires, since a core-shell structure is formed for further deposition of pyrolytic carbon, the grains of SiC nanowires are coarsened in the subsequent gas phase siliconization, and the enhancement effect is weakened. In addition, since there is no core-shell structure on the surface for meshing, the coating formed by surface deposition after gas phase siliconization is mainly SiC, and there is no obvious effect of reducing the ablation temperature. Therefore, compared with the surface containing silicon carbide-rich coating silicon carbide nanowire reinforced C / C-HfC-SiC composite material obtained in Comparative Example 2, the surface silicon-rich coating core-shell structure nanowire reinforced C / C-HfC-SiC composite material obtained in Example 1 has a reduced porosity of 59.7%, an increased flexural strength of 29.5%, an increased flexural modulus of 19.4%, a reduced ablation center temperature of 105°C, a reduced linear ablation rate of 80.7%, and a reduced mass ablation rate of 49.0% (see Table 2).

[0120] Table 1 Density and porosity changes before and after gas phase siliconization

[0121]

[0122] Table 2 Mechanical test results and ablation performance test results

[0123]

[0124]

[0125] As can be seen from Table 1 above, after the chemical vapor siliconization process, the density of the composite material is significantly improved and the porosity is significantly reduced. Compared with the silicon carbide nanowire-reinforced ceramic-based modified composite material with a silicon carbide-rich coating on the surface obtained in Comparative Example 2, the porosity of the core-shell structured nanowire-reinforced ceramic-based modified composite material obtained in Example 1 is reduced by 59.7% to only 3.93%, indicating that the sealing effect of the vapor phase siliconization process is obvious.

[0126] As can be seen from the comparison of Comparative Example 1, Comparative Example 2 and Example 1 in Table 2 above, after vapor phase siliconization, the bending strength and modulus of the core-shell structured nanowire reinforced ceramic-based modified composite material with a silicon-rich coating on the surface are significantly improved, the surface temperature is reduced, and the ablation performance is improved, indicating that the core-shell structured nanowire reinforced ceramic-based modified composite material containing a silicon-rich coating quickly prepared by the combined process has excellent mechanical and ablation properties.

[0127] like Figure 2From the comparison between Figure (a) and Figure (b), it can be seen that a large number of SiC nanowires are formed on the surface of the sample subjected to the first chemical liquid phase vapor deposition process in Example 1 after high temperature treatment, while no SiC nanowires are formed on the surface of the sample subjected to the first chemical liquid phase vapor deposition process in Comparative Example 1 after high temperature treatment.

[0128] like Figure 3 As shown, see Figure 3 (a) and (b) show the microscopic morphology of the surface of SiC nanowire reinforced C / C-HfC-SiC composites after the first chemical liquid phase vapor deposition process, see Figure 3 (a) shows the morphology of the surface without polishing, and a large number of SiC nanowires and bulk ceramic phases are introduced at the same time, see Figure 3 (b) shows the backscattering morphology of the surface after polishing. It can be seen that the white part is the ultra-high temperature ceramic phase, the gray part is the SiC phase, and the black part is the carbon fiber of pyrolytic carbon. Figure 3 In the inset of (b), it can be seen that the ceramic phase is co-deposited with the pyrolytic carbon around the carbon fibers; see Figure 3 (c) and (d) show the microscopic morphology of the surface and core-shell structure after the second chemical liquid phase vapor deposition process. Figure 3 (c) The surface core-shell structure is constructed, dividing the large pores on the surface into small pores, which is conducive to the rapid deposition of silicon-rich coating on the surface. Figure 3 The high-magnification morphology image (d) shows that a circle of pyrolytic carbon is uniformly formed on the periphery of the SiC nanowires, thus forming a core-shell structure with SiC nanowires as the core and PyC as the shell.

[0129] like Figure 4 As shown in the middle figure (a) and (b), it can be seen that the SiC nanowires formed after the first chemical liquid phase vapor deposition process present a bamboo-like morphology. After the second chemical liquid phase vapor deposition process to construct a core-shell structure, the surface of the SiC nanowires is evenly covered with pyrolytic carbon. The two are tightly connected and have a good interface bonding.

[0130] like Figure 5 As shown, the cross-sectional image ( Figure 5 (a, b) show that, macroscopically, a coating is deposited on the surface of the substrate after vapor siliconization, and the coating is well bonded to the substrate with a thickness of about 50 μm. Figure 5 (c) shows that the coating formed on the surface of the nanowire-reinforced ceramic matrix modified composite material of Comparative Example 2 after gas phase siliconization has SiC hexagonal crystals as the main phase, while Figure 5 (d) shows that the coating formed on the surface of the core-shell structure nanowire reinforced C / C-HfC-SiC composite material of Example 1 after vapor phase siliconization is mainly composed of white free silicon phase.

[0131] Figure 6 HS0 is the SiC nanowire-free reinforced C / C-HfC-SiC composite material obtained in Example 1, HS1 is the SiC nanowire-reinforced C / C-HfC-SiC composite material obtained in Example 2, and HS2 is the core-shell structured nanowire-reinforced C / C-HfC-SiC composite material obtained in Example 1. By comparison, it can be shown that after constructing the core-shell structure, the thermal conductivity of the ceramic-based modified composite material is improved, which contributes to the reduction of the surface ablation temperature in the subsequent ablation process.

[0132] Figure 7 The heat flux density is 2.38MW / m 2 The macroscopic morphology after 60 seconds of oxyacetylene flame ablation shows that the SiC nanowire-free reinforced C / C-HfC-SiC composite material ( Figure 7 (a)), Comparative Example 2 SiC nanowire reinforced C / C-HfC-SiC composite material with a surface rich in silicon carbide coating obtained by vapor phase siliconization ( Figure 7 (b)) Compared with the core-shell structure nanowire reinforced C / C-HfC-SiC composite material obtained by vapor phase siliconization in Example 1, the surface of the composite material contains a silicon-rich coating ( Figure 7 The ablated surface of Figure (c) is divided into three regions, namely the central region (region I), the transition region (region II) and the edge region (region III). The difference is that the central region in Figure (c) is denser and suffers less ablation damage.

[0133] Figure 8 Figure 1 is a microscopic morphology of the ablation center of the sample after oxyacetylene ablation. It can be seen that the surface of the ablation center of the SiC nanowire-free reinforced C / C-HfC-SiC composite material obtained by vapor siliconization in Comparative Example 1 contains a silicon carbide-rich coating on the surface. The oxide layer is covered on the carbon fiber, like a "coral reef" shape ( Figure 8 (a)); Comparative Example 2: SiC nanowire reinforced C / C-HfC-SiC composite material obtained by vapor phase siliconization with a surface containing a silicon carbide-rich coating ( Figure 8 (b)) The continuity and flatness of the ablated central oxide layer are further improved, while the core-shell structure nanowire reinforced C / C-HfC-SiC composite material obtained by vapor phase siliconization in Example 1 contains a silicon-rich coating on the surface ( Figure 8 (c) The oxide layer at the ablation center is flat and has no obvious cracks and large holes, which has the best anti-ablation performance.

[0134] The present invention introduces ultra-high temperature ceramics and nanowire reinforcement phases in a one-step method, and utilizes deposited pyrolytic carbon to construct a highly stable core-shell structure to effectively divide the large pore structure on the surface. The formed small grid structure, assisted by gas phase siliconization technology, allows the surface of the composite material to be quickly densified. The structure exhibits excellent performance in terms of load-bearing, heat transfer, and ablation resistance, and has good industrial application prospects and economic benefits.

[0135] The above contents are 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 rapid preparation method for a core-shell structured nanowire-reinforced ceramic-based modified composite material having a silicon-rich coating on the surface, characterized in that: The following steps are involved: S1: dissolving a mixed organic precursor formed by a silicon carbide precursor and an ultra-high temperature ceramic polymer precursor in an organic solvent to form a mixed organic precursor solution, subjecting a carbon fiber preform to a first chemical liquid phase vapor deposition in the mixed organic precursor solution, followed by cooling and recooling to obtain a composite material after deposition; S2: heat treating the deposited composite material, then cooling it down, and simultaneously forming silicon carbide nanowires, ceramic phase and pyrolytic carbon to obtain a silicon carbide nanowire reinforced ceramic matrix modified composite material; S3: subjecting the silicon carbide nanowire reinforced ceramic matrix modified composite material to a second chemical liquid phase vapor deposition in an organic solvent, followed by cooling and then depositing pyrolytic carbon on the surface of the silicon carbide nanowire to form a core-shell structure, thereby obtaining a core-shell structure nanowire reinforced ceramic matrix modified composite material; S4: The core-shell structured nanowire reinforced ceramic-based modified composite material is subjected to a gas phase silicon infiltration and pore sealing treatment to form a free silicon coating, thereby obtaining a core-shell structured nanowire reinforced ceramic-based modified composite material having a silicon-rich coating on the surface.

2. The rapid preparation method of the core-shell structured nanowire reinforced ceramic matrix modified composite material having a silicon-rich coating on the surface according to claim 1, characterized in that: In S1, the density of the carbon fiber preform is 0.4 to 1.2 g / cm 3 The carbon fiber preform is a cylindrical carbon fiber preform with a size of φ80-120 mm×10-30 mm.

3. The rapid preparation method of the core-shell structured nanowire reinforced ceramic matrix modified composite material having a silicon-rich coating on the surface according to claim 1, characterized in that: In S1, the ultrahigh temperature ceramic polymer precursor is any one of a hafnium carbide precursor, a zirconium carbide precursor and a tantalum carbide precursor.

4. The rapid preparation method of the core-shell structured nanowire reinforced ceramic matrix modified composite material having a silicon-rich coating on the surface according to claim 1, characterized in that: In S1 and S3, the organic solvent is any one of xylene, toluene, cyclohexane and kerosene.

5. The rapid preparation method of the core-shell structured nanowire reinforced ceramic matrix modified composite material with a silicon-rich coating on the surface according to claim 1, characterized in that: In S1, the mass ratio of the silicon carbide precursor, the ultrahigh temperature ceramic polymer precursor and the organic solvent is 1:(5-10):(1-10).

6. The rapid preparation method of the core-shell structured nanowire reinforced ceramic matrix modified composite material with a silicon-rich coating on the surface according to claim 1, characterized in that: In S1, the process of the first chemical liquid phase vapor deposition is as follows: The carbon fiber preform is placed in a liquid phase furnace filled with a mixed organic precursor solution, heated to 800-1200°C at a rate of 10-20°C / min, chemically vaporized for 16-24h, and then cooled to 600°C at a rate of 10-20°C / min; In S3, the process of the second chemical liquid phase vapor deposition is as follows: The silicon carbide nanowire reinforced ceramic matrix modified composite material is placed in a liquid phase furnace filled with an organic solvent, heated to 800-1200°C at a rate of 10-20°C / min, chemically vaporized for 5-15 hours, and then cooled to 600°C at a rate of 10-20°C / min.

7. The rapid preparation method of the core-shell structured nanowire reinforced ceramic matrix modified composite material with a silicon-rich coating on the surface according to claim 1, characterized in that: In S2, the heat treatment process is as follows: Under the protection of argon atmosphere, heat up to 1500-1800°C at a rate of 2-5°C / min and keep warm for 2-4h; In S4, the process of the gas phase siliconization sealing treatment is as follows: Keep warm at 1800-2150°C for 10-30 minutes.

8. A core-shell structured nanowire reinforced ceramic matrix modified composite material having a silicon-rich coating on the surface prepared by the preparation method according to any one of claims 1 to 7, characterized in that: Including core-shell structured nanowire reinforced ceramic matrix modified composite materials and free silicon coatings; The core-shell structure nanowire reinforced ceramic matrix modified composite material comprises a ceramic phase, carbon fiber, silicon carbide nanowires and pyrolytic carbon; The ceramic phase and pyrolytic carbon are co-deposited around the carbon fibers, the silicon carbide nanowires grow in large quantities in the internal voids and on the surface of the core-shell structure nanowire reinforced ceramic matrix modified composite material, pyrolytic carbon is deposited on the surface of the silicon carbide nanowires to form a core-shell structure, and the free silicon coating is deposited on the core-shell structure nanowire reinforced ceramic matrix modified composite material.

9. The core-shell structured nanowire-reinforced ceramic-based modified composite material having a silicon-rich coating on the surface according to claim 8, characterized in that: The core-shell structure divides the macroporous defect structure on the surface of the core-shell structure nanowire-reinforced ceramic-based modified composite material to construct a small grid structure forming a three-dimensional network; the free silicon coating fills and covers the small grid structure.

10. Use of the core-shell structured nanowire reinforced ceramic matrix modified composite material having a silicon-rich coating on the surface as claimed in any one of claims 8 to 9 in the field of thermal protection.

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