Preparation method of ultrahigh-temperature ceramic nanowire reinforced ceramic-based composite material

Abstract

The invention discloses a preparation method of an ultrahigh-temperature ceramic nanowire reinforced ceramic-based composite material, and relates to the technical field of ceramic-based composite materials. The preparation method specifically comprises the following steps: S1, preparing a porous preform; s2, preparing slurry; step S3, preparing an ultra-high temperature ceramic nanowire; and S4, densifying the composite material. By the adoption of the preparation method, damage to the mechanical property of the composite material caused by organic matter and fused salt can be reduced, the ultra-high-temperature ceramic nanowire with the complete morphology can be obtained, and the diameter of the prepared ultra-high-temperature ceramic nanowire ranges from 20 nm to 1000 nm.

Description

Technical Field

[0001] This invention relates to the technical field of ceramic matrix composites, and more specifically, to a method for preparing ultra-high temperature ceramic nanowire reinforced ceramic matrix composites. Background Technology

[0002] With the rapid development of modern technology, the requirements for material performance in various cutting-edge fields are constantly increasing. In the aerospace field, materials must maintain stable performance under harsh environments such as ultra-high temperature, water-oxygen corrosion, and extreme thermal shock to meet the stringent requirements of aircraft. Ceramic matrix composites, with their excellent advantages such as high strength, high modulus, low density, high temperature resistance, and chemical stability, have gradually become key candidate materials for aerospace hot-end components and thermal protection structures, demonstrating irreplaceable application potential.

[0003] However, during the preparation and processing of ceramic matrix composites, fibers are prone to mechanical damage and chemical corrosion, leading to a decrease in the mechanical properties of the composites and making it difficult to meet the requirements of practical applications. Using nanowires to reinforce and modify the ceramic matrix is ​​one of the effective ways to achieve material strength and improve its mechanical properties. Ultra-high temperature ceramic nanowires possess high melting points, high thermal stability, and chemical stability, while also exhibiting high modulus and high aspect ratio. Introducing ultra-high temperature ceramic nanowires into ceramic matrix composites is expected to improve the mechanical properties of the composites and has potential applications in aerospace hot-end components and thermal protection components. Currently, the most commonly used methods for preparing ultra-high temperature ceramic nanowire-reinforced composites include chemical vapor deposition (CVD), precursor impregnation pyrolysis (PIP), molten salt-assisted methods, and template methods.

[0004] Reference 1, "Integrative improvement on thermophysical properties and ablation resistance of laminated carbon / carbon composites modified by in-situugrown HfC nanowires onto carbon fiber cloths, 2021, 41(1):73-83," describes the fabrication of HfC nanowires on carbon fiber cloth using CVD. The cloth was then laminated and densified with pyrolytic carbon (PyC) to obtain HfC nanowire-toughened C / C composites. The introduction of HfC nanowires improved the mechanical properties of the C / C composites; however, this process is complex and has a long preparation cycle.

[0005] Patent 1 (CN108546142A) discloses a C fA method for preparing HfCnw micro / nano-scale toughened carbon-based composite materials. This method involves immersing a low-density C / C composite material in an ethanol (C2H5OH) solution of Ni(NO3)2·6H2O, then adding a peroxide initiator to initiate the crosslinking polymerization of the precursor PHC with divinylbenzene. HfC nanowires are then fabricated on the surface of the low-density C / C composite material using the PIP method, achieving micro / nano-scale toughening and yielding HfCnw micro / nano-scale toughened carbon-based composite materials. f The HfCnw micro / nano multi-scale toughened carbon-based composite material achieves large-scale in-situ growth of HfC nanowires and effective control over their morphology and purity. However, this process requires two high-temperature heat treatments to prepare HfC nanowires, which may cause some damage to the composite fiber and affect its mechanical properties.

[0006] Reference 2, “Effects of raw material ratio and technical parameters on microstructure of TaC whiskers prepared by molten salt method[J]. Ceramics International, 2025, 51(22):36134-36148,” describes the preparation of TaC nanowires using a molten salt-assisted method. By controlling the reaction parameters, single-crystal nanowires with the highest yield, purity, and aspect ratio were obtained. However, after the molten salt chemical reaction, molten salt coats the surface of the generated nanowires. Even after multiple washings, it is difficult to completely remove these salt impurities, and these residual impurities affect their mechanical properties.

[0007] Patent 2 (CN120057921A) discloses a component-tunable (Hf) x ,Zr y SiC nanowires and their preparation method. This method uses SiC nanowires as templates and employs CVD technology to obtain (Hf) nanowires with continuously tunable composition. x ,Zr y SiC nanowires. However, this template method relies on pre-prepared SiC nanowire templates, the structure and size of which directly affect the morphology and properties of the final product. Furthermore, the high-temperature chemical conversion process may result in template residue, increasing process complexity and potential costs.

[0008] In summary, current processes for preparing ultra-high temperature ceramic nanowires using CVD and template methods are relatively complex and require sophisticated equipment. While PIP and molten salt methods are simpler, the secondary high-temperature treatments and molten salt residues during their preparation can affect the mechanical properties of the materials. Therefore, it is necessary to optimize these preparation processes to achieve rapid fabrication of ultra-high temperature ceramic nanowires. Summary of the Invention

[0009] To overcome the shortcomings of the prior art, the present invention provides a method for preparing ultra-high temperature ceramic nanowire reinforced ceramic matrix composite materials, the preparation method specifically including the following steps: Step S1: Preparation of porous preform: Select fibers to prepare fiber preform, and deposit an interface layer and a SiC matrix layer sequentially on the surface of the fiber preform to obtain a porous preform; Step S2, Preparation of slurry: Mix the solvent, refractory metal chloride powder, carbon source and catalyst and stir evenly to prepare the slurry; Step S3: Preparation of ultra-high temperature ceramic nanowires: The slurry obtained in step S2 is introduced into the pores of the porous preform obtained in step S1 by vacuum impregnation. The porous preform after impregnation is dried and then subjected to high temperature heat treatment under a protective atmosphere to generate ultra-high temperature ceramic nanowires in situ, thus obtaining a porous composite material containing ultra-high temperature ceramic nanowires. Step S4, densification of composite material: The porous composite material containing ultra-high temperature ceramic nanowires obtained in step S3 is densified by using a reactive melt infiltration method to obtain an ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material.

[0010] Compared with existing technologies, the preparation method disclosed in this invention generates ultra-high temperature ceramic nanowires in situ through porous preform preparation, slurry preparation, vacuum impregnation combined with high temperature heat treatment, and densification by reactive melt infiltration, forming a complete preparation process system. The process is controllable and designable, which reduces the mechanical damage and chemical corrosion of fibers during the preparation process, and effectively strengthens the ceramic matrix through the in-situ generated nanowires. This solves the problem that existing preparation methods easily lead to a decrease in the mechanical properties of materials, significantly improves the strength and toughness of ceramic matrix composites, and provides a new solution for strengthening and toughening them.

[0011] In one possible implementation, in step S1, the fiber is selected from any one of carbon fiber, silicon carbide fiber, silicon nitride fiber, and oxide fiber; the structure of the fiber preform is any one of 2D, 2.5D, 3DN, and 3D.

[0012] Compared with existing technologies, the fibers selected in this invention can withstand the high-temperature environment of the preparation process, avoiding damage to the fibers due to poor material compatibility. Different structural preforms provide a stable structural base for subsequent processes, solving the problems of easy fiber damage and insufficient preform structural compatibility, and ensuring the stability of the composite material preparation process and the integrity of the final structure.

[0013] In one possible implementation, in step S1, the interface layer is one or more composite layers selected from pyrolytic carbon layer, boron nitride layer, silicon carbide layer, and silicon nitride layer, and the thickness of the interface layer is 50-800 nm.

[0014] Compared with the prior art, the interface layer type and thickness specified in this invention can effectively alleviate the thermal expansion mismatch between the fiber and the SiC matrix, reduce interface stress concentration, avoid fiber damage due to stress during preparation and high-temperature service, optimize the bonding state between the fiber and the matrix, solve the problem that poor bonding between the fiber and the matrix can easily lead to the degradation of mechanical properties, and improve the overall mechanical properties of the composite material.

[0015] In one possible implementation, in step S2, the refractory metal chloride powder is selected from at least one of hafnium chloride, zirconium chloride, tantalum chloride, titanium chloride, niobium chloride, molybdenum chloride, molybdenum dichloride, tungsten chloride, and tungsten hexachloride, and the molar concentration of the refractory metal chloride powder in the slurry is 0.5-5 mol / L.

[0016] Compared with the prior art, the present invention provides a suitable and sufficient metal source for the growth of ultra-high temperature ceramic nanowires by selecting the above-mentioned refractory metal chlorides and concentrations, ensuring that the in-situ generation reaction of nanowires is fully carried out, avoiding nanowire growth defects caused by insufficient metal source or improper concentration, and facilitating the formation of nanowires with complete morphology, thereby achieving effective reinforcement of the ceramic matrix.

[0017] In one possible implementation, in step S2, the solvent is selected from at least one of deionized water, xylene, and anhydrous ethanol, and the carbon source is selected from at least one of graphite, carbon black, resin, sucrose, and graphene, and the volume ratio of the carbon source to the solvent is 1:(2-10).

[0018] Compared with the prior art, the present invention selects the above-mentioned solvent, carbon source type and ratio, which can fully dissolve and disperse the components of the slurry, ensure the uniformity and stability of the slurry, and adapt to the vacuum impregnation process to achieve uniform introduction of the slurry into the pores of the preform. It avoids uneven carbon source distribution due to poor slurry dispersion, solves the problem of insufficient or uneven carbon source distribution in nanowire growth, and provides a stable carbon source environment for uniform nucleation and growth of nanowires.

[0019] In one possible implementation, in step S2, the catalyst is selected from at least one of ferric nitrate nonahydrate, nickel nitrate hexahydrate, copper nitrate trihydrate, ferrous chloride tetrahydrate, and nickel chloride hexahydrate, and the molar concentration of the catalyst in the slurry is 0.5-5 mol / L.

[0020] Compared with the prior art, the present invention selects the above-mentioned catalyst and concentration, which can efficiently catalyze the generation reaction of ultra-high temperature ceramic nanowires, precisely control the nucleation and growth rate of nanowires, avoid the nanowire size inhomogeneity and morphological defects caused by poor catalytic effect, solve the problem of uncontrollable nanowire morphology and size in the existing methods, obtain nanowires with controllable morphology and size, and give full play to their role in strengthening and toughening ceramic matrix composites.

[0021] In one possible implementation, in step S3, the protective atmosphere is argon or nitrogen, and the parameters of the high-temperature heat treatment are as follows: temperature is 1500-1700℃, time is 30-600min, heating rate is 1-5℃ / min, and cooling rate is 1-5℃ / min.

[0022] Compared with the prior art, the present invention selects the above-mentioned protective atmosphere and high-temperature heat treatment parameters to provide a stable high-temperature reaction environment for nanowire growth, avoid oxidation damage to the preform and the generated nanowires at high temperatures, and optimize the nanowire growth process by parameter control to avoid poor nanowire growth due to improper process parameters, ensure the integrity of nanowire morphology, and improve its reinforcing effect on the matrix.

[0023] In one possible implementation, in step S4, the reaction melt infiltration process is as follows: first, the porous composite material containing ultra-high temperature ceramic nanowires is subjected to vacuum impregnation treatment with graphite-based slurry; then, the porous composite material after vacuum impregnation is placed in a graphite crucible or graphite paper box for embedding and infiltration treatment; after the embedding and infiltration treatment is completed, the residual raw material on the surface is polished to obtain ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material.

[0024] Compared with the prior art, the present invention first replenishes the carbon source by vacuum impregnation with graphite-based slurry during the reaction melt infiltration process, then fully fills the pores of the porous composite material through embedding and infiltration, and finally removes the residual raw materials by grinding. This avoids poor densification effect due to insufficient pore filling and insufficient carbon source, and also solves the problem of residual raw materials affecting material performance. It significantly improves the density of the composite material and ensures the uniformity of its surface and internal properties.

[0025] In one possible implementation, the raw material used for the embedding and infiltration treatment is silicon powder or silicon-hafnium alloy, and the mass fraction of hafnium in the silicon-hafnium alloy is 70-75%, and the mass fraction of silicon is 25-30%.

[0026] Compared with the prior art, the present invention uses the above-mentioned melting infiltration raw materials and silicon-hafnium alloy components, which can fully react with the carbon source in the porous composite material to efficiently fill the pores and avoid insufficient densification due to poor compatibility of melting infiltration raw materials. At the same time, the silicon powder and silicon-hafnium alloy with specific components have excellent high temperature resistance and work synergistically with ultra-high temperature ceramic nanowires to solve the problem of easy decay of mechanical properties of composite materials at high temperatures, and further improve the high temperature mechanical properties and structural stability of composite materials.

[0027] In one possible implementation, the embedding and infiltration treatment is carried out in a vacuum environment, and the specific parameters are as follows: heating rate of 10-50℃ / min, holding temperature of 1500-1600℃, holding time of 30-60min, and cooling rate of 5-10℃ / min.

[0028] Compared with the prior art, the present invention uses the above-mentioned embedding and infiltration parameters, which can precisely control the rate and extent of the infiltration reaction, ensuring that the infiltration raw materials are fully melted and uniformly penetrate into the interior of the porous composite material. This avoids material structure damage and uneven pore filling caused by improper heating or cooling rates or unreasonable heat preservation parameters. It solves the problem of poor densification effect and easy material damage caused by improper infiltration process parameters in the past, improves the densification effect, and ensures the mechanical properties of the composite material. Attached Figure Description

[0029] Figure 1 This is the XRD pattern of the ultra-high temperature ceramic nanowires of Embodiment 1 of the present invention; Figure 2 This is a SEM image of the ultra-high temperature ceramic nanowires of Embodiment 1 of the present invention; Figure 3 This is the XRD pattern of the ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material of Example 1 of the present invention; Figure 4 This is a SEM image of the ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material of Example 1 of the present invention. Detailed Implementation

[0030] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0031] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0032] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0033] Example 1: This example provides an ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material, which is prepared by the following method: Step S1: Preparation of porous preform: Carbon fiber is selected as raw material. 0° non-woven fabric, fusible mesh, 90° non-woven fabric, and fusible mesh are sequentially stacked to a preset thickness. A 3DN structure carbon fiber preform is prepared by relay needle punching. After being cut to a suitable size, it is layered on a graphite mold and clamped and fixed with graphite bolts. A pyrolytic carbon interface layer and a SiC matrix layer are sequentially deposited on the surface of the carbon fiber preform using chemical vapor deposition. The thickness of the pyrolytic carbon interface layer is 200 nm, and the thickness of the SiC matrix layer is 3 μm, thus obtaining a porous preform. Step S2: Prepare the slurry: Select anhydrous ethanol as the solvent, add hafnium chloride powder, graphite, and ferric nitrate nonahydrate to the solvent in sequence, control the molar concentration of hafnium chloride powder in the slurry to be 1 mol / L, the volume ratio of graphite to anhydrous ethanol to be 1:2, and the molar concentration of ferric nitrate nonahydrate in the slurry to be 1 mol / L, stir for 12 h until uniform, and obtain the slurry; Step S3: Preparation of ultra-high temperature ceramic nanowires: The slurry obtained in step S2 is introduced into the pores of the porous preform obtained in step S1 using a vacuum impregnation method. The porous preform after impregnation is dried at 100°C. Then, the dried porous preform is placed in an alumina crucible and subjected to high-temperature heat treatment under an argon protective atmosphere. The heat treatment temperature is 1600°C, the holding time is 120 min, the heating rate is 5°C / min, and the cooling rate is 2°C / min. Ultra-high temperature ceramic nanowires are generated in situ, resulting in a porous composite material containing ultra-high temperature ceramic nanowires. Step S4, Densification of Composite Material: The porous composite material containing ultra-high temperature ceramic nanowires obtained in Step S3 is densified using a reactive melt infiltration method. First, the porous composite material is vacuum impregnated with a graphite-based slurry. Then, the vacuum-impregnated composite material is placed in a graphite crucible and embedded in a silicon-hafnium alloy with a hafnium mass fraction of 75% and a silicon mass fraction of 25%. The infiltration process is carried out in a vacuum environment with a heating rate of 25℃ / min, a holding temperature of 1600℃, a holding time of 30min, and a cooling rate of 8℃ / min. After the infiltration process, the residual material on the surface of the composite material is polished to obtain an ultra-high temperature ceramic nanowire-reinforced ceramic matrix composite material. After testing, the porosity of this ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material is 15%, and the flexural strength is 156 MPa.

[0034] Example 2: This example provides an ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material, which is prepared by the following method: Step S1: Preparation of porous preform: Carbon fiber is selected as raw material. 0° non-woven fabric, fusible mesh, 90° non-woven fabric, and fusible mesh are sequentially stacked to a preset thickness. A 3DN structure carbon fiber preform is prepared by relay needle punching. After being cut to a suitable size, it is layered on a graphite mold and clamped and fixed with graphite bolts. A pyrolytic carbon interface layer and a SiC matrix layer are sequentially deposited on the surface of the carbon fiber preform using chemical vapor deposition. The thickness of the pyrolytic carbon interface layer is 300 nm, and the thickness of the SiC matrix layer is 3 μm, thus obtaining a porous preform. Step S2: Prepare slurry: Select anhydrous ethanol as solvent, add zirconium chloride powder, carbon black and ferrous chloride tetrahydrate to the solvent in sequence, control the molar concentration of zirconium chloride powder in the slurry to be 1 mol / L, the volume ratio of carbon black to anhydrous ethanol to be 1:2, and the molar concentration of ferrous chloride tetrahydrate in the slurry to be 4 mol / L. Stir for 12 hours after mixing until uniform to obtain slurry. Step S3: Preparation of ultra-high temperature ceramic nanowires: The slurry obtained in step S2 is introduced into the pores of the porous preform obtained in step S1 using a vacuum impregnation method. The porous preform after impregnation is dried at 100°C. Then, the dried porous preform is placed in an alumina crucible and subjected to high-temperature heat treatment under an argon protective atmosphere. The heat treatment temperature is 1500°C, the holding time is 400 min, the heating rate is 5°C / min, and the cooling rate is 2°C / min. Ultra-high temperature ceramic nanowires are generated in situ, resulting in a porous composite material containing ultra-high temperature ceramic nanowires. Step S4, Densification of Composite Material: The porous composite material containing ultra-high temperature ceramic nanowires obtained in Step S3 is densified using a reactive melt infiltration method. First, the porous composite material is vacuum impregnated with a graphite-based slurry. Then, the vacuum-impregnated composite material is placed in a graphite crucible and embedded in a silicon-hafnium alloy with a hafnium mass fraction of 70% and a silicon mass fraction of 30%. The infiltration process is carried out in a vacuum environment with a heating rate of 35℃ / min, a holding temperature of 1600℃, a holding time of 60min, and a cooling rate of 5℃ / min. After the infiltration process, the residual material on the surface of the composite material is polished to obtain an ultra-high temperature ceramic nanowire-reinforced ceramic matrix composite material.

[0035] After testing, the porosity of this ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material was found to be 14%, and the flexural strength was 175 MPa.

[0036] Example 3: This example provides an ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material, which is prepared by the following method: Step S1: Preparation of porous preform: Using silicon nitride fiber as raw material, 0° non-woven fabric, fusible mesh, 90° non-woven fabric, and fusible mesh are sequentially stacked to a preset thickness. A 2.5D structure silicon nitride fiber preform is prepared by relay needle punching. After being cut to a suitable size, it is stacked on a graphite mold and fixed by clamping with graphite bolts. A boron nitride interface layer and a SiC matrix layer are sequentially deposited on the surface of the silicon nitride fiber preform by chemical vapor deposition. The thickness of the boron nitride interface layer is 50nm and the thickness of the SiC matrix layer is 3μm, thus obtaining a porous preform.

[0037] Step S2: Prepare slurry: Select anhydrous ethanol as solvent, add titanium chloride powder, resin and copper nitrate trihydrate to the solvent in sequence, control the molar concentration of titanium chloride powder in the slurry to be 1 mol / L, the volume ratio of resin to anhydrous ethanol to be 1:8, and the molar concentration of copper nitrate trihydrate in the slurry to be 3 mol / L. After mixing, stir for 12 hours until uniform to obtain slurry. Step S3: Preparation of ultra-high temperature ceramic nanowires: The slurry obtained in step S2 is introduced into the pores of the porous preform obtained in step S1 using a vacuum impregnation method. The porous preform after impregnation is dried at 100°C. Then, the dried porous preform is placed in an alumina crucible and subjected to high-temperature heat treatment under an argon protective atmosphere. The heat treatment temperature is 1700°C, the holding time is 600 min, the heating rate is 4°C / min, and the cooling rate is 1°C / min. Ultra-high temperature ceramic nanowires are generated in situ, resulting in a porous composite material containing ultra-high temperature ceramic nanowires. Step S4, Densification of Composite Material: The porous composite material containing ultra-high temperature ceramic nanowires obtained in step S3 is densified using a reactive melt infiltration method. First, the porous composite material is vacuum impregnated with a graphite-based slurry. Then, the vacuum-impregnated composite material is placed in a graphite crucible and embedded in a silicon-hafnium alloy for melt infiltration. The silicon-hafnium alloy has a mass fraction of 72% hafnium and 28% silicon. The melt infiltration is carried out in a vacuum environment with a heating rate of 25℃ / min, a holding temperature of 1580℃, a holding time of 45min, and a cooling rate of 10℃ / min. After the melt infiltration is completed, the residual raw material on the surface of the composite material is polished to obtain an ultra-high temperature ceramic nanowire-reinforced ceramic matrix composite material.

[0038] After testing, the porosity of this ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material was found to be 17%, and the flexural strength was 177 MPa.

[0039] Example 4: This example provides an ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material, which is prepared by the following method: Step S1: Preparation of porous preform: Using silicon carbide fiber as raw material, 0° non-woven fabric, fusible mesh, 90° non-woven fabric, and fusible mesh are sequentially stacked to a preset thickness. A 3DN structure silicon carbide fiber preform is prepared by relay needle punching. After being cut to a suitable size, it is stacked on a graphite mold and clamped and fixed with graphite bolts. A silicon carbide interface layer and a SiC matrix layer are sequentially deposited on the surface of the silicon carbide fiber preform by chemical vapor deposition. The thickness of the silicon carbide interface layer is 800 nm and the thickness of the SiC matrix layer is 3 μm, thus obtaining a porous preform. Step S2: Prepare the slurry: Select xylene as the solvent, add molybdenum chloride powder, sucrose, and ferric nitrate nonahydrate to the solvent in sequence, control the molar concentration of molybdenum chloride powder in the slurry to be 0.5 mol / L, the volume ratio of sucrose to xylene to be 1:10, and the molar concentration of ferric nitrate nonahydrate in the slurry to be 5 mol / L. After mixing, stir for 12 hours until uniform to obtain the slurry. Step S3: Preparation of ultra-high temperature ceramic nanowires: The slurry obtained in step S2 is introduced into the pores of the porous preform obtained in step S1 using a vacuum impregnation method. The porous preform after impregnation is dried at 100°C. Then, the dried porous preform is placed in an alumina crucible and subjected to high-temperature heat treatment under an argon protective atmosphere. The heat treatment temperature is 1600°C, the holding time is 120 min, the heating rate is 1°C / min, and the cooling rate is 5°C / min. Ultra-high temperature ceramic nanowires are generated in situ, resulting in a porous composite material containing ultra-high temperature ceramic nanowires. Step S4, Densification of Composite Material: The porous composite material containing ultra-high temperature ceramic nanowires obtained in step S3 is densified using a reactive melt infiltration method. First, the porous composite material is vacuum impregnated with graphite-based slurry. Then, the vacuum-impregnated composite material is placed in a graphite paper box and embedded and infiltrated with silicon powder. The infiltration process is carried out in a vacuum environment with a heating rate of 10℃ / min, a holding temperature of 1600℃, a holding time of 30min, and a cooling rate of 5℃ / min. After the infiltration process is completed, the residual material on the surface of the composite material is polished to obtain an ultra-high temperature ceramic nanowire-reinforced ceramic matrix composite material.

[0040] After testing, the porosity of this ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material was found to be 18%, and the flexural strength was 271 MPa.

[0041] Example 5: This example provides an ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material, which is prepared by the following method: Step S1: Preparation of porous preform: Using silica fiber as raw material, 0° non-woven fabric, fusible mesh, 90° non-woven fabric, and fusible mesh are sequentially stacked to a preset thickness. A 3D structured silica fiber preform is prepared by relay needle punching. After being cut to a suitable size, it is stacked on a graphite mold and clamped and fixed with graphite bolts. A silicon nitride interface layer and a SiC substrate layer are sequentially deposited on the surface of the silica fiber preform using chemical vapor deposition. The thickness of the silicon nitride interface layer is 180 nm, and the thickness of the SiC substrate layer is 3 μm, thus obtaining a porous preform. Step S2: Prepare the slurry: Select deionized water as the solvent, add hafnium chloride powder, graphite, and ferric nitrate nonahydrate to the solvent in sequence, control the molar concentration of hafnium chloride powder in the slurry to be 5 mol / L, the volume ratio of graphite to deionized water to be 1:6, and the molar concentration of ferric nitrate nonahydrate in the slurry to be 0.5 mol / L. After mixing, stir for 12 hours until uniform to obtain the slurry. Step S3: Preparation of ultra-high temperature ceramic nanowires: The slurry obtained in step S2 is introduced into the pores of the porous preform obtained in step S1 using a vacuum impregnation method. The porous preform after impregnation is dried at 100°C. Then, the dried porous preform is placed in an alumina crucible and subjected to high-temperature heat treatment under an argon protective atmosphere. The heat treatment temperature is 1700°C, the holding time is 30 min, the heating rate is 5°C / min, and the cooling rate is 2°C / min. Ultra-high temperature ceramic nanowires are generated in situ, resulting in a porous composite material containing ultra-high temperature ceramic nanowires. Step S4, Densification of Composite Material: The porous composite material containing ultra-high temperature ceramic nanowires obtained in step S3 is densified using a reactive melt infiltration method. First, the porous composite material is vacuum impregnated with graphite-based slurry. Then, the vacuum-impregnated composite material is placed in a graphite paper box and embedded and infiltrated with silicon powder. The infiltration process is carried out in a vacuum environment with a heating rate of 50℃ / min, a holding temperature of 1500℃, a holding time of 60min, and a cooling rate of 7℃ / min. After the infiltration process is completed, the residual material on the surface of the composite material is polished to obtain an ultra-high temperature ceramic nanowire-reinforced ceramic matrix composite material.

[0042] After testing, the porosity of this ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material was found to be 16%, and the flexural strength was 234 MPa.

[0043] Further testing and analysis were performed on Example 1, and the results are as follows: Figures 1-4 As shown, where Figure 1 This is the XRD pattern of the ultra-high temperature ceramic nanowires of Embodiment 1 of the present invention; from Figure 1It can be seen that the diffraction peaks of C, SiC and HfC can be identified. Among them, the diffraction peak of C is C fiber, the diffraction peak of SiC is SiC matrix, and the diffraction peak of HfC is HfC nanowire. HfC nanowire has good crystallinity.

[0044] Figure 2 This is a SEM image of the ultra-high temperature ceramic nanowires of Embodiment 1 of the present invention; from Figure 2 It can be seen that the prepared HfC nanowires have complete morphology, with diameters of 100-900 nm and lengths of 5-100 μm.

[0045] Figure 3 This is the XRD pattern of the ultra-high temperature ceramic nanowire-reinforced ceramic matrix composite material of Example 1 of the present invention; from Figure 3 It can be seen that the diffraction peaks of SiC, HfC and HfSi2 can be identified. Among them, the diffraction peak of SiC is the SiC matrix, the diffraction peak of HfC is the HfC nanowires and HfC matrix, and the diffraction peak of HfSi2 is the residual alloy.

[0046] Figure 4 This is a SEM image of the ultra-high temperature ceramic nanowire-reinforced ceramic matrix composite material of Example 1 of the present invention; from Figure 4 It can be seen that the prepared ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material has no obvious pores. The ceramic matrix generated by the RMI reaction is distributed on the outside of the CVI SiC matrix, and the HfC nanowires are wrapped in the ceramic matrix.

[0047] To address the technical problems of fiber damage and poor mechanical properties caused by defects in existing nanowire reinforcement processes in the preparation of ceramic matrix composites, this invention successfully prepared several ultra-high temperature ceramic nanowire-reinforced ceramic matrix composites by differentially selecting fiber raw materials, preform structures, and interface layer types and thicknesses, combining different types of solvents, refractory metal chlorides, carbon sources, and catalysts, and controlling their proportions. Simultaneously, gradient high-temperature heat treatment and reactive melt infiltration process parameters were set, resulting in the successful preparation of multiple ultra-high temperature ceramic nanowire-reinforced ceramic matrix composites. Testing showed that the prepared composites consistently maintained a porosity of 14-18% and possessed excellent flexural strength, verifying that the preparation process effectively reduces fiber damage during preparation. The in-situ generation of ultra-high temperature ceramic nanowires effectively strengthens and toughens the ceramic matrix composites. The overall process exhibits good controllability, and precise control of composite material properties can be achieved by adjusting the raw material ratios and process parameters. This effectively solves the pain points in existing technologies and provides a concrete and feasible implementation reference for the large-scale preparation and performance optimization of ultra-high temperature ceramic nanowire-reinforced ceramic matrix composites.

[0048] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A method for preparing an ultra-high temperature ceramic nanowire-reinforced ceramic matrix composite material, characterized in that, The preparation method specifically includes the following steps: Step S1: Preparation of porous preform: Select fibers to prepare fiber preform, and deposit an interface layer and a SiC matrix layer sequentially on the surface of the fiber preform to obtain a porous preform; Step S2, Preparation of slurry: Mix the solvent, refractory metal chloride powder, carbon source and catalyst and stir evenly to prepare the slurry; Step S3: Preparation of ultra-high temperature ceramic nanowires: The slurry obtained in step S2 is introduced into the pores of the porous preform obtained in step S1 by vacuum impregnation. The porous preform after impregnation is dried and then subjected to high temperature heat treatment under a protective atmosphere to generate ultra-high temperature ceramic nanowires in situ, thus obtaining a porous composite material containing ultra-high temperature ceramic nanowires. Step S4, densification of composite material: The porous composite material containing ultra-high temperature ceramic nanowires obtained in step S3 is densified by using a reactive melt infiltration method to obtain an ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material.

2. The preparation method according to claim 1, characterized in that, In step S1, the fiber is selected from any one of carbon fiber, silicon carbide fiber, silicon nitride fiber and oxide fiber; the structure of the fiber preform is any one of 2D, 2.5D, 3DN and 3D.

3. The preparation method according to claim 1, characterized in that, In step S1, the interface layer is one or more composite layers selected from pyrolytic carbon layer, boron nitride layer, silicon carbide layer, and silicon nitride layer, and the thickness of the interface layer is 50-800 nm.

4. The preparation method according to claim 1, characterized in that, In step S2, the refractory metal chloride powder is selected from at least one of hafnium chloride, zirconium chloride, tantalum chloride, titanium chloride, niobium chloride, molybdenum chloride, molybdenum dichloride, tungsten chloride, and tungsten hexachloride, and the molar concentration of the refractory metal chloride powder in the slurry is 0.5-5 mol / L.

5. The preparation method according to claim 1, characterized in that, In step S2, the solvent is selected from at least one of deionized water, xylene, and anhydrous ethanol, and the carbon source is selected from at least one of graphite, carbon black, resin, sucrose, and graphene, and the volume ratio of the carbon source to the solvent is 1:(2-10).

6. The preparation method according to claim 1, characterized in that, In step S2, the catalyst is selected from at least one of ferric nitrate nonahydrate, nickel nitrate hexahydrate, copper nitrate trihydrate, ferrous chloride tetrahydrate, and nickel chloride hexahydrate, and the molar concentration of the catalyst in the slurry is 0.5-5 mol / L.

7. The preparation method according to claim 1, characterized in that, In step S3, the protective atmosphere is argon or nitrogen, and the parameters for high-temperature heat treatment are as follows: temperature is 1500-1700℃, time is 30-600min, heating rate is 1-5℃ / min, and cooling rate is 1-5℃ / min.

8. The preparation method according to claim 1, characterized in that, In step S4, the processing procedure of the reactive melt infiltration method is as follows: first, the porous composite material containing ultra-high temperature ceramic nanowires is subjected to vacuum impregnation treatment with graphite-based slurry; then, the porous composite material after vacuum impregnation is placed in a graphite crucible or graphite paper box for embedding and infiltration treatment; after the embedding and infiltration treatment is completed, the residual raw material on the surface is polished to obtain ultra-high temperature ceramic nanowire reinforced ceramic matrix composite material.

9. The preparation method according to claim 8, characterized in that, The raw materials used in the embedding and infiltration treatment are silicon powder or silicon-hafnium alloy, and the mass fraction of hafnium in the silicon-hafnium alloy is 70-75%, and the mass fraction of silicon is 25-30%.

10. The preparation method according to claim 8, characterized in that, The embedding and infiltration treatment is carried out in a vacuum environment, and the specific parameters are as follows: heating rate is 10-50℃ / min, holding temperature is 1500-1600℃, holding time is 30-60min, and cooling rate is 5-10℃ / min.

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