A 2.5DC / ZrC / SiC(W0.45Cu0.45Ti0.1) composite material, its preparation method, and its application.

Abstract

The application discloses a 2.5D C / ZrC / SiC(W 0.45 Cu 0.45 Ti 0.1 ) composite material and a preparation method and application thereof, and belongs to the technical field of ultra-high-temperature ceramics and refractory metal composite materials. The specific method is as follows: a 2.5D braided body is obtained by needling and braiding PAN-based carbon fibers; a 2.5D carbon matrix is obtained by depositing pyrolytic carbon on the surface of the 2.5D braided body through a chemical vapor deposition method (CVD); a green body is obtained by introducing ZrC-SiC ceramic phases into the 2.5D carbon matrix through a slurry infiltration method (SI); and the composite material is prepared by high-temperature vacuum infiltration of the green body in a metal-molten salt mixed powder through a reaction infiltration method (RMI). The three technologies are coupled, which not only ensures the uniformity of the distribution of SiC and ZrC components, but also effectively reduces the preparation period, and realizes controllable adjustment of the mechanical properties and the oxidation resistance and ablation resistance.

Description

Technical Field

[0001] This invention belongs to the technical field of ultra-high temperature ceramics and refractory metal composite materials, and particularly relates to a 2.5DC / ZrC / SiC(W) composite material. 0.45 Cu 0.45 Ti 0.1 Composite materials, their preparation methods, and applications. Background Technology

[0002] Developing new-concept hypersonic, long-range precision strike weapons is one of the core technological approaches to breaking through existing anti-missile defense systems. These weapons require a range exceeding 13,000 km, an unpowered gliding distance of 11,500 km, and the ability to fly at speeds exceeding Mach 20 for extended periods within the atmosphere at altitudes of 35-65 km. This has been listed as a major innovation program and has received widespread attention. The stagnation point temperature of the sharp warhead of these weapons exceeds 3000 K, and severe ablation directly affects the warhead's lift-to-drag ratio. Therefore, the development of heat-resistant materials for the warhead cone is crucial to the success of this type of weapon development. Developing ultra-high temperature resistant, non-ablative heat-resistant materials has also become an inevitable requirement for the development of hypersonic, long-range precision strike weapons. Taking the anti-penetration frog missile as an example, its flight time is required to reach 500s and its flight speed to reach Mach 8-9. The leading edge of the aerodynamic rudder will be subjected to aerodynamic heating of about 50s and 2200℃. The ablation problem will significantly affect the flight accuracy. Similarly, high-temperature structural materials with excellent properties such as resistance to ultra-high temperature, high strength, and low density are urgently needed.

[0003] Traditional ultra-high temperature ceramic-modified carbon / carbon composites, using carbon fiber as the reinforcing phase, combine the thermal advantages of carbon materials—low coefficient of thermal expansion, high thermal conductivity, and high vaporization temperature—with good thermal shock resistance and ablation resistance, making them suitable for short-term ablation conditions at 3000℃. They also exhibit excellent tribological properties, with a low and stable coefficient of friction, making them a preferred material for various wear-resistant and friction components. However, this material is prone to excessive ablation in the gaseous environment of solid rocket motors (SRMs), resulting in significant application limitations. In contrast, metal-reinforced carbon / carbon-ultra-high temperature ceramic (C / C-UHTC) composites demonstrate superior mechanical properties, thermophysical properties, and high-temperature corrosion resistance, showing great application potential in improving the thrust performance of solid rocket motors.

[0004] Against this backdrop, the development of metal-reinforced C / C-UHTC composites has become urgent. These materials can simultaneously meet the dual requirements of solid rocket motors for excellent ablation performance and mechanical properties, while effectively maintaining the structural integrity of the material. In recent years, although traditional slurry impregnation processes have been continuously improved, the preparation of carbon-based composites modified with ultra-high temperature ceramics (UHTCs) still mainly relies on a single process or a combination of two processes. The combined application of slurry impregnation (SI) and reactive melting infiltration (RMI) is rarely reported. Therefore, developing SI impregnation slurries with high solid content, high stability, and low viscosity, combined with low-temperature melting infiltration technology to prepare carbon / zirconium carbide-refractory metal composites, has significant engineering application value for materials research and development and equipment upgrading in the aerospace field. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a 2.5DC / ZrC / SiC(W) 0.45 Cu 0.45 Ti 0.1 Composite materials, their preparation methods, and applications.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A 2.5DC / ZrC / SiC(W 0.45 Cu 0.45 Ti 0.1 The method for preparing composite materials includes the following steps: (1) Needle-punching and weaving were performed using PAN (polyacrylonitrile) based carbon fiber as the matrix to obtain a 2.5D braided body; (2) Pyrolytic carbon (PyC) was deposited on the surface of the 2.5D braided fabric by chemical vapor deposition to obtain a 2.5D carbon matrix; (3) The ZrC-SiC ceramic phase was introduced into the 2.5D carbon matrix by slurry infiltration to obtain a 2.5DC / ZrC / SiC green body; (4) The 2.5DC / ZrC / SiC preform was subjected to high-temperature vacuum infiltration in a metal-molten salt mixed powder using a reactive melting method to obtain 2.5DC / ZrC / SiC(W 0.45 Cu 0.45 Ti 0.1 Composite materials.

[0007] Furthermore, the density of the 2.5D braid is 0.4 g / cm³. 3 .

[0008] Furthermore, the specific operation steps of the chemical vapor deposition method are as follows: using chemical vapor deposition, a layer of pyrolytic carbon is deposited on the surface of the 2.5D braided fabric using methane gas to obtain a 2.5D carbon matrix; The conditions for the chemical vapor deposition process are as follows: under an inert atmosphere, the temperature is raised to 1150°C at a heating rate of 10°C / min, then methane gas is introduced at a flow rate of 300 mL / min for 15-30 min, and the temperature is maintained at 1150°C for 15-30 min, followed by natural cooling.

[0009] Furthermore, the specific operation steps of the slurry impregnation method are as follows: after vacuuming the 2.5D carbon matrix for 15-30 minutes, it is sequentially impregnated in the slurry under vacuum pressure and then dried to obtain a 2.5DC / ZrC / SiC green body.

[0010] Furthermore, the specific operation steps of the vacuum pressure impregnation are as follows: the 2.5D carbon matrix is ​​placed in the slurry, then placed in a vacuum pressure vessel, a vacuum pump is used to evacuate and maintain the vacuum for 30-90 minutes; after the vacuum is completed, argon gas is used to pressurize the material to 5-8 MPa and maintain the pressure for 1-6 hours, and finally the pressure is released to atmospheric pressure and the material is taken out and dried.

[0011] Furthermore, the slurry is prepared from ZrC powder with a particle size of 800 nm, SiC powder with a particle size of 800 nm, deionized water, and a dispersant; wherein the molar ratio of ZrC powder, SiC powder, and deionized water is 1:1:20; the dispersant is sodium hexametaphosphate (SHMP), added at 1 wt% of the total mass of ZrC powder and SiC powder. Within the dosage and ratio range defined in this invention, the prepared ZrC and SiC impregnation slurry has the advantages of low viscosity, high fluidity, good stability, and the ability to load a large number of ZrC and SiC particles, which is more conducive to impregnation. The efficient dispersion of the ZrC-SiC system by sodium hexametaphosphate is mainly attributed to its typical electrostatic-steric dual stabilization mechanism. As an inorganic anionic polymeric surfactant, the polyvalent phosphate anions dissociated from SHMP in solution can be strongly and specifically adsorbed on the surface of ZrC and SiC particles. This adsorption not only significantly increases the negative charge density on the particle surface (i.e., greatly increases the absolute value of the Zeta potential), resulting in strong electrostatic repulsion between particles; simultaneously, the appropriately long polymer anionic chains form a tight adsorption coating layer on the particle surface, providing additional steric hindrance. Under this powerful dual repulsion mechanism, the van der Waals forces between particles are completely overcome, effectively preventing particles from approaching each other and agglomerating, thus achieving long-term macroscopic suspension of the slurry.

[0012] Furthermore, the specific operation steps of the reaction melting infiltration method are as follows: the 2.5DC / ZrC / SiC billet is completely embedded in a metal-molten salt mixed powder, and then a high-temperature vacuum melting infiltration reaction is carried out, followed by cooling.

[0013] Furthermore, the specific operating steps of the high-temperature vacuum melting and infiltration reaction are as follows: the temperature is increased to 800°C at a heating rate of 5°C / min, and then increased to 1300°C at a heating rate of 3°C / min, and heated for 30 minutes at a temperature of 1300°C and a pressure of 10MPa.

[0014] Furthermore, the metal-molten salt mixed powder is an AR-grade mixture of WO3, Cu, Ti and molten salt; wherein the molar ratio of WO3, Cu and Ti is 45:45:10; the molten salt is NaCl and KCl, and the amount added is 5-80% of the mass of WO3, preferably 20%, and the molar ratio of NaCl and KCl is 1:1.

[0015] This invention employs molten salt-assisted melting infiltration, using AR-grade NaCl and KCl molten salts in a 1:1 molar ratio. On one hand, the addition of molten salt increases the vapor pressure of WO3 and lowers its melting point, allowing it to easily melt into the composite material at lower temperatures. On the other hand, the salt and WO3 can generate highly reactive WO3... x Cl y This significantly improves the reaction rate.

[0016] The present invention also provides a 2.5DC / ZrC / SiC(W) 0.45 Cu 0.45 Ti 0.1 The composite material was prepared by the above preparation method.

[0017] The present invention also provides the above-mentioned 2.5DC / ZrC / SiC(W) 0.45 Cu 0.45 Ti 0.1 Application of composite materials in the preparation of hypersonic vehicles.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects: This invention combines traditional CVD-SI-RMI processes. CVD generates a thin layer of pyrolytic carbon on the carbon fiber preform to protect the fibers, SI introduces a uniform UHTCs phase, and RMI densifies the composite material. In other words, the three methods work synergistically to achieve the preparation of 2.5DC / ZrC / SiC(W) 0.45 Cu 0.45 Ti 0.1 The optimization of the composite material process has shortened the preparation cycle of composite materials. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 In the embodiments of the present invention, 2.5DC / ZrC / SiC(W) 0.45 Cu 0.45 Ti 0.1 A schematic diagram of the composite material preparation process; Figure 2 The 2.5DC / ZrC / SiC(W) prepared in Example 1 0.45 Cu 0.45 Ti 0.1 SEM image of the composite material surface at low magnification (25x); Figure 3 The 2.5DC / ZrC / SiC(W) prepared in Example 1 0.45 Cu 0.45 Ti 0.1 SEM image of the composite material surface at medium magnification (500x); Figure 4 The 2.5DC / ZrC / SiC(W) prepared in Example 1 0.45 Cu 0.45 Ti 0.1 High-magnification (5500x) SEM image of the composite material surface; Figure 5 The 2.5DC / ZrC / SiC(W) prepared in Example 1 0.45 Cu 0.45 Ti 0.1 SEM image of the composite material cross section at low magnification (250x); Figure 6 The 2.5DC / ZrC / SiC(W) prepared in Example 1 0.45 Cu 0.45 Ti 0.1 SEM image of the composite material cross section at 1200x magnification; Figure 7 The 2.5DC / ZrC / SiC(W) prepared in Example 1 0.45 Cu 0.45 Ti 0.1 High-magnification (10000x) SEM image of the composite material cross-section; Figure 8 The 2.5DC / ZrC / SiC(W) prepared in Example 1 0.45 Cu 0.45 Ti0.1 High-magnification (5500x) SEM and EDS images of the carbon fiber region in the composite material; Figure 9 The 2.5DC / ZrC / SiC(W) prepared in Examples 1-4 0.45 Cu 0.45 Ti 0.1 Comparison of macroscopic photographs of composite materials before and after ablation; Figure 10 The 2.5DC / ZrC / SiC(W) prepared in Examples 1-4 0.45 Cu 0.45 Ti 0.1 The stress-strain curve of the composite material's linear mechanical properties; Figure 11 This is an optical macroscopic image showing the effect of dispersant type on the suspension stability of ZrC-SiC mixed slurry. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0023] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0024] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0025] This invention provides a 2.5DC / ZrC / SiC(W) 0.45 Cu 0.45 Ti 0.1 Preparation method of composite materials (operation flowchart as follows) Figure 1 (As shown), including the following steps: (1) Preparation of 2.5D braided material: Using PAN-based carbon fiber as the matrix, a density of 0.4 g / cm³ was obtained by needle punching and braiding process. 3 2.5D braided body; (2) Preparation of 2.5D carbon matrix: The above 2.5D braided body was placed in a chemical vapor deposition equipment and heated to 1150°C at a heating rate of 10°C / min under an inert atmosphere. Then, methane gas was introduced at a gas flow rate of 300 mL / min, maintained for 15-30 min, and held at 1150°C for 15-30 min. Finally, it was naturally cooled to deposit a layer of pyrolytic carbon on the surface of the preform to obtain a 2.5D carbon matrix. (3) Preparation of 2.5DC / ZrC / SiC billet: 1) Preparation of ZrC-SiC impregnation slurry: The slurry was prepared using ZrC powder with a particle size of 800 nm, SiC powder with a particle size of 800 nm, sodium hexametaphosphate dispersant, and deionized water as raw materials; wherein the molar ratio of ZrC powder, SiC powder and deionized water was 1:1:20; the dispersant was sodium hexametaphosphate, and the amount added was 1 wt% of the total mass of ZrC powder and SiC powder.

[0026] 2) Preparation of 2.5DC / ZrC / SiC green body: First, evacuate the 2.5D carbon matrix for 15-30 min, then put it into the prepared slurry and place it together in a vacuum pressure vessel. Continue to evacuate the vacuum with a vacuum pump and maintain the vacuum for 30-90 min. After evacuation, introduce argon gas until the pressure inside the vessel reaches 5-8 MPa, maintain the pressure for 1-6 h, and finally depressurize to atmospheric pressure. Take out the carbon matrix and dry it to obtain the 2.5DC / ZrC / SiC green body. (4) Preparation of composite materials: 1) Preparation of metal-molten salt mixed powder: A mixed powder is prepared using AR-grade WO3, Cu, and Ti as metal raw materials and AR-grade NaCl and KCl as molten salt raw materials; wherein the molar ratio of WO3, Cu, and Ti is 45:45:10, the molar ratio of NaCl and KCl is 1:1, and the total amount of NaCl and KCl added is 5-80% of the mass of WO3, preferably 20%; 2) Preparation of composite material: The 2.5DC / ZrC / SiC preform was completely embedded in the above-mentioned metal-molten salt mixed powder and placed in a melting infiltration device for high-temperature vacuum melting infiltration reaction. The melting infiltration process was as follows: the temperature was increased to 800℃ at a heating rate of 5℃ / min, then increased to 1300℃ at a heating rate of 3℃ / min, and kept at a constant temperature of 1300℃ and a pressure of 10MPa for 30min. After the reaction was completed, the mixture was cooled to obtain 2.5DC / ZrC / SiC (W 0.45 Cu 0.45 Ti 0.1 Composite materials.

[0027] Using the above preparation method, a 2.5DC / ZrC / SiC(W) alloy can be prepared. 0.45 Cu 0.45 Ti 0.1 Composite materials.

[0028] The prepared 2.5DC / ZrC / SiC(W 0.45 Cu 0.45 Ti 0.1 The composite material can be directly used to prepare hypersonic vehicles. Its ablation resistance principle is as follows: Due to the high heat flux density and dynamic pressure, key thermal protection system components of hypersonic vehicles, such as the nose cone, leading edge, scramjet engine combustion chamber, and nozzle, are subjected to extreme aerodynamic heating. With increasing flight speed, aerodynamic heating intensifies, causing the surface temperature to rise rapidly to over 2000℃ in a short period. Under this extreme thermal environment, the 2.5DC / ZrC / SiC (W) composite material prepared in this invention... 0.45 Cu 0.45 Ti 0.1 The excellent ablation resistance of the composite material enables it to adapt well to extreme service environments. During the ablation process, the composite material mainly undergoes the following reactions: W(s) + O2(g) → WO2(s) 2 / 3W(s) + O2(g) → 2 / 3WO3(s) 4Cu(s) + O2(g) → 2Cu2O(s) 2Cu(s) + O2(g) → 2CuO(s) 4CuO(s)→2Cu₂O+O₂(g) 2C(s) + O2(g) → 2CO(g) C(s) + O2(g) → CO2(g) 2C(s) + O2(g) → 2CO(g) CuO(s) + WO3(s) → CuWO4(s) Cu₂O(s) + WO₃(s) → Cu₂WO₄(s) 3CuO(s) + WO3(s) → Cu3WO6(s) 2SiC(s)+3O2(g)=2SiO2(l)+2CO(g) SiC(s) + O2(g) = SiO(g) + CO(g) SiC(s) + 2O2(g) = SiO2(l) + CO2(g) 2ZrC(s)+3O2(g)=2ZrO2(l)+2CO(g) ZrC(s) + 2O2(g) = ZrO2(l) + CO2(g) SiO2(l) = SiO2(g) Ti(s) + O2(g) = TiO2(s) At the start of ablation, the sample surface temperature rises rapidly. Cu and W are the first to come into contact with O2, absorbing a large amount of O2 and being oxidized into CuO and WO3, forming a dense oxide film that prevents O2 from penetrating the oxidized carbon fibers. They also absorb a large amount of heat, lowering the sample surface temperature. As Cu, W, and Ti are all oxidized to CuO, WO3, and TiO2, the temperature rises further. CuO and WO3 react further to form CuWO4 and begin to melt, destroying the dense oxide film. Solid SiC is oxidized into liquid SiO2, forming another dense oxide film that prevents O2 from further penetrating the carbon matrix. With further temperature increases, SiO2 vaporizes into gas due to the rising temperature, further absorbing a large amount of heat, and ZrC begins to form a continuous ZrO2 layer, further blocking O2 penetration. Therefore, the combined use of W, Cu, Ti, SiC, and ZrC can further improve the oxidation resistance of the composite material.

[0029] All raw materials used in this invention were purchased commercially. The reagents used in the following examples are: WO3 (Sinopharm Chemical Reagent Co., Ltd.), sodium hexametaphosphate (Sinopharm Chemical Reagent Co., Ltd.), Cu (Sinopharm Chemical Reagent Co., Ltd.), Ti (Sinopharm Chemical Reagent Co., Ltd.), NaCl (Sinopharm Chemical Reagent Co., Ltd.), KCl (Sinopharm Chemical Reagent Co., Ltd.), ZrC (Sinopharm Chemical Reagent Co., Ltd.), and SiC (Sinopharm Chemical Reagent Co., Ltd.); PAN-based carbon fiber was purchased from Jiangsu Tianniao High-Tech Co., Ltd.; and the needle-punching weaving used in the examples is a conventional technique in the art and will not be described in detail here.

[0030] Unless otherwise specified, "room temperature" in this invention refers to 20-30℃.

[0031] Unless otherwise specified, "atmospheric pressure" in this invention refers to 0.1 MPa.

[0032] The technical solution of the present invention will be further illustrated by the following embodiments.

[0033] Example 1 A 2.5DC / ZrC / SiC(W 0.45 Cu 0.45 Ti 0.1 The method for preparing composite materials includes the following steps: (1) Preparation of 2.5D braided material: Using PAN-based carbon fiber as the matrix, a density of 0.4 g / cm³ was obtained by needle punching and braiding process. 3 2.5D braided body; (2) Preparation of 2.5D carbon matrix: The 2.5D braided body prepared in step (1) is placed in a chemical vapor deposition equipment and heated to 1150°C at a heating rate of 10°C / min under an inert atmosphere. Then, methane gas is introduced at a gas flow rate of 300 mL / min and kept for 15-30 min. Finally, it is naturally cooled to deposit a layer of pyrolytic carbon on the surface of the preform to obtain a 2.5D carbon matrix. (3) Preparation of 2.5DC / ZrC / SiC billet: 1) Preparation of ZrC-SiC impregnation slurry: The slurry was prepared using ZrC powder with a particle size of 800 nm, SiC powder with a particle size of 800 nm, sodium hexametaphosphate dispersant, and deionized water as raw materials; wherein the molar ratio of ZrC powder, SiC powder, and deionized water was 1:1:20, and the amount of sodium hexametaphosphate added was 1 wt% of the total mass of ZrC powder and SiC powder; 2) Preparation of 2.5DC / ZrC / SiC green body: The 2.5D carbon matrix was first evacuated for 20 min, then placed in the prepared slurry and placed together in a vacuum pressure vessel. The vacuum pump was used to continue evacuating and maintaining the vacuum for 60 min. After the vacuum was completed, argon gas was introduced until the pressure inside the vessel reached 6 MPa. The pressure was maintained for 3 h, and finally the pressure was released to atmospheric pressure. The carbon matrix was taken out and dried to obtain the 2.5DC / ZrC / SiC green body. (4) Preparation of composite materials: 1) Preparation of metal-molten salt mixed powder: Weigh WO3 powder, Cu powder, Ti powder, NaCl molten salt and KCl molten salt, wherein the molar ratio of WO3, Cu and Ti is 45:45:10, the molar ratio of NaCl and KCl is 1:1, and the total amount of NaCl and KCl added is 20% of the mass of WO3. After mixing the raw materials, ball mill for 12 hours to obtain metal-molten salt mixed powder; 2) Preparation of composite material: The 2.5DC / ZrC / SiC preform was completely embedded in the above-mentioned metal-molten salt mixed powder and placed in a melting infiltration device for high-temperature vacuum melting infiltration reaction. The melting infiltration process was as follows: the temperature was increased to 800℃ at a heating rate of 5℃ / min, then increased to 1300℃ at a heating rate of 3℃ / min, and kept at a constant temperature of 1300℃ and a pressure of 10MPa for 30min. After the reaction was completed, the mixture was cooled to obtain 2.5DC / ZrC / SiC (W 0.45 Cu 0.45 Ti 0.1 Composite material (denoted as ZS-1).

[0034] Example 2 Same as Example 1, except that in step 1), the molar ratio of ZrC powder to SiC powder is 2:1, resulting in 2.5DC / ZrC / SiC (W 0.45 Cu 0.45 Ti 0.1 Composite material (denoted as ZS-2).

[0035] Example 3 Same as Example 1, except that in step 1), the molar ratio of ZrC powder to SiC powder is 3:1, resulting in 2.5DC / ZrC / SiC (W 0.45 Cu 0.45 Ti 0.1 Composite material (denoted as ZS-3).

[0036] Example 4 Same as Example 1, except that in step 1), the molar ratio of ZrC powder to SiC powder is 4:1, resulting in 2.5DC / ZrC / SiC (W 0.45 Cu 0.45 Ti 0.1 Composite material (denoted as ZS-4).

[0037] Comparative Example 1 Same as Example 1, except that sodium hexametaphosphate dispersant is not added in step 1).

[0038] Comparative Example 2 Same as Example 1, except that in step 1), the sodium hexametaphosphate dispersant is replaced with polyethyleneimine in an equal molar amount.

[0039] Comparative Example 3 Same as Example 1, except that in step 1), the sodium hexametaphosphate dispersant is replaced with polyethylene glycol in an equal molar amount.

[0040] Figure 2 The 2.5DC / ZrC / SiC(W) prepared in Example 1 0.45Cu 0.45 Ti 0.1 A low-magnification (25x) SEM image of the composite material surface; close observation of the high-brightness particles and skeleton edges reveals that although the overall structure is loose, there are obvious agglomerations, sintering necks, and adhesion phenomena between particles. This confirms that during the high-temperature process, the active Ti front did indeed undergo an interfacial reaction with the amorphous carbon, achieving localized solid-liquid wetting. This localized reaction "bridging" binds the originally dispersed ceramic particles, free carbon, and metallic phase together, allowing the material to maintain its macroscopic skeleton morphology even at such high porosity, without complete pulverization or collapse.

[0041] Figure 3 The 2.5DC / ZrC / SiC(W) prepared in Example 1 0.45 Cu 0.45 Ti 0.1 The image shows a 500x SEM image of the composite material surface. A bright, continuous W-Cu metallic phase is observed tightly coated on the surface of the polygonal crystal particles, even forming a smooth "filler" morphology in some gaps. This directly proves the success of the theoretical design of "step three" in the process. The reactive agent Ti indeed successfully acted as a "bridge" by reacting with amorphous carbon at a high temperature of 1300℃, significantly reducing the solid-liquid interfacial tension. This good localized coating indicates that the molten metal effectively wets the ceramic / carbon skeleton at the microscale.

[0042] Figure 4 The 2.5DC / ZrC / SiC(W) prepared in Example 1 0.45 Cu 0.45 Ti 0.1 A high-magnification (5500x) SEM image of the composite material surface shows a relatively smooth micro-region exhibiting continuous liquid-phase solidification characteristics in the lower right part of the image (presumably a Cu-rich or W-Cu-Ti solid solution phase). It can be clearly seen that this solidified phase is tightly bonded to the surrounding stepped, polyhedral hard phase (carbide ceramic framework), with no obvious cracks, debonding, or repulsion gaps at the interface. This provides the strongest microscopic evidence for Ti-element interface modification. At the microscale, the melt successfully spreads and adheres to the framework surface activated by the Ti-C reaction.

[0043] Figure 5 The 2.5DC / ZrC / SiC(W) prepared in Example 1 0.45 Cu 0.45 Ti 0.1The image shows a low-magnification (250x) SEM image of the composite material cross-section. The image reveals a clear contrast between light and dark areas on the polished section. The bright white areas represent the metallic / carbide phases composed of high atomic number elements; the dark background areas represent the porous C-ZrC-SiC framework with low atomic number elements. The bright white phase is widely distributed throughout the cross-sectional field of view, extending beyond the surface into the material's interior. This demonstrates that during the RMI process at 1300℃, the liquid phase effectively overcomes capillary resistance and successfully penetrates deep into the internal three-dimensional pore network, validating the overall effectiveness of the process.

[0044] Figure 6 The 2.5DC / ZrC / SiC(W) prepared in Example 1 0.45 Cu 0.45 Ti 0.1 The image shows a 1200x SEM image of the composite material cross-section. As can be seen, the high-brightness metallic / carbide phases in the field of view do not present as regular geometric blocks, but rather exhibit a highly irregular, vein-like, mosaic distribution, conforming to the microscopic contours of the dark matrix. This further confirms that during the RMI process at 1300℃, the well-flowing mixed melt successfully penetrated into the extremely complex and tortuous micron-scale three-dimensional pore network within the framework. This intricate interweaving state between the bright and dark phases creates a strong microscopic mechanical interlocking effect on a macroscopic level, contributing to a certain degree of improvement in the interlaminar shear strength of the material.

[0045] Figure 7 The 2.5DC / ZrC / SiC(W) prepared in Example 1 0.45 Cu 0.45 Ti 0.1 A high-magnification (10,000x) SEM image of the composite material cross-section shows a highly irregular deep pit (pore) in the center and right side of the field of view, with a size ranging from micrometers to submicrometers. The edge of this pore exhibits a natural, undulating granular outline, with scattered tiny debris inside. Within the relatively smooth continuous phase surrounding the pore, numerous particles with a size of several hundred nanometers are tightly embedded (the brighter fine grains in the image). These particles are extremely tightly bonded to the surrounding matrix, with no obvious interphase gaps observed. This cross-sectional view confirms the highly successful interfacial modification by Ti. These high-brightness submicrometer / nanoscale particles are perfectly encapsulated by a well-ductile continuous metallic phase. This indicates that even at the edge of the microscopic pore, the liquid metal still exhibits excellent wetting and spreading ability, achieving metallurgical-level interfacial bonding.

[0046] Figure 8 The 2.5DC / ZrC / SiC(W) prepared in Example 1 0.45 Cu 0.45Ti 0.1 High-magnification (5500x) SEM and EDS images of the carbon fiber region in the composite material are shown. The SEM image reveals a circular cross-section with a diameter of approximately 5-7 μm. The EDS surface scan shows an extremely high enrichment of carbon (C) in this circular region, with no distribution of Zr, Si, W, Ti, or other metallic elements. This central feature is a single carbon fiber cross-section within the preform. EDS results indicate that the molten metal and the matrix ceramic (ZrC / SiC) are mainly distributed around the fiber periphery. This demonstrates that even with the presence of reactive Ti during the 1300℃ infiltration process, the internal carbon fiber skeleton was not severely eroded or damaged, perfectly preserving its physical integrity as the primary load-bearing phase. The clarity of the interface indicates that the molten metal did not undergo destructive deep diffusion into the fiber interior.

[0047] In the matrix region surrounding the carbon fibers, surface scan signals of Zr, Si, W, and Cu are widely distributed and intertwined. This further confirms that the melt successfully penetrated into the micropores of the C-ZrC-SiC porous framework. The outer matrix exhibits a highly complex multiphase mixture state, with the metallic and ceramic phases achieving uniform interpenetration at the mesoscale.

[0048] Figure 9 The 2.5DC / ZrC / SiC(W) prepared in Examples 1-4 0.45 Cu 0.45 Ti 0.1A comparison of macroscopic photographs of the composite materials before and after ablation. The images show that the ablation center of ZS-1 presents a distinct dark pit (with a blackened bottom). This indicates that at lower ZrC contents, the generated liquid SiO2, although having some viscosity, is easily dispersed or vaporized under high Mach numbers or strong shear airflow. Simultaneously, the internal carbon skeleton is exposed and rapidly oxidized, leading to severe mechanical erosion and volume retreat in the central region. A small area of ​​yellow / green oxides appears in the center of ZS-2, while the center of ZS-3, although darker, shows a less concentrated ablation pit. This confirms that the evolution of ablation resistance is a continuous process following the compositional gradient. It gradually transitions from Cu-dependent sweating cooling (vaporization endothermic) and SiC glassy self-healing to a high dependence on the blocking effect of the rigid refractory skeleton of ZrO2. ZS-4 contrasts sharply with ZS-1; the ablation center of ZS-4 not only does not form a distinct deep pit but also exhibits a very prominent yellow-green / grayish-white oxide core. This raised crust is primarily composed of refractory solid ZrO2 (with a melting point as high as ~2700℃, often exhibiting a yellow / green hue due to lattice defects or impurities), formed by the high-temperature oxidation of ZrC. With the absolute dominance of ZrC, a large amount of ZrO2 is generated in situ in the stagnation region, forming a robust refractory framework. A small amount of SiO2 liquid phase is interspersed within, acting as a binder. This ZrO2-rich oxide is not blown away by the airflow; instead, it adheres firmly to the surface like "nails," forming an excellent physical and thermal barrier (thermal barrier effect), effectively preventing further diffusion of oxygen into the internal carbon framework and resisting the mechanical erosion of the airflow.

[0049] Table 1 shows the 2.5DC / ZrC / SiC (W) prepared in Examples 1-4. 0.45 Cu 0.45 Ti 0.1 Linear ablation rate and mass ablation rate of composite materials.

[0050] Table 1 Ablation properties of composite materials with different ZrC / SiC ratios As shown in Table 1, the mass ablation rate exhibits a sharp, monotonically decreasing trend from ZS-1 to ZS-4. In ZS-1, the system is rich in SiC. Under the scouring of a high-temperature, oxygen-enriched flow, SiC oxidizes to form liquid SiO2 and gaseous CO. Although SiO2 can play a certain sealing role, under the high shear force of the high-speed flow, the low-viscosity SiO2 droplets are easily blown away, corresponding to the darkened, deeply eroded pit morphology in the ZS-1 image. Conversely, in ZS-4, a large amount of ZrC oxidizes to form extremely refractory, high-density solid ZrO2 (melting point approximately 2700℃). This solid oxide does not vaporize or easily dispersed by the flow, but rather firmly "resides" and accumulates on the surface of the material's stagnation points (corresponding to the distinctly convex yellow-green oxide crust in the center of the ZS-4 image). Therefore, the increase in ZrC content greatly inhibits the volatilization and mechanical erosion loss of the material, resulting in an extremely low mass ablation rate. Unlike the monotonically decreasing mass ablation rate, the linear ablation rate exhibited a "V-shaped" trend, first decreasing and then increasing. ZS-3 showed the best dimensional stability; however, in ZS-4, the linear ablation rate rebounded to 3.50 μm / s. It is speculated that at this ratio, ZrC and SiC achieved a perfect synergistic ablation resistance balance. The solid ZrO2 generated by the oxidation of ZrC forms a robust refractory skeleton to resist mechanical ablation, while the liquid SiO2 generated by the oxidation of an appropriate amount of SiC acts as a high-temperature binder and sealing agent, filling the intergranular pores of the ZrO2 particles. This dense composite oxide layer of "skeleton + molten pool" is both robust and self-healing, effectively isolating oxygen from diffusing inward, thereby minimizing dimensional regression (linear ablation).

[0051] Figure 10 The 2.5DC / ZrC / SiC(W) prepared in Examples 1-4 0.45 Cu 0.45 Ti 0.1 The stress-strain curves of the mechanical properties of the composite material are shown in Table 2.

[0052] Table 2 As shown in Table 2, with the relative increase of ZrC content in the composite preform, the flexural strength of the material exhibits a clear parabolic trend of first increasing and then decreasing, reaching a maximum value of 138.38 MPa in the ZS-3 sample. Simultaneously, the fracture strain and ultimate deformation capacity of the material show a monotonically increasing trend, with the fracture strain increasing from 0.153% in ZS-1 to 0.302% in ZS-4, demonstrating excellent toughening potential. The strength of the composite material depends on the load-bearing capacity of the rigid ceramic skeleton and the filling and bonding quality of the pores by the molten metal. The microscopic mechanism by which ZS-3 exhibits optimal mechanical strength lies in its optimal multiphase structural synergistic equilibrium. As a refractory carbide with extremely high hardness and elastic modulus, the increase in ZrC content (from ZS-1 to ZS-3) significantly enhances the load-bearing cross-section of the internal rigid skeleton, effectively resisting the tensile / compressive stresses brought by external bending loads. Within the ZS-3 proportioning window, the gradation of rigid ZrC particles with SiC and the residual carbon skeleton is most reasonable. With active wetting modification by Ti, the highly fluid W-Cu melt can fully penetrate the pore network between ceramic particles, forming a dense, continuous binder phase. This significantly reduces internal macroscopic pores and loose microstructure, lowers the stress concentration effect of crack initiation, and thus pushes the macroscopic strength to its peak. When the ZrC ratio is further increased to ZS-4 (4:1), the strength drops sharply to 75.02 MPa. This is because excessive ZrC large particles disrupt the original component gradation, resulting in a lack of sufficient fine particles (such as SiC) to fill the gaps between large particles. At the same time, the overly dense hard phase may hinder the deep penetration of the metal melt, leading to microscopic "metal-poor phases" or closed-pore defects in local areas, weakening the bonding strength of the phase interface, and causing premature local shear failure of the material.

[0053] Figure 11The images show the effect of dispersant type on the suspension stability of ZrC-SiC mixed slurries. In the images, a represents Comparative Example 1, b represents Example 1, c represents Comparative Example 2, and d represents Comparative Example 3. As can be seen from the images, after adding different dispersants and allowing the ZrC-SiC mixed slurries with the same solid content and allowing them to stand for 3 hours, the blank slurry without any dispersant showed severe stratification, with a clear water layer precipitating on top and a thick sediment at the bottom. This is because ZrC and SiC particles have a large specific surface area, making them highly susceptible to flocculation and aggregation driven by van der Waals forces in the dispersion medium. The increased effective hydrodynamic radius of the aggregates leads to rapid gravitational settling. Furthermore, the slurries with added polyethyleneimine and polyethylene glycol also showed a clear upper layer. This indicates that for the high-density refractory ceramic particles in this system, conventional cationic or nonionic polymeric dispersants failed to provide sufficient repulsion barriers, and may even have exacerbated particle flocculation due to the "bridging effect" of long chains. The comparison revealed that the slurry containing sodium hexametaphosphate exhibited the best suspension stability. After standing for 3 hours, this slurry maintained a uniform black suspension state without any macroscopic solid-liquid interface. This indicates that sodium hexametaphosphate successfully broke the agglomeration tendency between particles, constructing a highly uniform and stable suspension system that fully meets the requirements of subsequent vacuum pressure microporous impregnation.

[0054] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A 2.5DC / ZrC / SiC(W 0.45 Cu 0.45 Ti 0.1 The method for preparing composite materials is characterized in that, Includes the following steps: (1) Needle-punching and weaving were performed using PAN-based carbon fiber as the matrix to obtain a 2.5D braided body; (2) Pyrolytic carbon was deposited on the surface of the 2.5D braided fabric by chemical vapor deposition to obtain a 2.5D carbon matrix; (3) The ZrC-SiC ceramic phase was introduced into the 2.5D carbon matrix by slurry infiltration to obtain a 2.5DC / ZrC / SiC green body; (4) The 2.5DC / ZrC / SiC preform was subjected to high-temperature vacuum infiltration in a metal-molten salt mixed powder using a reactive melting method to obtain 2.5DC / ZrC / SiC(W 0.45 Cu 0.45 Ti 0.1 Composite materials.

2. The preparation method according to claim 1, characterized in that, The specific operation steps of the chemical vapor deposition method are as follows: using chemical vapor deposition, a layer of pyrolytic carbon is deposited on the surface of the 2.5D braided fabric using methane gas to obtain a 2.5D carbon matrix; The conditions for the chemical vapor deposition process are as follows: under an inert atmosphere, the temperature is raised to 1150°C at a heating rate of 10°C / min, then methane gas is introduced at a flow rate of 300 mL / min for 15-30 min, and the temperature is maintained at 1150°C for 15-30 min, followed by natural cooling.

3. The preparation method according to claim 1, characterized in that, The specific operation steps of the slurry impregnation method are as follows: after vacuuming the 2.5D carbon matrix for 15-30 minutes, it is successively impregnated and dried in the slurry under vacuum pressure to obtain a 2.5DC / ZrC / SiC green body.

4. The preparation method according to claim 3, characterized in that, The specific steps of the vacuum pressure impregnation are as follows: the 2.5D carbon matrix is ​​placed in the slurry, then placed in a vacuum pressure vessel, vacuumed and maintained for 30-90 minutes; after completion, argon gas is used to pressurize to 5-8 MPa and maintained for 1-6 hours, and finally the pressure is released to normal pressure and the substrate is taken out and dried.

5. The preparation method according to claim 3, characterized in that, The slurry is made from ZrC powder, SiC powder, deionized water and dispersant. The molar ratio of ZrC powder, SiC powder and deionized water is 1:1:

20. The dispersant is sodium hexametaphosphate, and the amount added is 1 wt% of the total mass of ZrC powder and SiC powder.

6. The preparation method according to claim 1, characterized in that, The specific operation steps of the reaction melting infiltration method are as follows: the 2.5DC / ZrC / SiC billet is completely embedded in a metal-molten salt mixed powder, and then a high-temperature vacuum melting infiltration reaction is carried out, followed by cooling.

7. The preparation method according to claim 6, characterized in that, The specific operating steps of the high-temperature vacuum melting and infiltration reaction are as follows: heat to 800°C at a heating rate of 5°C / min, then heat to 1300°C at a heating rate of 3°C / min, and heat for 30 minutes at a temperature of 1300°C and a pressure of 10MPa.

8. The preparation method according to claim 6, characterized in that, The metal-molten salt mixed powder is a mixture of WO3, Cu, Ti and molten salt; The molar ratio of WO3, Cu and Ti is 45:45:

10. The molten salt is NaCl and KCl, and the amount added is 5-80% of the mass of WO3, with a molar ratio of NaCl to KCl of 1:

1.

9. A 2.5DC / ZrC / SiC(W) 0.45 Cu 0.45 Ti 0.1 Composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. A 2.5DC / ZrC / SiC(W) alloy as described in claim 9 0.45 Cu 0.45 Ti 0.1 Application of composite materials in the manufacture of hypersonic vehicles.

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