Ultrahigh-temperature micro-ablation material and preparation method thereof

Abstract

The application discloses a preparation method of an ultrahigh-temperature micro-ablation material, modification in the interior of a C / C blank body, obtaining a modified C / C blank body, placing the modified C / C blank body in slurry containing ultrahigh-temperature ceramics, sequentially performing normal pressure natural impregnation and physical auxiliary vibration impregnation, and drying to obtain a C / C-ultrahigh-temperature ceramic matrix composite blank body; then, the C / C-ultrahigh-temperature ceramic matrix composite blank body is densified through a precursor impregnation and pyrolysis process, and an ultrahigh-temperature ceramic matrix composite material is obtained. The ultrahigh-temperature ceramic slurry with high solid content and low viscosity is used for impregnation combined with the PIP process, the preparation process is simple and controllable, and the method is suitable for industrial production; in the provided ultrahigh-temperature micro-ablation material, the volume fraction of the ultrahigh-temperature ceramic is high (more than 20 vol.%), the relative content can be controlled in a large range, the ceramic phase and the fiber realize the characteristics of double-continuous distribution of component content and space, the ultrahigh-temperature micro-ablation material has excellent mechanical properties, oxidation resistance and ablation resistance, and can resist 2300 DEG C high-temperature ablation.

Description

Technical Field

[0001] This invention belongs to the field of ceramic matrix composite materials technology, specifically relating to an ultra-high temperature micro-ablation material and its preparation method. Background Technology

[0002] C / C composites are carbon-based composite materials with carbon fiber as reinforcement. They not only have the excellent mechanical properties of fiber-reinforced materials, but also have many advantages of carbon materials, such as low density, low coefficient of thermal expansion, high thermal and electrical conductivity, excellent thermal shock resistance, ablation resistance, and abrasion resistance. They have become ideal structural materials in aerospace, automotive, medical and other fields.

[0003] However, C / C composites oxidize at around 400℃ in air, significantly reducing their mechanical properties and service life. Since components such as aero-engines and automotive brake discs operate at temperatures exceeding 1400℃, existing C / C composites clearly cannot meet these requirements. Therefore, further improving the ablation resistance of C / C composites in high-temperature environments and enhancing their high-temperature application capabilities remains a key research focus and challenge for the present and future.

[0004] Matrix modification of C / C composites, using ultra-high temperature ceramic matrices such as ultra-high temperature carbides and borides to replace the carbon matrix, can significantly improve the ablation resistance and mechanical properties of C / C composites, meeting the service conditions of key components such as aircraft nose cones, wing leading edges, and aero-engine hot ends under extreme environments. Ultra-high temperature carbides possess high melting points, high strength, high hardness, and good chemical stability. Currently commonly used ultra-high temperature carbide ceramics mainly include SiC, HfC, ZrC, and TaC. Their melting points are much higher than their oxides, they do not require any solid-phase transformation, and they maintain good strength and thermal shock resistance at high temperatures. Ultra-high temperature borides mainly include HfB2, ZrB2, and TaB2. Benefiting from the strong covalent bonds in the boride structure, they possess characteristics such as high melting points, high strength, high hardness, low evaporation rate, and high thermal and electrical conductivity. Compared to C / (C-)Hf(Zr)C-SiC, the C / (C-)SiC-Hf(Zr)B2 composite material exhibits superior oxidation resistance over a wider temperature range. This is primarily because at relatively low oxidation temperatures (800℃~1000℃), a large amount of boron-containing oxides can be generated on the material surface. Under medium-temperature oxidation conditions (1000℃~1700℃), borosilicates and SiO2 liquid phases are formed on the material surface. At high temperatures (1700℃~2200℃ (or even higher), SiO2 is formed on the material surface. 2-ZrO2 solid solution and solid-phase ZrO2-stabilized glassy phase. In order to make the material have good ablation resistance in a wider temperature range, it is necessary to add multiple components to toughen and strengthen the material and improve its oxidation and ablation resistance through multi-component synergistic effects.

[0005] Currently, the methods for preparing C / C composites modified from multi-component ultra-high temperature ceramic matrices, both domestically and internationally, mainly focus on the precursor infiltration and pyrolysis (PIP) method and the reaction melt infiltration (RMI) method.

[0006] The literature [“Preparation of compact ZrC-SiC ceramic matrix from thermosetprecursors for C / C-ZrC-SiC composites with high mechanical properties. Mingdong Liao a, Manuel Reyes De Guzman b, Guobo Shen, et al. Journal of the European Ceramic Society, 44(2024)1983-1999”] discloses a method for preparing C / C-Zr-SiC composites with a dense ceramic matrix through precursor wetting and pyrolysis. They attribute the dense structure of the ZrC-SiC ceramics prepared by this method to a tightly cross-linked structure, allowing for direct crystallization without carbothermal reduction. The pyrolyzed precursor structure is more compact, resulting in a denser ceramic matrix and better interfacial bonding between the ceramic matrix and the carbon matrix. The composite material possesses a dense ZrC-SiC matrix and a slightly defective interface, exhibiting an ideal non-brittle fracture mode. The ZrC-SiC matrix has a high elastic modulus, but moderate thermal residual stress damage and interfacial bonding lead to significant crack flexure and fiber pull-out. However, precursor impregnation pyrolysis requires repeated impregnation and pyrolysis, during which the matrix is ​​prone to shrinkage and defect formation, resulting in a decline in the material's mechanical properties.

[0007] The literature [“Ultra-high-temperature ablation behavior of SiC-ZrC-TiC modified carbon / carbon composites fabricated via reactive metl infiltration. Yi Zeng, Dini Wang, Xiang Xiong et al. Journal of European Ceramic Society, 40(2020)651-659”] uses a reactive solution infiltration method to prepare a SiC-ZrC-TiC ternary ceramic matrix on C / C composites. This ceramic matrix is ​​composed of Zr-rich and Ti-rich solid solutions Zr1−xTixC and SiC. They believe that the good ablation resistance of the C / C-SiC-ZrC-TiC composite is mainly due to the multiphase oxide layer on the surface of the composite. By providing low volatility and high viscosity oxides, the multiphase oxide layer has strong resistance to high-temperature volatility and high-speed airflow erosion. However, this method requires high temperature conditions and is relatively energy-intensive. In addition, during the preparation process, the molten metal reacts with the carbon fibers, causing fiber damage. Unreacted metals inside the material will accelerate creep and disrupt phase equilibrium under the high temperature environment of service, thus reducing the material performance. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the first objective of this invention is to provide a method for preparing ultra-high temperature micro-ablation materials. This invention employs a multi-component structure with a coating, and the preparation process is simple, controllable, and suitable for industrial production.

[0009] The second objective of this invention is to provide an ultra-high temperature micro-ablation material prepared by the above-described preparation method. The ultra-high temperature micro-ablation material has a high volume fraction of ultra-high temperature ceramics, a uniform microstructure, excellent mechanical properties, antioxidant properties, and ablation resistance. It can withstand high-temperature ablation at 2300℃ and maintain good mechanical properties during the ablation process.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] This invention discloses a method for preparing an ultra-high temperature micro-ablation material. The method involves modifying the interior of a C / C preform to obtain a modified C / C preform. The modified C / C preform is then placed in a slurry containing ultra-high temperature ceramics and sequentially subjected to normal pressure natural impregnation and physical-assisted vibration impregnation. After drying, a C / C-ultra-high temperature ceramic matrix composite preform is obtained. The C / C-ultra-high temperature ceramic matrix composite preform is then densified through precursor impregnation pyrolysis (PIP) to obtain the ultra-high temperature micro-ablation material.

[0012] The preparation method of this invention first modifies the internal structure of the C / C preform to reduce the frictional resistance between the fiber and the ceramic powder and increase the chemical bonding effect. Then, by modifying the capillary force of the C / C preform itself and by assisting vibration operation, a high content of ultra-high temperature ceramic powder is introduced to form a bicontinuous and uniform distribution of UHTCs and carbon fibers. After impregnation and drying, a C / C-ultra-high temperature ceramic matrix composite preform can be obtained. Then, a silicon carbide matrix is ​​prepared by impregnation and low-temperature (~1300℃) pyrolysis densification, while simultaneously fixing and encapsulating the ultra-high temperature ceramic powder to obtain a C / C-multi-component ultra-high temperature ceramic matrix composite material. The preparation method of this invention can effectively avoid damage to the carbon fibers and ensure that the C / C-multi-component ultra-high temperature ceramic matrix composite material has excellent mechanical properties and ablation resistance.

[0013] In a preferred embodiment, the density of the C / C preform is 0.45-0.70 g / cm³. 3 .

[0014] In a preferred embodiment, the C / C preform is obtained by chemical vapor infiltration (CVI) deposition of a pyrolytic carbon coating on a carbon fiber preform, wherein the thickness of the pyrolytic carbon coating is 200-400 nm.

[0015] In a further preferred embodiment, the carbon fiber preform is selected from one of needle-punched preform (2.5D fabric) and fine-knitted puncture preform (3D fabric).

[0016] More preferably, the density of the carbon fiber preform is 0.40-0.65 g / cm³. 3 .

[0017] In a further preferred embodiment, the carbon fiber preform is first heat-treated at 1600-2000℃ under argon protection, and then subjected to chemical vapor infiltration (CVI) deposition of a pyrolytic carbon coating.

[0018] In a preferred embodiment, the internal modification process of the C / C preform is as follows: first, the C / C preform is placed in an oxidizing agent for oxidative etching, then the oxidized C / C preform is immersed in a solution containing a modifier for hydrolysis reaction, and then dried to obtain the final product. The modifier is selected from silane coupling agents and / or polyacrylic acid.

[0019] In a further preferred embodiment, the oxidant is selected from one of HNO3 solution, H3PO4 solution, and KMnO4 solution, preferably HNO3 solution, wherein the mass fraction of HNO3 in the HNO3 solution is 30-65%.

[0020] In a further preferred embodiment, the oxidation etching temperature is 50-60℃ and the time is 1-2h.

[0021] In a further preferred embodiment, the oxidation etching process is performed under ultrasonic assistance. To ensure that the ultra-high temperature powder is uniformly introduced into the interior of the modified C / C preform, ultrasonic-assisted oxidation etching allows for thorough and uniform oxidation etching throughout the C / C preform, thereby promoting uniform modification of the modifier.

[0022] In a further preferred embodiment, the solution containing the modifier is composed of ethanol, water, and the modifier, with a mass ratio of ethanol:water:modifier = 9-12:1:0.02-0.15.

[0023] In this invention, a solution containing the modifier is prepared using a mixed solvent of ethanol and water. The proportions of each component must be effectively controlled. If there is too little water, the modifier cannot be fully hydrolyzed; if there is too much water, the modifier will be over-hydrolyzed before it can bond with the fiber surface. Too much or too little water is not conducive to the bonding of the modifier with the fiber surface.

[0024] More preferably, the silane coupling agent is selected from at least one of γ-aminopropyltriethoxysilane (KH-550), γ-aminopropyltrimethoxysilane (A-1110), and γ-mercaptopropyltriethoxysilane (KH-580).

[0025] In a further preferred embodiment, the hydrolysis reaction is carried out at a temperature of 70-80°C for a time of 1-2 hours.

[0026] In a further preferred embodiment, the hydrolysis reaction is carried out under ultrasonic assistance. The inventors have discovered that performing the reaction under ultrasound can make the modification process more uniform; if it is not performed under ultrasound, the modification process is uneven, affecting the distribution of the ultra-high temperature ceramic powder inside the green body.

[0027] In a preferred embodiment, the slurry containing ultra-high temperature ceramics comprises ultra-high temperature ceramic powder, a dispersant, and a solvent.

[0028] In a further preferred embodiment, the slurry containing ultra-high temperature ceramics also contains silicon carbide powder.

[0029] In a further preferred embodiment, the ultra-high temperature ceramic powder in the slurry containing ultra-high temperature ceramics is selected from at least two of zirconium boride, hafnium boride, zirconium carbide, hafnium carbide, and lanthanum boride powder; preferably zirconium carbide and hafnium carbide, and the particle size of the ultra-high temperature ceramic powder is 0.2-0.7 μm.

[0030] The inventors discovered that at least two types of ultra-high temperature ceramic powders are required. If only one type is used, the synergistic effect between the ultra-high temperature ceramic components and between the ultra-high temperature ceramic components and SiC cannot be fully realized. On one hand, the oxide framework formed after the oxidation of the ultra-high temperature ceramic components can stabilize the ablation surface and resist ablation. On the other hand, the SiO2 formed after the oxidation of SiC, alone or in combination with the borosilicate formed by the oxidation of borates (B2O3), can fill the liquid-phase oxide film. Only the synergistic effect between at least two types of ultra-high temperature ceramic powders can ensure that the ablation surface of the material is composed of a stable ultra-high temperature oxide solid-phase framework and a liquid oxide film.

[0031] In addition, the particle size of the ultra-high temperature ceramic powder needs to be effectively controlled within the range of this invention in order to ensure that it is uniformly introduced into the interior of the C / C green body.

[0032] In a further preferred embodiment, the volume fraction of the ultra-high temperature ceramic powder in the ultra-high temperature ceramic slurry is 10-40 vol.%.

[0033] The ultra-high temperature ceramic slurry provided by this invention has a high solid content and low viscosity. By combining the ultra-high temperature ceramic slurry of this invention with normal pressure natural impregnation and physical-assisted vibration impregnation, ultra-high temperature ceramics with a volume fraction greater than 20 vol.% can be introduced into ultra-high temperature micro-ablation materials. Furthermore, by controlling the ratio and content of ultra-high temperature ceramic powder in the slurry, the content and type of ultra-high temperature ceramic components in C / C-ultra-high temperature ceramic matrix composites can be adjusted over a wide range, achieving a dual continuous distribution of ceramic phase and fiber, with continuous component content and spatial distribution, thereby improving the ablation resistance of the composite material at 2300℃.

[0034] In a further preferred embodiment, the dispersant is selected from one or two of polyethyleneimine, polyvinyl butyral, ammonium citrate, polyethylene glycol, polycarbosilane, and hydrogenated styrene-butadiene block copolymer.

[0035] In a further preferred embodiment, the amount of the dispersant added is 8-20% of the mass of the ultra-high temperature ceramic powder.

[0036] The inventors discovered that by controlling the amount of dispersant added within this preferred range, uniform dispersion of ceramic powder in the ultra-high temperature ceramic slurry can be achieved without adjusting the pH value. If too much dispersant is added, excessive dispersant will adhere to the surface of the ceramic powder, causing agglomeration and affecting dispersion and its introduction into the green body; if too little is added, the ceramic powder will be unevenly dispersed, prone to sedimentation, and unable to maintain a stable state within the experimental time, affecting impregnation.

[0037] In a further preferred embodiment, the solvent is one or two of deionized water, anhydrous ethanol, acetone, and xylene.

[0038] In a further preferred embodiment, the preparation process of the ultra-high temperature ceramic slurry is as follows: ultra-high temperature ceramic powder, silicon carbide powder, dispersant, and solvent are prepared according to the design ratio, and then ball milled at a speed of 180-220 r / min for a time of 2-3 h.

[0039] Further optimization yields a grinding ball to ultra-high temperature ceramic powder mass ratio of 2-4:1.

[0040] The preparation method provided by this invention modifies the surface properties of the C / C preform, reduces the frictional resistance between the fiber and the ceramic powder, and increases the chemical bonding effect. Under normal temperature and pressure, an ultra-high temperature ceramic matrix can be introduced into the preform through impregnation with an ultra-high temperature ceramic slurry. Furthermore, the pH value of the ultra-high temperature ceramic slurry does not need to be adjusted during the preparation process; only the amount of dispersant needs to be adjusted to achieve the formulation of a high-solid-content, low-viscosity ultra-high temperature ceramic slurry, enabling the high-content introduction of ultra-high temperature ceramic components. The ceramic matrix and carbon fiber are evenly distributed in a two-phase manner, without damaging the silicon carbide fibers. While ensuring the mechanical properties of the material, it can improve the ablation resistance of the composite material at 2300℃.

[0041] In a preferred embodiment, the natural impregnation time under normal pressure is 60-90 minutes.

[0042] In a preferred embodiment, the vibration frequency during the physical-assisted vibration impregnation is 800-1500 times / min, and the physical-assisted vibration impregnation time is 30-60 minutes. In actual operation, physical vibration assistance is achieved by using a physical-assisted vibration impregnation instrument.

[0043] In this invention, after the C / C green body has undergone modification pretreatment and the slurry has been properly prepared, the pretreated C / C green body only needs to be naturally impregnated in the slurry under normal pressure for 60-90 minutes, followed by physical-assisted vibration impregnation for 30-60 minutes to complete the impregnation. The auxiliary vibration can achieve dense stacking of ceramic particles, increasing the actual ceramic volume ratio in the C / C green body. The manufacturing process of this invention is efficient, easy to operate, and does not damage the fibers.

[0044] In this invention, natural impregnation is performed first, utilizing the capillary action of the green body to draw the slurry deep into the green body. During natural impregnation, the pores inside the green body contain not only ceramic powder but also solvent, meaning the powder does not fully fill the pores. Physically assisted vibration impregnation allows the powder to pack tightly into the pores, filling them as much as possible and increasing the amount of ceramic powder introduced. However, natural impregnation at normal pressure for 60-90 minutes is required before physically assisted vibration impregnation can be performed. Initiating physical vibration too early can cause the powder to become blocked in the pores during impregnation, hindering the subsequent introduction of the matrix, resulting in poor impregnation and uneven dispersion of the ceramic powder in the green body.

[0045] In a preferred embodiment, the drying temperature is 80-100℃ and the drying time is 1.5-8h.

[0046] In this invention, the drying process can be carried out using equipment such as freeze drying, vacuum drying oven, or conventional drying oven.

[0047] In a preferred embodiment, the density of the C / C-ultra-high temperature ceramic matrix composite material is 0.9-3.2 g / cm³. 3 .

[0048] In a preferred embodiment, the precursor impregnation pyrolysis densification process is as follows: the C / C-ultra-high temperature ceramic matrix composite material is impregnated in an impregnating agent, first by vacuum impregnation, then by pressure impregnation, after impregnation, it is cured, pyrolyzed, and then the impregnation-curing-pyrolysis process is repeated until densification is achieved; the impregnating agent is selected from PCS-xylene solution or liquid polycarbosilane, and in the PCS-xylene solution, the mass ratio of PCS:xylene is 0.5-1:0.5-1.

[0049] In a further preferred embodiment, the vacuum impregnation time is ≥4h, and the pressure impregnation pressure is 2.7-3MPa, and the time is 8-10h.

[0050] In a further preferred embodiment, the curing temperature is 110-220℃ and the time is 4-5h.

[0051] More preferably, the pyrolysis temperature is 1000-1300℃, the pyrolysis time is 0.5-1h, and the heating rate is 2-10℃ / min.

[0052] In a preferred embodiment, a surface coating is applied to the surface of the ultra-high temperature ceramic substrate obtained by pre-progenitor impregnation pyrolysis (PIP) to densify the ultra-high temperature micro-ablation material, and then dried to obtain the ultra-high temperature micro-ablation material.

[0053] In a further preferred embodiment, the coating used for brushing comprises an antioxidant coating formulated with Er-Y-Ls rare earth powder and SiC whiskers.

[0054] The present invention also provides an ultra-high temperature micro-ablation material prepared by the above preparation method, wherein the ultra-high temperature micro-ablation material comprises carbon fiber, pyrolytic carbon fiber encapsulating carbon fiber, ultra-high temperature ceramic matrix, and SiC matrix, wherein the ultra-high temperature ceramic in the ultra-high temperature ceramic matrix is ​​selected from at least two of zirconium boride, hafnium boride, zirconium carbide, hafnium carbide, and lanthanum boride, preferably zirconium carbide and hafnium carbide.

[0055] Further preferred, the density of the ultra-high temperature micro-ablation material is 2.8 g / cm³. 3 -3.5g / cm 3The flexural strength is 200-330 MPa, and the fracture toughness is 8.19-42.13 MPa·m. 1 / 2 The linear ablation rate in oxyacetylene at 2300 K is 0.06-0.56 μm / s, and the mass ablation rate is 0.26-1.92 mg / s.

[0056] Principles and advantages

[0057] This invention utilizes a high-solid-content, low-viscosity ultra-high temperature ceramic slurry, and leverages the capillary force of the C / C preform itself, along with auxiliary vibration, to achieve a large-scale introduction of ultra-high temperature ceramic powder. This results in a bicontinuous and uniform distribution of UHTCs and carbon fibers. After drying, the powder is repeatedly impregnated and cured using a PIP process, followed by low-temperature (~1300℃) pyrolysis densification to prepare a SiC matrix. Simultaneously, the ultra-high temperature ceramic powder is fixed and encapsulated, thus obtaining an ultra-high temperature micro-ablation material. The preparation method of this invention effectively avoids damage to the carbon fibers, ensuring that the ultra-high temperature micro-ablation material possesses excellent mechanical properties and ablation resistance.

[0058] The ultra-high temperature ceramic matrix method introduced in this invention does not damage the fibers, the matrix is ​​uniformly distributed, and the composite oxide film generated in situ by the multiphase ceramic matrix during the ablation process has high integrity. Through synergistic effect, it can achieve both anti-oxidation and anti-ablation effects. The oxide layer with high integrity and toughness effectively prevents the loss of liquid phase oxides, so that the material does not crack under the scouring of high temperature and high speed airflow. During the fracture process, the coupling effect of multiple toughening mechanisms such as crack deflection, crack bifurcation, fiber bridging, bundled fiber pull-out and interface debonding well maintains the non-brittle fracture characteristics of the material.

[0059] By controlling the ratio of ultra-high temperature ceramic slurry and the number of polymer impregnation and pyrolysis cycles, the components and content of ultra-high temperature ceramic matrix in the material can be controlled, thereby achieving control over the microstructure and properties of the material.

[0060] Compared with reactive infiltration and needle injection of ultra-high temperature ceramic slurry, the method of the present invention can introduce ultra-high temperature ceramic components at low temperature without damaging the carbon fiber and thus preserving the carbon fiber reinforcement effect.

[0061] The ultra-high temperature micro-ablation material prepared by this invention exhibits excellent ablation resistance, as well as high strength and corrosion resistance. The linear ablation rate of the Cf / HfC-ZrC-SiC composite material in the 2300K oxyacetylene experiment is only 0.06 μm / s. During the ablation process, the HfC-ZrC-SiC multiphase ceramic matrix can generate a composite oxide film composed of liquid-phase SiO2 and solid-phase HfO2 in situ. The synergistic effect of the two achieves both oxidation resistance and ablation resistance.

[0062] In summary, the production process of this invention is simple and easy to control, with low preparation cost, making it suitable for industrial production. The C / C-multi-component ultra-high temperature ceramic matrix composite material prepared by this invention has controllable microstructure and properties, uniform microstructure, high strength, high temperature resistance, corrosion resistance, and excellent ablation resistance. Attached Figure Description

[0063] Figure 1 The surface of the Cf / HfC-ZrC-SiC composite material after ablation in Example 1;

[0064] Figure 2 The surface center morphology of the Cf / HfC-ZrC-SiC composite material after ablation in Example 1;

[0065] Figure 3 The surface transition region morphology of the Cf / HfC-ZrC-SiC composite material after ablation in Example 1;

[0066] Figure 4 XRD pattern of Cf / HfC-ZrC-SiC composite material in Example 1. Detailed Implementation

[0067] The invention will be further illustrated below with examples.

[0068] Example 1

[0069] A method for preparing an ablation-resistant and high-temperature-resistant ceramic matrix composite material is provided, and the preparation steps are as follows:

[0070] Step 1, carbon fiber pretreatment and surface carbon coating deposition: with a density of 0.40 g / cm³ 3 The 2.5D needle-punched carbon felt was used as a preform and heat-treated at 1800℃ in an argon atmosphere with a heating rate of 10℃ / min and a holding time of 1h. A pyrolytic carbon interface layer was deposited on the degummed carbon fiber preform with propylene as the carbon source gas and a deposition time of 35h to obtain a C / C preform containing a PyC layer, wherein the thickness of the PyC layer is 300nm.

[0071] Step 2, C / C preform modification: The low-density preform obtained in step (2) is immersed in dilute nitric acid solution and ultrasonically oxidized and etched at 50°C for 1 hour, dried at 80°C, and then modified using a mixture of ethanol and water containing silane coupling agent KH-550. The mass ratio of ethanol:water:silane coupling agent KH-550 in the solution containing the modifier is 12:1:0.15. The preform is ultrasonically hydrolyzed at 80°C for 1 hour and dried at 80°C to obtain a surface-modified C / C preform.

[0072] Step 3, Modified C / C green body combined with ultra-high temperature ceramic slurry: Using polyethyleneimine (PEI) as a dispersant, an aqueous solution containing the dispersant was prepared. Then, HfC, ZrC, and SiC powders were added to the aqueous solution containing the dispersant and ball-milled in a planetary ball mill for 3 hours to prepare an HfC-ZrC-SiC water-based ceramic slurry with a solid content of 35 vol%. The amount of dispersant added was 20 wt% of the total mass of the powder. The average particle size of the HfC, ZrC, and SiC powders was 500 nm. The surface-modified C / C green body from Step 2 was immersed in the prepared HfC-ZrC-SiC water-based ceramic slurry and naturally immersed at normal pressure for 60 minutes, followed by physical-assisted vibration immersion for 30 minutes. During physical-assisted vibration immersion, the vibration frequency was 1400 times / min. The moisture in the three-dimensional needle-punched integral felt after immersion was removed, and the drying temperature was 100℃ for 8 hours.

[0073] Step 4, densification of C / C-ultra-high temperature ceramic matrix composite: The C / C-green body containing HfC-ZrC-SiC obtained in Step 3 is placed in a high-pressure impregnation kettle, and the pores in the green body are filled with polycarbosilane (PCS) by pressure impregnation. Then the impregnated green body is placed in a vacuum pyrolysis furnace for pyrolysis to obtain carbon fiber reinforced carbon and hafnium carbide-zirconium carbide-silicon carbide matrix (C / C-HfC-ZrC-SiC) composite material. During PIP densification, polycarbosilane (PCS) was used as the raw material, and xylene was used as the solvent. The mass ratio of PCS to xylene was 1:1. The impregnation pressure was 3 MPa, and the impregnation time was 8 hours. Subsequently, it was cured at 220°C for 5 hours. Then, the C / C-HfC-ZrC-SiC composite material was vacuum pyrolyzed at 1200°C for 30 minutes. The samples were cycled until the weight gain before and after the pyrolysis was ≤1%, thus obtaining a dense C / C-HfC-ZrC-SiC composite material. The resulting C / C-HfC-ZrC-SiC composite material had a ceramic volume ratio of 27.59% after slurry impregnation and a density of 3.02 g / cm³ after densification. 3 .

[0074] The C / C-HfC-ZrC-SiC composite material obtained in this embodiment has a flexural strength of 323.00 MPa and a fracture toughness of 42.13 MPa·m, as tested. 1 / 2 The linear ablation rate in the 2300K oxyacetylene experiment was 0.06 μm / s, and the mass ablation rate was 0.26 mg / s.

[0075] Example 2

[0076] The difference between this embodiment and Embodiment 1 is that in step 3, polyethyleneimine (PEI) is used as a dispersant and ethanol is used as a solvent to obtain an ethanol solution containing the dispersant. It is not necessary to adjust the pH of the solvent. Then, HfB2, ZrB2, and SiC powders are added to the ethanol solution containing the dispersant and ball-milled in a planetary ball mill for 3 hours to prepare an HfB2-ZrB2-SiC ceramic slurry with a solid content of 28 vol%. The amount of dispersant added is 12 wt% of the total mass of the powder, and the average particle size of the HfB2, ZrB2, and SiC powders is 500 nm.

[0077] The resulting C / C-HfB2-ZrB2-SiC composite material had a ceramic volume fraction of 15.11% after slurry impregnation and a density of 2.89 g / cm³. 3 .

[0078] The C / C-HfB2-ZrB2-SiC composite material obtained in this embodiment has a flexural strength of 235.49 MPa and a fracture toughness of 8.19 MPa·m. 1 / 2 The linear ablation rate in the 2300K oxyacetylene experiment was 0.53 μm / s, and the mass ablation rate was 0.87 mg / s.

[0079] Example 3:

[0080] The difference between this embodiment and Embodiment 1 is that in step 3, polycarbosilane (PCS) and hydrogenated styrene-butadiene block copolymer are used as dispersants. The two are dissolved in xylene to obtain a PCS-SEBS-xylene solution with a concentration of 0.8 g / mL. Then, HfC, LaB6, and SiC powders are added to the solution and ball-milled in a planetary ball mill for 3 hours to prepare an HfC-LaB6-SiC water-based ceramic slurry with a solid content of 25 vol%. The average particle size of the HfC, LaB6, and SiC powders is 500 nm.

[0081] The resulting C / C-HfC-LaB6-SiC composite material, after slurry impregnation, had a ceramic volume fraction of 16.95% and a density of 3.44 g / cm³. 3 .

[0082] The C / C-HfC-LaB6-SiC composite material obtained in this embodiment has a flexural strength of 208.09 MPa and a fracture toughness of 18.43 MPa·m, as tested. 1 / 2 The linear ablation rate in the 2300K oxyacetylene experiment was 0.33 μm / s, and the mass ablation rate was 1.92 mg / s.

[0083] Example 4:

[0084] The difference between this embodiment and Embodiment 1 is that in step 3, polyethyleneimine (PEI) is used as a dispersant and added to water to obtain an aqueous solution containing the dispersant. Then, ZrB2, ZrC, and SiC powders are added to the aqueous solution containing the dispersant and ball-milled in a planetary ball mill for 3 hours to prepare a ZrB2-ZrC-SiC water-based ceramic slurry with a solid content of 35 vol%. The amount of dispersant added is 13% of the total mass of the powder, and the average particle size of the ZrB2, ZrC, and SiC powders is 500 nm.

[0085] The resulting C / C-ZrB2-ZrC-SiC composite material had a ceramic volume fraction of 27.73% after slurry impregnation and a density of 2.88 g / cm³. 3 .

[0086] The C / C-ZrB2-ZrC-SiC composite material obtained in this embodiment has a flexural strength of 280.00 MPa and a fracture toughness of 31.03 MPa·m. 1 / 2 The linear ablation rate in the 2300K oxyacetylene experiment was 0.56 μm / s, and the mass ablation rate was 0.80 mg / s.

[0087] Comparative Example 1

[0088] The difference between this comparative example and Example 1 is that the low-density preform obtained in step 1 was immersed in dilute nitric acid (concentration) for oxidation etching treatment for 2 hours, and then immersed in polyethylene glycol solution, water at 80°C, ultrasonicated for 1 hour, and dried at 80°C until the solvent was completely evaporated for 2 hours to obtain a surface-modified C / C preform.

[0089] In step 3, polyethyleneimine (PEI) is added to water as a dispersant to obtain an aqueous solution containing the dispersant. The pH of the aqueous solution containing the dispersant is adjusted to 7 using acetic acid and ammonia. Then, HfC, ZrC, and SiC powders are added to the aqueous solution containing the dispersant and ball-milled in a planetary ball mill for 3 hours to prepare an HfC-ZrC-SiC water-based ceramic slurry. The average particle size of the powder is 500 nm.

[0090] In Comparative Example 1, the carbon fiber was modified without surface carbon coating after pretreatment. The slurry prepared by adjusting the pH could not penetrate the C / C preform well. Some slurry was severely delaminated after standing for half an hour after ball milling, causing the powder to form a shell on the surface and creating a large concentration gradient between the inner and outer surfaces. This resulted in uneven powder impregnation, affecting the composite effect of the modified C / C preform and the ultra-high temperature ceramic slurry, and the composite material could not be successfully prepared.

[0091] Comparative Example 2

[0092] The difference between this comparative example and Example 1 is that:

[0093] The low-density green body obtained in step 1 was immersed in H3PO4 or KMnO4 solution for ultrasonic oxidation etching for 1 hour, and then immersed in silane coupling agent KH-550 modifier for ultrasonic hydrolysis reaction at room temperature or below 30°C for 1 hour. It was then dried at 80°C until the solvent completely evaporated, yielding a modified C / C green body. White precipitates were observed on the surface of the green body. This was because the silane coupling agent was over-hydrolyzed or the hydrolysis temperature was too low, causing the silane coupling agent to form overpolymers or precipitate from the solution. This resulted in uneven modification inside the green body, preventing the ultra-high temperature ceramic slurry from effectively penetrating into the green body.

[0094] Comparative Example 3

[0095] The difference between this comparative example and Example 1 is that:

[0096] The slurry prepared in step 4 contains only one type of ultra-high temperature ceramic powder: HfC, ZrC, ZrB2, and HfB2.

[0097] The performance test results of the ultra-high temperature ceramic matrix composite material prepared in this comparative example are as follows:

[0098]

[0099] The results above show that when the ultra-high temperature ceramic phase is a single component, the mechanical properties and ablation resistance of the material are reduced, and the performance is significantly worse than that of the C / C-multi-component ultra-high temperature ceramic matrix composite in Example 1.

[0100] Comparative Example 4

[0101] The difference between this comparative example and Example 1 is that in step 3, polyethyleneimine (PEI) is added to water as a dispersant to obtain an aqueous solution containing the dispersant. The amount of the dispersant added is 5 wt% or 25 wt% of the total mass of the powder. Then, HfC, ZrC, and SiC powders are added to the aqueous solution containing the dispersant and ball-milled in a planetary ball mill for 3 hours to prepare an HfC-ZrC-SiC water-based ceramic slurry. The average particle size of the powder is 500 nm.

[0102] In Comparative Example 4, when the amount of dispersant added was 5 wt% of the total powder mass, the dispersant in the slurry could not fully combine with the ceramic powder, causing the powder to form a crust on the surface and creating a large concentration gradient between the inner and outer surfaces. This resulted in uneven powder impregnation, reduced the composite effect between the modified C / C green body and the ultra-high temperature ceramic slurry, and the composite material could not be successfully prepared. When the amount of dispersant added was 25 wt% of the total powder mass, the viscosity of the prepared slurry increased, the fluidity decreased, and the ceramic slurry formed a crust on the surface of the green body, failing to complete the composite between the green body and the slurry.

[0103] Comparative Example 5

[0104] The difference between this comparative example and Example 1 is that the surface-modified C / C preform from step 2 was immersed in a prepared HfC-ZrC-SiC water-based ceramic slurry and naturally impregnated under normal pressure for 30 minutes, followed by physical-assisted vibration impregnation for 60 minutes. The resulting C / C-HfC-ZrC-SiC composite material had a ceramic incorporation volume ratio of 11.01% after slurry impregnation. Compared with Example 1, the ceramic incorporation volume ratio was significantly reduced, indicating that the internal pores of the preform were not fully filled, the ceramic matrix was unevenly distributed, and the slurry impregnation effect was poor.

Claims

1. A method for preparing an ultra-high temperature micro-ablation material, characterized in that: The C / C preform is modified internally to obtain a modified C / C preform. The modified C / C preform is then placed in a slurry containing ultra-high temperature ceramics for sequential natural impregnation under normal pressure and physical-assisted vibration impregnation, followed by drying to obtain a C / C-ultra-high temperature ceramic matrix composite material. The C / C-ultra-high temperature ceramic matrix composite material is then densified by impregnation and pyrolysis with a precursor to obtain an ultra-high temperature micro-ablation material. The C / C preform is obtained by chemical vapor infiltration deposition of a pyrolytic carbon coating on a carbon fiber preform. The process of internal modification of C / C preform is as follows: first, C / C preform is placed in an oxidant for oxidative etching, then the oxidized C / C preform is immersed in a solution containing a modifier for hydrolysis reaction, and then dried to obtain the product. The modifier is selected from silane coupling agents. The oxidant is selected from one of HNO3 solution, H3PO4 solution, and KMnO4 solution; The silane coupling agent is selected from at least one of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and γ-mercaptopropyltriethoxysilane. The slurry containing ultra-high temperature ceramics includes ultra-high temperature ceramic powder, dispersant, and solvent; The slurry containing ultra-high temperature ceramics also contains silicon carbide powder; The ultra-high temperature ceramic powder in the slurry containing ultra-high temperature ceramics is selected from at least two of zirconium boride, hafnium boride, zirconium carbide, hafnium carbide, and lanthanum boride powders. The dispersant is selected from one or two of polyethyleneimine, polyvinyl butyral, ammonium citrate, polyethylene glycol, polycarbosilane, and hydrogenated styrene-butadiene block copolymer; The amount of the dispersant added is 8-20% of the mass of the ultra-high temperature ceramic powder; The natural impregnation time under normal pressure is 60-90 minutes; During the physical-assisted vibration impregnation, the vibration frequency is 800-1500 times / min, and the physical-assisted vibration impregnation time is 30-60min.

2. The method for preparing an ultra-high temperature micro-ablation material according to claim 1, characterized in that: The density of the C / C preform is 0.45-0.70 g / cm³. 3 ; The thickness of the pyrolytic carbon coating is 200-400 nm; The carbon fiber preform is selected from needle-punched preforms; The density of the carbon fiber preform is 0.40-0.65 g / cm³. 3 ; The carbon fiber preform is first heat-treated at 1600-2000℃ under argon protection, and then subjected to chemical vapor infiltration deposition of a pyrolytic carbon coating.

3. The method for preparing an ultra-high temperature micro-ablation material according to claim 1, characterized in that: The oxidation etching temperature is 50-60℃, and the time is 1-2 hours; The oxidation etching process is performed under ultrasonic assistance; The solution containing the modifier is composed of ethanol, water, and the modifier, with a mass ratio of ethanol:water:modifier = 9-12:1:0.02-0.

15. The hydrolysis reaction is carried out at a temperature of 70-80℃ for 1-2 hours. The hydrolysis reaction is carried out under ultrasonic assistance.

4. The method for preparing an ultra-high temperature micro-ablation material according to claim 1, characterized in that: The particle size of the ultra-high temperature ceramic powder is 0.2-0.7 μm; The volume fraction of the ultra-high temperature ceramic powder in the ultra-high temperature ceramic slurry is 10-40 vol.%. The solvent is one or two of deionized water, anhydrous ethanol, acetone, and xylene.

5. A method for preparing an ultra-high temperature micro-ablation material according to claim 1 or 4, characterized in that: The preparation process of the ultra-high temperature ceramic slurry is as follows: ultra-high temperature ceramic powder, silicon carbide powder, dispersant and solvent are prepared according to the design ratio, and then ball milling is performed. The ball milling speed is 180-220 r / min and the ball milling time is 2-3 h. The mass ratio of grinding balls to ultra-high temperature ceramic powder is 2-4:

1.

6. The method for preparing an ultra-high temperature micro-ablation material according to claim 1, characterized in that: The drying temperature is 80-100℃, and the drying time is 1.5-8 hours.

7. The method for preparing an ultra-high temperature micro-ablation material according to claim 1, characterized in that: The precursor impregnation pyrolysis densification process is as follows: a C / C-ultra-high temperature ceramic matrix green body is impregnated in an impregnating agent, first by vacuum impregnation, then by pressure impregnation, and after impregnation, it is cured and pyrolyzed to obtain the product; the impregnating agent is selected from PCS-xylene solution or liquid polycarbosilane, and in the PCS-xylene solution, the mass ratio of PCS:xylene is 0.5-1:0.5-1; The vacuum impregnation time is ≥4h, and the pressure impregnation pressure is 2.7-3MPa, and the time is 8-10h; The curing temperature is 110-220℃, and the time is 4-5 hours; The pyrolysis temperature is 1000-1300℃, the pyrolysis time is 0.5-1h, and the heating rate is 2-10℃ / min.

8. The method for preparing an ultra-high temperature micro-ablation material according to claim 1, characterized in that: The ultra-high temperature ceramic matrix composite material is obtained by applying a surface coating to the surface of the ultra-high temperature ceramic matrix obtained by impregnation and pyrolysis of the C / C-ultra-high temperature ceramic matrix composite material and drying it.

9. The ultra-high temperature micro-ablation material prepared by the preparation method according to any one of claims 1-8, characterized in that: The ultra-high temperature micro-ablation material comprises carbon fiber, pyrolytic carbon fiber encapsulating carbon fiber, ultra-high temperature ceramic matrix, and SiC matrix. The ultra-high temperature ceramic in the ultra-high temperature ceramic matrix is ​​selected from at least two of zirconium boride, hafnium boride, zirconium carbide, hafnium carbide, and lanthanum boride.

10. The ultra-high temperature micro-ablation material according to claim 9, characterized in that: The density of the ultra-high temperature micro-ablation material is 2.8 g / cm³. 3 -3.5g / cm 3 The flexural strength is 200-330 MPa, and the fracture toughness is 8.19-42.13 MPa·m. 1 / 2 The linear ablation rate in oxyacetylene at 2300 K is 0.06-0.56 μm / s, and the mass ablation rate is 0.26-1.92 mg / s.

Images