Method for the preparation of composite materials by slurry circulation suction filtration combined with impregnation and pyrolysis and materials

Abstract

This invention discloses a method for preparing composite materials using a combination of slurry circulation filtration and impregnation pyrolysis, belonging to the field of ultra-high temperature ceramic matrix composite material preparation technology. Ultra-high temperature ceramics (UHTC) are introduced into the interior of a carbon fiber preform through slurry circulation filtration, followed by the preparation of C / SiC-UHTC composite materials using a precursor impregnation pyrolysis process. Specific steps include: preparing a stable UHTC slurry; establishing a circulation filtration system; slurry circulation filtration / impregnation; preparing a PCS precursor solution; and precursor impregnation pyrolysis. This invention establishes a slurry circulation filtration system and optimizes the slurry impregnation process. Compared with traditional slurry impregnation methods, this method enhances slurry stability, maximizes the uniform distribution and penetration depth of the ceramic phase within the preform, and improves reaction efficiency and cost-effectiveness. Combined with precursor impregnation pyrolysis, the composite material is further densified, reducing the material preparation cycle and obtaining a dense, uniformly distributed, high-strength, ablation-resistant, and oxidation-resistant C / SiC-UHTC composite material.

Description

Technical Field

[0001] This invention discloses a method and materials for preparing C / SiC-UHTC composite materials by combining a slurry circulation filtration process with precursor impregnation and pyrolysis, belonging to the field of ultra-high temperature ceramic matrix composite material preparation technology. Background Technology

[0002] C / SiC composites integrate the high strength of continuous carbon fibers with the high modulus of the SiC matrix, exhibiting excellent comprehensive properties such as low density, small coefficient of thermal expansion, and high specific strength and specific modulus, making them ideal materials for thermal protection systems of high-speed aircraft. They have been successfully applied to key thermal protection components of aircraft including the French Hermes, the American X-37, and the X-43A. In recent years, with the development of high-speed aircraft towards wider airspace, longer operating times, and higher speeds, the thermal barrier problems faced by thermal protection systems have become particularly prominent. The surfaces of thermal protection structures such as the leading edge of the aircraft, the scramjet engine combustion chamber, and the nozzle need to withstand the aerodynamic heating effects of high heat flux and high dynamic pressure. Surface temperatures can rise to over 2000°C in a short time, placing more stringent requirements on the thermal shock, high-temperature mechanics, and oxidation resistance properties of thermal protection materials. However, the long-term service temperature of traditional C / SiC composites is generally limited to below 1650°C, making it difficult to meet the demands of these extreme thermal environments. Ultra-high temperature ceramics (UHTC) are a class of materials specifically designed for use in ultra-high temperature environments above 2000℃. They typically refer to carbides, nitrides, and borides of transition metals, possessing advantages such as high melting point, high thermal conductivity, moderate coefficient of thermal expansion, and excellent resistance to high-temperature oxidation and ablation. Studies have found that the oxidation products formed by the oxidation of multiphase ceramics such as HfB2-SiC, HfC-SiC, ZrB2-SiC, and ZrC-SiC under certain oxidizing atmospheres can effectively protect the matrix and ensure the material's resistance to oxidation and ablation. Therefore, adding UHTC to C / SiC to prepare C / SiC-UHTC composites is an effective method to significantly improve the material's high-temperature resistance and oxidation resistance.

[0003] Currently, methods for preparing fiber-reinforced ultra-high temperature ceramic matrix composites include: slurry impregnation (SI), chemical vapor infiltration (CVI), precursor impregnation pyrolysis (PIP), hot pressing sintering (HP), and reactive melt infiltration (RMI), or combinations of these methods. Sayir et al. at NASA's Glenn Research Center (producing carbon fiber reinforced hafnium carbide composites) used the CVI process to prepare C / H... f C, C / TaC, and C / H fC-TaC composites, however, primarily contain CVI products concentrated on the thin surface layer, with almost no penetration into the closed internal pores, resulting in low material density and poor mechanical properties. Furthermore, this technology faces challenges such as complex processes, long lead times, and high costs. Sciti et al. (Continuous C fibrecomposites with a porous ZrB Matrix2) combined vacuum impregnation with the HP process to prepare C... f Compared to CVI technology, ZrB2 has the advantage of shortening the production cycle; however, hot pressing and sintering easily damages the fibers, and its flexural strength does not meet the requirements of thermal protection system materials. Zhang et al. (Preparation, ablation behavior and thermal retardant ability of C / C-HfB2-SiC composites) prepared C / C-UHTC composites using RMI, which had high density and high ceramic content; however, the damage to carbon fibers during melt infiltration still reduced the mechanical properties of C / C-UHTC composites. The SI method has advantages such as simple preparation process, short cycle, low cost, and adjustable component content. The preparation process involves first dispersing ceramic powder in a solvent to form a suspension slurry, then placing the fiber preform in it, allowing the slurry to be introduced into the fiber interior through the pores. After curing and solvent evaporation, a fiber preform containing UHTC is obtained. However, related studies have shown that achieving uniform infiltration of a large amount of slurry into the fiber preform without damaging the fibers is challenging. Paul (UHTC–carbon fibre composites: Preparation, oxyacetylene torch testing and characterization) used the SI process to prepare C f -UHTC, through manual extrusion impregnation, ensures a high slurry intake, but the penetration depth of UHTC powder still does not exceed 1 / 3. Therefore, the SI method also faces problems such as the high density of ceramic particles in the slurry making it difficult to form a uniform and stable suspension, resulting in stratification and agglomeration, leading to uneven distribution of the introduced ceramic phase in the composite material; and the ceramic powder easily clogging the fiber preform, limiting its impregnation depth, which seriously affects the overall performance of the composite material.

[0004] In summary, to achieve the preparation of dense, high-performance C / SiC-UHTC composite materials, this invention proposes a novel slurry circulation filtration process. Given that the SI process itself is difficult to directly densify the material, a series of C / SiC-UHTC materials were prepared in conjunction with PIP (Polymer Impregnation). This process establishes a circulation filtration system to uniformly introduce the slurry into the carbon fiber preform, retaining the advantages of compositional design, improving the UHTC content and uniformity, and solving the problems of difficult slurry impregnation and limited impregnation depth in traditional slurry methods. Simultaneously, pressure impregnation reduces fiber damage. By adding dispersants and combining stirring, ball milling, and pH adjustment, a stable UHTC slurry is obtained, preventing ceramic particles from accumulating on the surface of the fiber preform. Finally, the combined PIP process achieves composite material densification, reducing the material preparation cycle and obtaining a dense, uniformly distributed, high-strength, ablation-resistant, and oxidation-resistant C / SiC-UHTC composite material. Summary of the Invention

[0005] The purpose of this invention is to provide a method and material for preparing composite materials by combining slurry circulation filtration and impregnation pyrolysis. Specifically, by mainly using slurry circulation filtration / impregnation, the invention solves the problems of difficult impregnation, limited impregnation depth, and clogging and uneven distribution of ceramic powder in traditional slurry methods. Combined with precursor impregnation pyrolysis, a C / SiC-UHTC composite material with uniform and dense ceramic phase distribution is obtained, which has high strength and resistance to oxidation and ablation.

[0006] To achieve the above objectives, this invention proposes a method and material for preparing composite materials by combining slurry circulation filtration with impregnation pyrolysis. The technical solution and specific steps are as follows:

[0007] (1) Preparation of stable UHTC slurry: First, the ceramic particles, dispersant and solvent are stirred and mixed evenly, and then a uniformly distributed stable UHTC slurry is obtained by wet ball milling and / or pH adjustment.

[0008] (2) Circulating filtration system: Construct a closed circulating filtration system, which includes a ceramic slurry storage tank, a filtration device and a high-efficiency circulating pump assembly;

[0009] Ceramic slurry storage tank: used for sealing after placing UHTC slurry;

[0010] The filtration device consists of two parts: an upper cylindrical container open at one end, connected to the outlet of a circulating pump via a pipe, and a plate with a central through-hole at the lower opening of the container. The lower opening of the container is sealed to the upper surface of the plate around the through-hole, with the through-hole located within the area enclosed by the lower opening. The lower cylindrical container open at the top, connected to a slurry storage tank via a pipe, also has a plate with a central through-hole at the upper opening of the container. The upper opening of the container is sealed to the lower surface of the plate around the through-hole, with the through-hole located within the area enclosed by the upper opening (preferably, a screen or sieve plate for supporting the fiber preform is provided inside or on the upper surface of the through-hole of the plate). The through-holes on the two plates are correspondingly arranged (preferably, the through-holes are coaxial and of similar size and shape). (Same); A double-layer clamping mold is formed by two flat plates with through holes, with a porous carbon fiber preform fixed in the middle by the double-layer clamping mold (preferably, it is coaxial with the through hole and the side length is 8-12mm longer than the side length of the through hole); wherein, the lower layer of the double-layer clamping mold is used for bearing (preferably, the central part is provided with a mesh screen or screen plate), and the upper layer is used for fixing. The fiber preform to be processed is placed at the corresponding through hole between the two flat plates, and an annular sealing ring is provided around the through hole between the two flat plates to seal the four sides of the fiber preform. The two flat plates are fixedly positioned and sealed as a whole by bolts provided around the sealing ring (or sealing gasket); the four sides of the through hole in the middle of the two flat plates are respectively attached to the surface of the porous carbon fiber preform, and the porous carbon fiber preform is located in the middle through hole of the sealing ring (or sealing gasket);

[0011] High-efficiency circulating pump: The outlet of the circulating pump is connected to the upper part of the filtration device on one side, and the inlet on the other side is connected to the ceramic slurry storage tank. After the circulating pump is started, a circulating filtration and impregnation system with pressure difference (the pressure difference between the upper and lower parts of the filtration device is 80-90 kPa, i.e., the pressure difference between the upper and lower containers) can be formed. The slurry is continuously driven through the fiber preform by the pressure difference, making it easier for UHTC particles to be captured by the fiber preform, thus improving the filtration speed and efficiency. The slurry filtered by the preform returns to the storage tank for the next round of filtration and impregnation.

[0012] (3) Slurry circulation filtration / impregnation: After completing the preparation work in step (2), start the circulation pump to perform circulation filtration and impregnation, ensuring that the slurry liquid level in the upper container completely covers the upper surface of the fiber preform, and complete one circulation filtration cycle.

[0013] After completing one cycle of filtration, the fiber preform is flipped over so that its bottom surface (lower surface) becomes the contact surface (upper surface), and the same cycle of filtration is performed again to ensure that the material is fully penetrated and the penetration depth is maximized, and finally a fiber preform rich in UHTC is prepared.

[0014] (4) Prepare PCS precursor solution: Mix PCS (polycarbosilane) powder with xylene in the required ratio to obtain PCS precursor solution;

[0015] (5) PCS precursor impregnation pyrolysis:

[0016] The UHTC-rich fiber preform obtained in step (3) was placed in a vacuum chamber. Under vacuum conditions, the PCS precursor solution prepared in step (4) was introduced into the mold containing the UHTC-containing fiber preform through a conduit, so that the UHTC-containing fiber preform was immersed in the PCS precursor solution. The sample was impregnated under vacuum for a period of time. Then the sample was cured in an oven. After curing, it was placed in a high-temperature pyrolysis furnace for pyrolysis to prepare C / SiC-UHTC composite material.

[0017] Repeat the above impregnation, curing and pyrolysis steps more than twice until the weight gain of the C / SiC-UHTC composite material is in the range of 0.1-1.5% (preferably 0.1-1%), to obtain a dense C / SiC-UHTC composite material.

[0018] In step (1) above, the UHTC slurry includes ceramic particles, a dispersant, and a solvent; the ceramic particles (UHTC) are one or more of ZrC, HfB2, HfC, ZrB2, and B4C, with a particle size range of 0.8-1.2 μm; the dispersant is one or more of polyethyleneimine, ammonium polyacrylate, and polyoxymethylene; the solvent is water and / or ethanol; the stirring time is 0.5-2 h (preferably 1-2 h); the ball milling speed is 100-300 r / min (preferably 200-30 r / min). The ball milling speed is 0 r / min, the ball milling time is 1-5 h (preferably 3-5 h), the ball material is alumina and / or zirconium oxide, the ball-to-material mass ratio is 1:(1-2) (preferably 1:(1.3-1.5)), and the ball diameter is 2-4 mm; the pH value is adjusted by 35-38% HCl, and the pH value range is 4-7 (preferably 5-7); the dispersant content in the slurry is 0.1-0.7 wt.% (preferably 0.1-0.5 wt.%), and the solid content of the slurry is 3-20% (preferably 5-15%).

[0019] The stability of the prepared slurry was determined by the zeta potential (a key indicator of particle dispersion stability in solution; a high absolute value (generally greater than or equal to 25 mV) indicates good slurry stability) and the standing test (no precipitation after standing for 100-120 min indicates good slurry stability).

[0020] In step (2) above, the closed-loop circulating filtration system mainly consists of a ceramic slurry storage tank, a filtration device, and a high-efficiency circulating pump; the slurry volume in the storage tank is 1-5L (preferably 3-5L); the carbon fiber is flat, with a thickness of 10-35mm (preferably, dimensions of 110*110*10-210*210*35mm (length*width*thickness)), and a density of 0.5-0.7g / cm³. 3 The carbon fiber preform clamping mold is located in the middle of the filtration device; the pressure difference between the upper and lower containers of the recirculating filtration impregnation system is 80-90 kPa; the high-efficiency circulating pump (such as the high-efficiency circulating pump of Jiangsu Jiuhong Pump Industry Co., Ltd.) is used to provide power, promote slurry circulation, and ensure the continuity and stability of the impregnation process.

[0021] In step (3) above, UHTC particles are introduced into the carbon fiber preform by circulating filtration. During this process, the carbon fiber preform acts as a "filter cloth". During impregnation, ceramic particles in the slurry are captured, and most of the solvent is filtered out from the preform. The filtered slurry is collected and then circulated through the fiber preform to solve the problems of difficulty in impregnating UHTC into the carbon fiber preform and limited impregnation depth. At the same time, the continuous flow of the slurry in the pipeline improves the stability of the slurry.

[0022] The time required for one cycle is determined based on the total slurry flow rate and slurry velocity required for the cycle, while the total slurry flow rate is determined based on the volume of fibers through which the slurry flows. During the cyclic filtration process, the slurry velocity is 0.4-1 L / s (preferably 0.6-0.8 L / s), and the slurry level is higher than the surface of the preform. The total slurry flow rate required for one cycle is 500-1000 times (preferably 600-800 times) the volume of the fiber preform through which the slurry flows. After the fibers are turned over, the same cyclic filtration process as described above is performed again.

[0023] After infiltration, the composite material is dried in an oven at 100-150℃ for 1-5 hours (preferably 2-4 hours). The area around the perimeter of the material (4-6 mm wide) that was fixed and covered by the upper and lower flat plate clamps is removed to obtain a fiber preform containing UHTC with a density ranging from 0.8 to 1.1 g / cm³. 3 .

[0024] In step (4) above, the PCS (polycarbosilane) precursor solution uses PCS (polycarbosilane) as an organic precursor, and its mass ratio with the solvent xylene is 1:(1-1.5) (preferably 1:(1-1.3)), and its volume is 1-5 times (preferably 2-4 times) the volume of the UHTC carbon fiber preform.

[0025] In step (5) above, the impregnation vacuum degree is 0.03-0.08MPa (preferably 0.04-0.07MPa), the holding time is 5-12h (preferably 6-10h), the curing temperature is 150-200℃ (preferably 160-190℃), the curing time is 1-12 (preferably 3-10), the pyrolysis temperature is 900℃-1100℃ (preferably 950-1050℃), and the pyrolysis time is 1-6 (preferably 1-5h).

[0026] This invention establishes a slurry circulation and filtration system, optimizing the slurry impregnation process. Compared with traditional slurry impregnation methods, this method enhances slurry stability, maximizes the uniform distribution and penetration depth of the ceramic phase within the preform, and improves reaction efficiency and cost-effectiveness. Combined with precursor impregnation and pyrolysis for further densification of the composite material, it reduces the material preparation cycle, resulting in a dense, uniformly distributed, high-strength, ablation-resistant, and oxidation-resistant C / SiC-UHTC composite material.

[0027] The effects and advantages of this invention are as follows:

[0028] 1. This invention establishes a slurry circulation and filtration system, optimizing the slurry impregnation process. During impregnation, the fibers act as a "filter cloth," and external pressure forces the slurry to circulate multiple times through the fiber preform, thereby introducing UHTC. Compared with traditional slurry impregnation, this method enhances slurry stability, maximizes the uniform distribution and penetration depth of the ceramic phase within the preform, and improves reaction efficiency and cost-effectiveness.

[0029] 2. By adding dispersants and combining stirring, ball milling, and pH adjustment, the slurry is modified to obtain a uniform and stable UHTC slurry. This avoids the accumulation of ceramic particles on the surface of the fiber preform due to stratification and sedimentation, which could lead to closed pores and affect the impregnation depth.

[0030] 3. This invention combines two processes: slurry-precursor impregnation and pyrolysis, which reduces the material preparation cycle. The resulting C / SiC-UHTC composite material is dense and has a uniform distribution of ceramic phase, exhibiting high strength and resistance to oxidation and ablation. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the circulating filtration / impregnation system.

[0032] Figure 2This is a schematic diagram of the fiber double-layer clamping / fixing mold structure in the circulating filtration / impregnation system. #1 is the lower plate of the double-layer mold, mainly used for fiber support. The side length of the mesh through-hole in the middle is 10mm shorter than the side length of the fiber. The through-hole design is intended to allow the slurry filtered by the fiber to be smoothly discharged into the lower half of the filtration device. #1(a) is a bolt hole, responsible for stable positioning. #1(b) is an annular sealing ring, responsible for sealing the fiber and stable positioning. #2 is the upper plate of the double-layer mold, mainly used for fixing the fiber. The through-hole in the middle allows the impregnated slurry to directly contact the fiber surface. Its size and specifications are consistent with the mesh through-hole of the lower plate and are coaxial. #3 is the carbon fiber preform used for circulating filtration / impregnation in the system. Its size is 10mm larger than the side length of the through-hole of the upper and lower fixing plates and is coaxial with the through-hole.

[0033] Figure 3 The curves of zeta potential and pH value of the ZrC ceramic slurry prepared in Example 1 are shown.

[0034] Figure 4 The static stability test diagram shows the ZrC ceramic slurry prepared in Example 1.

[0035] Figure 5 The image shows the microstructure of the ZrC fiber preform prepared in Example 1.

[0036] Figure 6 The image shows the cross-sectional microstructure of the C / SiC-ZrC composite material prepared in Example 1.

[0037] Figure 7 The mechanical property curves of the C / SiC-ZrC composite material prepared in Example 1 are shown. Detailed Implementation

[0038] To further understand the present invention, the following description is provided in conjunction with embodiments. However, these embodiments are merely illustrative of the features and advantages of the present invention and are not intended to limit the scope of the claims. In the following embodiments, C / SiC-UHTC composite materials are prepared according to different raw material ratios.

[0039] The method of the present invention specifically includes the following steps:

[0040] (1) Preparation of stable UHTC slurry: First, mix ceramic particles (one of ZrC, HfB2, HfC, ZrB2 and B4C, with a particle size range of 0.8-1.2μm), dispersant (one of polyethyleneimine, ammonium polyacrylate, and polyoxymethylene), and solvent (one of water or ethanol) evenly (stirring time 0.5-2h (preferably 1-2h), then wet ball mill (ball milling speed 100-300r / min (preferably 200-300r / min), ball milling time 1- The mixture is processed for 5 hours (preferably 3-5 hours), with the balls made of alumina or zirconium oxide, a ball-to-material mass ratio of 1:(1-2) (preferably 1:(1.3-1.5)), and a ball diameter of 2-4 mm. A stable UHTC slurry with uniform distribution is obtained by adjusting the pH value (by adjusting the pH value with a mass concentration of 35-38% HCl, with a pH range of 4-7 (preferably 5-7)). The dispersant content in the slurry is 0.1-0.7 wt.% (preferably 0.1-0.5 wt.%), and the solid content of the slurry is 3-20% (preferably 5-15%).

[0041] The stability of the prepared solution was determined by zeta potential and standing test. A zeta potential absolute value greater than or equal to 25 mV and no precipitation after standing for 100-120 min indicate that the slurry has good stability.

[0042] (2) Circulating filtration system: Construct a closed circulating filtration system, which includes a ceramic slurry storage tank, a filtration device and a high-efficiency circulating pump assembly.

[0043] Ceramic slurry storage tank: used for storing UHTC slurry and then sealing it, with a volume of 1-5L (preferably 3-5L);

[0044] The filtration device consists of two parts: an upper and a lower cylindrical container open at one end, with its upper part connected to the outlet of a circulating pump via a pipe. A flat plate with a square through-hole in the center is located at the lower opening of the container. The lower opening of the container is sealed to the upper surface of the flat plate around the through-hole, and the through-hole is located within the area surrounded by the lower opening. The lower cylindrical container open at one end, with its lower part connected to a slurry storage tank via a pipe. A flat plate with a square through-hole in the center is located at the upper opening of the container. The upper opening of the container is sealed to the upper surface of the flat plate around the through-hole, and the through-hole is located within the area surrounded by the lower opening. The surfaces are sealed together, and the through holes are located within the area surrounded by the upper opening. A screen for supporting the fiber preform is provided on the upper surface of the through holes of the two plates. The through holes on the two plates are correspondingly arranged, coaxial, and identical in size and shape. A double-layer clamping mold is formed by two plates with through holes, with a porous carbon fiber preform fixed in the middle by the double-layer clamping mold for isolation (the carbon fiber preform has dimensions of 210*210*10-210*210*35mm (length*width*thickness) and a density of 0.5-0.8g / cm³). 3(The side length is 10mm longer than the side length of the square through hole of the double-layer clamping plate); wherein, the lower layer of the double-layer clamping mold is used for bearing, and a mesh screen is set in the center part, and the upper layer is used for fixing. The fiber preform to be processed is placed in the corresponding through hole between the two plates, and an annular sealing ring is set around the through hole between the two plates to seal the four sides of the fiber preform. The two plates are fixedly positioned by bolts set around the outside of the sealing ring and are sealed as a whole; the four sides of the through hole in the middle of the two plates are respectively attached to the surface of the porous carbon fiber preform, and the porous carbon fiber preform is located in the through hole in the middle of the sealing ring;

[0045] High-efficiency circulating pump: The high-efficiency circulating pump (such as the high-efficiency circulating pump of Jiangsu Jiuhong Pump Industry Co., Ltd.) is used to provide power, promote slurry circulation, and ensure the continuity and stability of the impregnation process. The outlet of the circulating pump is connected to the upper part of the filtration device on one side, and the inlet on the other side is connected to the ceramic slurry storage tank. After the circulating pump is started, a circulating filtration and impregnation system with pressure difference (the pressure difference between the upper and lower parts of the filtration device is 80-90 kPa, that is, the pressure difference between the upper and lower containers) can be formed. The slurry is continuously driven through the fiber preform by the pressure difference, making it easier for UHTC particles to be captured by the fiber preform, improving the filtration speed and efficiency. The slurry filtered by the preform returns to the storage tank for the next round of filtration and impregnation.

[0046] (3) Slurry circulation filtration / impregnation: After completing the preparation work in step (2), start the circulation pump for circulation filtration and impregnation. During the process, the slurry flow rate is 0.4-1L / s (preferably 0.6-0.8L / s), and the slurry level is higher than the upper surface of the preform. When the total flow rate of the filtered slurry is 500-1000 times (preferably 600-800 times) of the fiber volume, flip the fiber preform upside down so that its bottom surface (lower surface) becomes the contact surface (upper surface). Repeat the same cycle filtration process as above to ensure that the material is fully penetrated and the penetration depth is maximized. After penetration, place the composite material in an oven at 100-150℃ and dry for 1-5 hours (preferably 2-4 hours). Cut off the area around the material (width equal to 5mm) that is fixed and covered by the upper and lower plate clamps to obtain a fiber preform containing UHTC with a density range of 0.8-1.1g / cm³. 3 .

[0047] In this process, the carbon fiber preform acts as a "filter cloth". During impregnation, ceramic particles in the slurry are captured by the fiber preform, and most of the solvent is filtered out from the preform. The filtered slurry is collected and then circulated through the fiber preform to solve the problems of UHTC being difficult to impregnate into the carbon fiber preform and the limited impregnation depth. At the same time, the continuous flow of the slurry in the pipeline improves the stability of the slurry.

[0048] (4) Prepare PCS precursor solution: Mix PCS (polycarbosilane) powder with xylene at a mass ratio of 1:(1-1.5) (preferably 1:(1-1.3)) to obtain PCS precursor solution, the volume of which is 1-5 times (preferably 2-4 times) the volume of UHTC carbon fiber preform.

[0049] (5) PCS precursor impregnation pyrolysis:

[0050] The UHTC-rich fiber preform obtained in step (3) is placed in a vacuum chamber. Under vacuum conditions (vacuum degree of 0.03-0.08MPa (preferably 0.04-0.07MPa)), the PCS precursor solution prepared in step (4) is introduced into the mold containing the UHTC-containing fiber preform through a conduit, so that the UHTC-containing fiber preform is immersed in the PCS precursor solution. The sample is impregnated under vacuum for a period of time (pressure holding time of 5-12h (preferably 6-10h)). The sample is then cured in an oven (curing temperature of 150-200℃ (preferably 160-190℃), curing time of 1-12 (preferably 3-10)). After curing, the sample is placed in a high-temperature pyrolysis furnace for pyrolysis (pyrolysis temperature of 900℃-1100℃ (preferably 950-1050℃), pyrolysis time of 1-6 (preferably 1-5h)) to prepare C / SiC-UHTC composite material.

[0051] Repeat the above impregnation, curing and pyrolysis steps more than twice until the weight gain of the C / SiC-UHTC composite material is in the range of 0.1-1.5% (preferably 0.1-1%), to obtain a dense C / SiC-UHTC composite material.

[0052] Test methods and reference standards:

[0053] • The Zeta potential curve of the ceramic slurry was measured using a Zetasizer Nano S90 nanoparticle size potentiometer.

[0054] Microscopic morphology and elemental analysis were performed using a Verios G4 UC scanning electron microscope equipped with energy dispersive spectroscopy (EDS).

[0055] • The bending strength was tested using an electronic universal testing machine of model MTS-CMT4503. The test method was the three-point bending method, and the test standard was QJ 2099-91.

[0056] • The samples were assessed for ablation using an oxyacetylene ablation test. The reference standard was GJB323A-96.

[0057] Example 1:

[0058] C / SiC-ZrC composite materials were prepared by doping ZrC powder with C / SiC.

[0059] ① ZrC particles with an average particle size of about 1 μm, polyethyleneimine dispersant with a molecular weight of 10,000, and deionized water solvent were selected as raw materials and stirred for 1 hour before being placed in a ball mill jar. Zirconia ball milling beads with a ball diameter of 3 mm were used, with a ball-to-material ratio of 1:1.5, and ball milling was carried out at a speed of 200 r / min for 3 hours. HCl with a mass concentration of 36% was added to adjust the pH value to 6 to obtain a stable ZrC ceramic slurry. The polyethyleneimine content was 0.1 wt.%, and the solid content of the slurry was 15%.

[0060] ② Selected product manufactured by Toray Industries, Japan, with dimensions of 210×210×10mm (length×width×thickness) and a density of 0.5g / cm³. 3 Carbon fiber needle-punched preforms.

[0061] ③ Establish the above-mentioned closed-loop circulating filtration and impregnation system consisting of a ceramic slurry storage tank, a filtration mold, and a high-efficiency circulating pump assembly.

[0062] ① The prepared ZrC ceramic slurry was injected into a slurry storage tank with a volume of 3L. ② The carbon fiber preform was clamped and fixed using a double-layer clamp and placed in a filtration device. The slurry storage tank and filtration device were sealed, and after checking for good airtightness, the circulation pump was turned on. The ceramic slurry flowed into the filtration device at a rate of 0.8L / s, with the slurry level higher than the surface of the fiber preform. Under the action of the circulation pump, the internal pressure difference of the system was 80Kpa. The pressure difference drove the slurry to circulate through the fiber preform. When the total flow rate of the filtered slurry was 600 times the fiber volume, the fiber was flipped over, with its lower surface turned upside down and placed on top. The same volume of slurry was then circulated and filtered again. After impregnation, the fiber preform was placed in an oven at 100℃ for 2 hours. The area covered by the clamps on all four sides was cut off, with a width of 5mm, resulting in a fiber preform containing ZrC particles with dimensions of 200×200×10mm and a density of 0.8g / cm³. 3 .

[0063] ④ Mix PCS (polycarbosilane) powder with a number average molecular weight of 1000 and xylene in a 1:1 mass ratio to prepare a PCS precursor solution, the volume of which is twice the volume of the ZrC fiber preform.

[0064] ⑤ The fiber preform containing ZrC particles obtained in ③ was placed in a vacuum chamber. Under a vacuum of 0.04 MPa, the PCS precursor solution prepared in ④ was introduced into the fiber preform mold, with its height being 1.5 times the height of the horizontally placed preform (thickness direction perpendicular to the horizontal plane), and pressure was maintained for 6 hours. After impregnation, the sample was placed in an oven and cured at 160℃ for 6 hours. After curing, the sample was placed in a high-temperature pyrolysis furnace for pyrolysis at 950℃ for 3 hours. After repeating the above impregnation, curing, and pyrolysis steps 10 times, the C / SiC-ZrC composite material gained 1% weight in the 10th iteration, resulting in a dense C / SiC-ZrC composite material.

[0065] Figure 3 The Zeta potential versus pH curves for the ZrC ceramic slurry prepared in Example 1 are shown. Zeta potential is an important indicator of particle dispersion stability in solution; generally, an absolute value greater than 25 mV indicates good slurry stability. In this example, the absolute value of the Zeta potential was the highest at pH 6, reaching 42 mV, indicating good stability of the prepared slurry. Figure 4 For the static stability test of the ZrC ceramic slurry prepared in Example 1, the ZrC slurry showed no sedimentation after being placed in room temperature air for 120 minutes, confirming its good stability and meeting the requirements of subsequent vacuum filtration and cyclic impregnation. Figure 5 The microstructure of the ZrC-containing fiber preform obtained after slurry circulation filtration / impregnation in Example 1. Figure 5 It can be seen that the ZrC particles are evenly distributed and mainly retained in the pores between the fiber bundles, without obvious aggregation. At the same time, the numerous pores in the fiber preform provide sufficient contact area for subsequent precursor impregnation, ensuring the smooth progress of the densification process. Figure 6 This is a cross-sectional microstructure image of the C / SiC-ZrC composite material prepared in Example 1. (Low magnification) Figure 6 (a) demonstrates the compactness of the composite matrix; high magnification Figure 6 (b) shows intact fiber morphology, indicating that it has not been significantly damaged; Figure 6 (ce) represents the EDS surface scan results, further confirming the uniformity of ZrC distribution within the composite material. Figure 7The mechanical test curves for the C / SiC-ZrC composite material prepared in Example 1 show a flexural strength of approximately 130 MPa. During loading, the stress-strain curve exhibits a characteristic step-down morphology, reflecting the pseudoplastic fracture behavior of the material and demonstrating good toughness. The high flexural strength is attributed to the excellent interfacial bonding and high fiber strength of the C / SiC-ZrC composite material prepared by the slurry circulation filtration process combined with precursor impregnation and pyrolysis (multiple impregnations of carbon fibers without etching). Simultaneously, the slurry circulation filtration / impregnation introduces uniformly distributed ZrC particles, making it easier for internal cracks to deflect under load, thereby releasing stress and improving flexural strength.

[0066] Furthermore, the C / SiC-ZrC composite material prepared in Example 1 exhibited good ablation resistance. Under the test conditions of 2100℃ and 180s, the linear ablation rate of the C / SiC-ZrC composite material was -0.95μm / s, and the mass ablation rate was 1.67mg / s.

[0067] Example 2

[0068] C / SiC-HfB2 composite materials were prepared by doping C / SiC with HfB2 powder.

[0069] ① Using HfB2 particles with an average particle size of 1.2 μm, ammonium polyacrylate dispersant with a molecular weight of 10,000, and deionized water solvent as raw materials, after stirring for 1.5 h, the mixture was placed in a ball mill jar. Zirconia ball milling beads with a ball diameter of 3 mm were used, with a ball-to-material ratio of 1:1.3. The mixture was ball milled at a speed of 300 r / min for 3 h. HCl with a mass concentration of 37% was added to adjust the pH value to 5. The ammonium polyacrylate content was 0.2 wt.%, and the slurry solid content was 12%.

[0070] ② Selected product manufactured by Toray Industries, Japan, with dimensions of 210×210×20mm (length×width×thickness) and a density of 0.6g / cm³. 3 Carbon fiber needle-punched preforms.

[0071] ③Establish a closed-loop circulating filtration and impregnation system consisting of a ceramic slurry storage tank, a filtration mold, and a high-efficiency circulating pump assembly.

[0072] ① The prepared HfB2 slurry was injected into a slurry storage tank with a volume of 4L. ② The carbon fiber preform was clamped and fixed using a double-layer clamp and placed in a filtration device. The slurry storage tank and filtration device were sealed, and after checking for good airtightness, the circulation pump was turned on. The ceramic slurry flowed into the filtration device at a rate of 0.6L / s, completely covering the surface of the fiber preform. Under the action of the circulation pump, the internal pressure difference of the system was 90Kpa. The pressure difference drove the slurry to circulate through the fiber preform. When the slurry flow rate was 700 times the fiber volume, the fiber was flipped over, with its lower surface on top, and the same volume of slurry was circulated and filtered again. After impregnation, the fiber preform was placed in an oven at 130℃ for 2.5h. The area covered by the clamps around the perimeter was cut off, approximately 5mm, resulting in a fiber preform containing HfB2 particles with dimensions of 200×200×20mm and a density of 0.89g / cm³. 3 .

[0073] ④ Mix PCS powder with a number average molecular weight of 1000 and xylene at a mass ratio of 1:1.3 to prepare a PCS precursor solution, the volume of which is 3 times the volume of the HfB2 fiber preform.

[0074] ⑤ The fiber preform containing HfB2 particles prepared in ③ was placed in a vacuum chamber. Under a vacuum of 0.05 MPa, the precursor solution prepared in ④ was introduced into the fiber preform mold to a height twice the height of the preform, and the pressure was maintained for 10 hours. After impregnation, the sample was placed in an oven and cured at 180℃ for 3 hours. After curing, the sample was placed in a high-temperature pyrolysis furnace for pyrolysis at 1000℃ for 1 hour. After repeating the above impregnation, curing, and pyrolysis steps 13 times, the weight gain of the C / SiC-HfB2 composite material was 0.8%, and a dense C / SiC-HfB2 composite material was obtained.

[0075] In this embodiment, the absolute value of the Zeta potential was a maximum of 40 mV at pH 5, indicating good stability of the prepared slurry. No sedimentation was observed after the HfB2 ceramic slurry was placed in room temperature air for 100 min, confirming its good stability and meeting the requirements for subsequent vacuum filtration and cyclic impregnation. The resulting C / SiC-HfB2 composite material was uniform and dense, with a flexural strength of approximately 125 MPa, while also exhibiting good toughness. Furthermore, this composite material possesses excellent ablation resistance; under the testing conditions of 2100℃ and 180 s, the linear ablation rate was -0.90 μm / s, and the mass ablation rate was 1.61 mg / s.

[0076] Example 3

[0077] C / SiC-ZrB2 composite materials were prepared by doping ZrB2 powder with C / SiC.

[0078] ① Using ZrB2 particles with an average particle size of approximately 0.8 μm, polyethyleneimine dispersant with a molecular weight of 10,000, and anhydrous ethanol solvent as raw materials, the mixture was stirred for 2 hours and then placed in a ball mill jar. Zirconia ball milling beads with a ball diameter of 3 mm were used, with a ball-to-material ratio of 1:1.4. The mixture was ball-milled at a speed of 250 r / min for 5 hours. HCl with a mass concentration of 38% was added to adjust the pH value to 6. The polyethyleneimine content was 0.3 wt.%, and the slurry solid content was 11%.

[0079] ② Selected from Toray Industries, Japan, measuring 210×210×30mm (length×width×thickness) with a density of 0.65g / cm³. 3 Carbon fiber needle-punched preforms.

[0080] ③Establish a closed-loop circulating filtration and impregnation system consisting of a ceramic slurry storage tank, a filtration mold, and a high-efficiency circulating pump assembly.

[0081] ① The prepared ZrB2 slurry was injected into a slurry storage tank with a volume of 5L. ② The carbon fiber preform was clamped and fixed using a double-layer clamp and placed in a filtration device. The slurry storage tank and filtration device were sealed, and after checking for good airtightness, the circulation pump was turned on. The ceramic slurry flowed into the filtration device at a rate of 0.7L / s, completely covering the surface of the fiber preform. Under the action of the circulation pump, the internal pressure difference of the system was 85Kpa. The pressure difference drove the slurry to circulate through the fiber preform. When the slurry flow rate was 750 times the fiber volume, the fiber was flipped over so that its lower surface was on top, and the same volume of slurry was circulated and filtered again. After impregnation, the fiber preform was placed in an oven at 150℃ for 4 hours. The area covered by the clamps around the perimeter was cut off, approximately 5mm, resulting in a fiber preform containing ZrB2 particles with dimensions of 200×200×30mm and a density of 1.0g / cm³. 3 .

[0082] ④ Mix PCS powder with a number average molecular weight of 1000 and xylene at a mass ratio of 1:1.1 to prepare a PCS precursor solution, the volume of which is 4 times the volume of the ZrB2 fiber preform.

[0083] ⑤ The fiber preform containing ZrB2 particles prepared in ③ was placed in a vacuum chamber. Under a vacuum of 0.07 MPa, the precursor solution prepared in ④ was introduced into the fiber preform mold to a height twice that of the preform, and the pressure was maintained for 7 hours. After impregnation, the sample was placed in an oven and cured at 170℃ for 10 hours. Then, it was placed in a high-temperature pyrolysis furnace and pyrolyzed at 1050℃ for 5 hours. After repeating the above impregnation, curing, and pyrolysis steps 8 times, the weight gain of the C / SiC-ZrB2 composite material was 0.9%, resulting in a dense C / SiC-ZrB2 composite material.

[0084] In this embodiment, the absolute value of the Zeta potential was the highest at pH 6, reaching 41 mV, indicating good stability of the prepared slurry. No sedimentation was observed after the ZrB2 ceramic slurry was placed in room temperature air for 110 min, confirming its good stability and meeting the requirements for subsequent vacuum filtration and cyclic impregnation. The resulting C / SiC-ZrB2 composite material was uniform and dense, with a flexural strength of approximately 121 MPa, while also exhibiting good toughness. Furthermore, this composite material possesses excellent ablation resistance; under the testing conditions of 2100℃ and 180 s, the linear ablation rate was -0.85 μm / s, and the mass ablation rate was 1.68 mg / s.

[0085] Example 4

[0086] C / SiC-B4C composite materials were prepared by doping C / SiC with B4C powder.

[0087] ① B4C particles with an average particle size of about 1 μm, polyoxymethylene dispersant and deionized water solvent were selected as raw materials. After stirring for 1.8 h, they were put into a ball mill jar. Alumina ball milling beads with a ball diameter of 3 mm were used, and the ball-to-material ratio was 1:1.5. The mixture was ball milled at a speed of 280 r / min for 4 h. HCl with a mass concentration of 36% was added to adjust the pH value to 7. The polyoxymethylene content was 0.5 wt.% and the slurry solid content was 9%.

[0088] ② The sample used is manufactured by Toray Industries, Japan, with dimensions of 210×210×35mm (length×width×thickness) and a density of 0.7g / cm³. 3 Carbon fiber needle-punched preforms.

[0089] ③Establish a closed-loop circulating filtration and impregnation system consisting of a ceramic slurry storage tank, a filtration mold, and a high-efficiency circulating pump assembly.

[0090] ① The prepared B4C ceramic slurry was injected into a slurry storage tank with a volume of 4.5L. ② The carbon fiber preform was clamped and fixed using a double-layer clamp and placed in a filtration device. The slurry storage tank and filtration device were sealed, and after checking for good airtightness, the circulation pump was turned on. The ceramic slurry flowed into the filtration device at a rate of 0.75L / s, completely covering the surface of the fiber preform. Under the action of the circulation pump, the internal pressure difference of the system was 80Kpa. The pressure difference drove the slurry to circulate through the fiber preform. When the total flow rate of the filtered slurry was 800 times the fiber volume, the fiber was flipped over so that its lower surface was on top, and the same volume of slurry was circulated and filtered again. After impregnation, the fiber preform was placed in an oven at 150℃ for 3 hours. The area covered by the clamps around the perimeter was cut off, approximately 5mm, resulting in a fiber preform containing B4C particles with dimensions of 200×200×35mm and a density of 1.1g / cm³. 3 .

[0091] ④ Mix PCS powder with a number average molecular weight of 1000 and xylene in a ratio of 1:1.2 to prepare a PCS precursor solution, the volume of which is 3 times the volume of the B4C fiber preform.

[0092] ⑤ The fiber preform containing B4C particles obtained in ③ was placed in a vacuum chamber. Under a vacuum of 0.06 MPa, the PCS precursor solution prepared in ④ was introduced into the fiber preform mold to a height twice that of the preform, and the pressure was maintained for 8 hours. After impregnation, the sample was placed in an oven and cured at 180℃ for 5 hours. After curing, the sample was placed in a high-temperature pyrolysis furnace for pyrolysis at 1050℃ for 4 hours. After repeating the above impregnation, curing, and pyrolysis steps 12 times, the C / SiC-B4C composite material gained 0.9% weight, resulting in a dense C / SiC-B4C composite material.

[0093] In this embodiment, the absolute value of the Zeta potential was the highest at pH 7, reaching 44 mV, indicating good stability of the prepared slurry. No sedimentation was observed after the B4C ceramic slurry was placed in room temperature air for 100 min, confirming its good stability and meeting the requirements for subsequent vacuum filtration and cyclic impregnation. The resulting C / SiC-B4C composite material was uniform and dense, with a flexural strength of approximately 133 MPa, while also exhibiting good toughness. Furthermore, this composite material possesses excellent ablation resistance; under the testing conditions of 2100℃ and 180 s, the linear ablation rate was -0.88 μm / s, and the mass ablation rate was 1.54 mg / s.

[0094] Example 5

[0095] C / SiC-HfC composite materials were prepared by doping C / SiC with HfC powder.

[0096] ① HfC particles with an average particle size of about 0.9 μm, polyoxymethylene dispersant, and deionized water solvent were selected as raw materials. After stirring for 1.8 h, the mixture was placed in a ball mill jar. Alumina ball milling beads with a ball diameter of 3 mm were used, with a ball-to-material ratio of 1:1.4. The mixture was ball milled at a speed of 290 r / min for 3.5 h. HCl with a mass concentration of 36% was added to adjust the pH value to 6. The polyoxymethylene content was 0.4 wt.%, and the slurry solid content was 5%.

[0097] ② Selected product manufactured by Toray Industries, Japan, with dimensions of 210×210×35mm (length×width×thickness) and a density of 0.6g / cm³. 3 Carbon fiber needle-punched preforms.

[0098] ③Establish a closed-loop circulating filtration and impregnation system consisting of a ceramic slurry storage tank, a filtration mold, and a high-efficiency circulating pump assembly.

[0099] ① The prepared HfC ceramic slurry was injected into a slurry storage tank with a volume of 5L. ② The carbon fiber preform was clamped and fixed using a double-layer clamp and placed in a filtration device. The slurry storage tank and filtration device were sealed, and after checking for good airtightness, the circulation pump was turned on. The ceramic slurry flowed into the filtration device at a rate of 0.8L / s, completely covering the surface of the fiber preform. Under the action of the circulation pump, the internal pressure difference of the system was 90Kpa. The pressure difference drove the slurry to circulate through the fiber preform. When the total flow rate of the filtered slurry was 800 times the fiber volume, the fiber was flipped over, with its lower surface on top, and the same volume of slurry was circulated and filtered again. After impregnation, the fiber preform was placed in an oven at 150℃ for 3 hours. The area covered by the clamps around the perimeter was cut off, approximately 5mm, resulting in a fiber preform containing ZrC particles with dimensions of 200×200×35mm and a density of 0.95g / cm³. 3 .

[0100] ④ Mix PCS powder with a number average molecular weight of 1000 and xylene in a 1:1 ratio to prepare a PCS precursor solution, the volume of which is 3.5 times the volume of the ZrC fiber preform.

[0101] ⑤ The fiber preform containing HfC particles obtained in ③ was placed in a vacuum chamber. Under a vacuum of 0.05 MPa, the PCS precursor solution prepared in ④ was introduced into the fiber preform mold to a height twice that of the preform, and the pressure was maintained for 9 hours. After impregnation, the sample was placed in an oven and cured at 190℃ for 3 hours. After curing, the sample was placed in a high-temperature pyrolysis furnace for pyrolysis at 1000℃ for 1 hour. After repeating the above impregnation, curing, and pyrolysis steps 7 times, the C / SiC-HfC composite material gained 1% weight, resulting in a dense C / SiC-HfC composite material. In this example, the absolute value of the Zeta potential was the maximum at pH 6, which is 43 mV, indicating good stability of the prepared slurry. No sedimentation was observed after the HfC ceramic slurry was placed in room temperature air for 110 minutes, confirming its good stability and meeting the requirements for subsequent vacuum filtration and cyclic impregnation. The resulting C / SiC-HfC composite material is uniform and dense, with a flexural strength of approximately 124 MPa, while also exhibiting good toughness. Furthermore, this composite material demonstrates excellent ablation resistance; under testing conditions of 2100℃ and 180 s, the linear ablation rate is -0.92 μm / s, and the mass ablation rate is 1.60 mg / s.

Claims

1. A method for preparing composite materials by slurry circulation filtration combined with impregnation and pyrolysis, characterized in that: The specific process is as follows: 1) The UHTC slurry is flowed through the porous carbon fiber preform to obtain a fiber preform containing UHTC; 2) Precursor impregnation and pyrolysis: The fiber preform containing UHTC was immersed in the PCS precursor solution under vacuum and impregnated under pressure for a period of time. The sample was then cured in an oven and placed in a high-temperature pyrolysis furnace for pyrolysis to prepare C / SiC-UHTC composite material. Repeat the above impregnation, curing and pyrolysis treatment steps more than twice until the weight gain of the C / SiC-UHTC composite material after the last treatment is in the range of 0.1-1.5%, and obtain a dense C / SiC-UHTC composite material. Weight gain rate = (m2-m1) / m1×100%, where m2 is the sample weight after completing the last impregnation, curing and pyrolysis step, and m1 is the sample weight after completing the penultimate impregnation, curing and pyrolysis step. The preparation of C / SiC-UHTC composite materials specifically includes the following steps: (1) Preparation of stable UHTC slurry: First, the ceramic particles, dispersant and solvent are stirred and mixed evenly, and then a uniformly distributed stable UHTC slurry is obtained by wet ball milling and pH adjustment. (2) Circulating filtration system: Construct a closed circulating filtration system, which includes a ceramic slurry storage tank, a filtration device and a high-efficiency circulating pump assembly; Ceramic slurry storage tank: used for sealing after placing UHTC slurry; The filtration device consists of two parts: an upper cylindrical container open at one end, connected to the outlet of a circulating pump via a pipe, and a plate with a central through-hole at the lower opening. The lower opening of the container is sealed to the upper surface of the plate around the through-hole, with the through-hole located within the area enclosed by the lower opening. The lower cylindrical container open at one end, connected to a slurry storage tank via a pipe, also has a plate with a central through-hole at the upper opening. The upper opening of the container is sealed to the lower surface of the plate around the through-hole, with the through-hole located within the area enclosed by the upper opening. The through-holes on the two plates correspond to each other. The setup consists of a double-layer clamping mold composed of two flat plates with through holes, with a porous carbon fiber preform fixed in the middle by the double-layer clamping mold. The lower layer of the double-layer clamping mold is used for support, and the upper layer is used for fixation. The fiber preform to be processed is placed in the corresponding through holes between the two flat plates, and annular sealing rings are set around the through holes between the two flat plates to seal the edges of the fiber preform. The two flat plates are firmly positioned and sealed by bolts set around the outside of the sealing rings. The edges of the through holes in the middle of the two flat plates are respectively attached to the surface of the porous carbon fiber preform, and the porous carbon fiber preform is located in the through holes in the middle of the sealing rings. High-efficiency circulating pump: The outlet of the circulating pump is connected to the upper part of the filtration device on one side, and the inlet on the other side is connected to the ceramic slurry storage tank. After the circulating pump is started, a pressure differential circulating filtration and impregnation system is formed. The pressure difference between the upper and lower parts of the filtration device is 80~90KPa. The pressure difference drives the slurry to continuously pass through the fiber preform, making it easier for UHTC particles to be captured by the fiber preform, improving the filtration speed and efficiency. The slurry filtered by the preform returns to the storage tank for the next round of filtration and impregnation. (3) Slurry circulation filtration and impregnation: After completing the preparation work in step (2), start the circulation pump to perform circulation filtration and impregnation, ensuring that the slurry liquid level in the upper container completely covers the upper surface of the fiber preform, and complete one circulation filtration cycle. After completing one cycle of filtration, the fiber preform is flipped over so that its bottom surface becomes the contact surface, and the same cycle of filtration is performed again to ensure that the material is fully penetrated and the penetration depth is maximized, and finally a fiber preform rich in UHTC is prepared. (4) Preparation of PCS precursor solution: Mix polycarbosilane PCS powder with xylene in the required ratio to obtain PCS precursor solution; (5) PCS precursor impregnation pyrolysis: The UHTC-rich fiber preform obtained in step (3) was placed in a vacuum chamber. Under vacuum conditions, the PCS precursor solution prepared in step (4) was introduced into the mold containing the UHTC-containing fiber preform through a conduit, so that the UHTC-containing fiber preform was immersed in the PCS precursor solution. The sample was impregnated under vacuum for a period of time. Then the sample was cured in an oven. After curing, it was placed in a high-temperature pyrolysis furnace for pyrolysis to prepare C / SiC-UHTC composite material. Repeat the above impregnation, curing and pyrolysis steps more than twice until the weight gain of the C / SiC-UHTC composite material is in the range of 0.1-1.5%, and obtain a dense C / SiC-UHTC composite material.

2. The method according to claim 1, characterized in that: The impregnation, curing and pyrolysis steps were repeated more than twice during the preparation of C / SiC-UHTC composite material until the weight gain of C / SiC-UHTC composite material was in the range of 0.1-1%, thus obtaining dense C / SiC-UHTC composite material.

3. The method according to claim 1 or 2, characterized in that: The UHTC slurry comprises ceramic particles, a dispersant, and a solvent; the ceramic particles are one or more of ZrC, HfB2, HfC, ZrB2, and B4C, with a particle size range of 0.8-1.2 μm; The dispersant is one or more of polyethyleneimine, ammonium polyacrylate, and polymethacrylate; the solvent is water and / or ethanol; the dispersant content in the slurry is 0.1-0.7 wt.%, and the solid content of the slurry is 3-20%; UHTC adhesion amount is expressed as the density of the UHTC-containing carbon fiber preform, i.e., the mass (g) of the UHTC-containing carbon fiber preform and the volume (cm³) of the carbon fiber preform. 3 The specific range is 0.8-1.1 g / cm³. 3 .

4. The method according to claim 3, characterized in that: The dispersant content in the slurry is 0.1-0.5 wt.%, and the solid content of the slurry is 5-15%.

5. The method according to claim 1, characterized in that: The PCS precursor solution uses PCS as an organic precursor, and its mass ratio with the solvent xylene is 1:(1-1.5), and its volume is 1-5 times the volume of the UHTC carbon fiber preform. The impregnation vacuum degree is 0.03-0.08MPa, the holding time is 5-12h, the curing temperature is 150-200℃, the curing time is 1-12h, and the pyrolysis temperature is 900℃-1100℃, with a pyrolysis time of 1-6h.

6. The method according to claim 5, characterized in that: The PCS precursor solution uses PCS as an organic precursor, and its mass ratio with the solvent xylene is 1:(1-1.3), and its volume is 2-4 times that of the UHTC carbon fiber preform. The impregnation vacuum degree is 0.04-0.07 MPa, the holding time is 6-10 h, the curing temperature is 160-190℃, the curing time is 3-10 h, and the pyrolysis temperature is 950-1050℃, with a pyrolysis time of 1-5 h.

7. The method according to claim 1, characterized in that: In step (1), the stirring time is 0.5-2h; the ball milling speed is 100-300r / min, the ball milling time is 1-5h, the ball material is alumina and / or zirconium oxide, the ball-to-material mass ratio is 1:(1-2), and the ball diameter is 2-4mm; the pH value is adjusted by mass concentration of 35-38% HCl, and the pH value range is 4-7. The stability of the prepared solution was determined by zeta potential and static incubation experiments.

8. The method according to claim 7, characterized in that: In step (1), the stirring time is 1-2 hours; the ball milling speed is 200-300 r / min, the ball milling time is 3-5 hours, the ball material is alumina and / or zirconium oxide, the ball-to-material mass ratio is 1:(1.3-1.5), and the ball diameter is 2-4 mm; the pH value is adjusted by a mass concentration of 35-38% HCl, and the pH value range is 5-7.

9. The method according to claim 1, characterized in that: The volume of the ceramic slurry in the storage tank in step (2) is 1-5L; the carbon fibers of the porous carbon fiber preform are flat, with a thickness of 10-35mm and a density of 0.5-0.7g / cm³. 3 .

10. The method according to claim 1 or 9, characterized in that: The time required for one cyclic filtration cycle is determined based on the total slurry flow rate and slurry velocity required for the cycle, while the total slurry flow rate is determined based on the volume of fibers through which the slurry flows. During the cyclic filtration process, the slurry velocity is 0.4-1 L / s, and the slurry level is higher than the surface of the preform. The total slurry flow rate required for one cyclic filtration cycle is 500-1000 times the volume of the fiber preform through which the slurry flows. After the fibers are turned over, the same cyclic filtration process as described above is performed again. After infiltration, the composite material is dried in an oven at 100-150℃ for 1-5 hours. The area around the material with a width of 4-6mm, which is fixed and covered by two upper and lower flat plate clamps, is cut off to obtain a fiber preform containing UHTC.

11. The method according to claim 10, characterized in that: In step (3), the slurry flow rate is 0.6-0.8 L / s, and the slurry level is higher than the surface of the preform. The total slurry flow rate required for one cycle of filtration is 600-800 times the volume of the fiber preform through which the slurry flows. After flipping the fiber, the same cycle of filtration is performed again. After infiltration, the composite material is dried in an oven at 100-150℃ for 2-4 hours.

12. A C / SiC-UHTC composite material prepared by the method of any one of claims 1-11.

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