Increase C through active cooling f Methods and applications for improving the oxidation and ablation resistance of HfB2-SiC composite materials

Abstract

Increase C through active cooling f This invention relates to a method and application for improving the oxidation and ablation resistance of HfB2-SiC composite materials. The invention aims to address technical problems in existing technologies such as oxidation and ablation, uneven cooling, and poor structural stability. The method involves: preparing a carbon fiber braid and coating the carbon fiber surface; preparing an HfB2 ceramic slurry; preparing a green body; and obtaining a low open porosity C2. f / HfB2-SiC composite material; directional microporous channels are prepared using micro-electrical discharge machining (EDM). This invention utilizes a directional pore channel structure and a low open porosity C f The / HfB2-SiC composite material, combined with an active cooling strategy, significantly improves the material's resistance to oxidation and ablation, as well as its cooling efficiency, under high heat flux environments. The composite material prepared in this invention is used as a thermal protection material in the cooling channels of thermal protection systems.

Description

Technical Field

[0001] This invention relates to the fields of composite material preparation and thermal protection. Background Technology

[0002] Hypersonic vehicles pose unprecedented challenges to thermal protection systems under extreme service environments, particularly critical components such as the leading edge and combustion chamber, which must simultaneously withstand dynamic high-temperature environments exceeding 2000°C and the erosion of highly oxidizing airflow. While traditional ceramic matrix composites, such as HfB2-SiC, exhibit good temperature resistance under static high-temperature conditions, their protective performance significantly degrades under the coupled effects of transient ultra-high temperatures and strong oxidation generated by actual high-Mach number flight. This degradation is primarily manifested in severe oxidative ablation of the material surface and structural failure of the protective layer due to accumulated thermal stress.

[0003] To address this technical challenge, current research focuses on two main directions: improving the intrinsic properties of materials and optimizing cooling structures. Regarding material systems, while introducing ultra-high temperature ceramic phases such as HfB2 can improve oxidation resistance to some extent, the improvement in intrinsic properties has reached its theoretical limit. In terms of cooling technology, traditionally sintered porous cooling structures suffer from inherent defects such as insufficient pore connectivity and uneven pore size distribution, leading to obstructed cooling medium flow and severe localized heat accumulation, resulting in thermal protection failure. In the active thermal protection design of some high-temperature materials, optimizing pore structures is often used to improve cooling performance. Directional pore channel structures have been proposed to improve heat transfer efficiency, but most existing designs fail to fully optimize the combination of pore structure and cooling channels, resulting in unsatisfactory cooling effects and failing to effectively solve the fundamental problem of synergistic optimization of oxidation ablation control and thermal management.

[0004] In-depth analysis reveals that optimizing cooling channel design to reduce surface response temperature and enhance material resistance to oxidation and ablation under extreme thermal environments remains a challenge. Particularly under non-uniform heat flux loads, core issues such as how cooling channels can adaptively match the dynamic thermal environment and how to ensure the structural integrity of cooling channels in high-temperature oxidizing environments remain to be addressed. Current research largely focuses on material composition optimization or cooling structure improvement in isolation, lacking a systematic consideration of the integrated material-structure-function design, which severely restricts performance breakthroughs in next-generation thermal protection systems. Summary of the Invention

[0005] This invention addresses the technical problems in existing technologies, such as oxidation ablation, uneven cooling, and poor structural stability, by providing a method to improve C through active cooling. f Methods and applications for improving the oxidation and ablation resistance of HfB2-SiC composite materials.

[0006] Increase C through active cooling f The method for improving the oxidation and ablation resistance of HfB2-SiC composite materials is carried out according to the following steps:

[0007] 1. Carbon fiber braids are prepared using carbon fiber, and a coating is applied to the surface of the carbon fiber using a chemical vapor deposition process;

[0008] 2. HfB2 powder, polyethyleneimine and ethanol solution are placed in a ball mill and mixed to prepare HfB2 ceramic slurry;

[0009] 3. Use a high-pressure pump to extract the HfB2 ceramic slurry prepared in step 2 and inject it into a container. At the same time, use a vacuum pump to evacuate the air below the filter element and control the relative pressure difference on both sides of the filter element to be greater than 0.5MPa. Impregnate the carbon fiber braid prepared in step 1 in the HfB2 ceramic slurry and then dry it to obtain a green body.

[0010] 4. The green body is impregnated in liquid polycarbosilane under ultra-high pressure, then cured at low temperature, and then sintered in a vacuum furnace.

[0011] By repeatedly cycling the process of impregnating liquid polycarbosilane, low-temperature curing, and vacuum sintering, a low open porosity C0 was obtained. f / HfB2-SiC composite material;

[0012] V. The low open porosity C prepared in step four is processed using a micro-electrical discharge machining method. f / HfB2-SiC composite material was used to prepare directional microporous channels, obtaining directional microchannels with low open porosity C f / HfB2-SiC composite material, completed.

[0013] The directional microchannel with low porosity C f / HfB2-SiC composite material is used as a thermal protection material in the cooling channels of thermal protection systems.

[0014] The composite material of this invention is made of C f It is composed of carbon fiber, HfB2, SiC and PyC; where C f (Carbon fiber): As a reinforcing phase, it plays a role in improving the mechanical properties of the material; HfB2: As a high-temperature resistant matrix material, it provides high thermal stability and oxidation resistance; SiC: It enhances the oxidation resistance and mechanical properties of the material; PyC: By depositing a PyC intermediate interface layer on the surface of carbon fiber through chemical vapor deposition (CVD) technology, it enhances the interfacial bonding force between carbon fiber and matrix material, thereby improving the interfacial strength and toughness of the material.

[0015] Liquid water (as coolant): Used in cooling channels, with a flow rate controlled at 0.1–1.0 g / s. The specific flow rate can be adjusted according to actual needs.

[0016] This invention employs micro-EDM technology to achieve low open porosity C f Oriented channels are fabricated in HfB2-SiC composite materials. By optimizing micro-electrical discharge machining parameters, the aperture and orientation of the channels are precisely controlled to achieve optimal cooling.

[0017] This invention uses chemical vapor deposition (CVD) technology to deposit a PyC mesophase layer on the surface of carbon fibers to enhance the interfacial bonding between carbon fibers and the matrix material.

[0018] This invention combines a coolant flow system with a material structure to ensure that the coolant can flow uniformly in the directional hole channels, thereby achieving a good cooling effect.

[0019] This invention uses ultra-high pressure precursor impregnation and pyrolysis technology for sintering, and further optimizes the mechanical properties and density of the material through cyclic low-temperature pressureless sintering.

[0020] Working principle:

[0021] Heat transfer and cooling: The material surface absorbs heat from the environment, the surface temperature rises, the surface thermal effect is enhanced, the material radiates heat to the environment to reduce the surface temperature, and the heat entering the material is transferred to the interior through heat transfer.

[0022] Convection heat transfer:

[0023] Because of the large temperature difference between the material and the fluid, and the fluid flowing in the channel, the relatively cooler fluid carries away the heat through convection, thereby lowering the material temperature.

[0024] Oxidation control: Under high heat flux density conditions, the core-shell structure oxide film (HfO2 and SiO2) formed on the material surface effectively inhibits further oxidation reactions and protects the structure of the composite material.

[0025] By combining the directional hole channel design and cooling strategy proposed in this invention, the existing technical problems have been successfully overcome, and the material's resistance to oxidation and ablation and its thermal protection performance under extreme thermal environments have been significantly improved, which has important practical application value.

[0026] This invention improves the flow path of coolant through directional perforated channels, ensuring uniform distribution of cooling effect, improving the cooling efficiency of materials, and thus reducing surface response temperature.

[0027] This invention combines a composite material with low open porosity and effectively improves the oxidation resistance of the composite material through a core-shell structure oxide layer (such as hafnium oxide coating the silicate glass phase and a dense oxide layer coating the unablated matrix of the composite material), preventing oxidation from spreading into the interior of the material and thus improving its resistance to oxidation and ablation.

[0028] Enhanced structural stability: This invention controls the morphology and distribution of active cooling channels in composite materials, improves the thermal stability and structural integrity of the materials, reduces thermal damage under high heat flux density, and ensures long-term stability in high-temperature environments.

[0029] Enhancing thermal protection under high heat flux density and extreme ambient temperatures: By integrating active cooling strategies with composite material structure optimization, not only is the cooling effect effectively improved, but the material's resistance to oxidation and ablation and its thermal protection performance under extreme environments are also enhanced.

[0030] Beneficial effects of this invention:

[0031] This invention achieves its goals through an innovative design of a directional pore channel structure and the use of a low open porosity C. f The / HfB2-SiC composite material, combined with an active cooling strategy, significantly improves the material's resistance to oxidation and ablation, as well as its cooling efficiency, under high heat flux environments. This invention C f During the oxidation process of the / HfB2-SiC composite material, hafnium can combine with oxygen to form HfO2 (with a melting point as high as 2810℃). Simultaneously, the oxidation products formed by the combination of boron and silicon with oxygen in the system can form a molten phase covering the ablation center and diffuse outwards in a molten state, thereby improving the composite material's resistance to oxidation and ablation at high temperatures. The molten phase mainly consists of silicate structures formed by the high-temperature melting of silicon carbide, or borosilicate structures formed through combination with boron. The viscosity characteristics of the glassy phase allow it to cover some matrix components, reducing the damage caused by pits and pores formed by carbon fiber oxidation and ablation. Most defects are filled by molten SiO2, promoting the formation and growth of HfO2, resulting in a continuous and dense structure. A dense oxide layer forms on the surface, further preventing oxygen penetration and acting as an effective barrier during the oxidation and ablation process.

[0032] 1. Significantly improves resistance to oxidation and ablation:

[0033] Problems with existing technology: In the existing technology, traditional ceramic matrix composites are prone to oxidation and ablation under high heat flux density and extreme ambient temperature, resulting in severe damage to the material surface and reducing the structural stability and thermal protection performance of the material.

[0034] Advantages of the invention: This invention employs a low open porosity C f The HfB2-SiC composite material utilizes HfB2, which has a high melting point and stronger resistance to oxidation and ablation, ensuring its usability even under extreme temperature conditions. Furthermore, the directional pore channel design and coolant flow effectively reduce the material's surface temperature, suppressing ablation. This is particularly beneficial at high heat flux densities (4MW / m³). 2In the ablation test, the surface temperature of the material decreased by 524°C; at the same time, in the high-temperature ablation test at 2800°C, the surface temperature could be reduced by more than 1300°C, which proves that the present invention can significantly improve the antioxidant ablation resistance of the composite material.

[0035] Quantitative effect: In the ablation test, 4MW / m 2 In the ablation test, the temperature of the central region remained at 1490℃, and in the high-temperature ablation test at 2800℃, the temperature of the central region remained at 1453℃. Compared with existing technologies, this reduces the surface response temperature and enhances stability under extreme thermal environments.

[0036] 2. Improve cooling efficiency:

[0037] Existing technical problems: In traditional composite materials, the design of cooling channels has not been effectively optimized, resulting in uneven cooling effects and excessive heat load in some areas, leading to thermal damage to the material.

[0038] Advantages of the invention: This invention, through its directional channel design, allows the coolant to flow in a specific direction, improving the coolant's flow efficiency. Compared to existing technologies, the optimized cooling channel structure effectively enhances heat exchange between the coolant and the material surface, thus improving cooling efficiency.

[0039] Quantitative effect: Under high heat flux density, the coolant flow rate is 0.17 g / s. By optimizing the coolant flow path, the cooling efficiency is significantly improved, ensuring a more uniform cooling effect.

[0040] 3. Improve the structural stability of materials:

[0041] Problems with existing technologies: Under high temperature and high pressure environments, composite materials in existing technologies are prone to structural instability due to oxidation, ablation, and thermal expansion, which reduces the service life and performance of the materials.

[0042] Advantages of the invention: This invention, through the preparation of materials with low open porosity and the design of directional pore channels, not only optimizes the thermal conductivity of the material but also effectively avoids structural damage to the material under high heat flux environments. By depositing a PyC intermediate phase layer on the carbon fiber surface, the interfacial bonding force between the carbon fiber and the matrix material is enhanced, thereby improving the structural stability of the material.

[0043] Qualitative results: In a long-term (400 seconds) high-temperature ablation test, the surface response temperature of the composite material prepared by this invention remained stable and no thermal blockage effect occurred, ensuring the long-term stability of the structure.

[0044] 4. Improve thermal protection efficiency:

[0045] Existing technical problems: Existing thermal protection materials lack effective cooling strategies when facing high-temperature environments such as hypersonic aircraft, resulting in excessive heat load and affecting the thermal protection effect.

[0046] Advantages of the invention: By integrating directional pore channel design with an active cooling strategy, this invention significantly improves the thermal protection performance of materials under extreme thermal environments. The interaction between the coolant and the composite material effectively removes heat, reducing heat accumulation on the material surface.

[0047] Quantitative effect: In the ablation test, the cooling channel effectively reduced the surface response temperature, avoiding the overheating problem and ablation damage that are common in traditional materials under high heat flux density, and improving the thermal protection capability of the material.

[0048] 5. Improve production efficiency and save materials:

[0049] Existing technical problems: The preparation process of traditional composite materials is complex and consumes a lot of raw materials, resulting in high costs.

[0050] Advantages of the invention: The preparation method of this invention simplifies the manufacturing process by optimizing micro-electro-discharge machining technology and coolant flow path design, while reducing unnecessary raw material waste. By precisely controlling the microchannel size through adjusting processing parameters and electrode dimensions, the material achieves performance requirements while maximizing material utilization efficiency, thus reducing production costs.

[0051] Qualitative effect: The innovative design of this invention optimizes the preparation process, reduces raw material consumption and energy consumption in the production process, and improves production efficiency.

[0052] 6. Wide range of applications:

[0053] Existing technical problems: The application range of existing composite materials is limited, especially in extreme environments with high temperature and high pressure, where their thermal protection performance and structural stability fail to meet the requirements of hypersonic vehicles.

[0054] Advantages of the invention: The composite material of the present invention has broad application prospects in thermal protection systems for aerospace, hypersonic vehicles and other high temperature and high pressure environments, especially in terms of cooling performance and oxidation resistance.

[0055] Qualitative effect: The composite material of the present invention can effectively meet the thermal protection requirements in extreme environments and can be widely used in engineering fields with extremely high temperature and high heat flux density, meeting the needs of cutting-edge technologies such as hypersonic aircraft.

[0056] This invention utilizes an innovative directional pore channel design and a low open porosity (C) fThe combination of / HfB2-SiC composite material not only solves the problems of uneven cooling effect and unstable material structure in the existing technology, but also significantly improves the material's resistance to oxidation and ablation and thermal protection performance, which has significant technical advantages and application value.

[0057] The composite material prepared by this invention can be widely used in the aerospace field for thermal protection systems under high temperature and high pressure environments. Furthermore, the directional pore channel design and active cooling strategy of the composite material can be used in thermal management systems under other high-temperature environments, providing a more efficient thermal protection solution. Attached Figure Description

[0058] Figure 1 The diagram shows the fabrication principle of directional microfluidic channels and images of the materials before and after processing. Figure a shows the fabrication process, Figure b shows the fabrication principle, and Figure c shows the fabricated low open porosity C. f A top view of the / HfB2-SiC composite material; Figure d shows the prepared low open porosity C. f A side view of the / HfB2-SiC composite material, Figure e shows the low open porosity C of the directional microchannels. f Top view of the / HfB2-SiC composite material;

[0059] Figure 2 The low open porosity C prepared in Example 1 f Physical image of the / HfB2-SiC composite material:

[0060] Figure 3 The low open porosity C prepared in Example 1 f Porosity diagram of / HfB2-SiC composite material;

[0061] Figure 4 The low open porosity C of the directional microchannel prepared in Example 2 f Physical image of the / HfB2-SiC composite material;

[0062] Figure 5 The low open porosity C of the directional microchannel prepared in Example 3 f Top view of HfB2-SiC composite material;

[0063] Figure 6 The low open porosity C of the directional microchannel prepared in Example 4 f Figure 1. Active cooling process of HfB2-SiC composite material during oxyacetylene ablation test;

[0064] Figure 7 Macroscopic images of the composite materials prepared in Examples 1 and 4 after passive ablation, after testing at different heat flux densities;

[0065] Figure 8The low open porosity C of the directional microchannel prepared in Example 4 f Response temperature test diagram of HfB2-SiC composite material surface under two ablation states (with coolant and without coolant);

[0066] Figure 9 This is a schematic diagram and macroscopic view of the distribution of directional through holes of different diameters prepared on a stepped sample using electrodes of different diameters in Example 5.

[0067] Figure 10 To improve the low open porosity C of the directional microchannels prepared in Example 5 under an oxygen-rich environment f Macroscopic images of the HfB2-SiC composite material before and after oxy-acetylene ablation test;

[0068] Figure 11 To improve the low open porosity C of the directional microchannels prepared in Example 5 under an oxygen-rich environment f Temperature rise curve of / HfB2-SiC composite material in oxy-acetylene ablation test;

[0069] Figure 12 The low open porosity C prepared in Example 1 f Ablation photograph of / HfB2-SiC composite material after oxy-acetylene ablation test;

[0070] Figure 13 The low open porosity C prepared in Example 1 f Temperature rise curve of / HfB2-SiC composite material after oxy-acetylene ablation test;

[0071] Figure 14 Low open porosity C of directional microchannels with different pore sizes prepared in Example 5 f Bar chart showing the cooling effect of / HfB2-SiC composite material when coolant is introduced. Detailed Implementation

[0072] Specific Implementation Method 1: This implementation method increases C through active cooling. f The method for improving the oxidation and ablation resistance of HfB2-SiC composite materials is carried out according to the following steps:

[0073] 1. Carbon fiber braids are prepared using carbon fiber, and a coating is applied to the surface of the carbon fiber using a chemical vapor deposition process;

[0074] 2. HfB2 powder, polyethyleneimine and ethanol solution are placed in a ball mill and mixed to prepare HfB2 ceramic slurry;

[0075] 3. Use a high-pressure pump to extract the HfB2 ceramic slurry prepared in step 2 and inject it into a container. At the same time, use a vacuum pump to evacuate the air below the filter element and control the relative pressure difference on both sides of the filter element to be greater than 0.5MPa. Impregnate the carbon fiber braid prepared in step 1 in the HfB2 ceramic slurry and then dry it to obtain a green body.

[0076] 4. The green body is impregnated in liquid polycarbosilane under ultra-high pressure, then cured at low temperature, and then sintered in a vacuum furnace.

[0077] By repeatedly cycling the process of impregnating liquid polycarbosilane, low-temperature curing, and vacuum sintering, a low open porosity C0 was obtained. f / HfB2-SiC composite material;

[0078] V. The low open porosity C prepared in step four is processed using a micro-electrical discharge machining method. f / HfB2-SiC composite material was used to prepare directional microporous channels, obtaining directional microchannels with low open porosity C f / HfB2-SiC composite material, completed.

[0079] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the volume concentration of the ethanol solution is 70%. Everything else is the same as in Specific Implementation Method One.

[0080] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the ball mill speed in step two is 250 r / min, and the mixing time is 2 h. Everything else is the same as in Specific Implementation Method One or Two.

[0081] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the impregnation time in the HfB2 ceramic slurry in step three is 1 to 6 hours. Everything else is the same as in Specific Implementation Methods One to Three.

[0082] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: in step four, the sample is immersed in liquid polycarbosilane for 1 to 8 hours at a pressure of 30 to 200 MPa. Everything else is the same as in Specific Implementation Methods One to Four.

[0083] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the low-temperature curing temperature in step four is 200℃. Everything else is the same as in Specific Implementation Methods One to Five.

[0084] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that: Step Five utilizes micro-electrical discharge machining technology, using a high-energy instantaneous current to create micropores with a low porosity C. fThe HfB2-SiC composite material burns through, forming directional microchannels for coolant flow during active cooling. Other aspects are the same as in any of the specific embodiments one through six.

[0085] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One through Seven in that: in step five, the micro-electrical discharge machining uses a copper tube electrode with dimensions of Ф0.1mm-Ф3.0mm. The machining parameters are: pulse width of the pulse power supply is 1-13 levels, pulse interval is 1-10 levels, power amplifier is 1-3 levels, machining voltage is 50V or 100V, and machining current is 6A-10A. Everything else is the same as in Specific Implementation Methods One through Seven.

[0086] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: in step five, the pore size of the directional microporous channel is controlled to be 0.2–1.0 mm. Everything else is the same as in Specific Implementation Methods One to Eight.

[0087] Specific Implementation Method Ten: This implementation method increases C through active cooling. f A method for preparing directional microchannels with low open porosity C to improve the antioxidant and ablation resistance of HfB2-SiC composite materials. f The application of / HfB2-SiC composite materials, specifically the directional microchannels with low open porosity C f / HfB2-SiC composite material is used as a thermal protection material in the cooling channels of thermal protection systems.

[0088] The scope of this invention is not limited to the above-described embodiments; a combination of one or more specific embodiments can also achieve the purpose of the invention.

[0089] Example 1:

[0090] This embodiment features a low porosity C f The preparation of the / HfB2-SiC composite material is carried out according to the following steps:

[0091] I. Carbon fiber braided body is prepared using carbon fiber, with a braided body size of 100×100×10mm. 3 The volume content is 10%, and a coating is applied to the surface of the carbon fiber using a chemical vapor deposition process.

[0092] 2. Take 600g of HfB2 powder after particle size distribution and 6g of polyethyleneimine (CH2CH2NH). n 1100g of a 70 vol.% ethanol solution was placed in a ball mill (ball-to-material ratio of 10:1) and mixed at a rate of 250 r / min for 2 h to prepare HfB2 ceramic slurry.

[0093] 3. The HfB2 ceramic slurry prepared in step 2 is injected into the container using a high-pressure pump. At the same time, the air is evacuated from the bottom of the filter element using a vacuum pump to control the relative pressure difference between the two sides of the filter element to be greater than 0.5 MPa. 18g of the carbon fiber braid prepared in step 1 is impregnated in the HfB2 ceramic slurry for 5 hours and then dried to obtain a green body.

[0094] 4. The green body is immersed in liquid polycarbonylsilane under ultra-high pressure for 8 hours, with the pressure controlled at 200 MPa. Then it is cured at a low temperature of 200℃ to obtain the green body. The green body is sintered in a vacuum furnace at a temperature of 1300℃ for 1 hour.

[0095] The process of impregnating liquid polycarbosilane, low-temperature curing, and vacuum sintering was repeated 8 times to obtain C with low open porosity. f / HfB2-SiC composite material.

[0096] Example 2:

[0097] This embodiment features a low porosity C f The preparation of the / HfB2-SiC composite material is carried out according to the following steps:

[0098] I. Carbon fiber braided body is prepared using carbon fiber, with a braided body size of 100×100×10mm. 3 The volume content is 15%, and a coating is applied to the surface of the carbon fiber using a chemical vapor deposition process.

[0099] 2. Take 630g of HfB2 powder after particle size distribution and 6.3g of polyethyleneimine (CH2CH2NH). n 1200g of a 70 vol.% ethanol solution was placed in a ball mill (ball-to-material ratio of 10:1) and mixed at a rate of 250 r / min for 2 h to prepare HfB2 ceramic slurry.

[0100] 3. The HfB2 ceramic slurry prepared in step 2 is injected into the container using a high-pressure pump. At the same time, the air is evacuated from the bottom of the filter element using a vacuum pump to control the relative pressure difference between the two sides of the filter element to be greater than 0.5 MPa. 26g of the carbon fiber braid prepared in step 1 is impregnated in the HfB2 ceramic slurry for 6 hours and then dried to obtain a green body.

[0101] 4. The green body is immersed in liquid polycarbonylsilane under ultra-high pressure for 2 hours, with the pressure controlled at 180 MPa. Then it is cured at a low temperature of 200℃ to obtain the green body. The green body is sintered in a vacuum furnace at a temperature of 1300℃ for 1 hour.

[0102] The process of impregnating liquid polycarbosilane, low-temperature curing, and vacuum sintering was repeated 8 times to obtain C with low open porosity. f / HfB2-SiC composite material.

[0103] Example 3:

[0104] This embodiment features a low porosity C f The preparation of the / HfB2-SiC composite material is carried out according to the following steps:

[0105] I. Carbon fiber braided body is prepared using carbon fiber, with a braided body size of 100×100×10mm. 3 The volume content is 25%, and a coating is applied to the surface of the carbon fiber using a chemical vapor deposition process.

[0106] 2. Take 600g of HfB2 powder after particle size distribution and 6g of polyethyleneimine (CH2CH2NH). n 1100g of a 70 vol.% ethanol solution was placed in a ball mill (ball-to-material ratio of 10:1) and mixed at a rate of 250 r / min for 2 h to prepare HfB2 ceramic slurry.

[0107] 3. Use a high-pressure pump to extract the HfB2 ceramic slurry prepared in step 2 and inject it into the container. At the same time, use a vacuum pump to evacuate the air below the filter element and control the relative pressure difference on both sides of the filter element to be greater than 0.5MPa. Impregnate 40g of the carbon fiber braid prepared in step 1 in the HfB2 ceramic slurry for 5h and then dry to obtain the green body.

[0108] 4. The green body is immersed in liquid polycarbonylsilane under ultra-high pressure for 2 hours, with the pressure controlled at 200 MPa. Then it is cured at a low temperature of 200℃ to obtain the green body. The green body is sintered in a vacuum furnace at a temperature of 1300℃ for 1 hour.

[0109] The process of impregnating liquid polycarbosilane, low-temperature curing, and vacuum sintering was repeated 8 times to obtain C with low open porosity. f / HfB2-SiC composite material.

[0110] Example 4:

[0111] This embodiment uses the low porosity C obtained in Example 1. f / HfB2-SiC composite material, the active cooling directional microchannels constructed on this composite material improve C f The oxidation and ablation resistance of HfB2-SiC composite materials is assessed using the following steps:

[0112] 1. The low open porosity C prepared in step four of Example 1 is processed using a micro-electrical discharge machining method. fDirectional microporous channels were fabricated using HfB2-SiC composite materials and then subjected to micro-electro-discharge machining (EDM). The process parameters were: pulse width of 6 levels, pulse interval of 6 levels, power amplifier of 3 levels, and electrode size of 0.2 mm. This resulted in a directional microchannel with low open porosity (C). f / HfB2-SiC composite material, completed construction.

[0113] The prepared C with directional microchannels and low open porosity f The / HfB2-SiC composite material exhibits good thermal stability, oxidation resistance, and cooling efficiency, making it suitable for medium / high heat flux density environments. The surface response temperature is significantly reduced, and its resistance to oxidation and ablation is enhanced.

[0114] Figure 1 The images show the fabrication process of the directional microchannels and the materials before and after processing. Figure a is the fabrication process, Figure b is a magnified view of a portion of the fabricated material, and Figure c is the fabricated material with low open porosity C. f A top view of the / HfB2-SiC composite material; Figure d shows the prepared low open porosity C. f A side view of the / HfB2-SiC composite material, Figure e shows the low open porosity C of the directional microchannels. f Top view of the / HfB2-SiC composite material;

[0115] Figure 2 The low open porosity C prepared in Example 1 f Physical image of the / HfB2-SiC composite material:

[0116] Figure 3 The low open porosity C prepared in Example 1 f Porosity diagram of / HfB2-SiC composite material;

[0117] Figure 4 The low open porosity C of the directional microchannel prepared in Example 2 f Physical image of the / HfB2-SiC composite material;

[0118] Figure 5 The low open porosity C of the directional microchannel prepared in Example 3 f Top view of HfB2-SiC composite material;

[0119] Figure 6 The low open porosity C of the directional microchannel prepared in Example 4 f Figure 1. Active cooling process of HfB2-SiC composite material during oxyacetylene ablation test;

[0120] Figure 7The images show macroscopic photographs of the composite materials prepared in Examples 1 and 4 after passive ablation, measured at different heat flux densities. The figures demonstrate that the ablation state of the materials improved after the introduction of active cooling, with no ablation occurring and only surface oxidation, proving the effectiveness of the method.

[0121] Figure 8 The low open porosity C of the directional microchannel prepared in Example 4 f The response temperature test diagrams of the / HfB2-SiC composite material surface under two ablation states (with and without coolant) demonstrate that introducing coolant using the method of this invention can lower the material surface temperature, with a maximum reduction of 524℃. At this point, the coolant consumption is only 0.17g / s, resulting in high cooling efficiency and a feasible solution.

[0122] Example 5:

[0123] This embodiment uses the low porosity C obtained in Example 1. f / HfB2-SiC composite material, the active cooling directional microchannels constructed on this composite material improve C f The oxidation and ablation resistance of HfB2-SiC composite materials is assessed using the following steps:

[0124] 1. The low open porosity C prepared in step four of Example 1 is processed using a micro-electrical discharge machining method. f Directional microporous channels were fabricated using HfB2-SiC composite material and then subjected to micro-electro-discharge machining (EDM). The process parameters were: pulse width at 2 levels, pulse interval at 3 levels, and power amplifier at 2 levels. Nineteen through-holes were fabricated on a stepped sample using electrodes of different diameters. The hole distribution is shown in the figure. Figure 9 (In the left-hand diagram a, 3mm, 6mm, and 7.5mm represent the distance of the directional microchannel from the center; the right-hand diagram b shows the low porosity C of the directional microchannels with four different pore sizes.) f The figure shows a macroscopic view of the porous sample surface prepared by micro-electro-discharge machining using different electrode diameters (HfB2-SiC composite material). Measured at randomly selected locations using an optical microscope, the actual average pore diameters for electrode diameters of 0.2 mm, 0.3 mm, 0.4 mm, and 0.5 mm were 0.3 ± 0.05 mm, 0.4 ± 0.05 mm, 0.5 ± 0.05 mm, and 0.6 ± 0.05 mm, respectively.

[0125] The composite material in this embodiment is suitable for applications requiring resistance to oxidation and ablation under extreme environments (2800℃). The stability of the material is improved under high temperature and high heat flux density, while maintaining good cooling effect.

[0126] The directional microchannels with low open porosity C prepared in the example f / HfB2-SiC composite material is used as a cooling element in the cooling channel of the cooling thermal management system; the coolant flow rate is controlled at 0.1~1.0g / s.

[0127] The low open porosity C of the directional microchannel prepared in Example 5 was tested under an oxygen-rich environment. f The / HfB2-SiC composite material underwent oxy-acetylene ablation tests, as follows: Figure 10 As shown, the temperature rise curve is as follows Figure 11 As shown in the macroscopic images of the material before and after ablation, exposure to an oxyacetylene flame resulted in the formation of a white oxide layer on the sample surface, accompanied by varying degrees of ablation damage and ablation pits; however, compared to C without active cooling microporous channel construction... f / HfB2-SiC composite material (Example 1) ablation photograph after oxy-acetylene ablation test ( Figure 12 ) and temperature rise curve ( Figure 13 There has been a significant improvement.

[0128] The porous sample prepared by this invention has directional through-hole cooling channels, and the liquid coolant flow rate is maintained at 0.75 g / s throughout the experiment.

[0129] The sample surface was cooled using an active cooling test device. The temperature difference (ΔT) of the surface response temperature was used as the evaluation criterion to assess the low open porosity C of the directional microchannels. f The active cooling performance of the coolant in the / HfB2-SiC composite material, such as Figure 14 As shown, the orifice size of the cooling channel is closely related to the cooling performance during active cooling. The optimal cooling performance is achieved when the channel diameter is within the range of 0.4-0.5 mm (machining tolerance ±0.05 mm). Under extreme conditions of approximately 2800℃ / 400s, the coolant maintained its function for 400s, achieving a maximum temperature reduction of 1329℃. This demonstrates the improvement of C through active cooling. f The effectiveness of methods for improving the oxidation and ablation resistance of / HfB2-SiC composite materials.

[0130] Table 1 shows the low porosity (C) of directional microchannels. f Comparison of surface temperatures of / HfB2-SiC composite materials after active cooling.

[0131] Table 1

[0132]

Claims

1. Increase C through active cooling f A method for improving the oxidation and ablation resistance of HfB2-SiC composite materials, characterized in that... This method is specifically carried out in the following steps:

1. Carbon fiber braids are prepared using carbon fiber, and a coating is applied to the surface of the carbon fiber using a chemical vapor deposition process; 2. HfB2 powder, polyethyleneimine and ethanol solution are placed in a ball mill and mixed to prepare HfB2 ceramic slurry; 3. The HfB2 ceramic slurry prepared in step 2 is injected into the container using a high-pressure pump. At the same time, the air is evacuated from the bottom of the filter element using a vacuum pump to control the relative pressure difference between the two sides of the filter element to be greater than 0.5 MPa. The carbon fiber braid prepared in step 1 is impregnated in the HfB2 ceramic slurry and then dried to obtain a green body.

4. The green body is impregnated in liquid polycarbosilane under ultra-high pressure, then cured at low temperature, and then sintered in a vacuum furnace. The impregnation liquid polysilane-low temperature curing-vacuum sintering process is cycled multiple times to obtain low open porosity C f / HfB2-SiC composite V. The low open porosity C prepared in step four is processed using a micro-electrical discharge machining method. f / HfB2-SiC composite material was used to prepare directional microporous channels, obtaining directional microchannels with low open porosity C f / HfB2-SiC composite material, completed; Step 5 utilizes micro-electrical discharge machining (EDM) technology, employing a high-energy instantaneous current to create micropores with a low porosity (C). f The HfB2-SiC composite material burns through to form directional microchannels for the flow of coolant during active cooling.

2. The method of improving C through active cooling as described in claim 1 f A method for improving the oxidation and ablation resistance of HfB2-SiC composite materials, characterized in that... The volume concentration of the ethanol solution in step two is 70%.

3. The method of increasing C by active cooling as described in claim 1 f A method for improving the oxidation and ablation resistance of HfB2-SiC composite materials, characterized in that... The ball mill used in step two operates at a speed of 250 r / min and a mixing time of 2 h.

4. The method of increasing C by active cooling as described in claim 1 f A method for improving the oxidation and ablation resistance of HfB2-SiC composite materials, characterized in that... Step 3 involves impregnation in HfB2 ceramic slurry for 1-6 hours.

5. The method of increasing C by active cooling as described in claim 1 f A method for improving the oxidation and ablation resistance of HfB2-SiC composite materials, characterized in that... Step 4: Immerse in liquid polycarbosilane for 1-8 hours at a pressure of 30-200 MPa.

6. The method of improving C through active cooling as described in claim 1 f A method for improving the oxidation and ablation resistance of HfB2-SiC composite materials, characterized in that... The low-temperature curing temperature described in step four is 200 ℃.

7. The method of increasing C by active cooling as described in claim 1 f A method for improving the oxidation and ablation resistance of HfB2-SiC composite materials, characterized in that... In step five, micro-electrical discharge machining is performed using copper tube electrodes with dimensions of Ф0.1 mm to Ф3.0 mm. The machining parameters are as follows: pulse width of the pulse power supply is 1 to 13 levels, pulse interval is 1 to 10 levels, power amplifier is 1 to 3 levels, machining voltage is 50 V or 100 V, and machining current is 6 A to 10 A.

8. The method of improving C by active cooling as described in claim 1 f A method for improving the oxidation and ablation resistance of HfB2-SiC composite materials, characterized in that... Step 5: Control the pore size of the directional micropore channel to be 0.2~1.0 mm.

9. The method of increasing C by active cooling as described in claim 1 f A method for preparing directional microchannels with low open porosity C to improve the antioxidant and ablation resistance of HfB2-SiC composite materials. f The application of / HfB2-SiC composite material is characterized by The directional microchannel with low porosity C f / HfB2-SiC composite material is used as a thermal protection material in the cooling channels of thermal protection systems.

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