High-density and ultra-high-density carbon / carbon composite material, and preparation method and application thereof

Abstract

The application belongs to the technical field of carbon / carbon composite material preparation, and particularly discloses high-density and ultrahigh-density carbon / carbon composite material, a preparation method thereof and application thereof. The preparation method comprises the following steps: performing densification treatment on a carbon fiber preform to obtain a high-density carbon / carbon composite material blank; and performing high-temperature and high-pressure alternating coupling field heat treatment on the high-density carbon / carbon composite material, so as to obtain high-density or ultrahigh-density carbon / carbon composite material. The carbon / carbon composite material prepared by the method has reduced internal porosity and interface microcracks, improved bulk density, reduced open porosity, improved graphitization degree of pyrolytic carbon and / or pitch carbon phase, improved thermal conductivity and thermal diffusivity in the thickness direction, and enhanced resistance to plasma ablation and laser ablation. The application further provides high-density carbon / carbon composite material and application thereof in high-temperature ablation-resistant components.

Description

Technical Field

[0001] This invention relates to the field of carbon / carbon composite material preparation technology, and in particular to a high-density (1.80~2.00 g / cm³) composite material. 3 ) and ultra-high density (>2.00 g / cm³) 3 Carbon / carbon composite materials, their preparation methods, and applications. Background Technology

[0002] Carbon / carbon (C / C) composites possess characteristics such as low density, high specific strength, low coefficient of thermal expansion, excellent thermal shock resistance, and stable high-temperature performance, making them widely used in aerospace thermal protection components, rocket engine nozzles, throat liners, and other high-temperature ablation-resistant parts. For service environments characterized by high heat flux, strong oxidation, and high-speed airflow, material density is a key factor affecting structural integrity, thermal conductivity, and ablation resistance. Increasing the density of C / C composites, reducing open porosity, and minimizing internal microcracks and interface defects can not only inhibit the diffusion of oxidizing gases and active media along pore channels into the material but also enhance the continuous thermal conduction path between carbon fibers and the carbon matrix, thereby improving the material's service reliability under extreme thermal environments. Therefore, the preparation of high-density, high-stability C / C composites has always been an important research direction and engineering requirement in the field of aerospace thermal protection materials.

[0003] Existing C / C composite materials are typically prepared using processes such as chemical vapor infiltration, chemical vapor deposition, resin impregnation-carbonization, pitch impregnation-carbonization, and subsequent high-temperature heat treatment. Among these, chemical vapor infiltration or chemical vapor deposition facilitates the formation of a pyrolytic carbon interface on the carbon fiber surface, while resin or pitch impregnation-carbonization helps fill the internal pores of the preform and form a carbon matrix. High-temperature heat treatment can improve the carbon matrix structure to some extent. These processes can obtain C / C composite preforms with certain density and structural stability, and are commonly used technical routes in the preparation of high-density C / C composite materials.

[0004] However, even after densification and high-temperature heat treatment, residual pores, microcracks, and interfacial defects between fibers / matrix or different carbon phases may still exist within the C / C composite material. These defects not only limit further increases in material density but also affect thermal conductivity in the thickness direction and structural stability under high-temperature ablation conditions. Simply increasing the density by adding more densification cycles often fails to effectively eliminate existing closed pores and interfacial microdefects. Conversely, simply using high-temperature heat treatment to promote carbon layer rearrangement and graphite crystal growth can easily induce new cracks and interfacial damage due to thermal expansion mismatch between carbon fibers, pyrolytic carbon, resin carbon, or pitch carbon, and may even cause existing interfacial defects to expand.

[0005] Therefore, there is an urgent need for a method to prepare high-density C / C composite materials that can be combined with conventional densification and high-temperature heat treatment processes. This method would not only obtain a C / C composite preform but also further promote the shrinkage of internal pores, interface bonding, and carbon phase ordering, while avoiding interface damage that may be caused by a single high-temperature treatment. Summary of the Invention

[0006] This invention aims to address at least one of the technical problems existing in the prior art. To this end, this invention provides a method for rapidly preparing high-density and ultra-high-density carbon / carbon composite materials. The method provided by this invention can solve the problems that existing C / C composite materials, after conventional densification and high-temperature heat treatment, still suffer from residual porosity, microcracks, and interface defects that are difficult to further eliminate; single high-temperature heat treatment easily causes interface damage; and the difficulty in synergistically improving material density, carbon phase ordering, thermal conductivity, and ablation resistance. The high-density and ultra-high-density carbon / carbon composite materials prepared by this invention have reduced internal porosity and interface microcracks, increased bulk density, decreased open porosity, increased graphitization degree of pyrolytic carbon and / or pitch carbon phases, improved thermal conductivity and thermal diffusivity in the thickness direction, and enhanced resistance to plasma ablation and laser ablation.

[0007] In a first aspect, the present invention provides a method for preparing high-density and ultra-high-density carbon / carbon composite materials, comprising the following steps:

[0008] The carbon fiber preform is densified to obtain a carbon / carbon composite preform; the carbon / carbon composite preform is then subjected to conventional heat treatment to obtain a density ≥1.50 g / cm³. 3 The pretreated carbon / carbon composite material is then subjected to high-temperature and high-pressure alternating coupled field heat treatment to obtain a density ≥1.80 g / cm³. 3 High-density and ultra-high-density carbon / carbon composite materials.

[0009] The high-density and ultra-high-density carbon / carbon composite materials prepared by this invention have densities ranging from 1.80 to 2.00 g / cm³. 3 The range includes high-density carbon / carbon composite materials with a density > 2.00 g / cm³. 3 It is an ultra-high density carbon / carbon composite material.

[0010] According to a specific embodiment of the present invention, the present invention introduces alternating high-temperature and high-pressure coupled field treatment after preform densification and high-temperature heat treatment, so that the material promotes carbon layer slip rearrangement and graphite microcrystal development in the high-temperature and low-pressure stage, and promotes pore shrinkage and interface bonding in the low-temperature and high-pressure stage, thereby achieving synergistic control of densification, graphitization and interface integrity of high-density and ultra-high-density C / C composite materials.

[0011] The method of this invention is applicable to C / C composites containing a pyrolytic carbon interface layer and a resin carbon matrix, as well as C / C composites containing a pitch carbon matrix. By combining carbon fiber preform densification, high-temperature heat treatment, and alternating high-temperature and high-pressure coupled field heat treatment, pore shrinkage, interfacial bonding, and graphite microcrystal development in different carbon matrices are promoted, thereby obtaining a high-density C / C composite material with low open porosity, stable interfacial structure, good thermal conductivity, and ablation resistance.

[0012] According to some embodiments of the present invention, the carbon fiber preform includes a two-dimensional carbon fiber preform, a three-dimensional carbon fiber preform, or a 2.5D carbon fiber preform; the carbon fiber includes PAN-based carbon fiber or pitch-based carbon fiber.

[0013] According to some embodiments of the present invention, the densification treatment is performed by a combination of one or more of the following methods: chemical vapor infiltration, chemical vapor deposition, resin impregnation-carbonization, or asphalt impregnation-carbonization.

[0014] According to some preferred embodiments of the present invention, the densification process is as follows: first, a pyrolytic carbon interface layer is deposited on the surface of the carbon fiber preform by chemical vapor infiltration or chemical vapor deposition, and then the carbon fiber preform is densified by resin impregnation-carbonization; or, the carbon fiber preform is densified by pitch impregnation-carbonization.

[0015] According to some embodiments of the present invention, the main gas source used for the chemical vapor deposition or chemical vapor permeation includes, but is not limited to, propylene, methane, propane, and natural gas.

[0016] According to some embodiments of the present invention, the resin used in the resin impregnation-carbonization process includes at least one of phenolic resin, furan resin, or other carbonizable resin.

[0017] According to some embodiments of the present invention, the asphalt used in the asphalt impregnation-carbonization process includes at least one of mesophase asphalt, petroleum asphalt, or coal tar pitch.

[0018] According to some embodiments of the present invention, the densification treatment is performed once or multiple times until the bulk density of the carbon / carbon composite preform reaches 1.50 g / cm³. 3 above.

[0019] According to some embodiments of the present invention, the heat treatment is performed at 2100~2450 °C for 1~3 h under a protective atmosphere.

[0020] According to some embodiments of the present invention, the high-temperature and high-pressure alternating coupled field heat treatment includes a high-temperature and low-pressure treatment stage and a low-temperature and high-pressure treatment stage;

[0021] The high-temperature and low-pressure treatment is performed at a temperature of 2500–2800 °C and a pressure of 5–25 MPa for 10–40 min.

[0022] The low-temperature high-pressure treatment is performed at a temperature of 2000–2300 °C and a pressure of 50–80 MPa for 10–40 minutes.

[0023] This invention places pretreated carbon / carbon composite materials in a high-temperature, high-pressure heat treatment apparatus capable of simultaneously applying temperature and pressure fields. At least one high-temperature, low-pressure stage and at least one low-temperature, high-pressure stage are applied, alternating between these two processes. During the high-temperature, low-pressure stage, pyrolytic carbon or pitch carbon in the carbon material undergoes carbon layer slip, orientation rearrangement, and graphite crystal growth, which is beneficial for improving the degree of carbon phase ordering. During the low-temperature, high-pressure stage, the internal pores and interfacial microcracks of the material further shrink, improving the interfacial adhesion between fibers and the matrix, as well as between different carbon phases. This method, through alternating high-temperature, low-pressure and low-temperature, high-pressure processes, can further achieve synergistic control of densification, graphitization, and interfacial integrity.

[0024] According to some preferred embodiments of the present invention, the high temperature and low pressure treatment is performed at a temperature of 2600-2700 ℃ and a pressure of 10-20 MPa for 15-20 min; the low temperature and high pressure treatment is performed at a temperature of 2100-2200 ℃ and a pressure of 60-70 MPa for 15-20 min.

[0025] According to some embodiments of the present invention, after the high temperature and high pressure alternating coupled field heat treatment, a cooling and depressurization process is also performed; specifically, after the high temperature and high pressure alternating coupled field heat treatment, under a protective atmosphere, the pressure is first kept at a temperature below 500°C to reduce the interface stress concentration caused by rapid cooling or rapid depressurization, and then depressurization is performed.

[0026] In a second aspect, the present invention provides a high-density and ultra-high-density carbon / carbon composite material, wherein the high-density carbon / carbon composite material is prepared by the preparation method described in the first aspect of the present invention.

[0027] A third aspect of the present invention provides the application of high-density and ultra-high-density carbon / carbon composite materials as described in the second aspect of the present invention in high-temperature ablation-resistant components.

[0028] According to some embodiments of the present invention, the high-temperature ablation-resistant component includes aerospace thermal protection components, rocket engine nozzles, or throat liners.

[0029] The beneficial effects of this invention are:

[0030] 1) This invention utilizes a shorter post-processing time (within 40 min) to further improve the material density; for materials with a high initial density (≥1.80 g / cm³), 3 For C / C composite materials, conventional densification processes (CVI, resin impregnation, bitumen impregnation, etc.) require a density greater than 1.95 g / cm³. 3 Traditional C / C composite materials require long-term CVI or multiple rounds of impregnation and carbonization processes, which can take several days to more than ten days. Even after conventional densification and high-temperature heat treatment, pores, microcracks, and interfacial gaps may still remain inside the material. This invention promotes pore shrinkage and interfacial bonding within a shorter holding time by alternating high-temperature low-pressure fields and low-temperature high-pressure fields, thereby further densifying the material and reducing open porosity.

[0031] 2) This invention realizes the continuous preparation of carbon fiber preforms through densification, high-temperature heat treatment, and alternating high-temperature and high-pressure field strengthening treatment. Starting from carbon fiber preforms, this invention combines typical densification processes, high-temperature heat treatment, and alternating high-temperature and high-pressure field strengthening treatment to form a complete preparation route for high-density and ultra-high-density carbon / carbon composite materials, which is beneficial to improving the overall efficiency and process continuity of the material preparation process.

[0032] 3) This invention is applicable to the preparation of high-density and ultra-high-density carbon / carbon composites with different matrix types; this invention is applicable to carbon / carbon composites containing pyrolytic carbon interface layers and resin carbon matrices, as well as carbon / carbon composites containing pitch carbon matrices; for carbon / carbon composites containing pyrolytic carbon interface layers and resin carbon matrices, this invention can promote the ordering of pyrolytic carbon interfaces, reduce interface defects, and improve material density; for carbon / carbon composites containing pitch carbon matrices, this invention can promote further graphitization and densification of the pitch carbon matrix, thereby improving the thermal stability and thermal conductivity of the material.

[0033] 4) This invention can take into account densification, graphitization, and interface integrity. Although a single high-temperature treatment is beneficial to graphitization, it may cause interfacial thermal stress damage. Although a single high-pressure treatment is beneficial to pore closure, it has limited effect on promoting carbon layer rearrangement and graphite crystal growth. This invention uses alternating high-temperature and low-pressure stages and low-temperature and high-pressure stages. The high-temperature and low-pressure stages promote carbon layer slip, orientation rearrangement, and graphite crystal growth, while the low-temperature and high-pressure stages promote pore shrinkage and interfacial adhesion, thereby achieving synergistic regulation of material densification, carbon phase ordering, and interfacial structural stability.

[0034] 5) This invention can improve the thickness-direction thermal conductivity and ablation resistance of carbon / carbon composite materials. After treatment by the method of this invention, the internal pores, cracks and interface defects of the material are reduced, and the thermal conduction channels between carbon fibers, pyrolytic carbon, resin carbon or pitch carbon are more continuous. At the same time, the graphitization degree of pyrolytic carbon and / or pitch carbon is improved and the defect density is reduced, which is beneficial to reduce phonon scattering and improve the thickness-direction thermal conductivity and thermal diffusivity of the material. The higher density and thermal conductivity can inhibit the diffusion of oxidizing gases and active media into the material along pores, cracks and interfaces, reduce local heat accumulation and thermal stress concentration at the ablation center, thereby improving the ablation resistance of the material under plasma ablation and laser ablation conditions.

[0035] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0037] Figure 1 The graph shows a comparison of the bulk density and open porosity test data of the C / C composite materials in Examples 1 and 2 of the present invention before and after high temperature and high pressure alternating coupled field heat treatment. The blue bars represent the material density and the purple bars represent the material open porosity.

[0038] Figure 2 The degree of graphitization and the size L of graphite crystallites in the C / C composite materials of Examples 1 and 2 of this invention before and after high-temperature and high-pressure alternating coupled field heat treatment are shown. c The test data comparison chart shows that the purple bars represent the degree of graphitization, and the blue bars represent the graphite crystallite size L. c ;

[0039] Figure 3 The figures show a comparison of the thermophysical properties of the C / C composite materials in Examples 1 and 2 of this invention before and after high-temperature and high-pressure alternating coupled field heat treatment; where (a) is the curve of thermal diffusivity change, (b) is the curve of thermal conductivity change, and (c) is the curve of specific heat capacity change.

[0040] Figure 4The figures show the microstructure and graphitization characterization results of the C / C composite materials of Examples 1 and 2 and Comparative Examples 1 and 2 before and after high-temperature and high-pressure alternating coupled field heat treatment of the present invention; wherein, (a) and (b) are scanning electron microscope images of the samples, (a-1) and (a-2) are Comparative Example 1, (b-1) and (b-2) are Comparative Example 2, (a-3) and (a-4) are Example 1, and (b-3) and (b-4) are Example 2; (c) and (d) are Raman spectra of the samples of Comparative Example 1 and Example 1, respectively, and (e) is a map of the selected Raman test area, with the left image corresponding to the sample of Comparative Example 1 and the right image corresponding to the sample of Example 1;

[0041] Figure 5 The images are scanning electron microscope (SEM) images of the C / C composite materials of Comparative Examples 3 and 4 of the present invention after being treated by a single high-temperature low-pressure field and a low-temperature high-pressure field; wherein, (a) is the SEM image of Comparative Example 3 and (b) is the SEM image of Comparative Example 4. Detailed Implementation

[0042] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Without departing from the concept of the present invention, equivalent substitutions or conventional adjustments made by those skilled in the art to the densification process, heat treatment parameters, sample size, carbon fiber preform type and carbon matrix precursor type should all fall within the scope of protection of the present invention.

[0043] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0044] Example 1

[0045] This embodiment provides a method for preparing a high-density C / C composite material containing a pyrolytic carbon interface layer and a resin carbon matrix.

[0046] The specific preparation steps are as follows:

[0047] 1) Carbon fiber pyrolysis carbon deposition and densification treatment:

[0048] Fine-woven PAN-based carbon fiber preforms were used as reinforcement. The preforms were first dried, degummed, and purged with an inert gas. Then, chemical vapor infiltration (CVI) was performed at 950 °C and 10 kPa using propylene as the carbon source and argon as the diluent gas. (The propylene flow rate can be controlled between 100 and 500 L / h depending on the furnace size and charge amount; for small-scale pilot furnaces, the baseline parameters of 960 °C, 300 L / h, and a single cycle of 100–120 h can be used). After each deposition cycle, the material surface was lightly machined to remove the sealing layer. This process was repeated four times to achieve a material density of approximately 1.5 g / cm³. 3 ;

[0049] Then, a vacuum-pressure impregnation process with furan resin was performed: the preform was first dried at 140 ℃ for 2.5 h, the resin was preheated to 50 ℃, degassed under vacuum and introduced to completely immerse the workpiece, the vacuum was maintained for 40 min, and then the pressure was increased to 4 MPa and held for 2 h; the impregnated preform was successively cured at 80 ℃, 120 ℃, 150 ℃ and 180 ℃, and then slowly heated and carbonized under vacuum or high-purity nitrogen and argon protection, with the heating rate controlled at 0.5 ℃ / min in the 200~600 ℃ range, and finally heated to 940 ℃ and held for 1.5 h; this impregnation-curing-carbonization process was repeated 3 times, and the density increased to 1.88 g / cm³.

[0050] 2) High-temperature heat treatment:

[0051] The C / C composite preform was subjected to high-temperature heat treatment in an argon atmosphere at 2350 °C for 2 hours. The resulting preform had a density of 1.87 g / cm³. 3 Pretreated C / C composite material, denoted as C / C resin The C / C composite material contains carbon fibers, a pyrolytic carbon interface layer, and a resin carbon matrix;

[0052] The obtained C / C composite material was processed into a cylindrical sample with a diameter of 30 mm and a thickness of 10 mm. The graphite paper or contaminants attached to the surface were removed, and the sample was cleaned and dried.

[0053] 3) High-temperature and high-pressure alternating coupled field heat treatment:

[0054] The pretreated C / C composite material samples were placed in a high-temperature and high-pressure heat treatment apparatus. First, the samples were heated to 2600℃ and subjected to a pressure of 10 MPa for 15 min. Then, the temperature was adjusted to 2100℃ and the pressure to 60 MPa, and the pressure was maintained for another 15 min. After treatment, the samples were cooled in a vacuum atmosphere. Once the temperature dropped below 500℃, the pressure was gradually released to obtain a high-density resin-based C / C composite material. Samples treated with alternating high-temperature and high-pressure fields were labeled as C / C composites. resin -AHT.

[0055] Example 2

[0056] This embodiment provides a method for preparing a high-density C / C composite material containing pitch carbon matrix.

[0057] The specific preparation steps are as follows:

[0058] 1) Carbon fiber pyrolysis carbon deposition and densification treatment:

[0059] Fine-woven PAN-based carbon fiber preforms were used as reinforcement, and mesophase pitch was used as the matrix carbon precursor. A pitch impregnation-carbonization process was employed to densify the carbon fiber preforms. Through four impregnation-carbonization cycles, the mesophase pitch entered the internal pores of the preforms and transformed into a pitch-carbon matrix, resulting in a pitch-densified C / C composite preform with a density of 1.93 g / cm³. 3 , denoted as C / C pitch ;

[0060] 2) High-temperature heat treatment:

[0061] The C / C composite preform was subjected to high-temperature heat treatment in an argon atmosphere at 2350 °C for 2 h to obtain a pretreated C / C composite material composed of carbon fiber and pitch carbon matrix with a density of 1.92 g / cm³. 3 ;

[0062] The obtained pretreated C / C composite material was processed into cylindrical samples with a diameter of 30 mm and a thickness of 10 mm, and then cleaned and dried.

[0063] 3) High-temperature and high-pressure alternating coupled field heat treatment:

[0064] The pretreated C / C composite material samples were placed in a high-temperature and high-pressure heat treatment apparatus. First, they were held at 2700 °C and 20 MPa for 20 min, then at 2200 °C and 70 MPa for another 20 min. After treatment, the samples were cooled in a vacuum atmosphere and gradually depressurized to obtain high-density asphalt-based C / C composite materials. The samples treated with alternating high-temperature and high-pressure fields are designated as C / C composites. pitch -AHT

[0065] Example 3

[0066] This embodiment provides a method for preparing high-density C / C composite materials using axially braided carbon fiber preforms.

[0067] The specific preparation steps are as follows:

[0068] 1) Asphalt impregnation isostatic pressing densification treatment:

[0069] A axially braided PAN-based carbon fiber preform is used as the reinforcement, and mesophase pitch is used as the matrix carbon precursor. The axially braided carbon fiber preform is subjected to pitch impregnation treatment to allow the mesophase pitch to fully enter the internal pores of the preform. Subsequently, isostatic pressing densification treatment is performed, and carbonization is carried out under a protective atmosphere to transform the mesophase pitch into pitch carbon matrix, thereby obtaining pitch-densified C / C composite material preform.

[0070] 2) High-temperature heat treatment:

[0071] The obtained C / C composite preform was subjected to high-temperature heat treatment in an argon atmosphere to obtain a pretreated C / C composite material composed of carbon fibers and pitch carbon matrix. After high-temperature heat treatment, the density of the pretreated C / C composite material was 2.01 g / cm³. 3 .

[0072] The obtained pretreated C / C composite material was processed into cylindrical samples, cleaned, and dried.

[0073] 3) High-temperature and high-pressure alternating coupled field heat treatment:

[0074] The pretreated C / C composite material samples were placed in a high-temperature, high-pressure heat treatment apparatus and subjected to high-temperature, low-pressure treatment followed by low-temperature, high-pressure treatment, with the same process parameters as in Example 2. After treatment, the samples were cooled in a vacuum and gradually depressurized to obtain a high-density asphalt-based C / C composite material. After high-temperature, high-pressure alternating coupled field heat treatment, the density of the resulting ultra-high-density C / C composite material increased to 2.03 g / cm³. 3 .

[0075] The results indicate that for axially braided carbon fiber preforms (C / C composites) that have undergone isostatic compaction with pitch impregnation and high-temperature heat treatment, alternating high-temperature and high-pressure coupled field treatment can further promote the shrinkage of residual pores and the densification of the pitch-carbon matrix structure, reducing the material density from 2.01 g / cm³. 3 Increased to 2.03 g / cm 3 .

[0076] Example 4

[0077] This embodiment provides a method for preparing ultra-high density C / C composite materials using three-dimensional braided pitch-based carbon fiber preforms.

[0078] The specific preparation steps are as follows:

[0079] 1) Asphalt impregnation and densification treatment:

[0080] A three-dimensional braided pitch-based carbon fiber preform is used as a reinforcement, and pitch is used as a matrix carbon precursor. The three-dimensional braided pitch-based carbon fiber preform is subjected to pitch impregnation-carbonization densification treatment, so that the mesophase pitch enters the internal pores of the preform and is transformed into pitch carbon matrix, thus obtaining pitch-densified C / C composite material preform.

[0081] 2) High-temperature heat treatment:

[0082] The obtained C / C composite preform was subjected to high-temperature heat treatment in an argon atmosphere to obtain a pretreated C / C composite material composed of pitch-based carbon fibers and a pitch-based carbon matrix. After high-temperature heat treatment, the density of the pretreated C / C composite material was 1.96 g / cm³. 3 .

[0083] The obtained pretreated C / C composite material was processed into samples, cleaned, and dried.

[0084] 3) High-temperature and high-pressure alternating coupled field heat treatment:

[0085] The pretreated C / C composite material samples were placed in a high-temperature, high-pressure heat treatment apparatus and subjected to high-temperature, low-pressure treatment followed by low-temperature, high-pressure treatment, with the same process parameters as in Example 2. After treatment, the samples were cooled in an argon atmosphere and gradually depressurized to obtain ultra-high-density asphalt-based C / C composite materials. After high-temperature, high-pressure alternating coupled-field heat treatment, the density of the obtained C / C composite material increased to 2.09 g / cm³. 3 .

[0086] The results indicate that for three-dimensional braided pitch-based carbon fiber preforms (C / C composites) that have undergone pitch impregnation densification and high-temperature heat treatment, alternating high-temperature and high-pressure coupled field treatment can further promote internal pore shrinkage, pitch carbon matrix densification, and carbon phase structure optimization, reducing the material density from 1.96 g / cm³. 3 Increased to 2.09 g / cm³ 3 To obtain ultra-high density C / C composite materials.

[0087] Comparative Example 1

[0088] This comparative example provides a method for preparing a C / C composite material containing a pyrolytic carbon interface layer and a resin carbon matrix. Steps 1) and 2) of this comparative example are the same as those in Example 1, but the high-temperature and high-pressure alternating coupled field heat treatment in step 3) is omitted. The sample obtained in step 2) is the final C / C composite material, and the sample is denoted as C / C. resin -BHT.

[0089] Comparative Example 2

[0090] This comparative example provides a method for preparing C / C composite materials containing pitch carbon matrix. Steps 1) and 2) of this comparative example are the same as those of Example 2, but the high-temperature and high-pressure alternating coupled field heat treatment in step 3) is omitted. The sample obtained in step 2) is the final C / C composite material, and the sample is denoted as C / C. pitch -BHT.

[0091] Comparative Example 3

[0092] This comparative example provides a method for preparing a C / C composite material containing a pyrolytic carbon interface layer and a resin carbon matrix. Steps 1) and 2) of this comparative example are the same as those in Example 1. In step 3), only the pretreated C / C composite material sample is subjected to a single high-temperature and low-pressure field treatment. Specifically, the pretreated C / C composite material sample from step 2) is placed in a high-temperature and high-pressure heat treatment device and kept at 2600 °C and 10 MPa for 30 min. Then, it is cooled and depressurized in a vacuum to obtain the final C / C composite material.

[0093] Comparative Example 4

[0094] This comparative example provides a method for preparing a C / C composite material containing a pyrolytic carbon interface layer and a resin carbon matrix. Steps 1) and 2) of this comparative example are the same as those in Example 1. In step 3), only the pretreated C / C composite material sample is subjected to a single low-temperature high-pressure field treatment. Specifically, the pretreated C / C composite material sample from step 2) is placed in a high-temperature and high-pressure heat treatment device and kept at 2200 °C and 70 MPa for 40 min. Then, it is cooled and depressurized in a vacuum to obtain the final C / C composite material.

[0095] Performance testing:

[0096] The bulk density, graphitization degree, open porosity, X-ray diffraction, Raman spectroscopy, thickness-direction thermophysical properties, and microstructure of the materials before and after high-temperature and high-pressure alternating coupled field heat treatment in each embodiment and comparative example were tested and observed. Plasma ablation test and laser ablation test were also performed.

[0097] In the plasma ablation test, Ar and H2 were used as working gases, N2 as the excitation gas, the inner diameter of the plasma torch was 4 mm, the distance between the nozzle and the sample surface was 55 mm, the ablation power was 50 kW, and the ablation time was about 60 s. In the laser ablation test, a fiber laser with a wavelength of 1068 nm was used, the laser power was 500 W, the spot diameter was 3 mm, and the ablation time was 10 s.

[0098] Some of the results are shown in Table 1 below:

[0099] In Embodiment 1 of the present invention, after heat treatment by alternating high temperature and high pressure coupled fields, as follows: Figure 1 As shown, the bulk density of its C / C composite material ranges from 1.87 g / cm³. 3 The ratio increased to 1.95 g / cm³. 3 Around 3.40%, the porosity decreased from approximately 4.38%. Figure 2 As shown, its overall graphitization degree increased from 66.86% to 77.11%; Raman spectroscopy analysis was performed on this sample, and different carbon phases were selected for electronic scanning. The selected areas are shown in the figure. Figure 4 (e). Raman spectroscopy test results ( Figure 4 (c) and (d) indicate that the graphitization degree of the pyrolytic carbon microregions increased from 75.81% to 98.74% (e.g., Figure 4 (as shown in Figure (d)); its microstructure is as follows Figure 4 As shown in Figure (a) (a-3, a-4), compared to Comparative Example 1 ( Figure 4 (a-1, a-2)) The pores and microcracks originally located between pyrolytic carbon and resin carbon inside the material were significantly reduced, and the bonding between the fiber / pyrolytic carbon interface and the pyrolytic carbon / resin carbon interface was more compact. The plasma ablation test results showed that before and after the high temperature and high pressure alternating coupled field heat treatment, the linear ablation rate of the sample decreased from 0.0459 mm / s to 0.0398 mm / s, and the mass ablation rate decreased from 0.0425 g / s to 0.0410 g / s. The laser ablation test results showed that before and after the high temperature and high pressure alternating coupled field heat treatment, the mass ablation rate of the sample decreased from 0.00397 mg / s to 0.00146 mg / s, and the linear ablation rate decreased by about 41%.

[0100] In Example 2, after heat treatment by alternating high temperature and high pressure coupled fields, as follows: Figure 1 As shown, the bulk density of its C / C composite material ranges from 1.93 g / cm³. 3 The value increased to 1.98 g / cm³. 3 Around 3.09%, the porosity decreased from approximately 4.09% to approximately 3.38%. Figure 2 As shown, its overall graphitization degree increased from 75.65% to 90.92%; compared with Comparative Example 2 ( Figure 4 (b-1, b-2) In its pitch carbon matrix, the carbon layers with a low degree of orientation are further transformed into a graphitized structure with obvious lamellar characteristics. The number and size of pores are reduced, and the overall structure of the material is more compact. Its microstructure is as follows: Figure 4 As shown in Figure (b) (b-3, b-4);

[0101] The thermophysical property test results of the high-density C / C composite materials in Examples 1 and 2, and Comparative Examples 1 and 2 are as follows: Figure 3 ( Figure 3As shown in Figures (a), (b), and (c), the results indicate that the thermal conductivity and thermal diffusivity in the thickness direction of the densified C / C composite material are improved after high-temperature and high-pressure alternating coupled field heat treatment. Among them, the room-temperature thermal conductivity in the thickness direction of the high-density C / C composite material in Example 2 reaches as high as 79.54 W·m. ⁻¹ ·K ⁻¹ The results demonstrate that the method of the present invention can promote the growth and orientation optimization of graphite crystallites in resin and pitch carbon matrices, reduce the Lc of graphite crystallites, and decrease the C / Cresin composite material from 3.3825 Å (Comparative Example 1) before alternating coupling field heat treatment to 3.3737 Å (Example 1); and the C / Cpitch composite material from 3.3749 Å (Comparative Example 2) before alternating coupling field heat treatment to 3.3618 Å (Example 2), thereby reducing the defect density and enhancing the thermal conductivity in the thickness direction of the material.

[0102] The test results for Comparative Example 1 showed that its bulk density was 1.87 g / cm³. 3 The overall graphitization degree was 66.86%; under plasma ablation conditions, the linear ablation rate was 0.0459 mm / s and the mass ablation rate was 0.0425 g / s; under 500 W laser ablation conditions, the mass ablation rate was 3.97 mg / s; compared with Example 1, the material in Comparative Example 1 had more internal pores and interface defects, a lower degree of ordering of the pyrolytic carbon interface, and weaker thermal conductivity in the thickness direction, making it more prone to local thermal accumulation, preferential interface oxidation, and thermal stress damage during ablation.

[0103] The test results for material in Comparative Example 2 show that its bulk density is 1.93 g / cm³. 3 The overall graphitization degree was 66.86%. Compared with Example 2, although the pitch carbon matrix in Comparative Example 2 had a certain degree of graphitization, it still had local insufficient orientation and residual pores. After the high temperature and high pressure alternating coupled field treatment described in Example 2, the pitch carbon matrix further formed a layered graphitized structure, and the graphitization degree and thermal conductivity in the thickness direction were significantly improved.

[0104] The test results of the material in Comparative Example 3 show that after treatment with a single high-temperature and low-pressure field, the bulk density of the material decreased from 1.87 g / cm³. 3 Increased to approximately 1.94 g / cm³ 3The open porosity decreased from 9.1% to approximately 3.1%, while the overall graphitization degree increased to 74.01%. This indicates that a single high-temperature, low-pressure field can promote material densification and carbon layer orientation rearrangement to a certain extent, thus improving the degree of graphitization. However, since this treatment method mainly relies on high temperature to promote carbon layer slip and graphite crystallite development, while the applied pressure is relatively low, its compaction effect on residual pores, interfacial gaps, and microcracks within the material is limited. Simultaneously, the thermal expansion mismatch between carbon fibers, pyrolytic carbon, and resin carbon under high temperature easily leads to local interfacial stress concentration, resulting in crack propagation or deterioration of the bonding state at the fiber / pyrolytic carbon interface or the pyrolytic carbon / resin carbon interface. The microstructure image is shown below. Figure 5 As shown in Figure (a), compared with the high temperature and high pressure alternating coupled field heat treatment used in Example 1, although the single high temperature and low pressure field treatment is beneficial to the ordering of carbon phase, it is difficult to achieve pore shrinkage, interface bonding and interface integrity at the same time. Its comprehensive densification effect and interface stability improvement effect are lower than those of the high temperature and high pressure alternating coupled field treatment.

[0105] The test results of the material in Comparative Example 4 show that after treatment with a single low-temperature high-pressure field, the bulk density of the material increased to approximately 1.96 g / cm³. 3 The open porosity decreased to approximately 5.0%, while the overall graphitization degree increased to 74.18%. This indicates that a single low-temperature, high-pressure field can compact the internal pores and some interfacial gaps of the material, resulting in an increase in material density and a decrease in open porosity. However, due to the relatively low processing temperature, carbon layer slippage, orientation rearrangement, and graphite crystallite growth were insufficient, limiting the improvement in the orderliness of the pyrolytic carbon and resin carbon matrix, and the improvement in thermal conductivity along the material thickness direction was not significant. Furthermore, under higher pressure, stress concentration may still occur at local interfaces, affecting the stability of the fiber / matrix interface, and its microstructure... Figure 5 As shown in Figure (b). Compared with the high-temperature and high-pressure alternating coupled field heat treatment used in Example 1, although the single low-temperature and high-pressure field treatment is beneficial to pore shrinkage and structural compaction, it is difficult to fully promote carbon phase graphitization and heat conduction channel optimization. Its comprehensive improvement effect on material density, graphitization degree, interface stability and ablation resistance is lower than that of the high-temperature and high-pressure alternating coupled field treatment.

[0106] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for preparing high-density and ultra-high-density carbon / carbon composite materials, characterized in that, Includes the following steps: The carbon fiber preform is densified to obtain a carbon / carbon composite preform; the carbon / carbon composite preform is then subjected to conventional heat treatment to obtain a density ≥1.50 g / cm³. 3 The pretreated carbon / carbon composite material is then subjected to high-temperature and high-pressure alternating coupled field heat treatment to obtain a density ≥1.80 g / cm³. 3 High-density or ultra-high-density carbon / carbon composite materials.

2. The method for preparing high-density and ultra-high-density carbon / carbon composite materials according to claim 1, characterized in that, The carbon fiber preform includes a two-dimensional carbon fiber preform, a three-dimensional carbon fiber preform, or a 2.5D carbon fiber preform; the carbon fiber includes PAN-based carbon fiber or pitch-based carbon fiber.

3. The method for preparing high-density and ultra-high-density carbon / carbon composite materials according to claim 1, characterized in that, The densification treatment is carried out by one or more of the following methods: chemical vapor infiltration, chemical vapor deposition, resin impregnation-carbonization, or asphalt impregnation-carbonization.

4. The method for preparing high-density and ultra-high-density carbon / carbon composite materials according to claim 3, characterized in that, The encryption process is as follows: First, a pyrolytic carbon interface layer is deposited on the surface of the carbon fiber preform using chemical vapor infiltration or chemical vapor deposition, and then resin impregnation-carbonization is used for densification; or pitch impregnation-carbonization is used to densify the carbon fiber preform.

5. The method for preparing high-density and ultra-high-density carbon / carbon composite materials according to claim 1, characterized in that, The conventional heat treatment is performed at 2100~2450 ℃ for 1~3 h under a protective atmosphere.

6. The method for preparing high-density and ultra-high-density carbon / carbon composite materials according to claim 1, characterized in that, The high-temperature and high-pressure alternating coupled field heat treatment includes a high-temperature and low-pressure treatment stage and a low-temperature and high-pressure treatment stage. The high-temperature and low-pressure treatment is performed at a temperature of 2500–2800 °C and a pressure of 5–25 MPa for 10–40 minutes. The low-temperature high-pressure treatment is performed at a temperature of 2000–2300 °C and a pressure of 50–80 MPa for 10–40 minutes.

7. The method for preparing high-density and ultra-high-density carbon / carbon composite materials according to claim 6, characterized in that, The high temperature and low pressure treatment is performed at a temperature of 2600–2700 ℃ and a pressure of 10–20 MPa for 15–20 min. The low-temperature high-pressure treatment is performed at a temperature of 2100–2200 °C and a pressure of 60–70 MPa for 15–20 minutes.

8. A high-density and ultra-high-density carbon / carbon composite material, characterized in that, The high-density carbon / carbon composite material is prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the high-density and ultra-high-density carbon / carbon composite materials as described in claim 8 in high-temperature ablation-resistant components.

10. The application according to claim 9, characterized in that, The high-temperature ablation-resistant components include aerospace thermal protection components, rocket engine nozzles or throat liners, and other structural or functional components used in extreme environments.

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