High-thermal-conductivity SiCf / SiC composite material and preparation method thereof

Abstract

The application discloses a high-thermal-conductivity SiC f / SiC composite material and a preparation method thereof, and the method comprises the following steps: pretreating a KD-SA type SiC fiber preform; depositing a carbon interface layer on the surface of the pretreated preform; placing the preform with the deposited carbon interface layer into a CVI SiC deposition furnace to perform chemical vapor deposition treatment, so as to obtain an intermediate with a deposited CVI SiC matrix; vacuum-impregnating the intermediate in liquid polycarbosilane precursor, impregnating for 5-8 hours, taking out, and then performing heat preservation at 140-160 DEG C for 1-3 hours under inert gas, and then performing heat preservation at 1000-1200 DEG C for 1-2 hours to perform cracking, and then cooling in the furnace, so as to obtain a crystalline PIP SiC matrix, and the vacuum impregnation is repeated for 6-8 times; preferably, high-temperature heat treatment is performed, so as to obtain a high-thermal-conductivity SiC f / SiC composite material. The composite material has the characteristics of high thermal conductivity and excellent high-temperature mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of ceramic matrix composite material preparation, and in particular, to a high thermal conductivity SiC f / SiC composite materials and their preparation methods. Technical Background

[0002] With the continuous improvement of thrust and thrust-to-weight ratio in aero-engines, the turbine inlet temperature needs to be continuously increased, and high-temperature alloy single-crystal blades are gradually unable to meet the service temperature requirements. SiC f / SiC composite materials possess excellent temperature resistance, excellent high-temperature oxidation resistance, low density, excellent high-temperature mechanical properties and creep resistance, and have gradually become one of the most promising candidate materials for hot-end components of aero-engines recognized internationally.

[0003] Most hot-end components of aero-engines are thin-walled, typically only a few millimeters or even 1-2 millimeters thick. Therefore, although some components may not experience significant loads during service, their location at the hot end of the aero-engine means they are subjected to rapid temperature changes both inside and outside the component, or front and back, resulting in a severe thermal stress environment. If the component has low thermal conductivity and cannot dissipate this heat, the thermal stress can be sufficient to cause crack initiation or even failure.

[0004] Reactive infiltration (RMI), chemical vapor infiltration (CVI), and precursor impregnation pyrolysis (PIP) are methods for preparing SiC. fCommon methods for preparing SiC composites include reactive infiltration, which utilizes the reaction of liquid Si or Si vapor with constructed SiC fibers / porous C intermediates at high temperatures to achieve densification. Due to the high preparation temperature (approximately 1500–1700℃), the SiC fibers require extremely high temperature resistance. Furthermore, the fibers are prone to silicification during the infiltration process, resulting in damage to the fiber structure and integrity, leading to performance degradation and loss of toughening effect. Additionally, some silicon residue remains during preparation; when the operating temperature exceeds the melting point of silicon, it melts and diffuses, causing a loss of material strength. This defect limits the application of the resulting composite material in high-temperature environments. Chemical vapor infiltration utilizes the pyrolysis of a gaseous precursor at high temperatures to gradually deposit products on the fiber surface and achieve densification. The advantages of chemical vapor infiltration (CVI) include low preparation temperature (~1000℃), minimal fiber damage, and the production of high-purity, highly crystalline SiC matrices, which are beneficial for strength, modulus, and resistance to water and oxygen corrosion. However, it suffers from low deposition rates, long processing times, high cost, and high porosity (close to 20%), making it unable to fill large and sharp pores between fiber bundles. Precursor impregnation (PIP) involves vacuum impregnating SiC fiber preforms with SiC precursors, followed by cross-linking and curing, and then high-temperature pyrolysis for ceramicization to achieve densification. Compared to reactive infiltration, it offers lower preparation temperatures (approximately 1000–1200℃), resulting in less fiber damage, no residual silicon phase, and near-net-shape forming, thus enabling the creation of complex shapes. However, the matrix obtained by PIP pyrolysis is typically porous due to the leakage of numerous small molecules during the pyrolysis process, and the ceramic yield is low. Furthermore, due to the volume shrinkage effect during the organic-to-inorganic conversion, the matrix obtained by PIP pyrolysis is often filled with microcracks and has an amorphous shape. The above two aspects (i.e., a porous matrix filled with microcracks) result in matrices prepared by PIP pyrolysis typically having relatively low thermal conductivity. Due to the high operating temperatures of hot-end components in aero-engines, composite materials with higher thermal conductivity are required to effectively and promptly transfer heat during service. Combined with appropriate cooling and heat dissipation designs, this improves heat dissipation efficiency, thereby enhancing the high-temperature resistance of hot-end components and extending their service life. Existing nickel-based superalloys have high density and a temperature limit of 1150℃.

[0005] Therefore, in order to meet the development requirements of new aero-engines for lightweight, high-temperature resistant ceramic matrix composites, there is an urgent need to develop a SiC material with high thermal conductivity. f / SiC composite materials are used to meet the application requirements of various thin-walled components in the hot end of aero engines. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention provides a high thermal conductivity SiC f / SiC composite material and its preparation method. The composite material prepared by the method of the present invention has good SiC matrix crystallinity, high density, high thermal conductivity, excellent high temperature resistance and high temperature mechanical properties, which can meet the application requirements of various thin-walled parts in the hot end of aero-engines.

[0007] To solve the above-mentioned technical problems, the present invention provides a high thermal conductivity SiC f The preparation method of / SiC composite material includes the following steps:

[0008] S1. Pre-treat the KD-SA type SiC fiber preform;

[0009] S2. A carbon interface layer is deposited and decomposed on the surface of the preform after the pretreatment in step S1.

[0010] S3. The preform obtained in step S2 is placed in a CVI SiC deposition furnace and subjected to chemical vapor deposition to obtain an intermediate with a CVI SiC matrix deposited on it; the density of the intermediate is 1.5-1.9 g / cm³. 3 ;

[0011] S4. The intermediate obtained in step S3 is vacuum impregnated in liquid polycarbosilane precursor for 5-8 hours. After being removed and dried, it is cross-linked and cured at 140-160℃ for 1-3 hours under inert gas. Then it is pyrolyzed at 1000-1200℃ for 1-2 hours and then cooled in the furnace to obtain a crystalline PIP SiC matrix. Repeat the above steps 6-8 times.

[0012] S5. Obtain SiC from step S4 f / SiC composite material, subjected to high-temperature heat treatment, yields SiC with high thermal conductivity. f / SiC composite materials;

[0013] In step S5, the high-temperature heat treatment conditions are: temperature 1400~1800℃, holding time 60min~120min.

[0014] Furthermore, in step S1, the KD-SA type SiC fiber is a reinforcing fiber, prepared at a temperature of 1900℃, with a grain size of 200-300nm; and the weaving method is 2.5D weaving.

[0015] Furthermore, in step S1, the pretreatment conditions for the KD-SA type SiC fiber preform are as follows: the SiC fiber preform is degummed at a temperature of 500-800℃ for 30-90 minutes under vacuum conditions.

[0016] Furthermore, in step S2, the specific process for depositing a carbon interface layer of pyrolysis on the surface of the preform after pretreatment in step S1 is as follows: the preform obtained in step S1 is placed in a CVI C deposition furnace, using propylene as the source gas and hydrogen as the carrier gas, with a propylene flow rate of 140-160 ml / min and a hydrogen flow rate of 140-160 ml / min, a deposition temperature of 900-1050℃, a deposition pressure of 1.5-2 kPa, and a deposition time of 10-15 h.

[0017] Furthermore, in step S2, the thickness of the resulting pyrolytic carbon interface layer is 200-400 nm.

[0018] Furthermore, in step S3, the specific process of chemical vapor deposition is as follows: the preform obtained in step S2 is placed in a CVI SiC deposition furnace, with methyltrichlorosilane as the precursor, hydrogen as the carrier gas, and argon as the dilution gas. The hydrogen flow rate is 280-320 ml / min, the argon flow rate is 180-220 ml / min, the deposition temperature is 1050-1100℃, the deposition pressure is 1.3-1.5 kPa, and the deposition time is 80-120 h.

[0019] Furthermore, in step S4, the inert atmosphere is nitrogen or argon with a purity of 99.999%.

[0020] This invention also provides a high thermal conductivity SiC f The / SiC composite material was prepared according to the above preparation method.

[0021] Furthermore, the high thermal conductivity SiC f The thermal conductivity of the SiC composite material is 10–25 W / m·K, and the density is ≥2.6 g / cm³. 3 .

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] 1. This invention provides a high thermal conductivity SiC f The preparation method of β-SiC composite material first uses KD-SA type SiC fibers as reinforcing fibers, then introduces a crystalline β-SiC matrix through CVI deposition and VHPCS impregnation-pyrolysis, and finally further improves the crystallinity of the matrix through high-temperature heat treatment at 1400-1800℃. Therefore, the high thermal conductivity SiC prepared by the method of this invention... f The SiC composite material exhibits a uniform structure, high density, and thermal conductivity comparable to nickel-based superalloys. The SiC obtained in this invention... f The density of the SiC composite material reaches 2.6 g / cm³. 3The thermal conductivity at room temperature is 16.147 W / m·K, and it first increases and then decreases slightly with increasing temperature, reaching a maximum of 20.744 W / m·K at 1000℃.

[0024] 2. The method of this invention uses KD-SA type SiC fiber as the reinforcing fiber of the composite material. KD-SA type SiC fiber, with its high crystallinity and near-stoichiometry, has high thermal conductivity and excellent temperature resistance, which can improve the performance of SiC composites. f The overall thermal conductivity and temperature resistance of the SiC composite material are relatively stable. Because the KD-SA type SiC fiber is prepared at 1900℃ and its grain size is relatively large, ranging from 200 to 300 nm, subsequent heat treatment at temperatures lower than the preparation temperature will not cause the fiber grains to grow, thus its strength is relatively stable.

[0025] 3. In the method of this invention, the PIP process uses liquid polycarbosilane (VHPCS) as a precursor, which is introduced into the matrix, which is also a highly crystalline PIP SiC matrix, through impregnation-curing-pyrolysis. Firstly, liquid polycarbosilane (VHPCS) is liquid at room temperature, requiring no solvent and resulting in high impregnation efficiency. Secondly, when heated, the active groups of liquid polycarbosilane undergo a cross-linking reaction, forming a three-dimensional network structure of macromolecules, effectively reducing the volatilization of small organic molecules and achieving a higher ceramic yield and a denser microstructure. Furthermore, its pyrolysis products are crystalline β-SiC grains with stable crystal phases, exhibiting a nano-polycrystalline morphology. High-temperature heat treatment further improves crystallinity, resulting in a SiC matrix with higher thermal conductivity and greater uniformity and density. The SiC prepared by this invention... f SiC composite materials, from the reinforcing SiC fibers to the SiC matrix, are composed of highly crystalline components with high density, low porosity, and minimal thermal scattering caused by pores. Therefore, SiC... f / SiC composites have high thermal conductivity.

[0026] 4. In the method of this invention, the substrates introduced through CVI and PIP processes are both highly crystalline β-SiC substrates. The substrate deposited by the CVI process is a crystalline β-SiC substrate, while the PIP process uses liquid polycarbosilane (VHPCS) as a precursor, and the substrate introduced after impregnation-curing-pyrolysis is also a highly crystalline PIP SiC substrate. Therefore, the SiC prepared by this invention... f / SiC composite materials, from the reinforcing SiC fibers to the SiC matrix, are all crystalline matrices with high thermal conductivity, which can effectively improve the SiC... fThe overall thermal conductivity of the β-SiC composite material was assessed. Finally, a high-temperature heat treatment at 1400℃-1800℃ was performed. With increasing heat treatment temperature, the diffraction peaks of β-SiC significantly increased, indicating a significant improvement in its crystallinity. Furthermore, the high-temperature heat treatment facilitated the sintering of the matrix after precursor decomposition, further increasing the matrix density. Therefore, the final high-temperature heat treatment can further improve the crystallinity and density of the matrix, thereby enhancing its thermal conductivity and high-temperature resistance, thus meeting the application requirements of various thin-walled components in the hot-end of aero-engines.

[0027] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0029] Figure 1 The high thermal conductivity SiC prepared in Example 1 of this invention f / SEM image of SiC composite material cross section;

[0030] Figure 2 The SiC samples prepared in Examples 1, 2, 2, and 3 are examples of this study. f Comparison of thermal conductivity of SiC composite materials;

[0031] Figure 3 The SiC prepared in Examples 1-3 and Comparative Example 2 are f XRD pattern of the SiC composite material;

[0032] Figure 4 The SiC prepared in Example 2 and Comparative Example 2 f A comparison of the thermal conductivity of SiC composite materials at different temperatures with that of nickel-based superalloys. Detailed Implementation

[0033] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, the present invention may be implemented in many different ways as defined and covered by the claims.

[0034] Example 1:

[0035] A high thermal conductivity SiC f The preparation method of / SiC composite material includes the following steps:

[0036] KD-SA type SiC fiber preforms with S1 and 2.5D braiding methods are heat-preserved at 600℃ for 1 hour under vacuum conditions for degumming treatment.

[0037] S2. The preform obtained in S1 is placed in a CVI C deposition furnace, with propylene (C3H6) as the source gas and hydrogen (H2) as the carrier gas. The propylene flow rate is 150 ml / min, the hydrogen flow rate is 150 ml / min, the deposition temperature is 960℃, the deposition pressure is 2 kPa, and the deposition time is 12 h. A cracked carbon (PyC) interface layer is deposited on the surface of SiC fiber.

[0038] S3. The preform obtained in S2 is placed in a CVI SiC deposition furnace. Methyltrichlorosilane (MTS) is used as a precursor, hydrogen (H2) is used as a carrier gas, and argon (Ar) is used as a dilution gas. The hydrogen flow rate is 300 ml / min and the argon flow rate is 200 ml / min. The CVI SiC matrix is ​​deposited at 1075℃ and 1.4 kPa pressure for 120 h to obtain an intermediate with a certain density.

[0039] S4. The intermediate obtained in S3 is vacuum impregnated in liquid polycarbosilane (VHPCS) precursor for 5-8 hours. After being removed and dried, it is cross-linked and cured at 150°C for 2 hours under nitrogen protection. Then, it is pyrolyzed at 1200°C for 1 hour under argon atmosphere and cooled in the furnace to obtain a crystalline PIP SiC matrix. The PIP cycle is repeated 8 times.

[0040] S5, Obtain SiC from S4 f The SiC composite material was subjected to high-temperature heat removal treatment at 1400℃ for 1 hour under vacuum conditions to obtain SiC with high thermal conductivity. f / SiC composite material.

[0041] Example 2:

[0042] The difference between Example 2 and Example 1 is that in step S5, the heat treatment temperature is 1800℃, while the rest is the same as in Example 1.

[0043] Example 3:

[0044] The difference between Example 2 and Example 1 is that in step S5, the heat treatment temperature is 1600℃, while the rest is the same as in Example 1.

[0045] Comparative Example 1:

[0046] The difference between Comparative Example 1 and Example 1 is that in step S1, second-generation SiC fiber is used as the reinforcing fiber, while the rest is the same as in Example 1.

[0047] Comparative Example 2:

[0048] The difference between Comparative Example 2 and Example 1 is that the operation in step S5 is not performed, while the remaining steps are the same as in Example 1.

[0049] Comparative Example 3:

[0050] The difference between Comparative Example 3 and Example 1 is that: (1) a polycarbosilane (PCS) xylene solution is used as a precursor for the PIP process in step S4; (2) the operation in step S5 is not performed; the remaining steps are the same as in Example 1.

[0051] Comparative Example 4:

[0052] The difference between Comparative Example 4 and Example 1 is that in step S5, the heat treatment temperature is 2000℃, and the rest is the same as in Example 1.

[0053] Comparative Example 5:

[0054] The difference between Comparative Example 5 and Example 1 is that in step S5, the heat treatment temperature is 1300°C, and the rest is the same as in Example 1.

[0055] The basic properties of second-generation SiC fibers and KD-SA fibers are shown in Table 1. As can be seen from Table 1, the preparation temperature of second-generation SiC fibers is 1300℃ (long-term service temperature is 1250℃). In fact, second-generation SiC fibers contain excessive disordered graphitic carbon and have small SiC grain sizes (only 5-10 nm). When the heat treatment temperature exceeds the preparation temperature, it causes grain growth in the second-generation SiC fibers, leading to a significant decrease in fiber strength. In contrast, KD-SA type SiC fibers are prepared at 1900℃, and their grain sizes are relatively large, ranging from 200 to 300 nm. When the subsequent heat treatment temperature is lower than the preparation temperature, it does not cause grain growth, thus its strength is relatively stable. Therefore, the SiC fibers prepared in Comparative Example 1... f After being heat-treated at 1400℃, the SiC composite material exhibits a severe decrease in room temperature bending mechanical properties and is prone to brittle fracture.

[0056] Table 1. Basic properties of second-generation SiC fibers and KD-SA type SiC fibers.

[0057]

[0058]

[0059] Figure 1 The high thermal conductivity SiC prepared in Example 1 f / SEM image of a cross-section of a SiC composite material. (Source: [Insert image here]) Figure 1 It can be seen that the high thermal conductivity SiC prepared in Example 1 f The SiC composite material exhibits a uniform and dense microstructure.

[0060] Figure 2 The SiC samples prepared in Examples 1, 2, 2, and 3 of this invention are as follows. f Comparison of thermal conductivity of SiC composite materials. Figure 3 SiC prepared in Examples 1-3 and Comparative Example 2 f XRD pattern of the / SiC composite material. Figure 4 The SiC samples prepared in Example 2 and Comparative Example 2 of this invention are examples of SiC samples prepared in this invention. f The thermal conductivity of the SiC composite material varies with temperature, and a horizontal comparison is made with that of nickel-based superalloys.

[0061] Table 2 compares the density and thermal conductivity data of Examples 1-3, Comparative Examples 1-5, nickel-based superalloys and RMI SiCf / SiC composite materials.

[0062] Table 2. Examples, Comparative Examples, Nickel-based Superalloys and RMI SiC f Comparison of density and thermal conductivity data of SiC composite materials

[0063]

[0064]

[0065] Depend on Figure 2 As shown in Table 2, the SiC prepared in Examples 1, 2 and Comparative Example 2... f The thermal conductivity of the SiC composite material is compared to that of the SiC prepared in Comparative Example 3. fThe SiC composite material showed significant improvement. Comparisons showed that the composite material prepared by the method of this invention had higher thermal conductivity and higher density. This is because Examples 1, 2, and Comparative Example 2 used KD-SA type SiC fibers as reinforcing fibers and liquid polycarbosilane (VHPCS) as a precursor for the PIP process; while Comparative Example 3 used second-generation SiC fibers as reinforcing fibers and a polycarbosilane (PCS) xylene solution as a precursor for the PIP process. Liquid polycarbosilane (VHPCS) is liquid at room temperature, requires no solvent, and has high impregnation efficiency. When heated, the active groups of liquid polycarbosilane undergo a cross-linking reaction, forming a three-dimensional network structure of macromolecules, which effectively reduces the volatilization of small organic molecules, resulting in higher ceramic yield and a denser microstructure. Its pyrolysis products are crystalline β-SiC grains with stable crystal phases, exhibiting a nano-polycrystalline morphology. High-temperature heat treatment further improved crystallinity, resulting in a SiC matrix with higher thermal conductivity and greater uniformity and density. Polycarbosilane (PCS) is solid at room temperature and requires solvent dissolution before it can be used to impregnate preforms. Due to the presence of the solvent, some PCS is carried away by solvent evaporation during the crosslinking and curing process, thus reducing the filling effect on pores and decreasing impregnation efficiency. Furthermore, the escape of a large number of low-molecular-weight components during pyrolysis results in a porous SiC matrix filled with microcracks, which typically exhibits relatively low thermal conductivity. Figure 3 It can be seen that the matrix obtained by liquid polycarbosilane pyrolysis exhibits obvious β-SiC diffraction peaks, indicating that it is not an amorphous structure. Therefore, the SiC prepared in this invention... f The SiC composite material, from the reinforcing SiC fibers to the SiC matrix, consists of highly crystalline components with high density, low porosity, and minimal thermal scattering caused by the pores. Therefore, the prepared SiC... f / SiC composites have high thermal conductivity.

[0066] The purpose of step five, high-temperature heat treatment, in this invention is to prevent damage to SiC. f While maintaining the strength of the SiC composite material, it is essential to maximize the crystallinity of the matrix to improve its thermal conductivity. As shown in Comparative Example 5, at a heat treatment temperature of 1300℃, SiC… f The thermal conductivity of the SiC composite material shows only a slight improvement compared to the untreated composite (as shown in Table 2). Figure 3 As shown, the diffraction peaks of β-SiC significantly increase with increasing heat treatment temperature, indicating that the crystallinity of the SiC matrix gradually improves. On the other hand, high-temperature heat treatment facilitates the sintering of the matrix after precursor decomposition, further increasing the matrix density. Therefore, increasing the heat treatment temperature can improve the crystallinity and density of the matrix, thereby enhancing its thermal conductivity and high-temperature resistance (see Table 2 for details). Figure 2 and Figure 4However, when the heat treatment temperature exceeds the fiber preparation temperature (Comparative Example 4), the fiber properties are damaged, resulting in poor SiC quality. f The SiC composite material suffers severe strength damage and exhibits brittle fracture. Based on this, SiC... f The heat treatment temperature for the SiC composite material is selected as 1400℃-1800℃, and the reinforcement used is KD-SA type SiC fiber preform.

[0067] In addition, Table 2 lists nickel-based superalloys and RMI-prepared SiC from Examples 1-3, Comparative Examples 1-5, and other literature. f Comparison of thermal conductivity data of / SiC composite materials at room temperature and high temperature. (From Table 2 and...) Figure 4 It can be seen that the SiC prepared by this invention f The SiC composite material has a higher density. Although its room temperature thermal conductivity is lower than that of RMI, its high-temperature thermal conductivity is higher. Due to the high preparation temperature of RMI, thermal damage to SiC fibers and the presence of residual silicon significantly limit the service temperature of RMI products. Nickel-based superalloys have higher thermal conductivity at high temperatures than the SiC prepared in this invention. f While SiC composite materials offer higher performance, the advantages of this invention are better demonstrated by considering the high density and limited high-temperature resistance of nickel-based superalloys.

[0068] In summary, this invention provides a high thermal conductivity SiC f The preparation method of β-SiC composite material first uses KD-SA type SiC fibers as reinforcing fibers, then introduces a crystalline β-SiC matrix through CVI deposition and VHPCS impregnation-pyrolysis, and finally further improves the crystallinity of the matrix through high-temperature heat treatment at 1400-1800℃. Therefore, the high thermal conductivity SiC prepared by the method of this invention... f The SiC composite material exhibits a uniform structure, high density, and thermal conductivity comparable to nickel-based superalloys. The SiC obtained in this invention... f The density of the SiC composite material reaches 2.6 g / cm³. 3 The thermal conductivity at room temperature is 16.147 W / m·K, and it first increases and then decreases slightly with increasing temperature, reaching a maximum of 20.744 W / m·K at 1000℃.

[0069] Because the preparation temperature of KD-SA type SiC fibers is 1900℃ and their grain size is relatively large (200-300 nm), subsequent heat treatment at temperatures lower than the preparation temperature will not cause grain growth, thus resulting in relatively stable strength. This invention uses KD-SA type SiC fibers as reinforcing fibers in composite materials. KD-SA type SiC fibers with high crystallinity and near-stoichiometry possess high thermal conductivity and excellent temperature resistance, which can improve the strength of SiC... f The SiC composite material exhibits improved overall thermal conductivity and temperature resistance. Furthermore, the matrices introduced through CVI and PIP processes in this invention are both highly crystalline β-SiC matrices. The CVI process deposits a crystalline β-SiC matrix, while the PIP process uses liquid polycarbosilane (VHPCS) as a precursor, introducing a highly crystalline PIP SiC matrix after impregnation, curing, and pyrolysis. Finally, a high-temperature heat treatment at 1400℃-1800℃ is performed. With increasing heat treatment temperature, the diffraction peaks of β-SiC significantly enhance, indicating a significant improvement in its crystallinity. On the other hand, high-temperature heat treatment facilitates the sintering of the matrix after precursor pyrolysis, further increasing the matrix density. Therefore, the final high-temperature heat treatment further improves the crystallinity and density of the matrix, thereby enhancing its thermal conductivity and high-temperature resistance, thus meeting the application requirements of various thin-walled components in the hot-end of aero-engines. Therefore, the SiC prepared in this invention… f / SiC composite materials, from the reinforcing SiC fibers to the SiC matrix, are all crystalline matrices with high thermal conductivity, which can effectively improve the SiC... f The overall thermal conductivity of the SiC composite material.

[0070] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high thermal conductivity SiC f The method for preparing / SiC composite materials is characterized by, Includes the following steps: S1. Pre-treatment of KD-SA type SiC fiber preforms; specifically: degumming of SiC fiber preforms at 500-800℃ for 30-90 minutes under vacuum conditions; the KD-SA type SiC fiber is a reinforcing fiber, prepared at 1900℃, with a grain size of 200-300 nm. S2. A carbon interface layer is deposited and decomposed on the surface of the preform after the pretreatment in step S1. The specific process is as follows: the preform obtained in step S1 is placed in a CVI C deposition furnace, with propylene as the source gas and hydrogen as the carrier gas. The propylene flow rate is 140-160 ml / min, the hydrogen flow rate is 140-160 ml / min, the deposition temperature is 900-1050℃, the deposition pressure is 1.5-2 kPa, and the deposition time is 10-15 h. S3. The preform obtained in step S2 is placed in a CVI SiC deposition furnace and subjected to chemical vapor deposition to obtain an intermediate with a CVI SiC matrix deposited on it; the density of the intermediate is 1.5-1.9 g / cm³. 3 The specific process of chemical vapor deposition is as follows: the preform obtained in step S2 is placed in a CVI SiC deposition furnace, with methyltrichlorosilane as the precursor, hydrogen as the carrier gas, and argon as the dilution gas. The hydrogen flow rate is 280-320 ml / min, the argon flow rate is 180-220 ml / min, the deposition temperature is 1050-1100 °C, the deposition pressure is 1.3-1.5 kPa, and the deposition time is 80-120 h. S4. The intermediate obtained in step S3 is vacuum impregnated in liquid polycarbosilane precursor for 5-8 hours. After being removed and dried, it is cross-linked and cured at 140-160℃ for 1-3 hours under inert gas. Then it is pyrolyzed at 1000-1200℃ for 1-2 hours and then cooled in the furnace to obtain a crystalline PIP SiC matrix. Repeat the above steps 6-8 times. S5. Obtain SiC from step S4 f / SiC composite materials are subjected to high-temperature heat treatment to improve the crystallinity and density of CVI SiC and PIP SiC matrices, thereby enhancing thermal conductivity and obtaining high thermal conductivity SiC. f / SiC composite materials; In step S5, the high-temperature heat treatment conditions are: temperature 1400~1800℃, holding time 60min~120min; The high thermal conductivity SiC f The thermal conductivity of the SiC composite material is 10~25 W / m·K, and the density is ≥2.6 g / cm³. 3 .

2. The high thermal conductivity SiC according to claim 1 f The method for preparing / SiC composite materials is characterized by, In step S1, the KD-SA type SiC fiber is woven using a 2.5D weave.

3. The high thermal conductivity SiC according to claim 1 f The method for preparing / SiC composite materials is characterized by, In step S2, the thickness of the resulting pyrolytic carbon interface layer is 200-400 nm.

4. The high thermal conductivity SiC according to claim 1 f The method for preparing / SiC composite materials is characterized by, In step S4, the inert gas is nitrogen or argon with a purity of 99.999%.

5. A high thermal conductivity SiCf / SiC composite material, characterized in that, Prepared by the preparation method according to any one of claims 1-4.

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