CN113754442B - A kind of SiC/SiC composite material high density multilayer matrix and preparation method - Google Patents

Abstract

The invention relates to a high-density multi-layer substrate of SiC/SiC composite material and a preparation method. The prepared SiC particle (SiC _p ) slurry is introduced into the porous SiC/SiC composite material by the methods of vacuum impregnation and pressure impregnation, Then, a certain content of pyrolytic carbon was prepared in porous SiC/SiC composites by CVI method, so that the SiC particles were evenly wrapped. Finally, the densification of SiC/SiC composites was completed by the reaction of pyrolytic carbon and molten silicon by RMI method. The sequential introduction of SiC particles with different particle sizes forms a layered structure, which has a genetic effect on the subsequent preparation of PyC and SiC matrix, and obtains a uniform and high volume fraction of SiC matrix phase, which increases the density of the composite material and increases the energy of crack propagation. Effectively improve the mechanical properties of composite materials. The composite material prepared by this method has a SiC matrix phase with high volume fraction and uniform distribution, high mechanical properties and low open porosity, which solves the problem of low SiC phase content and uneven distribution and strong toughness in the SiC/SiC matrix prepared by the current RMI process. insufficient problem.

Description

A kind of SiC/SiC composite material high density multilayer matrix and preparation method

technical field

The invention belongs to a preparation method of a composite material, and relates to a high-density multi-layer matrix of a SiC/SiC composite material and a preparation method.

Background technique

SiC/SiC composites have great application prospects in aerospace thermal structural components and other fields due to their many advantages such as high temperature resistance, wear resistance, corrosion resistance, high specific strength, high specific modulus, high toughness, and creep resistance. With the continuous development of my country's aerospace industry, the engine thrust-to-weight ratio has gradually increased, the high bypass ratio and total pressure ratio have continued to increase, higher service temperatures, higher stress requirements and corrosive environments. SiC is used for engine hot end structural components. /SiC composites put forward higher strength and toughness, higher damage tolerance, and higher density requirements. The preparation process of the material determines its microstructure and properties. It is urgent to develop advanced technology to prepare high-density, high-strength and tough SiC/SiC composites to meet new challenges.

The preparation methods of SiC/SiC include CVI (chemical vapor infiltration), PIP (precursor impregnation cracking), MI (melt infiltration), RMI (reactive melt infiltration) and combined processes. The composites prepared by CVI and PIP methods have large open porosity (10%-15%), which are easy to fail in high temperature corrosive environment, and do not meet the requirements of high density; the composites prepared by MI have a large amount of residual silicon (~13%). %) poor mechanical properties, when the temperature exceeds the melting point of Si, the performance drops sharply, and it is difficult to adapt to the high temperature and complex stress conditions of aero-engine; RMI process has the characteristics of short cycle, high density of composite materials, excellent mechanical properties, etc. The preferred method for SiC. During the RMI process, there may be a problem of the corrosion of the interface and fibers by the Si melt. Generally, the CVI method is used to deposit a certain thickness of protective layer on the interface surface to isolate the corrosion of the interface and fibers by the Si melt. It can be seen that the combination process of CVI combined with RMI is expected to obtain dense SiC/SiC with good performance.

Although layered SiC can be deposited on the interface surface by the CVI process, the CVI SiC mainly plays a protective role, and the matrix phase prepared by the RMI process is the key factor affecting the performance of the final SiC/SiC. The matrix prepared by the RMI method is generally a homogeneous or doped modified phase with a single structure, which cannot achieve good crack deflection, consumes crack energy, and achieves a high toughness matrix to meet the requirements of aero-engine thermal shock resistance. For example, Wang et al. The dense SiC/SiC composite prepared by reactive melt infiltration (RMI) technology has a bending strength of 288.2±0.88MPa and a fracture toughness of 16.0±0.25GPa, which is difficult to meet the high-strength and toughness stress requirements of aero-engines. Therefore, the structural design of the composite matrix prepared by the RMI method must be carried out.

The matrix of high-toughness ceramic matrix composites generally has a multi-layer structure, and the crack propagation energy can be effectively consumed by the deflection of cracks between layers, and the toughness of the material can be improved. The multi-layer matrix structure design mostly appears in the CVI matrix and the MAX phase modified matrix. For example, Xu Yongdong, Cheng Laifei, etc. can use the CVI process to prepare SiC/SiC composites with a multi-layer matrix structure, and the toughness is as high as 41.5MPa.m^ 1/2. However, the multilayer matrix structure has not been reported in the RMI process. In this work, slurry impregnated (SI) submicron SiC particles are used to coat CVI SiC protective layer, SI micron SiC particles fill the pores, and then CVI PyC is attached to the surface of SiC particles. , the inter-particle liquid silicon permeation channels are preserved, and a highly dense multilayer structure matrix is obtained after RMI.

SUMMARY OF THE INVENTION

technical problem to be solved

In order to avoid the deficiencies of the prior art, the present invention proposes a high-density multi-layer matrix of SiC/SiC composite material and a preparation method, and proposes a slurry impregnation (SI) combined with chemical vapor infiltration (CVI) and reactive melt infiltration (RMI) Method for preparing high-density SiC/SiC composites with multi-layer matrix structure.

Technical solutions

A high-density multi-layer matrix of SiC/SiC composite material, comprising SiC fibers, BN and CVI SiC; it is characterized in that: the SiC particle layer is the first layer structure outside the CVI SiC, and the outside of the SiC particle layer is SiC obtained by a dissolution-precipitation mechanism The reaction barrier layer and the SiC reaction diffusion layer controlled by the diffusion mechanism are formed, and then the Si thin layer composed of SiC nanocrystals wraps the SiC particle layer, the barrier layer and the diffusion layer, and the outermost layer is the SiC coarse-grained layer; the SiC particle layer It includes SiC _P with adherent distribution obtained by dipping, layered SiC _R formed by the reaction of PyC deposited on the surface of CVI SiC by CVI, and SiC nanocrystals and Si formed by dissolution and desorption of PyC; the SiC coarse-grained layer is composed of micron-sized particles Obtained by filling.

A method for preparing a high-density multilayer matrix of the SiC/SiC composite material, characterized in that the steps are as follows:

Step 1. Preparation of porous SiC/SiC composite material: use CVI process to deposit BN interface on the woven SiC fiber, and then use CVI process to deposit SiC matrix to a semi-densified state to obtain porous SiC/SiC composite material;

Step 2. Configure 300-500nm SiC particle water-based slurry: add 0.5-1.0 wt.% tetramethylammonium hydroxide TMAH and 3-5 vol.% SiC particles into deionized water, ball-milled Then obtain a uniformly dispersed slurry;

Step 3. Impregnation of 300-500nm SiC particle water-based slurry:

Vacuum impregnation: Put the porous SiC/SiC composite material into a glass drying dish, evacuate until the pressure in the glass dish is lower than 0.09Mpa, and keep it for 10 to 20 minutes, then immerse the SiC/SiC composite material in the slurry obtained in step 2 to maintain 10～15min;

Pressure impregnation: Put the porous SiC/SiC composite material together with the slurry into a closed container and pressurize it to 0.8Mpa, keep it for 20-30min, take it out, and dry it;

Step 4. Configure 3-5 μm SiC particle water-based slurry: add 0.1-0.3 wt.% tetramethylammonium hydroxide TMAH and 3-10 vol.% SiC particles into deionized water, ball-milled Then obtain a uniformly dispersed slurry;

Step 5. Impregnation of 3-5μm SiC particle water-based slurry:

Vacuum impregnation: Put the porous SiC/SiC composite material into a glass drying dish, evacuate until the pressure in the glass dish is lower than 0.09Mpa, and keep it for 20 to 30 minutes, then immerse the SiC/SiC composite material in the slurry obtained in step 4 to maintain 20～30min;

Pressure impregnation: Put the SiC/SiC composite material together with the slurry into a closed container and pressurize it to 0.8Mpa, keep it for 10-20min, take it out, and dry it;

Step 6, CVI pyrolytic carbon: put the impregnated SiC/SiC-SiCp into the CVI pyrolytic carbon deposition furnace to deposit pyrolytic carbon for 30-80 hours;

Step 7. Liquid silicon infiltration: wrap the SiC/SiC-SiCp-PyC composite material on which the pyrolytic carbon has been deposited with Si powder, and wrap the outermost layer with graphite paper, and then put the composite material wrapped with Si powder into the silicon infiltration furnace In the process, liquid silicon infiltration was performed in a vacuum environment of 1430-1550 °C for 20-60 min to complete the preparation of SiC/SiC composites.

The ball milling of the step 2: adding zirconia ball milling beads to the ball milling tank, wet milling for 20-24 hours, and the ball milling speed is 100-300 r/min.

The ball milling of the step 2: adding zirconia ball milling beads to the ball milling tank, wet milling for 10-12 hours, and the ball milling speed is 80-120 r/min.

beneficial effect

The present invention proposes a high-density multi-layer matrix of SiC/SiC composite material and a preparation method. First, the prepared small-size and large-size SiC particle (SiC _p ) slurry is introduced into the vacuum impregnation method and pressure impregnation method successively. In the porous SiC/SiC composite material, a certain content of pyrolytic carbon (PyC) was prepared in the porous SiC/SiC composite material by the CVI method to make it evenly wrap the SiC particles. The reaction completes the densification of the SiC/SiC composite. The sequential introduction of SiC particles with different particle sizes forms a layered structure, which has a genetic effect on the subsequent preparation of PyC and SiC matrix, which not only obtains a uniform and high volume fraction of the SiC matrix phase, effectively increases the density of the composite material, and increases crack propagation. The energy can effectively improve the mechanical properties of composite materials. The composite material prepared by this method has a SiC matrix phase with high volume fraction and uniform distribution, high mechanical properties and low open porosity, which solves the problem of low SiC phase content and uneven distribution and strong toughness in the SiC/SiC matrix prepared by the current RMI process. insufficient problem.

The thickness of the SiC particle layer and the pore structure formed by the accumulation of SiC particles are controlled by adjusting the volume fraction and the number of immersion times in the SiC slurry; by adjusting the temperature and time of the CVI pyrolytic carbon, the thickness of the outer pyrolytic carbon coating layer of the SiC particles is controlled and the morphology of the silicon infiltration pore channels; by adjusting the liquid silicon infiltration temperature and time, the liquid silicon infiltration depth and the carbon-silicon reaction degree are controlled, thereby realizing the optimization of the density and mechanical properties of the composite material.

The beneficial effects of the invention are:

1. Sequential introduction of small-sized and large-sized SiC particles (3-5 μm SiC, 300-500 nm SiC) forms a structure in which small-sized particles coat CVI SiC and large-sized particles fill pores. Coating CVI SiC with small-sized particles effectively hinders the erosion of silicon melt, and at the same time provides the possibility for the design of multilayer matrix structures; filling pores with large particles increases the volume fraction of SiC phase in the final composite and reduces the composite’s Open porosity.

2. The introduction of micron/submicron-scale SiC particles increases the specific surface area of the material, which not only accelerates the deposition rate of CVI pyrolytic carbon, but also produces a structure-induced effect on CVI pyrolytic carbon, which improves the degree of order of the pyrolytic carbon , which is conducive to the siliconization reaction.

3. CVI pyrolytic carbon-wrapped SiC particles are uniformly distributed, and the SiC matrix-wrapped SiC particles generated by the reaction of pyrolytic carbon and liquid silicon after RMI can also achieve uniform distribution, which is beneficial to the control of the composite phase composition.

4. While the pyrolytic carbon wraps the SiC particles, it also fills the pores inside the fiber bundle. After silicon infiltration, the SiC-wrapped SiC particles generated by the RMI reaction outside the fiber bundle and the SiC generated by the RMI reaction inside the fiber bundle are formed. This high SiC phase matrix composition feature is not only conducive to improving the density of the material, but also significantly Improve the mechanical properties of materials.

The introduction of SiC particles not only increases the content of SiC phase in the matrix, but also acts as a reinforcing phase to increase the cracking energy and increase the crack propagation path. Small-sized SiC particles and PyC coat CVI SiC and form a multi-layered RMI matrix after silicon infiltration, which is beneficial to improve the toughness of the material. The large-sized SiC particles are mostly distributed in the center of the pores of the porous SiC/SiC composites, and the surface of which is pyrolyzed and siliconized to form a dense matrix of reactive SiC to connect the SiC particles, which is beneficial to improve the strength of the material.

Description of drawings

Fig. 1 is the process flow diagram of the preparation method involved in the present invention.

FIG. 2 is a schematic diagram of the microstructure and composition of the SiC/SiC composite material prepared by the present invention.

It can be seen from the figure: the SiC particle layer is the first layer structure outside the CVI SiC, which mainly includes the adherent distribution of SiC _P obtained by dipping, and the layered SiC _R and PyC formed by the reaction of PyC deposited by CVI on the surface of CVI SiC. SiC nanocrystals and a small fraction of Si. This layer structure effectively hinders the erosion of the Si melt. The outside of the SiC particle layer is the SiC reaction barrier layer obtained by the dissolution-precipitation mechanism and the SiC reaction diffusion layer controlled by the diffusion mechanism. The Si thin layer composed of a large amount of Si and SiC nanocrystals formed by a small amount of reaction wraps the SiC particle layer, the barrier layer and the diffusion layer. The SiC coarse-grained layer is the outermost wrapping structure, which is characterized by homogeneous nucleation and growth of SiC, small growth obstruction, and coarse grains. After the adjacent grains contact, the growth stops and is connected into an irregular layer. The above multilayer matrix structure can effectively improve the fracture toughness of the material, which is 37.77±2.03.

The outermost layer of SiC particles is mainly obtained by filling pores with micron-sized particles. The main function of this layer is to increase the content of SiC phase in the matrix phase of the composite material. In addition, SiC particles can also deflect matrix cracks and improve the material strength. The room temperature bending strength of the composite material is 577.59±9.55.

FIG. 3 is a backscattering (BSE) photograph of the polished cross-sectional morphology of the SiC/SiC composite prepared in Example 3. FIG.

FIG. 4 is the X-ray diffraction (XRD) patterns of the SiC/SiC composites prepared in Examples 1, 2 and 3. FIG.

Detailed ways

The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

The method steps of preparing SiC/SiC composites by slurry impregnation (SI) combined with chemical vapor infiltration (CVI) and reactive melt infiltration (RMI) are as follows:

Step 1. Preparation of SiC/SiC preform:

In step 1.1, a SiC fiber braid is used to prepare a boron nitride (BN) interface phase on its surface, and the thickness of the interface phase is 300-500 nm.

In step 1.2, a CVI process is used to prepare a SiC matrix with a certain volume fraction in the SiC fiber preform obtained in step 1.1. Using trichloromethylsilane (MTS) as the precursor, hydrogen as the carrier gas, argon as the diluent gas, the flow ratio of the three is 1:5~50:2~20, the total pressure is 0.5~5kPa, and the deposition temperature is 873 ~1773K, the deposition time is about 600 hours. Thereby, a porous SiC/SiC composite material with a porosity of 28-36% and a density of 1.7-2.1 g/cm ³ is obtained, which is used for subsequent slurry impregnation.

Step 2. Configure 300-500nm SiC particle water-based slurry:

Step 2.1 Add SiC particles with a particle size of 300 to 500 nm and a volume fraction of 10 vol.% into HF acid, and magnetically stir at room temperature for 24 hours. The acid-washed SiC particles were centrifuged twice with deionized water and absolute ethanol at a speed of 5000 r/min, respectively, to obtain SiC particles with surface _SiO2 removed.

Step 2.2 Disperse tetramethylammonium hydroxide (TMAH) with a mass fraction of 0.5 to 1.0 wt.% in deionized water, and stir magnetically at room temperature to prepare a uniform solution.

Step 2.3 Add the SiC particles obtained in step 2.1 to the dispersion obtained in step 2.2, and then add an appropriate amount of zirconia ball milling beads into the ball milling jar, and wet-mill in the ball milling jar for 20 to 24 hours at a ball milling speed of 100 to 100 300 r/min to obtain a uniformly dispersed SiC slurry with a volume fraction of 3-5 vol.%.

Step 3. Impregnation of 300-500nm SiC particle water-based slurry:

Step 3.1 Put the porous SiC/SiC composite material and the SiC particle slurry prepared in step 2.3 into a glass drying dish, evacuate until the pressure in the glass dish is lower than 0.09MPa, and keep the porous SiC/SiC composite material after 10-20min. Immerse in the slurry for 10-15min.

Step 3.2 Put the porous SiC/SiC composite material together with the slurry into an airtight container and pressurize it to 0.8MPa, keep it for 20-30min, take it out, and dry it at 150°C for 3 hours.

Step 4. Configure 3~5μm SiC particle water-based slurry:

Step 4.1 Add SiC particles with a particle size of 3 to 5 μm and a volume fraction of 20 vol.% into HF acid, and magnetically stir at room temperature for 12 hours. The acid-washed SiC particles were centrifuged twice with deionized water and absolute ethanol at a speed of 5000 r/min, respectively, to obtain SiC particles with surface _SiO2 removed.

Step 4.2 Disperse tetramethylammonium hydroxide (TMAH) with a mass fraction of 0.1 to 0.3 wt.% in deionized water, and stir magnetically at room temperature to prepare a uniform solution.

Step 4.3 Add the SiC particles obtained in step 4.1 to the dispersion obtained in step 4.2, then add an appropriate amount of zirconia ball milling beads into the ball milling jar, and wet-mill in the ball milling jar for 10 to 12 hours at a ball milling speed of 80 to 80 120 r/min to obtain a uniformly dispersed SiC slurry with a volume fraction of 3-10 vol.%.

Step 5. Impregnation of 3-5μm SiC particle water-based slurry:

Step 5.1 Put the porous SiC/SiC composite material obtained in step 3.2 and the SiC particle slurry obtained in step 4.3 into a glass drying dish, evacuate until the pressure in the glass dish is lower than 0.09MPa, and keep it for 20-30min, then remove the The porous SiC/SiC composite was immersed in the slurry for 20-30 min.

Step 5.2 Put the porous SiC/SiC composite material obtained in step 5.1 together with the slurry into an airtight container and pressurize it to 0.8MPa, keep it for 10-20min, take it out, and dry it at 150°C for 3 hours.

Step 5 is repeated to obtain SiC/SiC-SiC _P composite material that meets the requirement of large-size SiC particle content by dipping several times.

Step 6. CVI pyrolysis carbon:

The impregnated SiC/SiC-SiC _p composites were put into a pyrolytic carbon deposition furnace, and propylene (C ₃ H ₆ ) was used as the precursor gas source to deposit pyrolytic carbon at 870 °C and 5 kPa, and the deposition time was 30 ~80 hours.

Step 7. Liquid Silicon Penetration:

The SiC/SiC-SiC _p -PyC composite material deposited with pyrolytic carbon is wrapped with Si powder, and the outermost layer is wrapped with graphite paper. The liquid silicon infiltration was carried out in a vacuum environment for 20-60 min to complete the preparation of the SiC/SiC composite material.

Specific examples:

Example 1

Step 1. Preparation of SiC/SiC preform:

In step 1.1, a SiC fiber braid is used to prepare a boron nitride (BN) interface phase on its surface, and the thickness of the interface phase is 300-500 nm.

In step 1.2, a CVI process is used to prepare a SiC matrix with a certain volume fraction in the SiC fiber preform obtained in step 1.1. Using trichloromethylsilane (MTS) as the precursor, hydrogen as the carrier gas, argon as the diluent gas, the flow ratio of the three is 1:5~50:2~20, the total pressure is 0.5~5kPa, and the deposition temperature is 873 ~1773K, the deposition time is about 600 hours. Thereby, a porous SiC/SiC composite material with a porosity of 28-36% and a density of 1.7-2.1 g/cm ³ is obtained, which is used for subsequent slurry impregnation.

Step 2. Configure 300-500nm SiC particle water-based slurry:

Step 2.1 Add SiC particles with a particle size of 300 to 500 nm and a volume fraction of 10 vol.% into HF acid, and magnetically stir at room temperature for 24 hours. The acid-washed SiC particles were centrifuged twice with deionized water and absolute ethanol at a speed of 5000 r/min, respectively, to obtain SiC particles with surface _SiO2 removed.

Step 2.2 Disperse tetramethylammonium hydroxide (TMAH) with a mass fraction of 0.5 to 1.0 wt.% in deionized water, and stir magnetically at room temperature to prepare a uniform solution.

Step 2.3 Add the SiC particles obtained in step 2.1 to the dispersion obtained in step 2.2, and then add an appropriate amount of zirconia ball milling beads into the ball milling jar, and wet-mill in the ball milling jar for 20 to 24 hours at a ball milling speed of 100 to 100 300 r/min to obtain a uniformly dispersed SiC slurry with a volume fraction of 3-5 vol.%.

Step 3. Impregnation of 300-500nm SiC particle water-based slurry:

Step 3.1 Put the porous SiC/SiC composite material and the SiC particle slurry prepared in step 2.3 into a glass drying dish, evacuate until the pressure in the glass dish is lower than 0.09MPa, and keep the porous SiC/SiC composite material after 10-20min. Immerse in the slurry for 10-15min.

Step 3.2 Put the porous SiC/SiC composite material together with the slurry into an airtight container and pressurize it to 0.8MPa, keep it for 20-30min, take it out, and dry it at 150°C for 3 hours.

Step 4. Configure 3~5μm SiC particle water-based slurry:

Step 4.1 Add SiC particles with a particle size of 3 to 5 μm and a volume fraction of 20 vol.% into HF acid, and magnetically stir at room temperature for 12 hours. The acid-washed SiC particles were centrifuged twice with deionized water and absolute ethanol at a speed of 5000 r/min, respectively, to obtain SiC particles with surface _SiO2 removed.

Step 4.2 Disperse tetramethylammonium hydroxide (TMAH) with a mass fraction of 0.1 to 0.3 wt.% in deionized water, and stir magnetically at room temperature to prepare a uniform solution.

Step 4.3 Add the SiC particles obtained in step 4.1 to the dispersion obtained in step 4.2, then add an appropriate amount of zirconia ball milling beads into the ball milling jar, and wet-mill in the ball milling jar for 10 to 12 hours at a ball milling speed of 80 to 80 120 r/min to obtain a uniformly dispersed SiC slurry with a volume fraction of 3-10 vol.%.

Step 5. Impregnation of 3-5μm SiC particle water-based slurry:

Step 5.1 Put the porous SiC/SiC composite material obtained in step 3.2 and the SiC particle slurry obtained in step 4.3 into a glass drying dish, evacuate until the pressure in the glass dish is lower than 0.09MPa, and keep it for 20-30min, then remove the The porous SiC/SiC composite was immersed in the slurry for 20-30 min.

Step 5.2 Put the porous SiC/SiC composite material obtained in step 5.1 together with the slurry into an airtight container and pressurize it to 0.8MPa, keep it for 10-20min, take it out, and dry it at 150°C for 3 hours.

Step 5 was repeated, and the cyclic impregnation was performed twice to obtain a SiC/SiC-SiC _P composite material that met the requirements for the content of large-sized SiC particles.

Step 6. CVI pyrolysis carbon:

The impregnated SiC/SiC-SiC _p composites were put into a pyrolytic carbon deposition furnace, and propylene (C ₃ H ₆ ) was used as the precursor gas source to deposit pyrolytic carbon at 870 °C and 5 kPa, and the deposition time was 30 ~50 hours.

Step 7. Liquid Silicon Penetration:

The SiC/SiC-SiC _p -PyC composite material deposited with pyrolytic carbon is wrapped with Si powder, and the outermost layer is wrapped with graphite paper. The liquid silicon infiltration was carried out in a vacuum environment for 20-60 min to complete the preparation of the SiC/SiC composite material.

It can be seen from Figure 4 that the matrix of the SiC/SiC composite material obtained in Example 1 is mainly SiC and only contains a small amount of Si, and the bending strength of the tested material is 511.46±6.90MPa.

Example 2

Step 1. Preparation of SiC/SiC preform:

In step 1.1, a SiC fiber braid is used to prepare a boron nitride (BN) interface phase on its surface, and the thickness of the interface phase is 300-500 nm.

In step 1.2, a CVI process is used to prepare a SiC matrix with a certain volume fraction in the SiC fiber preform obtained in step 1.1. Using trichloromethylsilane (MTS) as the precursor, hydrogen as the carrier gas, argon as the diluent gas, the flow ratio of the three is 1:5~50:2~20, the total pressure is 0.5~5kPa, and the deposition temperature is 873 ~1773K, the deposition time is about 600 hours. Thereby, a porous SiC/SiC composite material with a porosity of 28-36% and a density of 1.7-2.1 g/cm ³ is obtained, which is used for subsequent slurry impregnation.

Step 2. Configure 300-500nm SiC particle water-based slurry:

Step 2.1 Add SiC particles with a particle size of 300 to 500 nm and a volume fraction of 10 vol.% into HF acid, and magnetically stir at room temperature for 24 hours. The acid-washed SiC particles were centrifuged twice with deionized water and absolute ethanol at a speed of 5000 r/min, respectively, to obtain SiC particles with surface _SiO2 removed.

Step 2.2 Disperse tetramethylammonium hydroxide (TMAH) with a mass fraction of 0.5 to 1.0 wt.% in deionized water, and stir magnetically at room temperature to prepare a uniform solution.

Step 2.3 Add the SiC particles obtained in step 2.1 to the dispersion obtained in step 2.2, and then add an appropriate amount of zirconia ball milling beads into the ball milling jar, and wet-mill in the ball milling jar for 20 to 24 hours at a ball milling speed of 100 to 100 300 r/min to obtain a uniformly dispersed SiC slurry with a volume fraction of 3-5 vol.%.

Step 3. Impregnation of 300-500nm SiC particle water-based slurry:

Step 3.1 Put the porous SiC/SiC composite material and the SiC particle slurry prepared in step 2.3 into a glass drying dish, evacuate until the pressure in the glass dish is lower than 0.09MPa, and keep the porous SiC/SiC composite material after 10-20min. Immerse in the slurry for 10-15min.

Step 3.2 Put the porous SiC/SiC composite material together with the slurry into an airtight container and pressurize it to 0.8MPa, keep it for 20-30min, take it out, and dry it at 150°C for 3 hours.

Step 4. Configure 3~5μm SiC particle water-based slurry:

Step 4.1 Add SiC particles with a particle size of 3 to 5 μm and a volume fraction of 20 vol.% into HF acid, and magnetically stir at room temperature for 12 hours. The acid-washed SiC particles were centrifuged twice with deionized water and absolute ethanol at a speed of 5000 r/min, respectively, to obtain SiC particles with surface _SiO2 removed.

Step 4.2 Disperse tetramethylammonium hydroxide (TMAH) with a mass fraction of 0.1 to 0.3 wt.% in deionized water, and stir magnetically at room temperature to prepare a uniform solution.

Step 4.3 Add the SiC particles obtained in step 4.1 to the dispersion obtained in step 4.2, then add an appropriate amount of zirconia ball milling beads into the ball milling jar, and wet-mill in the ball milling jar for 10 to 12 hours at a ball milling speed of 80 to 80 120 r/min to obtain a uniformly dispersed SiC slurry with a volume fraction of 3-10 vol.%.

Step 5. Impregnation of 3-5μm SiC particle water-based slurry:

Step 5.1 Put the porous SiC/SiC composite material obtained in step 3.2 and the SiC particle slurry obtained in step 4.3 into a glass drying dish, evacuate until the pressure in the glass dish is lower than 0.09MPa, and keep it for 20-30min, then remove the The porous SiC/SiC composite was immersed in the slurry for 20-30 min.

Step 5.2 Put the porous SiC/SiC composite material obtained in step 5.1 together with the slurry into an airtight container and pressurize it to 0.8MPa, keep it for 10-20min, take it out, and dry it at 150°C for 3 hours.

Step 5 was repeated, and the cyclic impregnation was performed three times to obtain a SiC/SiC-SiC _P composite material that met the requirements of the content of large-sized SiC particles.

Step 6. CVI pyrolysis carbon:

The impregnated SiC/SiC-SiC _p composites were put into a pyrolytic carbon deposition furnace, and propylene (C ₃ H ₆ ) was used as the precursor gas source to deposit pyrolytic carbon at 870 °C and 5 kPa, and the deposition time was 30 ~50 hours.

Step 7. Liquid Silicon Penetration:

The SiC/SiC-SiC _p -PyC composite material deposited with pyrolytic carbon is wrapped with Si powder, and the outermost layer is wrapped with graphite paper. The liquid silicon infiltration was carried out in a vacuum environment for 20-60 min to complete the preparation of the SiC/SiC composite material.

It can be seen from Figure 4 that the matrix of the SiC/SiC composite material obtained in Example 2 is mainly SiC, and a relatively obvious layered structure appears on the periphery of CVI SiC. The bending strength of the tested material is 542.73±25.68Mpa, and the fracture toughness It is 37.77±2.03MPa.m^1/2.

Example 3

Step 1. Preparation of SiC/SiC preform:

In step 1.1, a SiC fiber braid is used to prepare a boron nitride (BN) interface phase on its surface, and the thickness of the interface phase is 300-500 nm.

In step 1.2, a CVI process is used to prepare a SiC matrix with a certain volume fraction in the SiC fiber preform obtained in step 1.1. Using trichloromethylsilane (MTS) as the precursor, hydrogen as the carrier gas, argon as the diluent gas, the flow ratio of the three is 1:5~50:2~20, the total pressure is 0.5~5kPa, and the deposition temperature is 873 ~1773K, the deposition time is about 600 hours. Thereby, a porous SiC/SiC composite material with a porosity of 28-36% and a density of 1.7-2.1 g/cm ³ is obtained, which is used for subsequent slurry impregnation.

Step 2. Configure 300-500nm SiC particle water-based slurry:

Step 2.1 Add SiC particles with a particle size of 300 to 500 nm and a volume fraction of 10 vol.% into HF acid, and magnetically stir at room temperature for 24 hours. The acid-washed SiC particles were centrifuged twice with deionized water and absolute ethanol at a speed of 5000 r/min, respectively, to obtain SiC particles with surface _SiO2 removed.

Step 2.2 Disperse tetramethylammonium hydroxide (TMAH) with a mass fraction of 0.5 to 1.0 wt.% in deionized water, and stir magnetically at room temperature to prepare a uniform solution.

Step 2.3 Add the SiC particles obtained in step 2.1 to the dispersion obtained in step 2.2, and then add an appropriate amount of zirconia ball milling beads into the ball milling jar, and wet-mill in the ball milling jar for 20 to 24 hours at a ball milling speed of 100 to 100 300 r/min to obtain a uniformly dispersed SiC slurry with a volume fraction of 3-5 vol.%.

Step 3. Impregnation of 300-500nm SiC particle water-based slurry:

Step 3.1 Put the porous SiC/SiC composite material and the SiC particle slurry prepared in step 2.3 into a glass drying dish, evacuate until the pressure in the glass dish is lower than 0.09MPa, and keep the porous SiC/SiC composite material after 10-20min. Immerse in the slurry for 10-15min.

Step 3.2 Put the porous SiC/SiC composite material together with the slurry into an airtight container and pressurize it to 0.8MPa, keep it for 20-30min, take it out, and dry it at 150°C for 3 hours.

Step 4. Configure 3-5μm SiC particle water-based slurry:

Step 4.1 Add SiC particles with a particle size of 3 to 5 μm and a volume fraction of 20 vol.% into HF acid, and magnetically stir at room temperature for 12 hours. The acid-washed SiC particles were centrifuged twice with deionized water and absolute ethanol at a speed of 5000 r/min, respectively, to obtain SiC particles with surface _SiO2 removed.

Step 4.2 Disperse tetramethylammonium hydroxide (TMAH) with a mass fraction of 0.1 to 0.3 wt.% in deionized water, and stir magnetically at room temperature to prepare a uniform solution.

Step 4.3 Add the SiC particles obtained in step 4.1 to the dispersion obtained in step 4.2, then add an appropriate amount of zirconia ball milling beads into the ball milling jar, and wet-mill in the ball milling jar for 10 to 12 hours at a ball milling speed of 80 to 80 120 r/min to obtain a uniformly dispersed SiC slurry with a volume fraction of 3-10 vol.%.

Step 5. Impregnation of 3-5μm SiC particle water-based slurry:

Step 5.1 Put the porous SiC/SiC composite material obtained in step 3.2 and the SiC particle slurry obtained in step 4.3 into a glass drying dish, evacuate until the pressure in the glass dish is lower than 0.09MPa, and keep it for 20-30min, then remove the The porous SiC/SiC composite was immersed in the slurry for 20-30 min.

Step 5.2 Put the porous SiC/SiC composite material obtained in step 5.1 together with the slurry into an airtight container and pressurize it to 0.8MPa, keep it for 10-20min, take it out, and dry it at 150°C for 3 hours.

Step 5 was repeated, and the cyclic impregnation was performed twice to obtain a SiC/SiC-SiC _P composite material that met the requirements for the content of large-sized SiC particles.

Step 6. CVI pyrolysis carbon:

The impregnated SiC/SiC-SiC _p composites were put into a pyrolytic carbon deposition furnace, and propylene (C ₃ H ₆ ) was used as the precursor gas source to deposit pyrolytic carbon at 870 °C and 5 kPa, and the deposition time was 50 ~80 hours.

Step 7. Liquid Silicon Penetration:

The SiC/SiC-SiC _p -PyC composite material deposited with pyrolytic carbon is wrapped with Si powder, and the outermost layer is wrapped with graphite paper. The liquid silicon infiltration was carried out in a vacuum environment for 20-60 min to complete the preparation of the SiC/SiC composite material.

It can be seen from Figures 3 and 4 that the matrix of the SiC/SiC composite material obtained in Example 3 is mainly SiC and only contains a small amount of Si. The bending strength of the material obtained by testing is 577.59±9.55, the density is 2.48g/cm ³ , and the The porosity is 7.61%, and the residual silicon content is 4.32vol.%.

Claims (3)

1. a preparation method of SiC/SiC composite material high-density multi-layer matrix, is characterized in that step is as follows: Step 1. Preparation of porous SiC/SiC composite material: use CVI process to deposit BN interface on the woven SiC fiber, and then use CVI process to deposit SiC matrix to a semi-densified state to obtain porous SiC/SiC composite material; Step 2. Prepare 300~500nm SiC particle water-based slurry: add 0.5~1.0wt.% tetramethylammonium hydroxide TMAH and 3~5vol.% SiC particles into deionized water, ball mill Then obtain a uniformly dispersed slurry; Step 3. Impregnation of 300~500nm SiC particle water-based slurry: Vacuum impregnation: Put the porous SiC/SiC composite into a glass drying dish, evacuate until the pressure in the glass dish is lower than 0.09Mpa, and keep it for 10~20min, then immerse the SiC/SiC composite into the slurry obtained in step 2 to maintain 10~15min; Pressure impregnation: Put the porous SiC/SiC composite material together with the slurry into a closed container and pressurize it to 0.8Mpa, keep it for 20~30min, take it out, and dry it; Step 4. Prepare 3~5μm SiC particle water-based slurry: add 0.1~0.3wt.% tetramethylammonium hydroxide TMAH and 3~10vol.% SiC particles into deionized water, ball mill Then obtain a uniformly dispersed slurry; Step 5. Impregnation of 3~5μm SiC particle water-based slurry: Vacuum impregnation: Put the porous SiC/SiC composite into a glass drying dish, evacuate until the pressure in the glass dish is lower than 0.09Mpa, keep it for 20~30min, and then immerse the SiC/SiC composite into the slurry obtained in step 4 to maintain 20~30min; Pressure impregnation: Put the SiC/SiC composite material together with the slurry into a closed container and pressurize it to 0.8Mpa, keep it for 10~20min, take it out, and dry it; Step 6, CVI pyrolytic carbon: put the impregnated SiC/SiC-SiCp into the CVI pyrolytic carbon deposition furnace to deposit pyrolytic carbon for 30 to 80 hours; Step 7. Liquid silicon infiltration: wrap the SiC/SiC-SiCp-PyC composite material on which the pyrolytic carbon has been deposited with Si powder, and wrap the outermost layer with graphite paper, and then put the composite material wrapped with Si powder into the silicon infiltration furnace In the process, liquid silicon infiltration was performed in a vacuum environment of 1430-1550 °C for 20-60 min to complete the preparation of SiC/SiC composites. 2. The method according to claim 1, characterized in that: the ball milling of the step 2: adding zirconia ball milling beads into the ball milling tank, wet milling for 20-24 hours, and the ball milling speed is 100-300 r/min. 3. The method according to claim 1, characterized in that: the ball milling of the step 2: adding zirconia ball milling beads to the ball milling tank, wet milling for 10-12 hours, and the ball milling speed is 80-120 r/min.

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