阅读说明：本技术 一种高致密SiC/SiC复合材料及其制备方法 (High-density SiC/SiC composite material and preparation method thereof ) 是由 宋环君 陈昊然 杨良伟 金鑫 李晓东 左红军 刘伟 于新民 刘俊鹏 孙同臣 于 2021-09-07 设计创作，主要内容包括：本发明提供了一种高致密SiC/SiC复合材料及其制备方法,该方法包括：(1)采用化学气相沉积法,在SiC纤维预制体的表面沉积PyC界面层,得到第一试样(2)在第一试样的表面沉积SiC界面层,得到第二试样(3)将第二试样浸渍在包含烧结助剂的前驱体浆料中,得到第三试样(4)将第三试样依次进行固化、裂解反应,得到第四试样(5)重复步骤(3)至(4)至少八次,然后进行烧结,得到高致密SiC/SiC复合材料。本发明制备的SiC/SiC复合材料高度致密化,具有优异的力学性能。(The invention provides a high-density SiC/SiC composite material and a preparation method thereof, wherein the method comprises the following steps: (1) depositing a PyC interface layer on the surface of the SiC fiber preform by adopting a chemical vapor deposition method to obtain a first sample (2), depositing a SiC interface layer on the surface of the first sample to obtain a second sample (3), soaking the second sample in precursor slurry containing a sintering aid to obtain a third sample (4), sequentially carrying out curing and cracking reactions on the third sample to obtain a fourth sample (5), repeating the steps (3) to (4) for at least eight times, and then sintering to obtain the high-density SiC/SiC composite material. The SiC/SiC composite material prepared by the invention is highly densified and has excellent mechanical properties.)

1. A preparation method of a high-density SiC/SiC composite material is characterized by comprising the following steps:

(1) depositing a PyC interface layer on the surface of the SiC fiber preform by adopting a chemical vapor deposition method to obtain a first sample;

(2) depositing a SiC interface layer on the surface of the first sample by adopting a chemical vapor deposition method to obtain a second sample;

(3) dipping the second sample in the precursor slurry to obtain a third sample; wherein the precursor slurry comprises a sintering aid;

(4) carrying out curing and cracking reactions on the third sample in sequence to obtain a fourth sample;

(5) repeating the steps (3) to (4) at least eight times to obtain a fifth sample;

(6) and sintering the fifth sample to obtain the high-density SiC/SiC composite material.

2. The production method according to claim 1, wherein in step (1):

the SiC fiber preform is woven by utilizing third-generation fibers; wherein the weaving mode is sewing, 2.5D, three-dimensional four-way or three-dimensional five-way weaving; and/or

The fiber volume fraction of the SiC fiber preform is 25-45%.

3. The production method according to claim 1, wherein in step (1):

when the chemical vapor deposition method is adopted, the selected carbon source gas is at least one of methane, ethane and propane;

the deposition temperature of the chemical vapor deposition method is 600-1200 ℃, the vacuum degree is-0.09-0.01 MPa, and the deposition time is 0.5-10 h; and/or

The thickness of the PyC interface layer is 100-600 nm.

4. The production method according to claim 1, wherein in step (2):

when the chemical vapor deposition method is adopted, the selected precursor is at least one of chloromethylsilane, bromomethylsilane, methylsilane and fluoromethylsilane;

the chemical vapor deposition method has the deposition temperature of 800-1200 ℃, the vacuum degree of-0.09-0.01 MPa and the deposition time of 10-30 h; and/or

The thickness of the SiC interface layer is 3-5 mu m.

5. The production method according to claim 1, wherein in step (3):

the precursor slurry comprises a sintering aid, SiC ceramic powder, a polymer precursor and a solvent;

the sintering aid is at least one of aluminum oxide, yttrium oxide, boron oxide, beryllium oxide, barium oxide and silicon dioxide;

the polymer precursor is at least one of solid polycarbosilane, perhydropolycarbosilane and allyl liquid polycarbosilane;

the solvent is at least one of butanone, xylene, divinylbenzene and toluene; and/or

The mass fraction of the sintering aid in the precursor slurry is 0.5-3%; the mass fraction of the SiC ceramic powder in the precursor slurry is 10-30%.

6. The method of claim 1, wherein:

in the step (3), the dipping temperature of the dipping is 20-60 ℃, the pressure is 1-5 MPa, and the dipping time is 1-5 h.

7. The production method according to claim 1, wherein in step (4):

the reaction temperature of the curing reaction is 100-350 ℃, the curing time is 1-5 h, and the curing pressure is 1-5 MPa; and/or

The reaction temperature of the cracking reaction is 700-1200 ℃, the vacuum degree is-0.09-0.01 MPa, and the cracking time is 2-4 h.

8. The method of claim 1, wherein:

in step (5), the number of times of repeating steps (3) to (4) is 8 to 10 times.

9. The production method according to any one of claims 1 to 8, characterized in that:

in the step (6), the sintering temperature is 1400-1800 ℃, and the sintering time is 1-4 h.

10. A highly dense SiC/SiC composite material characterized by being produced by the production method according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of aerospace material preparation processes, in particular to a preparation method of a high-density SiC/SiC composite material.

Background

The most advanced aeroengine turbine blades at present are mainly made of third generation single crystal high temperature alloy (nickel base alloy) with the density of about 8-9g/cm³The ultimate use temperature is 1100 ℃. In order to further improve the temperature before the turbine and reduce the weight of the engine, the research and development of novel ultra-light high-temperature materials are urgently needed. The SiC/SiC composite material has the characteristics of low density, high specific strength, high specific modulus, high toughness and the like, and meanwhile, the high-temperature oxidation resistance of the SiC/SiC composite material is far superior to that of a carbon fiber toughened composite material, so that the SiC/SiC composite material is considered as a key material of a future high-performance engine and is a fundamental guarantee for realizing the high thrust-weight ratio engine.

At present, the main processes for preparing SiC/SiC composite materials include a precursor impregnation cracking process (PIP), a chemical vapor infiltration process (CVI), a reaction infiltration process (RMI), and the like. But the chemical vapor infiltration process has the defects of long preparation period, low final density of the composite material caused by easy formation of closed pores on the surface of the fiber and the like; and the reaction infiltration process is easy to cause fiber damage in the high-temperature sintering process, so that the mechanical property of the composite material is lower. The precursor impregnation cracking process is an important method for preparing the SiC/SiC composite material due to the advantages of simple preparation process, low requirement on equipment and the like, however, the polymer precursor can release small molecular substances in the cracking process, so that holes are easily formed in the SiC/SiC composite material, the densification degree is low, and the mechanical property of the SiC/SiC composite material is reduced. Therefore, it is necessary to develop a method for preparing a high-density SiC/SiC composite material to overcome the problem of low density of the composite material caused by the traditional precursor impregnation cracking process (PIP).

Disclosure of Invention

The invention provides a high-density SiC/SiC composite material and a preparation method thereof, and the prepared SiC/SiC composite material is highly densified and has excellent mechanical properties.

In a first aspect, the invention provides a preparation method of a high-density SiC/SiC composite material, which comprises the following steps:

(1) depositing a PyC interface layer on the surface of the SiC fiber preform by adopting a chemical vapor deposition method to obtain a first sample;

(2) depositing a SiC interface layer on the surface of the first sample by adopting a chemical vapor deposition method to obtain a second sample;

(3) dipping the second sample in the precursor slurry to obtain a third sample; wherein the precursor slurry comprises a sintering aid;

(4) carrying out curing and cracking reactions on the third sample in sequence to obtain a fourth sample;

(5) repeating the steps (3) to (4) at least eight times to obtain a fifth sample;

(6) and sintering the fifth sample to obtain the high-density SiC/SiC composite material.

Preferably, in the step (1), the SiC fiber preform is woven by using third generation fibers; wherein the knitting mode is sewing, 2.5D, three-dimensional four-way or three-dimensional five-way knitting.

Preferably, in the step (1), the fiber volume fraction of the SiC fiber preform is 25-45%.

Preferably, in the step (1), the carbon source gas selected when the chemical vapor deposition method is adopted is at least one of methane, ethane and propane;

the chemical vapor deposition method has the deposition temperature of 600-1200 ℃, the vacuum degree of-0.09-0.01 MPa and the deposition time of 0.5-10 h.

Preferably, in the step (1), the thickness of the PyC interface layer is 100 to 600 nm.

Preferably, in the step (2), the precursor selected when the chemical vapor deposition method is adopted is at least one of chloromethylsilane, bromomethylsilane, methylsilane, and fluoromethylsilane;

the chemical vapor deposition method has the deposition temperature of 800-1200 ℃, the vacuum degree of-0.09-0.01 MPa and the deposition time of 10-30 h.

Preferably, in the step (2), the thickness of the SiC interface layer is 3-5 μm.

Preferably, in the step (3), the precursor slurry contains a sintering aid, SiC ceramic powder, a polymer precursor and a solvent;

the sintering aid is at least one of aluminum oxide, yttrium oxide, boron oxide, beryllium oxide, barium oxide and silicon dioxide;

the polymer precursor is at least one of solid polycarbosilane, perhydropolycarbosilane and allyl liquid polycarbosilane;

the solvent is at least one of butanone, xylene, divinylbenzene and toluene.

Preferably, in the step (3), the mass fraction of the sintering aid in the precursor slurry is 0.5-3%; the mass fraction of the SiC ceramic powder in the precursor slurry is 10-30%.

Preferably, in the step (3), the dipping temperature is 20-60 ℃, the pressure is 1-5 MPa, and the dipping time is 1-5 h.

Preferably, in the step (4), the reaction temperature of the curing reaction is 100-350 ℃, the curing time is 1-5 h, and the curing pressure is 1-5 MPa.

Preferably, in the step (4), the reaction temperature of the cracking reaction is 700-1200 ℃, the vacuum degree is-0.09-0.01 MPa, and the cracking time is 2-4 h.

Preferably, in step (5), the number of times steps (3) to (4) are repeated is 8 to 10 times.

Preferably, in the step (6), the sintering temperature is 1400-1800 ℃ and the sintering time is 1-4 h.

In a second aspect, the invention provides a high-density SiC/SiC composite material prepared by the preparation method of any one of the first aspect.

Compared with the prior art, the invention at least has the following beneficial effects:

in the dipping process, the high-density SiC/SiC composite material prepared by the invention is prepared by preparing uniformly dispersed precursor slurry, wherein the precursor slurry contains a sintering aid, the sintering aid is uniformly introduced into an unsintered ceramic matrix through the circulating dipping-curing-cracking process, and the precursor slurry is obtained through one-time high-temperature sintering.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 shows the microstructure of a highly dense SiC/SiC composite material according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer and more complete, the technical solutions in the embodiments of the present invention will be described below, it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all embodiments, and all other embodiments obtained by a person of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the protection scope of the present invention.

The invention provides a preparation method of a high-density SiC/SiC composite material, which comprises the following steps:

(1) depositing a PyC interface layer on the surface of the SiC fiber preform by adopting a chemical vapor deposition method to obtain a first sample;

(2) depositing a SiC interface layer on the surface of the first sample by adopting a chemical vapor deposition method to obtain a second sample;

(3) dipping the second sample in the precursor slurry to obtain a third sample; wherein the precursor slurry comprises a sintering aid;

(4) carrying out curing and cracking reactions on the third sample in sequence to obtain a fourth sample;

(5) repeating the steps (3) to (4) at least eight times to obtain a fifth sample;

(6) and sintering the fifth sample to obtain the high-density SiC/SiC composite material.

According to some preferred embodiments, in step (1), the SiC fiber preform is woven using three-dimensional weaving, wherein the weaving is stitching, 2.5D, three-dimensional four-way or three-dimensional five-way weaving.

According to some preferred embodiments, in the step (1), the fiber volume fraction of the SiC fiber preform is 25 to 45% (e.g., may be 25%, 30%, 35%, 40%, or 45%).

According to some preferred embodiments, in the step (1), the carbon source gas selected when the chemical vapor deposition method is adopted is at least one of methane, ethane and propane;

the chemical vapor deposition method has a deposition temperature of 600 to 1200 ℃ (for example, 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃ or 1200 ℃), a vacuum degree of-0.09 to-0.01 MPa (for example, -0.1MPa, -0.09MPa, -0.08MPa, -0.07MPa, -0.06MPa, -0.05MPa, -0.04MPa, -0.03MPa, -0.02MPa or-0.01 MPa), and a reaction time of 0.5 to 10 hours (for example, 0.5 hour, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours).

At least one of them is a mixture of any one or any several of them mixed in any ratio.

According to some preferred embodiments, in step (1), the thickness of the PyC interface layer is 100 to 600nm (e.g. may be 100nm, 200nm, 300nm, 400nm, 500nm or 600 nm).

In the present invention, a PyC (pyrolytic carbon) interface layer is first prepared by chemical vapor deposition, and then a SiC interface layer is further prepared on the PyC interface layer. According to some preferred embodiments, in the step (2), the precursor selected when the chemical vapor deposition method is adopted is at least one of chloromethylsilane, bromomethylsilane, methylsilane, and fluoromethylsilane;

the chemical vapor deposition method has a deposition temperature of 800 to 1200 ℃ (for example, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃ or 1200 ℃), a vacuum degree of-0.09 to-0.01 MPa (for example, 0.09MPa, -0.08MPa, -0.07MPa, -0.06MPa, -0.05MPa, -0.04MPa, -0.03MPa, -0.02MPa or-0.01 MPa), and a deposition time of 10 to 30 hours (for example, 10 hours, 15 hours, 20 hours, 25 hours or 30 hours).

According to some preferred embodiments, in step (2), the thickness of the SiC interface layer is 3 to 5 μm (e.g., may be 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm).

According to some preferred embodiments, in the step (3), the precursor slurry contains a sintering aid, SiC ceramic powder, a polymer precursor, and a solvent;

the sintering aid is at least one of aluminum oxide, yttrium oxide, boron oxide, beryllium oxide, barium oxide and silicon dioxide;

the polymer precursor is at least one of solid Polycarbosilane (PCS), perhydropolycarbosilane (AHPCS) and allyl Liquid Polycarbosilane (LPCS);

the solvent is at least one of butanone, xylene, divinylbenzene and toluene.

According to some preferred embodiments, in the step (3), the mass fraction of the sintering aid in the precursor slurry is 0.5-3%; the mass fraction of the SiC ceramic powder in the precursor slurry is 10-30%.

In the invention, the mass fraction of the polymer precursor is preferably 50-60%, and experiments prove that when the mass fraction of the sintering aid in the precursor slurry is lower than 0.5%, the sintering aid cannot fully play a role due to too low content of the added sintering aid, and cannot avoid the defects generated in the cracking and sintering processes of the ceramic matrix; when the mass fraction of the sintering aid in the precursor slurry is higher than 3%, segregation of the second phase at the grain boundary can be caused, and the high-temperature performance of the composite material is further reduced. When the content of the SiC ceramic powder is too low, the pores formed during the cracking of the polymer precursor cannot be effectively improved; when the content of the SiC ceramic powder is too high, the impregnation effect is affected, and the compactness of the composite material is low, so that the mass fraction of the SiC ceramic powder in the precursor slurry is 10-30%.

According to some preferred embodiments, in the step (3), the impregnation temperature of the impregnation is 20 to 60 ℃ (for example, 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃ or 60 ℃), the pressure is 1 to 5MPa (for example, 1MPa, 2MPa, 3MPa, 4MPa or 5MPa), and the impregnation time is 1 to 5 hours (for example, 1 hour, 2 hours, 3 hours, 4 hours or 5 hours).

According to some preferred embodiments, in the step (4), the curing reaction has a reaction temperature of 100 to 350 ℃ (for example, 100 ℃, 150 ℃, 200 ℃, 250 ℃, 300 ℃ or 350 ℃), a curing time of 1 to 5 hours (for example, 1 hour, 2 hours, 3 hours, 4 hours or 5 hours), and a curing pressure of 1 to 5MPa (for example, 1MPa, 2MPa, 3MPa, 4MPa or 5 MPa).

According to some preferred embodiments, in the step (4), the reaction temperature of the cleavage reaction is 700 to 1200 ℃ (for example, may be 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃ or 1200 ℃), the degree of vacuum is-0.09 to-0.01 MPa (for example, may be-0.09 MPa, -0.08MPa, -0.07MPa, -0.06MPa, -0.05MPa, -0.04MPa, -0.03MPa, -0.02MPa or-0.01 MPa), and the cleavage time is 2 to 4 hours (for example, may be 2 hours, 3 hours or 4 hours).

According to some preferred embodiments, in step (5), the number of times steps (3) to (4) are repeated is 8 to 10 times.

In the invention, sintering aid, ceramic powder, polymer precursor and solvent are prepared into precursor slurry which is uniformly dispersed, and then the sintering aid is uniformly dispersed into pores of fibers by a circulating dipping-curing-cracking process, wherein the sintering aid can form a solid solution or generate a liquid phase or prevent crystal form transformation or inhibit crystal grains from growing with SiC fiber preform, SiC ceramic powder and polymer precursor, thereby preventing the ceramic matrix from generating cracks in a cracking process by phase separation; in the dipping process, the ceramic powder can not only prevent the solvent from volatilizing to generate holes, but also fill the holes formed by the polymer precursor in the previous cracking process, so that the density of the composite material can be controllably improved through the cyclic dipping-curing-cracking.

According to some preferred embodiments, in the step (6), the sintering temperature is 1400 to 1800 ℃ (for example, 1400 ℃, 1500 ℃, 1600 ℃, 1700 ℃ or 1800 ℃), and the sintering time is 1 to 4h (for example, 1h, 2h, 3h or 4 h).

In the invention, the sintering aid can form liquid phase and solid solution in the sintering process, thereby reducing the sintering temperature and promoting the sintering densification.

Sintering aids are uniformly introduced into an unsintered ceramic matrix through circulating impregnation, curing and cracking, so that the sintering aids enter pores of fibers of the ceramic matrix, and the sintering aids introduced by impregnation can fully play a role only through one-time high-temperature sintering, thereby avoiding the fibers from being damaged for many times, and improving the mechanical property of the SiC/SiC composite material on the premise of ensuring the density of the SiC/SiC composite material.

The invention also provides a high-density SiC/SiC composite material, which is prepared by the preparation method of the high-density SiC/SiC composite material.

In order to more clearly illustrate the technical scheme and advantages of the invention, the following describes a preparation method of the high-density SiC/SiC composite material in detail through several embodiments.

Example 1

(1) Weaving third-generation SiC fibers into a 2.5D twill preform with the fiber volume fraction of 40%, selecting propane as a carbon source gas by adopting a chemical vapor deposition method, placing the SiC fiber preform in a chemical vapor deposition furnace, and depositing for 2.6 hours under the conditions of 900 ℃ and-0.05 MPa to obtain a first sample containing a PyC interface layer with the thickness of 150 nm;

(2) placing the first sample obtained in the step (1) in a chemical vapor deposition furnace, and depositing for 16h at 1100 ℃ and-0.05 MPa by using trichloromethylsilane as a precursor to obtain a second sample containing a SiC interface layer with the thickness of 3.8 microns;

(3) dipping the second sample in the precursor slurry, and dipping for 3.5h at 35 ℃ and 2MPa to obtain a third sample; the precursor slurry is a dimethylbenzene and divinylbenzene mixed solution containing alumina-yttria-boron oxide (2.4%), SiC ceramic powder (25%), and solid polycarbosilane (50%);

(4) curing the third sample in a high-pressure tank at 200 ℃ and 1.8MPa for 3h, and then cracking the third sample in a pyrolysis furnace at 900 ℃ and minus 0.06MPa for 2.5h to obtain a fourth sample;

(5) repeating the steps (3) to (4) for eight times to obtain a fifth sample;

(6) and (4) putting the fifth sample obtained in the step (5) into a high-temperature reaction furnace, and sintering for 1h at 1550 ℃ to obtain the high-density SiC/SiC composite material.

Example 2

(1) Weaving third-generation SiC fibers in three-dimensional four-direction to form a prefabricated body with the fiber volume fraction of 35%, selecting methane as a carbon source gas by adopting a chemical vapor deposition method, placing the SiC fiber prefabricated body in a chemical vapor deposition furnace, and depositing for 1h under the conditions of 800 ℃ and-0.08 MPa to obtain a first sample containing a PyC interface layer with the thickness of 100 nm;

(2) placing the first sample obtained in the step (1) in a chemical vapor deposition furnace, and depositing for 10 hours at 800 ℃ and under the condition of-0.09 MPa by taking methylsilane as a precursor to obtain a second sample containing a 3 mu mSiC interface layer;

(3) dipping the second sample in the precursor slurry, and dipping for 1h at 20 ℃ under 1MPa to obtain a third sample; the precursor slurry is a toluene solution containing alumina-silica-boron oxide (0.5%), SiC ceramic powder (10%) and perhydropolycarbosilane (55%);

(4) curing the third sample in a high-pressure tank at 100 ℃ and 1MPa for 1h, and then cracking the third sample in a pyrolysis furnace at 850 ℃ and minus 0.09MPa for 2h to obtain a fourth sample;

(5) repeating the steps (3) to (4) for eight times to obtain a fifth sample;

(6) and (4) putting the fifth sample obtained in the step (5) into a high-temperature reaction furnace, and sintering for 3 hours at 1400 ℃ to obtain the high-density SiC/SiC composite material.

Example 3

(1) Three-dimensional four-way weaving third-generation SiC fibers into a prefabricated body with the fiber volume fraction of 35%, selecting ethane as a carbon source gas by adopting a chemical vapor deposition method, placing the SiC fiber prefabricated body in a chemical vapor deposition furnace, and depositing for 2 hours under the conditions of 950 ℃ and-0.08 MPa to obtain a first sample containing a PyC interface layer with the thickness of 200 nm;

(2) placing the first sample obtained in the step (1) in a chemical vapor deposition furnace, and depositing for 30 hours at 900 ℃ and-0.08 MPa by taking methylsilane as a precursor to obtain a second sample containing a 4.1 mu m SiC interface layer;

(3) dipping the second sample in the precursor slurry, and dipping for 2h at 40 ℃ and 3MPa to obtain a third sample; the precursor slurry is a dimethylbenzene solution containing yttrium oxide-boron oxide (1%), SiC ceramic powder (15%) and allyl liquid polycarbosilane (60%);

(4) curing the third sample in a high-pressure tank at 200 ℃ and 2MPa for 2h, and then cracking the third sample in a pyrolysis furnace at 800 ℃ and minus 0.07MPa for 2.5h to obtain a fourth sample;

(5) repeating the steps (3) to (4) nine times to obtain a fifth sample;

(6) and (4) putting the fifth sample obtained in the step (5) into a high-temperature reaction furnace, and sintering for 2h at 1450 ℃ to obtain the high-density SiC/SiC composite material.

Example 4

(1) Stitching and weaving third-generation SiC fibers into a preform with the fiber volume fraction of 39%, selecting propane as a carbon source gas by adopting a chemical vapor deposition method, placing the SiC fiber preform in a chemical vapor deposition furnace, and depositing for 4 hours under the conditions of 1000 ℃ and-0.05 MPa to obtain a first sample containing a PyC interface layer with the thickness of 300 nm;

(2) placing the first sample obtained in the step (1) in a chemical vapor deposition furnace, and depositing for 25 hours at 1000 ℃ and-0.06 MPa by using trichloromethylsilane as a precursor to obtain a second sample containing a SiC interface layer with the thickness of 4 microns;

(3) dipping the second sample in the precursor slurry, and dipping for 3h at 40 ℃ and 3MPa to obtain a third sample; wherein the precursor slurry is a toluene/divinylbenzene solution containing alumina-boron oxide (2%), SiC ceramic powder (20%) and perhydropolycarbosilane (50%);

(4) curing the third sample in a high-pressure tank at 200 ℃ and 3MPa for 2h, and then cracking the third sample in a pyrolysis furnace at 900 ℃ and minus 0.05MPa for 3h to obtain a fourth sample;

(5) repeating the steps (3) to (4) for ten times to obtain a fifth sample;

(6) and (4) putting the fifth sample obtained in the step (5) into a high-temperature reaction furnace, and sintering for 1h at 1500 ℃ to obtain the high-density SiC/SiC composite material.

Example 5

(1) Weaving three-dimensional five-direction third-generation SiC fibers into a preform with the fiber volume fraction of 40%, selecting propane as a carbon source gas by adopting a chemical vapor deposition method, placing the SiC fiber preform in a chemical vapor deposition furnace, and depositing for 8 hours under the conditions of 980 ℃ and-0.07 MPa to obtain a first sample containing a PyC interface layer with the thickness of 500 nm;

(2) placing the first sample obtained in the step (1) in a chemical vapor deposition furnace, and depositing for 28 hours at 1000 ℃ and under the condition of-0.06 MPa by using trichloromethylsilane as a precursor to obtain a second sample containing a SiC interface layer with the thickness of 4.5 microns;

(3) dipping the second sample in the precursor slurry, and dipping for 4h at 50 ℃ and 4MPa to obtain a third sample; the precursor slurry is a toluene/divinylbenzene solution containing silica-boron oxide (3%), SiC ceramic powder (30%) and perhydropolycarbosilane (55%);

(4) curing the third sample in a high-pressure tank at 300 ℃ and 4MPa for 4h, and then cracking the third sample in a pyrolysis furnace at 1200 ℃ and under-0.01 MPa for 3.5h to obtain a fourth sample;

(5) repeating the steps (3) to (4) for eight times to obtain a fifth sample;

(6) and (4) putting the fifth sample obtained in the step (5) into a high-temperature reaction furnace, and sintering for 3h at 1500 ℃ to obtain the high-density SiC/SiC composite material.

Comparative example 1

Comparative example 1 is substantially the same as example 1 except that: in the step (3), the precursor slurry does not contain sintering aids and SiC ceramic powder; and in the step (6), the sintering temperature is 1600 ℃.

Comparative example 2

Comparative example 2 is substantially the same as example 1 except that: in the step (3), the precursor slurry does not contain a sintering aid; and in the step (6), the sintering temperature is 1600 ℃.

Comparative example 3

Comparative example 3 is substantially the same as example 1 except that: in the step (3), the precursor slurry does not contain SiC ceramic powder.

The highly dense SiC/SiC composite materials obtained in examples 1 to 5 and the SiC/SiC composite materials obtained in comparative examples 1 to 3 were processed to prepare test specimens, and the density and mechanical properties of each test specimen at 1300 ℃ were measured, respectively, and the test data are shown in Table 1.

TABLE 1

Examples	Density/g.cm-3	Flexural Strength/MPa	Tensile strength/MPa
				1	2.70	417	241
2	2.68	415	239
				3	2.70	416	240
4	2.67	413	237
				5	2.69	415	238
Comparative example	Density/g.cm-3	Flexural Strength/MPa	Tensile strength/MPa
				1	2.43	303	148
2	2.45	306	150
				3	2.48	310	155

As can be seen from table 1, the mechanical properties and density of the SiC/SiC composite material obtained by the preparation method of the present invention are significantly improved as compared with comparative example 1, comparative example 2, and comparative example 3. In addition, as shown in fig. 1, the test sample bar obtained in example 1 is subjected to morphology characterization to obtain a microscopic morphology image thereof, and it can be seen from fig. 1 that fiber pores of the SiC/SiC composite material prepared by the invention are uniformly filled, so that the compactness of the composite material can be improved, and further the bending strength and the tensile strength of the composite material are improved.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.