CN110423119B

CN110423119B - Preparation method of ablation-resistant C/SiC ceramic matrix composite

Info

Publication number: CN110423119B
Application number: CN201910725957.5A
Authority: CN
Inventors: 裴雨辰; 于艺; 于新民; 刘俊鹏; 宋环君; 金鑫; 张宝鹏; 刘伟; 王鹏; 李晓东
Original assignee: Aerospace Research Institute of Materials and Processing Technology
Current assignee: Aerospace Research Institute of Materials and Processing Technology
Priority date: 2019-08-07
Filing date: 2019-08-07
Publication date: 2020-09-01
Anticipated expiration: 2039-08-07
Also published as: CN110423119A

Abstract

The invention relates to a preparation method of an ablation-resistant C/SiC ceramic matrix composite. The method comprises the following steps: (1) providing a porous C/C composite preform; (2) preparing the prefabricated body into a C/SiC composite material; (3) mixing polysilazane, boron powder and a solvent, wherein the mass percentage of the polysilazane in the mixture is 30-40%, the mass percentage of the boron powder in the mixture is 10-30%, and uniformly stirring the mixture to obtain a SiBCN precursor solution; (4) and (3) carrying out impregnation, curing and cracking on the composite material by adopting SiBCN precursor solution to obtain the ablation-resistant C/SiC ceramic matrix composite material. The composite material with high density, low ablation rate and excellent comprehensive performance can be obtained by the method.

Description

Preparation method of ablation-resistant C/SiC ceramic matrix composite

Technical Field

The invention relates to the technical field of ceramic composite materials, in particular to a preparation method of an ablation-resistant C/SiC ceramic matrix composite material.

Background

In recent years, high temperature structural ceramic materials have been increasingly valued for their excellent properties. The silicon carbide ceramic has the advantages of high temperature resistance, thermal shock resistance, corrosion resistance, scouring resistance, wear resistance, good heat conduction performance and the like, and is an important candidate material of high-temperature structural ceramic. However, SiC is a covalent bond material, the sintering temperature is high, and the sintering is difficult to be carried out by adopting the conventional sintering methodCompact, usually requiring heating to a temperature above 2100 ℃ and, because of their sintering, requiring the addition of Al₂O₃、Y₂O₃Or MgO, which causes a decrease in mechanical properties and oxidation resistance of the material at high temperatures, and these materials react in a water vapor environment, so that their applications are limited.

Si-C, Si-N, C-N and other covalent bonds exist in the SiBCN structure, and the high-temperature performance of the SiBCN structure is better than that of SiC. The amorphous ceramic is a special structural material with short-range order and long-range disorder, can realize the preparation of a high-density composite material, reduces the porosity, greatly limits a channel for oxygen to enter at high temperature, and improves the ultrahigh temperature performance of the material; and can be crystallized under the condition of high temperature for a long time to generate a SiC phase and a BN phase with excellent high temperature resistance, so that the ultrahigh-temperature oxidation resistance and the mechanical property of the composite material are improved. Compared with SiC ceramic, the amorphous SiBCN ceramic has the excellent structural properties of high hardness, low density, oxidation resistance, creep resistance and the like of ceramic materials, is likely to be applied to extreme conditions of high temperature, high pressure, high frequency and the like, and can not be crystallized and reduce the quality even if the temperature is higher than 1700 ℃. It also has high hardness, low thermal expansion coefficient, high resistance and some photoluminescence properties.

At present, the research on amorphous SiBCN ceramics is less in China, and a great gap exists compared with the research in foreign countries. The preparation of the amorphous SiBCN ceramic mainly comprises a precursor method, a mechanical alloy technology and a hot-pressing sintering technology. Each method has its own features. The temperature required by the preparation by adopting a precursor method is low, so that the reduction of the high-temperature mechanical property of the ceramic caused by adding a harmful oxide sintering aid can be effectively avoided; can synthesize the needed precursor at the atomic level to obtain a product with high purity and uniform microstructure. However, precursor methods also have their limitations. For example, the synthesis time is long, the yield is low, the process is complex, and the precursor is greatly influenced by air and moisture. The SiBCN material prepared by the prior precursor method is only applied to films, fibers and components with smaller sizes, and the preparation of the SiBCN bulk material with large size is limited, so that the report on the mechanical property is also few. The mechanical alloying technology is still in the primary stage, is still incomplete in all aspects, and has a long way to go. Although dense ceramics can be obtained by hot-pressing sintering, the sintering needs to be carried out at high temperature, the time is long, the requirement on equipment is high, and the efficiency is not high. Therefore, the research of a more efficient method, higher synthesis yield and higher temperature resistance precursor becomes a hot spot of future research.

In addition, at present, amorphous ceramics are still in a laboratory stage, mainly applied as block materials, and researches on continuous carbon fiber impregnated multi-element amorphous ceramic composite materials are very little. The main problem to be solved in the research process is the bonding strength of the multi-amorphous phase and the carbon fiber matrix.

Disclosure of Invention

The invention aims to provide a preparation method of an ablation-resistant C/SiC ceramic matrix composite.

In order to achieve the purpose, the invention provides the following technical scheme:

a preparation method of an ablation-resistant C/SiC ceramic matrix composite material comprises the following steps:

(1) providing a porous C/C composite preform;

(2) preparing the prefabricated body into a C/SiC composite material;

(3) mixing polysilazane, boron powder and a solvent, wherein the mass percentage of the polysilazane in the mixture is 30-40%, the mass percentage of the boron powder in the mixture is 10-30%, and uniformly stirring the mixture to obtain a SiBCN precursor solution;

(4) and carrying out impregnation, curing and cracking on the composite material by adopting SiBCN precursor solution to obtain the ablation-resistant C/SiC ceramic matrix composite material.

Preferably, the boron powder accounts for 20% by mass.

Preferably, in step (3), the solvent is selected from any one or more of chloroform, carbon tetrachloride, acetone, ethyl acetate, tetrahydrofuran, toluene, xylene, dimethyl sulfoxide, chlorobenzene, dichlorobenzene or trichlorobenzene.

Preferably, the density is 0.8 to 1.0g/cm³The porous C/C composite preform of (1).

Preferably, the first and second electrodes are formed of a metal,preparing the prefabricated body into a material with the density of 1.8-2.0 g/cm³The C/SiC composite material of (1).

Preferably, in the step (2), the precursor is impregnated, cured and cracked by polycarbosilane solution to prepare the C/SiC composite material;

and if the impregnation, curing and cracking processes are carried out once and the density requirement cannot be met, repeating the impregnation, curing and cracking processes until the density requirement is met.

Preferably, in the step (4), the impregnation is vacuum impregnation, the vacuum degree is-0.1 to-0.3 MPa, the impregnation liquid submerges the workpiece for at least 10mm, and the impregnation time is 50 to 60 min;

curing at 120-180 ℃ and under air or inert atmosphere; and/or

The cleavage is carried out below 1400 ℃ and under an ammonia atmosphere.

Preferably, the impregnating, curing and cracking steps are repeated so that the weight gain of the material does not exceed 1%.

Preferably, carbon is deposited in the carbon fiber preform by a chemical vapor infiltration method to obtain the porous C/C composite preform.

Preferably, the carbon fiber preform adopts a needle-punched laminated weftless fabric felt, and more preferably adopts a density of 0.4-0.5g/cm³Needle punched laminated weftless fabric felt

Advantageous effects

The technical scheme of the invention has the following advantages:

the method uses an organic precursor as a raw material to impregnate a continuous carbon fiber woven body (preferably a needle-punched laminated weftless fabric felt), realizes the densification of the composite material by continuous impregnation and cracking, and selects polysilazane and boron powder as the raw material.

According to the invention, the continuous fiber braid is introduced, and the ultrahigh-temperature phase amorphous SiBCN ceramic is impregnated on the surface of the continuous carbon fiber to protect the matrix, so that the ultrahigh-temperature performance of the braided matrix is improved, and the composite material with higher density is obtained, and the high-temperature mechanical property of the braided matrix can be greatly improved, thereby solving the brittleness problem of the amorphous-structure multi-element ceramic and expanding the application range of the amorphous-structure multi-element ceramic.

The interface layer is prepared on the surface of the carbon fiber, and the element B is introduced while the SiC matrix is prepared to establish the chemical combination of the amorphous phase and the matrix, so that the combination strength of the multi-element amorphous phase and the carbon fiber matrix is improved.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

The invention provides a preparation method of an ablation-resistant C/SiC ceramic matrix composite, which comprises the following steps:

(1) providing a porous C/C composite material preform, preferably with a density of 0.8-1.0 g/cm³(may be any value within the range, for example, may be 0.8g/cm³、0.9g/cm³、1.0g/cm³) The porous C/C composite preform of (1).

According to the invention, a CVI densified carbon fiber preform can be adopted, the carbon fiber preform is placed in a chemical vapor deposition furnace, a green body is subjected to chemical deposition by using a CVI process, and a carbon source gas is cracked in a low vacuum environment, then diffuses into pores of the carbon fiber preform and deposits on the pore wall to obtain a porous C/C composite material preform. The densification process may use propylene as a carbon source gas and nitrogen as a carrier gas, and the deposition temperature may be 800 to 1100 ℃, and may be any value within the range, for example, 800 ℃, 850 ℃, 900 ℃, 950 ℃, 1000 ℃, 1050 ℃, 1100 ℃. In this step, the carbon fiber preform used is preferably a needle-punched laminated laid-up laid-fabric felt, more preferably having a density of 0.4 to 0.5g/cm³The needle punched laminated laid felt.

(2) Preparing the prefabricated body into a C/SiC composite material, preferably preparing the C/SiC composite material into a C/SiC composite material with the density of 1.8-2.0 g/cm³(may be any within the rangeThe desired value, for example, may be 1.8g/cm³、1.9g/cm³、2.0g/cm³) The C/SiC composite material of (1). In the step, the C/SiC composite material is prepared by adopting polycarbosilane solution to carry out precursor impregnation, curing and cracking. If the impregnation, curing and cracking process is carried out once and the density requirement cannot be met, the impregnation, curing and cracking process needs to be repeated until the density requirement is met. The polycarbosilane solution used comprises polycarbosilane and a solvent, and the solvent can adopt any one or more of chloroform, carbon tetrachloride, acetone, ethyl acetate, tetrahydrofuran, toluene, xylene, dimethyl sulfoxide, chlorobenzene, dichlorobenzene or trichlorobenzene. The polycarbosilane solution used in this step of the present invention may have a concentration of 60-70%, i.e., 60-70% by weight of polycarbosilane in the solution, and may have any value within this range, for example, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%.

For the impregnation, curing and cracking process in this step, reference may be made to the prior art, which is not described in detail herein.

(3) And mixing the polysilazane, the boron powder and the solvent, and uniformly stirring the mixture to obtain the SiBCN precursor solution.

The solute of the SiBCN precursor solution is polysilazane, wherein the polysilazane can be diluted by various polar or nonpolar dry solvents, but is sensitive to water and alcohol solvents and is easy to generate hydrolysis or alcoholysis reaction, so that the product is deteriorated, and therefore, any one or more of chloroform, carbon tetrachloride, acetone, ethyl acetate, tetrahydrofuran, toluene, xylene, dimethyl sulfoxide, chlorobenzene, dichlorobenzene or trichlorobenzene can be used as the solvent of the precursor solution in the step. In addition, the polysilazane should be protected from a protic substance such as an acid or a base. In the present invention, the mass percentage of polysilazane in the SiBCN precursor solution is preferably adjusted to be in the range of 30 to 40%, and any value in this range may be selected during the operation, for example, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%.

The proportion of boron powder added to the SiBCN precursor solution is 10 to 30%, and any value within this range may be selected during operation, and may be, for example, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, and most preferably 20%. The inventor finds that when the boron powder concentration in the SiBCN precursor solution is too high, the boron powder is easy to gather on the surface of the material, so that the channel of the SiBCN precursor solution entering the material is reduced, the densification efficiency is affected, and the density of the final material is reduced. And if the concentration of the boron powder is too low, the preparation period of the material is prolonged. Based on this finding, the present invention preferably adjusts the boron powder content of the SiBCN precursor solution to be in the range of 10 to 30% by mass.

In the subsequent impregnation and cracking stage, the SiBCN precursor solution preferably achieves crosslinking and curing under the conditions of 120-180 ℃ (which may be any value within the range, such as 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃, 160 ℃, 165 ℃, 170 ℃, 175 ℃ and 180 ℃), and the curing can be carried out under air or inert atmosphere. In addition to this curing method, the hydrosilylation reaction may be carried out using a platinum catalyst, and curing may be carried out at 80 to 100 ℃ (which may be any value within this range, for example, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃), and the curing time is generally 2 to 5 hours, depending on the curing temperature and the amount of catalyst used, and may be any value within this range, for example, 2 hours, 3 hours, 4 hours, 5 hours.

The condensate is first converted into amorphous ceramic through pyrolysis, and finally crystalline ceramic is obtained. The product is amorphous below 1400 deg.C, and begins to crystallize above 1400 deg.C. The composition of the ceramic product is closely related to the cracking atmosphere, and SiC and SiBCN are used under the condition of nitrogen or argon; mainly SiBCN under the atmosphere of ammonia gas; predominantly SiOCN under air conditions. Based on this, the present invention is carried out under the conditions of 1400 ℃ or lower in the cracking step in this step and in an ammonia gas atmosphere.

The impregnation is vacuum impregnation, the vacuum degree is-0.1 to-0.3 MPa, the impregnation liquid submerges the workpiece by at least 10mm, and the impregnation time is 50 to 60 min.

The curing conditions are as described above, and preferably the crosslinking curing is carried out at 120-180 ℃, and the curing can be carried out under air or inert atmosphere. In addition to this curing process, hydrosilylation can be carried out using a platinum catalyst at 80 to 100 ℃ for a period of time, generally 2 to 5 hours, depending on the curing temperature and the amount of catalyst used.

The cracking conditions are preferably 1400 ℃ or less and are carried out under an ammonia atmosphere.

In this step, the impregnation, curing and cracking steps are repeated so that the weight gain of the material does not exceed 1%.

The following are examples of the present invention.

Example 1

(1) Carrying out chemical deposition on the blank by using a CVI (chemical vapor infiltration) process to obtain a porous C/C composite material preform, and depositing until the density is 0.8g/cm³The densification process uses propylene as carbon source gas and nitrogen as carrier gas, and the deposition temperature is 900 ℃.

(2) Adopting polycarbosilane solution to carry out precursor impregnation, solidification and cracking to prepare C/SiC composite material, carrying out multiple times of impregnation and cracking to prepare the C/SiC composite material with the density of 1.8g/cm³The C/SiC composite material of (1).

(3) Chloroform is used as a solvent, and polysilazane and boron powder are added, wherein the content of the polysilazane in the mixed solution is 35 wt%, and the content of the boron powder in the mixed solution is 20 wt%. And stirring uniformly to obtain SiBCN precursor solution.

(4) And (3) carrying out impregnation, curing and cracking on the C/SiC composite material prepared in the step (2) by using the obtained precursor solution. The impregnation is vacuum impregnation with a vacuum degree of-0.1 MPa, the impregnation liquid submerges the workpiece by at least 10mm, and the impregnation time is 50 min. The curing is carried out at 140 ℃ in an inert atmosphere for 3 h. The cracking is carried out at 1300 ℃ under the atmosphere of ammonia gas, and amorphous products are obtained through cracking. And repeating the impregnation cracking process until the weight of the composite material is increased by less than 1%.

(5) And processing the obtained sample piece into a test sample strip, and testing the performance.

Examples 2 to 4

The preparation method is basically the same as that of example 1, except that:

for example 2, in step (2), multiple cycles of maceration were carried out to prepare a density of 1.9g/cm³The ceramic matrix composite of (1).

For example 3, in step (2), multiple cycles of maceration were carried out to prepare a density of 2.0g/cm³The ceramic matrix composite of (1).

For example 4, in step (2), multiple cycles of maceration were carried out to prepare a density of 2.5g/cm³The ceramic matrix composite of (1).

The test results of the test specimens are shown in Table 1.

TABLE 1

Comparing the test results of examples 1 to 4, the inventors found that as the density of the C/SiC composite material increases, the mechanical properties of the final composite material also become better. The inventors speculate that this is due to the relatively dense C/SiC composite material which protects the fibers and the interface layer well, thereby enhancing the mechanical properties. When the density of the C/SiC composite material is too high, the mechanical property of the composite material is better theoretically. However, the inventors found that when the density of the C/SiC composite material is too high, this corresponds to a low proportion of SiBCN amorphous ceramic in the final material, which results in a weak chemical bonding between the amorphous phase and the matrix, and thus a decrease in mechanical properties of the final material may occur. In addition, the inventors have also found that as the density of the C/SiC composite increases, the ablation resistance of the final material also increases, as shown in the TableThe compactness of the bright C/SiC composite material plays a key role, even if the proportion of SiBCN amorphous ceramic in the final material is lower and lower, the influence on the ablation resistance of the material is small, and the matrix with better compactness can still ensure the ablation resistance of the material. However, when the density of the C/SiC composite material is too high, the ratio of SiBCN amorphous ceramics in the final material is too low, and the mechanical property is not good, so that the long-time high-temperature oxidation resistance effect of the C/SiC composite material is affected. Based on the method, the density of the SiC matrix is preferably controlled to be 1.8-2.0 g/cm in the preparation process³. Example 5 to example 7

The preparation method is basically the same as that of example 1, except that:

for example 5, in step (2), the proportion of boron powder added to the solution was 20%.

For example 6, in step (2), the proportion of boron powder added to the solution was 30%.

For example 7, in step (2), the proportion of boron powder added to the solution was 40%.

The test results of the test specimens are shown in Table 2.

TABLE 2

As can be seen from Table 2, with the increase of the proportion of the boron powder, the material has a relatively wide temperature-resistant area, better and better ablation resistance and better mechanical properties. This is because the chemical bonding strength between the amorphous phase and the matrix becomes better and better with the increase of boron powder, thereby improving the mechanical properties of the material as a whole. And because the amorphous phase after high-temperature cracking accounts for a large amount, the boron nitride has the oxidation resistance temperature of 900 ℃ and good lubricity at high temperature, is an excellent high-temperature solid lubricant, has stable chemical property, is chemically inert to almost all molten metals, and can resist high temperature of 2000 ℃, so that the ablation resistance of the material is improved. However, when the amount of boron powder added is too high, the mechanical properties of the final material are rather reduced. This is because boron powder is easily accumulated on the surface of the material, and the channel of the SiBCN precursor solution entering the material is reduced, which affects the densification efficiency and effect, thereby causing the reduction of the mechanical properties of the material. When the boron powder is added in an excessive amount, the ablation resistance of the final material does not show a significant improvement. The inventors speculate that the density of the final material decreases due to the degree of densification of the material being affected, thereby affecting the ablation resistance of the material to some extent, and that even if the amorphous phase is slightly higher than before, the ablation resistance cannot be significantly improved.

The inventors have also found that when the deposition density and the SiC matrix density are the same, the composite material having a high final density (referring to the density of the material after repeated impregnation curing cracking with the SiBCN precursor solution) is enhanced in ablation resistance with the impregnation cracking of the SiBCN solution, which is not difficult to understand because the amorphous phase ceramic produced at high temperature has a strong ablation resistance level, and the greater the number of impregnation times, the greater the amount of the produced amorphous phase ceramic. When the temperature is lower than 1600 ℃, the SiC matrix has protective effect on the fiber, and SiO is generated at high temperature₂Has certain viscosity, and fills the gap on the surface of the material. When the temperature exceeds 2000 ℃, the generated amorphous phase has ultrahigh-temperature antioxidation.

However, this does not mean that the higher the density of the final material is, the better, besides the requirement of application environment for "light weight", the problem of non-uniform distribution of amorphous phase in the material is easy to occur due to too many times of impregnation, and the control of the finished product is not good.

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.

Claims

1. The preparation method of the ablation-resistant C/SiC ceramic matrix composite is characterized by comprising the following steps:

(1) providing a porous C/C composite preform;

(2) preparing the preform into a density of 1.8-2.0 g/cm³The C/SiC composite material of (1);

(4) dipping, curing and cracking the composite material by adopting SiBCN precursor solution to obtain the ablation-resistant C/SiC ceramic matrix composite material, wherein the dipping is vacuum dipping, the vacuum degree is-0.1 to-0.3 MPa, the dipping solution is at least 10mm over the workpiece, and the dipping time is 50 to 60 min; curing at 120-180 ℃ and under air or inert atmosphere; cracking at 1400 deg.C or below and under ammonia atmosphere; repeating the impregnating, curing and cracking steps such that the weight gain of the material does not exceed 1%.

2. The production method according to claim 1,

the mass percentage of the boron powder is 20%.

3. The production method according to claim 1,

in the step (3), the solvent is selected from any one or more of chloroform, carbon tetrachloride, acetone, ethyl acetate, tetrahydrofuran, toluene, xylene, dimethyl sulfoxide, chlorobenzene, dichlorobenzene or trichlorobenzene.

4. The production method according to claim 1,

providing a density of 0.8 to 1.0g/cm³The porous C/C composite preform of (1).

5. The production method according to any one of claims 1 to 4,

in the step (2), the polycarbosilane solution is adopted to carry out precursor impregnation, curing and cracking to prepare the C/SiC composite material;

if the density requirement cannot be met by carrying out the impregnation, curing and cracking procedures once,

the dipping, curing and cracking process is repeated until the density requirement is reached.

6. The production method according to claim 1,

and depositing carbon in the carbon fiber preform by adopting a chemical vapor infiltration method to obtain the porous C/C composite material preform.

7. The production method according to claim 6,

the carbon fiber prefabricated body adopts a needle punched laminated weftless fabric felt.

8. The production method according to claim 7,

the carbon fiber preform has a density of 0.4-0.5g/cm³The needle punched laminated laid felt.