CN113979752B - Mullite fiber reinforced ceramic matrix composite and preparation method thereof - Google Patents

Abstract

The invention particularly relates to a mullite fiber reinforced ceramic matrix composite and a preparation method thereof. The method comprises the following steps: 1) Preparation on the surface of mullite fiber (BN/SiC) _n Alternating the interface layers to obtain a reinforcement body containing a BN/SiC interface layer; wherein n represents the layer number of BN/SiC, and n is a natural number which is more than or equal to 1; (2) Taking liquid polycarbosilane as an impregnating solution to impregnate the reinforcement body containing the BN/SiC interface layer to obtain a first sample; (3) Sequentially solidifying and cracking the first sample to obtain a second sample; (4) And (4) repeating the steps (2) to (3) for at least 5 times to obtain the mullite fiber reinforced ceramic matrix composite. The mullite fiber reinforced ceramic matrix composite material prepared by the invention has excellent oxidation resistance.

Description

A kind of mullite fiber reinforced ceramic matrix composite material and preparation method thereof

technical field

The invention relates to the field of thermal structural composite materials, in particular to a mullite fiber reinforced ceramic matrix composite material and a preparation method thereof.

Background technique

C/SiC ceramic matrix composites have a series of excellent properties such as low density, high temperature resistance, high specific modulus, high specific strength and thermal shock resistance, and have broad application prospects in the aerospace field. However, the C/SiC-based composite material contains a large amount of carbon, and the carbon fiber and carbon matrix will be oxidized at high temperature, resulting in a decrease in the performance of the composite material; especially at a high temperature of 1000°C to 1200°C, the composite material is more prone to oxidation. Therefore, in view of the above deficiencies, it is necessary to provide a ceramic matrix composite material with excellent oxidation resistance.

Contents of the invention

The invention provides a mullite fiber reinforced ceramic matrix composite material and a preparation method thereof. The mullite fiber reinforced ceramic matrix composite material has excellent oxidation resistance.

In a first aspect, the present invention provides a method for preparing a mullite fiber reinforced ceramic matrix composite material, the preparation method comprising the following steps:

(1) Prepare (BN/SiC) _n alternating interfacial layers on the surface of the mullite fiber to obtain a reinforcement comprising a BN/SiC interfacial layer; wherein, n represents the number of layers of BN/SiC, n≥1 and is a natural number;

(2) using liquid polycarbosilane as an impregnating liquid, impregnating the reinforcing body comprising the BN/SiC interface layer to obtain a first sample;

(3) sequentially curing and cracking the first sample to obtain a second sample;

(4) Repeat steps (2) to (3) at least 5 times to obtain the mullite fiber reinforced ceramic matrix composite material.

Preferably, in step (1), the mullite fiber is a mullite fiber mat or a mullite fiber preform;

The mullite fiber preforms include 2D laminated preforms, 2.5D acupuncture preforms, 3D braided preforms, and stitched preforms;

The fiber volume fraction of the mullite fiber preform is 5-40%;

The mullite fiber preform is made from continuous mullite long fibers.

Preferably, n in the (BN/SiC) _n alternating interface layer is 3.

Preferably, said step (1) includes the following sub-steps:

(1.1) Depositing the mullite fiber preform in a first atmosphere comprising boron trichloride, ammonia, hydrogen and nitrogen, to obtain a third sample with a layer of BN deposited on the surface;

(1.2) Depositing the third sample in a second atmosphere comprising trichloromethylsilane, argon and hydrogen to obtain a fourth sample with a layer of SiC deposited on the surface;

(1.3) Repeating steps (1.1) to (1.2) n times, then raising the temperature to 1200-1300° C. and keeping it warm for 1-4 hours, to obtain the reinforcement body containing the BN/SiC interface layer.

Preferably, in step (1.1), the molar ratio of the boron trichloride to the ammonia is 1:(2-3); the deposition temperature is 650-850°C, the deposition pressure is 5-10kPa, and the deposition time 10 to 30 hours.

Preferably, in step (1.2), the molar ratio of the trichloromethylsilane to the hydrogen is 1:(2-3); the deposition temperature is 1000-1100°C, the deposition pressure is 5-10kPa, and the deposition time 10 to 30 hours.

Preferably, the thickness of the single-layer BN layer is 100-300 nm;

The thickness of the single SiC layer is 200-400 nm.

Preferably, in step (2), the vacuum degree of the impregnation is 5-20 kPa, the impregnation pressure is 2-5 MPa, and the impregnation time is 1-4 hours.

Preferably, in step (3), the curing reaction temperature is 250-300° C., the curing time is 1-4 hours, and the curing pressure is 2-5 MPa.

Preferably, in step (3), the cracking reaction temperature is 950-1300° C., the cracking time is 2-6 hours, and the cracking pressure is 5-10 MPa.

Preferably, in step (4), the number of times of repeating steps (2) to (3) is 5 to 8 times.

In the second aspect, the present invention provides a mullite fiber-reinforced ceramic matrix composite material, which is prepared by any of the preparation methods described in the first aspect above.

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

(1) The present invention adopts the mullite fiber prefabricated body as the reinforcing body, uses the liquid polycarbosilane as the ceramic substrate, by virtue of the low density, high temperature resistance and anti-oxidation characteristics of mullite, and introducing boron into the substrate, jointly improve The high-temperature thermal stability of the prepared mullite fiber-reinforced ceramic matrix composite material is improved, so that its mechanical properties and oxidation resistance at room temperature and 1200 °C are significantly better than the existing C/SiC ceramic matrix composite material, and has excellent Antioxidant properties.

(2) The present invention adopts CVI process to prepare (BN/SiC) _n alternating interface layer on the surface of mullite fiber, and then uses liquid polycarbosilane to perform several in-situ PIP processes to densify the silicon carbide matrix to obtain mullite fiber Reinforced ceramic matrix composites; in this way, the mullite fiber and silicon carbide ceramic matrix are connected through (BN/SiC) _n alternating interface layers, which can inhibit the damage caused by chemical infiltration and physical shrinkage to the fiber preform, and at the same time alleviate the damage caused by the fiber preform and The thermal stress caused by the difference in the intrinsic structure of the ceramic matrix improves the bonding strength between the two, making the prepared mullite fiber reinforced ceramic matrix composite more stable; when the crack extends to the (BN/SiC) _n alternating interface layer At the same time, the cracks will propagate between the layers to realize the toughening function, thereby enhancing the mechanical properties of the mullite fiber reinforced ceramic matrix composite.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are For some embodiments of the present invention, those skilled in the art can also obtain other drawings based on these drawings without creative work.

Fig. 1 is the flow chart of the preparation method of a kind of mullite fiber reinforced ceramic matrix composite material provided by the present invention;

Fig. 2 is a morphology diagram of a mullite fiber reinforced ceramic matrix composite material provided by the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the protection of the present invention. scope.

As shown in Figure 1, the present invention provides a kind of preparation method of mullite fiber reinforced ceramic matrix composite material, and this preparation method comprises the following steps:

(1) Prepare (BN/SiC) _n alternating interfacial layers on the surface of the mullite fiber preform to obtain a reinforcement containing BN/SiC interfacial layers; where n represents the number of layers of BN/SiC, n≥1 and is Natural number;

(2) using liquid polycarbosilane as an impregnating liquid, impregnating the reinforcing body comprising the BN/SiC interface layer to obtain a first sample;

(3) sequentially curing and cracking the first sample to obtain a second sample;

(4) Repeat steps (2) to (3) at least 5 times to obtain the mullite fiber reinforced ceramic matrix composite material.

It should be noted that n is 1, 2, 3, 4 or 5, etc., and n is specifically limited according to the actual requirements of the mullite fiber reinforced ceramic matrix composite material.

In the present invention, since mullite is the only stable binary compound in the Al ₂ O ₃ -SiO ₂ system, its components are all oxides, so compared with the traditional carbon fiber and carbon matrix, it is more stable under high temperature. No oxidation reaction occurs, so it has better stability in an oxidizing environment; at the same time, the boron nitride interface layer (BN layer) and SiC layer with high temperature oxidation resistance are composed of mullite fiber reinforced ceramic matrix composites. The periodic interface layer of the interface layer.

In the present invention, since the BN interface layer has a layered structure similar to pyrolytic carbon, a better weak interface layer can be obtained on the surface of the mullite fiber, and _B2O3 is produced under high-temperature oxidation _conditions , and the oxidation product of the SiC layer _SiO2 can produce borosilicate glass phase in situ, inhibit the further diffusion of oxidation, and then protect the BN layer and SiC layer from oxidation, and play an anti-oxidation role.

In a preferred embodiment, in step (1), the mullite fiber is a mullite fiber mat or a mullite fiber preform;

The mullite fiber preforms include 2D laminated preforms, 2.5D acupuncture preforms, 3D braided preforms, and stitched preforms;

The fiber volume fraction of the mullite fiber preform is 5-40% (for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35% or 40%);

The mullite fiber preform is made from continuous mullite long fibers.

According to some more preferred embodiments, n in the (BN/SiC) _n alternating interface layer is 3.

According to some preferred embodiments, the step (1) includes the following sub-steps:

(1.1) Depositing the mullite fiber preform in a first atmosphere comprising boron trichloride, ammonia, hydrogen and nitrogen, to obtain a third sample with a layer of BN deposited on the surface;

(1.2) Depositing the third sample in a second atmosphere comprising trichloromethylsilane, argon and hydrogen to obtain a fourth sample with a layer of SiC deposited on the surface;

(1.3) Repeat steps (1.1) to (1.2) n times, and then raise the temperature to 1200-1400°C (for example, it can be 1200°C, 1220°C, 1250°C, 1260°C, 1280°C, 1300°C, 1320°C, 1350°C , 1360°C, 1380°C or 1400°C) and keep it warm for 1 to 4h (for example, it can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h), to obtain the reinforcement comprising the BN/SiC interface layer .

In the present invention, preferably, the first atmosphere is composed of boron trichloride, ammonia, hydrogen and nitrogen; the second atmosphere is composed of trichloromethylsilane, argon and hydrogen. Compared with borazine, when the BN layer is deposited by the first atmosphere, the deposition temperature is lower, so the energy consumption required for the preparation process is lower and more energy-saving.

In the present invention, the purpose of heating up is to make the prepared BN layer undergo phase transition, obtain hexagonal boron nitride with a layered structure, so as to obtain a weak interface, so that cracks segregate repeatedly in the weak interface layer, consuming a large amount of fracture energy, Thereby improving the fracture toughness of the final composite material.

According to some preferred embodiments, in step (1.1), the molar ratio of the boron trichloride to the ammonia is 1:(2～3) (for example, it can be 1:2, 1:2.2, 1 :2.4, 1:2.5, 1:2.6, 1:2.8 or 1:3); the deposition temperature is 650-850°C (for example, it can be 650°C, 700°C, 750°C, 800°C or 850°C), and the deposition pressure 5-10kPa (for example, it can be 5kPa, 6kPa, 7kPa, 8kPa, 9kPa or 10kPa), and the deposition time is 10-30h (for example, it can be 10h, 15h, 20h or 30h).

According to some preferred embodiments, in step (1.2), the molar ratio of the trichloromethylsilane to the hydrogen is 1:(2-3) (for example, it can be 1:2, 1:2.2, 1 :2.4, 1:2.5, 1:2.6, 1:2.8 or 1:3); the deposition temperature is 1000～1100°C (for example, it can be 1000°C, 1020°C, 1050°C, 1080°C or 1100°C), the deposition pressure 5-10kPa (for example, it can be 5kPa, 6kPa, 7kPa, 8kPa, 9kPa or 10kPa), and the deposition time is 10-30h (for example, it can be 10h, 15h, 20h or 30h).

In the present invention, ammonia and boron trichloride are reaction gases in the first atmosphere, hydrogen is used for its catalytic effect, and nitrogen is used to fully mix ammonia, boron trichloride and hydrogen. Trichloromethylsilane and hydrogen in the second atmosphere are reaction gases for obtaining the SiC layer.

It should be noted that in the present invention, the BN layer is first prepared and then the SiC layer is prepared, because the BN layer has a layered structure similar to pyrolytic carbon, and a better weak interface layer can be obtained on the surface of the mullite fiber, which is beneficial to Improve the fracture toughness of the final ceramic matrix composite material. However, if the SiC layer is prepared first and then the BN layer is prepared, the bonding strength between the SiC layer and the mullite fiber is relatively high, which is not conducive to forming a weak interface on the surface of the mullite fiber.

According to some preferred embodiments, the thickness of the single-layer BN layer is 100-300nm (for example, it can be 100nm, 120nm, 150nm, 160nm, 180nm, 200nm, 220nm, 250nm, 260nm, 280nm or 300nm);

The thickness of the single SiC layer is 200-400nm (eg, 200nm, 220nm, 240nm, 250nm, 260nm, 280nm, 300nm, 320nm, 340nm, 350nm, 360nm, 380nm or 400nm).

In the present invention, since the high temperature resistance of SiC is better than that of BN, it is more conducive to the excellent high temperature stability of the prepared composite material, so the thickness of the single layer of SiC layer needs to be greater than the thickness of the single layer of BN layer. In this way, it can be avoided that when the thickness of the single-layer BN layer is relatively thick, it is easy to oxidize and generate a large amount of B ₂ O ₃ under high-temperature oxidation conditions, thereby affecting the interface performance and high-temperature stability of the material.

It should be noted that the thickness of the (BN/SiC) _n alternating interface layer can be controlled by adjusting the process parameters, and the performance of mullite fiber reinforced ceramic matrix composites can be improved by adjusting the number of layers (n) and thickness.

According to some preferred embodiments, in step (2), the impregnation vacuum is 5-20kPa (for example, it can be 5kPa, 8kPa, 10kPa, 12kPa, 15kPa, 18kPa or 20kPa), and the impregnation pressure is 2-5MPa (For example, it can be 2MPa, 3MPa, 4MPa or 5MPa), and the immersion time is 1-4h (for example, it can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h).

According to some preferred embodiments, in step (3), the curing reaction temperature is 250-300°C (for example, it can be 250°C, 260°C, 270°C, 280°C, 290°C or 300°C), and the curing The time is 1~4h (for example, it can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h or 4h), and the curing pressure is 2~5MPa (for example, it can be 2MPa, 2.5MPa, 3MPa, 3.5MPa, 4MPa , 4.5MPa or 5MPa).

According to some preferred embodiments, in step (3), the cracking reaction temperature is 950-1300°C (for example, it can be 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C or 1300°C), the cracking time is 2-6h (for example, it can be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h), and the cracking pressure is 5-10MPa (for example, it can be 5MPa, 6MPa, 7MPa, 8MPa, 9MPa or 10MPa).

In some more preferred embodiments, in step (4), the number of times of repeating steps (2) to (3) is 5 to 8 times (for example, it may be 5 times, 6 times, 7 times or 8 times).

The present invention also provides a mullite fiber reinforced ceramic matrix composite material, which is prepared by using the preparation method provided by the present invention.

In order to illustrate the technical solution and advantages of the present invention more clearly, a mullite fiber reinforced ceramic matrix composite material and its preparation method will be described in detail below through several examples.

Example 1

(1) On the surface of the mullite fiber preform (sewn preform, the fiber volume fraction is 35%), the (BN/SiC) ₃ alternating interface layer is prepared by chemical vapor deposition, and the reinforcement containing the BN/SiC interface layer is obtained :

(1.1) The mullite fiber preform is placed in the first atmosphere (the molar ratio of boron trichloride and ammonia is 1:2) including boron trichloride, ammonia, hydrogen and nitrogen, and heated at 700°C , 6kPa under the condition of depositing 20h, obtain the third sample of surface deposition one deck BN layer (the thickness of monolayer BN layer is 200nm);

(1.2) Place the third sample in a second atmosphere including trichloromethylsilane, argon and hydrogen (the molar ratio of trichloromethylsilane and hydrogen is 1:2), and Under conditions, deposit 30h, obtain the 4th sample of surface depositing a layer of SiC layer (the thickness of single-layer SiC layer is 400nm);

(1.3) Repeat steps (1.1) to (1.2) 3 times, then raise the temperature to 1300° C. and keep it warm for 2 hours to obtain a reinforcement comprising a (BN/SiC) ₃ interface layer;

(2) Using liquid polycarbosilane as the impregnating liquid, impregnate the reinforcing body containing the (BN/SiC) ₃ interface layer (impregnate for 3 hours under the conditions of a vacuum of 5kPa and a pressure of 4MPa), to obtain the first sample;

(3) The first sample was sequentially cured (cured at 250°C and 4MPa for 2h), and cracked (cracked at 1200°C and 6MPa for 2h) to obtain the second sample;

(4) Steps (2) to (3) were repeated six times to obtain a mullite fiber-reinforced ceramic matrix composite (its appearance and morphology are shown in Figure 2).

Example 2

Embodiment 2 is basically the same as Embodiment 1, except that the number of repetitions in step (4) is 8 times.

Example 3

Example 3 is basically the same as Example 1, except that n is 2 in step (1), that is, (BN/SiC) ₂ alternating interface layers are prepared.

Example 4

Embodiment 4 is basically the same as Embodiment 1, and its difference is:

The mullite fiber prefabricated body adopted in the step (1) is a stitched prefabricated body, and the fiber volume fraction is 30%;

In the step (1.1), the molar ratio of boron trichloride and ammonia is 1:3; depositing at 650°C and 5kPa for 30h, the thickness of the monolayer BN layer is 300nm;

In step (1.2), the molar ratio of trichloromethylsilane to hydrogen is 1:3; deposition is carried out at 1000°C and 5kPa for 30h, and the thickness of the single-layer SiC layer is 400nm;

In step (1.3), repeat steps (1.1) to (1.2) 4 times, then raise the temperature to 1200° C. and keep it warm for 4 hours to obtain a reinforcement comprising a (BN/SiC) ₄ interface layer;

Step (2) in the vacuum degree of 20kPa, the pressure is 2MPa under the conditions of immersion 1h;

In step (3), solidify at 280° C. and 5 MPa for 4 hours; and crack at 1300° C. and 10 MPa for 4 hours.

Example 5

Embodiment 5 is basically the same as Embodiment 1, and its difference is:

The mullite fiber adopted in the step (1) is a sutured mullite fiber prefabricated body, and the fiber volume fraction is 10%;

In the step (1.1), the molar ratio of boron trichloride and ammonia is 1:2.5; the deposition is carried out at 850°C and 10kPa for 10h, and the thickness of the single-layer BN layer is 100nm;

In step (1.2), the molar ratio of trichloromethylsilane to hydrogen is 1:2.5; deposition is carried out at 1050°C and 10kPa for 10h, and the thickness of the single-layer SiC layer is 200nm;

In step (1.3), repeat steps (1.1) to (1.2) 6 times, then raise the temperature to 1400° C. and keep it warm for 1 hour to obtain a reinforcement comprising (BN/SiC) ₆ interface layer;

Step (2) in the vacuum degree of 5kPa, the pressure is 5MPa under the conditions of immersion 4h;

In step (3), solidify at 300° C. and 2 MPa for 3 hours; and crack at 950° C. and 5 MPa for 3 hours.

Comparative example 1

Comparative Example 1 is basically the same as Example 1, with the difference that: in step (1), a carbon fiber prefabricated body is selected as the reinforcing body.

Comparative example 2

Comparative example 2 is substantially the same as embodiment 1, and its difference is: in step (1):

(1.1) The mullite fiber preform is placed in a second atmosphere (the molar ratio of trichloromethylsilane and hydrogen is 1:2) including trichloromethylsilane, argon and hydrogen, and at 1100 ° C, Under the condition of 6kPa, carry out deposition 30h, obtain the 3rd sample that surface deposits a layer of SiC layer (the thickness of monolayer SiC layer is 400nm);

(1.2) Place the third sample in the first atmosphere including boron trichloride, ammonia, hydrogen and nitrogen (the molar ratio of boron trichloride and ammonia is 1:2), and heat it at 700°C and 6kPa Deposit 20h under the condition of above, obtain the 4th sample of surface deposition one deck BN layer (the thickness of monolayer BN layer is 200nm);

(1.3) Steps (1.1) to (1.2) were repeated three times, and then the temperature was raised to 1300°C and kept for 2 hours to obtain a reinforcement containing a (SiC/BN) ₃ interface layer.

The composite materials obtained in Examples 1 to 5 and Comparative Examples 1 to 2 were used as samples, and were tested for flexural strength at room temperature (25°C), and oxidized in an air atmosphere at 1200°C for 10h to perform oxidation resistance Evaluation test, the test results are shown in Table 1.

Table 1

As can be seen from the data in Table 1, based on Example 1 and Comparative Example 1, it can be found that compared with the mullite fiber preform, due to the presence of carbon that is easily oxidized at high temperatures in the carbon fiber preform, the composite material prepared in Comparative Example 1 The weight loss at 1200 ° C is relatively large, so its oxidation resistance is poor; also based on Example 1 and Comparative Example 2, it can be found that in the composite material prepared in Comparative Example 2, due to the bonding between the SiC layer and the mullite fiber The strength is high, and it is not easy to form a weak interface, thus affecting the bending performance of the prepared composite material. In summary, the mullite fiber-reinforced ceramic matrix composite material prepared in the present invention has more excellent oxidation resistance under the premise of ensuring a certain bending strength.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention. Parts not described in detail in the present invention are well-known technologies for those skilled in the art.

Claims (11)

1. a kind of preparation method of mullite fiber reinforced ceramic matrix composite material, it is characterized in that, described preparation method comprises the steps: (1) Prepare (BN/SiC) _n alternating interfacial layers on the surface of the mullite fiber to obtain a reinforcement comprising a BN/SiC interfacial layer; wherein, n represents the number of layers of BN/SiC, n≥2 and is a natural number; Described step (1) comprises following sub-steps: (1.1) The mullite fiber is placed in the first atmosphere comprising boron trichloride, ammonia, hydrogen and nitrogen for deposition to obtain the third sample with a layer of BN layer deposited on the surface; the deposition temperature is 650～850℃; (1.2) Depositing the third sample in a second atmosphere comprising trichloromethylsilane, argon and hydrogen to obtain a fourth sample with a layer of SiC deposited on the surface; (1.3) Repeating steps (1.1) to (1.2) n times, then raising the temperature to 1200-1400° C. and keeping it warm for 1-4 hours, to obtain the reinforcement comprising the BN/SiC interface layer; (2) using liquid polycarbosilane as an impregnating liquid, impregnating the reinforcing body comprising the BN/SiC interface layer to obtain a first sample; (3) sequentially curing and cracking the first sample to obtain a second sample; (4) Repeat steps (2) to (3) at least 5 times to obtain the mullite fiber reinforced ceramic matrix composite material. 2. The preparation method according to claim 1, characterized in that: In step (1), the mullite fiber is a mullite fiber mat or a mullite fiber preform; The mullite fiber preforms include 2D laminated preforms, 2.5D acupuncture preforms, 3D braided preforms, and stitched preforms; The fiber volume fraction of the mullite fiber preform is 5-40%; The mullite fiber preform is made from continuous mullite long fibers. 3. The preparation method according to claim 1, characterized in that: n in the (BN/SiC) _n alternating interface layer is 3. 4. The preparation method according to claim 1, characterized in that: In step (1.1), the molar ratio of the boron trichloride to the ammonia gas is 1:(2-3); the deposition pressure is 5-10kPa, and the deposition time is 10-30h. 5. preparation method according to claim 1, is characterized in that: In step (1.2), the molar ratio of the trichloromethylsilane to the hydrogen is 1:(2-3); the deposition temperature is 1000-1100° C., the deposition pressure is 5-10 kPa, and the deposition time is 10-10 kPa. 30h. 6. The preparation method according to claim 1, characterized in that: The thickness of the single-layer BN layer is 100-300nm; The thickness of the single SiC layer is 200-400 nm. 7. preparation method according to claim 1, is characterized in that, in step (2): The vacuum degree of the immersion is 5-20kPa, the immersion pressure is 2-5MPa, and the immersion time is 1-4h. 8. preparation method according to claim 1, is characterized in that, in step (3): The curing reaction temperature is 250-300° C., the curing time is 1-4 hours, and the curing pressure is 2-5 MPa. 9. preparation method according to claim 1, is characterized in that, in step (3): The cracking reaction temperature is 950-1300° C., the cracking time is 2-6 hours, and the cracking pressure is 5-10 MPa. 10. The preparation method according to any one of claims 1 to 9, characterized in that: In step (4), the number of times of repeating steps (2) to (3) is 5 to 8 times. 11. A mullite fiber reinforced ceramic matrix composite material, characterized in that it is prepared by the preparation method according to any one of claims 1 to 10.

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