Zirconium carbide-based end cap and preparation method thereof

Abstract

The invention relates to the field of preparation of zirconium carbide workpieces, in particular to a zirconium carbide-based end cap and a preparation method thereof. Comprising the following steps: S1, preparing a preform: weaving a carbon fiber prepreg to prepare the preform; s2, preparation of a preparation body: depositing a BN interface layer and a SiC interface layer on the surface of the preform in the step S1 to prepare the preparation body; s3, preparation of a pre-finished product: putting the preparation body prepared in the step S2 into a vacuum heating furnace, mixing SiC and ZrC to form precursor slurry, adding the precursor slurry into the vacuum heating furnace, performing heating reaction, introducing reaction gas into the vacuum heating furnace in the reaction process, and enabling the reaction gas to react with oxygen; s4, cooling and taking materials; the purpose is to effectively improve the overall mechanical property of the prepared zirconium carbide-based end cap.

Description

Technical Field

[0001] The invention relates to the field of preparation of zirconium carbide workpieces, and in particular to a zirconium carbide-based end cap and a preparation method thereof. Background Art

[0002] The nose cap of a hypersonic vehicle is an important part of the vehicle's head. It is subjected to extremely high temperatures and pressures when the vehicle re-enters the atmosphere. The design of the nose cap is crucial to protecting the vehicle's internal structure, maintaining its aerodynamic shape, and ensuring flight safety.

[0003] Zirconium carbide has a series of advantages such as high temperature resistance, oxidation resistance, and high strength. Carbon fiber reinforced zirconium carbide-based composite materials combine the toughness of carbon fiber with the high melting point, high hardness, high temperature resistance, and ablation resistance of zirconium carbide. Therefore, they have broad application prospects in the fields of aerospace, energy electronics, etc. Carbon fiber reinforced ceramic-based composite materials are generally prepared by the impregnation-pyrolysis process. Since the zirconium carbide precursor often contains a certain oxygen content, zirconium oxide will be generated during the pyrolysis process. The zirconium oxide will corrode the carbon fiber, that is, a carbon thermal reduction reaction will occur, which will lead to a decrease in the mechanical properties of the prepared workpiece.

[0004] The zirconium carbide-based end cap of the present invention improves the overall mechanical properties of the end cap while ensuring the end cap's anti-ablation performance, thereby ensuring that the end cap can maintain structural integrity and functionality in extreme environments. Summary of the invention

[0005] In view of this, an object of the present invention is to provide a method for preparing a zirconium carbide-based end cap, which can effectively improve the overall mechanical properties of the prepared zirconium carbide-based end cap.

[0006] On the one hand, in order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is:

[0007] A method for preparing a zirconium carbide-based end cap comprises the following steps:

[0008] S1: preparing a preform: weaving carbon fiber prepreg to prepare a preform;

[0009] S2: preparing a preform: depositing a BN interface layer and a SiC interface layer on the surface of the preform in step S1 to prepare a preform;

[0010] S3: preparing a pre-finished product: placing the pre-formed product prepared in step S2 in a vacuum heating furnace, adding SiC and ZrC into a precursor slurry by mixing, heating and reacting, and introducing a reaction gas into the vacuum heating furnace during the reaction process, and the reaction gas is used to react with oxygen;

[0011] S4: Cooling and taking materials.

[0012] The technical effect is as follows: by preparing a preform, the carbon fiber prepreg is first woven into a preform, and a BN interface layer and a SiC interface layer are prepared on the surface of the preform by deposition. The adhesion of the BN interface layer can make the carbon fiber interface layer more resistant to oxidation, and SiC can further improve the protection of the carbon fiber, and can also improve the matching of the subsequent carbon fiber and the matrix; in step S3, in the preparation of the preform, the reaction of the mixture prepared by mixing SiC and ZrC with the preform can further improve the mechanical properties of the prepared workpiece. In order to prevent the corrosion of the carbon fiber in the prepreg caused by the intermediate product ZrO2 of the ZrC precursor decomposition during the reaction process, and at the same time improve the overall mechanical properties of the end cap, during the decomposition process, the reaction gas is introduced into the reaction container while the decomposition is carried out, and the generated oxygen is taken away in time by the reaction of the reaction gas and ZrO2, thereby reducing the corrosion of the carbon fiber and improving the mechanical properties of the prepared zirconium carbide-based workpiece.

[0013] Furthermore, in step S1, one side of the prepared preform is an outer surface, and the other side is an inner surface, the volume content of carbon fiber gradually decreases from the outer surface to the inner surface, and the outer surface is used for ablation.

[0014] Furthermore, the volume content of the carbon fiber on the inner surface is 39-42%, and the volume content of the carbon fiber on the outer surface is 29-32%.

[0015] Furthermore, in step S2, a BN interface layer is first deposited on the surface of the preform, and then a SiC interface layer is deposited on the surface of the BN interface layer.

[0016] The technical effect is: the BN interface layer has stronger antioxidant ability than the carbon fiber interface layer. Preparing a layer of SiC on the BN surface can not only improve the BN antioxidant ability, further improve the protection of the C fiber, but also improve the matching of the C fiber and the matrix.

[0017] Furthermore, in step S2, when preparing the preparatory body, the BN interface layer is deposited by BCl3:NH3:H2:Ar according to a molar ratio of 1:(1-5):(3-10):(3-20).

[0018] Furthermore, in step S3, when the prepared preform is placed in a vacuum heating furnace, SiC and ZrC are mixed into multiple mixtures of equal mass, the SiC content in each mixture gradually decreases, and then the multiple mixtures are introduced into the vacuum heating furnace in batches, and the mass ratio of SiC to ZrC to the mass of the preform in step S1 is (0.3-0.8):1.

[0019] Furthermore, in step S3, the reaction gas is mixed with nitrogen before being introduced, and the molar ratio of the reaction gas to the nitrogen is 1:(1-5).

[0020] Furthermore, the reaction gas in step S3 is methane.

[0021] Furthermore, in step S3, the introduction rate of the reaction gas is 100 SCCM-1 SLM.

[0022] On the other hand, in order to achieve the above-mentioned purpose, the present invention provides a zirconium carbide-based end cap, which is prepared by a preparation method of a zirconium carbide-based end cap.

[0023] The beneficial effects of the above technical solution are:

[0024] (1) In the present invention, a preform is prepared. Since the preform is woven from carbon fiber prepreg, one side of the preform is set as an ablation surface, and carbon fiber with a relatively low content is set on the ablation surface so that more matrix can be combined later to improve the ablation resistance of the preform. Then, a BN interface layer is deposited on the ablation surface, and a SiC interface layer is deposited outside the BN interface layer. The BN interface layer is used to protect the ablation surface. The SiC layer is set to improve the oxidation resistance of the BN interface layer, reduce the damage of oxygen to the BN interface layer, and also protect the preform containing carbon fiber inside;

[0025] (2) After a BN interface layer and a SiC layer are deposited on the surface of the preform to prepare a preform, the preform is deposited and filled. During the deposition process, in order to prevent the ZrO2 intermediate product of the ZrC precursor from corroding the carbon fiber during the cracking process and to improve the overall mechanical properties of the prepared workpiece, a reaction gas is introduced into the reaction vessel while the cracking process is being carried out. The reaction gas is used to react with ZrO2 to promptly remove excess oxygen, thereby reducing the corrosion of oxygen to the carbon fiber and improving the mechanical properties of the prepared zirconium carbide-based workpiece. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with specific embodiments:

[0027] Embodiment 1:

[0028] This embodiment discloses a method for preparing a zirconium carbide-based end cap, which mainly includes the following steps:

[0029] S1: preparing a preform; weaving a carbon fiber prepreg to prepare a preform, setting the preform to a hemispherical shape, wherein the outer spherical surface is an ablation surface, and the surface corresponding to the outer spherical surface is an inner surface, the carbon fiber volume fraction of the outer spherical surface is 30%, and the carbon fiber volume fraction of the inner surface is 40%, and the carbon fiber volume content gradually decreases from the inner surface to the outer spherical surface;

[0030] S2: Prepare a preform: Prepare a BN interface layer and a SiC interface layer on the surface of the preform in step S1 by vapor deposition; Specific process: Place the preform prepared in step S1 in a reactor, set the heating temperature of the reactor to 750°C, set the pressure to 5Kpa, introduce a BCl3 mixture into the reactor, the BCl3 flow rate is 50SCCM, wherein the BCl3 mixture consists of BCl3: NH3: H2: Ar in a molar ratio of 1: 3: 6: 12, and the deposition time is 3h; then heat the reactor to 1200°C and keep it warm for 2h; then continue to introduce a mixture of MTS and H2 into the reactor, wherein the MTS introduction rate is 130g / h, the MTS and H2 mixture consists of H2: MTS in a molar ratio of 5: 20, the deposition reaction time is 3h, and the temperature is lowered to obtain;

[0031] S3: Preparing pre-finished products: placing the pre-body into a vacuum sintering furnace, first in the first cycle, SiC and ZrC are mixed in a weight ratio of 3:1 to prepare a first filler, the first filler is filled into the vacuum sintering furnace to react with the pre-body, and the reaction is carried out at 65°C for 2 hours, and then the temperature of the vacuum sintering furnace is increased to 1350°C and kept warm for 2 hours; then in the second cycle, SiC and ZrC are mixed in a weight ratio of 2:1 to prepare a second filler, the second filler is added into the vacuum sintering furnace, and the reaction with the pre-body is continued at 65°C for 2 hours, and then the temperature is kept warm in the 1350°C vacuum sintering furnace for 2 hours; then in the third cycle, SiC and ZrC are prepared into a third filler in a weight ratio of 1:1, and the third The filler is added into the vacuum sintering furnace, reacted at 65°C for 2 hours, and then reacted at 1300°C for 2 hours; then the fourth cycle is carried out, SiC and ZrC are mixed in a weight ratio of 0:1 to prepare a fourth filler, the fourth filler is added into the vacuum sintering furnace, reacted at 65°C for 2 hours, and then kept warm in a vacuum sintering furnace at 1400°C for 2 hours; during the first, second, third and fourth cycles, the ratio of the sum of the weights of SiC and ZrC to the mass of the preparatory body in step S1 is 1:2, and during the reaction of the four cycles, a reaction gas is introduced into the vacuum sintering furnace, and in this embodiment, the reaction gas is composed of methane and N2 in a molar ratio of 1:3; the amount of methane introduced is 500SCCM;

[0032] S4: Cooling and taking materials.

[0033] Embodiment 2:

[0034] The difference between this embodiment and embodiment 1 is that in step S2, when the BCl3 mixture is introduced into the reaction furnace, the BCl3 mixture is composed of BCl3:NH3:H2:Ar in a molar ratio of 1:1:3:3, and the rest is the same as in embodiment 1;

[0035] Embodiment 3:

[0036] The difference between this embodiment and embodiment 1 is that in step S2, when the BCl3 mixture is introduced into the reactor, the BCl3 mixture consists of BCl3:NH3:H2:Ar in a molar ratio of 1:5:10:20, and the rest is the same as in embodiment 1.

[0037] Embodiment 4:

[0038] The difference between this embodiment and embodiment 1 is that in step S3, when the reaction gas is introduced into the vacuum sintering furnace, the reaction gas used is composed of methane and N2 in a molar ratio of 1:1, and the rest is the same as in embodiment 1.

[0039] Embodiment 5:

[0040] The difference between this embodiment and embodiment 1 is that in step S3, when the reaction gas is introduced into the vacuum sintering furnace, the reaction gas used is composed of methane and N2 in a molar ratio of 1:5, and the rest is the same as in embodiment 1.

[0041] Comparative Example

[0042] Comparative Example 1:

[0043] The difference between this comparative example and Example 1 is that in step S3, no reaction gas is introduced into the vacuum sintering furnace, and the rest is the same as in Example 1;

[0044] Comparative Example 2:

[0045] The difference between this comparative example and Example 1 is that in step S3, the reaction gas introduced is methane, and the rest is the same as in Example 1;

[0046] Experimental data

[0047] In this stage, the end caps prepared in Examples 1-5 and Comparative Examples 1-2 were used as experimental samples. The tensile strength of the experimental samples was tested according to the high temperature mechanical properties test method of continuous fiber reinforced ceramic matrix composite materials in GJB10311-2021, and the following experimental data were obtained; the test data are shown in the table:

[0048] sample Tensile strength(MPa) Example 1 110 Example 2 115 Example 3 108 Example 4 112 Example 5 120 Comparative Example 1 65 Comparative Example 2 83

Claims

1. A method for preparing a zirconium carbide-based end cap, characterized in that: The steps include: S1: preparing a preform: weaving carbon fiber prepreg to prepare a preform; S2: preparing a preform: depositing a BN interface layer and a SiC interface layer on the surface of the preform in step S1 to prepare a preform; S3: preparing a pre-finished product: placing the pre-formed product prepared in step S2 in a vacuum heating furnace, adding SiC and ZrC into a precursor slurry by mixing, heating and reacting, and introducing a reaction gas into the vacuum heating furnace during the reaction process, and the reaction gas is used to react with oxygen; S4: Cooling and taking materials.

2. The method for preparing a zirconium carbide-based end cap according to claim 1, characterized in that: In step S1, one side of the prepared preform is an outer surface, and the other side is an inner surface. The volume content of carbon fiber gradually decreases from the outer surface to the inner surface, and the outer surface is used for ablation.

3. The method for preparing a zirconium carbide-based end cap according to claim 2, characterized in that: The volume content of the carbon fibers on the inner surface is 39-42%, and the volume content of the carbon fibers on the outer surface is 29-32%.

4. The method for preparing a zirconium carbide-based end cap according to claim 1, characterized in that: In step S2, a BN interface layer is first deposited on the surface of the preform, and then a SiC interface layer is deposited on the surface of the BN interface layer.

5. The method for preparing a zirconium carbide-based end cap according to claim 1, characterized in that: In step S2, when preparing the preparatory body, the BN interface layer is deposited by BCl3:NH3:H2:Ar according to the molar ratio of 1:(1-5):(3-10):(3-20).

6. The method for preparing a zirconium carbide-based end cap according to claim 1, characterized in that: In step S3, when the prepared body is placed in a vacuum heating furnace, SiC and ZrC are mixed into multiple mixtures of equal mass, the SiC content in each mixture gradually decreases, and then the multiple mixtures are introduced into the vacuum heating furnace in batches.

7. The method for preparing a zirconium carbide-based end cap according to claim 1, characterized in that: In step S3, the reaction gas is mixed with nitrogen before being introduced, and the molar ratio of the reaction gas to the nitrogen is 1:(1-5).

8. The method for preparing a zirconium carbide-based end cap according to claim 7, characterized in that: The reaction gas in step S3 is methane.

9. The method for preparing a zirconium carbide-based end cap according to claim 1, characterized in that: In step S3, the introduction rate of the reaction gas is 100 SCCM-1 SLM.

10. A zirconium carbide based end cap, characterized in that: The zirconium carbide-based end cap is prepared by the preparation method of any one of claims 1-9.