Preparation method of C / C-SiBCN nozzle with excellent high-temperature mechanical properties

Abstract

The application relates to a preparation method of a C / C-SiBCN nozzle with excellent high-temperature mechanical properties, and relates to the preparation method of the C / C-SiBCN nozzle.The application solves the problems that the existing nozzle cannot realize lightweight and simultaneously meet the structural strength of a throat area, and solves the problem that the existing PIP process for preparing C / SiBCN composite materials needs high temperature and pressure, which causes damage to carbon fibers.The method comprises the following steps: 1, preparing a pyrolytic carbon interface layer on the surface of fibers in a carbon fiber preform;2, preparing a C / C-SiBCN composite material matrix to realize high degree of densification, lightweight and excellent high-temperature mechanical properties;3, preparing the C / C-SiBCN nozzle with a circumferential cross-stiffener on the outer surface of the throat area through precise mechanical machining.The application is used for preparing the C / C-SiBCN nozzle with excellent high-temperature mechanical properties.

Description

Technical Field

[0001] This invention relates to a method for preparing C / C-SiBCN nozzles. Background Technology

[0002] The nozzle is a common jet propulsion design in the aerospace field. As a primary thrust component, it must withstand high temperatures, high pressures, and intense heat flux under extreme service environments, while also meeting special requirements such as structural weight reduction, structural safety and reliability, and space constraints of the aircraft structure. Therefore, nozzle design must seek the optimal rational design amidst the contradictory relationships of various performance constraints, and needs to address requirements such as structural strength and reliability, lightweighting, high-temperature stability, and excellent high-temperature mechanical properties under harsh environments.

[0003] Taking the throat region, the most vulnerable part of the nozzle, as an example, such as Figure 2 The throat in a nozzle is a narrow passage connecting the nozzle and the combustion chamber. It guides the high-temperature, high-pressure airflow generated by combustion into the nozzle and is subjected to the impact and corrosion of the high-temperature, high-pressure airflow from the combustion chamber. Therefore, the throat is usually one of the most vulnerable parts of the tail nozzle.

[0004] To meet the requirements of high Mach number aircraft, the throat region must possess sufficiently high structural strength and be resistant to corrosion and airflow erosion. Furthermore, the aircraft must adhere to requirements for center of gravity configuration and overall mass control, necessitating the use of lightweight materials in the nozzle fabrication process. The selection of high-temperature alloys as throat materials is also constrained by overall mass control requirements, and the narrow airflow passage further limits their structural strength.

[0005] C / SiBCN ceramic matrix composites are considered among the materials with the greatest potential for service in extreme environments. C / SiBCN composites possess characteristics such as high-temperature resistance, oxidation resistance, and excellent mechanical properties, and have broad development and application prospects in aerospace and structural components serving in extreme environments. The PIP process is a common process for preparing C / SiBCN composites. It involves impregnating a carbon fiber preform in a vacuum environment, allowing liquid polyborosilazane to fill the porous preform, followed by curing and pyrolysis to obtain the C / SiBCN composite. However, polymer precursor pyrolysis is typically performed at high temperatures and pressures. Repeated high-temperature heat treatment can cause significant damage or even destruction to the exposed carbon fiber preform, severely weakening the reinforcing and toughening effects of the carbon fiber. Summary of the Invention

[0006] This invention aims to address the limitations of existing nozzles in simultaneously achieving both lightweight design and structural strength in the throat region. Furthermore, it addresses the issue of carbon fiber damage caused by the high temperature and pressure required for preparing C / SiBCN composite materials using the existing PIP process. Consequently, this invention provides a method for preparing C / C-SiBCN nozzles with superior high-temperature mechanical properties.

[0007] A method for preparing a C / C-SiBCN nozzle with excellent high-temperature mechanical properties, comprising the following steps:

[0008] 1. A pyrolytic carbon interface layer is prepared on the fiber surface of a carbon fiber preform using a chemical vapor infiltration process to obtain a PyC interface layer modified carbon fiber preform.

[0009] 2. ① The PyC interface layer modified carbon fiber preform is impregnated in liquid polyborosilazane under vacuum. Then, under nitrogen atmosphere and normal pressure, it is first kept at a temperature of 150℃~300℃ for 1h~3h, then kept at a temperature of 800℃~1100℃ for 1h~3h, and finally cooled down with the furnace.

[0010] ② Repeat step 2① 7 to 10 times to obtain the C / C-SiBCN composite matrix;

[0011] 3. Precision machining of the C / C-SiBCN composite matrix to obtain the C / C-SiBCN nozzle;

[0012] The outer surface of the throat region of the C / C-SiBCN nozzle is provided with a circumferentially cross-reinforcing rib structure.

[0013] The beneficial effects of this invention are:

[0014] (1) The present invention uses chemical vapor deposition (CVI) to prepare a suitable pyrolytic carbon (PyC) interface layer. The thicker interface layer can reduce the damage caused by repeated PIP and pyrolysis of carbon fibers, and can also achieve deflection during crack propagation to achieve toughening effect.

[0015] (2) The present invention achieves a high degree of densification of composite materials through a multi-round vacuum impregnation / pyrolysis PIP process. Under relatively low temperature and normal pressure atmosphere, it can further reduce the damage to carbon fibers, improve the stability of the internal structure of carbon fiber preforms, and improve the comprehensive mechanical properties of composite materials.

[0016] (3) The design of the circumferential cross stiffener structure in the nozzle throat region of the present invention enhances the structural strength of the nozzle throat and improves the pressure resistance of the nozzle throat region, thereby reducing the risk of instability during high Mach number flight. On the other hand, the material of the nozzle as a whole is C / C-SiBCN composite material, which has the characteristics of high temperature and high pressure resistance, excellent mechanical properties and lightweight, so that the nozzle can meet the overall mass control requirements while adding stiffeners to the throat region to protect the vulnerable parts.

[0017] (4) The C / C-SiBCN composite material prepared by low-temperature atmospheric pressure pyrolysis in this invention has a density of not less than 1.60 g / cm³. 3The porosity is not greater than 5.5%, the flexural strength at room temperature is not less than 365 MPa, the tensile strength is not less than 90 MPa, the compressive strength is not less than 470 MPa, and the flexural strength after holding at 1500℃ in a nitrogen atmosphere for 20 to 40 minutes is not less than 140 MPa.

[0018] Instruction manual illustrations

[0019] Figure 1 SEM image of the PyC interface layer modified carbon fiber preform prepared in step one of Example 1;

[0020] Figure 2 A schematic diagram of an existing C / C-SiBCN nozzle without circumferential cross-reinforcing ribs on the outer surface of the throat region;

[0021] Figure 3 This is a schematic diagram of the structure of a C / C-SiBCN nozzle with a circumferential cross-reinforcing rib structure on the outer surface of the throat region in step three of the present invention. 1 is the C / C-SiBCN nozzle, 2 is the combustion chamber, 3 is the circumferential cross-reinforcing rib structure, and 4 is the nozzle.

[0022] Figure 4 This is a cross-sectional view of a C / C-SiBCN nozzle with a circumferentially cross-reinforcing rib structure on the outer surface of the throat region in step three of the present invention.

[0023] Figure 5 This is a three-dimensional model of a C / C-SiBCN nozzle with a circumferentially cross-reinforcing rib structure on the outer surface of the throat region in step three of the present invention.

[0024] Figure 6 This is a physical image of a C / C-SiBCN nozzle with a circumferentially cross-reinforcing rib structure on the outer surface of the throat region in step three of embodiment one. Detailed Implementation

[0025] Specific implementation method one, combined with Figures 3 to 5 This embodiment describes a method for preparing a C / C-SiBCN nozzle with excellent high-temperature mechanical properties, which is carried out according to the following steps:

[0026] 1. A pyrolytic carbon interface layer is prepared on the fiber surface of a carbon fiber preform using a chemical vapor infiltration process to obtain a PyC interface layer modified carbon fiber preform.

[0027] 2. ① The PyC interface layer modified carbon fiber preform is impregnated in liquid polyborosilazane under vacuum. Then, under nitrogen atmosphere and normal pressure, it is first kept at a temperature of 150℃~300℃ for 1h~3h, then kept at a temperature of 800℃~1100℃ for 1h~3h, and finally cooled down with the furnace.

[0028] ② Repeat step 2① 7 to 10 times to obtain the C / C-SiBCN composite matrix;

[0029] 3. Precision machining of the C / C-SiBCN composite matrix to obtain the C / C-SiBCN nozzle;

[0030] The outer surface of the throat region of the C / C-SiBCN nozzle is provided with a circumferentially cross-reinforcing rib structure.

[0031] The beneficial effects of this embodiment are:

[0032] (1) In this embodiment, a suitable pyrolytic carbon (PyC) interface layer was prepared by chemical vapor deposition (CVI). The thicker interface layer can reduce the damage caused by repeated PIP and pyrolysis of carbon fibers, and can also achieve deflection during crack propagation to achieve toughening effect.

[0033] (2) This embodiment achieves a high degree of densification of the composite material through a multi-round vacuum impregnation / pyrolysis PIP process. Under relatively low temperature and normal pressure atmosphere, it can further reduce the damage to carbon fiber, improve the stability of the internal structure of carbon fiber preform, and improve the comprehensive mechanical properties of composite material.

[0034] (3) The design of the circumferential cross stiffener structure in the nozzle throat region of this embodiment enhances the structural strength of the nozzle throat and improves the pressure resistance of the nozzle throat region, thereby reducing the risk of instability during high Mach number flight. On the other hand, the material of the nozzle as a whole is C / C-SiBCN composite material, which has the characteristics of high temperature and high pressure resistance, excellent mechanical properties and lightweight, so that the nozzle can meet the overall mass control requirements while adding stiffeners to the throat region to protect the vulnerable parts.

[0035] (4) The density of the C / C-SiBCN composite material prepared by low-temperature atmospheric pressure pyrolysis in this embodiment is not less than 1.60 g / cm³. 3 The porosity is not greater than 5.5%, the flexural strength at room temperature is not less than 365 MPa, the tensile strength is not less than 90 MPa, the compressive strength is not less than 470 MPa, and the flexural strength after holding at 1500℃ in a nitrogen atmosphere for 20 to 40 minutes is not less than 140 MPa.

[0036] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the carbon fiber preform mentioned in step one is a 2.5D carbon fiber preform with a density of 0.50 g / cm³. 3 ~0.65g / cm 3 Everything else is the same as in Specific Implementation Method 1.

[0037] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the preparation of the pyrolytic carbon interface layer on the fiber surface of the carbon fiber preform using a chemical vapor infiltration process described in step one is specifically carried out according to the following steps: The carbon fiber preform is placed in a flowing C3H6 / N2 atmosphere, and under the conditions of a C3H6 flow rate of 8 mL / min to 12 mL / min, an N2 flow rate of 8 mL / min to 12 mL / min, and a temperature of 900℃ to 1000℃, deposition is carried out for 50 h to 80 h to obtain a PyC interface layer modified carbon fiber preform. Everything else is the same as in Specific Implementation Method One or Two.

[0038] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the thickness of the PyC interface layer is 0.8μm to 1.2μm; and the density of the PyC interface layer-modified carbon fiber preform is 0.70 g / cm³. 3 ~0.85g / cm 3 Everything else is the same as in specific implementation methods one through three.

[0039] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: in step two ①, vacuum impregnation is performed for 1 to 3 hours under a vacuum degree below 100 Pa. Everything else is the same as in Specific Implementation Methods One to Four.

[0040] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: in step two①, the heating rate is 1.5℃ / min to 3℃ / min, and the cooling rate is 2℃ / min to 5℃ / min. Everything else is the same as in Specific Implementation Methods One to Five.

[0041] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the viscosity of the liquid polyborosilicate described in step two① is 100cp to 200cp. Everything else is the same as in Specific Implementation Methods One to Six.

[0042] Specific implementation method eight, combined with Figures 3 to 5 The difference between this embodiment and one of the specific embodiments one to seven is that the circumferential cross-reinforcing rib structure described in step three is as follows: Two intersecting reinforcing rib plates form cross-reinforcing ribs, and 4 to 8 sets of cross-reinforcing ribs are arranged around the outer surface of the nozzle throat region. Everything else is the same as in specific embodiments one to seven.

[0043] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the thickness of the reinforcing rib plate is 4mm to 6mm. Everything else is the same as in Specific Implementation Methods One to Eight.

[0044] Specific implementation method ten, combined with Figures 3 to 5The difference between this embodiment and one of the specific embodiments one to nine is that the nozzle is a circular cross-section flow channel, with a combustion chamber and a nozzle at each end. The cross-sectional area of ​​the combustion chamber decreases in stages from the inlet to the outlet, while the cross-sectional area of ​​the nozzle increases linearly from the inlet to the outlet. Otherwise, it is the same as specific embodiments one to nine.

[0045] The beneficial effects of the present invention are verified using the following embodiments:

[0046] Example 1:

[0047] A method for preparing a C / C-SiBCN nozzle with excellent high-temperature mechanical properties, comprising the following steps:

[0048] 1. A pyrolytic carbon interface layer is prepared on the fiber surface of a carbon fiber preform using a chemical vapor infiltration process to obtain a PyC interface layer modified carbon fiber preform.

[0049] 2. ① The PyC interface layer modified carbon fiber preform is impregnated in liquid polyborosilazane under vacuum. Then, under nitrogen atmosphere and normal pressure, it is first kept at 170℃ for 2 hours, then kept at 1100℃ for 2 hours, and finally cooled down with the furnace.

[0050] ② Repeat step 2① 8 times to obtain the C / C-SiBCN composite matrix;

[0051] 3. Precision machining of the C / C-SiBCN composite matrix to obtain the C / C-SiBCN nozzle;

[0052] The outer surface of the throat region of the C / C-SiBCN nozzle is provided with a circumferentially cross-reinforcing rib structure.

[0053] The carbon fiber preform mentioned in step one is a 2.5D carbon fiber preform with a density of 0.62 g / cm³. 3 .

[0054] The preparation of a pyrolytic carbon interface layer on the fiber surface of the carbon fiber preform using chemical vapor infiltration process described in step one is carried out in the following steps: the carbon fiber preform is placed in a flowing C3H6 / N2 atmosphere, and under the conditions of C3H6 flow rate of 10 mL / min, N2 flow rate of 10 mL / min and temperature of 900℃, deposition is carried out for 70 h to obtain a PyC interface layer modified carbon fiber preform.

[0055] The PyC interface layer has a thickness of 1 μm; the density of the PyC interface layer modified carbon fiber preform is 0.85 g / cm³. 3 .

[0056] In step 2①, vacuum impregnation is performed for 2 hours under a vacuum degree of less than 100 Pa.

[0057] In step 2①, the heating rate is 3℃ / min and the cooling rate is 5℃ / min.

[0058] The liquid polyborosilicate mentioned in step 2① was purchased from the Institute of Chemistry, Chinese Academy of Sciences, with a viscosity of 200 cp.

[0059] The circumferential cross-reinforcing rib structure described in step three is as follows: cross-reinforcing ribs are formed by two intersecting reinforcing rib plates, and six sets of cross-reinforcing ribs are set to surround the outer surface of the nozzle throat area.

[0060] The thickness of the reinforcing rib is 5mm.

[0061] The nozzle is a circular cross-section flow channel with a combustion chamber and a nozzle at each end. The cross-sectional area of ​​the combustion chamber decreases in stages from the inlet to the outlet, while the cross-sectional area of ​​the nozzle increases linearly from the inlet to the outlet.

[0062] Figure 1 This is a SEM image of the PyC interface layer modified carbon fiber preform prepared in step one of Example 1. As shown in the image, PyC is uniformly deposited on the surface of the carbon fiber preform with a certain thickness of about 1 micrometer, which can effectively protect the carbon fiber and cause microcracks to deflect at the interface layer, thus achieving the effect of strengthening and toughening.

[0063] Figure 6 The image shows a physical picture of the C / C-SiBCN nozzle prepared in step three of Example 1. As can be seen from the figure, the PIP process using low-temperature atmospheric pressure pyrolysis can successfully prepare and fabricate the nozzle with the target structure design.

[0064] The C / C-SiBCN composite matrix prepared in step two of Example 1 was tested as follows: density and porosity were determined using the Archimedes drainage method; flexural strength was tested under the following conditions: span 36 mm, thickness 4 mm, width 7 mm, and testing speed 0.5 mm / min; compressive strength was tested according to GB / T 33540-2017 "Test Methods for Mechanical Properties of C / C Composite Materials"; tensile strength was tested according to GB / T33501-2017; and high-temperature flexural strength was tested under the following conditions: thickness 4 mm, width 7 mm, span 36 mm, and testing speed 0.5 mm / min.

[0065] The density of the C / C-SiBCN composite material is 1.63 g / cm³. 3 The porosity is 5.48%, the flexural strength at room temperature is 367.0 MPa, the tensile strength is 93.4 MPa, the compressive strength is 470.6 MPa, and the flexural strength after holding at 1500℃ in a nitrogen atmosphere for 20 min is 143 MPa.

Claims

1. A method for preparing a C / C-SiBCN nozzle with excellent high-temperature mechanical properties, characterized in that... It is done in the following steps:

1. A pyrolytic carbon interface layer is prepared on the fiber surface of a carbon fiber preform using a chemical vapor infiltration process to obtain a PyC interface layer modified carbon fiber preform. The carbon fiber preform is a 2.5D carbon fiber preform with a density of 0.50 g / cm³. 3 ~0.65g / cm 3 ; The preparation of a pyrolytic carbon interface layer on the fiber surface of a carbon fiber preform using a chemical vapor infiltration process is carried out in the following steps: the carbon fiber preform is placed in a flowing C3H6 / N2 atmosphere, and under the conditions of a C3H6 flow rate of 8 mL / min to 12 mL / min, a N2 flow rate of 8 mL / min to 12 mL / min, and a temperature of 900℃ to 1000℃, a deposition is carried out for 50 h to 80 h to obtain a PyC interface layer modified carbon fiber preform; The thickness of the PyC interface layer is 0.8 μm to 1.2 μm; the density of the PyC interface layer modified carbon fiber preform is 0.70 g / cm³. 3 ~0.85g / cm 3 ; 2. ① The PyC interface layer modified carbon fiber preform is impregnated in liquid polyborosilazane under vacuum. Then, under nitrogen atmosphere and normal pressure, it is first kept at 170℃ for 2 hours, then kept at 1100℃ for 2 hours, and finally cooled down in the furnace. In step 2①, the heating rate is 1.5℃ / min~3℃ / min, and the cooling rate is 2℃ / min~5℃ / min; the viscosity of the liquid polyborosilazane is 100cp~200cp. ② Repeat step 2① 7 to 10 times to obtain the C / C-SiBCN composite matrix; 3. Precision machining of the C / C-SiBCN composite matrix to obtain the C / C-SiBCN nozzle; The outer surface of the throat region of the C / C-SiBCN nozzle is provided with a circumferential cross-reinforcing rib structure; The circumferential cross reinforcing rib structure is as follows: two cross reinforcing rib plates intersect to form cross reinforcing ribs, and 4 to 8 sets of cross reinforcing ribs are set around the outer surface of the nozzle throat area; The thickness of the reinforcing rib is 4mm~6mm; The nozzle is a circular cross-section flow channel with a combustion chamber and a nozzle at each end. The cross-sectional area of ​​the combustion chamber decreases in stages from the inlet to the outlet, while the cross-sectional area of ​​the nozzle increases linearly from the inlet to the outlet.

2. The method for preparing a C / C-SiBCN nozzle with excellent high-temperature mechanical properties according to claim 1, characterized in that... In step 2①, vacuum impregnate for 1 to 3 hours under a vacuum degree of less than 100 Pa.

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