A method for producing an alumina fiber-reinforced ceramic matrix composite

Abstract

The application discloses a preparation method of an alumina fiber reinforced ceramic matrix composite material and belongs to the technical field of ceramic matrix composite materials. In view of the problems of low impregnation efficiency, too many impregnation times and high cost of the alumina fiber reinforced composite material prepared by the existing sol-gel process, the application improves the pressure impregnation process, optimizes the impregnation process through rotary evaporation, induces the sol and slurry matrix with low viscosity and difficult to gel to be self-gel, enables the ceramic matrix particles to be retained in the pores of the fiber fabric to the maximum extent, prevents the external crust and internal loose problems caused by repeated impregnation, makes the composite material more compact and higher in mechanical strength, and greatly reduces the amount of impregnated matrix, thereby reducing the preparation cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic matrix composites, and particularly relates to a method for preparing an alumina fiber reinforced ceramic matrix composite based on a sol-gel process. BACKGROUND

[0002] In recent years, oxide fiber reinforced ceramic matrix composites with oxidation resistance and low cost have developed rapidly. Many ceramic matrix composite systems have been widely used in engineering applications in both military and civilian markets. Among them, alumina fiber reinforced ceramic matrix composites have excellent mechanical, thermal and electrical properties and are widely used in many fields.

[0003] At present, the preparation methods of fiber reinforced ceramic matrix composites include precursor impregnation pyrolysis, reactive melt infiltration, chemical vapor infiltration, sol-gel method, slurry infiltration method, etc. Among them, the sol-gel method is to prepare a matrix sol by adjusting the specific formula ratio of ceramic matrix, metal salt and ester substance, etc. to prepare the raw materials, to fill the sol into the fiber preform with a specific structure by means of pressurization, impregnation, etc., and then to dry and heat treat after sol-gel, and to repeat the above process to realize the densification of the composite material. Because the process is relatively simple, the cycle is short, and the uniformity of the prepared composite material is good, the sol-gel method is the most widely used method for preparing alumina fiber reinforced ceramic matrix composites. However, in order to ensure the impregnation effect, the sol used for impregnation must have low viscosity, high solid content and the ability to induce gelation. This greatly limits the types of precursors that can be used. How to optimize the process steps of vacuum pressure impregnation, improve the single impregnation efficiency, and prepare fiber reinforced composites with good internal density and mechanical strength has become a difficult problem to be solved. SUMMARY

[0004] (I) Technical problems to be solved

[0005] In view of the problems of low impregnation efficiency, excessive impregnation times and high cost in the preparation of alumina fiber reinforced composites by the existing sol-gel process, the pressure impregnation process is improved in the application, the impregnation process is optimized by rotary evaporation, the sol and slurry matrix with low viscosity and poor gelation are induced to self-gel, and the ceramic matrix particles can be maximally retained in the pores of the fiber fabric. No matter what kind of sol or slurry is used as the impregnation matrix, water can be removed slowly with the help of rotary evaporation equipment, and finally the gel is solidified. The whole process is controllable, and the rotary speed and heating temperature can be controlled according to the selection of different impregnation matrixes, so that each kind of matrix can be uniformly and quickly gelled. By improving the single impregnation efficiency, the problems of external crust and internal loose caused by repeated impregnation are effectively prevented, the internal of the composite material is more dense, the mechanical strength is higher, the amount of impregnation matrix is greatly reduced, and the preparation cost is reduced.

[0006] (II) Technical Solution

[0007] To solve the above technical problems, the present application provides the following technical solution:

[0008] A preparation method of an alumina fiber reinforced ceramic matrix composite material, comprising the following steps:

[0009] (1) Removing the infiltrant on the surface of the alumina fiber fabric, and drying;

[0010] (2) Alumina sol impregnation: clamping a protective tool on the outside of the dried alumina fiber fabric, placing it in a rotary evaporation assisted gel impregnation device and vacuumizing, then sucking and injecting alumina sol from the lower gel inlet until the alumina fiber fabric is immersed, after the alumina sol flows out from the upper gel outlet, the rotary evaporation assisted gel impregnation device is gas pressurized;

[0011] (3) Rotary evaporation assisted gelation: under the condition that the gas pressure in the rotary evaporation assisted gel impregnation device is kept unchanged, the rotary device and the bottom heating device are turned on, the condenser valve is opened, and the temperature is raised for rotary evaporation for a period of time to evaporate the water in the alumina sol, increase the solid content and the sol viscosity, and until complete gelation;

[0012] (4) Gel drying: after complete gelation, the alumina fiber fabric is taken out and dried in a constant temperature oven to obtain a composite material roughcast;

[0013] (5) Roughcast sintering: the dried composite material roughcast is placed in a muffle furnace for sintering, and then naturally cooled to room temperature;

[0014] (6) Repeated impregnation: steps (2) to (5) are repeated for several times until the weight gain rate of the composite material is less than a threshold value, and an alumina fiber reinforced ceramic matrix composite material is obtained.

[0015] Preferably, in step (1), the alumina fiber fabric is selected from one of the following: Nextel 550 / 610 / 720, S-1920F / G or other 550 / 610 / 720 type fibers, and the fiber fabric structure is a 2.5D structure, a three-dimensional structure, a needle-punched structure or a stitched structure.

[0016] Preferably, in step (1), the infiltrant on the surface of the alumina fiber fabric is removed by sintering at 500-800℃, acetone cleaning at 50-60℃ or water washing at 60-90℃ for 21-23h, and the drying temperature is 70-90℃ and the drying time is 10-12h.

[0017] Preferably, in step (2), the vacuumizing time is 3-10h, the vacuum degree is -0.096 to -0.099MPa, the gas pressurizing pressure is 3.5-3.7MPa, and the pressure is maintained for at least 24h.

[0018] Preferably, the protective tool for clamping the fiber fabric in step (2) is an epoxy resin clamp plate.

[0019] Preferably, the rotary evaporation assisted gel impregnation device in steps (2) and (3) comprises a tank, a rotating device, a heating device, a condenser tube and a collection bottle, wherein the bottom of the tank is provided with a gel inlet, the top is provided with a gel outlet and a steam outlet, the steam outlet is connected to the collection bottle through a pipeline, the pipeline is provided with a condenser tube, and the collection bottle is used to collect the organic solvent after the steam is condensed; the rotating device is suspended inside the tank; the bottom of the tank is placed in the heating device for heating, and the heating device is provided with a hot water inlet.

[0020] Preferably, the rotating speed of the rotating device in step (3) is 50-500 r / min, the heating temperature of the heating device is 25-150 DEG C, and the rotary evaporation is 4-6 h. According to the selection of the impregnated substrate, the rotating speed and the heating temperature can be adjusted according to the situation to improve the impregnation effect.

[0021] Preferably, the solid content of the alumina sol in step (3) is 17%-22%, and the viscosity is 8-12 mPa s.

[0022] Preferably, the drying conditions in step (4) are as follows: first, constant temperature and humidity drying at a temperature of 40-50 DEG C and a humidity decreasing from 90% to 60%, and the drying time is 4-8 h; then, conventional drying at 80-200 DEG C, and the drying time is 5-12 h.

[0023] Preferably, the sintering conditions in step (5) are as follows: the sintering temperature is 600-1200 DEG C, and the holding time is 0.5-3 h.

[0024] Preferably, the threshold in step (6) is 1%.

[0025] (Three) beneficial effects

[0026] The technical scheme of the present application has the following advantages:

[0027] (1) The rotary evaporation assisted gel process used in the present application can greatly improve the single impregnation efficiency, and the weight gain rate of the fiber fabric after single impregnation can be increased by 30%-35%.

[0028] (2) The rotary evaporation assisted gel process used in the present application can be applied to different kinds of ceramic sols or slurries, and can assist the gelation and improve the utilization rate.

[0029] (3) The rotary evaporation assisted gel process used in the present application can make more matrix particles enter the inside of the fabric by continuously enriching the used sol or slurry, which makes the internal density of the prepared composite material better, and the density is greater than 2.6 g / cm 3It has higher mechanical strength, with a room temperature tensile strength greater than 140 MPa and a room temperature compressive strength greater than 160 MPa. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the rotary evaporation-assisted gel impregnation device used in this invention.

[0031] In the diagram: 1-tank body; 11-glue inlet, 12-glue outlet, 13-steam outlet, 2-rotating device, 3-heating device, 31-heating water inlet, 4-condenser, 5-collection bottle, 6-composite material. Detailed Implementation

[0032] To make the various technical features, advantages, or effects of the present invention more apparent and understandable, a detailed description is provided below in conjunction with the accompanying drawings.

[0033] Example 1

[0034] First, a three-dimensional alumina fiber fabric was woven using Nextel 720 continuous alumina fiber lay-up and stitching. The fabric was then placed in a cleaning fixture containing acetone and heated at 53°C for 21 hours to remove the sizing agent. After drying at 70°C for 12 hours, the sizing agent content was measured to be 0.02%. Next, a protective clamp was placed over the prefabricated fabric and it was placed stably in the impregnation fixture. A vacuum pump was then used to evacuate the fabric to a vacuum level of -0.099 MPa. This vacuum level was maintained for 3 hours without change. Alumina sol was then injected into the rotary evaporation-assisted gel impregnation device through the injection port. Once sol flowed from the upper outlet, injection was stopped, and a pressure of 3.6 MPa was introduced into the container and maintained for 24 hours. Subsequently, the condenser valve was opened, condensate was introduced, and the heating device (e.g., heating mantle, heating vessel) and the rotating device (e.g., stirrer) were turned on to begin rotary evaporation concentration. Rotary evaporation was performed for 5 hours to ensure the solid content of the alumina sol was within the range of 17%–22% and the viscosity was within the range of 8–12 mPa·s. Then, rotary evaporation was stopped, the pressure was released, and the rotary evaporation-assisted gel impregnation device was opened. The fiber fabric plate was removed and placed in a constant-temperature oven at 40℃ for 8 hours of constant-temperature humidification drying, followed by drying at 150℃ for 6 hours. Finally, the dried composite preform was sintered at 1100℃ for 2 hours; after natural cooling to room temperature, the impregnation was repeated once. The weight gain of the composite material was less than 1%, and the final density of the prepared alumina fiber-reinforced composite material was 2.61 g / cm³. 3 The room temperature tensile strength is 142 MPa, and the room temperature compressive strength is 166 MPa.

[0035] Example 2

[0036] First, the Nextel 610 continuous alumina fiber layers were stitched and woven into a three-dimensional fabric, and then the fiber fabric was placed in a cleaning tool containing water and heated to remove the sizing agent. The heating temperature was 80°C, and the heating time was 22 h. After drying at 90°C for 10 h, the sizing agent content was 0.02%. Then, the preform fabric was placed in a protective clamp and placed in an impregnation tool. Then, a vacuum pump was used to draw a vacuum to a vacuum degree of -0.098 MPa, and the vacuum degree was maintained for 7 h without change. Then, mullite sol was injected into the rotary evaporation assisted gel impregnation device through the glue injection port. After the glue flowed out of the upper glue outlet, the glue injection was stopped. The pressure in the container was increased to 3.7 MPa, and the pressure was maintained for 24 h. Then, the valve of the condenser was opened, and the condenser was connected to the rotary device. The rotary evaporation concentration was started. The rotary evaporation was performed for 4 h to ensure that the solid content of the alumina sol was in the range of 17% to 22% and the viscosity was in the range of 8 to 12 mPa-s. Then, the rotary evaporation was stopped, the pressure was released, and the rotary evaporation assisted gel impregnation device was opened. The fiber fabric plate was taken out and placed in a constant temperature oven for constant temperature and humidity drying at 45°C for 4 h. Then, the fabric was dried at 80°C for 12 h. Finally, the dried composite rough blank was sintered at 1200°C for 0.5 h. After natural cooling to room temperature, the impregnation was repeated once, the weight gain rate of the composite material was less than 1%, and the final prepared alumina fiber reinforced composite material had a density of 2.64 g / cm 3 , a room temperature tensile strength of 158 MPa, and a room temperature compressive strength of 177 MPa.

[0037] Example 3

[0038] First, the Nextel 720 continuous alumina fiber layers are stitched and woven into a three-dimensional fabric, and then the fiber fabric is placed in a sintering tool to heat and sinter to remove the infiltrant, with a heating temperature of 600°C and a heating time of 23h. After drying at 80°C for 11h, the infiltrant content is tested to be 0.02%. Then, the prepared body fabric is wrapped with a protective splint on the outside, and is placed in an impregnation tool. Then, a vacuum pump is used to draw a vacuum to a vacuum degree of -0.096MPa, and after the vacuum degree does not change for 10h, alumina slurry is injected into the rotary evaporation assisted gel impregnation device through the glue injection port. After the glue flows out of the upper glue outlet, the glue injection is stopped, and a gas pressure of 3.5MPa is injected into the container, and the pressure is maintained for 24h. Then, the valve of the condenser pipe is opened, the condenser water is introduced, and the heating device and the rotating device are opened, and the rotary evaporation concentration is started. After rotary evaporation for 6h, the solid content of the alumina sol is ensured to be in the range of 17% to 22%, and the viscosity is in the range of 8 to 12mPa·s, and then the rotary evaporation is stopped, and after the pressure is released, the rotary evaporation assisted gel impregnation device is opened, the fiber fabric plate is taken out, and is placed in a constant temperature oven for constant temperature and humidity drying at 50°C for 6h, and then is dried at 200°C for 5h. Finally, the dried composite rough blank is sintered at 600°C for 3h; after natural cooling to room temperature, the impregnation is repeated twice, the weight gain rate of the composite material is less than 1%, and the finally prepared alumina fiber reinforced composite material has a density of 2.71g / cm 3 , a room temperature tensile strength of 145MPa, and a room temperature compressive strength of 204MPa.

[0039] Comparative Example 1

[0040] This comparative example is a comparative example of Example 1, and the same materials and preparation conditions as in the example are used, except that the rotary evaporation assisted gel impregnation device is not used, and the rotary evaporation assisted gel process is not used, but a traditional impregnation device is used. The finally prepared alumina fiber reinforced composite material has a density of 2.54g / cm 3 , a room temperature tensile strength of 100MPa, and a room temperature compressive strength of 122MPa, and it can be seen that the performance of the prepared composite material is reduced.

[0041] Comparative Example 2

[0042] This comparative example is a comparative example of Example 2, and the same materials and preparation conditions as in the example are used, except that the rotary evaporation assisted gel impregnation device is not used, and the rotary evaporation assisted gel process is not used, but a traditional impregnation device is used. The finally prepared alumina fiber reinforced composite material has a density of 2.58g / cm 3 , a room temperature tensile strength of 130MPa, and a room temperature compressive strength of 139MPa, and it can be seen that the performance of the prepared composite material is reduced.

[0043] Comparative Example 3

[0044] The comparative example is the same as example 3 in the use of materials and preparation conditions, except that the spin-aided gel impregnation device is not used, the spin-aided gel process is not used, but a traditional impregnation device is used. The density of the alumina fiber reinforced composite material prepared finally is 2.62 g / cm 3 , the room temperature tensile strength is 90 MPa, and the room temperature compressive strength is 158 MPa. It can be seen that the performance of the prepared composite material is reduced.

[0045] Although the present application has been disclosed as above with examples, it is not intended to limit the present application. Any appropriate modification or equivalent replacement of the technical solutions of the present application made by those skilled in the art shall be covered within the protection scope of the present application, and the protection scope of the present application is defined by the claims.

Claims

1. A method for preparing an alumina fiber reinforced ceramic matrix composite material, comprising the following steps: (1) removing the sizing agent on the surface of the alumina fiber fabric, and drying; (2) impregnating alumina sol: clamping a protective tool on the outer part of the dried alumina fiber fabric, placing it in a rotary evaporation assisted gel impregnation device, and then sucking the alumina sol from the lower gel inlet until it covers the alumina fiber fabric, after the alumina sol flows out from the upper gel outlet, the rotary evaporation assisted gel impregnation device is subjected to gas pressurization; (3) rotary evaporation assisted gelation: under the condition that the gas pressure in the rotary evaporation assisted gel impregnation device is kept constant, the rotary device and the heating device at the bottom are turned on, the condenser valve is opened, and the temperature is raised for rotary evaporation for a period of time, the water in the alumina sol is evaporated, the solid content and the sol viscosity are increased, and the gelation is completed until the gelation is completed; (4) drying the gel: after the gelation is completed, the alumina fiber fabric is taken out and placed in a constant temperature oven for drying to obtain a composite material roughcast; (5) sintering the roughcast: placing the dried composite material roughcast in a muffle furnace for sintering, and then naturally cooling to room temperature; (6) repeating the impregnation: repeating steps (2) to (5) several times until the weight gain rate of the composite material is less than a threshold value, and obtaining the alumina fiber reinforced ceramic matrix composite material; In steps (2) and (3), the rotary evaporation assisted gel impregnation device comprises a tank, a rotary device, a heating device, a condenser tube and a collection bottle, wherein the bottom of the tank is provided with a gel inlet, the top is provided with a gel outlet and a steam outlet, the steam outlet is connected to the collection bottle through a pipeline, the pipeline is provided with a condenser tube, and the collection bottle is used to collect the organic solvent after the steam is condensed; the rotary device is suspended in the interior of the tank, the rotation rate of the rotary device is 50-500 r / min; the bottom of the tank is placed in the heating device for heating, the heating device is provided with a hot water inlet, the heating temperature of the heating device is 25-150℃, and the rotary evaporation is performed for 4-6 h.

2. The production method according to claim 1, wherein In step (1), the alumina fiber fabric is selected from one of the following: Nextel 550 / 610 / 720, S-1920F / G or other 550 / 610 / 720 type fibers, and the fiber fabric structure is 2.5D structure, three-dimensional structure, needle-punched structure or stitched structure.

3. The production method according to claim 1, wherein In step (1), the sizing agent on the surface of the alumina fiber fabric is removed by sintering at 500-800℃, acetone cleaning at 50-60℃ or water washing at 60-90℃ for 21-23 h; the drying temperature is 70-90℃, and the drying time is 10-12 h.

4. The production method according to claim 1, wherein In step (2), the vacuum pumping time is 3-10 h, the vacuum degree is -0.096 to -0.099 MPa, the gas pressure is 3.5-3.7 MPa, and the pressure is maintained for at least 24 h.

5. The production method according to claim 1, wherein In step (2), the protective tool for clamping the fiber fabric is an epoxy resin clamp plate.

6. The production method according to claim 1, wherein In step (3), the solid content of the alumina sol is 17%-22%, and the viscosity is 8-12 mPa·s.

7. The production method according to claim 1, wherein The drying condition in step (4) is: first, constant temperature and variable humidity drying with temperature of 40-50℃ and humidity decreasing from 90% to 60%, drying time of 4-8h; then, conventional drying at 80-200℃, drying time of 5-12h.

8. The production method according to claim 1, wherein The sintering condition in step (5) is: sintering temperature of 600-1200℃, holding time of 0.5-3h.

9. The production method according to claim 1, wherein The threshold in step (6) is 1%.

Images