CN108178648B - Three-dimensional carbon fiber reinforced alumina-zirconia composite material and preparation method thereof - Google Patents

Abstract

The invention discloses a three-dimensional carbon fiber reinforced alumina-zirconia composite material and a preparation method thereof. The preparation method comprises the following steps: (1) stabilizing the alumina-zirconia composite sol; (2) vacuuming the three-dimensional carbon fiber preform dipping in alumina-zirconia composite sol; (3) drying the impregnated three-dimensional carbon fiber preform; (4) heat treatment; (5) repeating the impregnation-drying-heat treatment process of steps (2) to (4) until three-dimensional Compared with the previous impregnation-drying-heat treatment process, the carbon fiber reinforced alumina-zirconia composite material has a weight gain of less than 1%, and a three-dimensional carbon fiber-reinforced alumina-zirconia composite material is obtained. The three-dimensional carbon fiber reinforced alumina-zirconia composite material prepared by the invention has the advantages of high temperature resistance, oxidation resistance and excellent mechanical properties.

Description

Three-dimensional carbon fiber reinforced alumina-zirconia composite material and preparation method thereof

technical field

The invention belongs to the high temperature resistant fiber reinforced ceramic matrix composite material and the technical field of preparation thereof, in particular to a three-dimensional carbon fiber preform reinforced alumina-zirconia composite ceramic composite material and a preparation method thereof.

Background technique

Alumina-zirconia composite ceramics have the advantages of high temperature resistance, oxidation resistance, creep resistance and corrosion resistance of alumina and zirconia. Engine turbine blades have been studied a lot. As a single ceramic, the fracture toughness of alumina-zirconia composite ceramics is relatively low, in most cases 4-5 MPa·m ^1/2 . Such a low fracture toughness makes it difficult for single alumina-zirconia composite ceramics to be practically used as structural materials, especially in the occasions with large mechanical load shock and thermal shock, which must be toughened.

Introducing fibers into a ceramic matrix has been shown to be the most effective toughening method to significantly increase fracture toughness. Among the reinforcing fibers, carbon fibers have become the most widely used reinforcements due to their advantages of low cost, high temperature resistance, high tensile strength, and easy weaving to form complex shapes. Therefore, if carbon fiber and alumina-zirconia composite ceramics can be composited together, combining the advantages of both, it is theoretically expected to obtain fiber-reinforced alumina-zirconia with high temperature resistance, oxidation resistance, high strength and high toughness. Multiphase ceramic composites.

According to the arrangement of fibers in the composite material, that is, the structural form of the fiber preform, it can be divided into one-dimensional, two-dimensional, and three-dimensional preform-reinforced composite materials. One-dimensional composite material refers to a slurry prepared by passing fiber bundles through a ceramic matrix powder (there is a binder in the slurry to adhere the ceramic powder to the fibers) into a non-woven fabric, and then the non-woven fabric is wound in different directions and different directions. Angle layup, or directly wound into the desired shape in different directions and angles, and then sintered at high temperature without pressure or hot pressing. The two-dimensional composite material refers to the composite material obtained by adhering the ceramic matrix on the surface of the fiber cloth by brushing or dipping the slurry prepared by the ceramic matrix powder, and then laminating the fiber cloth and sintering at high temperature without pressure or hot pressing. . The three-dimensional composite material refers to the composite material obtained by first making the fibers into a three-dimensional preform, and then introducing the ceramic matrix into the preform by means of gas phase method and liquid phase method. In comparison, the integrity of 3D composites is better (one-dimensional and two-dimensional composites have weak in-plane and interlayer properties), and the fiber content and arrangement direction are highly designable, making them more suitable for complex-shaped components. preparation.

However, due to the different structures of preforms, the densification of 3D composites is difficult to copy the preparation process of 1D and 2D composites. According to the structural characteristics of the three-dimensional preform, two densification methods are usually used at present: one is to heat the preform to the required temperature, then feed the gaseous raw material, and the raw material diffuses into the preform and reacts and deposits the ceramic matrix under the action of high temperature. As the deposition time prolongs, the pores in the preform are gradually filled with the ceramic matrix, and the density increases continuously, which is called the gas phase method; the second is to immerse the preform in the liquid raw material, dry to remove the solvent, and then heat treatment at high temperature to obtain the ceramic matrix. Repeating several cycles of "dipping-drying-heat treatment", the pores in the preform are gradually filled with the ceramic matrix, and the density increases continuously, which is called the liquid phase method. In contrast, the liquid phase method has low requirements on equipment, is not sensitive to the temperature field and chemical field in the equipment during compounding, and has more obvious advantages in the preparation of complex shapes and batch components. Moreover, for fiber-reinforced alumina-zirconia composite ceramic composites, there are currently too few gaseous raw materials suitable for the deposition of alumina and zirconia, and the deposition characteristics are not ideal. Liquid raw materials are relatively easy to obtain and have reliable performance.

For the liquid phase method, how to quickly prepare a three-dimensional fiber preform reinforced alumina-zirconia composite ceramic composite material with high density and high mechanical properties is a key problem that needs to be solved. The key technical points involved include: Liquid raw material properties, impregnation process, heat treatment process. There is no research report on the preparation of three-dimensional carbon fiber preform reinforced alumina-zirconia composite ceramic composites by liquid phase method.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a three-dimensional carbon fiber reinforced alumina-zirconia composite material with excellent high temperature resistance, oxidation resistance and mechanical properties and a preparation method thereof.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

A preparation method of a three-dimensional carbon fiber reinforced alumina-zirconia composite material, comprising the following steps:

(1) Preparation of alumina-zirconia composite sol: mixing alumina sol and zirconia sol, adding stabilizer to obtain alumina-zirconia composite sol;

(2) Impregnation: The three-dimensional carbon fiber preform is placed in a container, and after vacuuming, the alumina-zirconia composite sol obtained in step (1) is inhaled, and vacuum impregnation is performed, so that the alumina-zirconia composite sol is filled in the three-dimensional composite sol. In carbon fiber prefabs;

(3) Drying: The three-dimensional carbon fiber preform is taken out and dried to remove the solvent and stabilizer in the alumina-zirconia composite sol;

(4) Heat treatment: heat treatment under the protection of an inert atmosphere to obtain a three-dimensional carbon fiber reinforced alumina-zirconia composite intermediate;

(5) Repeat the impregnation-drying-heat treatment process of steps (2) to (4) until the weight gain of the three-dimensional carbon fiber reinforced alumina-zirconia composite material intermediate is less than 1% compared with the previous impregnation-drying-heat treatment process , to obtain three-dimensional carbon fiber reinforced alumina-zirconia composites.

In the above-mentioned preparation method of a three-dimensional carbon fiber reinforced alumina-zirconia composite material, preferably, in the step (1), the stabilizer includes one or more of HNO ₃ , HCl or H ₂ SO ₄ .

In the above-mentioned preparation method of the three-dimensional carbon fiber reinforced alumina-zirconia composite material, preferably, the added amount of the stabilizer is 20% to 30% of the mass of the alumina sol.

For the preparation method of the above three-dimensional carbon fiber reinforced alumina-zirconia composite material, preferably, in the step (1), in the alumina-zirconia composite sol, the solid content is 20wt% to 40wt%, and the alumina and The molar ratio of zirconia is 95/5 to 5/95, and the particle size of the composite sol is less than or equal to 30 nm.

In the above-mentioned preparation method of the three-dimensional carbon fiber reinforced alumina-zirconia composite material, preferably, in the step (3), the drying temperature is 350℃～750℃, and the drying time is 1h～6h.

In the above-mentioned preparation method of the three-dimensional carbon fiber reinforced alumina-zirconia composite material, preferably, in the step (2), the vacuum impregnation process conditions are: vacuum degree≤500Pa, and the impregnation time is 4h-8h.

In the above-mentioned preparation method of the three-dimensional carbon fiber reinforced alumina-zirconia composite material, preferably, in the step (2), after the vacuum impregnation, it also includes air pressure-assisted impregnation under a set pressure to make the alumina-zirconia The composite sol is further filled in the three-dimensional carbon fiber preform, and the process conditions of the air pressure-assisted impregnation are: the set pressure is 2MPa-10MPa, and the impregnation time is 2h-6h.

For the preparation method of the above-mentioned three-dimensional carbon fiber reinforced alumina-zirconia composite material, preferably, in the step (4), the process of the heat treatment is as follows: under the protection of an inert atmosphere, the temperature is 10°C/min～20°C/min. The temperature was raised to 1100°C to 1500°C at a rate of min, and the temperature was kept for 0.5h to 2h.

The preparation method of the above-mentioned three-dimensional carbon fiber reinforced alumina-zirconia composite material, preferably, before the step (2), it further includes a three-dimensional carbon fiber preform preprocessing step, specifically: placing the three-dimensional carbon fiber preform in a vacuum Or in an inert atmosphere, the temperature is raised to 1400°C to 1800°C at a rate of 10°C/min to 20°C/min and kept for 1h to 4h.

For the preparation method of the above-mentioned three-dimensional carbon fiber reinforced alumina-zirconia composite material, preferably, the three-dimensional carbon fiber preform is a three-dimensional carbon fiber preform obtained by lamination and stitching of carbon fiber cloth, and a carbon fiber cloth and a mesh tire alternately laminated and needled. One or more of three-dimensional carbon fiber preforms, three-dimensional carbon fiber preforms with a three-dimensional five-way braided structure, three-dimensional carbon fiber preforms with a two-dimensional semi-braided structure, and three-dimensional carbon fiber preforms with a three-dimensional four-way braided structure; the three-dimensional carbon fiber preforms The volume fraction of carbon fiber in the piece is 25% to 55%.

As a general inventive concept, the present invention also provides a three-dimensional carbon fiber reinforced alumina-zirconia composite material prepared by the above preparation method, including a three-dimensional carbon fiber preform and an alumina-zirconia composite ceramic, the alumina -In the zirconia multiphase ceramics, the molar content of zirconia is 5% to 95%, the alumina-zirconia multiphase ceramics are uniformly filled in the pores of the three-dimensional carbon fiber preform, and the three-dimensional carbon fiber reinforced alumina-oxidized The porosity of zirconium composites is 10% to 17%.

Compared with the prior art, the advantages of the present invention are:

1. The present invention uses the alumina-zirconia composite sol as the liquid raw material, and adopts the liquid phase method to prepare the three-dimensional carbon fiber reinforced alumina-zirconia composite material. The high solid content and nano-scale sol can make the alumina-zirconia particles fast, It is uniformly filled into the voids in the preform, and the densification efficiency is high compared to the technical route starting from the solution; The uniformity is good, and the temperature of forming alumina-zirconia composite ceramics is low, and the damage to the fiber is small.

In the process of preparing the three-dimensional carbon fiber reinforced alumina-zirconia composite material, acid solution is introduced into the liquid raw material alumina-zirconia composite sol as a stabilizer, which solves the problem that the hydrolysis speed of alumina sol and zirconia sol is obviously different. However, due to the problem of poor compatibility, a stable alumina-zirconia composite sol is obtained, which provides a reliable raw material guarantee for the preparation of composite materials. In the process of preparing the alumina-zirconia composite sol, the applicant found that the alumina sol and the zirconia sol were mixed and precipitated. The particles cannot be impregnated into the pores of the fiber preform and cannot be used as raw materials for the "impregnation-drying-heat treatment" technical route. Earlier attempts were made to stabilize the alumina-zirconia composite sol by diluting and adding chelating agents (the principle is to increase steric hindrance and reduce the collision probability of colloidal particles), but first, the stabilization effect is not ideal, and second, it will To a certain extent, the solid content of the composite sol is reduced, thereby reducing the preparation efficiency of the composite material. In order to better stabilize the alumina-zirconia composite sol, the applicant has conducted in-depth theoretical research and practical exploration on the causes of precipitation after mixing alumina sol and zirconia sol. The research results show that the alumina sol is alkaline, Zirconia sol is acidic, so when the two are mixed, the pH value is mismatched, the sol is destabilized, and precipitation occurs. The present invention reverses its thinking, according to the hydrolysis mechanism in the synthesis process of alumina sol and zirconia sol, by adding acid solution to partially peptize the hydrolyzed colloidal particles, thereby reducing the probability of collision instability, and adjusting the pH value of the two at the same time At the same level, the stability of the composite sol is significantly improved, and the solid content and composite efficiency of the composite sol are not reduced. In addition, the addition of the acid solution can also reduce the viscosity of the composite sol to a certain extent, thereby facilitating the impregnation into the fiber preform.

The acid solution is preferably a strong acid, and the stabilizing effect of the strong acid on the alumina-zirconia composite sol is better than that of the weak acid. Among them, nitric acid has the best stabilizing effect on the alumina-zirconia composite sol.

2. Since the alumina-zirconia composite sol contains stabilizers, it will remain in the gel in the form of acid radicals. If it cannot be removed at a lower temperature, it will affect the reaction of alumina and zirconia at high temperatures. With sintering, it will also damage the carbon fiber. The present invention chooses to remove it by increasing the drying temperature (350 ℃ ~ 750 ℃) in the drying stage. In this temperature range, the acid radical will be decomposed, for example, the nitrate radical can be decomposed into NO _x and O ₂ and be eliminated completely, so that at high temperature It will not affect the reaction and sintering shrinkage of alumina and zirconia due to gas volatilization, and will not cause obvious damage to the carbon fiber.

3. Preferably, in the sol used in the present invention, alumina and zirconia are both amorphous and nanoscale, and their surface energy is very high, so they have high sintering activity, which provides high-quality composite materials for high-temperature heat treatment. Raw material guarantee.

4. Preferably, in the impregnation stage of the present invention, the method of first vacuum impregnation and then air pressure assisted impregnation is adopted, and the air in the prefabricated void is firstly removed by vacuuming, so as to provide space for the infiltration of the sol, because the nano-sized single particles in the sol are uniform The dispersed alumina-zirconia composite colloidal particles have good stability, so they can quickly and uniformly enter the voids of the preform; and then through the action of external air pressure, the sol is further infiltrated into the preform, entering some complex pores. In the voids, some closed cells can even be destroyed to turn them into open cells, thereby improving the impregnation efficiency and filling degree.

5. Preferably, in the present invention, on the basis of selecting amorphous, small and stable alumina-zirconia composite sol as the matrix raw material of the composite material, through the research on the sintering shrinkage behavior of alumina-zirconia, heat treatment The temperature is set at 1100℃～1500℃, within this temperature range, it can not only ensure the conversion of alumina-zirconia into alumina-zirconia composite ceramics, but also obtain a higher matrix density (increase the substrate bearing load and The ability to transfer load), and finally obtain a three-dimensional carbon fiber preform reinforced alumina-zirconia composite ceramic composite with excellent comprehensive properties.

In a word, the present invention starts from the characteristics of liquid raw materials, impregnation process, drying process, and heat treatment temperature, and significantly improves the density of the three-dimensional carbon fiber preform reinforced alumina-zirconia composite ceramic composite material, which not only enhances the bearing capacity of the matrix itself Therefore, the prepared three-dimensional carbon fiber reinforced alumina-zirconia composite material exhibits excellent mechanical properties, high temperature resistance and oxidation resistance.

6. The three-dimensional carbon fiber reinforced alumina-zirconia composite material prepared by the present invention combines the advantages of carbon fiber, alumina-zirconia composite ceramics and three-dimensional prefabricated parts for the first time, and has high temperature resistance, oxidation resistance and excellent performance. mechanical properties, etc. Specifically, the mechanical properties of the three-dimensional carbon fiber preform are used to provide excellent mechanical properties, especially high fracture toughness, which overcomes the brittleness of the single alumina-zirconia composite ceramics; the use of alumina-zirconia composite ceramics provides excellent mechanical properties. The anti-oxidation properties of carbon fiber are wrapped and protected to provide excellent anti-oxidation properties of composite materials; the high-temperature resistance properties of carbon fibers and the high melting point of alumina-zirconia composite ceramics are used to provide excellent high-temperature resistance capabilities of composite materials. In addition, the porosity of the composite material is low (10% to 17%), that is, the content and density of the alumina-zirconia composite ceramics are high, so the mechanical properties, high temperature resistance and oxidation resistance of the composite material are improved. Further improve.

Description of drawings

FIG. 1 is a macro photo of the three-dimensional carbon fiber reinforced alumina-zirconia composite material prepared in Example 1 of the present invention.

FIG. 2 is a microstructure diagram of the three-dimensional carbon fiber reinforced alumina-zirconia composite material prepared in Example 1 of the present invention.

Figure 3 is the XRD pattern of the gel powder obtained by drying the matrix raw material alumina-zirconia composite sol (the molar ratio of Al ₂ O ₃ and ZrO ₂ is 1:0.3).

Figure 4 is the dried gel powder of the matrix raw material alumina-zirconia composite sol (the molar ratio of Al ₂ O ₃ and ZrO ₂ is 1:0.3) of the present invention. After being pressed into blocks, heat treatment at different temperatures After the line shrinks.

Figure 5 shows the XRD patterns of the dried gel powder of the matrix raw material alumina-zirconia composite sol (molar ratio of Al ₂ O ₃ and ZrO ₂ is 1:0.3) after heat treatment at different temperatures.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

Example 1:

A preparation method of a three-dimensional carbon fiber reinforced alumina-zirconia composite material of the present invention comprises the following specific process steps:

(1) Sol selection: Select an alumina-zirconia composite sol with a solid phase content of 30 wt% as the raw material for the alumina-zirconia composite ceramic matrix, wherein the molar ratio of alumina and zirconia is 1:0.3. HNO ₃ was added to the aluminum-zirconia composite sol as a stabilizer, and the amount of HNO ₃ was 25% of the weight of the alumina sol.

(2) Pre-processing of preforms: The three-dimensional carbon fiber preform obtained by lamination and stitching of carbon fiber cloth is selected as the reinforcement phase, and the volume fraction of fibers in the three-dimensional carbon fiber preform is 48%. The selected three-dimensional carbon fiber preforms were placed under vacuum, heated to 1400°C at a rate of 20°C/min and kept for 2 h, and then cooled with the furnace to complete the pretreatment of the preforms.

(3) Vacuum impregnation: place the pretreated three-dimensional carbon fiber preform in a vacuum tank, and when the vacuum degree reaches 300Pa, inhale the alumina-zirconia composite sol of step (1) to make the alumina-zirconia composite sol. The composite sol submerged the three-dimensional carbon fiber preform for 6 hours.

(4) Air pressure-assisted impregnation: Move the preform (still immersed in the sol) into the autoclave, inflate to 4MPa, and carry out air-pressure-assisted impregnation for 4h.

(5) Drying: The three-dimensional carbon fiber preform was taken out from the sol and dried at 500 °C for 2 h in an inert atmosphere.

(6) Heat treatment: under the protection of high-purity inert gas, the dried three-dimensional carbon fiber preform is heated to 1300 °C at a rate of 15 °C/min, and kept for 1 h, and then cooled with the furnace to obtain three-dimensional carbon fiber reinforced alumina-oxidized Zirconium composite intermediates.

(7) Repeat process: Repeat steps (3) to (6) for a total of 24 times. After the last treatment, the three-dimensional carbon fiber reinforced alumina-zirconia composite intermediate has a weight gain compared to the last treatment. The ratio was 0.77%, the composite process was completed, and the three-dimensional carbon fiber reinforced alumina-zirconia composite material was obtained.

Fig. 1 is a macro photo of the three-dimensional carbon fiber reinforced alumina-zirconia composite material prepared in this embodiment. After testing, the porosity of the three-dimensional carbon fiber reinforced alumina-zirconia composite material obtained in this embodiment is 13.1%, and the bending strength is 275.7MPa, and the fracture toughness was 13.9MPa·m ^1/2 . After heat treatment in a high temperature inert atmosphere at 1500℃ for 1h, the strength retention rate was 98.2%; after static air oxidation at 1500℃ for 0.5h, the strength retention rate was 94.4%.

Fig. 2 is a microstructure diagram of the three-dimensional carbon fiber reinforced alumina-zirconia composite material prepared in this example. It can be seen that its composition includes a three-dimensional carbon fiber preform and an alumina-zirconia composite ceramic, wherein the alumina- The zirconia composite ceramic is the matrix, the three-dimensional carbon fiber preform is the reinforcing phase, and the alumina-zirconia composite ceramic particles are sintered into blocks, which are uniformly filled in the fiber bundles, that is, the gaps between the individual fibers. In the alumina-zirconia composite ceramic matrix, the molar ratio of Al ₂ O ₃ and ZrO ₂ is 1:0.3.

Example 2:

A preparation method of a three-dimensional carbon fiber reinforced alumina-zirconia composite material of the present invention comprises the following specific process steps:

(1) Sol selection: Select an alumina-zirconia composite sol with a solid phase content of 35wt% as the raw material for the alumina-zirconia composite ceramic matrix, wherein the alumina to zirconia molar ratio is 95:5. _HNO3 was added to the aluminum-zirconia composite sol as a stabilizer, and the amount of _HNO3 was 20% of the weight of the alumina sol.

(2) Pre-processing of preforms: The three-dimensional carbon fiber preform with a three-dimensional four-way braided structure is selected as the reinforcement phase, and the volume fraction of fibers in the three-dimensional carbon fiber preform is 53%. The selected three-dimensional carbon fiber preforms were placed in a high-purity argon atmosphere, heated to 1800°C at a rate of 20°C/min and kept for 1 h, and then cooled with the furnace to complete the pretreatment of the preforms.

(3) Vacuum impregnation: place the pretreated three-dimensional carbon fiber preform in a vacuum tank, and when the vacuum degree reaches 100Pa, inhale the alumina-zirconia composite sol of step (1) to make the alumina-zirconia composite sol. The composite sol submerged the three-dimensional carbon fiber preform for 4 hours.

(4) Air pressure assisted impregnation: Move the preform (still soaked in sol) to the autoclave, inflate to 8MPa, carry out air pressure assisted impregnation, and keep it for 6h.

(5) Drying: The three-dimensional carbon fiber preform was taken out from the sol and dried at 400 °C for 4 h in an inert atmosphere.

(6) Heat treatment: under the protection of high-purity inert gas, the dried three-dimensional carbon fiber preform is heated to 1500 °C at a rate of 15 °C/min, and kept for 0.5 h, and then cooled with the furnace to obtain three-dimensional carbon fiber reinforced alumina- Zirconia composite intermediates.

(7) Repeat process: Repeat steps (3) to (6) for a total of 25 times. After the last treatment, the three-dimensional carbon fiber reinforced alumina-zirconia composite intermediate has a weight gain compared to the last treatment. The ratio was 0.93%, the composite process was completed, and the three-dimensional carbon fiber reinforced alumina-zirconia composite material was obtained.

After testing, the three-dimensional carbon fiber reinforced alumina-zirconia composite material prepared in this example has a porosity of 12.6%, a bending strength of 302.8 MPa, and a fracture toughness of 12.4 MPa·m ^1/2 . After heat treatment in a high temperature inert atmosphere at 1500℃ for 1h, the strength retention rate was 99.0%; after static air oxidation at 1500℃ for 0.5h, the strength retention rate was 98.3%. Its composition includes a three-dimensional carbon fiber preform and an alumina-zirconia composite ceramic, wherein the alumina-zirconia composite ceramic is the matrix, the molar content of zirconia in the composite ceramic is 5%, and the three-dimensional carbon fiber preform is the reinforcement. The alumina-zirconia composite ceramics are uniformly filled in the voids of the three-dimensional carbon fiber preform.

Example 3:

A preparation method of a three-dimensional carbon fiber reinforced alumina-zirconia composite material of the present invention comprises the following specific process steps:

(1) Sol selection: choose an alumina-zirconia composite sol with a solid phase content of 20wt% as the raw material for the alumina-zirconia composite ceramic matrix, wherein the alumina to zirconia molar ratio is 5:95. _HNO3 was added to the aluminum-zirconia composite sol as a stabilizer, and the amount of _HNO3 was 20% of the weight of the alumina sol.

(2) Pre-processing of preforms: The three-dimensional carbon fiber preform with a two-dimensional semi-woven structure is selected as the reinforcement phase, and the volume fraction of fibers in the three-dimensional carbon fiber preform is 46%. The selected three-dimensional carbon fiber preforms were placed under vacuum, heated to 1400°C at a rate of 15°C/min and kept for 3 hours, and then cooled with the furnace to complete the pretreatment of the preforms.

(3) Vacuum impregnation: place the pretreated three-dimensional carbon fiber preform in a vacuum tank, and when the vacuum degree reaches 200Pa, inhale the alumina-zirconia composite sol of step (1) to make the alumina-zirconia composite sol. The composite sol submerged the three-dimensional carbon fiber preform for 8 hours.

(4) Air pressure-assisted impregnation: Move the preform (still immersed in the sol) to the autoclave, inflate to 10MPa, and carry out air-pressure-assisted impregnation for 2h.

(5) Drying: The three-dimensional carbon fiber preform was taken out from the sol, and dried at 700 °C for 1 h in an inert atmosphere.

(6) Heat treatment: under the protection of high-purity inert gas, the dried three-dimensional carbon fiber preform is heated to 1200 °C at a rate of 10 °C/min, and kept for 1.5 hours, and then cooled with the furnace to obtain three-dimensional carbon fiber reinforced alumina- Zirconia composite intermediates.

(7) Repeat process: Repeat steps (3) to (6) for a total of 21 times. After testing, after the last treatment, the three-dimensional carbon fiber reinforced alumina-zirconia composite intermediate has increased in weight compared with the last treatment. The ratio was 0.85%, the composite process was completed, and a three-dimensional carbon fiber reinforced alumina-zirconia composite material was obtained.

After testing, the porosity of the zirconia prepared in this example is 16.1%, the bending strength is 218.4 MPa, and the fracture toughness is 11.3 MPa·m ^1/2 . After heat treatment at 1500℃ for 1h in a high temperature inert atmosphere, the strength retention rate was 92.5%; after static air oxidation at 1500℃ for 0.5h, the strength retention rate was 91.8%. Its composition includes three-dimensional carbon fiber preforms and alumina-zirconia composite ceramics, wherein the alumina-zirconia composite ceramics are the matrix, the molar content of zirconia in the composite ceramics is 95%, and the three-dimensional carbon fiber preforms are reinforced. Phase, alumina-zirconia composite ceramics are uniformly filled in the voids of 3D carbon fiber preforms

Example 4:

A preparation method of a three-dimensional carbon fiber reinforced alumina-zirconia composite material of the present invention comprises the following specific process steps:

(1) Sol selection: Select the alumina-zirconia composite sol with a solid phase content of 40wt% as the raw material of the alumina-zirconia composite ceramic matrix, wherein the alumina to-zirconia molar ratio is 1:3. HNO ₃ was added to the alumina-zirconia composite sol as a stabilizer, and the amount of HNO ₃ was 30% of the weight of the alumina sol.

(2) Pre-treatment of preforms: The three-dimensional carbon fiber preforms obtained by alternately laminating and needle punching carbon fiber cloth and mesh tires are selected as the reinforcing phase, and the volume fraction of fibers in the three-dimensional carbon fiber preforms is 28%. The selected three-dimensional carbon fiber preforms were placed under vacuum, heated to 1400°C at a rate of 10°C/min and kept for 4 h, and then cooled with the furnace to complete the pretreatment of the preforms.

(3) Vacuum impregnation: place the pretreated three-dimensional carbon fiber preform in a vacuum tank, and when the vacuum degree reaches 500Pa, inhale the alumina-zirconia composite sol of step (1) to make the alumina-zirconia composite sol. The composite sol submerged the three-dimensional carbon fiber preform for 8 hours.

(4) Air pressure-assisted impregnation: move the preform (still immersed in the sol) into the autoclave, inflate to 2MPa, carry out air-pressure-assisted impregnation, and keep it for 6h.

(5) Drying: The three-dimensional carbon fiber preform was taken out from the sol and dried at 400 °C for 6 h in an inert atmosphere.

(6) Heat treatment: under the protection of high-purity inert gas, the dried three-dimensional carbon fiber preform is heated to 1100 °C at a rate of 10 °C/min, and kept for 2 hours, and then cooled with the furnace to obtain three-dimensional carbon fiber reinforced alumina-oxidized Zirconium composite intermediates.

(7) Repeat process: Repeat steps (3) to (6) for a total of 27 times. After the last treatment, the three-dimensional carbon fiber reinforced alumina-zirconia composite intermediate has a weight gain compared to the last treatment. The ratio was 0.93%, the composite process was completed, and the three-dimensional carbon fiber reinforced alumina-zirconia composite material was obtained.

After testing, the three-dimensional carbon fiber reinforced alumina-zirconia composite material obtained in this example has a porosity of 14.6%, a bending strength of 154.3 MPa, and a fracture toughness of 7.7 MPa·m ^1/2 . After heat treatment at 1500℃ for 1 hour in a high temperature inert atmosphere, the strength retention rate is 93.6%; after static air oxidation at 1500℃ for 0.5h, the strength retention rate is 91.0%. Its composition includes a three-dimensional carbon fiber preform and an alumina-zirconia composite ceramic, wherein the alumina-zirconia composite ceramic is a matrix, the molar ratio of the alumina ceramic and the zirconia ceramic is 1:3, and the three-dimensional carbon fiber preform is The reinforcing phase, alumina-zirconia composite ceramics, is uniformly filled in the voids of the three-dimensional carbon fiber preform.

Example 5:

A preparation method of a three-dimensional carbon fiber reinforced alumina-zirconia composite material of the present invention comprises the following specific process steps:

(1) Sol selection: select an alumina-zirconia composite sol with a solid phase content of 30 wt% as the raw material of the alumina-zirconia composite ceramic matrix, wherein the molar ratio of alumina and zirconia is 1:1. HNO ₃ was added to the alumina-zirconia composite sol as a stabilizer, and the amount of HNO ₃ was 25% of the weight of the alumina sol.

(2) Pre-processing of preforms: The three-dimensional carbon fiber preform with a three-dimensional five-way braided structure is selected as the reinforcement phase, and the volume fraction of fibers in the three-dimensional carbon fiber preform is 50%. The selected three-dimensional carbon fiber preforms were placed in a high-purity argon atmosphere, heated to 1600°C at a rate of 15°C/min and kept for 2 hours, and then cooled with the furnace to complete the pretreatment of the preforms.

(3) Vacuum impregnation: place the pretreated three-dimensional carbon fiber preform in a vacuum tank, and when the vacuum degree reaches 400Pa, inhale the alumina-zirconia composite sol of step (1) to make the alumina-zirconia composite sol. The composite sol submerged the three-dimensional carbon fiber preform for 6 hours.

(4) Air pressure-assisted impregnation: Move the preform (still immersed in the sol) into the autoclave, inflate to 6MPa, and carry out air-pressure-assisted impregnation for 4h.

(5) Drying: The three-dimensional carbon fiber preform was taken out from the sol and dried at 600 °C for 3 h in an inert atmosphere.

(6) Heat treatment: under the protection of high-purity inert gas, the dried three-dimensional carbon fiber preform is heated to 1400 °C at a rate of 20 °C/min, and kept for 1 h, and then cooled with the furnace to obtain three-dimensional carbon fiber reinforced alumina-oxidized Zirconium composite intermediates.

(7) Repeat process: Repeat steps (3) to (6) for a total of 25 times. After the last treatment, the three-dimensional carbon fiber reinforced alumina-zirconia composite intermediate has a weight gain compared to the last treatment. The ratio was 0.79%, the composite process was completed, and the three-dimensional carbon fiber reinforced alumina-zirconia composite material was obtained.

After testing, the porosity of the three-dimensional carbon fiber reinforced alumina-zirconia composite material prepared in this example is 10.7%, the bending strength is 334.6MPa, and the fracture toughness is 14.5MPa·m ^1/2 . After heat treatment in a high temperature inert atmosphere at 1500℃ for 1h, the strength retention rate is 98.6%; after static air oxidation at 1500℃ for 0.5h, the strength retention rate is 98.8%. Its composition includes a three-dimensional carbon fiber preform and an alumina-zirconia composite ceramic, wherein the alumina-zirconia composite ceramic is a matrix, the molar ratio of the alumina ceramic and the zirconia ceramic is 1:1, and the three-dimensional carbon fiber preform is The reinforcing phase, alumina-zirconia composite ceramics, is uniformly filled in the voids of the three-dimensional carbon fiber preform.

It can be seen from Examples 1 to 5 that the three-dimensional carbon fiber reinforced alumina-zirconia composite material prepared by the preparation method of the present invention has low porosity, high mechanical properties and excellent high temperature oxidation resistance.

To sum up, the present invention is based on the characteristics, research status and existing problems of alumina-zirconia composite ceramics, and combines the advantages of carbon fibers, alumina-zirconia composite ceramics and three-dimensional preforms to provide three-dimensional carbon fiber prefabricated products. A new material system of reinforced alumina-zirconia composite ceramic composites has been developed, and a preparation method capable of obtaining excellent properties has been formed.

In the preparation method, firstly, by adding HNO ₃ as an additive, a stable alumina-zirconia composite sol was obtained, which provided a reliable raw material guarantee for the preparation of composite materials, and then alumina with a solid content of 20wt% to 40wt% was used -Zirconium oxide composite sol (colloidal particle size ≤30nm) is used as the matrix raw material, the porosity is only about 11%, the bending strength can reach 334.6MPa, and the fracture toughness can reach 14.5MPa in a limited period (25 periods). m ^1/2 three-dimensional pentagonal carbon fiber reinforced alumina-zirconia composite ceramic composites. Although there is no completely corresponding three-dimensional five-direction carbon fiber reinforced alumina-zirconia composite ceramic composite prepared by other methods, it can be compared with similar existing technologies: First, AlCl ₃ ·6H is used in the prior art. The sol prepared from ₂ O or Al(NO ₃ ) ₃ ·9H ₂ O inorganic salt was used as the matrix raw material, and three-dimensional four-dimensional carbon fiber reinforced alumina composites were prepared by 13 cycles of "dipping-drying-1260 ℃ heat treatment". When the compound is continued, the density will not increase, the porosity is about 30%, and the bending strength is only 100MPa ~ 150MPa; the second is to prepare the Y ₂ SiO ₅ coating with Si-containing organic salt and Y-containing organic salt solution, and it is necessary to remove a large amount of solvent and Additives, the preparation efficiency is very low, a typical parameter is 20 times of dipping and pulling heat treatment, and the thickness is only 2μm. Therefore, by comparison, it can be found that the use of high solid content alumina-zirconia composite sol as the raw material of alumina-zirconia composite ceramic matrix, compared with the technical route starting from the solution of organic or inorganic salts, in terms of preparation efficiency The advantages are self-evident.

In addition, the microstructure of the three-dimensional carbon fiber reinforced alumina-zirconia composite material of the present invention was observed by scanning electron microscope, as shown in FIG. It is evenly filled in the interior of the fiber bundle, that is, the space between the single fibers, avoiding the problem of uneven distribution of mud raw materials that is easy to occur. Therefore, the alumina-zirconia composite sol used in the present invention not only maintains the advantages of uniform filling of inorganic salt or organic salt solution raw materials, and the advantages of high-efficiency impregnation of mud raw materials, but also overcomes the density of inorganic salt or organic salt solution raw materials. The disadvantages of low chemical efficiency and uneven filling of mud raw materials.

Next, the present invention adopts the method of first vacuum impregnation and then air pressure-assisted impregnation, first vacuuming to remove the air in the prefabricated voids, and providing space for the infiltration of the sol. The zirconium composite colloidal particles have good stability, so they can quickly and evenly enter the voids of the preform; then, through the action of external air pressure, the sol is further infiltrated into the preform, entering into some complex pores, and even can Break some closed cells into open cells, thereby improving impregnation efficiency and filling degree.

Finally, in the sol used in the present invention, the alumina-zirconia is in an amorphous state and has a nanometer scale, and its surface energy is very high, so it has a high sintering activity. On this basis, through the research on the sintering shrinkage behavior of alumina-zirconia, the present invention sets the heat treatment temperature to 1100℃～1500℃, within this temperature range, it can not only ensure the conversion of alumina-zirconia into alumina -Zirconium oxide multiphase ceramics, which can achieve higher matrix density (improve the ability of the matrix to withstand and transmit loads), and will not cause the reaction between the matrix and carbon fibers (avoid the formation of chemically strong bonding interfaces and damage to carbon fibers. mechanical properties), and finally obtain a three-dimensional carbon fiber reinforced alumina-zirconia composite material with excellent comprehensive properties.

XRD detection of the gel powder obtained by drying the alumina-zirconia sol:

The phase composition of the gel powder (molar ratio of alumina to zirconia was 1:0.3) was analyzed by a D8 Advance X-ray diffractometer. The test conditions are: CuKα ray, tube current 40mA, tube voltage 40KV, 2θ=10～60°, scanning speed 4°/min.

The detection results are shown in Figure 3. It can be seen from the figure that the spectrum shows the characteristics of "steamed bread" peaks, and no sharp diffraction peaks of alumina or zirconia appear, indicating that the alumina-zirconia gel powder dried at 700 °C is a typical non- Shaped state, amorphous state has high surface energy, which can promote sintering densification.

After the gel powder obtained by drying the alumina-zirconia sol was pressed into a block, the linear shrinkage after heat treatment at different temperatures was tested:

Put the dried alumina-zirconia gel powder (the molar ratio of alumina to zirconia is 1:0.3) into a metal mold with a diameter of 40mm, and press the powder on a press at 100MPa to a diameter of 40mm and a thickness of 40mm. 5mm round block. Put the round block into the heat treatment furnace, after heat treatment at different temperatures for 1h, measure the change rate of diameter and thickness before and after heat treatment, and measure the average value of 5 points as the final result.

The test results are shown in Figure 4. It can be seen from the figure that after heat treatment at 1100°C to 1500°C, the linear shrinkage rate increases gradually with the increase of temperature in the range of 12% to 24%. At 1400°C to 1500°C, the linear shrinkage changed little, and it increased significantly, indicating that alumina-zirconia has better sintering activity. According to Fig. 4, it can be inferred that when the temperature is lower than 1100 °C, the linear shrinkage rate after heat treatment will be significantly reduced, which is not conducive to sintering and densification. will further increase to promote densification, but at this time, the carbon fiber and zirconia are likely to have a carbothermic reduction reaction, so the present invention selects the upper limit of the heat treatment temperature to be 1500°C.

XRD detection of alumina-zirconia gel powder after heat treatment at different temperatures:

The alumina-zirconia gel powder obtained after drying (molar ratio of alumina to zirconia is 1:0.3) was heat-treated at different temperatures for 1 h, and then the phase composition of the powder was analyzed by D8 Advance X-ray diffractometer. The test conditions are: CuKα ray, tube current 40mA, tube voltage 40KV, 2θ=10～60°, scanning speed 4°/min.

The test results are shown in Figure 5. It can be seen from the figure that the alumina-zirconia composite ceramic phase is formed at 1100 °C, and the alumina phase appears at 1200 °C. As the temperature increases, the crystallinity of the two phases increases significantly. It can be speculated that it is likely to present an amorphous state when it is lower than 1100 °C, so the lower limit of the heat treatment temperature of the present invention is 1100 °C; at 1500 °C, the crystallinity of the two phases is very high, and considering that after exceeding 1500 °C, carbon fiber and -oxidation Zirconium is highly likely to undergo a carbothermic reduction reaction, so the upper limit of the heat treatment temperature in the present invention is 1500°C.

The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All the technical solutions under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, improvements and modifications without departing from the principles of the present invention should also be regarded as the protection scope of the present invention.

Claims (9)

1. A preparation method of a three-dimensional carbon fiber reinforced alumina-zirconia composite material comprises the following steps:

(1) preparing alumina-zirconia composite sol: mixing the alumina sol and the zirconia sol, and adding a stabilizer to obtain alumina-zirconia composite sol; the stabilizer comprises HNO₃HCl or H₂SO₄One or more of;

(2) dipping: placing the three-dimensional carbon fiber prefabricated part into a container, vacuumizing, sucking the alumina-zirconia composite sol obtained in the step (1), and performing vacuum impregnation to fill the alumina-zirconia composite sol into the three-dimensional carbon fiber prefabricated part;

(3) and (3) drying: taking out the three-dimensional carbon fiber prefabricated part and drying to remove the solvent and the stabilizer in the alumina-zirconia composite sol;

(4) and (3) heat treatment: carrying out heat treatment under the protection of inert atmosphere to obtain a three-dimensional carbon fiber reinforced alumina-zirconia composite material intermediate;

(5) and (4) repeating the dipping-drying-heat treatment processes in the steps (2) to (4) until the weight of the three-dimensional carbon fiber reinforced alumina-zirconia composite material intermediate is increased by less than 1% compared with that in the last dipping-drying-heat treatment process, so as to obtain the three-dimensional carbon fiber reinforced alumina-zirconia composite material.

2. The method for preparing a three-dimensional carbon fiber reinforced alumina-zirconia composite material according to claim 1, wherein the stabilizer is added in an amount of 20 to 30% by mass of the alumina sol.

3. The method for preparing the three-dimensional carbon fiber reinforced alumina-zirconia composite material according to claim 2, wherein in the step (1), the alumina-zirconia composite sol has a solid content of 20-40 wt%, the molar ratio of alumina to zirconia is 95/5-5/95, and the size of the colloidal particles of the composite sol is less than or equal to 30 nm.

4. The method for preparing the three-dimensional carbon fiber reinforced alumina-zirconia composite material according to any one of claims 1 to 3, wherein in the step (3), the drying temperature is 350 ℃ to 750 ℃ and the drying time is 1h to 6 h.

5. The method for preparing the three-dimensional carbon fiber reinforced alumina-zirconia composite material according to claim 4, wherein the vacuum impregnation in the step (2) is performed under the following process conditions: the vacuum degree is less than or equal to 500Pa, and the dipping time is 4-8 h.

6. The method for preparing the three-dimensional carbon fiber reinforced alumina-zirconia composite material according to claim 5, wherein the step (2) further comprises performing air pressure assisted impregnation under a set pressure after vacuum impregnation, so that the alumina-zirconia composite sol is further filled in the three-dimensional carbon fiber preform, wherein the process conditions of the air pressure assisted impregnation are as follows: the set pressure is 2MPa to 10MPa, and the dipping time is 2h to 6 h.

7. The method for preparing the three-dimensional carbon fiber reinforced alumina-zirconia composite material according to claim 5 or 6, wherein the heat treatment in the step (4) comprises the following steps: under the protection of inert atmosphere, heating to 1100-1500 ℃ at the speed of 10-20 ℃/min, and keeping the temperature for 0.5-2 h.

8. The method for preparing a three-dimensional carbon fiber reinforced alumina-zirconia composite material according to claim 7, wherein the three-dimensional carbon fiber preform is one or more of a three-dimensional carbon fiber preform obtained by laminating and sewing carbon fiber cloth, a three-dimensional carbon fiber preform obtained by alternately laminating and needling carbon fiber cloth and a mesh tire, a three-dimensional carbon fiber preform with a three-dimensional five-way woven structure, a three-dimensional carbon fiber preform with a two-dimensional semi-woven structure, and a three-dimensional carbon fiber preform with a three-dimensional four-way woven structure; the volume fraction of carbon fibers in the three-dimensional carbon fiber prefabricated part is 25-55%.

9. The three-dimensional carbon fiber reinforced alumina-zirconia composite material prepared by the preparation method of any one of claims 1 to 8, which comprises a three-dimensional carbon fiber preform and an alumina-zirconia composite ceramic, wherein the alumina-zirconia composite ceramic contains 5 to 95 mol% of zirconia, the alumina-zirconia composite ceramic is uniformly filled in pores of the three-dimensional carbon fiber preform, and the porosity of the three-dimensional carbon fiber reinforced alumina-zirconia composite material is 10 to 17%.

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