CN114605161A

CN114605161A - Ceramic matrix composite with high fiber volume content and preparation method thereof

Info

Publication number: CN114605161A
Application number: CN202011409458.4A
Authority: CN
Inventors: 张剑; 高文博; 崔凤单; 吕毅; 赵英民; 张昊
Original assignee: Aerospace Research Institute of Materials and Processing Technology
Current assignee: Aerospace Research Institute of Materials and Processing Technology
Priority date: 2020-12-03
Filing date: 2020-12-03
Publication date: 2022-06-10
Anticipated expiration: 2040-12-03
Also published as: CN114605161B

Abstract

The invention relates to a ceramic matrix composite with high fiber volume content and a preparation method thereof. The reinforcing phase in the ceramic matrix composite material with high fiber volume content comprises continuous oxide fibers and chopped oxide fibers, the matrix phase is a porous oxide matrix, and the fiber volume content is more than 60 percent. The preparation method comprises the following steps: removing the impregnating compound on the surface of the fiber; preparing short fiber impregnation liquid; immersing a core mould in short fiber impregnation liquid, winding continuous oxide fibers on the core mould after the continuous oxide fibers pass through the short fiber impregnation liquid to form a fabric reinforcement, immersing the fabric reinforcement in the short fiber impregnation liquid, sealing a container, heating the container together to enable the short fiber impregnation liquid to generate gel, and taking out the fabric reinforcement after natural cooling; carrying out drying treatment; carrying out high-temperature heat treatment; and (5) performing densification treatment on the composite material. The invention can improve the total fiber volume content of the fiber reinforced ceramic matrix composite and improve the mechanical strength of the composite.

Description

Ceramic matrix composite with high fiber volume content and preparation method thereof

Technical Field

The invention relates to a ceramic matrix composite with high fiber volume content and a preparation method thereof, in particular to a forming process of an oxide fiber reinforced oxide ceramic matrix composite based on winding forming, belonging to the technical field of ceramic matrix composites.

Background

The ceramic material is characterized by having excellent properties such as high melting point, low density, corrosion resistance, oxidation resistance, ablation resistance and the like, and the homogeneous ceramic material, such as alumina ceramic or silicon carbide ceramic and the like, has high hardness and wear resistance, is widely applied to the industrial fields such as sealing elements, guide rails, bearings, nozzles, tools, cutting materials and the like, and the most outstanding problem of the homogeneous ceramic material in the application is the hard and brittle characteristic thereof. It is precisely because of the hard and brittle nature of homogeneous ceramic materials that they tend not to withstand severe mechanical and thermal shocks, with the risk of sudden catastrophic failure that always exists in use, which greatly limits their range of applications. In order to improve the reliability of ceramic materials, ceramic matrix composites have been developed.

Ceramic matrix composites are multiphase (at least two-phase) material systems formed by compounding ceramic material matrixes and reinforcements such as fibers, whiskers or particles and the like, and are important members of an advanced composite family. Like resin-based and metal-based composites, the fiber-reinforced toughening effect is the best in ceramic-based composites. The fiber reinforced ceramic matrix composite material adopts the interface layer function of proper weak combination to realize the toughening and reinforcing functions of the fiber reinforcement on the ceramic matrix, is insensitive to cracks, has very strong resistance to thermal shock and toughness compared with the traditional structural ceramic, can radically overcome the brittleness of the traditional structural ceramic, greatly improves the use reliability, and is the mainstream direction of the development of the ceramic matrix composite material.

Ceramic matrix composites fall into two broad categories, oxide ceramic matrix composites and non-oxide ceramic matrix composites. The non-oxide fiber reinforced ceramic matrix composite material with carbon and silicon carbide as main components has better wear resistance, temperature resistance and high thermal conductivity, and is widely applied to the fields of thermal structural parts of aerospace aircrafts, sliding bearings, high-performance brake discs, heat exchangers and the like. Compared with the oxide fiber reinforced ceramic matrix composite material which takes silicon oxide and aluminum oxide as main components, the oxide fiber reinforced ceramic matrix composite material is more oxidation-resistant and corrosion-resistant, has excellent dielectric property, and is mainly applied to the fields of engine combustion chambers, thermal protection systems of aerospace aircrafts, high-temperature resistant antenna covers, inner linings of industrial kilns, high-temperature carriers, catalytic purifiers, soot filters and the like at present. The special combination of high temperature resistance, oxidation resistance, corrosion resistance, high strength and electromagnetic transparency represents the unique characteristics of the application field of the oxide fiber reinforced ceramic matrix composite.

The fiber volume content, also called fiber volume fraction, refers to the volume occupied by the reinforcing fibers in the unit volume of the composite material, and the height of the fiber volume content has great influence on the mechanical properties of the composite material, such as stretching, bending, compression and the like. Generally speaking, composite materials with higher fiber volume fraction can provide better mechanical properties, but are limited by the restriction of the current preform fabric weaving process and dip molding process, the fiber volume content of common oxide ceramic matrix composite materials is basically between 30% and 50%, and the maximum fiber volume content is not more than 60%, in addition, the strength of the oxide fibers is not high, the mechanical strength of the oxide ceramic matrix composite materials is generally lower, and more functional components are used for non-main bearing force. Therefore, the prior art limits the preparation of the oxide ceramic matrix composite with high fiber volume content, and a preparation method of the ceramic matrix composite with higher fiber volume content is urgently needed to further improve the mechanical property of the oxide ceramic matrix composite and expand the application range of the oxide ceramic matrix composite.

Disclosure of Invention

The invention aims to solve the technical problem of providing a ceramic matrix composite with high fiber volume content and a preparation method thereof.

The technical scheme adopted by the invention for solving the technical problems is as follows:

the ceramic matrix composite material with high fiber volume content comprises a reinforcing phase and a matrix phase, wherein the reinforcing phase is continuous oxide fibers and chopped oxide fibers, the matrix phase is a porous oxide matrix, and the fiber volume content is more than 60 percent.

Further, the continuous oxide fibers and the chopped oxide fibers comprise one or more of glass fibers, quartz fibers, alumina fibers and mullite fibers, the porous oxide matrix comprises one or more of porous silica, alumina and mullite matrix, the internal pores of the porous oxide matrix are usually a collection of nano pores, micro pores and micro cracks, and the porosity is 30-40%.

The forming process of the ceramic matrix composite with high fiber volume content provided by the invention comprises the following steps:

1. pretreatment of fibers

The reinforcing phase selected by the invention comprises glass fiber, quartz fiber, alumina fiber and mullite fiber. Because the surface of the fiber is usually provided with a layer of impregnating compound when leaving the factory, the impregnating compound needs to be removed by selecting a proper pretreatment process before the composite material is prepared. The fabric pretreatment is a technique known in the art, and can be selected according to specific requirements, such as removing the fiber surface sizing agent by adopting a mode of combining acid washing, high-temperature heat treatment, acetone soaking and boiling.

2. Preparation of short fiber impregnation liquid

The short fiber impregnation liquid selected by the invention consists of short fibers and matrix sol. And (3) adding the chopped fibers with the impregnating compound removed in the step (1) into the matrix glue solution, and performing ultrasonic dispersion until a uniform suspension is formed.

In the step, the matrix glue solution is a dispersant, so long as the chopped fibers can be uniformly dispersed, and the general reference dosage is that the mass of the chopped fibers and the matrix glue solution is 1: the range of 20 to 50 can be selected according to specific conditions. And carrying out ultrasonic treatment at room temperature for a certain time to obtain a uniform suspension, or dispersing in other ways to ensure that the uniform suspension is formed.

The preferable matrix glue solution is concentrated to the density of 1.28 to E1.36g/cm³Commercially available silica sol or single phase mullite sol in CN 201410696774.2.

The preferred staple fiber is selected to be consistent with the continuous fiber type of the target composite, with a length of less than 5 mm. The matrix glue solution is selected according to the requirements of the target composite material.

3. Pre-shaping of textile reinforcements

And immersing the anticorrosive pressure-resistant core mold in short fiber impregnation liquid. The drawn continuous fibers are passed through a short fiber dip and then directly wound onto a mandrel immersed in the short fiber dip to form the desired textile reinforcement, as shown in fig. 2. Immersing the fabric reinforcement in short fiber impregnation liquid, sealing the container, heating the container together to enable the short fiber impregnation liquid taking the matrix sol as a main component to be gelled, and taking out the fabric reinforcement for later use after the container is naturally cooled.

The continuous fiber is a twisted yarn. The untwisted yarn used in winding the resin-based composite material results in an excessively high fiber volume content (more than 70%) in the composite material. For ceramic matrix composites, the bonding properties of the porous matrix are poor (silica sol systems are more obvious than aluminum sol systems), and too high a fiber volume content is not favorable for the molding of the composite. The twist of the twisted yarn is recommended to be 60-90 twist/m, so that the attachment and the wrapping of the short fiber are facilitated. FIG. 1 is a schematic cross-sectional view of a three ply twisted yarn.

The types of the continuous fibers and the matrix glue solution are selected according to the requirements of the target composite material. The specific gel condition is determined according to the matrix glue solution. The preferred matrix glue solution is used under the condition of keeping the temperature at 80 ℃ for 24 hours.

4. Drying treatment

The drying process of the fabric reinforcement with the gel mass (gel) is divided into two steps, namely slow drying at a lower temperature and a higher humidity and thorough drying by heating.

The slow drying can be carried out by a known technique, and the preferable constant temperature and humidity drying can be adopted. The constant temperature and humidity drying process is that the temperature is constant at 25 +/-5 ℃, the relative humidity is reduced from (90 +/-5)% to (55 +/-5)% in a gradient and descending way, a plurality of constant humidity drying sections are arranged between the relative humidity (90 +/-5)% and (55 +/-5)% and the moisturizing time of each section is adjusted within 10-24 hours according to the size of the reinforcement,

heating and drying, namely putting the fabric reinforcement dried at constant temperature and constant humidity into an oven for drying, wherein the oven drying system is as follows: heating to 250 deg.C from room temperature, maintaining for 1 hr, and naturally cooling to room temperature. This step is well known and can be adjusted and selected according to specific needs.

5. High temperature heat treatment

And (3) carrying out ceramic heat treatment on the dried fabric reinforcement in a high-temperature furnace such as a pit furnace, a trolley furnace or a muffle furnace, wherein the heat treatment temperature is selected according to the type of the matrix glue solution. The temperature rise rate of the heat treatment is preferably 5-10 ℃/min, and the temperature is kept at the highest temperature point for 1 h. The preferred heat treatment furnace is a shaft furnace with air blast for larger size blanks due to the more uniform temperature in the various zones in the shaft furnace. This step is well known and can be adjusted and selected according to specific needs.

6. Densification of composite materials

And repeatedly dipping the fabric reinforcement subjected to high-temperature heat treatment by using matrix sol, and realizing the densification of the composite material by using a sol-gel process until the composite material reaches the required density. The process can be referred to the well-known techniques in the published patent or literature.

Compared with the prior art, the invention has the beneficial effects that:

(1) according to the invention, the chopped fibers are added into the material matrix, so that the total fiber volume content of the fiber reinforced ceramic matrix composite material can be further improved, and the mechanical strength of the composite material is improved.

(2) The method of introducing the chopped fibers in the winding process enables the inner-layer fiber bundles and the outer-layer fiber bundles to be mutually locked, greatly improves the interlayer strength of the winding-formed ceramic matrix composite material, and solves the problem that the ceramic matrix is generally inferior to a resin matrix in the adhesion property when the method is applied to the winding-forming process to a certain extent.

(3) The invention uses the twisted yarn for winding, which is the key for realizing the winding and forming of the ceramic matrix composite material. The space between the tows overlapped by the twisted yarns effectively controls the upper limit of the fiber volume content of the reinforcement, so that the matrix content of the ceramic matrix composite material is not lower, and the ceramic matrix composite material is favorably formed.

(4) Compared with the traditional oxide ceramic matrix composite material forming process, the preparation method provided by the invention is a low-cost rapid forming process which greatly improves the yarn utilization rate and the fiber volume content, and is expected to be applied to large-scale low-cost rapid manufacturing of ceramic matrix composite materials.

Drawings

FIG. 1 is a schematic cross-sectional view of a triple-twisted yarn incorporating chopped fibers according to the present invention (1: chopped fibers, 2: continuous fiber tow).

FIG. 2 is a schematic view of the winding formation in the short fiber impregnation solution of the present invention (10: twisted yarn into which short fibers are introduced, 20: winding mandrel, 30: short fiber impregnation solution, 40: sealable container).

Detailed Description

The present invention will be further described with reference to the following examples.

The preparation process flow of the ceramic matrix composite with high fiber volume content is as follows:

firstly, pretreating continuous fibers and chopped fibers to prepare short fiber impregnation liquid; then, immersing the core mould in short fiber dipping solution to finish the winding and forming of fibers in the short fiber dipping solution; finally, the first composite molding of the fabric reinforcement is completed through gelling, drying and heat treatment. Subsequently, it is considered as a material green body, which is repeatedly impregnated with a matrix sol to achieve densification of the composite material until it reaches the desired density.

Example 1:

1. pretreatment of fibers

And twisting and plying three 200tex type B quartz fiber yarns with the twist of 60 twists/m. And putting the twisted fiber yarns and the short-cut quartz fibers with the diameter of 3mm into acetone for boiling, and removing the fiber surface sizing agent. After the last boiling, cooling the acetone to room temperature, soaking and washing the fiber in new acetone, and airing in a fume hood for later use.

2. Preparation of short fiber impregnation liquid

After commercial silica sol was concentrated to 1.28g/cm3 by ultrafiltration, chopped quartz fiber yarns from which the sizing agent was removed were added thereto, and ultrasonically dispersed until a uniform suspension was formed. Wherein the mass ratio of the short fibers to the matrix glue solution is 1: 20.

3. pre-shaping of textile reinforcements

And immersing a nylon core mould in the short fiber impregnation liquid, and directly winding the continuous quartz fiber subjected to drafting and removal of the impregnating compound on the core mould tightly after passing through the short fiber impregnation liquid to form the required fabric reinforcement. And (3) sealing the container containing the short fiber impregnation liquid and the nylon core mold, transferring the container into an oven, and keeping the temperature at 80 ℃ for 24 hours. In the process, the container needs to be sealed and airtight in order to ensure that the short fiber impregnation liquid is gelled, not dried and pulverized.

4. Drying treatment

And after the container is naturally cooled, taking out the fabric reinforcement in the gel block, and slowly drying in a constant temperature and humidity box. The constant temperature and humidity drying system comprises: the temperature is constantly 25 ℃; relative humidity of 90%, maintaining for 12h, then reducing the humidity to 80% in 30min, maintaining for 12h, then reducing the humidity to 70% in 30min, maintaining for 12h, then reducing the humidity to 60% in 30min, and maintaining for 12 h; the humidity was then reduced to 55% over 30min and held for 12 h.

Placing the fabric reinforcement dried at constant temperature and constant humidity into an oven for drying, wherein the oven drying system is as follows: the temperature was raised from room temperature to 50 ℃ over 15min for 1h, then to 100 ℃ over 30min for 1h, then to 200 ℃ over 50min for 1h, and finally to 250 ℃ over 25min for 1 h.

5. High temperature heat treatment

And after the oven is naturally cooled to room temperature, taking out the obtained fabric reinforcement for high-temperature heat treatment, wherein the heat treatment temperature is 800 ℃, the heating rate is 10 ℃/min, and the temperature is kept for 1h after reaching 800 ℃, so that the composite material blank is obtained.

6. Densification of composite materials

Concentrating the silica sol crude gel by ultrafiltrationThe density of the treated silica sol was 1.40g/cm³。

The fabric reinforcement is placed in a closed pressure container, and the container needs to be sealed and airtight after the mold is closed. Vacuumizing the closed pressure container until the vacuum degree is lower than 0.095MPa, and pre-treating to obtain the product with the density of 1.40g/cm³The silica sol is injected into a closed pressure container through vacuum suction and injection, and the injection rate is 1L/min until the container is filled. And (3) pressurizing the closed pressure container to 4.0MPa, wherein the pressurized gas is nitrogen, and maintaining the pressure for 20 hours. And (3) putting the sealed pressure container into an oven, heating to 80 ℃, and preserving heat for 24 hours. And demolding after the sealed pressure container is naturally cooled.

Putting the blank piece removed from the pressure container into an oven for drying, wherein the oven drying system is as follows: the temperature was raised from room temperature to 50 ℃ over 15min for 1h, then to 100 ℃ over 30min for 1h, then to 200 ℃ over 50min for 1h, and finally to 250 ℃ over 25min for 1 h. And after the oven is naturally cooled to room temperature, taking out the blank to carry out ceramic heat treatment, wherein the heat treatment temperature is 800 ℃, the heating rate is 10 ℃/min, and the blank is kept warm for 1h after reaching 800 ℃.

Repeating the above processes for three times to obtain the final product. Wherein the density of the second impregnation of the silica sol was changed to 1.38g/cm³The density of the third and fourth dipping silica sol is changed to 1.28g/cm³。

Example 2:

1. pretreatment of fibers

Three bundles of 67tex alumina fiber yarn were twisted and plied at a twist of 90 twists/m. And (3) putting the twisted fiber yarns and the 3mm short-cut alumina fibers into a muffle furnace, performing heat treatment at 500 ℃ for 2h, and removing the fiber surface sizing agent for later use.

2. Preparation of short fiber impregnation liquid

Adding the chopped alumina fiber yarns without the impregnating compound into the single-phase mullite sol prepared according to the CN201410696774.2 method, and ultrasonically dispersing until a uniform suspension is formed. Wherein the mass ratio of the short fibers to the matrix glue solution is 1: 50.

3. pre-shaping of textile reinforcements

And immersing a nylon core mould in the short fiber impregnation liquid, drawing, removing the impregnated continuous alumina fiber, passing through the short fiber impregnation liquid, and then directly winding the continuous alumina fiber on the core mould tightly to form the required fabric reinforcement. And (3) sealing the container containing the short fiber impregnation liquid and the nylon core mold, transferring the container into an oven, and keeping the temperature at 90 ℃ for 24 hours. In the process, the container needs to be sealed and airtight in order to ensure that the short fiber impregnation liquid is gelled, not dried and pulverized.

4. Drying treatment

And after the container is naturally cooled, taking out the fabric reinforcement in the gel block, and slowly drying in a constant temperature and humidity box. The constant temperature and humidity drying system comprises: the temperature is constantly 25 ℃; the relative humidity is 85%, the relative humidity is kept for 24h, then the relative humidity is reduced to 70% in 30min, the relative humidity is kept for 24h, then the relative humidity is reduced to 55% in 30min, and the relative humidity is kept for 24 h.

5. High temperature heat treatment

And after the oven is naturally cooled to room temperature, taking out the obtained fabric reinforcement for high-temperature heat treatment, wherein the heat treatment temperature is 1000 ℃, the heating rate is 10 ℃/min, and the temperature is kept for 1h after the temperature reaches 1000 ℃, so that a composite material blank is obtained.

7. Densification of composite materials

The fabric reinforcement is placed in a closed pressure container, and the container needs to be sealed and airtight after the mold is closed. And vacuumizing the closed pressure container until the vacuum degree is lower than 0.095MPa, and injecting the self-made mullite sol into the closed pressure container at the rate of 1L/min until the container is filled. And (3) pressurizing the closed pressure container to 3.6MPa, wherein the pressurized gas is nitrogen, and maintaining the pressure for 20 hours. And (3) putting the sealed pressure container into an oven, heating to 90 ℃, and preserving heat for 24 hours. And demolding after the sealed pressure container is naturally cooled.

Repeating the above process for 8 times to obtain the final product. Wherein the temperature of the 3 rd and 6 th heat treatment is 1000 ℃.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. The ceramic matrix composite material with high fiber volume content is characterized by comprising a reinforcing phase and a matrix phase, wherein the reinforcing phase comprises continuous oxide fibers and chopped oxide fibers, the matrix phase is a porous oxide matrix, and the fiber volume content is more than 60 percent.

2. The high fiber volume content ceramic matrix composite according to claim 1, wherein said continuous oxide fibers and chopped oxide fibers are one or more of glass fibers, quartz fibers, alumina fibers, and mullite fibers; the porous oxide matrix comprises one or more of porous silicon oxide, alumina and mullite matrix, the internal pores of the porous oxide matrix are the set of nano pores, micro pores and micro cracks, and the porosity is 30-40%.

3. A method of making the high fiber volume content ceramic matrix composite of claim 1, comprising the steps of:

1) removing the impregnating compound on the surface of the fiber;

2) adding the chopped oxide fibers without the impregnating compound into the matrix sol to form uniform suspension, namely short fiber impregnation liquid;

3) immersing a core mould in short fiber impregnation liquid, winding continuous oxide fibers on the core mould after the continuous oxide fibers pass through the short fiber impregnation liquid to form a fabric reinforcement, immersing the fabric reinforcement in the short fiber impregnation liquid, sealing a container, heating the container together to enable the short fiber impregnation liquid to generate gel, and taking out the fabric reinforcement after natural cooling;

4) drying the fabric reinforcement with the gel;

5) carrying out high-temperature heat treatment on the dried fabric reinforcement;

6) and repeatedly dipping the fabric reinforcement subjected to high-temperature heat treatment by using the matrix sol, and realizing the densification of the composite material by using a sol-gel process.

4. The method of claim 3, wherein the matrix sol is a silica sol or a single phase mullite sol.

5. The method of claim 3, wherein the chopped oxide fibers have a length of less than 5 mm.

6. The method according to claim 3, wherein the continuous oxide fibers are twisted yarns having a twist of 60-90 twists/m.

7. The method of claim 3, wherein the drying process comprises: the mixture is slowly dried and then placed in an oven to be heated for complete drying.

8. The method according to claim 7, wherein the slow drying is constant temperature and humidity drying, and the constant temperature and humidity drying process comprises the following steps: the temperature is constant at 25 +/-5 ℃, the relative humidity is reduced from (90 +/-5)% to (55 +/-5)% in a gradient and descending manner, a plurality of constant humidity drying sections are arranged between the relative humidity (90 +/-5)% and the relative humidity (55 +/-5)% and the moisturizing time of each section is adjusted within 10-24 hours according to the size of the reinforcement body.

9. The method of claim 7, wherein the drying is carried out by heating in an oven using an oven drying schedule of: heating to 250 deg.C from room temperature, maintaining for 1 hr, and naturally cooling to room temperature.

10. The method according to claim 3, wherein the temperature rise rate of the high-temperature heat treatment is 5-10 ℃/min, and the temperature is kept at the highest temperature point for 1 h.