CN113698219B

CN113698219B - Silicon nitride fiber reinforced ceramic matrix composite and preparation method thereof

Info

Publication number: CN113698219B
Application number: CN202110870006.4A
Authority: CN
Inventors: 张术伟; 门薇薇; 苏韬
Original assignee: AVIC Research Institute Special Structures Aeronautical Composites
Current assignee: AVIC Research Institute Special Structures Aeronautical Composites
Priority date: 2021-07-30
Filing date: 2021-07-30
Publication date: 2023-01-13
Anticipated expiration: 2041-07-30
Also published as: CN113698219A

Abstract

The invention belongs to the technical field of structure-function integrated ceramic matrix composite materials, and particularly relates to a silicon nitride fiber reinforced ceramic matrix composite material and a preparation method thereof. The composite material comprises three parts: the fiber consists of silicon nitride fiber, a quartz-based matrix and an interface coating between the fiber and the matrix, wherein the quartz-based matrix comprises silicon oxide, aluminum oxide and boron oxide, the components are mixed according to the proportion of 70-90% by mass of the silicon oxide, 23-8% by mass of the aluminum oxide and 2-7% by mass of boric acid, and the interface coating is one or the combination of two of a silicon-aluminum-oxygen coating and a silicon-nitrogen-oxygen coating. Thereby further improving the retention rate of the high-temperature mechanical property of the composite material. The composite material is high-temperature resistant, highly reliable and reusable under the high-Mach flight condition, and the use requirements of the antenna window material of the hypersonic aircraft in the near space are met.

Description

Silicon nitride fiber reinforced ceramic matrix composite and preparation method thereof

Technical Field

The invention belongs to the technical field of structure-function integrated ceramic matrix composite materials, and particularly relates to a silicon nitride fiber reinforced ceramic matrix composite material and a preparation method thereof.

Background

The research on the wave-transmitting material begins in the fourth and fifties of the twentieth century, the early wave-transmitting material mainly comprises resin and resin-based composite materials, and the application objects of the wave-transmitting material are low-Mach-number missile antenna covers. Along with the development of missiles in the direction of high Mach number and high maneuverability, higher requirements are put forward on the heat resistance, high temperature bearing and other properties of the wave-transmitting material of the antenna housing, the ceramic wave-transmitting material gradually becomes a research focus and gradually changes from an oxide system to a nitride system, and the material system develops in the direction of complex-phase ceramic and ceramic matrix composite. The development process of the high-temperature resistant wave-transmitting material is sequentially from microcrystalline glass, single-phase ceramic, complex-phase ceramic to continuous fiber reinforced ceramic matrix composite. The single-phase ceramic and the complex phase ceramic are still brittle materials essentially, and have the defects of poor toughness, difficult forming of large-size components, poor processability and the like, and especially the thermal shock resistance becomes a bottleneck restricting the further application of the single-phase and complex phase ceramic high-temperature wave-transmitting materials. With the development and the demand of hypersonic aircrafts, reentry aircrafts and near space combat aircrafts in the twenty-eighth century, the high temperature resistance, the impact resistance, the thermal oxidation resistance, the reliability and the reusability of the antenna housing face great challenges, and the continuous fiber reinforced ceramic matrix composite material gradually becomes a main choice of antenna window materials in a high thermal power state.

The main technical scheme at present is two systems of a quartz fiber reinforced quartz ceramic matrix composite and a nitride fiber reinforced nitride ceramic matrix composite.

The quartz fiber reinforced ceramic matrix composite material is mature, the material adopts a sol-gel process, firstly, a fiber preform is soaked in sol, the sol is aged and converted into gel with a three-dimensional space structure under a certain condition, and then the gel is dried and sintered to prepare the ceramic matrix composite material. At present, most of quartz fiber reinforced quartz ceramic-based wave-transparent radome materials are prepared by adopting a sol-gel process. The material system has the advantages that: the raw materials quartz fiber and silica sol are completely self-controllable in China, the preparation process is relatively simple, and the requirement on equipment is not high; the disadvantages are that: (1) The quartz fiber has low high temperature resistance, and needs high-temperature sintering in the preparation process of the composite material, thereby greatly influencing the mechanical property of the fiber; (2) The composite material has low mechanical property which is mainly reflected in that the mechanical strength at room temperature is low, the retention rate of the high-temperature mechanical property is low, the composite material is difficult to use for a long time or repeatedly at the temperature of more than 1000 ℃, and the requirements of the current near space aircraft on high Mach number long-time use and repeated use cannot be met.

The silicon nitride fiber reinforced ceramic-based nitride composite material is usually prepared by adopting a precursor impregnation cracking process, wherein the process comprises the steps of fully impregnating a fiber preform or a porous material in an organic precursor, carrying out crosslinking curing at a certain temperature after the impregnation is finished, and finally transferring the fiber preform or the porous material into a cracking furnace to crack at a certain temperature and in a certain atmosphere. After the cracking reaction, the organic precursor is converted into a ceramic matrix, and then the matrix is further sintered, so that the fiber reinforced ceramic matrix composite is obtained. The disadvantages of this composite material are mainly three: (1) Because the nitride fiber is blocked by foreign technologies, the breakthrough development of domestic high-quality nitride fiber in nearly two years leads to the main reason that the research development of the nitride fiber reinforced ceramic matrix composite material is slow; (2) Interface reaction is easy to occur between the nitride fiber and the nitride substrate in the high-temperature sintering preparation process, so that the fiber and the substrate are strongly combined, and the composite material is subjected to brittle fracture in the damage process.

(1) The invention selects silicon nitride fiber with high temperature resistance as a reinforcing material, and adopts a silicon nitride fiber widening cloth lamination sewing process to prepare a silicon nitride fiber prefabricated body as a reinforcing body of a composite material. The silicon nitride fiber widening cloth greatly reduces hooking among fiber bundles, can effectively improve the tensile strength of the fiber cloth, and further improves the tensile strength of the composite material.

(2) The preparation of the interface coating on the surface of the silicon nitride fiber of the reinforcement can effectively repair microcracks on the surface of the fiber, improve the strength of the fiber, and simultaneously form a weak interface bonding state between the fiber and a matrix, thereby avoiding brittle fracture of the composite material, and the high-temperature mechanical property of the composite material can be improved by adopting the high-temperature resistant coating as the coating.

(3) The silica sol, the alumina sol and the boric acid are adopted as raw materials, and the temperature resistance of the quartz matrix and the self-repairing capability of the matrix are improved by preparing the mixed sol on the premise of ensuring the electrical property of the matrix material of the ceramic composite material.

The method aims at the current situation that the existing quartz reinforced quartz ceramic matrix composite material is low in retention rate of high-temperature mechanical properties, and the nitride fiber reinforced nitride ceramic matrix composite material is immature and cannot meet the use requirements of a high-temperature-resistant, heat-resistant and oxidation-resistant, high-reliability and reusable antenna window material of a near-space hypersonic aircraft. (1) The invention solves the current situation that the mechanical property of the quartz fiber reinforced quartz ceramic composite material is lower; (2) The interface coating is prepared on the surface of the fiber, so that the problem of strong interface reaction between the silicon nitride fiber and a ceramic matrix is solved; (3) The temperature resistance and the self-healing capability of the organism material are effectively improved, so that the retention rate of the high-temperature mechanical property of the composite material is further improved. The composite material is high-temperature resistant, highly reliable and reusable under the high-Mach flight condition, and the use requirements of the antenna window material of the hypersonic aircraft in the near space are met.

Disclosure of Invention

The technical scheme of the invention is as follows:

a silicon nitride fiber reinforced ceramic matrix composite: the three parts are respectively as follows: the fiber consists of silicon nitride fiber, a quartz-based matrix and an interface coating between the fiber and the matrix, wherein the components of the quartz-based matrix comprise silicon oxide, aluminum oxide and boron oxide, the components are mixed according to the mass ratio of 70-90 percent of silicon oxide to aluminum oxide to boric acid to 23-8 percent of boron oxide to 2-7 percent of boron oxide, and the interface coating is one or the combination of two of a silicon-aluminum-oxygen coating and a silicon-nitrogen-oxygen coating.

A preparation method of a silicon nitride fiber reinforced ceramic matrix composite material comprises the following steps:

step 1, preparing a composite material interface coating: selecting a silicon nitride fiber reinforcement, in particular to a silicon nitride fiber widening cloth laminated sewing reinforcement, preparing an interface coating on the fiber surface of the silicon nitride fiber widening cloth laminated sewing reinforcement, drying and surface activating the silicon nitride fiber widening cloth laminated sewing reinforcement at the temperature of 120-180 ℃, and impregnating, drying and sintering the silicon nitride fiber widening cloth laminated sewing reinforcement through a precursor to prepare the silicon nitride fiber widening cloth laminated sewing reinforcement fiber surface coating. The prepared coating is a silicon-aluminum-oxygen coating and a silicon-nitrogen-oxygen coating, and the coating can be one or the combination of the two.

Step 2, preparation of quartz-based mixed sol: according to the mass ratio of 70-90% of silicon oxide, 23-8% of alumina and 2-7% of boric acid, mixing the silicon oxide sol, the alumina sol and the boric acid solution, and mechanically stirring to obtain uniform and stable silicon-aluminum-boron mixed sol, namely quartz-based mixed sol.

Step 3, dipping, curing and drying the silicon nitride fiber widening cloth laminated sewing reinforcement: by a vacuum impregnation process, the silicon-aluminum-boron mixed sol is fully impregnated into the silicon nitride fiber widening cloth laminated seam reinforcement with the fiber coating, and the mixed sol is cured and dried at the temperature of 80-180 ℃ to obtain the unsintered composite material.

And 4, sintering of the composite material: and (3) putting the dried composite material into a high-temperature sintering furnace, and sintering in an air atmosphere at the sintering temperature of 800-1000 ℃ for 40-150 min.

And 5, circulating the composite material impregnation curing and sintering process: and (3) removing the substrate compact layer on the surface of the composite material before each impregnation, and circularly repeating the step 3 and the step 4 for 3-7 times to obtain the silicon nitride fiber reinforced quartz-based ceramic composite material.

The silicon nitride fiber reinforcement further comprises a silicon nitride fiber unidirectional fiber reinforcement, a 2.5D silicon nitride fiber woven body and a 3D silicon nitride fiber woven body.

The drying and surface activation time in the step 1 is 3-4 h.

The impregnation in the step 1 is a vacuum-pressurization combined impregnation mode, and the impregnation time is 8-15 h.

And the curing and drying temperature in the step 3 is specifically carried out by adopting a gradient heating and drying mode.

The gradient temperature rise is specifically that the sol is fully solidified at 80 ℃ for 10-20 h, the temperature is raised to 110 ℃ and is kept for 3-6 h, and the temperature is continuously raised to 180 ℃ and is dried for more than 3 h.

In the step 4, the sintering can be carried out in a nitrogen atmosphere or a vacuum environment, the sintering temperature is 800-1300 ℃, and the heat preservation time is 40-150 min.

The width of the warp yarn and the weft yarn of the widening cloth is 4 mm-10 mm, the distance between the normal sewing yarns is 5 mm-12 mm, and the fiber volume fraction of the reinforcement is 32% -56%.

Technical effects

The invention prepares the silicon nitride fiber reinforced quartz-based ceramic composite material antenna window material with the bending strength of 130 MPa-220 MPa, the bending strength of 85 MPaa-158 MPa at 1100 ℃, the dielectric constant of 2.8-3.5 and the dielectric loss of less than or equal to 0.006 by using a plurality of key technologies such as novel high-temperature resistant silicon nitride fibers, a fiber woven body, a fiber and substrate interface coating, novel quartz-based mixed sol preparation and the like and by matching with a certain sintering system. The invention has good potential application value and economic benefit in the technical field of aviation and aerospace manufacturing, and has extremely high application value in the aspect of hypersonic aircrafts.

Drawings

FIG. 1 is a flow chart illustrating the preparation of a silicon nitride fiber reinforced ceramic matrix composite.

Detailed Description

The invention will be further described with reference to FIG. 1:

a silicon nitride fiber reinforced ceramic matrix composite: the three parts are respectively as follows: the fiber consists of silicon nitride fiber, a quartz-based matrix and an interface coating between the fiber and the matrix, wherein the quartz-based matrix comprises silicon oxide, aluminum oxide and boron oxide, the components are mixed according to the proportion of 70-90% by mass of the silicon oxide, 23-8% by mass of the aluminum oxide and 2-7% by mass of boric acid, and the interface coating is one or the combination of two of a silicon-aluminum-oxygen coating and a silicon-nitrogen-oxygen coating.

And 5, circulating the composite material impregnation curing and sintering processes: and (3) removing the substrate compact layer on the surface of the composite material before each impregnation, and circularly repeating the step 3 and the step 4 for 3-7 times to obtain the silicon nitride fiber reinforced quartz-based ceramic composite material.

The silicon nitride fiber reinforcement further comprises a silicon nitride fiber unidirectional fiber reinforcement, a 2.5D silicon nitride fiber woven body and a 3D silicon nitride fiber woven body. Aiming at the mechanical strength requirements and shape structures of different structural members, the composite materials meeting the requirements are prepared by selecting the fiber weaving modes.

The drying and surface activation time in the step 1 is 3-4 h. Too short a time results in insufficient drying, which is detrimental to the subsequent coating preparation.

The impregnation in the step 1 is a vacuum-pressurization combined impregnation mode, and the impregnation time is 8-15 h. The vacuum-pressurization combined dipping process can be adopted to fully dip the braided body, improve the density of the composite material and avoid the phenomenon of larger local porosity.

Compared with a quartz matrix, the matrix material prepared by mixing the sol according to the mass ratio of 70-90% of silicon oxide, 23-8% of aluminum oxide and 2-7% of boric acid has higher temperature resistance level and high-temperature self-healing capability.

In the step 4, the sintering can be carried out in a nitrogen atmosphere or a vacuum environment, the sintering temperature is 800-1300 ℃, and the heat preservation time is 40-150 min. The nitrogen atmosphere or vacuum environment can effectively protect the silicon nitride fiber and prevent the silicon nitride fiber from oxidation reaction at the temperature of over 1000 ℃.

The width of the warp yarn and the weft yarn of the widening cloth is 4 mm-10 mm, the distance between the normal sewing yarns is 5 mm-12 mm, and the fiber volume fraction of the reinforcement is 32% -56%. The width is too small to achieve the characteristic that the mechanical property of the composite material is improved by the widening cloth, and the quality of the widening cloth prepared by over widening cannot meet the requirement. Too small space between the sewing yarns can damage more transverse and longitudinal yarns of the widening cloth, so that the mechanical property of the composite material is reduced, and when the space is too large, the interlayer strength of the composite material can not meet the requirement.

Example 1

Selecting a 2.5D silicon nitride fiber woven body as a reinforcement of the composite material in the step 1, wherein the fiber volume fraction is 45%, drying and surface activating the reinforcement at a certain temperature, selecting a silicon-aluminum-oxygen system precursor to dip the silicon nitride fiber reinforcement, draining the redundant precursor solution, putting the reinforcement into a drying oven for drying, transferring the woven body into a box type sintering furnace for heating and sintering, and enabling the surface of the reinforcement fiber to generate a uniform silicon-aluminum-oxygen coating.

And 2, preparing the quartz-based mixed sol by taking the silica sol, the alumina sol and the boric acid solution as raw materials, selecting the silica-alumina-boric acid mass ratio of 75% to 20% to 5%, and mechanically stirring to obtain the uniform and stable quartz-based mixed sol.

And 3, vacuum dipping the 2.5D silicon nitride fiber woven body with the interface coating prepared in the step 1 by using the quartz-based mixed sol prepared in the step 2, and curing and drying the mixed sol at a certain temperature.

And 4, putting the dried composite material into a high-temperature sintering furnace, and sintering in a vacuum environment, wherein the sintering temperature is 1000 ℃, and the heat preservation time is 120min.

And 5, removing the substrate compact layer on the surface of the composite material, and circularly repeating the step 3 and the step 4 for 5 times to obtain the 2.5D silicon nitride fiber reinforced quartz-based ceramic composite material. The room-temperature bending strength of the sample was 150MPa, the 1100 ℃ bending strength was 105MPa, the dielectric constant was 3.2, and the dielectric loss tangent was 0.006.

Example 2

Selecting a silicon nitride widening cloth laminated seam reinforcement as a reinforcement of a composite material in the step 1, wherein the fiber volume fraction is 52%, drying and surface activating the reinforcement at a certain temperature, then, selecting a silicon-aluminum-oxygen system precursor to dip the silicon nitride fiber reinforcement, draining the redundant precursor solution, putting the reinforcement into a drying oven for drying, transferring the reinforcement into a box type sintering furnace, heating and sintering, and enabling the surface of the reinforcement fiber to generate a uniform silicon-aluminum-oxygen coating.

And (3) preparing quartz-based mixed sol in the step (2), namely taking silica sol, alumina sol and boric acid solution as raw materials, selecting the silica-alumina-boric acid mass ratio of 80 to 16 to 4, and mechanically stirring to obtain uniform and stable quartz-based mixed sol.

In step 3, the quartz-based mixed sol prepared in step 2 is adopted to impregnate the silicon nitride widening cloth laminated seam reinforcement with the interface coating prepared in step 1 in vacuum, and the mixed sol is cured and dried at a certain temperature.

And step 4, placing the dried composite material into a high-temperature sintering furnace, and sintering in a nitrogen atmosphere, wherein the sintering temperature is 1100 ℃, and the heat preservation time is 90min.

In the step 5, removing the substrate compact layer on the surface of the composite material, and circularly repeating the step 3 and the step 4 for 5 times to obtain the silicon nitride fiber reinforced quartz-based ceramic composite material. The room-temperature bending strength of the sample was 180MPa, the 1100 ℃ bending strength was 132MPa, the dielectric constant was 3.5, and the dielectric loss tangent was 0.005.

Example 3

Selecting a 3D four-way silicon nitride fiber woven body as a reinforcement of the composite material in the step 1, wherein the fiber volume fraction is 40%, drying and surface activating the reinforcement at a certain temperature, then, selecting a silicon-nitrogen-oxygen system precursor to dip the silicon nitride fiber reinforcement, draining the redundant precursor solution, putting the reinforcement into a drying oven for drying, transferring the woven body into a box type sintering furnace for heating and sintering, and enabling the surface of the reinforcement fiber to generate a uniform silicon-aluminum-oxygen coating. And then impregnating the fiber reinforcement with the silicon-aluminum-oxygen precursor, and draining, drying and sintering to obtain the composite coating silicon nitride fiber reinforcement.

And 2, preparing the quartz-based mixed sol by taking the silica sol, the alumina sol and the boric acid solution as raw materials, selecting the silica-alumina-boric acid mass ratio of 85 to 12 to 3, and mechanically stirring to obtain the uniform and stable quartz-based mixed sol.

And 3, vacuum dipping the 3D four-way silicon nitride fiber woven body with the interface coating prepared in the step 1 by using the quartz-based mixed sol prepared in the step 2, and curing and drying the mixed sol at a certain temperature.

And 4, putting the dried composite material into a high-temperature sintering furnace, and sintering in a nitrogen atmosphere environment, wherein the sintering temperature is 1100 ℃, and the heat preservation time is 60min.

And 5, removing the substrate compact layer on the surface of the composite material, and circularly repeating the step 3 and the step 4 for 5 times to obtain the silicon nitride fiber reinforced quartz-based ceramic composite material. The room-temperature bending strength of the sample was 130MPa, the 1100 ℃ bending strength was 85MPa, the dielectric constant was 3.0, and the dielectric loss tangent was 0.005.

(1) The silicon nitride fiber reinforced quartz-based ceramic composite material reinforcement comprises a silicon nitride fiber widening cloth laminated sewing reinforcement, a silicon nitride fiber unidirectional fiber reinforcement, a 2.5D silicon nitride fiber woven body and a 3D silicon nitride fiber woven body.

(2) In the preparation of the widening cloth laminated sewing fiber reinforcement, the width of the warp yarn and the weft yarn of the widening cloth is 4-10 mm, the distance between the normal sewing yarns is 5-12 mm, and the fiber volume fraction of the reinforcement is 32-56%.

(3) In the preparation of the composite material interface coating, a coating system is selected, the coating comprises a silicon-aluminum-oxygen coating and a silicon-nitrogen-oxygen coating, and the interface coating can be one or a combination of the two.

(4) The silicon nitride fiber reinforced quartz-based ceramic composite material is prepared from a silicon-aluminum-boron mixed sol, and in the preparation of the quartz-based mixed sol, the raw materials comprise a silica sol, an alumina sol and a boric acid solution, wherein the mass ratio of silica to alumina to boric acid is 70-90%, 23-8% and 2-7%.

(5) In the sintering step of the composite material, the sintering atmosphere of the material is nitrogen or a vacuum environment, the sintering temperature is 800-1200 ℃, and the heat preservation time is 40-150 min.

Claims

1. A silicon nitride fiber reinforced ceramic matrix composite: the fiber-reinforced silica-based composite material is characterized by comprising silicon nitride fibers, a quartz-based matrix and an interface coating between the fibers and the matrix, wherein the quartz-based matrix comprises the following components in parts by weight: mixing alumina and boric acid in the weight ratio of 70-90% to 23-8% to 2-7%, wherein the interface coating is one or the combination of silicon-aluminum-oxygen coating and silicon-nitrogen-oxygen coating; the preparation method of the silicon nitride fiber reinforced ceramic matrix composite material comprises the following steps:

step 1, preparing a composite material interface coating: selecting a silicon nitride fiber reinforcement, specifically a silicon nitride fiber widening cloth laminated sewing reinforcement, preparing an interface coating on the fiber surface of the silicon nitride fiber widening cloth laminated sewing reinforcement, drying and surface activating the silicon nitride fiber widening cloth laminated sewing reinforcement at the temperature of 120-180 ℃, and impregnating, drying and sintering the silicon nitride fiber widening cloth laminated sewing reinforcement through a precursor to prepare a silicon nitride fiber widening cloth laminated sewing reinforcement fiber surface coating; the prepared coating is one or the combination of two of a silicon-aluminum-oxygen coating and a silicon-nitrogen-oxygen coating;

step 2, preparation of quartz-based mixed sol: mixing silica sol, alumina sol and boric acid solution according to the mass ratio of 70-90% of silica to alumina to boric acid to 23-8% of boric acid to 2-7%, and mechanically stirring to obtain uniform and stable silica-alumina-boron mixed sol, namely quartz-based mixed sol;

step 3, dipping, curing and drying the silicon nitride fiber widening cloth laminated sewing reinforcement: fully dipping the silicon-aluminum-boron mixed sol into the silicon nitride fiber spreading cloth laminated seam reinforcement with the fiber coating through a vacuum dipping process, and curing and drying the mixed sol at the temperature of 80-180 ℃ to obtain an unsintered composite material;

and 4, sintering of the composite material: putting the dried composite material into a high-temperature sintering furnace, and sintering in air atmosphere at the sintering temperature of 800-1000 ℃ for 40-150 min;

2. The silicon nitride fiber reinforced ceramic matrix composite according to claim 1, wherein the drying and surface activation time in step 1 is between 3h and 4h.

3. The silicon nitride fiber reinforced ceramic matrix composite according to claim 1, wherein the impregnation in step 1 is vacuum-pressure combined impregnation, and the impregnation time is 8h to 15h.

4. The silicon nitride fiber reinforced ceramic matrix composite according to claim 1, wherein the curing and drying temperature in step 3 is performed by gradient temperature drying.

5. The silicon nitride fiber reinforced ceramic matrix composite according to claim 4, wherein the gradient temperature rise is specifically curing at 80 ℃ for 10h to 20h, so that the sol is fully cured, raising the temperature to 110 ℃ and keeping the temperature for 3h to 6h, and continuing raising the temperature to 180 ℃ and drying for more than 3 h.

6. The silicon nitride fiber reinforced ceramic matrix composite according to claim 1, wherein the sintering in step 4 is performed in a nitrogen atmosphere or in a vacuum atmosphere, the sintering temperature is 800 ℃ to 1300 ℃, and the holding time is 40min to 150min.

7. The silicon nitride fiber reinforced ceramic matrix composite according to claim 1, wherein the fiber reinforcement is stitched in the widened cloth lamination in step 1, the width of the widened cloth warp and weft is 4mm to 10mm, the spacing of the normal stitching yarns is 5mm to 12mm, and the fiber volume fraction of the reinforcement is 32% to 56%.