CN111217616B

CN111217616B - Preparation method of C/SiC structural material with near-zero expansion characteristic

Info

Publication number: CN111217616B
Application number: CN202010095425.0A
Authority: CN
Inventors: 范晓孟; 赵东林; 陈超; 殷小玮; 党潇琳
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2020-02-17
Filing date: 2020-02-17
Publication date: 2022-07-05
Anticipated expiration: 2040-02-17
Also published as: CN111217616A

Abstract

The invention relates to a preparation method of a C/SiC structural material with near-zero expansion characteristic, which comprises the steps of preparing continuous carbon fibers into fiber preforms, enabling the volume fraction of the fibers to be larger than or equal to 40%, preparing a pyrolytic carbon interface layer on the surfaces of fiber strands through a Chemical Vapor Infiltration (CVI) process, carrying out high-temperature treatment, depositing 13-18% of silicon carbide on the surfaces of the interface phases through the CVI process, rapidly preparing a multiphase ceramic matrix through slurry infiltration combined with a reaction melt infiltration process (RMI), and finally preparing a silicon carbide coating through the Chemical Vapor Deposition (CVD) process for surface sealing. The advantages are that: (1) the linear expansion coefficient of the existing ceramic matrix composite material is greatly reduced, and the linear expansion coefficient of the ceramic matrix composite material prepared by the method is close to zero (less than 1 multiplied by 10)^‑7K); (2) the uniformity and the density of the composite material are effectively improved; (3) the preparation period of the material is shortened.

Description

Preparation method of C/SiC structural material with near-zero expansion characteristic

Technical Field

The invention belongs to the field of preparation of ceramic matrix composite materials, and relates to a preparation method of a C/SiC structural material with near-zero expansion characteristic. The preparation method specifically comprises the steps of preparing a preform by using a continuous carbon fiber bundle wire, preparing an interface phase on the surface of the fiber bundle wire through a chemical vapor infiltration process, depositing a certain content of silicon carbide on the outer surface of the interface phase by adopting the chemical vapor infiltration process, rapidly preparing a silicide ceramic matrix by using a slurry infiltration combined reaction melt infiltration process, and finally preparing a silicon carbide coating through the chemical vapor deposition process. The method greatly reduces the linear expansion coefficient of the existing ceramic matrix composite material, and the linear expansion coefficient of the C/SiC structural material prepared by the method is close to zero (less than 1 multiplied by 10)^-7/K)。

Background

With the rapid development of scientific technology, the pace of exploring the universe by human beings is more and more distant, new discoveries of exploring the universe continuously refresh the cognition of human beings, and countries in the world, particularly developed countries, develop scientific exploration satellites and develop key technical researches of space observation without losing power. The strategic leading special item of the space science approved in 2010 in China defines the development direction of space astronomy in China in the future 15-20 years, and provides clear requirements for space astronomy observation technology with high energy resolution and high space resolution and high-precision earth observation technology. In order to meet the requirements of long-distance ultra-high precision observation, a space optical-mechanical structure serving as a carrying platform of an optical element must achieve ultra-staticity and ultra-stability, in the space optical-mechanical structure, the main influence factors of the surface tolerance of the optical element are a supporting structure of a reflector, the main influence factors of the position tolerance of the optical element include structural rigidity, thermal adaptability, supporting structure rigidity and the like of a camera frame, and meanwhile, the space optical-mechanical structure is subjected to vibration in a rocket launching process, severe change of environmental temperature, space radiation, space atomic oxygen impact and the like in a using process, so that the space optical-mechanical structure provides more severe requirements for structural materials of the space optical-mechanical structure, and the used materials must have excellent mechanical properties, ultra-low expansion, light weight, stable space environmental properties and the like.

The traditional space optical machine structure material mainly comprises an alloy material and a resin matrix composite material. Alloy materials such as INVAR alloy have low expansion coefficient of 1.6 × 10^-6A density of about 8.lg/cm³The processing and forming process is difficult, and the preparation of the optical-mechanical component with a complex structure is difficult to meet; the resin-based composite material has a low expansion coefficient of about 2 x 10^-6The product has the advantages of low radiation resistance, deformation due to moisture absorption, and deflation and denaturation in space environment. It is difficult to meet the requirements of new generation of space optical machine structure materials. The ceramic matrix composite has the advantages of low expansion coefficient, excellent mechanical property, low density, good space environment stability, high designability and the like, and is the most potential future space optical-mechanical structure material. However, the existing ceramic matrix composite has long manufacturing period and high cost, and the linear expansion coefficient is commonly 1-3 multiplied by 10^-6K, higher requirements (less than 1 × 10) for meeting advanced space optical-mechanical structure^-7There is also a greatly increased demand for/K).

Produced by German ECM company

The series products are put on the market and operated for years, are successfully applied to space telescopes such as GREGOR, SPIRALE, WSO/UV, JWST and the like,

the product is a chopped fiber reinforced ceramic matrix composite, and the preparation process mainly adopts a chopped fiber preform, forms a porous C/C preform through mould pressing, carbonization and graphitization, and adopts a liquid siliconizing process to prepare a silicon carbide substrate. Reported at present

The linear expansion coefficient of the material is 2.1 multiplied by 10^-6K^-1Bending strength of 111MPa and fracture toughness of 2.4 MPa-m^1/2. MELCO in Japan and ECM in Germany

Technically new C/SiC composites are being developed jointly, i.e.

The main improvement is that different types of chopped carbon fibers are mixed in the carbon fiber preform, the uniformity of the composite material is improved, and the linear expansion coefficient of the composite material is 2.1 multiplied by 10^-6K, but the ratio is obtained

More excellent mechanical property, the bending strength is 320MPa, and the fracture toughness is 3.9 MPa.m^1/2The excellent performance of the compound can be used for developing large-size astronomical telescopes, such as E-ELT, SPICA, ULT and the like

German ECM was introduced by the American general energy company

Technically, a 1.04m primary mirror is manufactured for a Solar Lite telescope, a 1.54m primary mirror prototype is manufactured for a Gregor telescope, and the material performance of the prototype is equal to that of Germany ECM

And (4) the equivalent.

The patent 201318009074.8 of Shanghai silicate research institute discloses a preparation method of a fiber-reinforced ceramic matrix composite material with a low thermal expansion coefficient, the patent adopts a preform with a continuous fiber woven structure, a chemical vapor infiltration process is firstly adopted, then an organic precursor-impregnation cracking process is adopted to prepare a silicon carbide matrix, and the linear expansion coefficient of the prepared material represents the general level of the linear expansion coefficient of the existing ceramic matrix composite material (namely 1-3 multiplied by 10)^-6/K)。

According to the report of the literature, the northwest industrial university adopts plain fiber cloth lamination to manufacture a preform, then adopts a chemical vapor infiltration process to prepare a silicon carbide substrate, and the linear expansion coefficient of the prepared ceramic matrix composite material is still 1-3 multiplied by 10^-6and/K is between.

By combining the reports, the linear expansion coefficient of the currently prepared C/SiC is higher, and the distance from the requirement of a future space structure material is less than 1 multiplied by 10^-7K) also have a considerable distance. The reason for this is that there are fewer cracks inside the matrix and there is no room for buffer expansion inside the material, so that the material exhibits a high linear expansion coefficient.

Disclosure of Invention

Technical problem to be solved

In order to avoid the defects of the prior art, the invention provides a preparation method of a C/SiC structural material with the near-zero expansion characteristic, which adopts a silicide ceramic matrix with a large number of cracks to be compounded with carbon fibers, realizes the preparation of the C/SiC structural material with the near-zero expansion characteristic, and greatly reduces the linear expansion coefficient of the conventional ceramic matrix composite material. Compared with the traditional chemical vapor deposition process, the invention adopts the reaction melt infiltration process to realize rapid densification, and provides a preparation method with short period, simple process and low cost.

Technical scheme

A preparation method of a C/SiC structural material with near-zero expansion characteristic is characterized by comprising the following steps: the method adopts a cracked silicide ceramic matrix to be compounded with carbon fibers, and comprises the following specific steps:

step 1, preparing a carbon fiber preform: weaving continuous carbon fiber bundles into plain woven carbon fiber cloth, laying the plain woven carbon fiber cloth layer by layer according to the designed number of layers, and sewing continuous carbon fibers along the thickness direction to obtain a carbon fiber preform with the fiber volume fraction being more than or equal to 40%;

step 2, depositing a pyrolytic carbon interface layer by a chemical vapor infiltration method: placing the carbon fiber preform in a high-temperature vacuum furnace, heating to 850 ℃ under the pressure of less than 300Pa, introducing argon and propylene, preserving heat for 65-200 h, and obtaining a pyrolytic carbon interface layer with the thickness of 150-500 nm on the surface of a fiber bundle; the argon flow is 3L/min; the flow rate of the propylene is 3L/min;

step 3, interface layer high-temperature treatment: performing high-temperature treatment on the carbon fiber preform subjected to interface layer deposition, vacuumizing until the pressure is less than 300Pa, the high-temperature treatment temperature is 1200-1300 ℃, and keeping the temperature for 1-2 hours;

and 4, depositing a silicon carbide substrate by a chemical vapor infiltration method: putting the prefabricated body processed in the step 3 into a deposition furnace, and vacuumizing to pressure<300Pa, raising the temperature to 1000-1100 ℃, introducing argon, hydrogen and methyl trichlorosilane MTS, and carrying out chemical reaction on the MTS to generate a silicon carbide substrate; keeping the temperature for 70-80 h to enable the MTS to continuously react in the deposition furnace to generate a nanocrystalline silicon carbide substrate; the argon flow is 3.5L/min; the hydrogen flow is 5L/min; said H₂The molar mass ratio of the MTS to the MTS is 10: 1;

controlling the content of the silicon carbide matrix through multiple deposition, so that the volume density of the material is controlled to be 1.3-1.5 g/cm³The open porosity is 20-30%, and the volume fraction of the silicon carbide matrix is 13-18%;

step 5, preparing a multiphase ceramic matrix by combining slurry permeation and a reaction melt permeation process: adding carbon powder or carbide powder into a solution taking sodium carboxymethylcellulose and polyethyleneimine as dispersing agents, mixing, and performing ball milling on the mixture for 24-48 hours on a roller ball mill to prepare slurry for infiltration;

soaking the prefabricated part processed in the step 4 in the slurry in a vacuum container with the air pressure lower than-0.09 Mpa, and keeping for 10-50 min; then putting the container containing the impregnated preform and the slurry into a closed device, pressurizing to 0.8-1.2 MPa, and keeping for 10-50 min; finally, taking out the prefabricated body from the slurry, putting the prefabricated body into an oven, drying for 1-3 h, and taking out; wrapping the prefabricated body in silicon powder, putting the silicon powder into a vacuum furnace, heating to 1450-1700 ℃, and preserving heat for 30-120 min to obtain a compact multiphase ceramic matrix with the volume fraction of 34% -39%;

step 6, preparing the surface silicon carbide coating by a chemical vapor deposition method: putting the compact multi-phase ceramic matrix into a deposition furnace, vacuumizing to the pressure of less than 300Pa, heating to 1000-1100 ℃, introducing argon, hydrogen and Methyl Trichlorosilane (MTS), carrying out chemical reaction on the MTS to generate a silicon carbide matrix, preserving heat for 80-160 h, generating a uniform and compact silicon carbide coating with the thickness of about 0.05-0.1 mm on the surface of the material, and sealing and filling micropores on the surface of the material to obtain the C/SiC structural material with the near-zero expansion characteristic;

the argon flow is 3.5L/min; the hydrogen flow is 5L/min; said H₂The molar mass ratio to MTS was 10: 1.

Weaving the continuous carbon fiber bundle wires into plain-weave carbon fiber cloth, and then laying the plain-weave carbon fiber cloth layer by layer according to the designed number of layers: but are not limited to 2D lay-up, 2.5D weaving and 3D solid woven forming structures.

Such carbides include, but are not limited to: b₄C. TiC, SiC or ZrC.

Advantageous effects

The invention provides a preparation method of a C/SiC structural material with near-zero expansion characteristic, which comprises the following steps: preparing continuous carbon fibers into a fiber preform, wherein the volume fraction of the fibers is more than or equal to 40%, preparing a pyrolytic carbon interface layer on the surface of a fiber bundle filament by a Chemical Vapor Infiltration (CVI) process, performing high-temperature treatment, depositing 13-18% volume fraction of silicon carbide on the surface of an interface phase by the CVI process, rapidly preparing a multiphase ceramic matrix by a slurry infiltration combined reaction melt infiltration process (RMI), and finally preparing a silicon carbide coating by the Chemical Vapor Deposition (CVD) process for surface sealing.

Because the compact silicide matrix has high brittleness, a great amount of cracks can be generated in the compact silicide matrix when the compact silicide matrix is cooled to normal temperature from preparation temperature, and the linear expansion coefficient is lower than 1 multiplied by 10^-7K; due to the use of the pyrolytic carbon interface layer, the bending strength of the prepared ceramic matrix composite material can reach 350MPa, and the fracture toughness reaches 16 MPa-m^1/2The method can meet the severe requirements of future space optical-mechanical systems on structural materials; the preparation process is simple, the period is short, and compared with the traditional ceramic matrix composite preparation process, the preparation process is shortened by one third; meanwhile, raw materials used in the material manufacturing process are all products purchased in the common market, so that the preparation cost of the composite material is greatly reduced. The process of the invention involves the cooperative optimization of a plurality of parameters of deposition time, high-temperature treatment temperature, slurry components, reaction melt infiltration process temperature, heat preservation time and the like of the thermal interface layer, and the process sequence is unchangeable, so that enough cracks can be introduced into the matrix, and the linear expansion coefficient is lower than 1 multiplied by 10^-7K^-1The requirements of (1).

The process has the advantages that: (1) the linear expansion coefficient of the existing ceramic matrix composite material is greatly reduced, and the linear expansion coefficient of the ceramic matrix composite material prepared by the method is close to zero (less than 1 multiplied by 10)^-7K); (2) the uniformity and the density of the composite material are effectively improved; (3) the preparation period of the material is shortened.

Drawings

FIG. 1: scanning Electron micrograph of composite prepared in example 1

FIG. 2: scanning electron microscope photograph of composite material prepared by original process

FIG. 3: scanning electron microscope photograph of C/SiC structural material with near-zero expansion characteristic

Detailed Description

The invention will now be further described with reference to the following examples and drawings:

example 1:

the plain weave carbon fiber cloth laying prefabricated body is used as a reinforcement, the fiber volume content is 40 percent, and the preparation is carried out on the surface of the prefabricated body fiber bundle through a chemical vapor infiltration processAnd carrying out high-temperature treatment on the carbon interface phase to obtain a carbon interface layer with the thickness of 150nm on the surface of the fiber bundle. The silicon carbide substrate is prepared by adopting a chemical vapor infiltration process, the deposition temperature is 1000 ℃, and the deposition time is 200 h. And then infiltrating carbon powder into the fiber preform by a slurry infiltration process, and rapidly preparing the silicon carbide substrate by a chemical vapor infiltration process, wherein the melt reaction temperature is 1450 ℃, and the heat preservation time is 2 hours. And finally, preparing a silicon carbide coating with the thickness of 0.1mm on the surface of the material by adopting a chemical vapor deposition process. The density of the obtained ceramic matrix composite material is 2.1g/cm³The porosity was 10%. Fig. 1 shows the microstructure of the material, and the main micro-components comprise carbon fiber bundles, a pyrolytic carbon interface layer, a silicon carbide matrix, multiphase ceramics and the like. The linear expansion coefficient of the composite material in the plane direction is 0.8 multiplied by 10 measured in the range of-20 ℃ to 50 DEG C^-7and/K is used. If a compact silicide matrix is introduced without adopting a reaction solution infiltration process, the microstructure photo is shown in figure 2, no obvious crack can be seen in the matrix, and the linear expansion coefficient is as high as 1.0 multiplied by 10^-6/K。

Example 2:

the plain weave carbon fiber cloth laying prefabricated body is used as a reinforcement, the fiber volume content is 40%, a carbon interface layer is prepared on the surface of a prefabricated body fiber bundle through a chemical vapor infiltration process, and the carbon interface layer with the thickness of 300nm is obtained on the surface of the fiber bundle through high-temperature treatment. The silicon carbide substrate is prepared by adopting a chemical vapor infiltration process, the deposition temperature is 1000 ℃, and the deposition time is 300 h. And infiltrating boron carbide powder into the fiber preform by a slurry infiltration process, and rapidly preparing the silicide matrix by a reaction melt infiltration process, wherein the melt reaction temperature is 1500 ℃, and the heat preservation time is 60 minutes. And finally, preparing a silicon carbide coating with the thickness of 0.05mm on the surface of the material by adopting a chemical vapor deposition process. The density of the obtained ceramic matrix composite material is 2.2g/cm³The porosity was 8%. The microstructure is shown in fig. 3, and the existence of cracks in the matrix can be clearly seen. The linear expansion coefficient of the composite material in the plane direction is 0.2 multiplied by 10 measured in the range of-20 ℃ to 50 DEG C^-7A bending strength of 350MPa and a fracture toughness of 16 MPa-m^1/2The comprehensive performance exceeds that of German HB-

The properties disclosed.

Example 3:

the plain weave carbon fiber cloth laying prefabricated body is used as a reinforcement, the fiber volume content is 40%, a carbon interface layer is prepared on the surface of a prefabricated body fiber bundle through a chemical vapor infiltration process and is subjected to high-temperature treatment, and the carbon interface layer with the thickness of 400nm is obtained on the surface of the fiber bundle. The silicon carbide substrate is prepared by adopting a chemical vapor infiltration process, the deposition temperature is 1000 ℃, and the deposition time is 150 h. And infiltrating silicon carbide powder into the fiber preform by a slurry infiltration process, rapidly preparing a silicide matrix by a reaction melt infiltration process, reacting the melt at 1600 ℃, keeping the temperature for 40 minutes, and preparing a silicon carbide coating with the thickness of 0.1mm on the surface of the material by a CVD process. The density of the obtained ceramic matrix composite material is 2.3g/cm³The porosity was 7%. Fig. 2 is the microstructure of the material, and the main micro-components comprise carbon fiber bundles, a pyrolytic carbon interface layer, a silicon-based ceramic matrix and the like. The linear expansion coefficient of the composite material in the plane direction is 0.4 multiplied by 10 measured in the range of-20 ℃ to 50 DEG C^-7/K。

Example 4:

the plain weave carbon fiber cloth laying prefabricated body is used as a reinforcement, the fiber volume content is 40%, a carbon interface layer is prepared on the surface of a prefabricated body fiber bundle through a chemical vapor infiltration process, and the carbon interface layer with the thickness of 500nm is obtained on the surface of the fiber bundle through high-temperature treatment. The silicon carbide substrate is prepared by adopting a chemical vapor infiltration process, the deposition temperature is 1000 ℃, and the deposition time is 300 h. And then infiltrating titanium carbide powder into the fiber preform by a slurry infiltration process, rapidly preparing a silicide matrix by a reaction melt infiltration process, reacting the melt at 1700 ℃, keeping the temperature for 30 minutes, and preparing a silicon carbide coating with the thickness of 0.1mm on the surface of the material by a chemical vapor deposition process. The density of the obtained ceramic matrix composite material is 2.4g/cm³The porosity was 6%. The linear expansion coefficient of the composite material in the plane direction is 0.5 multiplied by 10 measured in the range of-20 ℃ to 50 DEG C^-7/K。

Claims

1. A preparation method of a C/SiC structural material with near-zero expansion characteristic is characterized by comprising the following steps: the method adopts a silicide ceramic matrix with cracks to be compounded with carbon fibers, and comprises the following specific steps:

step 1, preparing a carbon fiber preform: weaving continuous carbon fiber bundles into plain woven carbon fiber cloth, laying the plain woven carbon fiber cloth layer by layer according to the designed number of layers, and sewing the plain woven carbon fiber cloth along the thickness direction by using continuous carbon fibers to obtain a carbon fiber preform with the fiber volume fraction being more than or equal to 40%;

and 4, depositing a silicon carbide substrate by a chemical vapor infiltration method: putting the prefabricated body processed in the step 3 into a deposition furnace, and vacuumizing to pressure<300Pa, raising the temperature to 1000-1100 ℃, introducing argon, hydrogen and methyl trichlorosilane MTS, and carrying out chemical reaction on the MTS to generate a silicon carbide substrate; keeping the temperature for 70-80 h to enable the MTS to continuously react in the deposition furnace to generate a nanocrystalline silicon carbide substrate; the argon flow is 3.5L/min; the hydrogen flow is 5L/min; said H₂The molar ratio of the MTS to the MTS is 10: 1;

in a vacuum container with the air pressure lower than-0.09 Mpa, impregnating the prefabricated body treated in the step 4 in the slurry, and keeping for 10-50 min; then putting the container containing the impregnated preform and the slurry into a closed device, pressurizing to 0.8-1.2 MPa, and keeping for 10-50 min; finally, taking out the prefabricated body from the slurry, putting the prefabricated body into an oven, drying for 1-3 h, and taking out; wrapping the prefabricated body in silicon powder, putting the silicon powder into a vacuum furnace, heating to 1450-1700 ℃, and preserving heat for 30-120 min to obtain a compact multi-phase ceramic matrix with the volume fraction of 34-39%;

step 6, preparing the surface silicon carbide coating by a chemical vapor deposition method: placing a carbon fiber preform with a compact multi-phase ceramic matrix into a deposition furnace, vacuumizing until the pressure is less than 300Pa, heating to 1000-1100 ℃, introducing argon, hydrogen and Methyl Trichlorosilane (MTS), carrying out a chemical reaction on the MTS to generate a silicon carbide matrix, preserving heat for 80-160 h, generating a uniform and compact silicon carbide coating with the thickness of 0.05-0.1 mm on the surface of the material, and sealing and filling micropores on the surface of the material to obtain the C/SiC structural material with the near-zero expansion characteristic;

the argon flow is 3.5L/min; the hydrogen flow is 5L/min; said H₂The molar ratio to MTS was 10: 1.

2. The method for preparing a C/SiC structural material having near-zero expansion characteristics according to claim 1, wherein: the method comprises the steps of weaving continuous carbon fiber bundles into plain woven carbon fiber cloth, and then laying the plain woven carbon fiber cloth into at least one of a 2D laying layer, a 2.5D weaving structure and a 3D three-dimensional weaving structure layer by layer according to the designed number of layers.

3. A method for preparing a C/SiC structural material of near-zero expansion characteristics according to claim 1 or 2, characterized in that: the carbide is B₄C. At least one of TiC, SiC, or ZrC.