CN102924106A - Method for preparing carbon-silicon carbon composite material and product thereof - Google Patents

Abstract

The invention discloses a method for preparing a carbon-silicon carbide ceramic composite material and a product prepared according to the method. The preparation steps include: first weaving carbon fibers into a three-dimensional fabric (hereinafter referred to as a carbon fiber prefabricated body); A layer of elemental silicon with a thickness of 0.1-2 μm is deposited on the carbon fiber prefabricated body; phenolic resin, carbon black, ethanol, ultrafine silicon carbide powder, polyvinylpyrrolidone and tetramethylammonium hydroxide are prepared in proportion to make a mixed slurry; the slurry The material is pressurized and impregnated into the above-mentioned carbon fiber prefabricated body in a vacuum environment to obtain a composite material body; the above-mentioned green body is heated and solidified; High performance carbon-silicon carbide ceramic composite.

Description

A kind of preparation method and product of carbon-silicon carbide composite material

technical field

The invention belongs to the field of inorganic non-metallic materials, and relates to a preparation process of a composite material, in particular to a preparation method of a carbon fiber reinforced silicon carbide ceramic composite material.

Background technique

Add continuous carbon fibers to silicon carbide ceramics to prepare carbon fiber reinforced silicon carbide (C _f /SiC) composites. Carbon fibers can enhance the strength and toughness of ceramic materials through mechanisms such as crack deflection and fiber extraction during the fracture process of ceramics.

The existing C _f /SiC composite materials preparation process mainly includes: chemical vapor deposition (CVI) process, precursor impregnation pyrolysis (PIP) process, slurry impregnation hot pressing (SIHP) process, liquid phase impregnation (LSI) process, etc.

The process of CVI is to place the carbon fiber preform in the CVI furnace, and the reaction gas is transported to the periphery of the preform through the directional flow generated by the pressure difference, and then diffuses into it, and chemical reaction occurs on the surface of the fiber and deposited in situ. The main advantage of preparing C _f /SiC composite materials by CVI process is that the ceramic matrix can be synthesized at a temperature far below the melting point of the matrix material, which reduces the degradation of fiber performance caused by the high-temperature chemical reaction between the fiber and the matrix; it can also be used in the preparation process. Maintain the integrity of the fiber preform structure and achieve near-net molding to prepare products with complex shapes. However, the CVI process also has defects such as a long preparation period, a large density difference along the gas diffusion path, and a large amount of porosity remaining in the composite material.

The SIHP process is to mix SiC powder, sintering aid powder and organic binder with a solvent to make slurry, carbon fiber is impregnated in slurry, spun into non-woven fabric, sliced, molded, and then hot-pressed and sintered. The densification of materials is mainly done by liquid phase sintering method. The C _f /SiC composite material produced by SIHP method has higher density and fewer defects, which is more suitable for the preparation of unidirectional composite material. However, the SIHP method is difficult to prepare components with complex shapes, and carbon fibers tend to react with the SiC matrix at the interface under high temperature and high pressure, resulting in a decrease in fiber performance, which is not conducive to improving the performance of the material.

The common process for preparing C _f /SiC composites by PIP method is to impregnate the carbon fiber preform with an organic precursor solution at a certain temperature and pressure. SiC ceramic substrate. The preparation temperature of the PIP method is low, it can be fired without pressure, the mechanical and chemical damage to the fiber is small, and it can prepare large and complex shaped components. However, the disadvantages of this process are also obvious. The densification of the material requires several impregnation-cracking cycles, and the production cycle is long; The higher the rate, the more difficult it is to prepare a completely dense material; the precursor and the fiber are prone to some form of chemical reaction during the cracking process. On the one hand, the fiber is severely damaged, and on the other hand, a strongly bonded interface layer is formed, resulting in The toughness is not high.

The LSI process includes three basic processes: first, the carbon fiber preform is placed in a closed mold, and the fiber-toughened polymer material is prepared by high-pressure punching or resin transfer molding; then, it is cracked in a high-temperature inert environment to obtain a low-density carbon matrix Composite material (C _f /C); finally, the molten Si is used for impregnation treatment through capillary action under vacuum, so that the Si melt reacts with the carbon matrix to form a SiC matrix. This process can control the density of the final composite by adjusting the bulk density and porosity of _Cf /C. The LSI process has a short preparation cycle, low cost, and low residual porosity, and can produce workpieces with complex net sizes and shapes; but this process also has shortcomings: while the molten Si reacts with the carbon matrix, it will inevitably react with carbon fibers. , the fiber is eroded leading to performance degradation.

The present invention overcomes the aforementioned drawbacks.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art, combine the advantages of LSI, CVI and PIP, etc., to provide a method that can not only improve the low density of C _f /SiC composite materials, but also effectively prevent The preparation process of the erosive effect of Si on carbon fibers.

Technical scheme of the present invention is achieved through following processing steps:

1) Weave carbon fibers with a diameter of 6-8 μm into a three-dimensional fabric to obtain a carbon fiber preform;

2) In a vacuum furnace with a vacuum degree of 1×10 ^-2 ~5×10 ^-3 Pa, vapor deposit a layer of metal silicon on the carbon fiber surface of the carbon fiber preform;

3) Prepare a mixed slurry by ball milling ultrafine silicon carbide powder, carbon black, phenolic resin, polyvinylpyrrolidone, tetramethylammonium hydroxide and ethanol according to the following ratio: 63~72 parts of silicon carbide powder, carbon black 5~6 parts, 1.5~2 parts of phenolic resin, 0.5~1.0 parts of tetramethylammonium hydroxide, 0.1~0.5 parts of polyvinylpyrrolidone, 40~45 parts of alcohol;

4) Place the carbon fiber preform in a graphite mold, apply a pressure of 0.1~2.0 MPa to the mixed slurry in an environment below atmospheric pressure, and pressurize it into the above carbon fiber preform to obtain a composite material green body;

5) Keep the above-mentioned composite material body and mold together at 100°C for 2 hours for drying and curing;

6) Put the above-mentioned body and mold that have been dried and solidified together in a vacuum furnace with a vacuum degree of 1×10 ^-2 ~1×10 ^-3 Pa, and heat up to 1450~1550°C for high-temperature siliconization reaction. That is, a carbon-silicon carbide composite material is made.

Compared with the prior art, the present invention has the following advantages:

1. The preparation process provided by the present invention is carried out at a lower temperature, which can significantly reduce the damage to the carbon fiber during the reaction process;

2. Compared with the existing preparation technology, the preparation process of the process of the present invention is short, and the preparation time is significantly reduced;

3. The C _f /SiC composite material prepared by the present invention has a high density close to the theoretical density.

Detailed ways

The following two specific embodiments are used to illustrate and help further understanding of the present invention. However, the specific details of the embodiments are only for illustrating the present invention, and do not represent all the technical solutions under the concept of the present invention, so they should not be construed as limiting the technical solutions of the present invention. Some insubstantial changes that do not deviate from the concept of the present invention, such as simple changes or replacements with technical features having the same or similar technical effects, all fall within the protection scope of the present invention.

Example 1

A method for preparing a carbon-silicon carbide composite material, the preparation process comprising the following steps:

Step 1, weaving carbon fibers with an average diameter of 6-8 μm into a three-dimensional fabric (hereinafter referred to as carbon fiber prefabricated body);

Step 2, put the carbon fiber prefabricated body into a closed container, place metal silicon in the container, and isolate it from the carbon fiber prefabricated body; place the above container and the materials in the container together in a vacuum degree of 1×10 ^- In a ² Pa vacuum furnace, heat up to 1500°C, hold for 1 hour, and take out the treated carbon fiber preform after cooling with the furnace;

Step 3, put 72g of silicon carbide powder with an average particle size of 0.1μm, 8g of carbon black, 2g of phenolic resin, 0.2g of polyvinylpyrrolidone, 0.5g of tetramethylammonium hydroxide and 40ml of ethanol into a high-energy ball mill, and add 300g Agate milling balls were prepared into mixed slurry after ball milling for 5 hours;

Step 4, placing the carbon fiber preform in a graphite mold, pressurizing the mixed slurry to 0.5 MPa in a vacuum environment of 0.01 MPa, and impregnating it into the above carbon fiber preform to obtain a composite material green body;

Step 5, heat the above green body and mold together at 100°C for 2 hours for drying and curing;

Step 6: Put the above green body and mold together in a vacuum furnace with a vacuum degree of 1×10 ^-3 Pa, raise the temperature to 1500°C for high-temperature siliconizing reaction, and obtain a high-density, high-performance carbon/silicon carbide ceramic composite Material.

Example 2

A method for preparing a carbon-silicon carbide composite material, the preparation process comprising the following steps:

Step 1, weaving carbon fibers with an average diameter of 6-8 μm into a three-dimensional carbon fiber prefabricated body;

Step 2, put the carbon fiber prefabricated body into a closed container, place metal silicon in the container, and isolate it from the carbon fiber prefabricated body, place the above container and the materials in the container together in a vacuum degree of 5×10 ^- In a ³ Pa vacuum furnace, heat up to 1500°C, hold for 3 hours, and take out the treated carbon fiber preform after cooling with the furnace;

Step 3, put 63g of silicon carbide powder with an average particle size of 0.22μm, 7g of carbon black, 2g of phenolic resin, 0.3g of polyvinylpyrrolidone, 0.5g of tetramethylammonium hydroxide and 40ml of ethanol into a high-energy ball mill, and add 300g Agate milling balls were prepared into mixed slurry after ball milling for 5 hours;

Step 4, placing the carbon fiber preform in a graphite mold, applying a pressure of 0.2 MPa to the mixed slurry in a vacuum environment of 0.01 MPa, and impregnating the above carbon fiber preform to obtain a composite material green body;

Step 5, heat the above green body and mold together at 100°C for 2 hours for drying and curing;

Step 6: Put the above green body and the mold together in a vacuum furnace with a vacuum degree of 1×10 ^-3 Pa, raise the temperature to 1480°C for siliconization reaction, and obtain a high-density, high-performance carbon-silicon carbide ceramic composite material .

Claims (4)

1. A preparation method of carbon-silicon carbide composite material, characterized in that the preparation method may further comprise the steps: Step 1, weaving carbon fibers with a diameter of 6-8 μm into a three-dimensional fabric to obtain a carbon fiber prefabricated body; Step 2, in a vacuum furnace with a vacuum degree of 1×10 ^-2 ~5×10 ^-3 Pa, vapor deposit a layer of metal silicon on the carbon fiber surface of the carbon fiber preform; Step 3, ball mill ultrafine silicon carbide powder, carbon black, phenolic resin, polyvinylpyrrolidone, tetramethylammonium hydroxide and ethanol according to the following proportions to prepare a mixed slurry: 63~72 parts of silicon carbide powder, carbon Black 5~6 parts, phenolic resin 1.5~2 parts, tetramethylammonium hydroxide 0.5~1.0 parts, polyvinylpyrrolidone 0.1~0.5 parts, alcohol 40~45 parts; Step 4, place the carbon fiber preform in a graphite mold, apply a pressure of 0.1 to 2.0 MPa to the mixed slurry in an environment below atmospheric pressure, and pressurize and impregnate it into the above carbon fiber preform to obtain a composite material green body; Step 5, heat the above-mentioned composite material green body and mold together at a temperature of 100° C. for 2 hours to perform drying and curing treatment; Step 6: Put the above-mentioned green body and mold that have been dried and cured together in a vacuum furnace with a vacuum degree of 1×10 ^-2 ~1×10 ^-3 Pa, and heat up to 1450~1550°C for high temperature siliconization reaction , which is made of carbon-silicon carbide composite material. 2. the preparation method of carbon-silicon carbide composite material according to right 1, is characterized in that: In step 2, a layer of metal silicon is deposited on the fiber surface of the carbon fiber preform by vapor phase deposition with a thickness of 0.1-2 μm. 3. according to the preparation method of the carbon-silicon carbide composite material described in right 1 or 2, it is characterized in that: The particle size of the mixed slurry used in step 3 is 0.05-0.25 μm. 4. according to the carbon-silicon carbide composite material prepared by the method described in claim 1.