JP2000211977A - Ceramic-based, fiber-reinforced composite material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide ceramic-based, fiber-reinforced composite material capable of preventing the degradation of ceramic fiber in reaction sintering and capable of sufficiently manifesting its strength characteristics, and to provide a method for producing the same composite material. SOLUTION: When this ceramic-based, fiber-reinforced composite material 10 contains ceramic fiber as a reinforcing ingredient in ceramic-based matrix 11, the surface of each ceramic fiber is coated with a boundary layer 14 for weakening a binding force between the matrix and the ceramic fiber, and an oxide layer is made to exist between the ceramic fiber and the layer 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material applied to a gas turbine component or the like and a method for producing the same, and more particularly to a ceramic-based fiber composite material having strength and a method for producing the same.

[0002]

2. Description of the Related Art In general, a ceramic sintered body does not decrease in strength up to a high temperature and has various properties such as hardness, electric insulation, abrasion resistance, heat resistance, corrosion resistance and light weight as compared with conventional metal materials. Are better. For this reason, they are used in a wide range of fields as structural materials and electronic materials, such as heavy electrical equipment, aircraft parts, automobile parts, electronic equipment, precision equipment parts, and semiconductor device materials.

[0003] However, ceramic sintered bodies are more vulnerable to tensile stress than compression. In particular, when a defect is latent, stress concentrates on the defect portion and the destruction progresses at a stretch,
It has a so-called brittle defect. In particular, in gas turbine parts and the like, the destruction of ceramic parts due to collision of foreign matter is a major hindrance to practical use. For this reason, in order to enable the application of the ceramic component to a portion where high reliability is required, it is strongly required to increase the toughness and increase the fracture energy of the ceramic sintered body.

In response to these demands, research and development of ceramic-based composite materials have been actively conducted in recent years.
Among them, a ceramic-based fiber composite material using continuous long fibers as a reinforcing material is particularly excellent in the effects of increasing fracture toughness and fracture energy, and exhibits a great effect in improving reliability.
Further, it is known that a composite material containing silicon carbide as a matrix has high heat resistance, and is therefore useful as a material constituting a high-temperature structural member.

A method for producing such a ceramic-based fiber composite material will be described below.

First, fifty silicon carbide ceramic fibers were added.
After bundling 0 to 2000 fibers into a fiber bundle, an interface layer made of boron nitride was formed on the fiber surface of the silicon carbide ceramic fiber bundle by using a CVD method.

Next, the fiber bundle coated with the interface layer was braided into a braided body (fiber structure) having 24 braids and 8 central yarns.

Thereafter, a slurry used in the slip casting method was obtained as follows. Using a predetermined amount of silicon carbide powder having a particle size of 1 to 10 μm, carbon powder having a particle size of 0.01 to 1 μm, a dispersant, a binder for maintaining the form of the powder when dried, and pure water, The slurry was obtained by wet mixing in a pot mill for 20 hours.

This slurry was filled between and around the fibers of the braided body, and a molded body reinforced with silicon carbide ceramic fibers by a slip casting method was obtained.

The obtained molded body was heated to 1420 to 1500 ° C. in a vacuum by a reaction sintering method and then impregnated with molten silicon. The carbon component in the compact and the molten silicon were reacted and sintered to obtain a silicon carbide-based matrix.

FIG. 2 is a sectional view of the ceramic-based fiber composite material thus obtained.

As shown in FIG. 2, in the ceramic-based fiber composite material 1, a plurality of silicon carbide ceramic fibers 3 having a substantially circular cross section are compounded in a ceramic-based matrix 2. Then, an interface layer 4 made of boron nitride is formed on the outer peripheral surface of the silicon carbide ceramic fiber 3.

The interface layer 4 made of boron nitride shown in FIG.
Substantially forms a boundary between the silicon carbide ceramic fibers 3 and the ceramic matrix 2, and weakens the bonding force between the fibers and the matrix. Due to this decrease in the bonding force, the fracture energy of the composite material is absorbed during the fracture behavior, and the catastrophic fracture of the ceramic matrix 2 is suppressed.

[0014]

However, although the catastrophic destruction can be suppressed by providing the interface layer 4 made of boron nitride, when the ceramic matrix 2 is formed by the reaction sintering method, it is melt-impregnated. There was a problem that silicon carbide ceramic fibers 3 were degraded by reaction due to silicon.

In the reaction sintering method, the silicon carbide ceramic fiber 3 reacts with molten silicon and deteriorates, so that the strength characteristics of the finally obtained ceramic base fiber composite material are not sufficiently exhibited. Was.

The present invention has been made to solve this problem, and provides a ceramic-based fiber composite material capable of preventing deterioration of ceramic fibers during reaction sintering and sufficiently exhibiting strength characteristics, and a method for producing the same. The purpose is to do.

[0017]

According to the first aspect of the present invention,
A ceramic-based fiber composite material in which ceramic fibers are combined with a ceramic-based matrix to improve the strength, wherein the ceramic-based fibers are coated on the surface of the ceramic fibers with an interface layer that weakens a bonding force between the matrix and the ceramic fibers. In the composite material, an oxide layer is provided between the ceramic fiber and the interface layer.

According to a second aspect of the present invention, in the ceramic-based fiber composite material according to the first aspect, the oxide layer is formed by oxidizing the ceramic fibers.

The third aspect of the present invention is the first or second aspect.
In the ceramic-based fiber composite material described, the ceramic fibers are mainly composed of carbon silicon, oxygen, titanium,
It is characterized in that either boron or nitrogen is used as an auxiliary component.

In the present invention, a silicon oxide ceramic fiber is heat-treated in an oxidizing atmosphere to form a silicon oxide layer on the surface of the ceramic fiber. This silicon oxide layer becomes a reaction prevention layer corresponding to the molten silicon, and can prevent reaction and deterioration of the silicon carbide ceramic fibers.

The silicon oxide layer formed on the fiber surface is very stable against contact with molten silicon. The silicon oxide layer is formed by oxidizing silicon contained in silicon carbide ceramic fibers. For this reason, the silicon oxide layer is very dense and free from defects, and has excellent adhesion to fibers. Therefore, it is effective as a barrier layer of molten silicon impregnated when the matrix group is formed by the reaction sintering method, and can prevent reaction and deterioration of the ceramic fiber.

According to a fourth aspect of the present invention, in the ceramic-based fiber composite material of the third aspect, the oxide layer is made of silicon oxide, and the thickness of the oxide layer is 0.05 μm or more. I do.

If the thickness of the silicon oxide layer is 0.05 μm or more, the ceramic fibers can be protected from molten silicon. It is more preferable that the thickness of the oxide layer be 0.1 μm or more and 2.0 μm or less.

Usually, the oxidation treatment is performed in a yarn state (500 to 2,000 ceramic base fibers are bundled). When a silicon oxide film having a thickness of more than 2.0 μm is formed in a yarn state, the silicon oxide films between the fibers adhere to each other. When a force is applied to the fixed fibers, peeling and cracking of the silicon oxide film occur, resulting in a film defect, thereby reducing the barrier property against molten silicon. For this reason, the thickness of the oxide layer is preferably set to 2.0 μm or less.

According to a fifth aspect of the present invention, in the ceramic-based fiber composite material according to any one of the first to fourth aspects, the ceramic-based matrix is made of silicon carbide formed by reaction sintering. I do.

In a sixth aspect of the present invention, there is provided a method for producing a ceramic-based fiber composite material, the method comprising: forming an oxide layer on the surface of the ceramic fiber by oxidizing the ceramic fiber; An interface layer forming step of forming an interface layer on the oxide layer to weaken a bonding force between adjacent ceramic base matrices, and a weaving step of weaving the ceramic fibers on which the oxide layer and the interface layer are formed, A matrix forming step of forming a ceramic matrix by a reaction sintering method by impregnating the woven ceramic fibers with molten ceramic.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

Example (Sample Nos. 1 and 2) In this example, the thickness of the oxide layer formed between the ceramic fibers and the interface layer was set to a thickness within the range of the present invention.

First, 500 to 2,000 silicon carbide ceramic fibers (Hinicalon manufactured by Nippon Carbon Co., Ltd.) were bundled to form a fiber bundle. This silicon carbide ceramic fiber bundle is placed in an oxidizing atmosphere at a temperature of 800 to 1200 ° C. for 3 hours.
Perform heat treatment from 0 minutes to 8 hours and apply a thickness of 0.0
A 5 μm silicon oxide layer was formed.

Thereafter, a chemical vapor deposition method (CVD; Chemical V)
An interface layer made of boron nitride was formed on the surface of the silicon oxide film using apor deposition.

Next, using the fiber bundle coated with the interface layer, a braiding (fiber structure) having 24 braids and 8 central yarns was formed.

Thereafter, as a slurry used for slip casting, a silicon carbide powder having a particle size of 1 to 10 μm, a carbon powder having a particle size of 0.01 to 1 μm, a dispersant, a binder for maintaining the powder form during drying, and a pure powder A predetermined amount of water was charged, and the mixture was wet-mixed with a pot mill for 15 to 40 hours.

This slurry is filled between and around the fibers of the braiding body, and is subjected to a slip casting method.
A molded body reinforced with silicon carbide ceramic fibers was produced.

Thereafter, the compact is placed in a vacuum at 1420 to 15
It was heated at a temperature of 00 ° C. to impregnate the molten silicon. By reacting and sintering the carbon component in the molded body with the molten silicon, a ceramic-based fiber composite material was obtained. This was designated as Sample No. It was set to 1.

FIG. 1 shows a sectional view of the ceramic-based fiber composite material obtained by the above-described procedure.

As shown in FIG. 1, a ceramic-based fiber composite material 10 is embedded in a ceramic-based matrix 11.
A plurality of silicon carbide ceramic fibers 12 having a substantially circular cross section are composited. On the outer peripheral surface of the silicon carbide ceramic fiber 12, a silicon oxide layer 13 as an oxide layer is formed.
An interface layer 14 made of boron nitride is formed on the outer peripheral surface of No. 3.

Next, the sample No. As No. 2, first, 500 to 2,000 silicon carbide ceramic fibers (Hinicalon manufactured by Nippon Carbon Co., Ltd.) were bundled to form a fiber bundle.
This silicon carbide ceramic fiber bundle is placed in an oxidizing atmosphere for 8 hours.
Heat treatment was performed at 00 to 1200 ° C. for 30 minutes to 8 hours to form a 2.0 μm thick silicon oxide layer on the fiber surface. The following steps were performed for sample No. By the same procedure as in Example 1, a ceramic-based fiber composite material was obtained.

The thus obtained sample No. 1 and sample no. The sintered body of No. 2 was processed into a predetermined size to obtain a test piece.

Using this test piece, a tensile test was performed.
The test piece fracture surface after the test was observed with a SEM backscattered electron image.
Table 1 shows the results.

[Table 1]

As shown in Table 1, in the strength test by the tensile test, the maximum strength at which the fiber bears the strength was 600
Values above MPa were obtained. Further, when the fracture surface of the test piece after the test was observed with a SEM backscattered electron image, almost no portion where the fiber was considered to have reacted with the molten silicon and deteriorated was confirmed.

Comparative Example (Sample Nos. 3 to 4) In this comparative example, the thickness of the silicon oxide layer was outside the range of the present invention.

Sample No. First, silicon carbide ceramic fiber (Hinicalon manufactured by Nippon Carbon Co., Ltd.)
00 to 2,000 fibers were bundled to form a fiber bundle. This silicon carbide ceramic fiber bundle is placed in an oxidizing atmosphere at 800 to 1
Heat treatment was performed at 200 ° C. for 30 minutes to 8 hours to form a 0.01 μm thick silicon oxide layer on the fiber surface. The following steps were performed for sample No. By the same procedure as in Example 1, a ceramic-based fiber composite material was obtained.

The sample No. As No. 4, first, 500 to 2,000 silicon carbide ceramic fibers (Hinicalon manufactured by Nippon Carbon Co., Ltd.) were bundled to form a fiber bundle.
This silicon carbide ceramic fiber bundle is placed in an oxidizing atmosphere for 8 hours.
Heat treatment was performed at 00 to 1200 ° C. for 30 minutes to 8 hours to form a silicon oxide layer having a thickness of 3.0 μm on the fiber surface. The following steps were performed for sample No. By the same procedure as in Example 1, a ceramic-based fiber composite material was obtained.

The thus obtained sample No. 3 and sample no. The sintered body of No. 4 was processed into a predetermined size to obtain a test piece.

Using this test piece, a tensile test was performed.
The test piece fracture surface after the test was observed with a SEM backscattered electron image.
Table 1 shows the results.

As shown in Table 1, in the strength test by the tensile test, the maximum strength at which the fiber bears the strength is 250.
It was about MPa. Also, the fracture surface of the test piece after the test was
Observation with a reflection image of M revealed that many portions of the fiber seemed to have reacted with and deteriorated with the molten silicon.

Further, the sample No. In No. 4, when the fiber immediately after the oxidizing treatment was observed by SEM, many defects such as peeling and cracks were confirmed in the oxide film.

According to this embodiment, an oxide layer made of silicon oxide is formed between the ceramic fiber and the interface layer,
Further, the thickness of this oxide layer is 0.1 μm or more and 2.0 μm or more.
When the content is within the following range, the reaction and deterioration of the ceramic-based fiber composite material due to the melting of silicon during the reaction sintering can be prevented, and a ceramic-based fiber composite material having high fiber strength can be obtained.

[0049]

As described above, according to the method for producing a ceramic-based fiber composite material of the present invention, the deterioration of the ceramic fibers during the reaction sintering is prevented, and the fiber strength is high and the reliability is high. A ceramic-based fiber composite material can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a ceramic-based fiber composite material according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the structure of a conventional ceramic-based fiber composite material.

[Explanation of symbols]

 Reference Signs List 10 ceramic-based fiber composite material 11 ceramic-based matrix 12 silicon carbide ceramic fiber 13 silicon oxide layer 14 interface layer

Claims (6)

[Claims] 1. A ceramic-based fiber composite material in which ceramic fibers are compounded in a ceramic-based matrix to improve strength, and an interface layer for weakening a bonding force between the matrix and the ceramic fibers is provided on the surface of the ceramic fibers. A coated ceramic-based fiber composite material, comprising an oxide layer between the ceramic fiber and the interface layer. 2. The ceramic-based fiber composite material according to claim 1, wherein the oxide layer is formed by oxidizing the ceramic fibers. 3. The ceramic-based fiber composite material according to claim 1, wherein the ceramic fibers have carbon silicon as a main component and any one of oxygen, titanium, boron and nitrogen as a sub-component. Ceramic based fiber composite material. 4. The ceramic-based fiber composite material according to claim 3, wherein the oxide layer is made of silicon oxide, and the thickness of the oxide layer is 0.05 μm or more. . 5. The ceramic-based fiber composite material according to claim 1, wherein the ceramic-based matrix is made of silicon carbide formed by reaction sintering. . 6. An oxide layer forming step of forming an oxide layer on the surface of the ceramic fiber by oxidizing the ceramic fiber, and an interface layer for weakening a bonding force between the ceramic fiber and a ceramic matrix adjacent to the ceramic fiber. Forming an interface layer on the oxide layer, weaving the ceramic fibers on which the oxide layer and the interface layer are formed, and impregnating the woven ceramic fibers with molten ceramic. A matrix forming step of forming a ceramic matrix by a reaction sintering method.