JP6122728B2 - SiC fiber reinforced SiC composite material and method for producing SiC fiber reinforced SiC composite material - Google Patents

Description

The present invention relates to a SiC fiber reinforced SiC composite material and a method for producing a SiC fiber reinforced SiC composite material.

Ceramic materials such as silicon carbide (SiC) and silicon nitride (Si ₃ N ₄ ) are excellent in heat resistance, chemical stability, and mechanical properties. Therefore, these ceramic materials are being developed as materials used in harsh environments such as the nuclear field, aerospace field, and power generation field, and in general fields such as pump mechanical seals. Of these ceramic materials, SiC is a structural material that is promising in a wide range of fields because of its excellent properties.

However, since SiC itself is a brittle material, a SiC fiber / SiC composite material composed of a SiC fiber and a SiC matrix has been proposed. However, even in the SiC fiber / SiC composite material, when a crack occurs in the SiC matrix, the crack propagates in the matrix and the crack may propagate to the SiC fiber.

Therefore, for example, Patent Document 1 includes SiC fine powder and a sintering aid for a coated SiC fiber in which a coating layer containing at least one of carbon, boron nitride, and silicon carbide is formed on the surface of the SiC fiber. And a SiC fiber reinforced mold comprising a first step of obtaining a preform by impregnating a slurry containing no organosilicon polymer and a second step of pressure-sintering the preform. A method of manufacturing a SiC composite material is disclosed.

JP 2010-70421 A

In the composite material manufactured by the method described in Patent Document 1, since the coating layer is formed on the surface of the SiC fiber, even if a crack occurs in the SiC matrix, the crack is prevented from propagating to the SiC fiber. Can do. Therefore, it is said that the composite material manufactured by the method described in Patent Document 1 has high strength.

However, carbon (pyrolytic carbon), boron nitride (pyrolytic boron nitride: PBN) and the like used as the material for the coating layer do not have corrosion resistance. Therefore, when the composite material manufactured by the method described in Patent Document 1 is used as a material for a nuclear structural member such as a light water reactor structural member, the coating layer reacts with water at a high temperature, and the coating layer is damaged. The strength of the composite material is reduced. In addition, since the PBN film forming temperature is required to be 1750 ° C. or higher, the damage applied to the SiC fiber during film formation is large, and it is difficult to obtain a high-strength composite material. Thus, the composite material obtained by the conventional manufacturing method has room for further improvement.

The present invention has been made to solve the above-described problems, and does not include a coating layer of a different material, and the SiC fiber-reinforced SiC composite material having high strength only by SiC and the production of the SiC fiber-reinforced SiC composite material. It aims to provide a method.

The SiC fiber reinforced SiC composite material of the present invention is a SiC fiber reinforced SiC composite material composed of SiC fibers and a SiC matrix, and has substantially spherical bubbles in the SiC matrix, and is a structural member for nuclear power. Features.

In the SiC fiber reinforced SiC composite material of the present invention, since the constituent material is SiC, high strength can be realized. Further, when bubbles are present in the SiC matrix, the SiC matrix becomes low elastic. Therefore, in the composite material of the present invention, even if a crack occurs in the SiC matrix, the progress of the crack can be prevented by the bubbles present in the SiC matrix, and the crack can be prevented from propagating to the SiC fiber.
Further, when the bubbles are substantially spherical, energy due to cracks generated by external impact is dispersed to the surroundings, and the progress of cracks can be prevented.
The “substantially spherical shape” may be a spherical shape to the extent that each effect of the present invention is exhibited, and may be a complete spherical shape or a substantially spherical shape.
As described above, the composite material of the present invention can be a high-strength composite material without including a coating layer or the like for preventing the propagation of cracks.

The bubbles are preferably surrounded by a shell made of SiC. The propagation of cracks can be further prevented by the shell forming the bubbles.

The diameter of the bubbles is preferably smaller than the diameter of the SiC fiber. When the diameter of the bubbles is small, the portion having a high elastic modulus of the SiC matrix can be reduced, so that the propagation of cracks can be further prevented.

As for the said SiC fiber, it is desirable for the SiC fiber bundle to comprise the SiC fiber bundle. When the SiC fibers are present in a bundle, it is difficult to form a space between the SiC fibers. Therefore, the existence ratio of the SiC fibers in the composite material can be increased, and a high-strength composite material can be obtained.

As for the content rate of the said bubble in the said SiC matrix in the range of the distance of the diameter of the said SiC fiber from the surface of the said SiC fiber, it is desirable that it is 10-50 vol%. That the content rate of the bubble in said range is 10-50 vol% means that a bubble exists in the vicinity of a SiC fiber. In this case, since the surface of the SiC fiber is covered with the low-elasticity matrix, the scratch that becomes the starting point of the crack is hardly attached to the surface of the SiC fiber.

The SiC fiber reinforced SiC composite material of the present invention is desirably a light water reactor structural member. When the composite material of the present invention is used as a material for a nuclear structural member such as a light water reactor structural member, the surface of the SiC fiber is thermally decomposed even if the composite material is deformed by a stress and a crack reaching the SiC fiber occurs. Since the coating layer made of carbon or the like is not formed, the problem that the coating layer reacts with water and the strength of the composite material is reduced can be prevented.

A method for producing a SiC fiber reinforced SiC composite material according to the present invention is a method for producing a SiC fiber reinforced SiC composite material that is a nuclear structural member, wherein a matrix precursor and a hollow body are added to a fiber assembly made of SiC fibers. An impregnation step of impregnating a slurry containing the impregnation product and a firing step of firing the impregnation product are characterized.

In the method for producing a SiC fiber-reinforced SiC composite material of the present invention, bubbles can be formed in the matrix by mixing a hollow body into the slurry. As a result, the above-described SiC fiber reinforced SiC composite material of the present invention can be manufactured.

The matrix precursor may be an organosilicon compound. By baking the organosilicon compound, a matrix made of SiC can be formed.

The matrix precursor may be composed of SiC particles and a sintering aid. A SiC matrix can be formed by sintering SiC particles using a sintering aid.

The average particle diameter of the SiC particles is preferably smaller than the average cell diameter of the hollow body. By making the average particle diameter of the SiC particles smaller than the average bubble diameter of the hollow body, it is possible to form a matrix having a low elastic modulus while reducing the concentration of stress generated inside the matrix.

As for the said SiC fiber, it is desirable for the SiC fiber bundle to comprise the SiC fiber bundle.

The fiber assembly is preferably at least one fiber assembly selected from the group consisting of a woven fabric, a mat, a braided (braided) molded product, and a filament winding molded product.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the SiC fiber reinforced SiC composite material which does not include the coating layer etc. of a dissimilar material, and is high intensity | strength only by SiC, and this SiC fiber reinforced SiC composite material can be provided.

Fig.1 (a) is sectional drawing which shows typically an example of the SiC fiber reinforced SiC composite material of this invention, FIG.1 (b) is A of SiC fiber reinforced SiC composite material shown to Fig.1 (a). FIG. FIG. 2 is an enlarged cross-sectional view of the SiC fiber-reinforced SiC composite material shown in FIG. FIG. 3 is a cross-sectional view schematically showing another example of the SiC fiber-reinforced SiC composite material of the present invention.

(Detailed description of the invention)
Hereinafter, the present invention will be specifically described. However, the present invention is not limited to the following description, and can be appropriately modified and applied without departing from the scope of the present invention.

[SiC fiber reinforced SiC composite material]
First, the SiC fiber reinforced SiC composite material of the present invention will be described.
The SiC fiber reinforced SiC composite material of the present invention is a SiC fiber reinforced SiC composite material composed of SiC fibers and a SiC matrix, and has substantially spherical bubbles in the SiC matrix, and is a structural member for nuclear power. Features.

Fig.1 (a) is sectional drawing which shows typically an example of the SiC fiber reinforced SiC composite material of this invention, FIG.1 (b) is A of SiC fiber reinforced SiC composite material shown to Fig.1 (a). FIG.
Fig.1 (a) is sectional drawing of the direction perpendicular | vertical to the length direction of a SiC fiber, FIG.1 (b) is sectional drawing of the direction parallel to the length direction of a SiC fiber.

An SiC fiber reinforced SiC composite material 10 shown in FIGS. 1A and 1B is a composite material composed of SiC fibers 11 and an SiC matrix 12. The SiC fiber-reinforced SiC composite material 10 has bubbles 13 in the SiC matrix 12.

In the SiC fiber-reinforced SiC composite material of the present invention, as the SiC fiber, Hi-Nicalon made by NGS Advanced Fiber, Tyranno-SA made by Ube Industries, etc. can be used.

Although the diameter of a SiC fiber can be suitably set according to the use of a SiC fiber reinforced SiC composite material, it is desirable that it is 5-25 micrometers. When the diameter of the SiC fiber is 5 μm or more, a sufficiently large diameter can be secured for the SiC particles and the hollow body to be used, so that a high-strength composite material can be obtained. If the diameter of the SiC fiber is 25 μm or less, the elongation rate of the surface can be reduced even if the SiC fiber is bent, so that it is difficult to break. The number of SiC fibers constituting the SiC fiber bundle is, for example, 50 to 2000.

The diameter of the SiC fiber can be measured by observing a cross section of the SiC fiber-reinforced SiC composite material with a scanning electron microscope (SEM).

In the SiC fiber-reinforced SiC composite material of the present invention, the matrix is a matrix made of SiC.

The SiC fiber-reinforced SiC composite material of the present invention has bubbles in the SiC matrix, but the bubbles may be dispersed throughout the SiC matrix or may be unevenly distributed in a part of the SiC matrix. In particular, if air bubbles are present in the vicinity of the SiC fiber, the elastic modulus of the SiC matrix in contact with the SiC fiber is lowered, so that cracks generated in the SiC matrix can be prevented from propagating to the SiC fiber.

The method of forming bubbles in the SiC matrix is not particularly limited, but it is desirable that the bubbles are formed by mixing a hollow body into the slurry, as will be described later.

It is desirable that the bubbles are surrounded by a shell made of SiC. Since the shell made of SiC is made of a material denser than the structure of the SiC matrix, the propagation of cracks can be further prevented by the shell forming bubbles. As described above, in the SiC fiber-reinforced SiC composite material of the present invention, it is desirable that the bubbles are surrounded by the shell, but the bubbles need not be surrounded by the shell.

It is desirable that the diameter of the bubbles is smaller than the diameter of the SiC fiber. When the diameter of the bubbles is small, the portion having a high elastic modulus of the SiC matrix can be reduced, so that the propagation of cracks can be further prevented.

Specifically, the bubble diameter is desirably 2 to 20 μm. If the diameter of the bubbles is 2 μm or more, bubbles that are sufficiently larger than the pores formed by the SiC particles can be formed, so that the effect of preventing the progress of cracks can be increased. When the bubble diameter is 20 μm or less, a highly flexible SiC fiber that does not break even when bent can be used, and thus a high-strength composite material can be obtained.

The bubble diameter indicates the diameter of a sphere (equivalent sphere) having the same volume as the bubble volume, and can be measured using a scanning electron microscope (SEM). Since it is a three-dimensional shape, the measurement is repeated using a focused ion beam (FIB) while gradually scraping to measure the bubble diameter.

The shape of the bubble is substantially spherical. When the bubbles are substantially spherical, energy due to cracks generated by an external impact is dispersed to the surroundings, and the progress of the cracks can be prevented.

The bubble content in the SiC matrix is not particularly limited, but the bubble content in the matrix in the range of the SiC fiber diameter from the surface of the SiC fiber is preferably 10 to 50 vol%, and 20 to 30 vol. % Is more desirable. That the content rate of the bubble in said range is 10-50 vol% means that a bubble exists in the vicinity of a SiC fiber. In this case, since the surface of the SiC fiber is covered with the low-elasticity matrix, the scratch that becomes the starting point of the crack is hardly attached to the surface of the SiC fiber. When the bubble content is 10 vol% or more, the matrix has sufficient mechanical strength, so that strength as a composite material can be ensured. When the bubble content is 50 vol% or less, the generated crack energy is easily dispersed to the surroundings and can be made difficult to break. In addition, when the bubble content is 20 vol% or more, the matrix has a higher mechanical strength, so that the strength as a composite material can be further ensured. When the bubble content is 30 vol% or less, the energy of the generated crack is more easily dispersed to the surroundings, and can be further prevented from cracking.
In addition, when a plurality of SiC fibers form a SiC fiber bundle, the bubble content is defined only for the matrix surrounding one SiC fiber.

FIG. 2 is an enlarged cross-sectional view of the SiC fiber-reinforced SiC composite material shown in FIG.
In FIG. 2, the diameter of the SiC fiber 11 is indicated by an arrow d. Therefore, the “range of the distance of the diameter of the SiC fiber from the surface of the SiC fiber” means a range at a distance d from the surface of the SiC fiber 11.

In the SiC fiber reinforced SiC composite material of the present invention, the porosity of the SiC matrix is preferably 10 to 50%, and more preferably 20 to 30%.

FIG. 3 is a cross-sectional view schematically showing another example of the SiC fiber-reinforced SiC composite material of the present invention.
In the SiC fiber reinforced SiC composite material of the present invention, as shown in FIG. 3, a SiC layer 20 may be formed on the surface of the SiC fiber reinforced SiC composite material 10. The SiC layer 20 is desirably a CVD-SiC layer formed by subjecting the SiC fiber-reinforced SiC composite material 10 to a CVD process.

[Method for producing SiC fiber-reinforced SiC composite material]
The SiC fiber reinforced SiC composite material of the present invention described above can be manufactured by the method for manufacturing the SiC fiber reinforced SiC composite material of the present invention.
A method for producing a SiC fiber reinforced SiC composite material according to the present invention is a method for producing a SiC fiber reinforced SiC composite material that is a nuclear structural member, wherein a matrix precursor and a hollow body are added to a fiber assembly made of SiC fibers. An impregnation step of impregnating a slurry containing the impregnation product and a firing step of firing the impregnation product are characterized.

First, a fiber assembly made of SiC fibers is prepared.
The fiber assembly can be obtained by a shaping process for imparting a shape to the SiC fiber. Specifically, the fiber assembly is desirably at least one fiber assembly selected from the group consisting of a woven fabric, a mat, a braided (braided) molded product, and a filament winding molded product.

Since the SiC fiber is as described in [SiC fiber reinforced SiC composite material], detailed description thereof is omitted.

For example, a fiber assembly can be formed by weaving SiC fiber bundles of 50 to 2000 SiC fibers into a sheet shape.

Next, the prepared fiber aggregate is impregnated with a slurry containing a matrix precursor and a hollow body to obtain an impregnated body (impregnation step).

Examples of the impregnation method include dipping, spraying, coating, coater, vacuum pressure impregnation and the like, and any method may be used.

As the hollow body contained in the slurry, inorganic balloons such as SiC balloons, silica balloons and carbon balloons; organic balloons such as resin balloons; resins; and reaction products thereof can be used.

When the hollow body is a SiC balloon, the SiC balloon can be made from an organosilicon compound such as polycarbosilane.

When the hollow body is a silica balloon, the silica balloon and the carbon powder react and remain as an SiC balloon by further containing carbon powder in the slurry. Moreover, when a hollow body is a carbon balloon, a carbon balloon and a silica powder react and remain as a SiC balloon by further making a slurry contain silica powder.

When the hollow body is made of a resin, the resin is preferably a thermoplastic resin. This is because these resins are thermally decomposed by firing to eliminate the shell.

The average cell diameter of the hollow body is desirably 2 to 20 μm, and more desirably 5 to 15 μm.
The average cell diameter of the hollow body can be measured by measuring the particle diameter with a laser diffraction particle size measuring machine and reducing the film thickness of the hollow body.

Although content of the hollow body in a slurry is not specifically limited, It is desirable that it is 20 to 65 weight% in solid content, and it is more desirable that it is 40 to 65 weight%.

The matrix precursor contained in the slurry may be an organosilicon compound, or may be composed of SiC particles and a sintering aid.

When the matrix precursor is an organosilicon compound, a matrix made of SiC can be formed by firing the organosilicon compound.

Examples of the organosilicon compound include silicon polymers such as polycarbosilane, polyvinylsilane, and polymethylsilane.

When the matrix precursor is an organosilicon compound, the content of the organosilicon compound in the slurry is not particularly limited, but the solid content is preferably 20 to 65 wt%, more preferably 40 to 65 wt%. desirable.

In the case where the matrix precursor is composed of SiC particles and a sintering aid, a SiC matrix can be formed by sintering the SiC particles using the sintering aid.

The average particle diameter of the SiC particles is preferably smaller than the average bubble diameter of the hollow body. By making the average particle diameter of the SiC particles smaller than the average bubble diameter of the hollow body, it is possible to form a matrix having a low elastic modulus while reducing the concentration of stress generated inside the matrix.

Specifically, the average particle diameter of the SiC particles is desirably 10 to 1000 nm, and more desirably 250 to 800 nm.
In addition, the average particle diameter of a SiC particle can be measured using a scanning electron microscope (SEM).

Although content of the SiC particle in a slurry is not specifically limited, It is desirable that it is 25 to 65 weight% in solid content, and it is more desirable that it is 45 to 65 weight%.
In particular, the ratio of SiC particles to hollow bodies (SiC particles: hollow bodies) is preferably 2: 1 to 7: 1 and more preferably 2: 1 to 4: 1.

Examples of the sintering aid include Al ₂ O ₃ , Y ₂ O ₃ , SiO ₂ , and CaO. These may be one type or a combination of a plurality of types. Moreover, it is desirable that the sintering aid is in a powder form.

Although content of the sintering auxiliary agent in a slurry is not specifically limited, It is desirable that it is 1-3 weight% in solid content, and it is more desirable that it is 1-2 weight%.

The slurry contains a dispersion medium (solvent). As the dispersion medium, water or an organic solvent can be used. Examples of the organic solvent include alcohol-based organic solvents such as ethanol and isopropanol; hydrocarbon-based organic solvents such as hexane, toluene and xylene.

In addition, you may dry the obtained impregnated body as needed.

Also, when many bubbles are formed in the vicinity of the SiC fiber, a slurry having a different hollow body content is prepared, and the fiber aggregate is impregnated with a high content slurry, and then impregnated with a low content slurry. That's fine.

Subsequently, the impregnated body is fired (firing step).

Examples of the method of firing the impregnated body include a method of pressure-sintering the impregnated body.
The pressure sintering method is not particularly limited, and examples thereof include known methods such as a hot press (HP) method and a hot isostatic press (HIP) method.

Although sintering temperature can be set suitably, it is desirable that it is 1000-2000 degreeC, and it is more desirable that it is 1200-1600 degreeC. Further, the pressure is desirably 1 to 30 MPa, and more desirably 5 to 20 MPa.

The impregnated body may be fired in a non-oxidizing atmosphere. For example, it can be performed in an inert gas atmosphere, a reducing atmosphere, a vacuum atmosphere, or the like. In these, it is desirable to carry out in inert gas atmosphere, such as hydrogen, nitrogen, helium, and argon.

By passing through the above process, the SiC fiber reinforced SiC composite material of this invention can be manufactured.

The SiC fiber reinforced SiC composite material of the present invention is desirably used in harsh environments such as the nuclear field, aerospace field, and power generation field, and particularly desirably in the nuclear field.
Specifically, the SiC fiber-reinforced SiC composite material of the present invention is a structural member for nuclear power, and is desirably a structural member for light water reactors.

Hereinafter, the effect of the manufacturing method of the SiC fiber reinforced SiC composite material and the SiC fiber reinforced SiC composite material of the present invention will be described.

In the SiC fiber reinforced SiC composite material of the present invention, since the constituent material is SiC, high strength can be realized. Further, when bubbles are present in the SiC matrix, the SiC matrix becomes low elastic. Therefore, in the composite material of the present invention, even if a crack occurs in the SiC matrix, the progress of the crack can be prevented by the bubbles present in the SiC matrix, and the crack can be prevented from propagating to the SiC fiber. As described above, the composite material of the present invention can be a high-strength composite material without including a coating layer or the like for preventing the propagation of cracks.

In the method for producing a SiC fiber-reinforced SiC composite material of the present invention, bubbles can be formed in the matrix by mixing a hollow body into the slurry. As a result, the above-described SiC fiber reinforced SiC composite material of the present invention can be manufactured.

The SiC fiber-reinforced SiC composite material of the present invention has an essential constituent element that has a bubble in the SiC matrix. In the method for producing a SiC fiber-reinforced SiC composite material according to the present invention, a fiber assembly made of SiC fibers is impregnated with a slurry containing a matrix precursor and a hollow body, and after obtaining the impregnated body, the impregnated body is fired. This is an essential component requirement.
The various constituents detailed in the detailed description of the present invention (for example, SiC fiber configuration, SiC matrix configuration, bubble configuration, hollow body configuration, SiC fiber reinforced SiC composite material manufacture) The desired effect can be obtained by appropriately combining the conditions and the like.

10 SiC fiber reinforced SiC composite material 11 SiC fiber 12 SiC matrix 13 Bubble 20 SiC layer

Claims (11)

A SiC fiber reinforced SiC composite material comprising a SiC fiber and a SiC matrix,
Having substantially spherical bubbles in the SiC matrix;
The bubbles are surrounded by a shell made of SiC;
A SiC fiber reinforced SiC composite material, which is a structural member for nuclear power. The SiC fiber reinforced SiC composite material according to claim 1, wherein a diameter of the bubble is smaller than a diameter of the SiC fiber. The SiC fiber reinforced SiC composite material according to claim 1 or 2 , wherein a plurality of the SiC fibers are combined to form a SiC fiber bundle. The SiC fiber reinforced SiC composite according to any one of claims 1 to 3 , wherein a content rate of the bubbles in the SiC matrix in a range of a distance of a diameter of the SiC fiber from a surface of the SiC fiber is 10 to 50 vol%. material. The SiC fiber reinforced SiC composite material according to any one of claims 1 to 4 , wherein the SiC fiber reinforced SiC composite material is a structural member for a light water reactor. A method for producing a SiC fiber-reinforced SiC composite material according to any one of claims 1 to 5 ,
An impregnation step of impregnating a fiber assembly composed of SiC fibers with a slurry containing a matrix precursor and a hollow body to obtain an impregnated body;
A method for producing a SiC fiber-reinforced SiC composite material, comprising: a firing step of firing the impregnated body. The method for producing a SiC fiber-reinforced SiC composite material according to claim 6 , wherein the matrix precursor is an organosilicon compound. The method for producing a SiC fiber-reinforced SiC composite material according to claim 6 , wherein the matrix precursor includes SiC particles and a sintering aid. The method for producing a SiC fiber-reinforced SiC composite material according to claim 8 , wherein an average particle diameter of the SiC particles is smaller than an average cell diameter of the hollow body. The method for producing a SiC fiber-reinforced SiC composite material according to any one of claims 6 to 9 , wherein a plurality of the SiC fibers constitute a SiC fiber bundle. The fiber aggregate, woven, mat, braided (braid) moldings, and, according to any one of claims 6-10 is at least one fiber aggregate selected from the group consisting of a filament winding molding material Manufacturing method of SiC fiber reinforced SiC composite material.

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