JP2002137978A - Method of manufacturing carbon material having oxidation proof protected layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a carbon material simply and economically which has oxidation-proof protecting layer without being oxidized practically even at a high temperature of at least 800 deg.C, preferably >=1000 deg.C in atmosphere, the physical property of which is high strength (high thermal shock resistance) at high temperatures, high reliability as a material (toughness, shock resistance, wear resistance), environmental resistance (resistances to corrosion, oxidation and radiation) or the like, in addition to that from the viewpoint of energy saving and workability, lightweighness is completed. SOLUTION: The oxidation-proof protective layer containing B4C(boron carbide) as a main ingredient of protecting layer is formed on a surface of the carbon material by dispersing and suspending BN(boron nitride) fine particles in dispersion medium, the obtained suspension is applied to the surface of the carbon material and drying and baking it at a high temperature in an inert atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a carbonaceous material having an oxidation-resistant protective layer that is not substantially oxidized at least at 800 ° C. in the atmosphere.

[0002]

BACKGROUND OF THE INVENTION Today, with the rapid pace of technological innovation, at least 800.degree.
The emergence of materials that are not substantially oxidized even at high temperatures of 000 ° C or higher has led to space development fields such as space planes and space planes, kiln tools used in the presence of oxygen, aluminum alloys and copper. There is a particular desire in the field of manufacturing parts made of alloys and the like. Of course, for use in such fields, high strength at high temperatures (high thermal shock resistance), high reliability as a material (toughness, impact resistance, wear resistance), and environmental resistance (corrosion resistance, oxidation resistance) Needless to say, lightness is required from the viewpoints of energy saving and workability in addition to the above properties.

[0003] In some of these fields, silicon nitride and silicon carbide materials having excellent heat resistance and high strength have been used in the past. It had drawbacks, was very brittle even with small scratches, and did not have sufficient strength against thermal and mechanical shocks.

As a means for overcoming the drawbacks of ceramics, a ceramic composite material (CMC) in which continuous ceramic fibers are composited has been developed, and applications in some fields have been developed. Among such attempts, ceramic long fibers with a diameter of around 10 μm were
Usually, hundreds to thousands of fibers are bundled to form a fiber bundle (yarn), and the fiber bundles are arranged in a two-dimensional or three-dimensional direction to form a unidirectional sheet (UD sheet) or various cloths. Or a cloth is laminated to form a preform (fiber preform) of a predetermined shape, and the inside of the preform is formed by a CVI method (chemical vapor deposition method), an inorganic polymer impregnation firing method, or the like. By forming a matrix, or by firing after filling the ceramic powder into the preformed body by a casting method,
A ceramic fiber composite material (CM) in which a matrix is formed and fibers are composited in a ceramic matrix
C) has been developed.

[0005] Specific examples of such CMC include a C / C composite in which a matrix made of carbon is formed at intervals between carbon fibers arranged in two-dimensional or three-dimensional directions, and a SiC made of SiC fibers and a SiC matrix.
Fiber reinforced SiC composite materials and the like are known. However, such SiC fiber reinforced SiC composite materials have oxidation resistance,
Although excellent in creep resistance, spalling resistance, etc.,
The fiber cost is as high as 100,000 yen / kg or more, and it is only evaluated in a few special fields such as nuclear power and aerospace. On the other hand, although the C / C composite has high strength and excellent thermal shock resistance, it has a problem that it burns easily in the presence of oxygen because it uses carbon fibers. Various methods have been proposed for improving the oxidation resistance of the C / C composite. The present inventors have also applied for a material having a surface coated with boron carbide and a manufacturing method. In this method, although the effect of improving the oxidation resistance is remarkable, a manufacturing method that maintains the same performance at a lower cost has been desired.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and aims at high strength at high temperatures (high thermal shock resistance),
In addition to high reliability (toughness, impact resistance, abrasion resistance) and environmental resistance (corrosion resistance, oxidation resistance, radiation resistance), etc. as materials, it also satisfies light weight from the viewpoint of energy saving and easy workability. At the same time, with a simpler method and lower cost,
At least 800 ° C. in air, preferably 1000 ° C.
It is an object of the present invention to provide a method for producing a carbonaceous material having an oxidation-resistant protective layer that is not substantially oxidized even at the above high temperature.

[0007]

That is, according to the present invention, after BN (boron nitride) powder is dispersed and suspended in a dispersion medium, the resulting suspension is placed on the surface of a carbonaceous material. , And then dried and baked at a high temperature in an inert atmosphere, so that the surface of the carbonaceous material is coated with B ₄ C (boron carbide).
A method for producing a carbonaceous material having an oxidation-resistant protective layer, characterized by forming an oxidation-resistant protective layer containing as a main component.

At this time, in the present invention, the carbonaceous material is
C / C composite, Si-SiC composite, SiC
It is preferably one kind of material selected from a system composite material or a metal silicide impregnated composite material.

In the present invention, the suspension is preferably applied while heating the carbonaceous material.
N is applied, dried, and baked at a temperature of 2000 ° C. or more.
It is preferable to form an oxidation-resistant protective layer containing ₄ C as a main component.

Further, in the present invention, the thickness of the oxidation-resistant protective layer is 30 to 300 μm, more preferably 50 to 200 μm.
μm is preferred.

From the above, according to the present invention, it is possible to produce a carbonaceous material having an oxidation-resistant protective layer that is not substantially oxidized at least at 800 ° C. (more preferably, 1000 ° C.) in the atmosphere. it can.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing a carbonaceous material having an oxidation-resistant protective layer according to the present invention, a suspension obtained by dispersing and suspending BN (boron nitride) powder in a dispersion medium is used. Is applied to the surface of the carbonaceous material, then dried, and in an inert atmosphere,
By sintering at high temperature, B ₄ C
It is formed by forming an oxidation-resistant protective layer containing (boron carbide) as a main component. As a result, in addition to high strength at high temperatures (high thermal shock resistance), high reliability as a material (toughness, impact resistance, abrasion resistance), environmental resistance (corrosion resistance, oxidation resistance, radiation resistance), etc. A carbon having an oxidation-resistant protective layer that satisfies both lightness from the viewpoint of energy saving and easy workability and that is not substantially oxidized even at a high temperature of at least 800 ° C., preferably 1000 ° C. or more in the atmosphere. Quality material can be produced in a simpler manner and at lower cost.

The main feature of the method for producing a carbonaceous material having an oxidation-resistant protective layer according to the present invention is that a suspension (slurry) of BN (boron nitride) powder is formed on the surface of the carbonaceous material. The BN (boron nitride) applied to the surface of the carbonaceous material is applied by drying at around the boiling point of the solvent, and then by baking at a high temperature, preferably 2000 ° C. or higher, in an atmosphere of an inert gas, It is to react with C (carbon) derived from a carbonaceous material to form an oxidation-resistant protective layer containing B ₄ C (boron carbide) as a main component on the surface of the carbonaceous material.

At this time, the composition of the suspension (slurry) used in the present invention is as follows: dispersion medium: BN powder (volume ratio) = 80:
It is preferably 20 to 70:30. This is for dispersing the BN particles uniformly in the slurry so as to prevent application unevenness or the like.

Incidentally, BN (boron nitride) used in the present invention
The powder preferably has an average particle size of 1 to 20 μm. When the average particle size is smaller than 1 μm, uniform dispersion in the dispersion medium is difficult. When the average particle size is larger than 20 μm, the oxidation-resistant protective layer of B ₄ C (boron carbide) formed by high-temperature sintering becomes uneven and gaps are formed. May occur and performance may be degraded. Further, the dispersion medium used in the present invention is not particularly limited,
It may be water, an organic solvent such as ethanol or xylene, or a mixture thereof.

In the present invention, the oxidation-resistant protective layer has a thickness of 30 to 300 μm, more preferably 50 to 200 μm.
μm is preferred. If the oxidation-resistant protective layer is thinner than 30 μm, the protective effect cannot be obtained. Progresses and the life tends to be short.

Since the carbonaceous material having the oxidation-resistant protective layer manufactured as described above does not require a large-scale apparatus such as thermal spraying, a significant cost reduction can be expected. Also,
When exposed to air at high temperature, the oxidation-resistant protective layer B ₄ C
Part of (boron carbide) forms boron oxide in a molten state, thereby protecting the surface of the base material as a carbonaceous material and improving wettability with the carbonaceous material as the base material. It is also excellent in that it is retained on the surface of the carbonaceous material and does not flow out, so that it is not substantially oxidized even in the air even at a high temperature exceeding 800 ° C. Here, the term "substantially not oxidized" means that the weight increase or decrease is 0.5% or less when the sample is held for at least 24 hours under a predetermined high temperature, for example, 800 ° C. in the atmosphere. Say.

The carbonaceous material having the oxidation-resistant protective layer manufactured as described above has excellent adhesion between the carbonaceous material as the substrate and the oxidation-resistant protective layer. Cracks and peeling in the oxidation-resistant protective layer due to the difference in thermal expansion from the porous material can be improved.

Further, in the carbonaceous material having the oxidation-resistant protective layer manufactured as described above, the formation of the oxidation-resistant protective layer can be performed by an existing carbonaceous material manufacturing process, thereby reducing costs. be able to.

From the above, the carbonaceous material having the oxidation-resistant protective layer manufactured as described above uses a lightweight carbonaceous material as the base material, which has high impact resistance, low coefficient of thermal expansion, and low weight. Due to this, the oxidation-resistant protective layer is formed on the surface while maintaining its properties as it is, so it shows high oxidation resistance even in the air, and has a thermal shock resistance, a fine powder caused by mechanical action such as abrasion. The occurrence is extremely low. Therefore, the carbonaceous material having the oxidation-resistant protective layer manufactured as described above can be used very suitably as a member for setters, a material for various kiln tools, and the like.

Next, the carbonaceous material used in the present invention uses a raw material mainly composed of carbon fibers as its base material. As the carbonaceous material used in the present invention,
First, carbon fiber is mentioned. Such a carbon fiber can be used irrespective of its production method and raw materials. In actual use, carbon fibers are used as a binder or the like, molded into a predetermined shape, and used. From the viewpoint of durability, the following C / C composite is preferable. Further, a composite material in which the C / C composite is impregnated with Si is also included in the carbonaceous material according to the present invention. The composite material impregnated with Si is defined below,
Si-SiC-based composite materials and SiC-based composite materials described in detail are preferably used. Here, in this specification, the carbonaceous material includes not only the carbon fiber itself but also a C / C composite included in the carbon fiber in a broad sense. In addition, the Si / SiC-based composite material, which is a carbon material which is obtained by impregnating the C / C composite with a predetermined amount of metallic silicon and which is a specially processed carbonaceous material, is also used.
The iC-based composite material is also included in the carbonaceous material. The properties, manufacturing method, and the like of these will be described in detail below. In order to avoid confusion in terms of names, in the following description of the present specification, a carbonaceous material refers to a C / C composite, a Si-SiC-based composite material, a SiC-based composite material, and a metal silicide-impregnated composite material. Is also used as a term that also encompasses Therefore, in the present invention, not only carbon fibers in a narrow sense but also the above-mentioned composite materials can be used as the base material.

In the present specification, a C / C composite is a powdery binder that acts as a matrix of a bundle of carbon fibers, and pitch and coke that become free carbon to the bundle of carbon fibers after firing. And further, if necessary, by containing a phenol resin powder or the like, thereby preparing a carbon fiber bundle, forming a flexible film made of a plastic such as a thermoplastic resin around the carbon fiber bundle, A preformed yarn as a conductive intermediate material is obtained.
No. 639, a sheet or woven cloth is formed, a required amount is laminated, and then a molded article obtained by molding by hot pressing or a fired article obtained by firing this molded article is obtained. Say. That is, in the present invention, C / C
The composite is composed of carbon fiber and carbon other than carbon fiber.The carbon fiber has a specific diameter and a laminated structure composed of a bundle of carbonaceous fiber fibers of a specific number. A composite material having a structure of a specific laminated structure and a matrix having a structure in which a matrix is formed and filled in a gap between the laminated structure and the laminated structure.

As a C / C composite used as a basic material, a carbon fiber having a diameter of about 10 μm is usually bundled with hundreds to tens of thousands to form a fiber bundle (yarn).
This fiber bundle is coated with a thermoplastic resin to obtain a flexible thread-like intermediate material, which is formed into a sheet by the method described in Japanese Patent Application Laid-Open No. 2-80639. Alternatively, a preformed body (fiber preform) having a predetermined shape is formed by arranging in a three-dimensional direction to form a unidirectional sheet (UD sheet) or various cloths, or by laminating the sheets or cloths. It is only necessary to use a material obtained by baking a film of a thermoplastic resin or the like made of an organic substance formed on the outer periphery of the fiber bundle of the preform and removing the film by carbonization. In this specification, the description of Japanese Patent Application Laid-Open No. 2-80639 is cited for reference. In the C / C composite used in the present invention, the carbon component other than the carbon fiber in the yarn is preferably a carbon powder, particularly preferably a graphitized carbon powder.

In the present invention, the Si—SiC-based composite material includes 55% by weight to 75% by weight of carbon and 1% by weight to
A yarn composed of 10% by weight of silicon and 10% by weight to 50% by weight of silicon carbide and containing at least a bundle of carbon fibers and a carbon component other than carbon fibers is three-dimensionally oriented in the layer direction. A combined yarn which is integrated so as not to be separated from each other, and a Si-SiC filled between the adjacent yarns in the combined yarn.
A matrix made of a base material,
A composite material having a dynamic friction coefficient of 6 and a controlled porosity of 0.5% to 10%. This material can be manufactured by the method disclosed in Japanese Patent Application No. 10-267402 filed on Sep. 4, 1998. Therefore,
The content of Japanese Patent Application No. 10-267402 is cited here.

Here, the Si—SiC-based material typically includes several different phases from a silicon phase remaining in an unreacted state to a substantially pure silicon carbide. Is composed of a silicon phase and a silicon carbide phase.
It refers to one that can include an iC coexisting phase. Therefore, Si-Si
The C-based material is, as described above, in the Si-SiC series,
It is a general term for materials contained in the range of 0 mol% to 50 mol% as the concentration of carbon. In the Si-SiC-based composite material according to the present invention, the matrix portion is formed of the Si-SiC-based material.

In addition, this Si—SiC-based composite material
Preferably, the matrix has a gradient composition in which the silicon content increases as the distance from the yarn surface increases. In the Si-SiC-based composite material, preferably, the yarn aggregate made of carbon fibers is composed of a plurality of yarn arrays, and each yarn array is formed by bundling a specific number of carbon fibers. The yarns are formed by two-dimensionally arranging the obtained yarns substantially in parallel, and a yarn aggregate is formed by stacking the respective yarn arrays. Thereby, Si-Si
The C-based composite material has a laminated structure in which a plurality of yarn arrays are laminated in a specific direction.

FIG. 1 is a schematic perspective view for explaining the concept of a yarn aggregate, and FIG.
FIG. 2B is a cross-sectional view taken along the line IIa, and FIG.
It is Ib line sectional drawing. The skeleton of the Si—SiC-based composite material 7 is constituted by the yarn aggregate 6. The yarn aggregate 6 includes the yarn arrays 1A, 1B, 1C, 1D, 1
E and 1F are vertically stacked. In each yarn array, the yarns 3 are two-dimensionally arranged, and the longitudinal directions of the yarns are substantially parallel. The longitudinal direction of each yarn in each vertically arranged yarn array is orthogonal. That is, each yarn array 1A, 1C, 1E
The longitudinal direction of each yarn 2A is parallel to each other and orthogonal to the longitudinal direction of each yarn 2B of each yarn array 1B, 1D, and 1F. Each yarn is made of carbon fiber,
The fiber bundle 3 is made of a carbon component other than carbon fibers.
The yarn assembly 6 having a three-dimensional lattice shape is formed by stacking the yarn arrays. Each yarn is crushed during a pressure forming process as described below, and has a substantially elliptical shape.

In each of the yarn arrays 1A, 1C, and 1E, a matrix 8A is provided between adjacent yarns.
And each matrix 8A extends along and parallel to the surface of the yarn 2A. In each of the yarn arrays 1B, 1D, and 1F, the gap between adjacent yarns is filled with a matrix 8B, and each matrix 8B extends along and parallel to the surface of the yarn 2B. In this example, the matrices 8A and 8B are respectively composed of silicon carbide phases 4A and 4B covering the surface of each yarn.
And Si-SiC-based material phases 5A and 5B having a lower carbon content than silicon carbide phases 4A and 4B. Silicon may be partially contained in the silicon carbide phase. In this example, silicon carbide phases 4A and 4B are also generated between yarns 2A and 2B that are vertically adjacent to each other.

Each of the matrices 8A and 8B is elongated, preferably linear, along the surface of the yarn, and each of the matrices 8A and 8B is orthogonal to one another. Then, the matrix 8A in the yarn arrays 1A, 1C, and 1E and the yarn array 1 orthogonal to the matrix 8A
The matrix 8B in B, 1D, and 1F is continuous at the gap between the yarns 2A and 2B, respectively. As a result, the matrices 8A and 8B form a three-dimensional lattice as a whole.

In the present invention, the SiC-based composite material has a structure composed of silicon carbide, carbon fiber, and a carbon component other than carbon fiber, and composed of a skeleton and a matrix formed around the skeleton. A composite material having at least 50% of silicon carbide.
% Is β type, the skeleton is formed of carbon fiber and carbon components other than carbon fiber, and silicon carbide may be present in a part of the skeleton, and the matrix is formed of silicon carbide. , The matrix and the skeleton are integrally formed, and the composite material is 0.5
% Composite material having a porosity of 5% to 5% and a two-peaked average pore size distribution.

Therefore, this SiC-based composite material uses, as the skeleton, a C / C composite in which each carbon fiber is composed of a carbon fiber bundle. Therefore, even if SiC is partially formed, Although the structure of each carbon fiber is not destroyed, the carbon fiber surface is converted to silicon carbide, so that the raw material C /
The inner bending / tensile strength of the mechanical strength of the C composite is slightly reduced. On the other hand, the compressive strength has a great feature that it is increased by densification due to penetration of Si.
Moreover, between adjacent yarns in the yarn assembly, Si
It has a composite structure in which a matrix made of a C-based material is formed. In this respect, it is different from the above-described Si-SiC-based composite material. This material can be manufactured by the method disclosed in Japanese Patent Application No. 11-31979 filed on Feb. 9, 1999. Therefore, Japanese Patent Application No.
The contents of No. 31979 are cited here.

In the present invention, the SiC-based material refers to a material containing silicon carbide having a different degree of bonding with carbon, and the SiC-based material is manufactured as follows. In the present invention, for C / C composite,
The metal silicon is impregnated. At this time, the metal silicon reacts with carbon atoms constituting carbon fibers in the composite and / or free carbon atoms remaining on the surface of the carbon fibers, and is partially carbonized. A partially carbonized silicon is formed between the yarns composed of the outermost surface of the C / C composite and the carbon fibers, and thus a matrix composed of silicon carbide is formed between the yarns. Is done.

The matrix may include several different phases, from a silicon carbide phase in which trace amounts of silicon and carbon are bonded to a pure silicon carbide crystal phase. However, this matrix contains only metallic silicon below the X-ray detection limit (0.3% by weight).
That is, although this matrix is typically made of a silicon carbide phase, the silicon carbide phase may include a SiC-based phase in which the content of silicon is inclined. Therefore, the SiC-based material refers to a concentration of carbon of at least 0.01 mol% to 50 mol% in such a SiC series.
It is a general term for materials included in the range up to%. In addition, in order to control the carbon concentration to less than 0.01 mol%, in relation to the amount of free carbon in the C / C composite,
It is not practical because strict measurement of the amount of metallic silicon to be added is required and temperature control in the final step is complicated. Therefore, theoretically, the carbon concentration is 0.001 mol
% Can be controlled.

The Si-based composite material will be further described with reference to the drawings. The skeleton of this SiC-based composite material is basically the same as that shown in FIG. FIG. 3 is a sectional view when the SiC-based composite material according to the present invention is cut along the line IIa-IIa in FIG.
FIG. 3A is a cross-sectional view taken along line IIb-IIb in FIG. The skeleton of the SiC-based composite material 17 is constituted by the yarn aggregate 16, similarly to the skeleton of the Si—SiC-based composite material 7. The yarn aggregate 16 includes the yarn arrays 11A and 11A.
B, 11C, 11D, 11E, and 11F are vertically stacked. In each yarn array, the yarns 13 are two-dimensionally arranged, and the longitudinal directions of the yarns are substantially parallel. The longitudinal direction of each yarn in each vertically arranged yarn array is orthogonal. That is, each yarn 12A of each yarn array 11A, 11C, 11E
Are parallel to each other and perpendicular to the longitudinal direction of each yarn 12B of each yarn array 11B, 11D, 11F. Each yarn is composed of a fiber bundle 13 composed of carbon fibers and carbon components other than carbon fibers. The yarn assembly 16 having a three-dimensional lattice shape is formed by stacking the yarn arrays. Each yarn is crushed during a pressing step, as described below, and is slightly oval.

Each yarn array 11A, 11C, 11E
In, the gap between adjacent yarns is filled with a matrix 18A, and each matrix 18A extends along and parallel to the surface of the yarn 12A. In each of the yarn arrangements 11B, 11D, 11F, the gap between adjacent yarns is filled with a matrix 18B, and each matrix 18B extends along the surface of the yarn 12B and parallel thereto. As shown in FIGS. 3A and 3B, the matrices 18A and 18A
B consists of a silicon carbide phase 14 covering the surface of each yarn. Part of the silicon carbide phase is the small protrusion 1
It may project to the surface as 9 or to the carbon fiber layer inside the composite member. Inside such small projections, pores (voids: 15) having an average pore diameter of about 100 μm are formed. In addition, since the small protrusions 19 are formed along the traces of the matrix composed of carbon components other than the carbon fibers of the raw material C / C composite, most of the small protrusions 19 have a space between the yarns and / or a yarn arrangement. By appropriately selecting the distance from the yarn array, it is possible to adjust the density of the small projections 19 per unit area. Silicon carbide phase 14 may be formed between adjacent yarns 12A and 12B.

Each of the matrices 18A and 18B is elongated, preferably linear, respectively, along the surface of the yarn, and each of the matrices 18A and 18B is orthogonal to one another. Then, the yarn arrays 11A, 11
The matrix 18A in C and 11E and the matrix 18B in the yarn arrays 11B, 11D and 11F orthogonal thereto are continuous at the gap between the yarns 12A and 12B, respectively. As a result, matrix 1
8A and 18B form a three-dimensional lattice as a whole.

Further, in the present invention, the metal silicide-impregnated composite material refers to a metal silicide, such as titanium silicide, zirconium silicide, tantalum silicide, niobium silicide, chromium silicide, tungsten silicide, and the like in the C / C composite described in detail above. Impregnated with molybdenum silicide (ordinary impregnation amount: 1 to 50% by weight). In other words, at least impregnated with a metal silicide means that the metal is impregnated with a desired amount of the metal silicide, and in addition, it is impregnated with metal silicon and silicon carbide (Si-SiC) or silicon carbide (SiC). It means that it may be impregnated.

[0038]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist. The oxidation resistance characteristics in the examples were measured by the following methods.

(Oxidation resistance measurement test)
After holding the sample in the atmosphere heated to ° C. for a predetermined time, the weight was measured and compared with the weight before the test, and the rate of change W _{2 ′} of the weight was determined by the following equation. W _{2 ′} = (W ₀ −W ₁ ) / W ₀ × 100 where W ₀ is the weight before the oxidation resistance test, W ₁ is the weight after the oxidation resistance test, and W _{2 ′} is the weight. (Decrease is distinguished by adding a minus sign in front of the number).

(Examples, Comparative Examples 1 and 2) (Production method of Si-SiC-based composite material) A carbon fiber having a diameter of 10 µm was impregnated with a carbon fiber having a diameter of 10 µm by impregnating a carbon fiber in one direction. Main bundle, fiber bundle (yarn)
To prepare a yarn array (prepreg sheet) in which the yarns are made into a mat, and arrange them as shown in FIG. 1 to obtain a prepreg sheet laminate, and apply a carbon-based adhesive to the prepreg sheet laminate. The yarns were fixed together. After the fixation, the fixed body was released from the mold, the released prepreg sheet laminate was placed in an oven, and the impregnated phenol resin was cured at 180 ° C. and normal pressure. Fired. Next, Si powder having a purity of 99.9% and an average particle diameter of 1 mm was added to the obtained carbon fiber reinforced carbon composite material, and the resulting mixture was subjected to a furnace temperature of 1300 ° C. and a furnace pressure of 1 mm.
hPa, put argon gas in the furnace for 2 minutes per minute.
It was kept for 4 hours while flowing at a rate of 0NL. Then
While keeping the furnace pressure unchanged, the furnace temperature was raised to 1600 ° C. to impregnate Si. Thus, a Si-SiC-based composite material comprising Si, SiC, and carbon fibers was obtained. The obtained fired body is cut and processed into an outer periphery to obtain 9 mm × 9 mm × 9 m.
A test piece having a size of m (Comparative Example 2) was manufactured.

(Method 1 for Producing Carbonaceous Material Having Oxidation-Protective Protective Layer) The test piece obtained above (Comparative Example 2) was set in a jig, and boron carbide having a purity of 99.5% and an average particle size of 25 μm was obtained. A carbonaceous material having an oxidation-resistant protective layer (Comparative Example 1) was produced by plasma spraying a powder (manufactured by ESK) and forming a boron carbide layer having a thickness of about 50 μm on the surface of the test piece. .

(Production method 2 of carbonaceous material having oxidation-resistant protective layer) Boron nitride having an average particle size of 10 μm
After mixing and suspending 26 wt% of e grade B50 (manufactured by HC Starck) and 74 wt% of water as a solvent, the obtained slurry (suspension) was mixed with the test piece (suspension) obtained above. Comparative Example 2) was applied to the surface while being heated to 150 ° C., and then baked at 2200 ° C. in an Ar atmosphere and atmospheric pressure, so that the surface of the test piece contained B ₄ C (boron carbide) as a main component. A carbonaceous material having an oxidation-resistant protective layer was manufactured by forming an oxidation-resistant protective layer of about 200 μm (Example).

Next, an oxidation resistance measurement test was performed on the carbonaceous materials (Examples, Comparative Examples 1 and 2) obtained by the above-described production methods. The oxidation resistance test was performed by exposing the sample to a furnace heated to 800 ° C. in an air atmosphere for 50 hours and measuring the change in weight. As a result, a test piece of the Si-SiC-based composite material (Comparative Example 2)
In this case, the weight loss rate after 50 hours was about 50%. Further, in the case of the carbonaceous material having the oxidation-resistant protective layer formed by thermal spraying (Comparative Example 1), no weight loss was shown even after 50 hours. Rather B ₄ C showed weight increase of 5-10% in the course of changing the B ₂ O _3. On the other hand, the carbonaceous material having the oxidation-resistant protective layer of the present invention (Example) showed no change in weight even after 50 hours as in the case of thermal spraying (Comparative Example 1). When the manufacturing costs were compared, the case where the oxidation-resistant protective layer was not provided (Comparative Example 2) was 1
Then, in the case of thermal spraying (Comparative Example 1), it is about twice as large as 2, whereas according to the method of the present invention, it is only about 1.1, an increase of about 10%. An oxidation-resistant protective layer could be formed.

[0044]

As described above, according to the present invention, high strength at high temperature (high thermal shock resistance), high reliability as a material (toughness, impact resistance, wear resistance), and environmental resistance (Corrosion resistance, oxidation resistance, radiation resistance), etc., and at the same time, satisfy the light weight from the viewpoint of energy saving and easy workability.
A carbonaceous material having an oxidation-resistant protective layer that is not substantially oxidized even at a high temperature of 1000 ° C. or higher can be manufactured by a simpler method and at low cost. Therefore, the carbonaceous material having the oxidation-resistant protective layer manufactured as described above can be used very suitably in the fields of, for example, materials for various kiln tools, manufacture of parts made of aluminum alloy and copper alloy, and the like.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a structure of a Si—SiC-based composite material and a yarn aggregate that is a basic structure of the SiC-based composite material used as a substrate of a carbonaceous material having an oxidation-resistant protective layer according to the present invention. FIG.

FIG. 2A is a cross-sectional view of a Si—SiC-based composite material cut along a line IIa-IIa in FIG. 1;
FIG. 2B is a cross-sectional view of the same material taken along line IIb-IIb in FIG. 1.

FIG. 3A shows a SiC-based composite material IIa in FIG.
FIG. 2B is a cross-sectional view taken along line IIa, and FIG.
It is sectional drawing at the time of cutting | disconnecting the same material along the IIb-IIb line of FIG.

[Explanation of symbols]

1A, 1B, 1C, 1D, 1E and 1F ... yarn arrangement, 2A ... yarn, 2B ... yarn, 3 ... fiber bundle (yarn), 4A ... silicon carbide phase, 4B ... silicon carbide phase, 4C ... silicon carbide phase, 5A ... Si-SiC material phase, 5B ... Si-
SiC-based material phase, 5C: Si-SiC-based material phase, 6: Yarn aggregate, 7: Fiber composite material, 8A: Matrix,
8B ... matrix, 11A, 11B, 11C, 11
D, 11E and 11F ... yarn arrangement, 12A ... yarn, 12B ... yarn, 13 ... fiber bundle (yarn), 14 ...
Silicon carbide phase, 15 ... voids, 16 ... yarn aggregate, 17 ...
Fiber composite material, 18A matrix, 18B matrix, 19 small projections.

Claims (6)

[Claims] 1. A BN (boron nitride) powder is dispersed and suspended in a dispersion medium, and the resulting suspension is applied to the surface of a carbonaceous material, dried, and dried under an inert atmosphere. A carbonaceous material having an oxidation-resistant protective layer, characterized in that an oxidation-resistant protective layer containing B ₄ C (boron carbide) as a main component is formed on the surface of the carbonaceous material by firing at a high temperature. Manufacturing method. 2. The method according to claim 1, wherein the carbonaceous material is C / C composite, S
The method for producing a carbonaceous material having an oxidation-resistant protective layer according to claim 1, wherein the carbonaceous material is one material selected from an i-SiC-based composite material, a SiC-based composite material, and a metal silicide-impregnated composite material. 3. The method for producing a carbonaceous material having an oxidation-resistant protective layer according to claim 1, wherein the application of the suspension is performed while heating the carbonaceous material. 4. The acid resistance according to claim 1, wherein BN is applied and dried, and then fired at a temperature of 2000 ° C. or more to form an oxidation resistant protective layer containing B ₄ C as a main component. A method for producing a carbonaceous material having a protective layer. 5. The oxidation-resistant protective layer has a thickness of 30 to 300 μm.
5. The method for producing a carbonaceous material having an oxidation-resistant protective layer according to claim 1, wherein m is m. 6. The method for producing a carbonaceous material having an oxidation-resistant protective layer according to claim 1, which is substantially not oxidized at least at 800 ° C. in the atmosphere.