JPH1059780A - Ceramic-base fiber composite material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more effectively inhibit the reaction of Si having high reactivity with fibers or fiber coating layers at the time of reactive sintering when a reactive sintering method for forming a dense SiO matrix is applied and at least a lubricative layer exists at the interface between the matrix and each fiber. SOLUTION: A bundle of ceramic fibers or an intermediate preform made of the bundle is coated to form lubricative layers (BN layers) capable of lubricating the fibers to at least a matrix on the surface of the fibers and a final preform is formed from the bundle or the intermediate preform. Carbon powder is impregnated into the final preform, molten Si is further impregnated and reactive sintering is carried out. The fibers are made composite in the resultant matrix contg. SiC as the principal phase and the objective ceramic-base fiber composite material is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic-based fiber composite material and a method of manufacturing the same, and more particularly to an improvement of a composite material using dense silicon carbide (SiC) formed by a reaction sintering method as a matrix. .

[0002]

2. Description of the Related Art In general, a ceramic sintered body has a small decrease in strength up to a high temperature, and has a hardness, an electrical insulation property, a wear resistance,
Materials such as heavy electrical equipment parts, aircraft parts, automobile parts, electronic equipment, precision machine parts, semiconductor device materials, and other electronic materials because of their superior properties such as corrosion resistance and light weight compared to conventional metal materials. And used in a wide range of fields as structural materials.

[0003] However, this ceramic sintered body is weaker in tensile stress than compressive stress, and has a defect of so-called brittleness, in which the breakage proceeds at a stretch under this tensile stress. Depending on the application, it is necessary to increase the toughness and increase the fracture energy. Such an attempt to improve brittleness is strongly demanded when applied to ceramic structural parts such as gas turbine parts, aircraft parts, and automobile parts, which require high reliability in addition to heat resistance and high-temperature strength.

[0004] In response to such demands, as a ceramic sintered body having improved fracture toughness, fracture energy, thermal shock resistance, etc., composites of fibers, whiskers, plates, particles, etc., made of inorganic substances or metals. Attention has been paid to ceramic-based composite materials formed by dispersing and compounding a material in a matrix, and research on its practical use is being vigorously pursued by internal and external research institutions. In particular, when a fiber is compounded to form a ceramic-based fiber composite material, its practical use is expected because the effect of improving the fracture resistance is large.

[0005] Among such ceramic-based fiber composite materials, a composite material using SiC as a matrix as a high-temperature material has been in the spotlight. As an example of a method for synthesizing the SiC matrix of this composite material, taking into account fiber heat resistance, a CVI method (Chemical V) having a relatively low synthesis temperature is considered.
apor Infiltration: Chemical vapor impregnation method), PC (precursor) method, reaction sintering method, etc. Among them, the denseness is a typical example that can easily improve the initial fracture strength characteristics and obtain high reliability. Attention has been focused on a reaction sintering method for forming a high quality SiC matrix.

On the other hand, in the above-described ceramic-based fiber composite material, it is extremely important to appropriately control the bonding state at the interface between the matrix and the fiber, in order to exert the composite effect of the fiber. Has become. If the fibers and ceramics are firmly bonded, the combined effects such as bridging and pull-out will not be sufficiently exhibited,
This is because brittle fracture is likely to occur. As a countermeasure, there is known a method of coating the fiber surface with a slip layer such as boron nitride (BN) that weakens the bond between the fiber and the matrix and causes the fiber to slip with respect to the matrix.

[0007]

However, there has been a problem that the above-mentioned slip layer is degraded, decomposed and disappears due to a reaction with a matrix forming material when the reaction sintering method is applied. For example, when applying a reactive sintering method of forming a SiC matrix by impregnating molten Si into a preform formed of ceramic fibers, the molten Si to be impregnated has high reactivity,
It easily reacts with the slip layer and the fiber itself, and as a result, there has been a problem that the above-described composite effect of the fiber cannot be sufficiently exhibited.

Therefore, when a reaction sintering method for forming a SiC matrix is applied when a slip layer is provided, a method of suppressing the reaction between molten Si and the slip layer or fibers is to provide a reaction suppression layer outside the slip layer. A method of forming a barrier layer (also referred to as a “barrier layer”), that is, a method of double-coating the fiber surface with a slip layer and a reaction suppression layer has also been proposed.
It has been difficult to completely suppress the reaction between the fiber and the fiber or fiber coating material.

The present invention has been made in view of such conventional problems, and employs a reaction sintering method for forming a dense SiC matrix, and a fiber coat formed at an interface between the matrix and the fiber. The layer having at least the slip layer is intended as a layer, and the reaction between Si and the fiber or the fiber coat layer having high reactivity during the reaction sintering is more effectively suppressed, and the fibers and the coat layer are obtained in the obtained matrix. Its purpose is to make it exist in a healthy state.

[0010]

In order to achieve the above object, the present inventor has carried out various studies on measures to suppress the reaction between the highly reactive molten Si which is a matrix forming material and the fiber coat layer or the fiber. As a result, the thickness of the slip layer formed on the fiber surface is non-uniform, and the main cause of the non-uniformity of the film thickness is during coating after preparation of the preform (hereinafter referred to as “final preform”). We paid attention to what was happening. This means that the reaction with the molten Si during the reaction sintering proceeds more easily in the portion where the thickness of the slip layer is thin or almost absent.

Accordingly, the inventor of the present invention has proposed a measure for improving the non-uniformity of the film thickness, not a final preform, but a fiber bundle before producing the final preform or a two-dimensional shape composed of the fiber bundle. It has been found that it is effective to coat a slip layer on a preform having an intermediate stage shape such as a predetermined shape (hereinafter, referred to as “intermediate preform”). Regarding this effectiveness, it is considered that the same applies when the reaction suppression layer is applied as a double coating. That is, if the fiber bundle or the intermediate preform is coated with a slipping layer or a reaction suppressing layer, the entire surface of each single fiber can be uniformly coated, so that the reactivity caused by the nonuniformity of the film thickness is reduced. The reaction between the high molten Si and the fiber or the fiber coat layer can be effectively suppressed.

Based on such findings, the method for producing a ceramic-based fiber composite material according to the present invention comprises a step of bundling ceramic fibers into a fiber bundle, and coating the fiber bundle or an intermediate preform comprising the fiber bundle. To form a final preform from the fiber bundle or the intermediate preform, and then apply a powder containing C to the final preform. After the impregnation, the fibers are compounded in a matrix having SiC as a main phase by impregnating with molten Si and performing reaction sintering.

According to such a production method, since the slip layer can be uniformly coated over the entire surface of each single fiber, the reaction with Si having high reactivity is suppressed, and the slip layer and the fiber are not coated. Can be obtained in a matrix in a healthy state.

In another aspect of the present invention, the fiber bundle includes
The surface of the slip layer in at least one of the intermediate preform and the final preform is coated with a reaction suppression layer that suppresses a reaction between the slip layer and the matrix.

In the above-described method for producing a ceramic-based fiber composite material according to the present invention, preferably, the slip layer is coated by a CVD method (chemical vapor deposition method).
Or a method of coating with a ceramic precursor (ceramic precursor) and heat-treating.

As a method of coating the reaction suppressing layer, a method of coating using a CVD method, a method of coating a CV
One of a method of coating using the method I and a method of coating with a ceramic precursor and heat-treating is used.

Further, as the material of the sliding layer, B,
A material containing at least one of N, Si, C, and O is used. For example, BN, C as components capable of expressing slip
And the like such as BN, C, etc.
₂ , a compound such as Si ₃ N ₄ , an amorphous component (Si—C—N—O compound), and the like, which share functions such as oxidation resistance, may be used.

As a material of the reaction suppressing layer, SiC,
At least one material of Si ₃ N ₄ and MoSi ₂ is used.

Further, the present inventor, when forming the final preform after coating the slip layer and the reaction suppressing layer, if the coating thickness is large, the coating film may be damaged due to the bending of the fiber during the formation of the final preform. Therefore, when an appropriate coat thickness for further exhibiting the above effects was examined, it was found that setting the thickness to 3 μm or less is effective.

Therefore, in the above-described method for producing a ceramic-based fiber composite material according to the present invention, preferably, the thickness of the slip layer is 3 μm or less. When a reaction suppression layer is provided, the thickness of the reaction suppression layer is 3 μm or less.

According to the above-described manufacturing method, the following ceramic-based fiber composite material according to the present invention can be manufactured.

That is, the ceramic-based fiber composite material according to the present invention comprises a matrix having SiC as a main phase formed by reaction sintering and ceramic fibers composited in the matrix. The main part is that there is a slip layer capable of expressing the slip of the fiber with respect to the matrix at least at the interface, and a fiber bundle obtained by bundling the fibers before the reaction sintering or an intermediate preform made of the fiber bundle By coating the fiber surface with the slip layer by applying a coating process to the interface between the matrix and the fiber by the reaction sintering using the final preform formed from the fiber bundle or the intermediate preform, the slip layer Are present so as to uniformly cover the entire surface of the fiber with a predetermined film thickness.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a ceramic-based fiber composite material and a method for producing the same according to the present invention will be specifically described.

(First Embodiment) In this embodiment, 50 μm SiC ceramic fibers having a diameter of 14 μm are used as the fibers.
0 fiber bundles bundled as a yarn (“SiC ceramic fiber yarn”: manufactured by Nippon Carbon Co., Ltd., trade name: Hynicalon, filament diameter: φ14 μm, 500F /
Y) was prepared. The fiber bundle is continuously coated with BN by a CVD method to form a 0.4 μm thick slip layer (B
An N layer) was formed, and the surface of the slip layer was continuously coated with SiC using a CVD method to form a 0.4 μm thick reaction suppression layer (SiC layer). A plain woven cloth (intermediate preform) was woven from the fiber bundle thus double-coated.

The plain woven cloth is laminated to form a final preform, which is set in a porous resin mold (fiber volume ratio (Vf = 27%)), impregnated with a slurry of ceramic raw material, and molded. By drying, a molded article was obtained. Here, as slurry, SiC powder (70w
t%) and carbon black (30 wt.
%) As a solid content, and a mixture of the solid content (50 wt%) with pure water (47 wt%) and a surfactant (3 wt%) was used.

Next, the above compact was brought into contact with a molten metal of Si (purity: 99.9 wt%),
The matrix was synthesized by reaction-sintering SiC by heating to 30 ° C. for melt impregnation to obtain a ceramic-based fiber composite material.

That is, in this embodiment, the fiber bundle is double-coated with the BN layer and the SiC layer, so that the uniformity of the film thickness of both layers present in the composite material finally obtained by the reaction sintering is obtained. Thus, the reaction between Si having high reactivity and the BN layer as the slip layer was suppressed, and the effect of the slip layer could be more effectively exhibited.

Therefore, in order to verify the characteristics of the ceramic-based fiber composite material, a test piece of a predetermined size ("Example 1") was cut out from the composite material, and various tests were performed on the test piece.

As a result, as shown in Example 1 in Table 1 below, the density of the obtained composite material was 3.0 g / cm ³ , and the three-point bending strength at room temperature was as follows: Is 200MPa, maximum strength σ2 is 350MP
When the fracture energy was examined based on the load-displacement curve of the three-point bending test, the effective fracture energy γ was 4.9 kJ / m ^2. Typical fracture behavior. In addition, when the fracture surface was observed by SEM (scanning electron microscope), it was clearly confirmed that the BN layer was uniformly and soundly present on the surface of each single fiber, and that the fiber withdrawal was remarkable. Was.

(Second Embodiment) In this embodiment, a fiber bundle made of the same SiC ceramic fiber as described above is prepared, and BN is continuously coated on the fiber bundle by the CVD method to obtain a 0.4 μm thick fiber bundle. A slip layer was formed, and a plain woven cloth was woven from the fiber bundle. This plain weave cloth is CVD
A reaction suppression layer having a thickness of 0.4 μm was formed by coating SiC using the method.

The plain woven cloths were laminated and set in the same mold as above, and thereafter, a ceramic-based fiber composite material was obtained by the same process as above. A test similar to the above was performed on the cut-out test piece ("Example 2").

As a result, as shown in Example 2 in Table 1 below, the density of the obtained composite material was 3.0 g / cm ³ , the initial matrix breaking strength σ1 was 190 MPa, and the maximum strength σ2 was 340 MPa. And the effective fracture energy γ was 4.8 kJ / m ² , indicating a metastable fracture behavior peculiar to the composite material, in which the fracture did not reach the complete fracture at once. In addition, SEM observation of the fracture surface also clearly confirmed that the BN layer was uniformly and soundly present on the surface of each single fiber as in the above, and that the fiber withdrawal was remarkable.

(Third Embodiment) In this embodiment, a fiber bundle made of the same SiC ceramic fibers as described above was prepared, and a plain woven cloth was woven from this fiber bundle. The plain woven cloth is continuously coated with BN using a CVD method to form a slip layer having a thickness of 0.4 μm, and the surface of the slip layer is continuously coated with SiC using a CVD method to form a 0.1 μm thick slip layer.
A reaction suppression layer having a thickness of 4 μm was formed.

The plain woven cloth was laminated and set in the same mold as above, and thereafter, a ceramic-based fiber composite material was obtained by the same process as above. A test similar to the above was performed on the cut-out test piece ("Example 3").

As a result, as shown in Example 3 in Table 1 below, the density of the obtained composite material was 3.0 g / cm ³ , the initial matrix breaking strength σ1 was 200 MPa, and the maximum strength σ2 was 320 MPa. The effective fracture energy γ was 4.3 kJ / m ² , and the composite material exhibited a stable fracture behavior peculiar to the composite material, in which the fracture did not reach a complete fracture at once. Also, by SEM observation of the fracture surface,
Similarly to the above, it was clearly recognized that the BN layer was uniformly and soundly present on the surface of each single fiber, and that the fiber was significantly pulled out.

(Fourth Embodiment) In this embodiment, Si
Forming a 4 μm thick reaction suppression layer made of C by the CVI method,
Other processes are the same as those in the second embodiment,
That is, before fabricating the final preform, the fiber bundle is coated with BN to weave a plain weave cloth, and a ceramic-based fiber composite material is obtained by reaction sintering using a process of coating this with SiC. Example 4 ") was subjected to the same test as described above.

As a result, as shown in Example 4 in Table 1 below, the density of the obtained composite material was 3.0 g / cm ³ , the initial matrix breaking strength σ1 was 180 MPa, and the maximum strength σ2 was 290 MPa. And the effective breaking energy γ was 4.0 kJ / m ² , indicating a metastable breaking behavior peculiar to the composite material in which the breaking did not take place until the complete breaking as in the above. In addition, SEM observation of the fracture surface also clearly confirmed that the BN layer was uniformly and soundly present on the surface of each single fiber as in the above, and that the fiber withdrawal was remarkable.

(Fifth Embodiment) In this embodiment, Si
A reaction-suppressing layer made of C was formed to a thickness of 2.5 μm by the CVI method, and otherwise the same process as in the second embodiment was used to obtain a ceramic-based fiber composite material. 5 ") was subjected to the same test as described above.

As a result, as shown in Example 5 in Table 1 below, the density of the obtained composite material was 3.0 g / cm ³ , the initial matrix breaking strength σ1 was 190 MPa, and the maximum strength σ2 was 300 MPa. And the effective fracture energy γ was 4.1 kJ / m ² , indicating a metastable fracture behavior peculiar to the composite material, in which the fracture did not reach the complete fracture at once. In addition, SEM observation of the fracture surface also clearly confirmed that the BN layer was uniformly and soundly present on the surface of each single fiber as in the above, and that the fiber withdrawal was remarkable.

(Sixth Embodiment) In this embodiment, the BN
Is formed by a CVI method to a thickness of 2.5 μm,
Otherwise, the same process as in the third embodiment was used to obtain a ceramic-based fiber composite material, and the cut test piece ("Example 6") was subjected to the same test as described above.

As a result, as shown in Example 6 in Table 1 below, the density of the obtained composite material was 3.0 g / cm ³ , the initial matrix breaking strength σ1 was 190 MPa, and the maximum strength σ2 was 320 MPa. And the effective fracture energy γ was 4.2 kJ / m ² , indicating a metastable fracture behavior peculiar to the composite material, in which the fracture did not reach the complete fracture at once. In addition, SEM observation of the fracture surface also clearly confirmed that the BN layer was uniformly and soundly present on the surface of each single fiber as in the above, and that the fiber withdrawal was remarkable.

(Other Embodiments) As other embodiments, 1): when the slip layer is made of a material containing at least one of B, N, Si, C and O other than BN,
2): When the reaction suppression layer is formed of Si ₃ N ₄ and when MoS
When configured with i _2, 3): If the sliding layer is formed by coating and heat treatment in the ceramic precursor,
4): The results were substantially the same for the case where the reaction suppression layer was coated by the CVI method and the case where the reaction suppression layer was formed by coating and heat treatment with a ceramic precursor.

Comparative Example 1 In Comparative Example 1, the thickness of the reaction suppressing layer made of SiC was set to 4 μm, and the other processes were the same as those in the first embodiment, that is, BN and SiC were used before the final preform was manufactured. Was coated on a fiber bundle, and a ceramic-based fiber composite material was obtained by reaction sintering using a step of weaving a plain woven cloth from the fiber bundle, and the cut-out test piece was subjected to the same test as described above.

As a result, as shown in Comparative Example 1 in Table 1 below, the density of the obtained composite material was 3.0 g / cm ³ , the initial matrix breaking strength σ1 was 280 MPa, and the maximum strength σ2 was The brittleness could not be confirmed and the effective breaking energy γ was 0.7 k
It was as small as J / m ^2, and the fracture was not instantaneous, but showed a more brittle fracture behavior. In addition, SE of the fracture surface
In the M observation, unlike the above examples, it was clearly observed that the BN layer disappeared in most places due to the reaction with the molten Si, and the fibers and the matrix were integrated at the disappeared places.

Comparative Example 2 In Comparative Example 2, the thickness of the slip layer made of BN was set to 4 μm, and the other processes were the same as those in the first embodiment, that is, BN and SiC were formed before the final preform was manufactured. A ceramic-based composite material was obtained by reaction sintering using a process of coating a fiber bundle and weaving a plain woven cloth from the fiber bundle, and the cut-out test piece was subjected to the same test as described above.

As a result, as shown in Comparative Example 2 in Table 1 below, the density of the obtained composite material was 3.0 g / cm ³ , the initial matrix breaking strength σ1 was 170 MPa, and the maximum strength σ2 was 180 MPa. The effective fracture energy γ was 1.7 kJ / m ² , and the fracture was not instantaneous as in Comparative Example 1, but showed a more brittle fracture behavior. Also, in SEM observation of the fractured surface, unlike the above examples, the situation where the BN layer disappeared in some places due to the reaction with the molten Si and the fiber and the matrix were integrated at the disappeared places was clearly seen. Admitted.

[0047]

[Table 1]

[0048]

As described above, according to the present invention, since the fiber bundle or the intermediate preform made of the fiber bundle is coated and the fiber surface is covered with the slip layer, the entire surface of the single fiber is coated with the slip layer. Can be uniformly coated, as a result, the reaction between the highly reactive Si and the composite fiber or the fiber coating material is more effectively suppressed, and the fiber and the coating layer are present in a healthy state in the matrix, and the slipping layer is formed. The effect can be exhibited more effectively. Therefore, it is possible to obtain a ceramic-based fiber composite material having a dense reaction sintered SiC having excellent oxidation resistance as a matrix without substantially deteriorating the characteristics of the fibers and the interface.

Claims (9)

[Claims] 1. A slip layer capable of bundling ceramic fibers into a fiber bundle and applying a coating treatment to the fiber bundle or an intermediate preform made of the fiber bundle so that the fiber surface can exhibit at least a fiber slip with respect to the matrix. To form a final preform from the fiber bundle or the intermediate preform, and then impregnating the final preform with a powder containing C and then impregnating with molten Si to cause reaction sintering. A method for producing a ceramic-based fiber composite material, wherein the fibers are compounded in a matrix containing SiC as a main phase. 2. The method according to claim 1, wherein the surface of the slip layer in at least one of the fiber bundle, the intermediate preform, and the final preform is coated with a reaction suppression layer that suppresses a reaction between the slip layer and a matrix. A method for producing a ceramic-based fiber composite material. 3. The method for producing a ceramic-based fiber composite material according to claim 1, wherein the slip layer is coated by a method of coating using a CVD method or a method of coating with a ceramic precursor and heat-treating. . 4. A method of coating the reaction suppressing layer by using a CVD method,
3. The method for producing a ceramic-based fiber composite material according to claim 2, wherein one of a method of coating using a method I and a method of coating with a ceramic precursor and heat-treating is used. 5. The material of the sliding layer is B, N, S
The method for producing a ceramic-based fiber composite material according to any one of claims 1 to 4, wherein a material containing at least one of i, C, and O is used. 6. A material for the reaction suppression layer, which is SiC,
5. The method according to claim ₂ , wherein at least one material selected from the group consisting of Si ₃ N ₄ and MoSi ₂ is used. 7. The method according to claim 1, wherein a thickness of the slip layer is 3 μm or less. 8. The method according to claim 2, wherein the thickness of the reaction suppression layer is 3 μm or less. 9. A matrix comprising SiC as a main phase formed by reaction sintering and ceramic fibers composited in the matrix, and at least at the interface between the fibers and the matrix, the fibers are formed with respect to the matrix. In the ceramic-based fiber composite material in which a slip layer capable of expressing slip exists, a fiber bundle obtained by bundling the fibers or an intermediate preform made of this fiber bundle is subjected to a coating treatment before the reaction sintering, so that a fiber surface is formed. By covering with a slip layer,
At the interface between the matrix and the fiber by the reaction sintering using the final preform formed from the fiber bundle or the intermediate preform, the slip layer is present uniformly covering the entire surface of the fiber with a predetermined thickness. A ceramic-based fiber composite material characterized in that: