JP3756583B2 - Ceramic-based fiber composite material and manufacturing method thereof - Google Patents

Description

【００４３】
なお、その他として、１）：すべり層として、ＢＮのほかにＢ、Ｎ、Ｃ、Ｓｉ、Ｏの少なくとも１種の材料からなるものを用いた場合、２）：製造方法として、セラミックスプリカーサを主成分としたスラリーを用いた場合と樹脂を主成分としたスラリーを用いた場合においても、上記と略同様の結果であった。
【００４４】
【発明の効果】
以上説明したように、この発明によれば、マトリックスは、その遊離Ｓｉ量が繊維束の内部とその近傍とで繊維束の外部よりも実質的に少ない組成を有しているため、反応焼結時に反応性が高い溶融Ｓｉと繊維又はすべり層との反応を繊維束の縁部近傍を含む内側でより有効に抑制でき、マトリックス中に繊維及びすべり層を健全な状態で存在させることができる。従って、耐酸化性に優れた緻密質な反応焼結ＳｉＣをマトリックスとするセラミックス基繊維複合材料を、繊維及び界面の特性を殆ど劣化させることなく取得できる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ceramic matrix fiber composite material and a method for producing the same, and more particularly to improvement of a composite material using dense silicon carbide (SiC) formed by a reactive sintering method as a matrix.
[0002]
[Prior art]
Generally, ceramic sintered bodies are less susceptible to strength reduction to high temperatures, and have superior properties such as hardness, electrical insulation, wear resistance, corrosion resistance, and light weight compared to conventional metal materials. It is used in a wide range of fields as electronic materials and structural materials such as heavy electrical equipment parts, aircraft parts, automobile parts, electronic equipment, precision machine parts, and semiconductor device materials.
[0003]
However, this ceramic sintered body is weaker in tensile stress than compressive stress, and has a drawback of so-called brittleness in which fracture proceeds at a stretch under this tensile stress. Depending on the application target, it is necessary to increase toughness and increase fracture energy. Such attempts to improve brittleness are strongly demanded when applied to ceramic structural parts such as gas turbine parts, aircraft parts, automobile parts and the like, which require particularly high reliability in addition to heat resistance and high temperature strength.
[0004]
Therefore, in response to such a request, as a ceramic sintered body with improved fracture toughness value, fracture energy value, thermal shock resistance, etc., composite materials such as fibers, whiskers, plates and particles made of inorganic substances and metals are matrixed. The ceramic matrix composite material formed by dispersing and compounding in the spotlight has attracted attention, and this practical research has been energetically promoted in domestic and foreign research institutions. In particular, when a fiber is composited to make a ceramic-based fiber composite material, since the effect of improving the fracture resistance is great, its practical application is expected.
[0005]
Among these ceramic-based fiber composite materials, composite materials using SiC as a matrix as a high-temperature material are particularly in the spotlight. As an example of a method for synthesizing the SiC matrix of this composite material, taking into account the heat resistance of the fiber, the CVI method (Chemical Vapor Infiltration), PC (Precursor) method, reaction firing, which have a relatively low synthesis temperature, are considered. Among them, a reactive sintering method for forming a dense SiC matrix has attracted attention as a typical example in which the initial fracture strength characteristics can be easily improved and high reliability can be obtained.
[0006]
On the other hand, in the ceramic-based fiber composite material as described above, it is an extremely important theme to appropriately control the bonding state at the interface between the matrix and the fiber in order to exert the fiber composite effect. . This is because if the fiber and the ceramic are firmly bonded, the combined effects such as bridging and pullout are not sufficiently exhibited, and brittle fracture is likely to occur. As a countermeasure, 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 slide against the matrix is known.
[0007]
[Problems to be solved by the invention]
However, the above-described sliding layer has a problem that, when the reaction sintering method is applied, the slip layer is deteriorated due to a reaction with the matrix forming material or the like, or decomposes and disappears. For example, when applying a reactive sintering method in which a preform formed of ceramic fibers is impregnated with molten Si to form a SiC matrix, the impregnated molten Si is highly reactive, so the slip layer or the fiber itself As a result, there may be a problem that the above-mentioned combined effect of fibers cannot be sufficiently exhibited.
[0008]
The present invention has been made in view of such conventional problems, and applies a reaction sintering method for forming a dense SiC matrix, and at least as a fiber coat layer formed at the interface between the matrix and the fibers. Targeting the presence of slip layers, the reaction between Si, which is highly reactive during sintering, and the fiber or slip layer is more effectively suppressed, and the fibers and slip layers are present in a healthy state in the resulting matrix. The purpose is to make it.
[0009]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present inventor has conducted various studies on a reaction suppression measure between molten Si having a high reactivity as a matrix forming material and a fiber or a sliding layer. In order to effectively prevent cracks caused by drying shrinkage, there is a restriction that the matrix composition must have almost zero drying shrinkage. Therefore, in the matrix after sintering, which becomes a bottleneck in terms of strength and heat resistance Attention was paid to the fact that this increased the chance of contact between molten Si and fibers during reaction sintering. An increase in the chance of contact between molten Si and fibers means that the reaction is more likely to proceed between the two.
[0010]
For this reason, a structure composed of fiber bundles for fibers to be combined is used as a measure for effectively suppressing the reaction between Si and fibers while containing a predetermined amount of free Si in the obtained matrix. However, the matrix portion between the inside and the vicinity of the fiber bundle has a drying shrinkage because the influence of the strength deterioration due to the cracks generated by the drying shrinkage is less than the matrix portion outside the fiber bundle. However, the present inventors have come up with the idea that it is effective to reduce the chance of contact between the fibers and the molten Si as a composition that reduces the residual free Si.
[0011]
That is, the present inventor can sufficiently prevent the deterioration of strength due to cracking due to drying shrinkage by allowing a predetermined amount of free Si to be contained in the matrix portion outside the fiber bundle, and the inside of the fiber bundle. Obtaining the knowledge that the reaction between molten Si impregnated at the time of reaction sintering and fibers, etc. can be effectively suppressed by making the composition of the free Si in the matrix portion in the vicinity thereof, and the following invention is completed. It came to.
[0012]
The ceramic-based fiber composite material according to the present invention comprises a matrix mainly composed of SiC formed by reactive sintering and ceramic fibers composited in the matrix, and at least the matrix is present at the interface between the fibers and the matrix. A ceramic-based fiber composite material in which a slip layer capable of expressing the slip of the fiber is present, wherein the fiber is a structure composed of fiber bundles, and the matrix has a free Si amount of is within the vicinity of the fiber bundle is in the range of 16 to 18 vol%, the outside of the fiber bundle in the range of 21 to 26 vol%, of the fiber bundle between the inside and the vicinity thereof of the fiber bundle It has a composition substantially smaller than that of the outside.
[0013]
The matrix desirably has a composition in which the amount of free Si outside the fiber bundle is smaller than 25% by volume. This is because when the amount of free Si outside the fiber bundle is 25% by volume or more, the ratio of Si to SiC increases and a decrease in strength is observed.
[0014]
More preferably, the matrix has a free b amount relative to a when the free Si amount inside and near the fiber bundle is a (volume%), and the free Si amount outside the fiber bundle is b (volume%). The ratio (b / a) of 1.25 shall be 1.25 or more. This is because the reaction suppression effect described above can be more reliably exhibited by adjusting the composition of the matrix with such an amount of free Si.
[0015]
The sliding layer is preferably made of a material containing at least one of B, N, Si, C, and O. For example, BN, C, etc. are desirable as components capable of developing slip, and SiC, SiO ₂ , Si ₃ N ₄ , amorphous components (Si—C—N—O compounds), etc. are used as components such as BN, C, etc. A combination of functions such as oxidation resistance may be used in combination.
[0016]
The ceramic-based fiber composite material can be manufactured using the following method.
[0017]
That is, in the method for producing a ceramic-based fiber composite material according to the present invention, a structure is formed with ceramic fibers, the structure is impregnated with a raw material for reactive sintering containing a C component, and then molten Si is impregnated. A method for producing a ceramic-based fiber composite material in which the fibers are combined in a matrix having SiC as a main phase by causing reaction sintering of the C component and molten Si, and after the reaction sintering As a method for controlling the amount of free Si in the matrix, a fiber bundle obtained by bundling the first reactive sintering raw material whose composition is adjusted in advance based on the residual amount of Si in the matrix before the reaction sintering. Then, the second reactive sintering raw material whose composition is adjusted in advance so that the residual amount of Si is larger than that of the first reactive sintering raw material is impregnated in and near the inside of the fiber bundle. Outside Characterized by using the method of impregnating.
[0018]
Further, as the first and second reaction sintering raw materials, preferably, a slurry mainly containing at least one of SiC powder, C powder, ceramic precursor, and resin is used.
[0019]
For example, when a slurry containing C powder is used, for example, two types of C powder having different particle sizes (particle size characteristics) are prepared, and a slurry containing a large amount of C powder having a small particle size is used as the first reaction sintering raw material. A slurry containing a large amount of C powder having a large particle size may be used as the second reaction sintering raw material.
[0020]
When a ceramic precursor (ceramic precursor) is used, a mixture of polycarbosilane and C powder is used as a first reaction sintering raw material, and a mixture of polycarbosilane, C powder and SiC powder is used as a second reaction. A raw material for sintering may be used.
[0021]
When the resin is used, the phenol resin may be used as the first reaction sintering material, and the mixture of the phenol resin and SiC powder may be used as the second reaction sintering material.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the ceramic-based fiber composite material and the manufacturing method thereof according to the present invention will be specifically described.
[0023]
In this embodiment, a fiber bundle (500 F / Y) of 500 SiC-ceramic fibers (manufactured by Nippon Carbon Co., Ltd., trade name: Hynicalon) having a diameter of 14 μm is used as the fiber, and BN is formed on the surface of the monofilament. Was prepared by forming a sliding layer having a predetermined thickness, and a plain woven cloth was woven from this fiber bundle.
[0024]
This plain weave cloth was immersed in the first slurry (slip) 1 and impregnated. As the first slurry 1, a mixture of granular carbon powder (30 wt%) having a center particle diameter of about 30 nm and pure water (65 wt%) and a surfactant (5 wt%) was used.
[0025]
Subsequently, the plain woven cloth is dried and laminated to form a preform, which is set in a porous resin mold (fiber volume ratio (Vf = 27%)) and impregnated with the second slurry (slip) 2. , Molded and dried to obtain a molded body. Here, as the second slurry 2, SiC powder (70 wt%) and granular carbon powder (30 wt%) having a central particle size of about 85 nm are used as solid contents, and pure water (47 wt%) is added to the solid contents (50 wt%). ) And a surfactant (3 wt%) were used.
[0026]
As described above, the two types of slurry are separately impregnated into the fiber bundle and the preform, so that depending on the C filling amount based on the particle size distribution and composition of the impregnated powder, A method of controlling the residual amount of Si between the inside (including the vicinity) and outside of the fiber bundle was used. Here, an increase in the C filling amount per unit volume of the void excluding the filling portion of the SiC powder means that the amount of Si remaining as unreacted during reaction sintering with molten Si is reduced.
[0027]
Therefore, the molded body produced by controlling the amount of residual Si as described above is brought into contact with Si molten metal (purity 99.9 wt%), heated to 1430 ° C. in vacuum for 5 hours, and melt impregnated to form a matrix. Then, a sintered ceramic composite material having a composition in which the amount of free Si in the matrix is less in the inside and in the vicinity of the fiber bundle than in the outside of the fiber bundle was obtained.
[0028]
Therefore, in this composite material, the reaction between the molten Si, which has high reactivity during reaction sintering, and the fiber or the slip layer is more effectively suppressed in and near the fiber bundle. It can exist in a healthy state.
[0029]
Next, in order to verify the characteristics of this ceramic matrix fiber composite material, the amount of free Si in the matrix is changed, and other than that, a plurality of ceramic matrix fiber composite materials are obtained by a manufacturing process substantially the same as described above. A test piece of size (“Examples 1 to 3”) was cut out and subjected to various tests shown in Table 1 below.
[0030]
Hereinafter, the characteristics of the ceramic-based fiber composite material of this embodiment will be described based on Table 1.
[0031]
Example 1
In Example 1, as shown in Table 1, the density of the obtained composite material is 3.0 g / cm ³ , the amount of free Si in the matrix (hereinafter, the inside and the vicinity of the fiber bundle is a, As for b), a was 16 vol%, b was 21 vol%, and the ratio (b / a) between them was 1.31.
[0032]
As for the room temperature three-point bending strength, the initial matrix breaking strength σ1 is 200 MPa and the maximum strength σ2 is 490 MPa. When the breaking energy is examined based on the load displacement curve of the three-point bending test, the effective breaking energy γ is 6.9 kJ. / M ² , and the fracture showed a stable fracture behavior peculiar to a composite material that does not reach a complete fracture at a stretch. Further, when the fracture surface was observed with an SEM (scanning electron microscope), it was clearly confirmed that the BN layer was present uniformly and soundly on the surface of each single fiber, and the fiber pullout was remarkable. It was.
[0033]
Example 2
In Example 2, as shown in Table 1, the density of the obtained composite material was 3.0 g / cm ^3. Regarding the amount of free Si in the matrix, a was 18 vol%, b was 21 vol%, both The ratio (b / a) was 1.17.
[0034]
As for the room temperature three-point bending strength, σ1 is 210 MPa, σ2 is 410 MPa, the effective fracture energy γ is 5.8 kJ / m ² , and the fracture does not reach a complete fracture at all. showed that. Further, SEM observation of the fracture surface clearly confirmed that the BN layer was present uniformly and soundly on the surface of each single fiber, and that the pull-out of the fiber was remarkable.
[0035]
Example 3
In Example 3, as shown in Table 1, the density of the obtained composite material is 3.0 g / cm ^3. Regarding the amount of free Si in the matrix, a is 17 vol%, b is 26 vol%, both The ratio (b / a) was 1.53.
[0036]
As for the room temperature three-point bending strength, σ1 is 200 MPa, σ2 is 440 MPa, the effective fracture energy γ is 6.1 kJ / m ² , and the fracture does not reach a complete fracture at all. showed that. Further, SEM observation of the fracture surface clearly confirmed that the BN layer was present uniformly and soundly on the surface of each single fiber, and that the pull-out of the fiber was remarkable.
[0037]
Comparative Example 1
In Comparative Example 1, the preform was impregnated with the second slurry without using the first slurry, and the ceramic matrix composite material was obtained by a manufacturing process substantially similar to the above for the others. A test similar to the above was performed on the piece.
[0038]
As a result, as shown in Table 1, the density of the obtained composite material was 3.0 g / cm ³ , and the amount of free Si in the matrix was 22 vol% for a and 21 vol% for b, and the ratio of both (B / a) was 0.95.
[0039]
As for the room temperature three-point bending strength, σ1 is 280 MPa, σ2 is 290 MPa, and the effective fracture energy γ is 3.6 kJ / m ² , which is smaller than those in each of the above examples. It showed brittle fracture behavior. Further, in the SEM observation of the fracture surface, it was clearly recognized that the BN layer disappeared at some locations due to the reaction with molten Si, and the fibers and the matrix were integrated at the disappeared locations.
[0040]
Comparative Example 2
In Comparative Example 2, b was set to 26 vol%, and the others were obtained by a manufacturing process substantially similar to that of Comparative Example 1 above, and a test was performed on this cut-out specimen. As a result, as shown in Table 1, the density of the obtained composite material was 3.0 g / cm ³ , and the amount of free Si in the matrix was 26 vol% for a and 26 vol% for b, and the ratio of the two (B / a) was 1.00.
[0041]
Regarding the room temperature three-point bending strength, σ1 is 290 MPa and σ2 is brittle when the maximum strength σ ₂ is brittle, and the effective fracture energy γ is 0.7 kJ / m ² , which is small compared to the above examples, Although not at a stretch, it showed more brittle fracture behavior. Further, in the SEM observation of the fracture surface, the situation where the BN layer disappeared in some places due to the reaction with molten Si in the same manner as in Comparative Example 1 above, and the situation where the fibers and the matrix were integrated at the disappeared places was clearly recognized. It was.
[0042]
[Table 1]

[0043]
In addition, 1): In the case of using at least one material of B, N, C, Si, O in addition to BN as the sliding layer, 2): The ceramic precursor is mainly used as the manufacturing method. The results were almost the same as above when the slurry as the component was used and when the slurry containing the resin as the main component was used.
[0044]
【The invention's effect】
As described above, according to the present invention, the matrix has a composition in which the amount of free Si is substantially less in the inside and in the vicinity of the fiber bundle than in the outside of the fiber bundle. At times, the reaction between molten Si having high reactivity and the fiber or the slip layer can be more effectively suppressed on the inside including the vicinity of the edge of the fiber bundle, and the fiber and the slip layer can be present in a healthy state in the matrix. Therefore, it is possible to obtain a ceramic-based fiber composite material having a dense reaction-sintered SiC excellent in oxidation resistance as a matrix without substantially deteriorating the properties of the fiber and the interface.

Claims (6)

It consists of a matrix mainly composed of SiC formed by reactive sintering and ceramic fibers compounded in this matrix.
A ceramic-based fiber composite material in which a slip layer capable of expressing at least the slip of the fiber with respect to the matrix exists at the interface between the fiber and the matrix,
The fiber is a structure composed of fiber bundles,
The amount of free Si in the matrix is in the range of 16 to 18 vol % inside and in the vicinity of the fiber bundle, and in the range of 21 to 26 vol% outside the fiber bundle ,
A ceramic-based fiber composite material characterized in that the inside and the vicinity of the fiber bundle have substantially less composition than the outside of the fiber bundle. The ceramic matrix fiber composite material according to claim 1, wherein the matrix has a composition in which the amount of free Si outside the fiber bundle is smaller than 25 vol % . The matrix has a ratio b of b to a where the amount of free Si inside and near the fiber bundle is a ( vol % ) and the amount of free Si outside the fiber bundle is b ( vol % ). The ceramic-based fiber composite material according to claim 1 or 2, wherein / a has a composition of 1.25 or more.   4. The ceramic-based fiber composite material according to claim 1, wherein the sliding layer is made of a material containing at least one of B, N, Si, C, and O. 5.   Forming a structure with ceramic fibers, impregnating the structure with a raw material for reaction sintering containing a C component, and then impregnating with molten Si to cause reaction sintering of the C component and molten Si Thus, a method for producing a ceramic-based fiber composite material in which the fibers are compounded in a matrix containing SiC as a main phase, and a method for controlling the amount of free Si in the matrix after the reaction sintering, The first reactive sintering raw material whose composition has been preliminarily adjusted based on the residual amount of Si in the matrix before being impregnated is impregnated in and near the fiber bundle in which the fibers are bundled, and then the first A method of impregnating the outside of the fiber bundle with a second reactive sintering raw material whose composition has been adjusted in advance so that the Si residual amount is larger than that of the reactive sintering raw material. Method of manufacturing the material.   6. The method for producing a ceramic-based fiber composite material according to claim 5, wherein a slurry containing at least one of SiC powder, C powder, ceramic precursor, and resin as a main component is used as the first and second reaction sintering raw materials. .