Ceramic matrix composite material and method of manufacturing the same

Abstract

To provide a ceramic matrix composite material (CMC) having a tensile strength of 150 MPa or over and high heat resistance of strength retention of the tensile strength after an extended period under a high temperature environment of 1,200°C for 100 hr of 80% or over.SOLUTION: A ceramic matrix composite material contains a ceramic matrix and a ceramic continuous fiber and contains a sinter retardant having an average particle diameter of 0.28 μm or over in the ceramic matrix.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to ceramic matrix composites and methods for making the same. [Background technology]

[0002] Ceramic matrix composites (hereinafter referred to as "CMCs"), which combine continuous ceramic fibers with a ceramic matrix, have higher resistance (damage tolerance) to the destruction of the entire material due to the progression of flaws than ordinary ceramics. For this reason, CMCs are being studied as a replacement for heat-resistant metals such as Ni-based alloys.

[0003] CMCs (hereinafter also referred to as "oxide-based CMCs"), which are made by using alumina or mullite-based oxides as continuous ceramic fibers and combining these continuous ceramic fibers with a ceramic matrix, have heat resistance up to 1200°C. For this reason, oxide-based CMCs are expected to be used as components for aircraft jet engines (see Non-Patent Document 1).

[0004] A known method for producing an oxide-based CMC is to impregnate continuous ceramic fibers with a slurry (hereinafter also referred to as "matrix slurry") in which raw ceramic matrix powder is dispersed in a solvent such as water, dry the slurry, and then sinter the resulting molded body at 1000°C or higher to obtain an oxide-based CMC (see Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] J.AerospaceLab,Issue3,(2011)1-12. [Non-patent document 2] J.Am.Ceram.Soc.,81[8],(1998)2077-86. [Non-patent document 3] Acta Mater.,47

[12] ,(1999)3411-3422 [Non-patent document 4] J.Euro.Ceram.Soc.,32,(2012)1965-1970 Summary of the Invention [Problem to be solved by the invention]

[0006] In general, when oxide-based CMCs are exposed to high temperatures of 1000°C or higher for long periods of time, the ceramic particles in the ceramic matrix (i.e., the ceramic particles that make up the ceramic matrix) undergo grain growth due to heat. This reduces the porosity of the ceramic matrix and causes adhesion between the ceramic matrix and the ceramic continuous fibers. As a result, the strength of the CMC decreases. Therefore, attempts have been made to suppress the grain growth of ceramic particles by adding magnesia or zirconia to the ceramic matrix as a sintering inhibitor (see Non-Patent Documents 3 and 4). However, the oxide-based CMCs obtained in these Non-Patent Documents all had low tensile strength and showed a significant decrease in strength when exposed to high-temperature environments.

[0007] An object of the present invention is to provide at least one of a ceramic composite material that has high tensile strength and is prevented from decreasing in strength after heat exposure treatment, and a method for producing the same. [Means for solving the problem]

[0008] The inventors attempted to incorporate a sintering inhibitor into the ceramic matrix raw materials and produced a CMC containing a ceramic matrix, continuous ceramic fibers, and a sintering inhibitor. As a result, they discovered a CMC that suppresses grain growth of ceramic particles in the ceramic matrix while resistant to loss of strength even when exposed to a high-temperature environment of 1200°C. Furthermore, they focused on the average particle size of the sintering inhibitor and discovered a CMC that maintains high strength by adjusting this, leading to the completion of the present invention.

[0009] That is, the present invention is as described in the claims, and the gist of the present disclosure is as follows. [1] A ceramic matrix composite material comprising a ceramic matrix and ceramic continuous fibers, and containing a sintering inhibitor having an average particle size of 0.28 μm or less in the ceramic matrix. [2] The ceramic matrix composite material according to the above [1], wherein the sintering inhibitor has an average distance between centers of gravity of 4.5 μm or less. [3] The ceramic matrix composite material according to the above [1] or [2], wherein the sintering inhibitor is at least one selected from the group consisting of silica, zirconia, yttria, magnesia, mullite, and strontium oxide. [4] A ceramic matrix composite according to any one of [1] to [3] above, wherein the ceramic continuous fibers are continuous fibers of one or more oxide ceramics selected from the group consisting of alumina, silica, mullite, and zirconia. [5] A ceramic matrix composite according to any one of [1] to [4] above, wherein the ceramic matrix is ​​one or more oxides selected from the group consisting of alumina, mullite, and zirconia. [6] A ceramic matrix composite material according to any one of [1] to [5] above, characterized in that it has a tensile strength of 150 MPa or more and a strength retention rate of 80% or more after heat exposure treatment at 1200°C for 100 hours. [7] A method for producing a ceramic matrix composite material according to any one of [1] to [6] above, which comprises impregnating continuous ceramic fibers with a ceramic matrix slurry prepared by adding a sintering inhibitor having a purity of 99% or more to a ceramic matrix raw material powder, drying the slurry, and sintering the resulting molded body. [8] The method for producing a ceramic matrix composite material according to [7] above, wherein the average particle size of the sintering inhibitor is more than 0.05 μm and not more than 30 μm. [Effects of the Invention]

[0010] The ceramic matrix composite material of the present invention achieves the objective of providing at least one of a ceramic composite material having a high tensile strength of 150 MPa or more and suppressing a decrease in strength after heat exposure treatment, for example, a ceramic composite material having a strength retention rate of 80% or more after heat exposure treatment at 1200°C for 100 hours and suppressing a decrease in strength, and a method for producing the same. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a graph showing the relationship between the average particle size of silica in the ceramic matrix and the tensile strength of the ceramic matrix composite materials of Examples 1 to 3 and Comparative Examples 1 and 2. [Figure 2] FIG. 2 is a graph showing the relationship between the tensile strength of the ceramic matrix composite materials and the average distance between the centers of gravity of silica particles in the ceramic matrix of Examples 1 to 3 and Comparative Examples 1 and 2. [Figure 3] FIG. 3 is a silicon mapping image of the sample of Example 1 taken at 5000x magnification. [Figure 4] FIG. 4 is a silicon mapping image of the sample of Comparative Example 1 taken at 5000x magnification. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described below.

[0013] In this specification, a "ceramic matrix composite" (CMC) is a material in which ceramic continuous fibers and a ceramic matrix are combined, and is a so-called ceramic fiber reinforced ceramic.

[0014] In this specification, "ceramic fiber" refers to spun polycrystalline ceramics, and further to filamentous polycrystalline ceramics. Ceramic fibers are classified into "ceramic short fibers" and "ceramic continuous fibers" depending on their fiber length. In this embodiment, "ceramic short fibers" refer to ceramic fibers with a fiber length of less than 500 μm, and "ceramic continuous fibers" refer to ceramic fibers other than ceramic short fibers (ceramic fibers with a fiber length of 500 μm or more). Furthermore, ceramic fibers may be an independent fiber, a ceramic fiber in a state where multiple fibers are aggregated, or even a fiber bundle. In this specification, a "fiber bundle" refers to a fiber in a state where two or more ceramic fibers are aggregated, or may be a fiber in a state where several hundred ceramic fibers are aggregated. A "ceramic fiber cloth" refers to a woven fabric of ceramic fibers, particularly a woven fabric of continuous ceramic fibers. It may also be a woven fabric of continuous ceramic fibers in fiber bundles.

[0015] In this specification, the term "ceramic matrix" refers to the matrix (parent phase) of a CMC composed of ceramic crystal particles, and may contain a sintering inhibitor.

[0016] In this specification, the term "sintering inhibitor" refers to a substance that has the function of inhibiting the grain growth of ceramic crystal particles during heat treatment.

[0017] The present invention relates to a CMC comprising a ceramic matrix (hereinafter simply referred to as "matrix") and ceramic continuous fibers (hereinafter simply referred to as "continuous fibers"), characterized in that the matrix contains a sintering inhibitor (hereinafter also referred to as "inhibitor") having an average particle size of 0.28 μm or less. That is, the CMC of the present invention is essentially a CMC consisting of a matrix, continuous fibers, and an inhibitor, and the inhibitor is contained in the matrix. The CMC is further characterized in that the matrix contains an inhibitor having a specific average particle size. If the average particle size of the inhibitor is higher than this value, the inhibitor will become coarse particles in the matrix. This may cause the inhibitor to become a source of fracture of the CMC.

[0018] The CMC of the present invention has an average particle size of the inhibitor (hereinafter also referred to as "average inhibitor particle size") of 0.28 μm or less. If the average inhibitor particle size exceeds 0.28 μm, the tensile strength of the CMC tends to decrease. The average inhibitor particle size is preferably 0.05 μm or more, 0.08 μm or more, or 0.10 μm or more, and 0.28 μm or less, or 0.26 μm or less. If the average inhibitor particle size is 0.05 μm or more, matrix grain growth (i.e., grain growth of the ceramic crystal grains that make up the matrix) is easily suppressed.

[0019] The average inhibitor particle size is the average particle size of the inhibitor. In the CMC of the present invention, the inhibitor is present in the matrix. Therefore, in the cross section of the CMC, the matrix is ​​observed using a field emission scanning electron microscope (hereinafter also referred to as "FE-SEM") equipped with an energy dispersive characteristic X-ray analyzer to obtain EDS mapping data of the elements corresponding to the inhibitor, and the data is converted into a two-dimensional EDS mapping image. The obtained two-dimensional EDS mapping image is then analyzed to obtain the average inhibitor particle size.

[0020] FE-SEM observation is performed using a general field emission scanning microscope equipped with an energy dispersive characteristic X-ray analyzer (for example, JSM-7600F, manufactured by JEOL Ltd.) The following conditions can be given as examples of conditions for FE-SEM observation. Accelerating voltage: 7 kV Observation magnification: 5000x

[0021] The measurement sample can be prepared by cutting the CMC with a diamond blade and preparing an observation surface using an Ar beam cross-section polisher.

[0022] The EDS mapping data can be converted into a two-dimensional EDS mapping image using image analysis software (e.g., ImageJ, manufactured by the National Institutes of Health, USA). Specifically, the EDS mapping data can be imported into the image analysis software and converted into a 256 × 192 pixel two-dimensional EDS mapping image.

[0023] Image analysis of the two-dimensional EDS mapping image can be performed using image analysis software (e.g., ImageJ, manufactured by the National Institutes of Health, USA). The two-dimensional EDS mapping image is imported into the image analysis software in grayscale. The grayscale image is binarized using 8-bit and a threshold value of 50 to obtain a processed image. Since the white areas in the processed image correspond to the inhibitor, the area-equivalent diameter of each white area in the processed image is calculated, and the average value is used to calculate the average particle diameter of the inhibitor. The number of inhibitors (white areas) used for the calculation can be 150±50.

[0024] In the CMC of the present invention, the average distance between the centers of gravity of the inhibitor is preferably 4.5 μm or less. More preferably, it is 0.01 to 4.0 μm, and even more preferably, it is 0.03 to 3.5 μm. When the average distance between the centers of gravity is 4.5 μm or less, the inhibitor is easily dispersed and present in the matrix. Furthermore, when the CMC is subjected to a heat exposure treatment, defects due to the inhibitor are less likely to occur.

[0025] The average distance between centers of gravity is calculated by analyzing the centers of gravity of the inhibitors from the matrix mapping image (a two-dimensional EDS mapping image obtained by converting EDS mapping data using image analysis software (e.g., ImageJ, manufactured by the National Institutes of Health)), connecting the centers of gravity with straight lines according to the following criteria (a) and (b), and then calculating the average length of the line segments.

[0026] (a) Connect the obtained center of gravity points with a straight line, and make sure that the line does not pass through any other particles.

[0027] (b) If the line segment connecting the center of gravity intersects with another line segment, use the shorter one.

[0028] The average distance between the centers of gravity obtained by this analysis indicates how far apart the inhibitors are located in the matrix. The larger the average distance between the centers of gravity, the weaker the inhibitor's effect in inhibiting sintering of the matrix.

[0029] The average distance between the centers of gravity can be calculated using image analysis software Nanohunter (product name: NS2K-PRO, manufactured by NanoSystems).

[0030] Specifically, the average center-of-gravity distance in the present invention can be determined by the following method: observing the matrix of a cross section of the CMC using an FE-SEM to obtain an EDS mapping image of the elements corresponding to the inhibitor, and then analyzing the image.

[0031] Using a processed image obtained in the same manner as for the average inhibitor particle size, the coordinates of the center of gravity of each white area in the processed image are determined by the following method.

[0032] The coordinates of the center of gravity of the white area are (Xg, Yg), and the coordinates of the center of gravity of each white area are calculated using the following formula: The long side of the processed image is taken as the X axis, and the short side is taken as the Y axis.

[0033] Xg = (the sum of the x coordinate values ​​of each unit pixel when the white area is divided) ÷ the sum of the number of unit pixels that make up the white area Yg = (the sum of the y coordinate values ​​of each unit pixel when the white area is divided) ÷ the sum of the number of unit pixels that make up the white area The centroids of different white regions are connected by straight lines according to the above criteria (a) and (b), and the average length of the resulting line segments is calculated and used as the average distance between centroids.

[0034] The coordinates of the center of gravity, the length of the line segment, and the average value can be calculated using image analysis software (e.g., NS2K-PRO, manufactured by Nano Systems). The number of inhibitors used for the calculation can be 150 ± 50.

[0035] The inhibitor may have a composition different from that of the matrix, and may be, for example, one or more selected from the group consisting of silica, zirconia, yttria, magnesia, mullite, and strontium oxide. Preferably, the inhibitor is one or more selected from the group consisting of silica, zirconia, yttria, magnesia, and mullite, and silica is particularly preferred.

[0036] The content of the inhibitor (hereinafter also referred to as "matrix inhibitor amount") is preferably 1% by mass or more and 10% by mass or less, more preferably 1.1% by mass or more and 9% by mass or less, and even more preferably 1.5% by mass or more and 6.5% by mass or less, based on the total mass of the matrix and inhibitor. On the other hand, since defects resulting from the inhibitor tend to be reduced, the amount of the matrix inhibitor is preferably 0.3% by mass or more or 0.4% by mass or more, and less than 5.0% by mass or 4.0% by mass or less.

[0037] The CMC of the present invention can be exemplified by a CMC in which the mass ratio of the inhibitor to the mass of the CMC (hereinafter also referred to as "CMC inhibitor amount") is 0.4 mass% or more, or 0.6 mass% or more, and 4.3 mass% or less, or 2.8 mass% or less. On the other hand, since defects resulting from the inhibitor tend to be reduced, the CMC inhibitor amount is preferably 0.1 mass% or more, or 0.2 mass% or more, and 3.0 mass% or less, or 2.5 mass% or less.

[0038] In the present invention, the mass of the CMC is the total mass of the matrix, the inhibitor, and the continuous fibers.

[0039] For example, in a CMC containing silica as an inhibitor and an alumina matrix, the amount of CMC inhibitor can be calculated by {(mass of silica [g]) / (mass of silica + mass of alumina + mass of continuous fiber) [g]} x 100. The amount of matrix inhibitor can also be calculated by {(mass of silica [g]) / (mass of silica + mass of alumina) [g]} x 100.

[0040] The CMC of the present invention preferably contains at least silica (SiO2) as an inhibitor. When silica is contained as an inhibitor, the grain growth of the matrix is ​​easily inhibited, and a CMC with higher heat resistance is easily obtained. In particular, when the matrix is ​​alumina, the effect of inhibiting the grain growth of the matrix is ​​more easily obtained.

[0041] The silica content (hereinafter also referred to as "CMC silica amount") is preferably 0.4 mass% or more or 0.6 mass% or more, and preferably 4.3 mass% or less or 2.8 mass% or less, relative to the mass of the CMC. On the other hand, since defects derived from silica tend to be reduced, it is preferably 0.1 mass% or more or 0.2 mass% or more and 3.0 mass% or less or 2.5 mass% or less. When the CMC silica amount is 0.1 mass% or more, matrix grain growth is more easily suppressed. On the other hand, when the CMC silica amount is 4.3 mass% or less, the ceramic continuous fiber and matrix are less likely to adhere to each other, and defects due to silica dissolution in the CMC are less likely to occur even when subjected to heat exposure treatment.

[0042] The matrix is ​​at least one of an oxide ceramic and a non-oxide ceramic, preferably an oxide ceramic, more preferably one or more selected from the group consisting of alumina, mullite, and zirconia, and even more preferably at least one of alumina and mullite.

[0043] Considering high heat resistance, the matrix is, for example, one or more oxides selected from the group consisting of alumina, mullite, and zirconia, and alumina is preferred from the viewpoint of higher heat resistance and strength.

[0044] The continuous fibers are not particularly limited as long as they are made of ceramics. However, they are preferably oxide ceramics, and further, continuous fibers of oxide ceramics of at least one selected from the group consisting of alumina, silica, mullite, and zirconia, or at least one of alumina and mullite, or even alumina and / or mullite. The ceramic continuous fibers may be continuous fibers made of the same type of ceramic as the matrix, or continuous fibers made of a different type of ceramic from the matrix. Here, continuous fibers refer to fibers that can be used at any length and can be woven into two-dimensional or three-dimensional structures. Generally, when producing CMCs, fibers in a state where several hundred fibers are aggregated are used as ceramic continuous fibers. The ceramic continuous fibers of this embodiment are preferably in the form of fiber bundles or woven fiber bundles, and are preferably ceramic continuous fibers in a woven fiber bundle state (hereinafter also referred to as "ceramic fiber cloth"). The oxide ceramic continuous fibers can be, for example, alumina continuous fibers, mullite continuous fibers, etc., and more preferably mullite continuous fibers. From the viewpoint of strength, the continuous fibers are preferably alumina continuous fibers. On the other hand, from the viewpoint of heat resistance, the continuous fibers are preferably mullite continuous fibers. The mullite continuous fibers may be continuous fibers made of mullite and alumina, or may contain alumina. An example of the continuous fibers made of mullite and alumina is continuous fibers in which the mass ratio of mullite (3Al2O3·2SiO2):alumina (Al2O3) is 70 mass%:30 mass% to 45 mass%:55 mass%.

[0045] The CMC of the present invention has high strength, and its tensile strength (particularly, the tensile strength of the CMC before thermal exposure treatment) is preferably 150 MPa or more, more preferably 150 to 700 MPa, and particularly preferably 150 to 650 MPa. The CMC of the present invention is also characterized in that its strength does not decrease even when exposed to a high-temperature environment of 1200°C. Therefore, the CMC of the present invention preferably has a strength retention rate (hereinafter simply referred to as "strength retention rate") of 80% or more, more preferably 85% or more, and even more preferably 90% or more after thermal exposure treatment at 1200°C for 100 hours. The strength retention rate of the CMC of the present invention can be, for example, 120% or less, 115% or less, or 105% or less. The tensile strength of the CMC of this embodiment after thermal exposure treatment may be higher than the tensile strength before thermal exposure treatment.

[0046] The tensile strength is a value determined using a strength tester (e.g., AG-XPlus, manufactured by Shimadzu Corporation) and a tensile test jig according to a method conforming to JIS R 1656. A measurement sample is prepared by processing a CMC into a width of 10±1 mm, a length of 110±10 mm, and a thickness of 2±1 mm, with aluminum tabs attached to both ends to form a tensile test piece. The tensile strength is measured twice at a loading rate of 0.5 mm / min, and the average value is used as the tensile strength of the CMC.

[0047] The heat exposure treatment can be exemplified by a method in which the CMC is heat-treated in the air at 1200° C. for 100 hours.

[0048] The fiber volume fraction of the CMC of the present invention is 30 vol% or more and 60 vol% or less. When the fiber volume fraction satisfies this range, the ceramic continuous fibers are appropriately present in the CMC and the shape of the CMC is easily maintained, making it easier to obtain a CMC with high strength.

[0049] The fiber volume fraction is the volume fraction of continuous fibers in the CMC [vol%]. It can be calculated using the following formula:

[0050] Fiber volume fraction [vol%] = (V f / V CMC ) x 100 In the above equation, V f is the volume of the continuous fiber, and V CMC is the volume of the CMC. Also, V f and V CMC are calculated from the following formulas, respectively. V f = m / ρ f V cmc = A×B×t

[0051] In the above formula, m is the mass of the continuous fiber [g] and ρ f is the density of the continuous fiber [g / cm 3 ], where A is the length of the CMC [cm], B is the width of the CMC [cm], and t is the thickness of the CMC [cm].

[0052] The density of the CMC of the present invention varies depending on the type of matrix, etc., but is, for example, 2.40 g / cm 3 More than 3.20g / cm 3 The following points can be mentioned.

[0053] The density is the measured density of the CMC [g / cm 3 ], and the ratio of the volume measured by the Archimedes method to the mass measured using an electronic balance according to JIS R 1634 [g / cm 3 ] is the value obtained from

[0054] The CMC of this embodiment can be used for known CMC applications, and can be used for components containing the CMC, particularly for applications requiring heat resistance, and can also be used for one or more applications selected from the group consisting of heat-resistant filters, turbine components, and nuclear-related components. Next, a method for producing the CMC of the present invention will be described.

[0055] Any manufacturing method can be used as long as a CMC having the above-mentioned characteristics can be obtained. The CMC of the present invention can be manufactured by impregnating continuous ceramic fibers with a ceramic matrix slurry prepared by adding a sintering inhibitor with a purity of 99% or higher to a ceramic matrix raw material powder, drying the resulting molded body, and sintering the resulting molded body.

[0056] A specific example of a method for producing a CMC of the present invention is a method for producing a ceramic matrix composite material, comprising the steps of: impregnating continuous ceramic fibers with a slurry containing a ceramic matrix raw material powder, a sintering inhibitor having an average particle size of more than 0.05 μm and not more than 30 μm, and a solvent to obtain a mixture, solidifying the mixture to obtain a green body, and sintering the green body.A specific example of a method for producing a CMC of the present invention is a method for producing a ceramic matrix composite material, comprising the steps of: impregnating continuous ceramic fibers with a slurry containing a ceramic matrix raw material powder, a sintering inhibitor having an average particle size of more than 0.05 μm and not more than 30 μm and a purity of 99%, and a solvent to obtain a mixture, solidifying the mixture to obtain a green body, and sintering the green body.

[0057] By impregnating continuous ceramic fibers with a slurry containing a ceramic matrix raw material powder, a sintering inhibitor having an average particle size of more than 0.05 μm and not more than 30 μm, and a solvent (hereinafter also referred to as the "impregnation process"), a composition in which the precursors of the matrix and inhibitor have diffused and infiltrated into the continuous ceramic fibers (continuous fibers), i.e., a mixture of matrix slurry and continuous fibers, is obtained.

[0058] The slurry containing ceramic matrix raw material powder, a sintering inhibitor having an average particle size of more than 0.05 μm and not more than 30 μm, and a solvent (hereinafter referred to as the "matrix slurry," and the sintering inhibitor contained in the matrix slurry is conveniently referred to as the "inhibitor source") only needs to have fluidity that allows it to be impregnated into continuous fibers. The viscosity of the matrix slurry may be, for example, 1 mPa·s or more or 5 mPa·s or more, and 500 mPa·s or less or 400 mPa·s or less. The viscosity of the matrix slurry is easily affected by the average particle size of the ceramic matrix raw material powder, the average particle size of the inhibitor source, and the content of the inhibitor source. In rare cases, it may also be affected by the content of adsorbed water in the ceramic matrix raw material powder and the inhibitor source.

[0059] Ceramic matrix raw material powder (hereinafter simply referred to as "raw material powder") is a powder that serves as the raw material for the matrix of a CMC, i.e., a precursor of the matrix. The raw material powder may be selected arbitrarily depending on the type of matrix of the target CMC, and may include, for example, oxide powder, one or more selected from the group consisting of alumina powder, mullite powder, zirconia powder, and silica powder, or at least one of alumina powder and mullite powder, or even alumina powder. Further, the raw material powder may include α-alumina powder, mullite powder, zirconia powder, or a composite powder thereof, and preferably contains at least α-alumina powder, and preferably is α-alumina powder.

[0060] The average particle size of the raw material powder (hereinafter also referred to as "raw material particle size") is preferably 0.1 μm or more and 5 μm or less, more preferably 0.1 μm or more and 2.0 μm or less, and even more preferably 0.1 μm or more and 0.5 μm or less. When the raw material particle size satisfies this range, the raw material powder tends to be uniformly dispersed around the continuous fibers.

[0061] The raw material particle size is the median diameter (D50) in the volume particle size distribution of the raw material powder measured by a wet method, and can be measured using a common device (e.g., MT3300EX-II, manufactured by Microtrackbell). The measurement sample can be a slurry in which the raw material powder is dispersed in pure water, and slow agglomerates are removed by a dispersion treatment such as ultrasonic treatment.

[0062] The content of the raw material powder in the matrix slurry (hereinafter also referred to as "solid content concentration") is preferably 50% by mass or more and 80% by mass or less, and more preferably 60% by mass or more and 80% by mass or less.

[0063] The solid content concentration is a mass concentration obtained by the ratio [mass %] of the total mass of the raw material powder and the inhibitor source to the total mass of the raw material powder, the inhibitor source, and the solvent.

[0064] Furthermore, the volume ratio of the raw material powder to the volume of the matrix slurry at 25°C and atmospheric pressure (hereinafter also referred to as "volume solid concentration") is preferably 20 vol% or more and 55 vol% or less, and more preferably 28 vol% or more and 55 vol% or less.

[0065] For example, in the case of a matrix slurry in which the raw material powder is alumina powder, the inhibitor source is silica, and the solvent is water, the solids concentration is {(mass of alumina powder [g] + mass of silica [g]) / (mass of silica + mass of alumina powder + mass of water) [g]} × 100, and the volumetric solids concentration is {(volume of alumina [cm 3 ] + volume of silica [cm 3 ]) / (volume of silica + volume of alumina + volume of water) [cm 3 ]} × 100. When calculating the volumetric solid concentration, the density at 25°C and atmospheric pressure can be used.

[0066] The solid content concentration can also be determined as the mass ratio of the remainder after drying the solvent of the matrix slurry to the mass of the matrix slurry.

[0067] The inhibitor source may be at least one of the same compound as the inhibitor contained in the CMC and its precursor, or may be a precursor of the inhibitor contained in the CMC. The inhibitor source may be a compound having a different composition from the raw material powder, such as at least one selected from the group consisting of silica, zirconia, yttria, magnesia, and mullite, or at least one selected from the group consisting of silica, zirconia, yttria, magnesia, and mullite, or at least one of silica and zirconia. Preferably, the inhibitor source contains at least silica, and more preferably silica.

[0068] The inhibitor source may be in any state that allows it to be mixed with the raw material powder, and is preferably at least one of powder and colloidal particles, more preferably powder.

[0069] The average particle diameter of the inhibitor source (hereinafter also referred to as "average inhibitor source particle diameter") is preferably more than 0.05 μm and not more than 30 μm. The average inhibitor source particle diameter is 30 μm or less, and preferably 10 μm or less, 5 μm or less, 1 μm or less, 0.8 μm or less, or 0.5 μm or less. If the average inhibitor source particle diameter exceeds 30 μm, coarse particles of the inhibitor are likely to be generated in the obtained CMC. The average inhibitor source particle diameter is 0.01 μm or more, and preferably 0.05 μm or more, 0.08 μm or more, 0.1 μm or more, or 0.2 μm or more. Preferred ranges of the average inhibitor source particle diameter include 0.06 μm or more and 10 μm or less, further 0.06 μm or more and 1 μm or less, and even further 0.08 μm or more and 0.5 μm or less. When the average inhibitor source particle diameter satisfies this range, the inhibitor source is less likely to aggregate in the matrix slurry. Furthermore, the resulting CMC is more likely to have the inhibitor dispersed uniformly throughout the matrix, which is believed to make it easier to meet the average inhibitor particle size requirement of the CMC of the present invention after sintering.

[0070] The average particle size of the inhibitor source may be measured in the same manner as the particle size of the raw material.

[0071] The purity of the inhibitor source is preferably high, preferably 99% or more, but may be up to or less than 100%.

[0072] The content of the inhibitor source in the matrix slurry may be the same as the content of the inhibitor in the target CMC. The content of the inhibitor source in the matrix slurry is, for example, preferably 0.3% by mass or more and 10% by mass or less, more preferably 0.4% by mass or more and 9% by mass or less, and even more preferably 0.5% by mass or more and 7% by mass or less, as a ratio of the mass of the inhibitor source to the total mass of the raw material powder and the inhibitor source (hereinafter also referred to as the "inhibitor source amount," or when the inhibitor is silica or the like, also referred to as the "silica source amount" or the like).

[0073] Furthermore, the mass ratio of the inhibitor source (hereinafter also referred to as "inhibitor source amount (slurry)") to the mass of the matrix slurry (i.e., the total mass of the raw material powder, inhibitor source, and solvent) can be, for example, 0.2 mass% or more, or 0.3 mass% or more, and 8 mass% or less, or 7 mass% or less.

[0074] For example, in a matrix slurry in which the matrix powder is alumina, the inhibitor source is silica, and the solvent is water, the amount of the inhibitor source can be calculated from {(mass of silica [g]) / (mass of silica + mass of alumina) [g]} × 100, and the amount of the inhibitor source (slurry) can be calculated from {(mass of silica [g]) / (mass of silica + mass of alumina + mass of water) [g]} × 100, respectively.

[0075] Furthermore, the mass ratio of the raw material powder (hereinafter also referred to as "raw material powder amount (slurry)") to the mass of the matrix slurry (i.e., the total mass of the raw material powder, inhibitor source, and solvent) can be, for example, 45 mass% or more or 55 mass% or more, and 80 mass% or less or 75 mass% or less.

[0076] For example, in a matrix slurry in which the matrix powder is alumina, the inhibitor source is silica, and the solvent is water, the amount of raw material powder (slurry) can be calculated by {(mass of alumina [g]) / (mass of silica + mass of alumina + mass of water) [g]} × 100.

[0077] Examples of the solvent contained in the matrix slurry include water, one or more alcohols selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, butyl alcohol, and isobutyl alcohol; one or more ketones selected from the group consisting of acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, and diacetone alcohol; one or more aromatic hydrocarbons selected from the group consisting of benzene, toluene, and xylene; one or more esters selected from the group consisting of ethyl acetate, methyl acetate, butyl acetate, methoxybutyl acetate, and isobutyl acetate; one or more aliphatic hydrocarbons selected from the group consisting of normal hexane, heptane, cyclohexane, and methylcyclohexane; one or more glycol ethers selected from the group consisting of ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and propylene glycol monomethyl ether; and one or more selected from the group consisting of N,N-dimethylformamide, tetrahydrofuran, N-methyl-2-pyrrolidone, 1,4-dioxane, and styrene. The solvent is preferably at least one of water and alcohol, and more preferably water.

[0078] In the manufacturing method of the present invention, any manufacturing method for the matrix slurry to be subjected to the impregnation step can be used, as long as the slurry is in a dispersed state of the raw material powder and the inhibitor source. The manufacturing method for the matrix slurry can be any method as long as the raw material powder, the inhibitor source, and the solvent are mixed. However, it is preferable to obtain the matrix slurry by pulverization and mixing. Specifically, the raw material powder, the inhibitor source, and the solvent are mixed and then pulverized in a ball mill. The balls used in the ball mill may be any balls capable of removing slow aggregation of the raw material powder, and may be ceramic balls larger than the average particle size of the raw material powder, etc. Examples of such balls include ceramic balls with a diameter of 0.5 mm to 20 mm, and even 1 mm to 15 mm. The ceramic balls may be at least one of alumina balls and zirconia balls, and may further be alumina balls.

[0079] The matrix slurry may contain a dispersant to disperse the raw material powder and the inhibitor source uniformly in the solvent. Examples of the dispersant include at least one of a dispersant having high affinity with the raw material powder and a dispersant having high solubility in the solvent, and examples thereof include one or more selected from the group consisting of anionic polymer dispersants, cationic polymer dispersants, nonionic polymer dispersants, anionic low-molecular-weight dispersants, cationic low-molecular-weight dispersants, nonionic low-molecular-weight dispersants, inorganic acids, and inorganic salts. Specific dispersants include, preferably, one or more selected from the group consisting of ammonium polyacrylate, ammonium polymethacrylate, sodium polyacrylate, sodium polymethacrylate, polyethyleneimine, polyethylene glycol, sodium dodecyl sulfonate, sodium dodecylbenzenesulfonate, benzalkonium chloride, distearyldimethylammonium chloride, polyoxyethylene alkyl ether, pentaethylene glycol monododecyl ether, octaethylene glycol monododecyl ether, polyoxyethylene alkyl phenyl ether, dilute nitric acid, dilute hydrochloric acid, dilute sulfuric acid, phosphoric acid, and sodium tripolyphosphate; more preferably, one or more selected from the group consisting of ammonium polyacrylate, ammonium polymethacrylate, sodium polyacrylate, sodium polymethacrylate, polyethyleneimine, dilute nitric acid, dilute hydrochloric acid, dilute sulfuric acid, and phosphoric acid; even more preferably, one or more selected from the group consisting of ammonium polyacrylate, ammonium polymethacrylate, dilute nitric acid, and dilute hydrochloric acid; and even more preferably, at least one of dilute nitric acid and dilute hydrochloric acid.

[0080] The content of the dispersant can be, for example, 0.01 mass% or more or 0.05 mass% or more, and 10 mass% or less or 8 mass% or less, relative to the mass of the matrix slurry (i.e., the total mass of the raw material powder, inhibitor source, solvent, and dispersant).

[0081] Examples of the ceramic continuous fibers to be impregnated into the matrix slurry include alumina continuous fibers, mullite continuous fibers, etc. Alumina-mullite continuous fibers, that is, continuous fibers made of alumina and mullite, are preferred.

[0082] The ceramic continuous fibers subjected to the impregnation step may be the same as the ceramic continuous fibers contained in the CMC, and are preferably continuous fibers of one or more types selected from the group consisting of alumina, silica, mullite, and zirconia, and more preferably continuous fibers of at least one of alumina and mullite.

[0083] The impregnation step produces a mixture of matrix slurry and continuous fibers. The impregnation method may be any method that allows the matrix slurry to diffuse into and infiltrate the continuous fibers, and examples of the method include at least one of vacuum impregnation and pressure impregnation.

[0084] The vacuum impregnation treatment may be carried out under the following conditions. Impregnation atmosphere: Vacuum degree 85% or more or vacuum degree 90% or more, and Vacuum degree 100% or less, vacuum degree less than 100%, or vacuum degree 99% or less Impregnation temperature: 0°C or higher or 10°C or higher, and Below 40℃ or below 35℃

[0085] The pressure impregnation treatment may be carried out under the following conditions. Impregnation pressure: 0.11 MPa or more or 0.15 MPa or more, and 2.0MPa or less or 1.8MPa or less Impregnation temperature: 0°C or higher or 10°C or higher, and Below 40℃ or below 35℃

[0086] A specific example of the impregnation method is to impregnate the continuous fibers into the matrix slurry at 25° C. under a vacuum of 95% or more but less than 100%.

[0087] The manufacturing method of this embodiment includes a step of solidifying the mixture to obtain a molded body (hereinafter also referred to as the "molding step"). This results in a molded body that serves as a precursor to the CMC of this embodiment. The molding method may be any method that solidifies the mixture and thereby obtains a mixture (molded body) having a specific shape, and examples of the molding method include one or more methods selected from the group consisting of heat treatment, freezing treatment, and additive treatment. Note that the molding step may be a combination of the above methods, or similar treatments may be performed multiple times.

[0088] The heat treatment may be carried out under the following conditions. Heat treatment temperature: 50°C or higher, 60°C or higher, or 80°C or higher, and 160℃ or less or 140℃ or less Number of heat treatments: 1 to 5

[0089] The heat treatment time can be adjusted as desired depending on the amount of the mixture to be treated and the heat treatment temperature, and can be, for example, from 1 hour to 10 hours, or from 2 hours to 8 hours.

[0090] The freezing treatment may be carried out under the following conditions. Freezing temperature: -200°C or higher or -180°C or higher, and -20℃ or below or -30℃ or below Sublimation pressure: 0.001 MPa or more or 0.002 MPa or more, and 0.05MPa or less or 0.03MPa or less Number of times of processing: 1 to 5 times

[0091] When the freezing treatment is carried out multiple times, the freezing temperature and sublimation pressure may be set to any desired conditions.

[0092] The additive treatment may involve mixing an additive such as a solidifying agent or a binder with the mixture and molding the mixture. The additive may be any known additive used in the production of CMC, such as agar, gelatin, methyl cellulose, camphene, sodium alginate, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, acrylic acid, methacrylic acid, acrylamide, N,N'-methylenebisacrylamide, N,N'-ethylenebisacrylamide methacrylamide, polyethylene glycol diacrylate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, urea, boron nitride (BN), aluminum nitride (AlN), silicon nitride (Si3N4), gallium nitride (GaN), zirconium nitride (ZrN), polyaluminum chloride ([Al2(OH) n Cl 6-n ] m , 1≦n≦5, m≦10), trimethoxyaluminum, triethoxyaluminum, tri-n-propoxyaluminum, tri-i-propoxyaluminum, tri-n-butoxyaluminum, tri-i-butoxyaluminum, tri-sec-butoxyaluminum, tri-t-butoxyaluminum, trimethoxyboron, triethoxyboron, tri-n-propoxyboron, tri-i-propoxyboron, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane Examples include one or more selected from the group consisting of silane, tetra-i-propoxysilane, tetra-n-butoxysilane, tetra-i-butoxysilane, tetra-n-butoxysilane, tetra-sec-butoxysilane, tetra-t-butoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, paraffin wax, and polyvinyl alcohol.

[0093] The additive treatment is preferably one or more methods selected from the group consisting of a method of mixing a solidifying agent and a binder with the mixture, a method of mixing a solidifying agent with the mixture, and a method of mixing a binder with the mixture, and the method of mixing a solidifying agent and a binder with the mixture is more preferred.

[0094] The manufacturing method of this embodiment may include a mixing step under similar conditions except that the mixing step and molding step are repeated, or that the molding step is performed under the same conditions as the mixing step except that the molding step is performed in place of the ceramic continuous fiber. For example, the manufacturing method of this embodiment may include the mixing step and molding step performed one to five times.

[0095] The method for producing a CMC of the present invention includes a step of sintering a compact (hereinafter also referred to as a "sintering step"). This allows the CMC of the present invention to be obtained. Sintering may be performed under any conditions that allow sintering of the raw material powder to proceed, and examples of sintering conditions include the following: Sintering atmosphere: oxidizing atmosphere or inert atmosphere, preferably air atmosphere Sintering temperature: 800°C or higher, 900°C or higher, or 1000°C or higher, and 1600℃ or less or 1500℃ or less Number of firings: 1 to 5

[0096] The firing time may be varied as desired depending on the size of the compact (or calcined compact) and the characteristics of the firing furnace used, and may be, for example, from 30 minutes to 120 hours. When firing is performed multiple times, the firing atmosphere and firing temperature may be set as desired.

[0097] In the present invention, "atmospheric sintering" refers to a method of sintering by heating an object to be sintered (such as a compact or a calcined body) without applying an external force.

[0098] The sintering step is preferably carried out in an air atmosphere at atmospheric pressure at 800°C or higher, preferably 800°C or higher and lower than 1000°C, to form a calcined body, and then sintering the calcined body in an air atmosphere at atmospheric pressure at 900°C or higher and 1600°C or lower, preferably 1000°C or higher and 1600°C or lower, more preferably 1000°C or higher and 1500°C or lower.

[0099] Another preferred sintering step is to sinter the compact at 800°C or higher but lower than 1000°C to obtain a calcined body, sinter the calcined body at 1000°C or higher but lower than 1150°C to obtain a primary sintered body, and then sinter the primary sintered body at 1150°C or higher but lower than 1500°C. This makes it easier to obtain a denser CMC. Sintering conditions for the sintering step include, for example, atmospheric sintering and an oxidizing atmosphere, preferably air. [Example]

[0100] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0101] (Heat exposure treatment) The sintered CMC was kept in an electric furnace (atmospheric pressure, air atmosphere) at 1200°C for 100 hours, and then cooled to room temperature.

[0102] (Tensile test) Using a diamond cutter, sintered or heat-treated CMC was cut to a width of 10 ± 1 mm, a length of 110 mm or more, or a length of 110 ± 10 mm and a thickness of 2 ± 1 mm, to prepare test specimens conforming to JIS R 1656. Aluminum tabs with a 14° incline were attached to both ends of the specimen using epoxy adhesive. Tensile tests were performed at a loading rate of 0.5 mm / min using a universal testing machine (AG-XPlus, Shimadzu Corporation) and a tensile test jig. The tensile strength of the CMC was calculated using the cross-sectional area of ​​the specimen, calculated from the thickness and width measured using a micrometer, and the maximum strength at fracture.

[0103] (Calculation of strength retention rate) The tensile strength of the CMC after the heat exposure treatment was divided by the tensile strength of the CMC before the heat exposure treatment, and the result was expressed as a percentage to obtain the strength retention rate.

[0104] (Calculation of average inhibitor particle size) CMC samples were cut into 5 mm square plates using a diamond cutter, and the cross sections were prepared for observation using an argon beam cross-section polisher. The observed cross sections were observed at 5000x magnification using a field emission scanning microscope equipped with an energy dispersive X-ray analyzer (JSM-7600F, manufactured by JEOL Ltd.). EDS mapping data of silicon (sintering inhibitor) in the matrix was obtained, and the data was converted into a two-dimensional EDS mapping image using image analysis software (ImageJ, manufactured by the National Institutes of Health, USA). The obtained mapping image (two-dimensional EDS mapping image) was binarized using the image analysis software ImageJ at 8-bit resolution with a threshold of 50 to obtain a processed image. The average particle size of silicon (sintering inhibitor) was calculated from the area of ​​the white regions using this processed image.

[0105] (Calculation of average distance between centers of gravity) Using the processed image obtained in the same manner as for the average inhibitor particle size, the coordinates of the center of gravity of each white area in the image corresponding to the sintering inhibitor were determined by the following method.

[0106] The coordinates of the center of gravity of the white area were defined as (Xg, Yg), and the coordinates of the center of gravity of each white area were calculated using the following formula: The long side of the processed image was the X axis, and the short side was the Y axis.

[0107] Xg = (the sum of the x coordinate values ​​when the white area is divided into unit pixels) ÷ the sum of the number of unit pixels that make up the white area Yg = (the sum of the y coordinate values ​​of each unit pixel when the white area is divided) ÷ the sum of the number of unit pixels that make up the white area The centroids of different white regions were connected by straight lines according to the following criteria (a) and (b), and the average length of the resulting line segments was calculated.

[0108] (a) Connect the center of gravity points so that they do not pass over other white areas.

[0109] (b) If a line connecting two center points intersects with a line connecting other center points, the shorter line is used.

[0110] The coordinates of the center of gravity, the length of the line segment, and the average value were calculated using image analysis software (software name: NS2K-PRO, manufactured by Nano Systems). The number of sintering inhibitors used in the calculation was 150±50.

[0111] (Raw material particle size and average inhibitor source particle size) The raw material particle size and the average inhibitor source particle size were determined using a laser diffraction / scattering particle size distribution analyzer (device name: MT3300EX-II, manufactured by Microtrackbell) according to the method of JIS R 1629. The measurement conditions are shown below. Light source: Semiconductor laser Voltage: 780mW Measurement sample: Slurry in which raw material powder is dispersed in pure water Refractive index of alumina: 1.77 Refractive index of zirconia: 2.17 Refractive index of silica: 1.48 Refractive index of solvent (water): 1.333 Calculation mode: MT3000EXII

[0112] As a pretreatment, the sample powder and 0.2% by mass of ammonium polyacrylate dispersant were suspended in pure water to form a slurry, which was then dispersed for 3 minutes using an ultrasonic homogenizer (device name: BRANSON SONIFIER 250, manufactured by Emerson).

[0113] (fiber volume fraction) The fiber volume fraction was calculated using the following formula from the mass of the ceramic continuous fiber, the density of the ceramic continuous fiber, and the volume of the CMC.

[0114] Fiber volume fraction [vol%] = (V f / VCMC )100 V f = m / ρ f V CMC = A×B×t In the above equation, V f is the volume of the ceramic continuous fiber, V CMC is the volume of the CMC, m is the mass of the ceramic continuous fiber [g], ρ f is the density of the ceramic continuous fiber [g / cm 3 ], A is the length of the CMC [cm], B is the width of the CMC [cm], and t is the thickness of the CMC [cm].

[0115] (density) Density is the ratio of the volume measured by Archimedes' method to the mass measured using an electronic balance according to JIS R 1634 (g / cm 3 Prior to the measurement, the mass of the dried CMC was measured, and then the CMC was placed in water and boiled for 3 hours as a pretreatment.

[0116] Example 1 363 g of α-alumina powder with an average particle size (raw material particle size) of 0.15 μm (raw material powder amount (slurry): 72.8 mass%), 11.3 g of silica raw material (silica powder) with an average particle size (inhibitor particle size) of 0.10 μm (inhibitor source amount (slurry): 2.2 mass%, inhibitor source amount: 3.1 mass%), and 125 g of pure water (25.0 mass% of the matrix slurry mass) were mixed, and then mixed with 1.2 kg of 10 mm diameter alumina balls and ball milled for 24 hours. This resulted in a matrix slurry with a volumetric solids concentration of 43 vol% (solids concentration 75 mass%) and a viscosity of 40.6 cP.

[0117] A commercially available mullite continuous fiber cloth (i.e., mullite and alumina continuous fiber cloth) (Nextel-720 manufactured by 3M) was heat-treated (desized) in air at 800°C. The desized mullite continuous fiber cloth was impregnated with a matrix slurry to obtain a mixture. The mixture was heat-treated twice at 120±10°C for 6±2 hours to obtain a molded body having a width of 110 mm, a length of 130 mm, and a thickness of approximately 2 mm (thickness: 2.0 mm). The molded body was sintered in air at 900°C under atmospheric pressure to obtain a calcined body. The calcined body was sintered in air at 1100°C for 2 hours, and then heat-treated (sintered) in air at 1200°C to obtain a CMC. The obtained CMC had a fiber volume fraction of 45 vol%, a tensile strength of 189 MPa, a tensile strength after heat exposure treatment of 175 MPa, a strength retention rate of 93%, an average particle size of silica in the matrix (average inhibitor particle size) of 0.11 μm (0.108 μm), and an average center-of-gravity distance of 2.0 μm.

[0118] Example 2 363 g of α-alumina powder with an average particle size (raw material particle size) of 0.15 μm (raw material powder amount (slurry): 72.8 mass%), 11.3 g of silica raw material (silica powder) with an average particle size (inhibitor particle size) of 0.24 μm (inhibitor source amount (slurry): 2.2 mass%, inhibitor source amount: 3.1 mass%), and 125 g of pure water (25.0 mass% of the matrix slurry mass) were mixed, mixed with 1.2 kg of 10 mm diameter alumina balls, and ball milled for 24 hours. This resulted in a matrix slurry with a volumetric solids concentration of 43 vol% (solids concentration 75 mass%) and a viscosity of 36.9 cP.

[0119] A commercially available mullite continuous fiber cloth (i.e., mullite and alumina continuous fiber cloth) (Nextel-720 manufactured by 3M) was heat-treated (desized) in air at 800°C. The desized mullite continuous fiber cloth was impregnated with a matrix slurry to obtain a mixture. The mixture was heat-treated twice at 120±10°C for 6±2 hours to obtain a molded body having a width of 110 mm, a length of 130 mm, and a thickness of approximately 2 mm (2.1 mm). The molded body was sintered in air at 900°C under atmospheric pressure to obtain a calcined body. The calcined body was sintered in air at 1100°C for 2 hours, and then heat-treated (sintered) in air at 1200°C to obtain a CMC. The obtained CMC had a fiber volume fraction of 43 vol%, a tensile strength of 189 MPa, a tensile strength after heat exposure treatment of 198 MPa, a strength retention rate of 105%, an average particle size of silica in the matrix (average inhibitor particle size) of 0.21 μm (0.211 μm), and an average center-of-gravity distance of 2.0 μm.

[0120] Example 3 363 g of α-alumina powder with an average particle size (raw material particle size) of 0.15 μm (raw material powder amount (slurry): 72.8 mass%), 11.3 g of silica raw material (silica powder) with a purity of 99.9% and an average particle size (inhibitor particle size) of 0.24 μm (inhibitor source amount (slurry): 2.2 mass%, inhibitor source amount: 3.1 mass%), and 125 g of water (25.0 mass% of the matrix slurry mass) were mixed, mixed with 1.2 kg of 10 mm diameter alumina balls, and ball milled for 24 hours. A ceramic matrix slurry with a volumetric solids concentration of 43 vol% (solids concentration 75 mass%) and a viscosity of 50.6 cP was obtained.

[0121] A commercially available alumina continuous fiber cloth (Nextel-610 manufactured by 3M) was heat-treated (desized) in air at 800°C. The desized alumina continuous fiber cloth was impregnated with a matrix slurry to obtain a mixture. The mixture was heat-treated twice at 120±10°C for 6±2 hours to obtain a molded body having a width of 110 mm, length of 130 mm, and thickness of approximately 2 mm (thickness of 1.9 mm). The molded body was sintered under atmospheric pressure at 900°C in air to obtain a calcined body. The calcined body was sintered in air at 1100°C for 2 hours, and then heat-treated (sintered) at 1200°C in air to obtain a CMC. The obtained CMC contained fibers with a fiber volume fraction of 43 vol%, had a tensile strength of 221 MPa, a tensile strength after heat exposure treatment of 192 MPa, a strength retention rate of 87%, an average particle size of silica in the matrix (average inhibitor particle size) of 0.22 μm (0.221 μm), and an average center-of-gravity distance of 2.3 μm.

[0122] Example 4 363 g of α-alumina powder with an average particle size (raw material particle size) of 0.15 μm (raw material powder amount (slurry): 72.8 mass%), 11.3 g of silica powder with a purity of 99.9% and an average particle size (inhibitor particle size) of 0.10 μm (inhibitor source amount (slurry): 2.2 mass%, inhibitor source amount: 3.1 mass%), and 125 g of water (25.0 mass% of the matrix slurry mass) were mixed, mixed with 1.2 kg of 10 mm diameter alumina balls, and ball milled for 24 hours. This resulted in a matrix slurry with a volumetric solids concentration of 43 vol% (solids concentration 75 mass%) and a viscosity of 28.6 cP.

[0123] A commercially available alumina continuous fiber cloth (3M Nextel-610) was heat-treated (desized) in air at 800°C. The desized alumina continuous fiber cloth was impregnated with matrix slurry to obtain a mixture. The mixture was heat-treated twice at 120±10°C for 6±2 hours to obtain a molded body measuring 110 mm wide x 130 mm long x approximately 2 mm thick (1.8 mm thick). The molded body was sintered in air at 900°C under atmospheric pressure to form a calcined body. The calcined body was sintered in air at 1100°C for 2 hours and then heat-treated (sintered) in air at 1200°C to obtain a CMC. The resulting CMC had a fiber volume fraction of 41 vol%, a tensile strength of 211 MPa, a tensile strength after heat exposure of 207 MPa, a strength retention rate of 98%, an average inhibitor particle size of 0.15 (0.151) μm, and an average center-of-gravity distance of 2.7 μm.

[0124] Example 5 358 g of α-alumina powder with an average particle size (raw material particle size) of 0.15 μm (raw material powder amount (slurry): 71.6 mass%), 11.3 g of silica powder with a purity of 99.9% and an average particle size (inhibitor particle size) of 0.24 μm (inhibitor source amount (slurry): 3.4 mass%, inhibitor source amount: 4.8 mass%), and 125 g of water (25.0 mass% relative to the mass of the matrix slurry) were mixed, mixed with 1.2 kg of alumina balls with a diameter of 10 mm, and ball milled for 24 hours to obtain a matrix slurry with a volumetric solid concentration of 43 vol% (solid concentration 75 mass%) and a viscosity of 48.9 cP.

[0125] A commercially available alumina continuous fiber cloth (Nextel-610 manufactured by 3M) was heat-treated (desized) in air at 800°C. The desized alumina continuous fiber cloth was impregnated with a matrix slurry to obtain a mixture. The mixture was heat-treated twice at 120±10°C for 6±2 hours to obtain a molded body having a width of 110 mm, length of 130 mm, and thickness of approximately 2 mm (thickness of 1.9 mm). The molded body was sintered under atmospheric pressure at 900°C in air to obtain a calcined body. The calcined body was sintered in air at 1100°C for 2 hours, and then heat-treated (sintered) at 1200°C in air to obtain a CMC. The obtained CMC had a fiber volume fraction of 39 vol%, a tensile strength of 189 MPa, a tensile strength after heat exposure treatment of 189 MPa, a strength retention rate of 100%, an average inhibitor particle size of 0.22 (0.219) μm, and an average center-of-gravity distance of 1.8 μm.

[0126] Example 6 363 g of α-alumina powder with an average particle size (raw material particle size) of 0.15 μm (raw material powder amount (slurry): 72.8 mass%), 11.3 g of silica powder with a purity of 99.9% and an average particle size (inhibitor particle size) of 2.4 μm (inhibitor source amount (slurry): 2.2 mass%, inhibitor source amount: 3.1 mass%), and 125 g of water (25.0 mass% of the matrix slurry mass) were mixed, mixed with 1.2 kg of 10 mm diameter alumina balls, and ball milled for 24 hours. This resulted in a matrix slurry with a volumetric solids concentration of 43 vol% (solids concentration 75 mass%) and a viscosity of 58.1 cP.

[0127] A commercially available alumina continuous fiber cloth (Nextel-610 manufactured by 3M) was heat-treated (desized) in air at 800°C. The desized alumina continuous fiber cloth was impregnated with a matrix slurry to obtain a mixture. The mixture was heat-treated twice at 120±10°C for 6±2 hours to obtain a molded body having a width of 110 mm, length of 130 mm, and thickness of approximately 2 mm (thickness of 1.9 mm). The molded body was sintered under atmospheric pressure at 900°C in air to obtain a calcined body. The calcined body was sintered in air at 1100°C for 2 hours, and then heat-treated (sintered) at 1200°C in air to obtain a CMC. The obtained CMC had a fiber volume fraction of 41 vol%, a tensile strength of 222 MPa, a tensile strength after heat exposure treatment of 211 MPa, a strength retention rate of 95%, an average inhibitor particle size of 0.17 μm (0.166 μm), and an average center-of-gravity distance of 2.4 μm.

[0128] Example 7 371 g of α-alumina powder with an average particle size (raw material particle size) of 0.15 μm (raw material powder amount (slurry): 74.3 mass%), 3.8 g of silica powder with a purity of 99.9% and an average particle size (inhibitor particle size) of 0.24 μm (inhibitor source amount (slurry): 0.75 mass%, inhibitor source amount: 1.0 mass%), and 125 g of water (25.0 mass% of the matrix slurry mass) were mixed, mixed with 1.2 kg of 10 mm diameter alumina balls, and ball milled for 24 hours. This resulted in a matrix slurry with a volumetric solids concentration of 43 vol% (solids concentration 75 mass%) and a viscosity of 50.6 cP.

[0129] A commercially available mullite continuous fiber cloth (i.e., mullite and alumina continuous fiber cloth) (Nextel-720 manufactured by 3M) was heat-treated (desized) in air at 800°C. The desized mullite continuous fiber cloth was impregnated with a matrix slurry to obtain a mixture. The mixture was heat-treated twice at 120±10°C for 6±2 hours to obtain a molded body having a width of 110 mm, a length of 130 mm, and a thickness of 2.1 mm. The molded body was sintered in air at 900°C under atmospheric pressure to obtain a calcined body. The calcined body was sintered in air at 1100°C for 2 hours, and then heat-treated (sintered) in air at 1200°C to obtain a CMC. The obtained CMC had a fiber volume fraction of 42 vol%, a tensile strength of 180 MPa, a tensile strength after heat exposure treatment of 181 MPa, a strength retention rate of 100%, an average inhibitor particle size of 0.11 (0.109) μm, and an average center-of-gravity distance of 2.2 μm.

[0130] Furthermore, the CMC of Example 7 was held in the air at 1200°C for 1000 hours and then cooled to room temperature. The tensile strength of the treated CMC was 153 MPa, and the ratio of the tensile strength of the treated CMC to the tensile strength of the CMC before treatment was 85%.

[0131] (Comparative Example 1) 363 g of α-alumina powder with an average particle size (raw material particle size) of 0.15 μm (raw material powder amount (slurry): 72.8 mass%), 11.3 g of silica powder with a purity of 99.9% and an average particle size (inhibitor particle size) of 0.05 μm (inhibitor source amount (slurry): 2.2 mass%, inhibitor source amount: 3.1 mass%), and 125 g of pure water (25.0 mass% of the matrix slurry mass) were mixed, mixed with 1.2 kg of 10 mm diameter alumina balls, and then ball milled for 24 hours. This resulted in a matrix slurry with a volumetric solids concentration of 43 vol% (solids concentration 75 mass%) and a viscosity of 21.6 cP.

[0132] A commercially available mullite continuous fiber cloth (i.e., mullite and alumina continuous fiber cloth) (Nextel-720 manufactured by 3M) was heat-treated (desized) in air at 800°C. The desized mullite continuous fiber cloth was impregnated with a matrix slurry to obtain a mixture. The mixture was heat-treated twice at 120±10°C for 6±2 hours to obtain a molded body having a width of 110 mm, a length of 130 mm, and a thickness of approximately 2 mm (2.4 mm). The molded body was sintered in air at 900°C under atmospheric pressure to obtain a calcined body. The calcined body was sintered in air at 1100°C for 2 hours, and then heat-treated (sintered) in air at 1200°C to obtain a CMC. The resulting CMC had a fiber volume fraction of 39 vol%, a tensile strength of 132 MPa, a tensile strength after heat exposure of 151 MPa, a strength retention rate of 109%, an average particle size of silica in the ceramic matrix (average inhibitor particle size) of 0.29 μm (0.287 μm), and an average center-of-gravity distance of 4.9 μm. The larger average particle size in the matrix (average inhibitor particle size) compared to the average particle size of the raw silica powder is presumed to be due to the silica powder agglomerating in the matrix slurry to form coarse particles. Furthermore, the large average center-of-gravity distance suggests that the sintering inhibitor in the CMC of Comparative Example 1 was ineffective in inhibiting the sintering of alumina, i.e., was ineffective in inhibiting the grain growth of the alumina crystal particles that make up the matrix, resulting in the low tensile strength of the CMC of Comparative Example 1.

[0133] (Comparative Example 2) 363 g of α-alumina powder with an average particle size (raw material particle size) of 0.15 μm (raw material powder amount (slurry): 72.8 mass%), 11.3 g of silica raw material (silica powder) with a purity of 99.9% and an average particle size (inhibitor particle size) of 38 μm (inhibitor source amount (slurry): 2.2 mass%, inhibitor source amount: 3.1 mass%), and 125 g of pure water (25.0 mass% of the matrix slurry mass) were mixed, then mixed with 1.2 kg of 10 mm diameter alumina balls and ball milled for 24 hours. This resulted in a matrix slurry with a volumetric solids concentration of 43 vol% (solids concentration 75 mass%) and a viscosity of 52.3 cP.

[0134] Commercially available mullite continuous fiber cloth (i.e., mullite and alumina continuous fiber cloth) (Nextel-720 manufactured by 3M) was heat-treated (desized) in air at 800°C and impregnated with matrix slurry to obtain a mixture. This mixture was then heat-treated twice at 120±10°C for 6±2 hours to obtain a molded body measuring 110 mm wide x 130 mm long x approximately 2 mm thick (2.4 mm thick). This molded body was sintered at 900°C in air under atmospheric pressure to obtain a calcined body. This calcined body was sintered in air at 1100°C, followed by heat treatment (sintering) at 1200°C in air to obtain a CMC. The obtained CMC had a fiber volume fraction of 41 vol%, a tensile strength of 115 MPa, a tensile strength after heat exposure treatment of 113 MPa, a strength retention rate of 98%, an average particle size of silica in the matrix (average inhibitor particle size) of 0.68 μm (0.675 μm), and an average center-of-gravity distance of 4.8 μm.

[0135] The reason why the average particle size (average inhibitor particle size) in the ceramic matrix was smaller than that of the raw silica powder is presumably because the silica was pulverized in the ball mill process during the preparation of the ceramic matrix slurry. However, because the average silica particle size (average inhibitor particle size) in the ceramic matrix was larger than that of Example 1 and the average distance between the centers of gravity was large, the effect of inhibiting the sintering of alumina was small, i.e., the effect of inhibiting the grain growth of the alumina crystal particles that make up the matrix was poor. This is thought to be the reason why the CMC of Comparative Example 2 exhibited low tensile strength.

[0136] (Comparative Example 3) 375 g of α-alumina powder (raw material powder amount (slurry): 75.0 mass%) with an average particle size (raw material particle size) of 0.15 μm and 125 g of pure water (25.0 mass% of the matrix slurry mass) were mixed, mixed with 1.2 kg of 10 mm diameter alumina balls, and then ball milled for 24 hours. This produced a matrix slurry with a volumetric solid concentration of 43 vol% (solid concentration 75 mass%) and a viscosity of 28.6 cP.

[0137] Commercially available mullite continuous fiber cloth (i.e., mullite and alumina continuous fiber cloth) (3M Nextel-720) was heat-treated (desized) in air at 800°C and impregnated with matrix slurry to obtain a mixture. The mixture was then heat-treated twice at 120±10°C for 6±2 hours to obtain a molded body measuring 110 mm wide, 130 mm long, and 2.1 mm thick. The molded body was sintered in air at 900°C under atmospheric pressure to produce a calcined body. The calcined body was sintered in air at 1100°C for 2 hours and then heat-treated (sintered) in air at 1200°C to obtain a CMC. The resulting CMC had a fiber volume fraction of 43 vol%, a tensile strength of 93 MPa, a tensile strength after heat exposure of 88 MPa, and a strength retention rate of 95%.

[0138] The CMC results obtained in the examples and comparative examples are shown in the table below.

[0139] [Table 1]

[0140] In Examples 1 to 7, the average inhibitor particle size was 0.28 μm or less, and it was confirmed that the strength before the heat exposure treatment was 150 MPa or more. In addition, the strength retention rate was 80% or more, and it was confirmed that the decrease in CMC strength due to the heat exposure treatment was suppressed. On the other hand, in the comparative examples, the average inhibitor particle size exceeded 0.28 μm, and the strength before the heat exposure treatment was less than 150 MPa, and the CMC strength was low.

[0141] It was also confirmed that the average interatomic distance was 4.5 μm or less in all of Examples 1 to 7. From this, it is presumed that the sintering inhibitor is uniformly dispersed in the matrix of the CMC of the Examples.

Claims

1. 1. A ceramic matrix composite material comprising a ceramic matrix and continuous ceramic fibers, wherein the ceramic matrix is ​​an oxide ceramic, the continuous ceramic fibers are continuous fibers of an oxide ceramic, the ceramic matrix contains a sintering inhibitor having an average particle size of 0.28 μm or less, the average distance between centers of gravity of the sintering inhibitor is 4.5 μm or less, and the sintering inhibitor is one or more selected from the group consisting of silica, zirconia, yttria, magnesia, mullite, and strontium oxide.

2. 2. The ceramic matrix composite material according to claim 1, wherein the ceramic continuous fibers are continuous fibers of one or more oxide ceramics selected from the group consisting of alumina, silica, mullite, and zirconia.

3. 3. The ceramic matrix composite material according to claim 1, wherein the ceramic matrix is ​​one or more oxides selected from the group consisting of alumina, mullite, and zirconia.

4. A ceramic matrix composite material described in any of claims 1 to 3, wherein the mass ratio of the sintering inhibitor to the mass of the ceramic matrix composite material is 0.1 mass% or more and 3.0 mass% or less.

5. A ceramic matrix composite material described in any one of claims 1 to 4, wherein the fiber volume fraction is 30 vol% or more and 60 vol% or less.

6. 6. The ceramic matrix composite material according to claim 1, wherein the tensile strength is 150 MPa or more and the strength retention rate after heat exposure treatment at 1200°C for 100 hours is 80% or more.

7. 7. The method for producing a ceramic matrix composite material according to claim 1, further comprising the steps of: impregnating continuous ceramic fibers with a ceramic matrix slurry prepared by adding a sintering inhibitor having a purity of 99% or higher to a ceramic matrix raw material powder; drying the slurry; and sintering the resulting molded body.

8. 8. The method for producing a ceramic matrix composite material according to claim 7, wherein the sintering inhibitor having a purity of 99% or more has an average particle size of more than 0.05 μm and not more than 30 μm.

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