Ceramic continuous fiber with coating layer and manufacturing method thereof, ceramic matrix composite material and manufacturing method thereof

Abstract

To provide a coating layer-bonded continuous ceramic fiber suitable for the production of a ceramic matrix composite material whose damage tolerance can be improved, and a ceramic matrix composite material that uses this coating layer-bonded continuous ceramic fiber.SOLUTION: Disclosed is a coating layer-bonded continuous ceramic fiber formed from a continuous ceramic fiber having a coating layer of a metal compound with a thickness of 7 nm or less on the surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a coated ceramic continuous fiber and a method for producing the same, and a ceramic matrix composite material and a method for producing the same. [Background technology]

[0002] Ceramic matrix composites (hereinafter referred to as "CMCs"), which combine continuous ceramic fibers with a ceramic matrix, are more resistant to destruction of the entire material due to the progression of scratches (damage tolerance) than ordinary ceramics, and are therefore being studied as an alternative material to heat-resistant metals such as Ni-based alloys.

[0003] Furthermore, because alumina and mullite-based oxides have high chemical stability, CMCs, which are made by forming alumina and mullite-based oxides into continuous ceramic fibers and combining these continuous ceramic fibers with a ceramic matrix, are expected to be used particularly as components for aircraft jet engines (e.g., Non-Patent Document 1).

[0004] The damage tolerance of CMCs is due to the selective delamination or fracture of the interface between the continuous ceramic fibers and the ceramic matrix, which inhibits the progression of flaws. Therefore, if the continuous ceramic fibers and the ceramic matrix adhere to each other, the progression of flaws cannot be inhibited and the material tends to be more susceptible to fracture.

[0005] To prevent adhesion between continuous ceramic fibers and the ceramic matrix, coating the surface of continuous ceramic fibers with compounds that promote interface destruction has been investigated. However, physical vapor deposition methods such as sputtering and ion plating tend to only coat the fiber surface. Therefore, chemical vapor deposition (CVD) and other coating methods using solutions have been investigated. For example, CVD methods using boron nitride and coating methods using zirconia nanosolutions (ZrO2 slurries) have been investigated (e.g., Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 11-049570 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-173376 [Non-patent literature]

[0007] [Non-Patent Document 1] J.AerospaceLab,Issue3,(2011)1-12. Summary of the Invention [Problem to be solved by the invention]

[0008] Generally, when producing a CMC, fibers (hereinafter also referred to as "fiber bundles") in the form of an aggregate of two or more fibers, such as hundreds of fibers, are used as the ceramic continuous fibers. However, with the CVD method described in Patent Document 1, it is difficult to coat the inside of the fiber bundle (the continuous fibers inside are difficult to coat), and the strength of the resulting CMC tends to be low. Furthermore, with the method described in Patent Document 2, it is difficult to control the film thickness, and the continuous fibers tend to aggregate together. As a result, the strength of the resulting CMC tends to be low.

[0009] The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a coated ceramic continuous fiber suitable for producing a ceramic matrix composite material capable of improving damage tolerance, and a ceramic matrix composite material using the same. [Means for solving the problem]

[0010] As a result of intensive research to solve the above problems, the inventors discovered that the damage tolerance of CMCs can be improved by using a ceramic continuous fiber with a coating layer in which the coating layer and its state are controlled, and thus completed the present invention.

[0011] That is, the present invention provides coated ceramic continuous fibers shown in [1] to [4], ceramic matrix composite materials shown in [5] and [6], a method for producing coated ceramic continuous fibers shown in [7], and a method for producing ceramic matrix composite materials shown in [8].

[0012] [1] A coated ceramic continuous fiber, characterized in that it is made of a ceramic continuous fiber having a coating layer of a metal compound with a thickness of 50 nm or less on its surface. [2] The coated ceramic continuous fiber according to [1], wherein the metal compound is at least one of a zirconium compound and a lanthanum compound. [3] The coated ceramic continuous fiber according to [1] or [2], wherein the metal compound is zirconia or lanthanum oxide. [4] A coated ceramic continuous fiber according to any one of [1] to [3], wherein the ceramic continuous fiber is at least one of an alumina continuous fiber and a mullite continuous fiber. [5] A ceramic matrix composite material having the coated ceramic continuous fiber according to any one of [1] to [4]. [6] The ceramic matrix composite according to [5], wherein the interfacial strength is 10 MPa or less. [7] A method for producing a coated ceramic continuous fiber according to any one of [1] to [4], the method comprising: an impregnation step of impregnating the ceramic continuous fiber with a solution containing a metal acetylacetonate complex; and a heat treatment step of heat treating the impregnated ceramic continuous fiber. [8] A method for producing a ceramic matrix composite material, comprising a compounding step of compounding the coated ceramic continuous fiber according to any one of [1] to [4] with a ceramic matrix. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide at least one of a coated ceramic continuous fiber suitable for producing a ceramic matrix composite material capable of improving damage tolerance, a ceramic matrix composite material using the same, a method for producing a coated ceramic continuous fiber, and a method for producing a ceramic matrix composite material. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1(a) is a transmission electron microscope (TEM) image of the zirconia-coated alumina continuous fiber of Example A1. FIG. 1(b) is an energy dispersive X-ray (EDS) image showing the aluminum distribution in the zirconia-coated alumina continuous fiber of FIG. 1(a). FIG. 1(c) is an EDS image showing the zirconium distribution in the zirconia-coated alumina continuous fiber of FIG. 1(a). FIG. 1(d) is an EDS image showing the oxygen distribution in the zirconia-coated alumina continuous fiber of FIG. 1(a). [Figure 2] FIG. 2 is a graph showing the results of X-ray photoelectron spectroscopy (hereinafter also referred to as "ESCA") analysis of the surface of the zirconia-coated alumina continuous fiber of Example A1. [Figure 3] Figure 3(a) is a TEM image of the zirconia-coated mullite continuous fiber of Example A2. Figure 3(b) is an EDS image showing the aluminum distribution in the zirconia-coated mullite continuous fiber of Figure 3(a). Figure 3(c) is an EDS image showing the silicon distribution in the zirconia-coated mullite continuous fiber of Figure 3(a). Figure 3(d) is an EDS image showing the zirconium distribution in the zirconia-coated mullite continuous fiber of Figure 3(a). Figure 3(e) is an EDS image showing the oxygen distribution in the zirconia-coated mullite continuous fiber of Figure 3(a). [Figure 4] FIG. 4 is a graph showing the results of ESCA analysis of the surface of the zirconia-coated mullite continuous fiber of Example A2. [Figure 5]Figure 5(a) is a TEM image of the lanthanum oxide-coated alumina continuous fiber of Example A3. Figure 5(b) is an EDS image showing the aluminum distribution in the lanthanum oxide-coated alumina continuous fiber of Figure 5(a). Figure 5(c) is an EDS image showing the lanthanum distribution in the lanthanum oxide-coated alumina continuous fiber of Figure 5(a). Figure 5(d) is an EDS image showing the oxygen distribution in the lanthanum oxide-coated alumina continuous fiber of Figure 5(a). [Figure 6] 6(a) to 6(c) are graphs showing the results of ESCA analysis of the surface of the lanthanum oxide-coated alumina continuous fiber of Example A3. [Figure 7] Figure 7(a) is a TEM image of the lanthanum oxide-coated mullite continuous fiber of Example A4. Figure 7(b) is an EDS image showing the aluminum distribution in the lanthanum oxide-coated mullite continuous fiber of Figure 7(a). Figure 7(c) is an EDS image showing the silicon distribution in the lanthanum oxide-coated mullite continuous fiber of Figure 7(a). Figure 7(d) is an EDS image showing the lanthanum distribution in the lanthanum oxide-coated mullite continuous fiber of Figure 7(a). Figure 7(e) is an EDS image showing the oxygen distribution in the lanthanum oxide-coated mullite continuous fiber of Figure 7(a). [Figure 8] 8(a) to 8(d) are graphs showing the results of ESCA analysis of the surface of the lanthanum oxide-coated mullite continuous fiber of Example A4. [Figure 9] FIG. 9 is an image of the alumina continuous fibers of Comparative Example A1 taken by a scanning electron microscope (hereinafter also referred to as "SEM"). [Figure 10] FIG. 10 is a schematic cross-sectional view showing an example of an interface strength measuring device. [Figure 11] FIG. 11 is a graph showing the stress-displacement curve in the push-out test of Measurement Example B1. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments.

[0016] [Ceramic continuous fiber with coating layer] In one embodiment, the coated ceramic continuous fiber comprises a ceramic continuous fiber having a metal compound coating layer of 50 nm or less on its surface. The coated ceramic continuous fiber of this embodiment can also be said to comprise a ceramic continuous fiber and a metal compound coating layer of 50 nm or less on the surface of the ceramic continuous fiber. In this specification, "continuous fiber" refers to a long fiber, particularly a filamentous long fiber that can be woven using a spinning and weaving machine. "Ceramic continuous fiber" refers to a continuous fiber made of ceramic. Furthermore, "coating layer" refers to a layer that covers at least a portion of the continuous fiber, and "metal compound coating layer" refers to a coating layer containing a metal compound. Furthermore, "coated ceramic continuous fiber" refers to a ceramic continuous fiber having a coating layer on its surface.

[0017] The coating layer of the coated ceramic continuous fiber of this embodiment has a coating layer thickness of 50 nm or less. A coating layer thickness of 50 nm or less can prevent aggregation of the continuous ceramic fibers. The coating layer thickness is preferably 20 nm or less, more preferably 10 nm or less. There is no particular lower limit to the coating layer thickness, but it is sufficient that the coating layer thickness is 1 nm or more. In this embodiment, the coating layer thickness refers to the thickness measured by TEM-EDS analysis based on the distribution of metal elements constituting the metal compound. For example, if the metal compound is a zirconium compound, the thickness is measured based on the distribution of zirconium, and if the metal compound is a lanthanum compound, the thickness is measured based on the distribution of lanthanum.

[0018] The metal compound in the coating layer is not particularly limited as long as it is a compound containing a metal. However, it is preferably at least one of a metal oxide and a metal nitride, and more preferably a metal oxide. The metal compound is preferably at least one selected from the group consisting of a zirconium compound, a lanthanum compound, a yttrium compound, an iron compound, and a cerium compound, more preferably at least one of a zirconium compound, a lanthanum compound, and an yttrium compound, and even more preferably a zirconium compound or a lanthanum compound. By including such a metal-containing compound as the coating layer, the coated ceramic continuous fiber becomes more suitable for use as a CMC. In another embodiment, the metal compound is preferably a compound of a metal capable of forming a metal acetylacetonate complex, and more preferably a compound of a metal capable of forming a metal acetylacetonate complex that does not react with the ceramic continuous fiber and the ceramic matrix. In this specification, "matrix" refers to the parent phase to be composited, and "ceramic matrix" refers to a matrix composed of ceramics.

[0019] The metal compound is preferably a metal oxide, particularly zirconia (ZrO2), lanthanum oxide (La2O3), yttrium oxide (Y2O3), iron oxide (Fe2O3), or cerium oxide (CeO2), as it is suitable for the coating layer from the viewpoints of heat resistance and chemical stability. The metal compound is more preferably zirconia (ZrO2), lanthanum oxide (La2O3), or yttrium oxide (Y2O3), and even more preferably zirconia (ZrO2) or lanthanum oxide (La2O3).

[0020] The ceramic continuous fiber of this embodiment is not particularly limited as long as it is a continuous fiber made of ceramic. Examples of the ceramic continuous fiber include at least one of an oxide ceramic continuous fiber and a non-oxide ceramic continuous fiber. The ceramic continuous fiber is preferably at least one selected from the group consisting of a silicon carbide continuous fiber, an alumina continuous fiber, and a mullite continuous fiber. The ceramic continuous fiber is more preferably at least one of an alumina continuous fiber and a mullite continuous fiber, and even more preferably a mullite continuous fiber. Furthermore, the ceramic continuous fiber preferably has hydroxyl groups on its surface.

[0021] The ceramic continuous fiber of this embodiment is preferably in the form of at least one of a fiber bundle and a woven fiber bundle, and is preferably a ceramic continuous fiber in the form of a woven fiber bundle (hereinafter also referred to as "ceramic fiber cloth").

[0022] The tensile strength of the coated ceramic continuous fiber of this embodiment measured in accordance with JIS R 1657 (hereinafter also referred to as "single fiber tensile strength") is preferably 1 GPa or more and 3 GPa or less, and more preferably 1.2 GPa or more and 2.8 GPa or less.

[0023] The coated ceramic continuous fiber of this embodiment is suitable for use as a CMC. The coated ceramic continuous fiber of this embodiment is suitable for preventing aggregation of continuous fibers, making it possible to suppress adhesion between the coated ceramic continuous fiber and the ceramic matrix. Therefore, when combined with a ceramic matrix and used as a CMC, it is possible to achieve high damage tolerance.

[0024] [Method for manufacturing coated ceramic continuous fibers] In one embodiment, a method for producing a coated ceramic continuous fiber includes an impregnation step of impregnating a ceramic continuous fiber with a solution containing a metal acetylacetonate complex, and a heat treatment step of heat-treating the impregnated ceramic continuous fiber. By impregnating the ceramic continuous fiber, chemical adsorption of the metal acetylacetonate onto the surface of the ceramic continuous fiber is promoted. The ceramic continuous fiber subjected to the impregnation step may be in the form of a fiber bundle or a ceramic fiber cloth, and is preferably a ceramic fiber cloth.

[0025] The metal acetylacetonate complex to be subjected to the impregnation step is preferably at least one of zirconium (IV) acetylacetonate (Zr(CH3COCHCOCH3)4), lanthanum (III) acetylacetonate dihydrate (La(CH3COCHCOCH3)3·2H2O), yttrium (III) acetylacetonate n-hydrate (Y(CH3COCHCOCH3)3·nH2O), iron (III) acetylacetonate (Fe(CH3COCHCOCH3)3), and cerium (III) acetylacetonate trihydrate (Ce(CH3COCHCOCH3)3·3H2O). or at least one of zirconium(IV) acetylacetonate (Zr(CH3COCHCOCH3)4), lanthanum(III) acetylacetonate dihydrate (La(CH3COCHCOCH3)3·2H2O), and yttrium(III) acetylacetonate n-hydrate (Y(CH3COCHCOCH3)3·nH2O), and more preferably at least one of zirconium(IV) acetylacetonate (Zr(CH3COCHCOCH3)4) and lanthanum(III) acetylacetonate dihydrate (La(CH3COCHCOCH3)3·2H2O).

[0026] The solvent for the solution containing the metal acetylacetonate complex is not particularly limited as long as it dissolves the metal acetylacetonate complex without decomposition. Preferred solvents include, for example, alcohols such as methanol, ethanol, and propanol, organic solvents such as acetone and benzene, water, and heavy water. The solvent is preferably at least one of water and alcohol, and more preferably at least one of methanol and ethanol.

[0027] The impregnation may be carried out under any conditions that allow the chemical adsorption reaction of the metal acetylacetonate complex onto the ceramic continuous fiber to proceed. For example, the impregnation temperature may be below the boiling point of the solvent, preferably room temperature (25±3°C), and the impregnation time may be from 30 minutes to 24 hours. Since this facilitates the chemical adsorption reaction, it is preferable to carry out the impregnation under heating at a temperature below the boiling point of the solvent.

[0028] The impregnation is preferably carried out so that the ratio of the area covered with the coating substance to the total surface area of ​​the ceramic continuous fiber (hereinafter also referred to as the "coverage") is 50% or more. Here, "coating substance" refers to the substance used for coating. If the coverage is 50% or more, when the coated ceramic continuous fiber obtained by the manufacturing method of this embodiment is used as a CMC, adhesion between the coated ceramic continuous fiber and the ceramic matrix tends to be suppressed. The impregnation is preferably carried out so that the coverage is 75% or more, preferably 90% or more. A coverage of 100% corresponds to a state in which the coating substance covers the entire surface of the ceramic continuous fiber, so the coverage is 100% or less.

[0029] The ceramic continuous fiber is preferably a ceramic continuous fiber having hydroxyl groups on the surface. In this case, the coverage can be calculated from the following formula. θ = 100 × nM × X / (S × nOH) (1) [θ is the coverage (%), S is the total surface area of ​​the ceramic continuous fiber (m 2 ), nOH is the number of hydroxyl groups on the surface of the ceramic continuous fiber per unit volume (number / m 2), nM is the number of metal atoms in the metal acetylacetonate complex used in the impregnation treatment, and X is the valence of the metal atom.

[0030] When using alumina continuous fiber, the number of surface hydroxyl groups, nOH, is 12.5 × 10 18 (pcs / m 2 ) and when using mullite continuous fiber, the number of surface hydroxyl groups nOH is 11.3 × 10 18 (pcs / m 2 )

[0031] The ceramic continuous fiber having hydroxyl groups on the surface thereof is preferably at least one of alumina continuous fiber and mullite continuous fiber, and more preferably mullite continuous fiber.

[0032] The method for producing a coated ceramic continuous fiber of this embodiment includes a step of heat-treating the ceramic continuous fiber obtained after the impregnation step. By heat-treating the ceramic continuous fiber obtained after the impregnation step, the metal acetylacetonate complexes chemically adsorbed to the ceramic continuous fiber are decomposed to form metal compounds. The heat treatment conditions are not particularly limited, and the heat treatment temperature is preferably 500°C or higher and 1200°C or lower, more preferably 700°C or higher and 1000°C or lower. The heat treatment atmosphere can be appropriately selected depending on the metal compound that constitutes the coating layer. For example, when the metal compound is converted into an oxide, an oxidizing atmosphere, preferably air, is used, while when the metal oxide is converted into a nitride, a nitrogen atmosphere is preferred.

[0033] In the method for producing the coated ceramic continuous fiber of this embodiment, it is preferable to alternately repeat the impregnation step and the heat treatment step two or more times (performing the second impregnation step and heat treatment step after the first heat treatment step), and it is more preferable to alternately repeat the impregnation step and the heat treatment step two or more times, five or more times.

[0034] [Ceramic matrix composites (CMC)] A ceramic matrix composite material in one embodiment has the above-described coated ceramic continuous fibers, and is preferably a material in which the above-described coated ceramic continuous fibers and a ceramic matrix are combined.

[0035] The ceramic matrix is ​​at least one of an oxide ceramic and a non-oxide ceramic, preferably an oxide ceramic, more preferably at least one of alumina and mullite, and even more preferably alumina and mullite. Furthermore, it is preferable that the ceramic matrix and the ceramic continuous fibers are made of the same material.

[0036] The interfacial strength of the ceramic matrix composite material of this embodiment is preferably 10 MPa or less, more preferably 1 MPa to 10 MPa, and even more preferably 3 MPa to 8 MPa. When the interfacial strength is 10 MPa or less, the interface between the coated ceramic continuous fiber and the ceramic matrix is ​​more easily broken, making it less likely that the entire material will be broken. When the interfacial strength is 1 MPa or more, the interface has a more appropriate strength.

[0037] In this embodiment, the interfacial strength can be measured by a push-out method using a cylindrical ceramic with a diameter of 2 mm and a length of 3.4 mm instead of continuous ceramic fibers. The CMC is fabricated using the ceramic in a similar manner to the CMC of this embodiment. For details about the push-out method, see Composites: Part A 32 (2001) 575-584. The tensile strength of the CMC (hereinafter also referred to as "bulk tensile strength") can be 50 MPa or more and 300 MPa or less, and preferably 50 MPa or more and 280 MPa or less. The bulk tensile strength can be measured by using a plate-shaped sample with a width of 10 mm, a length of 100 mm, and a thickness of 5.0 mm and pulling it at a loading rate of 0.5 mm / min.

[0038] The content of the coated ceramic continuous fibers in the CMC is preferably 10% by volume or more and 90% by volume or less, more preferably 20% by volume or more and 70% by volume or less, based on the total volume of the ceramic matrix composite (CMC).

[0039] [Manufacturing method for ceramic matrix composites (CMC)] A method for producing a ceramic matrix composite material in one embodiment includes a compounding step of compounding the above-described coated ceramic continuous fibers with a ceramic matrix.

[0040] Any method for forming the composite may be used, but a preferred method is to impregnate continuous ceramic fibers with a slurry containing the raw materials for the ceramic matrix (hereinafter also referred to as "raw material slurry"), and then heat treat the resulting mixture. The impregnation and heat treatment steps are preferably repeated two or more times, and more preferably repeated two to five times to achieve an appropriate interfacial strength.

[0041] Since the ceramic matrix tends to become dense, a more preferred method is to impregnate the raw material slurry with ceramic continuous fibers, then heat-treat the resulting calcined body at a temperature lower than the sintering temperature, impregnate the resulting calcined body with the raw material slurry, and sinter the impregnated calcined body.

[0042] For example, when the ceramic matrix is ​​at least one of alumina and mullite, it is preferable to impregnate the continuous ceramic fibers with a raw material slurry of at least one of alumina and mullite, heat treat the resulting calcined body in the air at 600°C to 1000°C to form a calcined body, impregnate the calcined body with the raw material slurry, and then sinter the impregnated calcined body at 1050°C to 1300°C to form a composite. Note that prior to sintering, the impregnated calcined body may be heat treated in the air at 600°C to 1000°C. In this case, the impregnation and heat treatment of the calcined body may be repeated two or more times, and preferably repeated two to five times.

[0043] The raw material slurry of at least one of alumina and mullite may be a slurry containing at least one selected from the group consisting of alumina, aluminum hydroxide, aluminum nitrate, polyaluminum chloride, and mullite. When the impregnation is performed multiple times, the compositions of the raw material slurries may be different. [Example]

[0044] The present invention will be described below using examples, but the present invention is not limited to these examples.

[0045] Example A1 (Preparation of zirconia-coated alumina continuous fibers) An impregnation solution was prepared by dissolving 3.5 g of zirconium (IV) acetylacetonate (Zr(CH3COCHCOCH3)4) in 350 mL of ethanol. Alumina continuous fibers (alumina fiber cloth, manufactured by 3M Japan Ltd., product name: Nextel 610) that had been desized at 700 °C in air were placed in the impregnation solution and allowed to soak at room temperature for 24 hours. The total surface area of ​​the alumina continuous fibers was 6.2 m 2 The amount of zirconium (IV) acetylacetonate was adjusted to be in large excess relative to the coverage calculated by the above formula (1) (100% coverage: 0.0158 g), so that the coverage of the surface hydroxyl groups of the alumina continuous fiber would be 100%. The alumina continuous fiber was then removed from the impregnation solution and heated in air at 900°C under normal pressure for 2 hours. This impregnation step and heat treatment step were repeated three times to obtain a zirconia-coated alumina continuous fiber.

[0046] The surface of the obtained zirconia-coated alumina continuous fiber was photographed using a TEM. Figure 1(a) is a TEM image of the zirconia-coated alumina continuous fiber of Example A1. Figure 1(b) is an EDS image showing the aluminum distribution in the zirconia-coated alumina continuous fiber of Figure 1(a). Figure 1(c) is an EDS image showing the zirconium distribution in the zirconia-coated alumina continuous fiber of Figure 1(a). Figure 1(d) is an EDS image showing the oxygen distribution in the zirconia-coated alumina continuous fiber of Figure 1(a). As shown in Figure 1(c), it was confirmed that a 3-5 nm coating layer containing zirconium was formed on the surface of the zirconia-coated alumina continuous fiber of Example A1. Furthermore, as shown in Figure 1(d), oxygen was detected in the coating layer, confirming that the coating layer was composed of zirconia (ZrO2), an oxide. That is, it was confirmed that a zirconia coating layer having a thickness of 3 to 5 nm was formed on the surface of the alumina continuous fiber.

[0047] (ESCA analysis) ESCA analysis was performed on the zirconia-coated alumina continuous fiber in the depth direction of the alumina continuous fiber using a multifunctional scanning X-ray photoelectron spectrometer (device name: PHI5000 VersaProbeII, manufactured by ULVAC-PHI, Inc.) under the following conditions.

[0048] X-ray source: Monochrome Al-Kα ray, 25W Accelerating voltage: 15 kV Irradiation current: 300nA Analysis area: 100μmφ Sputtering conditions: Ion gun: Ar monomer ion (1 kV or 4 kV) Sputtering depth: 0 to 200 nm (SiO2 equivalent) Sputtering area: 2 x 2 mm

[0049] Fig. 2 is a graph showing the results of ESCA analysis of the surface of the zirconia-coated alumina continuous fiber of Example A1. As shown in Fig. 2, it was confirmed that zirconium and oxygen were present near the surface (to a depth of about 15 nm) of the alumina continuous fiber.

[0050] (Measurement of single fiber tensile strength) The single fiber tensile strength of the obtained zirconia-coated alumina continuous fiber was measured in accordance with JIS R 1657. The single fiber tensile strength of the zirconia-coated alumina continuous fiber was 2.1 GPa, which was almost the same as the single fiber tensile strength (2.5 GPa) of the desized alumina continuous fiber.

[0051] Example A2 (Preparation of zirconia-coated mullite continuous fibers) An impregnation solution was prepared by dissolving 3.5 g of zirconium (IV) acetylacetonate (Zr(CH3COCHCOCH3)4) in 350 mL of ethanol. Desized (heat-treated in air at 800°C) mullite continuous fiber (mullite fiber cloth, manufactured by 3M Japan Ltd., product name: Nextel 720) was placed in the impregnation solution and allowed to soak for 24 hours at room temperature. The total surface area of ​​the mullite continuous fiber was 5.5 m 2 The amount of zirconium (IV) acetylacetonate was adjusted to be in large excess relative to the coverage calculated by the above formula (1) (100% coverage: 0.0125 g), so that the coverage of the surface hydroxyl groups of the mullite continuous fiber would be 100%. The mullite continuous fiber was then removed from the impregnation solution and heated in air at 900°C for 2 hours under normal pressure to obtain a zirconia-coated mullite continuous fiber.

[0052] The surface of the obtained zirconia-coated mullite continuous fiber was photographed by TEM. FIG. 3(a) is a TEM image of the zirconia-coated mullite continuous fiber of Example A2. FIG. 3(b) is an EDS image showing the aluminum distribution in the zirconia-coated mullite continuous fiber of FIG. 3(a). FIG. 3(c) is an EDS image showing the silicon distribution in the zirconia-coated mullite continuous fiber of FIG. 3(a). FIG. 3(d) is an EDS image showing the zirconium distribution in the zirconia-coated mullite continuous fiber of FIG. 3(a). FIG. 3(e) is an EDS image showing the oxygen distribution in the zirconia-coated mullite continuous fiber of FIG. 3(a). As shown in FIG. 3(d), it was confirmed that a coating layer containing zirconium and having a thickness of 3 to 7 nm was formed on the surface of the zirconia-coated mullite continuous fiber of Example A2. Furthermore, as shown in Figure 3(d), oxygen was detected in the coating layer, confirming that the coating layer was composed of zirconia (ZrO2), an oxide. In other words, it was confirmed that a zirconia coating layer with a thickness of 3 to 7 nm was formed on the surface of the mullite continuous fiber.

[0053] (ESCA analysis) ESCA analysis was performed in the depth direction of the zirconia-coated mullite continuous fiber under the same conditions as in Example A1. Fig. 4 is a graph showing the results of ESCA analysis of the surface of the zirconia-coated mullite continuous fiber of Example A2. As shown in Fig. 4, it was confirmed that zirconium and oxygen were present near the surface (to a depth of about 15 nm) of the mullite continuous fiber.

[0054] (Measurement of single fiber tensile strength) The single fiber tensile strength of the obtained zirconia-coated mullite continuous fiber was measured in accordance with JIS R 1657. The single fiber tensile strength of the zirconia-coated mullite continuous fiber was 1.3 GPa, which was almost the same as the single fiber tensile strength (1.5 GPa) of the desized mullite continuous fiber.

[0055] Example A3 (Preparation of lanthanum oxide coated alumina continuous fibers) Lanthanum oxide-coated alumina continuous fibers were obtained in the same manner as in Example A1, except that zirconium (IV) acetylacetonate was replaced with lanthanum (III) acetylacetonate dihydrate (La(CHCOCHCOCH) 2H0). The total surface area of ​​the alumina continuous fibers was 6.2 m. 2 The amount of lanthanum (III) acetylacetonate was adjusted to be in large excess (3.5 g) relative to the coverage calculated by the above formula (1) (100% coverage: 0.0188 g), so that the coverage of the surface hydroxyl groups of the alumina continuous fiber was 100%.

[0056] The surface of the obtained lanthanum oxide-coated alumina continuous fiber was photographed by TEM. Figure 5(a) is a TEM image of the lanthanum oxide-coated alumina continuous fiber of Example A3. Figure 5(b) is an EDS image showing the aluminum distribution in the lanthanum oxide-coated alumina continuous fiber of Figure 5(a). Figure 5(c) is an EDS image showing the lanthanum distribution in the lanthanum oxide-coated alumina continuous fiber of Figure 5(a). Figure 5(d) is an EDS image showing the oxygen distribution in the lanthanum oxide-coated alumina continuous fiber of Figure 5(a). As shown in Figure 5(c), it was confirmed that a 5-10 nm coating layer containing lanthanum was formed on the surface of the lanthanum oxide-coated alumina continuous fiber of Example A3. Furthermore, as shown in Figure 5(d), oxygen was detected in the coating layer, confirming that the coating layer was composed of the oxide lanthanum oxide (La2O3). That is, it was confirmed that a coating layer of lanthanum oxide having a thickness of 5 to 10 nm was formed on the surface of the alumina continuous fiber.

[0057] (ESCA analysis) ESCA analysis of the lanthanum oxide-coated alumina continuous fiber was performed under the same conditions as in Example A1. Figures 6(a) to 6(c) are graphs showing the results of ESCA analysis of the surface of the lanthanum oxide-coated alumina continuous fiber of Example A3. As shown in Figures 6(a) to 6(c), it was confirmed that lanthanum and oxygen were present near the surface of the alumina continuous fiber in addition to aluminum derived from the fiber.

[0058] (Measurement of single fiber tensile strength) The single fiber tensile strength of the obtained lanthanum oxide-coated alumina continuous fiber was measured in accordance with JIS R 1657. The single fiber tensile strength of the lanthanum oxide-coated mullite continuous fiber was 2.7 GPa, which was almost the same as the single fiber tensile strength (2.5 GPa) of the desized alumina continuous fiber.

[0059] Example A4 (Preparation of lanthanum oxide coated mullite continuous fibers) Lanthanum oxide-coated mullite continuous fibers were obtained in the same manner as in Example A2, except that zirconium (IV) acetylacetonate was replaced with lanthanum (III) acetylacetonate dihydrate (La(CHCOCHCOCH) 2H0). The total surface area of ​​the mullite continuous fibers was 5.5 m. 2 The amount of lanthanum (III) acetylacetonate was adjusted to be in large excess relative to the coverage calculated by the above formula (1) (100% coverage: 0.0149 g), so that the coverage of the surface hydroxyl groups of the mullite continuous fiber would be 100%.

[0060] The surface of the obtained lanthanum oxide-coated mullite continuous fiber was photographed using a TEM. Figure 7(a) is a TEM image of the lanthanum oxide-coated mullite continuous fiber of Example A4. Figure 7(b) is an EDS image showing the aluminum distribution in the lanthanum oxide-coated mullite continuous fiber of Figure 7(a). Figure 7(c) is an EDS image showing the silicon distribution in the lanthanum oxide-coated mullite continuous fiber of Figure 7(a). Figure 7(d) is an EDS image showing the lanthanum distribution in the lanthanum oxide-coated mullite continuous fiber of Figure 7(a). As shown in Figure 7(d), it was confirmed that a coating layer containing lanthanum and having a thickness of 10 nm to 32 nm was formed on the surface of the lanthanum oxide-coated mullite continuous fiber of Example A4. Furthermore, as shown in Figure 7(e), oxygen was detected in the coating layer, confirming that the coating layer was composed of the oxide lanthanum oxide (La2O3). That is, it was confirmed that a coating layer of lanthanum oxide having a thickness of about 30 nm was formed on the surface of the mullite continuous fiber.

[0061] (ESCA analysis) ESCA analysis of the lanthanum oxide-coated mullite continuous fiber was performed under the same conditions as in Example A1. Figures 8(a) to 8(d) are graphs showing the results of ESCA analysis of the surface of the lanthanum oxide-coated mullite continuous fiber of Example A4. As shown in Figures 8(a) to 8(d), it was confirmed that lanthanum and oxygen derived from lanthanum oxide were present near the surface of the mullite continuous fiber in addition to aluminum and silicon derived from the fiber.

[0062] (Measurement of single fiber tensile strength) The single fiber tensile strength of the obtained lanthanum oxide-coated mullite continuous fiber was measured in accordance with JIS R 1657. The single fiber tensile strength of the lanthanum oxide-coated mullite continuous fiber was 1.8 GPa, which was almost the same as the single fiber tensile strength (1.5 GPa) of the desized mullite continuous fiber.

[0063] Comparative Example A1 An alumina continuous fiber was dipped into a zirconia nanosolution (solid content 30% by mass, particle diameter 63 nm) and then heated in air at 900°C under normal pressure for 2 hours. This process was repeated three times, and the alumina continuous fiber was observed using an SEM. The alumina continuous fiber of Comparative Example A1 had a large zirconia particle diameter in the zirconia nanosolution, and it is expected that the thickness of the coating layer would exceed 50 nm.

[0064] Fig. 9 is an image of the alumina continuous fibers of Comparative Example A1 taken by SEM. As shown in Fig. 9, it was confirmed that the alumina continuous fibers of Comparative Example A1 were agglomerated by zirconia particles.

[0065] Example B1 (Fabrication of ceramic matrix composites (CMC)) A raw material powder was prepared by mixing 25% by mass of approximately spherical α-alumina powder with an average particle size of 0.19 μm and 75% by mass of mullite powder with an average particle size of 1.66 μm. 350 g of the raw material powder and 146 g of pure water were mixed in a ball mill to obtain a mixed slurry of alumina and mullite.

[0066] Next, the zirconia-coated alumina continuous fiber obtained in Example A1 was impregnated with a mixed slurry of alumina and mullite, and then dried at a temperature of 70°C and a relative humidity of 95% to obtain a molded body having a width of 110 mm, a length of 110 mm, and a thickness of approximately 5.0 mm. The molded body was dried overnight in the air at 120°C, and then heat-treated in the air at 900°C for 2 hours to obtain a calcined body.

[0067] The calcined body was dissolved in approximately 10% by mass of an aqueous solution of polyaluminum chloride ([Al(OH) n Cl 6-n ] m The CMC was impregnated into a CMC matrix (1≦n≦5, m≦10, m and n are integers), dried at room temperature, and then heat-treated at 900°C for 2 hours. This impregnation and heat treatment was repeated three times. After the third heat treatment, the calcined body was sintered in air at 1100°C for 2 hours to obtain a sintered CMC plate. The obtained CMC plate contained 33.4% by volume of fibers and had a density of 2.48 g / cm.3 The density of the CMC was measured by the Archimedes method.

[0068] (Measurement of bulk tensile strength) The obtained CMC was processed to a width of 10 mm, length of 100 mm, and thickness of 5.0 mm, and aluminum tabs were attached to both ends to prepare tensile test specimens. The width and thickness of the tensile test specimen were measured using a micrometer, and the length of the specimen was measured using a vernier caliper. A tensile strength test was performed at a loading rate of 0.5 mm / min using a strength tester (manufactured by Shimadzu Corporation, device name: AG-XPlus) and a tensile test jig. Five test specimens were used for the tensile strength test, and the average value of the five specimens was taken as the bulk tensile strength. The bulk tensile strength of the obtained CMC was 80 MPa.

[0069] (Interface strength measurement) The interfacial strength of the obtained CMC was measured by a push-out test in which an alumina rod coated with a metal acetylacetonate complex was prepared in the same manner as in the preparation of the coated ceramic continuous fiber, and only the alumina rod was pressed into the rod using a strength testing machine (manufactured by Shimadzu Corporation, device name: AG-2000B).

[0070] Fig. 10 is a schematic cross-sectional view showing an example of an interface strength measuring device. The interface strength measuring device 10 shown in Fig. 10 mainly comprises an evaluation sample 5 consisting of a surface-coated alumina rod 3 and a ceramic matrix 4, a strength tester 1 for pressing the surface-coated alumina rod 3 in direction A, an indenter 2 connected to the strength tester 1 for pressing the surface-coated alumina rod 3, and a fixing table 6 for fixing the ceramic matrix 4 portion of the evaluation sample 5.

[0071] To measure the interfacial strength, a cylindrical alumina rod (2 mm diameter x 3.4 mm length) was first prepared. The surface of the alumina rod (2 mm diameter x 3.4 mm length) was coated with the metal acetylacetonate complex used in the preparation of the coated ceramic continuous fiber to produce a surface-coated alumina rod 3. Next, the raw material powder used in the preparation of the CMC was prepared. The surface-coated alumina rod 3 was embedded in the raw material powder and molded using a die press and a cold isostatic press at a pressure of 200 MPa to produce a compact (21 mm diameter x 3.4 mm length) with the surface-coated alumina rod 3 embedded. The compact was then processed using the same procedure as in the preparation of the CMC to obtain an evaluation sample 5 consisting of the surface-coated alumina rod 3 and a ceramic matrix 4. Only the ceramic matrix 4 portion of the evaluation sample 5 was fixed to a fixing table 6, and the surface-coated alumina rod 3 portion was pressed using a stainless steel indenter 2 with a diameter of 1 mm. The stress-strain curve at this time was obtained. The interface strength τ is calculated from the maximum load P in the stress-strain curve and the contact area between the surface-coated alumina rod 3 and the ceramic matrix 4 using equation (2). τ=Pmax / (2πrl) (2) [In equation (2), Pmax is the maximum load in the stress-displacement curve in the push-out test, π is the ratio of the circumference of the alumina rod to its diameter, r is the radius of the alumina rod, and l is the length of the alumina rod.]

[0072] In other words, in this interfacial strength measurement, the interfacial strength between the surface-coated alumina and the ceramic matrix can be measured by pressing the surface-coated alumina rod into an evaluation sample in which the surface-coated alumina rod and the ceramic matrix are combined, and the interfacial strength of the CMC can be measured.

[0073] Measurement example B1 (interface strength measurement) A mixed slurry of alumina and mullite was prepared in the same manner as in Example B1 and dried to obtain a raw material powder. Next, 0.5 g of zirconium (IV) acetylacetonate (Zr(CH3COCHCOCH3)4) was dissolved in 50 mL of ethanol to obtain a powder with a total surface area of ​​0.094 m 2The alumina rod was impregnated at room temperature for 24 hours. The amount of the additive was in large excess of the amount required to achieve a 100% coverage calculated by the above formula (1). The coverage of the alumina rod was calculated using the above formula (1), similar to that of the ceramic continuous fiber. (The alumina rod is a ceramic having hydroxyl groups on its surface and is coated with a metal acetylacetonate complex (zirconium (IV) acetylacetonate), so the coverage can be calculated using the above formula (1).) The alumina rod was then removed and heat-treated in air at 900°C for 2 hours. The impregnation and heat-treatment steps (hereinafter also referred to as "surface coating treatment") were repeated three times to obtain a zirconia-coated alumina rod.

[0074] Next, a zirconia-coated alumina rod was embedded in the raw material powder and molded using a die press. The resulting compact was then processed using a cold isostatic press at 200 MPa to obtain a cylindrical compact with a diameter of 20 mm and a thickness of 4 mm, with the zirconia-coated alumina rod embedded in the center. The resulting compact was sintered in air at 900°C for 2 hours to produce a calcined compact. The calcined compact was then impregnated with a polyaluminum chloride aqueous solution and heat-treated three times using the same procedure as in Example B1, and then sintered in air at 1100°C for 2 hours, similar to Example B1, to produce a sintered compact in which the alumina rod and ceramic matrix were sintered together.

[0075] The resulting sintered body was ground with sandpaper so that the zirconia-coated alumina rods protruded from both sides of the cylinder, yielding a test piece (evaluation sample) with a diameter of 21 mm and a thickness of 3.4 mm. The interfacial strength measured by the push-out test was 9.8 MPa. Figure 11 is a graph showing the stress-displacement curve in the push-out test of Measurement Example B1. The arrow in Figure 11 indicates the maximum load (Pmax).

[0076] ·Measurement example B2 (interface strength measurement) A push-out test piece (evaluation sample) was obtained in the same manner as in Measurement Example B1, except that the alumina rod was surface-coated only once. The interfacial strength measured by the push-out test was 7.3 MPa. This measurement example shows that the interfacial strength is improved by repeating the surface coating treatment.

[0077] Measurement example B3 (interface strength measurement) Dissolve 0.00012 g of zirconium(IV) acetylacetonate (Zr(CH3COCHCOCH3)4) in 50 mL of ethanol to obtain a solution with a total surface area of ​​0.094 m 2 The alumina rod was impregnated at room temperature for 24 hours. At this time, the coverage calculated by formula (1) was 50%. A push-out test piece (evaluation sample) was obtained in the same manner as in Measurement Example B1, except that the zirconia-coated alumina rod thus prepared was used. The interfacial strength measured by the push-out test was 7.6 MPa. This measurement example shows that the interfacial strength improves by increasing the coverage.

[0078] ·Measurement example B4 (interface strength measurement) Dissolve 0.5 g of lanthanum acetylacetonate dihydrate (La(CH3COCHCOCH3)3·2H2O) in 50 mL of ethanol to obtain a total surface area of ​​0.094 m 2 The alumina rod was impregnated at room temperature for 24 hours. At this time, the amount added was in large excess of the amount required to achieve a coverage of 100% calculated by the above formula (1). A push-out test piece (evaluation sample) was obtained in the same manner as in Measurement Example B1, except that the coated alumina rod thus prepared was used. The interfacial strength measured by the push-out test was 7.0 MPa.

[0079] Example B2 (Fabrication of ceramic matrix composites (CMC)) 350 g of approximately spherical α-alumina powder with an average particle size of 0.19 μm and 146 g of pure water were mixed in a ball mill to obtain an alumina slurry.

[0080] The lanthanum oxide-coated mullite continuous fibers obtained in Example A3 were then impregnated in an alumina mixed slurry and dried to obtain a molded body measuring 110 mm in width, 110 mm in length, and approximately 0.5 mm in thickness. The molded body was dried overnight at 120°C in air, and then heat-treated at 1100°C in air for 2 hours to obtain CMC.

[0081] (Measurement of bulk tensile strength) The obtained CMC was processed to a width of 10 mm, length of 100 mm, and thickness of 0.5 mm, and aluminum tabs were attached to both ends to prepare tensile test specimens. The width and thickness of the tensile test specimens were measured using a micrometer, and the length of the specimen was measured using a vernier caliper. A tensile strength test was performed at a loading rate of 0.5 mm / min using a strength tester (manufactured by Shimadzu Corporation, device name: AG-XPlus) and a tensile test jig. Four specimens were used for the tensile strength test, and the average value of the four specimens was taken as the bulk tensile strength. The bulk tensile strength of the obtained CMC was 141 MPa.

[0082] Comparative Example B1 A CMC was obtained in the same manner as in Example B1, except that alumina continuous fibers (alumina fiber cloth, manufactured by 3M Japan Ltd., product name: Nextel 610) that had been desized (heat-treated in air at 700°C) were used instead of the zirconia-coated alumina continuous fibers (i.e., alumina continuous fibers that were not zirconia-coated were used). The fiber volume fraction of the CMC was 34.1% by volume, and the density of the CMC was 2.35 g / cm. 3 The bulk tensile strength was 9 MPa, which was lower than that of the CMC of Example B1.

[0083] ·Comparative measurement example B1 (interface strength measurement) A push-out test piece was obtained in the same manner as in Measurement Example B1, except that an alumina rod without surface coating treatment was used. The interfacial strength in the push-out test was 13.6 MPa. From this measurement example, it is thought that in the CMC of Comparative Example B1, failure occurred due to adhesion between the ceramic continuous fiber and the ceramic matrix.

[0084] Comparative example B2 A CMC was obtained in the same manner as in Example B2, except that desized (heat-treated in air at 700°C) mullite continuous fibers (mullite fiber cloth, manufactured by 3M Japan Ltd., product name: Nextel 720) were used instead of the lanthanum oxide-coated mullite continuous fibers (i.e., mullite continuous fibers not coated with lanthanum oxide were used). The bulk tensile strength was 107 MPa, which was lower than that of the CMC of Example B2.

[0085] From the above, comparing Measurement Example B1 and Comparative Measurement Example B1, it was found that the CMC of Example B1, which has a ceramic continuous fiber with a coating layer, is superior in strength to the CMC of Comparative Example B1, which has a ceramic continuous fiber without a coating layer on its surface. Furthermore, comparing the CMC of Example B2, which has a ceramic continuous fiber with a coating layer, and the CMC of Comparative Example B2, which has a ceramic continuous fiber without a coating layer on its surface, it was found that the CMC of Example B1 is superior in strength. These results confirm that the coated ceramic continuous fiber of the present invention is suitable for producing ceramic matrix composite materials with sufficiently high strength. [Industrial Applicability]

[0086] The coated ceramic continuous fiber of the present invention can be used as a CMC with high damage tolerance, such as tensile strength, because there is almost no aggregation of metal compounds in the surface coating of the continuous ceramic fiber. Furthermore, because the coated ceramic continuous fiber of the present invention can be produced by impregnating continuous ceramic fibers in a solvent containing a metal acetylacetonate complex, coating treatment can be easily performed on not only two-dimensional cloth-shaped woven fabrics but also woven or nonwoven fabrics with complex three-dimensional shapes, making it possible to widely use the fiber industrially. [Explanation of symbols]

[0087] 1...strength tester, 2...indenter, 3...surface-coated alumina rod, 4...ceramic matrix, 5...evaluation sample, 6...fixing table, 10...interfacial strength measuring device.

Claims

1. A coated ceramic continuous fiber, comprising a ceramic continuous fiber having a coating layer of a metal compound on the surface thereof with a thickness of 7 nm or less.

2. 2. The coated ceramic continuous fiber according to claim 1, wherein the metal compound is at least one of a zirconium compound and a lanthanum compound.

3. 3. The coated ceramic continuous fiber according to claim 1, wherein the metal compound is zirconia or lanthanum oxide.

4. 4. The coated ceramic continuous fiber according to claim 1, wherein the ceramic continuous fiber is at least one of an alumina continuous fiber and a mullite continuous fiber.

5. A ceramic matrix composite material comprising the coated ceramic continuous fiber according to any one of claims 1 to 4.

6. 6. The ceramic matrix composite material according to claim 5, wherein the interfacial strength is 10 MPa or less.

7. A method for producing a ceramic matrix composite material, comprising a compounding step of compounding the coated ceramic continuous fiber according to any one of claims 1 to 4 with a ceramic matrix.

Images