阅读说明：本技术 带有被覆层的陶瓷连续纤维及其制造方法、以及陶瓷基体复合材料及其制造方法 (Ceramic continuous fiber with coating layer and method for producing same, and ceramic matrix composite material and method for producing same ) 是由 山下勋 绳田祐志 于 2020-03-24 设计创作，主要内容包括：本发明公开了带有被覆层的陶瓷连续纤维,其特征在于,其是由在表面具有厚度为50nm以下的金属化合物的被覆层的陶瓷连续纤维形成的。另外,本发明公开了具有上述的带有被覆层的陶瓷连续纤维的陶瓷基体复合材料。(The present invention discloses a coated ceramic continuous fiber, which is characterized in that the coated ceramic continuous fiber is formed by a ceramic continuous fiber with a coating layer of a metal compound with the thickness of less than 50nm on the surface. Further, the present invention discloses a ceramic matrix composite having the above-described ceramic continuous fiber with a coating layer.)

1. A coated ceramic continuous fiber characterized by being formed of a ceramic continuous fiber having a coating layer of a metal compound having a thickness of 50nm or less on the surface thereof.

2. The coated continuous ceramic fiber according to claim 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 claim 1 or 2, wherein the metal compound is zirconia or lanthana.

4. The coated ceramic continuous fiber according to any one of claims 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 comprising the coated ceramic continuous fiber according to any one of claims 1 to 4.

6. The ceramic matrix composite according to claim 5, having an interfacial strength of 10MPa or less.

7. A method for producing a coated ceramic continuous fiber according to any one of claims 1 to 4,

the manufacturing method comprises the following steps:

an impregnation step of impregnating a solution containing a metal acetylacetone complex with ceramic continuous fibers; and the number of the first and second groups,

and a heat treatment step of heat-treating the impregnated ceramic continuous fibers.

8. A method for producing a ceramic matrix composite material, comprising the following compositing step: a coated ceramic continuous fiber according to any one of claims 1 to 4, which is combined with a ceramic matrix.

Technical Field

The present invention relates to a coated ceramic continuous fiber and a method for producing the same, and a ceramic matrix composite and a method for producing the same.

Background

A ceramic matrix composite material (hereinafter, also referred to as "CMC") in which ceramic continuous fibers are composited with a ceramic matrix has resistance (damage tolerance) to damage of the entire material due to progress of damage, as compared with a normal ceramic, and therefore, studies have been made as a substitute material for a heat-resistant metal such as a Ni-based alloy.

In addition, alumina and mullite oxides have high chemical stability, and therefore, CMC obtained by forming alumina and mullite oxides into ceramic continuous fibers and compositing the ceramic continuous fibers with a ceramic matrix is expected to be used as a member for an aircraft jet engine (for example, non-patent document 1).

The damage tolerance of CMC is caused by the inhibition of the progress of damage by the selective exfoliation or destruction of the interface between the ceramic continuous fiber and the ceramic matrix. Therefore, when the ceramic continuous fibers are bonded to the ceramic substrate, the progress of damage cannot be suppressed, and the material tends to be easily damaged.

In order to prevent adhesion between the ceramic continuous fibers and the ceramic matrix, it has been studied to coat the surfaces of the ceramic continuous fibers with a compound that promotes the destruction of the interface or the like. However, coating by physical vapor deposition such as sputtering or ion plating is likely to be coating only on the fiber surface. Thus, Chemical Vapor Deposition (CVD), coating using a solution, and the like have been studied, and for example, CVD using boron nitride and coating using a zirconium oxide nano solution (ZrO)₂Slurry of (4) and the like (for example, patent documents 1 and 2).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 11-049570

Patent document 2: japanese laid-open patent publication No. 2002-173376

Non-patent document

Non-patent document 1: AerosapaceLab, No. 3, (2011)1-12.

Disclosure of Invention

Problems to be solved by the invention

In general, when producing CMC, fibers in a state where 2 or more fibers are aggregated (hereinafter, also referred to as "fiber bundle") in units of several hundred are used as ceramic continuous fibers. However, in the CVD method described in patent document 1, the inside of the fiber bundle is hardly covered (the inside continuous fibers are hardly covered), and the strength of the obtained CMC tends to be low. In addition, according to the method described in patent document 2, it is difficult to control the film thickness, and the continuous fibers are easily aggregated. As a result, the strength of the obtained CMC tends to be low.

The present invention has been made in view of the above circumstances, and a main object thereof is to provide a coated ceramic continuous fiber suitable for producing a ceramic matrix composite material improved in damage tolerance, and a ceramic matrix composite material using the same.

Means for solving the problems

The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the damage tolerance of CMC can be improved by using a ceramic continuous fiber with a coating layer in which the coating layer and the state thereof are controlled, thereby completing the present invention.

Namely, the present invention provides the coated ceramic continuous fiber shown in [1] to [4 ]; [5] a ceramic matrix composite material described in [6 ]; [7] a method for producing the coated ceramic continuous fiber; and [8] a method for producing the ceramic matrix composite material.

[1] A coated ceramic continuous fiber characterized by being formed of a ceramic continuous fiber having a coating layer of a metal compound having a thickness of 50nm or less on the surface thereof.

[2] The coated continuous ceramic 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 lanthana.

[4] The 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 comprising the coated ceramic continuous fiber according to any one of [1] to [4 ].

[6] The ceramic matrix composite according to [5], which has an interface strength of 10MPa 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 a solution containing a metal acetylacetone complex with ceramic continuous fibers; and a heat treatment step of heat-treating the impregnated ceramic continuous fibers.

[8] A method for producing a ceramic matrix composite material, comprising the following compositing step: a composite of the coated ceramic continuous fiber according to any one of [1] to [4] and a ceramic substrate.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, at least one of a coated ceramic continuous fiber suitable for producing a ceramic matrix composite material with improved 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 can be provided.

Drawings

Fig. 1(a) is an image of the zirconia coated alumina continuous fiber of example a1 taken with a transmission electron microscope (hereinafter also referred to as "TEM"). Fig. 1(b) is an image showing the distribution of aluminum in the zirconia-coated alumina continuous fiber of fig. 1(a) by an energy-dispersive X-ray method (hereinafter, also referred to as "EDS"). Fig. 1(c) is an image showing the distribution of zirconium in the zirconia coated alumina continuous fiber of fig. 1(a) based on EDS. Fig. 1(d) is an image showing the distribution of oxygen in the zirconia coated alumina continuous fiber of fig. 1(a) based on EDS.

FIG. 2 is a graph showing the results of analysis by X-ray photoelectron spectroscopy (hereinafter, also referred to as "ESCA") analysis of the surface of a continuous alumina fiber coated with zirconia of example A1.

Fig. 3(a) is an image of the zirconia coated mullite continuous fiber of example a2 photographed by TEM. Fig. 3(b) is an image showing the distribution of aluminum in the zirconia-coated mullite continuous fiber of fig. 3(a) based on EDS. Fig. 3(c) is an image showing the distribution of silicon in the zirconia-coated mullite continuous fiber of fig. 3(a) based on EDS. Fig. 3(d) is an image showing the distribution of zirconium in the zirconia coated mullite continuous fiber of fig. 3(a) based on EDS. Fig. 3(e) is an image showing the distribution of oxygen in the zirconia-coated mullite continuous fiber of fig. 3(a) based on EDS.

FIG. 4 is a graph showing the results of ESCA analysis of the surface of the continuous zirconia coated mullite fiber of example A2.

FIG. 5(a) is an image of a continuous alumina fiber coated with lanthanum oxide of example A3 taken by TEM. Fig. 5(b) is an image showing the distribution of aluminum in the lanthana-coated alumina continuous fiber of fig. 5(a) based on EDS. Fig. 5(c) is an image showing the distribution of lanthanum in the alumina continuous fiber coated with lanthanum oxide of fig. 5(a) based on EDS. Fig. 5(d) is an image showing the distribution of oxygen in the lanthana-coated alumina continuous fiber of fig. 5(a) based on EDS.

FIG. 6(a) to (c) are graphs showing the results of ESCA analysis of the surface of the continuous alumina fiber coated with lanthanum oxide of example A3.

Fig. 7(a) is an image of the lanthanum oxide coated mullite continuous fiber of example a4 photographed by TEM. Fig. 7(b) is an image showing the distribution of aluminum in the lanthanum oxide coated mullite continuous fiber of fig. 7(a) based on EDS. Fig. 7(c) is an image showing the distribution of silicon in the lanthanum oxide coated mullite continuous fiber of fig. 7(a) based on EDS. Fig. 7(d) is an image showing the distribution of lanthanum in the lanthanum oxide-coated mullite continuous fiber of fig. 7(a) based on EDS. Fig. 7(e) is an image showing the distribution of oxygen in the lanthanum oxide coated mullite continuous fiber of fig. 7(a) based on EDS.

FIG. 8(a) to (d) of FIG. 8 are graphs showing the results of ESCA analysis of the surfaces of the lanthanum oxide-coated mullite continuous fiber of example A4.

Fig. 9 is an image of the alumina continuous fiber of comparative example a1 taken by a scanning electron microscope (hereinafter, also referred to as "SEM").

FIG. 10 is a schematic cross-sectional view showing an example of an interface strength measuring apparatus.

FIG. 11 is a graph showing a stress-displacement curve in the extrapolation test of measurement example B1.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

[ ceramic continuous fiber with coating layer ]

The coated ceramic continuous fiber according to one embodiment is formed of a ceramic continuous fiber having a coating layer of a metal compound having a thickness of 50nm or less on the surface thereof. The coated ceramic continuous fiber according to the present embodiment may include a ceramic continuous fiber and a coating layer of a metal compound having a thickness of 50nm or less provided on the surface of the ceramic continuous fiber. In the present specification, the term "continuous fiber" refers to a long fiber, particularly a filamentous long fiber that can be woven by a textile machine. The term "ceramic continuous fiber" refers to a continuous fiber made of ceramic. The term "coating layer" means a layer covering at least a part of the continuous fiber, and the term "coating layer of a metal compound" means a coating layer containing a metal compound. The "ceramic continuous fiber with a coating layer" means a ceramic continuous fiber having a coating layer on the surface thereof.

In the ceramic continuous fiber with a coating layer of the present embodiment, the thickness of the coating layer is 50nm or less. Since the thickness of the coating layer is 50nm or less, aggregation of the ceramic continuous fibers can be prevented. The thickness of the coating layer is preferably 20nm or less, more preferably 10nm or less. The lower limit of the thickness of the coating layer is not particularly limited, and the thickness of the coating layer may be 1nm or more. In the present embodiment, the thickness of the coating layer is measured by the distribution of the metal elements constituting the metal compound obtained by TEM-EDS analysis. For example, the thickness is measured by the distribution of zirconium when the metal compound is a zirconium compound, and the thickness is measured by the distribution of lanthanum when the metal compound is a lanthanum compound.

The metal compound in the coating layer is not particularly limited as long as it is a compound containing a metal, but is preferably at least one of an oxide and a nitride containing a metal, and more preferably an oxide containing a metal. The metal compound is preferably at least 1 selected from the group consisting of a zirconium compound, a lanthanum compound, an 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 having these metal-containing compounds as the coating layer, the ceramic continuous fiber with the coating layer becomes more suitable for use as 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 which does not react with the ceramic continuous fibers and the ceramic matrix as a compound of a metal capable of forming a metal acetylacetonate complex. In the present specification, the term "matrix" refers to a matrix phase to be combined, and the term "ceramic matrix" refers to a matrix made of ceramic.

The metal compound is preferably a metal oxide, and particularly preferably a metal oxide, because it is suitable for the coating layer from the viewpoint of heat resistance and chemical stabilityZirconium oxide (ZrO)₂) Lanthanum oxide (La)₂O₃) Yttrium oxide (Y)₂O₃) Iron oxide (Fe)₂O₃) Or cerium oxide (CeO)₂). The metal compound is more preferably zirconium oxide (ZrO)₂) Lanthanum oxide (La)₂O₃) Or yttrium oxide (Y)₂O₃) More preferably, zirconia (ZrO)₂) Or lanthanum oxide (La)₂O₃)。

The ceramic continuous fibers of the present embodiment are not particularly limited as long as they are continuous fibers made of ceramic. Examples of the ceramic continuous fibers include at least one of oxide ceramic continuous fibers and non-oxide ceramic continuous fibers. 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 fibers are more preferably at least one of alumina continuous fibers and mullite continuous fibers, and are further preferably mullite continuous fibers. The ceramic continuous fibers preferably have hydroxyl groups on the surface.

The ceramic continuous fibers of the present embodiment are preferably at least one of a fiber bundle state and a fiber bundle warp-knitted state, and are preferably ceramic continuous fibers (hereinafter, also referred to as "ceramic fiber cloth") in a fiber bundle warp-knitted state.

The tensile strength (hereinafter, also referred to as "single fiber tensile strength") of the ceramic continuous fiber with a coating layer according to the present embodiment, measured according to JIS R1657, is preferably 1GPa or more and 3GPa or less, and more preferably 1.2GPa or more and 2.8GPa or less.

The ceramic continuous fiber with a coating layer according to the present embodiment is suitably used as CMC. The coated ceramic continuous fiber of the present embodiment is suitable for preventing aggregation of continuous fibers, and therefore can suppress adhesion between the coated ceramic continuous fiber and the ceramic base. Therefore, when the composite is used as CMC by being combined with a ceramic substrate, high damage tolerance can be exhibited.

[ method for producing ceramic continuous fiber with coating layer ]

A method for manufacturing a ceramic continuous fiber with a coating layer according to an embodiment includes: an impregnation step of impregnating a solution containing a metal acetylacetone complex with ceramic continuous fibers; and a heat treatment step of heat-treating the impregnated ceramic continuous fibers. By impregnating the ceramic continuous fibers, the chemical adsorption of the metal acetylacetone to the surfaces of the ceramic continuous fibers can be promoted. The ceramic continuous fibers to be subjected to the impregnation step may be in the form of fiber bundles or may be in the form of ceramic fiber cloth, and ceramic fiber cloth is preferable.

The metal acetylacetone complex to be subjected to the impregnation step is, for example, zirconium (IV) acetylacetonate (Zr (CH)₃COCHCOCH₃)₄) Lanthanum (III) acetylacetonate dihydrate (La (CH)₃COCHCOCH₃)₃·2H₂O), yttrium (III) acetylacetonate n hydrate (Y (CH)₃COCHCOCH₃)₃·nH₂O), iron (III) acetylacetonate (Fe (CH)₃COCHCOCH₃)₃) And cerium (III) acetylacetonate trihydrate (Ce (CH)₃COCHCOCH₃)₃·3H₂O), preferably zirconium (IV) acetylacetonate (Zr (CH)₃COCHCOCH₃)₄) Lanthanum (III) acetylacetonate dihydrate (La (CH)₃COCHCOCH₃)₃·2H₂O), and yttrium (III) acetylacetonate n hydrate (Y (CH)₃COCHCOCH₃)₃·nH₂O), more preferably zirconium (IV) acetylacetonate (Zr (CH)₃COCHCOCH₃)₄) And lanthanum (III) acetylacetonate dihydrate (La (CH)₃COCHCOCH₃)₃·2H₂O).

The solvent in the solution containing the metal acetylacetonate complex is not particularly limited as long as it is a solvent in which the metal acetylacetonate complex is dissolved without decomposition. Preferable examples of the solvent include 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.

The impregnation may be carried out under conditions that allow the chemical adsorption reaction of the metal acetylacetone complex to the ceramic continuous fibers to proceed, and for example, the impregnation temperature may be a boiling point of the solvent or less, preferably room temperature (25 ± 3 ℃) or less, and the impregnation time may be 30 minutes to 24 hours. In order to facilitate the chemisorption reaction, it is preferable to impregnate the substrate with heat at a temperature not higher than the boiling point of the solvent.

The impregnation is preferably performed so that the ratio of the area covered with the coating material to the total surface area of the ceramic continuous fibers (hereinafter, also referred to as "coverage") is 50% or more. Here, the "coating material" refers to a material for coating. When the coverage is 50% or more, when the coated ceramic continuous fiber obtained by the production method of the present embodiment is made into CMC, the adhesion between the coated ceramic continuous fiber and the ceramic substrate tends to be suppressed. Preferably, the impregnation is performed so that the coverage is 75% or more, preferably 90% or more. The coverage rate of 100% corresponds to a state where the coating material covers the entire surface of the ceramic continuous fiber, and therefore the coverage rate is 100% or less.

In this case, the coverage can be determined by the following equation.

θ＝100×nM×X/(S×nOH) (1)

[ theta ] is a coverage percentage (%), and S is a total surface area (m) of the ceramic continuous fibers²) And nOH is the number of hydroxyl groups per unit volume of the surface of the ceramic continuous fiber (number/m)²) nM is the number (number) of metal atoms of the metal acetylacetone complex used for the impregnation treatment, and X is the valence of the metal atom.]

When alumina continuous fibers were used, the surface hydroxyl number nOH was 12.5X 10¹⁸(per m)²) When a mullite continuous fiber is used, the number of surface hydroxyl groups nOH is 11.3X 10¹⁸(per m)²)。

The ceramic continuous fiber having a hydroxyl group on the surface is preferably at least one of an alumina continuous fiber and a mullite continuous fiber, and more preferably a mullite continuous fiber.

The method for producing a ceramic continuous fiber with a coating layer according to the present embodiment includes a step of heat-treating the obtained ceramic continuous fiber after the impregnation step. By heat-treating the obtained ceramic continuous fiber after the impregnation step, the metal acetylacetone complex chemically adsorbed to the ceramic continuous fiber is decomposed to become a metal compound. The heat treatment conditions are not particularly limited, and the heat treatment temperature is preferably 500 ℃ or more and 1200 ℃ or less, more preferably 700 ℃ or more and 1000 ℃ or less. The heat treatment atmosphere may be appropriately selected depending on the metal compound constituting the coating layer, and for example, when the metal compound is an oxide, an oxidizing atmosphere is preferable, and in the air, and when the metal oxide is a nitride, a nitrogen atmosphere is preferable.

In the method for producing a ceramic continuous fiber with a coating layer according to the present embodiment, the impregnation step and the heat treatment step are preferably alternately repeated 2 or more times (the impregnation step and the heat treatment step are performed a second time after the first heat treatment step), and more preferably, the impregnation step and the heat treatment step are alternately repeated 2 or more times to 5 or more times.

Ceramic Matrix Composite (CMC)

The ceramic matrix composite material according to one embodiment has the above-described coated ceramic continuous fiber, and preferably is a composite material of the above-described coated ceramic continuous fiber and a ceramic matrix.

The ceramic substrate 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 still more preferably alumina and mullite. Further, the ceramic substrate and the ceramic continuous fibers are preferably made of the same material.

The interface strength of the ceramic matrix composite of the present embodiment is preferably 10MPa or less, more preferably 1MPa or more and 10MPa or less, and still more preferably 3MPa or more and 8MPa or less. If the interface strength is 10MPa or less, the interface between the coated ceramic continuous fiber and the ceramic matrix is more easily broken, and the entire material is less likely to be broken, and if the interface strength is 1MPa or more, the interface has more appropriate strength.

In the present embodiment, the interfacial strength may be measured by a method of extruding a measurement sample using a cylindrical ceramic having a diameter of 2mm × a length of 3.4mm, instead of the ceramic continuous fibers, and using CMC produced by the same method as the CMC of the present embodiment using the ceramic as the measurement sample. For the push-out method, reference may be made to compositions: part A32 (2001) 575-. The tensile strength (hereinafter, also referred to as "bulk tensile strength") of CMC is, for example, 50MPa to 300MPa, and preferably 50MPa to 280 MPa. The bulk tensile strength can be measured by using a plate-shaped measurement specimen having a width of 10mm, a length of 100mm and a thickness of 5.0mm, and drawing it at a load speed of 0.5 mm/min.

The content of the ceramic continuous fiber with a coating layer in the CMC is preferably 10 vol% or more and 90 vol% or less, and more preferably 20 vol% or more and 70 vol% or less, based on the total volume of the Ceramic Matrix Composite (CMC).

[ method for producing Ceramic Matrix Composite (CMC) ]

A method for producing a ceramic matrix composite material according to an embodiment includes the following composite step: the coated ceramic continuous fiber is combined with a ceramic matrix.

The method of forming the composite may be any method, but the following methods may be exemplified as a preferable method: a slurry containing a raw material of a ceramic substrate (hereinafter, also referred to as "raw material slurry") is impregnated with ceramic continuous fibers, and then heat-treated. The impregnation and heat treatment steps are preferably repeated 2 or more times, and more preferably repeated 2 or more times and 5 or less times in order to set an appropriate interface strength.

In order to facilitate densification of the ceramic substrate, the following method is more preferable: the method for producing a ceramic green body includes impregnating a raw material slurry with ceramic continuous fibers, heat-treating the raw material slurry at a temperature lower than a sintering temperature to prepare a pre-sintered body, further impregnating the pre-sintered body with the raw material slurry, and sintering the impregnated pre-sintered body.

For example, when the ceramic substrate is at least one of alumina and mullite, it is preferable that the ceramic continuous fibers are impregnated in a raw material slurry of at least one of alumina and mullite, then heat-treated at 600 ℃ to 1000 ℃ in the air to prepare a calcined body, the calcined body is impregnated in the raw material slurry, and then the impregnated calcined body is sintered at 1050 ℃ to 1300 ℃ to obtain a composite. The impregnated pre-fired body may be heat-treated at 600 to 1000 ℃ in the air before sintering. In this case, the impregnation and the heat treatment of the calcined body may be repeated 2 or more times, preferably 2 or more times to 5 or less times.

As the raw material slurry of at least either one of alumina and mullite, a slurry containing at least any one selected from the group consisting of alumina, aluminum hydroxide, aluminum nitrate, polyaluminum chloride, and mullite is cited. When the impregnation is performed a plurality of times, the composition of the raw material slurry may be different.

Examples

The present invention will be described below with reference to examples. However, the present invention is not limited to these examples.

Example A1

(preparation of alumina continuous fiber coated with zirconia)

Zirconium (IV) acetylacetonate (Zr (CH)₃COCHCOCH₃)₄)3.5g of the extract was dissolved in 350mL of ethanol to prepare an immersion liquid. An alumina continuous fiber (alumina fiber cloth, product name: Nextel 610 manufactured by 3M Japan Limited) which had been subjected to desizing (size) treatment in the air at 700 ℃ was put into the impregnation solution and impregnated at room temperature for 24 hours. The total surface area of the alumina continuous fibers was 6.2m²The amount of zirconium (IV) acetylacetonate was adjusted to be significantly excessive with respect to the coverage (100% coverage: 0.0158g) obtained by the above formula (1) so that the coverage of the hydroxyl groups on the surface of the alumina continuous fibers became 100%. Thereafter, the alumina continuous fibers were taken out from the impregnation solution and made largeHeating in air at 900 deg.C under normal pressure for 2 hr. The impregnation step and the heat treatment step were repeated 3 times, thereby obtaining zirconia-coated alumina continuous fibers.

The surface of the obtained alumina continuous fiber coated with zirconia was imaged by TEM. Fig. 1(a) is an image of the zirconia coated alumina continuous fiber of example a1 taken by TEM. Fig. 1(b) is an image showing the distribution of aluminum in the zirconia coated alumina continuous fiber of fig. 1(a) based on EDS. Fig. 1(c) is an image showing the distribution of zirconium in the zirconia coated alumina continuous fiber of fig. 1(a) based on EDS. Fig. 1(d) is an image showing the distribution of oxygen in the zirconia coated alumina continuous fiber of fig. 1(a) based on EDS. As shown in FIG. 1(c), it was confirmed that in the alumina continuous fiber coated with zirconium oxide of example A1, a coating layer containing zirconium of 3 to 5nm was formed on the surface of the alumina continuous fiber. Further, as shown in fig. 1(d), oxygen was detected in the coating layer, and it was confirmed that the coating layer was composed of zirconium oxide (ZrO) as an oxide₂) And (4) forming. That is, it was confirmed that a coating layer of zirconia having a thickness of 3 to 5nm was formed on the surface of the alumina continuous fiber.

(ESCA analysis)

ESCA analysis was performed in the depth direction of the alumina continuous fiber coated with zirconia by using a multi-function scanning X-ray photoelectron spectroscopy apparatus (apparatus name: PHI5000 Versa Probe II, ULVAC-PHI, manufactured by Inc.) under the following conditions.

An X-ray source: monochromatic Al-K alpha ray, 25W

Acceleration voltage: 15kV

Irradiation current: 300nA

Analysis area: 100 μm phi

Sputtering conditions: an ion gun: ar monomer ion (1kV or 4kV)

Sputtering depth: 0 to 200nm (as SiO)₂Conversion)

Sputtering area: 2X 2mm

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 in the vicinity of the surface of the alumina continuous fiber (depth of about 15 nm).

(measurement of Single fiber tensile Strength)

The single fiber tensile strength of the obtained zirconia-coated alumina continuous fiber was measured according to JIS R1657. The tensile strength of the single fibers of the alumina continuous fibers coated with zirconia was 2.1GPa, and was approximately the same as the tensile strength (2.5GPa) of the single fibers of the alumina continuous fibers subjected to the desizing treatment.

Example A2

(preparation of zirconia-coated mullite continuous fiber)

Zirconium (IV) acetylacetonate (Zr (CH)₃COCHCOCH₃)₄)3.5g of the extract was dissolved in 350mL of ethanol to prepare an immersion liquid. A degummed (heat-treated at 800 ℃ C. in the air) mullite continuous fiber (mullite fiber cloth, product name: Nextel 720, manufactured by 3M Japan Limited) was put into the impregnation liquid and impregnated at room temperature for 24 hours. The total surface area of the mullite continuous fibers was 5.5m²The amount of zirconium (IV) acetylacetonate was adjusted to be significantly excessive with respect to the coverage (100% coverage: 0.0125g) obtained by the above formula (1) so that the coverage of the hydroxyl groups on the surface of the mullite continuous fiber became 100%. Thereafter, the mullite continuous fiber was taken out from the impregnation solution and heated at 900 ℃ for 2 hours under normal pressure in the atmosphere to obtain a zirconia-coated mullite continuous fiber.

The surface of the obtained mullite continuous fiber coated with zirconia was imaged by TEM. Fig. 3(a) is an image of the zirconia coated mullite continuous fiber of example a2 taken by TEM. Fig. 3(b) is an image showing the distribution of aluminum in the zirconia-coated mullite continuous fiber of fig. 3(a) based on EDS. Fig. 3(c) is an image showing the distribution of silicon in the zirconia-coated mullite continuous fiber of fig. 3(a) based on EDS. Fig. 3(d) is an image showing the distribution of zirconium in the zirconia coated mullite continuous fiber of fig. 3(a) based on EDS. FIG. 3(e) shows the coating of FIG. 3(a) with zirconium oxide based on EDSAn image of the distribution of oxygen in the mullite continuous fiber. As shown in fig. 3(d), it was confirmed that in the mullite continuous fiber coated with zirconia of example a2, a coating layer containing zirconium of 3 to 7nm was formed on the surface of the mullite continuous fiber. Further, as shown in fig. 3(d), oxygen was detected in the coating layer, and it was confirmed that the coating layer was composed of zirconium oxide (ZrO) as an oxide₂) And (4) forming. That is, it was confirmed that a coating layer of zirconia having a thickness of 3 to 7nm was formed on the surface of the mullite continuous fiber.

(ESCA analysis)

ESCA analysis in the depth direction of the mullite continuous fiber was performed on the zirconia-coated mullite continuous fiber under the same conditions as in example a 1. Fig. 4 is a graph showing the results of ESCA analysis of the surface of the zirconia-coated mullite continuous fiber of example a 2. As shown in fig. 4, it was confirmed that zirconium and oxygen were present in the vicinity of the surface of the mullite continuous fiber (depth of about 15 nm).

(measurement of Single fiber tensile Strength)

The tensile strength of the resulting zirconia-coated mullite continuous fiber was measured according to JIS R1657. The tensile strength of the single fiber of the zirconia-coated mullite continuous fiber was 1.3GPa, and was approximately the same as the tensile strength (1.5GPa) of the single fiber of the desized mullite continuous fiber.

Example A3

(preparation of alumina continuous fiber coated with lanthanum oxide)

The zirconium (IV) acetylacetonate is converted into lanthanum (III) acetylacetonate dihydrate (La (CH)₃COCHCOCH₃)₃·2H₂Except for O), a lanthanum oxide-coated alumina continuous fiber was obtained in the same manner as in example a 1. The total surface area of the alumina continuous fibers was 6.2m²The amount of lanthanum (III) acetylacetonate was adjusted to be much larger (3.5g) than the coverage (100% coverage: 0.0188g) obtained by the above formula (1) so that the coverage of the surface hydroxyl groups of the alumina continuous fibers became 100%.

Coating obtained by TEMThe surface of the alumina continuous fiber of lanthanum oxide was photographed. Fig. 5(a) is an image of the alumina continuous fiber coated with lanthanum oxide of example a3 taken by TEM. Fig. 5(b) is an image showing the distribution of aluminum in the lanthana-coated alumina continuous fiber of fig. 5(a) based on EDS. Fig. 5(c) is an image showing the distribution of lanthanum in the alumina continuous fiber coated with lanthanum oxide of fig. 5(a) based on EDS. Fig. 5(d) is an image showing the distribution of oxygen in the lanthana-coated alumina continuous fiber of fig. 5(a) based on EDS. As shown in fig. 5(c), it was confirmed that in the alumina continuous fiber coated with lanthanum oxide of example a3, a coating layer containing lanthanum was formed on the surface of the alumina continuous fiber in a range of 5 to 10 nm. Further, as shown in fig. 5(d), oxygen was detected in the coating layer, and it was confirmed that the coating layer was composed of lanthanum oxide (La) as an oxide₂O₃) And (4) forming. That is, it was confirmed that a coating layer of lanthanum oxide having a thickness of 5 to 10nm was formed on the surface of the alumina continuous fiber.

(ESCA analysis)

ESCA analysis of alumina continuous fibers was performed on alumina continuous fibers coated with lanthanum oxide under the same conditions as in example a 1. FIGS. 6(a) to (c) are graphs showing the results of ESCA analysis of the surfaces of the continuous alumina fibers coated with lanthanum oxide of example A3. As shown in fig. 6(a) to (c), it was confirmed that lanthanum and oxygen were present in the vicinity of the surface of the alumina continuous fiber in addition to aluminum derived from the fiber.

(measurement of Single fiber tensile Strength)

The single fiber tensile strength of the obtained alumina continuous fiber coated with lanthanum oxide was measured according to JIS R1657. The single fiber tensile strength of the lanthanum oxide-coated mullite continuous fiber was 2.7GPa, and was approximately the same as the single fiber tensile strength (2.5GPa) of the desized alumina continuous fiber.

Example A4

(production of lanthanum oxide-coated mullite continuous fiber)

The zirconium (IV) acetylacetonate is converted into lanthanum (III) acetylacetonate dihydrate (La (CH)₃COCHCOCH₃)₃·2H₂Except for O), a lanthanum oxide-coated mullite continuous fiber was obtained in the same manner as in example a 2. The total surface area of the mullite continuous fibers was 5.5m²The amount of lanthanum (III) acetylacetonate was adjusted to be greatly excessive with respect to the coverage (100% coverage: 0.0149g) obtained by the above formula (1) so that the coverage of the hydroxyl groups on the surface of the mullite continuous fiber became 100%.

The surface of the obtained mullite continuous fiber coated with lanthanum oxide was photographed by TEM. Fig. 7(a) is an image of the lanthanum oxide coated mullite continuous fiber of example a4 taken by TEM. Fig. 7(b) is an image showing the distribution of aluminum in the lanthanum oxide coated mullite continuous fiber of fig. 7(a) based on EDS. Fig. 7(c) is an image showing the distribution of silicon in the lanthanum oxide coated mullite continuous fiber of fig. 7(a) based on EDS. Fig. 7(d) is an image showing the distribution of lanthanum in the lanthanum oxide-coated mullite continuous fiber of fig. 7(a) based on EDS. As shown in fig. 7(d), it was confirmed that in the mullite continuous fiber coated with lanthanum oxide of example a4, a coating layer containing lanthanum was formed on the surface of the mullite continuous fiber in a range of 10nm to 32 nm. Further, as shown in fig. 7(e), oxygen was detected in the coating layer, and it was confirmed that the coating layer was composed of lanthanum oxide (La) as an oxide₂O₃) And (4) forming. That is, it was confirmed that a coating layer of lanthanum oxide having a thickness of about 30nm was formed on the surface of the mullite continuous fiber.

(ESCA analysis)

ESCA analysis of the mullite continuous fiber coated with lanthanum oxide was performed under the same conditions as in example a 1. Fig. 8(a) to (d) are graphs showing the results of ESCA analysis of the surface of the lanthanum oxide-coated mullite continuous fiber of example a 4. As shown in fig. 8(a) to (d), it was confirmed that lanthanum derived from lanthanum oxide and oxygen were present near the surface of the mullite continuous fiber in addition to aluminum and silicon derived from the fiber.

(measurement of Single fiber tensile Strength)

The single fiber tensile strength of the obtained mullite continuous fiber coated with lanthanum oxide was measured according to JIS R1657. The single fiber tensile strength of the lanthanum oxide-coated mullite continuous fiber was 1.8GPa, and was approximately the same as the single fiber tensile strength (1.5GPa) of the desized mullite continuous fiber.

Comparative example A1

The alumina continuous fiber was immersed in a zirconia nano solution (solid content 30 mass%, particle diameter 63nm), and thereafter heated in the atmosphere at 900 ℃ for 2 hours under normal pressure. SEM observation of the alumina continuous fiber obtained by repeating this step 3 times was performed. In the alumina continuous fiber of comparative example a1, the particle size of zirconia in the zirconia nano solution was large, and it was predicted that the thickness of the coating layer was more than 50 nm.

Fig. 9 is an image of the alumina continuous fiber of comparative example a1 taken by SEM. As shown in fig. 9, it was confirmed that, in the alumina continuous fiber of comparative example a1, the continuous fibers aggregated with each other by the zirconia particles.

Example B1

(preparation of Ceramic Matrix Composite (CMC))

A raw material powder was prepared by mixing 25 mass% of a substantially spherical alpha-alumina powder having an average particle size of 0.19 μm and 75 mass% of mullite powder having an average particle size of 1.66 μm. 350g of the raw material powder was mixed with 146g of pure water by a ball mill to obtain a mixed slurry of alumina and mullite.

Subsequently, the zirconia-coated alumina continuous fiber obtained in example a1 was immersed in a mixed slurry of alumina and mullite, and then dried at a temperature of 70 ℃ and a relative humidity of 95%, thereby obtaining a molded article having a width of 110mm × a length of 110mm × a thickness of about 5.0 mm. The molded body was dried at 120 ℃ for one day and night in the air, and then heat-treated at 900 ℃ for 2 hours in the air to obtain a calcined body.

The obtained calcined body was impregnated with an aqueous solution of polyaluminum chloride ([ Al ] in an amount of about 10% by mass₂(OH)_nCl_6-n]_m1 ≦ n ≦ 5, m ≦ 10, m and n being integers) at room temperature and then at 900 ℃Heat treatment was performed for 2 hours. The impregnation and heat treatment were repeated 3 times. After the third heat treatment, the calcined body was sintered at 1100 ℃ for 2 hours in the air, whereby a plate-like CMC as a sintered body was obtained. The resulting platy CMC contained 33.4 volume percent fiber and had a CMC density of 2.48g/cm³. The density of CMC was measured by the archimedes method.

(measurement of volume tensile Strength)

The obtained CMC was processed into a width of 10mm, a length of 100mm and a thickness of 5.0mm, and aluminum tabs were attached to both ends to prepare tensile test pieces. The width and thickness of the tensile test piece were measured using a micrometer, and the length of the test piece was measured using a vernier caliper. A tensile strength test was carried out using a tensile tester (product name: AG-XPlus, manufactured by Shimadzu corporation) and a tensile test jig at a load speed of 0.5 mm/min. The number of test pieces for the tensile strength test was set to 5, and the average of these 5 pieces was defined as the bulk tensile strength. The bulk tensile strength of the obtained CMC was 80 MPa.

(measurement of interfacial Strength)

The interfacial strength of the obtained CMC was measured by preparing an alumina rod coated with a metal acetylacetone complex, and subjecting the alumina rod to a push-out test in which only the alumina rod was dented using a strength tester (AG-2000B, manufactured by Shimadzu corporation).

Fig. 10 is a schematic cross-sectional view showing an example of the interface strength measuring apparatus. The interfacial strength measuring apparatus 10 shown in fig. 10 is mainly composed of a sample 5 for evaluation (which is formed of a surface-coated alumina rod 3 and a ceramic base 4), a strength tester 1 for indenting the surface-coated alumina rod 3 in the direction a, an indenter 2 connected to the strength tester 1 for indenting the surface-coated alumina rod 3, and a fixing table 6 for fixing a portion of the ceramic base 4 of the sample 5 for evaluation.

For measuring the interfacial strength, first, a cylindrical alumina rod (diameter 2 mm. times. length 3.4mm) was prepared, and the surface of the alumina rod (diameter 2 mm. times. length 3.4mm) was coated with a metal acetylacetone complex used for producing a coated ceramic continuous fiber to produce a surface-coated alumina rod 3. Next, a raw material powder used for producing CMC was prepared, and molding was performed by cold isostatic pressing treatment at a die pressure and a pressure of 200MPa in a state where the surface-coated alumina rod 3 was embedded in the raw material powder, thereby producing a molded article (diameter 21mm × length 3.4mm) in a state where the surface-coated alumina rod 3 was embedded. Thereafter, the molded article was treated in the same manner as in the preparation of CMC to obtain a sample 5 for evaluation, which was composed of the surface-coated alumina rod 3 and the ceramic base 4. Only the ceramic substrate 4 of the sample 5 for evaluation was partially fixed to the fixing table 6, and the portion of the surface-coated alumina rod 3 was dented using a stainless steel indenter 2 having a diameter of 1mm, and the stress-strain curve at that time was obtained. The interface strength τ was calculated from the maximum load P of the stress-strain curve and the contact area between the surface-coated alumina rod 3 and the ceramic substrate 4 by the equation (2).

τ＝Pmax/(2πrl) (2)

In the formula (2), Pmax represents the maximum load of the stress-displacement curve in the extrapolation test, pi represents the circumferential ratio, r represents the radius of the alumina rod, and l represents the length of the alumina rod. ]

That is, in this interfacial strength measurement, in the evaluation sample in which the surface-coated alumina rod and the ceramic base are combined, the interfacial strength between the surface-coated alumina and the ceramic base can be measured by indenting the surface-coated alumina rod, and the interfacial strength of CMC can be measured.

Measurement example B1 (interfacial Strength measurement)

A mixed slurry of alumina and mullite was prepared in the same manner as in example B1, and dried to prepare a raw material powder. Then, zirconium (IV) acetylacetonate (Zr (CH)₃COCHCOCH₃)₄)0.5g of the composition was dissolved in 50mL of ethanol to obtain a total surface area of 0.094m at room temperature²The alumina rod (2) was impregnated for 24 hours. In this case, the amount of the additive is excessively larger than the amount of the additive required to make the coverage rate 100% as determined by the above formula (1). Here, the coating rate of the alumina rod is determined by the above formula (1) (this is the same as the ceramic continuous fiber)The coating rate can be determined from the above formula (1) because the alumina rod is a ceramic having hydroxyl groups on the surface and is coated with a metal acetylacetone complex (zirconium (IV) acetylacetonate). ). Thereafter, the alumina rod was taken out and heat-treated at 900 ℃ for 2 hours in the atmosphere. The impregnation step and the heat treatment step (hereinafter, also referred to as "surface coating treatment") were repeated 3 times to obtain zirconia coated alumina rods.

Next, a zirconia-coated alumina rod was embedded in the raw material powder, and after molding by pressing with a die, treatment was performed by pressing with a cold isostatic press at a pressure of 200MPa, thereby obtaining a molded body in which a zirconia-coated alumina rod was embedded in the center of a cylinder having a diameter of 20mm and a thickness of 4 mm. The obtained molded body was sintered at 900 ℃ for 2 hours in the air to obtain a calcined body. The obtained calcined body was impregnated with an aqueous solution of polyaluminum chloride and heat-treated 3 times in the same manner as in example B1, and then sintered at 1100 ℃ for 2 hours in the air in the same manner as in example B1 to prepare a sintered body in which an alumina rod and a ceramic body were integrally sintered.

The obtained sintered body was ground with sandpaper so that alumina rods coated with zirconia protruded from both side surfaces of the cylinder, to obtain a test piece (sample for evaluation) having a diameter of 21mm × a thickness of 3.4 mm. The interfacial strength based on the extrapolation test was 9.8 MPa. Fig. 11 is a graph showing a stress-displacement curve in the extrapolation test of measurement example B1. The arrow in fig. 11 indicates the maximum load (Pmax).

Measurement example B2 (interfacial Strength measurement)

A push-out test piece (sample for evaluation) was obtained in the same manner as in measurement example B1, except that the surface of the alumina rod was coated only 1 time. The interfacial strength based on the push-out test was 7.3 MPa. From this measurement example, it is understood that the interface strength is improved by repeating the surface coating treatment.

Measurement example B3 (interfacial Strength measurement)

Zirconium (IV) acetylacetonate (Zr (CH)₃COCHCOCH₃)₄)0.00012g of a solventIn 50mL of ethanol, the total surface area was set to 0.094m at room temperature²The alumina rod (2) was impregnated for 24 hours. At this time, the coverage rate obtained by the formula (1) was 50%. A push-out test piece (sample for evaluation) was obtained in the same manner as in measurement example B1, except that the zirconia coated alumina rod thus produced was used. The interfacial strength based on the extrapolation test was 7.6 MPa. From this measurement example, it is found that the interface strength is improved by increasing the coverage.

Measurement example B4 (interfacial Strength measurement)

Reacting lanthanum acetylacetonate dihydrate (La (CH)₃COCHCOCH₃)₃·2H₂O)0.5g was dissolved in 50mL of ethanol to obtain a total surface area of 0.094m at room temperature²The alumina rod (2) was impregnated for 24 hours. In this case, the amount of the additive is excessively larger than the amount of the additive required to make the coverage rate 100% as determined by the above formula (1). A push-out test piece (sample for evaluation) was obtained in the same manner as in measurement example B1, except that the coated alumina rod thus produced was used. The interfacial strength based on the extrapolation test was 7.0 MPa.

Example B2

(preparation of Ceramic Matrix Composite (CMC))

350g of substantially spherical α -alumina powder having an average particle size of 0.19 μm was mixed with 146g of pure water by a ball mill to obtain alumina slurry.

Subsequently, the lanthanum oxide-coated mullite continuous fiber obtained in example a3 was impregnated in an alumina mixed slurry and dried, thereby obtaining a molded article having a width of 110mm × a length of 110mm × a thickness of about 0.5 mm. The molded article was dried at 120 ℃ for one day and night in the air, and then heat-treated at 1100 ℃ for 2 hours in the air, thereby obtaining CMC.

(measurement of volume tensile Strength)

The obtained CMC was processed into a width of 10mm, a length of 100mm and a thickness of 0.5mm, and aluminum tabs were attached to both ends to prepare tensile test pieces. The width and thickness of the tensile test piece were measured using a micrometer, and the length of the test piece was measured using a vernier caliper. A tensile strength test was carried out using a tensile tester (product name: AG-XPlus, manufactured by Shimadzu corporation) and a tensile test jig at a load speed of 0.5 mm/min. The number of test pieces for the tensile strength test was set to 4, and the average of these 4 pieces was taken as the bulk tensile strength. The bulk tensile strength of the resulting CMC was 141 MPa.

Comparative example B1

CMC was obtained in the same manner as in example B1, except that a desized (heat-treated at 700 ℃ C. in the air) alumina continuous fiber (alumina fiber cloth, product name: Nextel 610 manufactured by 3M Japan Limited) was used in place of the zirconia-coated alumina continuous fiber (i.e., uncoated zirconia-coated alumina continuous fiber was used). The fiber volume fraction of CMC was 34.1 vol%, and the density of CMC was 2.35g/cm³. The bulk tensile strength was 9MPa, which is a CMC having a lower strength than the CMC of example B1.

Comparative measurement example B1 (interfacial strength measurement)

A push-out test piece was obtained in the same manner as in measurement example B1, except that an alumina rod which was not subjected to the surface coating treatment was used. The interfacial strength based on the extrapolation test was 13.6 MPa. According to this measurement example, it is considered that in the CMC of comparative example B1, breakage due to adhesion of the ceramic continuous fibers to the ceramic matrix occurs.

Comparative example B2

CMC was obtained in the same manner as in example B2, except that a desized (heat-treated at 700 ℃ C. in the air) mullite continuous fiber (mullite fiber cloth, product name: Nextel 720, manufactured by 3M Japan Limited) was used instead of the lanthanum oxide-coated mullite continuous fiber. The bulk tensile strength was 107MPa, which is a CMC having a lower strength than the CMC of example B2.

From the above results, it was found that the strength of the CMC of example B1 was more excellent in the CMC of example B1 having a ceramic continuous fiber with a coating layer and the CMC of comparative example B1 having a ceramic continuous fiber without a coating layer on the surface, from the comparison of measurement example B1 with comparative measurement example B1. In addition, the CMC of example B1 was found to be more excellent in strength between the CMC of example B2 having a ceramic continuous fiber with a coating layer and the CMC of comparative example B2 having a ceramic continuous fiber without a coating layer on the surface. From these results, it was confirmed that the coated ceramic continuous fiber of the present invention is suitable for producing a ceramic matrix composite having sufficiently high strength.

Industrial applicability

The ceramic continuous fiber with a coating layer of the present invention is hardly aggregated with metal compounds in the surface coating of the ceramic continuous fiber, and therefore can be used as CMC having high damage tolerance such as tensile strength. Further, since the ceramic continuous fiber with a coating layer of the present invention can be produced by impregnating the ceramic continuous fiber with a solvent containing a metal acetylacetone complex, the ceramic continuous fiber can be easily coated in a three-dimensional complicated shape fabric or nonwoven fabric shape in addition to a two-dimensional fabric shape fabric, and thus can be industrially widely used.

Description of the reference numerals

1 … strength tester, 2 … indenter, 3 … surface coating alumina rod, 4 … ceramic substrate, 5 … sample for evaluation, 6 … fixed table, 10 … interface strength measuring device.