Ceramic matrix composite material and its manufacturing method

Abstract

To provide a new technique for obtaining a matrix in a ceramic base composite material which suppresses crack generation while having heat resistance.SOLUTION: In a method for producing a ceramic base composite material comprising a matrix and reinforcement fibers provided in the matrix, the reinforcement fibers are arranged in the liquid raw material of the matrix (step S2), the reinforcement fibers in the liquid raw material are heated to a matrix formation temperature (step S31), and the reinforcement fibers in the liquid raw material are heated to heat resistance imparting temperature (step S32). The heat resistance imparting temperature is a temperature exceeding the matrix forming temperature. The step S31 and the step S32 are repeated.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a ceramic matrix composite material including a matrix formed of a ceramic and reinforcing fibers disposed within the matrix, and also to a method for producing the ceramic matrix composite material. [Background technology]

[0002] Ceramic matrix composites are used as high-temperature structural components in rocket engines, aircraft jet engines, etc. Ceramic matrix composites are materials that use a ceramic matrix with reinforcing fibers embedded within the matrix. Silicon carbide, for example, is used as the ceramic.

[0003] One method for generating a matrix for a ceramic-based composite material is the film boiling method. In the film boiling method, a matrix can be formed, for example, as follows: Reinforcing fibers are placed in a liquid matrix material (for example, LPCS: Liquid Polycarbosilane), and the reinforcing fibers are heated in this state. This causes a matrix made of LPCS to precipitate on the reinforcing fibers and form. The reinforcing fibers with the matrix formed thereon are then heat-treated at a higher temperature (for example, a high temperature of 1200°C or higher) in, for example, a heating furnace, thereby improving the heat resistance of the matrix. The film boiling method is described, for example, in Non-Patent Document 1 listed below. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Min Mei et al. “Preparation of C / SiC composites by pulse chemical liquid-vapor deposition process”, Materials Letters 82 (2012) 36-38 [Non-patent document 2] C. Besnarda et al. “Synthesis of hexacelsian barium aluminosilicate by film boiling chemical vapor process”, Journal of the European Ceramic Society 40 (2020) 3494-3497 [Non-patent document 3] Masanori SHIMIZU et al. "Crystallization Behavior and Change in Surface Area of ​​Alkoxide-Derived Mullite Precursor Powders with Different Compositions", Journal of the Ceramic Society of Japan 105 [2] 131-135 (1997) Summary of the Invention [Problem to be solved by the invention]

[0005] When reinforcing fibers on which a matrix has been formed by film boiling are heat treated at high temperatures as described above, the heat resistance of the matrix improves, but the volume of the matrix shrinks, resulting in cracks in the matrix. Furthermore, when a ceramic matrix composite material is produced by film boiling, as described above, after the matrix is ​​formed by film boiling, an additional heat treatment is performed on the matrix, for example, in a heating furnace, to improve the heat resistance of the matrix.

[0006] Therefore, an object of the present invention is to provide a method for producing a ceramic matrix composite material having a heat-resistant matrix without performing an additional heat treatment after film boiling treatment when the ceramic matrix composite material is produced by film boiling. Another object of the present invention is to provide a matrix that has heat resistance and is suppressed from cracking. [Means for solving the problem]

[0007] In order to achieve the above object, according to the present invention, there is provided a method for producing a ceramic matrix composite material comprising a matrix and reinforcing fibers disposed within the matrix, the method comprising the steps of: (A) disposing reinforcing fibers within the matrix liquid material; (B) heating the reinforcing fibers in the liquid feedstock to a matrix-forming temperature; (C) heating the reinforcing fibers in the liquid raw material to a heat resistance imparting temperature; The heat resistance imparting temperature is a temperature exceeding the matrix formation temperature, and the method for producing a ceramic matrix composite material is provided, in which the steps (B) and (C) are repeatedly carried out.

[0008] The present invention also provides a ceramic matrix composite material produced by this production method. [Effects of the Invention]

[0009] According to the manufacturing method of the present invention, a ceramic matrix composite material having a heat-resistant matrix can be manufactured without performing an additional heat treatment after the film boiling treatment. Furthermore, the ceramic matrix composite material of the present invention has a matrix that has heat resistance and is suppressed from generating cracks. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an enlarged schematic diagram showing a cross section of a ceramic matrix composite material according to an embodiment of the present invention. [Figure 2A] 2A-2A cross-sectional view of FIG. 1. [Figure 2B] FIG. 3 is a diagram showing a unit area in the cross section of FIG. 2A in the case of this embodiment. [Figure 2C] This corresponds to FIG. 2B, but shows a reference example. [Figure 3] This corresponds to an enlarged view of a portion of Figure 1. [Figure 4] 1 is a flowchart illustrating a method for manufacturing a ceramic matrix composite material according to an embodiment of the present invention. [Figure 5A] 1 shows an example of the configuration of a fixture used in a manufacturing method according to an embodiment of the present invention. [Figure 5B] FIG. 5B is a view taken along the arrows 5B-5B in FIG. 5A. [Figure 5C] FIG. 5C is a view taken along the line 5C-5C in FIG. 5A. [Figure 6] The fixture of FIG. 5A is shown positioned within a process vessel holding a liquid source material. [Figure 7] 1 is a graph showing temperature changes in a film boiling method in an example. [Figures 8A-8E] 1 is a scanning electron microscope image of a ceramic matrix composite material obtained in an example. [Figure 9] 1 is a graph showing temperature changes in a film boiling method in Comparative Example 1. [Figures 10A-10E] 1 is a scanning electron microscope image of the ceramic matrix composite material obtained in Comparative Example 1. [Figure 11] 10 is a graph showing temperature changes in a film boiling method in Comparative Example 2. [Figures 12A-12E] 1 is a scanning electron microscope image of the ceramic matrix composite material obtained in Comparative Example 2. [Figure 13A] 1 is a scanning electron microscope image of a ceramic matrix composite material of an example before a heat exposure test is performed. [Figure 13B] 1 is a scanning electron microscope image of a ceramic matrix composite material of an example after a heat exposure test. [Figure 14] 10 is another image taken by a scanning electron microscope of the ceramic matrix composite material of the example after the thermal exposure test. [Figure 15A] 1 is a scanning electron microscope image of the ceramic matrix composite material of Comparative Example 1 before a heat exposure test is performed. [Figure 15B] 1 is a scanning electron microscope image of the ceramic matrix composite material of Comparative Example 1 after a heat exposure test. [Figure 16] 1 is a graph showing the relationship between the mass and temperature of the ceramic-based composite materials of Example and Comparative Example 2. [Figure 17]1 shows the measured values ​​of through-crack rates for the ceramic matrix composite materials produced in the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will be described with reference to the drawings. In addition, common parts in the drawings are given the same reference numerals, and duplicated explanations will be omitted.

[0012] FIG. 1 is an enlarged schematic diagram showing the vicinity of the outer surface in a cross section of a ceramic matrix composite material 10 according to an embodiment of the present invention. FIG. 2A is a cross-sectional view taken along line 2A-2A in FIG. 1. The ceramic matrix composite material 10 may be used as a high-temperature structural member in a rocket engine, an aircraft jet engine, or the like. The ceramic matrix composite material 10 includes a matrix 3 and reinforcing fibers 5 disposed within the matrix 3.

[0013] The matrix 3 is made of ceramics and is the base material of the ceramic-based composite material 10. The matrix 3 may be made mainly of silicon carbide (SiC), but may also be made of other ceramics.

[0014] The reinforcing fibers 5 extend in a thread-like shape, and a plurality (e.g., a large number) of reinforcing fibers 5 are disposed inside the matrix 3. For example, a (woven or knitted) fibrous body formed of a large number of reinforcing fibers 5 may be disposed inside the matrix 3. The reinforcing fibers 5 may be ceramic fibers. The reinforcing fibers 5 may be, for example, carbon fibers or silicon carbide fibers. However, the reinforcing fibers 5 are not limited to these, and may be, for example, heat-resistant oxide fibers such as alumina fibers, mullite fibers, or zirconia fibers.

[0015] 1 and 2A, the matrix 3 may have a layer structure in which a plurality (a large number) of layers 7 are stacked one on top of the other. The layer structure will be described later.

[0016] The matrix 3 of the ceramic matrix composite material 10 according to this embodiment has heat resistance to the assumed upper limit temperature in the usage environment of the ceramic matrix composite material 10, while suppressing the occurrence of cracks (i.e., the size and number of cracks occurring in the matrix are suppressed). The assumed upper limit temperature may be, for example, a temperature in the range of 1400°C or higher and 1600°C or lower (e.g., 1400°C), but is not limited to this range.

[0017] An example of a ceramic-based composite material 10 will be described below based on the penetrating cracks 2a and the penetrating crack rate in the matrix 3. However, the ceramic-based composite material 10 according to this embodiment (i.e., the ceramic-based composite material 10 manufactured by the manufacturing method described below) is not limited to the configuration described below with respect to the penetrating crack rate, and may be any material as long as it has heat resistance to the expected upper limit temperature in its usage environment and suppresses the occurrence of cracks (penetrating cracks 2a and intermittent cracks 2b).

[0018] The through crack 2a is a crack that reaches both the outer surface 3a of the matrix 3 and the reinforcing fibers 5. That is, the through crack 2a is a crack that opens on the outer surface 3a and extends from the opening to the reinforcing fibers 5 in the matrix 3. The mid-way crack 2b is a crack that does not reach both the outer surface 3a of the matrix 3 or the reinforcing fibers 5. That is, the mid-way crack 2b includes a crack that reaches only one of the outer surface 3a of the matrix 3 or the reinforcing fibers 5, and a crack that reaches neither the outer surface 3a of the matrix 3 nor the reinforcing fibers 5.

[0019] In one example, the ceramic matrix composite material 10 may be configured so that the through-crack rate in any cross section (hereinafter simply referred to as material cross section) of the ceramic matrix composite material 10 is kept at or below an upper limit both before and after heating to the assumed upper limit temperature in the usage environment of the ceramic matrix composite material 10. This upper limit is, for example, 0.5% or less, but is not limited to this.

[0020] The through-crack rate is the ratio of the total width of through-cracks 2a in any unit area (see FIG. 2B described later) along the outer surface 3a in the material cross section to the length of the unit area. For any unit area in any material cross section, the upper limit of the through-crack rate of ceramic matrix composite material 10 may be, for example, 0.5% or less, 0.1% or less, or 0%, both before and after heating to the assumed upper limit temperature in the usage environment of ceramic matrix composite material 10.

[0021] In the cross section of the material, when the penetrating crack 2a extends longitudinally in the direction along the outer surface 3a, the width of the penetrating crack 2a within a unit area is the width in the direction perpendicular to the cross section of the material. Note that the cross section of the material is a cross section obtained by hypothetically cutting the ceramic matrix composite material 10 along a plane perpendicular to the outer surface 3a.

[0022] The penetration crack rate can be expressed by the following formula (1): That is, the value calculated by formula (1) is the penetration crack rate (%).

[0023]

number

[0024] Here, N is the number of through-type cracks 2a present in the unit area, m is the identification number of the through-type crack 2a, and w m is the width of the through crack 2a with identification number m, and Σ is the width of the crack 2a from m=1 to m=N. m and L is the length of the unit area in the direction along the outer surface 3 a of the matrix 3 .

[0025] The length of a unit area along the outer surface 3a of the matrix 3 is the length in the cross section of the material, and may be a length in the range of 100 μm or more and 1000 μm or less (e.g., 300 μm or 700 μm), but is not limited to this range.

[0026] 2B is a diagram showing a unit area in the cross section of FIG. 2A, which shows the present embodiment. FIG. 2C corresponds to FIG. 2B, but shows a reference example (e.g., Comparative Example 1 or 2, which will be described later). Two unit areas (areas surrounded by dashed lines) that are continuous with each other are shown in FIGS. 2B and 2C. The length (linear length) of the unit area along the outer surface 3a is indicated by a double-headed arrow.

[0027] In FIG. 2B showing an example of this embodiment, since no through cracks 2a exist, the through crack rate is zero.

[0028] 2C showing the reference example, there are two through-cracks 2a in each unit area. Therefore, the above formula (1) for calculating the through-crack rate becomes the following formula (2).

[0029]

number

[0030] Here, w1 is the width of one of the through-cracks 2a in the unit area (the dimension in the left-right direction in FIG. 2C), and w2 is the width of the other through-crack 2a in the unit area (the dimension in the left-right direction in FIG. 2C). In the reference example, the through-crack rate is, for example, greater than 1%.

[0031] As shown in FIGS. 1 and 2A, the matrix 3 may have a layered structure in which multiple (many) layers 7 are stacked. In this case, the entire matrix 3 may have this layered structure. That is, the entire matrix 3 may be formed of multiple layers 7 stacked on top of each other. Alternatively, the matrix 3 may have a region with a layered structure (e.g., a region from the outer surface 3a to the reinforcing fibers 5) and a region without a layered structure (e.g., a region between some adjacent reinforcing fibers 5). The region without a layered structure is, for example, a region where the deposition rate of the ceramic (matrix 3) becomes too fast due to the influence of the concentration of pyrolysis gas, temperature conditions, etc., in the manufacturing method described below. The thickness of each layer 7 in the layered structure may be 1 μm or more and 10 μm or less, or 2 μm or more and 8 μm or less, but is not limited to these thickness ranges.

[0032] In the layer structure, for example, for each reinforcing fiber 5, a plurality of layers 7 may be formed around the reinforcing fiber 5 so as to cover the reinforcing fiber 5. In this way, for each reinforcing fiber 5, a plurality (a large number) of layers 7 are laminated in order from the outer peripheral surface side so as to surround the outer peripheral surface of the reinforcing fiber 5 in its cross section. In this case, at a location where a layer 7 (or sublayer 7a, 7b, or 7c described below) formed around any one reinforcing fiber 5 comes into contact with a layer 7 (or sublayer 7a, 7b, or 7c) formed around another reinforcing fiber 5 or around each of a plurality of other reinforcing fibers 5, these mutually contacting layers 7 (or sublayers 7a, 7b, or 7c) are formed to form a common layer (or common sublayer) surrounding these reinforcing fibers 5. Each layer 7 located inside the common layer 7 and not a common layer 7 may be formed to surround only a corresponding reinforcing fiber 5. A plurality or a large number of common layers 7 may be formed.

[0033] The layer structure of the matrix 3 may have the following characteristics (A) to (C).

[0034] (A) The elastic modulus of the matrix 3 changes abruptly (e.g., discontinuously) at the boundary between adjacent layers 7. That is, for adjacent layers 7, the elastic modulus of the matrix 3 changes abruptly when moving from one of the layers 7 to the other of the layers 7. For each pair of adjacent layers 7, the elastic modulus of the matrix 3 may change abruptly at the boundary between the layers 7.

[0035] (B) The crystallinity of the matrix 3 changes abruptly (e.g., discontinuously) at the boundary between adjacent layers 7. That is, for adjacent layers 7, the crystallinity of the matrix 3 changes abruptly when moving from one of the layers 7 to the other. For each pair of adjacent layers 7, the crystallinity of the matrix 3 may change abruptly at the boundary between the layers 7. The crystallinity may be the ratio of the volume occupied by crystals to the total volume of the layer 7, the crystal grain size (e.g., average crystal grain size) in the layer 7, or a crystallinity that takes both of these into consideration. Note that the crystallinity that takes both of these into consideration may be, for example, the sum of the value obtained by multiplying the volume ratio by a predetermined coefficient k1 and the value obtained by multiplying the crystal grain size by a predetermined coefficient k2.

[0036] (C) The composition of the matrix 3 changes abruptly (e.g., discontinuously) at the boundary between adjacent layers 7. That is, for adjacent layers 7, the composition of the matrix 3 changes abruptly when moving from one of the layers 7 to the other. For each pair of adjacent layers 7, the composition of the matrix 3 may change abruptly at the boundary between the layers 7. Here, the composition may be the atomic ratio of the main elements (e.g., two specific elements) constituting the matrix 3. When the matrix 3 is mainly formed of silicon carbide, the composition may be the atomic ratio of carbon to silicon. That is, the composition may be the ratio of the number of C atoms to the number of Si atoms (hereinafter referred to as the C / Si ratio).

[0037] When the matrix 3 is mainly made of silicon carbide, carbon C that does not constitute silicon carbide may be present between two adjacent crystal grains (e.g., at the grain boundary) in the matrix 3, or SiC with a distorted crystal structure due to a larger number of carbon C atoms may be present. In this case, for example, the C / Si ratio may be greater than 1, and all silicon Si in the matrix 3 may constitute silicon carbide.

[0038] The above (A) may be obtained by the above (B), and the above (B) may be obtained by the above (C). For example, a layer 7 with a relatively high degree of crystallinity may be a layer 7 with a relatively high modulus of elasticity, and a layer 7 with a relatively low degree of crystallinity may be a layer 7 with a relatively low modulus of elasticity. The above-mentioned C / Si ratio may represent the above-mentioned degree of crystallinity and modulus of elasticity. In this case, a low C / Si ratio indicates a high degree of crystallinity and, consequently, a high modulus of elasticity. Therefore, a layer 7 with a lower C / Si ratio has a higher proportion of crystals or a larger crystal grain size, and therefore the layer 7 has a higher degree of crystallinity and a higher modulus of elasticity. On the other hand, a layer 7 with a higher C / Si ratio has a higher proportion of carbon (C), and therefore the layer 7 is closer to being amorphous or has a smaller crystal grain size, and therefore has a lower modulus of elasticity.

[0039] The layer structure of the matrix 3 does not necessarily have to have all of the characteristics (A) to (C) above, but may have any one or two of the characteristics (A) to (C). For example, it is sufficient that the elastic modulus of the matrix 3 changes at the boundary between adjacent layers 7, and one or both of the crystallinity and composition of the matrix 3 do not need to change. It is sufficient that the elastic modulus, crystallinity, or composition of the matrix 3 change at the boundary between adjacent layers 7 above, and it is not necessary for the change to be sudden as described above.

[0040] FIG. 3 corresponds to a partial enlarged view of FIG. 1. In the matrix 3, each layer 7, or some of the layers 7, may include multiple sublayers 7a, 7b, and 7c in order of proximity to the reinforcing fibers 5 corresponding to that layer 7, as shown in FIG. 3. In FIG. 3, the boundaries between adjacent sublayers are indicated by dashed lines, and the boundaries between adjacent layers 7 are indicated by solid lines. Each layer 7 having multiple sublayers may have the following characteristics (a) to (c). In the case of (A) above, the layer 7 may have the following characteristic (a), in the case of (B) above, the layer 7 may have the following characteristic (b), and in the case of (C) above, the layer 7 may have the following characteristic (c).

[0041] (a) The multiple sublayers 7a, 7b, and 7c (three in the example of FIG. 3 ) constituting the layer 7 have different elastic moduli, including the sublayer 7c with a relatively high elastic modulus and the sublayer 7a with a relatively low elastic modulus. In this case, the elastic modulus of the sublayer 7b may be between the elastic modulus of the sublayer 7c and the elastic modulus of the sublayer 7a. Furthermore, the elastic modulus of the matrix 3 of adjacent sublayers 7a, 7b, and 7c may change abruptly (e.g., discontinuously) at the boundary between them. Furthermore, the elastic modulus of the matrix 3 of each sublayer 7a, 7b, and 7c may be substantially uniform. Furthermore, the elastic modulus of a sublayer farther from the corresponding reinforcing fiber 5 in the layer 7 may be higher.

[0042] (b) The multiple sublayers 7a, 7b, and 7c (three in the example of FIG. 3 ) constituting the layer 7 have different crystallinity degrees, including the sublayer 7c with a relatively high crystallinity and the sublayer 7a with a relatively low crystallinity. In this case, the crystallinity of the sublayer 7b may be between the crystallinity of the sublayer 7c and the crystallinity of the sublayer 7a. Furthermore, the crystallinity of the matrix 3 of adjacent sublayers 7a, 7b, and 7c may change abruptly (e.g., discontinuously) at the boundary between the two sublayers. Furthermore, the crystallinity of the matrix 3 of each sublayer 7a, 7b, and 7c may be substantially uniform. Furthermore, the crystallinity of a sublayer farther from the corresponding reinforcing fiber 5 in the layer 7 may be higher.

[0043] (c) The multiple sublayers 7a, 7b, and 7c (three in the example of FIG. 3 ) constituting layer 7 have different atomic ratios (compositions) as described above, including sublayer 7c or 7a with a relatively high atomic ratio and sublayer 7a or 7c with a relatively low atomic ratio. In this case, the ratio of sublayer 7b may be between the ratio of sublayer 7c and the ratio of sublayer 7a. Furthermore, for the multiple sublayers 7a, 7b, and 7c, the ratio of matrix 3 between adjacent sublayers may change abruptly (e.g., discontinuously) at the boundary between them. Furthermore, the ratio of matrix 3 may be substantially uniform in each sublayer 7a, 7b, and 7c. If matrix 3 is primarily formed of silicon carbide, the C / Si ratio of a sublayer farther from the corresponding reinforcing fiber 5 in layer 7 may be lower.

[0044] The above (a) may be obtained by the above (b), and the above (b) may be obtained by the above (c). For example, a sublayer with a relatively high degree of crystallinity may be a sublayer with a relatively high modulus of elasticity, and a sublayer with a relatively low degree of crystallinity may be a sublayer with a relatively low modulus of elasticity. Note that layer 7 does not necessarily have all of the above characteristics (a) to (c), and may have one or two of the above characteristics (a) to (c). For example, it is sufficient that the modulus of elasticity of matrix 3 changes at the boundary between adjacent sublayers, and one or both of the crystallinity and composition of matrix 3 do not need to change. In particular, sublayers belonging to adjacent layers 7 and adjacent to each other across the boundary between the two layers 7 differ from each other in at least the modulus of elasticity, crystallinity, and composition. Furthermore, adjacent sublayers in one layer 7 differ from each other in at least the modulus of elasticity, crystallinity, and composition. Regarding (a), (b), or (c) above, the elastic modulus, crystallinity, or composition of the matrix 3 need only change at the boundary between adjacent sublayers, and does not necessarily have to change abruptly as described above.

[0045] The number of sublayers present in one layer 7 is not limited to three and may be two, four or more, because it can be affected by conditions when forming the matrix 3 (for example, the heating rate and the first target temperature, which will be described later). Furthermore, a layer 7 may exist in which the boundaries between the sublayers 7a, 7b, and 7c are not clearly defined. In this case, one layer 7 may have two sublayers or no sublayers.

[0046] The thickness of each of the sublayers 7a, 7b, and 7c may be 0.1 μm or more and 10.0 μm or less, or 0.3 μm or more and 10.0 μm or less, or 0.3 μm or more and 8.0 μm or less, or may be a value within other numerical ranges.

[0047] A plurality (a large number) of minute closed pores 9 may be formed inside the matrix 3 and are not open to its outer surface 3a. Each closed pore 9 is a void sealed by the matrix 3. Each closed pore 9 may have a size that allows it to be contained within one layer 7 or sublayer 7a, 7b, or 7c. For example, the size of each closed pore 9 (the maximum dimension in each direction) may be a value within the range of 2 μm or more and 8 μm or less. However, closed pores 9 having dimensions outside this range may also be present inside the matrix 3.

[0048] (Method for manufacturing ceramic matrix composite materials) Fig. 4 is a flowchart showing a method for manufacturing a ceramic-based composite material 10 according to an embodiment of the present invention. Fig. 5A shows an example of the configuration of a fixture 100 that can be used in this manufacturing method. The manufacturing method according to this embodiment provides the ceramic-based composite material 10 according to the above-described embodiment. This manufacturing method includes steps S1 to S3.

[0049] <Step S1> In step S1, a plurality (a large number) of reinforcing fibers 5 are prepared. For example, a (woven or knitted) fibrous body formed of a large number of reinforcing fibers 5 is prepared. The fibrous body may have a three-dimensional shape. The reinforcing fibers 5 prepared in step S1 may be, for example, carbon fibers or silicon carbide fibers, but are not limited to these, as described above.

[0050] <Step S2> In step S2, the multiple reinforcing fibers 5 (for example, the above-mentioned fibrous body) prepared in step S1 are placed in a liquid raw material for the matrix 3. This liquid raw material is a liquid that serves as a raw material for the matrix 3. When the matrix 3 is formed mainly from silicon carbide, the liquid raw material may be, for example, a liquid raw material for silicon carbide (LPCS: Liquid Polycarbosilane).

[0051] Mounting fixtures Step S2 may be performed using a fixture 100 shown in Fig. 5A. Fig. 5B is a view taken along the arrows 5B-5B in Fig. 5A. The fixture 100 includes a heating element 12, a pair of insulating plates 14, a porous body 16, an action mechanism 17, an insulating material 18, and a hanging portion 23.

[0052] The heating element 12 is induction heated and is made of, for example, graphite.

[0053] The pair of heat insulating plates 14 are arranged to sandwich the heating element 12. The heat insulating plates 14 are made of a material having heat insulating properties (e.g., alumina). The heat insulating plates 14 have a plate shape. When viewed in the thickness direction of the heat insulating plates 14, the heat insulating plates 14 and the heating element 12 may be circular and have the same radius, for example.

[0054] The porous body 16 is disposed between the heating element 12 and the insulating plate 14. The porous body 16 has a large number of holes formed therein through which a fluid can pass, and may be, for example, a stack of multiple wire meshes. The fixture 100 may have two porous bodies 16, as shown in FIG. 5A. That is, the porous body 16 may be disposed between the heating element 12 and one insulating plate 14, and between the heating element 12 and the other insulating plate 14.

[0055] The action mechanism 17 applies a force to sandwich the heating body 12, the porous body 16, and the fibrous body 15 between the pair of insulating plates 14 with the fibrous body 15 disposed between the heating body 12 and the porous body 16. As a result, the fibrous body 15 is held in the fixture 100 in a state where it is in contact with the heating body 12 and the porous body 16. When two porous bodies 16 are provided, the action mechanism 17 applies a force to sandwich the heating body 12, the two porous bodies 16, and the two fibrous bodies 15 between the pair of insulating plates 14 with the fibrous body 15 disposed between the heating body 12 and one of the porous bodies 16 and between the heating body 12 and the other porous body 16. As a result, the fibrous body 15 is held in the fixture 100 in a state where it is in contact with the heating body 12 and the corresponding porous body 16.

[0056] The action mechanism 17 has, for example, a bolt 17a and a nut 17b. The bolt 17a passes through the two heat insulating plates 14 and the heater 12 with a gap therebetween, and nuts 17b are threadedly engaged with both ends of each bolt 17a. By tightening the nuts 17b onto the bolts 17a in a direction that brings the two heat insulating plates 14 closer to each other, the porous body 16, the heater 12, and the fibrous body 15 are held between the pair of heat insulating plates 14. The bolt 17a may be made of a material that is not induction heated (e.g., alumina). A plurality of such action mechanisms 17 (two in the example of FIG. 5A) may be provided.

[0057] The heat insulating material 18 covers the outer peripheries 12a, 15a of the heating element 12 and the fibrous body 15 (two fibrous bodies 15 in the example of FIG. 5A). That is, the heating element 12 and the fibrous body 15 each have outer peripheries 12a, 15a surrounding a central axis oriented in the thickness direction of the insulating plate 14, and these outer peripheries 12a, 15a are covered by the heat insulating material 18 as shown in FIG. 5B. In FIG. 5A, only the portions of the heat insulating material 18 located on both sides (the left and right sides of this figure) of the heating element 12 and the fibrous body 15 are illustrated by two-dot chain lines. The heat insulating material 18 is made of a material with heat insulating properties. For example, the heat insulating material 18 may be a glass insulating cloth (woven fabric). In the examples of FIGS. 5A and 5B, wire 19 may be wrapped around the heat insulating material 18 from the outside to secure the heat insulating material 18 to the heating element 12, but the heat insulating material 18 may also be secured by other means.

[0058] In a state where the fibrous body 15 is attached to the mounting fixture 100 (hereinafter simply referred to as the attached state), as shown in FIG. 5A , the heating body 12, the fibrous body 15 (two fibrous bodies 15), and the porous body 16 (two porous bodies 16) are sandwiched between a pair of insulating plates 14, and the insulating material 18 covers the outer peripheries 12a, 15a of the heating body 12 and the fibrous body 15 as described above. In this attached state, each porous body 16 is open on the outer periphery. That is, each porous body 16 has an outer periphery 16a surrounding a central axis oriented in the thickness direction of the insulating plate 14, and the outer periphery 16a is open to the outside radially outward from the central axis. Note that in the attached state, the fibrous body 15 is in contact with the heating body 12 in the example of FIG. 5A , but it does not necessarily have to be in contact with the heating body 12.

[0059] The suspending unit 23 is used to suspend the fibrous body 15 and the heating body 12 in step 2. FIG. 5C is a view taken along the arrows 5C-5C in FIG. 5A. The suspending unit 23 has a plate-shaped member 23a and a rod-shaped member 23b. The plate-shaped member 23a extends elongatedly in the left-right direction of FIGS. 5A and 5C along the upper surface of the upper heat insulating plate 14. Bolts 17a pass through both ends of the plate-shaped member 23a with gaps. Both ends of the plate-shaped member 23a are sandwiched between the upper heat insulating plate 14 and upper nuts 17b, respectively. A connecting portion 23a1 is provided in the center of the plate-shaped member 23a. A rod-shaped member 23b is connected to this connecting portion 23a1. The rod-shaped member 23b extends upward from the connecting portion 23a1. Although not shown in the figure, for example, a protrusion as a bolt may be provided on the upper surface of the connecting portion 23a1, and a bolt hole may be formed on the lower end surface of the rod-shaped member 23b, and the connecting portion 23a1 and the rod-shaped member 23b may be connected by screwing the bolt into the bolt hole.

[0060] In step S2, in the above-described mounted state, the fibrous body 15 is placed in the processing vessel 11 together with the fixture 100, as shown in FIG. 6. As a result, the entire fibrous body 15 is positioned in the liquid source 13 held inside the processing vessel 11. At this time, the fibrous body 15 and the heater 12 are suspended by the suspension unit 23 so that the fixture 100, the heater 12, and the fibrous body 15 do not come into contact with the inner surface (bottom surface and inner peripheral surface) of the processing vessel 11. At this time, the rod-shaped member 23b of the suspension unit 23 is disposed so as to pass through the through-hole 11a1 of the lid member 11a that closes the opening at the top surface of the processing vessel 11, and the upper end portion of the rod-shaped member 23b may be connected to and supported by a structure (not shown) by appropriate means.

[0061] 5A and 5C, etc., as long as the suspending unit can suspend the fibrous body 15 and the heating body 12 so that the fixture 100, the heating body 12, and the fibrous body 15 do not come into contact with the inner surface of the processing vessel 11 (i.e., so that they are spaced apart from the inner surface of the processing vessel). Also, the heat insulating plates 14 may be omitted from the fixture.

[0062] Processing vessel 11 is made of a non-conductive material (e.g., glass) that is not induction heated. Processing vessel 11 may be formed with gas inlet hole 11b for introducing nitrogen gas into the gas phase portion within processing vessel 11 in step S3 (described later) and gas outlet hole 11a2 for discharging gas from the gas phase portion within processing vessel 11 in step S3.

[0063] <Step S3> In step S3, the matrix 3 is formed by film boiling (FB). That is, in step S2, a plurality of reinforcing fibers 5 (for example, the above-mentioned fibrous body 15) are placed in the liquid raw material 13, and the reinforcing fibers 5 and the liquid raw material 13 are heated. This heating causes ceramics to be generated from the liquid raw material 13 and to be deposited on each reinforcing fiber 5 as the matrix 3, thereby forming the matrix 3. That is, the liquid raw material 13 is heated by the heated reinforcing fibers 5, and turns into film boiling gas at the interface between the reinforcing fibers 5 and the liquid raw material 13. This film boiling gas generates and deposits ceramics (i.e., ceramic pyrolysis precipitates) on each reinforcing fiber 5. The ceramics generated on each reinforcing fiber 5 may be generated by one or both of the following methods (1) and (2).

[0064] (1) When the film boiling gas collides with the heated reinforcing fibers 5, it receives further thermal energy, which causes thermal decomposition and mineralization, resulting in precipitation of solid ceramics on the reinforcing fibers 5.

[0065] (2) Some of the gases contained in the film boiling gas have already been thermally decomposed into pyrolysis gases, and when these pyrolysis gases collide with the heated reinforcing fibers 5, they undergo mineralization and precipitate on the reinforcing fibers 5 as solid ceramics.

[0066] In the above-mentioned step S3, the heating temperature of the reinforcing fibers 5 (fibrous body 15) may be repeatedly increased and decreased. This results in the formation of the above-mentioned layer structure. That is, in step S3, the elastic modulus, crystallinity, composition, etc. of the ceramics change during the ceramic deposition process in response to repeated increases and decreases in the temperature of the reinforcing fibers 5, resulting in the formation of the layer structure of the matrix 3. Note that, in the steps S31a or S32 described below, as the temperature increases, the ratio of pyrolysis gas in the film boiling gas increases, which is thought to result in a change in the composition of the matrix 3 (for example, a decrease in the C / Si ratio).

[0067] Step S3 includes steps S31 and S32.

[0068] In step S31, the reinforcing fibers 5 in the liquid raw material 13 are heated to a matrix formation temperature. The matrix formation temperature is a temperature at which a matrix is ​​deposited on the reinforcing fibers 5 (fibrous body 15). The matrix formation temperature may be a temperature within a first temperature range, which will be described later. In step S31, ceramics as the matrix 3 is precipitated and deposited on the reinforcing fibers 5, thereby forming the matrix 3 on the reinforcing fibers 5.

[0069] In step S32, the reinforcing fibers 5 in the liquid raw material 13 are heated to a heat resistance imparting temperature. The heat resistance imparting temperature is a temperature that exceeds the matrix formation temperature. The heat resistance imparting temperature may be the assumed upper limit temperature of the ambient temperature in which the ceramic matrix composite material 10 is used. By step S32, the matrix 3 formed in the immediately preceding step S31 becomes heat resistant to the heat resistance imparting temperature (the assumed upper limit temperature).

[0070] Step S31 and step S32 are repeated in this order, thereby repeatedly forming the matrix 3 and imparting heat resistance to the matrix 3. That is, a new matrix 3 is repeatedly formed in step S31, and each time a new matrix 3 is formed, heat resistance is imparted to the new matrix 3.

[0071] Step S31 may include steps S31a to S31c.

[0072] In step S31a, the temperature of the reinforcing fibers 5 is increased so that the temperature falls within a first temperature range in which the matrix 3 is deposited on the reinforcing fibers 5. This causes ceramics to precipitate as the matrix 3 on the reinforcing fibers 5. That is, the matrix 3 is deposited and formed on the reinforcing fibers 5.

[0073] The temperature of the reinforcing fibers 5 may mean the temperature of the reinforcing fibers 5 themselves, or may mean the temperature of the heating element 12 in contact with the reinforcing fibers 5 (the same applies below). When the temperature of the reinforcing fibers 5 is within the first temperature range, the matrix 3 is deposited on the reinforcing fibers 5 as described above. The lower limit of the first temperature range may be the temperature at which deposition of the matrix 3 on the reinforcing fibers 5 begins, or may be a temperature higher than that temperature.

[0074] In step S31a, for example, as shown in Fig. 6, an AC magnetic field generated by the coil 21 is generated by passing an AC current through the coil 21, and the heating element 12 is induction-heated by this. This increases the temperature of the reinforcing fibers 5. The heat generated by the induction-heated heating element 12 heats each of the fibrous bodies 15 and the liquid raw material 13.

[0075] Step S31b may be performed after step S31a. For example, when the temperature of the fibrous body 15 (reinforcing fibers 5) reaches a first target temperature within a first temperature range in step S31a, the process may proceed to step S32. In one example, when the temperature measured by a temperature sensor attached to the surface of the heating body 12 reaches the first target temperature, the process proceeds to step S31b. Note that the first target temperature may be any temperature within the first temperature range, and may be the same or different between multiple iterations of step S31a that are repeated as described below.

[0076] In step S31b, the temperature of the reinforcing fibers 5 is lowered to a temperature within the second temperature range at which the matrix 3 does not deposit on the reinforcing fibers 5. This stops the deposition of the matrix 3 on the reinforcing fibers 5.

[0077] The upper limit of the second temperature range is lower than the lower limit of the first temperature range. The upper limit of the second temperature range may be a temperature at which deposition of the matrix 3 on the reinforcing fibers 5 stops when the temperature of the reinforcing fibers 5 drops from within the first temperature range, or may be a temperature lower than that temperature. In this case, the lower limit of the second temperature range may be equal to or higher than the boiling point of the liquid raw material 13, or the upper limit of the second temperature range may be lower than the boiling point of the liquid raw material.

[0078] In step S31b, for example, the heating of the reinforcing fibers 5 is stopped, and the stopped state of the heating of the reinforcing fibers 5 is maintained until the temperature of the reinforcing fibers 5 reaches a second target temperature within the second temperature range. Note that the second target temperature may be any temperature within the second temperature range, and may be the same or different among the multiple times of step S31b that are repeated as described below.

[0079] In step S31b, in addition to stopping the heating of the reinforcing fibers 5, the inside of the treatment vessel 11 may be cooled. For example, the liquid raw material 13 may be circulated by causing a portion of the liquid raw material 13 in the treatment vessel 11 to flow outside the treatment vessel 11, cooling the liquid raw material 13 using a heat exchanger, and then returning the cooled liquid raw material 13 to the treatment vessel 11. In this case, piping and a pump (not shown) for circulating the liquid raw material 13 in this manner may be provided.

[0080] When step S31b is completed (for example, when the temperature of the reinforcing fibers 5 reaches the second target temperature), the next step S31a or S32 is carried out after the judgment of step S31c.

[0081] In step S31c, if the number of times k that steps S31a and S31b have been repeated is equal to the predetermined number N at the time when the immediately preceding step S31b is completed (i.e., if step S31a has been performed the predetermined number N times), the process proceeds to step S32. Otherwise, the process returns to step S31a and steps S31a to S31c are performed again.

[0082] The predetermined number of times N may be two, or may be three or more. In one example, the predetermined number of times N may be two or more and five or less. The number of times k determined in step S31c is zero when proceeding from step S2 to step S31a, is incremented by one when returning from step S31c to step S31a, and is reset to zero when returning from step S32 to step S31 (step S31b), as described below. Note that the predetermined number of times N may be changed when proceeding from step S31c to step S32, or may be constant throughout step S3.

[0083] In step S32, the temperature of the reinforcing fibers 5 is increased so that the temperature of the reinforcing fibers 5 falls within a third temperature range that imparts heat resistance to the matrix 3. The third temperature range is higher than the first temperature range. That is, the lower limit of the third temperature range is higher than the upper limit of the first temperature range. The lower limit of the third temperature range may be the upper limit temperature (the above-mentioned assumed upper limit temperature) assumed in the environment in which the ceramic-based composite material 10 manufactured by this manufacturing method is used. By raising the temperature of the reinforcing fibers 5 to a temperature within the third temperature range, the reinforcing fibers 5 are heated to at least the assumed upper limit temperature in step S32.

[0084] In step S32, similarly to the case of step 31 described above, the heater 12 may be induction-heated by an AC magnetic field generated by the coil 21 by passing an AC current through the coil 21. As a result, the temperature of the reinforcing fibers 5 increases.

[0085] After step S32 is completed, if steps S31 and S32 have not been repeated the set number of times, the process returns to step S31 (e.g., step S31b). For example, if the temperature of the fibrous body 15 (reinforcing fibers 5) reaches a third target temperature within the third temperature range in step S32, the process may return to step S31 (e.g., step S31b). The third target temperature may be any temperature within the third temperature range, and may be the same or different between multiple repeated iterations of step S32.

[0086] The ceramic-based composite material 10 is manufactured by repeating steps S31 and S32 a set number of times (a set plurality of times) as described above. That is, by repeating steps S31 and S32, ceramics are sequentially deposited around each reinforcing fiber 5, and a ceramic matrix 3 is gradually formed. Therefore, for example, steps S31 and S32 may be repeated until the matrix 3 reaches a desired thickness. The set number of times is, for example, in the range of 3 to 30 times, but is not limited to this range. In this embodiment, step S32 may be performed last in step S3, as shown in FIG. 4.

[0087] By performing step S31a or step S32 once, one layer 7 is formed for each reinforcing fiber 5 by the ceramics applied to each reinforcing fiber 5 by the film boiling gas described above.

[0088] When forming a matrix 3 mainly made of silicon carbide, for example, the first temperature range is 800° C. or higher and 1200° C. or lower, the second temperature range is 200° C. or higher and 600° C. or lower, and the third temperature range is 1300° C. or higher (or 1400° C. or higher) and 1600° C. or lower. However, the first temperature range, the second temperature range, and the third temperature range may each be other ranges.

[0089] The first, second, and third temperature ranges may be determined depending on the type of liquid material 3 and the expected upper limit temperature. The upper limit of the first temperature range may be lower than the lower limit of the third temperature range. For example, the difference between the upper limit of the first temperature range and the lower limit of the third temperature range may be 100°C or more, 200°C or more, or 300°C or more.

[0090] Furthermore, when forming a matrix 3 mainly made of silicon carbide, the temperature increase rate of the reinforcing fibers 5 (or the heater 12) in steps S31a and S32 is preferably 1000°C / hour or more. In this case, the temperature increase rate may be 3000°C / hour or less, but may also exceed 3000°C / hour. However, the temperature increase rate may be other values.

[0091] Whether the matrix 3 is primarily made of silicon carbide or made of another material, the temperature increase rate in step S31a (or each of steps S31a and S32) is slow enough to form multiple sublayers in one layer 7 (each layer 7). For example, the temperature increase rate may be 3000°C / hour or less, 2000°C / hour or less, or 1500°C / hour or less. In this case, the temperature increase rate may be 1000°C / hour or more (or higher than 1000°C / hour).

[0092] In other words, it is preferable to heat the fibrous body 15 for an appropriate period of time to form the layer structure of the matrix 3 (e.g., multiple sublayers in one layer 7). For example, in one step S31a (or in one step S31a and one step S32), the time for which the temperature of the fibrous body 15 is raised (i.e., the total time for which the temperature of the fibrous body 15 is raised) may be longer than 10 minutes, 15 minutes or more, 20 minutes or more, or 30 minutes or more. In this case, the time for which the temperature of the fibrous body 15 is raised may be, for example, within 40 minutes, within 50 minutes, or within 60 minutes, but is not limited thereto, and may be longer than 60 minutes.

[0093] In step S3, the ceramic layer 7 undergoes a compositional change (crystallization) due to heat, resulting in a volumetric shrinkage. The amount of shrinkage differs for each of the sublayers 7a, 7b, and 7c. When the matrix 3 is primarily made of silicon carbide, for example, the sublayer 7a changes from a semi-inorganic, organic-like state to an inorganic state, resulting in a larger shrinkage amount and a higher C / Si ratio. This difference in shrinkage amounts causes tensile stress to act in the sublayers 7a and 7b, which have a larger shrinkage amount, and compressive stress to act in the sublayer 7c, which has a smaller shrinkage amount. This tensile stress generates minute closed pores 9 in the matrix 3. Because the tensile stress acts when the ceramic sublayers 7a, 7b, and 7c are formed, closed pores 9 often form as closed voids, especially in the sublayers 7a and 7b.

[0094] (Effects of the embodiment) In the manufacturing method according to the embodiment described above, in step S31, the reinforcing fibers 5 in the liquid raw material 13 are heated to a matrix deposition temperature, thereby forming a matrix 3 on the reinforcing fibers 5. In step S32, the reinforcing fibers 5 in the liquid raw material 13 are heated to a heat-resistance imparting temperature (for example, the upper limit temperature assumed in the usage environment of the ceramic-based composite material 10 to be manufactured). As a result, the matrix 3 formed in the immediately preceding step S31 becomes heat-resistant to that temperature. By repeating steps S31 and S32, the matrix 3 can be formed while imparting heat resistance to the matrix 3. These effects and additional effects will be described in more detail below.

[0095] In step S32, the processing temperature of the film boiling method is raised to the assumed upper limit temperature, thereby increasing the crystallinity of the matrix 3. This causes the mass of the matrix 3 to decrease and the volume to shrink. This volumetric shrinkage makes it prone to cracking, but in step S32, the cracking associated with high crystallization and the formation of the matrix 3 proceed simultaneously, resulting in a matrix 3 that is less susceptible to cracking (penetrating cracks 2a and intermittent cracks 2b).

[0096] Even if a crack that occurs in step S32 is not filled by the matrix 3 generated in step S32, the crack is filled by the matrix 3 formed in the next step S31. Therefore, the occurrence of cracks in the matrix 3 can be further suppressed.

[0097] Furthermore, by increasing the crystallinity of the matrix 3 as described above in step S32, the high-temperature oxidation resistance and radiation resistance are improved.

[0098] As described above, the occurrence of through cracks 2a can be suppressed, which can prevent the occurrence of paths through which gas or liquid from the outside penetrates into the matrix 3. This reduces the surface area of ​​the matrix that comes into contact with oxygen, improving high-temperature oxidation resistance. Furthermore, since the generation of paths for oxygen entry can be suppressed, the generation of paths through which oxygen can access the fiber surface from the outside can be reduced, resulting in improved high-temperature oxidation resistance.

[0099] Conventionally, the MI (Melt Infiltration) method is used to fill voids in a matrix by pouring molten metal into the matrix. When this molten metal comes into contact with the fibers, it reacts with them and can reduce the strength, rigidity, high-temperature oxidation resistance, melting point, and radiation resistance of the fibers. In contrast to this, in this embodiment, the occurrence of cracks that serve as paths for oxygen to penetrate into the matrix 3 can be suppressed as described above, and therefore the above-mentioned deterioration of the fibers by the MI method can be avoided.

[0100] Furthermore, since the occurrence of mid-term cracks 2b can be suppressed, the number of fracture origins in the matrix 3 is reduced, and the decrease in proportional strength (maximum stress in the elastic region where cracks do not occur or propagate) and strength (breaking stress) can be suppressed.

[0101] When step S31 includes the above-described steps S31a and S31b, the following effects are obtained.

[0102] If the lower limit of the second temperature range is equal to or higher than the boiling point of the liquid raw material 13, in step S31b, the temperature of the reinforcing fibers 5 is lowered to a temperature within the second temperature range, thereby calming the boiling of the liquid raw material. This makes it easier for the liquid raw material to penetrate into cracks that have occurred in the matrix 3 in step S31b. Therefore, in the next step S31a, the matrix 3 is more easily formed in the cracks.

[0103] If the upper limit of the second temperature range is lower than the boiling point of the liquid raw material, in step S31b, the temperature of the reinforcing fibers 5 drops to a temperature within the second temperature range, thereby stopping the boiling phenomenon of the liquid material. As a result, in a state where new film boiling gas is no longer generated, the liquid material replaces the film boiling gas that has already been generated, making it easier for the liquid material to penetrate into cracks that have occurred in the matrix 3. Therefore, in the next step S31a, it becomes easier for the matrix 3 to be formed in the cracks.

[0104] In the manufacturing method according to the above-described embodiment, the matrix 3 formed in the step S31 before the final step S31 among the repeated steps S31 has already been heated to the heat resistance imparting temperature at the time of the final step S31. Therefore, the matrix 3 formed in the step S31 before the final step S31 is less likely to crack during the final step S32. Therefore, even if cracks occur in the matrix 3 during the final step S32, the cracks will be limited to a thin layer of the matrix 3 formed in the step S31 immediately before the final step S32.

[0105] Furthermore, in the ceramic matrix composite material 10 manufactured by the manufacturing method according to the embodiment described above, the through cracks 2a are absent or suppressed, which makes it possible to omit an additional process for filling the through cracks 2a with the matrix 3.

[0106] Furthermore, in the manufacturing method according to the above-described embodiment, the process of imparting heat resistance to the matrix 3 (step S32) has already been performed in the process of forming the matrix 3. Therefore, it is possible to omit an additional heat treatment for imparting heat resistance to the matrix 3.

[0107] The ceramic matrix composite material 10 manufactured by the manufacturing method according to the embodiment described above has a matrix 3 that has heat resistance up to the expected upper limit temperature in the usage environment and that suppresses the occurrence of cracks. In one example, the ceramic matrix composite material 10 may be configured so that the through-crack rate is 0.5% or less, 0.1% or less, or 0% both before and after being heated to the expected upper limit temperature in the usage environment of the ceramic matrix composite material, but is not limited thereto.

[0108] Furthermore, the ceramic matrix composite material 10 produced by the production method according to the embodiment described above undergoes only a slight weight loss, as shown in the mass loss amounts in the examples described below, even when heated to the upper limit temperature in the usage environment of the ceramic matrix composite material 10. From this point of view as well, it can be said that the ceramic matrix composite material 10 according to this embodiment has high heat resistance.

[0109] According to the ceramic-based composite material 10 of this embodiment, the following effects (i) to (iv) can also be obtained.

[0110] (i) The above-described step S3 makes it possible to form sublayers 7a with a relatively low elastic modulus and sublayers 7c with a relatively high elastic modulus in each layer 7 of the layer structure. When the matrix 3 is mainly formed of silicon carbide, the sublayers 7a with a relatively low elastic modulus are sublayers with a high C / Si ratio, and the sublayers 7c with a relatively high elastic modulus are sublayers with a low C / Si ratio. The sublayers 7a with a low elastic modulus are easily adapted to deformations such as bending of the ceramic matrix composite material 10. This can suppress the occurrence of cracks in the ceramic matrix composite material 10. Meanwhile, the sublayers 7c with a high elastic modulus maintain a high elastic modulus. Therefore, by mixing the sublayers 7a with a low elastic modulus and the sublayers 7c with a high elastic modulus in the layer structure of the matrix 3, it is possible to suppress the occurrence of cracks while maintaining a high elastic modulus.

[0111] (ii) When stress is applied to a material, the resistance of the material to crack propagation due to the stress and breaking is expressed as fracture toughness. The higher the energy required for the material to break due to crack propagation, the higher the fracture toughness of the material. On the other hand, in a material where stress occurs, the energy generated is proportional to the cross-sectional area of ​​the material. Therefore, by forming a layer structure, the energy generated in the layer 7 with a small cross-sectional area is reduced. In other words, because the matrix 3 has a layer structure, the energy due to stress is dispersed to each layer 7 or each sub-layer 7a of the layer structure, making it difficult for cracks to propagate. This makes it difficult for cracks to propagate in the ceramic-based composite material 10.

[0112] (iii) In the matrix 3, the closed pores 9 are generated during the process of generating the matrix 3 in step S3 due to differences in the amount of shrinkage between the sublayers and the difference in strain between the ceramics, which shrink in volume, and the reinforcing fibers 5, which do not shrink in volume. The generation of these closed pores 9 relieves stress due to volumetric shrinkage in the matrix 3. In this way, the residual stress in the matrix 3 is suppressed, and therefore the generation of cracks in the matrix 3 can be suppressed. Furthermore, in a matrix 3 that does not have a layer structure, large cracks may occur due to the volumetric shrinkage described above. In contrast, since the matrix 3 according to this embodiment has a layer structure, closed pores 9 occur in each layer 7 or each sublayer 7a, 7b, 7c, and in many cases, their dimensions are suppressed to approximately equal to or less than the thickness of the layer 7 or sublayer. Therefore, since the closed pores 9 are minute and exist and closed within the layer 7 or sublayer, the closed pores 9 are unlikely to develop into large cracks.

[0113] (iV) In the ceramic-based composite material 10 of this embodiment, the matrix 3 has a layered structure in which many layers 7 are stacked. This layered structure can prevent cracks from occurring in the matrix 3. Once formed, each ceramic layer 7 has already been heated to a high temperature within the first temperature range. Therefore, the atoms or molecules within each layer 7 are strongly bonded by interatomic bonds, such as ionic or covalent bonds. Therefore, once formed, each layer 7 is less likely to undergo a reaction that further strengthens the interatomic bond during subsequent heating. Therefore, while the atoms or molecules within each layer 7 are strongly bonded by interatomic bonds, adjacent layers 7 are likely to be bonded by forces weaker than interatomic bonds (e.g., intermolecular forces) or by partial interatomic forces. Therefore, the bond between adjacent layers 7 is relatively weak. Therefore, strain is likely to occur at the interfaces between layers 7. Therefore, when an external force acts on the ceramic-based composite material 10, the external force is easily absorbed by the strain at the interfaces between layers 7. This can prevent cracks from occurring in the matrix 3 .

[0114] It is not necessary to obtain all of the above effects (i) to (iv), i.e., it is possible to obtain one or more of the above effects (i) to (iv).Furthermore, according to the present invention, it is not necessary to obtain any of the above effects (i) to (iv).

[0115] The state of the matrix 3 precipitated during the temperature increase / decrease process (steps S31a, S31b, and S32 described above) is thought to vary significantly depending on the temperature at which the precipitation begins. For example, in precipitation at low temperatures below 800°C, semi-inorganic substances that are close to organic accumulate as solids around the reinforcing fibers 5 and are then mineralized by thermal energy. On the other hand, at high temperatures above 1000°C, the ratio of pyrolysis gas in the film boiling gas is high, and semi-inorganic substances that are close to inorganic are precipitated from the beginning. In other words, the ratio of pyrolysis gas in the film boiling gas and the degree of mineralization of the pyrolysis gas vary depending on the temperature. These differences are thought to result in different material states (elastic modulus, crystallinity, and composition) of the inorganic substances formed, resulting in the formation of a layered structure. The same applies when the material of matrix 3 is other than silicon carbide: in the temperature-raising process (steps S31a and S32), the resulting ceramic (thermal analysis product) changes from semi-inorganic to inorganic, forming one layer of the layered structure, and when the temperature is lowered and then raised (after step S31b), the semi-inorganic material is deposited on the inorganic material, thereby forming the layered structure. Based on this principle, even when the material of matrix 3 is other than silicon carbide, it is possible to form a layered structure (each layer 7, or each layer 7 and its sublayers).

[0116] (Example) In the example, the reinforcing fibers 5 prepared in the above-mentioned step S1 were carbon fibers, the liquid raw material 13 used in steps S2 and S3 was LPCS (Liquid Polycarbosilane), and the manufacturing method shown in the flowchart of FIG. 4 was carried out using the configuration shown in FIG. 5A.

[0117] Fig. 7 is a graph showing the temperature change in step S3 in the example. Fig. 7 shows the temperature of the lower surface of the fibrous body 15 (i.e., the surface in contact with the heater 12) on the upper side of Fig. 5A. In Fig. 7, the horizontal axis represents the elapsed time (min), and the vertical axis represents the temperature.

[0118] 8A to 8E are scanning electron microscope images of the ceramic matrix composite material 10 obtained in this example. FIG. 8B is a partially enlarged view of FIG. 8A, and FIG. 8C is a partially enlarged view of FIG. 8B. FIG. 8D is a partially enlarged view of FIG. 8A, and FIG. 8E is a partially enlarged view of FIG. 8D. In particular, in FIGS. 8D and 8E, there are no through-type cracks 2a extending from the surface of the matrix to a depth of 5 μm or more.

[0119] (Comparative Example 1) In Comparative Example 1, the same reinforcing fibers 5 as in the Example were placed in the same liquid raw material 13 as in the Example using the configuration shown in Fig. 5A, as in step S2 described above. In this state, a matrix was formed by film boiling without substantially increasing or decreasing the temperature of the reinforcing fibers 5.

[0120] Fig. 9 is a graph showing temperature changes in the film boiling method in Comparative Example 1. Fig. 9 shows the temperature of the lower surface of the fibrous body 15 (i.e., the surface in contact with the heating body 12) on the upper side of Fig. 5A. In Fig. 9, the horizontal axis represents the elapsed time (min), and the vertical axis represents the temperature.

[0121] 10A to 10E are scanning electron microscope images of the ceramic matrix composite material obtained in Comparative Example 1. FIG. 10B is a partially enlarged view of FIG. 10A, and FIG. 10C is a partially enlarged view of FIG. 10B. FIG. 10D is a partially enlarged view of FIG. 10A, and FIG. 10E is a partially enlarged view of FIG. 10D. In particular, in FIGS. 10D and 10E, there are many through-type cracks 2a extending from the surface of the matrix to a depth of 10 μm or more. In addition, in FIGS. 10A to 10E, there are also many cracks that exist only inside the matrix.

[0122] (Comparative Example 2) In Comparative Example 2, the same reinforcing fibers 5 as in the Example were placed in the same liquid raw material 13 as in the Example using the configuration shown in Figure 5A, as in step S2 above. In this state, the above step S31 was performed without performing the above step S32.

[0123] Fig. 11 is a graph showing the temperature change in the above-mentioned step S31 in Comparative Example 2. Fig. 11 shows the temperature of the lower surface of the fibrous body 15 (i.e., the surface in contact with the heater 12) on the upper side of Fig. 5A. In Fig. 11, the horizontal axis represents the elapsed time (min), and the vertical axis represents the temperature.

[0124] 12A to 12E are scanning electron microscope images of the ceramic matrix composite material obtained in Comparative Example 1. FIG. 12B is a partial enlargement of FIG. 12A, and FIG. 12C is a partial enlargement of FIG. 12B. FIG. 12D is a partial enlargement of FIG. 12A, and FIG. 12E is a partial enlargement of FIG. 12D. In particular, in FIGS. 12D and 12E, there are a certain number of through-type cracks 2a extending from the surface of the matrix to a depth of 10 μm or more.

[0125] (Heat Exposure Test of Examples) A heat exposure test was carried out on the ceramic matrix composite material 10 manufactured according to the above-described example. In this test, the ceramic matrix composite material 10 was placed in a high-temperature environment at 1400° C. for a predetermined period of time.

[0126] Fig. 13A is a scanning electron microscope image of the ceramic matrix composite material 10 before the thermal exposure test. Fig. 13B and Fig. 14 correspond to Fig. 13A and the above-mentioned Fig. 8E, respectively, and are scanning electron microscope images of the ceramic matrix composite material 10 after the thermal exposure test.

[0127] As can be seen from FIGS. 13A and 13B, and FIGS. 8E and 14, the size and number of cracks in the matrix of the ceramic-based composite material 10 of the example hardly increased even after the heat exposure test.

[0128] (Heat exposure test of Comparative Example 1) The ceramic matrix composite material produced in the above-mentioned Comparative Example 1 was subjected to the same heat exposure test as in the Examples.

[0129] Figure 15A is a scanning electron microscope image of the ceramic matrix composite material before the thermal exposure test, and Figure 15B is a scanning electron microscope image of the ceramic matrix composite material after the thermal exposure test.

[0130] As can be seen from FIGS. 15A and 15B, the size and number of cracks in the matrix of the ceramic matrix composite material increased significantly due to the heat exposure test, unlike the case of the Examples.

[0131] (Mass loss in Example and Comparative Example 2) The ceramic matrix composite materials produced in the above-mentioned Example and Comparative Example 2 were each heated, and their masses were measured at each temperature.

[0132] The results of this experiment are shown in Figure 16. In Figure 16, the solid line indicates the case of the Example, and the dashed line indicates the case of Comparative Example 2. In Figure 16, the horizontal axis indicates the temperature of the ceramic matrix composite material, and the vertical axis indicates the mass of the ceramic matrix composite material as a ratio (%). That is, the ratio on the vertical axis is a value obtained by heating the ceramic matrix composite material immediately after production according to the Example or Comparative Example 2, and indicates the ratio (%) of the mass at each temperature to the mass (100%) of the ceramic matrix composite material immediately after production.

[0133] As can be seen from Figure 16, the ceramic matrix composite material of the example showed a mass loss rate of only about 0.1% even when heated to 1400°C. Furthermore, the mass of the ceramic matrix composite material of the example increased until it reached about 1300°C. These facts suggest that the deposition shrinkage, which is a cause of crack generation, is small at high temperatures.

[0134] On the other hand, in the ceramic matrix composite material of Comparative Example 2, the mass loss rate was larger than that of the Examples, at about 0.5%.

[0135] (Rate of through-type cracks in Examples and Comparative Examples) The following describes the through-crack rate in the above-mentioned examples, but the ceramic matrix composite material 10 according to this embodiment is not limited to a configuration having the following through-crack rate, and may be any material that has heat resistance to the expected upper limit temperature in its usage environment while suppressing the occurrence of cracks.

[0136] Fig. 17 shows the measured values ​​of the through-crack ratio for the ceramic matrix composite materials produced by the example and the comparative example. In Fig. 17, the horizontal axis shows the maximum temperature in the film boiling method or the heating temperature (°C) in the subsequent heat exposure treatment, and the vertical axis shows the through-crack ratio for through-cracks 2a extending from the outer surface of the matrix to a depth of 10 µm or more.

[0137] In FIG. 17, circles A and B indicate the measured values ​​of the through-crack rate of the ceramic matrix composite material 10 manufactured by the above-described embodiment, with circle A indicating the measured value immediately after the manufacturing, and circle B indicating the measured value after the manufacturing and subsequent heat exposure treatment. In FIG. 17, square marks C and D indicate the measured values ​​of the through-crack rate of the ceramic matrix composite material manufactured by the above-mentioned Comparative Example 2, with square mark C indicating the measured value immediately after the manufacturing, and square mark D indicating the measured value after the manufacturing and subsequent heat exposure treatment. 17, triangles E, F, and G indicate the measured values ​​of the through-crack rate of ceramic matrix composite materials manufactured in the same manner as in Comparative Example 1, except that the maximum temperature in the film boiling method in Comparative Example 1 was set to just under 900°C. Triangle E indicates the measured value immediately after manufacturing, and triangles F and G indicate the measured values ​​after heat exposure treatment at 1200°C and 1400°C, respectively, after manufacturing.

[0138] 17, in the ceramic matrix composite material 10 of the example, the through-crack rate was zero immediately after production, and remained at zero even after subsequent heat exposure treatment in which the material was heated to 1400°C. Thus, in the example, it is clear that the matrix 3 is substantially free of through-cracks 2a, which serve as paths for oxygen penetration, and has high heat resistance. On the other hand, in the ceramic matrix composite material of Comparative Example 2, the through crack rate was about 1.6% immediately after production, and increased to about 3.8% when heated to 1450°C in the subsequent heat exposure treatment. In the ceramic matrix composite material of Comparative Example 1, the through-crack rate was 4.1% immediately after production, and increased to approximately 5.1% when heated to 1200°C in a subsequent heat exposure treatment, and further increased to approximately 7.3% when heated to 1400°C in a further heat exposure treatment.

[0139] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the technical concept of the present invention. For example, any one of the following modified examples 1 to 4 may be adopted, or any combination of two or more of modified examples 1 to 4 may be adopted. In this case, the points not described below may be the same as those described above.

[0140] (Change example 1) Before the above-described step S2, a process for forming an interface layer on the outer peripheral surface of each reinforcing fiber 5 may be performed. This process may be performed by a known method (for example, the method described in JP 2003-321277 A). In this case, an interface layer is formed at the boundary between each reinforcing fiber 5 and the matrix 3. The interface layer may be a layer containing boron nitride. When an interface layer is provided, even if a crack occurs and propagates into the reinforcing fiber 5, the interface layer can prevent the crack from propagating into the reinforcing fiber 5. (Change example 2)

[0141] The material forming the matrix 3 may be other than silicon carbide. In this case, an inorganic polymer material that is a ceramic raw material containing an alkoxide solution and has a molecular weight low enough to be in a liquid state may be used as the liquid raw material 13 in the above-mentioned film boiling method. Other materials may also be used as the liquid raw material 13. In this way, the liquid raw material 13 in the above-mentioned film boiling method may be a liquid raw material other than the above-mentioned LPCS. For example, the liquid raw material 13 may be borazine, methyltrichlorosilane, cyclohexane, a silicon alkoxide solution, an aluminum alkoxide solution, a mixed solution of a silicon alkoxide solution and an aluminum alkoxide solution, or a zirconium alkoxide solution.

[0142] When the liquid raw material 13 is borazine, the ceramic produced by heating in step S3 is boron nitride (BN). Boron nitride has low adhesiveness to silicon carbide. Therefore, when the reinforcing fibers 5 are silicon carbide fibers, crack propagation can be suppressed at the interface between the boron nitride matrix 3 and the silicon carbide reinforcing fibers 5.

[0143] When liquid source material 13 is methyltrichlorosilane, the ceramics generated by heating in step S3 described above will be silicon carbide (SiC), which is a ceramic, in the same way as when liquid source material 13 is polycarbosilane (LPCS).

[0144] When the liquid raw material 13 is cyclohexane, the ceramic produced by heating in the above-mentioned step S3 is carbon, which has the same function as boron nitride.

[0145] When the liquid raw material 13 is a silicon alkoxide solution, the ceramics produced by heating in the above-mentioned step S3 are silicon dioxide. Silicon alkoxide solutions are cheaper than LPCS.

[0146] When the liquid raw material 13 is an aluminum alkoxide solution, the ceramics produced by heating in the above-mentioned step S3 will be alumina. Aluminum alkoxide solutions are cheaper than LPCS.

[0147] When the liquid raw material 13 is a mixed liquid of a silicon alkoxide solution and an aluminum alkoxide solution, the ceramics produced by heating in the above-mentioned step S3 will be mullite.

[0148] When the liquid raw material 13 is a zirconium alkoxide solution, the ceramics produced by the heating in the above-mentioned step S3 are zirconia. Zirconia is a ceramic with a higher melting point than silicon carbide, so it does not melt even in an ultra-high temperature environment and functions as a matrix.

[0149] According to the present invention, the liquid source 13 used in step S3 is not limited to the above-described specific example, and may be another liquid source. For example, another metal alkoxide solution may be used as the liquid source 13 in step S3. In this case, the ceramic produced by heating in step S3 may be an oxide ceramic. In this case, the liquid source 13 used in step S3 may be, for example, a mixture of three alkoxide solutions, as described in Non-Patent Document 2, so that the ceramic produced in step S3 is barium aluminosilicate (BaAl2Si2O8). The matrix 3 formed from this liquid source 13 may be at least partially crystallized.

[0150] When the matrix 3 is formed of mullite, the liquid raw material 13 used in the film boiling method may be a mixture of a plurality of alkoxide solutions as described in Non-Patent Document 3, and the matrix 3 formed from this liquid raw material 13 may be at least partially crystallized.

[0151] (Change example 3) The fixture described above is not limited to the above configuration, and may be any fixture to which a fibrous body, which is a component of a ceramic-based composite material, is attached and which is placed together with the fibrous body in the liquid matrix material to perform film boiling on the fibrous body.

[0152] (Change example 4) In the manufacturing method according to the embodiment described above, step S31b of lowering the temperature of the reinforcing fibers 5 so that the temperature of the reinforcing fibers 5 falls within the second temperature range described above may be omitted. In this case, in step S31, the state in which the reinforcing fibers 5 in the liquid raw material 13 are heated to the matrix formation temperature (a temperature within the first temperature range described above) may be continued for a predetermined time. After the heating in step S31 has been continued for the predetermined time, the process proceeds to step S32. In this case, other points may be the same as those described above.

[0153] In this modification, by repeating steps S31 and S32, the matrix 3 can be formed and at the same time, the matrix 3 can be given heat resistance. [Explanation of symbols]

[0154] 2a Penetrating crack 2b Interrupted crack 3. Matrix 3a outer surface 5. Reinforced Fiber 6 Interface layer 7 layers 7a,7b,7c sublayer 9 Closed pores 10 Ceramic-based composite materials 11 Processing container 11a Cover member 11a1 Through hole 11a2 Gas exhaust hole 11b Gas inlet hole 12 Heating element 12a outer circumference 13 Liquid matrix material 14 Insulation board 15 Fibrous body 15a outer circumference 16 Porous material (wire mesh) 17 Mechanism of action 17a Bolt 17b Nut 18. Insulation 19 Wire 21 Coil 23 Hanging part 23a Plate-shaped member 23a1 Joint part 23b Rod-shaped member 100 Mounting fixture

Claims

1. A method for producing a ceramic matrix composite material comprising a matrix and reinforcing fibers disposed within the matrix, comprising: (A) disposing reinforcing fibers in the liquid matrix material; (B) heating the reinforcing fibers in the liquid feedstock to a matrix-forming temperature; (C) heating the reinforcing fibers in the liquid raw material to a heat resistance imparting temperature; The heat resistance imparting temperature is a temperature exceeding the matrix formation temperature, and the steps (B) and (C) are repeated.

2. In (B), (B1) Raising the temperature of the reinforcing fibers to a matrix formation temperature within a first temperature range at which a matrix is ​​deposited on the reinforcing fibers; (B2) Lowering the temperature of the reinforcing fibers so that the temperature of the reinforcing fibers is within a second temperature range in which a matrix does not deposit on the reinforcing fibers; 2. The method for producing a ceramic matrix composite material according to claim 1, wherein in each step of (B), (B1) and (B2) are repeated.

3. 3. The method for producing a ceramic matrix composite material according to claim 1, wherein in step (C), the temperature of the reinforcing fibers is increased to a heat resistance imparting temperature within a third temperature range that imparts heat resistance to a usage environment of the ceramic matrix composite material.

4. 3. The method for producing a ceramic-based composite material according to claim 2, wherein the lower limit of the second temperature range is equal to or higher than the boiling point of the liquid raw material, or the upper limit of the second temperature range is lower than the boiling point of the liquid raw material.

5. A ceramic matrix composite material produced by the method for producing a ceramic matrix composite material according to claim 1, 2 or 4.

Images