Method for coating fibrous material

Abstract

This method for covering a fiber body comprises: an impregnation condition determination step for determining, when the fiber body is subjected to chemical vapor impregnation with a ceramic and covered thereby, the impregnation temperature and the impregnation pressure at which the film forming rate of the ceramic for the entire fiber body is maximized with respect to the impregnation temperature; and an impregnation step for supplying, to the fiber body, a film-formation gas containing a feedstock of the ceramic, and performing the chemical vapor impregnation at the impregnation temperature and the impregnation pressure determined during the impregnation condition determination step.

Description

Technical Field

[0001] The present disclosure relates to a method for coating a fibrous body.

Background Art

[0002] Conventionally, in the fields of aircraft and semiconductors, etc., parts have been manufactured by coating a fibrous body composed of carbon fibers, SiC fibers, etc. with ceramics. For example, in the aircraft field, a ceramics-based composite material (CMC, Ceramics Matrix Composites) is used as a part used in high-temperature parts such as aircraft engines. The ceramics-based composite material is a lightweight and high-temperature strength excellent material. The ceramics-based composite material is a composite material in which a preform, which is a fibrous body, is impregnated with ceramics and coated (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] By the way, when a fibrous body is impregnated with ceramics and coated, it is performed by a chemical vapor infiltration (CVI, Chemical Vapor Infiltration) method that utilizes a reaction from a gas phase with excellent diffusibility of the raw material of the ceramics. In the chemical vapor infiltration method, a film is formed while diffusing the raw material into the fibrous body at an extremely slow film formation rate. Therefore, a long time is required for the process of the chemical vapor infiltration method, which is a factor reducing the productivity of ceramics-based composite material parts, etc.

[0005] Therefore, an object of the present disclosure is to provide a method for coating a fibrous body that can coat a fibrous body with ceramics more rapidly.

[0006] A method for coating a fibrous body made of carbon or SiC fibers includes an impregnation condition determination step of determining an impregnation temperature and an impregnation pressure that maximizes the film formation rate of the ceramics throughout the fibrous body relative to the impregnation temperature when coating the fibrous body by chemical vapor impregnation with ceramics, and an impregnation step of supplying a film formation gas containing the raw materials of the ceramics to the fibrous body and chemically impregnating the spaces between the fibers in the fibrous body at the impregnation temperature and impregnation pressure determined in the impregnation condition determination step, wherein the ceramics are SiC, the raw material of the ceramics is methyltrichlorosilane, and the impregnation step is characterized in that the impregnation temperature is from 800°C to 1000°C and the impregnation pressure is a total pressure of 50 Torr or more. The impregnation condition determination step comprises: a fiber model setting step for setting a model of the fiber body; a raw material model setting step for setting a model of the raw material; a raw material diffusion model setting step for setting a raw material diffusion model for when the raw material is supplied to the fiber body and diffused; a reaction model setting step for setting a reaction model for when the ceramics are formed from the raw material diffused into the fiber body; a raw material concentration distribution calculation step for calculating the raw material concentration distribution of the raw material diffused into the fiber body; a film formation rate calculation step for calculating the film formation rate of the ceramics for the entire fiber body; and an impregnation condition determination step for determining the impregnation temperature and the impregnation pressure at which the film formation rate of the ceramics for the entire fiber body is maximized relative to the impregnation temperature. . [Effects of the Invention]

[0007] According to the above configuration, ceramics can be coated onto the fibrous material more quickly. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a flowchart showing the configuration of a method for coating a fiber in an embodiment of the present disclosure. [Figure 2] Figure 2 shows the configuration of a fiber coating device in an embodiment of the present disclosure. [Figure 3] Figure 3 is a diagram illustrating a method for setting up a fiber model in an embodiment of this disclosure. [Figure 4] Figure 4 is a diagram illustrating how to set up a raw material diffusion model in an embodiment of this disclosure. [Figure 5] Figure 5 is a diagram illustrating the transition process between Knudsen diffusion and molecular diffusion in an embodiment of this disclosure. [Figure 6] Figure 6 is a diagram illustrating how to determine the area S and volume V in an embodiment of this disclosure. [Figure 7] Figure 7 is a schematic diagram showing the raw material concentration distribution within the fiber in an embodiment of the present disclosure. [Figure 8]Figure 8 is a schematic diagram showing the ceramic film formation rate for the entire fiber in an embodiment of the present disclosure. [Figure 9] Figure 9 is a diagram illustrating a method for setting up a fiber model in an embodiment of this disclosure. [Figure 10] Figure 10 is a graph showing the mean free path of an MTS at a temperature of 800°C to 1050°C and a total pressure of 0 Torr to 800 Torr in an embodiment of the present disclosure. [Figure 11] Figure 11 is a graph showing the mean free path of an MTS at a temperature of 800°C to 1050°C and a total pressure of 0 Torr to 200 Torr in an embodiment of the present disclosure. [Figure 12] Figure 12 is a diagram illustrating the raw material diffusion model of MTS within a fiber in an embodiment of this disclosure. [Figure 13] Figure 13 is a graph showing the Knudsen diffusion coefficient Dk and molecular diffusion coefficient Dm of MTS at 950°C and a total pressure from 0 Torr to 300 Torr in embodiments of this disclosure. [Figure 14] Figure 14 is a graph showing the relationship between temperature and adhesion probability for the first and second film types in embodiments of this disclosure. [Figure 15] Figure 15 is a graph showing the raw material concentration distribution of MTS at 800°C in an embodiment of the present disclosure. [Figure 16] Figure 16 is a graph showing the raw material concentration distribution of MTS at 850°C in an embodiment of the present disclosure. [Figure 17] Figure 17 is a graph showing the raw material concentration distribution of MTS at 900°C in an embodiment of the present disclosure. [Figure 18] Figure 18 is a graph showing the raw material concentration distribution of MTS at 950°C in an embodiment of the present disclosure. [Figure 19] Figure 19 is a graph showing the raw material concentration distribution of MTS at 1000°C in an embodiment of the present disclosure. [Figure 20] Figure 20 is a graph showing the SiC film formation rate of the entire fiber at 800°C to 1000°C and a total pressure of 5 Torr to 760 Torr in embodiments of the present disclosure. [Figure 21] Figure 21 is a graph showing the SiC film formation rate of the entire fiber at 800°C to 1000°C and a total pressure of 5 Torr to 100 Torr in embodiments of the present disclosure. [Figure 22] Figure 22 is a diagram illustrating an impregnation evaluation method in an embodiment of this disclosure. [Figure 23] Figure 23 is a graph showing the chemical composition evaluation results of SiC in an embodiment of this disclosure. [Figure 24] Figure 24 is a graph showing the results of the SiC impregnation evaluation in an embodiment of this disclosure. [Figure 25] Figure 25 is a graph showing the evaluation results of the SiC film deposition rate in an embodiment of this disclosure. [Figure 26] Figure 26 is a graph showing the SiC film yield evaluation results in an embodiment of this disclosure. [Figure 27] Figure 27 is a graph showing the results of the evaluation of reaction by-products in an embodiment of this disclosure. [Modes for carrying out the invention]

[0009] Embodiments of the present disclosure will be described in detail below with reference to the drawings. Figure 1 is a flowchart showing the configuration of a fiber coating method. The fiber coating method comprises an impregnation condition determination step (S10) and an impregnation step (S12).

[0010] The fibrous coating method involves coating a fibrous body, such as carbon fiber or SiC fiber, with ceramics by chemical vapor impregnation. This fibrous coating method can be used, for example, in the manufacturing of parts in the aerospace and semiconductor industries. It can also be used, for example, in the manufacture of ceramic matrix composite materials applied to jet engine parts. In the manufacture of ceramic matrix composite materials, the fibers of the fibrous body are coated by chemical vapor impregnation with BN (boron nitride) or by chemical vapor impregnation with SiC (silicon carbide) to form a matrix.

[0011] First, a fiber coating apparatus used in the fiber coating method will be described. Figure 2 shows the configuration of the fiber coating apparatus 10. The fiber coating apparatus 10 is composed of a chemical vapor impregnation apparatus. The fiber coating apparatus 10 includes a reaction section 12, a gas supply section 14, a gas discharge section 16, and a control section 18.

[0012] The reaction unit 12 has the function of impregnating the fiber A with ceramics to form a film. The reaction unit 12 is equipped with a reactor 20. The reactor 20 has a reactor 22 and a heater 24 provided around the reactor 22. The reactor 20 can be configured as, for example, a horizontal hot-wall type electric furnace.

[0013] The reactor 22 is formed in a cylindrical or other tubular shape. The reactor 22 is formed so that the fiber A can be inserted into it. The reactor 22 is equipped with a thermometer (not shown), such as a thermocouple, for measuring the furnace temperature. The reactor 22 has a gas inlet 26 provided on one end in the longitudinal direction of the reactor 22 and a gas outlet 28 provided on the other end in the longitudinal direction of the reactor 22. The gas inlet 26 side of the reactor 22 corresponds to the upstream side of the reactor 22. The gas outlet 28 side of the reactor 22 corresponds to the downstream side of the reactor 22. A pressure gauge 30 for measuring the furnace pressure is provided at the gas outlet 28.

[0014] The gas supply unit 14 has the function of supplying ceramic raw materials and carrier gas to the reactor 22. The gas supply unit 14 includes a raw material container 32 for storing the raw materials, a first on-off valve 34, and a first mass flow controller 36. The first on-off valve 34 and the first mass flow controller 36 have the function of adjusting the flow rate of the raw materials.

[0015] The gas supply unit 14 includes a carrier gas container 38 for storing carrier gas, a second on-off valve 40, and a second mass flow controller 42. The second on-off valve 40 and the second mass flow controller 42 have the function of adjusting the flow rate of the carrier gas.

[0016] The gas supply unit 14 includes a gas pipe 44 for transporting raw materials and a gas pipe 46 for transporting carrier gas. The gas supply unit 14 also includes a gas pipe 48 for transporting film-forming gas containing raw materials. The film-forming gas may include raw materials and carrier gas.

[0017] The gas discharge section 16 has the function of discharging furnace gas from the reactor 22. The gas discharge section 16 is equipped with a third on-off valve 50, an exhaust pump 52, and a scrubber 54. The third on-off valve 50 has the function of adjusting the flow rate of the furnace gas to be discharged. The exhaust pump 52 has the function of exhausting the reactor 22. The scrubber 54 has the function of recovering reaction by-products, etc. The gas discharge section 16 has a gas pipe 56 for transporting the discharged furnace gas.

[0018] The exhaust pump 52 can be an oil-sealed rotary vacuum pump, a mechanical booster pump, a water-sealed vacuum pump, or the like. As will be described later, when the pressure inside the reactor 22 is to be increased to a total pressure of 50 Torr or more to coat the fiber A with ceramics, a water-sealed vacuum pump is preferable. This is because water-sealed vacuum pumps are easier to maintain than oil-sealed rotary vacuum pumps or mechanical booster pumps.

[0019] The control unit 18 has the function of controlling the reaction unit 12, the gas supply unit 14, and the gas discharge unit 16. The control unit 18 can be configured using a general computer system or the like.

[0020] The control unit 18 can adjust the flow rate of the raw material by controlling the first on-off valve 34 and the first mass flow controller 36. The control unit 18 can adjust the flow rate of the carrier gas by controlling the second on-off valve 40 and the second mass flow controller 42. By adjusting the flow rate of the raw material and the flow rate of the carrier gas, the control unit 18 can adjust the flow rate ratio of the raw material to the carrier gas, the partial pressure ratio of the raw material and the carrier gas in the reactor 22, and so on.

[0021] The control unit 18 can control the heater 24 to adjust the temperature inside the reactor 22. The control unit 18 can also control the third on-off valve 50 and the exhaust pump 52 to adjust the pressure inside the reactor 22.

[0022] Next, the impregnation condition determination step (S10) will be explained. The impregnation condition determination step (S10) is a step in which the impregnation temperature and the impregnation pressure that maximizes the film formation rate of the ceramics throughout the fiber when coating the fiber with ceramics by chemical vapor impregnation are determined relative to the impregnation temperature.

[0023] The impregnation condition determination step (S10) comprises a fiber model setting step, a raw material model setting step, a raw material diffusion model setting step, a reaction model setting step, a raw material concentration distribution calculation step, a film formation rate calculation step, and an impregnation condition determination step. Next, each step will be described in detail.

[0024] (Fiber model setup step) The fiber model setting step is the step of setting up a fiber model for the fiber that will coat the ceramics. Figure 3 is a diagram illustrating how to set up the fiber model. The fiber shown in Figure 3 is composed of a three-dimensional fabric woven from fiber bundles consisting of X, Y, and Z threads.

[0025] A fibrous body is woven from fiber bundles (yarns) that consist of hundreds to tens of thousands of individual fibers (filaments). Therefore, the fibrous body model sets the shape and dimensions of the fibrous body, the weave form, the fiber bundles, and the fibers within the fiber bundles. Regarding the shape and dimensions of the fibrous body, the thickness of the fibrous body is set. The reason for setting the thickness of the fibrous body is, as will be explained later, to simplify the phenomenon of raw material diffusion, we consider only the diffusion of raw materials that occurs in the thickness direction, which is the thinnest width of the fibrous body. In the fibrous body shown in Figure 3, the thickness in the Z-direction is set. The weave form is set to, for example, a 2D weave or a 3D weave. In the fibrous body shown in Figure 3, it is set to a 3D weave.

[0026] The fiber bundle has its fiber bundle diameter and the spacing between fiber bundles set. In the fiber body shown in Figure 3, the fiber bundle diameter of the fiber bundle consisting of X, Y, and Z threads, the spacing between X and Y threads, the spacing between X and Z threads, and the spacing between Y and Z threads are set. The fibers that make up the fiber bundle consisting of X, Y, and Z threads have their fiber diameter and the spacing between fibers set. In the fiber body shown in Figure 3, the fiber diameter of the fibers included in the X thread, etc., and the spacing between the fibers included in the X thread, etc. are set.

[0027] Furthermore, in order to calculate the raw material concentration distribution within the fiber in the raw material concentration distribution calculation step described later, a fiber unit cell representing the structure of the fiber model is set. The fiber unit cell can be made up of, for example, a rectangular parallelepiped. In the fiber shown in Figure 3, the fiber unit cell is configured to include X threads, Y threads, and Z threads.

[0028] (Raw material model setting step) The raw material model setting step is the step of setting the raw material model for the ceramic material to be coated onto the fiber. For example, if the ceramic is SiC, the raw material model can be set to an organic chlorosilane, etc. Examples of such organic chlorosilanes include methyltrichlorosilane (CH3SiCl3:MTS), dimethyldichlorosilane ((CH3)2SiCl2:DDS), trimethylchlorosilane ((CH3)3SiCl:TCS), and tetramethylsilane ((CH3)4Si:TMS). In the following explanation, compound names may be written using abbreviations. For example, methyltrichlorosilane may be written as MTS.

[0029] Furthermore, for example, if the ceramic is BN, the raw material model is boron trichloride (BCl3), diborane (B2H6), decaborane (B 10 H 14 It can be set to trimethylborone (B(CH3)3), trimethylborate (B(OCH3)3), etc.

[0030] (Raw material diffusion model setting step) The raw material diffusion model setting step is the step of setting a raw material diffusion model for when raw materials are supplied to a fiber and diffused. Figure 4 is a diagram illustrating the method of setting the raw material diffusion model, where Figure 4(a) is an explanatory diagram of Knudsen diffusion and Figure 4(b) is an explanatory diagram of molecular diffusion.

[0031] The raw material diffusion model is based on the mean free path of the raw material molecules. The mean free path λ of the raw material molecules can be calculated from equation 1, where d is the molecular radius, k is the Boltzmann constant, T is the temperature, and P is the pressure.

[0032]

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[0033] When the mean free path of the raw material molecules is greater than the spacing between fibers or between fiber bundles, the raw material diffusion model is set to Knudsen diffusion. As shown in Figure 4(a), Knudsen diffusion is a diffusion model in which raw material molecules diffuse while colliding with fibers, etc. Equations 2 and 3 show the Knudsen diffusion coefficient D. k This is the formula for calculating the molecular weight. v is the average molecular speed. a is the distance between fibers or between fiber bundles. R is the gas constant. T is the temperature. M is the molecular weight.

[0034]

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[0035]

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[0036] When the mean free path of the raw material molecules is smaller than the spacing between fibers or between fiber bundles, the raw material diffusion model is set to molecular diffusion. As shown in Figure 4(b), molecular diffusion is a diffusion model in which raw material molecules diffuse while colliding with each other. Note that the spacing between fiber bundles is usually much larger than the mean free path of the raw material molecules, so molecular diffusion is applied to the raw material diffusion model between fiber bundles.

[0037] Mathematical equations 4 through 6 are about the molecular diffusion coefficient D. m This is the formula for calculating the molecular diffusion coefficient D. m This is the two-body diffusion coefficient D in the Chapman-Enskog equation. 1.2 It can be calculated as follows: T is temperature, p is pressure, and M is molecular weight. Ω D σ is the reductive collision integral. TN is the normalization temperature. k is the Boltzmann constant. σ and ε are the Lenneard-Jones parameters. The Lenneard-Jones parameters can be obtained from literature, etc. Table 1 shows the Lenneard-Jones parameters for C2H2 (acetylene), CH4 (methane), H2 (hydrogen), and MTS as examples.

[0038]

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[0039]

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[0040]

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[0041] [Table 1]

[0042] FIG. 5 is a diagram for explaining the transition process between Knudsen diffusion and molecular diffusion. In FIG. 5, the pressure is taken on the horizontal axis, the mean free path is taken on the vertical axis, and the mean free path of the raw material molecules is shown. The arrow in FIG. 5 indicates the transition region between Knudsen diffusion and molecular diffusion.

[0043] The transition region between Knudsen diffusion and molecular diffusion occurs when the mean free path of the raw material molecules becomes the same as the interval a between the fibers. When the mean free path of the raw material molecules is larger than the interval a between the fibers, the diffusion of the raw material molecules becomes Knudsen diffusion. When the mean free path of the raw material molecules is smaller than the interval a between the fibers, the diffusion of the raw material molecules becomes molecular diffusion. Note that the Knudsen diffusion coefficient is at least two orders of magnitude smaller than the molecular diffusion coefficient. The fact that the Knudsen diffusion coefficient is at least two orders of magnitude smaller than the molecular diffusion coefficient is also shown in the graph for explaining the diffusion coefficient of MTS in FIG. 13 described later.

[0044] (Reaction model setting step) The reaction model setting step is a step of setting a reaction model when forming a ceramic film from the raw material diffused in the fiber body. The reaction model is set based on the film-forming species and the adhesion probability of the film-forming species. Then, based on the film-forming species and the adhesion probability of the film-forming species, the surface reaction rate constant k s is calculated. The surface reaction rate constant k s is the reaction rate constant per unit area.

[0045] The film-forming species is a chemical species that contributes to the formation of the ceramic film. The raw material diffused in the fiber body becomes the film-forming species and contributes to the formation of the ceramic film. The film-forming species may be, for example, the same substance as the raw material, or an intermediate product generated by thermal decomposition reaction of the raw material or reaction with other substances. The number of film-forming species is not particularly limited, and may be one type or two or more types. When there are two or more film-forming species, the contribution rate of each film-forming species to the formation of the ceramic film can be set. The contribution rate means the proportion of the contribution of each film-forming species to the film formation. The contribution rates of each film-forming species may be the same or different.

[0046] The adhesion probability of a film-forming species is the probability that the film-forming species reacts on the fiber surface and is converted into ceramics. When there are multiple film-forming species, each species forms a film independently according to its own adhesion probability and contribution rate. The resulting coating can then be considered as a superposition of coatings formed by each of the different film-forming species.

[0047] The type of film deposited, its contribution rate, and its adhesion probability may be determined through experiments or analyses, or by referring to literature. The type of film deposited, its contribution rate, and its adhesion probability can be determined, for example, by microcavity analysis using a known trench substrate or by multiscale analysis. Such analyses using trench substrates are described, for example, in brochure WO2015 / 129772.

[0048] The surface reaction rate constant ks is calculated based on the film type and the adhesion probability. Equation 7 is the formula for calculating the surface reaction rate constant ks. η is the adhesion probability and is a dimensionless number. v is the average velocity of the molecules and can be obtained from equation 3. The coefficient of 1 / 4 represents the integral for the film type entering from random directions.

[0049]

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[0050] (Raw material concentration distribution calculation step) The raw material concentration distribution calculation step is to calculate the raw material concentration distribution of the raw materials diffused within the fiber. To simplify the phenomenon, it is sufficient to consider only the raw material diffusion occurring in the thickness direction, which is the thinnest width of the fiber. The raw material concentration distribution in the thickness direction of the fiber can be determined from the basic equations derived from the mass balance in the thickness direction of the fiber and the boundary conditions, using equations 8 to 9.

[0051]

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[0052]

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[0053] The raw material concentration distribution in the thickness direction of the fiber is the relative raw material concentration C x It can be calculated using / C0. Relative raw material concentration C x / C0 represents the raw material concentration C at a depth x from the surface in the thickness direction of the fiber. x This is the ratio of the raw material concentration C0 on the surface in the thickness direction of the fiber. D is the diffusion coefficient of the raw material. v x is the reaction rate constant per unit volume. x is the depth from the surface in the thickness direction of the fiber. L is the thickness of the fiber.

[0054] The equation in equation 8 contains the φ shown in equation 9, which is the Thiele modulus. The Thiele modulus is a dimensionless number. The Thiele modulus is the relative raw material concentration C x / C0 is the diffusion coefficient D of the raw materials and the reaction rate constant k per unit volume. v This indicates that it is determined by a balance between the two factors.

[0055] More specifically, the diffusion coefficient D of the raw material is related to the proportion of the raw material that reaches the fiber through diffusion. The reaction rate constant k per unit volume. v This is related to the rate at which raw materials are consumed by the formation of ceramic films on the fiber surface. From this, the relative raw material concentration C x The / C0 ratio is determined by the balance between the proportion of raw materials that reach the fiber body through diffusion and the proportion of raw materials consumed by the formation of ceramic films on the fiber surface.

[0056] This section explains how to determine the diffusion coefficient D of the raw material. The diffusion coefficient D of the raw material can be determined from the raw material diffusion model set in the raw material diffusion model setting step. First, we will explain the case where the raw material diffusion model is Knudsen diffusion between fibers within a fiber bundle and molecular diffusion between fiber bundles. Since the Knudsen diffusion coefficient is more than two orders of magnitude smaller than the molecular diffusion coefficient, the rate at which the raw material reaches the fiber body by raw material diffusion between fibers within a fiber bundle is much slower than between fiber bundles. For this reason, when determining the raw material concentration distribution, it is not necessary to consider raw material diffusion between fibers within a fiber bundle. Therefore, the diffusion coefficient D of the raw material should be calculated by considering molecular diffusion between fiber bundles and using the molecular diffusion coefficient D m Use this.

[0057] Next, we will explain the case where the raw material diffusion model involves molecular diffusion both between fibers within a fiber bundle and between fiber bundles. Similar to between fiber bundles, molecular diffusion accelerates the rate at which the raw material reaches the fiber body. Therefore, the diffusion coefficient D of the raw material should take into account molecular diffusion both between fibers within the fiber bundle and between fiber bundles, resulting in a molecular diffusion coefficient D m Use this.

[0058] Thus, whether the raw material diffusion model between fibers in a fiber bundle is molecular diffusion or Knudsen diffusion, the diffusion coefficient D of the raw material is the molecular diffusion coefficient D m This is used.

[0059] Next, the reaction rate constant k per unit volume v We will explain how to find the reaction rate constant k per unit volume. v This is the surface reaction rate constant k obtained in the reaction model setting step. s It can be calculated based on the reaction rate constant k per unit volume. v The surface reaction rate constant k s This can be calculated using formula number 10. Area S is the surface area of ​​the fiber surface on which the ceramic film is formed within the fiber body. Volume V is the volume of the space remaining after removing the fibers from the fiber body.

[0060]

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[0061] Next, we will explain how to determine the area S and volume V. Figure 6 is a diagram illustrating how to determine the area S and volume V. Note that the area S and volume V are calculated from the fiber unit cell set in the fiber model setting step. As mentioned above, the fiber unit cell represents the composition of the fiber.

[0062] First, let's explain the case where the raw material diffusion model is Knudsen diffusion between fibers within a fiber bundle and molecular diffusion between fiber bundles. In this case, the Knudsen diffusion coefficient is more than two orders of magnitude smaller than the molecular diffusion coefficient, so the surface reaction on the outer surface of the fiber bundle is dominant over the surface reaction of the fibers within the fiber bundle. Therefore, the consumption of raw materials due to film formation on the outer surface of the fiber bundle is far greater than the consumption of raw materials due to film formation on the fibers within the fiber bundle.

[0063] Therefore, when determining the raw material concentration distribution, it is not necessary to consider the consumption of raw materials due to surface reactions of the fibers within the fiber bundle, and thus the surface area of ​​each fiber within the fiber bundle can be ignored. Consequently, the area S is the sum of the surface areas of the outer perimeters of each fiber bundle contained in the fiber body. The volume V is the volume of space remaining after removing all the fiber bundles from the fiber body.

[0064] Next, we will explain the case where the raw material diffusion model involves molecular diffusion both between fibers within a fiber bundle and between fiber bundles. In this case, the raw material undergoes molecular diffusion both between fibers within a fiber bundle and between fiber bundles. As a result, the consumption of raw materials due to film formation on the fibers within the fiber bundle is large, similar to the consumption of raw materials due to film formation on the outer surface of the fiber bundle. Therefore, the area S is the sum of the surface areas of each fiber within each fiber bundle contained in the fiber body. The volume V is the spatial volume of the fiber body excluding the fibers within all fiber bundles.

[0065] Then, the diffusion coefficient D of the raw materials and the reaction rate constant k per unit volume were calculated. v Substitute the values ​​into equations 8 and 9 to obtain the relative raw material concentration C within the fiber. xCalculate / C0. Note that if the raw material diffusion model between fibers within the fiber bundle is in the transition region between Knudsen diffusion and molecular diffusion, the relative raw material concentration C calculated as Knudsen diffusion will be used. x / C0 and the relative raw material concentration C calculated as molecular diffusion in the raw material diffusion model between fibers within the fiber bundle. x It is calculated by averaging with / C0.

[0066] Relative raw material concentration C within the fiber x / C0 is calculated by varying the impregnation pressure with respect to the impregnation temperature. The impregnation temperature can be set to the thermal decomposition temperature of the raw material, the reaction temperature with other substances, etc. There may be one or more impregnation temperature conditions. The impregnation pressure is not particularly limited, but for example it can be set to a total pressure of 760 Torr or less. The partial pressure ratio of the raw material and carrier gas contained in the film-forming gas is not particularly limited, but for example it can be set to 1:1.

[0067] Relative raw material concentration C within the fiber x / C0 is calculated from the surface of the fiber to the center in the thickness direction of the fiber. This is because the raw material diffuses not only from the surface in the thickness direction of the fiber, but also from the back surface in the thickness direction of the fiber. The modes of raw material diffusion from the surface and back surface in the thickness direction of the fiber can be considered to be substantially the same.

[0068] Figure 7 is a schematic diagram showing the raw material concentration distribution within the fiber. In the graph in Figure 7, the horizontal axis represents the depth x from the surface in the thickness direction of the fiber, and the vertical axis represents the relative raw material concentration C. x / C0 is taken, and the depth x from the surface in the thickness direction of the fiber and the relative raw material concentration C are taken. x The relationship with / C0 is shown. Figure 7 shows, as an example, the relative raw material concentration C within the fiber when the impregnation pressure is changed with respect to the impregnation temperature while the total pressure is 760 Torr or less. x The / C0 is schematically shown. If there are multiple impregnation temperature conditions rather than just one, it is advisable to create a graph like the one shown in Figure 7 for each impregnation temperature.

[0069] As shown in Figure 7, relative raw material concentration Cx / C0 decreases as the depth x from the surface in the thickness direction of the fiber increases. Relative raw material concentration C x The degree of decrease in / C0 decreases as the impregnation pressure decreases and increases as the impregnation pressure increases. In Figure 7, at the center of the fiber in the thickness direction, the relative raw material concentration C is highest at a total pressure of 5 Torr. x The degree of decrease in / C0 becomes smaller, and the relative raw material concentration is highest at a total pressure of 760 Torr. x The degree of decrease in / C0 increases. On the other hand, the amount of raw material supplied is such that more raw material is supplied to the fiber when the impregnation pressure is high, and less raw material is supplied to the fiber when the impregnation pressure is low. Therefore, the raw material concentration C at depth x from the surface in the thickness direction of the fiber. x This relates to the amount of raw material supplied into the fiber and the relative raw material concentration C within the fiber. x It is determined by balancing the degree of decrease in / C0.

[0070] (Film deposition rate calculation step) The film formation rate calculation step is to calculate the film formation rate of ceramics for the entire fiber. First, the film formation rate of ceramics at a depth x from the surface in the thickness direction within the fiber is calculated. The film formation rate Rx of ceramics at a depth x from the surface in the thickness direction within the fiber is given by the surface reaction rate constant k s And the raw material concentration C at a depth x from the surface in the thickness direction within the fiber. x Based on this, it can be calculated using the formula shown in Equation 11. Here, we assume that the reaction of the raw materials follows a first-order reaction. A first-order reaction is a type of reaction in which the reaction rate is proportional to the concentration of the raw materials. Surface reaction rate constant k s This can be calculated from equation 7. The raw material concentration C at a depth x from the surface in the thickness direction within the fiber. x This can be calculated using equations 8 to 9. The raw material concentration C0 on the surface in the thickness direction of the fiber can be determined by gas-phase composition analysis using a quadrupole mass spectrometer or the like, or by analysis.

[0071]

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[0072] Next, we calculate the ceramic film formation rate for the entire fiber. The ceramic film formation rate for the entire fiber is the ceramic film formation rate R at a depth x from the surface in the thickness direction of the fiber. x This is calculated by integrating it along the thickness direction of the fiber. More specifically, the ceramic film formation rate for the entire fiber is the ceramic film formation rate R at a depth x from the surface in the thickness direction of the fiber. x You can do this by integrating it from 0 to L / 2 in the thickness direction of the fiber and multiplying by 2.

[0073] Figure 8 is a schematic diagram showing the film formation rate of ceramics throughout the entire fiber. In the graph in Figure 8, the horizontal axis is plotted on impregnation pressure and the vertical axis on film formation rate, schematically showing the relationship between impregnation pressure and film formation rate with respect to impregnation temperature. The graph in Figure 8 shows that the film formation rate of ceramics throughout the entire fiber is highest at impregnation pressure P1. If there are multiple impregnation temperature conditions rather than just one, it is advisable to create a graph like the one shown in Figure 8 for each impregnation temperature.

[0074] (Impregnation condition determination step) The impregnation condition determination step involves determining the impregnation temperature and the impregnation pressure at which the film formation rate of the ceramics throughout the fiber is maximized relative to the impregnation temperature. The impregnation temperature is determined based on the thermal decomposition temperature of the raw materials, the reaction temperature of the raw materials with other substances, etc. The impregnation pressure at which the film formation rate of the ceramics throughout the fiber is maximized relative to the impregnation temperature is determined based on the graph in Figure 8. The impregnation pressure at which the film formation rate of the ceramics throughout the fiber is maximized relative to the impregnation temperature may include not only the impregnation pressure at which the film formation rate of the ceramics throughout the fiber is greatest, but also impregnation pressures in the vicinity of that pressure. In the graph in Figure 8, not only the impregnation pressure P1 at which the film formation rate of the ceramics throughout the fiber is greatest, but also impregnation pressures in the vicinity of the impregnation pressure P1 may be included.

[0075] Furthermore, the impregnation condition determination step may determine the impregnation temperature and pressure that maximize the film formation rate of the ceramics throughout the fiber. More specifically, if there are multiple impregnation temperature conditions, it is preferable to determine the impregnation temperature and pressure that maximize the film formation rate of the ceramics throughout the fiber. The impregnation temperature and pressure that maximize the film formation rate of the ceramics throughout the fiber may include not only the impregnation temperature and pressure that result in the highest film formation rate for the ceramics throughout the fiber, but also impregnation temperatures and pressures in the vicinity of that value. The impregnation conditions can be determined in this way.

[0076] Next, the impregnation process (S12) will be explained using the fiber coating apparatus 10 shown in Figure 1. The impregnation process (S12) is a process in which a film-forming gas containing ceramic raw materials is supplied to the fiber A, and chemical vapor impregnation is performed at the impregnation temperature and impregnation pressure determined in the impregnation condition determination process (S10).

[0077] First, the fiber A is set in the reactor 22 of the reactor 20. The reactor 22 is evacuated by the exhaust pump 52. Film-forming gas containing the raw materials and carrier gas is supplied to the reactor 22 from the gas supply unit 14. The control unit 18 controls the first on-off valve 34, the second on-off valve 40, and the exhaust pump 52 to control the pressure inside the reactor 22 to become the impregnation pressure determined in the impregnation condition determination step (S10). The control unit 18 controls the heater 24 to control the temperature inside the reactor 22 to become the impregnation temperature determined in the impregnation condition determination step (S10).

[0078] As a result, the raw material diffused into the fiber A undergoes a thermal decomposition reaction, etc., and the fiber A is coated with ceramics. More specifically, the raw material diffuses in parallel between the fiber bundles within the fiber A and between the fibers within the fiber bundles, so that the ceramics are chemically impregnated and coated in parallel between the fiber bundles and between the fibers within the fiber bundles. Since the impregnation pressure is set to the pressure that maximizes the film formation rate of the ceramics throughout the fiber as a result of the impregnation temperature, the fiber A can be impregnated and coated with ceramics more quickly.

[0079] Next, as a specific example of a method for coating fibrous materials, a method for manufacturing ceramic matrix composites will be described. The ceramic matrix composite material will be a SiC / SiC ceramic matrix composite material in which SiC is used for both the fibrous material and the matrix. Specifically, the case in which SiC / SiC ceramic matrix composite materials are coated with SiC to form a SiC matrix will be described.

[0080] In the impregnation condition determination step (S10), when coating the fiber body with SiC by chemical vapor impregnation, the impregnation temperature and the impregnation pressure that maximizes the film formation rate of SiC throughout the fiber body are determined relative to the impregnation temperature. As described above, the impregnation condition determination step (S10) comprises a fiber body model setting step, a raw material model setting step, a raw material diffusion model setting step, a reaction model setting step, a raw material concentration distribution calculation step, a film formation rate calculation step, and an impregnation condition determination step. Next, each step will be described in detail.

[0081] (Fiber model setup step) In the fiber model setting step, a fiber model of the fiber covering the SiC is set. Figure 9 is a diagram illustrating how to set the fiber model. Figure 9(a) shows the overall structure of the fiber. Figure 9(b) shows the structure of the X, Y, and Z threads. Figure 9(c) shows the structure of the fibers within the X, Y, and Z threads. Figure 9(d) shows the structure of the fiber unit cell.

[0082] As shown in Figure 9(a), the fibrous material was a three-dimensional fabric woven with X, Y, and Z threads. The X, Y, and Z threads are composed of bundles of fibers (filaments) called yarns. The X and Y threads are woven in the in-plane direction of the three-dimensional fabric. The Z thread is woven in the thickness direction of the three-dimensional fabric. The thickness of the fibrous material was set to 10 mm.

[0083] As shown in Figure 9(b), the X, Y, and Z threads were made up of fiber bundles of 800 fibers each. The cross-sectional shape of the X, Y, and Z threads was rectangular. The X and Z threads were each composed of one fiber. The Y thread was composed of two fibers. The cross-sectional dimensions of one X thread and one Z thread were 0.12 mm vertically and 1 mm horizontally. The cross-sectional dimensions of the two Y threads were 0.12 mm vertically and 2 mm horizontally.

[0084] The fibers in the X, Y, and Z threads were given a fiber radius of 5 μm and a center-to-center distance of 11 μm. As shown in Figure 9(c), the spacing between fibers within the fiber bundle consisting of the X, Y, and Z threads was 1 μm.

[0085] As shown in Figure 9(d), a representative fiber unit cell was defined for the fiber. The shape of the fiber unit cell was a rectangular parallelepiped. The fiber unit cell is composed of one X thread, two Y threads, and one Z thread. The dimensions of the fiber unit cell were 1.52 mm in length, 3.04 mm in width, and 0.23 mm in height.

[0086] (Raw material model setting step) In the raw material model setting step, a raw material model was set for the SiC raw material to coat the fiber. The raw material model was set to methyltrichlorosilane (CH3SiCl3:MTS).

[0087] (Raw material diffusion model setting step) In the raw material diffusion model setting step, a raw material diffusion model was set for when MTS, the raw material, is supplied to the fiber and diffused. First, the mean free path of MTS was calculated using equation 1. The molecular radius d was set to 1.45 Å, which is the molecular radius of MTS. The Boltzmann constant k was set to 1.38 × 10⁻⁶. ―23 The ratio was set to J / K. The temperature T was set to 800°C to 1050°C, taking into consideration the thermal decomposition temperature of MTS, etc. The pressure P was set to a total pressure of 0 Torr to 800 Torr.

[0088] Figure 10 is a graph showing the mean free path of MTS from 800°C to 1050°C and total pressure from 0 Torr to 800 Torr. Figure 11 is a graph showing the mean free path of MTS from 800°C to 1050°C and total pressure from 0 Torr to 200 Torr. In Figures 10 and 11, the horizontal axis is pressure and the vertical axis is mean free path, showing the mean free path of MTS at each temperature. Note that Figure 11 is an enlarged graph of Figure 10 for the range from total pressure 0 Torr to 200 Torr. It shows that the mean free path of MTS is approximately the same in the range from 800°C to 1050°C.

[0089] Next, a raw material diffusion model for MTS within the fiber was established. Figure 12 is a diagram illustrating the raw material diffusion model for MTS within the fiber. In Figure 12, pressure is plotted on the horizontal axis and the mean free path on the vertical axis, with the mean free path of the 950°C MTS shown in Figure 11 being shown as a representative example. The arrows in Figure 12 indicate the transition region where the raw material diffusion model changes.

[0090] First, let's explain the raw material diffusion model of MTS between fibers within a fiber bundle. In the fiber model, the spacing between fibers within the fiber bundle is set to 1 μm, so the pressure when the mean free path of MTS is 1 μm becomes the transition region where the raw material diffusion model of MTS changes. The pressure when the mean free path of MTS is 1 μm is a total pressure of 80 Torr. Therefore, the raw material diffusion model of MTS between fibers within a fiber bundle changes at a total pressure of 80 Torr in the range of 800°C to 1050°C.

[0091] At pressures less than 80 Torr, the raw material diffusion model for MTS between fibers in a fiber bundle is Knudsen diffusion. At pressures greater than 80 Torr, the raw material diffusion model for MTS between fibers in a fiber bundle is molecular diffusion. At a total pressure of 80 Torr, the raw material diffusion model for MTS between fibers in a fiber bundle is in the transition region between Knudsen diffusion and molecular diffusion.

[0092] Next, we will explain the raw material diffusion model for MTS between fiber bundles. The spacing between fiber bundles is usually much larger than 100 μm. This means that the spacing between fiber bundles is larger than the mean free path of MTS. Therefore, the raw material diffusion model for MTS between fiber bundles is molecular diffusion.

[0093] The Knudsen diffusion coefficient and molecular diffusion coefficient of MTS were calculated at temperatures ranging from 800°C to 1050°C and total pressures from 0 Torr to 800 Torr. Knudsen diffusion coefficient D of MTS k The formulas were calculated using equations from Mathematics II to Mathematics III. The interfiber spacing a was set to 1 μm. The gas constant R was set to 8.31 J·mol / K. The molecular weight M was set to 149.5 g / mol, which is the molecular weight of MTS.

[0094] Molecular diffusion coefficient D of MTS m The formulas from Equations 4 to 6 were used to calculate the molecular weight M, which is 149.5 g / mol, the molecular weight of MTS. The Boltzmann constant k was 1.38 × 10⁻⁶. ―23 The J / K ratio was used. The Lenneard-Jones parameters σ and ε were those of the MTS shown in Table 1.

[0095] As a representative example, the Knudsen diffusion coefficient and molecular diffusion coefficient of MTS at 950°C and a total pressure of 0 Torr to 300 Torr will be described. Figure 13 shows the Knudsen diffusion coefficient D of MTS at 950°C and a total pressure of 0 Torr to 300 Torr. k and molecular diffusion coefficient D m This is a graph showing the following. In Figure 13, the horizontal axis is pressure and the vertical axis is the diffusion coefficient, and the Knudsen diffusion coefficient D k and molecular diffusion coefficient D m This shows the Knudsen diffusion coefficient D. k The molecular diffusion coefficient D m This indicates that it is about two orders of magnitude smaller than that.

[0096] (Reaction model setup step) In the reaction model setting step, a reaction model is set for depositing SiC from MTS. The reaction model is set based on the type of SiC film to be deposited and the adhesion probability of that film type. The types of SiC films to be deposited include C-containing chemical species, Si-C-containing chemical species, and Si-containing chemical species.

[0097] When SiC is deposited by thermal decomposition reactions of MTS, etc., it is known that carbon-containing chemical species are rate-limiting in SiC deposition. It is also known that there are two types of carbon-containing chemical species with different reactivity. Therefore, these two types of carbon-containing chemical species were set as the first and second deposition species for SiC deposition. The first deposition species are C2H4 and C2H2. The second deposition species are C2H5 and CH3.

[0098] Next, the adhesion probabilities and contribution rates of the first and second film-forming types were determined. The adhesion probabilities and contribution rates of the first and second film-forming types were determined using known methods such as microcavity analysis and multiscale analysis with trench substrates, referring to pamphlet WO2015 / 129772, etc.

[0099] Figure 14 is a graph showing the relationship between temperature and adhesion probability for the first and second film-forming types. Figure 14(a) is the graph for the first film-forming type, and Figure 14(b) is the graph for the second film-forming type. In the graphs of Figures 14(a) and 14(b), the horizontal axis is temperature and the vertical axis is adhesion probability, showing the adhesion probability at each temperature. The adhesion probability for the first and second film-forming types changes with temperature.

[0100] Table 2 summarizes the adhesion probabilities of the first and second film-forming types at temperatures ranging from 800°C to 1000°C. The adhesion probabilities at 800°C and 850°C were obtained by extrapolating the adhesion probabilities from 900°C to 1000°C using an exponential function. Since the adhesion probabilities follow the Arrhenius equation, they can be fitted using an exponential function. The contribution rate of the first film-forming type was assumed to be 0.80, and the contribution rate of the second film-forming type was assumed to be 0.20.

[0101] [Table 2]

[0102] Surface reaction rate constant k s The surface reaction rate constant k was calculated based on the type of SiC film to be deposited and the adhesion probability. s The formula was derived from equation 7. The average molecular velocity v was derived from equation 3. The gas constant R was set to 8.31 J·mol / K. The molecular weight M was the molecular weight of the first and second film-forming species. The adhesion probability η was the adhesion probability of the first and second film-forming species shown in Table 2.

[0103] (Raw material concentration distribution calculation step) In the raw material concentration distribution calculation step, the raw material concentration distribution of MTS diffused within the fiber was calculated. The MTS raw material concentration distribution was defined as the MTS raw material concentration distribution in the thickness direction within the fiber. The MTS raw material concentration distribution was obtained from equations 8 to 9. The MTS raw material concentration distribution was calculated at temperatures from 800°C to 1000°C and total pressures from 5 Torr to 760 Torr. Next, the diffusion coefficient D of MTS and the reaction rate constant k per unit volume were determined. v I will explain how to find this.

[0104] First, let's explain the case where the temperature is between 800°C and 1000°C and the total pressure is less than 80 Torr. In this case, the raw material diffusion model for MTS is the Knudsen diffusion model between fibers within a fiber bundle, and the molecular diffusion model between fiber bundles. As shown in Figure 13, the Knudsen diffusion coefficient is more than two orders of magnitude smaller than the molecular diffusion coefficient, so there is no need to consider the diffusion of MTS between fibers within a fiber bundle. Therefore, the diffusion coefficient of MTS is defined as the molecular diffusion coefficient D m I used it.

[0105] k, the reaction rate constant per unit volume v This was calculated from equation 10. Surface reaction rate constant k sThe values ​​obtained in the reaction model setting step were used. Area S and volume V were calculated from the fiber unit cells. Since the Knudsen diffusion coefficient is more than two orders of magnitude smaller than the molecular diffusion coefficient, surface reactions on the outer surface of the fiber bundle are dominant over surface reactions of the fibers within the fiber bundle. For this reason, the surface area of ​​each fiber within the fiber bundle can be ignored. Therefore, area S was taken as the sum of the surface areas of the outer perimeters of each fiber bundle contained in the fiber bundle. Volume V was taken as the volume of space remaining after removing all fiber bundles from the fiber bundle.

[0106] Next, we will explain the case where the temperature is between 800°C and 1000°C and the total pressure is greater than 80 Torr. In this case, MTS undergoes molecular diffusion both between fibers within the fiber bundle and between fiber bundles. Therefore, the diffusion coefficient of MTS is the molecular diffusion coefficient D. m I used it.

[0107] k, the reaction rate constant per unit volume v This was calculated from equation 10. Surface reaction rate constant k s The values ​​obtained in the reaction model setting step were used. Area S and volume V were calculated from the fiber unit cells. Since MTS undergoes molecular diffusion both between fibers and between fiber bundles, the consumption of MTS due to film formation on the fibers within the fiber bundle is significant, as is the consumption of MTS due to film formation on the outer surface of the fiber bundle. For this reason, area S was defined as the sum of the surface areas of each fiber in each fiber bundle contained in the fiber body. Volume V was defined as the spatial volume of the fiber body excluding the fibers within all fiber bundles.

[0108] As described above, the molecular diffusion coefficient D of MTS m And the reaction rate constant k per unit volume v Substitute the values ​​from equation 8 to equation 9 to obtain the relative raw material concentration distribution C of MTS within the fiber. x / C0 was calculated. Relative raw material concentration C x / C0 represents the raw material concentration C at a depth x from the surface in the thickness direction of the fiber. x This is the ratio of the raw material concentration C0 on the surface in the thickness direction of the fiber. The thickness L of the fiber was set to 10 mm. The partial pressure ratio of MTS contained in the film formation gas to the carrier gas was set to 1:1. The carrier gas was H2 (hydrogen).

[0109] Furthermore, at temperatures between 800°C and 1000°C and a total pressure of 80 Torr, the raw material diffusion model between fibers within a fiber bundle enters a transition region between the Knudsen diffusion model and the molecular diffusion model. In this case, the relative raw material concentration C calculated as Knudsen diffusion is the raw material diffusion model between fibers within the fiber bundle. x / C0 and the relative raw material concentration C calculated as molecular diffusion in the raw material diffusion model between fibers within the fiber bundle. x It was calculated by averaging with / C0.

[0110] Figure 15 is a graph showing the raw material concentration distribution of MTS at 800°C. Figure 16 is a graph showing the raw material concentration distribution of MTS at 850°C. Figure 17 is a graph showing the raw material concentration distribution of MTS at 900°C. Figure 18 is a graph showing the raw material concentration distribution of MTS at 950°C. Figure 19 is a graph showing the raw material concentration distribution of MTS at 1000°C. In Figures 15 to 19, the horizontal axis represents the depth x from the surface in the thickness direction of the fiber, and the vertical axis represents the relative raw material concentration C. x / C0 is taken, and the relative raw material concentration C of MTS from a total pressure of 5 Torr to 760 Torr x This indicates / C0.

[0111] As shown in Figures 15 to 19, the relative raw material concentration C x / C0 decreases as the depth x from the surface in the thickness direction of the fiber increases. Relative raw material concentration C x The degree of C / C decrease decreases as the impregnation pressure decreases and increases as the impregnation pressure increases. In Figures 15 to 19, the relative raw material concentration C is highest at a total pressure of 5 Torr in the central part of the fiber in the thickness direction. x The degree of decrease in / C0 becomes smaller, and the relative raw material concentration is highest at a total pressure of 760 Torr. x The degree of decrease in / C0 increases. On the other hand, the amount of MTS supplied is such that more MTS is supplied to the fiber when the impregnation pressure is high, and less MTS is supplied to the fiber when the impregnation pressure is low. Therefore, the raw material concentration C at depth x from the surface in the thickness direction of the fiber. x This relates to the amount of MTS supplied into the fiber and the relative raw material concentration C within the fiber. x It is determined by balancing the degree of decrease in / C0.

[0112] (Film deposition rate calculation step) In the film formation rate calculation step, the SiC film formation rate for the entire fiber was calculated. First, the SiC film formation rate at depth x from the surface in the thickness direction of the fiber was calculated. SiC film formation rate R at depth x from the surface in the thickness direction of the fiber x The surface reaction rate constant k s And the raw material concentration C of MTS at a depth x from the surface in the thickness direction within the fiber. x Based on this, the surface reaction rate constant k was calculated using the formula shown in Equation 11. s This was calculated from equation 7. The raw material concentration C of MTS at a depth x from the surface in the thickness direction within the fiber. x This was calculated using equations 8 to 9. The raw material concentration C0 on the surface in the thickness direction of the fiber was determined by gas phase composition analysis and other methods using a quadrupole mass spectrometer, etc. This determined the SiC film formation rate R at a depth x from the surface in the thickness direction of the fiber. x They sought it.

[0113] Next, the SiC film formation rate for the entire fiber was calculated. The SiC film formation rate for the entire fiber is the SiC film formation rate R at a depth x from the surface in the thickness direction within the fiber. x This was calculated by integrating along the thickness direction of the fiber. Specifically, the SiC film formation rate for the entire fiber is the SiC film formation rate R at a depth x from the surface in the thickness direction within the fiber. x This was calculated by integrating the result from a fiber thickness of 0 mm to 5 mm and then doubling the result.

[0114] Figure 20 is a graph showing the SiC film deposition rate of the entire fiber at temperatures from 800°C to 1000°C and total pressures from 5 Torr to 760 Torr. Figure 21 is a graph showing the SiC film deposition rate of the entire fiber at temperatures from 800°C to 1000°C and total pressures from 5 Torr to 100 Torr. In Figures 20 and 21, the horizontal axis is pressure and the vertical axis is the SiC film deposition rate, showing the relationship between pressure and SiC film deposition rate at each temperature. Note that Figure 21 is an enlarged graph of the graph in Figure 20 for total pressures from 5 Torr to 100 Torr. Also, in Figure 20, the graphs for 900°C and 950°C overlap at total pressures above 100 Torr.

[0115] (Impregnation condition determination step) In the impregnation condition determination step, the impregnation temperature and the impregnation pressure that maximizes the SiC film formation rate of the entire fiber for a given impregnation temperature were determined. Specifically, from Figures 20 and 21, the impregnation temperature and the impregnation pressure that maximizes the SiC film formation rate of the entire fiber for a given impregnation temperature were determined. When the impregnation temperature is between 800°C and 1000°C, the SiC film formation rate of the entire fiber can be maximized with an impregnation pressure of 50 Torr to 80 Torr. When the impregnation temperature is 800°C, the SiC film formation rate of the entire fiber can be maximized with an impregnation pressure of 80 Torr. When the impregnation temperature is between 850°C and 1000°C, the SiC film formation rate of the entire fiber can be maximized with an impregnation pressure of 50 Torr.

[0116] In the impregnation condition determination step, the impregnation temperature and pressure that maximize the SiC film formation rate for the entire fiber may be determined. From Figures 20 and 21, the SiC film formation rate for the entire fiber can be maximized at an impregnation temperature of 850°C to 900°C and an impregnation pressure of 50 Torr. Alternatively, the SiC film formation rate for the entire fiber can be maximized at an impregnation temperature of 900°C and an impregnation pressure of 50 Torr. The impregnation conditions can be determined in this way.

[0117] Furthermore, for the impregnation temperatures of 800°C to 1000°C mentioned above, the upper limit of the impregnation pressure at which the SiC film formation rate of the entire fiber is maximized corresponds to the pressure in the transition region of the diffusion model between fibers within the fiber bundle. As shown in Figure 12, the raw material diffusion model between fibers within the fiber bundle transitions from Knudsen diffusion to molecular diffusion at a total pressure of 80 Torr. Therefore, for the impregnation temperatures of 800°C to 1000°C mentioned above, the impregnation pressure at which the SiC film formation rate of the entire fiber bundle is maximized corresponds to the pressure in the transition region of the diffusion model between fibers within the fiber bundle, starting from a total pressure of 50 Torr. The reason why the upper limit of the impregnation pressure at which the SiC film formation rate of the entire fiber bundle is maximized corresponds to the pressure in the transition region of the diffusion model between fibers within the fiber bundle is mainly due to the change in S / V of several tens in the transition region of the diffusion model between fibers within the fiber bundle.

[0118] The pressure corresponding to the transition region in the raw material diffusion model changes depending on the spacing between fibers within the fiber bundle. A total pressure of 80 Torr is the pressure in the transition region of the fiber-to-fiber diffusion model when the spacing between fibers within the fiber bundle is 1 μm. For example, from Figures 10 and 11, when the spacing between fibers within the fiber bundle is 0.5 μm, the total pressure is 140 Torr, which is the pressure in the transition region of the fiber-to-fiber diffusion model. When the spacing between fibers within the fiber bundle is 0.1 μm, the total pressure is 800 Torr, which is the pressure in the transition region of the fiber-to-fiber diffusion model.

[0119] In the fiber model described above, the spacing between fibers within the fiber bundle is set to 1 μm. Therefore, when the impregnation temperature is between 800°C and 1000°C, the SiC film formation rate for the entire fiber can be maximized when the impregnation pressure is between 50 Torr and 80 Torr. In the fiber model described above, by setting the spacing between fibers within the fiber bundle to less than 1 μm, when the impregnation temperature is between 800°C and 1000°C, the upper limit of the impregnation pressure is not limited to a total pressure of 80 Torr, and the SiC film formation rate for the entire fiber can be maximized when the impregnation pressure is 50 Torr or higher.

[0120] Next, the impregnation process (S12) will be explained. In the impregnation process (S12), SiC is chemically vapor-impregnated into the fiber body according to the impregnation conditions determined in the impregnation condition determination process (S10). The impregnation process (S12) will be explained using the fiber body coating apparatus 10 shown in Figure 1.

[0121] The fiber A is placed in the reactor 22 of the reactor 20. After the fiber A is placed, the reactor 22 is evacuated using the exhaust pump 52. Next, the raw material and carrier gas are introduced into the reactor 22 from the gas supply unit 14. MTS is used as the raw material. H2 is used as the carrier gas. The control unit 18 controls the first on-off valve 34 and the first mass flow controller 36 to adjust the flow rate of MTS. The control unit 18 controls the second on-off valve 40 and the second mass flow controller 42 to adjust the flow rate of H2. Then, the film-forming gas containing MTS and H2 is supplied to the reactor 22.

[0122] The control unit 18 controls the reaction unit 12, the gas supply unit 14, and the gas discharge unit 16 to adjust them to the impregnation temperature and impregnation pressure determined in the impregnation condition determination step (S10). The control unit 18 controls the heater 24 to heat the reactor 22, thereby adjusting the temperature inside the reactor 22 to the impregnation temperature determined in the impregnation condition determination step (S10). The control unit 18 controls the first on-off valve 34, the second on-off valve 40, the third on-off valve 50, and the exhaust pump 52 to adjust the pressure inside the reactor 22 to the impregnation pressure determined in the impregnation condition determination step (S10). If, as described above, the impregnation conditions are determined in the impregnation condition determination step (S10) to be an impregnation temperature of 800°C to 1000°C and an impregnation pressure of 50 Torr to 80 Torr, the control unit 18 controls the reactor to achieve these impregnation conditions.

[0123] The partial pressure ratio of MTS to H2 (hydrogen), MTS / H2, should ideally be between 0.3 and 2.5. By setting MTS / H2 to between 0.3 and 2.5, the chemical composition of SiC can be made to be stoichiometric or close to it. Note that the partial pressure ratio of MTS to H2 is the same as the molar ratio of MTS to H2.

[0124] The MTS / H2 ratio should be between 1.0 and 2.5. Setting the MTS / H2 ratio to 1.0 to 2.5 enhances the SiC impregnation. This allows for sufficient SiC film formation and coating not only between fiber bundles of fiber A, but also between fibers within the fiber bundles. Furthermore, setting the MTS / H2 ratio to 1.0 to 2.5 suppresses the precipitation of reaction by-products. These by-products will be discussed later.

[0125] The MTS / H2 ratio should be set to 1.0. Setting MTS / H2 to 1.0 allows the chemical composition of SiC to be closer to the stoichiometric composition, and also improves the impregnation properties of SiC. Furthermore, setting MTS / H2 to 1.0 can suppress the precipitation of reaction by-products.

[0126] In the impregnation process (S12), MTS diffused into fiber A undergoes thermal decomposition, etc., causing SiC to be formed and impregnated between the fiber bundles of fiber A and between the fibers within the fiber bundles. Since the impregnation is carried out at an impregnation pressure that maximizes the rate of SiC film formation throughout the fiber with respect to the impregnation temperature, the fiber can be quickly coated with SiC. Furthermore, since SiC is formed and impregnated in parallel between the fiber bundles of fiber A and between the fibers within the fiber bundles, the fiber can be coated with SiC even more quickly.

[0127] Next, the reaction by-products will be explained in detail. The main reaction by-product is chlorosilane polymer. Chlorosilane polymer is a reaction by-product that is produced when SiCl2, a chlorosilane polymer precursor, is cooled to around room temperature and polymerized. When chlorosilane polymer is hydrolyzed in air, it transforms into harmful silicon oxalic acid, etc. Note that SiCl2 is a substance produced when MTS is thermally decomposed, etc.

[0128] For example, when impregnation is performed at an impregnation temperature of 800°C to 1000°C and an impregnation pressure of 5 Torr, a large amount of reaction byproducts precipitate. This is because, at low impregnation pressures, the reaction rate of the gas-phase reaction in which SiCl2 is modified into other stable substances such as SiCl4 decreases. As a result, a large amount of SiCl2 remains, leading to the precipitation of a large amount of reaction byproducts.

[0129] On the other hand, when impregnation is carried out at an impregnation temperature of 800°C to 1000°C and an impregnation pressure of 50 Torr or higher, the formation of reaction byproducts can be suppressed. This is because, at higher impregnation pressures, the reaction rate of the gas-phase reaction in which SiCl2 is modified into other stable substances such as SiCl4 increases. As a result, the amount of remaining SiCl2 is almost eliminated, and the formation of reaction byproducts is suppressed. Since the formation of reaction byproducts can be suppressed, maintenance of the exhaust pump 52 becomes easier, for example.

[0130] The residence time of SiCl2 in reactor 22 should be set to 4 to 20 seconds at a total pressure of 50 Torr or higher. This promotes the gas-phase reaction in which SiCl2 is reformed into other stable substances, thereby further suppressing the formation of reaction byproducts. The residence time of SiCl2 in reactor 22 can be adjusted, for example, based on the inflow rate of the film-forming gas flowing into reactor 22 and the discharge rate of the furnace gas discharged from reactor 22.

[0131] Furthermore, in low-pressure environments where the impregnation pressure is such as a total pressure of 5 Torr, an oil-sealed rotary pump or a mechanical booster pump is used for the exhaust pump 52. On the other hand, in high-pressure environments where the impregnation pressure is such as a total pressure of 50 Torr or higher, it is not necessary to use a high-performance pump such as an oil-sealed rotary pump, and a water-sealed pump, for example, can be used. As a result, the failure rate of the exhaust pump 52 is reduced, and the productivity of the parts is improved.

[0132] As described above, with the above configuration, chemical vapor impregnation is performed under impregnation conditions consisting of an impregnation temperature and an impregnation pressure that maximizes the film formation rate of the ceramics throughout the fiber relative to the impregnation temperature, making it possible to coat the fiber with ceramics more quickly.

[0133] According to the above configuration, chemical vapor impregnation is performed under impregnation conditions consisting of impregnation temperature and impregnation pressure that maximize the film formation rate of ceramics throughout the fiber, making it possible to coat the fiber with ceramics even more rapidly.

[0134] According to the above configuration, since ceramics are chemically impregnated in parallel between the fiber bundles of the fiber body and between the fibers within the fiber bundles, it becomes possible to coat the fiber body with ceramics more quickly. [Examples]

[0135] A SiC film deposition evaluation test was conducted. The SiC film deposition evaluation test assessed the chemical composition of SiC, impregnation properties, film deposition rate, film yield, and reaction by-products. SiC film deposition was performed using the fiber coating apparatus shown in Figure 1. The raw material was MTS. The carrier gas was H2.

[0136] For SiC film deposition, a smooth substrate and a trench substrate were used. Both the smooth substrate and the trench substrate were Si substrates. The smooth substrate is a substrate with a smooth surface on which the SiC film is deposited. The trench substrate is a substrate with multiple grooves formed on its surface on which the SiC film is deposited. The grooves of the trench substrate had a width of approximately 1 μm and a depth of approximately 30 μm. The groove width of the trench substrate was set to simulate the spacing between fibers in a fiber bundle in a fibrous material. The smooth substrate was used to evaluate the chemical composition of the SiC, the film deposition rate, and the film yield. The trench substrate was used to evaluate the impregnation properties.

[0137] Next, we will explain the film formation conditions 1 to 4. Film formation conditions 2 to 4 were set based on the impregnation condition determination step (S10) described above. Specifically, film formation conditions 2 to 4 were set to impregnation conditions that maximize the SiC film formation rate of the entire fiber body when the groove width of the trench substrate is considered to be the spacing between fibers in the fiber bundle. Film formation condition 1 was set to impregnation conditions where the SiC film formation rate of the entire fiber body is not maximized when the groove width of the trench substrate is considered to be the spacing between fibers in the fiber bundle.

[0138] Film formation conditions 1 to 4 differed in their impregnation pressure, while other conditions such as impregnation temperature were kept the same. More specifically, the impregnation pressures for film formation conditions 1 to 4 differed in their total pressure (the sum of the partial pressures of MTS and H2) and their MTS / H2 ratio (the ratio of MTS to H2). The ratio of MTS to H2 is the same as the molar ratio of MTS to H2. The impregnation temperature for film formation conditions 1 to 4 was set to 950°C.

[0139] Under deposition condition 1, the total pressure was 5 Torr, MTS / H2 was 2.5, and the partial pressure of MTS was 3.57 Torr. Under deposition condition 2, the total pressure was 50 Torr, MTS / H2 was 2.5, and the partial pressure of MTS was 35.71 Torr. Under deposition condition 3, the total pressure was 50 Torr, MTS / H2 was 1.0, and the partial pressure of MTS was 25.00 Torr. Under deposition condition 4, the total pressure was 50 Torr, MTS / H2 was 0.3, and the partial pressure of MTS was 11.54 Torr.

[0140] Next, we will explain the evaluation method for the SiC film deposition evaluation test. First, we will explain the method for evaluating the chemical composition of SiC. The chemical composition of SiC was evaluated using X-ray photoelectron spectroscopy (XPS). In the chemical composition evaluation by XPS, Al-Kα (1486.6 eV) was used, and the Si(2P) and C(1s) core-level energy regions were evaluated. Furthermore, the chemical composition of SiC was evaluated separately for the upstream and downstream sides in the longitudinal direction of the reactor.

[0141] The impregnation evaluation method will be described. The impregnation evaluation was performed by step coverage using a trench substrate. FIG. 22 is a diagram for explaining the impregnation evaluation method. The step coverage is the ratio of the SiC film thickness Tt at the groove entrance to the SiC film thickness T b and is obtained by T b / T t . The step coverage indicates that the larger the T b / T t , the better the impregnation, and the smaller the T b / T t , the worse the impregnation.

[0142] The film formation rate evaluation method will be described. In the film formation rate evaluation method, first, SiC was formed on a smooth substrate by changing the film formation time, and the SiC film thickness was measured for each film formation time. The SiC film thickness was measured with a scanning electron microscope. Then, the film formation rate was determined from the relationship between the film formation time and the SiC film thickness. The film formation rate evaluation evaluated the maximum film formation rate in the reactor.

[0143] The film yield evaluation method will be described. The film yield was determined as the ratio of the SiC film formation amount (mol / s) to the MTS supply amount (mol / s). The film yield can be calculated by SiC film formation amount / MTS supply amount.

[0144] The evaluation method of reaction by-products will be described. The evaluation method of reaction by-products evaluated the deposits deposited in the exhaust pipe. Regarding the reaction by-products, mainly, the presence or absence of the generation of harmful chlorosilane polymers was evaluated.

[0145] Table 3 summarizes the SiC film formation conditions from film formation conditions 1 to 4 and the SiC film formation evaluation results. Next, the SiC film formation evaluation results from film formation conditions 1 to 4 will be described in detail.

[0146]

Table 3

[0147] (SiC Chemical Composition Evaluation Results) Figure 23 is a graph showing the results of the chemical composition evaluation of SiC. In the graph of Figure 23, the horizontal axis is the impregnation pressure and the vertical axis is MTS / H2, showing the chemical composition of SiC when film was deposited under film deposition conditions 1 to 4. The chemical composition of SiC is expressed as C / Si, which is the ratio of C to Si. The closer C / Si is to 1, the closer the SiC is to its stoichiometric composition.

[0148] Under film formation condition 1, the C / Si ratio of SiC was 1±0.5 throughout the entire reactor. Under film formation condition 2, the C / Si ratio of SiC was 1±0.2 upstream of the reactor, but 20 downstream. Under film formation condition 3, the C / Si ratio of SiC was 1±0.1 throughout the entire reactor. Under film formation condition 4, the C / Si ratio of SiC was 1±0.2 throughout the entire reactor.

[0149] The variation in the chemical composition of SiC was smaller upstream of film formation condition 2 and throughout the entire reactor under film formation conditions 3 and 4. Under film formation conditions 3 and 4, the variation in the chemical composition of SiC within the reactor was smaller than under film formation condition 2. On the other hand, under film formation condition 1, the variation in the chemical composition of SiC was larger.

[0150] (Impregnation evaluation results) Figure 24 is a graph showing the results of the SiC impregnation evaluation. In the graph of Figure 24, the horizontal axis is the partial pressure of MTS and the vertical axis is the step coverage, showing the step coverage when films were made under film formation conditions 1 to 4.

[0151] Under deposition condition 1, the step coverage was 0.60. Under deposition condition 2, the step coverage was 0.75. Under deposition condition 3, the step coverage was 0.80. Under deposition condition 4, the step coverage was 0.60. Thus, under deposition conditions 2 to 4, the SiC impregnation was equivalent to or better than under deposition condition 1. Under deposition conditions 2 and 3, the SiC impregnation was improved compared to deposition conditions 1 and 4. Under deposition condition 3, the SiC impregnation was further improved compared to deposition condition 2. Thus, films deposited at a total impregnation pressure of 50 Torr showed improved impregnation compared to films deposited at a total impregnation pressure of 5 Torr.

[0152] (Film deposition rate evaluation results) Figure 25 is a graph showing the evaluation results of the SiC film deposition rate. In the graph of Figure 25, the horizontal axis is the partial pressure of MTS and the vertical axis is the maximum film deposition rate, showing the maximum film deposition rate of SiC when film was deposited under deposition conditions 1 to 4.

[0153] Under deposition condition 1, the maximum deposition rate was 0.77 μm / h. Under deposition condition 2, the maximum deposition rate was 15.9 μm / h. Under deposition condition 3, the maximum deposition rate was 16.4 μm / h. Under deposition condition 4, the maximum deposition rate was 15.8 μm / h. Thus, the deposition rate of SiC was higher when the film was deposited at a total impregnation pressure of 50 Torr than when it was deposited at a total pressure of 5 Torr.

[0154] (Membrane yield evaluation results) Figure 26 is a graph showing the evaluation results of SiC film yield. In the graph in Figure 26, the horizontal axis is the partial pressure of MTS and the vertical axis is the film yield, showing the SiC film yield when film was deposited under deposition conditions 1 to 4.

[0155] Under film formation condition 1, the film yield was 8.4%. Under film formation condition 2, the film yield was 11.9%. Under film formation condition 3, the film yield was 19.8%. Under film formation condition 4, the film yield was 19.0%. Thus, films formed at a total impregnation pressure of 50 Torr showed a higher film yield than films formed at a total impregnation pressure of 5 Torr.

[0156] (Evaluation results of reaction by-products) Figure 27 is a graph showing the results of the evaluation of reaction by-products. In the graph of Figure 27, the horizontal axis is the impregnation pressure and the vertical axis is MTS / H2, showing the generation of reaction by-products when films were formed under film formation conditions 1 to 4.

[0157] Under film formation condition 1, a large amount of reaction byproducts precipitated on the exhaust piping at room temperature. Under film formation condition 2, the reaction byproducts disappeared, and soot precipitated. Under film formation condition 3, the reaction byproducts disappeared, and soot precipitated. Under film formation condition 4, a small amount of byproducts precipitated on the exhaust piping at room temperature. Thus, it was found that films formed at a total impregnation pressure of 50 Torr produced less reaction byproducts than films formed at a total pressure of 5 Torr.

[0158] Although several embodiments have been described, it is possible to modify or alter these embodiments based on the above disclosure. [Industrial applicability]

[0159] A method is provided for rapidly coating a fibrous material with ceramics.

Claims

1. A method for coating a fibrous body made of carbon or SiC fibers, When coating the fibrous material with ceramics by chemical vapor impregnation, the impregnation conditions determination step involves determining the impregnation temperature and the impregnation pressure at which the film formation rate of the ceramics on the entire fibrous material is maximized relative to the impregnation temperature. An impregnation step in which a film-forming gas containing the raw materials for the ceramics is supplied to the fiber body, and chemical vapor phase impregnation is performed between the fibers in the fiber body at the impregnation temperature and impregnation pressure determined in the impregnation condition determination step, A method for coating a fibrous material, comprising: The aforementioned ceramic is SiC, The raw material for the aforementioned ceramics is methyltrichlorosilane. The impregnation step is characterized in that the impregnation temperature is 800°C to 1000°C and the impregnation pressure is a total pressure of 50 Torr or more. The aforementioned impregnation condition determination step is: A fiber model setting step for setting the fiber model, A raw material model setting step for setting the model of the raw material, A raw material diffusion model setting step, which sets a raw material diffusion model for when the raw material is supplied to the fiber and diffused, A reaction model setting step for setting a reaction model for forming the ceramic film from the raw material diffused within the fiber body, A raw material concentration distribution calculation step for calculating the raw material concentration distribution of the raw material diffused within the fiber body, A film formation rate calculation step for calculating the film formation rate of the ceramics for the entire fiber body, An impregnation condition determination step that determines the impregnation temperature and the impregnation pressure at which the film formation rate of the ceramics in the entire fiber body is maximized relative to the impregnation temperature, A method for coating a fibrous material, comprising the following features.

2. A method for coating a fiber body according to claim 1, The impregnation condition determination step is a method for coating a fiber body, which determines the impregnation temperature and impregnation pressure that maximize the film formation rate of the ceramics over the entire fiber body.

3. A method for coating a fiber body according to claim 1 or 2, The impregnation step is a method for coating a fiber body, wherein the ceramics are chemically vapor-impregnated in parallel between the fiber bundles of the fiber body and between the fibers within the fiber bundles.

4. A method for coating a fiber body according to claim 1, The impregnation step is a method for coating a fiber, wherein the impregnation temperature is from 800°C to 1000°C and the impregnation pressure is from a total pressure of 50 Torr to 80 Torr.

5. A method for coating a fiber body according to claim 1, The impregnation step is a method for coating a fiber, wherein the impregnation temperature is from 800°C to 950°C and the impregnation pressure is from a total pressure of 50 Torr to 80 Torr.

6. A method for coating a fiber body according to claim 1, The impregnation step is a method for coating a fiber, wherein the impregnation temperature is 800°C to 900°C and the impregnation pressure is a total pressure of 50 Torr to 80 Torr.

7. A method for coating a fiber body according to claim 1, The impregnation step is a method for coating a fiber, wherein the impregnation temperature is from 850°C to 1000°C and the impregnation pressure is a total pressure of 50 Torr.

8. A method for coating a fiber body according to claim 1, The impregnation step is a method for coating a fiber body, wherein the impregnation temperature is 800°C and the impregnation pressure is a total pressure of 80 Torr.

9. A method for coating a fiber body according to claim 1, The impregnation step is a method for coating a fiber, wherein the impregnation temperature is 850°C to 900°C and the impregnation pressure is a total pressure of 50 Torr.

10. A method for coating a fiber according to any one of claims 1 to 9, The aforementioned film-forming gas comprises methyltrichlorosilane and hydrogen. The impregnation pressure is the partial pressure ratio of methyltrichlorosilane to hydrogen, MTS / H ２ A method for coating a fibrous material, wherein the coefficient is between 0.3 and 2.

5.

11. A method for coating a fiber body according to claim 10, The impregnation pressure is the partial pressure ratio of methyltrichlorosilane to hydrogen, MTS / H ２ A method for coating a fibrous material, wherein the coefficient is between 1.0 and 2.

5.

12. A method for coating a fiber body according to claim 10, The impregnation pressure is the partial pressure ratio of methyltrichlorosilane to hydrogen, MTS / H ２ However, the method for coating a fiber is 1.0.

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