Patent Description:
Ceramic matrix composites (CMCs) are known as high-strength and high-temperature materials and lightweight materials and are expected as alternatives to nickel-based alloys. For example, by applying the CMC to high-temperature portions of aircraft jet engines, weight reduction and low-fuel consumption of the engine can be expected. When the CMC is applied to the high-temperature portions of the aircraft jet engines, it is effective to use silicon carbide having excellent heat resistance as a matrix.

As a production method for a composite material such as CMC, a method is known of forming a silicon carbide film by depositing silicon carbide on a surface of each fiber of a fiber substrate using a chemical vapor deposition (CVD) method or a chemical vapor infiltration (CVI) method. Patent Document <NUM> proposes a method of allowing a raw material gas such as CH<NUM>SiCl<NUM> (MTS) or SiCl<NUM>, a carrier gas such as H<NUM> or He, and an additive gas such as C<NUM>H<NUM> or C<NUM>H<NUM> to flow into a reaction furnace and forming the silicon carbide film on the surface of the fiber using the CVD method or the CVI method.

<CIT>, <CIT>, <CIT> and <NPL> disclose all features in the preamble of claim <NUM>.

In the related art disclosed in Patent Document <NUM>, since the infiltratability of silicon carbide into the fiber substrate is low, in order to ensure the uniformity of the silicon carbide film formed on the surface of each fiber, it is required to reduce the growth rate of the silicon carbide film. Therefore, it is necessary to take about <NUM> to <NUM> hours to produce the composite material, and the productivity thereof is low.

An object of the present disclosure is to provide a production method for a composite material capable of producing a composite material with high productivity while ensuring uniformity of a silicon carbide film formed on a surface of a material forming a porous fiber substrate.

The problem is solved by the combination of features of claim <NUM>. Preferred embodiments are claimed in the dependent claims.

According to the production method for a composite material of the present disclosure, the uniformity of the silicon carbide film formed on the surface of the material forming the porous substrate such as a fiber substrate is excellent, and the composite material can be produced with high productivity.

A production method for a composite material of the present disclosure is a method of producing a composite material which includes a porous substrate and a silicon carbide film (SiC film) formed on a surface of a material forming the porous substrate. In the production method for a composite material of the present disclosure, a silicon source gas containing SiCl<NUM> or SiCl and a carbon source gas containing a carbon atom react with each other to form the silicon carbide film on the surface of the material forming the porous substrate.

In the present disclosure, the silicon carbide film may be formed on the surface of the material forming the porous substrate using a chemical vapor deposition (CVD) method or a chemical vapor infiltration (CVI) method.

The silicon source gas containing SiCl<NUM> or SiCl is obtained by, for example, bringing a silicon source containing a silicon atom into contact with a chlorine source containing a chlorine atom.

Hereinafter, an example of an embodiment of the production method for a composite material will be described.

In the production method for a composite material of the present embodiment, a silicon source containing a silicon atom, a chlorine source containing a chlorine atom, and a carbon source containing a carbon atom react with each other to form a silicon carbide film on a surface of a material forming a porous substrate.

The porous substrate includes fibers. As the material forming the porous substrate, only the fiber may be used, or a mixed material of fiber and powder may be used.

When a ceramic matrix composite (CMC) is produced by using the production method of the present disclosure, a fiber substrate including a plurality of fibers is used as the porous substrate. A substrate in which powder is attached to the fibers in the fiber substrate may also be used as the porous substrate.

Examples of the fiber include a silicon carbide fiber, an alumina fiber, a carbon fiber, a glass fiber and the like. The silicon carbide fiber may be used as the fiber from the viewpoint of excellent heat resistance. As the fiber, one type of the fiber may be used alone, or two or more types thereof may be used in combination.

The form of the fiber substrate is not particularly limited, and examples thereof include a textile fabric. A fiber bundle in which a plurality of fibers are bundled may be used in the fiber substrate, or a fiber substrate containing no fiber bundle may be used.

The shape of the fiber substrate is not particularly limited, and can be appropriately selected depending on applications.

In the present disclosure, from the viewpoint of both ensuring uniformity and achieving productivity of the silicon carbide film formed on the surface of the material forming the porous substrate, the silicon source and the chlorine source may be brought into contact with each other, and then the resultant product may react with the gas of the carbon source. The silicon source that is brought into contact with the chlorine source does not contain the chlorine atom.

The Cl<NUM> gas is used as the chlorine source from the viewpoint that the Cl<NUM> gas does not contain a carbon atom (in this case, the carbon source can be separately supplied in a free amount ratio). As the chlorine source, one type of the chlorine source may be used alone, or two or more types thereof may be used in combination.

A product generated by bringing the silicon source and the chlorine source into contact with each other may be a gas containing SiCl<NUM> or SiCl. This gas is used as the silicon source gas for forming the silicon carbide film on the porous substrate.

As a method for generating the gas containing SiCl<NUM> or SiCl, a method in which the chlorine source gas is brought into contact with the solid silicon may be used. By etching the solid silicon with the chlorine source gas, a gas containing SiCl<NUM> or SiCl is generated. As a method for generating the gas containing SiCl<NUM> or SiCl, a method in which the Cl<NUM> gas is brought into contact with the solid silicon is
used.

The silicon source gas as the product may be a gas containing SiCl<NUM> gas and not containing SiCl gas, or may be a gas containing both SiCl<NUM> gas and SiCl gas. When the gas as the product contains the SiCl gas, the gas also contains the SiCl<NUM> gas in thermodynamic theory. The gas containing SiCl<NUM> or SiCl may contain a silicon source gas other than SiCl<NUM> and SiCl, such as SiCl<NUM> or SiCl<NUM>.

When the product is the gas containing SiCl<NUM>, the partial pressure of the SiCl<NUM> gas when the total pressure of the gas is <NUM> atm (<NUM> MPa) can be appropriately set. For example, the partial pressure of the SiCl<NUM> gas can be set from the viewpoint of ensuring uniformity and achieving productivity of the silicon carbide film formed on the surface of each fiber. The partial pressure of the SiCl<NUM> gas may be an upper limit of a thermodynamic theoretical value thereof.

When the product is the gas containing SiCl, the partial pressure of the SiCl gas when the total pressure of the gas is <NUM> atm (<NUM> MPa) can be appropriately set. For example, the partial pressure of the SiCl gas can be set from the viewpoint of ensuring uniformity and achieving productivity of the silicon carbide film formed on the surface of each fiber. The partial pressure of the SiCl gas may be an upper limit of a thermodynamic theoretical value thereof.

The partial pressure of the SiCl<NUM> gas or the SiCl gas in the gas as the product can be adjusted by a temperature at which the silicon source and the chlorine source are brought into contact with each other.

Examples of the carbon source include hydrocarbons such as CH<NUM>, C<NUM>H<NUM>, C<NUM>H<NUM>, C<NUM>H<NUM>, C<NUM>H<NUM>, C<NUM>H<NUM>, and CCl<NUM>. As the carbon source, one type of the carbon source may be used alone, or two or more types thereof may be used in combination.

The carbon source may be at least one hydrocarbon of CH<NUM>, C<NUM>H<NUM>, C<NUM>H<NUM>, C<NUM>H<NUM>, C<NUM>H<NUM>, C<NUM>H<NUM>, and CCl<NUM>.

A carrier gas may be optionally used for a reaction for forming the silicon carbide film in the present disclosure. Examples of the carrier gas include gases such as H<NUM> gas, N<NUM> gas, He gas, and Ar gas, which are inert to the film forming reaction. H<NUM> gas may be used as the carrier gas from the viewpoint of improving the infiltratability of silicon carbide into the fiber substrate.

As the carrier gas, one type of the carrier gas may be used alone, or two or more types thereof may be used in combination.

The reaction temperature of forming the silicon carbide film can be appropriately set. For example, a lower limit of the reaction temperature may be selected based on the viewpoint of improving the growth rate of the silicon carbide film and improving the productivity of the composite material. An upper limit of the reaction temperature may be selected based on the viewpoint of improving the uniformity of the silicon carbide film formed on the surface of the material forming the porous substrate.

The reaction pressure of forming the silicon carbide film may be <NUM> to <NUM> Torr (<NUM> to <NUM> Pa), may be <NUM> to <NUM> Torr (<NUM> to <NUM> Pa), or may be <NUM> to <NUM> Torr (<NUM> to <NUM> Pa). When the reaction pressure is less than a lower limit of this range, there is a possibility that the infiltration rate is low and the productivity may be decreased. When the reaction pressure is more than an upper limit of this range, there is a possibility that the infiltration into the porous substrate is insufficient and the high-temperature strength may be decreased.

A manufacturing apparatus used in the present disclosure is not particularly limited, and examples thereof include a manufacturing apparatus <NUM> illustrated in <FIG>. The figures illustrated in the following description are examples, and the present disclosure is not limited thereto and can be appropriately modified within a range where the scope of the present disclosure is not changed.

The manufacturing apparatus <NUM> includes a tubular reaction furnace <NUM>, a chlorine source supply unit <NUM>, a carbon source supply unit <NUM>, and an exhaust unit <NUM>. The reaction furnace <NUM> is provided with a first reaction section <NUM> and a second reaction section <NUM> in this order from the upstream side of the reaction furnace <NUM>.

The first reaction section <NUM> is a section in which the silicon source is brought into contact with the chlorine source to react with each other.

The first reaction section <NUM> of this example is formed by partitioning the inside of the reaction furnace <NUM> by two partition members <NUM> and <NUM> which have gas permeability and are spaced apart from each other in a gas flow direction. A gap between the partition members <NUM> is filled with a solid silicon source <NUM> (Si powder). As the partition member <NUM>, a member which does not allow the Si powder to pass through and allows the chlorine source gas and the silicon source gas as a product to pass through may be used, and examples thereof include carbon felt.

The first reaction section <NUM> of the reaction furnace <NUM> is provided with a first heater <NUM> for adjusting a temperature at which the silicon source and the chlorine source are brought into contact with each other.

The second reaction section <NUM> is a section where the silicon source gas and the carbon source gas react to each other to form a silicon carbide film on a surface of each fiber of a fiber substrate <NUM>. The form of the second reaction section <NUM> is not particularly limited as long as the fiber substrate <NUM> can be installed at a position where the silicon carbide film is formed on the surface of each fiber by the reaction between the silicon source gas and the carbon source gas.

The second reaction section <NUM> of the reaction furnace <NUM> is provided with a second heater <NUM> for adjusting the reaction temperature of the film formation.

The chlorine source supply unit <NUM> supplies the chlorine source gas. The chlorine source supply unit <NUM> supplies the chlorine source gas to a portion on the upstream side of the first reaction section <NUM> of the reaction furnace <NUM>.

The carbon source supply unit <NUM> supplies the carbon source gas. The carbon source supply unit <NUM> supplies the carbon source gas to a portion between the first reaction section <NUM> and the second reaction section <NUM> of the reaction furnace <NUM>. The carrier gas may be supplied together with the carbon source gas from the carbon source supply unit <NUM>.

The exhaust unit <NUM> is provided on the downstream side of the reaction furnace <NUM> and includes a pressure regulating valve <NUM> and a vacuum pump <NUM>. The exhaust unit <NUM> depressurizes the inside of the reaction furnace <NUM> by using the pressure regulating valve <NUM> and the vacuum pump <NUM> to adjust the pressure inside the reaction furnace <NUM> to a predetermined level.

In the production method for a composite material using the manufacturing apparatus <NUM>, the chlorine source gas which is Cl<NUM> gas is supplied from the chlorine source supply unit <NUM> to the reaction furnace <NUM>, and the chlorine source gas and the solid silicon are brought into contact with each other in the first reaction section <NUM>. In the first reaction section <NUM>, the silicon source gas containing SiCl<NUM> or SiCl is generated as a product by bringing the chlorine source gas and the solid silicon into contact with each other, and is sent to the second reaction section <NUM>. In the second reaction section <NUM>, the silicon source gas that is the product in the first reaction section <NUM> reacts with the carbon source gas that is supplied from the carbon source supply unit <NUM>, and the silicon carbide is deposited on the surface of each fiber of the fiber substrate <NUM> to form the silicon carbide film. When the fiber substrate <NUM> contains powder, the silicon carbide film is formed on the surface of each fiber and a surface of each powder.

The manufacturing apparatus <NUM> may be used for forming a silicon carbide film on a surface of each powder of a porous substrate formed of powder to obtain a composite material.

When H<NUM> gas is used as the carrier gas, the flow rate of the H<NUM> gas supplied to the reaction furnace can be appropriately set. For example, a lower limit of the flow rate of the H<NUM> gas can be selected based on the viewpoint of improving the uniformity of the silicon carbide film formed on the surface of the material forming the porous substrate.

In the production method for a composite material of the present disclosure, after the silicon carbide film is formed by the CVD method or the CVI method, the matrix of silicon carbide may be formed by a polymer impregnation and pyrolysis (SPI) method or a melt infiltration (PIP) method.

According to the above described production method for a composite material of the present disclosure, a composite material in which the infiltratability of silicon carbide into the porous substrate is excellent and the uniformity of the silicon carbide film formed on the surface of the material forming the porous substrate is ensured can be produced with high productivity. The factors for obtaining such an effect are considered as follows.

In a conventional method of using MTS as a raw material gas to become a silicon source or a carbon source, methyl radicals are generated by thermal decomposition of MTS. In this case, since the methyl radicals are unstable, a film forming reaction on a surface of a porous substrate is likely to occur before the raw material gas is sufficiently infiltrated into the inside of the porous substrate, and the infiltratability of silicon carbide is lowered. On the other hand, in the present disclosure, since the silicon source and the carbon source are separately supplied to form the silicon carbide film, the generation of the methyl radicals can be suppressed. Therefore, even though the reaction temperature is raised to increase a film formation rate, the uniformity of the silicon carbide film can be ensured.

In addition, the SiCl<NUM> gas and the SiCl gas are excellent in the infiltratability into the porous substrate as compared with the SiCl<NUM> gas. Therefore, when the silicon source gas containing SiCl<NUM> or SiCl is used, the infiltratability of silicon carbide into the porous substrate is excellent, and the silicon carbide film can be uniformly formed in a short time.

In addition, in the conventional method, when a fiber substrate containing a fiber bundle is used, the infiltratability of silicon carbide into the inside of the fiber bundle tends to be low. However, according to the production method of the present disclosure, since the infiltratability of silicon carbide into the inside of the fiber bundle is excellent, it is possible to ensure the uniformity and achieve the productivity of the silicon carbide film even though the fiber bundle is used.

The production method for a composite material of the present disclosure is not limited to a method using the manufacturing apparatus <NUM>. For example, instead of the first heater <NUM> and the second heater <NUM> in the manufacturing apparatus <NUM>, a manufacturing apparatus provided with a heater that serves as both the first heater <NUM> and the second heater <NUM> may be used. In addition, a manufacturing apparatus in which the first reaction section and the second reaction section are separately provided as reaction furnaces may be used.

Hereinafter, the present disclosure will be specifically described with reference to Examples, but the present disclosure is not limited to the following descriptions.

A cross-section of a composite material obtained in each Example was observed with an optical microscope, the film thickness of the silicon carbide film was measured at any <NUM> points selected, and an average thereof was calculated. The infiltration rate of the silicon carbide was obtained by dividing the film thickness of the silicon carbide film by the reaction time.

By using the manufacturing apparatus <NUM> illustrated in <FIG>, a silicon carbide film was formed on the surface of each fiber of the fiber substrate <NUM> to obtain a composite material.

As the fiber substrate <NUM>, a fiber body formed by laminating <NUM> plain weave fabrics of silicon carbide fibers was used.

Si fine powder (trade name "SIE23PB", manufactured by Kojundo Chemical Laboratory Co. , the maximum particle diameter thereof is <NUM>) was used as the silicon source, Cl<NUM> gas was used as the chlorine source, CH<NUM> gas was used as the carbon source, and H<NUM> gas was used as the carrier gas. The CH<NUM> gas was supplied to the reaction furnace <NUM> together with the H<NUM> gas from the carbon source supply unit <NUM>. The flow rate of the Cl<NUM> gas was <NUM> SCCM, the flow rate of the CH<NUM> gas was <NUM> SCCM, and the flow rate of the H<NUM> gas was <NUM> SCCM. The temperature at which the Si powder and the Cl<NUM> gas were brought into contact with each other in the first reaction section <NUM> was <NUM>, and the reaction temperature of the film formation in the second reaction section <NUM> was <NUM>. The pressure in the reaction furnace <NUM> was <NUM> Torr (<NUM> Pa), and the reaction time for the film formation was two hours.

A cross-sectional photograph of the obtained composite material is shown in <FIG>. The average film thickness of the silicon carbide film formed on the surface of each fiber was <NUM>, and the infiltration rate of the silicon carbide was <NUM>/hr.

By the method described below, a silicon carbide film was formed on the surface of each fiber of the fiber substrate to obtain a composite material.

A mixed gas of MTS and H<NUM> was brought into contact with the fiber substrate, which is the same as used in Example <NUM>, at a temperature of <NUM> and a pressure of <NUM> Torr (<NUM> Pa). A ratio of MTS to H<NUM> was <NUM>:<NUM>. The reaction time was <NUM> hours.

The results of Example <NUM> and Comparative Example <NUM> are shown in Table <NUM>.

As illustrated in <FIG>, and Table <NUM>, in Example <NUM> using the production method of the present disclosure, the silicon carbide film was uniformly formed on the surface of each fiber. In addition, in Example <NUM>, a thicker silicon carbide film was formed in a shorter time than that of Comparative Example <NUM> using the conventional method, and the infiltratability of silicon carbide was excellent.

A composite material was produced in the same manner as in Example <NUM>, except that a fiber substrate including only one plain weave fabric of the silicon carbide fibers, or a fiber substrate formed by laminating <NUM> plain weave fabrics of silicon carbide fibers was used, and the flow rate of the H<NUM> gas was changed to <NUM> SCCM, <NUM> SCCM, or <NUM> SCCM.

<FIG> illustrates a graph plotting the infiltration rate of the silicon carbide with respect to the flow rate of the H<NUM> gas for each of the fiber substrates.

As illustrated in <FIG>, the higher the flow rate of the H<NUM> gas, the higher the infiltration rate of the silicon carbide.

Si powder (trade name "SIE23PB", Kojundo Chemical Laboratory Co. , the maximum particle diameter thereof is <NUM>) was filled in the reaction furnace, the Cl<NUM> gas was supplied to the reaction furnace to etch the Si powder, a gas obtained by this reaction was collected from an exhaust pipe and was analyzed by a mass spectrometer to obtain the partial pressure of each constituent gas. The partial pressure of each constituent gas was measured by changing the temperature in the reaction furnace from <NUM> to <NUM>. <FIG> illustrates a graph plotting the partial pressure of each constituent gas with respect to the temperature in the reaction furnace.

As illustrated in <FIG>, the partial pressure of the Cl<NUM> gas was decreased by two orders of magnitude in a case where the temperature of the reaction furnace was in the range of <NUM> to <NUM>. From this result, it is considered that the Cl<NUM> gas has a thermal decomposition temperature in a range of <NUM> to <NUM>, and Cl- exists in a gas generation field of <NUM> or higher.

Under the condition that the filling amount of the Si powder in the reaction furnace and the contact time between the Si powder and the Cl<NUM> gas were constant and the temperature in the reaction furnace was changed to <NUM>, <NUM>, <NUM>, or <NUM>, the Si powder was etched in the same manner as in Experimental Example <NUM>.

The mass of the Si powder before and after the reaction was measured at each temperature, and the temperature dependence of the mass reduction amount of the Si powder was determined. <FIG> illustrates an Arrhenius plot of the mass reduction amount of the Si powder. <FIG> illustrates a correlation between the temperature in the reaction furnace and the ratio of the mass reduction amount of the Si powder to the input amount of Cl. When the ratio of the mass reduction amount of the Si powder to the input amount of Cl is <NUM>%, all of the input Cl becomes SiCl.

As illustrated in <FIG>, the inclination in the plot of the mass reduction of the Si powder was changed at about <NUM>. It is considered that this result indicates that, in the generation of SiCl<NUM> and SiCl by bringing the Si powder into contact with the Cl<NUM> gas, SiCl<NUM> is dominantly generated at a temperature below the boundary of about <NUM>, and SiCl is dominantly generated at a temperature above the boundary of about <NUM>.

In addition, as illustrated in <FIG>, the ratio of the mass reduction amount of the Si powder to the input amount of Cl was more than <NUM>% at a temperature of about <NUM> or higher. This result indicates that a main product gas generated in this temperature range is SiCl.

Claim 1:
A production method for a composite material including a porous substrate and a silicon carbide film formed on a surface of a material forming the porous substrate, the porous substrate being a fiber substrate (<NUM>) including a plurality of fibers, the method comprising:
causing a silicon source (<NUM>) containing a silicon atom, a chlorine source containing a chlorine atom, and a carbon source containing a carbon atom to react with each other to form the silicon carbide film on the surface of the material,
characterized in that
the silicon source (<NUM>) is a solid silicon and the chlorine source is a Cl<NUM> gas.