JP2023064741A - Method for producing carbon fiber-reinforced silicon carbide composite material, and carbon fiber reinforced silicon carbide composite material - Google Patents

Abstract

To provide a method for producing a carbon fiber-reinforced silicon carbide composite material, the method exhibiting excellent productivity, reducing a processing cost, and capable of producing the carbon fiber-reinforced silicon carbide composite material that has high impact strength, and to provide the carbon fiber-reinforced silicon carbide composite material.SOLUTION: A carbon fiber-reinforced silicon carbide composite material is produced by conducting the steps of: impregnating carbon fibers with a thermosetting resin to obtain a sheet-molding compound; aging the sheet-molding compound by exposing it to an atmosphere of at least 130°C or less and higher than the boiling point of a solvent component under atmospheric pressure if the thermosetting resin contains a solvent component, or to an atmosphere of 75°C or more to 130°C or less if the thermosetting resin does not contain a solvent component; forming the sheet-molding compound obtained after aging to obtain a carbon fiber-reinforced plastic; sintering the carbon fiber-reinforced plastic to obtain a carbon fiber-reinforced carbon composite material; and melt-impregnating the carbon fiber-reinforced carbon composite material with a metallic Si.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a method for producing a carbon fiber reinforced silicon carbide based composite material and a carbon fiber reinforced silicon carbide based composite material.

Carbon fiber reinforced carbon composite materials (hereinafter also referred to as “C/C composite materials”) are excellent in heat resistance and thermal shock resistance, high strength and light weight, so they are used in aircraft and automobile brake discs, brake pads, etc. (for example, Patent Document 1). However, since the carbon material is generally oxidized at about 500° C., it cannot be used in the high-temperature atmosphere except for a very short period of time.

As a method of preventing deterioration of physical and chemical properties due to oxidation of the C / C composite material, the C / C composite material is melted and impregnated with metal Si, and the carbon in the composite material is reacted with the metal Si to form silicon carbide. It is made into a carbon fiber reinforced silicon carbide composite material (hereinafter also referred to as “SiC-C/C composite material”).

As a method for producing a SiC--C/C composite material, there is known a method of forming a laminate of sheets in which a non-woven fabric is impregnated with a matrix resin, and melting and impregnating the sheet with metallic Si after firing. For example, there is a method in which sheets obtained by entangling disentangled short carbon fibers are laminated, impregnated with resin or pitch, molded and then baked to melt and impregnate with metallic Si (Patent Document 2).

A method is also known in which a thermoplastic resin insert is sandwiched between sheet molding compounds from above and below and filled in a mold, and the resulting molded body is fired to remove the insert and melt and impregnate with metallic Si. there is (Patent document 3).

JP-A-7-33543 JP 2007-39319 A U.S. Pat. No. 7,163,653

In the manufacturing technology of SiC--C/C composite materials, it would be very useful if impact strength could be increased while increasing productivity and reducing processing costs.
The present invention provides a method for producing a SiC-C/C composite material that is excellent in productivity, can reduce processing costs, and can produce a SiC-C/C composite material with high impact strength, and a SiC-C/C composite material. intended to

The present invention has the following aspects.
[1] A step of impregnating carbon fibers with a thermosetting resin to obtain a sheet molding compound;
When the thermosetting resin contains a solvent component, the sheet molding compound is heated to a boiling point of the solvent component under atmospheric pressure of 130°C or higher, and when the thermosetting resin does not contain a solvent component, the boiling point of the sheet molding compound is 75°C or higher and 130°C. A step of aging by exposure to an atmosphere of ℃ or less;
a step of molding the aged sheet molding compound to obtain a carbon fiber reinforced plastic;
a step of baking the carbon fiber reinforced plastic to obtain a carbon fiber reinforced carbon composite;
and a step of melt-impregnating the carbon fiber-reinforced carbon composite material with metal Si.
[2] The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to [1], wherein the carbon fibers are pitch-based carbon fibers.
[3] The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to [1] or [2], wherein the carbon fibers have a fiber length of 10 mm or more and 60 mm or less.
[4] The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to any one of [1] to [3], wherein the FAW of the sheet molding compound is 200 g/m ² or more and 2000 g/m ² or less.
[5] The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to any one of [1] to [4], wherein the thermosetting resin is a phenol resin.
[6] The carbon fiber-reinforced silicon carbide-based composite material according to any one of [1] to [5], wherein the carbon fiber content per volume of the carbon fiber-reinforced plastic is 30% by volume or more and 60% by volume or less. Production method.
[7] The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to any one of [1] to [6], wherein the molding using the sheet molding compound is performed by a hot press method.
[8] The carbon according to [7], wherein at a temperature of 140° C. or less of the sheet molding compound molded by the hot press method, a pressure operation of releasing pressure from a pressurized state and pressurizing again is performed one or more times. A method for producing a fiber-reinforced silicon carbide-based composite.
[9] The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to any one of [1] to [8], wherein the carbon fiber-reinforced plastic is fired in an inert gas atmosphere.
[10] The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to any one of [1] to [9], wherein the impurity content of the metal Si is 1.5% by mass or less.
[11] The carbon fiber-reinforced silicon carbide-based composite material according to any one of [1] to [10], wherein the carbon fiber-reinforced carbon composite material is melt-impregnated with metal Si at 1400° C. or higher and 2000° C. or lower under vacuum conditions. manufacturing method.
[12] A carbon fiber reinforced silicon carbide composite material having streaks in a cross section cut in the direction of pressure during molding. A binarized image in which the streak region is white is obtained by binarizing the cross-sectional image using Otsu's method for a cross-sectional image in which the visual field range is 4 mm and the pressing direction during molding is the vertical direction. is obtained, and in a power spectrum image with a resolution of 1024 pixels × 1024 pixels obtained by fast Fourier transform processing the binarized image, the right from the center point of the power spectrum image is 0 °, and the counterclockwise direction is the positive direction 0 ° to 180 °, using an isosceles triangle with an apex angle of 10 ° and equilateral sides of 100 pixels, the average brightness of each of the 18 divided areas is the maximum value in the range of 70 ° to 110 °, The average of the directionality parameter δ defined by the following formula (1), where b is the maximum value in the range from 0° to 20° and 160° to 180°, and m is the minimum value in the range from 0° to 180°. A carbon fiber-reinforced silicon carbide-based composite material having a value of 14.0 or less.

[13] The carbon fiber-reinforced silicon carbide-based composite material according to [12], wherein the probability ε of the presence of the streak having a width of 0.50 mm or more in the binarized image is 20% or less.
[14] The carbon fiber-reinforced silicon carbide-based composite according to [12] or [13], which has the streaks with a longitudinal length of 0.3 mm or more and a transverse length of 0.2 mm or less. material.
[15] The carbon fiber-reinforced silicon carbide-based composite material according to any one of [12] to [14], wherein the average value of the white area ratio ζ in the binarized image is 55% or less.
[16] The carbon fiber-reinforced silicon carbide-based composite material according to any one of [12] to [15], which contains pitch-based carbon fibers.
[17] The carbon fiber-reinforced silicon carbide-based composite material according to any one of [12] to [16], wherein the streaks contain Si element.
[18] According to any one of [12] to [17], the ratio of short carbon fibers having a fiber length of 10 mm or more and 60 mm or less is 50% by mass or more with respect to the total 100% by mass of the carbon fibers contained. Carbon fiber reinforced silicon carbide composite.
[19] The carbon fiber-reinforced silicon carbide according to any one of [12] to [18], wherein the carbon fiber-reinforced carbon composite material has a porosity of 15% by volume or more and 40% by volume or less before being melt-impregnated with metal Si. system composites.

According to the present invention, a method for producing a SiC-C/C composite material, which is excellent in productivity, can reduce processing costs, and can produce a SiC-C/C composite material with high impact strength, and a SiC-C/C composite material can provide

FIG. 4 is a schematic diagram showing an example of a cross section of a carbon fiber bundle in which microcracks are generated in the firing process of the present invention. FIG. 4 is a schematic diagram showing an example of a cross section of a carbon fiber bundle in which microcracks are generated in a firing process when the carbon fiber bundle is flattened by pressure during molding. FIG. 4 is an explanatory diagram illustrating lengths in the longitudinal direction and the length in the lateral direction of the streaks in a cross section cut in the pressure direction during molding of the SiC—C/C composite material; FIG. 4 is a schematic diagram showing 18 regions divided by an isosceles triangle having an apex angle of 10° and an equilateral side of 100 pixels in a power spectrum image. Fig. 5(a) is a schematic diagram showing the dimensions of an impact test piece used for measuring impact strength, Fig. 5(a) is a diagram viewed from the side, Fig. 5(b) is a diagram viewed from the side opposite to the notched surface It is a view. 1 is a backscattered electron image of a cross section of the SiC--C/C composite material obtained in Example 1, taken with a scanning electron microscope (SEM), and binarized. 7(a) is a cross-sectional appearance of the SiC--C/C composite material obtained in Example 1, and FIG. 7(b) is a cross-sectional appearance of the SiC--C/C composite material obtained in Comparative Example 3. .

[Manufacturing method of carbon fiber reinforced silicon carbide-based composite material]
A method for producing a carbon fiber reinforced silicon carbide composite (SiC--C/C composite) of the present invention will be described below. However, what will be described below is an example of embodiments of the present invention, and the present invention is not limited to the following description at all as long as it does not exceed the gist of the present invention.

The method for producing the SiC-C/C composite material of the present invention is a method including the following sheet molding compound (hereinafter also referred to as "SMC") preparation step, aging step, molding step, firing step, and melt impregnation step. be.
SMC production step: SMC is produced by impregnating carbon fibers with a matrix resin and forming a sheet.
Aging step: The SMC is aged in a heated atmosphere.
Molding step: The SMC is molded to obtain a carbon fiber reinforced plastic (hereinafter also referred to as "CFRP").
Firing step: The CFRP is fired to form a carbon fiber reinforced carbon composite (C/C composite).
Melt-impregnation step: Melt-impregnate the C/C composite material with metal Si to obtain a SiC--C/C composite material.

(SMC manufacturing process)
Carbon fibers are impregnated with a thermosetting resin as a matrix resin to obtain a sheet-like SMC.

The carbon fiber is not particularly limited, and examples thereof include pitch-based carbon fiber and polyacrylonitrile (PAN)-based carbon fiber. Of these, pitch-based carbon fibers are preferred because of their excellent thermal conductivity and low reactivity with metal Si.

Pitch-based carbon fibers are obtained by melt-spinning raw material pitch to obtain pitch fibers, followed by infusibilization, carbonization, or further graphitization. Examples of the form of pitch-based carbon fibers include tows, strands, rovings, yarns, etc. composed of a plurality of single fibers, and short carbon fibers obtained by cutting these are preferred.
The number of filaments of the carbon fiber is preferably 1000 or more and 50000 or less, more preferably 6000 or more and 24000 or less.

The average fiber length of the carbon fibers is preferably 10 mm or longer, more preferably 12 mm or longer. If the average fiber length of the carbon fibers is equal to or greater than the lower limit, excellent rigidity is likely to be obtained. The average fiber length of carbon fibers is preferably 60 mm or less, more preferably 40 mm or less. If the average fiber length of the carbon fibers is equal to or less than the upper limit, excellent fluidity can be easily obtained during molding. The lower limit and upper limit of the average fiber length of the carbon fibers can be arbitrarily combined, for example, 10 mm or more and 60 mm or less are preferable, and 12 mm or more and 40 mm or less are more preferable.
The average fiber length of carbon fibers is a value obtained by the following measuring method. The resin in the composite material is burned off and only the carbon fibers are taken out, and the fiber length of the carbon fibers is measured with a vernier caliper or the like. The measurement is performed on 100 randomly selected carbon fibers, and the fiber length is calculated as their mass average.

The FAW (fiber mass per unit area) of SMC during molding is preferably 200 g/m ² or more, more preferably 250 g/m ² or more, and even more preferably 500 g/m ² or more. If FAW of SMC is more than the said lower limit, productivity will improve. The FAW of SMC during molding is preferably 2000 g/m ² or less, more preferably 1500 g/m ² or less, and even more preferably 1000 g/m ² or less. If the FAW of the SMC is equal to or less than the upper limit, the impregnating property of the resin is excellent. The lower and upper limits of FAW of SMC during molding can be arbitrarily combined, for example, 200 g/m ² or more and 2000 g/m ² or less are preferable, 250 g/m ² or more and 1500 g/m ² or less are more preferable, and 500 g/m ² It is more preferable that it is more than or equal to 1000 g/m ² or less.

The thermosetting resin is not particularly limited, and examples thereof include epoxy resins, phenol resins, unsaturated polyester resins, urethane resins, urea resins, melamine resins, and imide resins. Among them, epoxy resins, phenolic resins, unsaturated polyester resins, and imide-based resins are preferable as thermosetting resins, since SiC--C/C composite materials having excellent mechanical strength can be easily obtained. Phenolic resin is more preferable because it has a high ratio of carbonization without being burned off during firing. As the thermosetting resin, one type may be used alone, or two or more types may be used in combination.

Examples of phenolic resins include resol-type phenolic resins and novolac-type phenolic resins. The resol-type phenolic resin is not particularly limited, and known resins obtained by reacting phenols and aldehydes using a basic catalyst can be used. The novolak-type phenolic resin is not particularly limited, and known resins obtained by reacting phenols and aldehydes using an acidic catalyst can be used.
The number average molecular weight of the resol type phenol resin is preferably 300-800. The number average molecular weight of the novolac type phenol resin is preferably 500-1500.

Phenols are not particularly limited, and examples include phenol, cresol (o-cresol, m-cresol, p-cresol, etc.), xylenol (2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, etc.), ethylphenol (o-ethylphenol, m-ethylphenol, p-ethylphenol, etc.), butylphenol (isopropylphenol, butylphenol, p-tert -butylphenol, etc.), alkylphenols (p-tert-amylphenol, p-octylphenol, p-nonylphenol, p-cumylphenol, etc.), halogenated phenols (fluorophenol, chlorophenol, bromophenol, iodophenol, etc.), monovalent Phenol-substituted compounds (p-phenylphenol, aminophenol, nitrophenol, dinitrophenol, trinitrophenol, etc.), monovalent naphthols (1-naphthol, 2-naphthol, etc.), polyhydric phenols (resorcin, alkylresorcin , pyrogallol, catechol, alkylcatechol, hydroquinone, alkylhydroquinone, phloroglucine, bisphenol A, bisphenol F, bisphenol S, dihydroxynaphthalene, etc.).

Aldehydes are not particularly limited, and examples include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, hexamethylenetetramine, furfural, glyoxal, n-butyraldehyde, caproaldehyde, allylaldehyde, benzaldehyde, crotonaldehyde, acrolein, tetraoxymethylene, phenylacetaldehyde, o-tolualdehyde, salicylaldehyde and the like.

The basic catalyst is not particularly limited, and examples thereof include alkali metal hydroxides (sodium hydroxide, lithium hydroxide, potassium hydroxide, etc.), aqueous ammonia, tertiary amines (triethylamine, etc.), tetramethyl hydroxide. Ammonium, oxides and hydroxides of alkaline earth metals (calcium, magnesium, barium, etc.), alkaline substances (sodium carbonate, hexamethylenetetramine, etc.) and the like.

The acidic catalyst is not particularly limited, and examples thereof include organic carboxylic acids (oxalic acid, etc.), organic sulfonic acids (paratoluenesulfonic acid, phenolsulfonic acid, etc.), mineral acids (hydrochloric acid, sulfuric acid, phosphoric acid, etc.), and the like. be done.

Water or alcohols may be added as a solvent component to the thermosetting resin, since the viscosity is lowered and the carbon fibers are easily impregnated with the resin. Alcohols are not particularly limited, and examples thereof include methanol, ethanol, n-propyl alcohol and the like.
The ratio of the alcohol to 100 parts by mass of the matrix resin is preferably 1 to 8 parts by mass.

Additives such as a thickener, a curing agent, a polymerization initiator, a polymerization inhibitor, a pigment, an internal release agent, a flame retardant, a coupling agent, and a filler may be added to the matrix resin. As the additive, one type may be used alone, or two or more types may be used in combination.

Examples of thickeners include calcium hydroxide and magnesium oxide. Examples of curing agents include hexamethylenetetramine and the like. Examples of internal release agents include stearic acid and zinc stearate. Examples of flame retardants include aluminum hydroxide, antimony trioxide, and antimony pentoxide. Examples of coupling agents include silane coupling agents, titanate coupling agents, aluminate coupling agents, zirconate coupling agents, and the like.

The filler may be an inorganic filler or an organic filler. Examples of inorganic fillers include calcium carbonate, aluminum hydroxide, barium sulfate, clay, talc, silica, glass beads, alumina, mica, graphite, and carbon black. Examples of organic fillers include styrene resins and imide resins.

The method for producing SMC is not particularly limited. For example, using a known SMC manufacturing apparatus, the matrix resin paste is applied to each of the carrier films (polyethylene film, polypropylene film, etc.) arranged above and below so that the thickness is about 0.3 to 2.0 mm. do. A predetermined amount of carbon fiber cut to a predetermined length is dispersed on the paste applied on the lower carrier film, and the carbon dispersed in the paste (resin composition) applied on the upper and lower carrier films sandwich the fibers. Then, the whole of them is passed between impregnation rolls to impregnate the carbon fibers with the matrix resin to obtain the SMC.

(Aging process)
In the aging configuration, the SMC is aged in a heated atmosphere under specific conditions. By aging the SMC in a heated atmosphere, the SMC develops appropriate fluidity necessary for shaping the SMC into a desired shape in the subsequent molding process. In addition, "shaping" means imparting a desired shape by deformation without cutting a material such as SMC.

The primary purpose of aging the SMC in the present invention is to volatilize the solvent component contained in the matrix resin by exposing the SMC to a heated atmosphere. By volatilizing the solvent component in the aging process, the amount of volatilization in the subsequent molding process is reduced, and the formation of pores and cracks in the molded body (CFRP) can be suppressed.
A second purpose of aging the SMC in the present invention is to allow the polymerization reaction of the matrix resin to proceed to such an extent that curing is not completed. In general, the viscosity of uncured resin decreases from room temperature to curing temperature. At that time, the resin viscosity becomes lower as the polymerization reaction does not progress, and conversely becomes higher as the polymerization reaction progresses. If the resin viscosity is too low, the matrix resin impregnated in the SMC will be squeezed out during pressurization in the molding process, which may cause pores and cracks in the molded body. Conversely, if the resin viscosity is too high, the SMC will not flow even when pressurized in the molding process, making it impossible to shape it into a desired shape.

When the SMC matrix resin contains a solvent component, the temperature of the heating atmosphere is set so as to simultaneously achieve both the first and second purposes. Specifically, the temperature of the heating atmosphere should be equal to or higher than the boiling point of the solvent component under atmospheric pressure, and preferably equal to or higher than the boiling point +5°C. For example, when the matrix resin contains water as a solvent component, the temperature of the heating atmosphere is 100° C. or higher, preferably 105° C. or higher. When the temperature of the heating atmosphere is equal to or higher than the lower limit, the solvent component is easily volatilized, and the polymerization reaction of the matrix resin is easily allowed to proceed appropriately. Also, the temperature of the heating atmosphere is 130° C. or lower, preferably 120° C. or lower. When the temperature of the heating atmosphere is equal to or lower than the upper limit, excessive progress of the polymerization reaction of the matrix resin can be suppressed. The lower and upper limits of the temperature of the heating atmosphere can be combined arbitrarily. When the matrix resin contains a solvent component, the boiling point of the solvent component under atmospheric pressure is 130°C or higher, and the boiling point is +5°C or higher and 120°C or lower. is preferred.
When the matrix resin does not contain a solvent component, it is not necessary to consider the first purpose of volatilizing the solvent component, so only the second purpose of moderately progressing the polymerization reaction of the matrix resin can be considered. Therefore, the temperature of the heating atmosphere is preferably 75° C. or higher and 130° C. or lower, and preferably 100° C. or higher and 120° C. or lower.

Aging of SMC may be performed under atmospheric pressure, under increased pressure, or under reduced pressure. The gas that constitutes the heating atmosphere is not particularly limited, and examples thereof include air and inert gases such as nitrogen. The aging time is set arbitrarily considering conditions such as the type of matrix resin, the type of solvent component, the ratio of the solvent component contained in the matrix resin, and the RAW (resin mass per unit area) of SMC. do. Although the above conditions cannot be described unconditionally, it is possible to determine whether an appropriate dry state has been achieved by known methods such as measuring the weight of SMC before and after aging and measuring the gel time of SMC after aging.

(Molding process)
CFRP shaped into a desired shape is obtained by molding using SMC. The shape and dimensions of CFRP may be appropriately set according to the application.

Molding using SMC is preferably carried out by a hot press method from the viewpoint of thermally curing the SMC in a state in which the SMC is distributed inside the mold by applying pressure to the SMC. For example, SMC is filled into a mold and pressure-molded to obtain CFRP.
The molding temperature is preferably 130° C. or higher and 300° C. or lower, more preferably 150° C. or higher and 250° C. or lower.

The carbon fiber content Vf per volume of CFRP is preferably 30% by volume or more, more preferably 35% by volume or more. When Vf is equal to or higher than the lower limit, a reinforcing effect is likely to be obtained, and a SiC--C/C composite material having high mechanical strength is likely to be obtained. The Vf of CFRP is preferably 60% by volume or less, more preferably 50% by volume or less. The lower limit and upper limit of Vf of CFRP can be arbitrarily combined, for example, 30% by volume or more and 60% by volume or less, and more preferably 35% by volume or more and 50% by volume or less.
Vf can be adjusted by pressure during molding. For example, molding at high pressure tends to increase Vf. Conversely, molding at a low pressure tends to reduce Vf.

In the molding performed by the hot press method using SMC, when the temperature of the SMC rises, the pressure is released from the pressurized state and pressurized again at a temperature of 140 ° C. or less, and the pressure operation is performed one or more times. may be implemented. In the present invention, the SMC is made to exhibit fluidity suitable for molding by the aging process, but the fluidity of the SMC can also be increased by the pressure operation, and molding defects due to insufficient SMC fluidity can be easily suppressed.
Furthermore, when a phenolic resin is used as the matrix resin, the polymerization reaction is condensation polymerization, and water molecules are generated. Therefore, the pressure operation is also effective for the purpose of discharging the water molecules out of the mold. The pressure operation discharges water molecules out of the mold, thereby suppressing the generation of voids and cracks in the compact.
The effect of increasing the fluidity of SMC and the effect of discharging water molecules out of the mold are likely to be exhibited when the temperature of SMC is 40° C. or higher and 140° C. or lower. If the temperature is 40° C. or higher, the viscosity of the resin does not become too high, and the SMC becomes in a fluid state, so the effect of the pressure operation can be expected. If the temperature is 140° C. or lower, the pressure operation is performed before the polymerization reaction is completed, so the effect of the pressure operation can be expected.

(Baking process)
The CFRP obtained in the molding process is sintered to carbonize the matrix resin and, if necessary, the pitch contained therein to form a C/C composite material.
Firing is preferably performed in an inert gas atmosphere. The inert gas is not particularly limited, and can be exemplified by nitrogen gas, for example.

The firing temperature is preferably 700° C. or higher. If the firing temperature is equal to or higher than the lower limit, carbonization of the matrix resin and pitch can be sufficiently advanced. The firing temperature is preferably 2500° C. or lower, more preferably 1600° C. or lower. When the firing temperature is equal to or lower than the upper limit, the progress of the graphitization reaction of the carbon fibers is small, and it becomes easy to control the physical properties of the obtained composite material. The lower limit and upper limit of the firing temperature can be arbitrarily combined, and for example, 700° C. or higher and 2500° C. or lower are preferable, and 700° C. or higher and 1600° C. or lower are more preferable.

The C/C composite material obtained by firing is preferably densified. This makes it easier to obtain a SiC--C/C composite material with high thermal conductivity.
As a method of densification, for example, the C / C composite material after firing is impregnated with a thermosetting resin such as phenol resin, or a thermoplastic resin such as tar or pitch, and is heated to carbonize. Alternatively, a CVD method in which carbon is obtained by thermally decomposing a hydrocarbon gas such as methane or propane. The C/C composite material after sintering may be impregnated with pitch in a plurality of steps for carbonization.

The softening point of the pitch used for densification of the C/C composite material is preferably 70°C or higher, more preferably 80°C or higher. The softening point of the pitch is preferably 150°C or lower, more preferably 90°C or lower. The lower limit and upper limit of the softening point can be arbitrarily combined, for example, 70° C. or higher and 150° C. or lower are preferable, and 80° C. or higher and 90° C. or lower are more preferable.

The toluene-insoluble content of the pitch used for densifying the C/C composite material is preferably 10% by mass or more, more preferably 13% by mass or more. The toluene-insoluble content of the pitch is preferably 30% by mass or less, more preferably 20% by mass or less. The lower limit and upper limit of the toluene-insoluble content of the pitch can be arbitrarily combined, and for example, 10% by mass or more and 30% by mass or less are preferable, and 13% by mass or more and 20% by mass or less are more preferable.
The pitch used to densify the C/C composites is preferably substantially free of quinoline insolubles.
The pitch used for densifying the C/C composite preferably contains 40% by mass or more, preferably 50% by mass or more of fixed carbon. The pitches used for densifying the C/C composite material are not limited to those mentioned above.

The bulk density of the C/C composite material is preferably 1.2 g/cm ³ or more, more preferably 1.3 g/cm ³ or more. If the bulk density of the C / C composite material is at least the lower limit value, the carbon matrix that reacts with the metal Si is sufficient, and the presence of silicon carbide generated by the reaction is sufficient for the SiC-C / C composite material. A reinforcing effect can be expressed. The bulk density of the C/C composite material is preferably 1.7 g/cm ³ or less, more preferably 1.6 g/cm ³ or less. If the bulk density of the C/C composite material is equal to or less than the upper limit, metal Si is easily impregnated during melt impregnation with metal Si. Therefore, it is easy to suppress the occurrence of voids, cracks, and the like due to regions not impregnated with metal Si. The lower limit and upper limit of the bulk density of the C/C composite material can be combined arbitrarily, for example, preferably 1.2 g/cm ³ or more and 1.7 g/cm ³ or less, 1.3 g/cm ³ or more and 1.6 g/cm ³ or less is more preferable.

The carbon fiber content Vf per volume of the C/C composite material is preferably 20% by volume or more and 50% by volume or less. If the Vf of the C/C composite material is equal to or higher than the lower limit, the strength of the SiC--C/C composite material is improved. If the Vf of the C/C composite material is equal to or less than the upper limit, the carbon matrix easily reacts with metal Si, and silicon carbide is easily generated.

The porosity of the C/C composite material is preferably 15% by volume or more, more preferably 20% by volume or more. If the porosity of the C/C composite material is equal to or higher than the lower limit, the impregnation of metal Si becomes sufficient, and silicon carbide is easily generated sufficiently. The porosity of the C/C composite material is preferably 40% by volume or less, more preferably 35% by volume or less. If the porosity of the C/C composite material is equal to or less than the upper limit, the carbon matrix becomes sufficient, and the carbon matrix easily reacts with metal Si. The lower limit and upper limit of the porosity of the C/C composite material can be arbitrarily combined, for example, 15% by volume or more and 40% by volume or less are preferable, and 20% by volume or more and 35% by volume or less are more preferable.

The porosity of the C/C composite material is determined by Vf, the volume fraction (Vm) of carbon derived from the resin contained in the C/C composite material, and the volume fraction (Vc ) to obtain 100-Vf-Vm-Vc. Regarding Vm (%), since the weight loss when CFRP is sintered to form a C/C composite material is derived from the weight loss due to carbonization of the resin, the residual carbon ratio of the resin (the weight of the resin carbonized resin before carbonization Vm can be calculated by using the value divided by the weight), the amount of weight loss, the volume of the C/C composite material, and the specific gravity of the resin-derived carbon. Vf (%) of the C/C composite material can be calculated using the weight and volume of the C/C composite material obtained in the firing process, the specific gravity of the carbon fiber, the specific gravity of the resin-derived carbon, and Vm. Vc (%) can be calculated using the weight increase and volume of the C/C composite material due to densification, and the specific gravity of the carbide added during densification.

(Melting impregnation step)
The C/C composite material is melt-impregnated with metal Si, and the carbon in the C/C composite material is reacted with the metal Si to form silicon carbide to form a SiC--C/C composite material. The matrix in the resulting SiC--C/C composite consists of unreacted carbon and metallic Si and silicon carbide produced by the reaction.

Melt impregnation of metallic Si into the C/C composite material can be performed by various methods. For example, by holding the C / C composite material and metal Si at a temperature of 1400 ° C. or more and 2000 ° C. or less under vacuum conditions, the metal Si is melted and impregnated into the open pores of the C / C composite material. is reacted with the carbon of the C/C composite material to form a SiC--C/C composite material.

The impurity content of metal Si is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, and even more preferably 0.5% by mass or less. If the content of impurities in metal Si is equal to or less than the above upper limit, it is easy to suppress the impediment of impregnation and the occurrence of cracks in the composite material caused by impurities in melt impregnation of metal Si.

As described above, in the method for producing a SiC--C/C composite material of the present invention, CFRP molded using SMC is employed as an intermediate. SMC has excellent fluidity in the mold and is easy to mold into the desired shape, so there is no need to drill holes in the C/C composite material after firing, and compared to the conventional method using non-woven fabric etc. It excels in productivity and enables significant cost reduction.

The SiC--C/C composite material of the present invention has higher impact strength than other SiC--C/C composite materials for the following two reasons.
First, by adopting the aging conditions of the present invention, pores and cracks in the compact (CFRP) can be suppressed. Pores and cracks in the molded body are present in the SiC-C/C composite material in the state of being impregnated with metal Si or in the state of pores and cracks through the firing process and the melt impregnation process. . Since the mechanical strength including the impact strength is lowered in any state, it is presumed that the aging conditions of the present invention suppress the formation of pores and cracks, thereby increasing the mechanical strength.
Secondly, compared with the case where the aging conditions of the present invention are not adopted, the polymerization reaction of the resin proceeds moderately and the resin viscosity is high. Therefore, during molding, while the carbon fiber bundles contained in the SMC flow, their flattening and dispersion are suppressed compared to other SiC--C/C composite materials. As a result, when the SiC--C/C composite material is produced, it can be assumed that the carbon fiber bundles play a role in preventing the extension of cracks in impact fracture, and the impact strength increases.

[Carbon fiber reinforced silicon carbide composite]
The SiC--C/C composite material of the present invention can be produced by the method for producing the SiC--C/C composite material of the present invention. The SiC--C/C composite material of the present invention has streaks, that is, streak-like impregnated portions (matrix) in a cross section cut in the pressurizing direction during molding. The streak-like impregnated portion contains either one or both of metallic Si and silicon carbide.
The streak preferably contains Si element. The presence of Si element in the muscle can be confirmed by energy dispersive X-ray spectroscopy (EDX) analysis.

In the present invention, since flattening and dispersion of the carbon fiber bundles during molding of the SMC are suppressed by undergoing the aging process, as shown in FIG. Microcracks 3 between fibers 2 are lengthened in the pressurizing direction during molding. When the microcracks 3 are impregnated with metal Si, streaky impregnated portions oriented in the pressurizing direction during molding are generated. At the same time, metallic Si is also impregnated between the fiber bundles, resulting in streaky impregnated portions oriented in a direction perpendicular to the pressurizing direction during molding. Therefore, in the SiC--C/C composite material of the present invention, the streak-like impregnated portions are three-dimensionally randomly oriented in a cross section taken in the pressurizing direction during molding.

On the other hand, when the carbon fiber bundle is flattened by pressure during molding, as shown in FIG. becomes shorter in the pressurizing direction. The streaky impregnated portion in the direction of pressure, which is produced by impregnating the microcracks 6 with metal Si, is shortened. Therefore, streak-like impregnated portions oriented in a direction orthogonal to the direction in which pressure is applied during molding are relatively conspicuous, and the cross-sectional appearance in which these impregnated portions are randomly oriented in three dimensions is not obtained. . In particular, when molding by applying pressure to a molding raw material in which short carbon fibers are impregnated with resin, most of the short carbon fibers are present in the molded body in a direction orthogonal to the direction of pressure application, so the impregnated part is also affected during molding. It becomes easier to orient in a direction perpendicular to the direction in which pressure is applied.

A scanning electron microscope (SEM) is used for a cross section of the SiC-C/C composite material of the present invention cut in the direction of pressure during molding, with a viewing range of 2.4 mm × 2.4 mm. Take a picture with the pressure direction as the vertical direction. The obtained cross-sectional image is binarized using Otsu's method to obtain a binarized image in which the muscle region is white. Further, the binarized image is subjected to fast Fourier transform processing to obtain a power spectrum image with a resolution of 1024 pixels×1024 pixels. From the center point of the power spectrum image, the right side is 0°, and 0° to 180° with the counterclockwise direction as the positive direction is divided into 18 using isosceles triangles with a vertical angle of 10° and equilateral sides of 100 pixels. For the average luminance of each of the 18 divided regions, the maximum value in the range of 70 ° to 110 ° is a, the maximum value in the range of 0 ° to 20 ° and 160 ° to 180 ° is b, 0 ° to 180 ° Let m be the minimum value in the range. At this time, in the SiC-C/C composite material of the present invention, the average value of the directional parameter δ defined by the following formula (1) is 14.0 or less.

The observation method and image processing method using the SEM will be described in more detail.
For observation using the SEM and its image processing, three or more observation samples having an observable area of 50 mm ² or more were prepared at random from the SiC-C/C composite material, and the fields of view were not overlapped. Use images taken from 6 or more fields of view from the sample, and 20 or more fields of view in total.

First, by machining, an observation sample is obtained by exposing a cross section cut in the pressurizing direction during molding. Using an SEM, a backscattered electron image is taken of the observation sample in which the pressurizing direction during molding is the vertical direction and the viewing range is 2.4 mm×2.4 mm. For the obtained backscattered electron image, for example, ImageJ (Fiji) is used as image processing software, and streaks are obtained by the method of Otsu, which is generally used as a method of automatically obtaining a threshold value for binarizing a grayscale image. A binary image is obtained in which the impregnated portion (streak) is white and the other region is black. By these operations, the streaky impregnated portion can be clearly distinguished from other portions. Then, from the binarized image, using image processing software, it is possible to obtain the ratio ζ of the white area.
Backscattered electron images of 20 or more fields of view are analyzed, and the average value of their ratios ζ is obtained.
The ratio ζ indirectly indicates the area ratio in which either one or both of metal Si and silicon carbide are present. If the average value of the ratio ζ is 55% or less, the impact strength is improved due to the small amount of metallic Si or silicon carbide present in the SiC—C/C composite material.

In addition, Otsu's binarization method assumes that the luminance value histogram of a grayscale image forms two mountains corresponding to the object of the image and the background, respectively, and separates the group (class) of the object and the background of the image. It calculates the threshold at which the degree is the highest. The variance within each class and the variance between classes are calculated using each brightness value as a threshold, and the brightness value that minimizes the ratio between the variance within the class and the variance between classes is used as the threshold.

As shown in FIG. 3, the length of the longest line segment 7 in the white region in the binarized image is defined as the "longitudinal length of the muscle". In addition, the length of the longest line segment 8 perpendicular to the line segment in the white area is defined as "the length of the muscle in the lateral direction". Note that the line segment 9 drawn at the part where the streak branches is not regarded as the length in the lateral direction. Backscattered electron images of 20 or more fields of view are analyzed, and the probability ε of the presence of a streak having a width of 0.50 mm or more in the lateral direction is obtained.
The streaks having a width of 0.50 mm or more originate from pores and cracks existing in the compact. Streaks with a length of 0.50 mm or more in the transverse direction cannot obtain the reinforcing effect of the carbon fibers, and cause a reduction in the strength of the SiC--C/C composite material. Therefore, SiC--C/C composite materials with a probability ε of 20% or less have high strength.

In a cross section cut in the pressurizing direction during molding of the SiC-C/C composite material of the present invention, the length in the longitudinal direction is 0.3 mm or more and the length in the lateral direction is 0.2 mm or less. It is preferable that there is a streak with a length of 1.0 mm or less in the longitudinal direction. Also, the length in the lateral direction can be 0.01 mm or more. The length of the stripes in the longitudinal direction can be 1/200 or more and 1/10 or less of the average fiber length of the carbon fibers.

Next, the directivity parameter δ will be described in more detail.
Fast Fourier transform processing is performed on the binarized image using image processing software to obtain a power spectrum image. The resolution of the binarized image is 1024 pixels×1024 pixels, and the resolution of the power spectrum image is also 1024 pixels×1024 pixels. Then, as shown in FIG. 4, the right direction from the center point of the power spectrum image is 0°, the positive direction is counterclockwise, and the apex angle is 10° and the equilateral side is 100 pixels from 0° to 180°. Divide into 18 regions using triangles. After obtaining the average brightness of each of these 18 regions, let a be the maximum value of the average brightness in the range from 70° to 110°. Let b be the maximum value of the average luminance in the range from 0° to 20° and in the range from 160° to 180°. Let m be the minimum value of the average luminance in the range from 0° to 180°. Then, the directional parameter δ is calculated from the equation (1) using a, b, and m. Image processing is performed on the binarized images of 20 or more fields of view, the directional parameter δ is calculated for each, and the average value is obtained.
The directional parameter δ indicates the degree to which the streaky impregnated portions are oriented in a direction perpendicular to the pressurizing direction during molding. The greater the directivity parameter δ, the greater the ratio of the streaky impregnated portions oriented in the direction perpendicular to the pressurizing direction during molding. A SiC-C/C composite material having a directivity parameter δ of 14.0 or less has a small ratio of streaky impregnated portions resulting from flattening and dispersion of carbon fiber bundles, and has high impact strength.

The carbon fibers contained in the SiC-C/C composite material are preferably pitch-based carbon fibers from the viewpoint of excellent thermal conductivity.
In addition, the ratio of short carbon fibers having a fiber length of 10 mm or more and 60 mm or less with respect to the total 100% by mass of carbon fibers contained in the SiC-C/C composite material is preferably 50% by mass or more, and 70% by mass or more. More preferably, 80% by mass or more is even more preferable. If the ratio of short carbon fibers is equal to or higher than the lower limit, the reinforcing effect of the carbon fibers is likely to be obtained. The upper limit of the proportion of short carbon fibers is not particularly limited, and can be set to 100% by mass, for example.

Applications of the SiC-C/C composite material of the present invention are not particularly limited, and for example, it can be used as a sliding material. The SiC-C/C composite material of the present invention has excellent thermal conductivity, including in the thickness direction (pressing direction during molding), so it is particularly used for wheels of two-wheeled, four-wheeled vehicles, aircraft, etc. Brake discs and brakes Suitable for pads and the like.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited by the following description.

[Ratio ζ]
Observation samples were obtained from the SiC--C/C composite material of each example by machining, in which a cross section cut in the pressure direction during molding was exposed. Using an SEM, a backscattered electron image was taken of the observed sample in which the pressure direction during molding was the vertical direction and the viewing range was 2.4 mm×2.4 mm. Using ImageJ (Fiji) as image processing software, the obtained backscattered electron image was processed according to Otsu's method so that the streak-like impregnated portion (streak) was white and the other region was black. obtained a modified image. Then, the ratio ζ of the white area was obtained using image processing software. Backscattered electron images of 20 or more fields of view were analyzed, and the average value of these ratios ζ was obtained.

[Probability ε]
Using the binarized image obtained in the measurement of the ratio ζ, the length of the longest line segment in the white region is the “longitudinal length of the muscle”, and the longest line perpendicular to the line segment in the white region The length of each minute was obtained as the "length in the short direction of the muscle". Backscattered electron images of 20 or more fields of view were analyzed, and the probability ε of the presence of a streak having a length of 0.50 mm or more in the lateral direction was obtained.

[Directivity parameter δ]
The binarized image obtained in the measurement of the ratio ζ was subjected to fast Fourier transform processing using image processing software to obtain a power spectrum image. However, the resolution of the binarized image to be processed was 1024 pixels×1024 pixels, and the resolution of the power spectrum image was also 1024 pixels×1024 pixels. Then, the right direction from the center point of the power spectrum image is 0 °, the counterclockwise direction is 0 ° to 180 °, using an isosceles triangle with an apex angle of 10 ° and equilateral sides of 100 pixels, 18 divided into areas of After obtaining the average brightness of each of these 18 regions, the maximum value of the average brightness in the range of 70° to 110° is a, the average brightness in the range of 0° to 20° and the range of 160° to 180°. The directionality parameter δ was calculated from the above equation (1), where b is the maximum value and m is the minimum value of the average luminance in the range from 0° to 180°. Image processing was performed on the binarized images of 20 or more fields of view, and the average value of the directionality parameter δ calculated for each was obtained.

[Impact strength]
Using the SiC-C/C composite material obtained in each example, a notch with a length L of 50 mm, a width of 10 mm, a thickness of 10 mm, and a depth of 2 mm, shown in FIGS. A rectangular parallelepiped impact test piece was prepared. In the impact test piece, the depth direction of the notch, that is, the direction from the surface having the notch to the opposite surface (thickness direction) was parallel to the pressurizing direction during molding.
For each example, 6 or more impact test pieces were used, and measurements were carried out according to JIS7110 Izod impact strength test method. The value obtained by dividing the energy required to break the test piece by the cross-sectional area of the notch portion of the test piece was defined as the impact strength, and the average strength was defined as the impact strength of the SiC--C/C composite material. The impact was applied to the notched surface of the test piece in a direction parallel to the pressing direction during molding.

[Example 1]
Pitch-based carbon fibers (filament diameter: 10 μm, number of filaments: 12,000, average fiber length: 25.4 mm) are impregnated with a phenol resin containing 14% by mass of water as a matrix resin, and the FAW is 600 g / m ² . SMC was produced (SMC production process).
The SMC was then aged for 80 minutes in an air atmosphere at 115° C. (aging step).
After the aged SMC was filled in a mold, it was pressure-molded at a maximum temperature of 180° C. to obtain a plate-shaped CFRP having a carbon fiber volume content Vf of 43% by volume (molding step). . At this time, until the temperature reaches 130°C from 40°C, pressure is applied for 55 seconds, pressure is released for 5 seconds, and pressure is applied ^again . It was gradually increased to ² .
The resulting CFRP was sintered at 750° C. for 5 hours in a nitrogen atmosphere to obtain a C/C composite material (sintering step).
The resulting C/C composite material and metal Si were held at 1600° C. under vacuum conditions, and the C/C composite material was melt impregnated with metal Si to obtain a SiC—C/C composite material (melt impregnation process).
The porosity of the C/C composite before the melt impregnation step was 33% by volume. The mean values of probability ε and proportion ζ of the obtained SiC-C/C composites were 13% and 41%, respectively.

[Example 2]
An impregnation carbonization process in which pitch was impregnated and sintered at 750° C. for 5 hours was performed once before the C/C composite material obtained by sintering CFRP was melt-impregnated with metallic Si. A SiC--C/C composite material was obtained in the same manner as in Example 1 except for the above.
The porosity of the C/C composite before the melt impregnation step was 26% by volume. The mean values of the probability ε and fraction ζ of the obtained SiC-C/C composites were 9% and 19%, respectively.

[Example 3]
The C/C composite material obtained by sintering CFRP was impregnated with pitch and sintered at 750° C. for 5 hours. A SiC--C/C composite material was obtained in the same manner as in Example 1 except for the above.
The porosity of the C/C composite before the melt impregnation step was 22% by volume. The mean values of probability ε and proportion ζ of the obtained SiC-C/C composites were 10% and 17%, respectively.

[Example 4]
A SiC--C/C composite material was obtained in the same manner as in Example 1 except that the carbon fibers had an average fiber length of 38.1 mm.
The porosity of the C/C composite before the melt impregnation step was 34% by volume. The mean values of probability ε and proportion ζ of the obtained SiC-C/C composites were 13% and 38%, respectively.

[Example 5]
A SiC--C/C composite material was obtained in the same manner as in Example 1 except that the carbon fibers had an average fiber length of 12.7 mm.
The porosity of the C/C composite before the melt impregnation step was 33% by volume. The mean values of the probability ε and fraction ζ of the obtained SiC-C/C composites were 8% and 39%, respectively.

[Comparative Example 1]
A sheet having an FAW of 170 g/m ² containing a phenolic resin as a matrix resin is laminated on a nonwoven fabric in a mold, and pressure-molded at 250 ° C. to obtain a carbon fiber volume content Vf of 50% by volume. A plate-like CFRP was obtained. The resulting CFRP was sintered at 750° C. for 5 hours in a nitrogen atmosphere. The resulting C/C composite material and metal Si were held at 1600° C. under vacuum conditions, and the C/C composite material was melt-impregnated with metal Si to obtain a SiC—C/C composite material.
The porosity of the C/C composite before the melt impregnation step was 42% by volume. The mean values of probability ε and proportion ζ of the obtained SiC-C/C composites were 0% and 69%, respectively.

[Comparative Example 2]
The C/C composite material obtained by sintering CFRP was impregnated with pitch and sintered at 750° C. for 5 hours. A SiC--C/C composite material was obtained in the same manner as in Comparative Example 1 except for the above.
The porosity of the C/C composite before the melt impregnation step was 21% by volume. The mean values of probability ε and proportion ζ of the obtained SiC-C/C composites were 0% and 25%, respectively.

Table 1 shows the evaluation results of each example.
Further, for the SiC-C/C composite material obtained in Example 1, a backscattered electron image of a cross section cut in the pressure direction during molding was taken using an SEM, and the binarized image is shown in FIG. show.

[Comparative Example 3]
After SMC was produced in the same manner as in Example 1, the SMC was aged in an air atmosphere at 90° C. for 80 minutes in the aging step. A SiC--C/C composite material was obtained in the same manner as in Example 1 after the molding step.
The porosity of the C/C composite before the melt impregnation step was 41% by volume. The mean values of probability ε and proportion ζ of the obtained SiC-C/C composites were 28% and 46%, respectively.
7 shows the cross-sectional appearance (a) of the SiC--C/C composite material obtained in Example 1 and the cross-sectional appearance (b) of the SiC--C/C composite material obtained in Comparative Example 3. FIG. Compared with Example 1, Comparative Example 3 was unevenly impregnated with metal Si, and the presence of pores was also confirmed.

As shown in Table 1, the SiC-C/C composite materials of Examples 1 to 5 manufactured by performing a specific aging process using SMC are the SiC-C/C composite materials of Comparative Examples 1 and 2 using nonwoven fabrics. Compared to the C composite material, and compared to the SiC--C/C composite material of Comparative Example 3 which did not undergo a specific aging process, the impact strength was higher.

Claims (19)

impregnating carbon fibers with a thermosetting resin to obtain a sheet molding compound;
When the thermosetting resin contains a solvent component, the sheet molding compound is heated to a boiling point of the solvent component under atmospheric pressure of 130°C or higher, and when the thermosetting resin does not contain a solvent component, the boiling point of the sheet molding compound is 75°C or higher and 130°C. A step of aging by exposure to an atmosphere of ℃ or less;
a step of molding the aged sheet molding compound to obtain a carbon fiber reinforced plastic;
a step of baking the carbon fiber reinforced plastic to obtain a carbon fiber reinforced carbon composite;
and a step of melt-impregnating the carbon fiber-reinforced carbon composite material with metal Si. 2. The method for producing a carbon fiber-reinforced silicon carbide-based composite according to claim 1, wherein said carbon fibers are pitch-based carbon fibers. 3. The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to claim 1, wherein the carbon fibers have a fiber length of 10 mm or more and 60 mm or less. The method for producing a carbon fiber-reinforced silicon carbide composite material according to claim 1 or 2, wherein the sheet molding compound has a FAW of 200 g/m ² or more and 2000 g/m ² or less. 3. The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to claim 1, wherein said thermosetting resin is a phenolic resin. 3. The method for producing a carbon fiber-reinforced silicon carbide composite material according to claim 1, wherein the carbon fiber content per volume of said carbon fiber reinforced plastic is 30% by volume or more and 60% by volume or less. 3. The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to claim 1, wherein the molding using the sheet molding compound is performed by a hot press method. The carbon fiber reinforced carbonization according to claim 7, wherein at a temperature of 140 ° C. or less of the sheet molding compound molded by the hot press method, a pressure operation of releasing pressure from a pressurized state and pressurizing again is performed one or more times. A method for manufacturing a silicon-based composite material. 3. The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to claim 1, wherein the carbon fiber-reinforced plastic is fired in an inert gas atmosphere. 3. The method for producing a carbon fiber-reinforced silicon carbide-based composite material according to claim 1, wherein the impurity content of said metal Si is 1.5% by mass or less. The method for producing a carbon fiber reinforced silicon carbide composite material according to claim 1 or 2, wherein the carbon fiber reinforced carbon composite material is melt-impregnated with metal Si at 1400°C or higher and 2000°C or lower under vacuum conditions. A carbon fiber reinforced silicon carbide composite material having streaks in a cross section cut in the direction of pressure during molding, and a field of view of 2.4 mm × 2.4 mm taken with a scanning electron microscope for the cross section. A binarized image in which the muscle region is white is obtained by binarizing the cross-sectional image using Otsu's method for a cross-sectional image in which the pressure direction during molding is the vertical direction. In a power spectrum image with a resolution of 1024 pixels × 1024 pixels obtained by fast Fourier transforming the binarized image, the right from the center point of the power spectrum image is 0 °, and the counterclockwise direction is the positive direction. 0° to 180° is divided into 18 regions using an isosceles triangle with an apex angle of 10° and an equilateral side of 100 pixels. The average value of the directional parameter δ defined by the following formula (1), where b is the maximum value in the range from 20 ° and 160 ° to 180 ° and m is the minimum value in the range from 0 ° to 180 ° is 14.0 or less, a carbon fiber-reinforced silicon carbide-based composite material.

13. The carbon fiber-reinforced silicon carbide-based composite material according to claim 12, wherein the probability ε of existence of said streak having a width of 0.50 mm or more in said binarized image is 20% or less. 14. The carbon fiber reinforced silicon carbide-based composite material according to claim 12 or 13, having said streaks having a length in the longitudinal direction of 0.3 mm or more and a length in the transverse direction of 0.2 mm or less. 14. The carbon fiber reinforced silicon carbide-based composite material according to claim 12 or 13, wherein the average value of the ratio ζ of the area that is white in the binarized image is 55% or less. 14. The carbon fiber-reinforced silicon carbide-based composite material according to claim 12 or 13, which contains pitch-based carbon fibers. 14. The carbon fiber reinforced silicon carbide-based composite material according to claim 12 or 13, wherein said streaks contain Si element. The carbon fiber-reinforced silicon carbide-based composite material according to claim 12 or 13, wherein the proportion of short carbon fibers having a fiber length of 10 mm or more and 60 mm or less is 50% by mass or more with respect to the total 100% by mass of the carbon fibers contained. . 14. The carbon fiber-reinforced silicon carbide-based composite material according to claim 12 or 13, wherein the carbon fiber-reinforced carbon composite material has a porosity of 15% by volume or more and 40% by volume or less before being melt-impregnated with metal Si.

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