JP3001128B2 - Carbon-based composite fiber reinforced ceramic composite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon composite fiber reinforced ceramic composite material having high strength, high toughness and high heat resistance. The ceramic composite material of the present invention is used as a member of a turbine engine such as a rotor, a stator, or a combustor, a member of a rocket engine such as a nose cone or a nozzle, or a member of an internal combustion engine such as a piston head, an auxiliary combustion chamber, or a valve. Can be suitably used.

[0002]

2. Description of the Related Art Nitride ceramics such as silicon nitride and carbide ceramics such as silicon carbide are well known as ceramics having excellent heat resistance. The use as was limited. Recently,
Attempts have been actively made to improve the strength and toughness by combining the above-mentioned nitride ceramics or carbide ceramics with various reinforcing materials.

[0003] For example, "Journal of the
American Ceramics Society
y, Vol. 73, pages 678-683 (1990)
By compounding silicon nitride with 20% by volume of silicon carbide whiskers, the critical stress intensity factor (K _1C ) as a measure of fracture toughness is from 5 MPa · m ^1/2 to about 7.5 MPa ·
It is disclosed that it is improved to m ^1/2 . However, the composite material has a bending strength of about 700 MPa to about 550 MPa.
Is described in the above document. "Cer
amic Engineering and Scie
nce Proceeding "Vol. 6 632-645
On page (1985), silicon nitride is formed by compounding 30% by volume of silicon carbide fiber manufactured by Textron of the United States, so that K _1C is 7 MPa · m ^1/2 to about 8.5 MPa.
It is disclosed that the bending strength is reduced from about 900 MPa to about 400 MPa, although it is improved to m ^1/2 .

The Ceramic Society of Japan, 9
9, pp. 180-182 (1991), a composite material produced by depositing a silicon carbide matrix by a chemical vapor deposition method in a preform of silicon carbide fiber is described as follows:
It has a K _{1C of} 13 MPa · m ^1/2 and a bending strength of about 300 MPa. The flexural strength of this composite is, for example, Ceramic Bulletin "
No. 65, pages 326 to 335 (1986).
It is understood that it is very low compared to MPa.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to exhibit excellent strength and high fracture toughness from room temperature to high temperature, which can be suitably used for various heat engines including automobile engines. An object of the present invention is to provide a ceramic composite material. The object of the present invention is to provide (1) crystalline carbon oriented in the fiber axis direction, (2) amorphous carbon and / or crystalline carbon oriented in a direction different from the fiber axis direction, and (3) silicon; A carbon-based composite fiber composed of a silicon-containing component composed of carbon and oxygen is used as a reinforcing material, and a carbide-based nanocomposite or a nitride-based nanocomposite nanocomposited with carbide particles and / or nitride particles is used as a matrix. ,
This is achieved by a carbon-based composite fiber reinforced ceramic composite material.

The silicon-containing component (3) includes (i) an amorphous substance composed of silicon, carbon and oxygen, and (ii) β-S
an aggregate of crystalline fine particles of iC and C and amorphous SiO ₂ , and (iii) the amorphous substance of (i) and (i)
It is composed of a mixture with the aggregate of i). The ratio of each element of the silicon-containing component is generally 30 to 70% by weight of Si,
C: 20 to 60% by weight, and O: 0.5 to 10% by weight. The silicon-containing component may contain a metal element (hereinafter, referred to as “M”) selected from titanium, zirconium, and hafnium in addition to these elements. In this case, the silicon-containing component may be (iv) an amorphous substance composed of silicon, carbon, M, and oxygen, or (v) β-SiC, MC,
C, a solid solution of β-SiC and MC, and at least one type of crystalline fine particles selected from the group consisting of MC _1-x , and an aggregate (x is greater than 0) composed of amorphous SiO ₂ and MO ₂ (Vi) a number less than 1.) or (vi) a mixture of the above-mentioned (iv) amorphous substance and the above-mentioned (v) aggregate. The ratio of each element is usually Si: 5 to 70
%, C: 20 to 40% by weight, M: 0.5 to 45% by weight, O: 0.01 to 30% by weight.

In the carbon-based composite fiber of the present invention, the weight ratio of the component (1) to the sum of the components (2) and (3) is 1: 0.5 to 500.
0 and the weight ratio of the component (2) to the component (3) is preferably 1: 0.02 to 4. Carbon-based composite fibers are described in, for example, JP-A-3-104926,
It can be prepared according to the method described in JP-A-2-229218. The descriptions in these publications are incorporated as a part of the present specification. An example of a method for producing a carbon-based composite fiber is described below. First, a reaction product obtained by reacting an organosilicon polymer such as polycarbosilane with an optically isotropic pitch at a temperature of 250 to 500 ° C. is reacted with a halide, alkoxide or chelate compound of M for 100 minutes. ~ 500
The reaction product is then heated and melted with a mesophase, premesophase or potentially anisotropic pitch at a temperature of 300-500 ° C. In the resulting heated melt, at least a portion of the organosilicon polymer is chemically bonded to the pitch. Next, a carbon-based composite fiber can be produced by spinning the heated melt, infusing the spun fiber, and firing the infusibilized fiber at a temperature of 800 to 3000 ° C. in a vacuum or an inert gas atmosphere. .

The form of the carbon-based composite fiber is not particularly limited, and may be a plain weave, a satin weave, a multiaxial weave, a three-dimensional weave, or a nonwoven fabric knitted from a chop fiber or a continuous fiber. May be arranged in one direction.

The carbide-based nanocomposite or the nitride-based nanocomposite according to the present invention is characterized in that at least one of the dispersed particles, ie, the carbide particles and the nitride particles, is composed of the matrix-based carbide ceramic or nitride ceramic and the intragranular nanoparticle. Ceramics composed of composites, nanocomposites at grain boundaries, or nanocomposites at both intragranular and grain boundaries. Intragranular nanocomposite microstructure means that the matrix particles themselves are composited by dispersing nano-order dispersed particles in matrix particles of carbide-based ceramics or nitride-based ceramics, for example, as shown in the model in FIG. Organization. On the other hand, the grain boundary nanocomposite structure is, for example, a structure obtained by dispersing nano-order dispersed particles in a matrix boundary of a carbide-based ceramic or a nitride-based ceramic as shown in a model in FIG. . Such a carbide-based nanocomposite or a nitride-based nanocomposite can be prepared, for example, according to a method described in “The Ceramic Society of Japan”, Vol. 99, pages 947 to 982 (1991).

[0010] Specific examples of the nitride-based ceramics serving as a matrix and dispersed particles in the nanocomposite of the present invention include nitrides of elements such as silicon, boron, aluminum, magnesium, titanium, and molybdenum, and composites of these elements. Nitride and Sialon can be mentioned. Specific examples of the carbide-based ceramics serving as a matrix and dispersed particles in the nanocomposite material of the present invention include silicon, titanium, zirconium, aluminum, uranium, tungsten, tantalum, hafnium, boron, iron, and carbides of elements such as manganese. And complex carbides of these elements.

The system of the ceramic particles serving as the matrix is usually 0.05 to 1000 μm. The shape of the dispersed particles is not particularly limited, and may be spherical, polyhedral, plate-like, or acicular. The size of the dispersed particles is generally, when spherical or polyhedral, an equivalent diameter of 1 to 10,000 nm.
In the case of a plate or needle, the maximum length or thickness is 10,000 nm. The proportion of dispersed particles in the nanocomposite is generally between 1 and 50% by volume relative to the composite.
It is.

The carbon-based composite fiber-reinforced ceramic composite material of the present invention is obtained by blending a carbon-based composite fiber, a silicon nitride-based inorganic fiber, and a carbide-based nanocomposite or a nitride-based nanocomposite according to a method known per se, It can be prepared by sintering. When the carbon-based composite fibers are chopped, a mixture of the chopped fibers and the nanocomposite powder is prepared. When the carbon-based composite fiber is a long fiber, a woven fabric, a nonwoven fabric or a sheet-like material,
A laminate is prepared by alternately laminating layers composed of these and layers composed of nanocomposite powder. Then
After molding the above mixture or laminate into a desired shape,
Alternatively, by heating and sintering simultaneously with the molding, the carbon-based composite fiber reinforced ceramic composite material of the present invention can be obtained. The ratio of the carbon-based composite fiber in the composite material is usually from 1 to 70% by volume.

As a method for molding the mixture or the laminate, a method known per se, for example, a die pressing method, a rubber pressing method, an extrusion method, and a sheet method can be adopted. Known organic polymers such as polyvinyl alcohol, polyethylene oxide, and aluminum alkoxide, as well as polycarbosilane and polymetallocarbosilane, can be used as a binder at the time of molding.
There is no particular limitation on the sintering method, and a method known per se such as a method of sintering a molded product under normal pressure or reduced pressure, a hot press method or a hot isostatic press method in which molding and sintering are performed simultaneously. Can be adopted. The heat sintering temperature is usually 400 to 2500C. If the heating sintering temperature is too low, the nanocomposite as the matrix will not be sufficiently sintered, and if the temperature is too high, the carbon-based composite fibers will be decomposed.

As another method for preparing the carbon-based composite fiber-reinforced ceramic composite material of the present invention, instead of using a powder of a carbide-based nanocomposite or a powder of a nitride-based nanocomposite itself as a matrix raw material powder, a nanocomposite material is used. The same method as described above can be adopted, except that a mixed powder obtained by mixing a powder of a carbide-based ceramic and a powder of a nitride-based ceramic, which are raw materials for the above, is mixed by a known method. In this case, during the forming and sintering processes, the nanocomposite of the matrix and the composite of the matrix and the carbon-based composite fiber occur simultaneously or sequentially, and the carbon-based composite fiber-reinforced ceramic composite material of the present invention is prepared. You.

[0015]

Examples of the present invention will be described below. Reference Example 1 Among the petroleum fractions, high-boiling substances higher than gas oil were subjected to fluid catalytic cracking and rectification at a temperature of 500 ° C. in the presence of a silica-alumina-based cracking catalyst, and a residue was obtained from the bottom of the tower. Hereinafter, this residue is referred to as “FCC slurry oil”. The FCC slurry oil is heated to 450 ° C. under a stream of nitrogen gas to distill off distillates at the same temperature, and then the residue is filtered while hot at 200 ° C. to remove the infused portion at the same temperature to obtain pitch A. Was. The pitch A was subjected to polycondensation at 400 ° C. for 7 hours while removing light components generated by the reaction under a nitrogen stream to obtain a pitch B.

Reference Example 2 Polydimethylsilane synthesized by dechlorination-condensation of dimethyldichlorosilane with metallic sodium was heat-treated at 420 ° C. while stirring under a nitrogen stream to obtain a number average molecular weight of 12
00 was obtained.

Reference Example 3 To 49 g of the pitch A obtained in Reference Example 1, 21 g of the organosilicon polymer obtained in Reference Example 2 and 20 ml of xylene were added, and the temperature was increased while stirring.
For 6 hours to obtain 39 g of a precursor polymer. A xylene solution of 2.75 g of tetraoctoxytitanium (11 g of a 25% xylene solution) was added to 39 g of this precursor polymer, and after xylene was distilled off, the mixture was reacted at 340 ° C. for 2 hours to obtain 38 g of a random copolymer. 35 g of this random copolymer and 70 g of the pitch B obtained in Reference Example 1 were mixed and melted and heated at 310 ° C. for 1 hour under a nitrogen atmosphere to obtain a uniform polycyclic aromatic polycondensate containing silicon and titanium. A coalescence was obtained. This polycyclic aromatic polymer was melt-spun, and the spun fiber was thermally oxidized at 300 ° C. in air to make it infusible. The infusible fiber was fired at 1300 ° C. in an argon atmosphere to obtain a carbon-based composite fiber. This carbon-based composite fiber has a fiber diameter of 10 μm.
m, tensile strength 3.1 GPa, tensile modulus 320 GPa
(Measurement was based on the single fiber test method).

REFERENCE EXAMPLE 4 Hexamethyldisilazane and ammonia were subjected to a chemical vapor reaction at 1000.degree.
After heat treatment for a time, a composite powder composed of silicon, carbon and nitrogen was produced. This composite powder had an amorphous structure, and the content of oxygen as an impurity was 2% by weight or less.

Example 1 The composite powder composed of silicon, carbon and nitrogen obtained in Reference Example 4 was subjected to ball milling using a silicon nitride ball and a silicon nitride pot with a volume ratio of ethanol to distilled water of 4: 1. The slurry was crushed in a mixed solvent for 30 hours to obtain a slurry of the composite powder. 5% by weight of yttrium oxide powder and 5% by weight of aluminum oxide powder were added to the slurry as sintering aids, and 10% by weight of polyethylene oxide was added to the composite powder as a molding binder. The mixture was wet-mixed for hours to obtain a slurry of the matrix material. After opening the bundle of carbon-based composite fibers obtained in Reference Example 3 by blowing air,
It was immersed in the slurry of the matrix material described above, and a matrix powder was attached around each carbon-based composite fiber. The bundle of carbon-based composite fibers to which the matrix powder was attached was wound around a square drum, and then sufficiently dried to produce a prepreg sheet. After cutting this prepreg sheet into a desired shape, it is laminated in a graphite die coated with boron nitride as a release agent, and hot-pressed in an argon gas atmosphere at a temperature of 1800 ° C. and a pressure of 65 MPa, so that the SiC particles are removed. A carbon-based composite fiber reinforced ceramics composite material using the nanocomposite silicon nitride-based nanocomposite as a marix was obtained. The ratio of the carbon-based composite fibers in the composite material was 45% by volume. The flexural strength of this composite material is 1.98 GP at room temperature.
a It was 1.82 GPa at 1300 ° C. The fracture toughness value (K _1C ) of the composite material measured by the chevron notch method was 22.9 MPa · m ^1/2 .

Example 2 The composite powder obtained in Reference Example 4 was subjected to ball milling using a silicon nitride ball and a silicon nitride pot in a mixed solvent having a volume ratio of ethanol to distilled water of 4: 1. 3
The mixture was pulverized for 0 hour to obtain a composite powder slurry. After adding 8 wt% and 10 wt% of yttrium oxide as a sintering aid and polyethylene oxide as a forming binder to the composite powder, respectively, to the slurry, wet mixing was performed using silicon nitride balls for 12 hours. After that, the mixture was sufficiently dried to obtain a mixed powder of a matrix raw material. A sheet of the carbon-based composite fiber obtained by opening the bundle of the carbon-based composite fiber obtained in Reference Example 3 by blowing it into the air and the matrix raw material powder were coated with boron nitride as a mold release agent. The layers were alternately laminated in a graphite die and hot-pressed at 1300 ° C. and 50 MPa in an argon gas atmosphere to obtain a temporarily sintered body. After applying boron nitride as a release agent to this pre-sintered body, it is vacuum-encapsulated in a glass capsule, and in an argon gas at a temperature of 1750 ° C., 175 M
Hot isostatic pressing was performed at a pressure of Pa to obtain a carbon-based composite fiber-reinforced ceramic composite material having a matrix of a silicon nitride-based nanocomposite in which silicon carbide particles were nanocomposited. The proportion of carbon-based composite fibers in the composite material was 50% by volume, and the content of silicon carbide particles in the matrix was 30% by volume. The bending strength of this composite material was 2.02 at room temperature.
GPa was 1.91 GPa at 1300 ° C. Fracture toughness (K) of composite material measured by chevron notch method
_1C ) was 24.2 MPa · m ^1/2 .

Example 3 Yttrium oxide powder and aluminum oxide powder as sintering aids were added to the composite powder obtained in Reference Example 4 at 6% by weight and 2% by weight, respectively. Using a pot, the mixture was wet-pulverized in ethanol with a ball mill for 25 hours to obtain a slurry of a composite powder, and then the ethanol was evaporated to obtain a powder of a matrix raw material. The carbon-based composite fiber obtained in Reference Example 3 was cut into a length of 1 to 2 mm into a chopped fiber. The chopped fibers were dispersed in ethanol by using ultrasonic waves and an omni mixer. After the slurry of the matrix material prepared in Example 3 was added to the dispersion, the mixture was wet-mixed with a ball mill using nylon balls for 5 hours. From this mixed slurry, a thin prepreg sheet having a thickness of 1 mm in which chopped fibers were uniformly dispersed was prepared by a filtration method. After cutting the prepreg sheet into a desired shape, the prepreg sheet is laminated on a graphite die coated with boron nitride as a release agent, and heated at 65 ° C. in an argon gas atmosphere at a temperature of 1850 ° C.
By hot pressing at a pressure of MPa, a carbon-based composite fiber reinforced ceramic composite material having a matrix of a silicon nitride-based nanocomposite in which silicon carbide particles were nanocomposited was obtained. The ratio of the carbon-based composite fibers in the composite material was 30% by volume. The bending strength of this composite material is 1.6 at room temperature.
It was 1.61 GPa at 5300 and 1300 ° C. The fracture toughness value (K _1C ) of the composite material measured by the chevron notch method was 11.2 MPa · m ^1/2 .

[0022]

[Brief description of the drawings]

FIG. 1 is a model of an intragranular nanocomposite.

FIG. 2 is a model of a grain boundary nanocomposite.

────────────────────────────────────────────────── ─── Continuation of the front page Examiner Yuki Yamada (56) References JP-A-6-87657 (JP, A) JP-A-6-87671 (JP, A) JP-A-6-92737 (JP, A) Kaihei 6-107468 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/80

Claims (1)

(57) [Claims] (1) crystalline carbon oriented in the fiber axis direction,
(2) A carbon-based composite fiber composed of amorphous carbon and / or crystalline carbon oriented in a direction different from the fiber axis direction and (3) a silicon-containing component composed of silicon, carbon and oxygen is used as a reinforcing material. A carbon-based composite fiber-reinforced ceramic composite material comprising, as a matrix, a carbide-based nanocomposite or a nitride-based nanocomposite nanocomposited with carbide particles and / or nitride particles.