JP3001127B2 - Carbon-based composite fiber reinforced ceramic composite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a carbon-based 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 Oxide ceramics such as aluminum oxide have excellent heat resistance, but their use as engineering ceramics has been limited due to low toughness or insufficient strength. . Recently, attempts have been actively made to improve strength and toughness by compounding oxide ceramics with various reinforcing materials.

[0003] For example, "Pro.23rd.Autom"
ot. Technol. Dev. Contract C
oord. Meet. 1986 "has 20
By compounding volume% silicon carbide whisker,
The bending strength is increased from about 300 MPa to about 700 MPa, and the critical stress intensity factor (K _1C ) which is a measure of fracture toughness
Is from 4.5 MPa · m ^1/2 to about 8.5 MPa · m
It is disclosed that it is improved by ^half . However, when the whisker reinforced alumina composite material exceeds 1000 ° C., the bending strength is sharply reduced. The “Investigation of New Materials for Aircraft” published by the Japan Aerospace Industry Association in March 1998, page 193, shows that materials for rotors of gas turbines, etc., have a temperature in the range of 1250 ° C to 1450 ° C. It is described that the bending strength needs to be 450 MPa or more. The whisker reinforced alumina composite material cannot satisfy the characteristics required for the gas turbine member.

[0004] A method of improving the strength or heat resistance of oxide ceramics by nanocompositing is also known.
For example, in “Powder and Powder Alloy”, Vol. 37, p. 348 (1990), a ceramic nanocomposite made by adding 5% by volume of silicon carbide ultrafine particles to aluminum oxide has a heat resistance temperature of 1200 ° C. and a bending temperature of 1200 ° C. Strength about 155
It is disclosed that it exhibits an excellent property of 0 MPa. However, the K _{1C of} this composite material is about 4.8 MPa ·
m ^1/2 , which is lower than about 6 MPa · m ^1/2 which is K _1C of ordinary monolithic silicon nitride.

[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; Carbon-based composite fiber reinforced using carbon-based composite fiber composed of a silicon-containing component composed of carbon and oxygen as a reinforcing material, and using an oxide-based nanocomposite nanocomposited with carbide particles and / or nitride particles as a matrix Achieved by ceramic composites.

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.

In the present invention, the oxide-based nanocomposite serving as a matrix is characterized in that at least one kind of dispersed particles of carbide particles and nitride particles is composed of oxide ceramic and intragranular nanocomposite, grain boundary nanocomposite or intragranular. And ceramics composed of both nanocomposite structures of grain boundaries.
The intragranular nanocomposite structure is, for example, a structure obtained by dispersing nano-order dispersed particles in a matrix particle of an oxide ceramic and compounding the matrix particle itself, as in the model shown in FIG. On the other hand, the grain-boundary nanocomposite structure is a structure obtained by dispersing nano-order dispersed particles in a matrix boundary of an oxide ceramic as shown in, for example, a model in FIG. Such an oxide-based nanocomposite is described, for example, in “Academic Journal of the Ceramic Society of Japan”, Vol.
It can be prepared according to the method described on pages 47 to 982 (1991).

[0010] Specific examples of the oxide-based ceramics serving as a matrix in the oxide-based nanocomposite include aluminum and aluminum.
Magnesium, silicon, yttrium, indium, uranium, calcium, scandium, tantalum, niobium,
Neodymium, lanthanum, ruthenium, rhodium, beryllium, titanium, tin, strontium, barium, zinc,
Examples include oxides of elements such as zirconium and iron, and composite oxides of these metals. The particle size of these oxide ceramics is generally 0.05 to 1000 μm.
It is.

[0011] Specific examples of the nitride to be dispersed particles include:
Examples include nitrides of elements such as silicon, boron, aluminum, magnesium, titanium, and molybdenum, and composite nitrides of these elements, or sialon. Specific examples of the carbide of the dispersed particles include carbides of elements such as silicon, titanium, zirconium, aluminum, uranium, tungsten, tantalum, hafnium, boron, iron, and manganese, and composite carbides of these elements. There are no particular restrictions on the shape of the dispersed particles in the oxide-based nanocomposite, such as spherical, polyhedral, plate,
Any of a needle shape may be used. The size of the dispersed particles is generally 1 to 100 in the case of spherical or polyhedral.
In the case of a plate or needle, the maximum length or thickness is 10,000 nm. The proportion of dispersed particles in the oxide-based nanocomposite is generally between 1 and 50% by volume relative to the composite.

The carbon-based composite fiber-reinforced ceramic composite material of the present invention can be prepared by blending the carbon-based composite fiber and the oxide-based nanocomposite according to a method known per se and sintering the blended composite fiber. When the carbon-based composite fiber is a chopped material, a mixture in which the chopped fiber and the powder of the oxide-based nanocomposite are mixed 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 a layer composed of these and a layer composed of powder of the oxide-based nanocomposite. . Then, the above-mentioned mixture or laminate is heated and sintered after molding or at the same time as molding, whereby 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 and sintering temperature is too low, the oxide 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 of preparing the carbon-based composite fiber-reinforced ceramic composite material of the present invention, instead of using the oxide-based nanocomposite powder itself as the matrix raw material powder, the raw material of the oxide-based nanocomposite is used. The same method as described above can be adopted except that a mixed powder obtained by mixing the oxide ceramic powder and carbide particles and / or nitride particles by a known method is used. 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 0.3 μm average particle diameter was added to γ-alumina having an average particle diameter of 0.5 μm.
m of β-silicon carbide particles were added at 5% by volume, and a
Wet mixed for hours. Thereafter, the mixture was dried, and the powder subjected to dry mixing for further 12 hours was placed in a nitrogen gas atmosphere.
Hot pressing was performed in a graphite die at a pressure of 30 MPa and a temperature of 1500 to 1800 ° C. to obtain an alumina-based nanocomposite (SiC particles / Al ₂ O ₃ nanocomposite) reinforced with silicon carbide particles. The bending strength of this nanocomposite at room temperature is 1.
5 GPa and K _1C were 5 MPa · m ^1/2 , and the maximum operating temperature was 1200 ° C.

Reference Example 5 Magnesia having an average particle size of 0.1 μm was added to magnesia having an average particle size of 0.3 μm.
The following silicon carbide particles were added in an amount of 10% by volume, and 24
After wet mixing for hours, the mixture was dried. The mixed powder was placed in a nitrogen gas atmosphere at a pressure of 28 MPa,
Magnesia nanocomposite (SiC) reinforced with silicon carbide particles by hot pressing in a graphite die at a temperature of 1900 ° C
/ MgO nanocomposite). The bending strength of this nanocomposite at room temperature is 700 MPa, and K _1C is 4 MPa · m.
^The maximum operating temperature was 1/2300.

Example 1 The nanocomposite of the SiC particles / Al ₂ O ₃ nanocomposite obtained in Reference Example 4 was ground in a ball mill for 30 hours in distilled water using a silicon nitride ball and a silicon nitride pot. A slurry of the material was obtained. After adding 10% by weight of polyethylene oxide as a binder to the nanocomposite material to this slurry, the mixture was wet-mixed using silicon nitride balls for 12 hours to obtain a slurry of a matrix raw material. After the bundle of carbon-based composite fibers obtained in Reference Example 3 was opened by blowing air, the bundle was immersed in the slurry of the matrix material described above, and a matrix powder was attached around each of the carbon-based composite fibers. After winding a bundle of carbon-based composite fibers with matrix powder attached to a square drum,
After drying sufficiently, a prepreg sheet was prepared. After cutting the prepreg sheet into a desired shape, the prepreg sheet 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 1650 ° C. and a pressure of 65 MPa to obtain SiC particles / A carbon-based composite fiber reinforced ceramic composite material using an Al ₂ O ₃ nanocomposite as a matrix was obtained. The ratio of the carbon-based composite fiber in the composite material is 5
It was 5% by volume. The bending strength of this composite material was 1.93 GPa at room temperature and 1.8 GPa at 1300 ° C.
The fracture toughness value (K _1C ) of the composite material measured by the chevron notch method was 21.5 MPa · m ^1/2 .

Example 2 0.3 μm average particle diameter was applied to γ-alumina having an average particle diameter of 0.4 μm.
m-α-silicon nitride particles in an amount of 5% by volume, and a ball mill using an alumina ball.
After wet-mixing for hours, the mixture was sufficiently dried, and dry-mixed for further 10 hours to obtain a mixed powder as a raw material powder for the matrix. 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 above-mentioned matrix raw material powder were mixed with boron nitride as a release agent. Alternately laminated in a coated graphite die, in an argon gas atmosphere, at a temperature of 1600 ° C., 75M
By hot pressing with Pa, a carbon-based composite fiber-reinforced ceramic composite material having a matrix of SiC particles / Al ₂ O ₃ nanocomposite was obtained. The ratio of the carbon-based composite fibers in the composite material was 40% by volume. The bending strength of this composite material was 1.71 GPa at room temperature and 1.82 GPa at 1300 ° C. The fracture toughness value (K _1C ) of the composite material measured by the chevron notch method was 16.4 MPa · m ^1/2 .

Example 3 The SiC particles / MgO nanocomposite obtained in Reference Example 5 was mixed with a ball mill made of silicon nitride and a pot made of silicon nitride at a volume ratio of ethanol to distilled water of 4: 1. A nanocomposite slurry was prepared by grinding in a solvent for 30 hours. After adding 10% by weight of polyethylene oxide as a binder to the nanocomposite material to this slurry, the mixture was wet-mixed for 12 hours using a silicon nitride ball to obtain a matrix material slurry. In the same manner as in Example 1, the prepreg sheet was prepared by opening the carbon-based composite fiber, attaching the matrix material to the carbon-based composite fiber, winding and drying. This prepreg sheet was cut into a desired shape, laminated, and then degreased. This laminate was coated with boron nitride as a mold release agent, vacuum-encapsulated in a glass capsule, and then subjected to hot isostatic pressing at a temperature of 1850 ° C. and a pressure of 150 MPa in argon gas to obtain SiC particles / MgO nanoparticle. A carbon-based composite fiber reinforced ceramic composite material using the composite as a matrix was obtained. The ratio of the carbon-based composite fibers in this composite material was 45% by volume. The bending strength of this composite material was 1.57 GPa at room temperature and 1.54 GPa at 1300 ° C. The fracture toughness value (K _1C ) of the composite material measured by the chevron notch method was 19.4 MPa · m ^1/2 .

Example 4 The carbon-based composite fiber obtained in Reference Example 3 was cut into a length of 1 to 2 mm to obtain 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. 1 m thickness of chopped fibers uniformly dispersed by filtration from this mixed slurry
m in the form of a thin prepreg sheet. After cutting the prepreg sheet into a desired shape, the prepreg sheet 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 1850 ° C. and a pressure of 75 MPa to obtain a SiC. Thus, a carbon-based composite fiber reinforced ceramic composite material having a matrix of particles / MgO nanocomposite 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 was 0.85 GPa at room temperature and 0.82 GPa at 1300 ° C. The fracture toughness value (K _1C ) of the composite material measured by the chevron notch method was 9.8 MPa · m ^1/2 .

[0024]

[Brief description of the drawings]

FIG. 1 is a model of an intragranular nanocomposite.

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

──────────────────────────────────────────────────続 き Continuation of the front page Examiner Yuki Yamada (56) References JP-A-5-105521 (JP, A) JP-A-6-92745 (JP, A) JP-A-6-87670 (JP, A) JP-A-6-87673 (JP, A) JP-A-7-149577 (JP, A) (58) Fields investigated (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. An oxide-based nanocomposite nanocomposited with carbide particles and / or nitride particles is used as a matrix,
Carbon composite fiber reinforced ceramic composite material.