JP3001129B2 - Alumina-based inorganic 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 the K _1c of ordinary monolithic silicon nitride, which is about 6 MPa · m ^1/2 .

[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 use an alumina-based inorganic fiber as a reinforcing material and an oxide-based nanocomposite nanocomposited with carbide particles and / or nitride particles as a matrix.
This is achieved by an alumina-based inorganic fiber reinforced ceramic composite material.

The alumina-based inorganic fibers in the present invention are:
(1) an amorphous substance comprising aluminum and oxygen, and optionally these elements and at least one element selected from silicon, boron and zirconium, (2) Al ₂ O
₃ crystalline particles, or _Al 2 _{O 3} crystalline particles and SiO
₂ , at least one selected from B ₂ O ₃ and ZrO ₂
It is composed of an aggregate of seed crystalline particles or an amorphous substance, or (3) a mixture of the amorphous substance of (1) and the aggregate of (2). Such alumina-based inorganic fibers are commercially available as alumina-based fibers from, for example, 3M USA, Du Pont USA, Sumitomo Chemical Co., Ltd. or Mitsui Mining Co., Ltd.

The form of the alumina-based inorganic fiber is not particularly limited, and may be chopped fiber, plain woven, satin woven, multiaxial woven, three-dimensional woven or nonwoven woven from continuous fiber. May be arranged in one direction.

[0008] 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).

[0009] Specific examples of the oxide-based ceramics serving as a matrix in the oxide-based nanocomposite include 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.

[0010] 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 alumina-based fiber-reinforced ceramic composite material of the present invention can be prepared by blending and sintering an alumina-based fiber and an oxide-based nanocomposite according to a method known per se. When the alumina-based 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 alumina-based fiber is a long fiber, a woven fabric, a non-woven fabric or a sheet-like material, a laminate is prepared by alternately laminating layers composed of these and layers composed of powder of the oxide-based nanocomposite. Next, the alumina-fiber-reinforced ceramic composite material of the present invention can be obtained by heating and sintering the above-mentioned mixture or laminate after shaping it into a desired shape or simultaneously with the shaping. The ratio of the alumina-based fiber in the composite material is usually 1 to 70% by volume.

As a method for forming the above-mentioned mixture or 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 heating sintering temperature is usually 400 to 2100 ° C. If the heat sintering temperature is too low, the oxide nanocomposite as the matrix will not be sufficiently sintered, and if the temperature is too high, the alumina-based fibers will be decomposed.

In order to lower the sintering temperature, an organometallic polymer which can be converted into a ceramic after sintering to become one of the matrix components can be used as a sintering binder. Such organometallic polymers include, for example, “Ma
t. Res. Soc. Symp. Proc. 73, pages 801-808 (1986), "Advanc
es in Ceramics, Vol. 21, 121-12
It can be prepared according to the method disclosed on page 9 (1987). Specific examples of the organometallic polymer include a polymer of aluminum alkoxide, a polymer of magnesium alkoxide, and a copolymer of aluminum alkoxide and silicon alkoxide.

As another method for preparing the alumina-based inorganic 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 alumina-based inorganic fiber occur simultaneously or sequentially, and the alumina-based inorganic 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 0.3 μm average particle diameter on 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, K _1c was 5 MPa · m ^1/2 , and the maximum operating temperature was 1200 ° C.

Reference Example 2 An average particle size of 0.3 μm was added to γ-alumina having an average particle size of 0.4 μm.
m-α-silicon nitride particles were added at 10% by volume, and the mixture was wet-mixed in ethanol using a ball mill for 12 hours in a ball mill using alumina balls.
Dry mixing was performed for 2 hours. Alumina-based nanocomposite (Si ₃ N ₄ grains / Al ₂₎ reinforced with silicon nitride particles by hot pressing the mixed powder in a graphite die at a temperature of 1600 ° C. and a pressure of 30 MPa in a nitrogen gas atmosphere.
O ₃ nanocomposite). The bending strength at room temperature of this nanocomposite was 0.85 GPa, and the maximum use temperature was 1300 ° C.

REFERENCE EXAMPLE 3 A water / methanol mixed system (water: methanol = 3: 1) was added to a benzene solution of aluminum isopropoxide.
The mixture was stirred at pH 6.5 and room temperature for 20 hours to perform hydrolysis.
The resulting precipitate was filtered to obtain a wet gel serving as a sintered binder.

Example 1 The nanocomposite of the SiC particles / Al ₂ O ₃ nanocomposite obtained in Reference Example 1 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. This slurry was mixed with the sintered binder obtained in Reference Example 3 for 15 times with respect to the nanocomposite material powder.
After the addition by weight, the mixture was wet-mixed for 4 hours using silicon nitride balls to obtain a slurry of the matrix material. After a bundle of alumina-based fibers (ALTEX) manufactured by Sumitomo Chemical Co., Ltd. was opened by air blowing, the bundle was immersed in the slurry of the matrix material described above, and a matrix powder was attached around each of the alumina-based fibers. . The bundle of alumina fibers to which the matrix powder was adhered was wound around a square drum, and then sufficiently dried to produce a 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 mold release agent.
Hot press at a pressure of Pa to obtain SiC particles / Al ₂ O ₃
An inorganic fiber reinforced ceramics composite material with a nanocomposite matrix was obtained. The ratio of the alumina-based fibers in the composite material was 40% by volume. The bending strength of this composite material was 1.52 GPa at room temperature and 1.46 GPa at 1300 ° C. The fracture toughness value (K _1c ) of the composite material measured by the Sheplon notch method was 19.8 MPa · m ^1/2 .

Example 2 Alumina-based fibers (ALMAX) manufactured by Mitsui Mining Co., Ltd. were cut into lengths of 1 to 2 mm into chopped fibers. The chopped fibers were dispersed in ethanol using ultrasonic waves and an omni mixer. After the slurry of the matrix material prepared in Example 1 was added to the dispersion, the mixture was wet-mixed in ethanol by a ball mill using nylon balls for 4 hours. The ratio of the alumina-based fiber to the matrix was set to be 3: 7 by volume. Ethanol and water were evaporated from the mixed slurry to obtain a mixed powder of an alumina-based fiber and a matrix. This mixed powder is placed in a graphite die coated with boron nitride as a release agent, and hot-pressed in an argon atmosphere at a temperature of 1400 ° C. and a pressure of 75 MPa to convert the SiC particles / Al ₂ O ₃ nanocomposite into a matrix. An inorganic fiber reinforced ceramic composite material was obtained. The ratio of the alumina-based fibers in the composite material was 30% by volume. The bending strength of this composite material is 1.4 at room temperature.
It was 1.28 GPa at 8300 and 1300 ° C. The fracture toughness value (K _1c ) of the composite material measured by the chevron notch method was 9.2 MPa · m ^1/2 .

Example 3 The Si ₃ N ₄ particles / Al ₂ O ₃ nanocomposite obtained in Reference Example 2 was ground in a ball mill for 30 hours in distilled water using a silicon nitride ball and a silicon nitride pot. Thus, a nanocomposite slurry was obtained. The sintered binder obtained in Reference Example 3 was added to this slurry in one part per nanocomposite powder.
After the addition of 5% by weight, wet mixing was performed for 4 hours using silicon nitride balls to obtain a slurry of the matrix material. A bundle of alumina-based fibers (NEXTEL) manufactured by 3M in the United States was opened by air blowing, and then immersed in the above-mentioned slurry of the matrix raw material to adhere a matrix powder around each alumina-based fiber. The bundle of alumina fibers to which the matrix powder was adhered 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 1000 ° C. and a pressure of 50 MPa, and temporarily sintered. I got a body. After applying boron nitride as a mold release agent to this pre-sintered body and vacuum-encapsulating it in a glass capsule, hot isostatic pressing was performed at a temperature of 1200 ° C. and a pressure of 140 MPa in argon gas to obtain S
An inorganic fiber reinforced ceramic composite material using i ₃ N ₄ particles / Al ₂ O ₃ nanocomposite as a matrix was obtained. The ratio of the alumina-based fibers in the composite material was 45% by volume. The flexural strength of this composite material is 1.27 GPa at room temperature, 1300
It was 1.23 GPa at ° C. The fracture toughness value (K _1c ) of the composite material measured by the chevron notch method was 20.6
MPa · m ^1/2 .

[0021]

[Brief description of the drawings]

FIG. 1 is a model of an intragranular nanocomposite.

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

────────────────────────────────────────────────── ─── Continuing from the front page Examiner Yuki Yamada (56) References JP-A-6-87671 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 35/80

Claims (1)

(57) [Claims] An alumina-based inorganic fiber reinforced ceramic composite material comprising an alumina-based inorganic fiber as a reinforcing material and an oxide-based nanocomposite nanocomposited with carbide particles and / or nitride particles as a matrix.