JP3001130B2 - Alumina-based inorganic 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 an alumina-based fiber reinforced ceramic composite material having high strength, high toughness and high heat resistance. The ceramic composite material of the present invention can be used for turbine engine members such as rotors, stators and combustors, rocket engine members such as nose cones and nozzles, piston heads, auxiliary combustion chambers and internal combustion engines such as valves. It can be suitably used as a member.

[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 strengthening 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 "
Vol. 65, pages 326 to 335 (1986), has a flexural strength of about 700 of a monolithic silicon carbide.
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 above object of the present invention is achieved by an alumina-based inorganic fiber reinforced ceramic composite material having a matrix of a carbide-based nanocomposite or a nitride-based nanocomposite nanocomposited with carbide particles and / or nitride particles.

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.

In the present invention, the carbide-based nanocomposite or the nitride-based nanocomposite 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 structure is, for example, as shown in the model of FIG. 1, where nano-order dispersed particles are dispersed in matrix particles of carbide-based ceramics or nitride-based ceramics, and the matrix particles themselves are composited. 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).

[0009] 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 alumina-based inorganic fiber reinforced ceramic composite material of the present invention is prepared by blending alumina-based inorganic fiber and carbide-based nanocomposite or nitride-based nanocomposite according to a method known per se and sintering. can do. When the alumina-based inorganic fibers are chopped, a mixture of chopped fibers and nanocomposite powder is prepared. Alumina inorganic fiber is long fiber,
In the case of 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 a nanocomposite powder. Next, the alumina-based inorganic fiber reinforced ceramic composite material of the present invention can be obtained by forming the mixture or laminate into a desired shape or by heating and sintering at the same time as the formation. The proportion of alumina-based inorganic fibers in the composite material is
Usually, it is 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 heating sintering temperature is too low, the nanocomposite as the matrix will not be sufficiently sintered, and if the temperature is too high, the alumina-based inorganic 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, 801-808 (1986), JP-A-63-1
It can be prepared according to the method disclosed in JP-A-6325. Specific examples of the organometallic polymer include polycarbosilane, polycarbosilazane, and polysilazane.

As another method for preparing the alumina-based inorganic 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 raw material powder of a matrix, 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 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 Hexamethyldisilazane and ammonia were subjected to a chemical vapor reaction at 1000 ° C.
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.

Reference Example 2 300 g of liquefied monomethylamine was added to 3000 ml of dry petroleum ether cooled to -30 ° C., and 150 g of methyltrichlorosilane was added dropwise with stirring in a dry nitrogen gas atmosphere. Thereafter, the reaction was carried out at 40 ° C. for 1 hour. The product after the reaction was filtered in a dry nitrogen gas atmosphere,
Distillation was performed at 151 ° C. to obtain tris (N-methylamino) methylsilane. After reacting the obtained tris (N-methylamino) methylsilane in a nitrogen gas atmosphere at 520 ° C. for 3.5 hours, a low-boiling substance is removed in the same atmosphere, and a red-brown transparent solid serving as a sintering binder is obtained. Resin was obtained.

Reference Example 3 In dry nitrogen gas, 16.1 g of dichlorosilane was gradually added dropwise to 150 ml of pyridine at 0 ° C. to obtain a white solid adduct. This adduct was cooled to 0 ° C., and agitated and mixed with 11 g of ammonia with nitrogen gas to cause a reaction. After the reaction, the solid product was removed, and the solvent was removed by distillation under reduced pressure to obtain a glassy solid material to be a sintered binder.

Example 1 A composite powder slurry obtained by pulverizing the composite powder comprising silicon, carbon and nitrogen obtained in Reference Example 1 in hexane by a ball mill using a silicon nitride ball and a silicon nitride pot for 30 hours was obtained. Was. After adding 15% by weight of the sintered binder obtained in Reference Example 2 to the nanocomposite material to this slurry, the mixture was wet-mixed for 4 hours using silicon nitride balls to obtain a slurry of matrix material. A bundle of alumina fibers (ALTEX) manufactured by Sumitomo Chemical Co., Ltd. was opened by air blowing, and then immersed in the slurry of the matrix material described above to adhere a matrix powder around each alumina 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 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 hot-pressed in an argon gas atmosphere at a temperature of 1700 ° C. and a pressure of 70 MPa. An alumina-based inorganic fiber reinforced ceramics composite material was obtained using a silicon nitride-based nanocomposite in which silicon carbide particles were nanocomposited as a matrix. The percentage of fibers in the obtained composite material was 40% by volume. The bending strength of this composite material was 1.2 at room temperature.
It was 1.27 GPa at 4GPa and 1300 ° C. The fracture toughness value (K _1C ) of the composite material measured by the chevron notch method was 18.3 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 dichloromethane using both 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 for 4 hours by a ball mill using nylon balls.
The ratio of the alumina-based fiber to the matrix is 1: 1:
It was set to 4. A thin prepreg of an alumina-based fiber reinforced ceramic composite material was prepared from the above mixed slurry by a filtration method. After cutting the obtained sheet-like prepreg into a predetermined shape, it is laminated in a graphite die coated with boron nitride as a mold release agent, and is placed in an argon atmosphere at 1750.
Hot pressing was performed at a temperature of 75 ° C. and a pressure of 75 MPa to obtain an alumina-based inorganic fiber reinforced ceramic composite material having a matrix of a silicon nitride-based nanocomposite in which silicon carbide particles were nanocomposited. The bending strength of this composite material was 1.11 GPa at room temperature and 1.06 GPa at 1300 ° C. The fracture toughness value (K _1C ) of the composite material measured by the chevron notch method was 11.0 MPa · m ^1/2 .

Example 3 The composite powder comprising silicon, carbon and nitrogen obtained in Reference Example 1 was pulverized in hexane for 35 hours by a ball mill using a silicon nitride ball and a silicon nitride pot to obtain a slurry of the composite powder. Obtained. The sintered binder obtained in Reference Example 3 was added to this slurry in an amount of 10
After adding 2% by weight of aluminum oxide powder and 8% by weight of yttrium oxide powder, the mixture was wet-mixed using silicon nitride balls for 12 hours, and then the organic solvent was removed to remove the matrix material powder. Obtained. A graphite die obtained by coating a bundle of alumina-based fibers (NEXTEL) manufactured by US 3M Co., Ltd. with a sheet of alumina-based fibers obtained by blowing with air and the above-mentioned matrix material powder and applying boron nitride as a release agent Alternately stacked inside,
1000 ° C, 50MPa in argon gas atmosphere
Hot-pressed under the following pressure to obtain a temporarily sintered body. This temporary sintered body is coated with boron nitride as a mold release agent, vacuum-encapsulated in a glass capsule, and then hot isostatically pressed in argon gas at a temperature of 1680 ° C. and a pressure of 190 MPa, whereby silicon carbide particles are formed. Alumina-based inorganic fiber reinforced ceramic composites using nanocomposite silicon nitride-based nanocomposites as a matrix were obtained. The proportion of the alumina-based inorganic fibers in the composite material was 35% by volume. The bending strength of this composite material was 1.35 GPa at room temperature and 1.33 GPa at 1300 ° C.
Met. The fracture toughness value (K _1C ) of the composite material measured by the chevron notch method was 16.1 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.

────────────────────────────────────────────────── ─── Continued from the front page Examiner Yuki Yamada (56) References JP-A-6-87670 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35/80

Claims (1)

(57) [Claims] 1. Alumina-based inorganic fiber reinforced ceramics comprising alumina-based inorganic fibers as a reinforcing material and a matrix of a carbide-based nanocomposite or a nitride-based nanocomposite nanocomposited with carbide particles and / or nitride particles. Composite materials.