JP3412378B2 - Ceramic composite materials - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure which has high mechanical strength over a wide range from room temperature to high temperature, has good creep resistance, and is exposed to high temperature. The present invention relates to a ceramic composite material that can be suitably used as a material or a functional material. 2. Description of the Related Art SiC or Si ₃ N ₄ is expected as a ceramic material used at high temperatures, and researches on its practical use have been made. However, these materials have insufficient high-temperature characteristics and are not suitable for practical use. Is a problem in doing so. As an alternative material, SiC / S by chemical vapor impregnation method of SEP
The iC composite material has been in the spotlight and is now considered to be the world's highest temperature material, and its research and development is proceeding, but its working temperature range is set to 1,400 ° C. or less. At present, powder sintering is the main method for producing ceramics. The powder sintering method has been improved by improving powder characteristics such as finer powder and higher purity, and by manufacturing under well-controlled sintering conditions. The production of high strength ZrO ₂ ceramics with a room temperature strength of 3.0 GPa is now possible. Furthermore, it has become possible to produce a composite material in which different types of ceramic particles are nano-dispersed by a powder sintering method, and attempts have been made to improve strength, toughness, thermal characteristics, and the like. However, the sintered body obtained by the powder sintering method is a polycrystalline body, and has a problem that sufficient high-temperature strength cannot be obtained because of the presence of colonies, voids, grain boundary phases, and the like. On the other hand, Journal of the American Ceramics
The Society 76 Volume 1 No. 29-32 pages _{(1993), Al 2 O 3 -Y 3} Al 5 O 12 Co alumina and yttria-alumina garnet represented by crystallization (hereinafter "Y
AG "). Further, in this document, as a method for producing the composite, a mixed powder of Al ₂ O ₃ and Y ₂ O ₃ is melted,
A method of unidirectionally melting and solidifying in a crucible is disclosed. [0005] From the description on page 29, right column, lines 9 to 10 of the document and FIGS. 1 and 2 on the same page, it can be seen that the composite is composed of polycrystal and has a grain boundary phase. This can, for example, from the description "fracture is along the colony boundaries with crack running along the usual Al ₂ O _3-YAG interface" of the document 30 page left column, last line - the right column, line 1 Supported. Then, this colony boundary is indicated by a portion where the tissue is larger than other portions in FIG. [0006] As shown in FIG. 4, for example, the composite material disclosed in the above-mentioned document has a stress of 1,530 ° C. and 1,65 ° C. when the strain rate is constant.
At 0 ° C., it is almost the same as that of the sapphire fiber. Furthermore, according to the experiment of the present inventor, the composite described in the above document contains bubbles or voids inside the composite,
It was observed that the mechanical strength sharply decreased at high temperatures. Therefore, in view of the above problems of the prior art, the present inventor has a ceramic material having excellent mechanical strength and creep properties from room temperature to high temperature, and these properties are significantly improved especially at high temperature. We have been conducting diligent research to obtain. As a result, JP-A-7-14959
No. 7, No. 7-187893 and Japanese Patent Application No. 6-24079.
No. 2 discloses a composite material comprising an α-Al ₂ O ₃ phase and a YAG phase, wherein the phases are composed of a single crystal / single crystal, a single crystal / polycrystal, and a polycrystal / polycrystal. A new ceramic composite has been found. An object of the present invention is to provide the above-mentioned α-Al ₂
A ceramic composite material comprising an O ₃ phase and a YAG phase, wherein the phases are composed of a single crystal / single crystal, a single crystal / polycrystal and a polycrystal / polycrystal. Single crystal of simple oxide and simple oxide, simple oxide and complex oxide, or complex oxide and complex oxide /
An object of the present invention is to provide a ceramic composite material which is made of a single crystal and has excellent mechanical strength and creep characteristics from room temperature to high temperature, and in particular, these characteristics are significantly improved at high temperature. [0008] The object of the present invention is to provide a simple oxide and a simple oxide, a simple oxide and a complex oxide, or a complex oxide and a complex oxide according to the first aspect of the present invention. Single crystal /
This is achieved by a ceramic composite material comprising a solidified body composed of a single crystal. [0009] The oxide of the metal according to claim 1 includes:
For example, the following are mentioned. Al ₂ O ₃ , SiO ₂ , TiO ₂ , Y ₂ O ₃ , NiO The composite oxide formed by the combination of the oxides of two or more metals described in claim 1 includes, for example, The following are mentioned. _{3Al 2 O 3 · 2SiO 2 (} Mullite), Al 2
_{O 3 · TiO 2, 3Y 2} O 3 · 5Al 2 O 3, 2Y 2 O
_3. Al ₂ O ₃ Hereinafter, the ceramic composite material of the present invention will be described in detail. In the present invention, “single crystal” means a crystal structure in which only a diffraction peak from a specific crystal plane is observed in X-ray diffraction. In addition, the ceramic composite material of the present invention can be obtained by the method described in FIGS.
No colonies, grain boundary phases or coarse particles as observed in Example 1 were observed, and the sample was composed of a uniform structure, that is, a single crystal / single crystal. In the ceramic composite material of the present invention, a single crystal oxide and a single crystal oxide are homogeneously formed at a fine level.
Moreover, it forms a continuously connected sea-island structure. For example, in the case of a combination of Al ₂ O ₃ and SiO ₂ described in Table 1 of the embodiment, the single crystal α-Al ₂ O ₃ is a single crystal 3Al ₂
O ₃ · 2SiO ₂ are respectively formed the island. The size of the sea-island can be controlled by changing the coagulation conditions, but is generally 10 to 50 μm. Al ₂ O ₃ and 3Al ₂ O ₃ .2SiO ₂ are:
A eutectic is formed with Al ₂ O ₃ : 32 mol% and SiO ₂ : 68 mol%. In the ceramic composite material of the present invention, by changing the mixing ratio of the raw material powders Al ₂ O ₃ and SiO ₂ powder, About 20 to 80% by volume of single crystal α-Al ₂ O ₃ ,
It is possible to change its fraction in the range of single crystal 3Al ₂ O ₃ · 2SiO ₂ about 80 to 20 volume%. The ceramic composite material of the present invention can be prepared, for example, by the following method. First α-
The mixed powder is prepared by mixing the Al ₂ O ₃ powder and the SiO ₂ powder at a ratio that produces a ceramic composite material having a desired component ratio. There is no particular limitation on the mixing method, and any of a dry mixing method and a wet mixing method can be employed. As a medium when using the wet mixing method, an alcohol such as methanol or ethanol is generally used. Next, the mixed powder is melted in a known melting furnace, for example,
Using an arc melting furnace, a temperature at which both raw materials are melted, for example, in the case of Al ₂ O ₃ and SiO ₂ , 1,950 to 2,10
Heat to 0 ° C. to dissolve. Subsequently, the above-mentioned melted material is directly charged into a crucible and solidified in one direction, or the above-mentioned melted material is once solidified and then pulverized, and the pulverized material is charged into a crucible.
Then, the ceramic composite material of the present invention is produced by melting and solidifying in one direction. As another method, the melt is cast into a crucible held at a predetermined temperature,
A method of obtaining a solidified body while controlling the cooling rate can also be adopted. Atmospheric pressure during melting and solidification is usually 4 * 1
0 ⁴ Pa (300Torr) or lower, preferably 0.13P
a (10 ⁻³ Torr) or less. The moving speed of the crucible when solidifying in one direction, in other words, the growth speed of the ceramic composite material is usually 50 mm / hour or less, preferably 1 to 40 mm / hour. The adjustment conditions other than the atmospheric pressure and the moving speed are the same as those of the method known per se. If the atmospheric pressure or the moving speed of the crucible during the melting and solidification is out of the range, polycrystals may be formed,
Air bubbles or voids are easily generated, and it becomes difficult to obtain a composite material having excellent mechanical strength and creep characteristics. As an apparatus for one-way solidification, a crucible is housed in a vertically disposed cylindrical container so as to be movable in the vertical direction, and an induction coil for heating is provided outside the center of the cylindrical container. It is possible to use a device which is attached and has a vacuum pump for reducing the pressure in the container, which is known per se. On the other hand, in the present invention, an oxide other than the oxide constituting the ceramic composite material is added to form a solid solution or precipitate in at least one of the phases constituting the composite material, or By making it exist,
Mechanical and thermal properties can also be varied. Such a composite material can also be manufactured under the method and conditions described above. Examples of the heterogeneous oxide to be added include the following. Al ₂ O ₃ , SiO ₂ , TiO ₂ , Y ₂ O ₃ , NiO As a production method, first, for example, a raw material oxide powder is mixed at a ratio that produces a ceramic composite material having a desired component ratio. Then, a predetermined amount of the different oxide powder is added to the mixed powder to prepare the mixed powder. Continued
The obtained mixed powder is charged into a crucible placed in a chamber and solidified in one direction to produce a ceramic composite material of the present invention. In the composite material, by changing the amount of the oxide to be dissolved, the amount of the solid solution can be changed to exhibit desired mechanical properties, thermal properties, and the like. The amount of addition can be changed within the range of 0.001 to 10% by weight, and all of the addition may precipitate at the crystal interface without forming a solid solution. In addition, as a method for forming a solid solution, a method in which a ceramic composite material first produced by a unidirectional solidification method is buried in a different kind of oxide powder and heat-treated may be employed. The ceramic composite material of the present invention has dramatically improved heat resistance, durability, high-temperature strength and thermal stability at high temperatures, and can be used at high temperatures exceeding 1,200 ° C. In order to exhibit excellent properties, members such as turbine blades of jet engines and gas turbines for power generation,
It is highly useful as a jig for measuring high-temperature characteristics of various high-temperature materials. In addition, applications in which oxide-based ceramics such as Al ₂ O ₃ are specifically used, for example, heat exchangers for high temperatures, materials for nuclear fusion reactors, materials for nuclear reactors,
It is highly useful in a wide range of other fields such as wear-resistant members and corrosion-resistant members. Further, if the ceramic composite material is made into a fibrous or powdery form, for example, a Ni-based superalloy or a Co-based superalloy used in a turbine blade of a jet engine or a gas turbine for power generation, or a dispersion strengthening material of various ceramics is used. Can also be suitably used.
Furthermore, if the obtained powder is solidified on a surface of a metal material or the like by a coating method such as a plasma spraying method,
Improvements in oxidation resistance and wear resistance can also be expected. As a method of producing a fibrous ceramic composite material, a solidified body produced in advance by a unidirectional solidification method is formed into a wire rod having a diameter of about 1 mm, immersed in a heated and molten pool having the same composition, pulled up, and pulled up. A method of growing crystals can be employed. Alternatively, an edge-defined film-fed is pulled up by placing a narrow guide causing a capillary phenomenon in the melt pool heated and melted.
A method of irradiating a rod produced by a Growth (EFG method) or a sintering method with a CO ₂ laser or the like, melting the band, and solidifying it unidirectionally (Laser-heated f)
Lone zone method (LHFZ method) can also be adopted. In addition, as a method for producing a powdery ceramic composite material, a method in which a sample that has been heated and melted is dropped from a fine hole provided at the bottom of the crucible into a furnace with a gentle temperature gradient and solidified is adopted. Can be. Further, as a method of coating on the surface, a method of plasma spraying, a method of unidirectional solidification while immersing the material to be coated in a melt pool heated and melted, and a method of removing the crucible holding the melt by post-processing. Can be taken. EXAMPLES Examples and comparative examples are shown below. Example 1 Raw material powders α-Al ₂ O ₃ and SiO ₂ were mixed in a mixing ratio shown in Table 1 by a wet ball mill using an ethanol solvent, and ethanol was removed from the obtained slurry using a rotary evaporator. The obtained mixed powder was charged into a molybdenum crucible installed in a chamber, and 1.33
The crucible was heated to 1,950 to 2,100 ° C. using a high-frequency coil while maintaining the atmospheric pressure of Pa (10 ⁻² Torr) to dissolve the mixed powder. Next, under the same atmospheric pressure, the crucible was lowered at a speed of 5 mm / hour and solidified in one direction to obtain a ceramic composite material. FIG. 1 shows an optical micrograph of a cross-sectional structure perpendicular to the solidification direction of the composite material including α-Al ₂ O ₃ and 3Al ₂ O ₃ SiO ₂ thus obtained. In FIG. 1, the white part is 3Al ₂ O ₃ S
In the iO ₂ phase, the darker part is the α-Al ₂ O ₃ phase. This composite material was found to have no colony or grain boundary phase and to have a uniform sea-island structure free of bubbles or voids. Further, as a result of X-ray diffraction of a plane perpendicular to the solidification direction of the composite material, α-Al ₂ O ₃ and 3
Only diffraction peaks from specific surfaces of Al ₂ O ₃ SiO ₂ were observed, and the composite material was composed of two phases of α-Al ₂ O ₃ single crystal and 3Al ₂ O ₃ SiO ₂ single crystal It turns out. When the mechanical strength of this composite material at high temperature was measured,
The three-point bending strength was 400 MPa. The weight increase of this composite material after being kept in the air at 1700 ° C. for 50 hours was 0.003 g / cm ³ . In the following, Table 1 shows the constituent phases of the composite material obtained by preparing the raw material powders shown in Table 1 in the same manner and unidirectionally solidifying, and the crystal structure evaluation by X-ray diffraction. It was found that these composite materials had no colony or grain boundary phase, and had a uniform sea-island structure without bubbles or voids. [Table 1] Comparative Example 1 A ceramic composite material was prepared by repeating Example 1 except that the pressure in the chamber was changed to normal pressure. The 2 optical micrograph of a cross section perpendicular tissue to solidification direction of the resulting alpha-Al ₂ O ₃ and 3Al ₂ O ₃ composite material consisting 2SiO ₂ in the. This composite material was found to have a colony or grain boundary phase and bubbles. Also,
As a result of X-ray diffraction of a plane perpendicular to the solidification direction of the composite material,
diffraction peaks from a plurality of surfaces of α-Al ₂ O ₃ and 3Al ₂ O ₃ 2SiO ₂ were observed, the composite material was found to be composed of polycrystalline. Hereinafter, Table 2 shows the phase constitution of the composite material which was prepared in the same manner as the raw material powder shown in Table 2 and was unidirectionally solidified, and the crystal structure evaluation by X-ray diffraction. These composites were found to have colony and grain boundary phases, and even air bubbles. [Table 2] It has been found that the ceramic composite material of the present invention has good heat resistance, durability and creep characteristics at high temperatures.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an optical microscope photograph instead of a drawing showing the crystal structure of the composite material obtained in Example 1. FIG. 2 is an optical microscope photograph instead of a drawing showing the crystal structure of the composite material obtained in Comparative Example 1.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazutoshi Shimizu 5-1978 Kogushi, Oji, Ube City, Yamaguchi Prefecture Ube Industries, Ltd. Inside Ube Research Laboratories (72) Inventor Yasuhiko Shintoku Yasuhiko 1978 Address, Kogushi 5 Oji, Ube City, Yamaguchi Prefecture Ube Industries, Ltd. Ube Laboratory (56) References JP-A-61-201683 (JP, A) JP-A-2-204322 (JP, A) JP-A-2-153803 (JP, A) JP-A-6 JP-A-136353 (JP, A) JP-A-7-149597 (JP, A) JP-A-7-172829 (JP, A) JP-A-7-187893 (JP, A) JP-A-8-12422 (JP, A) JP-A-8-81257 (JP, A) JP-A-8-319198 (JP, A) JP-A-9-278521 (JP, A) Junichi Echigoya et al. Organization, Journal of the Japan Institute of Metals, 198 4 years April 20, Vol. 48, No. 4, pp. 430-434 (58) Field surveyed (Int. Cl. ⁷ , DB name) C30B 1/00-35/00 C04B 35/10 CA (STN) JICST file (JOIS) EUROPAT (QUESTEL)

Claims (1)

(57) [Claims 1] Selected from Al, Si, Ti, Y, Ni
A simple oxide formed from a metal , Al, Si, Ti,
A composite material comprising a single crystal of two or more oxides selected from the group consisting of a composite oxide formed from two or more metals selected from Y and Ni. (However, except that the constituent phases are Al ₂ O ₃ and Y ₃ Al ₅ O ₁₂ (YAG).)