JP3264106B2 - Ceramic composite materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention has high mechanical strength over a wide range from room temperature to high temperature, has good creep resistance, and has excellent oxidation resistance, and is suitable as a structural material exposed to high temperatures. The present invention relates to a ceramic composite material that can be used for:

[0002]

SiC or Si ₃ N ₄ is of the Prior Art Ceramic materials used at high temperatures is expected, although its practical application has been studied, these materials are not sufficient high temperature properties, problems in practical use It has become. As an alternative material, SiC / Si by chemical vapor impregnation of SEP
C-composite material is in the spotlight and is currently considered to be the world's best high-temperature material.
The operating temperature range is set to 1400 ° C. or less.

[0003] Journal of the Amer
ican Ceramics Society Volume 76 1
No. 29-32 (1993), Al ₂ O ₃ −
A composite comprising alumina represented by Y ₃ Al ₅ O ₁₂ eutectic and yttria-alumina-garnet (hereinafter sometimes referred to as “YAG”) is disclosed.
Further, this document discloses that the production method of the above-mentioned composite is Al
A method is disclosed in which a mixed powder of ₂ O ₃ and Y ₂ O ₃ is melted and then melted and solidified in one direction in a crucible.

From the description on page 29, right column, lines 9 to 10 and FIGS. 1 and 2 on the same page, it can be seen that the composite is made of polycrystal and has a grain boundary phase. In other words, this complex is composed of an aggregate of colonies. This can, for example, "is along the colony boundaries with destruction running along the usual Al ₂ O _3-YAG interface crack" of the document 30 page left column, last line - the right column, line 1
This is supported by the description. The boundary of the colony is shown in FIG. 2 on page 30 of the document where the tissue is larger than the other portions.

[0005]

As shown in FIG. 4, for example, as shown in FIG. 4, when the strain rate is constant and the stress is constant at 1530 ° C. and 1650 ° C.
About the same as that of sapphire fiber. further,
According to the experiments of the present inventors, the complex described in the above-mentioned literature is:
It was confirmed that the composite contained bubbles or voids, and the mechanical strength was rapidly reduced at high temperatures.

An object of the present invention is to provide a single crystal α-Al ₂ O ₃ and a polycrystalline YAG, which have excellent mechanical strength and creep characteristics from room temperature to high temperature, and that these characteristics particularly at high temperature are dramatically improved. It is to provide an improved ceramic composite material.

[0007]

Means for Solving the Problems The object of the present invention is to
This is achieved by a ceramic composite material composed of single crystal α-Al ₂ O ₃ and polycrystalline Y ₃ Al ₅ O ₁₂ .

Hereinafter, the ceramic composite material of the present invention will be described in detail. 1 and 2 show a plane perpendicular to the solidification direction of the ceramic composite material obtained in Example 1 to be described later and a plane inclined by about 9 degrees (Al _{2 in the} plane perpendicular to the solidification direction).
Since the diffraction peak of O ₃ was not obtained, the measurement was performed from a plane inclined by about 9 degrees. FIG. 3 is a diagram showing X-ray diffraction from the above.

FIG. 1 shows the (211) plane of YAG, (22)
0) plane, (422) plane, (431) plane, (541) plane,
2 corresponding to diffraction from the (721) plane and the (651) plane
θ = 18.06 degrees, 20.88 degrees, 36.58 degrees, 3
8.16 degrees, 49.1 degrees, 56.22 degrees and 60.64
A degree peak is observed.

FIG. 2 shows that (1) for Al ₂ O _3.
Only the peak at 2θ = 37.8 degrees corresponding to the diffraction from the 10) plane is observed, while for YAG, the (22)
Peaks at 2θ = 20.74 °, 42.5 ° and 54.92 ° corresponding to diffraction from the (0), (440), (640) and (660) planes are observed. 1 and 2
Therefore, the ceramic composite material of the present invention is a single crystal α-Al
_It can be seen that it is composed of ₂ O ₃ and polycrystalline YAG.

FIG. 3 is an optical micrograph of the ceramic composite material obtained in Example 1 described later. As shown in FIGS. 1 and 2 of the above-mentioned known document, colonies, grain boundary phases or coarse particles are Not observed. Note that a colony means a region surrounded by grain boundaries characterized by coarse particles.

On the other hand, FIG. 4 is an optical micrograph of a composite material obtained in Comparative Example 1 described later. This composite material has colonies and grains as shown in FIG. 1 and FIG. It turns out that it has a boundary phase or coarse particles.

In the ceramic composite material of the present invention, the single crystal α-Al ₂ O ₃ and the polycrystalline YAG form a sea-island structure uniformly at a fine level, and the single crystal α-Al ₂ O ₃ forms the sea. , Polycrystalline YAG form islands, respectively. The size of the sea-island can be controlled by changing the coagulation conditions, but is generally 5 to 50 μm.

Al ₂ O ₃ and YAG are Al ₂ O ₃ 55
A eutectic is formed by volume% and YAG 45 volume%. In the ceramic composite material of the present invention, Al _{2 of} the raw material powder is used.
By changing the mixing ratio of O ₃ and YAG powder, about 20 to 80% by volume of single crystal α-Al ₂ O _{3 and} polycrystalline YAG
The fraction can vary within the range of about 80 to 20% by 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 Y ₂ O ₃ 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. Then, using a known melting furnace, for example, an arc melting furnace, the mixed powder is melted at a temperature at which both raw materials are melted, for example, at 1 ° C.
Heat to 800 to 2500 ° C to dissolve.

Subsequently, the above-mentioned melt is charged into a crucible as it is and solidified in one direction to prepare a ceramic composite material of the present invention. As another method, a method in which the above-mentioned melt is once solidified and then pulverized, the pulverized material is charged in a crucible, and then dissolved and solidified in one direction can be adopted.

Atmospheric pressure during melt-solidification is usually 10
⁻³ torr or less. In addition, the moving speed of the crucible when solidifying in one direction, in other words, the growth speed of the ceramic composite material is usually larger than 50 mm / hour and less than 20 mm.
0 mm / hour. The preparation 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 during the melt-solidification is out of the range, colonies are formed and voids are easily formed at the colony interface, and it is difficult to obtain a composite material having excellent mechanical strength and creep characteristics. Become.

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 a substantially central portion of the cylindrical container. And a device known per se in which a vacuum pump for reducing the pressure in the container is installed can be used.

[0020]

EXAMPLES Examples and comparative examples are shown below.

Example 1 α-Al ₂ O ₃ powder (AKP-, trade name, manufactured by Sumitomo Chemical Co., Ltd.)
30) and Y ₂ O ₃ powder (fine powder type, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed by a wet ball mill using ethanol in a molar ratio of the former to the latter of 82% to 18%, and the resulting slurry was obtained. The ethanol was removed from the mixture using a rotary evaporator.

The α-Al ₂ O ₃ and Y ₂ thus obtained
The mixed powder made of O ₃ is charged into a crucible installed in a chamber, and the crucible is maintained at an atmospheric pressure of 10 ⁻⁵ torr, and the crucible is heated to 1850 to 1900 using a high-frequency coil.
C. to dissolve the mixed powder in the mold. Next,
The crucible was lowered at a speed of 60 mm / hour under the same atmospheric pressure as above, and was unidirectionally solidified to obtain a ceramic composite material.

FIGS. 1 and 2 show X-ray diffraction patterns of the composite material from a plane perpendicular to the solidification direction and a plane inclined at about 9 degrees.
In Figure 1 the diffraction peak was observed from the polycrystalline YAG, FIG. 2, for the _Al 2 _{O 3} only a diffraction peak from (110) plane of the single crystal _α-Al 2 _{O 3} is observed. This indicates that the composite material is composed of single-crystal α-Al ₂ O ₃ and polycrystalline YAG.

FIG. 3 shows an optical microscope photograph of this composite material. FIG. 3 shows that this composite material has no colony or grain boundary phase and has a uniform sea-island structure without bubbles or voids.

Table 1 shows the mechanical strength of this composite material.
In Table 1, the three-point bending strength and the compression creep characteristics are values measured in the air. The weight increase of this composite material after being kept in the air at 1700 ° C. for 100 hours was 0.007 mg / cm ³ .

Example 2 A ceramic composite material was obtained by repeating Example 1 except that the atmospheric pressure in the chamber and the crucible lowering speed were changed to 10 ⁻³ torr and 100 mm / hour, respectively.

The X-ray diffraction patterns from the plane perpendicular to the solidification direction of the composite material and the plane inclined at about 9 degrees are the same as FIG. 1 for the former and FIG. 2 for the latter. -Al ₂
It was found that it was composed of O ₃ and polycrystalline YAG.

From an optical micrograph of this composite material, it was observed that this composite material had no colony or grain boundary phase and had a uniform sea-island structure free of bubbles or voids.

Table 1 shows the mechanical properties of this composite material.
The weight increase of this composite material after being kept in the air at 1700 ° C. for 100 hours was 0.007 mg / cm ³ .

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. FIG. 4 shows an X-ray diffraction pattern of the obtained composite material.

FIG. 4 shows that the composite material has a colony or grain boundary phase and bubbles. Table 1 shows the mechanical properties of this composite material. The weight increase of this composite material after being kept in the air at 1700 ° C. for 100 hours was 0.02 mg / cm ³ .

[0032]

[Table 1]

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction diagram of the composite material obtained in Example 1.

FIG. 2 is an X-ray diffraction diagram of the composite material obtained in Example 1.

FIG. 3 is an optical microscope photograph instead of a drawing showing the particle structure of the composite material obtained in Example 1.

FIG. 4 is an optical microscope photograph instead of a drawing showing the particle structure of the composite material obtained in Comparative Example 1.

──────────────────────────────────────────────────続 き Continued on the front page (56) References TRIPLICANE A. et al. , Deformation behavior of an AI203-Y 3AI5012 eutectic compost in comparis on with sapphire and YAG, Journal of the Americas. 76, No. 1, pp. 29-32, Jan. 1993 (58) Field surveyed (Int. Cl. ⁷ , DB name) C30B 1/00-35/00 CA (STN) EPAT (QUESTEL) WPI (DIALOG)

Claims (1)

(57) [Claims] 1. Single crystal α-Al ₂ O ₃ and polycrystalline Y ₃ Al
Ceramic composite material consisting of ₅ O ₁₂ Prefecture.